• KSTLE International Journal
• /
• 제6권2호
• /
• pp.39-44
• /
• 2005

Friction and wear properties of the Boron carbide ($B_{4}C$) coating 100 nm thickness were studied under various relative humidity (RH). The boron carbide film was deposited on silicon substrate by DC magnetron sputtering method using $B_{4}C$ target with a mixture of Ar and methane ($CH_4$) as precursor gas. Friction tests were performed using a reciprocation type friction tester at ambient environment. Steel balls of 3 mm in diameter were used as counter-specimen. The results indicated that relative humidity strongly affected the tribological properties of boron carbide coating. Friction coefficient decreased from 0.42 to 0.09 as the relative humidity increased from $5\%$ to $85\%$. Confocal microscopy was used to observe worn surfaces of the coating and wear scars on steel balls after the tests. It showed that both the coating surface and the ball were significantly worn-out even though boron carbide is much harder than the steel. Moreover, at low humidity ($5\%$) the boron carbide showed poor wear resistance which resulted in the complete removal of coating layer, whereas at the medium and high humidity conditions, it was not. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses were performed to characterize the chemical composition of the worn surfaces. We suggest that tribochemical reactions occurred during sliding in moisture air to form boric acid on the worn surface of the coating. The boric acid and the tribochemcal layer that formed on steel ball resulted in low friction and wear of boron carbide coating.

• 한국약용작물학회지
• /
• 제25권6호
• /
• pp.367-374
• /
• 2017

Background: An imbalance in energy intake and expenditure can cause obesity, which is a major risk factor for chronic diseases such as heart disease, type 2 diabetes, insulin resistance, cancers and hyperlipidemia. Methods and Results: In this study, we evaluated the anti-obesity effects of a water extract from the young leaves of barley sprout (BS) in 3T3-L1 cells and in high-fat diet (HFD)-induced obese mice (HF). Lipid accumulation measurement indicates that BS markedly inhibited adipogenesis by reducing lipid droplet production in a dose-dependent manner. Furthermore, the mRNA expression of adipogenic transcription factors peroxisome proliferator-activated receptor-${\gamma}$ and fatty acid synthetase, CCAAT/enhancer binding protein-${\alpha}$ and fatty acid binding protein 4 in 3T3-L1 cells was significantly inhibited by BS treatment. In an in vivo test, the BS-administered group of HFD-induced mice showed less body weight gain, and lower liver and epididymal white adipose tissue weights. The BS-treated mice showed decreased serum levels of leptin and lipids compared to untreated HFD mice and the levels of adiponectin and the HDL-cholesterol/total cholesterol ratio increased. These results indicate that BS inhibits body fat accumulation by reducing the mRNA expression of lipogenesis transcription factors and increasing serum adipokine concentration in in vitro and in vivo tests. Conclusions: BS reduced high fat diet-induced weight gain and had a positive effect on dyslipidemia.

• 공업화학
• /
• 제9권5호
• /
• pp.689-697
• /
• 1998

가교도와 희석제량을 변화시켜 제조한 인산기를 갖는 MR형 양이온 교환수지(RGP)에 대하여 우라늄의 흡착평형, 흡착속도 및 흡착 율속 단계를 고찰하였다. RGP 수지에 대한 우라늄의 흡착 평형은 가교도, 희석제량 및 흡착온도 변화 모두 Freundlich 등온식과 Langmuir 등온식으로 잘 나타났다. RGP수지에 대한 우라늄의 흡착량과 흡착속도는 흡착 온도가 증가함에 따라 증가하였으며 이때 흡착열은 ${\Delta}H=11kcal/mol$ 이었다. RGP 수지에 대한우라늄의 흡착속도는 가교도의 영향인 경우 RGP-10(50)>RGP-1(50)>RGP-2(50)>RGP-5(50)RGP-0(50)>이며, 희석제량의 영향인 경우 RGP-2(75)>RGP-2(100)>RGP-2(50)>RGP-2(30)>RGP-2(0) 순으로 증가하였다. RGP수지에 대한 우라늄의 확산저항은 분자확산<세공확산<표면확산 순이었으며, 수지내의 우라늄의 확산 율속은 세공 확산보다 표면 확산이 율속이었다.

