bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessing weak intramolecular donor–acceptor interactions using 1H117Sn J‐HMQC spectroscopy
Authors: Biesemans Monique , Martins José C. , Jurkschat Klaus , Pieper Nicole , Seemeyer Stefan , Willem Rudolph 
Published: August 2004

AbstractIt is demonstrated that long‐range nJ(1H,117Sn) coupling constants down to 0.3 Hz, can be accurately quantified from non‐linear fitting of the sine modulation of the associated 1H117Sn correlation cross‐peak intensities sampled as a function of the heteronuclear antiphase coherence preparation time in the 1H117Sn J‐HMQC pulse sequence. The contribution of additional, undesired modulations is illustrated and assessed using the product operator formalism, and is traced back to contributions that arise from miss‐setting of the wandering 180° pulse angle in the constant time period. The power of the method and its use in the characterization of weak intramolecular donor–acceptor interactions are illustrated by the determination of long‐range nJ(1H,117Sn) coupling constants of bis[3‐(dimethylamino)propyl]tin derivatives, [Me2N(CH2)3]2SnR2 (2, R = Me; 3, R = Ph; 4, R = t‐Bu). By comparing these with the values found for the corresponding bis(4‐methylpentyl)tin derivatives, [Me2CH(CH2)3]2SnR2 (2′, R = Me; 3′, R = Ph), which lack such interactions, the use of long‐range coupling constants to detect intramolecular donor–acceptor interactions is evaluated. It is concluded that nJ(1H,117Sn) couplings up to six bonds through an organic carbon chain can be quantified, whether donor–acceptor interactions are present or not. Furthermore, evidence is presented that, when two scalar coupling pathways co‐exist, the pathway involving an intramolecular donor–acceptor interaction can have opposite sign, thus decreasing the overall coupling constant to a value smaller than that actually measured in the absence of a donor–acceptor interaction, where only one coupling pathway is active. There is nevertheless clear numerical value discrimination in the series of compounds investigated between long‐range couplings in derivatives without weak intramolecular donor–acceptor interactions and those where such interactions can exist. Copyright © 2004 John Wiley & Sons, Ltd.
NMR investigations of Co(III) coordination compounds oriented in a dilute lyotropic liquid crystal
Authors: Pellizer Giorgio , Asaro Fioretta , Pergolese Barbara 
Published: August 2004

AbstractA swollen lamellar phase, based on sodium dodecyl sulfate, pentanol and NaBr brine, was examined by means of NMR spectroscopy of isotopes with quadrupolar characteristics, namely 2H, 17O, 23Na and 81Br, present at natural abundance. Such a dilute lyotropic liquid crystal was capable of inducing a preferential orientation of the cobalt coordination compounds [Co(en)3]3+ and Co(acac)3, the 59Co NMR signals of which displayed quadrupolar splittings. Moreover, it imparted alignment in the magnetic field to the organocobaloxime [ClCD2Co(Hdmg)2H2O], as shown by the quadrupolar splitting of the deuterium of the axial ligand. Copyright © 2004 John Wiley & Sons, Ltd.
A simple molecule with a complex crystal structure: interplay of 31P solid‐state NMR spectroscopy and single‐crystal x‐ray diffraction in the structure determination of a ruthenium diphosphine diamine complex
Authors: Eichele Klaus , Nachtigal Christiane , Jung Susanne , Mayer Hermann A. , Lindner Ekkehard , Ströbele Markus 
Published: August 2004

AbstractA comprehensive 31P solid‐state NMR study of Ru(η1‐Ph2PCH2CH2OCH3)2(η2‐en)Cl2 (en = ethylenediamine) (1), by 1D (contact time variation, inversion–recovery, SPARTAN) and 2D techniques (homonuclear J‐resolved, SECSY) indicated that the crystal structure of 1 should be complex. The single‐crystal x‐ray structure determination confirmed the presence of eight independent molecules in the asymmetric unit, with 31P isotropic chemical shifts in the range 27.3–40.1 ppm, while the spans of the phosphorus chemical shift tensors are of the order of 170 ppm. Based on unique structural features and NMR data, one molecule has been tentatively assigned. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling of earth and water pressure development during diaphragm wall construction in soft clay
Authors: Schäfer R. , Triantafyllidis Th. 
Published: August 2004

