Biomedical subjects

Steven C Hill

Publications and source records attributed to Steven C Hill.

11 recordsLinked to original sources

PubMed2006

Reports of fewer activity limitations: recovery, survey fatigue, or switching respondent?

BACKGROUND: Very little is known about the validity and reliability of disability dynamics reported in household surveys, and some researchers argue that measurement error likely plays a large part in reported recovery from disability. OBJECTIVES: We assessed the reliability of reported recovery from activity limitations elicited from 2 types of questions. We assessed competing hypotheses explaining reported recoveries from disability: people are less likely to recover from more severe disabilities, switching between self- and proxy-response affects reported recovery, and survey fatigue reduces reported disability. METHODS: Using the second panel of the Medical Expenditure Panel Survey, we estimated kappas for 2 types of questions in the same interview about limitations in activities of daily living and instrumental activities of daily living. We estimated multinomial logit models of consistently reported recovery, consistently reported ongoing limitations, and inconsistent responses. Recovery is a function of severity, switching respondent, measures of survey burden (such as family size), age, and education. RESULTS: Within an interview, we found substantial reliability for both instrumental activities of daily living and activities of daily living limitations (kappa = 0.62 and 0.70, respectively). Sample members with more severe disabilities are less likely to report recovery, which is consistent with accurate reporting. Controlling for severity, the type of respondent affects reported recovery. Measures of survey burden did not affect reports. CONCLUSION: Researchers can be confident in reports of recovery in the Medical Expenditure Panel Survey, especially when disability status was self-reported in both interviews. Researchers may also want to control for proxy respondents and switching respondents in their analyses.

Activities of Daily Living↗

PubMed2005

Rural-urban differences in employment-related health insurance.

CONTEXT: Rural residents are disproportionately represented among the uninsured in the United States. PURPOSE: We compared nonelderly adult residents in 3 types of nonmetropolitan areas with metropolitan workers to evaluate which characteristics contribute to lack of employment-related insurance. RESEARCH DESIGN AND ANALYSIS: Data were obtained from the Medical Expenditure Panel Survey, pooled across 3 panels (1996--1998) to enhance the rural sample size. Econometric decomposition was used to quantify the contribution of employment structure to differences in the probability of being offered employment-related health insurance. FINDINGS: The most rural workers are 10.4 percentage points less likely to be offered insurance compared with urban workers; the difference is smaller for residents of other rural areas. In rural counties not adjacent to urban areas, lower wages and smaller employers each account for about one-third of the total difference. CONCLUSIONS: Health insurance disparities associated with rural residence are related to the structure of employment. Major factors include smaller employers, lower wages, greater prevalence of self-employment, and sociodemographic characteristics.

Adult↗

PubMed2004

Two-dimensional angular optical scattering patterns of microdroplets in the mid infrared with strong and weak absorption.

Two-dimensional angular optical scattering (TAOS) patterns of droplets composed of a mixture of H2O and D2O are detected in the mid infrared. First, a lens is used in the Abbé sine condition to collect a small solid angle of light, where the scattering pattern matches well numerical simulations based on Mie theory. Next, TAOS patterns from droplets spanning a large (approximately 27pi sr) solid angle are captured simultaneously at two wavelengths. The effects of absorption are evident in the patterns and are discernible without the need for curve matching by Mie theory.

Journal Article↗

PubMed2004

Does capitation matter? Impacts on access, use, and quality.

Provider capitation may constrain costs, but it also may reduce access and quality of care. We examine the impacts of capitating the usual source of care of enrollees in health maintenance organizations (HMOs). We account for the endogeneity of capitation and other characteristics using generalized methods of moments (GMM) estimation on a sample from the Medical Expenditure Panel Survey for 1996 and 1997. Being organized as a group/staff HMO generally has stronger impact on access and quality than capitation. Capitation by itself may increase access to consumers' usual sources of care, improve primary preventive care, and reduce coordination, but estimates with GMM were not statistically significant.

Adult↗

PubMed2003

Method for integrating the absorption cross sections of spheres over wavelength or diameter.

The absorption cross sections of spherical particles and droplets must be integrated over frequency or droplet size or both for various applications. Morphology-dependent resonances (MDRs) of the spheres can make evaluation of such integrals difficult because the MDRs can contribute significantly to the integrals even when their linewidths are extremely narrow, especially when the absorption is weak. A method of evaluating these integrals by use of Lorentzian approximations near MDRs is described. Calculated frequency-integrated absorption cross sections illustrate how the method obtains accurate cross sections with far fewer integration points than a method that uses equally spaced points. The method reported here suggests a way to integrate over frequency in more-complicated scattering and emission problems and should also be useful for integrating scattering and absorption by other shapes, e.g., spheroids and cylinders, for which the MDR positions and linewidths can be calculated.

Journal Article↗

PubMed2003

Plasma formation dynamics within a water microdroplet on femtosecond time scales.

