bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass spectrometry of labile onium ions and carbocation salts. Study by desorption‐ionization mass spectrometry: Fast atom bombardment, field desorption and 252Cf plasma desorption time‐of‐flight mass spectrometry
Authors: Laali Khosrow , Fishel Derry L. , Lattimer Robert P. , Hunt Jerry E. 
Published: May 2005

AbstractIn contrast to the accepted notion that mass spectrometry is impractical as an analytical tool in condensed‐phase preparative carbocation chemistry, it has been shown that desorption ionization techniques (fast atom bombard‐ment, field desorption and252Cf plasma desorption time‐of‐flight mass spectrometry) provide rapid and reliable methods for relative molecular mass determination for a wide variety of highly unstable, fragile carbocation salts and onium ions. In addition, interesting fragment ions and cluster ions (two cations and one anion) are observed. Application of these methods to study several dication ether salts has also been demonstrated.
Mass spectra of halogenated esters. 7. Methyl esters of 2‐chloro C2C20n‐alkanoic acids
Authors: Korhonen Ilpo O. O. 
Published: May 2005

AbstractThe mass spectral fragmentation of a homologous series of methyl esters of 2‐chloro n‐alkanoic acids ranging from acetic (C2) to eicosanoic (C20) acid on electron impact has been investigated. The fragmentation pathways were elucidated with the aid of the first field‐free region metastable ions, the results being presented with one compound, i.e. with ionized methyl 2‐chloro‐octauoate. Owing to the Cl/H exchanges and to the formation of the non‐chlorinated parent esters prior to the fragmentations the spectra show the peak pairs with and without the chlorine atom. The effects become more evident with increasing chain length; shown most visually by the abundance ratios of the McLafferty rearrangement ions atm/z108/110 and 74, and fragments at m/z121/123 and 87.
Characterization of sphingosine long‐chain bases by fast atom bombardment and high‐energy collision‐induced decomposition tandem mass spectrometry
Authors: Rubino Federico Maria , Zecca Luigi , Sonnino Sandro 
Published: May 2005

AbstractThe fragmentation of protonated and cationized sphingosine and sphinganine under metastable and high‐energy collision‐induced decomposition is reported. The protonated compounds undergo abundant charge‐remote fragmen tation of the long alkyl chain, while the cationized molecules yield much less abundant fragmentation and little or no electrocyclic fission of the hydrocarbon portion.
Stereochemical effects in mass spectrometry XV— chemical ionization of some substituted alkenes using dichlorocarbene as the reagent gas
Authors: Yang Hou‐Jun , Li XiȧO‐Ling , Pan Yuan‐Jiang , Chen Yao‐Zu 
Published: May 2005

AbstractChemical ionization (CI) of trans‐ and cis‐stilbene and of fumaric and maleic acid, using dichlorocarbene as reagent, was studied. In the CI ion source (CH4), dichlorocarbene added stereospecifically to the double bond of the sample molecule to form the corresponding ion of the 1,1‐dichloropropane derivative. From the different relative abundances of the characteristic fragment ions of these cyclopropanes, the geometric configuration of the original substituted olefins may be predicted.
Dynamic mechanical analysis of fiber reinforced composites
Authors: Reed Katherine E. 
Published: May 2005

AbstractDynamic mechanical and thermal properties were determined for unidirectional epoxy/glass composites at various fiber orientation angles. Resonant frequency and relative logarithmic decrement were measured as functions of temperature. In low angle and longitudinal specimens, a transition was observed above the resin glass transition temperature which was manifested mechanically as anadditional damping peak and thermally as a change in the coefficient of thermal expansion. The new transition was attributed to a heterogeneous resin matrix induced by the fiber. The temperature span of the glass‐rubber relaxation was found to broaden with decreasing orientation angle, reflecting the growth of fiber contribution and exhibiting behavior similar to that of Young's modulus. The change in resonant frequency through the glass transition was greatest for samples of intermediate fiber angle, demonstrating behavior similar to that of the longitudinal shear modulus.
Optimization of phenolic resins for friction materials
Authors: Lambla M. , Vo V. C. 
Published: May 2005

