On a characterization of the normal distribution by means of identically distributed linear forms

Let X₁, X₂,…, be independent, identically distributed random variables. Suppose that the linear forms L₁ = Σ_j=1^∞a_jX_j and L₂ = Σ_j=1^∞b_jX_j exist with probability one and are identically distributed; necessary and sufficient conditions assuring that X₁ is normally distributed are presented. The result is an extension of a theorem of Linnik (Ukrainian Math. J.5 (1953), 207–243, 247–290) concerning the case that the linear forms L₁ and L₂ have a finite number of nonvanishing components. This proof only makes use of elementary properties of characteristic functions and of meromorphic functions.     

Antioxidants and stabilizers: Part IC—Hydroperoxide deactivation by aliphatic sulfides. A model study

The hydroperoxide decomposing efficiencies of dioctadecylsulfide (I), dioctadecyldisulfide (IV) and dioctadecyl 3,3-thio-dipropionate (VII) have been compared at 75°C and 85°C. The formation of oxidation products from (I) and (IV) has been checked. Experimental evidence is given of the important rôle of the activation of the molecule of (IV) by the presence of two sulfidic sulfur atoms compared with the activation of the sulfur atom in (VII) by the alkoxycarbonyl group in the beta position. The explanation of the high efficiency of disulfide has been based on the formation of thiosulfinate—the key intermediate for the generation of peroxidolytic species—in the first reaction step.     

Distribution and valence of the cations in the spinel system Fe3O4-Fe2VO4

The Mössbauer spectra of the solid solution Fe[Fe_xV_2–x]O₄ within 1.0×2.0 consist of two sets of sextets corresponding to A- and B-sites. From the superimposed sextets of the B-site pattern result typical values of isomer shift and internal magnetic field strength due to different environments of the B-site iron. It is shown that V ions both enhance the conduction electron density at the neighbouring Fe ions and diminish the strength of the magnetic interactions.     

Efficient method for visualization and isolation of proteins resolved in polyacrylamide gels

Polyacrylamide gel electrophoresis is a popular method used to purify proteins for reconstitution experiments, amino acid composition and sequence determinations. In this report we describe methods that will be of general use in the isolation and characterization of proteins and the benefits of substituting boric acid for glycine in the electrophoresis tray buffers. We also describe how proteins resolved in a variety of gel systems (including those containing sodium dodecyl sulfate) may be rapidly visualized with 8-anilino-1-naphthalene sulfonic acid and efficiently transferred to a second gel for two-dimensional gel analysis, or isolated by electroelution for subsequent characterization.     

Enzyme and microbial sensors for phosphate, phenols, pesticides and peroxides

Biosensors employing a biocatalyst on a different level of integration have been developed for monitoring environmental pollution. These probes range from laboratory specimen to commercial detectors applied to analyzers. Recent developments on amperometric enzyme and microbial biosensors are presented here. A monoenzymatic bulk-type carbon electrode is described for biosensing organic hydroperoxides in aqueous solutions; peroxidase is immobilized within the electrode body and the direct electron transfer between electrode and enzyme is measured. Both, reversible and irreversible inhibitors of acetylcholinesterase have been quantified by using a kinetically controlled acetylcholine enzyme sequence electrode. The inhibitory effect of pesticides such as butoxycarboxime, dimethoate, and trichlorfon could be quantified within 6 min in molar concentrations. Different multi-enzyme electrodes have been developed for the determination of inorganic phosphate. These sensors represent examples of sequentially acting enzymes in combination with enzymatic analyte recycling. Using this type of amplification nanomolar concentrations can be measured.     

Kryoskopische Reinheitsbestimmung kleiner Substanzmengen nach der Methode der konstantgesteuerten aufgepr?gten W?rmerate

Zusammenfassung Zur Reinheitsbestimmung schmelzbarer, vorwiegend organischer Proben wurde eine kryoskopische Apparatur nachSmit gebaut. Sie arbeitet oberhalb 99 Mol-% im Halbmikrobereich, wobei der Absolutwert der Reinheit auf ±0,05 Mol-% genau meßbar ist. Die Probe, die ständig unter strömendem Stickstoff gehalten wird, umgibt als dünne Schicht ein Platin-Widerstandsthermometer, das sich in der Mitte eines elektrisch geheizten Aluminiumzylinders befindet. Konstanz der Wärmezufuhr wird gesichert durch Regelung der Temperaturdifferenz gegen ein gleichartiges zweites Thermometer, das dicht am geheizten Zylindermantel eingesteckt ist. Die Thermometer brauchen nicht geeicht zu werden. Die Regelung wird durch eine Doppel-Wheatstonebrücke vermittelt, deren einer Ausgang auf den Schreiber und deren anderer auf die Heizung wirkt. Die graphische Auswertung ist aus dem Zweiphasen-Diagramm fest-flüssig abgeleitet. Als Bezugsstandard ist eine zweite Probe zu messen, die man durch Verunreinigung der ursprünglichen Substanz um einen bekannten Betrag erhält.

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Summary A cryoscopic apparatus for the purity assay of fusible, mostly organic samples was built afterSmit. It works in the half-micro scale above 99 mole%, where the absolute value of the purity will lie within ±0.05 mole%. The sample, which is always kept under streaming nitrogen, surrounds as a thin layer a platinum resistance thermometer that stands in the center of an electrically heated aluminium cylinder. A constant supply of heat is ensured by controlling the temperature difference against a second thermometer of the same kind, which is inserted near the heated periphery of the cylinder. It is not necessary to calibrate the thermometers. Control is mediated by a double Wheatstone bridge, the one output of which acts on the recording device, the other on the heater. The graphical evaluation of the records derives from the two-phase diagram solid-liquid. As a referential instance, a second sample has to be measured, which is obtained from the specimen through artificial contamination by a known amount.

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Unter Mitarbeit von F.Weigand und R.Baumgart.

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Herrn Dr.Ebinger, AEG-Meßgerätefabrik Berlin-Reinickendorf und Herrn Dipl.-Ing. Lutz, AEG-Büro Mannheim, habe ich für ihre große Bereitwilligkeit zu danken, mit der sie auf die Wünsche zur Bauart der Brücke eingingen. — Für Anregungen danke ich Herrn Dr.Kienitz.