42,576 research outputs found

    Wakefield damping for the CLIC crab cavity

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    A crab cavity is required in the CLIC to allow effective head-on collision of bunches at the IP. A high operating frequency is preferred as the deflection voltage required for a given rotation angle and the RF phase tolerance for a crab cavity are inversely proportional to the operating frequency. The short bunch spacing of the CLIC scheme and the high sensitivity of the crab cavity to dipole kicks demand very high damping of the inter-bunch wakes, the major contributor to the luminosity loss of colliding bunches. This paper investigates the nature of the wakefields in the CLIC crab cavity and the possibility of using various damping schemes to suppress them effectively

    The Nambu-Jona-Lasinio model with staggered fermions

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    We investigate the neighbourhood of the chiral phase transition in a lattice Nambu--Jona-Lasinio model, using both Monte Carlo methods and lattice Schwinger-Dyson equations.Comment: Talks at LAT93, Dallas, U.S.A. Postscript file, 6 pages, figures include

    Chiral Perturbation Theory and Finite Size Effects on the Nucleon Mass in unquenched QCD

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    We calculate finite size effects on nucleon masses in chiral perturbation theory. We confront the theoretical predictions with N_f=2 lattice results and discuss chiral extrapolation formulae.Comment: talk at Lattice 03 (spectrum), 3 pages latex, 3 figures. Assignment of 2 data points to incorrect data sets in plot 1 and of 1 data point in plot 2 corrected. 1 fm lattice result updated. Conclusions unchange

    The Radiomycetaceae (Mucorales; Zygomycetes). Calcium Oxalate Crystals on the Sporangiolar Wall and Aerial Hyphae

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    Calcium oxalate crystals occur on the sporangiolar appendages and aerial hyphae of the two known genera (Hesseltinella, Radiomyces) of the mucoralean family Radiomycetaceae. In Hesseltinella the sporangiolar appendages are acicular with a polygonal, square, or hexagonal, discoid base. The appendage core consists of calcium oxalate and is composed of two portions: (1) a round, acicular spine with a more or less hexagonal base, and (2) a square, polygonal, or hexagonal, discoid base with a central perforation that generally contains the spine base. Both portions of the spine core appear to be readily separable. In species of Radiomyces the appendages are capitate with a crystal embedded in the distal, inflated end. Hyphal crystals bearing a short spine are similar in morphology to the sporangiolar appendages and are regularly produced by Hesseltinella. Initially these crystals are embedded in the hyphal wall. First, the spine is extruded out. Then some of the wall material is lost, exposing the base, a process concurrent with dehiscence of the crystal spine. In Radiomyces, the young aerial hyphae are typically smooth but calcium oxalate crystals were observed on aging mycelia

    Dynamics of semi-flexible polymer solutions in the highly entangled regime

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    We present experimental evidence that the effective medium approximation (EMA), developed by D.C. Morse [Phys. Rev. E {\bf 63}, 031502, (2001)], provides the correct scaling law of the macroscopic plateau modulus G0∝ρ4/3Lp−1/3G^{0}\propto\rho^{4/3}L^{-1/3}_{p} (where ρ\rho is the contour length per unit volume and LpL_{p} is the persistence length) of semi-flexible polymer solutions, in the highly entangled concentration regime. Competing theories, including a self-consistent binary collision approximation (BCA), have instead predicted G0∝ρ7/5Lp−1/5G^{0}\propto\rho^{7/5}L^{-1/5}_{p}. We have tested both the EMA and BCA scaling predictions using actin filament (F-actin) solutions which permit experimental control of LpL_p independently of other parameters. A combination of passive video particle tracking microrheology and dynamic light scattering yields independent measurements of the elastic modulus GG and LpL_{p} respectively. Thus we can distinguish between the two proposed laws, in contrast to previous experimental studies, which focus on the (less discriminating) concentration functionality of GG.Comment: 4 pages, 6 figures, Phys. Rev. Lett. (accepted

    Pancreatic transplantation at the University of Pittsburgh.

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    Campath-1H preconditioning with tacrolimus monotherapy is an effective immunosuppressive regimen for pancreas transplantation, with acceptable patient and graft survival rates early after transplantation. Rejection rates are low under this protocol if the tacrolimus level is kept consistently >10 ng/ml. This immunosuppressive protocol, combined with recent technical refinements, has resulted in lower rates of thrombosis and overall complications. Pancreatic transplantation en-bloc with visceral grafts has the following unique features: Diabetes is a rare indication, and HLA matching is not required. The gland is immunologically protected by the simultaneously transplanted visceral organs. Disease gravity, surgical complexity and gut alloimmunity influence the overall pancreatic allograft survival. The current UNOS listing criteria and data registry should be modified for obvious logistic and scientific reasons

    Two-neutron transfer in nuclei close to the dripline

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    We investigate the two-neutron transfer modes induced by (t,p) reactions in neutron-rich oxygen isotopes. The nuclear response to the pair transfer is calculated in the framework of continuum-Quasiparticle Random Phase Approximation (cQRPA). The cQRPA allows a consistent determination of the residual interaction and an exact treatment of the continuum coupling. The (t,p) cross sections are calculated within the DWBA approach and the form factors are evaluated by different methods : macroscopically, following the Bayman and Kallio method, and fully microscopically. The largest cross section corresponds to a high-lying collective mode built entirely upon continuum quasiparticle states.Comment: 12 pages, 7 figure

    Experimental summary 1988.

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    Disease complexes in wheat field screening trials. Glasshouse screening for wheat leaf disease resistance Effect of phosphate, stand density and Rovral on Pleiochaeta setosa in lupins. Genotype and Rovral for Pleiochaeta setosa in lupins. Control of Septoria in early sown wheat. Controlling Pyrenophora graminea leaf stripe in barley. Effect of environment on leaf stripe in barley Unusual seed quality problems
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