Mass-radius relation of Newtonian self-gravitating Bose-Einstein condensates with short-range interactions: II. Numerical results

We develop the suggestion that dark matter could be a Bose-Einstein condensate. We determine the mass-radius relation of a Newtonian self-gravitating Bose-Einstein condensate with short-range interactions described by the Gross-Pitaevskii-Poisson system. We numerically solve the equation of hydrostatic equilibrium describing the balance between the gravitational attraction and the pressure due to quantum effects (Heisenberg's uncertainty principle) and short-range interactions (scattering). We connect the non-interacting limit to the Thomas-Fermi limit. We also consider the case of attractive self-interaction. We compare the exact mass-radius relation obtained numerically with the approximate analytical relation obtained with a Gaussian ansatz. An overall good agreement is found

Random transitions described by the stochastic Smoluchowski-Poisson system and by the stochastic Keller-Segel model

We study random transitions between two metastable states that appear below a critical temperature in a one dimensional self-gravitating Brownian gas with a modified Poisson equation experiencing a second order phase transition from a homogeneous phase to an inhomogeneous phase. We numerically solve the $N$-body Langevin equations and the stochastic Smoluchowski-Poisson system which takes fluctuations (finite $N$ effects) into account. The system switches back and forth between the two metastable states (bistability) and the particles accumulate successively at the center or at the boundary of the domain. We show that these random transitions exhibit the phenomenology of the ordinary Kramers problem for a Brownian particle in a double-well potential. The distribution of the residence time is Poissonian and the average lifetime of a metastable state is given by the Arrhenius law, i.e. it is proportional to the exponential of the barrier of free energy $\Delta F$ divided by $k_B T$. Since the free energy is proportional to the number of particles $N$ for a system with long-range interactions, the lifetime of metastable states scales as $e^N$ and is considerable for $N\gg 1$. As a result, in many applications, metastable states of systems with long-range interactions can be considered as stable states. However, for moderate values of $N$, or close to a critical point $T_c$, the lifetime of the metastable states is reduced since the barrier of free energy decreases. In that case, the fluctuations become important and the mean field approximation is no more valid. This is the situation considered in this paper. By an appropriate change of notations, our results also apply to bacterial populations experiencing chemotaxis in biology. Their dynamics can be described by a stochastic Keller-Segel model that takes fluctuations into account and goes beyond the usual mean field approximation

Self-Consistent Mode-Coupling Approach to 1D Heat Transport

In the present Letter we present an analytical and numerical solution of the self-consistent mode-coupling equations for the problem of heat conductivity in one-dimensional systems. Such a solution leads us to propose a different scenario to accomodate the known results obtained so far for this problem. More precisely, we conjecture that the universality class is determined by the leading order of the nonlinear interaction potential. Moreover, our analysis allows us determining the memory kernel, whose expression puts on a more firm basis the previously conjectured connection between anomalous heat conductivity and anomalous diffusion.Comment: Submitted to Physical Review

Determinants of job insecurity in Argentina between 2003-2013: among the changes and continuities

El crecimiento económico experimentado por Argentina desde 2003 ha tenido su correlato en la mejora de los indicadores laborales. No obstante, la precarización laboral se ha mantenido, luego de una baja importante, hasta 2007, en valores muy elevados. Partiendo de la idea central que la precarización constituye para el capital una reducción de costos, el objetivo de este artículo es dar cuenta de los determinantes de la informalidad entre los trabajadores asalariados y establecer continuidades y cambios durante 2003 y 2013. Para ello, utilizamos una metodología cuantitativa con fuentes secundarias de información, dde acuerdo con las cuales realizamos dos tipo de análisis: el primero de carácter descriptivo, a partir del cual se busca dar cuenta de las características del mercado de trabajo argentino durante 1990 y 2013, y el segundo se realiza por medio de una regresión logística binomial, que permite acercarnos a los determinantes de la precarización de las condiciones de trabajo. En este sentido, se pudo observar que durante 2003 y 2013 se consolidó una precarización laboral, cuyos determinantes no lograron modificarse sustancialmente durante los años de referencia.The economic growth experienced by Argentina since 2003 has had its counterpart in improving labor indicators. However, job insecurity has remained, after a significant decline until 2007, in very high values. Based on the central idea that casualization is for capital cost reductions, the aim of this paper is to account for the determinants of informality among salaried workers, establishing continuities and changes between 2003 and 2013. For this we use a quantitative methodology with secondary sources of information, from which conducted two types of analysis, the first descriptive which seeks to account for the characteristics of the Argentine labor market between 1990 and 2013 and the second performed by a binomial logistic regression approach that allows the determinants of precarious working conditions. In this regard, it was observed that between 2003 and 2013, a labor casualization, whose determinants failed substantially changed between the reference years was consolidated.Fil: Delfini, Marcelo Fabián. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento; Argentin

Aneurysms of the intracranial segment of the ophthalmic artery trunk. case report and systematic literature review

