Activation,microstructure, and polarization of solid oxide fuel cell cathodes

Activation effect can be defined as the enhancement of the electrochemical performance or activity of the solid oxide fuel cell cathodes such as Sr-doped LaMnO₃ (LSM) with the polarization/current passage treatment under fuel cell operation conditions. In this paper, the activation effect of the cathodic polarization/current passage on the O₂ reduction reaction of the LSM-based cathodes is reviewed. In addition to the activation effect, cathodic polarization/current passage also has a significant effect on the microstructure of the LSM electrodes and the morphology between the LSM electrode and Y₂O₃-ZrO₂ electrolyte interface. A mechanism involving the incorporation of SrO species into the LSM lattice and the formation of oxygen vacancies is proposed for the activation effect of the polarization.     

Donor and acceptor properties of the chromium tricarbonyl substituent in benzylic and homobenzylic anions, cations, and radicals

Both benzylic cations and anions are strongly stabilized by chromium tricarbonyl complexation, while benzylic radicals are largely unaffected. Density functional theory calculations were performed on primary, secondary, and tertiary benzylic species to explore the effect of substitution on the stabilizing ability of the chromium tricarbonyl moiety. Complexed 1-indanyl species were also examined to elucidate the effect of conformational restraint. It was found that the strong stabilization of benzylic anions and the slight destabilization of benzylic radicals by chromium tricarbonyl are insensitive to skeletal changes. Chromium-complexed benzylic cations, however, are highly sensitive to changes in the organic framework, with increased substitution or constriction of conformational mobility eroding the effect of the metal. 2-Indanyl species were also examined to study the effect of the chromium tricarbonyl fragment on homobenzylic species. It was found that the metal fragment stabilizes distant anions by field and inductive effects and cations by a direct interaction of the metal with the cationic carbon. Homobenzylic radicals, however, do not interact with the chromium tricarbonyl moiety and suffer a slight inductive destabilization.     

Gel-synthesis, structure, and properties of sulfur-containing chitosan derivatives

The possibility of using the thermochemical approach to thermal decomposition of solids, previously developed by the author, to interpretation of the mechanism and kinetics of reduction of metal oxides with hydrogen was studied. Many properties of NiO reduction with hydrogen, including formation of metal nuclea, the nature of induction period, autocatalysis effect, equimolar and isobaric periods of reduction, the character of the effect of hydrogen pressure on reduction rate, and the nanocrystalline structure of a reduced metal, were explained in terms of the given approach.     

Structural,Mechanistic, Spectroscopic,and Preparative Studies on the Lewis Base Catalyzed,Enantioselective Sulfenofunctionalization of Alkenes

The full details of mechanistic investigation on enantioselective sulfenofunctionalization of alkenes under Lewis base catalysis are described. Solution spectroscopic identification of the catalytically active sulfenylating agent has been accomplished along with the spectroscopic identification of putative thiiranium ion intermediates generated in the enantiodetermining step. The structural insights gleaned from these studies informed the design of new catalyst architectures to improve enantioselectivity. In addition, structural modification of the sulfenylating agents had a significant and salutary effect on the enantioselectivity of sulfenofunctionalization which was demonstrated to be general for trans disubstituted alkenes. Whereas electronic modulation had little effect on the rate and selectivity, steric bulk on arylsulfenylphthalimides was very beneficial.     

Coordination polymers of indium, scandium, and yttrium

Data on inorganic and metal-organic indium, scandium, and yttrium coordination polymers mainly with halide (pseudohalide) and N,O-donor ligands have been generalized and systematized. The effect of the metal cation nature and coordination number, stereochemistry, and ligand environment on the formation of polymers of different dimensionality is considered. 129 references.     

