1,045 research outputs found
A novel cell counter method using micro lattice array engraved on surface of cell culture dish
No full textAn efficient cell count method using a lattice molded on indents of a culture dish
No full textCell count is an important task for obtaining biological and medical information. In this paper, a novel cell count method is presented for improving the efficiency of the procedure as well as reducing microbial contamination compared to the conventional cell count method using a hemocytometer. The proposed method involves a lattice array consisting of a 50 mu m x 50 mu m square with lines of 2-mu m width and 1.4-mu m depth on a surface indented from a culture dish bottom. This configuration enables observation of cells at the same focus as the lattice. Therefore, an instant cell count during incubation is possible without the tedious, error-prone preparation steps such as harvesting and loading required in conventional methods. In addition, cells can be preserved with minimal contact with the external environment. These advantages become magnified with a periodic long-term cell count. A polystyrene culture dish, 35 mm in diameter, was fabricated by injection molding using a nickel mold, wherein indents of 3 mm x 3 mm in area and I mm in height were electroplated based on microfabrication technology. For easy separation from the nickel mold, the four sides of the indents in the mold are inclined at 54.74 degrees via anisotropic silicon etching. The usefulness of the suggested method was verified using adhering HeLa (cervical carcinoma cell) cells and floating Jurkat cells. Both were placed in culture dishes and cultivated for 3 days in a carbon dioxide incubator (5% CO2, 95% air) at 37 degrees C, and then successfully observed through the divided lattice using an inverted microscope. The dish was also assessed with a hemocytometer by counting HEK 293T (human embryonic kidney) cells and yeast cells. (c) 2008 Elsevier B. V. All rights reserved
Effect of GPa pressure on microstructures and heat transfer phenomena of aluminum alloys during solidification
No full text학위논문(박사) - 한국과학기술원 : 재료공학과, 1994.8, [ iv, 116 p. ]한국과학기술원 : 재료공학과
Polymer waveguide variable optical attenuator and its reliability
No full textA variable optical attenuator (VOA) made of novel low-loss fluorinated polymers is demonstrated showing a low operating power of less than 30 mW, due to the superior thermo-optic effect of polymer material. Less than 1.0 dB of the device insertion loss is achieved by incorporating highly fluorinated polymers with a low absorption loss for 1550nm. Device characteristics with a closed-loop feedback control circuit are investigated, exhibiting low wavelength and negligible temperature dependence for the practical attenuation application. By following the completed reliability test of the Telcordia GR1221, the reliability issue of the polymeric device is carefully addressed in order to confirm that the device has sufficient reliability for commercial applications. (C) 2004 Elsevier B.V. All rights reserved
Thermooptic 2x2 asymmetric digital opticat switches with zero-voltage operation state
No full textThermooptic 2 x 2 switches with zero-voltage operation state are demonstrated. The devices made of ultraviolet curable fluorinated polymer are composed of four asymmetric digital optical switches and designed for bar-state operation with initial zero-voltage state. This zero-voltage operation is essential for protection switching in optical networks. The crosstalks of initial bar and cross states are more than 40 dB. The insertion loss and the polarization-dependent loss of the device are less than 1.8 and 0.1 dB for both states, respectively. The power consumption is about 350 mW. The wavelength and temperature dependences of the insertion loss are less than 0.3 dB
pH-responsive polyelectrolyte complexation on upconversion nanoparticles: a multifunctional nanocarrier for protection, delivery, and 3D-imaging of therapeutic protein
No full textThe delicate tertiary structure of proteins, their susceptibility to heat- and enzyme-induced irreversible denaturation, and tendency to get accumulated at the cell membrane during uptake are daunting challenges in proteinaceous therapeutic delivery.The delicate tertiary structure of proteins, their susceptibility to heat- and enzyme-induced irreversible denaturation, and their tendency to get accumulated at the cell membrane during uptake are daunting challenges in proteinaceous therapeutic delivery. Herein, a polyelectrolyte complex having encapsulated therapeutic protein has been designed on the surface of upconverting luminescent nanoparticles (NaYF 4 :20%Yb 3+ ,2%Er 3+ ). This nanosized complex system has been found to overcome the challenges