La Simetria, una altra manera de mirar els materials

La simetria és un fenomen omnipresent a la natura, ja que es dóna a tots el nivells i escales: des de l'univers considerat com un tot on la massa es divideix en matèria i antimatèria, fins als propis àtoms, amb la seva particular distribució de la càrrega negativa al voltant del nucli, passant pels éssers vius i els objectes inerts com ara els minerals i les molècules. En el present article es proposa aprofitar aquesta omnipresència de la simetria per introduir el seu estudi dins dels continguts pedagògics, ja que permet una millor comprensió i interrelació de molts conceptes fonamentals en química i física, i explicar les propietats dels materials. Es presenten els fonaments teòrics de la simetria restringida a dues dimensions i es suggereixen recursos didàctics atractius, com els dibuixos de M.C. Escher.Symmetry is present all over nature, taking place at all levels and scales: from Universe taken as a whole, where mass is divided in mater and anti-mater, to atoms themselves with their specific around the nucleus, including living creatures and inert objects as minerals and molecules. The present paper proposes using this omnipresence associated to symmetry to introduce its study within the pedagogic contents since it helps achieving a better comprehension and interrelation of many fundamental concepts in chemistry and physics, and it allows explaining the properties of materials. Thus, the paper introduces the basic concepts of symmetry restricted to 2 dimensions, suggesting attractive didactic resources, as M. C. Escher drawings

Propuesta de mejoramiento de la red de voz y datos de la Institución Educativa los Fundadores en el Municipio de Riosucio Caldas

En este proyecto se muestra el diseño de la red de sistemas de comunicaciones de la Institución Educativa Los Fundadores, el cual cumple respectivamente con las normas vigentes que rigen las redes de voz y datos como lo son la EIA/TIA En el diseño de la red de comunicaciones se muestra la distribución de los puntos de red, teléfono y televisión, que cumplen con las necesidades de la Institución Educativa Los Fundadores. Además de esto pueden ver con claridad la distribución de las salas de sistemas con sus respectivos racks. También se muestra una cotización del proyecto, el cual estará encargado de mejorar la red de Voz y Datos en base a sus ordenadores y de los sistemas de comunicaciones en la Institución

Robust Variational Physics-Informed Neural Networks

We introduce a Robust version of the Variational Physics-Informed Neural Networks (RVPINNs) to approximate the Partial Differential Equations (PDEs) solution. We start from a weak Petrov-Galerkin formulation of the problem, select a discrete test space, and define a quadratic loss functional as in VPINNs. Whereas in VPINNs the loss depends upon the selected basis functions of a given test space, herein we minimize a loss based on the residual in the discrete dual norm, which is independent of the test space's choice of test basis functions. We demonstrate that this loss is a reliable and efficient estimator of the true error in the energy norm. The proposed loss function requires computation of the Gram matrix inverse, similar to what occurs in traditional residual minimization methods. To validate our theoretical findings, we test the performance and robustness of our algorithm in several advection-dominated-diffusion problems in one spatial dimension. We conclude that RVPINNs is a robust method

Temperature fluctuations in a relativistic gas: Pressure corrections and possible consequences in the deconfinement transition

In this work, we study the effects of random temperature fluctuations on the equation of state of a non-interacting, relativistic fermion gas by means of the replica method. This picture provides a conceptual model for a non-equilibrium system, depicted as an ensemble of subsystems at different temperatures, randomly distributed with respect to a given mean value. We then assume the temperature displays stochastic fluctuations $T = T_0 + \delta T$ with respect to its ensemble average value $T_0$, with zero mean $\overline{\delta T} = 0$ and standard deviation $\overline{\delta T^2} = \Delta$. By means of the replica method, we obtain the average grand canonical potential, leading to the equation of state of the fermion gas expressed in terms of the excess pressure caused by these fluctuations with respect to the ideal gas at uniform temperature. We further extend our results for the ideal Bose gas as well. Our findings reveal an increase in pressure as the system's ensemble average temperature $T_0$ rises, consistently exceeding the pressure observed in an equilibrium state. Finally, we explore the implications for the deconfinement transition in the context of the simple Bag model, where we show that the critical temperature decreases.Comment: 9 pages, 3 figure

