271 research outputs found

    Concept mapping and other formalisms as mindtools for representing knowledge

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    We seek to provide an alternative theoretical perspective on concept mapping (a formalism for representing structural knowledge) to that provided by Ray McAleese in this issue of ALT-J (auto-monitoring). We begin with an overview of concept maps as a means of describing a learner's knowledge constructs, and then discuss a broader class of tools, Mindtools, of which concept maps are a member. We proceed by defining Mindtools as formalisms for representing knowledge, and further elaborate on concept maps as a formalism for representing a particular kind of knowledge: structural knowledge. We then address McAleese's use of the term auto-monitoring and some of the steps in his model of concept maps. Finally, we describe some limitations of concept mapping as a formalism and as a cognitive learning strategy

    The Iron Range Engineering PBL Curriculum: How Students Adapt to and Function within PBL

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    Iron Range Engineering is a unique complete-PBL curriculum for upper division students. Rather than studying about engineering in traditional engineering courses, IRE students solve complex and ill-structured industry problems in mining, milling, and manufacturing industries. To support students’ transition to PBL and to facilitate deep approaches to learning technical and professional competencies required for the engineers of the future, faculty have created a variety of structures. This paper describes IRE’s PBL implementation and reports the results of a qualitative study of their students

    Alternative Pathways To Engineering Success –Using Academic And Social Integration To Understand Two-Year Engineering Student Success

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    The need for educating engineers in the United States continues as the projected demand is still rising as the number of high school seniors planning to enter engineering careers has remained relatively stable (Sargent, 2014). Additionally, figures show that attrition rates in undergraduate engineering continue to be an area of concern, (Sargent, 2014; Gibbons, 2005; NSF, 2004). Given the projected increased demand for engineers, the engineering education community must explore a variety of pathways for engineering students to be successful. Organizations such as National Science Foundation (Laanan, Jackson, Darrow, 2010) have noted that beginning engineering study at a two-year campus and then transferring to an engineering bachelor’s degree-granting institution is an important path and source for additional engineering students. Although some have explored the logistical issues and curricular design components of two-year campuses that enables engineering students to complete their bachelor degrees elsewhere, there is very little that explores the non-curricular factors on these campuses that help such students successfully progress (Laanan, et al., 2010). Using Tinto’s theory of integration (1975, 1993), this study examines the relationship between student entry characteristics and measures of social and academic integration to engineering learning outcomes. Understanding how integration factors on two-year campuses impact engineering student success can be used to inform the design of curricular and campus-based experiences that support the success of engineering students on two-year campuses.  Results indicate the social and academic integration factors significantly predict engineering students’ learning outcomes, especially their commitment to engineering studies

    Average luminosity distance in inhomogeneous universes

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    The paper studies the correction to the distance modulus induced by inhomogeneities and averaged over all directions from a given observer. The inhomogeneities are modeled as mass-compensated voids in random or regular lattices within Swiss-cheese universes. Void radii below 300 Mpc are considered, which are supported by current redshift surveys and limited by the recently observed imprint such voids leave on CMB. The averaging over all directions, performed by numerical ray tracing, is non-perturbative and includes the supernovas inside the voids. Voids aligning along a certain direction produce a cumulative gravitational lensing correction that increases with their number. Such corrections are destroyed by the averaging over all directions, even in non-randomized simple cubic void lattices. At low redshifts, the average correction is not zero but decays with the peculiar velocities and redshift. Its upper bound is provided by the maximal average correction which assumes no random cancelations between different voids. It is described well by a linear perturbation formula and, for the voids considered, is 20% of the correction corresponding to the maximal peculiar velocity. The average correction calculated in random and simple cubic void lattices is severely damped below the predicted maximal one after a single void diameter. That is traced to cancellations between the corrections from the fronts and backs of different voids. All that implies that voids cannot imitate the effect of dark energy unless they have radii and peculiar velocities much larger than the currently observed. The results obtained allow one to readily predict the redshift above which the direction-averaged fluctuation in the Hubble diagram falls below a required precision and suggest a method to extract the background Hubble constant from low redshift data without the need to correct for peculiar velocities.Comment: 34 pages, 21 figures, matches the version accepted in JCA

    Analytical Estimate of the Effect of Spherical Inhomogeneities on Luminosity Distance and Redshift

