1,154 research outputs found
E-BioFlow: Different Perspectives on Scientific Workflows
We introduce a new type of workflow design system called\ud
e-BioFlow and illustrate it by means of a simple sequence alignment workflow. E-BioFlow, intended to model advanced scientific workflows, enables the user to model a workflow from three different but strongly coupled perspectives: the control flow perspective, the data flow perspective, and the resource perspective. All three perspectives are of\ud
equal importance, but workflow designers from different domains prefer different perspectives as entry points for their design, and a single workflow designer may prefer different perspectives in different stages of workflow design. Each perspective provides its own type of information, visualisation and support for validation. Combining these three perspectives in a single application provides a new and flexible way of modelling workflows
Exploring Preschool-Age Children’s Ability to Write Letters
The purpose of this study was to examine the letter-writing ability of preschool children aged 3-5 years and the relationship between early literacy skills (i.e., alphabet knowledge, phonological awareness, and name writing) and letter-writing ability. Thirty-six children were individually assessed on letter writing and early literacy skills thought to be important for letter writing success: letter-name knowledge, letter-sound knowledge, beginning sound awareness, and name writing (i.e., writing names using letters or letter-like forms). Results showed that preschool children demonstrated substantial abilities to write upper-case and lower-case letters and children\u27s age was significantly associated with letter-writing ability. Children\u27s lower-case letter-name knowledge, letter-sound knowledge, and name writing were significantly related to letter writing comprised of upper-case and lower-case letter writing. Letter-sound knowledge and name writing significantly predicted upper-case letter writing and only letter-sound knowledge significantly predicted lower-case letter writing
Ultrafast dynamics of coherences in the quantum Hall system
Using three-pulse four-wave-mixing optical spectroscopy, we study the
ultrafast dynamics of the quantum Hall system. We observe striking differences
as compared to an undoped system, where the 2D electron gas is absent. In
particular, we observe a large off-resonant signal with strong oscillations.
Using a microscopic theory, we show that these are due to many-particle
coherences created by interactions between photoexcited carriers and collective
excitations of the 2D electron gas. We extract quantitative information about
the dephasing and interference of these coherences.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let
Electrophysiological effects of progesterone on hepatocytes
AbstractThe addition of progesterone (1–100 μmol/l) to the extracellular fluid bathing rat hepatocytes led to a rapid and fully reversible depolarization of the cell membrane. The progesterone-induced depolarization was paralleled by a decrease of potassium selectivity and an increase of cell membrane resistance and was abolished in the presence of the potassium channel blocker barium. Accordingly, in whole cell recordings, progesterone led to a decrease of the cell membrane conductance. 17 α-Hydroxyprogesterone and β-estradiol were less effective by a factor of 10, whereas cholesterol, corticosterone and hydrocortisone did not significantly alter the potential difference across the cell membrane. In conclusion, acute administration of progesterone depolarized rat hepatocytes by decreasing the potassium conductance of the cell membrane
Can the magnetic moment contribution explain the A_y puzzle?
We evaluate the full one-photon-exchange Born amplitude for scattering.
We include the contributions due to the magnetic moment of the proton or
neutron, and the magnetic moment and quadrupole moment of the deuteron. It is
found that the inclusion of the magnetic-moment interaction in the theoretical
description of the scattering observables cannot resolve the long-standing
puzzle.Comment: 7 pages, 2 Postscript figures; to appear in Phys.Rev.
Integrating heterogeneous sequence information for transcriptome-wide microarray design; a Zebrafish example
BACKGROUND: A complete gene-expression microarray should preferably detect all genomic sequences that can be expressed as RNA in an organism, i.e. the transcriptome. However, our knowledge of a transcriptome of any organism still is incomplete and transcriptome information is continuously being updated. Here, we present a strategy to integrate heterogeneous sequence information that can be used as input for an up-to-date microarray design. FINDINGS: Our algorithm consists of four steps. In the first step transcripts from different resources are grouped into Transcription Clusters (TCs) by looking at the similarity of all transcripts. TCs are groups of transcripts with a similar length. If a transcript is much smaller than a TC to which it is highly similar, it will be annotated as a subsequence of that TC and is used for probe design only if the probe designed for the TC does not query the subsequence. Secondly, all TCs are mapped to a genome assembly and gene information is added to the design. Thirdly TC members are ranked according to their trustworthiness and the most reliable sequence is used for the probe design. The last step is the actual array design. We have used this strategy to build an up-to-date zebrafish microarray. CONCLUSIONS: With our strategy and the software developed, it is possible to use a set of heterogeneous transcript resources for microarray design, reduce the number of candidate target sequences on which the design is based and reduce redundancy. By changing the parameters in the procedure it is possible to control the similarity within the TCs and thus the amount of candidate sequences for the design. The annotation of the microarray is carried out simultaneously with the design
2s Hyperfine Structure in Hydrogen Atom and Helium-3 Ion
The usefulness of study of hyperfine splitting in the hydrogen atom is
limited on a level of 10 ppm by our knowledge of the proton structure. One way
to go beyond 10 ppm is to study a specific difference of the hyperfine
structure intervals 8 Delta nu_2 - Delta nu_1. Nuclear effects for are not
important this difference and it is of use to study higher-order QED
corrections.Comment: 10 pages, presented at Hydrogen Atom II meeting (2000
Long Range Magnetic Order and the Darwin Lagrangian
We simulate a finite system of confined electrons with inclusion of the
Darwin magnetic interaction in two- and three-dimensions. The lowest energy
states are located using the steepest descent quenching adapted for velocity
dependent potentials. Below a critical density the ground state is a static
Wigner lattice. For supercritical density the ground state has a non-zero
kinetic energy. The critical density decreases with for exponential
confinement but not for harmonic confinement. The lowest energy state also
depends on the confinement and dimension: an antiferromagnetic cluster forms
for harmonic confinement in two dimensions.Comment: 5 figure
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