Comparisons among ten models of acoustic backscattering used in aquatic ecosystem research

Author Posting. © Acoustical Society of America, 2015. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 138 (2015); 3742, doi:10.1121/1.4937607.Analytical and numerical scatteringmodels with accompanying digital representations are used increasingly to predict acoustic backscatter by fish and zooplankton in research and ecosystem monitoring applications. Ten such models were applied to targets with simple geometric shapes and parameterized (e.g., size and material properties) to represent biological organisms such as zooplankton and fish, and their predictions of acoustic backscatter were compared to those from exact or approximate analytical models, i.e., benchmarks. These comparisons were made for a sphere, spherical shell, prolate spheroid, and finite cylinder, each with homogeneous composition. For each shape, four target boundary conditions were considered: rigid-fixed, pressure-release, gas-filled, and weakly scattering. Target strength (dB re 1 m2) was calculated as a function of insonifying frequency (f = 12 to 400 kHz) and angle of incidence (θ = 0° to 90°). In general, the numerical models (i.e., boundary- and finite-element) matched the benchmarks over the full range of simulation parameters. While inherent errors associated with the approximate analytical models were illustrated, so were the advantages as they are computationally efficient and in certain cases, outperformed the numerical models under conditions where the numerical models did not convergeThis work was supported by the NOAA Fisheries Advanced Sampling Technologies Working Group, the Office of Naval Research, and the National Oceanic Partnership Program. Josiah S. Renfree

The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength Identification, Optical/NIR Spectroscopic Properties, and Photometric Redshifts of X-ray Sources

We report the multi-wavelength identification of the X-ray sources found in the Subaru-XMM-Newton Deep Survey (SXDS) using deep imaging data covering the wavelength range between the far-UV to the mid-IR. We select a primary counterpart of each X-ray source by applying the likelihood ratio method to R-band, 3.6micron, near-UV, and 24micron source catalogs as well as matching catalogs of AGN candidates selected in 1.4GHz radio and i'-band variability surveys. Once candidates of Galactic stars, ultra-luminous X-ray sources in a nearby galaxy, and clusters of galaxies are removed there are 896 AGN candidates in the sample. We conduct spectroscopic observations of the primary counterparts with multi-object spectrographs in the optical and NIR; 65\% of the X-ray AGN candidates are spectroscopically-identified. For the remaining X-ray AGN candidates, we evaluate their photometric redshift with photometric data in 15 bands. Utilising the multi-wavelength photometric data of the large sample of X-ray selected AGNs, we evaluate the stellar masses, M*, of the host galaxies of the narrow-line AGNs. The distribution of the stellar mass is remarkably constant from z=0.1 to 4.0. The relation between M* and 2--10 keV luminosity can be explained with strong cosmological evolution of the relationship between the black hole mass and M*. We also evaluate the scatter of the UV-MIR spectral energy distribution (SED) of the X-ray AGNs as a function of X-ray luminosity and absorption to the nucleus. The scatter is compared with galaxies which have redshift and stellar mass distribution matched with the X-ray AGN. The UV-NIR SEDs of obscured X-ray AGNs are similar to those of the galaxies in the matched sample. In the NIR-MIR range, the median SEDs of X-ray AGNs are redder, but the scatter of the SEDs of the X-ray AGN broadly overlaps that of the galaxies in the matched sample.Comment: Accepted for publication in PASJ Subaru special issue. 42 pages, 22 figures. Entire contents of Tables 3, 8, 9, 10, and 11, and ASCII format tables are available from http://www.astr.tohoku.ac.jp/~akiyama/SXDS/index.htm

Mesoscale Eddies Are Oases for Higher Trophic Marine Life

Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained by the inability of traditional sampling methods to adequately sample biological processes at the spatio-temporal scales at which they occur

