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Synthesizing Results From Empirical Research on Computer-Based Scaffolding in STEM Education: A Meta-Analysis
Computer-based scaffolding assists students as they generate solutions to complex problems, goals, or tasks, helping increase and integrate their higher order skills in the process. However, despite decades of research on scaffolding in STEM (science, technology, engineering, and mathematics) education, no existing comprehensive meta-analysis has synthesized the results of these studies. This review addresses that need by synthesizing the results of 144 experimental studies (333 outcomes) on the effects of computer-based scaffolding designed to assist the full range of STEM learners (primary through adult education) as they navigated ill-structured, problem-centered curricula. Results of our random effect meta-analysis (a) indicate that computer-based scaffolding showed a consistently positive (ḡ = 0.46) effect on cognitive outcomes across various contexts of use, scaffolding characteristics, and levels of assessment and (b) shed light on many scaffolding debates, including the roles of customization (i.e., fading and adding) and context-specific support. Specifically, scaffolding's influence on cognitive outcomes did not vary on the basis of context-specificity, presence or absence of scaffolding change, and logic by which scaffolding change is implemented. Scaffolding's influence was greatest when measured at the principles level and among adult learners. Still scaffolding's effect was substantial and significantly greater than zero across all age groups and assessment levels. These results suggest that scaffolding is a highly effective intervention across levels of different characteristics and can largely be designed in many different ways while still being highly effective.
Journal Article
Effectiveness of Computer-Based Scaffolding in the Context of Problem-Based Learning for Stem Education: Bayesian Meta-analysis
Computer-based scaffolding plays a pivotal role in improving students' higher-order skills in the context of problem-based learning for Science, Technology, Engineering and Mathematics (STEM) education. The effectiveness of computer-based scaffolding has been demonstrated through traditional meta-analyses. However, traditional meta-analyses suffer from small-study effects and a lack of studies covering certain characteristics. This research investigates the effectiveness of computer-based scaffolding in the context of problem-based learning for STEM education through Bayesian meta-analysis (BMA). Specifically, several types of prior distribution information inform Bayesian simulations of studies, and this generates accurate effect size estimates of six moderators (total 24 subcategories) related to the characteristics of computer-based scaffolding and the context of scaffolding utilization. The results of BMA indicated that computer-based scaffolding significantly impacted (g = 0.385) cognitive outcomes in problem-based learning in STEM education. Moreover, according to the characteristics and the context of use of scaffolding, the effects of computer-based scaffolding varied with a range of small to moderate values. The result of the BMA contributes to an enhanced understanding of the effect of computer-based scaffolding within problem-based learning.
Journal Article
Vascular Occlusions in Grapevines with Pierce's Disease Make Disease Symptom Development Worse
Vascular occlusions are common structural modifications made by many plant species in response to pathogen infection. However, the functional role(s) of occlusions in host plant disease resistance/susceptibility remains controversial. This study focuses on vascular occlusions that form in stem secondary xylem of grapevines (Vitis vinifera) infected with Pierce's disease (PD) and the impact of occlusions on the hosts' water transport and the systemic spread of the causal bacterium Xylella fastidiosa in infected vines. Tyloses are the predominant type of occlusion that forms in grapevine genotypes with differing PD resistances. Tyloses form throughout PD-susceptible grapevines with over 60% of the vessels in transverse sections of all examined internodes becoming fully blocked. By contrast, tylose development was mainly limited to a few internodes close to the point of inoculation in PD-resistant grapevines, impacting only 20% or less of the vessels. The extensive vessel blockage in PD-susceptible grapevines was correlated to a greater than 90% decrease in stem hydraulic conductivity, compared with an approximately 30% reduction in the stems of PD-resistant vines. Despite the systemic spread of X. fastidiosa in PD-susceptible grapevines, the pathogen colonized only 15% or less of the vessels in any internode and occurred in relatively small numbers, amounts much too small to directly block the vessels. Therefore, we concluded that the extensive formation of vascular occlusions in PD-susceptible grapevines does not prevent the pathogen's systemic spread in them, but may significantly suppress the vines' water conduction, contributing to PD symptom development and the vines' eventual death.
Journal Article
Differences in grapevine rootstock sensitivity and recovery from drought are linked to fine root cortical lacunae and root tip function
• Structural changes during severe drought stress greatly modify the hydraulic properties of fine roots. Yet, the physiological basis behind the restoration of fine root water uptake capacity during water recovery remains unknown.
• Using neutron radiography (NR), X-ray micro-computed tomography (micro-CT), fluorescence microscopy, and fine root hydraulic conductivity measurements (Lpr
), we examined how drought-induced changes in anatomy and hydraulic properties of contrasting grapevine rootstocks are coupled with fine root growth dynamics during drought and return of soil moisture.
• Lacunae formation in drought-stressed fine roots was associated with a significant decrease in fine root Lpr
for both rootstocks. However, lacunae formation occurred under milder stress in the drought-resistant rootstock, 110R. Suberin was deposited at an earlier developmental stage in fine roots of 101-14Mgt (i.e. drought susceptible), probably limiting cortical lacunae formation during mild stress. During recovery, we found that only 110R fine roots showed rapid re-establishment of elongation and water uptake capacity and we found that soil water status surrounding root tips differed between rootstocks as imaged with NR.
• These data suggest that drought resistance in grapevine rootstocks is associated with rapid re-establishment of growth and Lpr
near the root tip upon re-watering by limiting competing sites along the root cylinder.
Journal Article
An extraordinary scandal : the Westminster expenses crisis and why it still matters
The expenses scandal of 2009 represented Britain's biggest political crisis since the Profumo Affair. Andrew Walker, the tax expert who oversaw the parliamentary expenses system, and Emma Crewe, a social scientist specialising in the institutions of parliament, bring a fascinating insider/outsider perspective to this account.
Book
Water Uptake along the Length of Grapevine Fine Roots: Developmental Anatomy, Tissue-Specific Aquaporin Expression, and Pathways of Water Transport
To better understand water uptake patterns in root systems of woody perennial crops, we detailed the developmental anatomy and hydraulic physiology along the length of grapevine (Vitis berlandieri × Vitis rupestris) fine roots from the tip to secondary growth zones. Our characterization included the localization of suberized structures and aquaporin gene expression and the determination of hydraulic conductivity (Lp
r
) and aquaporin protein activity (via chemical inhibition) in different root zones under both osmotic and hydrostatic pressure gradients. Tissue-specific messenger RNA levels of the plasma membrane aquaporin isogenes (VvPIPs) were quantified using laser-capture microdissection and quantitative polymerase chain reaction. Our results highlight dramatic changes in structure and function along the length of grapevine fine roots. Although the root tip lacked suberization altogether, a suberized exodermis and endodermis developed in the maturation zone, which gave way to the secondary growth zone containing a multilayer suberized periderm. Longitudinally, VvPIP isogenes exhibited strong peaks of expression in the root tip that decreased precipitously along the root length in a pattern similar to Arabidopsis (Arabidopsis thaliana) roots. In the radial orientation, expression was always greatest in interior tissues (i.e. stele, endodermis, and/or vascular tissues) for all root zones. High Lp
r
and aquaporin protein activity were associated with peak VvPIP expression levels in the root tip. This suggests that aquaporins play a limited role in controlling water uptake in secondary growth zones, which contradicts existing theoretical predictions. Despite having significantly lower Lp
r
, woody roots can constitute the vast majority of the root system surface area in mature vines and thus provide for significant water uptake potential.
Journal Article