4,704 research outputs found

    Profiles of inflated surfaces

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    We study the shape of inflated surfaces introduced in \cite{B1} and \cite{P1}. More precisely, we analyze profiles of surfaces obtained by inflating a convex polyhedron, or more generally an almost everywhere flat surface, with a symmetry plane. We show that such profiles are in a one-parameter family of curves which we describe explicitly as the solutions of a certain differential equation.Comment: 13 pages, 2 figure

    Variability of the NGC 1333 IRAS 4A Outflow: Molecular Hydrogen and Silicon Monoxide Images

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    The NGC 1333 region was observed in the H2 1-0 S(1) line. The H2 images cover a 5' x 7' region around IRAS 4. Numerous H2 emission features were detected. The northeast-southwest bipolar outflow driven by IRAS 4A was studied by combining the H2 images with SiO maps published previously. The SiO-H2 outflows are continuous on the southwestern side but show a gap on the northeastern side. The southwestern outflow lobe curves smoothly, and the position angle increases with the distance from the driving source. The base and the outer tip of the northeastern outflow lobe are located at positions opposite to the corresponding parts of the southwestern lobe. This point-symmetry suggests that the outflow axis may be drifting or precessing clockwise in the plane of the sky and that the cause of the axis drift may be intrinsic to the outflow engine. The axis drift model is supported by the asymmetric lateral intensity profile of the SiO outflow. The axis drift rate is about 0.011 deg yr-1. The middle part of the northeastern outflow does not exactly follow the point symmetry because of the superposition of two different kinds of directional variability: the axis drift of the driving source and the deflection by a dense core. The axis drift model provides a good explanation for the large deflection angle of the northeastern outflow. Other H2 emission features around the IRAS 4 region are discussed briefly. Some of them are newly found outflows, and some are associated with outflows already known before

    Isospin relaxation time in heavy-ion collisions at intermediate energies

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    Using an isospin-dependent transport model, we have studied the isospin and momentum relaxation times in the heavy residues formed in heavy-ion collisions at intermediate energies. It is found that only at incident energies below the Fermi energy, chemical or thermal equilibrium can be reached before dynamical instability is developed in the heavy residues. Also, the isospin relaxation time is shorter (longer) than that for momentum at beam energies lower (higher) than the Fermi energy.Comment: 8 pages Latex + 2 ps Figs.; Phys. Rev. C in pres

    Dynamics of precipitation pattern formation at geothermal hot springs

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    We formulate and model the dynamics of spatial patterns arising during the precipitation of calcium carbonate from a supersaturated shallow water flow. The model describes the formation of travertine deposits at geothermal hot springs and rimstone dams of calcite in caves. We find explicit solutions for travertine domes at low flow rates, identify the linear instabilities which generate dam and pond formation on sloped substrates, and present simulations of statistical landscape evolution

    Hand problems among endourologists.

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    BACKGROUND AND PURPOSE: Endourology has evolved rapidly for the management of both benign and malignant disease of the upper urinary tract. Limited data exist, however, on the occupational hazards posed by complex endourologic procedures. The aim of this study was to determine the prevalence and possible causes of hand problems among endourologists who routinely perform flexible ureteroscopy compared with controls. MATERIALS AND METHODS: An online computer survey targeted members of the Endourological Society and psychiatrists in academic and community settings. A total of 600 endourologists and 578 psychiatrists were contacted by e-mail. Invited physicians were queried regarding their practice settings and symptoms of hand pain, neuropathy, and/or discomfort. RESULTS: Survey responses were obtained from 122 (20.3%) endourologists and 74 (12.8%) psychiatrists. Of endourologists, 61% were in an academic setting and 70% devoted their practice to endourology. Endourologists were in practice for a mean 13 years, performing 4.5 ureteroscopic cases per week with a mean operative time of 50 minutes. Hand/wrist problems were reported by 39 (32%) endourologists compared with 14 (19%) psychiatrists (P=0.0486, relative risk [RR]=1.69). Surgeons who preferred counterintuitive ureteroscope deflection were significantly more likely to have problems (56%) compared with intuitive users (27%) (RR 2.07, P=0.0139) or those with no preference (26%) (RR 2.15, P=0.0451). Overall, most respondents (85%) with hand/wrist problems needed either medical or surgical intervention. CONCLUSIONS: Hand and wrist problems are very common among endourologists. Future studies are needed to develop more ergonomic platforms and thereby reduce the endourologist\u27s exposure to these occupational hazards

    Evaluation of an Internet–Short Message Service–Based Intervention for Promoting Physical Activity in Hong Kong Chinese Adolescent School Children: A Pilot Study

