311 research outputs found
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Plant conservation in the Anthropocene - challenges and future prospects
Despite the massive efforts that have been made to conserve plant diversity across the world during the past few decades, it is becoming increasingly evident that our current strategies are not sufficiently effective to prevent the continuing decline in biodiversity. As a recent report by the CBD indicates, current progress and commitments are insufficient to achieve the Aichi Biodiversity Targets by 2020. Threatened species lists continue to grow while the world's governments fail to meet biodiversity conservation goals. Clearly, we are failing in our attempts to conserve biodiversity on a sufficient scale. The reasons for this situation are complex, including scientific, technical, sociological, economic and political factors. The conservation community is divided about how to respond. Some believe that saving all existing biodiversity is still an achievable goal. On the other hand, there are those who believe that we need to accept that biodiversity will inevitably continue to be lost, despite all our conservation actions and that we must focus on what to save, why and where. It has also been suggested that we need a new approach to conservation in the face of the challenges posed by the Anthropocene biosphere which we now inhabit. Whatever view one holds on the above issues, it is clear that we need to review the effectiveness of our current conservation strategies, identify the limiting factors that are preventing the Aichi goals being met and at the same time take whatever steps are necessary to make our conservation protocols more explicit, operational and efficient so as to achieve the maximum conservation effect. This paper addresses the key issues that underlie our failure to meet agreed targets and discusses the necessary changes to our conservation approaches. While we can justifiably be proud of our many achievements and successes in plant conservation in the past 30 years, which have helped slow the rate of loss, unless we devise a more coherent, consistent and integrated global strategy in which both the effectiveness and limitations of our current policies, action plans and procedures are recognized, and reflect this in national strategies, and then embark on a much bolder and ambitious set of actions, progress will be limited and plant diversity will continue to decline
Study of Oxidation and Combustion Characteristics of Iron Nanoparticles under Idealized and Enginelike Conditions
This document is the Accepted Manuscript version of a Published Work that appeared in final form in
Energy Fuels, copyright © American Chemical Society after peer review and technical editing by the publisher.[EN] The present work includes findings from proof-of-principle feasibility studies on iron nanopowder combustion under idealized, enginelike, and real engine conditions. The study was conducted under the scope of recent interest in metallic nanoparticles as alternative fuels for internal combustion engines. More specifically, Fe nanoparticles with different morphologies and average primary particle sizes ranging from 25 to 85 nm were studied with respect to their oxidation characteristics via thermogravimetric analysis as well as in customized shock tube, constant-volume vessel, and compression-ignition (CI) engine configurations. Combusted powder samples were in all cases examined via in situ and ex situ techniques for the identification of combustion products and their morphologies. The findings facilitated the determination of the main phenomena involved during oxidation. The results verified that combustion of Fe nanoparticles in a slightly modified CI engine is feasible, albeit with various technological challenges related to ignition and scavenging that inhibit combustion quality.The authors thank the European Commission for partial
funding of this work through the Project “COMETNANO”
(FP7-NMP4-SL-2009-229063).Mandilas, C.; Karagiannakis, G.; Konstandopoulos, AG.; Beatrice, C.; Lazzaro, M.; Di Blasio, G.; Molina, S.... (2016). Study of Oxidation and Combustion Characteristics of Iron Nanoparticles under Idealized and Enginelike Conditions. Energy and Fuels. 30(5):4318-4330. https://doi.org/10.1021/acs.energyfuels.6b00121S4318433030
Evolution of faint radio sources in the VIDEO-XMM3 field
© 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical SocietyIt has been speculated that low-luminosity radio-loud active galactic nuclei (AGN) have the potential to serve as an important source of AGN feedback, and may be responsible for suppressing star formation activity in massive elliptical galaxies at late times. As such the cosmic evolution of these sources is vitally important to understand the significance of such AGN feedback processes and their influence on the global star formation history of the Universe. In this paper, we present a new investigation of the evolution of faint radio sources out to z ~ 2.5. We combine a 1 square degree Very Large Array radio survey, complete to a depth of 100 μJy, with accurate 10 band photometric redshifts from the following surveys: Visible and Infrared Survey Telescope for Astronomy Deep Extragalactic Observations and Canada-France-Hawaii Telescope Legacy Survey. The results indicate that the radio population experiences mild positive evolution out to z ~ 1.2 increasing their space density by a factor of ~3, consistent with results of several previous studies. Beyond z = 1.2, there is evidence of a slowing down of this evolution. Star-forming galaxies drive the more rapid evolution at low redshifts, z 1.2. The evolution is best fitted by pure luminosity evolution with star-forming galaxies evolving as (1 + z)2.47 ± 0.12 and AGN as (1 + z)1.18 ± 0.21M.Peer reviewe
