636 research outputs found
Long-term and seasonal variations in CO2: linkages to catchment alkalinity generation
International audienceAs atmospheric emissions of S have declined in the Northern Hemisphere, there has been an expectation of increased pH and alkalinity in streams believed to have been acidified by excess S and N. Many streams and lakes have not recovered. Evidence from East Bear Brook in Maine, USA and modelling with the groundwater acid-base model MAGIC (Cosby et al. 1985a,b) indicate that seasonal and yearly variations in soil PCO2 are adequate to enhance or even reverse acid-base (alkalinity) changes anticipated from modest decreases of SO4 in surface waters. Alkalinity is generated in the soil by exchange of H+ from dissociation of H2CO3, which in turn is derived from the dissolving of soil CO2. The variation in soil PCO2 produces an alkalinity variation of up to 15 meq L-1 in stream water. Detecting and relating increases in alkalinity to decreases in stream SO4 are significantly more difficult in the short term because of this effect. For example, modelled alkalinity recovery at Bear Brook due to a decline of 20 meq SO4 L-1 in soil solution is compensated by a decline from 0.4 to 0.2% for soil air PCO2. This compensation ability decays over time as base saturation declines. Variable PCO2 has less effect in more acidic soils. Short-term decreases of PCO2 below the long-term average value produce short-term decreases in alkalinity, whereas short-term increases in PCO2 produce short-term alkalization. Trend analysis for detecting recovery of streams and lakes from acidification after reduced atmospheric emissions will require a longer monitoring period for statistical significance than previously appreciated. Keywords: CO2 , alkalinity, acidification, recovery, soils, climate chang
ENGINEERING AN OLEOGINOUS YEAST FOR THE PRODUCTION OF BIODIESEL
poster abstractThere are economic and social interests in replacing the current energy dependence we have on petroleum-based oleochemicals. Yarrowia lipolytica, an oleaginous yeast, has the ability to metabolize unique carbon sources, particularly hydrocarbons and to accumulate large amounts of lipids which could be developed into a source of biodiesel. The ability of Y. lipolytica to accumulate triacylglycerols in lipid droplets and the complete sequencing of its genome make Y. lipolytica a viable organism to genetically engineer for the production of large quantities of biodiesel precursors. The purpose of this project is to genetically modify Y. lipolytica to further increase its production of triacylglycerols by knocking out genes that encode enzymes involved in the ÎČ-oxidation of fatty acids. This genetic modification will be accomplished by using homologous recombination to disrupt the genes POX3-5 and POT1. The 5â and 3â untranslated regions of POX3-5 and POT1 were amplified by polymerase chain reaction and cloned to allow a drug resistance gene to be introduced between them. Following cloning, these genes will be knocked out from the Y. lipolytica genome using drug resistance as a marker. The disruption of these genes is expected to increase the accumulation of triacylglycerols in Y. lipolytica lipid droplets versus the wild-type. Progress towards the goals of this project will be reported
Spin tunnelling in mesoscopic systems
We study spin tunnelling in molecular magnets as an instance of a mesoscopic
phenomenon, with special emphasis on the molecule Fe8. We show that the tunnel
splitting between various pairs of Zeeman levels in this molecule oscillates as
a function of applied magnetic field, vanishing completely at special points in
the space of magnetic fields, known as diabolical points. This phenomena is
explained in terms of two approaches, one based on spin-coherent-state path
integrals, and the other on a generalization of the phase integral (or WKB)
method to difference equations. Explicit formulas for the diabolical points are
obtained for a model Hamiltonian.Comment: 13 pages, 5 figures, uses Pramana style files; conference proceedings
articl
Long-term response of spring wheat to N and P fertilization in southwestern Saskatchewan
Non-Peer Reviewe
Spatial evolution of an AMD stream in the Iberian Pyrite Belt: process characterization and control factors on the hydrochemistry
