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There is a consensus that we are conscious of something greater than ourselves, as if we are derived from some other primordial set of principles. Classical or Newtonian physics is based on the Laws of Nature. Conversely, in a recent series of articles, it has been hypothesized that the cell was formed from lipid molecules submerged in the primordial ocean that covered the earth 100 million years after it formed. Since lipids are amphiphiles, with both a positively- and negatively-charged pole, the negatively-charged pole is miscible in water. Under the influence of earth's gravity, the lipid molecules stand up perpendicularly to the surface of the water, packing together until the negative charge neutralizes the Van der Waals force for surface tension, causing the lipid molecules to 'leap' into the micellar form as a sphere with a semi-permeable membrane. Particles in the water freely enter and exit such spheres based on mass action. Over time such protocells evolved Symbiogenesis, encountering factors that posed existential threats, assimilating them to form physiology to maintain homeostatic control. Importantly, when differentiated lung or bone cells are exposed to zero gravity, they lose their phenotypic identity in their evolved state, which has been interpreted as transiting from local to non-local consciousness. [ABSTRACT FROM AUTHOR]

AbstractThis study investigates the impact of Casimir, Van der Waals, and electrostatic forces on nanomechanical switches’ thermomechanical and free vibration behavior. The analysis is conducted using a novel higher-order beam theory and the nonlocal strain gradient elasticity. The motion equations of the nanosensor/switch beam are derived using Hamilton’s principle and solved using Navier’s method for general boundary conditions. The nanoswitch is composed of electroelastic barium-titanate (BaTiO3) and magnetostrictive cobalt-ferrite (CoFe2O4) materials, which are modeled using a power-law approach to account for functionally graded material property variations across the beam’s thickness. The impact of different parameters, such as Casimir, Vander Waals, electrostatic forces, and variations in material composition, size parameters, and gap distance, on a nanoswitch system’s bucking and free vibration is comprehensively examined. With the intermolecular and electrostatic forces, the temperature dependency of barium-titanate and cobalt-ferrite nanoswitch materials, which have not been extensively studied in any previous research, is considered in the modeling of free vibration, and the buckling behavior of a nanoswitch for the first time. This research represents the first comprehensive analysis of these factors. Considering the investigated parameters, the study’s findings can provide helpful insights into developing micro/nano-electromechanical systems, including switches, sensors, and actuators. [ABSTRACT FROM AUTHOR]

Field electron emission characteristics of the carbon nanotube (CNT) film emitters were investigated according to densification conditions such as nitric acid, acetic acid, and salicylic acid. The emission performance of the CNT film emitters was strongly affected by the densification conditions. Salicylic acid exhibits the best field electron emission properties of the CNT film emitters, followed by nitric acid and acetic acid. The efficient densification of the CNT film emitter by salicylic acid is caused by the role of polarity and p orbitals, nitric acid by hydrogen ions, and acetic acid by weak polarity. After the densification with salicylic acid, the turn-on field of the CNT film emitter decreases from 1.94 V μ m−1 to 1.86 V μ m−1, the threshold field decreases from 3.41 V μ m−1 to 2.95 V μ m−1, the emission current significantly increases from 20.92 mA to 43.98 mA, and the degradation rate from the long-term emission stability decreases from 49.9% to 21%. The improved emission characteristics are attributed to the increased emission sites at the CNT film and the increased electrical conductivity of the CNT film. The densification is a useful way to enhance the field electron emission properties of CNT film emitters. [ABSTRACT FROM AUTHOR]

The Lamb shift, one of the most fundamental interactions in atomic physics, arises from the interaction of H atoms with the electromagnetic fluctuations of the quantum vacuum. The energy shift has been computed in a variety of ways. The energy shift, as Feynman, Power, and Milonni demonstrated, equals the change in the vacuum energy in the volume containing the H atoms due to the change in the index of refraction arising from the presence of the H atoms. Using this result and a group theoretical calculation of the contribution to the Lamb shift from each frequency of the vacuum fluctuations, in this paper we obtain an expression for the region of the vacuum energy for each frequency ω around the H atom due to the Lamb shift. This same field plays an essential role in the van der Waals force. We show the ground state atom is surrounded by a region of positive vacuum energy that extends well beyond the atom for low frequencies. This region can be described as a steady state cloud of vacuum fluctuations. For energies E = ℏ ω less than 1 eV, where ℏ is the reduced Planck constant and ω is frequency, the radius of the positive energy region is shown to be approximately 14.4/E Å. For a vacuum fluctuation of wavelength, λ , the radius is (α / 2 π) λ , where α is the fine-structure constant. Thus, for long wavelengths, the region has macroscopic dimensions. The energy–time uncertainty relation predicts a maximum possible radius that is larger than the radius based on the radiative shift calculations by a factor of 1 / 4 α . [ABSTRACT FROM AUTHOR]

Photocatalysis is a prospective technology to solve the current environment and energy crisis. The exploitation of 2D photocatalyst materials is a research hotspot owing to their large specific surface area, intrinsic defect and abundant active sites. Particularly, 2D/2D heterojunctions own intimate interfaces with expanded contact areas, which is beneficial to facilitate the separation and transportation of electron-hole pairs and further improve the photocatalytic activity. Currently, most studies focus on the band structure alignment in the design of 2D/2D heterojunctions, while the importance of interfacial binding forces is often ignored. This review aims at highlighting the critical role of interfacial binding forces in the photocatalytic activity of 2D/2D heterojunctions for the first time. First, we classify the types of interfacial forces, including electrostatic force, van der Waals force, covalent bond, hydrogen bond. Then we summarize several typical strategies for constructing 2D/2D heterojunctions with corresponding structural features. Importantly, the photocatalytic mechanism is discussed based on interfacial composition, charge transfer path and modification of active sites, and various photocatalytic applications are summarized. Finally, we outline the challenges and future development in this prospective research field. It is expected to fill the existing knowledge gap on interfacial binding forces for designing efficient 2D/2D heterojunctions rationally. • The types of different interfacial binding forces are introduced. • The construction strategies of different interfacial binding forces are reviewed. • The key role of interfacial binding forces of 2D/2D heterojunctions is summarized. • Prospects of 2D hybrids in energy and environment photocatalysis are discussed. [ABSTRACT FROM AUTHOR]

We consider steady states with mass constraint of the fourth-order thin-film equation with van der Waals force in a bounded domain which leads to a singular elliptic equation for the thickness with an unknown pressure term. By studying second-order nonlinear ordinary differential equation, \begin{equation*}h_{rr}+\frac{1}{r}h_{r}=\frac{1}{\alpha}h^{-\alpha}-p\end{equation*} we prove the existence of infinitely many radially symmetric solutions. Also, we perform rigorous asymptotic analysis to identify the blow-up limit when the steady state is close to a constant solution and the blow-down limit when the maximum of the steady state goes to the infinity. [ABSTRACT FROM AUTHOR]

