Mixing speed-controlled gold nanoparticle synthesis with pulsed mixing microfluidic system

Gold nanoparticles with diameters of a few tens of nanometer and a narrow size distribution were synthesized using a pulsed mixing method with a microfluidic system which consists of a Y-shaped mixing microchannel and two piezoelectric valveless micropumps. This mixing method enables control of the mixing speed of gold salts and reducing agent by changing the switching frequency of the micropumps, which was our focus to improve the particle size distribution, which is an essential parameter in gold nanoparticle synthesis. In the proposed method, the mixing time was inversely proportional to the switching frequency and the minimum mixing time was 95 ms at a switching frequency of 200 Hz. During synthesis experiments, the mean diameter of the synthesized gold nanoparticles was found to increase, and the coefficient of variation of particle size was found to decrease with decreasing mixing time. We successfully improved the coefficient of variation to less than 10% for a mean diameter of around 40 nm.     

Preparation of Laminin-apatite-polymer Composites Using Metastable Calcium Phosphate Solutions

1Introduction Themostimportantrequirementofapercutaneous deviceisthepreventionofbacterialinfectionthroughtheinterfacebetweenthematerialandtheskin.Therefore,a percutaneousdevicehastoadherefirmlytoskintissueandpreventepidermaldowngrowth.Previously,Aokietalp…     

Preparation of Laminin-apatite-polymer Composites Using Metastable Calcium Phosphate Solutions

A synthetic polymer with a laminin-apatite composite layer on its surface would be useful as a percutaneous device. The preparation of such a composite was attempted in the present study using poly（ ethylene terephthalate ） （PET） and polyethylene （PE） as the synthetic polymer. PET and PE plates and those pretreated with an oxygen plasma were alternately dipped in calcium and phosphate ion solutions, and then immersed in a metastable calcium phosphate solution supplemented with laminin （ LCP solution ）. The PET and PE plates pretreated with an oxygen plasma formed a uniform and continuous layer of a laminin-apatite composite on their surfaces. In contrast, the PET and PE plates that had not been pretreated with an oxygen plasma did not form a continuous layer of a laminin-apatite composite on their surfaces. The hydrophilic functional groups on the PET and PE surfaces introduced by the plasma treatment were responsible for the successful laminin-apatite coruposite coating.     

Electron injection in "electron-only" devices based on a symmetric metal/silole/metal structure

We report on electron injection from two different metal electrodes into three silole derivatives, namely 2,5-di-(3-biphenyl)-1,1-dimethyl-3,4-diphenylsilacyclopentadiene (PPSPP), 1,2-bis(1-methyl-2,3,4,5,-tetraphenylsilacyclopentadienyl) ethane (2PSP) and 2,5-bis-(2', 2'-bipyridin-6-yl)-1, 1-dimethyl-3,4-diphenylsilacyclopentadiene (PyPySPyPy), previously employed as emissive and electron transport materials in molecular organic light-emitting diodes (MOLEDs). Silole films were sandwiched between symmetric Mg:Ag or bilayer CsF-Al electrodes. The steady-state current density-voltage characteristics were measured as a function of the silole layer thickness for the two cathodes. The trap-free space-charge-limited current based on time-of-flight measurements compared with the injected electron current for PyPySPyPy indicated that Mg:Ag contacts limit the injected current, while CsF-Al contacts behave as quasi-ohmic contacts. Similar findings were obtained for 2PSP and PPSPP allowing steady-state derived electron mobility parameters to be extracted. Based on space-charge-limited conduction analysis of the measured current-voltage characteristics, PyPySPyPy is found to be a superior electron transporting silole with approximately an order of magnitude higher electron mobility (2.0/spl times/10/sup -4/ cm/sup 2//Vs) compared with those of 2PSP (2.4/spl times/10/sup -5/ cm/sup 2//Vs) and PPSPP (5.2/spl times/10/sup -5/ cm/sup 2//Vs), which is significantly higher than that of the prototype electron transport material tris (8-hydroxyquinolinolato) aluminum (III) (Alq/sub 3/) (6.5/spl times/10/sup -7/ cm/sup 2//Vs) at 0.6 MV/cm.     

