Paramagnetic resonance studies of Cu2+ doped in NH4Br

Electron Paramagnetic Resonance studies of Cu²⁺ doped in NH₄Br single crystals have been carried out for the first time. The room temperature data reveal that Cu²⁺ ions go predominantly to interstitial sites having square planar co-ordination of four Br^? ions. For this type of complexes the bromine: superhyperfine structure: is observed on the normal hyperfine structure lines of copper. Existence of other weak spectra indicates that a relatively few Cu⁺⁺ ions go substitutionally to (NH₄)⁺ ions, and are probably associated with a first or a second nearest neighbour cation vacancy, among the two, the latter being more predominant. However, the low temperature studies corresponding to the tetragonal phase of NH₄Br indicate that a number of Cu²⁺ ions at interstitial sites get readjusted to the lattice sites after phase transformation. The spectra in both the phases are analysed by the usual spin Hamiltonian method.     

Mean amplitudes of vibration: Bent XYZ molecules

The theory of mean-square amplitude matrices is applied to the bent XYZ molecules. The principal mean amplitudes of vibration for the molecules investigated here are reported for 300° K.     

Chemical examination of Embelia ribes—V Synthesis of some N-bis(anhydrobenzoquinones)

By the condensation of embelin (I) with various nitroso compounds, the corresponding N-bis-anhydrobenzoquinones (II) have been synthesized and their properties recorded.     

Competitive cascade cyclization of 2′-tosyloxychalcones: An easy access to thioflavones and thioaurones

Abstract

A new and efficient approach for the synthesis of thioflavones and thioaurones by competitive cascade cyclization of 2′-tosyloxychalcones has been developed. 2′-Tosyloxychalcones were smoothly converted into thioflavones and thioaurones by incorporation of sulfur atom using elemental sulfur and triethylamine in DMSO with good yields. The advantages of the methodology are the formation of both thioflavones and thioaurones in a single step. Easily accessible substrates, mild reaction conditions and compatibility with a broad range of functional groups make this protocol clean and inexpensive.     

Periodic multisequences with large error linear complexity

Generalizing the theory of k-error linear complexity for single sequences over a finite field, Meidl et al. (J. Complexity 23(2), 169–192 (2007)) introduced three possibilities of defining error linear complexity measures for multisequences. A good keystream sequence must possess a large linear complexity and a large k-error linear complexity simultaneously for suitable values of k. In this direction several results on the existence, and lower bounds on the number, of single sequences with large k-error linear complexity were proved in Meidl and Niederreiter (Appl. Algebra Eng. Commun. Comput. 14(4), 273–286 (2003)), Niederreiter (IEEE Trans. Inform. Theory 49(2), 501–505 (2003)) and Niederreiter and Shparlinski (In: Paterson (ed.) 9th IMA International Conference on Cryptography and Coding (2003)). In this paper we discuss analogous results for the case of multisequences. We also present improved bounds on the error linear complexity and on the number of sequences satisfying such bounds for the case of single sequences.     

An Easy,Efficient and Improved Synthesis of Sertaconazole Nitrate

Russian Journal of Organic Chemistry - An easy, efficient and improved synthetic route has been developed for the synthesis of Sertaconazole...     

Creeping flow of a power law fluid past a fluid sphere

The stress variational principle is employed to obtain the lower bound for the drag offered by the creeping flow of a power law fluid past a Newtonian fluid sphere. In spite of the unprescribed interfacial velocity, a bound-on-bound approach yields bounds that are close to the upper bound obtained by Mohan (1974). Furthermore, for very viscous drops (solid behavior) the theory gives lower bounds that differ considerably from those of Wasserman & Slattery (1964) and show good agreement with the results of Yoshioka & Adachi (1973). The approach presented in this work provides an insight into the method of analyzing multiphase flow situations involving non-Newtonian fluids.     

Catalytic Enantioselective Synthesis of 2,5-Dihydrooxepines

A Michael addition initiated cyclopropanation/retro-Claisen rearrangement tandem reaction was developed for the enantioselective synthesis of highly functionalized 2,5-dihydrooxepines. In the presence of a chiral oxazaborolidinium ion (COBI) catalyst, the reaction proceeds to give good yields and high enantioselectivity.     

Systematic Material Study Reveals TiNb2O7 as a Model Wide-Bandgap Photoanode Material for Solar Water Splitting

This work reveals that photoanodes based on TiNb₂O₇ (TNO) powder show remarkable water-oxidation properties including nearly ideal charge-transfer and charge-injection efficiencies. Furthermore, using a simplified photoanode construction and carefully surveying the structural and morphological characteristics of oriented and polycrystalline thin films and powder-based samples revealed that the water-splitting kinetics of TNO is negligibly effected by surface morphology; instead, internal grain boundaries likely play a driving role. The current powder-based TNO photoanodes exhibit ideal water-oxidation kinetics and oxidize water at minimal applied biases under illumination; consequently, TNO exhibits an early onset photocurrent voltage (0.4 V vs. RHE) that rivals that of other state-of-the-art photoanode materials.