Vacuum‐driven fluid manipulation by a piezoelectric diaphragm micropump for microfluidic droplet generation with a rapid system response time

Recently, we developed a convenient microfluidic droplet generation device based on vacuum‐driven fluid manipulation with a piezoelectric diaphragm micropump. In the present study built on our previous work, we investigate the influence of settings applied to the piezoelectric pump, such as peak‐to‐peak drive voltage (V_p‐p) and wave frequency, on droplet generation characteristics. Stepwise adjustments to the drive voltage in ±10‐V_p‐p increments over the range of 200?250 V_p‐p during droplet creation revealed that the droplet generation rate could be reproducibly controlled at a specific drive voltage. The droplet generation rate switched within <0.5 s after the input of a new voltage. Although the droplet generation rate depended on the drive voltage, this setting had almost no influence on droplet size. The frequency over the selected range (50?60 Hz) did not markedly influence the droplet generation rate or droplet size. We show that the current fluid manipulation system can be conveniently used for both droplet generation and for rapid droplet reading, which is required in many microfluidic‐based applications.     

Construction of self-assembled monolayer terminated with N-heterocyclic carbene-rhodium(I) complex moiety

Functionalization of self-assembled monolayer (SAM) of alkanethiolate with metal containing unit is one of the versatile methods to obtain functional surfaces such as heterogeneous catalysts. However, organic molecules that strongly bind to transition metals at SAM terminal are limited. Recently N-heterocyclic carbenes (NHCs) such as cyclic diaminocarbenes have emerged as strongly σ-donating ligands forming a robust bond with broad spectrum of transition metals. In the present study, for the purpose of establishment of a new robust basement for heterogeneous metal catalysts, a SAM of the alkanethiolate terminated with NHC-rhodium(I) complex moiety was prepared by utilizing a newly designed disulfide molecule bearing NHC-metal complex terminals. X-ray photoelectron spectroscopy (XPS) analysis and angle resolved XPS measurement revealed successful formation of the Rh-complex-terminated SAM on a gold substrate. Infrared reflection absorption spectroscopy (IRRAS) analysis suggested that the linker methylene chains connecting the rhodium complex moiety and the gold surface are in a loosely packed structure. This unique chemical species, NHC, would be a promising candidate as a basement for the construction of functional surface.     

Nonlinear Cauchy problems with small analytic data

We study the lifespan of solutions to fully nonlinear Cauchy problems with small real- or complex-analytic data. Our proofs are based on the method of majorants and the fixed point theorem for a contraction mapping.

     

A compact optical heterodyne interferometer by optical integration and its application

A compact high-resolution optical heterodyne interferometer combining a two-frequency light module and a minute optical system is described. The light module, which generates two independent frequencies of light, is fabricated by proton exchange method on LiNbO₃ substrate. We report an experiment evaluating measurement accuracy using a micro-displacement measurement system which incorporates this interferometer. Results of the experiment with a standard thickness sample show high thermal stability with maximum measurement error of 1.8 nm at a temperature from 19°C to 33°C. The system was used to measure the hysteresis of a piezoelectric element for displacements of several nm, thereby making it possible to analyze the system quantitatively in practice.     

Spherical dye-doped silica particles

Organic dyes such as water soluble porphyrins were incorporated into monodispersed SiO₂ particles using the sol-gel technique (the Stober synthesis) and their monomeric and dimeric properties were investigated by aiming at the microcavity effect. Doping efficiencies of dyes into SiO₂ particles depended on dye's hydrophilic properties. The doping efficiency of a porphyrin, TTMAPP, decreased with increasing the nominal content in the starting solution and the doping content showed the maximum value of 1.6×10^–5 mol/g SiO₂. With increasing the TTMAPP content, spectra of doped particles were changed from dimeric to monomeric nature; the absorption peak due to dimers disappeared and halfwidth of absorption at Soret band decreased. This unusual change was caused by the decrease of particle sizes by dye doping. The TTMAPP-doped sample having monomeric spectrum showed the fluorescence life time of 8.5 nsec and photochemical hole burning at about 5 K.     

