Arginase from kiwifruit: properties and seasonal variation

The in vitro activity of arginase (EC 3.5.3.1) was investigated in youngest-mature leaves and roots (1-3 mm diameter) of kiwifruit vines (Actinidia deliciosa var. deliciosa) during an annual growth cycle, and enzyme from root material partially purified. No seasonal trend in the specific activity of arginase was observed in roots. Measurements in leaves, however, rose gradually during early growth and plateaued c. 17 weeks after budbreak. Changes in arginase activity were not correlated with changes in the concentration of arginine (substrate) or glutamine (likely end-product of arginine catabolism) in either tissue during the growth cycle. Purification was by (NH4)2SO4 precipitation and DEAE-cellulose chromatography. The kinetic properties of the enzyme, purified 60-fold over that in crude extracts, indicated a pH optimum of 8.8, and a Km (L-arginine) of 7.85 mM. Partially-purified enzyme was deactivated by dialysis against EDTA, and reactivated in the presence of Mn²⁺, Co²⁺, and Ni²⁺

The XMM Cluster Survey: An independent demonstration of the fidelity of the eFEDS galaxy cluster data products and implications for future studies

We present the first comparison between properties of clusters of galaxies detected by the eROSITA Final Equatorial-Depth Survey (eFEDS) and the XMM Cluster Survey (XCS). We have compared, in an ensemble fashion, properties from the eFEDS X-ray cluster catalogue with those from the Ultimate XMM eXtragaLactic (XXL) survey project (XXL-100-GC). We find the redshift and temperature (TX) distributions to be similar, with a larger proportion of clusters above 4 keV in the XXL-100-GC sample; fractional temperature uncertainties are significantly larger in eFEDS compared to XXL. We find 62 eFEDS cluster candidates with XMM data (eFEDS-XMM sample); 10 do not have good enough XMM data to confirm or deny, 11 are classed as sample contaminants, and 4 have their X-ray flux contaminated by another source. The majority of eFEDS-XMM sources have longer XMM exposures than eFEDS, and most eFEDS positions are within 100 kpc of XCS positions. Our eFEDS-XCS sample of 37 clusters is used to calculate minimum sample contamination fractions of ∼18 and ∼9 per cent in the eFEDS X-ray and optically confirmed samples, respectively, in general agreement with eFEDS findings. We directly compare 29 X-ray luminosities (LX) measured by eFEDS and XCS, finding excellent agreement. Eight clusters have a TX measured by XCS and eFEDS, and we find that XMM temperatures are 25 ± 9 per cent larger than their eROSITA counterparts. Finally, we construct LX-TX scaling relations based on eFEDS and XCS measurements, which are in tension; the tension is decreased when we measure a third scaling relation with calibrated XCS temperatures

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 0.1 <0.9. Conversely, only 38 per cent 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 (LX -TX ), luminosity-richness (LX -λ), and temperature-richness (TX -λ) scaling relations. We find that the fitted forms of the LX -TX 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. LX -λ and TX -λ) 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

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$^2$, 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 $\lambda>$20 and within 0.1$< z <$0.9. Conversely, only 38\% of the redMaPPer catalogue is matched to an X-ray extended source. Next, using 120 optically clusters and 184 X-ray selected clusters, we investigate the form of the X-ray luminosity-temperature ($L_{X}-T_{X}$), luminosity-richness ($L_{X}-\lambda$) and temperature-richness ($T_{X}-\lambda$) scaling relations. We find that the fitted forms of the $L_{X}-T_{X}$ 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., $L_{X}-\lambda$ and $T_{X}-\lambda$) 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

The XMM Cluster Survey analysis of the SDSS DR8 redMaPPer catalogue: implications for scatter, selection bias, and isotropy in cluster scaling relations

