History, epidemiology and regional diversities of urolithiasis

Archeological findings give profound evidence that humans have suffered from kidney and bladder stones for centuries. Bladder stones were more prevalent during older ages, but kidney stones became more prevalent during the past 100 years, at least in the more developed countries. Also, treatment options and conservative measures, as well as ‘surgical’ interventions have also been known for a long time. Our current preventive measures are definitively comparable to those of our predecessors. Stone removal, first lithotomy for bladder stones, followed by transurethral methods, was definitively painful and had severe side effects. Then, as now, the incidence of urolithiasis in a given population was dependent on the geographic area, racial distribution, socio-economic status and dietary habits. Changes in the latter factors during the past decades have affected the incidence and also the site and chemical composition of calculi, with calcium oxalate stones being now the most prevalent. Major differences in frequency of other constituents, particularly uric acid and struvite, reflect eating habits and infection risk factors specific to certain populations. Extensive epidemiological observations have emphasized the importance of nutritional factors in the pathogenesis of urolithiasis, and specific dietary advice is, nowadays, often the most appropriate for prevention and treatment of urolithiasis

Microwave BARITT diode with retarding field-An investigation

Studies have been made on a new n+ipvn+ reach through structure operated as a BARITT diode. Unlike earlier BARITT structures, the present one has an additional region (the i-layer) added to it so as to provide a longer retarding field region. By taking advantage of the carrier diffusion at low velocities against an opposing field in this region, the injected current may be delayed relative to the a.c. voltage and improved efficiency BARITT diodes can be expected. In this paper, a one dimensional model is used to illustrate the basic operating mode and advantages of the structure. A d.c. analysis is performed and expressions for the reach through voltage and, critical voltage at which the space charge effects of the injected carriers become apparent are obtained. Furthermore an a.c. analysis is made and a relation for the transit time delay in the retarding field region is developed. © 1977.link_to_subscribed_fulltex

Multilayered ion-implanted BARITT diodes with improved efficiency

Based on the model suggested in an accompanying paper[1], diodes having the multilayered n+ipvn+ structure have been fabricated from silicon material using ion implantation techniques. Systematic descriptions of their fabrication and evaluation are presented. Microwave CW oscillations at C-band (∼7.5 Ghz) have been observed in some of our devices. The measured maximum power output was in the range of 40 mw and the efficiency was ∼5%. The obtained efficiency is the best reported for any BARITT diode. This result indicatest hat the retarding field region in BARITT diodes may be used advantageously to provide a favorable phase delay between the injected current and the a.c. voltage and leads to improved efficiency BARITT oscillators. © 1977.link_to_subscribed_fulltex