Influencia de las variables de ensayo en la conductividad térmica de hormigones aislantes refractarios

Se realizaron experiencias en base a los métodos IRAM 12 563 y ASTM C-417-58, modificando algunas de las condiciones especificadas; se consideraron como variables el espesor de la probeta de ensayo, el tiempo de calentamiento a la temperatura de régimen y el tratamiento térmico previo de la probeta de ensayo• Las muestras utilizadas son productos nacionales proporcionados por los usuarios. Se pretende así establecer las bases de futuras especificaciones relativas a las características de conductividad térmica y de módulo de rotura a la flexión, valores éstos no fijados en la actualidad.Several experiences were done following the IRAM 12563 and ASTM C-417-58 methods with some modifications in the specified conditions. The thickness of specimens, the heating time to the work temperature and the previous thermic treatment were considered as variables. The samples studied are argentine products. In this way we try to outline the basis for future specifications in connection with the characteristics of thermical conductivity and point of breakage in flexion. These values have not been established yet

Conformal metrics and true "gradient flows" for curves

We wish to endow the manifold M of smooth curves in Rn with a Riemannian metric that allows us to treat continuous morphs (homotopies) between two curves c0 and c1 as trajectories with computable lengths which are independent of the parameterization or representation of the two curves (and the curves making up the morph between them). We may then define the distance between the two curves using the trajectory of minimal length (geodesic) between them, assuming such a minimizing trajectory exists. At first we attempt to utilize the metric structure implied rather unanimously by the past twenty years or so of shape optimization literature in computer vision. This metric arises as the unique metric which validates the common references to a wide variety of contour evolution models in the literature as "gradient flows" to various formulated energy functionals. Surprisingly, this implied metric yields a pathological and useless notion of distance between curves. In this paper, we show how this metric can be minimally modified using conformal factors that depend upon a curve's total arclength. A nice property of these new conformal metrics is that all active contour models that have been called "gradient flows" in the past will constitute true gradient flows with respect to these new metrics under specific time reparameterizations

Deformacion bajo carga a elevadas temperaturas de materiales refractarios

Se presenta una técnica de ensayo que permite obtener resultados reales de deformación bajo carga a elevadas temperaturas . Se ensayaron siete arcillas refractarias argentinas, en estado natural y previamente calcinadas a 1 450°c. Se presentan las curvas de aplastamiento obtenidas y las características físico-químicas de los materiales ensayados. Se exponen conclusiones referentes al método de ensayo y al comportamiento de las arcillas estudiadas. Como complemento se dan a conocer los resultados obtenidos en ensayos realizados sobre ladrillos refractarios sílico- aluminosos de fabricación nacional.A testing technique is presented which allows to obtain more accurate results of deformation under load at high temperatures . Seven refractory clays were tested, in his natural state and heated at 145°C. Curves of deformation under load obtained and physico-chemical chracteristics of tested materials are given. Conclusions are drawn with reference to the testing method and the behaviour of studied clays. As a complement, results obtained when testing a series , of silico-aluminous refractory bricks, are included

Características químicas y físicas de arcillas refractarias argentinas

El trabajo tiene por objeto informar sobre las características físicas, químicas y datos de explotación de las principales arcillas refractarias del país, ubicadas en yacimientos distribuidos en diferentes provincias y que actualmente son utilizadas, principalmente, por la industria de materiales refractarios del tipo sí1ico-aluminoso. Se informan resultados relativos a: composición química, composición mineralógica por difracción de rayos X y A.T.D., refractariedad por medida del C.P.E., refractariedad bajo carga o valor soporte en función de la temperatura, dilatometría hasta temperaturas de 1 500°C, influencia de la temperatura de cocción en la porosidad aparente de la chamota de acuerdo a la especie mineralógica que predomina en la arcilla.This work has the purpose of reporting on the chemical and physical characteristics —as well as exploitation data— of the main refractory clays of the country lying on deposits distributed in various provinces and currently used mainly hy the industry of refractory materials of the alu- mino-siliceous type. Results are given that relate to chemical composition, mineralogical composition as determined hy X-raying and A.T. I)., refractariety measured hy E.P.C., refractariety under load or supporting rate as a function of the temperature, dilatometry at temperatures as high as 1 500°C, influence of temperature of calcining on the apparent porosity of the chamotte, according to the mineralogical species predominating in the given clay

Polarizable QM/MM Multiconfiguration Self-Consistent Field Approach with State-Specific Corrections: Environment Effects on Cytosine Absorption Spectrum

We present the formulation and implementation of a polarizable quantum mechanics/molecular mechanics (QM/MM) strategy to describe environment effects in multiconfiguration self-consistent field calculations. The strategy is applied to the calculation of the vertical absorption spectrum of cytosine in water. In our approach, mutual polarization of the solute and the solvent is solved self-consistently at the complete-active-space self-consistent-field (CASSCF) level, and the resulting set of charges and dipoles is used to calculate vertical excitation energies using the complete-active-space second-order perturbative (CASPT2) approach and its multistate (MS-CASPT2) variant. In order to treat multiple excited states, we converge the solvent polarization with respect to the state-averaged density of the solute. In order to obtain the final energies, however, we introduce a state-specific correction, where the solvent polarization is recomputed with the density of each state, and demonstrate that this correction brings the excitation energies closer to the values obtained with state-optimized orbitals. Comparison with PCM and nonpolarizable QM/MM calculations shows the importance of specific solute solvent interactions and environment polarization in describing experiments. Overall, the calculated excitations for the π → π* states in water show good agreement with the experimental spectrum, whereas the n → π* appear at energies above 6 eV, approximately 1 eV higher than in the gas phase. Beyond solvents, the new method will allow studying the impact of heterogeneous biological environments in multiple excited states, as well as the treatment of multichromophoric systems where charge transfer and exciton states play important roles

La liquidación express: la reforma del art. 39 bis del Código Fiscal ¿implica un mal uso del gobierno electrónico?

