900 research outputs found
The Aharonov-Bohm Effect in the Fractional Quantum Hall Regime
We have investigated experimentally resonant tunnelling through
single-particle states formed around an antidot by a magnetic field, in the
fractional quantum Hall regime. For 1/3 filling factor around the antidot,
Aharonov-Bohm oscillations are observed with the same magnetic field period as
in the integer quantum Hall regime. All our measurements are consistent with
quasiparticles of fractional charge e*. However, the results are also
consistent with particles of any charge (>= e*) as the system must rearrange
every time the flux enclosed increases by h/e.Comment: Postscript, 4 pages, gzipped (350 kB
Electron transport and energy relaxation in dilute magnetic alloys
We consider the effect of the RKKY interaction between magnetic impurities on
the electron relaxation rates in a normal metal. The interplay between the RKKY
interaction and the Kondo effect may result in a non-monotonic temperature
dependence of the electron momentum relaxation rate, which determines the Drude
conductivity. The electron phase relaxation rate, which determines the
magnitude of the weak localization correction to the resistivity, is also a
non-monotonic function of temperature. For this function, we find the
dependence of the position of its maximum on the concentration of magnetic
impurities. We also relate the electron energy relaxation rate to the
excitation spectrum of the system of magnetic impurities. The energy relaxation
determines the distribution function for the out-of-equilibrium electrons.
Measurement of the electron distribution function thus may provide information
about the excitations in the spin glass phase.Comment: 15 pages, 5 figure
Does a facilitated pathway improve access to dental services for homeless and disadvantaged adults?
Access to dental care is poorer for people experiencing homelessness and disadvantage due to barriers such as lengthy waiting lists, lack of transport, lack of information and fear of authorities and treatment. This study aimed to evaluate a system integration model for oral health care for clients of homeless services in Brisbane, Australia. This model aimed to provide a facilitated access pathway between homeless community organisations and a public dental service to improve access to dental care. Participants were adult (≥18 years) clients Brisbane homeless community organisations. Those who participated in the intervention evaluation completed a questionnaire, had their oral health screened and followed up for feedback at their dental appointment. Seventy-six clients of community organisations in Brisbane participated in the intervention and its evaluation. Fear was a barrier to accessing dental services for 23% (n = 18). Attendance to the subsequent appointments at the public dental clinic was high, with 85% (n = 64) attending their first appointment. A higher proportion of participants who had surgical and prosthodontic treatment needs at the screening did not attend their appointment compared to those with other needs. Overall the model piloted in this study had positive outcomes; with high attendance rates to the dental facility and positive experiences by participants
A novel approach to isolating improved industrial interspecific wine yeasts using chromosomal mutations as potential markers for increased fitness
Wine yeast breeding programs utilizing interspecific hybridization deliver cost-effective tools to winemakers looking to differentiate their wines through the development of new wine styles. The addition of a non-Saccharomyces cerevisiae genome to a commercial wine yeast can generate novel phenotypes ranging from wine flavor and aroma diversity to improvements in targeted fermentation traits. In the current study we utilized a novel approach to screen isolates from an evolving population for increased fitness in a S. cerevisiae × S. uvarum interspecific hybrid previously generated to incorporate the targeted phenotype of lower volatile acidity production. Sequential grape-juice fermentations provided a selective environment from which to screen isolates. Chromosomal markers were used in a novel approach to identify isolates with potential increased fitness. A strain with increased fitness relative to its parents was isolated from an early timepoint in the evolving population, thereby minimizing the risk of introducing collateral mutations and potentially undesirable phenotypes. The evolved strain retained the desirable fermentation trait of reduced volatile acidity production, along with other winemaking traits of importance while exhibiting improved fermentation kinetics.Jennifer R. Bellon, Christopher M. Ford, Anthony R. Borneman and Paul J. Chamber
Contagious Equine Metritis: Efficacy of US post-entry testing protocols for identifying carrier stallions and mares
The cosmological constant and the coincidence problem in a new cosmological interpretation of the universal constant c
In a recent paper (Vigoureux et al. Int. J. Theor. Phys. 47:928, 2007) it has
been suggested that the velocity of light and the expansion of the universe are
two aspects of one single concept connecting space and time in the expanding
universe. It has then be shown that solving Friedmann's equations with that
interpretation (and keeping c = constant) can explain number of unnatural
features of the standard cosmology (for example: the flatness problem, the
problem of the observed uniformity in term of temperature and density of the
cosmological background radiation, the small-scale inhomogeneity problem...)
and leads to reconsider the Hubble diagram of distance moduli and redshifts as
obtained from recent observations of type Ia supernovae without having to need
an accelerating universe. In the present work we examine the problem of the
cosmological constant. We show that our model can exactly generate
(equation of state with ) contrarily to the standard model which cannot generate it exactly. We
also show how it can solve the so-called cosmic coincidence problem
Study protocol; thyroid hormone replacement for untreated older adults with subclinical hypothyroidism - a randomised placebo controlled trial (TRUST)
Background:
Subclinical hypothyroidism (SCH) is a common condition in elderly people, defined as elevated serum thyroid-stimulating hormone (TSH) with normal circulating free thyroxine (fT4). Evidence is lacking about the effect of thyroid hormone treatment. We describe the protocol of a large randomised controlled trial (RCT) of Levothyroxine treatment for SCH.
