Life Cycle of Products and Cycles

The aim of this paper is to examine whether the development of waste recycling activities can be a source of economic fluctuation. We assume that the recycling sector has four fundamental characteristics. (i) The production factors are restricted by the production of the last period. (ii) These production factors are waste for which the price determination is non-competitive. (iii) It produces a recycled good, which is a perfect substitute to th primary good. (iv) It reduces waste stream. We consider the simplest economy with an infinitely lived agent and a life cycle hypothesis for the goods. We show that the equilibrium is unique and is always determinate. In spite of the lack of indeterminacy, however, our system can display cyclical behavior, depending on some usual conditions on parameters. Namely, the steady-state may undergo a Flip and a Hopf bifurcation.Cycles, recycling, waste.

Osteopenia da prematuridade

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2019A osteopenia é uma das comorbilidades inerentes à prematuridade, consistindo na diminuição da massa óssea total associada a disrupção do metabolismo mineral. Surge frequentemente 6 a 16 semanas após o nascimento e permanece assintomática na grande maioria dos casos. Existem múltiplos fatores que aumentam o risco de desenvolver esta doença, como por exemplo insuficiência placentária, diminuição da idade gestacional e do peso à nascença, restrição de fluidos, imobilização e certos fármacos. No entanto, o principal fator etiológico são as reservas ósseas reduzidas de fósforo e/ou cálcio. Apesar de não haver normas de orientação clínica universais relativamente ao diagnóstico, este baseia-se atualmente na evidência bioquímica de hipofosfatémia e hiperfosfatásia e evidência radiológica de osteopenia e/ou fratura. Poderíamos optar por um algoritmo diagnóstico mais complexo e abrangente, tendo também em consideração características clínicas e hormonais e outros parâmetros bioquímicos e ferramentas imagiológicas. Esta é uma doença autolimitada, mas com consequências a curto e a longo prazo que devem ser evitadas. Para tal, é essencial a prevenção, proporcionando o aporte de cálcio, fósforo e vitamina D adequado para promover o crescimento ósseo normal, preferivelmente por via entérica através de fórmulas pré-termo ou leite humano fortificado. A estratégia de tratamento é semelhante.Osteopenia is one of the inherent comorbidities of prematurity, consisting of a decrease in the total bone mass associated with the disruption of mineral metabolism. It often appears 6 to 16 weeks after birth and remains asymptomatic in the vast majority of the cases. There are multiple factors that increase the risk of developing this disease, such as placental insufficiency, reduction in gestational period, very low birth weight, fluid restriction, immobilization and certain drugs. However, the main etiological factor are the reduced bone stores of phosphorus and/or calcium. Although there are no universal guidelines for diagnosis, this is currently based on biochemical evidence of hypophosphatemia and hyperphosphatasia and radiological evidence of osteopenia and/or fracture. We could opt for a more complex and overarching diagnostic algorithm, also considering the clinical and hormonal characteristics and other biochemical parameters and imaging tools. This is a self-limiting disease, but with short- and long-term consequences that must be avoided. To this end, prevention is essential, providing adequate calcium, phosphorus and vitamin D supply to promote normal bone growth, preferably enterally using preterm formulas or fortified human milk. The treatment strategy is similar

A Stability Study of some Mixed Finite Elements for Large Deformation Elasticity Problems

We consider the finite elasticity problem for incompressible materials, proposing a simple bidimensional problem for which we provide an indication on the solution stability. Furthermore, we study the stability of discrete solutions, obtained by means of some well-known mixed finite elements, and we present several numerical experiments

Numerical analysis of a locking-free mixed finite element method for a bending moment formulation of Reissner-Mindlin plate model

This article deals with the approximation of the bending of a clamped plate, modeled by Reissner-Mindlin equations. It is known that standard finite element methods applied to this model lead to wrong results when the thickness t is small. Here, we propose a mixed formulation based on the Hellinger-Reissner principle which is written in terms of the bending moments, the shear stress, the rotations and the transverse displacement. To prove that the resulting variational formulation is well posed, we use the Babu\u161ka-Brezzi theory with appropriate t -dependent norms. The problem is discretized by standard mixed finite elements without the need of any reduction operator. Error estimates are proved. These estimates have an optimal dependence on the mesh size h and a mild dependence on the plate thickness t. This allows us to conclude that the method is locking-free. The proposed method yields direct approximation of the bending moments and the shear stress. A local postprocessing leading to H1 -type approximations of transverse displacement and rotations is introduced. Moreover, we propose a hybridization procedure, which leads to solving a significantly smaller positive definite system. Finally, we report numerical experiments which allow us to assess the performance of the method