of protein aggregation at the cell membrane. It has also defended the cargo from denaturation against (a) enzymatic action of proteinase K and (b) heat (up to 60 °C). Additionally, the nanoparticles at the core of the loaded carrier served as near-infrared (980 nm) responsive probe to accomplish extended-duration 3D imaging during protein delivery. The outer layer of polymer played pivotal role to protect/retrieve the protein structure from denaturation as investigated by circular dichroism studies. Both the masked surface-charges of protein and the nanoscale size of the loaded carrier have facilitated their efficient passage through the cell membrane as observed through 3D images/videos. This nanocarrier is the first of its kind for direct delivery of protein. Thus, the findings can be useful to protect and transport various proteinaceous materials to overcome challenges of accumulation at the cell-membrane and low-temperature storage, as nature does.The delicate tertiary structure of proteins, their susceptibility to heat- and enzyme-induced irreversible denaturation, and tendency to get accumulated at the cell membrane during uptake are daunting challenges in proteinaceous therapeutic delivery.The delicate tertiary structure of proteins, their susceptibility to heat- and enzyme-induced irreversible denaturation, and their tendency to get accumulated at the cell membrane during uptake are daunting challenges in proteinaceous therapeutic delivery. Herein, a polyelectrolyte complex having encapsulated therapeutic protein has been designed on the surface of upconverting luminescent nanoparticles (NaYF 4 :20%Yb 3+ ,2%Er 3+ ). This nanosized complex system has been found to overcome the challenges of protein aggregation at the cell membrane. It has also defended the cargo from denaturation against (a) enzymatic action of proteinase K and (b) heat (up to 60 °C). Additionally, the nanoparticles at the core of the loaded carrier served as near-infrared (980 nm) responsive probe to accomplish extended-duration 3D imaging during protein delivery. The outer layer of polymer played pivotal role to protect/retrieve the protein structure from denaturation as investigated by circular dichroism studies. Both the masked surface-charges of protein and the nanoscale size of the loaded carrier have facilitated their efficient passage through the cell membrane as observed through 3D images/videos. This nanocarrier is the first of its kind for direct delivery of protein. Thus, the findings can be useful to protect and transport various proteinaceous materials to overcome challenges of accumulation at the cell-membrane and low-temperature storage, as nature does
A Feasibility Study for the Development of a Vertical Shaft Construction Technique using Ring Cutting
No full textSupply facilities have to be buried due to urban development from rapid
population growth and a lack of land; therefore, vertical shaft construction has
increased for utility tunnels. Because utility tunnels are installed in urban areas, there
can be critical problems from faulty construction. Conventional construction methods
used in most vertical shafts cause a decrease in the groundwater level which is one
reason for ground settlement. Therefore, construction methods have been researched
that take into consideration the ground settlement of vertical shafts, and the ring cut
method was developed. This method first penetrates an outer section of the shaft to
prevent soil inflow and extends the seepage line. Using this method, ground settlement
caused by construction is expected to decrease. This study performed 2-dimensional
stress-seepage coupled numerical feasibility tests to analyze the effective penetration
depth of the ring cut method. Settlement and seepage were measured to evaluate its
performance. The obtained data will be used to optimize the newly developed method
Isotopic study of inorganic and methylmercury accumulation and distribution in Paralichthys olivaceus
No full textStudies of mercury bioaccumulation in fish continue to be an important scientific discipline for understanding the bioavailability and fate of mercury and for monitoring environmental levels of mercury in natural aquatic ecosystems. Many recent studies have utilized mercury stable isotope ratios in fish to monitor mercury sources and biogeochemical processes in diverse aquatic ecosystems. More experimental studies are however needed to precisely quantify the degree and mechanism(s) governing internal isotope fractionation of two mercury species, methylmercury (MMHg) and inorganic mercury (IHg), in fish. In order to better trace environmental sources of mercury using fish, we performed controlled experiments by raising Paralichthys olivaceus in captivity for 3 months and feeding