bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal behavior and flame retardancy of flexible poly(vinyl chloride) treated with Al(OH)3 and ZnO
Authors: Qu Hongqiang , Wu Weihong , Jiao Yunhong , Xu Jianzhong
Published: July 2005

Al(OH)3 as flame retardant and smoke suppressant for flexible poly(vinyl chloride) was evaluated alone and with ZnO, using thermal analytical techniques, limiting oxygen index and smoke density rating tests. The thermal behavior and flammability of the samples treated with Al(OH)3 and ZnO were studied by differential thermal analysis and thermogravimetric analysis. The activation energy was calculated by using the Vyazovkin model‐free kinetic and Kissinger methods. The results showed that the flame‐retardant and smoke‐suppressant properties of the samples treated with Al(OH)3 and ZnO were related to the content of ZnO and the thermal effect during the process of thermal degradation of the samples. Copyright © 2005 Society of Chemical Industry
The N‐terminal fragment of gelsolin inhibits the interaction of DNase I with isolated actin, but not with the cofilin‐actin complex
Authors: Chhabra Deepak , Nosworthy Neil J. , dos Remedios Cristobal G.
Published: July 2005

Apoptosis is essential in embryonic development, clonal selection of cells of the immune system and in the prevention of cancer. Apoptotic cells display characteristic changes in morphology that precede the eventual fragmentation of nuclear DNA resulting in cell death. Current evidence implicates DNase I as responsible for hydrolysis of DNA during apoptosis. In vivo, it is likely that cytoplasmic actin binds and inhibits the enzymatic activity and nuclear translocation of DNase I and that disruption of the actin–DNase I complex results in activation of DNase I. In this report we demonstrate that the N‐terminal fragment of gelsolin (N‐gelsolin) disrupts the actin–DNase I interaction. This provides a molecular mechanism for the role of the N‐gelsolin in regulating DNase I activity. We also show that cofilin stabilises the actin–DNase I complex by forming a ternary complex that prevents N‐gelsolin from releasing DNase I from actin. We suggest that both cofilin and gelsolin are essential in modulating the release of DNase I from actin.
Truncated cystatin C in cerebrospiral fluid: Technical artefact or biological process?
Authors: Carrette Odile , Burkhard Pierre R. , Hughes Severine , Hochstrasser Denis F. , Sanchez Jean‐Charles
Published: July 2005

Cystatin C, a low molecular weight cysteine proteinase inhibitor present in human body fluids at physiological concentrations, is more expressed in cerebrospinal fluid (CSF) than in plasma. Mass spectrometric characterization showed that after 3 months of storage of human CSF at −;20°C, cystatin C was cleaved in the peptide bond between R8 and L9 and lost its eight N‐termini amino acids, whereas this cleavage did not occur when stored at −80°C. This truncation occurred in all CSF samples studied irrespective of the underlying neurological status, indicating a storage‐related artefact rather than a physiological or pathological processing of the protein. These results stress the importance of optimal preanalytical storage conditions of any sample prior to proteomics studies.
Cryodetector mass spectrometry profiling of plasma samples for HELLP diagnosis: An exploratory study
Authors: Koy Cornelia , Heitner Juliane C. , Woisch Ralf , Kreutzer Michael , Serrano‐Fernandez Pablo , Gohlke Rüdiger , Reimer Toralf , Glocker Michael O.
Published: July 2005

The cryodetector MS‐based screening method enables the rapid and reliable separation of hemolysis, elevated liver enzymes, and low platelets syndrome (HELLP) patients from healthy women. For developing the assay, plasma protein abundances from patients suffering from HELLP were profiled before and after delivery and compared to healthy pregnant and nonpregnant control individuals, using a TOF mass spectrometer equipped with a cryodetector system. The spectra were well reproducible when acquisition conditions were kept constant and the overall appearance of the profiles was well comparable. Peak areas of ten selected ion signals (9.5, 11.8, 14.0, 28.1, 43.4, 50.5, 60.1, 66.6, 74.5, and 79.8 kDa) from each spectrum were subjected to statistical analysis. Significant differences in ion intensities between the groups could be measured even without sample fractionation. The most striking difference between most of the spectra from HELLP patients and nonHELLP samples was the presence/absence of the 11.8 kDa ion signal (p‐value: 0.0000365), most likely belonging to serum amyloid A (SAA). Other significant differences in ion intensities between HELLP and control samples were observed in the peak areas of the 14.0, 28.1, 50.5, and 74.5 kDa ion signals. Using the cryodetector MS data for sorting plasma samples into either the HELLP group (n = 8) or the nonHELLP group (n = 22), a sensitivity of 87.5% and a specificity of 100% were achieved. The positive predictive value of our screening assay was 100% and a negative predictive value of 95.6% was obtained with the samples included in this study.
Polymeric and colloidal features of latex particles with surface amino groups obtained by semicontinuous seeded cationic emulsion polymerization*
Authors: Ramos Jose , Forcada Jacqueline
Published: July 2005

