203 research outputs found
Optical absorption spectra and monomer interaction in polymers. Investigation of exciton coupling in DNA hairpins
We investigate the effect of exciton coupling on the optical absorption
spectrum of polymer molecules under conditions of strong inhomogeneous
broadening. We demonstrate that the dependence of the maximum in the rescaled
absorption spectrum on the number of monomers is determined by the average
monomer excitation energies and their resonant coupling and insensitive to the
inhomogeneous broadening. Thus the absorption spectrum can be used to determine
optical interactions between monomers. The results are applied to the
absorption spectra of poly-A poly-T DNA hairpins and used to interpret the
dependence of the absorption spectrum on the number of monomers. We also
discuss exciton localization in these hairpins.Comment: Submitted to Journal of Chemical Physic
Revision of the 15N(p,{\gamma})16O reaction rate and oxygen abundance in H-burning zones
The NO cycle takes place in the deepest layer of a H-burning core or shell,
when the temperature exceeds T {\simeq} 30 {\cdot} 106 K. The O depletion
observed in some globular cluster giant stars, always associated with a Na
enhancement, may be due to either a deep mixing during the RGB (red giant
branch) phase of the star or to the pollution of the primordial gas by an early
population of massive AGB (asymptotic giant branch) stars, whose chemical
composition was modified by the hot bottom burning. In both cases, the NO cycle
is responsible for the O depletion. The activation of this cycle depends on the
rate of the 15N(p,{\gamma})16O reaction. A precise evaluation of this reaction
rate at temperatures as low as experienced in H-burning zones in stellar
interiors is mandatory to understand the observed O abundances. We present a
new measurement of the 15N(p,{\gamma})16O reaction performed at LUNA covering
for the first time the center of mass energy range 70-370 keV, which
corresponds to stellar temperatures between 65 {\cdot} 106 K and 780 {\cdot}106
K. This range includes the 15N(p,{\gamma})16O Gamow-peak energy of explosive
H-burning taking place in the external layer of a nova and the one of the hot
bottom burning (HBB) nucleosynthesis occurring in massive AGB stars. With the
present data, we are also able to confirm the result of the previous R-matrix
extrapolation. In particular, in the temperature range of astrophysical
interest, the new rate is about a factor of 2 smaller than reported in the
widely adopted compilation of reaction rates (NACRE or CF88) and the
uncertainty is now reduced down to the 10% level.Comment: 6 pages, 5 figure
Hepatic fat loss in advanced nonalcoholic steatohepatitis: Are alterations in serum adiponectin the cause?
Gramene: a growing plant comparative genomics resource
Gramene (www.gramene.org) is a curated resource for genetic, genomic and comparative genomics data for the major crop species, including rice, maize, wheat and many other plant (mainly grass) species. Gramene is an open-source project. All data and software are freely downloadable through the ftp site (ftp.gramene.org/pub/gramene) and available for use without restriction. Gramene's core data types include genome assembly and annotations, other DNA/mRNA sequences, genetic and physical maps/markers, genes, quantitative trait loci (QTLs), proteins, ontologies, literature and comparative mappings. Since our last NAR publication 2 years ago, we have updated these data types to include new datasets and new connections among them. Completely new features include rice pathways for functional annotation of rice genes; genetic diversity data from rice, maize and wheat to show genetic variations among different germplasms; large-scale genome comparisons among Oryza sativa and its wild relatives for evolutionary studies; and the creation of orthologous gene sets and phylogenetic trees among rice, Arabidopsis thaliana, maize, poplar and several animal species (for reference purpose). We have significantly improved the web interface in order to provide a more user-friendly browsing experience, including a dropdown navigation menu system, unified web page for markers, genes, QTLs and proteins, and enhanced quick search functions
Covering one eye in fixation-disparity measurement causes slight movement of fellow eye
In the subjective measurement of fixation disparity (FD), the subject fuses contours presented in the peripheral macular areas of both eyes (fusion lock). The position of the eyes relative to each other is monitored by means of two haploscopically seen vertical lines presented in the central macular area, one above and one below a binocularly seen horizontal line. The subject is instructed to shift one of the vertical lines horizontally until the two are aligned, while fixating their intersection with the horizontal line. It has recently been questioned whether the foveolae really are pointed towards the perceived intersection. In this study, we monitored the position of one eye while intermittently covering the fellow eye, while the subject maintained fixation of the intersection of the remaining vertical line and the horizontal line. We found slight differences in position of the measured eye, depending on whether the other eye was covered or not, i.e. depending on the presence or absence of fusion in the macular periphery. These differences were more pronounced in the non-dominant eye
Human breast cancer stem cell markers CD44 and CD24: enriching for cells with functional properties in mice or in man?
