Effect of Dilution on First Order Transitions: The Three Dimensional Three States Potts Model

We have studied numerically the effect of quenched site dilution on a first order phase transition in three dimensions. We have simulated the site diluted three states Potts model studying in detail the second order region of its phase diagram. We have found that the $\nu$ exponent is compatible with the one of the three dimensional diluted Ising model whereas the $\eta$ exponent is definitely different.Comment: RevTex. 6 pages and 6 postscript figure

Zone center phonons of the orthorhombic RMnO3 (R = Pr, Eu, Tb, Dy, Ho) perovskites

A short range force constant model (SRFCM) has been applied for the first time to investigate the phonons in RMnO3 (R = Pr, Eu, Tb, Dy, Ho) perovskites in their orthorhombic phase. The calculations with 17 stretching and bending force constants provide good agreement for the observed Raman frequencies. The infrared frequencies have been assigned for the first time. PACS Codes: 36.20.Ng, 33.20.Fb, 34.20.CfComment: 8 pages, 1 figur

Sense and sensitivity of double beta decay experiments

The search for neutrinoless double beta decay is a very active field in which the number of proposals for next-generation experiments has proliferated. In this paper we attempt to address both the sense and the sensitivity of such proposals. Sensitivity comes first, by means of proposing a simple and unambiguous statistical recipe to derive the sensitivity to a putative Majorana neutrino mass, m_bb. In order to make sense of how the different experimental approaches compare, we apply this recipe to a selection of proposals, comparing the resulting sensitivities. We also propose a "physics-motivated range" (PMR) of the nuclear matrix elements as a unifying criterium between the different nuclear models. The expected performance of the proposals is parametrized in terms of only four numbers: energy resolution, background rate (per unit time, isotope mass and energy), detection efficiency, and bb isotope mass. For each proposal, both a reference and an optimistic scenario for the experimental performance are studied. In the reference scenario we find that all the proposals will be able to partially explore the degenerate spectrum, without fully covering it, although four of them (KamLAND-Zen, CUORE, NEXT and EXO) will approach the 50 meV boundary. In the optimistic scenario, we find that CUORE and the xenon-based proposals (KamLAND-Zen, EXO and NEXT) will explore a significant fraction of the inverse hierarchy, with NEXT covering it almost fully. For the long term future, we argue that Xe-based experiments may provide the best case for a 1-ton scale experiment, given the potentially very low backgrounds achievable and the expected scalability to large isotope masses.Comment: 30 pages, 12 figures, 6 table

Optic radiation structure and anatomy in the normally developing brain determined using diffusion MRI and tractography

The optic radiation (OR) is a component of the visual system known to be myelin mature very early in life. Diffusion tensor imaging (DTI) and its unique ability to reconstruct the OR in vivo were used to study structural maturation through analysis of DTI metrics in a cohort of 90 children aged 5–18 years. As the OR is at risk of damage during epilepsy surgery, we measured its position relative to characteristic anatomical landmarks. Anatomical distances, DTI metrics and volume of the OR were investigated for age, gender and hemisphere effects. We observed changes in DTI metrics with age comparable to known trajectories in other white matter tracts. Left lateralization of DTI metrics was observed that showed a gender effect in lateralization. Sexual dimorphism of DTI metrics in the right hemisphere was also found. With respect to OR dimensions, volume was shown to be right lateralised and sexual dimorphism demonstrated for the extent of the left OR. The anatomical results presented for the OR have potentially important applications for neurosurgical planning

Medicinal Plants of Chile: Evaluation of their Anti-Trypanosoma cruzi Activity

San Martin, J (San Martin, Jose). Univ Talca, Inst Biol Vegetal & Biotecnol, Talca, ChileThe extracts of several plants of Central Chile exhibited anti-Trypanosoma cruzi trypomastigotes activity. Most active extracts were those obtained from Podanthus ovatifolius, Berberis microphylla, Kageneckia oblonga, and Drimys winteri. The active extract of Drimys winteri (IC50 51.2 mu g/mL) was purified and three drimane sesquiterpenes were obtained: polygodial, drimenol, and isodrimenin. Isodrimenin and drimenol were found to be active against the trypomastigote form of T cruzi with IC50 values of 27.9 and 25.1 mu M, respectivel

Ianus: an Adpative FPGA Computer

Dedicated machines designed for specific computational algorithms can outperform conventional computers by several orders of magnitude. In this note we describe {\it Ianus}, a new generation FPGA based machine and its basic features: hardware integration and wide reprogrammability. Our goal is to build a machine that can fully exploit the performance potential of new generation FPGA devices. We also plan a software platform which simplifies its programming, in order to extend its intended range of application to a wide class of interesting and computationally demanding problems. The decision to develop a dedicated processor is a complex one, involving careful assessment of its performance lead, during its expected lifetime, over traditional computers, taking into account their performance increase, as predicted by Moore's law. We discuss this point in detail

New Energy Calibration of the CMAM 5MV Tandem Accelerator

Abstract Ion accelerators are fundamental in the ongoing research on materials for future energy sources, being the primary tool for understanding the behaviour of different classes of materials (functional, structural, diagnostic) under e.g. the intense radiation expected in fission reactors or the critical thermal operational conditions in IV generation fission reactors. The relevance of ion accelerators research extends straightforwardly to the modification and analysis of materials to be used in future developments of diverse non-nuclear sources like photovoltaic, fuel batteries, etc. From the analytical point of view, the energy of the accelerated ion needs, in many cases, to be known with a precision higher than e.g. the width of reaction resonances that are used for controlling either the yield of a reaction or the penetration depth of the ion, imposing a calibration of the accelerator terminal voltage. This paper reports on the new energy calibration performed for the 5 MV CMAM tandem accelerator

The structure of a polyketide synthase bimodule core

Polyketide synthases (PKSs) are predominantly microbial biosynthetic enzymes. They assemble highly potent bioactive natural products from simple carboxylic acid precursors. The most versatile families of PKSs are organized as assembly lines of functional modules. Each module performs one round of precursor extension and optional modification, followed by directed transfer of the intermediate to the next module. While enzymatic domains and even modules of PKSs are well understood, the higher-order modular architecture of PKS assembly lines remains elusive. Here, we visualize a PKS bimodule core using cryo-electron microscopy and resolve a two-dimensional meshwork of the bimodule core formed by homotypic interactions between modules. The sheet-like organization provides the framework for efficient substrate transfer and for sequestration of trans-acting enzymes required for polyketide production

Crystallization Kinetics of LaF3 Nanocrystals in an Oxyfluoride Glass

Nanocrystallization of LaF3 in a glass of composition 55SiO2– 20Al2O3–15Na2O–10LaF3 (mol%) has been achieved by heat treatment above the glass transition temperature. A maximum crystal size of 14 nm has been attained, with the crystalline fraction and crystal size dependent on the time and temperature of thermal treatment. The effect of lanthanum fluoride crystallization is noticeable from the microstructural and compositional changes in the glass matrix, which have been studied using several techniques, including viscosity, dilatometry, X-ray diffraction, and quantitative Rietveld refinement, transmission electron microscopy, and differential scanning calorimetry. The crystallization mechanism is shown to occur via regions of La- and Si-phase separation in the glass, from which the fluoride crystals develop during heat treatment. The interface between the glass matrix and the crystals in the demixed ranges is enriched in network formers, mainly SiO2, creating a viscous barrier, which inhibits further crystal growth and limits the crystal size to the nanometric range.Peer reviewe