Lecture on topological crystallography

This is an expository article on modern crystallography based on discrete geometric analysis, a hybrid field of several traditional disciplines: graph theory, geometry, theory of discrete groups, and probability, which has been developed in the last decade. The mathematical part relying on algebraic topology is fairly elementary, but may be still worthwhile for crystallographers who want to learn how well-established mathematics is effectively used in the practical science. A brief history of crystallography is also explained.     

Isotope Effect on Physical Properties of BEDT-TTF Based Organic Superconductors

Abstract

The isotope shifts of the superconducting transition temperature for K-(BEDT-TTF)₂Cu[N(CN)₂]Br were evaluated from the resistivity and dc magnetization measurements. The deuteration of the terminal ethylene groups of the donor molecule lowered T_c by 0.4 to 0.5K, whereas the ¹³C substitution on the same fragments gave no isotope shifts within the experimental accuracy.     

Total Synthesis of Vancomycin Aglycon—Part 3: Final Stages

A triazene-based synthetic strategy for the construction of the complex biaryl ethers and a Suzuki coupling reaction were the key steps in the synthesis of precursor 1 of the aglycon of vancomycin, which already contains the complete skeleton of the target compound. The cleavage of the triazene unit from the D ring and the removal of the other protecting groups led to the aglycon of vancomycin. These strategies should be particularly valuable for the synthesis of other naturally occurring glycopeptide antibiotics and offer opportunities for the synthesis of combinatorial libraries of compounds of the vancomycin family for chemical biology studies.     

Phase behavior and photocrosslinking kinetics of semi-interpenetrating polymer networks prepared from miscible polymer blends

Mixtures of polystyrene derivatives (PSCS) and poly(vinyl methyl ether) (PVME) were made photocrosslinkable by chemically labeling PSCS chains with photoreactive anthracene. Miscibility of these anthracene-labeled PSCS/PVME blends was examined by light scattering under several crosslinking conditions in the one-phase region via photodimerization of anthracenes. As the reaction proceeds, the coexistence curve of PSCS/PVME blends shifts toward the low temperature side. By following the changes in concentration of anthracenes with irradiation time, it was found that the crosslinking reaction of PSCS chains in the blends does not follow the mean-field kinetics. However, it can be well expressed by the Kohlrausch–Williams–Watts (KWW) relaxation mechanism, indicating that the crosslinking reaction proceeds inhomogeneously in the blends. By scaling the reaction time with the average reaction rate obtained from the KWW equation modified for the reaction kinetics, all the crosslinking data obtained in the miscible region of the reacted blends fall on a single master curve. These experimental results suggest the universal behavior of the photocrosslinking kinetics obtained under the “shallow quench” conditions in the region far away from the coexistence curve of the reacting blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 455–462, 1998     

A Narrative Review of Sulfur Compounds in Whisk(e)y

The production process of whisky consists of malting, mashing, fermentation, distillation and maturation. Sulfur volatile compounds generated during this process have long attracted interest because they influence quality in general. More than forty compounds have been reported: they are formed during malting, fermentation, and distillation, but some may decrease in concentration during distillation and maturation. In sensory analysis, sulfur characteristics are described as sulfury, meaty, cereal, feinty, and vegetable, among others. Their contribution to overall quality depends on their concentration, with a positive contribution at low levels, but a negative contribution at high levels. Chemical analyses of sulfur volatiles have been developed by using sulfur-selective detectors and multi-dimensional gas chromatography to overcome the numerous interferences from the matrix. Formation pathways, thresholds, and contribution have not been elucidated completely; therefore, methods for integrating diverse data and knowledge, as well as novel technical innovations, will be needed to control sulfur volatiles in the future.     

Diagnostics of laser-ablated carbon plumes by photoionization using a tunable laser

Tunable laser pulses at wavelengths from 250 to 880 nm were fired at plumes produced by laser ablation of a carbon target in He atmosphere. We observed an electrical current due to photoionization, which roughly reflected the behavior of carbon clusters in the plume. The photoionization current had dynamic temporal variations, comprising a rapid increase at the beginning (T_D<0.2 ms, where T_D is the time after a YAG laser pulse for laser ablation irradiates the target), a gradual increase for 0.2D<3 ms, and a slow decrease for T_D>7 ms. The increasing phase of the photoionization current was synchronized with the decreasing phase of C₂ radical density. For He gas pressures lower than 0.8 Torr no photoionization current was detected. The growth rate of the photoionization current was higher for a higher He gas pressure.     

Standard realizations of crystal lattices via harmonic maps

An Eells-Sampson type theorem for harmonic maps from a finite weighted graph is employed to characterize the equilibrium configurations of crystals. It is thus observed that the mimimum principle frames symmetry of crystals.

     

Constituents of the underground parts of Glehnia littoralis

From the underground parts of Glehnia littoralis FR. Schmidt ex Miquel (Umbelliferae), 26 compounds, including two new lignan glycosides [giehlinosides A (1) and B (2)], a new neolignan glycoside [glehlinoside C (3)], and a new phenylpropanoid glycoside 14-[beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranosyloxyl-3-methoxypropiophenone (4)1, were obtained and their structures were determined by analysis of their spectral data. The 1,1-diphenyl-2-picrylhydrazyl radical-scavenging assay disclosed quercetin (8), isoquercetin (9), rutin (10), chlorogenic acid (11), and caffeic acid (24) as the major antioxidative constituents in this crude drug.