1,084 research outputs found
On the ubiquity of molecular anions in the dense interstellar medium
Results are presented from a survey for molecular anions in seven nearby
Galactic star-forming cores and molecular clouds. The hydrocarbon anion C6H- is
detected in all seven target sources, including four sources where no anions
have been previously detected: L1172, L1389, L1495B and TMC-1C. The C6H-/C6H
column density ratio is greater than about 1.0% in every source, with a mean
value of 3.0% (and standard deviation 0.92%). Combined with previous
detections, our results show that anions are ubiquitous in dense clouds
wherever C6H is present. The C6H-/C6H ratio is found to show a positive
correlation with molecular hydrogen number density, and with the apparent age
of the cloud. We also report the first detection of C4H- in TMC-1 (at 4.8-sigma
confidence), and derive an anion-to-neutral ratio C4H-/C4H = (1.2 +- 0.4) x
10^-5 (= 0.0012 +- 0.0004%). Such a low value compared with C6H- highlights the
need for a revised radiative electron attachment rate for C4H. Chemical model
calculations show that the observed C4H- could be produced as a result of
reactions of oxygen atoms with C5H- and C6H-
Molecular Tracers of Embedded Star Formation in Ophiuchus
In this paper we analyze nine SCUBA cores in Ophiuchus using the
second-lowest rotational transitions of four molecular species (12CO, 13CO,
C18O, and C17O) to search for clues to the evolutionary state and
star-formation activity within each core. Specifically, we look for evidence of
outflows, infall, and CO depletion. The line wings in the CO spectra are used
to detect outflows, spectral asymmetries in 13CO are used to determine infall
characteristics, and a comparison of the dust emission (from SCUBA
observations) and gas emission (from C18O) is used to determine the fractional
CO freeze-out.
Through comparison with Spitzer observations of protostellar sources in
Ophiuchus, we discuss the usefulness of CO and its isotopologues as the sole
indicators of the evolutionary state of each core. This study is an important
pilot project for the JCMT Legacy Survey of the Gould Belt (GBS) and the
Galactic Plane (JPS), which intend to complement the SCUBA-2 dust continuum
observations with HARP observations of 12CO, 13CO, C18O, and C17O J = 3 - 2 in
order to determine whether or not the cold dust clumps detected by SCUBA-2 are
protostellar or starless objects.
Our classification of the evolutionary state of the cores (based on molecular
line maps and SCUBA observations) is in agreement with the Spitzer designation
for six or seven of the nine SCUBA cores. However, several important caveats
exist in the interpretation of these results, many of which large mapping
surveys like the GBS may be able to overcome to provide a clearer picture of
activity in crowded fields.Comment: 43 pages including 19 postscript figures. Accepted for publication in
the PAS
Correlated Photons from Collective Excitations of Three-Level Atomic Ensemble
We systematically study the interaction between two quantized optical fields
and a cyclic atomic ensemble driven by a classic optical field. This so-called
atomic cyclic ensemble consists of three-level atoms with Delta-type
transitions due to the symmetry breaking, which can also be implemented in the
superconducting quantum circuit by Yu-xi Liu et al. [Phys. Rev. Lett. 95,
087001 (2005)]. We explore the dynamic mechanisms to creating the quantum
entanglements among photon states, and between photons and atomic collective
excitations by the coherent manipulation of the atom-photon system. It is shown
that the quantum information can be completely transferred from one quantized
optical mode to another, and the quantum information carried by the two
quantized optical fields can be stored in the collective modes of this atomic
ensemble by adiabatically controlling the classic field Rabi frequencies.Comment: 10 pages, 2 figure
A Surface-Gated InSb Quantum Well Single Electron Transistor
Single electron charging effects in a surface-gated InSb/AlInSb QW structure
are reported. This material, due to its large g-factor and light effective
mass, offers considerable advantages over more commonly used materials, such as
GaAs, for quantum information processing devices. However, differences in
material and device technology result in significant processing challenges.
Simple Coulomb blockade and quantised confinement models are considered to
explain the observation of conductance oscillations in these structures. The
charging energy is found to be comparable with the energy spectrum for single
particle states
Systems mapping workshops and their role in understanding medication errors in healthcare
In this paper for Applied Ergonomics, one of the two leading journals for ergonomics/human factors, Buckle et al. discuss the role of mapping workshops in understanding medication errors in healthcare. They draw upon research that used mapping workshops as a method that systems designers, including human factors/ergonomics specialists, can use to help generate a knowledge base for better design requirements.
Buckle et al. applied systems mapping workshops for the first time to the problem of medication errors in healthcare. The workshops were designed using experiential group work principles. They involved a range of stakeholders from within the health service as well as those who supply the health sector, including designers who may be able to enhance the safety of products and systems used in healthcare.
