Barro's fertility equations: the robustness of the role of female education and income

Barro and Lee (1994) and Barro and Sala-i-Martin (1995) find that real per-capita GDP and both male and female education have important effects on fertility in their cross-country empirical studies. In order to assess the robustness of their results, their estimated models are subjected to specification and diagnostic testing, the effects on the model of using the improved Barro and Lee (1996) cross-country data on educational attainment of the population aged 15 and over are examined, and the different specifications used by Barro and Lee and by Barro and Sala-i-Martin compared. The results obtained suggest that their fertility equations do not perform well in terms of diagnostic testing, and are very sensitive to the use of different vintages of the educational attainment proxies and of the Summers-Heston cross-country income data. A robust explanation of fertility, to link with empirical growth equations, has, therefore, not yet been found; further work is required in this area

Time-Separable Preference and Intertemporal-Substitution Models of Business Cycles

Time-separability of utility means that past work and consumption do not influence current and future tastes. This form of preferences does not restrict the size of intertemporal-substitution effects--notably, we can still have a strong response of labor supply to temporary changes in wages. However, there are important constraints on the relative responses of leisure and consumption to changes in relative-price and in permanent income. When the usual aggregation is permissible, time-separability has some important implications for equilibrium theories of the business cycle. Neglecting investment, we, find that changes in perceptions about the future -- which night appear currently as income effects -- have no influence on current equilibrium output. With investment included, no combination of income effects and shifts to the perceived profitability of investment will yield positive co-movements of output, employment, investment and consumption. Therefore, misperceived monetary disturbances or other sources of changed beliefs about the future cannot be used to generate empirically recognizable business cycles. Some richer specifications of intertemporal production opportunities may eventually yield more satisfactory answers. Because of the positive correlation between cyclical movements of consumption and work, equilibrium theories with time-separable preferences inevitably predict a procyclical behavior for the real wage rate, arising from shifts to labor's marginal product. Empirically, we regard the cyclical behavior of real wages as an open question. Aside from analyzing autonomous real shocks to productivity, we suggest that such shifts may occur as firms vary their capital utilization in response to intertemporal relative prices. However, we still lack some parts of a complete theory.

Confronting quintessence models with recent high-redshift supernovae data

We confront the predictions of different quintessence models with recent measurements of the luminosity distance from two sets of supernovae type Ia. In particular, we consider the 157 SNe Ia in the Gold dataset with z < 1.7, and the more recent data containing 71 supernovae obtained by the Supernova Legacy Survey (SNLS) with z < 1. We numerically solve the evolution equations for the Ratra-Peebles inverse power-law model, the double exponential and the hyperbolic cosine quintessence models. We obtain confidence regions from the two datasets in the Omega(M)-alpha and Omega(M)-w(phi) planes for the different models and compare their predictions with dark energy models with constant equation of state

A stochastic programming model for dynamic portfolio management with financial derivatives

Stochastic optimization models have been extensively applied to financial portfolios and have proven their effectiveness in asset and asset-liability management. Occasionally, however, they have been applied to dynamic portfolio problems including not only assets traded in secondary markets but also derivative contracts such as options or futures with their dedicated payoff functions. Such extension allows the construction of asymmetric payoffs for hedging or speculative purposes but also leads to several mathematical issues. Derivatives-based nonlinear portfolios in a discrete multistage stochastic programming (MSP) framework can be potentially very beneficial to shape dynamically a portfolio return distribution and attain superior performance. In this article we present a portfolio model with equity options, which extends significantly previous efforts in this area, and analyse the potential of such extension from a modeling and methodological viewpoints. We consider an asset universe and model portfolio set-up including equity, bonds, money market, a volatility-based exchange-traded-fund (ETF) and over-the-counter (OTC) option contracts on the equity. Relying on this market structure we formulate and analyse, to the best of our knowledge, for the first time, a comprehensive set of optimal option strategies in a discrete framework, including canonical protective puts, covered calls and straddles, as well as more advanced combined strategies based on equity options and the volatility index. The problem formulation relies on a data-driven scenario generation method for asset returns and option prices consistent with arbitrage-free conditions and incomplete market assumptions. The joint inclusion of option contracts and the VIX as asset class in a dynamic portfolio problem extends previous efforts in the domain of volatility-driven optimal policies. By introducing an optimal trade-off problem based on expected wealth and Conditional Value-at-Risk (CVaR), we formulate the problem as a stochastic linear program and present an extended set of numerical results across different market phases, to discuss the interplay among asset classes and options, relevant to financial engineers and fund managers. We find that options’ portfolios and trading in options strengthen an effective tail risk control, and help shaping portfolios returns’ distributions, consistently with an investor's risk attitude. Furthermore the introduction of a volatility index in the asset universe, jointly with equity options, leads to superior risk-adjusted returns, both in- and out-of-sample, as shown in the final case-study

