A four-body convex central configuration with perpendicular diagonals is necessarily a kite

This is a post-peer-review, pre-copyedit version of an article published in Qualitative Theory of Dynamical Systems. The final authenticated version is available online at: http://dx.doi.org/10.1007/s12346-017-0238-z.We prove that any four-body convex central configuration with perpendicular diagonals must be a kite configuration. The result extends to general power-law potential functions, including the planar four-vortex problem.Peer ReviewedPostprint (author's final draft

Classifying Four-Body Convex Central Configurations

We classify the full set of convex central configurations in the Newtonian four-body problem. Particular attention is given to configurations possessing some type of symmetry or defining geometric property. Special cases considered include kite, trapezoidal, co-circular, equidiagonal, orthodiagonal, and bisecting-diagonal configurations. Good coordinates for describing the set are established. We use them to prove that the set of four-body convex central configurations with positive masses is three-dimensional, a graph over a domain $D$ that is the union of elementary regions in $\mathbb{R}^{+^3}$.Comment: 28 pages, 14 figure

Payments for ecosystem services in the tropics: a closer look at effectiveness and equity

We undertake a review of academic literature that examines the effectiveness and equity-related performance of PES initiatives targeting biodiversity conservation in tropical and sub-tropical countries. We investigate the key features of such analyses as regards their analytical and methodological approach and we identify emerging lessons from PES practice, leading to a new suggested research agenda. Our results indicate that analyses of PES effectiveness have to date focused on either ecosystem service provision or habitat proxies, with only half of them making explicit assessment of additionality and most describing that payments have been beneficial for land cover and biodiversity. Studies evaluating the impact of PES on livelihoods suggest more negative outcomes, with an uneven treatment of the procedural and distributive considerations of scheme design and payment distribution, and a large heterogeneity of evaluative frameworks. We propose an agenda for future PES research based on the emerging interest in assessing environmental outcomes more rigorously and documenting social impacts in a more comparative and contextually situated form

Distinct positions underpin ecosystem services for poverty alleviation

AbstractAs the concept of ecosystem services is applied more widely in conservation, its users will encounter the issue of poverty alleviation. Policy initiatives involving ecosystem services are often marked by their use of win-win narratives that conceal the trade-offs they must entail. Modelling this paper on an earlier essay about conservation and poverty, we explore the different views that underlie apparent agreement. We identify five positions that reflect different mixes of concern for ecosystem condition, poverty and economic growth, and we suggest that acknowledging these helps to uncover the subjacent goals of policy interventions and the trade-offs they involve in practice. Recognizing their existence and foundations can ultimately support the emergence of more legitimate and robust policies.</jats:p

Payments for ecosystem services and the fatal attraction of win-win solutions

In this commentary we critically discuss the suitability of payments for ecosystem services and the most important challenges they face. While such instruments can play a role in improving environmental governance, we argue that over-reliance on payments as win-win solutions might lead to ineffective outcomes, similar to earlier experience with integrated conservation and development projects. Our objective is to raise awareness, particularly among policy makers and practitioners, about the limitations of such instruments and to encourage a dialogue about the policy contexts in which they might be appropriate. © 2013 Wiley Periodicals, Inc

Parallelizing irregular C codes assisted by interprocedural shape analysis

In the new multicore architecture arena, the problem of improving the performance of a code is more in the soft-ware side than in the hardware one. However, optimizing irregular dynamic data structure based codes for such ar-chitectures is not easy, either by hand or compiler assisted. Regarding this last approach, shape analysis is a static tech-nique that achieves abstraction of dynamic memory and can help to disambiguate, quite accurately, memory references in programs that create and traverse recursive data struc-tures. This kind of analysis has promising applicability for accurate data dependence tests in loops or recursive func-tions that traverse dynamic data structures. However, sup-port for interprocedural programs in shape analysis is still a challenge, especially in the presence of recursive func-tions. In this work we present a novel fully context-sensitive interprocedural shape analysis algorithm that supports re-cursion and can be used to uncover parallelism. Our ap-proach is based on three key ideas: i) intraprocedural sup-port based on “Coexistent Links Sets ” to precisely describe the memory configurations during the abstract interpreta-tion of the C code; ii) interprocedural support based on “Recursive Flow Links ” to trace the state of pointers in previous calls; and iii) annotations of the read/written heap locations during the program analysis. We present prelim-inary experiments that reveal that our technique compares favorably with related work, and obtains precise memory abstractions in a variety of recursive programs that create and manipulate dynamic data structures. We have also im-plemented a data dependence test over our interprocedural shape analysis. With this test we have obtained promis-ing results, automatically detecting parallelism in three C codes, which have been successfully parallelized

AISA Eagle II hyperspectral data for carbonate geological mapping in a vegetated high relief area: a geologically orientated atmospheric correction

