bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production and fragmentation of multiply charged ions in ‘electron‐free’ matrix‐assisted laser desorption/ionization
Authors: Frankevich Vladimir , Zhang Juan , Dashtiev Maxim , Zenobi Renato 
Published: October 2003

AbstractAn unusually large fraction of multiply charged ions is observed in ‘electron‐free’ matrix‐assisted laser desorption/ionization (MALDI). Here we investigate how the yield of multiply charged ions depends on experimental parameters in MALDI. It is found to increase if measures are taken to limit the number of electrons in the plume, for example, by using non‐metallic MALDI targets or low laser pulse energies. The ionization energy of the matrix is another important parameter that affects the yield of multiply charged ions: matrices with high ionization energies lead to greater intensities of multiply charged ions. It is furthermore proposed that some of the fragment ions observed in MALDI are due to reactions of analyte with electrons in the plume. The possibility of electron capture dissociation of multiply charged ions produced by MALDI is shown. Copyright © 2003 John Wiley & Sons, Ltd.
Automated multiple‐layer spotting for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of synthetic polymers utilizing ink‐jet printing technology
Authors: Meier Michael A. R. , de Gans Berend‐Jan , van den Berg Antje M. J. , Schubert Ulrich S. 
Published: October 2003

AbstractRecently, a new multiple‐layer matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) sample spotting technique for poly(ethylene glycol), offering improved analysis possibilities, was described. In this contribution the application of ink‐jet printing to automated, multiple‐layer MALDI‐TOFMS sample preparation of synthetic polymers is presented, allowing accurate deposition of matrix, additive and analyte solutions. The new sample preparation technique was evaluated for poly(ethylene glycol) as well as poly(methyl methacrylate) standards, and optimized settings for both synthetic polymers have been obtained. Copyright © 2003 John Wiley & Sons, Ltd.
PEAKS: powerful software for peptide de novo sequencing by tandem mass spectrometry
Authors: Ma Bin , Zhang Kaizhong , Hendrie Christopher , Liang Chengzhi , Li Ming , Doherty‐Kirby Amanda , Lajoie Gilles 
Published: October 2003

AbstractA number of different approaches have been described to identify proteins from tandem mass spectrometry (MS/MS) data. The most common approaches rely on the available databases to match experimental MS/MS data. These methods suffer from several drawbacks and cannot be used for the identification of proteins from unknown genomes. In this communication, we describe a new de novo sequencing software package, PEAKS, to extract amino acid sequence information without the use of databases. PEAKS uses a new model and a new algorithm to efficiently compute the best peptide sequences whose fragment ions can best interpret the peaks in the MS/MS spectrum. The output of the software gives amino acid sequences with confidence scores for the entire sequences, as well as an additional novel positional scoring scheme for portions of the sequences. The performance of PEAKS is compared with Lutefisk, a well‐known de novo sequencing software, using quadrupole‐time‐of‐flight (Q‐TOF) data obtained for several tryptic peptides from standard proteins. Copyright © 2003 John Wiley & Sons, Ltd.
Phenol, chlorobenzene and chlorophenol isomers: resonant states and dissociative electron attachment
Authors: Khatymov Roustem V. , Muftakhov Mars V. , Mazunov Victor A. 
Published: October 2003

AbstractThis paper reports a study of resonant dissociative electron attachment (DEA) to the phenol, chlorobenzene, p‐, m‐, and o‐chlorophenol molecules. On the basis of spectroscopic and thermochemical approaches the resonant states of the molecular negative ions (NIs) and the structures of some dissociative decay products are assigned. In the electron energy range up to 3 eV, DEA processes are determined by the two 2[π*]‐shape resonances resulting mainly in formation of [MH]− and/or Cl− ions. At higher electron energies the energy correlation between peaks in the negative ion effective yield curves and bands of UV spectra allowed identification of the core‐excited resonances. The peculiarities of Cl− ion formation and the vibrational fine structure on the effective yield curves of the [MH]− ions are discussed. The mass spectrometric procedures for measurement of relative cross sections for NI formation are described. Copyright © 2003 John Wiley & Sons, Ltd.
A method for reducing the time required to match protein sequences with tandem mass spectra
Authors: Craig Robertson , Beavis Ronald C. 
Published: October 2003