AbstractThe physicomechanical properties of phenolic composites containing a large amount of mineral fillers were enhanced through a chemical modification of the basic resin. Various phenolic compounds were first introduced in the condensation mixture leading to modified novolaks, but the final properties of the resulting composites were only slightly improved. Better results were obtained using an optimum content of epoxy‐novolak or melamine in the last stage of processing as confirmed by static and dynamic mechanical analysis. The new procedure introduced recently by Halpin and Sendeckyj for fitting fatigue models was applied to our particle‐filled material. The results confirm the reinforcement of the composite through the co‐reactivity of phenolic resins with the introduced species in the final curing stage.
Characterization of the rheological behavior of fiber‐filled polypropylene melts under steady and oscillatory shear using cone‐and‐plate and rotational parallel plate rheometry
Authors: Mutel A. T. , Kamal M. R. 
Published: May 2005

AbstractUtilization of cone‐and‐plate and rotational parallel plate rheometry to characterize the rheological behavior of fiber‐filled polymer melts at low shear rates was evaluated. The effect of flow geometry and dimensions on the viscoelastic and viscometric functions was considered. Stress growth functions were found to be dependent on the dimensions of the flow channel. However, viscometric functions were not affected by the dimensions or the geometry of the flow channel. The initial state of orientation was found to be an important factor in determining the flow found to be an important factor in determining the flow behavior. Oscillatory shear tests yielded highly strain‐dependent loss and storage moduli even at very small strain amplitudes. However, the stress response was found to be sinusoidal in most cases, although the properties were strain dependent.
Characteristics of thermoplastics containing electrically conducting asymmetric particles: Anisotropic electrical conductivity of injection molded parts and extrusion behavior
Authors: Martinsson Jan , White James L. 
Published: May 2005

AbstractThe characteristics of compounds of acrylonitrile‐buta‐diene‐styrene and high impact polystyrene resins, filled with carbon fibers, steel fibers, carbon black, and aluminum flakes have been investigated with special emphasis on electrical conductivity and flow behavior in a capillary rheometer. Compression and injection molded compounds were found to be highly electrically anisotropic. The components of the electrical conductivity tensor, K11, K22 and K33, were measured, Generally K11, the flow direction conductivity, has the highest value and the thickness direction, and K33 has the lowest. The injection molded parts were usually electrically heterogeneous with the conduetivities highest at the greatest distances from the gate. The results were interpreted in terms of particle orientation and distribution. Shear viscosities were measurable for all but the aluminum flake compounds which exhibited fluctuating pressure drops. The flow of these compounds through dies was investigated. Examination of material from the die entrance indicated streamline flow without entrance vortices. Sometimes high entrance concentration of particulates were observed especially for the aluminum flakes. Extrudates were found to contain oriented particles.
Reaction injection molding of mica reinforced polyurethane
Authors: Rémillard B. , Vu‐Khanh T. , Fisa B. , Naik S. 
Published: May 2005

AbstractReaction injection molded polyurethanes are reinforced with inorganic materials to improve stiffness and structural integrity at elevated temperatures and to reduce the coefficient of thermal expansion. This work describes the reinforcement obtained with an experimental grade of mica designed to achieve low viscosity of mica suspensions in polyol. The effect of mica on properties is essentially identical to that of glass flake (i.e., improved stiffness at the cost of reduced impact strength). Compared to hammer milled glass fiber, mica and glass flakes yield more isotropic, albeit weaker, materials. The study of unreinforced polyurethane shows that mechanical properties (tensile and impact strength, flexural modulus) are approximately proportional to the square of foam density.
The influence of fibers on the crystallization of poly(ethylene terephthalate) as related to processing of composites
Authors: Reinsch Veronika E. , Rebenfeld Ludwig 
Published: May 2005

AbstractThe effect of fiber reinforcement on the isothermal crystallization of poly(ethylene terephthalate) (PET) was investigated using differential scanning calorimetry (DSC). Unidirectional fiber composites were prepared using glass and aramid fibers in PET. The rate of crystallization, as reflected by crystallization half‐time, and the degree of crystallinity of PET are seen to depend on the type of reinforcing fiber as well as on crystallization temperature. Crystallization kinetics are also analyzed using an Avrami model for the volume of polymer crystallized as a function of time. The crystalline morphology of PET in fiber‐reinforced systems was studied using polarized light microscopy. Results concerning nucleation densities and growth morphologies are used in explaining differences seen in crystallization kinetics in fiber‐reinforced systems.
Morphological aspects of the interface in the PEEK‐carbon fiber system
Authors: Lustiger A. 
Published: May 2005

