



@article {3287,
	title = {External uterine contractions signal analysis in relation to labor progression and dystocia},
	journal = {IFMBE Proceedings},
	volume = {41},
	year = {2014},
	note = {Export Date: 21 November 2014},
	month = {2014},
	pages = {555 - 558},
	abstract = {Labor dystocia is a major cause of operative delivery, which is associated with increased risks for both mother and fetus. We assessed linear and non-linear dynamics of external uterine contraction signals, in relation to labor progression and dystocia. Linear time domain, spectral and entropy methods were used to analyze external uterine contraction recordings obtained during the last two hours of labor, in 28 cases with normal and 27 cases with operative deliveries (forceps, vacuum or caesarean). Progression of labor was associated with a statistically significant increase in most linear time domain and spectral indices, both in normal and operative deliveries, whereas most entropy indices increased in normal deliveries, but did not change in operative deliveries. On the other hand, when compared with normal births, operative deliveries were associated with significantly increased entropy indices before the last hour of labor and significantly decreased (a probably associated) sympatho-vagal balance in the last hour of labor. Linear and non-linear analysis of external uterine contraction recordings may provide useful physiopathological and clinical information on the progression of labor and the diagnosis of dystocia. {\textcopyright} Springer International Publishing Switzerland 2014.},
	keywords = {Cardiotocography, Dystocia, entropy, External uterine contractions, Spectral analysis},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84891293956\&partnerID=40\&md5=2d53a97f6000b704bf67435b61662c09},
	author = {Gon{\c c}alves, H. and Pinto, P. and Ayres-de-Campos, D. and Bernardes, J.}
}
@article {3288,
	title = {Fetal behavioral dynamics in cephalic versus breech presentations},
	journal = {Developmental Psychobiology},
	volume = {56},
	year = {2014},
	note = {Export Date: 21 November 2014},
	pages = {1595 - 1600},
	abstract = {Differences in fetal neurodevelopment can have important implications on future perceptual and learning capabilities. The aim of this study was to assess autonomic nervous system and complexity dynamics in fetal heart rate (FHR) tracings from 27 singleton fetuses in cephalic or breech presentations, matched for gestational age (37+3-40+4 weeks), weight, gender and outcome. Breeches exhibited significantly higher mean FHR and LF/(MF+HF) ratio, as well as lower entropy, denoting increased sympatho-vagal balance and decreased complexity, consistent with the occurrence of more active fetal behavioral states. These findings suggest that there are neurodevelopment differences between fetuses in cephalic and breech presentation.},
	keywords = {Breech presentation, Development, entropy, Fetal behavior, Heart rate, Spectral analysis},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84907881885\&partnerID=40\&md5=efdb9069ff9f41b3b0d0e85ee6b9abb1},
	author = {Gon{\c c}alves, H. and Ayres-de-Campos, D. and Bernardes, J.}
}
@book {2198,
	title = {Automatic localization of the optic disc in retinal images based on the entropy of vascular directions},
	series = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)Lect. Notes Comput. Sci.},
	volume = {7325 LNCS},
	year = {2012},
	note = {Conference code: 91199Export Date: 21 November 2012Source: Scopusdoi: 10.1007/978-3-642-31298-4_50Language of Original Document: EnglishCorrespondence Address: Mendon{\c c}a, A.M.; Instituto de Engenharia Biom{\'e}dica, Universidade Do Porto, Rua Roberto Frias, s/n, 4200-465 Porto, Portugal; email: amendon@fe.up.ptReferences: Jelinek, H., Cree, M., (2010) Automated Image Detection of Retinal Pathology, , CRC Press, Taylor \& Francis Group, Boca Raton;Couper, D.J., Klein, R., Hubbard, L.D., Wong, T.Y., Sorlie, P., Cooper, L.S., Brothers, R.J., Nieto, F.J., Reliability of Retinal Photography in the Assessment of Retinal Microvascular Characteristics: The Atherosclerosis Risk in Communities Study (2002) American Journal of Ophthalmology, 133 (1), pp. 78-88; 
Sinthanayothin, C., Boyce, J.F., Cook, H.L., Williamson, T.H., Automated localization of the optic disc, fovea, and retinal blood vessels from digital colour fundus images (1999) Br. J. Ophthalmol., 83, pp. 902-910; 
Aquino, A., Geg{\'u}ndez-Arias, M.E., Marin, D., Detecting the Optic Disc Boundary in Digital Fundus Images Using Morphological, Edge Detection and Feature Extraction Techniques (2010) IEEE Trans. Medical Imaging, 29 (11), pp. 1860-1869; 
Aquino, A., Geg{\'u}ndez-Arias, M.E., Marin, D., Automated Optic Disc Detection in Retinal Images of Patients with Diabetic Retinopathy and Risk of Macular Edema (2012) Int. J. of Biological and Life Sciences, 8 (2), pp. 87-92; 
Lalonde, M., Beaulieu, M., Gagnon, L., Fast and Robust Optic Disc Detection Using Pyramidal Decomposition and Hausdorff-based Template Matching (2001) IEEE Trans. Medical Imaging, 20 (11), pp. 1193-1200; 
Osareh, A., Mirmehdi, M., Thomas, B., Markham, R., Classification and Localisation of Diabetic-Related Eye Disease (2002) LNCS, 2353, pp. 502-516. , Heyden, A., Sparr, G., Nielsen, M., Johansen, P. (eds.) ECCV 2002. Springer, Heidelberg; 
Lowell, J., Hunter, A., Steel, D., Basu, A., Ryder, R., Fletcher, E., Kennedy, L., Optic Nerve head Segmentation (2004) IEEE Trans. Medical Imaging, 23 (2), pp. 256-264; 
Abdel-Ghafar, R.A., Morris, T., Progress towards automated detection and characterization of the optic disc in glaucoma and diabetic retinopathy (2007) Medical Informatics and the Internet in Medicine, 32 (1), pp. 19-25; 
Hoover, A., Glodbaum, M., Locating the Optic Nerve in a Retinal Image Using the Fuzzy Convergence of the Blood Vessels (2003) IEEE Trans. Medical Imaging, 22 (8), pp. 951-958; 
Foracchia, M., Grisan, E., Ruggeri, A., Detection of Optic Disc in Retinal Images by Means of a Geometrical Model of Vessel Structure (2004) IEEE Trans. Medical Imaging, 23 (10), pp. 1189-1195; 
Haar, F., (2005) Automatic Localization of the Optic Disc in Digital Colour Images of the Human Retina, , Msc Thesis, University of Utrecht; 
Youssif, A., Ghalwash, A.Z., Ghoneim, A., Optic Disc Detection from Normalized Digital Fundus Images by Means of a Vessels{\textquoteright} Direction Matched Filter (2008) IEEE Trans. Medical Imaging, 27 (1), pp. 11-18; 
Niemeijer, M., Abr{\`a}moff, M.D., Van Ginneken, B., Fast detection of the optic disc and fovea in color fundus photographs (2009) Medical Image Analysis, 13, pp. 859-870; 
Xu, X., Gravin, M.K., Abr{\`a}moff, M.D., Reinhardt, J.M., Simultaneous Automatic Detection of the Optic Disc and Fovea on Fundus Photographs (2011) Proc. SPIE Medical Imaging 2011: Image Processing, 7962, pp. 7962T. , Dawant, B.M., Haynor, D.R. (eds.) SPIE; 
http://www.isi.uu.nl/Research/Databases/DRIVEhttp://www.ces.clemson.edu/~ahoover/stare, The STARE projectMendon{\c c}a, A., Campilho, A., Segmentation of Retinal Blood Vessels by Combining the Detection of Centerlines and Morphological Reconstruction (2006) IEEE Trans. Medical Imaging, 25 (9), pp. 1200-1213; 
Chaudhuri, S., Chattererjee, S., Katz, N., Glodbaum, M., Detection of blood Vessels in Retinal Images using Two-Dimensional Matched Filters (1989) IEEE Trans. Medical Imaging, 28 (3), pp. 263-269
},
	month = {2012///},
	pages = {424 - 431},
	address = {Aveiro},
	abstract = {This paper proposes an automatic method for estimating the location of the optic disc in color images of the retina. The proposed methodology is founded in a new concept, the entropy of vascular directions, which proved to be a reliable measure for assessing the convergence of vessels around an image point. To improve the robustness of the method, the search for the maximum value of entropy is restricted to image areas with high intensity. This new method was evaluated in two publicly available databases, containing both normal and pathological images, and was able to obtain a valid location for the optic disc in 115 out of the 121 images of the two datasets. {\textcopyright} 2012 Springer-Verlag.},
	keywords = {Automatic localization, Automatic method, Color images, Data sets, entropy, High intensity, Image analysis, Image points, Maximum values, Ophthalmology, optic disc, Pathological images, Retinal image, Retinal image analysis, vessel segmentation},
	isbn = {03029743 (ISSN); 9783642312977 (ISBN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84864128693\&partnerID=40\&md5=faf6f5351e81f8c595247728be684d95},
	author = {Mendon{\c c}a, A.M. and Cardoso, F. and Sousa, A.V. and Campilho, A.}
}
@article {2230,
	title = {Complexity and categorical analysis may improve the interpretation of agreement studies using continuous variables},
	journal = {Journal of Evaluation in Clinical PracticeJ. Eval. Clin. Pract.},
	volume = {17},
	year = {2011},
	note = {Cited By (since 1996): 2Export Date: 21 November 2012Source: ScopusCODEN: JECPFdoi: 10.1111/j.1365-2753.2011.01668.xPubMed ID: 21489051Language of Original Document: EnglishCorrespondence Address: Costa-Santos, C.; Department of Biostatistics and Medical Informatics, Faculty of Medicine, University of Porto, Al. Prof. Hern{\^a}ni Monteiro, 4200-319 Porto, Portugal; email: csantos@med.up.ptReferences: Costa Santos, C., Costa Pereira, A., Bernardes, J., Agreement studies in obstetrics and gynaecology: Inappropriateness, controversies and consequences (2005) BJOG: An International Journal of Obstetrics and Gynaecology, 112 (5), pp. 667-669. , DOI 10.1111/j.1471-0528.2004.00505.x;Khan, K.S., Chien, P.F., Evaluation of a clinical test. I: Assessment of reliability (2001) BJOG, 108, pp. 562-567; 
Luiz, R.R., Szklo, M., More than one statistical strategy to assess agreement of quantitative measurements may usefully be reported (2005) Journal of Clinical Epidemiology, 58 (3), pp. 215-216. , DOI 10.1016/j.jclinepi.2004.07.007; 
Costa-Santos, C., Bernardes, J., Ayres-De-Campos, D., Costa, A., Costa, C., The limits of agreement and the intraclass correlation coefficient may be inconsistent in the interpretation of agreement (2011) Journal of Clinical Epidemiology, 64 (3), pp. 264-269; 
Costa-Santos, C., Antunes, L., Souto, A., Bernardes, J., Assessment of disagreement: A new information-based approach (2010) Annals of Epidemiology, 20, pp. 555-561; 
Luiz, R.R., Costa, A.J.L., Kale, P.L., Werneck, G.L., Assessment of agreement of a quantitative variable: A new graphical approach (2003) Journal of Clinical Epidemiology, 56 (10), pp. 963-967. , DOI 10.1016/S0895-4356(03)00164-1; 
Plsek, P.E., Greenhalgh, T., The challenge of complexity in health care (2001) British Medical Journal, 323 (7313), pp. 625-628; 
Shiell, A., Hawe, P., Gold, L., Complex interventions or complex systems? Implications for health economic evaluation (2008) BMJ, 336 (7656), pp. 1281-1283; 
Wilson, T., Holt, T., Complexity science: Complexity and clinical care (2001) British Medical Journal, 323 (7314), pp. 685-688; 
Miles, A., Complexity in medicine and healthcare: People and systems, theory and practice (2009) Journal of Evaluation in Clinical Practice, 15 (3), pp. 409-410; 
Shannon, {\^I}., A mathematical theory of communication (1948) Bell System Technical Journal, 27, pp. 379-423. , 623- 656; 
Bernardes, J., Costa-Pereira, A., Ayres-De-Campos, D., Van Geijn, H.P., Pereira-Leite, L., Evaluation of interobserver agreement of cardiotocograms (1997) International Journal of Gynecology and Obstetrics, 57 (1), pp. 33-37. , DOI 10.1016/S0020-7292(97)02846-4, PII S0020729297028464; 
Ayres-De-Campos, D., Bernardes, J., Costa-Pereira, A., Pereira-Leite, L., Inconsistencies in classification by experts of cardiotocograms and subsequent clinical decision (1999) British Journal of Obstetrics and Gynaecology, 106, pp. 1307-1310; 
Rooth, G., Guidelines for the use of fetal monitoring (1987) International Journal of Gynaecology and Obstetrics, 25, pp. 159-167; 
Grant, J.M., The fetal heart rate is normal, isn{\textquoteright}t it? Observer agreement of categorical assessments (1991) Lancet, 337, pp. 215-218; 
M{\"u}ller, R., B{\"u}ttner, P., A critical discussion of intraclass correlation coefficients (1994) Statistics in Medicine, 13, pp. 2465-2476; 
Byrt, T., Bishop, J., Carlin, J.B., Bias, prevalence and kappa (1993) Journal of Clinical Epidemiology, 46 (5), pp. 423-429. , DOI 10.1016/0895-4356(93)90018-V; 
West, B.J., Homeostasis and Gauss statistics: Barriers to understanding natural variability (2010) Journal of Evaluation in Clinical Practice, 16, pp. 403-408; 
Goncalves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Medical and Biological Engineering and Computing, 44 (10), pp. 847-855. , DOI 10.1007/s11517-006-0105-6; 
Costa Santos, C., Vitanyi, P.M.B., Bernardes, J., Antunes, L., Clustering fetal heart rate tracings by compression (2006) Proceedings - IEEE Symposium on Computer-Based Medical Systems, 2006, pp. 685-690. , DOI 10.1109/CBMS.2006.68, 1647650, Proceedings - 19th IEEE International Symposium on Computer-Based Medical Systems, CBMS 2006
