Vaporization thermodynamic studies by high-temperature mass spectrometry on some three-phase regions over the MnO-TeO2 binary line in the Mn-Te-O ternary system

Knudsen effusion mass spectrometric measurements have been performed in the temperature range of 850-950 K over four three-phase mixtures, each phase mixture having at least one phase lying on the MnO-TeO2 binary line of the Mn-Te-O phase diagram, and the rest of the phases lying above this binary line. The three-phase mixtures investigated are Mn3O4 + MnO + Mn6Te5O16; Mn3O4 + Mn6Te5O16 + MnTeO3; Mn3O4 + Mn3TeO6 + MnTeO3; and Mn3TeO6 + MnTeO3 + Mn2Te3O8. The vapor pressures of the gaseous species TeO2, TeO, and Te2 over these three-phase mixtures were measured, and various heterogeneous solid-gas reactions were evaluated along with the homogeneous gas-phase reaction TeO2(g) + 0.5Te2(g) = 2 TeO(g). The enthalpy and Gibbs free energy of formation of the four ternary Mn-Te-O phases were deduced at T = 900 K. These values (in kJ.mol-1), along with the estimated uncertainties in them are Delta(f)H(o)m = 4150 +/- 19, 752 +/- 11, 1710 +/- 11, 1924 +/- 40, and Delta(f)G(o)m= 2835 +/- 28, 511 +/- 11, 1254 +/- 19, 1238 +/- 38, for Mn6Te5O16, MnTeO3, Mn3TeO6, and Mn2Te3O8, respectively. A thermochemical assessment was made to examine the conditions under which the ternary Mn-Te-O phases could be formed on a stainless steel clad of mixed-oxide-fueled (MO2; M = U + Pu) fast breeder nuclear reactors. The phase Mn3TeO6 could be formed when the fuel is even slightly hyperstoichiometric (O/M = 2.0002) and the phase Mn6Te5O16 could also be formed when O/M = 2.0004. The threshold tellurium potential for the formation of Mn3TeO6 is higher than that for MnTe0.80 and CrTe1.10, but is comparable to that for MoTe1.10, and even lower than that for FeTe0.81 or NiTe0.63.     

High-throughput and high-resolution two dimensional mapping of pI and m/z using a microchip in a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer

We have developed a high-throughput, two-dimensional-mapping (isoelectric point [pI], mass-to-charge ratio [m/z]) method by combining a capillary isoelectric focusing chip sealed with removable resin tape and a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer. Sample proteins are separated in a meandering channel on the chip and immediately frozen. The tape is then removed and the proteins are freeze-dried. The freeze-drying maintains the separation state of the proteins and prevents movement of the sample solution, which can reduce pI resolution. A matrix solution is then applied and mass spectrometry is carried out by laser irradiation. The whole process takes less than 70 min, more than 10 times faster than with two-dimensional, polyacrylamide gel electrophoresis.     

Structure-property correlation of CdSe clusters using experimental results and first-principles DFT calculations

Structures and properties of CdSe quantum dots (clusters) up to a diameter of approximately 2 nm were investigated by combining experimental absorption, photoluminescence (PL), and X-ray diffraction (XRD) spectroscopies as well as ab initio DFT calculations. These CdSe clusters were nucleated and grown from solutions containing respective cadmium and selenium precursors following the hot-injection technique that allows one to obtain size-controlled CdSe clusters having PL efficiency up to 0.5. The DFT calculations were performed at the B3LYP/Lanl2dz level and followed by time-dependent TDDFT calculations to estimate n energy singlet transitions. On the basis of the results of these experimental and theoretical studies, an approach to determine whether the proposed cluster with a mean diameter of approximately 2 nm is more physically reasonable is discussed. It was shown that the minimum nucleus of a CdSe cluster consists of (CdSe)(3) with a six-membered ring and planar structure. No PL is observed for this structure. The formation of the next stable cluster depends on whether hexadecylamine (HDA) was used for the growth of the CdSe clusters. In the absence of HDA, the second cluster was found to be (CdSe)(6) characterized by a broad PL spectrum, while in the presence of HDA, it was found to be (CdSe)(n) (where n > or = 14) with a sharp PL spectrum.     

Dioxotungsten 1,2-benzenedithiolate complex stabilized by NH...S hydrogen bonds

Novel dioxo-tungsten(VI) bis(1,2-benzenedithiolate) complexes with neighboring amide groups, as models for tungsten enzymes, (NEt4)2[W(VI)O2{1,2-S(2)-3,6-(RCONH)2C6H2}2] (R = CH3, t-Bu), were designed and synthesized. The presence of the NH...S hydrogen bond was confirmed through IR spectrometry and X-ray crystallographic analysis. In the W(VI)O2 complexes, the NH...S hydrogen bond trans to the oxo ligand is stronger than that cis to oxo. On the basis of comparisons with [W(VI)O2(1,2-S2C6H4)2](2-), the NH...S hydrogen bond positively shifted the W(VI)/W(V) redox potentials and depressed the reduction by benzoin or triphenylphosphine. These results suggest that the NH...S hydrogen bond stabilizes the oxo ligand through trans influence and regulates O-atom transfer in tungsten and molybdenum enzymes.     

