15,135 research outputs found
Short-time behavior of a classical ferromagnet with double-exchange interaction
We investigate the critical dynamics of a classical ferromagnet on the simple
cubic lattice with double-exchange interaction. Estimates for the dynamic
critical exponents and are obtained using short-time Monte Carlo
simulations. We also estimate the static critical exponents and
studying the behavior of the samples at an early time. Our results are in good
agreement with available estimates and support the assertion that this model
and the classical Heisenberg model belong to the same universality class
Optical and Near Infrared Study of the Cepheus E outflow, a very low excitation object
We present images and spectra of the Cepheus E (Cep E) region at both optical
and infrared wavelengths. Only the brightest region of the southern lobe of the
Cep E outflow reveals optical emission, suggesting that the extinction close to
the outflow source plays an important r\^ole in the observed difference between
the optical and IR morphologies. Cep E is a unique object since it provides a
link between the spectroscopic properties of the optical Herbig-Haro (HH)
objects and those of deeply embedded outflows.Comment: Accepted Astron. J., 8 files: paper, tables plus 6 figure
Clinical, histological and prognostic features of a novel nail-bed lesion of cats: 41 cases
There is a distinct subset of lesions arising on the digits of cats, located at or close to the nail-bed epithelium, which are typically composed of proliferative fibroblast-like cells, multinucleate giant cells and areas of osseous metaplasia, but currently there is no published literature detailing the clinical or histological features of these lesions. This study identified 41 such cases from two large commercial diagnostic laboratories and assessed various histological and clinical features; 22 cases had additional follow-up data available
Variação da produtividade do arroz de terras altas influenciados pela seca meteorológica em Goiás.
A seca é um fenômeno meteorológico caracterizado pela falta de precipitação pluvial, que pode causar grandes prejuízos à produção agrícola. O presente trabalho tem como objetivo caracterizar a ocorrência de seca, utilizando o Índice Padronizado de Precipitação (SPI) em cinco microrregiões do estado de Goiás e sua influencia na produtividade de arroz de terras altas. As cinco microrregiões estudadas foram: Anápolis, Ceres, Iporá, Anicuns e Goiânia. A série de dados históricos de precipitação foi disponibilizada pela Agência Nacional de Águas (ANA), coletados em um município pertencente à microrregião analisada. O período de estudo foi de 1975 a 2005. Os dados de produtividade, para o mesmo período foi disponibilizado pela AGROTEC. Os valores do SPI foram caracterizados pela a ocorrência dos eventos de seca, frequência relativa, comparação com os dados de produtividade do arroz de terras altas e o percentual de acerto do índice. Foi possível observar que o SPI não acompanhou totalmente a variação da produtividade do arroz de terras altas. O SPI apresentou percentuais de acerto baixos, em todas as microrregiões, ficando próximo a 51%
The Ratio of Ortho- to Para-H2 in Photodissociation Regions
We discuss the ratio of ortho- to para-H2 in photodissociation regions
(PDRs). We draw attention to an apparent confusion in the literature between
the ortho-to-para ratio of molecules in FUV-pumped vibrationally excited
states, and the H2 ortho-to-para abundance ratio. These ratios are not the same
because the process of FUV-pumping of fluorescent H2 emission in PDRs occurs
via optically thick absorption lines. Thus, gas with an equilibrium ratio of
ortho- to para-H2 equal to 3 will yield FUV-pumped vibrationally excited
ortho-to-para ratios smaller than 3, because the ortho-H2 pumping rates are
preferentially reduced by optical depth effects. Indeed, if the ortho and para
pumping lines are on the ``square root'' part of the curve-of-growth, then the
expected ratio of ortho and para vibrational line strengths is the square root
of 3, ~ 1.7, close to the typically observed value. Thus, contrary to what has
sometimes been stated in the literature, most previous measurements of the
ratio of ortho- to para-H2 in vibrationally excited states are entirely
consistent with a total ortho-to-para ratio of 3, the equilibrium value for
temperatures greater than 200 K. We present an analysis and several detailed
models which illustrate the relationship between the total ratios of ortho- to
para-H2 and the vibrationally excited ortho-to-para ratios in PDRs. Recent
Infrared Space Observatory (ISO) measurements of pure rotational and
vibrational H2 emissions from the PDR in the star-forming region S140 provide
strong observational support for our conclusions.Comment: 23 pages (including 5 figures), LaTeX, uses aaspp4.sty, accepted for
publication in Ap
Infrared scintillation yield in gaseous and liquid argon
The study of primary and secondary scintillations in noble gases and liquids
is of paramount importance to rare-event experiments using noble gas media. In
the present work, the scintillation yield in gaseous and liquid Ar has for the
first time been measured in the near infrared (NIR) and visible region, both
for primary and secondary (proportional) scintillations, using Geiger-mode
avalanche photodiodes (G-APDs) and pulsed X-ray irradiation. The primary
scintillation yield of the fast component was measured to be 17000 photon/MeV
in gaseous Ar in the NIR, in the range of 690-1000 nm, and 510 photon/MeV in
liquid Ar, in the range of 400-1000 nm. Proportional NIR scintillations
(electroluminescence) in gaseous Ar have been also observed; their
amplification parameter at 163 K was measured to be 13 photons per drifting
electron per kV. Possible applications of NIR scintillations in high energy
physics experiments are discussed.Comment: 6 pages, 5 figures. Submitted to Europhysics Letter. Revised Figs. 3
and
System and market failures: the unavailability of magnesium sulphate for the treatment of eclampsia and pre-eclampsia in Mozambique and Zimbabwe.
Low cost and effective drugs, such as magnesium sulphate, need to be included in initiatives to improve access to essential medicines in Afric
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