21,362 research outputs found
Quantum phase-space analysis of the pendular cavity
We perform a quantum mechanical analysis of the pendular cavity, using the
positive-P representation, showing that the quantum state of the moving mirror,
a macroscopic object, has noticeable effects on the dynamics. This system has
previously been proposed as a candidate for the quantum-limited measurement of
small displacements of the mirror due to radiation pressure, for the production
of states with entanglement between the mirror and the field, and even for
superposition states of the mirror. However, when we treat the oscillating
mirror quantum mechanically, we find that it always oscillates, has no
stationary steady-state, and exhibits uncertainties in position and momentum
which are typically larger than the mean values. This means that previous
linearised fluctuation analyses which have been used to predict these highly
quantum states are of limited use. We find that the achievable accuracy in
measurement is far worse than the standard quantum limit due to thermal noise,
which, for typical experimental parameters, is overwhelming even at 2 mK.Comment: 25 pages, 6 figures To be published in Phys. Rev.
Combined production of broilers and fruits
Combined production of broilers and fruit trees is a subject often discussed in organic fruit
production in Denmark. Very little research has been carried out on this type of production
system. In organic production in Denmark, nearly no pesticides are allowed, so the need
for alternative pest control is large. Apple sawfly (Hoplocampa testudinea) and pear midge
(Contarinia pyrivora) cause big crop losses in apples and pears respectively, in unsprayed
organic fruit production. Both insects infest fruitlets and cause these to drop prematurely
after which the pests pupate in the topsoil. In the present experiment a research orchard
with the varieties ‘Discovery’ and ‘Conference’ were used as outdoor area for broilers to
minimise the population of sawflies and pear midges, and to reduce the need for weeding
and manuring. The trees were kept unsprayed. Fruit yield and fruit quality were assessed
at harvest. White sticky traps were placed in the test area in order to measure the
occurrence of sawfly over time. The infestation of pear midge was investigated counting
the infested fruitlets in clusters on trees at the centre of the plots. The catch of apple
sawflies was reduced in the combined apple and broiler production, but no significant
effect on the yield or the fruit quality was seen. Experiences from on-farm research show
that combining fruit and egg-production is one way to reduce the problem with apple
sawfly, but poultry alone is not a sufficient way of controlling sawflies. The welfare and
health of the broilers were excellent under fruit trees
Prevalence and predictors of postdischarge antibiotic use following mastectomy
OBJECTIVESurvey results suggest that prolonged administration of prophylactic antibiotics is common after mastectomy with reconstruction. We determined utilization, predictors, and outcomes of postdischarge prophylactic antibiotics after mastectomy with or without immediate breast reconstruction.DESIGNRetrospective cohort.PATIENTSCommercially insured women aged 18–64 years coded for mastectomy from January 2004 to December 2011 were included in the study. Women with a preexisting wound complication or septicemia were excluded.METHODSPredictors of prophylactic antibiotics within 5 days after discharge were identified in women with 1 year of prior insurance enrollment; relative risks (RR) were calculated using generalized estimating equations.RESULTSOverall, 12,501 mastectomy procedures were identified; immediate reconstruction was performed in 7,912 of these procedures (63.3%). Postdischarge prophylactic antibiotics were used in 4,439 procedures (56.1%) with immediate reconstruction and 1,053 procedures (22.9%) without immediate reconstruction (P<.001). The antibiotics most commonly prescribed were cephalosporins (75.1%) and fluoroquinolones (11.1%). Independent predictors of postdischarge antibiotics were implant reconstruction (RR, 2.41; 95% confidence interval [CI], 2.23–2.60), autologous reconstruction (RR, 2.17; 95% CI, 1.93–2.45), autologous reconstruction plus implant (RR, 2.11; 95% CI, 1.92–2.31), hypertension (RR, 1.05; 95% CI, 1.00–1.10), tobacco use (RR, 1.07; 95% CI, 1.01–1.14), surgery at an academic hospital (RR, 1.14; 95% CI, 1.07–1.21), and receipt of home health care (RR, 1.11; 95% CI, 1.04–1.18). Postdischarge prophylactic antibiotics were not associated with SSI after mastectomy with or without immediate reconstruction (bothP>.05).CONCLUSIONSProphylactic postdischarge antibiotics are commonly prescribed after mastectomy; immediate reconstruction is the strongest predictor. Stewardship efforts in this population to limit continuation of prophylactic antibiotics after discharge are needed to limit antimicrobial resistance.Infect Control Hosp Epidemiol2017;38:1048–1054</jats:sec
vbyCaHbeta CCD Photometry of Clusters. VIII. The Super-Metal Rich, Old Open Cluster NGC 6791
CCD photometry on the intermediate-band vbyCaHbeta system is presented for
the metal-rich, old open cluster, NGC 6791. Preliminary analysis led to [Fe/H]
above +0.4 with an anomalously high reddening and an age below 5 Gyr. A revised
calibration between (b-y)_0 and [Fe/H] at a given temperature shows that the
traditional color-metallicity relations underestimate the color of the turnoff
stars at high metallicity. With the revised relation, the metallicity from hk
and the reddening for NGC 6791 become [Fe/H] = +0.45 +/- 0.04 and E(b-y) =
0.113 +/- 0.012 or E(B-V) = 0.155 +/- 0.016. Using the same technique,
reanalysis of the photometry for NGC 6253 produces [Fe/H] = +0.58 +/-0.04 and
E(b-y) = 0.120 +/- 0.018 or E(B-V) = 0.160 +/- 0.025. The errors quoted include
both the internal and external errors. For NGC 6791, the metallicity from m_1
is a factor of two below that from hk, a result that may be coupled to the
consistently low metal abundance from DDO photometry of the cluster and the
C-deficiency found from high dispersion spectroscopy. E(B-V) is the same value
predicted from Galactic reddening maps. With E(B-V) = 0.15 and [Fe/H] = +0.45,