Aneurysms arising from the ophthalmic artery trunk (OAT) are very rare, particularly in the artery's intracranial course. The onset of a subarachnoid hemorrhage (SAH) from a ruptured OAT aneurysm in this segment is extremely rare. We present a case and discuss the anatomy, clinical significance, and therapeutic options for an aneurysm at this site. We also retrospectively analyzed the record of a patient with a ruptured aneurysm of the intracranial segment of the OAT and conducted a comprehensive and systematic review of the PubMed and Scopus databases for literature on this pathology. Only one case report of SAH from an aneurysm of the intracranial segment of the OAT was published in the literature. Only in our case was the intracranial OAT segment aneurysm discovered in the acute phase of SAH. Conventional angiography with three-dimensional acquisition may help detect aneurysms at this level. Detailed knowledge of the anatomy of the OAT is of paramount importance for both surgical and endovascular approaches. Surgical treatment is complex because of difficulties in accessing the orbital region and the risk of optic nerve and vascular injuries. Endovascular treatment, when feasible, could be a good alternative to reduce the risk of loss of vision related to surgical manipulation

Energy diffusion in hard-point systems

We investigate the diffusive properties of energy fluctuations in a one-dimensional diatomic chain of hard-point particles interacting through a square--well potential. The evolution of initially localized infinitesimal and finite perturbations is numerically investigated for different density values. All cases belong to the same universality class which can be also interpreted as a Levy walk of the energy with scaling exponent 3/5. The zero-pressure limit is nevertheless exceptional in that normal diffusion is found in tangent space and yet anomalous diffusion with a different rate for perturbations of finite amplitude. The different behaviour of the two classes of perturbations is traced back to the "stable chaos" type of dynamics exhibited by this model. Finally, the effect of an additional internal degree of freedom is investigated, finding that it does not modify the overall scenarioComment: 16 pages, 15 figure

Lumbar ganglion cyst: Nosology, surgical management and proposal of a new classification based on 34 personal cases and literature review

AIM To analyze different terms used in literature to identify lumbar extradural cysts and propose a common scientific terminology; to elaborate a new morphological classification of this pathology, useful for clinical and surgical purposes; and to describe the best surgical approach to remove these cysts, in order to avoid iatrogenic instability or treat the pre-existing one. METHODS We retrospectively reviewed 34 patients with symptomatic lumbar ganglion cysts treated with spinal canal decompression with or without spinal fixation. Microsurgical approach was the main procedure and spinal instrumentation was required only in case of evident preoperative segmental instability. RESULTS The complete cystectomy with histological examination was performed in all cases. All patients presented an improvement of clinical conditions, evaluated by Visual Analogic Scale and Japanese Orthopaedic Association scoring. CONCLUSION Spinal ganglion cysts are generally found in the lumbar spine. The treatment of choice is the microsurgical cystectomy, which generally does not require stabilization. The need for fusion must be carefully evaluated: Preoperative spondylolisthesis or a wide joint resection, during the operation, are the main indications for spinal instrumentation. We propose the terms "ganglion cyst" to finally identify this spinal pathology and for the first time its morphological classification, clinically useful for all specialists

CVD nano-coating of carbon composites for space materials atomic oxygen shielding

The present work analyzes the possibility to employ carbon nanostructures as a basic material to prevent the erosion effects of atomic oxygen suffered by the carbon fiber reinforced polymeric material used in low earth orbit space environment. The application of thin protecting coatings to base materials is a widely used method for preventing the atomic oxygen induced erosion, and thus degradation. The generic purpose is to integrate carbon nanostructures onto carbon composites surface in order to develop the basic substrate of advanced nanocomposite for atomic oxygen protection. The final goal is the characterization of carbon nanostructures-reinforced carbon composites by means of on-ground atomic oxygen simulation facility, with the future objective to assess and optimize the process of carbon-multiscale advanced composites production. With such an aim, a wide investigation on the methane chemical vapor deposition (CVD) over catalyzed carbon fiber-based substrates has been carried out. The as grown nanostructures have been analyzed in terms of morphology, as well as regarding the main features of the resulting growth (yield, purity, homogeneity, coating uniformity, etc.) and the influence of the deposition route operating parameters (catalyst typology, gas flowing rate, growth time/temperature, etc.). A high degree of reproducibility in terms of the relationship between the carbon deposit type/yield and the main process variables (catalyst and protocol) has been thus obtained. Finally, atomic oxygen ground tests have been conducted in order to evaluate the coating process effectiveness. The on-ground test in atomic oxygen environment, with respect to the performances of the reference carbon composites (in terms of total mass loss and atomic oxygen rate of erosion), showed a worsening for the disordered carbon deposit, while an intriguing improvement was achieved by the high-yield carbon nano-filaments deposition

Las relaciones laborales en una trama automotriz argentina

The aim of the current paper, is to analyze the labour relations developed in the Argentinean productive automotive network through the study of the components of collective bargaining, which were shaped in the Collective Labour Agreements. The emphasis will be mainly on the characteristics that the process and the job organization have. The analysis of the labour relations, in the frame of the relations among the companies, has special relevance as it suggests a connection between the focal point and the suppliers, which affects the outlines of the labour relations developed in the participant enterprises. That allows us to capture them in their real dimension, as it is throughout the course of the productive chain, where the elements that characterize the complexity of the analysis must be looked for

Relaciones laborales y gestión de recursos humanos" en filiales de empresas multinacionales en Argentina,"

Sociedad & Economía #20. Año 2011Convergencia, Individualización, Relaciones colectivas, Gestión de la fuerza de Trabajo, Prácticas de Gestión de Recursos Humanos