AbstractAlthough high modulus PAN based carbon fibers (HMS) induce transcrystallinity in PEEK and a wide variety of other semi‐crystalline polymers, the interfacial strength is lower than PEEK in contact with low modulus carbon fibers (AS4) where transcrystallinity is not induced. In the PEEK/HMS system, crystalline lamellae were found to be oriented edge‐on to the fibers, while in AS4 they were oriented flat‐on, reflecting the difference in surface energies between the two fibers. The intrinsic effect of transcrystallinity on the fiber matrix interaction is therefore obscured when the chemistry of the interaction varies.
Analysis of deformation processes in glassy polycarbonate using internal friction measurements during a tensile test
Authors: Parisot J. , Rafi O. , Choi W. J. 
Published: May 2005

AbstractInternal friction has been measured by torsion at 1 Hz during tensile tests performed on glassy polycarbonate at room‐temperature. Steady‐state flow and transient effects have been studied during continuous tensile tests and strain‐rate changes. During steady‐state, internal friction and flow‐stress vary in a similar way with strain‐rate. But during transients, internal friction varies continuously while flow‐stress passes through a maximum (or a minimum). These results are interpreted assuming that non‐elastic deformation of glassy polymers requires some microscopic discontinuous processes such as motion of defects. Two parameters are considered: the velocity v and the density ρ of mobile defects. Assuming that the former is directly related to the flow stress, it has been shown that internal friction is related to the density of mobile defects ρ. This feature is used to interpret the different stages of a tensile test curve. Activation volumes for both velocity and density of mobile defects are calculated from experimental data.
A thermoviscoelastic model for residual stress in injection molded thermoplastics
Authors: Rezayat Mohsen , Stafford Roger O. 
Published: May 2005

AbstractThe main sources for residual stress build‐up and warpage in injection‐molded thermoplastic parts are the holding pressures at the gate and the asymmetry in temperature at the mold walls. Accurate computation of these stresses requires a viscoelastic model since creep and stress relaxation behavior of polymers is magnified at the temperature range for filling, packing, and cooling stages of the injection molding process. Furthermore, injection molded parts can rarely be treated as isotropic; orientation, crystallinity, and presence of fibers require a more general material‐model presentation. In this paper, we present a transversely isotropic thermoviscoelastic model for injection‐molded thermoplastic parts, provide a description of the material properties, and briefly discuss measurement techniques and their limitations.
New polythiourethane hardeners for epoxy resins
Authors: Strzelec Krzysztof , Leśniak Elżbieta , Janowska Grażyna 
Published: May 2005

AbstractNew mercaptan‐terminated polythiourethanes were synthesized from low‐molecular‐weight dimercaptan oligomers and diisocyanates. The characteristic bands in the FT‐IR spectra, and the specific peaks in the 1H‐NMR spectra correlate rather well with the proposed structures of these polymers. Chemical analysis of the epoxy group conversion and swelling measurements were conducted in order to determine the crosslink densities of the cured epoxy resins. The curing characteristics and thermal behaviour of the formulated curing mixtures indicate that the epoxy/polythiourethane stoichiometry and thermal history during cure may greatly affect the curing mechanism and final properties of the epoxy networks. Mechanical studies indicated that the application of polythiourethane hardeners improves the flexibility with increasing tensile strength and impact toughness. The prepared polythiourethane hardeners have an acceptable odour and give a perfectly homogeneous system with the epoxy resins and have good storage stability with other coreactants such as diamines. Copyright © 2005 Society of Chemical Industry
Proteomic expression analysis of colorectal cancer by two‐dimensional differential gel electrophoresis
Authors: Alfonso Patricia , Núñez Antonio , Madoz‐Gurpide Juan , Lombardia Luis , Sánchez Lydia , Casal J. Ignacio 
Published: May 2005

