Questioning and the quality of knowledge constructed in a CSCL context: a study on two grade-levels of students

This paper aims to study the relationship between questioning and the quality of knowledge constructed in a CSCL context. In previous studies, different units of analysis are employed and the patterns of relationships are not consistent for different age groups. The analytic units of a thread, an individual, and a group are employed in this study, and two grades of students (grade 6 and grade 10) are investigated. At the thread level, we aim to examine to what extent questioning can be a mechanism for knowledge advancement, and we find that the tenth-graders are capable to advance knowledge through questioning, while for the sixth-graders, more facilitation seems to be needed. At the individual level, we find that for the sixth-graders, those asking good questions are likely to express high-level explanations, suggesting that individual competence plays an important role in advancing knowledge among these younger students. For the tenth-graders, a 'division of labor' is observed that good questions are generated by some students while high-level explanations by others. At the group level, a high and positive correlation is found for both grades. The findings suggest further research is needed to examine other possible mechanisms for knowledge advancement in online collaborative discourse. © 2012 Springer Science+Business Media B.V.postprin

Two Wide Planetary-mass Companions to Solar-type Stars in Upper Scorpius

At wide separations, planetary-mass and brown dwarf companions to solar-type stars occupy a curious region of parameter space not obviously linked to binary star formation or solar system scale planet formation. These companions provide insight into the extreme case of companion formation (either binary or planetary), and due to their relative ease of observation when compared to close companions, they offer a useful template for our expectations of more typical planets. We present the results from an adaptive optics imaging survey for wide (~50–500 AU) companions to solar-type stars in Upper Scorpius. We report one new discovery of a ~14 M_J companion around GSC 06214−00210and confirm that the candidate planetary-mass companion 1RXS J160929.1−210524 detected by Lafrenière et al. is in fact comoving with its primary star. In our survey, these two detections correspond to ~4% of solar-type stars having companions in the 6–20 M_J mass and ~200–500 AU separation range. This figure is higher than would be expected if brown dwarfs and planetary-mass companions were drawn from an extrapolation of the binary mass function. Finally, we discuss implications for the formation of these objects

Field Induced Magnetic Ordering and Single-ion Anisotropy in the Quasi-1D Haldane Chain Compound SrNi2V2O8: A Single Crystal investigation

Field-induced magnetic ordering in the Haldane chain compound SrNi$_{2}$V$_{2}$O$_{8}$ and effect of anisotropy have been investigated using single crystals. Static susceptibility, inelastic neutron scattering, high-field magnetization, and low temperature heat-capacity studies confirm a non-magnetic spin-singlet ground state and a gap between the singlet ground state and triplet excited states. The intra-chain exchange interaction is estimated to be $J \sim 8.9{\pm}$0.1 meV. Splitting of the dispersions into two modes with minimum energies 1.57 and 2.58 meV confirms the existence of single-ion anisotropy $D(S^z){^2}$. The value of {\it D} is estimated to be $-0.51{\pm}0.01$ meV and the easy axis is found to be along the crystallographic {\it c}-axis. Field-induced magnetic ordering has been found with two critical fields [$\mu_0H_c^{\perp c} = 12.0{\pm}$0.2 T and $\mu_0H_c^{\parallel c} = 20.8{\pm}$0.5 T at 4.2 K]. Field-induced three-dimensional magnetic ordering above the critical fields is evident from the heat-capacity, susceptibility, and high-field magnetization study. The Phase diagram in the {\it H-T} plane has been obtained from the high-field magnetization. The observed results are discussed in the light of theoretical predictions as well as earlier experimental reports on Haldane chain compounds

What Happens in Project-based Learning?

There is an accumulating literature over the last decade on collaborative learning in various types of settings, from more focussed learning tasks to open enquiry to problem-based projects. Project-based teamwork was valued as students were required to work together for knowledge sharing, knowledge building and problem-solving, and thus provide them with opportunities to be acculturated as members of a knowledge community. Over the last couple of years, it has also become extremely popular in Hong Kong schools to assign group projects to students. This was often justified on the grounds that project work promotes the information retrieval and self-directed learning abilities of students; collaborative learning is good and students should learn to collaborate with each other. However, as a pedagogical strategy, very little is known about the actual impact of group projects on learning in Hong Kong and whether the assumed advantages and expected learning outcomes do come about. Is group-based projects the panacea for the evils of teacher-centred delivery? This paper explores the question “what happens in project-based learning?” based on the observations made during the SLITS (Self-directed Learning with Information Technology Scheme) project. The project involved 40 groups of students working on projects of their own choice, each group being facilitated by a teacher. There were several key findings from this study: 1. Participation in such a project may not necessarily lead to deep learning; 2. Learning to collaborate in a group is in itself an important part of the problem-solving process; 3. There are different models of collaboration and only those models which engage the students continuously in interactive decision making during the learning process would lead to collaborative knowledge building; 4. Effective collaboration is in itself crucial for sustaining motivation and interest in the learning process; and 5. Facilitation is required for guiding both the collaborative as well as the enquiry processes. This paper will report on these findings as well as describe the key features of good collaboration and good facilitation identified through the study.published_or_final_versionCentre for Information Technology in Education, University of Hong Kon

de-Broglie Wave-Front Engineering

We propose a simple method for the deterministic generation of an arbitrary continuous quantum state of the center-of-mass of an atom. The method's spatial resolution gradually increases with the interaction time with no apparent fundamental limitations. Such de-Broglie Wave-Front Engineering of the atomic density can find applications in Atom Lithography, and we discuss possible implementations of our scheme in atomic beam experiments.Comment: The figures' quality was improved, the text remains intact. 5 pages, 3 figures; submitted to PR

