Content Management Systems: Enriched learning opportunities for all?

This article examines the popular claim of Content Management Systems (CMSs) that providing a rich toolset and leaving the use under learner control is beneficial to learning. By means of a literature review, the current contribution examines whether all students are capable of using CMS tools so that their learning is enhanced. In contrast to what is assumed, the study conceptualizes tool use as a complex self-regulation strategy that cannot be taken for granted. Specifically, the article reviews empirical studies in relation to three topics: (a) personal agency in tool use, (b) performance effects of tool use and (c) influencing tool use variables. Findings reveal that not every student profited from the CMS learning opportunities; in multiple studies students differed in their tool use, and these differences had significant performance effects. Hence, these findings suggest that the pedagogical claim CMSs make is problematic. Besides this accumulated corpus of knowledge, the review revealed serious limitations in the retrieved studies which could hamper our findings. As a consequence, the review establishes a need for further research into students’ CMS tool use from an instructional design perspective. In addition to the theoretical framework, several directions for future research are given.     

Degenerative process and cell death in salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi-engorged female exposed to the acaricide permethrin

Ticks are ectoparasites of great medical and veterinary importance around the world and synthetic chemicals such as permethrin have been used for their control. This study provides a cytochemistry analysis of both degenerative and cell death processes in salivary glands of the brown dog tick Rhipicephalus sanguineus semi-engorged females exposed to 206, 1,031, and 2,062 ppm of permethrin. The results presented herein demonstrate that permethrin is a potent chemical acaricide that would act on the glandular tissue's morphophysiology in this tick species by eliciting severe changes in the acinus shape, intense vacuolation of the acinar cells' cytoplasm, marked glandular tissue disorganization, culminating in an advanced degenerative stage with consequent formation of many apoptotic bodies (cell death). In addition, permethrin induced major changes in the acinar cells' nucleus, such as a change both in its shape and size, chromatin marginalization, nuclear fragmentation, and appearance of picnotic nuclei, especially when the highest concentrations of the product were used. Thus, permethrin induced early degeneration of this tissue characterized by significant changes in the structure of acinar cells and production of enzymes related to the cell death process, in addition to interfering directly in the genetic material of these cells.     

Influence of chlorhexidine in cavities prepared with ultrasonic or diamond tips on microtensile bond strength

This study evaluated the effect of chlorhexidine (CLX) in cavities prepared with either ultrasound-mounted CVDentUS diamond tips or conventional diamond burs on dentin bond strength after 24 h and 180 days. Forty-eight dentin surfaces from sound third molars were flattened and divided into four groups (n = 12), according to the type of cavity preparation (CVDentUS ultrasound tip or conventional diamond) and with or without 2% CLX (Consepsis) treatment. After application of the adhesive system (Clearfil SE Bond), microhybrid composite resin blocks (Charisma) were made on the dentin surface in increments. After 24 h, the specimens were sectioned into stick-shaped samples with an adhesive interface of approximately 1 mm². From each tooth, half of the sticks were evaluated after 24 h of storage in distilled water and the other half after 180 days, using a universal testing machine. Three-way analysis of variance showed no significant triple interactions (p = 0.722) or double interactions between factors. Higher bond strength values were observed with the use of ultrasonic tips (p = 0.019), irrespective of whether or not CLX was applied in either time period. No difference in bond strength values was observed in terms of CLX application (p = 0.581). No significant difference in bond strength values was shown after storage for 24 h or 180 days (p = 0.302). In conclusion, the ultrasonic tips promoted greater bond strength to dentin, irrespective of whether or not CLX was applied, and storage time.     

Crack closure and influence of cycle ratio R on fatigue crack growth in type 304 stainless steel at room temperature

Crack growth rate and crack closure during fatigue of type 304 stainless steel are measured with an optical microscope and television camera. Based on the crack closure data an effective stress intensity range ΔK_eff is calculated. The da/dn vs ΔK_eff-curves indicate that crack closure could account for the R-influence as normally derived from da/dn vs ΔK-curves. Measurements of striation spacing lead to the conclusion that at higher da/dn values crack growth mechanisms dependent on K_max play an important role; these mechanisms are probably responsible for the R-influence in the range of the higher da/dn-values.     

Multifilament Nb3Sn superconductors produced by the E.C.N. technique

Multifilament Nb3Sn conductors are produced by reduction of composites containing bundles of niobium tubes filled with NbSn2-powder and surrounded by pure copper. Heat treatment at temperatures between 575 and 675°C after final reduction causes the tin from the NbSn2-powder to diffuse into the niobium tubes, which results in a final Nb3Sn-layer at the inner side of the tube. Two types of experimental wire are produced, the first type consisting of 4 bundles of 9 tubular filaments, the powder cores having diameters of about 35 micron, the outer size of the wire being 1 mm square. The second type consists of 4 bundles of 45 tubular filaments. This type is fabricated in 3 sizes: round φ 2.3 and square 1.4 and 1.0 mm, corresponding with powder core diameters of 26,18 and 13 microns respectively. Critical current densities in the Nb3Sn-layers reach values of about 4 - 6 × 10⁹A/m²at 8 Tesla and 1,6 - 2,4 × 10⁹A/m²at 12 Tesla. Maximum critical temperatures are about 18.1 K with a ΔTcof 0.3 K.     

