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921.
Organoclays can be prepared by modification of the surface with a cationic surface active compound and used for the immobilisation or separation of non-polar contaminants from polluted waters. In this work pumice is used instead of clay material. Batch system experiments were performed for the modification of pumice surface with hexadecyltrimethylammonium bromide. Modification of pumice and then the sorption of pesticide, Fenvalerate, from water have been traced by FT-IR spectroscopy. 相似文献
922.
Zusammenfassung Es werden Messungen des dielektrischen Verlustes tan im Temperaturbereich von 1 bis 80 °K und bei verschiedenen Frequenzen zwischen 10 Hz und 10 kHz an einer Reihe von Polymeren mitgeteilt.Der dielektrische Verlust sinkt im allgemeinen mit Annäherung an den absoluten Nullpunkt monoton ab. Es scheint dies anzudeuten, daß immer ein dielektrischer Untergrund, beruhend auf allgemeinen thermischen Fluktuationen, existiert, der im übrigen für Polymere mit polaren Gruppen höher liegt als für unpolar gebaute. Zu tiefsten Temperaturen hin überlagert sich diesem allgemeinen Trend oft noch ein Maximum, wenngleich bei Temperaturen bis 1 °K herab zuweilen nur erst in einer Konstanz der Verlustwinkel-Werte angedeutet. Es sieht also so aus, als ob auch noch bei tiefsten Temperaturen singuläre Relaxationsmechanismen eine Rolle spielen können. In einer Reihe von Fällen findet man weitere Relaxationsprozesse zwischen 15 und 40 °K.Soweit sich Aktivierungsgrößen aus der Auftragung der Maximallage in der Temperatur mit der Frequenz nach Abtrennung des allgemeinen Untergrundes abschätzen lassen, werden diese mit sinkender Temperaturlage immer kleiner.Die dielektrischen Verluste sind in allen Fällenextrem abhängig von der Vorgeschichte der Proben und zwar insofern, daß offensichtlich Verspannungen im Material infolge von Deformationsprozessen und anderen Behandlungen zu einer erheblichen Erhöhung der Verluste führen, sowohl des Untergrundes als der singulären Mechanismen.
Summary Investigations of dielectric loss in the temperature range 1–80 °K and with frequencies between 10 c/sec and 10 kc/sec for diverse polymers a presented. For all polymers the dielectric loss decreases in principle monotonely with the approximation of the absolute Zero-point.Thus we suppose the existence of a common dielectric background loss depending from the thermal fluctuations in the material. Moreover this background losses are higher for substances with polar groups.At the lowest temperatures in most cases there seems to appear a loss peak. For temperatures down to 1 °K often this can be only suggested from the constancy of losses. But it seems to be a quite normal fact, that for extremely deep temperatures something as a singular relaxation mechanism may exist.Further discrete mechanisms exist for the range between 15 and 40 °K. Activation energy evaluated formally from the experimental dates in the normal manner after separation of the peaks from the background becomes smaller and smaller with decreasing temperatures.In all investigated cases the dielectric losses are very sensible to prehistory of the samples. It seems, that expecially stress, by deformation and other treatments, gives rise for an increase of loss for the background as for discrete mechanisms.相似文献
923.
Direct and selective catalytic arylation of alpha-C-H bond in pyridine with iodobenzene was achieved in up to 70% yield. Phosphido-bridged bisruthenium complexes 6a and 6b arising from Ru3(CO)12 and PPh3 were identified as active catalysts. The formation of complexes 6a and 6b was investigated, a sequence of C-H and C-P bond cleavage, cluster fragmentation, and disproportionation was established, and the intermediate ruthenium complexes lying on this pathway were isolated and fully characterized. 相似文献
924.
Caneschi A Dei A Fabrizi de Biani F Gütlich P Ksenofontov V Levchenko G Hoefer A Renz F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(18):3926-3930
An electronic switch at the molecular level has been realized by using a class of ionic compounds of the formula [Co(L)(diox)]Y (L = tetraazamacrocyclic ligand, Y = mononegative anion). Such compounds undergo temperature- and pressure-induced intramolecular one-electron transfer equilibria. The transition temperature of interconversion varies with the nature of the counterions Y (Y = PF6, BPh4, I). Surprisingly the effect of the anion on the transition temperature is not only governed by its volume but also by its coulombic interaction. 相似文献
925.
Compton scattering normalization method is described for the analysis of uranium bearing ore respect to the usage of K X-rays of uranium. Minimum backscatter energy is obtained at a scatter angle of 180° with fixed point source geometry and collimation in appropriate conclusions. By normalizing the intensities of uranium K-lines to the Compton profile in the measured spectra, the results do not depend on several measuring parameters such as primary radiation intensity, matrix, composition, mass of the sample and measuring time. The method presented in this study indicates the convenience of uranium K-lines analysis for thick targets with an adequate measuring geometry. 相似文献
926.
