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排序方式: 共有753条查询结果,搜索用时 218 毫秒
1.
Marcus Heinze Sandra Starke Marcel Händler Hartmut Komber Marco Drache Norbert Moszner Brigitte Voit Doris Pospiech 《应用聚合物科学杂志》2019,136(48):48256
We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The 1H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of rHEMA = 1.83; rECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256. 相似文献
2.
Dr. Brigitte Oesterdiekhoff 《Informatik-Spektrum》2004,27(5):448-452
3.
We present here the results of a study of the separation process in the extraction matrix of a novel high-intensity magnetic separator (HIMS). The matrix uses an ordered array of grooved plates (replacing conventional collectors, which are generally made of wires). Only experimental results are available for grooved plates in the literature, but here we propose a new theoretical approach. We report on the particles' behavior, the existence of a percolation phenomenon, and the filtration efficiency, in order to analyze and compare the performance of matrix structures (Lenoir's and Jones'). We discuss the causes of the percolation phenomenon and its effect on filtration efficiency. Correspondence between the theory and the experiments is good. We suggest appropriate uses of each matrix structure according to the property of the processed particles. 相似文献
4.
Peter Horn Peter Schaaf Brigitte Holbach Stefan Hölzl Heinz Eschnauer 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1993,196(5):407-409
For provenance assignments of wines strontium isotope ratios can be used because soils from different wine-growing regions, and hence the wines grown there, each show specific ratios. Some successful applications are demonstrated.
87Sr/86Sr aus Gestein und Boden in Rebe und Wein
Zusammenfassung Zur Herkunftsbestimmung von Weinen können Strontium-Isotopenverhältnisse herangezogen werden, da die Böden verschiedener Weinbaugebiete, und damit die dort gezogenen Weine, jeweils spezifische Verhältnisse aufweisen. Einige erfolgreiche Anwendungen werden demonstriert.相似文献
5.
As-produced nanotubes form a light, fragile and isotropic soot. Different efforts are made to process nanotubes into macroscopic forms of more practical use and more controlled properties. We briefly review in this paper two methods recently proposed to make films of magnetically aligned nanotubes and fibers by using an electrophoretic method. Preferential orientation of the nanotubes in the plane of the films or along the fiber axis is an important feature of the obtained materials. Then we describe in details a different, spinning like, process for making fibers out of single wall carbon nanotubes. This process consists of dispersing the nanotubes in a surfactant solution, re-condensing the nanotubes in the flow of a polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. The behaviors of the surfactant-stabilized dispersions, which are also presented, are critical for this process. The degree of nanotubes alignment in dried fibers has been characterized by X-ray scattering. It is found to be smaller than the alignment obtained in the previous materials. However, the processing is simpler and faster and potentially scalable for large-scale production. 相似文献
6.
For networks that are directed or can be represented by a directed network,reversing one or more of the uni-directional links may provide the ability to reconnect a network that has been disconnected by link failure.In this paper,a new approach to reconfigure such networks is proposed.We develop a linear time algorithm which,when reachability has been destroyed by the removal of a single link,optimally restores reachability through the reversal of selected links.Multi-link failure reconnectability is discussed and an algorithm with polynomial complexity is given which provides a nearly optimum solution to reconnect the network.We show that the reliability of a network that allows reversals is at least twice more than that in which reversals are not permitted.Unfortunately,the reconnection of some networks cannot be established.Therefore,we discuss the maximization of reachability of such networks so that each node can reach maximum number of the other nodes. 相似文献
7.
