A review on some classes of algebraic systems

ABSTRACT

In this paper, we review some algebraic control system. Precisely, linear and bilinear systems on Euclidean spaces and invariant and linear systems on Lie groups. The fourth classes of systems have a common issue: to any class, there exists an associated subgroup. From this object, we survey the controllability property. Especially, from those coming from our contribution to the theory.     

Fast Positive Feedback Between the Adrenocortical Stress Response and a Brain Mechanism Involved in Aggressive Behavior.

Aggressive behavior induces an adrenocortical stress response, and sudden stressors often precipitate violent behavior. Experiments in rats revealed a fast, mutual, positive feedback between the adrenocortical stress response and a brain mechanism controlling aggression. Stimulation of the aggressive area in the hypothalamus rapidly activated the adrenocortical response, even in the absence of an opponent and fighting. Hypothalamic aggression, in turn, was rapidly facilitated by a corticosterone injection in rats in which the natural adrenocortical stress response was prevented by adrenalectomy. The rapidity of both effects points to a fast, mutual, positive feedback of the controlling mechanisms within the time frame of a single conflict. Such a mutual facilitation may contribute to the precipitation and escalation of violent behavior under stressful conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A new mobile robot control approach via fusion of control signals.

This paper proposes an alternative approach to address the problem of coordinating behaviors in mobile robot navigation: fusion of control signals. Such approach is based on a set of two decentralized information filters, which accomplish the data fusion involved. Besides these two fusion engines, control architectures designed according to this approach also embed a set of different controllers that generate reference signals for the robot linear and angular speeds. Such signals are delivered to the two decentralized information filters, which estimate suitable overall reference signals for the robot linear and angular speeds, respectively. Thus, the background for designing such control architectures is provided by the nonlinear systems theory, which makes this approach different from any other yet proposed. This background also allows checking control architectures designed according to the proposed approach for stability. Such analysis is carried out in the paper, and shows that the robot always reaches its final destination, in spite of either obstacles along its path or the environment layout. As an example, a control architecture is designed to guide a mobile robot in an experiment, whose results allows checking the good performance of the control architecture and validating the design approach proposed as well.     

Scale-effects on mean and standard deviation of the mechanical properties of condensed matter: an energy-based unified approach

The size effects on the mean values of the mechanical properties of condensed matter and on the related variances are analysed by means of a unified approach based on the multiscale character of energy dissipation. In particular, the scaling law for fragmentation energy density is obtained taking into account the self-similarity of fragments. It is based on a generalization of the three classical comminution laws that has been performed to evaluate the energy dissipation, computing volume and surface area of the particles for one- two- and three-dimensional fragmented objects. The result is general and can be applied to different fractal energy dissipation mechanisms, e.g., plasticity. Based on this approach, the scaling laws for mean and standard deviation values of the main mechanical properties of materials can be derived, like Young's and shear elastic moduli, ultimate normal and shear stresses and strains, fracture energy and toughness.     

Morphological changes induced by colchicine in the chick optic cup in early stages of development. A stereological study

In this study chick embryo optic cups at HH stage 13 of development were analyzed under normal conditions and after inoculation with colchicine for 1, 2, 4, and 8 h. Several changes were seen after these periods of treatment: 1) modifications of the structure, with thicker regions in the cup and a general decrease in the total volume according to the duration of exposure to the drug (about 4 times less than normal, 5,035 x 10(3) microns 3 vs 1,334 x 10(3) microns 3 after 8 h of treatment); 2) enlargement of the ventricular cavity and its closure, due to failure of approximation of retinal and pigmentary layers; 3) failure of lens development, with delay and impairment of pit formation and deformation of all structures; lens volume was less than normal (about 4 times less, 2,148 x 10(3) microns 3 vs 658 x 10(3) microns 3 after 8 h of treatment); 4) a general segregation of the cells making up the structure, principally in the more active proliferating zones. The local alterations found are described.     

Diagnostic value of the study of caffeine elimination in chronic liver diseases

Data from the past few years have shown that as caffeine metabolizes solely in the liver, caffeine elimination can serve as a liver function test. We have collected data by monitoring 40 persons with liver diseases (11 chronic alcoholic hepatitis, 24 liver cirrhosis, 5 non-cirrhotic liver disease). Eight subjects served as controls. The patients with liver cirrhosis were classified according to the Child--Pugh scoring system. To determine caffeine elimination blood samples were collected before and at 3, 6, 9 and 12 hours after oral administration of 0.2 g caffeine. Fasting serum caffeine concentration and concentration 12 hours after administration, serum clearance, half life, peak concentration and volume of distribution have been compared. The respective values measured in patients with non-cirrhotic liver diseases did not differ significantly from the controls. The disappearance of caffeine was significantly decreased in cirrhotics. Our results demonstrated a good correlation between impairment of caffeine elimination and assessment of severity of liver disease by the Child--Pugh classification. Measuring serum levels in samples taken 12 hours after caffeine administration is a simple and useful method in the diagnosis of liver diseases at cirrhotic stage.     

Low birth weight as an additional indication for chromosomal analysis

INTRODUCTION: Even though there are few epidemiological studies evaluating the birth weights of different groups of malformed babies with chromosomal abnormalities, it is widely known that infants with trisomy 18, and to a lesser degree those with trisomy 13 and other chromosomal alterations, have low birth weights. PATIENTS AND METHODS: In this study we present the analysis of the birth weights and gestational ages of a large sample of babies (23,155 malformed and a similar number of nonmalformed babies), separating the different groups of chromosomal anomalies and comparing the weight in the clinical groups of malformed infants. RESULTS: Most of the groups with chromosomal abnormalities present lower birth weights in comparison to the other groups. CONCLUSIONS: The results of our study support the conclusion that the relationship between chromosomal alterations and low birth weight is sufficiently important that such a low birth weight in children with minor or major anomalies should be considered as one more indication to perform chromosomal analysis.     

Retinal vessel dilatation and elongation precedes diabetic macular oedema

Rolandic discharge (RD), noted in the electroencephalography (EEG) of patients with benign epilepsy in childhood with centrotemporal spikes (BECCT) has several unique features. One feature is that the amount or frequency of RDs does not correlate well with the incidence of seizures in BECCT although it is a key finding in the diagnosis of this epileptic syndrome. In this study, we examined the efficacy of antiepileptic drugs focusing on the disappearance of RDs in relationship with seizure control. Forty patients with BECCT who were not medically treated prior to this study were randomly sorted into three groups. Twenty patients were assigned for clonazepam (CZP) treatment, 10 patients for valproate (VPA) and the remaining 10 patients for carbamazepine (CBZ). Each drug was administered for 4 consecutive weeks. EEGs were recorded twice during the study, before and 4 weeks after the medication trial. The effects of each treatment on RDs were assessed. RDs disappeared in 15 of the 20 cases treated with CZP (75%) within 4 weeks while the same was observed in only one of the 10 cases treated with VPA (10%). CBZ failed to demonstrate any effect on RD. In the group treated with CZP, there were no differences in seizure incidence, seizure type and blood concentration of CZP between the patients whose RDs disappeared and those whose RDs remained.