384 research outputs found
Sea-Ice Distribution in the Bering and Chukchi Seas: Information from Historical Whaleshipsâ Logbooks and Journals
Satellite data have revealed dramatic losses of Northern Hemisphere sea ice since the end of the 1970s. To place these changes in a longer-term context, we draw on daily observations taken from logbooks and journals of whaling vessels cruising in the Bering and Chukchi seas to investigate sea-ice conditions in this region of the Arctic between 1850 and 1910. We compare these observations to sea-ice data from 1972 to 1982, which predate the majority of the recent changes and cover a period recognized as a relative maximum in recent Bering Sea ice extent. Records from May indicate that end-of-winter sea-ice extent in the Bering Sea during the mid 19th century closely resembled that in the 1972 â 82 data. However, the historical data reveal that sea ice was more extensive during summer, with the greatest difference occurring in July. This pattern indicates a later and more rapid seasonal retreat. These conclusions highlight the value of historical data, which we have far from exhausted in this study.Des donnĂ©es satellitaires rĂ©vĂšlent que lâhĂ©misphĂšre nord a enregistrĂ© des pertes dramatiques de glaces de mer depuis la fin des annĂ©es 1970. Afin de mettre ces changements dans un plus long contexte, nous nous appuyons sur les observations quotidiennes tirĂ©es de journaux et de carnets de bord de baleiniers ayant parcouru la mer de BĂ©ring et la mer des Tchouktches dans le but dâĂ©tudier les glaces de mer de cette rĂ©gion de lâArctique entre les annĂ©es 1850 et 1910. Nous comparons ces observations aux donnĂ©es sur les glaces de mer recueillies de 1972 Ă 1982 â soit avant que la plupart des rĂ©cents changements nâaient Ă©tĂ© enregistrĂ©s â ce qui couvre une pĂ©riode reconnue comme un maximum relatif en matiĂšre dâĂ©tendue rĂ©cente des glaces dans la mer de BĂ©ring. Les donnĂ©es enregistrĂ©es en mai laissent entrevoir que lâĂ©tendue des glaces de mer en fin dâhiver dans la mer de BĂ©ring au milieu du XIXe siĂšcle ressemblait beaucoup Ă lâĂ©tendue des glaces dont tĂ©moignent les donnĂ©es prĂ©levĂ©es entre 1972 et 1982. Cependant, les donnĂ©es historiques rĂ©vĂšlent que les glaces de mer Ă©taient plus considĂ©rables au cours de lâĂ©tĂ©, la plus grande diffĂ©rence se manifestant au mois de juillet. Cette tendance indique donc un retrait saisonnier plus tardif et plus rapide. Les conclusions mettent en Ă©vidence lâimportance des donnĂ©es historiques, que nous sommes loin dâavoir Ă©puisĂ©es dans le cadre de cette Ă©tude
A genomic analysis and transcriptomic atlas of gene expression in Psoroptes ovis reveals feeding- and stage-specific patterns of allergen expression
Background: Psoroptic mange, caused by infestation with the ectoparasitic mite, Psoroptes ovis, is highly contagious, resulting in intense pruritus and represents a major welfare and economic concern for the livestock industry Worldwide. Control relies on injectable endectocides and organophosphate dips, but concerns over residues, environmental contamination, and the development of resistance threaten the sustainability of this approach, highlighting interest in alternative control methods. However, development of vaccines and identification of chemotherapeutic targets is hampered by the lack of P. ovis transcriptomic and genomic resources.
Results: Building on the recent publication of the P. ovis draft genome, here we present a genomic analysis and transcriptomic atlas of gene expression in P. ovis revealing feeding- and stage-specific patterns of gene expression, including novel multigene families and allergens. Network-based clustering revealed 14 gene clusters demonstrating either single- or multi-stage specific gene expression patterns, with 3075 female-specific, 890 male-specific and 112, 217 and 526 transcripts showing larval, protonymph and tritonymph specific-expression, respectively. Detailed analysis of P. ovis allergens revealed stage-specific patterns of allergen gene expression, many of which were also enriched in "fed" mites and tritonymphs, highlighting an important feeding-related allergenicity in this developmental stage. Pair-wise analysis of differential expression between life-cycle stages identified patterns of sex-biased gene expression and also identified novel P. ovis multigene families including known allergens and novel genes with high levels of stage-specific expression.
