Clay-anchored non-heme iron-salen complex catalyzed cleavage of CC bond in aqueous medium

Clay-anchored iron[N,N′-ethylenebis(salicylideneaminato)] complex, synthesized by direct exchange, oxidizes various olefins and chalcones in aqueous acetonitrile using hydrogen peroxide as terminal oxidant. Aldehyde and its derivatives are obtained as oxidation products by the cleavage of CC double bond. In comparison with the catalysis by iron-salen complex in solution, the clay catalyzed pathway not only increases the rate of reaction significantly, but also provides selective oxidation toward the aldehyde. Some chalcones also give very good yield in water, compared to the solution and clay catalyzed pathways.     

The effectiveness of resources created by students as partners in explaining the relevance of mathematics in engineering education

First-year engineering students often struggle to see the relevance of theoretical mathematical concepts for their future studies and professional careers. This is an issue, as students who do not see relevance in fundamental parts of their studies may disengage from these parts and focus their efforts on other subjects they think will be more useful to them. In this study, we surveyed engineering students enrolled in a first-year mathematics subject on their perceptions of the relevance of the individual mathematical topics taught. Surveys were administered at the start of semester when some of these topics were unknown to them, and again at the end of semester when students had not only studied all these topics but also watched a set of animated videos. These videos had been produced by higher-year students to explain where they had seen applications of the mathematical concepts presented in the first year. We notice differences between the perceived relevance of topics for future study and for professional careers, with relevance to study rated higher than relevance to careers. We also find that the animations are seen as helpful in understanding the relevance of first-year mathematics. The majority of students indicated that lecturers with students as partners should work collaboratively to produce future videos.     

Osmium assisted C-H activation and CN cleavage of N-(2′-hydroxyphenyl) benzaldimines. Synthesis, structure and electrochemical properties of some organoosmium complexes

Reaction of N-(2′-hydroxyphenyl)-4-R-benzaldimines (L-R, R = OCH₃, CH₃, H, Cl and NO₂) with [Os(PPh₃)₃Br₂] in refluxing 2-methoxyethanol in the presence of triethylamine affords two families of organoosmium complexes (1-R and 2-R). In both 1-R and 2-R complexes a benzaldimine ligand is coordinated to the metal center as tridentate C,N,O-donor. In the 1-R complexes, a bidentate N,O-donor imionsemiquinonate ligand, derived from the hydrolysis of another benzaldimine, and a PPh₃ ligand are also coordinated to osmium. In the 2-R complexes, a carbonyl, derived from decarbonylation of 4-R-benzaldehyde (derived from the same hydrolysis stated above), and two PPh₃ ligands take up the remaining coordination sites on osmium. Structures of the 1-Cl and 2-OCH₃ complexes have been determined by X-ray crystallography. All the 1-R and 2-R complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on the 1-R complexes shows a reversible Os(III)-Os(IV) oxidation within 0.47-0.67 V (vs SCE), followed by an irreversible oxidation of the imionsemiquinonate ligand within 1.10-1.36 V. An irreversible Os(III)-Os(II) reduction is also displayed by the 1-R complexes within −1.02 to −1.14 V. Cyclic voltammetry on the 2-R complexes shows a reversible Os(II)-Os(III) oxidation within 0.29-0.51 V, followed by a quasi-reversible oxidation within 1.04-1.29 V, and an irreversible reduction of the coordinated benzaldimine ligand within −1.16 to −1.31 V.     

Eu luminescence in La5Si2BO13 with apatite related structure and magnetic studies in Ln5Si2BO13 (Ln=Gd, Dy)

Eu³⁺ photoluminescence is studied in La₅Si₂BO₁₃ with apatite related structure. La_5−xEu_xSi₂BO₁₃ [x=0.05, 0.1, 0.3, 0.5, 0.7, 1.0, 2.0] compositions are synthesized. The emission results shows that Eu³⁺ ions occupy two different cationic sites viz., La(1) and La(2). The increase in the intensity of ⁵D₀-⁷F₀ line with increasing Eu³⁺ content shows the preferential occupancy of Eu³⁺ in La(2) site due to the existence of short La(2)-O(4) (free oxide ion) bond. The observation of antiferromagnetic interactions in Gd and Dy analogues supports the structural features elucidates from photoluminescence studies.     