Adaptive selection of primal constraints for isogeometric BDDC deluxe preconditioners

Isogeometric analysis has been introduced as an alternative to finite element methods in order to simplify the integration of computer-aided design (CAD) software and the discretization of variational problems of continuum mechanics. In contrast with the finite element case, the basis functions of isogeometric analysis are often not nodal. As a consequence, there are fat interfaces which can easily lead to an increase in the number of interface variables after a decomposition of the parameter space into subdomains. Building on earlier work on the deluxe version of the BDDC (balancing domain decomposition by constraints) family of domain decomposition algorithms, several adaptive algorithms are developed in this paper for scalar elliptic problems in an effort to decrease the dimension of the global, coarse component of these preconditioners. Numerical experiments provide evidence that this work can be successful, yielding scalable and quasi-optimal adaptive BDDC algorithms for isogeometric discretizations

The subpopulation pattern of eel sperm is affected by post-activation time, hormonal treatment and thermal regime

[EN] There has been a marked reduction in natural stocks of eels (genus Anguilla) over the past 60 years, and the culture of eels is still based on the capture of very large quantities of juveniles. It is necessary to close the life cycle in captivity in order to ease the pressure on wild populations. The aims of the present study were to evaluate sperm subpopulations (through cluster analysis of computer-aided sperm analysis data) in the European eel (Anguilla anguilla) and to assess the effects of motility acquisition time after activation (i.e. at 30, 60 and 90 s), the thermal regimen (i.e. 10 degrees C (T10) or 15 degrees C (T15) and up to 20 degrees C, or constant at 20 degrees C (T20)) and hormonal treatments (i.e. human chorionic gonadotropin (hCG), recombinant (r) hCG or pregnant mare serum gonadotropin (PMSG)) on these subpopulations. In all cases, we obtained three subpopulations of spermatozoa: low velocity and linear (S1); high velocity with low linearity (S2); and high velocity and linear (S3; considered high quality). Total motility and S1 were affected by acquisition time; thus, 30 s is recommended as the standard time for motility acquisition. When eels were kept at 20 degrees C (T20), motility data fitted quadratic models, with the highest motility and proportion of S3 between Weeks 8 and 12 after the first injection. Lower temperatures (T10, T15) delayed spermiation and the obtaining of high-quality spermatozoa (S3), but did not seem to alter the spermiation process (similar subpopulation pattern). Conversely, the hormonal treatments altered both the dynamics of the subpopulation pattern and the onset of spermiation (with PMSG delaying it). Total motility and the yield of S3 with the widely used hCG treatment varied throughout the spermiation period. However, using rhCG allowed us to obtain high-quality and constant motility for most of the study (Weeks 7-20), and the S3 yield was also higher overall (61.8 +/- 1.3%; mean +/- s.e.m.) and more stable over time than the other hormonal treatments (averaging 53.0 +/- 1.4%). Using T20 and rhCG would be more economical and practical, allowing us to obtain a higher number of S3 spermatozoa over an extended time.This study was funded by the European Community's 7th Framework Program under the Theme 2 'Food, Agriculture and Fisheries, and Bio-technology', grant agreement no. 245257 (PRO-EEL) and Generalitat Valenciana (ACOMP/2012/086). VG and MCV have predoctoral grants from the Spanish Ministry of Economy and Competitiveness (AGL2010-16009) and Universitat Politecnica de Valencia (UPV) PAID Program (2011-S2-02-6521), respectively. DSP was supported by a contract cofinanced by Ministry of Science and Innovation (MICINN) and UPV (PTA2011-4948-I). FM-P was supported by the Ramon y Cajal program (MICINN, RYC-2008-02560).Gallego Albiach, V.; Vilchez Olivencia, MC.; Peñaranda, D.; Pérez Igualada, LM.; Herraez, MP.; Asturiano Nemesio, JF.; Martinez-Pastor, F. (2015). The subpopulation pattern of eel sperm is affected by post-activation time, hormonal treatment and thermal regime. Reproduction, Fertility and Development. 27(3):529-543. https://doi.org/10.1071/RD13198S52954327