ABSTRACT
In this paper we study the propagation of acoustic waves in a one-dimensional medium with a short range correlated elasticity distribution. In order to generate local correlations we consider a disordered binary distribution in which the effective elastic constants can take on only two values, η(A) and η(B). We add an additional constraint that the η(A) values appear only in finite segments of length n. This is a generalization of the well-known random-dimer model. By using an analytical procedure we demonstrate that the system displays n - 1 resonances with frequencies ω(r). Furthermore, we apply a numerical transfer matrix formalism and a second-order finite-difference method to study in detail the waves that propagate in the chain. Our results indicate that all the modes with ω ≠ ω(r) decay and the medium transmits only the frequencies ω(r).
ABSTRACT
We numerically study the propagation of acoustic waves in a one-dimensional medium with a scale-free long-range correlated elasticity distribution. The random elasticity distribution is assumed to have a power spectrum S(k) â¼ 1/k(α). By using a transfer-matrix method we solve the discrete version of the scalar wave equation and compute the localization length. In addition, we apply a second-order finite-difference method for both the time and spatial variables and study the nature of the waves that propagate in the chain. Our numerical data indicate the presence of extended acoustic waves for a high degree of correlations. In contrast with local correlations, we numerically demonstrate that scale-free correlations promote a stable phase of free acoustic waves in the thermodynamic limit.
ABSTRACT
We have studied learning, memory and cortical cholinergic parameters after oral administration of 20% v/v ethanol solution to male Fisher rats for 6 months. A group of rats were trained to behave efficiently in an eight-arm radial maze and after that split into two subgroups submitted to ethanol or control treatment. Ethanol-treated rats had more difficulty in relearning the same task 1 year later, compared to ethanol-untreated rats (control). Differences in working memory performance were found, but only in the first 10 training sessions. Another group of rats, which had not been pretrained, was also split into two subgroups submitted to ethanol or control treatment. After that, these rats were trained in the radial maze task for the first time. No significant difference was found between the reference memory performance of the untreated subgroup and the treated one. These two subgroups did not significantly differ in their working memory performance either. Moreover, there were no significant differences between treated and control subjects in the following biochemical brain cortical parameters: in vitro acetylcholinesterase (AChE) activity, and stimulated acetylcholine (ACh) release. This work presents an experimental design that allows assessment of remote memory performance after ethanol chronic consumption and shows that the experimental subject is able to retain the behaviors learned 1 year before. It was concluded that chronic ethanol treatment may cause retrograde amnesia, which does not seem to be linked with a cortical cholinergic deficit.
Subject(s)
Alcohol Drinking/psychology , Cerebral Cortex/drug effects , Memory Disorders/chemically induced , Memory Disorders/psychology , Parasympathetic Nervous System/drug effects , Space Perception/drug effects , Acetylcholine/metabolism , Acetylcholinesterase/metabolism , Animals , Body Weight/drug effects , Brain Chemistry/drug effects , Cerebral Cortex/enzymology , Cerebral Cortex/metabolism , Ethanol/blood , Male , Maze Learning/drug effects , Parasympathetic Nervous System/enzymology , Parasympathetic Nervous System/metabolism , Rats , Rats, Inbred F344ABSTRACT
Hereditary fructose intolerance (HFI) is a rare autosomal recessive, metabolic disorder, that results from a deficiency of aldolase B (fructose-biphosphate aldolase) in the liver, kidney and intestine. Recent molecular studies have identified the mutation A149P in most European patients. We describe the first case of HFI with molecular analysis in a Portuguese child, presenting the same mutation of the aldolase B gene. The role of molecular studies in the diagnosis of HFI risk patients and their families is emphasized.
Subject(s)
Fructose Intolerance/diagnosis , Alleles , Biopsy , Fructose Intolerance/diet therapy , Fructose Intolerance/genetics , Fructose Intolerance/metabolism , Humans , Infant , Liver/enzymology , Liver/pathology , Male , MutationABSTRACT
The authors try to identify the prejudices and traditions in nursing, thinking about the maintenance of the myths, stigmas and stereotypes throughout its history, facing the GADAMER's ideas.
Subject(s)
History of Nursing , Prejudice , Female , History, 20th Century , Humans , Women's Rights/historyABSTRACT
This paper is an explorative--descriptive study trying to reach the following objectives: to know the interpersonal relationship between the elder and his relatives and verify what is the elder's perception about the elderly process. The authors interviewed 20 persons (10 men and 10 women) after 60 years of age. The results showed probably will give some guidance for the nursing assistance to the elderly population.
