• Restorative Dentistry and Endodontics
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• 제14권1호
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• pp.7-24
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• 1989

The purpose of the study was to evaluate the cytotoxic effects of polycarboxylate cements and zinc phosphate cements in vitro. Human fibroblasts were cultured in ${\alpha}$-MEM, and each cement was manually mixed and filled in glass ring cylinder (8${\times}$8mm in diameter, in height.) Cement filled cylinders were placed in the center of the dish (35mm in diameter) containing 3ml of ${\alpha}$-MEM. Millipore filters to simulate dentinal barrier were also placed between the cylinder and the dish, then stored in 5% $CO_2$ containing chamber for 1 and 2 weeks at the temperature of $36.6^{\circ}C$. The results of the experiments were analyzed by counting the cells in the period of one week and two weeks respectively, and were assessed by calculating the cell multiplication rate and the relative growth rate. The experimental groups and the control group were compared. The results of the study were summarized as follows. 1. Durelone brand of the polycarboxylate cements showed marked cytotoxicity after one week, but after two weeks the toxicity decreased remarkably. Poly-F brand exhibited moderate cytotoxicity after one week, but after two weeks the toxicity slightly decreased. HY-BOND brand was weakly cytotoxic after one week, but after two weeks the toxicity became significant. 2. The cytotoxicity of the zinc phosphate cements was negligible after one week, but after two weeks Lee Smith brand revealed considerable cytotoxicity. 3. In general, the zinc phosphate cements were less cytotoxic than the polycarboxylate cements.

• 한국미생물·생명공학회지
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• 제17권3호
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• pp.193-197
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• 1989

Spanner chain의 탄소수가 2,4 또는 6개의 alkylene diisothiocyanate를 합성 후 cefadroxil-2DMF와 반응시켜 spanner chain의 탄소수 2, 4 또는 6개로 연결되어 있고 양쪽에 thioureido group과 $\beta$-lactam ring을 가진 bivalent ligand 구조의 alkylene bisdithioureido $\beta$-lactam 유도체를 합성하고 그 화합물들의 항균작용에 대하여 연구하였다. 그 유도체의 I식 화합물은 $C_{36}$H$_{38}$N$_{8}$O$_{10}$S$_4$, II식 화합물은 $C_{38}$H$_{42}$N$_{8}$O$_{10}$S$_4$, III식 화합물은 $C_{40}$H$_{46}$N$_{8}$O$_{10}$S$_4$의 분자식이다. $\beta$-lactam 감수성 균주에 대한 항균력은 spnner chain의 탄소수가 많을수록 감소하였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.249-254
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• 1997

ABA-type block copolymers composed of poly(L-leucine)(PLL) as the A component and poly(ethylene glycol)(PEG) as the B component were synthesized by ring-opening polymerization of L-leucine N-carboxyanhydride initiated by primary amino group located at both ends of PEG chain. A silver sulfadiazine(AgSD)-impregnated wound dressing of sponge-type was prepared by the lyophilization method. Morphological structure of this wound dressing obtained by scanning electron microscopy(SEM) was composed of a dense skin layer and a macroporous inner sponge layer. Equilibrium water content(EWC) of wound dressing was above 10%. It increased with an increased of PEO content in the block copolymer due to the hydrophilicity of PEO. AgSD release from AgSD- impregnated wound dressing in PBS buffer(pH=7.4) was dependent on PEG composition in the block copolymer. Therefore, EWC and release of AgSD can be control by PEG composition. Antibacterial capacity of AgSD-impregnated wound dressing was examined in agar plate against Pseudmonas aeruginosa and Stapplococus aruous. Cytotoxicity of the wound dressing was evaluated by studing mouse skin fibroblast(L929). From the behavior of antimicrobial releasing and the investigation of the suppression of bacterial proliferation, it was supposed that the wound dressing containing antibiotics could protect the wound surfaces from bacterial invasion to suppress the bacterial proliferation effectively. In cytotoxicity observation, cellular damage was reduced by the control led released of AgSD from the LEL sponge matrix of AgSD-medicated wound dressing. In vivo test, granulous tissue formation and wound contraction or the AgSD and DHEA impregnated wound dressing were aster than any other groups.

