Modelling the evolution of the coronavirus disease (COVID-19) in Saudi Arabia.

Introduction: The ongoing COVID-19 pandemic has claimed hundreds of thousands of lives around the world. Health planners are seeking ways to forecast the evolution of the pandemic. In this study, a mathematical model was proposed for Saudi Arabia, the country with the highest reported number of COVID-19 cases in the Arab world.

Bifurcation analysis of a SEIR epidemic system with governmental action and individual reaction.

In this paper, the dynamical behavior of a SEIR epidemic system that takes into account governmental action and individual reaction is investigated. The transmission rate takes into account the impact of governmental action modeled as a step function while the decreasing contacts among individuals responding to the severity of the pandemic is modeled as a decreasing exponential function. We show that the proposed model is capable of predicting Hopf bifurcation points for a wide range of physically realistic parameters for the COVID-19 disease.

Silver Quantum Dot Decorated 2D-SnO Nanoflakes for Photocatalytic Degradation of the Water Pollutant Rhodamine B.

Decoration of 2D semiconductor structures with heterogeneous metal quantum dots has attracted considerable attention due to advanced optical, electrical, and catalytic properties that result from the large surface-to-volume ratio associated with these structures. Herein, we report on silver quantum dot decorated 2D SnO nanoflakes for the photocatalytic abatement of water effluents, the synthesis of which was achieved through a straightforward and mild hydrothermal procedure. The photocatalysts were systematically investigated using UV-Vis, XRD, electron microscopy (SEM, HR-TEM), EDX, XPS and FTIR.

Precipitation of Ibuprofen Sodium using compressed carbon dioxide as antisolvent.

Precipitation with compressed antisolvent (PCA) process was used to produce fine particles of Ibuprofen Sodium with the ultimate goal of obtaining controlled particle size and size distribution of this non-steroidal anti-inflammatory drug. This systematic investigation shows that particle size and size distribution of the final product can be controlled reproducibly by varying a number operating parameters such as antisolvent addition rate, temperature, concentration, and solution addition rate. The mechanisms that control particle size and particle size distribution were explained by invoking the differences in the relative weight of primary, secondary nucleation and growth kinetic phenomena.