bluuebunny/crossref_metadata_2025_split huggingface dataset:
Annealing simulations to determine the matrix interface structure of SiC quantum dots embedded in SiO2
Authors: Knaup Jan M. , Vörös Márton , Déak Peter , Gali Adam , Frauenheim Thomas , Kaxiras Efthimios 
Published: November 2009

AbstractWe use the Density Functional based Tight‐Binding (SCC‐DFTB) method in a Quantum Mechanics/Molecular Mechanics embedding scheme to simulate single SiC quantum dots of different shapes and with diameters of up to 1 nm, embedded in a block of α ‐Quartz with cell vectors of a = 15 nm and c = 13 nm.First results show that during the annealing process three recurring motives appear at the SiC/SiO2 interface of the embedded nanocrystals: Si‐Si bonds often in Si interstitial‐like configurations, C‐C bonds involving all possible combinations of sp3 and sp2 hybridized carbon and threefold coordinated oxygen atoms. All of these defects, alone or in complexes, may play a crucial role in quenching the luminescence of these embedded nanocrystals. Detailed studies of the spectroscopic properties if the point defects identified in this work is indicated (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interface with organic molecules: Cysteine on Au(110)
Authors: Höffling Benjamin , Ortmann Frank , Hannewald Karsten , Bechstedt Friedhelm 
Published: November 2009

AbstractWe study the adsorption of the amino acid cysteine on the Au(110) surface by means of density functional theory. Different adsorbate‐substrate geometries are investigated regarding geometry, adsorption energy, and changes in the density of states.In particular we compare flat versus upright adsorption configurations in which the molecule registers to the surface via a deprotonized thiolate head group and eventually the amino side group. Sulfur‐gold and amino‐gold bonding geometries are discussed with their implications for electronic properties (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dielectric functions of Si nanoparticles within a silicon nitride matrix
Authors: Keita A.‐S. , Naciri A. En , Delachat F. , Carrada M. , Ferblantier G. , Slaoui A. 
Published: November 2009

AbstractWe report on the study of the influence of ammonia flow on physical properties of Plasma Enhanced Chemical Vapor Deposition (PECV)‐grown silicon nanoparticles (np‐Si) within a silicon nitride matrix. To achieve this goal, we have used spectroscopic ellipsometry (SE) to determine the np‐Si dielectric functions (DFs). On the one hand, the DF have been modeled using single parametric oscillators given by Tauc‐Lorentz and Forouhi‐Bloomer dispersion models. On the other hand, wavelength‐by‐wavelength numerical inversion, carried out without considering any fitting parameter, have represented another way to derive the DFs of the np‐Si. Besides a comparison has been done between results given by Bruggeman Effective Medium Approximation (BEMA) and Maxwell‐Garnett law. The results have shown that SE can be used to find out the band gap and mean size of np‐Si according to quantum confinement theory. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure and effective masses in strained silicon
Authors: Bouhassoune Mohammed , Schindlmayr Arno 
Published: November 2009

AbstractThe structural and electronic properties of strained silicon are investigated quantitatively with ab initio computational methods. For this purpose we combine densityfunctional theory within the local‐density approximation and the GW approximation for the electronic self‐energy. From the variation of the total energy as a function of applied strain we obtain the elastic constants, Poisson ratios and related structural parameters, taking a possible internal relaxation fully into account. For biaxial tensile strain in the (001) and (111) planes we then investigate the effects on the electronic band structure. These strain configurations occur in epitaxial silicon films grown on SiGe templates along different crystallographic directions.The tetragonal deformation resulting from (001) strain induces a valley splitting that removes the sixfold degeneracy of the conduction‐band minimum. Furthermore, strain in any direction causes the band structure to warp. We present quantitative results for the electron effective mass, derived from the curvature of the conduction band, as a function of strain and discuss the implications for the mobility of the charge carriers. The inclusion of proper self‐energy corrections within the GW approximation in our work not only yields band gaps in much better agreement with experimental measurements than the localdensity approximation, but also predicts slightly larger electron effective masses (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interface bands in carbon nanotube superlattices
Authors: Jaskólski W. , Pelc M. , Santos H. , Chico L. , Ayuela A. 
Published: November 2009

