Human dispersals out of Africa via the Levant

Homo sapiens dispersed from Africa into Eurasia multiple times in the Middle and Late Pleistocene. The route, across northeastern Africa into the Levant, is a viable terrestrial corridor, as the present harsh southern Levant would probably have been savannahs and grasslands during the last interglaciation. Here, we document wetland sediments with luminescence ages falling in the last interglaciation in the southern Levant, showing protracted phases of moisture availability. Wetland sediments in Wadi Gharandal containing Levallois artifacts yielded an age of 84 ka. Our findings support the growing consensus for a well-watered Jordan Rift Valley that funneled migrants into western Asia and northern Arabia.

The Corrosion Inhibition of Montmorillonite Nanoclay for Steel in Acidic Solution

The aim of this research is to study the anticorrosive behavior of a coating consisting of modified montmorillonite nanoclay as an inorganic green inhibitor. The anticorrosion protection for mild steel in 1.0 M HCl solution is studied via weight loss, electrochemical methods, SEM, and XRD. The results proved that montmorillonite nanoclay acts as a good inhibitor with a mixed-type character for steel in an acidic solution. Both anodic and cathodic processes on the metal surface are slowed down. There is a clear direct correlation between the added amount of montmorillonite nanoclay and the inhibition efficiency, reaching a value of 75%. The inhibition mechanism involves the adsorption of the montmorillonite nanoclay onto the metal surface. Weight loss experiments are carried out with steel samples in 1.0 M HCl solution at room temperature, and the same trend of inhibition is produced. SEM was used to image the surface at the different stages of the corrosion inhibition process, and also to examine the starting nanoclay and steel. XRD was used to characterize the nanoparticle structure of the coating. Montmorillonite nanoclay is an environmentally friendly material that improved the corrosion resistance of mild steel in an acidic medium.

Facile Production Method of PbS Nanoparticles via Mechanical Milling of Galena Ore

In this research, some physical properties such as the density, specific heat capacity, and micro-hardness of galena ore lumps purchased from the public market were determined. The microscopic study, using the scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), confirmed that the as-received galena ore was mostly lead sulfide (PbS). The XRD pattern of the galena powder also elucidated that all the peaks were assigned to PbS. In addition, the as-received galena was roughly crushed, and fine-milled using a high-vibration milling machine with tungsten carbide rings. Nanoscale particles of about 90 nm were produced in a very short milling time of around 15 min. The obtained nanoscale powder was well investigated in the SEM at low and high magnifications to assess the exact range of particle size. Meanwhile, the SEM was employed to investigate the microstructure of sintered samples, where a part of the milled galena powder was compacted and sintered at 700 °C for 2 h. Again, the result of this investigation proved the formation of PbS with even smaller grain size compared with the grain size of the starting galena ore. A high relative sinter density of approximately 97% for galena powder was achieved by sintering under vacuum.