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991.
992.
The reaction between the diglycidylether of bisphenol A (DGEBA) and 4,9-dioxa-1,12-dodecanediamine (DDDD) has been studied by means of isothermal and dynamic differential scanning calorimetry. The enthalpy of the reaction of an epoxy group with an amino-hydrogen has been determined to be 112 ± 5 kJ/mol. A kinetic model has been validated. It involves two competitive mechanisms: one is catalysed by the hydroxy groups initially present on the epoxy chain or generated during the reaction (activation energy 77 ± 5 kJ/mol), the other is not catalysed with a higher activation energy (103 ± 3 kJ/mol). For each isothermal curing, the kinetics are not modified by gelation. Evaluated from the gel times, the overall activation energy of the reaction is equal to 62 ± 2 kJ/mol. 相似文献
993.
Lipid composition of normal and hypertrophic bovine thyroids 总被引:1,自引:0,他引:1
The phospholipid content of bovine thyroid tissue amounts to 70% of total lipid. Triglycerides and cholesterol are the main neutral lipids. Only trace amounts of free fatty acid and esterified cholesterol are found, while two not yet identified components also are present. The distribution of lipid phosphorus in the different phospholipid classes is as follows: phosphatidyl choline, 43.0%; phosphatidyl ethanolamine, 25.2%; phosphatidyl serine, 5.6%; phosphatidyl inositol, 6.5%; sphingomyelin, 14.0%; cardiolipin, 2.8%; lysophosphatidyl choline, <1%; and phosphatidic acid, <1%. The phosphatidyl ethanolamines are rich in plasmalogens. The fatty acid patterns in the different lipid classes are reported. The essential differences between normal and hypertrophic bovine thyroid tissue are higher water content and lower triglyceride and sphingomyelin values for hypertrophic tissue. 相似文献
994.
Haifaa Mokbel Cyril Poriel Joëlle Rault‐Berthelot Frédéric Dumur Didier Gigmes Joumana Toufaily Tayssir Hamieh Daniela Cordella Christophe Detrembleur Jacques Lalevée 《应用聚合物科学杂志》2016,133(12)
A novel photoinitiator based on a spiroxanthene scaffold in the presence of an iodonium salt is proposed for the cationic ring‐opening polymerization of a diepoxide, as well as for the free‐radical polymerization of an acrylate upon violet LED exposure (385 and 405 nm). Good‐to‐excellent rates of polymerization and final conversions are obtained. These systems are characterized by a higher reactivity compared with that of anthracene/iodonium salt used as reference for cationic near UV polymerization. The addition of a poly(ionic liquid) improves the cationic polymerization profiles. The photochemical mechanisms are studied by steady‐state photolysis, fluorescence, and electron spin resonance spin‐trapping techniques. Molecular orbital calculations give an insight into the light absorption properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43213. 相似文献
995.
The use of liquid sodium as a coolant in sodium-cooled fast reactors (SFR) circuits requires studying the consequences of a sodium fire for safety analysis, and particularly the toxicological impact of sodium fire aerosols. More particularly, the carbonation of sodium fire aerosols from sodium hydroxide (NaOH) to sodium carbonate (Na2CO3) is investigated. A new kinetic model, based on the CO2 reactive absorption and the two-film theory, is developed to describe the carbonation process of NaOH solutions, taking into account the NaOH aerosols' initial characteristics in equilibrium with the atmosphere. This model is applied for the case of NaOH aerosols considering the CO2 absorption at the particle external surface. The estimation for the model parameters is detailed as function of NaOH degree of conversion, relative humidity (RH), and temperature. By comparisons with available experimental data, the absorption interfacial area is empirically estimated over the studied range of RH and initial particle diameter. The global sensitivity study of the model confirms its capabilities to describe NaOH aerosols' carbonation, waiting for new experimental data for validation.
© 2016 American Association for Aerosol Research 相似文献
996.
Luisa F. González Yves Andrès Myriam Liard Christophe Renner Laurence Le Coq 《Aerosol science and technology》2016,50(6):555-567
Filtration performances of air handling unit (AHU) filters for particles and microbial aerosols were investigated. The influence of the AHU operational conditions on the behavior of microorganisms collected on the filters was also studied. A lab-scale AHU with two filtration stages was developed and validated for the study of downsized filters with industrial geometries. Three types of filters of different efficiency were considered: G4, F7, and F9, according to European standard EN 779. Two configurations of filters were studied: G4 pleated/F7 bag and F7/F9 bag. Filters were sequentially clogged by alumina particles, which provided a mineral fraction in the particulate cake, and then by micronized rice particles, which provided the fungus Penicillium chrysogenum and an organic fraction that acts as a substrate for microorganisms. Finally, a microbial aerosol composed of endospores of Bacillus subtilis and spores of Aspergillus niger was nebulized to contaminate filters. After clogging, periods of 5 days on and 2 day weekend stops with restarts of ventilation were simulated for 6 weeks. The results showed that the filter efficiency for particles was quite comparable to that for microbial aerosols expressed in cultivable concentration. The particulate cake composed of alumina and micronized rice particles enabled the growth of the endogenous species P. chrysogenum and the survival of exogenous species B. subtilis and A. niger on filters. During restarts of ventilation, low particle concentrations were detected downstream of the second filtration stages by release but the microbial concentration from the fraction of air sampled was below the detection limit.
