Generalized Topological Essentiality and Coincidence Points of Multivalued Maps

A concept of generalized topological essentiality for a large class of multivalued maps in topological vector Klee admissible spaces is presented. Some direct applications to differential equations are discussed. Using the inverse systems approach the coincidence point sets of limit maps are examined. The main motivation as well as main aim of this note is a study of fixed points of multivalued maps in Fréchet spaces. The approach presented in the paper allows to check not only the nonemptiness of the fixed point set but also its topological structure.      

A comparison of potentiometric,spectrophotometric and atomic absorption spectrometric methods for the determination of mercury in wastes

The potentiometric titration with dithiooxamide applied to mercury determinations in industrial wastes is compared with cold-vapour atomic absorption spectrometry and spectrophotometry with dithizone. The potentiometric method is shown to have adequate sensitivity and selectivity as well as economic advantages.     

Vibrational spectra and chemical quantum calculations for 2-adamantylamino-5-nitropyridine crystals--a novel material for laser Raman converters

Polycrystalline infrared and polarized FT-Raman spectra have been measured for 2-adamantylamino-5-nitropyridine, a novel organic material for laser Raman converters. The assignment of IR and Raman bands is given on the basis of DFT calculations. The spectroscopic studies have not indicated the presence of any significant intermolecular interactions in the crystal structure of this compound. The lines observed in the stimulated Raman spectrum of this crystal are assigned to the respective molecular vibrations.     

α-Hydroxymethylaspartic acid: Synthesis and absolute configuration by X-ray analysis of its derivative (+)-4-benzoylamino-4-carboxy-γ-butyrolactone

(+)-4-Benzoylamino-4-carboxy--butyrolactone was synthesized, and its structure solved by direct methods and refined toR=0.033. The molecule adopts a skew conformation with a C7-N1-C8-C12 torsion angle of 59.6(2)°. The lactone ring has an envelope conformation, with the C(8) atom deflected from the ring plane. The absolute configuration of (+)-benzylami-no-4-carboxy--butyrolactone5 was assigned asR by the application of Hamilton's test to the unique diffraction data, and confirmed by the estimation of the Bijvoet coefficientB fromhkl and diffraction data. This result proves theR configuration for (+) enantiomer of the parent-hydroxymethylaspartic acid.     

Self-Assembly and Ordering of Peptide-Based Cavitands in Water and DMSO: The Power of Hydrophobic Effects Combined with Neutral Hydrogen Bonds

Directional self-assembly of uncharged molecules in water is a major challenge in supramolecular chemistry. Herein, it is demonstrated that peptide-based cavitands wrap around a hydrophobic core (fullerene C₆₀) by a combination of the hydrophobic effect and hydrogen-bonding interactions to form highly ordered three-component complexes in water that resemble the molten-globule stage of protein folding. The complexes were characterized by DOSY NMR spectroscopy, small-angle X-ray scattering, and circular dichroism, and their structures were confirmed by X-ray crystallography. Enhancement of the CD signals by nearly one order of magnitude and increased hydrolytic stability of hydrazone bonds of the complexes relative to the nonassembled species were observed. In contrast, DMSO and DMSO/water mixtures were found to be highly disintegrative for these complexes. Interestingly, some cavitands can only be synthesized in the presence of the hydrophobic template followed by disassembly of the complexes.     

Conformational flexibility and pseudosymmetric aggregation in a betainium salt hydrate

Structural Chemistry - The cation of 3-(trimethylammonium)-benzoic acid exhibits a considerable conformational flexibility connected to the orientation of carboxyl group, coupled to the proton...     

Ten years of charge-inverted hydrogen bonds

Structural Chemistry - This article is a review of the current state of knowledge about the so-called charge-inverted hydrogen bond—the type of interaction proposed 10 years ago. Numerous...     

X-ray structure and NMR assignment of 3,4-dimethylthioquinoline

The title compound (C₁₁H₁₁NS₂) is monoclinic:P2₁/c,a=15.200(4),b=14.644(4),c=10.098(3),Z=8. The structure was solved by direct methods, and refined to anR value of 0.047 with 2886 independent reflections. There are two nonequivalent molecules in the unit cell. BothS-methyl groups have different spatial orientation: the-methyl group side-chain is approximately coplanar with the pyridine ring and turned to the ortho-position, but -methyl group side-chain is turned over this ring. Both¹H and¹³C NMR spectra were assigned using 1D and 2D experiments. The NOE measurements are consistent with inter-proton distances from X-ray data.Part XV in the series of Azinyl sulfides.     

X-ray structure of 4-chloro-3′-methylthio-3,4′-diquinolinyl sulfide

The title compound crystallizes in a monoclinic space groupP2₁/n witha=9.524(3),b=6.782(2),c=26.217(6) Å, =92.52(4)°. The values of the Cl...S and S...S distances are well below the sum of the van der Waals radii of the heteroatoms. Also, the Cl–C–C(S) and (Cl)C–C–S bond angles are below the standard 120°. This indicates a attractive interaction between both pairs ofortho-situated heteroatoms.Part XXXVIII in the Series of Azinyl Sulfides.