bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of modification sites during peptide synthesis using liquid secondary ion/collision‐induced dissociation mass spectrometry and a computer program
Authors: Rozenski Jef , Samson Isabelle , Janssen Gerard , Busson Roger , Van Aerschot Arthur , Herdewijn Piet 
Published: May 2005

AbstractSide‐reactions often occur during peptide synthesis resulting in modified amino acid moieties. To identify these residues, liquid secondary ion/collision‐induced dissociation mass spectra were recorded. The main fragments are generated by cleavage of the peptide bond. To facilitate interpretation of the spectra and assignment of the structure, a simple, but flexible and efficient, computer program is presented. The program allows the verification of the correct structure of the synthesized peptides and the deduction of the type of side‐products formed, such as alkylation of tryptophan residues.
Determination of tetrahydrocannabinolic acid—carrier protein conjugate by matrix‐assisted laser desorption/ionization mass spectrometry and antibody formation
Authors: Goto Yuri , Shima Yumi , Morimoto Satoshi , Shoyama Yukihiro , Murakami Hiroki , Kusai Akihiko , Nojima Kazutetsu 
Published: May 2005

AbstractIn order to form the monoclonal antibody against tetrahydrocannabinolic acid (THCA), THCA was coupled with bovine serum albumin (BSA) or human serum albumin (HSA) using β‐alanine as a linker or without β‐alanine to produce individual antigen conjugates. The number of haptens contained in the antigen conjugates was determined by matrix‐assisted laser desorption ionization mass spectrometry using BSA or HSA as an internal standard. The formation of monoclonal antibody is also discussed.
Characterization of chlorins within a natural chlorin mixture using electrospray/ion trap mass spectrometry
Authors: Chillier Xavier Fr. D. , Van Berkel Gary J. , Gülaçar Fazil O. , Buchs Armand 
Published: May 2005

AbstractChlorins in a sedimentary mixture were characterized, without prior isolation of individual components, using electrospray ionization combined with ion trap mass spectrometry. Collision‐induced dissociation in the atmospheric sampling interface and multi‐step mass spectrometry (i.e. MSn where n ⩾ 2) were used in order to obtain structural information about the macrocycle. Fragmentation pathways are proposed for different macrocycle types based on data from model chlorins. Three unknown chlorins (RMM = 888, 844 and 790) are assigned as having bacteriochlorophyll macrocycle types esterifled to unusual side‐chains (i.e. dihydrophytol for the unknown with a bacteriopheophorbide a structure, phytol and an alcohol with a molecular mass of 242 u for the two unknowns with a proposed bacteriopyropheophorbide d structure).
Chemical reactions occurring at the interface of epoxy matrix and aminosilane coupling agents in fiber‐reinforced composites
Authors: Chiang Chwan‐Hwa , Koenig Jack L. 
Published: May 2005

AbstractThe chemical reactions at the interface between an anhydride‐cured epoxy resin and an aminosilane treated fiber have been investigated using Fourier transform infrared methods (FT‐IR). The results indicate that chemical bonds are formed in the interfacial region between the matrix and the coupling agents. The amount of interfacial bonding depends on the composition and the processing conditions.
Interferometric measurement of inhomogeneous swelling
Authors: Sargent J. P. , Ashbee K. H. G. 
Published: May 2005

AbstractDifferential thermal contraction between matrix and fiber materials in composites and between adhesive and adherend materials in adhesive joints occurs during cooling from the resin cure temperature and gives rise to non‐uniform internal stress fields. Resin swelling associated with water uptake during service gives rise to inhomogeneous stress, the magnitude and distribution of which is the subject of the present investigation. Thin layers of cured epoxy resin have been allowed to absorb water at their edges only, and the swelling normal to these layer planes has been measured by studying optical interference patterns. The stresses resulting from inhomogeneous swelling, a few tens of bars, are of similar magnitude to those resulting from inhomogeneous shrinkage during cooling from resin cure temperatures.
Fiber rearrangements during the molding of continuous fiber composites. I. Flat cloth to a hemisphere
Authors: Robertson R. E. , Hsiue E. S. , Sickafus E. N. , Yeh G. S. Y. 
Published: May 2005

