1,698 research outputs found
Sigma terms from an SU(3) chiral extrapolation
We report a new analysis of lattice simulation results for octet baryon
masses in 2+1-flavor QCD, with an emphasis on a precise determination of the
strangeness nucleon sigma term. A controlled chiral extrapolation of a recent
PACS-CS Collaboration data set yields baryon masses which exhibit remarkable
agreement both with experimental values at the physical point and with the
results of independent lattice QCD simulations at unphysical meson masses.
Using the Feynman-Hellmann relation, we evaluate sigma commutators for all
octet baryons. The small statistical uncertainty, and considerably smaller
model-dependence, allows a signifcantly more precise determination of the
pion-nucleon sigma commutator and the strangeness sigma term than hitherto
possible, namely {\sigma}{\pi}N=45 \pm 6 MeV and {\sigma}s = 21 \pm 6 MeV at
the physical point.Comment: 4 pages, 4 figure
Operationalising a Threshold Concept in Economics: A Pilot Study Using Multiple Choice Questions on Opportunity Cost
This paper addresses the emerging educational framework that envisions threshold concepts as mediators of learning outcomes. While the threshold concepts framework is highly appealing on a theoretical level, few researchers have attempted to measure threshold concept acquisition empirically. Achieving this would open a new arena for exploration and debate in the threshold concepts field, and provide potential results to inform teaching practice. We begin the process of operationalising threshold concepts in economics by attempting to measure students' grasp of the threshold concept of opportunity cost in an introductory economics class. We suggest two potential measures and correlate them with an array of ex ante and ex post variables, including students' expectations of success, prior misconceptions about economics and the work of economists, and actual success in the course. Results cast new light onto the factors that influence the acquisition of threshold concepts, the relationship between threshold concept acquisition and final learning outcomes, and the empirical viability of threshold concepts generally.
Gene action of blast disease reaction and grain yield traits in finger millet
Gene action of blast reaction, yield and yield associated traits in finger millet were studied using a 4x4 North Carolina Design II mating scheme. The four female and four male parents and their 16 crosses were evaluated at Alupe and Kakamega in western Kenya in a randomized complete block design under both artificially induced and natural disease pressure. General combining ability (GCA) and specific combining ability (SCA) estimates of the traits were calculated to determine the genotypes breeding value. The GCA variance predominated over SCA variance for all traits except finger width hence these traits can be improved through selection. With high, desirable GCA effects, male parent KNE 392 and female parents KNE 744 and IE 11 are suitable for blast resistance breeding while male parent Okhale 1 is suitable for grain yield improvement. The frequency distribution for the segregating F2 generation for the three blast types differed within and between crosses which could be due to differences in gene numbers or gene combinations being expressed in the different parents used. Convergent crossing or gene pyramiding for durable resistance could be possible
The Chern-Simons number as an order parameter: classical sphaleron transitions for SU(2)-Higgs field theories for m(H)approximate to 120 GeV
The classical transitions between topologically distinct vacua in a SU(2)-Higgs model, using a Higgs field of mass approximately 120 GeV, is examined to probe the crossover region between the symmetric and broken phase. Assuming the Higgs mass is constant, we find the width of this crossover region is approximately 20% of the average temperature. We suggest that this observable is a better parameter to explore this region of phase space than equal-time correlation functions, (C) 1998 Published by Elsevier Science B.V. All rights reserved
The Light Hadron Mass Spectrum with Non-Perturbatively O(a) Improved Wilson Fermions
We compute the light hadron mass spectrum in quenched lattice QCD at using the Sheikholeslami-Wohlert fermionic action. The calculation is done
for several choices of the coefficient , including and the
recently proposed optimal value . We find that the individual
masses change by up to 30\% under improvement. The spectrum calculation
suggests for the optimal value of the coefficient.Comment: 15 pages, uuencoded Z-compressed postscript file. Also available from
http://www.desy.de/pub/preprints/desy/199
Capillary Pressure and Contact Line Force on a Soft Solid
The surface free energy, or surface tension, of a liquid interface gives rise
to a pressure jump when the interface is curved. Here we show that a similar
capillary pressure arises at the interface of soft solids. We present
experimental evidence that immersion of a thin elastomeric wire into a liquid
induces a substantial elastic compression due to the solid capillary pressure
at the bottom. We quantitatively determine the effective surface tension from
the elastic displacement field, and find a value comparable to the liquid-vapor
surface tension. Most importantly, these results also reveal the way the liquid
pulls on the solid close to the contact line: the capillary force is not
oriented along the liquid-air interface, nor perpendicularly to the solid
surface, as previously hypothesized, but towards the interior of the liquid
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