9 research outputs found
The XMM Cluster Survey: Exploring scaling relations and completeness of the Dark Energy Survey Year 3 redMaPPer cluster catalogue
We cross-match and compare characteristics of galaxy clusters identified in
observations from two sky surveys using two completely different techniques.
One sample is optically selected from the analysis of three years of Dark
Energy Survey observations using the redMaPPer cluster detection algorithm. The
second is X-ray selected from XMM observations analysed by the XMM Cluster
Survey. The samples comprise a total area of 57.4 deg, bounded by the area
of 4 contiguous XMM survey regions that overlap the DES footprint. We find that
the X-ray selected sample is fully matched with entries in the redMaPPer
catalogue, above 20 and within 0.10.9. Conversely, only 38\%
of the redMaPPer catalogue is matched to an X-ray extended source. Next, using
120 optically clusters and 184 X-ray selected clusters, we investigate the form
of the X-ray luminosity-temperature (), luminosity-richness
() and temperature-richness () scaling relations.
We find that the fitted forms of the relations are consistent
between the two selection methods and also with other studies in the
literature. However, we find tentative evidence for a steepening of the slope
of the relation for low richness systems in the X-ray selected sample. When
considering the scaling of richness with X-ray properties, we again find
consistency in the relations (i.e., and )
between the optical and X-ray selected samples. This is contrary to previous
similar works that find a significant increase in the scatter of the luminosity
scaling relation for X-ray selected samples compared to optically selected
samples.Comment: Accepted for publication to MNRA
Economics of supply reliability of irrigation water
In this study, we have assessed the economic impact of potential increase in supply
reliability of irrigation water in the Hinds Plains Area in the Ashburton district. The
Hinds catchment has a number of irrigation schemes namely, Rangitata Diversion
Race (provides water for Mayfield Hinds and Valetta Schemes), Barrhill Chertsey,
Eiffelton and Lynford Schemes. All these schemes have varying supply reliability
which ranges from 40% to 80% approximately. First, we estimated the relationship
between water availability and pasture growth using experimental data. We then
employed this relationship to estimate the potential incremental pasture growth with
assumed increased supply reliability (95%) at farm level. We estimated the farm level
benefit of increased pasture production in terms of saved costs in supplementary feed.
These farm level estimates were used to assess the catchment level farm income gain.
The catchment level income gain was then employed to assess the regional level
economic gain (GDP and employment) by the socio-accounting matrix input-output
model (SAMI-O) simulation. Income gain at catchment level is estimated to vary
from 17million. This implies an additional gain in regional level income
(GDP) of 91million and additional employment of 137 FTE to 207 FTE. The
study indicates the importance of an increase in irrigation efficiency at farm level for
the local and regional economy and also discusses the potential environmental
impacts of increase irrigation efficiency at catchment level
In Silico Comparison of the Hemicelluloses Xyloglucan and Glucuronoarabinoxylan in Protecting Cellulose from Degradation
We used a previously developed simulation model of a plant cell wall and its enzymatic degradation to compare the abilities of two hemicelluloses, glucuronoarabinoxylan (GAX) and xyloglucan (XG), to protect cellulose microfibrils (CMFs) from attack by cellulose-degrading enzymes. Additionally, we investigated the effect of XG abundance on the degradation rate of CMFs in the presence of the same enzymes. Simulations were run using hypothetical cell-wall compositions in which the numbers and arrangement of CMFs and (1,3;1,4)-β-glucan were kept constant, but the proportions of GAX and XG were altered. Scenarios considered walls with low and equal proportions of either GAX or XG, and also low, medium and high proportions of XG in the absence of GAX. The rate of CMF degradation was much lower in walls with GAX than walls with XG, except for early in the simulation when the reverse held, suggesting that XGs were protecting CMFs by competitive inhibition. Increasing XG content reduced both the degradation rate of CMFs and the percent of XG degraded, indicating that activity of enzymes decreased with XG density despite XG being degradable. Glucose oligosaccharide breakdown products were analysed on the basis of the originating polysaccharide and their degree of polymerisation (DP). The presence of GAX as opposed to equal amounts of XG had some significant effects on the amount and profile of breakdown products from XG and CMFs
Decadal Changes in Soil Carbon and Nitrogen under a Range of Irrigation and Phosphorus Fertilizer Treatments
We determined decadal changes in soil carbon (C) and nitrogen (N) due to different irrigation regimes and phosphorus fertilization of pastures. Archived soil samples (0–75 mm) collected annually from two long-term trials in New Zealand were analyzed for %C and %N from three P input treatments (ranging from 0 to 376 kg superphosphate ha−1 yr−1, 1952–2009) and three irrigation treatments (unirrigated and irrigated when soil moisture content fell below either 10 or 20%, 1959–2002). In the fertilizer trial, soil C increased linearly from 2.7 to 4.2%, and there was no difference in rates of increase in C between treatments, despite much greater aboveground production when P was added. This lack of difference was attributed to higher stocking rates on treatments with higher production, and to the possibility that root inputs (which differed less between treatments) was a more important control of soil C accumulation. Nitrogen (%) was lower in the unfertilized than fertilized treatments due to lower clover N fixation, which was constrained by P availability. Soil C (%) was significantly greater in the unirrigated treatment than the irrigated treatments throughout the trial. Aboveground production was much greater in the irrigated than dryland treatment but root biomass was lower. Irrigation must have increased C and N losses, possibly via increased respiration rates during seasonally dry periods. Our study showed that P fertilizer application did not result in an increase in surface soil C and that flood irrigation resulted in a constrained increase in surface soil C content
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The XMM cluster survey: exploring scaling relations and completeness of the dark energy survey year 3 redMaPPer cluster catalogue
We cross-match and compare characteristics of galaxy clusters identified in observations from two sky surveys using two completely different techniques. One sample is optically selected from the analysis of 3 years of Dark Energy Survey observations using the redMaPPer cluster detection algorithm. The second is X-ray selected from XMM observations analysed by the XMM Cluster Survey. The samples comprise a total area of 57.4 deg2, bounded by the area of four contiguous XMM survey regions that overlap the DES footprint. We find that the X-ray-selected sample is fully matched with entries in the redMaPPer catalogue, above λ > 20 and within 0.