63 research outputs found
Lutte contre Rhizoctonia solani KĂŒhn, parasite du cotonnier par le nĂ©matode Aphelenchus avenae Bastian
Brieskorn manifolds as contact branched covers of spheres
We show that Brieskorn manifolds with their standard contact structures are
contact branched coverings of spheres. This covering maps a contact open book
decomposition of the Brieskorn manifold onto a Milnor open book of the sphere.Comment: 8 pages, 1 figur
Ultrametric spaces of branches on arborescent singularities
Let be a normal complex analytic surface singularity. We say that is
arborescent if the dual graph of any resolution of it is a tree. Whenever
are distinct branches on , we denote by their intersection
number in the sense of Mumford. If is a fixed branch, we define when and
otherwise. We generalize a theorem of P{\l}oski concerning smooth germs of
surfaces, by proving that whenever is arborescent, then is an
ultrametric on the set of branches of different from . We compute the
maximum of , which gives an analog of a theorem of Teissier. We show that
encodes topological information about the structure of the embedded
resolutions of any finite set of branches. This generalizes a theorem of Favre
and Jonsson concerning the case when both and are smooth. We generalize
also from smooth germs to arbitrary arborescent ones their valuative
interpretation of the dual trees of the resolutions of . Our proofs are
based in an essential way on a determinantal identity of Eisenbud and Neumann.Comment: 37 pages, 16 figures. Compared to the first version on Arxiv, il has
a new section 4.3, accompanied by 2 new figures. Several passages were
clarified and the typos discovered in the meantime were correcte
Regionally aggregated, stitched and deâdrifted CMIPâclimate data, processed with netCDFâSCM v2.0.0
The world's most complex climate models are currently running a range of experiments as part of the Sixth Coupled Model Intercomparison Project (CMIP6). Added to the output from the Fifth Coupled Model Intercomparison Project (CMIP5), the total data volume will be in the order of 20PB. Here, we present a dataset of annual, monthly, global, hemispheric and land/ocean means derived from a selection of experiments of key interest to climate data analysts and reduced complexity climate modellers. The derived dataset is a key part of validating, calibrating and developing reduced complexity climate models against the behaviour of more physically complete models. In addition to its use for reduced complexity climate modellers, we aim to make our data accessible to other research communities. We facilitate this in a number of ways. Firstly, given the focus on annual, monthly, global, hemispheric and land/ocean mean quantities, our dataset is orders of magnitude smaller than the source data and hence does not require specialized âbig dataâ expertise. Secondly, again because of its smaller size, we are able to offer our dataset in a text-based format, greatly reducing the computational expertise required to work with CMIP output. Thirdly, we enable data provenance and integrity control by tracking all source metadata and providing tools which check whether a dataset has been retracted, that is identified as erroneous. The resulting dataset is updated as new CMIP6 results become available and we provide a stable access point to allow automated downloads. Along with our accompanying website (cmip6.science.unimelb.edu.au), we believe this dataset provides a unique community resource, as well as allowing non-specialists to access CMIP data in a new, user-friendly way
Climate change projections using the IPSL-CM5 Earth System Model: from CMIP3 to CMIP5
We present the global general circulation model IPSL-CM5 developed to study the long-term response of the climate system to natural and anthropogenic forcings as part of the 5th Phase of the Coupled Model Intercomparison Project (CMIP5). This model includes an interactive carbon cycle, a representation of tropospheric and stratospheric chemistry, and a comprehensive representation of aerosols. As it represents the principal dynamical, physical, and bio-geochemical processes relevant to the climate system, it may be referred to as an Earth System Model. However, the IPSL-CM5 model may be used in a multitude of configurations associated with different boundary conditions and with a range of complexities in terms of processes and interactions. This paper presents an overview of the different model components and explains how they were coupled and used to simulate historical climate changes over the past 150 years and different scenarios of future climate change. A single version of the IPSL-CM5 model (IPSL-CM5A-LR) was used to provide climate projections associated with different socio-economic scenarios, including the different Representative Concentration Pathways considered by CMIP5 and several scenarios from the Special Report on Emission Scenarios considered by CMIP3. Results suggest that the magnitude of global warming projections primarily depends on the socio-economic scenario considered, that there is potential for an aggressive mitigation policy to limit global warming to about two degrees, and that the behavior of some components of the climate system such as the Arctic sea ice and the Atlantic Meridional Overturning Circulation may change drastically by the end of the twenty-first century in the case of a no climate policy scenario. Although the magnitude of regional temperature and precipitation changes depends fairly linearly on the magnitude of the projected global warming (and thus on the scenario considered), the geographical pattern of these changes is strikingly similar for the different scenarios. The representation of atmospheric physical processes in the model is shown to strongly influence the simulated climate variability and both the magnitude and pattern of the projected climate changes
Plant species diversity for sustainable management of crop pests and diseases in agroecosystems: a review
Optimization of Secondary Air Injection in a Wood-Burning Cookstove: An Experimental Study
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Solving the Air Pollution Crisis: Mitigation and Monitoring
