Determining efficient temperature sets for the simulated tempering method

In statistical physics, the efficiency of tempering approaches strongly depends on ingredients such as the number of replicas $R$, reliable determination of weight factors and the set of used temperatures, ${\mathcal T}_R = \{T_1, T_2, \ldots, T_R\}$. For the simulated tempering (SP) in particular -- useful due to its generality and conceptual simplicity -- the latter aspect (closely related to the actual $R$) may be a key issue in problems displaying metastability and trapping in certain regions of the phase space. To determine ${\mathcal T}_R$'s leading to accurate thermodynamics estimates and still trying to minimize the simulation computational time, here it is considered a fixed exchange frequency scheme for the ST. From the temperature of interest $T_1$, successive $T$'s are chosen so that the exchange frequency between any adjacent pair $T_r$ and $T_{r+1}$ has a same value $f$. By varying the $f$'s and analyzing the ${\mathcal T}_R$'s through relatively inexpensive tests (e.g., time decay toward the steady regime), an optimal situation in which the simulations visit much faster and more uniformly the relevant portions of the phase space is determined. As illustrations, the proposal is applied to three lattice models, BEG, Bell-Lavis, and Potts, in the hard case of extreme first-order phase transitions, always giving very good results, even for $R=3$. Also, comparisons with other protocols (constant entropy and arithmetic progression) to choose the set ${\mathcal T}_R$ are undertaken. The fixed exchange frequency method is found to be consistently superior, specially for small $R$'s. Finally, distinct instances where the prescription could be helpful (in second-order transitions and for the parallel tempering approach) are briefly discussed.Comment: 10 pages, 14 figure

Utilização de energia solar e cercas eletrificadas no manejo das pastagens no Acre.

Este documento apresenta informações que visam orientar técnicos e produtores rurais do Acre para o uso eficiente da energia solar e das cercas eletrificadas no manejo de suas propriedades.bitstream/item/116523/1/7296.pd

Editorial: Post-anesthesia Cognitive Dysfunction: How, When and Why

This work has been funded by FEDER funds through COMPETE 2020 and the POCI (POCI-01-0145-FEDER-029542), Portugal 2020, and by Fundação para a Ciência e a Tecnologia under the project PTDC/CVT-CVT/29542/2017

Analysis of Abstracts Presented at the Prosthodontic Research Section of IADR General Sessions 2004–2005: Demographics, Publication Rates, and Factors Contributing to Publication

Purpose: The purposes of this study were to describe the demographics of abstracts presented at the prosthodontics section of IADR General Sessions from 2004 to 2005, evaluate the publication rate of abstracts, and analyze the relationship between variables in abstracts and publication. Materials and Methods: Prosthodontics research section abstracts from the IADR General Session in 2004 and 2005 were evaluated for: number of authors, presentation type, origin, affiliation, topic, study design, statistics, study outcome, and funding. The publication rate was calculated following a PubMed search. The journal of publication, year of publication, and the length of time before publication were analyzed. Descriptive statistics were used for the data analysis; the relationships between presentation type, study design, study outcome, statistics, funding, and publication were analyzed using logistic regression (α= 0.05). Results: From 346 abstracts, 37.0% were published. For oral presentations, 40.7% were published; 35.8% of poster presentations were published. The mean duration before publication was 26.4 months. North America had the most abstracts, and Europe had the most publications. Fixed prosthodontic research had the highest number and proportion for publication. A significant association with publication was noted for neutral study outcomes (p= 0.018), studies with funding (p= 0.035), and abstracts from Europe (p= 0.001). Conclusions: The majority of abstracts from the prosthodontics research section of IADR General Sessions from 2004 and 2005 remain unpublished. A significant association for publication was noted with neutral outcomes, funding, and abstracts from Europe

Consorciação de gramíneas e leguminosas forrageiras no Acre.

As consorciações entre sete gramíneas e seis leguminosas forrageiras foram avaliadas no campo experimental do Projeto de Melhoramento de Pastagens da Amazônia Legal - PROPASTO, localizado no município de Senador Guiomard - Acre, em área de floresta tropical úmida. A importância do trabalho está relacionada ao fato das leguminosas constituirem o meio natural e, possivelmente, o mais importante método de incorporar nitrogênio do sistema solo/planta, além de contribuir para aumentar a qualidade da forragem. Foram efetuadas avaliações qualitativas e quantitativas das consorciações no período de fevereiro/77 a fevereiro/80 a intervalos de 45 a 56 dias no período chuvoso e seco, respectivamente. A consorciação de Quicuio da Amazônia (Brachiaria humidícula) com Puerária (Pueraria phaseoloides) apresentou a melhor persistência de produção e composição botânica no período seco e chuvoso. A utilização da Puerária em consorciação com gramíneas aumentou o valor nutritivo da pastagem, permitindo aumentar a performance animal e, consequentemente, a rentabilidade do empreendimento.bitstream/item/161391/1/1018.pd

Magnetoelectric coupling on fused azulene oligomers

The global magnetic phase diagram for fused azulene oligomers is obtained by using a fermionic Hubbard model, which is an intermediate between the molecular Pariser-Parr-Pople empiric Hamiltonian and the spin-1/2 antiferromagnetic Heisenberg model. We employ the density matrix renormalization group (DMRG) approach to explore the ground state properties of azulene-like molecules as a function of the electronic correlation and the oligomer size. It is shown that, depending on the length of the oligomer, fused azulene transitions from a singlet (S=0) to a higher-spin (S=1,2) ground state. Near the quantum magnetic phase transition the electric dipole moment, present on fused azulene molecules, couples with the magnetic moment leading to a divergent magnetoelectric susceptibility at the boundary lines of the magnetic phase diagram. These spontaneous electric and magnetic polarizations, together with the magnetoelectric coupling between them, indeed corroborate that these fused azulene oligomers can be viewed as a purely organic multiferroic material, being a magnetoelectric molecule.Fil: Valentim, Alexandra. Universidade Estadual da Paraiba; Brasil. Universidade Federal de Minas Gerais; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia, Daniel Julio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro | Universidad Nacional de Cuyo. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Plascak, J. A.. University of Georgia; Estados Unidos. Universidade Federal de Minas Gerais; Brasil. Universidade Estadual da Paraiba; Brasi