The origin of fine scale acoustic stratigraphy in deep-sea carbonates

In this paper we investigate the origin and geologic significance of the closely spaced high-frequency subbottom acoustic reflectors characteristic of pelagic carbonates. A detailed survey was conducted of a small area in the equatorial Pacific with the Marine Physical Laboratory\u27s Deep-Tow instrument package, providing high-resolution 4-kHz profiles and precise positioning of core samples. The cores were sampled at closely spaced intervals for sound velocity and saturated bulk density. Acoustic impedances were calculated, and a reflection coefficient log determined for the upper 10 m of the sediment column. The reflection coefficient log revealed no interfaces with large reflection coefficients that correlated with the reflectors seen on the Deep-Tow 4-kHz seismic profile. The calculated reflection coefficients were very low (typically 10−3–10−5) and varied about a wavelength that was on the order of the wavelength of the 4-kHz pulse, implying that interference plays a role in the composition of the seismic record. Convolving the outgoing 4-kHz pulse with the reflection coefficient log generated a synthetic seismogram that very closely resembled the 4-kHz reflection profile. Varying the frequency of the outgoing pulse changed the amplitude and position of the reflectors seen on the synthetic seismograms. Thus we conclude that the reflectors seen on the 4-kHz seismic profile were not caused by discrete geologic horizons but rather are the result of the interference of many small layers

U.S. Law of the Sea Cruise to Map the Foot of the Slope and 2500-m Isobath of the U.S. Arctic Ocean Margin, Barrow to Barrow. Cruise Report

U.S. Law of the Sea cruise to map the foot of the slope and 2500-m isobath of the US Arctic Ocean margin CRUISES HE-0302 August 30 to September 11, 2003 Barrow, AK to Barrow, A

U.S. Law of the Sea Cruise to Map the Foot of the Slope and 2500-m Isobath of the U.S. Arctic Ocean Margin. Cruise Report for 2004

U.S. Law of the Sea cruise to map the foot of the slope and 2500-m isobath of the US Arctic Ocean margin CRUISES HE-0405 October 6 to October 26, 2004 Nome, AK to Barrow, A

Assessing Bottom Gear Impact in the WGOM Closure Area: A Multifaceted Approach

Mashkoor Malik presented the results of a UNH Center for Coastal and Ocean Mapping (CCOM) study of the seafloor of the WGOMCA. Objectives The objectives for the CCOM study were to: • Construct a bathymetric map of Jeffrey’s Ledge to serve as a framework for subsequent studies. • Test the potential use of multibeam sonar to monitor fishing gear impacts. • Determine if it is possible to observe closure impacts with multibeam sonar

Understanding safety-critical interactions with a home medical device through Distributed Cognition

As healthcare shifts from the hospital to the home, it is becoming increasingly important to understand how patients interact with home medical devices, to inform the safe and patient-friendly design of these devices. Distributed Cognition (DCog) has been a useful theoretical framework for understanding situated interactions in the healthcare domain. However, it has not previously been applied to study interactions with home medical devices. In this study, DCog was applied to understand renal patients’ interactions with Home Hemodialysis Technology (HHT), as an example of a home medical device. Data was gathered through ethnographic observations and interviews with 19 renal patients and interviews with seven professionals. Data was analyzed through the principles summarized in the Distributed Cognition for Teamwork methodology. In this paper we focus on the analysis of system activities, information flows, social structures, physical layouts, and artefacts. By explicitly considering different ways in which cognitive processes are distributed, the DCog approach helped to understand patients’ interaction strategies, and pointed to design opportunities that could improve patients’ experiences of using HHT. The findings highlight the need to design HHT taking into consideration likely scenarios of use in the home and of the broader home context. A setting such as home hemodialysis has the characteristics of a complex and safety-critical socio-technical system, and a DCog approach effectively helps to understand how safety is achieved or compromised in such a system

U.S. Law of the Sea Cruise to Map and Sample the US Arctic Ocean Margin

U.S. Law of the Sea cruise to map and sample the US Arctic Ocean margin CRUISE HEALY 1202 August 25 to September 27, 2012 Barrow, AK to Dutch Harbor, A

Investigation of bottom fishing impacts on benthic structure using multibeam sonar, sidescan and video

Bottom fishing gear is known to alter benthic structure, however changes in the shape of the sea floor are often too subtle to be detected by acoustic remote sensing. Nonetheless, long linear features were observed during a recent high-resolution multibeam sonar survey of Jeffreys Ledge, a prominent fishing ground in Gulf of Maine, located about 50 km from Portsmouth, NH. These marks, which have a relief of only few centimeters, are presumed to be caused by bottom dredging gear used in the area for scallop and clam fisheries. The extraction of these small features from a noisy data set (including several instrumental artifacts) presented a number of challenges. To enhance the detection and identification of these features, data artifacts were identified and removed selectively using frequency filtering. Verification was attempted with sidescan sonar and video surveys. While clearly visible on the sidescan sonar records, the bottom marks were not discernable in the video survey. The inability to see the bottom marks with video may be related to the age of the marks, and has important ramifications about appropriate methodologies for quantifying gear impact. Results from multibeam sonar, sidescan sonar and video surveys suggest that the best methodology to deal with inspection of bottom fishing marks is to integrate data in a 3D GIS-like environment

Bandwidth Allocation for a Revenue-Aware Network Utility Maximisation

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