110 research outputs found
ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE 1 (ADPG1) releases latent defense signals in stems with reduced lignin content
There is considerable interest in engineering plant cell wall components, particularly lignin, to improve forage quality and biomass properties for processing to fuels and bioproducts. However, modifying lignin content and/or composition in transgenic plants through down-regulation of lignin biosynthetic enzymes can induce expression of defense response genes in the absence of biotic or abiotic stress. Arabidopsis thaliana lines with altered lignin through down-regulation of hydroxycinnamoyl CoA:shikimate/quinate hydroxycinnamoyl transferase (HCT) or loss of function of cinnamoyl CoA reductase 1 (CCR1) express a suite of pathogenesis-related (PR) protein genes. The plants also exhibit extensive cell wall remodeling associated with induction of multiple cell wall-degrading enzymes, a process which renders the corresponding biomass a substrate for growth of the cellulolytic thermophile Caldicellulosiruptor bescii lacking a functional pectinase gene cluster. The cell wall remodeling also results in the release of size- and charge-heterogeneous pectic oligosaccharide elicitors of PR gene expression. Genetic analysis shows that both in planta PR gene expression and release of elicitors are the result of ectopic expression in xylem of the gene ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE 1 (ADPG1), which is normally expressed during anther and silique dehiscence. These data highlight the importance of pectin in cell wall integrity and the value of lignin modification as a tool to interrogate the informational content of plant cell walls
A systematic cross-search for radio/infrared counterparts of XMM-Newton sources
We present a catalog of cross-correlated radio, infrared and X-ray sources
using a very restrictive selection criteria with an IDL-based code developed by
us. The significance of the observed coincidences was evaluated through Monte
Carlo simulations of synthetic sources following a well-tested protocol. We
found 3320 coincident radio/X-ray sources with a high statistical significance
characterized by the sum of error-weighted coordinate differences. For 997 of
them, 2MASS counterparts were found. The percentage of chance coincidences is
less than 1%. X-ray hardness ratios of well-known populations of objects were
used to provide a crude representation of their X-ray spectrum and to make a
preliminary diagnosis of the possible nature of unidentified X-ray sources. The
results support the fact that the X-ray sky is largely dominated by Active
Galactic Nuclei at high galactic latitudes (|b| >= 10^\circ). At low galactic
latitudes (|b| <= 10^\circ) most of unidentified X-ray sources (~94%) lie at
|b| <= 2^\circ. This result suggests that most of the unidentified sources
found toward the Milky Way plane are galactic objects. Well-known and
unidentified sources were classified in different tables with their
corresponding radio/infrared and X-ray properties. These tables are intended as
a useful tool for researchers interested in particular identifications.Comment: Accepted for publication in Ap&SS. 47 pages, 10 figures. On-line
material: figures and table
CGC, Hydrodynamics, and the Parton Energy Loss
Hadron spectra in Au+Au collisions at RHIC are calculated by hydrodynamics
with initial conditions from the Color Glass Condensate (CGC). Minijet
components with parton energy loss in medium are also taken into account by
using parton density obtained from hydrodynamical simulations. We found that
CGC provides a good initial condition for hydrodynamics in Au+Au collisions at
RHIC.Comment: Quark Matter 2004 contribution, 4 pages, 2 figure
Predictions for Pb Collisions at TeV: Comparison with Data
Predictions made in Albacete {\it et al} prior to the LHC Pb run at
TeV are compared to currently available data. Some
predictions shown here have been updated by including the same experimental
cuts as the data. Some additional predictions are also presented, especially
for quarkonia, that were provided to the experiments before the data were made
public but were too late for the original publication are also shown here.Comment: 55 pages 35 figure
Theoretical Overview Quark Matter '04
The much wider transverse-momentum range accessible in heavy-ion collisions
at RHIC and at the LHC allows us to disentangle the dynamics of partonic
equilibration from the dynamics of delayed hadronization. This provides a novel
tool for testing the equilibration mechanisms underlying QCD thermodynamics.
Here, I argue, on the basis of simple formation-time arguments, why this is so,
and I review recent theoretical developments in this context.Comment: 12 pages, Latex, 3 eps figures, invited introductory talk at Quark
Matter 2004, Oakland, January 11-17, 200
Thermal Dileptons at LHC
We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb
collisions at LHC. Hadronic emission in the low-mass region is calculated using
in-medium spectral functions of light vector mesons within hadronic many-body
theory. In the intermediate-mass region thermal radiation from the Quark-Gluon
Plasma, evaluated perturbatively with hard-thermal loop corrections, takes
over. An important source over the entire mass range are decays of correlated
open-charm hadrons, rendering the nuclear modification of charm and bottom
spectra a critical ingredient.Comment: 2 pages, 2 figures, contributed to Workshop on Heavy Ion Collisions
at the LHC: Last Call for Predictions, Geneva, Switzerland, 14 May - 8 Jun
2007 v2: acknowledgment include
Proceedings of the 38th International Symposium on Multiparticle Dynamics (ISMD08)
Proceedings of ISMD08Comment: Edited by: J. Bartels, K. Borras, G. Gustafson, H. Jung, K. Kutak, S.
Levonian, and J. Mnic
QCD and strongly coupled gauge theories : challenges and perspectives
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe
Study of production and cold nuclear matter effects in pPb collisions at=5 TeV
Production of mesons in proton-lead collisions at a nucleon-nucleon centre-of-mass energy = 5 TeV is studied with the LHCb detector. The analysis is based on a data sample corresponding to an integrated luminosity of 1.6 nb(-1). The mesons of transverse momenta up to 15 GeV/c are reconstructed in the dimuon decay mode. The rapidity coverage in the centre-of-mass system is 1.5 < y < 4.0 (forward region) and -5.0 < y < -2.5 (backward region). The forward-backward production ratio and the nuclear modification factor for (1S) mesons are determined. The data are compatible with the predictions for a suppression of (1S) production with respect to proton-proton collisions in the forward region, and an enhancement in the backward region. The suppression is found to be smaller than in the case of prompt J/psi mesons
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