654 research outputs found
Aggregation Behavior And Chromonic Liquid Crystal Properties Of An Anionic Monoazo Dye
X-ray scattering and various optical techniques are utilized to study the aggregation process and chromonic liquid crystal phase of the anionic monoazo dye Sunset Yellow FCF. The x-ray results demonstrate that aggregation involves pi-pi stacking of the molecules into columns, with the columns undergoing a phase transition to an orientationally ordered chromonic liquid crystal phase at high dye concentration. Optical absorption measurements on dilute solutions reveal that the aggregation takes place at all concentrations, with the average aggregation number increasing with concentration. A simple theory based on the law of mass action and an isodesmic aggregation process is in excellent agreement with the experimental data and yields a value for the bond energy between molecules in an aggregate. Measurements of the birefringence and order parameter are also performed as a function of temperature in the chromonic liquid crystal phase. The agreement between these results and a more complicated theory of aggregation is quite reasonable. Overall, these results both confirm that the aggregation process for some dyes is isodesmic and provide a second example of a well-characterized chromonic system
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
A Molecular and Preclinical Comparison of the PD-1 targeted T cell Checkpoint Inhibitors Nivolumab and Pembrolizumab
T cell checkpoint inhibition has a profound impact on cancer care and the two Programmed cell death protein 1 (PD-1) targeted antibodies nivolumab and pembrolizumab have been leading this therapeutic revolution. Their clinical comparability is a highly relevant topic of discussion, but to a significant degree is a consequence of their molecular properties. Here we provide a molecular, preclinical, and early clinical comparison of the two antibodies, based on the available data and recent literature. We acknowledge the limitations of such comparisons, but suggest that based on the available data, differences in clinical trial outcomes between nivolumab and pembrolizumab are more likely drug-independent than drug-dependent.Wellcome Trust Translational Medicine and Therapeutics Grant
RJAG/07
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
Fast, Linear Time Hierarchical Clustering using the Baire Metric
The Baire metric induces an ultrametric on a dataset and is of linear
computational complexity, contrasted with the standard quadratic time
agglomerative hierarchical clustering algorithm. In this work we evaluate
empirically this new approach to hierarchical clustering. We compare
hierarchical clustering based on the Baire metric with (i) agglomerative
hierarchical clustering, in terms of algorithm properties; (ii) generalized
ultrametrics, in terms of definition; and (iii) fast clustering through k-means
partititioning, in terms of quality of results. For the latter, we carry out an
in depth astronomical study. We apply the Baire distance to spectrometric and
photometric redshifts from the Sloan Digital Sky Survey using, in this work,
about half a million astronomical objects. We want to know how well the (more
costly to determine) spectrometric redshifts can predict the (more easily
obtained) photometric redshifts, i.e. we seek to regress the spectrometric on
the photometric redshifts, and we use clusterwise regression for this.Comment: 27 pages, 6 tables, 10 figure
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.
Luttinger liquid phenomenology and angle resolved photoemission for single layer \chem{Bi_2Sr_{2-x}La_xCuO_{6+\delta}} high--temperature superconductor
Recently observed splitting in angular resolved photoemission spectroscopy
(ARPES) on \chem{Bi_2Sr_{2-x}La_xCuO_{6+\delta}} high--temperature
superconductor (Janowitz C. {\it et al.}, {\it Europhys. Lett.}, {\bf 60}
(2002) 615) is interpreted within the phenomenological Luttinger--liquid
framework, in which both the non--Fermi liquid scaling exponent of the spectral
function and the spin--charge separation are introduced. The anomalous Green
function with adjustable parameters fits very well to the Fermi edge and the
low--energy part of ARPES along the line in the Brillouin zone. In
contrast to one--dimensional models with Luttinger--liquid behavior we find
that both the anomalous scaling and the parameter describing
the spin--charge separation are momentum dependent. The higher--energy part of
the spectra is not accounted for by this simple Luttinger--liquid form of the
Green function. In this energy regime additional scattering processes are
plausible to produce the experimentally observed wide incoherent background,
which diminishes as the inverse of the energy.Comment: 7 pages, 3 figures, EPL styl
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