Monodisperse latex particles with different amounts of surface amino and amidine groups were synthesized by means of a semicontinuous seeded cationic emulsion polymerization of styrene and a cationic monomer. High partial overall conversions for styrene and limited ones for the cationic monomer were achieved. A reliable method for the quantification of surface amidine and amino groups was developed. It was found that the amount of surface amidine groups provided by the cationic initiator was higher when the amount of cationic monomer added increased. The value for the partition coefficient of the cationic monomer indicated that this polymerizes with the same probability in the water phase as in the particle. The colloidal stability, in terms of critical coagulation concentration, shows that the latexes would be useful as polymeric supports in immunoassays. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3878–3886, 2005
Synthesis of high molecular weight polystyrene and poly(methyl methacrylate) with low polydispersity by [Cp2ZrCl2] catalyzed aqueous polymerization
Authors: Patra Braja N. , Bhattacharjee Manish
Published: July 2005

An early transition metal metallocene compound, Cp2ZrCl2, with an anionic surfactant, sodium n‐dodecyl sulfate (SDS) as emulsifier has been found to be an effective catalyst for polymerization of monomers like styrene and methylmethacrylate in aqueous medium. The molecular weights of the polymers have been found to be very high with low molecular weight distribution. The added surfactant has been found to play the dual role of stabilizer of the cation as well as an emulsifying agent for the monomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3797–3803, 2005
Dendronized polymers with tailored surface groups
Authors: Nyström Andreas , Hult Anders
Published: July 2005

A series of polymers tethered with bis‐MPA dendrons was synthesized by a combination of divergent growth and atom transfer radical polymerization (ATRP). Macromonomers of first and second generation were synthesized utilizing the acetonide protected anhydride of bis‐MPA as the generic esterfication agent. The macromonomers were polymerized in a controlled fashion by ATRP utilizing Cu(I)/Cu(II) and N‐propyl‐2‐pyridylmethanamine as the halogen/ligand system. The end‐groups of these polymers were further tailored to achieve hydroxyl, acetate, and aliphatic hexadecyl functionality. With this approach all polymers will emanate from the same backbone, enabling for an evaluation of both the generation and end‐group dependent properties. Furthermore, a dendronized tri‐block copolymer was synthesized. All materials were analyzed by 1H and 13C NMR, as well as size‐exclusion chromatography (SEC). The SEC analysis revealed that the molecular weights of the divergently grown dendronized polymers increased with increasing generation while the polydispersity (PDI) was kept low. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3852–3867, 2005
Synthesis of carbohydrate‐segmented polydimethylsiloxanes by hydrosilylation
Authors: Henkensmeier Dirk , Abele Bors Cajus , Candussio Anton , Thiem Joachim
Published: July 2005

Carbohydrate‐modified polysiloxanes have been presented several times within the last decade. In this work, a new route to carbohydrate‐segmented polysiloxanes is presented. A series of allyl‐group‐containing bifunctional carbohydrate derivatives was synthesized and reacted with hydrodimethylsilyl‐terminated polysiloxane in hydrosilylation reactions with Speier's catalyst. The carbohydrate monomers and the resulting materials were fully characterized with 1H and 13C NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3814–3822, 2005
Unconstrained geometry complexes: Ethylene/α‐olefin copolymerizations with a tetramethyldisilyl‐bridged Cp‐amido titanium complex
Authors: Hung Joyce , Waymouth Robert M.
Published: July 2005

A new disilyl‐bridged complex, [(N‐tert‐butylamido)(3‐indenyl)tetramethyldisilyl]titanium dichloride (3), was synthesized and activated with methylaluminoxane (MAO) for propylene homopolymerization and ethylene/propylene and ethylene/1‐hexene copolymerizations. A polypropylene with a slight isotactic enrichment was obtained. The number of regioerrors present in the polypropylene was somewhat smaller than that found in most polypropylenes made from monosilyl‐bridged [(N‐tert‐butylamido)(3‐indenyl)dimethylsilyl]titanium dichloride. The regioerrors detected in the copolymers obtained from 3/MAO were on the order of the amounts observed in polymers made with the monosilyl‐bridged constrained geometry catalysts. Ethylene copolymers of propylene and 1‐hexene had random sequence distributions and showed significant comonomer incorporation. Because of the presence of regioerrors, a modified method for determining the monomer composition and sequence distribution was developed from the direct measurement of the monomer content from the number of methylene and methine carbons per polymer chain, regardless of propylene inversion. An estimate of the error in the copolymerization reactivity ratio determination for regioirregular ethylene/α‐olefin copolymers was obtained by the calculation of the reactivity ratios from monomer dyad sequences, with consideration given to the contribution of major regioirregular sequences. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3840–3851, 2005
Systematic parallel investigation of RAFT polymerizations for eight different (meth)acrylates: A basis for the designed synthesis of block and random copolymers
Authors: Fijten Martin W. M. , Paulus Renzo M. , Schubert Ulrich S.
Published: July 2005

Poly(acrylate)s as well as poly(methacrylate)s were successfully synthesized via reversible addition‐fragmentation chain‐transfer (RAFT) polymerizations using 2‐cyano‐2‐butyl dithiobenzoate (CBDB) as RAFT‐agent. Four different ratios of RAFT to initiator were screened for four acrylates and four methacrylates using automated parallel synthesizer robots. The reactions were monitored by gel permeation chromatography (GPC) and gas chromatography (GC). The knowledge obtained during this screening was used for the designed synthesis of block and random copolymers containing a water‐ and a non water‐soluble monomer. The results obtained from GPC analysis together with 1H NMR spectroscopy demonstrate the possibility to design and prepare well‐defined block and random copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3831–3839, 2005
Isothermal and nonisothermal crystallization kinetics of irradiated nylon 1212
Authors: Song Jianbin , Ren Minqiao , Chen Qingyong , Sun Xiaohong , Zhang Huiliang , Song Chunlei , Zhang Hongfang , Mo Zhishen
Published: July 2005

