Observational evidence for a broken Li Spite plateau and mass-dependent Li depletion

We present NLTE Li abundances for 88 stars in the metallicity range -3.5 < [Fe/H] < -1.0. The effective temperatures are based on the infrared flux method with improved E(B-V) values obtained mostly from interstellar NaI D lines. The Li abundances were derived through MARCS models and high-quality UVES+VLT, HIRES+Keck and FIES+NOT spectra, and complemented with reliable equivalent widths from the literature. The less-depleted stars with [Fe/H] < -2.5 and [Fe/H] > -2.5 fall into two well-defined plateaus of A_{Li} = 2.18 (sigma = 0.04) and A_{Li} = 2.27 (sigma = 0.05), respectively. We show that the two plateaus are flat, unlike previous claims for a steep monotonic decrease in Li abundances with decreasing metallicities. At all metallicities we uncover a fine-structure in the Li abundances of Spite plateau stars, which we trace to Li depletion that depends on both metallicity and mass. Models including atomic diffusion and turbulent mixing seem to reproduce the observed Li depletion assuming a primordial Li abundance A_{Li} = 2.64, which agrees well with current predictions (A_{Li} = 2.72) from standard Big Bang nucleosynthesis. Adopting the Kurucz overshooting model atmospheres increases the Li abundance by +0.08 dex to A_{Li} = 2.72, which perfectly agrees with BBN+WMAP.Comment: A&A Letters, in pres

Electronic Transport Through EuO Spin Filter Tunnel Junctions

Epitaxial spin filter tunnel junctions based on the ferromagnetic semiconductor europium monoxide, EuO, are investigated by means of density functional theory. In particular, we focus on the spin transport properties of Cu(100)/EuO(100)/Cu(100) junctions. The dependence of the transmission coefficient and the current-voltage curves on the interface spacing and on the EuO thickness is explained in terms of the EuO density of states and the complex band structure. Furthermore we also discuss the relation between the spin transport properties and the Cu-EuO interface geometry. The level alignment of the junction is sensitively affected by the interface spacing, since this determines the charge transfer between EuO and the Cu electrodes. Our calculations indicate that EuO epitaxially grown on Cu can act as a perfect spin filter, with a spin polarization of the current close to 100%, and with both the Eu-5d conduction band and the Eu-4f valence band states contributing to the coherent transport. For epitaxial EuO on Cu a symmetry filtering is observed, with the \Delta_1 states dominating the transmission. This leads to a transport gap larger than the fundamental EuO band gap. Importantly the high spin polarization of the current is preserved up to large bias voltages

Brazilian Society of Plant Breeding. Printed in Brazil Marker-assisted selection for quantitative traits

ABSTRACT -Although thousands of scientific articles have been published on the subject of marker-assisted selection (MAS) an

Scaling properties of growing noninfinitesimal perturbations in space-time chaos

We study the spatiotemporal dynamics of random spatially distributed noninfinitesimal perturbations in one-dimensional chaotic extended systems. We find that an initial perturbation of finite size $\epsilon_0$ grows in time obeying the tangent space dynamic equations (Lyapunov vectors) up to a characteristic time $t_{\times}(\epsilon_0) \sim b - (1/\lambda_{max}) \ln (\epsilon_0)$, where $\lambda_{max}$ is the largest Lyapunov exponent and $b$ is a constant. For times $t < t_{\times}$ perturbations exhibit spatial correlations up to a typical distance $\xi \sim t^z$. For times larger than $t_{\times}$ finite perturbations are no longer described by tangent space equations, memory of spatial correlations is progressively destroyed and perturbations become spatiotemporal white noise. We are able to explain these results by mapping the problem to the Kardar-Parisi-Zhang universality class of surface growth.Comment: 4.5 pages LaTeX (RevTeX4) format, 3 eps figs included. Submitted to Phys Rev

Improving the precision of genotype selection in wheat performance trials

The aim of this study was to verify whether using the Papadakis method improves model assumptions and experimental accuracy in field trials used to determine grain yield for wheat lineages indifferent Value for Cultivation and Use (VCU) regions. Grain yield data from 572 field trials at 31 locations in the VCU Regions 1, 2, 3 and 4 in 2007-2011 were used. Each trial was run with and without the use of the Papadakis method. The Papadakis method improved the indices of experimental precision measures and reduced the number of experimental repetitions required to predict grain yield performance among the wheat genotypes. There were differences among the wheat adaptation regions in terms of the efficiency of the Papadakis method, the adjustment coefficient of the genotype averages and the increases in the selective accuracy of grain yield

QTL mapping of soybean cyst nematode race 9: a generalized linear modeling approach

