A Cohen-type theorem for Artinian modules

We show that a finitely embedded module M over a commutative ring R is Artinian if the factor module M/(0 :_M P) is finitely embedded for every prime ideal P of R. Received: 10 June 2005     

Lower-frequency infrared spectra and structures of some typical aliphatic polyamides

The Polarized lower-frequency infrared spectra (800–33 cm^-1) of nylon 66 (α form), nylon 77 (γ form), and nylon 6 (both α and γ form) have been examined. The spectral changes which occur on complex formation of the polyamides with iodine-potassium iodide solution and on subsequent iodine desorption have been studied in relation to the changes in the polymer structures. On the basis of these results, most of the stronger bands have been reasonably assigned to the vibrations characteristic of the amide group and the methylene chain of the polyamides, and some new structure–frequency correlations have been established for the polymers.     

Flow-injection determination of inorganic pyrophosphate with use of an enzyme thermistor containing immobilized inorganic pyrophosphate

Inorganic pyrophosphate immobilized on controlled-pore glass is used in a simple flow enzyme thermistor system. The heat produced in hydrolysis of pyrophosphate is enhanced. by using Tris-HCl buffer, pH 7.2, containing 1 mM magnesium chloride, as carrier stream. The calibration graph is linear for 0.1–20 mM pyrophosphate; 500 assays are possible without loss of enzyme activity. For 0.5-ml injections of 10 mM pyrophosphate, the relative standard deviation was 2.0% (n=30). A single determination takes 6 min. Calcuim and strontium interfere.     

Triglyceride determination with use of an enzyme thermistor

The application of a split-flow type of enzyme thermistor for determining triglycerides is described. The device measures the protonation heat produced when a triglyceride is passed through a column containing triacyl glycerol lipase covalently bound to controlled-pore glass beads. The time required for a determination is less than 5 min, and the calibration graph for a triolein standard is linear up to 5 mM. The procedure is used for determining triglycerides in human blood sera and is compared with a conventional spectrophotometric method.     

Catalytic enantioselective desymmetrization of meso-N-acylaziridines with TMSCN

A catalytic enantioselective desymmetrization of meso-N-p-nitrobenzoylaziridines with TMSCN was developed using a chiral gadolinium catalyst generated from Gd(OiPr)3 and d-glucose-derived ligand 1. In this reaction, the addition of a catalytic amount of trifluoroacetic acid (TFA) improved enantioselectivity. High enantioselectivity was obtained from a range of meso-aziridines at 0-60 degrees C. The product could be easily transformed into beta-amino acids. Thus, the developed catalytic enantioselective desymmetrization reaction allowed for efficient catalytic synthesis of chiral cyclic beta-amino acids. The incorporation of TFA into the catalyst complex was observed using ESI-MS. Generation of this new complex might be the origin of the improved enantioselectivity.     

Samarium(II) iodide-induced tandem reductive coupling-Dieckmann condensation reaction: one-step synthesis of bicyclic oxacyclopentanecarboxylate from bis-α,β-unsaturated esters

The tandem cyclization of bis-α,β-unsaturated esters with SmI₂-Sm-THF in the presence of catalytic amount of methanol was found to stereoselectively provide bicyclo[4.3.0]nonan-8-ones and bicyclo[3.3.0]octan-3-ones.     

Concurrent determination of magnesium and calcium in iron ores by atomic absorption spectroscopy

Summary Examinations were made for the concurrent determination of magnesium and calcium in iron ores when present in about equal amounts, using the magnesium-calcium coupled type hollow-cathode lamp in atomic absorption spectroscopy, and a method of measurement was established. Concurrent determination was found to be easily possible by removal of the majority of iron by extraction with methyl isobutyl ketone and addition of strontium. Analytical precision was calculated and found to give satisfactory results (standard deviations: ±0.004% for Ca, ±0.006% for Mg).

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Zusammenfassung Untersuchungen wurden angestellt über die Bestimmung von Magnesium und Calcium nebeneinander in ungefähr gleichen Mengen in Eisenerzen durch Atomabsorptionsspektrometrie. Verwendet wird die Ca-Mg-Doppel-Hohlkathodenlampe. Die Hauptmenge des Eisens wird durch Extraktion mit Methylisobutylketon zuvor entfernt. Außerdem ist zur Vermeidung einer Störung ein Zusatz von Strontium erforderlich. Es werden zufriedenstellende Ergebnisse erhalten (Standardabweichung: ±0,004% für Ca, ±0,006% für Mg).

     

Determination of vitamin B12 as cobalt by electrothermal atomic absorption spectrometry using the solid sampling technique

Summary An investigation has been carried out to establish a rapid method for the determination of vitamin B₁₂ as cobalt in solid pharmaceutical samples by electrothermal atomization atomic absorption spectrometry with the solid sampling technique using an inner miniature cup. Calibration graphs of peak area versus mass of the element were constructed by use of a synthetic reference material (SyRM). The SyRM is prepared by coprecipitation of cobalt ions with magnesium(II) 8-quinolinate. In order to determine the accuracy of the proposed method, three pharmaceutical preparations were analyzed according to the proposed method using standardization against the SyRM and the results obtained compared with those when solutions of the same samples were analyzed by other techniques. There is good agreement between the results obtained from the proposed and the other method. The detection limit for cobalt in a solid pharmaceutical preparation is 0.15 ng/mg (i.e. 4 ng/mg of vitamin B₁₂) for a typical sample mass of 1.0 mg.

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Bestimmung von Vitamin B₁₂ als Cobalt mit Hilfe der elektrothermischen Feststoff-AAS