Structural design of a double-layered porous hydrogel for effective mass transport

Mass transport in porous materials is universal in nature, and its worth attracts great attention in many engineering applications. Plant leaves, which work as natural hydraulic pumps for water uptake, have evolved to have the morphological structure for fast water transport to compensate large water loss by leaf transpiration. In this study, we tried to deduce the advantageous structural features of plant leaves for practical applications. Inspired by the tissue organization of the hydraulic pathways in plant leaves, analogous double-layered porous models were fabricated using agarose hydrogel. Solute transport through the hydrogel models with different thickness ratios of the two layers was experimentally observed. In addition, numerical simulation and theoretical analysis were carried out with varying porosity and thickness ratio to investigate the effect of structural factors on mass transport ability. A simple parametric study was also conducted to examine unveiled relations between structural factors. As a result, the porosity and thickness ratio of the two layers are found to govern the mass transport ability in double-layered porous materials. The hydrogel models with widely dispersed pores at a fixed porosity, i.e., close to a homogeneously porous structure, are mostly turned out to exhibit fast mass transport. The present results would provide a new framework for fundamental design of various porous structures for effective mass transport.     

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

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.     

DISTRIBUTIVE PARTITIONING OPERATION IN MATHEMATICAL SITUATIONS INVOLVING FRACTIONAL QUANTITIES

In the present study, we describe a participating student’s (Carol’s) distributive partitioning scheme and operations along with Steffe’s and his colleagues’ studies about children’s constructions of fraction knowledge as a particular model of mathematical learning. Analysis of Carol’s mathematical behaviors indicates that an operationally common mathematical behavior (distributive partitioning operation) was revealed in various mathematical problem situations such as fraction multiplication, fraction division, and multiplicative transformation between fractional quantities. It both provides a rationale for why becoming versed in one mathematical subject could facilitate working with another mathematical subject and also implies the necessity of describing and defining students’ mathematical behaviors from an operational view of knowledge, which might lead to building foundations of a substantial cognitive map for students’ mathematical development.     

An Autoethnographical Study of Culture,Power, Identity and Art Education in Post‐Colonial South Korea

This article reflects my experiences of learning art in the 1970s and 1980s and my teaching career in school art education in twenty‐first century South Korea. This autobiographical reflection shows how I have struggled with my identity as an art teacher in the post‐colonial context of Western influences on Korean society since World War II. There has been greater tension and a greater struggle for different values, practices and identities when new values and practices have been introduced into the particular socio‐cultural context of South Korea. My struggles with particular kinds of pedagogic identity valued within the rapidly changing political, economic and cultural context of Western influences on Korean art education demonstrate the hidden structural mechanism of the relationship between culture, power and identity in the post‐colonial world of globalisation. This study as an autoethnographical research provides critical insights into how identities are produced by pedagogic discourses and practices of art education that are constructed through the specific systems of practice and language which transmit and regulate such identities and values.     

Patterns and predictors of father-infant engagement across race/ethnic groups

This study examines whether levels of father engagement (e.g., verbal stimulation, caregiving, and physical play) vary by race/ethnicity using a model that controls for fathers' human capital, mental health, and family relationships. It also tests whether the models work similarly across race/ethnic groups. Its sample of N=5,089 infants and their families is drawn from the Early Childhood Longitudinal Study - Birth Cohort (ECLS-B). We found that, after including controls, African American and Latino fathers had higher levels of engagement in caregiving and physical play activities than White fathers. There were no differences in verbal stimulation activities across race/ethnicity. Fathers' education (college level) predicted more verbally stimulating activities whereas fathers' report of couple conflict predicted less caregiving and physical play. Although levels of engagement differed across the groups, the overall models did not differ by race/ethnicity, except for physical play. African American mothers who reported high levels of depressive symptoms had partners who engaged in more physical play than White mothers with high levels of depressive symptoms.     

How do congressional members appear on the web? Tracking the web visibility of South Korean politicians

The web visibility of politicians has substantial implications for the internet and politics. In this regard, the present paper examines the web visibility of South Korea's 18th National Assembly members. This study identifies those members with the highest web visibility and determines the factors affecting their web visibility by using a set of socio-demographic variables indicating web visibility. The concept of web visibility is operationally defined as the number of web mentions of each congressional member. Web mentions of the name of each congressional member were collected across many platforms, including blogs, images, news, and websites, by using a Naver search tool based on the API, and relationships between the web visibility of the members and their socio-demographic attributes (their gender, age, term, constituency, and party affiliation) were analyzed using Kruskal–Wallis, Median, and Mann–Whitney U tests. The most visible politicians in the Korean webosphere had highly qualified political careers and prominence, and the difference in politicians' web visibility depended on their political attributes (their term, constituency, and party), not on their demographic attributes (their gender and age). These findings suggest that politicians who build political power and influence through their political career in the offline world are likely to be more visible in the webosphere. Further, an integrated indicator based on politicians' web visibility status can reflect their “ubiquitous presence” in Korea's digitalized society.     

Understanding Complex Ecosystems Through an Agent-Based Participatory Watershed Simulation

Journal of Science Education and Technology - The properties and functions of complex systems apply across a variety of domains of science and are at the heart of the solutions to many global...     

Root causes of errant ordered radiology exams: Results of a needs assessment

A comprehensive needs assessment was conducted at ATA hospital to determine the root causes of a high number of errant radiology orders from requesting physicians. The Human Performance Technology Model, Gilbert's Behavior Engineering Model, and Rummler and Brache's Nine Performance Variables Model guided the needs assessment process. Three solutions were proposed. The development of the long‐term solution, a software utility, has been initiated. The Behavior Engineering Model was used to identify possible solutions to post‐training performance gaps identified during the evaluation.