How sensitive are Latin American exports to Chinese competition in the U.S. market ?

This paper estimates the elasticity of substitution of U.S. imports using detailed trade data over the 1990-2003 period. The authors use a two-stage least squares framework in order to identify the elasticity parameter of interest. The authors use the elasticity estimates to assess the extent to which Latin American and Chinese goods compete in the U.S. market by providing forecasts of how alternative policy scenarios may affect exports to the United States. The analysis considers the following scenarios: (i) currency revaluation in China; (ii) elimination of U.S. tariffs on Latin American exports under a hemispheric free trade agreement; and (iii) the elimination of quotas on apparel and textile exports under the Multi-Fiber Agreement. The findings show that a 20-percent appreciation of the renminbi reduces Chinese exports to the United States by a fifth, although since other regions increase sales to that market (0.5 percent for Latin America), U.S. imports decline by only 1.7 percent. Hemispheric free trade would increase Latin America's exports to the United States by around 3 percent. The removal of the quotas would lead to a sharp increase in Chinese sales to the United States (40 percent), but Latin America would see its share of the U.S. market decline by around 2 percent (2.5 percentage points). China's gains would come mainly at the expense of other regions of the world.Economic Theory&Research,Free Trade,Markets and Market Access,Trade Policy,Debt Markets

Natural Resource Dependence in Rural Mexico

The relationship between poverty and natural resources is complex and the empirical evidence to date, mostly from studies of forest activities and poverty, is inconclusive. The main purpose of this paper is to empirically identify the effects of household characteristics and of inequality at the village level on natural resource extraction and dependence. To do so we use data from the Mexico National Rural Household Survey (ENHRUM). Our results show that in rural Mexico natural resource extraction is predominantly an activity carried out by poor households. The same is true for dependence. We also show that there are important differences across Mexico in terms of both participation and dependence on resource income. These differences are most evident when one compares the south and north of the country. We also show that when relatively rich households participate in resource extraction their natural resource income is considerably higher than that of the poor.Resource extraction, Dependence, Poverty, Mexico, Community/Rural/Urban Development, Environmental Economics and Policy, International Development,

Machine learning for many-body physics: The case of the Anderson impurity model

Machine learning methods are applied to finding the Green's function of the Anderson impurity model, a basic model system of quantum many-body condensed-matter physics. Different methods of parametrizing the Green's function are investigated; a representation in terms of Legendre polynomials is found to be superior due to its limited number of coefficients and its applicability to state of the art methods of solution. The dependence of the errors on the size of the training set is determined. The results indicate that a machine learning approach to dynamical mean-field theory may be feasible.Comment: 18 pages, 11 figures. Sections II. A and B have been modified and an appendix was adde

Multiple Contiguous-Level Cervical Disc Arthroplasties: Unique Considerations

Arthroplasty is an established treatment for single and multiple level cervical disc disease. Multiple contiguous arthroplasties introduce unique changes in spinal kinematics that warrant study independent of single-level surgery. The literature regarding the biomechanics, indications, outcomes and complications specific to multiple level arthroplasties was reviewed. Appropriate application of this technology has been shown to be a safe and potentially advantageous alternative to arthrodesis

Immune drug discovery from venoms

This review catalogues recent advances in knowledge on venoms as standalone therapeutic agents or as blueprints for drug design, with an emphasis on venom-derived compounds that affects the immune system. We discuss venoms and venom-derived compounds that affect total immune cell numbers, immune cell proliferation, immune cell migration, immune cell phenotype and cytokine secretion. Identifying novel compounds that 'tune' the system, up-regulating the immune response during infectious disease and cancer and down-regulating the immune response during autoimmunity, will greatly expand the tool kit of human immunotherapeutics. Targeting these pathways may also open therapeutic options that alleviate symptoms of envenomation. Finally, combining recent advances in venomics with progress in low cost, high-throughput screening platforms will no doubt yield hundreds of prototype immune modulating compounds in the coming years

Proper Motions of the Jets in the Region of HH 30 and HL/XZ Tau. Evidence for a Binary Exciting Source of the HH 30 Jet

