3-D Airgun Source Characterization and Propagation Modeling

In the summer of 2003 the Littoral Acoustic Demonstration Center (LADC) conducted a calibration experiment for a 3190‐in3 21 element seismic exploration array. Shots were recorded and calibrated to produce absolute broadband (up to 25 kHz) pressure‐time dependencies for a wide range of offsets and arrival angles. Experimental data are analysed to obtain maximum received pressure levels (200 dB re 1 μPa) and maximum sound exposure levels (177 dB re 1 μPa2 sec) for each shot. The analysis is important for investigating the potential impact on marine mammals and fish. Experimental data are modelled by using the underwater acoustic propagation model (RAM) and seismic airgun modeling packages (Gundalf and Nucleus) for a variety of offsets and arrival angles. Experimental and simulated data have demonstrated good agreement in absolute pressure amplitudes and frequency interference patterns for frequencies up to 800 Hz

Proteomic and ultrastructural analyses of human lipofuscin [Abstract]

Purpose: The progressive accumulation of lipofuscin in the retinal pigment epithelium (RPE), correlates with the pathogenesis of age–related macular degeneration (AMD). We seek a better molecular understanding of the sources and consequences of lipofuscin accumulation, including the protein content of lipofuscin. Methods: Human RPE lipofuscin was purified by conventional sucrose density gradient centrifugation methods. Lipofuscin granule purity was evaluated by light, fluorescence, confocal, and electron microscopy. Lipofuscin preparations were extracted with chloroform/methanol then the chloroform insoluble material was extracted with SDS and subjected to SDS–PAGE, gel bands excised and proteins identified by LC MS/MS. Western analysis was used to probe for oxidative protein modifications. Results: Ultrastructural analyses of lipofuscin purified by conventional methods revealed a heterogeneous core structure composed of lipofuscin granules surrounded by substantial extra–granular material. The chloroform insoluble lipofuscin fraction of the conventional preparation exhibited many fuzzy Coomassie blue stained SDS–PAGE bands, suggesting post–translational modifications. Western blot analysis confirmed the presence of abundant carboxyethylpyrrole adducts. Over 160 proteins were identified, ~33% of which exhibited apparent mass additions. Essentially "pure" lipofuscin granules, free of extra–granular material, were obtained by proteolytic digestion of the conventional preparation. Boiling the purified granules in SDS has so far failed to yield SDS–PAGE detectable bands with Coomassie or silver staining. Conclusions: Lipofuscin granules appear to be embedded in a protein "matrix" similar in content to drusen. Proteomic characterization of purified lipofuscin granules is underway

Environmental Acoustic Recording System (EARS) In the Gulf of Mexico

The Littoral Acoustic Demonstration Center (LADC) was formed in early 2001 to utilize Environmental Acoustic Recording System (EARS) buoys developed by the Naval Oceanographic Office (NAVOCEANO) which has provided technical guidance and support to LADC. The purpose of LADC is to make environmental measurements, which is not part of the mission of NAVOCEANO. This chapter describes the Gulf of Mexico marine mammal measurements and related data analysis of LADC. LADC has also used the buoys to characterize the three-dimensional acoustic field of a seismic airgun array and to analyze the noise due to nearby storms. LADC is a consortium of scientists from universities and the U.S. Navy. The following institutions are or have been represented: initially, the University of New Orleans, the University of Southern Mississippi, and the Naval Research Laboratory-Stennis Space Center; and then the University of Louisiana at Lafayette, the Applied Research Laboratories at the University of Texas at Austin, and Oregon State University. The scientists are listed in the first section of the chapter. A technical overview of EARS technology is given in Sect. 6.2. The current Generation 2 EARS buoys can record four channels of up to 25 kHz each or one channel up to 96 kHz. LADC has conducted marine mammal experiments in the Gulf of Mexico in 2001, 2002, 2007, and 2010. The 2007 experiments were at sites 9 and 23 miles from the Macondo Well Oil Spill. These sites as well as the 2001 and 2002 sites were recorded in the 2010 experiment to measure changes related to earlier measurements. LADC has also done seismic airgun array experiments in 2003 and 2007. The marine mammal experiments are summarized in Sect. 3, where experiments in the Mediterranean Sea, which had LADC participation, are also listed. The remaining Sects. 6.4 through 6.11 describe the analysis to date of LADC data and also the analysis by LADC scientists of workshop data for detection, classification, and localization purposes. Section 6.4 describes sperm whale click structure analysis for click-train demarcation and identification of individual whales. The tendency of whales diving together to establish different cadences for their echolocation clicks to keep from interfering with each other is presented in Sect. 6.5. The identification of individual whales by clustering echolocation clicks of sperm and beaked whales and coda clicks of sperm whales is discussed in Sect. 6.6. The application of click change detection to know if the same or a different whale are speaking on successive clicks is described in Sect. 6.7. This method allows one to follow a turning sperm whale. A technique for localizing individual clicking whales is presented in Sect. 6.8. The integration of the above techniques is discussed in Sect. 6.9, which also suggests how whales might identify each other. Sperm whale coda classification and repertoire analysis are the subject of Sect. 6.10. Finally, statistical modeling for population estimation is given in Sect. 6.11

