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.     

Green‐Solvent‐Processed Molecular Solar Cells

High‐efficiency bulk heterojunction (BHJ) organic solar cells with power conversion efficiencies of more than 5 % can be fabricated using the green solvent 2‐MeTHF. The active layers comprise a blend of a molecular semiconductor donor with intermediate dimensions (X2) and the soluble fullerene derivative [6,6]‐phenyl‐C₆₁‐butyricacidoctylester (PC₆₁BC₈). A switch of the processing solvent from chloroform to 2‐MeTHF leads to no negative impacts on the morphology and charge‐transport properties of optimally performing BHJ films. Examinations by absorption spectroscopy, atomic force microscopy, and grazing incidence wide‐angle X‐ray scattering reveal no significant modification of morphology. These results show that green solvents can be excellent alternatives for large‐area printing of high‐performance organic photovoltaics (OPVs) and thus open new opportunities for sustainable mass production of organic solar cells and other optoelectronic devices.     

Analysis of carrageenans by matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry. I. kappa-Carrageenans.

Matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectra of small kappa-carrageenans are reported and discussed. MALDI spectra can be obtained in both positive and negative ion mode. In the absence of extraneous metal ions, positive ions are formed by the attachment of one Na(+) ion to the carrageenan, whereas for negative ions one Na(+) ion is detached from the sulfate group. Multiply charged species are not observed in MALDI. Intense ESI spectra can be obtained in negative ion mode and now multiply charged species are seen. Alkali exchange experiments show that in these small carrageenan anions one, but only one, alkali metal ion is bound in a bidentate coordination with two ionic sulfate groups. G2-type ab initio calculations on model ions HO(-) [M(+)] (-)OH (M = Li, Na, K, Cs), as well as arguments based on a simple Coulombic interaction model, show that the bidentate stabilization energy drops rapidly as the size of the alkali cation increases. Exchange of Na(+) with Li(+) leads to expulsion of the Na(+) ion generating, in ESI, intense multiply charged anions. An attempt is made to rationalize this behavior in terms of hydration effects.     

In vivo measurement of the local optical properties of tissue by use of differential path-length spectroscopy

We demonstrate the capability of differential path-length spectroscopy (DPS) to determine the local optical properties of tissue in vivo. DPS measurements on bronchial mucosa are analyzed and yield information on the local blood oxygenation, blood content, average microvessel diameter, and wavelength dependence of the reduced scattering coefficient. Our data collected to date show that cancerous bronchial mucosa has a lower capillary oxygenation and a larger average capillary diameter than normal bronchial mucosa.