Group III-nitrides have attracted significant attention in recent years for their wide tunable band-gaps and excellent optoelectronic capabilities, which are advantageous for several applications including light-emitting diodes, lasers, photodetectors, and large-size low-cost power electronic devices. However, conventional epitaxy accompanied by the covalent bond formation renders the transfer of nitride epilayers difficult, thereby limiting the application potential of nitrides in wearable and flexible electronics. Furthermore, interfacial covalent bonds also limit substrate selection and hinder the development of heterogeneous integration between nitrides and other material systems. 2D materials can mitigate these problems significantly. On the one hand, due to the weak van der Waals forces between the layers of 2D materials, influences of lattice mismatch can be avoided to improve crystal quality. On the other hand, delamination and transfer of nitride epilayers can be achieved easily. Therefore, this study focuses on providing comprehensive guidelines regarding the exfoliation of epitaxial layers using 2D materials to provide new design freedoms for nitride devices. Different 2D buffers and release layers have also been discussed. Furthermore, the limitations, promising solutions, future directions, and applicability of this strategy to flexible nitride devices are presented. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid algorithm based on the ant colony and Physarum Polycephalum algorithms. The positive feedback mechanism is used to find the globally optimal path. The crossover and mutation operations of the genetic algorithm are introduced into the path search mechanism for the first time. The Van der Waals force is applied to the pheromone updating mechanism. Simulation results show that the improved algorithm has advantages in quality and speed of solution compared with other mainstream algorithms. This paper provides fast and accurate route methods for solving the Traveling Salesman Problem first and a delivery scheme is also presented for UAVs to realize "contactless delivery" to users in the Changchun Mingzhu District during the COVID-19 epidemic, which confirms the practicability and robustness of the algorithm. [ABSTRACT FROM AUTHOR]

Casimir–van der Waals forces are important in the self-assembly processes of nanoparticles. In this paper, using a hybrid approach based on Lifshitz theory of Casimir–van der Waals interactions and corrections due to the shape of the nanoparticles, it is shown that for non-spherical nanoparticles, the usual Hamaker approach overestimates the magnitude of the interaction. In particular, the study considers nanoplates of different thicknesses, nanocubes assembled with their faces parallel to each other, and tilted nanocubes, where the main interaction is between edges. [ABSTRACT FROM AUTHOR]

The coal deformation was induced by the gas adsorption of N2, CH4, and CO2. However, the differences between different gas adsorption performances and the deformation mechanism of coal need to be further studied. In this study, the experiments were conducted using self‐developed equipment to reveal the adsorption characteristics of different gases. The results showed that the gas adsorption capacity followed the sequence of CO2 > CH4 > N2. The gas adsorption capacity was negatively correlated with temperature. The maximum decrease in adsorption capacity (23.70%) was N2. The gas adsorption capacity was positively correlated with gas pressure. The maximum increase in gas adsorption capacity (232.79%) was N2. Correspondingly, the coal deformation of CO2 was the largest, and that of N2 was the smallest. The maximum decrease in deformation (31.09%) was CO2 during the temperature increase. The initial coal deformation rates of N2, CH4, and CO2 were 0.060, 0.091, and 0.042 mm·h−1, respectively. The maximum increase of deformation (234.65%) was CH4 with the gas pressure increase. The initial coal deformation rates of N2, CH4, and CO2 were 0.024, 0.045, and 0.016 mm·h−1, respectively. This work guided further clarifying the mechanism of different gases' adsorption capacity and coal deformation. [ABSTRACT FROM AUTHOR]

The molecular behavior of aromatic compounds on the biochar surface， especially the mechanism of weak interaction， is not yet clear. In order to reveal the mechanism of weak interaction between biochar and phenol， adsorption isotherm and adsorption kinetics experiments， as well as FT-IR characterization were used to analyze the binding energy， reduced density gradient (RDG) and electron density topological relationship between biochar and phenol of different adsorption configurations with density functional theory (DFT). Results showed that the adsorption isotherm reaches the equilibrium after 72h， pH significantly affects the saturated adsorption capacity， and the adsorption capacity is the largest at pH=6. The functional groups on the biochar surface are the adsorption centers. The adsorption enthalpy (ΔH) is always in the range of hydrogen bond energy. The weak interaction of the four adsorption configurations (A/B/C/D) is dominated by van der Waals forces and weak hydrogen bonds. The B configuration has the lowest binding energy and the most stable. The C configuration has the strongest weak interaction， and the D configuration is the weakest. [ABSTRACT FROM AUTHOR]

Recent studies have revealed the importance of powder transport by gas-phase flows in the laser-interaction zone in laser powder bed additive manufacturing. The understanding of such a mass transfer mechanism is necessary for developing and optimizing laser-assisted processes of additive manufacturing. Powder bed surface relief around the remelted track is experimentally characterized by metallography and laser scanning profilometry in single-track experiments with powders of various materials and various particle sizes. Denudation zones with sharp irregular boundaries containing particle agglomerates are observed for finer powders with smaller particles. Denudation zones without well-defined boundaries containing single particles are observed for coarser powders. The balance of forces applied to a particle is theoretically analyzed to understand powder rearrangement in the laser-interaction zone. The drag force is estimated by a similarity point-source model of the entrainment flow with a correction for the finite size of the evaporation spot. The adhesion force appears to be greater than the gravity one for the fine powders and lower than the gravity for the coarse powders, thus explaining the observed difference in the denudation zone morphology. The measured variation of the denudation width with the material properties and the particle size is consistent with the theoretical predictions. [ABSTRACT FROM AUTHOR]

Investigation on the adhesion effect of lunar dust particles on contacting interface improves in lunar dust protection and prolongs the equipment service life. In this work, the contact mathematical adhesion model between an ultra-fine lunar dust particle and the aluminum-based rough surface is established based on the fractal theory. The research shows that the van der Waals force dominates adhesion force for ultra-fine lunar dust particles in space environment and is directly related to the rough surface fractal parameters, namely the fractal dimension parameter D , fractal roughness G as well as root-mean-square roughness(rms). Based on van der Waals adhesion model, the optimum rough surface fractal parameters are obtained through model optimization when the van der Waals force is minimal. The van der Waals forces reaches the minimum for lunar dust particle with diameters of 500 nm and 2.5 μm when the rms is 2.689 nm and 4.7 nm respectively. To validate the effectiveness of using fractal theory to the surface topography in van der Waals force calculation, the dust residual rates have been compared with the aluminum surfaces prepared using chemical etching method, electrochemical etching method, and combined chemical method. Based on the AFM topography of the surfaces, the van der Waals forces have been calculated between the lunar dust particles and the surfaces prepared using different etching methods. The centrifugal experiments suggest that van der Waals force is positively related to the dust residual rates. In summary, the fractal theory is effective in describing the surface roughness in lunar dust adhesion problems and it can be used in future lunar dust protection surface design and applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Analytical expressions for calculating Hamaker constant (HC) and van der Waals (VDW) energy/force for interaction of a particle with a solid water interface has been reported for over eighty years. This work further developed novel analytical expressions and numerical approaches for determining HC and VDW interaction energy/force for the particle approaching and penetrating air–water interface (AWI), respectively. The expressions of HC and VDW interaction energy/force before penetrating were developed through analysis of the variation in free energy of the interaction system with bringing the particle from infinity to the vicinity of the AWI. The surface element integration (SEI) technique was modified to calculate VDW energy/force after penetrating. We explain why repulsive VDW energy exists inhibiting the particle from approaching the AWI. We found very significant VDW repulsion for a particle at a concave AWI after penetration, which can even exceed the capillary force and cause strong retention in water films on a solid surface and at air–water-solid interface line. The methods and findings of this work are critical to quantification and understanding of a variety of engineered processes such as particle manipulation (e.g., bubble flotation, Pickering emulsion, and particle laden interfaces). [ABSTRACT FROM AUTHOR]

