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排序方式: 共有326条查询结果,搜索用时 15 毫秒
1.
2.
Joo H. Kang Eujin Um Alexander Diaz Harry Driscoll Melissa J. Rodas Karel Domansky Alexander L. Watters Michael Super Howard A. Stone Donald E. Ingber 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(42):5657-5666
Magnetic nanoparticles have been employed to capture pathogens for many biological applications; however, optimal particle sizes have been determined empirically in specific capturing protocols. Here, a theoretical model that simulates capture of bacteria is described and used to calculate bacterial collision frequencies and magnetophoretic properties for a range of particle sizes. The model predicts that particles with a diameter of 460 nm should produce optimal separation of bacteria in buffer flowing at 1 L h−1. Validating the predictive power of the model, Staphylococcus aureus is separated from buffer and blood flowing through magnetic capture devices using six different sizes of magnetic particles. Experimental magnetic separation in buffer conditions confirms that particles with a diameter closest to the predicted optimal particle size provide the most effective capture. Modeling the capturing process in plasma and blood by introducing empirical constants (ce), which integrate the interfering effects of biological components on the binding kinetics of magnetic beads to bacteria, smaller beads with 50 nm diameters are predicted that exhibit maximum magnetic separation of bacteria from blood and experimentally validated this trend. The predictive power of the model suggests its utility for the future design of magnetic separation for diagnostic and therapeutic applications. 相似文献
3.
Seong-Jai Cho Chang-Do Um Seock-Sam Kim 《Journal of the American Ceramic Society》1996,79(5):1247-1251
Wear and wear transition in silicon carbide ceramics during sliding have been investigated. Three different microstructures, i.e., solid-state-sintered silicon carbide, liquidphase-sintered silicon carbide, and a liquid-phase-sintered SiC-TiB2 composite, were produced by hot pressing. Wear data and examinations of worn surfaces showed that the wear behavior of these silicon carbide ceramics was significantly different. In the solid-state-sintered silicon carbide, the wear occurred by a grooving process. In the liqudphase-sintered silicon carbide and composite, on the other hand, an abrupt transition in the wear mechanism from an initial grooving process to a grain pullout process occurred during the test. The transition occurred significantly earlier in the composite than in the carbide. The different wear behavior in these silicon carbide ceramics is discussed in relation to the grain or interphase boundary strength. 相似文献
4.
Chung-In Um Jae-Rok Kahng Kyu-Hwang Yeon Thomas F. George 《Journal of Low Temperature Physics》1996,102(3-4):307-324
Using the variational density matrix method, we obtain a temperature-dependent elementary excitation spectrum for two-dimensional liquid4He. For more precise results, we use a Jastrow-Feenberg-type trial wave function and include the contribution of elementary diagrams within the hypernetted chain approximation. The behavior of the excitation spectrum as a function of the temperature and density in two dimensions is similar to that of the bulk system, but has a smaller roton minimum. The roton minimum of the excitation spectrum decreases with increasing temperature and increases with increasing density at low densities but decreases at large densities. The results agree well with Monte Carlo calculations and are closer than pevious theories to experimental measurements of4He film adsorbed on substrates. 相似文献
5.
Jung-Ho Um Yong-Ki Kim Hyun-Jo Lee Miyoung Jang Jae-Woo Chang 《Journal of Systems Architecture》2012,58(9):354-371
Due to the advancement of wireless internet and mobile positioning technology, the application of location-based services (LBSs) has become popular for mobile users. Since users have to send their exact locations to obtain the service, it may lead to several privacy threats. To solve this problem, a cloaking method has been proposed to blur users’ exact locations into a cloaked spatial region with a required privacy threshold (k). With the cloaked region, an LBS server can carry out a k-nearest neighbor (k-NN) search algorithm. Some recent studies have proposed methods to search k-nearest POIs while protecting a user’s privacy. However, they have at least one major problem, such as inefficiency on query processing or low precision of retrieved result. To resolve these problems, in this paper, we propose a novel k-NN query processing algorithm for a cloaking region to satisfy both requirements of fast query processing time and high precision of the retrieved result. To achieve fast query processing time, we propose a new pruning technique based on a 2D-coodinate scheme. In addition, we make use of a Voronoi diagram for retrieving the nearest POIs efficiently. To satisfy the requirement of high precision of the retrieved result, we guarantee that our k-NN query processing algorithm always contains the exact set of k nearest neighbors. Our performance analysis shows that our algorithm achieves better performance in terms of query processing time and the number of candidate POIs compared with other algorithms. 相似文献
6.
7.
