Large time behavior for vortex evolution in the half-plane

In this article we study the long-time behavior of incompressible ideal flow in a half plane from the point of view of vortex scattering. Our main result is that certain asymptotic states for half-plane vortex dynamics decompose naturally into a nonlinear superposition of soliton-like states. Our approach is to combine techniques developed in the study of vortex confinement with weak convergence tools in order to study the asymptotic behavior of a self-similar rescaling of a solution of the incompressible 2D Euler equations on a half plane with compactly supported, nonnegative initial vorticity.Comment: 30 pages, no figure

The determinants of work autonomy and employee involvement: A multilevel analysis

Although work autonomy (WA) and employee involvement (EI) are often subsumed into a single construct in the literature, we argue that there is theoretical and empirical ground to meaningfully distinguish the two notions. To better understand a) the extent to which WA and EI are distinct constructs and b) the factors that explain their respective levels, we use the 2010 European Working Conditions Survey to build sound indexes of WA and EI, provide a picture of the level of both constructs in 31 European countries and analyse their predictors through multilevel structural models. The results show that WA and EI differ significantly in what concerns their macro-level but not micro-level predictors. Whereas union density and generalised trust strongly influence EI, only generalised trust impacts WA. Documenting that generalised trust as a macro-social trait is powerfully associated with organizational choices is a key contribution of the paper.info:eu-repo/semantics/acceptedVersio

Career stages and occupations impacts on workers motivations

Purpose: The career concept has become fuzzier due to changing work patterns, the ageing workforce, and the environmental changes occurring during employee lifespans. Together this requires a renewed and broader reaching contextualization of this concept. The aim of this article is to set out an integrative approach arguing that the integration of career stage models with occupational groups proves more explanative of intrinsic and extrinsic worker motivations Design/methodology/approach: Secondary data from 23 European countries was drawn from the European Social Survey 2006. The construct validity and reliability of indicators was analysed. Hypotheses were tested using discriminant analysis. Findings: Results showed that neither occupations nor career stages are determinants per se of intrinsic motivations, but are better explained by their mutual integration. Career stages were shown to predict per se extrinsic motivations. Research limitations/implications: The recourse to the ESS pre-determined scales and the application of age ranges as proxies for careers stages suggested the usage of more specific measures in future studies. Practical implications: Career management and compensation policies might be better tailored to worker motivations by considering the age ranges (as proxies of career stages) and workers’ occupations. Originality/value: Findings evidenced the explanatory value of occupations for worker motivations and allowed putting into perspective the contextualization of not only boundaryless and protean career concepts, but also career stage theories. Data supports the ecological validity of applying a career stages and occupations framework to a highly diversified and representative sample of European countries.info:eu-repo/semantics/acceptedVersio

Participation of wind power producers in intra-day markets : a case-study

ABSTRACT: The evolution of renewable energy has increased substantially over the past decade. Wind power producers (WPPs) can submit bids to energy markets, making short-term commitments to produce specific quantities of energy. This article presents a case-study to analyze the benefits of the active participation of wind power producers in energy markets, particularly intra-day markets. The case-study is carried out with the help of the MATREM system. The preliminary results indicate a reduction of the deviations of WPPs, but also a decreasing in their remuneration. Thus, the results highlight to some extent the importance of new market mechanisms to enable the active participation of WPPs in markets, without support policies.info:eu-repo/semantics/publishedVersio

