Upper Paleozoic to Lower Mesozoic Tetrapod Ichnology Revisited : Photogrammetry and Relative Depth Pattern Inferences on Functional Prevalence of Autopodia

In recent years photogrammetry has become an essential tool in the study of tetrapod footprints. Morphological analyses of footprints are interpretative; thus, researchers should use as much information as possible in order to eventually provide an objective conclusion. In this regard, photogrammetry is an extremely helpful tool to avoid potential biases and to better present ichnological data. We review the use of this technique in several Permian and Triassic tetrapod ichnological studies, with considerations on (1) ichnotaxonomy, (2) track-trackmaker correlation, (3) locomotion and/or behavior, (4) substrate induced effects, and (5) preservation of the fossil record and heritage. Furthermore, based on the available three-dimensional (3D) data on Permian and Triassic material, we present a first qualitative interpretation of relative depth patterns and the related functional prevalence (most deeply impressed area) within footprints. We identified three main groups: (1) anamniote, captorhinomorph/parareptile tracks (medial-median functional prevalence), (2) diapsid tracks (median functional prevalence), and (3) synapsid tracks (median-lateral functional prevalence). The use of 3D photogrammetric models brings new light to the tetrapod footprint record, helping to better understand tetrapod communities throughout the late Paleozoic (and the end-Guadalupian and end-Permian extinctions) and the tetrapod recovery during the early Mesozoic

Effects of polysaccharide-based edible coatings enriched with dietary fiber on quality attributes of fresh-cut apples

Little information is available regarding the incorporation of dietary fiber into edible films and coatings. In this work, apple fiber and inulin were incorporated into polysaccharide-based (alginate, pectine and gellan gum) edible coating formulations and their effects on the quality attributes of fresh-cut apples were evaluated. Antioxidant properties, color, firmness, sensory quality and microbial growth of fresh-cut apple were studied during 16 days of storage at 4 A degrees C. Results show that dietary fiber extracts incorporated to gellan gum, pectin and alginate-based coatings together with calcium chloride and ascorbic acid successfully maintained the firmness and color of coated fresh-cut apples in comparison with uncoated control samples, which presented severe texture softening and browning. The firmness of apple pieces coated with polysaccharide-based coating formulations incorporating apple fiber doubled, and sometimes tripled, that of uncoated samples. Any of the assayed coatings exhibited a positive effect on the sensory properties of fresh-cut apples. The incorporation of apple fiber, together with the use of ascorbic acid, contributed to keep the antioxidant potential of the fruit at least during the first week of storage. Furthermore, gellan gum coatings had a marked effect in reducing mesophilic and psychrophilic counts on fresh-cut apples throughout storage regardless the addition of dietary fibers. The results achieved demonstrate the feasibility of the addition of dietary fiber to edible coating formulations for increasing the nutritional value of fresh-cut apples without compromising their fresh-like quality attributes.This work was supported by Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT, Argentina) and by Spanish Ministry of Economy and Competitiveness, through the project AGL2010-21572. An ICREA Academia Award is also acknowledged

On the origin of ambiguity in efficient communication

This article studies the emergence of ambiguity in communication through the concept of logical irreversibility and within the framework of Shannon's information theory. This leads us to a precise and general expression of the intuition behind Zipf's vocabulary balance in terms of a symmetry equation between the complexities of the coding and the decoding processes that imposes an unavoidable amount of logical uncertainty in natural communication. Accordingly, the emergence of irreversible computations is required if the complexities of the coding and the decoding processes are balanced in a symmetric scenario, which means that the emergence of ambiguous codes is a necessary condition for natural communication to succeed.Comment: 28 pages, 2 figure

Análisis del discurso de los profesores en formación en un contexto de innovación pedagógica en geometría