AbstractWe study the electronic band structure of several carbon nanotube superlattices built of two kinds of intermolecular junctions: (12, 0)/(6, 6) and (8, 0)/(14, 0). In particular, we focus on the energy bands originating from interface states. We find that in case of the metallic (12, 0)/(6, 6) superlattices, the interface bands change periodically their character from bonding‐ to antibonding‐like vs. increasing length of the (6, 6) tube.We show that these changes are related to the decay of the charge density Friedel oscillations in the metallic (6, 6) tube. However, when we explore other chiralities without rotational symmetry, no changes in bondingantibonding character are observed for semiconductor superlattices, as exemplified in the case of (8, 0)/(14, 0) superlattices. Our results indicate that unless metallic tubes are employed in the junctions, the bondingantibonding crossings are not present (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of [U‐13C6]glucose in human plasma using liquid chromatography/isotope ratio mass spectrometry compared with two other mass spectrometry techniques
Authors: Schierbeek Henk , Moerdijk‐Poortvliet Tanja C. W. , van den Akker Chris H. P. , te Braake Frans W. J. , Boschker Henricus T. S. , van Goudoever Johannes B. 
Published: November 2009

AbstractThe use of stable isotope labelled glucose provides insight into glucose metabolism. The 13C‐isotopic enrichment of glucose is usually measured by gas chromatography/mass spectrometry (GC/MS) or gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). However, in both techniques the samples must be derivatized prior to analysis, which makes sample preparation more labour‐intensive and increases the uncertainty of the measured isotopic composition. A novel method for the determination of isotopic enrichment of glucose in human plasma using liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) has been developed. Using this technique, for which hardly any sample preparation is needed, we showed that both the enrichment and the concentration could be measured with very high precision using only 20 µL of plasma. In addition, a comparison with GC/MS and GC/IRMS showed that the best performance was achieved with the LC/IRMS method making it the method of choice for the measurement of 13C‐isotopic enrichment in plasma samples. Copyright © 2009 John Wiley & Sons, Ltd.
Detection of pathogenic Verticillium spp. using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Tao Jie , Zhang Guiming , Jiang Zide , Cheng Yinghui , Feng Jianjun , Chen Zhinan 
Published: November 2009

AbstractVerticillium spp. have been listed by the European and Mediterranean Plant Protection Organization (EPPO) and China as plant quarantine pests. Although attempts have been made to develop a simple routine laboratory assay to detect these organisms, none are routinely used. We describe for the first time a robust assay for reliable identification of Verticillium spp. using protein fingerprinting data obtained by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry(MALDI‐TOF‐MS). Several sample preparation methods and matrices were investigated to improve mass spectra for the routine identification of six species of Verticillium spp.(Verticillium dahiliae, V. alboatrum, V. fungicola, V. nigrescens, and V. lecanii) by MALDI‐TOF‐MS. Using the optimized experimental method, we constructed a protein fingerprint database for six species of Verticillium and established a analysis criteria of log(Score). This MALDI‐TOF‐MS protocol should prove useful as a rapid and reliable assay for distinguishing different Verticillium spp. Copyright © 2009 John Wiley & Sons, Ltd.
Investigation of the photochemical behaviour of pyrethroids lacking the cyclopropane ring by photo‐solid‐phase microextraction and gas chromatography/mass spectrometry
Authors: Fernandez‐Alvarez Maria , Llompart Maria , Garcia‐Jares Carmen , Dagnac Thierry , Lores Marta 
Published: November 2009

