4,989 research outputs found
Analytic theory of correlation energy and spin polarization in the 2D electron gas
We present an analytic theory of the pair distribution function and the
ground-state energy in a two-dimensional (2D) electron gas with an arbitrary
degree of spin polarization. Our approach involves the solution of a
zero-energy scattering Schr\"odinger equation with an effective potential which
includes a Fermi term from exchange and kinetic energy and a Bose-like term
from Jastrow-Feenberg correlations. The form of the latter is assessed from an
analysis of data on a 2D gas of charged bosons. We obtain excellent agreement
with data from quantum Monte Carlo studies of the 2D electron gas. In
particular, our results for the correlation energy show a quantum phase
transition occurring at coupling strength from the paramagnetic
to the fully spin-polarized fluid.Comment: 9 pages, 4 figure
Diagnosis of Tuberculosis among Children and Adolescents
The authors discuss the challenging aspects of the diagnosis of tuberculosis in children and adolescents, since there is no gold standard for its diagnosis. The different clinical and radiological presentations and the low bacteriological positivity of tuberculosis in childhood are grounds for confrontation to the present. Immunological tests called interferon gamma release assays (IGRAs) failed to overcome the tuberculin skin test in practice. Advances with nucleic acid amplification tests, on the other hand, have contributed to the diagnosis of tuberculosis among adolescents. Standardized systems for diagnosis can be useful as tools for screening or for decision‐making in childhood tuberculosis
Avaliação retrospectiva de sistema de pontuação pelo Ministério da Saúde do Brasil, no diagnóstico de tuberculose pulmonar na criança: estudo controle de casos
Based on a retrospective case-control study we evaluated the score system adopted by the Ministry of Health of Brazil (Ministério da Saúde - MS), to diagnose pulmonary tuberculosis (PTB) in childhood. This system is independent of bacteriological or histopathological data to define a very likely (>; or = 40 points), possible (30-35 points) or unlikely (;10mm (OR = 8.23). The best cut-off point to the diagnosis of PTB was 30 points, where the score system was more accurate, with sensitivity of 88.9% and specificity of 86.5%.Avaliou-se o sistema de pontuação adotado pelo Ministério da Saúde do Brasil para o diagnóstico de tuberculose pulmonar (TP) na infância através de estudo caso-controle retrospectivo. Tal sistema independe de dados bacteriológicos ou histopatológicos e define o diagnóstico de tuberculose como muito provável (>; ou = 40 pontos); possível (30 a 35 pontos) ou pouco provável (; 10 mm (OR = 8,23). O melhor ponto de corte para o diagnóstico de TP foi 30 pontos, no qual houve maior acurácia do sistema, com sensibilidade de 99,9% e especificidade de 86,5%
Random Walks Along the Streets and Canals in Compact Cities: Spectral analysis, Dynamical Modularity, Information, and Statistical Mechanics
Different models of random walks on the dual graphs of compact urban
structures are considered. Analysis of access times between streets helps to
detect the city modularity. The statistical mechanics approach to the ensembles
of lazy random walkers is developed. The complexity of city modularity can be
measured by an information-like parameter which plays the role of an individual
fingerprint of {\it Genius loci}.
Global structural properties of a city can be characterized by the
thermodynamical parameters calculated in the random walks problem.Comment: 44 pages, 22 figures, 2 table
Semiclassical theory for spatial density oscillations in fermionic systems
We investigate the particle and kinetic-energy densities for a system of
fermions bound in a local (mean-field) potential V(\bfr). We generalize a
recently developed semiclassical theory [J. Roccia and M. Brack, Phys. Rev.\
Lett. {\bf 100}, 200408 (2008)], in which the densities are calculated in terms
of the closed orbits of the corresponding classical system, to
dimensions. We regularize the semiclassical results for the U(1) symmetry
breaking occurring for spherical systems at and near the classical
turning points where the Friedel oscillations are predominant and well
reproduced by the shortest orbit going from to the closest turning point
and back. For systems with spherical symmetry, we show that there exist two
types of oscillations which can be attributed to radial and non-radial orbits,
respectively. The semiclassical theory is tested against exact
quantum-mechanical calculations for a variety of model potentials. We find a
very good overall numerical agreement between semiclassical and exact numerical
densities even for moderate particle numbers . Using a "local virial
theorem", shown to be valid (except for a small region around the classical
turning points) for arbitrary local potentials, we can prove that the
Thomas-Fermi functional reproduces the oscillations in
the quantum-mechanical densities to first order in the oscillating parts.Comment: LaTeX, 22pp, 15 figs, 1 table, to be published in Phys. Rev.
Predicting the onset and persistence of episodes of depression in primary health care. The predictD-Spain study: Methodology
Background:
The effects of putative risk factors on the onset and/or persistence of depression remain unclear. We aim to develop comprehensive models to predict the onset and persistence of episodes of depression in primary care. Here we explain the general methodology of the predictD-Spain study and evaluate the reliability of the questionnaires used.