• 한국산림과학회지
• /
• 제78권4호
• /
• pp.419-424
• /
• 1989

내화제간(耐火劑間)의 상대적(相對的)인 내화효과(耐火效果)를 비교(比較), 검토(檢討)하여 보기 위하여 메란티(meranti) 합판(合板)에 5종(種)의 내화제(耐火劑)와 수처리(水處理)를 하고 열판건조(熱板乾燥)시킨 다음, ASTM D 2863-77의 산소지수법(酸素指數法)에 의거하여 Up and Down법(法)을 통하여 각각의 산소지수(酸素指數)를 구하였다. 시험결과(試驗結果)에 의하면 황산(黃酸)암모늄이 28.4, 제(第)1인산(燐酸)암모늄이 26.7, 제(第)2인산(燐酸)암모늄이 43.4, 붕사(硼砂)-붕산(硼酸)이 30.1, 미날리스가 32.4, 그리고 수처리(水處理)가 25.5의 산소지수(酸素指數)를 나타냈는데, 연소성(燃燒性)이 큰 물질(物質)일수록 낮은 산소지수(散素指數)를 지닌다는 사실(事實)로 미루어 볼 때 내화제간(耐火劑間)의 내화효과(耐火效果)는 제(第)2인산(燐酸)암모늄, 미날리스, 붕사(硼砂)-붕산(硼酸), 황산(黃酸)암모늄, 제(第)1인산(燐酸)암모늄의 순(順)으로 크다는 것을 구명할 수 있었다.

• 한국임상수의학회지
• /
• 제37권1호
• /
• pp.1-8
• /
• 2020

Canine otitis externa is a common disorder in small animal practice with prevalence up to 20%. In a large percentage of cases, canine otitis externa is a chronic and recurrent disease also associated with drug-resistant bacteria that is difficult to treat with traditional antibiotics. Photodynamic therapy (PDT) is a new strategy to exterminate pathogenic microorganisms such as bacteria and fungi. The purpose of this study was to investigate the effectiveness of photodynamic therapy against canine otitis externa using three photosensitizer (PS); 5-Aminolevulinic acid (5-ALA) and Methyl aminolevulinic acid (MAL) with semiconductor laser diode (SLD, 635nm of wave length), Chlorophyll-lipoid complex (CLC) with light-emitting diode (LED, 660nm of wave length). After PDT, dogs showed improved Otitis Index Score (OTIS) in swelling, exudate, odor, and pain. A result of the cytology test revealed decrease of bacteria and malassezia count in the oil immersion field and colony forming units count. PDT was effective as a bacteriocide of methicillin-resistant Staphylococcus pseudintermedius (MRSP) and a fungicide of Malassezia pachydermatis. MAL and 5-ALA were more effective PS against canine otitis externa than CLC. These results suggest that PDT is a new strategy to exterminate pathogenic microorganisms such as bacteria and fungi. PDT can be considered as a new therapeutic approach for canine recurrent otitis externa and a countermeasure to drug resistance that is a disadvantage of traditional antibiotic and antifungal therapy.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제37권2호
• /
• pp.36-42
• /
• 2018

Recently, silk sericin has attracted attention because of its unique properties as a biomaterial, including its UV resistance, moisturizing effect on skin, and wound-healing effect. Therefore, the preparation of sericin in various forms such as gel, film, fiber, and sponge is studied for cosmetic and biomedical applications, and the effect of the preparation conditions on the structure and properties of sericin forms is examined to maximize its performance. In this study, silk sericin films were prepared under different preparation conditions and heat-treated at high temperatures ($100-250^{\circ}C$) to examine the effect of heat treatment on the film structure. The order of the crystallinity index of the untreated sericin film is as follows: F25 (sericin film cast from formic acid) > WE25 (ethanol treated sericin film cast from water at $250^{\circ}C$) > W25 (sericin film cast from water at $250^{\circ}C$) > W100 (sericin film cast from water at $100^{\circ}C$). As the heat-treatment temperature was increased, the color of the sericin films changed gradually from colorless to yellow, brown, and black depending on the temperature. The crystallinity of the sericin film changed after the heat treatment, depending on the preparation condition. Whereas a sericin film cast from formic acid (F25) started to lose its crystallinity at $200^{\circ}C$, thus undergoing the highest loss of crystallinity among the sericin films studied, the rest (W25, WE25, and W100) showed a decrease in crystallinity at $250^{\circ}C$, owing to the disruption of the ${\beta}$-sheet crystallites due to heat.

• 공업화학
• /
• 제30권3호
• /
• pp.352-357
• /
• 2019

본 연구에서는 3-butenoic acid와 폴리옥시에틸렌(20) 스테아릴 에테르를 사용하여 비닐기를 가진 반응성 유화제를 합성하였다. 합성 반응성 유화제는 FT-IR 및 $^1H-NMR$에 의해 확인되었다. 또한, 아크릴계 점착제의 제조에서 합성된 반응성 유화제와 통상적으로 사용되는 비이온성 유화제를 사용하여 각각의 점착제의 특성을 비교하였다. 고형분 함량은 56.8~57.4%의 범위에서 측정되었다. 초기 접착의 경우, 반응성 유화제로 제조된 S20BA는 $^{\sharp}13$으로 측정되었다. 제조된 접착제의 박리강도는 $0.66{\sim}1.05kg_f$의 범위에서 측정되었고 S20BA를 사용한 경우 가장 높은 박리 강도가 측정되었다. 내열성 시험 결과, S20BA의 내열성이 $840^{\circ}C$로 가장 높았다. 피부용 접착제에 대한 응용성을 평가하기 위하여 pH는 중성 7로 측정되었으며, 일차 피부 자극 시험의 결과로 비자극성으로 측정되었다.

