mohammad moaf

In this experimental investigation, the heat transfer and pressure drop of helical tubes with various helical diameters have been studied considering air injections. The tube was rested in vertical form and was put under constant heat flux. The flow had a downward form and the air was injected into the water stream outside the helical tube. According to the achievements, air injection has a notable impact on the heat transfer coefficient of each helical tube. The results showed that employing air bubbles could increase the Nusselt Number by up to 14%. To make an acceptable comparison among all states, the Cost Benefit Ratio (C.B.R.) factor was evaluated. The results showed that pipes with a bigger diameter had the best C.B.R factor values. It means that the air injection in the tubes with larger diameters was more beneficial than tubes with smaller helix diameters. The best value was attained for helix diameter of 18 cm and VF of 0.33 with a C.B.R factor of 0.84. Also, the worst value was 1.18 for a helix diameter of 10 cm.

Scientists perceive drug users (DUs) as a high‑risk population for hepatitis B virus (HBV) infection. Effective strategies aiming at the reduction of HBV infection can be depicted when its epidemiological status is clearly defned. The present study provides new insight into associated risk factors of HBV infection and its seroepidemiological status among DUs attending drop‑in centers (DICs).
This was a cross‑sectional study, which was implemented in 7 DICs of Isfahan province. The sample size included 539 participants. Demographic data and risk factors for HBV infection were obtained by a trained social worker using a self‑made structured questionnaire. Venous blood sample was obtained and tested for hepatitis B surface antigen (HBsAg), hepatitis B surface antibody, and total hepatitis B core antibody (HBcAb) using enzyme‑linked immunosorbent assay.
Mean age of the participants was 31.76 ± 8.4 years. They were generally male, Iranian, urban, with an education level of high school or less. The prevalence of HBV infection (HBsAg and/or HBcAb) was 18% (88.490). Regression analysis showed that age, bloodletting, and drug injection, being the sexual partner of injecting DU (IDU), as well as frequency and duration of imprisonment positively correlated with HBV infection.
Drug injection bloodletting, and being the sexual partner of IDU, as well as frequency and duration of imprisonment could be considered as contributing factors in HBV infection.