7,330 research outputs found
Seleção preliminar de parâmetros fÃsicos mais adequados para estudar o efeito da compactação de amostras de solo sobre a produção de matéria seca vegetal de feijoeiro (Phaseolus vulgaris L.)
Amostras dos horizontes de um Oxisol e de um Alfisol submetidas a compactação, cuja intensidade foi determinada através da medida da resistência a penetração de penotrógrafo de cone, foram cultivadas com feijoeiro cultivar Rio Pardo 896 durante 67 dias, em vasos com 3,8 litros de terra, em casa de vegetação, com a unidade na faixa correspondente as tensões entre 100 e 300 m bares
Wave Scattering through Classically Chaotic Cavities in the Presence of Absorption: An Information-Theoretic Model
We propose an information-theoretic model for the transport of waves through
a chaotic cavity in the presence of absorption. The entropy of the S-matrix
statistical distribution is maximized, with the constraint : n is the dimensionality of S, and meaning complete (no) absorption. For strong absorption our result
agrees with a number of analytical calculations already given in the
literature. In that limit, the distribution of the individual (angular)
transmission and reflection coefficients becomes exponential -Rayleigh
statistics- even for n=1. For Rayleigh statistics is attained even
with no absorption; here we extend the study to . The model is
compared with random-matrix-theory numerical simulations: it describes the
problem very well for strong absorption, but fails for moderate and weak
absorptions. Thus, in the latter regime, some important physical constraint is
missing in the construction of the model.Comment: 4 pages, latex, 3 ps figure
Eficiência nutricional de feijoeiro (Phaseolus vulgaris) em oxisol e alfisol em função dos nÃveis de compactação dos solos.
Dois cultivares de feijoeiro foram cultivados sobre amostras de terra de um oxisol e de um alfisol, adubadas e não adubadas, sujeitas a 3 nÃveis de compactação, e confinadas em vasos com capacidade para 3,8 L
Efeito do nÃvel de fertilidade de dois solos submetidos a compactação sobre o comportamento do acumulo de matéria seca e nutrientes por feijoeiro (Phaseolus vulgaris L.)
Resumo
III.9 Star-planet Interactions
This book is dedicated to all the people interested in the CoRoT mission and the beautiful data that were delivered during its six year duration. Either amateurs, professional, young or senior researchers, they will find treasures not only at the time of this publication but also in the future twenty or thirty years. It presents the data in their final version, explains how they have been obtained, how to handle them, describes the tools necessary to understand them, and where to find them. It also highlights the most striking first results obtained up to now. CoRoT has opened several unexpected directions of research and certainly new ones still to be discovered
High-resolution abundance analysis of HD 140283
HD 140283 is a reference subgiant that is metal poor and confirmed to be a
very old star. The abundances of this type of old star can constrain the nature
and nucleosynthesis processes that occurred in its (even older) progenitors.
The present study may shed light on nucleosynthesis processes yielding heavy
elements early in the Galaxy. A detailed abundance analysis of a high-quality
spectrum is carried out, with the intent of providing a reference on stellar
lines and abundances of a very old, metal-poor subgiant. We aim to derive
abundances from most available and measurable spectral lines. The analysis is
carried out using high-resolution (R = 81 000) and high signal-to-noise ratio
(800 < S/N/pixel < 3400) spectrum, in the wavelength range 3700 - 10475,
obtained with a seven-hour exposure time, using the ESPaDOnS at the CFHT. The
calculations in LTE were performed with the OSMARCS 1D atmospheric model and
the spectrum synthesis code Turbospectrum, while the analysis in NLTE is based
on the MULTI code. We present LTE abundances for 26 elements, and NLTE
calculations for the species C I, O I, Na I, Mg I, Al I, K I, Ca I, Sr II, and
Ba II lines. The abundance analysis provided an extensive line list suitable
for metal-poor subgiant stars. The results for Li, CNO, alpha-, and iron peak
elements are in good agreement with literature. The newly NLTE Ba abundance,
along with a NLTE Eu correction and a 3D Ba correction from literature, leads
to [Eu/Ba] = +0.59 +/- 0.18. This result confirms a dominant r-process
contribution, possibly together with a very small contribution from the main
s-process, to the neutron-capture elements in HD 140283. Overabundances of the
lighter heavy elements and the high abundances derived for Ba, La, and Ce
favour the operation of the weak r-process in HD 140283.Comment: 34 pages, 27 figure
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