• Journal of Microbiology and Biotechnology
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• v.32 no.4
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• pp.522-530
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• 2022

In this study we aimed to develop novel ZnO-NP/chitosan/β-glycerophosphate (ZnO-NP/CS/β-GP) antibacterial hydrogels for biomedical applications. According to the mass fraction ratio of ZnO-NPs to chitosan, mixtures of 1, 3, and 5% ZnO-NPs/CS/β-GP were prepared. Using the test-tube inversion method, scanning electron microscopy and Fourier-transform infrared spectroscopy, the influence of ZnO-NPs on gelation time, chemical composition, and cross-sectional microstructures were evaluated. Adding ZnO-NPs significantly improved the hydrogel's antibacterial activity as determined by bacteriostatic zone and colony counting. The hydrogel's bacteriostatic mechanism was investigated using live/dead fluorescent staining and scanning electron microscopy. In addition, crystal violet staining and MTT assay demonstrated that ZnO-NPs/CS/β-GP exhibited good antibacterial activity in inhibiting the formation of biofilms and eradicating existing biofilms. CCK-8 and live/dead cell staining methods revealed that the cell viability of gingival fibroblasts (L929) cocultured with hydrogel in each group was above 90% after 24, 48, and 72 h. These results suggest that ZnO-NPs improve the temperature sensitivity and bacteriostatic performance of chitosan/β-glycerophosphate (CS/β-GP), which could be injected into the periodontal pocket in solution form and quickly transformed into hydrogel adhesion on the gingiva, allowing for a straightforward and convenient procedure. In conclusion, ZnO-NP/CS/β-GP thermosensitive hydrogels could be expected to be utilized as adjuvant drugs for clinical prevention and treatment of peri-implant inflammation.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.108-114
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• 1999

Surface acoustic wave (SAW) device is very attractive for gas sensor applications because of their small size, low cost, high sensitivity, and good reliability. A dual delay line surface acoustic wave $NO_2$ gas sensors have been designed and fabricated on the $LiTaO_3$ piezoelectric single crystal substrate. The capacitance of the fabricated IDTs was 326.34pF at the frequency of 79.3MHz. The maximum reflection loss of the impedence-matched IDTs was -16.74dB at the frequency of 79.3MHz. The SAW oscillator was constructed and the stable oscillation was obtained by controlling the gain of rf amplifier properly. The oscillation frequency shift of the SAW oscillator to the $NO_2$ gas was 28Hz/ppm.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.322-329
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• 1999

The hydrodynamic theory of dentin sensitivity states that movement of tubular contents or tubular fluid, in either direction of dentinal tubule, causes dentin sensitivity. A corollary of that theory is that anything that can decrease dentinal fluid movement or dentin permeability should decrease dentin sensitivity. A wide variety of physicochemical methods have been used to reduce the permeability and sensitivity of exposed dentin. The purpose of this study was to evaluate the ability of 4 kinds of clinical desensitizing agents(2% NaF, 30% Potassium oxalate, MS Coat$^{(R)}$, Tubulitec system$^{(R)}$) to reduce the rate of fluid flow through dentin in vitro. Sixty coronal dentin discs, 1mm in thickness, were prepared from extracted third molars, free from decay and wear. Dentin discs were treated with 3% EDTA(Tubulicid Plus$^{(R)}$(Dental Therapeutics AB, Sweden)) to remove the smear layer and debris occluding the tubular orifices. After placing the discs in a split chamber device, the rate at which physiologic saline solution could filter across dentin under 150cm $H_2O$ hydrostatic pressure was measured. The occlusal side of the discs were then treated with MS Coat$^{(R)}$, 2% NaF, Tubulitec system$^{(R)}$, and 30% Potassium oxalate, and the filter ratio of the saline solution was measured again. The following conclusions were drawn : 1. Hydraulic conductance which was measured after the application of desensitizing agents was decreased in all the groups(p<0.05). 2. % change of hydraulic conductance was compared but no significant difference was found among the four desensitizing agents(p>0.05). 2% NaF, 30% Potassium oxalate, MS Coat$^{(R)}$ and Tubulitec system$^{(R)}$ decreased the permeability of dentin. It is considered that above four agents can be used in treating the hypersensitive teeth.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.324-327
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• 2002

