Small band gap superlattices as intrinsic long wavelength infrared detector materials

Intrinsic long wavelength (lambda greater than or equal to 10 microns) infrared (IR) detectors are currently made from the alloy (Hg, Cd)Te. There is one parameter, the alloy composition, which can be varied to control the properties of this material. The parameter is chosen to set the band gap (cut-off wavelength). The (Hg, Cd)Te alloy has the zincblend crystal structure. Consequently, the electron and light-hole effective masses are essentially inversely proportional to the band gap. As a result, the electron and light-hole effective masses are very small (M sub(exp asterisk)/M sub o approx. M sub Ih/M sub o approx. less than 0.01) whereas the heavy-hole effective mass is ordinary size (M sub hh(exp asterisk)/M sub o approx. 0.4) for the alloy compositions required for intrinsic long wavelength IR detection. This combination of effective masses leads to rather easy tunneling and relatively large Auger transition rates. These are undesirable characteristics, which must be designed around, of an IR detector material. They follow directly from the fact that (Hg, Cd)Te has the zincblend crystal structure and a small band gap. In small band gap superlattices, such as HgTe/CdTe, In(As, Sb)/InSb and InAs/(Ga,In)Sb, the band gap is determined by the superlattice layer thicknesses as well as by the alloy composition (for superlattices containing an alloy). The effective masses are not directly related to the band gap and can be separately varied. In addition, both strain and quantum confinement can be used to split the light-hole band away from the valence band maximum. These band structure engineering options can be used to reduce tunneling probabilities and Auger transition rates compared with a small band gap zincblend structure material. Researchers discuss the different band structure engineering options for the various classes of small band gap superlattices

Strain-Induced Conduction Band Spin Splitting in GaAs from First Principles Calculations

We use a recently developed self-consistent GW approximation to present first principles calculations of the conduction band spin splitting in GaAs under [110] strain. The spin orbit interaction is taken into account as a perturbation to the scalar relativistic hamiltonian. These are the first calculations of conduction band spin splitting under deformation based on a quasiparticle approach; and because the self-consistent GW scheme accurately reproduces the relevant band parameters, it is expected to be a reliable predictor of spin splittings. We also discuss the spin relaxation time under [110] strain and show that it exhibits an in-plane anisotropy, which can be exploited to obtain the magnitude and sign of the conduction band spin splitting experimentally.Comment: 8 pages, 4 figures, 1 tabl

Spin noise spectroscopy to probe quantum states of ultracold fermionic atomic gases

Ultracold alkali atoms provide experimentally accessible model systems for probing quantum states that manifest themselves at the macroscopic scale. Recent experimental realizations of superfluidity in dilute gases of ultracold fermionic (half-integer spin) atoms offer exciting opportunities to directly test theoretical models of related many-body fermion systems that are inaccessible to experimental manipulation, such as neutron stars and quark-gluon plasmas. However, the microscopic interactions between fermions are potentially quite complex, and experiments in ultracold gases to date cannot clearly distinguish between the qualitatively different microscopic models that have been proposed. Here, we theoretically demonstrate that optical measurements of electron spin noise -- the intrinsic, random fluctuations of spin -- can probe the entangled quantum states of ultracold fermionic atomic gases and unambiguously reveal the detailed nature of the interatomic interactions. We show that different models predict different sets of resonances in the noise spectrum, and once the correct effective interatomic interaction model is identified, the line-shapes of the spin noise can be used to constrain this model. Further, experimental measurements of spin noise in classical (Boltzmann) alkali vapors are used to estimate the expected signal magnitudes for spin noise measurements in ultracold atom systems and to show that these measurements are feasible

Reversal of spin polarization in Fe/GaAs (001) driven by resonant surface states: First-principles calculations

A minority-spin resonant state at the Fe/GaAs(001) interface is predicted to reverse the spin polarization with voltage bias of electrons transmitted across this interface. Using a Green's function approach within the local spin density approximation we calculate spin-dependent current in a Fe/GaAs/Cu tunnel junction as a function of applied bias voltage. We find a change in sign of the spin polarization of tunneling electrons with bias voltage due to the interface minority-spin resonance. This result explains recent experimental data on spin injection in Fe/GaAs contacts and on tunneling magnetoresistance in Fe/GaAs/Fe magnetic tunnel junctions

