• Journal of Microbiology and Biotechnology
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• 제27권9호
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• pp.1609-1616
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• 2017

The complex roles of cell surface modification in the biofilm formation of Campylobacter jejuni, a major cause of worldwide foodborne diarrheal disease, are poorly understood. In a screen of mutants from random transposon mutagenesis, an insertional mutation in the eptC gene (cj0256) resulted in a significant decrease in C. jejuni NCTC11168 biofilm formation (<20%) on major food contact surfaces, such as polystyrene and borosilicate glass, when compared with wild-type cells (p < 0.05). In C. jejuni strain 81-176, the protein encoded by eptC modified cell surface structures, such as lipid A, the inner core of lipooligosaccharide, and the flagellar rod protein (FlgG), by attaching phosphoethanolamine. To assess the role of eptC in C. jejuni NCTC11168, adherence and motility tests were performed. In adhesion assays with glass surfaces, the eptC mutant exhibited a $0.77log\;CFU/cm^2$ decrease in adherence compared with wild-type cells during the initial 2 h of the assay (p < 0.05). These results support the hypothesis that the modification of cell surface structures by eptC affects the initial adherence in biofilm formation of C. jejuni NCTC11168. In motility tests, the eptC mutant demonstrated reduced motility when compared with wild-type cells, but wild-type cells with the transposon inserted in a gene irrelevant to biofilm formation (cj1111c) also exhibited decreased motility to a similar extent as the eptC mutant. This suggests that although eptC affects motility, it does not significantly affect biofilm formation. This study demonstrates that eptC is essential for initial adherence, and plays a significant role in the biofilm formation of C. jejuni NCTC11168.

• Environmental Engineering Research
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• 제19권3호
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• pp.255-259
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• 2014

In this research, we compared the COD removal efficiencies of titanium dioxide ($TiO_2$) thin films coated on the surfaces of borosilicate glass that prepared by three different numbers of coating layer; i) 3 layers ii) 4 layers and iii) 5 layers by sol-gel method. All of the prepared $TiO_2$ thin films consisted of pure anatase crystalline structure with grain sizes in the range 20-250 nm. The calculated optical band gaps of the $TiO_2$ thin films were 3.24. The total apparent surface area per total weight of $TiO_2$ thin films were 4.74, 3.86 and $2.79m^2g^{-1}$ for 3, 4 and 5 layers coating, respectively. The kinetics of the photodegradation reactions of COD under UVA light source were described by the Langmuir-Hinshelwood (L-H) kinetic model. The specific rates of the photodegradation of $TiO_2$ thin films at 3 layers coating was $1.40{\times}10^{-4}min^{-1}mW^{-1}$, while for the 4 layers coating and the 5 layers coating were $1.50{\times}10^{-4}$ and $4.60{\times}10^{-4}min^{-1}mW^{-1}$, respectively. The photocatalytic performance of COD degradation was higher with smaller grain size, higher surface area and narrow optical band gaps. Moreover, the numbers of coating layer on substrate also have great influence for kinetic of COD removal.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.245-245
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• 2007

본 연구는 $Bi_2O_3$, ZnO 및 $Nb_2O_5$로 이루어진 두 가지의 $Bi_2(Zn_{1/3}Nb_{2/3})_2O_7$와 $(Bi_{1.5}Zn_{0.5})(Zn_{0.5}Nb_{1.5})O_7$ pyrochlore를 제조한 후, ZBS 및 BZBS 유리를 각각 첨가하여 저온 소결 및 마이크로파 유전 특성을 고찰하였다. 두 가지의 pyrochlore에 대하여 하소 온도에 따른 상 합성 유무를 고찰한 결과 $900^{\circ}C$에서 단일 상을 갖는 pyrochlore를 제조할 수 있었다. 두 가지의 pyrochlore에 ZnO-rich ZBS 유리와 $Bi_2O_3$-rich BZBS 유리를 3, 5 wt%로 첨가한 후 $800{\sim}950^{\circ}C$에서 소결한 결과 ZBS 및 BZBS 유리를 5wt%를 첨가하였을 때 $900^{\circ}C$에서 소결이 가능하였다. 또한 마이크로파 유전 특성을 고찰한 결과, $(Bi_{1.5}Zn_{0.5})(Zn_{0.5}Nb_{1.5})O_7$의 pyrochlore는 고주파에서 유전 특성 측정이 되지 않았다. $Bi_2(Zn_{1/3}Nb_{2/3})_2O_7$의 pyrochlore의 경우 5 wt% ZBS 및 BZBS 유리를 첨가하여 $900^{\circ}C$에서 소결한 시편의 마이크로파 유전 특성은 ${\varepsilon}_r$= 62.8~68.3, $Q{\times}f$ value= 3,500~2,700 GHz을 나타내었다.

