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Biomedical subjects

G Nardulli

Publications and source records attributed to G Nardulli.

15 recordsLinked to original sources
PubMed2001

Diluted neural networks with adapting and correlated synapses.

We consider the dynamics of diluted neural networks with clipped and adapting synapses. Unlike previous studies, the learning rate is kept constant as the connectivity tends to infinity: the synapses evolve on a time scale intermediate between the quenched and annealing limits and all orders of synaptic correlations must be taken into account. The dynamics is solved by mean-field theory, the order parameter for synapses being a function. We describe the effects, in the double dynamics, due to synaptic correlations.

Biophysical Phenomena↗
PubMed1999

Chaos in neural networks with a nonmonotonic transfer function.

Time evolution of diluted neural networks with a nonmonotonic transfer function is analytically described by flow equations for macroscopic variables. The macroscopic dynamics shows a rich variety of behaviors: fixed-point, periodicity, and chaos. We examine in detail the structure of the strange attractor and in particular we study the main features of the stable and unstable manifolds, the hyperbolicity of the attractor, and the existence of homoclinic intersections. We also discuss the problem of the robustness of the chaos and we prove that in the present model chaotic behavior is fragile (chaotic regions are densely intercalated with periodicity windows), according to a recently discussed conjecture. Finally we perform an analysis of the microscopic behavior and in particular we examine the occurrence of damage spreading by studying the time evolution of two almost identical initial configurations. We show that for any choice of the parameters the two initial states remain microscopically distinct.

Models, Theoretical↗
PubMed1994

Preeclampsia and calcium adenosine triphosphatase activity of red blood cell ghosts.

OBJECTIVE: The current work was undertaken to study the calcium adenosine triphosphatase activity of red blood cell membranes from pregnant women with preeclampsia. STUDY DESIGN: Six normotensive and six preeclamptic pregnant women at 38 to 39 weeks of gestation were studied. The diagnosis of preeclampsia was made on the basis of blood pressure (> 140/90 mm Hg), proteinuria (> 0.5 gm of urinary protein per day), or edema. Hemoglobin-free red blood cell ghosts were prepared from the heparinized blood samples and were used to determine the calcium adenosine triphosphatase activity. RESULTS: It was found that the calcium adenosine triphosphatase activity of preeclamptic women is diminished by about 50% compared with that of normotensive pregnant women. CONCLUSION: A diminution of the calcium adenosine triphosphatase activity of erythrocytes in preeclampsia might be an indication that the in vivo activity of the calcium pump of these cells is diminished, which could, in turn, drive the cells to increase their cytoplasmic free calcium concentration.

Adult↗
PubMedDate not supplied

[Value of three-dimensional measurement of the caudate lobe in the diagnosis of liver cirrhosis by ultrasound].

To assess the changes of the caudate lobe in the sonographic diagnosis of liver cirrhosis, 96 patients were studied at the Hospital Vargas de Caracas. 27 with histologically proved cirrhosis. 43 with other disease (30 no related with liver and 13 with hepatic disease without cirrhosis, and 26 patients without clinical evidence of liver disease. The longitudinal (CL), transverse (CT), and anteroposterior (CAP) diameters of the caudate lobe and the transverse diameter of the right lobe (RL) were measured and one, two and three dimensional caudate lobe, indexes and ratios were calculated. The analysis of these criteria revealed that the ratio of the three dimensional caudate index (C13) to the right lobe diameter (C13)/RL = iCL x CT x CAP/RL was superior to all other calculated criteria.

Adolescent↗
PubMedDate not supplied

[Use of polyethylene glycol in the treatment of puerperal constipation].

We evaluated the efficiency of polyethylene glycol at low dosage as a treatment for constipation in the puerperium. A prospective, open label and control study was performed in 225 puerpery patients. We observed a 94.7% of study group patients and a 10.7% of a control group patients had a evacuation in the first 48 hours, (p < 0.01). Decreased consistency of the stools was seen in the PEG group (74.3%). According to our findings, low doses of PEG were useful and safe as a treatment for constipation in the puerperium, without side effects.

Adult↗