• Particle-size effects on aeolian deposition and sediment structure were examined. • Two distinct structures form during air-fall deposition as particle sizes vary. • The relevance between interparticle forces and gravity control structure formation. • A dimensionless granular bond number Bo captures the relevance of governing forces. • Open and collapsible structures form due to special accumulation behavior at Bo < 10. Aeolian deposition is significant to the landscape formation on Earth and even other planetary bodies. Particle size controls the transport distance of particles. However, the understanding of particle-size effects on the structure and mechanical behavior of aeolian accumulations remains limited. We investigate the effect of particle size on the structure and collapse of aeolian sediments by one-dimensional compression and collapse tests following the initial air-fall deposition of particles of various sizes from sand to fine silt. Results reveal that the relevance between interparticle forces and gravity controls the formation of two distinct sediment structures as the particle size varies. A loose structure with a packing density close to the simple cubic packing forms for sands and is not collapsible. An open structure with higher porosity forms as particle size becomes smaller. The structure can stack vertically. The stacking height, porosity, and collapsibility increase as particle size decreases. A dimensionless granular bond number Bo captures the relevance between van der Waals forces and gravity. A threshold particle size corresponding to Bo = 10 is identified, below which open and collapsible structures form. The structure forms due to distinctive accumulation behavior. Particle interaction forces create porous aggregates, stabilize the aggregate as it contacts the deposit, and retain open pores. The effect of fine particles on properties of deposited mixtures is also analyzed. Results are relevant to understanding the formation of collapsible aeolian deposits on Earth and may contribute to the estimation of the physical properties of aeolian sediments on other planetary bodies. [ABSTRACT FROM AUTHOR]

[Display omitted] • CsPbBr 3 with quantum-limited domain effects have reversible hydrochromic properties. • Different Organic solvents cause polarity-related discoloration of composites. • A detection model was developed for all-organic solvent polarity detection. Hydrochromic materials have received much attention in anticounterfeiting due to their reversible photoemission properties toward water. However, existing hydrochromic materials usually suffer from slow hydrochromic response and limited stability, repeatability, and color tunability. This paper found for the first time that CsPbBr 3 /Cs 4 PbBr 6 composites with quantum-limited domain effects had reversible hydrochromism. CsPbBr 3 /Cs 4 PbBr 6 composites were successfully synthesized in molecular sieve MCM-41 using an improved mechanochemical method. The composites underwent a reversible phase transition from Cs 4 PbBr 6 /CsPbBr 3 to CsPbBr 3 upon treatment with a trace amount of water, the photoluminescence colors underwent a change from blue to green, and reversion occurred due to heating. Mechanistic investigation revealed that quantum dots underwent soft agglomeration due to van der Waals forces in polar solvent environments, affecting the action of quantum domain-limiting effects. Therefore, organic solvents with different polarities can cause different degrees of reversible discoloration of the material. This study provides new ideas for understanding the phase transition and agglomeration of metal halide perovskite quantum dots in polar solvent environments. Additionally, it offered new options for aqueous color-changing materials and organic solvent polar detection materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Wettability effect has long been a concern in various aqueous lubrication systems including biological and industrial applications. The wettability may affect lubrication performance by changing interfacial viscosity or hydration force. The key point to reveal the mechanism is to design an ideal experimental system to exclude other bulk factors other than surface wettability. In this work, silicon surfaces with different treatments were used to study the single factor effect of wettability on aqueous lubrication. The normal and friction forces of these surfaces were quantified by atomic force microscopy (AFM) in water environment. The interfacial viscosity was evaluated according to the probe dynamic approaching process. Macroscale and microscale lubrication experiments of other materials were also conducted as verification and supplement. A semi-quantitative relationship between friction and wettability was revealed and attributed to the competition between the attractive van der Waals interactions and wettability-dependent repulsive hydration interaction, which determined the strength of the adhesive interaction and dominated the sliding energy dissipation. The contribution of viscous effect of water was considered to be relatively minor. The findings provide an in-depth understanding of aqueous lubrication and outline important guidelines for tuning adhesion and friction. [ABSTRACT FROM AUTHOR]

The development of micromanipulation technology has an important impact on the research in the microfield, which mainly focuses on the preparation and assembly of microcomponents, in which the microcomponent picking technology is used. The existing picking methods mainly use manipulation tools to clamp or adsorb components, which may destroy or fail to pick objects in the process of manipulation, and the efficiency is relatively low. In order to solve the problems in the existing manipulation methods, a new metal microcomponent picking method based on electrochemistry is proposed, which mainly uses the electrochemical principle to produce metal deposition, connect the manipulation tool and the object, and indirectly control the object by moving the manipulation tool. In this paper, the simulation software ABAQUS is used to pick up the microcopper wires with the length of 100, 200 and 300 μ m by using a pipette with a nozzle diameter of 15 μ m. The force curve between the tool and the object during the manipulation process is obtained. The feasibility of the method is verified by theoretical analysis and simulation experiments. [ABSTRACT FROM AUTHOR]

