9,638 research outputs found

    The NASA Spitzer Space Telescope

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    The National Aeronautics and Space Administration's Spitzer Space Telescope (formerly the Space Infrared Telescope Facility) is the fourth and final facility in the Great Observatories Program, joining Hubble Space Telescope (1990), the Compton Gamma-Ray Observatory (1991–2000), and the Chandra X-Ray Observatory (1999). Spitzer, with a sensitivity that is almost three orders of magnitude greater than that of any previous ground-based and space-based infrared observatory, is expected to revolutionize our understanding of the creation of the universe, the formation and evolution of primitive galaxies, the origin of stars and planets, and the chemical evolution of the universe. This review presents a brief overview of the scientific objectives and history of infrared astronomy. We discuss Spitzer's expected role in infrared astronomy for the new millennium. We describe pertinent details of the design, construction, launch, in-orbit checkout, and operations of the observatory and summarize some science highlights from the first two and a half years of Spitzer operations. More information about Spitzer can be found at http://spitzer.caltech.edu/

    Infrared receivers for low background astronomy: Incoherent detectors and coherent devices from one micrometer to one millimeter

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    The status of incoherent detectors and coherent receivers over the infrared wavelength range from one micrometer to one millimeter is described. General principles of infrared receivers are included, and photon detectors, bolometers, coherent receivers, and important supporting technologies are discussed, with emphasis on their suitability for low background astronomical applications. Broad recommendations are presented and specific opportunities are identified for development of improved devices

    Territorial Tactics: The Socio-spatial Significance of Private Policing Strategies in Cape Town

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    This paper analyses the policing strategies of private security companies operating in urban space. An existing literature has considered the variety of ways that territory becomes of fundamental importance in the work of public police forces. However, this paper examines territory in the context of private security companies. Drawing on empirical research in Cape Town, it examines how demarcated territories become key subjects in private policing. Private security companies are responsible for a relatively small section of the city, while in contrast the public police ultimately have to see city space as a whole. Hence, private policing strategy becomes one of displacement, especially of so-called undesirables yielding a patchworked public space associated with private enclaves of consumption. The conclusions signal the historical resonances and comparative implications of these political-legal-security dynamics. © 2013 Urban Studies Journal Limited

    Community pharmacists' opinions of their role in administering non-prescription medicines in an emergency

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    Objective: To obtain community pharmacists’ opinions of their role in administering Pharmacy (S2) and Pharmacist Only (S3) Medicines in a medical emergency. These medicines can only be sold in a pharmacy and are not available for self-selection by patients. Whilst qualified pharmacy assistants can supply S2 medicines, pharmacists must be directly involved in the supply of S3 medicines. Setting: Community pharmacies in South East Queensland, Australia. Method: A survey of 151 Gold Coast and Toowoomba community pharmacists was conducted during October 2009. Main outcome measures: Pharmacists were asked their opinions as to whether the administration of S2 and S3 medicines should fall within their scope of practice, whether they had administered S2 and S3 medicines in a medical emergency in the past and if clarification of this role was required. Results: The study achieved a 30% (n = 45) response rate and demonstrated similar results regarding whether pharmacists should administer salbutamol (22/44), adrenaline (23/42), glyceryl trinitrate (22/43) and aspirin (18/36) in a medical emergency. The majority (36/43) believed that role clarification was required. Pharmacists were more likely to administer an S3 medicine in a medical emergency when they considered potential outcomes first, had no easy access to a doctor and the patient could not administer the medicine they carried with them themselves (40/45).Conclusion: Community pharmacists have direct access to S2 and S3 medicines that could be required in the management of a variety of medical emergencies. This study demonstrates that some pharmacists have administered S2 and S3 medicines in an emergency situation. However, there are currently no clear guidelines for pharmacists when faced with a medical emergency other than to act within their professional competence. To promote patient safety through the appropriate use of S2 and S3 medicines in the event of a medical emergency, additional training of pharmacists on the administration of these readily accessible medicines is needed. Clarification of the role of pharmacists in an emergency situation is required

    A Nonlinear Force-Free Magnetic Field Approximation Suitable for Fast Forward-Fitting to Coronal Loops. II. Numeric Code and Tests