[EN] Carbonated rocks are crucial targets for oil exploration, outcropping often in large areas with minimum spectral differences among geological units. The typical carbonate spectral absorptions in 2200 nm and 2300 nm, are excluded from the wavelength range of AISA Eagle II. AISA Eagle II hyperspectral data are processed in flight lines of 1024 swath pixels in the visible to near-infrared wavelength range (400 to 970 nm). The flight has a spatial resolution of 1 m and records a total of 128 channels with a spectral resolution of 4,8 nm. The area of study is a carbonate rocky mountain densely vegetated, covered by variably dense trees and bushes. Masking vegetation cover and shade effects is prior to any geological analysis using hyperspectral image processing. Carbonate units occur in mountain slopes, with small areas of ridges of rock outcrops and wide fans of loose material. The background soil of different geological units differ spectrally only by overall reflectance. Instead, limestone rocky outcrops display spectral responses with smooth typical iron oxide absorptions that distinguish them apart from loose boulders of limestone. Trying to enhance spectral differences in the visible wavelength range among carbonate geological units, an atmospheric correction using field spectra from geologically selected targets in a limestone quarry was performed. This way, it was possible to map apart lithologically similar detrital units dominated by carbonate in a river plain. The limy river bottom displays spectra with a straight line in the visible wavelength range due to abundant organic matter and small grain size. The spectra of the upper terraces record spectral absorption features related to iron oxide contents similar to the rock outcrops in ridges of mountains. The use of field spectra from geologically selected targets improves the mapping capability of hyperspectral imagery in areas with geological units with a homogeneous spectral response.[ES] Las calizas son rocas críticas en la exploración de petróleo. Desarrollan series estratigráficas a menudo espesas, que afloran con frecuencia en zonas extensas de la superficie terrestre. Estas formaciones litológicas predominantemente carbonatadas presentan diferencias espectrales mínimas entre sí, que permiten su diagnóstico por su respuesta espectral y su cartografía con imágenes. Las bandas de absorción espectral típicas de los carbonatos en 2200 nm y 2300 nm no forman parte del intervalo de longitudes de onda del espectrómetro AISA Eagle II (400 nm-970 nm), con una resolución espectral de 4,8 nm en 128 canales, y 1 m de resolución espacial en el vuelo de estudio. La zona de estudio se encuentra localizada en el Prepirineo español formando un relieve rocoso carbonatado con vegetación densa. El suelo de las distintas formaciones geológicas carbonatadas cartografiadas se distingue espectralmente sólo por su reflectancia global. Los afloramientos rocosos de calizas in situ presentan respuestas espectrales con absorciones típicas de óxidos de hierro. La expresión espectral de las formaciones calizas en las imágenes iniciales mostraban defectos sistemáticos. Para conseguir espectros geológicamente diagnosticables con espectrotecas de referencia, se ha ensayado una corrección atmosférica con espectros de campo tomados en una cantera de calizas, y en afloramientos rocosos de formaciones calcáreas seleccionados, con un espectrómetro de campo y laboratorio ASD Fieldspec 3. En las imágenes hiperespectrales así corregidas, se cartografían formaciones geológicas litológicamente similares correspondientes a la cuenca fluvial del río Noguera Ribagorzana, a su paso por Alfarrás (Lérida), en la que los sedimentos de la llanura aluvial con limos de materiales comparativamente más finos y materia orgánica, presentan espectros típicos con un trazo rectilíneo en el visible, que no aparecía en las imágenes anteriores a la corrección. El uso de espectros de campo seleccionados con criterios geológicos para la corrección atmosférica de imágenes hiperespectrales, mejora la capacidad de las imágenes para elaborar cartografías de formaciones litológicamente similares usando espectrotecas de referencia.El sensor AISA Eagle II fue cedido en préstamo por SPECIM al Institut Cartogràfic i Geològic de Catalunya (ICGC) para su prueba en vuelo y pre-tratamiento digital. Los estudios de interpretación geológica se han realizado en un convenio entre la Universidad de Barcelona y REPSOL Exploración para formación postdoctoral. Las bases para comenzar este trabajo surgieron durante la tesis doctoral de Buzzi (BES-2008-003648).Buzzi, J.; Costa, E.; Riaza, A.; Fernández, O.; García-Sellés, D.; Corbera, J. (2018). Cartografía de calizas con datos