An overview of filtration efficiency through the masks: Mechanisms of the aerosols penetration.

The masks have always been mentioned as an effective tool against environmental threats. They are considered as protective equipment to preserve the respiratory system against the non-desirable air droplets and aerosols such as the viral or pollution particles. The aerosols can be pollution existence in the air, or the infectious airborne viruses initiated from the sneezing, coughing of the infected people. The filtration efficiency of the different masks against these aerosols are not the same, as the particles have different sizes, shapes, and properties. Therefore, the challenge is to fabricate the filtration masks with higher efficiency to decrease the penetration percentage at the nastiest conditions. To achieve this concept, knowledge about the mechanisms of the penetration of the aerosols through the masks at different effective environmental conditions is necessary. In this paper, the literature about the different kinds of face masks and respiratory masks, common cases of their application, and the advantages and disadvantages of them in this regard have been reviewed. Moreover, the related mechanisms of the penetration of the aerosols through the masks are discussed. The environmental conditions affecting the penetration as well as the quality of the fabrication are studied. Finally, special attention was given to the numerical simulation related to the different existing mechanisms.

Effect of antibiotics on the properties of poly(methylmethacrylate)-based bone cement.

The goal of this study was to examine the relationship between gentamicin concentration in Palacos R bone cement (in the mass fraction range of 0-9.4%) and various properties of the cement. The results from the thermal, density, and static compression tests show that gentamicin favors the cement polymerization in its final steps, and forms a diphasic structure with the cement [poly(methylmethacrylate)] matrix. The static compression properties in the dry state are only slightly modified by the presence of the antibiotic. Concerning aging in water at 37 degrees C, two types of behavior can be distinguished: below a critical concentration, approximately 3-4%, the extraction of gentamicin by water is slow and there is only a slight change of static compression properties. In contrast, above this critical concentration, the gentamicin extraction is fast and almost complete after 48 weeks, and there is a considerable loss of static compression properties.

Chemiluminescence of diglycidyl ether of bisphenol A--norbornene anhydride networks.

Networks were prepared by curing diglycidyl ether of bisphenol A (DGEBA) with variable concentrations of norbornene anhydride (NA). Almost completely cured samples with anhydride/epoxide (A/E) molar ratios of respectively 0.8, 0.9, 1.0 and 1.1, and one incompletely cured sample with A/E = 1.0, were studied by chemiluminescence in the temperature range 135-220 degrees C, using isothermal stationary or non-stationary (atmosphere change) exposures. The comparison of kinetic curves of intensity variation reveals: the importance of unreacted epoxide groups as sources of highly emissive radical species, the lowering effect of oxidation products, and the increasing effect of the decrease of macromolecular mobility due to crosslinking in the case of the incompletely cured sample. Most of the features of kinetic curves obtained in non-stationary experiments are explained in terms of radical formation mechanisms during exposure in inert atmosphere. The results show clearly that chemiluminescence is due to reactions of peroxy radicals rather than hydroperoxide groups.