EARS Buoy Applications By LADC: I. Marine Animal Acoustics

Littoral Acoustic Demonstration Center (LADC) scientists have investigated sperm and beaked whale clicks as recorded on Environmental Acoustic Recording System (EARS) buoys to analyze whale behavior and the possibility of identifying individual whales acoustically. The research began in 2001 and continues through the present. LADC has conducted three experiments in the northern Gulf of Mexico and participated with the Naval Undersea Research Centre with three experiments in the Ligurian Sea. Initially the research centered on sperm whale coda clicks and echolocation clicks. In 2007 it was extended to the study of beaked whale echolocation clicks. The measured data suggest that click properties can be used to identify individual whales. Initially the identifications were done by grouping clicks using self-organizing maps and other means of cluster analysis. Each cluster or class represents an individual whale. These methods have been refined and have become reasonably robust. Verification of the identification has been a problem since using visual observations has not been satisfactory. Presently localization of the clicking animals is being coupled with cluster analysis to verify the identifications. A new finding that rhythms of echolocation clicks can be used to identify sperm whale individuals is now a part of the research, and cluster analysis, rhythm analysis, and localization are mutually reinforcing the identifications. Other results using EARS buoys for marine animal acoustics are listed among the key findings of LADC acoustic research

Light-Evoked Responses of the Retinal Pigment Epithelium: Changes Accompanying Photoreceptor Loss in the Mouse

Mutations in genes expressed in the retinal pigment epithelium (RPE) underlie a number of human inherited retinal disorders that manifest with photoreceptor degeneration. Because light-evoked responses of the RPE are generated secondary to rod photoreceptor activity, RPE response reductions observed in human patients or animal models may simply reflect decreased photoreceptor input. The purpose of this study was to define how the electrophysiological characteristics of the RPE change when the complement of rod photoreceptors is decreased. To measure RPE function, we used an electroretinogram (dc-ERG)-based technique. We studied a slowly progressive mouse model of photoreceptor degeneration (PrphRd2/+), which was crossed onto a Nyxnob background to eliminate the b-wave and most other postreceptoral ERG components. On this background, PrphRd2/+ mice display characteristic reductions in a-wave amplitude, which parallel those in slow PIII amplitude and the loss of rod photoreceptors. At 2 and 4 mo of age, the amplitude of each dc-ERG component (c-wave, fast oscillation, light peak, and off response) was larger in PrphRd2/+ mice than predicted by rod photoreceptor activity (RmP3) or anatomical analysis. At 4 mo of age, the RPE in PrphRd2/+ mice showed several structural abnormalities including vacuoles and swollen, hypertrophic cells. These data demonstrate that insights into RPE function can be gained despite a loss of photoreceptors and structural changes in RPE cells and, moreover, that RPE function can be evaluated in a broader range of mouse models of human retinal disease