A note on attractors with finite fractal dimension

Conditions for the finite fractal dimension of precompact invariantsets are formulated and exponential attractors for discreteand continuous dynamical systems are constructed.     

Structural investigations of microbial cellulose produced in stationary and agitated culture

Structural characteristics of microbial cellulose synthesized by two different methods have been compared using FT-IR and X-ray diffraction techniques. Cellulose synthesized by Acetobacter xylinum NQ-5 strain from agitated culture conditions is characterized by a lower I_? mass fraction than cellulose that was produced statically. Such a decrease was in good correlation with smaller crystallite sizes of microfibrils produced in agitated culture. Formation of characteristic cellulose spheres during agitation has been investigated by various electron and light microscopic methods. On this basis, a hypothetical mechanism of sphere formation and cell arrangement in the agitated culture has been proposed. During agitation, cells are stacked together in organized groups around the outer surface of the cellulose sphere.     

Photoluminescence of cobalt in CdIn2S4

The photoluminescence of cobalt (0.05 mol %) doped CdIn₂S₄ has been measured in the range 8500–16500 cm^-1. Luminescence is observed from both tetrahedrally and octahedrally coordinated Co²⁺ ions in the partially inverted spinel. Vibrationally assisted transitions from the ²E(G) state of both of these sites are identified. The ⁴A₂(F) level of the tetrahedrally coordinated Co²⁺ is found to be 1927 cm^-1 above the CdIn₂S₄ valence band and the spin-orbit splitting factor is measured to be λ = -133 cm^-1.     

The 7-line luminescence spectrum of (Neeh) in GaP:N,a correction

A new interpretation is given for the weak, green photoluminescence in GaP:N. The high energy part of this spectrum is due to the zero phonon recombination of excitons bound to neutral carbon and magnesium acceptors. The low energy part involves emission lines of unknown origin and a partial overlap of grating ghosts due to the nitrogen A-line.     

An apparent Landau-type second order transition in the spinel CdIn2S4

Experimental evidence is given of a second order transition in the spinel CdIn₂S₄. The specific heatc _p shows a step at the transition temperature (T _c=403°K), the thermal expansion coefficientα remains unaffected. An analysis yields a critical region of this transition considerably narrower (5°K) than expected from the critical regions of transitions of a similar type (quartz: 160°K,β-brass: 250°K) and therefore the critical region has not been observed experimentally, i.e. the transition appears to follow Landau’s theory. Landau’s group theoretical analysis of second order transitions in crystals leads to a model for the transition in CdIn₂S₄ on the atomic scale. If the temperature is decreased below the critical temperature a 1:1 ordering occurs between Cd and In on the tetrahedral sites. With this model the gross features of this transition can be qualitatively understood: The unaffected thermal expansion and the long relaxation times for the establishment of equilibrium approachingT _c. Also the narrow critical region can be explained in terms of a large correlation length in CdIn₂S₄. Finally it is shown that a generalized formulation of the thermodynamic part of Landau’s theory correlates thermodynamic quantities far above and far below the critical temperature, as illustrated for CdIn₂S₄. This generalization allows also a more satisfactory determination of the critical region.     

On the reaction mechanism of adduct formation in LOV domains of the plant blue-light receptor phototropin

The blue-light sensitive photoreceptor, phototropin, is a flavoprotein which regulates the phototropism response of higher plants. The photoinduced triplet state and the photoreactivity of the flavin-mononucleotide (FMN) cofactor in two LOV domains of Avena sativa, Adiantum capillus-veneris, and Chlamydomonas reinhardtii phototropin have been studied by time-resolved electron paramagnetic resonance (EPR) and UV-vis spectroscopy at low temperatures (T < or = 80 K). Differences in the electronic structure of the FMN as reflected by altered zero-field splitting parameters of the triplet state could be correlated with changes in the amino acid composition of the binding pocket in wild-type LOV1 and LOV2 as well as in mutant LOV domains. Even at cryogenic temperatures, time-resolved EPR experiments indicate photoreactivity of the wild-type LOV domains, which was further characterized by UV-vis spectroscopy. Wild-type LOV1 and LOV2 were found to form an adduct between the FMN cofactor and the functional cysteine with a yield of 22% and 68%, respectively. The absorption maximum of the low-temperature photoproduct of wild-type LOV2 is red-shifted by about 15 nm as compared with the FMN C(4a)-cysteinyl adduct formed at room temperature. In light of these observations, we discuss a radical-pair reaction mechanism for the primary photoreaction in LOV domains.     

Thermal behavior of ethylene copolymers with di- and tri-alkenylsilsesquioxane comonomers synthesized by post-metallocene catalysts

Journal of Thermal Analysis and Calorimetry - This paper reported thermal properties of ethylene copolymers with di- and tri-alkenylsilsesquioxanes (POSS) synthesized by bis(phenoxy-imine) Ti, Zr,...