1,227 research outputs found
Subexponential groups in 4-manifold topology
We present a new, more elementary proof of the Freedman-Teichner result that
the geometric classification techniques (surgery, s-cobordism, and
pseudoisotopy) hold for topological 4-manifolds with groups of subexponential
growth. In an appendix Freedman and Teichner give a correction to their
original proof, and reformulate the growth estimates in terms of coarse
geometry.Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol4/paper14.abs.htm
Wangara Day 33 : reevaluation of lower order turbulence closure prediction of the PBL
commentaire n° 24Note de jurisprudenceDes contreparties ne sont dues aux salariĂ©s pour les temps dâhabillage et de dĂ©shabillage que si une tenue de travail est exigĂ©e et quâils doivent sâen vĂȘtir et dĂ©vĂȘtir uniquement sur le lieu de travail en vertu de dispositions lĂ©gales, de stipulations conventionnelles, en vertu du rĂšglement intĂ©rieur ou dâun contrat de travail
Topological rigidity and H_1-negative involutions on tori
We prove there is only one involution (up to conjugacy) on the n-torus which
acts as on the first homology group when is of the form
, is of the form , or is less than . In all other cases we prove
there are infinitely many such involutions up to conjugacy, but each of them
has exactly fixed points and is conjugate to a smooth involution. The key
technical point is that we completely compute the equivariant structure set for
the corresponding crystallographic group action on in terms of
the Cappell -groups arising from its infinite dihedral
subgroups. We give a complete analysis of equivariant topological rigidity for
this family of groups.Comment: 50 pages, to appear in Geometry & Topolog
Mpemba Effect, Shechtman's Quasicrystals and Students' Exploring Activities
In the 1960s, Tanzanian student Erasto Mpemba and his teacher published an
article with the title "Cool" in the journal Physics Education (Mpemba, E. B. -
Osborne, D. G.: Cool?. In: Physics Education, vol.4, 1969, pp. 172-175.). In
this article they claimed that hot water freezes faster than cold water. The
article raised not only a wave of discussions, and other articles about this
topic, but also a whole series of new experiments, which should verify this
apparent thermodynamic absurdity and find an adequate explanation. Here we give
a review with references to explanations and we bring some proposals for
experimental student work in this area. We introduce Mpemba Effect not only as
a paradoxical physics phenomenon, but we shall present a strong educational
message that the Mpemba story brings to the teachers and their students. This
message also creates a bridge between this phenomenon and the discovery for
which the 2011 Nobel Prize in Chemistry was awarded. It leads to critical
adoption of traditional knowledge and encourages resilience in investigative
exploration of new things
Nuclear Physics Neutrino PreTown Meeting: Summary and Recommendations
In preparation for the nuclear physics Long Range Plan exercise, a group of
104 neutrino physicists met in Seattle September 21-23 to discuss both the
present state of the field and the new opportunities of the next decade. This
report summarizes the conclusions of that meeting and presents its
recommendations. Further information is available at the workshop's web site.
This report will be further reviewed at the upcoming Oakland Town Meeting.Comment: Latex, 31 pages. This version has been updated to include final
Comments from the working group
Spin dynamics simulations of the magnetic dynamics of RbMnF and direct comparison with experiment
Spin-dynamics techniques have been used to perform large-scale simulations of
the dynamic behavior of the classical Heisenberg antiferromagnet in simple
cubic lattices with linear sizes . This system is widely recognized
as an appropriate model for the magnetic properties of RbMnF.
Time-evolutions of spin configurations were determined numerically from coupled
equations of motion for individual spins using a new algorithm implemented by
Krech {\it etal}, which is based on fourth-order Suzuki-Trotter decompositions
of exponential operators. The dynamic structure factor was calculated from the
space- and time-displaced spin-spin correlation function. The crossover from
hydrodynamic to critical behavior of the dispersion curve and spin-wave
half-width was studied as the temperature was increased towards the critical
temperature. The dynamic critical exponent was estimated to be , which is slightly lower than the dynamic scaling prediction, but in
good agreement with a recent experimental value. Direct, quantitative
comparisons of both the dispersion curve and the lineshapes obtained from our
simulations with very recent experimental results for RbMnF are presented.Comment: 30 pages, RevTex, 9 figures, to appear in PR
Transcriptional profiling of maturing tomato (Solanum lycopersicum L.) microspores reveals the involvement of heat shock proteins, ROS scavengers, hormones, and sugars in the heat stress response
Above-optimal temperatures reduce yield in tomato largely because of the high heat stress (HS) sensitivity of the developing pollen grains. The high temperature response, especially at this most HS-sensitive stage of the plant, is poorly understood. To obtain an overview of molecular mechanisms underlying the HS response (HSR) of microspores, a detailed transcriptomic analysis of heat-stressed maturing tomato microspores was carried out using a combination of Affymetrix Tomato Genome Array and cDNA-amplified fragment length polymorphism (AFLP) techniques. The results were corroborated by reverse transcription-PCR (RT-PCR) and immunoblot analyses. The data obtained reveal the involvement of specific members of the small heat shock protein (HSP) gene family, HSP70 and HSP90, in addition to the HS transcription factors A2 (HSFA2) and HSFA3, as well as factors other than the classical HS-responsive genes. The results also indicate HS regulation of reactive oxygen species (ROS) scavengers, sugars, plant hormones, and regulatory genes that were previously implicated in other types of stress. The use of cDNA-AFLP enabled the detection of genes representing pollen-specific functions that are missing from the tomato Affymetrix chip, such as those involved in vesicle-mediated transport and a pollen-specific, calcium-dependent protein kinase (CDPK2). For several genes, including LeHSFA2, LeHSP17.4-CII, as well as homologues of LeHSP90 and AtVAMP725, higher basal expression levels were detected in microspores of cv. Hazera 3042 (a heat-tolerant cultivar) compared with microspores of cv. Hazera 3017 (a heat-sensitive cultivar), marking these genes as candidates for taking part in microspore thermotolerance. This work provides a comprehensive analysis of the molecular events underlying the HSR of maturing microspores of a crop plant, tomato
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