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排序方式: 共有468条查询结果,搜索用时 15 毫秒
71.
Vladislav Sadykov Natalia MezentsevaVladimir Usoltsev Ekaterina SadovskayaArkady Ishchenko Svetlana PavlovaYulia Bespalko Tamara KharlamovaEkaterina Zevak Aleksei SalanovTamara Krieger Vladimir BelyaevOleg Bobrenok Nikolai UvarovYury Okhlupin Oleg SmorygoAlevtina Smirnova Prabhakar SinghAleksandr Vlasov Mikhail KorobeynikovAleksandr Bryazgin Peter KalininAndrei Arzhannikov 《Journal of power sources》2011,196(17):7104-7109
This work presents the results related to the functionally graded fluorite (F)-perovskite (P) nanocomposite cathodes for IT SOFC. Nanocrystalline fluorites (GDC, ScCeSZ) and perovskites (LSrMn, LSrFNi) were synthesized by Pechini method. Nanocomposites were prepared by the ultrasonic dispersion of F and P powders in isopropanol with addition of polyvinyl butyral. Different techniques for deposition and sintering of functionally graded cathode materials were applied including traditional approaches as well as original methods, such as radiation-thermal sintering under electron beam or microwave radiation. Morphology, microstructure and elemental composition of nanocomposites was characterized by XRD and HRTEM/SEM with EDX. Even for dense composites, the sizes of perovskite and fluorite domains remain in the nanorange providing developed P-F interfaces. Oxygen isotope heteroexchange and conductivity/weight relaxation studies demonstrated that these interfaces provide a path for fast oxygen diffusion. The redistribution of the elements between P and F phases in nanocomposites occurs without formation of insulating zirconate phases. Button-size fuel cells with nanocomposite functionally graded cathodes, thin YSZ layers and anode Ni/YSZ cermet (either bulk or supported on Ni-Al foam substrates) were manufactured. For optimized composition and functionally graded design of P-F nanocomposite cathodes, a stable performance in the intermediate temperature range with maximum power density up to 0.5 W cm−2 at 700 °C in wet H2/air feeds was demonstrated. 相似文献
72.
73.
Ekaterina V. Skorb Helmuth Möhwald 《Advanced materials (Deerfield Beach, Fla.)》2013,25(36):5029-5043
Encapsulation systems are urgently needed both as micrometer and sub‐micrometer capsules for active chemicals' delivery, to encapsulate biological objects and capsules immobilized on surfaces for a wide variety of advanced applications. Methods for encapsulation, prolonged storage and controllable release are discussed in this review. Formation of stimuli responsive systems via layer‐by‐layer (LbL) assembly, as well as via mobile chemical bonding (hydrogen bonds, chemisorptions) and formation of special dynamic stoppers are presented. The most essential advances of the systems presented are multifunctionality and responsiveness to a multitude of stimuli – the possibility of formation of multi‐modal systems. Specific examples of advanced applications – drug delivery, diagnostics, tissue engineering, lab‐on‐chip and organ‐on‐chip, bio‐sensors, membranes, templates for synthesis, optical systems, and antifouling, self‐healing materials and coatings – are provided. Finally, we try to outline emerging developments. 相似文献
74.
Allu Amarnath Reddy Dilshat U. Tulyaganov Maria J. Pascual Vladislav V. Kharton Ekaterina V. Tsipis Vladislav A. Kolotygin José M.F. Ferreira 《International Journal of Hydrogen Energy》2013
This article reports on the influence of strontium for calcium substitution in diopside–Ba disilicate glass–ceramics on stabilization thermal parameters and improvement adhesion to interconnect material of SOFCs. Sr replaced 10, 20, 30 and 40% of Ca in the Ca0.9MgAl0.1La0.1Si1.9O6 component of the parent glass having the following composition, mol.%: 22.14 CaO, 24.60 MgO, 0.52 BaO, 1.23 Al2O3, 1.23 La2O3, 47.79 SiO2, 1.69 B2O3, 0.79 NiO. 29Si–MAS–NMR and 27Al MAS–NMR spectra of the glasses revealed irrelevant chemical shifts for silicon and aluminum atoms upon changing the SrO content. Tg decreased and coefficient of thermal expansion (CTE) increased by Sr for Ca substitution in pyroxene glasses. Additionally SrO-containing glasses exhibited a viscosity of ∼106 dPa s at 900 °C, which is suitable for joining of SOFC metallic/ceramic components by glass/glass–ceramic sealing upon stack hermetization. Glass–ceramics revealed long term (up to 1000 h) thermal stability at 900 °C and suitable CTE values (10.0–11.3) × 10−6 K−1, high electrical resistivity, good adhesion and minimal reactivity with SOFC components. 相似文献
75.