them food pellets spiked with either MMHg or IHg (0.4 and 1.6 ug/g). Total mercury (THg) and MMHg concentrations and mercury isotope ratios (δ202Hg, Δ199Hg) were measured in the muscle, liver, kidney, and intestine tissues of fish. Fish fed with food pellets spiked with varying concentrations of MMHg equilibrated to the isotopic composition of the food regardless of the tissue type and MMHg concentration. In contrast, fish fed with food pellets spiked with varying concentrations of IHg showed a tissue specific variation. Kidney and muscle tissues with relatively large proportions of MMHg from THg (>60%) exhibited small isotopic shifts toward the IHg food pellets after 3 months. The mercury isotope ratios of intestine comprised mostly of IHg (>90%) equilibrated to the isotopic composition of the food. Interestingly, liver tissues comprised mostly of MMHg (~100%) showed δ202Hg value that is ~0.7 permil higher than the IHg food pellet, suggesting the presence of significant mass-dependent fractionation (MDF) in the fish liver. Our study demonstrates how the isotope ratios of different mercury species behave in the internal system of fish and that the mechanism responsible for MDF needs to be elucidated particularly for using fish tissues to monitor sites contaminated with IHg.1
Inertial focusing in triangular microchannels with various apex angles
No full textWe consider inertial focusing of particles in channels with triangular cross sections. The number and the location of inertial focusing positions in isosceles triangular channels can change with varying blockage ratios (a/H) and Reynolds numbers (Re). In triangular channels, asymmetric velocity gradient induced by the sloped sidewalls leads to changes in the direction and the strength of the inertial lift forces. Therefore, varying the configuration (specifically, angle) of the triangular cross section is expected to lead to a better understanding of the nature of the inertial lift forces. We fabricated triangular microchannels with various apex angles using channel molds that were shaped by a planing process, which provides precise apex angles and sharp corners. The focusing position shift was found to be affected by the channel cross section, as expected. It was determined that the direction of the focusing position shift can be reversed depending on whether the vertex is acute or obtuse. More interestingly, corner focusing modes and splitting of the corner focusing were observed with increasing Re, which could explain the origin of the inertial focusing position changes in triangular channels. We conducted fluid dynamic simulations to create force maps under various conditions. These force maps were analyzed to identify the basins of attraction of various attractors and pinpoint focusing locations using linear stability analysis. Calculating the relative sizes of the basins of attractions and exhaustively identifying the focusing positions, which are very difficult to investigate experimentally, provided us a better understanding of trends in the focusing mechanism.This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Kim, Jeong-ah, Aditya Kommajosula, Yo-han Choi, Je-Ryung Lee, Eun-chae Jeon, Baskar Ganapathysubramanian, and Wonhee Lee. "Inertial focusing in triangular microchannels with various apex angles." Biomicrofluidics 14, no. 2 (2020): 024105. and may be found at DOI:10.1063/1.5133640. Posted with permission.</p
Relationship between serum selenium concentrations and systemic inflammatory response, prognostic markers according to severity in the admitted patients
No full text의학과/석사중환자에서 발생하는 패혈증과 전신염증반응은 중환자의 사망률을 높이는 중요한 인자이며, 산화 스트레스는 전신염증반응의 예후를 악화시킬 수 있는 요인으로서 최근 그 중요성이 높아지고 있다. 셀레늄은 인간에게 필요한 미량원소로서 체내에서 산화 스트레스에 대해 세포 보호기능을 하는 것으로 알려져 있으며 최근 중환자에서의 셀레늄 보충요법이 병원 내 감염과 같은 합병증을 줄이고 사망률을 낮춘다는 연구 결과가 보고되고 있으나, 아직 우리나라에서 셀레늄이 환자의 중증도에 따른 차이를 보이는 지와 기존의 전신염증반응 및 예후 관련 지표와 연관성을 보이는 지에 대해서는 아직 그 임상 자료가 부족한 상태이다. 이에 본 연구에서는 환자의 중증도에 따른 혈청 셀레늄 농도의 차이 여부와 C-반응단백, procalcitonin, APACHE II 점수 등의 전신염증반응 및 예후 관련 지표와의 상관관계를 확인하여 향후 중환자의 치료에 있어 셀레늄의 역할에 대한 연구의 기초자료를 마련하고자 하였다. 대상은 급성 내과적 질환으로 입원한 일반병실군, 중환자실군 각각 26명, 36명의 환자로 하였다. 환자군은 전신염증반응증후군(systemic inflammatory response syndrome, SIRS)의 기준에 만족하면 중환자실군으로, 만족하지 않으면 일반병실군으로 분류 하였으며 입원 당시 혈청 셀레늄 농도, 입원 후 치료 경과에 따른 셀레늄 농도의 변화 및 C-반응단백, procalcitonin, 알부민, 림프구, APACHE II 점수 등의 전신염증반응 및 예후 관련 지표와의 연관성을 비교분석 하였다. 이상의 모든 분석 결과, 내원 시 측정한 혈청 셀레늄은 중환자실군에서 일반병실군보다 유의하게 낮았다(p<0.001). 또한 혈청 셀레늄은 APACHE II 점수가 증가함에 따라 감소하였고(r=-0.475, p<0.001) 알부민과 림프구가 증가함에 따라 증가하였다(r=0.387, p=0.020 / r=0.307, p=0.016). 결론적으로 환자의 중증도에 따른 혈청 셀레늄 농도의 유의한 차이를 확인하였다. 또한 기존의 전신염증반응 및 예후 관련 지표들과 상관관계를 보여줌으로써, 이 연구 결과가 향후 중환자의 진단과 치료에 있어서 셀레늄의 유용성과 효과에 대한 연구에 널리 적용될 수 있을 것으로 판단된다.ope
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