Analysis of Dissipated Power Caused by Lubrication in Ringless Reciprocating Systems

The purpose of this paper was to evaluate the electromotor input power loss caused by oil viscosity between piston and cylinder in reciprocating systems such as compressors, presses and pumps with crank and slider driver without oil ring or ringless pistons. Using the numerical and analytical approaches respectively for nonlinear and linear oil velocity profiles assumed between piston and cylinder, dissipated power caused by oil viscosity was calculated and results of these two approaches were compared to validate finite difference results. Finally, the effect of vertical or horizontal position of piston and cylinder were compared in the case of nonlinear oil velocity profile for different applications

Investigating the role of temperature on thermal stress and fracture propagation in geothermal systems

Available geothermal energy extractable by conventional techniques is in dry and comparatively impermeable rocks. Enhanced Geothermal System (EGS) technologies enhance geothermal resources in the hot dry rock (HDR) through fracture operations, usually through hydro-shearing. Large scale deployment of geothermal power production requires the demonstration of successful EGS projects extracting heat from reservoirs constituting a variety of geological conditions. In this part, numerical models are very important to show how geothermal power plant operations can be less risky and safer. Owing the fact that, some major challenges in these operations are interaction between shear and tensile fractures with natural faults. These interactions can be seen in two different cases, either these faults are badly oriented or these faults are fill in pore fluids or gases which are mainly high pressure. Fluids and gases are important on account for because of the fact that these pore fluids can over whelmed the injection pressure and cause well blow out. Furthermore, to prevent these operational hazards, we use field data and analysis in combination with experimental tests and numerical/analytical models with finite element method software such as COMSOL Multiphysics. Further work will be required for improving enhanced geothermal production by optimizing hydro-shearing practices

Molecular study of PKD1 & PKD2 genes by linkage analysis and determining the genotype/phenotype correlations in several Iranian families with autosomal dominant polycystic kidney disease

Background: Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder with genetic heterogeneity. Up to three loci are involved in this disease, PKD1 on chromosome 16p 13.3, PKD2 on 4q21, and a third locus of unknown location. Methods: Here we report the first molecular genetic study of ADPKD and the existence of locus heterogeneity for ADPKD in the Iranian population by performing linkage analysis on 15 affected families. Results: Eleven families showed linkage to PKD1 and two families showed linkage to PKD2. In two families, PKD1 markers are common in all affected members but PKD2 markers were not informative. Conclusion: The results of this study demonstrate significant locus heterogeneity in autosomal dominant PKD in Iran. Analysis of clinical data confirms a milder ADPKD phenotype for PKD2 families. Our results showed relatively high heterozygosity rates and PIC values for some markers, while the most informative markers were KG8 and 16AC2.5 for PKD1 gene and AFM224x6 for PKD2 gene

Prevalence of chronic kidney disease and its associated risk factors: The first report from Iran using both microalbuminuria and urine sediment

Background: The incidence of major risk factors of chronic kidney disease (CKD) in the world is on the rise, and it is expected that this incidence and prevalence, particularly in developing countries, will continue to increase. Using data on urinary sediment and microalbuminuria, we aimed to estimate the prevalence of CKD in northeast Iran. Methods: In a cross-sectional study, the prevalence of CKD in a sample of 1557 regionally representative people, aged � 18 years, was analyzed. CKD was determined based on glomerular filtration rate (GFR) and microalbuminuria. Life style data, urine and blood samples were collected. Urine samples without any proteinuria in the initial dipstick test were checked for qualitative microalbuminuria. If the latter was positive, quantitative microalbuminuria was evaluated. Results: 1557 subjects with a mean age of 56.76 ± 12.04 years were enrolled in this study. Based on the modifcation of diet in renal disease (MDRD) equation, 137 subjects (8.89%) were categorized as CKD stages III-V. Based on urine abnormalities, the prevalence of combined CKD stages I and II was 10.63%, and based on macro- and microalbuminuria it was 14.53%. The prevalence of CKD was significantly associated with sex, age, marital status, education, diabetes mellitus (DM), hypertension (HTN), ischemic heart disease (IHD), waist to hip ratio, myocardial infarction (MI), and cerebrovascular accident (CVA). Conclusion: CKD and its main risk factors are common and represent a definite health threat in this region of Iran. Using and standardizing less expensive screening tests in low resource countries could be a good alternative that may improve the outcome through early detection of CKD

