Carrier-controlled ferromagnetism in SrTiO3

Magnetotransport and superconducting properties are investigated for uniformly La-doped SrTiO3 films and GdTiO3/SrTiO3 heterostructures, respectively. GdTiO3/SrTiO3 interfaces exhibit a high-density two-dimensional electron gas on the SrTiO3-side of the interface, while for the SrTiO3 films carriers are provided by the dopant atoms. Both types of samples exhibit ferromagnetism at low temperatures, as evidenced by a hysteresis in the magnetoresistance. For the uniformly doped SrTiO3 films, the Curie temperature is found to increase with doping and to coexist with superconductivity for carrier concentrations on the high-density side of the superconducting dome. The Curie temperature of the GdTiO3/SrTiO3 heterostructures scales with the thickness of the SrTiO3 quantum well. The results are used to construct a stability diagram for the ferromagnetic and superconducting phases of SrTiO3.Comment: Revised version that is closer to the published version; Fig. 2 correcte

Atomic Layer Deposition of Tin Monosulfide Thin Films

Thin film solar cells made from earth-abundant, non-toxic materials are needed to replace the current technology that uses $Cu(In,Ga)(S,Se)_2$ and $CdTe$, which contain scarce and toxic elements. One promising candidate absorber material is tin monosulfide ($SnS$). In this report, pure, stoichiometric, single-phase SnS films were obtained by atomic layer deposition (ALD) using the reaction of $bis(N,N′-diisopropylacetamidinato)tin(II)$ $[Sn(MeC(N-^{i}Pr)_{2})_{2}]$ and hydrogen sulfide $(H_2 S)$ at low temperatures (100 to 200 $°C$). The direct optical band gap of SnS is around 1.3 eV and strong optical absorption $(\alpha > 10^4 cm^{−1})$ is observed throughout the visible and near-infrared spectral regions. The films are p-type semiconductors with carrier concentration on the order of $10^{16} cm^{−3}$ and hole mobility $0.82–15.3cm^{2}V^{−1}s^{−1}$ in the plane of the films. The electrical properties are anisotropic, with three times higher mobility in the direction through the film, compared to the in-plane direction.Chemistry and Chemical Biolog

Public Perceptions of Values Associated with Wildfire Protection at the Wildland-Urban Interface: A Synthesis of National Findings

The wildland-urban interface (WUI) continues to transform rural landscapes as previously undeveloped areas are populated with residential and commercial structures which, in turn, impact ecosystems and create landscapes of risk. Within this context, the science of wildfire risk mitigation has experienced renewed and enhanced support among scientists and managers. However, risk mitigation measures have not found purchase in either the public’s acceptance or involvement in this new role of and for fire. This may partially result from little regard for the effects of wildfire prevention efforts on values other than protecting homes and other structures. We report findings from qualitative interviews conducted across the United States to identify and define various values at risk from wildfire. Values influencing risk mitigation emerged from the biophysical, sociodemographic, and sociocultural contexts of wildfire. Findings demonstrate how wildfire is intertwined with diverse sets of risks experienced in daily life. We provide a discussion of how this research impacts the transformation of landscapes and risk management strategies. Identifying and better understanding the effects of values associated with wildfire—and landscape change in the WUI—will allow natural resource managers and decision makers to develop more effective fuel treatment programs and land use policies

ALD of Tin Monosulfide, SnS

Earth and Planetary Science

Low Temperature Atomic Layer Deposition of Tin Dioxide, SnO2_2

Chemistry and Chemical Biolog

Adaptations to Climate in Candidate Genes for Common Metabolic Disorders

Evolutionary pressures due to variation in climate play an important role in shaping phenotypic variation among and within species and have been shown to influence variation in phenotypes such as body shape and size among humans. Genes involved in energy metabolism are likely to be central to heat and cold tolerance. To test the hypothesis that climate shaped variation in metabolism genes in humans, we used a bioinformatics approach based on network theory to select 82 candidate genes for common metabolic disorders. We genotyped 873 tag SNPs in these genes in 54 worldwide populations (including the 52 in the Human Genome Diversity Project panel) and found correlations with climate variables using rank correlation analysis and a newly developed method termed Bayesian geographic analysis. In addition, we genotyped 210 carefully matched control SNPs to provide an empirical null distribution for spatial patterns of allele frequency due to population history alone. For nearly all climate variables, we found an excess of genic SNPs in the tail of the distributions of the test statistics compared to the control SNPs, implying that metabolic genes as a group show signals of spatially varying selection. Among our strongest signals were several SNPs (e.g., LEPR R109K, FABP2 A54T) that had previously been associated with phenotypes directly related to cold tolerance. Since variation in climate may be correlated with other aspects of environmental variation, it is possible that some of the signals that we detected reflect selective pressures other than climate. Nevertheless, our results are consistent with the idea that climate has been an important selective pressure acting on candidate genes for common metabolic disorders.</p