O-atom-transfer oxidation of [molybdenum(IV) oxo{3,6-(acylamino)2- 1,2-benzenedithiolato}2]2- promoted by intramolecular NH...S hydrogen bonds

Novel molybdenum dithiolene compounds having neighboring amide groups as models for molybdoenzymes, (NEt(4))(2)[Mo(IV)O{1,2-S(2)-3,6-(RCONH)(2)C(6)H(2)}(2)] (R = CH(3), CF(3), t-Bu, Ph(3)C), were designed and synthesized. The contributions of the NH...S hydrogen bond to the electrochemical properties of the metal ion and the reactivity of the O-atom-transfer reaction were investigated by a comparison with [Mo(IV)O(1,2-S(2)C(6)H(4))(2)](2)(-). The MoOS(4) core of [Mo(IV)O{1,2-S(2)-3,6-(CH(3)CONH)(2)C(6)H(2)}(2)](2)(-) shows no significant geometrical difference from that of [Mo(IV)O(1,2-S(2)C(6)H(4))(2)](2)(-) in the crystal. The hydrogen bonds positively shifted the Mo(IV/V) redox potential and accelerated the reduction of Me(3)NO.     

Generation of allylic indium by hydroindation of 1,3-dienes and one-pot reaction with carbonyl compounds

A hydroindation of 1,3-dienes by dichloroindium hydride (HInCl2) generates allylic indiums that react with carbonyl or imine moieties in a one-pot treatment. The former reaction proceeds in a radical manner, and the latter is ionic allylation. Moreover, both reactions require no additives such as radical initiators, Lewis acids, or transition metal catalysts.     

Immunoassay for acetamiprid detection: application to residue analysis and comparison with liquid chromatography

This work describes the fundamental ability of a commercial ELISA to determine acetamiprid and the application of the ELISA to residue analysis in fruit and vegetable samples. The ELISA exhibited satisfactory sensitivity (I ₅₀ 0.6 ng/g; limit of detection 0.053 ng/g) and a high selectivity for acetamiprid versus other neonicotinoid analogs (thiacloprid amide). Methanol, which influenced the sensitivity of the ELISA the least, was selected as the extractant for the ELISA analysis. Simple dilution of sample extracts with water eliminated matrix interferences. Average recoveries from the acetamiprid-spiked agricultural samples were >95% using a simple extraction method. Analytical results obtained from the ELISA were comparable to those obtained from the reference HPLC method (r>0.99). The ELISA applied to the residue analysis of acetamiprid in agricultural products is a rapid, simple, and cost-effective method, and could be successfully applied to the detection of acetamiprid before the distribution of produce.     

Study of water properties in nanospace

Here we report an anomalous behavior of water, especially its viscosity and hydrodynamic flow, in a nanometer-confined space. As a typical model of a nanometer-confined space, the nanopillar chip, which was developed for DNA size-based separation was used, and single-particle tracking (SPT) technique was applied to investigate water viscosity and hydrodynamic flow in the nanopillar chip. The diffusion coefficients of nanospheres were almost one-third of the theoretical value derived from the Stokes-Einstein equation. This result gave indirect proof that water viscosity in a nanometer-confined space is higher than in a bulk solution. In order to improve resolution and throughput of the nanopillar chip for DNA separation, these potential factors affecting performance should be seriously considered.     

Observation of strong low-lying E1 strength in the two-neutron halo nucleus 11Li

An exclusive measurement has been made of the Coulomb dissociation of the two-neutron halo nucleus 11Li at 70 MeV/nucleon at RIKEN. Strong low-energy (soft) E1 excitation is observed, peaked at about Ex = 0.6 MeV with B(E1) = 1.42(18) e2fm2 for Erel < or = 3 MeV, which was largely missed in previous measurements. This excitation represents the strongest E1 transition ever observed at such low excitation energies. The spectrum is reproduced well by a three-body model with a strong two-neutron correlation, which is further supported by the E1 non-energy-weighted cluster sum rule.     

Carbon tetrachloride as a thermoporometry liquid probe to study the cross-linking of styrene copolymer networks

Mesh size distributions (MSDs) of swollen cross-linked styrene copolymer networks have been measured by thermoporometry using CCl(4) as a probe liquid. All numerical relationships required for the calculation of the MSD were established for both the liquid-to-solid and the solid-to-solid thermal transitions of CCl(4) and successfully validated on test samples. It was found that the polymer network, for both thermally and photo-cross-linked materials, was completely built in about 4 h of exposure. A clear correlation was established between the average mesh size of the swollen polymer network on one hand and the benzoyl peroxide groups content and swelling ratio on the other hand.