The crystallization behavior of nylon 1212, irradiated at 60Co γ‐rays (50 kGy), was studied by a rheometer, polarized optical microscopy (POM), and differential scanning calorimeter (DSC). The results showed that irradiated nylon 1212 samples exhibited abnormal crystallization behavior during the crystallization process: The Avrami exponent n was calculated and was found to be in the range from 2.06–2.41 for isothermal crystallization, and from 2.67–4.91 for nonisothermal crystallization; the spherulite morphology also changed largely by polarized optical microscopy (POM); the crystallization activation energy ΔE for isothermal and nonisothermal crystallization process of irradiated nylon 1212 are determined to be 57.4 kJ/mol and 78.65 kJ/mol, respectively, which are lower than that of nonirradiated nylon 1212. At the same time, a new method by a combination of the Avrami and Ozawa equations was successfully applied to analyze the noncrystallization process of irradiated nylon 1212. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2326–2333, 2005
Thermoplastic blend demixing by a high‐pressure, high‐temperature process
Authors: Barbosa Silvia , Diaz Mónica , Mabe Guillermo , Brignole Esteban A. , Capiati Numa
Published: July 2005

The analysis of a thermoplastic polymer blend requires a precise separation of the blend components, which is usually performed by selective solvent extraction. However, when the components are high‐molecular‐weight polymers, a complete separation is very difficult. The use of fluids in near critical and supercritical conditions becomes a promising alternative to reach a much more precise separation. In this work, a method to separate reactive and physical blends from high‐molecular‐weight commercial polymers is proposed. Polyethylene (PE)/polystyrene (PS) blends were separated into their components with n‐propane, n‐pentane, and n‐heptane at near critical and supercritical conditions. The selectivity of each solvent was experimentally studied over a wide range of temperatures for assessing the processing windows for the separation of pure components. The entire PE phase was solubilized by n‐pentane and n‐heptane at similar temperatures, whereas propane at supercritical conditions could not dissolve the fraction of high‐molecular‐weight PE. The influence of the blend morphology and composition on the efficiency of the polymer separation was studied. In reactive blends, the in situ copolymer formed was solubilized with the PE phase by chemical affinity. The method proposed for blend separation is easy, rapid, and selective and seems to be a promising tool for blend separation, particularly for reactive blends, for which the isolation of the copolymer is essential for characterization © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2361–2369, 2005
Modification of the structure and properties of poly(vinylidene fluoride–trifluoroethylene) 56/44 mol % copolymer by a proton‐irradiation treatment
Authors: Lam T. Y. , Lau S. T. , Chan H. L. W. , Choy C. L. , Cheung W. Y. , Wong S. P.
Published: July 2005

The effects of high‐energy proton irradiation on the structure and properties of 56/44 mol % poly(vinylidene fluoride–trifluoroethylene) copolymer were studied with differential scanning calorimetry (DSC), X‐ray diffraction (XRD), relative permittivity, and polarization hysteresis measurements. Copolymer films prepared by hot compression molding were irradiated with a broad range of proton dosages (10–107 Mrad) at room temperature. The DSC results showed that the ferroelectric transition was strongly affected by the proton dosages. The XRD data indicated the reduction of polar ordering in the copolymer by the proton‐irradiation treatment. From the relative permittivity and polarization behavior, the copolymer film was found to be converted from a normal ferroelectric material to a relaxor ferroelectric material as the proton dosage was increased to 50 Mrad. The electrostrictive coefficient of the 56/44 mol % copolymer was enhanced after irradiation, and the optimized proton dosage for attaining the highest electrostrictive strain response was determined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2334–2339, 2005
Intussusceptions arising from two different sites in a child with cystic fibrosis
Authors: Hafen Gaudenz M. , Taylor Andrew C. , Oliver Mark R. , Stokes Keith B. , Rao Padma , Robertson Colin F. , Ranganathan Sarath C.
Published: July 2005

Abdominal pain is common in individuals with cystic fibrosis (CF). We report on a 17‐year old boy with CF and two recognized intussusceptions: the first colonic intussusception was presumed due to distal intestinal obstruction syndrome, and the second enteric one due to polypoid lesions containing heterotopic gastric mucosa. The presentation, pathology, management, and a literature review of intussusception in CF are discussed. Pediatr Pulmonol. © 2005 Wiley‐Liss, Inc.
Prediction of the conformation and geometry of loops in globular proteins: Testing ArchDB, a structural classification of loops
Authors: Fernandez‐Fuentes Narcis , Querol Enrique , Aviles Francesc X. , Sternberg Michael J. E. , Oliva Baldomero
Published: July 2005