• Journal of Biosystems Engineering
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• 제39권1호
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• pp.21-33
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• 2014

Background: Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO's) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.

• 대한화학회지
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• 제24권1호
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• pp.25-33
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• 1980

토양에서 분리한 Pseudomonadaceae 속 박테리아로부터 pyrocatechase를 추출, 분리 정제하였으며, 이 효소의 특성을 검토한 결과 pyrocatechase는 catechol에 대하여 기질 특이성을 보여줌을 알았다. 효소 활성도의 최적조건은 pH 7∼10 부근과 온도 $35^{\circ}C$임을 알았으며, catechol에 대한 $K_m$값은 $1.9{\times}10^{-6}M$ 로 얻어졌다. 기질 유도체에 의한 효소 저해 실험결과 벤젠 고리의 ortho 위치에 두개의 수산기는 효소-기질간의 결합반응에 참여될 것이라고 추측했다. 기타 SH-잔기와 작용하는 화합물 또는 중금속 이온등의 첨가에 따른 효소 활성도의 저해 효과를 검토 하였으며, 효소 활성부위에 대하여도 검토해 보았다.

• 대한화학회지
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• 제32권6호
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• pp.581-587
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• 1988

EtOH-$H_2O, Acetone-H_2O$의 이성분 혼합용매계에서 치환 브롬화벤질류의 가용매분해반응을 $25^{\circ}C$ 와 $45^{\circ}C$에서 전기전도도법으로 연구하였다. 반응속도상수는 벤젠고리에 전자주게 치환기가 도입되거나, 물함량이 증가할수록 컸으며 전자받게 치환기로 바뀜에 따라 용매의 이온화능, Y에 대한 치환 브롬화벤젠류의 가용매분해반응의 감도, m은 연속적으로 감소하였고, 반면에 친핵도에 대한 감도는 증가하였다. 이 결과로 부터 전자주게에서 전자받게로 치환기가 변함에 따라 전이상태는 loose한 결합상태에서 tight한 상태로 변함을 알 수 있었다. 이 결과는 PES 모형과 양자역학적 해석 방법에 의한 전이상태 구조변화의 논의와도 일치하였다.

• 한국컴퓨터정보학회논문지
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• 제16권8호
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• pp.67-76
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• 2011

본 논문은 초등학교 정규교과에서 로봇활용수업의 효과 분석을 위해 교과별 목표 달성에 적합한 로봇 및 PC연동 어플리케이션을 개발하고 수업적용을 통해 학습자의 반응을 살펴보았다. 연구결과 사후 이미지 프로파일의 대부분의 항목에서 로봇에 대한 긍정적인 응답이 나타났으며 특히, '이론적-실천적', '비협동적-협동적' 두 항목에서 유의미한 차이가 발견되었다(p<.05). 또한 학습자가 그린 사후 이미지 분석 결과 사전에 비해 구체적인 학습상황과 연계된 로봇 이미지가 형성된 것으로 나타났다. “로봇활용수업”에 대한 학습자 인식을 살펴보기 위한 면담결과 로봇의 직 간접 체험 모두 긍정적인 학습참여를 유도하고 실제적 학습경험을 제공하였다고 나타내었다. 또한 로봇활용수업을 통해 모둠 구성원과 자연스러운 협력활동이 관찰되었고 학생들도 동료와 협력활동에 대해 긍정적으로 인식하고 있었다. 이와 같은 결과는 로봇활용 교육이 새로운 학습 패러다임으로서의 가능성을 보여준다고 볼 수 있다.

• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.3052-3058
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• 2014

In this article, we have designed and synthesized a novel donor-${\pi}$-acceptor (D-${\pi}$-A) type porphyrin-based sensitizer (denoted UI-5), in which a carboxyl anchoring group and a 9,9-dimethyl fluorene were introduced at the meso-positions of porphyrin ring via phenylethynyl and ethynyl bridging units, respectively. Long alkoxy chains in ortho-positions of the phenyls were supposed to reduce the degree of dye aggregation, which tends to affect electron injection yield in a photovoltaic cell. The cyclic voltammetry was employed to determine the band gap of UI-5 to be 1.41 eV based on the HOMO and LUMO energy levels, which were estimated by the onset oxidation and reduction potentials. The incident monochromatic photon-to-current conversion efficiency of the UI-5 DSSC assembled with double-layer (20 nm-sized $TiO_2$/400 nm-sized $TiO_2$) film electrodes appeared lower upon overall ranges of the excitation wavelengths, but exhibited a higher value over the NIR ranges (${\lambda}$ = 650-700 nm) compared to the common reference sensitizer N719. The UI-5-sensitized cell yielded a relatively poor device performance with an overall conversion efficiency of 0.74% with a short circuit photocurrent density of $3.05mA/cm^2$, an open circuit voltage of 0.54 mV and a fill factor of 0.44 under the standard global air mass (AM 1.5) solar conditions. However, our report about the synthesis and the photovoltaic characteristics of a porphyrin-based sensitizer in a D-${\pi}$-A structure demonstrated a significant complex relationship between the sensitizer structure and the cell performance.

• 한국결정학회지
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• 제1권1호
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• pp.49-56
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• 1990

Albite-anorthite 계의 조성을 갖는 유리를 결정화 시키면 사장석의 공융상 외에도 육방정과 사방정의 두불안정상이 정출되며 이들의 결정화도를 X-선 회절에 의하여 측정하였다. 사방정의 불안 정상은 albite 70∼80%를 갖는 조성에서 가장 많이 결정화가 일어나며 육방정은 anorthite가 주로된 조성영역에서 결정화가 많이 일어났다. 불안정상 중에서 사방정의 걱정구조를 정산하기 위하여 Nao7 Cao.3 Al13 Si27 O7의 조성을 갖는 단결정편을 분리하여 X-선 회절강도를 측정하였다. 이 결정의 격자상수는 a=8.237(1)A. b=8.644(1)A c=4.818(1)A이며 공간군은 P22,2,이다. 최종정산한 구조의 R값은 0.040이었고 Rw는 0.028이었다. 한위치를 7 3의 비율로 통계적으로 차지하고 있는 Na와 Ca의 위치는 충진율 0.5를 가지며 두 위치로 분열되어 있다. Si가 A1원자는 육환구조내에서는 통계적으로 분포되어 있고 육환층과 층사이에서는 규칙적인 배열을 보이고 있다.

• 한국결정학회지
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• 제13권3_4호
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• pp.158-164
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• 2002

Tetrahomodioxa p-phenylcalix(4)arene dihexylether (C/sub 66/H/sub 68/O/sub 6/)를 합성하여 분자 및 결정 구조를 X-선 회절법으로 연구하였다. p-Phenylphenol의 탈수, 고리화 반응으로 만든 tetrahomodioxa p-phenylcalix(4)arene을 DMF에서 NaH와 hexyl iodide를 환류시켜 합성하였다. 결정은 사방정계이고 공간군은 P2₁2₁2₁, a =9.764(2), b = 16.167(2), c = 32.994(3) Å, V=5208(1) ų, Z= 4, Dc=1.221 gcm/sup -3/이다. 직접법으로 구조를 해석하였으며, 최소자승법으로 정밀화하여 최종 신뢰도 R 값은 2009개의 회절 반점에 대해 0.070 이었다. 이 분자는 마주 보고 있는 phenyl group 두 쌍이 거의 평행을 이루며, C-1,2-alternate conformation이고, lower rim의 1,3 위치에 hexyl 기가 치환된 비대칭 homooxacalixarene이다.