排序方式: 共有11条查询结果,搜索用时 15 毫秒
1.
Zhang X Sieval AB Hummelen JC Hessen B 《Chemical communications (Cambridge, England)》2005,(12):1616-1618
Polyethene with fullerene moieties pendant on short-chain branches was prepared by the catalytic copolymerization of ethene and a fullerene-containing vinylic comonomer, yielding polyethene copolymers containing up to 25 wt% of C60. 相似文献
2.
Markov DE Amsterdam E Blom PW Sieval AB Hummelen JC 《The journal of physical chemistry. A》2005,109(24):5266-5274
Exciton diffusion and photoluminescence quenching in conjugated polymer/fullerene heterostructures are studied by time-resolved photoluminescence. It is observed that heterostructures consisting of a spin-coated poly(p-phenylene vinylene) (PPV)-based derivative and evaporated C60 are ill-defined because of diffusion of C60 into the polymer, leading to an overestimation of the exciton diffusion length. This artifact is resolved by the use of a novel, thermally side-chain polymerizing and cross-linking fullerene derivative (F2D) containing two diacetylene moieties, forming a completely immobilized electron acceptor layer. With this heterostructure test system, an exciton diffusion length of 5 +/- 1 nm is derived for this PPV derivative from time-integrated luminescence quenching data. 相似文献
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Amran AB Majid Aznan Fazli Ismail Muhamad Samudi Yasir Redzuwan Yahaya Ismail Bahari 《Journal of Radioanalytical and Nuclear Chemistry》2013,297(2):277-284
Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of 226Ra, 232Th and 40K in the studied building materials samples were found to be in the range of 3.7–359.3, 2.0–370.8 and 10.3–1,949.5 Bq kg?1 respectively. The annual radiation dose rates (μSv year?1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of 226Ra, 232Th and 40K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers. 相似文献
5.
Sudharshan Prabhu Rekha PD Chiu-Chung Young Asif Hameed Shih-Yao Lin Arun AB 《Applied biochemistry and biotechnology》2013,171(4):817-831
Zeaxanthin carotenoids are class of commercially important natural products and diverse biomolecules produced by plants and many microorganisms. Bacteria often produce a cocktail of polar and nonpolar carotenoids limiting their industrial applications. Marine members of the family Flavobacteriaceae are known to produce potential carotenoids such as astaxanthin and zeaxanthin. A few bacterial species have been reported for the predominant production zeaxanthin. Here, we report the molecular identification of the zeaxanthin as a major carotenoid produced by two novel bacteria (YUAB-SO-11 and YUAB-SO-45) isolated from sandy beaches of South West Coast of India and the effect of carbon sources on the production of zeaxanthin. The strains were identified based on the 16S rRNA gene sequencing as a member of genus Muricauda. The closest relatives of YUAB-SO-11 and YUAB-SO-45 were Muricauda aquimarina (JCM 11811T) (98.9 %) and Muricauda olearia (JCM 15563T) (99.2 %), respectively, indicating that both of these strains might represent a novel species. The highest level of zeaxanthin production was achieved (YUAB-SO-11, 1.20?±?0.11 mg g?1) and (YUAB-SO-45, 1.02?±?0.13 mg g?1) when cultivated in marine broth supplemented with 2 % NaCl (pH 7) and incubated at 30 °C. Addition of 0.1 M glutamic acid, an intermediate of citric acid cycle, enhanced the zeaxanthin production as 18 and 14 % by the strains YUAB-SO-11 and YUAB-SO-45 respectively. The zeaxanthin showed in vitro nitric oxide scavenging, inhibition of lipid peroxidation, and 2,2-diphenyl-1-picryl hydrazyl scavenging activities higher than the commercial zeaxanthin. The results of this study suggest that two novel strains YUAB-SO-11 and YUAB-SO-45 belonging to genus Muricauda produce zeaxanthin as a predominant carotenoid, and higher production of zeaxanthin was achieved on glutamic acid supplementation. The pigment showed good in vitro antioxidant activity, which can be exploited further for commercial applications. 相似文献
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de Smet LC Stork GA Hurenkamp GH Sun QY Topal H Vronen PJ Sieval AB Wright A Visser GM Zuilhof H Sudhölter EJ 《Journal of the American Chemical Society》2003,125(46):13916-13917
This paper presents the first functionalization of silicon surfaces with well-defined, covalently attached monolayers containing saccharides. Two methods were used to this aim: a thermal method (refluxing in mesitylene) and a recently developed, extremely mild photochemical method (irradiation with 447 nm at room temperature). The results were analyzed by FT-IR and angle-resolved X-ray photoelectron spectroscopy. The use of a two-dimensional detector in ARXPS allows for unparalleled, subnanometer resolution in the determination of the elemental composition of monolayers. Even for monolayers with a total thickness of only approximately 1.5 nm, a clear elemental depth profile can be obtained. Such analyses display for sialic acid-containing monolayers that the mild photochemical attachment does not destroy the (rather fragile) sialic acid moiety and that the sugar is present at the top of the monolayer and thus available for biological interactions. 相似文献
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MR Eskildsen AB Abrahamsen PL Gammel DJ Bishop NH Andersen K Mortensen PC Canfield 《Pramana》2002,58(5-6):903-905
We compare the results of small angle neutron scattering on the flux line lattice (FLL) obtained in the borocarbide superconductor
LuNi2B2C with the applied field along the c- and a-axes. For H‖c the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated. Above
10 K the transition onset field. H
2(T), rises sharply, bending away from H
c2(T) in contradiction to theoretical predictions of the two merging. For H‖a a first order FLL reorientation transition is observed at H
tr=3–3.5 kOe. Below H
tr the FLL nearest neighbor direction is parallel to the b-axis, and above H
tr to the c-axis. This transition cannot be explained using nonlocal corrections to the London model. 相似文献
8.