In protein structure prediction, a central problem is defining the structure of a loop connecting 2 secondary structures. This problem frequently occurs in homology modeling, fold recognition, and in several strategies in ab initio structure prediction. In our previous work, we developed a classification database of structural motifs, ArchDB. The database contains 12,665 clustered loops in 451 structural classes with information about ϕ–ψ angles in the loops and 1492 structural subclasses with the relative locations of the bracing secondary structures. Here we evaluate the extent to which sequence information in the loop database can be used to predict loop structure. Two sequence profiles were used, a HMM profile and a PSSM derived from PSI‐BLAST. A jack‐knife test was made removing homologous loops using SCOP superfamily definition and predicting afterwards against recalculated profiles that only take into account the sequence information. Two scenarios were considered: (1) prediction of structural class with application in comparative modeling and (2) prediction of structural subclass with application in fold recognition and ab initio. For the first scenario, structural class prediction was made directly over loops with X‐ray secondary structure assignment, and if we consider the top 20 classes out of 451 possible classes, the best accuracy of prediction is 78.5%. In the second scenario, structural subclass prediction was made over loops using PSI‐PRED (Jones, J Mol Biol 1999;292:195–202) secondary structure prediction to define loop boundaries, and if we take into account the top 20 subclasses out of 1492, the best accuracy is 46.7%. Accuracy of loop prediction was also evaluated by means of RMSD calculations. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Main‐chain conformational tendencies of amino acids
Authors: Anderson Robert J. , Weng Zhiping , Campbell Robert K. , Jiang Xuliang
Published: July 2005

A Ramachandran plot is a visual representation of the main‐chain conformational tendencies of an amino acid. Despite forty years of research, the shape of Ramachandran plots is still a matter of debate. The issue in making a Ramachandran plot based on experimental data is deciding whether sparse data represent genuine conformations. We present here a simple solution to settle the ambiguities of the sparse data, and explain how we verified the accuracies of our plots using an independent dataset. To obtain our results, we then measured the pair‐wise distances of main‐chain conformational tendencies among amino acids, and showed that the conformational relationships of amino acids are well preserved in a two‐dimensional map, leading to the conclusion that the conformational diversity space of amino acids is largely two dimensional. We further noticed that amino acids in early and late evolutionary stages are located in different zones in the two‐dimensional map. In addition to these conclusions, we here present an amino acid substitution table derived from experimental data. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Hybrid native partitioning of interactions among nonconserved residues in chimeric proteins
Authors: Hernández Griselda , LeMaster David M.
Published: July 2005

Given any operational criterion for pairwise interatomic interactions, for a pair of structurally homologous proteins there exists for both proteins a unique equivalent partitioning of the nonconserved residue positions into mutually non‐interacting clusters. In the formation of a chimeric protein derived from these two parental sequences, if nonnative‐like interactions are to be avoided in its tertiary structure, then all of the nonconserved residues of each cluster must necessarily be either maintained or interchanged simultaneously. This hybrid native partitioning criterion is applied to known gene shuffling results. When the degree of estimated disruption is modest, the HybNat algorithm provides an efficient predictor of structural integrity. This supports the expectation that a substantial fraction of sequences that conform to the hybrid native partitioning criterion will yield tertiary structures that largely preserve the native‐like interactions of the parental proteins. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Structural analysis of a set of proteins resulting from a bacterial genomics project
Authors: Badger J. , Sauder J.M. , Adams J.M. , Antonysamy S. , Bain K. , Bergseid M.G. , Buchanan S.G. , Buchanan M.D. , Batiyenko Y. , Christopher J.A. , Emtage S. , Eroshkina A. , Feil I. , Furlong E.B. , Gajiwala K.S. , Gao X. , He D. , Hendle J. , Huber A. , Hoda K. , Kearins P. , Kissinger C. , Laubert B. , Lewis H.A. , Lin J. , Loomis K. , Lorimer D. , Louie G. , Maletic M. , Marsh C.D. , Miller I. , Molinari J. , Muller‐Dieckmann H.J. , Newman J.M. , Noland B.W. , Pagarigan B. , Park F. , Peat T.S. , Post K.W. , Radojicic S. , Ramos A. , Romero R. , Rutter M.E. , Sanderson W.E. , Schwinn K.D. , Tresser J. , Winhoven J. , Wright T.A. , Wu L. , Xu J. , Harris T.J.R.
Published: July 2005

The targets of the Structural GenomiX (SGX) bacterial genomics project were proteins conserved in multiple prokaryotic organisms with no obvious sequence homolog in the Protein Data Bank of known structures. The outcome of this work was 80 structures, covering 60 unique sequences and 49 different genes. Experimental phase determination from proteins incorporating Se‐Met was carried out for 45 structures with most of the remainder solved by molecular replacement using members of the experimentally phased set as search models. An automated tool was developed to deposit these structures in the Protein Data Bank, along with the associated X‐ray diffraction data (including refined experimental phases) and experimentally confirmed sequences. BLAST comparisons of the SGX structures with structures that had appeared in the Protein Data Bank over the intervening 3.5 years since the SGX target list had been compiled identified homologs for 49 of the 60 unique sequences represented by the SGX structures. This result indicates that, for bacterial structures that are relatively easy to express, purify, and crystallize, the structural coverage of gene space is proceeding rapidly. More distant sequence‐structure relationships between the SGX and PDB structures were investigated using PDB‐BLAST and Combinatorial Extension (CE). Only one structure, SufD, has a truly unique topology compared to all folds in the PDB. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Co‐translational myristoylation alters the quaternary structure of HIV‐1 Nef in solution
Authors: Dennis Caitríona A. , Baron Andrew , Grossmann J. Günter , Mazaleyrat Sabine , Harris Mark , Jaeger Joachim
Published: July 2005

