Homogeneous cosmologies from the quasi-Maxwell formalism

We show how to use the quasi-Maxwell formalism to obtain solutions of Einstein's field equations corresponding to homogeneous cosmologies - namely Einstein's universe, Godel's universe and the Ozsvath-Farnsworth-Kerr class I solutions - written in frames for which the associated observers are stationary.Comment: 15 pages, references adde

Judicial Risk and Credit Market Performance: Micro Evidence from Brazil Payroll Loans

A large body of literature has stressed the institution-development nexus as critical in explaining differences in countries' economic performance. The empirical evidence, however, has been mainly at the aggregate level, associating macro performance with measures of quality of institutions. This paper, by relating a judicial decision on the legality of payroll debit loans in Brazil to bank-level decision variables, provides micro evidence on how creditor legal protection affects market performance. Payroll loans are personal loans with principal and interests payments directly deducted from the borrowers' payroll check, which, in practice, makes a collateral out of future income. In June 2004, a high-level federal court upheld a regional court ruling that had declared payroll deduction illegal. Using personal loans without payroll deduction as a control group, we assess whether the ruling had an impact on market performance. Evidence indicates that it had an adverse impact on risk perception, interest rates, and amount lent.

On the global uniqueness for the Einstein-Maxwell-scalar field system with a cosmological constant. Part 3: Mass inflation and extendibility of the solutions

This paper is the third part of a trilogy dedicated to the following problem: given spherically symmetric characteristic initial data for the Einstein-Maxwell-scalar field system with a cosmological constant $\Lambda$, with the data on the outgoing initial null hypersurface given by a subextremal Reissner-Nordstrom black hole event horizon, study the future extendibility of the corresponding maximal globally hyperbolic development as a "suitably regular" Lorentzian manifold. In the first part of this series we established the well posedness of the characteristic problem, whereas in the second part we studied the stability of the radius function at the Cauchy horizon. In this third and final paper we show that, depending on the decay rate of the initial data, mass inflation may or may not occur. When the mass is controlled, it is possible to obtain continuous extensions of the metric across the Cauchy horizon with square integrable Christoffel symbols. Under slightly stronger conditions, we can bound the gradient of the scalar field. This allows the construction of (non-isometric) extensions of the maximal development which are classical solutions of the Einstein equations. Our results provide evidence against the validity of the strong cosmic censorship conjecture when $\Lambda>0$.Comment: 48 pages, 5 figures; v2: some presentation changes, mostly in the Introduction; v3: substantial changes in Section 5; v4: expanded Introduction; some presentation changes; matches final published versio

On the global uniqueness for the Einstein-Maxwell-scalar field system with a cosmological constant. Part 2: Structure of the solutions and stability of the Cauchy horizon

This paper is the second part of a trilogy dedicated to the following problem: given spherically symmetric characteristic initial data for the Einstein-Maxwell-scalar field system with a cosmological constant $\Lambda$, with the data on the outgoing initial null hypersurface given by a subextremal Reissner-Nordstrom black hole event horizon, study the future extendibility of the corresponding maximal globally hyperbolic development as a "suitably regular" Lorentzian manifold. In the first paper of this sequence, we established well posedness of the characteristic problem with general initial data. In this second paper, we generalize the results of Dafermos on the stability of the radius function at the Cauchy horizon by including a cosmological constant. This requires a considerable deviation from the strategy followed by Dafermos, focusing on the level sets of the radius function instead of the red-shift and blue-shift regions. We also present new results on the global structure of the solution when the free data is not identically zero in a neighborhood of the origin. In the third and final paper, we will consider the issue of mass inflation and extendibility of solutions beyond the Cauchy horizon.Comment: 44 pages, 13 figures; v2: a few small changes; v3: a paragraph was added in the Introduction, minor clarifications were made thoughout, the list of references was expanded, matches final published versio

Biomarkers: a strategic tool in the assessment of environmental quality of coastal waters

