2,417 research outputs found
Cross Sections for He, Li, and Be Isotopes Produces in the a + a Reactions at 198.4 MeV
This research was sponsored by the National Science Foundation Grant NSF PHy 87-1440
Thermodynamic database for the Co-Pr system
AbstractIn this article, we describe data on (1) compositions for both as-cast and heat treated specimens were summarized in Table 1; (2) the determined enthalpy of mixing of liquid phase is listed in Table 2; (3) thermodynamic database of the Co-Pr system in TDB format for the research articled entitle Chemical partitioning for the Co-Pr system: First-principles, experiments and energetic calculations to investigate the hard magnetic phase W
UV induced ubiquitination of the yeast Rad4-Rad23 complex promotes survival by regulating cellular dNTP pools
Regulating gene expression programmes is a central facet of the DNA damage response. The Dun1 kinase protein controls expression of many DNA damage induced genes, including the ribonucleotide reductase genes, which regulate cellular dNTP pools. Using a combination of gene expression profiling and chromatin immunoprecipitation, we demonstrate that in the absence of DNA damage the yeast Rad4�Rad23 nucleotide excision repair complex binds to the promoters of certain DNA damage response genes including DUN1, inhibiting their expression. UV radiation promotes the loss of occupancy of the Rad4�Rad23 complex from the regulatory regions of these genes, enabling their induction and thereby controlling the production of dNTPs. We demonstrate that this regulatory mechanism, which is dependent on the ubiquitination of Rad4 by the GG-NER E3 ligase, promotes UV survival in yeast cells. These results support an unanticipated regulatory mechanism that integrates ubiquitination of NER DNA repair factors with the regulation of the transcriptional response controlling dNTP production and cellular survival after UV damage
Network Landscape from a Brownian Particle's Perspective
Given a complex biological or social network, how many clusters should it be
decomposed into? We define the distance from node to node as
the average number of steps a Brownian particle takes to reach from .
Node is a global attractor of if for any of
the graph; it is a local attractor of , if (the set of
nearest-neighbors of ) and for any . Based
on the intuition that each node should have a high probability to be in the
same community as its global (local) attractor on the global (local) scale, we
present a simple method to uncover a network's community structure. This method
is applied to several real networks and some discussion on its possible
extensions is made.Comment: 5 pages, 4 color-figures. REVTeX 4 format. To appear in PR
Significant enhancement of flux pinning in MgB2 superconductor through nano-Si addition
Polycrystalline MgB2 samples with 10 wt % silicon powder addition were
prepared by an in-situ reaction process. Two different Si powders, one with
coarse (44 mm) and the other with nano-size (<100 nm) particles were used for
making samples. The phases, microstructures, and flux pinning were
characterized by XRD, TEM, and magnetic measurements. It was observed that the
samples doped with nano-sized Si powder showed a significantly improved field
dependence of the critical current over a wide temperature range compared with
both undoped samples and samples with coarse Si added. Jc is as high as 3000
A/cm2 in 8 T at 5 K, one order of magnitude higher than for the undoped MgB2.
X-ray diffraction results indicated that Si had reacted with Mg to form Mg2Si.
Nano-particle inclusions and substitution, both observed by transmission
electron microscopy, are proposed to be responsible for the enhancement of flux
pinning in high fields. However, the samples made with the coarse Si powders
had a poorer pinning than the undoped MgB2.Comment: 3 pages, 6 figure
Uncertainty Principle for Control of Ensembles of Oscillators Driven by Common Noise
We discuss control techniques for noisy self-sustained oscillators with a
focus on reliability, stability of the response to noisy driving, and
oscillation coherence understood in the sense of constancy of oscillation
frequency. For any kind of linear feedback control--single and multiple delay
feedback, linear frequency filter, etc.--the phase diffusion constant,
quantifying coherence, and the Lyapunov exponent, quantifying reliability, can
be efficiently controlled but their ratio remains constant. Thus, an
"uncertainty principle" can be formulated: the loss of reliability occurs when
coherence is enhanced and, vice versa, coherence is weakened when reliability
is enhanced. Treatment of this principle for ensembles of oscillators
synchronized by common noise or global coupling reveals a substantial
difference between the cases of slightly non-identical oscillators and
identical ones with intrinsic noise.Comment: 10 pages, 5 figure
Measurement of Trace I-129 Concentrations in CsI Powder and Organic Liquid Scintillator with Accelerator Mass Spectrometry
Levels of trace radiopurity in active detector materials is a subject of
major concern in low-background experiments. Procedures were devised to measure
trace concentrations of I-129 in the inorganic salt CsI as well as in organic
liquid scintillator with Accelerator Mass Spectrometry (AMS) which leads to
improvement in sensitivities by several orders of magnitude over other methods.
No evidence of their existence in these materials were observed. Limits of < 6
X 10^{-13} g/g and < 2.6 X 10^{-17} g/g on the contaminations of I-129 in CsI
and liquid scintillator, respectively, were derived.These are the first results
in a research program whose goals are to develop techniques to measure trace
radioactivity in detector materials by AMS.Comment: Proceedings of 10th International Conference on Accelerator Mass
Spectrometr
An improved \eps expansion for three-dimensional turbulence: summation of nearest dimensional singularities
An improved \eps expansion in the -dimensional () stochastic
theory of turbulence is constructed by taking into account pole singularities
at in coefficients of the \eps expansion of universal quantities.
Effectiveness of the method is illustrated by a two-loop calculation of the
Kolmogorov constant in three dimensions.Comment: 4 page
Modeling of Thermodynamic Properties and Phase Equilibria for the Al-Sm Binary System
The thermodynamic properties and associated phase equilibria for the Al-Sm binary system are examined, and experimental results regarding the stability of the Al3Sm, Al11Sm3, and Al4Sm intermetallics are incorporated. In the analysis presented, the liquid phase is described using a three-species association model, the intermediate phases are treated as stoichiometric compounds, and the terminal phases are treated as solid solutions with a single sublattice model. In addition to the stable phases, thermodynamic descriptions of the metastable Al11Sm3-α and Al4Sm-γ phases are employed, and both stable and metastable phase equilibria are presented over the full composition range, providing a general model, which is consistent with available experimental data. Metastable liquidus curves are examined with respect to the observed crystallization behavior of amorphous Al-Sm alloys
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