We have studied the solution properties of Nef, a 24‐kDa cotranslationally myristoylated protein produced by HIV‐1 and other primate lentiviruses. Nef is found in the cytosol and also in association with cytoplasmic membranes, the latter, mediated in part by the myristoyl group attached to the N‐terminal glycine. Recombinant Nef was coexpressed in Escherichia coli in tandem with N‐myristoyl‐transferase and is fully myristoylated. Analysis by circular dichroism showed the myristoylated form to contain a greater α‐helical content than the nonmyristoylated form. Analysis of modified and unmodified Nef in solution using small angle X‐ray scattering, dynamic laser light scattering and analytical ultracentrifugation consistently showed differences in the oligomeric states of the two forms of Nef. Myristoylated Nef is predominantly monomeric and small oligomers which are also present, can be converted to the monomeric form under reducing conditions. By contrast, the nonmyristoylated form exists as a stable hexadecamer in solution which disassociates into tetramers upon addition of reducing agents. Shape reconstructions from small angle scattering curves of nonmyristoylated Nef are compatible with a large disc‐like structure in the hexadecameric oligomer consisting of four Nef tetramers. From these findings, we hypothesize that Nef undergoes a substantial conformational change from an “open” into a “closed” form whereby the myristate group is sequestered in a hydrophobic pocket. The myristoylated protein can switch to the open conformation by association of the N‐terminal region of molecule with membranes. These changes would allow Nef to carry out various functions depending on the conformational and oligomeric states. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Statistical characterization of salt bridges in proteins
Authors: Sarakatsannis James N. , Duan Yong
Published: July 2005

The structure and folding mechanism of a given protein are determined by many factors, including the electrostatic interactions between charged residues of protein molecules known in general as salt bridges. In this study, analyses were conducted on 10,370 salt bridges in 2017 proteins and the results compared to previous statistical surveys of 36 protein structures. Although many of the general trends remained consistent with other studies, more detailed information was illuminated by the larger dataset. In particular, it was shown that there is a strong correlation between secondary structure and salt bridge formation, and that salt bridges display preferential formation in an environment of about 30% solvent accessible surface area. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Comparative analysis of amino acid distributions in integral membrane proteins from 107 genomes
Authors: Nilsson Johan , Persson Bengt , von Heijne Gunnar
Published: July 2005

We have performed a comparative analysis of amino acid distributions in predicted integral membrane proteins from a total of 107 genomes. A procedure for identification of membrane spanning helices was optimized on a homology‐reduced data set of 170 multi‐spanning membrane proteins with experimentally determined topologies. The optimized method was then used for extraction of highly reliable partial topologies from all predicted membrane proteins in each genome, and the average biases in amino acid distributions between loops on opposite sides of the membrane were calculated. The results strongly support the notion that a biased distribution of Lys and Arg residues between cytoplasmic and extra‐cytoplasmic segments (the positive‐inside rule) is present in most if not all organisms. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Effect of thickness and cold substrate on transport properties of thermally evaporated CdTe thin films
Authors: El‐Mongy A. Abd , Hashem H. M. , Ramadan A. A.
Published: July 2005

The correlation between the structural characteristics (stoichiometry and crystallite size) of CdTe films and their electronic transport properties were the aims of the present study to bring attention to the dual importance of grain size and conversion of the semiconductivity type with changing film thickness. Two main parameters were considered: the substrate temperature and film thickness. Transport properties were influenced by grain boundaries as well as by native doping. Optical measurements showed two main direct transitions at energies: E1 ≈ 1.55 eV (fundamental gap) and E2 ≈ 2.49 eV (due to valence band splitting). Both transitions were found to be thickness dependent with a marked change at a film thickness of about 300 nm. In the case of low substrate temperature, the scaling relation between resistivity and grain size showed a deviation from linear behavior at a size of 20 nm and the transmission coefficient is reduced. Also, the deposition on cold substrate enhanced both dark and photoconductivity for films of thickness ≥300 nm. It is also proved that the carrier transport was affected by the transmission coef‐ficient for carriers to pass a single grain boundary as well as the number of grain boundaries per mean free path. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hall effect of copper nitride thin films
Authors: Yue G. H. , Liu J. Z. , Li M. , Yuan X. M. , Yan P. X. , Liu J. L.
Published: July 2005

The Hall effect of copper nitride (Cu3N) thin films was investigated in our work. Cu3N films were deposited on glass substrates by radio‐frequency (RF) magnetron sputtering at different temperatures using pure copper as the sputtering target. The Hall coefficients of the films are demonstrated to be dependent on the deposition gas flow rate and the measuring temperature. Both the Hall coefficient and resistance of the Cu3N films increase with the nitrogen gas flow rate at room temperature, while the Hall mobility and the carrier density of the films decrease. As the temperature changed from 100 K to 300 K, the Hall coefficient and the resistivity of the films decreased, while the carrier density increased and Hall mobility shows no great change. The energy band gap of the Cu3N films deduced from the curve of the common logarithm of the Hall coefficient against 1/T is 1.17–1.31 eV. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
TEM observation on the microstructure of Co doped C films
Authors: Mi W. B. , Li Z. Q. , Wu P. , Jiang E. Y. , Bai H. L.
Published: July 2005

