Stochastic volatility models and the Taylor effect

It has been often empirically observed that the sample autocorrelations of absolute financial returns are larger than those of squared returns. This property, know as Taylor effect, is analysed in this paper in the Stochastic Volatility (SV) model framework. We show that the stationary autoregressive SV model is able to generate this property for realistic parameter specifications. On the other hand, the Taylor effect is shown not to be a sampling phenomena due to estimation biases of the sample autocorrelations. Therefore, financial models that aims to explain the behaviour of financial returns should take account of this property

Trade and Private R&D in Mexico

Using the National Survey on Employment, Wages, Technology and Training (Enestyc), this paper tries to find the relationship between increasing trade and the proportion of total income Mexican manufacturing firms invest on R&D. Based on two cross-sectional and a panel estimation procedures, the results confirm the idea that increasing the exposure to foreign markets affect the innovative efforts of Mexican firms. We also find that the firms engaging in some kind of R&D do not conform a random sample. More specifically, our results show that, in 1992, the probability of finding a firm engaging resources in some kind of R&D increased with size, a market diversification measure, and a measure of industrial market power at a 2-digit level, while the intensity of the R&D effort depended, on market power and an industry concentration measure. For the 1999 estimation our results show that the probability of R&D investment at a firm level increased with size, a market diversification measure, and exposure to foreign competition, while the magnitude of the R&D effort of a firm was determined by the decrease in average import tariffs at the industry level and by the exporting efforts of the firm. We find strong complementarities between public and private innovation efforts in both years, but find that younger firms are doing stronger R&D efforts in 1999. The 1992- 99 balanced panel results show that exporting firms invest more in R&D while import competing firms invest less, once size, market power and other control variables are taken into account. Our estimation indicates that exporting give firms a great incentive to innovate, and that not only large, but also small firms contribute to the R&D efforts of a nation.R&D, trade liberalization, foreign direct investment, exposure to foreing markets

Prácticas, representaciones y experiencias: propuestas teórico-metodológicas en investigaciones socio-antropológicas sobre el cuerpo

Las diversas corrientes teóricas de la antropología del cuerpo conllevan propuestas metodológicas. Desde el llamado pionero de Marcel Mauss para investigar las técnicas corporales, se han desplegado diferentes temáticas de interés, enfoques teóricos y perspectivas metodológicas para el abordaje del cuerpo en contextos socio-culturales específicos. Se considerarán aquí distintos grupos de perspectivas teórico-metodológicas sobre el cuerpo, que se distinguen por centrar sus enfoques en distintas dimensiones: las representaciones, los discursos, las prácticas y las experiencias. Luego de plantear las implicancias metodológicas de las perspectivas revisadas, se intentarán buscar modos de integración entre ellas.The several theoretical approaches of anthropology of the body involve methodological proposals. From Marcel Mauss pioneering call to investigate body techniques, various topics of interest have been deployed, as well as theoretical and methodological approaches for addressing the body in specific sociocultural contexts. Considered here are different groups of theoretical and methodological proposals about the body, which are distinguished by their focus on distinct dimensions: representations, discourses, practices and experiences. After setting forth the methodological implications of the revised perspectives, will try to find ways of integration between them.Fil: Mora, Ana Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Humanidades y Ciencias Sociales. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales; Argentin

Development of new bioactive systems for regenerative medicine using 3D printing and microfluidic technologies

Regenerative medicine is an interdisciplinary field that combines different principles of engineering and life sciences to potentially promote the regeneration and healing of injured tissues. The use of biomaterials to replace damaged tissues or to contribute to their healing is an important component of current regenerative medicine strategies. Biomaterials are defined as any material intended to interface with biological systems to treat or replace any tissue, organ, or function in the body. They can be classified in metals, ceramics, polymers, and composites depending on chemical composition.Presidente: Belen Levenfeld Laredo - Secretaria: M. Dolores Gurruchaga Torrecilla - Vocal: Francisco M. Goycoole

Modeling an Aquifer: Numerical Solution to the Groundwater Flow Equation

We present a model of groundwater dynamics under stationary flow and governed by Darcy's Law of water motion through porous media, we apply it to study a 2D aquifer with water table of constant slope comprised of an homogeneous and isotropic media, the more realistic case of an homogeneous anisotropic soil is also considered. Taking into account some geophysical parameters we develop a computational routine, in the Finite Difference Method, that solves the resulting elliptic partial equation, both in a homogeneous isotropic and homogeneous anisotropic media. After calibration of the numerical model, this routine is used to begin a study of the Ayamonte-Huelva aquifer in Spain, a modest analysis of the system is given, we compute the average discharge vector as well as its root mean square as a first predictive approximation of the flux in this system, providing us a signal of the location of best exploitation; long term goal is to develop a complete computational tool for the analysis of groundwater dynamics.Comment: 13 pages and 12 figure

Embryo-maternal interactions leading to embryonic development and survival in the bovine : role of progesterone and prostaglandins

