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

Atributos biológicos do solo numa cronossequência de pastagens em sistema ILP no Cerrado.

Neste estudo, objetivou-se avaliar as alterações exercidas pela dinâmica de rotação de culturas anuais e pastagem sobre o componente biológico do solo, com ênfase na cronossequência da fase pastagem, dentro do sistema de integração lavoura-pecuária.bitstream/item/35587/1/comt-198.pd

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

Determination of biodiesel content in diesel fuel by time-domain nuclear magnetic resonance (TD-NMR) spectroscopy.

Made available in DSpace on 2017-11-10T23:23:51Z (GMT). No. of bitstreams: 1 PDeterminationofbiodiesel....pdf: 437412 bytes, checksum: d307482ebfb6b8d028f228e92b223fe9 (MD5) Previous issue date: 2017-11-1

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

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, $d\phi_\nu/dE_\nu \sim \alpha E_\nu^\beta$, we quantify the discriminating power of the IceCube detector and discuss how well we can determine magnitude ($\alpha$) as well as slope ($\beta$) 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

The seasonal characterization and temporal evolution of nitrogen, phosphorus and potassium in the surface and groundwater of an agricultural hydrographic basin in the midwestern Brazilian Savanna.

The Brazilian savanna (Cerrado Biome) is one of the most important regions in the world in terms of food production, with the use of fertilizers based on nitrogen, phosphorus and potassium (NPK). When not applied properly, fertilizers can alter and affect water quality. The objective of this study was to evaluate the presence of these compounds in surface and groundwater in the Upper Jardim River Hydrographic Unit, Federal District, thus characterizing seasonal variations during the dry and rainy seasons in two periods. A total of 207 groundwater samples and 23 surface water samples were collected in the years 2014, 2015, 2019 and 2020. The parameters analyzed were pH and nitrate, nitrite, ammonium, phosphate and potassium ions. In groundwater samples, pH values were significantly higher and ion levels lower in samples collected during the early years (except for nitrate), and the ammonium concentrations were lower in the dry season than the rainy (in 2014 and 2019). In surface samples, total phosphorus levels were significantly higher in the rainy/2019 compared to the rainy/2020 season, while this tendency was inverted for potassium during the dry season. The use of NPK-based fertilizers has increased considerably in recent years in the region due to the expansion of the agricultural area, and although the results of the study show that concentrations in water are much lower than the maximum values allowed by Brazilian legislation, continuous monitoring is necessary to guarantee water quality

Teor relativo de clorofila em folhas de milho inoculado com Azospirillum braziliense sob diferentes doses de nitrogênio e manejo com braquiária.

A cultura do milho safrinha, implantada no início dos anos 80, no Estado do Paraná, ganhou destaque no fim dessa década como mais uma alternativa econômica na entressafra. Com objetivo de avaliar o teor relativo de clorofila em folhas de milho em função de doses de nitrogênio, inoculação das sementes e diferentes manejos, foi realizado um experimento de campo em Nitossolo Vermelho distroférrico, em Maringá (PR). Utilizaram-se três doses de nitrogênio (25, 50 e 75 kg ha-1), inoculante contendo estirpes de Azospirillum brasiliense no tratamento das sementes de milho e dois manejos distintos de milho solteiro e consorciado com Brachiaria ruziziensis. Os tratamentos foram arranjados com fatorial nas parcelas (doses de nitrogênio x presença e ausência de Azospirillum brasiliense) e em faixa nas subparcelas o milho safrinha (milho solteiro e consorciado com braquiária), sob o delineamento blocos ao acaso, com quatro repetições dos blocos, totalizando 64 parcelas. O teor relativo de clorofila nas folhas aumentou linearmente com as doses de nitrogênio utilizadas. Da mesma forma, as médias de todos os tratamentos que receberam a inoculação das sementes com Azospirillum brasiliense foram maiores que os tratamentos não inoculados. Por outro lado, o manejo não influenciou no teor relativo de clorofila nas folhas