Evaluation of environmental and occupational exposure to mercury among Iranian dentists

The purpose of the study was to evaluate the environmental and occupational exposure to mercury (Hg), and to examine the various parameters, which contribute to high levels of mercury of Iranian dentists in Tehran. One-hundred hair and nail samples were collected from dentists. In addition, fifty samples from a control group and twenty-five additional samples from dental nurses were taken for comparison. The survey included a structured questionnaire designed to provide information about the parameters that influenced their occupational and environmental exposure to Hg. Overall mean concentrations in the hair and nails of the dentists was 2.84+/-0.47 and 3.56+/-0.53 mg/kg dry wt respectively. The equivalent values were 0.61+/-0.07 mg/kg in hair and 0.39+/-0.06 mg/kg in nails for the control group. In addition, mean concentrations in the dental nurses were 0.92+/-0.23 and 1.77+/-0.51 mg/kg in hair and nails respectively. The study showed that use of masks had a significant effect on Hg levels (p=0.02 for hair and p=0.03 for nails) and use of gloves only had significant effect on nails Hg (p=0.05). Hg concentrations in nails were significantly lower among the dentists who always used gloves and masks. Also, fish consumption and number of patients visited per day had a significant effect on hair (p=0.02 and p=0.02 respectively) and nails (p=0.03 and p=0.02 respectively) Hg. On the other hand, there was a significant effect of age in relation to Hg concentration in the hair and nails of the dentists (p=0.006 for hair and p=0.01 for nails). Multiple regressions were computed between hair Hg and the various assessed variables. The only positive results were between Hg concentration and masks for the dentists (p=0.03), and Hg concentration and the number of fish meals for the control group (p=0.009).     

Optimization of the Length of Silicon Nanowires Prepared from MACE Method Using Gene Expression Programming and Genetic Algorithm

Silicon - Metal-assisted chemical etching (MACE) of silicon is used in this study to fabricate silicon nanowire arrays (SiNWs) of different length. This method was modeled using gene expression...     

Selecting the Appropriate Carbon Source in the Synthesis of SiC Nano-Powders Using an Optimized Fuzzy Model

Silicon - In this study, different sources of carbon in the synthesis of silicon carbide were evaluated using a multi-attribute group decision-making fuzzy model including IF-MAGDM method. In this...     

K‐factor estimation in shadowed Ricean mobile communication channels

In this paper, a composite model for the received signal at the mobile unit is used to derive new moment‐based estimators for the Ricean K‐factor when shadowing is present. The results are then used to analytically evaluate the performance of the previously proposed moment‐based estimators for K. It is proven that unlike existing moment‐based estimators, the proposed estimators perform well in the presence of shadowing. Using simulations, it is also shown that the mean‐squared error of the proposed estimators is significantly lower than that of the previously proposed estimators. Copyright © 2009 John Wiley & Sons, Ltd.