Quantifying spin Hall angles from spin pumping: Experiments and Theory

Spin Hall effects intermix spin and charge currents even in nonmagnetic materials and, therefore, ultimately may allow the use of spin transport without the need for ferromagnets. We show how spin Hall effects can be quantified by integrating permalloy/normal metal (N) bilayers into a coplanar waveguide. A dc spin current in N can be generated by spin pumping in a controllable way by ferromagnetic resonance. The transverse dc voltage detected along the permalloy/N has contributions from both the anisotropic magnetoresistance (AMR) and the spin Hall effect, which can be distinguished by their symmetries. We developed a theory that accounts for both. In this way, we determine the spin Hall angle quantitatively for Pt, Au and Mo. This approach can readily be adapted to any conducting material with even very small spin Hall angles.Comment: 4 pages, 4 figure

Seleção de matrizes e tipo de propágulo na enxertia de substituição de copa em Ilex paraguariensis.

Objetivou-se avaliar a técnica da sobreenxertia em Ilex paraguariensis, visando a substituição de copas. Para tanto, foi avaliada a influência da posição do enxerto na planta matriz, a idade e a matriz, bem como, a definição da melhor época para avaliação do pegamento e vigor dos enxertos. Árvores com 13 anos de idade localizadas em Colombo ? PR, foram submetidas ao corte a 10 cm do solo para indução de brotações, sobre as quais foi realizada a enxertia por garfagem no topo em fenda cheia. Os enxertos foram coletados de sete árvores matrizes com idade de 10 anos e sete árvores com idade acima de 80 anos. Das matrizes selecionadas foram retirados enxertos observando-se a posição apical, mediana e basal dentro da planta matriz. O experimento foi instalado em delineamento inteiramente casualizado com três repetições e 42 tratamentos, no esquema fatorial hierárquico 2 x 7 x 3 (duas idades; 7 matrizes, para cada idade; e 3 posições de coleta). A variável resposta de interesse foi proporção de pegamentos e número e comprimento de brotos. Obteve-se um comportamento diferenciado das matrizes quando amostradas em diferentes posições de coleta. A herdabilidade individual dos efeitos genotípicos, estimada para o pegamento dos enxertos, foi superior a 74%, para todos os períodos de avaliação, cujo valor é considerado alto. O coeficiente de variação genética foi da ordem de 34%, para os períodos de acompanhamento iguais ou superiores a 90 dias, indicando boas perspectivas de ganho no melhoramento do material genético. O coeficiente de variação experimental, nesse mesmo período, ficou entre 78% e 94%. Não houve diferenças entre os parâmetros genéticos a partir dos 90 dias. Pode-se concluir que a sobreenxertia de erva-mate diretamente a campo é tecnicamente viável; melhores taxas de pegamento são obtidas em árvores mais novas e com brotações apicais; e as matrizes apresentam respostas diferenciadas quanto ao pegamento na enxertia

The role of landscape history in determining allelic richness of European ground squirrels (Spermophilus citellus) in Central Europe

Genetic diversity is of paramount importance for individual fitness and evolutionary potential of populations. For conservation planning it is crucial to know how genetically diverse a species is and what factors may explain variation of genetic diversity among populations. Our aim was to evaluate the effects of landscape history, ecological isolation, and local population size on allelic richness of local populations in European ground squirrels (Spermophiluscitellus). We genotyped 144 individuals from nine local populations collected in two neighbouring regions with decades of different landscape history. We assessed allelic richness, ecological isolation and local population size by eleven polymorphic microsatellites, the isolation index of Rodríguez and Delibes,and standardised counts of burrows openings, respectively. Statistical models indicated a strong effect of landscape history on allelic richness of local populations. Ecological isolation of local populations apparently played only a marginal role, and local population size was an unimportant factor. Our modelling results highlight the dominant role of landscape history for the genetic diversity of S. citellus. The strong landscape history effect encountered presently includes a different region-specific socio-economic development due to distinct agricultural systems in the two regions, especially after World War II. Levels of ecological isolation of local populations have diverged in an extent too small to explain variation of local allelic richness. The lack of significant effect of local population size suggests that census sizes of the populations studied are all not critically low. Moreover,census and estimated effective population sizes were not closely related. Establishing corridors or translocating S. citellus in the species’ historical range should be encouraged to promote gene flow between local populations and counteract the loss of genetic diversity by drift, provided that no conflicting factors (ecological, epidemiological, etc.) exist

Determinants of individuals' objective and subjective financial fragility during the COVID-19 pandemic