AbstractThe goal of this series of reports is to develop rapid computational procedures for determining the rearrangement of fibers that occurs during the molding of continuous fiber composite components for flat layups. This report considers the shaping of a cloth into a hemisphere. /the numerical procedure developed predicts that a cloth can be shaped into a hemisphere without wrinkling. This prediction is compared with experiment, and various paramenters connected with the shaping calculation are discussed.
Elevated temperature testing for comparison of glass/resin composites
Authors: Silverman E. M. 
Published: May 2005

AbstractStatic test methods were used to evaluate and compare the thermal and mechanical properties of several glass/thermoset laminated composites between 25° and 400°C. The unidirectional matrix composites consisted of phenolic‐modified epoxy, epoxy novolac, epoxy, and modified phenolic resins. These materials were selected as potential alternative materials for rotary compressor vanes. Dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA) techniques were selected to evaluate elevated temperature performance. The short‐beam shear test was chosen to measure interlaminar shear properties. The results indicated that an elevated‐temperature matrix, such as the modified phenolic resin, may not result in optimum composite strengths. Instead, an epoxy resin reinforced with glass fibers provides a better balance between elevated‐temperature performance and interlaminar shear strength. The test results of this study, in addition to being adequate for discriminating the materials for initial selection purposes, were obtained quickly and easily. Moreover, the thermal results provide a more realistic understanding of composite elevated‐temperature characteristic than do those of the present standard test.
Polymerization of filled propylene: A new principle for formation of conducting composites
Authors: Berlin Y. , Beshenko S. I. , Zhorin V. A. , Galashina N. M. , Enikolopian N. S. 
Published: May 2005

AbstractA new approach to the formation of electrically conducting polymeric materials has been formulated. It is based on the phenomenon of pressure‐induced injection of charge carriers from conducting particles into dielectric media. This process has been recently discovered by the authors. In practice, this approach can be accomplished by synthesizing macromolecules of proper dielectric next to the surface of a conducting filler. The experiments supporting the validity of the main assumptions are used to provide a background for the “polymerization filling” concept. The application of this principle makes it possible to obtain systems with larger specific conductivity than with the usual “blended” composites.
Extensional flow of mica‐filled polyethylene
Authors: Utracki L. A. , Lara J. 
Published: May 2005

AbstractExtensional flow of mica‐filled high density polyethylene was studied at 150°C in a Rheometrics elongational rheometer. The constant strain‐rate mode at a rate of 10−3 to 1.0 s−1, and the constant stress mode were used. The mica content was 0, 25, 40, and 60 weight percent. In both testing modes, the steady state elongational viscosities were obtained; those for the filled samples were about ten to twenty times larger than the shear viscosity at corresponding (low) rates of deformation.
Jute reinforced polyester structures
Authors: Semsarzadeh Mohammad A. , Lotfali Abdol R. , Mirzadeh Hamid 
Published: May 2005

AbstractLarge diameter pipes and structures are manufactured with jute reinforced polyester resin. A modified filament winding machine is used to take the jute cloth on the rotating mold acting as a collapsible mandrel. The effect of calendering, fillers and poly(vinyl acetate) on jute reinforcing cloth and the results on the ultimate mechanical properties of the composite are studied. The effect of load during the curing of polyester and its effect on the strength of structure is reported. These findings are used in manufacturing of large diameter structures with improved mechanical properties.
Effect of particulate reinforcement on creep behavior of polyurethane foams
Authors: Alperstein D. , Narkis M. , Kenig S. , Siegmann A. 
Published: May 2005

AbstractThe compressive creep behavior of rigid unreinforced and particulate reinforced polyurethane foams at different densities, filler contents, temperatures, and loads was investigated. The creep behavior could be described by a power function of time and its temperature dependence by an Arrhenius type relation. The addition of particulate rigid fillers enhances the creep resistance as well as the foam elastic modulus. Particulate reinforcement of polyurethane foams was found to be efficient for the higher foam densities, especially for higher filler levels.
Mechanical degradation of glass fibers during compounding with polypropylene
Authors: Fisa B. 
Published: May 2005

