9,222 research outputs found
Quiet eye facilitates sensorimotor preprograming and online control of precision aiming in golf putting
Introduction An occlusion protocol was used to elucidate the respective roles of preprograming and online control during the quiet eye period of golf putting.
Methods Twenty-one novice golfers completed golf putts to 6ft and 11ft targets under full vision or with vision occluded on initiation of the backswing.
Results Radial error (RE) was higher, and quiet eye was longer, when putting to the 11ft vs. 6ft target, and in the occluded vs. full vision condition. Quiet eye duration, as well as preprograming, online and dwell durations, were longer in low-RE compared to high-RE trials. The preprograming component of quiet eye was significantly longer in the occluded vision condition, whereas, the online and dwell components were significantly longer in the full vision condition.
Conclusion The findings demonstrate an increase in preprograming when vision is occluded. However, this was not sufficient to overcome the need for online visual control during the quiet eye period. These findings suggest the quiet eye period is composed of preprograming and online control elements, however, online visual control of action is critical to performance
The Structure of the Non-SUSY Baryonic Branch of Klebanov-Strassler
We study the two-dimensional space of supergravity solutions corresponding to
non-supersymmetric deformations of the baryonic branch of Klebanov-Strassler.
By combining analytical methods with a numerical survey of the parameter space,
we find that this solution space includes as limits the softly-broken N=1
solutions of Gubser et al. and those of Dymarsky and Kuperstein. We also
identify a one-dimensional family of solutions corresponding to a natural
non-supersymmetric generalisation of Klebanov-Strassler, and one corresponding
to the limit in which supersymmetry is completely absent, even in the far UV.
For almost all of the parameter space we find indications that much of the
structure of the supersymmetric baryonic branch survives.Comment: 29 pages plus appendices, 11 figure
Revisiting Deniability in Quantum Key Exchange via Covert Communication and Entanglement Distillation
We revisit the notion of deniability in quantum key exchange (QKE), a topic
that remains largely unexplored. In the only work on this subject by Donald
Beaver, it is argued that QKE is not necessarily deniable due to an
eavesdropping attack that limits key equivocation. We provide more insight into
the nature of this attack and how it extends to other constructions such as QKE
obtained from uncloneable encryption. We then adopt the framework for quantum
authenticated key exchange, developed by Mosca et al., and extend it to
introduce the notion of coercer-deniable QKE, formalized in terms of the
indistinguishability of real and fake coercer views. Next, we apply results
from a recent work by Arrazola and Scarani on covert quantum communication to
establish a connection between covert QKE and deniability. We propose DC-QKE, a
simple deniable covert QKE protocol, and prove its deniability via a reduction
to the security of covert QKE. Finally, we consider how entanglement
distillation can be used to enable information-theoretically deniable protocols
for QKE and tasks beyond key exchange.Comment: 16 pages, published in the proceedings of NordSec 201
Measurement of Permanent Electric Dipole Moments of Charged Hadrons in Storage Rings
Permanent Electric Dipole Moments (EDMs) of elementary particles violate two
fundamental symmetries: time reversal invariance (T) and parity (P). Assuming
the CPT theorem this implies CP-violation. The CP-violation of the Standard
Model is orders of magnitude too small to be observed experimentally in EDMs in
the foreseeable future. It is also way too small to explain the asymmetry in
abundance of matter and anti-matter in our universe. Hence, other mechanisms of
CP violation outside the realm of the Standard Model are searched for and could
result in measurable EDMs.
Up to now most of the EDM measurements were done with neutral particles. With
new techniques it is now possible to perform dedicated EDM experiments with
charged hadrons at storage rings where polarized particles are exposed to an
electric field. If an EDM exists the spin vector will experience a torque
resulting in change of the original spin direction which can be determined with
the help of a polarimeter. Although the principle of the measurement is simple,
the smallness of the expected effect makes this a challenging experiment
requiring new developments in various experimental areas.
