Multiple Outcomes of Class Visits to Natural History Museums: The Students’ View

The purpose of this study was to describe and understand the range of outcomes of class visits to natural history museums. The theoretical framework is based on the multifaceted process of learning in free choice learning environments, and emphasizes the unique and individual learning experience in museum settings. The study’s significance is in highlighting several possible cognitive as well as non-cognitive learning effects in museums class visits, by providing the student’s point of view. Data was collected by semi-structured interviews with 50 students in grades 6–8 on the day following the visit. We present evidence that students expressed several learning outcomes, connected directly and indirectly to the scientific content of the visit. Content oriented outcomes included acquiring scientific knowledge and making connections to prior knowledge; social oriented outcomes were identified in students’ statements regarding communicating knowledge and social aspects of learning; and interest oriented outcomes were evidenced by students’ expressions about emotions, interest and curiosity. The aggregate data addressed the common outcomes and the impact of class visits to natural history museums in the short term. Comparisons between two types of museums show significant differences in several aspects, regarding the exhibit and/or the activity type. Practical ideas for structuring the ultimate experience are included.     

Zero-voltage switching converter absorbing parasitic parameters for super high frequency induction heating

This paper presents a novel mega-Hz-level super high frequency zero-voltage soft-switching converter for induction heating power supplies. The prominent advantage of this topology is that it can absorb both inductive and capacitive parasitic components in the converter. The switch devices operate in a zero-voltage soft-switching mode. Consequently, the high voltage and high current spikes caused by parasitic inductors or capacitors oscillation do not occur in this circuit, and the high power loss caused by high frequency switching can be greatly reduced. A large value inductor is adopted between the input capacitor and the switches, thus, this novel converter shares the benefits of both voltage-type and current-type circuits simultaneously, and there are no needs of dead time between two switches. The working principles in different modes are introduced. Results of simulation and experiments operated at around 1 MHz frequency verify the validity of parasitic components absorption and show that this convener is competent for super high frequency applications.     

Social conversation and effective discussion in online group learning

This paper studies the social talk of high school students in online discussion forums. On-task talk has generally been assessed as valuable discussion because it contributes directly to productive learning. Off-task conversation, on the other hand, is often regarded as useless and a waste of time. Should this social talk indeed be regarded as an off-task activity? Is social talk such as greeting, excusing, comforting and sharing personal feelings irrelevant to learning? This study analyzes threads and argues that social talk is interwoven with on-task talk. It is interesting to note that a substantial quantity of off-task messages served the latent function of guiding group discussion toward making progress in solving collaborative problems in a subtle and indirect manner. The power of “soft talk” embedded in off-task social conversation is explored and fully discussed.     

A general approximation framework for direct optimization of information retrieval measures

Recently direct optimization of information retrieval (IR) measures has become a new trend in learning to rank. In this paper, we propose a general framework for direct optimization of IR measures, which enjoys several theoretical advantages. The general framework, which can be used to optimize most IR measures, addresses the task by approximating the IR measures and optimizing the approximated surrogate functions. Theoretical analysis shows that a high approximation accuracy can be achieved by the framework. We take average precision (AP) and normalized discounted cumulated gains (NDCG) as examples to demonstrate how to realize the proposed framework. Experiments on benchmark datasets show that the algorithms deduced from our framework are very effective when compared to existing methods. The empirical results also agree well with the theoretical results obtained in the paper.     

BMD and Serum Intact Osteocalcin in Postmenopausal Osteoporosis Women

India seems to have the highest prevalence of osteoporosis. With growing awareness of osteoporosis and its impact on life span especially in India, special attention is being paid to early detection, management and treatment of postmenopausal osteoporosis in women. Measurement of BMD and osteocalcin are of value in estimating bone turnover rates. The aim of this study is (1) to measure the specific, sensitive bone formation marker such as osteocalcin and BMD in postmenopausal osteoporosis women and postmenopausal non-osteoporosis women; (2) the follow up study to evaluate the impact of specific antiresorptive therapy (alendronate + calcium + vitamin D) regimen in postmenopausal osteoporosis by assaying osteocalcin and BMD. Sixty clinically diagnosed postmenopausal osteoporosis patients and 60 normal subjects (postmenopausal non-osteoporosis women) were recruited as control. Mean bone mineral density T score and Z score was significantly decreased (P < 0.001) in postmenopausal osteoporosis patients as compared to controls. Highly significant increase in the mean score of BMD—T score and Z score from baseline to post therapy of 3 months was observed in postmenopausal osteoporosis women. Serum osteocalcin levels were significantly increased (P < 0.001) as compared to control group. Serum osteocalcin levels were decreased significantly (P < 0.001) from baseline to post therapy of 3 months in postmenopausal osteoporosis women. BMD is the best quantifiable predictor of osteoporotic fracture and osteocalcin is specific, sensitive, promising, currently used marker for better prognosis of osteoporosis and for monitoring responses to antiresorptive therapy.     

