675 research outputs found
Work-rate of substitutes in elite soccer: A preliminary study
The aim of this study was to investigate the work-rate of substitutes in professional soccer. A computerised player tracking system was used to assess the work-rates of second-half substitutes (11 midfielders and 14 forwards) in a French Ligue 1 club. Total distance, distance covered in five categories of movement intensity and recovery time between high-intensity efforts were evaluated. First- and second-half work-rates of the replaced players were compared. The performance of substitutes was compared to that of the players they replaced, to team-mates in the same position who remained on the pitch after the substitution and in relation to their habitual performances when starting games. No differences in work-rate between first- and second-halves were observed in all players who were substituted. In the second-half, a non-significant trend was observed in midfield substitutes who covered greater distances than the player they replaced whereas no differences were observed in forwards. Midfield substitutes covered a greater overall distance and distance at high-intensities (p<0.01) and had a lower recovery time between high-intensity efforts (p<0.01) compared to other midfield team-mates who remained on the pitch. Forwards covered less distance (p<0.01) in their first 10-minutes as a substitute compared to their habitual work-rate profile in the opening 10-minutes when starting matches while this finding was not observed in midfielders. These findings suggest that compared to midfield substitutes, forward substitutes did not utilise their full physical potential. Further investigation is warranted into the reasons behind this finding in order to optimise the work-rate contributions of forward substitutes
Investment Incentives and Market Power: An Experimental Analysis
We examine investment incentives and market power in an experimental market. We characterize market power as the strategic interdependence of subjects' investment decisions and output decisions. The market is designed so that investment and output decisions can be jointly characterized as strategies within a game. A Nash-Cournot equilibrium of the game provides a way of characterizing how investment incentives and market power interact. Subjects could invest in two different production technologies and could produce output to serve as many as two different demand conditions. The technologies were analogous to "baseload" capacity and "peaking" capacity in wholesale electricity markets. The Nash-Cournot benchmark constituted a good indicator of subjects' output decisions in that output cycled around the Cournot benchmark. Thus, on average, consumers extracted the surplus available to them in the equilibrium. While we do not observe Edgeworth Cycles in prices or outputs, we do see them in the producer surplus series. Producers dissipated some of the surplus they could have extracted in the equilibrium by overinvesting in peaking capacity and underinvesting in baseload capacity. Inefficient investment diminished total system efficiency, but producers' investments in total production capacity tracked the Nash-Cournot benchmark. In contrast, monopoly explanations such as collusion do not characterize the data.capacity investment, Cournot, supply function equilibrium, Edgeworth Cycles, market power, electricity markets, investment incentives
Kinetic Antiferromagnetism in the Triangular Lattice
We show that the motion of a single hole in the infinite Hubbard model
with frustrated hopping leads to weak metallic antiferromagnetism of kinetic
origin. An intimate relationship is demonstrated between the simplest versions
of this problem in 1 and 2 dimensions, and two of the most subtle many body
problems, namely the Heisenberg Bethe ring in 1-d and the 2-dimensional
triangular lattice Heisenberg antiferromagnet.Comment: 10 pages, 2 figures, 5 supplementary figures; Figures fixe
DNA Methyltransferase 3 (MET3) is regulated by Polycomb group complex during Arabidopsis endosperm development
Complex epigenetic changes occur during plant reproduction. These regulations ensure the proper transmission of epigenetic information as well as allowing for zygotic totipotency. In Arabidopsis, the main DNA methyltransferase is called MET1 and is responsible for methylating cytosine in the CG context. The Arabidopsis genome encodes for three additional reproduction-specific homologs of MET1, namely MET2a, MET2b and MET3. In this paper, we show that the DNA methyltransferase MET3 is expressed in the seed endosperm and its expression is later restricted to the chalazal endosperm. MET3 is biallelically expressed in the endosperm but displays a paternal expression bias. We found that MET3 expression is regulated by the Polycomb complex proteins FIE and MSI1. Seed development is not impaired in met3 mutant, and we could not observe significant transcriptional changes in met3 mutant. MET3 might regulates gene expression in a Polycomb mutant background suggesting a further complexification of the interplay between H3K27me3 and DNA methylation in the seed endosperm
New universality class for the three-dimensional XY model with correlated impurities: Application to He in aerogels
Encouraged by experiments on He in aerogels, we confine planar spins in
the pores of simulated aerogels (diffusion limited cluster-cluster aggregation)
in order to study the effect of quenched disorder on the critical behavior of
the three-dimensional XY model. Monte Carlo simulations and finite-size scaling
are used to determine critical couplings and exponents. In agreement with
experiments, clear evidence of change in the thermal critical exponents
and is found at nonzero volume fractions of impurities. These changes
are explained in terms of {\it hidden} long-range correlations within disorder
distributions.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Gate fidelity and coherence of an electron spin in a Si/SiGe quantum dot with micromagnet
The gate fidelity and the coherence time of a qubit are important benchmarks
for quantum computation. We construct a qubit using a single electron spin in a
Si/SiGe quantum dot and control it electrically via an artificial spin-orbit
field from a micromagnet. We measure an average single-qubit gate fidelity of
99 using randomized benchmarking, which is consistent with
dephasing from the slowly evolving nuclear spins in substrate. The coherence
time measured using dynamical decoupling extends up to 400 s for
128 decoupling pulses, with no sign of saturation. We find evidence that the
coherence time is limited by noise in the 10 kHz 1 MHz range, possibly
because charge noise affecting the spin via the micromagnet gradient. This work
shows that an electron spin in a Si/SiGe quantum dot is a good candidate for
quantum information processing as well as for a quantum memory, even without
isotopic purification
Asymmetric expression of Argonautes in reproductive tissues
The Arabidopsis genome encodes ten Argonautes proteins showing distinct expression pattern as well as intracellular localisation during sexual reproduction
Fractal formation and ordering in random sequential adsorption
We reveal the fractal nature of patterns arising in random sequential
adsorption of particles with continuum power-law size distribution, , . We find that the patterns become more and
more ordered as increases, and that the Apollonian packing is obtained
at limit. We introduce the entropy production rate as a
quantitative criteria of regularity and observe a transition from an irregular
regime of the pattern formation to a regular one. We develop a scaling theory
that relates kinetic and structural properties of the system.Comment: 4 pages, RevTex, 4 postscript figures. To appear in Phys.Rev.Let
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