4,490 research outputs found
Elucidating genomic regions determining enhanced leaf growth and delayed senescence in elevated carbon dioxide
No full textLimited information is available on the genetic variation and control for plant growth response to elevated CO2 (e[CO2]). Such information is necessary to understand plant adaptation and evolution in future rising CO2. Here, quantitative trait loci (QTL) for leaf growth, development, quality and leaf senescence were determined in a tree pedigree – an F2 hybrid of Populus trichocarpa T. & G and Populus deltoides Marsh, following season-long exposure to either current day ambient carbon dioxide (a[CO2]) or e[CO2] at 600 µL L1. Leaf growth and development differed between the grandparents such that P. trichocarpa showed greater response to e[CO2]. In the F2 generation, leaf development and quality traits including leaf area, leaf shape, epidermal cell area, and stomatal number, specific leaf area (SLA), and the phenology trait, canopy senescence index, were sensitive to e[CO2]. Sixty-nine QTL were mapped for the 19 traits of plants in a[CO2] while 60 QTL were mapped for plants in e[CO2]. The results suggest that although many QTL mapped to common positions in a[CO2] and e[CO2], confirming their importance in determining growth, there was also differential genetic control for a number of traits including leaf senescence. Candidate genes were shown to collocate to regions where response QTL mapped. This study is the first to identify candidate genes that may be important in determining plant adaptation to future high-CO2 world.<br/
The physiological, transcriptional and genetic responses of an ozone-sensitive and an ozone tolerant poplar and selected extremes of their F2 progeny
No full textRelatively little is known about the transcriptional response or genetic control of response and adaptation of trees to tropospheric ozone exposure. Such understanding is needed as up to 50% of forests, globally, may be subjected to phytotoxic concentrations of ozone. The physiological, transcriptional and genetic response to ozone was examined in Populus trichocarpa and P. deltoides, which show extreme sensitivity and tolerance to ozone, respectively. Using an inbred F(2) mapping population derived from these two species, we mapped quantitative trait loci (QTL) for traits associated with ozone response, examined segregation of the transcriptional response to ozone and co-located genes showing divergent responses between tolerant and sensitive genotypes with QTL. QTL were identified linking detrimental effects of ozone with leaf and biomass traits and differential responses were found for key genes involved in ethylene production and response
The technical potential of Great Britain to produce ligno cellulosic biomass for bioenergy in current and future climates
No full textProcess and empirical-based models that describe lignocellulosic biomass yield of the perennial energy grass Miscanthus (MiscanFor©), short rotation coppice (SRC) trees and shrubs, poplar and willow (ForestGrowth-SRC) and a number of short rotation forest trees (ESC-CARBINE), were used to estimate the yield potential for current and future climates across Great Britain (GB). In current climates, modelled yields for all feedstock crops varied between 8.1 and 10.6 Mg dry weight (DW) ha?1 yr?1 with willow SRC and poplar SRF producing the lowest and highest yields respectively. For the medium emissions scenario (UKCP09) in 2050, mean yield for all feedstock crops varied between 7.6 and 12.7 Mg DW ha?1 yr?1 with willow SRC and poplar SRF once again the lowest and the highest recorded yields. There were clear geographical trends within GB. Miscanthus yield was higher than all others in the south-west (13.1 Mg DW ha?1 yr?1), SRC willow and SRC poplar in the north-west (12.1–15.8 Mg DW ha?1 yr?1) and in the midlands and south-east, SRF poplar was the highest yielding (10.5–11.6 Mg DW ha?1 yr?1). These geographical trends changed little with climate out to 2050, with mean yield of each ‘best feedstock’ increasing from 12.7 to 14.2 Mg DW ha?1 yr?1. Out to 2050, SRC declined slightly and Miscanthus and SRF poplar increased as the ‘best feedstock’ option. Except for a few localized examples, only SRF poplar had a higher yield than SRC or Miscanthus. These data suggest that in current and future climates, lignocellulosic biomass plantation species can be selected and optimized for best yield performance in different regions of GB. This modelling framework provides a valuable starting-point for which to test the performance of new genetic material, as this becomes available and parameterized for the models and socio-economic scenarios that may impact on the bioenergy industry
Development and evaluation of ForestGrowth-SRC a process-based model for short rotation coppice yield and spatial supply reveals poplar uses water more efficiently than willow