The reflective narratives of three pre-service teachers are analysed from the perspective of discourse analysis and reflection on practice, applied to the acquisition of geometric competences and the role of dynamic geometry. In the context of the master's degree for future secondary school teachers in mathematics and a pedagogical innovation project, where two of the authors gave training sessions entitled ‘automated visualization’ and ‘technological mediation’, the pre-service teachers were given a questionnaire in which they were asked to return to what they had learned, questioning the contribution of their training to their future teaching practice. In the narratives collected, three degrees of reflection can be found, ranging from the naivety of certain assessments to professional initiatives and purely mathematical perspectives. The didactical and mathematical consequences of this analysis are presented and discussed, highlighting, in particular, the intrinsic difficulty of ensuring that relevant, but potentially disruptive, ideas of pedagogical innovation are conveyed to pre-service teachers against the weight of tradition and personal beliefs in mathematics teaching.Les récits réflexifs de trois enseignants stagiaires sont analysés sous l’angle de l'analyse du discours et de la réflexion sur la pratique, appliquée à l'acquisition de compétences géométriques et au rôle de la géométrie dynamique. Dans le cadre de la maîtrise pour la formation des futurs enseignants du secondaire en mathématiques et d'un projet d'innovation pédagogique, intitulée « visualisation automatisée » et « médiation technologique », les enseignants stagiaires ont reçu un questionnaire où ils devaient revenir sur ce qu'ils ont appris, s’interrogeant sur l’apport de leur formation en vue de leur pratique pédagogique à venir. Dans les récits recueillis, on trouve trois degrés de réflexion qui vont de la naïveté de certaines appréciations aux intentions d’initiatives professionnelles, en passant par des perspectives guidées principalement par les mathématiques. Les conséquences didactiques et mathématiques de cette analyse sont présentées et discutées, soulignant notamment la difficulté intrinsèque de faire en sorte que des idées d'innovation pédagogique pertinentes, mais potentiellement perturbatrices soient dévolues aux enseignants stagiaires, face au poids de la tradition et des croyances personnelles en matière d'enseignement des mathématiques.Se analizan las narrativas reflexivas de tres profesores en formación, desde las perspectivas del análisis del discurso, aplicadas a la adquisición de las competencias geométricas y al papel de la geometría dinámica. En el contexto del máster universitario para futuros profesores de matemáticas de Secundaria y de un proyecto de innovación pedagógica, en el que dos de los autores impartieron sesiones de formación tituladas “visualización automática” y “mediación tecnológica”, se entregó a los profesores en formación un cuestionario en el que se les pedía que reflexionaran sobre lo que habían aprendido, cuestionando la contribución de su formación a su futura práctica docente. En las narrativas recogidas encontramos tres grados de reflexión que van desde la ingenuidad en ciertas apreciaciones hasta las iniciativas profesionales y las perspectivas puramente matemáticas. Se presentan y discuten las implicaciones didácticas y matemáticas de este análisis, destacando en particular la dificultad intrínseca de garantizar que las ideas relevantes, pero potencialmente perturbadoras, de la innovación pedagógica, lleguen a los profesores en formación, frente al peso de la tradición y las creencias personales en educación matemática

Diversity, competition, extinction: the ecophysics of language change

As early indicated by Charles Darwin, languages behave and change very much like living species. They display high diversity, differentiate in space and time, emerge and disappear. A large body of literature has explored the role of information exchanges and communicative constraints in groups of agents under selective scenarios. These models have been very helpful in providing a rationale on how complex forms of communication emerge under evolutionary pressures. However, other patterns of large-scale organization can be described using mathematical methods ignoring communicative traits. These approaches consider shorter time scales and have been developed by exploiting both theoretical ecology and statistical physics methods. The models are reviewed here and include extinction, invasion, origination, spatial organization, coexistence and diversity as key concepts and are very simple in their defining rules. Such simplicity is used in order to catch the most fundamental laws of organization and those universal ingredients responsible for qualitative traits. The similarities between observed and predicted patterns indicate that an ecological theory of language is emerging, supporting (on a quantitative basis) its ecological nature, although key differences are also present. Here we critically review some recent advances lying and outline their implications and limitations as well as open problems for future research.Comment: 17 Pages. A review on current models from statistical Physics and Theoretical Ecology applied to study language dynamic

Means of Choice for Interactive Management of Dynamic Geometry Problems Based on Instrumented Behaviour

ABSTRACT: Our paper presents a project that involves two research questions: does the choice of a related problem by the tutorial system allow the problem solving process which is blocked for the student to be restarted? What information about learning do related problems returned by the system provide us? We answer the first question according to the didactic engineering, whose mode of validation is internal and based on the confrontation between an a priori analysis and an a posteriori analysis that relies on data from experiments in schools. We consider the student as a subject whose adaptation processes are conditioned by the problem and the possible interactions with the computer environment, and also by his knowledge, usually implicit, of the institutional norms that condition his relationship with geometry. Choosing a set of good problems within the system is therefore an essential element of the learning model. Since the source of a problem depends on the student’s actions with the computer tool, it is necessary to wait and see what are the related to problems that are returned to him before being able to identify patterns and assess the learning. With the simultaneity of collecting and analysing interactions in each class, we answer the second question according to a grounded theory analysis. By approaching the problems posed by the system and the designs in play at learning blockages, our analysis links the characteristics of problems to the design components in order to theorize on the decisional, epistemological, representational, didactic and instrumental aspects of the subject-milieu system in interaction

Cranial biomechanics in basal urodeles: the Siberian salamander (Salamandrella keyserlingii) and its evolutionary and developmental implications

Developmental changes in salamander skulls, before and after metamorphosis, afect the feeding capabilities of these animals. How changes in cranial morphology and tissue properties afect the function of the skull are key to decipher the early evolutionary history of the crown-group of salamanders. Here, 3D cranial biomechanics of the adult Salamandrella keyserlingii were analyzed under diferent tissue properties and ossifcation sequences of the cranial skeleton. This helped unravel that: (a) Mechanical properties of tissues (as bone, cartilage or connective tissue) imply a consensus between the stifness required to perform a function versus the fxation (and displacement) required with the surrounding skeletal elements. (b) Changes on the ossifcation pattern, producing fontanelles as a result of bone loss or failure to ossify, represent a trend toward simplifcation potentially helping to distribute stress through the skull, but may also imply a major destabilization of the skull. (c) Bone loss may be originated due to biomechanical optimization and potential reduction of developmental costs. (d) Hynobiids are excellent models for biomechanical reconstruction of extinct early urodeles