93 research outputs found

    Differences in isoprene and monoterpene emissions from cold-tolerant eucalypt species grown in the UK

    Get PDF
    The UK may be required to expand its bioenergy production in order to make a significant contribution towards the delivery of its ‘net zero’ greenhouse gas emissions target by 2050. However, some trees grown for bioenergy are emitters of volatile organic compounds (VOCs), including isoprene and terpenes, precursors in the formation of tropospheric ozone, an atmospheric pollutant, which require assessment to understand any consequent impacts on air quality. In this initial scoping study, VOC emission rates were quantified under UK climate conditions for the first time from four species of eucalypts suitable for growing as short-rotation forest for bioenergy. An additional previously characterised eucalypt species was included for comparison. Measurements were undertaken using a dynamic chamber sampling system on 2-3 year-old trees grown under ambient conditions. Average emission rates for isoprene, normalised to 30 °C and 1000 μmol m−2 s−1 PAR, ranged between 1.3 μg C gdw−1 h−1 to 10 μg C gdw−1 h−1. All the eucalypt species measured were categorised as ‘medium’ isoprene emitters (1–10 μg C gdw−1 h−1). Total normalised monoterpene emission rates were of similar order of magnitude to isoprene or approximately one order of magnitude lower. The composition of the monoterpene emissions differed between the species and major compounds included eucalyptol, α-pinene, limonene and β-cis-ocimene. The emission rates presented here contribute the first data for further studies to quantify the potential impact on UK atmospheric composition, if there were widespread planting of eucalypts in the UK for bioenergy purposes

    A comparison of isoprene and monoterpene emission rates from the perennial bioenergy crops short-rotation coppice willow and Miscanthus and the annual arable crops wheat and oilseed rape

    Get PDF
    Biogenic volatile organic compounds (BVOC) emissions from bioenergy crops may differ from those of conventional crops. We compared emission rates of isoprene and a number of monoterpenes from the lignocellulosic bioenergy crops short-rotation coppice (SRC) willow and Miscanthus, with the conventional crops wheat and oilseed rape. BVOC emission rates were measured via dynamic vegetation enclosure and GC-MS analysis approximately monthly between April 2010 and August 2012 at a location in England and from SRC willow at two locations in Scotland. The largest BVOC emission rates were measured from willow in England, and varied between years. Isoprene emission rates varied between <lod and 1960 μg g−1 h−1. Of the monoterpenes detected from willow, α-pinene emission rates were highest (<lod to 803 μg g−1 h−1), followed by <lod to 268 μg g−1 h−1 for δ-3-carene, <lod to 125 μg g−1 h−1 for β-pinene and <lod to 80.4 μg g−1 h−1 for limonene. BVOC emission rates measured in Scotland were much lower. Low emission rates of isoprene and α-pinene were measured from Miscanthus in 2010 (<lod to 6.42 μg g−1 h−1 and <lod to 20.8 μg g−1 h−1, respectively) but were not detected in subsequent years. Emission rates from wheat of isoprene were negligible but relatively high for monoterpenes (<lod to 422 μg g−1 h−1 and <lod to 104 μg g−1 h−1 for α-pinene and limonene, respectively). No significant emission rates of BVOCs were measured from oilseed rape. The measured emission rates followed a clear seasonal trend. Crude extrapolations based solely on data gathered here indicate that isoprene emissions from willow could correspond to 0.004-0.03% (UK) and 0.76-5.5% (Europe) of current global isoprene if 50% of all land potentially available for bioenergy crops is planted with willow

    The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits: IV. Gravitational instability rarely forms wide, giant planets<sup>⋆</sup>

    Get PDF
    Understanding the formation and evolution of giant planets (≥\ge1 MJupM_{Jup}) at wide orbital separation (≥\ge5 AU) is one of the goals of direct imaging. Over the past 15 years, many surveys have placed strong constraints on the occurrence rate of wide-orbit giants, mostly based on non-detections, but very few have tried to make a direct link with planet formation theories. In the present work, we combine the results of our previously published VLT/NaCo large program with the results of 12 past imaging surveys to constitute a statistical sample of 199 FGK stars within 100 pc, including 3 stars with sub-stellar companions. Using Monte Carlo simulations and assuming linear flat distributions for the mass and semi-major axis of planets, we estimate the sub-stellar companion frequency to be within 0.75-5.7% at the 68% confidence level (CL) within 20-300 AU and 0.5-75 MJupM_{Jup}, which is compatible with previously published results. We also compare our results with the predictions of state-of-the-art population synthesis models based on the gravitational instability (GI) formation scenario by Forgan & Rice (2013), with and without scattering. We estimate that in both the scattered and non-scattered populations, we would be able to detect more than 30% of companions in the 1-75 MJupM_{Jup} range (95% CL). With the 3 sub-stellar detections in our sample, we estimate the fraction of stars that host a planetary system formed by GI to be within 1.0-8.6% (95% CL). We also conclude that even though GI is not common, it predicts a mass distribution of wide-orbit massive companions that is much closer to what is observed than what the core accretion scenario predicts. Finally, we associate the present paper with the release of the Direct Imaging Virtual Archive (DIVA, http://cesam.lam.fr/diva/), a public database that aims at gathering the results of past, present, and future direct imaging surveys.Comment: 20 pages, 11 figures. Accepted for publication in A&

    Higher gametocyte production and mosquito infectivity in chronic compared to incident Plasmodium falciparum infections.

