348 research outputs found

    Measurements of CH4, N2O, CO, H2O and O3 in the middle atmosphere by the ATMOS experiment on Spacelab 3

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    The volume mixing ratios of five minor gases (CH4, N2O, CO, H2O, and O3) were retrieved through the middle atmosphere from the analysis of 0.01/cm resolution infrared solar occultation spectra recorded near 28 N and 48 S latitudes with the ATMOS (Atmospheric Trace Molecule Spectroscopy) instrument, flown on board Spacelab 3. The results, which constitute the first simultaneous observations of continuous profiles through the middle atmosphere for these gases, are in general agreement with reported measurements from ground, balloon and satellite-based instruments for the same seasons. In detail, the vertical profiles of these gases show the effects of the upper and middle atmospheric transport patterns dominant during the season of these observations. The profiles inferred at different longitudes around 28 N suggest a near-uniform zonal distribution of these gases. Although based on fewer observations, the sunrise occultation measurements point to a larger variability in the vertical distribution of these gases at 48 S

    Gaussian Fluctuation in Random Matrices

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    Let N(L)N(L) be the number of eigenvalues, in an interval of length LL, of a matrix chosen at random from the Gaussian Orthogonal, Unitary or Symplectic ensembles of N{\cal N} by N{\cal N} matrices, in the limit N{\cal N}\rightarrow\infty. We prove that [N(L)N(L)]/logL[N(L) - \langle N(L)\rangle]/\sqrt{\log L} has a Gaussian distribution when LL\rightarrow\infty. This theorem, which requires control of all the higher moments of the distribution, elucidates numerical and exact results on chaotic quantum systems and on the statistics of zeros of the Riemann zeta function. \noindent PACS nos. 05.45.+b, 03.65.-wComment: 13 page

    Impact of previous hepatitis B infection on the clinical outcomes from chronic hepatitis C? A population-level analysis

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    Chronic coinfection with hepatitis C virus (HCV) and hepatitis B virus (HBV) is associated with adverse liver outcomes. The clinical impact of previous HBV infection on liver disease in HCV infection is unknown. We aimed at determining any association of previous HBV infection with liver outcomes using antibodies to the hepatitis B core antigen (HBcAb) positivity as a marker of exposure. The Scottish Hepatitis C Clinical Database containing data for all patients attending HCV clinics in participating health boards was linked to the HBV diagnostic registry and mortality data from Information Services Division, Scotland. Survival analyses with competing risks were constructed for time from the first appointment to decompensated cirrhosis, hepatocellular carcinoma (HCC) and liver‐related mortality. Records of 8513 chronic HCV patients were included in the analyses (87 HBcAb positive and HBV surface antigen [HBsAg] positive, 1577 HBcAb positive and HBsAg negative, and 6849 HBcAb negative). Multivariate cause‐specific proportional hazards models showed previous HBV infection (HBcAb positive and HBsAg negative) significantly increased the risks of decompensated cirrhosis (hazard ratio [HR]: 1.29, 95% CI: 1.01‐1.65) and HCC (HR: 1.64, 95% CI: 1.09‐2.49), but not liver‐related death (HR: 1.02, 95% CI: 0.80‐1.30). This is the largest study to date showing an association between previous HBV infection and certain adverse liver outcomes in HCV infection. Our analyses add significantly to evidence which suggests that HBV infection adversely affects liver health despite apparent clearance. This has important implications for HBV vaccination policy and indications for prioritization of HCV therapy

    A special irreducible matrix representation of the real Clifford algebra C(3,1)

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    4x4 Dirac (gamma) matrices (irreducible matrix representations of the Clifford algebras C(3,1), C(1,3), C(4,0)) are an essential part of many calculations in quantum physics. Although the final physical results do not depend on the applied representation of the Dirac matrices (e.g. due to the invariance of traces of products of Dirac matrices), the appropriate choice of the representation used may facilitate the analysis. The present paper introduces a particularly symmetric real representation of 4x4 Dirac matrices (Majorana representation) which may prove useful in the future. As a byproduct, a compact formula for (transformed) Pauli matrices is found. The consideration is based on the role played by isoclinic 2-planes in the geometry of the real Clifford algebra C(3,0) which provide an invariant geometric frame for it. It can be generalized to larger Clifford algebras.Comment: 23 pages LaTeX, to appear in the J. Math. Phys. (v2: appendix B on Pauli matrices and references are added, minor other changes

    Jack vertex operators and realization of Jack functions

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    We give an iterative method to realize general Jack functions from Jack functions of rectangular shapes. We first show some cases of Stanley's conjecture on positivity of the Littlewood-Richardson coefficients, and then use this method to give a new realization of Jack functions. We also show in general that vectors of products of Jack vertex operators form a basis of symmetric functions. In particular this gives a new proof of linear independence for the rectangular and marked rectangular Jack vertex operators. Thirdly a generalized Frobenius formula for Jack functions was given and was used to give new evaluation of Dyson integrals and even powers of Vandermonde determinant.Comment: Expanded versio

