Sympathetic cooling of polyatomic molecules with S-state atoms in a magnetic trap

We present a rigorous theoretical study of low-temperature collisions of polyatomic molecular radicals with (1)S(0) atoms in the presence of an external magnetic field. Accurate quantum scattering calculations based on ab initio and scaled interaction potentials show that collision-induced spin relaxation of the prototypical organic molecule CH(2)(X(3)B(1)) (methylene) and nine other triatomic radicals in cold (3)He gas occurs at a slow rate, demonstrating that cryogenic buffer-gas cooling and magnetic trapping of these molecules is feasible with current technology. Our calculations further suggest that it may be possible to create ultracold gases of polyatomic molecules by sympathetic cooling with alkaline-earth atoms in a magnetic trap.     

Chemical Modification of Dextran through Reaction with Biscyclopentadienyltitanium Dichloride and Dibutyltin Dichloride as a Function of the Reaction System

Abstract

Dextran was modified through condensation with biscyclopentadienyltitanium dichloride and dibutyltin dichloride by employing a number of solution and interfacial condensation systems. The modified dextran is rapidly synthesized (within 30 s) in good yield with moderate to high degrees of substitution. The products are complex with chains composed of a variety of substituted and un-substituted glycopyranose units.     

Facile preparation of macroscopic soft colloidal crystals with fiber symmetry

A facile, efficient way to fabricate macroscopic soft colloidal crystals with fiber symmetry by drying a latex dispersion in a tube is presented. A transparent, stable colloidal crystal was obtained from a 25 wt % latex dispersion by complete water evaporation for 4 days. The centimeter-long sample was investigated by means of synchrotron small-angle X-ray diffraction (SAXD). Analysis of a large number of distinct Bragg peaks reveals that uniaxially oriented colloidal crystals with face-centered cubic lattice structure were formed. The measurement of evaporation rates under different conditions indicates that the water evaporates primarily through the optically clear regions (i.e., via the solid material) even when the region is more than 2 mm thick.     

Pattern formation of colloidal suspensions by dip‐coating: An in situ grazing incidence X‐ray scattering study

Dip‐coating of a colloidal suspension is investigated in situ with microbeam grazing incidence small‐angle X‐ray scattering. We focus on the real‐time monitoring of a vertical dip‐coating process yielding insights into structural changes during pattern formation of the thin film. With the selected configuration a fixed spot on the sample surface is probed and the structural information at the time the contact line passes this spot is obtained, hence revealing the structure at the vicinity of the flowing meniscus owing to the microfocused beam. After dip‐coating the morphology is analyzed with atomic force microscopy, yielding real space information about the arrangement of individual nanoparticles at the film surface.

     

A-site ordering versus electronic inhomogeneity in colossally magnetoresistive manganite films

Epitaxial La(3/4)Ca(1/4)MnO3/MgO(100) (LCMO) thin film shows an unusual rhombohedral (R-3c) structure with a new perovskite superstructure at room temperature due to the CE-type ordering of La and Ca with modulation vector q=1/4[011]. A-site ordered film was found to be electronically homogeneous down to the 1 nm scale as revealed by scanning tunnelling microscopy/spectroscopy. In contrast, orthorhombic and A-site disordered LCMO demonstrate a mesoscopic phase separation far below the Curie temperature (TC). Unique La/Ca ordering compensates the cation mismatch stress within one supercell, a(S) approximately 1.55 nm, and enhances the electronic homogeneity. The phase separation does not seem to be a unique mechanism for the colossal magnetoresistance (CMR) as very large CMR approximately 500% was also observed in A-site ordered films.     

Structure and Characterization of the Condensation Products of Dextran and Organostannane Halides

The modification of dextran, a water-soluble polysaccharide, through condensation with organostannane halides was accomplished utilizing the interfacial technique. Structural analysis agreed with condensation of the dextran-hydroxyls forming tin ether linkages with the dextran. Thermal degradation occurs through several stability plateaus and in air occurs through an oxidative pathway(s). Some of the products inhibit bacteria commonly responsible for mildew and rot.     

Oh the mechanism of stereoregulation in the allylnickel complex catalyzed butadiene polymerization

After a brief account of the present knowledge on the mechanism of the allylnickel complex catalyzed stereospecific butadiene polymerization, synthesis and catalytic properties of the cationic allylnickel(II) complexes, [C₃H₅NiL₂]PF₆ (L = P(OAlk)₃, P(OAr)₃, PPh₃, AsPh₃, SbPh₃, MeCN, Me₃CNC, 1,5–COD), are described. From kinetic and ³¹P-NMR spectroscopic investigations, especially with [C₃H₅Ni(P(OPh)₃)₂]PF₆ as a typical trans-catalyst, the definite course of the catalytic stereoregulation has been elucidated.     

Evaporation‐Driven Self‐Assembly of Colloidal Silica Dispersion: New Insights on Janus Particles

The evaporation driven self‐assembly of novel colloidal silica Janus particles was evaluated by scanning electron microscopy in comparison to unfunctionalized silica particles. The cyclodextrin‐ and azobenzene‐modified compound was obtained utilizing Pickering emulsion approach, in which the particles were immobilized on solidified wax droplets and subsequently functionalized. Silica particles were modified with 3‐aminopropyl trimethoxysilane and afterward reacted with tosyl‐β‐CD or phenylazo(benzoic acid), respectively. Mesoscopic structures of the colloidal dispersions, as dried films from aqueous solution, have been investigated by scanning electron microscopy and dynamic light scattering. Interestingly, it has been observed that the Janus particles show a significantly different evaporation‐induced assembly than the unmodified particles.