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    Evaluation of acceptability and preliminary efficacy of an Internet and short message service (SMS) intervention for promoting physical activity (PA) in Hong Kong Chinese school children. An 8-week quasi-experimental study non-randomly assigned 78 school children (mean age=12.8 years) to (a) an intervention group that received a stage-matched, Internet PA program two times a week and tailored SMS messages daily; or (b) a no-treatment control. Data were collected from September 2008 until June 2009. Acceptability measures included exposure rate and participant\u27s satisfaction. Efficacy measures were changes in stage of motivational readiness (SMR) and self-reported PA level. Intervention participants demonstrated significant pre-post increments in SMR (Z=−2.558, p=0.011) and self-reported PA level [F(1, 76)=4.50, p=0.04]. There was a non-significant trend between groups in both SMR (p=0.24) and PA (p=0.13). Despite the similar ratings of satisfaction between Internet (M=3.12±0.74) and SMS (M=3.12±0.84), participants displayed distinct patterns of exposure with 66% exhibiting a weekly login rate of 0.5 times/person and an average of 3.75 minutes/visit/person. In contrast, 79% of participants read an average of 1.3 SMS/person/week and 47% voluntarily replied to 3.8 SMS/person. These findings demonstrate the acceptability and preliminary efficacy of an Internet-SMS-based intervention for promoting PA in Hong Kong school children. The divergent exposure rates between the Internet and SMS may be a unique pattern for adolescents in early SMR. Future research should be cognizant of the importance of SMR since it may influence utilization and/or adherence

    U.S. SPACE FORCE (USSF) ACQUISITION OCCUPATIONAL COMPETENCY INTEGRATION INTO A TALENT OPERATIONS PLATFORM

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    The idea of using competencies as a vehicle for effective talent management has been an idea explored by many organizations. Recently all service components across the Department of Defense (DOD) have begun a revolution within talent management, particularly with job placement. The DOD’s newest component, the United States Space Force (USSF), actively seeks to implement a competency-based process as dictated by the Guardian Ideal. This capstone report provides USSF with recommendations on effectively integrating a scalable competency-driven system into a talent operations platform that manages Guardian talent during assignment placement. The team evaluated civilian and governmental talent operations systems and processes through interviews with relevant talent management personnel within the DOD and industry. This qualitative analysis fueled the team’s development of a simulation model to identify the effects of competency integration on the system and its interaction with external variables. Throughout the research, the team confirmed that all services desire the effective integration of competencies but lack the implementation of accountable competencies by a validation method. The team recommends Space Force develop a way to validate and input competency assessments by implementing the competency framework within a software system in terms of a scoring algorithm to provide a clear picture for Guardians and Commanders to determine the best fit for vacant billets.Space Force Talent Management Office (ETMO)Major, United States ArmyCaptain, United States ArmyCaptain, United States ArmyCaptain, United States ArmyCaptain, United States ArmyApproved for public release. Distribution is unlimited

    Probing the isospin dependent mean field and nucleon nucleon cross section in the medium by the nucleon emissions

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    We study the isospin effects of the mean field and two-body collision on the nucleon emissions at the intermediate energy heavy ion collisions by using an isospin dependent transport theory. The calculated results show that the nucleon emission number NnN_{n} depends sensitively the isospin effect of nucleon nucleon cross section and weakly on the isospin dependent mean field for neutron-poor system in higher beam energy region . In particular, the correlation between the medium correction of two-body collision and the momentum dependent interaction enhances the dependence of nucleon emission number NnN_{n} on the isospin effect of nucleon nucleon cross section. On the contrary, the ratio of the neutron proton ratio of the gas phase to the neutron proton ratio of the liquid phase, i.e., the degree of isospin fractionation b/b_{b}/_{b} depends sensitively on the isospin dependent mean field and weakly on the isospin effect of two-body collision for neutron-rich system in the lower beam energy region. In this case, NnN_{n} and b/b_{b}/_{b} are the probes for extracting the information about the isospin dependent nucleon nucleon cross section in the medium and the isospin dependent mean field,respectively.Comment: 4 pages,4 figure

    NNLO phase space master integrals for two-to-one inclusive cross sections in dimensional regularization

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    We evaluate all phase space master integrals which are required for the total cross section of generic 2 -> 1 processes at NNLO as a series expansion in the dimensional regulator epsilon. Away from the limit of threshold production, our expansion includes one order higher than what has been available in the literature. At threshold, we provide expressions which are valid to all orders in terms of Gamma functions and hypergeometric functions. These results are a necessary ingredient for the renormalization and mass factorization of singularities in 2 -> 1 inclusive cross sections at NNNLO in QCD.Comment: 37 pages, plus 3 ancillary files containing analytic expressions in Maple forma
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