Características dieléctricas de diversos polímeros (PVC, EVA, HDPE, y PP) reforzados con neumáticos fuera de uso (GTR)

La masiva fabricación de neumáticos y la dificultad para su almacenamiento o eliminación constituye un grave problema medioambiental. En la actualidad, se utilizan diversos metodos para el reciclaje de los neumáticos, como por ejemplo la trituración mecánica, que separa el caucho vulcanizado del acero y las fibras, utilizandose este caucho en numerosas aplicaciones industriales como pavimentos, aislantes, calzados, etc. El presente artículo se centra en buscar una nueva aplicación para estos neumáaticos reutilizados (GTR), y para ello, se ha mezclado el polvo de los neumáticos con diferentes polímeros termoplásticos como son el Policloruro de Vinilo (PVC), el Polietileno de Alta Densidad (HDPE), el Etileno Acetato de Vinilo (EVA) y el Polipropileno (PP), comprobando hasta que valores de concentracion en GTR admitenestos nuevos compuestos manteniendo dentro de unos valores aceptables sus propiedades dielectricas, y por tanto, sus posibles aplicaciones industriales en la fabricación de aislantes para cables eléctricos. Concretamente, el polvo de los neumáticos reutilizados y con un tamaño de partícula inferior a 200 μm, ha sido mezclado con los polímeros con cuatro concentraciones diferentes, 5%, 10%, 20% y 50% en GTR para asi determinar su comportamiento mediante los ensayos dieléctricos realizados en un rango de temperaturas que varia desde los 30oC hasta los 120oC, y con unas frecuencias entre 1・10  -2 Hz, hasta 3・10  6Hz, analizandose la conductividad, la permitividad, el factor de perdidas dieléctricas, las relajaciones, etc. Finalmente, las superficies de fractura de las muestras compuestas han sido evaluadas por microscopía electronicade barrido (SEM)

Reduction and approximation in gyrokinetics

The gyrokinetics formulation of plasmas in strong magnetic fields aims at the elimination of the angle associated with the Larmor rotation of charged particles around the magnetic field lines. In a perturbative treatment or as a time-averaging procedure, gyrokinetics is in general an approximation to the true dynamics. Here we discuss the conditions under which gyrokinetics is either an approximation or an exact operation in the framework of reduction of dynamical systems with symmetryComment: 15 pages late

Physical chemical properties and kinetics of redox processes in water/soybean oil microemulsions

Water/oil microemulsions (w/o ME) constituted by water, soybean oil, SDS (sodium dodecyl sulfate) and several short-chain alcohols were characterized from the viewpoint of its physical-chemical and electroanalytical properties. Different co-surfactants and surfactant:co-surfactant ratios were used, and the ME with the most favourable composition was used to study the kinetics of redox processes. For this purpose, cyclic voltammetry measurements using a Pt disk working ultramicroelectrode, an Ag/AgCl reference electrode and a Pt auxiliary electrode, and ferrocene as a probe, were performed. It was verified that the thermodynamic stability of the MEs increases with the co-surfactant content. The molecular structure and water solubility of the co-surfactant affect the electrical conductivity and the hydrodynamic radio of the MEs. Owing to the low diffusion coefficients verified in the MEs, measurements in transient state using conventional sweeping rates could be performed. Ferrocene oxidation in the ME has been demonstrated to proceed in quasi-reversibility conditions. Thus, the possibility of carrying out studies of cyclic voltammetry in vegetable oils under the w/o ME form was demonstrated

Ignition conditions for inertial confinement fusion targets with a nuclear spin-polarized DT fuel

The nuclear fusion cross-section is modified when the spins of the interacting nuclei are polarized. In the case of deuterium?tritium it has been theoretically predicted that the nuclear fusion cross-section could be increased by a factor d = 1.5 if all the nuclei were polarized. In inertial confinement fusion this would result in a modification of the required ignition conditions. Using numerical simulations it is found that the required hot-spot temperature and areal density can both be reduced by about 15% for a fully polarized nuclear fuel. Moreover, numerical simulations of a directly driven capsule show that the required laser power and energy to achieve a high gain scale as d-0.6 and d-0.4 respectively, while the maximum achievable energy gain scales as d0.9