柔性植物影响下水沙运动及物质输运研究进展

水生植物是河流、湖泊、滨海湿地环境中不可缺少的一部分,植物的存在使水动力条件发生了改变,进而影响了泥沙悬浮和污染物的输运。从恒定流和波浪两种水动力条件出发,针对柔性植物影响下的水流阻力、水流结构、紊动特性、特征流速、消波系数、泥沙运动、污染物输运等方面,综述了国内外的主要成果,并指出复杂水动力条件下的植物-水流-泥沙-污染物之间的相互作用规律是今后研究的重点和难点。     

When a game supports prevocational math education but integrated reflection does not

The present study addressed the effectiveness of an educational math game for improving proportional reasoning in prevocational education, and examined the added value of support in the form of reflection. The study compared four conditions: the game with reflection prompts, the game with reflection prompts plus procedural information, the game with procedural information only and the game without additional support. It was found that students' proportional reasoning skill improved after playing the game. The game managed to target prevocational students with low prior knowledge, a group that has the potential to understand proportional reasoning but has not yet encountered the right learning situation to live up to their potential. However, it was also found that students need to be computational fluent to profit from the game. Furthermore, no added value of the support was found. The way the support was structured may have been too demanding for most of the students. The fact that the prevocational students (and specifically those with low prior knowledge) improved by playing the game is noteworthy, because the topic of proportional reasoning is demanding for this group of students who often have lower abilities as well as in some cases a high resistance to learning.     

Effect of decreasing platinum amount in Pt–Sn–Ni alloys supported on carbon as electrocatalysts for ethanol electrooxidation

Literature describes the influence of morphological and structural electrocatalysts characteristics, on the catalytic activity toward ethanol electrooxidation. Thus, in this work Pt and ternary Pt–Sn–Ni alloys nanoparticles, supported on Vulcan carbon, were obtained by impregnation/reduction method. The aim of this work was to evaluate the influence of the decrease of platinum and increase of nickel content of the electrocatalysts obtained. The electrocatalysts were characterized by Rutherford backscattering spectroscopy, X-ray diffraction, transmission electronic microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The results obtained showed that it was possible to obtain Pt–Sn–Ni nanoparticles with a uniform size distribution in a narrow particle size range with a composition control. Moreover, the simultaneous addition of Sn and Ni to Pt did not affect reticular lattice a value, but the crystallite size decreases significantly. Besides, electrochemical results suggest that the substitution of platinum by nickel, in the electrocalatyst alloys studied, does not compromise the catalytic activity toward ethanol eletrooxidation.     

Supporting learners: Increasing complexity?

The different papers in this special issue all addressed learning with complex tasks. All of these papers reached only partially the expected results. This discussion on possible factors that may explain these unexpected results. A first issue that is questioned is the functionality of the tools in the studies. Secondly, the learners lack of compliance is addressed. It may have been that the learners did not take the opportunities offered to them. Third, the use of the support by the learners itself is questioned. Although some methodological issues can be raised, the different papers made a worthwhile attempt to grasp the complexity in a learning environment. Moreover, they highlight the importance of a consolidated framework to determine relevant factors that should be considered when dealing with complexity.     

Tool-use in a blended undergraduate course: In Search of user profiles

The popularity of today’s blended courses in higher education is driven by the assumption that students are provided with a rich toolset that supports them in their learning process. However, little is known on how students actually use these tools and how this affects their performance for the course. The current study investigates how students use the entire toolset at their disposal, whether tool-use patterns can be found and if these patterns affect performance for the course. Logging students (n = 156) actions throughout the content management system and registering students’ use of the face-to-face support in an undergraduate course, the study reveals large student differences and an underuse for some tool-types. Further to this, K-means cluster analysis reveals three distinct tool-use patterns or user profiles: the no-users, the intensive users and the incoherent users. These patterns are characterized by different tool-choices and even different use intensity among students. Evidence is retrieved that these tool-use differences are problematic since multivariate analysis of variance reveals significant performance effects. Hence, these results imply that not all students seem to profit from the learning affordances that are provided. Similar as evidence in controlled settings, the results suggest that learner control in using tools cannot be taken for granted. Consequently, this study legitimates more research into the influencing (student and context) variables that can explain these differences.