17,714 research outputs found
Higgs self coupling measurement in e+e- collisions at center-of-mass energy of 500 GeV
Feasibility of the measurement of the trilinear self-couplings of the Higgs
boson is studied. Such a measurement would experimentally determine the
structure of the Higgs potential. Full hadronic and semi-leptonic final states
of the double-Higgs strahlung have been investigated.Comment: 10 pages, 5 tables, 8 figure
Stochastic pump of interacting particles
We consider the overdamped motion of Brownian particles, interacting via
particle exclusion, in an external potential that varies with time and space.
We show that periodic potentials that maintain specific position-dependent
phase relations generate time-averaged directed current of particles. We obtain
analytic results for a lattice version of the model using a recently developed
perturbative approach. Many interesting features like particle-hole symmetry,
current reversal with changing density, and system-size dependence of current
are obtained. We propose possible experiments to test our predictions.Comment: 4 pages, 2 figure
Deuterium on Venus: Observations from Earth
In view of the importance of the deuterium-to-hydrogen ratio in understanding the evolutionary scenario of planetary atmospheres and its relationship to understanding the evolution of our own Earth, we undertook a series of observations designed to resolve previous observational conflicts. We observed the dark side of Venus in the 2.3 micron spectral region in search of both H2O and HDO, which would provide us with the D/H ratio in Venus' atmosphere. We identified a large number of molecular lines in the region, belonging to both molecules, and, using synthetic spectral techniques, obtained mixing ratios of 34 plus or minus 10 ppm and 1.3 plus or minus 0.2 ppm for H2O and HDO, respectively. These mixing ratios yield a D/H ratio for Venus of D/H equals 1.9 plus or minus 0.6 times 10 (exp 12) and 120 plus or minus 40 times the telluric ratio. Although the detailed interpretation is difficult, our observations confirm that the Pioneer Venus Orbiter results and establish that indeed Venus had a period in its early history in which it was very wet, perhaps not unlike the early wet period that seems to have been present on Mars, and that, in contrast to Earth, lost much of its water over geologic time
Anomalous spatial diffusion and multifractality in optical lattices
Transport of cold atoms in shallow optical lattices is characterized by slow,
nonstationary momentum relaxation. We here develop a projector operator method
able to derive in this case a generalized Smoluchowski equation for the
position variable. We show that this explicitly non-Markovian equation can be
written as a systematic expansion involving higher-order derivatives. We use
the latter to compute arbitrary moments of the spatial distribution and analyze
their multifractal properties.Comment: 5 pages, 3 figure
First order-rewritability and containment of conjunctive queries in horn description logics
International audienceWe study FO-rewritability of conjunctive queries in the presence of ontologies formulated in a description logic between EL and Horn-SHIF, along with related query containment problems. Apart from providing characterizations, we establish complexity results ranging from EXPTIME via NEXPTIME to 2EXPTIME, pointing out several interesting effects. In particular, FO-rewriting is more complex for conjunctive queries than for atomic queries when inverse roles are present, but not otherwise
Intensified production of zeolite A: Life cycle assessment of a continuous flow pilot plant and comparison with a conventional batch plant
This study investigates on the environmental impact of an intensified technology for the manufacturing of Zeolite A, one of the largest zeolites employed worldwide by volume and value. The technology under consideration is an oscillatory continuous-flow synthesis, developed industrially by Arkema, and currently at pilot-scale. Life cycle assessment (LCA) is used in this work to measure the sustainability of this emerging technology in an anticipatory fashion, before its full deployment, with the aim of driving the process development toward the minimization of the environmental footprint. The assessment explores the full life-cycle of the production system and comprises comparative analysis, scenario analysis, and a hotspot analysis. Finally, the continuous-flow technology is benchmarked against the environmental impact of a conventional batch production of zeolite A, based on a full-scale commercial plant. The results evidence that significant benefits would stem from shifting from batch to continuous-flow production. The comparative analysis reveals that the extent of the latter advantages depends on the impact category under consideration and directs the next steps of CF system's process development toward pivotal aspects such as the recirculation system to further reduce the system's environmental impacts. Regardless of the chosen production technology, a large share of the total environmental impact hinges on the production of NaOH, a building block of the synthesis, and hence is hardly mitigatable. On the whole, the findings of this work emphasize the need of prioritizing LCA during the development phase of emerging technologies and underline its efficacy to prevent waste of resources and capitals
First principles study of local electronic and magnetic properties in pure and electron-doped NdCuO
The local electronic structure of Nd2CuO4 is determined from ab-initio
cluster calculations in the framework of density functional theory.
Spin-polarized calculations with different multiplicities enable a detailed
study of the charge and spin density distributions, using clusters that
comprise up to 13 copper atoms in the CuO2plane. Electron doping is simulated
by two different approaches and the resulting changes in the local charge
distribution are studied in detail and compared to the corresponding changes in
hole doped La2CuO4. The electric field gradient (EFG) at the copper nucleus is
investigated in detail and good agreement is found with experimental values. In
particular the drastic reduction of the main component of the EFG in the
electron-doped material with respect to LaCuO4 is explained by a reduction of
the occupancy of the 3d3z^2-r^2 atomic orbital. Furthermore, the chemical
shieldings at the copper nucleus are determined and are compared to results
obtained from NMR measurements. The magnetic hyperfine coupling constants are
determined from the spin density distribution
Catastrophic Failure Modes Assessment of the International Space Station Alpha
This report summarizes a series of analyses to quantify the hazardous effects of meteoroid/debris penetration of Space Station Alpha manned module protective structures. These analyses concentrate on determining (a) the critical crack length associated with six manned module pressure wall designs that, if exceeded, would lead to unstopped crack propagation and rupture of manned modules, and (b) the likelihood of crew or station loss following penetration of unsymmetrical di-methyl hydrazine tanks aboard the proposed Russian FGB ('Tug') propulsion module and critical elements aboard the control moment gyro module (SPP-1). Results from these quantified safety analyses are useful in improving specific design areas, thereby reducing the overall likelihood of crew or station loss following orbital debris penetration
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