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排序方式: 共有1518条查询结果,搜索用时 18 毫秒
91.
Paweł Wyżga Igor Veremchuk Matej Bobnar Primož Koželj Steffen Klenner Rainer Pöttgen Andreas Leithe-Jasper Roman Gumeniuk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(23):5245-5256
The homogeneity range of ternary iron indium thiospinel at 873 K was investigated. A detailed study was focused on two distinct series (y=z): 1) a previously reported charge-balanced (In0.67+0.33y□0.33−0.33y)tetr[In2−zFez]octS4 (A1-series; □ stands for vacancy; the abbreviations “tetr” and “oct” indicate atoms occupying tetrahedral 8a and octahedral 16d sites, respectively) and 2) a new charge-unbalanced (In0.67+y□0.33−y)tetr[In2−zFez]octS4 (A2-series). Fe atoms were confirmed to exclusively occupy an octahedral position in both series. An unusual reduction of the unit cell parameter with increasing Fe content is explained by differences in the ionic radii between Fe and In, as well as by an additional electrostatic attraction originating from charge imbalance (latter only in A2-series). The studied compound is an n-type semiconductor, and its charge carrier concentration increases or decreases for larger Fe content within the A1- and A2-series, respectively. The thermal conductivity κtot is significantly reduced upon increasing vacancy concentration, whereas the change of power factor is insufficient to drastically improve the thermoelectric figure of merit. 相似文献
92.
93.
Chlorophyll‐Derived Yellow Phyllobilins of Higher Plants as Medium‐Responsive Chiral Photoswitches 下载免费PDF全文
Dr. Chengjie Li Dr. Klaus Wurst Dr. Steffen Jockusch Prof. Karl Gruber Dr. Maren Podewitz Prof. Klaus R. Liedl Prof. Bernhard Kräutler 《Angewandte Chemie (International ed. in English)》2016,55(51):15760-15765
The fall colors are signs of chlorophyll breakdown, the biological process in plants that generates phyllobilins. Most of the abundant natural phyllobilins are colorless, but yellow phyllobilins (phylloxanthobilins) also occur in fall leaves. As shown here, phylloxanthobilins are unique four‐stage photoswitches. Which switching mode is turned on is controlled by the molecular environment. In polar media, phylloxanthobilins are monomeric and undergo photoreversible Z/E isomerization, similar to that observed for bilirubin. Unlike bilirubin, however, the phylloxanthobilin Z isomers photodimerize in apolar solvents by regio‐ and stereospecific thermoreversible [2+2] cycloadditions from self‐assembled hydrogen‐bonded dimers. X‐ray analysis revealed the first stereostructure of a phylloxanthobilin and its hydrogen‐bonded self‐templating architecture, helping to rationalize its exceptional photoswitch features. The chemical behavior of phylloxanthobilins will play a seminal role in identifying biological roles of phyllobilins. 相似文献
94.
95.
FT Raman investigation of sodium cellulose sulfates (NaCS) was reported. Different NaCS were prepared by two diverse sulfation
methods and their total degrees of substitution (DS) of sulfate groups were determined through either 13C-NMR spectroscopy or elemental analysis. Subsequently, these NaCS were characterized with FT Raman spectroscopy. The caused
bands through the introduction of the sulfate groups in cellulose chain were explained and assigned. Additionally, a strong
linear correlation between the areas under the bands ascribed to the stretching vibrations of C–O–S groups and the total DS
of NaCS was presented. A rapid method of quantifying the total DS of NaCS was established. Finally, sodium sulfate (Na2SO4), a salt that is very often produced during the sulfation of cellulose, was found to be analyzable even with a weight content
of 0.12% in NaCS. The method of quantifying the content of this salt in NaCS was investigated with Raman spectroscopy. 相似文献
96.
We prove that the SLE
κ
trace in any simply connected domain G is continuous (except possibly near its endpoints) if κ < 8. We also prove an SLE analog of Makarov’s Theorem about the support of harmonic measure. 相似文献
97.
Samy Chammaa Dr. Bianca Sperl Anke G. Roth Aybike Yektaoglu Steffen Renner Dr. Thorsten Berg Prof. Dr. Christoph Arenz Prof. Dr. Athanassios Giannis Prof. Dr. Tudor I. Oprea Dr. Daniel Rauh Dr. Markus Kaiser Dr. Herbert Waldmann Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(21):3666-3670
98.
99.
Steffen Härtel Svitlana Tykhonova Marcus Haas Horst A. Diehl 《Journal of fluorescence》2002,12(3-4):465-479
Fluorescence spectroscopy and microscopy are powerful techniques to detect dynamic properties in artificial and natural lipid membrane systems. Unfortunately, most fluorescent dyes that sense dynamically relevant membrane parameters are UV sensitive. Their major disadvantage is a high susceptibility to fluorescence bleaching. Additionally, the risk for hazardous damages in biological components generally increases with decreasing excitation wavelength. Therefore the use of non-UV–sensitive membrane dyes would provide significant advantage, particularly for applications in fluorescence microscopy, which usually implies high local excitation intensities. We applied steady-state fluorescence spectroscopy techniques to several UV and non-UV membrane dyes to detect and compare dynamically relevant excitation and emission characteristics. Small unilamellar liposomes (composed of egg yolk phosphatidylcholine) served as a model system for biological membranes. The dynamic properties of the membranes were varied by two independent parameters: the intrinsic cholesterol content (0–50 mol%) and temperature (10–50°C). We tested four non-UV–sensitive membrane dyes: 9-diethylamino-5H-benzophenoxazine-5-one (Nile Red), 4-(dicyanovinyl)julolidine (DCVJ), N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide (FM 4-64), and 1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine perchlorate (DiIC18). We also tested three derivatives of DiIC18: DiIC16 and DiIC12 differ in acyl chain length and Fast-DiIC18 provides double bonds between hydrocarbon atoms. The spectral results were compared to established fluorescence characteristics of four UV membrane dyes: the anisotropy of 1-6-phenyl-1,3,5,-hexatrien (DPH), two derivatives of DPH (TMA-DPH and COO–-DHP), and the generalized polarization of 6-dodecanoyl-2-dimethyl-aminonaphthalene (Laurdan). Our results indicate that the tested non-UV dyes do not reveal dynamically relevant membrane parameters in a direct manner. However, spectral characteristics make DiIC18, Nile Red, and DCVJ promising probes for the microscopic detection of lateral lipid organization, an indirect indicator of membrane dynamics. In particular, DiIC18 showed very selective shifts in the emission spectra at defined temperatures and cholesterol contents that have not been reported elsewhere. 相似文献
100.
In the presence of scalar (J) and residual dipolar (D) couplings, the transfer efficiency of homonuclear Hartmann-Hahn and COSY-type mixing depends on the ratio D/J and on the mixing sequence. This dependence is analyzed theoretically and the results are confirmed experimentally. At least two different mixing sequences are required to yield good transfer efficiencies for all ratios D/J. In contrast to COSY-type experiments, homonuclear Hartmann-Hahn sequences can provide efficient transfer even if the sum of D and J is zero, i.e., if the coupling vanishes in the weak coupling limit. 相似文献