2,707 research outputs found
Measurements of heavy ion beam losses from collimation
The collimation efficiency for Pb ion beams in the LHC is predicted to be
lower than requirements. Nuclear fragmentation and electromagnetic dissociation
in the primary collimators create fragments with a wide range of Z/A ratios,
which are not intercepted by the secondary collimators but lost where the
dispersion has grown sufficiently large. In this article we present
measurements and simulations of loss patterns generated by a prototype LHC
collimator in the CERN SPS. Measurements were performed at two different
energies and angles of the collimator. We also compare with proton loss maps
and find a qualitative difference between Pb ions and protons, with the maximum
loss rate observed at different places in the ring. This behavior was predicted
by simulations and provides a valuable benchmark of our understanding of ion
beam losses caused by collimation.Comment: 12 pages, 20 figure
Vergleich internationaler Konsensus-Empfehlungen zur Erkennung des präsymptomatischen Hochrisikopatienten für den Herzinfarkt in Deutschland
Summary : The recommendations of the International Task Force for the Prevention of Coronary Heart Disease/International Atherosclerosis Society (ITF/IAS), the US-American Adult Treatment Panel III of the National Cholesterol Education Programs (ATP III) and the 3rd Joint European Guidelines (3JE) for the prevention coronary heart disease (CHD) show good agreement in tertiary prevention. All three guidelines recommend that patients with manifest CHD should have a blood pressure below 140/90 mm Hg and LDL-cholesterol below 2.6 mmol/l (100 mg/dl). By contrast, the three recommendations differ with respect to the prevention of cardiovascular events in asymptomatic high risk patients (secondary prevention), notably in the strategy to be used for risk assessment. Both the ITF/IAS guidelines and the 3JE guidelines can be adapted and realized in the various European countries. We therefore compared the prognostic values of the three recommendations by applying them to the data of male participants of the Prospective Cardiovascular Münster (PROCAM) Study. The ITF/IAS recommendations show the highest specificity (94.5%), positive predictive value (32.0%) and diagnostic efficacy (90.5%); the 3JE guidelines have the highest sensitivity (64.6%) but lowest specificity (77.9%), positive predictive value (17.5%) and diagnostic efficacy (77.0%). The application of the 3JE recommendations would target 25% of German men aged 35-65 years as cardiovascular high risk patients, by contrast to 7.5% through application of the ITF/IAS guidelines. In view of the limited resources in the public health systemthe application of the ITF/IAS guidelines in Germany appears more appropriat
Nonlinearities and Effects of Transverse Beam Size in Beam Position Monitors (revised)
The fields produced by a long beam with a given transverse charge
distribution in a homogeneous vacuum chamber are studied. Signals induced by a
displaced finite-size beam on electrodes of a beam position monitor (BPM) are
calculated and compared to those produced by a pencil beam. The non-linearities
and corrections to BPM signals due to a finite transverse beam size are
calculated for an arbitrary chamber cross section. Simple analytical
expressions are given for a few particular transverse distributions of the beam
current in a circular or rectangular chamber. Of particular interest is a
general proof that in an arbitrary homogeneous chamber the beam-size
corrections vanish for any axisymmetric beam current distribution.Comment: REVTeX, 8 pages, 9 figures. Corrected Eqs. (7),(22),(25) and Figs.
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Laminin α5 guides tissue patterning and organogenesis
Laminins (LM) are extracellular matrix molecules that contribute to and are required for the formation of basement membranes. They participate in the modulation of epithelial/mesenchymal interactions and are implicated in organogenesis and maintenance of organ homeostasis. Among the LM molecules, the LM α5 chain (LMα5) is one of the most widely distributed LM in the developing and mature organism. Its presence in some basement membranes during embryogenesis is absolutely required for maintenance of basement membrane integrity and thus for proper organogenesis. LMα5 also regulates the expression of genes important for major biological processes, in part by repressing or activating signaling pathways, depending upon the physiological context
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