Dr. Fredj Ben Bdira Dr. Christopher A. Waudby Dr. Alexander N. Volkov Dr. Sybrin P. Schröder Dr. Eiso AB Prof. Dr. Jeroen D. C. Codée Prof. Dr. Hermen S. Overkleeft Prof. Dr. Johannes M. F. G. Aerts Dr. Hugo van Ingen Prof. Dr. Marcellus Ubbink 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20689-20695
The single-domain GH11 glycosidase from Bacillus circulans (BCX) is involved in the degradation of hemicellulose, which is one of the most abundant renewable biomaterials in nature. We demonstrate that BCX in solution undergoes minimal structural changes during turnover. NMR spectroscopy results show that the rigid protein matrix provides a frame for fast substrate binding in multiple conformations, accompanied by slow conversion, which is attributed to an enzyme-induced substrate distortion. A model is proposed in which the rigid enzyme takes advantage of substrate flexibility to induce a conformation that facilitates the acyl formation step of the hydrolysis reaction. 相似文献
9.
AB E Pugh DJ Kaptein R Boelens R Bonvin AM 《Journal of the American Chemical Society》2006,128(23):7566-7571
We present a method that significantly enhances the robustness of (automated) NMR structure determination by allowing the NOE data corresponding to unassigned NMR resonances to be used directly in the calculations. The unassigned resonances are represented by additional atoms or groups of atoms that have no interaction with the regular protein atoms except through distance restraints. These so-called "proxy" residues can be used to generate NOE-based distance restraints in a similar fashion as for the assigned part of the protein. If sufficient NOE information is available, the restraints are expected to place the proxies at positions close to the correct atoms for the unassigned resonance, which can facilitate subsequent assignment. Convergence can be further improved by supplying additional information about the possible identities of the unassigned resonances. We have implemented this approach in the widely used automated assignment and structure calculation protocols ARIA and CANDID. We find that it significantly increases the robustness of structure calculations with regard to missing assignments and yields structures of higher quality. Our approach is still able to find correctly folded structures with up to 30% randomly missing resonance assignments, and even when only backbone and beta resonances are present! This should be of significant value to NMR-based structural proteomics initiatives. 相似文献
10.
Mikhnenko OV Cordella F Sieval AB Hummelen JC Blom PW Loi MA 《The journal of physical chemistry. B》2008,112(37):11601-11604
The temperature dependence of the exciton dynamics in a conjugated polymer is studied using time-resolved spectroscopy. Photoluminescence decays were measured in heterostructured samples containing a sharp polymer-fullerene interface, which acts as an exciton quenching wall. Using a 1D diffusion model, the exciton diffusion length and diffusion coefficient were extracted in the temperature range of 4-293 K. The exciton dynamics reveal two temperature regimes: in the range of 4-150 K, the exciton diffusion length (coefficient) of approximately 3 nm (approximately 1.5 x 10 (-4) cm2/s) is nearly temperature independent. Increasing the temperature up to 293 K leads to a gradual growth up to 4.5 nm (approximately 3.2 x 10 (-4) cm2/ s). This demonstrates that exciton diffusion in conjugated polymers is governed by two processes: an initial downhill migration toward lower energy states in the inhomogenously broadened density of states, followed by temperature activated hopping. The latter process is switched off below 150 K. 相似文献