Strong Isospin Breaking in CP-even and CP-odd K -> pi pi Decays

Complete next-to-leading (chiral) order (NLO) expressions for the strong isospin-breaking (IB) contributions in K -> pi pi are used to discuss (1) for CP-even, the impact on the magnitude of the Delta I=1/2 Rule, and (2) for CP-odd, the strong IB correction, Omega_st, for the gluonic penguin contribution to epsilon'/epsilon, with particular emphasis on the strong low-energy constant (LEC) and loop contributions, numerical values for which are model-independent at NLO.Comment: 4 pages. Contribution to the proceedings of the 7th Conference on the Intersections of Particle and Nuclear Physics (CIPANP), May 22-28 2000, Quebec City, Canada. Uses AIP 6x9 LaTeX styl

Isospin Breaking in the Extraction of Isovector and Isoscalar Spectral Functions from e^+e^- --> hadrons

A finite energy sum rule (FESR) analysis of the isospin-breaking vector current correlator is used to determine the isospin-breaking electromagnetic (EM) decay constants of the low-lying vector mesons. These results are used to evaluate the corrections required to extract the flavor diagonal 33 and 88 resonance contributions from the full resonance EM contributions to the EM spectral function. A large (~15%) correction is found in the case of the omega contribution to the isoscalar spectral function. The implications of these results for sum rules based on the isovector-isoscalar spectral difference are considered.Comment: Presentation to the 3rd International Conference on Symmetries in Subatomic Physics, Adelaide, Mar. 13-17, 200

The Changing Economic Status of U.S. Disabled Men: Trends and Their Determinants, 1982–1991

In this paper, we track the level of economic well-being of the population of men who began receiving Social Security Disability Insurance (SSDI) benefits in 1980–81 from the time just after they became beneficiaries (in 1982) to 1991, nearly a decade later. We present measures of the economic well-being of disabled individuals and their nondisabled peers as indicators of the relative economic position of these two groups. These measures also provide an intertemporal comparison of well-being and hardship as disabled persons and their nondisabled peers age and retire. We first show several economic well-being indicators for this group of new male recipients of disability benefits in 1982 and 1991. Then, we compare their economic position to that of a matched group of nondisabled males with sufficient work histories to have been disability-insured, that is, eligible for SSDI benefits had they been unable to engage in substantial gainful employment. Because labor market changes over this decade have led to a relative deterioration in the position of younger and less-educated workers, we compare men with disabilities to those without disabilities and distinguish different age and educational levels within the groups. In studying these comparative trends in well-being, we focus on the prevalence of poverty and its correlates. We conclude by assessing the antipoverty effectiveness of Social Security income support for both younger and older men who became SSDI recipients in 1980–81.

The Changing Economic Status of Disabled Women, 1982–1991: Trends and Their Determinants

This study provides an assessment of the intertemporal economic well-being of a representative sample of women who began receiving Social Security Disability Insurance (SSDI) in 1980–81. We compare their economic circumstances over the 1982–1991 period with those of disabled men who also began receiving SSDI in those years and with those of a matched sample of nondisabled women who had sufficient work experience for benefit eligibility should they have become disabled. In 1982, the new SSDI women beneficiaries were a relatively poor segment of U.S. society: one quarter of them lived in poverty and 48 percent had incomes below 150 percent of the poverty line. As of 1991, over one-half of these disabled women lived in families with income below 150 percent of the poverty line. Social Security benefits to disabled women have played an important, and growing, role in sustaining economic status. Nevertheless, the level of well-being of these women lies substantially below that of the comparison groups. We statistically relate the poverty status of these new female recipients to sociodemographic factors that would be expected to contribute to lower levels of well-being, and we simulate the effect of Social Security benefits in reducing poverty and replacing earnings. We suggest a number of SSDI-related policy changes that could, at low cost, reduce poverty among the poorest women.

