Array processing and forward modeling methods for the analysis of stiffened, fluid-loaded cylindrical shells

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution March 1994This thesis investigates array processing and forward modeling methods for the analysis of experimental, structural acoustic data to understand wave propagation on fluid-loaded, elastic, cylindrical shells in the mid-frequency range, 2 < ka < 12. The transient, acoustic, in-plane, bistatic scattering response to wideband, plane waves at various angles of incidence was collected by a synthetic array for three shells, a finite, air-filled, empty thin shell, a duplicate shell stiffened with four unequally spaced ring-stiffeners and a duplicate ribbed shell augmented by resiliently-mounted, wave-bearing, internal structural elements. Array and signal processing techniques, including source deconvolution, array weighting, conventional focusing and the removal of the geometrically scattered contribution, are used to transform the collected data to a more easily interpreted representation. The resulting waveforms show that part of the transient, dynamic, structural response of the shell surface which is capable of radiating to the far field. Compressional membrane waves are directly observable in this representation and evidence of flexural membrane waves is present. Comparisons between the shells show energy compartmentalized by the ring stiffeners and coupled into the wave-bearing internals. Energy calculations show a decay rate of 30dB/msec due to radiation for the Empty shell but only 10dB/msec for the other shells at bow incidence. The Radon Transform is used to estimate the reflection coefficient of compressional waves at the shell endcap as 0.2. The measurement array does not provide enough resolution to allow use of this technique to determine the reflection, transmission and coupling coefficients at the ring stiffeners. Therefore, a forward modeling technique is used to further analyze the 0° incidence case. This modeling couples a Transmission Line model of the shell with a Simulated Annealing approach to multi-dimensional, parameter estimation. This procedure estimates the compressional wavespeed at 5284m/sec and a compressional decay rate of 49dB/msec. Small cross-coupling coefficients between flexural and compressional wavetypes at the slope discontinuities on the Empty shell are found to be responsible for most of the radiation later in time. High reflection coefficients at the ring stiffeners on the Ribbed shell are shown to cause energy compartmentalization in the bays between ribs and pressure doubling of incident structural waves at the ribs.Support for this thesis was provided by Office of Naval Research, Structural Mechanics and Advanced Vehicle Technology Divisions, it is most gratefully acknowledged

Array processing and forward modeling methods for the analysis of stiffened, fluid-loaded cylindrical shells

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994.Includes bibliographical references (leaves 154-157).by Joseph E. Bondaryk.Ph.D

Nitrate esters of heteroaromatic compounds as Candida albicans CYP51 enzyme inhibitors

Four heteroaromatic compounds bearing nitrate esters were selected using a virtual-screening procedure as putative sterol 14a-demethylase (CYP51) Candida albicans inhibitors. Compounds were examined for their inhibition on C. albicans growth and biofilm formation as well as for their toxicity. NMR spectroscopy studies, in silico docking, and molecular dynamics simulations were used to investigate further the selectivity of these compounds to fungal CYP51. All compounds exhibited good antimicrobial properties, indicated with low minimal inhibitory concentrations and ability to inhibit formation of fungal biofilm. Moreover, all of the compounds had the ability to inhibit growth of C. albicans cells. N-(2-Nitrooxyethyl)-1Hindole- 2-carboxamide was the only compound with selectivity on C. albicans CYP51 that did not exhibit cytotoxic effect on cells isolated from liver and should be further investigated for selective application in new leads for the treatment of candidiasis.This work was supported financially by the Serbian Ministry of Education, Science, and Technological Development (Grant number 173032). Binding studies to CaCYP51 were supported by the Slovenian Research Agency (Grants P1-0010 and J1-8145) and by a program of scientific and technological cooperation between the Republic of Serbia and the Republic of Slovenia “A combined methodology towards the development of novel, selective inhibitors of Candida CYP51”.info:eu-repo/semantics/publishedVersio

Recommendations on the use of innovative medical technologies in cardiology and cardiac surgery and solutions leading to increased availability for Polish patients

There is a great need for innovative technologies that will improve the health and quality of life (QoL) of Polish patients with cardiac problems. It is important that the safety and effectiveness of the technology are confirmed by scientific evidence on which guidelines and clinical recommendations are based. Scientific evidence for medical devices is also increasingly important for decision-making in finance approval from public funds. New technologies in cardiology and cardiac surgery contribute to improved patient QoL, increased treatment effectiveness and facilitated diagnosis. Hence, it is necessary to increase accessibility to such technologies, primarily through the development of clinical recommendations, and education of medical personnel in conjunction with public funding. The aim of this publication is to present the recommendations of leading experts in the field of cardiology and cardiosurgery, supported by clinical research results, regarding the use of the cited innovative medical technologies and solutions leading to their increased availability for Polish patients.

Digital Signal Processing

Contains an introduction and reports on fifteen research projects.National Science Foundation FellowshipU.S. Navy - Office of Naval Research (Contract N00014-81-K-0742)National Science Foundation (Grant ECS 84-07285)Sanders Associates, Inc.U.S. Air Force - Office of Scientific Research (Contract F19628-85-K-0028)AT&T Bell Laboratories Doctoral Support ProgramCanada, Bell Northern Research ScholarshipCanada, Fonds pour la Formation de Chercheurs et /'Aide a la Recherche Postgraduate FellowshipCanada, Natural Science and Engineering Research Council Postgraduate FellowshipAmoco Foundation FellowshipFannie and John Hertz Foundation Fellowshi

Innovative medical technologies in the percutaneous treatment of tricuspid regurgitation in Poland

Tricuspid regurgitation (TR) usually develops secondarily to left-sided heart diseases, whereas primary lesions to the valve apparatus is less common. Untreated severe TR has a poor prognosis and surgical treatment, i.e., valve repair or replacement, is the only treatment option with class I recommendation. However, cardiac surgical procedures may be associated with a high risk of complications. Recent advances in percutaneous approaches to managing structural heart diseases, especially mitral valve diseases, have enabled the implementation of this therapeutic strategy in the population of patients with TR. This paper presents data on the clinical efficacy, cost-effectiveness and expected population size for one of these procedures, namely the TriClip TTVr System procedure. Its efficacy was assessed in the TRILUMINATE study involving 85 patients with co-morbidities and at high surgical risk. After 1 year of follow-up, the reduction in the TR grade was reported in 71% of patients. Clinical improvement in New York Heart Association functional class, a 6-minute walk test, and the quality of life were also observed. A published analysis comparing percutaneous treatment modalities with a drug therapy based on data from medical registers was utilized, and propensity score matching was also employed. Percutaneous treatment reduced 1-year mortality and rehospitalisation risk. The economic analysis showed the use of TriClip TTVr System is cost-effective: the cost of an additional quality-adjusted life year ranged from approximately PLN 85,000 to PLN 100,000, which is below the official threshold in Poland. The potential annual number of candidates for this treatment modality in Poland is estimated at 265