bluuebunny/crossref_metadata_2025_split huggingface dataset:
Verfestigung und Verschleißverhalten von weißen Gußeisen bei abrasiver Beanspruchung
Authors: Al‐Rubaie K. S. , Pohl M. 
Published: December 2004

AbstractWeiße Gußeisen werden häufig dort eingesetzt, wo starke abrasive Belastung auftritt. Die Mikrostruktur und die mechanischen Eigenschaften dieser Legierungen spielen eine wesentliche Rolle, um die durch Verschleiß verursachten Verluste zu kontrollieren. Hinsichtlich der mechanischen Eigenschaften wird in zahlreichen Veröffentlichungen berichtet, daß die Werkstoffhärte allein das Verschleißverhalten nicht bestimmt. Dabei gilt allgemein, daß die während des Verschleißvorganges entstehende Verfestigung den Verschleißwiderstand wesentlich beeinflußt.In der vorliegenden Arbeit werden Ni‐Hard 4 und hochchromhaltige weiße Gußeisen bezüglich ihres Verschleißverhaltens anhand eines Schleifpapierverfahrens untersucht. Die Ergebnisse dieser Untersuchungen tragen u.a. zur Klärung der Korrelations mechanismen zwischen Oberflächenverfestigung und abrasivem Verschleißverhalten bei.
Einfluß des ZrO2‐Zusatzes auf mechanische Eigenschaften und den ungeschmierten Gleitverschleiß von TiB2‐ZrO2‐Mischkeramiken
Authors: Schneider J. , Zum Gahr K.‐H. , Müller R. , Franz E. ‐D. 
Published: December 2004

AbstractTiB2‐ZrO2‐Mischkeramiken wurden durch Heißpressen hergestellt und mechanische sowie tribologische Eigenschaften in Abhängigkeit vom Volumenanteil und der Modifikation des zugegebenen ZrO2 bestimmt. Durch die Zugabe von ZrO2 konnte die zum Erreichen hoher Enddichten notwendige Preßtemperatur auf 1500°C gesenkt und das Kornwachstum des TiB2 verhindert werden. Die Mischkeramiken wiesen gegenüber reiner TiB2‐Keramik, bei einer reduzierten Härte, höhere Festigkeiten und Bruchzähigkeiten auf. Die tribologischen Untersuchungen wurden unter ungeschmierter, reversierender Gleitbeanspruchung in Paarung mit Al2O3‐, Si3N4‐ und SiC‐Gegenkörpern sowie unter Furchungsbeanspruchung durch SiC‐Abrasivpartikel durchgeführt. Im Gleitkontakt zeigten die Mischkeramiken einen hohen Verschleißwiderstand, führten jedoch zu einem starken Verschleiß der keramischen Gegenkörper und hohen Reibungszahlen verglichen mit selbstgepaarten, monolithischen Al2O3‐ und ZrO2‐Keramiken. Unter Furchungsbeanspruchung durch SiC‐Abrasivpartikel lag der Verschleißwiderstand der TiB2‐ZrO2‐Keramiken um einen Faktor biszu 30 höher als der monolithischer Al2O3‐Keramik. Der Verschleißwiderstand der TiB2‐ZrO2‐Kermiken nahm mit abnehmendem ZrO2‐Anteil zu und erreichte bei den mit teilstabilisiertem, tetragonalem ZrO2 höhere Werte als bei den mit unstabilisiertem, monoklinen ZrO2 hergestellten Mischkeramiken.
Adiabatic flow curves of metallic materials at high strain rates
Authors: El‐Magd E. , Scholles H. , Weisshaupt H. 
Published: December 2004

AbstractDynamic compression tests are carried out on Armco iron, Cr‐V‐steel, Ni‐Cr‐Mo‐V‐steel, an austenitic Ni‐Cr‐Mo‐steel, tantalum, nickel and Ni3Al and magnesium. The flow curves are analysed to determine the influence of the deformation energy which is tranformed into heat on the flow behaviour and mechancial stability. Not only the material properties but also the conditions of friction between the specimen and the compression tool are found to have a greate influence on the flow stress reduction and stability. High frictional forces promote mechanical instability of materials with low strain hardening and low strain rate sensitivity.
Einfluß Von Mittelbeanspruchungen auf das Wechselverformungsverhalten and die verformungsinduzierte Martensitbildung des Stahls X6CrNiTi1810
Authors: Nebel Th. , Walther F. , Bassler H.‐J. , Eifler D. 
Published: December 2004

