1,527 research outputs found
Temperature independent diffuse scattering and elastic lattice deformations in relaxor PbMg1/3Nb2/3O3
The results of diffuse neutron scattering experiment on PbMg1/3Nb2/3O3 single
crystal above the Burns temperature are reported. It is shown that the high
temperature elastic diffuse component is highly anisotropic in low-symmetry
Brillouin zones and this anisotropy can be described using Huang scattering
formalism assuming that the scattering originates from mesoscopic lattice
deformations due to elastic defects. The qualitative agreement between this
model and the experimental data is achieved with simple isotropic defects. It
is demonstrated that weak satellite maxima near the Bragg reflections can be
interpreted as the finite resolution effect.Comment: 7 pages, 7 figure
Spurious trend switching phenomena in financial markets
The observation of power laws in the time to extrema of volatility, volume
and intertrade times, from milliseconds to years, are shown to result
straightforwardly from the selection of biased statistical subsets of
realizations in otherwise featureless processes such as random walks. The bias
stems from the selection of price peaks that imposes a condition on the
statistics of price change and of trade volumes that skew their distributions.
For the intertrade times, the extrema and power laws results from the format of
transaction data
Transverse Pressure and Strangeness Dynamics in Relativistic Heavy Ion Reactions
Transverse hadron spectra from proton-proton, proton-nucleus and
nucleus-nucleus collisions from 2 AGeV to 21.3 ATeV are investigated within two
independent transport approaches (HSD and UrQMD). For central Au+Au (Pb+Pb)
collisions at energies above 5 AGeV, the measured
transverse mass spectra have a larger inverse slope parameter than expected
from the default calculations. The additional pressure - as suggested by
lattice QCD calculations at finite quark chemical potential and
temperature - might be generated by strong interactions in the early
pre-hadronic/partonic phase of central Au+Au (Pb+Pb) collisions. This is
supported by a non-monotonic energy dependence of in the present
transport model.Comment: Proceedings of Strange Quark Matter 200
A new look at acid catalyzed deacetylation of carbohydrates : A regioselective synthesis and reactivity of 2-O-acetyl aryl glycopyranosides
Abstract In the present work we report that acetyl groups of per – acetylated aryl glycosides have different reactivity during the acidic deacetylation using HCl/EtOH in CHCl3, which leads to preferential deacetylation at O-3, O-4 and O-6. Thereby, the one-step preparation of 2-O-acetyl aryl glycosides with simple aglycon was accomplished for the first time. It was proved that the found reagent is to be general and unique for the preparation of series of 2-О-acetyl aryl glycosides. We have determined the influence of both carbohydrate moiety and the aglycon on the selectivity of deacetylation reaction by kinetic experiments. Using DFT/B3LYP/6-31G(d,p) and semi-empirical АМ1 methods we have found that the highest activation barrier is for 2-О-acetyl group. This completely explains the least reactivity of 2-О-acetyl group.Peer reviewe
Jets as a Probe of Dense Matter at RHIC
Jet quenching in the matter created in high energy nucleus-nucleus collisions
provides a tomographic tool to probe the medium properties. Recent experimental
results on jet production at the Relativistic Heavy-Ion Collider (RHIC) are
reviewed. Jet properties in p+p and d+Au collisions have been measured,
establishing the baseline for studying jet modification in heavy-ion
collisions. Current progress on detailed studies of high transverse momentum
production in Au+Au collisions is discussed, with an emphasis on dihadron
correlation measurements.Comment: 8 pages, 9 figures. Plenary talk given at 17th International
Conference on Ultra Relativistic Nucleus-Nucleus Collisions (Quark Matter
2004), Oakland, California, 11-17 Jan 2004. Submitted to J.Phys.
Adatom diffusion on vicinal surfaces with permeable steps
We study the behavior of single atoms on an infinite vicinal surface assuming
certain degree of step permeability. Assuming complete lack of re-evaporation
an ruling out nucleation the atoms will inevitably join kink sites at the steps
but can do many attempts before that. Increasing the probability of step
permeability or the kink spacing lead to increase of the number of steps
crossed before incorporation of the atoms into kink sites. The asymmetry of the
attachment-detachment kinetics (Ehrlich-Schwoebel effect) suppresses the step
permeability and completely eliminates it in the extreme case of infinite
Ehrlich-Schwoebel barrier. The average number of permeability events per atom
scales with the average kink spacing. A negligibly small drift of the adatoms
in a direction perpendicular to the steps leads to a significant asymmetry of
the distribution of the permeability events the atoms thus visiting more
distant steps in the direction of the drift.Comment: 12 pages, 6 figure
Structural heterogeneity and diffuse scattering in morphotropic lead zirconate-titanate single crystals
Complementary diffuse and inelastic synchrotron X-ray scattering measurements
of lead zirconate-titanate single crystals with composition near the
morphotropic phase boundary (x=0.475) are reported. In the temperature range
293 K < T < 400 K a highly anisotropic quasielastic diffuse scattering is
observed. Above 400 K this scattering disappears. Its main features can be
reproduced by model of inhomogeneous lattice deformations caused by inclusions
of a tetragonal phase into a rhombohedral or monoclinic phase. This observation
supports the idea that PZT at its morphotropic phase boundary is essentially
structurally inhomogeneous.Comment: 4 pages, 4 figure
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