Error analysis of free probability approximations to the density of states of disordered systems

Theoretical studies of localization, anomalous diffusion and ergodicity breaking require solving the electronic structure of disordered systems. We use free probability to approximate the ensemble- averaged density of states without exact diagonalization. We present an error analysis that quantifies the accuracy using a generalized moment expansion, allowing us to distinguish between different approximations. We identify an approximation that is accurate to the eighth moment across all noise strengths, and contrast this with the perturbation theory and isotropic entanglement theory.Comment: 5 pages, 3 figures, submitted to Phys. Rev. Let

Neorealism and the Organization of American States (OAS): an examination of CARICOM rationality toward Venezuela and the United States

Since 2017, CARICOM member states have been divided in the positions they take on Organization of American States (OAS) resolutions addressing political instability in Venezuela. This article uses a neorealism framework to determine whether or not the provision of energy investments by Venezuela and the United States to CARICOM member countries is an attempt on their part to skew the OAS voting mechanism in their national interests. The article also examines the extent to which CARICOM member states’ response to Venezuela’s and United States’ interest in the OAS demonstrates a pattern of rationality. The findings suggest that though the OAS provides a medium for states to negotiate mutually beneficial solutions, states are rational actors and even where they do corporate, dominant states may try to manifest their self-interest

Cauchy's infinitesimals, his sum theorem, and foundational paradigms

Cauchy's sum theorem is a prototype of what is today a basic result on the convergence of a series of functions in undergraduate analysis. We seek to interpret Cauchy's proof, and discuss the related epistemological questions involved in comparing distinct interpretive paradigms. Cauchy's proof is often interpreted in the modern framework of a Weierstrassian paradigm. We analyze Cauchy's proof closely and show that it finds closer proxies in a different modern framework. Keywords: Cauchy's infinitesimal; sum theorem; quantifier alternation; uniform convergence; foundational paradigms.Comment: 42 pages; to appear in Foundations of Scienc

Mathematical and Statistical Techniques for Systems Medicine: The Wnt Signaling Pathway as a Case Study

The last decade has seen an explosion in models that describe phenomena in systems medicine. Such models are especially useful for studying signaling pathways, such as the Wnt pathway. In this chapter we use the Wnt pathway to showcase current mathematical and statistical techniques that enable modelers to gain insight into (models of) gene regulation, and generate testable predictions. We introduce a range of modeling frameworks, but focus on ordinary differential equation (ODE) models since they remain the most widely used approach in systems biology and medicine and continue to offer great potential. We present methods for the analysis of a single model, comprising applications of standard dynamical systems approaches such as nondimensionalization, steady state, asymptotic and sensitivity analysis, and more recent statistical and algebraic approaches to compare models with data. We present parameter estimation and model comparison techniques, focusing on Bayesian analysis and coplanarity via algebraic geometry. Our intention is that this (non exhaustive) review may serve as a useful starting point for the analysis of models in systems medicine.Comment: Submitted to 'Systems Medicine' as a book chapte

Divergent Perturbation Series

Various perturbation series are factorially divergent. The behavior of their high-order terms can be found by Lipatov's method, according to which they are determined by the saddle-point configurations (instantons) of appropriate functional integrals. When the Lipatov asymptotics is known and several lowest order terms of the perturbation series are found by direct calculation of diagrams, one can gain insight into the behavior of the remaining terms of the series. Summing it, one can solve (in a certain approximation) various strong-coupling problems. This approach is demonstrated by determining the Gell-Mann - Low functions in \phi^4 theory, QED, and QCD for arbitrary coupling constants. An overview of the mathematical theory of divergent series is presented, and interpretation of perturbation series is discussed. Explicit derivations of the Lipatov asymptotic forms are presented for some basic problems in theoretical physics. A solution is proposed to the problem of renormalon contributions, which hampered progress in this field in the late 1970s. Practical schemes for summation of perturbation series are described for a coupling constant of order unity and in the strong-coupling limit. An interpretation of the Borel integral is given for 'non-Borel-summable' series. High-order corrections to the Lipatov asymptotics are discussed.Comment: Review article, 45 pages, PD