16 research outputs found
Excitation function of elliptic flow in Au+Au collisions and the nuclear matter equation of state
We present measurements of the excitation function of elliptic flow at
midrapidity in Au+Au collisions at beam energies from 0.09 to 1.49 GeV per
nucleon. For the integral flow, we discuss the interplay between collective
expansion and spectator shadowing for three centrality classes. A complete
excitation function of transverse momentum dependence of elliptic flow is
presented for the first time in this energy range, revealing a rapid change
with incident energy below 0.4 AGeV, followed by an almost perfect scaling at
the higher energies. The equation of state of compressed nuclear matter is
addressed through comparisons to microscopic transport model calculations.Comment: 10 pages, 4 eps figures, submitted for publication. Data files will
be available at http://www.gsi.de/~fopiwww/pub
Homologous DNA pairing domain peptides of RecA protein: intrinsic propensity to form beta-structures and filaments.
The 20 amino acid residue peptides derived from RecA loop L2 have been shown to be the pairing domain of RecA. The peptides bind to ss- and dsDNA, unstack ssDNA, and pair the ssDNA to its homologous target in a duplex DNA. As shown by circular dichroism, upon binding to DNA the disordered peptides adopt a beta-structure conformation. Here we show that the conformational change of the peptide from random coil to beta-structure is important in binding ss- and dsDNA. The beta-structure in the DNA pairing peptides can be induced by many environmental conditions such as high pH, high concentration, and non-micellar sodium dodecyl sulfate (6 mM). This behavior indicates an intrinsic property of these peptides to form a beta-structure. A beta-structure model for the loop L2 of RecA protein when bound to DNA is thus proposed. The fact that aromatic residues at the central position 203 strongly modulate the peptide binding to DNA and subsequent biochemical activities can be accounted for by the direct effect of the aromatic amino acids on the peptide conformational change. The DNA-pairing domain of RecA visualized by electron microscopy self-assembles into a filamentous structure like RecA. The relevance of such a peptide filamentous structure to the structure of RecA when bound to DNA is discussed
Inhomogeneity of dielectric properties of cadmium zinc-telluride crystals grown from melt
Dielectric properties of Cd₁₋xZnxTe crystals made from different ingot regions were investigated in a low-frequency region. Wavelet analysis was used for take-off of regular component in dependence of both parts of dielectric permittivity from spatial coordinate. It is ascertained that dielectric response of crystals has a relaxational character. Regular changes of response characteristics in ingot growth direction were revealed. Such peculiarities of properties are explained with changes during growth process not only in ratio of solid solution basic components, but also of intrinsic structure defects, especially related with cadmium vacancies
Transverse momentum spectra of charged particles in proton-proton collisions at 1as=900 GeV with ALICE at the LHC
The inclusive charged particle transverse momentum distribution is measured in proton-proton collisions at s=900 GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region (|\u3b7|<0.8) over the transverse momentum range 0.15<10 GeV/c. The correlation between transverse momentum and particle multiplicity is also studied. Results are presented for inelastic (INEL) and non-single-diffractive (NSD) events. The average transverse momentum for |\u3b7|<0.8 is \u3008pT\u3009INEL=0.483\ub10.001 (stat.)\ub10.007 (syst.) GeV/c and \u3008pT\u3009NSD=0.489\ub10.001 (stat.)\ub10.007 (syst.) GeV/c, respectively. The data exhibit a slightly larger \u3008pT\u3009 than measurements in wider pseudorapidity intervals. The results are compared to simulations with the Monte Carlo event generators PYTHIA and PHOJET. \ua9 2010