Stability of syzygy bundles

We show that given integers $N$, $d$ and $n$ such that ${N\ge2}$, ${(N,d,n)\ne(2,2,5)}$, and ${N+1\le n\le\tbinom{d+N}{N}}$, there is a family of $n$ monomials in $K[X_0,\ldots,X_N]$ of degree $d$ such that their syzygy bundle is stable. Case ${N\ge3}$ was obtained independently by Coand\v{a} with a different choice of families of monomials [Coa09]. For ${(N,d,n)=(2,2,5)}$, there are $5$ monomials of degree~$2$ in $K[X_0,X_1,X_2]$ such that their syzygy bundle is semistable.Comment: 16 pages, to appear in the Proceedings of the American Mathematical Societ

Stability and Unobstructedness of Syzygy Bundles

It is a longstanding problem in Algebraic Geometry to determine whether the syzygy bundle $E_{d_1,..., d_n}$ on \PP^N defined as the kernel of a general epimorphism \xymatrix{\phi:\cO(-d_1)\oplus...\oplus\cO(-d_n)\ar[r] &\cO} is (semi)stable. In this note, we restrict our attention to the case of syzygy bundles $E_{d,n}$ on \PP^N associated to $n$ generic forms $f_1,...,f_n\in K[X_0,X_1,..., X_N]$ of the same degree $d$. Our first goal is to prove that $E_{d,n}$ is stable if $N+1\le n\le\tbinom{d+2}{2}+N-2$. This bound improves, in general, the bound $n\le d(N+1)$ given by G. Hein in \cite{B}, Appendix A. In the last part of the paper, we study moduli spaces of stable rank $n-1$ vector bundles on \PP^N containing syzygy bundles. We prove that if $N+1\le n\le\tbinom{d+2}{2}+N-2$ and $N\ne 3$, then the syzygy bundle $E_{d,n}$ is unobstructed and it belongs to a generically smooth irreducible component of dimension $n\tbinom{d+N}{N}-n^2$, if $N \geq 4$, and $n\tbinom{d+2}{2}+n\tbinom{d-1}{2}-n^2$, if N=2.Comment: 32 pages, minor change

Boletín NUESTRA AMÉRICA XXI - Desafíos y alternativas, num.0, septiembre 2016

Una excelente iniciativa del Grupo de Trabajo Crisis y economía mundial, coordinado por María Josefina Morales y Gabriela Roffinelli

Geochemistry and Fe speciation in active volcanic environments – the case of Fogo Island, Cape Verde

Topsoils developed in different geological formations/ages, and the top layer of the lava flow from the most recent eruption (2014/2015) of Fogo Island (Cape Verde archipelago), were studied. The specific objectives of this work are: i) to estimate the REE contents and patterns in the whole sample of topsoils developed on different geological formations/ages and their correlation with the iron speciation; and ii) to study the top layer of a lava flow from the most recent eruption after two years of exposure. REE contents are in general higher in the topsoils of the pre-caldera than in those developed on the post-caldera formation, particularly the light REE probably due to their incorporation into hematite. Positive Eu anomalies found in recent topsoils suggest the existence of hydrothermal processes with intrusion of hot fluids with higher concentration of Eu2+. In the top layer of the lava flow of the most recent eruption, Fe is incorporated in pyroxenes and iron oxides (magnetite and/or maghemite). This study can be a benchmark for further knowledge of the chemical evolution and weathering rate in semi-arid climate of Fogo Island.The authors would like to thank the financial support by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the projects UID/GEO/04035/2013 and UID/Multi/04349/2013

Boletín NUESTRA AMÉRICA XXI - Desafíos y alternativas, num.6, abril 2017

Una excelente iniciativa del Grupo de Trabajo Crisis y economía mundial, coordinado por María Josefina Morales y Gabriela Roffinelli

Desarrollo y crisis en el capitalismo

Revisión realizada en 2012, del desenvolvimiento de la economía mundial y los cambios que se han venido dando en el contexto de la crisis reciente, así como diversos aspectos de las transformaciones en proceso y de la situación económica y social en América Latina. La primera parte está dedicada a la crisis mundial en el marco del funcionamiento del capitalismo y la globalización, y de la permanencia de los factores económicos y financieros que propiciaron su estallido. Se consideran los efectos de la misma según los países y regiones, y se observa su incidencia en los procesos de reconfiguración en marcha, así como las estrategias y políticas seguidas para hacerle frente, sin olvidar las propuestas que se han adelantado para explicarla. En la segunda parte de la obra se analizan los problemas de la región latinoamericana y los de algunos de los países que la integran. Los temas incluyen el desempleo juvenil y el modelo agro-exportador, la inversión extranjera directa y las elecciones presidenciales, entre otros

Metal mobility and bioaccessibility from cyanide leaching heaps in a historical mine site

