4,404 research outputs found
Classical stability of a homogeneous, anisotropic inflating space-time
We study the classical stability of an anisotropic space-time seeded by a
spacelike, fixed norm, dynamical vector field in a vacuum-energy-dominated
inflationary era. It serves as a model for breaking isotropy during the
inflationary era. We find that, for a range of parameters, the linear
differential equations for small perturbations about the background do not have
a growing mode. We also examine the energy of fluctuations about this
background in flat-space. If the kinetic terms for the vector field do not take
the form of a field strength tensor squared then there is a negative energy
mode and the background is unstable. For the case where the kinetic term is of
the form of a field strength tensor squared we show that perturbations about
the background have positive energy at lowest order.Comment: 12 pages, no figures; references added, content in section V revised
and some clarification made in text; minor typos corrected, v4 closely
resembles version published in Phys. Rev. D; in v5 - incorrect argument in
section V removed and one reference adde
Crew Resource Management and Its Possible Role in Nursing Risk Management
Crew Resource Management (CRM) was introduced within the aviation industry in the late 1970s after an aircraft ran out of fuel whilst the pilots were trying to solve an undercarriage problem. To reduce such errors and ultimately lower the probability of failure and the severity of risks that occur, training in CRM was rolled out across the whole industry. It has been successful over the last few years in major reductions in the number of crashes and fatalities in the commercial aviation sector. Nursing has similar concerns in that errors can ultimately result in fatalities. There are parallels in the needs and expectations of pilots and nurses to assess risk, reduce risk and deliver reliable and dependable professional services. In this paper the parallels of pilots and nurses demands are compared to assess if the lessons learned in aviation can assist nurses deliver procedures with lower risks. The analysis will draw on the demands and expectations and how they both deal with risk, challenging errors and ensuring that identified risks are not overlooked or ignored. Finally, suggestions of adopting, sharing and benchmarking between these two industries can adopt best practices so that both industries can learn from each other
Stimulating Multiple-Demand Cortex Enhances Vocabulary Learning
It is well established that networks within multiple-demand cortex (MDC) become active when diverse skills and behaviors are being learnt. However, their causal role in learning remains to be established. In the present study, we first performed functional magnetic resonance imaging on healthy female and male human participants to confirm that MDC was most active in the initial stages of learning a novel vocabulary, consisting of pronounceable nonwords (pseudowords), each associated with a picture of a real object. We then examined, in healthy female and male human participants, whether repetitive transcranial magnetic stimulation of a frontal midline node of the cingulo-opercular MDC affected learning rates specifically during the initial stages of learning. We report that stimulation of this node, but not a control brain region, substantially improved both accuracy and response times during the earliest stage of learning pseudoword– object associations. This stimulation had no effect on the processing of established vocabulary, tested by the accuracy and response times when participants decided whether a real word was accurately paired with a picture of an object. These results provide evidence that noninvasive stimulation to MDC nodes can enhance learning rates, thereby demonstrating their causal role in the learning process. We propose that this causal role makes MDC candidate target for exper- imental therapeutics; for example, in stroke patients with aphasia attempting to reacquire a vocabulary
Chiral Perturbation Theory for , , and
We use heavy vector meson chiral perturbation theory
to predict differential decay distributions for and in the kinematic region where
(here or ) is much smaller than the
chiral symmetry breaking scale. Using the large number of colors limit we also
predict the rate for in this region (now
). Comparing our prediction with experimental data, we determine
one of the coupling constants in the heavy vector meson chiral Lagrangian.Comment: 14 pages, latex 2e. We include the decay of the tau into the omega,
pi minus and the tau neutrino, and extract a value for the coupling constant
g2, using experimental dat
Risk factors for wound infection in surgery for spinal metastasis
Wound infection rates are generally higher in patients undergoing surgery for spinal metastasis. Risk factors of wound infection in these patients are poorly understood.
Purpose
To identify demographic and clinical variables that may be associated with patients experiencing a higher wound infection rate.
Study design
Retrospective study with prospectively collected data of spinal metastasis patients operated consecutively at a University Teaching Hospital, adult spine division which is a tertiary referral centre for complex spinal surgery.
Patient sample
Ninety-eight patients were all surgically treated, consecutively from January 2009 to September 2011. Three patients had to be excluded due to inadequate data.
Outcome measures
Physiological measures, with presence or absence of microbiologically proven infection.
Methods
Various demographic and clinical data were recorded, including age, serum albumin level, blood total lymphocyte count, corticosteroid intake, Malnutrition Universal Screening Tool (MUST) score, neurological disability, skin closure material used, levels of surgery and administration of peri-operative corticosteroids. No funding was received from any sources for this study and as far as we are aware, there are no potential conflict of interest-associated biases in this study.
Results
Higher probabilities of infection were associated with low albumin level, seven or more levels of surgery, use of delayed/non-absorbable skin closure material and presence of neurological disability. Of these factors, levels of surgery were found to be statistically significant at the 5 % significance level.
Conclusion
Risk of infection is high (17.9 %) in patients undergoing surgery for spinal metastasis. Seven or more vertebral levels of surgery increase the risk of infection significantly (p < 0.05). Low albumin level and presence of neurological disability appear to show a trend towards increased risk of infection. Use of absorbable skin closure material, age, low lymphocyte count, peri-operative administration of corticosteroids and MUST score do not appear to influence the risk of infection
Chiral effective action with heavy quark symmetry
We derive an effective action combining chiral and heavy quark symmetry,
using approximate bosonization techniques of QCD. We explicitly show that the
heavy-quark limit is compatible with the large (number of color) limit in
the meson sector, and derive specific couplings between the light and heavy
mesons (, , ...) and their chiral partners. The relevance of this
effective action to solitons with heavy quarks describing heavy baryons is
discussed.Comment: 14 pages, SUNY-NTG-92/2
Black Holes with a Generalized Gravitational Action
Microscopic black holes are sensitive to higher dimension operators in the
gravitational action. We compute the influence of these operators on the
Schwarzschild solution using perturbation theory. All (time reversal invariant)
operators of dimension six are included (dimension four operators don't alter
the Schwarzschild solution). Corrections to the relation between the Hawking
temperature and the black hole mass are found. The entropy is calculated using
the Gibbons-Hawking prescription for the Euclidean path integral and using
naive thermodynamic reasoning. These two methods agree, however, the entropy is
not equal to 1/4 the area of the horizon.Comment: plain tex(uses phyzzx.tex), 8 pages, CALT-68-185
Explorations in anatomy: the remains from Royal London Hospital
This paper considers the faunal remains from recent excavations at the Royal London Hospital. The remains date to the beginning of the 19th century and offer an insight into the life of the hospital's patients and practices of the attached medical school. Many of the animal remains consist of partially dissected skeletons, including the unique finds of Hermann's tortoise (Testudo hermanni) and Cercopithecus monkey. The hospital diet and developments in comparative anatomy are discussed by integrating the results with documentary research. They show that zooarchaeological study of later post-medieval material can significantly enhance our understanding of the exploitation of animals in this perio
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