23 research outputs found

    The Physics of the B Factories

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    Embryology and anatomy of the vesicoureteric junction with special reference to the etiology of vesicoureteral reflux

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    Concerning the ureterovesical junction – the region most important for the anti-reflux mechanism – there is still a lot of misunderstanding and misinterpretation with regard to normal fetal development. Data are scarce on possible causes of primary vesicoureteral reflux and on involved mechanisms of the so-called maturation process of refluxing ureteral endings. The ratio of the intravesical ureteral length to the ureteral diameter is obviously lower than assumed so far, as clearly revealed by some studies. Therefore it can be doubted that the length and course of the intravesical ureter is of sole importance in the prevention of reflux. Additionally refluxing intravesical ureteral endings present with dysplasia, atrophy, and architectural derangement of smooth muscle fibers. Besides, a pathologically increased matrix remodeling combined with deprivation of the intramural nerve supply has been confirmed. Consequently, symmetrical narrowing of the very distal ureteral smooth muscle coat creating the active valve mechanism to defend reflux is not achievable. It is apparent that primary congenital vesicoureteral reflux seems to be the result of an abnormality within the ureterovesical junction with an insufficient muscular wrap. Nature is believed to establish much more sophisticated mechanisms than the so-called passive anti-reflux mechanism. Remodeling processes within the ureterovesical junction of refluxing ureteral endings support that maturation itself is nothing else than wound or defect healing and not a restitution of a morphological normal ureterovesical junction. Lacking the nerve supply a restoration of any muscular structure can not be achieved

    Modal analysis for global control of broadband noise in a rectangular enclosure

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    Modal analysis for examination of the possibility of the global reduction of broadband noise in a rectangular enclosure has been studied in this paper. By developing a modal model of the acoustic environment of the enclosure the shape modes and their frequencies are obtained and on suitable bandwidth for the controller design is calculated. In order to simplify the analysis the noise sources are assumed localized and internal in one corner of the kiosk. The analysis results show that due to the existence of some degenerate modes in this application, the control action is complicated. Simulation results demonstrate how positions and number of loudspeakers and microphones will change the performance of the controller and its corresponding control effort. Based on these results and analysis a reasonable size for the controller and proper locations for sensors and actuators are proposed. Simulation results also confirm the effectiveness of the proposed system in reduction of the acoustic potential energy in the kiosk
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