• Journal of Microbiology and Biotechnology
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• 제16권8호
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• pp.1229-1235
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• 2006

A lab-on-a-chip (LoC) was designed for simultaneous monitoring of microorganisms, antibiotic residues, somatic cells, and pH in raw milk. The LoC was fabricated from polydimethylsiloxane (PDMS) using microelectromechanical system (MEMS) technology, which consisted of two parts; a protein array and microchannel. The protein array was fabricated by immobilizing five types of antibodies corresponding to two microorganisms, two antibiotic residues, and somatic cells. A sol-gel film was deposited on a glass substrate to immobilize the antibodies. The target analytes in raw milk could be bound with the corresponding antibody by an immunoreaction, and the antigen-antibody complex was detected using fluorescence microscopy. SNARF-dextran was used as a pH indicator, and the SNARF-entrapped hydrogel was attached to the microchannel in the chip. After injecting the milk sample into the channel, the pH was measured by monitoring the change in fluorescence intensity by fluorescence microscopy. The on-chip simultaneous assay of two microorganisms (E. coli O157:H7 and Streptococcus agalactiae), two antibiotic residues (penicillin G and dihydrostreptomycin), and neutrophils was successfully accomplished using the proposed LoC system.

• Geomechanics and Engineering
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• 제17권5호
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• pp.445-452
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• 2019

Gel-type biopolymers have recently been introduced as environmentally friendly soil binders and have shown substantial strengthening effects in laboratory experimental programs. Although the strengthening effects of biopolymer-treated sands have been verified in previous direct shear tests and uniaxial compression tests, there has been no attempt to examine shear behavior under different confining stress conditions. This study therefore aimed to investigate the strengthening effects of biopolymer-treated sand using laboratory triaxial testing with a focus on confining pressures. Three representative confining pressure conditions (${\sigma}_3=50kPa$, 100 kPa, and 200 kPa) were tested with varying biopolymer contents ($m_{bp}/m_s$) of 0.5%, 1.0%, and 2.0%, respectively. Based on previous studies, it was assumed that biopolymer-treated sand is susceptible to hydraulic conditions, and therefore, the experiments were conducted in both a hydrated xanthan gum condition and a dehydrated xanthan gum condition. The results indicated that the shear resistance was substantially enhanced and there was a demonstrable increase in cohesion as well as the friction angle when the biopolymer film matrix was comprehensively developed. Accordingly, it can be concluded that the feasibility of the biopolymer treatment will remain valid under the confining pressure conditions used in this study because the resisting force of the biopolymer-treated soil was higher than that in the untreated condition, regardless of the confining pressure.

• 한국안광학회지
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• 제13권2호
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• pp.1-7
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• 2008

목적: 본 연구에서는 건안에 착용되어 지속적으로 건조한 상태에 노출되거나 관리 부주의로 건조한 상태가 되었던 소프트콘택트렌즈(soft contact lens, SCL)에 발생되는 렌즈의 형태 및 렌즈 착용시의 누액 안정성에 나타나는 변 화를 알아보고자 하였다. 방법: 함수율과 두께, 재질이 상이한 소프트콘택트렌즈들을 각각 인위적으로 2회 또는 4회 건조시키고 다시 수화시킨 후 렌즈 전체직경 및 곡률반경을 측정하였다. 또한, 소프트콘택트렌즈 착용시의 눈물파 괴시간(tear film break-up time, TBUT)의 변화를 측정하였다. 결과: 건조과정에 의하여 함수율 70% 소프트콘택트 렌즈와 59% 소프트콘택트렌즈 모두에서 전체직경의 감소가 나타났으며, 함수율 59% 소프트콘택트렌즈의 전체직경의 변화 정도가 더 컸다. 함수율 59%의 소프트콘택트렌즈는 건조횟수가 증가함에 따라 곡률반경이 증가하였다. 그러나, 함수율 70%의 소프트콘택트렌즈는 2회 건조시에는 곡률반경에 변화가 없었으며, 4회 건조시에는 곡률반경이 크게 증가하였다. -1.00 D 소프트콘택트렌즈는 -9.00 D 소프트콘택트렌즈 보다 직경의 감소 정도가 더 컸다. 또한, -1.00 D 소프트콘택트렌즈는 건조횟수가 증가하면 곡률반경의 증가정도가 커지는 반면, -9.00 D 소프트콘택트렌즈는 2회 건조시나 4회 건조시에 곡률반경의 차이가 없었다. 실리콘 하이드로겔 렌즈 재질인 lotrafilcon B의 직경 및 곡률반경 변화는 HEMA와 N-vinyl pyrrolidone의 공중합체인 hilafilcon B보다 더 적었다. 렌즈를 착용하였을 때의 TBUT는 건조되었던 소프트콘택트렌즈를 착용시 감소하였다. 결론: 소프트콘택트렌즈가 건조되었을 때 수화 과정을 거치더라도 렌즈의 전체직경 및 곡률반경이 변하였으며, 렌즈 착용시의 TBUT가 감소하였으며, 이러한 변화는 건조 되었던 소프트콘택트렌즈를 착용하였을 때의 착용감 저하의 주요 원인으로 작용할 것이다. 건조로 인한 소프트콘택 트렌즈의 형태 변화 및 TBUT 변화는 함수율, 두께, 재질에 따라 상이하였다.