3,635 research outputs found
Fatiguing Effects of Indirect Vibration Stimulation in Upper Limb Muscles- pre, post and during Isometric Contractions Superimposed on Upper Limb Vibration
© 2019 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/ , which permits unrestricted use, provided the original author and source are credited.Whole-body vibration and upper limb vibration (ULV) continue to gain popularity as exercise intervention for rehabilitation and sports applications. However, the fatiguing effects of indirect vibration stimulation are not yet fully understood. We investigated the effects of ULV stimulation superimposed on fatiguing isometric contractions using a purpose developed upper limb stimulation device. Thirteen healthy volunteers were exposed to both ULV superimposed to fatiguing isometric contractions (V) and isometric contractions alone Control (C). Both Vibration (V) and Control (C) exercises were performed at 80% of the maximum voluntary contractions. The stimulation used was 30 Hz frequency of 0.4 mm amplitude. Surface-electromyographic (EMG) activity of the Biceps Brachii, Triceps Brachii and Flexor Carpi Radialis were measured. EMG amplitude (EMGrms) and mean frequency (MEF) were computed to quantify muscle activity and fatigue levels. All muscles displayed significantly higher reduction in MEFs and a corresponding significant increase in EMGrms with the V than the Control, during fatiguing contractions (p < 0.05). Post vibration, all muscles showed higher levels of MEFs after recovery compared to the control. Our results show that near-maximal isometric fatiguing contractions superimposed on vibration stimulation lead to a higher rate of fatigue development compared to the isometric contraction alone in the upper limb muscles. Results also show higher manifestation of mechanical fatigue post treatment with vibration compared to the control. Vibration superimposed on isometric contraction not only seems to alter the neuromuscular function during fatiguing efforts by inducing higher neuromuscular load but also post vibration treatment.Peer reviewedFinal Published versio
Long-term polarization observations of Mira variable stars suggest asymmetric structures
Mira and semi-regular variable stars have been studied for centuries but
continue to be enigmatic. One unsolved mystery is the presence of polarization
from these stars. In particular, we present 40 years of polarization
measurements for the prototype o Ceti and V CVn and find very different
phenomena for each star. The polarization fraction and position angle for Mira
is found to be small and highly variable. On the other hand, the polarization
fraction for V CVn is large and variable, from 2 - 7 %, and its position angle
is approximately constant, suggesting a long-term asymmetric structure. We
suggest a number of potential scenarios to explain these observations.Comment: 2 pages, 1 figure, poster presented at IAU Symposium 301, Precision
Asteroseismology, August 2013, Wroclaw, Polan
Enhancement of electron-hole superfluidity in double few-layer graphene
We propose two coupled electron-hole sheets of few-layer graphene as a new
nanostructure to observe superfluidity at enhanced densities and enhanced
transition temperatures. For ABC stacked few-layer graphene we show that the
strongly correlated electron-hole pairing regime is readily accessible
experimentally using current technologies. We find for double trilayer and
quadlayer graphene sheets spatially separated by a nano-thick hexagonal
boron-nitride insulating barrier, that the transition temperature for
electron-hole superfluidity can approach temperatures of 40 K.Comment: 17 pages, 5 figure
Wigner crystallization in transition metal dichalcogenides: A new approach to correlation energy
We introduce a new approach for the correlation energy of one- and two-valley
two-dimensional electron gas (2DEG) systems. Our approach is based on a random
phase approximation at high densities and a classical approach at low
densities, with interpolation between the two limits. This approach gives
excellent agreement with available Quantum Monte Carlo (QMC) calculations. We
employ the two-valley 2DEG model to describe the electron correlations in
monolayer transition metal dichalcogenides (TMDs). The zero-temperature
transition from a Fermi liquid to a quantum Wigner crystal phase in monolayer
TMDs is obtained using density-functional theory within the local-density
approximation. Consistent with QMC, we find that electrons crystallize at
in one-valley 2DEG. For two-valleys, we predict Wigner
crystallization at , indicating that valley degeneracy has little
effect on the critical , in contrast to an earlier claim.Comment: 5 pages, 3 figure
Multiband Mechanism for the Sign Reversal of Coulomb Drag Observed in Double Bilayer Graphene Heterostructures
Coupled 2D sheets of electrons and holes are predicted to support novel
quantum phases. Two experiments of Coulomb drag in electron-hole (e-h) double
bilayer graphene (DBLG) have reported an unexplained and puzzling sign reversal
of the drag signal. However, we show that this effect is due to the multiband
character of DBLG. Our multiband Fermi liquid theory produces excellent
agreement and captures the key features of the experimental drag resistance for
all temperatures. This demonstrates the importance of multiband effects in
DBLG: they have a strong effect not only on superfluidity, but also on the
drag.Comment: 5 pages, 3 figure
Crack detection in a rotating shaft using artificial neural networks and PSD characterisation
Peer reviewedPostprin
Bitcoin forensics: a tutorial
Over the past eighteen months, the digital cryptocurrency Bitcoin has experienced significant growth in terms of usage and adoption. It has also been predicted that if this growth continues then it will become an increasingly useful tool for various illegal activities. Against this background, it seems safe to assume that students and professionals of digital forensics will require an understanding of the subject. New technologies are often a major challenge to the field of digital forensics due to the technical and legal challenges they introduce. This paper provides a set of tutorials for Bitcoin that allows for leaners from both backgrounds to be taught how it operates, and how it may impact on their working practice. Earlier this year they were delivered to a cohort of third year undergraduates. To the author’s knowledge, this represents the first integration of the topic into a digital forensics programme by a higher education provider
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