169 research outputs found
Approaching the knee -- balloon-borne observations of cosmic ray composition
Below the knee in the cosmic ray spectrum, balloon and spacecraft experiments
offer the capability of direct composition and energy measurements on the
primary particles. A major difficulty is obtaining enough exposure to extend
the range of direct measurements sufficiently high in energy to permit overlap
with ground-based observations. Presently, balloon and space measurements
extend only up to ~100 TeV, well below the range of ground-based experiments.
The prospect of Ultra-Long Duration Balloon missions offers the promise of
multiple long flights that can build up exposure. The status of balloon
measurements to measure the high energy proton and nuclear composition and
spectrum is reviewed, and the statistical considerations involved in searching
for a steepening in the spectrum are discussed. Given the very steeply falling
spectrum, it appears unlikely that balloon experiments will be able to extend
the range of direct measurements beyond 1000 TeV any time in the near future.
Especially given the recent suggestions from KASCADE that the proton spectrum
steepens only at 4000-5000 TeV, the chance of detecting the knee with direct
measurements of protons to iron on balloons is not likely to occur without
significant increases in the payload and flight duration capabilities of high
altitude balloons.Comment: 10 pages, to be published, J. Phys. Conf. Ser. (Proc. Workshop on
Physics at the End of the Galactic Cosmic Ray Spectrum, Aspen, April 2005
Magnetic structure of Yb2Pt2Pb: Ising moments on the Shastry-Sutherland lattice.
Neutron diffraction measurements were carried out on single crystals and powders of Yb2Pt2Pb, where Yb moments form two interpenetrating planar sublattices of orthogonal dimers, a geometry known as Shastry-Sutherland lattice, and are stacked along the c axis in a ladder geometry. Yb2Pt2Pb orders antiferromagnetically at TN=2.07K, and the magnetic structure determined from these measurements features the interleaving of two orthogonal sublattices into a 5×5×1 magnetic supercell that is based on stripes with moments perpendicular to the dimer bonds, which are along (110) and (−110). Magnetic fields applied along (110) or (−110) suppress the antiferromagnetic peaks from an individual sublattice, but leave the orthogonal sublattice unaffected, evidence for the Ising character of the Yb moments in Yb2Pt2Pb that is supported by point charge calculations. Specific heat, magnetic susceptibility, and electrical resistivity measurements concur with neutron elastic scattering results that the longitudinal critical fluctuations are gapped with ΔE≃0.07meV
Fluorescent carbon dioxide indicators
Over the last decade, fluorescence has become the dominant tool in biotechnology and medical imaging. These exciting advances have been underpinned by the advances in time-resolved techniques and instrumentation, probe design, chemical / biochemical sensing, coupled with our furthered knowledge in biology. Complementary volumes 9 and 10, Advanced Concepts of Fluorescence Sensing: Small Molecule Sensing and Advanced Concepts of Fluorescence Sensing: Macromolecular Sensing, aim to summarize the current state of the art in fluorescent sensing. For this reason, Drs. Geddes and Lakowicz have invited chapters, encompassing a broad range of fluorescence sensing techniques. Some chapters deal with small molecule sensors, such as for anions, cations, and CO2, while others summarize recent advances in protein-based and macromolecular sensors. The Editors have, however, not included DNA or RNA based sensing in this volume, as this were reviewed in Volume 7 and is to be the subject of a more detailed volume in the near future
Isospin Physics in Heavy-Ion Collisions at Intermediate Energies
In nuclear collisions induced by stable or radioactive neutron-rich nuclei a
transient state of nuclear matter with an appreciable isospin asymmetry as well
as thermal and compressional excitation can be created. This offers the
possibility to study the properties of nuclear matter in the region between
symmetric nuclear matter and pure neutron matter. In this review, we discuss
recent theoretical studies of the equation of state of isospin-asymmetric
nuclear matter and its relations to the properties of neutron stars and
radioactive nuclei. Chemical and mechanical instabilities as well as the
liquid-gas phase transition in asymmetric nuclear matter are investigated. The
in-medium nucleon-nucleon cross sections at different isospin states are
reviewed as they affect significantly the dynamics of heavy ion collisions
induced by radioactive beams. We then discuss an isospin-dependent transport
model, which includes different mean-field potentials and cross sections for
the proton and neutron, and its application to these reactions. Furthermore, we
review the comparisons between theoretical predictions and available
experimental data. In particular, we discuss the study of nuclear stopping in
terms of isospin equilibration, the dependence of nuclear collective flow and
balance energy on the isospin-dependent nuclear equation of state and cross
sections, the isospin dependence of total nuclear reaction cross sections, and
the role of isospin in preequilibrium nucleon emissions and subthreshold pion
production.Comment: 101 pages with embedded epsf figures, review article for
"International Journal of Modern Physics E: Nuclear Physics". Send request
for a hard copy to 1/author
Single-incision technique for the internal fixation of distal fractures of the tibia and fibula: a combined anatomic and clinical study
Using of FPGA coprocessor for improving the execution speed of the pattern recognition algorithm for ATLAS - high energy physics experiment
Pattern recognition algorithms are used in experimental High Energy physics for getting parameters (features) of particles tracks in detectors. It is particularly important to have fast algorithms in trigger system. This paper investigates the suitability of using FPGA coprocessor for speedup of the TRT-LUT algorithm - one of the feature extraction algorithms for second level trigger for ATLAS experiment (CERN). Two realization of the same algorithm have been compared: C++ realization tested on a computer equipped with dual Xeon 2.4 GHz CPU, 64-bit, 66MHz PCI bus, 1024Mb DDR RAM main memories with Red Hat Linux 7.1 and hybrid C++ - VHDL realisation tested on same PC equipped in addition by MPRACE board (FPGA-Coprocessor board based on Xilinx Virtex-II FPGA and made as 64-bit, 66 MHz PCI card developed at the University of Mannheim). Usage of the FPGA coprocessor can give some reasonable speedup in contrast to general purpose processor only for those algorithms (or parts of algorithms), for which there is a possibility to fulfil calculations with a major degree of parallelism. In case of TRT-LUT algorithm it is the most time consuming parts and using of FPGA coprocessor can give us speed-up by factor more then two for hybrid FPGA/CPU realisation in comparison with CPU only implementation
Towards a storage-ring measurement of the hyperfine induced 2s2p ^3P_0 → 2s^2 ^1S_0 transition rate in berylliumlike sulfur
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