In this paper, we present the X-ray analysis of Sloan Digital Sky Survey DR8 redMaPPer (SDSSRM) clusters using data products from the XMM Cluster Survey (XCS). In total, 1189 SDSSRM clusters fall within the XMM-Newton footprint. This has yielded 456 confirmed detections accompanied by X-ray luminosity (LX) measurements. Of these clusters, 381 have an associated X-ray temperature measurement (TX). This represents one of the largest samples of coherently derived cluster TX values to date. Our analysis of the X-ray observable to richness scaling relations has demonstrated that scatter in the TX-λ relation is roughly a third of that in the LX-λ relation, and that the LX-λ scatter is intrinsic, i.e. will not be significantly reduced with larger sample sizes. Analysis of the scaling relation between LX and TX has shown that the fits are sensitive to the selection method of the sample, i.e. whether the sample is made up of clusters detected 'serendipitously' compared to those deliberately targeted by XMM. These differences are also seen in the LX-λ relation and, to a lesser extent, in the TX-λ relation. Exclusion of the emission from the cluster core does not make a significant impact on the findings. A combination of selection biases is a likely, but yet unproven, reason for these differences. Finally, we have also used our data to probe recent claims of anisotropy in the LX-TX relation across the sky. We find no evidence of anistropy, but stress this may be masked in our analysis by the incomplete declination coverage of the SDSS

The XMM Cluster Survey analysis of the SDSS DR8 redMaPPer Catalogue:mplications for scatter, selection bias, and isotropy in cluster scaling relations

In this paper, we present the X-ray analysis of SDSS DR8 redMaPPer (SDSSRM) clusters using data products from the XMM Cluster Survey (XCS). In total, 1189 SDSSRM clusters fall within the XMM-Newton footprint. This has yielded 456 confirmed detections accompanied by X-ray luminosity (LX) measurements. Of these clusters, 381 have an associated X-ray temperature measurement (TX). This represents one of the largest samples of coherently derived cluster TX values to date. Our analysis of the X-ray observable to richness scaling relations has demonstrated that scatter in the TX − λ relation is roughly a third of that in the LX − λ relation, and that the LX − λ scatter is intrinsic, i.e. will not be significantly reduced with larger sample sizes. Analysis of the scaling relation between LX and TX has shown that the fits are sensitive to the selection method of the sample, i.e. whether the sample is made up of clusters detected “serendipitously” compared to those deliberately targeted by XMM. These differences are also seen in the LX − λ relation and, to a lesser extent, in the TX − λ relation. Exclusion of the emission from the cluster core does not make a significant impact on the findings. A combination of selection biases is a likely, but yet unproven, reason for these differences. Finally, we have also used our data to probe recent claims of anisotropy in the LX − TX relation across the sky. We find no evidence of anistropy, but stress this may be masked in our analysis by the incomplete declination coverage of the SDSS

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 0.1 <z <0.9. Conversely, only 38 per cent 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 (LX -TX ), luminosity-richness (LX -λ), and temperature-richness (TX -λ) scaling relations. We find that the fitted forms of the LX -TX 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. LX -λ and TX -λ) 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

Changes in natural ¹⁵n abundance in pastoral soils receiving differing amounts of superphosphate fertilizer and irrigation for 50 years

Intensification of pastoral agriculture has led to increased N losses to the wider environment. This has led to an emphasis on improving our understanding of soil N dynamics, and development of management practices which mitigate N losses. The natural abundance of the stable isotope δ¹⁵N relative to ¹⁴N (δ¹⁵N) in soils can provide an integrated measure of past N cycle processes, and in particular soil δ15N can reflect past N losses, because during most N transformation processes 14N is preferentially lost. We therefore hypothesized that pastoral soils under intensive management regimes (with high N inputs, cycling, and loss) would become progressively enriched with ¹⁵N relative to soils under less intensive management. To test this hypothesis we analyzed archived surface soils from two long-term grazed field trials in New Zealand, where different rates of irrigation and superphosphate fertilizer had been applied for ∼50 yr. In all treatments except one (a control treatment receiving no fertilizer), δ¹⁵N increased with time and the increase was greater in treatments receiving more superphosphate or irrigation (average increases ranged from ∼0.015–0.034 ‰ yr–1). Pasture production and grazing intensity also increased with increasing fertilizer rate and irrigation frequency, and we found positive correlations between the average rate of change in soil δ¹⁵N, and total pasture production (r² = 0.77, p = 0.02), clover production (r² = 0.95, p < 0.001), and calculated N losses (r² = 0.98, p < 0.001) over ∼50 yr. We suggest that most of the difference in δ¹⁵N observed between treatments was due to the influence fertilizer and irrigation had on pasture production, and the resulting effects this had on isotope fractionating N loss processes. Soil δ¹⁵N could therefore be a useful indicator of past management intensity and N cycling and loss from pastoral systems