886 research outputs found
First-principles LDA+U and GGA+U study of neptunium dioxide
We have performed a systematic first-principles investigation to calculate
the electronic structures, mechanical properties, and phonon dispersion curves
of NpO. The local density approximation and the generalized gradient
approximation formalisms have been used to account for the strong on-site
Coulomb repulsion among the localized Np electrons. By choosing the
Hubbard \emph{U} parameter around 4 eV, the orbital occupancy characters of Np
5\emph{f} and O 2\emph{p} are in good agreement with recent experiments [J.
Nucl. Mater. \textbf{389}, 470 (2009)]. Comparing with our previous study of
ThO, we note that stronger covalency exists in NpO due to the more
localization behavior of 5\emph{f} electrons of Np in line with the
localization-delocalization trend exhibited by the actinides series.Comment: 7 pages, 6 figure
General Tasks and Extension-Based Proofs
The concept of extension-based proofs models the idea of a valency argument
which is widely used in distributed computing. Extension-based proofs are
limited in power: it has been shown that there is no extension-based proof of
the impossibility of a wait-free protocol for -set agreement among processes. A discussion of a restricted type of reduction has shown
that there are no extension-based proofs of the impossibility of wait-free
protocols for some other distributed computing problems.
We extend the previous result to general reductions that allow multiple
instances of tasks. The techniques used in the previous work are designed for
certain tasks, such as the -set agreement task. We give a necessary and
sufficient condition for general colorless tasks to have no extension-based
proofs of the impossibility of wait-free protocols, and show that different
types of extension-based proof are equivalent in power for colorless tasks.
Using this necessary and sufficient condition, the result about reductions can
be understood from a topological perspective
Identification of androgen response elements in the insulin-like growth factor I upstream promoter
Journal ArticleTestosterone stimulates the expression of IGF-I in cells and tissues that include prostate, muscle and muscle satellite cells, and the uterus. Here, the molecular mechanisms of this effect of testosterone were explored. Testosterone increased IGF-I mRNA levels in HepG2 and LNCaP cells and stimulated the activity of reporter genes controlled by 1.6 kb of the upstream promoter of the human IGF-I gene. An androgen-responsive region that was located between -1320 and -1420 bases upstream of the first codon was identified by truncation studies. The androgen-responsive region was found to contain two sequences resembling known androgen receptor (AR)-binding sites from the Pem1 gene. Reporter genes incorporating these sequences were strongly stimulated by androgens. Each of the androgen-responsive elements (AREs) bound recombinant AR-DNA-binding domain in gel-shift experiments; binding was greatly enhanced by sequences flanking the apparent AR-binding half-sites. Testosterone induced recruitment of AR to sequences of genomic DNA containing these AREs. The two AREs were activated 5-fold more by AR than glucocorticoid receptor. Collectively, these findings indicate the presence of two AREs within the IGF-I upstream promoter that act in cis to activate IGF-I expression. These AREs seem likely to contribute to the up-regulation of the IGF-I gene in prostate tissues, HepG2 cells, and potentially other tissues
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