12,664 research outputs found
Sensible heat flux of oil palm plantation: Comparing Aerodynamic and Penman-Monteith Methods
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Differential stability of 2'F-ANA*RNA and ANA*RNA hybrid duplexes: roles of structure, pseudohydrogen bonding, hydration, ion uptake and flexibility
No full text14 pags., 7 figs., 3 tabs.Hybrids of RNA with arabinonucleic acids 2′F-ANA and ANA have very similar structures but strikingly different thermal stabilities. We now present a thorough study combining NMR and other biophysical methods together with state-of-the-art theoretical calculations on a fully modified 10-mer hybrid duplex. Comparison between the solution structure of 2′F-ANA•RNA and ANA•RNA hybrids indicates that the increased binding affinity of 2′F-ANA is related to several subtle differences, most importantly a favorable pseudohydrogen bond (2′F-purine H8) which contrasts with unfavorable 2′-OH-nucleobase steric interactions in the case of ANA. While both 2′F-ANA and ANA strands maintained conformations in the southern/eastern sugar pucker range, the 2′F-ANA strand's structure was more compatible with the A-like structure of a hybrid duplex. No dramatic differences are found in terms of relative hydration for the two hybrids, but the ANA•RNA duplex showed lower uptake of counterions than its 2′F-ANA•RNA counterpart. Finally, while the two hybrid duplexes are of similar rigidities, 2′F-ANA single strands may be more suitably preorganized for duplex formation. Thus the dramatically increased stability of 2′F-ANA•RNA and ANA•RNA duplexes is caused by differencesin at least four areas, of which structure and pseudohydrogen bonding are the most important. © The Author(s) 2010. Published by Oxford University Press.Spanish Ministerio de Ciencia e Innovacion (grants
CTQ2007-68014-C02-02 to CG and BIO2009-10964 to
MO); Fundacion Marcelino Botin (grant to MO);
Canadian Institutes for Health Research (grant to
M.J.D.); Natural Sciences and Engineering Research
Council of Canada (postgraduate scholarship to
J.K.W.). Funding for open access charge: Canadian
Institutes for Health Research
Water management reduces greenhouse gas emissions in a Mediterranean rice paddy field
No full textRice paddy fields are one of the largest anthropogenic sources of methane (CH4), the second most important anthropogenic greenhouse gas (GHG) after carbon dioxide (CO2). For this reason most studies on the GHG budget in these agricultural systems focus on the evaluation of CH4 production. However, these systems also exchange other GHGs with the atmosphere, such as CO2 and nitrous oxide (N2O). To estimate the total global warming potential (GWP) of rice cultivation, a field experiment was carried out in a Mediterranean rice paddy field in the Po Valley (Italy), the largest rice producing region in Europe. For two consecutive years, ecosystem CO2 and CH4 fluxes were assessed using the eddy covariance technique and CH4 and N2O fluxes were measured with closed chambers. The net biome productivity indicated a nearly carbon (C) neutral system in 2009 while it accumulated C in 2010, due to the application of organic fertilizers and the midseason drainage of the otherwise flooded field, the latter having the additional benefit of leading to lower water consumption. The rice paddy field acted as a strong GHG source with a GWP of 1148 g CO(2-)eq m(-2) yr(-1) in 2009 and decreased four-fold in 2010 (289 g CO(2-)eq m(-2) yr(-1)). In both years, the site was a large CH4 source. Differences in the GHG budget between the two years of measurements were mainly caused by the lower CH4 emissions in 2010 (21.0 g CH4 m(-2) compared to 37.4 g CH4 m(-2) in 2009), probably driven by drainage of the otherwise flooded field in the middle of the growing season during 2010 and moderately larger CO2 uptake. The increased N2O fluxes (29%), had a marginal contribution to the GWP. However, midseason drainage, which needs to be evaluated in combination with the concurrent application of organic fertilizers, resulted in small decreases of yield. Our results therefore suggest that an adequate management of the water table level reduces CH4 fluxes and has the potential to decrease the GWP and water losses through evapotranspiration of rice paddy fields, confirming that full GHG budgets should be assessed in combination with yields in order to develop and evaluate effective mitigation strategies. (C) 2016 Elsevier B.V. All rights reserved.FPVI project Nitroeurope-I
Comparison of Aerodynamic, Bowen-Ratio, and Penman-Monteith Methods in Estimating Evapotranspiration of Oil Palm Plantation
Full text linkOil palm is one important agricultural commodity that has high economic value. Oil palm productivity is significantly influenced by its water use (needs). Measurement and estimation of oil palm evapotranspiration is needed for determination of its water needs. Various methods are available and this study compare three methods, consisting of aerodynamic, Bowen-Ratio and Penman-Monteith methods in analyzing water needs/use of oil palms plantation located in PTPN VI Jambi. Peak of evapotranspiration rate occured in the afternoon around 13.00 and 14.00 local time. Bowen-Ratio method has higher estimation value of evapotranspiration than the other two methods. Ratio between evapotranspiration and global radiation of two and ten-years old oil palm plantations remain similar, around 47%. Penman Monteith method has the nearest estimation value to reference method (aerodynamic method) showed by the smallest RMSE value, 0.087 for two years oil palm and 0.157 for ten-years old oil palm
Oil palm plantations are large sources of nitrous oxide, but where are the data to quantify the impact on global warming?