Remote acoustic sizing of tethered fish using broadband acoustics

Remote fish sizing is desirable in fisheries (e.g., pre-catch) and research (e.g., platforms without biological sampling capacity) applications. In those contexts, the high spatial resolution of pulse compressed broadband echoes combined with narrow beamwidth transducers makes it feasible to resolve the scattering from different parts of the fish body and hence can be used to measure the body size. A motorized apparatus was used to suspend individual fish in the acoustic beam of two laterally oriented transducers (45–90 kHz, 160–260 kHz, 12.2 m range) with precise control of rotation angle. Broadband scattering was measured from tethered Atlantic mackerel (Scomber scombrus), saithe (Pollachius virens), and pollack (Pollachius pollachius) ranging in standard length from 239 to 491 mm as a function of orientation angle to validate sizing based on the acoustic resolution of fish body parts. Under these controlled conditions, fish size was underestimated by 11–19 mm, varying with broadband pulse characteristics, orientation angle, species, and fish size. The best remote acoustic sizing results were obtained using 160–260 kHz pulses with a slow rise and fall of pulse amplitude (aka, taper)

Experimental Evidence of Threat-Sensitive Collective Avoidance Responses in a Large Wild-Caught Herring School

Aggregation is commonly thought to improve animals' security. Within aquatic ecosystems, group-living prey can learn about immediate threats using cues perceived directly from predators, or from collective behaviours, for example, by reacting to the escape behaviours of companions. Combining cues from different modalities may improve the accuracy of prey antipredatory decisions. In this study, we explored the sensory modalities that mediate collective antipredatory responses of herring (Clupea harengus) when in a large school (approximately 60 000 individuals). By conducting a simulated predator encounter experiment in a semi-controlled environment (a sea cage), we tested the hypothesis that the collective responses of herring are threat-sensitive. We investigated whether cues from potential threats obtained visually or from the perception of water displacement, used independently or in an additive way, affected the strength of the collective avoidance reactions. We modified the sensory nature of the simulated threat by exposing the herring to 4 predator models differing in shape and transparency. The collective vertical avoidance response was observed and quantified using active acoustics. The combination of sensory cues elicited the strongest avoidance reactions, suggesting that collective antipredator responses in herring are mediated by the sensory modalities involved during threat detection in an additive fashion. Thus, this study provides evidence for magnitude-graded threat responses in a large school of wild-caught herring which is consistent with the “threat-sensitive hypothesis”

Comparisons of echo-integration performance from two multiplexed echosounders

A time-series of acoustically derived aquatic biomass estimates relies on the acoustic equipment maintaining the same performance throughout the time-series. This is normally achieved through a regular calibration process. When the acoustic equipment changes it is necessary to verify that the new equipment produces a similar result to the old equipment, otherwise an unknown bias can be introduced into the time-series. The commonly used Simrad EK60 echosounder has been superseded by the Simrad EK80 echosounder and the performance of these two scientific echosounder systems was compared using interleaved pinging through the same transducer. This was repeated for multiple transducer frequencies (18, 38, 70, 120, and 200 kHz) and from two vessels (Norway’s G.O. Sars in the North Sea and The Netherlands’ Tridens in the Northeast Atlantic Ocean). The broadband facility of the EK80 was not used. Regressions of the grid-integrated backscatter from the two systems werehighly linear. The difference in area backscattering coefficients in typical survey conditions was less than 0.6 dB (12%) at the main survey frequency of 38 kHz. In most conventional fish acoustic surveys, the observed differences are less than other sources of survey bias and uncertainty

Learning process promoted by sensemaking and trust: a study related to unexpected events

The objective of this study is to understand the interrelations among the micro processes which comprise sensemaking (WEICK, 1995) and the construction of trust (LUHMANN, 1996) in unexpected events. Unexpected events transcend routine and planning orders. However, when they happen, they demand from the organizations solutions as efficient and effectual as those programmed events. The methodology consists of the analysis of six semi-structured interviews and Conversation Analysis (CA) of the main extracts of the conversation between the agents and the supervisor from the beginning of event until its conclusion (recorded in real time). As empirical evidence, an unexpected event at the Operations Center of the Brazilian Electrical System (COS) of an important Brazilian state, on September 24 and 25, 2009 is investigated. The conclusion is that there is an interrelationship between micro processes of sensemaking, considered as ambiguity, experience and interactions, and the micro processes of trust, considered as complexity, familiarity and social behavior

Efficacy and Safety of Delayed-release Dimethyl Fumarate for Relapsing-remitting Multiple Sclerosis in Prior Interferon Users: An Integrated Analysis of DEFINE and CONFIRM.

