Continuous-flow chemical processing on a microchip by combining microunit operations and a multiphase flow network

A new design and construction methodology for integration of complicated chemical processing on a microchip was proposed. This methodology, continuous-flow chemical processing (CFCP), is based on a combination of microunit operations (MUOs) and a multiphase flow network. Chemical operations in microchannels, such as mixing, reaction, and extraction, were classified into several MUOs. The complete procedure for Co(II) wet analysis, including a chelating reaction, solvent extraction, and purification was decomposed into MUOs and reconstructed as CFCP on a microchip. Chemical reaction and molecular transport were realized in and between continuous liquid flows in a multiphase flow network, such as aqueous/aqueous, aqueous/organic, and aqueous/organic/aqueous flows. When the determination of Co(II) in an admixture of Cu(II) was carried out using this methodology, the determination limit (2sigma) was obtained as 18 nM, and the absolute amount of Co chelates detected was 0.13 zmol, that is, 78 chelates. The sample analysis time was faster than that of a conventional processing system. Moreover, troublesome operations such as phase separation and acid and alkali washing, all necessary for the conventional system, were simplified. The CFCP methodology proposed here can be applied to various on-chip applications.     

Finite element analysis of harmonic waves in layered and fibre-reinforced composites

The problem of harmonic waves in layered and fibre-reinforced composites is solved by a method of finite elements. Piecewise linear approximating functions are used for the displacement and stress fields in a mixed variational formulation, recently proposed by one of the writers in the form of a new quotient. Numerical computations are made for approximate phase-velocities of harmonic waves in layered composites, where asymmetric and symmetric triangular meshes, and square meshes with interior nodes, are used. To illustrate the accuracy and effectiveness of the method, these approximate solutions are compared with those given by means of exponential test functions, and the exact ones by Rytov, etc. Calculations are also performed for harmonic waves in fibre-reinforced composites. Dispersion curves for these waves are obtained and displayed graphically.     

Initial growth behaviour of indium phosphide on molybdenum substrates

We describe the initial stages of indium phosphide growth on preferentially etched molybdenum using an In-PCl₃-H₂ reaction system. It is shown that the island size of a few microns increases while the island density decreases with growth temperature. The saturation island density is found to be 10⁴–10⁸ cm^-2 and increases exponentially with the reciprocal of the growth temperature. The difference between the island saturation phenomenon that we observed and that described by the present nucleation theories may involve a smaller supersaturation in the vapour phase and the molecular diffusion of associated species on the molybdenum surface.     

Solid Solution Nanocrystals in the CeO2‐Y3NbO7 System: Hydrothermal Formation and Control of Crystallite Growth of Ceria

New solid solution nanocrystals with fluorite‐type cubic structure in the ceria (CeO₂)‐yttrium niobate (1/4Y₃NbO₇) system were directly formed at 120°C–240°C from the precursor solution mixtures of (NH₄)Ce(NO₃)₆, YCl₃·6H₂O, and NbCl₅ under mild hydrothermal conditions in the presence of aqueous ammonia. The hydrothermal formation of cubic solid solution nanocrystals in the wide composition range of CeO₂ (mol%) = 10–100 in the CeO₂–1/4Y₃NbO₇ system was effectively achieved via the assistance of the presence of CeO₂ component more than 10 mol% as a promoter with the same fluorite‐type structure. The optical band gap of the solid solutions gradually decreased with increased CeO₂ component. The high phase stability of the solid solutions in the CeO₂–1/4Y₃NbO₇ system was confirmed, i.e., the single cubic phase of the solid solutions was maintained after heat treatment at 600°C–1500°C for 1 h in air. The presence of Y₃NbO₇ as an inhibitor and the substitutional incorporation of Y₃NbO₇ into the lattice, CeO₂ effectively controlled the crystallite growth of CeO₂, and nano‐sized cubic solid solutions with high specific surface areas were maintained after heat treatment up to 800°C–1000°C for 1 h air.     

Reducing the driving voltage of organic light-emitting diodes by inserting a transparent ultrathin layer of oxidized silver as a hole-injecting layer

Organic light-emitting diodes (OLEDs) containing a transparent ultrathin layer of oxidized silver as a hole-injecting layer, placed between a indium–tin-oxide (ITO) electrode and the hole-transporting layer, were fabricated, and their electrical and luminescent properties were investigated. The OLEDs had a structure that consisted of an ITO layer; followed by an ultrathin Ag layer oxidized by a ultraviolet (UV)–ozone surface treatment; a N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-biphenyl)-4,4′-diamine (α-NPD) layer; a 5,6,11,12-tetraphenylnaphthacene (rubrene)-doped 9,10-diphenylanthracene (DPA) layer; a tris-(8-hydroxyquinoline) aluminum (Alq₃) layer; a lithium fluoride (LiF) layer; and a Al layer. The operating voltages of the OLEDs with the oxidized Ag (i.e., AgO_x) layer were drastically lower than those of the layer-free OLEDs, because the AgO_x layer, which had high oxidizability, contributed to hole injection as it oxidized the surface of the α-NPD layer. However, the external quantum efficiency of the OLEDs with the AgO_x layer was lower than that of the AgO_x layer-free OLEDs, suggesting that the carrier balance (i.e., the balance between the holes and electrons) became uneven in the emission layer, owing to the insertion of the AgO_x layer. It was assumed that this imbalance resulted from the number of holes in the emission layer being higher because of the increase in hole injection in the AgO_x layer.     