},
	month = {2011///},
	pages = {511 - 514},
	abstract = {Rationale Complex clinical scenarios involving a high degree of uncertainty frequently lead to a poor agreement over diagnosis and management. However, inconsistent results can be found with the most widely used measures of agreement for continuous variables - the limits of agreement and the intraclass correlation coefficient. Aims and objectives We aim to improve the interpretation of agreement studies using continues variables. Methods and results Evaluation of agreement may be improved by complexity analysis and by categorization of variables, followed by the use of the proportions of agreement. Conclusions The average never characterizes a complex phenomenon and the methods used to access agreement in continuous variables are based on the mean. For future agreement studies, involving complex continuous variables, we recommend a complexity and categorical analysis. {\textcopyright} 2011 Blackwell Publishing Ltd.},
	keywords = {article, Biomedical research, Cardiotocography, clinical decision making, clinical practice, complexity, Data Interpretation, Statistical, Decision Making, entropy, Female, fetus heart rate, Heart Rate, Fetal, human, Humans, observer variation, Pregnancy, Pregnancy Outcome, priority journal, Reproducibility of Results, statistical data interpretation, Uncertainty},
	isbn = {13561294 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-79956081274\&partnerID=40\&md5=bd7376dca48228f4c4b1b21389689596},
	author = {Costa-Santos, C. and Bernardes, J. and Antunes, L. and Ayres-de-Campos, D.}
}
@book {2217,
	title = {New results on minimum error entropy decision trees},
	series = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)Lect. Notes Comput. Sci.},
	volume = {7042 LNCS},
	year = {2011},
	note = {Conference code: 87418Export Date: 21 November 2012Source: Scopusdoi: 10.1007/978-3-642-25085-9_42Language of Original Document: EnglishCorrespondence Address: De S{\'a}, J.P.M.; INEB-Instituto de Engenharia Biom{\'e}dica, FEUP, Universidade Do Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal; email: jmsa@fe.up.ptReferences: Rokach, L., Maimon, O., Decision Trees (2005) Data Mining and Knowledge Discovery Handbook, , Maimon, O., Rokach, L. (eds.) Springer, Heidelberg;Marques De S{\'a}, J.P., Sebasti{\~a}o, R., Gama, J., Tree Classifiers Based on Minimum Error Entropy Decisions (2011) Can. J. Artif. Intell., Patt. Rec. and Mach. Learning, , in press; 
Silva, L., Felgueiras, C.S., Alexandre, L., Marques De S{\'a}, J., Error Entropy in Classification Problems: A Univariate Data Analysis (2006) Neural Computation, 18, pp. 2036-2061; 
Asuncion, A., Newman, D.J., (2010) UCI Machine Learning Repository, , http://www.ics.uci.edu/~mlearn/MLRepository.html; 
Kearns, M., A Bound on the Error of Cross Validation Using the Approximation and Estimation Rates, with Consequences for the Training-Test Split (1997) Neural Computation, 9, pp. 1143-1161; 
Molinaro, A.M., Simon, R., Pfeiffer, R.M., Prediction Error Estimation: A Comparison of Resampling Methods (2005) Bioinformatics, 21, pp. 3301-3307; 
Dem{\v s}ar, J., Statistical Comparisons of Classifiers over Multiple Data Sets (2006) J. of Machine Learning Research, 7, pp. 1-30; 
Garc{\'\i}a, S., Fern{\'a}ndez, A., Luengo, J., Herrera, F., Advanced Nonparametric Tests for Multiple Comparisons in the Design of Experiments in Computational Intelligence and Data Mining: Experimental Analysis of Power (2010) Information Sciences, 180, pp. 2044-2064; 
Hochberg, Y., Tamhane, A.C., (1987) Multiple Comparison Procedures, , John Wiley \& Sons, Inc; 
Salzberg, S.L., On Comparing Classifiers: Pitfalls to Avoid and a Recommended Approach (1997) Data Mining and Knowledge Discovery, 1, pp. 317-328; 
Jensen, D., Oates, T., Cohen, P.R., Building Simple Models: A Case Study with Decision Trees (1997) LECTURE NOTES IN COMPUTER SCIENCE, (1280), pp. 211-222. , Advances in Intelligent Data Analysis Reasoning about Data; 
Li, R.-H., Belford, G.G., Instability of Decision Tree Classification Algorithms (2002) Proc. 8th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, pp. 570-575
Sponsors: Universidad de La Frontera (UFRO); The International Association for Pattern Recognition (IAPR); Asociacon Chilena de Reconocimiento de Patrones (AChiRP); Asociacion Cubana de Reconocimiento de Patrones (ACPR); Mex. Assoc. Comput. Vis., Neural Comput. Rob. (MACVNR)},
	month = {2011///},
	pages = {355 - 362},
	address = {Pucon},
	abstract = {We present new results on the performance of Minimum Error Entropy (MEE) decision trees, which use a novel node split criterion. The results were obtained in a comparive study with popular alternative algorithms, on 42 real world datasets. Carefull validation and statistical methods were used. The evidence gathered from this body of results show that the error performance of MEE trees compares well with alternative algorithms. An important aspect to emphasize is that MEE trees generalize better on average without sacrifing error performance. {\textcopyright} 2011 Springer-Verlag.},
	keywords = {Algorithms, Alternative algorithms, Computer vision, Decision Theory, decision trees, entropy, entropy-of-error, Error entropy, Error performance, Forestry, New results, node split criteria, Real-world datasets, Vision},
	isbn = {03029743 (ISSN); 9783642250842 (ISBN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-81855161442\&partnerID=40\&md5=0d71ee4459a1a6a01536cfec0ff05664},
	author = {De S{\'a}, J.P.M. and Sebasti{\~a}o, R. and Gama, J. and Fontes, T.}
}
@article {2260,
	title = {Analysis of heart rate variability in a rat model of induced pulmonary hypertension},
	journal = {Medical Engineering and PhysicsMed. Eng. Phys.},
	volume = {32},
	year = {2010},
	note = {Cited By (since 1996): 1Export Date: 21 November 2012Source: ScopusCODEN: MEPHEdoi: 10.1016/j.medengphy.2010.04.018PubMed ID: 20547091Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Geoci{\^e}ncias, Ambiente e Ordenamento do Territ{\'o}rio, Faculdade de Ci{\^e}ncias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal; email: hernani.goncalves@fc.up.ptChemicals/CAS: monocrotaline, 315-22-0, 8051-27-2; Ketamine, 6740-88-1; Monocrotaline, 315-22-0References: (2005), ACOG, American College of Obstetricians and Gynecologists. ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists, Number 70, December 2005. Obstet Gynecol 106(6):1453-60Akhavein, F., St.-Michel, E.J., Seifert, E., Rohlicek, C.V., Decreased left ventricular function, myocarditis, and coronary arteriolar medial thickening following monocrotaline administration in adult rats (2007) J Appl Physiol, 103 (1), pp. 287-295;Beckers, F., Verheyden, B., Aubert, A.E., Aging and nonlinear heart rate control in a healthy population (2006) Am J Physiol Heart Circ Physiol, 290 (6), pp. H2560-H2570; 
Bernardes, J., Costa-Pereira, A., A more objective fetal heart rate baseline estimation (1996) Br J Obstet Gynaecol, 103, pp. 714-715; 
Bernardes, J., Gon{\c c}alves, H., Ayres-de-Campos, D., Rocha, A.P., Linear and complex heart rate dynamics vary with sex in relation to fetal behavioural states (2008) Early Hum Dev, 84, pp. 433-439; 
Bruijnzeel, A.W., Stam, R., Croiset, G., Wiegant, G.M., Long-term sensitization of cardiovascular stress responses after a single stressful experience (2001) Physiol Behav, 73 (1-2), pp. 81-86; 
Cerutti, C., Gustin, M.P., Paultre, C.Z., Lo, M., Julien, C., Vincent, M., Autonomic nervous-systempulmonary-edema and cardiovascular variability in rats-a spectral-analysis approach (1991) Am J Physiol, 261 (84), pp. H1292-H1299; 
Court, D.J., Parer, J.T., Nathanielsz, P.W., Parer, J.T., (1984) Experimental studies of fetal asphyxia and fetal heart rate interpretation Research in Perinatal Medicine, pp. 113-169. , Perinatology Press, New York; 
Dudewicz, E., Mishra, S., (1988) Modern mathematical statistics, , Jonh Wiley and Sons, Inc; 
Falcao-Pires, I., Gon{\c c}alves, N., Henriques-Coelho, T., Roncon-Albuquerque, R., Moreira-Gon{\c c}alves, D., Leite-Moreira, A.F., Administration of Apelin modulates myocardial. expression of Apelin-APJ and improves right ventricular performance in MCT-induced pulmonary hypertension (2008) Circulation, 118, pp. S285; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: the effect on linear and nonlinear parameters (2006) Physiol Meas, 27 (3), pp. 307-319; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Med Biol Eng Comput, 44 (10), pp. 847-855; 
Gon{\c c}alves, H., Bernardes, J., Rocha, A.P., Ayres-de-Campos, D., Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period (2007) Early Hum Dev, 83, pp. 585-591; 
Gon{\c c}alves, H., Henriques-Coelho, T., Bernardes, J., Rocha, A.P., Nogueira, A., Leite-Moreira, A., Linear and nonlinear heart rate analysis in a rat model of acute anoxia (2008) Physiol Meas, 29, pp. 1133-1143; 
Henriques-Coelho, T., Correia-Pinto, J., Roncon-Albuquerque, R., Baptista, M.J., Lourenco, A.P., Oliveira, S.M., Endogenous production of ghrelin and beneficial effects of its exogenous administration in monocrotaline-induced pulmonary hypertension (2004) Am J Physiol Heart Circ Physiol, 287 (6), pp. H2885-H2890; 
Henriques-Coelho, T., Oliveira, S.M., Moura, R.S., Roncon-Albuquerque, R., Neves, A.L., Santos, M., Thymulin inhibits monocrotaline-induced pulmonary hypertension modulating interleukin-6 expression and suppressing p38 pathway (2008) Endocrinology, 149 (9), pp. 4367-4373; 
Hessel, M.H.M., Steendijk, P., den Adel, B., Schutte, C.I., van der Laarse, A., Characterization of right ventricular function after monocrotaline-induced pulmonary hypertension in the intact rat (2006) Am J Physiol Heart Circ Physiol, 291 (5), pp. H2424-H2430; 
Kuwahara, M., Yayou, K., Ishii, K., Hashimoto, S., Tsubone, H., Sugano, S., Power spectral analysis of heart rate variability as a new method for assessing autonomic activity in the rat (1994) J Electrocardiol, 27 (4), pp. 333-337; 
Leineweber, K., Brandt, K., Wludyka, B., Beilfuss, A., Ponicke, K., Heinroth-Hoffmann, I., Ventricular hypertrophy plus neurohumoral activation is necessary to alter the cardiac beta-adrenoceptor system in experimental heart failure (2002) Circ Res, 91 (11), pp. 1056-1062; 
Louren{\c c}o, A.P., Roncon-Albuquerque, R., Bras-Silva, C., Faria, B., Wieland, J., Henriques-Coelho, T., Myocardial dysfunction and neurohumoral activation without remodeling in left ventricle of monocrotaline-induced pulmonary hypertensive rats (2006) Am J Physiol Heart Circ Physiol, 291 (4), pp. H1587-H1594; 
Magenes, G., Signorini, M.G., Arduini, D., Cerutti, S., Fetal heart rate variability due to vibroacoustic stimulation: linear and nonlinear contribution (2004) Methods Inf Med, 43 (1), pp. 47-51; 
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Montenegro, N., Bernardes, J., Ayres-de-Campos, D., Matias, A., Areias, J.C., Monitoring of cardiac-extracardiac haemodynamics and automated fetal heart rate preceding intrauterine death (1996) Eur J Obstet Gynecol Reprod Biol, 64 (1), pp. 3-6; 
Moraru, L., Cimponeriu, L., Tong, S., Thakor, N., Bezerianos, A., Characterization of heart rate variability changes following asphyxia in rats (2004) Methods Inf Med, 43 (1), pp. 118-121; 
Oppenheimer, L.W., Lewinsky, R.M., Power spectral analysis of fetal heart rate (1994) Baillieres Clin Obstet Gynaecol, 8 (3), pp. 643-661; 
Parati, G., Mancia, G., Di Rienzo, M., Castiglioni, P., Taylor, J.A., Studinger, P., Point: Counterpoint: Cardiovascular variability is/is not an index of autonomic control of circulation (2006) J Appl Physiol, 101 (2), pp. 676-682; 
Pincus, S., Viscarello, R., Approximate Entropy: A regularity measure for fetal heart rate analysis (1992) Obstet Gynecol, 79, pp. 249-255; 
Pincus, S., Aproximate entropy (ApEn) as a complexity measure (1995) Chaos, 5, pp. 110-117; 
Pincus, S.M., Gevers, E.F., Robinson, I.C.A.F., VanDenBerg, G., Roelfsema, F., Hartman, M.L., Females secrete growth hormone with more process irregularity than males in both humans and rats (1996) Am J Physiol-Endocrinol Metab, 270 (1), pp. E107-E115; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am J Physiol Heart Circ Physiol, 278, pp. H2039-H2049; 
Sanyal, S.N., Ono, K., Derangement of autonomic nerve control in rat with right ventricular failure (2002) Pathophysiology, 8 (3), pp. 197-203; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans Biomed Eng, 50, pp. 365-373; 
(1996), Task force, Heart rate variability - standards of measurement, physiological interpretation and clinical use Circulation 93 1043-65 Task force of the European Society of Cardiology and the North American Society of Pacing and ElectrophysiologyTaylor, J.A., Studinger, P., Cardiovascular variability is/is not an index of autonomic control of circulation (2006) J Appl Physiol, 101 (2), pp. 690-691; 
Welch, P.D., The use of Fast Fourier Transform for the estimation of power spectra: a method based on time averaging over short, modified periodograms (1967) IEEE Trans Audio Electroacous, AU-15 (2), pp. 70-73; 
