1,678 research outputs found
Development of the sources of work stress inventory.
This article describes the development of the Sources of Work Stress Inventory (SWSI). Factor analyses of the generated items produced (a) a General Work Stress Scale and (b) eight Sources of Work Stress scales, namely Bureaucracy/Autonomy, Relationships, Tools and Equipment, Workload, Role Ambiguity, Work/Home Interface, Job Security and Career Advancement. Rasch rating scale analyses supported the construct validity and reliability of the scales. A multiple regression analysis confirmed the expected strong relationship between the different sources of work stress and the experience of stress in the workplace. It is concluded that the SWSI shows promise as a measure of work stress in the South African context
Bronchodilator tolerance and rebound bronchoconstriction during regular inhaled β -agonist treatment
AbstractThere is uncertainty about the development of airway tolerance to β -agonists and the phenomenon of rebound bronchoconstriction on β -agonist withdrawal. We have recently completed a study of the regular terbutaline and budesonide treatment in asthma. We report our observations on the effect of starting and stopping terbutaline treatment on morning and evening peak flows.The study was a randomized four-way, double-dummy, cross-over comparison of regular inhaled terbutaline (500–1000 μ g four times daily), budesonide, combined treatment and matching placebo. Each treatment was given for 6 weeks following a 4 week single-blind placebo washout. Ipratropium was used for symptom relief. No other asthma medication was permitted during either the treatment or wash-out periods. Evaluable data were obtained from 52 subjects for both placebo and terbutaline treatment. Changes in mean morning and evening peak flows during terbutaline treatment were compared to the baseline peak flows during the last 2 weeks of the preceding washout. The peak flow changes on stopping terbutaline were also analysed.Mean morning peak flow was not significantly different during terbutaline treatment when compared to either baseline or placebo treatment. Evening peak flows were significantly higher during terbutaline treatment [mean increase 23·1l min−1(95%CI=18·8, 27·4)]. Analysis of the peak flow changes on a day-by-day basis revealed an initial increase in morning peak flows for the first 2 days of treatment of 19·2 and 13·4l min−1[increases of 25·0 and 17·3l min−1in comparison with the corresponding values during placebo (P<0·01)] followed by a return to baseline. The increase in evening peak flows was also greater for the first 2 days of treatment than for the remainder of the treatment period (P<0·01). On ceasing terbutaline treatment there was a fall in mean morning peak flow below the baseline on the following morning of 21·6l min−1(P<0·05 compared to placebo).The temporary increase in morning peak flows and greater than expected rise in evening peak flows for the first 2 days of treatment suggest the development of tolerance to the bronchodilator effect of terbutaline. Similarly, the fall in morning peak flows on treatment withdrawal suggests rebound bronchoconstriction. These effects are likely to be mediated by downregulation of the β -receptor during treatment. The clinical significance of these changes is uncertain in view of the stability of overall asthma control during terbutaline treatment, but sudden withdrawal of β -agonist treatment could conceivably lead to a deterioration in asthma control
Bound States and Power Counting in Effective Field Theories
The problem of bound states in effective field theories is studied. A
rescaled version of nonrelativistic effective field theory is formulated which
makes the velocity power counting of operators manifest. Results obtained using
the rescaled theory are compared with known results from NRQCD. The same ideas
are then applied to study Yukawa bound states in 1+1 and 3+1 dimensions, and to
analyze when the Yukawa potential can be replaced by a delta-function
potential. The implications of these results for the study of nucleon-nucleon
scattering in chiral perturbation theory is discussed.Comment: 23 pages, eps figures, uses revte
Partial Regularity of solutions to the Four-dimensional Navier-Stokes equations at the first blow-up time
The solutions of incompressible Navier-Stokes equations in four spatial
dimensions are considered. We prove that the two-dimensional Hausdorff measure
of the set of singular points at the first blow-up time is equal to zero.Comment: 19 pages, a comment regarding five or higher dimensional case is
added in Remark 1.3. accepted by Comm. Math. Phy
Non-adiabatic quantum effects from a Standard Model time-dependent Higgs vev
We consider the time-dependence of the Higgs vacuum expectation value (vev)
given by the dynamics of the Standard Model and study the non-adiabatic
production of both bosons and fermions, which is intrinsically
non-perturbative. In the Hartree approximation, we analyse the general
expressions that describe the dissipative dynamics due to the back-reaction of
the produced particles. In particular, we solve numerically some relevant cases
for the Standard Model phenomenology in the regime of relatively small
oscillations of the Higgs vev.Comment: 35 pages, 15 figures and 2 table
Residual meson-meson interaction from lattice gauge simulation in a simple QED model
The residual interaction for a meson-meson system is computed utilizing the
cumulant, or cluster, expansion of the momentum-space time correlation matrix.
