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41.
Herbert Puderbach Hans Jürgen Ghausen 《Spectrochimica Acta Part B: Atomic Spectroscopy》1984,39(12):1547-1551
Results of examinations with TEM, SEM, EDX, ISS, SIMS and AES on sulphuric acid anodized films on aluminium are reported. Important technical information about the 20-μm thick coatings were obtained by monolayer and depth analysis. The fine structure of the oxide film and its modifications during a sealing process are discussed. Possibilities to prevent sealing smut on the surface are shown. The metal distribution inside the films which are coloured electrolytically with metal salts, is investigated. 相似文献
42.
Zhu H Chai J Chandrasekhar V Roesky HW Magull J Vidovic D Schmidt HG Noltemeyer M Power PP Merrill WA 《Journal of the American Chemical Society》2004,126(31):9472-9473
The reaction of beta-diketiminated aluminum(I) monomer LAl with a large bulky azide N3Ar' (L = HC(CMeNAr)2, Ar' = 2,6-Ar2C6H3, Ar = 2,6-iPr2C6H3) in the temperature range from -78 degrees C to room temperature affords two different isomers 2 and 3, which have been characterized by spectroscopic and X-ray structural analyses, as well as elemental analysis. The variable-temperature 1H NMR kinetic studies of this reaction indicate the existence of the monomer LAlNAr' (1) at low temperature and the thermal stability of the compounds increases in the order of 1 < 2 < 3. 相似文献
43.
An optical biosensor for the determination of hydrogen peroxide based on immobilized horseradish peroxidase is described. The fluorescence of the dimeric product of the enzyme catalysed oxidation of homovanillic acid is utilized to determine the concentration of H2O2. The membrane-bound enzyme is attached to a bifurcated fibre bundle permitting excitation and detection of the fluorescence by a fluorometer. The response of the sensor is linear from 1 to 130 M hydrogen peroxide; the coefficient of variation is 3%. The sensor is stable for more than 10 weeks. The operating pH for maximal sensor response is 8.15. This allows the sensor to be used in combination with oxidase reactions producing hydrogen peroxide, as is demonstrated with a co-immobilized lactate oxidase-horseradish peroxidase optode for the determination of L-lactate. The fluorescence intensity of this sensor depends linearly on the concentration of lactate between 3 and 200 M and a throughput of 10 samples per hour is possible. The precision is in the same range as that of the monoenzyme optode. The lifetime of the bienzyme sensor for lactate is considerably shorter than that of the peroxidase sensor; it is limited by the stability of the immobilized lactate oxidase enzyme. The sensor has been applied to the determination of lactate in control serum. 相似文献
44.
45.
On the Limits of the Zintl Concept. The New Compound Ba7Ga4Sb9 The new compound Ba7Ga4Sb9 crystallizes in the orthorhombic system, space group Pmmn (No. 59) with the lattice constants GaSb4 tetrahedra are connected by common corners and edges to strings, which are connected by long Sb? Sb bonds to sheets, separated by the Ba ions. The compound is not in accordance to the Zintl concept. 相似文献
46.
Organoboranes, readily available via the hydroboration of unsaturated organic compounds, exhibit a remarkable versatility
in their reactions. The boron atom in these organoboranes can be readily converted into a wide variety of organic groups under
very mild conditions, providing simple versatile syntheses of organic compounds. Exploration of these substitution reactions
reveal that, with rare exceptions, the organoboranes transfer the alkyl group to other elements of synthetic interest with
complete retention of stereochemistry. Recently we have discovered a method of synthesizing essentially optically pure organoborane
intermediates. These optically active alkyl groups attached to boron can also be transferred with complete retention of optical
activity. Consequently, it is now possible to achieve by a rational synthesis the preparation of almost any optically active
compound with a chiral center, either R- or S-, in essentially 100% enantiomeric excess. 相似文献
47.
Robert Fugmann Herbert Nickelsen Ingeborg Nickelsen Jakob H. Winter 《Angewandte Chemie (International ed. in English)》1970,9(8):589-595
In mechanized systems used for searching in literature stores there is a steadily growing necessity not only to be able to formulate concepts as a search condition but also the characteristic connections under which these concepts appear in the inquiry. In this way the precision of the mechanized literature search is considerably increased. TOSAR has been developed in order to improve computerized literature searching in this respect. 相似文献
48.
P. Quevauviller M. Lachica E. Barahona A. Gomez G. Rauret A. Ure H. Muntau 《Fresenius' Journal of Analytical Chemistry》1998,360(5):505-511
Single extraction tests are commonly used to study the eco-toxicity and mobility of metals in soils, e.g. to assess the bioavailable
metal fraction (and thus to estimate the related phyto-toxic and nutritional deficiency effects) and the environmentally accessible
trace metals upon disposal of e.g. sediment on to a soil (e.g. contamination of ground waters). However, the lack of uniformity
in the different procedures does not allow the results to be compared worldwide nor the procedures to be validated. This paper
describes the interlaboratory testing of EDTA- and DTPA-extraction procedures for soil analysis, followed by the preparation
of a calcareous soil reference material (CRM 600), the homogeneity and stability studies and the analytical work performed
for the certification of the EDTA- and DTPA- extractable contents of some trace metals (following the standardized extraction
procedures).
Received: 21 May 1997 / Revised: 4 July 1997 / Accepted: 9 July 1997 相似文献
49.
Roesky HW Murugavel R Walawalkar MG 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):324-331
Metal hydroxides represent a very interesting and highly useful class of compounds that have been known to chemists for a very long time. While alkali and alkaline earth metal hydroxides (s‐block) are commonplace chemicals in terms of their abundance and their use in a chemical laboratory as bases, the interest in Brønsted acidic molecular terminal hydroxides of p‐block elements, such as aluminum and silicon, has been of recent origin, with respect to the variety of applications these compounds can offer both in materials science and catalysis. Moreover, these systems are environmentally friendly, relative to the metal halides, owing to their ‐OH functionality (resembling that of water). Design and conceptualization of the corresponding terminal thiols, selenols, and tellurols (M? SH, M? SeH, and M? TeH) offer even more challenging problems to synthetic inorganic chemists. This concept summarizes some of the recent strategies developed to stabilize these otherwise very unstable species. The successful preparation of a number of silicon trihydroxides a few years back resulted in the generation of several model compounds for metal–silicates. The recent synthesis of unusual aluminum compounds such as RAl(OH)2, RAl(SH)2, and RAl(SeH)2 with terminal EH (E=O, Se, or Se) groups is likely to change the ways in which some of the well‐known catalytic conversions are being carried out. The need for very flexible and innovative synthetic strategies to achieve these unusual compounds is emphasized in this concept. 相似文献
50.
The ring-oven technique is a special type of spot analysis. In this review, papers published since 1976 are discussed. The aspects dealt with include developments in the technique and its use, the identification and determination of inorganic ions, organic substances, enzymatic analysis, applications to air and water samples, and combinations with other techniques. 相似文献