Unlike acidic sulfide mine wastes, where metal/loid mobility and bioaccessibility has been widely studied, less attention has been paid to alkaline cyanide heap leaching wastes. Thus, the main goal of this study is to evaluate the mobility and bioaccessibility of metal/loids in Fe-rich (up to 55%) mine wastes resulting from historical cyanide leaching activities. Wastes are mainly composed of oxides/oxyhydroxides (i.e. goethite and hematite), oxyhydroxisulfates (i.e. jarosite), sulfates (i.e., gypsum, evaporitic sulfate salts), carbonates (i.e., calcite, siderite) and quartz, with noticeable concentrations of metal/loids (e.g., 1453–6943 mg/kg of As, 5216–15,672 mg/kg; of Pb, 308–1094 mg/kg of Sb, 181–1174 mg/kg of Cu, or 97–1517 mg/kg of Zn). The wastes displayed a high reactivity upon rainfall contact associated to the dissolution of secondary minerals such as carbonates, gypsum, and other sulfates, exceeding the threshold values for hazardous wastes in some heap levels for Se, Cu, Zn, As, and sulfate leading to potential significant risks for aquatic life. High concentrations of Fe, Pb, and Al were released during the simulation of digestive ingestion of waste particles, with average values of 4825 mg/kg of Fe, 1672 mg/kg of Pb, and 807 mg/kg of Al. Mineralogy may control the mobility and bioaccessibility of metal/loids under rainfall events. However, in the case of the bioaccessible fractions different associations may be observed: i) the dissolution of gypsum, jarosite and hematite would mainly release Fe, As, Pb, Cu, Se, Sb and Tl; ii) the dissolution of an un-identified mineral (e.g., aluminosilicate or Mn oxide) would lead to the release of Ni, Co, Al and Mn and iii) the acid attack of silicate materials and goethite would enhance the bioaccessibility of V and Cr. This study highlights the hazardousness of wastes from cyanide heap leaching, and the need to adopt restoration measures in historical mine sites.This work was supported by the Spanish Ministry of Economic and Competitiveness through the projects TRAMPA (PID2020–119196RBC21) and by H2020 European Institute of Innovation and Technology (EIT RawMaterials) through the project Modular recovery process services for hydrometallurgy and water treatment (MORECOVERY). This work was partially supported by FCT (Portugal) through contract UID/ Multi/04349/2019. C.R C´anovas thanks the Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference RYC2019–027949-I. M.D. Basallote thanks the Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference IJC 2018–035056-I. The authors would also like to thank to Prof. Edward D. Burton, Ph.D (Editor) and three anonymous reviewers for the support and comments that notably improved the quality of the original paper

New Geological Evidence of the 1755 Lisbon Tsunami from the Rock of Gibraltar (Southern Iberian Peninsula)

This paper presents the easternmost mineralogical and geochemical evidence of the 1755 Lisbon tsunami found in the Western Mediterranean. This multidisciplinary analysis of a sediment core obtained in Gibraltar (southern Iberian Peninsula) has allowed us to differentiate a tsunamiite from an old lagoon (The Inundation). This tsunamigenic layer has increased levels of calcite and aragonite and higher concentrations of Ba and ferromagnesian elements in comparison with the underlying lagoonal sediments of this core. This layer is also differentiated by its paleontological record, with the introduction of marine species within this lagoon. The uppermost part of the core includes a transition from swampy/marsh paleoenvironments to terrestrial scenarios, with a final anthropogenic filling occurring during the last century

Seguridad Social Latinoamericana No. 5, Junio 2021

El Grupo de Trabajo “Seguridad Social y Sistemas de Pensiones”, que reúne a 38 investigadores de las ciencias sociales, se propone propiciar el debate crítico sobre los distintos programas de la Seguridad Social existentes en América Latina y el Caribe. Se plantea profundizar el análisis de los cambios observados en los procesos de trabajo, la estructura económico-social, los mercados laborales y la demografía. Pretende evaluar sus impactos en las trayectorias institucionales de la Seguridad Social y sus diseños. También intentará avanzar en la comprensión integral de los procesos de formulación de políticas públicas referidas a esa temática: los sistemas de pensiones, sistemas de asignaciones familiares, los sistemas de atención a la salud, entre otros. Fomentar los canales de diálogo y de articulación con instituciones de los Estados, de las organizaciones sociales y del mundo del trabajo, será su prioridad

Factores de mayor incidencia en la adopción de innovaciones TIC a escala de país: importancia de las relaciones directas e indirectas entre factores

Esta investigación modelizó los factores que influyen en la adopción de innovaciones TIC en las empresas (ICT), determinando su influencia directa e indirecta, y la importancia de cada constructo en el modelo. Se identificaron los factores incidentes en la adopción de ICT mediante el modelo TOE. Las hipótesis se testaron usando una muestra de empresas con información agrega-da a nivel de país, y se empleó PLS-SEM como método de estimación y comprobación de las hipótesis. Posteriormente, se em-plearon los algoritmos Betweenness , y Beta Centrality para determinar el papel de cada factor en la red. El constructo más determinante fue la Globalización de las firmas debido a la influencia indirecta de éste en el modelo. Igualmente, resultó clave el constructo del entorno tecnológico ICT por su gran influencia sobre la adopción de innovaciones, así como por su papel transmisor de los efectos indirectos de los demás constructos.Ministerio de Economía y Competitividad CS2015-67662-