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排序方式: 共有1539条查询结果,搜索用时 359 毫秒
81.
Kyoung-Im Cho Sang-Ho Koo Tae-Joon Cha Jung-Ho Heo Hyun-Su Kim Gee-Bum Jo Jae-Woo Lee 《International journal of molecular sciences》2014,15(8):14803-14818
Increased atrial oxidative stress has an important role in inducing and maintaining atrial fibrillation (AF), and the activation of the small GTPase Rac1 contributes to the oxidative stress. We investigated the relationship of Rac1, atrial endothelial thromboprotective markers and AF inducibility and if simvastatin has a potential beneficial effect on a myocardial infarction (MI)-induced heart failure (HF) rat model. Rats were randomized into three groups (shams, MI group and simvastatin treatment group) and underwent echocardiography, AF induction studies and left atrial (LA) fibrosis analysis. Atrial Rac 1, sodium calcium exchanger (INCX), sarcoplasmic reticulum calcium ATPase (SERCA), endothelial nitric oxide synthase (eNOS) and induced nitric oxide synthase (iNOS) were measured. AF inducibility, AF duration and LA fibrosis were significantly higher in the MI group (p < 0.001 vs. sham), which were significantly reduced by simvastatin (p < 0.05 vs. MI). The reduced expressions of atrial eNOS, SERCA, thrombomodulin, tissue factor pathway inhibitor and tissue plasminogen activator in the MI group were significantly improved by simvastatin. Furthermore, the increased expression of atrial iNOS, INCX and Rac1 activity were significantly decreased by the simvastatin. Oxidative stress, endothelial dysfunction and thrombogenicity are associated with the promotion of AF in a rat model of ischemic HF. These were associated with increased Rac1 activity, and simvastatin treatment prevents these changes. 相似文献
82.
Tae-Hyung Koo Jyoti S Borah Zhi-Cai Xing Sung-Mo Moon Yongsoo Jeong Inn-Kyu Kang 《Nanoscale research letters》2013,8(1):124
Self-assembled layers of vertically aligned titanium nanotubes were fabricated on a Ti disc by anodization. Pamidronic acids (PDAs) were then immobilized on the nanotube surface to improve osseointegration. Wide-angle X-ray diffraction, X-ray photoelectron microscopy, and scanning electron microscopy were employed to characterize the structure and morphology of the PDA-immobilized TiO2 nanotubes. The in vitro behavior of osteoblast and osteoclast cells cultured on an unmodified and surface-modified Ti disc was examined in terms of cell adhesion, proliferation, and differentiation. Osteoblast adhesion, proliferation, and differentiation were improved substantially by the topography of the TiO2 nanotubes, producing an interlocked cell structure. PDA immobilized on the TiO2 nanotube surface suppressed the viability of the osteoclasts and reduced their bone resorption activity. 相似文献
83.
Se‐Hee Jo Jeung Kun Kim Chang Geun Yoo Jin‐Il Kim Yoon‐Mo Koo Sunyong Mun 《加拿大化工杂志》2007,85(6):874-882
A ternary separation usually requires the use of two simulated moving bed (SMB) units in series. Since an increase in the number of SMB units leads to a significant increase in capital and operational costs, the use of a single SMB unit is preferred if its structure can be modified to treat a ternary separation. Such a modified single SMB unit has been typified by a five‐zone SMB or a two‐zone SMB so far. The separation performances‐of a five‐zone SMB and a two‐zone SMB are compared in this paper by using the ternary amino acid mixture as a model system. A five‐zone SMB is designed with the safety margin method while a two‐zone SMB is optimized using genetic algorithm. A five‐zone SMB based on the maximum allowable safety margin, although it may not guarantee the global optimum solution, results in much better separation performance than a two‐zone SMB at its global optimum state. 相似文献
84.
In-Hwan Shin Jae-Mean Koo Chang-Sung Seok Sung-Ho Yang Tack-Woon Lee Bum-Soo Kim 《Surface & coatings technology》2011
Plasma-sprayed thermal barrier coatings (TBCs) are applied to protect the blades of a gas turbine system from high-temperature gas and to lower the surface temperature of the blades. The failure of TBC is directly connected to the failure of the blades because the spallation of a ceramic layer leads to the acceleration of local corrosion and oxidation at the location of failure. Therefore, the spallation life of TBC is very important in the evaluation of the reliability of a gas-turbine blade.In this study, thermal fatigue tests were performed at 1100 °C and 1151 °C. Then, c-scanning and bond strength tests were performed for TBC specimens that were thermally aged by thermal fatigue tests. From the results, an empirical equation based on the ratio of the delamination area and the thermal cycle number was presented and the spallation life of a TBC specimen could be roughly estimated using the relationship between the delaminated area and the number of cycles. 相似文献
85.
Flame retardancy and mechanical properties of polyamide 6 with melamine polyphosphate and ionic liquid surfactant‐treated montmorillonite 下载免费PDF全文
The mechanical properties and inflammability of polyamide 6 (PA6) nanocomposites incorporated with Montmorillonite organoclay (MMT) modified with thermal stable ionic liquid surfactants were investigated. The compatibility between ionic liquid‐treated MMT and PA6 matrix was improved and the intercalation morphology was achieved, which resulted in the increaseof tensile modulus. However, the addition of organo‐MMTs alone did not improve the inflammability of the PA6 nanocomposite, because of strong melt‐dripping behavior of PA6 matrix. Addition of auxiliary melamine polyphosphate (MPP) intumescent flame retardant to the nanocomposite prevented the melt dripping and enhanced inflammability performance. The enhanced inflammability of PA6/organoclay/MPP nanocomposites was attributed to the synergistic effect between imidazolium or phosphonium organo‐MMTs and intumescent flame retardant MPP. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40648. 相似文献
86.
