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排序方式: 共有543条查询结果,搜索用时 15 毫秒
121.
Svetlana A. Kuznetsova Olga S. Khalipova Konstantin V. Lisitsa Alexander A. Ditts Alexandra G. Malchik Yu-Wen Chen Vladimir V. Kozik 《应用聚合物科学杂志》2021,138(34):50851
Anion exchange resins are widely used in template synthesis of oxide composites. The present work is aimed to study the thermal destruction of anion exchangers with divinyl-benzene and polyacrylate matrices in order to obtain hollow spherical MoO3/TiO2–SiO2 composites from these resins preliminarily saturated with paramolybate ion and coated with tetrabutoxytitanium sol with tetroethoxysilane. It is shown that the processes of resins decomposition affect the strength of spherical composites. Decomposition of the resin with a polyacrylate matrix, accompanied by random nucleation and burnout of the organic matrix at 350°C, leads to the formation of spherical oxide composites with cracks on the surface. The decomposition reactions of the resin with a divinylbenzene matrix occurring at the boundaries of the phases of cylindrical and spherical symmetry, as well as a lower burnout temperature of the organic matrix (290°C), contribute to the formation of dense MoO3/TiO2–SiO2 spheres. Hollow spherical composites 0.3–0.5 mm in size are orthorhombic α-MoO3 coated with a mixture of titanium dioxide with anatase structure and amorphous silicon dioxide. 相似文献
122.
Renée Grataroli Monique Charbonnier Gilles Nalbone Denis Lairon Christiane Chabert Jacques C. Hauton Huguette Lafont 《Lipids》1985,20(11):765-772
Intralipid was incubated with pancreatic lipase (EC 3.1.1.3) and/or phospholipase A2 (EC 3.1.1.4) at two bile salts/phosphatidylcholine molar ratios and at two different triglyceride hydrolysis rates using
various amounts of lipase.
Incubations were studied by gel filtration. Results show: (i) During lipase action, three phases of lipids coexist: an emulsified
phase, a micellar phase and an intermediate heavy phase sized between the two others. The equilibrium between each phase is
dependent upon the bile salts concentration. (ii) Under these conditions, pancreatic lipase was at 60% bound to the emulsified
phase, whereas pancreatic phospholipase A2 was bound at 94% to the micellar phase. 相似文献
123.
Medium carbon V-N treated steel grade applied for long products and small drop forged parts investigated in a state of incomplete solution of V(C,N) precipitates. Activation energy changes investigated in the 850–1200°C temperature range and 0.6–30 s?1 strain rate range is revealed to be temperature dependent. Calculated for σp flow stress value this energy in some cases expresses a combination of various processes. It is found that DRX starts well below ?p. Softening during a short interpass time is caused by dynamic recrystallization DRX during forming and is followed by metadynamic recrystallization MDRX and static recrystallization SRX. At longer interpass times softening progress is hindered by precipitation. 相似文献
124.
Christiane Normand 《International Journal of Heat and Mass Transfer》1990,33(12):2615-2623
The stability of a vertical cylindrical column of water with the horizontal bottom boundary maintained at 0°C and the temperature of the top boundary varying between 4 and 8°C is considered. A weakly non-linear analysis shows that the bifurcation is either supercritical or subcritical depending upon the values of two parameters: the aspect ratio of the cylinder (height/radius) which is varied between 2 and 4, and the penetration parameter μ defined as the ratio of the whole height over the height of the 4°C isotherm. For a given value of the aspect ratio, the bifurcation is supercritical when the whole height is unstable (μ = 1) and becomes subcritical above a particular value of μ when penetration occurs (μ > 1). 相似文献
125.
