Fluorinated lithium 1,3-diketonates as reagents to modify podands and crown-ethers

Fluorinated enaminoketones, a new type of ligands, bearing two independent coordination centers (polyether's and fluorinated enaminoketones fragments) have been obtained. The crystal structure of the Cu(II) complex of 1,5-bis-[2-(4′,4′,4′-trifluoro-1′-methyl-3′-oxo-but-1′-enylamino)-phenoxy]-3-oxapentane (10) has been elucidated by X-ray crystallography. The results obtained show that the complex 10 consists of two crystallographically independent molecules C₂₆H₂₄CuF₆N₂O₅ (A and B), and the metal atom in the complex 10 has four-coordinated arrangement, as a polyhedron with a distorted square with two nitrogen and two oxygen atoms located in corners.     

Perception of interrupted speech: cross-rate variation in the intelligibility of gated and concatenated sentences

Temporal constraints on the perception of variable-size speech fragments produced by interruption rates between 0.5 and 16 Hz were investigated by contrasting the intelligibility of gated sentences with and without silent intervals. Concatenation of consecutive speech fragments produced a significant decrease in intelligibility at 2 and 4 Hz, while having little effect at lower and higher rates. Consistent with previous studies, these findings indicate that (1) syllable-sized intervals associated with intermediate-rate interruptions are more susceptible to temporal distortions than the longer word-size or shorter phoneme-size intervals and (2) suggest qualitative differences in underlying perceptual processes at different rates.     

On spatial variations of nematic ordering

We present a theory of orientational order in nematic liquid crystals which interpolates between several distinct approaches based on the director field (Oseen and Frank), order parameter tensor (Landau and de Gennes), and orientation probability density function (Onsager). As in density-functional theories, the suggested free energy is a functional of spatially-dependent orientation distribution, however, the nonlocal effects are taken into account via phenomenological elastic terms rather than by means of a direct pair-correlation function. In illustration of this approach we consider a simplified model with orientation parameter on a circle and reveal its relation to the complex Ginzburg-Landau theory.     

Improved tomographic reconstructions using adaptive time‐dependent intensity normalization

The first processing step in synchrotron‐based micro‐tomography is the normalization of the projection images against the background, also referred to as a white field. Owing to time‐dependent variations in illumination and defects in detection sensitivity, the white field is different from the projection background. In this case standard normalization methods introduce ring and wave artefacts into the resulting three‐dimensional reconstruction. In this paper the authors propose a new adaptive technique accounting for these variations and allowing one to obtain cleaner normalized data and to suppress ring and wave artefacts. The background is modelled by the product of two time‐dependent terms representing the illumination and detection stages. These terms are written as unknown functions, one scaled and shifted along a fixed direction (describing the illumination term) and one translated by an unknown two‐dimensional vector (describing the detection term). The proposed method is applied to two sets (a stem Salix variegata and a zebrafish Danio rerio) acquired at the parallel beam of the micro‐tomography station 2‐BM at the Advanced Photon Source showing significant reductions in both ring and wave artefacts. In principle the method could be used to correct for time‐dependent phenomena that affect other tomographic imaging geometries such as cone beam laboratory X‐ray computed tomography.     

The PVA‐PAAN intrapolymer complexes as sensors with optical response

Sorbtion of some impurities from aqueous solutions by polymer complex poly(vinylalcohol) with poly(acrylamide) grafted copolymers (PVA‐PAA_N) was studied by means of spectrophotometry and steady‐state fluorescence methods. The experiments showed that the PVA‐PAA_N films effectively sorbs impurities molecules of average benzene ring from water. Simultaneously, the processes of polymer films dissolving in water take place. The thermal annealing (with the help of special methods) PVA‐PAA_N film gives a possibility to obtain non‐dissolving polymer films which possess high sorbtion ability. Such films are proposed to be used as the sensors with optical response.