Co doped C films with different Co volume fraction xv were fabricated using facing‐target sputtering at room temperature. The as‐deposited films are composed of ∼2 nm amorphous Co granules dispersed in a‐C matrix, and their morphology is composition independent. The graphitized carbon nanostructure appears in the as‐deposited C films (xv = 43) after being irradiated by electron beam for several minutes. Annealing at 300–450 °C causes the crystallization of amorphous Co followed by an increase of grain size. The constrictions arising from the structural environment result in the coexistence of the hcp and fcc Co phases at temperatures higher than the phase transformation point of 425 °C. Annealed at 650 °C, crystalline Co particles transform into hcp structure with stacking faults and amorphous C graphitizes. The graphite (002) lattice in the annealed C films preferentially grows up on the surface of Co particles. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High purity alpha silicon nitride nanowires – synthesis and dielectric properties
Authors: Xie T. , Wu Y. C. , Cai W. P. , Zhang L. D.
Published: July 2005

High purity single crystal alpha silicon nitride (α‐Si3N4) nanowires were obtained in high yield via a simple vapor phase reaction approach without the presence of catalyst. The produced α‐Si3N4 nanowires have diameters mostly ranging from 30 to 100 nm and lengths of several hundred micrometers. The nanowires were grown via vapor–solid (VS) mechanism. The room‐temperature dielectric properties show that the effective dielectric constants of α‐Si3N4 nanowires is higher than that of the α‐Si3N4 micropowders, especially at low frequencies. Analysis of the dielectric properties indicates that the small size effect of nanowires has great influence on the dielectric behavior of the samples. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The role of interfaces on the magnetic behavior of granular CuFeCo alloys
Authors: Ghafari M. , Volland A. , Hahn H.
Published: July 2005

Granular thin films of face centered tetragonal (fct) FeCo‐clusters in a γ‐CuCo matrix show a giant magneto resistance effect. Cu100–x(Fe50Co50)x samples with 63 ≤ x ≤ 88 were examined using Mössbauer Spectroscopy, electron microscopy, Magnetoresistance, SQUID and Rutherford Backscattering Spectroscopy. In ultrafine particles with fct‐FeCo imbedded in a CuCo matrix the giant magneto resistance effect is strongly correlated to the ratio of interface/bulk. The magnetic interfaces form an additional scattering centere for the electrons which causes an increase of the GMR effect. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim )
Polariton correlation in microcavities produced by parametric scattering
Authors: Langbein Wolfgang
Published: July 2005

The spontaneous and self‐stimulated parametric emission from a semiconductor microcavity after resonant pulsed excitation is measured. The emission of the lower polariton branch is resolved in two‐dimensional momentum space, using either time‐resolved or spectrally resolved detection. The polariton–polariton scattering dynamics is generally in good agreement with the theory using the nonlinearity due to the excitonic part and the dispersion due to the photonic part of the polariton. The peculiar figure‐8 shaped distribution in momentum space of the final states of the parametric scattering is observed. Renormalization of the dispersion due to the bound biexciton state is found to influence the final state distribution. Using two pump directions the shape of the final state distribution can be changed to a peanut or oval for the mixed parametric processes. In this dual pump configuration, we find that polaritons in two distinct idler‐modes interfere if and only if they share the same signal‐mode, showing the existence of polariton pair correlations that store the “which‐way” information. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microcavities in Ecole Polytechnique Fédérale de Lausanne, Ecole Polytechnique (France) and elsewhere: past, present and future
Authors: Weisbuch Claude , Benisty Henri
Published: July 2005

We present an overview of semiconductor microcavity research, with emphasis on the activities carried out at Ecole Polytechnique Fédérale de Lausanne and Ecole Polytechnique (Palaiseau, France). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discrimination between diastereoisomeric dipeptides by IR–UV double resonance spectroscopy and ab initio calculations
Authors: Abo‐Riziq Ali G. , Bushnell John E. , Crews Bridgit , Callahan Michael P. , Grace Louis , De Vries Mattanjah S.
Published: July 2005

We studied diastereoisomeric dipeptides, containing two chiral centers, by comparing ab initio calculations with laser desorption jet‐cooling experiments. We studied the hetero‐dipeptides LL–VF (L‐Val‐L‐Phe) and DL–VF and the homo‐dipeptides LL–FF (L‐Phe‐L‐Phe) and LD–FF. Changing one of the chiral centers in each molecule leads to changes in the spectra that can be used to distinguish between diastereoisomeric pairs. We observed three different conformers for LL–VF, four for DL–VF, two for LL–FF, and one for LD–FF. By comparing the results from IR–UV double resonant spectroscopy with ab initio calculations, we can draw conclusions about the conformational structures. At the same time, the experimental data serve as a test for the computational results. We discuss the possibilities and limitations of the interplay between theory and experiment. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Structure and nonlinear optical properties of the HMT–CDA 1:1 adduct: Experimental and DFT approach
Authors: Venkatraman Ramaiyer , Ray Paresh Chandra , Fronczek Frank R. , Singh Jagdish P.
Published: July 2005

Equimolar amounts of hexamethylenetetramine (HMT) and trans‐1,2‐cyclohexanedicarboxylic acid (CDA) formed a self‐assembled unit through a hydrogen bonding network. Room temperature single‐crystal diffraction studies and Fourier transform infrared (FTIR) spectroscopy of the system indicated adduct formation between HMT and CDA. The crystalline adduct sample exhibited appreciable macroscopic nonlinear optical (NLO) properties. Density functional theory (DFT) calculations, using the 6‐31G(d,p) basis set, have been performed to investigate the gas‐phase structure and IR frequencies. The dynamic NLO properties were calculated with the ZINDO/CV method, including solvent effects. Theoretical parameters (geometry and vibrational frequencies) predicted by the DFT method for the adduct are in good agreement with the experimental data. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Analysis of aflatoxin B1‐lysine adduct in serum using isotope‐dilution liquid chromatography/tandem mass spectrometry
Authors: McCoy Leslie F. , Scholl Peter F. , Schleicher Rosemary L. , Groopman John D. , Powers Carissa D. , Pfeiffer Christine M.
Published: July 2005