AbstractAn algorithm for reducing the time necessary to match a large set of peptide tandem mass spectra with a list of protein sequences is described. This algorithm breaks the process into multiple steps. A rapid survey step identifies all protein sequences that are reasonable candidates for a match with a set of tandem mass spectra. These candidates are then used as models, which are refined by detailed analysis of the set of tandem mass spectra for evidence of incomplete enzymatic hydrolysis, non‐specific hydrolysis and chemical modifications of amino acid residues resulting from either post‐translational modifications or sample handling. Compared with current one‐step methods for matching proteins to mass spectra, this multiple‐step method can decrease the time required for the calculation by several orders of magnitude. Copyright © 2003 John Wiley & Sons, Ltd.
Trypsin digestion of proteins on intact immobilized pH gradient strips for surface matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric analysis
Authors: Iyer Srinivas , Olivares José 
Published: October 2003

AbstractIsolelectric focusing (IEF) of proteins on immobilized pH gradient (IPG) strips is an integral part of two‐dimensional (2D) electrophoresis‐based proteomics. Proteins can be effectively analyzed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) on the intact strip itself, leading to the creation of a virtual 2D map giving pI and MW information, bypassing the second dimension SDS‐PAGE. Further, trypsin digestion of proteins on the strip can significantly aid the identification of IPG‐separated proteins. However, the small size of the peptides leads to diffusion along and outside the gel matrix. In this study, we describe a simple spray‐based procedure to perform ‘on‐strip’ trypsin digestion of proteins embedded in IPG strips. Examination of intact myoglobin and its tryptic peptides shows that post‐digestion diffusion of tryptic peptides is significantly minimized using this approach. Copyright © 2003 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization time‐of‐flight analysis of low‐concentration oligonucleotides and mini‐sequencing products
Authors: Liu Yiding , Sun Xiyuan , Guo Baochuan 
Published: October 2003

AbstractA new sample preparation procedure has been developed to improve the matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) analysis of low‐concentration oligonucleotides. In this method, a few μL of the oligonucleotide solutions are first dispensed and allow drying and shrinking to a small spot on an anchoring target. Thereafter, a small volume (0.1 μL) of the saturated 3‐hydroxypicolinic acid (3‐HPA) solution is added to the top of the shrunk oligonucleotide spot. It is found that the sample prepared by this procedure is more homogenous and substantially reduces the need to search for ‘sweet’ spots. Importantly, the increased shot‐to‐shot and sample‐to‐sample reproducibility makes it possible to perform high‐throughput and quantitative analysis. We demonstrated that this procedure allowed the robust detection of oligonucleotides at a level of 0.01 μM and mini‐sequencing products produced using only 50 fmol of the extension primer. Copyright © 2003 John Wiley & Sons, Ltd.
Gas‐phase ligation of Cr+ and Fe+ with 4,9‐diazapyrene
Authors: Kazazić Saša , Klasinc Leo , Kovač Branka , Srzić Dunja 
Published: October 2003

AbstractThe ligation of Cr+ and Fe+ with 4,9‐diazapyrene (DAP) within a Fourier transform mass spectrometer was studied and compared with previous results for the ligands pyrene (Py) and 9‐azaphenanthrene (Ap). The results confirm that Fe+, which reacts more slowly but in the same way as Cr+ to bind two Py ligands, behaves quite differently with the nitrogen heterocycles DAP and Ap: it reacts rapidly and it binds three and four of them, respectively. Copyright © 2003 John Wiley & Sons, Ltd.
Surface oxidation kinetics of SiC powders in wet and dry air studied by x‐ray photoelectron spectroscopy and bremsstrahlung‐excited Auger electron spectroscopy
Authors: Wittberg Thomas N. , Wang Pu Sen , Hsu Stephen M. 
Published: October 2003

AbstractSilicon carbide powder samples were heated at temperatures between 600 °C and 850 °C in wet and dry air to investigate the effect of moisture on the oxidation kinetics. Equations were derived to calculate the surface oxide thickness from both the Si 2p XPS spectra and from the Si KLL bremsstrahlung‐excited Auger spectra. The oxide film growth rates are shown to be parabolic. The film thickness formed during oxidation in wet air was larger than that in dry air for the same temperature and heating time. The activation energy for wet oxidation was found to be significantly lower than that for dry oxidation within this temperature range. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of surface orientation on the segregation kinetics of Sb from a Cu single crystal
Authors: Terblans J. J. , van Wyk G. N. 
Published: October 2003

