2,715 research outputs found
Carbon nanotube: a low-loss spin-current waveguide
We demonstrate with a quantum-mechanical approach that carbon nanotubes are
excellent spin-current waveguides and are able to carry information stored in a
precessing magnetic moment for long distances with very little dispersion and
with tunable degrees of attenuation. Pulsed magnetic excitations are predicted
to travel with the nanotube Fermi velocity and are able to induce similar
excitations in remote locations. Such an efficient way of transporting magnetic
information suggests that nanotubes are promising candidates for memory devices
with fast magnetization switchings
Avaliação do timol na prevenção da degradação biológica de nitrogênio em águas naturais.
SBQ SUL
Características morfoagronômicas e bromatológicas de acessos de nim indiano.
No Nordeste brasileiro, o nim foi amplamente difundido e utilizado na arborização urbana, na utilização de frutos em escala industrial e é também uma opção para lenha. Em 2009, a Embrapa Tabuleiros Costeiros, acreditando no seu potencial para extração de óleo, implantou um Banco de Germoplasma da espécie, em Aracaju. Ainda em fase de ampliação, o BAG é avaliado constantemente. O objetivo do presente trabalho foi avaliar algumas características bromatológicas e morfológicas, no período de 2013-2014. Avaliou-se os teores de matéria seca, de proteína bruta e extrato etéreo, além da altura da planta (h), inserção da copa (IC), diâmetro do caule (DC), diâmetro à altura do peito (DAP) e raio da copa (RC). Quanto aos descritores morfológicos avaliados, não houve diferença signifi cativa entre as espécies. A análise bromatológica resultou em 28,92% de matéria seca, 6,87% de proteína bruta e 16,97% de extrato etéreo
Parâmetros genéticos para características reprodutivas de um rebanho da raça Santa Inês criado no Semiárido nordestino.
Resumo: Com o objetivo de estimar os parâmetros genéticos para características reprodutivas da raça Santa Inês, criado no semiárido nordestino, foram utilizadas informações do rebanho pertencente a Embrapa Caprinos e Ovinos, localizada no município de Sobral, no estado do Ceará, ocorridas entre os anos de 2006 e 2013. As estimativas dos parâmetros genéticos e fenotípicos foram obtidas para as características intervalo de partos (IEP), dias para o parto (DP), período de gestação (PG) e número de serviços por concepção (NSC), pelo método da Máxima Verossimilhança Restrita, utilizando o algoritmo livre de derivadas DFREML, sob modelo animal multicaracterística, usando o software Multiple Trait Derivative-Free Restricted Maximum Likelihood (MTDFREML). As estimativas de herdabilidade para IEP, DP, PG e NSC foram 0,07, 0,07, 0,60 e 0,68, respectivamente. Os valores estimados neste estudo indicam que o fenótipo não é um bom indicador do genótipo para IEP e DP, havendo forte influência de fatores ambientais na expressão destas características. É importante considerar a possibilidade de viés com a seleção para IEP neste rebanho, por conta do uso de estações de monta anuais. [Genetic parameters for reproductive traits in a flock of Santa Inês sheep breed raised in Semiarid northeastern] Abstract: In order to estimate genetic parameters for reproductive traits of Santa Inês sheep breed, raised in semiarid northeastern, were used information from the flock belonging to Embrapa Goats and Sheep, located in Sobral, Ceará state, occurred between the years 2006 and 2013. Estimates of genetic and phenotypic parameters for lambing interval (IEP), lambing date (DP), gestation length (PG) and number of services per conception (NSC) were obtained by Restricted Maximum Likelihood method using the derivative-free algorithm DFREML under multi-trait animal model using the software Multiple Trait Derivative-Free Restricted Maximum Likelihood (MTDFREML). The heritabilities estimated for IEP, DP, PG and NSC were 0.07, 0.07, 0.60 and 0.68, respectively. The values estimated in this study indicate that the phenotype is not a good indicator of genotype for IEP and DP, with strong influence of environmental factors on the expression of these traits. It is important to consider the possibility of bias to this selection for IEP in this flock, due to the use of annual breeding seasons
Capture Velocity for a Magneto-Optical Trap in a Broad Range of Light Intensity
In a recent paper, we have used the dark-spot Zeeman tuned slowing technique
[Phys. Rev. A 62, 013404-1, (2000)] to measure the capture velocity as a
function of laser intensity for a sodium magneto optical trap. Due to technical
limitation we explored only the low light intensity regime, from 0 to 27
mW/cm^2. Now we complement that work measuring the capture velocity in a
broader range of light intensities (from 0 to 400 mW/cm^2). New features,
observed in this range, are important to understant the escape velocity
behavior, which has been intensively used in the interpretation of cold
collisions. In particular, we show in this brief report that the capture
velocity has a maximum as function of the trap laser intensity, which would
imply a minimum in the trap loss rates.Comment: 2 pages, 2 figure
Measuring the Spectra of High Energy Neutrinos with a Kilometer-Scale Neutrino Telescope
We investigate the potential of a future kilometer-scale neutrino telescope
such as the proposed IceCube detector in the South Pole, to measure and
disentangle the yet unknown components of the cosmic neutrino flux, the prompt
atmospheric neutrinos coming from the decay of charmed particles and the
extra-galactic neutrinos, in the 10 TeV to 1 EeV energy range.
Assuming a power law type spectra,
, we quantify the discriminating
power of the IceCube detector and discuss how well we can determine magnitude
() as well as slope () of these two components of the high
energy neutrino spectrum, taking into account the background coming from the
conventional atmospheric neutrinos.Comment: 21 pages, 7 figure
IceCube-Plus: An Ultra-High Energy Neutrino Telescope
While the first kilometer-scale neutrino telescope, IceCube, is under
construction, alternative plans exist to build even larger detectors that will,
however, b e limited by a much higher neutrino energy threshold of 10 PeV or
higher rather than 10 to 100 GeV. These future projects detect radio and
acoustic pulses as w ell as air showers initiated by ultra-high energy
neutrinos. As an alternative, we here propose an expansion of IceCube, using
the same strings, placed on a gri d with a spacing of order 500 m. Unlike other
proposals, the expanded detector uses methods that are understood and
calibrated on atmospheric neutrinos. Atmosp heric neutrinos represent the only
background at the energies under consideratio n and is totally negligible.
Also, the cost of such a detector is understood. We conclude that supplementing
the 81 IceCube strings with a modest number of addi tional strings spaced at
large distances can almost double the effective volume of the detector.
Doubling the number of strings on a 800 m grid can deliver a d etector that
this a factor of 5 larger for horizontal muons at modest cost.Comment: Version to be published in JCA
Total and non-fibrous carbohydrates intake and digestibility of five forage sorghum silages harvested in a Brazilian semi-arid region.
Sorghum has potential to be used as a feed source for ruminants, especially in semi-arid regions, owing to its high resistance to drought and extreme temperatures factors that contribute to increase its yield for silage production as compared to traditional crops (i.e. corn) grown under arid conditions
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