The occurrence of surge or stall in a centrifugal compressor and the role of the tip clearance flow in the instability in the centrifugal compressor are investigated in this study. A computational method is used to study the flow field in the centrifugal compressor in order to gain a better understanding of the surge or stall mechanism. It is found that, near surge or stall conditions, the tip leakage flow at the leading edge deflects more upstream; as the deflection increases, a more severe spillage occurs which finally leads to instability of the compressor. A ring air jet injection is used to eliminate the instabilities and to extend the stable flow range of the compressor. Using an air jet injection, the stable flow range of the compressor was successfully increased with minimal decrease in the efficiency of the compressor. The effects of different injection parameters such as the mass flow, the yaw angle, the injection angle, the slot width and the slot distance on the compressor flow field are studied, and an optimum design for the air jet injection is developed. Further investigation of the compressor with the optimum injection configuration shows that, near surge or stall conditions, the tip leakage at the leading edge is still under control, manifesting a much smaller spillage than does the Dresser–Rand Datum compressor without an air injection. The dominant factor for the instability of the compressor with an injection is found to be the leading-edge separation rather than the tip leakage.
Background: Male hypogonadism is associated with type II diabetes mellitus due totesticular dysfunction. Medicinal plants have received considerable attention for themanagement of diabetes and its complications.Objective: The aim of present study was to evaluate the anti-diabetic and protectiveinfluence of Crocin on testopathy in diabetic rats.Materials and Methods: In this experimental study, type II of diabetes mellitus wasinduced by high-fat diet and low dose of streptozotocin. Male Wistar rats (8 weeks,150–200 gr, 18 rats; n= 6 per group) were divided into a control group (standarddiet), diabetic group (streptozotocin+high-fat diet), and treatment group (High-fatdiet+streptozotocin+Crocin at 20 mg/kg/day, i.p. for 60 days). After 60 days, animalswere euthanized, testis and epididymis were dissected, and weights of testes andsperm count were analyzed. Hematoxylin-eosin-stained was done for histopathologicalexamination. Blood samples were collected for the assessment of serum glucose andcholesterol.Results: High-fat diet and streptozotocin significantly increased the serum glucoseand cholesterol levels as compared to the control group (p≤ 0. 001). Moreover, therewas a significant decrease in the weight of right (p= 0.008) and left testes (p≤ 0. 001)and also the total sperm count (p= 0.023) in the diabetic group compared with thecontrol
AbstractObjectiveOxidative stress in diabetic mellitus is a consequence of oxidative stress, which plays a critical role in the pathogenesis of diabetic tissue damage. Receptors for advanced glycation end products and for oxidized low-density lipoproteins (LDL) have critical contribution in oxidative tissue damage. The present study investigated whether anti-diabetic effects of Crocin via modulation of mRNA expression of RAGE and LOX-1 receptors in diabetic rats.MethodsIn the current study, high-fat cholesterol (HFC) and streptozotocin (40 mg/kg) used to induce type II diabetes. Experimental groups as follows: (Group 1: control); (Group 2: control treatment [Crocin]); (Group 3: DM [STZ]); (Group 4: DM treatment [STZ + Crocin]); (Group 5; DM + HFC [STZ + HFC]); (Group 6; DM + HFC treatment [STZ + HFC + Crocin]). Crocin (20 mg/kg/day, i.p.) administered in treatment groups for 60 days. Serum glucose and cholesterol levels evaluated on days 5, 30 and 60 after induction of DM. Pancreatic tissue from all group removed on day 60 for histological and RT-PCR analysis.ResultsApplication of Crocin significantly decreased serum cholesterol levels on day 60 after induction of DM in diabetic + HFC rats. Moreover, Crocin significantly decreased serum glucose levels on days 30 and 60 both in diabetic and diabetic + HFC rats. Crocin partially prevented the atrophic effects of STZ on both exocrine and endocrine parts of pancreas. Additionally, Crocin significantly decreased LOX-1 and RAGE mRNA expression OF pancreas in diabetic rats.ConclusionThe current study suggested that Crocin suppressed atrophic change of the pancreas by decrease of LOX-1 and RAGE mRNA expression in diabetic rats.
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