Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Sexual Risk Behavior Associated with Transition to Injection Among Young Non-Injecting Heroin Users

The aim of this study was to investigate the effects of transitioning from non-injection heroin use to injection drug use on sexual risk behavior. Non-injecting heroin users age 16–30 were enrolled from 2002 to 2005, and were re-interviewed at six-month intervals for up to three years; 561 participants completed at least one follow-up interview. The majority of participants were non-Hispanic (NH) Black (54%), 23% were Hispanic, and 21% were NH white. During follow-up, 154 participants (27.5%) transitioned to injecting drugs. Logistic regression analyses were conducted using generalized estimating equations (GEE) to estimate the effect of transition to injection drug use on changes in sexual risk behavior during follow-up. Transition to injection drug use during follow-up was associated with increased likelihood of sexual risk behavior, especially for men. Harm reduction efforts that focus on preventing initiation or return to injection among non-injecting drug users may also ameliorate HIV sexual risk behaviors