13,880 research outputs found

    Effects of a multi-component exercise program and calcium–vitamin-D3-fortified milk on bone mineral density in older men : a randomised controlled trial

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    Summary We examined the independent and combined effects of a multi-component exercise program and calcium&ndash;vitamin-D3-fortified milk on bone mineral density (BMD) in older men. Exercise resulted in a 1.8% net gain in femoral neck BMD, but additional calcium&ndash;vitamin D3 did not enhance the response in this group of older well-nourished men.Introduction This 12-month randomised controlled trial assessed whether calcium&ndash;vitamin-D3-fortified milk could enhance the effects of a multi-component exercise program on BMD in older men.Methods Men (n&thinsp; =&thinsp;180) aged 50&ndash;79 years were randomised into: (1) exercise + fortified milk; (2) exercise; (3) fortified milk; or (4) controls. Exercise consisted of high intensity progressive resistance training with weight-bearing impact exercise. Men assigned to fortified milk consumed 400 mL/day of low fat milk providing an additional 1,000 mg/day calcium and 800 IU/day vitamin D3. Femoral neck (FN), total hip, lumbar spine and trochanter BMD and body composition (DXA), muscle strength 25-hydroxyvitamin D and parathyroid hormone (PTH) were assessed.Results There were no exercise-by-fortified milk interactions at any skeletal site. Exercise resulted in a 1.8% net gain in FN BMD relative to no-exercise (p&thinsp;&lt;&thinsp;0.001); lean mass (0.6 kg, p&thinsp;&lt;&thinsp;0.05) and muscle strength (20&ndash;52%, p&thinsp;&lt;&thinsp;0.001) also increased in response to exercise. For lumbar spine BMD, there was a net 1.4&ndash;1.5% increase in all treatment groups relative to controls (all p&thinsp;&lt;&thinsp;0.01). There were no main effects of fortified milk at any skeletal site.Conclusion A multi-component community-based exercise program was effective for increasing FN BMD in older men, but additional calcium&ndash;vitamin D3 did not enhance the osteogenic response.<br /

    Direct and Heterodyne Detection of Microwaves in a Metallic Single Wall Carbon Nanotube

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    This letter reports measurements of microwave (up to 4.5 GHz) detection in metallic single-walled carbon nanotubes. The measured voltage responsivity was found to be 114 V/W at 77K. We also demonstrated heterodyne detection at 1 GHz. The detection mechanism can be explained based on standard microwave detector theory and the nonlinearity of the DC IV-curve. We discuss the possible causes of this nonlinearity. While the frequency response is limited by circuit parasitics in this measurement, we discuss evidence that indicates that the effect is much faster and that applications of carbon nanotubes as terahertz detectors are feasible

    Electroweak Theory Without Higgs Bosons

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    A perturbative SU(2)_L X U(1)_Y electroweak theory containing W, Z, photon, ghost, lepton and quark fields, but no Higgs or other fields, gives masses to W, Z and the non-neutrino fermions by means of an unconventional choice for the unperturbed Lagrangian and a novel method of renormalisation. The renormalisation extends to all orders. The masses emerge on renormalisation to one loop. To one loop the neutrinos are massless, the A -> Z transition drops out of the theory, the d quark is unstable and S-matrix elements are independent of the gauge parameter xi.Comment: 27 pages, LaTex, no figures; revised for publication; accepted by Int. J. Mod. Phys. A; includes biographical note on A. F. Nicholso

    Atlantic menhaden, Brevoortia tyrannus, Purse Seine Fishery, 1972-84, with a brief discussion of age and size composition of the Landings

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    This report summarizes (I) annual purse seine landings of Atlantic menhaden, Brevoortia tyrannus, for 1972-84, (2) estimated numbers of fish caught by fishing area. (3) estimates of nominal fishing effort and catch-per-unit-effort, (4) mean fish length and weight, and (5) major changes in the fishery. During the 1970s stock size and recruitment increased and the age composition broadened. reversing trends witnessed during the fishery's decline in the 1960s. Landings steadily improved and by 1980 the total coast wide landings exceeded 400,000 metric tons. Nevertheless, the character of the fishery changed considerably. Eleven reduction plants processed fish at seven ports in 1972, but in 1984 only eight plants operated at live ports. Beginning in the mid-1960s the center of fishing aclivity shifted from the Middle Atlantic area to the Chesapeake Bay area, which has continued to dominate the fishery in landings and effort through the 1970s and 1980s. During this period the average size and age of fish in the catches declined. (PDF file contains 30 pages.

