Feshbach resonances in ultracold ^{6,7}Li + ^{23}Na atomic mixtures

We report a theoretical study of Feshbach resonances in $^{6}$Li + $^{23}$Na and $^{7}$Li + $^{23}$Na mixtures at ultracold temperatures using new accurate interaction potentials in a full quantum coupled-channel calculation. Feshbach resonances for $l=0$ in the initial collisional open channel $^6$Li$(f=1/2, m_f=1/2) + ^{23}$Na$(f=1, m_f=1)$ are found to agree with previous measurements, leading to precise values of the singlet and triplet scattering lengths for the $^{6,7}$Li$+^{23}$Na pairs. We also predict additional Feshbach resonances within experimentally attainable magnetic fields for other collision channels.Comment: 4 pages, 3 figure

Blackbirds and Starling Killed at Winter Roosts from PA-14 Applications, 1974-1992: Implications for Regional Population Management

The surfactant PA-14, registered with the U.S. Environmental Protection Agency (EPA) in 1973 by the federal Animal Damage Control (ADC) program, was used for 19 years (1974-1992) for lethal control of roosting blackbirds (Icterinae) and European starlings (Sturnus vulgaris) in the United States. In 1992, the ADC program withdrew the registration of PA-14 because of costs required to provide additional EPA-requested data. There were 83 roosts encompassing 178 ha treated with 33,300 L of PA-14 from 1974-1992. An estimated 38.2 million birds (48% common grackles [Ouiscalus quiscula], 30% European starlings, 13% red-winged blackbirds [Agelaius phoeniceus], and 9% brownheaded cowbirds [Molothrus ater]) were killed, an average of 2.0 million/year. The annual kill represented ≤ 1.3% of the national winter population of blackbirds and starlings. We found no evidence using North American Breeding Bird Survey (BBS) data that PA-14 applications caused declines in regional breeding populations. Furthermore, there was no evidence of secondary poisoning or other adverse environmental effects from PA-14 applications. If regional population management of blackbirds and starlings is to be implemented to reduce agricultural damage or conflicts with native songbirds, new approaches, such as reproductive control, are needed because PA-14 alone will not be adequate. However, PA-14 could have a role in such regional programs in addition to solving localized roost problems. PA-14 was a useful management tool safely applied in human-populated areas (where most roost problems occur); its reregistration should be considered as part of an integrated management program for blackbirds and starlings

Temperature dependent asymmetry of the nonlocal spin-injection resistance: evidence for spin non-conserving interface scattering

We report nonlocal spin injection and detection experiments on mesoscopic Co-Al2O3-Cu spin valves. We have observed a temperature dependent asymmetry in the nonlocal resistance between parallel and antiparallel configurations of the magnetic injector and detector. This strongly supports the existence of a nonequilibrium resistance that depends on the relative orientation of the detector magnetization and the nonequilibrium magnetization in the normal metal providing evidence for increasing interface spin scattering with temperature.Comment: 5 pages, 4 figures, accepted for publication in PRL, minor corrections (affiliation, acknowledgements, typo

Transport behavior of holes in boron delta-doped diamond structures

Boron delta-doped diamond structures have been synthesized using microwave plasma chemical vapor deposition and fabricated into FET and gated Hall bar devices for assessment of the electrical characteristics. A detailed study of variable temperature Hall, conductivity, and field-effect mobility measurements was completed. This was supported by Schr€dinger-Poisson and relaxation time o calculations based upon application of Fermi’s golden rule. A two carrier-type model was developed with an activation energy of $0.2 eV between the delta layer lowest subband with mobility$1 cm2/Vs and the bulk valence band with high mobility. This new understanding of the transport of holes in such boron delta-doped structures has shown that although Hall mobility as high as 900 cm2/Vs was measured at room temperature, this dramatically overstates the actual useful performance of the device

Mott-Hubbard insulators for systems with orbital degeneracy

We study how the electron hopping reduces the Mott-Hubbard band gap in the limit of a large Coulomb interaction U and as a function of the orbital degeneracy N. The results support the conclusion that the hopping contribution grows as roughly \sqrt{N}W, where W is the one-particle band width, but in certain models a crossover to a \sim NW behavior is found for a sufficiently large N.Comment: 7 pages, revtex, 6 figures more information at http://www.mpi-stuttgart.mpg.de/dokumente/andersen/fullerene

Some Remarks on Effective Range Formula in Potential Scattering

In this paper, we present different proofs of very recent results on the necessary as well as sufficient conditions on the decrease of the potential at infinity for the validity of effective range formulas in 3-D in low energy potential scattering (Andr\'e Martin, private communication, to appear. See Theorem 1 below). Our proofs are based on compact formulas for the phase-shifts. The sufficiency conditions are well-known since long. But the necessity of the same conditions for potentials keeping a constant sign at large distances are new. All these conditions are established here for dimension 3 and for all angular momenta $\ell \geq 0$

Taxonomic bias in amphibian research : Are researchers responding to conservation need?