We present [SII] images of the HH 30 and HL/XZ Tau region obtained at two epochs, as well as long-slit optical spectroscopy of the HH 30 jet. We measured proper motions of about 100-300 km/s for the HH 30 jet and counterjet, and of about 120 km/s for the HL Tau jet. Inclination angles with respect to the plane of the sky are 0-40 deg for the HH 30 jet and 60 deg for the HL Tau jet. Comparison with previous observations suggests that most of the jet knots consist of persisting structures. Also, we corroborate that the HH 30-N knots correspond to the head of the HH 30 jet. The overall HH 30 jet structure can be well described by a wiggling ballistic jet, arising either by the orbital motion of the jet source around a primary or by precession of the jet axis because of the tidal effects of a companion. In the first scenario, the orbital period would be 53 yr and the total mass 0.25-2 solar masses. In the precession scenario, the mass of the jet source would be 0.1-1 solar masses, the orbital period <1 yr, and the mass of the companion less than a few times 0.01 solar masses, thus being a substellar object or a giant exoplanet. In both scenarios a binary system with a separation <18 AU (<0.13 arcsec) is required. Since the radius of the flared disk observed with the HST is about 250 AU, we conclude that this disk appears to be circumbinary rather than circumstellar, suggesting that the search for the collimating agent of the HH 30 jet should be carried out at much smaller scales.Comment: 42 pages, 7 figures, 5 tables. To Appear in The Astronomical Journal, Vol. 133 No. 6 (June 2007

Range Spectral Filtering in SAR Interferometry: Methods and Limitations

A geometrical decorrelation constitutes one of the sources of noise present in Synthetic Aperture Radar (SAR) interferograms. It comes from the different incidence angles of the two images used to form the interferograms, which cause a spectral (frequency) shift between them. A geometrical decorrelation must be compensated by a specific filtering technique known as range filtering, the goal of which is to estimate this spectral displacement and retain only the common parts of the images’ spectra, reducing the noise and improving the quality of the interferograms. Multiple range filters have been proposed in the literature. The most widely used methods are an adaptive filter approach, which estimates the spectral shift directly from the data; a method based on orbital information, which assumes a constant-slope (or flat) terrain; and slope-adaptive algorithms, which consider both orbital information and auxiliary topographic data. Their advantages and limitations are analyzed in this manuscript and, additionally, a new, more refined approach is proposed. Its goal is to enhance the filtering process by automatically adapting the filter to all types of surface variations using a multi-scale strategy. A pair of RADARSAT-2 images that mapped the mountainous area around the Etna volcano (Italy) are used for the study. The results show that filtering accuracy is improved with the new method including the steepest areas and vegetation-covered regions in which the performance of the original methods is limited.This work was supported by the Spanish Ministry of Science and Innovation (State Agency of Research, AEI) and the European Funds for Regional Development (ERFD) under Projects PID2020-117303GB-C21 and PID2020-117303-C22

An Improved Phase Filter for Differential SAR Interferometry Based on an Iterative Method

Phase quality is a key element in the analysis of the deformation of the Earth's surface carried out with differential synthetic aperture radar interferometry. Various decorrelation sources may degrade the surface deformation estimates, and thus, phase filters are needed for this kind of application. The well-known Goldstein filter is the most widely used due to its simple implementation and computational efficiency. In the past years, improved filters have been proposed, which are based on this filter but introduce variations in the data processing. The effectiveness of these filters mostly depends on the size of the filtering window, the weight of the smoothed spectrum, and the kernel used to filter the spectrum. In this paper, we evaluate the performance of four of these filters and present a new method that outperforms all of them. The proposed filter is based on an iterative method in which the original phase is denoised progressively with adaptive filtering windows of different sizes. The effectiveness of the filter is controlled by the interferometric coherence, a direct indicator of the phase quality. Moreover, we introduce some modifications regarding the processing of the power spectrum. Specifically, we propose to smooth the original phase using a new filter which is based on a Chebyshev interpolation scheme. The performance of the new filter has been tested on both simulated and real interferograms, acquired by RADARSAT-2 and the Uninhabited Aerial Vehicle Synthetic Aperture Radar, which mapped two different geological events that caused surface deformation.This work was supported in part by the Spanish Ministry of Economy, Industry and Competitiveness, in part by the State Agency of Research (AEI), in part by the European Funds for Regional Development under Project TIN2014-55413-C2-2-P and Project TEC2017-85244-C2-1-P, in part by the U.K. Natural Environmental Research Council through the Looking Inside the Continents under Grant NE/K011006/1, in part by the Rapid deployment of a seismic array in Ecuador following the April 16th 2016 M7.8 Pedernales earthquake under Grant NE/P008828/1, and in part by the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics under Grant COMET, GA/13/M/031