The relationship between EQ-5D, HAQ and pain in patients with rheumatoid arthritis: further validation and development of the limited dependent variable, mixture model approach

Objective To provide robust estimates of EQ-5D as a function of the Health Assessment Questionnaire (HAQ) and pain in patients with rheumatoid arthritis. Method Repeated observations of patients diagnosed with RA in a US observational cohort (n=100,398 observations) who provided data on HAQ, pain on a visual analogue scale and the EQ-5D questionnaire. We use a bespoke mixture modelling approach to appropriately reflect the characteristics of the EQ-5D instrument and compare this to results from linear regression. Results The addition of pain alongside HAQ as an explanatory variable substantially improves explanatory power. The preferred model is a four component mixture. Unlike the linear regression it exhibits very good fit to the data, does not suffer from problems of bias or predict values outside the feasible range. Conclusions It is appropriate to model the relationship between HAQ and EQ-5D but only if suitable statistical methods are applied. Linear models underestimate the QALY benefits, and therefore the cost effectiveness, of therapies. The bespoke mixture model approach outlined here overcomes this problem. The addition of pain as an explanatory variable greatly improves the estimates

Do Teens Make Rational Choices? The Case of Teen Nonmarital Childbearing

With emphasis on the role of economic incentives, we explore the determinants of a woman’s choice of whether or not to give birth as an unmarried teenager. Our data are taken from the Panel Study of Income Dynamics. Guided by a simple utility-maximization model, we represent the income possibilities available to teenaged women if they do and do not give birth out of wedlock. We estimate these choice-conditioned income possibilities through a two-stage probit procedure, relying on the observed incomes of a secondary sample of somewhat older women. The response of the young women in our primary sample to these income expectations is measured after controlling for the effects of a variety of other factors, including the characteristics of the girl’s family, the social and economic environment in which she lives (including such policy-related factors as expenditures by states on family planning programs and education), and her own prior choices. We use the estimated structural parameters from our model to simulate the effects of a variety of policy interventions on the probability of becoming an unmarried teen mother. Our estimations provide evidence that income expectations have a persistent influence on the childbearing decision. They also provide evidence that the provision of public family planning expenditures and increases in parental education could reduce the prevalence of teen nonmarital births.

A comparison of direct and indirect methods for the estimation of health utilities from clinical outcomes

Background: Analysts often need to estimate health state utility values as a function of other outcome measures. Utility values like EQ-5D have several unusual characteristics that make standard statistical methods inappropriate. We have developed a bespoke approach based on mixture models to directly estimate EQ-5D. An indirect method, “response mapping”, first estimates the level on each of the five dimensions of the EQ-5D descriptive system and then calculates the expected tariff score. These methods have never previously been compared. Methods: We use a large observational database of patients diagnosed with Rheumatoid Arthritis (n=100,398 observations). Direct estimation of UK EQ-5D scores as a function of Health Assessment Questionnaire (HAQ), pain and age was performed using a limited dependent variable mixture model. Indirect modelling was undertaken using a set of generalized ordered probit models with expected tariff scores calculated mathematically. Linear regression was reported for comparison purposes. Results: The linear model fits poorly, particularly at the extremes of the distribution. Both the bespoke mixture model and the generalized ordered probit approach offer improvements in fit over the entire range of EQ-5D. Mean average error is 10% and 5% lower compared to the linear model respectively. Root mean squared error is 3% and 2% lower. The mixture model demonstrates superior performance to the indirect method across almost the entire range of pain and HAQ. Limitations: There is limited data from patients in the most extreme HAQ health states. Conclusions: Modelling of EQ-5D from clinical measures is best performed directly using the bespoke mixture model. This substantially outperforms the indirect method in this example. Linear models are inappropriate, suffer from systematic bias and generate values outside the feasible range

Experimental Studies of the NaCs 53Π0 and a3Σ+ States

We report high resolution measurements of 372 NaCs 53Π0(v, J) ro-vibrational level energies in the range 0 ≤ v ≤ 22. The data have been used to construct NaCs 53Π0 potential energy curves using the Rydberg–Klein-Rees and inverted perturbation approximation methods. Bound-free 53Π0(v, J) → 1(a)3Σ+ emission has also been measured, and is used to determine the repulsive wall of the 1(a)3Σ+ state and the 53Π0 → 1(a)3Σ+ relative transition dipole moment function. Hyperfine structure in the 53Π0 state has not been observed in this experiment. This null result is explained using a simple vector coupling model