AbstractIn a previous theoretical study it has been suggested that the bulk vacancy formation energy near a surface depends on the orientation of the surface. It has been suggested also that this dependency of the vacancy formation energy would influence the bulk diffusion coefficient near the surface. The experimental results presented in this paper support this hypothesis. The experimental results were obtained by measuring the bulk‐to‐surface segregation of Sb for a Cu(111) single crystal with 0.088 at.% Sb and for a Cu(110) single crystal with 0.082 at.% Sb. The experimental results were fitted with the vacancy‐modified Darken model and it was clear that the bulk diffusion coefficient beneath the (110) surface is higher than the bulk diffusion coefficient beneath the (111) surface. Copyright © 2003 John Wiley & Sons, Ltd.
Crystallinity of adsorbed EVA nanofilms: relevance to confinement and interfacial interactions
Authors: Elzein Tamara , Brogly Maurice , Schultz Jacques 
Published: October 2003

AbstractWe used infrared spectroscopy to estimate the crystalline component concentration in thin films of ethylene‐co‐vinyl acetate (EVA) copolymers spin‐coated on gold and functionalized substrates. Bulk calibration methods are elaborated that allow the establishment of quantitative relationships between infrared response and the degree of crystallinity via simple equations. These equations are applied and transposed to the study of thin films in such a way as to avoid preferential orientation effects induced by adsorption. Therefore, for calibration we select groups that vibrate in the same direction and belong to the crystalline phase. Our results show a decrease of the crystalline amount in EVA9, 14, 24 and 28 thin films, as determined on the basis of infrared spectroscopy experiments. The low crystallinity degree calculated for EVA thin films is in good agreement with the reduced crystalline morphology observed by atomic force microscopy.Observed amorphization is considered to be induced by confinement (gold substrates) and interfacial interactions (functionalized substrates), which lead to a disordered chain conformation that makes crystallization less favourable. Copyright © 2003 John Wiley & Sons, Ltd.
Formation of a tetragonal Cu3Au alloy at gold/copper interfaces
Authors: Sarkar Subhendu , Datta Alokmay , Chakraborty Purushottam , Satpati Biswarup 
Published: October 2003

AbstractA gold–copper alloy with a nominal composition of Cu3Au but with a tetragonal (c = 4a) structure is observed to form at Au/Cu interfaces of gold/copper multilayers deposited on amorphous substrates by d.c. magnetron sputtering. The formation of this non‐equilibrium structure (tentatively D023) under‐ambient conditions is detected by secondary ion mass spectrometry, x‐ray diffraction and high‐resolution cross‐sectional transmission electron microscopy. Co‐sputtering of Au and Cu under similar conditions produces only conventional fcc Cu3Au alloy phases, suggesting that interfacial confinement plays a significant role in producing the novel Cu3Au alloy phase in gold/copper multilayers. Copyright © 2003 John Wiley & Sons, Ltd.
In situ infrared spectroscopic studies of ultrathin inorganic film growth on zinc in non‐polymerizing cold plasmas
Authors: Shirtcliffe Neil James , Stratmann Martin , Grundmeier Guido 
Published: October 2003

AbstractThe effect of cold plasmas of oxygen, hydrogen, water and carbon dioxide on zinc samples was investigated. Oxygen plasma is known for its cleaning effect, hydrocarbons and water are removed from metal surfaces and the oxide layer is thickened. It was found that other oxygen‐containing gases had a similar effect. In addition, surface layers of other compounds were produced. The samples were investigated using XPS, Kelvin probe measurements and in situ infrared reflection absorption spectroscopy. Copyright © 2003 John Wiley & Sons, Ltd.
Anisotropy analysis of the surface energy of diamond cubic crystals
Authors: Zhang Jian‐Min , Ma Fei , Xu Ke‐Wei , Xin Xiao‐Tian 
Published: October 2003

AbstractThe surface energies for 24 surfaces of diamond structure cubic crystals of C, Si and Ge have been calculated using the modified embedded‐atom method. The results show that the three lowest surface energies correspond to the (111), (211) and (433) surfaces. Considering surface energy minimization solely, the (111), (211) and (433) textures should be favourable successively in diamond cubic films. The appearance of abnormal grains or textures with (111) and (211) orientations in Si, Ge and C films results from surface energy minimization. Copyright © 2003 John Wiley & Sons, Ltd.
Studies about the dispersion process and structure of impregnated CuO/ZrO2 systems
Authors: Yang Peng‐Cheng , Cai Xiao‐Hai , Zhao Li‐Yan , Xie You‐Chang , Xie Yaning , Hu Tiandou , Zhang Jing 
Published: October 2003