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    Based on a second-order approximation of nonlinear force-free magnetic field solutions in terms of uniformly twisted field lines derived in Paper I, we develop here a numeric code that is capable to forward-fit such analytical solutions to arbitrary magnetogram (or vector magnetograph) data combined with (stereoscopically triangulated) coronal loop 3D coordinates. We test the code here by forward-fitting to six potential field and six nonpotential field cases simulated with our analytical model, as well as by forward-fitting to an exactly force-free solution of the Low and Lou (1990) model. The forward-fitting tests demonstrate: (i) a satisfactory convergence behavior (with typical misalignment angles of μ≈1∘−10∘\mu \approx 1^\circ-10^\circ), (ii) relatively fast computation times (from seconds to a few minutes), and (iii) the high fidelity of retrieved force-free α\alpha-parameters (αfit/αmodel≈0.9−1.0\alpha_{\rm fit}/\alpha_{\rm model} \approx 0.9-1.0 for simulations and αfit/αmodel≈0.7±0.3\alpha_{\rm fit}/\alpha_{\rm model} \approx 0.7\pm0.3 for the Low and Lou model). The salient feature of this numeric code is the relatively fast computation of a quasi-forcefree magnetic field, which closely matches the geometry of coronal loops in active regions, and complements the existing {\sl nonlinear force-free field (NLFFF)} codes based on photospheric magnetograms without coronal constraints.Comment: Solar PHysics, (in press), 25 pages, 11 figure

    Can We Improve the Preprocessing of Photospheric Vector Magnetograms by the Inclusion of Chromospheric Observations?

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    The solar magnetic field is key to understanding the physical processes in the solar atmosphere. Nonlinear force-free codes have been shown to be useful in extrapolating the coronal field upward from underlying vector boundary data. However, we can only measure the magnetic field vector routinely with high accuracy in the photosphere, and unfortunately these data do not fulfill the force-free condition. We must therefore apply some transformations to these data before nonlinear force-free extrapolation codes can be self-consistently applied. To this end, we have developed a minimization procedure that yields a more chromosphere-like field, using the measured photospheric field vectors as input. The procedure includes force-free consistency integrals, spatial smoothing, and -- newly included in the version presented here -- an improved match to the field direction as inferred from fibrils as can be observed in, e.g., chromospheric Hα\alpha images. We test the procedure using a model active-region field that included buoyancy forces at the photospheric level. The proposed preprocessing method allows us to approximate the chromospheric vector field to within a few degrees and the free energy in the coronal field to within one percent.Comment: 22 pages, 6 Figur

    Multiple Reggeon Exchange from Summing QCD Feynman Diagrams

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    Multiple reggeon exchange supplies subleading logs that may be used to restore unitarity to the Low-Nussinov Pomeron, provided it can be proven that the sum of Feynman diagrams to all orders gives rise to such multiple regge exchanges. This question cannot be easily tackled in the usual way except for very low-order diagrams, on account of delicate cancellations present in the sum which necessitate individual Feynman diagrams to be computed to subleading orders. Moreover, it is not clear that sums of high-order Feynman diagrams with complicated criss-crossing of lines can lead to factorization implied by the multi-regge scenario. Both of these difficulties can be overcome by using the recently developed nonabelian cut diagrams. We are then able to show that the sum of ss-channel-ladder diagrams to all orders does lead to such multiple reggeon exchanges.Comment: uu-encoded latex file with 11 postscript figures (20 pages

    A Nonlinear Force-Free Magnetic Field Approximation Suitable for Fast Forward-Fitting to Coronal Loops. I. Theory

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    We derive an analytical approximation of nonlinear force-free magnetic field solutions (NLFFF) that can efficiently be used for fast forward-fitting to solar magnetic data, constrained either by observed line-of-sight magnetograms and stereoscopically triangulated coronal loops, or by 3D vector-magnetograph data. The derived NLFFF solutions provide the magnetic field components Bx(x)B_x({\bf x}), By(x)B_y({\bf x}), Bz(x)B_z({\bf x}), the force-free parameter α(x)\alpha({\bf x}), the electric current density j(x){\bf j}({\bf x}), and are accurate to second-order (of the nonlinear force-free α\alpha-parameter). The explicit expressions of a force-free field can easily be applied to modeling or forward-fitting of many coronal phenomena.Comment: Solar Physics (in press), 26 pages, 11 figure

    The Trans-Pacific Partnership Agreement: Looking Ahead to the Next Steps

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    Pressure has been building for the conclusion of the 12-country Trans-Pacific Partnership (TPP) negotiations. Getting the deal done is important, but the TPP is not just another free trade agreement (FTA). It represents the chance to set a trade agenda for the future across a wide range of topics for countries throughout the Asia-Pacific region. This means that the agreement should not be settled in haste. More importantly, it also means that key decisions need to be reached about broader issues related to the institutional structure of the TPP. These decisions must be made now, before the deal is closed, on issues such as how to create the TPP as a living agreement, the formation of a TPP Secretariat, and the clarification of entry conditions for future members such as the People’s Republic of China (PRC). These choices must be made deliberately and carefully even while officials are struggling with reaching closure on the most highly sensitive issues still remaining in the agreement. It will not be easy, but wise decisions are necessary now to ensure the long-term success of the TPP
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