hiperespectrales AISA Eagle II en una zona montañosa con vegetación densa: cómo orientar geológicamente la corrección atmosférica. Revista de Teledetección. (51):125-133. https://doi.org/10.4995/raet.2018.8998SWORD12513351ASD. 2006. FieldSpecR 3 User Manual, ASD Document 600540 Rev. F. Analytical Spectral Devices, Inc. Disponible en: http://www.asdi.com [Último acceso: junio de 2018].Buzzi, J. 2012. Imaging spectroscopy to evaluate the contamination from sulphide mine waste in the Iberian Pyrite Belt using hyperspectral sensors (Huelva, Spain), Tesis Doctoral Universidad de León, 212 p.Buzzi, J., Riaza, A., García-Meléndez, Carrère, V., Bachmann, M. 2011. Aplicación de modelos Gaussianos modificados a datos hiperespectrales de una zona contaminada por drenaje ácido. Caso del río Odiel (Huelva, España). XIV Congreso de la Asociación Española de Teledetección, Mieres, 21- 23 Septiembre 2011, 285-288.Clark, R.N., Swayze, G.E., Wise, R., Livo, E., Hoefen, T., Kokaly, R., Sutley, S.J. 2007. USGS Digital Spectral Library splib06a. Digital Data Series 231, USGS: Denver, Co, USA, 2007.EXELIS, 2011. ENVI User's Guide. Exelis Visual Information Solutions: Boulder, Co, USA.Hunt, G.R., Salisbury, J.W. 1971a. Visible and Near-infrared Spectra of Minerals and Rocks: II. Carbonates. Modern Geology, 2, 23-30.Hunt, G.R., Salisbury, J.W., Lenhof, J. 1971b. Visible and Near-infrared Spectra of Minerals and Rocks: III Oxides and Hydroxides. Modern Geology, 2, 191-205.Hunt, G.R., Salisbury, J.W., 1976. Visible and Near-infrared Spectra of Minerals and Rocks: XI. Sedimentary Rocks. Modern Geology, 5, 211-217.López-Mir, B., Antón Muñoz, J., García-Senz, J. 2016, 3D geometric reconstruction of Upper Cretaceous passive diapirs and salt withdrawal basins in the Cotiella Basin (southern Pyrinees), Journal of the Geological Society, 173, 616-627. https://doi.org/10.1144/jgs2016-002Martínez, L., Tardà, A., Palà, V., Arbiol, R. 2006. Atmospheric correction algorithm applied to CASI multi-height hyperspectral imagery. Proceedings Second International Symposium Recent Advances in Quantitative Remote Sensing, 25-29 Septiembre 2006.Riaza, A. Buzzi, J., García-Meléndez, E., del Moral, B., Carrère, V., Richter, R. 2017. Monitoring salt crusts on an AMD contaminated coastal wetland using hyperspectral Hyperion data (Estuary of the River Odiel, SW Spain). International Journal of Remote Sensing, 38(12), 3735-3762. https://doi.org/10.1080/01431161.2017.1302621Riaza, A., García-Meléndez, E., Carrère, V., Mueller, A. 2014. Cartografía de sales marinas y fluviales en estuarios receptores de aguas ácidas con imágenes hiperespectrales Hyperion (Marismas del río Odiel, Huelva). Revista de Teledetección, 41, 1-7. https://doi.org/10.4995/raet.2014.2255Riaza, A., Buzzi, J., García-Meléndez, E., Carrère, V., Müller, A. 2011. Monitoring the extent of contamination from acid mine drainage in the Iberian Pyrite Belt (SW Spain) using hyperspectral imagery. Remote Sensing, 3, 2166-2186. https://doi.org/10.3390/rs3102166Riaza, A., Buzzi, J., García-Meléndez, E., Vázquez, I., Bellido, E., Carrère, V., Müller, A. 2012. Pyrite mine waste and water mapping using Hymap and Hyperion hyperspectral data. Environmental Earth Sciences, 66-7, 1957-1971. https://doi.org/10.1007/s12665-011-1422-

Energy levels of periodic solutions of the circular 2+2 Sitnikov problem

We study a 2+2 body problem introduced in a previous paper as the circular double Sitnikov problem. Since the secondary bodies are moving on the same perpendicular line where evolve the primaries, almost every solution is a collision orbit. We extend the solutions beyond collisions with a symplectic regularization and study the set of energy surfaces that contain periodic orbits and their foliations .Comment: 20 pages, 5 figures. This is not the final version

Linear stability of the Lagrangian triangle solutions for quasihomogeneous potentials

In this paper we study the linear stability of the relative equilibria for homogeneous and quasihomogeneous potentials. Firstly, in the case the potential is a homogeneous function of degree $-a$, we find that any relative equilibrium of the $n$-body problem with $a>2$ is spectrally unstable. We also find a similar condition in the quasihomogeneous case. Then we consider the case of three bodies and we study the stability of the equilateral triangle relative equilibria. In the case of homogeneous potentials we recover the classical result obtained by Routh in a simpler way. In the case of quasihomogeneous potentials we find a generalization of Routh inequality and we show that, for certain values of the masses, the stability of the relative equilibria depends on the size of the configuration.Comment: 21 pages 4 figure