Single-Crystal Alkali Antimonide Photocathodes: High Efficiency in the Ultrathin Limit.

The properties of photoemission electron sources determine the ultimate performance of a wide class of electron accelerators and photon detectors. To date, all high-efficiency visible-light photocathode materials are either polycrystalline or exhibit intrinsic surface disorder, both of which limit emitted electron beam brightness. In this Letter, we demonstrate the synthesis of epitaxial thin films of Cs_{3}Sb on 3C-SiC (001) using molecular-beam epitaxy. Films as thin as 4 nm have quantum efficiencies exceeding 2% at 532 nm. We also find that epitaxial films have an order of magnitude larger quantum efficiency at 650 nm than comparable polycrystalline films on Si. Additionally, these films permit angle-resolved photoemission spectroscopy measurements of the electronic structure, which are found to be in good agreement with theory. Epitaxial films open the door to dramatic brightness enhancements via increased efficiency near threshold, reduced surface disorder, and the possibility of engineering new photoemission functionality at the level of single atomic layers.

Factors associated with nursing home staff turnover.

This study examines whether, while controlling for local economic conditions, job design and other organizational factors affect facility aide turnover rates in a sample of 250 nursing homes from 10 states. Facility characteristics were largely based on administrator and director of nursing interviews conducted in 1993 as part of the Health Care Financing Administration's evaluation of the Resident Assessment Instrument (RAI) implementation. Aide turnover was significantly reduced by involvement in interdisciplinary care plan meetings. Turnover rates were higher in for-profit homes. Aide involvement in assessments, aide training and workload, case mix severity, payor source mix, and facility size were not significantly related to aide turnover.

Effect of the Medicare Catastrophic Coverage Act on payer source changes among nursing home residents.

The Medicare Catastrophic Coverage Act (MCCA) of 1989 was designed to expand Medicare's post-acute care benefits, reduce copayments, and raise the asset limit for Medicaid eligibility. This analysis uses a semi-Markov transition model to estimate the effect of the MCCA on changes to Medicare coverage and the spend-down rate among 5,551 new nursing home admissions followed for an average of 2.5 years. We found that Medicare use increased in 1989 and the risk of transiting from Medicare to self-pay decreased compared to 1988. Spend-down from self-pay to Medicaid was 60% more likely in 1990. The MCCA clearly increased access to Medicare coverage of nursing home care among individuals previously paying privately.