the available isochrones predict an age of 7.0 +/- 1.0 Gyr and an apparent
modulus of (m-M) = 13.60 +/- 0.15, with the dominant source of the uncertainty
arising from inconsistencies among the isochrones. The reanalysis of NGC 6253
with the revised lower reddening confirms that on both the hk and m_1
metallicity scales, NGC 6253, while less than half the age of NGC 6791, remains
at least as metal-rich as NGC 6791, if not richer.Comment: Accepted for Astronomical Journal. 42 p. latex file includes 11
figures and 3 tables, one of which is a short version of a data table to
appear in online AJ in its entiret
Supercooled Liquid Dynamics Studied via Shear-Mechanical Spectroscopy
We report dynamical shear-modulus measurements for five glass-forming liquids
(pentaphenyl trimethyl trisiloxane, diethyl phthalate, dibutyl phthalate,
1,2-propanediol, and m-touluidine). The shear-mechanical spectra are obtained
by the piezoelectric shear-modulus gauge (PSG) method. This technique allows
one to measure the shear modulus ( Pa) of the liquid within a
frequency range from 1 mHz to 10 kHz. We analyze the frequency-dependent
response functions to investigate whether time-temperature superposition (TTS)
is obeyed. We also study the shear-modulus loss-peak position and its
high-frequency part. It has been suggested that when TTS applies, the
high-frequency side of the imaginary part of the dielectric response decreases
like a power law of the frequency with an exponent -1/2. This conjecture is
analyzed on the basis of the shear mechanical data. We find that TTS is obeyed
for pentaphenyl trimethyl trisiloxane and in 1,2-propanediol while in the
remaining liquids evidence of a mechanical process is found. Although
the the high-frequency power law behavior of the shear-loss
may approach a limiting value of when lowering the temperature, we
find that the exponent lies systematically above this value (around 0.4). For
the two liquids without beta relaxation (pentaphenyl trimethyl trisiloxane and
1,2-propanediol) we also test the shoving model prediction, according to which
the the relaxation-time activation energy is proportional to the instantaneous
shear modulus. We find that the data are well described by this model.Comment: 7 pages, 6 figure
Quantum field effects in coupled atomic and molecular Bose-Einstein condensates
This paper examines the parameter regimes in which coupled atomic and
molecular Bose-Einstein condensates do not obey the Gross-Pitaevskii equation.
Stochastic field equations for coupled atomic and molecular condensates are
derived using the functional positive-P representation. These equations
describe the full quantum state of the coupled condensates and include the
commonly used Gross-Pitaevskii equation as the noiseless limit. The model
includes all interactions between the particles, background gas losses,
two-body losses and the numerical simulations are performed in three
dimensions. It is found that it is possible to differentiate the quantum and
semiclassical behaviour when the particle density is sufficiently low and the
coupling is sufficiently strong.Comment: 4 postscript figure
Understanding the fidelity effect when evaluating games with children
There have been a number of studies that have compared evaluation results from prototypes of different fidelities but very few of these are with children. This paper reports a comparative study of three prototypes ranging from low fidelity to high fidelity within the context of mobile games, using a between subject design with 37 participants aged 7 to 9. The children played a matching game on either an iPad, a paper prototype using screen shots of the actual game or a sketched version. Observational data was captured to establish the usability problems, and two tools from the Fun Toolkit were used to measure user experience. The results showed that there was little difference for user experience between the three prototypes and very few usability problems were unique to a specific prototype. The contribution of this paper is that children using low-fidelity prototypes can effectively evaluate games of this genre and style
A comparison of observed and simulated site response in the Rhône valley
Site effects in the city of Sion in the Rhône valley are analysed from weak motion signals recorded on a dense temporary array. We simulate the recorded events with a 3-D finite difference method for frequencies up to 4 Hz using a recently developed velocity model of the Sion basin. Site-to-reference Fourier spectral ratios are computed from 16 local and regional events. All sites exhibit amplification factors of up to 12 between 0.5 and 0.6 Hz, which can be reproduced by the numerical simulations. By rotating the weak motion to directions parallel and perpendicular to the valley axis, we show that this low-frequency amplification is caused by the SH00 and SV0 fundamental modes of 2-D resonance. Additional peaks of amplification can be observed at higher frequencies, with amplification factors of up to 20 at some sites. Application of the high-resolution frequency-wavenumber and the multiple signal characterization method to the vertical component of recorded and simulated signals show that edge-generated surface waves arriving from almost all directions dominate the wavefield at 1.25 and 2.50 Hz. Peak ground velocities computed from the simulated ground motion show interference patterns that depend strongly on the incidence direction, and the computed amplification of peak ground velocities are generally in agreement with the observations. We conclude that the complex 3-D geometry of the basin needs to be considered to evaluate site effects up to at least 2.5 H
A method to polarise antiprotons in storage rings and create polarised antineutrons
An intense circularely polarised photon beam interacts with a cooled
antiproton beam in a storage ring. Due to spin dependent absorption cross
sections for the reaction gamma+antiproton > pi- + antineutron a built-up of
polarisation of the stored antiprotons takes place. Figures-of-merit around 0.1
can be reached in principle over a wide range of antiproton energies. In this
process antineutrons with Polarisation > 70% emerge. The method is presented
for the case of 300 MeV/c cooled antiproton beam
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