Nonlinear Acoustics in Underwater and Biomedical Applications: Array Performance Degradation and Time Reversal Invariance

This dissertation describes a model for acoustic propagation in inhomogeneous flu- ids, and explores the focusing by arrays onto targets under various conditions. The work explores the use of arrays, in particular the time reversal array, for underwater and biomedical applications. Aspects of propagation and phasing which can lead to reduced focusing effectiveness are described. An acoustic wave equation was derived for the propagation of finite-amplitude waves in lossy time-varying inhomogeneous fluid media. The equation was solved numerically in both Cartesian and cylindrical geometries using the finite-difference time-domain (FDTD) method. It was found that time reversal arrays are sensitive to several debilitating factors. Focusing ability was determined to be adequate in the presence of temporal jitter in the time reversed signal only up to about one-sixth of a period. Thermoviscous absorption also had a debilitating effect on focal pressure for both linear and nonlinear propagation. It was also found that nonlinearity leads to degradation of focal pressure through amplification of the received signal at the array, and enhanced absorption in the shocked waveforms. This dissertation also examined the heating effects of focused ultrasound in a tissue-like medium. The application considered is therapeutic heating for hyperther- mia. The acoustic model and a thermal model for tissue were coupled to solve for transient and steady temperature profiles in tissue-like media. The Pennes bioheat equation was solved using the FDTD method to calculate the temperature fields in tissue-like media from focused acoustic sources. It was found that the temperature-dependence of the medium's background prop- erties can play an important role in the temperature predictions. Finite-amplitude effects contributed excess heat when source conditions were provided for nonlinear ef- fects to manifest themselves. The effect of medium heterogeneity was also found to be important in redistributing the acoustic and temperature fields, creating regions with hotter and colder temperatures than the mean by local scattering and lensing action. These temperature excursions from the mean were found to increase monotonically with increasing contrast in the medium's properties.Office of Naval Research (Code 321-TS

Disabilities and Activities of Daily Living Among Veterans With Old Hip Disarticulation and Transpelvic Amputation

Background: The Iran-Iraq imposed war lasted eight years and was one of the longest wars of the last century. Twenty-three years have passed since the war ended, but little has been discussed about the long-term results of war amputations in the literature. Objectives: In this long-term study, we have evaluated the activities of daily living among veterans with hip or hemipelvis amputations. Patients and Methods: A cross-sectional study was performed on Iran-Iraq war veterans with hip or hemipelvis amputations in Iran. Eighty-four (96.5%) veterans out of 87 registered veterans with hip or hemipelvis amputations participated in the study. The degree of independence for activities of daily living (ADL) was assessed by the Barthel index. The degree of independence for instrumental activities of daily living (IADL) was assessed by the Lawton-Brody scale. Results: The average follow-up time was 26.6 ± 3.7 years. The average age of veterans was 44.1±7 years old. Of 84 amputees, 57 (67.85%) had limitations in at least one domain of the ADL. The most common single item that affected the patients was ascending and descending stairs seen in 45 (78.9%) veterans, followed by eating seen in 4 (7.01%) veterans. In addition, 70 (83.33%) had limitations in at least one domain of the IADL. The most common single item that affected the veterans was shopping seen in 56 (80%), followed by responsibility for own medications seen in 13 (18.57%) veterans. Spearman correlation coefficient of the sum scores of ADL and IADL showed an intermediate to strong correlation (r = 0.58). Conclusions: Increasing dependency in ADL is accompanied by increasing dependency in IADL. In the past, the duty of health care providers was saving the life of veterans due to injuries while at present, because these injuries occurred in young and healthy individuals, the need for increased function is being highlighted

Absorbing boundary conditions for the Westervelt equation

The focus of this work is on the construction of a family of nonlinear absorbing boundary conditions for the Westervelt equation in one and two space dimensions. The principal ingredient used in the design of such conditions is pseudo-differential calculus. This approach enables to develop high order boundary conditions in a consistent way which are typically more accurate than their low order analogs. Under the hypothesis of small initial data, we establish local well-posedness for the Westervelt equation with the absorbing boundary conditions. The performed numerical experiments illustrate the efficiency of the proposed boundary conditions for different regimes of wave propagation

