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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Narcisa M. Bandarra Regina M. Campos Irineu Batista M. Leonor Nunes José M. Empis 《Journal of the American Oil Chemists' Society》1999,76(8):905-913
The prevention of oxidation of a refined sardine oil by α-tocopherol at 0.04%, by several phospholipids [phosphatidylcholine
(PC), phosphatidylethanolamine (PE), and cardiolipin (CL)] at 0.5%, as well as by combinations of α-tocopherol with each phospholipid,
was investigated. The evolution of the oxidation process during 1 mon at 40±2°C was followed by a series of methods, measuring
peroxide value (PV), diene, triene, and polyene index, and absorbance at 430 nm, while α-tocopherol and phospholipid content
were being monitoried. Among these indices, PV was found to be the most adequate to follow the process. PC was the most effective
individual antioxidant as shown by the PV values obtained at the end of the storage period, which were 54.0, 83.4, 87.9, and
97.7 meq O2/kg for PC, CL, PE, and α-tocopherol, respectively. The highest synergistic effect was obtained with a mixture of α-tocopherol
and PE, and the second and third best by mixtures made with PC and CL, respectively. The corresponding PV values recorded
at the end of the period were 27.0, 35.0, and 58.0 meq O2/kg. The high degree of synergy between PE and tocopherol is probably due to the occurrence of a simultaneous antioxidant
mechanism involving Maillard compounds. 相似文献
982.
Frédéric Boschini André Rulmont Rudi Cloots Bénédicte Vertruyen 《Journal of the European Ceramic Society》2009,29(8):1457-1462
Pure crystalline BaZrO3 powders can be produced by precipitation in highly basic aqueous solution. The influence of several synthesis parameters is studied. At high OH? concentration ([NaOH] = 20 mol/l), it is possible to obtain the well-crystallized stoichiometric perovskite phase at relatively low temperature (~80 °C), after a short reaction time (15 min) and without requiring any precaution to avoid the presence of CO2. This synthesis method yields spherical particles, whose size can be controlled by changing the concentration of the Ba + Zr solution. No calcination treatment is necessary since the precipitate is crystalline. Suitable choice of the synthesis parameters ([NaOH] = 20 mol/l, [Ba + Zr] = 1 mol/l, reaction time = 15 min) yields a sub-micron precipitate with excellent densification behaviour. Corrosion tests in BaO–CuO melt show that ~98% dense BaZrO3 obtained by sintering at 1650 °C for 13 h could be used for crucibles in the synthesis of YBa2Cu3O7 superconducting single crystals. 相似文献
983.
The time dependence of deviations from the Gaussian state in a freely cooling homogeneous system of smooth inelastically
colliding spheres is investigated by kinetic theory. We determine the full time dependence of the coefficients of an expansion
around the Gaussian state in Generalized Laguerre polynomials. Approximating this system of equations to sixth order, we find
that the asymptotic state, where the mean energy T follows Haff's law with time independent cooling rate, is reached within a few collisions per particle. Two-dimensional molecular dynamics simulations confirm our
results and show exponential behavior in the high-energy tails.
Received: 10 January 2000 相似文献
984.
Ignacio Moreno-Villoslada Felipe González Luis Arias José Miguel Villatoro Ricardo Ugarte Susan Hess Hiroyuki Nishide 《Dyes and Pigments》2009,82(3):401-408
The aggregation behavior of C.I. Basic Violet 10 in the presence of poly(sodium 4-styrenesulfonate) was modified, as a consequence of short-range interactions. In aqueous acidic media, the cationic dye forms hydrophobic ion pairs with polymeric benzene sulfonate groups which tend to aggregate in H-contacts, this tendency being readily influenced by the relative concentration of the macromolecule with respect to that of the dye. In the case of dilute aqueous dye solutions (≤10?4 M), for which the probability of dye self-aggregation is small, C.I. Basic Violet 10 self-contacts are forced in the presence of a moderate excess of poly(sodium 4-styrenesulfonate). At dye concentrations >10?4 M, for which the probability of dye self-aggregation increases, dye-dye contacts are minimized in the presence of a large excess of the polymer. Hence, the luminescence of dye solutions can be tuned insorar as, that of dilute dye solutions is quenched whilst that of concentrated dye solutions can be enhanced. This behavior was not observed for other polyelectrolytes such as poly(sodium vinylsulfonate), or the more hydrophobic poly(sodium 2-(N-acrylamido)-2-methyl-propanesulfonate). 相似文献
985.
The pairing problem of a three electrons system has been studied by using a real-space method and the generalized Hubbard Hamiltonian. This method includes the correlated hopping interactions as an extension of the previously proposed mapping method, and is based on mapping the correlated many-body problem onto an equivalent site- and bond-impurity tight-binding one in a higher dimensional space, where the problem was solved in a non-perturbative way. In a linear chain, we analyzed the pairing phase diagram of three correlated holes for different values of the Hamiltonian parameters. For some values of the hopping parameters we obtain an analytical solution for all kind of interactions. 相似文献
986.
987.
Jesús Chacón José Sánchez Antonio Visioli Luis Yebra Sebastián Dormido 《Journal of Process Control》2013,23(6):826-838
This work is focused on the study of limit cycles that appear in a control scheme which is based on the use of a PI controller with an event-based send-on-delta sampling (SOD). The processes investigated are integrator processes plus time delay (IPTD) and first and second order processes plus time delay, which are of interest because they are frequently used to model many industrial processes. The SOD sampling is characterized as a non-linearity of n levels with hysteresis. An algorithm to calculate the limit cycles properties is proposed, and then the results obtained in simulations are compared with experiments performed on a real plant, a distributed solar collector field at the Solar Platform of Almería (PSA, Spain). 相似文献
988.
The ninth edition of the biennial conference series “Nexus: Relationships Between Architecture and Mathematics” took place at the Politecnico di Milan in June 2012. There are many connections between architecture and mathematics: mathematic principles may be used as a basis for an architectural design, or as a tool for analyzing an existing monument; architecture may be a concrete expression of mathematical ideas, becoming, in a sense, “visual mathematics”. The purpose of the Nexus conference series is to bring together all those working with ideas related to both architecture and mathematics, and to allow researchers to exchange ideas first-hand. Papers presented at the conference are published in the Nexus Network Journal, providing a permanent archive of studies in architecture and mathematics, and in 2012 a special volume of papers from the Ph.D. Day and the poster session was published. 相似文献
989.
990.
Raúl Gallego David García‐López Juan Carlos Merino José María Pastor 《应用聚合物科学杂志》2013,127(4):3009-3016
Polyamide 6/ethylene–propylene–diene metallocene terpolymer/(ethylene–propylene–diene copolymer)‐graft‐(maleic anhydride) blends with clay (3 and 5 wt % depending on the formulation), different clays (montmorillonite and sepiolite) and different surface functionalization (ammonium salts and silanes) were studied to analyze the effect of the shape of clay and type of modifier on their properties. The results have shown that sepiolite has higher influence on the morphology and on the mechanical properties than montmorillonite. In that sense, blends with 3 wt % of sepiolite have reached the best balanced properties, i.e., tensile modulus and impact strength, than their homologous with montmorillonite. Furthermore, the blends with 3 wt % of sepiolite have reached the highest mechanical properties compared with blends with higher montmorillonite content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献