Identification of breast cancer stem cells as the cells within breast tumors that have the ability to give rise to cells that make up the bulk of the tumor mass has shifted the focus of cancer research. However, there is still much debate concerning the unique nature of the markers that distinguish cancer stem cells in the breast. As such, understanding whether CD44+/CD24- breast cancer cells are merely more successful in overcoming an engraftment incompatibility that exists when injecting human cells into the mouse adipose tissue or are indeed bona fide cancer stem cells is of great importance
Gramene: a growing plant comparative genomics resource
Gramene (www.gramene.org) is a curated resource for genetic, genomic and comparative genomics data for the major crop species, including rice, maize, wheat and many other plant (mainly grass) species. Gramene is an open-source project. All data and software are freely downloadable through the ftp site (ftp.gramene.org/pub/gramene) and available for use without restriction. Gramene's core data types include genome assembly and annotations, other DNA/mRNA sequences, genetic and physical maps/markers, genes, quantitative trait loci (QTLs), proteins, ontologies, literature and comparative mappings. Since our last NAR publication 2 years ago, we have updated these data types to include new datasets and new connections among them. Completely new features include rice pathways for functional annotation of rice genes; genetic diversity data from rice, maize and wheat to show genetic variations among different germplasms; large-scale genome comparisons among Oryza sativa and its wild relatives for evolutionary studies; and the creation of orthologous gene sets and phylogenetic trees among rice, Arabidopsis thaliana, maize, poplar and several animal species (for reference purpose). We have significantly improved the web interface in order to provide a more user-friendly browsing experience, including a dropdown navigation menu system, unified web page for markers, genes, QTLs and proteins, and enhanced quick search functions
Gramene: a growing plant comparative genomics resource
Gramene (www.gramene.org) is a curated resource for genetic, genomic and comparative genomics data for the major crop species, including rice, maize, wheat and many other plant (mainly grass) species. Gramene is an open-source project. All data and software are freely downloadable through the ftp site (ftp.gramene.org/pub/gramene) and available for use without restriction. Gramene's core data types include genome assembly and annotations, other DNA/mRNA sequences, genetic and physical maps/markers, genes, quantitative trait loci (QTLs), proteins, ontologies, literature and comparative mappings. Since our last NAR publication 2 years ago, we have updated these data types to include new datasets and new connections among them. Completely new features include rice pathways for functional annotation of rice genes; genetic diversity data from rice, maize and wheat to show genetic variations among different germplasms; large-scale genome comparisons among Oryza sativa and its wild relatives for evolutionary studies; and the creation of orthologous gene sets and phylogenetic trees among rice, Arabidopsis thaliana, maize, poplar and several animal species (for reference purpose). We have significantly improved the web interface in order to provide a more user-friendly browsing experience, including a dropdown navigation menu system, unified web page for markers, genes, QTLs and proteins, and enhanced quick search functions
Superconductivity at 5 K in potassium doped phenanthrene
Organic materials are believed to be potential superconductor with high
transition temperature (TC). Organic superconductors mainly have two families:
the quasi-one dimensional (TMTSF)2X and two dimensional (BEDT-TTF)2X (Ref. 1
and 2), in which TMTSF is tetramethyltetraselenafulvalene (C10H12Se4) and
BEDT-TTF or "ET" is bis(ethylenedithio)tetrathiafulvalene (C10H8S8). One key
feature of the organic superconductors is that they have {\pi}-molecular
orbitals, and the {\pi}-electron can delocalize throughout the crystal giving
rise to metallic conductivity due to a {\pi}-orbital overlap between adjacent
molecules. The introduction of charge into C60 solids and graphites with
{\pi}-electron networks by doping to realize superconductivity has been
extensively reported3,4. Very recently, superconductivity in alkali-metal doped
picene with {\pi}-electron networks was reported5. Here we report the discovery
of superconductivity in potassium doped Phenanthrene with TC~5 K. TC increases
with increasing pressure, and the pressure of 1 GPa leads to an increase of 20%
in TC, suggesting that the potassium doped phenanthrene shows unconventional
superconductivity. Both phenanthrene and picene are polycyclic aromatic
hydrocarbons, and contain three and five fused benzene rings, respectively. The
ribbon of fused benzene rings is part of graphene. Therefore, the discovery of
superconductivity in K3Phenanthrene produces a novel broad class of
superconductors consisting of fused hydrocarbon benzene rings with
{\pi}-electron networks. The fact that TC increases from 5 K for KxPhenanthrene
with three benzene rings to 18 K for Kxpicene with five benzene rings suggests
that such organic hydrocarbons with long benzene rings is potential
superconductor with high TC.Comment: 20 pages, 3 figures, one supplementary information. submitted to
Nature Communication
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