Soil aggregate breakdown is the key step of splash erosion. Recent studies have shown that it is the soil internal forces that induce aggregate breakdown and subsequent splash erosion. However, little is known about the size characteristics of soil aggregate breakdown and corresponding effects on splash erosion. In this study, Cinnamon soil and Heilu soil were adopted to investigate the effects of soil internal forces on the characteristics of aggregate fragments and splash erosion through wet sieving and rainfall simulation. The results showed the following. (1) With a decrease in electrolyte concentration in soil solution, soil net repulsive force increased; meanwhile, aggregate stability decreased and splash erosion rate increased. Additionally, when the electrolyte concentration was less than 10−2 mol L−1, soil net repulsive force hardly changed, and aggregate stability and splash erosion rate accordingly varied very little. (2) With the increase in the soil net repulsive force, the content of fragments <0.053 mm released from aggregates increased, whereas the content of fragments >0.25 mm decreased, thus suggesting that the aggregates tended to break into fine fractions as soil net repulsive forces increased. (3) Regression analyses showed that soil splash erosion rate decreased linearly with increases in the aggregate stability; moreover, correlation analyses showed that splash erosion rate was significantly and positively correlated with the fragments with a diameter of <0.053 mm, and negatively correlated with the fragments with a diameter of >0.25 mm. This study suggests that soil internal forces induce the aggregate crush and determine the size distribution of fragments available for mobilization by the raindrop impact force. Also, the raindrop impact force is the driving mechanism leading to the movement of fragments. This study provides new insights into the mechanism responsible for splash erosion and could be valuable for controlling soil erosion. Highlights: Soil aggregates breakdown dynamics and splash erosion were quantitatively investigated.Soil internal forces determined the size distribution of fragments after aggregates breakdown.The movement of soil fragments largely depended on raindrop impact force.Splash erosion was driven by the soil internal forces and raindrop impact force. [ABSTRACT FROM AUTHOR]

We developed a method of measuring microscopic ζ potential (ZP) from force vs distance (FD) curves observed by atomic force microscope (AFM). ZP in microscopic regions on wafer surfaces may be one of the most important design guides of chemical mechanical polishing slurries applicable to ultrafine patterned wafers, while ZP is generally observed as an average information for a wide area. Our method is based on the linear correlation between jump-in loads in FD curves observed by the AFM for the blanket wafers (SiO2, SiN and poly-Si) in water systems and ZP of each wafer surface measured by the flow potential method. In the applications of our AFM-based measurement method, material-dependency of ZP on the SiO2/SiN patterned wafer surface and an additive material in a slurry (anionic polymer) adsorbing selectively on the SiN surface of the SiO2/SiN patterned wafer were observed. [ABSTRACT FROM AUTHOR]

Printable organic electronics are attractive owing to its high throughput and easy fabrication. Traditional coating methods (such as inkjet printing) are liquid‐solid contact‐based that deposit liquid solutions onto solid surfaces. Film quality is limited by surface energy of target surfaces and surface tension of the solvents. Furthermore, these printing methods are challenging to directly fabricate films on non‐flat or curved surfaces owing to the fluidity of liquid solution drops. In this work, a water transfer printing method that is solid‐solid contact‐based and assisted by Van der Waals force is reported. Nanometer‐thick films can be deposited on various surfaces: both high‐ and low‐surface energy, both flat and non‐flat surfaces. Water plays two roles: 1) as the transfer medium substrate and providing weak adhesion force between water and the transferred film; 2) high surface tension of water providing room to create surface tension gradient and producing Marangoni force to unfold the crumpled nanometer‐thick films. Electronic and optoelectronics on wrinkled skin and curved surfaces are demonstrated with this water transfer printing method. [ABSTRACT FROM AUTHOR]

• Stable Pickering emulsion stabilized by pristine TiO 2 nanoparticles was developed. • Emulsions were stabilized by van der Waals force of hydrophilic TiO 2 nanoparticles. • New composite beads were prepared with the obtained vdW -Pickering emulsion. • The composite materials showed high UV blocking ability and enhanced photostability. • Pickering emulsion stabilizing method developed here is simple, general and green. Highly hydrophilic nanoparticles are generally considered not suitable for stabilizing Pickering emulsions, since they could not be effectively wetted by the oil phase at the water-oil interface. However, highly hydrophilic nanoparticles with good dispersity are possibly absorbed and packed onto the surface of the oil droplets in water via the van der Waals attraction between the nanoparticles and the oil droplets. Hence, a novel " van der Waals emulsion" should be possible to be stabilized by highly hydrophilic nanoparticles. Oil-in-water emulsions solely stabilized by pristine TiO 2 nanoparticles (i.e., TiO 2 without any modification or additives) were prepared. The emulsification behavior under varying pH value, oil fraction, particle content and temperature of the emulsion were explored. Composite wax-based beads which encapsulated chemical sunscreen and was coated by TiO 2 nanoparticles, was also fabricated using the obtained emulsion as the templates. The emulsions displayed the highest stability near the isoelectric points of the TiO 2 nanoparticles, which was attributed to the van der Waals attraction between TiO 2 nanoparticles and oil droplets. Such mechanism was supported by a theoretical analysis based on calculation of the Hamaker constants and experimental evidences. Therefore, this work presents a simple, general and green method for preparing particle-stabilized emulsions. [ABSTRACT FROM AUTHOR]

he preparation and optoelectronic properties of WS2-MoS2 vertical heterostructure were mainly studied. Molybdenum oxide (MoO3), tungsten oxide (WO3) and sulfur powder (S) were employed as reactants, and then high quality WS2-MoS2 vertical heterostructures were prepared by using an improved one-step chemical vapor deposition method (CVD). Raman spectroscopy (Raman), photoluminescence spectroscopy (PL), optical microscope (OM), atomic force microscope (AFM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and other related devices were used to characterize the morphology and element composition of the heterostructures. At last, the photodetector based on WS2-MoS2 vertical heterostructure was produced, and the photoelectric characteristics of the fabricated device including the output characteristic curve, transfer characteristic curve and photocurrent curve were measured. The test results show that the photodetector based on WS2-MoS2 vertical heterostructure exhibits wonderful photoresponse characteristics under the 532 nm laser mode. It obviously means that the photodetector based on WS2-MoS2 vertical heterostructure can be applied to the preparation of high-efficiency optoelectronic devices and have broad application prospects in the field of microelectronics. [ABSTRACT FROM AUTHOR]

In current work, the surface/interface parameters effects and walled number of fluid‐conveying multi walled piezoelectric nanoresonator (FC‐MWPENR) are investigated on dimensionless natural frequency (DNF) with considering viscous fluid velocity. The mentioned nanostructures (FC‐MWPENR) are subjected to nonlinear electrostatic excitation, nonlinear van der Waals interaction and also viscoelastic foundation. For this aim, Hamilton's approach, the Lagrange–Euler's and the assumed mode methods are used. The influences of FC‐MWPENR walled number are considered for analysis of dimensionless natural frequency respect to the surface/interface effect such as Lame's constants (λI,S,μI,S), residual stress (τ0I,S), piezoelectric constants (e31psk,e32psk), and mass density (ρI,S). [ABSTRACT FROM AUTHOR]

