Finding critical points using improved scaling Ansaetze

Analyzing in detail the first corrections to the scaling hypothesis, we develop accelerated methods for the determination of critical points from finite size data. The output of these procedures are sequences of pseudo-critical points which rapidly converge towards the true critical points. In fact more rapidly than previously existing methods like the Phenomenological Renormalization Group approach. Our methods are valid in any spatial dimensionality and both for quantum or classical statistical systems. Having at disposal fast converging sequences, allows to draw conclusions on the basis of shorter system sizes, and can be extremely important in particularly hard cases like two-dimensional quantum systems with frustrations or when the sign problem occurs. We test the effectiveness of our methods both analytically on the basis of the one-dimensional XY model, and numerically at phase transitions occurring in non integrable spin models. In particular, we show how a new Homogeneity Condition Method is able to locate the onset of the Berezinskii-Kosterlitz-Thouless transition making only use of ground-state quantities on relatively small systems.Comment: 16 pages, 4 figures. New version including more general Ansaetze basically applicable to all case

Otimização de protocolos de extração de RNA em diferentes tecidos de milho.

Neste trabalho, foram testados cinco métodos de extração de RNA (CTAB microextração, Concert? Invitrogen, Concert? Adaptado, TRI Reagente® Sigma e TRI Reagente® Adaptado), em dois diferentes tecidos de milho (mesocótilo e raiz), com o objetivo de estabelecer um método eficiente de extração de RNA, visando posteriormente estudos de expressão gênica. Observou-se que o método Concert,utilizando o protocolo adaptado, foi o mais eficiente para a extração de RNA de ambos os tecidos de plântulas de milho, originando 2351,35 ?g por 100 mg de tecido para mesocótilo e 893,75 ?g por 100 mg de tecido para raiz, considerando tanto a quantidade como a qualidade das amostras, podendo ser submetidas às etapas posteriores de tratamento com DNAse e construção de cDNA para estudos de expressão gênica. Pôde-se observar que pequenas modificações nos protocolos, como, por exemplo, mudança no tempo e na posição dos tubos durante a incubação e o incremento de duas lavagens com clorofórmio, podem melhorar muito tanto a qualidade quanto a quantidade do RNA extraído

Finite-size scaling of the quasiespecies model

We use finite-size scaling to investigate the critical behavior of the quasiespecies model of molecular evolution in the single-sharp-peak replication landscape. This model exhibits a sharp threshold phenomenon at Q=Q_c=1/a, where Q is the probability of exact replication of a molecule of length L and a is the selective advantage of the master string. We investigate the sharpness of the threshold and find that its characteristic persist across a range of Q of order L^(-1) about Q_c. Furthermore, using the data collapsing method we show that the normalized mean Hamming distance between the master string and the entire population, as well as the properly scaled fluctuations around this mean value, follow universal forms in the critical region.Comment: 8 pages,tex. Submitted to Physical Review

Intra-host evolution of multiple genotypes of hepatitis C virus in a chronically infected patient with HIV along a 13-year follow-up period

AbstractThe intra-host evolutionary process of hepatitis C virus (HCV) was analyzed by phylogenetic and coalescent methodologies in a patient co-infected with HCV-1a, HCV-2a, HCV-3a and human immunodeficiency virus (HIV) along a 13-year period.Direct sequence analysis of the E2 and NS5A regions showed diverse evolutionary dynamics, in agreement with different relationships between these regions and the host factors.The Bayesian Skyline Plot analyses of the E2 sequences (cloned) yielded different intra-host evolutionary patterns for each genotype: a steady state of a “consensus” sequence for HCV-1a; a pattern of lineage splitting and extinction for HCV-2a; and a two-phase (drift/diversification) process for HCV-3a.Each genotype evolving in the same patient and at the same time presents a different pattern apparently modulated by the immune pressure of the host.This study provides useful information for the management of co-infected patients and provides insights into the mechanisms behind the intra-host evolution of HCV

Ocular surface analysis in patients affected with rheumatic diseases

Objective. The international criteria for primary Sjogren's Syndrome (SS I) diagnosis (Vitali et al. 2002) include the Schirmer test I and vital dye staining as tests for ocular surface involvement, but diagnosis can be reached also when the item for ocular signs is not satisfied. The purpose of our study was to evaluate the ocular surface in patients with Sjogren's Syndrome, non- Sjogren's autoimmune diseases and Sicca Syndrome, to understand whether the SS I diagnosis can be targeted also on other tests related to the ocular surface status. Methods. Clinical and cytological data were collected from 122 patients: 40 patients had diagnosis of Primary Sjogren's Syndrome, 51 a non Sjogren's autoimmune disease and 31 had symptoms of dry eye. A validated questionnaire on symptoms was filled by each patient; clinical tests included: Schirmer test I, Jones test, Ferning test, Break Up Time, corneal aesthesiometry, tear clearance test, vital dye staining of the ocular surface, scraping and impression conjunctival cytology. Data were statistically evaluated by using SPSS software and Mann-Whitney analysis on unpaired data. Results. Data show that the subjective symptoms score, tear production, tear turnover, corneal sensitivity and ocular surface integrity are affected in SS I patients, with a statistically significant difference when matched to the other two groups. Conclusions. Our results suggest to enlarge the spectrum of ocular surface analysis, to support and orient a differential diagnosis among the autoimmune diseases

Study of RFe12−xMox (R =Y, Ho) compounds by neutron powder diffraction, ac susceptibility and magnetization

Neutron powder diffraction, magnetization and ac susceptibility measurements were performed on compounds of the series RFe12−xMox (R D Y and Ho, x D 1, 2, 3). The influence of the Mo content on both structural and magnetic properties is discussed. Comparison with published data for different Mo concentrations is made. It is found that the effect of Mo substitution for Fe on structural and magnetic properties can be described by two regimes separated by a critical Mo content around x=2.Portuguese-French JNICT-CNRS collaboration

Wrapped fivebranes and N=2 super Yang-Mills theory

We construct D=10 supergravity solutions corresponding to type IIB fivebranes wrapping a two-sphere in a Calabi-Yau two-fold. These are related in the IR to the large N limit of pure N=2 SU(N) super Yang-Mills theory. We show that the singularities in the IR correspond to the wrapped branes being distributed on a ring. We analyse the dynamics of a probe fivebrane and show that it incorporates the full perturbative structure of the gauge theory. For a class of solutions the two-dimensional moduli space is non-singular and we match the result for the corresponding slice of the Coulomb branch of the gauge theory.Comment: 24 Latex pages, two figures;v2 typos corrected, references adde