Gait Extraction and Description by Evidence-Gathering

Using gait as a biometric is of increasing interest, yet there are few model-based, parametric, approaches to extract and describe moving articulated objects. One new approach can detect moving parametric objects by evidence gathering, hence accruing known performance advantages in terms of performance and occlusion. Here we show how that the new technique can be extended not only to extract a moving person, but also to extract and concurrently provide a gait signature for use as a biometric. We show the natural relationship between the bases of these approaches, and the results they can provide. As such, these techniques allow for gait extraction and description for recognition purposes, and with known performance advantages of a well-established vision technique

Meltwater Intrusions Reveal Mechanisms for Rapid Submarine Melt at a Tidewater Glacier

Submarine melting has been implicated as a driver of glacier retreat and sea level rise, but to date melting has been difficult to observe and quantify. As a result, melt rates have been estimated from parameterizations that are largely unconstrained by observations, particularly at the near-vertical termini of tidewater glaciers. With standard coefficients, these melt parameterizations predict that ambient melting (the melt away from subglacial discharge outlets) is negligible compared to discharge-driven melting for typical tidewater glaciers. Here, we present new data from LeConte Glacier, Alaska, that challenges this paradigm. Using autonomous kayaks, we observe ambient meltwater intrusions that are ubiquitous within 400 m of the terminus, and we provide the first characterization of their properties, structure, and distribution. Our results suggest that ambient melt rates are substantially higher (×100) than standard theory predicts and that ambient melting is a significant part of the total submarine melt flux. We explore modifications to the prevalent melt parameterization to provide a path forward for improved modeling of ocean-glacier interactions.This work was funded by NSF OPP Grants 1503910, 1504191, 1504288, and 1504521 and National Geographic Grant CP4-171R-17. Additionally, this research was supported by the NOAA Climate and Global Change Postdoctoral Fellowship Program, administered by UCAR’s Cooperative Programs for the Advancement of Earth System Science (CPAESS) under award #NA18NWS4620043B. These observations would not be possible without the skilled engineering team who developed the autonomous kayaks—including Jasmine Nahorniak, June Marion, Nick McComb, Anthony Grana, and Corwin Perren—and also the Captain and crew of the M/V Amber Anne. We thank Donald Slater and an anonymous reviewer for valuable feedback that improved this manuscript. Data availability: All of the oceanographic data collected by ship and kayak have been archived with the National Centers for Environmental Information (Accession 0189574, https://accession.nodc.noaa.gov/ 0189574). The glacier data have been archived at the Arctic Data Center (https://doi.org/10.18739/A22G44).Ye

Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017

We present a workflow to track icebergs in proglacial fjords using oblique time-lapse photos and the Lucas-Kanade optical flow algorithm. We employ the workflow at LeConte Bay, Alaska, where we ran five time-lapse cameras between April 2016 and September 2017, capturing more than 400 000 photos at frame rates of 0.5–4.0 min−1. Hourly to daily average velocity fields in map coordinates illustrate dynamic currents in the bay, with dominant downfjord velocities (exceeding 0.5 m s−1 intermittently) and several eddies. Comparisons with simultaneous Acoustic Doppler Current Profiler (ADCP) measurements yield best agreement for the uppermost ADCP levels (∼ 12 m and above), in line with prevalent small icebergs that trace near-surface currents. Tracking results from multiple cameras compare favorably, although cameras with lower frame rates (0.5 min−1) tend to underestimate high flow speeds. Tests to determine requisite temporal and spatial image resolution confirm the importance of high image frame rates, while spatial resolution is of secondary importance. Application of our procedure to other fjords will be successful if iceberg concentrations are high enough and if the camera frame rates are sufficiently rapid (at least 1 min−1 for conditions similar to LeConte Bay).This work was funded by the U.S. National Science Foundation (OPP-1503910, OPP-1504288, OPP-1504521 and OPP-1504191).Ye

Citizenship Matters: Non-Citizen COVID-19 Mortality Disparities in New York and Los Angeles

