Critical Behavior of an Ising System on the Sierpinski Carpet: A Short-Time Dynamics Study

The short-time dynamic evolution of an Ising model embedded in an infinitely ramified fractal structure with noninteger Hausdorff dimension was studied using Monte Carlo simulations. Completely ordered and disordered spin configurations were used as initial states for the dynamic simulations. In both cases, the evolution of the physical observables follows a power-law behavior. Based on this fact, the complete set of critical exponents characteristic of a second-order phase transition was evaluated. Also, the dynamic exponent $\theta$ of the critical initial increase in magnetization, as well as the critical temperature, were computed. The exponent $\theta$ exhibits a weak dependence on the initial (small) magnetization. On the other hand, the dynamic exponent $z$ shows a systematic decrease when the segmentation step is increased, i.e., when the system size becomes larger. Our results suggest that the effective noninteger dimension for the second-order phase transition is noticeably smaller than the Hausdorff dimension. Even when the behavior of the magnetization (in the case of the ordered initial state) and the autocorrelation (in the case of the disordered initial state) with time are very well fitted by power laws, the precision of our simulations allows us to detect the presence of a soft oscillation of the same type in both magnitudes that we attribute to the topological details of the generating cell at any scale.Comment: 10 figures, 4 tables and 14 page

Topological Effects caused by the Fractal Substrate on the Nonequilibrium Critical Behavior of the Ising Magnet

The nonequilibrium critical dynamics of the Ising magnet on a fractal substrate, namely the Sierpinski carpet with Hausdorff dimension $d_H$ =1.7925, has been studied within the short-time regime by means of Monte Carlo simulations. The evolution of the physical observables was followed at criticality, after both annealing ordered spin configurations (ground state) and quenching disordered initial configurations (high temperature state), for three segmentation steps of the fractal. The topological effects become evident from the emergence of a logarithmic periodic oscillation superimposed to a power law in the decay of the magnetization and its logarithmic derivative and also from the dependence of the critical exponents on the segmentation step. These oscillations are discussed in the framework of the discrete scale invariance of the substrate and carefully characterized in order to determine the critical temperature of the second-order phase transition and the critical exponents corresponding to the short-time regime. The exponent $\theta$ of the initial increase in the magnetization was also obtained and the results suggest that it would be almost independent of the fractal dimension of the susbstrate, provided that $d_H$ is close enough to d=2.Comment: 9 figures, 3 tables, 10 page

OPTIMAL DISTRIBUTED CONTROL OF STOCHASTIC ELLIPTIC SYSTEMS WITH CONSTRAINTS

The objective of this paper is to study the optimality for stochastic non cooperative elliptic systems. A distributed control problem for a stochastic elliptic systems with constraints on states and controls is studied. First, the existence and uniqueness of the state process for these systems are proved. The necessary and sufficient conditions of optimality are derived for the Dirichlet and Neumann problems

On the occurrence of oscillatory modulations in the power-law behavior of dynamic and kinetic processes in fractals

The dynamic and kinetic behavior of processes occurring in fractals with spatial discrete scale invariance (DSI) is considered. Spatial DSI implies the existence of a fundamental scaling ratio (b_1). We address time-dependent physical processes, which as a consequence of the time evolution develop a characteristic length of the form $\xi \propto t^{1/z}$, where z is the dynamic exponent. So, we conjecture that the interplay between the physical process and the symmetry properties of the fractal leads to the occurrence of time DSI evidenced by soft log-periodic modulations of physical observables, with a fundamental time scaling ratio given by $\tau = b_1 ^z$. The conjecture is tested numerically for random walks, and representative systems of broad universality classes in the fields of irreversible and equilibrium critical phenomena.Comment: 6 pages, 3 figures. Submitted to EP

Log-periodic modulation in one-dimensional random walks

We have studied the diffusion of a single particle on a one-dimensional lattice. It is shown that, for a self-similar distribution of hopping rates, the time dependence of the mean-square displacement follows an anomalous power law modulated by logarithmic periodic oscillations. The origin of this modulation is traced to the dependence on the length of the diffusion coefficient. Both the random walk exponent and the period of the modulation are analytically calculated and confirmed by Monte Carlo simulations.Comment: 6 pages, 7 figure

Analytical Solution of the Voter Model on Disordered Networks

We present a mathematical description of the voter model dynamics on heterogeneous networks. When the average degree of the graph is $\mu \leq 2$ the system reaches complete order exponentially fast. For $\mu >2$, a finite system falls, before it fully orders, in a quasistationary state in which the average density of active links (links between opposite-state nodes) in surviving runs is constant and equal to $\frac{(\mu-2)}{3(\mu-1)}$, while an infinite large system stays ad infinitum in a partially ordered stationary active state. The mean life time of the quasistationary state is proportional to the mean time to reach the fully ordered state $T$, which scales as $T \sim \frac{(\mu-1) \mu^2 N}{(\mu-2) \mu_2}$, where $N$ is the number of nodes of the network, and $\mu_2$ is the second moment of the degree distribution. We find good agreement between these analytical results and numerical simulations on random networks with various degree distributions.Comment: 20 pages, 8 figure

