Shinji Katsura

Indoor air cleaning using a pulsed discharge plasma

The purpose of this paper is to develop a high-efficiency air-cleaning system for air pollutants such as tobacco smoke found in indoor environments. The authors investigated the basic characteristics of treating particulate matter and acetaldehyde (CH/sub 3/CHO) in a one-pass test using a pulse generator and a plasma-driven catalyst reactor, both of which are attachable to an air conditioner. Using a circulation test, the decrease in acetaldehyde concentration was measured in a closed vessel where the reactor had been placed. The removal efficiencies of particulate matter and acetaldehyde in the one-pass test (residence time of 10 ms) were 70% and 27%, respectively. In the circulation test, 98% of the suspended particles were collected after 2 min of operation and the acetaldehyde concentration decreased by 70% after 50 mins. It is believed that the TiO/sub 2/ catalyst is excited by plasma-induced high-energy particles (electrons, photons, and metastable molecules), resulting in an enhanced pollutant removal. These test results indicate that the combination of plasma with TiO/sub 2/ is a potential alternative in treating the pollutants in environmental tobacco smoke.

Evaluation of cell characteristics by step-wise orientational rotation using optoelectrostatic micromanipulation

The characteristics of a single cell can be studied using optoelectrostatic micromanipulation (OEMM) techniques. Escherichia coli (E. coli) and Schizosaccharomyces pombe (S. Pombe) cells were characterized by step-wise orientational rotation driven by a high-frequency alternating electric field. The peak voltage and frequency of the electric field ranged from 2.5 to 80 V (average electric field: 0.25/spl times/10/sup 5/-0.8/spl times/10/sup 6/ V/m) and from 5 kHz to 2 MHz, respectively. The characteristics were measured by a microelectrode system installed on a microscope stage. An yttrium aluminum garnet (YAG) laser was introduced to hold a cell at its focal point. The characteristics show that a live cell has a peak critical orientational rotation frequency (PCRF) at 1 MHz and the PCRF of a dead cell depends on the process of killing, i.e., thermal, chemical, ultraviolet light or electric pulse. The orientational rotation can be utilized to investigate the dielectric properties of an individual cell.

Reforming of heavy oil using nonthermal plasma

Reforming of heavy oils into light hydrocarbons has been experimentally studied using nonthermal plasma. The purpose of this study was to improve the understanding of the parameters for optimal design of the heavy oil reforming plasma reactor driven by AC high voltage. The low molecular weight hydrocarbons obtained constitute the NO/sub x/ removal system using light olefin hydrocarbons, such as ethylene and propylene as additives. In this paper, we examined the effect of the parameters such as gap distance of the electrodes and power applied. Results indicated that the reactions occurring in this heavy oil conversion process showed an important selective behavior. The major products obtained were hydrogen and hydrocarbon compounds with one, two, three, and four atoms of carbon, such as CH/sub 4/, C/sub 2/H/sub 4/, C/sub 2/H/sub 6/, C/sub 3/H/sub 6/, and C/sub 4/H/sub 10/, ethylene being the main compound. The optimum set of values for the parameters studied gave rise to efficiencies on the order of 2.3 /spl mu/mol/J.

Reactivity of methane in nonthermal plasma in the presence of oxygen and inert gases at atmospheric pressure

Partial oxidation of methane to methanol and formaldehyde as liquid fuels with oxygen diluted with inert gases was investigated experimentally using the pulsed discharge plasma method under conditions of room temperature and atmospheric pressure. The experimental results indicated that ethylene (C/sub 2/H/sub 4/), ethane (C/sub 2/H/sub 6/), methanol (CH/sub 3/OH), formaldehyde (HCHO), hydrogen (H/sub 2/), water (H/sub 2/O), carbon monoxide (CO), and carbon dioxide (CO/sub 2/) were detected as products and, especially, methanol, formaldehyde, and carbon monoxide were the major products of the plasma chemical reactions. Particularly, it was found that the methanol and formaldehyde production has an optimum specific input energy (SIE: defined as the electrical applied energy per unit volume). The highest methanol and formaldehyde production ability and selectivity were achieved with a relatively low SEE of 360 J/L and concentration of Argon of 50 vol.%. Under this optimum condition, the maximum liquid fuel (methanol and formaldehyde) production ability of about 0.7 /spl mu/mole/J, and selectivity of 64 mol%, were obtained.

