Hydrophilic surface modification of polypropylene films by CCl4 plasma

The CCl₄ plasma treatment of polypropylene films was investigated from the viewpoint of hydrophilic surface modification using a contact-angle meter, ATR FTIR spectroscopy, and angular XPS. Hydrophilicity and chemical composition of the CCl₄ plasma treatment was effective in hydrophilic modification. The advancing contact angle of water for polypropylene films was decreased from 99° to 81-7° by the CCl₄ plasma treatment, and the surface energy increased from 27.2 to 38.9-67.7 mJ/m² when the discharge current varied from 50 to 150 mA. The CCl₄ plasma initiated chlorination, oxidation, and aluminum sputtering reactions. The chlorination of polypropylene films was favorable in a mild CCl₄ plasma operated at discharge current of 50 mA. The oxidation and aluminum sputtering reactions were predominant over the chlorination in strong CCl₄ plasmas operated at discharge currents of more than 75 mA. The chlorination initiated by the mild CCl₄ plasma was restricted near the film surface within 36 Å deep. The regions modified with the strong CCl₄ plasma reached inner layers of 36-49 Å deep. Hydrophilicity caused by the CCl₄ plasma treatment may be due not only to chlorine functionalities but also to oxygen and aluminum functionalities. © 1993 John Wiley & Sons, Inc.     

A design of high optical efficiency wedge type light guide plate adopting twin inclined cylindrical surface

We propose wedge type light guide plate (LGP) adopting twin inclined cylindrical surfaces (TICS) at the incident part of a LGP. It has higher optical efficiency than conventional wedge type LGP. In dimension of LGP which the thickness of incident part is 1.5 mm and that of luminance part is 0.7 mm, the optical efficiency of wedge type LGP adopting TICS is expected to be 96% in comparison with a normal flat LGP. In addition, there is an advantage to reduce the non‐uniformity of vicinity of light emitted diodes (LEDs) by TICS reflecting light laterally. However, it is necessary that the LED centers are aligned with the intersections of TICS. The misalignment of LED causes non‐uniformity of optical profile that is slightly larger than a normal LGP.     

Connection‐Strength Estimation of Neuronal Networks by Fitting for Izhikevich Model

Recently, there has been abundant research using multineuron recording, but there are many problems with extracting the features from the obtained spike time series, which are huge in volume and complex. Here we introduce a new method of estimating synaptic connection strengths between neurons by fitting to the Izhikevich model by maximum likelihood estimation. We demonstrate that our method can estimate connection strengths from spike time series given by a simulated neural ensemble and can estimate nonconnectivity between two independent cultured neuronal networks. These results suggest that our method is applicable to network and plasticity analysis of neuronal networks.     

Preparation of Lanthanum Nickel Oxide-Coated Ni Sheet Anodes and Their Application to Electrolytic Production of (CF3)3N in (CH3)4NF·4.0HF Melt

A new process for electrolytic production of a perfluorinated compound, (CF₃)₃N, using lanthanum nickel oxide-coated Ni sheet anode in the (CH₃)₄NF·4.0HF melt at room temperature, was developed. Thin films of the lanthanum nickel oxides were prepared on Ni sheets by sol-gel coating method using polyvinlylpyrrolidone(PVP). The main components of the thin films were La₂O₃, LaNiO₃, and La₂NiO₄ at 500, 750 and 1000 °C, respectively. The anode performance in the (CH₃)₄NF·4.0HF melt depends greatly on the main component of the thin film, and the LaNiO₃-coated Ni sheet anode gives the best anode performance. The potential of LaNiO₃-coated Ni sheet anode remains constant at 5.9 V during electrolysis at 20 mA·cm⁻² in the (CH₃)4NF·4.0HF melt for 100 h. This is because LaNiO₃ and NiF₃, and/or Ni₂F₅, the latter of which was formed during electrolysis, in the film give a high electronic conductivity to the surface film during electrolysis. The maximum mole fraction of (CF₃)₃N (21.4%) was obtained at 20 mA·cm⁻² in (CH₃)₄NF·4.0HF melt using the LaNiO₃-coated Ni sheet.     

