• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.597-601
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• 2013

In this study, we present simple microfluidic approach for the synthesis of monodisperse microcapsules by using droplet-based system. We generate double emulsion through single step in the microfluidic device having single junction while conventional approaches are limited in surface treatment for the generation of double emulsion. First, we have injected disperse fluid containing FC-77 oil and photocurable ethoxylated trimethylolpropane triacrylate (ETPTA) and water containing 3 wt% poly(vinyl alcohol) (PVA) as continuous phase into microfluidic device. Under the condition, we easily generate double emulsion with high monodispersity by using flow focusing. The double emulsion droplets are transformed into microcapsules under the UV irradiation via photopolymerization. In addition, we control thickness of double emulsion's shell by controlling flow rate of ETPTA. We also show that the size of double emulsions can be controlled by manipulation of flow rate of continuous phase. Furthermore, we synthesize microcapsules encapsulating various materials for the application of drug delivery systems.

• The korean journal of orthodontics
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• v.43 no.1
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• pp.23-28
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• 2013

Objective: The purpose of this study was to evaluate the effect of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) on the shear bond strength (SBS) of brackets bonded to non-demineralized teeth with either phosphoric acid etching or self-etching primer. Methods: Sixty human premolars were randomly assigned to 1 of 4 treatment groups (n = 15 each): phosphoric acid etching (group 1); self-etching primer (group 2); CPP-ACP for 2 weeks + phosphoric acid etching (group 3), and CPP-ACP for 2 weeks + self-etching primer (group 4). After bonding of the maxillary premolar metal brackets, specimens were subjected to shear forces in a testing machine. Scanning electron microscopy was used to observe etching patterns on the enamel surfaces of all teeth. A 2-way analysis of variance was used to test for effects of CPP-ACP and etching system on SBS. Results: Significantly higher mean SBSs were observed in groups subjected to phosphoric acid etching (i.e., groups 1 and 3; p < 0.05). On the other hand, SBSs did not appear to be influenced by CPP-ACP (i.e., groups 3 and 4; p > 0.05). We observed a uniform and clear etched pattern on the enamel surface of the phosphoric acid etching groups. Conclusions: CPP-ACP does not significantly affect the SBS of orthodontic brackets bonded to non-demineralized teeth, regardless of which adhesive method is used to bond the brackets.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.225-229
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• 2015

This study was performed to investigate crystal structure of cubic spinel-type monophase oxide composed of the Mn-Co-Ni ternary system. Starting material was prepared by mixing Mn, Co, Ni oxides then evaporation to dryness. The XRD patterns were analyzed by in-situ XRD as increasing temperature from room temperature to $1400^{\circ}C$ in air atmosphere. The cubic spinel phase was existed in a temperature range from $900^{\circ}C$. However, separation of NiO phase was detected from $1300^{\circ}C$, which was the origin of deterioration in the crytallinity. The surface morphology of the manufactured NTC thermistors were analyzed by FE-SEM for comparison of good and bad samples.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.6-12
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• 2014

In the present work, $WO_3$ and $WO_3-TiO_2$ were prepared by the chemical deposition method. Structural variations, surface state and elemental compositions were investigated for preparation of $WO_3-TiO_2$ sonocatalyst. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM) were employed for characterization of these new photocatalysts. A rhodamine B (Rh.B) solution under ultrasonic irradiation was used to determine the catalytic activity. Excellent catalytic degradation of an Rh.B solution was observed using the $WO_3-TiO_2$ composites under ultrasonic irradiation. Sonocatalytic degradation is a novel technology of treating wastewater. During the ultrasonic treatment of aqueous solutions sonoluminescence, cavitaties and "hot spot" occurred, leading to the dissociation of water molecules. In case of a $WO_3$ coupled system, a semiconductor coupled with two components has a beneficial role in improving charge separation and enhancing $TiO_2$ response to ultrasonic radiations. In case of the addition of $WO_3$ as new matter, the excited electrons from the $WO_3$ particles are quickly transferred to $TiO_2$ particle, as the conduction band of $WO_3$ is 0.74 eV which is -0.5 eV more than that of $TiO_2$. This transfer of charge should enhance the oxidation of the adsorbed organic substrate. The result shows that the photocatalytic performance of $TiO_2$ nanoparticles was improved by loading $WO_3$.

• KSBB Journal
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• v.15 no.1
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• pp.42-48
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• 2000

Urokinase (UK), a thrombolytic enzyme used to clear catheters obstructed by blood clots, can be also used industrially in the recombinant protein purification system to cleave a fusion protein linked with a certain fragment of GST. We have immobilized UK by covalent attachment to activated Sepharose 6B-Cl gels and evaluated its performance to cleave a fusion protein of hGH and GST. The Sepharose gels were activated by etherification with glycidol (2,3-epoxypropanol) and further oxidized with periodate resulting in glyceryl-Sepharose gels. After the activation treatment, surface density of the aldehyde groups was 7-30 $\mu$mol-aldehde/mL-gel. Immobilization yield was higher than 99% at high pH (10.5), and the immobilized UK maintained ca. 80% specific activity of the soluble UK. In a column reaction the cleavage yield heavily depended on the feed rate, and it was nearly 86% of that from soluble UK. And the immobilized UK was successfully regenerated by unfolding and refolding with 6M GuHCl. After cleavaging reaction, the monomeric hGH was purified by using expanded bed adsorption chromatography.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.291-297
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• 1999

The plasma etching of tungsten thin films has been studied with $SF_6$ gas in RIE system. The etch rate of ${\alpha}$-phase W film with $SF_6$ gas plasma has been showed to depend strongly on process parameters ($SF_6$, $SF_6-N_2$ gas). Effect of $N_2$ addition and etching selectivity between W film and photoresist have also been studied in detail. Etching profiles between W film and photoresist were investigated by SEM. The compounds on W surface after $SF_6-N_2$ gas plasma treatment were examined by XPS and the concentration of F ions was detected by OES during plasma on.