Yum, M.K., Park, E.Y., Kim, C.R., Hwang, J.H., Alterations in irregular and fractal heart rate behavior in growth restricted fetuses (2001) Eur J Obstet Gynecol, 94, pp. 51-58
},
	month = {2010///},
	pages = {746 - 752},
	abstract = {Monocrotaline (MCT) is commonly used to experimentally induce pulmonary hypertension (PH), which might lead to chronic heart failure. In this study, linear and non-linear heart rate (HR) dynamics were weekly assessed in MCT-treated and non-treated Wistar rats.The HR of 10 adult Wistar rats injected with MCT (MCT group) and of 10 similar rats injected with vehicle (non-MCT group), anesthetized with Ketamine, was weekly recorded during 4 weeks. The first four segments of 1-min length of each HR recording were analysed using linear, time and frequency domains, and approximate (ApEn) and sample (SampEn) entropy indices, considering recently proposed values for the threshold parameter of ApEn and SampEn. Statistical analysis was performed using 95\% confidence intervals and statistical tests.Along the study period, an overall weekly maintenance of HR indices, or a decrease, namely in weeks 1-2, was manifest, in the MCT group, except for LF and LF/HF, in week 1, denoting a short-term increase in sympathetic activity without any other changes. On the other hand, a maintenance of HR indices, or an increase, namely on week 4, was observed in the non-MCT group, except for LF/HF, denoting a long-term increase of the overall activity of HR control systems, with a parasympathetic like dominance.Studies on long-term HR dynamics should be performed in very carefully controlled experimental settings, as significant weekly changes may occur, both among anesthetized MCT-treated and non-treated rats. {\textcopyright} 2010 IPEM.},
	keywords = {adrenergic activity, Amines, animal experiment, animal model, Animals, article, cholinergic activity, Chronic heart failures, Confidence interval, controlled study, Disease Models, Animal, Electrocardiography, entropy, Female, Frequency domain analysis, Frequency domains, Heart, heart electrophysiology, Heart rate, Heart rate variability, Heart rate variability (HRV), Heart rates, Hypertension, Pulmonary, Injections, Subcutaneous, Ketamine, Maintenance, Monocrotaline, Non-linear, nonhuman, priority journal, Pulmonary hypertension, rat, Rat model, Rats, Rats, Wistar, Statistical analysis, statistical parameters, Sympathetic activities, Threshold parameters, Time and frequency domain analysis, Time domain analysis, Time Factors, Wistar rat, Wistar rats},
	isbn = {13504533 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-77955279673\&partnerID=40\&md5=5fa2879d821f37e48f50a723fa1cb225},
	author = {Gon{\c c}alves, H. and Henriques-Coelho, T. and Bernardes, J. and Rocha, A.P. and Brand{\~a}o-Nogueira, A. and Leite-Moreira, A.}
}
@article {2253,
	title = {The MEE principle in data classification: A perceptron-based analysis},
	journal = {Neural ComputationNeural Comp.},
	volume = {22},
	year = {2010},
	note = {Cited By (since 1996): 3Export Date: 21 November 2012Source: Scopusdoi: 10.1162/NECO_a_00013PubMed ID: 20569178Language of Original Document: EnglishCorrespondence Address: Silva, L.M.; Instituto de Engenharia Biom{\'e}dica, Divis{\~a}o de Sinal e Imagem, Porto 4200-465, Portugal; email: lmsilva@fe.up.ptReferences: Alexandre, L.A., Marques de S{\'a}, J., Error entropy minimization for LSTM training (2006) Proceedings of the 16th International Conference on Artificial Neural Networks, pp. 244-253. , Berlin: Springer;Asuncion, A., Newman, D., (2007) UCI machine learning repository. Irvine University of California, Irvine, , http://www.ics.uci.edu/~mlearn/MLRepository.html, School of Information and Computer Sciences. Available online at; 
Bishop, C., (1995) Neural networks for pattern recognition, , New York: OxfordUniversity Press; 
Erdogmus, D., Hild K., II., Pr{\'\i}ncipe, J.C., Blind source separation using R{\'e}nyi{\textquoteright}s α-marginal entropies (2002) Neurocomputing, 49, pp. 25-38; 
Erdogmus, D., Pr{\'\i}ncipe, J.C., Comparison of entropy and mean square error criteria in adaptive system training using higher order statistics (2000) Proceedings of the Intl. Conf. on ICA and Signal Separation, pp. 75-80. , Berlin: Springer-Verlag; 
Erdogmus, D., Pr{\'\i}ncipe, J.C., An error-entropy minimization algorithm for supervised training of nonlinear adaptive systems (2002) IEEE Transactions on Signal Processing, 50 (7), pp. 1780-1786; 
Erdogmus, D., Pr{\'\i}ncipe, J.C., Convergence properties and data efficiency of the minimum error entropy criterion in adaline training (2003) IEEE Transactions on Signal Processing, 51 (7), pp. 1966-1978; 
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Jacobs, R., Jordan, M., Nowlan, S., Hinton, G., Adaptive mixtures of local experts (1991) Neural Computation, 3, pp. 79-87; 
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Santos, J.M., Marques de S{\'a}, J., Alexandre, L.A., Sereno, F., Optimization of the error entropy minimization algorithm for neural network classification (2004) Intelligent engineering systems through artificial neural networks, pp. 81-86. , C. Dagli, A. Buczak, D. Enke, M. Embrechts, \& O. Ersoy (Eds.), Washington, DC: ASME; 
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Silva, L.M., Embrechts, M., Santos, J.M., Marques de S{\'a}, J., The influence of the risk functional in data classification with MLPs (2008) Proceedings of the International Conference on Artificial Neural Networks, pp. 185-194. , Berlin: Springer-Verlag; 
Silva, L.M., Felgueiras, C., Alexandre, L.A., Marques de S{\'a}, J., Error entropy in classification problems: A univariate data analysis (2006) Neural Computation, 18 (9), pp. 2036-2061; 
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Watanabe, S., Pattern recognition as a quest for minimum entropy (1981) Pattern Recognition, 13 (5), pp. 381-387
},
	month = {2010///},
	pages = {2698 - 2728},
	abstract = {This letter focuses on the issue of whether risk functionals derived from information-theoretic principles, such as Shannon or R{\'e}nyi{\textquoteright}s entropies, are able to cope with the data classification problem in both the sense of attaining the risk functional minimum and implying the minimum probability of error allowed by the family of functions implemented by the classifier, here denoted by min Pe. The analysis of this so-called minimization of error entropy (MEE) principle is carried out in a single perceptron with continuous activation functions, yielding continuous error distributions. In spite of the fact that the analysis is restricted to single perceptrons, it reveals a large spectrum of behaviors that MEE can be expected to exhibit in both theory and practice. In what concerns the theoretical MEE, our study clarifies the role of the parameters controlling the perceptron activation function (of the squashing type) in often reaching the minimum probability of error. Our study also clarifies the role of the kernel density estimator of the error density in achieving the minimum probability of error in practice. {\textcopyright} 2010 Massachusetts Institute of Technology.},
	keywords = {algorithm, Algorithms, artificial intelligence, artificial neural network, automated pattern recognition, Computer simulation, entropy, letter, Mathematical Concepts, mathematical phenomena, Models, Statistical, Neural Networks (Computer), Pattern Recognition, Automated, standard, statistical model},
	isbn = {08997667 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-78149334887\&partnerID=40\&md5=97c7445cfa4693d406d979afc4b42319},
	author = {Silva, L.M. and Marques de S{\'a}, J. and Alexandre, L.A.}
}
@book {2299,
	title = {Decision trees using the minimum Entropy-of-error principle},
	series = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)Lect. Notes Comput. Sci.},
	volume = {5702 LNCS},
	year = {2009},
	note = {Conference code: 77256Export Date: 21 November 2012Source: Scopusdoi: 10.1007/978-3-642-03767-2_97Language of Original Document: EnglishCorrespondence Address: De S{\'a}, J. P. M.; INEB-Instituto de Engenharia Biom{\'e}dica, Porto, Portugal; email: jmsa@fe.up.ptReferences: Asuncion, A., Newman, D.J., (2007) UCI Machine Learning Repository, , http://www.ics.uci.edu/̃mlearn/MLRepository.html, Univ. of California, SICS, Irvine, CA;Breiman, L., Friedman, J.H., Olshen, R.A., Stone, C.J., (1993) Classification and Regression Trees, , Chapman \& Hall/CRC, Boca Raton; 
Devroye, L., Gi{\"o}rfi, L., Lugosi, G., (1996) A Probabilistic Theory of Pattern Recognition, , Springer, Heidelberg; 
Forina, M., Armanino, C., Eigenvector Projection and Simplified Nonlinear Mapping of Fatty Acid Content of Italian Olive Oils (1981) Ann. Chim, 72, pp. 127-155; 
Loh, W.-Y., Shih, Y.-S., Split Selection Methods for Classification Trees (1997) Statistica Sinica, 7, pp. 815-840; 
Marques de S{\'a}, J.P., (2007) Applied Statistics Using SPSS, STATISTICA, MATLAB and R, , 2nd edn. Springer, Heidelberg; 
Quinlan, J.R., Induction of Decision Trees (1986) Machine Learning, 1, pp. 81-106; 
Quinlan, J.R.: C4.5 Programs for Machine Learning. Morgan Kaufmann, San Francisco (1993)Silva, L.M., Felgueiras, C.S., Alexandre, L.A., Marques de S{\'a}, J., Error Entropy in Classification Problems: A Univariate Data Analysis (2006) Neural Comp, 18, pp. 2036-2061; 
Silva, L.M., Embrechts, M.J., Santos, J.M., de S{\'a}, J.M., The influence of the risk functional in data classification with mLPs (2008) LNCS, 5163, pp. 185-194. , K{\r u}rkov{\'a}, V, Neruda, R, Koutn{\'\i}k, J, eds, ICANN 2008, Part I, Springer, Heidelberg
Sponsors: University of Munster; International Association for Pattern Recognition; Olympus Soft Imaging Solutions GmbH; Philips},
	month = {2009///},
	pages = {799 - 807},
	address = {Munster},
	abstract = {Binary decision trees based on univariate splits have traditionally employed so-called impurity functions as a means of searching for the best node splits. Such functions use estimates of the class distributions. In the present paper we introduce a new concept to binary tree design: instead of working with the class distributions of the data we work directly with the distribution of the errors originated by the node splits. Concretely, we search for the best splits using a minimum entropy-of-error (MEE) strategy. This strategy has recently been applied in other areas (e.g. regression, clustering, blind source separation, neural network training) with success. We show that MEE trees are capable of producing good results with often simpler trees, have interesting generalization properties and in the many experiments we have performed they could be used without pruning. {\textcopyright} 2009 Springer Berlin Heidelberg.},
	keywords = {Binary decision trees, Binary trees, Blind source separation, Class distributions, decision trees, Electronic medical equipment, entropy, entropy-of-error, Generalization properties, Image analysis, Minimum entropy, Neural network training, Neural networks, New concept, node split criteria, Univariate},
	isbn = {03029743 (ISSN); 3642037666 (ISBN); 9783642037665 (ISBN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-70349306674\&partnerID=40\&md5=39d60bd9d77f6ad61720d8ddd3f68e4d},
	author = {De S{\'a}, J.P.M. and Gama, J. and Sebasti{\~a}o, R. and Alexandre, L.A.}
}
@article {2314,
	title = {Sex differences in linear and complex fetal heart rate dynamics of normal and acidemic fetuses in the minutes preceding delivery},
	journal = {Journal of Perinatal MedicineJ. Perinat. Med.},
	volume = {37},
	year = {2009},
	note = {Cited By (since 1996): 4Export Date: 21 November 2012Source: ScopusCODEN: JPEMAdoi: 10.1515/JPM.2009.024PubMed ID: 19021459Language of Original Document: EnglishCorrespondence Address: Bernardes, J.; Faculdade de Medicina, Universidade Do Porto, Ginecologia e Obstetr{\'\i}cia, Al. Hernani Monteiro, Porto, 4200, Portugal; email: jbernardes59@gmail.comReferences: Ayres-de-Campos, D., Bernardes, J., Costa-Pereira, A., Pereira-Leite, L., Inconsistencies in classification by experts of cardiotocograms and subsequent clinical decision (1999) Br J Obstet Gynaecol, 106, pp. 1307-1310;Ayres-de-Campos, D., Bernardes, J., Garrido, A., Marques-de-S{\`a}, J.P., Pereira-Leite, L., SisPorto 2.0 - a program for automated analysis of cardiotocograms (2000) J Matern Fetal Med, 9, pp. 311-318; 
Ayres-de-Campos, D., Costa-Santos, C., Bernardes, J., SisPorto Multicentre Validation Study Group. Prediction of neonatal state by computer analysis of fetal heart rate tracings: The antepartum arm of the SisPorto multicentre validation study (2005) Eur J Obstet Gynecol Reprod Biol, 118, pp. 52-60; 
Ayres-de-Campos, D., Sousa, P., Costa, A., Bernardes, J., Omniview-SisPorto 3.5 - a central fetal monitoring station with online alerts based on computerized cardio-tocogram+ST event analysis (2008) J Perinat Med, 36, pp. 260-264; 
Beckers, F., Verheyden, B., Aubert, A.E., Aging and non-linear heart rate control in a healthy population (2006) Am J Physiol Heart Circ Physiol, 290, pp. H2560-H2570; 