Development of an Optoelectrostatic Micropump Using a Focused Laser Beam in a High-Frequency Electric Field

In this paper, fluid flow generated by laser irradiation in a high-frequency electric field was investigated with a view to using it as the driving force for a micropump. We discovered an optoelectrostatic phenomenon known as optoelectrostatic microvortex (OEMV) ten years ago. The OEMV is generated around the focal point of a laser beam located in the center of an intense high-frequency electric field. The direction of the opposed flow is parallel to the ac electric field and perpendicular to the sides of the electrodes. In this paper, the laser focus was positioned near one of the electrodes. One-directional flow was generated toward the other electrode. This flow was generated in a microchannel by simultaneous application of an Nd:YAG laser (1064 nm) and an ac voltage. The flow velocity increased with both increasing laser power and increasing ac voltage. In addition, the flow velocity was affected by the ac frequency. The flow velocity around the focal point was several hundred micrometers per second. At a distance of 3 mm from the laser spot, a flow velocity of 25 mum/s (0.74 muL/s) was observed

A new DNA combing method for biochemical analysis

A simple molecular combing method for analysis of biochemical reactions, called the moving droplet method, has been developed. In this method, small droplets containing DNA molecules run down a sloped glass substrate, and this creates a moving interface among the air, droplet, and substrate that stretches the DNA molecules. This method requires a much smaller volume of sample solution than other established combing methods, allowing wider application in various fields. Using this method, lambdaDNA molecules were stretched and absorbed to a glass substrate, and single-molecule analysis of DNA synthesis by DNA polymerases was performed.

Dilution effect with inert gases in direct synthesis of methanol from methane using nonthermal plasma

Direct synthesis of methanol from CH/sub 4/ and O/sub 2/ has been experimentally studied using pulsed discharge plasma in a concentric-cylinder-type reactor. The methanol production was enhanced by dilution of source gas with inert gas, such as Ar and He. The methanol production became about 2.5 times larger at the dilution ratio of 2.5, and gradually decreased with increase of the dilution ratio and decrease of O/sub 2/ partial pressure. C/sub 2/H/sub 6/ was formed as one of the by-products, and its concentration increased with the increase of the dilution ratio. This tendency was the same for Ar and He. When the partial pressure of O/sub 2/ was kept constant, on the other hand, the methanol production increased and saturated with the increasing of the dilution, but concentration of C/sub 2/H/sub 6/ stayed about the same level. Reaction selectivity of the methanol synthesis depended on the dilution ratio of the inert gas.

The influence of reaction conditions on SO/sub 2/ oxidation in a discharge plasma reactor

In this work, we report several approaches for the removal of SO/sub 2/ using nonthermal pulsed discharge plasma processing under absence of NH/sub 3/. The gas-phase reaction was found to be less attractive due to its high energy cost. The increase in temperature decreased the SO/sub 2/ removal rate, resulting in high energy cost. In case of the wet type plasma reactor, the discharge plasma greatly enhances the liquid phase oxidation of SO/sub 3//sup 2-/ to SO/sub 4//sup 2-/. The presence of TiO/sub 2/ catalyst increased the gas phase oxidation and the liquid phase oxidation as well.

Effect of additives and catalysts on removal of nitrogen oxides using pulsed discharge

Effect of additives and catalysts has been investigated on NO/sub x/ (including N/sub 2/O) removal using discharge plasma. Additives such as H/sub 2/O, C/sub 2/H/sub 4/ are considered to be the source of OH and CH radicals. Though they are one of the important factors to enhance the NO/sub x/ removal chemical reactions, no systematic experiment has been carried out yet. It was confirmed that the hydrocarbon addition plays a dominant role in the NO/sub x/ removal efficiency compared to the water vapor addition. Effect of catalysts such as Ca(OH)/sub 2/ was investigated, and were found to enhance NO/sub x/ and N/sub 2/O removal efficiency.

The Effect of Physical Form of DNA on ExonucleaseIII Activity Revealed by Single-molecule Observations

Single-molecule studies have revealed molecular behaviors usually hidden in the ensemble and time averaging of bulk experiments. Single-molecule measurement that can control physical form of individual DNA molecules is a powerful method to obtain new knowledge about correlation between DNA-tension and enzyme activity. Here we study the effect of physical form of DNA on exonucleaseIII (ExoIII) reaction. ExoIII has a double-stranded DNA specific 3′→5′ exonuclease activity and the digestion is distributive. We observed the ExoIII digestion of individual stretched DNA molecules from the free ends. The sequentially captured photographs demonstrated that the digested DNA molecule linearly shortened with the reaction time. We also carried out the single-molecule observation under random coiled form by pausing the buffer flow. The digestion rates obtained from both single-molecule experiments showed that the digestion rate under the stretched condition was two times higher than the random coiled condition. The correlation between physical form of DNA and digestion rate of ExoIII was clearly demonstrated by single-molecule observations.