Metallic behavior in Si/SiGe 2D electron systems

We calculate the temperature, density, and parallel magnetic field dependence of low temperature electronic resistivity in 2D high-mobility Si/SiGe quantum structures, assuming the conductivity limiting mechanism to be carrier scattering by screened random charged Coulombic impurity centers. We obtain comprehensive agreement with existing experimental transport data, compellingly establishing that the observed 2D metallic behavior in low-density Si/SiGe systems arises from the peculiar nature of 2D screening of long-range impurity disorder. In particular, our theory correctly predicts the experimentally observed metallic temperature dependence of 2D resistivity in the fully spin-polarized system

Magnetoresistance of a two-dimensional electron gas in a parallel magnetic field

The conductivity of a two-dimensional electron gas in a parallel magnetic field is calculated. We take into account the magnetic field induced spin-splitting, which changes the density of states, the Fermi momentum and the screening behavior of the electron gas. For impurity scattering we predict a positive magnetoresistance for low electron density and a negative magnetoresistance for high electron density. The theory is in qualitative agreement with recent experimental results found for Si inversion layers and Si quantum wells.Comment: 4 pages, figures included, PDF onl

Microsatellite primers for red drum (Sciaenops ocellatus)

In this note, we document polymerase-chain-reaction (PCR) primer pairs for 101 nuclear-encoded microsatellites designed and developed from a genomic library for red drum (Sciaenops ocellatus). Details of the genomic library construction, the sequencing of positive clones, primer design, and PCR protocols may be found in Karlsson et al. (2008). The 101 microsatellites (GENBA NK Accession Numbers EU015882-EU015982) were amplified successfully and used to genotype 24 red drum obtained from Galveston Bay, Texas (Table 1). A total of 69 of the microsatellites had an uninterrupted (perfect) dinucleotide motif, and 30 had an imperfect dinucleotide motif; one microsatellite had an imperfect tetranucleotide motif, and one had an imperfect and compound motif (Table 1 ). Sizes of the cloned alleles ranged from 84 to 252 base pairs. A ‘blast’ search of the GENBANK database indicated that all of the primers and the cloned alleles were unique (i.e., not duplicated)

Very high two-dimensional hole gas mobilities in strained silicon germanium

We report on the growth by solid source MBE and characterization of remote doped Si/SiGe/Si two-dimensional hole gas structures. It has been found that by reducing the Ge composition to <=13% and limiting the thickness of the alloy layer, growth temperatures can be increased up to 950 °C for these structures while maintaining good structural integrity and planar interfaces. Record mobilities of 19 820 cm2 V−1 s−1 at 7 K were obtained in normal structures. Our calculations suggest that alloy scattering is not important in these structures and that interface roughness and interface charge scattering limit the low temperature mobilities

There\u27s No Place like Home: Reshaping Community Interventions and Policies to Eliminate Environmental Hazards and Improve Population Health for Low-Income and Minority Communities

Substandard housing and environmental conditions threaten the health and wellbeing of individuals residing throughout the United States Empirical evidence on the relationship between housing and health has increased exponentially However despite the growth in research residents continue to be exposed to environmental health hazards Minorities and people in poverty are exposed to environmental health hazards at a disproportionately high rate Hazards such as lead mold pest infestation radon and carbon monoxide among others threaten individual safety and health and limit one\u27s ability to access opportunity in society Moreover the effects of exposure can be farreaching Common approaches to healthy communities and homes fail to protect residents from exposure to environmental health hazards Federal state and local jurisdictions often rely on education and research regulation of real estate transactions heightened standards for special populations enactment of minimum habitability standards hazard mitigation and communitylevel interventions Taken together these approaches are fragmented reactive rather than preventive and underresourced As a result they are inadequate to prevent negative health consequences that accrue to residents This article analyzes the relationship between policies governing healthy communities and housing and health outcomes for residents Part I discusses how environmental and housing conditions affect community and individual health with a particular focus on conditions that cause lead poisoning asthma and respiratory distress and cancer Part II examines current federal state and local approaches to healthy housing policy including interventions directed at individual housing units as well as the community atlarge This part also analyzes the limitations of these policies that prevent residents from attaining good health Part III offers recommendations to improve health outcomes for individuals and communitie

Energy use for urban water management by utilities and Households in Los Angeles

Reducing energy consumption for urban water management may yield economic and environmental benefits. Few studies provide comprehensive assessments of energy needs for urban water sectors that include both utility operations and household use. Here, we evaluate the energy needs for urban water management in metropolitan Los Angeles (LA) County. Using planning scenarios that include both water conservation and alternative supply options, we estimate energy requirements of water imports, groundwater pumping, distribution in pipes, water and wastewater treatment, and residential water heating across more than one hundred regional water agencies covering over 9 million people. Results show that combining water conservation with alternative local supplies such as stormwater capture and water reuse (nonpotable or indirect potable) can reduce the energy consumption and intensity of water management in LA. Further advanced water treatment for direct potable reuse could increase energy needs. In aggregate, water heating represents a major source of regional energy consumption. The heating factor associated with grid-supplied electricity drives the relative contribution of energy-for-water by utilities and households. For most scenarios of grid operations, energy for household water heating significantly outweighs utility energy consumption. The study demonstrates how publicly available and detailed data for energy and water use supports sustainability planning. The method is applicable to cities everywhere

Evolution of Quantum Criticality in CeNi_{9-x}Cu_xGe_4

Crystal structure, specific heat, thermal expansion, magnetic susceptibility and electrical resistivity studies of the heavy fermion system CeNi_{9-x}Cu_xGe_4 (0 <= x <= 1) reveal a continuous tuning of the ground state by Ni/Cu substitution from an effectively fourfold degenerate non-magnetic Kondo ground state of CeNi_9Ge_4 (with pronounced non-Fermi-liquid features) towards a magnetically ordered, effectively twofold degenerate ground state in CeNi_8CuGe_4 with T_N = 175 +- 5 mK. Quantum critical behavior, C/T ~ \chi ~ -ln(T), is observed for x about 0.4. Hitherto, CeNi_{9-x}Cu_xGe_4 represents the first system where a substitution-driven quantum phase transition is connected not only with changes of the relative strength of Kondo effect and RKKY interaction, but also with a reduction of the effective crystal field ground state degeneracy.Comment: 15 pages, 9 figure

Therapist-Guided Practical Skills in the Treatment of Complex Dissociation

The Contextual Trauma Therapy (CTT) model includes a collaborative relationship, client-guided conceptualization, and therapist-guided practical skills. This workshop will discuss the application of therapist-guided skills for complex dissociation: 1) promoting a safe and stabile therapeutic setting, 2) improving emotion regulation, distress tolerance, and experiential presence, 3) therapist modeling of skills in session, and 4) collaborating with clients to foster utilization of skills beyond sessions. Presenters will provide examples of applications of this CTT component, benefits when clients incorporate consistent practice of these skills, and challenges associated with encouraging clients to extend the use of these skills in their personal lives

How Common is Energetic ^3He in the Inner Heliosphere?

Using data from the SIS and ULEIS instruments on the Advanced Composition Explorer (ACE) we have identified periods during which energetic ^3He is present in near-Earth interplanetary space between November 1997 and May 2002. The data, which cover the energy intervals 0.2–1 MeV/nuc (ULEIS) and 4.5–16.3 MeV/nuc (SIS), show that ^3He is present a significant fraction of the time, as would be required if these suprathermal particles were the major source of the ^3He being accelerated by shocks in the interplanetary medium. Specifically, we find that energetic ^3He is present at least ~ 60% of the time, and perhaps significantly more often