AbstractThe dispersion process and structure of impregnated CuO/ZrO2 systems were studied by x‐ray diffraction (XRD) and extended x‐ray absorption fine structure (EXAFS). The results showed that, after being calcined at 773 K, monolayer dispersed cupric nitrate decomposed into monolayer dispersed cupric oxide on zirconia's surface. The dispersion threshold of CuO was related to its precursor, cupric nitrate. The surface‐dispersed Cu nearest coordination structure changed into about five equally long Cu–O bonds. Copyright © 2003 John Wiley & Sons, Ltd.
Study of interface diffusion and reaction between Zr3N4 and stainless steel
Authors: Wang Li , Yin Musheng , Zhu Yongfa 
Published: October 2003

AbstractThe effect of annealing treatment on the interface diffusion and reaction between Zr3N4/stainless steel was studied by AES depth profiling along with line shape analysis. The Zr3N4 film was deposited on stainless‐steel substrates by reactive magnetron sputtering. Scanning electron microscopy, electron diffraction, AES and UV–VIS reflection were performed to characterize the deposited film. The results indicated that the interface diffusion between Zr3N4 and stainless steel took place during deposition and can be promoted by annealing treatment, but no interface reaction took place before or after annealing treatment. High‐temperature and long‐time annealing treatment resulted in obvious oxidation of the Zr3N4 layer. The UV–VIS reflection results indicated that the absorption band of Zr3N4 film shifted to shorter wavelength after annealing treatment. Copyright © 2003 John Wiley & Sons, Ltd.
Monte‐Carlo simulation of x‐ray photoelectron emission from silver
Authors: Zhang Zengming , Koshikawa Takanori , Iyasu Takeshi , Shimizu Ryuichi , Goto Keisuke , Tanaka Akihiro 
Published: October 2003

AbstractSilver 3d x‐ray photoelectron spectroscopy (XPS) spectra were simulated with the Monte‐Carlo method using an effective energy‐loss function that was derived from a reflected electron energy‐loss spectroscopy (REELS) analysis based on an extended Landau approach. After confirming that Monte‐Carlo simulation based on the use of the effective energy‐loss function can successfully describe the experimental REELS spectrum and Ag 3d XPS spectrum, we applied Monte‐Carlo simulation to predict the angular distribution of Ag 3d x‐ray photoelectrons for different x‐ray incidence angles and different photoelectron take‐off angles. The experimental photoelectron emission microscope that we are constructing was confirmed as being close to the optimum configuration, in which the x‐ray incident angle as measured from the surface normal direction is 74° and the photoelectron take‐off angle is set normal to the surface. The depth distribution functions of the Ag 3d X‐ray photoelectrons for different energy windows suggest that the photoelectron emission microscope will exhibit greater surface sensitivity for narrower photoelectron energy windows. Copyright © 2003 John Wiley & Sons, Ltd.
AES and LEED study of well‐ordered oxide film grown on Cu–9at.%Al(111)
Authors: Yoshitake M. , Bera S. , Yamauchi Y. 
Published: October 2003

AbstractAn alloy of Cu–9at.%Al(111) has been oxidized in a low‐energy electron diffraction (LEED)/AES and a scanning AES instrument at elevated temperatures. Dosing with 1300 L of oxygen at 995 K gives rise to well‐ordered oxide layer formation on the Cu–9at.%Al alloy. The structure of the ordered oxide confirmed by LEED is ($7/\sqrt{3} \times 7/\sqrt{3}$) R30°. The chemical state of the oxide was Al2O3. The morphology of the surface observed with SEM in the scanning AES instrument revealed flat oxide growth with triangular defects of the same orientation. The possible epitaxy between the alloy substrate and alumina layer has been discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Density–depth profiles of an As‐implanted Si wafer studied by repeated planar sputter etching and total reflection x‐ray fluorescence analysis
Authors: Klockenkämper R. , Krzyżanowska H. , von Bohlen A. 
Published: October 2003