We demonstrate that a highly confined plasma inclusion is formed inside a micrometric water droplet that is excited by a femtosecond laser. An 800-nm laser pulse generates a plasma inclusion by laser-induced breakdown that is subsequently probed by the elastic scattering of a second (400-nm) time-delayed ultrashort pulse. For a 25-microm-radius droplet and an incident intensity of 7 x 10(12) W/cm2 the radius of the highly localized plasma is 1.9 +/- 0.4 microm. We probed the plasma formation dynamics on femtosecond time scales by varying the delay between the pump and the probe pulses. Good agreement with numerical simulations of the process was found.

Journal Article↗

PubMed2003

SSI enrollees' health care in TennCare.

How well does TennCare, Tennessee's Medicaid managed care program, meet the needs of blind/disabled Supplemental Security Income (SSI) enrollees? People with disabilities have extensive health care needs and greater barriers to accessing care, so efforts to reduce service use may decrease their health and independence. On the other hand, managed care plans may better coordinate care. Computer-assisted telephone surveys of urban SSI and other urban TennCare enrollees were conducted to assess these issues. SSI enrollees in TennCare had mixed experiences, and they faced problems in areas particularly important to people with disabilities. Relative to other TennCare enrollees, SSI enrollees had similar or slightly worse access to care and satisfaction. A significant minority of SSI enrollees reported unmet needs for care, such as not getting referrals to specialists, prescription drugs, and special medical equipment. Lack of care coordination was a problem for some SSI enrollees.

Persons with Disabilities↗

PubMed2002

White-light nanosource with directional emission.

We report the first observation of white-light emission from femtosecond laser-induced plasma in a water droplet. Such emission is not observed with water in a cell. The microdroplet acts as a lens, focusing the incident light to nanosized regions within itself and directing the emission from these regions primarily back toward the laser source. This focusing increases the intensity so that multiphoton ionization generates plasma and causes it to reach the critical density during the initial part of the pulse, enabling the rest of the pulse to heat the plasma enough to emit in the visible.

Journal Article↗

PubMed2002

Backward-enhanced fluorescence from clusters of microspheres and particles of tryptophan.

Measured fluorescence from single-particle clusters of dye-doped polystyrene microspheres, dried nonspherical particles of tryptophan, and single polystyrene microspheres is enhanced in the backward direction (180 degrees from the incident laser). This enhancement (a factor of 2-3 compared to 90 degrees), which can be interpreted as a consequence of the reciprocity principle, increases with the particle refractive index.

Journal Article↗

PubMed2002

Plan characteristics and SSI enrollees' access to and quality of care in four TennCare MCOs.

OBJECTIVE: To assess hypotheses about which managed care organization (MCO) characteristics affect access to care and quality of care--including access to specialists, providers' knowledge about disability, and coordination of care--for people with disabilities. DATA SOURCES/STUDY SETTING: Survey of blind/disabled Supplemental Security Income (SSI) enrollees in four MCOs serving TennCare, Tennessee's Medicaid managed care program, in Memphis, conducted from 1998 through spring 1999. STUDY DESIGN: We compared enrollee reports of access and quality across the four MCOs using regression methods, and we use case study methods to assess whether patterns both within and across MCOs are consistent with the hypotheses. DATA COLLECTION: We conducted computer-assisted telephone surveys and used regression analysis to compare access and quality controlling for enrollee characteristics. PRINCIPAL FINDINGS: Although the four MCOs' characteristics varied, access to providers, coordination of care, and access to some services were generally similar across MCOs. Enrollees in one plan, the only MCO with a larger provider network and that paid physicians on a fee-for-service basis, reported their providers were more knowledgeable, and they had more secondary preventive care visits. Differences found in access to specialists and delays in approving care appear to be unrelated to characteristics reported by the MCOs, but instead may be related to how tightly utilization is reviewed. CONCLUSIONS: Plan networks, financial incentives, utilization management methods, and state requirements are important areas for further study, and, in the meantime, ongoing monitoring of SSI enrollees in each MCO may be important for detecting problems and successes.

Continuity of Patient Care↗

PubMed2002

Risk selection among SSI enrollees in TennCare.

The issue of risk selection is especially important for states that enroll blind and disabled beneficiaries of Supplemental Security Income (SSI) in Medicaid managed care. SSI beneficiaries have persistent needs for care, have a wide variety of chronic conditions, and often need atypical and complex services. Risk selection occurs when the health care needs of beneficiaries enrolled in a specific plan differ systematically from the needs of the overall beneficiary population and payments do not reflect those needs. We assess the extent of risk selection among managed care plans for SSI beneficiaries over the first three years of Tennessee's Medicaid managed care program, TennCare. Using claims data containing fee-for-service expenditures prior to enrollment in managed care, we find substantial evidence of persistent risk selection among plans. Results are robust to most alternative measures of risk selection for most plans.

Aid to Families with Dependent Children↗