The effects of loading SiO 2 -ZnO nanoparticles on EG-water surface tension were examined in this study. Using SITA dynotester, surface tension was measured at 25–50° C. The dispersed nanoparticles reduce the density of liquid molecules at the interface and weaken the cohesion which in turn attenuate the surface tension. On the other hand, the strong force of Van der Waals between nanoparticles strengthens the surface tension. Laboratory results showed that the effects of the reduction in cohesive force could not compensate by the Van der Waals force which consequently the EG-water surface tension reduced up to 13.2%. For the base fluid, the sensitivity of surface tension to the temperature was 0.1233 mN / m ° C , while this figure for the nanofluid at 0.1 and 2 vol% was 0.0952 and 0.0566 mN / m ° C , respectively. Therefore, it is claimed that the presence of nanoparticles decreased surface tension sensitivity to temperature. Finally, a correlation-based on the regression technique was developed by which the nanofluid surface tension behavior navigated with acceptable accuracy. Unlabelled Image • Surface tension of the SiO 2 -ZnO/EG-water nanofluid is evaluated experimentally. • Effects of nanoparticle concentration and temperature on the results are examined. • Surface tension of considered nanofluid samples is lower than the base fluid. • Presence of nanoparticles altered the surface tension sensitivity to temperature. • A correlation is developed for the surface tension of nanofluid. [ABSTRACT FROM AUTHOR]

• Adhesiveness of powders at high temperatures is important characteristic. • Calcium carbonate particles are effectively used in various industrial fields. • Adhesiveness of calcium carbonate increased at high temperature without sintering. • Thermal expansion of calcium carbonate was observed during adhesiveness increase. • Alumina nanoparticles addition can effectively decrease adhesiveness of calcium carbonate. Understanding the adhesiveness of fine particulate materials at high temperatures is important to achieving the stable, economical operation of various industrial systems. In the present research, two types of calcium carbonate (CaCO 3) particles having different mean particle sizes (often used as heat carriers in energy systems) were evaluated. The tensile strengths of beds of these materials were determined at various temperatures by tensile strength measurement tester. The adhesiveness was found to increase greatly at 500 °C even without chemical reactions or sintering, and X-ray diffraction analyses showed thermal expansion of the CaCO 3 crystals at 500 °C. Pure alumina (Al 2 O 3) and silica (SiO 2) microparticles did not exhibit the same pronounced increases in tensile strength or crystal expansion at this same temperature. Because the surface distances between these primary particles were presumably small, it is proposed that van der Waals forces between the particles greatly increased at high temperatures. The addition of Al 2 O 3 nanoparticles to the CaCO 3 decreased the tensile strengths of the powder beds both at ambient temperature and at 500 °C. The experimental data confirm that the surface distances between primary particles were increased upon incorporating the nanoparticles, such that the tensile strength decreased during heat treatment. [ABSTRACT FROM AUTHOR]

As essential multifunctional materials, metal-organic complexes are attractive candidates showing superior sensing performance. However, the development of complex-based electronic sensors is still greatly limited by the low conductivity and unsatisfactory properties. Here, we report a new complex with formula of [Cd 2 (TAA) 4 (2,2′-bpy) 2 ] (denoted as CdL, HTAA = 3-thiopheneacetic acid, 2,2′-bpy = 2,2′-bipyridine) synthesized via room-temperature precipitation. Hirshfeld surface analysis reveals the important effects of hydrogen bonds (54.6%) and Van der Waals interaction (31.5%) for constructing its 2D supermolecular structure. Favored by these intermolecular interactions, the semiconducting CdL exhibits high electronic conductivity at room temperature (1.71 × 10−5 S/cm). Consequently, the CdL powder was fabricated into a planar impedimetric device with high performance. Particularly, the CdL sensor exhibited high sensitivity (1.2 × 103), fast response (6 s), and small hysteresis (0.92%) in total relative humidity range of 33%−97%. In addition, complex impedance analysis was adopted to clarify the sensing mechanism of CdL. This contribution demonstrates the possible application of low-dimensional complexes in humidity sensors. [Display omitted] • A new semiconducting complex CdL was obtained via room-temperature precipitation. • The CdL holds 2D supramolecular networks assembled by hydrogen bonds and Van der Waals force. • Hirshfeld surface analysis confirmed the intermolecular interactions. • The CdL was assembled into impedimetric humidity sensor for the first time showing high performance. [ABSTRACT FROM AUTHOR]

Roughness and microstructures at the micro and the nano scales have significant influence on the van der Waals forces between the adhering particles and the surface. Previous theoretical models may treat the particle-asperity interactions in an unprecise manner, which may result in inaccurate estimations of the van der Waals force especially when the sphere is much larger than the asperities. In this paper, we proposed a numerical model to calculate the van der Waals force between a spherical particle and a rough surface with periodic nanostructures. The 3D sinusoidal rough surfaces are simplified with their asperities modelled as hemispheres, and the contact is within the Derjaguin-Muller-Toporov (DMT) regime. The proposed model calculates the van der Waals forces between the sphere and all the asperities in the contact surface, which will provide more accurate estimations of the van der Waals force. Moreover, the effect of the planar distribution of asperities on the van der Waals forces is considered, which includes the cases when asperities have close-packed hexagonal lattice, square, and hollow-centered hexagonal packing distributions. The theoretical results calculated using the proposed model are verified by comparing the results to previous theoretical and experimental results and the comparison shows that the proposed numerical model predicts the van der Waals force accurately. • The proposed model in this study considers the contributions to the van der Waals forces from all the asperities under the spherical particle. • This predicts the van der Waals force more precisely than previous models. [Display omitted] • A model has been proposed to calculate the particle-surface van der Waals forces. • The proposed model considered the effect of planar distribution of asperities. • This model can be extended to surfaces with different periodic microstructures. [ABSTRACT FROM AUTHOR]

In this paper, a numerical approach is suggested to find a semi-analytical solution for the common nonlinear boundary value problems (BVPs) of cantilever-type micro-electromechanical system (MEMS) and nano-electromechanical system (NEMS) with a set of model parameters. The nonlinear BVPs that are studied involve the states of the single and double cantilever-shaped beams under the influence of Casimir and Van der Waals force for proper distances of separation. The method is based upon an integral operator that is formed considering Green's function connected with the execution of Picard's or Mann's fixed point schemes. The numerical results for different cases of beam are presented and compared with those obtained by previous works to show the applicability, efficiency, and high accuracy of the suggested method. [ABSTRACT FROM AUTHOR]