The Female Index (FI) is a relative measure of host suitability of a soybean line for a particular nematode population and often shows a non-normal distribution. Moreover, most quantitative trait loci (QTL) mapping methods assume that the phenotype follows a normal distribution such as composite interval mapping (CIM). Therefore, a generalized linear modeling (GLM) approach was employed to map QTL for resistance to race 9 of the soybean cyst nematode (SCN) using a total of 83 simple sequence repeat markers (SSR). Two GLM models were tested: model 1, where the FI was treated as a continuous variable, assuming a Gamma distribution with a logarithmic link function; and model 2, where the FI was treated as a categorical trait in a five-item hierarchy, assuming a multinomial distribution with a cumulative logit link function. The FI data of 108 recombinant inbred lines (RIL) confirmed the non-normal distribution for race 9 of the SCN (Shapiro-Wilk?s w=0.86, P<0.0001, skewness=1.52 and kurtosis=2.93). Eight RIL were confirmed to be resistant (FI≤10), and 23 to be highly susceptible (FI≥100). Both GLM models identified one QTL for SCN on the molecular linkage group G, between the markers Satt275 and Satt038 at 48.4 centiMorgans (P=0.017 and 0.033, for models 1 and 2, respectively). Additionally, these results were also compared with the CIM and Bayesian interval mapping (BIM) methods, assuming experimental data with a non-normal response, to determine the robustness and statistical power of these two methods for mapping QTLs. The results make clear that generalized linear modeling approach can be used as an efficient method to map QTLs in a continuous trait with a non-Gaussian distribution. CIM and BIM were robust enough for a reliable mapping of QTLs underlying nonnormally distributed data.Fil: Arriagada, Osvin. Universidad de Talca; ChileFil: Ferreira, Marcia F. S.. Universidade Federal Do Espirito Santo; BrasilFil: Cervigni, Gerardo Domingo Lucio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Centro de Estudios Fotosintéticos y Bioquímicos (i); ArgentinaFil: Schuster, Ivan. Central Cooperative for Agricultural Research; BrasilFil: Scapim, Carlos A.. Universidade Estadual de Maringá; BrasilFil: Mora, Freddy. Universidad de Talca; Chil

EFEITO DA TEMPERATURA E LUMINOSIDADE NA REGENERAÇÃO IN VITRO DE PLANTAS DE TRIGO

In vitro calli cultivation conditions, light and temperature can influence the embryogenic and plant regeneration response. These two factors have not been studied in details in the literature, and its determination could contribute to the settlement of a more efficient tissue culture protocol. Immature embryos of wheat genotype CD104 were used as source of explants. The embryos were cultivated in MS medium with decreasing concentrations of 2,4-D forming three different phases: induction, maintenance and regeneration for a period of 21 days each one. Six different treatments were applied and, these differed exclusively by the induction phase, with two temperature conditions (4 °C and 25 oC) and two light conditions (photoperiod/darkness). Two different conditions of light were evaluated: 1) Constant photoperiod of 16/8 hrs (21 days) and 2) Completely darkness (10 days) and later transference of calli to light/photoperiod (16/8 hrs) in cultivation chamber (11 days). The data showed that the best results obtained for induction capacity, embryogenic and regeneration capacities (100% and 95%; 58,5% and 54,7%; 37,8% and 30,7%, respectively) were in 4 oC light and 4 oC darkness conditions, revealing that low temperature applied at the induction phase had a positive effect on calli regeneration. The treatment conditions of 25oC and light got the lowest values for calli induction (46%), embryogenic capacity (23,9%) and regeneration (23,9%), what can be inferred as an unfavorable condition to embryogenic establishment.Nas condições de cultivo dos calos, a luminosidade e temperatura podem influenciar a resposta embriogênica e a regeneração de plantas. Estes dois fatores não têm sido examinados minuciosamente na literatura e o seu estudo poderia contribuir para o estabelecimento de protocolos mais eficientes. O genótipo CD104 foi avaliado sobre o estabelecimento de embriogênese somática. Foram usados como fonte de explante, embriões imaturos que foram cultivados em meio MS com dosagens decrescentes de 2,4-D formando três fases distintas: inducão, manutenção e regeneração. Cada fase teve duração de 21 dias. Seis diferentes combinações entre temperaturas (4 oC e 25 oC) e luminosidade (fotoperíodo/escuro) foram aplicados na fase de indução. Nos tratamentos que avaliaram o efeito da luminosidade, foram testadas duas condições:1) Condição de fotoperíodo constante (16/8 horas luz/escuro) por 21 dias ; 2) escuro (10 dias) e posteriormente transferência dos calos para fotoperíodo de 16/8 horas em câmara de cultivo (11 dias). Os dados demonstram que os melhores resultados obtidos para capacidade de indução, capacidade embriogênica e regeneração (100% e 95%; 58,5% e 54,7%; 37,8% e 30,7%, respectivamente) ocorreram com aplicação da condição 4 oC + luz e 4 oC + escuro, evidenciando que temperaturas baixas na indução podem favorecer a maior obtenção de plântulas. O tratamento com temperaturas de 25 oC e fotoperíodo apresentou os menores valores para a indução de calos (46%), capacidade embriogênica (23,9%) e regeneração (23,9%), mostrando que a presença de luminosidade e temperaturas de 25 oC podem desfavorecer a embriogênese