615 research outputs found
Coupling to a phononic mode in : Angle-resolved photoemission
The kink in the dispersion and the drop in the width observed by
angle-resolved photoemission in the nodal direction of the Brillouin zone of
(abbreviated as (Pb)Bi2212) has
attracted broad interest [1-3]. Surprisingly optimally lead-doped (Pb)Bi2212
with as well as the shadow band were not investigated so
far, although the origin of the kink and the drop is still under strong debate.
In this context a resonant magnetic-mode scenario and an electron-phonon
coupling scenario are discussed controversially. Here we analyze the relevant
differences between both scenarios and conclude that the kink and the drop are
caused by a coupling of the electronic system to a phononic mode at least in
the nodal direction. It is found that besides the dispersion and the drop in
the width also the peak height as a new criterion can be used to define the
energy scale of the interaction, giving a new means for a precise and
consistent determination of the kink energy
Strong spin triplet contribution of the first removal state in the insulating regime of Bi2Sr2Ca1-xYxCu2O8+delta
The experimental dispersion of the first removal state in the insulating
regime of Bi2Sr2Ca1-xYxCu2O8+delta is found to differ significantly from that
of other parent materials: oxyclorides and La2CuO4 . For Y-contents of 0.92 > x
> 0.55 due to nonstoichiometric effects in the Bi-O layers, the hole
concentration in the CuO2 -layers is almost constant and on the contrary the
crystal lattice parameters a,b,c change very strongly. This (a,b) parameter
increase and c parameter decrease results in an unconventional three peak
structure at (0,0);(pi/2, pi/2);(pi,pi) for x=0.92. We can describe the
experimental data only beyond the framework of the 3-band pd-model involving
the representations of a new triplet counterpart for the Zhang-Rice singlet
state.Comment: 16 pages, 4 figure
Formal Framework for Property-driven Obfuscations
We study the existence and the characterization of function transformers that minimally or maximally modify a function in order to reveal or conceal a certain property. Based on this general formal framework we develop a strategy for the design of the maximal obfuscating transformation that conceals a given property while revealing the desired observational behaviou
The use of error-category mapping in pharmacokinetic model analysis of dynamic contrast-enhanced MRI data.
This study introduces the use of 'error-category mapping' in the interpretation of pharmacokinetic (PK) model parameter results derived from dynamic contrast-enhanced (DCE-) MRI data. Eleven patients with metastatic renal cell carcinoma were enrolled in a multiparametric study of the treatment effects of bevacizumab. For the purposes of the present analysis, DCE-MRI data from two identical pre-treatment examinations were analysed by application of the extended Tofts model (eTM), using in turn a model arterial input function (AIF), an individually-measured AIF and a sample-average AIF. PK model parameter maps were calculated. Errors in the signal-to-gadolinium concentration ([Gd]) conversion process and the model-fitting process itself were assigned to category codes on a voxel-by-voxel basis, thereby forming a colour-coded 'error-category map' for each imaged slice. These maps were found to be repeatable between patient visits and showed that the eTM converged adequately in the majority of voxels in all the tumours studied. However, the maps also clearly indicated sub-regions of low Gd uptake and of non-convergence of the model in nearly all tumours. The non-physical condition ve ≥ 1 was the most frequently indicated error category and appeared sensitive to the form of AIF used. This simple method for visualisation of errors in DCE-MRI could be used as a routine quality-control technique and also has the potential to reveal otherwise hidden patterns of failure in PK model applications.This work was supported by GlaxoSmithKline UK, Wellcome Trust, Cambridge NIHR Biomedical Research Centre, Cambridge Experimental Cancer Medicine Centre, Cancer Research UKThis is the published version. It first appeared at http://www.sciencedirect.com/science/article/pii/S0730725X1400321X
Novel Fine-Structure in the Low-Energy Excitation Spectrum of a High-Tc Superconductor by Polarization Dependent Photoemission
Angle-resolved photoemission spectroscopy is performed on single crystals of
the single-layer high-Tc superconductor Bi(2)Sr(2-x)La(x)CuO(6+d) at optimal
doping (x=0.4) in order to study in great detail the Zhang-Rice (ZR) singlet
band at the Fermi level. Besides the high crystal quality the advantages of a
single-layer material are the absence of bilayer effects and the distinct
reduction of thermal broadening. Due to the high energy and angle resolution
and, most important, due to the controlled variation of the polarization vector
of the synchrotron radiation the emission from the ZR singlet band reveals a
distinct fine-structure. It consists of two maxima, the first showing only weak
and the second at EF extremely strong polarization dependence. However, our
observation has enormous consequences for line shape analyses and the
determination of pseudo gaps by photoemission.Comment: 10 pages, 2 figures. to appear in PRB (Rapid Comm.
Spectroscopic signatures of spin-charge separation in the quasi-one-dimensional organic conductor TTF-TCNQ
The electronic structure of the quasi-one-dimensional organic conductor
TTF-TCNQ is studied by angle-resolved photoelectron spectroscopy (ARPES). The
experimental spectra reveal significant discrepancies to band theory. We
demonstrate that the measured dispersions can be consistently mapped onto the
one-dimensional Hubbard model at finite doping. This interpretation is further
supported by a remarkable transfer of spectral weight as function of
temperature. The ARPES data thus show spectroscopic signatures of spin-charge
separation on an energy scale of the conduction band width.Comment: 4 pages, 4 figures; to appear in PR
Interval valued (\in,\ivq)-fuzzy filters of pseudo -algebras
We introduce the concept of quasi-coincidence of a fuzzy interval value with
an interval valued fuzzy set. By using this new idea, we introduce the notions
of interval valued (\in,\ivq)-fuzzy filters of pseudo -algebras and
investigate some of their related properties. Some characterization theorems of
these generalized interval valued fuzzy filters are derived. The relationship
among these generalized interval valued fuzzy filters of pseudo -algebras
is considered. Finally, we consider the concept of implication-based interval
valued fuzzy implicative filters of pseudo -algebras, in particular, the
implication operators in Lukasiewicz system of continuous-valued logic are
discussed
- …