ON ADAPTATION TO CLIMATE CHANGE AND RISK EXPOSURE IN THE NILE BASIN OF ETHIOPIA

This study investigates the impact of climate change adaptation on farm households’ downside risk exposure (e.g., risk of crop failure) in the Nile Basin of Ethiopia. The analysis relies on a moment-based specification of the stochastic production function. We estimate a simultaneous equations model with endogenous switching to account for the heterogeneity in the decision to adapt or not, and for unobservable characteristics of farmers and their farm. We find that (i) climate change adaptation reduces downside risk exposure, i.e., farm households that implemented climate change adaptation strategies get benefits in terms of a decrease in the risk of crop failure; (ii) farm households that did not adapt would benefit the most in terms of reduction in downside risk exposure from adaptation; and (iii) there are significant differences in downside risk exposure between farm households that did and those that did not adapt to climate change. The analysis also shows that the quasi-option value, that is the value of waiting to gather more information, plays a significant role in farm households’ decision to adapt to climate change. Farmers that are better informed may value less the option to wait to adapt, and so are more likely to adapt than other farmers.adaptation, climate change, endogenous switching, Ethiopia, risk exposure, stochastic production function, skewness, Resource /Energy Economics and Policy, Risk and Uncertainty, D80, Q18, Q54,

Impedance matching in photonic crystal microcavities for Second Harmonic Generation

By numerically integrating the three-dimensional Maxwell equations in the time domain with reference to a dispersive quadratically nonlinear material, we study second harmonic generation in planar photonic crystal microresonators. The proposed scheme allows efficient coupling of the pump radiation to the defect resonant mode. The out-coupled generated second harmonic is maximized by impedance matching the photonic crystal cavity to the output waveguide.Comment: 4 pages, 4 figures. To be published in Optics Letter

On Adaptation to Climate Change and Risk Exposure in the Nile Basin of Ethiopia

This study investigates the impact of climate change adaptation on farm households’ downside risk exposure (e.g., risk of crop failure) in the Nile Basin of Ethiopia. The analysis relies on a moment-based specification of the stochastic production function. We estimate a simultaneous equations model with endogenous switching to account for the heterogeneity in the decision to adapt or not, and for unobservable characteristics of farmers and their farm. We find that (i) climate change adaptation reduces downside risk exposure; farm households that implemented climate change adaptation strategies get benefits in terms of a decrease in the risk of crop failure; (ii) farm households that did not adapt would benefit the most in terms of reduction in downside risk exposure from adaptation; and (iii) there are significant differences in downside risk exposure between farm households that did and those that did not adapt to climate change. The analysis also shows that the quasi-option value, that is the value of waiting to gather more information, plays a significant role in farm households’ decision on whether to adapt to climate change. Farmers that are better informed may value less the option to wait to adapt, and so are more likely to adapt than other farmers.adaptation, climate change, endogenous switching, Ethiopia, risk exposure, stochastic production function, skewness

Gain assisted nanocomposite multilayers with near zero permittivity modulus at visible frequencies

We have fabricated a layered nano-composite by alternating metal and gain medium layers, the gain dielectric consisting of a polymer incorporating optically pumped dye molecules. Exploiting an improved version of the effective medium theory, we have chosen the layers thicknesses for achieving a very small value of the real part of the permittivity epsilon_\| (parallel to the layers plane) at a prescribed visible wavelength. From standard reflection-transmission experiments on the optically pumped sample we show that, at a visible wavelength, both the real and the imaginary parts of the permittivity epsilon_\ attain very small values and we measure | \epsilon_\| | = 0.04 at lambda = 604 nm, amounting to a 21.5-percent decrease of the minimum | \epsilon_\| | in the absence of optical pumping. Our investigation thus proves that a medium with a dielectric permittivity with very small modulus, a key condition which should provide efficient subwavelength optical steering, can be actually synthesized.Comment: Submitted for publication on Applied Physics Letter

Labour Market and Fiscal Policy

This paper investigates the dynamic impacts of rural road improvements on farm productivity and crop choices in Zambia’s Eastern Province. There are several channels through which the feeder road improvements impact on farmers. Our aim is to estimate whether the differential outcomes in the five treatment districts and three control districts generated by the expansion of market agricultural activities among small to medium scale farmers could be explained by rural road improvements that took place after the new Chiluba MMD government in 1995 had completed an IMF rights accumulation programme bringing the principal marketing agent system to an end. Our district-level empirical analysis is an extension to the Brambilla and Porto(2005, 2007) cross-provincial level approach which proposes a dynamic approach accounting for entry and exit into the agricultural cotton sector to avoid biases in the estimates of aggregate productivity, when measuring productivity in agriculture applied to a repeated cross-sections of farm-level data from the Zambian post-harvest survey (PHS). Despite the limitations of the PHS data covering the period from 1996/1997 to 2001/2002 when the Eastern Province Feeder Road Project (EPFRP) was being implemented. The identification strategy relies on differences-in-differences of outcomes (i.e., cotton productivity) approach across two phases (pre-treatment and post-treatment). We use maize productivity to difference out unobserved household and aggregate agricultural year effects. Through our descriptive analysis we do find that changes in land allocation and in yields to Eastern Province’s most important cash crop – cotton did occur at the district level. However, it is difficult to conclude that these changes are linked directly to the improved accessibility obtained from the implementation of the EPFRP based on our differences-in-differences estimator or our Tobit model.Impact evaluation, Cash crop choice; Cotton productivity; Africa; Zambia (Eastern Province).

Flexible metamaterials at visible wavelengths

We report on the fabrication and characterization of plasmonic structures on flexible substrates (Metaflex) and demonstrate the optical properties of a single layer of Metaflex. The layer exhibits a plasmonic resonance in the visible region around 620 nm. We show experimental and numerical results for both nano-antennas and fishnet geometries. We anticipate the use of Metaflex as a building block for flexible metamaterials in the visible range.Publisher PDFPeer reviewe