390 research outputs found
Technical note: Novel estimates of the leaf relative uptake rate of carbonyl sulfide from optimality theory
In order to estimate the gross primary productivity (GPP) of terrestrial ecosystems from the canopy uptake of carbonyl sulfide (COS), the leaf relative uptake rate (LRU) of COS with respect to carbon dioxide needs to be known a priori. Currently, the variability of the LRU between plant species in different biomes of the world is poorly understood, making the choice of an appropriate LRU uncertain and hampering further progress towards developing COS as an alternative tracer of GPP. Here we propose a novel approach for estimating LRU based on plant optimality principles, validate it against in situ leaf gas exchange measurements and provide global monthly climatological estimates. The global vegetation season average simulated LRUs fall into the range of 0.5–1.4 and are thus lower than any other published global estimates. We advocate these LRU estimates to be adopted by global modellers in order to test to what degree these are compatible with our current understanding of the sources and sinks in the global COS budget.</p
On the variability of the leaf relative uptake rate of carbonyl sulfide compared to carbon dioxide: Insights from a paired field study with two soybean varieties
Carbonyl sulfide (COS) has been proposed as a promising tracer for the estimation of the gross primary productivity (GPP) from ecosystem to global scale in recent years. Despite substantial work at spatial scales from leaf to regions, the uncertainty of COS-based GPP estimates are poorly known compared to widely used GPP estimates derived from the net ecosystem CO2 exchange. One key uncertainty in this context is the leaf relative uptake (LRU) of the COS with respect to the GPP, which must be known a priori. To investigate the influence of environmental factors, like drought, on the variability of the LRU, we conducted an experiment using ecosystem flux measurements of COS, CO2 and H2O from two eddy covariance towers above a soybean field, growing a commercial cultivar and a chlorophyll deficient mutant variety, in two separate plots. Our findings suggest that the LRU does not only differ between plant varieties due to differences in the ratio of the internal to ambient CO2 mole fraction and the internal resistance to COS, but also changes in response to drought. We also found the internal resistance to COS uptake to be a significant factor in controlling the total COS flux for both varieties, but more so for the commercial cultivar. Our study indicates that species-specific differences in the LRU need to be investigated further, and that environmental stress might complicate the usage of COS as a tracer for predicting GPP at ecosystem and global scale
Soil carbonyl sulfide exchange in relation to microbial community composition: Insights from a managed grassland soil amendment experiment
The viability of carbonyl sulfide (COS) measurements for partitioning ecosystem-scale net carbon dioxide (CO2)
fluxes into photosynthesis and respiration critically depends on our knowledge of non-leaf sinks and sources of
COS in ecosystems. We combined soil gas exchange measurements of COS and CO2 with next-generation sequencing
technology (NGS) to investigate the role of soil microbiota for soil COS exchange. We applied different
treatments (litter and glucose addition, enzyme inhibition and gamma sterilization) to soil samples from a
temperate grassland to manipulate microbial composition and activity. While untreated soil was characterized
by consistent COS uptake, other treatments reduced COS uptake and even turned the soil into a net COS source.
Removing biotic processes through sterilization led to positive or zero fluxes. We used NGS to link changes in the
COS response to alterations in the microbial community composition, with bacterial data having a higher explanatory
power for the measured COS fluxes than fungal data. We found that the genera Arthrobacter and
Streptomyces were particularly abundant in samples exhibiting high COS emissions. Our results indicate cooccurring
abiotic production and biotic consumption of COS in untreated soil, the latter linked to carbonic
anhydrase activity, and a strong dependency of the COS flux on the activity, identity, abundance of and substrate
available to microorganisms.Austrian National Science Fund (FWF) | Ref. P27176-B16Tyrolean Science Fund (TWF) | Ref. UNI-0404/1801Ministerio de Economía y Competitividad | Ref. RYC-2016-2123
Redshift and Shear Calibration: Impact on Cosmic Shear Studies and Survey Design
The cosmological interpretation of weak lensing by large-scale structures
requires knowledge of the redshift distribution of the source galaxies. Current
lensing surveys are often calibrated using external redshift samples which span
a significantly smaller sky area in comparison to the lensing survey, and are
thus subject to sample variance. Some future lensing surveys are expected to be
calibrated in the same way, in particular the fainter galaxy populations where
the entire color coverage, and hence photometric redshift estimate, could be
challenging to obtain. Using N-body simulations, we study the impact of this
sample variance on cosmic shear analysis and show that, to first approximation,
it behaves like a shear calibration error 1+/-epsilon. Using the Hubble Deep
Field as a redshift calibration survey could therefore be a problem for current
lensing surveys. We discuss the impact of the redshift distribution sampling
error and a shear calibration error on the design of future lensing surveys,
and find that a lensing survey of area Theta square degrees and limiting
magnitude m_lim}, has a minimum shear and redshift calibration accuracy
requirements given by epsilon = epsilon_0 10^{beta(m_lim-24.5)} / sqrt(Theta/
200). Above that limit, lensing surveys would not reach their full potential.
