Quantitative 13C-NMR spectroscopy of coals using 200 MHz-spectrometers

Summary A technique is described for recording all carbons in coals almost quantitatively using 200 MHz NMR-spectrometers. A spinning rate of 8 kHz and single pulse excitation are employed to achieve this aim. The determined aromaticities obtained by means of single-pulse excitation and cross-polarisation experiments are compared. Furthermore, dipolar dephasing experiments are applied to illustrate that a great part of Cq-carbon cannot be observed using the cross-polarisation technique.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Ein Kriterium für die Richtigkeit der Milnor-Vermutung

Let F denote a field of characteristic ≠2. The Witt ring WF (i.e. the ring of similarity classes of quadratic forms with coefficients in F) will be characterized by taking the similarity classes of certain Pfister forms [2] as generators and using suitable relations among them (theorem 1). In order to characterize GF, the graded ring associated to WF, in terms of generators and relations Milnor [4] constructed a homomorphism from his ring k_*F onto GF and conjectured this homomorphism to be an isomorphism. This conjecture turns out to be equivalent to a problem on ideals in a commutative ring (theorem 2).     

PORPHYRIN-INDUCED PHOTODAMAGE TO ISOLATED HUMAN NEUTROPHILS

Abstract— Human neutrophils were irradiated with light at 340–380 nm in the presence of low concentrations of protoporphyrin or uroporphyrin. At increasing light doses or increasing concentrations of protoporphyrin, the neutrophils rapidly lost the ability of locomotion. Also, neutrophil chemiluminescence and hexose-monophosphate shunt activity rapidly declined. An early event was leakage of endogenous K⁺ followed by lactate dehydrogenase and at a later stage leakage of particle-bound acid phosphatase. A number of cellular enzymes were inactivated, the susceptibility to inactivation decreased in the order: succinate dehydrogenase > lactate dehydrogenase > glutamate dehydrogenase > acid phosphatase. Uroporphyrin had no effect on neutrophil functions, leakage of K⁺, or cellular enzymes. The results suggest that photodamage to the plasma membrane and the mitochondria are earlier events than photodamage to lysosomes.     

Inventory management of spare parts in an energy company

We address the problem of how to determine control parameters for the inventory of spare parts of an energy company. The prevailing policy is based on an (s, S) system subject to a fill rate constraint. The parameters are decided based mainly on the expert judgment of the planners at different plants. The company is pursuing to conform all planners to the same approach, and to be more cost efficient. Our work focuses on supporting these goals. We test seven demand models using real-world data for about 21?000 items. We find that significant differences in cost and service level may appear from using one or another model. We propose a decision rule to select an appropriate model. Our approach allows us to recommend control parameters for 97.9% of the items. We also explore the impact of pooling inventory for different demand sources and the inaccuracy arising from duplicate item codes.     

Degradation of Some Octa-O-Benzoylaldobiononitriles: Studies of the Products by NMR Spectroscopy

Abstract

The Zemplén degradation of 2, 3, 5, 6, 2′, 3′, 4′, 6′-octa-O-benzoylcellobiononitrile (1), -lactobiononitrile (2), and -maltobiononitrile (3) was carried out giving a mixture of the four 3-O-(D-hexopyranosyl)-D-arabinoses. Their reduction gave the 3-O-(D-hexopyranosyl)-D-arabinitols, and their benzoylation gave the 1, 2, 4, 5, 2′, 3′, 4′, 6′-octa-O-benzoyl-(D-hexopyranosyl)-D-arabinitols. Their ¹H and ¹³C NMR spectra are described, and their conformations are determined to be planar zig-zag for the acyclic moieties.     

Stereospecific Photoredox-Catalyzed Vinylations to Functionalized Alkenes and C-Glycosides**

We report an efficient radical-mediated C−C coupling through photoredox-catalyzed reactions of 4-alkyl-dihydropyridines (DHPs) and vinylbenziodoxol(on)es (VBX, VBO). This transition-metal-free and mild photocatalytic method has excellent functional group tolerance and affords vinylated products in good yields, with complete retention of the alkene configuration. The utility of the methodology is demonstrated by the diastereoselective synthesis of C-vinyl glycosides. Preliminary mechanistic studies suggest that the C−C bond formation is stereospecific and proceeds through a concerted radical coupling transition state.     

Porous Salts Containing Cationic Al24-Hydroxide-Acetate Clusters from Scalable,Green and Aqueous Synthesis Routes

The solution chemistry of aluminum is highly complex and various polyoxocations are known. Here we report on the facile synthesis of a cationic Al₂₄ cluster that forms porous salts of composition [Al₂₄(OH)₅₆(CH₃COO)₁₂]X₄, denoted CAU-55-X, with X=Cl⁻, Br⁻, I⁻, HSO₄⁻. Three-dimensional electron diffraction was employed to determine the crystal structures. Various robust and mild synthesis routes for the chloride salt [Al₂₄(OH)₅₆(CH₃COO)₁₂]Cl₄ in water were established resulting in high yields (>95 %, 215 g per batch) within minutes. Specific surface areas and H₂O capacities with maximum values of up to 930 m² g⁻¹ and 430 mg g⁻¹ are observed. The particle size of CAU-55-X can be tuned between 140 nm and 1250 nm, permitting its synthesis as stable dispersions or as highly crystalline powders. The positive surface charge of the particles, allow fast and effective adsorption of anionic dye molecules and adsorption of poly- and perfluoroalkyl substances (PFAS).