Percolation Transition in the Heterogeneous Vortex State in NbSe2

A percolation transition in the vortex state of a superconducting 2H-NbSe2 crystal is observed in the regime where vortices form a heterogeneous phase consisting of ordered and disordered domains. The transition is signaled by a sharp increase in critical current that occurs when the volume fraction of disordered domains, obtained from pulsed measurements of the current-voltage characteristics, reaches the value Pc= 0.26. Measurements on different vortex states show that while the temperature of the transition depends on history and measurement speed, the value of Pc and the critical exponent characterizing the approach to it, r =1.97 $\pm$ 0.66, are universal

Camera motion estimation through planar deformation determination

In this paper, we propose a global method for estimating the motion of a camera which films a static scene. Our approach is direct, fast and robust, and deals with adjacent frames of a sequence. It is based on a quadratic approximation of the deformation between two images, in the case of a scene with constant depth in the camera coordinate system. This condition is very restrictive but we show that provided translation and depth inverse variations are small enough, the error on optical flow involved by the approximation of depths by a constant is small. In this context, we propose a new model of camera motion, that allows to separate the image deformation in a similarity and a ``purely'' projective application, due to change of optical axis direction. This model leads to a quadratic approximation of image deformation that we estimate with an M-estimator; we can immediatly deduce camera motion parameters.Comment: 21 pages, version modifi\'ee accept\'e le 20 mars 200

A Study of First Year Undergraduate Computing Students\u27 Experience of Learning Software Development in the Absence of a Software Development Process

Despite the ever-growing demand for software development graduates, it is recognised that a significant barrier for increasing graduate numbers lies in the inherent difficulty in learning how to develop software. This paper presents a study that is part of a larger research project aimed at addressing the gap in the provision of educational software development processes for freshman, novice undergraduate learners, to improve proficiency levels. As a means of understanding how such learners problem solve in software development in the absence of a formal process, this study examines the experiences and depth of learning acquired by a sample set of novice, freshman university learners. The study finds that without the scaffolding of an appropriate structured development process tailored to novices, students are in danger of failing to engage with the problem solving skills necessary for software development, particularly the skill of designing solutions prior to coding

An 18S rDNA Perspective on the Classification of Criconematoidea

In the nematode family Criconematidae, a taxonomy primarily based on cuticle characters has created classifications that are notoriously volatile. Molecular characters may lead to their stabilization. A phylogenetic tree of Criconematoidea was constructed using 166 new near full-length 18S rDNA sequences and 58 sequences from GenBank. Bayesian and maximum likelihood (ML) analyses produced trees with similar topologies. Major features include a strongly supported clade that includes Criconematidae and Hemicycliophoridae, excluding Paratylenchidae and Tylenchulidae. Another well-supported clade groups Criconema, Ogma, Crossonema, and Hemicriconemoides plus Xenocriconemella, combining nematodes with cuticular scales with those without scales at any life stage. Mesocriconema, Discocriconemella limitanea, Hemicaloosia, and Lobocriconema are recognized as monophyletic groups, but Criconemoides is paraphyletic. Both trees support an unexpected sister relationship between Bakernema and Hemicycliophora. The 18S rDNA dataset was insufficient for distinguishing genus boundaries between Criconema, Ogma, and Crossonema. The relationships depicted by the 18S rDNA phylogeny suggest that key morphological characters used in the classification of Criconematidae are not homologous

A Software Development Process for Freshman Undergraduate Students

This conceptual paper presents work which is part of an ongoing research project into the design of a software development process aimed at freshman, undergraduate computing students. The process of how to plan and develop a solution is a topic that is addressed very lightly in many freshman, undergraduate courses which can leave novices open to developing habit-forming, maladaptive cognitive practices. The conceptual software development process described in this paper has a learning process at its core which centres on declarative knowledge (in the form of threshold concepts) and procedural knowledge (in the form of computational thinking skills) scaffolding freshman software development from initial planning through to final solution. The process - known as Computational Analysis and Design Engineered Thinking (CADET) - aims to support the structured development of both software and student self-efficacy

Morphological and Molecular Characterization of \u3ci\u3eDiscocriconemella inarata\u3c/i\u3e, an Endemic Nematode from North American Native Tallgrass Prairies

Discocriconemella inarata, a plant parasitic nematode species originally discovered in a virgin tallgrass prairie in northwest Iowa, was re-examined by molecular and morphological analyses of topotype material. This species has never been recorded in cultivated fields and could potentially serve as an indicator for high quality prairie habitats. DNA sequence from a conserved 3’ portion of the 18S ribosomal gene exhibited an identical match between D. inarata topotype specimens and topotype specimens of Mesocriconema xenoplax from Fresno, California. Higher resolution sequence analyses using the internal transcribed spacer 1 (ITS1) and a portion of the mitochondrial gene cytochrome b (cytb) allowed discrimination of D. inarata apart from M. xenoplax. This pair of species formed a well-supported clade with other Mesocriconema species exclusive of tropical Discocriconemella species. Scanning electron microscopy confirmed the absence of submedian lobes on D. inarata, suggesting a secondary loss of this defining morphological characteristic for Mesocriconema. Observations and measurements of D. inarata juveniles were added for the first time. Surveys of other prairies within the Great Plains expanded the known distribution of this species

Density of critical points for a Gaussian random function

Critical points of a scalar quantitiy are either extremal points or saddle points. The character of the critical points is determined by the sign distribution of the eigenvalues of the Hessian matrix. For a two-dimensional homogeneous and isotropic random function topological arguments are sufficient to show that all possible sign combinations are equidistributed or with other words, the density of the saddle points and extrema agree. This argument breaks down in three dimensions. All ratios of the densities of saddle points and extrema larger than one are possible. For a homogeneous Gaussian random field one finds no longer an equidistribution of signs, saddle points are slightly more frequent.Comment: 11 pages 1 figure, changes in list of references, corrected typo

Review: The Journal of Dramaturgy, volume 24, issue 1

Contents include: Editor\u27s Note, 2014 LMDA Conference Elliott Hayes Award for Outstanding Achievement in Dramaturgy: Introduction, On the Impact of Mentorship, Advocacy, and Dramaturgical Innovation in Boston and Beyond: A Keynote Address, Iconicity and the Archive: Martha Graham\u27s Imperial Gesture 1935/2013, Towards an Aesthetic Dramaturgy,https://soundideas.pugetsound.edu/lmdareview/1052/thumbnail.jp