• Journal of Embryo Transfer
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• v.32 no.3
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• pp.183-192
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• 2017

The mammary gland tumor (MGT) is the most common neoplasia in intact female dogs. Of these, 50% are malignant and metastasis to the other sites are often occurred. Therefore, it is very important for decision of treatment plan and prognosis to differentiate benign tumor from malignancies. Calcification of MGT is a very important imaging finding. The purpose of this study was to investigate the radiological and computed tomographic images of the MGT and the morphology and distribution of calcifications in the MGT using the Breast Imaging Reporting and Data System classification. A total of 42 dogs with MGT were included in this study. The dogs were divided into two groups into benign and malignant groups based upon histologic or cytologic results. The appearance of calcification in the tumor on radiographs and CT images was analyzed for the HU value of pre- and post-contrast injection, margin, surface, and shape of the tumor and the lymph node abnormalities. On radiographs, the positive predictive value of malignant and benign tumors was 72.72 and 85.71%, respectively. On CT examinations, the positive predictive value of malignant and benign tumors was the same value of 83.33%. The maximum diameter of the tumor and the presence of abnormal lymph nodes on CT images showed a strong correlation with malignancies. Therefore, it is thought that radiographs and CT provide useful information for evaluating MGT in dogs.

• The Journal of Engineering Research
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• v.1 no.1
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• pp.15-22
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• 1997

The crystallization behaviours of cordierite gel derived from sol-gel method and glass prepared from conventional melting method with or without $TiO_2$ as nucleants are compared. The densification temperature of gel is $810^{\circ}C$ and its chemical structure identified by IR analysis is same as that of glass melted by conventional method. The beginning crystallization temperature of gel is $965^{\circ}C$ lower than that of melted glass with 10wt% $TiO_2$, which is $978^{\circ}C$. The crystalline phases developed from gel during heat treatment are identified as spinel, $\beta$-quartz solid solution and $\alpha$-cordierite crystal and crystalline phases in case of glass are (Mg,Al)TiOn and $\beta$-quartz solid solution and $\alpha$-cordierite crystal, respectively. The crystallization in melted glass with nucleants occurs through bulk crystallization and in case of that without nucleants surface crystallization occurs, while the crystallization in gel is internal crystallization from interface between particles formed after densification.

• Korean Journal of Materials Research
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• v.31 no.9
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• pp.502-510
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• 2021

Hierarchically porous carbon materials with high nitrogen functionalities are extensively studied as high-performance supercapacitor electrode materials. In this study, nitrogen-doped porous carbon textile (N-PCT) with hierarchical pore structures is prepared as an electrode material for supercapacitors from a waste cotton T-shirt (WCT). Porous carbon textile (PCT) is first prepared from WCT by two-step heat treatment of stabilization and carbonization. The PCT is then nitrogen-doped with urea at various concentrations. The obtained N-PCT is found to have multi-modal pore structures with a high specific surface area of 1,299 m² g^-1 and large total pore volume of 1.01 cm³ g^-1. The N-PCT-based electrode shows excellent electrochemical performance in a 3-electrode system, such as a specific capacitance of 235 F g^-1 at 1 A g^-1, excellent cycling stability of 100 % at 5 A g^-1 after 1,000 cycles, and a power density of 2,500 W kg^-1 at an energy density of 3.593 Wh kg^-1. Thus, the prepared N-PCT can be used as an electrode material for supercapacitors.

• Microbiology and Biotechnology Letters
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• v.49 no.2
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• pp.148-156
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• 2021

Single-chain antibodies against epidermal growth factor receptor variant III (EGFRvIII) are potentially promising agents for developing antibody-based cancer treatment strategies. We described in our previous study the successful expression of an anti-EGFRvIII scFv antibody in Escherichia coli. However, we could also observe the formation of insoluble aggregates in the periplasmic space, limiting the production yield of the active product. In the present study, we investigated the mechanisms by which growth conditions could affect the expression of the soluble anti-EGFRvIII scFv antibody in small-scale E. coli NiCo21(DE3) cultures, attempting to maximize production. The secreted scFv molecules were purified using Ni-NTA magnetic beads and protein characterization was performed using SDS-PAGE and western blot analyses. We used the ImageJ software for protein quantification and determined the antigen-binding activity of the scFv antibody against the EGFRvIII protein. Our results showed that the highest percentage of soluble scFv expression could be achieved under culture conditions that combined low IPTG concentration (0.1 mM), low growth temperature (18℃), and large culture dish surface area. We found moderate-yield soluble scFv production in the culture medium after lactose-mediated induction, which was also beneficial for downstream protein processing. These findings were confirmed by conducting western blot analysis, indicating that the soluble, approximately 30-kDa scFv molecule was localized in the periplasm and the extracellular space. Moreover, the antigen-binding assay confirmed the scFv affinity against the EGFRvIII antigen. In conclusion, our study reveals that low-speed protein expression is preferable to obtain more soluble anti-EGFRvIII scFv protein in an E. coli expression system.