4,257 research outputs found
Biophysical modelling of a drosophila photoreceptor
It remains unclear how visual information is co-processed
by different layers of neurons in the retina. In particular, relatively little is known how retina translates vast environmental light changes into
neural responses of limited range. We began examining this question in a bottom-up way in a relatively simple °y eye. To gain understanding of how complex bio-molecular interactions govern the conversion of light input into voltage output (phototransduction), we are building a
biophysical model of the Drosophila R1-R6 photoreceptor. Our model, which relates molecular dynamics of the underlying biochemical reactions to external light input, attempts to capture the molecular dynamics of
phototransduction gain control in a quantitative way
FAST scanning in the developing world emergency department
Objectives. To assess the utility of an existing ultrasound machine for the purposes of focused assessment sonography in trauma (FAST) scanning in a developing world emergency department (ED).Design. Prospective study undertaken over a 12-month period.Trauma patients attending the ED were FAST scanned by one of three trained emergency medicine doctors.Setting. The ED at a government hospital in rural KwaZulu-Natal (KZN), the referral centre for 22 peripheral hospitals.Subjects. All patients presenting to the ED who had sustainedabdominal or thoracic trauma.Outcome measures. Scans were recorded as positive or negativefor free intra-abdominal or pericardial fluid. All results were confirmed by computed tomography, laparotomy or a second trained ED ultrasonographer, followed by a period of clinical observation.Results. 72 FAST scans were included, 52 for blunt trauma and20 for penetrating trauma. Of the 72 scans, 15 (20.8%) werepositive. FAST scanning had 100% specificity and overall sensitivity of 71.4%. When considering blunt trauma alone the sensitivity improved to 81.3%, while in penetrating trauma it was much poorer (62.5%).Conclusions. We propose a valuable role for FAST scanningin all peripheral hospitals for the assessment of patients sustaining blunt trauma. In rural areas with limited resources FAST scans may assist in the appropriate timely transfer of trauma patients for further imaging or definitive surgical intervention
The Past Has Ears (PHE): XR Explorations of Acoustic Spaces as Cultural Heritage
Hearing is one of our most pervasive senses. There is no
equivalent to closing our eyes, or averting our gaze, for the ears. When
we think about great architectural achievements in European history,
such as ancient amphitheatres or Gothic cathedrals, their importance
is strongly tied to their acoustic environment. The acoustics of a heritage
site is an intangible consequence of the space's tangible construction
and furnishings. Inspired by the project's namesake (Phe, for the
constellation Phoenix), and the relatively recent res at Cathedrale de
Notre Dame de Paris and Teatro La Fenice opera hall, the PHE project
focuses on virtual reconstruction of heritage sites, bringing them back
from the ashes. In addressing the intangible acoustic heritage of architectural
sites, three main objectives have been identied for this research
project: Documentation, Modelling, and Presentation. In parallel, three
heritage sites are participating as case studies: Tindari Theatre (IT),
Notre-Dame de Paris Cathedral (FR), and The Houses of Parliament
(UK). The acoustics of a space is immersive, spatial, and due to the nature
of auditory perception egocentric, in contrast to visual perception
of an object, which can be observed from outside". Consequently, presentation
methods for communicating acoustic heritage must represent
the spatially immersive and listener-centric nature of acoustics. PHE will
lead development of a museum grade hardware/software prototype for
the presentation of immersive audio experiences adaptable to multiple
platforms, from on-site immersive speaker installations, to mobile XR
via smartphone applications
Basins of attraction of a nonlinear nanomechanical resonator
We present an experiment that systematically probes the basins of attraction
of two fixed points of a nonlinear nanomechanical resonator and maps them out
with high resolution. We observe a separatrix which progressively alters shape
for varying drive strength and changes the relative areas of the two basins of
attraction. The observed separatrix is blurred due to ambient fluctuations,
including residual noise in the drive system, which cause uncertainty in the
preparation of an initial state close to the separatrix. We find a good
agreement between the experimentally mapped and theoretically calculated basins
of attraction
Hooge's Constant of Carbon Nanotube Field Effect Transistors
The 1/f noise in individual semiconducting carbon nanotubes (s-CNT) in a
field effect transistor configuration has been measured in ultra-high vacuum
and following exposure to air. The amplitude of the normalized current spectral
noise density is independent of source-drain current, indicating the noise is
due to mobility rather than number fluctuations. Hooge's constant for s-CNT is
found to be 9.3 plus minus 0.4x10^-3. The magnitude of the 1/f noise is
substantially degreased by exposing the devices to air
Comparing the effectiveness of small-particle versus large-particle inhaled corticosteroid in COPD
