1,351 research outputs found

    Identifying hotspots of chimpanzee group activity from transect surveys in Taï National Park, Côte d'Ivoire

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    Locating activity hotspots - areas of higher density, more intense use, or distinct social units - is a prerequisite for answering many questions in animal ecology. However, for many species, carrying out such research from direct observations in tropical habitat is time-consuming and unrealistic for non-habituated animals. This study aimed to locate chimpanzee home ranges from transect nest counts. For validation purposes, 233 line transects were sampled within the home ranges of four habituated social groups of chimpanzees in Taï National Park, Côte d'Ivoire. In total, 373 km of transects were surveyed over 188 days and 683 nests of chimpanzee were recorded. First, we characterized heterogeneity of nest distribution patterns, including variation in density and group size within the area. Second, we used scan statistics, a likelihood-based cluster technique to locate chimpanzee social groups and compared them with the known home range boundaries. Chimpanzee nest distribution was characterized by a positive density and group-size gradient away from the range periphery. Furthermore, nest distribution clusters corresponding to the four groups could be successfully identified, although additional clusters for, for example, low-density areas between social groups seem to be an unavoidable by-product. The approach taken can be extended to a wide spectrum of data stemming from direct observations, camera traps, acoustic or genetic sampling to derive information about structure and patchiness of wild animal population

    Decoherence of Quantum-Enhanced Timing Accuracy

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    Quantum enhancement of optical pulse timing accuracy is investigated in the Heisenberg picture. Effects of optical loss, group-velocity dispersion, and Kerr nonlinearity on the position and momentum of an optical pulse are studied via Heisenberg equations of motion. Using the developed formalism, the impact of decoherence by optical loss on the use of adiabatic soliton control for beating the timing standard quantum limit [Tsang, Phys. Rev. Lett. 97, 023902 (2006)] is analyzed theoretically and numerically. The analysis shows that an appreciable enhancement can be achieved using current technology, despite an increase in timing jitter mainly due to the Gordon-Haus effect. The decoherence effect of optical loss on the transmission of quantum-enhanced timing information is also studied, in order to identify situations in which the enhancement is able to survive.Comment: 12 pages, 4 figures, submitte

    Dynamics of relativistic solitons

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    Relativistic solitons are self-trapped, finite size, electromagnetic waves of relativistic intensity that propagate without diffraction spreading. They have been predicted theoretically within the relativistic fluid approximation, and have been observed in multi-dimensional particle in cell simulations of laser pulse interaction with the plasma. Solitons were observed in the laser irradiated plasmas with the proton imaging technique as well. This paper reviews many theoretical results on relativistic solitons in electron-ion plasmas.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

    Healthy Team Healthy U: A Prospective Validation of an Evidence-Based Worksite Health Promotion and Wellness Platform

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    Objective: To evaluate the effects of a research tested, team-based health promotion and wellness program combined with digital technologies and implemented in a diverse worksite setting among hospital, clinic and university employees. Methods: A prospective cohort study of employees completing biometrics and questionnaires before and after the initial 12-session wellness program and its 12-session booster, one year later. Results: After both the initial intervention and booster, blood pressure and weight were reduced, with greater reductions among employees with pre-hypertension and hypertension and those with a BMI > 25. After both the initial intervention and booster, there was a significant increase in, 1) daily intake of fruit and vegetable servings; 2) days per week of > 30 minutes of exercise; 3) days per week of strength training and 4) levels of moderately vigorous and vigorous daily physical activity. Self-reported indices of depression and work related stress were reduced, while participants reported increased happiness after the initial program and booster. Post booster, average sleep quality and sleep duration increased, among higher risk employees reporting < 6 hours of daily sleep. Employees reported receiving encouragement from co-workers to engage in healthful activities, exercising with fellow employees more, and indicated they would recommend the program to co-workers. Longitudinal analysis revealed the durability of the initial intervention outcomes with further beneficial effects after the booster. Conclusion: A research-tested, comprehensive team-based health promotion and wellness program, combined with digital technologies, positively impacted employee health behaviors, mood, sleep, worker cohesion and biometrics among a diverse multi-site workforce. Positive program effects were durable, with enhanced results after the booster

    Sediment and terrestrial organic carbon budgets for the offshore Ayeyarwady Delta, Myanmar: Establishing a baseline for future change

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    Large river deltas serve as globally important archives of terrestrial and shallow marine biogeochemical signatures and because of rapid sedimentation have the potential to impact global biogeochemical cycling. The Ayeyarwady Delta in Myanmar ranks as the world\u27s third largest river delta in terms of sediment supply; however, modern increases in regional anthropogenic impacts risk severe alteration to sediment and TerrOC loads within this major system. By investigating modern sediment and terrestrial organic carbon (TerrOC) accumulation within the offshore Ayeyarwady Delta this study estimates baseline sediment and TerrOC budgets for this understudied mega-delta. Using 210Pb geochronology of 27 sediment cores collected from the continental shelf, we estimate that 405 (+52/-47) Mt of sediment, or ~70-80% of fluvial sediment discharged from the Ayeyarwady and Thanlwin rivers (the main inputs to the delta), accumulates there annually. Sediment not retained on the shelf is likely partitioned between the Ayeyarwady floodplain, shoreline accretion, and minor deep-sea export. Estimates of TerrOC (based on δ13C mixing models) were coupled with modern sediment accumulation rates to determine an annual burial of 1.93 (+1.09/-0.15) Mt C on the shelf, with TerrOC burial fluxes being highest in the foreset beds of the subaqueous delta, coincident with the area of highest sediment accumulation rate. Based on estimates of the Ayeyarwady and Thanlwin rivers\u27 TerrOC delivery, an apparent ~100% of TerrOC input is preserved on the continental shelf. However, an across shelf trend of increasing TerrOC degradation with distance offshore is also observed, indicating that while the shelf has high apparent TerrOC sequestration, carbon remineralization is also occurring prior to deposition within the subaqueous delta. Based on these conflicting outcomes, we suggest that input of TerrOC from additional sources other than the Ayeyarwady and Thanlwin rivers roughly balance the observed carbon remineralization. Main additional sources of TerrOC include the Sittang and several smaller rivers, and the Ayeyarwady delta plain below the river gauging station. As anthropogenic development within the Ayeyarwady and Thanlwin watersheds continues to increase, these sediment and TerrOC budgets provide a baseline from which future changes within the offshore Ayeyarwady Delta can be monitored
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