Thin polymeric coatings are commonly used for altering surface properties and modulating the interfacial performance of materials. Possible contributions from the substrate to the interfacial forces and effects are, however, usually ignored and are not well understood, nor is it established how the coating thickness modulates and eventually eliminates contributions from substrates to the van der Waals (vdW) interfacial force. In this study we quantified, by colloid-probe atomic force microscope (AFM) and by theoretical calculations, the interfacial vdW contributions from substrates acting through ethanol plasma polymer (EtOHpp) coatings of a range of thicknesses on Au and Si bulk materials. In approach force curves against EtOHpp-coated Au substrates the magnitude of the vdW force decreased as the EtOHpp coating thickness increased to 18 nm and then plateaued with further increases in coating thickness, providing direct evidence for a contribution to the total interfacial vdW force from the Au substrate acting through thin coatings. The experimental observations accord with theoretical calculations of the thickness dependence of Hamaker coefficients derived from rigorous simulation using the Lifshitz theory. In addition, the measured forces agree well with theoretical predictions including correction for finite roughness. Thus, our experimental and theoretical results establish how the thickness of polymer thin film coatings modulates the total interfacial vdW force and how this can be used to tune the net vdW force so as to either contain a large substrate contribution or arise predominantly from the polymeric overlayer. Our findings enable rational design of coating thickness to tailor interfacial interactions and material performance. [ABSTRACT FROM AUTHOR]

The effect of external acoustic fields on hydrodynamic behavior of cohesive micron-sized particles in a pseudo-2D fluidized bed is studied using CFD-DEM simulations. The forces acting on a particle consist of the contact force and cohesive force between particles, the drag force by the surrounding fluid and the sound force by an acoustic field. A wide range of sound pressure levels and sound frequencies are investigated in terms of their effects on the pressure drop, bed expansion, distribution of particle velocity and concentration, as well as the sizes of bubbles and agglomerates. Comparing to the system without acoustic force, the application of acoustic field is found to induce the breakup of the formed agglomerates, and ultimately lead to a stable bubbling fluidization regime. A useful range of frequencies between 80 Hz to 100 Hz is found with a pressure level of 120 dB, resulting in most remarkable improvement of the process performance. Unlabelled Image • CFD-DEM simulations of fluidization of cohesive particles with acoustic fields. • The sound effects on pressure drop, bed expansion, solids motion, bubble and agglomerate size. • A useful range of sound frequencies and sound pressure level is proposed. [ABSTRACT FROM AUTHOR]

• The SPH method is developed to model the van der Waals force. • We utilize SPH to simulate the rupture of thin liquid film without resort to lubrication theory. • We introduce the coordinate transformation in SPH to handle the rupture of thin liquid films. • Both van der Waals force and surface tension are imposed on the outmost layer of SPH particles. The rupture of thin liquid films driven by the van der Waals force is of significance in many engineering processes, and most previous studies have relied on the lubrication approximation. In this paper, we develop a smoothed particle hydrodynamics (SPH) representation for the van der Waals force and simulate the rupture of thin liquid films without resort to lubrication theory. The van der Waals force in SPH is only imposed on one layer, i.e., the outermost layer of fluid particles, where a weighting function is deployed to evaluate the contributions of particles on or near the interface. However, to obtain an accurate hydrostatic pressure in reaction to the van der Waals force, a smaller smoothing length is used for the calculation of the weighting function than that used for SPH discretizations of the bulk fluid. The same surface particles are also used to model the surface tension. To deal with the rupture of a thin liquid film with a very small aspect ratio ε (ε = thickness/length), a coordinate transformation is introduced to shrink the length of the liquid film to achieve accurate numerical resolution with a manageable number of particles. As verifications of our physical model and numerical algorithm, we simulate the hydrostatic pressure in a stationary film and the relaxation of an initially square droplet and compare the SPH results with the analytical solutions. The method is then applied to simulate the rupture of thin liquid films with moderate and small aspect ratios (ε = 0.5 and 0.005). The convergence of the method is verified by refining particle spacing to four different levels. The effect of the capillary number on the rupture process is analyzed. [ABSTRACT FROM AUTHOR]

In this work, nonlinear vibration and frequency response analysis of a double-walled piezoelectric nanoresonator based on a cylindrical nanoshell is performed using the Gurtin–Murdoch surface/interface theory. The piezoelectric nanoresonator is simultaneously subjected to the visco-Pasternak medium and nonlinear van der Waals and electrostatic forces. It is found that the electrostatic and piezoelectric voltages, length to radius ratio, nanoresonator gap width, linear and nonlinear van der Waals coefficients and other parameters can effectively change the flexural rigidity of the system, which in turn affects the nonlinear frequency response. Also, increasing or decreasing of some parameters leads to increase or decrease in the resonance amplitude, resonant frequency, instability of the system, nonlinear behavior and bandwidth. [ABSTRACT FROM AUTHOR]

Cohesion may have a significant effect on particle fluidization. Strong cohesive forces may result in a non-fluidized bed of particles. The effect of cohesive forces mainly depends on the magnitude of the forces and the particle weight. Geldart's classification places materials into four groups based on particle diameter and density difference between the particles and the fluid. Each group has different fluidization characteristics caused by the cohesive forces; specifically, in Geldart's experiments, these were Van der Waals forces (VdWFs). This study presents an investigation of the cohesive forces in fluidized beds. Using Geldart's classification, it attempts to predict the classification of moist particulate materials, affected by the liquid bridge forces (LBFs) and fluidized in air. In order to do so, a model which calculates the LBFs was developed. The classification of the wet particles is predicted by calculating an equivalent diameter and using it in the Geldart chart. Unlabelled Image • Particles classified as D according to Geldart act like A or even C at a certain MC. • An analytical model predicting the wet fluidized bed behavior was developed. • Using the new analytical model, a parametric study was performed. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is a rapid and flexible technique for the production of metal parts and prototypes from metal powders. The quality of parts manufactured using AM is a strong function of powder physical and mechanical properties. Previous work has shown that powders with a large fraction of fine particles produce better parts in terms of smooth finished surface and high mass density. However, an excessive fine fraction in the source powder causes serious flowability issues, leading to unexpected voids or discontinuities in the finished product. This effect of the fine fraction on the flowability of metal powder is widely encountered but poorly understood in the AM industry. This study presents a three-dimensional (3D) discrete element method (DEM) model to simulate the microscale mechanisms of powder flow considering the effects of van der Waals force. This microscale force has a negligible influence on the flowability of coarse grains, but the effect becomes the dominant factor governing the behavior of fine fractions (micrometer scale). The results show that the numerical model presented in this paper is capable of reproducing the experimental dependency of the powder flowability on the fine fraction. Moreover, it also successfully captures the characteristics of particle flow under the influence of microscale van der Waals force. Image 1 • Powder flowability can be hindered by the van der Waals force effect. • Force ratio and potential energy ratio can be used to quantify powder flowability. • Spreadability increases and then decreases with adding fines. • The flowability decreases with increasing fine fraction. [ABSTRACT FROM AUTHOR]

