The statistics of the COVID-19 confirmed-cases and deaths in 10 highly infected countries was collected • The effectiveness of the social distancing measures on the spread of COVID-19 was analyzed • It takes 1-4 weeks since the promulgation of highest level of measures until the number of cases starts to decrease. • The effectiveness of the social distancing measures on the spread of COVID-19 was different between the 10 focused countries.

Despite years of intensive research, little is known about oligomeric structures present during Alzheimer’s disease (AD). Excess of amyloid beta (Aβ) peptides and their aggregation are the basis of the amyloid cascade hypothesis, which attempts to explain the causes of AD. Because of the intrinsically disordered nature of Aβ monomers and the high aggregation rate of oligomers, their structures are almost impossible to resolve using experimental methods. For this reason, we used a physics-based coarse-grained force field to extensively search for the conformational space of the Aβ42 tetramer, which is believed to be the smallest stable Aβ oligomer and the most toxic one. The resulting structures were subsequently optimized, tested for stability, and compared with the proposed experimental fibril models, using molecular dynamics simulations in two popular all-atom force fields. Our results show that the Aβ42 tetramer can form polymorphic stable structures, which may explain different pathways of Aβ aggregation. The models obtained comprise the outer and core chains and, therefore, are significantly different from the structure of mature fibrils. We found that interaction with water is the reason why the tetramer is more compact and less dry inside than fibrils. Physicochemical properties of the proposed all-atom structures are consistent with the available experimental observations and theoretical expectations. Therefore, we provide possible models for further study and design of higher order oligomers.

Lanthanum (La)-doped zinc oxide nanoparticles were synthesized with different La concentrations by employing a gel combustion method using poly(vinyl alcohol) (PVA). The as-synthesized photocatalysts were characterized using various techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), photoluminescence (PL) spectroscopy, and UV–visible absorption spectroscopy. The average size of ZnO nanoparticles decreased from 34.3 to 10.3 nm with increasing concentrations of La, and the band gap, as evaluated by linear fitting, decreased from 3.10 to 2.78 eV. Additionally, it was found that the photocatalytic activity of doped samples, as investigated by using methyl orange dye under visible lights, improved in response to the increase in La concentration. The decomposition of methyl orange reached 85.86% after 150 min in visible light using La0.1Zn0.9O as the photocatalyst.

In this research, structural, magnetic properties and photocatalytic activity of cobalt ferrite spinel (CoFe2O4) nanoparticles were studied. The samples were characterized by X-ray powder diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), transmission electronic microscopy (TEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), and UV-visible diffused reflectance spectroscopy (DRS) analysis. The XRD analysis revealed the formation of the single-phase CoFe2O4 with a cubic structure that is annealed at 500–700 °C in 3 h. The optical band gap energy for CoFe2O4 was determined to be in the range of 1.57–2.03 eV. The effect on the magnetic properties of cobalt ferrites was analyzed by using a vibrating sample magnetometer (VSM). The particle size and the saturation magnetization of cobalt ferrite nanoparticles increased with increasing annealing temperature. The photocatalytic activity of CoFe2O4 nanoparticles was investigated by using rhodamine B dye under visible light. The decomposition of rhodamine B reached 90.6% after 270 min lighting with the presence of H2O2 and CF500 sample.

Combined voltammetric and in-situ STM studies were employed to gain information about the structure of a sulfate-modified Cu(111) electrode surface exposed to an acidic electrolyte containing a redox-active porphyrin (meso-tetra(N-methyl-4-pyridyl)-porphine, abbreviated as [H 2 TMPyP] 4+ ). A particular focus of this study lies on the characterization of the interfacial structure under reactive conditions, for example, during an ongoing electron transfer reaction. The oxidized form of [H 2 TMPyP] 4+ cannot be stabilized within the narrow potential window of copper. A two-electron transfer reduction affects the central porphine core even at the anodic limit of the copper potential window close to the onset of the oxidative copper dissolution reaction. This porphyrin-related electron transfer reaction can take place even in the presence of a preadsorbed sulfate/ water coadsorption layer. The latter causes a charge inversion at the metal/anion interface with an excess of negative charges within the sulfate/water layer. Enhanced electrostatic interactions between this sulfate/water coadsorption layer and the cationic porphyrin reactants and reaction products are discussed as the physical origin for the formation of a paired anion-cation layer at the interface that retains its structural integrity even during the ongoing electron transfer reaction, at least on the time scale of the STM experiment. It is the starting sulfate desorption at more negative potentials that causes the loss of lateral order within this paired anion-cation layer. Highly water-soluble cationic porphyrin species coadsorb/codesorb together with the sulfate anions onto/from the Cu(111) electrode.

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