12,223 research outputs found

    Implementation of ILLIAC 4 algorithms for multispectral image interpretation

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    Research has focused on the design and partial implementation of a comprehensive ILLIAC software system for computer-assisted interpretation of multispectral earth resources data such as that now collected by the Earth Resources Technology Satellite. Research suggests generally that the ILLIAC 4 should be as much as two orders of magnitude more cost effective than serial processing computers for digital interpretation of ERTS imagery via multivariate statistical classification techniques. The potential of the ARPA Network as a mechanism for interfacing geographically-dispersed users to an ILLIAC 4 image processing facility is discussed

    Remote terminal system evaluation

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    An Earth Resources Data Processing System was developed to evaluate the system for training, technology transfer, and data processing. In addition to the five sites included in this project two other sites were connected to the system under separate agreements. The experience of these two sites is discussed. The results of the remote terminal project are documented in seven reports: one from each of the five project sites, Purdue University, and an overview report summarizing the other six reports

    Optimal squeezing, pure states, and amplification of squeezing in resonance fluorescence

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    It is shown that 100% squeezed output can be produced in the resonance fluorescence from a coherently driven two-level atom interacting with a squeezed vacuum. This is only possible for N=1/8N=1/8 squeezed input, and is associated with a pure atomic state, i.e., a completely polarized state. The quadrature for which optimal squeezing occurs depends on the squeezing phase Φ,\Phi , the Rabi frequency Ω,\Omega , and the atomic detuning Δ\Delta . Pure states are described for arbitrary Φ,\Phi , not just Φ=0\Phi =0 or π\pi as in previous work. For small values of N,N, there may be a greater degree of squeezing in the output field than the input - i.e., we have squeezing amplification.Comment: 6 pages & 7 figures, Submitted to Phys. Rev.

    Dust emission from a parsec-scale structure in the Seyfert 1 nucleus of NGC 4151

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    We report mid-IR interferometric measurements with \sim 10 mas resolution, which resolve the warm (T = 285 +25 / -50 K) thermal emission at the center of NGC 4151. Using pairs of VLT 8.2 m telescopes with MIDI and by comparing the data to a Gaussian model, we determined the diameter of the dust emission region, albeit only along one position angle, to be 2.0 +/- 0.4 pc (FWHM). This is the first size and temperature estimate for the nuclear warm dust distribution in a Seyfert 1 galaxy. The parameters found are comparable to those in Seyfert 2 galaxies, thus providing direct support for the unified model. Using simple analytic temperature distributions, we find that the mid-infrared emission is probably not the smooth continuation of the hot nuclear source that is marginally resolved with K band interferometry. We also detected weak excess emission around 10.5 micron in our shorter baseline observation, possibly indicating that silicate emission is extended to the parsec scale.Comment: 5 pages, 4 figures, accepted for publication in The Astrophysical Journal Letter

    Exploring the inner region of Type 1 AGNs with the Keck interferometer

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    The exploration of extragalactic objects with long-baseline interferometers in the near-infrared has been very limited. Here we report successful observations with the Keck interferometer at K-band (2.2 um) for four Type 1 AGNs, namely NGC4151, Mrk231, NGC4051, and the QSO IRAS13349+2438 at z=0.108. For the latter three objects, these are the first long-baseline interferometric measurements in the infrared. We detect high visibilities (V^2 ~ 0.8-0.9) for all the four objects, including NGC4151 for which we confirm the high V^2 level measured by Swain et al.(2003). We marginally detect a decrease of V^2 with increasing baseline lengths for NGC4151, although over a very limited range, where the decrease and absolute V^2 are well fitted with a ring model of radius 0.45+/-0.04 mas (0.039+/-0.003 pc). Strikingly, this matches independent radius measurements from optical--infrared reverberations that are thought to be probing the dust sublimation radius. We also show that the effective radius of the other objects, obtained from the same ring model, is either roughly equal to or slightly larger than the reverberation radius as a function of AGN luminosity. This suggests that we are indeed partially resolving the dust sublimation region. The ratio of the effective ring radius to the reverberation radius might also give us an approximate probe for the radial structure of the inner accreting material in each object. This should be scrutinized with further observations.Comment: accepted for publication in A&A Letter

    The Design and Operation of The Keck Observatory Archive

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    The Infrared Processing and Analysis Center (IPAC) and the W. M. Keck Observatory (WMKO) operate an archive for the Keck Observatory. At the end of 2013, KOA completed the ingestion of data from all eight active observatory instruments. KOA will continue to ingest all newly obtained observations, at an anticipated volume of 4 TB per year. The data are transmitted electronically from WMKO to IPAC for storage and curation. Access to data is governed by a data use policy, and approximately two-thirds of the data in the archive are public.Comment: 12 pages, 4 figs, 4 tables. Presented at Software and Cyberinfrastructure for Astronomy III, SPIE Astronomical Telescopes + Instrumentation 2014. June 2014, Montreal, Canad

    Geometry of lipid vesicle adhesion

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    The adhesion of a lipid membrane vesicle to a fixed substrate is examined from a geometrical point of view. This vesicle is described by the Helfrich hamiltonian quadratic in mean curvature; it interacts by contact with the substrate, with an interaction energy proportional to the area of contact. We identify the constraints on the geometry at the boundary of the shared surface. The result is interpreted in terms of the balance of the force normal to this boundary. No assumptions are made either on the symmetry of the vesicle or on that of the substrate. The strong bonding limit as well as the effect of curvature asymmetry on the boundary are discussed.Comment: 7 pages, some major changes in sections III and IV, version published in Physical Review

    Prevalence and profile of Australian chiropractors treating athletes or sports people: A cross-sectional study

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    © 2018 Objectives: A range of health-care professionals including chiropractors provide treatment for sports-related health problems. This study reports analyses from the first national workforce survey to determine practitioner and practice-related factors associated with the frequent treatment of athletes or sports people by Australian chiropractors. Design and setting: A 21-item questionnaire collecting information pertaining to practitioner and practice-related characteristics was distributed to all Australian registered chiropractors, as part of the Australian Chiropractic Research Network (ACORN) project and attracted a response rate of 43% (n = 2005). Statistical analyses compared the frequency of treating athletes or sports people against a wide range of relevant practitioner and practice characteristics. Results: Of the respondents, 49.5% (n = 936) reported frequently treating athletes or sports people, and these chiropractors were more likely to be male as well as report more patient care hours and patient visits per week than those chiropractors who did not frequently treat athletes or sports people. Chiropractors who frequently treat athletes or sports people were also more likely to perform multi-modal management, have multi-disciplinary practitioner relations, use diagnostic equipment and discuss nutrition and medication use as part of their patient care than those chiropractors who did not frequently treat athletes or sports people. Conclusions: Nearly half of participating Australian chiropractors treat athletes or sports people frequently. The current and potential role of chiropractors in sports medicine appears significant. Further research is needed to examine the role, practices and outcomes of such chiropractic care helping to, provide treatment and policy development in this area of clinical management

    Time evolution of the Rabi Hamiltonian from the unexcited vacuum

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    The Rabi Hamiltonian describes a single mode of electromagnetic radiation interacting with a two-level atom. Using the coupled cluster method, we investigate the time evolution of this system from an initially empty field mode and an unexcited atom. We give results for the atomic inversion and field occupation, and find that the virtual processes cause the field to be squeezed. No anti-bunching occurs.Comment: 25 pages, 8 figures, RevTe
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