Richtmyer-Meshkov instability is a fingering instability which occurs at a material interface accelerated by a shock wave. We present an analytic, explicit prediction for the growth rate of the unstable interface. The theoretical prediction agrees, for the first time, with the experimental data on air-SF6, and is in remarkable agreement with the results of recent full non-linear numerical simul...

background fractures of the knee account for about 6% of all trauma admissions. while its management is mostly focused on fracture treatment, it is not the only factor that defines the final outcome. objectives this study aimed to study objective and subjective outcomes after proximal tibial versus distal femoral fractures in terms of knee instability and health-related quality of life. patient...

Using air to displace a viscous fluid contained in a Hele-Shaw cell can create a fingering pattern at the interface between the fluids if the capillary number exceeds a critical value. This Saffman-Taylor instability is revisited for the inverse case of a viscous fluid displacing air when partially wettable hydrophilic particles are lying on the walls. Though the inverse case is otherwise stabl...

BACKGROUND Air pollution is a major problem in urban\industrial areas, like Tehran, and has several impacts on human health. This study aimed at assessing concentrations of criteria air pollutants (CO, SO(2), NO(2), O(3), PM(10)) in Tehran, extracting patterns of hourly, daily, weekly, and monthly variations of concentrations, and making comparisons to National Standards and WHO Guidelines. M...

Augmented breaths promote respiratory instability and have been implicated in triggering periods of sleep-disordered breathing. Since respiratory instability is well known to be exacerbated by hypocapnia, we asked whether one of the destabilizing effects of hypocapnia might be related to an increased prevalence of augmented breaths. With this question in mind, we first sought to determine wheth...

the intensity of noise, heat and light were measured in 10 different groups of food processing plants with 3820 employees. noise was measured in 265 working places and if the over-all noise was more than t.l.v. (90dba), the octave band analysis was carried out. effective temperature (e.t) or corrected effective temperature (c.e.t) were measured in 183 working places and air velocity relative hu...

the aim of this study is to evaluate the obstacles due to a dpsir model combined with fuzzy analytic hierarchy process technique. hence, to prioritize the responses regarding the driving forces, pressures, states and impacts, the hierarchy of the model is established. evaluations and prioritization of model results of urban transport situation in tehran have provided a number of necessary issue...

The Clean Air Act, as amended in 1977, requires periodic review and revision of all national ambient air quality standards (NAAQS) to insure that they are based on the latest scientific information. This article presents an overview of how EPA currently reviews and establishes NAAQS. The role of scientific information and expertise in the process is illustrated by a review of several key issues...