No full textVacuum Insulation Panels Applied in Building Constructions
No full textDue to sustainability and due to international treaties, it is desired and required to reduce greenhouse gas emissions drastically. One contributor to these emissions is the burning of fossil fuels for generating power and electricity to be used in and for buildings. Buildings and building-related processes are responsible for about 40% of the primary energy consumption in the European Union. More than half of this energy is applied for heating systems in dwellings and commercial buildings. The European Union therefore has laid down new energy performance requirements for buildings in the European Directive on the Energy Performance of Buildings. Moreover, a reduction of energy losses of buildings during their occupational phase is important for facilitating the implementation of sustainable energy sources in the built environment. Increasing the insulation value of the envelope of buildings may contribute to this reduction of primary energy use. Two strategies can be followed. The first strategy is to increase the thickness of the thermal insulation layer. Until recently, this strategy has primarily been adopted. If, however, German or Swiss Passivhaus standard is applied, the thickness of this insulation layer would increase to beyond 30 cm, resulting in very thick building enclosures. The second, more innovative, strategy for reducing energy losses through the building skin would be the application of more effective thermal insulators. One such more effective thermal insulator is a vacuum insulation panel, abbreviated as VIP. A VIP consists of an open-celled core material which is evacuated and then tightly sealed into a barrier envelope to maintain this vacuum. The vacuum inside the pores of the core material reduces the thermal conductivity of the product significantly, as a result of which the thickness of the insulation layer can be reduced to obtain a certain performance. This reduction of thickness is among the most promising features for large-scale application of VIPs in the building industry. However, integration of VIPs into buildings must be performed very meticulously for several reasons; first, due to its nature a VIP cannot be processed on site and needs careful planning in advance; second, it is very sensitive to mechanical damage thus requiring careful handling; third, thermal bridges along the panel’s edges reduce its performance; fourth, the composite system is highly subjected to aging. This dissertation therefore looks into many of these aspects, presents several calculation tools and shows how VIPs can be applied in façade panels, EPS insulation boards and as under-floor insulation. With the wide-spread proliferation of VIPs in buildings a more sustainable and healthy environment can then be achieved.Building TechnologyArchitectur
Validating the MERIS Terrestrial Chlorophyll Index (MTCI) with ground chlorophyll content data at MERIS spatial resolution
No full textThe Medium Resolution Imaging Spectrometer (MERIS) Terrestrial Chlorophyll Index (MTCI), a standard level 2 European Space Agency (ESA) product, provides information on the chlorophyll content of vegetation (amount of chlorophyll per unit area of ground). This is a combination of information on Leaf Area Index (LAI, area of leaves per unit area of ground) and the chlorophyll concentration of those leaves. The MTCI correlates strongly with chlorophyll content when using model, laboratory and field spectrometry data. However, MTCI calculated with MERIS data has only been correlated with surrogate chlorophyll content data. This is because of the logistical difficulties of determining the chlorophyll content of the area covered by a MERIS pixel (9 × 104 m2). This paper reports the first attempt to determine the relationship between MTCI and chlorophyll content using actual MERIS data and actual chlorophyll content data.During the summer of 2006 LAI and chlorophyll concentration data were collected for eight large (> 25 ha) fields around Dorchester in southern England. The fields contained six crops (beans, linseed, wheat, grass, oats and maize) at different stages of maturity and with different canopy structures, LAIs and chlorophyll concentrations. A stratified sampling method was used in which each field contained sampling units in proportion to the spatial variability of the crop. Within each unit 25 random points were sampled. This approach captured the variability of the field and reduced the potential bias introduced by the planting pattern or later agricultural treatments (e.g. pesticides or herbicides). At each random point LAI was estimated using an LAI-2000 plant canopy analyser and chlorophyll concentration was estimated using a Minolta-SPAD chlorophyll meter. In addition, for each field a calibration set of 30 contiguous SPAD measurements and associated leaf samples were collected.The relationship between MTCI and chlorophyll content was positive. The coefficient of determination (R 2) was 0.62, root mean square error (RMSE) was 244 g per MERIS pixel and accuracy of estimation (in relation to the mean) was 65%. However, one field included a high proportion of seed heads, which artificially increased the measured LAI and thus chlorophyll content. Removal of this field from the dataset resulted in a stronger relationship between MTCI and chlorophyll content with an R 2 of 0.8, an RMSE of 192 g per MERIS pixel and accuracy of estimation (in relation to the mean) of 71%.<br/
