On the influence of the architecture of poly(ethylene glycol)-based thermoresponsive polymers on cell adhesion

Thermoresponsive polymer surface coatings are a promising tool for cell culture applications. They allow for a mild way of cell detachment that preserves the activity of membrane proteins—a prerequisite for reliable cell analysis. To enlarge the application range of these coatings to cells with different adhesion properties, we synthesized various novel poly(ethylene glycol)-based thermoresponsive polymers and describe how (i) their chemical structure and (ii) their surface density affect their efficiency. In order to quantify the influence of both factors, the time for cell spreading and rounding efficiency were observed. As a result, efficiency of cell rounding, which is closely correlated to cell detachment, is less affected by both factors than the time needed for cell spreading. This time can effectively be adjusted by the molecular architecture which includes the length of the polymer backbone and the side chains. Based on this work, recommendations are given for future optimization of functionality of thermoresponsive polymer coatings for cell culture applications.     

Collective effectiveness in the XV de France: selections and time matter

The aim of this study was to quantify the impact of selections and shared selections in the rugby union. Players’ names, positions, and number of selections were collected for all XV de France’s games (1906–2014). Every team’s percentage of renewal of workforce was calculated for backs and forwards. During the 1987–2014 period, all second row forwards (locks), halfbacks, and centres’ shared selections (number of times when two players have competed together) were recreated. The Best vs. Rest method was applied to these remodelled dyads. They were analysed and compared with surrounding teammates as well as opponents. Head coaches similarly change their workforce for upcoming matches after winning or losing (around 30%), but losing teams renew significantly more positions in their line-ups. The recreated halfbacks, locks, and centres reveal a common pattern. Whether victorious or not, the ‘renewed couples’ victory percentage will congregate towards the XV de France’s victory percentage. For all the best recreated couples, the cumulated number of selections for forwards’ is always higher than the ones part of less efficient teams: 231.3?±?80 vs. 212.9?±?91 selections for locks’ teammates (Effect sizes (ES) small, possibly positive, 54.8%). In best recreated couples, number 8’s are significantly more experienced than their counterparts in less efficient pairs (ES small, likely positive, 76.3%). The XV de France’s collective effectiveness relies on a balance between stability and workforce renewal, which allows the building of specific position interactions and builds on experimented forwards packs. Selections and shared selections are serious collective performance parameters associated with performance.     

Reliability of unipodal and bipodal counter movement jump landings in a recreational male population

Movement patterns during landing have been suggested to be related to injury risk. The purpose of this study was to determine the inter-session reliability of kinematic variables and ground reaction forces during landing in a population of male recreational athletes after a counter movement jump. Both unipodal and bipodal landings were evaluated. Furthermore, the possibility to improve landing reliability with a verbal instruction was also studied. Twenty-four male volunteers with no history of lower extremity trauma were randomly assigned to two groups (with and without verbal landing instruction). An optoelectronic 3D system and force plates were used to measure the lower limb joint angles and the ground reaction forces during landing. Intraclass correlation values show moderate to excellent inter-session reliability for the bipodal task (ICC average: 0.80, range: 0.46–0.97) and poor to excellent reliability for the unipodal task (ICC average: >0.75, range: 0.20–0.95). However, large standard errors of measurement values at the ankle joint at impact (27.6?±?11.5°) and for the vertical ground reaction forces (394?±?1091 N) show that some variables may not be usable in practice. The verbal instruction had a negative effect on the reliability of unipodal landing but improved the reliability of bipodal landing. These findings show that the reliability of a landing task is influenced by its motor complexity as well as the instruction given to the subject.     

Dielectrophoretic capture of low abundance cell population using thick electrodes

Enrichment of rare cell populations such as Circulating Tumor Cells (CTCs) is a critical step before performing analysis. This paper presents a polymeric microfluidic device with integrated thick Carbon-PolyDimethylSiloxane composite (C-PDMS) electrodes designed to carry out dielectrophoretic (DEP) trapping of low abundance biological cells. Such conductive composite material presents advantages over metallic structures. Indeed, as it combines properties of both the matrix and doping particles, C-PDMS allows the easy and fast integration of conductive microstructures using a soft-lithography approach while preserving O₂ plasma bonding properties of PDMS substrate and avoiding a cumbersome alignment procedure. Here, we first performed numerical simulations to demonstrate the advantage of such thick C-PDMS electrodes over a coplanar electrode configuration. It is well established that dielectrophoretic force (F_DEP) decreases quickly as the distance from the electrode surface increases resulting in coplanar configuration to a low trapping efficiency at high flow rate. Here, we showed quantitatively that by using electrodes as thick as a microchannel height, it is possible to extend the DEP force influence in the whole volume of the channel compared to coplanar electrode configuration and maintaining high trapping efficiency while increasing the throughput. This model was then used to numerically optimize a thick C-PDMS electrode configuration in terms of trapping efficiency. Then, optimized microfluidic configurations were fabricated and tested at various flow rates for the trapping of MDA-MB-231 breast cancer cell line. We reached trapping efficiencies of 97% at 20 μl/h and 78.7% at 80 μl/h, for 100 μm thick electrodes. Finally, we applied our device to the separation and localized trapping of CTCs (MDA-MB-231) from a red blood cells sample (concentration ratio of 1:10).     

