The effectiveness of adaptive versus non-adaptive learning with digital educational games

For the training of academic skills, digital educational games with integrated adaptivity are promising. Adaptive games are considered superior to non-adaptive games, because they constantly assess children's performance, and accordingly adapt the difficulty of the tasks corresponding to the children's individual level. However, empirical evidence with regard to the effectivity of adaptive compared to non-adaptive games is limited. A study was conducted with 191 children from the third year of Kinder garten who were enrolled in one of three conditions, that is, playing an adaptive version of the reading game (RG), a non-adaptive version of the RG or training with pen-and-paper exercises. In all three conditions, children trained emergent reading (phonological awareness and letter knowledge) once a week for 30 min over a period of 5 weeks. Children's performance on cognitive (phonological awareness, letter knowledge, reading fluency) and non-cognitive (motivation, self-concept) factors was assessed. Results revealed a significant improvement in phonological awareness and letter knowledge in all conditions. However, no differences between the conditions were observed with respect to children's improvement on phonological awareness and letter knowledge or on their post-test scores for reading fluency. With regard to motivation and self-concept, again, no differences in these non-cognitive factors were observed across conditions.     

The effect of backbone fluorination on the carrier mobility in alkoxy and alkyl substituted conducting polymers of the poly(phenylenevinylene) type

Summary We report the synthesis of some new backbone fluorinated polymers of the poly(phenylenevinylene) type. The new polymers were characterised by NMR, SEC and X-ray powder diffraction. The charge carrier mobilities were determined using pulse radiolysis time resolved microwave conductivity (PR-TRMC) and the carrier mobilities were compared to the similar non-fluorinated analogues. The changes in charge carrier mobilities as a function of molecular substitution pattern is discussed in terms of other materials properties such as electronic structure and absorption properties. The major result is that it was found possible for this type of material to alter the electronic energy levels by molecular substitution without imparting significant changes in the magnitude of the charge carrier mobilities and the optical properties.     

Thermal Generation of Residual Stress Fields for Purpose of Distortion Minimization

Thermal treatments of steel components with the goal of hardening often result in distortion by releasing the residual stresses which were brought into the specimen during the preceding processing steps. The goal of the presented work is the minimization of this distortion. By generating definite residual stress fields and investigating the resulting distortion, the distortion mechanism can be observed in detail. A flexible and reproducible way to generate such residual stress fields inside a specimen is by means of local thermal treatment with a laser beam. Computer simulations as well as experiments were carried out using an idealized tooth of a gearwheel (finger sample) as a model system. The deformation of the samples due to the laser heat treatment and the stress fields generated inside the samples were determined with respect to different process parameters.     

Altered hippocampal kainate-receptor mRNA levels in temporal lobe epilepsy patients

This study determined whether hippocampal kainate (KA) receptor mRNA levels were increased or decreased in temporal lobe epilepsy patients compared with nonseizure autopsies. Hippocampal sclerosis (HS; n = 17), nonsclerosis (non-HS; n = 11), and autopsy hippocampi (n = 9) were studied for KA1-2 and GluR5-7 mRNA levels using semiquantitative in situ hybridization techniques, along with neuron densities. Compared with autopsy hippocampi, HS and non-HS cases showed decreased GluR5 and GluR6 hybridization densities per CA2 and/or CA3 pyramid. Furthermore, HS patients demonstrated increased KA2 and GluR5 hybridization densities per granule cell compared with autopsy hippocampi. These findings indicate that chronic temporal lobe seizures were associated with differential changes in hippocampal KA1-2 and GluR5-7 hybridization densities that vary by subfield and pathology group. In temporal lobe epilepsy patients, these results support the hypothesis that pyramidal cell GluR5 and GluR6 mRNA levels are decreased as a consequence of seizures, and in HS patients granule cell KA2 and GluR5 mRNA levels are increased in association with aberrant fascia dentata mossy fiber sprouting and/or hippocampal neuronal loss.     

