Device Acquires and Retains Rock or Ice Samples

The Rock Baller is a sample acquisition tool that improves sample retention. The basic elements of the Rock Baller are the tool rotation axis, the hub, the two jaws, and the cutting blades, which are located on each of the jaws. The entire device rotates about the tool rotation axis, which is aligned parallel to the nominal normal direction of the parent rock surface. Both jaws also rotate about the jaw axis, which is perpendicular to the tool rotation axis, at a rate much slower than the rotation about the tool rotation axis. This movement gradually closes the jaws into a nearly continuous hemispherical shell that encloses the sample as it is cut from the parent rock. When required the jaws are opened to release the sample. The hemispherical cutting method eliminates the sample retention problems associated with existing sample acquisition methods that employ conventional cylindrical cutting. The resulting samples are hemispherical, or nearly hemispherical, and as a result the aspect ratio (sample depth relative to sample radius) is essentially fixed. This fixed sample aspect ratio may be considered a drawback of the Rock Baller method, as samples with a higher aspect ratio (more depth, less width) may be considered more scientifically valuable because such samples would allow for a broader inspection of the geological record. This aspect ratio issue can be ameliorated if the Rock Baller is paired with a device similar to the Rock Abrasion Tool (RAT) used on the Mars Exploration Rovers. The RAT could be used to first grind into the surface of the parent rock, after which the Rock Baller would extract a sample from a depth inside the rock that would not have been possible without first using the RAT. Other potential applications for this technology include medical applications such as the removal of tissue samples or tumors from the body, particularly during endoscopic, laparoscopic, or thoracoscopic surgeries

Disentangling surface and bulk transport in topological-insulator pp-nn junctions

By combining $n$-type $\mathrm{Bi_2Te_3}$ and $p$-type $\mathrm{Sb_2Te_3}$ topological insulators, vertically stacked $p$-$n$ junctions can be formed, allowing to position the Fermi level into the bulk band gap and also tune between $n$- and $p$-type surface carriers. Here we use low-temperature magnetotransport measurements to probe the surface and bulk transport modes in a range of vertical $\mathrm{Bi_2Te_3/Sb_2Te_3}$ heterostructures with varying relative thicknesses of the top and bottom layers. With increasing thickness of the $\mathrm{Sb_2Te_3}$ layer we observe a change from $n$- to $p$-type behavior via a specific thickness where the Hall signal is immeasurable. Assuming that the the bulk and surface states contribute in parallel, we can calculate and reproduce the dependence of the Hall and longitudinal components of resistivity on the film thickness. This highlights the role played by the bulk conduction channels which, importantly, cannot be probed using surface sensitive spectroscopic techniques. Our calculations are then buttressed by a semi-classical Boltzmann transport theory which rigorously shows the vanishing of the Hall signal. Our results provide crucial experimental and theoretical insights into the relative roles of the surface and bulk in the vertical topological $p$-$n$ junctions.Comment: 11 pages, 5 figure

Desempenho agronômico de genótipos de feijão em dois níveis de investimento.

O objetivo deste trabalho foi avaliar a produtividade de grãos de cultivares de feijão em dois níveis de investimento. O maior nível de investimento, caracterizado pelo uso de maior dose de fertilizante e maior número de aplicações de fungicidas, não influenciou na produtividade de cultivares de feijão, em relação ao manejo usual

Habilidade competitiva de genótipos de feijão comum do grupo "preto" com plantas daninhas.

A hipótese dessa pesquisa é de que há variabilidade entre genótipos de feijão do grupo Preto quanto à competitividade com plantas daninhas e é possível identificar características de plantas que explicam expressivamente a habilidade competitiva. O objetivo desse trabalho foi avaliar a habilidade competitiva de genótipos de feijão do grupo preto com plantas daninhas. As perdas de produtividade de grãos em genótipos de feijão preto, decorrentes da interferência exercida pelas plantas daninhas, variaram de 30,8 a 54,9 %, sendo que os genótipos que apresentaram as menores perdas de produtividade também suprimiram em maior grau o crescimento das plantas daninhas. Houve tendência de aumento das reduções de produtividade de grãos em razão da interferência de plantas daninhas com o aumento da produtividade verificada na ausência de interferência. Não foi possível identificar características de plantas que afetam significativamente a habilidade dos genótipos de feijão em competir com plantas daninhas

Rendimento e composição química de espécies em consórcio com milho safrinha e rendimento da soja em sucessão, em MS.

bitstream/item/66219/1/32015.pdfFERTBI

Direct observation and imaging of a spin-wave soliton with p−p-like symmetry

The prediction and realization of magnetic excitations driven by electrical currents via the spin transfer torque effect, enables novel magnetic nano-devices where spin-waves can be used to process and store information. The functional control of such devices relies on understanding the properties of non-linear spin-wave excitations. It has been demonstrated that spin waves can show both an itinerant character, but also appear as localized solitons. So far, it was assumed that localized solitons have essentially cylindrical, $s-$like symmetry. Using a newly developed high-sensitivity time-resolved magnetic x-ray microscopy, we instead observe the emergence of a novel localized soliton excitation with a nodal line, i.e. with $p-$like symmetry. Micromagnetic simulations identify the physical mechanism that controls the transition from $s-$ to $p-$like solitons. Our results suggest a potential new pathway to design artificial atoms with tunable dynamical states using nanoscale magnetic devices

Second harmonic generation in SiC polytypes

LMTO calculations are presented for the frequency dependent second harmonic generation (SHG) in the polytypes 2H, 4H, 6H, 15R and 3C of SiC. All independent tensor components are calculated. The spectral features and the ratios of the 333 to 311 tensorial components are studied as a function of the degree of hexagonality. The relationship to the linear optical response and the underlying band structure are investigated. SHG is suggested to be a sensitive tool for investigating the near band edge interband excitations.Comment: 12 pages, 10 figure