Phänomenologische Untersuchungen zur Mischbarkeit von Polymeren

The compatibility of styrene-acrylonitrile (SAN)-copolymers with polymethylmethacrylate was investigated by means of optical methods, of electron microscopy and of torsion pendulum measurements. SAN-copolymers are compatible with polymethylmethacrylate in the range of 9 to 27 wt.-% of acrylonitrile. The comparison of the solubility parameter δ shows, that one cannot predict exactly the compatibility of polymers. However, a necessary but not sufficient condition seems to be      

The quality of life after the implantation of a cardioverter/defibrillator in malignant arrhythmias

Quality of life after implantation of an automatic implantable cardioverter/defibrillator (ICD) was assessed by questionnaire in 43 patients (38 males, 5 females; mean age 57 +/- 16 years) with treatment-resistant symptomatic ventricular arrhythmias. 37 of the 43 patients felt better after ICD implantation. 23 were always conscious of having an ICD, but 18 had got used to it in less than 2 months. 15 patients reported being afraid of an ICD shock, while eight noted physical discomfort caused by the ICD. Limitations concerning their professional, recreational and social activities were reported by six patients. 41 of the 43 patients confirmed that the ICD had been helpful, enabling 23 to return to an active life. 42 would recommend implantation to others if indicated. These data demonstrate that there is a remarkably high degree of acceptance of the ICD. Survival rate after implantation is thus not the only criterion of success. All aspects of the quality of life should be taken into consideration before implantation is decided upon.     

Molecular Conformation and Applicaton of Stereoregular PMMA Langmuir-Blodgett Films

Molecular conformations of stereoregular poly(methyl methacrylate) (PMMA) monolayers have been investigated by scanning probe microscopes. Isotactic and syndiotactic PMMAs were found to have right and left hand helical structures, respectively. On the contrary atactic PMMA showed rather random arrangement of the chains. It has been demonstrated that the PMMA Langmuir-Blodgett(LB) films can be utilized to form nanoscale patterns down to 50 nm and to form a geodesic lens. It has also been manifested that the quantum efficiency of a polymer electroluminescent device can be significantly enhanced by inserting the PMMA LB films between the emitting layer and the cathode. All the applications utilize the unique characteristics of the LB films to form thin and uniform films in the molecular level.     

Platelets interact with soluble and insoluble collagens through characteristically different reactions

Platelet interaction with soluble and insoluble collagens was characterized through binding studies. In contrast to resting platelets, cells reacted with activators, TS2/16 (integrin alpha2 beta1-activating antibody), thrombin, collagen-related peptide, or ADP, exhibited specific soluble collagen binding that is Mg2+-dependent, but inhibited by prostaglandin I2, Ca2+, and Gi9 (anti-integrin alpha2 beta1 antibody). Each platelet has 1500-3500 soluble collagen binding sites, with a dissociation constant of 3. 5-9 x 10(-8) M. This is the first study to show the specific binding of soluble collagen to platelets; our data strongly suggest that the receptor is integrin alpha2 beta1 after it becomes activated upon platelet activation. These results suggest that activation of platelets transforms integrin alpha2 beta1 to a state with higher affinity binding sites for soluble collagen. The soluble collagen-platelet interaction was compared with the platelet interaction with fibrillar collagen, which has until now not been demonstrated to bind specifically to platelets. Here, we demonstrated specific, biphasic fibrillar collagen binding. One phase is rapid and metal ion-independent, and accounts for most of the binding. The other phase is slow and Mg2+-dependent. The characteristic differences in the specific bindings of soluble and fibrous collagens demonstrate the different contributions of two different collagen receptors.     

Multiple phosphorylation of chicken protein tyrosine phosphatase 1 and human protein tyrosine phosphatase 1B by casein kinase II and p60c-src in vitro

The objectives of this study were to evaluate milk choline as an indicator of choline absorption and to use milk choline to evaluate the efficacy of a rumen-protected choline supplement. In a preliminary 4-wk experiment, two Holstein cows in early lactation were abomasally infused with either 0 or 60 g/d of choline chloride in 2 L of water, which was used as a carrier. Choline infusion increased milk choline secretion from 1.95 to 3.95 g/d during the 2-wk choline infusion period. In Experiment 2, four Holstein cows in early lactation were abomasally infused with 0, 25, 50, and 75 g/d of choline chloride in 2 L of water using a 4 x 4 Latin square design with 1-wk experimental periods. Milk choline secretion was 2.56, 3.62, 3.72, and 3.82 g/d for the respective choline treatments. In Experiment 3, 10 Holstein cows in midlactation were fed either 0 or 50 g/d of choline using an experimental rumen-protected choline supplement during a 2-wk experiment. Milk choline secretion was increased from 2.12 to 2.99 g/d with the supplemental choline. Results of these experiments demonstrated that milk choline is responsive to postruminal choline supply and can be used as a qualitative indicator of choline absorption.     

Texturvererbung und Transformation aus der austenitischen in die martensitische Phase bei streckbelasteten 18/8 CrNi-Rundstählen

Fasertexturen – Blechtexturen. Transformationsmechanismen fcc – hcp – bcc. Selektion der Gleit- und Scherrichtungen durch Textur und Zugspannung. Texturmessung mit Neutronenbeugung. Rekonstruktion der gemessenen bcc-Texturverteilung als Vererbung aus der fcc-Phase bei gleichzeitiger Verkippung der neugebildeten bcc-Kristallite durch weitere Verformung. Gemisch aus Nishiyama-Wasserman- und Kurdjumov-Sachs-Transformation mit jeweils zwei erlaubten Gleit- und Scherrichtungen.     

Über die Bestimmung minimaler Wege und Gerüste in Graphen

An algorithm (M) for the determination of minimal paths and spanning trees in graphs with weighted edges is described. (M) produces a connection between some known constructions.     

Chain length effect of alkenyl succinic anhydride on thermal and mechanical properties of the cured epoxy resins

As epoxy curing agents three alkenyl succinic anhydrides (ASA) with varying side chain length (2-octenyl, 2-dodecenyl and 2-hexadecenyl succinic anhydride) were prepared by the ene synthesis and thermal and mechanical properties of a bisphenol A epoxy resin cured with the ASA's were measured. With increase in the side chain length of the ASA the Tg, the tensile strength and the impact strength decreased. All the cured samples exhibited excellent transparency and flexibility.