4,417 research outputs found
La distancia que separa las concepciones didĂĄcticas de lo que se hace en clase : el caso de los trabajos de laboratorio en biologĂa
En este artĂculo se analizan las concepciones sobre los trabajos de laboratorio en biologĂa de un grupo de alumnos de 4Âș año de la escuela secundaria. A travĂ©s de un cuestionario verbal abierto y una tarea de selecciĂłn de tarjetas, se indagĂł quĂ© tipo de trabajos experimentales los alumnos llevan a cabo en sus clases, quĂ© se aprende de ellos y quĂ© posibilidades encuentran en otras modalidades de trabajos experimentales propuestas por los especialistas en didĂĄctica. Los resultados señalan una brecha entre lo que los alumnos refieren que se realiza en sus clases y las propuestas de los especialistas. En la escuela, predominan las tareas escasamente reflexivas (actividades de carĂĄcter descriptivo para verificar e ilustrar temas estudiados), que no ayudan a desarrollar habilidades vinculadas con la investigaciĂłn, ya que exigen seguir una serie de pasos estipulados en vez de alentar el planteamiento de problemas, la formulaciĂłn de hipĂłtesis, la bĂșsqueda de respuestas y la interpretaciĂłn de lo observado.Sixteen-year-old students' ideas about Biological laboratory work done in their classes are revealed through an open questionnaire. They were also validated through a selection task in which students were presented four different instructional situations involving practical work and had to decide which was more frequent in their classes, what can be learned through them, and their personal preferences about the way they would like to be taught. The results show a wide gap between what students say they do in their classes and what experts in the field say that should be done. In schools they are taught through non reflective tasks (with only descriptive demands), which rarely help them develop inquiry skills. They are expected to follow the instructions of their teachers instead of posing problems, thinking of hypotheses, trying to find answers and analyzing what they observe
Automated Morphological Measurements of Brain Structures and Identification of Optimal Surgical Intervention for Chiari i Malformation
The herniation of cerebellum through the foramen magnum may block the normal flow of cerebrospinal fluid determining a severe disorder called Chiari I Malformation (CM-I). Different surgical options are available to help patients, but there is no standard to select the optimal treatment. This paper proposes a fully automated method to select the optimal intervention. It is based on morphological parameters of the brain, posterior fossa and cerebellum, estimated by processing sagittal magnetic resonance images (MRI). The processing algorithm is based on a non-rigid registration by a balanced multi-image generalization of demons method. Moreover, a post-processing based on active contour was used to improve the estimation of cerebellar hernia. This method allowed to delineate the boundaries of the regions of interest with a percentage of agreement with the delineation of an expert of about 85%. Different features characterizing the estimated regions were then extracted and used to develop a classifier to identify the optimal surgical treatment. Classification accuracy on a database of 50 patients was about 92%, with a predictive value of 88% (tested with a leave-one-out approach)
Ăvaluation de la formulation dâun gel Ă base de HA et de cellules progĂ©nitrices foetales pour le traitement topique des brĂ»lures
Les brûlures de 2Úme degré profond et 3Úme degré engendrent des perturbations cutanées, telles une mauvaise oxygénation tissulaire ou une perte de liquide et de protéines. Le risque de déshydratation et d'infections est donc prévenu dans les centres suisses de grands brûlés par l'application d'une couverture précoce appelée "pansement biologique". Il s'agit d'une matrice biodégradable, principalement à base de collagÚne dans la pratique quotidienne, contenant des cellules progénitrices de peau foetale ensemencées.
Ce travail a pour but d'Ă©valuer la faisabilitĂ© du point de vue thĂ©orique et en partie pratique d'un nouveau type de pansement biologique sous forme de gel Ă base dâacide hyaluronique et de cellules progĂ©nitrices foetales. Lâacide hyaluronique (HA) est un biopolymĂšre naturellement prĂ©sent dans le derme et dont les propriĂ©tĂ©s sont prĂ©cieuses pour la rĂ©gĂ©nĂ©ration cutanĂ©e. De plus, lâapplication dâun pansement biologique sous forme de gel permettrait de bĂ©nĂ©ficier des bienfaits des hydrogels et de faciliter son application par les chirurgiens.
Dans un premier temps, lâanalyse bibliographique a rĂ©vĂ©lĂ© les nombreux avantages de lâacide hyaluronique et les multiples Ă©tudes qui dĂ©montrent ses bĂ©nĂ©fices chez les grands brĂ»lĂ©s.
