The wetting properties of frosted glass

Frosted glass is a common, low cost material. Its roughness can be used to control how it is wet by water. In this paper, the wetting properties of silicone oil and water are investigated. For the oil, wetting is total since the oleophilic character of the glass is enhanced by its roughness. Due to the remarkable optical properties of frosted glass, the spreading of oil droplets on its surface was recorded over three months. Frosted glass is a parahydrophilic surface because of its large contact angle hysteresis (up to 80° ). The behaviour of oil and water droplets was compared on a long piece of inclined frosted glass. The trajectories (and the spreading) of the droplets were studied and phenomenological laws were deduced to describe the dependence of the droplet speed on the initial volume of the droplet and the angle of inclination. Such dependences of speed at long travel distances (100 times the capillary length) were deduced and rationalised with a simple model that takes into account the thickness of the wake. Moreover, we analysed the flow inside the wake of water droplets sliding on inclined frosted glass. Suggestions are given on how to exploit drainage of the water droplet wake and the high hysteresis of water within the framework of open microfluidics.

The impact of titanium oxide nanoparticles and low direct electric current on biofilm dispersal of $Bacillus~cereus$ and $Pseudomonas~aeruginosa$: A comparative study

Bacteria growing in biofilms cause a wide range of environmental, industrial and public health risks. Because biofilm bacteria are very resistant to antibiotics, there is an urgent need in medicine and industry to develop new approaches to eliminating bacterial biofilms. One strategy for controlling these biofilms is to generate an antibiofilm substance locally at the attachment surface. Direct electric current (DC) and nanoparticles (NPs) of metal oxides have outstanding antimicrobial properties. In this study we evaluated the effect of titanium oxide nanoparticle (TiO$_2$-NP) concentrations from 5 to 160 $\mu$g/mL on Bacillus cereus and Pseudomonas aeruginosa biofilms, and compared this with the effect of a 9 V, 6 mA DC electric field for 5, 10 and 15 min. TiO$_2$-NPs were characterized using transmission and scanning electron microscopes, X-ray diffraction and FTIR. They exhibited an average size of 22-34 nm. The TiO$_2$-NP concentrations that attained LD50 were $104 \pm 4$ $\mu$g/mL and $63 \pm 3$ $\mu$g/mL for B. cereus and P. aeruginosa, respectively. The eradication percentages obtained by DC at 5, 10, and 15 min exposure were 21%, 29%, and 33% respectively for B. cereus and 30%, 39%, and 44% respectively for P. aeruginosa. Biofilm disintegration was verified by exopolysaccharide, protein content and cell surface hydrophobicity assessment, as well as scanning electron microscopy. These data were correlated with the reactive oxygen species produced. The results indicated that both DC and TiO$_2$-NPs have a lethal effect on these bacterial biofilms, and that the DC conditions used affect the biofilms in a similar way to TiO$_2$-NPs at concentrations of 20-40 $\mu$g/mL.

Serendipitous observation of a coronal mass ejection during the total solar eclipse of 14 December 2020

We report observations of the total solar eclipse of 14 December 2020, during which a coronal mass ejection was seen to propagate. A comprehensive set of photographs covering a high dynamic range of exposure enabled characterization of its dimensions. Displacement of the front can be seen during the few minutes of totality.

An ab initio study of small gas molecule adsorption on the edge of N-doped sawtooth penta-graphene nanoribbons

Adsorption of the toxic gas molecules carbon monoxide (CO), carbon dioxide (CO2) and ammonia (NH3 ) on the edge of N-doped sawtooth penta-graphene nanoribbons (N:SSPGNRs) was studied using first-principles methods. Basing our study on density functional theory (DFT), we investigated adsorption configurations, adsorption energy, charge transfer, and the electronic properties of CO-, CO2 - and NH3- adsorbed ontoN:SSPGNRs. We found that CO and CO2 are chemisorbed on the edge of N:SSPGNR, while NH3 is physisorbed. Current-voltage (I–V) characteristics were also investigated using the non-equilibrium Green’s function (NEGF) approach. Gas molecules can modify the current of a device based on N:SSPGNRs. The results indicate the potential of using N:SSPGNRs for detection of these toxic gas molecules.

Radial percolation reveals that Cancer Stem Cells are trapped in the core of colonies

Using geometrical arguments, it is shown that Cancer Stem Cells (CSCs) must be confined inside solid tumors under natural conditions. Aided by an agent-based model and percolation theory, the probability of a CSC being positioned at the border of a colony is estimated. This probability is estimated as a function of the CSC self-renewal probabilityps; i.e., the chance that a CSC remains undifferentiated after mitosis. In the most common situations ps is low, and most CSCs produce differentiated cells at a very low rate. Theresults presented here show that CSCs form a small core in the center of a cancer cell colony; they become quiescent due to the lack of space to proliferate, which stabilizestheir population size. This result provides a simple explanation for the CSC niche size, dispensing with the need for quorum sensing or other proposed signaling mechanisms. Italso supports the hypothesis that metastases are likely to start at the very beginning of tumor development.

