Clouds of Small Things: Provisioning Infrastructure-as-a-Service from within Community Networks

Community networks offer a shared communication infrastructure where communities of citizens build and own open networks. While the IP connectivity of the networking devices is successfully achieved, the number of services and applications available from within the community network is typically small and the usage of the community network is often limited to providing Internet access to remote areas through wireless links. In this paper we propose to apply the principle of resource sharing of community networks, currently limited to the network bandwidth, to other computing resources, which leads to cloud computing in community networks. Towards this vision, we review some characteristics of community networks and identify potential scenarios for community clouds. We simulate a cloud computing infrastructure service and discuss different aspects of its performance in comparison to a commercial centralized cloud system. We note that in community clouds the computing resources are heterogeneous and less powerful, which affects the time needed to assign resources. Response time of the infrastructure service is high in community clouds even for a small number of resources since resources are distributed, but tends to get closer to that of a centralized cloud when the number of resources requested increases. Our initial results suggest that the performance of the community clouds highly depends on the community network conditions, but has some potential for improvement with network-aware cloud services. The main strength compared to commercial cloud services, however, is that community cloud services hosted on community-owned resources will follow the principles of community network and will be neutral and open

Who and how should participate in health care priority setting? Evidence from a Portuguese survey

This article provides highlights of the evolution of the health care rationing debate towards a more transparent and open approach involving public participation. Discretionary models that have dominated health sector decision-making are being questioned by different sectors of society. Using data from 442 college students, we explore public’s views on its involvement in health care rationing decisions. Findings suggest that although citizens wish to be consulted, they believe doctors should play the most important role on the rationing decisions. Nonetheless, the confidence in doctors is not independent of the criteria used to support their decisions.Priorities setting, Public involvement; Explicit rationing; Health-care.

Environmental tobacco smoke risk perception and smoking behavior in Portugal

This study analyzes public attitudes towards environmental tobacco smoking (ETS) risks. ETS legislation and smoking behaviors using recent data from Special Eurobarometer 272 that is a unique database on public perception of ETS. Some major conclusions are drawn: (1) both smokers and non-smokers are aware of health consequences from ETS, (2) moderate and heavy smokers tend to be less concerned with seriousness of the health consequences, (3) that the belief that ETS increases the risk of a serious disease decreases the probability of being smoker, (4)ETS beliefs do not affect the quitting decision, (5) those who smoke at home appear to be aware of health consequences of ETS, (6) ETS health risk beliefs is negatively associated with the number of cigarette consumed.

A (Semi)Parametric Functional Coefficient Logarithmic Autoregressive Conditional Duration Model

Conteúdo online de acesso restrito pelo editorIn this article, we propose a class of logarithmic autoregressive conditional duration (ACD)-type models that accommodates overdispersion, intermittent dynamics, multiple regimes, and asymmetries in financial durations. In particular, our functional coefficient logarithmic autoregressive conditional duration (FC-LACD) model relies on a smooth transition autoregressive specification. The motivation lies on the fact that the latter yields a universal approximation if one lets the number of regimes grows without bound. After establishing sufficient conditions for strict stationarity, we address model identifiability as well as the asymptotic properties of the quasi-maximum likelihood (QML) estimator for the FC-LACD model with a fixed number of regimes. In addition, we also discuss how to consistently estimate a semiparametric variant of the FC-LACD model that takes the number of regimes to infinity. An empirical illustration indicates that our functional coefficient model is flexible enough to model IBM price durations.CNPq; Pronex/FAPER

A parallel multigrid solver for multi-patch Isogeometric Analysis

Isogeometric Analysis (IgA) is a framework for setting up spline-based discretizations of partial differential equations, which has been introduced around a decade ago and has gained much attention since then. If large spline degrees are considered, one obtains the approximation power of a high-order method, but the number of degrees of freedom behaves like for a low-order method. One important ingredient to use a discretization with large spline degree, is a robust and preferably parallelizable solver. While numerical evidence shows that multigrid solvers with standard smoothers (like Gauss Seidel) does not perform well if the spline degree is increased, the multigrid solvers proposed by the authors and their co-workers proved to behave optimal both in the grid size and the spline degree. In the present paper, the authors want to show that those solvers are parallelizable and that they scale well in a parallel environment.Comment: The first author would like to thank the Austrian Science Fund (FWF) for the financial support through the DK W1214-04, while the second author was supported by the FWF grant NFN S117-0

Natural nanomaterials : reappraising the elusive structure of the nano-sized mineral ferrihydrite through X-Ray absorption spectroscopy at the iron K-edge

Ferrihydrite is natural ferric oxyhydroxide occurring exclusively nanocrystalline. With ideal formula 5 Fe2 O3 . 9 H2 O, ferrihydrite is quite abundant in sediments, weathering crusts and mine wastes, being characteristic of red pre-soils formed by loose weathered rock plus mineral debris (regoliths) and commonly designated as “2-line” or “6-line” on the basis of the broadened maxima observed in the X-ray diffraction pattern. Synthetic nanocrystalline “6-line” ferrihydrite was recently studied through methods based on atomic-pair distribution functions disclosing the possible occurrence of icosahedral clusters formed by twelve octahedra centred by an inner tetrahedron, all filled by Fe 3+ ions. However, Mössbauer studies were inconclusive about the existence of 4-coordinated iron, thus suggesting that the tetrahedral cation may well be Si4+. In view of such structural uncertainty, a XANES study at the Fe K-edge was undertaken on ferrihydrite from a regolith to ascertain the occurrence of tetrahedral iron. Comparison with data collected from well crystallized iron oxide and hydroxide minerals where Fe 3+/2+ ions occur in octahedral and tetrahedral coordination is described and the results so far obtained are discussed, showing that supplementary study is needed on the elusive structure of ferrihydrite

Formaldehyde and urea removal in a denitrifying granular sludge blanket reactor

Simultaneous formaldehyde biodegradation, urea hydrolysis and denitrification in anoxic batch assays and in a continuous laboratory anoxic reactor were investigated. In batch assays, the initial formaldehyde biodegradation rate was around 0.7 g CH2O g VSS−1 d−1 and independent of the urea concentration (90– 370 mg N–NH2CONH2 l−1). Urea was completely hydrolyzed to ammonium in the presence of 430 mg l−1 formaldehyde and complete denitrification took place in all cases (125 mg N–NO−3 l−1). Formaldehyde removal efficiencies above 99.5% were obtained in a lab-scale denitrifying upflow sludge blanket reactor at organic loading rates between 0.37 and 2.96 kg COD m−3 d−1 (625–5000 mg CH2O l−1). The urea loading rate was increased from 0.06 to 0.44 kg N m−3 d−1 (100–800 mg N–NH2CONH2 l−1) and hydrolysis to ammonium was around 77.5% at all loading rates. The denitrification process was always almost complete (100–800 mg N–NO3− l−1), due to the high COD/N ratio of 6.7 in the influent. A minimum value of 3.5 was found to be required for full denitrification. The composition of the biogas indicated that denitrification and methanogenesis occurred simultaneously in the same unit. A good granulation of the sludge was observed