Transport and separation of micron sized particles at isotachophoretic transition zones

Conventionally, isotachophoresis (ITP) is used for separation of ionic samples according to their electrophoretic mobilities. We demonstrate that the scope of ITP applications may be extended toward particle concentration and separation. Owing to the distributions of electrolyte concentration and electric field inside a transition zone between two electrolytes, a number of different forces act on a small particle. As far as possible, we provide estimates for the order of magnitude of these forces and analyze their scaling with the particle size and the electric-field strength. Furthermore, we experimentally demonstrate that polymer beads of 5 μm diameter dispersed in a high mobility “leading” electrolyte are picked up and carried along by an ITP transition zone which is formed with a low mobility “trailing” electrolyte. By studying the particle positions and trajectories, we show that impurities in the electrolytes play a significant role in the experiments. Additionally, it is experimentally shown that different types of beads can be separated at an ITP transition zone. In particular, beads of 1 μm diameter are not carried along with the transition zone, in contrast to the 5 μm beads. The presented technique thus adds to the portfolio of electrokinetic transport, concentration, and separation methods in microfluidics.     

The impact of technology on publishing

Technology today more than ever has a disruptive impact on publishing. The Internet, printing-on-demand and the e-book are the main drivers of change, impacting all aspects of the publishing value chain—from the way books are published (authors can go direct to the reader), distributed (electronic marketplaces), sold (e-tailers) and read (electronic books). The author examines the context of the publishing industry in which these changes are occurring, describes the main drivers and impacts of these changes and illustrates them with an example from the information publishing industry. This paper is based on a presentation made during the conference ‘Blinded by the E-Light’ sponsored by Vista Computer Services (www.vistacomp.com) on June 15, 2000 in New York, NY.     

Um Compasso Para Aprender: A Randomized Trial of a Social-Emotional Learning Program in Homicide-Affected Communities in Brazil

Despite global demand, the large-scale effects of social-emotional learning (SEL) programming in developing countries remain underexplored. Using a randomized control trial, this study examined the effectiveness of a school-wide SEL intervention—Programa Compasso (PC)—among 3,018 sociodemographically diverse, Portuguese-speaking children (M_age = 9.85 years) attending 90 public primary schools across Rio de Janeiro, Brazil in 2017. Average impacts of PC on children’s executive function, emotion knowledge, and behavior problems after one school year were null. Moderation analyses did, however, reveal evidence for positive impacts of PC on children’s labeling of emotional expressions and inhibitory control within low-homicide communities (d = 0.15 SDs), and null effects on these same outcomes in high-violence areas. Implementation and cultural considerations are discussed.     

The Effects of Teacher Professional Development on Children’s Attendance in Preschool

Abstract

Student absenteeism is a widespread and critical issue in early childhood education. Current efforts to reduce student absenteeism in both preschool and K–12 settings have largely been family- and parent-focused interventions. Yet, interventions targeting teachers and schools may similarly be effective tools to improve student attendance. We utilize data from a large-scale, experimental evaluation of an early childhood professional development intervention to examine whether it impacted children’s absenteeism and chronic absenteeism. Although the professional development targeted the quality of teacher-child interactions and did not target children’s absenteeism, we find that the professional development reduced student absence rates by 1.0 percentage points (equivalent to approximately an additional 1.9?days of preschool). The professional development also reduced chronic absenteeism by 6.0 percentage points. Impacts were concentrated among lower-income children. Implications for policies targeting student absenteeism in preschool settings are discussed.     

Cognitive Interviewing: A Qualitative Tool for Improving Questionnaires in Sport Science

This study sought to determine whether body fat percentage estimates using an inexpensive bioelectrical impedance analysis (BIA) device (Tanita TBF-521, Tanita Corp, of America, Arlington Heights, IL) could be freely substituted for those obtained utilizing skinfolds (method equivalence). Data were analyzed from measurements on 38 children age 6 to 12 years. Random effect intraclass correlation (r = .930; 95% confidence interval [CI] = .87 to .96), fixed effect intraclass correlation (r = .932; 95% CI = .87 to .96), and least-products regression supported the equivalence of the 2 methods. The technical error between the 2 methods (3.7; coefficient of variation = 12.2%) was small and also supported the equivalence of the two methods. The ability of the BIA device to categorize into normal and obese categories when compared to the skinfold technique was also impressive (κ = .95; 95% CI = .73 to .99). However, the results of the limits of agreement analysis showed that the approximate 95% CI for the differences between methods was wide (-9.1 to 11.4).