Bekedam, D.J., Engelsbel, S., Mol, B.W., Buitendijk, S.E., van der Pal-de Bruin, K.M., Male predominance in fetal distress during labor (2002) Am J Obstet Gynecol, 187, pp. 1605-1607; 
Bennet, L., Booth, L.C., Ahmed-Nasef, N., Dean, J.M., Davidson, J., Quaedackers, J.S., Male disadvantage? Fetal sex and cardiovascular responses to asphyxia in preterm fetal sheep (2007) Am J Physiol Regul Integr Comp Physiol, 293, pp. R1280-R1286; 
Bernardes, J., Moura, C., Marques-de-S{\'a}, J.P., Pereira-Leite, L., The Porto system for automated cardiotocographic signal analysis (1991) J Perinat Med, 19, pp. 61-65; 
Bernardes, J., Costa-Pereira, A., Ayres-de-Campos, D., van Geijn, H.P., Pereira-Leite, L., Evaluation of interobserver agreement of cardiotocograms (1997) Int J Gynecol Obstet, 57, pp. 33-37; 
Bernardes, J., Ayres-de-Campos, D., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int J Gynaecol Obstet, 62, pp. 141-147; 
Bernardes, J., Gon{\c c}alves, H., Ayres-de-Campos, D., Rocha, A.P., Linear and complex heart rate dynamics vary with sex in relation to fetal behavioural states (2008) Early Hum Dev, 84, pp. 433-439; 
Boog, G., Analyse informatis{\'e}e du rythme cardiaque foetal au cours de la grosssesse et de l{\textquoteright}accouchement. (2004) Encyclop{\'e}die M{\'e}dico- Chirurgicale, 148, pp. 1-10; 
Browner, W.S., Newman, T.B., Cummings, S.R., Hulley, S.B., (2001) Estimating sample size and power: The nitty-gritty, pp. 65-84. , Hulley SB, Cummings SR, Browner WS, Grady D, Hearst N, Newman TB, editors. Philadelphia: Lippincot Williams \& Wilkins; 
Chaffin, D.G., Barnard, J.M., Phernetton, T., Reed, K.L., Decreased approximate entropy of heart rate variability in the hypoxic ovine fetus (1998) J Matern Fetal Invest, 8, pp. 23-26; 
Dawes, G.S., Moulden, M., Redman, C.W., Improvements in computerized fetal heart rate analysis antepartum (1996) J Perinat Med, 24, pp. 25-36; 
Dawes, N.W., Dawes, G.S., Moulden, M., Redman, C.W., Fetal heart rate patterns in term labor vary with sex, gestational age, epidural analgesia, and fetal weight (1999) Am J Obstet Gynecol, 180, pp. 181-187; 
DiPietro, J.A., Costigan, K.A., Shupe, A.K., Pressman, E.K., Johnson, T.R., Fetal neurobehavioral development: Associations with socioeconomic class and fetal sex (1998) Dev Psychobiol, 33, pp. 79-91; 
Dudewicz, E., Mishra, S., (1998) Modern mathematical statistics, , John Wiley and Sons, Inc; 
Fleisher, L.A., Dipietro, J.A., Johnson, T.R., Pincus, S., Complementary and non-coincident increases in heart rate variability and irregularity during fetal development (1997) Clin Sci (Lond), 92, pp. 345-349; 
Fusheng, Y., Bo, H., Qingyu, T., (1998) Approximate entropy and its application in biosignal analysis, 2, pp. 72-91. , editor. Nonlinear biomedical signal processing, Dynamical analysis and modelling. IEEE Press;; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters (2006) Physiol Meas, 27, pp. 307-319; 
Goncalves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Med Biol Eng Comput, 44, pp. 847-855; 
Goncalves, H., Bernardes, J., Rocha, A.P., Ayres-de-Campos, D., Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period (2007) Early Hum Dev, 83, pp. 585-591; 
Groome, L.J., Mooney, D.M., Holland, S.B., Smith, L.A., Atterbury, J.L., Dykman, R.A., Behavioral state affects heart rate response to low-intensity sound in human fetuses (1999) Early Hum Dev, 54, pp. 39-54; 
Ingemarsson, I., Herbst, A., Thorngren-Jerneck, K., Long-term outcome after umbilical artery acidemia at term birth: Influence of gender and duration of fetal heart rate abnormalities (1997) Br J Obstet Gynaecol, 104, pp. 1123-1127; 
Jensen-Urstad, K., Storck, N., Bouvier, F., Ericson, M., Lindblad, L.E., Jensen-Urstad, M., Heart rate variability in healthy subjects is related to age and gender (1997) Acta Physiol Scand, 160, pp. 235-241; 
King, T., Parer, J., The physiology of fetal heart rate patterns and perinatal asphyxia (2000) J Perinat Neonat Nurs, 14, pp. 19-39; 
Kuo, T.B., Yang, C.C., Sexual dimorphism in the complexity of cardiac pacemaker activity (2002) Am J Physiol Heart Circ Physiol, 283, pp. H1695-H1702; 
Li, X., Tang, D., Zhou, S., Zhou, G., Wang, C., Zhuang, Y., Redistribution of power spectrum of heart rate variability during acute umbilical artery embolism and hypoxemia in late-gestation fetal sheep (2004) J Obstet Gynecol Reprod Biol, 114, pp. 137-143; 
Magenes, G., Signorini, M.G., Arduini, D., Classification of cardiotocographic records by neural networks (2000) IJCNN 2000, Proceedings of the IEEE-INNS-ENNS International Joint Conference on Neural Networks, 3, pp. 637-641; 
Martinez, W.L., Martinez, A.R., (2002) Computational statistics handbook with MATLAB, , CRC Press;; 
Pincus, S., Approximate entropy as a measure of system complexity (1991) Proc Natl Acad Sci USA, 88, pp. 2297-2301; 
Pincus, S., Viscarello, R., Approximate Entropy: A regularity measure for fetal heart rate analysis (1992) Obstet Gynecol, 79, pp. 249-255; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am J Physiol Heart Circ Physiol, 278, pp. H2039-H2049; 
Ryan, S.M., Goldberger, A.L., Pincus, S.M., Mietus, J., Lipsitz, L.A., Gender- and age-related differences in heart rate dynamics: Are women more complex than men? (1994) J Am Coll Cardiol, 24, pp. 1700-1707; 
Sheiner, E., Hadar, A., Hallak, M., Katz, M., Mazor, M., Shoham-Vardi, I., Clinical significance of fetal heart rate tracings during the second stage of labor (2001) Obstet Gynecol, 97, pp. 747-752; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Transactions on Biomedical Engineering, 50, pp. 365-373; 
Siira, S.M., Ojala, T.H., Vahlberg, T.J., Jalonen, J.O., V{\"a}lim{\"a}ki, I.A., Ros{\'e}n, K.G., Marked fetal acidosis and specific changes in power spectrum analysis of fetal heart rate variability recorded during the last hour of labor (2005) Br J Obstet Gynaecol, 112, pp. 418-423; 
Suzuki, T., Okamura, K., Kimura, Y., Watanabe, T., Yaegashi, N., Murotsuki, J., Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs (2000) Am J Obstet Gynecol, 182, pp. 1227-1232; 
},
	month = {2009///},
	pages = {168 - 176},
	abstract = {Aim: To assess linear and complex heart rate dynamics in relation to fetal gender in normal and acidemic fetuses during the minutes preceding delivery. Methods: Linear and non-linear fetal heart rate indices, namely mean FHR, long-term irregularity index, short-term variability, low and high frequency spectral indices, approximate and sample entropy, were assessed in 36 female and 30 male fetuses, adjusted for gestational age and weight, during the minutes preceding delivery. Analysis was performed in the initial and final minutes of each tracing in fetuses with umbilical artery blood pH at delivery >=7.20, 7.11-7.19 and <=7.10. Results: Progression of labor was associated with a significant decrease in non-linear indices and an increase in almost all linear indices, both in female and male fetuses, but changes were more marked in female fetuses. Non-acidemic females showed higher mean FHR in the final minutes of labor, compared with males. Acidemic females had higher linear indices when compared to similar male fetuses. Conclusions: During the minutes preceding delivery, female fetuses express higher linear indices than male fetuses, suggesting greater activation of the autonomic nervous system, while maintaining similar complexity indices, which suggests different reaction and adaptation capabilities to stress and distress. {\textcopyright} 2009 by Walter de Gruyter.},
	keywords = {acidemia, Acidemic fetuses, article, autonomic nervous system, Birth Weight, blood pH, Cross-Sectional Studies, delivery, Delivery, Obstetric, entropy, Entropy and spectral analysis, Female, Fetal Heart, fetus, fetus heart rate, Gestational Age, Heart Rate, Fetal, human, Humans, Hydrogen-Ion Concentration, Intrapartum, labor, Labor, Obstetric, male, Pregnancy, priority journal, Retrospective Studies, Sex Characteristics, sex difference, Umbilical Arteries, umbilical artery},
	isbn = {03005577 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-59449089216\&partnerID=40\&md5=7a093bd5c056231b3f8150912abca652},
	author = {Bernardes, J. and Gon{\c c}alves, H. and Ayres-de-Campos, D. and Rocha, A.P.}
}
@conference {2326,
	title = {Characterization of heart rate variability loss with aging and heart failure using sample entropy},
	booktitle = {Computers in CardiologyComput Cardiol},
	series = {Computers in Cardiology 2008, CAR},
	volume = {35},
	year = {2008},
	note = {Conference code: 75561Export Date: 21 November 2012Source: ScopusArt. No.: 4748972CODEN: COCADdoi: 10.1109/CIC.2008.4748972Language of Original Document: EnglishCorrespondence Address: Goya-Esteban, R.; Universidad Rey Juan Carlos, Camino del Molino s/n, Fuenlabrada-28943 Madrid, Spain; email: rebegoya@gmail.comReferences: Pincus, S.M., Approximate entropy as a measure of system complexity (1991) Proc Natl Acad Sci, 88, pp. 2297-2301;Pincus, S.M., Goldberger, A.L., Physiological time-series analysis: What does regularity quantify? (1994) Am J Physiol Heart Circ Physiol, 35, pp. 1643-1656; 
Pincus, S.M., Assesing serial irregularity and its implications for health (2001) Annals New York Academy of Sciences, 954, pp. 245-267; 
Marques-de, S.J., Characterization of fetal heart rate using approximate entropy (2005) IEEE Computers in Cardiology, 32, pp. 671-673; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am J Physiol Heart Circ Physiol, 278, pp. 2039-2049; 
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},
	month = {2008///},
	pages = {41 - 44},
	address = {Bologna},
	abstract = {Entropy based measures, such as Sample Entropy (SampEn), have been widely used for quantifying the Heart Rate Variability (HRV) for cardiac risk stratification purposes, with the hypothesis that decreasing entropy points to a perturbation of the complex physiological mechanisms or disease. However, in the literature, higher entropy values have been reported for some pathologies than for healthy subjects, which could be due to the use of a threshold value r tuned relative to the signal standard deviation. In the present paper we apply SampEn to assess the variability of the RR time series from healthy subjects and subjects with Congestive Heart Failure (CHF) in order to discriminate between both groups, as well as to characterize the variability loss due to aging. We conclude that the use of a fixed threshold value r in the SampEn algorithm instead of its conventional setting (as a percentage of the standard deviation of each data series), improves the discrimination capabilities between healthy and CHF subjects, and it allows to quantify the loss of HRV due to aging in healthy subjects.},
	keywords = {Cardiology, Congestive heart failures, Data series, entropy, Entropy values, Fixed thresholds, Healthy subjects, Heart failures, Heart rate variabilities, Heart valve prostheses, Physiological mechanisms, Risk stratifications, Sample entropies, Signal standard deviations, Standard deviations, Table lookup, Time series},
	isbn = {02766574 (ISSN); 1424437067 (ISBN); 9781424437061 (ISBN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-62249148798\&partnerID=40\&md5=8e431df62b6a4b2d13e5d71570608d91},
	author = {Goya-Esteban, R. and De S{\'a}, J.P.M. and Rojo-{\'A}lvarez, J.L. and Barquero-P{\'e}rez, O.}
}
@article {2335,
	title = {Data classification with multilayer perceptrons using a generalized error function},
	journal = {Neural NetworksNeural Netw.},
	volume = {21},
	year = {2008},
	note = {Cited By (since 1996): 6Export Date: 21 November 2012Source: ScopusCODEN: NNETEdoi: 10.1016/j.neunet.2008.04.004PubMed ID: 18572384Language of Original Document: EnglishCorrespondence Address: Silva, L.M.; INEB-Instituto de Engenharia Biom{\'e}dica, Porto, Portugal; email: lmsilva@fe.up.ptReferences: Baum, E.B., Wilczek, F., Supervised learning of probability distributions by neural networks (1987) NIPS, pp. 52-61. , Anderson D.Z. (Ed), American Institute of Physics;Bishop, C., (1995) Neural networks for pattern recognition, , Oxford University Press; 
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},
	month = {2008///},
	pages = {1302 - 1310},
	abstract = {The learning process of a multilayer perceptron requires the optimization of an error function E (y, t) comparing the predicted output, y, and the observed target, t. We review some usual error functions, analyze their mathematical properties for data classification purposes, and introduce a new one, E                        Exp, inspired by the Z-EDM algorithm that we have recently proposed. An important property of E
                        Exp is its ability to emulate the behavior of other error functions by the sole adjustment of a real-valued parameter. In other words, E
                        Exp is a sort of generalized error function embodying complementary features of other functions. The experimental results show that the flexibility of the new, generalized, error function allows one to obtain the best results achievable with the other functions with a performance improvement in some cases. {\textcopyright} 2008 Elsevier Ltd. All rights reserved.
