924 research outputs found
Phase transitions and the internal noise structure of nonlinear Schr\"odi nger equation solitons
We predict phase-transitions in the quantum noise characteristics of systems
described by the quantum nonlinear Schr\"odinger equation, showing them to be
related to the solitonic field transition at half the fundamental soliton
amplitude. These phase-transitions are robust with respect to Raman noise and
scattering losses. We also describe the rich internal quantum noise structure
of the solitonic fields in the vicinity of the phase-transition. For optical
coherent quantum solitons, this leads to the prediction that eliminating the
peak side-band noise due to the electronic nonlinearity of silica fiber by
spectral filtering leads to the optimal photon-number noise reduction of a
fundamental soliton.Comment: 10 pages, 5 figure
Considerations for the optimal management of antibiotic therapy in elderly patients
Objectives: To maximise efficacy and minimise toxicity, special considerations are required for antibiotic prescription in elderly patients. This review aims to provide practical suggestions for the optimal management of antibiotic therapy in elderly patients. Methods: This was a narrative review. A literature search of published articles in the last 15 years on antibiotics and elderly patients was performed using the Cochrane Library and PubMed electronic databases. The three priority areas were identified: (i) pharmacokinetics/pharmacodynamics (PK/PD) for optimising dosage regimens and route of administration; (ii) antibiotic dosages in some special subpopulations; and (iii) treatment considerations relating to different antibiotic classes and their adverse events. Results: Clinicians should understand the altered PK/PD of drugs in this population owing to co-morbid conditions and normal physiological changes associated with ageing. The body of evidence justifies the need for individualised dose selection, especially in patients with impaired renal and liver function. Clinicians should be aware of the major drug–drug interactions commonly observed in the elderly as well as potential side effects. Conclusion: Antibiotic therapy in the elderly requires a comprehensive approach, including strategies to improve appropriate antibiotic prescribing, limit their use for uncomplicated infections and ensure the attainment of an optimal PK/PD target. To this purpose, further studies involving the elderly are needed to better understand the PK of antibiotics. Moreover, it is necessary to assess the role therapeutic drug monitoring in guiding antibiotic therapy in elderly patients in order to evaluate its impact on clinical outcome
The Detection of New Methanol Masers in the 5_{-1}-4_0E Line
Fifty-one objects in the 5_{-1}-4_0E methanol line at 84.5 GHz were detected
during a survey of Class I maser sources. Narrow maser features were found in
17 of these. Broad quasi-thermal lines were detected towards other sources. One
of the objects with narrow features, the young bipolar outflow L 1157 was also
observed in the 8_0-7_1A+ line at 95.2 GHz; a narrow line was detected at this
frequency. Analysis showed that the broad lines are usually inverted. The
quasi-thermal profiles imply that the line opacities are not larger than
several units. These results confirm the plausibility of models in which
compact Class I masers appear in extended sources as a result of an appropriate
velocity field.
Measurements of linear polarization at 84.5 GHz in 13 sources were made. No
polarization was found except a tentative detection of a weak polarization in M
8E
Molecular line contamination in the SCUBA-2 450 {\mu}m and 850 {\mu}m continuum data
Observations of the dust emission using millimetre/submillimetre bolometer
arrays can be contaminated by molecular line flux, such as flux from 12CO. As
the brightest molecular line in the submillimetre, it is important to quantify
the contribution of CO flux to the dust continuum bands. Conversion factors
were used to convert molecular line integrated intensities to flux detected by
bolometer arrays in mJy per beam. These factors were calculated for 12CO line
integrated intensities to the SCUBA-2 850 {\mu}m and 450 {\mu}m bands. The
conversion factors were then applied to HARP 12CO 3-2 maps of NGC 1333 in the
Perseus complex and NGC 2071 and NGC 2024 in the Orion B molecular cloud
complex to quantify the respective 12CO flux contribution to the 850 {\mu}m
dust continuum emission. Sources with high molecular line contamination were
analysed in further detail for molecular outflows and heating by nearby stars
to determine the cause of the 12CO contribution. The majority of sources had a
12CO 3-2 flux contribution under 20 per cent. However, in regions of molecular
outflows, the 12CO can dominate the source dust continuum (up to 79 per cent
contamination) with 12CO fluxes reaching \sim 68 mJy per beam.Comment: Accepted 2012 April 19 for publication in MNRAS. 21 pages, 13
figures, 3 table
Global Study of Electron-Quark Contact Interactions
We perform a global fit of data relevant to contact interactions,
including deep inelastic scattering at high from ZEUS and H1, atomic
physics parity violation in Cesium from JILA, polarized on nuclei
scattering experiments at SLAC, Mainz and Bates, Drell-Yan production at the
Tevatron, the total hadronic cross section at LEP, and
neutrino-nucleon scattering from CCFR. With only the new HERA data, the
presence of contact interactions improves the fit compared to the Standard
Model. When other data sets are included, the size of the contact contributions
is reduced and the overall fit represents no real improvement over the Standard
Model.Comment: 26 pages (now single-spaced), Revtex, 2 eps figures, uses epsf.sty.
