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  • 1
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    Source and sink carbon dynamics and carbon allocation in the Amazon basin (2015)
    Wiley
    Details
    Publication Date: 2015-04-25
    Description: Changes to the carbon cycle in tropical forests could affect global climate, but predicting such changes has been previously limited by lack of field based data. Here we show seasonal cycles of the complete carbon cycle for fourteen, one hectare intensive carbon cycling plots which we separate into three regions: humid lowland, highlands and dry lowlands. Our data highlight three trends: (1) there is differing seasonality of total NPP with the highlands and dry lowlands peaking in the dry season and the humid lowland sites peaking in the wet season; (2) seasonal reductions in wood NPP are not driven by reductions in total NPP but by carbon during the dry season being preferentially allocated towards either roots or canopy NPP; and (3) there is a temporal decoupling between total photosynthesis and total carbon usage or plant carbon expenditure (PCE). This decoupling indicates the presence of non-structural carbohydrates (NSC) which may allow growth and carbon to be allocated when it is most ecologically beneficial rather when it is most environmentally available.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Identification and use of white clayey deposits from the area of Tamra (northern Tunisia) as ceramic raw materials (2011)
    Mineralogical Society of Great Britain and Ireland
    Details
    Publication Date: 2011-03-18
    Description: White clayey geomaterials were collected from northeast of the Nefza region (northern Tunisia). These deposits belong to the Mio-Pliocene molassic basins (basin of Tamra-Sidi Dris, Boukhchiba) and Oligocene Numidien in the area of El Aouinet. Analysis by X-ray diffraction showed associations of halloysite and kaolinite (Tamra), kaolinite and illite (Aouinet zone) and mixed layers, kaolinite and feldspars (Boukhchiba zone). Semi-industrial processed bricks showed promising characteristics and were visibly free of defects. Ceramic tiles had a bending strength that met the required standards but water absorption was somewhat high. So, to achieve higher quality, optimisation needs to be carried out in the formulation of batches or in the processing conditions. Finally, the incorporation in whitish sanitary-ware glaze formulations generated smooth coating layers that showed the required strong brightness and were free of defects.
    Print ISSN: 0009-8558
    Electronic ISSN: 1471-8030
    Topics: Geosciences
    Published by Mineralogical Society of Great Britain and Ireland
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  • 3
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    Drought impact on forest carbon dynamics and fluxes in Amazonia (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-03-06
    Description: In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23-0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the absence of growth. We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Doughty, Christopher E -- Metcalfe, D B -- Girardin, C A J -- Amezquita, F Farfan -- Cabrera, D Galiano -- Huasco, W Huaraca -- Silva-Espejo, J E -- Araujo-Murakami, A -- da Costa, M C -- Rocha, W -- Feldpausch, T R -- Mendoza, A L M -- da Costa, A C L -- Meir, P -- Phillips, O L -- Malhi, Y -- England -- Nature. 2015 Mar 5;519(7541):78-82. doi: 10.1038/nature14213.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK. ; Department of Physical Geography and Ecosystem Science, Lund University, Solvegatan 12, 223 62 Lund, Sweden. ; Universidad Nacional San Antonio Abad de Cusco, Apartado Postal Nro 921, Cusco, Peru ; Museo de Historia Natural Noel Kempff Mercado, Universidad Autonoma Gabriel Rene Moreno, Av. Irala 565, Casilla 2489, Santa Cruz, Bolivia. ; Universidade Federal do Para, Instituto de Geociencias, Faculdade de Meteorologia, Rua Augusto Correa, n degrees 01, CEP 66075 - 110, Belem, Para, Brazil. ; IPAM Instituto de Pesquisa Ambiental da Amazonia Rua Horizontina, 104, Centro, 78640-000 Canarana, Mato Grosso, Brazil. ; Department of Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK. ; 1] School of Geosciences, University of Edinburgh, Edinburgh EH9 3FF, UK [2] Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia. ; School of Geography, University of Leeds, Leeds LS2 9JT, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25739631" target="_blank"〉PubMed〈/a〉
    Keywords: Brazil ; Carbon/*metabolism ; Carbon Dioxide/metabolism ; Cell Respiration ; *Droughts ; *Forests ; Photosynthesis ; Trees/cytology/metabolism ; *Tropical Climate
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 4
    Electronic Resource
    Electronic Resource
    Imazaquin mobility in tropical soils in relation to soil moisture and rainfall timing (2002)
    Oxford, UK : Blackwell Science Ltd
