Zur Analytik mikrobiocider Isothiazolone

Zusammenfassung Zur Isolierung von 2-Methyl-isothiazol-3-on und 5-Chlor-2-methyl-isothiazol-3-on bzw. 2-n-Octylisothiazol-3-on aus den entsprechenden handelsüblichen Formulierungen wie Kathon CG bzw. Kathon 893 wird eine einfache, rasch durchzuführende Methode beschrieben. Die Methode basiert auf Fraktionierung durch Anwendung der Flash-Chromatographie — einer optimierten Variante der Niederdruck-Säulen-Chromatographie.Die erhaltenen Fraktionen wurden mit Hilfe von Dünnschicht-Chromatographie und Hochleistungs-Flüssigkeits-Chromatographie auf ihre Identität und Reinheit untersucht. Anschließend wurden die Gehalte mit einer im Halbmikromaßstab ausgeführten maßanalytischen Absolutmethode bestimmt. Diese Lösungen können als Eichbzw. Kalibrierungsstandards für Quantifizierungszwecke verwendet werden.

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Analysis of microbiocidal isothiazolonesIV. Separation of commercial formulations by flash chromatography and determination of the content by an iodometric absolute method

Summary A method is described for the separation of 2-methyl-isothiazol-3-one and 5-chloro-2-methyl-isothiazol-3-one resp. 2-n-octyl-isothiazol-3-one from corresponding commercial formulations as Kathon CG resp. Kathon 893. This simple and fast method is based on fractionation by flash chromatography — an optimized version of low-pressure column chromatography.The fractions received were analyzed by thin-layer chromatography and high-performance liquid chromatography regarding their identity and purity. The isothiazolone contents were determined by an iodometric absolute method. These solutions can be used as calibration standards for quantification.

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Teil III: Fresenius Z Anal Chem (1985) 322:465     

Beta-delayed proton emitter kr

The nucleide ⁷³Kr has been identified by on-line mass separation as a precursor of β-delayed proton emission. The proton branch is (6.8 ±1.2) × 10⁻³ proton/decay. The protons populate the ground state and also the first excited 2⁺ state at 866 keV in ⁷²Se with a relative intensity of (35±9) %. The value of Q_EC−B_p, where B_p is the proton separation energy for the nucleus ⁷³Br, is found to be 4.85 ±0.30 MeV based on the fraction of proton events preceded by positron decay.     

Identification of threo-ig-fluoro.9,10-Dihydroxystearic acid:a novel cofluorinated fatty acid from dichapetalum toxicarium seeds.

A novel co-fluorinated fatty acid has been isolated from seeds of Dichapetalum toxicarium and identified as threo-18-fluoro-9,10-dihydroxystearic acid (1).     

Comments on "Speech Understanding and Aging"

The hypothesis advanced by the CHABA Working Group on Speech Understanding and Aging [J. Acoust. Soc. Am. 83, 859-895 (1986)] that the systematic decline in speech understanding with age might be explained by concomitant decline in extra-auditory cognitive factors was tested by examining speech audiometric findings in patients with dementia. The fact that performance was consistent with normal central auditory function in 12 of 23 such patients, in spite of deficits in immediate memory for spoken material, tolerance of distraction, mental tracking and sequencing, cognitive flexibility, and set shifting argues against the hypothesis that speech understanding deficits in the elderly can be explained as the simple consequence of cognitive decline.     

Polylactide. II. Viscosity–molecular weight relationships and unperturbed chain dimensions

Mark–Houwink equations for benzene and chloroform solutions of S-polylactide and racemic polylactide were established by end-group analysis of partly hydrolyzed polymers. Unperturbed chain dimensions calculated for both polymers reveal a considerable difference and suggest a helical conformation for S-polylactide in solution. This finding supports ¹H-NMR observations that reveal chemical shift differences that appear when the same configurational sequence is present in two stable conformational states.     

10-Gbit/s dispersion-managed soliton transmission over 16,500 km in standard fiber by reduction of soliton interactions

We show experimentally and numerically that in high-speed strongly dispersion-managed standard fiber soliton systems nonlinear interactions limit the propagation distance. We present results that show that the effect of these interactions can be significantly reduced by appropriate location of the amplifier within the dispersion map. Using this technique, we have been able to extend the propagation distance of 10-Gbit/s 2(31)-1pseudorandom binary sequence soliton data to 16, 500km over standard fiber by use of dispersion compensation. To our knowledge this distance is the farthest transmission over standard fiber without active control ever reported, and it was achieved with the amplifier placed after the dispersion-compensating fiber in a recirculating loop.     

Defining continuity of real functions of real variables

Continuity of a real function of a real variable has been defined in various ways over almost 200 years. Contrary to popular belief, the definitions are not all equivalent, because their consequences for four somewhat pathological functions reveal five essentially different cases. The four defensible ones imply just two cases for continuity on an interval if that is defined by using pointwise continuity at each point. Some authors had trouble: two different textbooks each gave two arguably inconsistent definitions, three more changed their definitions in their second editions, two more claimed continuity at a point for functions not defined there, and one gave a definition implying it for a function with no limit there.     

Containment of socially optimal policies in multiple-facility Markovian queueing systems

We consider a Markovian queueing system with N heterogeneous service facilities, each of which has multiple servers available, linear holding costs, a fixed value of service and a first-come-first-serve queue discipline. Customers arriving in the system can be either rejected or sent to one of the N facilities. Two different types of control policies are considered, which we refer to as ‘selfishly optimal’ and ‘socially optimal’. We prove the equivalence of two different Markov Decision Process formulations, and then show that classical M/M/1 queue results from the early literature on behavioural queueing theory can be generalized to multiple dimensions in an elegant way. In particular, the state space of the continuous-time Markov process induced by a socially optimal policy is contained within that of the selfishly optimal policy. We also show that this result holds when customers are divided into an arbitrary number of heterogeneous classes, provided that the service rates remain non-discriminatory.