The effect of builders on the activity of protease enzymes

The effect of builders on the stability of protease enzyme activity was studied in an effort to identify superior builders which are soluble in water and compatible with enzymes formulated into heavy duty laundry powders. Various poly(styrenesulfonate-methacrylate) copolymers, polyacrylate and tripolyphosphate anionic builders, as well as various poly(vinylalcohol-vinylacetate) nonionic copolymers, namely PVAs, were used. Zeolite 4A was also used as a typical nonphosphate particulate builder in the detergents. The protease used is frombacillus stearothermophilus. The calcium content was determined to be 16.7 mole/mole of protease by atomic spectrophotometry. In binary systems composed of a fixed concentration of 10 U/mL protease and varied concentrations of compound, builder or surfacant, it was found that compounds having the larger calcium ion binding capacity (C.B.C.) lowered the relative activity of protease enzyme. The activity of protease enzyme alone was lowered about 20% by addition of 0.02% sodium dodecylbenzene sulfonate (DBS). The anionic builders added to the binary system of fixed 10 U/mL protease and 0.02% DBS reduce the protease enzyme activity in proportion to the magnitude of their C.B.C. Addition of anionic builders further lowered the protease enzyme activity. The nonionic builders and the nonionic surfactant can enhance the protease enzyme activity by protection of protease against the inhibitor, DBS. It is certain that calcium atoms contained in the protease must play an important role for the protease enzyme activity and its stability. Calcium atoms must have a great influence on the formation of protease-substrate complex, protease-compound complex and substrate-compound complex, because the protease, protein substrate and anionic compound would all be negatively charged in alkaline solutions. Builders for enzyme-containing detergents should be constructed to be insensitive to calcium ion.     

Improvement of life time of minority carriers in GaAs epi-layer grown on Ge substrate

A buffer layer structure on Ge substrate was studied for MOCVD growth of a high-quality GaAs layer. The buffer layer structure was designed taking into consideration both lattice constants and thermal expansion coefficients of GaAs and Ge. It consisted of a preliminarily grown thin layer of Al_xGa_1−xAs and a GaAs layer. Photoluminescence (PL) decay of a GaAs layer in an Alo_0.2Ga_0.8As-GaAs-Al_0.2Ga_0.8As double-hetero (DH) structure, which was grown on the buffer layer structure, was observed by time-resolved PL method to estimate the quality of epilayers in the DH structure. The PL decay time strongly depended on Al content (x) of the Al_xGa_1−x As preliminary layer, and the highest value was obtained when the x was 0.25. A PL decay time above 20 ns was successfully obtained for the DH structure grown on the buffer layer structure, which consisted of a 0.05 μm thick Al_0.25Ga_0.75As layer and a 1 μm thick GaAs layer. Although this value was half of that for the DH structure grown on GaAs substrate, it was much longer than the value of 3 ns for the DH structure grown on Ge substrate with a conventional GaAs buffer layer 1 μm thick.     

Thin-film c-Si solar cells prepared by metal-induced crystallization

We prepared a thin-film polycrystalline silicon solar cell using metal-induced crystallization (MIC) of an amorphous silicon film and a thin Ni layer. The MIC using a 0.6-nm-thick Ni layer produced a highly activated n-type crystalline layer at a 550°C annealing temperature. The Ni concentration in the i-layer of a solar cell prepared by successively depositing i- and p-layers on an MIC n-layer using plasma-enhanced CVD was lower than 1×10¹⁶/cm³. This solar cell was highly responsive in the long-wavelength region of its quantum efficiency, indicating that the n/i interface and i-layer region near the n-layer were of high quality.     

Relationship between occurrence of mastitis pathogens in dairy cattle herds and raw-milk indicators of hygienic-sanitary quality

Mastitis is an inflammation of the mammary glands and in most cases it is caused by the presence of microorganisms. High mastitis rates in dairy cattle herds can cause an increase in total microorganism counts of bulk tank milk. The present paper was aimed at verifying whether the occurrence of mastitis in dairy cattle herds is reflected in raw-milk indicators of hygienic-sanitary quality. To observe the correlation among the analysed variables, we performed a logarithmical transformation (log10) of different indicator counts of raw milk and compared them with the occurrence of mastitis in dairy cattle herds. Few correlations were observed among mastitis cases in dairy cattle herds and the raw-milk indicators of hygienic-sanitary quality. We observed a negative correlation between the log10 of mesophilic aerobic plate counts and psychotropic aerobic plate counts when compared with the occurrence of no bacterial growth. The log10 of thermophilic aerobic plate counts and yeasts and mould aerobic plate counts presented a positive correlation with the cases of infectious mastitis and mastitis caused by Staphylococcus spp.     

Solid‐state characterization and the thermal properties of stereoregular poly(vinyl chloride) prepared by urea clathrate polymerization

The solid‐state characterization of highly stereoregular poly(vinyl chloride) (PVC) prepared by urea clathrate polymerization was carried out by using various instrumental analyses. The structural differences of PVC appeared most remarkably in solubility to organic solvents, IR, WAXD, and solid‐state ¹³C‐NMR spectra. The value of the glass transition temperature (T_g) was about 90°C, not as high as expected, although its detection was quite difficult. The thermal stability was poor, as evidenced by the easy discoloration of this polymer by heat treatment, which was related to the absence of a termination reaction. Dynamic ESR spectra in the solid state clearly indicate that the radical formation occurs at such a low temperature as 160°C in the initial degradation stage. The degradation characteristics of urea clathrate PVC were critically discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2820–2825, 1999