Conclusions: The genomic and transcriptomic atlas described here represents a unique resource for the acarid-research community, whilst the OrcAE platform makes this freely available, facilitating further community-led curation of the draft P. ovis genome
Hybrid selfâassembling peptide/gelatin methacrylate (gelma) bioink blend for improved bioprintability and primary myoblast response
Organ fabrication as the solution to renewable donor demands requires the ability to spatially deposit viable cells into biologically relevant constructs necessitating reliable and effective cell deposition through bioprinting and the subsequent ability to mature. However, effective bioink development demands advances in both printability and control of cellular response. Effective bioinks are designed to retain shape fidelity, influence cellular behavior, having bioactive morphologies stiffness and highly hydrated environment. Hybrid hydrogels are promising candidates as they reduce the need to reâengineer materials for tissueâspecific properties, with each component offering beneficial properties. Herein, a multicomponent bioink is developed whereby gelatin methacrylate (GelMA) and fluorenylmethoxycarbonyprotected selfâassembling peptides (FmocâSAPs) undergo coassembly to yield a tuneable bioink. This study shows that the reported fibronectinâinspired fmocâSAPs present cell attachment epitopes RGD and PHSRN in the form of bioactive nanofibers and that the GelMA enables superior printability, stability in media, and controlled mechanical properties. Importantly, when in the hybrid format, no disruption to either the methacrylate crosslinking of GelMA, or selfâassembled peptide fibril formation is observed. Finally, studies with primary myoblasts show over 98% viability at 72âh and differentiation into fused myotubes at one and two weeks demonstrate the utility of the material as a functional bioink for muscle engineering. In this work, muscle tissue is 3Dâbioprinted with a novel bioink formulation. The bioink presents fibrous bioactive properties of the body's native scaffold, while also improving biofabrication outcomes. Selfâassembling peptides are combined with GelMA creating a hybrid bioink. This work sets the stage for future hybrid bioinks for muscle biofabrication
A genomic analysis and transcriptomic atlas of gene expression in Psoroptes ovis reveals feeding- and stage-specific patterns of allergen expression
Background: Psoroptic mange, caused by infestation with the ectoparasitic mite, Psoroptes ovis, is highly contagious, resulting in intense pruritus and represents a major welfare and economic concern for the livestock industry Worldwide. Control relies on injectable endectocides and organophosphate dips, but concerns over residues, environmental contamination, and the development of resistance threaten the sustainability of this approach, highlighting interest in alternative control methods. However, development of vaccines and identification of chemotherapeutic targets is hampered by the lack of P. ovis transcriptomic and genomic resources.
Results: Building on the recent publication of the P. ovis draft genome, here we present a genomic analysis and transcriptomic atlas of gene expression in P. ovis revealing feeding- and stage-specific patterns of gene expression, including novel multigene families and allergens. Network-based clustering revealed 14 gene clusters demonstrating either single- or multi-stage specific gene expression patterns, with 3075 female-specific, 890 male-specific and 112, 217 and 526 transcripts showing larval, protonymph and tritonymph specific-expression, respectively. Detailed analysis of P. ovis allergens revealed stage-specific patterns of allergen gene expression, many of which were also enriched in "fed" mites and tritonymphs, highlighting an important feeding-related allergenicity in this developmental stage. Pair-wise analysis of differential expression between life-cycle stages identified patterns of sex-biased gene expression and also identified novel P. ovis multigene families including known allergens and novel genes with high levels of stage-specific expression.