U.S. non-citizen residents are burdened by inequitable access to socioeconomic resources, potentially placing them at heightened risk of COVID-19-related disparities. However, COVID-19 impacts on non-citizens are not well understood. Accordingly, the current study investigated COVID-19 mortality disparities within New York (NYC) and Los Angeles (LAC) to test our hypothesis that areas with large proportions of non-citizens will have disproportionately high COVID-19 mortality rates. We examined ecological associations between March 2020–January 2021 COVID-19 mortality rates (per 100,000 residents) and percent non-citizens (using ZIP Code Tabulation Areas (ZCTA) for NYC and City/Community units of analysis for LAC) while controlling for sociodemographic factors. Multiple linear regression analyses revealed significant positive associations between the percentage of non-citizen residents and COVID-19 mortality rates in NYC (95% CI 0.309, 5.181) and LAC (95% CI 0.498, 8.720). Despite NYC and LAC policies intended to provide sanctuary and improve healthcare access for non-citizen residents, communities with larger proportions of non-citizens appear to endure higher COVID-19 mortality rates. The challenges that non-citizens endure—e.g., inequitable access to public benefits—may discourage help-seeking behaviors. Thus, improved health surveillance, public health messaging, and sanctuary policies will be essential for reducing COVID-19 mortality disparities in communities with large shares of non-citizens

Using Maximal Isometric Force to Determine the Optimal Load for Measuring Dynamic Muscle Power

Maximal power output occurs when subjects perform ballistic exercises using loads of ~30-50% of one-repetition maximum (1-RM). However, performing 1-RM testing prior to power measurement requires considerable time, especially when testing involves multiple exercises. Maximal isometric force (MIF), which requires substantially less time to measure than 1-RM, might be an acceptable alternative for determining the optimal load for power testing. PURPOSE: To determine the optimal load based on MIF for maximizing dynamic power output during leg press and bench press exercises. METHODS: Twenty healthy volunteers (12 men and 8 women; mean +/- SD age: 31+/-6 y; body mass: 72 +/- 15 kg) performed isometric leg press and bench press movements, during which MIF was measured using force plates. Subsequently, subjects performed ballistic leg press and bench press exercises using loads corresponding to 20%, 30%, 40%, 50%, and 60% of MIF presented in randomized order. Maximal instantaneous power was calculated during the ballistic exercise tests using force plates and position transducers. Repeated-measures ANOVA and Fisher LSD post hoc tests were used to determine the load(s) that elicited maximal power output. RESULTS: For the leg press power test, six subjects were unable to be tested at 20% and 30% MIF because these loads were less than the lightest possible load (i.e., the weight of the unloaded leg press sled assembly [31.4 kg]). For the bench press power test, five subjects were unable to be tested at 20% MIF because these loads were less than the weight of the unloaded aluminum bar (i.e., 11.4 kg). Therefore, these loads were excluded from analysis. A trend (p = 0.07) for a main effect of load existed for the leg press exercise, indicating that the 40% MIF load tended to elicit greater power output than the 60% MIF load (effect size = 0.38). A significant (p . 0.05) main effect of load existed for the bench press exercise; post hoc analysis indicated that the effect of load on power output was: 30% > 40% > 50% = 60%. CONCLUSION: Loads of 40% and 30% of MIF elicit maximal power output during dynamic leg presses and bench presses, respectively. These findings are similar to those obtained when loading is based on 1-RM

Relationship Between Cognitive Performance and Lower Extremity Biomechanics: Implications for Sports-Related Concussion

Background: Collegiate athletes with prior sports-related concussion (SRC) are at increased risk for lower extremity (LE) injuries; however, the biomechanical and cognitive mechanisms underlying the SRC-LE injury relationship are not well understood. Purpose: To examine the association between cognitive performance and LE land-and-cut biomechanics among collegiate athletes with and without a history of SRC and to determine the association among multiple cognitive testing batteries in the same athlete cohort. Study Design: Controlled laboratory study. Methods: A cohort of 20 collegiate athletes with prior SRC (9 men, 11 women; mean ± standard deviation [SD] age, 20.5 ± 1.3 years; mean ± SD time since last SRC, 461 ± 263 days) and 20 matched controls (9 men, 11 women; mean ± SD age, 19.8 ± 1.3 years) completed land-and-cut tasks using the dominant and nondominant limbs. LE biomechanical variables and a functional visuomotor reaction time (FVMRT) were collected during each trial. Athletes also completed the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) and Senaptec Sensory Station assessments. Results: In the SRC cohort, Pearson correlation coefficients indicated slower FVMRT was moderately correlated with decreased dominant limb (r = –0.512) and nondominant limb (r = –0.500) knee flexion, while increased dominant limb knee abduction moment was moderately correlated with decreased ImPACT Visual Memory score (r = –0.539) and slower ImPACT Reaction Time (r = 0.515). Most computerized cognitive measures were not associated with FVMRT in either cohort (P...) (See full abstract in article)