Oriol Marc Martínez-Fernández Silverio Behutiye Woubshet Farré Carles Kozik Rafał Seppänen Pertti Vollmer Anna Maria Rodríguez Pilar Franch Xavier Aaramaa Sanja Abhervé Antonin Choraś Michał Partanen Jari 《Software Quality Journal》2020,28(3):931-963
Software Quality Journal - Quality requirements (QRs) are a key artifact needed to ensure the quality and success of a software system. Despite their importance, QRs rarely get the same degree of... 相似文献
126.
Detection of β‐Amyloid by Sialic Acid Coated Bovine Serum Albumin Magnetic Nanoparticles in a Mouse Model of Alzheimer's Disease
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Seyedmehdi Hossaini Nasr Hovig Kouyoumdjian Christiane Mallett Sherif Ramadan David C. Zhu Erik M. Shapiro Xuefei Huang 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(3)
The accumulation and formation of β‐amyloid (Aβ) plaques in the brain are distinctive pathological hallmarks of Alzheimer's disease (AD). Designing nanoparticle (NP) contrast agents capable of binding with Aβ highly selectively can potentially facilitate early detection of AD. However, a significant obstacle is the blood brain barrier (BBB), which can preclude the entrance of NPs into the brain for Aβ binding. In this work, bovine serum albumin (BSA) coated NPs are decorated with sialic acid (NP‐BSAx‐Sia) to overcome the challenges in Aβ imaging in vivo. The NP‐BSAx‐Sia is biocompatible with high magnetic relaxivities, suggesting that they are suitable contrast agents for magnetic resonance imaging (MRI). The NP‐BSAx‐Sia binds with Aβ in a sialic acid dependent manner with high selectivities toward Aβ deposited on brains and cross the BBB in an in vitro model. The abilities of these NPs to detect Aβ in vivo in human AD transgenic mice by MRI are evaluated without the need to coinject mannitol to increase BBB permeability. T2*‐weighted MRI shows that Aβ plaques in mouse brains can be detected as aided by NP‐BSAx‐Sia, which is confirmed by histological analysis. Thus, NP‐BSAx‐Sia is a promising new tool for noninvasive in vivo detection of Aβ plaques. 相似文献
127.
Previous research has emphasized the virtues of customer insights as a key source of competitive advantage. The rise of customers’ social media use allows firms to collect customer data in an ever-increasing volume and variety. However, to date, little is known about the capabilities required of firms to turn social media data into valuable customer insights and exploit these insights to create added value for customers. Based on the dynamic capabilities perspective, in particular the concept of absorptive capacity (ACAP), the authors conducted multiple case studies of seven mid-sized and large B2C firms in Switzerland and Germany. The results provide an in-depth analysis of the underlying processes of ACAP as well as contingent factors – that is, physical, human and organizational resources that underpin the firms’ ACAP. 相似文献
128.
K. Elise Watchorn Gordon Goldsborough Christiane Hudon Zofia E. Taranu 《Journal of Great Lakes research》2021,47(3):690-702
A time-series (1990–2013) of classified vegetation cover maps was produced for Netley-Libau Marsh, a 26,000 ha coastal wetland on Lake Winnipeg, to assess its current status and verify earlier trends of emergent vegetation loss. Open water area in the marsh was measured from late-summer Landsat images for 20 years; three classes of vegetation types (emergents, wet meadows, upland) could also be identified for 12 images covering the same period. Temporal changes in area and distribution of marsh vegetation were related to adjoining Lake Winnipeg water-level and Red River discharge, as well as marsh connectivity and bathymetry. From 1990 to 2002, an increase in open-water areas and decrease in emergent vegetation coincided with rising levels and flows. The year 2003 marked major wetland regeneration and a decrease of open-water area under extremely low water-levels and flows. From 2005 to 2013, open-water area remained consistent, under high but variable levels and flows. A strong negative correlation was found between area of emergent vegetation and mean Red River discharge in the previous June-July. Superimposition of the limit of new emergent vegetation observed in 2003 with depth contours surveyed in 2010 revealed the dynamic nature of marsh bathymetry. Periods of extremely low water as short as one year (2003) induced a marked expansion in emergent vegetation cover that persisted over the next ten years despite higher water-levels. Rather than being gradual, changes in the spatial extent of Netley-Libau Marsh vegetation appeared to proceed by fits and starts, wherein periods of relative stasis were disrupted by major changes in abundance. 相似文献
129.
