938 research outputs found
Ticking terahertz wave generation in attoseconds
We perform a joint measurement of terahertz waves and high-order harmonics
generated from noble atoms driven by a fundamental laser pulse and its second
harmonic. By correlating their dependence on the phase-delay of the two pulses,
we determine the generation of THz waves in tens of attoseconds precision.
Compared with simulations and models, we find that the laser-assisted
soft-collision of the electron wave packet with the atomic core plays a key
role. It is demonstrated that the rescattering process, being indispensable in
HHG processes, dominant THz wave generation as well but in a more elaborate
way. The new finding might be helpful for the full characterization of the
rescattering dynamics.Comment: 4 figure
Complexity measures and uncertainty relations of the high-dimensional harmonic and hydrogenic systems
In this work we find that not only the Heisenberg-like uncertainty products
and the R\'enyi-entropy-based uncertainty sum have the same first-order values
for all the quantum states of the -dimensional hydrogenic and
oscillator-like systems, respectively, in the pseudoclassical ()
limit but a similar phenomenon also happens for both the
Fisher-information-based uncertainty product and the Shannon-entropy-based
uncertainty sum, as well as for the Cr\'amer-Rao and Fisher-Shannon
complexities. Moreover, we show that the LMC (L\'opez-Ruiz-Mancini-Calvet) and
LMC-R\'enyi complexity measures capture the hydrogenic-harmonic difference in
the high dimensional limit already at first order
Flow field analysis of trucks and a design of an additional drag reduction device
Numerical simulation of the outflow field of a truck is carried out by using aerodynamic analysis software based on a computational fluid dynamics model. The velocity and pressure distribution of the outflow field around the truck are obtained and the cause of generating aerodynamic drag is analyzed. The flow separation in the front and at the tail of the truck is the main cause of air resistance generation. Three kinds of truck fairing are proposed based on the aerodynamic drag reduction mechanism. The influence of a drag reduction device on aerodynamic characteristics is analyzed based on the pressure distribution, velocity distribution and turbulent kinetic energy distribution around the truck. The research shows that three kinds of drag reduction devices for a truck have great effect on drag reduction, with the bottom fairing showing the best drag reduction effect. This study provides a theoretical basis for drag reduction and energy saving for the truck
Arginyltransferase, Its Specificity, Putative Substrates, Bidirectional Promoter, and Splicing-derived Isoforms
Substrates of the N-end rule pathway include proteins with destabilizing N-terminal residues. Three of them, Asp, Glu, and (oxidized) Cys, function through their conjugation to Arg, one of destabilizing N-terminal residues that are recognized directly by the pathway's ubiquitin ligases. The conjugation of Arg is mediated by arginyltransferase, encoded by ATE1. Through its regulated degradation of specific proteins, the arginylation branch of the N-end rule pathway mediates, in particular, the cardiovascular development, the fidelity of chromosome segregation, and the control of signaling by nitric oxide. We show that mouse ATE1 specifies at least six mRNA isoforms, which are produced through alternative splicing, encode enzymatically active arginyltransferases, and are expressed at varying levels in mouse tissues. We also show that the ATE1 promoter is bidirectional, mediating the expression of both ATE1 and an oppositely oriented, previously uncharacterized gene. In addition, we identified GRP78 (glucose-regulated protein 78) and protein-disulfide isomerase as putative physiological substrates of arginyltransferase. Purified isoforms of arginyltransferase that contain the alternative first exons differentially arginylate these proteins in extract from ATE1-/- embryos, suggesting that specific isoforms may have distinct functions. Although the N-end rule pathway is apparently confined to the cytosol and the nucleus, and although GRP78 and protein-disulfide isomerase are located largely in the endoplasmic reticulum, recent evidence suggests that these proteins are also present in the cytosol and other compartments in vivo, where they may become N-end rule substrates
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