A method for quantitative analysis of aflatoxin B1‐lysine adduct (B1‐Lys) in serum by liquid chromatography using tandem mass spectrometry (LC/MS/MS) is presented. The protein in a 250‐µL sample was digested in the presence of a stable‐isotope internal standard during a 4‐h incubation at 37°C with Pronase™. B1‐Lys and the internal standard were extracted using mixed‐mode solid‐phase extraction cartridges and eluted with 2% formic acid in methanol. Following evaporation and reconstitution, extracts were injected onto a Luna C‐18(2) column and eluted with a step gradient of acetonitrile and 0.06% formic acid. The B1‐Lys and the internal standard were detected in a positive ionization selective reaction monitoring mode with a ThermoFinnigan TSQ Quantum triple quadrupole mass spectrometer. Calibration curves were linear for concentrations from 0.05–8.0 ng/mL. The method was validated with aflatoxin B1 dosed rat serum diluted to anticipated high and low concentrations. Total imprecision determined from 30 measurements over 15 days was 5.6% and 9.1%, respectively. Recoveries of 78.8 ± 6.4% for B1‐Lys and 85.4 ± 12.4% for the internal standard were based on the full extraction and reconstitution processes. The method can be used to quantitate B1‐Lys at the 0.5 pg/mg albumin level and is suitable for routine analysis. Copyright © 2005 John Wiley & Sons, Ltd.
Application of positive ion chemical ionisation and tandem mass spectrometry combined with gas chromatography to the trace level analysis of ethyl carbamate in bread
Authors: Hamlet Colin G. , Jayaratne Sanal M. , Morrison Carol
Published: July 2005

A rapid, sensitive and selective method has been developed and validated for the analysis of the contaminant ethyl carbamate (EC) in bread products at the part‐per‐billion level. The new procedure uses positive ion chemical ionisation (PICI) and tandem mass spectrometry (MS/MS), combined with gas chromatography (GC), on a ‘bench‐top’ triple‐quadrupole mass spectrometer. Ammonia was the PICI reagent gas of choice because of its ability to produce abundant [M+H]+ and [M+NH4]+ ions from EC and deuterium‐labelled EC (LEC) used as an internal standard. For identification and quantification, selected reaction monitoring (SRM) was used to follow the precursor‐to‐product ion transitions of m/z 107 → 90, m/z 107 → 62 and m/z 90 → 62 for EC, as well as m/z 112 → 63 for the LEC internal standard. The limits of detection and quantification were 0.6 and 1.2 µg kg−1, respectively, and the recovery of the method was 101 ± 10% at 10 µg kg−1 and 98 ± 5% at 100 µg kg−1. The precision of the method, established under conditions of intermediate reproducibility, did not exceed a relative standard deviation of 7%. The quantitative performance of the new GC/PICI‐SRM procedure compared favourably with that of a reference method based on GC/MS and selected ion monitoring (correlation coefficient, r = 0.997). However, the new method had the advantages of reduced sample preparation time, improved sensitivity and unambiguous identification of EC at all concentrations. Application of the new method to the analysis of 50 UK breads showed that levels of EC ranged from 0.6 to 2.3 µg kg−1 in retail products and from 3.1 to 12.2 µg kg−1 for breads prepared using domestic breadmaking machines (dry weight basis). Toasting bread in a domestic toaster led to increases of between two‐ and three‐fold in mean EC concentrations. Copyright © 2005 John Wiley & Sons, Ltd.
Proton affinity of diastereoisomers of modified prolines using the kinetic method and density functional theory calculations: role of the cis/trans substituent on the endo/exo ring conformation
Authors: Mezzache S. , Pepe C. , Karoyan P. , Fournier F. , Tabet J.‐C.
Published: July 2005

The proton affinity (PA) of cis/trans‐3‐prolinoleucines and cis/trans‐3‐prolinoglutamic acids have been studied by the kinetic method and density functional theory (DFT) calculations. Several conformations of the neutral and the protonated modified prolines, in particular the endo and exo ring conformations, were analyzed with respect to their contribution to the PA values. When the substituent is an alkyl, both the diastereoisomers have the same PA value. However, the PA values for the diastereoisomers are different when the substituted chain contains functional groups (e.g. a carboxyl group). This variation in PA values could be attributed to the existence of intramolecular hydrogen bonds. Copyright © 2005 John Wiley & Sons, Ltd.
Development of microwave‐assisted derivatization followed by gas chromatography/mass spectrometry for fast determination of amino acids in neonatal blood samples
Authors: Deng Chunhui , Yin Xinying , Zhang Lijuan , Zhang Xiangmin
Published: July 2005