    Get PDF
    Plasmodium falciparum gametocyte kinetics and infectivity may differ between chronic and incident infections. In the current study, we assess parasite kinetics and infectivity to mosquitoes among children (aged 5-10 years) from Burkina Faso with (a) incident infections following parasite clearance (n = 48) and (b) chronic asymptomatic infections (n = 60). In the incident infection cohort, 92% (44/48) of children develop symptoms within 35 days, compared to 23% (14/60) in the chronic cohort. All individuals with chronic infection carried gametocytes or developed them during follow-up, whereas only 35% (17/48) in the incident cohort produce gametocytes before becoming symptomatic and receiving treatment. Parasite multiplication rate (PMR) and the relative abundance of ap2-g and gexp-5 transcripts are positively associated with gametocyte production. Antibody responses are higher and PMR lower in chronic infections. The presence of symptoms and sexual stage immune responses are associated with reductions in gametocyte infectivity to mosquitoes. We observe that most incident infections require treatment before the density of mature gametocytes is sufficient to infect mosquitoes. In contrast, chronic, asymptomatic infections represent a significant source of mosquito infections. Our observations support the notion that malaria transmission reduction may be expedited by enhanced case management, involving both symptom-screening and infection detection

    The ethical nature of critical research in information systems.

    Get PDF
    Critical research in information systems is based on and inspired by ethics and morality. In order to support this proposition, this paper will suggest a way of classifying critical research that differs from definitions common IS research. According to the current definition, research is critical when it is motivated by the intention to change social realities and promote emancipation. Based on this critical intention, critical research is furthermore characterized by critical topics, critical theories, and critical methodologies. Using these criteria of critical research, the paper argues that critical research is ethical in nature. To support this view, the paper introduces the concepts of ethics and morality by analysing two traditions of moral philosophy, here called the ‘German tradition’ and the ‘French tradition’. Using three examples of current critical research in information systems, the paper will show that ethics and morality strongly influence critical intention, topics and theories. Having thus established the ethical nature of critical research, the paper concludes by discussing the weaknesses of critical research from the point of view of ethics and morality

    Integrative neurobiology of metabolic diseases, neuroinflammation, and neurodegeneration

    Get PDF
    Alzheimer’s disease (AD) is a complex, multifactorial disease with a number of leading mechanisms, including neuroinflammation, processing of amyloid precursor protein (APP) to amyloid β peptide, tau protein hyperphosphorylation, relocalization and deposition. These mechanisms are propagated by obesity, the metabolic syndrome and type-2 diabetes mellitus. Stress, sedentariness, dietary overconsumption of saturated fat and refined sugars, and circadian derangements/disturbed sleep contribute to obesity and related metabolic diseases, but also accelerate age-related damage and senescence that all feed the risk of developing AD too. The complex and interacting mechanisms are not yet completely understood and will require further analysis. Instead of investigating AD as a mono- or oligocausal disease we should address the disease by understanding the multiple underlying mechanisms and how these interact. Future research therefore might concentrate on integrating these by systems biology approaches, but also to regard them from an evolutionary medicine point of view. The current review addresses several of these interacting mechanisms in animal models and compares them with clinical data giving an overview about our current knowledge and puts them into an integrated framework

    Biogenic volatile organic compounds as a potential stimulator for organic contaminant degradation by soil microorganisms

    Get PDF
    The effects of monoterpenes on the degradation of 14C-2,4-dichlorophenol (DCP) were investigated in soils collected from areas surrounding monoterpene and non-monoterpene emitting vegetation. Indigenous microorganisms degraded 14C-2,4-DCP to 14CO2, after 1 d contact time. Degradation was enhanced by prior exposure of the soils to 2,4-DCP for 32 d, increasing mineralization extents up to 60%. Monoterpene amendments further enhanced 2,4-DCP degradation, but only following pre-exposure to both 2,4-DCP and monoterpene, with total 2,4-DCP mineralisation extents of up to 71%. Degradation was greatest at the higher monoterpene concentrations (≥ 1 μg kg-1). Total mineralisation extents were similar between concentrations, but higher than the control and the 0.1 μg kg-1 amendment, indicating that increases in monoterpene concentration has a diminishing enhancing effect. We suggest that monoterpenes can stimulate the biodegradation of 2,4-DCP by indigenous soil microorganisms and that monoterpene amendment in soils is an effective strategy for removing organic contaminants
    • …
    corecore