1,852 research outputs found
On the eigenvalue spacing distribution for a point scatterer on the flat torus
We study the level spacing distribution for the spectrum of a point scatterer
on a flat torus. In the 2-dimensional case, we show that in the weak coupling
regime the eigenvalue spacing distribution coincides with that of the spectrum
of the Laplacian (ignoring multiplicties), by showing that the perturbed
eigenvalues generically clump with the unperturbed ones on the scale of the
mean level spacing. We also study the three dimensional case, where the
situation is very different.Comment: 25 page
Point perturbations of circle billiards
The spectral statistics of the circular billiard with a point-scatterer is
investigated. In the semiclassical limit, the spectrum is demonstrated to be
composed of two uncorrelated level sequences. The first corresponds to states
for which the scatterer is located in the classically forbidden region and its
energy levels are not affected by the scatterer in the semiclassical limit
while the second sequence contains the levels which are affected by the
point-scatterer. The nearest neighbor spacing distribution which results from
the superposition of these sequences is calculated analytically within some
approximation and good agreement with the distribution that was computed
numerically is found.Comment: 9 pages, 2 figure
Pulmonary fibrosis presenting as an early manifestation of microscopic polyangiitis
Microscopic polyangiitis (MPA) is a systemic small vessel vasculitis that is included in the pulmonary-renal syndromes. Although glomerulonephritis represents the major clinical feature of MPA indicative of renal involvement, diffuse alveolar haemorrhage is the classic manifestation of pulmonary involvement. However, pulmonary fibrosis is a less frequently reported pulmonary manifestation. Herein we describe a patient who was diagnosed with MPA presenting with radiographic evidence of pulmonary interstitial fibrosis as an early clinical manifestation accompanied by constitutional symptoms such as fever and weight loss. We also include a short literature review focusing on the association between pulmonary fibrosis and MPA
Level spacing distribution of pseudointegrable billiard
In this paper, we examine the level spacing distribution of the
rectangular billiard with a single point-like scatterer, which is known as
pseudointegrable. It is shown that the observed is a new type, which is
quite different from the previous conclusion. Even in the strong coupling
limit, the Poisson-like behavior rather than Wigner-like is seen for ,
although the level repulsion still remains in the small region. The
difference from the previous works is analyzed in detail.Comment: 11 pages, REVTeX file, 3 PostScript Figure
Scale Anomaly and Quantum Chaos in the Billiards with Pointlike Scatterers
We argue that the random-matrix like energy spectra found in pseudointegrable
billiards with pointlike scatterers are related to the quantum violation of
scale invariance of classical analogue system. It is shown that the behavior of
the running coupling constant explains the key characteristics of the level
statistics of pseudointegrable billiards.Comment: 10 pages, RevTex file, uuencode
Surface patterning of carbon nanotubes can enhance their penetration through a phospholipid bilayer
Nanotube patterning may occur naturally upon the spontaneous self-assembly of
biomolecules onto the surface of single-walled carbon nanotubes (SWNTs). It
results in periodically alternating bands of surface properties, ranging from
relatively hydrophilic to hydrophobic, along the axis of the nanotube. Single
Chain Mean Field (SCMF) theory has been used to estimate the free energy of
systems in which a surface patterned nanotube penetrates a phospholipid
bilayer. In contrast to un-patterned nanotubes with uniform surface properties,
certain patterned nanotubes have been identified that display a relatively low
and approximately constant system free energy (10 kT) as the nanotube traverses
through the bilayer. These observations support the hypothesis that the
spontaneous self-assembly of bio-molecules on the surface of SWNTs may
facilitate nanotube transduction through cell membranes.Comment: Published in ACS Nano http://pubs.acs.org/doi/abs/10.1021/nn102763
Psychological distress and quality of life in lung cancer: The role of health-related stigma, illness appraisals and social constraints
Objective: Health-related stigma is associated with negative psychological and quality of life outcomes in lung cancer patients. This study describes the impact of stigma on lung cancer patients\u27 psychological distress and quality of life and explores the role of social constraints and illness appraisal as mediators of effect. Methods: A self-administered cross-sectional survey examined psychological distress and quality of life in 151 people (59% response rate) diagnosed with lung cancer from Queensland and New South Wales. Health-related stigma, social constraints and illness appraisals were assessed as predictors of adjustment outcomes. Results: Forty-nine percent of patients reported elevated anxiety; 41% were depressed; and 51% had high global distress. Health-related stigma was significantly related to global psychological distress and quality of life with greater stigma and shame related to poorer outcomes. These effects were mediated by illness appraisals and social constraints. Conclusions: Health-related stigma appears to contribute to poorer adjustment by constraining interpersonal discussions about cancer and heightening feelings of threat. There is a need for the development and evaluation of interventions to ameliorate the negative effects of health-related stigma among lung cancer patients