},
	keywords = {algorithm, Algorithms, analytical error, article, calculation, Classification, Complementary features, Cybernetics, data analysis, Data classification, Data classifications, Data Interpretation, Statistical, Electric loads, entropy, Error functions, learning, Learning processes, mathematical analysis, Mathematical properties, Models, Statistical, Multilayer neural networks, Multilayer perceptron, Multilayer perceptrons, Multilayers, Neural networks, Neural Networks (Computer), Pattern recognition systems, perceptron, Performance improvements, priority journal, Probability density function},
	isbn = {08936080 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-54449100428\&partnerID=40\&md5=30f8de18c0272f4a440395045bd3c164},
	author = {Silva, L.M. and Marques de S{\'a}, J. and Alexandre, L.A.}
}
@article {2349,
	title = {Frequency domain and entropy analysis of fetal heart rate: Appealing tools for fetal surveillance and pharmacodynamic assessment of drugs},
	journal = {Cardiovascular and Hematological Disorders - Drug TargetsCardiovasc. Hematol. Disord. Drug Targets},
	volume = {8},
	year = {2008},
	note = {Cited By (since 1996): 1Export Date: 21 November 2012Source: Scopusdoi: 10.2174/187152908784533720Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Matem{\'a}tica Aplicada, Faculdade de Ci{\^e}ncias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal; email: hernani.goncalves@fc.up.ptChemicals/CAS: atropine, 51-55-8, 55-48-1; betamethasone, 378-44-9; lidocaine, 137-58-6, 24847-67-4, 56934-02-2, 73-78-9; magnesium sulfate, 7487-88-9; opiate, 53663-61-9, 8002-76-4, 8008-60-4; propranolol, 13013-17-7, 318-98-9, 3506-09-0, 4199-09-1, 525-66-6; salbutamol, 18559-94-9References: Task-Force. Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (1996) Eur. Heart J, 17, pp. 354-381;Beckers, F., Verheyden, B., Aubert, A.E., Aging and nonlinear heart rate control in a healthy population (2006) Am. J. Physiol. Heart Circ. Physiol, 29, pp. H2560-H2570; 
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},
	month = {2008///},
	pages = {91 - 98},
	abstract = {Recently, frequency domain and entropy analysis of fetal heart rate (FHR) have been assessed in several studies, providing new insights into physiologic regulatory mechanisms, constituting appealing tools for pharmacodynamic assessment, namely during fetal life. There is evidence that entropy and frequency domain analysis convey information on cortical and autonomic nervous system activities, respectively. Use of internal versus external FHR acquisition sensors and the signal sampling frequency may dramatically affect results. Most FHR frequency domain indices are significantly increased with rising fetal activity, namely during active wakefulness and active sleep, whereas the opposite occurs with nonlinear indices. This is in favour of increased activity of the autonomous nervous system and decreased activity of the central nervous system complexity control systems, during periods of fetal activity. Progression of labor is associated with a significant increase in FHR frequency domain indices, whereas entropy indices are significantly decreased. This denotes activation of the autonomic nervous system in the final minutes of labour, associated with decreased central nervous system activity. The emerging knowledge on FHR frequency domain and entropy analysis substantiates a continued interest of these methods in evaluation of the fetal pathophysiologic regulatory mechanisms, and opens new perspectives for clinical and pharmacodynamic assessment. {\textcopyright} 2008 Bentham Science Publishers Ltd.},
	keywords = {acidemia, adrenergic receptor stimulating agent, alpha adrenergic receptor blocking agent, anticonvulsive agent, article, atropine, autonomic nervous system function, beta adrenergic receptor blocking agent, betamethasone, Cardiotocography, central depressant agent, central nervous system function, cholinergic receptor blocking agent, chronotropism, Computerized analysis, drug effect, drug mechanism, electronic sensor, entropy, External and internal monitoring, Female, Fetal behavioral states, Fetal heart rate (FHR), Fetal monitoring, fetus, fetus heart rate, fetus monitoring, frequency analysis, Frequency domain and entropy analysis, gestation period, Heart rate variability, Heart Rate, Fetal, human, Humans, instrumentation, labor, lidocaine, local anesthetic agent, magnesium sulfate, mathematical computing, methodology, nonhuman, opiate, pharmacodynamics, physiology, Pregnancy, prenatal screening, propranolol, pulse rate, review, salbutamol, signal detection},
	isbn = {1871529X (ISSN)},
	author = {Gon{\c c}alves, H. and Rocha, A.P. and Ayres-de-Campos, D. and Bemardes, J.}
}
@article {2365,
	title = {LEGClust - A clustering algorithm based on layered entropic subgraphs},
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},
	month = {2008///},
	pages = {62 - 75},
	abstract = {Hierarchical clustering is a stepwise clustering method usually based on proximity measures between objects or sets of objects from a given data set. The most common proximity measures are distance measures. The derived proximity matrices can be used to build graphs, which provide the basic structure for some clustering methods. We present here a new proximity matrix based on an entropic measure and also a clustering algorithm (LEGClust) that builds layers of subgraphs based on this matrix, and uses them and a hierarchical agglomerative clustering technique to form the clusters. Our approach capitalizes on both a graph structure and a hierarchical construction. Moreover, by using entropy as a proximity measure we are able, with no assumption about the cluster shapes, to capture the local structure of the data, forcing the clustering method to reflect this structure. We present several experiments on artificial and real data sets that provide evidence on the superior performance of this new algorithm when compared with competing ones. {\textcopyright} 2007 IEEE.},
	keywords = {algorithm, Algorithms, article, artificial intelligence, automated pattern recognition, Cluster Analysis, Clustering, Clustering algorithms, computer assisted diagnosis, Distance measurement, Entropic subgraphs, entropy, Graph theory, Graphs, Hierarchical clustering, Hierarchical systems, Image enhancement, Image Interpretation, Computer-Assisted, Imaging, Three-Dimensional, methodology, Pattern Recognition, Automated, reproducibility, Reproducibility of Results, sensitivity and specificity, three dimensional imaging},
	isbn = {01628828 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-36448984894\&partnerID=40\&md5=f549049e4ae5bff1f3a95aaae22cefb8},
	author = {Santos, J.M. and De S{\'a}, J.M. and Alexandre, L.A.}
}
@article {2339,
	title = {Linear and nonlinear heart-rate analysis in a rat model of acute anoxia},
	journal = {Physiological MeasurementPhysiol. Meas.},
	volume = {29},
	year = {2008},
	note = {Cited By (since 1996): 6Export Date: 21 November 2012Source: ScopusCODEN: PMEAEdoi: 10.1088/0967-3334/29/9/010PubMed ID: 18784391Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Matem{\'a}tica Aplicada, Faculdade de Ci{\^e}ncias, Universidade Do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal; email: hernani.goncalves@fc.up.ptReferences: American College of Obstetricians and Gynecologists. ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists, Number 70, December 2005 (2005) Obstet. Gynecol., 106, pp. 1453-1460;Ayres-De-Campos, D., Bernardes, J., Garrido, A., Marques-De-S{\'a}, J., Pereira-Leite, L., SisPorto 2.0: A program for automated analysis of cardiotocograms (2000) J. Mat. Fet. Med., 9 (5), pp. 311-318; 
Ayres-De-Campos, D., Santos, C., Bernardes, J., Prediction of neonatal state by computer analysis of fetal heart rate tracings: The antepartum arm of the SisPorto{\textregistered} validation study (2005) Eur. J. Obstet. Gynecol. Reprod. Biol., 118 (1), pp. 52-60; 
Beckers, F., Verheyden, B., Aubert, A.E., Aging and nonlinear heart rate control in a healthy population (2006) Am. J. Physiol. Heart Circ. Physiol., 290 (6), pp. 2560-H2570; 
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Gon{\c c}alves, H., Bernardes, J., Rocha, A.P., Ayres-De-Campos, D., Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period (2007) Early Human Develop., 83 (9), pp. 585-591; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-De-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters (2006) Physiol. Meas., 27 (3), pp. 307-319; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-De-Campos, D., Bernardes, J., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Med. Biol. Eng. Comput., 44 (10), pp. 847-855; 
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Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans. Biomed. Eng., 50 (3), pp. 365-373; 
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},
	month = {2008///},
	pages = {1133 - 1143},
	abstract = {The objective of this study was the assessment of heart-rate (HR) dynamics with linear and nonlinear methods during episodes of mechanical ventilation and acute anoxia in rats. Namely, to assess whether linear and nonlinear HR analysis was able to discriminate acute anoxia from baseline in rats and if this was consistent with human foetal and adult studies. Five HR segments of 1 min duration, during baseline recording, mechanical ventilation and first, second and third minutes of induced acute anoxia, were analysed in ten adult Wistar rats. Linear time and frequency domain and nonlinear methods were used, namely mean HR (mHR), long-term irregularity (LTI), interval index (II), low frequency (LF) and high frequency (HF), approximate entropy (ApEn) and sample entropy (SampEn). New parameters for the entropy indices are proposed for the analysis of rats{\textquoteright} HR. Bootstrap percentile confidence intervals and nonparametric statistical tests were used in the evaluation of the differences between segments. During mechanical ventilation a clear spectral band was detectable at the ventilation rate, but mHR, II and the {\textquoteright}new{\textquoteright} entropy indices were the only significantly changed indices. In the transition from baseline-mechanical- ventilation to mechanical-ventilation-induced anoxia, a statistically significant decrease of mHR, II and entropy indices was observed, clearly discriminating these two instances, whereas most linear indices increased. With continued anoxia, most linear indices decreased significantly, whereas entropy remained stably low. These results are consistent with other foetal human and non-human studies and evidence that the rat model may be used for further research on linear and nonlinear analysis of heart-rate dynamics. The transition from baseline to acute anoxia was encompassed by signs of increased activation of the autonomic nervous system sympathetic branch, and decreased or blunted activity of the HR complexity regulatory centres. {\textcopyright} 2008 Institute of Physics and Engineering in Medicine.},
	keywords = {acute disease, animal experiment, animal model, Animals, Anoxia, article, artificial ventilation, bootstrapping, controlled study, entropy, Female, Fetal monitoring, frequency analysis, Heart rate, Heart rate variability, Humans, Linear analysis, linear system, lung ventilation, Models, Cardiovascular, nonhuman, nonlinear system, priority journal, rat, Rats, Rats, Wistar, Rattus, Rattus norvegicus, Respiration, Artificial, Statistical analysis, Variability, Wistar rat, Wistar rats},
	isbn = {09673334 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-51849120545\&partnerID=40\&md5=56be327bb0d959060a2f4a0f080ae264},
	author = {Gon{\c c}alves, H. and Henriques-Coelho, T. and Bernardes, J. and Rocha, A.P. and Nogueira, A. and Leite-Moreira, A.}
}
@article {2375,
	title = {Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period},
	journal = {Early Human DevelopmentEarly Hum. Dev.},
	volume = {83},
	year = {2007},
	note = {Cited By (since 1996): 17Export Date: 21 November 2012Source: ScopusCODEN: EHDEDdoi: 10.1016/j.earlhumdev.2006.12.006PubMed ID: 17261357Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Universidade do Porto, Faculdade de Ci{\^e}ncias, Departamento de Matem{\'a}tica Aplicada, Porto, Portugal; email: hernani.goncalves@fc.up.ptReferences: Nijhuis, J.G., Prechtl, H.F., Martin, C.B.J., Bots, R.S., Are there behavioural states in the human fetus? (1982) Early Hum Dev, 6, pp. 177-195;Nijhuis, I., ten Hof, J., Development of fetal heart rate and behavior: indirect measures to assess the fetal nervous system (1999) Eur J Obstet Gynaecol Reprod Biol, 87, pp. 1-2; 
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Ayres-de-Campos, D., Santos, C., Bernardes, J., Prediction of neonatal state by computer analysis of fetal heart rate tracings: the antepartum arm of the SisPorto{\textregistered} multicentre validation study (2005) Eur J Obstet Gynaecol Reprod Biol, 118, pp. 52-60; 
Ayres-de-Campos, D., Bernardes, J., Garrido, A., de S{\'a}, J.M., Pereira-Leite, L., SisPorto 2.0: a program for automated analysis of cardiotocograms (2000) J Matern Fetal Med, 9, pp. 311-318; 
Rooth, G., Huch, A., Huch, R., FIGO news. Guidelines for the use of fetal monitoring (1987) Int J Gynaecol Obstet, 25, p. 159; 
