Numerical simulation on the opto-electro-kinetic patterning for rapid concentration of particles in a microchannel     

Dong Kim  Jaesool Shim  Han-Sheng Chuang  Kyung Chun Kim 《Biomicrofluidics》2015,9(3)

This paper presents a mathematical model for laser-induced rapid electro-kinetic patterning (REP) to elucidate the mechanism for concentrating particles in a microchannel non-destructively and non-invasively. COMSOL^®(v4.2a) multiphysics software was used to examine the effect of a variety of parameters on the focusing performance of the REP. A mathematical model of the REP was developed based on the AC electrothermal flow (ACET) equations, the dielectrophoresis (DEP) equation, the energy balance equation, the Navier-Stokes equation, and the concentration-distribution equation. The medium was assumed to be a diluted solute, and different electric potentials and laser illumination were applied to the desired place. Gold (Au) electrodes were used at the top and bottom of a microchannel. For model validation, the simulation results were compared with the experimental data. The results revealed the formation of a toroidal microvortex via the ACET effect, which was generated due to laser illumination and joule-heating in the area of interest. In addition, under some conditions, such as the frequency of AC, the DEP velocity, and the particle size, the ACET force enhances and compresses resulting in the concentration of particles. The conditions of the DEP velocity and the ACET velocity are presented in detail with a comparison of the experimental results.  相似文献   

Collagen-based brain microvasculature model in vitro using three-dimensional printed template     

Jeong Ah Kim  Hong Nam Kim  Sun-Kyoung Im  Seok Chung  Ji Yoon Kang  Nakwon Choi 《Biomicrofluidics》2015,9(2)

We present an engineered three-dimensional (3D) in vitro brain microvasculature system embedded within the bulk of a collagen matrix. To create a hydrogel template for the functional brain microvascular structure, we fabricated an array of microchannels made of collagen I using microneedles and a 3D printed frame. By culturing mouse brain endothelial cells (bEnd.3) on the luminal surface of cylindrical collagen microchannels, we reconstructed an array of brain microvasculature in vitro with circular cross-sections. We characterized the barrier function of our brain microvasculature by measuring transendothelial permeability of 40 kDa fluorescein isothiocyanate-dextran (Stoke''s radius of ∼4.5 nm), based on an analytical model. The transendothelial permeability decreased significantly over 3 weeks of culture. We also present the disruption of the barrier function with a hyperosmotic mannitol as well as a subsequent recovery over 4 days. Our brain microvasculature model in vitro, consisting of system-in-hydrogel combined with the widely emerging 3D printing technique, can serve as a useful tool not only for fundamental studies associated with blood-brain barrier in physiological and pathological settings but also for pharmaceutical applications.  相似文献   

Hybrid capillary-inserted microfluidic device for sheathless particle focusing and separation in viscoelastic flow     

Jeonghun Nam  Justin Kok Soon Tan  Bee Luan Khoo  Bumseok Namgung  Hwa Liang Leo  Chwee Teck Lim  Sangho Kim 《Biomicrofluidics》2015,9(6)

A novel microfluidic device which consists of two stages for particle focusing and separation using a viscoelastic fluid has been developed. A circular capillary tube was used for three-dimensional particle pre-alignment before the separation process, which was inserted in a polydimethylsiloxane microchannel. Particles with diameters of 5 and 10 μm were focused at the centerline in the capillary tube, and the location of particles was initialized at the first bifurcation. Then, 5 and 10 μm particles were successfully separated in the expansion region based on size-dependent lateral migration, with ∼99% separation efficiency. The proposed device was further applied to separation of MCF-7 cells from leukocytes. Based on the cell size distribution, an approximate size cutoff for separation was determined to be 16 μm. At 200 μl/min, 94% of MCF-7 cells were separated with the purity of ∼97%. According to the trypan blue exclusion assay, high viability (∼90%) could be achieved for the separated MCF-7 cells. The use of a commercially available capillary tube enables the device to be highly versatile in dealing with particles in a wide size range by using capillary tubes with different inner diameters.  相似文献   

Interactive Kiosk at the Texas Tech University Libraries     

Ryan Litsey  Susan Hidalgo  Kaley Daniel  Julie Barnett  Amy Kim  Shannon Jones 《Journal Of Access Services》2015,12(1-2):31-41

The academic library, given its often privileged position on campus, is the information source that can include directional as well as general campus facts among the myriad of print and e-resources for reference. Also, an academic library's audiences can be quite varied and include prospective students or parents seeking more general knowledge of the building and the campus. Many times this need for information drives patrons to the library service desks. Sometimes, especially during the high-demand seasons of new student orientation and beginning of the fall semesters, the desk is so busy that many patrons will leave because they don't have the time to wait. To address this immediate need for information, Texas Tech University Libraries developed an interactive kiosk to provide general information for frequently asked questions in a more efficient, creative, and interactive way. The kiosk provides a fun method of satisfying a patron's information needs without the requirement of a staff member or the need to wait in line for help. The kiosk is available as long as the Library is open and provides a variety of useful answers to general questions, as well as facts about the Library.  相似文献   