A novel ionization/sampling method termed triboionization was developed. Triboionization is an ionization method that only uses cohesive substances, such as food wrap or sticky tape, and does not require an electrode, electric power supply, heat source, light source, radiation, or gas, unlike most other conventional ambient ionization methods. In this study, the sample compound attached to adhesive tape or plastic wrap was quickly peeled off at a distance of approximately 2 cm from the atmospheric interface of a mass spectrometer. All of the five types of food wrap and 13 types of adhesive tape tested successfully ionized caffeine. Nine out of ten model compounds were detected as the corresponding molecular ions in the positive or negative mode by this ionizing contrivance using an oriented polypropylene adhesive tape. The detected molecular ions were typically protonated molecules or sodium adducts in the positive mode or deprotonated molecules in the negative mode. The elemental compositions of the observed ions were confirmed within 5 ppm by high-resolution mass spectrometry. The triboionization phenomenon was considered to depend on physical and electronic events caused by peeling off a cohesive substance. Triboionization is able to provide a compact ion source using only mechanical mechanisms. Additionally, triboionization allows sticky tape to be used as a convenient sampling device for surface analysis. [ABSTRACT FROM AUTHOR]

• Cake formation in cross-flow microfiltration was numerically studied. • Our simulation model used lattice Boltzmann method and discrete element method. • The effects of attractive forces and particle concentrations were studied. • The attractive force between particles affected the cake layer growth. • The effects of particle concentration depended on the attractive interactions. We present a two-dimensional simulation model to explore cake formation in cross-flow filtration. The model uses the lattice Boltzmann method (LBM) for fluid computation and the discrete element method (DEM) for particle computation; they were fully coupled with the smoothed profile method. We verified our model by simulating filtration under different transmembrane pressures. We then investigated the effects of attractive forces and particle concentration on the cake formation mechanism. Generally, as the attractive interaction and particle concentration increased, the particles formed a cake layer with a looser body and rough surface, due to the decrease in the mobility of the particles in contact with the cake surface. It is concluded that the effects of particle concentration are affected by the different conditions of attractive interactions between the particles. [ABSTRACT FROM AUTHOR]

• The mechanical behavior of a clamped–clamped microbeam with middle paddle is analyzed. • The pull in voltage declines and the deflection enlarges as the intermolecular forces increase. • Presence of the electrostatic force accelerated the instability resulting from the capillary force. • Fringing field effect considerably affected determination of the bifurcation points. The present study is aimed to investigate pull-in instability, static deformation, natural frequency, primary and subharmonic resonances in the clamped–clamped microbeam with middle T-shaped paddle in presence of electrostatic force, Casimir force, van der Waals force and fringing field effect; besides, it is focused on investigating the effect of capillary force on instability and adhesion considering the effects of middle layer elongation and axial force. The microbeam is modeled as an Euler Bernoulli beam. In order to solve the nonlinear equations, the Galerkin-based rank reduction method was used. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. The obtained results showed that the van der Waals and Casimir forces had attractive nature and led to the increased static deformation as well as occurrence of the pull-in at lower voltages; besides, the effects of attraction in Casimir was more than that in van der Waals. Results showed that with increase in the dimensionless length, which is influenced by the capillary force, the maximum static deformation was increased as well, leading to instability in capillary coefficients. Furthermore, presence of the electrostatic force also accelerated the instability resulting from the capillary force. Effects of the axial force and elongation in the clamped state resulted in the reduced static deformation as well as delayed instability. It is shown that changing the Casimir and Van der Waals forces as well as the fringing field effect, in addition to causing changes in the voltage and range, considerably affected determination of the bifurcation points. To validate the analytical results, numerical simulation is performed. [ABSTRACT FROM AUTHOR]

Four polyacrylate resins (PARs) with different side chain were successfully prepared, which can selectively adsorb organics with moderate polarity (dielectric constant ranging from 2.21 to 21). PARs can also selectively remove low concentration of toluene (5 ppm) and chloroform (1 ppm) in water with maximum removal efficiencies of 98.16% and 95.65%, and the treated wastewater meet the requirements of world health organization (WHO). [Display omitted] • Four polyacrylate resins (PARs) with different side chain were prepared. • PARs can selectively adsorb organics with moderate polarity. • PARs can selectively remove dissolved organics with moderate polarity in water. • Van der Waals interaction is the main driving force of PARs for organic adsorption. Efficient removal of trace amounts of dissolved organics with moderate polarity (DOMP) in water via adsorption method is a challenge. Most typical adsorption materials such as activated carbon exhibits poor selectivity and few polymers can remove DOMP in water. Herein, four polyacrylate resin (PAR)-based materials with different side chain are successfully fabricated, which can selectively adsorb pure organics with moderate polarity (dielectric constant ranging from 2.21 to 21). Interestingly, PARs can also selectively remove low concentration of toluene (5 ppm) and chloroform (1 ppm) in water with maximum removal efficiencies of 98.16% and 95.65%, respectively. Molecular dynamic (MD) simulations reveals that the driving force and selectivity of the adsorption behaviors can be attributed to the van der Waals interactions between the side chain of PARs and organics. Our study provides a designing strategy and novel material for efficient removal of organic pollutants with trace amounts in water. [ABSTRACT FROM AUTHOR]

• The lipolysis of oleogels was significantly lower than that of oils. • The reduced lipolysis in LOG was highest (46.23%) while SOG was lowest. • The most robust gel was revealed in LOG to induce the contact obstacle for lipase. • C18:3 was positively correlated with gel strength while it was negative for C18:2. • The strongest van der Waals' force was induced with C18:3 to enhance gel strength. This study aimed to evaluate the influence of gelation and unsaturated fatty acids on the reduced extent of lipolysis between diosgenin (DSG)-based oleogels and oils with various unsaturated fatty acids. Overall, the lipolysis of oleogels was significantly lower than oils. The highest reduced extent of lipolysis (46.23 %) was obtained in linseed oleogels (LOG) while sesame oleogels possessed the lowest (21.17 %). It was suggested LOG discovered the strong van der Waals force to induce the robust gel strength and tight cross-linked network and then increase the contact difficulty between lipase and oils. Correlation analysis revealed that C18:3n-3 was positively correlated with hardness and G' while C18:2n-6 was negative. Thus, the effect on the reduced extent of lipolysis with abundant C18:3n-3 was most significant while that rich in C18:2n-6 was least. These discoveries provided a deepening insight into DSG-based oleogels with various unsaturated fatty acids to design desirable properties. [ABSTRACT FROM AUTHOR]