Bernardes, J., Moura, C., de S{\'a}, J.P.M., Pereira-Leite, L., The Porto system for automated cardiotocographic signal analysis (1991) J Perinat Med, 19, pp. 61-65; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: the effect on linear and nonlinear parameters (2006) Physiol Meas, 27, pp. 307-319; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans Biomed Eng, 50 (3), pp. 365-373; 
Pincus, S., Viscarello, R., Approximate Entropy: a regularity measure for fetal heart rate analysis (1992) Obstet Gynaecol, 79 (2), pp. 249-255; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am J Physiol Heart Circ Physiol, 278, pp. H2039-H2049; 
Pincus, S., Approximate entropy (ApEn) as a complexity measure (1995) Chaos, 5 (1), pp. 110-117; 
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Felgueiras, C., de S{\'a}, J.P.M., Bernardes, J., Gama, S., Fractal characterisation of fetal heart rate sequences (1998) Biomed Eng, 36 (2), pp. 197-201; 
Vieira, P., Marques-de-S{\'a}, J.P., Bernardes, J., Fractal analysis of foetal heart rate (2004) Proceedings of biosignal 2004, pp. 53-55. , Jan J., Kozumpl{\'\i}k J., and Provazn{\'\i}k I. (Eds), Vutium Press, Brno University of Technology; 
di Renzo, G.C., Montani, M., Fioriti, V., Clerici, G., Branconi, F., Pardini, A., Fractal analysis: a new method for evaluating fetal heart rate variability (1996) J Perinat Med, 24 (3), pp. 261-269
},
	month = {2007///},
	pages = {585 - 591},
	abstract = {Background: Fetal behavioral states are important indicators of fetal physiology and pathology associated to typical fetal heart rate (FHR) patterns. Aim: To provide linear and nonlinear analysis of FHR patterns associated with fetal behavioral states regarding a better understanding of these states and patterns. Study design and subjects: Fifty FHR tracings from normal term pregnancies with a median duration of 40.3~min were acquired with the SisPorto{\textregistered} 2.01 system for computerized analysis of cardiotocograms. Each tracing was divided into consecutive 10-minute segments and each segment was classified by two experts as pattern A, B, C or D. Outcome measures: Linear and nonlinear indices were computed in each segment, namely mean FHR, long-term irregularity index (LTI), very low (VLF), low (LF) and high (HF) frequency spectral indices, approximate entropy (ApEn) and sample entropy (SampEn). Kappa statistic (κ) and proportions of agreement (Pa) were used for assessment of inter-observer agreement. Bootstrap percentile confidence intervals and nonparametric statistical tests were calculated for statistical inference. Results: Overall agreement between experts in pattern classification was good to excellent with values for κ and Pa of 0.74 (95\% CI: 0.64-0.94) and 0.94 (95\% CI: 0.92-0.96), respectively. Most linear domain indices increased significantly with rising fetal activity whereas the opposite occurred with nonlinear indices, except for SampEn(2, 0.1). LF/(MF + HF) ratio also significantly increased with fetal activity, denoting an increased sympatho-vagal balance. Conclusions: Results support the hypothesis that entropy and linear variability indices measure different FHR features. FHR patterns associated with active sleep (B) and active wakefulness (D) evidenced more signs of autonomous nervous system activity, with sympatho-vagal imbalance, and less signs related to complexity or irregularity control systems than patterns associated with calm sleep (A) and calm wakefulness (C). {\textcopyright} 2006 Elsevier Ireland Ltd. All rights reserved.},
	keywords = {adult, article, behavior change, Cardiotocography, Computerized analysis, controlled study, entropy, Female, Fetal behavioral states, Fetal heart rate, Fetal monitoring, fetus, fetus heart rate, fetus monitoring, Heart Rate, Fetal, human, Humans, Image Interpretation, Computer-Assisted, Linear Models, Nonlinear Dynamics, Pregnancy, SisPorto, Spectral analysis, vagus nerve stimulation},
	isbn = {03783782 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-34249751815\&partnerID=40\&md5=3a787d5accf317ad2b020e59ddb6a465},
	author = {Gon{\c c}alves, H. and Bernardes, J. and Paula Rocha, A. and Ayres-de-Campos, D.}
}
@article {2405,
	title = {Error entropy in classification problems: A univariate data analysis},
	journal = {Neural ComputationNeural Comp.},
	volume = {18},
	year = {2006},
	note = {Cited By (since 1996): 7Export Date: 21 November 2012Source: Scopusdoi: 10.1162/neco.2006.18.9.2036PubMed ID: 16846386Language of Original Document: EnglishCorrespondence Address: Silva, L.M.; Institute de Engenharia Biom{\'e}dica, Laborat{\'o}rio Sinal e Imagem Biom{\'e}dica, 4200-465, Porto, Portugal; email: lmsilva@fe.up.ptReferences: Devroye, L., Gyorfi, L., Lugosi, G., (1996) A Probabilistic Theory of Pattern Recognition, , Berlin: Springer-Verlag;Erdogmus, D., Principe, J., Comparison of entropy and mean square error criteria in adaptive system training using higher order statistics (2000) Proceedings of the Intl. Conf., on ICA and Signal Separation, pp. 75-80. , Helsinki, Finland; 
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Santos, J., Marques De Sa, J., Alexandre, L., Sereno, F., Optimization of the error entropy minimization algorithm for neural network classification (2004) Intelligent Engineering Systems Through Artificial Neural Networks, 14, pp. 81-86. , C. Dagli, A. Buczak, D. Enke, M. Embrechts, \& O. Ersoy (Eds.), New York: American Society of Mechanical Engineers; 
Shannon, C.E., A mathematical theory of communication (1948) Bell System Technical Journal, 27, pp. 379-423; 
Silva, L., Marques De Sa, J., Alexandre, L., Neural network classification using Shannon{\textquoteright}s entropy (2005) European Symposium on Artificial Neural Networks, , Bruges, Belgium: d-side publications; 
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Stoller, D., Univariate two-population distribution free discrimination (1954) Journal of the American Statistical Association, 49, pp. 770-777
},
	month = {2006///},
	pages = {2036 - 2061},
	abstract = {Entropy-based cost functions are enjoying a growing attractiveness in unsupervised and supervised classification tasks. Better performances in terms both of error rate and speed of convergence have been reported. In this letter, we study the principle of error entropy minimization (EEM) from a theoretical point of view. We use Shannon{\textquoteright}s entropy and study univariate data splitting in two-class problems. In this setting, the error variable is a discrete random variable, leading to a not too complicated mathematical analysis of the error entropy. We start by showing that for uniformly distributed data, there is equivalence between the EEM split and the optimal classifier. In a more general setting, we prove the necessary conditions for this equivalence and show the existence of class configurations where the optimal classifier corresponds to maximum error entropy. The presented theoretical results provide practical guidelines that are illustrated with a set of experiments with both real and simulated data sets, where the effectiveness of EEM is compared with the usual mean square error minimization. {\textcopyright} 2006 Massachusetts Institute of Technology.},
	keywords = {article, Classification, entropy, methodology, Models, Theoretical, normal distribution, theoretical model},
	isbn = {08997667 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33748288090\&partnerID=40\&md5=47b51b3d90bc273df156889a92fef01d},
	author = {Silva, L.M. and Felgueiras, C.S. and Alexandre, L.A. and Marques de S{\'a}, J.}
}
@book {2395,
	title = {Error entropy minimization for LSTM training},
	series = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)Lect. Notes Comput. Sci.},
	volume = {4131 LNCS - I},
	year = {2006},
	note = {Conference code: 68317Cited By (since 1996): 3Export Date: 21 November 2012Source: ScopusLanguage of Original Document: EnglishCorrespondence Address: Alexandre, L.A.; Department of Informatics, IT-Networks and Multimedia Group, University of Beira Interior, Covilh{\~a}, Portugal; email: lfbaa@di.ubi.ptReferences: Hochreiter, S., Schmidhuber, J., Long short-term memory (1997) Neural Computation, 9 (8), pp. 1735-1780;Gers, F., Schmidhuber, J., Cummins, F., Learning to forget: Continual prediction with LSTM (2000) Neural Computation, 12 (10), pp. 2451-2471; 
Gers, F., Schmidhuber, J., Recurrent nets that time and count (2000) Proc. IJCNN{\textquoteright}2000, Int. Joint Conf. on Neural Networks, , Como, Italy; 
P{\'e}rez-Ortiz, J., Gers, F., Eck, D., Schmidhuber, J., Kalman filters improve LSTM network performance in problems unsolvable by traditional recurrent nets (2003) Neural Networks, 16 (2), pp. 241-250; 
Haykin, S., (1999) Neural Networks: A Comprehensive Foundation, 2nd Edition, , Prentice Hall; 
Erdogmus, D., Principe, J., An error-entropy minimization algorithm for supervised training of nonlinear adaptive systems (2002) IEEE Trans. Signal Processing, 50 (7), pp. 1780-1786; 
Santos, J., Alexandre, L., Sereno, F., Marques De S{\'a}, J., Optimization of the error entropy minimization algorithm for neural network classification (2004) ANNIE 2004, Intelligent Engineering Systems Through Artificial Neural Networks, 14, pp. 81-86. , St.Louis, USA, ASME Press Series; 
Santos, J., Alexandre, L., Marques De S{\'a}, J., The error entropy minimization algorithm for neural network classification (2004) Proceedings of the 5th International Conference on Recent Advances in Soft Computing, pp. 92-97. , Lofti, A., ed.: Nottingham, United Kingdom; 
Silva, L., Marques De S{\'a}, J., Alexandre, L., Neural network classification using Shannon{\textquoteright}s entropy (2005) 13th European Symposium on Artificial Neural Networks - ESANN 2005, pp. 217-222. , Bruges, Belgium
},
	month = {2006///},
	pages = {244 - 253},
	address = {Athens},
	abstract = {In this paper we present a new training algorithm for the Long Short-Term Memory (LSTM) recurrent neural network. This algorithm uses entropy instead of the usual mean squared error as the cost function for the weight update. More precisely we use the Error Entropy Minimization approach, were the entropy of the error is minimized after each symbol is present to the network. Our experiments show that this approach enables the convergence of the LSTM more frequently than with the traditional learning algorithm. This in turn relaxes the burden of parameter tuning since learning is achieved for a wider range of parameter values. The use of EEM also reduces, in some cases, the number of epochs needed for convergence. {\textcopyright} Springer-Verlag Berlin Heidelberg 2006.},
	keywords = {Algorithms, Convergence of numerical methods, Cost function, entropy, Error Entropy Minimization, Errors, Long Short-Term Memory (LSTM), Neural networks, Optimization},
	isbn = {03029743 (ISSN); 3540386254 (ISBN); 9783540386254 (ISBN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33749837658\&partnerID=40\&md5=5f40159a3f1faf4760405dd581e79bf7},
	author = {Alexandre, L.A. and Marques De S{\'a}, J.P.}
}
@article {2419,
	title = {Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters},
	journal = {Physiological MeasurementPhysiol. Meas.},
	volume = {27},
	year = {2006},
	note = {Cited By (since 1996): 15Export Date: 21 November 2012Source: ScopusCODEN: PMEAEdoi: 10.1088/0967-3334/27/3/008PubMed ID: 16462016Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Matem{\'a}tica Aplicada, Faculdade de Ci{\^e}ncias, Universidade Do Porto, Porto, Portugal; email: hernani.goncalves@fc.up.ptReferences: Ayres-De-Campos, D., Bernardes, J., Garrido, A., Marques-De-S{\'a}, J., Pereira-Leite, L., SisPorto 2.0: A program for automated analysis of cardiotocograms (2000) J. Matern. Fetal Med., 9 (5), pp. 311-318;Ayres-De-Campos, D., Bernardes, J., Reynolds, A., Saraiva, J.P., Santos, C., Pereira-Leite, L., Computer evaluation of internal versus external FHR monitoring in the minutes preceding delivery (2000) Int. J. Gynecol. Obstet., 70, pp. 60-B61; 
Ayres-De-Campos, D., Santos, C., Bernardes, J., Prediction of neonatal state by computer analysis of fetal heart rate tracings: The antepartum arm of the SisPorto {\textregistered}multicentre validation study (2005) Eur. J. Obstet. Gynecol. Reprod. Biol., 118 (1), pp. 52-60; 
Bakker, P.C., Colenbrander, G.J., Verstraeten, A.A., Geijn, V., The quality of intrapartum fetal heart rate monitoring (2004) Eur. J. Obstet. Gynecol. Reprod. Biol., 116 (1), pp. 22-27; 
Bernardes, J., Ayres-De-Campos, D., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int. J. Gynecol. Obstet., 62 (2), pp. 141-147; 
Bernardes, J., Costa-Pereira, A., The effect of different sampling intervals on the measurement of intrapartum fetal heart rate variability (1997) Obstet. Gynecol., 90 (2), pp. 318-319; 
Bernardes, J., Garrido, A., Computerized fetal heart rate analysis in labour based on 2-s sampling. Can it proceed with confidence? (1995) Eur. J. Obstet. Gynecol. Reprod. Biol., 63 (1), pp. 105-107; 
Bernardes, J., Moura, C., Marques-De-S{\'a}, J.P., Pereira-Leite, L., The Porto system for automated cardiotocographic signal analysis (1991) J. Perinat. Med., 19, pp. 61-65; 
Bernardes, J., Moura, C., Marques-De-S{\'a}, J.P., Van Geijn, H.P., Pereira-Leite, L., The Porto system (1994) A Critical Appraisal of Fetal Surveillance, pp. 315-324; 
