1,020 research outputs found
Baffin Island Fjord Macrobenthos: Bottom Communities and Environmental Significance
Cluster analysis of the benthos from ten Baffin Island fjords defines six faunal associations. The macrotidal Sunneshine Fiord has a shallow kelp-related Isopod Association. Cambridge Fiord supports a shallow Onuphid Association controlled by gravel from dropstones. A widespread Portlandia Association typified the shallow zones of more recently glaciated fjords where sedimentation rates are high. An Ophiuroid-Anemone Association was defined from current-affected submarine channel environments. A Maldanid Association covered the greatest area in all fjords and passed into an Elasipod Association in the deepest water in Cambridge Fiord. Fjord-head faunas are used to model ecological changes accompanying glacier retreat, from monospecific Portlandia, through mature Portlandia Association to Onuphid Association accompanied by diverse filter feeders and herbivores. Chlamys islandica was found living in Cambridge Fiord, which substantially increases its northern limit.Key words: macrobenthos, Arctic, cluster analysis, bivalve, Quaternary, sedimentMots clés: macrobenthos, Arctique, analyse d’ensemble, bivalve, quaternaire, sédiment
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3D modeling of metallic grain growth
This paper will describe simulating metallic grain growth using the Gradient Weighted Moving Finite Elements code, GRAIN3D. The authors also describe the set of mesh topology change operations developed to respond to changes in the physical topology such as the collapse of grains and to maintain uniform calculational mesh quality. Validation of the method is demonstrated by comparison to analytic calculations. The authors present results of multigrain simulations where grain boundaries evolve by mean curvature motion and include results which incorporate grain boundary orientation dependence
A two-mass expanding exact space-time solution
In order to understand how locally static configurations around
gravitationally bound bodies can be embedded in an expanding universe, we
investigate the solutions of general relativity describing a space-time whose
spatial sections have the topology of a 3-sphere with two identical masses at
the poles. We show that Israel junction conditions imply that two spherically
symmetric static regions around the masses cannot be glued together. If one is
interested in an exterior solution, this prevents the geometry around the
masses to be of the Schwarzschild type and leads to the introduction of a
cosmological constant. The study of the extension of the Kottler space-time
shows that there exists a non-static solution consisting of two static regions
surrounding the masses that match a Kantowski-Sachs expanding region on the
cosmological horizon. The comparison with a Swiss-Cheese construction is also
discussed.Comment: 15 pages, 5 figures. Replaced to match the published versio
Estimating water footprints of vegetable crops : influence of growing season, solar radiation data and functional unit
Water footprint (WF) accounting as proposed by the Water Footprint Network (WFN)
can potentially provide important information for water resource management, especially in water
scarce countries relying on irrigation to help meet their food requirements. However, calculating
accurate WFs of short-season vegetable crops such as carrots, cabbage, beetroot, broccoli and lettuce
presented some challenges. Planting dates and inter-annual weather conditions impact WF results.
Joining weather datasets of just rainfall, minimum and maximum temperature with ones that include
solar radiation and wind-speed affected crop model estimates and WF results. The functional unit
selected can also have a major impact on results. For example, WFs according to the WFN approach
do not account for crop residues used for other purposes, like composting and animal feed. Using
yields in dry matter rather than fresh mass also impacts WF metrics, making comparisons difficult.
To overcome this, using the nutritional value of crops as a functional unit can connect water use
more directly to potential benefits derived from different crops and allow more straightforward
comparisons. Grey WFs based on nitrogen only disregards water pollution caused by phosphates,
pesticides and salinization. Poor understanding of the fate of nitrogen complicates estimation of
nitrogen loads into the aquifer.The first author, Betsie le Roux, conducted this research and wrote the paper as part of
her Ph.D. studies; Michael van der Laan supervised the research.The Water Research Commission (WRC) and the National Research Foundation (NRF) of South Africa.http://www.mdpi.com/journal/wateram2017Plant Production and Soil Scienc
Water footprints of vegetable crop wastage along the supply chain in Gauteng, South Africa
Food production in water-scarce countries like South Africa will become more challenging
in the future because of the growing population and intensifying water shortages. Reducing food
wastage is one way of addressing this challenge. The wastage of carrots, cabbage, beetroot, broccoli
and lettuce, produced on the Steenkoppies Aquifer in Gauteng, South Africa, was estimated for each
step along the supply chain from the farm to the consumer. Water footprints for these vegetables were
used to determine the volume of water lost indirectly as a result of this wastage. Highest percentage
wastage occurs at the packhouse level, which is consistent with published literature. Some crops
like lettuce have higher average wastage percentages (38%) compared to other crops like broccoli
(13%) and cabbage (14%), and wastage varied between seasons. Care should therefore be taken when
applying general wastage values reported for vegetables. The classification of “waste” presented
a challenge, because “wasted” vegetables are often used for other beneficial purposes, including
livestock feed and composting. It was estimated that blue water lost on the Steenkoppies Aquifer
due to vegetable crop wastage (4 Mm3 year-1) represented 25% of the estimated blue water volume
that exceeded sustainable limits (17 Mm3 year-1).The Water Research
Commission (WRC project No. K5/2273//4). The first author,
Betsie le Roux, received financial support for research from the WRC and a bursary from the National Research