For a next generation PET that realizes high sensitivity and high resolution, we proposed a design of a depth of interaction detector. A unit of the detector is constructed of four stages rectangular blocks of 2 by 2 Gd$_2$SiO$\sub$5/: Ce (GSO) crystal array optically coupled to position sensitive photomultiplier tube (PS-PMT). The 256ch flat panel PS-PMT is under development by Hamamatsu Photonics K.K., JAPAN. It has large cathode area, 51.7 by 51.7 mm$^2$, and the ratio of the effective area to external size is about 90%. The feature will contribute high packing fraction, accordingly high sensitivity. The 256 anodes are arranged in 16 by 16 at intervals of 3.0 mm. So as to evaluate the detector capability for identifying crystal of interaction, we got positioning image histograms with coupling a 16 by 5 array of GSO crystals, 2.9 by 2.9 by 7.5 mm$^3$, to the PS-PMT by irradiating a gamma ray uniformly from a point source. Flat panel PS-PMT is a new promising device for PET. We need to evaluate it if its performance is sufficiency. The performance was compared to the one with a 16ch PS-PMT.

• Bulletin of the Korean Chemical Society
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• v.28 no.4
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• pp.538-542
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• 2007

Polymeric electrodes for lead ion based on N,N'-bis-thiophen-2-ylmethylene-pyridine-2,6-diamine as an ion carrier were prepared. The membrane electrode (m-3) containing o-NPOE as a plasticizer and 50 mol% additive of ionophore gives an excellent Nernstian response (29.59 mV/decade) and the limit of detection of ?log a (M) = 5.74 to Pb2+ in Pb(NO3)2 solution at room temperature. The prepared electrode provided good sensitivity and outstanding selectivity and response for Pb2+ over a wide variety of other metal ions in pH 7.0 buffer solutions. The good sensitivity and selectivity towards lead ion are attributed to the strong complexation of lead ion to N,N'-bis-thiophen-2-ylmethylene-pyridine-2,6-diamine which has geometrically the proper cavity to coordinate to the ligand.

• Journal of the Korean Ceramic Society
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• v.38 no.7
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• pp.634-638
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• 2001

본 연구에서는 마이크로 내시경용 바이오 센서로 응용하기 위한 Al/PZT/RuO$_2$로 이루어진 마이크로 캔틸레버를 제작하였으며, 공진 특성 및 병원체의 흡착에 따른 공진 특성 그리고 검출 감도(sensitivity)에 미치는 구조적인 영향을 전산모사를 통하여 알아보았다. 길이 100$mu extrm{m}$, 폭 50$\mu\textrm{m}$, 두께 0.3$\mu\textrm{m}$/0.25$\mu\textrm{m}$/0.7$\mu\textrm{m}$ (Al/PZT/RuO$_2$)의 크기의 제작된 마이크로 캔틸레버는 89kHz의 공진주파수를 가지고 있음을 전산모사를 통해 알 수 있었다. 바이오 센서로 응용될 때의 검출 감도는 흡착 질량의 증가에 비례하여 향상되었으며, 5% 이상의 검출 감도를 갖기 위해서는 흡착 질량이 약 5 나노그램 이상이 되어야 함을 확인할 수 있었다. 캔틸레버의 크기를 결정하는 길이, 폭, 두께중 사용 주파수 대역은 길이의 조절을 통하여 결정할 수 있고, 검출 감도의 향상을 위해서는 가능한 한 두께를 얇게 해야 함을 알 수 있었다. 반면에 폭의 변화는 공진주파수나 검출 감도에 거의 영향을 미치지 않았다.