    Weed research 42 (2002), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This research studied the influence of soil type, soil moisture and incubation time before rain on the mobility of imazaquin in two highly weathered tropical soils, named clay and sandy clay. The soils were packed in glass columns and treated at three different moisture contents. Then, the applied imazaquin (150 g a.i. ha−1) was incubated for 0, 1 and 30 d before rainfall simulation began. Leaching was significantly higher in the sandy clay soil, when imazaquin was applied to moist samples and rainfall occurred soon after application (in this case, 73.4% of applied imazaquin was leached). Leaching was always low in the clay soil (in all cases, 〈1.8% of applied imazaquin was leached). In addition, imazaquin leaching potential was overestimated by the low Kd value (1.24 L kg−1) measured for the clay soil using batch equilibration data. For this soil, the vacuum displacement method also failed to predict leaching (in this case, 28.9% of applied imazaquin was leached). Consequently, batch equilibration and vacuum displacement methods cannot be used to predict leaching of anionic organic molecules, such as imazaquin, in fine-textured tropical soils. Moreover, soil type and weather patterns or irrigation timing must be considered before imazaquin application to avoid environmental or carry-over problems and to achieve maximum effectiveness of the herbicide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.2002.00284.x
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  • 5
    Electronic Resource
    Electronic Resource
    The relationship between vesicular-arbuscular mycorrhiza and lime: Associated effects on the growth and nutrition of brachiaria grass (Brachiaria decumbens) (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 65-71 
    Details
    ISSN: 1432-0789
    Keywords: Vesicular-arbuscular mycorrhiza ; Liming ; Endogonaceae ; Soil acidity ; Brachiaria grass ; Symbiosis ; Plant nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We studied the effects of limining on growth and nutrient concentrations of Brachiaria decumbens inoculated with five vesicular-arbuscular mycorrhizal (VAM) fungal assemblages which orginated from soils with different acidity. Liming increased plant growth when applied at rates up to 3 g kg-1 soil and depressed growth at higher rates. Mycorrhizal plants grew better than non-mycorrhizal ones in unlimed soil and also liming rates of 4.5 and 6.0 g kg-1 soil. The growth amelioration effects of VAM in highly acid or over-limed soils were related to nutrient uptake. VAM fungi isolated from an acidic soil exhibited a high symbiotic effectiveness and were better adapted to unlimed soil than those that originated from non-acidic soils. VAM root colonization, 90 days after planting, was little affected by liming. Fungal spore production and species compositions were highly affected by liming. A mixture of Glomus diaphanum and Glomus occultum predominated in unlimed soils inoculated with VAM assemblages isolated from non-acidic soils. In these fungal assemblages, an increased liming rate favored Glomus etunicatum over the other VAM fungi. Gigaspora margarita sporulated abundantly when introduced into unlimed soils, but rarely in limed soils. VAM appear to be crucial for the establishment of brachiaria pastures in the nutrient-deficient acidic soils of Central Brazil. It is suggested that liming may cause striking shifts in VAM populations which may, in turn, have a long-term impact on agricultural productivity in the tropics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336127
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  • 6
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    Increase in dNTP pool size during the DNA damage response plays a key role in spontaneous and induced-mutagenesis in Escherichia coli (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-11-14
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 7
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    Trypanosoma cruzi as an effective cancer antigen delivery vector [Immunology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-12-07
    Description: One of the main challenges in cancer research is the development of vaccines that induce effective and long-lived protective immunity against tumors. Significant progress has been made in identifying members of the cancer testis antigen family as potential vaccine candidates. However, an ideal form for antigen delivery that induces robust and sustainable antigen-specific T-cell responses, and in particular of CD8+ T lymphocytes, remains to be developed. Here we report the use of a recombinant nonpathogenic clone of Trypanosoma cruzi as a vaccine vector to induce vigorous and long-term T cell-mediated immunity. The rationale for using the highly attenuated T. cruzi clone was (i) the ability of the parasite to persist in host tissues and therefore to induce a long-term antigen-specific immune response; (ii) the existence of intrinsic parasite agonists for Toll-like receptors and consequent induction of highly polarized T helper cell type 1 responses; and (iii) the parasite replication in the host cell cytoplasm, leading to direct antigen presentation through the endogenous pathway and consequent induction of antigen-specific CD8+ T cells. Importantly, we found that parasites expressing a cancer testis antigen (NY-ESO-1) were able to elicit human antigen-specific T-cell responses in vitro and solid protection against melanoma in a mouse model. Furthermore, in a therapeutic protocol, the parasites expressing NY-ESO-1 delayed the rate of tumor development in mice. We conclude that the T. cruzi vector is highly efficient in inducing T cell-mediated immunity and protection against cancer cells. More broadly, this strategy could be used to elicit a long-term T cell-mediated immunity and used for prophylaxis or therapy of chronic infectious diseases.