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41.
Marina Heinonen Katri Haila Anna-Maija Lampi Vieno Piironen 《Journal of the American Oil Chemists' Society》1997,74(9):1047-1052
The effects of low concentrations of β-carotene, α-, and γ-tocopherol were evaluated on autoxidation of 10% oil-in-water emulsions
of rapeseed oil triacylglycerols. At concentrations of 0.45, 2, and 20 μg/g, β-carotene was a prooxidant, based on the formation
of lipid hydroperoxides, hexanal, or 2-heptenal. In this emulsion, 1.5, 3, and 30 μg/g of γ-tocopherol, as well as 1.5 μg/g
of α-tocopherol, acted as antioxidants and inhibited both the formation and decomposition of lipid hydroperoxides. Moreover,
at a level of 1.5 μg/g, γ-tocopherol was more effective as an antioxidant than α-tocopherol. At levels of 0.5 μg/g, both α-
and γ-tocopherol significantly inhibited the formation of hexanal but not the formation of lipid hydroperoxides. Oxidation
was effectively retarded by combinations of 2 μg/g β-carotene and 1.5 μg/g γ- or α-tocopherol. The combination of β-carotene
and α-tocopherol was significantly better in retarding oxidation than α-tocopherol alone. While γ-tocopherol was an effective
antioxidant, a synergistic effect between β-carotene and γ-tocopherol could not be shown. The results indicate that there
is a need to protect β-carotene from oxidative destruction by employing antioxidants, such as α- and γ-tocopherol, should
β-carotene be used in fat emulsions. 相似文献
42.
S. Lucas E. Gonzlez M.P. Calvo C. Palencia E. Alonso M.J. Cocero 《The Journal of Supercritical Fluids》2007,40(3):462-469
Supercritical impregnation of Radiata pine with ethyl acetate and decanal using CO2 as carrier solvent has been studied at pilot plant scale. Radiata pine is one of the most common wood species that is originally from Australia and is widely grown in Spain and Portugal and ethyl acetate and decanal were selected as organic compounds.Some experiences were carried out to obtain the optimal operating conditions for the supercritical impregnation process. Experiments were conducted at pressures of 7–15 MPa, temperatures of 35–50 °C and solvent flow rate between 1.5 and 3.5 kg/h. The results of this study have indicated that the treatment gives much better preservative penetration and retention operating with low pressures (7.5 MPa), low temperatures (close to 35 °C) and moderate CO2 flow rate (3.5 kg/h) in the selected operating range. Moreover, a simple mathematical model of two adjustable parameters (external mass transfer coefficient and partition coefficient) has demonstrated to fit the experimental impregnation curves with reasonable accuracy (average absolute deviation, 3–10%). 相似文献
43.
Toshiaki Enoki Yousuke Kobayashi Chika Katsuyama Vladimir Yu. Osipov Marina V. Baidakova Kazuyuki Takai Ken-ichi Fukui Alexander Ya. Vul'' 《Diamond and Related Materials》2007,16(12):2029-2034
The structure, electronic and magnetic properties of nanodiamond and nanographite/nanographene are investigated. Detonation nanodiamond particles that are covered with amorphous graphitic composites are hydrothermally treated to remove the graphitic surface composites and to terminate the surface carbon atoms with hydrogen. The number of localized spins of dangling bonds and the hydrogen concentration increase upon the increase in the hydrothermal treatment time up to 40 h. Above 40 h, both drop discontinuously, a surface structural reconstruction was suggested. The creation of dangling bonds and an incomplete hydrogenation of the surface carbon atoms destabilize the surface, resulting in the structural reconstruction. Nanodiamond particles are thermally converted to nanographite/nanographene. A single nanographene sheet is successfully prepared by heat-treating nanodiamond particles. The edge of graphene sheet with its edge carbon atoms being hydrogen-terminated is investigated by UHV-STM/STS. Zigzag edges are found to have non-bonding π-state of edge origin, in good agreement with theoretical prediction. 相似文献
44.
Marina Fridin Mark Belokopytov 《International journal of human-computer interaction》2014,30(6):459-469
Embodied robots are known to be preferable in most cases to their virtual agents for interaction with and performance by human subjects. This study compared the efficacy of an embodied robot-coacher and its virtual agent in involving preschool children in the performance of playlike motor tasks. The robot or its virtual agent demonstrated movements, asked the children to repeat them, and provided positive feedback on their performance. The difficulty of the motor tasks was increased over the course of the session. Two groups of children were studied, one of them with and the other without previous experience of interaction with the embodied robot. In the experienced group, involvement in motor tasks was successfully induced by both the embodied robot and its virtual agent, but the children interacted less well with the virtual agent than with the embodied robot. Children in the inexperienced group did not interact at all during the experiment with the virtual agent. Because participants in the experiment were preschool children in their natural environment, this study proposes the combined use of an embodied robot and its virtual agent for motor involvement. 相似文献
45.