Gocke D Walter L Gauchenova E Kolter G Knoll M Berthold CL Schneider G Pleiss J Müller M Pohl M 《Chembiochem : a European journal of chemical biology》2008,9(3):406-412
Benzoylformate decarboxylase (BFD) from Pseudomonas putida is an exceptional thiamin diphosphate-dependent enzyme, as it catalyzes the formation of (S)-2-hydroxy-1-phenylpropan-1-one from benzaldehyde and acetaldehyde. This is the only currently known S-selective reaction (92 % ee) catalyzed by this otherwise R-selective class of enzymes. Here we describe the molecular basis of the introduction of S selectivity into ThDP-dependent decarboxylases. By shaping the active site of BFD through the use of rational protein design, structural analysis, and molecular modeling, optimal steric stabilization of the acceptor aldehyde in a structural element called the S pocket was identified as the predominant interaction for adjusting stereoselectivity. Our studies revealed Leu461 as a hot spot for stereoselectivity in BFD. Exchange to alanine and glycine resulted in variants that catalyze the S-stereoselective addition of larger acceptor aldehydes, such as propanal with benzaldehyde and its derivatives-a reaction not catalyzed by the wild-type enzyme. Crystal structure analysis of the variant BFDL461A supports the modeling studies. 相似文献
76.
Daniela Boettger Holger Bergmann Barbara Kuehn Dr. Ekaterina Shelest Prof. Dr. Christian Hertweck 《Chembiochem : a European journal of chemical biology》2012,13(16):2363-2373
Fungal hybrid enzymes consisting of a polyketide synthase (PKS) and a nonribosomal peptide synthetase (NRPS) module are involved in the biosynthesis of a vast array of ecologically and medicinally relevant natural products. Whereas a dozen gene clusters could be assigned to the requisite PKS–NRPS pathways, the programming of the multifunctional enzymes is still enigmatic. Through engineering and heterologously expressing a chimera of PKS (lovastatin synthase, LovB) and NRPS (cytochalasin synthase, CheA) in Aspergillus terreus, we noted the potential incompatibility of a fungal highly reducing PKS (hrPKS) with the NRPS component of fungal PKS–NRPS hybrids. To rationalize the unexpected outcome of the gene fusion experiments, we conducted extensive bioinformatic analyses of fungal PKS–NRPS hybrids and LovB‐type PKS. From motif studies and the function of the engineered chimeras, a noncanonical function of C‐terminal condensation (C) domains in truncated PKS–NRPS homologues was inferred. More importantly, sequence alignments and phylogenetic trees revealed an evolutionary imprint of the PKS–NRPS domains, which reflect the evolutionary history of the entire megasynthase. Furthermore, a detailed investigation of C and adenylation (A) domains provides support for a scenario in which not only the A domain but also the C domain participates in amino acid selection. These findings shed new light on the complex code of this emerging class of multifunctional enzymes and will greatly facilitate future combinatorial biosynthesis and pathway engineering approaches towards natural product analogues. 相似文献
77.
Ekaterina A. Zimnik Mikhail Y. Semenov Yulia V. Semenova Tamara V. Khodzher 《Water and Environment Journal》2012,26(4):540-549
It was shown that the balance between organic and inorganic compounds is mostly conditioned by watershed size and relief, rather than chemistry. The rise and fall of dissolved organic carbon concentration are irreversely proportional to those of acid neutralizing capacity and follow the changes in water flowpaths. This relationship was used to distinguish between dissolved matter sources, and to characterize quantitatively and qualitatively their contribution to surface water chemistry. The proposed approach has restricted applicability to the watersheds composed of sedimentary materials and to the watersheds with high percentage of wetlands. The applicability of the approach is also limited to a variety of environmental conditions. Big watersheds should be divided into lower order subcatchments to reduce uncertainty in interpretation of results. In small and medium watersheds, the proposed approach can be used for predicting water chemistry under different environmental conditions and for tracing contaminants. 相似文献
78.
