Polymer membranes in medicine

Mass transfer within the human body primarily occurs across biological membranes. Medicine mimics nature and uses synthetic membranes for therapeutic purposes. The state of the art of polymer membrane applications in medicine is reviewed. The target for membrane material developments is mainly the improvement of the patients' safety and convenience. To provide optimal blood compatibility a new biocompatible polymer for hemodialysis membranes has been developed in our group: a polycarbonate with polyether blocks. The copolymer is suitable for production of membranes with excellent performance. In addition to therapeutic purposes polymer membranes can provide diagnostic functions. Recently a blood glucose test strip based on a synthetic membrane has been developed. The membrane separates off the erythrocytes and contains enzymes and reagents. It enables the diabetic a precise and convenient measurement.     

EARLY CELL KINETIC EFECTS OF A SINGLE DOSE OF NARROW-BANDED ULTRAVIOLET B IRRADIATION ON THE RAT CORNEAL EPITHELUM

Abstract— The right eyes of 40 rats were exposed to a signal erythemogenic dose fo ultraviolet B irradiation (UVB) at 297nm. The irradiation was directed perpenddicualr to the center of the cornea. The left eyes served as controls. The animals were randomly assigned into 10 groups. The labelling index (LI) after pluse labeling the tritiated thymidine and the mitotic rate (MR) after Colcemid administration were registered in the corneal epithelium at predetermined intervals up to 96 h after the irradiation. A mathematical method was used to corealted corresponding corneal areas from the different animals. In the central the LI was considerably reduced up to 36h after the irradiation. The LI increased toward the peripheral cornea and reached normal values at the limbal area. The MR was also reduced up to 36h. However, this reduction was over the entire epithelium. The block in cell proliferation was followed by increased proliferation.     

Simulation and Experiment in X-ray Topography and Diffractometry

X-ray double crystal topography and high resolution diffractometry reveal very small deformations of the crystal lattice. However, this information can be directly obtained from the topographs or diffractometer curves only if certain conditions are fulfilled. Generally a deformation model has to be used, that is compared to the measurements by simulation calculations based on the dynamical diffraction theory. Trial and error allow to adapt the parameters of the model. An example illustrates that with a few parameters an automatic fit is possible.     

Polymerforschung und -technologie im Iran

Im Laufe der letzten Jahre wurden - von den meisten westlichen Fachkollegen unbemerkt - an mehreren iranischen Universitäten und Forschungsinstituten Abteilungen eingerichtet, die sich in Forschung und Lehre mit Chemie, Physik, Anwendungs- und Verfahrenstechnik der Polymere beschäftigen. Das 1986 gegründete Polymer Research Center of Iran organisierte im Mai dieses Jahres das 1. Internationale Seminar.     

General Method to Increase Carboxylic Acid Content on Nanodiamonds

Carboxylic acid is a commonly utilized functional group for covalent surface conjugation of carbon nanoparticles that is typically generated by acid oxidation. However, acid oxidation generates additional oxygen containing groups, including epoxides, ketones, aldehydes, lactones, and alcohols. We present a method to specifically enrich the carboxylic acid content on fluorescent nanodiamond (FND) surfaces. Lithium aluminum hydride is used to reduce oxygen containing surface groups to alcohols. The alcohols are then converted to carboxylic acids through a rhodium (II) acetate catalyzed carbene insertion reaction with tert–butyl diazoacetate and subsequent ester cleavage with trifluoroacetic acid. This carboxylic acid enrichment process significantly enhanced nanodiamond homogeneity and improved the efficiency of functionalizing the FND surface. Biotin functionalized fluorescent nanodiamonds were demonstrated to be robust and stable single-molecule fluorescence and optical trapping probes.     

Study of sintering processes in copper and nickel by positron annihilation

In the advanced stage of non-isothermal sintering, vacancy clusters are present as prevailing type of defects. Their concentration considerably decreases at further temperature increase, and it can be concluded that thermally activated conversion of multiple vacancies into climbable dislocations takes place. Hence, in conformity with recent experiments, coincidence of intensive material transport ($ \dot \varepsilon $ e-maximum) and decrease of defect concentration (recovery) can be understood.     

Ultrasonic measurement technique to study thermometric effects in glass

Ultrasonic measurements of shear wave propagation in alkali containing glasses reveal temporal instabilities and thermal after-effects which parallel thermometric effects, the secular rise and zero point depression in the ice point of glass thermometers. The ultrasonic method of observing these effects has advantages over the thermometric technique. Sound velocity is a dynamic quantity proportional to the elastic moduli and density which can be measured on an absolute basis and over a frequency range if desired. Thus in measuring instabilities in the elastic properties of glass the ultrasonic method provides additional information over the use of the thermometric technique whose measured changes relate only to density changes in the glass and only on a relative basis. In addition sound velocity can be measured over as wide a temperature range as desired extending from cryogenic to above glass transition range temperatures. Also no fixed reference points are required as with thermometers. Sample preparation is relatively simple and the availability of ‘packaged’ ultrasonic measurement facilities makes this method of measuring very small changes (ppm) in elastic properties very attractive.Data as a function of time and temperature are presented for a series of alkali-lead-silicates incorporating separately Li, Na, K, Rb, Cs, and for a lead silicate containing the alkaline earth Ba. The results indicate the reversible nature of the instabilities and after-effects and express their magnitudes and sensitivities to the temperature and temperature interval of measurement. They are also related to the thermal history of the glass, and the concentration and species of the incorporated alkali.