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211.
Scanning tunneling microscopy (STM) images show that adsorbed formate has a profound affect on the step edges of Cu(1 1 0) surfaces at room temperature. For low exposures, the presence of formate enhances step fluctuations as confirmed by a correlation function analysis. For formate coverages approaching 0.5 monolayers, drastic restructuring of step edges is observed. Quantum chemical calculations help to explain this behavior. 相似文献
212.
Real-time two-dimensional wavelet compression and its application to real-time modeling of ion mobility data 总被引:1,自引:0,他引:1
Real-time data analysis is important in many applications. However, many chemometric algorithms have difficulty processing data in real-time. A novel real-time two-dimensional wavelet compression (WC2) has been developed to compress data as it is acquired from analytical instrumentation. The WC algorithm was enhanced so that data with an arbitrary number of points were compressed, and truncation or padding to a dyadic number was avoided. After compression, the noise level is reduced while useful chemical information is retained. A modified simple-to-use interactive self-modeling mixture analysis (SIMPLISMA) algorithm was applied to the wavelet-compressed data and the model was transformed back to the original representation while leaving the data compressed. The reduced size of the wavelet-compressed data furnished a faster implementation of SIMPLISMA that facilitates real-time acquisition.
This real-time WC2-SIMPLISMA algorithm was applied to the rapid identification of explosives by ion mobility spectrometry (IMS). SIMPLISMA resolved concentration profiles and component spectra were displayed simultaneously while the data was acquired from an ion mobility spectrometer with a LabVIEW virtual instrument (VI). 相似文献
213.
Myong-Hun Chang Joseph E. Harrington Jr. 《Computational & Mathematical Organization Theory》1998,3(4):267-288
Two organizational structures for a retail chain are examined fortheir effect on the rate of firm innovation. A centralized organization isdefined as one in which store practices are mandated from corporateheadquarters (HQ) and this results in HQ being the sole source of new ideas.A decentralized organization gives freedom to store managers to adopt theirown ideas and disseminates innovations made by store managers. Thedifference in average profit between the centralized and decentralizedorganizations is found to be a non-monotonic function of innovativeopportunities. The centralized organization is preferred when innovativeopportunities are moderate while the decentralized organization is preferredwhen such opportunities are rich. Centralization also tends to fare betterin environments in which ideas are relatively complex. 相似文献
214.
It has previously been shown that the plateau modulus, GNo, and thus the entanglement molecular weight, Me, of flexible polymers can be correlated to the unperturbed chain dimension, <R2>o/M, and mass density, , via the use of the packing length, p. For polyolefins, a method was recently proposed whereby knowledge of the average molecular weight per backbone bond, mb, allows <R2>o/M and consequently GNo and Me to be estimated. This is particularly valuable for polyolefin copolymers since the melt chain dimensions are often unknown. This work corroborates these theoretical predictions by studying the rheology of a series of carefully synthesized ethylene/octene copolymers with varying octene content (19–92 wt%). Furthermore, the results reported herein also allow the advancement of rheological characterization techniques of polymer melts. For instance, based on the analysis of the linear viscoelastic properties of these copolymers, it has been found that several rheological parameters scale with the copolymer comonomer content. Analysis of the viscoelastic material functions in terms of the evolution of the phase angle, , as a function of the absolute value of the complex modulus, |G*|, (the so-called van Gurp–Palmen plots), provides a fast and reliable rheological means for determining the composition of ethylene/-olefin copolymers. The crossover parameters, Gco(=G=G) and co(=1/co) also scale with copolymer composition.Submitted for publication to Rheologica Acta
An erratum to this article is available at . 相似文献
An erratum to this article is available at . 相似文献
215.