The cumulant expansion serves to define asymptotic, or free, meson-meson
operators. The definition of an effective interaction is then based on a
comparison of the full (interacting) and the free (noninteracting) time
correlation matrices. The proposed method, which may straightforwardly be
transcribed to other hadron-hadron systems, here is applied to a simple 2+1
dimensional U(1) lattice gauge model tuned such that it is confining. Fermions
are treated in the staggered scheme. The effective interaction exhibits a
repulsive core and attraction at intermediate relative distances. These
findings are consistent with an earlier study of the same model utilizing
L\"{u}scher's method where scattering phase shifts are obtained directly.Comment: 28 pages, compressed postscript fil
Hydrodynamic Synchronisation of Model Microswimmers
We define a model microswimmer with a variable cycle time, thus allowing the
possibility of phase locking driven by hydrodynamic interactions between
swimmers. We find that, for extensile or contractile swimmers, phase locking
does occur, with the relative phase of the two swimmers being, in general,
close to 0 or pi, depending on their relative position and orientation. We show
that, as expected on grounds of symmetry, self T-dual swimmers, which are
time-reversal covariant, do not phase-lock. We also discuss the phase behaviour
of a line of tethered swimmers, or pumps. These show oscillations in their
relative phases reminiscent of the metachronal waves of cilia.Comment: 17 pages, 8 figure
Larval fish dispersal in a coral-reef seascape
Free to read at publisher's site. Larval dispersal is a critical yet enigmatic process in the persistence and productivity of marine metapopulations. Empirical data on larval dispersal remain scarce, hindering the use of spatial management tools in efforts to sustain ocean biodiversity and fisheries. Here we document dispersal among subpopulations of clownfish (Amphiprion percula) and butterflyfish (Chaetodon vagabundus) from eight sites across a large seascape (10,000 km(2)) in Papua New Guinea across 2 years. Dispersal of clownfish was consistent between years, with mean observed dispersal distances of 15 km and 10 km in 2009 and 2011, respectively. A Laplacian statistical distribution (the dispersal kernel) predicted a mean dispersal distance of 13-19 km, with 90% of settlement occurring within 31-43 km. Mean dispersal distances were considerably greater (43-64 km) for butterfly-fish, with kernels declining only gradually from spawning locations. We demonstrate that dispersal can be measured on spatial scales sufficient to inform the design of and test the performance of marine reserve networks
Detection Limits for Super-Hubble Suppression of Causal Fluctuations
We investigate to what extent future microwave background experiments might
be able to detect a suppression of fluctuation power on large scales in flat
and open universe models. Such suppression would arise if fluctuations are
generated by causal processes, and a measurement of a small suppression scale
would be problematic for inflation models, but consistent with many defect
models. More speculatively, a measurement of a suppression scale of the order
of the present Hubble radius could provide independent evidence for a
fine-tuned inflation model leading to a low-density universe. We find that,
depending on the primordial power spectrum, a suppression scale modestly larger
than the visible Horizon can be detected, but that the detectability drops very
rapidly with increasing scale. For models with two periods of inflation, there
is essentially no possibility of detecting a causal suppression scale.Comment: 8 pages, 4 figures, revtex, In Press Physical Review D 200
The status of GEO 600
The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode
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