Geometrical effects in microfluidic-based microarrays for rapid, efficient single-cell capture of mammalian stem cells and plant cells

In this paper, a detailed numerical and experimental investigation into the optimisation of hydrodynamic micro-trapping arrays for high-throughput capture of single polystyrene (PS) microparticles and three different types of live cells at trapping times of 30 min or less is described. Four different trap geometries (triangular, square, conical, and elliptical) were investigated within three different device generations, in which device architecture, channel geometry, inter-trap spacing, trap size, and trap density were varied. Numerical simulation confirmed that (1) the calculated device dimensions permitted partitioned flow between the main channel and the trap channel, and further, preferential flow through the trap channel in the absence of any obstruction; (2) different trap shapes, all having the same dimensional parameters in terms of depth, trapping channel lengths and widths, main channel lengths and widths, produce contrasting streamline plots and that the interaction of the fluid with the different geometries can produce areas of stagnated flow or distorted field lines; and (3) that once trapped, any motion of the trapped particle or cell or a shift in its configuration within the trap can result in significant increases in pressures on the cell surface and variations in the shear stress distribution across the cell’s surface. Numerical outcomes were then validated experimentally in terms of the impact of these variations in device design elements on the percent occupancy of the trapping array (with one or more particles or cells) within these targeted short timeframes. Limitations on obtaining high trap occupancies in the devices were shown to be primarily a result of particle aggregation, channel clogging and the trap aperture size. These limitations could be overcome somewhat by optimisation of these device design elements and other operational variables, such as the average carrier fluid velocity. For example, for the 20 μm polystyrene microparticles, the number of filled traps increased from 32% to 42% during 5–10 min experiments in devices with smaller apertures. Similarly, a 40%–60% reduction in trapping channel size resulted in an increase in the amount of filled traps, from 0% to almost 90% in 10 min, for the human bone marrow derived mesenchymal stem cells, and 15%–85% in 15 min for the human embryonic stem cells. Last, a reduction of the average carrier fluid velocity by 50% resulted in an increase from 80% to 92% occupancy of single algae cells in traps. Interestingly, changes in the physical properties of the species being trapped also had a substantial impact, as regardless of the trap shape, higher percent occupancies were observed with cells compared to single PS microparticles in the same device, even though they are of approximately the same size. This investigation showed that in microfluidic single cell capture arrays, the trap shape that maximizes cell viability is not necessarily the most efficient for high-speed single cell capture. However, high-speed trapping configurations for delicate mammalian cells are possible but must be optimised for each cell type and designed principally in accordance with the trap size to cell size ratio.     

Effectiveness of Spanish intervention for first-grade English language learners at risk for reading difficulties

The effectiveness of an explicit, systematic reading intervention for first-grade students whose home language was Spanish and who were at risk for reading difficulties was examined. Participants were 69 students in 20 classrooms in 7 schools from 3 districts who initially did not pass the screening in Spanish and were randomly assigned within schools to a treatment or comparison group; after 7 months, 64 students remained in the study. The intervention matched the language of instruction of their core reading program (Spanish). Treatment groups of 3 to 5 students met daily for 50 min and were provided systematic and explicit instruction in oral language and reading by trained bilingual intervention teachers. Comparison students received the school's standard intervention for struggling readers. Observations during core reading instruction provided information about the reading instruction and language use of the teachers. There were no differences between the treatment and comparison groups in either Spanish or English on any measures at pretest, but there were significant posttest differences in favor of the treatment group for the following outcomes in Spanish: Letter-Sound Identification (d = 0.72), Phonological Awareness composite (d = 0.73), Woodcock Language Proficiency Battery-Revised Oral Language composite (d = 0.35), Word Attack (d = 0.85), Passage Comprehension (d = 0.55), and two measures of reading fluency (d = 0.58-0.75).     

Conceptual framework for structuring future agricultural colleges and universities in industrial countries

Abstract

Agricultural colleges and universities in industrial countries are faced with declining numbers of students and the need to carefully evaluate alternative structures and functions to meet the challenges of a sustainable food supply. Current education and research are compartmentalized into classical departments and disciplines that often ignore the complex realities of natural, agricultural, and other human-designed systems. Communication with the agricultural industry likewise is confined to answers to specific questions that are perceived to be within the domain of specialized research and expertise. There is relative isolation from the natural resource environment and the urban society context. We propose two models for greater integration of learning activities among departments as well as moving more research and education into the field and food system. These alternative strategies broaden the concept of ‘faculty’ to include educators from farming, business, government, and non-profit groups, and promote team research and education within the context of the natural environment and with urban society. This type of action research and action learning can provide answers to immediate questions as well as contribute to a long-term, sustainable, locally-based food system through students who are prepared to deal with complex issues in the future.     

