In this paper, we propose an efficient numerical method to solve the diffusive logistic model with a free boundary which is often used to simulate the spreading of the new or invasive species. The boundary movement is tracked by the level-set method, where the Hamilton-Jacobi weighted essentially nonoscillatory (HJ-WENO) scheme is utilized to capture the boundary curve embedded by the Cartesian grids via the embedded boundary method. Then the radial basis function-finite difference (RBF-FD) method is adopted to the spatial discretization and the IMEX scheme is considered for time integration. A variety of numerical examples are carried out to demonstrate the evolution of diffusive logistic model in different initial boundaries.

Considering the important demand of fresh water and its scarce availability, water desalination is an interesting technology, producing about 44 Mm³/year worldwide, but, in general the most common desalination techniques are highly energy demanding. Freezing-Melting (F/M) desalination uses just up to 70% less thermal energy, but is the least used process mainly, due to the difficulty of the salt separation. This study proposes a model able to analyses the thermodynamic potential that allows the salt diffusion during the F/M process, using an aqueous solution of sodium chloride. This should allow to obtain a sensitive analysis of the process to promote the separation between the high concentration brine and the ice with liquid separation by physical process. The unidimensional model is based on the evolution of both processes: thermal and mass diffusions, depending on temperature and saline gradients, predicting whether the salt will remain inside the ice or not. Thus, the thermal potential is adjusted to frozen only when the salt has been "pushed" towards the brine. Mostly models have base their results on the assumption of a “certain value of saline concentration of the liquid fraction”, value in which there is great disagreement. In this paper the calculations are based on the concentration in the solid-liquid interface, which has been extensively studied and there is a coincidence in those results, being the main advantage of the proposed model.

The present study describes the activities performed to test a new method for measuring the mobility of polycyclic aromatic hydrocarbons (PAHs) in the solid phase of sediments within the context of environmental pollution risk assessment. The method is based on the design of a new configuration (new materials) of the commercial passive sampler Chemcatcher as probe for predicting the bioavailability of persistent organic pollutants in marine sediments (or in water saturated soils).

Tunneled central venous catheters (CVC) are mainly considered as rescue vascular access option in dialysis but still used in about one quarter of prevalent patients worldwide as being associated with poor performances and higher risks. Study design. In this retrospective single-center study, we aimed to report on clinical performances achieved with high-flow tunneled CVC (DualCath, DCath) and compared it with arteriovenous accesses (AVAs; AV fistula, AV graft, Thomas Shunt) in a hospital-based dialysis unit. Methods. Sixty-eight stage 5 chronic kidney disease dialysis dependent patients (CKD5D) receiving high volume hemodiafiltration were followed-up for 30 months. The study consisted of two phases: baseline cross-sectional and longitudinal follow-up of key performance indicators. Clinical performances consisting of effective blood flow and blood volume, recirculation, urea and ionic Kt/V and total Kt, ultrafiltration volume and percent reduction of ß2-M were measured monthly as part of quality control in our unit. Results. At baseline, effective blood flow with DCath was close to 400 ml/min, similar to AVAs. Recirculation with DCath (7%, 6-13%) was higher than AVAs. Diffusive dialysis dose delivered with DCath (spKt and eKt/V) and convective dialysis dose achieved with DCath were slightly lower than AVAs, but still much higher than recommended by guidelines. Percent reduction of ß2-M achieved with DCath was also 4 to 10% lower than AVAs. On longitudinal follow-up, main clinical performance indicators of DCath (total Kt and total ultrafiltration volume, L/session) were maintained very stable over time and close to those achieved with AVAs. Conclusions. As shown in this study, high-flow DualCath tunneled two single lumen silicone catheters may be used to deliver high volume hemodiafiltration in a reliable and consistent manner without compromising clinical performances. These results rely from the specific design of the two silicone cannulas and the strict adherence to best catheter practices.

The application of smartphone-based color evaluation of passive sampling devices for gases has only been sparsely reported. The present review aims to compile available publications with respect to the configuration of the passive samplers, conditions of smartphone photographing, analytical procedure for color detection and quantification (including calibration processes), and their application to different target gases. The performance of the methods - whenever available - is presented regarding the analytical specifications selectivity, sensitivity, and limit of detection in comparison with other color evaluation methods of passive samplers. Practical aspects like requirements of instrumentation and ease of use will be outlined in view of the potential employment in education and citizen science projects. In one section of the review the inconsistent terminology of passive and diffusive sampling is discussed in order to clarify the distinction of information obtained from the uptake of the passive samplers between gas-phase concentration and the accumulated deposition flux of gaseous analytes. Colorimetric gas sensors are included in the review when applied in passive sampling configurations and evaluation is performed with smartphone-based color evaluation. Differences in the analytical procedures employed after the passive sampling step and prior to the detection of the colored compounds are also presented.