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81.
Maria A. Grompone Bruno Irigaray Martín Gil 《European Journal of Lipid Science and Technology》2005,107(10):762-766
The rhea (Rhea americana) is a large running bird of the ratite family, native to South America. Oil extracted from rhea fat tissue is used in cosmetic manufacture. Here, the thermal behaviour and the fatty acid and triacylglycerol composition of Uruguayan rhea oil are studied. The results are compared with those obtained from two commercial samples of emu oil. The fatty acid profiles of emu and rhea oils are similar. Small variations are reflected in the non‐identical thermal behaviour of the oils. The solid content of both oils is fairly similar at room temperature. Thus, emu oil and rhea oil may replace one another in certain formulations, without resulting in important changes in physicochemical behaviour. The semisolid rhea oil was fractionated in two successive stages: an olein was obtained at 15 °C, which was refractionated at 10 °C. The thermogram of the olein obtained by cooling at 15 °C does not have the peak found at 34 °C in the thermogram of the original oil and is a softer product than the original oil. A further stage of fractionation of this olein produced a new liquid phase of slightly different thermal behaviour from that of the original olein. This product has a solid fat index around 7% at 15 °C and has melted completely at 20 °C. This second olein has more appropriate physical characteristics than those of the olein obtained from the first fractionation when used in liquid cosmetic formulations. 相似文献
82.
Summary
We prepared the photorefractive sol-gel glass based on organic-inorganic hybrid materials containing a charge transporting
molecule, second-order nonlinear optical chromophore, photosensitizer, and plasticizer. Carbazole and 2-{ 4-[(2-hydroxyethyl)
methylamino]benzylidene}malononitrile were reacted with 3-isocyanatopropyl triethoxysilane and the functionalized silanes
were employed to fabricate the efficient photorefractive media including 2,4,7-trinitrofluorenone (TNF) to form a charge transfer
complex. The simplest way to vary the composition in the matrix was to mix the desired amount of the functionalized alkoxysilane.
The prepared sol-gel glass samples contained a large amount of nonlinear optical (NLO) chromophore compared to that of the
charge transporting molecules. They showed a large net gain coefficient and high diffraction efficiency at certain conditions.
Received:27 May 2002/Revised version:23 August 2002/Accepted:7 September 2002
Correspondence to Dong Hoon Choi E-mail: dhchoi@khu.ac.kr 相似文献
83.
Summary A confined stiff chain model is suggested for the prediction of the rotational diffusion coefficient of a rigid rodlike polymer with a slight flexibility above the region of dilute solution (c1/L3). It shows a fairly good agreement with the experimental data of various polymers. Among them, PBLG and PBT with more rigidity are more consistent with the model when the log-jamming effect is considered. The predicted rotational diffusivity shows approximately the inverse seventh-power of length, which is less than 9 of Doi-Edwards tube model, but larger than the experimental value 5.7 of M-virus, while it shows the inverse power of concentration is a little larger than the value 2 of tube model except for the rodlike virus M-13. 相似文献
84.
A heating process for obtaining free-standing carbon nanotube emitters is presented with the aim of improving field-emission properties from the screen-printed multiwalled carbon nanotube (MWCNT) films. Using an atmosphere with an optimum combination of nitrogen and air for heat treatment of CNT films, the CNT emitters can be made to protrude from the surface. This allows for a high emission current and the formation of very uniform emission sites without special surface treatment. The morphological change of the CNT film by this technique has eliminated additional processing steps, such as surface treatment which may result in secondary contamination and damage to the film. Despite its simplicity the process provides a high reproducibility in emission current density which makes the films suitable for practical applications. 相似文献
85.
Polypropylene (PP)/layered silicate nanocomposites were prepared via simple melt mixing of three components, PP, layered silicates modified with octadecylamine (C18-MMT) and antioxidant, to investigate the role of antioxidant. TEM and X-ray scattering results confirmed the intercalated state of silicates in PP/layered silicate nanocomposites with antioxidant. In rheological and mechanical study, the nanocomposites with antioxidant showed higher properties than those of the unfilled PP. The nanocomposite with 5 wt% C18-MMT and 0.5 phr antioxidant exhibited about 1.4 times higher tensile modulus and 1.3 times higher storage modulus than the unfilled PP. However, PP/C18-MMT without antioxidant showed lower rheological values owing to the thermal decomposition of PP and the poor compatibility between PP and C18-MMT. It could be concluded that antioxidants played an important role in enhancing the compatibility between PP and C18-MMT. According to the real time X-ray diffraction, the nanocomposite showed the weak ordering of PP crystals than the unfilled PP in the load-extension plateau region of elongation. 相似文献
86.
