2,132 research outputs found
Comover Enhancement of Quarkonium Production
Quarkonium data suggest an enhancement of the hadroproduction rate from
interactions of the heavy quark pair with a comoving color field generated in
the hard gg -> Q\bar{Q} subprocess. We review the motivations and principal
consequences of this comover enhancement scenario (CES).Comment: 7 pages, 1 eps figure, to appear in the proceedings of the CERN
2001-2002 workshop `Hard Probes in Heavy Ion Collisions at the LHC
Commodities: an asset class in their own right?
Investor interest in commodities has risen in recent years in line with the spectacular surge in most commodity prices. Some institutional investors, for instance Dutch or Californian pension funds, have confirmed that they have gained or intend to gain moderate exposure (less than 5% of their assets) to commodities. In parallel, the development of new investment vehicles has enabled individual investors also to gain commodity exposure. Expectations of continued strong economic growth in Asia, which should result in Asian countriesâ sustained demand for commodities, may be the driver of the increased appetite for these assets. Interest also seems to be spurred by studies by academics and market analysts that highlight commodities as an effective way of diversifying portfolio risk. This assessment and interpretation suggest that investors are slowly but sustainably including commodities in their portfolios. Can we however assert that commodities constitute an asset class in their own right? This study suggests they do, given that over the long term, returns on commodity-related investments appear to outperform risk-free returns, seem to have a low or negative correlation with other asset classes and can apparently not be replicated with a simple linear combination of assets.
A dynamic motion simulator for future European docking systems
Europe's first confrontation with docking in space will require extensive testing to verify design and performance and to qualify hardware. For this purpose, a Docking Dynamics Test Facility (DDTF) was developed. It allows reproduction on the ground of the same impact loads and relative motion dynamics which would occur in space during docking. It uses a 9 degree of freedom, servo-motion system, controlled by a real time computer, which simulates the docking spacecraft in a zero-g environment. The test technique involves and active loop based on six axis force and torque detection, a mathematical simulation of individual spacecraft dynamics, and a 9 degree of freedom servomotion of which 3 DOFs allow extension of the kinematic range to 5 m. The configuration was checked out by closed loop tests involving spacecraft control models and real sensor hardware. The test facility at present has an extensive configuration that allows evaluation of both proximity control and docking systems. It provides a versatile tool to verify system design, hardware items and performance capabilities in the ongoing HERMES and COLUMBUS programs. The test system is described and its capabilities are summarized
Standardisering og beskrivelse af sammenhĂŠngen imellem fiskeriindsats og fiskeridĂždelighed for de danske demersale fiskerier i Kattegat
FabR regulates Salmonella biofilm formation via its direct target FabB
Background: Biofilm formation is an important survival strategy of Salmonella in all environments. By mutant screening, we showed a knock-out mutant of fabR, encoding a repressor of unsaturated fatty acid biosynthesis (UFA), to have impaired biofilm formation. In order to unravel how this regulator impinges on Salmonella biofilm formation, we aimed at elucidating the S. Typhimurium FabR regulon. Hereto, we applied a combinatorial high-throughput approach, combining ChIP-chip with transcriptomics.
Results: All the previously identified E. coli FabR transcriptional target genes (fabA, fabB and yqfA) were shown to be direct S. Typhimurium FabR targets as well. As we found a fabB overexpressing strain to partly mimic the biofilm defect of the fabR mutant, the effect of FabR on biofilms can be attributed at least partly to FabB, which plays a key role in UFA biosynthesis. Additionally, ChIP-chip identified a number of novel direct FabR targets (the intergenic regions between hpaR/hpaG and ddg/ydfZ) and yet putative direct targets (i.a. genes involved in tRNA metabolism, ribosome synthesis and translation). Next to UFA biosynthesis, a number of these direct targets and other indirect targets identified by transcriptomics (e.g. ribosomal genes, ompA, ompC, ompX, osmB, osmC, sseI), could possibly contribute to the effect of FabR on biofilm formation.
Conclusion: Overall, our results point at the importance of FabR and UFA biosynthesis in Salmonella biofilm formation and their role as potential targets for biofilm inhibitory strategies
Isolation of a proline-rich mycobacterial protein eliciting delayed-type hypersensitivity reactions only in guinea pigs immunized with living mycobacteria.
Double scaling limits of random matrices and minimal (2m,1) models: the merging of two cuts in a degenerate case
In this article, we show that the double scaling limit correlation functions
of a random matrix model when two cuts merge with degeneracy (i.e. when
for arbitrary values of the integer ) are the same as the
determinantal formulae defined by conformal models. Our approach
follows the one developed by Berg\`{e}re and Eynard in \cite{BergereEynard} and
uses a Lax pair representation of the conformal models (giving
Painlev\'e II integrable hierarchy) as suggested by Bleher and Eynard in
\cite{BleherEynard}. In particular we define Baker-Akhiezer functions
associated to the Lax pair to construct a kernel which is then used to compute
determinantal formulae giving the correlation functions of the double scaling
limit of a matrix model near the merging of two cuts.Comment: 37 pages, 4 figures. Presentation improved, typos corrected.
Published in Journal Of Statistical Mechanic
- âŠ