7,799 research outputs found
A Stabilization Mechanism of Zirconia Based on Oxygen Vacancies Only
The microscopic mechanism leading to stabilization of cubic and tetragonal
forms of zirconia (ZrO) is analyzed by means of a self-consistent
tight-binding model. Using this model, energies and structures of zirconia
containing different vacancy concentrations are calculated, equivalent in
concentration to the charge compensating vacancies associated with dissolved
yttria (YO) in the tetragonal and cubic phase fields (3.2 and 14.4% mol
respectively). The model is shown to predict the large relaxations around an
oxygen vacancy, and the clustering of vacancies along the directions,
in good agreement with experiments and first principles calculations. The
vacancies alone are shown to explain the stabilization of cubic zirconia, and
the mechanism is analyzed.Comment: 19 pages, 6 figures. To be published in J. Am. Ceram. So
Push clocks: a new approach to charge-coupled devices clocking
A new approach to charge-coupled device clocking has been developed—dynamic push clocks. With dynamic push clocks, the charge is transferred by pushing it from one storage site to another. The push clock approach results in a larger signal dynamic range, larger signal-to-noise ratio, and better performance at both high and low frequencies
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Regulation of nitric oxide signaling by formation of a distal receptor-ligand complex.
The binding of nitric oxide (NO) to the heme cofactor of heme-nitric oxide/oxygen binding (H-NOX) proteins can lead to the dissociation of the heme-ligating histidine residue and yield a five-coordinate nitrosyl complex, an important step for NO-dependent signaling. In the five-coordinate nitrosyl complex, NO can reside on either the distal or proximal side of the heme, which could have a profound influence over the lifetime of the in vivo signal. To investigate this central molecular question, we characterized the Shewanella oneidensis H-NOX (So H-NOX)-NO complex biophysically under limiting and excess NO conditions. The results show that So H-NOX preferably forms a distal NO species with both limiting and excess NO. Therefore, signal strength and complex lifetime in vivo will be dictated by the dissociation rate of NO from the distal complex and the rebinding of the histidine ligand to the heme
Poems
Poems include: 5th Ave.--New York City, by Edwina Hearn, Trenchcoated and Delivered, by Erika T. Lersch, and Blue, by Michael Anthony Moor
Continuity of translation and separable invariant subspaces of Banach spaces associated to locally compact groups
Evaluation of Ultrasonic Time-of-Flight Diffraction Data for Selected Control Rod Drive Nozzles from Davis Besse Nuclear Power Plant
Pacific Northwest National Laboratory (PNNL) examined ultrasonic (UT) time-of-flight diffraction (TOFD) data from ten (10) nozzles in the Davis Besse Nuclear Power Plant reactor closure head. The TOFD data was acquired by AREVA after a bare metal visual examination of the pressure vessel head indicated potential leakage in at least one nozzle. A detailed analysis of the UT data shows that Nozzle 4 has three indications consistent with cracking in the penetration tube. One of the indications starts at the wetted side of the weld and progresses to the annulus. In addition, examination of UT data from the annulus region of Nozzle 4 displays an irregular pattern that could be associated with boric acid deposits and leakage/wastage in the interference fit. The review of TOFD data for the other nine nozzles resulted in several indications being detected in the weld region and near the inner diameter (ID) and outer diameter (OD) surfaces of the penetration tube, but no other indications that are consistent with cracking that may have resulted in leakage were observed. A review of the back-wall reflections in the other nine nozzles also did not show strong indications of leakage, although Nozzle 67 displayed an irregularly-shaped region of high ultrasonic transmission near 180 degrees on the interference fit
Rietveld refinements of the crystal structures of Rb2XSi5O12 (X = Mn, Ni)
Poster Number: CCG06
Synthetic analogues of the silicate framework mineral leucite (KAlSi2O6) with the stoichiometry
Rb2XSi5O12 (X = Mn, Ni) have been prepared by high temperature solid-state synthesis. Ambient temperature X-ray powder diffraction data have been collected on these samples. Analysis of
these powder diffraction data show that these samples both consist of single phases [1] isostructural with the Pbca cation-ordered framework leucite structure of Cs2CdSi5O12 [2].
Rietveld refinement [3] shows that for X = Mn this crystal structure has complete Mn and Si cation order over the tetrahredrally coordinated sites (T-sites) in the silicate framework. However, for X = Ni, Rietveld refinement suggests that there may be some Ni and Si cation T-site cation disorder
Antibody-based detection of protein phosphorylation status to track the efficacy of novel therapies using nanogram protein quantities from stem cells and cell lines
This protocol describes a highly reproducible antibody-based method that provides protein level and phosphorylation status information from nanogram quantities of protein cell lysate. Nanocapillary isoelectric focusing (cIEF) combines with UV-activated linking chemistry to detect changes in phosphorylation status. As an example application, we describe how to detect changes in response to tyrosine kinase inhibitors (TKIs) in the phosphorylation status of the adaptor protein ​CrkL, a major substrate of the oncogenic tyrosine kinase ​BCR-​ABL in chronic myeloid leukemia (CML), using highly enriched CML stem cells and mature cell populations in vitro. This protocol provides a 2.5 pg/nl limit of protein detection (<0.2% of a stem cell sample containing <104 cells). Additional assays are described for phosphorylated tyrosine 207 (pTyr207)-​CrkL and the protein tyrosine phosphatase ​PTPRC/​CD45; these assays were developed using this protocol and applied to CML patient samples. This method is of high throughput, and it can act as a screen for in vitro cancer stem cell response to drugs and novel agents
First Passage Times for Continuous Quantum Measurement Currents
The First Passage Time (FPT) is the time taken for a stochastic process to
reach a desired threshold. It finds wide application in various fields and has
recently become particularly important in stochastic thermodynamics, due to its
relation to kinetic uncertainty relations (KURs). In this letter we address the
FPT of the stochastic measurement current in the case of continuously measured
quantum systems. Our approach is based on a charge-resolved master equation,
which is related to the Full-Counting statistics of charge detection. In the
quantum jump unravelling we show that this takes the form of a coupled system
of master equations, while for quantum diffusion it becomes a type of quantum
Fokker-Planck equation. In both cases, we show that the FPT can be obtained by
introducing absorbing boundary conditions, making their computation extremely
efficient. The versatility of our framework is demonstrated with two relevant
examples. First, we show how our method can be used to study the tightness of
recently proposed KURs for quantum jumps. Second, we study the homodyne
detection of a single two-level atom, and show how our approach can unveil
various non-trivial features in the FPT distribution.Comment: 8 pages, 2 figure
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