Short-term Response of Soil Iron to Nitrate Addition

The inhibition of soil Fe(III) reduction by fertilizer NO3 − applications is complex and not completely understood. This inhibition is important to study because of the potential impact on soil physicochemical properties. We investigated the effect of adding NO3 − to a moderately well-drained agricultural soil (Sadler silt loam) under Fe(III)-reducing (anoxic) conditions. Stirred-batch experiments were conducted where NO3 − was added (0.05 and 1 mM) to anoxic slurries and changes in dissolved Fe(II) and Fe(III), oxalate-extractable Fe(II), and dissolved NO3 − were monitored as a function of time. Addition of 1 mM NO3 − inhibited Fe(II) production sharply with reaction time, from 10% after 1 h to 85% after 24 h. The duration of inhibition in Fe(II) production was closely related to the presence of available NO3 −, suggesting preferential use of NO3 − by nitrate reductase enzyme. Active nitrate reductase was confirmed by the fivefold decline in NO3 − reduction rates in the presence of tungstate (WO4 2−), a well-known inhibitor of nitrate reductase. In addition, NO3 −–dependent Fe(II) oxidation was observed to contribute to the inhibition in Fe(II) production. This finding was attributed to a combination of chemical reoxidation of Fe(II) by NO2 −– and NO3 −–dependent Fe(II) oxidation by autotrophic bacteria. These two processes became more important at a greater initial oxalate-Fe(II)/NO3 − concentration ratio. The inhibitory effects in Fe(II) production were short-term in the sense that once NO3 − was depleted, Fe(II) production resumed. These results underscore the complexity of the coupled N–Fe redox system in soils

Nitrite Reduction by Siderite

Nitrate-dependent Fe(II) oxidation is an important process in the inhibition of soil Fe(III) reduction, yet the mechanisms are poorly understood. One proposed pathway includes chemical reoxidation of mineral forms of Fe(II) such as siderite [FeCO3(s)] by NO2 −. Accordingly, the objective of this study was to investigate the reactivity of FeCO3(s) with NO2 −. Stirred-batch reactions were performed in an anoxic chamber across a range of pH values (5.5, 6, 6.5, and 7.9), initial FeCO3(s) concentrations (5, 10, and 15 g L−1) and initial NO2 − concentrations (0.83–9.3 mmol L−1) for kinetic and stoichiometric determinations. Solid-phase products were characterized using x-ray diffraction (XRD). Siderite abiotically reduced NO2 − to N2O. During the process, FeCO3(s) was oxidized to lepidocrocite [γ-FeOOH(s)] based on the appearance of XRD peaks located at 0.624, 0.329, and 0.247 nm. The rate of NO2 − reduction was first order in total NO2 − concentration and FeCO3(s), with a second-order rate coefficient (k) of 0.55 ± 0.05 M−1 h−1 at pH 5.5 and 25°C. The reaction was proton assisted and k values increased threefold as pH decreased from 7.9 to 5.5. The influence of pH on NO2 − reduction was rationalized in terms of the availability of FeCO3(s) surface sites (\u3eFeHCO3 0, \u3eFeOH2 +, and \u3eCO3Fe+) and HNO2 concentration. These findings indicate that if FeCO3(s) is present in an Fe(III)-reducing soil where fertilizer NO3 − is applied, it can participate in secondary chemical reactions with NO2 − and lead to an inhibition in Fe(III) reduction. This process is relevant in soil environments where NO3 −– and Fe(III)-reducing zones overlap or across aerobic–anaerobic interfaces

Real-world scenario improvements in serum phosphorus levels and pill burden in peritoneal dialysis patients treated with sucroferric oxyhydroxide

BackgroundA database analysis was conducted to assess the effectiveness of sucroferric oxyhydroxide (SO) on lowering serum phosphorus and phosphate binder (PB) pill burden among adult peritoneal dialysis (PD) patients prescribed SO as part of routine care.MethodsAdult PD patients (n = 258) prescribed SO through a renal pharmacy service were analyzed. Baseline was 3 months before SO prescription. SO-treated follow-up was for 6 months or until either a new PB was prescribed, SO was not refilled, PD modality changed, or patient was discharged. In-range serum phosphorus was defined as ≤5.5 mg/dL.ResultsAt baseline, mean serum phosphorus was 6.59 mg/dL with 10 prescribed PB pills/day. The proportion of patients achieving in-range serum phosphorus increased by 72% from baseline to month 6. Prescribed PB pills/day decreased by 57% (10 at baseline to 4.3 at SO follow-up, p < 0.0001). The mean length of SO follow-up was 5.1 months; SO follow-up ended for 38, 27, and 50 patients at months 4, 5, and 6, respectively, due to no further PB fills, and for 10, 11, and 4 patients at months 4, 5, and 6, respectively, due to another PB prescribed. In patients with baseline serum phosphorus >5.5 mg/dL who achieved in-range serum phosphorus during SO follow-up for ≥1 quarter, a notable improvement in serum phosphorus (6.54 to 5.10 mg/dL, p < 0.0001) was observed, and there was a 53% reduction in PB pill burden (9.9 to 4.7, p < 0.0001).ConclusionAmong PD patients prescribed SO as part of routine care, improvements in serum phosphorus control and >50% reduction in PB pills/day were observed

Observation and Spectral Measurements of the Crab Nebula with Milagro

The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100 GeV - 100 TeV gamma ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ~1 and ~100 TeV. The TeV emission is believed to be caused by inverse-Compton up-scattering scattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fit. The fit is consistent with values measured by IACTs between 1 and 20 TeV. Fixing the spectral index to values that have been measured below 1 TeV by IACT experiments (2.4 to 2.6), the fit to the Milagro data suggests that Crab exhibits a spectral steepening or cutoff between about 20 to 40 TeV.Comment: Submitted to Astrophysical Journa

Maximum static inspiratory and expiratory pressures with different lung volumes

BACKGROUND: Maximum pressures developed by the respiratory muscles can indicate the health of the respiratory system, help to determine maximum respiratory flow rates, and contribute to respiratory power development. Past measurements of maximum pressures have been found to be inadequate for inclusion in some exercise models involving respiration. METHODS: Maximum inspiratory and expiratory airway pressures were measured over a range of lung volumes in 29 female and 19 male adults. A commercial bell spirometry system was programmed to occlude airflow at nine target lung volumes ranging from 10% to 90% of vital capacity. RESULTS: In women, maximum expiratory pressure increased with volume from 39 to 61 cmH(2)O and maximum inspiratory pressure decreased with volume from 66 to 28 cmH(2)O. In men, maximum expiratory pressure increased with volume from 63 to 97 cmH(2)O and maximum inspiratory pressure decreased with volume from 97 to 39 cmH(2)O. Equations describing pressures for both sexes are: P(e)/P(max )= 0.1426 Ln( %VC) + 0.3402 R(2 )= 0.95 P(i)/P(max )= 0.234 Ln(100 - %VC) - 0.0828 R(2 = )0.96 CONCLUSION: These results were found to be consistent with values and trends obtained by other authors. Regression equations may be suitable for respiratory mechanics models