21,615 research outputs found
Reply to "Comment on 'Quantization of FRW spacetimes in the presence of a cosmological constant and radiation'"
The Comment by Amore {\it et al.} [gr-qc/0611029] contains a valid criticism
of the numerical precision of the results reported in a recent paper of ours
[Phys. Rev. D {\bf 73}, 044022 (2006)], as well as fresh ideas on how to
characterize a quantum cosmological singularity. However, we argue that,
contrary to what is suggested in the Comment, the quantum cosmological models
we studied show hardly any sign of singular behavior.Comment: 4 pages, accepted by Physical Review
Energy scales and the non-Fermi liquid behavior in YbRh2Si2
Multiple energy scales are detected in measurements of the thermodynamic and
transport properties in heavy fermion metals. We demonstrate that the
experimental data on the energy scales can be well described by the scaling
behavior of the effective mass at the fermion condensation quantum phase
transition, and show that the dependence of the effective mass on temperature
and applied magnetic fields gives rise to the non-Fermi liquid behavior. Our
analysis is placed in the context of recent salient experimental results. Our
calculations of the non-Fermi liquid behavior, of the scales and thermodynamic
and transport properties are in good agreement with the heat capacity,
magnetization, longitudinal magnetoresistance and magnetic entropy obtained in
remarkable measurements on the heavy fermion metal YbRh2Si2.Comment: 8 pages, 8 figure
Sistema de classificação fuzzy para o risco de infestação por plantas daninhas considerando a sua variabilidade espacial.
Este artigo trata do problema de classificação do risco de infestação por plantas daninhas usando técnicas geoestatísticas, análise de imagens e modelos de classificação fuzzy. Os principais atributos utilizados para descrever a infestação incluem a densidade de sementes, bem como a sua extensão, a cobertura foliar e a agressividade das plantas daninhas em cada região. A densidade de sementes reflete a produção de sementes por unidade de área, e a sua extensão, a influência das sementes vizinhas; a cobertura foliar indica a extensão dos agrupamentos das plantas daninhas emergentes; e a agressividade descreve a porcentagem de ocupação de espécies com alta capacidade de produção de sementes. Os dados da densidade de sementes, da cobertura foliar e da agressividade para as diferentes regiões são obtidos a partir de simulação com modelos matemáticos de populações. Neste artigo propõe-se um sistema de classificação fuzzy utilizando os atributos descritos para inferir os riscos de infestação de regiões da cultura por plantas daninhas. Resultados de simulação são apresentados para ilustrar o uso desse sistema na aplicação localizada de herbicida
The treatment of the infrared region in perturbative QCD
We discuss the contribution coming from the infrared region to NLO matrix
elements and/or coefficient functions of hard QCD processes. Strictly speaking,
this contribution is not known theoretically, since it is beyond perturbative
QCD. For DGLAP evolution all the infrared contributions are collected in the
phenomenological input parton distribution functions (PDFs), at some relatively
low scale Q_0; functions which are obtained from a fit to the `global' data.
However dimensional regularization sometimes produces a non-zero result coming
from the infrared region. Instead of this conventional regularization
treatment, we argue that the proper procedure is to first subtract from the NLO
matrix element the contribution already generated at the same order in \alpha_s
by the LO DGLAP splitting function convoluted with the LO matrix element. This
prescription eliminates the logarithmic infrared divergence, giving a
well-defined result which is consistent with the original idea that everything
below Q_0 is collected in the PDF input. We quantify the difference between the
proposed treatment and the conventional approach using low-mass Drell-Yan
production and deep inelastic electron-proton scattering as examples; and
discuss the potential impact on the `global' PDF analyses. We present arguments
to show that the difference cannot be regarded as simply the use of an
alternative factorization scheme.Comment: 15 pages, 5 figures, title changed, text considerably modified to
improve presentation, and discussion section enlarge
Reliability and validity of the Chester step test in patients with interstitial lung disease
The Chester Step Test (CST) is a simple and inexpensive field test, which requires minimal physical space to assess exercise capacity. Such characteristics make the CST suitable to be used in different settings, however, its measurement properties in patients with interstitial lung diseases (ILD) are unknown.
A cross-sectional study was conducted in patients with ILD. First, a CST-1 and a 6-minute walk test (6MWT) were performed. After 48-72 hours, a CST-2 was repeated. A 2nd rater was present in one of the sessions. Relative reliability was measured using intraclass correlation coefficient (ICC1,1 and ICC2,1). Absolute reliability was determined using standard error of measurement (SEM), minimal detectable change at 95% confidence interval (MDC95) and the Bland-Altman method. The values of SEM and MDC95 were also expressed as a percentage of the mean. Construct validity was explored using Spearman correlation coefficient (rs) between the number of steps taken in the best CST and the distance performed in the 6MWT.
Sixty-six patients with ILD (65.5±12.9 years; 48.5%men; FVC 79.4±18.8pp; DLCO 49.0±18.3pp) participated in the study. Relative (ICC 0.95-1.0) and absolute reliability were excellent without evidence of systematic bias. The SEM and MDC95 were 11.8 (14.7%) and 32.6 steps (40.7%), respectively. The correlation between CST and 6MWT was significant, positive, and high (rs=0.85, p=0.001).
The CST is a reliable and valid test and might be especially useful to assess exercise capacity in patients with ILD in limited space environments.publishe
On the physics and technology of gaseous particle detectors
Despite an already long and fruitful history, gaseous elementary-particle
detectors remain today an important mainstay of high-energy and nuclear physics
experiments and of radiation detection in general. In here we briefly describe
some of the gaseous detector's main technologies and applications, along with
some unsolved gas-discharge physics aspects of practical relevance.Comment: Submitted to Plasma Sources in Science and Technolog
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