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    Increase in dNTP pool size during the DNA damage response plays a key role in spontaneous and induced-mutagenesis in Escherichia coli [Genetics] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-11-30
    Description: Exposure of Escherichia coli to UV light increases expression of NrdAB, the major ribonucleotide reductase leading to a moderate increase in dNTP levels. The role of elevated dNTP levels during translesion synthesis (TLS) across specific replication-blocking lesions was investigated. Here we show that although the specialized DNA polymerase PolV is necessary for replication across UV-lesions, such as cyclobutane pyrimidine dimers or pyrimidine(6-4)pyrimidone photoproduct, Pol V per se is not sufficient. Indeed, efficient TLS additionally requires elevated dNTP levels. Similarly, for the bypass of an N-2-acetylaminofluorene-guanine adduct that requires Pol II instead of PolV, efficient TLS is only observed under conditions of high dNTP levels. We suggest that increased dNTP levels transiently modify the activity balance of Pol III (i.e., increasing the polymerase and reducing the proofreading functions). Indeed, we show that the stimulation of TLS by elevated dNTP levels can be mimicked by genetic inactivation of the proofreading function (mutD5 allele). We also show that spontaneous mutagenesis increases proportionally to dNTP pool levels, thus defining a unique spontaneous mutator phenotype. The so-called “dNTP mutator” phenotype does not depend upon any of the specialized DNA polymerases, and is thus likely to reflect an increase in Pol III's own replication errors because of the modified activity balance of Pol III. As up-regulation of the dNTP pool size represents a common physiological response to DNA damage, the present model is likely to represent a general and unique paradigm for TLS pathways in many organisms.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    On the Role of Water in Natural-Zeolite-Catalyzed Cracking of Athabasca Oilsands Bitumen (2014)
    American Chemical Society (ACS)
    Details
    Publication Date: 2014-05-01
    Description: Energy & Fuels DOI: 10.1021/ef500532w
    Print ISSN: 0887-0624
    Electronic ISSN: 1520-5029
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Process Engineering, Biotechnology, Nutrition Technology
    Published by American Chemical Society (ACS)
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  • 10
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    Repeat-Enriched Proteins Are Related to Host Cell Invasion and Immune Evasion in Parasitic Protozoa (2013)
    Oxford University Press
    Details
    Publication Date: 2013-03-21
    Description: Proteins containing repetitive amino acid domains are widespread in all life forms. In parasitic organisms, proteins containing repeats play important roles such as cell adhesion and invasion and immune evasion. Therefore, extracellular and intracellular parasites are expected to be under different selective pressures regarding the repetitive content in their genomes. Here, we investigated whether there is a bias in the repetitive content found in the predicted proteomes of 6 exclusively extracellular and 17 obligate intracellular protozoan parasites, as well as 4 free-living protists. We also attempted to correlate the results with the distinct ecological niches they occupy and with distinct protein functions. We found that intracellular parasites have higher repetitive content in their proteomes than do extracellular parasites and free-living protists. In intracellular parasites, these repetitive proteins are located mainly at the parasite surface or are secreted and are enriched in amino acids known to be part of N- and O-glycosylation sites. Furthermore, in intracellular parasites, the developmental stages that are able to invade host cells express a higher proportion of proteins with perfect repeats relative to other life cycle stages, and these proteins have molecular functions associated with cell invasion. In contrast, in extracellular parasites, degenerate repetitive motifs are enriched in proteins that are likely to play roles in evading host immune response. Altogether, our results support the hypothesis that both the ability to invade host cells and to escape the host immune response may have shaped the expansion and maintenance of perfect and degenerate repeats in the genomes of intra- and extracellular parasites.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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