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31.
Summary Salts of the anions [SnX5]–, [SnX4Cl, [SnX3Cl2]–, [SnX3]–, [PbX3]–, [SbX4]–, [SbX3Cl]–, [SbX2Cl2]–, [BiX4]–, [AuCl2]–, [AuX2]–, [AuXCl]–, [AuX4]–, [Au2X6]2– and [PtX4]2–, where X– = C6F5S–, have been isolated and characterised. The neutral SbX3 and BiX3 species, have also been isolated and shown to be pyramidal monomers (19F.n.m.r., i.r., and Raman spectral evidence). Various physical properties of the complexes prepared, as well as their stereochemistries (where these could be ascertained), are similar to those of the known corresponding halogeno compounds of these elements. These results further demonstrate the pseudo-halide nature of the pentafluorothiophenoxide ion.Author to whom all correspondence should be directed at: Laboratoire de Chimie de Coordination, Uniyersité Louis Pasteur, 67008 Strasbourg, France. 相似文献
32.
Automatic classification of two-dimensional gel electrophoresis pictures by heuristic clustering analysis: a step toward machine learning 总被引:3,自引:0,他引:3
The interpretation of two-dimensional gel electrophoresis (2-DGE) profiles can be facilitated by artificial intelligence and machine learning programs. We have incorporated into our 2-DGE computer analysis system (termed MELANIE-Medical Electrophoresis Analysis Interactive Expert system) a program which automatically classifies 2-DGE patterns using heuristic clustering analysis. This program is a step toward machine learning. In this publication, we describe the classification method and the preliminary results obtained with liver biopsy electrophoretograms. Heuristic clustering is also compared to other classification techniques. 相似文献
33.
Corsi DM Vander Elst L Muller RN van Bekkum H Peters JA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(7):1383-1389
We conducted relaxometric and water exchange studies of the cationic [Gd((S,S,S,S)-THP)(H2O)]3+ complex (THP 1,4,7,10-tetrakis(2-hydroxy-propyl)-1,4,7,10-tetraazacyclododecane). While the NMRD profiles obtained are typical for DOTA-like complexes (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate), variable-temperature 7O NMR investigations revealed a relatively high water exchange rate (k(298)(ex) = 1.89 x 10(7) s(-1)). These results differ from those reported for other cationic tetraamide macrocyclic Gd(III) complexes, which exhibit characteristically low exchange rates. Since the low exchange rates are attributed partially to the geometry of the M isomer (square antiprismatic) in the tetraamide derivatives, the atypical water exchange rate observed in [Gd((S,S,S,S)-THP-(H2O)]3+ may result from a twisted square antiprismatic structure in this complex and from the relatively high steric strain at the water coordination site as a result of the presence of methyl groups at the alpha-position with respect to the Gd(III)-bound O atoms of THP. 相似文献
34.
Abstract The most widely used agents for photodynamic therapy are the porphyrin photosensitizers. It has been shown that hematoporphyrin derivative (HpD) can cause murine marrow hypercellularity and splenic hypertrophy. We have examined the effect on survival and marrow cellularity of high dose l,3-bis(2-chloroethyl)-l-nitrosourea (BCNU) after HpD or dihematoporphyrin ether (DHE) pretreatment in C57BL/6J mice.
The lethal toxicity of the LDS0 + 10% dose of BCNU (60 mg kg−1 ) was significantly reduced by pretreatment with HpD when the HpD was administered at least 3 days prior to the BCNU. HpD administered 1 or 2 days prior to BCNU or after BCNU had no effect. The percent death rate was reduced from 80 to 0% when HpD was administered 7 and 5 days prior to BCNU.
No alteration of the lethal toxicity rate of BCNU at doses of 80 mg kg−1 were identified with DHE pretreatment although some increase in median survival was noted in two groups. Some reduction in lethal toxicity was noted when 60 mg kg−1 BCNU was used and the pretreatment dose of DHE was 10 or 25 mg kg−1 given twice 3 days apart. Furthermore, a significant reduction of BCNU induced marrow cell depletion was found when low doses of DHE were used as pretreatment. High doses of DHE resulted in marrow depletion. Both HpD and DHE altered the toxicity of BCNU.
Should porphyrin photosensitizers, which alone have little toxicity, prove to protect against nitrosourea toxicity then an important dose limiting factor (myelotoxicity) could be altered if not reduction in the tumouricidal activity occurs. 相似文献
The lethal toxicity of the LD
No alteration of the lethal toxicity rate of BCNU at doses of 80 mg kg
Should porphyrin photosensitizers, which alone have little toxicity, prove to protect against nitrosourea toxicity then an important dose limiting factor (myelotoxicity) could be altered if not reduction in the tumouricidal activity occurs. 相似文献
35.
