new microwave shield preparation for super high frequency range: occupational approach to radiation protection

Background: Widespread use of X-band frequency [a part of the super high frequency microwave] in the various workplaces would contribute to occupational exposure with potential of adverse health effects

According to limited study on microwave shielding for the workplace, this study tried to prepare a new microwave shielding for this purpose

Methods: We used El-403 epoxy thermosetting resin as a matrix and nickel oxide nanoparticle with the diameter of 15-35 nm as filler. The Epoxy/ Nickel oxide composites with 5, 7, 9 and 11 wt% were made in three different thicknesses [2, 4 and 6 mm]

According to transmission / reflection method, shielding effectiveness [SE] in the X-band frequency range [8-12.5 GHz] was measured by scattering parameters directly given by the 2-port Vector Network Analyzer. The fabricated composites characterized by X-ray Diffraction and Field Emission Scanning Electron Microscope

Results: The best average of shielding effectiveness in each thickness of fabricated composites obtained by 11%-2 mm, 7%-4 mm and 7%-6 mm composites with SE values of 46.80%, 66.72% and 64.52%, respectively. In addition, the 11%-6 mm, 5%-6 mm and 11%-4 mm-fabricated composites were able to attenuate extremely the incident microwave energy at 8.01, 8.51 and 8.53 GHz by SE of 84.14%, 83.57 and 81.30%, respectively

Conclusions: The 7%-4mm composite could be introduced as a suitable alternative microwave shield in radiation protection topics in order to its proper SE and other preferable properties such as low cost and weight, resistance to corrosion etc. It is necessary to develop and investigate the efficacy of the fabricated composites in the fields by future studies

Optimization of a novel setup for an on-line study of elemental mercury adsorption by cold-vapor atomic absorption spectrometry

The objective of this work was developing a simple and stable time-based on-line setup for assessing the potential of mercury [Hg] vapor adsorption of the commercial sorbents used in air sampling and control operation followed by cold vapor atomic absorption spectrometry [CVAAS]. A special designed separation chamber was used where reduction of the injected Hg [II] solution took place. Purge gas passes through this chamber resulting to a prompt release of mercury vapor, purging into the adsorbent that regulated at the desired adsorption temperature. After sorbent saturation, in order to study the adsorption parameters of sorbents [activated carbon and bone char] such as breakthrough time [BTT], and adsorptive capacity, mercury gas stream was passed through the sorbents, directly transport to the CVAAS. Preliminary experiments concerning the reductant solution showed that SnCl[2] offers higher stability than NaBH[4]. Around the loading range 0.125-2.5 ml min-1 of 100 micro g l[-1] Hg[II] solution, a linear calibration curve with the equation peak area=0.134; loading flow=-0.017 and a correlation coefficient r=0.996 was obtained, and the detection limit was improved up to c[L]=1micro g l[-1]. The relative standard deviation of five measurements of lowest flow loading of Hg [II] was RSD=2.8%. The significant differences were observed in the breakthrough time and mercury adsorptive capacity between activated carbon and bone char [P=0.010]. This novel setup is suitable for an on-line study of elemental mercury adsorption, determination of breakthrough time and adsorption capacity, and because of its stable performance during all experiments; it can be applied to the time based studies

[ comparative study of health quality of air in Tehran and Isfahan; 2008-2009]

Air pollution is one of the most important problems in industrial cities and has affect on the lives of all people. In order to set the control programs, air pollution monitoring and determination of air quality are necessary. The aim of this study was to compare health quality of air in Tehran and Isfahan cities. This was a descriptive-analytic study. The moment concentrations of Tehran and Isfahan air pollutants was gathered through Direct reading method and referring to the Environmental protection organization, respectively. Then, Pollution Standard Index [PSI] was calculated based on the five criteria pollutants levels [O3, PM10, SO2, NO2 and CO] for Tehran and Isfahan cities through linear interpolation. Based on these levels and with regard to the National air quality standards for each pollutant air quality was categorized as good, moderate, unhealthy, very unhealthy and dangers in 2008-2009. Data were analyzed using t-test and SPSS software V.16. The results showed that in 2008-2009, with attention to Iran environmental protection organization standards, in 43 and 67 days, PSI was lower than 100 and in the other 323 and 299 days, PSI was higher than 100, respectively for Tehran and Isfahan. The critical pollutant was ozone and carbon monoxide in summer and carbon monoxide and Particulate Matter [PM10] in winter, respectively for Tehran and Isfahan. T-test between PSI mean of two cities showed a significant difference [p-value <0.0001]. The air quality of the two cities was unhealthy in 2008-2009 and was in the very "serious situation" with regard to public health, especially for sensitive groups

[ effect of hydrogen peroxide and solvent on photolysis of PCBs to reduce occupational exposure]

Polychlorinated biphenyls [PCBs] are toxic bio-accumulate components and may increase risk of adverse effects on human health and the environment. For different social, technical and economic reasons, significant quantities of PCBs contaminated transformer oil are still in use or storied. The study aimed to determine the effect of hydrogen peroxide and solvent on photolysis of PCBs to reduce occupational exposure. The photochemical annular geometry [500 ml volume] reactor was designed with a cylindrical low-pressure mercury lamp [UV-C Cathodeon TUV 6WE] with emission at 254 nm. The radiant power emitted by the lamp was 6w. The whole lamp was immersed in a reactor thermostat controlling of temperature at 32 +/- 2 oC. The PCBs was determined using GC/ECD and data was analyzed by SPSS. Degradation of total PCBs in terms of%10 and%20 of volume of H2O2 were 41%, 75% and 94%, respectively. The degradation of total PCBs in terms of ratio to solvent with oil transformer in 1:1, 2:1 and 3:1 was 61%, 75% and 94%, respectively. Our study show that UV-C photolysis of H2O2 leads to a degradation efficiency of PCBs only in the presence of isooctane, therefore indicating that the intermediates formation after ethanol oxidation are able to initiate PCBs degradation