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    We provide an analytical estimate of the effect of a spherical inhomogeneity on light beams that travel through it. We model the interior of the inhomogeneity in terms of the Lemaitre-Tolman-Bondi metric. We assume that the beam source is located outside the inhomogeneity. We study the relative deviations of travelling time, redshift, beam area and luminosity distance from their values in a homogeneous cosmology. They depend on the ratio Hb=H r_0 of the radius r_0 of the inhomogeneity to the horizon distance 1/H. For an observer located at the center, the deviations are of order Hb^2. For an observer outside the inhomogeneity, the deviations of crossing time and redshift are of order Hb^3. The deviations of beam area and luminosity distance are of order Hb^2. However, when averaged over all possible locations of the observer outside the inhomogeneity, they also become of order Hb^3. We discuss the implications for the possibility of attributing the observed cosmological acceleration to the emergence of large-scale structure.Comment: 11 pages, references added, discussion expande

    Allelic Ratios and the Mutational Landscape Reveal Biologically Significant Heterozygous SNVs

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    The issue of heterozygosity continues to be a challenge in the analysis of genome sequences. In this article, we describe the use of allele ratios to distinguish biologically significant single-nucleotide variants from background noise. An application of this approach is the identification of lethal mutations in Caenorhabditis elegans essential genes, which must be maintained by the presence of a wild-type allele on a balancer. The h448 allele of let-504 is rescued by the duplication balancer sDp2. We readily identified the extent of the duplication when the percentage of read support for the lesion was between 70 and 80%. Examination of the EMS-induced changes throughout the genome revealed that these mutations exist in contiguous blocks. During early embryonic division in self-fertilizing C. elegans, alkylated guanines pair with thymines. As a result, EMS-induced changes become fixed as either G→A or C→T changes along the length of the chromosome. Thus, examination of the distribution of EMS-induced changes revealed the mutational and recombinational history of the chromosome, even generations later. We identified the mutational change responsible for the h448 mutation and sequenced PCR products for an additional four alleles, correlating let-504 with the DNA-coding region for an ortholog of a NFκB-activating protein, NKAP. Our results confirm that whole-genome sequencing is an efficient and inexpensive way of identifying nucleotide alterations responsible for lethal phenotypes and can be applied on a large scale to identify the molecular basis of essential genes

    Interneuronal mechanism for Tinbergen's hierarchical model of behavioral choice

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    Recent studies of behavioral choice support the notion that the decision to carry out one behavior rather than another depends on the reconfiguration of shared interneuronal networks. We investigated another decision-making strategy, derived from the classical ethological literature, which proposes that behavioral choice depends on competition between autonomous networks. According to this model, behavioral choice depends on inhibitory interactions between incompatible hierarchically organized behaviors. We provide evidence for this by investigating the interneuronal mechanisms mediating behavioral choice between two autonomous circuits that underlie whole-body withdrawal and feeding in the pond snail Lymnaea. Whole-body withdrawal is a defensive reflex that is initiated by tactile contact with predators. As predicted by the hierarchical model, tactile stimuli that evoke whole-body withdrawal responses also inhibit ongoing feeding in the presence of feeding stimuli. By recording neurons from the feeding and withdrawal networks, we found no direct synaptic connections between the interneuronal and motoneuronal elements that generate the two behaviors. Instead, we discovered that behavioral choice depends on the interaction between two unique types of interneurons with asymmetrical synaptic connectivity that allows withdrawal to override feeding. One type of interneuron, the Pleuro-Buccal (PlB), is an extrinsic modulatory neuron of the feeding network that completely inhibits feeding when excited by touch-induced monosynaptic input from the second type of interneuron, Pedal-Dorsal12 (PeD12). PeD12 plays a critical role in behavioral choice by providing a synaptic pathway joining the two behavioral networks that underlies the competitive dominance of whole-body withdrawal over feeding

    A two-neuron system for adaptive goal-directed decision-making in Lymnaea

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    During goal-directed decision-making, animals must integrate information from the external environment and their internal state to maximize resource localization while minimizing energy expenditure. How this complex problem is solved by the nervous system remains poorly understood. Here, using a combined behavioural and neurophysiological approach, we demonstrate that the mollusc Lymnaea performs a sophisticated form of decision-making during food-searching behaviour, using a core system consisting of just two neuron types. The first reports the presence of food and the second encodes motivational state acting as a gain controller for adaptive behaviour in the absence of food. Using an in vitro analogue of the decision-making process, we show that the system employs an energy management strategy, switching between a low- and high-use mode depending on the outcome of the decision. Our study reveals a parsimonious mechanism that drives a complex decision-making process via regulation of levels of tonic inhibition and phasic excitation
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