AFM substantiation of the fracture behavior and mechanical properties of sol–gel derived silica packed epoxy networks

Silica packed epoxy networks are prepared in two steps via in situ, solvent free sol–gel processing of tetraethoxysilane in liquid epoxy monomer and curing the mixture with a flexible diamine afterwards. The influence of filler content and processing conditions on the mechanical properties and the fracture behavior is studied by means of the static mechanical analysis and AFM characterization of the pristine and the fractured polymer surfaces, and a mechanism to enhance polymer strength and toughness is proposed. The in–situ evolution and packing of silica nanostructures into epoxy networks influences the overall morphology and performance of polymers under high stress. It is found that smaller silica domains distributed at the molecular level cause efficient crack distribution by absorbing energy and thus improve the strength and toughness of silica packed epoxy polymers.     

Iodine-mediated regioselective C2-amination of indoles and a concise total synthesis of (±)-folicanthine

Highly substituted 2-aminated indoles can be prepared in moderate to excellent yields by regioselective C2-amination of indoles promoted by iodine. As a key step in a concise synthesis of (±)-folicanthine, its core structure was easily obtained by one step cyclization-dimerization of substituted tryptophan in high yield on a gram scale.     

One-pot access to indolo[2,3-b]quinolines by electrophile-triggered cross-amination/Friedel-Crafts alkylation of indoles with 1-(2-tosylaminophenyl)ketones

Activation of C2 and C3 of indoles by molecular iodine (I(2)) and base followed by in situ reaction with 1-(2-tosylaminophenyl)ketones or 2-tosylaminobenzaldehyde can afford highly substituted indolo(2,3-b)quinolines in moderate to excellent yields (up to 99%). The reaction provides a metal-free selective difunctionalization of indoles. The synthetic potential of the protocol has been illustrated by the synthesis of neocryptolepine and its 11-methyl analogue.     

Synthesis and Structural Characterization of Dibromidobis(N,N′-dimethylthiourea-κS)cadmium(II) and Diiodidobis(N,N′-dimethylthiourea-κS)cadmium(II)

Abstract  

Cadmium(II) complexes, dibromidobis(N,N′-dimethylthiourea-S)cadmium(II), [Cd(Dmtu)₂Br₂] (1) and diiodidobis(N,N′-dimethylthiourea-S)cadmium(II), [Cd(Dmtu)₂I₂] (2), have been prepared and their structures have been determined by X-ray crystal structure analysis. Compound 1 crystallized in the monoclinic space group C2/c, and the metal ion is situated on a twofold rotation axis. Compound 2 also crystallized in a monoclinic space group, P2₁/c, but here the molecules have no crystallographic symmetry. In both compounds the cadmium atom is bonded to two halide ions and to two dimethylthiourea molecules through the sulfur atoms in a tetrahedral environment. The molecules are linked via N–H⋯Halide hydrogen bonds to form infinite one-dimensional chains in 1 and infinite two dimensional networks in 2. The complexes were also characterized by IR and NMR spectroscopy and the data are consistent with the structures of the compounds.     

Reactivity of the Coordinated Hydroperoxo Ligand

The reactivity of the hydroperoxo complex [Co(CN)(5)OOH](3)(-) has been studied in aqueous solution. The complex undergoes acid-catalyzed aquation (k = 1.89(5) x 10(-)(2) s(-)(1), pK(a) = 5.21(4), T = 20 degrees C, I = 0.1 M). Assuming an I(d) mechanism, this allows the relative affinity for Co(III) to be deduced as H(2)O(2) < H(2)O < HO(2)(-) and implies H(2)O(2) to be a very weak ligand. At neutral pH the hydroperoxo complex effects efficient oxygen atom transfer to L-methionine to give an intermediate identified as [Co(CN)(5)(L-methionine S-oxide)](2)(-), which then dissociates to [Co(CN)(5)OH(2)](2)(-) and L-methionine S-oxide. The reaction is acid catalyzed and is proposed to take place via nucleophilic attack of sulfur on the proximal oxygen of the hydroperoxo ligand with concerted loss of water. The significance of these results for the interaction of hydrogen peroxide with labile metal ions is discussed.     

