While nitrogen (N) fixation is an important process in nitrogen (N) biogeochemical cycling, supplying a significant portion of the N in natural ecosystems, few quantitative constraints exist concerning its contribution to the N enrichment and export from river ecosystems. This study estimates the N fixation rates of urban rivers in the Yangtze Estuary area using acetylene reduction. The results demonstrate that the prominent spatiotemporal variability of river N fixation rates is driven by various environmental factors. River N fixation rates are significantly higher in the summer (90.57 ± 14.60 ngN·L·h) than in the winter (57.98 ± 15.73 ngN·L·h). Spatially, rivers draining urban and suburban areas have higher N fixation rates than those draining rural areas. The N fixation rates are positively correlated with the N fixing cyanobacteria density, water temperature, light, and the water phosphorus (P) concentration, but they are negatively correlated with the dissolved N concentration (NH-N and NO-N). The N fixation rates annually range from 53.20 to 89.24 ngN·L·h for all of the sampling rivers, which is equivalent to a depth integrated (0-0.6 m) N input of 0.163-0.274 gN·m·a. The determined annual N input via N fixation is generally higher than that of marine systems, but it is lower than that of eutrophic lakes. This study provides robust evidence that N fixation can supply a substantial portion of the N input to human-impacted river ecosystems, which has not been sufficiently accounted for when determining the N mass balance of riverine ecosystems. A high N fixation rate may increase the ratio of N to P input to river systems, and therefore render P the limiting factor in aquatic eutrophication.
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http://dx.doi.org/10.1007/s11356-019-06780-w | DOI Listing |
Patient Saf Surg
January 2025
Department of Trauma, University Hospital Zurich, Raemistrasse 100, Zurich, 8091, Switzerland.
Introduction: Regional anesthesia increases in popularity in orthopaedic surgery. It is usually applied in elective surgeries of the extremities. The aim of this study was to assess indication of the use of general anesthesia in the surgical treatment of distal radius fractures.
View Article and Find Full Text PDFJ Evol Biol
December 2024
Department of Mathematics and Statistics, University of Reading, UK.
The time needed for the evolution of mating cues that distinguish species, such as species-specific songs or plumage coloration in birds, has received little attention. Aiming to gain some understanding of the timing of the evolutionary process we here present models of how mating cues evolve in populations split into subpopulations between which there may (parapatry) or may not (allopatry) be migration. Mating cues can be either neutral or directly selected.
View Article and Find Full Text PDFPurpose: Double-level osteotomies (DLOs) have shown promising results for knee joint preservation, however, most ultimately progress in terms of degenerative disease resulting in conversion to total knee arthroplasty (TKA). Therefore, the purpose of this study was to examine the time to TKA conversion, long-term clinical outcomes and revision rates of patients who have undergone TKA after prior ipsilateral DLO.
Methods: Patients who underwent simultaneous or staged DLO and subsequently underwent conversion to TKA at a single academic institution from 1997 to 2022 were evaluated.
Nature
January 2025
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, USA.
The low reduction potentials required for the reduction of dinitrogen (N) render metal-based nitrogen-fixation catalysts vulnerable to irreversible damage by dioxygen (O). Such O sensitivity represents a major conundrum for the enzyme nitrogenase, as a large fraction of nitrogen-fixing organisms are either obligate aerobes or closely associated with O-respiring organisms to support the high energy demand of catalytic N reduction. To counter O damage to nitrogenase, diazotrophs use O scavengers, exploit compartmentalization or maintain high respiration rates to minimize intracellular O concentrations.
View Article and Find Full Text PDFAims: The Peri-Implant and PeriProsthetic Survival AnalysiS (PIPPAS) study aimed to investigate the risk factors for one-year mortality of femoral peri-implant fractures (FPIFs).
Methods: This prospective, multicentre, observational study involved 440 FPIF patients with a minimum one-year follow-up. Data on demographics, clinical features, fracture characteristics, management, and mortality rates were collected and analyzed using both univariate and multivariate analyses.
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