High repetition-rate neutron generation by several-mJ, 35 fs pulses interacting with free-flowing D2O

Using several-mJ energy pulses from a high-repetition rate (1/2 kHz), ultrashort (35 fs) pulsed laser interacting with a 10 lm diameter stream of free-flowing heavy water (D2O), we demonstrate a 2.45 MeV neutron flux of 105/s. Operating at high intensity (of order 1019W/cm2), laser pulse energy is efficiently absorbed in the pre-plasma, generating energetic deuterons. These collide with deuterium nuclei in both the bulk target and the large volume of low density D2O vapor surrounding the target to generate neutrons through dðd; nÞ3 He reactions. The neutron flux, as measured by a calibrated neutron bubble detector, increases as the laser pulse energy is increased from 6 mJ to 12 mJ. A quantitative comparison between the measured flux and the results derived from 2D-particle-in-cell simulations shows comparable neutron fluxes for laser characteristics similar to the experiment. The simulations reveal that there are two groups of deuterons. Forward moving deuterons generate deuterium–deuterium fusion reactions in the D2O stream and act as a point source of neutrons, while backward moving deuterons propagate through the low-density D2O vapor filled chamber and yield a volumetric source of neutrons

Prevalence and socio-demographic correlates for serious injury among adolescents participating in the Djibouti 2007 Global School-based Health Survey

<p>Abstract</p> <p>Background</p> <p>Mental health and injury are neglected public health issues especially in low-income nations. The objective of the study was to determine the prevalence and socio-demographic correlates for serious injury in the last 12 months.</p> <p>Findings</p> <p>The study used data of the 2007 Djibouti Global School-based Health Survey. Logistic regression analysis was used to establish associations. Of the 1, 777 respondents, 61.1% (63.2% males and 57.8% females) reported having sustained serious injury (SSI). Compared to participants who were not bullied, those who reported being bullied 3-9 days per month were more likely to have sustained serious injury in the last 12 months (AOR = 1.27; 95% CI [1.06, 1.52] for 3-5 days of bullying victimization per month, and AOR = 3.19; 95% CI [2.28, 4.47] for 6-9 days per month. Adolescents who were engaged in physical fighting were 47% (AOR = 1.47, 95% CI [1.40, 1.55] more likely to have sustained serious injury compared to those who were not engaged in the fighting. Meanwhile, adolescents who used substances (cigarettes, other forms of tobacco or drugs) were 30% (AOR = 1.30, 95% CI [1.19, 1.42]) more likely to have sustained serious injury compared to those who did not use substances.</p> <p>Conclusions</p> <p>Serious injury is common among adolescents in Djibouti, and we suggest that health workers attending to injured adolescents explore the patients' psycho-social environment. Further, we suggest longitudinal studies where reduction of substance use and bullying may be assessed if they have an impact in reducing serious injury among adolescents.</p

Prevalence of youth access to alcohol or a gun in the home

Objectives: To estimate the national prevalence of youth access to alcohol, a gun, or both alcohol and a gun, in their home and to describe the demographic characteristics associated with access to either alcohol or a gun. Methods: Cross sectional data from the 1995 in-home survey of the National Longitudinal Study of Adolescent Health, which used a nationally representative randomly selected school based sample (n=18 924) of adolescents in grades 7–12, were analyzed. The current analyses were restricted to those adolescents 12–18 years of age (n=18 454). Crude logistic regression analyses was used to determine the demographic characteristics associated with access to alcohol or a gun in the home. Results: Overall, 28.7% of US adolescents reported having easy access to alcohol in the home. Availability of alcohol was associated with race/ethnicity, mother's education, family structure, and welfare status. Similarly, 24.3% of US adolescents reported easy access to a gun in the home. Availability of a gun in the home was associated with gender, race/ethnicity, mother's education, family structure, and welfare status. Among those that reported that a gun was available in their home, most reported availability of a shotgun (63.0%) followed by a rifle (61.3%), handgun (57.3%), and other gun (16.4%). Ten per cent of adolescents reported availability of both alcohol and a gun in their home. Conclusions: One quarter of US adolescents reported easy access to either alcohol or a gun in their home. Given the risks associated with the misuse of alcohol and guns among adolescents, efforts to increase public awareness of the availability of alcohol and guns in the home are needed