• KSTLE International Journal
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• 제6권2호
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• pp.33-38
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• 2005

Submicron-scale patterns made of polymethyl methacrylate (PMMA) were fabricated on silicon-wafer using a capillarity-directed soft lithographic technique. Polyurethane acrylate (PUA) stamps (Master molds) were used to fabricate the patterns. Patterns with three different aspect ratios were fabricated by varying the holding time. The patterns fabricated were the negative replica of the master mold. The patterns so obtained were investigated for their adhesion and friction properties at nano-scale using AFM. Friction tests were conducted in the range of 0-80 nN. Glass (Borosilicate) balls of diameter 1.25 mm mounted on cantilever (Contact Mode type NPS) were used as tips. Further, micro-friction tests were performed using a ball-on-flat type micro-tribe tester, under reciprocating motion, using a soda lime ball (1 mm diameter) under a normal load of 3,000 mN. All experiments were conducted at ambient temperature ($24{\pm}1^{\circ}C$) and relative humidity ($45{\pm}5\%$). Results showed that the patterned samples exhibited superior tribological properties when compared to the silicon wafer and non-patterned sample (PMMA thin film) both at the nano and micro-scales, owing to their increased hydrophobicity and reduced real area of contact. In the case of patterns it was observed that their morphology (shape factor and size factor) was decisive in defining the real area of contact.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• Nuclear Engineering and Technology
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• 제56권8호
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• pp.3378-3384
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• 2024

Investigations were conducted on the addition of barium's impact on the radiation shielding and physical attributes of five different glasses, designated S1-S5, with varying BaO contents. Using two point sources namely Co⁶⁰ and Cs¹³⁷ along with a scintillation detector [NaI(TL)], experimental measurements were made of the shielding parameters of γ-rays, namely the effective atomic number (Z_eff), electron density (N_el), half-value layer (HVL), linear attenuation coefficient (μ), mass attenuation coefficient (μ_m), mean free path (λ), and radiation protection effectiveness at the energies of 0.664, 1.177, and 1.334 MeV, and comparisons made with recently considered glasses as well as frequently employed materials for γ-ray shielding. The results show that the examined glasses' physical and radiation shielding qualities are improved by the addition of BaO. The μ values increased from 0.245 to 0.275 cm^-1 (0.662 MeV), from 0.174 to 0.198 cm^-1 (1.173 MeV), and from 0.161 to 0.189 (1.332 MeV). The observed values of HVL decreased from 2.83, 3.98, and 4.3 cm to 2.5, 3.5, and 3.62 cm at 0.662, 1.173, and 1.332 MeV, respectively, for the samples S1 and S5. In addition, the S5 glass sample was determined to have the best protection against photon among all the samples that were evaluated, as well as against recently considered glasses and those materials often utilized for gamma-ray shielding purposes.

• 마이크로전자및패키징학회지
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• 제11권3호
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• pp.17-22
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• 2004

[ $CaZrO_3$ ]세라믹스에 대하여 $CaTiO_3$세라믹스의 첨가량 변동에 따른 마이크로파 유전특성을 조사하였다. 또한 중유전율 LTCC 기능성 기판으로 활용하기 위하여 저융점의 유리 프리트를 첨가하여 $CaZrO_3-CaTiO_3$ 세라믹스의 저온 소결 거동과 마이크로파 유전특성을 평가하였다. 저온 소결 조제로 사용된 저응점의 유리 프리트를 $10-20 wt\%$ 범위로 첨가함으로서 $CaZrO_3-CaTiO_3$ 세라믹스의 소결온도를 $1450^{\circ}C$에서 $900^{\circ}C$이하로 낮출 수 있었다. 음의 온도계수를 갖는 $CaZrO_3$ 및 유리프리트에 대하여 양의 온도계수를 갖는 $CaTiO_3$ 세라믹스의 분율을 적정히 제어함으로서 제로의 온도계수를 구현할 수 있었다. $CaZrO_3-CaTiO_3$ 세라믹스에 저온 소결용 유리 프리트를 $15 wt\%$ 첨가하여 $875^{\circ}C$에서 소결한 경우. 유전율(k) 23, 품질계수(Q${\times}$f) 2500, 공진 주파수 온도계수$(T_f) -3 ppm/^{\circ}C$의 매우 양호한 마이크로파 유전특성을 나타내었다.