Some clarifications, minor corrections, 2 new references, also 3 new tables
which present 95% CL bounds on the contact interaction scales Lambd
Spatially Resolved Chemistry in Nearby Galaxies I. The Center of IC 342
We have imaged emission from the millimeter lines of eight molecules--C2H,
C34S, N2H+, CH3OH, HNCO, HNC, HC3N, and SO--in the central half kpc of the
nearby spiral galaxy IC 342. The 5" (~50 pc) resolution images were made with
OVRO. Using these maps we obtain a picture of the chemistry within the nuclear
region on the sizescales of individual GMCs. Bright emission is detected from
all but SO. There are marked differences in morphology for the different
molecules. A principal component analysis is performed to quantify similarities
and differences among the images. This analysis reveals that while all
molecules are to zeroth order correlated, that is, they are all found in dense
molecular clouds, there are three distinct groups of molecules distinguished by
the location of their emission within the nuclear region. N2H+, C18O, HNC and
HCN are widespread and bright, good overall tracers of dense molecular gas. C2H
and C34S, tracers of PDR chemistry, originate exclusively from the central
50-100 pc region, where radiation fields are high. The third group of
molecules, CH3OH and HNCO, correlates well with the expected locations of
bar-induced orbital shocks. The good correlation of HNCO with the established
shock tracer molecule CH3OH is evidence that this molecule, whose chemistry has
been uncertain, is indeed produced by processing of grains. HC3N is observed to
correlate tightly with 3mm continuum emission, demonstrating that the young
starbursts are the sites of the warmest and densest molecular gas. We compare
our HNC images with the HCN images of Downes et al. (1992) to produce the first
high resolution, extragalactic HCN/HNC map: the HNC/HCN ratio is near unity
across the nucleus and the correlation of both of these gas tracers with the
star formation is excellent. (Abridged).Comment: 54 pages including 10 figures and 8 tables. Accepted for publication
in Ap
Dynamical quantum noise in Bose-Einstein condensates
We introduce the study of dynamical quantum noise in Bose-Einstein
condensates through numerical simulation of stochastic partial differential
equations obtained using phase space representations. We derive evolution
equations for a single trapped condensate in both the positive- and Wigner
representations, and perform simulations to compare the predictions of the two
methods. The positive- approach is found to be highly susceptible to the
stability problems that have been observed in other strongly nonlinear, weakly
damped systems. Using the Wigner representation, we examine the evolution of
several quantities of interest using from a variety of choices of initial state
for the condensate, and compare results to those for single-mode models.Comment: 8 figures, submitted to Phys. Rev.
Bell-inequality violation with "thermal" radiation
The model of a quantum-optical device for a conditional preparation of
entangled states from input mixed states is presented. It is demonstrated that
even thermal or pseudo-thermal radiation can be entangled in such a way, that
Bell-inequalities are violated
HARP/ACSIS: A submillimetre spectral imaging system on the James Clerk Maxwell Telescope
This paper describes a new Heterodyne Array Receiver Programme (HARP) and
Auto-Correlation Spectral Imaging System (ACSIS) that have recently been
installed and commissioned on the James Clerk Maxwell Telescope (JCMT). The
16-element focal-plane array receiver, operating in the submillimetre from 325
to 375 GHz, offers high (three-dimensional) mapping speeds, along with
significant improvements over single-detector counterparts in calibration and
image quality. Receiver temperatures are 120 K across the whole band and
system temperatures of 300K are reached routinely under good weather
conditions. The system includes a single-sideband filter so these are SSB
figures. Used in conjunction with ACSIS, the system can produce large-scale
maps rapidly, in one or more frequency settings, at high spatial and spectral
resolution. Fully-sampled maps of size 1 square degree can be observed in under
1 hour.
The scientific need for array receivers arises from the requirement for
programmes to study samples of objects of statistically significant size, in
large-scale unbiased surveys of galactic and extra-galactic regions. Along with
morphological information, the new spectral imaging system can be used to study
the physical and chemical properties of regions of interest. Its
three-dimensional imaging capabilities are critical for research into
turbulence and dynamics. In addition, HARP/ACSIS will provide highly
complementary science programmes to wide-field continuum studies, and produce
the essential preparatory work for submillimetre interferometers such as the
SMA and ALMA.Comment: MNRAS Accepted 2009 July 2. 18 pages, 25 figures and 6 table
Symptoms of anxiety and depression across adulthood and blood pressure in late middle age: the 1946 British birth cohort.
Previous studies testing the hypothesis that symptoms of anxiety and depression increase blood pressure (BP) levels show inconsistent and limited findings. We examined the association between those symptoms across adult life and BP in late middle age
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