    On the theory of composition in physics

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    We develop a theory for describing composite objects in physics. These can be static objects, such as tables, or things that happen in spacetime (such as a region of spacetime with fields on it regarded as being composed of smaller such regions joined together). We propose certain fundamental axioms which, it seems, should be satisfied in any theory of composition. A key axiom is the order independence axiom which says we can describe the composition of a composite object in any order. Then we provide a notation for describing composite objects that naturally leads to these axioms being satisfied. In any given physical context we are interested in the value of certain properties for the objects (such as whether the object is possible, what probability it has, how wide it is, and so on). We associate a generalized state with an object. This can be used to calculate the value of those properties we are interested in for for this object. We then propose a certain principle, the composition principle, which says that we can determine the generalized state of a composite object from the generalized states for the components by means of a calculation having the same structure as the description of the generalized state. The composition principle provides a link between description and prediction.Comment: 23 pages. To appear in a festschrift for Samson Abramsky edited by Bob Coecke, Luke Ong, and Prakash Panangade

    Quantum Dissipation and Decay in Medium

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    Quantum dissipation in thermal environment is investigated, using the path integral approach. The reduced density matrix of the harmonic oscillator system coupled to thermal bath of oscillators is derived for arbitrary spectrum of bath oscillators. Time evolution and the end point of two-body decay of unstable particles is then elucidated: After early transient times unstable particles undergo the exponential decay, followed by the power law decay and finally ending in a mixed state of residual particles containing contributions from both on and off the mass shell, whose abundance does not suffer from the Boltzmann suppression.Comment: 19 pages, LATEX file. Substantially expanded and revised for publication, including more complete description of application to unstable particle decay in thermal medium. Some minor mistake of numerical factors correcte

    High willingness to use drug consumption rooms among people who inject drugs in Scotland: findings from a national bio-behavioural survey among people who inject drugs

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    Background To address rising drug-related harms (including significant transmission of HIV) among people who inject drugs (PWID) in Glasgow, officials have proposed the introduction of the UK's first drug consumption room (DCR) in Glasgow city centre. Using a nationally representative sample, this study aimed to determine willingness to use a DCR among PWID nationally, in Glasgow city centre (the proposed DCR location), other Scottish city centres (excluding Glasgow) and the rest of Scotland (excluding city centres). Methods Bio-behavioural survey, of 1469 current PWID (injected in last 6 months) across Scotland during 2017-18. Willingness to use DCRs was examined by drug-related risk behaviours and harms overall in Scotland, and then stratified by Glasgow city centre (n = 219), other Scottish city centres (n = 226) and the rest of Scotland (n = 1024). Results The majority of PWID overall in Scotland (75%) were willing to use a DCR; willingness was higher among those recruited in Glasgow city centre (83%) and other Scottish city centres (83%), compared to the rest of Scotland (72%) (p < 0.001). Willingness was greater among PWID who reported (compared to those who did not report) injecting heroin (76%, p = 0.002), cocaine injecting (79%, p = 0.014), homelessness (86%, p < 0.001), public injecting (87%, p < 0.001) and an overdose (80%, p = 0.026). Willingness was found to be associated with a cumulative multiple risk variable: increased from 66% among those with a score of zero to 85% with a score of at least three (p < 0.001). Conclusions The vast majority of PWID at greatest risk of drug-related harm in Glasgow and elsewhere in Scotland would be willing to use a DCR, supporting proposals for the introduction of DCRs nationally

    Severe Unresolved Cholestasis Due to Unknown Etiology Leading to Early Allograft Failure Within the First 3 Months of Liver Transplantation

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    Background Causes of severe cholestasis after liver transplantation (LT) are multi-factorial. Although the etiology is predictable in some, others culminate in graft/patient loss without a definitive cause identified. Severe cholestasis is usually associated with overlapped histological findings of rejection and biliary features, and diagnostic interpretation may pose a challenge.Methods This is 10-year retrospective analysis of patients with unexplained severe cholestasis resulting in death/graft loss within 90 days of LT. Of 1 583 LT during the study period, 90-day graft failure occurred in 129 (8%) cases; a total of 45 (3%) patients had unresolving severe cholestasis (bilirubin, &gt;100 mol/L; alkaline phosphatase, &gt;400 UI/L after 15 days from LT), excluding those due to primary nonfunction/sepsis/vascular causes (n = 84). Demographics, allograft biopsies, radiological investigations, and clinical outcome were analyzed.Results All patients had persistent abnormal liver biochemistry. Doppler ultrasound scan was normal in all cases. Thirty-five (78%) recipients had at least 1 allograft biopsy (2 [1-9]). On the first biopsy, 22 (63%) patients had acute rejection, 4 (18%) early-chronic rejection, 12 (34%) antibody-mediated rejection. In subsequent biopsies chronic rejection was evident in 5 (14%) cases. Donor-specific antibodies were detected in all patients tested. Biliary anatomy was studied in detail in 9 (20%) patients, all presenting biliary strictures. The majority (n = 39; 87%) died within 32 (10-91) days, only survivors were from retransplantation (n = 3;6.5%) and biliary intervention (n = 3;6.5%).Conclusions Unresolving severe cholestasis after LT is a key parameter predicting patient/allograft outcome. Histologically, rejection seems to overlap with biliary strictures; hence, allograft biopsy with signs of rejection should not be a reason to overlook biliary problems, in particular when biliary features are present. Only extensive radiological investigation/intervention or retransplantation prevents patient/allograft loss
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