• 방사성폐기물학회지
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• 제3권1호
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• pp.57-65
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• 2005

본 연구는 사용 후 핵연료의 금속전환 공정에서 발생되는 폐용융염을 고형화하는 방법으로 GRSS(Gel-Route Slabilization/Solidifcation)개념을 이용한 전처 리법을 제안하였다. Sodium silicate와 H3p04로 구성된 물질계에서는 SiO$_2$에 의해 형성되는 반응모듈 내에서 휘발성 핵종은 열적으로 안정한 화합물로 전환된다. 얻어진 생성물은 붕규산 유리매질과의 반응을 통하여 Li는 Li$_{3}$PO$\_4$ 형태로 유지되며 Cs 및 Sr은 유리매질내에 포용될 수 있다. 또한 sodium silicate, H$_{3}$PO$_4$ 및 ZrCl$_4$로 이루어진 물질계를 이용하여 내구성이 우수한 WZP 세라믹 고화매질을 합성하였다. $700^{circ}C$이상에서 NZP구조가 형성되며, Cs가 Li보다 우선하여 NZP구조를 형성하였다. 이상의 결과로부터, GRSS를 이용한 폐용융염의 전처리는 단순한 공정과 열적 안정성을 통하여 검증된 고화매질로 고형화가 가능토록하는 유효한 접근법이라 할 수 있으며, 수화학적 안정성의 검증을 통하여 ANL의 제올라이트를 이용한 고화법에 대한 대안이 될 것으로 기대된다.

• 대한치과보철학회지
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• 제38권5호
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• pp.595-605
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• 2000

Dental ceramics have good aesthetics, biocompatibility, low thermal conductivity, abrasion resistance, and color stability. However poor resistance to fracture and shrinkage during firing process have been limiting factors in their use, particularly in multiunit ceramic restorations. A new method for making all-ceramic crowns that have high strength and low processing shrinkage has been developed and is referred to as the Vita In-Ceram method. This study was performed to investigate the effect of $CeO_2$ addition in borosilicate glasses on the strength of alumina-glass composites. Porous alumina compacts were prepared by slip casting and sintered at $1,100^{\circ}C$ for 2 hours. Dense composites were made by infiltration of molten glass into partially sintered alumina at $1,140^{\circ}C$ for 4 hours. Specimens were polished sequentially from #800 to #2000 diamond disk. and the final surface finishing on the tensile side was received an additional polishing sequence through $1{\mu}m$ diamond paste. Biaxial flexure test was conducted by using ball-on-three-ball method at a crosshead speed of 0.5mm/min. To examine the microstructural aspect of crack propagation in the alumina-glass composites, Vickers-produced indentation crack was made on the tensile surface at a load of 98.0 N and dwell time of 15 sec, and the radial crack patterns were examined by an optical microscope and a scanning electron microscope. The results obtained were summarized as follows; 1. The porosity rates of partially sintered alumina decreased with the rising of firing temperature. 2. The maximum biaxial flexure strength of 423.5MPa in alumina-glass composites was obtained with an addition of 3 mol% $CeO_2$ in glass composition and strength values showed the aspect of decrease with the increase of $CeO_2$ content. 3 The biaxial flexure strength values of alumina-glass composites were decreased with rising the firing temperature. 4. Observation of the fracture surfaces of alumina-glass composites indicated that the enhancement of strength in alumina-glass composites was due to the frictional or geometrical inter-locking of rough fracture surfaces and ligamentary bridging by intact islands of materials left behind the fracture front.

• 한국결정성장학회지
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• 제17권2호
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• pp.82-89
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• 2007

붕규산염계 유리에 EAF Dust를 $40{\sim}80wt%$ 첨가하고 후 용융하여 유리를 제조한 후 $700^{\circ}C$/10hr으로 열처리하여 결정화유리 시편을 합성하였다. FT-IR, SEM, 그리고 EDS 분석을 통하여 조성 및 열처리 조건에 따른 시편내 결정상 및 결합상태 변화를 관찰하고, 이를 TCLP(Toxic Characterization Leaching Procedure) 실험에서 얻은 결과와 연계시켜 시편의 화학적 내구성을 연구하였다. 유리에 더스트 첨가량이 증가함에 따라 FT-IR 스펙트럼 상의 가교산소 진동피크($1050{\sim}1060cm^{-1}$)와 비가교산소 진동피크($960cm^{-1}$)가 합쳐진 넓은 피크($1000cm^{-1}$ 부근)가 저파수쪽으로 이동하였다. 동시에 boroxol ring의 $B_2O_3$ 구조가 tetrhedral-, trigonal- 그리고 di-borate로 변화되는 것을 확인하였다. 결정화유리 시편에서 Fe-O 피크가 확인되었으며 이는 spinel이 생성되었다는 XRD 결과와 일치하였다. TCLP를 행한 유리시편의 표면은 균열이 심하였으나 결정화유리는 큰 변화가 없어, 결정상 생성이 화학적 내구성을 향상시킴을 확인하였다. Fe의 용출량은 더스트가 80wt% 첨가된 결정화유리의 경우, 유리시편에 비하여 1/15로 감소하였다. Zn은 더스트 첨가량이 70wt% 이하인 결정화유리에서 용출량이 유리에 비해 높았으나 80wt% 이상 시편에서는 유리보다 감소하였고 이는 willemite 생성과 연관이 있는 것으로 사료된다.