Conclusions: The genomic and transcriptomic atlas described here represents a unique resource for the acarid-research community, whilst the OrcAE platform makes this freely available, facilitating further community-led curation of the draft P. ovis genome
Progressive and biased divergent evolution underpins the origin and diversification of peridinin dinoflagellate plastids
Dinoflagellates are algae of tremendous importance to ecosystems and to public health. The cell biology and genome organization of dinoflagellate species is highly unusual. For example, the plastid genomes of peridinin-containing dinoflagellates encode only a minimal number of genes arranged on small elements termed "minicircles". Previous studies of peridinin plastid genes have found evidence for divergent sequence evolution, including extensive substitutions, novel insertions and deletions, and use of alternative translation initiation codons. Understanding the extent of this divergent evolution has been hampered by the lack of characterized peridinin plastid sequences. We have identified over 300 previously unannotated peridinin plastid mRNAs from published transcriptome projects, vastly increasing the number of sequences available. Using these data, we have produced a well-resolved phylogeny of peridinin plastid lineages, which uncovers several novel relationships within the dinoflagellates. This enables us to define changes to plastid sequences that occurred early in dinoflagellate evolution, and that have contributed to the subsequent diversification of individual dinoflagellate clades. We find that the origin of the peridinin dinoflagellates was specifically accompanied by elevations both in the overall number of substitutions that occurred on plastid sequences, and in the Ka/Ks ratio associated with plastid sequences, consistent with changes in selective pressure. These substitutions, alongside other changes, have accumulated progressively in individual peridinin plastid lineages. Throughout our entire dataset, we identify a persistent bias toward non-synonymous substitutions occurring on sequences encoding photosystem I subunits and stromal regions of peridinin plastid proteins, which may have underpinned the evolution of this unusual organelle.Wellcome Trus
Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement
The 2015 Paris Agreement of the United Nations Framework Convention on Climate Change aims to keep global average temperature increases well below 2 °C of preindustrial levels in the Year 2100. Vital to its success is achieving a decrease in the abundance of atmospheric methane (CH4), the second most important anthropogenic greenhouse gas. If this reduction is to be achieved, individual nations must make and meet reduction goals in their nationally determined contributions, with regular and independently veriïŹable global stock taking. Targets for the Paris Agreement have been set, and now the capability must follow to determine whether CH4 reductions are actually occurring. At present, however, there are signiïŹcant limitations in the ability of scientists to quantify CH4 emissions accurately at global and national scales and to diagnose what mechanisms have altered trends in atmospheric mole fractions in the past decades. For example, in 2007, mole fractions suddenly started rising globally after a decade of almost no growth. More than a decade later, scientists are still debating the mechanisms behind this increase. This study reviews the main approaches and limitations in our current capability to diagnose the drivers of changes in atmospheric CH4 and, crucially, proposes ways to improve this capability in the coming decade. Recommendations include the following: (i) improvements to processâbased models of the main sectors of CH4 emissionsâproposed developments call for the expansion of tropical wetland ïŹux measurements, bridging remote sensing products for improved measurement of wetland area and dynamics, expanding measurements of fossil fuel emissions at the facility and regional levels, expanding countryâ speciïŹc data on the composition of waste sent to landïŹll and the types of wastewater treatment systems implemented, characterizing and representing temporal proïŹles of crop growing seasons, implementing parameters related to ruminant emissions such as animal feed, and improving the detection of small ïŹres associated with agriculture and deforestation; (ii) improvements to measurements of CH4 mole fraction and its isotopic variationsâdevelopments include greater vertical proïŹling at background sites, expanding networks of dense urban measurements with a greater focus on relatively poor countries, improving the precision of isotopic ratio measurements of 13CH4, CH3D, 14CH4, and clumped isotopes, creating isotopic reference materials for internationalâscale development, and expanding spatial and temporal characterization of isotopic source signatures; and (iii) improvements to inverse modeling systems to derive emissions from atmospheric measurementsâadvances are proposed in the areas of hydroxyl radical quantiïŹcation, in systematic uncertainty quantiïŹcation through validation of chemical transport models, in the use of source tracers for estimating sectorâlevel emissions, and in the development of