This paper deals with the development and calibration of a single degree-of-freedom probe that is capable of regulating an input position and measuring force or applying a constant input force and measuring deflection. Such a probe is useful in making sensitive measurements on thin films, nano- and microstructures, and fluids. The probe is actuated by an electrostatic comb drive with an integrated capacitive sensor. COTS electronics and a capacitance-to-voltage IC are used to develop a closed-loop controller for the system, capable of regulating position over a range of about 40 μm to within a 5 nm resolution and controlling forces up to 300 μN with a resolution of 25 nN. The design and fabrication of the probe are discussed. The calibration of the device is performed using multiple methods to cross check each other. The use of the probe is demonstrated in the measurement of surface tension and probing the response of a soft polymer to small forces. 相似文献
87.
We evaluated the buckling limit of a conceptually designed reactor vessel of the Advanced Burner Test Reactor (ABTR) for a
horizontal safe shutdown earthquake (SSE) seismic load. In this evaluation, both seismic isolation and non-isolation designs
were considered for thin reactor vessels subjected to elevated temperature services. For calculating the buckling load, two
kinds of methods, a numerical simulation method using finite element analysis and an evaluation formula driven from a theoretical
basis, were used. To consider the material aging effect caused by a 60-year design lifetime and 510°C normal operating temperature,
an isochronous stress-strain curve corresponding to these conditions was used for the nonlinear elastic-plastic buckling analysis
method. From the evaluation results of the buckling load, it was found that plasticity behavior significantly affects the
buckling strength, but that the initial geometrical imperfections have little effect. Also, the non-seismic isolation design
does not satisfy the buckling limit rules of the ASME BPV Section III, Subsection NH, but the seismic isolation design does
satisfy it with sufficient margins. 相似文献
88.
Young Ho Shin Seong-Mo Koo Dae Sung Kim Young-Ho Lee Bambang Veriansyah Jaehoon Kim Youn-Woo Lee 《The Journal of Supercritical Fluids》2009,50(3):250-256
A detailed investigation was made into the production of high temperature lithium cobalt oxide (HT-LiCoO2) particles by continuous hydrothermal synthesis via the reaction of cobalt nitrate, lithium hydroxide, and hydrogen peroxide. The experiments were carried out in both subcritical and supercritical water, at temperatures ranging from 300 to 411 °C, with residence times less than 1 min in all instances. Although Co3O4 particles were synthesized in subcritical water at similar reaction conditions designed for comparison, well-ordered particles of HT-LiCoO2 were obtained in supercritical water. In supercritical conditions, the variations in temperature and residence time did not have significant impacts on the average particle size, particle size distribution, or morphology of obtained HT-LiCoO2. However, it was important to supply excessive lithium hydroxide and hydrogen peroxide in order to synthesize single-phased HT-LiCoO2 particles without undesired by-products. The hydrothermal synthetic route for LiCoO2, CoO, and Co3O4 in both subcritical and supercritical conditions was postulated. 相似文献
89.
In Chul Lee Young Su Kang Hee Jang Moon Seok Pil Jang Jin Kon Kim Jaye Koo 《Journal of Mechanical Science and Technology》2010,24(7):1425-1431
Modulated liquid jets injected into subsonic cross-flows are empirically studied by using a mechanical liquid jet modulation
apparatus. Experimental investigations were conducted using water over a range of cross-flow velocities from 5 m/s to 143
m/s and with modulated liquid jet frequencies from 35.7 Hz to 166.2 Hz and so on. PDPA(phase Doppler particle anemometry)
was employed to measure droplet diameter and velocity with various spray cross-sections from Z/d=20 to Z/d=60. The spray structure,
penetration depth, SMD(Sauter mean diameter), volume flux and velocity characteristics of modulated liquid jets injected into
cross-flows were examined. As oscillation of the periodic pressure that could make liquid jet moved up and down in cross-flow
field, the mixing process was facilitated. This phenomenon has the advantage of mixing the spray concentration from the center
area to the outer area. Also, a bulk liquid jet puff was detected in the upper field of the liquid jet surface. The modulation
effect appears significant in the extent of the spray oscillation. The correlation equations for the liquid jet boundary of
the upper and lower regions which related to the Strouhal number have been presented to predict the spray structure under
modulation conditions. Because of the modulation frequency, an inclination of averaged SMD for the structured layer was evanescent
which contributed to the promotion of the macroscopic spray mixing process. Cross-sectional characteristics of SMD had the
same tendency over a range of various modulation frequencies. As the modulation frequency increased, the region of volume
flux distribution also increased. 相似文献
90.
Kyung-Hoon Bang Gui-Yung Chung Hyung-Hoi Koo 《Korean Journal of Chemical Engineering》2011,28(1):272-278
The preparation of C/C composites by the chemical vapor infiltration (CVI) of the pyrolysis carbon from propane was studied. Pyrolysis carbon was deposited at 30 torr and at temperatures between 1,173 and 1,233 K. The rate of carbon deposition increased slightly with time. The main gas products in the exit gas were methane, ethylene, and acetylene. The fraction of ethylene decreased and that of acetylene increased with the reaction temperature and the propane concentration. The produced propyl radicals reacted further at a high temperature and at a high propane concentration. These trends were similar to those of the reported data. Changes of the shapes of deposited carbon in the pores of preform were confirmed with SEM photos. The mathematical modeling of the system with the deposition rate constant from the reference estimated experimental data well. 相似文献