Mapping out the glassy landscape of a mesoscopic elastoplastic model.

We develop a mesoscopic model to study the plastic behavior of an amorphous material under cyclic loading. The model is depinning-like and driven by a disordered thresholds dynamics that is coupled by long-range elastic interactions. We propose a simple protocol of "glass preparation" that allows us to mimic thermalization at high temperatures as well as aging at vanishing temperature. Various levels of glass stabilities (from brittle to ductile) can be achieved by tuning the aging duration. The aged glasses are then immersed into a quenched disorder landscape and serve as initial configurations for various protocols of mechanical loading by shearing. The dependence of the plastic behavior upon monotonous loading is recovered. The behavior under cyclic loading is studied for different ages and system sizes. The size and age dependence of the irreversibility transition is discussed. A thorough characterization of the disorder-landscape is achieved through the analysis of the transition graphs, which describe the plastic deformation pathways under athermal quasi-static shear. In particular, the analysis of the stability ranges of the strongly connected components of the transition graphs reveals the emergence of a phase-separation like process associated with the aging of the glass. Increasing the age and, hence, the stability of the initial glass results in a gradual break-up of the landscape of dynamically accessible stable states into three distinct regions: one region centered around the initially prepared glass phase and two additional regions characterized by well-separated ranges of positive and negative plastic strains, each of which is accessible only from the initial glass phase by passing through the stress peak in the forward and backward, respectively, shearing directions.

Rheology and shear band suppression in particle and chain mixtures.

Using numerical simulations we consider an amorphous particle mixture which exhibits shear localization, and find that the addition of even a small fraction of chains strongly enhances the material strength, creating pronounced overshoot features in the stress-strain curves. The strengthening occurs in the case where the chains are initially perpendicular to the shear direction, leading to a suppression of the shear band. This also leads to stiffening effects that are typical of polymeric systems. For large strain, the chains migrate to the region where a shear band forms, resulting in a stress drop. For chains larger than the linear system size we find oscillatory behavior, which does not resemble polymeric systems since the second stress peak is larger than the first. Our results are also useful for providing insights into methods of controlling and strengthening granular materials against failure.

Convulsive attacks due to antidepressant drug overdoses: case reports and discussion.

Antidepressant drug overdoses have been reported to induce seizures, but the etiology of this phenomenon is still unclear. Recently we treated three patients who suffered from epileptic seizures after acute overdoses of three antidepressant drugs: (a) Dibenzepin HCl (Noveril), (b) Maprotiline HCl (Ludiomil), and (c) Clorimipramine (Anafranil). After a review of the pertinent literature, the possible role of antidepressant drugs in the genesis of epileptic seizures is discussed.

Pain and hyperpathia in pontine haemorrhage.

A 56-year-old man had acute onset of left sided weakness, spontaneous pain and hyperpathia in the left limbs. CT demonstrated a small pontine haemorrhage, in the floor of the fourth ventricle.

Therapeutic potentials of centrally acting dopamine and alpha 2-adrenoreceptor agonists.

The antiparkinsonian activity of several dopamine agonists was investigated in an animal model and clinically in parkinsonian patients. The semisynthetic ergoline, pergolide, the partial ergoline, LY 141865 and the 8-alpha-aminoergoline, CU 32-085 were found to be effective antitremor agents in monkeys with ventromedial tegmental lesions. The administration of pergolide or LY 141865 results in a relief of tremor with a concomitant occurrence of severe abnormal involuntary movements, while the administration of CU 32-085 results in a relief of tremor with the occurrence of only minor abnormal involuntary movements. Clinical studies have revealed that pergolide is an effective drug in patients with advanced Parkinson's disease, and it reduces the "on-off" phenomena. The possible regulation of dopamine neurotransmission by the norepinephrine neuronal systems was reviewed. Preliminary data suggest that clonidine may interact with presynaptic dopamine receptors.

The behavioral effect of salbutamol (a beta-adrenergic receptor stimulant) on reserpine- and propranolol-treated rats.

Reserpine- and propranolol-treated rats were given salbutamol, a beta-adrenergic stimulant, intra-peritoneally in an open control study. The results suggest that salbutamol has a therapeutic effect on the depressive behavior of reserpine- and propranolol-treated rats.

CSF renin activity in hypertensive and normotensive patients.

CSF samples of hypertensive and normotensive matched groups were assayed and compared for renin activity (RA). The measurements yield low values of RA in both groups without significant difference between them. There was no correlation between the CSF level of RA of each patient and his own concomitant plasma renin activity (PRA). Although the presence of RA in the CSF was confirmed in this study, no direct correlation seems to exist between it values and the elevated blood pressure; therefore, the pathophysiological significance of the renin-angiotensin system in the CSF and its relation to centrally generated hypertension remains questionable.

[Effect of bromocriptine on secretion of the enzyme dopamine-B-hydroxylase (DBH) in patients with Parkinson's disease]. / L'effetto della Bromocriptina sulla secrezione dell'enzima dopamina-B-idrossilasi (DBH) nei malati de Parkinson.

The activity of DBH enzyme was measured in plasma of 7 non treated patients suffering from Parkinson's disease; a 10 mg dose of Bromocryptine was administered per os to these patients. Attained results were compared to the enzyme activity in a group of control of 7 healthy individuals. It was pointed out that in patients suffering from Parkinson's disease the decrease of DBH level in plasma after the administration of Bromocryptine was of 32.6% +/- SE 4.4% while in the group of control the decrease was only of 15% +/- SE 4.9%. This decrease in the plasmatic level of the enzyme after the administration of Bromocryptine should be due to the marked antagonistic activity of Bromocryptine on pre-synaptic dopaminergic receptors. This should mean that peripheric pre-synaptic dopaminergic receptors are involved in the physiopathology of Parkinson's disease.