Calculation of Vibrational Relaxation Times Using a Kinetic Theory Approach.

In the present work, a method for computation of vibrational relaxation times based on a kinetic theory definition is utilized to calculate vibrational relaxation times of molecules present in air (N, O, and NO) in collisions with air species particles. An overview of available experiment VT relaxation time measurements, as well as quasi-classical trajectory (QCT) calculation results, and various empirical models, is given. Different inelastic cross-section models are used for the computation of the relaxation times, and their parameters are adjusted to fit the available experimental data and QCT results.

Mutual effect of vibrational relaxation and chemical reactions in viscous multitemperature flows.

We study coupling of vibrational relaxation and chemical reactions in nonequilibrium viscous multitemperature flows. A general theoretical model is proposed on the basis of the Chapman-Enskog method modified for strongly nonequilibrium reacting flows; the model differs from models commonly used in computational fluid dynamics since it is able to capture additional cross-coupling terms arising in viscous flow due to compressibility and mutual influence of all nonequilibrium processes occurring in a mixture. The set of fluid dynamic equations is derived starting from the Boltzmann equation; the relaxation terms in these equations are described using the kinetic transport theory formalism.

World Health Organization regional assessments of the risks of poliovirus outbreaks.

While global polio eradication requires tremendous efforts in countries where wild polioviruses (WPVs) circulate, numerous outbreaks have occurred following WPV importation into previously polio-free countries. Countries that have interrupted endemic WPV transmission should continue to conduct routine risk assessments and implement mitigation activities to maintain their polio-free status as long as wild poliovirus circulates anywhere in the world. This article reviews the methods used by World Health Organization (WHO) regional offices to qualitatively assess risk of WPV outbreaks following an importation.

Polio control after certification: major issues outstanding.

Now that the global eradication of wild poliovirus is almost within sight, planning for the post-certification era is becoming a priority issue. It is agreed that a stockpile of appropriate polio vaccines will need to be established, and a surveillance and response capacity will need to be maintained, in order to protect the world against any possible future outbreaks attributable either to the persistence of wild poliovirus or vaccine-derived polioviruses (VDPVs) or to the unintentional or intentional release of poliovirus from a laboratory or vaccine store. Although it has been suggested that the stockpile should consist of monovalent oral poliovirus vaccine (mOPV), many questions remain concerning its nature, financing, management, and use--in particular, because of uncertainties over future national vaccination policies, and over the availability of different vaccines, after the certification of wild poliovirus eradication.

Importation and circulation of poliovirus in Bulgaria in 2001.

Objective: To characterize the circumstances in which poliomyelitis occurred among three children in Bulgaria during 2001 and to describe the public health response.

Methods: Bulgarian authorities investigated the three cases of polio and their contacts, conducted faecal and serological screening of children from high-risk groups, implemented enhanced surveillance for acute flaccid paralysis, and conducted supplemental immunization activities.

Findings: The three cases of polio studied had not been vaccinated and lived in socioeconomically deprived areas of two cities.