1,394 research outputs found
Neutral mode heat transport and fractional quantum Hall shot noise
We study nonequilibrium edge state transport in the fractional quantum Hall
regime for states with one or several counter-propagating neutral modes. We
consider a setup in which the neutral modes are heated by a hot spot, and where
heat transported by the neutral modes causes a temperature difference between
the upper and lower edges in a Hall bar. This temperature difference is probed
by the excess noise it causes for scattering across a quantum point contact. We
find that the excess noise in the quantum point contact provides evidence for
counter-propagating neutral modes, and we calculate its dependence on both the
temperature difference between the edges and on source drain bias.Comment: 4 pages, 3 figure
Orientational Defects in Ice Ih: An Interpretation of Electrical Conductivity Measurements
We present a first-principles study of the structure and energetics of
Bjerrum defects in ice Ih and compare the results to experimental electrical
conductivity data. While the DFT result for the activation energy is in good
agreement with experiment, we find that its two components have quite different
values. Aside from providing new insight into the fundamental parameters of the
microscopic electrical theory of ice, our results suggest the activity of traps
in doped ice in the temperature regime typically assumed to be controlled by
the free migration of L defects.Comment: 4 pages, 4 Figures, 1 Tabl
Hole burning in a nanomechanical resonator coupled to a Cooper pair box
We propose a scheme to create holes in the statistical distribution of
excitations of a nanomechanical resonator. It employs a controllable coupling
between this system and a Cooper pair box. The success probability and the
fidelity are calculated and compared with those obtained in the atom-field
system via distinct schemes. As an application we show how to use the
hole-burning scheme to prepare (low excited) Fock states.Comment: 7 pages, 10 figure
Superfluid spin transport through antiferromagnetic insulators
A theoretical proposal for realizing and detecting spin supercurrent in an isotropic antiferromagnetic insulator is reported. Superfluid spin transport is achieved by inserting the antiferromagnet between two metallic reservoirs and establishing a spin accumulation in one reservoir such that a spin bias is applied across the magnet. We consider a class of bipartite antiferromagnets with Néel ground states, and temperatures well below the ordering temperature, where spin transport is mediated essentially by the condensate. Landau-Lifshitz and magnetocircuit theories are used to directly relate spin current in different parts of the heterostructure to the spin-mixing conductances characterizing the antiferromagnet∣∣metal interfaces and the antiferromagnet bulk damping parameters, quantities all obtainable from experiments. We study the efficiency of spin angular-momentum transfer at an antiferromagnet∣∣metal interface by developing a microscopic scattering theory for the interface and extracting the spin-mixing conductance for a simple model. Within the model, a quantitative comparison between the spin-mixing conductances obtained for the antiferromagnet∣∣metal and ferromagnet∣∣metal interfaces is made.Physic
Effect of plyometric training on handspring vault performance and functional power in youth female gymnasts
This study aimed to determine the effect of plyometric training (PT) when added to habitual gymnastic training (HT) on handspring vault (HV) performance variables. Twenty youth female competitive gymnasts (Age: 12.5 ± 1.67 y) volunteered to participate and were randomly assigned to two independent groups. The experimental plyometric training group (PTG) undertook a six-week plyometric program, involving two additional 45 min PT sessions a week, alongside their HT, while the control group (CG) performed regular HT only. Videography was used (120 Hz) in the sagittal plane to record both groups performing three HVs for both the baseline and post-intervention trials. Furthermore, participants completed a countermovement jump test (CMJ) to assess the effect of PT on functional power. Through the use of Quintic biomechanics software, significant improvements (P < 0.05) were found for the PTG for run-up velocity, take-off velocity, hurdle to board distance, board contact time, table contact time and post-flight time and CMJ height. However, there were no significant improvements on pre-flight time, shoulder angle or hip angle on the vault for the PTG. The CG demonstrated no improvement for all HV measures. A sport-specific PT intervention improved handspring vault performance measures and functional power when added to the habitual training of youth female gymnasts. The additional two hours plyometric training seemingly improved the power generating capacity of movement-specific musculature, which consequently improved aspects of vaulting performance. Future research is required to examine the whether the improvements are as a consequence of the additional volume of sprinting and jumping activities, as a result of the specific PT method or a combination of these factors
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