Novel time-saving first-principles calculation method for electron-transport properties

We present a time-saving simulator within the framework of the density functional theory to calculate the transport properties of electrons through nanostructures suspended between semi-infinite electrodes. By introducing the Fourier transform and preconditioning conjugate-gradient algorithms into the simulator, a highly efficient performance can be achieved in determining scattering wave functions and electron-transport properties of nanostructures suspended between semi-infinite jellium electrodes. To demonstrate the performance of the present algorithms, we study the conductance of metallic nanowires and the origin of the oscillatory behavior in the conductance of an Ir nanowire. It is confirmed that the $s$-$d_{z^2}$ channel of the Ir nanowire exhibits the transmission oscillation with a period of two-atom length, which is also dominant in the experimentally obtained conductance trace

First-principles transport calculation method based on real-space finite-difference nonequilibrium Green's function scheme

We demonstrate an efficient nonequilibrium Green's function transport calculation procedure based on the real-space finite-difference method. The direct inversion of matrices for obtaining the self-energy terms of electrodes is computationally demanding in the real-space method because the matrix dimension corresponds to the number of grid points in the unit cell of electrodes, which is much larger than that of sites in the tight-binding approach. The procedure using the ratio matrices of the overbridging boundary-matching technique [Phys. Rev. B {\bf 67}, 195315 (2003)], which is related to the wave functions of a couple of grid planes in the matching regions, greatly reduces the computational effort to calculate self-energy terms without losing mathematical strictness. In addition, the present procedure saves computational time to obtain Green's function of the semi-infinite system required in the Landauer-B\"uttiker formula. Moreover, the compact expression to relate Green's functions and scattering wave functions, which provide a real-space picture of the scattering process, is introduced. An example of the calculated results is given for the transport property of the BN ring connected to (9,0) carbon nanotubes. The wave function matching at the interface reveals that the rotational symmetry of wave functions with respect to the tube axis plays an important role in electron transport. Since the states coming from and going to electrodes show threefold rotational symmetry, the states in the vicinity of the Fermi level, whose wave function exhibits fivefold symmetry, do not contribute to the electron transport through the BN ring.Comment: 34 page

Imprint of Gravitational Lensing by Population III Stars in Gamma Ray Burst Light Curves

We propose a novel method to extract the imprint of gravitational lensing by Pop III stars in the light curves of Gamma Ray Bursts (GRBs). Significant portions of GRBs can originate in hypernovae of Pop III stars and be gravitationally lensed by foreground Pop III stars or their remnants. If the lens mass is on the order of $10^2-10^3M_\odot$ and the lens redshift is greater than 10, the time delay between two lensed images of a GRB is $\approx 1$s and the image separation is $\approx 10 \mu$as. Although it is difficult to resolve the two lensed images spatially with current facilities, the light curves of two images are superimposed with a delay of $\approx 1$ s. GRB light curves usually exhibit noticeable variability, where each spike is less than 1s. If a GRB is lensed, all spikes are superimposed with the same time delay. Hence, if the autocorrelation of light curve with changing time interval is calculated, it should show the resonance at the time delay of lensed images. Applying this autocorrelation method to GRB light curves which are archived as the {\it BATSE} catalogue, we demonstrate that more than half light curves can show the recognizable resonance, if they are lensed. Furthermore, in 1821 GRBs we actually find one candidate of GRB lensed by a Pop III star, which may be located at redshift 20-200. The present method is quite straightforward and therefore provides an effective tool to search for Pop III stars at redshift greater than 10. Using this method, we may find more candidates of GRBs lensed by Pop III stars in the data by the {\it Swift} satellite.Comment: 13 pages, 13 figures, accepted for publication in Ap

Growth Phases and Differential Growth Between Sexes of Uca maracoani Latreille, 1802-1803 (Crustacea, Brachyura, Ocypodidae)

Among crustacean decapods, fiddler crabs of the genus Uca are the most characteristic of the intertidal zones of tropical and subtropical estuaries. The present study determined the growth phases and the beginning of differential growth between the sexes, based on analyses of relative growth of Uca maracoani. Collections were made in the Jabaquara mangrove, located in Paraty, Rio de Janeiro, Brazil. Specimens were collected manually during low tide periods. In the laboratory, crabs were sexed and measured. We measured carapace width (CW), carapace length (CL), propodus length (PL; the right one for females and the major one for males), propodus height (PH), abdomen width (AW), and gonopod length (GL; for males). The beginning of differential growth between the sexes could be identified by the allometric technique. Males and females showed 3 distinct growth phases. Differential growth between sexes began when males reached 7 mm and females 9.2 mm CW. The growth pattern among different phases and the beginning of differential growth seemed to maintain a strict relationship with the ontogenetic changes, mainly those related to behavioral and reproductive aspects. This information is important for general biological knowledge of this species, mainly concerning aspects of its growth

Avaliação de cultivares de soja com relação à preferência a Bemisia tabaci Biótipo B (Hemiptera: Aleyrodidae) com chance de escolha a campo.