It is demonstrated that a certain amount of order can be extracted from an apparently random distribution of pores in sedimentary rocks by exploiting the scaling characteristics of the geometry of the porespace with the help of fractal statistics. A simple fractal model of a sedimentary rock is built, and is tested against both the Archie law for conductivity and the Carman-Kozeny equation for permeability. We demonstrate how multifractal scaling of pore-volume can be used as a tool for rock characterization by computing its experimentalf() spectrum, which can be modelled by a simple two-scale Cantor set. 相似文献
36.
Muller A Zhou Y Zhang L Bogge H Schmidtmann M Dressel M Slageren J 《Chemical communications (Cambridge, England)》2004,(18):2038-2039
The highly charged nanocontainer capsule of the type [pentagon]12[linker]30 identical with [(Mo)Mo5O21(H2O)6]12[Mo2O4(SO4)]30 with 20 nanosized pores and channels allows the entrance of cations like Pr3+: the latter are positioned at two different sites and have two different coordination shells, corresponding to a coordination chemistry under confined conditions; a fascinating aspect is that capsule encapsulated water shells fixed by hydrogen bonds act formally as polydentate ligands. 相似文献
37.
Fontaine P Goldmann M Muller P Fauré MC Konovalov O Krafft MP 《Journal of the American Chemical Society》2005,127(2):512-513
We report the first direct evidence for the formation of circular surface micelles (hemimicelles) on the surface of water. These highly monodisperse 30 nm hemimicelles, made from a semifluorinated alkane deposited as a Langmuir monolayer, form organized hexagonal arrays as determined by small-angle X-ray diffraction conducted directly on the water surface at grazing incidence. 相似文献
38.
Luce VanderElst Audrey Sessoye Sophie Laurent RobertN. Muller 《Helvetica chimica acta》2005,88(3):574-587
The self‐diffusion (Dc) coefficients of various lanthanum(III) diamagnetic analogues of open‐chain and macrocyclic complexes of gadolinium used as MRI contrast agents were determined in dilute aqueous solutions (3–31 mM ) by pulsed‐field‐gradient (PFG) high‐resolution 1H‐NMR spectroscopy. The self‐diffusion coefficient of H2O (Dw) was obtained for the same samples to derive the relative diffusion constant, a parameter involved in the outersphere paramagnetic‐relaxation mechanism. The results agree with an averaged relative diffusion constant of 2.5 (±0.1)×10?9 and of 3.3 (±0.1)×10?9 m2 s?1 at 25 and 37°, respectively, for 'small' contrast agents (Mr 500–750 g/mol), and with the value of bulk H2O (2.2×10?9 and 2.9×10?9 m2 s?1 at 25° and at 37°, respectively) for larger complexes. The use of the measured values of Dc for the theoretical fitting of proton NMRD curves of gadolinium complexes shows that the rotational correlation times (τR) are very close to those already reported. However, differences in the electronic relaxation time (τSO) at very low field and in the correlation time (τV) related to electronic relaxation were found. 相似文献
39.
Pericàs MA Puigjaner C Riera A Vidal-Ferran A Gómez M Jiménez F Muller G Rocamora M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(18):4164-4178
New families of enantiopure bis(oxazolines) with 4,5-trans (5 a-g) or 4,5-cis (6 c) stereochemistry at the individual rings have been prepared in high yield. Their eta(3)-allyl palladium complexes (8 a-g, 9 c and 10) have been used as catalytic precursors in allylic alkylation reactions with excellent enantioselectivities (up to 96 %) for the trans oxazoline derivatives, while Pd/6 c system was inactive. NMR studies on palladium eta(3)-1,3-diphenylallyl intermediates (11 a, c and e) showed the presence of syn/syn- and syn/anti-allyl isomers in solution; this resembles the first example of eta(3)-eta(1)-eta(3) isomerism in Pd allylic complexes containing bis(oxazolines) derived from malonic acid. 相似文献
40.
R. Kubiak T. Muller T. Maurer K. W. Eichhorn 《International journal of environmental analytical chemistry》2013,93(1-4):349-358
Abstract Comparative volatilization experiments were carried out using isoproturon and parathion-methyl sprayed on French beans in field experiments and on plant stands (0.5 m2) in the volatilization chamber developed by the SLFA Neustadt using both compounds 14C-labelled. The experimental conditions in the field experiments concerning wind speed, temperature and humidity fluctuations were simulated in the volatilization chamber. The laboratory experiment reflected the actual outdoor situation, showing only a negligible amount of volatile isoproturon directly measured in air samples, and providing no reduction of the A.I. residues in plants compared with the initial value in the corresponding field experiment. 77.2% of the parathion-methyl applied to the plants were volatilized and measured directly in air samples in the volatilization chamber while a reduction by 74.7% was found for the corresponding field experiment by residue analysis of the plants after 24 h. No details could be given concerning the nature of the evaporated portions in the field experiment. 相似文献