AbstractThe characterization of by‐products arising from the UV photodegradation of two insecticide pyrethroids lacking the cyclopropane ring (flucythrinate and fenvalerate) has been investigated by gas chromatography coupled with mass spectrometry (GC/MS). Twenty photoproducts were tentatively identified mainly based on the interpretation of the experimental mass spectra or by using reference mass spectra. Some of these compounds had not previously been detected. Furthermore, the generation of some of the photoproducts might be a matter for concern due to their potential toxicity. The corresponding photodegradation routes, including postulation of the intermediate radicals, have also been proposed. These photodegradation studies were performed by photo‐solid‐phase microextraction (photo‐SPME) in which the SPME fibre was exposed to light after extraction of the target analytes from aqueous solutions. The degradation kinetics of the investigated pyrethroids and the photoformation‐photodegradation curves of the photoproducts generated in situ were also monitored through the ion chromatograms obtained for different irradiation times and the corresponding mass spectra. Copyright © 2009 John Wiley & Sons, Ltd.
Isotope abundance analysis for improved sample identification with tandem mass spectrometry
Authors: Alon Tal , Amirav Aviv 
Published: November 2009

AbstractTandem mass spectrometry (MS/MS) is widely used for trace level sample analysis in complex mixtures. However, sample identification in MS/MS is challenging and not as trustworthy as with electron ionization (EI) mass spectral libraries. This paper presents a novel method for the combination of isotope abundance analysis (IAA) and EI‐MS/MS for improved sample identification even at trace level in complex matrices. Accordingly, the first quadrupole is scanned in a narrow range around the molecular ion group of isotopomers such as M+, [M+1]+ and [M+2]+, Q2 serves for collision‐induced dissociation to produce product ions while Q3 transfers the major sample product ions with low resolution, thus encompassing and uniformly transmitting all the product ion isotopomers. IAA can then be used to derive elemental formula information from the cleansed experimental data. IAA‐MS/MS was experimentally tested with perfluorotributylamine and a very good matching factor of 995 (out of 1000) was obtained for IAA on m/z 502, 503 and 504 (fragment ion isotopomers) while Q3 transmitted the m/z 264 product ion with a mass window of 6 m/z units. The IAA‐MS/MS method was further tested with the pesticide diazinon on its molecular ions m/z 304, 305 and 306 while Q3 was locked on its m/z 179 product ion with a mass window of 6 m/z units. Again, very good matching factors were obtained, even for 40 pg diazinon on‐column during its GC/MS analysis (match = 981). IAA‐MS/MS combines the traditional benefits of MS/MS in the removal of matrix interferences with the IAA power of elemental analysis. Copyright © 2009 John Wiley & Sons, Ltd.
Investigation of the identification point system adaptation in cocaine, benzoylecgonine and ecgonine methyl ester using a single quadrupole mass spectrometer
Authors: Pistos C. , Karampela S. , Papoutsis I. , Athanaselis S. , Spiliopoulou Ch. , Maravelias C. 
Published: November 2009

AbstractAt present, no official criteria exist for drug identification using single quadrupole mass spectrometers although the European Union (EU) criteria for compound identification have been adopted. These criteria are evaluated with respect to the confirmation of cocaine and its metabolites by single quadrupole liquid chromatography/mass spectrometry (LC/MS) and problems are highlighted. Spiked samples, proficiency testing samples, certified reference materials and samples from real cases that had screened positive for cocaine derivatives by immunoassay were subjected to confirmation by LC/MS using single ion monitoring with in‐source fragmentation. The EU criteria for compound identification were applied for the confirmation of cocaine, benzoylecgonine and ecgonine methyl ester. The use of the identification point (IP) system in spiked, proficiency testing samples and certified reference materials provided acceptable results in all cases while in some cases real positive samples did not provide acceptable results. Failure to meet the EU criteria was attributed to low fragmentation at the lower concentrations and the ion suppression effect while both factors affected compliance with the IP system. The identification of cocaine and its metabolites was considerably improved by using a combination of ammonium formate and formic acid as the LC mobile phase. It appears that poor in‐source fragmentation in single quadrupole LC/MS and ion suppression may constitute a problem with drug identification when implementing the IP system in real samples, resulting in false negative results. Further investigation is needed for the use of such IP systems to be suitable for use in LC/MS methods. Copyright © 2009 John Wiley & Sons, Ltd.
Comprehensive analysis of short peptides in sera from patients with IgA nephropathy
Authors: Kaneshiro Nagayuki , Xiang Yang , Nagai Kouhei , Kurokawa Manae S , Okamoto Kazuki , Arito Mitsumi , Masuko Kayo , Yudoh Kazuo , Yasuda Takashi , Suematsu Naoya , Kimura Kenjiro , Kato Tomohiro 
Published: November 2009

