419 research outputs found
07071 Abstracts Collection -- Web Information Retrieval and Linear Algebra Algorithms
From 12th to 16th February 2007, the Dagstuhl Seminar 07071 ``Web Information Retrieval and Linear Algebra Algorithms\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl.
During the seminar, several participants presented their current
research, and ongoing work and open problems were discussed. Abstracts of
the presentations given during the seminar as well as abstracts of
seminar results and ideas are put together in this paper. The first section
describes the seminar topics and goals in general.
Links to extended abstracts or full papers are provided, if available
Impaired phloem loading in zmsweet13a,b,c sucrose transporter triple knock-out mutants in Zea mays
Preconditioning of Improved and ``Perfect'' Fermion Actions
We construct a locally-lexicographic SSOR preconditioner to accelerate the
parallel iterative solution of linear systems of equations for two improved
discretizations of lattice fermions: the Sheikholeslami-Wohlert scheme where a
non-constant block-diagonal term is added to the Wilson fermion matrix and
renormalization group improved actions which incorporate couplings beyond
nearest neighbors of the lattice fermion fields. In case (i) we find the block
llssor-scheme to be more effective by a factor about 2 than odd-even
preconditioned solvers in terms of convergence rates, at beta=6.0. For type
(ii) actions, we show that our preconditioner accelerates the iterative
solution of a linear system of hypercube fermions by a factor of 3 to 4.Comment: 27 pages, Latex, 17 Figures include
Preferential expression of an ammonium transporter and of two putative nitrate transporters in root hairs of tomato.
Antisense repression of the chloroplast triose phosphate translocator affects carbon partitioning in transgenic potato plants.
Hadron Masses From Novel Fat-Link Fermion Actions
The hadron mass spectrum is calculated in lattice QCD using a novel fat-link
clover fermion action in which only the irrelevant operators in the fermion
action are constructed using smeared links. The simulations are performed on a
16^3 x 32 lattice with a lattice spacing of a=0.125 fm. We compare actions with
n=4 and 12 smearing sweeps with a smearing fraction of 0.7. The n=4 Fat-Link
Irrelevant Clover (FLIC) action provides scaling which is superior to
mean-field improvement, and offers advantages over nonperturbative 0(a)
improvement, including a reduced exceptional configuration problem.Comment: 12 pages, 4 figures, new simulation with mean-field improved clover,
further discussion of actio
The Mass Spectrum of Light and Heavy Hadrons from Improved Lattice Actions
We use improved lattice actions for glue, light quarks and heavy quarks for
which we use lattice NRQCD to compute hadron masses. Our results are in good
agreement with experiment, except for charmed hadrons. It seems that charmed
quar ks are not well approximated as heavy quarks nor as light quarks.Comment: 14 pages +6 pages figures, plain-tex fil
Male-female communication triggers calcium signatures during fertilization in Arabidopsis
Cell-cell communication and interaction is critical during fertilization and triggers free cytosolic calcium ([Ca2+](cyto)) as a key signal for egg activation and a polyspermy block in animal oocytes. Fertilization in flowering plants is more complex, involving interaction of a pollen tube with egg adjoining synergid cells, culminating in release of two sperm cells and their fusion with the egg and central cell, respectively. Here, we report the occurrence and role of [Ca2+](cyto) signals during the entire double fertilization process in Arabidopsis. [Ca2+](cyto) oscillations are initiated in synergid cells after physical contact with the pollen tube apex. In egg and central cells, a short [Ca2+](cyto) transient is associated with pollen tube burst and sperm cell arrival. A second extended [Ca2+](cyto) transient solely in the egg cell is correlated with successful fertilization. Thus, each female cell type involved in double fertilization displays a characteristic [Ca2+](cyto) signature differing by timing and behaviour from [Ca2+](cyto) waves reported in mammals
- …