Cognitive Variables in Problem Solving: A Nonlinear Approach

We employ tools of complexity theory to examine the effect of cognitive variables, such as working-memory capacity, degree of field dependence–independence, developmental level and the mobility–fixity dimension. The nonlinear method correlates the subjects rank-order achievement scores with each cognitive variable. From the achievement scores in organic-synthesis problems of various mental demands, rank-order sequences of the subjects, according to their scores, were generated, and in the place of each subject, his/her score was replaced by the value of the corresponding cognitive variable. Then each sequence was mapped onto a one-dimensional random walk, and when treated as a dynamic flow, was found to possess fractal geometry, with characteristics depending on the complexity of the problem. The findings were interpreted using concepts from complexity theory, such as order, correlation exponents, and entropy. The method provides meaningful results and adds to the understanding of information processing and the role of cognitive variables within the frame of predictive models in problem solving. Although the method is applied to a particular kind of problems (chemical, organic-synthesis problems), it can be generalized to other problems, not only in chemistry, but also in other sciences and in mathematics. Finally, the educational implications are discussed.     

Instructional Misconceptions in Acid-Base Equilibria: An Analysis from a History and Philosophy of Science Perspective

The implications of history and philosophy of chemistry are explored in the context of chemical models. Models and modeling provide the context through which epistemological aspects of chemistry can be promoted. In this work, the development of ideas and models about acids and bases (with emphasis on the Arrhenius, the Brønsted–Lowry, and the Lewis models) are presented. In addition, misconceptions (alternative and instructional ones) on acid-base (ionic) equilibria are examined from the history and philosophy of science perspective. The relation between the development of the models and students misconceptions are investigated. Finally, the hypothesis that history and philosophy could help educators anticipate students misconceptions is examined.     

Students’ Knowledge of Nuclear Science and Its Connection with Civic Scientific Literacy in Two European Contexts: The Case of Newspaper Articles

Nuclear science has uses and applications that are relevant and crucial for world peace and sustainable development, so knowledge of its basic concepts and topics should constitute an integral part of civic scientific literacy. We have used two newspaper articles that deal with uses of nuclear science that are directly relevant to life, society, economy, and international politics. One article discusses a new thermonuclear reactor, and the second one is about depleted uranium and its danger for health. 189 first-year undergraduate physics and primary education Greek students were given one of the two articles each, and asked to answer a number of accompanying questions dealing with knowledge that is part of the Greek high school curriculum. The study was repeated with 272 first-year undergraduate physics, physics education, science education, and primary education Turkish students. Acceptable or partially acceptable answers were provided on average by around 20 % of Greek and 11 % of Turkish students, while a large proportion (on the average, around 50 % of Greek and 27 % of Turkish students) abstained from answering the questions. These findings are disappointing, but should be seen in the light of the limited or no coverage of the relevant learning material in the Greek and the Turkish high-school programs. Student conceptual difficulties, misconceptions and implications for research and high school curricula are discussed.     

Predicting LD on the basis of motivation, metacognition, and psychopathology: an ROC analysis

We examined how strongly motivation, metacognition, and psychopathology acted as predictors of learning disabilities (LD). The results from five studies suggested that level of motivation (as shown through self-efficacy, motivational force, task avoidance, goal commitment, or self-concept) was highly accurate in classifying students with or at risk for LD. Metacognition and psychopathology were also strong predictors. Classification accuracy using receiver operating characteristic (ROC) curves ranged between 77% and 96%. These rates were much higher than the chance-level (i.e., 50%-55%) rates sometimes yielded by cognitive indices. Linear discriminant function (LDF) analysis substantiated classification accuracy. These results suggest that motivation, metacognition, and psychopathology are strong predictors of LD. Understanding the influence of these characteristics may help researchers and practitioners more accurately screen and treat students with LD.     

Development of Lexical Mediation in the Relation Between Reading Comprehension and Word Reading Skills in Greek

This study focuses on the shared variance between reading comprehension and word-level reading skills in a population of 534 Greek children in Grades 2 through 4. The correlations between measures of word and pseudoword accuracy and fluency, on the one hand, and vocabulary and comprehension skills, on the other, were sizeable and stable or increasing with grade. However, the unique contribution of word reading to comprehension became negligible after vocabulary measures were entered in hierarchical regression analyses, particularly for higher grades, suggesting that any effects of decoding on comprehension may be mediated by the lexicon, consistent with lexical quality hypothesis. Structural modeling with latent variables revealed an invariant path across grades in which vocabulary was defined by its covariation with reading accuracy and fluency and affected comprehension directly. It is argued that skilled word reading influences comprehension by strengthening lexical representations, at least when phonological decoding can be relatively effortless.     