• Journal of Microbiology and Biotechnology
• /
• 제31권8호
• /
• pp.1060-1068
• /
• 2021

Community-associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA) is notorious as a leading cause of soft tissue infections. Despite several studies on the Agr regulator, the mechanisms of action of Agr on the virulence factors in different strains are still unknown. To reveal the role of Agr in different CA-MRSA, we investigated the LACΔagr mutant and the MW2Δagr mutant by comparing LAC (USA300), MW2 (USA400), and Δagr mutants. The changes of Δagr mutants in sensitivity to oxacillin and several virulence factors such as biofilm formation, pigmentation, motility, and membrane properties were monitored. LACΔagr and MW2Δagr mutants showed different oxacillin sensitivity and biofilm formation compared to the LAC and MW2 strains. Regardless of the strain, the motility was reduced in Δagr mutants. And there was an increase in the long chain fatty acid in phospholipid fatty acid composition of Δagr mutants. Other properties such as biofilm formation, pigmentation, motility, and membrane properties were different in both Δagr mutants. The Agr regulator may have a common role like the control of motility and straindependent roles such as antibiotic resistance, biofilm formation, change of membrane, and pigment production. It does not seem easy to control all MRSA by targeting the Agr regulator only as it showed strain-dependent behaviors.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• 제24권2호
• /
• pp.187-196
• /
• 2021

Purpose: The rising prevalence of childhood obesity in the past decades has caused non-alcoholic fatty liver disease (NAFLD) to become the most common cause of pediatric chronic liver disease worldwide. This study was aimed at determining the effect of vitamin D (Vit D) on ultrasonography and laboratory indices of NAFLD and some blood biochemical indicators in children. Methods: In this interventional study liver ultrasonography was performed in 200 children with overweight and obesity. A 108 had fatty liver among which 101 were randomly divided into two groups of study (n=51) and control (n=50). The study group was treated with Vit D, 50000 U once a week whereas the control group received placebo with the same dose and package, both for 12 weeks. At the end of the intervention lab tests and ultrasound study was performed once again to evaluate the response to treatment. Results: It was found out that Vit D supplementation improved the fatty liver grade in the study group. The mean changes in hemoglobin (Hb), uric acid, highdensity lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), insulin, albumin and alanine aminotransferase (ALT) was significantly higher in the study group compared to controls (p<0.05). After the intervention and means adjustment, a significant difference was obtained in HDL-C, insulin, LDL-C and homeostasis model assessment of insulin resistance (HOMA-IR) between the two groups. Conclusion: Vit D supplementation in addition to improving the fatty liver grade in ultrasonography and increasing the blood Vit D level, increases the HDL and Hb level besides decreasing uric acid, LDL, HOMA-IR, insulin and ALT levels.

• The Korean Journal of Physiology and Pharmacology
• /
• 제26권6호
• /
• pp.501-509
• /
• 2022

Irisin is a myokine caused by exercise that improves insulin resistance and weight loss. However, under unfavorable conditions such as air pollution, and during the pandemic, outdoor activities are uncomfortable. Therefore, in this study, the effect of heat therapy (half bath 42 ± 0.5℃ for 30 min) on irisin circulation levels as an exercise alternative for middle-aged obese women after menopause was investigated. Subjects were 33 women aged 49.54 ± 6.04 years, with parameters of height, 160.12 ± 4.33 cm, weight, 69.71 ± 7.52 kg, body surface area 1.73 ± 0.13 m², body mass index, 27.19 ± 3.40 kg/m². The results suggest that circulating irisin levels showed a significant increase after one-time thermotherapy (TH-1). However, the increase in circulating irisin levels after 15 treatments (TH-15, 5 days/week, 3 weeks) was significantly varied. The level of adiponectin, which increases fatty oxidation to reduce fatty deposition, increased significantly at TH-1, but further increased at TH-15, which was significantly different from the level of TH-1. In addition, the basic serum free fatty acid (FFA) level was significantly increased at TH-15 compared to TH-1. Significant differences were also found in the lipid profile (body mass index, waist circumference, and % body fat). Thermotherapy can significantly increase the tympanic temperature and induce changes in circulating irisin and adiponectin levels. Thus, it resulted in positive changes in FFA and lipid profiles. Therefore, repeated thermotherapy is effective in increasing circulating irisin levels in postmenopausal obese women.