Diffusive epidemic process: theory and simulation

We study the continuous absorbing-state phase transition in the one-dimensional diffusive epidemic process via mean-field theory and Monte Carlo simulation. In this model, particles of two species (A and B) hop on a lattice and undergo reactions B -> A and A + B -> 2B; the total particle number is conserved. We formulate the model as a continuous-time Markov process described by a master equation. A phase transition between the (absorbing) B-free state and an active state is observed as the parameters (reaction and diffusion rates, and total particle density) are varied. Mean-field theory reveals a surprising, nonmonotonic dependence of the critical recovery rate on the diffusion rate of B particles. A computational realization of the process that is faithful to the transition rates defining the model is devised, allowing for direct comparison with theory. Using the quasi-stationary simulation method we determine the order parameter and the survival time in systems of up to 4000 sites. Due to strong finite-size effects, the results converge only for large system sizes. We find no evidence for a discontinuous transition. Our results are consistent with the existence of three distinct universality classes, depending on whether A particles diffusive more rapidly, less rapidly, or at the same rate as B particles.Comment: 19 pages, 5 figure

Viabilidade do uso de diferentes tipos de lonas plásticas para expurgo de milho em palha e sorgo.

Os insetos-pragas constituem um dos principais problemas para o armazenamento de milho a nivel de fazenda. O expurgo destas pragas com fosfina, e utilizando tendas plasticas, tem sido o unico metodo de controle que atinge os insetos alojados no interior das espigas e dos graos. Ate o momento tem sido recomendada a realizacao do expurgo utilizando somente lonas plásticas fabricadas em PVC, porem o custo bastante elevado destas lonas tem dificultado a adocao de tecnologia do expurgo. O objetivo deste trabalho foi comparar a eficiencia de diversos tipos de lonas plasticas para expurgo. Foram estudados, no 1o. ensaio, 4 tipos de lonas x 3 dosagens de fosfina x 2 tipos de piso (cimento e chao nao batido). Os principais resultados foram os seguintes: a) no piso de cimento, tanto a lona do PVC quanto as de polietileno (Terreiro, Amarelona e Preta), com aditivo experimental) deram bons resultados com todas as dosagens; b) no piso de terra, somente a lona de PVC apresentou resultado satisfatorio. No 2o. ensaio foram estudadas lonas de PVC e Terreiro no piso de cimento, chao bem batido e piso de chao revestido pela lona Terreiro. Neste caso, todas as lonas deram igual resultado em qualquer tipo de piso

Avaliação da lama de cal como material corretivo de solo.

O trabalho avaliou a lama de cal gerada pela Iguaçu Celulose, Papel, S.A., em Piraí do Sul, Paraná, como corretivo de solo e verificar se o material atende às exigências para ser considerado como tal. Para tanto, foram conduzidos ensaios para se avaliar o efeito desse subproduto na acidez do solo comparado ao carbonato de cálcio

Redshift-Distance Survey of Early-type Galaxies. I. Sample Selection, Properties and Completeness

This is the first in a series of papers describing the recently completed all-sky redshift-distance survey of nearby early-type galaxies (ENEAR) carried out for peculiar velocity analysis. The sample is divided into two parts and consists of 1607 elliptical and lenticular galaxies with cz < 7000 km/s and with blue magnitudes brighter than m_B=14.5 (ENEARm), and of galaxies in clusters (ENEARc). Galaxy distances based on the Dn-sigma and Fundamental Plane (FP) relations are now available for 1359 and 1107 ENEARm galaxies, respectively, with roughly 80% based on new data gathered by our group. The Dn-sigma and FP template distance relations are derived by combining 569 and 431 galaxies in 28 clusters, respectively, of which about 60% are based on our new measurements. The ENEARm redshift-distance survey extends the earlier work of the 7S and the recent Tully-Fisher surveys sampling a comparable volume. In subsequent papers of this series we intend to use the ENEAR sample by itself or in combination with the SFI Tully-Fisher survey to analyze the properties of the local peculiar velocity field and to test how sensitive the results are to different sampling and to the distance indicators. We also anticipate that the homogeneous database assembled will be used for a variety of other applications and serve as a benchmark for similar studies at high-redshift.Comment: 43 pages, 15 figures, submitted to the Astronomical Journa

Morphological dissimilarity among mangabeira tree populations from Amapá and Paraíba, Brazil.

Mangabeira fruits are collected from native populations under anthropic pressure. It is therefore essential to obtain morphogenetic information to genetically improve populations, thereby preventing genetic erosion. This research was carried out in the state Amapá and aimed to verify the morphological dissimilarity between two populations, one composed of 36 native progenies and one of eight progenies from Paraiba, outlined in lattices with two replications and six plants per part. The evaluated characteristics were: agronomic value (VA), treetop circumference (CCP), plant height (ALP), estimated number of fruits per plant (NEF), fruit color (COF), average weight of 10 fruits (PMF), fruit diameter (DF), average pulp weight of ten fruits (PMP), average length of 10 fruits (CMF), average number of seeds of 10 fruits (NMS). Our results indicate that the phenotype was mainly determined by responses to environmental changes; in the correlations, inherent fruit characteristics (weight, size, and color) did not affect the VA, while biometric characters influenced VA values. Higher plants presented larger fruits and a larger diameter, bigger quantities, there is also apparent contrast, with a larger amount of smaller size; the populations are dissimilar, indicating the possibility of obtaining of diverging superior segregating

Double crystallographic groups and their representations on the Bilbao Crystallographic Server

A new section of databases and programs devoted to double crystallographic groups (point and space groups) has been implemented in the Bilbao Crystallographic Server (http://www.cryst.ehu.es). The double crystallographic groups are required in the study of physical systems whose Hamiltonian includes spin-dependent terms. In the symmetry analysis of such systems, instead of the irreducible representations of the space groups, it is necessary to consider the single- and double-valued irreducible representations of the double space groups. The new section includes databases of symmetry operations (DGENPOS) and of irreducible representations of the double (point and space) groups (REPRESENTATIONS DPG and REPRESENTATIONS DSG). The tool DCOMPATIBILITY RELATIONS provides compatibility relations between the irreducible representations of double space groups at different k-vectors of the Brillouin zone when there is a group-subgroup relation between the corresponding little groups. The program DSITESYM implements the so-called site-symmetry approach, which establishes symmetry relations between localized and extended crystal states, using representations of the double groups. As an application of this approach, the program BANDREP calculates the band representations and the elementary band representations induced from any Wyckoff position of any of the 230 double space groups, giving information about the properties of these bands. Recently, the results of BANDREP have been extensively applied in the description and the search of topological insulators.Comment: 32 pages, 20 figures. Two extra figures and minor typo mistakes fixed. Published versio

Methodological assessment of HCC literature

Despite the fact that the hepatocellular carcinoma (HCC) represents a major health problem, very few interventions are available for this disease, and only sorafenib is approved for the treatment of advanced disease. Of note, only very few interventions have been thoroughly evaluated over time for HCC patients compared with several hundreds in other, equally highly lethal, tumours. Additionally, clinical trials in HCC have often been questioned for poor design and methodological issues. As a consequence, a gap between what is measured in clinical trials and what clinicians have to face in daily practice often occurs. As a result of this scenario, even the most recent guidelines for treatment of HCC patients use low strength evidence to make recommendations. In this review, we will discuss some of the potential methodological issues hindering a rational development of new treatments for HCC patient