Design and testing of an acoustic ultra-short baseline navigation system

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1992An ultra-short baseline acoustic navigation system has been developed which is capable of determining bearing to a sound source with an error of less than 1° in typical operational conditions. The system has a demonstrated ability to operate in an environment in which multipath interference is significant. A DSP microprocessor is used to process signals received by two hydrophones from a 26 kHz toneburst sound source. This processing power is used to implement features not commonly available with commercial systems. The system has the capability to make an on-line measurement of the signal-tonoise ratio, which can be used to estimate the confidence which should be placed in the data. Estimates of phase difference and signal power are generated many times within each received pulse, so the effects of multi path interference throughout the pulse can be observed. Results of tests at several ranges are presented, and compared to performance models developed in the thesis. System performance is quantified, and an effort is made to understand the effects of multipath arrivals

An integrated modal approach to surface and volume scattering in ocean acoustic waveguides

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution January 1996Acoustic propagation in the ocean can be strongly affected by small random variations in ocean properties, including rough surfaces and volume fluctuations in the ocean or seabed. Such inhomogeneities scatter part of the incident acoustic field, stripping energy from the coherent part of the field. This scattered energy, or reverberation, propagates further in the modes of the ocean waveguide. The distribution of energy among modes is changed and the coherence of the acoustic field is reduced. This thesis introduces several models which describe scattering of low-frequency sound. First, the rough surface scattering theory of Kuperman and Schmidt is reformulated in terms of normal modes. Scattering from rough fluid-fluid interfaces and rough elastic halfspaces is modeled, and statistics of the acoustic field are calculated. Numerical results show the modal formulation agrees well with Kuperman and Schmidt's model, while reducing computation times by several orders of magnitude for the scenarios considered. Next, a perturbation theory describing scattering from sound speed and density fluctuations in acoustic media is developed. The theory is used to find the scattered field generated by volume fluctuations in sediment bottoms. Modal attenuations due to sediment volume scattering are calculated, and agreement is demonstrated with previous work. The surface and volume scattering theories are implemented in a unified modal reverberation code and used to study bottom scattering in shallow water. Numerical examples are used to demonstrate the relationship between volume and surface scattering. Energy distribution among scattered field modes is found to be a complicated function of the scattering mechanism, the scatterer statistics, and the acoustic environment. In particular, the bottom properties strongly influence the coherence of the acoustic field. Examples show that excitation of fluid-elastic interface waves is a potentially important scattering path. Cross-modal coherences are calculated and used to study the loss of signal coherence with range. Finally, earlier work on scattering from the Arctic ice sheet is extended. Simulations of long-range transmissions are compared with data from the April 1994 trans-Arctic propagation test. The results show modal attenuations and group speeds can be predicted reasonably well, indicating that acoustic monitoring of Arctic climate is feasible.I am extremely grateful for the financial support of the Office of Naval Research, under contracts N00014-92-J -1282 and N00014-95-1-0307

Community Change for Youth Development in Kansas City

Kansas City, Missouri, is one of six sites in Community Change for Youth Development (CCYD), a national demonstration project aiming to increase basic supports and opportunities available to youth aged 12-20. The lead agency is the YMCA of Greater Kansas City; because of its considerable organizational capacity and relationship with funders, the YMCA was successful in operating and expanding CCYD. This report focuses on the benefits of working with the YMCA of Greater Kansas City and the challenges faced by the organization in leading a community-based initiative in three urban neighborhoods

Computerised lung sound analysis to improve the specificity of paediatric pneumonia diagnosis in resource-poor settings: protocol and methods for an observational study

Introduction: WHO case management algorithm for paediatric pneumonia relies solely on symptoms of shortness of breath or cough and tachypnoea for treatment and has poor diagnostic specificity, tends to increase antibiotic resistance. Alternatives, including oxygen saturation measurement, chest ultrasound and chest auscultation, exist but with potential disadvantages. Electronic auscultation has potential for improved detection of paediatric pneumonia but has yet to be standardised. The authors aim to investigate the use of electronic auscultation to improve the specificity of the current WHO algorithm in developing countries. Methods: This study is designed to test the hypothesis that pulmonary pathology can be differentiated from normal using computerised lung sound analysis (CLSA). The authors will record lung sounds from 600 children aged ≤5 years, 100 each with consolidative pneumonia, diffuse interstitial pneumonia, asthma, bronchiolitis, upper respiratory infections and normal lungs at a children\u27s hospital in Lima, Peru. The authors will compare CLSA with the WHO algorithm and other detection approaches, including physical exam findings, chest ultrasound and microbiologic testing to construct an improved algorithm for pneumonia diagnosis. Discussion: This study will develop standardised methods for electronic auscultation and chest ultrasound and compare their utility for detection of pneumonia to standard approaches. Utilising signal processing techniques, the authors aim to characterise lung sounds and through machine learning, develop a classification system to distinguish pathologic sounds. Data will allow a better understanding of the benefits and limitations of novel diagnostic techniques in paediatric pneumonia

Isolation of Angola-like Marburg virus from Egyptian rousette bats from West Africa.