Analysis of amino acids in blood samples is an important tool for the diagnosis of neonatal amino acid metabolism disorders. In the work, a novel, rapid and sensitive method was developed for the determination of amino acids in neonatal blood samples, which was based on microwave‐assisted silylation followed by gas chromatography/mass spectrometry (GC/MS). The amino acids were derivatized with N,O‐bis(trimethylsilyl)trifluoroacetamide (BSTFA) under microwave irradiation. The controlled reaction was carried out employing BSTFA under conventional heating at 120°C for 30 min. Experimental results show that microwave irradiation can accelerate the derivatization reaction of amino acids with BSFTA, and much shorten analysis time. The method validations (linear range, detection limit, precision and recovery) were studied. Finally, the method was tested by determination of amino acids in neonatal blood by the measurement of their trimethylsilyl derivatives by GC/MS in electron impact (EI) mode. Two biomarkers of L‐phenylalanine and L‐tyrosine in phenylketonuria (PKU)‐positive blood and control blood were quantitatively analyzed by the proposed method. The results demonstrated that microwave‐assisted silylation followed by GC/MS is a rapid, simple and sensitive method for amino acid analysis and is also a potential tool for fast screening of neonatal aminoacidurias. Copyright © 2005 John Wiley & Sons, Ltd.
Application of liquid chromatography/electrospray ionization tandem mass spectrometry to the analysis of polyphenolic compounds from an infusion of Byrsonima crassa Niedenzu
Authors: Sannomiya Miriam , Montoro Paola , Piacente Sonia , Pizza Cosimo , Brito Alba R. M. S. , Vilegas Wagner
Published: July 2005

A fast and reliable method, based on high‐performance liquid chromatography coupled to electrospray ionization ion trap tandem mass spectrometry (HPLC/ESI‐ITMS), was developed to investigate the infusion prepared from the leaves of Byrsonima crassa Niedenzu (Malpighiaceae), a native plant used in Brazil against gastric disorders. The use of on‐line reverse‐phase HPLC/ESI‐ITMS allowed separation of three major classes of compounds and identification of over 20 very polar compounds characterized as galloylquinic acids, proanthocyanidins, and flavonoid glycosides, as well as the dimeric flavonoid amentoflavone and minor amounts of galloyl hexose and galloyl saccharose. This approach provided data that will allow establishment of a method for a future standardization of the infusion. Copyright © 2005 John Wiley & Sons, Ltd.
Major volatile compounds in head‐space above olive oil analysed by selected ion flow tube mass spectrometry
Authors: Davis Brett M. , Senthilmohan Senti T. , Wilson Paul F. , McEwan Murray J.
Published: July 2005

Selected ion flow tube mass spectrometry (SIFT‐MS) is a technique that is well suited to the real‐time analysis of head‐space. SIFT‐MS gives a non‐discriminatory snapshot of the volatiles present and their amounts, and is considered to display less bias than chromatographic techniques as neither sample pre‐treatment nor separation are necessary in most cases. The technique has been used for analysis of virgin olive oil head‐space on more than 100 different oils. Twenty of these are reported. The results obtained using this technique differ from those normally reported from chromatographic analyses in that the dominant species in the head‐space of all oils tested were methanol and ethanol. These volatiles were present in the head‐space in the concentration ranges of 2.8–11.3 ppm (methanol) and 0.4–4.9 ppm (ethanol). (E)‐2‐Hexenal, normally reported as the dominant olive oil volatile, is found in significantly lower concentrations and is in the range of 0.02–1.6 ppm. Copyright © 2005 John Wiley & Sons, Ltd.
Self‐aspirating atmospheric pressure chemical ionization source for direct sampling of analytes on surfaces and in liquid solutions
Authors: Asano Keiji G. , Ford Michael J. , Tomkins Bruce A. , Van Berkel Gary J.
Published: July 2005

A self‐aspirating heated nebulizer probe is described and demonstrated for use in the direct analysis of analytes on surfaces and in liquid samples by atmospheric pressure chemical ionization (APCI) mass spectrometry. Functionality and performance of the probe as a self‐aspirating APCI source is demonstrated using reserpine and progesterone as test compounds. The utility of the probe to sample analytes directly from surfaces was demonstrated first by scanning development lanes of a reversed‐phase thin‐layer chromatography plate in which a three‐component dye mixture, viz., Fat Red 7B, Solvent Green 3, and Solvent Blue 35, was spotted and the components were separated. Development lanes were scanned by the sampling probe operated under computer control (x, y plane) while full‐scan mass spectra were recorded using a quadrupole ion trap mass spectrometer. In addition, the ability to sample the surface of pharmaceutical tablets (viz., Extra Strength Tylenol® and Evista® tablets) and to detect the active ingredients (acetaminophen and raloxifene, respectively) selectively was demonstrated using tandem mass spectrometry (MS/MS). Finally, the capability to sample analyte solutions from the wells of a 384‐well microtiter plate and to perform quantitative analyses using MS/MS detection was illustrated with cotinine standards spiked with cotinine‐d3 as an internal standard. Published in 2005 by John Wiley & Sons, Ltd.
Geoffrey Vickers: philosopher of responsibility
Authors: Williams Garrath
Published: July 2005

In this article I discuss Geoffrey Vickers' ideas from the perspective of moral and political philosophy. His thought is presented through three key terms, which I suggest can encapsulate his philosophy: (i) our human capacity to respond aptly to our situation; (ii) the analysis of modern society in terms of institutions; and (iii) the moral importance of responsibility to the maintenance of human culture and cooperation. Copyright © 2005 John Wiley & Sons, Ltd.