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Sökning: WFRF:(Reading J)

  • Resultat 1-9 av 9
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  • Correa, R. E., et al. (författare)
  • Submarine groundwater discharge and associated nutrient and carbon inputs into Sydney Harbour (Australia)
  • 2020
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 580
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of urbanization and scales on submarine groundwater discharge (SGD) remain poorly understood. Here, we used radium isotopes to quantify SGD-derived fluxes of nitrogen, phosphorus and dissolved organic carbon (DOC) into Sydney Harbour estuary, Australia. Sydney is the most populated city of Oceania, with several localised cases of historical groundwater pollution. We sampled top and bottom waters at the harbour scale (~20 km) and also at four small scale embayments (~2 km). A decreasing gradient in radium isotope concentrations from upstream to downstream was observed. Mass balances constructed with 224Ra, 223Ra, and 226Ra revealed that total SGD ranged from 42 to 121 × 104 m3 d−1 depending on assumptions and isotope. These fluxes were related mostly to saline SGD (recirculated seawater), and are equivalent to >60 times the mean annual freshwater river discharge into Sydney Harbour (0.68 × 104 m3 d−1). The estimated SGD rates (2.2 ± 1.5 cm d−1) were comparable to the global average radium-derived-SGD in other urban estuaries (~3.1 cm d−1). No obvious relationships were observed between SGD and scale in Sydney Harbour. However, higher SGD rates estimated for embayments closer to the ocean indicate that a combination of waves, tides and urbanization control SGD. SGD derived fluxes exceeded maximum riverine nutrient fluxes by a factor of 2 for DOC, 6 for PO4 3−, 40 for NH4 + and 1.3 for NOX. Previous work has suggested that nutrients enter Sydney Harbour primarily through rivers or stormwater following episodic rain events. Our results imply that diffuse saline SGD can also be an important but overlooked source of nutrients, potentially sustaining primary productivity in times of no river flow. © 2019 Elsevier B.V.
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  • Reading, M. J., et al. (författare)
  • Spatial Distribution of CO2, CH4, and N2O in the Great Barrier Reef Revealed Through High Resolution Sampling and Isotopic Analysis
  • 2021
  • Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 48:15
  • Tidskriftsartikel (refereegranskat)abstract
    • Methane (CH4) and nitrous oxide (N2O) dynamics in coastal coral reef areas are poorly understood. We measured dissolved carbon dioxide (CO2) and CH4 (with delta C-13-CO2 and delta C-13-CH4 isotope fractions) and N2O in the Great Barrier Reef (GBR) to determine spatial distributions and emissions. CO2 (379-589 mu atm) was oversaturated due to calcification and riverine sources, as indicated by depleted delta C-13-CO2 values. CH4 (1.5-13.5 nM) was also oversaturated from nearshore biogenic sources indicated by depleted delta C-13-CH4 and probable offshore aerobic production. N2O (5.5-6.6 nM) was generally undersaturated, with uptake highest near the coast. Daily CO2 emissions were 5826 +/- 1191 tonnes, with CO2 equivalent ((eq)) N2O uptake (191 +/- 44 tonnes) offsetting 3.3% of CO2 or 89% of CH4eq (214 +/- 45 tonnes) emissions based on 20-year global warming potentials. The GBR was a slight CO2 and CH4 source and N2O sink during our study. However, further work is required to constrain diurnal, seasonal, and spatial dynamics.
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  • Reading, M. J., et al. (författare)
  • Submarine groundwater discharge drives nitrous oxide source/sink dynamics in a metropolitan estuary
  • 2021
  • Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 66:5, s. 1665-1686
  • Tidskriftsartikel (refereegranskat)abstract
    • Coastal waterways can be significant sources of the potent greenhouse gas nitrous oxide (N2O) due to nitrogen inputs and eutrophication. Here, we quantify groundwater derived N2O inputs and atmospheric emissions within a modified urban embayment (Sydney Harbour, Australia). Overall, we found low N2O saturation (91-171%) and air-water fluxes (-2.2 to 24.6 mu mol m(-2) d(-1)). Concentrations were highest in upstream brackish areas and a commercial/industrial subembayment. Dissolved inorganic nitrogen concentrations were low and inversely correlated to N2O throughout the harbor. N2O surface water dynamics were apparently driven by saline submarine groundwater discharge, as quantified by the radioisotope tracer radon-222. Groundwater discharge was highest within the embayments and mangrove-lined upper estuary. While groundwater was a net N2O source to surface waters, two upstream sub-embayments featured groundwater N2O concentrations lower than surface water, suggesting a sink driven by surface waters recirculating in intertidal sediments. Surface-water N2O was undersaturated within one upstream embayment, likely due to N2O consumption within sediments. Contrastingly, the downstream embayments featured higher groundwater N2O and accounted for 45% +/- 21% of the groundwater N2O flux. Sydney Harbour was a net source of N2O to the atmosphere (mean 0.6 +/- 0.3 mu mol m(-2) d(-1)) with larger N2O fluxes occurring from relatively small areas. N2O emissions (expressed in CO2 equilivents) were equivalent to 17% of CO2 emission estimates from previous studies. The low N2O emissions in Sydney Harbour contrast with other modified estuaries which often emit higher N2O fluxes due to larger nitrogen inputs.