AbstractThe influence of a diaphragm wall construction on the stress field in a soft clayey soil is investigated by the use of a three‐dimensional FE‐model of seven adjacent wall panels. The installation procedure comprises the excavation and the subsequent pouring of each panel taking into account the increasing stiffness of the placed fresh concrete. The soft clay deposit is described by a visco‐hypoplastic constitutive model considering the rheological properties and the small‐strain stiffness of the soil. The construction process considerably affects the effective earth and pore water pressures adjacent to the wall. Due to concreting, a high excess pore water pressure arises, which dissipates during the following construction steps. The earth pressure finally shows an oscillating, distinct three‐dimensional distribution along the retaining wall which depends on the installation sequence of the panels and the difference between the fresh concrete pressure and the total horizontal earth pressure at rest. In comparison to FE‐calculations adopting the earth pressure at rest as initial condition, greater wall deflections and surface ground settlements during the subsequent pit excavation can be expected, as the average stress level especially in the upper half of the wall is increased by the construction procedure of the retaining structure. Copyright © 2004 John Wiley & Sons, Ltd.
Medical event profiling of COPD patients
Authors: Hansell A. L. , Lam K. A. , Richardson S. , Visick G. , Soriano J. B. 
Published: August 2004

AbstractPurposeThis analysis proposes appropriate descriptive and analytical statistical techniques to profile medical events requiring GP consultation using the example of chronic obstructive pulmonary disease (COPD).MethodsConsultation patterns were examined for 1807 cases with a diagnosis compatible with COPD in 1998 and a group of controls matched by sex, age and practice from the General Practice Research Database, a nationally representative UK primary care database. Consulting patterns by Read code chapter and chapter subdivision were examined using cluster analysis, logistic regression and classification and regression trees (CART).ResultsCART and multivariate logistic regression analyses suggested that COPD patients were more likely to consult with pulmonary circulatory disease (multivariate OR: 7.46 (95% confidence intervals: 2.05, 20.01) ), non‐COPD respiratory diseases (2.77 (2.28, 3.37)), mycoses (2.0 (1.43, 2.71)), ‘symptoms or ill‐defined conditions’ (1.95 (1.68, 2.29)), or other forms of heart disease (1.84 (1.92, 2.64)), and less likely to consult with hypertensive diseases (0.73 (0.57, 0.96)). Regression also showed positive associations with digestive system diseases (OR: 1.31 (1.02, 1.68)) and negative associations with ‘other viral or chlamydial disease’ (0.16 (0.03, 0.88)). A borderline significance reduced risk for cancers was seen in univariate logistic regression analyses. Cluster analyses were not useful in discriminating between cases and controls.ConclusionsThese analyses provide information about the natural history of COPD and could be used to help interpret or detect adverse drug reactions if repeated before and after introduction of a treatment. COPD can be considered a multicomponent disease with more frequent comorbidities than age‐ and gender‐matched individuals without COPD. Copyright © 2004 John Wiley & Sons, Ltd.
The secretome of the plant pathogenic bacterium Erwinia chrysanthemi
Authors: Kazemi‐Pour Nasrin , Condemine Guy , Hugouvieux‐Cotte‐Pattat Nicole 
Published: August 2004

AbstractErwinia chrysanthemi causes soft‐rot diseases of many plants by secreting a battery of enzymes which degrade the plant cell walls. We initiated a proteomic analysis to create a reference map of the E. chrysanthemi secretome. Extracellular proteins were isolated from E. chrysanthemi culture supernatants and resolved by two‐dimensional electrophoresis. By analysis of mutants, Western blotting, and matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) 55 spots representing 25 unique proteins were identified. In uninduced conditions, we identified spots corresponding to the cellulase Cel5, the proteases PrtA, PrtB, and PrtC, the flagellin FliC, and some intracellular proteins whose presence probably resulted from spontaneous cell lysis. We identified another secreted protein, AvrL, homologous to an avirulence protein of Xanthomonas campestris. After culture in conditions inducing pectinase production, i.e., in the presence of galacturonate and plant extract, we identified spots corresponding to the endopectate lyases PelA, PelB, PelC, PelD, PelE, PelI, PelL, and PelZ, the pectin acetylesterases PaeX and PaeY, the pectin methylesterase PemA, and the polygalacturonase PehX. In the presence of other inducing compounds, we detected the rhamnogalacturonate lyase RhiE and the esterase FaeD. Analysis of mutants, altered for one type of secretion system, was performed to determine the targets of each system. The type I system Prt was necessary for the secretion of three proteases. No proteins secreted by the type III Hrp system could be detected in E. chrysanthemi supernatants. In addition to the already known substrates (eleven pectinases and one cellulase), this analysis revealed that the type II Out system mediates secretion of the esterase FaeD and of the Avr‐like protein AvrL.
Lipid raft proteomics: Analysis of in‐solution digest of sodium dodecyl sulfate‐solubilized lipid raft proteins by liquid chromatography‐matrix‐assisted laser desorption/ionization tandem mass spectrometry
Authors: Li Nan , Shaw Andrew R. E. , Zhang Nan , Mak Allan , Li Liang 
Published: August 2004