Complementary efforts to measure EDMs of proton, deuteron and light nuclei
are pursued at Brookhaven National Laboratory and at Forschungszentrum Juelich
with an ultimate goal to reach a sensitivity of 10^{-29} e cm.Comment: 8 pages, 2 figure
Temporal estimation in prediction motion tasks is biased by a moving destination
© 2018 The Authors. An ability to predict the time-to-contact (TTC) of moving objects that become momentarily hidden is advantageous in everyday life and could be particularly so in fast-ball sports. Prediction motion (PM) experiments have sought to test this ability using tasks where a disappearing target moves toward a stationary destination. Here, we developed two novel versions of the PM task in which the destination either moved away from (Chase) or toward (Attract) the moving target. The target and destination moved with different speeds such that collision occurred 750, 1,000 or 1,250 ms after target occlusion. To determine if domain-specific experience conveys an advantage in PM tasks, we compared the performance of different sporting groups ranging from internationally competing athletes to nonsporting controls. There was no difference in performance between sporting groups and non-sporting controls but there were significant and independent effects on response error by target speed, destination speed, and occlusion period. We simulated these findings using a revised version of the linear TTC model of response timing for PM tasks (Yakimoff, Bocheva, & Mitrania, 1987; Yakimoff, Mateeff, Ehrenstein, & Hohnsbein, 1993) in which retinal input from the moving destination biases the internal representation of the occluded target. This revision closely reproduced the observed patterns of response error and thus describes a means by which the brain might estimate TTC when the target and destination are in motion
Entropy flow in near-critical quantum circuits
Near-critical quantum circuits are ideal physical systems for asymptotically
large-scale quantum computers, because their low energy collective excitations
evolve reversibly, effectively isolated from the environment. The design of
reversible computers is constrained by the laws governing entropy flow within
the computer. In near-critical quantum circuits, entropy flows as a locally
conserved quantum current, obeying circuit laws analogous to the electric
circuit laws. The quantum entropy current is just the energy current divided by
the temperature. A quantum circuit made from a near-critical system (of
conventional type) is described by a relativistic 1+1 dimensional relativistic
quantum field theory on the circuit. The universal properties of the
energy-momentum tensor constrain the entropy flow characteristics of the
circuit components: the entropic conductivity of the quantum wires and the
entropic admittance of the quantum circuit junctions. For example,
near-critical quantum wires are always resistanceless inductors for entropy. A
universal formula is derived for the entropic conductivity:
\sigma_S(\omega)=iv^{2}S/\omega T, where \omega is the frequency, T the
temperature, S the equilibrium entropy density and v the velocity of `light'.
The thermal conductivity is Real(T\sigma_S(\omega))=\pi v^{2}S\delta(\omega).
The thermal Drude weight is, universally, v^{2}S. This gives a way to measure
the entropy density directly.Comment: 2005 paper published 2017 in Kadanoff memorial issue of J Stat Phys
with revisions for clarity following referee's suggestions, arguments and
results unchanged, cross-posting now to quant-ph, 27 page
Trial protocol OPPTIMUM : does progesterone prophylaxis for the prevention of preterm labour improve outcome?
Background
Preterm birth is a global problem, with a prevalence of 8 to 12% depending on location. Several large trials and systematic reviews have shown progestogens to be effective in preventing or delaying preterm birth in selected high risk women with a singleton pregnancy (including those with a short cervix or previous preterm birth). Although an improvement in short term neonatal outcomes has been shown in some trials these have not consistently been confirmed in meta-analyses. Additionally data on longer term outcomes is limited to a single trial where no difference in outcomes was demonstrated at four years of age of the child, despite those in the “progesterone” group having a lower incidence of preterm birth.
Methods/Design
The OPPTIMUM study is a double blind randomized placebo controlled trial to determine whether progesterone prophylaxis to prevent preterm birth has long term neonatal or infant benefit. Specifically it will study whether, in women with singleton pregnancy and at high risk of preterm labour, prophylactic vaginal natural progesterone, 200 mg daily from 22 – 34 weeks gestation, compared to placebo, improves obstetric outcome by lengthening pregnancy thus reducing the incidence of preterm delivery (before 34 weeks), improves neonatal outcome by reducing a composite of death and major morbidity, and leads to improved childhood cognitive and neurosensory outcomes at two years of age. Recruitment began in 2009 and is scheduled to close in Spring 2013. As of May 2012, over 800 women had been randomized in 60 sites.