In Phase III studies (DEFINE [Determination of the Efficacy and Safety of Oral Fumarate in Relapsing-Remitting MS]/CONFIRM [Comparator and an Oral Fumarate in Relapsing-Remitting Multiple Sclerosis]), delayed-release dimethyl fumarate (DMF) demonstrated significant efficacy and a favorable benefit-risk profile in patients with relapsing-remitting multiple sclerosis (RRMS). Post hoc analyses of integrated data from DEFINE/CONFIRM were conducted to evaluate the effect of DMF in patients previously treated with interferon (IFN) beta. Patients (age 18-55 years; Expanded Disability Status Scale score, 0-5.0) were randomized to receive DMF 240 mg BID or TID, placebo, or glatiramer acetate (CONFIRM only) for up to 2 years. Previous IFN users received at least 1 IFN treatment >3 months before randomization. Data for DMF 240 mg BID (approved dosing regimen) are reported. In the integrated intention-to-treat population, 172 and 169 patients receiving DMF or placebo, respectively, had received ≥1 prior IFN. In this subgroup, significant reductions with DMF versus placebo were observed for the annualized relapse rate (rate ratio, 0.55 [95% CI, 0.40-0.77]), new/newly enlarging T2-hyperintense lesions (lesion mean ratio, 0.16 [95% CI, 0.09-0.29]), odds of having more gadolinium-enhancing lesions (odds ratio, 0.17 [95% CI, 0.07-0.44]), and new T1-hypointense lesions (lesion mean ratio, 0.25 [95% CI, 0.14-0.45]). Median Expanded Disability Status Scale scores remained stable during the study period. Adverse events associated with DMF included flushing and gastrointestinal events. In this post hoc analysis in patients with previous IFN treatment, DMF demonstrated significant efficacy over 2 years versus placebo and an adverse event profile consistent with the overall population of DEFINE/CONFIRM. ClinicalTrials.gov identifiers: DEFINE, NCT00420212; and CONFIRM, NCT00451451

Comparison of model results for two prolate spheroids.

<p>Length-normalised target strength (<i>nTS</i>) of a prolate spheroid with <i>ka</i>  = 12 and <i>kb</i>  = 5 (upper curves) and <i>ka</i>  = 12 and <i>kb</i>  = 1 (lower curves) as a function of angle off broadside from the prolate-spheroid-modal-series (PSMS), Kirchhoff-approximation (KA), Kirchhoff-ray-mode (KRM), and finite element (FE) models, where <i>a</i> is the semi-major axis and <i>b</i> the semi-minor axis of the prolate spheroid. The shaded ellipses show the relative shapes of the prolate spheroids.</p

Comparison of Kirchhoff-ray-mode model to published results.

<p>Length-normalised target strength (<i>nTS</i>) of the axisymmetric shape given in Figure 11 of Reeder and Stanton <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064055#pone.0064055-Reeder1" target="_blank">[11]</a> calculated by the Kirchhoff-ray-mode model (solid lines) and digitised from Figure 11 of Reeder and Stanton <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064055#pone.0064055-Reeder1" target="_blank">[11]</a> (dotted lines) for <i>kb</i>  = 1 (grey) and <i>kb</i>  = 5 (black). The implementation of this model used a finer angle resolution than by Reeder and Stanton <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064055#pone.0064055-Reeder1" target="_blank">[11]</a> and shows more precisely the null responses in the backscatter.</p