AbstractThe objective was to study the fiber length degradation during compounding of glass fiber with polypropylene. The effect of parameters such as viscosity, total work, concentration on fiber length and dispersion was studied using an automatic particle size analyzer. The length degradation is most severe during the very first stage of the process, i.e., when fiber bundles are being filamentized. The mode of glass fiber incorporation into the melt (fiber addition to the molten resin versus to polypropylene powder prior to compounding) was found to have no effect on the final fiber length. Matrix resin viscosity affects the fiber length significantly. Concentration dependencies of fiber length for different times of compounding suggest that the degradation results from both fiber‐fiber and fiber‐melt interactions.
Mechanical properties of drawn poly(methyl methacrylate) filled with ultrafine particles
Authors: Sumita Masao , Shizuma Tadao , Miyasaka Keizo , Ishikawa Kinzo 
Published: May 2005

AbstractThe elastic and yield properties of drawn poly(methyl methacrylate) (PMMA) filled with ultrafine SiO2 are described as functions of filler content and size. The drawn PMMA composites were made by uniaxially drawing to x4.0 at 100°C and at a rate of 20 mm/min. Four compliance values, i.e., S33, S11, S13, and S44 were determined. These values decreased with filler content and decreasing filler size. The relative compliance values Sde/Sdo(Sde is the compliance of drawn PMMA composites and Sdo is that of drawn unfilled PMMA) are almost equivalently changed with changes in filler content. The elastic properties of drawn PMMA composites are thus reinforced isotopically. This is characteristic of PMMA which has a large side group. The yield behavior of drawn PMMA composites have similar filler size and content dependence to those of elastic properties except that the transverse yield stresses become more brittle with filler content. The anisotropy in yield stress is relatively larger than that of elastic properties. This is probably because the anti‐reiforcing effect, such as fibrillation becomes prominent with increasing filler content in the perpendicular direction.
Structure‐property relations in polypropylene mica composites
Authors: Xavier S. F. , Sharma Y. N. 
Published: May 2005

AbstractPolypropylene composite samples with concentrations of mica of 10, 20, 30, 40, 45, 50, and 60 wt percent were prepared under identical conditions by injection molding. The influence of mica concentration on the structure and mechanical properties of the composites was investigated using a polarizing microscope, scanning electron microscope, differential scanning calorimetry, and stress‐strain characteristics. Flexural and impact strengths show an initial rise and then gradual fall with increasing mica concentration. An optimum of these properties occurred at ∼20 wt percent mica. Tensile modulus and heat distortion temperature show a continuous rise; whereas the percent elongation decreased with mica content. These changes in properties are discussed in terms of a skin‐core morphology, transcrystallinity, crystallinity, fracture surface morphology, flake orientation, and interfacial adhesion in these composites. This study helps in optimizing the mica concentration for injection molded composites.
The effect of thermal stresses on the EMI (electromagnetic interference) shielding of conductive plastics
Authors: Bigg D. M. 
Published: May 2005

AbstractThe electrical properties of a number of filled and coated plastics were examined after subjecting the materials to rigorous thermal cycling between −20 and 80°C. Filled compounds that obtained their conductivity through the addition of carbon based conductive fillers maintained their conductivity throughout the thermal cycling. Compositions which contained metal fillers were able to maintain their conductivity only when a high temperature thermally stable polymer was used as the polymer matrix. Plaques coated by a zinc arc spray or with acrylic paints containing graphite, silver, and nickel particles were unaffected by thermal cycling. Plaques coated with an acrylic paint containing copper particles lost most of their conductivity during the changes in sample temperature.
Mechanical and rheological properties of multicomponent polypropylene blends
Authors: Pukánszky Béla , Tüdõs Ferenc , Kelen Tibor 
Published: May 2005