Jasminum sambac: A Potential Candidate for Drug Development to Cure Cardiovascular Ailments

Jasminum sambac (L.) is a South Asian folkloric medicinal plant that has traditionally been used to treat cardiovascular problems. The current investigation was meticulously organized to explore the pharmacological foundation for the medicinal uses of J. sambac pertaining to cardiovascular ailments and to investigate the core mechanisms. Mechanistic investigation revealed that crude leaf extract of J. sambac produced ex-vivo vasorelaxant effects in endotheliumintact aorta ring preparation and hypotensive effect was recorded via pressure and force transducers coupled to the Power Lab Data Acquisition System. Moreover; J. sambac showed cardioprotective effects against adrenaline -induced left ventricular hypertrophy in rabbits observed hemodynamic. CK-MB, LDH, troponin, CRP, ALT, AST, ALP levels were shown to be lower in the myocardial infarction model, as were necrosis, oedema, and inflammatory cell recruitment in comparison to control. J. sambac has shown good antioxidant potential as well as prolonged the noradrenaline induced platelet adhesion. The vasorelaxant and cardioprotective effects in both in vivo and ex vivo experiments, which are enabled by activation of muscarinic receptor and/or releasing the nitric oxide and by reducing the adrenaline, induced oxidative stress, justifying its usage in cardiovascular disorders.     

重金属氟化玻璃的光学特性研究

介绍含有镧、铈、铪、锆等重金属氟化玻璃（ＨＭＦ）的光学性质。光激发荧光的测量是在含有不同浓度金属铈（５％及８％）的氟化玻璃中进行的。在氟环境中,这种玻璃表现出很强的激发特性和发射荧光光谱。在激发光波长为２９０ｎｍ时,样品光谱峰值较宽并位于３１０ｎｍ处。相同元素构成的样品都有几乎相同的光谱,只有当玻璃中用锆代替铪时,其出射光强相当小。折射实验表明,含有铪、镧、铈的样品折射率都很低。同时还观察到,相同     

Band gap anomaly in ternary chalcopyrite semiconductors,the role of p-d hybridization

Summary The anomalous reductions in the energy band gap of the chalcopyrite semiconductors as compared to their relative binary analogs are estimated quantitatively by using a simple relation that involves quantum defect electronegativity scale and the average principal quantum number. The chemical and the structural contribution to this anomaly is discussed in details and it is shown that the relation can be easily extended to explain the variation in the band gap of some cross-substitutional alloys.

---

Riassunto Le anomale riduzioni del gap di energia nei semiconduttori a struttura calcopirite rispetto ai loro analoghi binari sono stimate quantitativamente usando una semplice relazione che implica l’uso della scala delle elettronegatività e il numero quantico principale medio. Il contributo chimico e strutturale a questa anomalia è discusso ed è mostrato che la relazione può essere agevolmente estesa per spiegare la variazione del gap in alcune soluzioni solide.

---

Резюме Количественно оцениваются аномальные уменьшения ширины запрещенной зоны в полупроводниках халькопирита, по сравнению с бинарными аналогами. Подробно обсуждается химичекий и структурный вклад в эту аномалию. Показывается, что предложенный подход можно легко обобщить для объяснения изменения ширины запрещенной зоны в некоторых кросс-замещенных сплавах.

     

Pseudopotential orbital radii and tetragonal distortions in ternary and quaternary chalcopyrite compounds

Use of density-functional pseudopotential (DFP) orbital radii has been made to analyse the distortion in ternary and quaternary semiconducting compounds. For ternary chalcopyrites, the present results are discussed in comparison with some earlier calculations based on quantum-defect (QD) orbital radii.