Puis, une partie expĂ©rimentale a Ă©tĂ© effectuĂ©e afin de tester la tolĂ©rance des cellules progĂ©nitrices foetales au contact avec diffĂ©rentes concentrations dâacide hyaluronique. Les rĂ©sultats posent les bases et encouragent lâexĂ©cution de futures expĂ©riences Ă ce sujet
Nonlinear convective motion of the asthenosphere and the lithosphere melting: a model for the birth of a volcano
The processes of heat transfer occurring between the Earth's asthenosphere and lithosphere are responsible for partial melting of rocks, leading to the magma generation and its migration and segregation in the crust and, possibly, to volcanoes generation at the surface. Convection is the dominant mechanism regulating the heat transfer from the asthenosphere to the lithosphere, although many aspects of the whole process are not yet clear. Therefore, the knowledge of the physical processes leading to the melting of the lithospheric rocks has important consequences in understanding the interior Earth dynamics, the surface volcanic dynamics, and its related hazards. Rock melting occurs when the temperature gradient meets the rock solidus. Here, we propose a nonlinear convective 1D analytical model (representing an approximation of more 3D complex models). The steady-state solution of our equation is in good agreement with the estimated geotherms of the asthenosphere. A perturbative approach leads to a heat swelling at the boundary between asthenosphere and lithosphere able to determine its melting and the birth of a volcano
Tectonic stress and renewed uplift at Campi Flegrei caldera, southern Italy: New insights from caldera drilling
Deep drilling is a key tool for the investigation of active volcanoes in the modern Earth Sciences, as this provides the only means to obtain direct information on processes that occur at depth. Data acquired from drilling projects are fundamental to our understanding of volcano dynamics, and for mitigation of the hazards they pose for millions of people who live close to active volcanoes. We present here the first borehole measurement of the stress field in the crust of Campi Flegrei (southern Italy), a large active caldera, and one of the highest risk volcanoes worldwide. Measurements were performed to depths of âŒ500 m during a pilot study for the Campi Flegrei Deep Drilling Project. These data indicate an extensional stress field, with a minimum horizontal stress of ca. 75% to 80% of the maximum horizontal stress, which is approximately equal to the vertical stress. The deviation from lithostatic conditions is consistent with a progressive increase in applied horizontal stress during episodes of unrest, since at least 1969. As the stress field is evolving with time, the outcome of renewed unrest cannot be assessed by analogy with previous episodes. Interpretations of future unrest must therefore accommodate the possibility that Campi Flegrei is approaching conditions that are more favourable to a volcanic eruption than has previously been the case. Such long-term accumulation of stress is not expected to be unique to Campi Flegrei, and so might provide a basis for improved forecasts of eruptions at large calderas elsewhere
Carbon beam dosimetry in bony tissue inhomogeneties: TRiP98 validation with experimental measurements
Red cell distribution width (RDW) and complete blood cell count-derived measures in non-arteritic anterior ischemic optic neuropathy
Purpose: To assess the role of complete blood cell count (CBC) dimensional indices and CBC-derived measures in non-arteritic anterior ischemic optic neuropathy (NA-AION). Methods: In this retrospective case-control survey, 37 newly diagnosed NA-AION patients and 37 sex-and age-matched cataract controls were enrolled in 2017-2018. On the same day of NA-AION diagnosis, a blood sample was collected and CBC was determined using an automatic blood counter. CBC dimensional indices, such as mean platelet volume (MPV) and red cell distribution width (RDW), and CBC-combined indices, including neutrophil/lymphocyte ratio (NLR), derived NLR [dNLR = neutrophils/(white blood cells-neutrophils)], and platelet/lymphocyte ratio (PLR), were evaluated. Erythrocyte sedimentation rate (ESR) was also measured. Results: Mean platelet count, median MPV, RDW, NLR, and dNLR were 221±48 x 109/L, 8.2 fL (IQR=7.6-8.9), 13% (IQR=12-14.5), 2.50 (IQR=1.77-3.06), and 1.73 (IQR=1.31-2.07) in NA-AION patients and 248±56 x 109/L, 7.60 fL (IQR=7.05-8.25), 12% (IQR=11.6-13), 1.95 (IQR=1.43-2.49) and 1.36 (IQR=1.07-1.69) in controls. NA-AION patients showed significantly lower platelet count (p=0.03) and significantly higher median values of MPV (p=0.01), RDW (p=0.015), NLR (p=0.03), and dNLR (p=0.01). Multivariate logistic regression models disclosed a significant correlation only between higher levels of RDW and NA-AION (pâ€0.05). The attributable risk of the association between NA-AION and RDW was 33%. Conclusions: Results suggest that RDW may be somehow involved in the pathogenesis of NA-AION. However, high-quality cohort studies are warranted to confirm whether, or not, an altered RDW may be considered a potential biomarker of this vascular disorder affecting the optic nerve
Phases of N=1 USp(2N_c) Gauge Theories with Flavors
We studied the phase structures of N=1 supersymmetric USp(2N_c) gauge theory
with N_f flavors in the fundamental representation as we deformed the N=2
supersymmetric QCD by adding the superpotential for adjoint chiral scalar
field. We determined the most general factorization curves for various breaking
patterns, for example, the two different breaking patterns of quartic
superpotential. We observed all kinds of smooth transitions for quartic
superpotential. Finally we discuss the intriguing role of USp(0) in the phase
structure and the possible connection with observations made recently in
hep-th/0304271 (Aganagic, Intriligator, Vafa and Warner) and in hep-th/0307063
(Cachazo).Comment: 61pp; Improved the presentation, references are added and to appear
in PR
Hidden local symmetry and color confinement
The hidden local symmetry is a successful model to describe the properties of
the vector mesons in QCD. We point out that if we identify this hidden gauge
theory as the magnetic picture of QCD, a linearized version of the model
simultaneously describes color confinement and chiral symmetry breaking. We
demonstrate that such a structure can be seen in the Seiberg dual picture of a
softly broken supersymmetric QCD. The model possesses exact chiral symmetry and
reduces to QCD when mass parameters are taken to be large. Working in the
regime of the small mass parameters, we show that there is a vacuum where
chiral symmetry is spontaneously broken and simultaneously the magnetic gauge
group is Higgsed. If the vacuum we find persists in the limit of large mass
parameters, one can identify the rho meson as the massive magnetic gauge boson,
that is an essential ingredient for color confinement.Comment: 20 pages, 3 figure
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