Effects of nitrate,fulvate, phosphate,phthalate, salicylate and catechol on the sorption of uranyl onto SiO<Subscript>2</Subscript>: a comparative study

We have performed a large number of batch sorption experiments of uranyl onto SiO₂ and examined the effects of nitrate or ionic strength, phosphate, fulvic acid(FA), phthalic acid (PH), salicylic acid (SA), and catechol (CA) on the uranyl sorption onto SiO₂. Three sorption edges and three sorption isotherms at ionic strengths 0.05, 0.1, and 0.5 mol/L KNO₃ were used to investigate the effect of ionic strength or nitrate on the sorption and the Langmuir, Freundlich, and Dubinin-Radushkevich models are used to simulate the sorption isotherms, respectively. Five sorption edges in the presence of phosphate, FA, PH, SA, and CA were compared with that in the absence of complexing ligand. The results suggest that the effect of complexation of uranyl with nitrate on the uranyl sorption can be negligible and the sorption can be described Freundlich and D-R model very well. The positive effect of phosphate on the uranyl sorption was found, though the extent of effect was decreased with increasing pH. The positive effect and the negative effect of FA on the uranyl sorption were found at low pH and high pH ranges, respectively. The sorption edge of uranyl sorption remained unaffected in the presence of PH in the pH 2–10. In the presence of SA, the no effect and the negative effect on the uranyl sorption were, respectively, found at low pH and high pH ranges. The negative effect of CA on the uranyl sorption was found in the pH 2–10.     

The effect of ligand solvation on the complexation of Dy3+ with benzoic,p-,o-, andm-aminobenzoic,and pyridine-4-carboxylic acids,and pyridine and 4-aminopyridine in aqueous and aqueous-organic media

The effect of a substituent inm-,o-, andp-aminobenzoic and isonicotinic acids and 4-amiopyridine on the stability of their complexes with Dy³⁺ in H₂O and H₂O-DMSO(DMF) has been studied by pH-metric and magnetoopticrl titration. An increase in the efficiency of the salvation of a ligand decreases the effect of a substituent on the stability of the complex.     

Reorganization and caging of DPPC, DPPE, DPPG, and DPPS monolayers caused by dimethylsulfoxide observed using Brewster angle microscopy

The interaction between dimethylsulfoxide (DMSO) and phospholipid monolayers with different polar headgroups was studied using "in situ" Brewster angle microscopy (BAM) coupled to a Langmuir trough. For a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer, DMSO was shown to significantly impact the structure of the liquid expanded (LE) and gaseous phases. The domains reorganized to much larger domain structures. Domains in the liquid condensed (LC) phase were formed on the DMSO-containing subphase at the mean molecular area where only gaseous and LE phases were previously observed on the pure water subphase. These results clearly demonstrate the condensing and caging effect of DMSO molecules on the DPPC monolayer. Similar effects were found on dipalmitoyl phosphatidyl ethanolamine, glycerol, and serine phospholipids, indicating that the condensing and caging effect is not dependent upon the phospholipid headgroup structure. The DMSO-induced condensing and caging effect is the molecular mechanism that may account for the enhanced permeability of membranes upon exposure to DMSO.     

Nature of one-dimensional short hydrogen bonding: bond distances, bond energies, and solvent effects

On the basis of recently synthesized calix[4]hydroquinone (CHQ) nanotubes which were self-assembled with infinitely long one-dimensional (1-D) short hydrogen bonds (SHB), we have investigated the nature of 1-D SHB using first-principles calculations for all the systems including the solvent water. The H-bonds relay (i.e., contiguous H-bonds) effect in CHQs shortens the H...O bond distances significantly (by more than 0.2 A) and increases the bond dissociation energy to a large extent (by more than approximately 4 kcal/mol) due to the highly enhanced polarization effect along the H-bond relay chain. The H-bonds relay effect shows a large increase in the chemical shift associated with the SHB. The average binding energies for the infinite 1-D H-bond arrays of dioles and dions increase by approximately 4 and approximately 9 kcal/mol per H-bond, respectively. The solvent effect (due to nonbridging water molecules) has been studied by explicitly adding water molecules in the CHQ tube crystals. This effect is found to be small with slight weakening of the SHB strength; the H...O bond distance increases only by 0.02 A, and the average binding energy decreases by approximately 1 kcal/mol per H-bond. All these results based on the first-principles calculations are the first detailed analysis of energy gain by SHB and energy loss by solvent effect, based on a partitioning scheme of the interaction energy components. These reliable results elucidate not only the self-assembly phenomena based on the H-bond relay but also the solvent effect on the SHB strength.     

