Diazoverbindungen. 72. (Diazoalkyl)phosphane – Synthese durch elektrophile Diazoalkansubstitution und oxidative Additionsreaktionen am Phosphor

Diazo Compounds. 72. Diazoalkylphosphanes – Synthesis by Electrophilic Diazoalkane Substitution and Oxidative Addition Reactions at Phosphorus Electrophilic diazoalkane substitution of the diazomethyl compounds 1a,b with the chloro phosphanes 2a-o in the presence of lithium diethylamide yields the diazoalkyl phosphanes 3a-z . Oxidative addition of oxygen, sulfur and selenium at phosphorus leads into the series of oxo, thioxo and selenoxo phosphanes having diazoalkyl substituents ( 4a-d, 5a-m and 7a-d ). The silyl group of 5n,o is cleaved by chromatography on aluminium oxide to yield the (diazomethyl)phosphane sulfides 6a,b .     

Synthese von Heterocyclen mit Hydroxymethylenketonen. XIV [1]. Zur Regioselektivität der Reaktion von Acetylacetaldehyd mit Tryptamin

Synthesis of Heterocyclic Compounds with Hydroxymethylene Ketones. XIV. Contribution to the Regioselectivity of the Reaction of Acetoacetaldehyde with Tryptamine The range of substitution products of tryptamine with acetoacetaldehyde as substituent at the basic or the indole nitrogen ( 2, 3 ) is completed by a product containing the substituent in the indole α-position ( 5 ). It is formed by ring opening of the tetrahydro-β-carboline 4 . The reaction conditions are commented and the ¹H-NMR spectra comparatively discussed. The synthesis of the azocino-indole 7 is described.     

Photoinitiierte Polymerisation mit Dialkoxythiocarbonyldisulfiden – eine Polymerisationsreaktion mit Primärradikalabbruch

Photoinitiated Polymerization with Dialkoxy Thiocarbonyl Disulfides – a Polymerization Reaction with Primary Radical Termination The photoinduced free radical polymerization of methyl methacrylate (MMA) and some other vinyl monomers using dialkoxy thiocarbonyl disulfides ( 1 – 4 ) as photoinitiators was studied. The photolysis of these initiators leads to cleavage of the S S bond, which was determined by spin trapping experiments with phenyl tert-butyl nitrone. No evidence was found for a further thermal decomposition of the primary alkoxy thiocarbonyl sulfide radicals (R·) at room temperature. In the absence of scavengers the primary radicals react back exclusively to the initial compounds, due to a strong cage effect. By means of UV spectroscopic measurements and in the presence of MMA the quantum yields of the initiator decomposition were detected to be 0.8. The polymerization of acrylic and methacrylic derivatives can be initiated by the R·, contrary to the situation with fumarates and maleates. The mechanism of MMA polymerization depends on the light intensity absorbed by the initiators. At high intensities the combination of primary and polymer radicals terminates the chain reaction. This follows from the measured monomer exponent of α = 2, the light intensity exponent of β = 0,2 and the number of thiocarbonyl end groups of 2 in the polymers isolated. Contrary to this, in the low intensity region the experimental data obey the ideal kinetic equation. Kinetic modelling gives evidence for an interaction of the monomer with the cage radicals.     

Production of Polyunsaturated Fatty Acids by Mortierella alpina Using Submerse and Solid State Fermentation

A new isolate of Mortierella alpina, > 98 % identical with M. alpina ATCC 16266, was cultivated in a defined glucose‐based medium with three organic nitrogen sources (glycine, urea and Na‐L‐glutamate) at three different concentrations in shaking flasks at 20 °C. The results were compared to the cultivation in complex medium with yeast extract as nitrogen source. In the defined media, high yields of polyunsaturated fatty acids (PUFAs) and arachidonic acid (ARA), respectively, were obtained with Na‐L‐glutamate. However, the absolute highest yields of PUFA and ARA were measured with the yeast extract medium. An optimized yeast extract complex medium was used for a submerse bioreactor cultivation in a 45‐L scale. Furthermore, M. alpina was cultivated in a solid state fermenter, using an oat bran water mixture as substrate.     

Thin film lithium niobate for use in silicon based devices

The incorporation of a thin film of lithium niobate (LiNbO3) in a conventional MOS (metal-oxide-semiconductor) structure gives the possibility of two fundamentally different types of computer memory architectures. One, based on ferroelectric switching involves the reorganization of charge in the transistor channel to compensate for the change in polarization. Another, based on the bulk photovoltaic effect, involves a shift in the transistor threshold with exposure to differing intensities of incident light. With the use of a molybdenum liftoff process, transistors have been fabricated in which LiNbO3 replaces the usual gate oxide of an MOS transistor. Transistor parameters such as the transconductance, output conductance, and amplification for these devices are reported.     

Reoptimization of the Shortest Common Superstring Problem

A reoptimization problem describes the following scenario: given an instance of an optimization problem together with an optimal solution for it, we want to find a good solution for a locally modified instance.     

Impacts of Climate Variables on Residential Water Consumption in the Czech Republic

The paper investigates whether there is a statistically significant impact of short-term climate variables (specifically air temperature and rainfall) on residential water consumption at two selected case sites in the Czech Republic. The analysis is based on a unique time series of daily data from 2004–2009. The statistical methods used are CART methodology and a decomposition of these time series based on a locally weighted regression method. Apart from the data analysis results, the investigation raises several methodological questions regarding the use of daily data and the scope of analysis based on such data sets.     

Electrical switching in lithium niobate thin films

The ferroelectric switching properties of thin films of lithium niobate (LiNbO3) on silicon have been investigated. The polarization is shown to be partially reversible with an applied electric field at room temperature. The samples were films of LiNbO3 which were magnetron sputter deposited on silicon substrates. A double pulse method was used to investigate the ferroelectric switching properties of the films. Evidence for partial stable switching of the LiNbO3 film was observed at a field of roughly 500 kV/cm.     

Analysis of polycyclic aromatic hydrocarbons in soil: minimizing sample pretreatment using automated Soxhlet with ethyl acetate as extraction solvent

A simplified sample pretreatment method for industrially PAH-contaminated soils applying automated Soxhlet (Soxtherm) with ethyl acetate as extraction solvent is presented. Laborious pretreatment steps such as drying of samples, cleanup of crude extracts, and solvent exchange were allowed to be bypassed without notable performance impact. Moisture of the soil samples did not significantly influence recoveries of PAHs at a wide range of water content for the newly developed method. However, the opposite was true for the standard procedure using the more apolar 1:1 (v/v) n-hexane/acetone solvent mixture including postextraction treatments recommended by the U.S. EPA. Moreover, ethyl acetate crude extracts did not appreciably effect the chromatographic performance (HPLC-(3D)FLD), which was confirmed by a comparison of the purity of PAH spectra from both pretreatment methods. Up to 20% (v/v) in acetonitrile, ethyl acetate proved to be fully compatible with the mobile phase of the HPLC whereas the same concentration of n-hexane/acetone in acetonitrile resulted in significant retention time shifts. The newly developed pretreatment method was applied to three historically contaminated soils from different sources with extraction efficiencies not being significantly different compared to the standard procedure. Finally, the certified reference soil CRM 524 was subjected to the simplified procedure resulting in quantitative recoveries (>92%) for all PAHs analyzed.