AbstractLipid rafts are glycolipid‐ and cholesterol‐enriched membrane microdomains implicated in membrane signaling and trafficking. The highly hydrophobic nature of lipid raft proteins pose significant problems of solubilization and recovery that hinder analysis by mass spectrometry (MS) and may under‐report the composition of lipid rafts. In a previous investigation of the monocyte lipid raft in which proteins were digested with trypsin following polyacrylamide gel electrophoresis we identified 52 proteins. Here we report the development of a sodium dodecyl sulfate (SDS)‐aided approach in which proteins are digested in solution and examined by high‐performance liquid chromatography‐matrix‐assisted laser desorption/ionization‐tandem mass spectrometry (HPLC‐MALDI‐MS/MS) using a novel LC‐MALDI interface thereby circumventing the need to separate proteins on gels. Using this approach we identified 71 proteins in the lipid raft, 45 of which were not detected using in‐gel digestion. Among the new proteins are α‐ and β‐tubulin, tubulinspecific chaperone A, a folding protein involved in tubulin dimer assembly, and KIF13, a microtubule motor protein indicating that proteins involved in microtubule assembly and trafficking are more readily detected using an in‐solution approach. To investigate why tubulin was not identified by in‐gel digestion, we compared the distribution of α‐tubulin and the raft marker flotillin‐2 in buoyant density gradients before and after separation on SDS‐gels. Both proteins were present in the raft fractions, but tubulin was selectively lost following separation on SDS‐gels. Assemblies of cytoskeletal proteins with lipid rafts may therefore be resolved using in‐solution digestion that would be missed using gel‐based approaches.
(−)‐Sparteine: The compound that most significantly influenced my research
Authors: Okamoto Yoshio 
Published: August 2004

AbstractA chiral diamine alkaloid, (−)‐sparteine (Sp), has been found to be very effective as a ligand for Grignard reagents when used for the enantiomer‐selective polymerization of racemic RS‐1‐phenylethyl methacrylate. The enantiomeric excess of the initially polymerized monomer is 93%, and at about a 60% conversion, nearly optically pure R‐monomer is recovered. This enantiomer selectivity is today the highest in polymer chemistry. Triphenylmethyl methacrylate (TrMA) is a unique monomer that gives a highly isotactic polymer even during radical polymerization. When TrMA is polymerized with the Sp complex with n‐butyllithium in toluene at −78 °C, an optically active, isotactic polymer [poly(triphenylmethyl methacrylate) (PTrMA)] with a one‐handed helical conformation is obtained. The helical structure is maintained even at room temperature in solution. Analogous helical polymethacrylates that show various conformational changes have also been found. One‐handed helical PTrMA exhibits high chiral recognition to a variety of racemates as a chiral stationary phase (CSP) for high‐performance liquid chromatography. This finding has led to the development of very powerful CSPs based on polysaccharides, such as cellulose and amylose. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4480–4491, 2004
Enantiomer‐selective radical cyclopolymerization of rac‐2,4‐pentanediyl dimethacrylate using a ruthenium‐mediated chiral atom transfer radical polymerization initiating system
Authors: Tsuji Masashi , Aoki Towako , Sakai Ryosuke , Satoh Toshifumi , Kaga Harumi , Kakuchi Toyoji 
Published: August 2004