Zirconia-rich subsolidus phase relationships in the ZrO2 –Sc2 O3 and ZrO2 –In2 O3 systems were investigated. Phase inconsistencies in the ZrO2 –Sc2 O3 system resulted from a diffusionless cubic-to-tetragonal ( t' ) phase transformation not being recognized in the past. Through three different measuring techniques, along with microstructural observations, the solubility limits of the tetragonal and cubic phases were determined. 相似文献
87.
Hyun-Seob?Song Joo?Sung?Lee Jae?Chun?HyunEmail author 《Korean Journal of Chemical Engineering》2002,19(6):949-953
A mathematical model for the pyrolysis reaction of polystyrene (PS) in a semi-batch reactor has been presented. The thermal
degradation of PS was flexibly modeled by a combination of random and specific chain-end scissions. Numerical simulation was
used to investigate the effect of operating conditions on the PS products spectrum, the results of which were validated by
the experimental data. It was found that as the reaction temperature increased (decreased), the monomer fraction in the products
became lower (higher) while the trimer higher (lower). No significant variation in the product composition was, however, observed
while constant temperature was maintained. These results indicate the reaction temperature is an effective manipulated variable
for the control of products composition of PS pyrolysis. The calculation of the optimum temperature trajectories through the
optimization study can thus be of interest for achieving productivity enhancement in plastics pyrolysis processes.
This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University. 相似文献
88.
In this paper, manufacturing technology of the tubular single lap adhesive joint was studied to obtain reliable and optimal joint quality. In addition, a surface preparation method and a bonding process for the joint were devised. The effect of the adhesive thickness and the adherend roughness on the fatigue strength of the joint was experimentally investigated. From experiments, it has been found that the fatigue strength of the joint increased as the adhesive thickness decreased and the optimal arithmetic surface roughness of the adherends was about 2 μm. 相似文献
89.
Various dynamical characters of continuous stirred tank reaclors (CSTR) are introduced with respect to the effects of reaction
types, extra thermal capacitance, periodic forcing, and coupling of CSTRs. The subject includes the classical dynamics of
two-dimensional model and the variety of complex dynamics in three or higher dimensional systems such as periodic bifurcations
to torus or chaos, aperiodic oscillations on invariant torus, and universal dynamics of alternating periodic-chaotic sequences
with k.2v-cycles for every natural number k. Particularly this review intends to bring about the problems that the engineers must be
prepared to encounter in solving various physical systems including chemically reacting systems. 相似文献
90.
Highly Efficient Overall Water Splitting Through Optimization of Preparation and Operation Conditions of Layered Perovskite Photocatalysts 总被引:1,自引:0,他引:1
Jindo Kim Dong Won Hwang Hyun Gyu Kim Sang Won Bae Jae Sung Lee Wei Li Se Hyuk Oh 《Topics in Catalysis》2005,35(3-4):295-303
The layered perovskite materials were found to give the high photocatalytic activity in water splitting reaction under UV
irradiation, where the electronic structure of perovskite slab constructing the layered structure (the total cation valency)
was the most crucial factor to the high photocatalytic activity. Both the excessive cation valency and the layered structure
were required for active photocatalysts, while the slab thickness of layered perovskites had an insignificant effect on water-splitting
activity. In order to identify key variables that affected photocatalytic activity and to optimize the performance of (110)
layered perovskite, La2Ti2O7 was modified by various methods. The optimum amount of loaded nickel had a great effect and the amount depended on the surface
area of the perovskite phase. When an alkaline-earth element such as Ba, Sr, and Ca was doped on La2Ti2O7, the photocatalytic activity was enhanced markedly. Introduction of an alkaline hydroxide into the reaction system as an
external additive enhanced the activity further showing extremely high quantum yields close to 50%. 相似文献