1,665 research outputs found
Edwardsiella ictaluri encodes an acid-activated urease that is required for intracellular replication in channel catfish (Ictalurus punctatus) macrophages
Genomic analysis indicated that Edwardsiella ictaluri encodes a putative urease pathogenicity island containing the products of nine open reading frames, including urea and ammonium transporters. In vitro studies with wild-type E. ictaluri and a ureG::kan urease mutant strain indicated that E. ictaluri is significantly tolerant of acid conditions (pH 3.0) but that urease activity is not required for acid tolerance. Growth studies demonstrated that E. ictaluri is unable to grow at pH 5 in the absence of urea but is able to elevate the environmental pH from pH 5 to pH 7 and grow when exogenous urea is available. Substantial production of ammonia was observed for wild-type E. ictaluri in vitro in the presence of urea at low pH, and optimal activity occurred at pH 2 to 3. No ammonia production was detected for the urease mutant. Proteomic analysis with two-dimensional gel electrophoresis indicated that urease proteins are expressed at both pH 5 and pH 7, although urease activity is detectable only at pH 5. Urease was not required for initial invasion of catfish but was required for subsequent proliferation and virulence. Urease was not required for initial uptake or survival in head kidney-derived macrophages but was required for intracellular replication. Intracellular replication of wild-type E. ictaluri was significantly enhanced when urea was present, indicating that urease plays an important role in intracellular survival and replication, possibly through neutralization of the acidic environment of the phagosome. Copyright © 2009, American Society for Microbiology. All Rights Reserved
Application of Modern Fortran to Spacecraft Trajectory Design and Optimization
In this paper, applications of the modern Fortran programming language to the field of spacecraft trajectory optimization and design are examined. Modern object-oriented Fortran has many advantages for scientific programming, although many legacy Fortran aerospace codes have not been upgraded to use the newer standards (or have been rewritten in other languages perceived to be more modern). NASA's Copernicus spacecraft trajectory optimization program, originally a combination of Fortran 77 and Fortran 95, has attempted to keep up with modern standards and makes significant use of the new language features. Various algorithms and methods are presented from trajectory tools such as Copernicus, as well as modern Fortran open source libraries and other projects
Protecting quantum entanglement from leakage and qubit errors via repetitive parity measurements
Protecting quantum information from errors is essential for large-scale
quantum computation. Quantum error correction (QEC) encodes information in
entangled states of many qubits, and performs parity measurements to identify
errors without destroying the encoded information. However, traditional QEC
cannot handle leakage from the qubit computational space. Leakage affects
leading experimental platforms, based on trapped ions and superconducting
circuits, which use effective qubits within many-level physical systems. We
investigate how two-transmon entangled states evolve under repeated parity
measurements, and demonstrate the use of hidden Markov models to detect leakage
using only the record of parity measurement outcomes required for QEC. We show
the stabilization of Bell states over up to 26 parity measurements by
mitigating leakage using postselection, and correcting qubit errors using
Pauli-frame transformations. Our leakage identification method is
computationally efficient and thus compatible with real-time leakage tracking
and correction in larger quantum processors.Comment: 22 pages, 15 figure
Moral Attributes In A Dictator Game
This paper investigates whether or not the moral factors captured in an emotional intelligence assessment matter in the economic decisions made by subjects in a dictator game. We find a statistically significant relationship between the amount of the dictator’s contribution and a few of the factors of the Intrapersonal Dimension of the EQ-i. We also find a significant relationship between dictator contributions and an adjusted EQ-i score, measures of independence, know-my-own and empathy. Our results may be relevant to researchers interested in understanding the preference set of economic decision-makers. Moreover, for those interested in refining experimental design protocols, we show the EQ-i to be a useful resource to control for a few of the moral attributes Levitt et al. (2006) suggest are so very important in understanding laboratory and field experiments.
Electrodynamics of Abrikosov vortices: the Field Theoretical Formulation
Electrodynamic phenomena related to vortices in superconductors have been
studied since their prediction by Abrikosov, and seem to hold no fundamental
mysteries. However, most of the effects are treated separately, with no guiding
principle. We demonstrate that the relativistic vortex worldsheet in spacetime
is the object that naturally conveys all electric and magnetic information, for
which we obtain simple and concise equations. Breaking Lorentz invariance leads
to down-to-earth Abrikosov vortices, and special limits of these equations
include for instance dynamic Meissner screening and the AC Josephson relation.