Woohyeon Shin Jun Seop Kim Heesung Kim Hui Ju Choi Hee Jung Lee Moon Kwang Um Moon Kee Choi Kyeongwoon Chung 《大分子材料与工程》2021,306(5):2100007
Hydrogels are recognized as one of the most promising materials for e-skin devices because of their unique applicable functionalities such as flexibility, stretchability, biocompatibility, and conductivity. Beyond the excellent sensing functionalities, the e-skin devices further need to secure a target-oriented 3D structure to be applied onto various body parts having complex 3D shapes. However, most e-skin devices are still fabricated in simple 2D film-type devices, and it is an intriguing issue to fabricate complex 3D e-skin devices resembling target body parts via 3D printing. Here, a material design guideline is provided to prepare multifunctional hydrogels and their target-oriented 3D structures based on extrusion-based 3D printing. The material design parameters to realize target-oriented 3D structures via 3D printing are systematically derived from the correlation between material design of hydrogels and their gelation characteristics, rheological properties, and 3D printing processability for extrusion-based 3D printing. Based on the suggested material design window, ion conductive self-healable hydrogels are designed and successfully applied to extrusion-based 3D printing to realize various 3D shapes. 相似文献
8.
The farnesoid X receptor (FXR, NR1H4) has been recognized as an attractive therapeutic target because it is a nuclear hormone
receptor that controls the expression level of cholesterol-7α-hydroxylase, which in turn regulates bile acid production and
cholesterol excretion. To compare receptor activity between each domain and the full-length protein, human FXR cDNA was cloned
from a human liver cDNA library. Three human FXR cDNA, designated FXR20, FXR33, and FXR53 cDNA, were subcloned and ligated into a pET28a expression vector. Each protein was expressed in Escherichia coli (BL21) and purified by nickel-nitrilotriacetic acid column chromatography. Approximately 5 mg of FXR33 (1–182 amino acids deleted from FXR, 37 kDa) and 2 mg of FXR53 (the full-length protein of FXR, 59 kDa) was purified from 1 L of Luria-Bertani culture, achieving at least 90% purity. The
coactivator recruitment assay for FXR activation was carried out with the three variants of the FXR protein by using dissociation-enhanced
lanthanide fluoroimmunoassay-europium-N1-labeled anti-His antibody. From an optimized assay, a saturated hyperbolic fluorescence signal curve was produced when 250
nM of FXR33 and 100 nM of steroid receptor coactivator-1 peptide, a coactivator of FXR consisting of 26 amino acids, were used with a
concentration dependence on chenodeoxycholic acid (from 0 to 200 μM). The ligand-binding domain of FXR (FXR33) was the most suitable protein for studying the activation of FXR with a fluorescence-based assay, because it showed better
structural stability than either the full length of FXR (FXR53) or the DNA-binding domain of FXR (FXR20). 相似文献
9.
Chung-In Um In-Han Kim Yeon-Mu Choi Thomas F. George 《Journal of Low Temperature Physics》1994,95(3-4):547-578
The temperature variations of the diffusion coefficientD(T), thermal diffusion ratio k
T
(T) and thermal conductivity (T) in a dilute solution of3He atom in two-dimensional liquid helium are evaluated explicitly by solving the kinetic equations via phonon-phonon, phonon-roton, roton-roton, impurityelementary excitation and impurity-impurity scatterings. In the low-temperature region, the main contributions toD(T) and (T) come from the interactions between phonons and impurities, while in the high-temperature region the interactions between impurities and whole elementary excitations contribute more strongly toD(T) and (T) than those of only elementary excitations. For a dilute solution, the thermal diffusion ratio k
T
(T), neglecting the internal mass counterflow, is much smaller than the effective thermal diffusion ratio k
T
*
(T), which is a function of thermostatic properties. The effective thermal conductivity eff is much larger than the thermal conductivity and has different temperature dependence from the thermal conductivity. The behaviors of the two-dimensional diffusion coefficient and thermal conductivity are much like the bulk case, where they exhibit exponential decay with increasing temperature, although they are much smaller than those of the bulk case. 相似文献
10.
Continuous generation of hydrogel beads and encapsulation of biological materials using a microfluidic droplet-merging channel 总被引:1,自引:0,他引:1
In this paper, we describe a method for encapsulation of biomaterials in hydrogel beads using a microfluidic droplet-merging
channel. We devised a double T-junction in a microfluidic channel for alternate injection of aqueous fluids inside a droplet
unit carried within immiscible oil. With this device, hydrogel beads with diameter <100 μm are produced, and various solutions
containing cells, proteins and reagents for gelation could merge with the gel droplets with high efficiency in the broad range
of flow rates. Mixing of reagents and reactions inside the hydrogel beads are continuously observed in a microchannel through
a microscope. By enabling serial injection of each liquid with the dispersed gel droplets after they are produced from the
oil-focusing channel, the device simplifies the sample preparation process, and gel-bead fabrication can be coupled with further
assay continuously in a single channel. Instantaneous reactions of enzyme inside hydrogel and in-situ formation of cell-containing
beads with high viability are demonstrated in this report. 相似文献