Two-dimensional simulation of nitrate transport in an agriculture-intensive region

A two-dimensional steady-state solute transport model is developed to simulate movement of non-point sources of pollution in anisotropic porous media. The migration of chemicals dissolved in groundwater is governed by advective-dispersive processes which are also affected by the velocity of the flowing groundwater. Therefore, groundwater flow equation is solved for hydraulic gradient and hydraulic conductivity to approximate the average linear velocity of the fluid. The advection-dispersion is used to approximate the spatial and temporal distribution of non-reactive dissolved chemical in a flowing groundwater. A computer code is developed in MATLAB to solve the groundwater flow and solute transports equations by finite difference methods. The developed program is verified with soil-tank experimental data. The solute transport model is used to simulate non-point source of nitrate pollution in an agriculture-intensive region. Finally, the model outputs are analyzed to understand the factors that influence the pollution transport in the study area

Mn(III) Schiff base complexes containing crown ether rings immobilized onto MCM-41 matrix as heterogeneous catalysts for oxidation of alkenes

Six catalysts MnL1–MnL6, containing two crown ether rings and their analogs supported on the MCM-41 heterogeneous substrate (MnL1@MCM41-MnL5@MCM41) were synthesized and characterized. A mixture of molecular oxygen, as an oxidant, and these catalysts were used for the epoxidation of styrene. As a general result, the supported catalysts showed better performance compared with the unsupported analogs. On the other hand, the supported species, in addition to recyclability, did not require an axial base and reducing agent

Thermal efficiency enhancement of parabolic trough receivers using synthesized graphene oxide/SiO2 nanofluid and a rotary turbulator

Enhancing the thermal efficiency of parabolic solar collectors is still a challenging issue. In this study, two strategies including using nanofluid and a rotary turbulator are applied to ameliorate thermal efficiency. Here, graphene oxide/SiO2 nanofluids are fabricated in different concentrations and their thermophysical properties are measured. Subsequently, a numerical model is carried out to study the influence of applying nanofluid and the rotary turbulator on thermal efficiency. The results indicate that using nanofluid leads to a 9% increase in thermal efficiency and adding the turbulator enhances thermal efficiency by more than 20%. Although hydraulic analysis reveals the Performance Evaluation Criteria remains in an acceptable range, the friction factor and Nusselt number increase by the addition of nanoparticles to the basefluid

Cardioembolic stroke, the most common subtype of stroke in COVID 19: A single center experience from Isfahan, Iran

Background: Some studies showed the cerebrovascular manifestation in patients with recently pandemic coronavirus 2 named the coronavirus disease 2019 (COVID-19). However, there are rare reports about stroke subtypes in these patients. Here, we reported the stroke subtype in patients with laboratory-confirmed diagnosis of COVID-19 and treated at our hospitals, which are located in Isfahan, Iran. Materials and Methods: This is a retrospective, observational case series. Data were collected from March 01, 2020, to May 20, 2020, at three designated special care centers for COVID-19 of Isfahan University of Medical Sciences. The study included 1188 consecutive hospitalized patients with laboratory-confirmed diagnosis of COVID-19. Results: Of 1188 COVID-19 patients, 7 (0.5%) patients developed stroke. Five (0.4%) had ischemic arterial stroke, 1 (0.08%) hemorrhagic stroke and 1(0.08 %) cerebral venous and sinus thrombosis. Sixty percent of ischemic stroke were cardioembolic stroke (CE) and the rest 2 (40%) were embolic stroke of undetermined source. Three male patients (40%) had stroke as a presenting and admitted symptom of COVID-19. Four patients (57%) had severe COVID-19. Conclusion: Stroke was an uncommon manifestation in COVID-19 patients. CE was a common subtype of stroke in COVID-19 patients in our centers