DellaGreca M Isidori M Lavorgna M Monaco P Previtera L Zarrelli A 《Journal of chemical ecology》2004,30(4):867-879
Twenty-five 9,10-dihydrophenanthrenes, four phenanthrenes, a dihydrodibenzoxepin, and a pyrene, isolated from the wetland plant Juncus acutus, were tested to detect their effects on the green alga Selenastrum capricornutum. Nine of the compounds were isolated and identified for the first time. Most of the compounds caused inhibition of algal growth. The 9,10-dihydrophenanthrenes 1, 5, 21, and 22 were the most active. 相似文献
46.
Carla Marina Santos Feldhaus Roseli Künzel Máximo Siu Li Ana Paula de Azevedo Marques 《Journal of the American Ceramic Society》2021,104(10):5192-5204
The compounds based on calcium molybdate (CaMoO4) are the subject of extensive research due to their excellent optical properties and a broad range of potential technological applications. In this work, we report a systematic study of CaMoO4:Tm3+ phosphors synthesized by coprecipitation and processed in a microwave-hydrothermal system at low temperature (100°C) and stirring. The effect of the Tm3+ doping content (0%–12%) is studied in full detail to understand their role in the CaMoO4:Tm3+ morphological, structural, and luminescent properties. The X-ray diffraction, Raman, and Fourier Transform Infrared spectroscopic techniques revealed that all the prepared powders have a tetragonal crystal structure with a distinct density of cation vacancies and structural disorders. The band gap remains almost constant for doping levels lower than 8%, but it narrows strongly for powders doped with 12% Tm3+ ions. The designed phosphors have shown two emission bands in which intensity depends on the Tm3+ ions doping level. For doping levels lower than 2%, the photoluminescence profile displays a broad emission band peaking at 543 nm (green). For concentrations higher than 4%, the band centered at 543 nm decreases in intensity and the near-infrared emission band at around 800 nm, assigned to 3F3, 3H4 → 3H6 transitions from Tm3+ ion, become more intense. The outcomes of this work reveal that appropriated Tm3+ ions doping levels can be applied to suppress the PL emission in the visible range and improve that in the near-infrared region in CaMoO4-based materials. 相似文献
47.
Yoav Dan Marina Buzhor Daniel Raichman Eti Menashe Oren Rachmani Elizabeth Amir 《应用聚合物科学杂志》2021,138(6):49820
A modular method for functionalization of nonwoven fabrics was developed using a two-step process. In the first step, the fabrics were grafted with a linker molecule, 10-undecenoyl chloride, via esterification, followed by attachment of a functional material under UV irradiation. Perfluorodecanethiol and 3-mercaptopropionic acid (MPA) were connected to the linker-modified fabrics using thiol-ene click chemistry. Perfluorodecanethiol modified fabrics exhibited hydrophobicity with water contact angle of about 140° while MPA-modified fabrics were able to lower the pH of a solution by about 1.6. We additionally demonstrated the possibility to connect functional polymers to the linker-modified fabrics by radical graft polymerization of acrylic acid; this produced a thin layer of the polymer on the surface of the fabric. Fabrics modified with poly(acrylic acid) exhibited increased hydrophilicity with water contact angle of 0° for both cotton and viscose-polyester fabrics, while the water absorption capability for polypropylene fabrics increased from about 50 to 1200%. 相似文献
48.
Comparative data on the molecular weight distribution of polymers obtained by polymerization of ethylene, propylene and 1-hexene, and copolymerization of ethylene with α-olefins over the titanium-magnesium catalysts (TMC) in the absence and presence of hydrogen are presented. In contrast to the ethylene polymerization, in the cases of propylene and 1-hexene polymerization and copolymerization of ethylene with α-olefins, the hydrogen addition is characterized by noticeable narrowing of the molecular weight distribution (MWD) due to lower contribution of the MWD component with high molecular weight. This result is an evidence of the increased reactivity of TMC active sites producing high molecular weight poly-α-olefins and copolymers of ethylene with α-olefins in the chain transfer reaction with hydrogen. It is suggested that the increased reactivity of these sites in the transfer reaction with hydrogen appears after the 2,1-addition of α-olefin to the growing polymer chain. 相似文献
49.
Irina A. Stenina Polina A. Yurova Tatyana S. Titova Marina A. Polovkova Oleg V. Korchagin Vera A. Bogdanovskaya Andrey B. Yaroslavtsev 《应用聚合物科学杂志》2021,138(27):50644
Nafion-117/PEDOT composite membranes were synthesized by in situ chemical polymerization of 3,4-ethylenedioxythiophene (EDOT) using ammonium persulfate as an oxidant. The polymerization of EDOT in Nafion membranes for various EDOT/oxidant treatment sequences was studied for the first time. PEDOT introduction leads to a slight decrease in both the ion-exchange capacity and water uptake of the composite membranes, as well as to an increase in cationic transport. Membranes initially treated with an oxidant exhibit better conductivity and lower hydrogen permeability. The effect of both modification of Nafion-117 membranes by PEDOT and hot-pressing of hydrogen-oxygen membrane-electrode assemblies (MEAs) on the performance of proton-exchange membrane fuel cells was studied. The maximum power density of the fabricated MEAs increases 1.5-fold: from 510 (for a pristine Nafion-117 membrane) to 810 mW cm−2 (for a membrane modified by PEDOT). The current density at a voltage of 0.4 V reaches 1248 and 2246 mA cm−2, respectively. 相似文献
50.