How liberals and conservatives respond to feasibility and desirability appeals in anti-tobacco campaigns     

Younghwa Lee  Sukki Yoon  Seungwoo Chun  Chanmo Park  Kacy Kim 《亚洲交流杂志》2019,29(1):55-72

Using two experiments, this study aims to investigate how politically liberal or conservative message recipients respond to anti-tobacco appeals. The results show that in Study 1, respondents were exposed to a message about price policy. In Study 2, they were exposed to a message about a warning policy. In both studies, liberal participants more favorably evaluated anti-tobacco messages emphasizing feasibility rather than desirability, whereas conservative participants more positively evaluated messages emphasizing desirability rather than feasibility. Implications for policymakers and marketers are discussed.  相似文献   

What Motivates Parents to Mediate Children’s Use of Smartphones? An Application of the Theory of Planned Behavior     

Wonsun Shin  Hye Kyung Kim 《广播与电子媒介杂志》2019,63(1):144-159

Applying the Theory of Planned Behavior (TPB), this study examines parents’ attitudes, social norms, self-efficacy, and intentions regarding parental mediation of children’s smartphone use. A survey conducted with parents of young smartphone users aged 10–17 shows that parents tend to perceive discussion-based active mediation to be more desirable, as compared to rule-making restrictive mediation. Findings also indicate that the extent to which parents believe that they have control over their parental mediation practices plays an important role in forming positive intentions to practice parental mediation, regardless of the mediation domain.  相似文献   

Preparation of glucosamine by hydrolysis of chitosan with commercial α-amylase and glucoamylase     

Pan SK  Wu SJ  Kim JM 《Journal of Zhejiang University. Science. B》2011,12(11):931-934

Objective  

In order to overcome the defects of chemical hydrolysis approach to prepare glucosamine, an enzymatic hydrolysis method was developed.  相似文献   

An Entrance for the Uninterested: Who Watches Soft News and How Does It Affect Their Political Participation?     

Kim Andersen 《Mass Communication and Society》2019,22(4):487-507

As soft news shows in television present politics in an entertaining format, they are likely to attract and grab the attention of people who do not have a high interest in politics. Consequently, soft news might mobilize these citizens to engage in politics. This study tests this potential by using a 2-wave panel survey among a national sample of voters (N = 2,680) collected in relation to the 2015 National Election in Denmark. The results show that people with lower political interest were indeed more likely to increase their use of soft news during the election campaign and that, as a consequence, these low-motivated people also increased their passive participation, such as seeking additional information about the election. Further, the results show that this type of passive participation is likely to function as a stepping-stone to active forms of participation, such as attending political events or contacting politicians.  相似文献   

Learning in Action: How Competent Professionals Learn     

Eulho Jung  Minkyoung Kim  Charles M. Reigeluth 《Performance Improvement Quarterly》2016,28(4):55-69

The studies pertaining to expertise development are diverse and broad (Bjork, 1994; Einstein & McDaniel, 2005; Schneider, Healy, & Bourne, 2002), yet empirical research that bridges expertise development into instructional design theories is still in its very formative stages (Ertmer et al., 2008; Fadde, 2009). This article is intended to identify the instructional principles that are effective in accelerating the performance of journeymen, considering the significant impact of the journeyman stage and the need for hastening performance in that stage. With the introduction to the major scholarly works and principles that have led to the elaboration of training methods, strategies, and materials, this review of literature proposes a learning model that has four components: (1) development plan, (2) action, (3) reflection‐on‐action, and (4) remedies.  相似文献   

Parental Cultural Socialization of Mexican‐American Adolescents’ Family Obligation Values and Behaviors          下载免费PDF全文

Kim M. Tsai  Eva H. Telzer  Nancy A. Gonzales  Andrew J. Fuligni 《Child development》2015,86(4):1241-1252

The current study examined how parents’ cultural socialization efforts contribute to adolescents’ family obligation values and behaviors and how these processes may depend upon the relational climate at home. Utilizing survey and daily diary methodologies, 428 Mexican‐American adolescents (50% males; M_age = 15 years) and their parents (83% mothers; M_age = 42 years) participated in the study. Adolescents reported on their family obligation values and engagement in family assistance tasks across 14 days. Parents reported on their cultural socialization practices. Results indicated that parental cultural socialization was associated with adolescents’ family obligation values and behaviors when parent–child relationships were low in conflict and high in support. Findings suggest that the transmission of cultural values and practices is best facilitated through positive parent–child relationships.  相似文献