Inactivation of microorganisms, such as Escherichia coli, by exposure to a microplasma is experimentally investigated. A microplasma is an atmospheric-pressure nonthermal plasma. Microplasmas, which generate high-intensity electric fields, can be formed using relatively low discharge voltages (0.7-1.1 kV) across small discharge gaps (0-100 μm). The key benefits of the practical application of exposure to a microplasma are as follows: 1) the low discharge voltage and 2) the simple apparatus because a vacuum enclosure is not required. Hence, the apparatus for generating a microplasma could be relatively small and inexpensive and could be integrated into a portable device. The ozone generated by a microplasma at a low power level was measured, although the specific power density of the microplasma was larger than that of large-scale conventional plasmas. The emission spectra of the microplasma discharge in N 2 was measured: 1) to confirm the UV light emission and 2) to identify the active chemical species generated by the microplasma discharge. The emission spectra was also measured with the presence of water droplets. The UV light from the microplasma discharge showed excited nitrogen molecules and OH radicals. In this paper, two cultures of bacteria, i.e., gram-negative Escherichia coli HB101 and gram-positive Bacillus subtilis JCB 20036 were the target microorganisms to be inactivated. In the experiments reported here, the number of bacteria decreased after microplasma treatment. The inactivation rate increases as the discharge voltage increases. Escherichia coli is completely inactivated when air is used as carrier gas at a plasma discharge voltage of 1.05 kV. Using nitrogen as carrier gas, the highest inactivation rate is 77% at a discharge voltage of 1.15 kV. In addition, Bacillus subtilis is inactivated with a rate of 97% at 1.07 kV with air as carrier gas. Using nitrogen as carrier gas and a discharge voltage of 1 kV results in an inactivation rate of 70% of bacteria. The inactivation of microorganisms by microplasma may be due to several factors either individually or in combination of the following: 1) the excited molecules and ions; 2) ozone; 3) high electrical fields; and 4) UV light. The effect of active species such as OH radicals may also be important since all the bacteria were carried within a small water droplet in between the electrodes.

a b s t r a c tConventionally, tea flavor is analyzed through the use of a combination of gas chromatography-mass spectrometry and human taste panel. These methods present time-consuming or inaccurate factor. In this work, a rapid, accurate and nondestructive approach was put forward to identify coumarin-enriched Japanese green teas and evaluate their particular flavor using electronic nose (E-nose) technique. The multivariable analyses including principal component analysis and cluster analysis were applied to distinguish the tea samples and evaluate the particular (coumarin-like) flavor of coumarin-enriched tea under different infusion conditions. A correct classification was achieved for the seven tea samples with different content of coumarin. The E-nose successfully characterized the drying temperature-dependently trend of coumarin content during the manufacture process of coumarin-enriched green tea. It also revealed that the comparatively low-infusion temperature and long-infusion time were favorable for the emission of coumarin-like flavor of the tea infusion. In addition, a comparatively newly developed ''absolute value expression" (AVE) method was employed to divide the tea flavors into quality and express them numerically. Using AVE, the role of coumarin in the total flavor of coumarin-enriched green tea was elucidated. These results suggest that E-nose could be employed to identify the green teas with particular flavor and evaluate the tea flavor.

Non-member Micro discharge is investigated which is occurred with a pair of electrodes covered with dielectric barrier. The discharge gap is set at an order of micro meters by changing a spacer from 0 to 100 µm. Paschen's law states the minimum sparking voltage of various gases for respective discharge gaps in atmospheric pressure. In this paper, characteristics of micro discharges, such as discharge voltages, discharge currents, discharge power, which is obtained with the help of Lissajous figures, and the relationships between these characteristics are presented. Characteristics of ozone generation and treatment of high concentration NOx, which is contained in exhaust gas of automobiles, are investigated. Byproducts are confirmed by FT-IR and GC-MS.

In this paper, microplasma is investigated, which occurs between the narrow gap of the electrodes covered with dielectric materials. The discharge gap is set on the order of micrometers by changing a spacer from 0 to 100 μm. In this paper, the characteristics of microplasma, such as discharge voltages, discharge currents, and discharge power that is obtained with the help of Lissajous figures, and the relationships between these electric characteristics are presented. The characteristics of ozone generation by a microplasma electrode are investigated. Treatment by microplasma for the simulated exhaust gas, which contains NO x and C 3 H 8 as a role of HC and CO, is estimated experimentally. In the absence of O 2 , the exhaust gas is decomposed by nitrogen atomic species in particular. In the presence of O 2 , it is decomposed by nitrogen atomic species and oxidized by ozone. By-product analysis of treated gases is carried out by Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry. When HC, NO x , and N 2 are included in the simulated exhaust gas, HCN, N 2 O, and CH 4 are confirmed as byproducts of the microplasma treatment.

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In this paper, microplasma is investigated, which occurs between the narrow gap of the electrodes covered with dielectric materials. The discharge gap is set on the order of micrometers by changing a spacer from 0 to 100 μm. In this paper, the characteristics of microplasma, such as discharge voltages, discharge currents, and discharge power that is obtained with the help of Lissajous figures, and the relationships between these electric characteristics are presented. The characteristics of ozone generation by a microplasma electrode are investigated. Treatment by microplasma for the simulated exhaust gas, which contains NO x and C 3 H 8 as a role of HC and CO, is estimated experimentally. In the absence of O 2 , the exhaust gas is decomposed by nitrogen atomic species in particular. In the presence of O 2 , it is decomposed by nitrogen atomic species and oxidized by ozone. By-product analysis of treated gases is carried out by Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry. When HC, NO x , and N 2 are included in the simulated exhaust gas, HCN, N 2 O, and CH 4 are confirmed as byproducts of the microplasma treatment.