Magnetic Anisotropy of Co2+ as Signature of Intrinsic Ferromagnetism in ZnO:Co

We report on the magnetic properties of thoroughly characterized Zn1-xCoxO epitaxial thin films, with low Co concentration, x=0.003-0.005. Magnetic and EPR measurements, combined with crystal field theory, reveal that isolated Co2+ ions in ZnO possess a strong single ion anisotropy which leads to an "easy plane" ferromagnetic state when the ferromagnetic Co-Co interaction is considered. We suggest that the peculiarities of the magnetization process of this state can be viewed as a signature of intrinsic ferromagnetism in ZnO:Co materials.Comment: 4 pages, 4 figure

Modelling estuarine biogeochemical dynamics: from the local to the global scale

Estuaries act as strong carbon and nutrient filters and are relevant contributors to the atmospheric CO2 budget. They thus play an important, yet poorly constrained, role for global biogeochemical cycles and climate. This manuscript reviews recent developments in the modelling of estuarine biogeochemical dynamics. The first part provides an overview of the dominant physical and biogeochemical processes that control the transformations and fluxes of carbon and nutrients along the estuarine gradient. It highlights the tight links between estuarine geometry, hydrodynamics and scalar transport, as well as the role of transient and nonlinear dynamics. The most important biogeochemical processes are then discussed in the context of key biogeochemical indicators such as the net ecosystem metabolism (NEM), air–water CO2 fluxes, nutrient-filtering capacities and element budgets. In the second part of the paper, we illustrate, on the basis of local estuarine modelling studies, the power of reaction-transport models (RTMs) in understanding and quantifying estuarine biogeochemical dynamics. We show how a combination of RTM and high-resolution data can help disentangle the complex process interplay, which underlies the estuarine NEM, carbon and nutrient fluxes, and how such approaches can provide integrated assessments of the air–water CO2 fluxes along river–estuary–coastal zone continua. In addition, trends in estuarine biogeochemical dynamics across estuarine geometries and environmental scenario are explored, and the results are discussed in the context of improving the modelling of estuarine carbon and CO2 dynamics at regional and global scales

In situ generation of coronal Alfvén waves by jets

Within the framework of 3D resistive magnetohydrodynamic, we simulate the formation of a plasma jet with the morphology, upward velocity up to 130 km s−1, and time-scale formation between 60 and 90 s after beginning of simulation, similar to those expected for type II spicules. Initial results of this simulation were published in paper by, e.g. González-Avilés et al. (2018), and present paper is devoted to the analysis of transverse displacements and rotational-type motion of the jet. Our results suggest that 3D magnetic reconnection may be responsible for the formation of the jet in paper by González-Avilés et al. (2018). In this paper, by calculating times series of the velocity components vx and vy in different points near to the jet for various heights we find transverse oscillations in agreement with spicule observations. We also obtain a time-distance plot of the temperature in a cross-cut at the plane x = 0.1 Mm and find significant transverse displacements of the jet. By analysing temperature isosurfaces of 104 K with the distribution of vx, we find that if the line-of-sight (LOS) is approximately perpendicular to the jet axis then there is both motion towards and away from the observer across the width of the jet. This red–blue shift pattern of the jet is caused by rotational motion, initially clockwise and anti-clockwise afterwards, which could be interpreted as torsional motion and may generate torsional Alfvén waves in the corona region. From a nearly vertical perspective of the jet the LOS velocity component shows a central blue-shift region surrounded by red-shifted plasma

Predicting Future Trends of Terrestrial Dissolved Organic Carbon Transport to Global River Systems

A fraction of CO2 uptake by terrestrial ecosystems is exported as organic carbon (C) through the terrestrial-aquatic continuum. This translocated C plays a significant role in the terrestrial C balance; however, obtaining global assessments remains challenging due to the predominant reliance on empirical approaches. Leaching of dissolved organic C (DOC) from soils to rivers represents an important fraction of this C export and is assumed to drive a large proportion of the net-heterotrophy of river systems and the related CO2 emissions. Using the model JULES-DOCM, we projected DOC leaching trends over the 21st century based on three scenarios with high (RCP 2.6), intermediate (RCP 4.5), and low (RCP 8.5) climate mitigation efforts. The RCP 8.5 scenario led to the largest DOC leaching increase of +42% to 395 Tg C yr−1 by 2100. In comparison, RCP 2.6 and RCP 4.5 led to increases of 10% and 21%, respectively. Under RCP 8.5, the sub-tropical zone showed the highest relative increase of 50% above current levels. In the boreal and tropical zones, the simulations revealed similar increases of 48% and 41%, respectively. However, given the pre-eminence of the tropics in DOC leaching, the absolute increment is markedly substantial from this region (+59 Tg C yr−1). The temperate zone displayed the lowest relative increase with 35%. Our analysis identified the rising atmospheric CO2 concentration and its fertilizing effect on terrestrial NPP as the main reason for the future increase in DOC leaching