The opportunity for using these methods to study patient safety issues arose as a result of a scoping study undertaken on behalf of the UK Department of Health and The Design Council. As the scope of patient safety issues within the healthcare system and the range of stakeholder groups is large (National Patient Safety Agency 2005), it was believed that mapping workshops might enhance system design in health. The results were rich from a design perspective, giving specific details of actual incidences, contexts and practices, with further depth of information emerging in the group working sessions. A wealth of detail on aspects of medication error, especially in the community, emerged from creative, primary, secondary and patient-support group sessions. As a process, similar stakeholder workshops could help designers understand better the complexity and range of factors to be taken into account.
The methods are now being used in many areas of healthcare and social care design, for example by the Technology Strategy Board funded research into Telecare (see http://www.aktive.org.uk/)
Shoulder posture and median nerve sliding
Background: Patients with upper limb pain often have a slumped sitting position and poorshoulder posture. Pain could be due to poor posture causing mechanical changes (stretch; localpressure) that in turn affect the function of major limb nerves (e.g. median nerve). This studyexamines (1) whether the individual components of slumped sitting (forward head position, trunkflexion and shoulder protraction) cause median nerve stretch and (2) whether shoulderprotraction restricts normal nerve movements.Methods: Longitudinal nerve movement was measured using frame-by-frame cross-correlationanalysis from high frequency ultrasound images during individual components of slumped sitting.The effects of protraction on nerve movement through the shoulder region were investigated byexamining nerve movement in the arm in response to contralateral neck side flexion.Results: Neither moving the head forward or trunk flexion caused significant movement of themedian nerve. In contrast, 4.3 mm of movement, adding 0.7% strain, occurred in the forearm duringshoulder protraction. A delay in movement at the start of protraction and straightening of thenerve trunk provided evidence of unloading with the shoulder flexed and elbow extended and thescapulothoracic joint in neutral. There was a 60% reduction in nerve movement in the arm duringcontralateral neck side flexion when the shoulder was protracted compared to scapulothoracicneutral.Conclusion: Slumped sitting is unlikely to increase nerve strain sufficient to cause changes tonerve function. However, shoulder protraction may place the median nerve at risk of injury, sincenerve movement is reduced through the shoulder region when the shoulder is protracted andother joints are moved. Both altered nerve dynamics in response to moving other joints and localchanges to blood supply may adversely affect nerve function and increase the risk of developingupper quadrant pain
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
JHK Observations of Faint Standard Stars in the Mauna Kea Near-Infrared Photometric System
JHK photometry in the Mauna Kea Observatory (MKO) near-IR system is presented
for 115 stars. Of these, 79 are UKIRT standards and 42 are LCO standards. The
average brightness is 11.5 mag, with a range of 10 to 15. The average number of
nights each star was observed is 4, and the average of the internal error of
the final results is 0.011 mag. These JHK data agree with those reported by
other groups to 0.02 mag. The measurements are used to derive transformations
between the MKO JHK photometric system and the UKIRT, LCO and 2MASS systems.
The 2MASS-MKO data scatter by 0.05 mag for redder stars: 2MASS-J includes H2O
features in dwarfs and MKO-K includes CO features in giants. Transformations
derived for stars whose spectra contain only weak features cannot give accurate
transformations for objects with strong absorption features within a filter
bandpasses. We find evidence of systematic effects at the 0.02 mag level in the
photometry of stars with J<11 and H,K<10.5. This is due to an underestimate of
the linearity correction for stars observed with the shortest exposure times;
very accurate photometry of stars approaching the saturation limits of infrared
detectors which are operated in double-read mode is difficult to obtain. Four
stars in the sample, GSPC S705-D, FS 116 (B216-b7), FS 144 (Ser-EC84) and FS 32
(Feige 108), may be variable. 84 stars in the sample have 11< J< 15 and
10.5<H,K<15, are not suspected to be variable, and have magnitudes with an
estimated error <0.027 mag; 79 of these have an error of <0.020 mag. These
represent the first published high-accuracy JHK stellar photometry in the MKO
photometric system; we recommend these objects be employed as primary standards
for that system [abridged].Comment: Accepted for publication in MNRAS, 14 pages, 5 Figure
Band anticrossing in GaNxSb1–x
Fourier transform infrared absorption measurements are presented from the dilute nitride semiconductor GaNSb with nitrogen incorporations between 0.2% and 1.0%. The divergence of transitions from the valence band to E– and E+ can be seen with increasing nitrogen incorporation, consistent with theoretical predictions. The GaNSb band structure has been modeled using a five-band k·p Hamiltonian and a band anticrossing fitting has been obtained using a nitrogen level of 0.78 eV above the valence band maximum and a coupling parameter of 2.6 eV
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