Induction of diabetes by Streptozotocin in rats

The objective of this study is to induce experimental diabetes mellitus by Streptozotocin in normal adult Wistar rats via comparison of changes in body weight, consumption of food and water, volume of urine and levels of glucose, insulin and C-peptide in serum, between normal and diabetic rats. Intra-venous injection of 60mg/kg dose of Streptozotocin in adult wistar rats, makes pancreas swell and at last causes degeneration in Langerhans islet beta cells and induces experimental diabetes mellitus in the 2–4 days. Induction of experimental diabetes mellitus is indeed the first step in the plan of purification of pancreatic Langerhans islet cells of normal rats for transplanting under the testis subcutaneous of experimentally induced diabetic rats. Streptozotocin induces one type of diabetes which is similar to diabetes mellitus with non-ketosis hyperglycemia in some animal species. For induction of experimental diabetes in male adult rats weighted 250–300 grams (75–90 days), 60mg/kg of Streptozotocin was injected intravenously. Three days after degeneration of beta cells, diabetes was induced in all animals. The diabetic and normal animals were kept in the metabolic cages separately and their body weight, consumption of food and water, urine volume, the levels of serum glucose, insulin and C-peptide quantities in all animals were measured and then these quantities were compared. For a microscopic study of degeneration of Langerhans islet beta cells of diabetic rats, sampling from pancreas tissue of diabetic and normal rats, staining and comparison between them, were done. Induction of diabetes with Streptozotocin decreases Nicotinamide-adenine dinucleotide (NAD) in pancreas islet beta cells and causes histopathological effects in beta cells which probably intermediates induction of diabetes. In this study, we used Streptozotocin for our experiments in induction of experimental diabetes mellitus. After Induction of diabetes, consumption of food and water, volume of urine and glucose increased in the diabetic animals in comparison with normal animals, but the weight of body and the volume of insulin and C-peptide decreased in the diabetic animals. Sampling and staining of pancreas tissue of diabetic and normal rats showed that the Langerhans islet beta cells of diabetic rats have been clearly degenerated. In three days, Streptozotocin makes pancreas swell and at last causes degeneration in Langerhans islet beta cells and induces experimental diabetes. It also changes normal metabolism in diabetic rats in comparison with normal rats. Consumption of water and food, volume of urine, serum glucose increases in diabetic animals in comparison with normal rats but the levels of serum insulin, C-peptide and body weight decreases.     

How Does the Degree of Guidance Support Students’ Metacognitive and Problem Solving Skills in Educational Robotics?

Educational robotics (ER) is an innovative learning tool that offers students opportunities to develop higher-order thinking skills. This study investigates the development of students’ metacognitive (MC) and problem-solving (PS) skills in the context of ER activities, implementing different modes of guidance in two student groups (11–12 years old, N1 = 30, and 15-16 years old, N2 = 22). The students of each age group were involved in an 18-h group-based activity after being randomly distributed in two conditions: “minimal” (with minimal MC and PS guidance) and “strong” (with strong MC and PS guidance). Evaluations were based on the Metacognitive Awareness Inventory measuring students’ metacognitive awareness and on a think-aloud protocol asking students to describe the process they would follow to solve a certain robot-programming task. The results suggest that (a) strong guidance in solving problems can have a positive impact on students’ MC and PS skills and (b) students reach eventually the same level of MC and PS skills development independently of their age and gender.     

To see or not to see: analyzing difficulties in geometry from the perspective of visual perception

In this paper, we consider theories about processes of visual perception and perception-based knowledge representation (VPR) in order to explain difficulties encountered in figural processing in junior high school geometry tasks. In order to analyze such difficulties, we take advantage of the following perspectives of VPR: (1) Perceptual organization: Gestalt principles, (2) recognition: bottom-up and top-down processing; and (3) representation of perception-based knowledge: verbal vs. pictorial representation, mental images and hierarchical structure of images. Examples given in the paper were mostly taken from Gal's study (2005) which aimed at identifying and analyzing Problematic Learning Situations (after Gal & Linchevski, 2000) in junior high school geometry classes. Gal's study (2005) suggests that while this theoretical perspective became part of teachers' pedagogic content knowledge, the teachers were aware of their students' thinking processes and their ability to analyze and cope with their students’ difficulties in geometry was improved.