NONLINEAR LASERSPECTROSCOPIC INVESTIGATIONS OF THE PIGMENT-PIGMENT INTERACTION WITHIN THE LIGHT-HARVESTING COMPLEX OF PHOTOSYSTEM II

Using a pump and test beam technique in the frequency domain with pump pulses in the nanosecond time range, the nonlinear transmission properties were investigated at room temperature in photosystem (PS) II membrane fragments and isolated light-harvesting chlorophyll a/b-protein preparations (LHC II preparations). In LHC II preparations and PS II membrane fragments, respectively, pump pulses of 620 nm and 647 nm cause a transmission decrease limited to a wavelength region in the nearest vicinity of the pump pulse wavelength (full width at half maximum ' 0.24 nm). In contrast, at 670 nm neither a transmission decrease nor a narrow band feature were observed. The data obtained for PS II membrane fragments and LHC II preparations at shorter wavelengths (620 nm, 647 nm) were interpreted in terms of excited state absorption of whole pigment-protein clusters within the light-harvesting antenna of photosystem II. The interpretation of the small transmission changes as homogeneously broadened lines led to a transversal relaxation time for chlorophyll in the clusters of about 4 ps.     

Numeric simulation of epoxy cure in molds

Thermodynamic and kinetic parameters have been determined suitable for the numerical simulation of the curing reaction of the epoxy/anhydride based casting resin system Araldite CY 225/HY 225/filler. In particular, the decisive role of the heating rate on the evaluation of the kinetic parameters from dynamic DSC-experiments is discussed.

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Zusammenfassung Mit Hilfe der Mikrokalorimetrie wurden thermodynamische (Reaktionsenthalpien) und kinetische (Arrhenius-Konstanten, Reaktionsordnung) Parameter eines gefüllten Epoxid/Anhydrid-Giessharz-Systems (Araldit CY 225/HY 225/Quarzmehl) bestimmt.Die Eignung dieser Parameter zur praxisrelevanten Simulation der HÄrtungsreaktion in Giessformen wird demonstriert. Es zeigt sich, dass die Heizrate im dynamischen DSC-Experiment bei der Bestimmung der kinetischen Parameter eine entscheidende Rolle spielt.

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We wish to thank Dr. P. Bujard, Ciba-Geigy SA, for the measurement of the thermal conductivity data, and Mrs. Emmi Stoisser for technical assistance.     

Semi-wet growth and characterization of multi-functional nano-engineered mixed metal oxides for industrial application

This review paper covers the low temperature wet growth of nano-engineered particles of ZnO-based mixed metal oxides, their growth mechanism, and characterization using X-ray diffraction, SEM, TEM and IR, UV–visible, and XPS spectral techniques. Main focus of this article is centered on low temperature semi-wet methods of synthesis that are suitable for large scale production of zinc oxide-based systems mixed with iron oxide, copper oxide, nickel oxide and cobalt oxide. These mixed metal oxides have broad industrial applications as catalyst, semiconductors, adsorbents, superconductors, electro-ceramics, and antifungal agents in addition to extensive applications in medicines. This paper discusses the low-cost and environment friendly synthesis of these mixed metal oxides, measurement of properties and applicability of these materials systems.     

Ein singuläres bewegungsinvariantes Variationsproblem

Ohne Zusammenfassung     

Manganese‐Catalyzed Dehydrogenative Alkylation or α‐Olefination of Alkyl‐Substituted N‐Heteroarenes with Alcohols

Catalysis with earth‐abundant transition metals is an option to help save our rare noble‐metal resources and is especially interesting when novel reactivity or selectivity patterns are observed. We report here on a novel reaction, namely the dehydrogenative alkylation or α‐olefination of alkyl‐substituted N‐heteroarenes with alcohols. Manganese complexes developed in our laboratory catalyze the reaction with high efficiency whereas iron and cobalt complexes stabilized by the same ligands are essentially inactive. Hydrogen is liberated during the reaction, and bromine and iodine functional groups as well as olefins are tolerated. A variety of alkyl‐substituted N‐heteroarenes can be functionalized, and benzylic and aliphatic alcohols undergo the reaction.     

Spherically symmetric inhomogeneous dust collapse in higher dimensional space-time and cosmic censorship hypothesis

We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. We show that the central singularity of collapse can be a strong curvature or a weak curvature naked singularity depending on the initial density distribution.     

Synaptic depression and short-term habituation are located in the sensory part of the mammalian startle pathway

Background  

Short-term habituation of the startle response represents an elementary form of learning in mammals. The underlying mechanism is located within the primary startle pathway, presumably at sensory synapses on giant neurons in the caudal pontine reticular nucleus (PnC). Short trains of action potentials in sensory afferent fibers induce depression of synaptic responses in PnC giant neurons, a phenomenon that has been proposed to be the cellular correlate for short-term habituation. We address here the question whether both this synaptic depression and the short-term habituation of the startle response are localized at the presynaptic terminals of sensory afferents. If this is confirmed, it would imply that these processes take place prior to multimodal signal integration, rather than occurring at postsynaptic sites on PnC giant neurons that directly drive motor neurons.     

Synthesis and Structure of 1,1'‐Bis(pyridinylamino)ferrocenes

Ferrocenyl bridged bisaminopyridines were synthesized from 2‐bromopyridine or 2‐bromo‐4‐methylpyridine and 1,1'‐diaminoferrocene using palladium catalysed aryl amination. X‐ray crystal structure analysis of the two bisaminopyridines revealed the formation of dimers in the solid state. The formation of the dimers occurs via four H‐bonds between the amino N‐H function and the pyridine nitrogen atoms.