AbstractThe enantiomer‐selective radical polymerization of rac‐2,4‐pentanediyl dimethacrylate, an equimolar mixture of (2S,4S)‐2,4‐pentanediyl dimethacrylate (SS‐1) and (2R,4R)‐2,4‐pentanediyl dimethacrylate (RR‐1), was carried out with a chiral atom transfer radical polymerization initiating system consisting of methyl 2‐bromoisobutyrate (3), dichlorotris(triphenylphosphine)ruthenium [RuCl2(PPh3)3], and a chiral additive in anisole at 60 °C. When (S)‐1,1′‐bi‐2‐naphthol (a‐3) was used as the chiral additive, the recovered monomer was enriched in SS‐1, and the enantiomeric excess was 16.9% at a 22.6% monomer conversion. The specific rotation ([α]435, c 0.3, CHCl3) of the resulting polymer was +40.3° at a 22.6% monomer conversion. For the copolymerization of SS‐1 and RR‐1 with 3/RuCl2(PPh3)3/a‐3 in anisole at 60 °C, the monomer reactivity ratio for RR‐1 (rR) was determined to be 4.94, and that for SS‐1 (rS) was 0.27. For the homopolymerizations of SS‐1 and RR‐1 with 3/RuCl2(PPh3)3/a‐3 in anisole at 60 °C, the polymerization rate of RR‐1 was considerably faster than that of SS‐1, and the rate constants for the homopolymerizations were determined to be kSS = 2.0 × 10−3 h−1 and kRR = 8.2 × 10−3 h−1, respectively. With the values of kSS, kRR, rR, and rS, the relative ratio kSS/kRR/kSR/kRS was determined to be 1.2:4.9:4.5:1, which indicated that both the growing end of SS‐1 and that of RR‐1 preferentially reacted with RR‐1. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4563–4569, 2004
Helicity induction on a poly(phenylacetylene) bearing a phosphonate residue by chiral dendrons
Authors: Kamikawa Yuko , Kato Takashi , Onouchi Hisanari , Kashiwagi Daisuke , Maeda Katsuhiro , Yashima Eiji 
Published: August 2004

AbstractA series of optically active dendrons with a primary amino group at the terminal were prepared from L‐ or D‐glutamic acid, and their helicity induction abilities for a poly(phenylacetylene) bearing a phosphonate pendant were characterized with ultraviolet–visible and circular dichroism spectroscopy. The magnitude of the Cotton effects of the polymer induced by the dendrons significantly increased upon complexation with a higher generation dendron. The effect of the chirality of the glutamate residues (L and D) on the helicity induction was also studied. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4580–4586, 2004
X‐ray photoelectron spectroscopic study of surface modification of low‐k organic materials by plasma treatment
Authors: Uchida Y. , Fukuda T. , Yanazawa H. 
Published: August 2004

AbstractThe surface modification of SiLK™ resin (trademark of the Dow Chemical Company) by means of N2 or Ar plasma treatment was studied using XPS. This surface modification is supposed to improve the adhesion of tantalum. XPS spectra of the surface of plasma‐treated resin exhibited an oxygen peak, and also a nitrogen peak after N2 plasma treatment, in addition to a carbon peak. The plasma treatment was found to break some of the CC bonds and to cause the disappearance of components related to aromatic rings. In consequence, carbon components with low amounts of oxygen are produced which are probably from the atmosphere. In addition, the N2 plasma also nitrides the surface layer. The Ar plasma produces damage, such as unbonded carbon atoms, that can reach deeper into the resin films if the exposure time is long enough; while N2 plasma prevents the penetration of damage, probably because of the nitride layer on the surface. The plasma treatment produces phenomena like the restructuring of carbon bonds. Furthermore, the XPS analysis indicates that oxidation of the resin at the surface suppresses the reaction between the resin and Ta, resulting in a more metal‐like Ta layer. The reconstructed surface layer resulting from the bonding of unbonded carbon atoms with other atoms should provide better adhesion, thus allowing deposition of a Ta layer with a different chemical state. Copyright © 2004 John Wiley & Sons, Ltd.
EXELFS characterization of Mg vanadate
Authors: Márquez F. 
Published: August 2004

AbstractIn this paper we show the preliminary results obtained by EXELFS spectroscopy (in reflection mode) on polycrystalline magnesium orthovanadate. The oscillating features observed beyond the V L2, 3‐edge have been isolated and analysed following the EXAFS procedure. EXELFS revealed that by thermal treatment in air or vacuum, reversible structural variations occur around vanadium. Thus, by calcination in air at 573 K, vanadium appeared in the +5 state (orthovanadate) showing a VO distance of 0.183 nm. By thermal annealing at 823 K in vacuum, vanadium was partially reduced to V4+ and the VO distance decreased from 0.183 nm to 0.163 nm. Copyright © 2004 John Wiley & Sons, Ltd.
XPS investigations of Sn, SnPd and SnPd/Cu clusters produced by electroless deposition onto NiTi micronic particles formed by atomization
Authors: Silvain J. F. , Fouassier O. 
Published: August 2004

AbstractXPS analysis of electroless deposition of successive SnPd and Cu films on a NiTi surface has been performed in order to explain the nucleation and growth. Chemical interaction of Sn with the NiTi surface is shown to be associated with the growth of Sn oxide and hydroxide that can be formed after the reaction of Sn atoms with TiO2 oxide. 3D growth of pure metallic palladium occurs, leading to the formation of nanometric metallic Pd clusters. The interaction of copper atoms with the palladium surface leads to the formation of interfacial PdCu intermetallic and consequently to strong interfacial adhesion. Copyright © 2004 John Wiley & Sons, Ltd.
Surface roughness and island formation effects in ARXPS quantification
Authors: Martín‐Concepción A. I. , Yubero F. , Espinós J. P. , Tougaard S. 
Published: August 2004