This paper presents hydrochemical data of an AMD stream in the Iberian Pyrite Belt, obtained from its source, in the Poderosa Mine Portal, till its confluence at the Odiel River. The main objective is to establish potential interdependent relations between sulfate and metalsâ loads and the following physical-chemical variables: pH, electric conductivity (EC), redox potential (EH), and dissolved oxygen (O2). All the parameters show a global increasing tendency since the tunnelâs exit to the confluence at Odiel River. The TDS and EC are two relevant exceptions. They behave similarly, showing a decreasing trend and a strong inflection that describes a minimum immediately after the discharging point. The spatial analysis combined with statistical tools put in evidence the typical AMD processes and the respective physical-chemical implications. Inputs with distinctive hydrochemical signatures impose relevant modifications in the Poderosa creek waters. This indicates low hydrochemical inertia and high vulnerability to external stimulus.Financial support for this research was provided by DGCICYT National Plan, project CGL2010-21268-C02-01 and the Andalusian Autonomous Government Excellence Projects, Project RNM-6570
Advances in ab-initio theory of Multiferroics. Materials and mechanisms: modelling and understanding
Within the broad class of multiferroics (compounds showing a coexistence of
magnetism and ferroelectricity), we focus on the subclass of "improper
electronic ferroelectrics", i.e. correlated materials where electronic degrees
of freedom (such as spin, charge or orbital) drive ferroelectricity. In
particular, in spin-induced ferroelectrics, there is not only a {\em
coexistence} of the two intriguing magnetic and dipolar orders; rather, there
is such an intimate link that one drives the other, suggesting a giant
magnetoelectric coupling. Via first-principles approaches based on density
functional theory, we review the microscopic mechanisms at the basis of
multiferroicity in several compounds, ranging from transition metal oxides to
organic multiferroics (MFs) to organic-inorganic hybrids (i.e. metal-organic
frameworks, MOFs)Comment: 22 pages, 9 figure
Intercalibration of the barrel electromagnetic calorimeter of the CMS experiment at start-up
Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated
Examining Contextual Factors and Individual Value Dimensions of Healthcare Providers Intention to Adopt Electronic Health Technologies in Developing Countries
Part 5: Research in ProgressInternational audienceDespite substantial research on electronic health (e-Health) adoption, there still exist vast differences between resource-rich and resource-poor populations regarding Information Technology adoption. To help bridge the technological gulf between developed and developing countries, this research-in-progress paper examines healthcare providersâ intention to adopt e-health technologies from two perspectives 1) contextual factors (i.e. specific to developing world settings) and 2) individual value dimensions (i.e. cultural, utilitarian, social and personal). The primary output of this paper is a theoretical model merging both the contextual factors and value dimensions; this forms a strong baseline to examine and help ensure the successful adoption of e-Health technologies within developing countries. Future research will be performed to validate the model developed in this paper, with a specific focus on mobile Health in Malawi, Africa
A function-based typology for Earthâs ecosystems
As the United Nations develops a post-2020 global biodiversity framework for the Convention on Biological Diversity, attention is focusing on how new goals and targets for ecosystem conservation might serve its vision of âliving in harmony with natureâ1,2. Advancing dual imperatives to conserve biodiversity and sustain ecosystem services requires reliable and resilient generalizations and predictions about ecosystem responses to environmental change and management3. Ecosystems vary in their biota4, service provision5 and relative exposure to risks6, yet there is no globally consistent classification of ecosystems that reflects functional responses to change and management. This hampers progress on developing conservation targets and sustainability goals. Here we present the International Union for Conservation of Nature (IUCN) Global Ecosystem Typology, a conceptually robust, scalable, spatially explicit approach for generalizations and predictions about functions, biota, risks and management remedies across the entire biosphere. The outcome of a major cross-disciplinary collaboration, this novel framework places all of Earthâs ecosystems into a unifying theoretical context to guide the transformation of ecosystem policy and management from global to local scales. This new information infrastructure will support knowledge transfer for ecosystem-specific management and restoration, globally standardized ecosystem risk assessments, natural capital accounting and progress on the post-2020 global biodiversity framework
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