Biomedical subjects

P Arena

Publications and source records attributed to P Arena.

6 recordsLinked to original sources

PubMed2000

Chaotic behavior in noninteger-order cellular neural networks

In this paper, a simple system showing chaotic behavior is introduced. It is based on the well-known concept of cellular neural networks (CNNs), which have already given good results in generating complex dynamics. The peculiarity of the CNN model consists in the fact that it replaces the traditional first-order cell with a noninteger-order one. The introduction of the fractional cell, with a suitable choice of the coupling parameters, leads to the onset of chaos in a simple two-cell system. A theoretical approach, based on the harmonic balance theory, has been used to investigate the existence of chaos. A circuit realization of the proposed fractional two-cell chaotic CNN is reported and the corresponding strange attractor is also shown.

Journal Article↗

PubMed1999

Concerns about breast cancer and relations to psychosocial well-being in a multiethnic sample of early-stage patients.

Much work on psychosocial sequelae of breast cancer has been guided by the assumption that body image and partner reaction issues are focal. In a tri-ethnic sample of 223 women treated for early-stage breast cancer within the prior year, the authors assessed a wider range of concerns and relations to well-being. Strongest concerns were recurrence, pain, death, harm from adjuvant treatment, and bills. Body-image concerns were moderate; concern about rejection was minimal. Younger women had stronger sexual and partner-related concerns than older women. Hispanic women had many stronger concerns and more disruption than other women. Life and pain concerns and sexuality concerns contributed uniquely to predicting emotional and psychosexual disruption; life and pain concerns and rejection concerns contributed to predicting social disruption. In sum, adaptation to breast cancer is a process bearing on several aspects of the patient's life space.

Adaptation, Psychological↗

PubMed1996

[Condition at birth of a group of neonates suffering from intrauterine growth retardation].

The authors monitored a group of pregnant patients who presented fetuses with intrauterine retarded growth syndrome. Only pregnant women who were monitored until the time of birth were included in the study. Patients were divided into three groups depending on the week of gestation in which birth occurred and two subgroups were identified within each group depending on the type of birth. Three perinatal deaths (5%) were recorded in the group of patients at risk, a percentage that is comparable to data reported in the literature, in spite of careful monitoring (flow metric and cardiographic). Cesarian section was resorted to in 86.4% of cases and 67.7% of neonates presented decisively "poor" conditions at birth.

Female↗

PubMed1996

Multi-layer neural network analysis of cerebrospinal fluid pressure patterns in idiopathic normal-pressure hydrocephalus.

The cerebrospinal fluid (CSF) pressure patterns have been reported as one of the most relevant indexes for the diagnosis and treatment of idiopathic normal-pressure hydrocephalus (INPH). Forty consecutive patients coming from our observations with the classic Hakim's triad underwent continuous CSF pressure monitoring via lumbar puncture for at least 12 hours. Twenty-eight patients were diagnosed as having INPH and underwent CSF shunt. A multi-layer neural network (perceptron) was employed to study the pressure patterns in order to try an alternative classification to the "expert" neurosurgeon one. Differences between expert and neural network classifications were indeed observed. Such differences may depend on the small group studied or on the inadequacy of CFS pressure patterns in correctly individuating those INPH patients who benefit from shunt surgery. The authors think that neural network processing of INPH could add relevant information to select the "responder" patients to surgery: in fact neural networks represent a powerful methodology for aiding the expert to select the proper choice on the basis of "what learnt" by the networks themselves.

Cerebrospinal Fluid↗

PubMed1995

Multilayer perceptrons to approximate complex valued functions.

In this paper the approximation capabilities of different structures of complex feedforward neural networks, reported in the literature, have been theoretically analyzed. In particular a new density theorem for Complex Multilayer Perceptrons with complex valued non-analytical sigmoidal activation functions has been proven. Such a result makes Multilayer Perceptrons with complex valued neurons universal interpolators of continuous complex valued functions. Moreover the approximation properties of superpositions of analytic activation functions have been investigated, proving that such combinations are not dense in the set of continuous complex valued functions. Several numerical examples have also been reported in order to show the advantages introduced by Complex Multilayer Perceptrons in terms of computational complexity with respect to the classical real MLP.

Neural Networks, Computer↗

PubMed1978

Sex liability to single structural defects.

Forty-two of 52 single, localized defects of morphogenesis showed a nonrandom predeliction to one sex. For some of these malformations, the sex liability may be explained on the basis of normal anatomic or hormonal differences between the sexes. For example, the male excess of "prune belly" or triad syndrome is considered due to the fact that most cases are secondary to obstruction in the penile urethra, and the male excess of pyloric stenosis is hypothesized as being secondary to the muscle hypertrophying effect of testosterone in the male neonate. The sex differences for most of the defects suggest that genes on the X and/or Y chromosome exert a role in morphogenesis that extends well beyond the development of sex-related structures.

Congenital Abnormalities↗