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.

The galilean satellites and jupiter: voyager 2 imaging science results.

Abstract: Voyager 2, during its encounter with the Jupiter system, provided images that both complement and supplement in important ways the Voyager 1 images. While many changes have been observed in Jupiter's visual appearance, few, yet significant, changes have been detected in the principal atmospheric currents. Jupiter's ring system is strongly forward scattering at visual wavelengths and consists of a narrow annulus of highest particle density, within which is a broader region in which the density is lower. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but does reveal a complex and, as yet, little-understood system of overlapping bright and dark linear features. Ganymede is found to have at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered.

Efficacy and safety of ephedra and ephedrine for weight loss and athletic performance: a meta-analysis.

Abstract: ContextEphedra and ephedrine sometimes are used for weight loss or enhanced athletic performance, but the efficacy and safety of these compounds are uncertain.ObjectiveTo assess the efficacy and safety of ephedra and ephedrine used for weight loss and enhanced athletic performance.Data SourcesWe searched 9 databases using the terms ephedra, ephedrine, adverse effect, side effect, efficacy, effective, and toxic. We included unpublished trials and non–English-language documents. Adverse events reported to the US Food and Drug Administration MedWatch program were assessed.Study SelectionEligible studies were controlled trials of ephedra or ephedrine used for weight loss or athletic performance and case reports of adverse events associated with such use. Eligible studies for weight loss were human studies with at least 8 weeks of follow-up; and for athletic performance, those having no minimum follow-up. Eligible case reports documented that ephedra or ephedrine was consumed within 24 hours prior to an adverse event or that ephedrine or an associated product was found in blood or urine, and that other potential causes had been excluded. Of the 530 articles screened, 52 controlled trials and 65 case reports were included in the adverse events analysis. Of more than 18 000 other case reports screened, 284 underwent detailed review.Data ExtractionTwo reviewers independently identified trials of efficacy and safety of ephedra and ephedrine on weight loss or athletic performance; disagreements were resolved by consensus. Case reports were reviewed with explicit and implicit methods.Data SynthesisNo weight loss trials assessed duration of treatment greater than 6 months. Pooled results for trials comparing placebo with ephedrine (n = 5), ephedrine and caffeine (n = 12), ephedra (n = 1), and ephedra and herbs containing caffeine (n = 4) yielded estimates of weight loss (more than placebo) of 0.6 (95% confidence interval, 0.2-1.0), 1.0 (0.7-1.3), 0.8 (0.4-1.2), and 1.0 (0.6-1.3) kg/mo, respectively. Sensitivity analyses did not substantially alter the latter 3 results. No trials of ephedra and athletic performance were found; 7 trials of ephedrine were too heterogeneous to synthesize. Safety data from 50 trials yielded estimates of 2.2- to 3.6-fold increases in odds of psychiatric, autonomic, or gastrointestinal symptoms, and heart palpitations. Data are insufficient to draw conclusions about adverse events occurring at a rate less than 1.0 per thousand. The majority of case reports are insufficiently documented to allow meaningful assessment.ConclusionsEphedrine and ephedra promote modest short-term weight loss (≈0.9 kg/mo more than placebo) in clinical trials. There are no data regarding long-term weight loss, and evidence to support use of ephedra for athletic performance is insufficient. Use of ephedra or ephedrine and caffeine is associated with increased risk of psychiatric, autonomic, or gastrointestinal symptoms, and heart palpitations.

A logic programming framework for planning and simulation

Abstract: A common theme underlying various models that explain information technology adoption is the inclusion of perceptions of an innovation as key independent variables. Although a fairly significant body of research that empirically tests these models is now in existence, some questions with regard to both the antecedents as well as the consequents of perceptions remain unanswered. This paper reports the results of a field study examining adoption of an information technology innovation represented by an expert systems application. Two research objectives that have both theoretical and practical relevance motivated and guided the study. One, the study challenges an assumption which is implicit in technology acceptance models: that of the non-existence of moderating influences on the relationship between perceptions and adoption decisions. Specifically, the study examines the effects of an important moderating influence – personal innovativeness – on this relationship. Two, the study seeks to shed further light on the determinants of perceptions by examining the relative efficacy of mass media and interpersonal communication channels in facilitating perception development. Theoretical and practical implications that follow from the results are discussed.