Eui-Sun Choi

Measurement of hydroxyl radical density generated from the atmospheric pressure bioplasma jet

Atmospheric pressure bioplasmas are being used in a variety of bio-medical and material processing applications, surface modifications of polymers. This plasma can generate the various kinds of radicals when it contacs with the water. Especially, hydroxyl radical species have very important role in the biological and chemical decontamination of media in this situation. It is very important to investigate the hydroxyl radical density in needle-typed plasma jet since it plays a crucial role in interaction between the living body and plasma. We have generated the needle-typed plasma jet bombarding the water surface by using an Ar gas flow and investigated the emission lines by OES (optical emission spectroscopy). It is noted that the electron temperature and plasma density are measured to be about 1.7 eV and 3.4 × 1012 cm−3, respectively, under Ar gas flow ranged from 80 to 300 sccm (standard cubic centimeter per minute) in this experiment. The hydroxyl radical density has also been investigated and measured to be maximum value of 2.6 × 1015 cm−3 for the gas flow rate of 150 sccm in the needle-typed plasma jet by the ultraviolet optical absorption spectroscopy.

Work function change on O-plasma treated indium–tin-oxide

Abstract The change in work function was studied on Indium–tin-oxide (ITO) surface after O-plasma treatment using γ-focused ion beam (γ-FIB). As the surface of ITO experienced more O-plasma treatment, both the surface resistivity and the work function got higher. Auger electron spectroscopy identified the increase of oxygen as well as the decrease of Sn. The rise of work function and surface resistivity is considered to be due to the change in oxygen and Sn on the surface of ITO.

Microwave Dielectric Properties of Ti-Te system Ceramics for Triplexer Filter

In this study, the compositions for the microwave dielectric materials were investigated to obtain the improved dielectric properties, the high temperature stability, and the sintering temperature of less than 900 ℃, which was necessary for cofiring with the internal conductor of silver. In addition, the dielectric sheets were prepared by the tape casting technique, after which the sheets were laminated and sintered. In this process, the optimum ratio of powder and binder, laminating pressure, temperature, and possibility for cofiring with the internal conductor were studied. Finally, multilayer chip treplexer filter for the 800?2,000 ㎒ range were fabricated, and the frequency characteristics of the triplexer filter were investigated. When the 0.6TiTe₃O?-0.4MgTiO₃+3wt%SnO+7wt%H₃BO₃ ceramics were sintered at 820 ℃ for 0.3 hours, the microwave dielectric properties of the dielectric constant of 29.91, quality factor of 33,000 ㎓, and temperature coefficient of resonant frequency of -2.76 ppm/ ℃ were obtained. Using the Advanced Design System (ADS) and High Frequency Structure Simulator (HFSS), the multilayer chip triplexer filter acting at the range of 800?2,000 ㎒ were simulated and manufactured. The manufactured triplexer filter had the excellent frequency properties in the CDAM800, GPS and PCS frequency regions, respectively.

STRUCTURAL AND RF PROPERTIES OF Co2Z FERRITE FOR ANTENNA SUBSTATE

The sintering behavior and high frequency electro-magnetic properties of Ba3Co2Fe24O41 ceramics were investigated for the small antenna application. All samples of the Ba3Co2Fe24O41 ceramics were prepared by the solid-state reaction method and sintered at 1150°C 1400°C. From the XRD patterns of calcined Ba3Co2Fe24O41 powders, the most suitable condition for calcining was 600°C–1000°C. Ba3Co2Fe24O41 phase was observed in sintered Ba3Co2Fe24O41 ceramics as main phase. Bulk densities increased with sintering temperature and decreased at 1400°C. Permittivity and permeability of the Ba3Co2Fe24O41 ceramics increased or decreased with sintering temperature, respectively. On the other hand, loss tangent of permittivity and of permeability showed contrary tendency with permittivity and permeability. The permittivity and loss tangent of permittivity of Ba3Co2Fe24O41 ceramics sintered at 1300°C were 19.896 and 0.171 at 210 MHz. and the measured value of permeability and loss tangent of permeability were 14.218 and 0.204, respectively.

Atmospheric pressure air plasma jet assisted blood coagulation

In physical sciences, “plasma” refers to the forth state of matter, while in medicine and biology plasma is known as the non-cellular fluid component of blood. Interestingly, cold atmospheric pressure plasma jets have attracted the most attention as a promising tool for biomedical applications.

Design of the Crab label tag with a loop matching feed and a modified dipole structure at 900

The Crab label tag with a loop matching feed and a modified dipole antenna structure was proposed. The antenna impedance is conjugated easily to a radio frequency identification IC chip impedance by a loop matching feed. The reading range of the crab structure tag is 0.9-1.0 m from the upper side of the formula milk can lid. The fabricated label tag size is 44.0 × 44.0 ㎟. The operating frequency at -3 dB return loss is 861.0-929.0 ㎒, and the maximum reading range at the anechoic chamber is 1.5 m.