A mosca-branca está entre as várias pragas que atacam a cultura da soja. São insetos que sugam a seiva das plantas hospedeiras, tanto na fase jovem como na adulta, podendo causar danos diretos a planta, como seu enfraquecimento e o desenvolvimento de fumagina sobre as folhas, com reflexos na produtividade, e danos indiretos, devido à sua capacidade de transmitir viroses. Entre os vários métodos de controle, o uso de cultivares menos preferidas, pode ser uma ferramenta para o manejo sustentável desta praga. Assim este experimento foi realizado no município de Primavera do Leste, MT, com o objetivo de avaliar diferentes cultivares de soja com relação à preferência a mosca-branca Bemisia tabaci biótipo B em testes com chance de escolha a campo. O delineamento experimental foi de blocos ao acaso com quatro repetições. A parcela foi constituída de 12 linhas com 8m de comprimento. As cultivares (crescimento/ grupo de maturação) testadas foram: 1. TMG1188 RR (semideterminado/8.8), 2. NA8015 RR (indeterminado/8.3), 3. TMG1288 RR (determinado/8.8), 4. TMG133 RR (determinado/8.5), 5. TMG1176(determinado/7.6), 6. TMG127 RR (indeterminado/7.2), 7, TMG132 RR (determinado/8.5) e 8. P98Y11 (determinado/8.1). Avaliou-se o número de ninfas em 10 folíolos centrais do terço médio da planta de cada parcela aos, 35, 41, 50 e 62 dias após plantio. As cultivares P98Y11; TMG132 RR e TMG1176 RR foram às menos infestadas com ninfas de mosca-branca no período avaliado, com infestação 71% menor que as cultivares mais infestadas. A maior população de ninfas foi observada aos 41 dias após o plantio com um número médio de 214 ninfas por folíolo. A população de ninfas caiu para 97,3 ninfas/folíolo na 3ª avaliação e reduziu para 0,5 ninfas/folíolo aos 62 dias após o plantio em todas as cultivares avaliadas, quando foram finalizadas as avaliações

Light elements in the Earth’s core

Constraining the core’s composition is essential for understanding Earth accretion, core formation and the sustainment of Earth’s magnetic field. Earth’s outer and inner core exhibit a density deficit relative to pure iron, attributed to the presence of substantial amounts of low atomic number ‘light’ elements, such as sulfur, silicon, oxygen, carbon and hydrogen. However, owing to its inaccessibility, estimates of core composition can only be indirectly obtained by matching results from high-pressure experiments and theoretical calculations with seismic observations. In this Review, we discuss the properties and phase relations of iron alloys under high-pressure and high-temperature conditions relevant to the Earth’s core. We synthesize mineral physics data with cosmochemical and geochemical estimates to give the likely range of compositions for the outer (Fe + 5% Ni + 1.7% S + 0–4.0% Si + 0.8–5.3% O + 0.2% C + 0–0.26% H by weight) and inner (Fe + 5% Ni + 0–1.1% S + 0–2.3% Si + 0–0.1% O + 0–1.3% C + 0–0.23% H by weight) core. While the exact composition of the core remains unknown, tighter constraints on core temperature and better connections between the solid inner core and the liquid outer core compositions will help narrow the range of potential light element compositions

Measurement of the τ lepton polarization and R ( D ∗ ) in the decay ¯ B → D ∗ τ − ¯ ν τ with one-prong hadronic τ decays at Belle

With the full data sample of 772×106 B¯B pairs recorded by the Belle detector at the KEKB electron-positron collider, the decay ¯B→D∗τ−¯ντ is studied with the hadronic τ decays τ−→π−ντ and τ−→ρ−ντ. The τ polarization Pτ(D∗) in two-body hadronic τ decays is measured, as well as the ratio of the branching fractions R(D∗)=B(¯B→D∗τ−¯ντ)/B(¯B→D∗ℓ−¯νℓ), where ℓ− denotes an electron or a muon. Our results, Pτ(D∗)=−0.38±0.51(stat)+0.21−0.16(syst) and R(D∗)=0.270±0.035(stat)+0.028−0.025(syst), are consistent with the theoretical predictions of the standard model. The polarization values of Pτ(D∗)\u3e+0.5 are excluded at the 90% confidence level

Morfologia comparada das gônadas de pentatomídeos de importância agrícola.

Os percevejos fitófagos são de grande importância agrícola e afetam a produtividade de algumas culturas. O presente trabalho teve como objetivo avaliar o sistema reprodutor desses percevejos, e fazer uma análise comparativa para constatar se pode haver distinções morfológicas intra e inter-específicas