Using the galaxy number counts from the Hubble Ultra-Deep Field, we find
(epsilon_0,beta)=(0.015,-0.18) and (epsilon_0,beta)=(0.011,-0.23) for ground
and space based surveys respectively. Lensing surveys with no or limited
redshift information and/or poor shear calibration accuracy will loose their
potential to analyse the cosmic shear signal in the sub-degree angular scales,
and therefore complete photometric redshift coverage should be a top priority
for future lensing surveys.Comment: Accepted version to Astroparticle Physic
Urban eddy covariance measurements reveal significant missing NOx emissions in Central Europe
Nitrogen oxide (NOx) pollution is emerging as a primary environmental concern across Europe. While some large European metropolitan areas are already in breach of EU safety limits for NO2, this phenomenon does not seem to be only restricted to large industrialized areas anymore. Many smaller scale populated agglomerations including their surrounding rural areas are seeing frequent NO2 concentration violations. The question of a quantitative understanding of different NOx emission sources is therefore of immanent relevance for climate and air chemistry models as well as air pollution management and health. Here we report simultaneous eddy covariance flux measurements of NOx, CO2, CO and non methane volatile organic compound tracers in a city that might be considered representative for Central Europe and the greater Alpine region. Our data show that NOx fluxes are largely at variance with modelled emission projections, suggesting an appreciable underestimation of the traffic related atmospheric NOx input in Europe, comparable to the weekend-weekday effect, which locally changes ozone production rates by 40%
Technical Note: Novel Estimates of the Leaf Relative Uptake Rate of Carbonyl Sulfide from Optimality Theory
In order to estimate the gross primary productivity (GPP) of terrestrial ecosystems from the canopy uptake of carbonyl sulfide (COS), the leaf relative uptake rate (LRU) of COS with respect to carbon dioxide needs to be known a priori. Currently, the variability of the LRU between plant species in different biomes of the world is poorly understood, making the choice of an appropriate LRU uncertain and hampering further progress towards developing COS as an alternative tracer of GPP. Here we propose a novel approach for estimating LRU based on plant optimality principles, validate it against in situ leaf gas exchange measurements and provide global monthly climatological estimates. The global vegetation season average simulated LRUs fall into the range of 0.5-1.4 and are thus lower than any other published global estimates. We advocate these LRU estimates to be adopted by global modellers in order to test to what degree these are compatible with our current understanding of the sources and sinks in the global COS budget
Ageing is associated with molecular signatures of inflammation and type 2 diabetes in rat pancreatic islets.
AIMS/HYPOTHESIS: Ageing is a major risk factor for development of metabolic diseases such as type 2 diabetes. Identification of the mechanisms underlying this association could help to elucidate the relationship between age-associated progressive loss of metabolic health and development of type 2 diabetes. We aimed to determine molecular signatures during ageing in the endocrine pancreas. METHODS: Global gene transcription was measured in pancreatic islets isolated from young and old rats by Ilumina BeadChip arrays. Promoter DNA methylation was measured by Sequenom MassArray in 46 genes that showed differential expression with age, and correlations with expression were established. Alterations in morphological and cellular processes with age were determined by immunohistochemical methods. RESULTS: Age-related changes in gene expression were found at 623 loci (>1.5-fold, false discovery rate [FDR] <5%), with a significant (FDR < 0.05) enrichment in genes previously implicated in islet-cell function (Enpp1, Abcc8), type 2 diabetes (Tspan8, Kcnq1), inflammatory processes (Cxcl9, Il33) and extracellular matrix organisation (Col3a1, Dpt). Age-associated transcriptional differences negatively correlated with promoter DNA methylation at several loci related to inflammation, glucose homeostasis, cell proliferation and cell-matrix interactions (Il33, Cxcl9, Gpr119, Fbp2, Col3a1, Dpt, Spp1). CONCLUSIONS/INTERPRETATION: Our findings suggest that a significant proportion of pancreatic islets develop a low-grade 'chronic' inflammatory status with ageing and this may trigger altered functional plasticity. Furthermore, we identified changes in expression of genes previously linked to type 2 diabetes and associated changes in DNA methylation that could explain their age-associated dysregulation. These findings provide new insights into key (epi)genetic signatures of the ageing process in islets.Biotechnology and Biological Sciences Research Council (Grant ID: BB/H003312/1), British Heart Foundation, FP6 Epigenome Network of Excellence programme, GlaxoSmithKline, Nuffield Foundation, Royal Society, Medical Research Council (Grant ID: MRC_MC_UU_12012/4)This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00125-015-3837-
The Rewiring of Ubiquitination Targets in a Pathogenic Yeast Promotes Metabolic Flexibility, Host Colonization and Virulence
Funding: This work was funded by the European Research Council [http://erc.europa.eu/], AJPB (STRIFE Advanced Grant; C-2009-AdG-249793). The work was also supported by: the Wellcome Trust [www.wellcome.ac.uk], AJPB (080088, 097377); the UK Biotechnology and Biological Research Council [www.bbsrc.ac.uk], AJPB (BB/F00513X/1, BB/K017365/1); the CNPq-Brazil [http://cnpq.br], GMA (Science without Borders fellowship 202976/2014-9); and the National Centre for the Replacement, Refinement and Reduction of Animals in Research [www.nc3rs.org.uk], DMM (NC/K000306/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Acknowledgments We thank Dr. Elizabeth Johnson (Mycology Reference Laboratory, Bristol) for providing strains, and the Aberdeen Proteomics facility for the biotyping of S. cerevisiae clinical isolates, and to Euroscarf for providing S. cerevisiae strains and plasmids. We are grateful to our Microscopy Facility in the Institute of Medical Sciences for their expert help with the electron microscopy, and to our friends in the Aberdeen Fungal Group for insightful discussions.Peer reviewedPublisher PD
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