Antibacterial effect,efflux pump inhibitory (NorA,TetK and MepA) of Staphylococcus aureus and in silico prediction of α, β and δ-damascone compounds

ObjectiveThe present study aimed to evaluate the antibacterial effect and inhibitory capacity against NorA, TetK and MepA efflux pump of Staphylococcus aureus multiresistant by in vitro and in silico approach of α, β and δ-damascone compounds.ResultsThe compounds α, β and δ-damascone showed a clinically relevant effect against S. aureus ATCC 6538 standard strain. A modulating effect was also observed in association with antibiotics against MDR strains. Regarding the inhibition of the efflux pump, the compounds showed a modulating effect with antibiotics, against SA-1199, SA-1199B, SA IS-58 and K2068. Only δ-damascone demonstrated an efflux pump inhibitory effect. Regarding ADME properties, α, β and δ-damascone showed similar physicochemical properties with good pharmacokinetic characteristics, such as lipophilicity, oral bioavailability and low toxicity. In addition, they exhibited the binding energy and Ligand Efficiency (LE) ?81.17 (5.4), ?77.48(-5.4) and ?64.55 (-5.1), which shows good interactions with the critical residues of the MepA receptor.ConclusionsFrom the results it is concluded that the compounds α, β and δ-damascone do not have antibacterial activity, but show a modulating effect in association with antibiotics, as well as not showing direct activity on the efflux pump, but they do have a modulating effect with antibiotics and with EtBr (α and β-damascone).     

Synthesis, stereochemistry, and circular dichroism of optically active o-substituted diphenyl sulphilimines and related compounds

Optically active o-substituted diphenyl N-substituted sulphilimines are readily synthesised by the reaction of the corresponding sulphides and t-butyl hypochlorite in the presence of l-menthol and amide anions. (−)-N-p-Tolylsulphonylsulphilimines (1, 2) obtained were converted to the corresponding (−)-N-unsubstituted sulphilimines (8, 9) by treating them with concentrated sulphuric acid. When (−)-S-o-anisyl S-phenyl N-(unsubstituted) sulphilimine (8) was treated with acylating agents or acrylonitrile, the corresponding optically active (−)-N-substituted sulphilimines were prepared with complete retention at sulphur. The absolute configuration of (−)-S-o-anisyl S-phenyl N-p-tolylsulphonylsulphilimine (1) was determined by converting it to (+)-S-o-anisyl sulphoxide (17). CD curves of (−)-o-substituted diarylsulphilimines exhibited a negative Cotton effect at around 270–285 nm, which was assigned to (S)-configuration at sulphur by comparing with the analogous sulphoxides. The substituent on the imino group of the sulphilimine gave no appreciable effect on the CD behavior and the lack of substituent effect was considered to be due to the semi-polar character of the S(IV)-N bond. Unusual effect of o-methoxy group on the CD curves was discussed in connection with solvent effect. Mechanism of this asymmetric synthesis has been investigated, and it has become apparent that the diastereomeric menthoxysulphonium chloride was an excess of (RR)-configuration was formed initially and the amide anion attacks the S atom of the salt with net inversion.     

Synthesis, structure, and physicochemical properties of gel-forming dextran phosphates

Dextran phosphates with the degree of substitution of 0.29–1.09 with phosphoric acid groups and of 0.14–0.83 with carbamate groups were prepared in the orthophosphoric acid-urea system. The effect of the component ratio in the esterifying mixture, temperature, and pressure in the reaction zone on the structure and physicochemical properties of dextran phosphate hydrogels and on the gel fraction yield was examined.     