On a deeper level, we explore the electrodynamics of two-form sources in the
absence of electric monopoles, in which the electromagnetic field strength
itself acquires the characteristics of a gauge field. This novel framework
leaves room for unexpected surprises.Comment: LaTeX, 23 pages, 5 figure
An Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primar Star
We describe optical photometric and spectroscopic observations of the bright
variable BG Geminorum. Optical photometry shows a pronounced ellipsoidal
variation of the K0 I secondary, with amplitudes of ~0.5 mag at VRI and a
period of 91.645 days. A deep primary eclipse is visible for wavelengths <
4400A; a shallower secondary eclipse is present at longer wavelengths. Eclipse
timings and the radial velocity curve of the K0 secondary star indicate an
interacting binary where a lobe-filling secondary, M_2 ~ 0.5 Msun, transfers
material into a extended disk around a massive primary, M_1 ~ 4.5 Msun. The
primary star is either an early B-type star or a black hole. If it did contain
a black hole, BG Gem would be the longest period black hole binary known by a
factor of 10, as well as the only eclipsing black hole binary system.Comment: 27 pages, includes 8 figures and 5 tables, accepted to A
Dns of supersonic turbulent boundary layers over weakly and strongly adiabatic walls
We present spatially developing direct numerical simulations (DNS) of turbulent boundary layers at Mach 3 and Mach 7 with Reτ ≈ 600. In this work we make an explicit distinction in the wall thermal boundary condition, which, to our knowledge, has not been addressed in the literature. Namely, we deem "weakly adiabatic" walls as those whose temperature is fixed at the recovery temperature, and "strongly adiabatic" walls as those that enforce null heat transfer in the local and instantaneous sense. These two boundary conditions are bracketing cases for real materials that have finite, non-zero thermal diffusivities. Using scaling arguments, we propose a dimensionless quantity, the "fluctuation Nusselt number," as the relevant similarity parameter describing the thermal damping at the wall. Furthermore, we demonstrate that this parameter can vary by many orders of magnitude due to different thermal diffusivities of relevant wall materials and different edge Mach numbers. By design, the "weakly adiabatic" boundary condition damps near wall temperature fluctuations, which helps to enforce the assumption of weak total temperature fluctuations built into much of the theory for compressible boundary layers. Adopting a "strongly adiabatic" wall will place greater strain on these assumptions and may be more relevant to flight conditions of interest. Here we present data at Mach 3 for both boundary conditions, and at Mach 7 for the "strongly adiabatic" case. The simulations are spatially developing and have large domains to prevent unphysical forcing due to the inflow and spanwise boundary conditions, as discussed in Beekman, Priebe, Kan & Martin. 1 For all three data sets we present basic turbulence statistics and note that a non negligible effect is observed due to the differences in wall boundary condition
Depression and anxiety, an Indicated Prevention (DIP) protocol in homes for the elderly: feasibility and (cost) effectiveness of a stepped care programme
BACKGROUND: Depressive and anxiety disorders are a very common, serious and underdetected problem in homes for the elderly. Elderly persons in residential homes are at high risk for developing major depressive and anxiety disorders, and, therefore, deserve attention with regard to prevention. METHODS/DESIGN: This protocol describes a randomised trial on the feasibility and (cost) effectiveness of a stepped-care programme for prevention of depressive and anxiety disorders in homes for the elderly. The main outcome measure is the incidence of depressive and anxiety disorder in one year with a two years follow up. Secondary outcomes are symptoms of depression and anxiety, quality of life, direct health care costs and satisfaction with treatment. DISCUSSION: The number of studies examining the effects of preventive interventions on the incidence of mental disorders in the elderly population is very small. However, indicated prevention by means of a stepped-care programme seems to be an important option for decreasing the burden of illness for residents and their caregivers. This study contributes to the body of knowledge in this field. Positive effects may contribute to further use and development of tailored, (cost-) effective and easy to use interventions in a preventive stepped-care programme. TRIAL REGISTRATION: The Dutch Cochrane Centre, ISRCTN2754073
- …