Exceptional electrostatic phenomenon in ultrathin nanorods: the terminal σ‑hole

An in-depth understanding of the physicochemical properties of nanorods during the initial growth process has a profound impact on the rational design of high-performance nanorods catalysts. Herein, we conducted a systematic DFT study on the transition metal Co, Ni and alloyed nanoclusters/rods systems to simulate an atomic process from the initial nanoclusters growth to nanorods/wires. We found that the highly active sites of nanorods depend on an interesting electrostatic phenomenon. The surface electrostatic potential analysis shows that all nanoclusters and nanorods structures have formed σ-hole. Unlike nanoclusters, the σ-hole only appears at terminal sites in nanorods, called terminal σ-hole. The elemental composition in nanorods has a certain influence on the maximal surface electrostatic potential (VS,max) i.e., terminal σ-hole. Interestingly, we found that the terminal σ-hole formed in nanorods is generally higher in magnitude than smaller nanoclusters. First-principle calculations show that terminal σ-hole is closely related to the physicochemical activities of nanorods. For example, the work function of the directions forming terminal σ-hole is smaller than other directions. More interestingly, we found that in almost all nanorods, compared with other atoms, the d-orbital of the atoms forming terminal σ‑hole shifts close to the Fermi level and exhibits a shallower d-band center, showing higher chemical activity. In short, it is the first time that we discovered terminal σ-hole in nanorods, explained the theoretical basis of terminal σ-hole in nanorod systems, and provided theoretical guidance for the rational design of high-performance nanorods catalysts.

Statistical optimization of amorphous iron phosphate: inorganic sol–gel synthesis-sodium potential insertion

Iron phosphate, Fe2 (HPO4)3*4H2O, is synthesized at ambient temperature, using the inorganic sol–gel method coupled to the microwave route. The experimental conditions for the gelling of Fe (III)-H3PO4 system are previously defined. Potentiometric Time Titration (PTT) and Potentiometric Mass Titration (PMT) investigate the acid–base surface chemistry of obtained phosphate. Variations of surface charge with the contact time, Q a function of T, are examined for time contact varying in the range 0–72 h. The mass suspensions used for this purpose are 0.75, 1.25 and 2.5 g L−1. The point of zero charge (PZC) and isoelectric point (IEP) are defined using the derivative method examining the variations $$\frac{{{\text{dpH}}}}{{{\text{d}}t}} = f\left( {{\text{pH}}} \right)$$ dpH d t = f pH , at lower contact time. A shift is observed for PZC and IEP towards low values that are found to be 2.2 ± 0.2 and 1.8 ± 0.1, respectively. In acidic conditions, the surface charge behavior of synthesized phosphate is dominated by $$\overline{{ > {\text{POH}}}}$$ > POH ¯ group which pKa = 2.45 ± 0.15. Q against T titration method is performed for synthesized Fe2 (HPO4)3*4H2O in NaCl electrolytes. The maximal surface charge (Q) is achieved at the low solid suspension. Hence, for m = 0.75 g L−1, Q value of 50 coulombs is carried at μ = 0.1 and pH around 12, while charge value around 22 coulombs is reached in the pH range: 3–10. The effect of activation time, Q and pH on sodium insertion in iron phosphate, were fully evaluated. To determine the optimal conditions of the studied process, mathematical models are used develop response surfaces in order to characterize the most significant sodium interactions according to the variation of the pH, Q, the contact time and the contents of the synthesized material.

On the Structure and Kinematics of an Algerian Eddy in the Southwestern Mediterranean Sea

An Algerian Eddy, anticyclonic vortex generated by the instability of the Algerian Current in the southwestern Mediterranean Sea, is studied using data provided by drifters (surface currents), Argo floats (temperature and salinity profiles), environmental satellites (absolute dynamic topography maps and ocean color images) and operational oceanography products. The eddy was generated in May 2018 and lasted as an isolated vortex until November 2018. Its morphology and kinematics are described in June–July 2018 when drifters were trapped in its core. During that period, the eddy was slowly moving to the NE (~2 km/day), with an overall diameter of about 200 km (slowly growing with time) and maximal surface swirl velocity of ~50 cm/s at a radius of ~50 km. Geostrophic currents derived from satellite altimetry data compare well with low-pass filtered drifter velocities, with only a slight overestimation, which is expected as its maximum vorticity corresponds to a small Rossby number of ~0.6. Satellite ocean color images and some drifters show that the eddy has an elliptical spiral structure. The looping tracks of the drifters trapped in the eddy were analyzed using two statistical methods: least-squares ellipse fitting and wavelet ridge analysis, revealing a typical eccentricity of about 0.5, a wide range of inclination and a rotation period between 3 and 10 days. Clusters of drifters on the northeastern limb of the eddy were also considered to estimate divergence and vorticity. The results indicate convergence (divergence) and downwelling (upwelling) at scales of 20–50 km near the northeastern (northwestern) edge of the eddy, in agreement with the quasi-geostrophic theory. Vertically, the eddy extends mostly down to 250 m depth, with a warm, low-salinity and low-density signature and with geostrophic currents near 50 cm/s in the top layer (down to ~80 m) reducing to less than 10 cm/s near 250 m. Near the surface, colder water is advected into it.

A compact integrated microfluidic oxygenator with high gas exchange efficiency and compatibility for long-lasting endothelialization

A novel microfluidic architecture allowing simple parallel stacking of the different 4 inch circular units of curved blood capillaries covering a maximal surface area with high compacity is proposed for blood oxygenation at high flow rate.

