A radiation shielding sensitivity analysis based on metal hydrides multilayers.

In order to shield neutron and gamma rays efficiently, a multilayer model is designed with metal hydrides and heavy metals and is analysed based on Monte Carlo simulations. In terms of shielding performance, the hydrogen in metal hydrides acts as a moderator to slow down the neutron energy and heavy metals are good for absorbing gamma rays. A simulation and calculational analysis are carried out with various parameters such as spectrum change, shield thickness, and number of multilayers. In addition, the rate of DPA (displacement per atom) is analysed to estimate both the lifetime and radiation resistance with the MCNP code. From lots of simulations, ZrH2 and W couples are the best candidate especially for shielding gamma rays, while TiH2 with W is good for neutron shielding. The concept of multilayer metal hydride such as TiH2 and ZrH2 coupled with W could be one of best combinations to shield both neutron and gamma-rays in many nuclear facilities such as nuclear reactor, fusion reactor and other applications.

Occurrence and characterization of oseltamivir-resistant influenza virus in children between 2007-2008 and 2008-2009 seasons.

PURPOSE: There was a global increase in the prevalence of oseltamivir-resistant influenza viruses during the 2007-2008 influenza season. This study was conducted to investigate the occurrence and characteristics of oseltamivir-resistant influenza viruses during the 2007-2008 and 2008-2009 influenza seasons among patients who were treated with oseltamivir (group A) and those that did not receive oseltamivir (group B). METHODS: A prospective study was conducted on 321 pediatric patients who were hospitalized because of influenza during the 2007-2008 and 2008-2009 influenza seasons. Drug resistance tests were conducted on influenza viruses isolated from 91 patients. RESULTS: There was no significant difference between the clinical characteristics of groups A and B during both seasons. Influenza A/H1N1, isolated from both groups A and B during the 2007-2008 and 2008-2009 periods, was not resistant to zanamivir. However, phenotypic analysis of the virus revealed a high oseltamivir IC50 range and that H275Y substitution of the neuraminidase (NA) gene and partial variation of the hemagglutinin (HA) gene did not affect its antigenicity to the HA vaccine even though group A had a shorter hospitalization duration and fewer lower respiratory tract complications than group B. In addition, there was no significant difference in the clinical manifestations between oseltamivir-susceptible and oseltamivir-resistant strains of influenza A/H1N1. CONCLUSION: Establishment of guidelines to efficiently treat influenza with oseltamivir, a commonly used drug for treating influenza in Korean pediatric patients, and a treatment strategy with a new therapeutic agent is required.