1,152 research outputs found
Hall effect in the marginal Fermi liquid regime of high-Tc superconductors
The detailed derivation of a theory for transport in quasi-two-dimensional
metals, with small-angle elastic scattering and angle-independent inelastic
scattering is presented. The transport equation is solved for a model Fermi
surface representing a typical cuprate superconductor. Using the small-angle
elastic and the inelastic scattering rates deduced from angle-resolved
photoemission experiments, good quantitative agreement with the observed
anomalous temperature dependence of the Hall angle in optimally doped cuprates
is obtained, while the resistivity remains linear in temperature. The theory is
also extended to the frequency-dependent complex Hall angle
Normal tissue complication probability (NTCP) parameters for breast fibrosis: pooled results from two randomised trials
Introduction: the dose–volume effect of radiation therapy on breast tissue is poorly understood. We estimate NTCP parameters for breast fibrosis after external beam radiotherapy.Materials and methods: we pooled individual patient data of 5856 patients from 2 trials including whole breast irradiation followed with or without a boost. A two-compartment dose volume histogram model was used with boost volume as the first compartment and the remaining breast volume as second compartment. Results from START-pilot trial (n?=?1410) were used to test the predicted models.Results: 26.8% patients in the Cambridge trial (5?years) and 20.7% patients in the EORTC trial (10?years) developed moderate-severe breast fibrosis. The best fit NTCP parameters were BEUD3(50)?=?136.4?Gy, ?50?=?0.9 and n?=?0.011 for the Niemierko model and BEUD3(50)?=?132?Gy, m?=?0.35 and n?=?0.012 for the Lyman Kutcher Burman model. The observed rates of fibrosis in the START-pilot trial agreed well with the predicted rates.Conclusions: this large multi-centre pooled study suggests that the effect of volume parameter is small and the maximum RT dose is the most important parameter to influence breast fibrosis. A small value of volume parameter ‘n’ does not fit with the hypothesis that breast tissue is a parallel organ. However, this may reflect limitations in our current scoring system of fibrosi
Adiabatic following criterion, estimation of the nonadiabatic excitation fraction and quantum jumps
An accurate theory describing adiabatic following of the dark, nonabsorbing
state in the three-level system is developed. An analytical solution for the
wave function of the particle experiencing Raman excitation is found as an
expansion in terms of the time varying nonadiabatic perturbation parameter. The
solution can be presented as a sum of adiabatic and nonadiabatic parts. Both
are estimated quantitatively. It is shown that the limiting value to which the
amplitude of the nonadiabatic part tends is equal to the Fourier component of
the nonadiabatic perturbation parameter taken at the Rabi frequency of the
Raman excitation. The time scale of the variation of both parts is found. While
the adiabatic part of the solution varies slowly and follows the change of the
nonadiabatic perturbation parameter, the nonadiabatic part appears almost
instantly, revealing a jumpwise transition between the dark and bright states.
This jump happens when the nonadiabatic perturbation parameter takes its
maximum value.Comment: 33 pages, 8 figures, submitted to PRA on 28 Oct. 200
Mass equidistribution of Hilbert modular eigenforms
Let F be a totally real number field, and let f traverse a sequence of
non-dihedral holomorphic eigencuspforms on GL(2)/F of weight (k_1,...,k_n),
trivial central character and full level. We show that the mass of f
equidistributes on the Hilbert modular variety as max(k_1,...,k_n) tends to
infinity.
Our result answers affirmatively a natural analogue of a conjecture of
Rudnick and Sarnak (1994). Our proof generalizes the argument of
Holowinsky-Soundararajan (2008) who established the case F = Q. The essential
difficulty in doing so is to adapt Holowinsky's bounds for the Weyl periods of
the equidistribution problem in terms of manageable shifted convolution sums of
Fourier coefficients to the case of a number field with nontrivial unit group.Comment: 40 pages; typos corrected, nearly accepted for
CLEANING PICTORIAL HERITAGE: MANAGEMENT AND DISSEMINATION OF CLEANING RECORDS AND STRATIGRAPHIC DATA
[EN] At present, the process of documentation can be considered the cornerstone of the different tasks within the field of conservation and restoration of cultural heritage. However, this is not the case with cleaning. Despite its importance in the conservation of pictorial heritage, little effort has been made to improve the management and dissemination of information. Cleaning is one of the most usual procedures, yet, at the same time, it is also one of the most problematic and controversial. Therefore, it would be very useful that the information generated by cleaning could be widely disseminated and serve as reference for researchers and conservators around the world. When a conservator carries out a cleaning operation on a painting, two kinds of interrelated data are produced: stratigraphic data and cleaning records. Stratigraphic data are those concerning the configuration and composition of the stratigraphic structure on which the cleaning is carried out. Cleaning records gather together data concerning the actual cleaning process. All this information is key for conservators when working on other paintings. The information published is usually insufficient to understand how the intervention was carried out, so there is a need for standardized systems which allow a great deal of information to be gathered and disseminated with ease. This paper explains a selection of proposals, some of which are already in use, and others which are being developed: stratigraphic unit recording sheets, solubility test recording sheets and stratigraphic diagrams.Barros García, JM.; Guillen Juan, CM. (2012). CLEANING PICTORIAL HERITAGE: MANAGEMENT AND DISSEMINATION OF CLEANING RECORDS AND STRATIGRAPHIC DATA. International Journal of Heritage in the Digital Era. 1(1_suppl):159-164. doi:10.1260/2047-4970.1.0.159S15916411_supplBarker, P. (2003). Techniques of Archaeological Excavation. doi:10.4324/9780203442173Barros García, J. M. (2009). Recording stratigraphic relationships among non-original deposits on a 16th century painting. Journal of Cultural Heritage, 10(3), 338-346. doi:10.1016/j.culher.2009.01.00
Persistent Spin Currents in Helimagnets
We demonstrate that weak external magnetic fields generate dissipationless
spin currents in the ground state of systems with spiral magnetic order. Our
conclusions are based on phenomenological considerations and on microscopic
mean-field theory calculations for an illustrative toy model. We speculate on
possible applications of this effect in spintronic devices.Comment: 9 pages, 6 figures, updated version as published, Journal referenc
Quantum Griffiths effects and smeared phase transitions in metals: theory and experiment
In this paper, we review theoretical and experimental research on rare region
effects at quantum phase transitions in disordered itinerant electron systems.
After summarizing a few basic concepts about phase transitions in the presence
of quenched randomness, we introduce the idea of rare regions and discuss their
importance. We then analyze in detail the different phenomena that can arise at
magnetic quantum phase transitions in disordered metals, including quantum
Griffiths singularities, smeared phase transitions, and cluster-glass
formation. For each scenario, we discuss the resulting phase diagram and
summarize the behavior of various observables. We then review several recent
experiments that provide examples of these rare region phenomena. We conclude
by discussing limitations of current approaches and open questions.Comment: 31 pages, 7 eps figures included, v2: discussion of the dissipative
Ising chain fixed, references added, v3: final version as publishe
- …