Synthesis of thermosensitive copolymer beads containing pyridinium groups and their antibacterial activity

Thermosensitive 4VP‐NIPAAm‐4G copolymer beads containing pyridyl groups were first prepared by suspension copolymerization of 4‐vinylpyridine (4VP), N‐isopropylacrylamide(NIPAAm), and tetraethylene glycol dimethacrylate (4G; crosslinking reagent) in a saturated Na₂SO₄ aqueous solution in the presence of surfactant and MgCO₃ as dispersants. Then the copolymer beads containing pyridinium groups were obtained by the quaternization of the copolymer beads with various alkyl iodides (CH₃I, C₄H₉I, C₈H₁₇I) in N,N‐dimethylformamide. The 4VP‐NIPAAm‐4G (15 : 97 : 3) copolymer bead and the 4VP‐NIPAAm‐4G copolymer beads quaternized with butyl iodide exhibited high thermosensitivity in water, although the 4VP‐NIPAAm‐4G copolymer beads quaternized with methyl iodide or octyl iodide hardly exhibited thermosensitivity. All the quaternized copolymer beads exhibited antibacterial activity against Escherichia coli (E. coli), although the 4VP‐NIPAAm‐4G copolymer bead did not. In particular, the copolymer bead quaternized with butyl iodide exhibited the highest antibacterial activity against E. coli at 30°C. It was also found that the antibacterial activity of the quaternized 4VP‐NIPAAm‐4G copolymer beads was greatly affected by not only chain length of alkyl groups in alkyl iodides, with which the 4VP‐NIPAAm‐4G copolymer beads were quaternized, but also by temperature of the solutions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chaotic transport in antidot lattices

A review is given of quantum effects and roles of chaos in transport in antidot lattices mainly from a theoretical point of view. The topics include diffusive orbits combined with a magnetic focusing effect as the origin of the commensurability peaks, semiclassical quantization of periodic orbits as the origin of the Aharonov-Bohm type oscillation superimposed, and the importance of inherent disorder in the antidot potential itself.     

Pb-free surface-finishing on electronic components’ terminals for Pb-free soldering assembly

Pb-free solderable surface finishing is essential to implement Pb-free solder assembly in order to meet with the growing demand of environmental consciousness to eliminate Pb from electronic products. Two types of widely applicable Pb-free surface finishing technologies are developed. One is the multilayer-system including Pd with Ni undercoat. Heat-resistance of Pd enables whole-surface-plating on to leadframe before IC-assembling process. The other is the double-layer-system with low-melting-point-materials, for example, thicker Sn underlayer and thinner Sn-Bi alloy overlayer, dilutes Sn-Bi alloy’s defects of harmful reactivity along with substrate metal and mechanical brittleness with keeping its advantages of solder-wettability and no whisker.     

Electrolyte properties of 1-alkyl-2,3,5-trimethylpyrazolium cation-based room-temperature ionic liquids for lithium secondary batteries

The physicochemical and electrochemical properties of three 1-alkyl-2,3,5-trimethylpyrazolium cation-based room-temperature ionic liquids with various alkyl chain lengths were investigated. The temperature dependences of density, viscosity, and ionic conductivity were obtained by precise measurements. Electrolyte properties of these room-temperature ionic liquids were also examined from the viewpoint of their uses in lithium secondary batteries ([LiCoO₂ positive electrode|electrolyte|lithium metal negative electrode]). It was found that the alkyl chain length affects the charge–discharge performances of cells.     

Social modification using implementation of partial agency toward objects

This article considers what kind of partial agency can be implemented for objects to bring about better agencies for interacting with humans. We humans have the ability to inform our fellows about our intentions, internal states, and requirements through verbal means, gestures, attitudes, timings, and other representations. These representations help us to maintain our belief that we are sufficient agents. Robots and virtual agents also mimic these representations; they act as if they have such an agency. However, their agencies are sometimes too excessive compared to their task. This mismatch leads to a high cognitive load being placed on users and consequently leads to breakdowns in interaction; it prevents human-agent interaction from being a modality in certain applications. We have devised an agency with multiple selectable features. We believe that selectable features promote good designs of virtual agents, robots, machinery, and home appliances according to their intended traits. We categorized these agencies into several groups and discuss what elements lead to these features. The article also describes a method of identifying these features in human behavior.     