Whose story is this? Discrepancy triggers readers’ attention to source information in short narratives

Three experiments investigated the role of source information (i.e., who said what) in readers’ comprehension of short informational texts. Based on the Discrepancy-Induced Source Comprehension assumption (Braasch, Rouet, Vibert, & Britt, 2012), we hypothesized that readers would be more likely to make use of source information when summarizing stories that included discrepant statements. Readers would also memorize source information more accurately. Experiments 1 and 2 found that American and French college students were more likely to refer to source information when they summarized news reports containing discrepant assertions. A detailed content analysis of the summaries also indicated that students use hedging and several other tactics to resolve contradictions. Experiment 3 replicated Braasch et al.’s finding that sources of discrepant stories were more likely to be recalled than sources of consistent stories. Experiment 3 also extended these findings using longer texts and a different reading task. Altogether the data support the Documents Model framework of multiple source comprehension.     

Effects of academic training on metatextual knowledge and hypertext navigation

We investigated the effects of college training on students’ metatextual knowledge, hypertext navigation strategies and their acquisition of problem-relevant information. Ten psychology undergraduates and nine clinical psychology post-graduate students were asked to study a 3,400-word, 14-section hypertext with the purpose of drafting a short essay on a specific, complex issue in the area of teenage psychopathology. The specialists outperformed the novices on a metatextual knowledge test. They spent more time visiting relevant sections of the hypertext, and wrote essays containing more critical information. They also displayed a better incidental memory for the hypertext structure. We discuss the data in terms of the late acquisition of metatextual knowledge and study strategies.     

Effects of orthographic consistency and word length on the dynamics of written production in adults: psycholinguistic and rTMS experiments

Reading and Writing - Recent studies on written word production aim at studying how information is transmitted between central (linguistic) and peripheral (motor) processes. Neurocognitive models...     

Tackling the anxiety of learning statistics: The mystery of the red envelope

Most graduate programs in management require students to carry out a substantive research project. However, few management students have a comfortable command of the statistical techniques needed to realize such quantitative projects. This can lead to student anxiety and stress, which challenges instructors to devise ways to build students’ self-efficacy with statistical analysis. Drawing on game-based learning principles, we developed an exercise to help students in a graduate-level research methods course practice these statistical techniques. Designed around a series of four gamified challenges, students perform basic statistical analyses (correlations, t-tests, and simple linear regression) to solve puzzles and unlock a reward hidden in a mysterious red envelope. We used the exercise on seven occasions (five times in the methods course and twice in a graduate program preparatory course). After launching it in fall 2021, we observed that students were engaged and enthusiastic about the exercise. To ascertain its effectiveness more systematically, we collected data in five subsequent sections using a pretest/posttest design (N = 84) which showed that perceptions of statistics self-efficacy increased following the exercise. We conclude by suggesting that our exercise can be tailored to other learning contexts such as management and statistics-centered courses.     

Obstetrical complications and violent delinquency: testing two developmental pathways

This study focused on the interaction between specific obstetrical complications and early family adversity in predicting violent behavior during childhood and adolescence, in a sample of 849 boys from low socioeconomic areas of Montreal, Canada. Obstetrical complication data from medical records were used to create three scales using a nonlinear principal component analysis followed by rotation. Family adversity and teacher-rated physical aggression were assessed when the boys were in kindergarten and self-reports of delinquency were collected when they were 17. Elevated scores on the Deadly Risk Situation scale of obstetrical complications (preeclampsia, umbilical cord prolapse, and induced labor) increased the risk of being violent at both 6 and 17 years of age, only among boys who grew up in high adverse familial environments. Moreover, this interaction partly accounted for the continuity between violence in childhood and adolescence. Interventions for young pregnant women from deprived environments and their babies are discussed in light of these results.