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  • Nakatani, Yoshio, et al. (författare)
  • Role of Alanine Racemase Mutations in Mycobacterium tuberculosis D-Cycloserine Resistance
  • 2017
  • Ingår i: Antimicrobial Agents and Chemotherapy. - : AMER SOC MICROBIOLOGY. - 0066-4804 .- 1098-6596. ; 61:12
  • Tidskriftsartikel (refereegranskat)abstract
    • A screening of more than 1,500 drug-resistant strains of Mycobacterium tuberculosis revealed evolutionary patterns characteristic of positive selection for three alanine racemase (Alr) mutations. We investigated these mutations using molecular modeling, in vitro MIC testing, as well as direct measurements of enzymatic activity, which demonstrated that these mutations likely confer resistance to D-cycloserine.
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  • Reading, M. J., et al. (författare)
  • Land use drives nitrous oxide dynamics in estuaries on regional and global scales
  • 2020
  • Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 65:8, s. 1903-20
  • Tidskriftsartikel (refereegranskat)abstract
    • Urban and agricultural development of coastal catchments is known to increase dissolved nitrogen inputs into estuaries; however, much less is known about how land use influences the production of the powerful greenhouse gas nitrous oxide (N2O). Here, we assess dissolved N2O dynamics in four nearby estuaries across a regional land use gradient and summarize the literature to put the observations into global perspective. During summer dry conditions, N2O saturation ranged from 131.4% +/- 45.0% in the most pristine system (28% modified) to 198.6% +/- 52.3% within the most modified urban system (91% modified). The N2O saturation in the wetter winter campaign was higher and more variable than the summer dry campaign (range 84.7-677.7%) likely due to direct transport of N2O into the estuaries from catchment runoff and/or produced through denitrification fueled by high nitrate inputs. During both seasons, N2O was lowest in areas adjacent to fringing mangroves and highest in upstream fresh/saltwater mixing areas. Coupling our results with previously published N2O data from 50 estuarine systems worldwide revealed that estuarine N2O increases concomitantly with catchment modification, dissolved inorganic nitrogen availability, and decreasing oxygen concentrations. Based on these results, a 1% increase in anthropogenic modification to global catchments (i.e., agricultural development and/or urbanization) may increase estuarine N2O saturation by 2.6% +/- 1.2%. These findings indicate that future estuarine N2O emissions are likely to increase as anthropogenic modification of coastal catchments intensifies.
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  • Schubert, Jessica, et al. (författare)
  • Low-density lipoprotein cholesterol reduction and statin intensity in myocardial infarction patients and major adverse outcomes : A Swedish nationwide cohort study
  • 2021
  • Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 0195-668X .- 1522-9645. ; 42:3, s. 243-252
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: Clinical trials have demonstrated that a reduction in low-density lipoprotein cholesterol (LDL-C) reduces cardiovascular (CV) events. This has, however, not yet been shown in a real-world setting. We aimed to investigate the association between LDL-C changes and statin intensity with prognosis after a myocardial infarction (MI). Methods and results: Patients admitted with MI were followed for mortality and major CV events. Changes in LDL-C between the MI and a 6-to 10-week follow-up visit were analysed. The associations between quartiles of LDL-C change and statin intensity with outcomes were assessed using adjusted Cox regression analyses. A total of 40 607 patients were followed for a median of 3.78 years. The median change in LDL-C was a 1.20 mmol/L reduction. Patients with larger LDL-C reduction (1.85 mmol/L, 75th percentile) compared with a smaller reduction (0.36 mmol/L, 25th percentile) had lower hazard ratios (HR) for all outcomes (95% confidence interval): composite of CV mortality, MI, and ischaemic stroke 0.77 (0.70-0.84); all-cause mortality 0.71 (0.63-0.80); CV mortality 0.68 (0.57-0.81); MI 0.81 (0.73-0.91); ischaemic stroke 0.76 (0.62-0.93); heart failure hospitalization 0.73 (0.63-0.85), and coronary artery revascularization 0.86 (0.79-0.94). Patients with ≥50% LDL-C reduction using high-intensity statins at discharge had a lower incidence of all outcomes compared with those using a lower intensity statin. Conclusions: Larger early LDL-C reduction and more intensive statin therapy after MI were associated with a reduced hazard of all CV outcomes and all-cause mortality. This supports clinical trial data suggesting that earlier lowering of LDL-C after an MI confers the greatest benefit.
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