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: Health care & Population. The organization has 9602 authors who have published 18570 publications receiving 744658 citations.

Report of the IAU/IAG/COSPAR working group on cartographic coordinates and rotational elements of the planets and satellites: 1991

Abstract: Every three years the IAU/IAG Working Group on cartographic coordinates and rotational elements of the planets and satellites revises tables giving the directions of the north poles of rotation and the prime meridians of the planets, satellites, and asteroids. Also presented are revised tables giving their sizes and shapes. Changes since the previous report are summarized in the Appendix.

On the Epistemology of the Inexact Sciences

Abstract: This is a new epistemological approach to the inexact sciences. The purpose of all science is to explain and predict in an objective manner. While in the exact sciences explanation and prediction have the same logical structure, this is not so in the inexact sciences. This permits various methodological innovations in the inexact sciences, e.g., expert judgment and simulation.

Evidence for a subsurface ocean on Europa

Abstract: Ground-based spectroscopy of Jupiter's moon Europa, combined with gravity data, suggests that the satellite has an icy crust roughly 150 km thick and a rocky interior In addition, images obtained by the Voyager spacecraft revealed that Europa's surface is crossed by numerous intersecting ridges and dark bands (called lineae) and is sparsely cratered, indicating that the terrain is probably significantly younger than that of Ganymede and Callisto It has been suggested that Europa's thin outer ice shell might be separated from the moon's silicate interior by a liquid water layer, delayed or prevented from freezing by tidal heating; in this model, the lineae could be explained by repetitive tidal deformation of the outer ice shell However, observational confirmation of a subsurface ocean was largely frustrated by the low resolution (>2 km per pixel) of the Voyager images Here we present high-resolution (54 m per pixel) Galileo spacecraft images of Europa, in which we find evidence for mobile 'icebergs' The detailed morphology of the terrain strongly supports the presence of liquid water at shallow depths below the surface, either today or at some time in the past Moreover, lower-resolution observations of much larger regions suggest that the phenomena reported here are widespread

Validity of the Agency for Healthcare Research and Quality Clinical Practice Guidelines: How Quickly Do Guidelines Become Outdated?

Abstract: ContextPractice guidelines need to be up-to-date to be useful to clinicians. No published methods are available for assessing whether existing practice guidelines are still valid, nor does any empirical information exist regarding how often such assessments need to be made.ObjectivesTo assess the current validity of 17 clinical practice guidelines published by the US Agency for Healthcare Research and Quality (AHRQ) that are still in circulation, and to use this information to estimate how quickly guidelines become obsolete.Design, Setting, and ParticipantsWe developed criteria for defining when a guideline needs updating, mailed surveys to members of the original AHRQ guideline panels (n = 170; response rate, 71%), and searched the literature for evidence through March 2000 (n = 6994 titles yielding 173 articles plus 159 new guidelines on the same topics).Main Outcome MeasuresIdentification of new evidence calling for a major, minor, or no update of the 17 guidelines; survival analysis of the rate at which guidelines became outdated.ResultsFor 7 guidelines, new evidence and expert judgment indicated that a major update is required; 6 were found to be in need of a minor update; 3 were judged as still valid; and for 1 guideline, we could reach no conclusion. Survival analysis indicated that about half the guidelines were outdated in 5.8 years (95% confidence interval [CI], 5.0-6.6 years). The point at which no more than 90% of the guidelines were still valid was 3.6 years (95% CI, 2.6-4.6 years).ConclusionsMore than three quarters of the AHRQ guidelines need updating. As a general rule, guidelines should be reassessed for validity every 3 years.