Setup of a High-Speed Optical System for The Characterization of Cavitation Instabilities in Space Rocket Turbopumps

The present paper illustrates the set-up and the preliminary results of an experimental investigation of cavitation flow instabilities carried out by means of a high-speed camera on a three bladed inducer in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at Alta S.p.A. The brightness thresholding technique adopted for cavitation recognition is described and implemented in a semi-automatic algorithm. In order to test the capabilities of the algorithm, the mean frontal cavitating area has been computed under different operating conditions. The tip cavity length has also been evaluated as a function of time. Inlet pressure signal and video acquisitions have been synchronized in order to analyze possible cavitation fluid-dynamic instabilities both optically and by means of pressure fluctuation analysis. Fourier analysis showed the occurrence of a cavity length oscillation at ..

Setup of a High-Speed Optical System for the Characterization of Flow Instabilities Generated by Cavitation

The present paper illustrates the setup and the preliminary results of an experimental investigation of cavitation flow instabilities carried out by means of a high-speed camera on a three-bladed inducer in the cavitating pump rotordynamic test facility (CPRTF) at Alta S.p.A. The brightness thresholding technique adopted/or cavitation recognition is described and implemented in a semi-automatic algorithm. In order to test the capabilities of the algorithm, the mean frontal cavitating area has been computed under different operating conditions. The tip cavity length has also been evaluated as a function of time. Inlet pressure signal and video acquisitions have been synchronized in order to analyze possible cavitation fluid-dynamic instabilities both optically and by means of pressure fluctuation analysis. Fourier analysis showed the occurrence of a cavity length oscillation at a frequency of 14.7 Hz, which corresponds to the frequency of the rotating stall instability dete..

Characterization of Cavitation Instabilities in Axial Inducers by Means of High-Speed Movies

The present paper illustrates the set-up and the preliminary results of an experimental investigation of cavitation flow instabilities carried out by means of a high-speed camera on a three bladed inducer in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at Alta S.p.A. The brightness thresholding technique adopted for cavitation recognition is described. A semi-automatic binary algorithm has been used for processing high speed videos of the cavitating inducer. In order to test the capabilities of the algorithm, the mean frontal cavitating area has been computed under different operating conditions. The tip cavity length has also been evaluated as a function of time. Fourier analysis showed the occurrence of a cavity length oscillation at a frequency of 15.7 Hz, which corresponds to the frequency of the rotating stall instability previously detected on the same inducer by means of pressure oscillations analysis

Lack of association between endothelial nitric oxide synthase gene polymorphisms, microalbuminuria, and endothelial dysfunction in hypertensive men

BACKGROUND: The Glu298Asp, T786C and 4a/4b genetic polymorphisms within the endothelial nitric oxide synthase (e-NOS) gene may predispose to hypertension, ischaemic heart disease and renal damage, possibly by reducing the generation of nitric oxide (NO), a fundamental substance in renal and cardiovascular biology. That same mechanism may contribute to raise albuminuria, a correlate of endothelial dysfunction and a marker of early kidney damage and poor cardiovascular prognosis in patients with hypertension. To assess that hypothesis, we evaluated the association of albuminuria with eNOS genotypes and their interacting potential with the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism. We also tested their impact on systemic NO availability, as reflected by endothelial-mediated forearm vasodilatation. METHODS: Albuminuria (three overnight collections), blood pressure, body mass index, renal function, glucose, lipids and prevalence of the metabolic syndrome were measured in 235 genetically unrelated, never-treated, uncomplicated white men with essential hypertension. Endothelial function was assessed in a patient subgroup (n = 94) by measuring plethysmographic forearm blood flow vasodilatation in response to intra-arterial acetylcholine with sodium nitroprusside as a control. Polymerase chain reaction or a 5' nuclease assay were used to characterize the eNOS and ACE I/D variants. RESULTS: Albuminuria or microalbuminuria (albuminuria > or = 15 microg/min) showed no association with eNOS polymorphisms either per se or after accounting for the co-existing ACE I/D genetic configuration. Forearm responses to acetylcholine did not differ by eNOS polymorphisms. Cardiovascular, renal, metabolic parameters were homogeneously distributed across different genetic backgrounds. CONCLUSION: eNOS polymorphisms apparently play no role in promoting hypertensive renal damage, and do not influence endothelial-mediated vasodilatation in never-treated men with essential hypertensio

