1,467 research outputs found
Transitions of social-ecological subsistence systems in the Arctic
Transitions of social-ecological systems (SES) expose governance systems
to new challenges. This is particularly so in the Arctic where resource systems
are increasingly subjected to global warming, industrial development and globalization
which subsequently alter the local SES dynamics. Based on common-pool
resource theory, we developed a dynamic conceptual model explaining how exogenous
drivers might alter a traditional subsistence system from a provisioning to
an appropriation actions situation. In a provisioning action situation the resource
users do not control the resource level but adapt to the fluctuating availability of
resources, and the collective challenge revolve around securing the subsistence in
the community. An increased harvest pressure enabled by exogenous drivers could
transform the SES to an appropriation action situation where the collective challenge
has changed to avoid overuse of a common-pool resource. The model was
used as a focal lens to investigate the premises for broad-scale transitions of subsistence-oriented
SESs in Arctic Alaska, Canada and Greenland. We synthesized
data from documents, official statistics and grey and scientific literature to explore
the different components of our model. Our synthesis suggests that the traditional
Arctic subsistence SESs mostly comply with a provisioning action situation.
Despite population growth and available technology; urbanization, increased wage
labor and importation of food have reduced the resource demand, and we find no
evidence for a broad-scale transition to an appropriation action situation throughout
the Western Arctic. However, appropriation challenges have emerged in some
cases either as a consequence of commercialization of the resource or by severely
reduced resource stocks due to various exogenous drivers. Future transitions of
SESs could be triggered by the emergence of commercial local food markets and
Arctic warming. In particular, Arctic warming is an intensifying exogenous driver
that is threatening many important Arctic wildlife resources inflicting increased
appropriation challenges to the governance of local harvest.Ye
Simple vertex correction improves GW band energies of bulk and two-dimensional crystals
The GW self-energy method has long been recognized as the gold standard for
quasiparticle (QP) calculations of solids in spite of the fact that the neglect
of vertex corrections and the use of a DFT starting point lacks rigorous
justification. In this work we remedy this situation by including a simple
vertex correction that is consistent with an LDA starting point. We analyse the
effect of the self-energy by splitting it into a short-range and long-range
term which are shown to govern respectively the center and size of the band
gap. The vertex mainly improves the short-range correlations and therefore has
a small effect on the band gap, while it shifts the band gap center up in
energy by around 0.5 eV in good agreement with experiments. Our analysis also
explains how the relative importance of short- and long-range interactions in
structures of different dimensionality is reflected in their QP energies.
Inclusion of the vertex comes at practically no extra computational cost and
even improves the basis set convergence compared to GW. The method thus
provides an efficient and rigorous improvement over the GW approximation and
sets a new standard for quasiparticle calculations of solids
Foreword
Proteins that contain long disordered regions are prevalent in the proteome and frequently associated with diseases. However, the mechanisms by which such intrinsically disordered proteins (IDPs) recognize their targets are not well understood. Here, we report the first experimental investigation of the interaction kinetics of the nuclear co-activator binding domain of CREB-binding protein and the activation domain from the p160 transcriptional co-activator for thyroid hormone and retinoid receptors. Both protein domains are intrinsically disordered in the free state and synergistically fold upon binding each other. Using the stopped-flow technique, we found that the binding reaction is fast, with an association rate constant of 3 x 10(7) M-1 s(-1) at 277 K. Mutation of a conserved buried intermolecular salt bridge showed that electrostatics govern the rapid association. Furthermore, upon mutation of the salt bridge or at high salt concentration, an additional kinetic phase was detected (similar to 20 and similar to 40 s(-1), respectively, at 277 K), suggesting that the salt bridge may steer formation of the productive bimolecular complex in an intramolecular step. Finally, we directly measured slow kinetics for the IDP domains (similar to 1 s(-1) at 277 K) related to conformational transitions upon binding. Together, the experiments demonstrate that the interaction involves several steps and accumulation of intermediate states. Our data are consistent with an induced fit mechanism, in agreement with previous simulations. We propose that the slow transitions may be a consequence of the multipartner interactions of IDPs
Benchmark Database of Transition Metal Surface and Adsorption Energies from Many-Body Perturbation Theory
We present an extensive set of surface and chemisorption energies calculated
using state of the art many-body perturbation theory. In the first part of the
paper we consider ten surface reactions in the low coverage regime where
experimental data is available. Here the random phase approximation (RPA) is
found to yield high accuracy for both adsorption and surface energies. In
contrast all the considered density functionals fail to describe both
quantities accurately. This establishes the RPA as a universally accurate
method for surface science. In the second part, we use the RPA to construct a
database of 200 high quality adsorption energies for reactions involving OH,
CH, NO, CO, N, N, O and H over a wide range of 3d, 4d and 5d transition
metals. Due to the significant computational demand, these results are obtained
in the high coverage regime where adsorbate-adsorbate interactions can be
significant. RPA is compared to the more advanced renormalised adiabatic LDA
(rALDA) method for a subset of the reactions and they are found to describe the
adsorbate-metal bond as well as adsorbate-adsorbate interactions similarly. The
RPA results are compared to a range of standard density functional theory
methods typically employed for surface reactions representing the various rungs
on Jacob's ladder. The deviations are found to be highly functional, surface
and reaction dependent. Our work establishes the RPA and rALDA methods as
universally accurate full ab-initio methods for surface science where accurate
experimental data is scarce. The database is freely available via the
Computational Materials Repository (CMR)
Lameness in piglets - should pain killers be included at treatment?