Effects of low pressure exhaust gas recirculation on regulated and unregulated gaseous emissions during NEDC in a light-duty diesel engine
Regulated and unregulated gaseous emissions with high pressure and low pressure EGR (exhaust gas recirculation) system were tested in a 4-cylinder, light-duty diesel EURO IV engine typically used in European vehicles. Four different engine calibrations with the low pressure EGR system were studied. Regulated emissions of NOX, CO, HC and CO2 were measured for each configuration. Unburned Hydrocarbon Speciation, HCHO (formaldehyde), HCOOH (formic acid) and N2O (nitrous oxide) were also measured in order to determine the MIR (maximum incremental reactivity) of the gaseous emissions. Pollutants were measured without the DOC (diesel oxidation catalyst) to gather data about raw emissions. When the low pressure EGR system was used, decreases in NOX, N2O and fuel consumption were observed and significant increases HC, CO and unregulated emissions; this is the result of a lower intake manifold temperature, which provides a higher gas density which modifies the combustion process. The potential of tropospheric ozone production was higher in all cases when the low pressure EGR was used. © 2011 Elsevier Ltd.Bermúdez, V.; Luján, JM.; Pla Moreno, B.; Linares Rodríguez, WG. (2011). Effects of low pressure exhaust gas recirculation on regulated and unregulated gaseous emissions during NEDC in a light-duty diesel engine. Energy. 36(9):5655-5665. doi:10.1016/j.energy.2011.06.061S5655566536
Quantum Locality
It is argued that while quantum mechanics contains nonlocal or entangled
states, the instantaneous or nonlocal influences sometimes thought to be
present due to violations of Bell inequalities in fact arise from mistaken
attempts to apply classical concepts and introduce probabilities in a manner
inconsistent with the Hilbert space structure of standard quantum mechanics.
Instead, Einstein locality is a valid quantum principle: objective properties
of individual quantum systems do not change when something is done to another
noninteracting system. There is no reason to suspect any conflict between
quantum theory and special relativity.Comment: Introduction has been revised, references added, minor corrections
elsewhere. To appear in Foundations of Physic
The Bristol Method: Green Capital Student Capital - The power of student sustainability engagement
THE BRISTOL METHODThe Bristol Method is a knowledge-transfer programme aimed at helping people in other cities understand and apply the lessons that Bristol has learned in becoming a more sustainable city, not just in 2015 but in the last decade. Each module of the Bristol Method is presented as an easy-to-digest ‘how to’ guide on a particular topic, which use Bristol’s experiences as a case study. The modules contain generic advice and recommendations that each reader can tailor to their own circumstances.This module focusses on the Green Capital: Student Capital project, and explains how the University of the West of England, Bristol (UWE) and the University of Bristol – with their respective students’ unions – have been working in partnership with the city and local communities, using Higher Education Funding Council for England Catalyst funding to promote student involvement in Green Capital activities across Greater Bristol.Student Capital created a broad programme of citywide impact during European Green Capital. It delivered a programme of student and staff engagement in enhancing sustainability within the city and has developed student and staff engagement with sustainability action. Through action research approaches it is also providing lessons for how institutions can collaborate across cities and communities to have internal and external impacts for sustainability. This report is for anyone seeking to increase sustainability engagement. In it we tell the story of the Student Capital project, explaining the processes and the outcomes, and suggesting pieces of advice and lessons for what went well, and what could have been done better or differently
Design of synthetic EGR and simulation study of the effect of simplified formulations on the ignition delay of isooctane and n-heptane
[EN] A method to create synthetic mixtures that simulate the Exhaust Gas Recirculation (EGR) of an internal
combustion engine, using O2, N2, CO2, H2O and Ar, has been designed. Different simplifications of this
synthetic EGR have been validated in order to reproduce ignition delays. To do this, a parametric study
has been carried out with CHEMKIN. The ignition delay of each simplified mixture and the ignition delay
