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61.
The aim of this study was to investigate the influence of cosolvent polarity on the rheological flow properties of aqueous and hydroalcoholic gels obtained from the Carbopol Ultrez 10 base and used for topical applications. Specifically, we have examined the effect of pH (range 4.0--7.0) on the consistency and flow properties of dispersed systems in water and mixtures--15 : 85% v/v of methanol : water, ethanol : water, n-propanol : water and n-butanol : water--at a constant polymer concentration of 0.3% w/w. The gels, which had decreasing polarity values in the jellifying medium, showed qualitatively similar flow behavior, characteristic of pseudoplastic systems, and all of the flow curves were adjusted to the Ostwald model. Sigmoidal dose response functions were calculated to describe the flow and consistency indexes as a function of pH. As a result, the influence of alcohol polarity on the polymer network has been assessed meaningfully using the empirical parameters obtained: maximum consistency index value (k(max)), pH value required for 50% development of polymer network (pH(50)), and asymptotic flow index value (n(min)) for the fully structured gels. 相似文献
62.
Pénicaud A Poulin P Derré A Anglaret E Petit P 《Journal of the American Chemical Society》2005,127(1):8-9
Upon reduction with alkali metals, single-wall carbon nanotubes (SWNTS) are shown to form polyelectrolyte salts that are soluble in polar organic solvents without any sonication, use of surfactants, or functionalization whatsoever, thus forming true thermodynamically stable solutions of naked SWNTs. 相似文献
63.
A laboratory information management system (LIMS) can make a major contribution to the quality and therefore to the efficiency
and competitiveness of a laboratory. Since it can impact all aspects of a laboratory's organization it must be the key if
not the principal player of the laboratory's quality system. It should support the laboratory in establishing, maintaining
and applying quality procedures thereby enabling the laboratory to achieve its quality goals. As a tool, LIMS permits the
laboratory to input and use its own know-how and experience to optimize the total organization (internal and external) and
workflow of generated information. However, perceived "quality" in the context of an LIMS, can be viewed as being made up
of different facets such as the security, reliability and accessibility of information as well as its turn around time and
production cost. This paper reviews the role of a LIMS in the laboratory and the contribution that both system design and
functionality can have on "building quality ".
Received: 5 October 1998 · Accepted: 20 October 1998 相似文献
64.
The synthesis of the indoles 7 , 15 , 16 with a 3-methoxyphenyl group, attached via an α-side chain of 1,2,or 3 CH2 units, is reported. These compounds, after appropriate protection at C(3), were transformed into the N-[(dimethylamino)methyl]indoles 22 , 23 , and 24 , respectively. When treated with AcCl, these N-Mannich bases gave, in two cases, stable N-(chloromethyl)indoles 25 and 26 . In the presence of SnCl4, ring closure occurred via electrophilic attack of 1-methylideneindolium ions on the methoxyphenyl group. Formation of seven-membered rings (→ 27 , 28 ) and eight-membered rings (→ 29 ) was found to be a favorable process. Cyclization to six-membered rings did not occur within this series. 相似文献
65.
Molinier V Fenet B Fitremann J Bouchu A Queneau Y 《Journal of colloid and interface science》2005,286(1):360-368
The micellization of pure monosubstituted sucrose fatty acid esters in water, namely sucrose octanoate, sucrose decanoate, sucrose laurate, sucrose dodec-5-cis-enoate, sucrose myristate, and sucrose palmitate, has been investigated by means of two NMR methods, pulsed field gradient spin-echo NMR (PFGSE-NMR), giving access to the self-diffusion coefficients of free molecules and micelles in solution, and the ERETIC method (electronic reference to access in vivo concentrations) for the measurement of concentrations by external calibration of a synthetic NMR signal. The early micellar regions and, when possible, the premicellar regions were investigated. By this method, we obtained the hydrodynamic radii of micelles, displaying a linear progression in relation to the chain length and an accurate determination of critical micellar concentration (CMC) for each sucrose ester. The effect of the regiochemistry of fatty chain grafting has been investigated, showing special behavior for 1'-O-sucrose palmitate. 相似文献
66.
G. Surpateanu A. Lablache-Combier M. Constantinescu J. Marko 《Tetrahedron letters》1984,25(50):5751-5754
E and Z isomers of p-nitrobenzoyl, 4-p-tolyl[1-2-4]triazolum methylide 5b and p-nitrobenzoyl, 4-p-phenyl[1-2-4]triazolium methylide 5e, have been characterised. 相似文献
67.
Bruno Berthon Alain Forestiere Gérard Leleu Bernard Sillion 《Tetrahedron letters》1981,22(41):4073-4076
Linear primary alcohols with at least 7 carbon atoms are quite quantitatively transformed in esters, by CuO, at temperatures > 170°, without air in liquid phase. Preponderant influence of carbon in position 2 is evidenced. In the same conditions lactones are obtained from diols, and benzylic alcohols undergoes, by hydride transfer, a disproportionation into toluene, benzaldehyde and water. 相似文献
68.
Three pyochelin analogues and their methyl esters all containing a thiazole ring have been synthesised from the same Weinreb amide key intermediate. One of these analogues called HPTT-COOH, a molecule released in the course of pyochelin and yersiniabactin biosynthesis, was efficiently synthesised using a new base induced conversion of the key compound 2′-(2-hydroxyphenyl)-2′-thiazoline-4′-(N-methoxy,N-methyl) carboxamide into 2′-(2-hydroxyphenyl)-2′-thiazole-4′-(N-methoxy,N-methyl) carboxamide. 相似文献
69.
Mechanisms explaining the formation of pyrroles obtained by UV irradiation of thiophen, the two methylthiophens, the four dimethylthiophens, 2-phenylthiophen, furan, the two methylfurans, and 2,4- and 2,5-dimethylfuran in the presence of n-propylamine are discussed. A comparison of the structure of thiocarbonyl and carbonyl intermediates most likely to be formed by UV irradiation of the substrates with the structure of the experimentally obtained pyrroles indicates that the formation of pyrroles from thiophenes and furans seems to follow mechanisms described in Schemes 1 and 4. 相似文献
70.
Vidal-Madjar C Florentina CC Gherghi I Jaulmes A Pantazaki A Taverna M 《Journal of chromatography. A》2004,1042(1-2):15-22
The binding of an anticancer drug (actinomycin D or ACTD) to double-stranded DNA (dsDNA) was studied by means of high-performance liquid chromatography (HPLC). ACTD is an antitumor antibiotic containing one chromophore group and two pentapeptidic lactone cycles that binds dsDNA. Incubations of ACTD with DNA were performed at physiological pH. The complexed and free ligand concentrations of the mixture were quantified at 440 nm from their separation on a size-exclusion chromatographic (SEC) column using the same buffer for the elution and the sample incubation. The DNA and the ACTD-DNA complexes were eluted at the column exclusion volume while the ligand was retained on the support. An apparent binding curve was obtained by plotting the amount emerging at the exclusion column volume against that eluted at free ACTD retention volume. A dissociating effect was evidenced and the binding parameters were significantly different from those obtained at equilibrium by visible absorbance titration. The equilibrium binding parameters determined by absorption spectroscopy were used as starting data in the numerical simulations of the chromatographic process. The results showed a strong dependency of the apparent binding parameters on the reaction kinetics. Finally the comparison of the apparent binding curve obtained from the HPLC experiments and from the numerical simulations permitted an evaluation of the dissociation rate constant (kd = 0.004 s(-1)). 相似文献