Open-ended Cases in Agroecology: Farming and Food Systems in the Nordic Region and the US Midwest

Abstract

Our aim is to describe open-ended case studies for learning real-life problem solving skills, and relate this approach to conventional, closed-ended decision case studies. Teaching methods are open-ended cases in agroecology, an alternative to traditional strategies that lead students through prepared materials and structured discussions to determine an outcome already known to the instructor. Our method promotes a culture of curiosity. Multiple evaluation criteria show how this learning strategy provides students with practice in researching, envisioning and designing potential scenarios for clients in the field. In agroecology case studies, students and instructors are co-learners in a discovery process that includes gathering information from key clients, interviewing major stakeholders, and building an understanding of the current context of the local farming and food systems. Two agroecology courses in Norway, a field course in the US Midwest, and an experimental course in Sweden and Vietnam illustrate this learning strategy. Student evaluations of learning have been highly positive, and skills and methods from courses have been applied in their thesis projects and professional careers.

Practical results reveal that students are well prepared for an uncertain, complex, multi-dimensional and dynamic future, have the capacity to develop alternative future scenarios, and have practiced methods to evaluate options based on production, economic, environmental and social criteria and impacts. This innovative strategy is offered as a complement or alternative to conventional decision case studies and evaluated as an approach to experiential learning, an important and effective method for adult learners.     

Cognitive load and knowledge sharing in Learning Networks

Learning Networks (LNs) are online social networks designed to support nonformal learning; they are therefore particularly suitable for self-directed learners. In LNs, learners need to construct knowledge through knowledge sharing with other participants. However, without support, learners have to organize knowledge sharing themselves and this could induce extraneous cognitive load. When working on complex learning tasks, this organizing process could have a detrimental effect on knowledge construction. To optimize cognitive load, we propose using a peer support system that applies the mechanisms of peer tutoring to support knowledge sharing. Its mechanisms reduce, we argue, the extraneous load imposed by having to organize knowledge sharing as well as induce germane load by directing the freed-up cognitive capacity to processes that contribute to knowledge construction.     

Continuous walking and time- and intensity-matched interval walking: Cardiometabolic demand and post-exercise enjoyment in insufficiently active,healthy adults

ABSTRACT

We compared cardiometabolic demand and post-exercise enjoyment between continuous walking (CW) and time- and intensity-matched interval walking (IW) in insufficiently active adults. Sixteen individuals (13 females and three males, age 25.3 ± 11.1 years) completed one CW and one IW session lasting 30 min in a randomised-counterbalanced design. For CW, participants walked at a mean intensity of 65–70% predicted maximum heart rate (HR_max). For IW, participants alternated between 3 min at 80% HR_max and 2 min at 50% HR_max. Expired gas was measured throughout each protocol. Participants rated post-exercise enjoyment following each protocol. Mean HR and V˙O₂ showed small positive differences in IW vs. CW (2, 95%CL 0, 4 beat.min^?1; d = 0.23, 95%CL 0.06, 0.41 and 1.4, 95%CL 1.2 ml.kg^?1.min^?1, d = 0.36, 95%CL 0.05, 0.65, respectively). There was a medium positive difference in overall kcal expenditure in IW vs. CW (25, 95%CL 7 kcal, d = 0.58, 95%CL 0.33, 0.82). Post-exercise enjoyment was moderately greater following IW vs. CW (9.1, 95%CL 1.4, 16.8 AU, d = 0.62, 95%CL 0.06, 0.90), with 75% of participants reporting IW as more enjoyable. Interval walking elicits meaningfully greater energy expenditure and is more enjoyable than CW in insufficiently active, healthy adults.     

Contextual effects on predicting risk for reading difficulties in first and second grade

This study utilized early reading assessment data from a randomized trial of 210 urban and rural schools in Texas to examine contextual effects on risk prediction in first and second grade. The primary objective was to examine the roles of (a) individual differences, (b) the grade 1 classroom, and (c) the pairing of first and second grade teachers in determining grade 2 outcomes in word reading and fluency. A second objective was to investigate whether the administration format of the assessment (paper, paper plus desktop, handheld plus desktop) or the level of teacher support (web mentoring, no mentoring) moderated the prediction. These moderator variables proved not to be significant. Subsequent analyses found that a combination of student pretest and mean of pretest classroom was a better predictor than student pretest alone. Additionally, the effect of student scores varied by teacher-pair. On average, intraclass correlations (ICCs) ranged from 6% to 17%. Differences in ICCs at the classroom level were much greater than at the school level, and differences in urban schools were twice that of rural schools.     

Multiracial Children in Child Development Textbooks

The 2000 US census was the first to allow respondents to check more than one race/ethnic response for their identity. About 6.8 million Americans did so, and a disproportionate percentage of them were children under age 18 years old. The purpose of this article is to examine the extent to which this change is reflected in contemporary child psychology textbooks. Twelve books were examined to determine whether they covered multiracial and multiethnic children. Results of this study showed that only two of these books addressed issues related to the healthy development of multiracial/multiethnic children in any detail; and, while several used terms such as biracial and bicultural, these terms were always used to describe single-race minority children living in a majority context. The discussion section covers possible reasons for this omission.