A method for continuous-range sequence analysis with Jensen-Shannon divergence

Mutual Information (MI) is a useful Information Theory tool for the recognition of mutual dependence between data sets. Several methods have been developed fore estimation of MI when both data sets are of the discrete type or when both are of the continuous type. However, MI estimation between a discrete range data set and a continuous range data set has not received so much attention. We therefore present here a method for the estimation of MI for this case, based on the kernel density approximation. This calculationmay be of interest in diverse contexts. Since MI is closely related to the Jensen Shannon divergence, the method developed here is of particular interest in the problems of sequence segmentation and set comparisons.

The electrical and mechanical properties of Cadmium chloride reinforced PVA:PVP blend films

In this study, pure polymer blend (PVA:PVP) film and salt (CdCl2·H2O) reinforced polymer blend films were prepared at different weight ratios (10 wt%, 20 wt%, 40 wt%) using the casting method. The effect of the salt weight ratio on the dielectric properties of the polymer blend films reinforced by CdCl2·H2O salt were investigated, and the experimental results showed that the dielectric constant and the dielectric loss factor decreased as the frequency increased for all polymer blend films. Moreover, the above-mentioned properties increased with increasing salt weight ratios at the same frequency. The experimental results also showed an increase in AC electrical conductivity with increasing frequency, for all polymer blend films, and the AC electrical conductivity also increased with an increase in the weight ratio of the salt at the same frequency. The effect of the salt weight ratio on the mechanical properties of the salt-reinforced PVA:PVP polymer blend films was also studied. The experimental results obtained from the tensile test of the salt-reinforced polymer blend films show significant change in the values of tensile strength, elongation at break, and Young’s modulus with increasing salt weight ratios; the hardness value first increases then decreases with increasing salt weight ratios, and the fracture energy value increases with increasing salt weight ratios, thus they could be good candidates for hard adhesives with low flexibility.

Optimizing the shielding properties of strength-enhanced concrete containing marble

The purpose of this study is to develop a low cost, locally produced concrete mixture with optimum marble content. The resulting mixture would have enhanced strength properties compared to the non-marble reference concrete, and improved radiation shielding properties. To accomplish these goals five concrete mixtures were prepared, containing 0, 5, 10, 15, and 20% marble waste powder as a cement replacement on the basis of weight.These samples were subjected to a compressive strength test. The shielding parameters such as mass attenuation coefficients μm, mean free path MFP, effective atomic number $Z_{eff}$ and exposure build-up factors EBF were measured, and results were compared with those obtained using the WinXcom program and MCNPX code in the photon energy range of 0.015 - 3 MeV. Moreover, the macroscopic fast neutron removal cross-section (neutron attenuation coefficient) was calculated and the results presented. The results show that the sample which contains 10% marble has the highest compressive strength and potentiallygood gamma ray and neutron radiation shielding properties.

Flavodoxin in a binary surfactant system consisting of the nonionic 1-decanoyl-rac-glycerol and the zwitterionic lauryldimethylamine-N-oxide: molecular dynamics simulation approach

Due to the short time constant of the spin-spin relaxation process, there is a limitation in the preparation of NMR sample solution for large proteins. To overcome this problem, reverse micelle systems are used. Here, molecular dynamics simulation was used to study the structure of flavodoxin in a quaternary mixture of 1-decanoyl-rac-glycerol, lauryldimethylamine-N-oxide, pentane and hexanol. Hexanol was used as co-solvent. Simulations were performed at three different co-solvent concentrations. The proportion of components in the mixture was selected according to experimental conditions. For comparison, simulation of flavodoxin in water was also performed. The simulation results show that the C$$\alpha$$-RMSD for the protein in water is less than for the surfactant mixture. Also, the radius of gyration of flavodoxin increased in the presence of surfactants. The distance between the two residues trp-57 and phe-94, as a measure of protein activity, was obtained from the simulations. The results showed that in the surfactant mixtures this distance increases. Analysis of the secondary structure of the protein shows that the N-terminal part of the flavodoxin is more affected by surfactants. The flavodoxin diffusion coefficient in the surfactant mixture decreased in relation to its diffusion coefficient in water.

Further results on why a point process is effective for estimating correlation between brain regions

Signals from brain functional magnetic resonance imaging (fMRI) can be efficiently represented by a sparse spatiotemporal point process, according to a recently introduced heuristic signal processing scheme. This approach has already been validated for relevant conditions, demonstrating that it preserves and compresses a surprisingly large fraction of the signal information. Here we investigated the conditions necessary for such an approach to succeed, as well as the underlying reasons, using real fMRI data and a simulated dataset. The results show that the key lies in the temporal correlation properties of the time series under consideration. It was found that signals with slowly decaying autocorrelations are particularly suitable for this type of compression, where inflection points contain most of the information.