AbstractWe analyzed serum short peptides comprehensively to know whether they were useful to characterize IgA nephropathy (IgAN). Serum samples from 26 patients with untreated IgAN and 25 healthy donors were tested. Short peptides with molecular weights of ∼7 kDa, purified from the serum samples by magnetic‐beads‐based weak cation exchange, were detected by mass spectrometry. Then the peptide peaks detected were subjected to the multivariate data analysis by SIMCA‐P+® containing principal component analysis (PCA) and orthogonal partial‐least‐squares‐discriminate analysis (OPLS‐DA). A total of 92 peptide peaks were detected in the tested serum samples. The OPLS‐DA analysis revealed that the profile of all the peptide peak intensities discriminated the IgAN group and the healthy group completely with a high R2 value (0.919) and a high Q2 value (0.861). Further, the profile of only five peptide peaks was found to discriminate the two groups. By tandem mass spectrometry and database searching, three of the five peptides which increased in the IgAN group were identified as fragments of fibrinogen alpha chain, and the two peptides which increased in the healthy group were identified as fragments of complement C3f and kininogen‐1 light chain. Taken together, the profile of the serum short peptides would be useful to discriminate IgAN and healthy conditions. Further, the five peptides may be candidate serum markers for IgAN and may be related to pathogenesis of IgA. Copyright © 2009 John Wiley & Sons, Ltd.
Reverse thin layer method for enhanced ion yield of oligosaccharides in matrix‐assisted laser desorption/ionization
Authors: Nishikaze Takashi , Amano Junko 
Published: November 2009

AbstractA sample preparation method that is suitable for sensitive detection of underivatized oligosaccharides by matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) has been investigated. As compared with the conventional dried‐droplet or ethanol (EtOH) recrystallization method, superior mass spectra in terms of ion yield and signal‐to‐noise (s/n) ratio were obtained when methanol (MeOH) was used as a solvent for the mixture of matrix and oligosaccharides. Based on these results, a new sample preparation method, named the ‘reverse thin layer method’, was developed. This method comprises two steps: first, complete drying of the oligosaccharide solution on the MALDI target plate; and second, deposition of the matrix dissolved in a small amount of MeOH. Using this method, a relatively homogeneous matrix crystal was generated and higher yields of both positive and negative ions were obtained from oligosaccharides compared with conventional methods. Notably, the method can be applied to various matrices including both solid and liquid matrices. Copyright © 2009 John Wiley & Sons, Ltd.
Real‐time trace detection and identification of chemical warfare agent simulants using recent advances in proton transfer reaction time‐of‐flight mass spectrometry
Authors: Petersson Fredrik , Sulzer Philipp , Mayhew Chris A. , Watts Peter , Jordan Alfons , Märk Lukas , Märk Tilmann D. 
Published: November 2009

AbstractThis work demonstrates for the first time the potential of using recent developments in proton transfer reaction mass spectrometry for the rapid detection and identification of chemical warfare agents (CWAs) in real‐time. A high‐resolution (m/Δm up to 8000) and high‐sensitivity (∼50 cps/ppbv) proton transfer reaction time‐of‐flight mass spectrometer (PTR‐TOF 8000 from Ionicon Analytik GmBH) has been successfully used to detect a number of CWA simulants at room temperature; namely dimethyl methylphosphonate, diethyl methylphosphonate, diisopropyl methylphosphonate, dipropylene glycol monomethyl ether and 2‐chloroethyl ethyl sulfide. Importantly, we demonstrate in this paper the potential to identify CWAs with a high level of confidence in complex chemical environments, where multiple threat agents and interferents could also be present in trace amounts, thereby reducing the risk of false positives. Instantaneous detection and identification of trace quantities of chemical threats using proton transfer reaction mass spectrometry could form the basis for a timely warning system capability with greater precision and accuracy than is currently provided by existing analytical technologies. Copyright © 2009 John Wiley & Sons, Ltd.
Cooperative control of multiple surface vessels in the presence of ocean currents and parametric model uncertainty
Authors: Almeida J. , Silvestre C. , Pascoal A. 
Published: November 2009