Roland A. Obermüller Christoph Etzlstorfer Heinz Falk 《Monatshefte für Chemie / Chemical Monthly》2002,133(1):89-96
Summary. A hypericin derivative was synthesized in which instead of the methyl groups two benzene rings were condensed to the chromophoric
system in order to extend its conjugation. This derivative showed lowered fluorescence and concomitantly enhanced sensitized
production of active oxygen species as compared to hypericin. However, in contrast to intuition its long wavelength band remained
unshifted in comparison to its parent compound hypericin. Geometry and absorption properties were also investigated by means
of semiempirical calculations.
Received July 27, 2001. Accepted August 9, 2001 相似文献
927.
R Krivanek P Rybar S Küpcü U B Sleytr T Hianik 《Bioelectrochemistry (Amsterdam, Netherlands)》2002,55(1-2):57-59
In this work, we performed targeted immobilization of immunoglobulins by means of bacterial S-layer proteins from Bacillus coagulans E38-66/V1 recrystallized on liposomes, which were exploited as immobilization matrix for antibody (Ab)-human IgG. The study of interaction of rabbit or swine anti-human IgG as antigens (Ag) was performed by means of measuring changes of ultrasound velocity. We showed that at a temperature of 25 degrees C, the increment of ultrasound velocity [u] linearly decreased following an increase of concentration of Ag. The decrease of [u] was presumably due to changes of hydration of the membrane due to the binding process. Approximately 10 times lower changes of [u] were observed at 45 degrees C for Ag-Ab interaction as well as for nonspecific interaction of Ag with liposomes covered by S-layer without Ab. No substantial differences in the behaviour of [u] were observed for interactions of human IgG with rabbit or swine anti-human IgG. 相似文献
928.
Monika Schuster Robert Inführ Claudia Turecek Jürgen Stampfl Franz Varga Robert Liska 《Monatshefte für Chemie / Chemical Monthly》2006,137(7):843-853
Summary. To substitute cross-linked photopolymers in rapid prototyping of mold materials and therefore extend the range of materials
which can be casted, organo-soluble photopolymers were developed. Branched bisalkylacrylamides were suitable as base component
for such formulations, due to their high reactivity, good mechanical properties, and excellent solubility of the formed polymers.
These molding materials were used to prepare cellular biocompatible materials which could be used as bone replacement materials.
Biocompatible crosslinkers based on methacrylates from hydrolyzed gelatine or lactic acid ethyleneglycol blockcopolymers and
commercially available reactive diluents are the base components of such a formulation. Biocompatibility was investigated
by osteoblast-like cells. Cellular biocompatible parts were obtained by thermal polymerization in soluble mould materials
prepared by 3D-photoshaping. 相似文献
929.
Zhu L Ostash B Rix U Nur-E-Alam M Mayers A Luzhetskyy A Mendez C Salas JA Bechthold A Fedorenko V Rohr J 《The Journal of organic chemistry》2005,70(2):631-638
The angucycline antibiotic family of the landomycins displays potent antitumor activity. To elucidate early post polyketide synthase (PKS) tailoring steps of the landomycin E biosynthetic pathway in Streptomyces globisporus 1912, the mutant S. globisporus M12 was prepared through gene replacement experiment of lndM2. It encodes an enzyme with putative oxygenase and reductase domains, according to sequencing of the gene and its counterpart lanM2 from S. cyanogenus S136 landomycin A biosynthetic gene cluster. The isolation of the novel shunt products 11-hydroxytetrangomycin and 4-hydroxytetrangomycin along with the well-known angucyclines tetrangomycin and tetrangulol from the culture of S. globisporus M12 provides evidence for the involvement of lndM2 in the early biosynthetic pathway of the landomycins, in particular in the formation of the alicyclic 6-hydroxy function of the landomycin aglycon. We therefore propose LndM2 to be responsible for both hydroxylation of the 6-position and its subsequent reduction. These reactions are necessary before the glycosylation reactions can occur. The results are in agreement with the originally published structure of landomycin but do not support the recently suggested revised structure. 相似文献
930.
Sun G Kappl M Pakula T Kremer K Butt HJ 《Langmuir : the ACS journal of surfaces and colloids》2004,20(19):8030-8034
Forces across polymer melts are poorly understood despite their importance for adhesion and fabricating composite materials. Using an atomic force microscope (AFM), this interaction was measured for poly(dimethyl siloxane) (PDMS). The structure of the polymer at the surface changed during the first approximately 10 h. Afterward, short-range attractive forces were observed with short-chain PDMS (M(w) = 4200 g/mol). Using PDMS with a molecular weight (M(w) = 18 000 g/mol) above the entanglement limit, we measured a monotonically decaying repulsive force, which indicates that a quasi-immobilized layer had formed at the solid surface. Due to the small radius of curvature of the tip, forces could be measured in equilibrium. 相似文献