Electroviscous Forces on a Charged Cylinder Moving Near a Charged Wall

The refined theory of the electroviscous lift forces is presented for the case when the separation distance between the particle and the wall is larger than the double-layer thickness. The theory is based on the lubrication approximation for motion of a long cylinder near a solid wall in creeping flow. The approximate analytical formula for the lift force valid for Pe相似文献   

Periodate-triggered cross-linking of DOPA-containing peptide-protein complexes

Chemical cross-linking is a powerful methodology for analyzing proteins-small molecule and protein-protein interactions. We describe the development of a new chemical cross-linking reaction for the study of protein complexes. Specifically, we show that molecules containing an ortho dihydroxyarene unit can be oxidized selectively with sodium periodate in the presence of native proteins, producing an ortho quinone intermediate that can cross-link with suitable nearby protein residues. We demonstrate the efficacy and specificity of this chemistry for a peptide-protein complex and also deduce the binding site of an artificial activation domain on a proteasome subcomplex.     

Anion-exchange separation of metal ions in dimethyl sulphoxide-methanol-hydrochloric acid

The effect of dimethyl sulphoxide on the anion-exchange behaviour of many metals m a methanolic system with hydrochloric acid was explored. Distribution coefficients for 26 elements were determined in a mixed solvent system of dimethyl sulphoxide-methanol-0.6M hydrochloric acid, in which the proportions of dimethyl sulphoxide and methanoi were varied. Lead(II) and silver(I) complexes are soluble in this system. Interesting effects were noted for gold(III), iron(III), molybdenum(VI) and uranium(VI). As a measure of the usefulness of the systems studied, 27 anion-exchange separations of two- to four-component mixtures of metal ions were carried out, each with quantitative results.     

Polyoxometalate‐Mediated One‐Pot Synthesis of Pd Nanocrystals with Controlled Morphologies for Efficient Chemical and Electrochemical Catalysis

Polyoxometalates (POMs), as inorganic ligands, can endow metal nanocrystals (NCs) with unique reactivities on account of their characteristic redox properties. In the present work, we present a facile POM‐mediated one‐pot aqueous synthesis method for the production of single‐crystalline Pd NCs with controlled shapes and sizes. The POMs could function as both reducing and stabilizing agents in the formation of NCs, and thus gave a fine control over the nucleation and growth kinetics of NCs. The prepared POM‐stabilized Pd NCs exhibited excellent catalytic activity and stability for electrocatalytic (formic acid oxidation) and catalytic (Suzuki coupling) reactions compared to Pd NCs prepared without the POMs. This shows that the POMs play a pivotal role in determining the catalytic performance, as well as the growth, of NCs. We envision that the present approach can offer a convenient way to develop efficient NC‐based catalyst systems.     

Direct patterning of composite biocompatible microstructures using microfluidics

This study demonstrates a versatile and fast method for patterning three-dimensional (3D) monolithic microstructures made of multiple (up to 24 demonstrated) types of materials, all spatially aligned, inside a microchannel. This technique uses confocal scanning or conventional fluorescence microscopy to polymerize selected regions of a photocurable material, and microfluidics to automate the delivery of a series of washes and photocurable reagents. Upon completion of lithographic cycles, the aligned 3D microstructures are suitable for microfluidic manipulation and analysis. We demonstrated the fabrication of composite 3D microstructures with various geometries, size scales (up to 1 mm2), spatial resolution (down to 3 microm), and materials. For a typical multi-cycle process, the total fabrication time was tens of minutes, compared to tens of hours for conventional methods. In the case of 3D hydrogels, a potential use is the direct patterning of inhomogeneous 3D microenvironments for studying cell behavior.     

X-ray structure analysis of poly[di-(3,4-dimethylphenoxy)phosphazene]

The crystal structure of oriented poly[di-(3,4-dimethylphenoxy) phosphazene] (PDMP) was determined by x-ray diffraction. Unit-cell parameters were found to be a = 15.85, b = 19.43, and c = 9.85 Å. The unit cell is metrically orthorhombic with monoclinic space group P2₁. There were 48 refinable diffraction spots in the observed reciprocal lattice region, of which 28 were observed and 20 were unobserved. A refined model yielded the following residuals: R^(obs) = 0.162 and 0.138. It was shown that a two-chain unit cell with a [T₃C]₂ (trans, trans, trans, cis, trans, trans, trans, cis) backbone conformation was the correct structure. The dimethylphenoxy side groups were arranged in nearly parallel planes, slightly off-normal to the fiber c axis. The polymer chains are extremely tightly packed and contain close but reasonable steric contacts.     

Measurement of static strain at 2,000° F

This paper describes the work being done at Hughes Aircraft Company using capacitance strain gages to measure static strains at temperatures up to and including 2,000° F. A new configuration of the capacitance gage is described with a gage length of 0.50 in. Methods of attaching the gage have been developed for welding, bonding and flame-spray installations. Instrumentation procedures and methods are defined. Statistical accuracy and test results are discussed on the results obtained from a lot of 60 gages. Results discussed were obtained on Rene 41, titanium and L605 stainless steel. Data analysis on the gage includes gage factor, gage factor vs. temperature, apparent strain, linearity, hysteresis, temperature effects, drift, and zero shift.     

Highly flexible pseudocapacitor based on freestanding heterogeneous MnO2/conductive polymer nanowire arrays

Flexible electronics such as wearable electronic clothing, paper-like electronic devices, and flexible biomedical diagnostic devices are expected to be commercialized in the near future. Flexible energy storage will be needed to power these devices. Supercapacitor devices based on freestanding nanowire arrays are promising high power sources for these flexible electronics. Electrodes for these supercapacitor devices consisting of heterogeneous coaxial nanowires of poly (3,4-ethylenedioxythiophene) (PEDOT)-shell and MnO(2)-core materials have been shown in a half cell system to have improved capacitance and rate capabilities when compared to their pure nanomaterials; however, their performance in a full cell system has not been fully investigated. Herein, these coaxial nanowires are tested in both a symmetric and an asymmetric (utilizing a PEDOT nanowire anode) full cell configuration in the aspect of charge storage, charge rate, and flexibility without using any carbon additives and polymer binders. It is found that the asymmetric cell outperforms the symmetric cell in terms of energy density, rate capability, and cycle ability. The asymmetric device's electrode materials display an energy density of 9.8 Wh/kg even at a high power density of 850 W kg(-1). This device is highly flexible and shows fast charging and discharging while still maintaining 86% of its energy density even under a highly flexed state. The total device is shown to have a total capacitance of 0.26 F at a maximum voltage of 1.7 V, which is capable of providing enough energy to power small portable devices.