AbstractThe identification of specific protein markers for colorectal cancer would provide the basis for early diagnosis and detection, as well as clues for understanding the molecular mechanisms governing cancer progression. In this report, we describe the proteomic analysis of the samples of colorectal cancer corresponding to seven patients. We have used the highly sensitive two‐dimensional differential gel electrophoresis (2‐D DIGE) coupled with mass spectrometry (MS) for the identification of proteins differentially expressed in tumoral and neighboring normal mucosa. We have detected differences in abundance of 52 proteins with statistical variance of the tumor versus normal spot volume ratio within the 95th confidence level (Student's t‐test; p < 0.05). Forty‐one out of 52 analyzed proteins were unambiguously identified by matrix‐assisted laser desorption/ionization‐time of flight MS coupled with database interrogation as being differentially expressed in colorectal cancer. An ontology analysis of these proteins revealed that they were mainly involved in regulation of transcription (synovial sarcoma X5 protein, metastasis‐associated protein 1), cellular reorganization and cytoskeleton (cytokeratins, vimentin, β actin), cell communication and signal transduction (annexins IV and V, relaxin, APC), and protein synthesis and folding (heat shock protein 60, calreticulin, cathepsin D, RSP4) among others. Preliminary studies demonstrated that the differentially expressed proteins found by 2‐D DIGE could be confirmed and validated by immunoblotting and immunohistochemistry analyses in those few cases where antibodies were available. We believe that the incorporation of more samples and new datasets will permit the definition of a collection of proteins with a potential interest as biomarkers for colorectal cancer.
Carbonylated proteins in bronchoalveolar lavage of patients with sarcoidosis, pulmonary fibrosis associated with systemic sclerosis and idiopathic pulmonary fibrosis
Authors: Rottoli Paola , Magi Barbara , Cianti Riccardo , Bargagli Elena , Vagaggini Cecilia , Nikiforakis Nikolaos , Pallini Vitaliano , Bini Luca 
Published: May 2005

AbstractOxygen‐derived free radicals produced by phagocytes have been postulated to contribute to lung tissue damage occurring during diffuse lung diseases (DLD). The two‐dimensional electrophoretic (2‐DE) analysis of bronchoalveolar lavage (BAL) protein composition revealed different protein profiles in sarcoidosis (S), idiopathic pulmonary fibrosis (IPF) and systemic sclerosis (SSc) with a significant increase of low molecular weight proteins in IPF. Some of these proteins are involved in antioxidant processes. The aims of this report were to analyse the oxidative stress occurring in patients with DLD through determination of BAL protein carbonyl content and to identify target proteins of oxidation by a proteomic approach (2‐DE combined with immunoblotting with specific antibodies for carbonyl groups). Carbonylated proteins detected by enzyme‐linked immunosorbent assay (ELISA) were increased in BAL of patients with S, IPF and SSc compared to healthy controls with a significant difference for S and IPF. The proteomic approach to the analysis of BAL revealed that protein carbonylation was a process involving specific carbonylation‐sensitive proteins and that in IPF a greater number of proteins target of oxidation were present. In conclusion, to our knowledge, this is the first report providing a database of proteins target of oxidation in BAL of patients with sarcoidosis, idiopathic pulmonary fibrosis and systemic sclerosis.
Application of fluorescence difference gel electrophoresis saturation labelling for the analysis of microdissected precursor lesions of pancreatic ductal adenocarcinoma
Authors: Sitek Barabara , Lüttges Jutta , Marcus Katrin , Klöppel Günter , Schmiegel Wolff , Meyer Helmut E. , Hahn Stephan A. , Stühler Kai 
Published: May 2005

