Solid-solid phase equilibria in the NaCl-KCl system

Solid solutions, structurally ordered but compositionally disordered mixtures, can form for salts, metals, and even organic compounds. The NaCl-KCl system forms a solid solution at all compositions between 657 °C and 505 °C. Below a critical temperature of 505 °C, the system exhibits a miscibility gap with coexisting Na-rich and K-rich rocksalt phases. We calculate the phase diagram in this region using the semi-grand canonical Widom method, which averages over virtual particle transmutations. We verify our results by comparison with free energies calculated from thermodynamic integration and extrapolate the location of the critical point. Our calculations reproduce the experimental phase diagram remarkably well and illustrate how solid-solid equilibria and chemical potentials, including those at metastable conditions, can be computed for materials that form solid solutions

Landscape-scale variation in forest structure and biomass along an elevation gradient in the Atlantic Forest of the Serra do Mar, Brazil.

Landscape-scale quantification of forest structure, disturbance patterns and biomass distribution can improve our understanding of the environmental controls on the functioning of forested ecosystems. Assessing the detailed structure of the complex tropical forest canopy is a challenging task, especially in areas of steep topography where field access is limited. We used airborne lidar (light detection and ranging) data to describe the landscape-scale variation in canopy structure and gap distribution in a 1000-ha area along an elevation gradient from 0 to 1200m in the Atlantic Forest of the Serra do Mar in southeast Brazil. Mean canopy heights (MCHs) were greatest (21-22m) at intermediate elevations (200-700m) in the submontane forest where terrain slope was also the steepest (~40º). Canopy gap fraction was highest (~30%) and MCH lowest (~16m) in the montane forest areas (900-1100m) on flatter sites atop the plateau (~24º slopes). We used forest inventory data from nine 1-ha permanent field plots (PFPs) within the study area to assess aboveground biomass (AGB) stocks and changes. We established regression models based on lidar-derived canopy structure and field-based biometry data, and used these to extrapolate AGB predictions across the landscape. Comparing canopy height and disturbance distributions in the PFPs with the distributions across the broader landscape, we found that submontane PFPs showed closer correspondence with their surrounding areas, while montane PFPs consistently overestimated landscape-scale canopy height (thus AGB pools) and underestimated gap fraction (therefore AGB changes)

Low-regret climate change adaptation in coastal megacities – evaluating large-scale flood protection and small-scale rainwater detention measures for Ho Chi Minh City, Vietnam

Urban flooding is a major challenge for many megacities in low-elevation coastal zones (LECZs), especially in Southeast Asia. In these regions, the effects of environmental stressors overlap with rapid urbanization, which significantly aggravates the hazard potential. Ho Chi Minh City (HCMC) in southern Vietnam is a prime example of this set of problems and therefore a suitable case study to apply the concept of low-regret disaster risk adaptation as defined by the Intergovernmental Panel on Climate Change (IPCC). In order to explore and evaluate potential options of hazard mitigation, a hydro-numerical model was employed to scrutinize the effectiveness of two adaptation strategies: (1) a classic flood protection scheme including a large-scale ring dike as currently constructed in HCMC and (2) the widespread installation of small-scale rainwater detention as envisioned in the framework of the Chinese Sponge City Program (SCP). A third adaptation scenario (3) assesses the combination of both approaches (1) and (2). From a hydrological point of view, the reduction in various flood intensity proxies that were computed within this study suggests that large-scale flood protection is comparable but slightly more effective than small-scale rainwater storage: for instance, the two adaptation options could reduce the normalized flood severity index (INFS), which is a measure combining flood depth and duration, by 17.9 % and 17.7 %, respectively. The number of flood-prone manufacturing firms that would be protected after adaptation, in turn, is nearly 2 times higher for the ring dike than for the Sponge City approach. However, the numerical results also reveal that both response options can be implemented in parallel, not only without reducing their individual effectiveness but also complementarily with considerable added value. Additionally, from a governance perspective, decentralized rainwater storage conforms ideally to the low-regret paradigm: while the existing large-scale ring dike depends on a binary commitment (to build or not to build), decentralized small- and micro-scale solutions can be implemented gradually (for example through targeted subsidies) and add technical redundancy to the overall system. In the end, both strategies are highly complementary in their spatial and temporal reduction in flood intensity. Local decision-makers may hence specifically seek combined strategies, adding to singular approaches, and design multi-faceted adaptation pathways in order to successfully prepare for a deeply uncertain future.</p