Marburg virus (MARV) causes sporadic outbreaks of severe Marburg virus disease (MVD). Most MVD outbreaks originated in East Africa and field studies in East Africa, South Africa, Zambia, and Gabon identified the Egyptian rousette bat (ERB; Rousettus aegyptiacus) as a natural reservoir. However, the largest recorded MVD outbreak with the highest case-fatality ratio happened in 2005 in Angola, where direct spillover from bats was not  shown. Here, collaborative studies by the Centers for Disease Control and Prevention, Njala University, University of California, Davis USAID-PREDICT, and the University of Makeni identify MARV circulating in ERBs in Sierra Leone. PCR, antibody and virus isolation data from 1755 bats of 42 species shows active MARV infection in approximately 2.5% of ERBs. Phylogenetic analysis identifies MARVs that are similar to the Angola strain. These results provide evidence of MARV circulation in West Africa and demonstrate the value of pathogen surveillance to identify previously undetected threats

College students and use of K2: an emerging drug of abuse in young persons

<p>Abstract</p> <p>Background</p> <p>K2 or "spice" has emerged as a popular legal alternative to marijuana among adolescents and young adults. However, no data has been published assessing prevalence of and associations with ever K2 use in any population. This study's aims were to examine prevalence of ever K2 use among a sample of college students, to determine characteristics of persons who use K2, and to access the association between K2 and other drug use.</p> <p>Findings</p> <p>Ever use of K2 was reported by 69 (8%) of the sample of 852 college students. Response rate was 36%. Bivariate and multivariate analyses assessed whether sociodemographic characteristics and other drug use were associated with ever use of K2. Ever use of K2 was reported by 69 (8%) of the sample. Among these 69 individuals, 61 (88%) had used a cigarette and 25 (36%) had used a hookah to smoke K2. In multivariate analyses, K2 use was more common in males (vs. females, adjusted Odds Ratio (aOR) = 2.0, 95% Confidence Interval (CI) = 1.2-3.5, <it>p </it>= 0.01) and 1^stor 2^ndyear college students (vs. 3^rdyear or above, aOR = 2.4, 95% CI = 1.2-5.0, <it>p </it>= 0.02).</p> <p>Conclusions</p> <p>Ever use of K2 in this sample was higher than ever use of many other drugs of abuse that are commonly monitored in adolescents and young adults. Although DEA had banned five synthetic cannabinoids recently, clinicians and public health officials concerned with substance abuse in youth should be aware of and monitor the use of this drug in college students over time.</p

Dynamics of Cough Frequency in Adults Undergoing Treatment for Pulmonary Tuberculosis.

Background: Cough is the major determinant of tuberculosis transmission. Despite this, there is a paucity of information regarding characteristics of cough frequency throughout the day and in response to tuberculosis therapy. Here we evaluate the circadian cycle of cough, cough frequency risk factors, and the impact of appropriate treatment on cough and bacillary load. Methods: We prospectively evaluated human immunodeficiency virus-negative adults (n = 64) with a new diagnosis of culture-proven, drug-susceptible pulmonary tuberculosis immediately prior to treatment and repeatedly until treatment day 62. At each time point, participant cough was recorded (n = 670) and analyzed using the Cayetano Cough Monitor. Consecutive coughs at least 2 seconds apart were counted as separate cough episodes. Sputum samples (n = 426) were tested with microscopic-observation drug susceptibility broth culture, and in culture-positive samples (n = 252), the time to culture positivity was used to estimate bacillary load. Results: The highest cough frequency occurred from 1 pm to 2 pm, and the lowest from 1 am to 2 am (2.4 vs 1.1 cough episodes/hour, respectively). Cough frequency was higher among participants who had higher sputum bacillary load (P < .01). Pretreatment median cough episodes/hour was 2.3 (interquartile range [IQR], 1.2-4.1), which at 14 treatment days decreased to 0.48 (IQR, 0.0-1.4) and at the end of the study decreased to 0.18 (IQR, 0.0-0.59) (both reductions P < .001). By 14 treatment days, the probability of culture conversion was 29% (95% confidence interval, 19%-41%). Conclusions: Coughs were most frequent during daytime. Two weeks of appropriate treatment significantly reduced cough frequency and resulted in one-third of participants achieving culture conversion. Thus, treatment by 2 weeks considerably diminishes, but does not eliminate, the potential for airborne tuberculosis transmission