On the effect of treating poly(acrylic acid) with argon and tetrafluoromethane plasmas: Kinetics and degradation mechanism

Poly(acrylic acid) (PAAc) films were treated with either an argon or a tetrafluoromethane (CF₄) plasma and subsequently analyzed with X-ray photoelectron spectroscopy (XPS). PAAc films were decarboxylated during both types of plasma treatments. In addition, during the CF₄ plasma treatment, the PAAc films became fluorinated. The plasma phase during the argon plasma treatment of PAAc films was investigated with optical emission spectroscopy. It was shown that during this plasma treatment carbon dioxide, water, and possibly hydrogen were liberated from the PAAc surface. By covering the surface of PAAc films with different materials (lithium fluoride, UV fused silica, and glass) during the plasma treatment, it was possible to differentiate between photochemically induced and particle-induced changes of the surface. This method was used to show that decarboxylation during the argon plasma treatment was caused by vacuum UV radiation (wavelength < 150 nm) and the decarboxylation/fluorination during the CF₄ plasma treatment was induced by reactive fluorine-containing species from the plasma phase. Furthermore, during both processes, etching of the PAAc surface occurred. Based on these mechanisms, kinetic models were derived that could be used to describe the measured kinetic data adequately. © 1994 John Wiley & Sons, Inc.     

Activity–Composition Relations of Chromium Oxide in Silicate Melts at 1500°C under Strongly Reducing Conditions

The solubility and activity–composition relations of chromium oxide in melts of the systems CaO–CrO _x –SiO₂ and CaO–Al₂O₃–CrO _x –SiO₂ have been determined at 1500°C by equilibrating melts with Pt–Cr alloys at known oxygen pressures. It is shown that the increase in the concentration of divalent chromium ions, as the oxygen pressure and the basicity of melt decrease, results in a dramatic increase in the solubility of chromium oxide in the liquid phase. An increase in the Al₂O₃ content of the melt leads to a decrease in the solubility of chromium oxide over the whole composition range studied. The activity coefficient of CrO has been found to increase with increasing melt basicity and decreasing oxygen pressure whereas the activity coefficient of CrO_1.5 decreases sharply with increasing melt basicity for siliceous melts but levels off at a basicity ratio (wt% CaO/wt% SiO₂) of about 0.7. An increase in the Al₂O₃ content of the melts results in an increase in the activity coefficient of CrO.     

Probabilistic motion-compensated prediction in distributed video coding

Distributed video coding (DVC) constitutes an original coding framework to meet the stringent requirements imposed by uplink-oriented and low-power mobile video applications. The quality of the side information available to the decoder and the efficiency of the employed channel codes are primary factors determining the success of a DVC system. This contribution introduces two novel techniques for probabilistic motion compensation in order to generate side information at the Wyner-Ziv decoder. The employed DVC scheme uses a base layer, serving as a hash to facilitate overlapped block motion estimation at the decoder side. On top of the base layer, a supplementary Wyner-Ziv layer is coded in the DCT domain. Both proposed probabilistic motion compensation techniques are driven by the actual correlation channel statistics and reuse information contained in the hash. Experimental results report significant rate savings caused by the novel side information generation methods compared to previous techniques. Moreover, the compression performance of the presented DVC architecture, featuring the proposed side-information generation techniques, delivers state-of-the-art compression performance.     

Visual Inspection of Multivariate Graphs

Most graph visualization techniques focus on the structure of graphs and do not offer support for dealing with node attributes and edge labels. To enable users to detect relations and patterns in terms of data associated with nodes and edges, we present a technique where this data plays a more central role. Nodes and edges are clustered based on associated data. Via direct manipulation users can interactively inspect and query the graph. Questions that can be answered include, “which edge types are activated by specific node attributes?” and, “how and from where can I reach specific types of nodes?” To validate our approach we contrast it with current practice. We also provide several examples where our method was used to study transition graphs that model real‐world systems.