Local and global Fokker-Planck neoclassical calculations showing flow and bootstrap current modification in a pedestal

In transport barriers, particularly H-mode edge pedestals, radial scale lengths can become comparable to the ion orbit width, causing neoclassical physics to become radially nonlocal. In this work, the resulting changes to neoclassical flow and current are examined both analytically and numerically. Steep density gradients are considered, with scale lengths comparable to the poloidal ion gyroradius, together with strong radial electric fields sufficient to electrostatically confine the ions. Attention is restricted to relatively weak ion temperature gradients (but permitting arbitrary electron temperature gradients), since in this limit a delta-f (small departures from a Maxwellian distribution) rather than full-f approach is justified. This assumption is in fact consistent with measured inter-ELM H-Mode edge pedestal density and ion temperature profiles in many present experiments, and is expected to be increasingly valid in future lower collisionality experiments. In the numerical analysis, the distribution function and Rosenbluth potentials are solved for simultaneously, allowing use of the exact field term in the linearized Fokker-Planck collision operator. In the pedestal, the parallel and poloidal flows are found to deviate strongly from the best available conventional neoclassical prediction, with large poloidal variation of a different form than in the local theory. These predicted effects may be observable experimentally. In the local limit, the Sauter bootstrap current formulae appear accurate at low collisionality, but they can overestimate the bootstrap current near the plateau regime. In the pedestal ordering, ion contributions to the bootstrap and Pfirsch-Schluter currents are also modified

Calculation of the bootstrap current profile for the TJ-II stellarator

Calculations of the bootstrap current for the TJ-II stellarator are presented. DKES and NEO-MC codes are employed; the latter has allowed, for the first time, the precise computation of the bootstrap transport coefficient in the long mean free path regime of this device. The low error bars allow a precise convolution of the monoenergetic coefficients, which is confirmed by error analysis. The radial profile of the bootstrap current is presented for the first time for the 100_44_64 configuration of TJ-II for three different collisionality regimes. The bootstrap coefficient is then compared to that of other configurations of TJ-II regularly operated. The results show qualitative agreement with toroidal current measurements; precise comparison with real discharges is ongoing

Diverse anthropogenic disturbances shift Amazon forests along a structural spectrum.

Amazon forests are being degraded by myriad anthropogenic disturbances, altering ecosystem and climate function. We analyzed the effects of a range of land-use and climate-change disturbances on fine-scale canopy structure using a large database of profiling canopy lidar collected from disturbed and mature Amazon forest plots. At most of the disturbed sites, surveys were conducted 10?30 years after disturbance, with many exhibiting signs of recovery. Structural impacts differed in magnitude more than in character among disturbance types, producing a gradient of impacts. Structural changes were highly coordinated in a manner consistent across disturbance types, indicating commonalities in regeneration pathways. At the most severely affected site ? burned igapó (seasonally flooded forest) ? no signs of canopy regeneration were observed, indicating a sustained alteration of microclimates and consequently greater vulnerability to transitioning to a more open-canopy, savanna-like state. Notably, disturbances rarely shifted forests beyond the natural background of structural variation within mature plots, highlighting the similarities between anthropogenic and natural disturbance regimes, and indicating a degree of resilience among Amazon forests. Studying diverse disturbance types within an integrated analytical framework builds capacity to predict the risk of degradation-driven forest transitions

SSEDIC.2020 on Mobile eID

Mobile electronic identity (eID) management solutions are on the rise worldwide and see a rapid take-up by stakeholders. In this paper experts from the SSEDIC.2020 network study and review the status of mobile eID deployment and use in e-government as well as industry with a focus on Europe. The findings demonstrate that mobile eID solutions have the potential to become a major means for digital identification but significant efforts still must be made to drive broad adoption across European member states, to guide secure integration of mobile solutions in the industry and to arrive at dedicated standards