Background: Joint swelling and lameness are the most obvious and persistent clinical signs of infectious arthritis in piglets. For a positive treatment effect of piglets with arthritis, early initiated treatments with antibiotics are desired. Hitherto pain-reducing drugs have rarely been used within veterinary medicine, but the potential of non steroid anti-inflammatory drugs (NSAID) are interesting from an animal welfare perspective. Therefore, the aim of this study was to compare the long term efficiency of treating lameness with and without pain relief. Further, the incidences of affected joints in lame piglets were analysed.
Results: In total 415 of the 6,787 liveborn piglets included in the study were diagnosed with lameness (6.1 %). Around 86 % of these diagnoses took place during the first 3 weeks of life. There was no difference in the incidence of lameness between the sexes, but lameness was most commonly diagnosed in the offspring to old sows (>4 parturitions). Lameness was diagnosed in about every second litter and on average about two pigs were diagnosed in the affected litters. The incidence of affected litters as well as affected piglets increased with ageing of the sows. Treatments with antibiotics solely and in combination with NSAID improved (P < 0.01 to 0.001) the clinical status from day to day, but the clinical response did not differ between the two treatment groups. Piglets that remained healthy were 1.1 and 1.7 kg heavier (P < 0.001) than piglets diagnosed with lameness at 5 and 9 weeks of age, respectively. There were no differences in piglet body weights between the treatment strategies at any time.
Conclusions: The clinical response to penicillin was good. It was neither improved nor reduced by a concurrent administration of NSAIDs. Nevertheless NSAIDs may improve the animal welfare due to pain relief. An important finding of this study was that decreasing pain due to lameness not was negative in a long term perspective, i.e. reducing pain did not lead to overstrain of affected joints and no clinical signs of adverse effects were noted. Therefore the use of NSAIDs ought to be considered to improve the animal welfare, at least in severe cases
Finite element simulation and testing of ISW CFRP anchorage
Several Carbon Fibre Reinforced Polymers (CFRP) systems have been used successfully for strengthening of structures during the last decades. However, the fracture often occurs in the concrete adherent or in the adhesive interface when used for steel strengthening. As a consequence the CFRP is poorly utilized with a non ductile and brittle failure mode as the outcome. Mechanical anchorage can be used to utilize the full capacity of the CFRP materials but cannot yet challenge systems used for steel. Such systems can be used to transfer stresses from the CFRP material efficiently to the remaining structure. However, reaching the full capacity of the CFRP material is difficult since anchoring often courses premature failure modes such as crushing of the Fibre Reinforced Polymers (FRP), slip in the FRP and adjacent adherent, cutting of the fibres, bending of fibres and frontal overload. This paper presents a novel mechanical integrated sleeve wedge anchorage which seem very promising when perusing the scope of ultimate utilization of CFRP 8mm rods (with a tension capacity of approximately 140kN). Compression transverse to the CFRP is evaluated to prevent premature failure. The anchorage is modelled in the 3D finite Element program ABAQUS, just as digital image correlation (DIC) testing was performed to verify the finite element simulation. Also a new optimized design was produced to ensure that the finite element simulation and anchorage behaviour correlated well. It is seen that the simulation and DIC testing correspond well when strains on the barrel surface are compared. As a consequence it was possible to produce a new optimized anchorage which utilized the full capacity of the 8mm CFRP rod
Field emissions of N2O during biomass production may affect the sustainability of agro-biofuels
Field emissions of N2O during cultivation of bioenergy crops may counterbalance a considerable part of the avoided fossil CO2 emissions that are achieved by fossil fuel displacemen
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