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21.
22.
A. Brilingas R. L. Davidovich J. Grigas S. Lapinskas M. A. Medkov V. Samulionis V. Skritskii 《physica status solidi (a)》1986,96(1):101-109
Results are presented of the investigation of the dielectric and acoustic properties of K3BiCl6 · · 2 KC1 · KH3F4 crystal which undergoes an improper ferroelectric phase transition at Tc = 130K. In the paraelectric phase the dielectric permittivity does not depend on temperature or frequency. In the ferroelectric phase relaxational dielectric dispersion of the Debye type occurs along the polar c-axis in the frequency range 105 to 1011 Hz. It is characterized by two relaxation times, τd = 1.3 × 10−9 s and τ 1.5 × 10−11 s. The dispersion in the interval 105 to 109 Hz is caused by the domain walls and produces the main contribution Δεd = 40 to the static dielectric per-mittivity of multi-domain crystals and the changes in the ultrasound velocity and attenuation. The dielectric contribution of the ferroelectric dispersion in the frequency range 1 to 80 GHz is Δε = 10 and ε∞ = 10. 相似文献
23.
A. Brilingas N. J. Bucko J. Grigas W. Samulionis J. D. Sheshnitsch 《Crystal Research and Technology》1978,13(2):221-226
Measurements of the temperature dependences of the real and imaginary part of the complex dielectric permittivity at microwave frequencies together with the damping constant and the velocity of ultrasonic waves in Ag5SbS4 crystals have been made. The Peculiarities of the crystals grown and the nature of the phase transition in Ag5SbS4 are discussed. 相似文献
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25.
Jennifer Solarczek Dr. Felix Kaspar Pia Bauer Prof. Anett Schallmey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(72):e202202343
Halohydrin dehalogenases are promiscuous biocatalysts, which enable asymmetric ring opening reactions of epoxides with various anionic nucleophiles. However, despite the increasing interest in such asymmetric transformations, the substrate scope of G-type halohydrin dehalogenases toward cyclic epoxides has remained largely unexplored, even though this subfamily is the only one known to display activity with these sterically demanding substrates. Herein, we report on the exploration of the substrate scope of the two G-type halohydrin dehalogenases HheG and HheG2 and a newly identified, more thermostable member of the family, HheG3, with a variety of sterically demanding cyclic epoxides and anionic nucleophiles. This work shows that, in addition to azide and cyanide, these enzymes facilitate ring-opening reactions with cyanate, thiocyanate, formate, and nitrite, significantly expanding the known repertoire of accessible transformations. 相似文献
26.
Marcel Staar Steffi Henke Prof. Wulf Blankenfeldt Prof. Anett Schallmey 《ChemCatChem》2022,14(9):e202200145
A major drawback for practical application of halohydrin dehalogenase HheG in biocatalysis is its rather low thermal stability and low organic solvent tolerance. We therefore pursued a stabilization of HheG via immobilization as cross-linked enzyme crystals. Since glutaraldehyde inactivates HheG, we introduced a cysteine residue in the crystal interface, which enabled thiol-specific cross-linking at well-defined cross-linking sites. Variant HheG D114C displayed improved crystallizability and yielded stable and catalytically active CLECs using bis-maleimidoethane as cross-linker. Effective cross-linking at the predefined site could be confirmed via the CLEC crystal structure. Compared to soluble enzyme, the CLECs displayed significantly improved stability and activity at higher temperatures, lower pH values and in the presence of water-miscible organic solvents, which enabled their reuse over 21 days in the azidolysis of cyclohexene oxide. 相似文献
27.
Anett Kondor Christian Quellet András Dallos 《Surface and interface analysis : SIA》2015,47(11):1040-1050
The surface characterizations of the WFK16000 standard cotton by dispersive, specific and total surface energy heterogeneity profiles with surface energy distributions and acid–base properties determined by surface energy analyser are presented in this work. The Dorris–Gray and Schultz methods for the determination of the dispersive surface energy component are compared, and their critical analysis is given. It is concluded that the Dorris–Gray method is more applicable at elevated temperature. Furthermore, Henry's coefficient, standard free enthalpy, enthalpy and entropy data at infinite dilution and adsorption isotherms for some fragrances (benzyl acetate, Cyclal C, diphenyl oxide, eucalyptol, linalool and viridine) measured on dry cotton fibres by inverse gas chromatography at various temperatures are given. The temperature‐dependent form of the Langmuir equation has been fitted to the multiple temperature adsorption isotherms with good agreement. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
28.
Vesenka J Bagg D Wolff A Reichert A Moeller R Fritzsche W 《Colloids and surfaces. B, Biointerfaces》2007,58(2):256-263
Scanning probe microscopy was used to examine the orientation of Tet1.5 quadruplex DNA polymers, a.k.a. “G-wires”, after adsorption onto freshly cleaved Phyllosilicate micas. The G-wires appear to have a preferential orientation at 60° intervals after thorough rinsing and slow drying. The angles the G-wires made with the fast scan direction of the SPM probe were measured and the frequency-angle information was quantitatively characterized by an empirical correlation coefficient. Careful measurements indicate the Tet1.5 G-wires orient along the b lattice vector of mica, the next nearest neighbor potassium vacancy. A model is proposed to explain this auto-orientation affect due to alignment of the G-wires’ phosphate backbone through magnesium tether cations. Pairs of adjacent, parallel phosphate groups of the G-wires (0.95 nm apart) appear to align with the next nearest neighbor potassium vacancy sites of mica (0.90 nm apart). This behavior is not observed in solution. The potential for using the auto-orientation phenomena in the development of high-density biomolecular nano-electronic devices is explored. 相似文献
29.
Elia Calderini Dr. Julia Wessel Dr. Philipp Süss Dr. Patrick Schrepfer Dr. Rainer Wardenga Prof. Dr. Anett Schallmey 《ChemCatChem》2019,11(8):2099-2106
Halohydrin dehalogenases (HHDHs) are valuable biocatalysts for the synthesis of β-substituted alcohols based on their epoxide ring-opening activity with a number of small anionic nucleophiles. In an attempt to further broaden the scope of substrates accepted by these enzymes, a panel of 22 HHDHs was investigated in the conversion of aliphatic and aromatic vicinally di-substituted trans-epoxides using azide as nucleophile. The majority of these HHDHs was able to convert aliphatic methyl-substituted epoxide substrates to the corresponding azidoalcohols, in some cases even with absolute regioselectivity. HheG from Ilumatobacter coccineus exhibited also high activity towards sterically more demanding di-substituted epoxides. This further expands the range of β-substituted alcohols that are accessible by HHDH catalysis. 相似文献
30.
A new algorithm for waveguide and leaky modes spectrum calculation in multilayer planar waveguides is proposed. The method
is of high computational efficiency due to the preliminary search for propagation constants approximation. Numerical efficiency
of this algorithm is demonstrated for several waveguide structures. Waveguide and leaky modes propagation constants calculated
for these structures using proposed method are in good agreement with previously published results. 相似文献