Dr. Keith Izod Dr. Ewan R. Clark Pamela Foster Rebecca J. Percival Ian M. Riddlestone Prof. William Clegg Dr. Ross W. Harrington 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(19):6094-6107
Treatment of the thioether‐substituted secondary phosphanes R2PH(C6H4‐2‐SR1) [R2=(Me3Si)2CH, R1=Me ( 1PH ), iPr ( 2PH ), Ph ( 3PH ); R2=tBu, R1=Me ( 4PH ); R2=Ph, R1=Me ( 5PH )] with nBuLi yields the corresponding lithium phosphanides, which were isolated as their THF ( 1 – 5Pa ) and tmeda ( 1 – 5Pb ) adducts. Solid‐state structures were obtained for the adducts [R2P(C6H4‐2‐SR1)]Li(L)n [R2=(Me3Si)2CH, R1=nPr, (L)n=tmeda ( 2Pb ); R2=(Me3Si)2CH, R1=Ph, (L)n=tmeda ( 3Pb ); R2=Ph, R1=Me, (L)n=(THF)1.33 ( 5Pa ); R2=Ph, R1=Me, (L)n=([12]crown‐4)2 ( 5Pc )]. Treatment of 1PH with either PhCH2Na or PhCH2K yields the heavier alkali metal complexes [{(Me3Si)2CH}P(C6H4‐2‐SMe)]M(THF)n [M=Na ( 1Pd ), K ( 1Pe )]. With the exception of 2Pa and 2Pb , photolysis of these complexes with white light proceeds rapidly to give the thiolate species [R2P(R1)(C6H4‐2‐S)]M(L)n [M=Li, L=THF ( 1Sa , 3Sa – 5Sa ); M=Li, L=tmeda ( 1Sb , 3Sb – 5Sb ); M=Na, L=THF ( 1Sd ); M=K, L=THF ( 1Se )] as the sole products. The compounds 3Sa and 4Sa may be desolvated to give the cyclic oligomers [[{(Me3Si)2CH}P(Ph)(C6H4‐2‐S)]Li]6 (( 3S )6) and [[tBuP(Me)(C6H4‐2‐S)]Li]8 (( 4S )8), respectively. A mechanistic study reveals that the phosphanide–thiolate rearrangement proceeds by intramolecular nucleophilic attack of the phosphanide center at the carbon atom of the substituent at sulfur. For 2Pa / 2Pb , competing intramolecular β‐deprotonation of the n‐propyl substituent results in the elimination of propene and the formation of the phosphanide–thiolate dianion [{(Me3Si)2CH}P(C6H4‐2‐S)]2?. 相似文献
216.
217.
Stabilization of a Diphosphagermylene through pπ–pπ Interactions with a Trigonal‐Planar Phosphorus Center 下载免费PDF全文
Dr. Keith Izod Daniel G. Rayner Dr. Salima M. El‐Hamruni Dr. Ross W. Harrington Dr. Ulrich Baisch 《Angewandte Chemie (International ed. in English)》2014,53(14):3636-3640
N‐Heterocyclic carbenes and their heavier homologues are, in part, stabilized by delocalization of the N lone pairs into the vacant p‐orbital at carbon (or a heavier Group 14 element center). These interactions are usually absent in the corresponding P‐substituted species, owing to the large barrier to planarization of phosphorus. However, judicious selection of the substituents at phosphorus has enabled the synthesis of a diphosphagermylene, [(Dipp)2P]2Ge, in which one of the P centers is planar (Dipp=2,6‐diisopropylphenyl). The planar nature of this P center and the correspondingly short P? Ge distance suggest a significant degree of P? Ge multiple bond character that is due to delocalization of the phosphorus lone pair into the vacant p‐orbital at germanium. DFT calculations support this proposition and NBO and AIM analyses are consistent with a Ge? P bond order greater than unity. 相似文献
218.
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Characterization of alumina-supported catalysts required determination of rhodium by atomic-absorption spectroscopy (AAS). Catalysts were loaded with 0.1-2.0% rhodium chloride and calcined at 400 degrees . Rhodium remaining as the chloride was regarded as the soluble form, while that converted into the oxide or bonded to the alumina was regarded as the bonded form. By selective dissolution procedures, soluble rhodium was leached from the substrate and determined by AAS. Total rhodium was determined after the catalyst had been fused with sodium peroxide. Bonded rhodium can be determined by difference or by analysing leached residue. Optimization of AAS conditions, use of spectroscopic buffer solution and elimination of interelement interferences are discussed. 相似文献