Electrosynthesis of Aryliminophosphoranes in Continuous Flow

A practical electrochemical method for synthesizing aryliminophosphoranes from widely available nitro(hetero)arenes in a continuous-flow system is presented. The utilization of flow technology offers several advantages to our approach, including the elimination of the need for a supporting electrolyte and enhanced scalability. Our method demonstrates good tolerance towards various functional groups, with electron-deficient nitroarenes being particularly suitable for this strategy. In addition, we have demonstrated the versatility of aryliminophosphoranes as intermediates in synthesizing anilines, amines, and amides. To further enhance the utility of our approach, we have developed a telescoped method that utilizes a tube-in-tube setup for the in-situ production of isocyanates

Ion and fluid transport properties of small airways in cystic fibrosis

Rationale: Small airways constitute amajor site of pathology in cystic fibrosis (CF) and provide most of the surface area of the conducting airways of the lung. Little is known, however, about the impact of CF on ion and fluid transport in small (bronchiolar) airways. Objectives: To describe the ion and fluid transport properties of CF bronchiolar epithelium. Methods: Primary cultures of human bronchial and bronchiolar (non-CF and CF) epithelial cells were obtained. The bioelectric properties were studied in Ussing chambers and the airway surface liquid (ASL) height was measured with confocal microscopy. Main Results: Primary cultures of ΔF508 CF bronchiolar epithelial cells displayed higher transepithelial resistance than non-CF cultures, whereas baseline short circuit current and amiloride-inhibitable short circuit current were similar in both preparations. The ASL height was significantly smaller in CF compared with non-CF preparations. In the presence of amiloride, addition of forskolin increased short circuit current in non-CF but not in CF bronchiolar cultures, and the ATP-induced increase in short circuit current was lower in CF than in non-CF cultures. Non-CF bronchiolar preparations displayed larger short circuit current and fluid secretion in responses to forskolin than non-CF bronchial preparations, suggesting that CFTR-dependent Cl- transport may play a more important role in the regulation of fluid transport in small airways than in large airways. Conclusion: In CF small airways, defective Cl- secretion combined with unregulated (persistent) Na+ absorption results in ASLdepletion

Seasonal dynamics of the depth and rate of anaerobic oxidation of methane in Aarhus Bay (Denmark) sediments

A reactive-transport model has been applied to investigate the dynamics of the sulfate-methane transition zone (SMTZ) in nearshore sediments of Aarhus Bay (Denmark). The sediments are influenced by seasonal variations of temperature and particulate organic carbon (POC) deposition flux at the sediment-water interface. Initially, the model was calibrated at steady state using field data collected at two sites (M1 and M5) in December 2004, and included a dynamic gas phase which determines the depth of the SMTZ. Simulations were then performed under transient conditions of heat propagation in the porous medium, which influenced the solubility of gaseous methane, the diffusion of solutes as well as the kinetic and bioenergetic constraints on redox conditions in the system. Results revealed important variations in local rates of anaerobic oxidation of methane (AOM) over a seasonal cycle due to temperature variation. Seasonal perturbations in POC depositional flux had no influence on AOM rates but did have a strong bearing on sulfate reduction rates in the surface layers of the simulations at both stations. At M5, where the SMTZ was located 63 cm below the sediment-water interface, depth integrated AOM rates varied between 76 and 178 nmol cm-2 d-1. At M1, where the deeper SMTZ (221 cm) experienced less thermal variation, AOM rates varied relatively less (20 to 24 nmol cm-2 d-1). Furthermore, local and depth-integrated AOM rates over the year did not show a simple response to bottom water temperature but exhibited a hysteresis-type behavior related to time lags in solute transport and heat propagation. Overall, the solute concentration profiles were not very sensitive to the seasonal variability in rates or gas transport and the modeled vertical displacement of the SMTZ was limited to <1 cm at M1 and 2–3 cm at M5. The results suggest that the significantly larger apparent displacement observed in the field from repeated coring (80 cm and 16 cm at M1 and M5, respectively) must be attributed to other factors, of which spatial heterogeneity in gas transport rate appears to be the most likely