Preparative route to 2‐ethoxycarbonylimidazole‐4‐phosphonate and diethylimidazole‐2,4‐dicarboxylate

Practical synthesis of 2‐ethoxycarbonylimidazole‐4‐phosphonate ( 1a ) and diethyl imidazole‐2,4‐dicar‐boxylate ( 1b ) are described.     

Design,Synthesis, and Structural Analysis of Divalent NI Compounds and Identification of a New Electron‐Donating Ligand

The dative‐bond representation (L→E) in compounds with main group elements (E) has triggered extensive debate in the recent past. The scope and limits of this nonclassical coordination bond warrant comprehensive exploration. Particularly compounds with (L→N←L′)⁺ arrangement are of special interest because of their therapeutic importance. This work reports the design and synthesis of novel chemical species with the general structural formula (L→N←L′)⁺ carrying the unusual ligand cyclohexa‐2,5‐diene‐4‐(diaminomethynyl)‐1‐ylidene. Four species belonging to the (L→N←L′)⁺ class carrying this unconventional ligand were synthesized. Quantum chemical and X‐ray diffraction analyses showed that the electronic and geometric parameters are consistent with those of already reported divalent N^I compounds. The molecular orbital analysis, geometric parameters, and spectral data clearly support the L→N and N←L′ interactions in these species. The newly identified ligand has the properties of a reactive carbene and high nucleophilicity.     

Synthesis,characterization and biological properties of sulfonamide‐derived compounds and their transition metal complexes

Sulfonamide‐derived compounds and their first row d‐transition metal chelates [cobalt(II), copper(II), nickel(II) and zinc(II)] have been synthesized and characterized. The nature of bonding and structure of all the synthesized compounds have been proposed from magnetic susceptibility and conductivity measurements, IR, ¹H and ¹³C NMR, electron spectra, mass spectrometry and CHN analysis data. The structure of ligand, 4‐{[(E)‐(5‐chloro‐2‐hydroxyphenyl) methylidene] amino}‐N‐(4,6‐dimethyl pyrimidin‐2‐yl) benzene sulfonamide has also been determined by X‐ray diffraction method. An octahedral geometry has been suggested for all the complexes. The ligands and metal complexes have been screened for their in vitro antibacterial, antifungal and cytotoxic activity. The results of these studies revealed that all compounds showed moderate to significant antibacterial activity against one or more bacterial strains and good antifungal activity against various fungal strains. Copyright © 2009 John Wiley & Sons, Ltd.     

Notable third-order optical nonlinearities of a Keplerate-type polyoxometalate in solution and in thin films of PMMA

The third-order nonlinear optical properties of a Keplerate-type polyoxometalate (NH₄)₁₈[(Bu₄N]₂₄[Mo₁₃₂O₃₇₂(H₂O)₇₂(CH₃COO)₃₀]?ca.7NH₄CH₃COO?ca.173H₂O (denoted Bu₄N-{Mo₁₃₂}) in solution and in films of poly(methylmethacrylate) (denoted PMMA) matrix have been studied by the Z-scan method at 532 nm with a pulse duration of 20 ps. Experimental results show that both the solution and the solid films of Bu₄N-{Mo₁₃₂} have nonlinear self-defocusing effects and notable nonlinear reverse saturable absorption. Embedding Bu₄N-{Mo₁₃₂} as inclusion into PMMA host significantly improves the nonlinear absorption coefficient β, while it reduces the nonlinear refractive coefficient as a result of the higher concentration of Bu₄N-{Mo₁₃₂} in PMMA matrix than in solution. The magnitude of β for solid-state Bu₄N-{Mo₁₃₂} in films increases with the increasing amount of incorporated Bu₄N-{Mo₁₃₂}, while the third-order nonlinear refractive index n ₂ decreases. Experimental results prove the high stability of Bu₄N-{Mo₁₃₂} in PMMA films in inorganic acidic and basic solutions. These studies indicate that Bu₄N-{Mo₁₃₂} in thin solid films of PMMA are potential candidates for fabricating nonlinear optical devices.     