Electronic Devices Based on Purified Carbon Nanotubes Grown By High Pressure Decomposition of Carbon Monoxide
The excellent properties of transistors, wires, and sensors made from
single-walled carbon nanotubes (SWNTs) make them promising candidates for use
in advanced nanoelectronic systems. Gas-phase growth procedures such as the
high pressure decomposition of carbon monoxide (HiPCO) method yield large
quantities of small diameter semiconducting SWNTs, which are ideal for use in
nanoelectronic circuits. As-grown HiPCO material, however, commonly contains a
large fraction of carbonaceous impurities that degrade properties of SWNT
devices. Here we demonstrate a purification, deposition, and fabrication
process that yields devices consisting of metallic and semiconducting nanotubes
with electronic characteristics vastly superior to those of circuits made from
raw HiPCO. Source-drain current measurements on the circuits as a function of
temperature and backgate voltage are used to quantify the energy gap of
semiconducting nanotubes in a field effect transistor geometry. This work
demonstrates significant progress towards the goal of producing complex
integrated circuits from bulk-grown SWNT material.Comment: 6 pages, 4 figures, to appear in Nature Material
Airway pressure release ventilation in mechanically ventilated patients with COVID-19: a multicenter observational study
Background Evidence prior to the coronavirus disease 2019 (COVID-19) pandemic suggested that, compared with conventional ventilation strategies, airway pressure release ventilation (APRV) can improve oxygenation and reduce mortality in patients with acute respiratory distress syndrome. We aimed to assess the association between APRV use and clinical outcomes among adult patients receiving mechanical ventilation for COVID-19 and hypothesized that APRV use would be associated with improved survival compared with conventional ventilation. Methods A total of 25 patients with COVID-19 pneumonitis was admitted to intensive care units (ICUs) for invasive ventilation in Perth, Western Australia, between February and May 2020. Eleven of these patients received APRV. The primary outcome was survival to day 90. Secondary outcomes were ventilation-free survival days to day 90, mechanical complications from ventilation, and number of days ventilated. Results Patients who received APRV had a lower probability of survival than did those on other forms of ventilation (hazard ratio, 0.17; 95% confidence interval, 0.03–0.89; P=0.036). This finding was independent of indices of severity of illness to predict the use of APRV. Patients who received APRV also had fewer ventilator-free survival days up to 90 days after initiation of ventilation compared to patients who did not receive APRV, and survivors who received APRV had fewer ventilator-free days than survivors who received other forms of ventilation. There were no differences in mechanical complications according to mode of ventilation. Conclusions Based on the findings of this study, we urge caution with the use of APRV in COVID-19
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Shifting the social determinants of food insecurity during the COVID-19 pandemic: the Australian experience
We aimed to explore experiences of government-led actions on the social determinants of food insecurity during Australia’s COVID-19 pandemic response (which included novel, yet temporary, social protection measures to support Australians facing hardship during state-wide lockdowns). During November–December 2020, we conducted in-depth interviews with 24 Victorians who received government income support (prior to COVID-19) and the temporary COVID-19 specific payments. Interviews were guided by a theoretical understanding of the social determinants of health and health inequities, which we aligned to the social policy context. Data were audio-recorded, transcribed, inductively coded, categorised and thematically analysed. Our sample included mostly women (n = 19) and single parents (n = 13). Interviews reflected four key themes. Firstly, participants described ‘battles all around them' (i.e., competing financial, health and social stressors) that were not alleviated by temporary social policy changes and made healthy eating difficult to prioritise during the pandemic. Secondly, housing, income, job, and education priorities rendered food a lower and more flexible financial priority – even with 18 participants receiving temporary income increases from COVID-19 Supplements. Thirdly, given that food remained a lower and more flexible financial priority, families continued to purchase the cheapest and most affordable options (typically less healthful, more markedly price discounted). Finally, participants perceived the dominant public and policy rhetoric around income support policies and healthy eating to be inaccurate and shaming – often misrepresenting their lived experiences, both prior to and during COVID-19. Participants reported entrenched struggles with being able to afford basic living costs in a dignified manner during COVID-19, despite temporary social protection policy changes. To reduce inequities in population diets, a pre-requisite to health, all stakeholders must recognise an ongoing responsibility for adopting long-term food and social policies that genuinely improve lived experiences of food insecurity and poverty
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