Meeting infinitely many cells of a partition once

We investigate several versions of a cardinal characteristic defined by Frankiewicz. Vojtáš showed , and Blass showed . We show that all the versions coincide and that is greater than or equal to the splitting number. We prove the consistency of and of . Received: 2 October 1996 / Revised version: 22 May 1997     

TERAHERTZ QUALITY CONTROL OF POLYMERIC PRODUCTS

We report on experiments that evaluate the potential of terahertz (THz) time-domain spectroscopy (TDS) for quality control of polymeric compounds. We investigate specimens out of a polyethylene compound with silver-coated titanium dioxide nanospheres and a glass-fiber reinforced epoxy composite. We further examine an industrial polymer product produced by injection molding. Our data demonstrates that THz imaging is a powerful tool for contactless quality control in the polymer industry.     

LiTiCl3: Synthesis and thermal behaviour

LiTiCl₃ is obtained as one example within an ample solid solution, Li_24–2nTi_nCl₂₄ (?4?n?10), by synpropotionation of TiCl₃ and Ti in the presence of LiCl (2:1:3 molar ratio) in sealed tantalum tubes at 750°C. It crystallizes with the inverse spinel-type structure according to (Li_0.67)^[4](Li_0.67Ti_1.33)^[4]Cl₄ with, at 25°C, a = 1048.62(4) pm, space group Fd3m. Thermal expansion is linear with α = 4.85 × 10^?5K^?1 up to about 300°C and thereafter, when the migration of Li⁺ from tetrahedral to octahedral interstices becomes increasingly important, it exhibits a relative decrease resulting, finally, in the phase transition to a NaCl-type structure that is observed for the first time at about 575°C.     

Stereochemie von Metallocenen, 13. Mitt.: Optisch aktive Derivate des Methylcymantrens: Darstellung,Rotationsdispersion und konfigurative Korrelation

Zusammenfassung Optisch aktive Methylcymantren-- und--carbonsäuren wurden durch Racematspaltung ihrer Phenäthylaminsalze erhalten. Bei der Umwandlung in die entsprechenden Acetyl- bzw. Vinyl-methylcymantrene treten charakteristische Drehwertänderungen auf. Aus diesen, vor allem aber aus der Rotationsdispersion, ließ sich auf Grund von Konformationsanalysen und Vergleichen zwischen offenkettigen und cyclischen Verbindungen sowie mit analogen Methylferrocenderivaten für die -substituierten Produkte mit großer Sicherheit die absolute Konfiguration ableiten: (1S) für (+)-Methylcymantren--carbonsäure und ihre Folgeprodukte. Dieser Befund wurde durch kinetische Racematspaltung des Anhydrides der racem. Säure mit (–)--Phenäthylamin gestützt.

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Optically active methylcymantrene-- and--carboxylic acids were obtained by resolution of their salts with -phenethylamine. Upon transformation into the corresponding acetyl and vinyl methylcymantrenes, characteristic shifts of the optical rotation are observed. From these data, and especially from the rotatory dispersions, on the basis of conformational analyses and comparisons between open chain and cyclic compounds as well as with analogous methylferrocene derivatives, the absolute configurations of the -substituted products could be deduced with reasonable probability: (1S) for (+)-methylcymantrenecarboxylic acid and its subsequent products. This result was supported by kinetic resolution of the anhydride of the racemic carboxylic acid with (–)--phenethylamine.

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Mit 3 Abbildungen     

Chronocoulometric study of the electrochemistry of Prussian blue

During the electrochemical oxidation of Prussian blue (PB) to Prussian yellow (PY), an electrocatalytic oxygen production proceeds at the electrode when aqueous electrolyte solutions are used. The formed oxygen is scavenged by the PY, probably by absorption, and it is consumed during the electrochemical reduction of PY to PB by a heterogeneous chemical reaction of PB with oxygen to PY and hydrogen peroxide. Because of this catalytic regeneration of PY, it is impossible to determine the amount of low-spin iron by chronocoulometry using a potential program in which PB is first oxidized to PY and then the charge is measured to reduce PY to PB. The latter charge is biased by the electrocatalytic PY regeneration.     

Detection of Amadori compounds by capillary electrophoresis coupled to tandem mass spectrometry

Capillary electrophoresis coupled to mass spectrometry (CE-MS) is reported for the first time as an alternative and powerful analytical method for the characterization and monitoring of N-substituted 1-amino-1-deoxyketoses (Amadori compounds). It allows rapid separation and identification of Amadori compounds, while benefiting from the well-known advantages of MS, such as specificity and sensitivity. Amadori compounds of several amino acids, such as glycine, valine, isoleucine, methionine, proline, and phenylalanine, as well as a cysteine-derived compound, were separated and/or discriminated using CE-MS/MS under standard conditions. The technique may also be useful to study the stability and degradation kinetics of other labile charged Maillard intermediates that play an important role in food and medical science.     

Enzyme activity electrophoresis and rocket immunoelectrophoresis for the qualitative and quantitative analysis of Geotrichum candidum lipase activity

The development and application of a rocket immunoelectrophoretic and an enzyme activity electrophoretic assay for the qualitative analysis of Geotrichum candidum lipase activity is presented. The sensitivities of the four assays were (in arbitrary units): enzyme activity electrophoresis, 1-0.5; rocket immunoelectrophoresis, 0.5-0.2; radial diffusion, 1; titrimetry, 1. The electrophoretic methods made it possible to distinguish between high and low molecular weight forms of the G. candidum lipases. The enzyme activity electrophoretic methods can be combined with other electrophoretic techniques, as demonstrated here with isoelectric focusing, and produce useful information on physico-chemical differences between different molecular forms of the lipase, e.g. forms with different pI.