El presente trabajo desarrolla la problemática que se suscita en relación a la llamada “Liquidación Express” efectuada por la Agencia de Recaudación de la Provincia de Buenos Aires (ARBA). El eje central de dicha cuestión se basará no sólo en el aspecto jurídico y axiológico de la temática, sino que el análisis se hará también desde una visión amplia que implica evaluar el contexto que favorece y contiene a la problemática. Se analizan actos puntuales de ARBA, los cuales desde el aspecto jurídico no respetan la garantía de revisión judicial suficiente y vulneran el derecho de defensa de los contribuyentes. Dichos actos se encuentran facilitados por el uso de los beneficios que proporciona solamente al Estado el Gobierno Electrónico.This paper analyzes the problem of the Express Liquidation executed by the Fiscal Agency of Province of Buenos Aires (ARBA). The focal point of the analysis is based not only in the legal and axiological aspects involved, but also in a broad viewpoint that allows the evaluation of a context that favors and contains the problem. We analyze actual actions of ARBA which, from the legal side does not respect taxpayers’ constitutional rights, such as the judiciary revision warranty and the right to defense. Those acts are facilitated by the use of tools and mechanisms that the E Government provides exclusively to the State.Finanzas y Derecho FinancieroFacultad de Ciencias Jurídicas y Sociale

La liquidación express: la reforma del art. 39 bis del Código Fiscal ¿implica un mal uso del gobierno electrónico?

El presente trabajo desarrolla la problemática que se suscita en relación a la llamada “Liquidación Express” efectuada por la Agencia de Recaudación de la Provincia de Buenos Aires (ARBA). El eje central de dicha cuestión se basará no sólo en el aspecto jurídico y axiológico de la temática, sino que el análisis se hará también desde una visión amplia que implica evaluar el contexto que favorece y contiene a la problemática. Se analizan actos puntuales de ARBA, los cuales desde el aspecto jurídico no respetan la garantía de revisión judicial suficiente y vulneran el derecho de defensa de los contribuyentes. Dichos actos se encuentran facilitados por el uso de los beneficios que proporciona solamente al Estado el Gobierno Electrónico.This paper analyzes the problem of the Express Liquidation executed by the Fiscal Agency of Province of Buenos Aires (ARBA). The focal point of the analysis is based not only in the legal and axiological aspects involved, but also in a broad viewpoint that allows the evaluation of a context that favors and contains the problem. We analyze actual actions of ARBA which, from the legal side does not respect taxpayers’ constitutional rights, such as the judiciary revision warranty and the right to defense. Those acts are facilitated by the use of tools and mechanisms that the E Government provides exclusively to the State.Finanzas y Derecho FinancieroFacultad de Ciencias Jurídicas y Sociale

Dye Stabilization and Wavelength Tunability in Lasing Fibers Based on DNA

Lasers based on biological materials are attracting an increasing interest in view of their use in integrated and transient photonics. Deoxyribonucleic acid (DNA) as optical biopolymer in combination with highly emissive dyes has been reported to have excellent potential in this respect. However, achieving miniaturized lasing systems based on solid-state DNA shaped in different geometries to confine and enhance emission is still a challenge, and the physicochemical mechanisms originating fluorescence enhancement are not fully understood. Herein, a class of wavelength-tunable lasers based on DNA nanofibers is demonstrated, for which optical properties are highly controlled through the system morphology. A synergistic effect is highlighted at the basis of lasing action. Through a quantum chemical investigation, it is shown that the interaction of DNA with the encapsulated dye leads to hindered twisting and suppressed channels for the nonradiative decay. This is combined with effective waveguiding, optical gain, and tailored mode confinement to promote morphologically controlled lasing in DNA-based nanofibers. The results establish design rules for the development of bright and tunable nanolasers and optical networks based on DNA nanostructures

Light absorption enhancement in thin film hydrgenated amorphus Si solar cells

In this paper, light absorption enhancement in thin film solar cell (SC) is reported and analyzed. The suggested design is based on a nanostructured pattern that increases the diffuse scattered component of radiation and hence the absorption through the active layer. An ion beam sputtering (lBS) approach is used to texture large areas of the glass substrate with high aspect-ratio ripples in order to increase light scattering. Then, thin film SC supported on the textured glass is simulated and analyzed using 3D finite difference time domain (FDTD) method. The suggested SC can offer an ultimate efficiency of 19.26% with short circuit current of 15.76 mA/cm2 with an enhancement of 31.435% over the SC without texturing surface