Foundation (NRF) of South Africa (NRF Grant number: 88572).http://www.mdpi.com/journal/wateram2019Plant Production and Soil Scienc
Crop coefficient approaches based on fixed estimates of leaf resistance are not appropriate for estimating water use of citrus
The estimation of crop water use is critical for accurate irrigation scheduling and
water licenses. However, the direct measurement of crop water use is too expensive
and time consuming to be performed under all possible conditions, which
necessitates the use of water use models. The FAO-56 procedure is a simple,
convenient and reproducible method, but as canopy cover and height vary greatly
among different orchards, crop coefficients may not be readily transferrable from one
orchard to another. Allen and Pereira (2009) therefore incorporated a procedure into
the FAO-56 approach which estimates crop coefficients based on a physical
description of the vegetation and an adjustment for relative crop stomatal control
over transpiration. Transpiration crop coefficients derived using this procedure and
fixed values for citrus, did not provide good estimates of water use in three citrus
orchards. However, when mean monthly leaf resistance was taken into account, good agreement was found with measured values. A relationship between monthly
reference evapotranspiration and mean leaf resistance provided a means of
estimating mean leaf resistance which estimated transpiration crop coefficients with
a reasonable degree of accuracy. The use of a dynamic estimate of mean leaf
resistance therefore provided reasonable estimates of transpiration in citrus.South Africa‟s Water Research Commission (Project K5/1770, Water use of fruit tree orchards), with cofounding from the South African National Department of Agriculture, Forestry and Fisheries.http://link.springer.com/journal/2712016-12-30hb201
Modelling water use of subtropical fruit crops : the challenges
Subtropical fruit crops form an important part of the fruit industry in many countries. Many of these crops are grown in semi-arid regions or subtropical regions where rainfall is seasonal and as a result the vast majority of these perennial, evergreen orchards are under irrigation. This represents a significant irrigation requirement and with more emphasis being placed on the conservation of water and orchard profitability, it is becoming increasingly important to accurately estimate water use of these crops and schedule irrigation accordingly. The FAO-56 procedure is a simple, convenient and reproducible method for estimating water use. However, the transferability of crop coefficients between different orchards and growing regions is not always readily achieved, due largely to differences in canopy size and management practices. In addition, as subtropical crops tend to exhibit a higher degree of stomatal control over transpiration than most other agricultural crops, some measure of canopy or leaf resistance must be taken into account when using models based on atmospheric demand. The challenge is therefore to provide reliable and dynamic estimates of canopy resistance from relatively simple parameters which can be of use to irrigation consultants and farmers for determining the water requirements of these crops. The challenge remains to ensure that these dynamic estimates are realistic and readily applicable to a number of growing regions. The derivation of transpiration crop coefficients, based on canopy cover and height and a dynamic estimate of leaf resistance, provided reasonable estimates of transpiration in three orchards in contrasting climates, suggesting that this approach could prove useful in future for subtropical crops.http://www.actahort.org2018-05-10hj2017Plant Production and Soil Scienc
Tagged IDS causes efficient and engraftment-independent prevention of brain pathology during lentiviral gene therapy for Mucopolysaccharidosis type II
Mucopolysaccharidosis type II (OMIM 309900) is a lysosomal storage disorder caused by iduronate 2-sulfatase (IDS) deficiency and accumulation of glycosaminoglycans, leading to progressive neurodegeneration. As intravenously infused enzyme replacement therapy cannot cross the blood-brain barrier (BBB), it fails to treat brain pathology, highlighting the unmet medical need to develop alternative therapies. Here, we test modified versions of hematopoietic stem and progenitor cell (HSPC)-mediated lentiviral gene therapy (LVGT) using IDS tagging in combination with the ubiquitous MND promoter to optimize efficacy in brain and to investigate its mechanism of action. We find that IDS tagging with IGF2 or ApoE2, but not RAP12x2, improves correction of brain heparan sulfate and neuroinflammation at clinically relevant vector copy numbers. HSPC-derived cells engrafted in brain show efficiencies highest in perivascular areas, lower in choroid plexus and meninges, and lowest in parenchyma. Importantly, the efficacy of correction was independent of the number of brain-engrafted cells. These results indicate that tagged versions of IDS can outperform untagged IDS in HSPC-LVGT for the correction of brain pathology in MPS II, and they imply both cell-mediated and tag-mediated correction mechanisms, including passage across the BBB and increased uptake, highlighting their potential for clinical translation.</p
Coming full circle: Differential empowerment in the EU accession process
The EU accession process brings a profound transformation not only to candidate countries’
institutions and policies, but also to the political opportunity structure in place, creating new
possibilities for previously marginalised actors. Studying the differential empowerment of
NGOs throughout the Croatian accession process, this paper makes two related claims: first,
differential empowerment depends crucially on domestic actors’ awareness for and ability to
use new opportunities to their advantage. Second, an overreliance on EU leverage poses
important temporal and substantive limits on NGO empowerment and leads to a rapid decline
of their relevance in the post-accession phase. I argue that a more sustainable shift in the
domestic power balance would require both the EU and domestic civil society actors to place
more emphasis on fostering improved practices of civil society inclusion in domestic policymaking
settings throughout the accession process
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