1,438 research outputs found
Determination of MIC and Disk Diffusion Quality Control Guidelines for Meropenem–Vaborbactam, a Novel Carbapenem/Boronic Acid β-Lactamase Inhibitor Combination
Meropenem–vaborbactam is a carbapenem/cyclic boronic acid β-lactamase inhibitor combination primarily active against Gram-negative bacilli, including those harboring class A serine carbapenemases such as Klebsiella pneumoniae carbapenemase (KPC). A Clinical and Laboratory Standards Institute M23-A4 (Tier 2) quality control study established broth microdilution and disk diffusion ranges for reference strains. Two KPC-producing K. pneumoniae ATCC strains are recommended for quality control testing
The three-quark static potential in perturbation theory
We study the three-quark static potential in perturbation theory in QCD. A
complete next-to-leading order calculation is performed in the singlet, octets
and decuplet channels and the potential exponentiation is demonstrated. The
mixing of the octet representations is calculated. At next-to-next-to-leading
order, the subset of diagrams producing three-body forces is identified in
Coulomb gauge and its contribution to the potential calculated. Combining it
with the contribution of the two-body forces, which may be extracted from the
quark-antiquark static potential, we obtain the complete
next-to-next-to-leading order three-quark static potential in the
colour-singlet channel.Comment: 36 pages, 11 figures, version published in Phys.Rev.
Real-time determination of laser beam quality by modal decomposition
We present a real-time method to determine the beam propagation ratio M2 of
laser beams. The all-optical measurement of modal amplitudes yields M2
parameters conform to the ISO standard method. The experimental technique is
simple and fast, which allows to investigate laser beams under conditions
inaccessible to other methods.Comment: 8 pages, 4 figures, published in Optics Expres
Brans-Dicke cylindrical wormholes
Static axisymmetric thin-shell wormholes are constructed within the framework
of the Brans-Dicke scalar-tensor theory of gravity. Examples of wormholes
associated with vacuum and electromagnetic fields are studied. All
constructions must be threaded by exotic matter, except in the case of
geometries with a singularity of finite radius, associated with an electric
field, which can have a throat supported by ordinary matter. These results are
achieved with any of the two definitions of the flare-out condition considered.Comment: 11 pages, 3 figures; v3: corrected version, conclusions unchange
Offsets and the Path to Carbon Neutrality in Higher Education and Study Abroad
Professors Paul Sylvester, Early & Middle Grades Education, and Michael Di Giovine, Anthropology, in conversation with Bradley Flamm - Offsets and the Path to Carbon Neutrality in Higher Education and Study Abroa
Wormholes, Gamma Ray Bursts and the Amount of Negative Mass in the Universe
In this essay, we assume that negative mass objects can exist in the
extragalactic space and analyze the consequences of their microlensing on light
from distant Active Galactic Nuclei. We find that such events have very similar
features to some observed Gamma Ray Bursts and use recent satellite data to set
an upper bound to the amount of negative mass in the universe.Comment: Essay awarded ``Honorable Mention'' in the Gravity Foundation
Research Awards, 199
Energetics in Condensate Star and Wormholes
It is known that the total gravitational energy in localized sources having
static spherical symmetry and satisfying energy conditions is negative
(attractive gravity). A natural query is how the gravitational energy behaves
under circumstances where energy conditions are violated. To answer this, the
known expression for the gravitational energy is suitably modified to account
for situations like the ones occurring in wormhole spacetime. It is then
exemplified that in many cases the modified expression yields desirable
answers. The implications are discussed.Comment: 16 pages, 1 figure, references added, To appear in PR
Global embedding of the Kerr black hole event horizon into hyperbolic 3-space
An explicit global and unique isometric embedding into hyperbolic 3-space,
H^3, of an axi-symmetric 2-surface with Gaussian curvature bounded below is
given. In particular, this allows the embedding into H^3 of surfaces of
revolution having negative, but finite, Gaussian curvature at smooth fixed
points of the U(1) isometry. As an example, we exhibit the global embedding of
the Kerr-Newman event horizon into H^3, for arbitrary values of the angular
momentum. For this example, considering a quotient of H^3 by the Picard group,
we show that the hyperbolic embedding fits in a fundamental domain of the group
up to a slightly larger value of the angular momentum than the limit for which
a global embedding into Euclidean 3-space is possible. An embedding of the
double-Kerr event horizon is also presented, as an example of an embedding
which cannot be made global.Comment: 16 pages, 13 figure
Computational Study of an Axisymmetric Dual Throat Fluidic Thrust Vectoring Nozzle for a Supersonic Aircraft Application
A computational investigation of an axisymmetric Dual Throat Nozzle concept has been conducted. This fluidic thrust-vectoring nozzle was designed with a recessed cavity to enhance the throat shifting technique for improved thrust vectoring. The structured-grid, unsteady Reynolds- Averaged Navier-Stokes flow solver PAB3D was used to guide the nozzle design and analyze performance. Nozzle design variables included extent of circumferential injection, cavity divergence angle, cavity length, and cavity convergence angle. Internal nozzle performance (wind-off conditions) and thrust vector angles were computed for several configurations over a range of nozzle pressure ratios from 1.89 to 10, with the fluidic injection flow rate equal to zero and up to 4 percent of the primary flow rate. The effect of a variable expansion ratio on nozzle performance over a range of freestream Mach numbers up to 2 was investigated. Results indicated that a 60 circumferential injection was a good compromise between large thrust vector angles and efficient internal nozzle performance. A cavity divergence angle greater than 10 was detrimental to thrust vector angle. Shortening the cavity length improved internal nozzle performance with a small penalty to thrust vector angle. Contrary to expectations, a variable expansion ratio did not improve thrust efficiency at the flight conditions investigated
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