Nondestructive SEM for surface and subsurface wafer imaging

The scanning electron microscope (SEM) is considered as a tool for both failure analysis as well as device characterization. A survey is made of various operational SEM modes and their applicability to image processing methods on semiconductor devices

Density and spin response functions in ultracold fermionic atom gases

We propose a new method of detecting the onset of superfluidity in a two-component ultracold fermionic gas of atoms governed by an attractive short-range interaction. By studying the two-body correlation functions we find that a measurement of the momentum distribution of the density and spin response functions allows one to access separately the normal and anomalous densities. The change in sign at low momentum transfer of the density response function signals the transition between a BEC and a BCS regimes, characterized by small and large pairs, respectively. This change in sign of the density response function represents an unambiguous signature of the BEC to BCS crossover. Also, we predict spin rotational symmetry-breaking in this system

Age-Independent Increases in Male Salivary Testosterone During Horticultural Activity Among Tsimane Forager-Farmers

Testosterone plays an important role in mediating male reproductive trade-offs in many vertebrate species, augmenting muscle and influencing behavior necessary for male-male competition and mating-effort. Among humans, testosterone may also play a key role in facilitating male provisioning of offspring as muscular and neuromuscular performance are deeply influenced by acute changes in testosterone. This study examines acute changes in salivary testosterone among 63 Tsimane men ranging in age from 16–80 (mean 38.2) years during one-hour bouts of treechopping while clearing horticultural plots. The Tsimane forager-horticulturalists living in the Bolivian Amazon experience high energy expenditure associated with food production, have high levels of parasites and pathogens, and display significantly lower baseline salivary testosterone than age-matched US males. Mixed-effects models controlling for BMI and time of specimen collection reveal increased salivary testosterone (p\u3c0.001) equivalent to a 48.6% rise, after one hour of tree chopping. Age had no effect on baseline (p=0.656) or change in testosterone (p=0.530); self-reported illness did not modify testosterone change (p=0.488). A comparison of these results to the relative change in testosterone during a competitive soccer tournament in the same population reveals larger relative changes in testosterone following resource production (tree chopping), compared to competition (soccer). These findings highlight the importance of moving beyond a unidimensional focus on changes in testosterone and male-male aggression to investigate the importance of testosterone-behavior interactions across additional male fitness-related activities. Acutely increased testosterone during muscularly intensive horticultural food production may facilitate male productivity and provisioning

Electron-Spin Filters Based on the Rashba Effect

Semiconductor electron-spin filters of a proposed type would be based on the Rashba effect, which is described briefly below. Electron-spin filters more precisely, sources of spin-polarized electron currents have been sought for research on, and development of, the emerging technological discipline of spintronics (spin-based electronics). There have been a number of successful demonstrations of injection of spin-polarized electrons from diluted magnetic semiconductors and from ferromagnetic metals into nonmagnetic semiconductors. In contrast, a device according to the proposal would be made from nonmagnetic semiconductor materials and would function without an applied magnetic field. The Rashba effect, named after one of its discoverers, is an energy splitting, of what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. The present proposal evolved from recent theoretical studies that suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling. Accordingly, a device according to the proposal would be denoted an asymmetric resonant interband tunneling diode [a-RITD]. An a-RITD could be implemented in a variety of forms, the form favored in the proposal being a double-barrier heterostructure containing an asymmetric quantum well. It is envisioned that a-RITDs would be designed and fabricated in the InAs/GaSb/AlSb material system for several reasons: Heterostructures in this material system are strong candidates for pronounced Rashba spin splitting because InAs and GaSb exhibit large spin-orbit interactions and because both InAs and GaSb would be available for the construction of highly asymmetric quantum wells. This mate-rial system affords a variety of energy-band alignments that can be exploited to obtain resonant tunneling and other desired effects. The no-common-atom InAs/GaSb and InAs/AlSb interfaces would present opportunities for engineering interface potentials for optimizing Rashba spin splitting

Validation of the Cardiosphere Method to Culture Cardiac Progenitor Cells from Myocardial Tissue

