1,964 research outputs found
High field magneto-transport in high mobility gated InSb/InAlSb quantum well heterostructures
We present high field magneto-transport data from a range of 30nm wide
InSb/InAlSb quantum wells. The low temperature carrier mobility of the samples
studied ranged from 18.4 to 39.5 m2V-1s-1 with carrier densities between
1.5x1015 and 3.28x1015 m-2. Room temperature mobilities are reported in excess
of 6 m2V-1s-1. It is found that the Landau level broadening decreases with
carrier density and beating patterns are observed in the magnetoresistance with
non-zero node amplitudes in samples with the narrowest broadening despite the
presence of a large g-factor. The beating is attributed to Rashba splitting
phenomenon and Rashba coupling parameters are extracted from the difference in
spin populations for a range of samples and gate biases. The influence of
Landau level broadening and spin-dependent scattering rates on the observation
of beating in the Shubnikov-de Haas oscillations is investigated by simulations
of the magnetoconductance. Data with non-zero beat node amplitudes are
accompanied by asymmetric peaks in the Fourier transform, which are
successfully reproduced by introducing a spin-dependent broadening in the
simulations. It is found that the low-energy (majority) spin up state suffers
more scattering than the high-energy (minority) spin down state and that the
absence of beating patterns in the majority of (lower density) samples can be
attributed to the same effect when the magnitude of the level broadening is
large
Accidental lean: Performance improvement in an NHS hospital and reflections on the role of operations strategy
N
Tentative Evidence for Relativistic Electrons Generated by the Jet of the Young Sun-like Star DG Tau
Synchrotron emission has recently been detected in the jet of a massive
protostar, providing further evidence that certain jet formation
characteristics for young stars are similar to those found for highly
relativistic jets from AGN. We present data at 325 and 610 MHz taken with the
GMRT of the young, low-mass star DG Tau, an analog of the Sun soon after its
birth. This is the first investigation of a low-mass YSO at at such low
frequencies. We detect emission with a synchrotron spectral index in the
proximity of the DG Tau jet and interpret this emission as a prominent bow
shock associated with this outflow. This result provides tentative evidence for
the acceleration of particles to relativistic energies due to the shock impact
of this otherwise very low-power jet against the ambient medium. We calculate
the equipartition magnetic field strength (0.11 mG) and particle energy
(4x10^40 erg), which are the minimum requirements to account for the
synchrotron emission of the DG Tau bow shock. These results suggest the
possibility of low energy cosmic rays being generated by young Sun-like stars.Comment: 19 pages, 2 figures, accepted for publication in ApJ Letter
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
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-
Pathway map development for medical device event reporting in operating theatres: a human factors approach to improving the existing system
OBJECTIVES: This study aimed to develop the actual pathway to reporting and information transfer in operating theatres in relation to medical technology malfunction/failure. This with the aim of understanding the differences with the pathway published by NHS Improvement and identification of points for improvement. DESIGN: This is a qualitative study involving stakeholder interviews with doctors, nurses, manufacturers, medical device safety officer and Medicines and Healthcare products Regulatory Agency. SETTING: Data were collected on reporting pathway used in operating theatres. Clinical staff who took part worked in different trusts throughout UK while manufacturers provided devices in UK and EU/USA. PARTICIPANTS: Semistructured interviews were completed with 15 clinicians and 13 manufacturers. Surveys were completed by 38 clinicians and 5 manufacturers. Recognised methods of pathway development were used. The Lean Six Sigma principles adapted to healthcare were used to develop suggestions for improvement. MAIN OUTCOME MEASURES: To identify the differences between the set pathway to reporting and information transfer to what is occurring on a day-to-day basis as reported by staff. Identify points in the pathway where improvements could be applied. RESULTS: The developed pathway demonstrated great complexity of the current reporting system for medical devices. It identified numerous areas that give rise to problems and multiple biases in decision making. This highlighted the core issues leading to under-reporting and lack of knowledge on device performance and patient risk. Suggestions for improvement were deduced based on end user requirements and identified problems. CONCLUSIONS: This study has provided a detailed understanding of the key problem areas that exist within the current reporting system for medical devices and technology. The developed pathway sets to address the key problems to improve reporting outcomes. The identification of pathway differences between 'work as done' and 'work as imagined' can lead to development of quality improvements that could be systematically applied
Phase-dependent light propagation in atomic vapors
Light propagation in an atomic medium whose coupled electronic levels form a
diamond-configuration exhibits a critical dependence on the input conditions.
In particular, the relative phase of the input fields gives rise to
interference phenomena in the electronic excitation whose interplay with
relaxation processes determines the stationary state. We integrate numerically
the Maxwell-Bloch equations and observe two metastable behaviors for the
relative phase of the propagating fields corresponding to two possible
interference phenomena. These phenomena are associated to separate types of
response along propagation, minimize dissipation, and are due to atomic
coherence. These behaviors could be studied in gases of isotopes of
alkali-earth atoms with zero nuclear spin, and offer new perspectives in
control techniques in quantum electronics.Comment: 16 pages, 11 figures, v2: typos corrected, v3: final version, to
appear in Phys. Rev.
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
ProteinArchitect: Protein Evolution above the Sequence Level
While many authors have discussed models and tools for studying protein evolution at the sequence level, molecular function is usually mediated by complex, higher order features such as independently folding domains and linear motifs that are based on or embedded in a particular arrangment of features such as secondary structure elements, transmembrane domains and regions with intrinsic disorder. This 'protein architecture' can, in its most simplistic representation, be visualized as domain organization cartoons that can be used to compare proteins in terms of the order of their mostly globular domains.Here, we describe a visual approach and a webserver for protein comparison that extend the domain organization cartoon concept. By developing an information-rich, compact visualization of different protein features above the sequence level, potentially related proteins can be compared at the level of propensities for secondary structure, transmembrane domains and intrinsic disorder, in addition to PFAM domains. A public Web server is available at www.proteinarchitect.net, while the code is provided at protarchitect.sourceforge.net.Due to recent advances in sequencing technologies we are now flooded with millions of predicted proteins that await comparative analysis. In many cases, mature tools focused on revealing hits with considerable global or local similarity to well-characterized proteins will not be able to lead us to testable hypotheses about a protein's function, or the function of a particular region. The visual comparison of different types of protein features with ProteinArchitect will be useful when assessing the relevance of similarity search hits, to discover subgroups in protein families and superfamilies, and to understand protein regions with conserved features outside globular regions. Therefore, this approach is likely to help researchers to develop testable hypotheses about a protein's function even if is somewhat distant from the more characterized proteins, by facilitating the discovery of features that are conserved above the sequence level for comparison and further experimental investigation
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
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