• Analytical Science and Technology
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• v.6 no.3
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• pp.247-254
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• 1993

Strontium can not be determined by conventional dc polarography method since it is very difficult to be reduced at the drop mercury electrode(DME) in aqueous solution. However the analytical sensitivity was improved by adsorptive stripping voltammetry in which electro-reduction of ligand in a complex formed between strontium and o-cresolphthaleoxone was performed. Strontium could be determined in range of $5{\sim}30{\mu}g/L$ concentration. This method was affected by coexistent alkali earth metal ions. Consequently ion exchange separation is recommended to analyze strontium in samples.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.40-41
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• 2007

$SnO_2$ nanowires are used at the nanoscale level for the electrical transduction of the gas interaction with these sensing materials. We report on a study of high sensitivity and fast NOx gas sensor. We focused on improving the response time and refresh time by growth nanowires on the trench structure of Si substrate as air path. To improve refresh time we applied the trench structure with depth of $10\;{\mu}m$ by the inductively coupled plasma reactive ion etching(ICP-RIE). The fabricated device was measured at temperature of $200{\sim}300^{\circ}C$. The sensor exhibit ultra-fast and reversible electrical response (t90% ~4 s for response and ~3 s for recovery).

• Journal of Trauma and Injury
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• v.28 no.3
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• pp.104-107
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• 2015

Purpose: Nitric oxide (NO) is a vasodilator and inhaled NO (iNO) is used in acute respiratory distress syndrome (ARDS) to improve alveolocapillary gas exchange. The mechanism to improve oxygenation is likely to redistribute blood flow from unventilated areas to ventilated areas. Though improvement of oxygenation, iNO therapy has not been shown to improve mortality and considered as only rescue therapy in severe hypoxemia. We conducted the study to investigate an efficacy of iNO in trauma patients with severe hypoxemia. Methods: We reviewed the trauma patients who underwent iNO therapy retrospectively from 2010 to 2014. Degree of hypoxemia was represented as $PaO_2/FiO_2$ ratio (PFR) and the severity of patient was represented with sequential organ failure assessment (SOFA) score. Patients were divided into the survivor group and non-survivor group according to the 28-day mortality. Results: A total of 20 patients were enrolled. The mortality of 28-day was 40%. There were no significant differences between survivor and non-survivor group in age, sex, severity of injury, PFR and SOFA score. There was significant difference in initiation time of iNO after injury (p=0.047). Maximum combinations of sensitivity and specificity for timing of iNO therapy were observed using cut-off of 3-day after injury with a sensitivity of 88% and specificity of 75%. Conclusion: Though iNO therapy does not influence the mortality, iNO therapy may decrease the mortality caused by respiratory failure in the early phase of trauma.

• Journal of Sensor Science and Technology
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• v.1 no.2
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• pp.131-145
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• 1992

This paper has been described a process technology for the fabrication of Si-on-insulator(SOI) transducers and circuits. The technology utilizes Si-wafer direct bonding(SDB) and mechanical-chemical(M-C) local polishing to create a SOI structure with a high-qualify, uniformly thin layer of single-crystal Si. The electrical and piezoresistive properties of the resultant thin SOI films have been investigated by SOI MOSFET's and cantilever beams, and confirmed comparable to those of bulk Si. Two kinds of pressure transducers using a SOI structure have been proposed. The shifts in sensitivity and offset voltage of the implemented pressure transducers using interfacial $SiO_{2}$ films as the dielectrical isolation layer of piezoresistors were less than -0.2% and +0.15%, respectively, in the temperature range from $-20^{\circ}C$ to $+350^{\circ}C$. In the case of pressure transducers using interfacial $SiO_{2}$ films as an etch-stop layer during the fabrication of thin Si membranes, the pressure sensitivity variation can be controlled to within a standard deviation of ${\pm}2.3%$ from wafer to wafer. From these results, the developed SDB process and the resultant SOI films will offer significant advantages in the fabrication of integrated microtransducers and circuits.