At least four laboratories have shown that endogenous cardiac progenitor cells (CPCs) can be grown directly from adult heart tissue in primary culture, as cardiospheres or their progeny (cardiosphere-derived cells, CDCs). Indeed, CDCs are already being tested in a clinical trial for cardiac regeneration. Nevertheless, the validity of the cardiosphere strategy to generate CPCs has been called into question by reports based on variant methods. In those reports, cardiospheres are argued to be cardiomyogenic only because of retained cardiomyocytes, and stem cell activity has been proposed to reflect hematological contamination. We use a variety of approaches (including genetic lineage tracing) to show that neither artifact is applicable to cardiospheres and CDCs grown using established methods, and we further document the stem cell characteristics (namely, clonogenicity and multilineage potential) of CDCs.CPCs were expanded from human endomyocardial biopsies (n = 160), adult bi-transgenic MerCreMer-Z/EG mice (n = 6), adult C57BL/6 mice (n = 18), adult GFP(+) C57BL/6 transgenic mice (n = 3), Yucatan mini pigs (n = 67), adult SCID beige mice (n = 8), and adult Wistar-Kyoto rats (n = 80). Cellular yield was enhanced by collagenase digestion and process standardization; yield was reduced in altered media and in specific animal strains. Heparinization/retrograde organ perfusion did not alter the ability to generate outgrowth from myocardial sample. The initial outgrowth from myocardial samples was enriched for sub-populations of CPCs (c-Kit(+)), endothelial cells (CD31(+), CD34(+)), and mesenchymal cells (CD90(+)). Lineage tracing using MerCreMer-Z/EG transgenic mice revealed that the presence of cardiomyocytes in the cellular outgrowth is not required for the generation of CPCs. Rat CDCs are shown to be clonogenic, and cloned CDCs exhibit spontaneous multineage potential.This study demonstrates that direct culture and expansion of CPCs from myocardial tissue is simple, straightforward, and reproducible when appropriate techniques are used

Sheep Updates 2007 - part 4

This session covers eight papers from different authors: GRAZING 1. The impact of high dietary salt and its implications for the management of livestock grazing saline land, Dean Thomas, Dominique Blache, Dean Revell, Hayley Norman, Phil Vercoe, Zoey Durmic, Serina Digby, Di Mayberry, Megan Chadwick, Martin Sillence and David Masters, CRC for Plant-based Management of Dryland Salinity, Faculty of Natural & Agricultural Sciences, The University of Western Australia, WA. 2. Sustainable Grazing on Saline Lands - outcomes from the WA1 research project, H.C. Norman1,2, D.G. Masters1,2, R. Silberstein1,2, F. Byrne2,3, P.G.H. Nichols2,4, J. Young3, L. Atkins1,2, M.G. Wilmot1,2, A.J. Rintoul1,2, T. Lambert1,2, D.R. McClements2,4, P. Raper4, P. Ward1,2, C. Walton5 and T. York6 1CSIRO Centre for Environment and Life Sciences, Wembley, WA 2CRC for Plant-based Management of Dryland Salinity. 3School of Agricultural and Resource Economics, University of Western Australia. 4Department of Agriculture and Food WA. 5Condering Hills, Yealering. 6Anameka Farms, Tammin. MEAT QUALITY 3. Development of intramuscular fat in prime lambs, young sheep and beef cattle, David Pethick1, David Hopkins2 and Malcolm McPhee3,1School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, WA, 2NSW Department of Primary Industries, Cowra, NSW,3NSW Dept. of Primary Industries, University of New England, Armidale, NSW, 4. Importance of drinking water temperature for managing heat stress in sheep, Savage DB, Nolan JV, Godwin IR, Aoetpah A, Nguyen T, Baillie N and Lawler C University of New England, Armidale, NSW, Australia EWE MANAGEMENT TOOLS 5. E - sheep Management of Pregnant Merino Ewes and their Finishing Lambs, Ken GeentyA, John SmithA, Darryl SmithB, Tim DyallA and Grant UphillA A Sheep CRC and CSIRO Livestock Industries, Chiswick, NSW B Turretfield Research Station, SARDI, Roseworthy, SA 6. Is it important to manage ewes to CS targets? John Young, Farming Systems Analysis Service, Kojonup, WA MULESING 7. Mulesing accreditation - Vital for Wool\u27s Future, Dr Michael Paton, Department of Agriculture and Food WA, 8. Mulesing Alternatives, Jules Dorrian, Affiliation Project Manager Blowfly Control Australian Wool Inovatio