Discussion
OPPTIMUM will provide further evidence on the effectiveness of vaginal progesterone for prevention of preterm birth and improvement of neonatal outcomes in selected groups of women with singleton pregnancy at high risk of preterm birth. Additionally it will determine whether any reduction in the incidence of preterm birth is accompanied by improved childhood outcome
Scallop swimming kinematics and muscle performance: modelling the effects of "within-animal" variation in temperature sensitivity
Escape behaviour was investigated in Queen scallops (Aequipecten opercularis) acclimated to 5, 10 or 15 degrees C and tested at their acclimation temperature. Scallops are active molluscs, able to escape from predators by jet-propelled swimming using a striated muscle working in opposition to an elastic hinge ligament. The first cycle of the escape response was recorded using high-speed video ( 250 Hz) and whole-animal velocity and acceleration determined. Muscle shortening velocity, force and power output were calculated using measurements of valve movement and jet area, and a simple biomechanical model. The average shortening speed of the adductor muscle had a Q(10) of 2.04, significantly reducing the duration of the jetting phase of the cycle with increased temperature. Muscle lengthening velocity and the overall duration of the clap cycle were changed little over the range 5 - 15 degrees C, as these parameters were controlled by the relatively temperature-insensitive, hinge ligament. Improvements in the average power output of the adductor muscle over the first clap cycle ( 222 vs. 139 W kg(-1) wet mass at 15 and 5 degrees C respectively) were not translated into proportional increases in overall swimming velocity, which was only 32% higher at 15 degrees C ( 0.37m s(-1)) than 5 degrees C (0.28 m s(-1))
Key actors in driving behavioural change in relation to on-farm biosecurity; a Northern Ireland perspective
Background: Agriculture and farming are valued contributors to local economy in Northern Ireland (NI). There is limited knowledge about farmers’ behaviours and attitudes towards disease biosecurity measures. As part of a larger project, a scenario-based workshop with key stakeholders was organised by the Agri-Food and Biosciences Institute (AFBI)-NI in December 2015.
Results: A total of 22 participants belonging to 12 different institutions took part in the workshop. Participants were presented with an overview of previously conducted biosecurity research in NI and England. In small groups, participants were subsequently asked to discuss and give their opinions about a series of questions across four key areas in a semi-structured approach with an external facilitator. The key areas were 1- disease risk perception at the farm level; 2-perceived barriers to implementing on farm biosecurity measures; 3- avenues to successful behaviour change and 4-key industry responsibilities and roles. The discussion showed that training in biosecurity for farmers is important and necessary. Training was recommended to be provided by veterinary surgeons, preferably via a face-to-face format. The discussion addressing disease disclosure proved particularly challenging between those who were prospective buyers of cattle, and those who sold cattle.
Conclusions: This workshop provided a unique and invaluable insight into key issues regarding farm level biosecurity activities. From a policy perspective, delivering improved on-farm biosecurity must be addressed via a multidisciplinary approach. This can only be achieved with active involvement, commitment and support of a number of key industry and government stakeholders
Field and laboratory studies reveal interacting effects of stream oxygenation and warming on aquatic ectotherms
Aquatic ecological responses to climatic warming are complicated by interactions between thermal effects and other environmental stressors such as organic pollution and hypoxia. Laboratory experiments have demonstrated how oxygen limitation can set heat tolerance for some aquatic ectotherms, but only at unrealistic lethal temperatures and without field data to assess whether oxygen shortages might also underlie sublethal warming effects. Here, we test whether oxygen availability affects both lethal and nonlethal impacts of warming on two widespread Eurasian mayflies, Ephemera danica, Müller 1764 and Serratella ignita (Poda 1761). Mayfly nymphs are often a dominant component of the invertebrate assemblage in streams, and play a vital role in aquatic and riparian food webs. In the laboratory, lethal impacts of warming were assessed under three oxygen conditions. In the field, effects of oxygen availability on nonlethal impacts of warming were assessed from mayfly occurrence in 42 293 UK stream samples where water temperature and biochemical oxygen demand were measured. Oxygen limitation affected both lethal and sublethal impacts of warming in each species. Hypoxia lowered lethal limits by 5.5 °C (±2.13) and 8.2 °C (±0.62) for E. danica and S. ignita respectively. Field data confirmed the importance of oxygen limitation in warmer waters; poor oxygenation drastically reduced site occupancy, and reductions were especially pronounced under warm water conditions. Consequently, poor oxygenation lowered optimal stream temperatures for both species. The broad concordance shown here between laboratory results and extensive field data suggests that oxygen limitation not only impairs survival at thermal extremes but also restricts species abundance in the field at temperatures well below upper lethal limits. Stream oxygenation could thus control the vulnerability of aquatic ectotherms to global warming. Improving water oxygenation and reducing pollution can provide key facets of climate change adaptation for running waters
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