Tese de Doutoramento em Ciências Veterinárias. Especialidade de ClínicaThe objectives of this thesis were to evaluate steroidogenic and prostanoid embryo-maternal interactions leading to embryonic development and survival in cattle, and to evaluate therapeutic strategies at embryo transfer (ET) designed to enhance embryo survival. In vitro experiments (three experimental chapters) - bovine early (Day 7) embryos i) had transcription of genes coding for enzymes progesterone (P4) and of prostaglandins (PGs) synthesis pathways (StAR, P450scc,3β-HSD, PTGS2, PGFS, PGES); ii) produced these mediators (P4, PGF2α, PGE2) into culture medium; iii) had a significant increase in transcription levels of the above genes (except StAR) associated to first embryonic cellular differentiation; iv) derived from pre-pubertal oocyte donors had transcription levels of the above genes similar to those of embryos derived from post-pubertal cyclic heifers (except for 3β-HSD, which tended to be higher in embryos from cyclic heifers). Additionally, v) in a developed luteal cells (LC) co-culture model, LC induced an embryotrophic effect, significantly increasing blastocyst yield and quality; however, this embryotrophic effect was not associated with an increase in embryonic gene transcription or production of P4, PGF2α, PGE2; vi) Embryos co-cultured with LC did not exert a luteotrophic effect upon the cells; and vii) oil overlaying of culture wells exerted an embryotrophic effect, but absorbed P4 from culture medium. In vivo experiments (two experimental chapters) - novel in-vivo models considering poor developmental competence embryos (demi-embryos) and either sub-normal fertility recipients (lactating high-yielding dairy cow) or high fertility recipients (virgin dairy heifers) were used to evaluate the effect of hCG and carprofen treatment at embryo transfer on embryo survival and on plasma P4 and PSPB concentrations of recipients. Conclusions were that: i) treatment with hCG induced formation of secondary CL, increased plasma P4 concentrations, survival rate of demi-embryos and pregnancy rate of recipients (only in cows). Embryos were rescued beyond maternal recognition of pregnancy (MPR), but later embryonic survival, growth until implantation and placental PSPB secretion until Day 63 of pregnancy (only tested in cows) were not affected; ii) embryonic survival following MRP is not under direct dependency of maternal P4 concentrations; iii) treatment with carprofen had no significant effect on plasma P4 concentrations and embryonic survival, but decreased the luteotrophic effect of hCG.RESUMO - Interações embrio-maternas relevantes para o desenvolvimento e sobrevivência embrionários em bovinos – papel da progesterona e das prostaglandinas - Os objetivos desta tese foram: avaliar interações embrio-maternas esteroidogénicas e prostanoides no desenvolvimento e sobrevivência embrionárias; testar estratégias terapêuticas na transferência embrionária (TE) com vista ao aumento da sobrevivência embrionária. Experiências in vitro (três capítulos experimentais) – embriões bovinos (Dia 7): i) revelaram transcrição de genes codificantes das enzimas das vias sintéticas da progesterona (P4) e PGs (PTGS2, PGFS, PGES, StAR, P450scc,3β-HSD); ii) produziram estes mediadores (P4, PGF2α, PGE2) para o meio de cultura; iii) apresentaram um aumento significativo dos níveis de transcrição destes genes (à exceção da StAR) associado à primeira diferenciação celular embrionária; iv) derivados de dadoras de oócitos pré-púberes revelaram níveis de transcrição dos genes mencionados similares aos de embriões de dadoras cíclicas (à exceção dos níveis de transcrição para a 3β-HSD, tendencialmente mais elevados em embriões provenientes de fêmeas cíclicas). Adicionalmente, v) num modelo de co-cultura de células lúteas desenvolvido, estas exerceram um efeito embriotrófico, aumentando significativamente a taxa de desenvolvimento e qualidade embrionárias; porém, este efeito não foi associado a aumento na transcrição génica ou produção de P4, PGF2α, PGE2; vi) Embriões em co-cultura com células lúteas não exerceram um efeito luteotrófico nas células; e vii) o uso de óleo mineral na cobertura dos poços de cultura exerceu um efeito embriotrófico, mas absorveu P4 do meio. Experiências in vivo (dois capítulos experimentais) – novos modelos in vivo - embriões de baixa competência de desenvolvimento (hemi-embriões) e recetoras sub-férteis (vacas leiteiras de alta produção) ou com fertilidade alta (novilhas leiteiras virgens) - foram usados na avaliação do efeito na sobrevivência embrionária e nas concentrações plasmáticas de P4 e PSPB das recetoras, de tratamentos, na TE, com hCG ou carprofen. Concluiu-se que: i) o tratamento com hCG induziu a formação de CLs secundários, aumentou as concentrações plasmáticas de P4, a taxa de sobrevivência dos hemi-embriões e as taxas de gestação das recetoras (em vacas). Os embriões foram resgatados para além do reconhecimento materno da gestação (RMG), mas a sobrevivência embrionária posterior, o crescimento até à implantação e a secreção placentária de PSPB até ao Dia 63 de gestação (testados em vacas) não foram afetados; ii) a sobrevivência embrionária após o RMG não está diretamente dependente das concentrações de P4 maternas; iii) o tratamento com o carprofeno não afetou significativamente as concentrações de P4 ou a sobrevivência embrionária, mas diminuiu o efeito luteotrófico da hCG