[U(bipy)4]: A Mistaken Case of U0?

After more than 50 years, the synthesis and electronic structure of the first and only reported “U⁰ complex” [U(bipy)₄] ( 1 ) has been reinvestigated. Additionally, its one‐electron reduced product [Na(THF)₆][U(bipy)₄] ( 2 ) has been newly discovered. High resolution crystallographic analyses combined with magnetic and computational data show that 1 and its derivative 2 are best described as highly reduced species containing mid‐to‐high‐valent uranium ligated by redox non‐innocent ligands.     

Study of the surface properties and surface concentration of ionic liquid–alcohol mixtures

Surface properties for three binary mixtures containing a 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) and a long-chain alcohol (1-butanol, 1-pentanol and 1-hexanol) were determined by surface tension data at the following temperatures: (298.15, 308.15, 318.15, 328.15 and 338.15) K. The surface tension data over the entire mole fraction range are correlated by the Fu et al.(FLW) and Myers-Scott (MS) models. There is good agreement between the experimental data and the results of correlations for 15 binary systems (the three systems at five temperatures) with an average relative error below 1.5%. In addition, the UNIFAC group contribution method is applied for calculation of activity coefficients of components in solution. Moreover, the relative adsorptions of alcohol at the air/liquid interface are determined using Gibbs adsorption isotherm. The obtained results show that the values of adsorption for mixtures of alcohols/[BMIM][SCN] increase with increasing the alkyl chain length of alcohol and decreasing temperature.     

Electrospun superhydrophobic polystyrene hollow fiber as a probe for liquid–liquid microextraction with gas chromatography‐mass spectrometry

A superhydrophobic polystyrene hollow fiber was electrospun around a copper spring collector. This approach led to the construction of a hollow fiber membrane, and the copper spring acted as a scaffold. The characteristic properties of the hollow fiber were studied by scanning electron microscopy. The membrane was used as a probe to transfer the extracting solvent from aquatic media to a gas chromatograph. After performing the liquid–liquid microextraction procedure on 10 mL of water sample by octanol, the whole solution was passed through the prepared polystyrene hollow fiber. Propanol, containing 2 mg/L lindane as the internal standard, was used for desorption and an aliquot of 2 μL of the desorbing solvent was subsequently injected into gas chromatography with mass spectrometry. Effects of different parameters influencing the extraction efficiency were optimized. The limits of detection and quantification were 2 and 6 ng/L, respectively. The relative standard deviations at a concentration level of 100 ng/L were between 2 and 6% (n = 3) while the method linearity ranged from 6 to 200 ng/L. Some real water samples were analyzed by the developed method and relative recoveries were in the range of 76–107%.     

Highly polyhapto-aromatic interactions in thallium(I) coordination

In the solid state, the Tl(I) complex of 4-hydroxybenzoate (HB⁻), [Tl(HB)]_n (1), can be regarded as containing polymeric chains linked through 2 × η⁶ interactions of the Tl atoms with phenyl groups from adjacent units. The thallium atoms contain close Tl^I ? π (aromatic) contacts, thus attaining a total hapticity of 16 with environments TlO₄C₁₂. The unusually high coordination number in the this compound may reflect the capacity of Tl(I) to act as both a Lewis acid and a Lewis base.     

THE DUAL ABSORPTIVE MODE AND πP ELASTIC SCATTERING REVISITED

Using the Regge pole phase rule for contrilbutions to both amplitudes the DAM is applied to ^πp elastic scattering in the p_lab≥10 GeV/c and |t|≤0.8(GeV/c)² region. It is found that the DAM has a mixed success in describing ^πp scattering. The p contribution to both amplitudes is in accord with the DAM while the f-non-flip contribution does not have a peripheral zero.The Pomeron imaginary part is in accord with the DAM with a non-negligible Pomeron phase so that the DAM approximation Rep=O is unsatisfactory. There is also a Pomeron-flip contribution contrary to the expectation of the model. The O-flip contribution is taken into account and a small f-flip contribution i s also required.     

Nonexistence of time‐periodic solutions of the Dirac equation in an axisymmetric black hole geometry

We prove that in the nonextreme Kerr‐Newman black hole geometry, the Dirac equation has no normalizable, time‐periodic solutions. A key tool is Chan‐drasekhar's separation of the Dirac equation in this geometry. A similar nonexistence theorem is established in a more general class of stationary, axisymmetric metrics in which the Dirac equation is known to be separable. These results indicate that, in contrast to the classical situation of massive particle orbits, a quantum mechanical Dirac particle must either disappear into the black hole or escape to infinity. © 2000 John Wiley & Sons, Inc.     

Refinement of the primary hydration shell model for molecular dynamics simulations of large proteins

A realistic representation of water molecules is important in molecular dynamics simulation of proteins. However, the standard method of solvating biomolecules, that is, immersing them in a box of water with periodic boundary conditions, is computationally expensive. The primary hydration shell (PHS) method, developed more than a decade ago and implemented in CHARMM, uses only a thin shell of water around the system of interest, and so greatly reduces the computational cost of simulations. Applying the PHS method, especially to larger proteins, revealed that further optimization and a partial reworking was required and here we present several improvements to its performance. The model is applied to systems with different sizes, and both water and protein behaviors are compared with those observed in standard simulations with periodic boundary conditions and, in some cases, with experimental data. The advantages of the modified PHS method over its original implementation are clearly apparent when it is applied to simulating the 82 kDa protein Malate Synthase G. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009     

Artificial neural network for quantitative determination of total protein in yogurt by infrared spectrometry

A method has been introduced for quantitative determination of protein content in yogurt samples based on the characteristic absorbance of protein in 1800-1500 cm^− 1 spectral region by mid-FTIR spectroscopy and chemometrics. Successive Projection Algorithm (SPA) wavelength selection procedure, coupled with feed forward Back-Propagation Artificial Neural Network (BP-ANN) model was the benefited chemometric technique. Relative Error of Prediction (REP) in BP-ANN and SPA-BP-ANN methods for training set was 7.25 and 3.70 respectively. Considering the complexity of the sample, the ANN model was found to be reliable, while the proposed method is rapid and simple, without any sample preparation step.     

Multichannel vector sum phase shifter

A novel multichannel vector sum phase shifter that is suitable for phased array antenna applications is demonstrated. Each channel is implemented using a distinct optical wavelength. Selective control of each channel is performed using an acousto-optic polarization coupler. The concept is successfully demonstrated for two individually controlled channels. For each channel, a continuously variable frequency linear phase shift is demonstrated between DC and 7 GHz, with the phasing range exceeding 100 degrees.