AbstractPolypropylene (PP) compositions containing CaCO3 filler, EPDM (ethylene‐propylene‐ethylidenenorbornene) elastomer, and a non‐reactive surfactant were investigated in the mixing chamber of a plastograph. Rheological properties were determined from the registered torque (M) vs. time and temperature (T) vs. time curves, while tensile characteristics of the blends were measured on compression molded plates. The homogenization process can be followed with the aid of 1 n M vs. 1/T diagrams. In the first few minutes of the mixing, beside homogenization, a significant breaking down of the elastomer takes place, and the size of the particles attains an equilibrium value. Dispersion time increases with increasing amount of EPDM and surface active‐agent. Morphological investigations indicate the presence of a continuous PP phase containing dispersed CaCO3 and elastomer particles. The rheological and tensile characteristics are seemingly determined by the total amount of additives, which imply that the elastomer and the filler has the same effect on the properties of the composite. Separation of the effects proved, however, that the effect of the two components are dissimilar, the filler exerts a larger influence on the investigated properties.
Statistical distribution of strength of fiber‐reinforced composite materials
Authors: Wetherhold Robert C. 
Published: May 2005

AbstractThe Weibull distribution is presented as a physically consistent description of strength distribution in brittle composites. Methods are developed for obtaining point and one‐sided interval estimates for the parameters of the Weibull distribution. Strength data are obtained for 25 replicates of nine different sheet molded and injection molded composites, and the developed statistical methods are applied to these data. Details of the materials and processing are given. Strength results indicate that the reliability calculations using the one‐sided interval estimates are uniformly conservative for all materials. In addition, it is shown that composites produced with a less automated production process show more strength variability. Machining of an injection molded composite surface appears to lower strength and increase strength variability by introducing flaws which act as fracture initiation sites.
Measurement of the thermal conductivity of composites using heat flow sensors
Authors: Penn B. G. , Ledbetter F. E. , White W. T. , Clemons J. M. 
Published: May 2005

AbstractA thermal conductivity measuring apparatus that uses heat flow sensors to measure the heat flux through samples was constructed of inexpensive materials. This device was used to measure the thermal conductivity (k) of two composites used in the space program that consist of fibrous or granular components embedded in a resin matrix. The k‐values that were determined ranged from 0.035 to 0.059 Btu/h‐ft2‐°F/ft (−163 to 553°F) and 0.029 to 0.035 Btu/h‐ft2‐°F/ft (77 to 212°F). Thermal conductivity values of the composites conformed to the rule of mixture. The accuracy of the system was found to be comparable to the guarded hotplate and it requires neither a skilled operator nor extensive maintenance.
Air entrapment in sheet molding compounds (SMC)
Authors: Slotfeldt‐Ellingsen Dag , Magnus Elisabeth , Ekern Eric , Holtmon Egil , Corneliussen Lars 
Published: May 2005

AbstractEntrapped air can commonly lead to large delaminations in thick walled sheet molding compound (SMC) products. In this work different sources of air entrapment in SMC are investigated. The critical process is shown to be the impregnation of the fibers. If no surface active additives are used, large volumes of air may be entrapped in this process, unless the viscosity of the compound is very low. In this situation of poor wetting, the viscosity of the compound during fiber impregnation will critically determine the interlaminar, tensile strength of the product. However, if surface active additives are used, the air escapes entrapment even at relatively high viscosities. The lowering of the viscosity, which is a side effect of the additives, has practically no importance under these conditions of good wetting. Large numbers of small air bubbles are also entrapped during the mixing of the components, but it is shown that these bubbles have very little effect on the mechanical properties of the finished part.
The effects of tension on the absorbance of water into neat and glass‐bead‐filled, cross‐linked polyester
Authors: Janas V. F. , Smith L. S. , McCullough R. L. 
Published: May 2005