Rolipram inhibited U937 cell phosphodiesterase-4 in either the presence or absence of saturating (100 micrograms/ml) phosphatidic acid in an apparently phospholipid-independent manner, exhibiting similar kinetics (Ki values = 0.41 and 0.59 microM, respectively). At low concentrations (10 and 100 nM), however, rolipram caused a rightward shift of the phosphatidic acid concentration-response curve for phosphodiesterase-4 activation, suppressing activation by up to 70%. Maximum inhibition of phosphodiesterase-4 activation occurred at phosphatidic acid concentrations of 5-40 micrograms/ml. The results suggest that rolipram is capable of inhibiting phosphodiesterase-4 by both phospholipid-dependent and phospholipid-independent mechanisms. 相似文献
8.
The reachability of a strongly connected network may be destroyed after link damage,Since many networds have directed links with the potential for reversal,the reachability may be restored by reversing the direction of links.In this paper,the reliability of a network that allows reversal of links in discussed. 相似文献
9.
Jean-Marie Degroodt Brigitte Wyhowski de Bukanski Sarah Srebrnik 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1992,195(6):566-568
Summary A method combining immunoaffmity-chromatography (IAC) and high-performance liquid chromatography (HPLC) for the analysis of Salbutamol in liver with a low quantification limit of 1 g/kg has been developed. Salbutamol was extracted with 0.01 mol/L HCl and purified by IAC. The samples were analysed on a liquid Chromatograph fitted with a C18 -Bondapak column. A fluorometer was used for the detection of salbutamol. Recoveries of 67–80% could be obtained.
Immunoaffinitätschromatographische Reinigung von Salbutamol in Leber und Rückstandsbestimmung mittels HPLC und fluorimetrischer Detektion
Zusammenfassung Eine Methode, die Immunoaffinitäts-und Hochleistungsflüssigchromatographie verbindet, ist für die Analyse von Salbutamol in Leber entwickelt worden. Eine niedrige Bestimmungsgrenze von 1 g/kg Leber wurde erreicht. Salbutamol wurde mit 0,01 mol/L Salzsäure freigesetzt und durch Immunoaffinitätschromatographie gereinigt. Die Proben wurden durch Flüssigchromatographie auf einer C18 -Bondapak-Säule analysiert. Ein Fluorimeter wurde für die Detektion von Salbutamol benutzt. Ausbeuten von 67 bis 80% konnten erreicht werden.相似文献
10.
Janaina Braga do?CarmoEmail author Christopher?Neill Diana?C.?Garcia-Montiel Marisa?de Cássia Piccolo Carlos?C.?Cerri Paul?A.?Steudler Cristiano Alberto?de Andrade Caio?C.?Passianoto Brigitte?J.?Feigl Jerry?M.?Melillo 《Nutrient Cycling in Agroecosystems》2005,71(3):213-225
The clearing of tropical rain forest in the Amazon basin has created large areas of cattle pasture that are now declining in productivity. Practices adopted by ranchers to restore productivity to degraded pastures have the potential to alter soil N availability and gaseous N losses from soils. We examined how soil inorganic N pools, net N mineralization and net nitrification rates, nitrification potential and NO and N2O emissions from soils of a degraded pasture responded to the following restoration treatments: (1) soil tillage followed by replanting of grass and fertilization, (2) no-till application of non-selective herbicide, planting of rice, harvest followed by no-till replanting of grass and fertilization, and (3) the same no-till sequence with soybeans instead of rice. Tillage increased soil NH4+ and NO3? pools but NH4+ and NO3? pools remained relatively constant in the control and no-till treatments. Cumulative rates of net N mineralization and net nitrification during the first 6 months after treatment varied widely but were hightest in the tilled treatment. Emissions of NO and N2O fluxes increased with tillage and with N fertilization. There were no clear relationships among rates of N fertilizer application, net N mineralization, net nitrification, NO, N2O and total N oxide emissions. Our results indicate that pasture restoration sequences involving tilling and fertilizing will increase emissions of N oxides, but the magnitude of the increase is likely to differ based on timing of fertilizer application relative to the presence of plants and the magnitude of plant N demand. Emissions of N oxides appear to be decreased by the use of restoration sequences that minimize reductions in pasture grass cover. 相似文献