A Study on MgO-Ta 2 O 5 System Ceramics for Microwave Component Application

In this study, the microwave dielectric properties of the Mg4Ta2O9 and Mg5Ta4O15 ceramics with composition ratio and sintering temperature were investigated and the dielectric resonators with these ceramics were simulated. TiO2 was doped in the Mg4Ta2O9 ceramics for improvement of temperature property. The (1-x)Mg4Ta2O9-xTiO2 and Mg5Ta4O15 ceramics were prepared by solid-state reaction method. According to the X-ray diffraction data, the (1-x)Mg4Ta2O9-xTiO2 ceramics had main phase of the Mg4Ta2O9 and MgTi2O5 peaks were appeared by additions of TiO2. In the Mg5Ta4O15 ceramics, the Mg4Ta2O9 and MgTa2O6 phase were coexisted and Mg5Ta4O15 phase was appeared with increments of sintering temperature. Microwave dielectric properties of (1-x)Mg4Ta2O9-xTiO2 ceramics were affected by MgTi2O5 and TiO2 phase. The quality factor had a little decrement compared to pure Mg4Ta2O9, but there was excellent improvement in TCRF by addition of TiO2. Densifications of the Mg4Ta2O9 and MgTa2O6 and existence of the Mg5Ta4O15 phase had influence on the microwave dielectric properties of the Mg5Ta4O15 ceramics. Dielectric constant, quality factor and TCRF of the (1-x)Mg4Ta2O9-xTiO2 and Mg5Ta4O15 ceramics sintered at 1450°C were 11.56-22.5, 24980-186410GHz, -36.02-+19.72ppm/°C and 8.2, 89473GHz, -10.91ppm/°C, respectively. ADS was used for simulation of DR. The simulated DR with the 0.5Mg4Ta2O9-0.5TiO2 and Mg5Ta4O15 ceramics had the S21 of -35.034dB at 11.97GHz and -28.493 dB at 10.50GHz, respectively.

Measurement of hydroxyl radical and nitric oxide density generated from the atmospheric pressure bioplasma jet

Summary form only given. The atmospheric-pressure (AP) plasma jet has recently been used in emerging novel biomedical applications. Besides its sterilization effects, the first practical studies on plasma-based treatment of chronic wounds or tumor treatment with on AP plasma jet was very promising [1,2]. These plasma jet sources could generate numerous chemical species of reactive oxygen species (ROS) and reactive nitrogen species (RNS) when it contacts with water surface. This ROS having very short lifetime and extremely reactive properties is used to sterilize the biomaterials and these species are inside the biological cells and near the interface between the plasma zone and cells. These hydroxyl radical, OH, of ROS as well as nitric oxide, NO, can be generated by simple nonthernal bioplasma jet source operated at the atmospheric pressure when it contacts with the water surface. Especially, hydroxyl radical and nitric oxide species are a very important role in the biological and chemical decontamination of media in this situation. If the technical requirements for medical instrumentation are to be met, advanced plasma sources must have specified radical species. It is very important to investigate the hydroxyl radical density and the nitric oxide density in needle-typed plasma jet since it plays a crucial role in interaction between the living body and plasma. We have generated the needle-typed plasma jet bombarding the water surface by using an Ar gas flow and investigated the emission lines by OES (optical emission spectroscopy).

Effect of non-thermal plasma on cells in presence of ionic liquids

Summary form only given. Non-thermal plasma is emerging as a novel tool for the treatment of living tissues for biological and medical purpose1. In this study we described the effect of plasma on human cancer cells in presence of ionic liquids (ILs)2. ILs having unique protective metabolic roles and they are acting as antioxidants, providing protects macromolecules, enhance protein folding and regulate cell volume. ILs is beneficial for the development of new bioactive materials, for example as anti-microbial or anti-septics or as anti-fouling reagents, or even as potential anti-cancer therapeutic agent3. Based on these interesting properties of ILs, non-thermal plasma in presence of ILs appears to provide a new outlook. A result of this study reveals that ILs in presence of plasma inhibits the cancer cells growth. ILs may also act as protecting agent for normal healthy cells from the damaging/toxic effect of plasma.

Microwave Properties of Co 2 Ferrite for Miniaturization of Antenna

The sintering behavior and microwave properties of ferrite ( ceramics) were investigated for microwave applications. Also PIFA type antenna with ferrite was simulated. All samples were prepared by the solid state reaction method and sintered at . All ceramics had relatively density above of 92% compare with theoretical density of ceramics. From the XRD pattens, the Z-type phase was existed as main phase in ceramics. The permittivity and permeability of ceramics were increased with Zn additions and decreased rapidly over frequency of 200~600 MHz. Several PIFA type antennas with ferrite and FR4 were simulated. All antenna structure had return loss of less than -10 dB at each resonant frequency. Simulated antenna using both ferrite and FR4 showed size reduction of 25% without a significant decrement of efficiency.