Estimating total momentum at finite distances

We study the difficulties associated with the evaluation of the total Bondi momentum at finite distances around the central source of a general (asymptotically flat) spacetime. Since the total momentum is only rigorously defined at future null infinity, both finite distance and gauge effects must be taken into account for a correct computation of this quantity. Our discussion is applicable in general contexts but is particularly relevant in numerically constructed spacetimes for both extracting important physical information and assessing the accuracy of additional quantities.Comment: 10 pages, 1 figure. Typos corrected. Comments added and a new Appendix. To be published in PR

Matching factors for Delta S=1 four-quark operators in RI/SMOM schemes

The non-perturbative renormalization of four-quark operators plays a significant role in lattice studies of flavor physics. For this purpose, we define regularization-independent symmetric momentum-subtraction (RI/SMOM) schemes for Delta S=1 flavor-changing four-quark operators and provide one-loop matching factors to the MS-bar scheme in naive dimensional regularization. The mixing of two-quark operators is discussed in terms of two different classes of schemes. We provide a compact expression for the finite one-loop amplitudes which allows for a straightforward definition of further RI/SMOM schemes.Comment: 22 pages, 5 figure

Deuterium toward the WD0621-376 sight line: Results from the Far Ultraviolet Spectroscopic Explorer (FUSE) Mission

Far Ultraviolet Spectroscopic Explorer observations are presented for WD0621-376, a DA white dwarf star in the local interstellar medium (LISM) at a distance of about 78 pc. The data have a signal-to-noise ratio of about 20-40 per 20 km/s resolution element and cover the wavelength range 905-1187 \AA. LISM absorption is detected in the lines of D I, C II, C II*, C III, N I, N II, N III, O I, Ar I, and Fe II. This sight line is partially ionized, with an ionized nitrogen fraction of > 0.23. We determine the ratio $D/O = (3.9 \pm ^{1.3}_{1.0})\times 10^{-2}$ (2$\sigma$). Assuming a standard interstellar oxygen abundance, we derive ${\rm D/H} \approx 1. 3 \times 10^{-5}$. Using the value of N(H I) derived from EUVE data gives a similar D/H ratio. The D I/N I ratio is $(3.3 \pm ^{1.0}_{0.8})\times 10^{-1}$ (2$\sigma$).Comment: accepted for publication in the ApJ

Partially quenched chiral perturbation theory in the epsilon regime at next-to-leading order

We calculate the partition function of partially quenched chiral perturbation theory in the epsilon regime at next-to-leading order using the supersymmetry method in the formulation without a singlet particle. We include a nonzero imaginary chemical potential and show that the finite-volume corrections to the low-energy constants $\Sigma$ and $F$ for the partially quenched partition function, and hence for spectral correlation functions of the Dirac operator, are the same as for the unquenched partition function. We briefly comment on how to minimize these corrections in lattice simulations of QCD. As a side result, we show that the zero-momentum integral in the formulation without a singlet particle agrees with previous results from random matrix theory.Comment: 19 pages, 4 figures; minor changes, to appear in JHE

Relativistic MHD and black hole excision: Formulation and initial tests

A new algorithm for solving the general relativistic MHD equations is described in this paper. We design our scheme to incorporate black hole excision with smooth boundaries, and to simplify solving the combined Einstein and MHD equations with AMR. The fluid equations are solved using a finite difference Convex ENO method. Excision is implemented using overlapping grids. Elliptic and hyperbolic divergence cleaning techniques allow for maximum flexibility in choosing coordinate systems, and we compare both methods for a standard problem. Numerical results of standard test problems are presented in two-dimensional flat space using excision, overlapping grids, and elliptic and hyperbolic divergence cleaning.Comment: 22 pages, 8 figure

Resistance profiles and genetic diversity of Escherichia coli strains isolated from acute bovine mastitis

Between March 2011 and February 2012 83 E. coli strains were isolated from mastitis milk samples from 83 different animals (67 farms) and tested for their sensitivity to various antibiotics by means of disk diffusion method and genotyped by determination of the phylogenetic groups as well as by pulsed field gel electrophoresis (PFGE). The antibiotics were chosen on the basis of their licenses for intramammary application in Switzerland. As many as 16.9 % of the isolates were resistant to one or more antimicrobial agents. Amoxicillin-clavulanic acid, gentamicin and third generation cephalosporins proved effective against the majority of these strains. Nevertheless, one blaCTX-M-14 harbouring extended-spectrum-beta-lactamase producing strain was found. Genetic analysis grouped most of the strains (87 %) into phylogenetic groups A and B1. PFGE genotyping demonstrated that E. coli from cows with mastitis even from the same farm were genotypically very diverse. = Entre mars 2011 et février 2012, 83 souches d'E. coli issues de 83 vaches différentes provenant de 67 exploitations ont été collectées et testées quant à leur sensibilité vis-à-vis de divers antibiotiques. Ces antibiotiques ont été choisis sur la base de leurs autorisations pour l'application intra mammaire en Suisse et le test a été effectué par diffusion sur gel d'agar. En outre toutes les souches ont été typisées quant à leur appartenance aux groupes phylogénétiques. 16.9 % des souches présentaient une résistance à un ou plusieurs antibiotiques. L'amoxicilline-acide clavulanique, la gentamicine et les céphalosporines de troisièmes générations se montraient efficaces contre la majorité des souches d'E. coli. On a toutefois trouvé une souche fabriquant un extended-spectrum-beta-lactamase qui portait le gène blaCTX-M-14. L'analyse génétique groupait la majorité des souches (87 %) dans les groupes phylogénétiques A et B1. La génotypisation par PFGE montrait une grande diversité entre les souches, même si elles provenaient de la même exploitation. = Zwischen März 2011 und Februar 2012 wurden 83 E. coli Stämme von 83 verschiedenen Kühen aus 67 Betrieben gesammelt und auf ihre Empfindlichkeit gegenüber verschiedenen Antibiotika getestet. Die Antibiotika wurden aufgrund der Zulassung für eine intramammäre Applikation in der Schweiz ausgesucht und die Empfindlichkeitstestung mittels Agardiffusions-Methode durchgeführt. Zudem wurden alle Stämme hinsichtlich ihrer Zugehörigkeit zu den phylogenetischen Gruppen wie auch mittels Pulsfeldgelelektrophorese (PFGE) genotypisiert. 16.9 % aller Stämme zeigten Resistenzen gegenüber einem oder mehreren Antibiotika. Amoxicillin-Clavulansäure, Gentamicin und Cephalosporine der dritten Generation erwiesen sind als wirksam gegen die Mehrheit der E. coli Stämme. Jedoch wurde ein extended-Spectrum-beta-Lactamase Bildner, welcher das blaCTX-M-14-Gen trägt, gefunden. Die genetische Analyse gruppierte das Gros der Stämme (87 %) in die phylogentischen Guppen A und B1. Die weitere Genotypisierung mittels PFGE zeigte eine grosse Diversität unter den E. coli Stämmen, auch wenn diese vom selben Betrieb stammten