Sorption of butane, propane, ethane, methane, and carbon dioxide on asphaltene

Isotherms of sorption of butane, propane, ethane, methane, and carbon dioxide on an asphaltene sample of known elemental composition were measured. The effect of the pressure and temperature on the shape the sorption isotherms for all the adsorption systems studied was examined. The values of the initial heat of sorption were determined and compared to the energies of interaction of the molecules with asphaltene. The results obtained suggest that asphaltene is a swellable amorphous sorbent.     

Morphology and Transport Properties of Hybrid Materials Based on Perfluorinated Membranes,Polyaniline, and Platinum

The transport properties and morphological characteristics of perfluorinated membranes after deposition of the layer of platinum dispersion on the surface are studied. The significant effect of preliminary modification of perfluorinated membraned with polyaniline on the diffusion permittivity of the composite and the morphology of the layer of platinum dispersion is determined. Testing the composites as proton conductors with a catalytic layer on the surface in an air–hydrogen fuel cell has shown the effect of the asymmetry of the electrochemical characteristics of the membrane–electrode assembly at various orientations of the layer of platinum dispersion towards hydrogen and air flows. A higher catalytic activity of the composite membranes in the oxygen reduction reaction is determined in the case platinum dispersion is deposited onto the membrane preliminarily modified with polyaniline.

     

Synthesis,Structure, and Characteristics of Ultra-High-Molecular-Weight Poly-N-methacryloyloxyethyl-N,N,N-Trimethylammonium Methyl Sulfate

Two procedures for synthesis of water-soluble poly-N-methacryloyloxyethyl-N,N,N-trimethylammonium methyl sulfate are compared. Synthesis occurred by the radical mechanism with the Co(III)-glycine system and with acid catalytic initiation. The effect of the initiator nature and the reaction conditions on the course of polymerization was studied.     

Effect of Hydrogen,Electron Donor,and Polymerization Temperature on Poly(propylene) Microstructure

Summary: Polypropylene made with an industrial heterogeneous Ziegler-Natta catalyst was characterized using high temperature GPC, ¹³C NMR, and Crystallization Elution Fractionation (CEF). The effect of hydrogen and electron donor during polymerization on poly(propylene) microstructure was investigated at two temperatures. In addition to the expected electron donor effect on polypropylene tacticity, hydrogen was also found to increase polypropylene tacticity. The effect of changing these polymerization conditions on molecular weight and polydispersity was also investigated. Finally, CEF profiles show how the crystallizability of polypropylene increases by adding hydrogen and electron donor to the reactor.     

Triorganosilyl Ethers of Benzaldehyde,m-Methoxybenzaldehyde and Anisoles

Synthesis of six new triorganosiloxybenzaldehydes, two m-methoxy-(triorganosiloxy)benzaldehydes, and seven methoxy(triorganosiloxy)benzenes are reported. From comparison of the stability of these compounds in the atmosphere, it is concluded that formyl group shows unfavorable influence and methoxy group shows favorable influence on the stability of these compounds. The oposite influences of these two groups on phenoxysilane linkage seems to connect with the oposite directiones of inductive effect of formyl group and resonance effect of methoxy group on the benzene ring.     