Dirkje S Postma,1 Nicolas Roche,2 Gene Colice,3 Elliot Israel,4 Richard J Martin,5 Willem MC van Aalderen,6 Jonathan Grigg,7 Anne Burden,8 Elizabeth V Hillyer,8 Julie von Ziegenweidt,8 Gokul Gopalan,9 David Price8,10 1University of Groningen, Department of Pulmonary Medicine and Tuberculosis, University Medical Center Groningen, Groningen, the Netherlands; 2Respiratory and Intensive Care Medicine, Cochin Hospital Group, APHP, Paris-Descartes University (EA2511), Paris, France; 3Pulmonary, Critical Care and Respiratory Services, Washington Hospital Center and George Washington University School of Medicine, Washington DC, USA; 4Pulmonary and Critical Care Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; 5Department of Medicine, National Jewish Health, Denver, CO, USA; 6Dept of Pediatric Respiratory Medicine and Allergy, Emma Children's Hospital AMC, Amsterdam, the Netherlands; 7Blizard Institute, Queen Mary University London, London, UK; 8Research in Real Life, Ltd, Cambridge, UK; 9Respiratory, Global Scientific Affairs, Teva Pharmaceuticals, Frazer, PA, USA; 10Academic Primary Care, Division of Applied Health Sciences, University of Aberdeen, Aberdeen, UK Purpose: Small airway changes and dysfunction contribute importantly to airway obstruction in chronic obstructive pulmonary disease (COPD), which is currently treated with inhaled corticosteroids (ICS) and long-acting bronchodilators at Global initiative for Obstructive Lung Disease (GOLD) grades 2–4. This retrospective matched cohort analysis compared effectiveness of a representative small-particle ICS (extrafine beclomethasone) and larger-particle ICS (fluticasone) in primary care patients with COPD. Patients and methods: Smokers and ex-smokers with COPD ≥40 years old initiating or stepping-up their dose of extrafine beclomethasone or fluticasone were matched 1:1 for demographic characteristics, index prescription year, concomitant therapies, and disease severity during 1 baseline year. During 2 subsequent years, we evaluated treatment change and COPD exacerbations, defined as emergency care/hospitalization for COPD, acute oral corticosteroids, or antibiotics for lower respiratory tract infection. Results: Mean patient age was 67 years, 57%–60% being male. For both initiation (n=334:334) and step-up (n=189:189) patients, exacerbation rates were comparable between extrafine beclomethasone and fluticasone cohorts during the 2 year outcome period. Odds of treatment stability (no exacerbation or treatment change) were significantly greater for patients initiating extrafine beclomethasone compared with fluticasone (adjusted odds ratio 2.50; 95% confidence interval, 1.32–4.73). Median ICS dose exposure during 2 outcome years was significantly lower (P<0.001) for extrafine beclomethasone than fluticasone cohorts (315 µg/day versus 436 µg/day for initiation, 438 µg/day versus 534 µg/day for step-up patients). Conclusion: We observed that small-particle ICS at significantly lower doses had comparable effects on exacerbation rates as larger-particle ICS at higher doses, whereas initiation of small-particle ICS was associated with better odds of treatment stability during 2-years' follow-up. Keywords: COPD exacerbation, extrafine particle, matched cohort analysis, real life, small airway
Resonant decay of flat directions
We study preheating, i.e., non-perturbative resonant decay, of flat direction
fields, concentrating on MSSM flat directions and the right handed sneutrino.
The difference between inflaton preheating and flaton preheating, is that the
potential is more constraint in the latter case. The effects of a complex
driving field, quartic couplings in the potential, and the presence of a
thermal bath are important and cannot be neglected.
Preheating of MSSM flat directions is typically delayed due to out-of-phase
oscillations of the real and imaginary components and may be preceded by
perturbative decay or -ball formation. Particle production due to the
violation of adiabaticity is expected to be inefficient due to back reaction
effects. For a small initial sneutrino VEV, with
the mass of the right handed sneutrino and a yakawa coupling, there are
tachyonic instabilities. The -term quartic couplings do not generate an
effective mass for the tachyonic modes, making it an efficient decay channel.
It is unclear how thermal scattering affects the resonance.Comment: 20 pages, 4 figure
Curvaton Potential Terms, Scale-Dependent Perturbation Spectra and Chaotic Initial Conditions
The curvaton scenario predicts an almost scale-invariant spectrum of
perturbations in most inflation models. We consider the possibility that
renormalisable phi^4 or Planck scale-suppressed non-renormalisable curvaton
potential terms may result in an observable deviation from scale-invariance. We
show that if the curvaton initially has a large amplitude and if the total
number of e-foldings of inflation is less than about 300 then a running blue
perturbation spectrum with an observable deviation from scale-invariance is
likely. D-term inflation is considered as an example with a potentially low
total number of e-foldings of inflation. A secondary role for the curvaton, in
which it drives a period of chaotic inflation leading to D-term or other flat
potential inflation from an initially chaotic state, is suggested.Comment: 12 pages LaTeX, minor corrections, to be published in JCA
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