Characterization and determination of linear alkylbenzenesulfonates in environmental water samples by high-performance liquid chromatography with a hydrophilic polymer column and electrospray ionization mass spectrometric detection.

A liquid chromatography-mass spectrometry (LC/MS) method was developed for the separation and determination of linear alkylbenzenesulfonates (C10-C14 LAS) in environmental water samples using a hydrophilic polymer column (Shodex Mspak GF-310 4D). This method involves a solid-phase extraction of the LAS samples with a Sep-Pak PS-2 cartridge. The LAS components were separated on the column with a mobile phase of 29% (w/v) acetonitrile-water containing 0.8 mM di-n-butylammonium acetate and 0.2 M acetic acid, and were detected by mass spectrometry with electrospray ionization. Detection limits of the developed method based on selected ion monitoring (SIM) technique for the C10-C14 LAS standards were 13-47 ng L(-1). The concentrations of the C10-C14 LAS in the environmental water samples ranged between 5-317 microg L(-1) for a river water sample and 0.4-6.4 microg L(-1) for a seawater sample. Linear relationships between the logarithms of retention factors and the alkyl chain lengths for each phenyl positional isomer of LAS could successfully be used for the identification of the isomer peaks.     

Nonlinear transient analysis of moderately thick laminated composite sector plates

This study presents a simple formulation for the nonlinear dynamic analysis of shear-deformable laminated sector plates made up of cylindrically orthotropic layers. The non-axisymmetric formulation in cylindrical coordinates is discretized in space domain using two-dimensional Chebyshev polynomials. Houbolt time marching is used for temporal discretization. Quadratic extrapolation is used for linearization along with fixed-point iteration for obtaining the results. Several combinations of simply supported, clamped and free edge conditions are considered. Convergence study has been carried out and the results are compared with the results of square plates. Effects of boundary conditions, moduli ratio, lamination scheme, sector angle and annularity on the transient deflection response are plotted graphically. Transient responses are compared for step, saw-tooth and sinusoidal loadings.     

Influence of swirl on the stability of a rod in annular leakage flow

The influence of swirl (flow rotation) on the stability of a rod in annular leakage flow is investigated. Under the assumption of laminar flow and plane vibrations (no whirling), it is shown that the swirl acts, in effect, as an elastic foundation with negative foundation stiffness, the magnitude being proportional to the mean circumferential flow rate squared. Consequently, swirl always lowers the critical axial flow speed in case of divergence instability of a rod of finite length. Numerical analysis is needed to predict the effect of swirl in case of flutter instability of a finite rod; this is not performed here. However, for the flutter-like instability of travelling waves in an infinite rod-channel system, it is shown analytically that swirl again always lowers the critical axial flow speed. Finally, it is found that by circumferential flow alone, the travelling waves are extinguished at a certain flow rate, followed by a divergence-like instability.     

Multifractal PDF analysis for intermittent systems

The formula for probability density functions (PDFs) has been extended to include PDF for energy dissipation rates in addition to other PDFs such as for velocity fluctuations, velocity derivatives, fluid particle accelerations, energy transfer rates, etc., and it is shown that the formula actually explains various PDFs extracted from direct numerical simulations and experiments performed in a wind tunnel. It is also shown that the formula with appropriate zooming increment corresponding to experimental situation gives a new route to obtain the scaling exponents of velocity structure function, including intermittency exponent, out of PDFs of velocity fluctuations.     

Asymmetric synthesis of α,α-disubstituted α-amino alcohol derivatives

We herein report an asymmetric synthesis of α,α-disubstituted α-amino alcohol derivatives 3, key intermediates of a novel immunomodulator, using enzymatic desymmetrization of 2-alkyl-2-tert-butoxycarbonylamino-1,3-propanediols 1a and 1b. This method makes it possible to prepare a chiral analogue of FTY720 4. These synthetic procedures allow for a broad structure variation in order to evaluate structure–activity relationships and the mechanism of action for sphingosine 1-phosphate-1 (S1P₁) receptor agonist.     

Low temperature static magnetization of an organic ferromagnet, β-p-NPNN

A ³He refrigerator mountable to a commercial SQUID magnetometer has been developed, which enables us to measure static magnetizations of a sample at temperatures below 2 K conveniently. The design and usage of the system are outlined. We have applied this to study static magnetic properties of an organic ferromagnet, β-p-NPNN, and have confirmed that the saturation magnetization is 1 μ_B per molecule. No hysteretic behavior has been detected, when the field was applied along the easy axis. This indicates that β-p-NPNN is a very soft magnet, as expected for an isotropic Heisenberg magnet based on organic radicals.     

A ruthenium-catalyzed one-pot method for α-alkylation of ketones with aldehydes

Ketones react with an array of aldehydes in dioxane at 80 °C in the presence of a catalytic amount of RuCl₂(PPh₃)₃ along with KOH to give the corresponding α-alkylated ketones in moderate to good yields. A reaction pathway involving base-catalyzed cross-aldol reaction between ketones and aldehydes to form α,β-unsaturated ketones and regioselective reduction of carbon-carbon double bond of α,β-unsaturated ketones is proposed for this catalytic process.     

Carbonyldinitrosyltris(fluorosulfato)tungstate(II) and ‐Molybdate(II) Anions: Synthesis,Spectroscopy, and Density Functional Theory Calculations

Carbonyldinitrosyltris(fluorosulfato)tungstate(II) and ‐molybdate‐(II) anions, [fac‐M(CO)(NO)₂(SO₃F)₃]^? (M=W, Mo), which are novel weakly coordinating anions that contain a metal carbonyl/nitrosyl moiety, have been generated in fluorosulfonic acid and completely characterized by multinuclear NMR, IR, and Raman spectroscopy as well as ESI mass spectrometry. ESI MS measurements performed for the first time on a superacidic solution system unambiguously reveal the formation of the monoanionic, mononuclear W and Mo complexes formulated as [M(CO)(NO)₂(SO₃F)₃]^? (M=W, Mo). Multinuclear NMR spectroscopic studies at natural abundance and ¹³C and ¹⁵N enrichment clearly indicate the presence of one CO ligand, two equivalent NO ligands, and two types of nonequivalent SO₃F^? groups in a 2:1 ratio. The IR and Raman spectra reveal that the two equivalent NO ligands have a cis conformation, thus indicating a fac structure. Density functional calculations at the B3LYP level of theory predict that these anions have a singlet ground state (¹A′) with a C_s symmetry along with C–O and N–O vibrational frequencies that are in agreement with the experimental observations. Mulliken population analysis shows that the monovalent negative charge is dispersed on the bulky sphere, the surface of which is covered by all the negatively charged O and F atoms with charge densities much lower than SO₃F^?, suggesting that [fac‐M(CO)(NO)₂(SO₃F)₃]^? (M=W, Mo) are weakly nucleophilic and poorly coordinating anions.     

Enhanced electrochromic absorption in Ag nanoparticle embedded conjugated polymer composite films

Ag/MEH-PPV {poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]} composite films were prepared by the pulse current electrodeposition of Ag nanoparticles followed by spin coating of MEH-PPV and their enhanced electrochromic coloration was investigated. A relatively uniform Ag nanoparticle array was obtained by the electrodeposition and distinct plasmon absorption bands of Ag nanoparticles were observed. The absorption maximum of Ag/MEH-PPV was much higher than that of MEH-PPV, indicating that the Ag nanoparticles induced an enhanced absorption. In addition, the electrochromic absorption was 1.6 times higher at 500 nm wavelength, with a clearly different coloration compared to MEH-PPV.