Full text linkOil palm plantations have rapidly expanded over the last 30 years, and now occupy 10% of the world’s permanent cropland. The growth of one of the world’s most efficient and versatile crop has alleviated poverty and increased food and energy security, but not without side effects. Losses of forest biodiversity hits the news. Although equally important, climate change issues have not reached this limelight. Data on greenhouse gas emissions associated with oil palm production is limited, especially for the potent greenhouse gas nitrous oxide (N2O). This paper provides an overview of the data availability, and identifies knowledge gaps to steer future research to provide the data required for climate change models and more accurate international and national nitrous oxide emission accounting
Expansion of oil palm and other cash crops causes an increase of the land surface temperature in the Jambi province in Indonesia
Full text linkIndonesia is currently one of the regions with the highest transformation rate of land surface worldwide related to the expansion of oil palm plantations and other cash crops replacing forests on large scales. Land cover changes, which modify land surface properties, have a direct effect on the land surface temperature (LST), a key driver for many ecological functions. Despite the large historic land transformation in Indonesia toward oil palm and other cash crops and governmental plans for future expansion, this is the first study so far to quantify the impacts of land transformation on the LST in Indonesia. We analyze LST from the thermal band of a Landsat image and produce a high-resolution surface temperature map (30 m) for the lowlands of the Jambi province in Sumatra (Indonesia), a region which suffered large land transformation towards oil palm and other cash crops over the past decades. The comparison of LST, albedo, normalized differenced vegetation index (NDVI) and evapotranspiration (ET) between seven different land cover types (forest, urban areas, clear-cut land, young and mature oil palm plantations, acacia and rubber plantations) shows that forests have lower surface temperatures than the other land cover types, indicating a local warming effect after forest conversion. LST differences were up to 10.1 ± 2.6 °C (mean ± SD) between forest and clear-cut land. The differences in surface temperatures are explained by an evaporative cooling effect, which offsets the albedo warming effect. Our analysis of the LST trend of the past 16 years based on MODIS data shows that the average daytime surface temperature in the Jambi province increased by 1.05 °C, which followed the trend of observed land cover changes and exceeded the effects of climate warming. This study provides evidence that the expansion of oil palm plantations and other cash crops leads to changes in biophysical variables, warming the land surface and thus enhancing the increase of the air temperature because of climate change
Measured greenhouse gas budgets challenge emission savings from palm-oil biodiesel
Full text linkSpecial
thanks to our field assistants in Indonesia (Basri, Bayu and Darwis) and to Frank Tiedemann,
Edgar Tunsch, Dietmar Fellert and Malte Puhan for technical assistance. We
thank PTPN VI and the owner of the plantation at Pompa Air for allowing us to conduct
our research at their plantation. We would also like to thank the Spanish national project
GEISpain (CGL2014-52838-C2-1-R) and the DAAD (scholarship from the programme
‘Research Stays for University Academics and Scientist 2018, ref. no. 91687130)' for
partly financing A. Meijide during the preparation of this paper.The potential of palm-oil biofuels to reduce greenhouse gas (GHG) emissions compared with fossil fuels is increasingly questioned. So far, no measurement-based GHG budgets were available, and plantation age was ignored in Life Cycle Analyses (LCA). Here, we conduct LCA based on measured CO2, CH4 and N2O fluxes in young and mature Indonesian oil palm plantations. CO2 dominates the on-site GHG budgets. The young plantation is a carbon source (1012 ± 51 gC m−2 yr−1), the mature plantation a sink (−754 ± 38 gC m−2 yr−1). LCA considering the measured fluxes shows higher GHG emissions for palm-oil biodiesel than traditional LCA assuming carbon neutrality. Plantation rotation-cycle extension and earlier-yielding varieties potentially decrease GHG emissions. Due to the high emissions associated with forest conversion to oil palm, our results indicate that only biodiesel from second rotation-cycle plantations or plantations established on degraded land has the potential for pronounced GHG emission savings.This study was financed by the Deutsche Forschungsgemeinschaft (DFG, German
Research Foundation)— Project-ID 192626868—in the framework of the collaborative
German-Indonesian research project CRC990 (subprojects A03, A04 and A05).Spanish national project GEISpain (CGL2014-52838-C2-1-R) and the DAAD (scholarship from the programme ‘Research Stays for University Academics and Scientist 2018, ref. no. 91687130
Representações da sexualidade na obra de Ana Saldanha
Full text linkMestrado em Línguas, Literaturas e CulturasA presente dissertação analisa as diferentes representações da sexualidade na obra literária para jovens de Ana Saldanha. A leitura analítica incide sobre as narrativas da autora que abordam a temática da sexualidade juvenil e as suas problemáticas, com o objetivo de estudar a forma como as mesmas contribuem para a construção da identidade pessoal e sexual do potencial recetor juvenil. Desta forma, pretende-se detetar os conflitos psicológicos dos protagonistas, os seus valores e problemas, assim como os novos valores, problemas e preocupações sociais que emergem das narrativas; compreender de que forma a autora exprime a sua capacidade em observar o quotidiano e as relações humanas; identificar os pilares em que se apoia o universo social em estudo (família, escola, grupo de amigos); enquadrar as personagens numa sociedade pós-industrial e de informação que exige ao adolescente uma superação de desafios e de novos problemas.This dissertation analyzes the different representations of sexuality in Ana Saldanha’s literary work for youth. The analytical reading focuses on the author's narratives that address the issue of teenage sexuality and its problems, aiming to study their contribution in the construction of personal and sexual identity of the potential juvenile receiver. Thus, it is intended to detect the psychological conflicts of the protagonists, their values and problems, as well as the new values, social concerns and problems that emerge from the narratives; understand how the author expresses her ability to observe daily life and human relations; identify the pillars on which relies the social universe under study (family, school, friends); framing the characters in a post-industrial and information society which requires the teenager to relentlessly surmount challenges and new problems
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