AbstractThe effects of tension on the absorbance of water at 60°C into neat and glass‐bead‐filled, cross‐linked polyester are reported. Experimental apparatus and procedure to determine water uptake for these materials subjected to three tensile stresses in the range of 0 to 30 percent of the breaking stress of the neat dry polyester are described. It was found, for bead‐filled samples, that a load of approximately 4.9 × 106 N/m2 caused the absorption level to increase by 30 percent over that of an unloaded sample. Tensile load was found to have no effect on the absorption characteristics of neat polyester. However, breaking stress was reduced to less than 15 percent of that in the dry neat material. Optical microscope examinations of damage at the fracture surfaces and at the sample cores indicate that the excess moisture uptake in bead‐filled samples was not due to microcrack formation.
The effect of chemical exposure on the EMI shielding of conductive plastics
Authors: Bigg D. M. 
Published: May 2005

AbstractThe electrical properties of a number of filled plastics were examined after subjecting the materials to exposure to isopropyl alcohol, a 25°C detergent/water solution, an 80°C detergent/water solution, and at various chemical plant sites. Compositions which contained metal fillers maintained their conductivity only when a high temperature thermally stable polymer was used as the polymer matrix, while compositions which are made conductive through a carbon filler network maintained their conductivity under most of the exposure conditions examined even when low temperature polymers were used as matrices.
Some features of the injection molding of short fiber reinforced thermoplastics in center sprue‐gated cavities
Authors: Darlington M. W. , Smith A. C. 
Published: May 2005

AbstractThis paper describes an investigation into the fiber orientation in a number of center sprue fed cavities in short glass fiber filled polypropylene and nylon. The data have been interpreted in terms of a generalized five‐layer structure resulting from the frozen skin formation and the high and low shear levels in the flowing melt. The implications for scaling up the mold size are discussed from the results obtained with different shot volumes. The fiber structure was observed to depend on location in the molding, local injection time, and injection rate. In addition the occurrence of fiber‐free layers within the moldings using the filled polypropylene increases with an increase in shot volume, which produces an inherent ‘scale‐up’ problem. Notwithstanding the mold geometry subtleties, the fiber orientation in all the moldings follows similar patterns and trends.
A cure‐rate model for the shuttle filament‐wound case
Authors: Cagliostro D. E. , Islas A. , Hsu Ming‐ta 
Published: May 2005

AbstractAn epoxy and carbon fiber composite has been used to produce a light‐weight rocket case for the Space Shuttle. A kinetic model is developed which can predict the extent of epoxy conversion during the winding and curing of the case. The model accounts for both chemical and physical kinetics. In the model, chemical kinetics occur exclusively up to the time the transition temperature equals the reaction temperature. At this point the resin begins to solidify and the rate of this process limits the rate of epoxy conversion. A comparison of predicted and actual epoxy conversion is presented for isothermal and temperature‐programmed cure schedules.
Self‐Reinforced melt processible polymer composites: Extrusion, compression, and injection molding
Authors: Isayev A. I. , Modic M. 
Published: May 2005

AbstractRheological properties, extrusion, fiber spinning, compression, and injection molding of blends of polycarbonate and two thermotropic liquid crystal polymers based on wholly aromatic copolyesters have been studied. Blends were prepared using an internal Banbury mixer and static Koch mixer. Based upon differential scanning calorimetry and dynamic mechanical measurements, these blends have been shown to be incompatible in the entire range of concentrations. During extrusion and injection molding at high strain rates, it has been observed that thermotropic liquid crystal polymer at concentrations 2.5, 5, and 10 percent by weight in situ forms high modulus and high strength fibers within the polycarbonate matrix leading to self‐reinforced polymer composites. The tensile strength of the composite containing 10 percent of liquid crystal polymer exceeds that of the pure components. In addition, anisotropy of properties of the injection molded parts has been found to substantially reduce in a comparison with that of liquid crystal polymer. The processing conditions and technique for the production of self‐reinforced polymer composite during processing of the blends have been identified. This has been done by measurements of mechanical properties, direct observation of morphology, and by theoretical calculation using simplified composite theory for the unidirectional continuous fiber‐reinforced composites. At the high concentrations, 25 and 50 percent by weight, thermotropic liquid crystal polymer forms large spherical droplets inside polycarbonate leading to highly brittle material. This is in distinction from the fibrous, high modulus tough composites formed at the lower concentrations.