利用双模板剂的多级孔ZSM-11分子筛的合成、表征和催化性能

ZSM-11与ZSM-5分子筛具有相似的孔道结构,通常表现出相似的催化性能,但近年来的研究发现,ZSM-11分子筛在某些反应过程具有明显优于ZSM-5的催化性能,因而逐渐引起科研界和工业界的广泛重视.但受其微孔尺寸的限制,在使用过程中往往容易积碳,并导致快速失活.为此,向微孔体系引入介孔制备多级孔ZSM-11分子筛是一种规避上述问题的有效方式.我们研究组前期已对分子筛进行碱处理脱硅及在该体系中加入CTAB制备多级孔分子筛进行了系统研究.在此基础上本文通过改变介孔模板剂十六烷基三甲基溴化铵(CTAB)和微孔模板剂四丁基溴化铵(TBABr)的摩尔比(R),采用一步法制备了一系列多级孔ZSM-11分子筛材料,并通过多种表征手段对材料的性质进行了系统研究.随着R值的增加,广角XRD测试结果表明,产物的结晶度逐渐下降,同时小角XRD测试结果表明产物中逐渐产生有序介孔相; XRF测试结果表明,产物的总包硅铝比呈上升趋势; SEM表征结果表明,首先棒状纳米晶团聚体形貌的ZSM-11分子筛的晶粒尺寸逐渐降低,随后晶粒之间插入无定形样品,直至最终产物几乎完全为无定形材料构成; TEM图片与上述表征结果一致,样品初始晶格条纹清晰且晶粒边缘规整,随后晶粒边缘开始弯曲不平,接着晶体样品中开始产生有序介孔材料,最终几乎完全变为有序介孔材料.综合上述表征结果和相关文献可推测,该有序介孔材料为类MCM-41材料.另外,我们采用N2物理吸附对材料的织构性质进行了考察,发现随着R值增大,产物的微孔减少,介孔增多.然而TEM结果表明,在类MCM-41产生之前,样品中介孔的增多并非来源于晶内孔,而是来源于晶粒之间的堆积孔,这是由于在合成过程中CTAB胶束嵌入ZSM-11的晶粒之间所导致.合成体系的碱度对产物的物化性质和织构性质也起了非常重要的作用.我们将这个体系与NaOH+CTAB对分子筛进行脱硅后处理体系进行了对比,发现虽然前者只能产生晶间孔而后者可产生晶内孔,但碱度对两者的作用相似,即降低碱度均可导致类MCM-41有序介孔相的产生.此外,还通过NH3-TPD和Py-IR技术对材料的酸性进行了考察.基于上述研究结果,提出了多级孔ZSM-11分子筛的形成机理.随着R值的变化,CTAB分别起了覆盖效应、胶束效应和模板效应.这些效应在合成多级孔ZSM-11分子筛过程中相互协同,同时又与TBABr的结构导向效应相互竞争,进而影响合成产物的孔结构、形貌、酸性以及用于二甲醚和苯烷基化的催化性能.     

Electrostatic calculation of linear and non-linear optical properties of ice Ih,II, IX and VIII

Macroscopic first- and third-order susceptibilities of ice Ih, ice II, ice IX and ice VIII are calculated using static and frequency-dependent electronic and static vibrational molecular (hyper)polarizabilities at the MP2 level. The molecular properties are in good agreement with experiment and with high-level ab initio calculations. Intermolecular electrostatic and polarization effects due to induced dipoles are taken into account using a rigorous local-field theory. The electric field due to permanent dipoles is used to calculate effective in-crystal (hyper)polarizabilities. The polarizability depends only weakly on the permanent field, but the dipole moment and the hyperpolarizabilities are strongly affected. The calculated linear susceptibility is in good agreement with available experimental data for ice Ih, and the third-order susceptibility for a third harmonic generation experiment is in reasonable agreement with experimental values for liquid water. The molecular vibrational contributions have a small effect on the susceptibilities. The electric properties of a water tetramer are calculated and used to estimate the effect of non-dipolar interactions on the susceptibilities of ice Ih, which are found to be small.     

A study of oxidation of benzidine, o,o′-tolidine,and o,o′-dianisidine

The oxidation of benzidine, o,o′-tolidine, and o,o′-dianisidine by the acetate complex of trivalent cobalt was studied chiefly in glacial acetic acid medium, considering the possible formation of semiquinone and quinonediimine compounds. The effect of uv light on the solutions of these compounds in glacial acetic acid and in benzene was followed spectrophotometrically and chromatographically and compared with the effect of Co(III) acetate. Certain possibilities explaining the course of the studied reactions are discussed.