Crystal structure of the clathrate of 5,12-dihydro-5,12-o-benzenonaphthacene-1,4-dione with benzene (2:1).

In the crystal of the title compound, the quinone fragment of the host (1) participates in weak D-A interactions with a neighboring naphthalene moiety of 1 and with the guest molecule via fairly short intermolecular face-to-face contacts. An intermolecular electrostatic interaction between a quinone-oxygen atom and a neighboring quinone ring is suggested by short O...C contacts. There exist several C-H...O hydrogen bonds, one of which seems to contribute to the formation of a centrosymmetric dimer of 1.     

Preparation and thermal analysis of synthetic malachite CuCO3·Cu(OH)2

The synthesis of malachite CuCO₃·Cu(OH)₂ or Cu₂CO₃(OH)₂ was studied through titrations of copper(II) salt solutions with a solution of sodium carbonate at different temperatures. The precipitates were characterized by TG, IR and chemical analysis. The composition varies depending on thepH of the solution and the temperature. Purer malachite was synthesized by simple mixing of a solution of copper(II) nitrate or sulfate with a solution of sodium carbonate at 50°C.The kinetics of the thermal decomposition of synthetic malachite was described by eitherR ₃ orA _m(m=1.2–1.4) law, according to TG analysis, both isothermal and nonisothermal. The Arrhenius parameters determined using three different integral methods showed the kinetic compensation effect, which is correlated to the working temperature interval analyzed.The authors thank Mr. H. Takemoto for analyzing kinetics of the thermal decomposition of synthetic malachite.     

Effect of extracts of Zingiberaceae herbs on gastric secretion in rabbits

Some of the Zingiberaceae herbs are known to be useful as stomachics. Water extracts and methanol extracts of eight such herbs were examined in intact unanesthetized rabbits for their effect on gastric secretion. Oral administration of either water extracts or methanol extracts caused a significant decrease in gastric secretion. A significant effect of these extracts appeared at 3 h after administration. The effect of water extracts on gastric secretion was very similar to that of cimetidine, with a significant decrease in acid output. The effect of the methanol extracts was primarily observed as decreased pepsin output.     

Overproduction of riboflavin by anArthrobacter sp. mutant resistant to 5-fluorouracil

Effects of pH and dissolved oxygen concentration on batchwise riboflavin production by a 5-fluorouracil (5-FU)-resistant mutant ofArthrobacter sp. were investigated. The reaction was carried out in a jar fermentor. The optimal pH of culture medium was around 7.3. Dissolved oxygen concentration was almost constant during fermentation at 600 rpm of agitation rate. Production of riboflavin reached a maximum of 160 mg/L after 70 h fermentation under the agitation rate of 600 rpm, aeration rate of 1.0 L/min, and pH 7.0.     

Effect of titanium dioxide on photostability of solid-state mequitazine

TiO(2) has been widely used in pharmaceutical products, and it also has been used as a photocatalyst. In this study, the influence of photocatalytic activity on the stability of solid-state mequitazine, an H(1)-blocker, was investigated. The photo-degradation of mequitazine with TiO(2) occurred under irradiation with both light sources. The degree of degradation of mequitazine with anatase was higher than that of rutile. The degradation was significantly enhanced with increasing relative humidity. The relationship between the apparent degradation rate constant and water vapor pressure could be clearly described by a simple power law. The major photo-degradation products of mequitazine, resulting from photocatalytic activity of TiO(2), were mequitazine-S-oxide and mequitazine-sulphone. A remarkable degradation of mequitadine occurred with addition of TiO(2), and its photocatalytic activity was controlled by water vapor pressure. The photo-degradation of mequitazine with TiO(2) is a different process from mequitazine without TiO(2), because mequitazine-S-oxide and mequitazine-sulphone are not formed with normal photo-degradation of mequitazine.