time and spaceresolved national inventories. These and other recommendations are proposed for the major areas of CH4 science with the aim of improving capability in the coming decade to quantify atmospheric CH4 budgets on the scales necessary for the success of climate policies. Plain Language Summary Methane is the second largest contributor to climate warming from human activities since preindustrial times. Reducing humanâmade emissions by half is a major component of the 2015 Paris Agreement target to keep global temperature increases well below 2 °C. In parallel to the methane emission reductions pledged by individual nations, new capabilities are needed to determine independently whether these reductions are actually occurring and whether methane concentrations in the atmosphere are changing for reasons that are clearly understood. At present signiïŹcant challenges limit the ability of scientists to identify the mechanisms causing changes in atmospheric methane. This study reviews current and emerging tools in methane science and proposes major advances needed in the coming decade to achieve this crucial capability. We recommend further developing the models that simulate the processes behind methane emissions, improving atmospheric measurements of methane and its major carbon and hydrogen isotopes, and advancing abilities to infer the rates of methane being emitted and removed from the atmosphere from these measurements. The improvements described here will play a major role in assessing emissions commitments as more cities, states, and countries report methane emission inventories and commit to speciïŹc emission reduction targets. </div
The faint young Sun problem
For more than four decades, scientists have been trying to find an answer to
one of the most fundamental questions in paleoclimatology, the `faint young Sun
problem'. For the early Earth, models of stellar evolution predict a solar
energy input to the climate system which is about 25% lower than today. This
would result in a completely frozen world over the first two billion years in
the history of our planet, if all other parameters controlling Earth's climate
had been the same. Yet there is ample evidence for the presence of liquid
surface water and even life in the Archean (3.8 to 2.5 billion years before
present), so some effect (or effects) must have been compensating for the faint
young Sun. A wide range of possible solutions have been suggested and explored
during the last four decades, with most studies focusing on higher
concentrations of atmospheric greenhouse gases like carbon dioxide, methane or
ammonia. All of these solutions present considerable difficulties, however, so
the faint young Sun problem cannot be regarded as solved. Here I review
research on the subject, including the latest suggestions for solutions of the
faint young Sun problem and recent geochemical constraints on the composition
of Earth's early atmosphere. Furthermore, I will outline the most promising
directions for future research. In particular I would argue that both improved
geochemical constraints on the state of the Archean climate system and
numerical experiments with state-of-the-art climate models are required to
finally assess what kept the oceans on the Archean Earth from freezing over
completely.Comment: 32 pages, 8 figures. Invited review paper accepted for publication in
Reviews of Geophysic
Environmental baseline monitoring for shale gas development in the UK: identification and geochemical characterisation of local source emissions of methane to atmosphere
Baseline mobile surveys of methane sources using vehicle-mounted instruments have been performed in the Fylde and Ryedale regions of Northern England over the 2016â19 period around proposed unconventional (shale) gas extraction sites. The aim was to identify and characterise methane sources ahead of hydraulically fractured shale gas extraction in the area around drilling sites. This allows a potential additional source of emissions to atmosphere to be readily distinguished from adjacent sources, should gas production take place.
The surveys have used ethane:methane (C2:C1) ratios to separate combustion, thermogenic gas and biogenic sources. Sample collection of source plumes followed by high precision ÎŽ13C analysis of methane, to separate and isotopically characterise sources, adds additional biogenic source distinction between active and closed landfills, and ruminant eructations from manure.
The surveys show that both drill sites and adjacent fixed monitoring sites have cow barns and gas network pipeline leaks as sources of methane within a 1âŻkm range. These two sources are readily separated by isotopes (ÎŽ13C of â67 to â58â° for barns, compared to â43 to â39â° for gas leaks), and ethane:methane ratios (0.05 for gas leaks). Under a well-mixed daytime atmospheric boundary layer these sources are generally detectable as above baseline elevations up to 100âŻm downwind for gas leaks and up to 500âŻm downwind for populated cow barns. It is considered that careful analysis of these proxies for unconventional production gas, if and when available, will allow any fugitive emissions from operations to be distinguished from surrounding sources
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