Is forest related decision-making in European treeline areas socially innovative? A Q-methodology enquiry into the perspectives of international experts

Treeline areas provide a range of ecosystem services, but there are diverging views as to how and for whose benefit, these ecosystem services are managed. Applying a Q-method, we explore experts' attitudes towards forest related decision-making and governance in treeline areas to reveal the attitudinal divergences that exist and analyse patterns of shared assumptions forming attitude-related communities. Experiences, trends, opportunities and challenges in European treeline area decision-making are considered. Our results reveal four attitude-related communities, representing four distinctive types of expert attitudes. Findings demonstrate a number of similarities in attitudes among experts indicating, for example, that treeline area decision-making is hardly socially innovative as it tends to happen in a top-down manner. However, some do and others don't see tree-line governance beneficial from an ecological perspective. The attitudinal heterogeneity identified offers insights into treeline decision-making and could, therefore, be useful to public decision-makers in addressing the opinions of each attitudinal group on a case-by-case basis. The general conclusions are that forest related decision-making in treeline areas requires social innovation and a high level of stakeholder competence and capacity-building; and that an improved knowledge of experts' attitudes, together with an emphasis on increased participation in decision-making, could be of help to policy and practice communities in triggering innovative changes locally

QED Fermions in a noisy magnetic field background

We consider the effects of a noisy magnetic field background over the fermion propagator in QED, as an approximation to the spatial inhomogeneities that would naturally arise in certain physical scenarios, such as heavy-ion collisions or the quark-gluon plasma in the early stages of the evolution of the Universe. We considered a classical, finite and uniform average magnetic field background $\langle\mathbf{B}(\mathbf{x})\rangle = \mathbf{B}$, subject to white-noise spatial fluctuations with auto-correlation of magnitude $\Delta_B$. By means of the Schwinger representation of the propagator in the average magnetic field as a reference system, we used the replica formalism to study the effects of the magnetic noise in the form of renormalized quasi-particle parameters, leading to an effective charge and an effective refraction index, that depend not only on the energy scale, as usual, but also on the magnitude of the noise $\Delta_B$ and the average field $\mathbf{B}$

Loss of pancreas upon activated Wnt signaling is concomitant with emergence of gastrointestinal identity

Organ formation is achieved through the complex interplay between signaling pathways and transcriptional cascades. The canonical Wnt signaling pathway plays multiple roles during embryonic development including patterning, proliferation and differentiation in distinct tissues. Previous studies have established the importance of this pathway at multiple stages of pancreas formation as well as in postnatal organ function and homeostasis. In mice, gain-of-function experiments have demonstrated that activation of the canonical Wnt pathway results in pancreatic hypoplasia, a phenomenon whose underlying mechanisms remains to be elucidated. Here, we show that ectopic activation of epithelial canonical Wnt signaling causes aberrant induction of gastric and intestinal markers both in the pancreatic epithelium and mesenchyme, leading to the development of gut-like features. Furthermore, we provide evidence that β -catenin-induced impairment of pancreas formation depends on Hedgehog signaling. Together, our data emphasize the developmental plasticity of pancreatic progenitors and further underscore the key role of precise regulation of signaling pathways to maintain appropriate organ boundaries

Tuning of defects in ZnO nanorod arrays used in bulk heterojunction solar cells.

With particular focus on bulk heterojunction solar cells incorporating ZnO nanorods, we study how different annealing environments (air or Zn environment) and temperatures impact on the photoluminescence response. Our work gives new insight into the complex defect landscape in ZnO, and it also shows how the different defect types can be manipulated. We have determined the emission wavelengths for the two main defects which make up the visible band, the oxygen vacancy emission wavelength at approximately 530 nm and the zinc vacancy emission wavelength at approximately 630 nm. The precise nature of the defect landscape in the bulk of the nanorods is found to be unimportant to photovoltaic cell performance although the surface structure is more critical. Annealing of the nanorods is optimum at 300°C as this is a sufficiently high temperature to decompose Zn(OH)2 formed at the surface of the nanorods during electrodeposition and sufficiently low to prevent ITO degradation.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

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