Increasing mechanical resilience and enhanced electrical conductivity through the incorporation of CNF reinforcing additives in PA6 nanocomposites

Structural Chemistry - In pursuit of strong, tough, and functional advanced composite materials, a series of polymer nanocomposite blends were prepared from the engineering thermoplastic polyamide...     

Siderophore-Mediated Iron Uptake Promotes Yeast–Bacterial Symbiosis

In the present study, siderophore produced by the marine yeast Aureobasidium pullulans was characterized as hydroxamate by chemical and bioassays. The hydroxamate assignment was supported by the appearance of peaks at 1,647.21?C1,625.99?cm^?1 and at 1,435.04?cm^?1 in the infrared spectrum. The purified siderophore exhibited specific growth-promoting activity under iron-limited conditions for siderophore auxotrophic probiotic bacteria. Cross-utilization of siderophore indicates a symbiotic relationship between the yeast A. pullulans and the selected probiotic bacterial strains. Statistical optimization of medium components for improved siderophore production in A. pullulans was depicted by response surface methodology. The shift in UV?CVis spectroscopy indicates the photoreactive property and subsequent oxidative cleavage of purified siderophore on exposure to sunlight.     

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.     

Structural Effects in Lithiocuprate Chemistry: The Elucidation of Reactive Pentametallic Complexes

TMPLi (TMP=2,2,6,6‐tetramethylpiperidide) reacts with Cu^I salts in the presence of Et₂O to give the dimers [{(TMP)₂Cu(X)Li₂(OEt₂)}₂] (X=CN, halide). In contrast, the use of DMPLi (DMP=cis‐2,6‐dimethylpiperidide) gives an unprecedented structural motif; [{(DMP)₂CuLi(OEt₂)}₂LiX] (X=halide). This formulation suggests a hitherto unexplored route to the in situ formation of Gilman‐type bases that are of proven reactivity in directed ortho cupration.     

Atomgewichte

Analytical and Bioanalytical Chemistry -     

Semi-empirical calculations and the assignment of valence photoelectron spectra of large molecules : Phenalen-9-amino-1-imine.

The He(I) photoelectron spectrum of phenalen-9-amino-1-imine (C₁₃H₁₀N₂) has been assigned using the SPINDO and HAM/3 semi-empirical methods. The molecular orbital patterns and properties suggested by the calculations are compared for the low energy region (7–12 ev).     

The photoelectron spectra of arsenic tribromide and arsenic triiodide

The vapor-phase HeI photoelectron spectra of AsBr₃, and AsI₃ have been measured using a spectrometer modified to accept solid samples at elevated temperatures. The interpretation of the low ionization potential bands is complicated by the spin-orbit interaction which occurs among the ion states. Non-empirical valence-electron molecular orbital wavefunctions of AsBr₃ and ASI₃ have been used with a semi-empirical spin-orbit Hamiltonian to give theoretical splitting patterns. The proposed assignments are based on the magnitudes of the splittings indicated by the calculations.     

New twists on the perovskite theme: crystal structures of the elusive phases R and S of NaNbO3

The crystal structure of NaNbO(3) has been studied in detail in the temperature regime 360 < T < 520 °C using a combination of high-resolution neutron and synchrotron X-ray powder diffraction, supported by first-principles calculations. A systematic symmetry-mode analysis is used to determine the presence of the key active distortion modes that, in turn, provides a small and an unambiguous set of trial structural models. A unique model for Phase S (480 < T < 510 °C) is elucidated, having a 2 × 2 × 4 superlattice of the aristotype perovskite structure, space group Pmmn. This unusual and unique structure features a novel example of a compound octahedral tilt system in a perovskite. Two possible structural models for Phase R (370 < T < 470 °C) are determined, each having a 2 × 2 × 6 superlattice and differing only in the nature of the complex tilt system along the 'long' axis. It is impossible to identify a definitive model from the present study, although reasons for preferring one over the other are discussed. Some of the possible pitfalls in determining such complex, pseudosymmetric crystal structures from powder diffraction data are also highlighted.     

Non-empirical valence-electron molecular orbital calculations: spin-orbit splitting in the ion states of the tin and antimony halides

The non-empirical valence-electron (NEVE) molecular orbital method can accommodate molecules containing p-block atoms up to the fourth row in a minimum STO basis calculation. Unlike many MO methods in current use, the NEVE method allows comparisons down the Periodic Table. The present study illustrates this for the tin tetrahalides and antimony trihalides. The calculated orbital eigenvalues correlate well with the photoelectron spectra of these compounds, and by using a semi-empirical spin-orbit hamiltonian theoretical spin-orbit splitting patterns are obtained. The calculated splittings are generally smaller for the antimony trihalides, and a revised assignment of the photoelectron spectrum of antimony tri iodide is suggested.