Analytical approach for determination of effective point of measurement for cylindrical lonization chamber

Cylindrical ionization chamber is used for measurements of patient dose in radiation therapy. By determination the effective point of measurement we can determine the dose distribution and the parameters of treatment. Therefore in this research we introduce an analytical approach for determination this point in CC13 cylindrical ionization chamber that used for dosimetry of linear accelerator. In this study a CC13 ionization chamber was used for dose measurement of 6 and 18 photon beams of Variant accelerator in different field sizes, 5*5 cm[2] up to 35*35cm[2]. Measurements were performed in blue phantom, up to 5cm depth and data fit software was used for evaluation of experimental data. with our formalism the Pdis quantity in 6MV for 5x5 thought 35x35cm2 were measured 3.088 to 2.88 mm and in 18 MV are measured 4.62 to 4.20 mm. The first critical point of each curve is caused by changing environment from air to water during measuring of ionization. In fact it can be considered critical point as effective point of measurement of ionization chamber. Investigation shows that any increasing in field size, decrease and increasing of energy increase the depth of this critical point

[Biodegradation of aromatic compounds in crude oil by isolated microorganisms from environment]

Oil pollutions are one of the most important environmental problems worldwide that researchers have tried different methods for its degradation. In this regards biological methods attracted the attention of the researchers more than other methods. The main objective of this study was to find microorganisms that could degrade aromatic components in the floating crude oil. In order to find such microorganisms, some samples were taken from areas contaminated by petroleum compounds. Microorganisms that could live with crude oil as sole carbon source were isolated. From these samples 14 microorganisms isolated which all were bacteria. The variations of aromatic compounds concentration were measured by gas chromatography method. Among 14 microorganisms that called A-3 and A-14 had more ability and degraded the aromatic components 89% and 86% respectively. By microbiological techniques it was found that A-14 is pseudomonas aerogenusa. The results of this study showed that biodegradation of aromatic compounds that are one of the most toxic materials in crude oil are possible. Also indicated that some oil-degrading microorganisms exist in the nature that do not need to adaptation for biodegradation of oily compounds

Parental consanguinity among parents of neonates with congenital hypothyroidism in Isfahan

We determined the prevalence of congenital hypothyroidism and the rate of consanguinity among parents of hypothyroid neonates among 93 381 neonates born in 17 hospitals in Isfahan from May 2002 to April 2005. Serum thyroxine [T4] and thyroid stimulating hormone [TSH] levels were measured on the 3rd-7th day of birth and neonates with abnormal levels were recalled and the levels reassessed. Those with TSH