Diffusion and Correlations in Lattice Gas Automata

We present an analysis of diffusion in terms of the spontaneous density fluctuations in a non-thermal two-species fluid modeled by a lattice gas automaton. The power spectrum of the density correlation function is computed with statistical mechanical methods, analytically in the hydrodynamic limit, and numerically from a Boltzmann expression for shorter time and space scales. In particular we define an observable -- the weighted difference of the species densities -- whose fluctuation correlations yield the diffusive mode independently of the other modes so that the corresponding power spectrum provides a measure of diffusion dynamics solely. Automaton simulations are performed to obtain measurements of the spectral density over the complete range of wavelengths (from the microscopic scale to the macroscopic scale of the automaton universe). Comparison of the theoretical results with the numerical experiments data yields the following results: (i) the spectral functions of the lattice gas fluctuations are in accordance with those of a classical `non-thermal' fluid; (ii) the Landau-Placzek theory, obtained as the hydrodynamic limit of the Boltzmann theory, describes the spectra correctly in the long wavelength limit; (iii) at shorter wavelengths and at moderate densities the complete Boltzmann theory provides good agreement with the simulation data. These results offer convincing validation of lattice gas automata as a microscopic approach to diffusion phenomena in fluid systems.Comment: 9 pages (revtex source), 12 Postscript figure

A Rare, Late Complication after Automated Implantable Cardioverter-Defibrillator Placement

This article describes an interesting case of automated implantable cardioverter defibrillator (AICD) extrusion fifteen months after implantation. The case report is followed by a discussion of the causes and treatment of skin erosion following pacemaker/AICD insertion

Protecting Directors and Officers from Liability Arising from Aggressive Earnings Management

A lingering topic in corporate governance is whether corporate directors should be protected against shareholder lawsuits and whether such protection reduces the incentives of directors to monitor appropriately the behaviour of corporate officers. To achieve this goal, we examine whether corporations whose corporate managers’ wealth is protected under a directors’ and officers’ liability insurance policy (D&O insurance hereafter) are more to report accounting results aggressively. Using discretionary accruals as our measure of accounting aggressiveness, the results in our paper suggest that the magnitude of discretionary accruals has no real impact on the demand for D&O insurance, be it on the decision to purchase insurance or on the amount of limit chosen. The positivity of discretionary accruals appears, however, to have an impact on the decision to purchase insurance. Surprisingly, although these insurance policies protect directors and officers in the event they make a “mistake” in their role as representatives of the company, directors do not seem to see this as an invitation to be a little less careful when overseeing the firm’s accounting practices. Un sujet qui demeure d’actualité quand on pense à la gouvernance des entreprises est le niveau de protection auquel les dirigeants devraient avoir droit en cas de poursuite par les actionnaires. Pour atteindre ce but, nous examinons s’il y a un lien entre la gestion agressive des courus discrétionnaires et la demande d’assurance de la responsabilité civile des administrateurs et dirigeants d’entreprise (ARCAD ci-après). Nous trouvons dans la présente étude que la taille des courus ne semble avoir aucun impact sur la demande d’assurance, que ce soit le fait même d’avoir un contrat ou la limite de la police. Le fait que les courus soient positifs semble toutefois avoir un impact sur le fait que les entreprises possèdent une ARCAD ou non. Nous demeurons perplexes de voir que même si l’ARCAD protège les dirigeants contre le coût de poursuites au civile, ces mêmes dirigeants ne voient pas cela comme une invitation au laxisme dans la supervision des pratiques comptables des entreprises.directors’ and officers’ liability insurance policy, aggressive accounting practices, earnings management , ARCAD, pratiques comptables agressives, résultats financiers de gestion.

Lattice gas automaton approach to "Turbulent Diffusion"

A periodic Kolmogorov type flow is implemented in a lattice gas automaton. For given aspect ratios of the automaton universe and within a range of Reynolds number values, the averaged flow evolves towards a stationary two-dimensional $ABC$ type flow. We show the analogy between the streamlines of the flow in the automaton and the phase plane trajectories of a dynamical system. In practice flows are commonly studied by seeding the fluid with suspended particles which play the role of passive tracers. Since an actual flow is time-dependent and has fluctuations, the tracers exhibit interesting intrinsic dynamics. When tracers are implemented in the automaton and their trajectories are followed, we find that the tracers displacements obey a diffusion law, with ``super-diffusion'' in the direction orthogonal to the direction of the initial forcing.Comment: 7 revtex4 pages including 3 figure