Fructosamine as a complementary fasting blood sugar test for glycemic control in diabetic patients on hemodialysis

Objective: Diabetic patients with end-stage renal disease (ESRD) are more anemic and have low false hemoglobin A1c (Hb A1c) levels. In diabetic mellitus (DM) patients undergoing hemodialysis (DM-HD), fructosamine or glycated serum proteins (GSP) circulate longer than hemoglobin (Hb) in blood and can act as better indicators for monitoring blood glucose at average levels. Materials and Methods: In a total of 57 patients (30/57 DM-HD patients and 27/57 DM patients without renal failure DM-non HD), Hb A1c and fructosamine along with other serum parameters were measured. Hb A1c was measured by ion-exchange chromatography, and fructosamine was measured by spectrophotometry. Results: Fructosamine mean in DM-HD and DM-non-HD patients was 494.25 ± 233.88 μmol/L and 398.34 ± 205.05 μmol/L respectively (P=0.0169). The Hb A1c mean for the study groups was 7.88 ± 2.27% and 9.47 ± 2.51% (P=0.086). The fructosamine/Hb A1c ratio in DM-HD patients was significantly higher than that in DM-non-HD patients (P=0.002). Conclusion: Fructosamine can be potentially considered as a complementary test along with fasting blood sugar to assess control of DM patients with ESRD

Metabolic risk factors and risk of Covid-19: A systematic review and meta-analysis

Objective Based on the epidemiologic findings of Covid-19 incidence; illness and mortality seem to be associated with metabolic risk factors. This systematic review and meta-analysis aimed to assess the association of metabolic risk factors and risk of Covid-19. Methods This study was designed according to PRISMA guidelines. Two independent researchers searched for the relevant studies using PubMed, Web of Science, Cochrane Library, and Scopus. The search terms developed focusing on two main roots of "Covid-19"and "metabolic risk factors". All relevant observational, analytical studies, review articles, and a meta-analysis on the adult population were included in this meta-analysis. Meta-analysis was performed using the random effect model for pooling proportions to address heterogeneity among studies. Data were analyzed using STATA package version 11.2, (Stata- Corp, USA). Results Through a comprehensive systematic search in the targeted databases we found 1124 papers, after running the proses of refining, 13 studies were included in the present meta-analysis. The pooled prevalence of obesity in Covid-19 patients was 29 (95 CI: 14-47). For Diabetes and Hypertension, these were 22 (95 CI: 12 33) and 32 (95 CI: 12 56), respectively. There was significant heterogeneity in the estimates of the three pooled prevalence without any significant small-study effects. Such warning points, to some extent, guide physicians and clinicians to better understand the importance of controlling co-morbid risk factors in prioritizing resource allocation and interventions. Conclusion The meta-analysis showed that hypertension is more prevalent than obesity and diabetes in patients with Covid-19 disease. The prevalence of co-morbid metabolic risk factors must be adopted for better management and priority settings of public health vaccination and other required interventions. The results may help to improve services delivery in COVID-19 patients, while helping to develop better policies for prevention and response to COVID-19 and its critical outcomes. © 2020 Moazzami et al

The role of hemodialysis machines dedication in reducing Hepatitis C transmission in the dialysis setting in Iran: A multicenter prospective interventional study

BACKGROUND: Hepatitis C virus (HCV) infection is a significant problem among patients undergoing maintenance hemodialysis (HD). We conducted a prospective multi-center study to evaluate the effect of dialysis machine separation on the spread of HCV infection. METHODS: Twelve randomly selected dialysis centers in Tehran, Iran were randomly divided into two groups; those using dedicated machines (D) for HCV infected individuals and those using non-dedicated HD machines (ND). 593 HD cases including 51 HCV positive (RT-PCR) cases and 542 HCV negative patients were enrolled in this study. The prevalence of HCV infection in the D group was 10.1% (range: 4.6%– 13.2%) and it was 7.1% (range: 4.2%–16.8%) in the ND group. During the study conduction 5 new HCV positive cases and 169 new HCV negative cases were added. In the D group, PCR positive patients were dialyzed on dedicated machines. In the ND group all patients shared the same machines. RESULTS: In the first follow-up period, the incidence of HCV infection was 1.6% and 4.7% in the D and ND group respectively (p = 0.05). In the second follow-up period, the incidence of HCV infection was 1.3% in the D group and 5.7% in the ND group (p < 0.05). CONCLUSIONS: In this study the incidence of HCV in HD patients decreased by the use of dedicated HD machines for HCV infected patients. Additional studies may help to clarify the role of machine dedication in conjunction with application of universal precautions in reducing HCV transmission

