Model-based localization of deep-diving cetaceans using towed line array acoustic data

Passive acoustic monitoring using a towed line array of hydrophones is a standard method for localizing cetaceans during line-transect cetacean abundance surveys. Perpendicular distances estimated between localized whales and the trackline are essential for abundance estimation using acoustic data. Uncertainties in the acoustic data from hydrophone movement, sound propagation effects, errors in the time of arrival differences, and whale depth are not accounted for by most two-dimensional localization methods. Consequently, location and distance estimates for deep-diving cetaceans may be biased, creating uncertainty in abundance estimates. Here, a model-based localization approach is applied to towed line array acoustic data that incorporates sound propagation effects, accounts for sources of error, and localizes in three dimensions. The whale’s true distance, ship trajectory, and whale movement greatly affected localization results in simulations. The localization method was applied to real acoustic data from two separate sperm whales, resulting in three-dimensional distance and depth estimates with position bounds for each whale. By incorporating sources of error, this three-dimensional model-based approach provides a method to address and integrate the inherent uncertainties in towed array acoustic data for more robust localization

Analysis of a 290-Year Net Accumulation Time Series from Mt. Logan, Yukon

A 102.5-m mechanically continuous firn and ice core sequence retrieved from the Northwest Col of Mt. Logan (latitude 60°30\u27N; longitude 140°35\u27W; site location 5340 m a.s.l.) in the Yukon Territory, Canada, has been analyzed continuously for stable isotopes, pH and liquid electrolytic conductivity. Specific sections of the core have been analyzed for total β-activity (0-22 m) and trace ion concentrations (across major volcanic events) in order to date the core. In the lower half of the core, nitrate and some other ionic species are used to identify annual increments except between AD 1693 and AD 1720 and between AD 1729 and AD 1735 where only average annual increments are given. Annual increments were converted to water equivalents, then corrected for ice flow thinning as well as for origin, since a significant net accumulation gradient exists across the borehole site. The time series was subjected to cross correlation analysis, using instrumental data for the last 80 years, and to spectral analyses, using a 250-year sequence

Depth- and range-dependent variation in the performance of aquatic telemetry systems: Understanding and predicting the susceptibility of acoustic tag-receiver pairs to close proximity detection interference

BACKGROUND: Passive acoustic telemetry using coded transmitter tags and stationary receivers is a popular method for tracking movements of aquatic animals. Understanding the performance of these systems is important in array design and in analysis. Close proximity detection interference (CPDI) is a condition where receivers fail to reliably detect tag transmissions. CPDI generally occurs when the tag and receiver are near one another in acoustically reverberant settings. Here we confirm transmission multipaths reflected off the environment arriving at a receiver with sufficient delay relative to the direct signal cause CPDI. We propose a ray-propagation based model to estimate the arrival of energy via multipaths to predict CPDI occurrence, and we show how deeper deployments are particularly susceptible. METHODS: A series of experiments were designed to develop and validate our model. Deep (300 m) and shallow (25 m) ranging experiments were conducted using Vemco V13 acoustic tags and VR2-W receivers. Probabilistic modeling of hourly detections was used to estimate the average distance a tag could be detected. A mechanistic model for predicting the arrival time of multipaths was developed using parameters from these experiments to calculate the direct and multipath path lengths. This model was retroactively applied to the previous ranging experiments to validate CPDI observations. Two additional experiments were designed to validate predictions of CPDI with respect to combinations of deployment depth and distance. Playback of recorded tags in a tank environment was used to confirm multipaths arriving after the receiver\u27s blanking interval cause CPDI effects. RESULTS: Analysis of empirical data estimated the average maximum detection radius (AMDR), the farthest distance at which 95% of tag transmissions went undetected by receivers, was between 840 and 846 m for the deep ranging experiment across all factor permutations. From these results, CPDI was estimated within a 276.5 m radius of the receiver. These empirical estimations were consistent with mechanistic model predictions. CPDI affected detection at distances closer than 259-326 m from receivers. AMDR determined from the shallow ranging experiment was between 278 and 290 m with CPDI neither predicted nor observed. Results of validation experiments were consistent with mechanistic model predictions. Finally, we were able to predict detection/nondetection with 95.7% accuracy using the mechanistic model\u27s criterion when simulating transmissions with and without multipaths. DISCUSSION: Close proximity detection interference results from combinations of depth and distance that produce reflected signals arriving after a receiver\u27s blanking interval has ended. Deployment scenarios resulting in CPDI can be predicted with the proposed mechanistic model. For deeper deployments, sea-surface reflections can produce CPDI conditions, resulting in transmission rejection, regardless of the reflective properties of the seafloor

Climatic indicators in an ice core from the Yukon [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Stable isotope data obtained from snow and ice cores retrieved from an altitude of 5340m on Mt. Logan (60°30'N; 140°36'W) indicate that "isotopic seasons" are not generally in phase with calendar seasons. The former are phase lagged with respect to the latter by up to several months and appear to be correlated with SST'S and ocean heat transfer curves and/or the position of the Aleutian low rather than with air temperature or the temperature difference between the ocean surface and the core site

Burn out and perceived quality of life in resident physician of maternal-child area

El síndrome de burnout es un trastorno tridimensional resultante del estrés laboral, caracterizado por Cansancio Emocional (AE), Despersonalización (DP) y Baja realización personal (RP);observado especialmente en trabajos que involucran el contacto con personas. Entre los médicos, los residentes constituyen una población especialmente vulnerable

Blackcurrants Reduce the Risk of Postmenopausal Osteoporosis: A Pilot Double-Blind, Randomized, Placebo-Controlled Clinical Trial.

Beneficial effects of blackcurrant supplementation on bone metabolism in mice has recently been demonstrated, but no studies are available in humans. The current study aimed to examine the dose-dependent effects of blackcurrant in preventing bone loss and the underlying mechanisms of action in adult women. Forty peri- and early postmenopausal women were randomly assigned into one of three treatment groups for 6 months: (1) a placebo (control group, n = 13); (2) 392 mg/day of blackcurrant powder (low blackcurrant, BC, group, n = 16); and (3) 784 mg/day of blackcurrant powder (high BC group, n = 11). The significance of differences in outcome variables was tested by repeated-measures ANOVA with treatment and time as between- and within-subject factors, respectively. Overall, blackcurrant supplementation decreased the loss of whole-body bone mineral density (BMD) compared to the control group (p \u3c 0.05), though the improvement of whole-body BMD remained significant only in the high BC group (p \u3c 0.05). Blackcurrant supplementation also led to a significant increase in serum amino-terminal propeptide of type 1 procollagen (P1NP), a marker of bone formation (p \u3c 0.05). These findings suggest that daily consumption of 784 mg of blackcurrant powder for six months mitigates the risk of postmenopausal bone loss, potentially through enhancing bone formation. Further studies of larger samples with various skeletal conditions are warranted to confirm these findings