Haptoglobin Phenotype, Preeclampsia Risk and the Efficacy of Vitamin C and E Supplementation to Prevent Preeclampsia in a Racially Diverse Population

Haptoglobin's (Hp) antioxidant and pro-angiogenic properties differ between the 1-1, 2-1, and 2-2 phenotypes. Hp phenotype affects cardiovascular disease risk and treatment response to antioxidant vitamins in some non-pregnant populations. We previously demonstrated that preeclampsia risk was doubled in white Hp 2-1 women, compared to Hp 1-1 women. Our objectives were to determine whether we could reproduce this finding in a larger cohort, and to determine whether Hp phenotype influences lack of efficacy of antioxidant vitamins in preventing preeclampsia and serious complications of pregnancy-associated hypertension (PAH). This is a secondary analysis of a randomized controlled trial in which 10,154 low-risk women received daily vitamin C and E, or placebo, from 9-16 weeks gestation until delivery. Hp phenotype was determined in the study prediction cohort (n = 2,393) and a case-control cohort (703 cases, 1,406 controls). The primary outcome was severe PAH, or mild or severe PAH with elevated liver enzymes, elevated serum creatinine, thrombocytopenia, eclampsia, fetal growth restriction, medically indicated preterm birth or perinatal death. Preeclampsia was a secondary outcome. Odds ratios were estimated by logistic regression. Sampling weights were used to reduce bias from an overrepresentation of women with preeclampsia or the primary outcome. There was no relationship between Hp phenotype and the primary outcome or preeclampsia in Hispanic, white/other or black women. Vitamin supplementation did not reduce the risk of the primary outcome or preeclampsia in women of any phenotype. Supplementation increased preeclampsia risk (odds ratio 3.30; 95% confidence interval 1.61-6.82, p<0.01) in Hispanic Hp 2-2 women. Hp phenotype does not influence preeclampsia risk, or identify a subset of women who may benefit from vitamin C and E supplementation to prevent preeclampsia

The Complement Anaphylatoxin C5a Induces Apoptosis in Adrenomedullary Cells during Experimental Sepsis

Sepsis remains a poorly understood, enigmatic disease. One of the cascades crucially involved in its pathogenesis is the complement system. Especially the anaphylatoxin C5a has been shown to have numerous harmful effects during sepsis. We have investigated the impact of high levels of C5a on the adrenal medulla following cecal ligation and puncture (CLP)-induced sepsis in rats as well as the role of C5a on catecholamine production from pheochromocytoma-derived PC12 cells. There was significant apoptosis of adrenal medulla cells in rats 24 hrs after CLP, as assessed by the TUNEL technique. These effects could be reversed by dual-blockade of the C5a receptors, C5aR and C5L2. When rats were subjected to CLP, levels of C5a and norepinephrine were found to be antipodal as a function of time. PC12 cell production of norepinephrine and dopamine was significantly blunted following exposure to recombinant rat C5a in a time-dependent and dose-dependent manner. This impaired production could be related to C5a-induced initiation of apoptosis as defined by binding of Annexin V and Propidium Iodine to PC12 cells. Collectively, we describe a C5a-dependent induction of apoptotic events in cells of adrenal medulla in vivo and pheochromocytoma PC12 cells in vitro. These data suggest that experimental sepsis induces apoptosis of adrenomedullary cells, which are responsible for the bulk of endogenous catecholamines. Septic shock may be linked to these events. Since blockade of both C5a receptors virtually abolished adrenomedullary apoptosis in vivo, C5aR and C5L2 become promising targets with implications on future complement-blocking strategies in the clinical setting of sepsis

Vagal Stimulation Modulates Inflammation through a Ghrelin Mediated Mechanism in Traumatic Brain Injury

Traumatic brain injury (TBI) releases a cascade of inflammatory cytokines. Vagal nerve stimulation (VNS) and ghrelin have known anti-inflammatory effects; furthermore, ghrelin release is stimulated by acetylcholine. We hypothesized VNS decreases post-TBI inflammation through a ghrelin-mediated mechanism. TBI was created in five groups of mice: sham, TBI, TBI/ghrelin, TBI/VNS, and TBI/VNS/ghrelin receptor antagonist (GRa). Serum and tissue ghrelin, and serum TNF-α were measured. Ghrelin increased following VNS 2 h post-TBI compared to sham or TBI. At 6 h, TBI and TBI/VNS/GRa had increased TNF-α compared to sham while TBI/VNS and TBI/ghrelin had TNF-α level comparable to sham. The highest ghrelin was measured in stomach where TBI decreased ghrelin in contrast to an increase by VNS. In conclusion, VNS increased serum ghrelin and decreased TNF-α following TBI. This was abrogated with GRa. Our data suggests that ghrelin plays an important role in the anti-inflammatory effects of VNS following TBI