The LuckyCam Survey for Very Low Mass Binaries II: 13 new M4.5-M6.0 Binaries

We present results from a high-angular-resolution survey of 78 very low mass (VLM) binary systems with 6.0 = 0.15 arcsec/yr. 21 VLM binaries were detected, 13 of them new discoveries. The new binary systems range in separation between 0.18 arcsec and 1.3 arcsec. The distance-corrected binary fraction is 13.5% (+6.5%/-4%), in agreement with previous results. 9 of the new binary systems have orbital radii > 10 AU, including a new wide VLM binary with 27 AU projected orbital separation. One of the new systems forms two components of a 2300 AU separation triple system. We find that the orbital radius distribution of the binaries with V-K < 6.5 in this survey appears to be different from that of redder (lower-mass) objects, suggesting a possible rapid change in the orbital radius distribution at around the M5 spectral type. The target sample was also selected to investigate X-ray activity among VLM binaries. There is no detectable correlation between excess X-Ray emission and the frequency and binary properties of the VLM systems.Comment: 11 pages, 8 figures. Submitted to MNRA

The effect of the visual exercise environment on the response to psychological stress: a pilot study

Background: Performing physical activity whilst exposed to nature can improve health. However, there is little evidence of its impact on stress outcomes. The aim of this study was to examine the influence of the visual exercise environment on the response to a psychosocial stressor. Methods: Eighteen participants were randomised to one of three conditions: i. control; ii. Nature or; iii. Built condition. Participants exercised for 30min on a treadmill at 50% of their VO2max whilst viewing a video of either a natural or built environment or a blank screen. Following the exercise, participants completed the Trier Social Stress Test (TSST), a standardised laboratory stressor. Salivary samples were collected before, during and after the TSST to calculate cortisol reactivity and recovery. Results: One-way ANOVA revealed a significant effect of viewing condition on cortisol reactivity [F (2, 11) = 4.686, p = .034; n2p= .460]; with significantly lower reactivity in the built compared to the nature condition (p = .027, d=1.73). There was no effect of condition on cortisol recovery (P>0.05; n2p= .257). Conclusions: In the context of the adverse health impact of lower (i.e. blunted) cortisol responding, these findings could indicate a negative impact of the built environment on stress responses

Breastfeeding, the use of docosahexaenoic acid-fortified formulas in infancy and neuropsychological function in childhood

OBJECTIVE: To investigate the relation between breastfeeding, use of docosahexaenoic acid (DHA)-fortified formula and neuropsychological function in children. DESIGN: Prospective cohort study. SETTING: Southampton, UK. SUBJECTS: 241 children aged 4 years followed up from birth. MAIN OUTCOME MEASURES: IQ measured by the Wechsler Pre-School and Primary Scale of Intelligence (3rd edn), visual attention, visuomotor precision, sentence repetition and verbal fluency measured by the NEPSY, and visual form-constancy measured by the Test of Visual-Perceptual Skills (Non-Motor). RESULTS: In unadjusted analyses, children for whom breast milk or DHA-fortified formula was the main method of feeding throughout the first 6 months of life had higher mean full-scale and verbal IQ scores at age 4 years than those fed mainly unfortified formula. After adjustment for potential confounding factors, particularly maternal IQ and educational attainment, the differences in IQ between children in the breast milk and unfortified formula groups were severely attenuated, but children who were fed DHA-fortified formula had full-scale and verbal IQ scores that were respectively 5.62 (0.98 to 10.2) and 7.02 (1.56 to 12.4) points higher than children fed unfortified formula. However, estimated total intake of DHA in milk up to age 6 months was not associated with subsequent IQ or with score on any other test. CONCLUSIONS: Differences in children's intelligence according to type of milk fed in infancy may be due more to confounding by maternal or family characteristics than to the amount of long-chain polyunsaturated fatty acids they receive in milk

Generic Invertibility of Multidimensional FIR Filter Banks and MIMO Systems

We study the invertibility of M-variate Laurent polynomial N × P matrices. Such matrices represent multidimensional systems in various settings such as filter banks, multiple-input multiple-output systems, and multirate systems. Given an N × P Laurent polynomial matrix H(z1,..., zM) of degree at most k, we want to find a P × N Laurent polynomial left inverse matrix G(z) of H(z) such that G(z)H(z) = I. We provide computable conditions to test the invertibility and propose algorithms to find a particular inverse. The main result of this paper is to prove that H(z) is generically invertible when N −P ≥ M; whereas when N −P &lt; M, then H(z) is generically noninvertible. As a result, we propose an algorithm to find a particular inverse of a Laurent polynomial matrix that is faster than current algorithms known to us