Spatial Heterogeneity in Dead Sea Surface Temperature Associated with Inhomogeneity in Evaporation

Spatial heterogeneity in Dead Sea surface temperature (SST) was pronounced throughout the daytime, based on METEOSAT geostationary satellite data (2005–2015). In summer, SST peaked at 13 LT (local time), when SST reached 38.1 °C, 34.1 °C, and 35.4 °C being averaged over the east, middle, and west parts of the lake, respectively. In winter, daytime SST heterogeneity was less pronounced than that in summer. As the characteristic feature of the diurnal cycle, the SST daily temperature range (the difference between daily maxima and minima) was equal to 7.2 °C, 2.5 °C, and 3.8 °C over the east, middle, and west parts of the Dead Sea, respectively, in summer, compared to 5.3 °C, 1.2 °C, and 2.3 °C in winter. In the presence of vertical water mixing, the maximum of SST should be observed several hours later than that of land surface temperature (LST) over surrounding land areas due to thermal inertia of bulk water. However, METEOSAT showed that, in summer, maxima of SST and LST were observed at the same time, 13 LT. This fact is evidence that there was no noticeable vertical water mixing. Our findings allowed us to consider that, in the absence of water mixing and under uniform solar radiation in the summer months, spatial heterogeneity in SST was associated with inhomogeneity in evaporation. Maximal evaporation (causing maximal surface water cooling) took place at the middle part of the Dead Sea, while minimum evaporation took place at the east side of the lake.

Calculating the characteristics of flash floods on small rivers in the Mountainous Crimea

The maximal surface runoff from territory of the Crimean Mountains is represented as a runoff of small rivers that flow through the western and eastern part of the northern slope and from the southern coast. The materials from 54 water gauging stations (WGS) were used to characterize the maximum runoff during rain and meltwater-rain floods on the rivers in the Crimean Mountains. A modified reduction structure of a calculation formula was used for valuation of the maximal runoff of different origin flash flood for rivers at the Mountainous Crimea. The main parameters of the proposed model are summarized as dependencies on the average height of the catchments and generalized in the form of a map. It is also possible to use the second variant of the suggested method taking into account the factor of underlying surface is introduced. Comparison of the calculated values of maximal runoff shows good convergence with both the initial information, and the largest values in the observation period.

High validity of measuring the width and volume of medial meniscal extrusion three-dimensionally using an MRI-derived tibial model

Background Medial meniscal extrusion (MME) is an important marker of knee osteoarthritis (KOA) progression. The purposes of this study were: 1) to determine whether there are morphological differences between CT- and MRI-derived tibial plateau models; and 2) to determine whether measurement of MME volume and width using an MRI-derived tibial model is as accurate as measurements on a CT-derived tibial model. Methods This was a cross-sectional study that enrolled ten participants with medial KOA (Kellgren-Lawrence grade 1 to 3). Primary outcome was surface difference of the medial tibial plateau between CT- and MRI-derived models. Furthermore, volume and cross-sectional area of the medial tibial plateau were compared between CT- and MRI-derived models. Measurements of MME volume and width were compared between CT- and MRI-derived tibial models. Results Minimal and maximal surface differences of the medial tibial plateau between the CT- and MRI-derived models were − 0.15 [− 0.44, 0.14] mm (mean [95% confidence interval]) and 0.24 [− 0.09, 0.57] mm, respectively. There were no significant differences in volume and cross-sectional area of the medial tibial plateau between CT- and MRI-derived tibial models. The MME volumes measured on CT- and MRI-derived models were 942.6 [597.7, 1287.6] mm3 and 916.2 [557.9, 1274.6] mm3, respectively (p = 0.938). The MME widths measured on CT- and MRI-derived models were 4.2 [1.9, 6.5] mm and 4.5 [2.2, 6.9] mm, respectively (p = 0.967). Conclusions CT- and MRI-derived models of the medial tibial plateau did not show significant morphological differences. Both CT- and MRI-derived tibia can be used as a reference to measure MME in early-to-moderate medial KOA.

Classification of j-maximal spacelike affine translation surfaces in the Minkovski space i31 with density

An affine translation surface is a graph of a function introduced by Liu and Yu in 2013. The article considers the spacelike affine translation surfaces in the Minkowski space with density establishing the Lagrange’s equation type for -maximal surface, classifying -maximal spacelike affine translation surfaces. The result obtains two parameters and . From that, the Calabi – Bernstein theorem in this space is not true because two function and are defined on

Scaffolds with a High Surface Area-to-Volume Ratio and Cultured Under Fast Flow Perfusion Result in Optimal O2 Delivery to the Cells in Artificial Bone Tissues

Tissue engineering has the potential for repairing large bone defects, which impose a heavy financial burden on the public health. However, difficulties with O2 delivery to the cells residing in the interior of tissue engineering scaffolds make it challenging to grow artificial tissues of clinically-relevant sizes. This study uses image-based simulation in order to provide insight into how to better optimize the scaffold manufacturing parameters, and the culturing conditions, in order to resolve the O2 bottleneck. To do this, high resolution 3D X-ray images of two common scaffold types (salt leached foam and non-woven fiber mesh) are fed into Lattice Boltzmann Method fluid dynamics and reactive Lagrangian Scalar Tracking mass transfer solvers. The obtained findings indicate that the scaffolds should have maximal surface area-to-solid volume ratios for higher chances of the molecular collisions with the cells. Furthermore, the cell culture media should be flown through the scaffold pores as fast as practically possible (without detaching or killing the cells). Finally, we have provided a parametric sweep that maps how the molecular transport within the scaffolds is affected by variations in rates of O2 consumption by the cells. Ultimately, the results of this study are expected to benefit the computer-assisted design of tissue engineering scaffolds and culturing experiments.