262 research outputs found

    Defining biodiverse reforestation: Why it matters for climate change mitigation and biodiversity

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    Reforestation to capture and store atmospheric carbon is increasingly championed as a climate change mitigation policy response. Reforestation plantings have the potential to provide conservation co-benefits when diverse mixtures of native species are planted, and there are growing attempts to monetise biodiversity benefits from carbon reforestation projects, particularly within emerging carbon markets. But what is meant by ‘biodiverse’ across different stakeholders and groups implementing and overseeing these projects and how do these perceptions compare with long-standing scientific definitions? Here, we discuss approaches to, and definitions of, biodiversity in the context of reforestation for carbon sequestration. Our aim is to review how the concept of biodiversity is defined and applied among stakeholders (e.g., governments, carbon certifiers and farmers) and rights holders (i.e., First Nations people) engaging in reforestation, and to identify best-practice methods for restoring biodiversity in these projects. We find that some stakeholders have a vague understanding of diversity across varying levels of biological organisation (genes to ecosystems). While most understand that biodiversity underpins ecosystem functions and services, many stakeholders may not appreciate the difficulties of restoring biodiversity akin to reference ecosystems. Consequently, biodiversity goals are rarely explicit, and project goals may never be achieved because the levels of restored biodiversity are inadequate to support functional ecosystems and desired ecosystem services. We suggest there is significant value in integrating biodiversity objectives into reforestation projects and setting specific restoration goals with transparent reporting outcomes will pave the way for ensuring reforestation projects have meaningful outcomes for biodiversity, and legitimate incentive payments for biodiversity and natural capital accounting

    Magnetic Field Effects on Neutron Diffraction in the Antiferromagnetic Phase of UPt3UPt_3

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    We discuss possible magnetic structures in UPt3_3 based on our analysis of elastic neutron-scattering experiments in high magnetic fields at temperatures T<TNT<T_N. The existing experimental data can be explained by a single-{\bf q} antiferromagnetic structure with three independent domains. For modest in-plane spin-orbit interactions, the Zeeman coupling between the antiferromagnetic order parameter and the magnetic field induces a rotation of the magnetic moments, but not an adjustment of the propagation vector of the magnetic order. A triple-{\bf q} magnetic structure is also consistent with neutron experiments, but in general leads to a non-uniform magnetization in the crystal. New experiments could decide between these structures.Comment: 5 figures included in the tex

    Strictly Toral Dynamics

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    This article deals with nonwandering (e.g. area-preserving) homeomorphisms of the torus T2\mathbb{T}^2 which are homotopic to the identity and strictly toral, in the sense that they exhibit dynamical properties that are not present in homeomorphisms of the annulus or the plane. This includes all homeomorphisms which have a rotation set with nonempty interior. We define two types of points: inessential and essential. The set of inessential points ine(f)ine(f) is shown to be a disjoint union of periodic topological disks ("elliptic islands"), while the set of essential points ess(f)ess(f) is an essential continuum, with typically rich dynamics (the "chaotic region"). This generalizes and improves a similar description by J\"ager. The key result is boundedness of these "elliptic islands", which allows, among other things, to obtain sharp (uniform) bounds of the diffusion rates. We also show that the dynamics in ess(f)ess(f) is as rich as in T2\mathbb{T}^2 from the rotational viewpoint, and we obtain results relating the existence of large invariant topological disks to the abundance of fixed points.Comment: Incorporates suggestions and corrections by the referees. To appear in Inv. Mat

    A synthesis of carbon dioxide emissions from fossil-fuel combustion

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    This synthesis discusses the emissions of carbon dioxide from fossil-fuel combustion and cement production. While much is known about these emissions, there is still much that is unknown about the details surrounding these emissions. This synthesis explores our knowledge of these emissions in terms of why there is concern about them; how they are calculated; the major global efforts on inventorying them; their global, regional, and national totals at different spatial and temporal scales; how they are distributed on global grids (i.e., maps); how they are transported in models; and the uncertainties associated with these different aspects of the emissions. The magnitude of emissions from the combustion of fossil fuels has been almost continuously increasing with time since fossil fuels were first used by humans. Despite events in some nations specifically designed to reduce emissions, or which have had emissions reduction as a byproduct of other events, global total emissions continue their general increase with time. Global total fossil-fuel carbon dioxide emissions are known to within 10 % uncertainty (95 % confidence interval). Uncertainty on individual national total fossil-fuel carbon dioxide emissions range from a few percent to more than 50 %. This manuscript concludes that carbon dioxide emissions from fossil-fuel combustion continue to increase with time and that while much is known about the overall characteristics of these emissions, much is still to be learned about the detailed characteristics of these emissions

