Definição de shelf life para produtos químicos: a importância de um guia de estabilidade específico para o segmento

The chemical industries worldwide are passing through a very particular moment of re-adaptation due to the implementation of an European regulation called, Registration, Evaluation, Authorization and Restriction of Chemicals (REACH). In Brazil, the Brazilian Chemical Industry needs urgently a specific guide of chemical products stability. The main purpose of this work is to present a proposal of a guide of stability for chemical products based on the reference guides of the International Conference on Harmonization (ICH). Thus, this work proposes an innovation in terms of methodology which will be useful for shelf life definition purpose for chemical industry products.

UNA PROPUESTA PARA ENSEÑAR EL EFECTO DE LA FORMA DE LAS MOLÉCULAS EN LA REACTIVIDAD QUÍMICA

We address the concept of steric effect in the pursuit of establishing quantitative correlations between reactivity of molecules and their molecular shape. To this end, a set of series of SN2 reactions were modeled to compute the energy barrier height and the molecular volume, atomic charges and dipole moment of molecules. We introduced the Kappa index to characterize the shape of molecules. Quantitative correlations between the change in the energy barrier with properties of molecules and Kappa index were presented and discussed.

An Inspection System to Identify Fatigue Damage on Steel-Bridge Structures

Crack formation and growth in steel bridge structural elements may be due to loading oscillations. The welded elements are liable to internal discontinuities along welded joints and sensible to stress variations. The evaluation of the remaining life of a bridge is needed to make cost-effective decisions regarding inspection, repair, rehabilitation, and replacement. A steel beam model has been proposed to simulate crack openings due to cyclic loads. Two possible alternatives have been considered to model crack propagation, which the initial phase is based on the linear fracture mechanics. Then, the model is extended to take into account the elastoplastic fracture mechanic concepts. The natural frequency changes are directly related to moment of inertia variation and consequently to a reduction in the flexural stiffness of a steel beam. Thus, it is possible to adopt a nondestructive technique during steel bridge inspection to quantify the structure eigenvalue variation that will be used to localize the grown fracture. A damage detection algorithm is developed for the proposed model and the numerical results are compared with the solutions achieved by using another well know computer code.

Modelos de crescimento kaleckianos: uma apreciação

The purpose of this article is to survey the main papers that founded a kaleckian approach of the economic growth. It presents a certain moment of the historical evolution of the non-neoclassical macrodynamics. This analysis can be understood under the political economy tradition in putting together social classes (capitalists and workers), distributive conflict and the relationship between distribution and accumulation.

Heidegger and Blumenberg on modernity

The debate surrounding the way in which Heidegger and Blumenberg understand the modern age is an opportunity to discuss two different approaches to history. On one hand, from Heidegger's perspective, history should be understood as starting from how Western thought related to Being, which, in metaphysical thinking, took the form of the forgetfulness of Being. Thus, the modern age represents the last stage in the process of forgetfulness of Being, which announces the moment of the rethinking of the relationship with Being by appealing to the authentic disclosure of Being. On the other hand, Blumenberg understands history as the result of the reoccupation process, which means replacing old theories with other new ones. Thus, to the historical approach it is not important to identify epochs as periods of time between two events, but to think about the discontinuities occurring throughout history. Starting from here, the modern age will be thought of not as an expression of the radicalization of the forgetfulness of Being, but as a response to the crises of medieval conceptions. For the same reason, the interpretation of history as a history of the forgetfulness of Being is considered by Blumenberg to subordinate history to an absolute principle, without taking into account its protagonists' needs and necessities.