Image, brand and price info: do they always matter the same?

We study attention processes to brand, price and visual information about products in online retailing websites, simultaneously considering the effects of consumers’ goals, purchase category and consumers’ statements. We use an intra-subject experimental design, simulated web stores and a combination of observational eye-tracking data and declarative measures. Image information about the product is the more important stimulus, regardless of the task at hand or the store involved. The roles of brand and price information are dependent on the product category and the purchase task involved. Declarative measures of relative brand importance are found to be positively related with its observed importance

Clustering Analyses of 300,000 Photometrically Classified Quasars--I. Luminosity and Redshift Evolution in Quasar Bias

Using ~300,000 photometrically classified quasars, by far the largest quasar sample ever used for such analyses, we study the redshift and luminosity evolution of quasar clustering on scales of ~50 kpc/h to ~20 Mpc/h from redshifts of z~0.75 to z~2.28. We parameterize our clustering amplitudes using realistic dark matter models, and find that a LCDM power spectrum provides a superb fit to our data with a redshift-averaged quasar bias of b_Q = 2.41+/-0.08 ($P_{<\chi^2}=0.847$) for $\sigma_8=0.9$. This represents a better fit than the best-fit power-law model ($\omega = 0.0493\pm0.0064\theta^ {-0.928\pm0.055}$; $P_{<\chi^2}=0.482$). We find b_Q increases with redshift. This evolution is significant at >99.6% using our data set alone, increasing to >99.9999% if stellar contamination is not explicitly parameterized. We measure the quasar classification efficiency across our full sample as a = 95.6 +/- ^{4.4}_{1.9}%, a star-quasar separation comparable with the star-galaxy separation in many photometric studies of galaxy clustering. We derive the mean mass of the dark matter halos hosting quasars as MDMH=(5.2+/-0.6)x10^{12} M_solar/h. At z~1.9 we find a $1.5\sigma$ deviation from luminosity-independent quasar clustering; this suggests that increasing our sample size by a factor of 1.8 could begin to constrain any luminosity dependence in quasar bias at z~2. Our results agree with recent studies of quasar environments at z < 0.4, which detected little luminosity dependence to quasar clustering on proper scales >50 kpc/h. At z < 1.6, our analysis suggests that b_Q is constant with luminosity to within ~0.6, and that, for g < 21, angular quasar autocorrelation measurements are unlikely to have sufficient statistical power at z < 1.6 to detect any luminosity dependence in quasars' clustering.Comment: 13 pages, 9 figures, 2 tables; uses amulateapj; accepted to Ap

Electronic transport in two dimensional graphene

We provide a broad review of fundamental electronic properties of two-dimensional graphene with the emphasis on density and temperature dependent carrier transport in doped or gated graphene structures. A salient feature of our review is a critical comparison between carrier transport in graphene and in two-dimensional semiconductor systems (e.g. heterostructures, quantum wells, inversion layers) so that the unique features of graphene electronic properties arising from its gap- less, massless, chiral Dirac spectrum are highlighted. Experiment and theory as well as quantum and semi-classical transport are discussed in a synergistic manner in order to provide a unified and comprehensive perspective. Although the emphasis of the review is on those aspects of graphene transport where reasonable consensus exists in the literature, open questions are discussed as well. Various physical mechanisms controlling transport are described in depth including long- range charged impurity scattering, screening, short-range defect scattering, phonon scattering, many-body effects, Klein tunneling, minimum conductivity at the Dirac point, electron-hole puddle formation, p-n junctions, localization, percolation, quantum-classical crossover, midgap states, quantum Hall effects, and other phenomena.Comment: Final version as accepted for publication in Reviews of Modern Physics (in press), 69 pages with 38 figure