The very steep spectrum radio halo in Abell 697

In this paper we present a detailed study of the giant radio halo in the galaxy cluster Abell 697, with the aim to constrain its origin and connection with the cluster dynamics. We performed high sensitivity GMRT observations at 325 MHz, which showed that the radio halo is much brighter and larger at this frequency, compared to previous 610 MHz observations. In order to derive the integrated spectrum in the frequency range 325 MHz--1.4 GHz, we re--analysed archival VLA data at 1.4 GHz and made use of proprietary GMRT data at 610 MHz. {Our multifrequency analysis shows that the total radio spectrum of the giant radio halo in A\,697 is very steep, with $\alpha_{\rm~325 MHz}^{\rm~1.4 GHz} \approx 1.7-1.8$. %\pm0.1$. Due to energy arguments, a hadronic origin of the halo is disfavoured by such steep spectrum. Very steep spectrum halos in merging clusters are predicted in the case that the emitting electrons are accelerated by turbulence, observations with the upcoming low frequency arrays will be able to test these expectations.}Comment: 10 pages, 8 figures, A&A in pres

An optimization-based heuristic for the multi-objective undirected capacitated arc routing problem

The Multi-objective Undirected Capacitated Arc Routing Problem (MUCARP) is the optimization problem aimed at finding the best strategy for servicing a subset of clients localized along the links of a logistic network, by using a fleet of vehicles and optimizing more than one objective. In general, the first goal consists in minimizing the total transportation cost, and in this case the problem brings back to the well-known Undirected Capacitated Arc Routing Problem (UCARP). The motivation behind the study of the MUCARP lies in the study of real situations where companies working in the logistic distribution field deal with complex operational strategies, in which different actors (trucks, drivers, customers) have to be allocated within an unified framework by taking into account opposite needs and different employment contracts. All the previous considerations lead to the MUCARP as a benchmark optimization problem for modeling practical situations. In this paper, the MUCARP is heuristically tackled. In particular, three competitive objectives are minimized at the same time: the total transportation cost, the longest route cost (makespan) and the number of vehicles (i.e., the total number of routes). An approximation of the optimal Pareto front is determined through an optimization-based heuristic procedure, whose performances are tested and analyzed on classical benchmark instances

Solving simulation optimization problems on grid computing systems

The optimal assignment of berth slots and cranes to shipping services is the central logistics problem at modern marine container terminals and should be formulated to specifically account for its stochastic nature. We use a computational grid to solve a major seaport logistic problem by a simulation optimization approach centred around a queuing network model of the logistic process of interest. We emphasize the power of grid computing for the simulation optimization studies and we design and implement an algorithm for distributing the computational load to parallel processors. Performance of the algorithm is demonstrated numerically using real-sized problem instances

CT colonography: Results and limitations

Meta-analysis of data from studies of CT colonography suggests that it has excellent per-patient average sensitivity and average specificity for detection of adenomatous polyps and cancer. However, while its potential as a screening test is undoubted, there are several current limitations that will need to be overcome before it can be considered seriously by health policy makers. These revolve around issues of generalisability, which is inhibited most by a lack of trained observers and access to CT scanners, and a paucity of data relating to cost-effectiveness. Whether offering CT colonography as an alternative to competing strategies will genuinely enhance compliance also needs further and more detailed attention. (C) 2006 Published by Elsevier Ireland Ltd

Respostas comportamentais de vacas holandesas de alta produção criadas em ambientes quentes, mediante ao sistema de resfriamento adiabático evaporativo

O presente trabalho objetivou avaliar o comportamento de vacas holandesas em free-stall, no Centro de Pesquisa Agropecuária dos Tabuleiros Costeiros – CPATC – EMBRAPA (Sergipe, Brasil). Foram utilizadas 20 vacas em lactação, divididas em dois grupos - a) tratados com aspersão de água (SRAE) nos horários mais quentes do dia (10 às 14 horas) e b) controle. As avaliações foram feitas durante três dias ininterruptos, tendo sido as mesmas divididas em intermitentes (ingestão de alimentos, ruminação e outras atividades - ócio) e contínuas (consumo de água, sal e aspectos fisiológicos – urinar e defecar). Foram registradas as atividades dos animais, a freqüência de utilização dos locais (corredores ou baias) e as posições no lote (de pé ou deitadas). O consumo de água foi mais freqüente durante a tarde, nas vacas do grupo controle. As vacas ruminaram e descansaram deitadas com quatro patas na baia, freqüentemente, no intervalo das 23 às 05 horas, o grupo controle descansou deitado no corredor, mostrando certo desconforto, este grupo defecou com maior intensidade que as vacas do SRAE, a urinação, por sua vez esteve majoritariamente presente nas vacas do SRAE. O comportamento confirmou que o microclima do free-stall afetou diretamente o bem-estar e a adaptabilidade dos animais no nordeste