Jian Liu Heng Quan Yang Freddy Kleitz Zhi Gang Chen Tianyu Yang Ekaterina Strounina Gao Qing Lu Shi Zhang Qiao 《Advanced functional materials》2012,22(3):591-599
This contribution describes the preparation of multifunctional yolk–shell nanoparticles (YSNs) consisting of a core of silica spheres and an outer shell based on periodic mesoporous organosilica (PMO) with perpendicularly aligned mesoporous channels. The new yolk–shell hybrid materials were synthesised through a dual mesophase and vesicle soft templating method. The mesostructure of the shell, the dimension of the hollow space (4~52 nm), and the shell thickness (16~34 nm) could be adjusted by precise tuning of the synthesis parameters, as evidenced by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen sorption investigations. Various metal nanoparticles (e.g., Au, Pt, and Pd) were encapsulated and confined in the void space between the core and the shell using impregnation and reduction of adequate metal precursors. The selective oxidation of various alcohol substrates was then carried out to illustrate the benefits of such an architecture in catalysis. High conversion (~100%) and excellent selectivity (~99%) were obtained over Pd nanoparticles encapsulated in the hybrid PMO yolk–shell structures. 相似文献
79.
Ekaterina I. Lesnova Olga V. Masalova Kristina Yu. Permyakova Vyacheslav V. Kozlov Tatyana N. Nikolaeva Alexander V. Pronin Vladimir T. Valuev-Elliston Alexander V. Ivanov Alla A. Kushch 《International journal of molecular sciences》2021,22(13)
Hepatitis C virus (HCV) is one of the main triggers of chronic liver disease. Despite tremendous progress in the HCV field, there is still no vaccine against this virus. Potential vaccines can be based on its recombinant proteins. To increase the humoral and, especially, cellular immune response to them, more effective adjuvants are needed. Here, we evaluated a panel of compounds as potential adjuvants using the HCV NS5B protein as an immunogen. These compounds included inhibitors of polyamine biosynthesis and urea cycle, the mTOR pathway, antioxidants, and cellular receptors. A pronounced stimulation of cell proliferation and interferon-γ (IFN-γ) secretion in response to concanavalin A was shown for antioxidant N-acetylcysteine (NAC), polyamine biosynthesis inhibitor 2-difluoromethylornithine (DFMO), and TLR9 agonist CpG ODN 1826 (CpG). Their usage during the immunization of mice with the recombinant NS5B protein significantly increased antibody titers, enhanced lymphocyte proliferation and IFN-γ production. NAC and CpG decreased relative Treg numbers; CpG increased the number of myeloid-derived suppressor cells (MDSCs), whereas neither NAC nor DFMO affected MDSC counts. NAC and DFMO suppressed NO and interleukin 10 (IL-10) production by splenocytes, while DFMO increased the levels of IL-12. This is the first evidence of immunomodulatory activity of NAC and DFMO during prophylactic immunization against infectious diseases. 相似文献
80.
Ekaterina S. Lokteva Aleksey E. LazhkoElena V. Golubina Vadim V. TimofeevAlexander V. Naumkin Tatiana V. YagodovskayaSergey N. Gaidamaka Valery V. Lunin 《The Journal of Supercritical Fluids》2011,58(2):263-271
Carbonaceous deposits formation was established as the primary reason of Pd/TiO2 catalyst deactivation during reductive processing of CCl4 to form hydrodechlorination and oligomerization products. Three methods of carbonaceous deposits elimination were tested: (1) extraction by supercritical CO2, (2) oxidation by ozone in supercritical CO2, and (3) low-temperature glow-discharge oxygen plasma treatment. Synchronic thermal analysis confirms effective carbonaceous deposits removal during regeneration by ozone or low temperature glow-discharge oxygen plasma; by XPS deep oxidation of surface Pd after oxidative treatment (by ozone or oxygen plasma) was found. Thus H2 reduction was proposed as the second step making possible full regeneration of initial catalytic activity of Pd/TiO2. 相似文献