AbstractAnhand von einstufigen spannungs‐ und totaldehnungskontrollierten Versuchen werden Zusammenhänge zwischen dem zyklischen Verformungsverhalten und der verformungsinduzierten Martensitbildung des metastabilen austenitischen Stahls X6CrNiTi1810 (Werkstoff‐Nr. 1.4541) bei Raumtemperatur und T = 300°C untersucht. Besondere Beachtung findet hierbei der Einfluß von Mittelbeanspruchungen. Alle Versuche wurden mit einem dreieckförmigen Beanspruchung‐Zeit‐Verlauf und einer Frequenz von 5 Hz durchgeführt. Zur Charakterisierung des Wechselverformungsverhaltens dient neben den aus σ‐Hysteresen ermittelten mechanischen Kennwerten, der on‐line mittels eines Wirbelstromsensors gemessene magnetische Phasenanteil. Ausgewählte Versuchsergebnisse werden vorgestellt und diskutiert.
Swallowing abnormalities and dyskinesia in Parkinson's disease
Authors: Monte Francisca Sueli , da Silva‐Júnior Francisco Pereira , Braga‐Neto Pedro , Nobre e Souza Miguel Ângelo , Sales de Bruin Veralice Meireles 
Published: December 2004

AbstractGastrointestinal abnormalities in Parkinson's disease (PD) have been known for almost two centuries, but many aspects concerning their pathophysiology have not been completely clarified. The aim of this study was to characterize the oropharyngeal dynamics in PD patients with and without levodopa‐induced dyskinesia. Fifteen dyskinetic, 12 nondyskinetic patients, and a control group were included. Patients were asked about dysphagia and evaluated with the Unified Parkinson's Disease Rating Scale Parts II and III and the Hoehn and Yahr scale. Deglutition was assessed using modified barium swallow with videofluoroscopy. Nondyskinetic patients, but not the dyskinetic ones, showed less oropharyngeal swallowing efficiency (OPSE) for liquid food than controls (Dunnett, P = 0.02). Dyskinetic patients tended to have a greater OPSE than nondyskinetic (Dunnett, P = 0.06). Patients who were using a higher dose of levodopa had a greater OPSE and a trend toward a smaller oral transit time (Pearson's correlation, P = 0.01 and 0.08, respectively). Neither the report of dysphagia nor any of the PD severity parameters correlated to the videofluoroscopic variables. In the current study, dyskinetic patients performed better in swallowing function, which could be explained on the basis of a greater levodopa dose. Our results suggest a role for levodopa in the oral phase of deglutition and confirm that dysphagia is not a good predictor of deglutition alterations in PD. © 2004 Movement Disorder Society
Determination of Na+ binding parameters by relaxation analysis of selected 23Na NMR coherences: RNA, BSA and SDS
Authors: Torres Allan M. , Philp David J. , Kemp‐Harper Richard , Garvey Chris , Kuchel Philip W. 
Published: December 2004

AbstractNuclear magnetic resonance provides several unique means of investigating the interactions between different inorganic ions and various macromolecules. 23Na is a quadrupolar nucleus, meaning that relaxation analysis of the various coherences allows the measurement of its binding to biological macromolecules. In this study, we analyzed the quadrupolar relaxation of 23Na+ longitudinal magnetization and single‐ and triple‐quantum coherences in aqueous systems containing RNA, bovine serum albumin and sodium dodecyl sulfate micelles. The effectiveness of the James–Noggle method for determining binding constants was evaluated in these systems, and also the applicability of various 23Na coherences in providing information on the extent and affinity of binding to the three different classes of biomolecules. Copyright © 2004 John Wiley & Sons, Ltd.
Vitellogenesis in the red crab Charybdis feriatus: Hepatopancreas‐specific expression and farnesoic acid stimulation of vitellogenin gene expression
Authors: Mak Abby Sin Chi , Choi Chi Lung , Tiu Shirley Hiu Kwan , Hui Jerome Ho Lam , He Jian‐Guo , Tobe Stephen S. , Chan Siu‐Ming 
Published: December 2004

AbstractVitellogenesis in the mature female crab Charybdis feriatus occurs all year round during which active synthesis of the vitellogenin (Vg) precursor occurs. Several polypeptides from the ovaries were shown to be immuno‐reactive to the shrimp vitellin (Vn) antibody. N‐terminal amino acid sequence determination revealed that several ovarian polypeptides and one polypeptide secreted by the hepatopancreas were identical to part of the C. feriatus Vg (CfVg) precursor. The full‐length cDNA sequence encoding a protein with high amino acid sequence similarity to the Vg of the shrimp Metapenaeus ensis was cloned. In common with the shrimp M. ensis MeVg2, the crab vitellogenin gene is expressed only in the hepatopancreas. The expression level of CfVg is undetectable in the non‐reproductive females, increases to maximum at the middle stages of vitellogenesis and drops to a lower level in late vitellogenesis. Expression of CfVg also extended to females that are undergoing brooding of developing larvae. Although the 8 kb transcript for the full‐length cDNA was detected, smaller transcripts specific to CfVg mRNA were also detected, suggesting the occurrence of alternative splicing/expression of the CgVg gene to produce the smaller transcripts. Using a short term in vitro hepatopancreas explant culture assay, we have demonstrated that low concentrations of farnesoic acid (FA) stimulate CfVg gene expression in the hepatopancreas. Although both methyl farnesoate (MF) and juvenile hormone III also caused up‐regulation of the CfVg gene, their effects are only significant at much higher concentrations. Mol. Reprod. Dev. 70: 288–300, 2005. © 2005 Wiley‐Liss, Inc.
Expression patterns of initiator and effector caspases in denervated human skeletal muscle
Authors: Tews Dominique S. , Behrhof Wera , Schindler Susanne 
Published: December 2004

AbstractThere is evidence that apoptotic cell death contributes to the loss of denervated muscle fibers. In 17 patients with neurogenic muscular atrophy, we studied the expression of the apoptosis mediators APAF‐1/caspase‐9 and degrading caspases‐2, ‐3, and ‐7 by immunohistochemical and western blot analyses. Muscle with neurogenic atrophy showed distinct upregulation of caspase‐9 and ‐7 and no expression for APAF‐1 (apoptosis protease‐activating factor‐1) and caspase‐2 and ‐3. Expression of caspase‐7 was restricted to atrophic fibers, but caspase‐9 was also found in normal‐sized muscle fibers where its expression was often confined to single fiber segments. These findings indicate that upregulated expression of caspase‐9 can initiate the proteolytic cascade involving the downstream executioner caspase‐7, which mediates degradation of denervated muscle fibers. However, apoptotic events may be restricted to single muscle‐fiber segments, where apoptotic cell degradation contributes to the long‐term process of atrophy. Pharmacological inhibition of caspases may be a therapeutic strategy in diminishing muscle atrophy. Muscle Nerve, 2005
In situ polymerization of thermoplastic composites based on cyclic oligomers
Authors: Parton Hilde , Verpoest Ignaas 
Published: December 2004

AbstractThe high melt viscosity of thermoplastics is the main issue when producing continuously reinforced thermoplastic composites. For this reason, production methods for thermoplastic and thermoset composites differ substantially. Lowering the viscosity of thermoplastics to a value below 1 Pa.s enables the use of thermoset production methods such as resin transfer molding (RTM). In order to achieve these low viscosities, a low viscous mixture of prepolymers and catalyst can be infused into a mold where the polymerization reaction takes place. Only a limited number of polymerization reactions are compatible with a closed mold process. These polymerization reactions proceed rapidly compared to the curing reaction of thermosets used in RTM. Therefore, the processing window is narrow, and managing the processing parameters is crucial. This paper describes the production and properties of a glass fiber reinforced polyester produced from cyclic oligoesters. POLYM. COMPOS., 26:60–65, 2005. © 2004 Society of Plastics Engineers
Dynamic mechanical characterization of cure of a polyimide‐graphite fiber composite (PMR 15/Celion 6000)
Authors: Hurwitz F. I. 
Published: December 2004

AbstractDynamic mechanical studies of thermosetting PMR 15 polyimide/Celion 6000 composites were used to characterize cure behavior. Variation in composite shear modules with cure time for laminates partially cured under 3.45 MPa pressure was compared with that of laminates fully cured under pressure to select a partially cured system whose behavior corresponded with that of the pressure‐cured composites. An empirical kinetic model was developed that relates relative composite shear moduli to cure time and temperature. This model, coupled with standard statistical techniques, was used in the determination of an overall activation energy, E = 145 kj/mole (35 kcal/mole) and order of reaction, n, for the cure reaction(s). The empirical relationship defining dynamic modulus as a function of time and temperature remained linear well into the glassy region. Changes in dynamic glass‐transition temperature and breadth of the transition peaks with cure time are discussed. Shear modulus and damping were found to be more sensitive measures of relative extent of cure than Fourier transform infrared spectroscopy.
Dynamic‐mechancial response of graphita/epoxy composite laminates and neat resin
Authors: Yang P. , Carlsson L. , Sternstein S. S. 
Published: December 2004

AbstractThe dynamic mechanical properties of carbon‐fiber‐reinforced, epoxy‐matric‐composite laminates subjected to loading perpendicular to the plane of lamination and of neat epoxy resin are reported. The dynamic mechanical measurements were performed in the frequency range from 0.1 to 40 Hz and at temperatures between 20° and 200°C at deformation levels within the linear viscoelastic region by the use of a Dynastat apparatus. It is found that thein‐phase and out‐of phase stiffnesses superpose to form master curves covering a frequency range of 12 decades. By a suitable scaling procedure of the master curves, it is found that thein‐phase stiffiness has tbe same shape and the out‐of‐phase stiffness has the same dispersion for all laminates irrespective of the stacking sequence and are nearly identical to those for neat epoxy resin, An empirical function for the relaxation modulus is developed that, when converted to dynamic modulus, gives a good overall agreement for both components of the dynamic stiffness as a function of frequency. Absorbed moisture is found to cause a reduction in thhe elevated temperature mechanical properties of a laminate due to a reduction in the glass‐transition temperature of the resin. It is also found thatthemositure absorption is a reversible process, in the sense that the initially dry properties of the laminate are recovered afterredrying the wet sample.
Synthesis and characterization of free radical cured Bis‐methacryloxy bisphenol‐A epoxy networks
Authors: Yilgör I. , Yilgör E. , Banthia A. K. , Wilkes G. L. , McGrath J. E. 
Published: December 2004

AbstractSynthesis and free‐radical curing reaction of the bisglycidylmethacrylate of bisphenol‐A (Bis‐GMA) were investigated. Bis‐GMA resin was synthesized by reacting Epon 825 with methacrylie acid, followed by characterization using IR and NMR spectroscopy. Various modifiers having reactive double bonds were co‐cured with the methacryloxy resins using a free‐radical initiator. The networks obtained were compared with a cycloaliphatic amine‐cured epoxy network. Thermal characterization shows that methacryloxy‐cured systems are more resistant to mechanical penetration and have higher glass‐transition temperatures and better stability with regard to thermal decomposition as compared with the conventional diamine‐cured epoxy networks. Dynamic mechanical experiments and stress‐strain tests also indicate that Bis‐GMA based networks have higher tensile moduli and lower elongation at break. Using different modifiers such as 2‐ethylhexyl acrylate, the tensile and impact properties of the networks can be improved.
Epitaxial crystallization of nylon 6 cast from solution on the surface of poly(p‐phenylene terephthalamide) filament
Authors: Kumamaru F. , Oono T. , Kajiyama T. , Suehiro K. , Takayanagi M. 
Published: December 2004

AbstractPoly(p‐phenylene terephthalamide) (PPTA) fiber has the characteristics of high modulus and strength, and has been employed as the reinforcement in composite materials. The interfacial interaction between the PPTA filament and nylon 6 matrix has been investigated to make use of these characteristics of PPTA in fiber‐reinforced composite systems. In the case of composites composed of the PPTA filament and nylon 6, two types of expitaxial crystallization have been observed depending on the concentration of a formic acid solution. From concentrated solution, nylon 6 forms a columnar cystal around the PPTA filament. A two‐dimensional spherulite model, (i.e., a disk shape) is proposed for the aggregated structure of nylon 6 chains on the basis of wide‐angles x‐ray diffraction, small‐angle x‐ray scattering studies, and scanning electron microscopic ebservation. The a*‐axis of the nylon 6 crystal is directed radially in its columnar crystal. In the inner portion, close to the interface, the be‐plane is in contact with the surface of the PPTA filament, also, the directions of the b‐ and c‐axes are paral el and perpendicular to the PPTA filament axis, respectively. On the other hand, their axes rotate about the a*‐axis in the outer portion, far from the interface region. Furthermore, a different type of epitaxy was observed in the case of crystallization from a dilute solution of nylon 6 in formic acid. These two types of crystal growth were investigated from the view of crystallization condition and crystallographic lattice matching at the interface region between the PPTA filament a nylon 6. It is concluded that the hydrogen bonding between PPTA and nylon 6 molecules at the interface plays an important role for epitaxial crystallization, in addition to lattice matching.
Mechanical degradation of mica during processing with polypropylene
Authors: Fisa B. , Sanschagrin B. , Favis B. 
Published: December 2004

AbstractMechanical degradation of reinforcing fillers during processing is a problem that has been seldom studied due to a lack of particle size determination techniques. Using phlogopite mica as an example, a method allowing a rapid and accurate characterization of flake size and aspect ratio will be described. The influence of several parameters on the mechanical degradation of mica flakes in a mica/polypropylene system has been studied using a laboratory roller blade mixer. The degradation was found to occur in two stages. The first stage takes place immediately after the addition of mica, where the average flake size decreases very rapidly by as much as 20 percent. In the second stage, the particle size remains essentially constant with the time of mixing at low concentrations (2 percent wt); at higher concentrations (40 percent wt) there is a slow reduction in the flake size. The influence of other parameters such as system viscosity, mode of mica addition, silane treatment, and the initial particle size is also discussed.
Elongational behavior of short glass fiber reinforced polypropylene melts
Authors: Kamal M. R. , Mutel A. T. , Utracki L. A. 
Published: December 2004

AbstractThe Rheometrics Elongational Rheometer was employed to study the uniaxial extensional flow of glass fiber filled polypropylene melts, in which the fiber concentration, c, varied between zero and 40 weight percent. The constant strain rate mode was used for strain rates, \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \varepsilon \limits^. $\end{document}, between 0.003 and 0.6 s−1. Steady state elongational viscosities were observed in most cases for fiber filled polypropylene melts, even at rates at which the stress continued to increase for unfilled polypropylene. The rate of relative stress growth increased with \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \varepsilon \limits^. $\end{document} and was affected by the addition of fibers. The steady elongational viscosity of the fiber reinforced melts was found to decrease with increasing \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \varepsilon \limits^. $\end{document} and to increase with increasing c. Yield stresses were observed in elongational flow at high concentrations, although there was no clear evidence of yield in steady shear.
Evidence of interaction of fillers with matrix polymers via transition maps
Authors: Beatty Charles L. 
Published: December 2004

AbstractSurface modifications of fillers can be detected via dielectric relaxation spectroscopy with surface coatings that interact with the matrix polymer resulting in higher glass transition temperatures of the matrix polymer. Increasing the surface area of filler present by increasing the amount of filler systematically shifts the glass transition temperature of the matrix polymer to higher values. Increasing the surface area of the filler by making the surface microporous improves many mechanical properties but may not immobilize as many matrix polymer molecules if a weak boundary layer is present.
Structural changes of chlorinated paraffins at processing conditions of particulate filled polypropylene
Authors: Ishida Hatsuo , Huang Zhen‐Hua 
Published: December 2004

AbstractStructural changes of chlorinated paraffin (CP) have been studied using UV‐visible absorption spectroscopy in the 180 to 220°C temperature range. Formation and further reaction of conjugated polyene sequence with and without MgO is of major concern. It was found that CP dehydrochlorinated at normal processing temperatures of polypropylene in the absence of MgO. A mixture of various polyene sequences was formed. Unlike a stabilizing effect on poly(vinyl chloride), MgO showed a catalytic effect for dehydrochlorination of CP. As a result, longer conjugation was formed with MgO at the same conditions except for the absence of MgO. The longer polyenes were selectively reacted at the conditions studied. A possible chemical bond formation at the particulate filler/polypropylene matrix interface was suggested as one of the reinforcement mechanisms of the composite.
Thermally conductive polymer compositions
Authors: Bigg D. M. 
Published: December 2004

AbstractWhile polymers are widely used for their excellent insulating properties, there is a growing need for thermally conductive polymer compounds. The thermal conductivity of metal particle, mineral particle, and carbon fiber filled compounds are examined at volume concentrations up to the maximum packing fraction of each filler. From these data the coefficients in Nielsen's model were determined for each type of filler. Gaps in available thermal conductivity data were then predicted using these coefficients, the properties of the polymer and filler, and the volume concentration of the filler. Gaps were found to exist mostly for compounds containing short fiber reinforced compounds. A comparison of predicted values of thermal conductivity for such systems with the sparse data available shows that Nielsen's model cannot be applied to highly filled fiber reinforced composites because it cannot account for the anisotropy of such compositions.
Tensile behavior of clay‐filled polyester composites
Authors: Newaz Golam M. 
Published: December 2004

AbstractIn this study, the tensile behavior of clay‐filled unsaturated orthophthalic polyester composites was evaluated. Specifically, ultimate strength, yield strength, fracture strain, and Young's modulus of two composites with small but varying fractions of clay particulates were determined. Several predictive approaches were considered for correlation with experimental values. Only the Young's modulus of the composites could be predicted satisfactorily. The irregular shape and size distribution of clay particulates seriously complicate attempts to analytically model the mechanical behavior of filled composites. Microcracking response of the composites was evaluated using an acoustic emission (AE) technique. The addition of clay is shown to embrittle the composites and is confirmed by the AE count rate and amplitude distribution data. Scanning electron microscopy of the fracture surface shows evidence of flaw initiated fracture. This study provides an insight into the influence of clay particulates in altering the properties of a polyester matrix.