    The global carbon budget 1959-2011

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    Accurate assessments of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the climate policy process, and project future climate change. Present-day analysis requires the combination of a range of data, algorithms, statistics and model estimates and their interpretation by a broad scientific community. Here we describe datasets and a methodology developed by the global carbon cycle science community to quantify all major components of the global carbon budget, including their uncertainties. We discuss changes compared to previous estimates, consistency within and among components, and methodology and data limitations. CO2 emissions from fossil fuel combustion and cement production (EFF) are based on energy statistics, while emissions from Land-Use Change (ELUC), including deforestation, are based on combined evidence from land cover change data, fire activity in regions undergoing deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. Finally, the global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms. For the last decade available (2002–2011), EFF was 8.3 &pm; 0.4 PgC yr−1, ELUC 1.0 &pm; 0.5 PgC yr−1, GATM 4.3 &pm; 0.1PgC yr−1, SOCEAN 2.5 &pm; 0.5 PgC yr−1, and SLAND 2.6 &pm; 0.8 PgC yr−1. For year 2011 alone, EFF was 9.5 &pm; 0.5 PgC yr−1, 3.0 percent above 2010, reflecting a continued trend in these emissions; ELUC was 0.9 &pm; 0.5 PgC yr−1, approximately constant throughout the decade; GATM was 3.6 &pm; 0.2 PgC yr−1, SOCEAN was 2.7 &pm; 0.5 PgC yr−1, and SLAND was 4.1 &pm; 0.9 PgC yr−1. GATM was low in 2011 compared to the 2002–2011 average because of a high uptake by the land probably in response to natural climate variability associated to La Niña conditions in the Pacific Ocean. The global atmospheric CO2 concentration reached 391.31 &pm; 0.13 ppm at the end of year 2011. We estimate that EFF will have increased by 2.6% (1.9–3.5%) in 2012 based on projections of gross world product and recent changes in the carbon intensity of the economy. All uncertainties are reported as &pm;1 sigma (68% confidence assuming Gaussian error distributions that the real value lies within the given interval), reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. This paper is intended to provide a baseline to keep track of annual carbon budgets in the future

    Single Spin Measurement using Single Electron Transistors to Probe Two Electron Systems

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    We present a method for measuring single spins embedded in a solid by probing two electron systems with a single electron transistor (SET). Restrictions imposed by the Pauli Principle on allowed two electron states mean that the spin state of such systems has a profound impact on the orbital states (positions) of the electrons, a parameter which SET's are extremely well suited to measure. We focus on a particular system capable of being fabricated with current technology: a Te double donor in Si adjacent to a Si/SiO2 interface and lying directly beneath the SET island electrode, and we outline a measurement strategy capable of resolving single electron and nuclear spins in this system. We discuss the limitations of the measurement imposed by spin scattering arising from fluctuations emanating from the SET and from lattice phonons. We conclude that measurement of single spins, a necessary requirement for several proposed quantum computer architectures, is feasible in Si using this strategy.Comment: 22 Pages, 8 Figures; revised version contains updated references and small textual changes. Submitted to Phys. Rev.