AbstractThe implantation of a high dose of high‐energy ions into an Si wafer causes amorphization of the original monocrystalline structure within a near‐surface layer. The in‐depth distribution of both Si atoms of the wafer and As ions implanted at a dose of 1 × 1017 ions cm−2 and an energy of 100 keV is studied. A novel method combining a repeated planar and broad sputter etching with differential weighing, surface analysis by total reflection x‐ray fluorescence and Tolansky interferometry is used for this investigation. Different depth profiles are recorded on the nanometre scale for the concentration defined as the mole ratio of As and Si, for the mass density of the implanted layer and for the number density of As and Si. The results generally correspond with measurements of Rutherford backscattering spectrometry and only deviate when the assumptions made for the mass density do not fit well. An appropriate approach to this quantity involves the number density of implanted ions but, furthermore, considers a variation of the number density of Si atoms during implantation, especially for a high dose and high‐energy implantation. The variation can be taken into account by a factor γ, where γ > 1 indicates compression and γ < 1 indicates extension of the original crystalline structure. For the above mentioned implantation, γ is measured separately for each sublayer to obtain accurate depth profiles. Copyright © 2003 John Wiley & Sons, Ltd.
First‐principles study of metal/nitride polar interfaces: Ti/TiN
Authors: Liu L. M. , Wang S. Q. , Ye H. Q. 
Published: October 2003

AbstractWe have examined the optimal interface structure, ideal work of adhesion and bonding character of polar Ti(110)/TiN(111) interfaces by first‐principles density‐functional plane‐wave pseudopotential calculations. Both Ti‐ and N‐terminated interfaces, including six different interface structures, were calculated. The interface structure for each termination, continuing the TiN crystal structure across the interface, has the largest work of adhesion. Although both terminations yield substantial adhesion energies in the range 3–7 J m−2, the N‐terminated interface is ∼4 J m−2 stronger than the Ti‐terminated interface. Analysis of the interfacial electronic structure shows that the Ti‐terminated interface is a mixed strong, metallic and weak covalent character, whereas the N‐terminated interface is a polar covalent bond similar to the Ti/TiC interface. Further study of the separation of the optimal interface shows that the cleavages will never fracture at the interface due to the strong bonding, which is consistent with the experimental results. Copyright © 2003 John Wiley & Sons, Ltd.
Lead underpotential deposition on Au(110)
Authors: Hale Penny , Thurgate Stephen , Wilkie Peter 
Published: October 2003

AbstractThe electrochemical underpotential deposition (UPD) of lead on Au(110) was investigated by XPS using a custom‐built ultrahigh vacuum apparatus containing a chamber for electrochemical studies. A two‐step deposition process for lead UPD was confirmed. A large increase in the surface concentration of oxygen was found in solutions containing lead. The presence of lead was detected on the gold surface at all potentials within the range investigated (−500 mV to 1500 mV vs. Ag/AgCl). Degradation of chlorine by x‐rays was observed. The change in surface components with potential was investigated and linked to models of UPD and oxidation. The initial random deposition of lead from solution led to surface disordering. Copyright © 2003 John Wiley & Sons, Ltd.
XPS C 1s binding energies for fluorocarbon–hydrocarbon microblock copolymers
Authors: Lei Yu‐Guo , Ng Kai‐Mo , Weng Lu‐Tao , Chan Chi‐Ming , Li Lin 
Published: October 2003

AbstractFluorocarbon–hydrocarbon microblock copolymers –(CF2)n–(CH2)m– (n = 4, 6, 8; m = 6, 8, 10) were synthesized. Binding energies of the C 1s and F 1s peaks of these copolymers were measured using x‐ray photoelectron spectroscopy. The binding energy of the C 1s peaks of the carbon atoms of the hydrocarbon segments was set at 285.0 eV as the binding energy reference. Unexpectedly, the binding energy of the C 1s peak corresponding to the CF2 group of the microblock copolymers was determined to be ∼291.4 eV, which is ∼0.8 eV lower than that of the CF2 group of tetrafluoroethylene. Copyright © 2003 John Wiley & Sons, Ltd.
Characterization of Pea Starches in the Presence of Alkali and Borax
Authors: Han Jee‐Yup , Tyler Robert T. 
Published: October 2003

AbstractRefined field pea (Pisum sativum L.) starches were prepared from air‐classified pea starch by washing or from whole pea by wet milling, and analyzed for their physicochemical and pasting characteristics in the presence of alkali and borax. Commercial corn and high amylose corn starches were included in the study for comparative purposes. The two pea starches exhibited similar physicochemical characteristics. Amylose content markedly influenced pasting and other characteristics of the corn starches. Pea starch and high amylose corn starch exhibited little viscosity development during pasting in deionized water. The presence of alkali or borax significantly altered the peak viscosities and cold paste stabilities of all four starches in a concentration dependent manner. Alkali and borax increased peak and cold paste viscosity and reduced syneresis in all cases.