ChemInform Abstract: A New Naturally‐Occurring Nanoporous Copper Sheet‐Silicate with 6482 Cages Related to Synthetic “CuSH” Phases.

The structure of a new naturally‐occurring nanoporous copper silicate of formula Na₂CaCu₂Si₈O₂₀ ·H₂O is reported and its relations to synthetic nanoporous, so‐called CuSH phases is discussed.     

Tribological Behavior of Multiply-Alkylated Cyclopentanes (MACs)-Cu Nanoparticles Composite Thin Film

Multiply-alkylated cyclopentanes (MACs) composite thin films containing Cu nanoparticles are fabricated on the octadecyltrichlorosilane (OTS)-modified substrate by a spin-coating technique. The thickness, wetting behavior, and nanoscale morphologies of the films are characterized by means of ellipsometry, contact angle measurement, and atomic force microscope (AFM). The friction and wear behaviors of the thin films sliding against Si₃N₄ ball are examined on a UMT-2MT tribometer in a ball-on-disk contact mode. The worn surfaces of the OTS-MAC-Cu composite film and the counterpart Si₃N₄ balls are investigated with a scanning electron microscope. Water contact angle on OTS-MAC-Cu composite film is higher than that of OTS-MAC film. OTS-MAC-Cu composite film exhibits higher load-carrying capacity and better friction reduction and antiwear behavior as compared with OTS-MAC film. This may be attributed to the load-carrying and self-repairing property of the Cu nanoparticles in the composite film and the formation of a transfer layer composed of OTS, MAC, and Cu on the rubbing surface of the counterpart ball.     

X-ray absorption study of Cu,Zn SOD under high pressure

Abstract

We have investigated Cu, Zn Superoxide Dismutase (Cu, Zn SOD) metal sites at high pressure using X-ray absorption. XAS (X-ray Absorption Spectroscopy) gives information on local structure and it is particularly suited to metal site investigation. To the best of our knowledge, this is the first time that protein conformational states have been investigated using the high pressure XAS technique. Cu, Zn SOD catalyses the dismutation of toxic oxygen radicals produced in cells; this reaction occurs at the copper metal site. Structural changes around the copper, induced by pressure, can be directly related to protein substates. Their characterisation is thus important in the understanding of protein activity.

The high-pressure device was a Paris-Edinburgh large volume cell.

Experiments were performed on lyophilised Cu, Zn SOD between 0 and 48 kbar at the copper and zinc K-edges. The two metal local atomic environments have a different behaviour as pressure increases: copper exhibits a more flexible environment; on the contrary, zinc shows small structural modifications. We have identified a state, formed between 3 and 8 kbar, which is stable up to 48 kbar.     

EPR and optical spectra of cupric ions doped in powder strontium maleate tetrahydrate and magnesium Bis (hydrogen maleate) hexahydrate

Abstract

EPR spectra of Cu²⁺ ions doped in a strontium maleate tetrahydrate and magnesium bis (hydrogen maleate) hexahydrate have been studied in X-band at room temperature and at liquid nitrogen temperature. Spin-Hamiltonian parameters have been calculated. Molecular orbital coefficients are obtained by correlating optical absorption data with EPR results.     

Comparison of Methods for the Computation of Multivariate t Probabilities

This article compares methods for the numerical computation of multivariate t probabilities for hyper-rectangular integration regions. Methods based on acceptance-rejection, spherical-radial transformations, and separation-of-variables transformations are considered. Tests using randomly chosen problems show that the most efficient numerical methods use a transformation developed by Genz for multivariate normal probabilities. These methods allow moderately accurate multivariate t probabilities to be quickly computed for problems with as many as 20 variables. Methods for the noncentral multivariate t distribution are also described.     

A new control chart in contaminated data of t‐Student distribution for individual observations

Control charts are the most popular tool for monitoring production quality. In traditional control charts, it is usually supposed that the observations follow a multivariate normal distribution. Nevertheless, there are many practical applications where the normality assumption is not fulfilled. Furthermore, the performance of these charts in the presence of measurement errors (outliers) in the historical data has been improved using robust control charts when the observations follow a normal distribution. In this paper, we develop a new control chart for t‐Student data based on the trimmed T² control chart () through the adaptation of the elements of this chart to the case of this distribution. Simulation studies show that a control chart performs better than T² in t‐Student samples for individual observations. Copyright © 2012 John Wiley & Sons, Ltd.     

Size dependent deformation behaviour and dislocation mechanisms in 〈1 0 0〉 Cu nanowires

Abstract

Molecular dynamics simulations have been performed to understand the size-dependent tensile deformation behaviour of 〈1 0 0〉 Cu nanowires at 10 K. The influence of nanowire size has been examined by varying square cross-section width (d) from 0.723 to 43.38 nm using constant length of 21.69 nm. The results indicated that the yielding in all the nanowires occurs through nucleation of partial dislocations. Following yielding, the plastic deformation in small size nanowires occurs mainly by slip of partial dislocations at all strains, while in large size nanowires, slip of extended dislocations has been observed at high strains in addition to slip of partial dislocations. Further, the variations in dislocation density indicated that the nanowires with d > 3.615 nm exhibit dislocation exhaustion at small strains followed by dislocation starvation at high strains. On the other hand, small size nanowires with d < 3.615 nm displayed mainly dislocation starvation at all strains. The average length of dislocations has been found to be same and nearly constant in all the nanowires. Both the Young’s modulus and yield strength exhibited a rapid decrease at small size nanowires followed by gradual decrease to saturation at larger size. The observed linear increase in ductility with size has been correlated with the pre- and post-necking deformation. Finally, dislocation–dislocation interactions leading to the formation of various dislocation locks, the dislocation–stacking fault interactions resulting in the annihilation of stacking faults and the size dependence of dislocation–surface interactions have been discussed.     

Stress-assisted nucleation and growth of γ″ and γ′ precipitates in a Cu–1.2 wt%Be–0.1 wt%Co alloy aged at 320°C

An investigation by high-resolution transmission electron microscopy of the precipitation process during ageing a Cu–1.2?wt%Be–0.1?wt%Co alloy at 320°C has revealed that the transition phases follow a γ″→ γ″?+?γ′?→?γ sequence. The γ′ phase heterogeneously precipitates on the γ″ phase. The effects of an external stress on the nucleation and growth of disc-shaped γ″ and plate-shaped γ′ precipitates have been examined for the alloy aged at 320°C. A compressive stress applied in the [001] direction during ageing preferentially accelerates the nucleation and growth of the γ″ variant normal to the [001] axis among three crystallographically equivalent variants and the specific four γ′ variants formed on the γ″ variant normal to the [001] axis. A tensile stress does not significantly affect those of γ″ and γ′ precipitates. The critical diameter of the disc-shaped γ″ nucleus is estimated as about 1?nm from evaluation of the interaction energy between the applied stress and the misfit strains of γ″ precipitates. It is proposed that applied external stress does not affect the diffusion rate but the interphase boundary velocity.