Lung cancer incidence trends in Iran and in six geographical regions of the country (2000 - 2005)

Background: Lung cancer, the most common type of cancer in humans, is the leading cause of cancer deaths globally, accounting for 1.38 million deaths per year (18.2 of all cancer deaths). Lung cancer is the third most common type of cancer in Iran. Objectives: The present study investigated the incidence of lung cancer in six geographical regions of Iran. Materials and Methods: Data for annual cases of lung cancer were obtained from the national cancer registry during the years 2000 - 2005. The rates of incidence were standardized using world health organization (WHO) population data, and confidence intervals were calculated at 95. Iran was divided into six areas according to geographical differences. The Poisson regression model was used to test the significance of changes in the incidence rates during the study period Results: The age-standardized rates of lung cancer for men and women increased from 0.8 and 0.3 per 100,000 people in 2000 to 4 and 1.5 in 2005, respectively. The highest rate of lung cancer was observed in the mountainous region, and the lowest rate occurred in the western provinces of the Caspian sea region. Despite the difference in the slope of changes, there is an increasing trend in the incidence of lung cancer in all geographical areas. Conclusions: The current incidence rates of lung cancer in all the geographical areas examined are generally increasing. Unfortunately, the rates of urbanization, environmental pollution, and smoking tendency are also increasing in Iran; to control these trends and adjust these risk factors, officials should help more with public-program planning. © 2016, Shiraz University of Medical Sciences

La facultad va a la escuela del barrio

En los últimos años el Ministerio de Cultura y Educación de la Nación desarrolló diversos programas vinculados al equipamiento de laboratorios escolares (EQUIPA, PRODYMES, etc.) tendientes a fomentar la enseñanza de la Ciencia y la Tecnología mediante la demostración y experimentación. Como consecuencia se distribuyó en escuelas públicas de todo el país, una importante cantidad de material didáctico relacionado con las áreas de Ciencias Naturales y Tecnología del EGB. Este material en la mayoría de los casos no se utiliza. En muchos establecimientos aún se mantiene embalado y los docentes no saben de su existencia, en otros desconocen como utilizarlo, o tienen temor a la ruptura o pérdida del mismo. En este contexto, un grupo de alumnos, docentes e investigadores de las Facultades de Ciencias Exactas y Ciencias Naturales y Museo de la Universidad Nacional de La Plata y del Centro de Investigaciones Ópticas en el marco de un proyecto de extensión universitaria (“La Facultad va a la Escuela del Barrio”) comenzamos, a principios del 2002, a ofrecer nuestra colaboración a las escuelas públicas de La Plata y alrededores para optimizar el uso de este material, brindando asistencia para el montaje de laboratorios, realizando prácticas que involucren el uso del equipamiento, etc. Un aspecto fundamental de este proyecto es que se trabaja con los docentes y no con los alumnos, con el fin de generar un vínculo dinámico y horizontal entre pares con distinta formación. Los resultados de nuestra experiencia confirman la necesidad de acompañar a los docentes en un proceso que no debería agotarse en la capacitación puntual tradicional, sino, por el contrario, establecer mecanismos de trabajo conjunto para que el docente pueda desarrollar su actividad en el aula en mejores condiciones.Sección NaturalesDepartamento de Ciencias Exactas y Naturale

Tracking and coordinating an international curation effort for the CCDS Project

The Consensus Coding Sequence (CCDS) collaboration involves curators at multiple centers with a goal of producing a conservative set of high quality, protein-coding region annotations for the human and mouse reference genome assemblies. The CCDS data set reflects a ‘gold standard’ definition of best supported protein annotations, and corresponding genes, which pass a standard series of quality assurance checks and are supported by manual curation. This data set supports use of genome annotation information by human and mouse researchers for effective experimental design, analysis and interpretation. The CCDS project consists of analysis of automated whole-genome annotation builds to identify identical CDS annotations, quality assurance testing and manual curation support. Identical CDS annotations are tracked with a CCDS identifier (ID) and any future change to the annotated CDS structure must be agreed upon by the collaborating members. CCDS curation guidelines were developed to address some aspects of curation in order to improve initial annotation consistency and to reduce time spent in discussing proposed annotation updates. Here, we present the current status of the CCDS database and details on our procedures to track and coordinate our efforts. We also present the relevant background and reasoning behind the curation standards that we have developed for CCDS database treatment of transcripts that are nonsense-mediated decay (NMD) candidates, for transcripts containing upstream open reading frames, for identifying the most likely translation start codons and for the annotation of readthrough transcripts. Examples are provided to illustrate the application of these guidelines