Pollution control of actual flue gas using pulsed power at a thermal power plant

There are several important environmental problems in the world. One of them is acid rain caused by combustion flue gases from thermal power plants, factories, and automobiles. Different kinds of gas discharges, such as surface discharge, dc and ac corona discharge, silent discharge, and electron beam controlled discharge, have been studied for the removal of NO_x and SO₂ from flue gases. The recent development of repetitive pulsed power generators gives the pulsed steamer corona discharges a chance of success in the removal of NO_x and SO₂. In this paper, the experimental results of NO_x and SO₂ removal by a repetitive pulse power generator are described. The actual flue gas at a thermal power plant was used. It is shown that about 90% of the NO was removed at a flow rate of 0.8 liters/min and a repetition rate of 7 pps. © 2001 Scripta Technica, Electr Eng Jpn, 134(4): 28–35, 2001     

Experimental analysis of temperature dependence in 1.3-μmAlGaInAs-InP strained MQW lasers

We have analyzed experimentally the temperature and pressure dependences of the lasing characteristics of 1.3-μm AlGaInAs-InP strained multiple-quantum-well lasers, by focusing on the ratio of the nonradiative recombination current to the total current. The temperature dependence of the radiative current was studied by observing the spontaneous emission through a window in the substrate. It was found to increase linearly with temperature, exactly as expected for an ideal quantum well over the entire temperature range from 100 to 360 K. Further, it was shown that pure radiative recombination dominated the total current below a breakpoint temperature T_b of 220 K. Above this temperature, the onset of loss processes including Auger recombination caused a superlinear increase in the threshold current. Analysis of the linear and nonlinear components allowed us to determine the ratio of the nonradiative to radiative currents at threshold. We find that, relative to similar GaInAsP/InP lasers, there is a decrease in the nonradiative component of the current, resulting in a higher characteristic temperature T₀ in the AlGaInAs-InP lasers. At 300 K, the radiative recombination current is more than 70% of the total threshold current. This result is consistent with the observation that the threshold current increases by about 8% in 12-kbar hydrostatic pressure, while in GaInAsP lasers, a decrease of 10% or more is always observed over this pressure range     

Optimization method of P+ ω PSS parameters for stability and robustness enhancement in a multimachine power system

Recent steady increase of electric power demand causes power sources to be large and far from cities. Wide area power interchanges lead to larger and more complex power systems. This makes the network susceptible to poor damping power swing oscillations of relatively low frequencies which influence the whole system. This paper describes a newly developed generator's double input signal PSS (P+ ω input PSS) design method. Several power system conditions (power flow and/or power patterns) are considered to satisfy a well‐stabilized power system for each system condition. Major features of this method are: (1) Weighting factor for eigenvalue sensitivity of the oscillation mode is considered when the parameters of the PSS are updated during the optimization process. (2) The new method provides good results for the generator's local and interarea oscillation modes under peak and off‐peak power flow conditions. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 19–31, 2000     

Effect of Poly(vinyl alcohol) Adsorption on Binder Segregation during Drying

The effect of poly(vinyl alcohol) adsorption on segregation was quantitatively studied by a model experiment of one–dimension drying and simulated by a mathematical model. It was clear that the adsorption of PVA on alumina particle was a slow process, and the adsorbed binder was not desorbed at higher temperature. PVA segregation can significantly be limited by fully adsorbing the binder before drying. The simulation and experiments agreed very well. The effects of drying temperature, initial concentration of the binder, and thickness of specimen on the surface segregation are discussed quantitatively. Mathematical simulation has a great potential for predicting the segregation of soluble components during drying, especially for such cases as thin films and small granules where it is difficult to determine the distribution of the component directly.     

Flexible feature discovery and structural information control

In this paper, we propose a new information theoretic method called structural information control for flexible feature discovery. The new method has three distinctive characteristics, which traditional competitive learning fails to offer. First, the new method can directly control competitive unit activation patterns, whereas traditional competitive learning does not have any means to control them. Thus, with the new method, it is possible to extract salient features not discovered by traditional methods. Second, competitive units compete witheach other by maximizing their information content about input patterns. Consequently, this information maximization makes it possible to control flexibly competition processes. Third, in structural information control, it is possible to define many different kinds of information content, and we can choose a specific type of information according to a given objective. When applied to competitive learning, structural information can be used to control the number of dead or spare units, and to extract macro as well as micro features of input patterns in explicit ways. We first applied this method to simple pattern classification to demonstrate that information can be controlled and that different neuron firing patterns can be generated. Second, a dipole problem was used to show that structural information could provide representations similar to those by the conventional competitive learning methods. Finally, we applied the method to a language acquisition problem in which networks must flexibly discover some linguistic rules by changing structural information. Especially, we attempted to examine the effect of the information parameter to control the number of dead neurons, and thus to examine how macro and micro features in input patterns can explicitly be discovered by structural information.     

Applying dynamic thermography in the diagnosis of breast cancer

The major difficulty in the interpretation of breast thermography is the complexities of the vascular patterns (false negatives and false positives), and a secondary problem is the existence of cold tumors (false negatives). To overcome these difficulties, we investigated dynamic thermography after cold stress. When a breast is exposed to cold stress, the vascular pattern disappears, and after the stress is removed, the pattern gradually recovers. This phenomenon of thermal recovery can be visualized by sequential thermography or by digital subtraction thermography. In this study, we have attempted to increase the sensitivity of breast thermography by using thermal recovery and sequential and subtraction thermography, hoping that even small tumors with negative steady-state thermography may appear in dynamic thermography