A new detection method for the primary cosmic heavy nuclei by the plastic track detector CR-39

A new multiple scanning method is developed and applied to detect cosmic heavy nuclei. The plastic track detectors CR-39 exposed to cosmic heavy nuclei are over-etched in 8.0N NaOH for 94 h at 80°C. We found that the etched cones can easily be scanned on the plastic plates without using an optical microscope. The trajectories of heavy nuclei can be reconstructed with the naked eyes by superposing four or more over-etched plates. The charge detection threshold is obtained by this method, and appears to be 10. The charge resolution is estimated to be 1.0 charge units for iron nuclei. By adopting this method, the scanning time is much shortened and CR-39 plastic chamber size can easily be scaled up. The method is very useful for detecting particles with low flux intensity, like for searching magnetic monopoles or for measuring the high energy spectra of cosmic heavy nuclei.     

Structural studies of enzyme-based microfluidic biofuel cells

An enzyme-based glucose/O₂ biofuel cell was constructed within a microfluidic channel to study the influence of electrode configuration and fluidic channel height on cell performance. The cell was composed of a bilirubin oxidase (BOD)-adsorbed O₂ cathode and a glucose anode prepared by co-immobilization of glucose dehydrogenase (GDH), diaphorase (Dp) and VK₃-pendant poly-l-lysine. The consumption of O₂ at the upstream cathode protected the downstream anode from interfering O₂ molecules, and consequently improved the cell performance (maximum cell current) ca. 10% for the present cell. The cell performance was also affected by the channel height. The output current and power of a 0.1 mm-height cell was significantly less than those of a 1 mm-height cell because of the depletion of O₂, as determined by the shape of the E–I curve at the cathode. On the other hand, the volume density of current and power was several times higher for the narrower cell.     

CO gas sensor devices plasma-polymerized from tetramethyltin

Thin films plasma-polymerized from tetramethyltin was applied for CO gas sensor device. The films formed from tetramethyltin contains alkyl chains with organic tin moieties, and pyrolysis of them at 350–500°C yields carbonized films with SnO₂ moieties. The electrical resistance for the films pyrolized at 350–500°C decreases in exposing to CO gas. The sensitivity, the ratio of the electrical resistance between in air and in CO atmosphere, is enhanced by catalytic actions of palladium chloride, specially in operation at low temperatures below 50°C. The gas sensitivity between CO and other gases such as ethanol, methane, and propane gases is good. The possible determination of CO gas concentration by the sensor device is in ranges from 10 to 1000 ppm.     

Mechanism‐Based Trapping of the Quinonoid Intermediate by Using the K276R Mutant of PLP‐Dependent 3‐Aminobenzoate Synthase PctV in the Biosynthesis of Pactamycin

Mutational analysis of the pyridoxal 5′‐phosphate (PLP)‐dependent enzyme PctV was carried out to elucidate the multi‐step reaction mechanism for the formation of 3‐aminobenzoate (3‐ABA) from 3‐dehydroshikimate (3‐DSA). Introduction of mutation K276R led to the accumulation of a quinonoid intermediate with an absorption maximum at 580 nm after the reaction of pyridoxamine 5′‐phosphate (PMP) with 3‐DSA. The chemical structure of this intermediate was supported by X‐ray crystallographic analysis of the complex formed between the K276R mutant and the quinonoid intermediate. These results clearly show that a quinonoid intermediate is involved in the formation of 3‐ABA. They also indicate that Lys276 (in the active site of PctV) plays multiple roles, including acid/base catalysis during the dehydration reaction of the quinonoid intermediate.     

Experimental study of cell pattern formation induced by internal heat sources in a horizontal fluid layer

This study determines the flow structure in a convection cell with an internally heated layer by PIV to elucidate the convection cell transition mechanisms. The vertical velocity component is determined and the cell behaviour with respect to Rayleigh number is investigated quantitatively. Cell expansion process is described as a consequence of development of the descending flow at the centre of cells. The results suggest that a spoke-like structure is stable in this system in ideal conditions and a double-cell structure is formed when there are restrictions on the system, i.e. finite lateral boundaries.