of the complete mixture have been simulated for different initial pressures, temperatures, equivalence
ratios, oxygen mass fractions and for two different fuels, isooctane and n-heptane. The results obtained
with each simplification have been compared with the results obtained with the complete EGR, and
based on this comparison the errors in ignition delay have been calculated. The behavior of the errors
in ignition delay with the variation of the different parameters of the simulations has been studied. In
summary, it can be seen that the relative error increases with temperature and decreases with pressure,
equivalence ratio and oxygen mass fraction. Finally, the limit oxygen mass fractions for the use of each
simplification have been obtained. Based on these results, it can be concluded that the only gas that
can be obviated to keep the error in ignition delay under 1% is ArThe authors would like to thank different members of the CMT-Motores Termicos team of the Universitat Politecnica de Valencia for their contribution to this work. The authors would also like to thank the Spanish Ministry of Education for financing the PhD. Studies of Dario Lepez-Pintor (Grant FPU13/02329). This work was partly founded by the Generalitat Valenciana, project PROMETEOII/2014/043.Desantes, J.; López, JJ.; Molina, S.; López Pintor, D. (2015). Design of synthetic EGR and simulation study of the effect of simplified formulations on the ignition delay of isooctane and n-heptane. Energy Conversion and Management. 96:521-531. https://doi.org/10.1016/j.enconman.2015.03.003S5215319
Using statistical and artificial neural networks to predict the permeability of loosely packed granular materials
Well-known analytical equations for predicting permeability are generally reported to overestimate this important property of porous media. In this work, more robust models developed from statistical (multivariable regression) and Artificial Neural Network (ANN) methods utilised additional particle characteristics [‘fines ratio’ (x50/x10) and particle shape] that are not found in traditional analytical equations. Using data from experiments and literature, model performance analyses with average absolute error (AAE) showed error of ~40% for the analytical models (Kozeny–Carman and Happel–Brenner). This error reduces to 9% with ANN model. This work establishes superiority of the new models, using experiments and mathematical techniques
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Life cycle (well-to-wheel) energy and environmental assessment of natural gas as transportation fuel in Pakistan
Consumers and organizations worldwide are searching for low-carbon alternatives to conventional gasoline and diesel vehicles to reduce greenhouse gas (GHG) emissions and their impact on the environment. Natural gas as an alternative transportation fuel has made significant inroads in the light and heavy duty vehicles market over the last fifteen years. In a sustainable development view, both vehicle emissions and energy supply chain analysis from well-to-wheel must be addressed. The aim of this research is to provide a Well-to-Wheel (WtW) assessment of energy consumptions and GHG emissions for 25 combinations of automotive fuel and matching powertrain systems, with a special focus on the natural gas pathways. Although several well-to-wheel studies available in literature are comprehensive in relation to developed countries’ conditions, it is problematic to apply the results to developing countries fuel markets, since the local fuel conditions and respective vehicle powertrain technologies are considerably different. This study deal with a comparative well-to-wheel analysis of natural gas, diesel and gasoline fuels looking at the Pakistanis situation but the models and approaches for this study can be applied to other countries having similar characteristics, as long as all the assumptions are well defined and modified to find a substitute automotive energy source and establish an energy policy in a specific region. The well-to-tank step was made using the GREET model, developed by the U.S. Argonne National Laboratory while tank-to-wheel analysis was performed using AVL Cruise, a commercially-available backward vehicle simulator. Later both stages were integrated in a well-to-wheel stage where relevant indexes were proposed and discussed. The results indicate that natural gas vehicles are 5 – 17% and 23 – 36% less fuel efficient, depending on the engine technology employed as compared to gasoline and diesel powertrain, respectively. Natural gas appears as an environmental efficient pathway regarding GHG emissions, especially compared to gasoline. In addition, using 20-year GWPs instead of 100-year GWPs increases WtW GHG emissions by 19–26% for natural gas pathways
Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy
Background
A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets.
Methods
Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis.
Results
A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001).
Conclusion
We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty
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