Flux line lattice symmetries in the borocarbide superconductor LuNi2B2C

We compare the results of small angle neutron scattering on the flux line lattice (FLL) obtained in the borocarbide superconductor LuNi₂B₂C with the applied field along the c- and a-axes. For H‖c the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated. Above 10 K the transition onset field. H ₂(T), rises sharply, bending away from H _c2(T) in contradiction to theoretical predictions of the two merging. For H‖a a first order FLL reorientation transition is observed at H _tr=3–3.5 kOe. Below H _tr the FLL nearest neighbor direction is parallel to the b-axis, and above H _tr to the c-axis. This transition cannot be explained using nonlocal corrections to the London model.     

Synthesis (via reductive elimination or metathesis) and x-ray crystal structure of a tetrameric meso-tin(II) metallocycle Sn(CHSiMe3C6H4︹CHSiMe3−o)2, and characterisation of meso,meso−Sn(CHSiMe3C6H4︹CHSiMe3−o)2

A yellow, diamagnetic tin(II) metallocycle, $meso?S\stackrel{︹}{n(CHSiM{e}_3{C}_6{H}_4}CHSiM{e}_3?o)$ (I) showing a monomeric parent ion in its mass spectrum and a first ionisation energy at 7.6 eV in its photoelectron spectrum, is tetrameric in the solid with an Sn₄ ring (Sn—Sn 2.852(3)Å), as determined by X-ray structure analysis, and was isolated as a minor product on treating SnCl₄ with [{o-C₆H₄ (CHSiMe₃)₂}{Li(tmeda)}₂] (II) at ?78° C (but not +30° C) [tmeda = Me₂NCH₂CH₂NMe₂] in OEt₂. The major product is the spirocyclic complex $S\stackrel{︹}{n(CHSiM{e}_3{C}_6{H}_4}CHSiM{e}_3?o{)}_2$ in which both ligands are in the meso configuration; compound I was more conveniently obtained from II and Sn(OC₆H₂Me-4-Bu^t₂-2,6)₂     

Constructing 2D porous material based on the assembly of large organic ions: p-sulfonatocalix[8]arene and tetraphenylphosphonium ions

In the presence of tetraphenylphosphonium and aquated ytterbium(III) ions, conformationally flexible p-sulfonato-calix[8]arene forms an extended structure with two dimensional porosity involving the assembly of phosphonium cations and 'molecular capsules' comprised of two calixarenes shrouding three phosphonium cations.     

Infrared-induced reaction of Cl atoms trapped in solid parahydrogen

The 355 nm photodissociation of Cl(2) trapped in a solid parahydrogen matrix at 2 K leads to the formation of isolated Cl photofragments. At these low temperatures (k(B)T approximately 1.4 cm(-1)), the Cl atoms can not react with the parahydrogen matrix since the reaction Cl + H(2)(v = 0, j = 0) --> HCl(v = 0, j = 0) + H is endothermic by 360 cm(-1). Irradiation of the Cl atom doped parahydrogen solid with broadband infrared radiation from 4000 cm(-1) to 5000 cm(-1) induces reaction of atomic Cl with the parahydrogen matrix to form HCl. The infrared-induced chemistry is attributed to solid parahydrogen absorptions that lead to the creation of vibrationally excited H(2)(v = 1), which supply the necessary energy to induce reaction. The kinetics of this low temperature infrared-induced reaction is studied using Fourier Transform infrared spectroscopy of the HCl reaction product. The HCl formation kinetics is first-order and the magnitude of the effective rate constant for the infrared-induced reaction depends on the properties of the near infrared radiation.     

Lanthanide-induced helical arrays of [{Co(III) sepulchrate} intersection {p-sulfonatocalix[4]arene}] supermolecules

In the presence of lanthanide ions, a Co(III) sepulchrate cation [Co(diHOsar)]3+ and sodium p-sulfonatocalix[4]arene form a 1:1 host-guest complex which is self-assembled into a zeolite-like lattice network comprised of parallel, single stranded helices.     

Encapsulation and Sustained Release of Curcumin using Superparamagnetic Silica Reservoirs

For controlled release and targeted delivery of curcumin in an aqueous medium a method of encapsulating curcumin and magnetic nanoparticles inside porous silica matrix has been developed. Curcumin and superparamagnetic nanoparticles are loaded inside porous silica in a single process. The graphic shows the TEM image of microtomed sample of Fe₃O₄ particles surrounded by a silica matrix.

     

SOME POSTERIOR DISTRIBUTIONS FOR THE LAPLACE MEAN

Two posterior distributions for the mean of the Laplace distribution are obtained by deriving the distributions of the product XY and the ratio X/Y when X and Y are Student＇s t and Laplace random variables distributed independently of each other. Tabulations of the associated percentage points are given along with computer programs for generating them.     

Selective 1,3-complexation of p-(t)Bu-calix[4]arene by [TiCp(2)Me(2)

Reaction of p-(t)Bu-calix[4]arene with dimethyl titanocene results in high yield selective 1,3-dimetallation of the calixarene in the cone conformation by selective cleavage of one methyl group.     

'Molecular capsules' based on p-sulfonatocalix[6]arene shrouding two tetraphenylphosphonium cations

p-Sulfonatocalix[6]arene in the double cone conformation forms a molecular capsule-like arrangement confining two tetraphenylphosphonium cations, as part of an extended structure involving layers of additional tetraphenylphosphonium cations, aquated lanthanide ions and a large array of water molecules.     

Solvent-free, direct synthesis of supramolecular nano-capsules

The single step direct synthesis of pyrogallol[4]arene via a solvent free protocol yields the pure product as a self-assembled nano-capsule, comprised of six macrocyclic building blocks.