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141.
Il Nuovo Cimento D - Electron-electron and electron-ion structural correlations in simple liquid metals are treated by using effective pair potentials to incorporate quantal effects into a... 相似文献
142.
Ferraz Cristina De Araújo Álvaro A. Pastore Gláucia M. 《Applied biochemistry and biotechnology》2002,98(1-9):841-847
The production of biosurfactant, a surface-active compound, by two Serratia marcescens strains was tested on minimal culture medium supplemented with vegetable oils, considering that it is well known that these
compounds stimulate biosurfactant production. The vegetable oils tested included soybean, olive, castor, sunflower, and coconut
fat. The results showed a decrease in surface tension of the culture medium without oil from 64.54 to 29.57, with a critical
micelle dilution (CMD−1) and CMD−2 of 41.77 and 68.92 mN/m, respectively. Sunflower oil gave the best results (29.75 mN/m) with a CMD−1 and CMD−2 of 36.69 and 51.41 mN/m, respectively. Sunflower oil contains about 60% of linoleic acid. The addition of linoleic acid decreased
the surface tension from 53.70 to 28.39, with a CMD−1 of 29.72 and CMD−2 of 37.97, suggesting that this fatty acid stimulates the biosurfactant production by the LB006 strain. In addition, the crude
precipitate surfactant reduced the surface tension of water from 72.00 to 28.70 mN/m. These results suggest that the sunflower
oil’s linoleic acid was responsible for the increase in biosurfactant production by the LB006 strain. 相似文献
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144.
An expansion of the utilisation of o-phthalaldehyde in sulphuric acid medium as spray reagent was carried out when tryptophan and some tryptophan-derived indole alkylamines such as tryptamine, serotonin, bufotenine, dehydrobufotenine and bufotenidine were examined by thin-layer chromatography. Rf-values and limits of detection ranging from 20 (serotonin) to 100 (dehydrobufotenine) ng per spot were found. Application of this reagent for the detection of some of these compounds was carried out, using either methanolic extracts or column chromatographic fractions of the skin secretion of the toads Bufo ictericus and Odontophrynus cultripes. 相似文献
145.
Comparison of properties of three domains of titin, I1, I27, and I28, in a simple geometry-based model shows that despite a high structural homology between their native states different domains show similar but distinguishable mechanical properties. Folding properties of the separate domains are predicted to be diversified which reflects sensitivity of the kinetics to the details of native structures. The Go-like model corresponding to the experimentally resolved native structure of the I1 domain is found to provide the biggest thermodynamic and mechanical stability compared to the other domains studied here. We analyze elastic, thermodynamic, and kinetic properties of several structures corresponding to the I28 domain as obtained through homology-based modeling. We discuss the ability of the models of the I28 domain to reproduce experimental results qualitatively. A strengthening of contacts that involve hydrophobic amino acids does not affect theoretical comparisons of the domains. Tandem linkages of up to five identical or different domains unravel in a serial fashion at low temperatures. We study the nature of the intermediate state that arises in the early stages of the serial unraveling and find it to qualitatively agree with the results of Marszalek et al. 相似文献
146.
Martucci A Alberti A Cruciani G Frache A Marchese L Pastore HO 《The journal of physical chemistry. B》2005,109(28):13483-13492
Thermally induced processes of CoAPO-34, an aluminophosphate molecular sieve with chabasite-type structure, synthesized in the presence of morpholine as a structure-directing agent and HF as a mineralizing agent, have been studied by in situ X-ray synchrotron powder diffraction augmented with Fourier transform (FT) IR analysis. A time-resolved experiment was performed using a translating imaging plate system. At room temperature, the structure refinement by full-profile Rietveld analysis showed P-1 symmetry and the presence of one Al site with sixfold coordination. At around 400 degrees C, both fluorine and morpholine are lost, and the four-connected chabazite (CHA)-type topology is restored. Notwithstanding the metrically rhombohedral values of the cell parameters, the symmetry remains triclinic P-1. Inhomogeneous dealumination of the framework begins at 725 degrees C, accompanied by a strong triclinization of the unit cell and followed by the collapse of the structure above 775 degrees C. The insertion of cobalt ions within the CHA framework was monitored by FTIR spectroscopy, which showed that bridged Co(2+)-O(H)-P hydroxyls are present after morpholine removal. 相似文献
147.
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149.
P Pastore T Rizzetto O Curcuruto M D Cin A Zaramella D Marton 《Rapid communications in mass spectrometry : RCM》2001,15(22):2051-2057
The composition of a commercial dehydroascorbic acid (DA) solution at pH 2 was investigated by liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) to establish the nature of its different forms and its decomposition products. In freshly prepared solutions, dimeric forms of DA and the hydrated bicyclic hemiketal of DA are the species mainly present in solution. In the presence of light, the initial dimeric species disappears over time to give other dehydrated dimers some of which decompose to the monomer. The comparison of these data with similar data obtained for ascorbic acid (AA) solutions under the same experimental conditions revealed that, in the presence of light, the aging of such AA solutions gives rise to only the hemiketal form of DA, and that no dimeric species of DA were formed. The presence of the hemiketal form of DA was not revealed by analysis of the same AA solutions using the conventional LC/UV technique. The natural form of DA from the oxidation of AA is the hydrated bicyclic form. 相似文献
150.
R E Pastore 《The Journal of the Acoustical Society of America》1988,84(6):2262-2270
Kewley-Port, Watson, and Foyle [J. Acoust. Soc. Am. 83, 1133-1145 (1988)] describe a study that uses several different procedures to measure thresholds for stimuli whose components differ in temporal onset. Unfortunately, misunderstandings and misconceptions (shared with other recent publications) resulted in conclusions that are both unnecessary and unwarranted. The Kewley-Port et al. article is discussed in terms of often replicated published findings on temporal order thresholds, and current misconceptions of perceptual concepts and models. 相似文献