Thermodynamic analysis of humidification dehumidification desalination cycles

Humidification–dehumidification desalination (HDH) is a promising technology for small-scale water production applications. There are several embodiments of this technology which have been investigated by researchers around the world. However, from a previous literature [1], we have found that no study carried out a detailed thermodynamic analysis in order to improve and/ or optimize the system performance. In this paper, we analyze the thermodynamic performance of various HDH cycles by way of a theoretical cycle analysis. In addition, we propose novel high performance variations on those cycles. These high-performance cycles include multi-extraction, multi-pressure and thermal vapor compression cycles. It is predicted that the systems based on these novel cycles will have gained output ratio in excess of 5 and will outperform existing HDH systems.King Fahd University of Petroleum and MineralsCenter for Clean Water and Clean Energy at MIT and KFUP

Distributed Feed Fuel Cell Stack

A fuel cell having a distributed fuel feed in which the heat generation profile can be better controlled. Fuel channel stack and system efficiency improvements are achieved.Sponsorship: Illinois Institute of TechnologyUnited States Paten

Plasma membrane depolarization reveals endosomal escape incapacity of cell-penetrating peptides.

Cell-penetrating peptides (CPPs) are short (<30 amino acids), generally cationic, peptides that deliver diverse cargos into cells. CPPs access the cytosol either by direct translocation through the plasma membrane or via endocytosis followed by endosomal escape. Both direct translocation and endosomal escape can occur simultaneously, making it non-trivial to specifically study endosomal escape alone. Here we depolarize the plasma membrane and showed that it inhibits the direct translocation of several CPPs but does not affect their uptake into endosomes. Despite good endocytic uptake many CPPs previously considered to access the cytosol via endosomal escape, failed to access the cytosol once direct translocation was abrogated. Even CPPs designed for enhanced endosomal escape actually showed negligible endosomal escape into the cytosol. Our data reveal that cytosolic localization of CPPs occurs mainly by direct translocation across the plasma membrane. Cell depolarization represents a simple manipulation to stringently test the endosomal escape capacity of CPPs

Natural variability in seawater temperature compromises the metabolic performance of a reef-forming cold-water coral with implications for vulnerability to ongoing global change

13 pages, 5 figures, 3 tablesSeawater temperature is one of the main variables that determines cold-water coral distribution worldwide. As part of an initiative to explore new areas of deep-sea habitats along the Southeast United States (SEUS) continental margin, a series of expeditions were carried out as part of the Deep-Sea Exploration to Advance Research on Corals/Canyons/Cold seeps (DEEP SEARCH) project. During these explorations, a cold-water coral reef complex composed mainly of Lophelia pertusa was located off the coast of South Carolina at 650–850 m depth. In this geographic area the species normally has a thermal tolerance between 6 and 12 °C with the capacity to form extensive calcium carbonate structures, thus creating complex habitat for a variety of associated species. Owing to the paucity of these structures and the unusual environmental conditions of this geographic area, with regular arrival of warm surface waters from the Gulf Stream, the main aim of this study was to understand the physiological response of L. pertusa to the variation in extreme temperature events in this region. Short-term experiments simulated the rate of temperature increase from the ambient temperature (8 °C) to the environmental maximum (14 °C) (heat-wave treatment). We found that temperature had a significant effect on the metabolic functions through an increase in respiration (0.108 to 0.247 µmol O2 g−1DW h−1) and excretion rates (0.002 to 0.011 µmol NH3 g−1DW h−1) at 14 °C. Oxygen to Nitrogen ratios (O:N) also showed an effect of temperature where corals switched from lipid-dominated toward a mix of lipid-protein and protein-dominated catabolism. To further characterize the metabolic response, feeding assays (capture rate of Artemia) were performed at the same temperature range with an overall three-fold decrease in capture rates under 14 °C compared to ambient temperature, thus increasing the probability of temperature-induced metabolic stress. Our results suggest that temperature variations affect the metabolic response of cold-water corals, particularly along the SEUS continental margin. Since the incursion of warm surface water to deeper zones is predicted to increase in frequency and duration due to climate change, L. pertusa may be implicated negatively, followed by ecological consequences for the survival and functionality for the ecosystem it supportsThis work was supported by the National Oceanographic Partnership Program with funding from the Bureau of Ocean Energy Management (contract M17PC00009 to TDI Brooks International), the U.S. Geological Survey, and the NOAA Office of Ocean Exploration and Research (for ship time). Additional support comes from the NOAA Deep-Sea Coral Research and Technology Program. [...] CEG acknowledge financial support from the Fulbright-Colciencias Doctoral Scholarship Program (568-2012), and the Doctoral Dissertation Grant from Temple University. AG acknowledge financial support from a Juan de la Cierva 2015 research grant (IJCI-2015-23962) from the Spanish governmentWith the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe