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  • 1
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dual-in-line packages (DIPs) were formed from epoxy molding compounds with various physical properties using a transfer molding machine. The compounds were prepared by changing kinds and amounts of additives and addition methods. The thermal shock test was carried out by the following procedures. The plastic package was soaked alternately in liquid nitrogen (-196°C) and in liquid solder (250°C) in the cycle of 140 s. The packages were intermittently subjected to optical microscopic inspection for crack initiation. The median life to crack initiation is defined to be the number of the cycles when half of the specimens exhibited crack initiation. Glass transition temperature, coefficient of linear expansion, and flexural modulus were measured to calculate thermal stress in plastic packages. According to the linear fracture mechanics, the following expression was obtained among the median life N, thermal stress σt and strength σb. N =/σ b2 We found the linear relation between logarithm of Nσ b2 and logarithm of σb/σ t for various packages, and obtained that the value of C and m are estimated as 3 × 104 MPa2 and 5.5, respectively. Therefore, the median life can be predicted from the glass transition temperature, coefficient of linear expansion, flexural modulus, and strength of plastic materials for packages.
    Additional Material: 8 Ill.
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  • 2
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 4
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 5
    ISSN: 0021-9304
    Keywords: vancomycin ; fibrin glue ; graft infection ; prevention ; Dacron graft ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We investigated the tissue distribution of vancomycin (VCM) incorporated in fibrin glue (FG) in a rat model. One VCM-loaded FG Dacron graft (VCM-FG, VCM 0.6 mg/graft) was implanted in the subcutaneous tissue of the anterior abdominal wall of each rat. VCM was injected intravenously at an equal dose (0.6 mg/rat) after implantation of one control graft (without VCM-FG). After the implantation and the iv injection of an equal dose of VCM (0.6 mg/rat), the tissue distribution of VCM for up to 24 h was determined through analysis of the implanted VCM-FG grafts, which releasd VCM over a 24 h period. The area under the VCM concentration-time curve (AUC) of the tissue was 89.58 μg·h/g after the implantation of the VCM-FG graft, and 7.40 μg·h/g after the iv injection of VCM, respectively. The targeting index of the tissue, defined as the ratio of AUC after the implantation of the VCM-FG graft to that after VCM iv injection, was 12.11. None of the six VCM-FG Dacron grafts after implantation became infected following inoculation with S. aureus ATCC 25923 (0.1 mL 108 CFU/mL). These results suggest that this VCM-FG Dacron graft delivery may be useful in preventing local infection by enhancing the delivery of VCM to the local areas of the implanted site in rats. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 36, 564-567, 1997.
    Additional Material: 2 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird der Mechanismus der Monomerübertragung bei der kationischen Polymerisation von o- und p-Methoxystyrol untersucht. Zu diesem Zweck wurden die Monomeren bei 30°, 0° und -20 °C mit BF3 · O(C2H5)2 polymerisiert und das Verhältnis der Monomerübertragungskonstanten (ktm/kp) sowie der Einfluß des Lösungsmittels (CCl4, CHCl3, CH2Cl2 und C2H4Cl2) auf ktm/kp bestimmt. Weiterhin wurden o- und p-Methoxystyrol copolymerisiert und der Einfluß der elektrostatischen und sterischen Eigenschaften der Substituenten auf die Monomeriibertragung studiert.Es wurde gefunden, daß das Verhältnis ktm/kp, bei o-Methoxystyrol vom Lösungsmittel unbeeinflußt bleibt, während es bei p-Methoxystyrol mit wachsender Dielektrizitätskon-stante des Lösungsmittels abnimmt, wie es schon bei der Polymerisation von Styrol und Chlorstyrol festgestellt wurdc. Es wurde weiterhin gefunden, daß die Methoxysubstitution des Styrols in p-Stellung den Wachstumsschritt mehr beschleunigt als die Monomerüber-tragung. Bei Substitution in o-Stellung liegen die umgekehrten Verhältnisse vor.Aus diesen Ergebnissen und denen an Styrol und Chlorstyrol kann geschlossen werden, daO die Monomerübertragung bei der Polymerisation von Styrolderivaten über eine Alkylierungsreaktion zwischen dem wachsenden Ionenpaar und der Phenylgruppe im Monomeren läuft.Die Ergebnisse quantenmechanischer Berechnungen des Wachstumsschritts und der Monomerübertragung nach der Molekular- Orbital-Methode sowie UR-Analysen der Endgruppen des resultierenden Polymeren bestatigen den Mechanismus.Es wird ebenfalls die spontane Abbruchsreaktion bei der Polymerisation von Methoxystyrol diskutiert
    Notes: In order to investigate the machanism of the monomer transfer reaction in cationic polymerization, o- and p-methoxystyrene were polymerized by BF3 et2O at 30°, 0° and -20 °C. to estimate monomer transfer constant ratio, and the effects of solvents (CCl4, CHCl3, CH2Cl2 and C2H4Cl2) were studied. Considering the experimental results in copolymerizations of styrene with o- and p-methoxystyrene together, the electrostatic and steric effect of the substituent on the monomer transfer reaction were investigated.It was found that the nature of the solvent did not affect ktm/kp of o-methoxystyrene, but that ktm/kp of p-methoxystyrene decreased with increasing dielectric constant of the solvent as was found in the polymerization of styrene and chlorostyrenes. It was also found that methoxy substitution at para-position of styrene increased the activity of styrene in the propagation reaction more than in the monomer transfer reaction, but that methoxy substitution at ortho-position of styrene increased the activity of styrene in the monomer transfer reaction more than in the propagation reaction.From these results and by considering the results on styrerne and chlorostyrenes, it was conceivable that the monomer transfer reaction in the polymerization of styrene derivatives proceeds through an alkylation reaction between the growing ion-pair and the phenyl group in the monomer.The results of the molecular orbital calculation on the propagation and the monomer transfer reaction of methoxystyrenes and the infrared analysis of the end group of the resultant polymers supported the mechanism.The spontaneous termination reaction in the polymerization of methoxystyrenes is discussed, too.
    Additional Material: 8 Ill.
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  • 7
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The temperature dependence of the electrical conductivity, σ, for a collagen solution was measured in the temperature region including the thermal denaturation temperature, td. The σ increased with temperature, t, but decreased at ca. 40°C, and then again increased. In this temperature region, a change of optical rotation, αD, was observed. The change is due to the thermal denaturation. The differential curve of σ vs. t gave clear deflection points and a large peak at ca. 40°C. The td could be estimated from the peak temperature. The td decreased with the increase in the concentration of collagen and with the decrease in the heating rate. These measurements were carried out for the collagen prepared by various methods. Some of them showed one peak; others had two peaks. The td obtained by the measurement of σ correlated with that obtained by the measurement of αD. The activation energy of σ, ΔEa, obtained from the linear relationship between log σ and 1/T, increased with the concentration of collagen, but was unchanged for the heating rate. The ΔEa obtained for various types of collagen showed a constant value. © 1993 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 8
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The temperature dependence of the pH for an acid-soluble collagen in solution was measured, so that the pH largely increased in the temperature region including ca. 40°C of the thermal denaturation temperature. As the changes of the optical rotation, αD, and the electrical conductivity, σ, were observed in this temperature region, the change of the pH is due to the thermal denaturation of collagen. The differential curve of pH vs. t gave clear deflection points and a large peak at ca. 40°C. The thermal denaturation temperature, td, could be estimated from the peak temperature. The td obtained by the measurement of the αD, tdαD, decreased with the decrease in the heating rate and with the increase in the concentration of collagen. However, the td obtained through the measurement of the pH, tdpH, was independent of the variations of the heating rate and the concentration of collagen. These measurements were carried out for different kinds of collagens prepared by various methods. Some of them had one kind of peak; others had two kinds of peaks. The tdpH correlated with the tdαD for different kinds of collagen preparations. Therefore, the measurement of the temperature dependence of the pH was useful for the determination of the td. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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