AbstractThis paper addresses the problem of cooperative path‐following of multiple autonomous vehicles. Stated briefly, the problem consists of steering a group of vehicles along specified paths while keeping a desired spatial formation. For a given class of autonomous surface vessels, it is shown how Lyapunov‐based techniques and graph theory can be brought together to design a decentralized control structure, where the vehicle dynamics and the constraints imposed by the topology of the inter‐vehicle communication network are explicitly taken into account. To achieve path‐following for each vehicle, a nonlinear adaptive controller is designed that yields convergence of the trajectories of the closed‐loop system to the path in the presence of constant unknown ocean currents and parametric model uncertainty. The controller derived implicitly compensates for the effect of the ocean current without the need for direct measurements of its velocity. Vehicle cooperation is achieved by adjusting the speed of each vehicle along its path according to information exchanged on the positions of a subset of the other vehicles, as determined by the communication topology adopted. Global stability and convergence of the closed‐loop system are guaranteed. Illustrative examples are presented and discussed. Copyright © 2009 John Wiley & Sons, Ltd.
Interfacial reactions in an interpenetrating polymer network thin film on an aluminum substrate
Authors: Tang Dongyan , Guo Yudi , Zhang Xiaohong , Liu Jie 
Published: November 2009

AbstractWe have adopted the dip‐pulling method and a thinning technique to obtain interpenetrating polymer network (IPN) thin films with suitable thickness and adhesive strength on Al substrates. X‐ray photoelectron spectroscopy (XPS) and attenuated total reflection infrared spectroscopy (ATR‐FTIR) were used to study the interfacial reactions, metal transformations, and nonmetal bond types between IPN and Al. By probing the binding energy shifts of nitrogen, aluminum, and oxygen atom species at different IPN/Al interfacial layers, the reactions between the polyurethane in IPN and the OH group in aluminum substrate could be determined. Moreover, the additional structures formed by the double bond between the nitrogen and nitrogen in the NCO group in IPN suggested the existence of covalent bonding in the adhesion areas. Sufficient interfacial reactions occurring between IPN and Al effectively restricted the IPN peel off from Al substrate. Copyright © 2009 John Wiley & Sons, Ltd.
Bayesian spatial modeling of disease risk in relation to multivariate environmental risk fields
Authors: Kim Ji‐in , Lawson Andrew B. , McDermott Suzanne , Aelion C. Marjorie 
Published: November 2009

AbstractThe relationship between exposure to environmental chemicals during pregnancy and early childhood development is an important issue that has a spatial risk component. In this context, we have examined mental retardation and developmental delay (MRDD) outcome measures for children in a Medicaid population in South Carolina and sampled measures of soil chemistry (e.g. As, Hg, etc.) on a network of sites that are misaligned to the outcome residential addresses during pregnancy. The true chemical concentration at the residential addresses is not observed directly and must be interpolated from soil samples. In this study, we have developed a Bayesian joint model that interpolates soil chemical fields and estimates the associated MRDD risk simultaneously. Having multiple spatial fields to interpolate, we have considered a low‐rank Kriging method for the interpolation that requires less computation than the Bayesian Kriging. We performed a sensitivity analysis for a bivariate smoothing, changing the number of knots and the smoothing parameter. These analyses show that a low‐rank Kriging method can be used as an alternative to a full‐rank Kriging, reducing the computational burden. However, the number of knots for the low‐rank Kriging model needs to be selected with caution as a bivariate surface estimation can be sensitive to the choice of the number of knots. Copyright © 2009 John Wiley & Sons, Ltd.