Peter Fürst Christiane Krüger Hans-Albert Meemken und Wilhelm Groebel 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1987,185(5):394-397
Zusammenfassung Tetrachlorbenzyltoluole, die den Hauptanteil in den PCB-Ersatzprodukten Ugilec 141 und Ugilec T bilden, haben in letzter Zeit eine weite Verbreitung als Hydraulikflüssigkeit im Untertagebergbau gefunden. Der Einsatz erfolgt zwar in geschlossenen Systemen, offenbar kommt es aber trotzdem zu nicht unerheblichen Verlusten, wobei die Hydraulikflüssigkeit freigesetzt wird und z. B. über Grubenabwässer in die Umwelt gelangt. So konnten in Flußfischen aus Gebieten mit intensivem Bergbau Te trachlorbenzyltoluole bis zu einer Konzentration von 25 mg/kg eßbarem Anteil bestimmt werden. Die Extraktion der Tetrachlorbenzyltoluole erfolgt aus dem gefriergetrockneten Probenmaterial mit Petrolether. Nach gelchromatographischer Abtrennung des Fettes an Bio-Beads S-X3 schließt sich eine Adsorptionschromatographie an Kieselgel nach Specht u. Tillkes an. Für die analytische Bestimmung wird die kombinierte Capillargaschromatographie/Massenspektrometrie eingesetzt. Die große Spezifität der massenselektiven Detektion, verbunden mit der hohen Trennkraft der Capillargaschromatographie, erlaubt es, Ugilec bis zu einer Konzentration von 0,02 mg/kg, auch in Gegenwart eines hohen PCB-Überschusses, in Fischen sicher nachzuweisen.
Levels of the PCB-substitute Ugilec (tetrachlorobenzyltoluenes) in fish from areas with extensive mining
Summary Tetrachlorobenzy1toluenes, which represent the major constituent of the PCB substitutes Ugilec 141 and Ugilec T, have been widely used in the last few years as hydraulic fluids in underground mining. Their use has been termed a closed application, but there are obviously considerable losses. Tetrachlorobenzyltoluenes released underground can enter the environment via pit water, mine outputs or ventilation systems and as a consequence they can contaminate the food-chain, especially in fish. In fish from areas where there is extensive mining concentrations of tetrachlorobenzy1toluenes in edible portions ranged up to 25 mg/kg. The compounds were extracted from the freeze-dried material with petroleum ether. Gel chromatography on Bio-Beads S-X3 was chosen for the removal of fat followed by adsorption chromatography on silica gel according to the method of Specht and Tillkes. A combination of gas chromatography/mass spectrometry employing an ion trap detector was used for the separation and detection of the compounds. The great selectivity of mass selective detection combined with the high resolving power of capillary gas chromatography made it possible to determine and confirm the presence of Ugilec in fish down to a level of 0.02 mg/kg, even if there was a large PCB surplus.相似文献
130.
Solenne Rivière Christin Vielmuth Christiane Ennenbach Dr. Aliaa Abdelrahman Carina Lemke Prof. Dr. Michael Gütschow Prof. Dr. Christa E. Müller Prof. Dr. Dirk Menche 《ChemMedChem》2020,15(14):1348-1363
The archazolids are potent antiproliferative compounds that have recently emerged as a novel class of promising anticancer agents. Their complex macrolide structures and scarce natural supply make the development of more readily available analogues highly important. Herein, we report the design, synthesis and biological evaluation of four simplified and partially saturated archazolid derivatives. We also reveal important structure-activity relationship data as well as insights into the pharmacophore of these complex polyketides. 相似文献