Amphibians are very diverse, widely distributed, and the most endangered class of vertebrates. As with other taxa, effective conservation of amphibians needs to be supported by detailed scientific knowledge. However, species rich and broadly distributed taxa are typically characterized by high variability in research effort. Our objective was therefore to understand which factors (ecological and cultural) have led some amphibian species to be more researched than others. We used two proxies of research effort: i) the total number of articles on Web of Science (WoS) that mention the scientific name (or synonyms) of each species, and; ii) the number of conservation science articles on WoS that mention the scientific name (or synonyms) of each species. These measures were used as dependent variables in zero hurdle regression models with the aim of identifying the most important factors driving species-level knowledge production. Well researched species (generally, and for conservation) tend to have a longer history of scientific research, come from countries with high scientific capacity, have large body size, and to be present in man-made habitats. Endangered species tend to be less researched, generally and for conservation, possibly because they are often more difficult to study: many endangered amphibians are restricted to small, fragmented and remote habitats in countries with low scientific capacity. We conclude with a discussion of how taxonomic biases in research effort on amphibians can be addressed given the limited funds available for conservation research.Peer reviewe

Multi-trait ensemble genomic prediction and simulations of recurrent selection highlight importance of complex trait genetic architecture for long-term genetic gains in wheat

Cereal crop breeders have achieved considerable genetic gain in genetically complex traits, such as grain yield, while maintaining genetic diversity. However, focus on selection for yield has negatively impacted other important traits. To better understand multi-trait selection within a breeding context, and how it might be optimized, we analysed genotypic and phenotypic data from a genetically diverse, 16-founder wheat multi-parent advanced generation inter-cross population. Compared to single-trait models, multi-trait ensemble genomic prediction models increased prediction accuracy for almost 90 % of traits, improving grain yield prediction accuracy by 3–52 %. For complex traits, non-parametric models (Random Forest) also outperformed simplified, additive models (LASSO), increasing grain yield prediction accuracy by 10–36 %. Simulations of recurrent genomic selection then showed that sustained greater forward prediction accuracy optimized long-term genetic gains. Simulations of selection on grain yield found indirect responses in related traits, involving optimized antagonistic trait relationships. We found multi-trait selection indices could effectively optimize undesirable relationships, such as the trade-off between grain yield and protein content, or combine traits of interest, such as yield and weed competitive ability. Simulations of phenotypic selection found that including Random Forest rather than LASSO genetic models, and multi-trait rather than single-trait models as the true genetic model accelerated and extended long-term genetic gain whilst maintaining genetic diversity. These results (i) suggest important roles of pleiotropy and epistasis in the wider context of wheat breeding programmes, and (ii) provide insights into mechanisms for continued genetic gain in a limited genepool and optimization of multiple traits for crop improvement

Limited haplotype diversity underlies polygenic trait architecture across 70 years of wheat breeding

Background Selection has dramatically shaped genetic and phenotypic variation in bread wheat. We can assess the genomic basis of historical phenotypic changes, and the potential for future improvement, using experimental populations that attempt to undo selection through the randomizing effects of recombination. Results We bred the NIAB Diverse MAGIC multi-parent population comprising over 500 recombinant inbred lines, descended from sixteen historical UK bread wheat varieties released between 1935 and 2004. We sequence the founders’ genes and promoters by capture, and the MAGIC population by low-coverage whole-genome sequencing. We impute 1.1 M high-quality SNPs that are over 99% concordant with array genotypes. Imputation accuracy only marginally improves when including the founders’ genomes as a haplotype reference panel. Despite capturing 73% of global wheat genetic polymorphism, 83% of genes cluster into no more than three haplotypes. We phenotype 47 agronomic traits over 2 years and map 136 genome-wide significant associations, concentrated at 42 genetic loci with large and often pleiotropic effects. Around half of these overlap known quantitative trait loci. Most traits exhibit extensive polygenicity, as revealed by multi-locus shrinkage modelling. Conclusions Our results are consistent with a gene pool of low haplotypic diversity, containing few novel loci of large effect. Most past, and projected future, phenotypic changes arising from existing variation involve fine-scale shuffling of a few haplotypes to recombine dozens of polygenic alleles of small effect. Moreover, extensive pleiotropy means selection on one trait will have unintended consequences, exemplified by the negative trade-off between yield and protein content, unless selection and recombination can break unfavorable trait-trait associations

Electronic structure of NiS1−x_{1-x}Sex_x across the phase transition

We report very highly resolved photoemission spectra of NiS(1-x)Se(x) across the so-called metal-insulator transition as a function of temperature as well as composition. The present results convincingly demonstrate that the low temperature, antiferromagnetic phase is metallic, with a reduced density of states at E$_F$. This decrease is possibly due to the opening of gaps along specific directions in the Brillouin zone caused by the antiferromagnetic ordering.Comment: Revtex, 4 pages, 3 postscript figure