931 research outputs found

    The structure of wool and wool textile production, trade and consumption 1958-69

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    This paper is a revision and updating of the Agricultural Economics Research Unit Research report no. 55.In this paper we have set out, in the form of charts and tables, the results of an attempt to measure the disposition of wool produced by the major producing and consuming countries in the post-war period. Our aim is to present a picture of the structure of the world wool market, by tracing through the major flows of wool from the point of raw production to its final use in the form of wool type textiles measured in clean fibre content, and to identify the growing points of world demand for wool. The paper is mainly descriptive and no attempt is made at analysis, though the data presented was assembled in the course of an analysis of factors affecting wool prices. In such an analysis we would be concerned, as with the analysis of prices of other agricultural products, with the interaction of supply and demand. But unlike other New Zealand export products, for example meat, in which we confine our attention to one particular type of meat in a few particular countries, we focus on wool because of the infinite possibilities of substitution possible between different grades and types. And we have to take as our market the world as a whole, since nearly every country in the world consumes wool in greater or smaller quantities, if only in the form of small quantities of imported wool textiles

    Underuse of coronary revascularization procedures in patients considered appropriate candidates for revascularization.

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    Background: Ratings by an expert panel of the appropriateness of treatments may offer better guidance for clinical practice than the variable decisions of individual clinicians, yet there have been no prospective studies of clinical outcomes. We compared the clinical outcomes of patients treated medically after angiography with those of patients who underwent revascularization, within groups defined by ratings of the degree of appropriateness of revascularization in varying clinical circumstances.Methods: This was a prospective study of consecutive patients undergoing coronary angiography at three London hospitals. Before patients were recruited, a nine-member expert panel rated the appropriateness of percutaneous transluminal coronary angioplasty (PTCA) and coronary-artery bypass grafting (CABG) on a nine-point scale (with 1 denoting highly inappropriate and 9 denoting highly appropriate) for specific clinical indications. These ratings were then applied to a population of patients with coronary artery disease. However, the patients were treated without regard to the ratings. A total of 2552 patients were followed for a median of 30 months after angiography.Results: Of 908 patients with indications for which PTCA was rated appropriate (score, 7 to 9), 34 percent were treated medically; these patients were more likely to have angina at follow-up than those who underwent PTCA (odds ratio, 1.97; 95 percent confidence interval, 1.29 to 3.00). Of 1353 patients with indications for which CABG was considered appropriate, 26 percent were treated medically; they were more likely than those who underwent CABG to die or have a nonfatal myocardial infarction - the composite primary outcome (hazard ratio, 4.08; 95 percent confidence interval, 2.82 to 5.93) - and to have angina (odds ratio, 3.03; 95 percent confidence interval, 2.08 to 4.42). Furthermore, there was a graded relation between rating and outcome over the entire scale of appropriateness (P for linear trend = 0.002).Conclusions: On the basis of the ratings of the expert panel, we identified substantial underuse of coronary revascularization among patients who were considered appropriate candidates for these procedures. Underuse was associated with adverse clinical outcomes. (N Engl J Med 2001;344:645-54.) Copyright (C) 2001 Massachusetts Medical Society

    A Mini-PET beamline for optimized proton delivery to the ISOTRACEℱ target system

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    Introduction The ISOTRACEℱ Super-Conducting Cyclotron is PMB-Alcen’s redeveloped and modernized version of Oxford Instrument’s OSCAR superconducting cyclotron [1]. Its extracted 80+ mi-croamperes of 12 MeV protons are used for the production of PET radioisotopes. Following the philosophy of Dickie, Stevenson, Szlavik [2] for minimizing dose to personnel, and as developed by Dehnel et al [3,4], and Stokely et al [5], the ISOTRACEℱ shall utilize an innovative, light-weight, integrated and self-supporting Mini-Beamline. This permits the relatively high residual radiation fields around PET targets to be moved ~1 metre away from the cyclotron, and facilitates the use of local shielding (around the targets) that limits prompt gammas and neutrons, but more importantly attenuates the residual target radiation, so that maintenance/research staff can work on the cyclotron in a relatively low activity environment. In addition, the mini-beamline for PET utilizes a compound quadrupole/steerer doublet that permits active and dynamic focusing/steering of the extracted proton beam for optimized production and minimized losses [3], so it improves on the successful work of Theroux et al [6]. The integrated beamline unit is extremely small, so that it is very unlike bulky traditional PET and SPECT beamlines that require substantial support structures, such as described by Dehnel in [7,8]. Material and Methods The ISOTRACEℱ cyclotron is pictured in FIG. 1. The exit port flange and gate valve to which the integrated mini-beamline for PET shall be mounted is shown. Immediately upstream of the exit port, hidden from view, is a 4 jaw collimator (called BPI for Beam Position Indicator) with spilled beam current readbacks to the control system. TABLE 1 shows the nominal beam emittance and Twiss parameter values at the exit port flange location. This ion-optical information is necessary to simulate ion beam transport, develop the mini-beamline, and determine a nominal tune (i.e. magnet settings). Results and Conclusion TABLE 2 shows the ion-optical system parameters. FIGS. 2 and 3 show the horizontal and vertical beam profiles. The Horizontally focusing Quadrupole magnet (HQ), and Vertically focusing Quadrupole magnet (VQ) aperture diameter, 33 mm, was chosen to give sufficient beam acceptance. The focusing strength is a function of BL, so the effective length, L = 150 mm, was chosen to ensure Bmax less than 0.3 Tesla, while keeping overall magnet mass down. The quad-rupole magnets are fitted with water-cooled compound coils in which the copper/mylar strip wound portion of each coil is a winding for the quadrupole focusing function, and the wire wound portion is for the steering function. To increase beam acceptance and provide additional section strength for the pipe support function, the internal aperture of the low-activation aluminium beam pipe and the external shape are in the shape of a cross. FIG. 4 shows the beam crosssection at the mid-point of the downstream quadrupole magnet, and illustrates the additional acceptance as compared to a round beampipe. In order to machine the interior profile, the pipe is comprised of two premachined pieces that are friction stirwelded together. FIG. 5 is an isometric of the mini-beamline for PET. The four upstream HQ compound coils are excited with a 75A power supply for the horizontally focusing quadrupole magnet function, and a ± 10A power supply for a vertical steering function. The same power supplies are used for the four downstream VQ compound coils for the purpose of a vertically focusing quadrupole magnet function and horizontal steering function