We examine determinants of the objective and subjective financial fragility of 2100 individuals across Australia, France, Germany, and South Africa during the COVID-19 pandemic. Objective financial fragility reflects individuals’ (in)ability to deal with unexpected expenses, while subjective financial fragility reflects their emotional response to financial demands. Controlling for an extensive set of socio-demographics, we find that negative personal experiences during the pandemic (i.e., reduced or lost employment; COVID-19 infection) are associated with higher objective and subjective financial fragility. However, individuals’ cognitive (i.e., financial literacy) as well as non-cognitive abilities (i.e., internal locus of control; psychological resilience) help to counteract this higher financial fragility. Finally, we examine the role of government financial support (i.e., income support; debt relief) and find that it is negatively related to financial fragility only for the economically weakest households. Our results have implications for public policymakers, providing levers for reducing individuals’ objective and subjective financial fragility

Electronic structure investigation of Ti3AlC2, Ti3SiC2, and Ti3GeC2 by soft-X-ray emission spectroscopy

The electronic structures of epitaxially grown films of Ti3AlC2, Ti3SiC2 and Ti3GeC2 have been investigated by bulk-sensitive soft X-ray emission spectroscopy. The measured high-resolution Ti L, C K, Al L, Si L and Ge M emission spectra are compared with ab initio density-functional theory including core-to-valence dipole matrix elements. A qualitative agreement between experiment and theory is obtained. A weak covalent Ti-Al bond is manifested by a pronounced shoulder in the Ti L-emission of Ti3AlC2. As Al is replaced with Si or Ge, the shoulder disappears. For the buried Al and Si-layers, strongly hybridized spectral shapes are detected in Ti3AlC2 and Ti3SiC2, respectively. As a result of relaxation of the crystal structure and the increased charge-transfer from Ti to C, the Ti-C bonding is strengthened. The differences between the electronic structures are discussed in relation to the bonding in the nanolaminates and the corresponding change of materials properties.Comment: 15 pages, 8 figure

Anisotropic fragmentation in low-energy dissociative recombination

On a dense energy grid reaching up to 75 meV electron collision energy the fragmentation angle and the kinetic energy release of neutral dissociative recombination fragments have been studied in a twin merged beam experiment. The anisotropy described by Legendre polynomials and the extracted rotational state contributions were found to vary on a likewise narrow energy scale as the rotationally averaged rate coefficient. For the first time angular dependences higher than 2$^{nd}$ order could be deduced. Moreover, a slight anisotropy at zero collision energy was observed which is caused by the flattened velocity distribution of the electron beam.Comment: 8 pages, 4 figures; The Article will be published in the proceedings of DR 2007, a symposium on Dissociative Recombination held in Ameland, The Netherlands (18.-23. July 2008); Reference 19 has been published meanwhile in S. Novotny, PRL 100, 193201 (2008

Nuclear mitochondrial DNA sequences in the rabbit genome

Numtogenesis is observable in the mammalian genomes resulting in the integration of mitochondrial segments into the nuclear genomes (numts). To identify numts in rabbit, we aligned mitochondrial and nuclear genomes. Alignment significance threshold was calculated and individual characteristics of numts were analysed. We found 153 numts in the nuclear genome. The GC content of numts were significantly lower than the GC content of their genomic flanking regions or the genome itself. The frequency of three mammalian-wide interspersed repeats were increased in the proximity of numts. The decreased GC content around numts strengthen the theory which supposes a link between DNA structural instability and numt integration

Feature extraction for proteomics imaging mass spectrometry data

Imaging mass spectrometry (IMS) has transformed proteomics by providing an avenue for collecting spatially distributed molecular data. Mass spectrometry data acquired with matrix assisted laser desorption ionization (MALDI) IMS consist of tens of thousands of spectra, measured at regular grid points across the surface of a tissue section. Unlike the more standard liquid chromatography mass spectrometry, MALDI-IMS preserves the spatial information inherent in the tissue. Motivated by the need to differentiate cell populations and tissue types in MALDI-IMS data accurately and efficiently, we propose an integrated cluster and feature extraction approach for such data. We work with the derived binary data representing presence/absence of ions, as this is the essential information in the data. Our approach takes advantage of the spatial structure of the data in a noise removal and initial dimension reduction step and applies k -means clustering with the cosine distance to the high-dimensional binary data. The combined smoothing-clustering yields spatially localized clusters that clearly show the correspondence with cancer and various noncancerous tissue types. Feature extraction of the high-dimensional binary data is accomplished with our difference in proportions of occurrence (DIPPS) approach which ranks the variables and selects a set of variables in a data-driven manner. We summarize the best variables in a single image that has a natural interpretation. Application of our method to data from patients with ovarian cancer shows good separation of tissue types and close agreement of our results with tissue types identified by pathologists.Lyron J. Winderbaum, Inge Koch, Ove J. R. Gustafsson, Stephan Meding and Peter Hoffman