Air pollution is one of the worldâs greatest environmental health risks, responsible for over 7 million premature deaths annually. Around half of these premature mortalities are linked to biomass cooking fires that release harmful air pollutants into peopleâs homes, such as particulate matter (PM). Although nearly 3 billion people worldwide depend on biomass cooking fuels, relatively little scientific research exists on mitigating the smoke they generate. One promising approach for reducing emissions is the injection of secondary air into the biomass cookstoveâs combustion chamber. However, cold secondary air can also quench the combustion process when improperly injected, and so many secondary air injection cookstove designs do not actually reduce harmful smoke emissions relative to a traditional three stone fire (TSF). Since wood is a common cooking fuel throughout the world, this dissertation presents an experimental
wood-burning cookstove platform, dubbed the âModular (MOD) stoveâ, to identify and optimize secondary air
injection parameters that reduce the emission of harmful pollutants. The MOD stove enables systematic, repeatable experiments in which various secondary air injection design features, such as flow rate and location, can be quickly and easily adjusted. Over 130 experimental trials were conducted, demonstrating that wood combustion is highly sensitive to small changes in the secondary air injection parameters. Using a systematic experimental approach, an optimal design configuration was identified that reduces mass emissions of PM2.5, carbon monoxide (CO), and black carbon (BC) by ~90% relative to a traditional TSF, while also improving thermal efficiency. Using an updated version of the MOD stove, an additional 111 performance tests were conducted to quantify the practical design requirements (e.g., secondary air pressure and temperature) to achieve â„ 90% mass emission reductions relative to a TSF. Using this experimental data, I demonstrate that low-cost (<$10) fans and blowers are currently available to drive the secondary flow, and this hardware can be independently powered using an inexpensive thermoelectric generator mounted nearby. Furthermore, size-resolved PM measurements demonstrate that secondary air injection effectively inhibits particle growth, but the total number of particles generated remains relatively unaffected. I investigate the potential impacts for human health and explore methods to mitigate the PM formation mechanisms that persist. As a whole, the MOD stove platform demonstrates that secondary air injection is a practical, effective, and potentially economical method for meaningfully reducing smoke emissions from biomass cookstoves. However, designs should be experimentally validated and optimized, and further research is needed to eliminate the persistent formation of ultrafine particles that are particularly harmful to human health. Ambient air pollution is also widespread, and linked to significant adverse health outcomes. Over 90% of the worldâs population lives in areas where ambient air pollution concentrations exceed World Health Organization recommendations, resulting in ~4 million premature deaths annually. The health impacts of ambient air pollution are particularly acute in urban settings. In 2010, premature deaths due to ambient air pollution were about 50% more common in urban than in rural environments, and this could increase to nearly 90% by 2050. Although ground-based air quality measurements are needed to address this growing health crisis, traditional regulatory monitoring networks do not provide sufficient spatial coverage and resolution to adequately assess air pollution exposures in urban environments. Distributed networks of low-cost air quality sensors are emerging to fill this gap. Black carbon (BC) is an important component of PM pollution, strongly linked to adverse human health outcomes and climate change, but low-cost sensors for monitoring this critical pollutant are lacking. This dissertation presents the Aerosol Black Carbon Detector (ABCD), specifically designed for distributed air quality monitoring networks. As such, the ABCD integrates a compact weatherproof enclosure, solar-powered rechargeable battery, and cellular communication to enable long-term, outdoor deployments. Most importantly, the ABCD incorporates a number of novel design features to provide uniquely accurate BC concentration measurements in tough operating environments that debilitate existing commercial instruments. Over 100 ABCDs were operated outdoors, and their measurement performance was comparable to that of a commercial BC instrument collocated inside a regulatory monitoring station. The validated fleet of ABCDs was deployed to 100 sampling sites in West Oakland, California â a neighborhood disproportionately affected by air pollution associated with the nearby Port of Oakland and surrounding highways. Over 100 days, the wireless sensor network successfully collected 84.0% of the 240,000 hourly BC concentration measurements desired (100 sampling sites Ă 2,400 hours). The widespread failure of miniature vacuum pumps was responsible for most missing measurements. The resulting BC concentration maps demonstrate that concentrations vary sharply over short distances (~100 m) and timespans (~1 hour), and generally depend on surrounding land use, traffic patterns, and location relative to prevailing winds. BC concentrations at each sampling site are highly repeatable over the diurnal and weekly cycles, and periodic trends are analyzed throughout the community. Using these trends as a reference, unusually polluted locations are detected, and likely emissions sources nearby are identified. In this way, the 100x100 Network demonstrates the value of low-cost sensor networks to accurately characterize urban air pollution distributions, and provide regulatory agencies, governments, and community stakeholders with actionable insights to mitigate the sources. Air pollution is a pervasive and persistent health threat that can only be tackled if we work to both mitigate and monitor emission sources. As such, the MOD stove studies presented here are targeted towards abating the worldâs deadliest polluters. However, even the best of emissions reduction efforts are left blind without accurate measurements of the resulting air quality. The ABCD meets this need, providing accurate BC monitoring capabilities in a uniquely practical and economical package. Together, these complementary technologies will help underpin more comprehensive, data-driven efforts to quantifiably reduce harmful air pollution exposure throughout the world, and ultimately prevent millions of premature deaths
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