Methods:
Participants are community-dwelling subjects aged ≥65 years with SCH, diagnosed by elevated TSH levels (≥4.6 and ≤19.9 mU/L) on a minimum of two measures ≥ three months apart, with fT4 levels within laboratory reference range. The study is a randomised double-blind placebo-controlled parallel group trial, starting with levothyroxine 50 micrograms daily (25 micrograms in subjects <50Kg body weight or known coronary heart disease) with titration of dose in the active treatment group according to TSH level, and a mock titration in the placebo group. The primary outcomes are changes in two domains (hypothyroid symptoms and fatigue / vitality) on the thyroid-related quality of life questionnaire (ThyPRO) at one year. The study has 80% power (at p = 0.025, 2-tailed) to detect a change with levothyroxine treatment of 3.0% on the hypothyroid scale and 4.1% on the fatigue / vitality scale with a total target sample size of 750 patients.
Secondary outcomes include general health-related quality of life (EuroQol), fatal and non-fatal cardiovascular events, handgrip strength, executive cognitive function (Letter Digit Coding Test), basic and instrumental activities of daily living, haemoglobin, blood pressure, weight, body mass index and waist circumference. Patients are monitored for specific adverse events of interest including incident atrial fibrillation, heart failure and bone fracture.
Discussion:
This large multicentre RCT of levothyroxine treatment of subclinical hypothyroidism is powered to detect clinically relevant change in symptoms / quality of life and is likely to be highly influential in guiding treatment of this common condition.
Trial registration:
Clinicaltrials.gov NCT01660126; registered 8th June 2012
Tracking Curvaton(s)?
The ratio of the curvaton energy density to that of the dominant component of
the background sources may be constant during a significant period in the
evolution of the Universe. The possibility of having tracking curvatons, whose
decay occurs prior to the nucleosynthesis epoch, is studied. It is argued that
the tracking curvaton dynamics is disfavoured since the value of the curvature
perturbations prior to curvaton decay is smaller than the value required by
observations. It is also argued, in a related context, that the minimal
inflationary curvature scale compatible with the curvaton paradigm may be
lowered in the case of low-scale quintessential inflation.Comment: 20 pages, 4figure
Gravitational Coupling and Dynamical Reduction of The Cosmological Constant
We introduce a dynamical model to reduce a large cosmological constant to a
sufficiently small value. The basic ingredient in this model is a distinction
which has been made between the two unit systems used in cosmology and particle
physics. We have used a conformal invariant gravitational model to define a
particular conformal frame in terms of large scale properties of the universe.
It is then argued that the contributions of mass scales in particle physics to
the vacuum energy density should be considered in a different conformal frame.
In this manner, a decaying mechanism is presented in which the conformal factor
appears as a dynamical field and plays a key role to relax a large effective
cosmological constant. Moreover, we argue that this model also provides a
possible explanation for the coincidence problem.Comment: To appear in GR
Global Fluctuation Spectra in Big Crunch/Big Bang String Vacua
We study Big Crunch/Big Bang cosmologies that correspond to exact world-sheet
superconformal field theories of type II strings. The string theory spacetime
contains a Big Crunch and a Big Bang cosmology, as well as additional
``whisker'' asymptotic and intermediate regions. Within the context of free
string theory, we compute, unambiguously, the scalar fluctuation spectrum in
all regions of spacetime. Generically, the Big Crunch fluctuation spectrum is
altered while passing through the bounce singularity. The change in the
spectrum is characterized by a function , which is momentum and
time-dependent. We compute explicitly and demonstrate that it arises
from the whisker regions. The whiskers are also shown to lead to
``entanglement'' entropy in the Big Bang region. Finally, in the Milne orbifold
limit of our superconformal vacua, we show that and, hence, the
fluctuation spectrum is unaltered by the Big Crunch/Big Bang singularity. We
comment on, but do not attempt to resolve, subtleties related to gravitational
backreaction and light winding modes when interactions are taken into account.Comment: 68 pages, 1 figure; typos correcte
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