Utility of calculated 13C NMR chemical shifts in differentiating conformational isomers: a study of metal-complexed and uncomplexed bispidines

Calculated 13C NMR chemical shifts were key to assigning the structures of the conformational forms of complexed and uncomplexed bispidine derivatives.     

Black holes in brane worlds

A Kerr metric describing a rotating black hole is obtained on the three brane in a five-dimensional Randall-Sundrum brane world by considering a rotating five-dimensional black string in the bulk. We examine the causal structure of this space-time through the geodesic equations.     

Zirconium complexes having a chiral phosphanylamide in the co-ordination sphere

The chiral phosphanylamido ligand, (N(CHMePh)(PPh2))-, has been introduced into co-ordination chemistry. As starting material the oily amines HN(R-*CHMePh)(PPh2)(1a) and HN(S-*CHMePh)(PPh2)(1b) were used. To reconfirm their absolute structure, 1b was oxidized with H2O2 in air to obtain HN(S-*CHMePh)(P(O)Ph2)(2) as a solid compound. The solid-state structure of 2 was established by single-crystal X-ray diffraction. The lithium salts of both enantiomers Li(N(R-*CHMePh)(PPh2))(3a) and Li(N(S-*CHMePh)(PPh2))(3b) were prepared by deprotonation reaction of 1a,b. Compounds 3a,b were further reacted with zirconocen dichloride to give the chiral metallocenes [(eta5-C5H5)2Zr(Cl)(eta2-N(R-*CHMePh)(PPh2))](4a) and [(eta5-C5H5)2Zr(Cl)(eta2-N(S-*CHMePh)(PPh2))](4b). In an alternative approach to give chiral zirconium compounds, the neutral amine 1b was reacted with [(PhCH2)4Zr] to give the enantiomeric pure complex [(PhCH2)3Zr(eta2-N(S-*CHMePh)(PPh2))](5). The solid-state structures of all zirconium complexes were determined by single-crystal X-ray diffraction.     

FTIR, XRD, SEM and solid state NMR investigations of carbonate-containing hydroxyapatite nano-particles synthesized by hydroxide-gel technique

Nano-crystalline hydroxyapatite (HA), Ca₁₀(PO₄)₆(OH)₂ has been synthesized by a precipitate conversion technique using hydroxide gel at lower temperatures, e.g. 80 °C. HA crystallizes in hexagonal structure (space group: P6₃/m) having lattice parameters: and and around 17 nm in crystallite-size for the 80 °C-heated sample. SEM micrographs show hexagonal crystallites of average particle dimensions approximately 50×20 nm for 80 °C heated sample. The structure analysis by XRD, FTIR, ¹H and ³¹P MAS NMR show the existence of structural disorder at the particle surface that either does not form hydrogen bonding due to lack of adequate bonding parameters or forms a very weak dipolar bonding. The structural disorder has been explained as a result of chemical interactions between the phosphate groups either with the surface adsorbed water or the hydroxyl groups at the surface of the nano-particles.     

An HPTLC Method for the Simultaneous Analysis of Compactin and Citrinin in Penicillium citrinum Fermentation Broth

JPC – Journal of Planar Chromatography – Modern TLC - A simple and precise high-performance thin-layer chromatographic (HPTLC) method has been established for simultaneous analysis of...     

Phase transformation and optical properties of Cu-doped ZnS nanorods

ZnS nanorods doped with 0-15 mol% of Cu have been prepared by simple solvothermal process. With gradual increase in the Cu concentration, phase transformation of the doped ZnS nanorods from wurtzite to cubic was observed. Twins and stacking faults were developed due to atomic rearrangement in the heavily doped ZnS nanorods during phase transformation. UV-vis-NIR absorbance spectroscopy ruled out the presence of any impure Cu-S phase. The doped ZnS nanorods showed luminescence over a wide range from UV to near IR with peaks at 370, 492-498, 565 and 730 nm. The UV region peak is due to the near-band-edge transition, whereas, the green peak can be related to emission from elementary sulfur species on the surfaces of the nanorods. The orange emission at 565 nm may be linked to the recombination of electrons at deep defect levels and the Cu(t₂) states present near the valence band of ZnS. The near IR emission possibly originated from transitions due to deep-level defects.     

Convex fuzzy mapping with differentiability and its application in fuzzy optimization

The concepts of differentiability, convexity, generalized convexity and minimization of a fuzzy mapping are known in the literature. The purpose of this present paper is to extend and generalize these concepts to fuzzy mappings of several variables using Buckley–Feuring approach for fuzzy differentiation and derive Karush–Kuhn–Tucker condition for the constrained fuzzy minimization problem.     

Time-average measurement of velocity, density, temperature, and turbulence velocity fluctuations using Rayleigh and Mie scattering

Measurement of time-averaged velocity, density, temperature, and turbulence velocity fluctuations in sparsely seeded gas flows using a non-intrusive, point-wise technique based on Rayleigh and Mie scattering is discussed. A Fabry-Perot interferometer (FPI) is used to spectrally resolve laser light scattered by molecules and particulates in gas flows. The spectral content of the scattered light provides information about velocity, density, and temperature of the gas. A CCD camera is used to record images of the fringes formed by scattered light passing through the interferometer. Models of the spectral components are used in a least squares fitting routine to estimate the parameters from fringe images. Flow measurements are presented for subsonic and supersonic jet flows. The application range for this technique is mostly for high velocity situations (>25 m/s). Velocity, density, temperature, and turbulence velocity fluctuations were determined with accuracies within 5 m/s, 4%, 2%, and 5 m/s, respectively.