Are There Differential Effects of Price and Policy on College Students' Drinking Intensity?

This paper investigates whether college students' response to alcohol price and policies differ according to their drinking intensity. Individual level data on drinking behavior, price paid per drink, and college alcohol policies come from the student and administrator components of the 1997 and 1999 waves of the Harvard School of Public Health (HSPH) College Alcohol Study (CAS). Students drinking behavior is classified on the basis of the number of drinks they typically consume on a drinking occasion, and the number of times they have been drunk during the 30 days prior to survey. A generalized ordered logit model is used to determine whether key variables impact differentially the odds of drinking and the odds of heavy drinking. We find that students who faced a higher money price for alcohol are less likely to make the transition from abstainer to moderate drinker and moderate drinker to heavy drinker, and this effect is equal across thresholds. Campus bans on the use of alcohol are a greater deterrent to moving from abstainer to moderate drinker than moderate drinker to heavy drinker.

Periodic substorm activity in the geomagnetic tail

On 19 May 1978 an anusual series of events is observed with the Quadrispherical LEPEDEA on board the ISEE-1 satellite in the Earth's geomagnetic tail. For 13 hours periodic bursts of both ions and electrons are seen in all the particle detectors on the spacecraft. On this day periodic activity is also seen on the ground, where multiple intensifications of the electrojets are observed. At the same time the latitudinal component of the interplanetary magnetic field shows a number of strong southward deflections. It is concluded that an extended period of substorm activity is occurring, which causes repeated thinnings and recoveries of the plasma sheet. These are detected by ISEE, which is situated in the plasma sheet boundary layer, as periodic dropouts and reappearances of the plasma. Comparisons of the observations at ISEE with those at IMP-8, which for a time is engulfed by the plasma sheet, indicate that the activity is relatively localized in spatial extent. For this series of events it is clear that a global approach to magnetospheric dynamics, e.g., reconnection, is inappropriate

Evaporation and growth of crystals - propagation of step density compression waves at vicinal surfaces

We studied the step dynamics during crystal sublimation and growth in the limit of fast surface diffusion and slow kinetics of atom attachment-detachment at the steps. For this limit we formulate a model free of the quasi-static approximation in the calculation of the adatom concentration on the terraces at the crystal surface. Such a model provides a relatively simple way to study the linear stability of a step train in a presence of step-step repulsion and an absence of destabilizing factors (as Schwoebel effect, surface electromigration etc.). The central result is that a critical velocity of the steps in the train exists which separates the stability and instability regimes. When the step velocity exceeds its critical value the plot of these trajectories manifests clear space and time periodicity (step density compression waves propagate on the vicinal surface). This ordered motion of the steps is preceded by a relatively short transition period of disordered step dynamics.Comment: 18 pages, 6 figure