Boog, G., Analyse informatis{\'e}e du rythme cardiaque fetal au cours de la grosssesse et de l{\textquoteright}accouchement (2004) Encyclop{\'e}die M{\'e}dico-Chirurgicale, 148; 
Boos, A., Jagger, M.H., Paret, G.W., Hausmann, J.W., A new, lightweight fetal telemetry system (1995) Hewlett-Packard J., pp. 82-93; 
Carter, M.C., Signal processing and display-cardiotocographs (1993) Br. J. Obstet. Gynaecol., 100, pp. 21-23; 
Chaffin, D.G., Barnard, J.M., Phernetton, T., Reed, K.L., Decreased approximate entropy of heart rate variability in the hypoxic ovine fetus (1998) J. Matern. Fetal Invest., 8, pp. 23-26; 
Chang, A., Sahota, D.S., Reed, N.N., James, D.K., Mohajer, M.P., Computerised fetal heart rate analysis in labour-effect of sampling rate (1995) Eur. J. Obstet. Gynecol. Reprod. Biol., 59 (2), pp. 125-129; 
Court, D.J., Parer, J.T., Experimental studies of fetal asphyxia and fetal heart rate interpretation (1984) Research in Perinatal Medicine, pp. 113-169; 
Dawes, G., Computerized fetal heart rate analysis (1994) A Critical Appraisal of Fetal Surveillance, pp. 311-314; 
Dawes, G.S., Moulden, M., Sheil, O., Redman, C.W.G., Approximate entropy, a statistic of regularity, applied to fetal heart rate data before and during labour (1992) Obstet. Gynecol., 80, pp. 763-768; 
Dawes, G.S., Moulden, M., Redman, C.W., Criteria for the design of fetal heart rate analysis systems (1990) Int. J. Biomed. Comput., 25 (4), pp. 287-294; 
Di Renzo, G.C., Montani, M., Fioriti, V., Clerici, G., Branconi, F., Pardini, A., Indraccolo, R., Cosmi, E.V., Fractal analysis: A new method for evaluating fetal heart rate variability (1996) J. Perinat. Med., 24, pp. 261-269; 
Echeverria, J.C., Hayes-Gill, B.R., Crowe, J.A., Woolfson, M.S., Croaker, G.D., Detrended fluctuation analysis: A suitable method for studying fetal heart rate variability? (2004) Physiol. Meas., 25 (3), pp. 763-774; 
Felgueiras, C., Marques-De-S{\'a}, J.P., Bernardes, J., Gama, S., Fractal characterisation of fetal heart rate sequences (1998) Biomed. Eng., 36, pp. 197-201; 
Felgueiras, C.S., Marques-De-S{\'a}, J.P., Bernardes, J., Gama, S., On the reconstruction of fetal heart rate sequences (1996) Actas Do 4{\textdegree} Congresso Portugu{\^e}s de Engenharia Biom{\'e}dica-BioEng{\textquoteright}96, pp. 61-vii65; 
Fukushima, T., Flores, C.A., Hon, E.H., Davidson Jr., E.C., Limitations of autocorrelation in fetal heart rate monitoring (1985) Am. J. Obstet. Gynecol., 153, pp. 685-692; 
Fusheng, Y., Bo, H., Qingyu, T., Approximate entropy and its application in biosignal analysis (1998) Nonlinear Biomedical Signal Processing-Volume II: Dynamical Analysis and Modelling, pp. 72-91; 
Gough, N.A., Fractal analysis of fetal heart rate variability (1993) Physiol. Meas., 14 (3), pp. 309-315; 
Hayes, M., (1996) Statistical Digital Signal Processing and Modelling; 
Hewlett-Packard, (1993) Hewlett-Packard Series 50 Service Manual, M1351A and 1353A; 
Hirsch, M., Karin, J., Akselrod, S., Heart rate variability in the fetus (1995) Heart Rate Variability, pp. 517-531; 
Lawson, G.W., Belcher, R., Dawes, G.S., Redman, C.W., A comparison of ultrasound (with autocorrelation) and direct electrocardiogram fetal heart rate detector systems (1983) Am. J. Obstet. Gynecol., 147, pp. 721-722; 
Li, X., Tang, D., Zhou, S., Zhou, G., Wang, C., Zhuang, Y., Wu, G., Shen, L., Redistribution of power spectrum of heart rate variability during acute umbilical artery embolism and hypoxemia in late-gestation fetal sheep (2004) Eur. J. Obstet. Gynecol. Reprod. Biol., 114 (2), pp. 137-143; 
Lunghi, F., Magenes, G., Pedrinazzi, L., Signorini, M.G., Detection of fetal distress through a support vector machine based on fetal heart rate parameters (2005) Comput. Cardiol., 32, pp. 247-250; 
Magenes, G., Signorini, M.G., Arduini, D., Classification of cardiotocographic records by neural networks (2000) IJCNN 2000: Proc. IEEE-INNS-ENNS Int. Joint Conf. on Neural Networks, pp. 637-641; 
Electronic fetal heart rate monitoring: Research guidelines for interpretation (1997) Am. J. Obstet. Gynecol., 177 (6), pp. 1385-1390; 
Nijhuis, I., Ten Hof, J., Development of fetal heart rate and behavior: Indirect measures to assess the fetal nervous system (1999) Eur. J. Obstet. Gynecol. Reprod. Biol., 87 (1), pp. 1-2; 
Oppenheimer, L.W., Lewinsky, R.M., Power spectral analysis of fetal heart rate (1994) Baillieres Clin. Obstet. Gynaecol., 8, pp. 643-661; 
Peters, C.H., Ten Broeke, E.D., Andriessen, P., Vermeulen, B., Berendsen, R.C., Wijn, P.F., Oei, S.G., Beat-to-beat detection of fetal heart rate: Doppler ultrasound cardiotocography compared to direct ECG cardiotocography in time and frequency domain (2004) Physiol. Meas., 25 (2), pp. 585-593; 
Pincus, S., Approximate entropy as a measure of system complexity (1991) Proc. Natl. Acad. Sci. USA, 88, pp. 2297-2301; 
Pincus, S., Approximate entropy (ApEn) as a complexity measure (1995) Chaos, 5 (1), pp. 110-117; 
Pincus, S., Viscarello, R., Approximate entropy: A regularity measure for fetal heart rate analysis (1992) Obstet. Gynecol., 79, pp. 249-255; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am. J. Physiol. Heart Circ. Physiol., 278, pp. 2039-H2049; 
Salamalekis, E., Thomopoulos, P., Giannaris, D., Salloum, I., Vasios, G., Prentza, A., Koutsouris, D., Computerised intrapartum diagnosis of fetal hypoxia based on fetal heart rate monitoring and fetal pulse oximetry recordings utilising wavelet analysis and neural networks (2002) BJOG, 109 (10), pp. 1137-1142; 
Signorini, M., Cerutti, S., Nonlinear properties of Cardiovascular Time Series (1999) Methodology and Clinical Applications of Blood Pressure and Heart Rate Analysis, pp. 73-89; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans. Biomed. Eng., 50 (3), pp. 365-373; 
Suzuki, T., Okamura, K., Kimura, Y., Watanabe, T., Yaegashi, N., Murotsuki, J., Uehara, S., Yajima, A., Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs (2000) Am. J. Obstet. Gynecol., 182 (5), pp. 1227-1232; 
Heart rate variability. Standards of measurement, physiological interpretation, and clinical use (1996) Eur. Heart J., 17, pp. 354-381; 
Wilcox, M.A., Wang, W., Sahota, D.S., Dawkins, R.R., Chung, T.K., Chang, A.M., The effect of different sampling intervals on the measurement of intrapartum fetal heart rate variability (1997) Obstet. Gynecol., 89 (4), pp. 577-580; 
Yum, M.K., Kim, K., Kim, J.H., Park, E.Y., A consistent abnormality in the average local smoothness of fetal heart rate in growth-restricted fetuses affected by severe pre-eclampsia (2004) Hypertens. Res., 27 (12), pp. 911-918
},
	month = {2006///},
	pages = {307 - 319},
	abstract = {The effect of foetal heart rate (FHR) acquisition mode on linear and nonlinear parameters is still largely unknown. In 33 normal labouring women, FHR signals were acquired simultaneously by an external ultrasound sensor applied to the maternal abdomen and an internal scalp electrode, in the minutes preceding delivery. For each case, the initial and final 5, 10 and 20 min segments were analysed, considering FHR signals at a frequency of 4 Hz (the frequency at which they are transmitted by the majority of commercialized foetal monitors). Several time and frequency domain linear and nonlinear FHR indices were computed in these segments, namely mean FHR, very low frequency (VLF), low frequency (LF), high frequency (HF), approximate entropy (ApEn) and sample entropy (SampEn). Parametric confidence intervals, statistical tests and correlation coefficients were calculated in order to evaluate the effect of internal versus external FHR monitoring modes on the considered indices. The whole evaluation was repeated using FHR signals at a frequency of 2 Hz. Most time domain linear indices were similar with external and internal monitoring in the initial and final segments of the tracings. However, linear frequency domain indices were poorly correlated in the final segments and had significantly different mean values in the initial segments. Nonlinear indices were significantly different in both initial and final segments. The correlation between 4 and 2 Hz sampled parameters was high for both linear and nonlinear indices (most correlation coefficient values ranging between 0.95 and 1) but nonlinear index values were significantly higher at 2 Hz. In conclusion, the mode used to acquire FHR signals and the sampling rate employed can significantly affect most FHR indices. {\textcopyright} 2006 IOP Publishing Ltd.},
	keywords = {abdomen, Algorithms, article, Cardiotocography, commercial phenomena, Confidence interval, controlled study, correlation coefficient, delivery, Diagnosis, Computer-Assisted, Electrocardiography, electrode, entropy, External and internal monitoring, Female, fetus electrocardiography, fetus monitoring, Foetal heart rate (FHR), Frequency domain analysis, Heart, Heart rate, human, intermethod comparison, intrapartum care, Linear and nonlinear analysis, Linear Models, mathematical computing, Nonlinear Dynamics, normal human, priority journal, Reproducibility of Results, sensitivity and specificity, sensor, Signal Processing, Computer-Assisted, Statistical significance, ultrasound, Variability},
	isbn = {09673334 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-32144438860\&partnerID=40\&md5=dd6dbb9f364b7f974c7048c4cf08d53f},
	author = {Gon{\c c}alves, H. and Rocha, A.P. and Ayres-de-Campos, D. and Bernardes, J.}
}
@article {2400,
	title = {Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery},
	journal = {Medical and Biological Engineering and ComputingMed. Biol. Eng. Comput.},
	volume = {44},
	year = {2006},
	note = {Cited By (since 1996): 20Export Date: 21 November 2012Source: ScopusCODEN: MBECDdoi: 10.1007/s11517-006-0105-6PubMed ID: 16988896Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Matem{\'a}tica Aplicada, Faculdade de Ci{\^e}ncias, Universidade do Porto, Rua do Campo Alegre - 687, 4169-007 Porto, Portugal; email: hernani.goncalves@fc.up.ptChemicals/CAS: AcidsReferences: ACOG technical bulletin. Fetal heart rate patterns: Monitoring, interpretation, and management (1995) Int J Gynecol Obstet, 51, pp. 65-74. , ACOG;Ayres-de-Campos, D., Bernardes, J., Costa-Pereira, A., Pereira-Leite, L., Inconsistencies in expert{\textquoteright}s classification of cardiotocograms and subsequent clinical decision (1999) Br J Obstet Gynecol, 106, pp. 1307-1310; 
Ayres-de-Campos, D., Bernardes, J., Garrido, A., de S{\'a}, J.M., Pereira-Leite, L., Sisporto 2.0: A program for automated analysis of cardiotocograms (2000) J Mat Fet Med, 9, pp. 311-318; 
Bernardes, J., de Campos, D.A., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int J Gynecol Obstet, 62, pp. 141-147; 
Bernardes, J., Costa-Pereira, A., de Campos, D.A., van Geijn, H.P., Pereira-Leite, L., Evaluation of interobserver agreement of cardiotocograms (1997) Int J Gynecol Obstet, 57 (1), pp. 33-37; 
Bernardes, J., Moura, C., de S{\'a}, J.P.M., Pereira-Leite, L., The porto system for automated cardiotocographic signal analysis (1991) J Perinat Med, 19, pp. 61-65; 
Boog, G., Analyse informatisTe du rythme cardiaque foetal au cours de la grossesse et de l{\textquoteright}accouchement (2004) EncyclopTdie MTdico-Chirurgicale, 148, pp. 1-10. , (5-049-D-23); 
Carter, M.C., Signal processing and display - Cardiotocographs (1993) Br J Obstet Gynaecol, 100 (9), pp. 21-23; 
Chaffin, D.G., Barnard, J.M., Phernetton, T., Reed, K.L., Decreased approximate entropy of heart rate variability in the hypoxic ovine fetus (1998) J Matern Fetal Invest, 8, pp. 23-26; 
Chung, D.Y., Sim, Y.B., Park, K.T., Yi, S.H., Shin, J.C., Kim, S.P., Spectral analysis of fetal heart rate variability as a predictor of intrapartum fetal distress (2001) Int J Gynecol Obstet, 73, pp. 109-116; 
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Dawes, G.S., Moulden, M., Sheil, O., Redman, C.W.G., Approximate entropy, a statistic of regularity, applied to fetal heart rate data before and during labour (1992) Obstet Gynecol, 80 (5), pp. 763-768; 
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Felgueiras, C., de S{\'a}, J.P.M., Bernardes, J., Gama, S., Fractal characterisation of fetal heart rate sequences (1998) Biomed Eng, 36 (2), pp. 197-201; 
Fusheng, Y., Bo, H., Qingyu, T., Approximate entropy and its application in biosignal analysis (1998) Nonlinear Biomedical Signal Processing. Dynamical Analysis and Modelling, 2, pp. 72-91. , In: Akay M (ed) IEEE Press, New York; 
Gon{\c c}alves, H., Rocha, A.P., de Campos, D.A., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters (2006) Physiol Meas, 27, pp. 307-319; 
Gough, N.A., Fractal analysis of foetal heart rate variability (1993) Physiol Meas, 14 (3), pp. 309-315; 
Hayes, M., (1996) Statistical Digital Signal Processing and Modelling, , Wiley, New York; 
Hewlett-Packard, (1993) Hewlett-Packard Series 50 Service Manual, , M1351A and 1353A. Germany; 
King, T., Parer, J., The physiology of fetal heart rate patterns and perinatal asphyxia (2000) J Perinat Neonat Nurs, 14 (3), pp. 19-39; 
Li, X., Tang, D., Zhou, S., Zhou, G., Wang, C., Zhuang, Y., Wu, G., Shen, L., Redistribution of power spectrum of heart rate variability during acute umbilical artery embolism and hypoxemia in late-gestation fetal sheep (2004) Eur J Obstet Gynecol Reprod Biol, 114, pp. 137-143; 