AbstractIn order to identify new molecular markers for pancreatic intra‐epithelial neoplasias (PanINs), the precursor lesions of pancreatic ductal adenocarcinoma, we established a proteomics approach analysing microdissected PanIN cells. Due to the limited amount of proteins available from microdissection, we developed a procedure including fluorescence dye saturation labelling in combination with high resolution two‐dimensional gel electrophoresis. With this procedure we were able to analyse proteins extracted from 1000 microdissected cells with a high resolution of up to 2500 protein spots. Using protein lysates from the pancreatic carcinoma tissue as a reference proteome, we were able to successfully identify the proteins. Thus, we could match approximately 2200 protein spots (92%) of the microdissected sample proteome to the reference proteome for protein identification using matrix‐assisted laser desorption/ionisation‐time of flight mass spectrometry and nanoliquid chromatography‐electrospray ionisation tandem mass spectrometry after in‐gel digestion. The first proteome analysis of microdissected PanIN‐2 grades revealed eight differentially expressed proteins. The differential expression of the three actin filament‐associated proteins – transgelin, vimentin and MRCL3 as well as actin itself – indicates a relevant role of the actin cytoskeleton during pancreatic tumour progression. Additionally, two members of the annexin family (annexin A2 and A4) implicate a functional contribution of exocytotic and endocytotic pathways at that stage.
Open Air Deposition of SiO2 Films by an Atmospheric Pressure Line‐Shaped Plasma
Authors: Zhu Xiaodong , Arefi‐Khonsari Farzaneh , Petit‐Etienne Camille , Tatoulian Michael 
Published: May 2005

AbstractSummary: A line‐shaped atmospheric pressure filamentary plasma is developed to carry out the open air deposition of silicon oxide films from N2/hexamethyldisoxane (HMDSO) mixtures with/without adding oxygen. FT‐IR, XPS, SEM, and ellipsometry were used to analyse the samples. It is found that the deposited films present mainly inorganic characteristics even without an oxygen admixture in the open air system. Smooth, continuous, and uniform films can be formed at relatively low monomer content. By increasing the monomer content for a fixed power density or oxygen in the input gases, the deposition rates increase and then show a plateau, suggesting that there exists saturation values for the deposition rates corresponding to the monomer and oxygen content. By the comparison of films deposited in the open air device and in a controlled nitrogen atmosphere in the same device, the important role of the oxygen in the open air reactor has been shown. This study exhibits a potential of open air deposition at atmospheric pressure to form SiO2 films for large‐scale deposition.An FT‐IR spectrum of an SiOx film deposited in open air without adding any oxygen to the discharge.magnified imageAn FT‐IR spectrum of an SiOx film deposited in open air without adding any oxygen to the discharge.
Computer Simulation of Randomly Packed Spheres ‐ a Tool for Investigating Polydisperse Materials
Authors: Schlüßler Karl Heinz , Walter Lutz 
Published: May 2005

AbstractIn the field of material science, especially for polydisperse materials, many questions arise which cannot be answered sufficiently and precisely without information which represents the random character of the structure in space. Computer simulation is here an effective tool used to create random arrangements of particles which may be regarded as a realistic representation of the underlying material. Of course, the presumption that the shape of each particle is a sphere is an idealization which is a certain handicap in modeling all the possible system properties. Nevertheless, it can be demonstrated that, by having an adequate subroutine, many phenomena which are influenced by the local topology of the particles and their interaction forces can be studied in more detail.
On the Detonation Characteristics of CHNO‐Type Condensed Explosives. A parameter study
Authors: Swaminathan V. , Rajagopalan S. 
Published: May 2005

AbstractThe object of the present paper is to carry out a parametric study which takes into consideration the variations of the detonation characteristics such as CJ pressure, CJ temperature, velocity of detonation (VOD), and gas volume of CHNO‐based condensed explosive systems in connection with the changes in input parameters like loading density and heat of formation of the explosive in question. Meaningful equations which describe adequately the interrelationships between the parameters were derived for a typical CHNO‐type explosive. The study is likely to be of considerable help in determining the variations in the magnitudes of the detonation parameters corresponding to a given change in the relevant input characteristics. The results of such studies should also be important in estimating the uncertainty of a parameter, like VOD, arising from the uncertainty in the heat of formation of the explosive which is often determined experimentally and whose values is often of questionable validity. The principal features that emerge from the investigations in this paper are: (1) while CJ pressure and VOD tend to increase sizably with the loading density of the explosive, CJ temperature and CJ volume decrease with an increase in the loading density; and (2) all the four parameters, viz., CJ pressure, CJ temperature, VOD, and CJ volume increase, however, being of a marginal nature, barring the CJ temperature whose variations with the heat of formation are not insignificant.