The genome of Aeromonas salmonicida subsp. salmonicida A449: insights into the evolution of a fish pathogen

Background Aeromonas salmonicida subsp. salmonicida is a Gram-negative bacterium that is the causative agent of furunculosis, a bacterial septicaemia of salmonid fish. While other species of Aeromonas are opportunistic pathogens or are found in commensal or symbiotic relationships with animal hosts, A. salmonicida subsp. salmonicida causes disease in healthy fish. The genome sequence of A. salmonicida was determined to provide a better understanding of the virulence factors used by this pathogen to infect fish. Results The nucleotide sequences of the A. salmonicida subsp. salmonicida A449 chromosome and two large plasmids are characterized. The chromosome is 4,702,402 bp and encodes 4388 genes, while the two large plasmids are 166,749 and 155,098 bp with 178 and 164 genes, respectively. Notable features are a large inversion in the chromosome and, in one of the large plasmids, the presence of a Tn21 composite transposon containing mercury resistance genes and an In2 integron encoding genes for resistance to streptomycin/spectinomycin, quaternary ammonia compounds, sulphonamides and chloramphenicol. A large number of genes encoding potential virulence factors were identified; however, many appear to be pseudogenes since they contain insertion sequences, frameshifts or in-frame stop codons. A total of 170 pseudogenes and 88 insertion sequences (of ten different types) are found in the A. salmonicida genome. Comparison with the A. hydrophila ATCC 7966T genome reveals multiple large inversions in the chromosome as well as an approximately 9% difference in gene content indicating instances of single gene or operon loss or gain. A limited number of the pseudogenes found in A. salmonicida A449 were investigated in other Aeromonas strains and species. While nearly all the pseudogenes tested are present in A. salmonicida subsp. salmonicida strains, only about 25% were found in other A. salmonicida subspecies and none were detected in other Aeromonas species. Conclusion Relative to the A. hydrophila ATCC 7966T genome, the A. salmonicida subsp. salmonicida genome has acquired multiple mobile genetic elements, undergone substantial rearrangement and developed a significant number of pseudogenes. These changes appear to be a consequence of adaptation to a specific host, salmonid fish, and provide insights into the mechanisms used by the bacterium for infection and avoidance of host defence systems.Peer reviewed: YesNRC publication: Ye

Subglacial Discharge Reflux and Buoyancy Forcing Drive Seasonality in a Silled Glacial Fjord

Fjords are conduits for heat and mass exchange between tidewater glaciers and the coastal ocean, and thus regulate near-glacier water properties and submarine melting of glaciers. Entrainment into subglacial discharge plumes is a primary driver of seasonal glacial fjord circulation; however, outflowing plumes may continue to influence circulation after reaching neutral buoyancy through the sill-driven mixing and recycling, or reflux, of glacial freshwater. Despite its importance in non-glacial fjords, no framework exists for how freshwater reflux may affect circulation in glacial fjords, where strong buoyancy forcing is also present. Here, we pair a suite of hydrographic observations measured throughout 2016–2017 in LeConte Bay, Alaska, with a three-dimensional numerical model of the fjord to quantify sill-driven reflux of glacial freshwater, and determine its influence on glacial fjord circulation. When paired with subglacial discharge plume-driven buoyancy forcing, sill-generated mixing drives distinct seasonal circulation regimes that differ greatly in their ability to transport heat to the glacier terminus. During the summer, 53%–72% of the surface outflow is refluxed at the fjord's shallow entrance sill and is subsequently re-entrained into the subglacial discharge plume at the fjord head. As a result, near-terminus water properties are heavily influenced by mixing at the entrance sill, and circulation is altered to draw warm, modified external surface water to the glacier grounding line at 200 m depth. This circulatory cell does not exist in the winter when freshwater reflux is minimal. Similar seasonal behavior may exist at other glacial fjords throughout Southeast Alaska, Patagonia, Greenland, and elsewhere.This work was supported by NSF Arctic Natural Sciences grants OPP-1503910, 1504191, 1504288, and 1504521. The authors thank Pat Dryer, Dylan Winters, Erin Pettit, and the crews of the R/V Pelican and M/V Stellar for their contributions to the fieldwork. The authors thank Petersburg High School and the U.S. Forest Service for accommodating this project, and our two anonymous reviewers for their feedback in improving the manuscript. The authors also acknowledge the Shtax'héen Kwáan Tlingits, whose ancestral lands lie in this region.Ye