    Thomas rotation and Thomas precession

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    Exact and simple calculation of Thomas rotation and Thomas precessions along a circular world line is presented in an absolute (coordinate-free) formulation of special relativity. Besides the simplicity of calculations the absolute treatment of spacetime allows us to gain a deeper insight into the phenomena of Thomas rotation and Thomas precession.Comment: 20 pages, to appear in Int. J. Theo. Phy

    On the relation of Thomas rotation and angular velocity of reference frames

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    In the extensive literature dealing with the relativistic phenomenon of Thomas rotation several methods have been developed for calculating the Thomas rotation angle of a gyroscope along a circular world line. One of the most appealing concepts, introduced in \cite{rindler}, is to consider a rotating reference frame co-moving with the gyroscope, and relate the precession of the gyroscope to the angular velocity of the reference frame. A recent paper \cite{herrera}, however, applies this principle to three different co-moving rotating reference frames and arrives at three different Thomas rotation angles. The reason for this apparent paradox is that the principle of \cite{rindler} is used for a situation to which it does not apply. In this paper we rigorously examine the theoretical background and limitations of applicability of the principle of \cite{rindler}. Along the way we also establish some general properties of {\it rotating reference frames}, which may be of independent interest.Comment: 14 pages, 2 figure

    New Discrete Basis for Nuclear Structure Studies

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    A complete discrete set of spherical single-particle wave functions for studies of weakly-bound many-body systems is proposed. The new basis is obtained by means of a local-scale point transformation of the spherical harmonic oscillator wave functions. Unlike the harmonic oscillator states, the new wave functions decay exponentially at large distances. Using the new basis, characteristics of weakly-bound orbitals are analyzed and the ground state properties of some spherical doubly-magic nuclei are studied. The basis of the transformed harmonic oscillator is a significant improvement over the harmonic oscillator basis, especially in studies of exotic nuclei where the coupling to the particle continuum is important.Comment: 13 pages, RevTex, 6 p.s. figures, submitted to Phys. Rev.

    Gamow Shell Model Description of Weakly Bound Nuclei and Unbound Nuclear States

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    We present the study of weakly bound, neutron-rich nuclei using the nuclear shell model employing the complex Berggren ensemble representing the bound single-particle states, unbound Gamow states, and the non-resonant continuum. In the proposed Gamow Shell Model, the Hamiltonian consists of a one-body finite depth (Woods-Saxon) potential and a residual two-body interaction. We discuss the basic ingredients of the Gamow Shell Model. The formalism is illustrated by calculations involving {\it several} valence neutrons outside the double-magic core: 6−10^{6-10}He and 18−22^{18-22}O.Comment: 19 pages, 20 encapsulated PostScript figure

    OGLE-2013-BLG-0102LA,B: Microlensing binary with components at star/brown-dwarf and brown-dwarf/planet boundaries

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    We present the analysis of the gravitational microlensing event OGLE-2013-BLG-0102. The light curve of the event is characterized by a strong short-term anomaly superposed on a smoothly varying lensing curve with a moderate magnification Amax∌1.5A_{\rm max}\sim 1.5. It is found that the event was produced by a binary lens with a mass ratio between the components of q=0.13q = 0.13 and the anomaly was caused by the passage of the source trajectory over a caustic located away from the barycenter of the binary. From the analysis of the effects on the light curve due to the finite size of the source and the parallactic motion of the Earth, the physical parameters of the lens system are determined. The measured masses of the lens components are M1=0.096±0.013 M⊙M_{1} = 0.096 \pm 0.013~M_{\odot} and M2=0.012±0.002 M⊙M_{2} = 0.012 \pm 0.002~M_{\odot}, which correspond to near the hydrogen-burning and deuterium-burning mass limits, respectively. The distance to the lens is 3.04±0.31 kpc3.04 \pm 0.31~{\rm kpc} and the projected separation between the lens components is 0.80±0.08 AU0.80 \pm 0.08~{\rm AU}.Comment: 6 figures, 2 tables, ApJ submitte
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