1,201 research outputs found
Isospectral Mathieu-Hill Operators
In this paper we prove that the spectrum of the Mathieu-Hill Operators with
potentials ae^{-i2{\pi}x}+be^{i2{\pi}x} and ce^{-i2{\pi}x}+de^{i2{\pi}x} are
the same if and only if ab=cd, where a,b,c and d are complex numbers. This
result implies some corollaries about the extension of Harrell-Avron-Simon
formula. Moreover, we find explicit formulas for the eigenvalues and
eigenfunctions of the t-periodic boundary value problem for the Hill operator
with Gasymov's potential
Discordance in investigator-reported and adjudicated sudden death in TIOSPIR
Accurate and consistent determination of cause of death is challenging in chronic obstructive pulmonary disease (COPD) patients. TIOSPIR (N=17 135) compared the safety and efficacy of tiotropium Respimat 5/2.5 µg with HandiHaler 18 µg in COPD patients. All-cause mortality was a primary end-point. A mortality adjudication committee (MAC) assessed all deaths. We aimed to investigate causes of discordance in investigator-reported and MAC-adjudicated causes of death and their impact on results, especially cardiac and sudden death. The MAC provided independent, blinded assessment of investigator-reported deaths (n=1302) and assigned underlying cause of death. Discordance between causes of death was assessed descriptively (shift tables). There was agreement between investigator-reported and MAC-adjudicated deaths in 69.4% of cases at the system organ class level. Differences were mainly observed for cardiac deaths (16.4% investigator, 5.1% MAC) and deaths assigned to general disorders including sudden death (17.4% investigator, 24.6% MAC). Reasons for discrepancies included investigator attribution to the immediate (e.g. myocardial infarction (MI)) over the underlying cause of death (e.g. COPD) and insufficient information for a definitive cause. Cause-specific mortality varies in COPD, depending on the method of assignment. Sudden death, witnessed and unwitnessed, is common in COPD and often attributed to MI without supporting evidence
An experimental and analytical study of plasma closing switches filled with environmentally friendly gases
In recent years there has been a desire within the pulsed power community to find potential alternative gases to sulphur hexafluoride (SF6) for use within pulsed power systems. Within plasma closing switches (PCSs), the desire to use environmentally friendly gases has come as a result of environmental concerns over the emissions of currently used gases into the atmosphere and contributing to the global warming problem. One of the main issues in finding a suitable replacement gas or gases for use in PCSs is that the performance characteristics of a switch filled with an alternative gas or gas mixture should be comparable to the performance characteristics of conventional SF6-filled switches. The research presented in this paper is an expansion of previous work conducted and forms an experimental and analytical evaluation of breakdown characteristics in two commonly used PCS topologies (a two-electrode self-breakdown switch and a field distortion switch) when filled with different gases (air, oxygen-nitrogen mixtures, argon oxygen mixture, nitrogen and carbon dioxide) over a range of pressures from 0.1 MPa to 0.45 MPa and for a range of inter-electrode distances
Major epidemiological changes in sudden infant death syndrome : a 20-year population-based study in the UK
Background
Results of case-control studies in the past 5 years suggest that the epidemiology of sudden infant death syndrome (SIDS) has changed since the 1991 UK Back to Sleep campaign. The campaign's advice that parents put babies on their back to sleep led to a fall in death rates. We used a longitudinal dataset to assess these potential changes.
Methods
Population-based data from home visits have been collected for 369 consecutive unexpected infant deaths (300 SIDS and 69 explained deaths) in Avon over 20 years (1984—2003). Data obtained between 1993 and 1996 from 1300 controls with a chosen “reference” sleep before interview have been used for comparison.
Findings
Over the past 20 years, the proportion of children who died from SIDS while co-sleeping with their parents, has risen from 12% to 50% (p<0·0001), but the actual number of SIDS deaths in the parental bed has halved (p=0·01). The proportion seems to have increased partly because the Back to Sleep campaign led to fewer deaths in infants sleeping alone—rather than because of a rise in deaths of infants who bed-shared, and partly because of an increase in the number of deaths in infants sleeping with their parents on a sofa. The proportion of deaths in families from deprived socioeconomic backgrounds has risen from 47% to 74% (p=0·003), the prevalence of maternal smoking during pregnancy from 57% to 86% (p=0·0004), and the proportion of pre-term infants from 12% to 34% (p=0·0001). Although many SIDS infants come from large families, first-born infants are now the largest group. The age of infants who bed-share is significantly smaller than that before the campaign, and fewer are breastfed.