The potential for bioenergy crops to contribute to meeting GB heat and electricity demands
No full textThe paper presents a model system, which consists of a partial equilibrium model and process-based terrestrial biogeochemistry models, to determine the optimal distributions of both Miscanthus (Miscanthus × giganteus) and short rotation coppice willow (SRC) (Salix. viminalis L. x S. viminalis var Joruun) in Great Britain (GB), as well as their potential contribution to meet heat and electricity demand in GB. Results show that the potential contribution of Miscanthus and SRC to heat and electricity demand is significant. Without considering farm-scale economic constraints, Miscanthus and SRC could generate, in an economically competitive way compared with other energy generation costs, 224 800 GWh yr?1 heat and 112 500 GWh yr?1 electricity, with 8 Mha of available land under Miscanthus and SRC, accounting for 66% of total heat demand and 62% of total electricity demand respectively. Given the pattern of heat and electricity demand, and the relative yields of Miscanthus and SRC in different parts of GB, Miscanthus is mainly favoured in the Midlands and areas in the South of GB, whereas SRC is favoured in Scotland, the Midlands and areas in the South of G
Book Review: Reginald M.J. Oduor’s Introduction to Ethics
No full textTITLE OF BOOK: Introduction to Ethics
AUTHOR: Reginald M.J. Oduor
Nairobi: Sophia Publications Ltd., 2009, 116 pages
COVER: Paperback
ISBN: 9966-7457-0-X
This book is a product of more than a decade of Oduor’s experience in teaching ethics (moral philosophy) at the University of Nairobi. In the course of this introduction, the reader gets to see the techniques of philosophic reflection in action, as they are employed to scrutinise various pertinent moral questions
Placebo effects of caffeine on maximal voluntary concentric force of the knee flexors & extensors
No full textIntroduction: We examined the placebo effect of caffeine and the combined effect of caffeine and caffeine expectancy on maximal voluntary strength. Methods: Fourteen men completed 4 randomized single-blind experimental trials: 1) Told caffeine, given caffeine (5mg.kg) (CC); 2) Told caffeine, given placebo (CP); 3) Told placebo, given placebo (PP); 4) Told placebo, given caffeine (PC). Maximal voluntary concentric force and fatigue resistance of the knee flexors and extensors was measured using isokinetic dynamometry. Results: A significant and equal improvement in peak concentric force was found in the CC and PC trials. Despite participants believing caffeine would evoke a performance benefit, there was no effect of CP. Conclusion: Caffeine caused an improvement in some aspects of muscle strength, however there was no additional effect of expectancy. Performance was poorer in participants who believed caffeine would have the largest benefit, which highlights a link between expected ergogenicity, motivation, and personality characteristics. Publisher statement: This is the peer reviewed version of the following article: Tallis, J. , Muhammad, B. , Islam, M. and Duncan, M.J. (2016) Placebo effects of caffeine on maximal voluntary concentric force of the knee flexors & extensors. Muscle & Nerve, volume 54 (3): 479-486, which has been published in final form at http://dx.doi.org/10.1002/mus.25060 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving
Comments on “Precipitation kinetics of Al–1.12Mg2Si–0.35Si and Al–1.07Mg2Si–0.33Cu alloys”
No full textIt is shown that in analysing DSC data of precipitation reactions in Al–1.12Mg2Si–0.35Si, Al–1.07Mg2Si–0.33Cu and Al–1.0Mg2Si–0.5Ag alloys in work by Gaber et al., accurate values for the activation energies are obtained by applying the method derived by the present author (the Type B-1.92 method). Values obtained from other analysis methods reported by Gaber et al. are less accurate. Averaging activation energies obtained by different methods introduces inaccuracies and obscures these inaccuracies, especially if the set of methods applied includes highly inaccurate ones, such as the Ozawa and Takhor methods
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