Ultrasensitive CE for heavy metal ions using the variations in the chemical structures formed from new octadentate fluorescent probes and cationic polymers

Novel fluorescent probes have been developed for the ultratrace detection of heavy metal ions by capillary electrophoresis using laser-induced fluorescence detection. Based on a molecular design, the probes are composed of an octadentate chelating moiety, a macrocyclic DOTA (tetraazacyclododecanetetraacetic acid) and an acyclic DTPA (diethylenetriaminepentaacetic acid) frame, a spacer and a fluorophore (fluorescein). These were chosen on the basis of their ability to form kinetically inert and highly emissive complexes, and to prevent a quenching effect even with heavy and paramagnetic metal ions. Addition of a cationic polymer, polybrene, in the separation buffer provided high resolution and simultaneous detection of Ca(2+), Mg(2+), Cu(2+), Zn(2+), Ni(2+), Co(2+), Mn(2+), Cd(2+) and Pb(2+). The direct fluorescence detection of these metal ions with high sensitivity at lower ppt levels, typically 2-7 × 10(-11) M (potentially sub-ppt), was successfully achieved. While separation of anionic compounds using a counter cation ("Ion Association (IA)" mode) is typically controlled by the ion association equilibrium constants, K(ass), it was found that differences in the mobilities, μ(ep(IAC)), of the ion association complexes formed between the probe complexes and counter cations are the driving forces for separation in this new method. This suggests that each of the polybrene-probe complexes has different chemical structures among metal ions, which were able to be determined by CD spectra in this investigation. This novel separation mode was termed the "Ion Association Complex (IAC)" mode, distinct from the IA mode.     

Reflectivity measurements of superionic conductors for Li ion secondary battery materials

The reflection measurements of superionic conductors LiCoO₂ and Li_1-xCoO₂, which are already in use for the positive electrode material of 4 V rechargeable lithium batteries, have been performed in the millimeter wave region from 6 to 60 cm⁻¹ using the electron storage ring facilities of Institute of Molecular Science in Okazaki. The increase of the reflectivity has been observed in the low wavenumber region below 10 cm^-1 above 300 K in Li_1-xCoO₂ for the first time, while the reflectivity of LiCoO₂ has almost the constant value in all observed temperature region between 77 to 380 K. The results will be discussed in connection with our previous results of LiNiO₂.     

Modeling and design of a tuned liquid damper using triangular-bottom tank by a concentrated mass model

Nonlinear Dynamics - Rectangular flat-bottom liquid tanks known as tuned liquid dampers (TLDs) are often used as passive mechanical dampers. Sloped- and triangular-bottom TLDs have been reported to...     

Synthesis and crystal structures of CaY2Ge3O10 and CaY2Ge4O12

New compounds CaY₂Ge₃O₁₀ and CaY₂Ge₄O₁₂ were prepared by heating mixtures of CaCO₃, Y₂O₃ and GeO₂ at 1200 °C. CaY₂Ge₃O₁₀ is stable at 1300 °C, while CaY₂Ge₄O₁₂ decomposes into a melt and CaY₂Ge₃O₁₀ at approximately 1250 °C. We obtained single crystals of CaY₂Ge₃O₁₀ by cooling a sample with an initial composition of Ca:Y:Ge=1:2:8 from 1300 °C with a rate of −6 °C/h. The crystal structure of CaY₂Ge₃O₁₀ was determined by single crystal X-ray diffraction. CaY₂Ge₃O₁₀ crystallizes in the monoclinic space group P2₁/c with a=6.0906(8), b=6.8329(8), and β=109.140(3)°, Z=4, and R₁=0.029 for I>2σ(I). In the structure of CaY₂Ge₃O₁₀, Ca and Y atoms are situated disorderly in three 7-fold coordination sites between isolated germanate groups of triple GeO₄ tetrahedra, Ge₃O₁₀. The structural formula of CaY₂Ge₃O₁₀ is expressed as (Ca_0.45Y_0.55)(Ca_0.46Y_0.54)(Ca_0.09Y_0.91)Ge₃O₁₀. The crystal structure of CaY₂Ge₄O₁₂ was analyzed by the Rietveld method for the X-ray powder diffraction pattern. CaY₂Ge₄O₁₂ is isotypic with SrNa₂P₄O₁₂, crystallizing in the orthorhombic space group P4/nbm, a=9.99282(6), , Z=2, R_wp=0.092, R_p=0.067. CaY₂Ge₄O₁₂ contains four-membered GeO₄-tetrahedra rings, Ge₄O₁₂. Eight-fold coordinated square-anitiprism sites and 6-fold octahedral sites between the layers of the Ge₄O₁₂ rings are occupied by Y atom and Ca/Y atoms, respectively The structural formula is Y(Ca_0.5Y_0.5)₂Ge₄O₁₂.     