Cytochemical energy-filtering transmission electron microscopy of mitochondrial free radical formation in paraquat cytotoxicity.

The generation of oxygen free radicals was investigated using cytochemistry and its energy-filtering transmission electron microscopy in reference to the toxic mediator for the herbicide paraquat. When isolated intact mitochondria from rat livers were incubated in a medium containing paraquat and NADH, a mitochondrial NADH-quinone oxidoreductase activity generated superoxide anions to cause the destruction of mitochondria which resulted in cell death. The superoxide anions were immediately converted into hydrogen peroxide, which then formed cerium perhydroxide deposits in the presence of cerium ions and precipitated on the outer surface of the mitochondrial outer membrane. This localization was also specifically identified by energy spectral imaging and image-electron energy loss spectral analyses. Precipitation reaction was scavenged by the addition of either cytochrome c or catalase and inhibited by dicoumarol (an inhibitor of NAD(P)H-quinone oxidoreductases). These cytochemical energy-filtering transmission electron microscopic results indicated that paraquat generated free radicals from the outer membrane of mitochondria.     

Liquidus and solidus temperatures of Ni-solid solution in Ni-Al-X (X: V, Nb and Ta) ternary systems

A systematic investigation was carried out to determine both liquidus and solidus surfaces of the Ni-solid solution (γ) in the Ni-Al-X ternary phase diagrams successively by differential thermal analysis (DTA) technique. Each of the Group V elements of the periodic table, V, Nb, and Ta, was chosen as a ternary additive X in the present study. The γ-solvus was also taken into account in determining a temperature range for a solid solution treatment above the γ-solvus, i.e., “the window,” as well as the maximum solubility limit of γ-Ni solid solution.     

Optical and electrical anisotropies of polydiacetylene derivative film aligned by shear stress

The molecular alignment of polydiacetylene (PDA) derivatives and their optical and electrical properties of thin films based on PDA derivatives have been studied. The PDA derivatives were aligned depending on the direction of applied shear stress in the film. From measurements of the polarized absorption and current–voltage characteristics, the optical and electrical anisotropies have been observed, that was discussed by taking the PDA main chain alignment into consideration.     

Multiple roles for endothelin in melanocyte development: regulation of progenitor number and stimulation of differentiation

Melanocytes in the skin are derived from the embryonic neural crest. Recently, mutations in endothelin 3 and the endothelin receptor B genes have been shown to result in gross pigment defects, indicating that this signalling pathway is required for melanocyte development. We have examined the effects of endothelins on melanocyte progenitors in cultures of mouse neural crest. Firstly, they stimulate an increase in progenitor number and act synergistically with another factor, Steel factor, in the survival and proliferation of the progenitors. These findings are consistent with findings from mice with natural mutations in the endothelin receptor B gene, which show an early loss of melanocyte progenitors. Secondly, endothelins induce differentiation of the progenitors into fully mature pigmented melanocytes. This finding is consistent with the expression of endothelins in the skin of mice at the initiation of pigmentation. The melanocytes generated in endothelin-treated cultures also become responsive to alpha melanocyte-stimulating hormone, which then acts to regulate the activity of the pigmentation pathway. These findings indicate two key roles for endothelin in melanocyte development: regulation of expansion of the progenitor pool and differentiation of progenitors into mature melanocytes.     

Dynamic local lattice distortion in YBa2Cu4O8

Significant changes in the local atomic structure and lattice dynamics were observed by pulsed neutron inelastic scattering measurements on YBa₂Cu₄O₈ both around the superconducting transition temperature and around the spin-gap temperature. These observations and earlier results of numerical calculations on the enhancement of electron-lattice interaction by electron correlation lead to a novel picture of unconventional lattice-induced superconductivity related to antiferroelectric instability.