© 2016 American Association for Aerosol Research 相似文献
997.
Packaging technology for improving shelf‐life of fruits based on a nanoporous–crystalline polymer 下载免费PDF全文
Paola Rizzo Antonietta Cozzolino Alexandra R. Albunia Angelo Maria Giuffrè Vincenzo Sicari Luciano Di Maio Christophe Daniel Vincenzo Venditto Maurizio Galimberti Giuseppe Mensitieri Gaetano Guerra 《应用聚合物科学杂志》2018,135(19)
The ability of films with an active layer of nanoporous–crystalline syndiotactic polystyrene (s‐PS) to prolong shelf‐life, not only of climacteric but also of non‐climacteric fruits, is discussed. Studies on oxygen and carbon dioxide concentrations in the environment of packaged fruits as well as in s‐PS active layers have been combined. Reported results indicate that prolonged shelf‐life can be associated with large increases and decreases of carbon dioxide and oxygen concentrations inside the package, respectively. These data are consistent with a higher barrier offered to both gases by nanoporous–crystalline s‐PS layers. This barrier phenomenon is due to reduction of gas diffusivity typical of nanoporous–crystalline polymer films, which is further enhanced by orientation, parallel to the film plane, of crystalline planes of closely packed s‐PS helices. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46256. 相似文献
998.
Solution structure of human corticotropin releasing factor by 1H NMR and distance geometry with restrained molecular dynamics 总被引:1,自引:0,他引:1
Romier Christophe; Bernassau Jean-Marie; Cambillau Christian; Darbon Herve 《Protein engineering, design & selection : PEDS》1993,6(2):149-156
The structure of human corticotropin releasing factor (hCRF)has been determined by proton nuclear magnetic resonance (1HNMR) in a mixed-solvent system of 66% trifluoroethanol/34% H2Oat pH 3.8 and 37°C. Nearly complete resonance assignmentwas achieved by using standard two-dimensional methods. Distancerestraints for structure calculations were obtained by qualitativeanalysis of intra- and interresidue nuclear Overhauser effects.Structures were obtained from the distance restraints by distancegeometry, followed by refinement using molecular dynamics andwere completed with amide hydrogen exchange data. The structureof hCRF in this solvent comprises an extended N-terminal tetrapeptideconnected to a well-defined -helix between residues 6 and 36.The first half of the -helix (residues 620) is clearlyamphipathic. The five carboxy-terminal residues are predominantlydisordered. 相似文献
999.
The Effects of Electronic Impurities and Electron–Hole Recombination Dynamics on Large‐Grain Organic–Inorganic Perovskite Photovoltaic Efficiencies 下载免费PDF全文
Jean‐Christophe Blancon Wanyi Nie Amanda J. Neukirch Gautam Gupta Sergei Tretiak Laurent Cognet Aditya D. Mohite Jared J. Crochet 《Advanced functional materials》2016,26(24):4283-4292
Hybrid organic‐inorganic perovskites have attracted considerable attention after promising developments in energy harvesting and other optoelectronic applications. However, further optimization will require a deeper understanding of the intrinsic photophysics of materials with relevant structural characteristics. Here, the dynamics of photoexcited charge carriers in large‐area grain organic‐inorganic perovskite thin films is investigated via confocal time‐resolved photoluminescence spectroscopy. It is found that the bimolecular recombination of free charges is the dominant decay mechanism at excitation densities relevant for photovoltaic applications. Bimolecular coefficients are found to be on the order of 10?9 cm3 s?1, comparable to typical direct‐gap semiconductors, yet significantly smaller than theoretically expected. It is also demonstrated that there is no degradation in carrier transport in these thin films due to electronic impurities. Suppressed electron–hole recombination and transport that is not limited by deep level defects provide a microscopic model for the superior performance of large‐area grain hybrid perovskites for photovoltaic applications. 相似文献
1000.
固定频率升压转换器采用不连续导电模式(DCM)工作,能够有效地用于快速调光操作,提供比采用连续导电模式(CCM工作的竞争器件更优异的瞬态响应,这种转换器非常适合于以恒流模式驱动LED串。但驱动LED的升压转换器的交流分析,与使用标准电阻型负载的升压转换器的交流分析不同,在推导最终的传递函数时必须非常审慎。本文分为两个单元:⑴理论分析,介绍如何推导驱动LED串的升压转换器的小信号响应;⑵实际考虑,深入研究实施方案,并验证经验结果及与理论推导比较。 相似文献