Investigaciones y estudios sobre revoques simil piedra

En los últimos años se vienen realizando tareas de reparación, reciclaje y restauración en edificios y construcciones, muchos de los cuales son importantes monumentos, siendo algunos de ellos considerados los edificios mas valiosos del patrimonio arquitectónico del país. No obstante en muchos de los casos los proyectos están por debajo de los niveles técnicos, lógicos y serios que se deberían considerar al efectuar estas intervenciones. En este trabajo se pretende aportar al desarrollo de investigaciones y técnicas de laboratorio que permitirían encarar estos emprendimientos con base científica al suplantar revoques o revestimientos originales y alterados por patologías por materiales y técnicas actuales. Se consideran las determinaciones clásicas de análisis físico, químico y petrográfico de los materiales intervinientes y se presentan algunas técnicas sencillas para relacionar la porosidad y permeabilidad de los revestimientos y su velocidad de deterioro principalmente las vinculadas con las alteraciones visuales. Además, se comentan resultados preliminares del análisis de microfotografías de revestimientos simil piedra tomadas en edificios actualmente en proceso de restauración con las formulaciones propuestas para el reemplazo. Con los datos obtenidos podemos orientar fuertemente que tipo de mortero puede ser más adecuado para sustituir revestimientos alterados por el agua en edificios históricos

Modeling of a Cable-Based Revolute Joint Using Biphasic Media Variable Stiffness Actuation

In recent times, safe interactions between humans and robots are required for innumerable tasks and environments. This safety can be achieved using compliance design and control of mechanisms. Cable-driven mechanisms are used when applications need to have light structures, meaning that their actuators must be relocated to ground and forces are transferred along tensioned cables. This paper presents a compliant cable-driven revolute joint using biphasic media variable stiffness actuators. Actuator's stiffness is controlled by changing pressure of control fluid into distribution lines. The used control fluid is biphasic, composed of separated gas and liquid fractions with predefined ratio. The mathematical model of the actuator is presented along with its position and stiffness model-based control, then, equations relating to the dynamics of the mechanism are provided with a joint stiffness and orientation controller. Results from simulations are discussed

Bosonic Field Propagators on Algebraic Curves

In this paper we investigate massless scalar field theory on non-degenerate algebraic curves. The propagator is written in terms of the parameters appearing in the polynomial defining the curve. This provides an alternative to the language of theta functions. The main result is a derivation of the third kind differential normalized in such a way that its periods around the homology cycles are purely imaginary. All the physical correlation functions of the scalar fields can be expressed in terms of this object. This paper contains a detailed analysis of the techniques necessary to study field theories on algebraic curves. A simple expression of the scalar field propagator is found in a particular case in which the algebraic curves have $Z_n$ internal symmetry and one of the fields is located at a branch point.Comment: 26 pages, TeX + harvma

Fractional Calculus: Historical Notes Apuntes Históricos del Cálculo Fraccionario

En este trabajo, presentamos algunos apuntes históricos del cálculo fraccionario Local, y destacamos algunas propiedades y aplicaciones de estas nuevas herramientas matemicasIn this paper, we present some historical notes to Generalized Calculus, sometimes called Local Fractional Calculus, and highlight some properties and applications of these new mathematical tool

Transfer Hydrogenation of Azo Compounds with Ammonia Borane Using a Simple Acyclic Phosphite Precatalyst

Tris(quinolin-8-yl)phosphite, P(Oquin)(3), promotes the dehydrogenation of H3N center dot BH3 (AB) and the transfer hydrogenation of azoarenes using ammonia borane (AB) as H-2 source. The metal-free reduction of azoarenes proceeds under mild reaction conditions upon which several diphenylhydrazine derivatives are obtained in high yields. The reactivity of P(Oquin)(3) toward AB was evaluated through NMR in situ tests. The rate of the reaction, activation parameters, deuterium kinetic isotope effect (DKIE) and linear-free energy relationship were investigated. Such mechanistic and kinetic studies suggest that P(Oquin)(3) is a precatalyst and that AB is likely involved in more than one stage of the reaction pathway. Furthermore, the kinetic data indicate that the reaction proceeds through an ordered transition state, possibly associative

Self-consistent model for the saturation mechanism of the response to harmonic forcing in the backward-facing step flow

Certain flows denominated as amplifiers arc characterized by their global linear stability while showing large linear amplifications to sustained perturbations. As the forcing amplitude increases, a strong saturation of the response appears when compared to the linear prediction. However, a predictive model that describes the saturation of the response to higher amplitudes of forcing in stable laminar flows is still missing. While an asymptotic analysis based on the weakly nonlinear theory shows qualitative agreement only for very small forcing amplitudes, the linear response to harmonic forcing around the mean flow computed by direct numerical simulations presents a good prediction of the saturation also at higher forcing amplitudes. These results suggest that the saturation process is governed by the Reynolds stress and thus motivate the introduction of a simple self-consistent model. The model consists of a decomposition of the full nonlinear Navier-Stokes equations in a wan flow equation together with a linear perturbation equation around the mean flow, which arc coupled through the Reynolds stress. The full fluctuating response and the resulting Reynolds stress are approximated by the first harmonic calculated from the linear response to the forcing around the aforementioned mean flow. This closed set of coupled equations is solved in an iterative manner as partial nonlinearity is still preserved in the mean flow equation despite the assumed simplifications. The results show an accurate prediction of the response energy when compared to direct numerical simulations. The approximated coupling is strong enough to retain the main nonlinear effects of the saturation process. Hence, a simple physical picture is formalized, wherein the response modifies the mean flow through the Reynolds stress in such a way that the correct response energy is attained

Low temperature exposure induces browning of bone marrow stem cell derived adipocytes in vitro

Brown and beige adipocytes are characterised as expressing the unique mitochondrial uncoupling protein (UCP)1 for which the primary stimulus in vivo is cold exposure. The extent to which cold-induced UCP1 activation can also be achieved in vitro, and therefore perform a comparable cellular function, is unknown. We report an in vitro model to induce adipocyte browning using bone marrow (BM) derived mesenchymal stem cells (MSC), which relies on differentiation at 32 °C instead of 37 °C. The low temperature promoted browning in adipogenic cultures, with increased adipocyte differentiation and upregulation of adipogenic and thermogenic factors, especially UCP1. Cells exhibited enhanced uncoupled respiration and metabolic adaptation. Cold-exposed differentiated cells showed a marked translocation of leptin to adipocyte nuclei, suggesting a previously unknown role for leptin in the browning process. These results indicate that BM-MSC can be driven to forming beige-like adipocytes in vitro by exposure to a reduced temperature. This in vitro model will provide a powerful tool to elucidate the precise role of leptin and related hormones in hitherto functions in the browning process

Monopoles and Holography

We present a holographic theory in AdS_4 whose zero temperature ground state develops a crystal structure, spontaneously breaking translational symmetry. The crystal is induced by a background magnetic field, but requires no chemical potential. This lattice arises from the existence of 't Hooft-Polyakov monopole solitons in the bulk which condense to form a classical object known as a monopole wall. In the infra-red, the magnetic field is screened and there is an emergent SU(2) global symmetry.Comment: 33 pages, 16 figures; v2: ref adde