Geometrically necessary dislocation structure organization in FCC bicrystal subjected to cyclic plasticity

Crystal plasticity finite element analysis of cyclic deformation of compatible type FCC bicrystals are performed. The model specimen used in the analysis is a virtual FCC bicrystal with an isotropic elastic property; therefore, the effect of constraint due to elastic incompatibility does not appear. The results of the analysis show the strain-amplitude-dependence of both the organization of the GND structure and the stress–strain behavior. The calculated stress–strain curve with the largest strain amplitude shows additional cyclic hardening. The microscopic mechanisms of the strain-amplitude-dependent organization of the GND structure and additional cyclic hardening behavior are discussed in terms of the activation of secondary slip system(s). Finally, the effects of the elastic anisotropy, the lattice friction stress and the interaction between dislocations are also argued.     

Characterization of host-guest complexes of cucurbit[n]uril (n = 6, 7) by electrospray ionization mass spectrometry

When an intramolecular cavity exists in a molecule, it can trap another chemical species to form a host-guest complex. We examine the formation of such an inclusion complex with cucurbit[n]uril (CBn, n = 6, 7) as the host to trap alkali metal or ammonium ions as the guest, by electrospray ionization mass spectrometry (ESI-MS). The results show that the inclusion complexes are formed between the three-dimensional cylinder of CBn hosts and the guest cations. Selectivity of the complex formation is dependent both on (1) ion-dipole interactions between the cylindrical portal of the CBn hosts and the guest cations and (2) the hydrophobic interactions at the inner cavity of CBn.     

Experimental detection of domain wall propagation above the Walker field

The domain wall (DW) velocity above the Walker field drops abruptly with increasing magnetic field, because of the so-called Walker breakdown, where the DW moves with a precessional mode. On applying the higher field, the DW velocity again starts to increase gradually. We report the DW propagation around this local minimum regime in detail, investigated through the time-resolved electrical detection technique, with a magnetic tunnel junction. Just above the Walker field, we succeeded in detecting the precessional motion of the DW in a real-time regime, while a different mode appeared around the local minimum of the DW velocity.     

Cluster SIMS using metal cluster complex ions

Metal cluster complexes are chemically synthesized organometallic compounds, which have a wide range of chemical compositions with high molecular weight. Using a metal cluster complex ion source, sputtering characteristics of silicon bombarded with normally incident Ir₄(CO)₇⁺ ions were investigated. Experimental results showed that the sputtering yield at 10 keV was 36, which is higher than that with Ar⁺ ions by a factor of 24. In addition, secondary ion mass spectrometry (SIMS) of boron-delta-doped silicon samples and organic films of poly(methyl methacrylate) (PMMA) was performed. Compared with conventional O₂⁺ ion beams, Ir₄(CO)₇⁺ ion beams improved depth resolution by a factor of 2.5 at the same irradiation conditions; the highest depth resolution of 0.9 nm was obtained at 5 keV, 45° with oxygen flooding of 1.3 × 10⁻⁴ Pa. Furthermore, it was confirmed that Ir₄(CO)₇⁺ ion beams significantly enhanced secondary ion intensity in high-mass region.     

A Theoretical Study of the Epoxidation of Olefins by Peracids

For the parent reacting system, HCOOOH + CH(2)=CH(2) --> HCOOH + ethylene oxide, the overall potential energy surface has been determined using ab initio methods. The oxygen-addition transition state is found to be remarkably similar to that deduced experimentally. The O-H bond is retained in the transition state. Reasonable kinetic isotopic effects are obtained theoretically. The transition state leads to an unprecedented transient intermediate. That intermediate is converted to a hydrogen-bonded system between ethylene oxide and formic acid. Substituent effects on transition-state geometries are small, but the effects on activation energies are large.     

Elliptic averaging methods using the sum of Jacobian elliptic delta and zeta functions as the generating solution

The present paper describes an improved version of the elliptic averaging method that provides a highly accurate periodic solution of a non-linear system based on the single-degree-of-freedom Duffing oscillator with a snap-through spring. In the proposed method, the sum of the Jacobian elliptic delta and zeta functions is used as the generating solution of the averaging method. The proposed method can be used to obtain the non-odd-order solution, which includes both even- and odd-order harmonic components. The stability analysis for the approximate solution obtained by the present method is also discussed. The stability of the solution is determined from the characteristic multiplier based on Floquet’s theorem. The proposed method is applied to a fundamental oscillator in a non-linear system. The numerical results demonstrate that the proposed method is very effective for analyzing the periodic solution of half-swing mode for systems based on Duffing oscillators with a snap-through spring.