Eine einfache Methode zur Bestimmung der alkalischen Bestandteile von Backpulvern sowie von Waschl?sungen aus Alkaligemischen

Ohne Zusammenfassung     

Wismut

Ohne Zusammenfassung     

Nachweis und Bestimmung des Eisens, sowie seine Trennung von anderen Elementen

Ohne Zusammenfassung     

Elektrometrie

Ohne Zusammenfassung     

7,11-epi-thyrsiferol: completion of its synthesis, evaluation of its antimitotic properties, and the further development of an SAR model

We (a) describe the completion of a total synthesis of 7,11-epi-thyrsiferol (4), (b) compare the antimitotic activities of thyrsiferol (2), Delta15,28-dehydrothyrsiferol (3), and 7,11-epi-thyrsiferol (4), (c) evaluate the synergistic behavior of the title compound and colchicine to inhibit cell proliferation, and (d) describe the results of conformational searches that provide additional insight concerning the SAR profile of the thyrsiferol family of natural products.     

Infrared negative luminescent devices and higher operating temperature detectors

Infrared LEDs and negative luminescent devices, where less light is emitted than in equilibrium, have been attracting an increasing amount of interest recently. They have a variety of applications, including as a ‘source’ of IR radiation for gas sensing; radiation shielding for, and non-uniformity correction of, high sensitivity staring infrared detectors; and dynamic infrared scene projection. Similarly, infrared (IR) detectors are used in arrays for thermal imaging and, discretely, in applications such as gas sensing. Multi-layer heterostructure epitaxy enables the growth of both types of device using designs in which the electronic processes can be precisely controlled and techniques such as carrier exclusion and extraction can be implemented. This enables detectors to be made which offer good performance at higher than normal operating temperatures, and efficient negative luminescent devices to be made which simulate a range of effective temperatures whilst operating uncooled. In both cases, however, additional performance benefits can be achieved by integrating optical concentrators around the diodes to reduce the volume of semiconductor material, and so minimise the thermally activated generation-recombination processes which compete with radiative mechanisms. The integrated concentrators are in the form of Winston cones, which can be formed using an iterative dry etch process involving methane/hydrogen and oxygen. We present results on negative luminescence in the mid- and long-IR wavebands, from devices made from indium antimonide and mercury cadmium telluride, where the aim is sizes greater than 1 cm×1 cm. We also discuss progress on, and the potential for, operating temperature and/or sensitivity improvement of detectors, where very high-performance imaging is anticipated from systems which require no mechanical cooling.     

Accurate base composition of double-strand DNA by mass spectrometry

An accurate molecular weight (M_r) assignment for a double-strand (ds) DNA determines or greatly restricts the possible number of each of its four bases, while the compositions for its two single-strand (ss) components can also be derived from their M_r values. For a ds 64-mer (39 kDa), the ss-M_r values (± 0.5 Da) of its high-resolution mass spectrum from an electrospray ionization/Fourier transform instrument yield only the correct ds- and ss-base compositions. Literature mass spectra of lower mass accuracy show that such data can also restrict their possible composition assignments, with further discrimination using the abundance vs. base composition of small fragment ions from the dissociation of the ss molecular ions.     

Practical analysis of high purity chemicals--V. Precision silver chloride gravimetry

A reasonably simple gravimetric silver chloride procedure with fairly wide tolerance in conditions is presented in full detail with all critical steps and precautions delineated. The procedure allows the precision determination of chloride by analysts having limited expertise with exacting gravimetric methods, and can be performed with equipment common to nearly all laboratories and without dependence on a standard substance. The elapsed and actual working times for the assessment of a solid sample in triplicate are 65 and 10-12 hr respectively. The application of the procedure to the assay of some high-purity chloride salts and to the standardization of hydrochloric acid solutions is described.