Modeling information sources as integrals for effective and efficient source selection

In this paper, a new source selection algorithm for uncooperative distributed information retrieval environments is presented. The algorithm functions by modeling each information source as an integral, using the relevance score and the intra-collection position of its sampled documents in reference to a centralized sample index and selects the collections that cover the largest area in the rank-relevance space. Based on the above novel metric, the algorithm explicitly focuses on addressing the two goals of source selection; high-recall, which is important for source recommendation applications and high-precision which is important for distributed information retrieval, aiming to produce a high-precision final merged list.     

Kinematic and kinetic differences in the execution of vertical jumps between people with good and poor ankle joint dorsiflexion

Abstract

The aim of the present study was to investigate the kinematic and kinetic differences in the execution of vertical jumps between individuals with good and poor ankle dorsiflexion. Fifteen physical education students were assigned to the flexible group (FG), while another 15 were assigned to the inflexible group (IFG). The two groups executed countermovement jumps (CMJ) and drop jumps from a 60 cm height (DJ60). For the CMJ, the FG jumped higher (32.0 ± 4.0 cm vs. 30.2 ± 4.9 cm, P = 0.27) and used a greater range of motion in all leg joints. The IFG jumpers raised their heels off the ground and had a greater horizontal distance between the centre of mass of the trunk and the centre of the hip joint (L_CMh 25.6 ± 3.4 cm vs. 30.9 ± 4.3 cm, P < 0.001). In the DJ60 the FG jumped higher (22.4 ± 5.9 cm vs. 19.5 ± 4.6 cm, P = 0.14) with a greater vertical shift of the body centre of mass (BCM) (S = 0.45 ± 0.11 cm vs. 0.36 ± 0.05 cm, P < 0.01) and better joint coordination. The IFG jumpers changed the position of their trunk and heels depending on the jump type. Trainers should reconsider the technical issues of vertical jumps according to the flexibility of the ankle joint.     

Tracking the singular arc of a continuous bioreactor using sliding mode control

A sliding mode controller is developed for optimal transient operation of a continuous bioreactor. The sliding mode is the singular arc from the solution of an optimal control problem. The proposed controller is applied through simulations to an anaerobic digester and its performance is evaluated in terms of optimality and robustness properties.     

Feeling obliged to “Do Well” or “Not to Fail”? The distinction between approach and avoidance dimensions of oughts

The present studies examined the proposition that there are approach and avoidance dimensions in feelings of obligations, that are associated with a specific network of behaviors, affect, and cognitions in achievement situations. Across 4 studies, results indicated that being motivated by ought-approach was associated with significantly higher positive affect and persistence compared with being motivated by ought-avoidance. Also, arousal and affect could be explained by one's disposition for approach- or avoidance-based oughts. Being motivated by ought-approach was significantly more adaptive compared with avoidance and multiple-ought terms. It was concluded that obligations based on approach or avoidance tendencies represent diverse motivational systems with different cognitions and affective responses.     

Rapid magnetic heating treatment by highly charged maghemite nanoparticles on Wistar rats exocranial glioma tumors at microliter volume

One of the most significant challenges implementing colloidal magnetic nanoparticles in medicine is the efficient heating of microliter quantities by applying a low frequency alternating magnetic field. The ultimate goal is to accomplish nonsurgically the treatment of millimeter size tumors. Here, we demonstrate the synthesis, characterization, and the in vitro as well as in vivo efficiency of a dextran coated maghemite (γ-Fe₂O₃) ferrofluid with an exceptional response to magnetic heating. The difference to previous synthetic attempts is the high charge of the dextran coating, which according to our study maintains the colloidal stability and good dispersion of the ferrofluid during the magnetic heating stage. Specifically, in vitro 2 μl of the ferrofluid gives an outstanding temperature rise of 33 °C within 10 min, while in vivo treatment, by infusing 150 μl of the ferrofluid in animal model (rat) glioma tumors, causes an impressive cancer tissue dissolution.