AbstractQuantification of surface nano‐structures by angle‐resolved XPS (ARXPS) is straightforward and works quite reliably for perfectly flat surfaces of amorphous materials. For rough surfaces, the interpretation of ARXPS is, however, complicated because the angular variation of the XPS peak intensity depends on the surface roughness. Even for ideally flat substrates, ARXPS analysis of laterally inhomogeneous surface structures grown on the surface is quite complex. The reason is that neighboring nano‐clusters shadow the XPS peak intensity. The effect depends on cluster shape as well as the distribution of clusters on the surface. In addition the effects depend on the flatness of the underlying substrate. The interpretation of ARXPS then becomes quite complex. In the present paper, we have studied this problem by analyzing ZnO nano‐clusters grown on substrates of SiO2 and Al2O3. Thus we compared the results of quantification by the four techniques: ARXPS, XPS‐peak shape analysis, Rutherford backscattering spectroscopy and x‐ray fluorescence spectrometry. While the latter three techniques gave consistent results, the results of the ARXPS analysis were way off. This deviation is discussed in terms of the above‐mentioned shadowing effect of neighboring clusters as well as roughness of the underlying substrates. Different normalization methods in the ARXPS analysis procedure are compared and it is found that some of the observed problems for the substrate peaks (but not for the peaks from the overlayer film) can be reduced by applying reference samples with similar roughness for normalization of the data. In conclusion, the ARXPS technique is very much dependent on surface roughness as well as on the morphology of the thin films. Thus for reliable quantification with ARXPS it is necessary to have independent knowledge on surface roughness as well as the distribution of islands of the thin films. Copyright © 2004 John Wiley & Sons, Ltd.
Elastic electron backscattering from silicon surfaces: effect of charge‐carrier concentration
Authors: Zemek J. , Jiricek P. , Lesiak B. , Jablonski A. 
Published: August 2004

AbstractSilicon wafers, p‐ and n‐doped with different free‐carrier charge concentrations, were selected as model materials to study a possible influence of charge‐carrier concentrations (or electrical conductivity) on measured elastic electron backscattering probabilities and electron inelastic mean free paths determined by elastic peak electron spectroscopy. This research is motivated by contrast changes frequently observed in scanning electron microscopy of semiconductor structures with different types of doping (p‐ and/or n‐) and/or different electrical conductivities. The results show that the measured elastic electron backscattering probabilities and the inelastic mean free paths differ only within experimental uncertainties. They are independent of the type (p‐ and/or n‐) of doping and the free‐carrier charge concentration. Copyright © 2004 John Wiley & Sons, Ltd.
Depth profiling of rolled aluminium alloys by means of GDOES
Authors: Kuypers S. , Buytaert G. , Terryn H. 
Published: August 2004

AbstractRolling of aluminium alloys is known to alter the surface properties. Radiofrequency glow discharge optical emission spectrometry (RF GDOES) was introduced to study the elemental composition of the surface and near‐surface regions of a commercial AA3005 hot‐rolled aluminium alloy, before and after annealing treatments for full (bulk) recrystallization. Qualitative GDOES depth profiles (signal intensity as a function of sputtering time) suggest enrichment of some and depletion of other alloying elements as well as the introduction of impurity elements within the disturbed surface layer of the alloy. The depth profiles are correlated with SEM/EDXA observations in the GDOES craters. Copyright © 2004 John Wiley & Sons, Ltd.
Quantitative evaluation of contributions to interface broadening in metal/silicon multilayers
Authors: Kovač Janez , Zalar Anton 
Published: August 2004

AbstractAuger electron spectroscopy (AES) depth profiling is a widely used technique to study buried interfaces in thin‐film structures. It involves a sputtering process that may cause topographical and compositional changes in the surface region of the ion‐bombarded sample. In order to reveal the original in‐depth elemental distribution, it is important to know the influence of the sputtering process.AES depth profiling of Si/Ti, Si/Ni, Si/Nb and Si/W layered structures was performed with 1 and 3 keV Ar+ ions at an incidence angle of 47°. The mixing–roughness–information depth (MRI) model was used to estimate different contributions to the interface broadening. A stronger broadening of the metal/Si interfaces than that of the Si/metal interfaces can be explained by ion bombardment induced roughening and mixing of metallic atoms with the silicon ones. Copyright © 2004 John Wiley & Sons, Ltd.