Elements of Small Orders in K_2FⅡ

In"Elements of small orders in K_2(F)"(Algebraic K-Theory,Lecture Notes in Math.,966,1982,1-6.),the author investigates elements of the form {a,Φ_n(a)} in the Milnor group K_2F of a field F,whereΦ_n(x)is the n-th cyclotomic polynomial.In this paper,these elements are generalized.Applying the explicit formulas of Rosset and Tate for the transfer homomorphism for K_2,the author proves some new results on elements of small orders in K_2F.     

A comparative study of the electrodeposition and the aqueous chemical growth techniques for the utilization of ZnO nanorods on p-GaN for white light emitting diodes

Vertically well aligned zinc oxide nanorods (ZnO NRs) were grown on p-GaN by electrodeposition (ED) and aqueous chemical growth (ACG) techniques and the structures were employed to fabricate white light emitting diodes (LEDs). Room temperature current voltage (I–V$I–V$), photoluminescence (PL), and electroluminescence (EL) measurements were performed to investigate and compare both LEDs. In general, the I–V$I–V$ characteristics and the PL spectra of both LEDs were rather similar. Nevertheless, the EL of the ED samples showed an extra emission peak shoulder at 730 nm. Moreover, at the same injection current, the EL spectrum of the ED light emitting diode showed a small UV shift of 12 nm and its white peak was found to be broader when compared to the ACG grown LED. The broadening of the EL spectrum of the LED grown by ED is due to the introduction of more radiative deep level defects. The presented LEDs have shown excellent color rendering indexes reaching a value as high as 95. These results indicate that the ZnO nanorods grown by both techniques possess very interesting electrical and optical properties but the ED is found to be faster and more suitable for the fabrication of white LEDs.     

ON CLASSES OF REGULAR GRAPHS WITH CONSTANT METRIC DIMENSION

In this paper,we are dealing with the study of the metric dimension of some classes of regular graphs by considering a class of bridgeless cubic graphs called the flower snarks Jn,a class of cubic convex polytopes considering the open problem raised in [M.Imran et al.,families of plane graphs with constant metric dimension,Utilitas Math.,in press] and finally Harary graphs H 5,n by partially answering to an open problem proposed in [I.Javaid et al.,Families of regular graphs with constant metric dimension,Utilitas Math.,2012,88:43-57].We prove that these classes of regular graphs have constant metric dimension.     

The Relevance of Powder/Liquid Wettability to the Cohesiveness of Carbon Black Agglomerates

Particle size enlargement operations often involve the use of a liquid to improve powder cohesiveness. Capillary suction and surface tension forces acting through liquid menisci between particles are the primary source of the cohesive bonding. The strength of these forces, and consequently the strength of the wet agglomerate, is dependent upon the total liquid content, its distribution within the agglomerate, and the powder wettability (characterized by the liquid surface tension and powder/liquid contact angle). The tensile strength of powder compacts containing submicron carbon black particles has been measured as a function of saturation level for several liquids. It is found that the compact strength increases with increasing surface tension for liquids that exhibit a zero contact angle. Above the critical surface tension for wetting a more complicated situation exists where both the surface tension and contact angle are important.     

Parallel permit grammars and some graph representations of Petri nets

The graph of a set grammar is introduced in such a way that each set rule of the grammar is represented by a cartesian subgraph of it. The correspondence between cartesian subgraphs and transitions of Petri nets (which satisfy the axiom of extensionality) is established. The set grammars with input (initial) and output (terminal) elements are studied in an analogy to Chomsky's string grammars and their strong equivalence. Permit rules and parallel permit rules are introduced in such a way that parallel permit grammars are more general tools than Petri nets themselves, because the equivalence between homogeneous parallel permit grammars and set grammars (and Petri nets) is proved.