A 3D model for thickness and diffusion capacitance of emitter-base junction in a bifacial polycrystalline solar cell

Through this paper, we present n+-p-p+ solar cell. Mathematical relations describing the generated carriers&#8217; density are expressed, using among others a new approach involving both junction and back surface recombination velocities in a 3D modelling study.Based on the normalized carriers&#8217; density versus the base depth and operating an open circuit voltage, we study the space-charge layer thickness (Z) versus various parameters such as the grain size (g) and the grain boundaries recombination velocity (Sgb). Hence, the relationship between Z and the diffusion capacitance show that junction in the n+-p-p+ solar cell, when the columnar orientation is considered, is characterized by the plane capacitor properties

Evolution of the anti-truncated stellar profiles of S0 galaxies since z=0.6z=0.6 in the SHARDS survey: I - Sample and Methods

The controversy about the origin of the structure of S0--E/S0 galaxies may be due to the difficulty of comparing surface brightness profiles with different depths, photometric corrections and PSF effects (almost always ignored). We aim to quantify the properties of Type-III (anti-truncated) discs in a sample of S0 galaxies at 0.2<z<0.6. In this paper, we present the sample selection and describe in detail the methods to robustly trace the structure in their outskirts and correct for PSF effects. We have selected and classified a sample of 150 quiescent galaxies at 0.2<z<0.6 in the GOODS-N field. We perform a quantitative structural analysis of 44 S0-E/S0 galaxies. We corrected their surface brightness profiles for PSF distortions and analysed the biases in the structural and photometric parameters when the PSF correction is not applied. Additionally, we have developed Elbow, an automatic statistical method to determine whether a possible break is significant - or not - and its type and made it publicly available. We found 14 anti-truncated S0-E/S0 galaxies in the range 0.2<z<0.6 (~30% of the final sample). This fraction is similar to the those reported in the local Universe. In our sample, ~25% of the Type-III breaks observed in PSF-uncorrected profiles are artifacts, and their profiles turn into a Type I after PSF correction. PSF effects also soften Type-II profiles. We found that the profiles of Type-I S0 and E/S0 galaxies of our sample are compatible with the inner profiles of the Type-III, in contrast with the outer profiles. We have obtained the first robust and reliable sample of 14 anti-truncated S0--E/S0 galaxies beyond the local Universe, in the range 0.2<z<0.6. PSF effects significantly affect the shape of the surface brightness profiles in galaxy discs even in the case of the narrow PSF of HST/ACS images, so future studies on the subject should make an effort to correct them.Comment: Accepted for publishing in Astronomy & Astrophysics. 75 pages, 57 figure

La production de sorgho dans un parc à Piliostigma reticulatum en zone nord-soudanienne du Burkina Faso

Sorghum production in a Piliostigma reticulatum Park in the North Sudanian Zone of Burkina Faso. En zone sahélo-soudanienne, les systèmes de production sont des associations cultures-ligneux. Les ligneux sélectionnés sont des espèces fruitières et/ou à rôle écologique prouvé. Face à l'aridification climatique, les populations adoptent de plus en plus l'espèce Piliostigma reticulatum. De manière à quantifier l'impact de cette espèce sur la production du sorgho, principale culture de la région, quinze pieds de Piliostigma reticulatum, âgés de 7 ans ont été suivis en association avec le sorgho blanc, pendant trois ans. Les paramètres suivis sont: la croissance et les composantes du rendement. Des échantillons de sol ont été prélevés pour déterminer les effets de l'espèce sur les propriétés du sol. Les trois traitements comparés étaient: culture sous houppier, culture à la limite du houppier et culture hors houppiers. Sous le houppier de Piliostigma reticulatum, le statut du carbone organique est amélioré de 67 % dans l'horizon 0-10 cm et de 46% dans l'horizon 10-20 cm. Le taux d'azote total est amélioré de 62% dans l'horizon 0-10 cm. En outre, le rapport C/N présente des valeurs relativement faibles. A 30 jour après le semis, on constate une meilleure croissance du sorgho sous houppier par rapport aux placettes hors houppier. Cependant, selon les années, la meilleure croissance initiale sous houppier ne se traduit pas nécessairement par des gains de production en paille et en grains du sorgho par rapport aux autres placettes. Des investigations complémentaires sont nécessaires pour expliquer ces observations et évaluer l'intérêt de cette association pour les agriculteurs

3C a multi-wavelength database for the future GTC cosmological surveys

The 3C Database aims to provide complete multi-wavelength information over different cosmological fields, such as GOODS, Groth or Sa68 allowing detailed studies on wide samples of galaxies