1,135 research outputs found
System Tests of the ATLAS Pixel Detector
The innermost part of the ATLAS (A Toroidal LHC ApparatuS) experiment at the
LHC (Large Hadron Collider) will be a pixel detector, which is presently under
construction. Once installed into the experimental area, access will be
extremely limited. To ensure that the integrated detector assembly operates as
expected, a fraction of the detector which includes the power supplies and
monitoring system, the optical readout, and the pixel modules themselves, has
been assembled and operated in a laboratory setting for what we refer to as
system tests. Results from these tests are presented.Comment: 5 Pages, 9 Figures, to appear in Proceedings of the Eleventh Workshop
on Electronics for LHC and Future Experiment
Large phenotype jumps in biomolecular evolution
By defining the phenotype of a biopolymer by its active three-dimensional
shape, and its genotype by its primary sequence, we propose a model that
predicts and characterizes the statistical distribution of a population of
biopolymers with a specific phenotype, that originated from a given genotypic
sequence by a single mutational event. Depending on the ratio g0 that
characterizes the spread of potential energies of the mutated population with
respect to temperature, three different statistical regimes have been
identified. We suggest that biopolymers found in nature are in a critical
regime with g0 in the range 1-6, corresponding to a broad, but not too broad,
phenotypic distribution resembling a truncated Levy flight. Thus the biopolymer
phenotype can be considerably modified in just a few mutations. The proposed
model is in good agreement with the experimental distribution of activities
determined for a population of single mutants of a group I ribozyme.Comment: to appear in Phys. Rev. E; 7 pages, 6 figures; longer discussion in
VII, new fig.
The solute transport and binding profile of a novel nucleobase cation symporter 2 from the honeybee pathogen Paenibacillus larvae
Here, we report that a novel nucleobase cation symporter 2 encoded in the genome of the honeybee bacterial pathogen Paenibacillus larvae reveals high levels of amino acid sequence similarity to the Escherichia coli and Bacillus subtilis uric acid and xanthine transporters. This transporter is named P. larvae uric acid permease-like protein (PlUacP). Even though PlUacP displays overall amino acid sequence similarities, has common secondary structures, and shares functional motifs and functionally important amino acids with E. coli xanthine and uric acid transporters, these commonalities are insufficient to assign transport function to PlUacP. The solute transport and binding profile of PlUacP was determined by radiolabeled uptake experiments via heterologous expression in nucleobase transporter-deficient Saccharomyces cerevisiae strains. PlUacP transports the purines adenine and guanine and the pyrimidine uracil. Hypoxanthine, xanthine, and cytosine are not transported by PlUacP, but, along with uric acid, bind in a competitive manner. PlUacP has strong affinity for adenine Km 7.04 ± 0.18 Όm, and as with other bacterial and plant NCS2 proteins, PlUacP function is inhibited by the proton disruptor carbonyl cyanide m-chlorophenylhydrazone. The solute transport and binding profile identifies PlUacP as a novel nucleobase transporter
Ultralong Copper Phthalocyanine Nanowires with New Crystal Structure and Broad Optical Absorption
The development of molecular nanostructures plays a major role in emerging
organic electronic applications, as it leads to improved performance and is
compatible with our increasing need for miniaturisation. In particular,
nanowires have been obtained from solution or vapour phase and have displayed
high conductivity, or large interfacial areas in solar cells. In all cases
however, the crystal structure remains as in films or bulk, and the
exploitation of wires requires extensive post-growth manipulation as their
orientations are random. Here we report copper phthalocyanine (CuPc) nanowires
with diameters of 10-100 nm, high directionality and unprecedented aspect
ratios. We demonstrate that they adopt a new crystal phase, designated
eta-CuPc, where the molecules stack along the long axis. The resulting high
electronic overlap along the centimetre length stacks achieved in our wires
mediates antiferromagnetic couplings and broadens the optical absorption
spectrum. The ability to fabricate ultralong, flexible metal phthalocyanine
nanowires opens new possibilities for applications of these simple molecules
Sonoluminescing air bubbles rectify argon
The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the
percentage of inert gas within the bubble. We propose a theory for this
dependence, based on a combination of principles from sonochemistry and
hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent
reaction to water soluble gases implies that strongly forced air bubbles
eventually consist of pure argon. Thus it is the partial argon (or any other
inert gas) pressure which is relevant for stability. The theory provides
quantitative explanations for many aspects of SBSL.Comment: 4 page
The use of high resolution graphite furnace molecular absorption spectrometry (HR -MAS) for total fluorine determination in extractable organofluorines (EOF)
Acknowledgment A.A. would like to thank the Ministry of Education and University of Jeddah in Saudi Arabia through the Cultural Bureau of Saudi Arabia, London for their financial support during the study period. A.O. wishes to thank the Royal Society of Chemistry Analytical Trust Fund for funding. M.S. would like to thank the Conselho Nacional de Desenvolvimento CientĂfico e TecnolĂłgico - CNPq for the financial support. L.S., J.B. and J.F. thank Formas for financial support (Grant number 2013â00794).Peer reviewedPostprin
Fully Dynamic Maintenance of Arc-Flags in Road Networks
International audienceThe problem of finding best routes in road networks can be solved by applying Dijkstra's shortest paths algorithm. Unfortunately, road networks deriving from real-world applications are huge yielding unsustainable times to compute shortest paths. For this reason, great research efforts have been done to accelerate Dijkstra's algorithm on road networks. These efforts have led to the development of a number of speed-up techniques, as for example Arc-Flags, whose aim is to compute additional data in a preprocessing phase in order to accelerate the shortest paths queries in an on-line phase. The main drawback of most of these techniques is that they do not work well in dynamic scenarios. In this paper we propose a new algorithm to update the Arc-Flags of a graph subject to edge weight decrease operations. To check the practical performances of the new algorithm we experimentally analyze it, along with a previously known algorithm for edge weight increase operations, on real-world road networks subject to fully dynamic sequences of operations. Our experiments show a significant speed-up in the updating phase of the Arc-Flags, at the cost of a small space and time overhead in the preprocessing phase
The Hardware of the ATLAS Pixel Detector Control System
The innermost part of the ATLAS (A Toroidal LHC ApparatuS) experiment will be a pixel detector, built of 1744 individual detector modules. To operate the modules, readout electronics, and other detector components, a complex power supply and control system is necessary. The specific powering and control requirements are described, along with the custom made components of our power supply and control systems. These include remotely programmable Regulator Stations, the power supply system for the optical transceivers, several monitoring units and the Interlock System
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