RAND Corporation

About: RAND Corporation is a nonprofit organization based out in Santa Monica, California, United States. It is known for research contribution in the topics: Population & Health care. The organization has 9602 authors who have published 18570 publications receiving 744658 citations.

A new look at the saturn system: the voyager 2 images.

Abstract: Voyager 2 photography has complemented that of Voyager I in revealing many additional characteristics of Saturn and its satellites and rings. Saturn's atmosphere contains persistent oval cloud features reminiscent of features on Jupiter. Smaller irregular features track out a pattern of zonal winds that is symmetric about Saturn's equator and appears to extend to great depth. Winds are predominantly eastward and reach 500 meters per second at the equator. Titan has several haze layers with significantly varying optical properties and a northern polar "collar" that is dark at short wavelengths. Several satellites have been photographed at substantially improved resolution. Enceladus' surface ranges from old, densely cratered terrain to relatively young, uncratered plains crossed by grooves and faults. Tethys has a crater 400 kilometers in diameter whose floor has domed to match Tethys' surface curvature and a deep trench that extends at least 270° around Tethys' circumference. Hyperion is cratered and irregular in shape. Iapetus' bright, trailing hemisphere includes several dark-floored craters, and Phoebe has a very low albedo and rotates in the direction opposite to that of its orbital revolution with a period of 9 hours. Within Saturn's rings, the "birth" of a spoke has been observed, and surprising azimuthal and time variability is found in the ringlet structure of the outer B ring. These observations lead to speculations about Saturn's internal structure and about the collisional and thermal history of the rings and satellites.

Functioning and well-being outcomes of patients with depression compared with chronic general medical illnesses

Abstract: Background: Cross-sectional studies have found that depression is uniquely associated with limitations in wellbeing and functioning that were equal to or greater than those of chronic general medical conditions such as diabetes and arthritis. However, whether these relative limitations persist over time is not known. Methods: We conducted a 2-year observational study of 1790 adult outpatients with depression, diabetes, hypertension, recent myocardial infarction, and/or congestive heart failure. Change in functional status and wellbeing was compared for depressed patients vs patients with chronic general medical illnesses, controlling statistically for medical comorbidity, sociodemographics, system, and specialty of care. Results: Over 2 years of follow-up, limitations in functioning and well-being improved somewhat for depressed patients; even so, at the end of 2 years, these limitations were similar to or worse than those attributed to chronic medical illnesses. Similar patterns were observed for depressed patients in the mental health specialty sector and those in the general medical sector, but the patients in the mental health specialty sector improved more. More severely depressed patients improved more in functioning, but even initially depressed patients without depressive disorder had substantial persistent limitations. Conclusion: Depressed patients have substantial and long-lasting decrements in multiple domains of functioning and well-being that equal or exceed those of patients with chronic medical illnesses.

Data Analysis Using Stein's Estimator and its Generalizations

Abstract: In 1961, James and Stein exhibited an estimator of the mean of a multivariate normal distribution having uniformly lower mean squared error than the sample mean. This estimator is reviewed briefly in an empirical Bayes context. Stein's rule and its generalizations are then applied to predict baseball averages, to estimate toxomosis prevalence rates, and to estimate the exact size of Pearson's chi-square test with results from a computer simulation. In each of these examples, the mean square error of these rules is less than half that of the sample mean.