Magnetic Control of Soft Chiral Phonons in PbTe.

PbTe crystals have a soft transverse optical phonon mode in the terahertz frequency range, which is known to efficiently decay into heat-carrying acoustic phonons, resulting in anomalously low thermal conductivity. Here, we studied this phonon via polarization-dependent terahertz spectroscopy. We observed softening of this mode with decreasing temperature, indicative of incipient ferroelectricity, which we explain through a model including strong anharmonicity with a quartic displacement term.

Observation of Photoinduced Terahertz Gain in GaAs Quantum Wells: Evidence for Radiative Two-Exciton-to-Biexciton Scattering.

We have observed photoinduced negative optical conductivity, or gain, in the terahertz frequency range in a GaAs multiple-quantum-well structure in a strong perpendicular magnetic field at low temperatures. The gain is narrow band: it appears as a sharp peak (linewidth <0.45  meV) whose frequency shifts with applied magnetic field.

Single-shot terahertz time-domain spectroscopy in pulsed high magnetic fields.

We have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective echelon to create time-delayed beamlets across the intensity profile of the optical gate beam before it spatially and temporally overlaps with the terahertz radiation in a ZnTe detection crystal. After imaging the gate beam onto a camera, we can retrieve the terahertz time-domain waveform by analyzing the resulting image.

Rapid scanning terahertz time-domain magnetospectroscopy with a table-top repetitive pulsed magnet.

We have performed terahertz time-domain magnetospectroscopy by combining a rapid scanning terahertz time-domain spectrometer based on the electronically controlled optical sampling method with a table-top minicoil pulsed magnet capable of producing magnetic fields up to 30 T. We demonstrate the capability of this system by measuring coherent cyclotron resonance oscillations in a high-mobility two-dimensional electron gas in GaAs and interference-induced terahertz transmittance modifications in a magnetoplasma in lightly doped n-InSb.

Providing culturally competent services for American Indian and Alaska Native veterans to reduce health care disparities.

Objectives: We conducted an exploratory study to determine what organizational characteristics predict the provision of culturally competent services for American Indian and Alaska Native (AI/AN) veterans in Department of Veterans Affairs (VA) health facilities.

Methods: In 2011 to 2012, we adapted the Organizational Readiness to Change Assessment (ORCA) for a survey of 27 VA facilities in the Western Region to assess organizational readiness and capacity to adopt and implement native-specific services and to profile the availability of AI/AN veteran programs and interest in and resources for such programs.

Results: Several ORCA subscales (Program Needs, Leader's Practices, and Communication) statistically significantly predicted whether VA staff perceived that their facilities were meeting the needs of AI/AN veterans.

A table-top, repetitive pulsed magnet for nonlinear and ultrafast spectroscopy in high magnetic fields up to 30 T.

We have developed a mini-coil pulsed magnet system with direct optical access, ideally suited for nonlinear and ultrafast spectroscopy studies of materials in high magnetic fields up to 30 T. The apparatus consists of a small coil in a liquid nitrogen cryostat coupled with a helium flow cryostat to provide sample temperatures down to below 10 K. Direct optical access to the sample is achieved with the use of easily interchangeable windows separated by a short distance of ~135 mm on either side of the coupled cryostats with numerical apertures of 0.

Fermi-edge superfluorescence from a quantum-degenerate electron-hole gas.

Nonequilibrium can be a source of order. This rather counterintuitive statement has been proven to be true through a variety of fluctuation-driven, self-organization behaviors exhibited by out-of-equilibrium, many-body systems in nature (physical, chemical, and biological), resulting in the spontaneous appearance of macroscopic coherence. Here, we report on the observation of spontaneous bursts of coherent radiation from a quantum-degenerate gas of nonequilibrium electron-hole pairs in semiconductor quantum wells.

Rural native veterans in the Veterans Health Administration: characteristics and service utilization patterns.

Purpose: The Department of Veterans Affairs (VA) and the Indian Health Service (IHS) signed a Memo of Understanding in 2010 to strengthen their partnership in improving health care services for Native veterans, who are disproportionately rural. This paper describes the demographic and service use profile of rural Native veterans who access VA health care.

Methods: Data were abstracted from the 2008 Veteran Health Administration (VHA) medical dataset, and the characteristics of rural Native veterans were compared to rural non-Native veterans.

Cardiovascular knowledge among urban American Indians and Alaska Natives: first steps in addressing cardiovascular health.

Background: Cardiovascular disease (CVD) is common among American Indians/Alaska Natives (AI/ANs). Given limited access to health care, urban AI/ANs may be at particular risk. Lack of available data, however, limits our understanding of cardiovascular health in this population.