INTEGRIN BETA 3 PLA1/PLA2 POLIMORPHISM DOES NOT CONTRIBUTE TO COMPLICATIONS IN BOTH TYPE 1 AND TYPE 2 DIABETES

BACKGROUND: The glycoprotein IIIa (beta3 integrin) is an integral part of two glicoprotein receptors of platelets and, respectively, endothelium and vascular smooth muscle cells. The gene encoding the GPIIIa, a receptor for fibrinogen, vWF and fibronectin, shows polymorphism (PlA1/PlA2); the PlA2 allele has been associated with myocardial infarction, stroke and cardiovascular disease. METHODS: Seven hundred and thirty-two subjects with type 1 diabetes and 605 subjects with type 2 were recruited. The prevalence of complications in type 1 diabetes was: microalbuminuria (uA) 17%, overt nephropathy (MA) 10%; background retinopathy (bR) 27%, proliferative retinopathy (pR) 22%; hypertension (HYP) 13%; coronary heart disease (CHD) 9%. The respective figures for type 2 diabetes were: uA 34%, MA 21%; bR 38%, pR 18%; HYP 80%; CHD 26%. A 247 bp fragment (exon 2) was amplified by PCR. For the detection of the point mutation CDGE (Constant Denaturing Gel Electrophoresis) after optimum denaturing conditions setting by DGGE (Denaturing Gradient GE) and/or RFLP by NciI digestion were employed. RESULTS: In type 1 diabetes, PlA1PlA1/PlA1PlA2 distribution was 77/23%. No differences were found among normoalbuminuric (nA: 76/24%), microalbuminuric (uA: 79/21%) and macroalbuminuric subjects (MA: 75/25%, p=0.79) as well as among subjects with no retinopathy (Ret-) (74/26%), bR (76/24%) and pR (78/22%, p=0.81), and between HYP- (78/22%) and HYP+ (72/28%, p=0.27) as well as CHD- (76/24%) and CHD+ (75/25%, p=0.72). Systolic blood pressure, HbA1c and retinopathy were independent predictors of nephropathy. No contribution of diastolic BP, sex, BMI, duration of diabetes and PlA2 allele was found for the risk of nephropathy. In type 2 diabetes, PlA1PlA1/PlA1PlA2/PlA2PlA2 distribution was 74.4/23.3/2.3%, with no differences foud among nA (73/25/2%), uA (75/23/2%) and MA (81/17/2%, p=0.66). No significant difference was detected among subjects with Ret- (74/22/4%), bR (77/22/1%) and pR (77/22/1%, p=0.62). Also, no differences were found between HYP- (81/17/2%) and HYP+ (74/24/2%, p=0.28) as well CHD- (76/22/2%) and CHD+ (74/24/2%, p=0.93). Systolic BP, HbA1c, presence of retinopathy, gender and BMI were independent predictors of nephropathy. Diastolic BP, duration of diabetes and PlA2 allele did not contribute to the risk of nephropathy. CONCLUSIONS: The PlA1/PlA2 polymorphism of the GPIIIa gene does not contribute to the development of nephropathy or retinopathy in type 1 and type 2 diabetes. Furthermore, no association was found between the PlA1/PlA2 polymorphism, hypertension, and coronary heart diseas

Cystatin C and estimates of renal function: Searching for a better measure of kidney function in diabetic patients

BACKGROUND: Early identification of impairment in renal function is crucial in diabetic patients. Serum cystatin C may be the most sensitive indicator of glomerular filtration rate (GFR) in the clinical setting. METHODS: We compared cystatin C with creatinine, the Cockcroft-Gault (C-G) formula, and the Modification of Diet in Renal Disease (MDRD) study equation for the assessment of early decreased renal function in 288 diabetic patients (125 type 1, 163 type 2) with renal impairment [GFR: 4-222 mL x min(-1) x (1.73 m(2))(-1)]. Relationships of cystatin C, creatinine, and iohexol clearance were linearized by plotting their reciprocals in a simple regression model. Diagnostic efficiency was calculated from ROC curves. RESULTS: In this study population, cystatin C (P = 0.0013) was better correlated with GFR (r = 0.857) than were creatinine (r = 0.772), C-G (r = 0.750), and MDRD (r = 0.806), a result replicated in patients with normal renal function (P = 0.023, type 1; P = 0.011, type 2), but not in those with decreased GFR. Mean cystatin C concentrations showed step-by-step statistically significant increases as GFR decreased, allowing very early detection of reduction in renal function. At 90 mL x min(-1) x (1.73 m(2))(-1) and 75 mL x min(-1) x (1.73 m(2))(-1) cut-points, diagnostic efficiencies of cystatin C (89% and 92%) were better than those of the other variables (79%-82% and 85%-86%, respectively; P = 0.01). CONCLUSIONS: All data supported the value of serum cystatin C compared with conventional estimates based on serum creatinine measurement for detecting very early reduction of renal function. Use of cystatin C to measure renal function will optimize early detection, prevention, and treatment strategies for diabetic nephropathy