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排序方式: 共有1153条查询结果,搜索用时 15 毫秒
941.
Sonia Licia Baldochi Kiyoshi Shimamura Kenji Nakano Na Mujilatu Tsuguo Fukuda 《Journal of Crystal Growth》1999,200(3-4)
Ce-doped and Ce : Na-codoped BaLiF3 single crystals were grown by the Czochralski technique under reactive atmosphere. Na+-ions, used as a charge-compensating impurity, compete with Ce3+-ions for Ba2+ sites in the host, reducing the Ce3+ incorporation and degrading the mechanical integrity of crystals. Ce-doped BaLiF3 showed potential for UV tunable lasers. 相似文献
942.
Casado-Terrones S Cortacero-Ramírez S Carrasco-Pancorbo A Segura-Carretero A Fernández-Gutiérrez A 《Analytical and bioanalytical chemistry》2006,386(6):1835-1847
The performance of two capillary electrophoresis (CE) instruments, one commercial and one homemade device, were compared for
the determination of derivatised aminated compounds with fluorescein isothiocyanate (FITC). The commercial CE system first
uses an argon ion laser as excitation source; the homemade CE device uses an inexpensive blue-light-emitting diode (LED) as
the light source and a charge-coupled device (CCD) as the detection system. After fine optimisation of several separation
parameters in both devices, a co-electroosmotic flow CE methodology was achieved in coated capillary tubing with 0.001% hexadimetrine
bromide (HDB), and 50 mmol L−1 sodium borate at pH 9.3 with 20% 2-propanol for the determination of several amines and aminoacids. Analytical performances,
applicability in beer samples and other aspects such as cost or potential for miniaturization have been compared for both
devices. 相似文献
943.
Walther Caminati Sonia Melandri Paolo Moreschini Paolo G. Favero 《Angewandte Chemie (International ed. in English)》1999,38(19):2924-2925
A shortening of the C−H bond lengths and a blue shift of the C−H stretching frequencies for the C-F⋅⋅⋅H-C groups indicates that anti-hydrogen bonds are present the difluoromethane dimer. The most stable conformer has three such interactions (shown schematically). 相似文献
944.
945.
Sonia Antolínez Juan C. Lpez Jos L. Alonso 《Angewandte Chemie (International ed. in English)》1999,38(12):1772-1774
Two hydrogen-bond complexes formed between tetrahydropyran and hydrogen chloride have been observed by using a molecular beam Fourier transform microwave spectrometer. The rotation constants are consistent with Cs symmetry, with HCl pointing to the domain of the axial and equatorial lone pair at the oxygen atom (shown on the left and right, respectively). The axial form has been found to be the more stable one. 相似文献
946.
Sonia K. Pollitt Peter G. Schultz 《Angewandte Chemie (International ed. in English)》1998,37(15):2104-2107
Incorporation of an unnatural amino acid containing a photolabile group in the side chain allows specific interactions between two proteins to be prevented. The photocaged ras protein in which Asp 38 has been substituted by its β-nitrobenzyl ester (Nb) is unable to interact with its effector protein p120–GAP (see drawing below) although it has the same intrinsic GTPase activity. After photocleavage of the Nb group, 50% of the p120–GAP-dependent GTPase activity relative to the wild-type protein is restored. 相似文献
947.
Marlene Costa Sonia Losada-Barreiro Antnio Vicente Carlos Bravo-Díaz Ftima Paiva-Martins 《Molecules (Basel, Switzerland)》2022,27(3)
Selecting effective antioxidants is challenging since their efficiency in inhibiting lipid oxidation depends on the rate constants of the chemical reactions involved and their concentration at the reaction site, i.e., at the interfacial region. Accumulation of antioxidants at the interface of emulsions is key to modulate their efficiency in inhibiting lipid oxidation but its control was not well understood, especially in emulsions. It can be optimized by modifying the physicochemical properties of antioxidants or the environmental conditions. In this work, we analyze the effects of surfactant concentration, droplet size, and oil to water ratio on the effective interfacial concentration of a set of chlorogenic acid (CGA) esters in fish oil-in-water (O/W) emulsions and nanoemulsions and on their antioxidant efficiency. A well-established pseudophase kinetic model is used to determine in the intact emulsified systems the effective concentrations of the antioxidants (AOs). The relative oxidative stability of the emulsions is assessed by monitoring the formation of primary oxidation products with time. Results show that the concentration of all AOs at the interfacial region is much higher (20–90 fold) than the stoichiometric one but is much lower than those of other phenolipid series such as caffeic or hydroxytyrosol derivatives. The main parameter controlling the interfacial concentration of antioxidants is the surfactant volume fraction, ΦI, followed by the O/W ratio. Changes in the droplet sizes (emulsions and nanoemulsions) have no influence on the interfacial concentrations. Despite the high radical scavenging capacity of CGA derivatives and their being concentrated at the interfacial region, the investigated AOs do not show a significant effect in inhibiting lipid oxidation in contrast with what is observed using other series of homologous antioxidants with similar reactivity. Results are tentatively interpreted in terms of the relatively low interfacial concentrations of the antioxidants, which may not be high enough to make the rate of the inhibition reaction faster than the rate of radical propagation. 相似文献
948.
949.
950.
Camilla Calabrese Assimo Maris Luca Dore Pantea Fathi Sonia Melandri 《Molecular physics》2015,113(15-16):2290-2295
In order to facilitate its detection in astronomical observations, the measurement of the rotational spectrum of acrylic acid has been extended to 397 GHz using a free space cell at room temperature. 295 new lines were assigned to the s-cis conformer and 286 new lines to the s-trans conformer of acrylic acid. Using the determined experimental parameters, the predictions of the rotational transition frequencies up to 900 GHz and their intensities were obtained at temperatures of 100 and 200 K and at room temperature. Based on these predictions, a search of the most intense transitions of acrylic acid in star-forming regions was performed using published data from the HERSCHEL Science Archive. No lines were found but the possibility of observing rotational transitions of acrylic acid in astronomical objects is discussed. 相似文献