Renal Function and Risk Factors of Moderate to Severe Chronic Kidney Disease in Golestan Province, Northeast of Iran

Introduction: The incidence of end-stage renal disease is increasing worldwide. Earlier studies reported high prevalence rates of obesity and hypertension, two major risk factors of chronic kidney disease (CKD), in Golestan Province, Iran. We aimed to investigate prevalence of moderate to severe CKD and its risk factors in the region. Methods: Questionnaire data and blood samples were collected from 3591 participants (≥18 years old) from the general population. Based on serum creatinine levels, glomerular filtration rate (GFR) was estimated. Results: High body mass index (BMI) was common: 35.0 of participants were overweight (BMI 25-29.9) and 24.5 were obese (BMI ≥30). Prevalence of CKD stages 3 to 5 (CKD-S3-5), i.e., GFR &lt;60 mL/min/1.73 m2, was 4.6. The odds ratio (OR) and 95 confidence interval (95 CI) for the risk of CKD-S3-5 associated with every year increase in age was 1.13 (1.11- 1.15). Men were at lower risk of CKD-S3-5 than women (OR = 0.28; 95 CI 0.18-0.45). Obesity (OR = 1.78; 95 CI 1.04-3.05) and self-reported diabetes (OR = 1.70; 95 CI 1.00-2.86), hypertension (OR = 3.16; 95 CI 2.02-4.95), ischemic heart disease (OR = 2.73; 95 CI 1.55-4.81), and myocardial infarction (OR = 2.69; 95 CI 1.14-6.32) were associated with increased risk of CKD-S3-5 in the models adjusted for age and sex. The association persisted for self-reported hypertension even after adjustments for BMI and history of diabetes (OR = 2.85; 95 CI 1.77-4.59). Conclusion: A considerable proportion of inhabitants in Golestan have CKD-S3-5. Screening of individuals with major risk factors of CKD, in order to early detection and treatment of impaired renal function, may be plausible. Further studies on optimal risk prediction of future end-stage renal disease and effectiveness of any screening program are warranted. © 2010 Najafi et al

Dental caries in primary and permanent teeth in children's worldwide, 1995 to 2019: a systematic review and meta-analysis

Background: Early childhood caries (ECC) is a type of dental caries in the teeth of infants and children that is represented as one of the most prevalent dental problems in this period. Various studies have reported different types of prevalence of dental caries in primary and permanent teeth in children worldwide. However, there has been no comprehensive study to summarize the results of these studies in general, so this study aimed to determine the prevalence of dental caries in primary and permanent teeth in children in different continents of the world during a systematic review and meta-analysis. Methods: In this review study, articles were extracted by searching in the national and international databases of SID, MagIran, IranMedex, IranDoc, Cochrane, Embase, ScienceDirect, Scopus, PubMed, and Web of Science (ISI) between 1995 and December 2019. Random effects model was used for analysis and heterogeneity of studies was evaluated by using the I2 index. Data were analyzed by using the Comprehensive Meta-Analysis (Version 2) software. Findings: In this study, a total of 164 articles (81 articles on the prevalence of dental caries in primary teeth and 83 articles on the prevalence of dental caries in permanent teeth) were entered the meta-analysis. The prevalence of dental caries in primary teeth in children in the world with a sample size of 80,405 was 46.2% (95% CI: 41.6–50.8%), and the prevalence of dental caries in permanent teeth in children in the world with a sample size of 1,454,871 was 53.8% (95% CI: 50–57.5%). Regarding the heterogeneity on the basis of meta-regression analysis, there was a significant difference in the prevalence of dental caries in primary and permanent teeth in children in different continents of the world. With increasing the sample size and the year of study, dental caries in primary teeth increased and in permanent teeth decreased. Conclusion: The results of this study showed that the prevalence of primary and permanent dental caries in children in the world was found to be high. Therefore, appropriate strategies should be implemented to improve the aforementioned situation and to troubleshoot and monitor at all levels by providing feedback to hospitals