Ecosystems are under the pressure of complex mixtures of contaminants whose effects are not always simple to assess. Biomarkers, acting as early warning signals of the presence of potentially toxic xenobiotics, are useful tools for assessing either exposure to, or the effects of these compounds providing information about the toxicant bioavailability. In fact, it has been argued that a full understanding of ecotoxicological processes must consider an integrated multi-level approach, in which molecular impact is related with higher-order biological consequences at the individual, population and community levels. Monitoring programs should make use of this tool to link contaminants and ecological responses fulfilling strategies like those launched by OSPAR (Commissions of Oslo and Paris) Convention on the protection of the marine environment of the North-East Atlantic and the International Council for the Exploration of the Sea (ICES). An overview of the work done in the past few years using biomarkers as in situ tools for pollution assessment in Portuguese coastal waters is presented as a contribution to the set up of a biomonitoring program for the Portuguese coastal zone. Considering the data set available the biomonitoring proposal should include the analysis of biomarkers and effects at individual levels. The aim of the program will include a spatial and temporal characterization of the biomarkers acetyl-cholinesterase, metallothioneins, DNA damage, adenylate energy charge and scope-for-growth levels. The investigation of the spatial variation of biomarkers is crucial to define sites for long term monitoring, which will be integrated with a chemical monitoring program. This framework will be a major contribution to the implementation of a national database for the use of biomarkers along the Portuguese coast.info:eu-repo/semantics/publishedVersio

Concentración de metales en poblaciones de Marphysa sanguinea (Montagu, 1813) en el estuario del Sado: Efecto de su peso en la bioacumulación

Concentrations of Fe, Zn, Cu, Pb and Cd were measured in four surface sediments, whole worm tissues and faeces collected along Águas de Moura channel in Sado estuary. Six wet-weight worm classes were used to analyze the influence of weight. The metal concentration in colonized sediments is high for Fe and Cu, moderate for Pb and Zn, and low for Cd. The analyses of whole worm tissues show that Zn, Cd and Cu are accumulated. Considering the elevated sediment concentrations to which this species is exposed, the high levels of Zn and Cu suggest sequestration and Cu adaptation. However, the low Fe concentration indicates that this metal is not readily available. The similar Pb behaviour also suggests low availability or Fe interference. The high correlation in the sediment between Pb and Fe reinforces this suggestion. The results obtained show that Pb, Zn and Fe are the most important metals in the different weight classes. The overall results of this study show: (1) that this worm is able to adapt physiologically to elevated levels of metals; and (2) that the weight of the worms needs to be taken into account in environmental management programmes.Se midieron las concentraciones de Fe, Zn, Cu, Pb y Cd en 4 sedimentos de superficie, tejidos y excrementos de poliquetos recogidos en el canal de Agua de Moura, en el estuario del Sado. Para estudiar la influencia del peso se analizaron los poliquetos en 6 grupos de acuerdo con su peso húmedo. La concentración de metales en los sedimentos colonizados fue alta en Fe y Cu, moderada en Pb y Zn, y baja en Cd. Los resultados muestran que el Zn, Cu y Cd se acumulan en los tejidos. Los altos niveles de Cu y Zn sugieren secuestro y la existencia de una adaptación al Cu, relacionada con los altos niveles existentes en el sedimento. Por el contrario, la baja concentración de Fe indica una baja disponibilidad. El comportamiento similar del Pb también sugiere una baja disponibilidad y una injerencia de Fe. De hecho, la correlación significativa (

The singularity problem and phase-space noncanonical noncommutativity

The Wheeler-DeWitt equation arising from a Kantowski-Sachs model is considered for a Schwarzschild black hole under the assumption that the scale factors and the associated momenta satisfy a noncanonical noncommutative extension of the Heisenberg-Weyl algebra. An integral of motion is used to factorize the wave function into an oscillatory part and a function of a configuration space variable. The latter is shown to be normalizable using asymptotic arguments. It is then shown that on the hypersufaces of constant value of the argument of the wave function's oscillatory piece, the probability vanishes in the vicinity of the black hole singularity.Comment: 4 pages, revtex

a Fast Lock-Free Application Cache

When compared to blocking concurrency, non-blocking concurrency can provide higher performance in parallel shared-memory contexts, especially in high contention scenarios. This paper proposes FLeeC, an application-level cache system based on Memcached, which leverages re-designed data structures and non-blocking (or lock-free) concurrency to improve performance by allowing any number of concurrent writes and reads to its main data structures, even in high-contention scenarios. We discuss and evaluate its new algorithms, which allow a lock-free eviction policy and lock-free fast lookups. FLeeC can be used as a plug-in replacement for the original Memcached, and its new algorithms and concurrency control strategies result in considerable performance improvements (up to 6×).publishersversionpublishe