Metal Ceramic Segmented Ring Transducer under Deep Submergence Conditions

Segmented ring transducers are widely used for low frequency, broadband, deep submergence applications. These transducers can be made out of piezoceramic wedges or slabs and metallic wedges. Higher diameter, low frequency transducers are generally made out of piezoceramic slabs and metal wedges due to ease of manufacture and low cost. In this paper, metal ceramic segmented ring transducers are modelled using ATILA, a finite element software for the design of underwater transducers. Transducer variants were modelled with different wedge and piezoceramic materials. Transducers modelled were manufactured, assembled and tested. Various stages of manufacture like piezoceramic stacking, transducer assembly, pre-stressing with fibre winding, and encapsulation are explained. Acoustic performances of the transducers manufactured were measured in an open tank and inside a pressurised vessel from 10 bar to 70 bar. Performance parameters like resonance frequency, transmitting voltage response and directivity were measured. Results indicate that the transducer has usable bandwidth of about two octaves and stable response. One of the transducers was also tested in a high pressure test facility at 600 bar to check its pressure withstanding capability

Prevalence, clinical profiles, and outcome of hypertension in renal transplant recipients

Background: Hypertension is more prevalent risk factor for cardiovascular morbidity and mortality among renal transplant recipients. Materials and Methods: It is a retrospective study conducted to assess the prevalence, clinical profiles, and outcome of hypertension in renal transplant recipients. Posttransplant hypertension was defined as systolic blood pressure (BP) ≥140 mmHg, diastolic BP ≥80 mmHg, or the need of antihypertensive medication. Donor and recipient demographical details were obtained from medical records. Patients who underwent second renal transplant or graft nephrectomy were excluded from the study. Results: Among 375 patients, 88% were male. The mean age of our study population was 35.82 ± 9.37 years. Almost 82.67% of patients had posttransplant hypertension, of which 80.97% had pretransplant hypertension. Nearly 19.03% patients developed hypertension posttransplant. Following transplantation, hypertension resolved in 12.85%. The prevalence of well controlled, poorly controlled, and resistant posttransplant hypertension was 49.68%, 50.32%, and 7.42%, respectively. Majority of them (90.97%) received calcium channel blockers. In univariate analyses, recipient sex, pretransplant hypertension, etiology of kidney disease, female donors, female donors of male recipient's subgroup, use of cyclosporine, left ventricular mass, weight gain, and presence of metabolic syndrome were statistically significant. In multiple logistic regression analyses, recipient sex, presence of metabolic syndrome, and use of cyclosporine were associated with posttransplant hypertension. Kaplan–Meier analyses showed low graft survival in posttransplant hypertensive patients when compared to normotensives. Conclusion: The prevalence of hypertension in our renal transplant recipients was 82.67%. Early identification of risk factors, treatment, and adequate BP control will improve the long-term patient, graft survival