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.

On a Linear-Programming, Combinatorial Approach to the Traveling-Salesman Problem

Abstract: This paper elaborates a method of attack on traveling-salesman problems, proposed by the authors in an earlier paper, in which linear programming is used to reduce the combinatorial magnitude of such problems. To illustrate the method, a step-by-step solution of Barachet's ten-city example is presented.

The War on Drugs: Methamphetamine, Public Health, and Crime

Abstract: In mid-1995, a government effort to reduce the supply of methamphetamine precursors successfully disrupted the methamphetamine market and interrupted a trajectory of increasing usage. The price of methamphetamine tripled and purity declined from 90 percent to 20 percent. Simultaneously, amphetaminerelated hospital and treatment admissions dropped 50 percent and 35 percent, respectively. Methamphetamine use among arrestees declined 55 percent. Although felony methamphetamine arrests fell 50 percent, there is no evidence of substantial reductions in property or violent crime. The impact was largely temporary. The price returned to its original level within four months; purity, hospital admissions, treatment admissions, and arrests approached preintervention levels within eighteen months. (JEL I12, K42).

Estimating the Lyapunov Exponent of a Chaotic System with Nonparametric Regression

Abstract: We discuss procedures based on nonparametric regression for estimating the dominant Lyapunov Exponent λ1 from time series data generated by a nonlinear autoregressive system with additive noise. For systems with bounded fluctuations, λ1 > 0 is the defining feature of chaos. Thus our procedures can be used to examine time series data for evidence of chaotic dynamics. We show that a consistent estimator of the partial derivatives of the autoregression function can be used to obtain a consistent estimator of λ1. The rate of convergence we establish is quite slow; a better rate of convergence is derived heuristically and supported by simulations. Simulation results from several implementations—one “local” (thin-plate splines) and three “global” (neural nets, radial basis functions, and projection pursuit)—are presented for two deterministic chaotic systems. Local splines and neural nets yield accurate estimates of the Lyapunov exponent; however, the spline method is sensitive to the choice of the emb...

Occurrence of Secondary Ischemic Events Among Persons With Atherosclerotic Vascular Disease

Abstract: Background and Purpose— Few data exist for large managed care populations on the occurrence of subsequent acute ischemic events in persons with established atherosclerotic vascular disease. We estimated the occurrence of secondary stroke, acute myocardial infarction (AMI), and vascular deaths among 2 large, managed care samples. Methods— With the use of International Classification of Diseases, Ninth Revision, Clinical Modification codes, patients aged ≥40 years and with stroke, AMI, or peripheral arterial disease (PAD) were identified from administrative data of UnitedHealthcare plans during 1995–1998. Stroke, AMI, and PAD cohorts were identified within a commercial insurance sample and a Medicare sample. Cumulative occurrences of subsequent stroke, AMI, or vascular death were estimated by survival analysis. Results— In the stroke commercial cohort (n=1631; mean age, 62.1 years), cumulative occurrence of subsequent events was 4.2%, 6.5%, 9.8%, and 11.8% at 0.5, 1, 2, and 3 years, respectively; cumulative...

Antecedents of Physical and Sexual Victimization Among Homeless Women: A Comparison to Homeless Men

Abstract: Homeless women experience extensive health risks including physical and sexual victimization. Few studies that have gathered information on homeless persons have reported results separately for women or have compared them directly with men. Research that both investigates antecedents of victimization among homeless women and compares them to those for men is necessary to determine whether prevention efforts must be different for each group. We investigated potential antecedents of recent (past 30 days) physical and sexual victimization in a probability sample of 394 homeless women and compared findings to those for 1159 homeless men. As hypothesized, mental disorder, substance dependence, and engaging in economic survival strategies significantly predicted victimization among homeless women. With few dissimilarities, these characteristics also predicted victimization among homeless men. Although differences in the needs and experiences of homeless women and men must be recognized, both women and men require assistance to establish and maintain safe residences, treatment of any substance use and mental disorder, and alternatives to economic survival strategies that place them at risk for victimization.