3,816 research outputs found

    Telerobotic controller development

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    To meet NASA's space station's needs and growth, a modular and generic approach to robotic control which provides near-term implementation with low development cost and capability for growth into more autonomous systems was developed. The method uses a vision based robotic controller and compliant hand integrated with the Remote Manipulator System arm on the Orbiter. A description of the hardware and its system integration is presented

    An intelligent, free-flying robot

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    The ground based demonstration of the extensive extravehicular activity (EVA) Retriever, a voice-supervised, intelligent, free flying robot, is designed to evaluate the capability to retrieve objects (astronauts, equipment, and tools) which have accidentally separated from the Space Station. The major objective of the EVA Retriever Project is to design, develop, and evaluate an integrated robotic hardware and on-board software system which autonomously: (1) performs system activation and check-out; (2) searches for and acquires the target; (3) plans and executes a rendezvous while continuously tracking the target; (4) avoids stationary and moving obstacles; (5) reaches for and grapples the target; (6) returns to transfer the object; and (7) returns to base

    The Development of Jomo Kenyatta International Airport as a Regional Aviation Hub

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    Air transportation plays an important role in the social and economic development of the global system and the countries that seek to participate in it. As Africa seeks to take its place in the global economy, it is increasingly looking to aviation as the primary means of connecting its people and goods with the world. It has been suggested that Africa as a continent needs to move toward a system of hubs to optimize its scarce resources. Jomo Kenyatta International Airport in Nairobi, Kenya, is one of the airports in the eastern region of Africa that is seeking to fill this role. This paper discusses the prospects for success and the challenges that it will need to overcome, including projections through 2020 for the growth in passenger and cargo traffic

    Asymptotic normalization coefficients for 8B->7Be+p from a study of 8Li->7Li+n

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    Asymptotic normalization coefficients (ANCs) for 8Li->7Li+n have been extracted from the neutron transfer reaction 13C(7Li,8Li)12C at 63 MeV. These are related to the ANCs in 8B->7Be+p using charge symmetry. We extract ANCs for 8B that are in very good agreement with those inferred from proton transfer and breakup experiments. We have also separated the contributions from the p_1/2 and p_3/2 components in the transfer. We find the astrophysical factor for the 7Be(p,gamma)8B reaction to be S_17(0)=17.6+/-1.7 eVb. This is the first time that the rate of a direct capture reaction of astrophysical interest has been determined through a measurement of the ANCs in the mirror system.Comment: 5 pages, 3 figures, 2 table

    Tests of Transfer Reaction Determinations of Astrophysical S-Factors

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    The 16O(3He,d)17F{}^{16}O ({}^{3}He,d) {}^{17}F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of 17F{}^{17}F. The coefficients provide the normalization for the tails of the overlap functions for 17F16O+p{}^{17}F \to{}^{16}O + p and allow us to calculate the S-factors for 16O(p,γ)17F{}^{16}O (p,\gamma){}^{17}F at astrophysical energies. The calculated S-factors are compared to measurements and found to be in very good agreement. This provides the first test of this indirect method to determine astrophysical direct capture rates using transfer reactions. In addition, our results yield S(0) for capture to the ground and first excited states in 17F^{17}F, without the uncertainty associated with extrapolation from higher energies.Comment: 6 pages, 2 figure

    Asymptotic Normalization Coefficients for 13C+p->14N

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    The 13C(14N,13C)14N^{13}C(^{14}N,^{13}C)^{14}N proton exchange reaction has been measured at an incident energy of 162 MeV. Angular distributions were obtained for proton transfer to the ground and low lying excited states in 14N^{14}N. Elastic scattering of 14N^{14}N on 13C^{13}C also was measured out to the rainbow angle region in order to find reliable optical model potentials. Asymptotic normalization coefficients for the system 13C+p14N^{13}C+p\to {}^{14}N have been found for the ground state and the excited states at 2.313, 3.948, 5.106 and 5.834 MeV in 14N^{14}N. These asymptotic normalization coefficients will be used in a determination of the S-factor for 7Be(p,γ)8B^{7}Be(p,\gamma)^{8}B at solar energies from a measurement of the proton transfer reaction 14N(7Be,8B)13C^{14}N(^{7}Be,^{8}B)^{13}C.Comment: 5 pages, 6 figure

    Conformational changes of calmodulin upon Ca2+ binding studied with a microfluidic mixer

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    A microfluidic mixer is applied to study the kinetics of calmodulin conformational changes upon Ca2+ binding. The device facilitates rapid, uniform mixing by decoupling hydrodynamic focusing from diffusive mixing and accesses time scales of tens of microseconds. The mixer is used in conjunction with multiphoton microscopy to examine the fast Ca2+-induced transitions of acrylodan-labeled calmodulin. We find that the kinetic rates of the conformational changes in two homologous globular domains differ by more than an order of magnitude. The characteristic time constants are ≈490 μs for the transitions in the C-terminal domain and ≈20 ms for those in the N-terminal domain of the protein. We discuss possible mechanisms for the two distinct events and the biological role of the stable intermediate, half-saturated calmodulin

    Weighing Super-Massive Black Holes with Narrow Fe Kα\alpha Line

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    It has been suggested that the narrow cores of the Fe Kα\alpha emission lines in Active Galactic Nuclei (AGNs) are likely produced in the torus, the inner radius of which can be measured by observing the lag time between the VV and KK band flux variations. In this paper we compare the virial products of the infrared time lags and the narrow Fe Kα\alpha widths for 10 type 1 AGNs with the black hole masses from other techniques. We find the narrow Fe Kα\alpha line width is in average 2.60.4+0.9^{+0.9}_{-0.4} times broader than expected assuming an isotropic velocity distribution of the torus at the distance measured by the infrared lags. We propose the thick disk model of the torus could explain the observed larger line width. Another possibility is the contamination by emission from the broad line region or the outer accretion disk. Alternatively, the narrow iron line might originate from the inner most part of the obscuring torus within the sublimation radius, while the infrared emission from outer cooler part. We note the correlation between the black hole masses based on this new technique and those based on other known techniques is statistically insignificant. We argue that this could be attributed to the small sample size and the very large uncertainties in the measurements of iron K line widths. The next generation of X-ray observatories could help verify the origin of the narrow iron Kα\alpha line and the reliability of this new technique.Comment: 12 pages, 2 figures, 2 tables, Science China G, in pres

    Expanding the parameters of academia

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    This paper draws on qualitative data gathered from two studies funded by the UK Leadership Foundation for Higher Education to examine the expansion of academic identities in higher education. It builds on Whitchurch’s earlier work, which focused primarily on professional staff, to suggest that the emergence of broadly based projects such as widening participation, learning support and community partnership is also impacting on academic identities. Thus, academic as well as professional staff are increasingly likely to work in multi-professional teams across a variety of constituencies, as well as with external partners, and the binary distinction between ‘academic’ and ‘non-academic’ roles and activities is no longer clear-cut. Moreover, there is evidence from the studies of an intentionality about deviations from mainstream academic career routes among respondents who could have gone either way. Consideration is therefore given to factors that influence individuals to work in more project-oriented areas, as well as to variables that affect ways in which these roles and identities develop. Finally, three models of academically oriented project activity are identified, and the implications of an expansion of academic identities are reviewed
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