Bottom interaction of low-frequency acoustic signals at small grazing angles in the deep ocean

Also published as: Journal of the Acoustical Society of America 69 (1981): 84-94The results of a deep-ocean bottom interaction experiment are presented in which the effects of both bottom refraction and subbottom reflection were observed. Data were obtained in the Hatteras Abyssal Plain using a deep towed 220-Hz pulsed cw source and two receivers anchored near the bottom. For ranges between 1 and 6 km, corresponding to bottom grazing angles less than 13°, the quadrature components of the received signals were recorded digitally. The observed amplitude shows a strong spatial interference pattern which is composed of the direct and bottom interacting arrivals. It is shown that for small source-receiver separations, the bottom return is dominated by a strong subbollom reflection. With increasing separation, this arrival evolves into a refracted arrival due to the presence of a positive sound-speed gradient in the sediment overlying the subbottom. Because of the gradient, a caustic is formed, and corresponding high intensity regions are observed in the data at the expected ranges. Values of sediment layer thickness, sound-speed gradient, and sound-speed drop at the water-bollom interface are obtained from best fits to the data using ray theory, normal mode theory, and the parabolic equation method. These values are consistent with those obtained in nearby locations by other workers. The success of the parabolic equation method indicates that at small grazing angles, the bottom interaction process may be modeled as a propagation process combined with the effect of a perfect, soft subbollom reflector. A value of sediment attenuation, 0.0015 dB/mat 220Hz, is also inferred from the data and is among the lowest values reported to date in the literature.Prepared for the Office of Naval Research under Contract N00014-77-C-0196 administered through NORD

Remembering Harry Pratter (1917-2002)

At this year\u27s annual Alumni Weekend, colleagues, family, friends, and former students of the inimitable Professor Harry Pratter, who died in March 2002, gathered to share their recollections of his life and career. Pratter, who was born in the Ukraine and emigrated to the United States as a child, began teaching at the Law School in 1950, after earning his JD from the University of Chicago. He taught many different subjects, including Commercial Law, Negotiable Instruments, Conflicts of Law, Contracts, Torts, and Family Law. But more fundamentally, he taught life, according to Professor Fred Aman, longtime dean of the school. For Harry, says Aman, there was no such thing as just a legal problem. There were only human problems with which the law must deal. The following remembrances were presented by Pratter\u27s former students

Remembering Harry Pratter (1917-2002)

At this year\u27s annual Alumni Weekend, colleagues, family, friends, and former students of the inimitable Professor Harry Pratter, who died in March 2002, gathered to share their recollections of his life and career. Pratter, who was born in the Ukraine and emigrated to the United States as a child, began teaching at the Law School in 1950, after earning his JD from the University of Chicago. He taught many different subjects, including Commercial Law, Negotiable Instruments, Conflicts of Law, Contracts, Torts, and Family Law. But more fundamentally, he taught life, according to Professor Fred Aman, longtime dean of the school. For Harry, says Aman, there was no such thing as just a legal problem. There were only human problems with which the law must deal. The following remembrances were presented by Pratter\u27s former students

Diagnosis of the significance of inconsistencies in software designs: a framework and its experimental evaluation

This paper presents: (a) a framework for assessing the significance of inconsistencies which arise in object-oriented design models that describe software systems from multiple perspectives, and (b) the findings of a series of experiments conducted to evaluate it. The framework allows the definition of significance criteria and measures the significance of inconsistencies as beliefs for the satisfiability of these criteria. The experiments conducted to evaluate it indicate that criteria definable in the framework have the power to create elaborate rankings of inconsistencies in models

Mortality of fish subjected to explosive shock as applied to oil well severance on Georges Bank

A very extensive bibliography of papers on underwater explosions and their effects on marine life has been collected and summarized. When exposed to blast effects, vertebrates with swim bladders or lungs that contain gas are at least an order of magnitude more sensitive than other life. Regression analysis of several different experiments on explosive damage to fish has been combined with reports of fish concentrations and explosives used in oil well severance in order to estimate the probable extent of damage to fish populations from a limited number of severance explosions. Damage per explosion should not be significant and is probably considerably less than that caused by a one hour tow of a bottom trawl net.Prepared for the Technology Assessment and Research Program of the Minerals Management Service, Department of the Interior, under Contract 14-08-0001-18920

Patient-reported outcomes measures and patient preferences for minimally invasive glaucoma surgical devices.

BackgroundMany therapeutic options are available to glaucoma patients. One recent therapeutic option is minimally invasive glaucoma surgical (MIGS) devices. It is unclear how patients view different treatments and which patient-reported outcomes would be most relevant in patients with mild to moderate glaucoma. We developed a questionnaire for patients eligible for MIGS devices and a patient preference study to examine the value patients place on certain outcomes associated with glaucoma and its therapies.ObjectivesTo summarize the progress to date.MethodsQuestionnaire development: We drafted the questionnaire items based on input from one physician and four patient focus groups, and a review of the literature. We tested item clarity with six cognitive interviews. These items were further refined. Patient preference study: We identified important benefit and risk outcomes qualitatively using semi-structured, one-on-one interviews with patients who were eligible for MIGS devices. We then prioritized these outcomes quantitatively using best-worst scaling methods.ResultsQuestionnaire testing: Three concepts were deemed relevant for the questionnaire: functional limitations, symptoms, and psychosocial factors. We will evaluate the reliability and validity of the 52-item draft questionnaire in an upcoming field test. Patient preference study: We identified 13 outcomes that participants perceived as important. Outcomes with the largest relative importance weights were "adequate IOP control" and "drive a car during the day."ConclusionsPatients have the potential to steer clinical research towards outcomes that are important to them. Incorporating patients' perspectives into the MIGS device development and evaluation process may expedite innovation and availability of these devices

Can an Off-Nominal Landing by an MMRTG-Powered Spacecraft Induce a Special Region on Mars When No Ice Is Present?

This work aims at addressing whether a catastrophic failure of an entry, descent, and landing event of a Multimission Radioisotope Thermoelectric Generator-based lander could embed the heat sources into the martian subsurface and create a local environment that (1) would temporarily satisfy the conditions for a martian Special Region and (2) could establish a transport mechanism through which introduced terrestrial organisms could be mobilized to naturally occurring Special Regions elsewhere on Mars. Two models were run, a primary model by researchers at the Lawrence Berkeley National Laboratory and a secondary model by researchers at the Jet Propulsion Laboratory, both of which were based on selected starting conditions for various surface composition cases that establish the worst-case scenario, including geological data collected by the Mars Science Laboratory at Gale Crater. The summary outputs of both modeling efforts showed similar results: that the introduction of the modeled heat source could temporarily create the conditions established for a Special Region, but that there would be no transport mechanism by which an introduced terrestrial microbe, even if it was active during the temporarily induced Special Region conditions, could be transported to a naturally occurring Special Region of Mars

Performance guidelines for the swine operation

1 online resource (PDF, 6 pages)This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu