Dependence of the thermoluminescent high-temperature ratio (HTR) of LiF:Mg,Ti detectors on proton energy and dose

The high-temperature ratio (HTR) is a parameter quantifying changes of the shape of the high-temperature part of the LiF:Mg,Ti glow-curve after exposure to densely ionizing radiation. It was introduced in order to estimate the effective LET of an unknown radiation field and to correct the decreased relative TL efficiency for high Linear Energy Transfer (LET) radiation. In the present work the dependence of HTR on proton energy (14.5 to 58 MeV) and dose (0.5 to 30 Gy) was investigated. All measured HTR values were at the level of 1.2 or higher, therefore significantly different from the respective value for gamma rays (HTR is equal to 1), but HTR was found to be insensitive to changes of proton energy above 20 MeV. As a result the relationship between HTR and relative TL efficiency is not unequivocal. The HTR was found to be dependent on absorbed dose even for the lowest studied doses.Comment: Manuscript has been presented at the 17th International Conference on Solid State Dosimetry, Recife, Brasil, September 22-27,201

Random Dirac operators with time-reversal symmetry

Quasi-one-dimensional stochastic Dirac operators with an odd number of channels, time reversal symmetry but otherwise efficiently coupled randomness are shown to have one conducting channel and absolutely continuous spectrum of multiplicity two. This follows by adapting the criteria of Guivarch-Raugi and Goldsheid-Margulis to the analysis of random products of matrices in the group SO$^*(2L)$, and then a version of Kotani theory for these operators. Absence of singular spectrum can be shown by adapting an argument of Jaksic-Last if the potential contains random Dirac peaks with absolutely continuous distribution.Comment: parts of introduction made more precise, corrections as follow-up on referee report

Results of the minimally invasive coronary artery bypass grafting angiographic patency study

ObjectiveMinimally invasive coronary artery bypass grafting is safe and widely applicable, and may be associated with fewer transfusions and infections, and better recovery than standard coronary artery bypass grafting. However, graft patency rates remain unknown. The Minimally Invasive Coronary Artery Bypass Grafting Patency Study prospectively evaluated angiographic graft patency 6 months after minimally invasive coronary artery bypass grafting.MethodsIn this dual-center study, 91 patients were prospectively enrolled to undergo minimally invasive coronary artery bypass grafting via a 4- to 7-cm left thoracotomy approach. The left internal thoracic artery, the ascending aorta for proximal anastomoses, and all coronary targets were directly accessed without endoscopic or robotic assistance. The study primary outcome was graft patency at 6 months, using 64-slice computed tomography angiography. Secondary outcomes included conversions to sternotomy and major adverse cardiovascular events (Clinical Trial Registration Unique identifier: NCT01334866).ResultsThe mean age of patients was 64 ± 8 years, the mean ejection fraction was 51% ± 11%, and there were 10 female patients (11%) in the study. Surgeries were performed entirely off-pump in 68 patients (76%). Complete revascularization was achieved in all patients, and the median number of grafts was 3. There was no perioperative mortality, no conversion to sternotomy, and 2 reopenings for bleeding. Transfusion occurred in 24 patients (26%). The median length of hospital stay was 4 days, and all patients were followed to 6 months, with no mortality or major adverse cardiovascular events. Six-month computed tomography angiographic graft patency was 92% for all grafts and 100% for left internal thoracic artery grafts.ConclusionsMinimally invasive coronary artery bypass grafting is safe, feasible, and associated with excellent outcomes and graft patency at 6 months post-surgery

Disordered quantum wires: microscopic origins of the DMPK theory and Ohm's law

We study the electronic transport properties of the Anderson model on a strip, modeling a quasi one-dimensional disordered quantum wire. In the literature, the standard description of such wires is via random matrix theory (RMT). Our objective is to firmly relate this theory to a microscopic model. We correct and extend previous work (arXiv:0912.1574) on the same topic. In particular, we obtain through a physically motivated scaling limit an ensemble of random matrices that is close to, but not identical to the standard transfer matrix ensembles (sometimes called TOE, TUE), corresponding to the Dyson symmetry classes \beta=1,2. In the \beta=2 class, the resulting conductance is the same as the one from the ideal ensemble, i.e.\ from TUE. In the \beta=1 class, we find a deviation from TOE. It remains to be seen whether or not this deviation vanishes in a thick-wire limit, which is the experimentally relevant regime. For the ideal ensembles, we also prove Ohm's law for all symmetry classes, making mathematically precise a moment expansion by Mello and Stone. This proof bypasses the explicit but intricate solution methods that underlie most previous results.Comment: Corrects and extends arXiv:0912.157

Spectral averaging techniques for Jacobi matrices with matrix entries

A Jacobi matrix with matrix entries is a self-adjoint block tridiagonal matrix with invertible blocks on the off-diagonals. Averaging over boundary conditions leads to explicit formulas for the averaged spectral measure which can potentially be useful for spectral analysis. Furthermore another variant of spectral averaging over coupling constants for these operators is presented

Localization via fractional moments for models on Z\mathbb{Z} with single-site potentials of finite support

One of the fundamental results in the theory of localization for discrete Schr\"odinger operators with random potentials is the exponential decay of Green's function and the absence of continuous spectrum. In this paper we provide a new variant of these results for one-dimensional alloy-type potentials with finitely supported sign-changing single-site potentials using the fractional moment method.Comment: LaTeX-file, 26 pages with 2 LaTeX figure

Evaluation of the relative TL efficiency of the thermoluminescent detectors to heavy charged particles

The relative thermoluminescence efficiency, amp; 951;, is in general not constant but depends on ionisation density. Evaluation of the amp; 951; is therefore important especially for correct interpretation of measurements of densely ionising radiation doses in proton radiotherapy or in space dosimetry. The correct determination of the amp; 951; is not always straightforward especially when more strongly ionising radiation is to be measured. In the present work, the process of calculation of the amp; 951; based on two kinds of heavy charged particles was studied. Several factors which may influence the value of the amp; 951; and their significance for the final result were discussed. These include for example non uniform deposition of the dose within the detector volume, self attenuation of thermoluminescent light, choice of the reference radiation, etc. The presented approach was applied to the experimental results of amp; 951; of LiF Mg,Ti detectors irradiated with two kinds of heavy charged particles, protons and alpha particles. The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email journals.permissions oup.co

Minimally Invasive Valve Surgery and Single Vessel Coronary Artery Bypass via Limited Anterior Right Thoracotomy

Background: Coronary artery bypass grafting with aortic valve replacement (AVR) or mitral valve replacement (MVR) is traditionally performed via sternotomy. Minimally invasive coronary surgery (MICS) and minimally invasive valve surgery have been successfully performed independently. Patients with critical right coronary artery (RCA) stenosis not amenable to percutaneous intervention are candidates for valve replacement and single vessel coronary artery bypass. We present our series of six patients who underwent a concomitant valve and single vessel intervention via right thoracotomy. Methods: Between January 2011 and June 2013, six patients underwent right thoracotomy with valve replacement and single vessel bypass. Four aortic and two mitral valves were replaced and all received single vessel RCA bypass using reversed saphenous vein graft. Thoracotomy was via right anterior approach for AVR and right lateral for MVR. The patients were assessed postoperatively for overall outcomes. Results: The average age was 74 years (range 69-81); two patients were elective (AVR-1; MVR-1) and four were urgent (AVR-3; MVR-1). For MICS AVR and MICS MVR, the average cardiopulmonary bypass time was 171 +/- 30 and 169 +/- 7 minutes and the average aortic cross-clamp time was 122 +/- 36 and 112 +/- 2 minutes, respectively. Three patients were discharged home, one patient to a nursing home, and two to rehab. No patients required conversion to sternotomy; one patient developed atrial fibrillation, and one sepsis. Conclusion: Concomitant valve replacement and single bypass grafting via right anterior mini-thoracotomy is a viable option for select patients, particularly in non-stentable RCA stenosis. In the appropriate patient population, combined coronary artery bypass grafting and valve surgery can be safely performed via right thoracotomy