Wet deposition of hydrocarbons in the city of Tehran-Iran

Air pollution in the city of Tehran has been a major problem for the past three decades. The direct effects of hydrocarbon contaminants in the air are particularly important such as their carcinogenic, mutagenic, and teratogenic effects which can be transported to other environments via dry and wet deposition. In the present study, rainwater samples were collected and analyzed for 16 polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethyl benzene, and xylene (BTEX) as well as fuel fingerprints in two ranges of gasoline (C5–C11) and diesel fuel (C12–C20) using a gas chromatograph equipped with a flame ionization detector (GC/FID). Mean concentrations of ∑16 PAHs varied between 372 and 527 µg/L and for BTEX was between 87 and 188 µg/L with maximum of 36 µg/L for toluene. Both gasoline range hydrocarbons (GRH) and diesel range hydrocarbons (DRH) were also present in the collected rainwater at concentrations of 190 and 950 µg/L, respectively. Hydrocarbon transports from air to soil were determined in this wet deposition. Average hydrocarbon transportation for ∑PAHs, BTEX, GRH, and DRH was 2,747, 627, 1,152, and 5,733 µg/m2, respectively

Detection of plasmid-mediated qnr genes among the quinolone-resistant Escherichia coli isolates in Iran

Introduction: Plasmid-mediated quinolone resistance, which complicates treatment, has been increasingly identified in Escherichia coli isolates worldwide. The purpose of this study was to identify the plasmid-mediated qnrA and qnrB genes among the quinolone-resistant Escherichia coli isolated from urinary tract infections in Iran. Methodology: A total of 140 Escherichia coli isolates were collected between March and October 2012 from urinary tract infections in Khorram Abad, Iran. All isolates were tested for quinoloe resistance using the disk diffusion method. Also, all quinolone-resistant isolates were screened for the presence of the qnrA and qnrB genes by polymerase chain reaction. Minimum inhibitory concentrations (MICs) of ciprofloxacin for the qnr-positive isolates were determined. Results: One hundred sixteen (82.8) of 140 Escherichia coli isolates were nalidixic acid-resistant; among them, 14 (12.1) and 9 (7.8) were qnrA and qnrB-positive, respectively. Two quinolone-resistant isolates harbored both qnrA and qnrB. Among 63 ciprofloxacin-resistant isolates, 14 (22.2) and 9 (14.3) were found to carry qnrA and qnrB genes, respectively. The ciprofloxacin MIC range was 0.25-512 μg/mL for 23 qnr-positive Escherichia coli isolates, 18 of which had MICs values of 4-512 μg/mL. Conclusion: Our study shows that the frequency of plasmid-mediated quinolone resistance genes among E. coli isolates in Iran is high. © 2014 Firoozeh et al

Detection of qnrA gene among quinolone-resistant Escherichia coli isolated from urinary tract infections in Khorram Abad during 2011-2012

Background: Quinolone-resistance in Escherichia coli is ordinarily associated with mutations in the gyrA and parC genes. Plasmid-mediated quinolone resistance (PMQR) was increasingly identified in Enterobacteriaceae family worldwide. The aim of this study was to determine the prevalence of qnrA gene among quinolone-resistant E. coli isolates in Khorram Abad, Iran. Materials and Methods: In this cross-sectional study, one-hundred forty E. coli isolates were collected from urine samples of the patients. Isolates were screened for ciprofloxacin and nalidixic acid resistance using disk diffusion method according to clinical and laboratory standards institute (CLSI) guidelines. Moreover, PCR was used to evaluate the presence of qnrA gene in quinolone-resistant isolates. Results: One-hundred sixteen (82.8) and 63 (43) out of 140 E. coli isolates showed resistance to nalidixic acid and ciprofloxacin, respectively. The results showed that 14 (12.1) nalidixic acid- resistant and 9 (14.3) ciprofloxacin-resistant isolates were positive for qnrA gene. Conclusion: The identification of qnrA gene among quinolone-resistant E. coli isolates shows that the emergence of PMQR in this region requires serious preventive measures

Study of bulk micromachining for 〈100〉 silicon

Anisotropic etching of silicon is achieved in the presence of ultra-violet exposure in a solution containing hydrofluoric/nitric/acetic acids (HNA). The HNA solution is typically used for polishing silicon and etching polysilicon due to its isotropic etching property. In the technique proposed in this paper which is called UV-HNA, the etching of silicon is enhanced in the direction determined by UV exposure. A mixture of HF/HNO3/CH3COOH with a relative composition of 1:15:5 seems suitable for revealing 〈111〉 planes with an etch rate of 10 μm/h at 35 °C. The bottom of the etched craters is hillock-free and etch rates as high as 60 μm/h can be achieved using higher concentration of HF acid in HNA solution. In the latter case the etching is more isotropic and mask undercut is observed. Also membranes with a depth of 400 μm are fabricated on n-type Si 〈100〉 with a thickness of 500 μm by means of standard 34 wt% solution of KOH at temperature of 60 °C. Problems encountered during the experiment, and their solutions are discussed and results of these experiments are reported