    Quantum phase transitions and thermodynamic properties in highly anisotropic magnets

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    The systems exhibiting quantum phase transitions (QPT) are investigated within the Ising model in the transverse field and Heisenberg model with easy-plane single-site anisotropy. Near QPT a correspondence between parameters of these models and of quantum phi^4 model is established. A scaling analysis is performed for the ground-state properties. The influence of the external longitudinal magnetic field on the ground-state properties is investigated, and the corresponding magnetic susceptibility is calculated. Finite-temperature properties are considered with the use of the scaling analysis for the effective classical model proposed by Sachdev. Analytical results for the ordering temperature and temperature dependences of the magnetization and energy gap are obtained in the case of a small ground-state moment. The forms of dependences of observable quantities on the bare splitting (or magnetic field) and renormalized splitting turn out to be different. A comparison with numerical calculations and experimental data on systems demonstrating magnetic and structural transitions (e.g., into singlet state) is performed.Comment: 46 pages, RevTeX, 6 figure

    Determinación de patotipos de Verticillium dahliae Kleb. provenientes de las regiones olivícolas del centro y oeste de Argentina y pruebas de virulencia en algodón

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    La verticilosis causada por el hongo habitante de suelo Verticillium dahliae Kleb. es una enfermedad que afecta el cultivo del olivo (Olea europaea L.) y algodón (Gossypium hirsutum L.), entre otros. De acuerdo a su patogenicidad, los aislados del patógeno pueden clasificarse como patotipos defoliantes (D) y no defoliantes (ND). Los objetivos de este estudio fueron: i) determinar los patotipos de una colección de 42 aislados de V. dahliae provenientes de plantas de olivo de las provincias de Catamarca, Córdoba, La Rioja y Mendoza existente en el IPAVE-INTA Córdoba, y ii) evaluar la virulencia de ocho cepas recientemente aisladas pertenecientes a dicha colección. Se utilizó la técnica de PCR anidado para el análisis molecular de los aislados del hongo y la evaluación de la virulencia se realizó mediante inoculaciones artificiales en plantines de algodón con un diseño completamente aleatorizado. El 100 % de los aislados fueron caracterizados como ND. Dos cepas provenientes de La Rioja, dos de Catamarca y una de Mendoza, fueron significativamente más virulentas (p< 0,05) para el área bajo la curva de progreso de la enfermedad relativa, severidad media final, porcentaje de severidad media e índice de severidad.Verticillium wilt caused by the soil-borne fungus Verticillium dahliae Kleb. is a disease that affects olive (Olea europaea L.) and cotton crops, among others. According to their pathogenicity, V. dahliae isolates can be classified as defoliating (D) and non-defoliating (ND). The objectives of this study were: i) to determine the pathotypes of a collection of 42 V. dahliae isolates from olive plants in the provinces of Catamarca, Córdoba, La Rioja and Mendoza kept at IPAVE-INTA Córdoba, and (ii) to evaluate the virulence of eight recently isolated isolates belonging to this collection. Nested PCR was used for molecular analysis of the 42 fungal isolates and virulence evaluation was performed by artificial inoculations on cotton seedlings with a completely randomized design. The total of the isolates was characterized as ND. Two strains from La Rioja, two from Catamarca and one from Mendoza, were significantly more virulent (p<0.05) for the relative area under disease progress curve, final mean severity, average severity percentage and severity index.Instituto de Patología VegetalFil: Gonzalez, Valeria Mariel. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; ArgentinaFil: Paccioretti, Mauro Andres. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Rattalino, Donna. Universidad Nacional de Chilecito; ArgentinaFil: Taborda, R.J. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; ArgentinaFil: Carrasco, Franca Denise. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Catamarca; ArgentinaFil: Arias, Maria Fernanda. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; ArgentinaFil: Otero, Maria Laura. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Otero, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFyMA); Argentin

    Detecting Microscopic Black Holes with Neutrino Telescopes

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    If spacetime has more than four dimensions, ultra-high energy cosmic rays may create microscopic black holes. Black holes created by cosmic neutrinos in the Earth will evaporate, and the resulting hadronic showers, muons, and taus may be detected in neutrino telescopes below the Earth's surface. We simulate such events in detail and consider black hole cross sections with and without an exponential suppression factor. We find observable rates in both cases: for conservative cosmogenic neutrino fluxes, several black hole events per year are observable at the IceCube detector; for fluxes at the Waxman-Bahcall bound, tens of events per year are possible. We also present zenith angle and energy distributions for all three channels. The ability of neutrino telescopes to differentiate hadrons, muons, and possibly taus, and to measure these distributions provides a unique opportunity to identify black holes, to experimentally constrain the form of black hole production cross sections, and to study Hawking evaporation.Comment: 20 pages, 9 figure
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