On a Vector Version of a Fundamental Lemma of J. L. Lions

Let ? be a bounded and connected open subset of R~N with a Lipschitzcontinuous boundary,the set ? being locally on the same side of ??.A vector version of a fundamental lemma of J.L.Lions,due to C.Amrouche,the first author,L.Gratie and S.Kesavan,asserts that any vector field v =(vi) ∈(D′(?))~N,such that all the components 1/2(?_jv_i + ?_iv_j),1 ≤ i,j ≤ N,of its symmetrized gradient matrix field are in the space H~(-1)(?),is in effect in the space(L~2(?))~N.The objective of this paper is to show that this vector version of J.L.Lions lemma is equivalent to a certain number of other properties of interest by themselves.These include in particular a vector version of a well-known inequality due to J.Neˇcas,weak versions of the classical Donati and Saint-Venant compatibility conditions for a matrix field to be the symmetrized gradient matrix field of a vector field,or a natural vector version of a fundamental surjectivity property of the divergence operator.     

用模糊集方法计算工程质量等级确定质量系数

采用工程模糊集理论方法,用科学合理的数字来衡量工程质量.提出将专家定量评分法与定性评议法科学地统一起来,使权重的确定更为合理与科学.同时,用实例进行实证分析.     

Nichtsteroide Entzündungshemmer, 4 Umlagerungen von Heterocyclen, 11 Ketenoide Umlagerung und Oxidation von 2-Pyronen zu 1,4-Naphthochinon-5-alkansäuren

Fused 2-pyrones4, obtained by the thermal condensation of ketones1 with reactive malonates2, rearrange above 200°C to yield condensed dihydroxynaphthalines5. The latter compounds can be oxidized to give 3-hydroxy-1,4-naphthoquinone-5-alkanoic acids. The reaction of ketone8 with magic malonates2 or chlorocarbonyl ketene9 affords the pyrones11 in low yields. The 2-pyrones11 could not be rearranged to13; a possible explanation for this behaviour is presented.

Herrn Prof. emer. Dr.E. Ziegler, der vor 30 Jahren erstmals die ketenoide Reaktionsweise von Malonsäurederivaten beschrieb [16], in Dankbarkeit und Freundschaft gewidmet.     

Thermodynamic studies on thin liquid films. I. General formulation

From the viewpoint that thermodynamic study is essential to elucidate the structure and properties of thin liquid films, thermodynamic equations based on a new convention and employing pressure as a thermodynamic variable are developed for adsorption at film interfaces of a plane-parallel film. The equations together with quasi-thermodynamic ones correlate the dependence of film tension on concentration, temperature, pressure, and disjoining pressure to film density, entropy and volume changes associated with adsorption, and thermodynamic film thickness, respectively. Based on the formulation adopting pressure as a variable, equations are also derived for the differences in thermodynamic quantity between the film and the bulk interfaces coexisting at equilibrium.This revised version was published online in October 2004.Due to an unfortunate error Figure 1 has been omitted in the first version of the article which was published online first on April 23, 2004.     

Gas chromatographic analysis of xylidine isomers on heteroaromatic compounds

Summary Nicotinic acid, picolinic acid, isonicotinic acid, histidine and other amphoteric heteroaromatic compounds, uracil, thymine, isatin and other heteroaromatic compounds having imino and carbonyl groups as well as IH-benzotriazole, benzoguanamine and guanidine phosphate effectively resolved all the xylidine (dimethylaniline) isomers. Furthermore, the mixed phases of nicotinamide + p-amino-benzoic acid and melamine+barbituric acid also provided an appreciable resolution. These analyses were carried out using a support which were not treated with an alkali.     

Structure formation of surfactants in concentrated sulphuric acid: a light scattering study

A common cationic surfactant,n-hexadecylammonium hydrogensulphate, dissolved in concentrated sulphuric acid, has been studied by static and dynamic light scattering. Micelle formation has been observed even in this unusual solvent. An apparent molar mass of 45 500±4.5% was found for the aggregates. A translational diffusion coefficientD ₀=5.5×10^–9 cm²/s was measured which gave a hydrodynamically effective radius ofR _h=17.7 nm. The geometric radius of gyration wasR _g=76.2 nm. The ratioR _g/R _h=4.33 is indicative for rodlike structures. Assuming a polydispersity ofL _w/L _n=2 this corresponds to a cylinder ofL _w=152 nm. An axial ratiop _w=(L _w/d)=60.4 nm was estimated which leads to a cylinder diameter of 2.53 nm. At surfactant concentrations higher than 5% (w/vol) the rod-like micelles aggregate to form more globular structures. The time correlation function, recorded by dynamic light scattering, exhibited a two-step decay which indicates a bimodal distribution of particle sizes. The fast motion coincides with that of the micelles at low concentrations while the other is slower than the fast one by three orders of magnitude and corresponds to the translational motion of large clusters.