Tests of Bayesian Model Selection Techniques for Gravitational Wave Astronomy

The analysis of gravitational wave data involves many model selection problems. The most important example is the detection problem of selecting between the data being consistent with instrument noise alone, or instrument noise and a gravitational wave signal. The analysis of data from ground based gravitational wave detectors is mostly conducted using classical statistics, and methods such as the Neyman-Pearson criteria are used for model selection. Future space based detectors, such as the \emph{Laser Interferometer Space Antenna} (LISA), are expected to produced rich data streams containing the signals from many millions of sources. Determining the number of sources that are resolvable, and the most appropriate description of each source poses a challenging model selection problem that may best be addressed in a Bayesian framework. An important class of LISA sources are the millions of low-mass binary systems within our own galaxy, tens of thousands of which will be detectable. Not only are the number of sources unknown, but so are the number of parameters required to model the waveforms. For example, a significant subset of the resolvable galactic binaries will exhibit orbital frequency evolution, while a smaller number will have measurable eccentricity. In the Bayesian approach to model selection one needs to compute the Bayes factor between competing models. Here we explore various methods for computing Bayes factors in the context of determining which galactic binaries have measurable frequency evolution. The methods explored include a Reverse Jump Markov Chain Monte Carlo (RJMCMC) algorithm, Savage-Dickie density ratios, the Schwarz-Bayes Information Criterion (BIC), and the Laplace approximation to the model evidence. We find good agreement between all of the approaches.Comment: 11 pages, 6 figure

Non-parametric comparison of histogrammed two-dimensional data distributions using the Energy Test

When monitoring complex experiments, comparison is often made between regularly acquired histograms of data and reference histograms which represent the ideal state of the equipment. With the larger HEP experiments now ramping up, there is a need for automation of this task since the volume of comparisons could overwhelm human operators. However, the two-dimensional histogram comparison tools available in ROOT have been noted in the past to exhibit shortcomings. We discuss a newer comparison test for two-dimensional histograms, based on the Energy Test of Aslan and Zech, which provides more conclusive discrimination between histograms of data coming from different distributions than methods provided in a recent ROOT release.The Science and Technology Facilities Council, U

Susceptibility patterns and cross-resistance evaluation of several biofilm-producing P. aeruginosachallenged by antibiotics

P.aeruginosa (PA) is an opportunistic pathogen responsible for high percentage of nosocomial infections. Its virulence and persistence rises when bacteria switch from planktonic to biofilm state and when facing antimicrobial pressures. This study aimed to evaluate the antimicrobial tolerance and regrowth of several biofilmproducing PA after antibiotic treatment, and the occurrence of cross-resistance to other antimicrobials. PAO, ATCC, CGCT and an isolated strain were used to form 1-day old biofilms in the presence of ciprofloxacin (CIP). Biofilm regrowth was evaluated after 48h, 72h and 96h after addition of, respectively, fresh medium, medium with antibiotic and antibiotic-free medium again. The final 4-days old biofilms were then attacked with CIP, gentamicin, rifampicin and benzalkonium chloride. After 24h and 72h of biofilm growth, it was observed a good reduction of the biofilm mass, respiratory activity and CFU/cm2. However, PA biofilm regrowth with similar or even higher cell numbers, comparatively to control, were noticed always the antibiotic-free medium was added. Data allowed speculating that the adhered bacteria that survived to antibiotic therapy may become more resistant to CIP or to other antimicrobials. Luckily, data did not show evidence of cross-resistance to the antimicrobials tested. Biofilms formed in the presence of CIP appeared to be more susceptible to the anti-biofilm action of antimicrobials. Although it has been observed marked biofilm regrowth after good levels of biofilm eradication due to antibiotic treatment, the resulting biofilms challenged by CIP seemed to be less tolerant to the action of other antimicrobials.IBB-CEB and FCT (PTDC/SAU-ESA/64609/2006; SFRH/BD/31065/2006; SFRH/ BD/47613/2008

Renewable energy support policy based on contracts for difference and bilateral negotiation

ABSTRACT: The European Union has been one of the major drivers of the development of renewable energy. The energy policies of most European countries have involved subsidized tariffs, such as the feed-in tariff in Portugal, the regulated tariff and the market price plus premium in Spain, and the Renewables Obligation in UK, that came into effect in 2002. Recently, UK has made some reforms and started to consider contracts for difference (CfDs) as a key element of the energy policy. This paper presents a support policy based on CfDs and bilateral negotiation. The first phase consists in a CfD auction and the second phase involves a bilateral negotiation between a Government and each of the selected investors. The paper also presents a case-study to analyze the potential benefits of the support policy. It was performed with the help of the MATREM system. The preliminary results indicate some advantages for the Government (and, in some cases, for the investors as well).info:eu-repo/semantics/publishedVersio