FARM SIZE AND THE DETERMINANTS OF PRODUCTIVE EFFICIENCY IN THE BRAZILIAN CENTER-WEST

This paper explores the determinants of technical efficiency, and the relationship between farm size and efficiency, in the Center-West of Brazil. This is the region where agricultural production and total factor productivity have grown the fastest since 1970. It is also a region characterized by unusually large farms. Technical efficiency is studied with Data Envelopment Analysis and county level data disaggregated by farm size and type of land tenure. The efficiency measure is regressed on a set of explanatory variables which includes farm size, type of land tenure, composition of output, access to institutions, and indicators of technology and input usage. The relationship between farm size and efficiency is found to be non-linear, with productivity first falling and then rising with size. Access to institutions, credit, and modern inputs are found to be important determinants of the differences in efficiency across farms. Improved access could strengthen the efficiency advantage of small and medium farms.Industrial Organization, Productivity Analysis,

Interfaces between highly incompatible polymers of different stiffness: Monte Carlo simulations and self-consistent field calculations

We investigate interfacial properties between two highly incompatible polymers of different stiffness. The extensive Monte Carlo simulations of the binary polymer melt yield detailed interfacial profiles and the interfacial tension via an analysis of capillary fluctuations. We extract an effective Flory-Huggins parameter from the simulations, which is used in self-consistent field calculations. These take due account of the chain architecture via a partial enumeration of the single chain partition function, using chain conformations obtained by Monte Carlo simulations of the pure phases. The agreement between the simulations and self-consistent field calculations is almost quantitative, however we find deviations from the predictions of the Gaussian chain model for high incompatibilities or large stiffness. The interfacial width at very high incompatibilities is smaller than the prediction of the Gaussian chain model, and decreases upon increasing the statistical segment length of the semi-flexible component.Comment: to appear in J.Chem.Phy

Locational Determinants of Rural Non-agricultural Employment: Evidence From Brazil

By paying particular attention to the local economic context, this paper analyzes the determinants of non-agricultural employment and earnings in non-agricultural jobs. The empirical analysis is based on the Brazilian Demographic Census, allowing for disaggregated controls for the local economy. Education stands out as one of the key determinants of employment outcome and earnings potential. Failure to control for locational effects, however, can lead to biased estimation of the importance of individual and household-specific characteristics. The empirical results show that local market size and distance to population centers have a significant impact on non-agricultural employment prospects and earnings.Rural non-agricultural employment, economic geography, Latin America, Brazil

A Direct Upper Limit on the Density of Cosmological Dust from the Absence of an X-ray Scattering Halo around the z=4.3 QSO 1508+5714

We report on the results of a search for an intergalactic X-ray dust scattering halo in a deep observation of the bright, high-redshift quasar QSO 1508+5714 with the Chandra X-ray Observatory. We do not detect such a halo. Our result implies an upper limit on the density of diffuse, large-grained intergalactic dust of Omega_ dust < 2 x 10^-6, assuming a characteristic grain size of 1micron. The result demonstrates the sensitivity of this technique for detecting very small amounts of intergalactic dust which are very hard to detect otherwise. This will allow us to put important constraints on systematic effects induced by extinction on the interpretation of the SN Ia Hubble Diagram, as well as on the amount and properties of cosmological dust being expelled into the intergalactic medium at early z~2 times.Comment: 14 pages, 2 figures. to appear in ApJ, vol. 651, Nov. 200