Magnetotransport properties and magnetocaloric effect in La0.67Ca0.33Mn1−xTMxO3 (TM=Cu,Zn) perovskite manganites

The magnetic and transport properties of the perovskites La_0.67Ca_0.33Mn_1-xTM_xO₃ were found to be sufficiently changed with the substitution of Mn-sites by other 3d transition-metal cations (TM=Cu,Zn; x=0.15). The values of T_C, T_M−I, and T_CMR were surveyed when Mn was replaced by Cu and Zn. The magnetic field induced resistivity and magnetic entropy change of these samples showed abrupt changes near T_C (194.2 and 201.5 K for Cu and Zn-doped case respectively) and attained the highest values among the doped cases (up to 20% Cu). The maximum values (obtained at H=4 kOe) of magnetoresistance ratio (CMR) were 27.8%, and 24.5% and of magnetic entropy change (−ΔS_M) were 3.9 and 3.2 J/kg K for Cu and Zn-doped, respectively.     

Multiple color reflection in a single unit cell using double-layer electrochromic reaction

Multiple color states have been realized in single unit cell using double electrochromic (EC) reaction. The precise control of bistability in EC compounds which can maintain several colors on the two separated electrodes allows this new type of pixel to be realized. The specific electrical driving gives a way to maintain both sides in the reduced EC states and this colors overlapping in the vertical view direction can achieve the black state. The four color states (G, B, W, BK) in one cell/pixel can make a valuable progress to achieve a high quality color devices such like electronic paper, outdoor billboard, smart window and flexible display using external light source.     

On Gorenstein graphs

We classify all Gorenstein claw-free graphs. Moreover, we provide a new way to construct a Gorenstein graph from another one.

     

A new in situ synchrotron X-ray diffraction technique to study the chemical delithiation of LiFePO4

We report a new synchrotron based in situ X-ray diffraction (XRD) technique to study the chemical delithiation of LiFePO(4). This technique provides a new powerful tool to study chemical reactions with excellent time-resolving power for dynamic studies.     

Photoenzymatic synthesis through sustainable NADH regeneration by SiO2-supported quantum dots

Sustainable photochemical NADH regeneration and redox-enzymatic synthesis are accomplished by using CdS nanocrystals grown on the surface of SiO(2) beads. CdS nanocrystals grown on SiO(2) beads worked efficiently as a visible-light absorbing photocatalyst for in situ NADH regeneration with high catalytic activity and minimal loss of activity despite repeated uses.     

Correlations between phase behaviors and ionic conductivities of (ionic liquid + alcohol) systems

To understand the basic properties of ionic liquids (ILs), we examined the phase behavior and ionic conductivity characteristics using various compositions of different ionic liquids (1-ethyl-3-methylimidazolium hexafluorophosphate [emim] [PF6] and 1-benzyl-3-methylimidazolium hexafluorophosphate [bzmim] [PF6]) in several different alcohols (ethanol, propanol, 1-butanol, 2-butanol, and hexanol). We conducted a systematic study of the impact of different factors on the phase behavior of imidazolium-based ionic liquids in alcohols. Using a new experimental method with a liquid electrolyte system, we observed that the ionic conductivity of the ionic liquid/alcohol was sensitive to the surrounding temperature. We employed Chang et al.’s thermodynamic model [Chang et al. (1997, 1998) [21], [22]] based on the lattice model. The obtained co-ordinated unit parameter from this model was used to describe the phase behavior and ionic conductivities of the given system. Good agreement with experimental data of various alcohol and ILs systems was obtained in the range of interest.     

The effect of Al2O3-coating coverage on the electrochemical properties in LiCoO2 thin films

The electrochemical properties of nanoscale Al₂O₃-coated LiCoO₂ thin films were examined as a function of the coating coverage. Al₂O₃-coated LiCoO₂ films showed enhanced cycle-life performance with increasing degree of coating coverage, which was attributed to the suppression of Co dissolution and F⁻ concentration in the electrolyte. Moreover, an Al₂O₃-coating layer with partial coverage clearly improved the electrochemical properties, even at 60 °C or with a water-contaminated electrolyte. Even though metal-oxide coating on LiCoO₂ has been actively investigated, the mechanisms of nanoscale coating have yet to be clearly identified. In this article, surface analysis suggested that the Al₂O₃-coating layer had transformed to an AlF₃ ∙3H₂O layer during cycling, which inhibited the generation of HF by scavenging H₂O molecules present in the electrolyte.     

Oxidative Dissolution of Silver Nanoparticles by Biologically Relevant Oxidants: A Kinetic and Mechanistic Study

The oxidative dissolution of silver nanoparticles (AgNPs) plays an important role in the synthesis of well‐defined nanostructured materials, and may be responsible for their activities in biological systems. In this study, we use stopped‐flow spectrophotometry to investigate the kinetics and mechanism of the oxidative dissolution of AgNPs by H₂O₂ in quasi‐physiological conditions. Our results show that the reaction is first order with respect to both [Ag⁰] and [H₂O₂], and parallel pathways that involve the oxidation of H₂O₂ and HO₂^? are proposed. The order of the reaction is independent of the size of the AgNPs (≈5–20 nm). The rate of dissolution increases with increasing pH from 6.0 to 8.5. At 298 K and I=0.1 M , the value of k_b is five orders of magnitude higher than that of k_a (where k_a and k_b are the rate constants for the oxidative dissolution of AgNPs by H₂O₂ and HO₂^?, respectively). In addition, the effects of surface coating and the presence of halide ions on the dissolution rates are investigated. A possible mechanism for the oxidative dissolution of AgNPs by H₂O₂ is proposed. We further demonstrate that the toxicities of AgNPs in both bacteria and mammalian cells are enhanced in the presence of H₂O₂, thereby highlighting the biological relevance of investigating the oxidative dissolution of AgNPs.     

Multi‐metal shell coated with surface modification of polystyrene bead cores to improve its adhesion metal shell

We investigated the delamination problem at the metal‐polymer interface and the mechanical buckling of the metal layer at a localized area of the metallic shell under compression between two parallel plates. First, polystyrene (PS) beads were synthesized by dispersion polymerization and then their sulfonation process. After sequential electroless deposition, the average size of multi‐metal coated sulfonated polystyrene (SPS) bead was ca 4.95 µm. Using the electromechanical indentation, the electrical resistance of a single metal‐coated SPS bead decreased with increasing compressive strain without delamination at the metal‐polymer interface, and its electrical resistance showed 5.65 Ω. Copyright © 2009 John Wiley & Sons, Ltd.     

DC programming and DCA for globally solving the value-at-risk

The value-at-risk is an important risk measure that has been used extensively in recent years in portfolio selection and in risk analysis. This problem, with its known bilevel linear program, is reformulated as a polyhedral DC program with the help of exact penalty techniques in DC programming and solved by DCA. To check globality of computed solutions, a global method combining the local algorithm DCA with a well adapted branch-and-bound algorithm is investigated. An illustrative example and numerical simulations are reported, which show the robustness, the globality and the efficiency of DCA.