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排序方式: 共有1794条查询结果,搜索用时 15 毫秒
41.
Melanie Holzwarth Sabine Korhummel Reinhold Carle Dietmar R. Kammerer 《European Food Research and Technology》2012,234(2):207-222
Strawberry purées were prepared using a commercial polygalacturonase (PG) and a highly purified pectinesterase (PE) preparation,
respectively. To elucidate the effect of pectin on color stability following enzymatic pulp maceration, pectin composition
was studied by isolating and fractionating the alcohol-insoluble residue from the strawberry purées. The purées were stored
at +20 and +4 °C in the dark over a period of 24 weeks monitoring the amounts of monomeric and polymeric anthocyanins as well
as antioxidant activities (FRAP, TEAC). Individual anthocyanins were analyzed by HPLC–DAD–MS
n
, and color measurements were obtained in the CIE L*a*b* system. Pectin composition was significantly modified following enzymatic maceration of the purées. While PG treatment generally
resulted in pectin losses, oxalate-soluble pectins were increased in PE-treated purées. After 24 weeks of storage, the best
anthocyanin retention was observed in PE-treated purées. Such products also revealed greatest anthocyanin half-life values
and lowest proportion of polymeric pigments. Compared to an untreated control, enzymatic purée maceration using the PG was
also beneficial for pigment retention, but less effective than PE. In contrast, color and antioxidant activity were independent
of both enzymatic treatments. An initial heating step (90 °C, 10 s) for immediate inactivation of native enzymes such as polyphenoloxidases
slightly improved pigment stability, while lowered temperature during mash maceration was less effective. However, by far
best color and pigment retention were achieved when the purées were stored at 4 °C in the dark. 相似文献
42.
Bert J. Campo David Bevk Jurgen Kesters Jan Gilot Henk J. Bolink Jun Zhao Jean-Christophe Bolsée Wibren D. Oosterbaan Sabine Bertho Jan D’Haen Jean Manca Laurence Lutsen Guy Van Assche Wouter Maes René A.J. Janssen Dirk Vanderzande 《Organic Electronics》2013,14(2):523-534
The introduction of functional moieties in the donor polymer (side chains) offers a potential pathway toward selective modification of the nanomorphology of conjugated polymer:fullerene active layer blends applied in bulk heterojunction organic photovoltaics, pursuing morphology control and solar cell stability. For this purpose, two types of poly(3-alkylthiophene) random copolymers, incorporating different amounts (10/30/50%) of ester-functionalized side chains, were efficiently synthesized using the Rieke method. The solar cell performance of the functionalized copolymers was evaluated and compared to the pristine P3HT:PCBM system. It was observed that the physicochemical and opto-electronic characteristics of the polythiophene donor material can be modified to a certain extent via copolymerization without (too much) jeopardizing the OPV efficiency, as far as the functionalized side chains are introduced in a moderate ratio (<30%) and that preference is given to side chains with a small molar volume. A range of complementary techniques – UV–Vis spectroscopy, (modulated temperature) differential scanning calorimetry, transmission electron microscopy and X-ray diffraction analysis – indicated that variations in polymer crystallinity, while maintaining a high level of regioregularity, are probably the main factor responsible for the observed differences. 相似文献
43.
Kate Ryan Sabine M. Neumayer Harsha Vardhan R. Maraka Nicolae-Viorel Buchete Andrei L. Kholkin James H. Rice 《Science and Technology of Advanced Materials》2013,14(1):172-179
AbstractNanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to e.g. biosensing, electrochemical, electromechanical or electronic applications. 相似文献
44.
45.
This article addresses the relation between day-specific experiences of job stressors and the pursuit of off-job activities. Following the limited-resources model of self-regulation, the authors proposed that job stressors and long working hours are negatively related to pursuit of sport activities after work because, after stressful days, employees have no resources left for initiating and persisting in effortful behaviors such as sport. Routines for off-job activities were hypothesized to be positively related to the pursuit of sport activities after work. Seventy-eight police employees completed a daily survey over 5 working days and indicated that they perceive sport to be highly useful for recovery. Random coefficient modeling showed that job stressors (particularly situational constraints) encountered on a specific day were negatively related to self-regulatory resources and to the amount of time spent on sport activities after work, whereas the relation with low-effort activities was positive. Thus, after a stressful day when an effective recovery activity such as sport is highly needed, persons tend to engage less in such an activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
Radiation‐induced graft copolymerization of hydroxyethyl methacrylate with hydroxyethyl acrylate, acrylic acid or glycidyl methacrylate on ethylene tetrafluoroethylene (ETFE) films allow for tailor‐made synthesis of membranes for high and low temperature fuel cell applications. According to the operating temperatures proton conductivity may be achieved via doping with phosphoric acid or a two‐step sulfonation of the functional monomers. Fuel cell tests provide power densities and internal resistances, which indicate that the membranes are suitable for high and low temperature fuel cells. 相似文献
47.
48.
Jalal Poostforooshan Stephan Rennecke Manuel Gensch Sabine Beuermann Gabriella-Paula Brunotte Gerhard Ziegmann 《Aerosol science and technology》2014,48(10):1111-1122
This article presents a novel method to encapsulate gas-borne nanoparticles with a polymeric shell. This method implies heterogeneous condensation of monomer vapor around the surface of nanoparticles as nuclei and polymerization is then subsequently started by addition of NH3 as aerosol initiator. Ag and SiO2 nanoparticles were generated as inorganic core by spark discharge and nebulization, respectively, and glycidyl methacrylate (GMA) was used as organic monomer. The effect of several parameters, including vapor pressure of monomer and properties of inorganic core such as morphology, material, particle size, and production method on the thickness of polymeric shell and morphology of resulting nanocomposites has been investigated. The particle size distribution and morphology of the resulting core-shell nanoparticles have been studied via scanning mobility particle sizer (SMPS) and transmission electron microscope (TEM). Finally, the coating efficiency was determined by aerosol photoemission (APE) and the results show that monomer and polymer coating efficiency are 99% and 60%, respectively.
Copyright 2014 American Association for Aerosol Research 相似文献
49.
50.
Janine Will Lars Schneider Dr. Jonathan Becker Jun.-Prof. Dr. Sabine Becker Andreas Miska Christopher Gawlig Prof. Dr. Siegfried Schindler 《Israel journal of chemistry》2020,60(10-11):999-1003
A new tripodal imine ligand tris(2-(propan-2-ylideneamino)ethyl)amine (imine3tren) was prepared in order to stabilize high valent iron-oxido complexes. Iron complexes were synthesized in template reactions from iron(II) salts, tris(2-aminoethyl)amine (tren) and acetone. Due to the reversibility of the imine formation, complexes with different ligands were obtained depending on the reaction conditions. Three complexes, [Fe(imine3tren)(OAc)2] ( 1 ), [Fe(imine3tren)(OAc)]OTf ( 2 ) and [(imine3tren)2Fe2(F)2](SbF6)2 ( 3 ), could be synthesized and structurally characterized. However, reactions with hydrogen peroxide, iodosobenzene or ozone did not lead to any kind of “oxygen adduct” complex that could be spectroscopically observed. 相似文献