In situ control of cellular growth and migration on substrates using microelectrodes

We describe an electrochemical method to direct the growth and migration of mammalian cells on a substrate during cultivation in situ. Exposing the albumin-coated substrate to an oxidizing agent, hypobromous acid, electrochemically generated at the tip of the scanning microelectrode, locally switched the substrate from cytophobic to cell-adhesive. This transformation generated the formation of cellular micropatterns. Since the concentration of the oxidizing agent required for the surface processing did not cause significant damage to the cell cultures, we were able to direct in situ cellular proliferation and migration by drawing adhesive micropatterns over the preexisting cellular pattern.     

Photoinduced Hydrogen Evolution with Viologen-Linked Porphyrins

Viologen-linked water-soluble porphyrins with different methylene chain lengths between porphyrin and viologen were synthesized. These compounds were applied to photoinduced hydrogen evolution in a system containing NADPH, viologen-linked porphyrin, and hydrogenase under steady-state irradiation.     

Heat transfer and fluid dynamics of air–water two-phase flow in micro-channels

Heat transfer, pressure drop, and void fraction were simultaneously measured for upward heated air–water non-boiling two-phase flow in 0.51 mm ID tube to investigate thermo–hydro dynamic characteristics of two-phase flow in micro-channels. At low liquid superficial velocity j_l frictional pressure drop agreed with Mishima–Hibiki’s correlation, whereas agreed with Chisholm–Laird’s correlation at relatively high j_l. Void fraction was lower than the homogeneous model and conventional empirical correlations. To interpret the decrease of void fraction with decrease of tube diameter, a relation among the void fraction, pressure gradient and tube diameter was derived. Heat transfer coefficient fairly agreed with the data for 1.03 and 2.01 mm ID tubes when j_l was relatively high. But it became lower than that for larger diameter tubes when j_l was low. Analogy between heat transfer and frictional pressure drop was proved to hold roughly for the two-phase flow in micro-channel. But satisfactory relation was not obtained under the condition of low liquid superficial velocity.     

Cell separation by the combination of microfluidics and optical trapping force on a microchip

We investigated properties of cells affecting their optical trapping force and successfully established a novel cell separation method based on the combined use of optical trapping force and microfluidics on a microchip. Our investigations reveal that the morphology, size, light absorption, and refractive index of cells are important factors affecting their optical trapping force. A sheath flow of sample solutions created in a microchip made sample cells flow in a narrow linear stream and an optical trap created by a highly focused laser beam captured only target cells and altered their trajectory, resulting in high-efficiency cell separation. An optimum balance between optical trapping force and sample flow rate was essential to achieve high cell separation efficiency. Our investigations clearly indicate that the on-chip optical trapping method allows high-efficiency cell separation without cumbersome and time-consuming cell pretreatments. In addition, our on-chip optical trapping method requires small amounts of sample and may permit high-throughput cell separation and integration of other functions on microchips. Figure Optical trapping in a microchannel allows high-efficiency separation of cells, e.g., dead and live HeLa cells

Core-hole effect on XANES and electronic structure of minor actinide dioxides with fluorite structure

The authors investigated theoretically core-hole effects on X-ray absorption near-edge structures (XANES) of Np and Am L_III in neptunium dioxide (NpO₂) and americium dioxide (AmO₂) with CaF₂-type crystal lattices using the all-electron full-potential linearized augmented plane-wave (FP-LAPW) method. The peak creation mechanism of XANES was shown by examining the electronic structures of these oxides, which indicated that core-hole screening was more marked for AmO₂ than for NpO₂ because of the difference in the charge transfer between these oxides. Furthermore, the results of charge density analysis suggested that the white line was assigned to the quasi-bound state composed of the localized Np d or Am d components and O components, and that the tail structure was created as a result of delocalized standing waves between the Np or Am atoms.     

CP/MAS 13C NMR characterization of the isomeric states and intermolecular packing in tris(8-hydroxyquinoline) aluminum(III) (Alq3)

The isomeric states and intermolecular packing of tris(8-hydroxyquinoline) aluminum(III) (Alq(3)) in the alpha-, gamma-, and delta-crystalline forms and in the amorphous state, which are important for understanding the light-emitting and electron-transport properties, have been analyzed by CP/MAS (13)C NMR. This simple NMR experiment shows that the isomeric state of alpha- and amorphous Alq(3) is meridional, whereas that of gamma- and delta-Alq(3) is facial. In the amorphous Alq(3), the inclusion of facial isomers has been under debate. Our experiments show that meridional isomers are dominant in the amorphous Alq(3), although the existence of facial isomers cannot be completely denied. The local structure of amorphous Alq(3) is similar to that of alpha-Alq(3) and is significantly different from those of gamma- and delta-Alq(3). Among these Alq(3) samples, the effect of intermolecular interaction is not found only for gamma-Alq(3). This finding can explain the good solvent solubility of gamma-Alq(3), compared with the other crystalline forms. It is also shown that the structures are locally disordered not only for amorphous Alq(3) but also for alpha-Alq(3), although clear X-ray diffraction peaks are observed for alpha-Alq(3). In contrast, the local structures of gamma- and delta-Alq(3) are well defined. A clear relation is found between the spectral patterns of CP/MAS (13)C NMR and the fluorescence wavelengths; the samples, which consist of facial isomers, show blue-shifted fluorescence compared with those of meridionals.     

Investigation of step-edge Josephson device of YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−<Emphasis Type="Italic">d</Emphasis></Subscript> formed on MgO by a pulsed laser deposition method

We fabricated step-edge Josephson junctions of YBa₂Cu₃O_7−d on MgO substrates by a pulsed laser deposition method for high frequency applications. On the basis of temperature dependence of critical current, noticeable deterioration has not been observed in a step-edge area. The dynamic resistance was between 2 and 3Ω under the superconducting critical temperature. A deviation from a resistively shunted junction model was observed, which implies the excess current not flowing through Josephson junctions.     

On‐Top π‐Stacking of Quasiplanar Molecules in Hole‐Transporting Materials: Inducing Anisotropic Carrier Mobility in Amorphous Films

Dimers of partially oxygen‐bridged triarylamines were designed and synthesized as hole‐transporting materials. X‐ray structural analyses revealed that these compounds form on‐top π‐stacking aggregates in the crystalline state. TRMC measurements showed that high levels of anisotropic charge transport were induced in the direction of the π‐stacking. Surprisingly, even in vacuum‐deposited amorphous films, these compounds retained some of the face‐on π‐stacking, thus facilitating an out‐of‐plane carrier mobility.