    The effects of pesticides on the diversity of culturable soil bacteria

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    The numbers of culturable soil bacteria in plots that had received either no pesticides or the full combination (aldicarb, chlorfenvinphos, benomyl, glyphosate, plus chlorotoluron or triadimefon) over a 20 year period were compared. Differences were very small although there were consistently higher numbers on the treated plot, possibly reflecting the greater crop yields which had been reported previously. There was no significant difference in numbers of bacterial colonies with homology to a nif gene probe in soils from the two plots. Genetic fingerprinting of Pseudomonas fluorescens isolates from the plots, using ERIC-PCR, showed that the dominant strains in the two populations were not the same although there was no obvious difference in the degree of diversity. Substrate utilization by microbial populations from the two plots was compared using Biolog plates. The population from the pesticide-treated plot showed a higher rate of substrate utilization which could reflect a slightly higher inoculum of heterotrophic bacteria, but could also indicate greater metabolic diversity in the population

    Human-agent collectives

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    We live in a world where a host of computer systems, distributed throughout our physical and information environments, are increasingly implicated in our everyday actions. Computer technologies impact all aspects of our lives and our relationship with the digital has fundamentally altered as computers have moved out of the workplace and away from the desktop. Networked computers, tablets, phones and personal devices are now commonplace, as are an increasingly diverse set of digital devices built into the world around us. Data and information is generated at unprecedented speeds and volumes from an increasingly diverse range of sources. It is then combined in unforeseen ways, limited only by human imagination. People’s activities and collaborations are becoming ever more dependent upon and intertwined with this ubiquitous information substrate. As these trends continue apace, it is becoming apparent that many endeavours involve the symbiotic interleaving of humans and computers. Moreover, the emergence of these close-knit partnerships is inducing profound change. Rather than issuing instructions to passive machines that wait until they are asked before doing anything, we will work in tandem with highly inter-connected computational components that act autonomously and intelligently (aka agents). As a consequence, greater attention needs to be given to the balance of control between people and machines. In many situations, humans will be in charge and agents will predominantly act in a supporting role. In other cases, however, the agents will be in control and humans will play the supporting role. We term this emerging class of systems human-agent collectives (HACs) to reflect the close partnership and the flexible social interactions between the humans and the computers. As well as exhibiting increased autonomy, such systems will be inherently open and social. This means the participants will need to continually and flexibly establish and manage a range of social relationships. Thus, depending on the task at hand, different constellations of people, resources, and information will need to come together, operate in a coordinated fashion, and then disband. The openness and presence of many distinct stakeholders means participation will be motivated by a broad range of incentives rather than diktat. This article outlines the key research challenges involved in developing a comprehensive understanding of HACs. To illuminate this agenda, a nascent application in the domain of disaster response is presented

    Origin and evolution of the zodiacal dust cloud

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    The astrophysical importance of the zodiacal cloud became more apparent. The most useful source of information on the structure of the zodiacal cloud is the Infrared Astronomical Satellite (IRAS) observations. A substantial fraction of the extensive IRAS data set was analyzed. Also, a numerical model was developed (SIMUL) that allows to calculate the distribution of night-sky brightness that would be produced by any particular distribution of dust particle orbits. This model includes the effects of orbital perturbations by both the planets and solar radiation, it reproduces the exact viewing geometry of the IRAS telescope, and allows for the eccentricity of the Earth's orbit. SIMUL now is used to model not just the solar system dust bands discovered by IRAS but the whole zodiacal cloud

    Systematic study of Optical Feshbach Resonances in an ideal gas

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    Using a narrow intercombination line in alkaline earth atoms to mitigate large inelastic losses, we explore the Optical Feshbach Resonance (OFR) effect in an ultracold gas of bosonic 88^{88}Sr. A systematic measurement of three resonances allows precise determinations of the OFR strength and scaling law, in agreement with coupled-channels theory. Resonant enhancement of the complex scattering length leads to thermalization mediated by elastic and inelastic collisions in an otherwise ideal gas. OFR could be used to control atomic interactions with high spatial and temporal resolution.Comment: Significant changes to text and figure presentation to improve clarity. Extended supplementary material. 4 pages, 4 figures; includes supplementary material 8 pages, 4 figures. Submitted to Physical Review Letter
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