1,129 research outputs found
On the Eigenvalue Density of Real and Complex Wishart Correlation Matrices
Wishart correlation matrices are the standard model for the statistical
analysis of time series. The ensemble averaged eigenvalue density is of
considerable practical and theoretical interest. For complex time series and
correlation matrices, the eigenvalue density is known exactly. In the real
case, however, a fundamental mathematical obstacle made it forbidingly
complicated to obtain exact results. We use the supersymmetry method to fully
circumvent this problem. We present an exact formula for the eigenvalue density
in the real case in terms of twofold integrals and finite sums.Comment: 4 pages, 2 figure
Properties of nonaqueous electrolytes Sixth summary report, 20 Sep. 1967 - 19 Mar. 1968
Physical properties and structural studies on propylene carbonate, dimethyl formamide, and acetonitrile solvent electrolyte
Quantum Dynamics of a Bose Superfluid Vortex
We derive a fully quantum-mechanical equation of motion for a vortex in a
2-dimensional Bose superfluid, in the temperature regime where the normal fluid
density is small. The coupling between the vortex "zero mode" and
the quasiparticles has no term linear in the quasiparticle variables -- the
lowest-order coupling is quadratic. We find that as a function of the
dimensionless frequency , the standard
Hall-Vinen/Iordanskii equations are valid when (the
"classical regime"), but elsewhere, the equations of motion become highly
retarded, with significant experimental implications when .Comment: 12 pages (4 pages + supp info), 2 figures, accepted to PR
Mortality and cancer incidence following occupational radiation exposure: third analysis of the National Registry for Radiation Workers
Mortality and cancer incidence were studied in the National Registry for Radiation Workers in, relative to earlier analyses, an enlarged cohort of 174 541 persons, with longer follow-up (to 2001) and, for the first time, cancer registration data. SMRs for all causes and all malignant neoplasms were 81 and 84 respectively, demonstrating a ‘healthy worker effect'. Within the cohort, mortality and incidence from both leukaemia excluding CLL and the grouping of all malignant neoplasms excluding leukaemia increased to a statistically significant extent with increasing radiation dose. Estimates of the trend in risk with dose were similar to those for the Japanese A-bomb survivors, with 90% confidence intervals that excluded both risks more than 2–3 times greater than the A-bomb values and no raised risk. Some evidence of an increasing trend with dose in mortality from all circulatory diseases may, at least partly, be due to confounding by smoking. This analysis provides the most precise estimates to date of mortality and cancer risks following occupational radiation exposure and strengthens the evidence for raised risks from these exposures. The cancer risk estimates are consistent with values used to set radiation protection standards
Gap Probabilities for Edge Intervals in Finite Gaussian and Jacobi Unitary Matrix Ensembles
The probabilities for gaps in the eigenvalue spectrum of the finite dimension
random matrix Hermite and Jacobi unitary ensembles on some
single and disconnected double intervals are found. These are cases where a
reflection symmetry exists and the probability factors into two other related
probabilities, defined on single intervals. Our investigation uses the system
of partial differential equations arising from the Fredholm determinant
expression for the gap probability and the differential-recurrence equations
satisfied by Hermite and Jacobi orthogonal polynomials. In our study we find
second and third order nonlinear ordinary differential equations defining the
probabilities in the general case. For N=1 and N=2 the probabilities and
thus the solution of the equations are given explicitly. An asymptotic
expansion for large gap size is obtained from the equation in the Hermite case,
and also studied is the scaling at the edge of the Hermite spectrum as , and the Jacobi to Hermite limit; these last two studies make
correspondence to other cases reported here or known previously. Moreover, the
differential equation arising in the Hermite ensemble is solved in terms of an
explicit rational function of a {Painlev\'e-V} transcendent and its derivative,
and an analogous solution is provided in the two Jacobi cases but this time
involving a {Painlev\'e-VI} transcendent.Comment: 32 pages, Latex2
Patterns and Predictors of Relapse Following Radical Chemoradiation Therapy Delivered Using Intensity Modulated Radiation Therapy With a Simultaneous Integrated Boost in Anal Squamous Cell Carcinoma
Purpose:
To describe the patterns and predictors of treatment failure in patients receiving definitive chemoradiotherapy (CRT) for anal squamous cell carcinoma (ASCC), delivered using intensity modulated radiotherapy (IMRT).
Materials and methods:
A retrospective cohort analysis of consecutive patients treated with curative intent for ASCC using CRT delivered with a standardised IMRT technique in five UK cancer centres. Patients were included from the start of UK IMRT guidance in February 2013 to 31st October 2017. Collected data included baseline demographics, treatment details, tumour control, sites of relapse and overall survival. Statistical analysis to calculate outcomes and predictive factors for outcome measures were performed using SPSS and R.
Results:
The medical records of 385 consecutive patients were analysed. Median follow-up was 24.0 months. 86.7% of patients achieved a complete response (CR) within 6 months of completing chemoradiotherapy. 3yr disease free survival (DFS) and overall survival (OS) were 75.6% and 85.6% respectively. Of all relapses, 83.4% occurred at the site of primary disease. There were two isolated relapses in regional nodes not involved at outset. Predictive factors for cancer recurrence included male sex, high N-stage and failure to complete radiotherapy as planned.
Conclusions:
The treatment results compare favourably to published outcomes from similar cohorts using 3D conformal CRT. The observed patterns of failure support the current UK IMRT voluming guidelines and dose levels, highlighting our prophylactic nodal dose is sufficient to prevent isolated regional relapse in uninvolved nodes. Further investigation into strategies to optimise CR should remain a priority in ASCC, as the site of primary disease remains the overwhelming site of relapse
The Calogero-Moser equation system and the ensemble average in the Gaussian ensembles
From random matrix theory it is known that for special values of the coupling
constant the Calogero-Moser (CM) equation system is nothing but the radial part
of a generalized harmonic oscillator Schroedinger equation. This allows an
immediate construction of the solutions by means of a Rodriguez relation. The
results are easily generalized to arbitrary values of the coupling constant. By
this the CM equations become nearly trivial.
As an application an expansion for in terms of eigenfunctions of
the CM equation system is obtained, where X and Y are matrices taken from one
of the Gaussian ensembles, and the brackets denote an average over the angular
variables.Comment: accepted by J. Phys.
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