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961.
Microwave irradiation reduces the reaction time for the solid-phase synthesis of peptoids. Under these conditions, coupling of each residue requires only 1 min. The purity and yields of peptoids synthesized in this way are as good as or better than those achieved using standard methods. [reaction: see text] 相似文献
962.
The Floating Point Systems, Inc. Model 164 Attached Processor (FPS-164) is a high-speed, pipelined, parallel processor designed for large-scale scientific computation. Benchmark studies of operations common in quantum chemistry codes are discussed and the performance of the FPS-164 is compared with other commonly available computers. A complete system of electronic structure codes has been implemented on the FPS-164 using the Fortran-77 cross-compiler and calls to optimized vector and matrix routines. The conversion of a generalized valence bond (GVB ) code illustrates the strategy adopted to adapt Fortran codes to the FPS-164. A typical production example, a large scale (GVB ) and configuration interaction calculation on the vinyl radical, shows a net throughput equivalent to nearly nine VAX 11/780 computers. 相似文献
963.
964.
Ion-selective poly(vinyl chloride) membrane electrodes for the opium alkaloids papaverine and ethaverine are presented. The electrode membranes contain ion pairs of the alkaloids with the anionic counter ion tetraphenylborate. The detection limits for all electrodes were approximately 2 x 10(-6) mol dm-3 at pH 5.0 in 100 mmol dm-3 buffered solutions and the measured slopes were close to the values theoretically expected. The selectivity coefficient observed for the ethaverine-tetraphenylborate electrode is 10(-1.1) with respect to papaverine. The suitability of the membranes for single-use electrodes is discussed. 相似文献
965.
Dr. F. David Peat 《Theoretical chemistry accounts》1972,24(1):11-15
It is suggested that certain transition density matrices, N-representable in a limit, be used in a variational calculation. It is noted that such trial matrices should yield reasonable values for the ground state energies of small atoms or molecules provided a set of overlap integrals is maximised.
Zusammenfassung Es wird vorgeschlagen, bestimmte Übergangsdichtematrizen, die im Limit N-darstellbar sind, in einer Variationsrechnung zu benutzen. Es wird festgestellt, daß solche Näherungsmatrizen gute Werte für die Energie des Grundzustandes kleiner Atome oder Moleküle geben sollten, falls im Satz von Überlappungsintegralen maximiert wird.
Résumé On propose d'utiliser dans un calcul variationnel certaines matrices densité de transition, N représentables à la limite. Ces matrices d'essai devraient fournir des valeurs raissonnables pour l'énergie de l'état fondamental dans les petits atomes et les petites molécules à condition de maximiser un ensemble d'intégrales de recouvrement.相似文献
966.
Prof. Dr. Hans Nowotny Josef Tomiska László Erdélyi Adolf Neckel 《Monatshefte für Chemie / Chemical Monthly》1977,108(1):7-19
By means of vapor pressure measurements using theTorker method (Torsion-Knudsen Effusion Recoil) as well as theKnudsen tanspiration technique in connection with a mass spectrometer, the heats of formation of the following compounds were found to be –6.5±0.7 kcal/g atom (Mn0.366Si0.634), –7.8±0.6 kcal/g atom (Mn0.50Si0.50), –7.3±0.6 kcal/g atom (Mn0.625Si0.375), and –6.6±0.6 kcal/g atom (Mn0.75Si0.25).
Mit 7 Abbildungen 相似文献
Mit 7 Abbildungen 相似文献
967.
A. K. Maheshwari Dr. D. S. Jain J. N. Gaur 《Monatshefte für Chemie / Chemical Monthly》1977,108(2):279-283
The reduction of Cd(II) in propylenediamine was found to be reversible and diffusion controlled. The complexes of Cd(II) with propylenediamine in 25%, 50%, and 75% dimethylformamide have been studied polarographically using theDeFord andHume's treatment as extended byIrving. Increase in the stability constants was observed with increase in dimethylformamide percentage. The percentage composition of the various complexed and uncomplexed species in 25% and 50% dimethylformamide are presented. 相似文献
968.
Dr. Margareta Ruse Rodica Vulcu Iuliana Jepan 《Monatshefte für Chemie / Chemical Monthly》1976,107(4):1007-1010
Phenylpyruvic acid reacts with p-nitroaniline to yield the 3-hydroxypyrrolinone2a, and with anilines bearing+M substituents in the p-position to yield the 3-enaminopyrrolinones1b-1e.
Mit 1 Abbildung
5. Mitt.:M. Ruse, E. Hamburg undM. Petri, Chem. Ber.103, 3727 (1970). 相似文献
Mit 1 Abbildung
5. Mitt.:M. Ruse, E. Hamburg undM. Petri, Chem. Ber.103, 3727 (1970). 相似文献
969.
Tomcík P Jencusová P Krajcíková M Bustin D Brescher R 《Analytical and bioanalytical chemistry》2005,383(5):864-868
An interdigitated microelectrode array (IDA) was applied to the determination of formaldehyde released from textiles produced
in industry. The proposed method is based on formaldehyde reaction with hypobromite which is formed in weakly basic media
by control current electrooxidation of bromide on the generator segment of the IDA array. The unreacted hypobromite diffuses
through the gap between individually polarisable IDA segments and it is amperometrically detected on the collector segment
of the IDA. The efficiency of this nonconvective transfer process in the absence of formaldehyde was substantially higher
(78%) in comparison with that when using the rotating ring disc electrode. The influence of the added formaldehyde on the
transfer process can be utilised to develop a simple and sensitive analytical procedure for formaldehyde detection with a
detection limit of 4×10−6 mol dm−3. 相似文献
970.
Ródenas-Torralba E Cava-Montesinos P Morales-Rubio A Cervera ML De La Guardia M 《Analytical and bioanalytical chemistry》2004,379(1):83-89
The aim of this study is to show the advantages of the emerging multicommutation methodology based on the use of solenoid valves for Te determination in milk by hydride generation atomic fluorescence spectrometry (HG-AFS). The delivery of a series of alternating sequential insertions of small volumes of samples and reagents gives rise to new hydrodynamic processes and exciting analytical potentials by controlling the time of flow through the on/off-switched solenoid valves. This drastically reduces the reagent consumption by a factor of 4 and the generation of effluents (590 mL h–1 instead of 750 mL h–1 generated by the continuous-mode measurement) and also provides an improvement in the laboratory productivity by an increase of the sample throughput (85 h–1 compared to 20 h–1 found in the continuous mode). So, multicommutation is an environmentally and economically sustainable alternative to the methodology based on continuous measurements. The multicommutation-based method developed was applied to tellurium determination in commercially available milk samples; a calibration range of 0.0–0.5 ng mL–1 and a detection limit of 0.20 ng L–1 with average relative standard deviation of 2.1% were found. Comparable results were obtained for a series of samples using both continuous and multicommutation HG-AFS modes. 相似文献