Perkembangan koleksi e-books di perpustakaan akademik: Pengalaman Universiti Terbuka Malaysia (OUM)

Pengalaman menyediakan perkhidmatan dan akses kepada koleksi e-books dalam persekitaran akademik adalah suatu yang baru di negara ini. Prasarana di Institusi Pengajian Tinggi berbeza dan amat berkait rapat dengan konsep dan fokus pembelajaran, pengajaran dan penyelidikan universiti. Memandangkan konsep pengajian di OUM merupakan gabungan (blended) yang dikenali sebagai pembelajaran terbuka dan jarak-jauh (Open and Distance Learning), maka membangunkan perpustakaan digital dan menggalakkan penggunaan koleksi digital (pangkalan data/koleksi e-buku dan e-jurnal berteks penuh) adalah cabaran dan pengalaman yang unik. Kertas kerja ini memfokus kepada memaparkan pengalaman tersebut, berdasarkan maklumbalas dan maklumat statistik yang diperolehi dalam laporan bulanan. Ianya menumpukan kepada beberapa strategi perpustakaan dalam menyediakan perkhidmatan dan kemudahan tersebut agar dapat dimanfaatkan oleh pengguna semua

Vascular risk factors, cognitve decline, and dementia

Dementia is one of the most important neurological disorders in the elderly. Aging is associated with a large increase in the prevalence and incidence of degenerative (Alzheimer’s disease) and vascular dementia, leading to a devastating loss of autonomy. In view of the increasing longevity of populations worldwide, prevention of dementia has turned into a major public health challenge. In the past decade, several vascular risk factors have been found to be associated with vascular dementia but also Alzheimer’s disease. Some longitudinal studies, have found significant associations between hypertension, diabetus mellitus, and metabolic syndrome, assessed at middle age, and dementia. Studies assessing the link between hypercholesterolemia, atrial fibrillation, smoking, and dementia have given more conflicting results. Furthermore, some studies have highlighted the possible protective effect of antihypertensive therapy on cognition and some trials are evaluating the effects of statins and treatments for insulin resistance. Vascular risk factors and their treatments are a promising avenue of research for prevention of dementia, and further long-term, placebo-controlled, randomized studies, need to be performed

Diseño y caracterización estructural de sistemas minimizados para el estudio de interacciones biomoleculares mediante RMN

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Bioquímica y Biología Molecular, leída el 26/10/2018The molecular processes that take place in living organisms are regulated by an intricate network of large complexes interacting among them. In this context, the biomolecular recognition processes involving each component are essential to produce the fully biologically active complex. Understanding the fine details on how these processes occur, which are the important players in each step of the recognition, which forces are involved, how they are balanced and drive the process, etc., is the current challenge in Biology. One approximation to solve these open questions is the characterization of these systems at atomic resolution. However, the study of the native biomolecular associations in the form of multiple interacting networks, at this resolution level, is extremely difficult. Given these premises, the best approach is to perform an experimental analysis of the biological systems of interest by using simplified versions with the help of model systems...Los procesos moleculares que tienen lugar en los organismos vivos se regulan a través de una enmarañada red de grandes complejos biológicos que interaccionan entre sí. En este contexto, los mecanismos de reconocimiento biomolecular que se producen en cada uno de ellos son esenciales para dar lugar al complejo activo y biológicamente funcional. Por su importancia, uno de los retos actuales en Biología es comprender a fondo los detalles específicos que definen estos procesos. Por ejemplo, necesitamos conocer cómo y cuándo ocurren, cuáles son los factores esenciales en cada tipo de reconocimiento, qué fuerzas están en juego, cómo se equilibran y dirigen estos mecanismos, etc. Una de las estrategias más apropiadas para esclarecer estas incógnitas es la caracterización de estos sistemas a escala atómica. Sin embargo, el estudio de estas asociaciones biomoleculares que forman grandes redes de interacciones, a este nivel de detalle, es extremadamente complicado. En este escenario, una aproximación realista para el estudio de un sistema biológico complejo consiste en llevar a cabo la caracterización experimental de versiones simplificadas del mismo en sistemas modelo...Depto. de Bioquímica y Biología MolecularFac. de Ciencias QuímicasTRUEunpu