Methods:
This is a prospective cohort study. A systematic random sample of general practice attendees aged 18 to 75 has been recruited in seven Spanish provinces. Depression is being measured with the CIDI at baseline, and at 6, 12, 24 and 36 months. A set of individual, environmental, genetic, professional and organizational risk factors are to be assessed at each follow-up point. In a separate reliability study, a proportional random sample of 401 participants completed the test-retest (251 researcher-administered and 150 self-administered) between October 2005 and February 2006. We have also checked 118,398 items for data entry from a random sample of 480 patients stratified by province.
Results:
All items and questionnaires had good test-retest reliability for both methods of administration, except for the use of recreational drugs over the previous six months. Cronbach's alphas were good and their factorial analyses coherent for the three scales evaluated (social support from family and friends, dissatisfaction with paid work, and dissatisfaction with unpaid work). There were 191 (0.16%) data entry errors.
Conclusion:
The items and questionnaires were reliable and data quality control was excellent. When we eventually obtain our risk index for the onset and persistence of depression, we will be able to determine the individual risk of each patient evaluated in primary health car
Radiologic findings of pulmonary tuberculosis in adolescents
AbstractObjectiveTo describe radiologic findings of pulmonary tuberculosis (TB) in adolescents.MethodsRetrospective, cross-sectional, observational study of 850 patients with TB, aged 10 to 19 years, and notified to the Brazilian Ministry of Health. Data were collected from the TB notification and medical records in the cities of Manaus, Amazonas State, and Salvador, Bahia State, in the 1996–2003 period. Data are shown in tables and analyzed using the chi-square and Mann-Whitney tests, with a 5% significance level.ResultsMean age was 15.6 years; 443 (52.1%) patients were males. The most common radiologic lesion was the upper pulmonary lobe infiltrate (53.3%), and isolated cavitation was found in 32.4% of the patients. Both lungs were affected in 29.2% of the patients. The finding of bilateral radiologic lesions was significantly associated with longer disease duration (p = 0.0005).ConclusionsPulmonary TB in adolescents has similar characteristics to TB in adults, evidencing the important role played by adolescents in community disease transmission
“A few sparks of inspiration”?: Analysing the outcomes of European Union cultural policy coordination
This article examines the outcomes of cultural policy coordination in the European Union using a case study of one policy priority in the 2011–2014 Work Plan for Culture. The Open Method of Coordination brings Member States together to exchange and cooperate on key policy priorities. Drawing on interviews with key actors as well as participant observation material, the article demonstrates the limited influence of the culture OMC on domestic policy, showing that domestic usage tends to be on the scale of individuals and organisations rather than Member State-wide. The article finishes by contextualising the outcomes, highlighting the constraints and challenges of intergovernmental coordination in fields where the EU holds a supporting competence
Microscopic dynamics in liquid metals: the experimental point of view
The experimental results relevant for the understanding of the microscopic
dynamics in liquid metals are reviewed, with special regards to the ones
achieved in the last two decades. Inelastic Neutron Scattering played a major
role since the development of neutron facilities in the sixties. The last ten
years, however, saw the development of third generation radiation sources,
which opened the possibility of performing Inelastic Scattering with X rays,
thus disclosing previously unaccessible energy-momentum regions. The purely
coherent response of X rays, moreover, combined with the mixed
coherent/incoherent response typical of neutron scattering, provides enormous
potentialities to disentangle aspects related to the collectivity of motion
from the single particle dynamics.
If the last twenty years saw major experimental developments, on the
theoretical side fresh ideas came up to the side of the most traditional and
established theories. Beside the raw experimental results, therefore, we review
models and theoretical approaches for the description of microscopic dynamics
over different length-scales, from the hydrodynamic region down to the single
particle regime, walking the perilous and sometimes uncharted path of the
generalized hydrodynamics extension. Approaches peculiar of conductive systems,
based on the ionic plasma theory, are also considered, as well as kinetic and
mode coupling theory applied to hard sphere systems, which turn out to mimic
with remarkable detail the atomic dynamics of liquid metals. Finally, cutting
edges issues and open problems, such as the ultimate origin of the anomalous
acoustic dispersion or the relevance of transport properties of a conductive
systems in ruling the ionic dynamic structure factor are discussed.Comment: 53 pages, 41 figures, to appear in "The Review of Modern Physics".
Tentatively scheduled for July issu
A framework for deriving semantic web services
Web service-based development represents an emerging approach for the development of distributed information systems. Web services have been mainly applied by software practitioners as a means to modularize system functionality that can be offered across a network (e.g., intranet and/or the Internet). Although web services have been
predominantly developed as a technical solution for integrating software systems, there is a more business-oriented aspect that developers and enterprises need to deal with in order to benefit from the full potential of web services in an electronic market. This ‘ignored’ aspect is the representation of the semantics underlying the services themselves as well as the ‘things’ that the services manage. Currently languages like the Web Services Description Language (WSDL) provide the syntactic means to describe web services, but
lack in providing a semantic underpinning. In order to harvest all the benefits of web services technology, a framework has been developed for deriving business semantics from syntactic descriptions of web services. The benefits of such a framework are two-fold. Firstly, the framework provides a way to gradually construct domain ontologies from previously defined technical services. Secondly, the framework enables the
migration of syntactically defined web services toward semantic web services. The study follows a design research approach which (1) identifies the problem area and its relevance from an industrial case study and previous research, (2) develops the
framework as a design artifact and (3) evaluates the application of the framework through a relevant scenario
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