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Pincus, S., Approximate entropy as a measure of system complexity (1991) Proc Natl Acad Sci USA, 88, pp. 2297-2301; 
Pincus, S., Approximate entropy (apen) as a complexity measure (1995) Chaos, 5 (1), pp. 110-117; 
Pincus, S., Viscarello, R., Approximate entropy: A regularity measure for fetal heart rate analysis (1992) Obstet Gynecol, 79 (2), pp. 249-255; 
di Renzo, G.C., Montani, M., Fioriti, V., Clerici, G., Branconi, F., Pardini, A., Indraccolo, R., Cosmi, E.V., Fractal analysis: A new method for evaluating fetal heart rate variability (1996) J Perinat Med, 24 (3), pp. 261-269; 
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(2001) Evidence-Based Clinical Guideline Number 8. The Use of Electronic Fetal Monitoring, , Royal College of Obstetricians and Gynaecologists Royal College of Obstetricians and Gynaecologists, London; 
Salamalekis, E., Thomopoulos, P., Giannaris, D., Salloum, I., Vasios, G., Prentza, A., Koutsouris, D., Computerised intrapartum diagnosis of fetal hypoxia based on fetal heart rate monitoring and fetal pulse oximetry recordings utilising wavelet analysis and neural networks (2002) BJOG, 109 (10), pp. 1137-1142; 
Signorini, M.G., Cerutti, S., Nonlinear properties of cardiovascular time series (1999) Methodology and Clinical Applications of Blood Pressure and Heart Rate Analysis, pp. 73-89. , In: Di Rienzo M, Mancia G, Parati G, Pedotti A, Zanchetti A (eds) IOS Press, Amsterdam; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans Biomed Eng, 50 (3), pp. 365-373; 
Siira, S.M., Ojala, T.H., Vahlberg, T.J., Jalonen, J.O., Valimaki, I.A., Rosen, K.G., Ekholm, E.M., Marked fetal acidosis and specific changes in power spectrum analysis of fetal heart rate variability recorded during the last hour of labour (2005) Br J Obstet Gynaecol, 112, pp. 418-423; 
Suzuki, T., Okamura, K., Kimura, Y., Watanabe, T., Murotsuki, N.Y.J., Uehara, S., Yajima, A., Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs (2000) Am J Obstet Gynecol, 182, pp. 1227-1232; 
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Teich, M.C., Lowen, S.B., Jost, B.M., Vibe-Rheymer, K., Heneghan, C., Heart rate variability: Measures and models (1998) Nonlinear Biomedical Signal Processing. Dynamic Analysis and Modeling, 2, pp. 159-213. , In: Akay M (ed) IEEE Press, New York; 
Yum, M.K., Kim, K., Kim, J.H., Park, E.Y., A consistent abnormality in the average local smoothness of fetal heart rate in growth-restricted fetuses affected by severe pre-eclampsia (2004) Hypertens Res, 27 (12), pp. 911-918
},
	month = {2006///},
	pages = {847 - 855},
	abstract = {Linear and nonlinear fetal heart rate (FHR) indices, namely mean FHR, interval index (II), very low, low and high frequencies, approximate (ApEn) and sample entropy (SampEn), were computed, immediately before delivery, in the initial and final FHR tracing segments, from 48 normal, 10 mildly acidemic and 10 moderate-to-severely acidemic fetuses. Progression of labor was associated with a significant increase in linear frequency domain indices whereas nonlinear indices were significantly decreased. Moderate-to-severe fetal acidemia was associated with a significant decrease in nonlinear indices. The best discrimination between moderate-to-severe acidemic fetuses and the remaining cases was obtained combining II and ApEn(2,0.15), with a specificity of 71\% and a sensitivity of 80\%. These findings support the hypothesis of increased autonomic nervous system activity in the final minutes of labor and of decreased central nervous system activity, both in the final minutes of labor and in moderate-to-severe acidemic fetuses. {\textcopyright} International Federation for Medical and Biological Engineering 2006.},
	keywords = {acidemia, Acidosis, Acids, article, autonomic nervous system, Biological materials, Cardiology, Central nervous system, clinical article, controlled study, delivery, Delivery, Obstetric, Discriminant Analysis, disease severity, entropy, Fetal Diseases, Fetal heart rate, Fetal heart rate (FHR), Fetal monitoring, fetus, fetus heart rate, Frequency domain analysis, Heart Rate, Fetal, human, Humans, hypothesis, labor, Linear and nonlinear indices, linear system, Neurology, newborn, nonlinear system, Prenatal Care, Second stage of labor, sensitivity and specificity, Severity of Illness Index},
	isbn = {01400118 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33749566759\&partnerID=40\&md5=88f9959edd8363f90b13742d0ce5221b},
	author = {Gon{\c c}alves, H. and Rocha, A.P. and Ayres-de-Campos, D. and Bernardes, J.}
}
@article {2457,
	title = {Neural networks trained with the EEM algorithm: Tuning the smoothing parameter},
	journal = {WSEAS Transactions on SystemsWSEAS Trans. Syst.},
	volume = {4},
	year = {2005},
	note = {Cited By (since 1996): 3Export Date: 21 November 2012Source: ScopusLanguage of Original Document: EnglishCorrespondence Address: Santos, J.M.; Intituto de Engenharia Biom{\'e}dica, Porto, Portugal; email: jms@isep.ipp.ptReferences: Erdogmus, D., Principe, J., "An Error-Entropy Minimization Algorithm for Supervised Training of Nonlinear Adaptive Systems" (2002) Trans. On Signal Processing, 50 (7), pp. 1780-1786;Santos, J.M., Alexandre, L.A., Marques de S{\'a}, J., "The error entropy minimization algorithm for neural network classification" (2004) Proceedings of the 5th International Conference on Recent Advances in Soft Computing, pp. 92-97. , A. Lofti, Ed. Nottingham Trent University; 
Santos, J.M., Marques de S{\'a}, J., Alexandre, L.A., Sereno, F., "Optimization of the error entropy minimization algorithm for neural network classification" (2004) Intelligent Engineering Systems Through Artificial Neural Networks, 14, pp. 81-86. , C.H. Dagli, A.L. Buczak, D.L. Enke, M.J. Embrechts, and O. Ersoy, Eds., ASME Press; 
Erdogmus, D., Principe, J., "Entropy Minimization Algorithm for Neural Networks" (2001) Proceedings of the Intl. Joint Conf. on Neural Networks, pp. 3003-3008; 
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Silverman, B.W., (1986) Density Estimation for Statistics and Data Analisys, 26. , Chapman \& Hall; 
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Jacobs, R., Jordan, M., Nowlan, S., Hinton, G., "Adaptive mixtures of local experts" (1991) Neural Computation, pp. 79-87
},
	month = {2005///},
	pages = {295 - 299},
	abstract = {The training of Neural Networks and particularly Multi-Layer Perceptrons (MLP{\textquoteright}s) is made by minimizing an error function usually known as "cost function". In our previous works, we apply the Error Entropy Minimization (EEM) algorithm in classification and its optimized version using, as cost function, the entropy of the errors between the outputs and the desired targets of the neural network. One of the difficulties in implementing the EEM algorithm is the choice of the smoothing parameter, also known as window size, in the Parzen Window probability density function estimation for the computation of the entropy and its gradient. We present here a formula yielding the value of the smoothing parameter, depending on the number of data samples and on the neural network output dimension. Several experiments with real data sets were made in order to show the validity of the proposed formula.},
	keywords = {Cost function, entropy, Error entropy minimization (EEM) algorithm, Learning algorithms, Learning systems, Neural networks, Optimization, Parzen, Probability density function, Smoothing parameter},
	isbn = {11092777 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-21844450579\&partnerID=40\&md5=31c652daee111a68194cd4f006d7ca7b},
	author = {Santos, J.M. and Marques de S{\'a}, J. and Alexandre, L.A.}
}
@article {2528,
	title = {Wettability and surface charge of Si                    3N
                    4-bioglass composites in contact with simulated physiological liquids
},
	journal = {BiomaterialsBiomaterials},
	volume = {23},
	year = {2002},
	note = {Cited By (since 1996): 18Export Date: 21 November 2012Source: ScopusCODEN: BIMADdoi: 10.1016/S0142-9612(02)00155-2Language of Original Document: EnglishCorrespondence Address: Santos, J.D.; Laborat{\'o}rio de Biomateriais, Inst. de Engenharia Biomedica (INEB), Rua do Campo Alegre, 823, 4150 Porto, Portugal; email: jdsantos@fe.up.ptChemicals/CAS: Serum Albumin, Bovine; Silicon Compounds; silicon nitride, 12033-89-5References: Von Recum, A.F., (1999) Handbook of biomaterials evaluation: scientific, technical, and clinical testing of implant materials, 2nd. ed., , Hemisphere Pub;Davies, J.E., The importance and measurement of surface charge species in cell behaviour at the biomaterial interface (1998) Surface characterisation of biomaterials, 6, pp. 219-234. , Ratner, editor. Progress in Biomedical Engineering. Amsterdam: Elsevier; 
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Dewez, J.L., Schneider, Y.J., Rouxhet, P.G., Coupled influence of substratum hydrophilicity and surfactant on epithelial cell adhesion (1996) J Biomed Mater Res, 30, pp. 373-383; 
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Anselme, K., Osteoblast adhesion on biomaterials (2000) Biomaterials, 7, pp. 667-681; 
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Nishizawa, K., Toriyama, M., Effects of the surface wettability and zeta potential of bioceramics on the adhesiveness of anchorage-dependent animal-cells (1993) J Ferment Bioeng, 6, pp. 435-437; 
Suzuki, T., Nishizawa, K., Yokogawa, Y., Kameyama, T., Time-dependent variation of the surface structure of bioceramics in tissue culture medium and the effect on adhesiveness of cells (1996) J Ferment Bioeng, 3, pp. 226-232; 
Parfitt, G.D., (1967) Principles of the colloidal state, , London: Royal Institute of Chemistry; 
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Amaral, M., Lopes, M.A., Silva, R.F., Santos, J.D., Densification route and mechanical properties of Si3N4-bioglass biocomposites (2002) Biomaterials, 23, pp. 857-862; 
Santos, J.D., Amaral, M., Oliveira, S.M., Lopes, M.A., Silva, R.F., Silicon nitride-bioglass {\textregistered} composite for biomedical applications (2001) Key Eng Mater, 192-195, pp. 589-592; 
Krajewski, A., Piancastelli, A., Malavolti, R., Albumin adhesion on ceramics and correlation with their Z-potential (1998) Biomaterials, 19, pp. 637-641; 
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Vogler, E.A., Interfacial chemistry in biomaterials science (1993) Wettability, surfactant science series, 49, pp. 183-250. , Berg J.C., editor, Chapter 4; 
Lopes, M.A., Monteiro, F.J., Santos, J.D., Serro, A.P., Saramago, B., Hydrophobicity, surface tension, and zeta potential measurements of glass-reinforced hydroxyapatite composites (1999) J Biomed Mater Res, 45, pp. 370-375; 
Ferraz, M.P., Monteiro, F.J., Serro, A.P., Saramago, B., Gibson, I.R., Santos, J.D., Effect of chemical composition on hydrophobicity and zeta potential of plasma sprayed HA/CaO-P 2O 5 glass coatings (2001) Biomaterials, 22, pp. 3105-3112; 
Agathopoulos, S., Nikolopoulos, P., Wettability and interfacial interactions in bioceramic-body-liquid systems (1995) J Biomed Mater Res, 29, pp. 421-429; 
Agathopoulos, S., Nikolopoulos, P., Determination of the energy of the interactions between oxides and biological liquids (1995) Fourth Euro ceramics, 8, pp. 319-324. , A. Ravaglioli; 
Wang, L., Sigmund, W., Aldinger, F., Systematic approach for dispersion of silicon nitride powder in organic media: I, surface chemistry of the powder (2000) J Am Ceram Soc, 4, pp. 691-696; 
Galassi, C., Bertoni, F., Water-based Si 3N 4 suspensions: Part I effect of processing routes on the surface chemistry and particle interactions (2000) J Mater Res, 1, pp. 155-163; 
Haynes, C.A., Norde, W., Globular proteins at solid/liquid interfaces (1994) Colloids Surf B: Biointerfaces, 2, pp. 517-566
},
	month = {2002///},
	pages = {4123 - 4129},
	abstract = {Wettability and surface charge studies were performed on a novel Si                        3N
                        4-30wt\% bioglass biocomposite. Contact angle and surface tension variation with time were determined at 25{\textdegree}C, respectively, by the sessile and pendant drop techniques, for distinct testing liquids: water, diiodomethane, simulated body fluid (SBF) and bovine serum albumin (BSA) dissolved in SBF solution. This biocomposite revealed a hydrophilic character (θ=26.6{\textpm}2.0{\textdegree}) and a surface tension value (66.6mJm
},
	keywords = {3N, 4-bioglass composites, Adsorption, aqueous solution, article, Biocomposites, Biomaterials, body fluid, Body fluids, Bovinae, bovine serum albumin, cation, Cattle, ceramics, chemistry, conformation, Conformations, Contact angle, electrochemistry, enthalpy, entropy, glass, Glass ceramics, Hydrogen-Ion Concentration, hydrophilicity, liquid, methyl iodide, methylene iodide, pH, Physiological models, priority journal, Serum Albumin, Serum Albumin, Bovine, Si, Silicon compounds, silicon derivative, Silicon nitride, simulation, Support, Non-U.S. Gov{\textquoteright}t, Surface charge, Surface chemistry, Surface Properties, surface property, Surface tension, temperature, time, unclassified drug, Water, wettability, Wetting, Zeta potential},
	isbn = {01429612 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0035988674\&partnerID=40\&md5=25e46c5fc9e81d6c3655190ab01b33ea},
	author = {Amaral, M. and Lopes, M.A. and Santos, J.D. and Silva, R.F.}
}