Interpretation
Factors that contribute to SIDS have changed in their importance over the past 20 years. Although the reasons for the rise in deaths when a parent sleeps with their infant on a sofa are still unclear, we strongly recommend that parents avoid this sleeping environment. Most SIDS deaths now occur in deprived families. To better understand contributory factors and plan preventive measures we need control data from similarly deprived families, and particularly, infant sleep environments
Respiratory virus infection up-regulates TRPV1, TRPA1 and ASICS3 receptors on airway cells.
Receptors implicated in cough hypersensitivity are transient receptor potential vanilloid 1 (TRPV1), transient receptor potential cation channel, Subfamily A, Member 1 (TRPA1) and acid sensing ion channel receptor 3 (ASIC3). Respiratory viruses, such as respiratory syncytial virus (RSV) and measles virus (MV) may interact directly and/or indirectly with these receptors on sensory nerves and epithelial cells in the airways. We used in vitro models of sensory neurones (SHSY5Y or differentiated IMR-32 cells) and human bronchial epithelium (BEAS-2B cells) as well as primary human bronchial epithelial cells (PBEC) to study the effect of MV and RSV infection on receptor expression. Receptor mRNA and protein levels were examined by qPCR and flow cytometry, respectively, following infection or treatment with UV inactivated virus, virus-induced soluble factors or pelleted virus. Concentrations of a range of cytokines in resultant BEAS-2B and PBEC supernatants were determined by ELISA. Up-regulation of TRPV1, TRPA1 and ASICS3 expression occurred by 12 hours post-infection in each cell type. This was independent of replicating virus, within the same cell, as virus-induced soluble factors alone were sufficient to increase channel expression. IL-8 and IL-6 increased in infected cell supernatants. Antibodies against these factors inhibited TRP receptor up-regulation. Capsazepine treatment inhibited virus induced up-regulation of TRPV1 indicating that these receptors are targets for treating virus-induced cough
The phosphorylation of ribosomal protein S6 by protein kinases from cells infected with pseudorabies virus
More Natural Models of Electoral Control by Partition
"Control" studies attempts to set the outcome of elections through the
addition, deletion, or partition of voters or candidates. The set of benchmark
control types was largely set in the seminal 1992 paper by Bartholdi, Tovey,
and Trick that introduced control, and there now is a large literature studying
how many of the benchmark types various election systems are vulnerable to,
i.e., have polynomial-time attack algorithms for.
However, although the longstanding benchmark models of addition and deletion
model relatively well the real-world settings that inspire them, the
longstanding benchmark models of partition model settings that are arguably
quite distant from those they seek to capture.
In this paper, we introduce--and for some important cases analyze the
complexity of--new partition models that seek to better capture many real-world
partition settings. In particular, in many partition settings one wants the two
parts of the partition to be of (almost) equal size, or is partitioning into
more than two parts, or has groups of actors who must be placed in the same
part of the partition. Our hope is that having these new partition types will
allow studies of control attacks to include such models that more realistically
capture many settings
Three-dimensional femtosecond laser nanolithography of crystals
Nanostructuring hard optical crystals has so far been exclusively feasible at
their surface, as stress induced crack formation and propagation has rendered
high precision volume processes ineffective. We show that the inner chemical
etching reactivity of a crystal can be enhanced at the nanoscale by more than
five orders of magnitude by means of direct laser writing. The process allows
to produce cm-scale arbitrary three-dimensional nanostructures with 100 nm
feature sizes inside large crystals in absence of brittle fracture. To showcase
the unique potential of the technique, we fabricate photonic structures such as
sub-wavelength diffraction gratings and nanostructured optical waveguides
capable of sustaining sub-wavelength propagating modes inside yttrium aluminum
garnet crystals. This technique could enable the transfer of concepts from
nanophotonics to the fields of solid state lasers and crystal optics.Comment: Submitted Manuscript and Supplementary Informatio
Statistical mechanics of voting
Decision procedures aggregating the preferences of multiple agents can
produce cycles and hence outcomes which have been described heuristically as
`chaotic'. We make this description precise by constructing an explicit
dynamical system from the agents' preferences and a voting rule. The dynamics
form a one dimensional statistical mechanics model; this suggests the use of
the topological entropy to quantify the complexity of the system. We formulate
natural political/social questions about the expected complexity of a voting
rule and degree of cohesion/diversity among agents in terms of random matrix
models---ensembles of statistical mechanics models---and compute quantitative
answers in some representative cases.Comment: 9 pages, plain TeX, 2 PostScript figures included with epsf.tex
(ignore the under/overfull \vbox error messages
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