An electromechanical integrated electrostatic harmonic actuator is promising for the miniaturization of electromechanical devices. As the dimensions of the actuator decrease, the effects of the van der Waals force become obvious. In this study, by considering the nonlinearity of electrostatic and van der Waals forces, nonlinear vibration equations of the flexible ring of an electrostatic harmonic actuator are deduced. Using these equations, the nonlinear free vibration and nonlinear forced response of the actuator are investigated. The effects of the van der Waals force on the nonlinear vibration of the flexible ring are analyzed. Results show that these effects of the van der Waals force are relatively obvious under some conditions and should be considered. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we have presented generalized closed form solutions to estimate the permissible dimensional limits for the basic design parameters as well as the accurate pull-in characteristics of electrostatically actuated fixed-fixed nano beam. The coupled electromechanical problem for the nano beam is formulated using Galerkin's approximation while considering the effects of fringe field, mid-plane stretching and intermolecular forces like van der Waals and Casimir. The resulting integrals and higher order polynomials are solved numerically to determine the closed form expressions for allowable detachment length, minimum feasible gap, and critical pull-in parameters. The derived expressions are compared quantitatively with other reported results which show reasonable agreement. The advantage here is that the derived expressions do not involve any complex mathematical operation unlike in existing literature, and thus the expressions can be readily used for quick and accurate estimation of the design parameters. As the applied voltage exceeds beyond pull-in limit, it can lead to severe structural failure during operation; hence the designers must be aware of the accurate pull-in expressions as derived in this paper. It has been observed that the incorporation of the intermolecular forces together with the fringe effect leads to significant reduction in pull-in voltage whereas the mid-plane stretching parameter shows the opposite effect. It is further envisaged that, the proposed generalized closed form expressions will serve as quick guidelines for reliable and safe design and fabrication of various similar electrostatically actuated nanosystems. Highlights • We present general closed form solutions for the threshold for design parameters and pull-in voltage of fixed-fixed nanobeam. • This study ensures reliable and safe design of nanobeam without having structural failure during fabrication or operation. • Coupled electromechanical problem is solved considering the fringe field, mid-plane stretching and intermolecular forces. • The derived expressions are simple and they do not involve complex mathematical operation unlike in reported literature. • The derived closed form expressions will serve as quick guidelines for optimum design and successful fabrication of nanobeam. [ABSTRACT FROM AUTHOR]

3D printing or assembly techniques in the micro/nano-world enable production of micro-parts for building small machines or structures for biomedicine applications, such as cultivation of living cells in the field of Tissue Engineering. Micro-sized assembly requires automated manipulation procedures and methods for determination of suitable objects for assembly. The latter is possible by van der Waals force measurement and determination of distance at the van der Waals peak between two objects in contact. They are dependent not only on the Hamaker coefficients of the materials in contact and their geometries, but also on the nano-roughness asperities and crystal structure asperities of the contact surfaces. A method is presented for measuring van der Waals force and determining micro-objects' (sizes between 10-100 μm) distances between materials in contact at the van der Waals peak in the presence of nano-roughness and crystal structure roughness. The proposed model was validated by experimental lab results between various materials and shapes (glass and polystyrene beads, metallic wires). [ABSTRACT FROM AUTHOR]

We extend our recent (Rastegar, Ahmadi, and Babu 2017) experimental and computational study of the performance of fibrous filters for the removal of large particles from aqueous dispersions by including the effect of flow velocity on the fiber efficiency and residence time. Dispersions of particles in the size range of 35–600 nm and zeta potential range of −50 to 50 mV were considered. The effect of velocity on minimum efficiency and most penetrating particle size was investigated. The Navier–Stokes equations were solved numerically for a single fiber at different inlet velocities using the ANSYS-FLUENT package and the motion of particles was tracked using the Lagrangian analysis including the hydrodynamic drag, lift, gravity, hydrodynamic retardation, Brownian, van der Waals (vdW), and electric double layer (EDL) forces. The hydrodynamic retardation, EDL, and vdW forces were incorporated in the calculations by developing a user-defined function (UDF) that was compiled with the code. Particular attention was given to the effect of velocity on fiber efficiency due to Brownian, EDL, and vdW forces. It was shown that the CFD results are in a good agreement with the efficiencies calculated from the experimental data obtained by filtering aqueous colloidal ceria dispersions of different zeta potentials at different flow rates. [ABSTRACT FROM AUTHOR]

Abstract In the present study, a uniformly curved Euler-Bernoulli beam model is developed to analyze the hygro-thermal vibration and stability of curved double-walled carbon nanotubes (CDWCNT) conveying fluid subjected to a magnetic field based on hygro-thermal elasticity and Eringen's nonlocal theory. The CDWCNT includes the interaction of van der Waals (vdW) force between the inner and outer tubes and it is considered to be embedded in a visco-elastic foundation which is formulated using Kelvin-Voigt model. Hamilton's principle and the assumption of inextensibility of the tubes are applied to derive the nonlocal equations of motion and associated boundary conditions. The differential quadrature method is utilized to discretize the nonlocal governing equations and boundary conditions from which vibration frequencies of the CDWCNT are obtained for clamped-clamped, hinged-hinged and clamped-hinged end conditions. The effects of boundary conditions, different chirality, nonlocal parameter, hygro-thermal loading, magnetic field, fluid velocity, vdW interaction coefficient and visco-elastic foundation are studied on vibration and stability of the CDWCNT. It is explicitly shown that the hygro-thermal vibration response of the CDWCNT is considerably influenced by these parameters. The results given by present study are compared to those obtained from literature to validate the results. Highlights • A curved double-walled carbon nanotube conveying fluid is considered based on the curved Euler-Bernoulli beam model. • The CDWCNT is subjected to hygro-thermal loading and magnetic field, and interaction of vdW forces is considered. • The inner and outer tubes are assumed to be inextensible. • The effects of nonlocal parameter, hygro-thermal loading, magnetic field, fluid velocity and vdW coefficient are studied. [ABSTRACT FROM AUTHOR]

Quinone outside inhibitors (QoIs), which inhibit the mitochondrial respiratory system by binding to the Qo site of Complex III in fungi, are widely used as pesticides with broad spectrum antifungal activity. However, excessive use of QoIs leads to pesticide resistance through mutation of amino acid residues in the Qo site. Recently, metyltetraprole, a novel QoI that is effective against wild-type and resistant mutant fungi, was developed. Interestingly, metyltetraprole has a very similar structure to other QoIs, azoxystrobin and pyraclostrobin, which do not act on resistant mutants. However, it is unknown how slight structural differences in these inhibitors alter their effectiveness towards fungi with amino acid mutations in the Qo site of Complex III. Therefore, we studied the features of interactions of inhibitors effective towards resistant mutants by quantitatively comparing the interaction profiles of three QoIs at the atomic level. First, we reproduced the binding affinity by the thermodynamic integration (TI) method, which treated explicitly environmental molecules and considered the pseudo-binding pathway. As such, a good correlation (R2 = 0.74) was observed between the binding free energy calculated using the TI method and experimentally observed pIC50 value in 12 inhibitor-target pairs, including wild-type and mutant Complex III in two fungal species, Zymoseptoria tritici and Pyrenophora teres. Trajectory analysis of this TI calculation revealed that the effectiveness against resistant mutant fungi strongly depended on the interaction of constituent parts of the inhibitor disposed near the active center of the target protein. Specifically, the key in the effectiveness against resistant mutant fungi is that the corresponding component part, tetrazolinone moiety of metyltetraprole, traded off Coulomb and van der Waals interactions in response to subtle changes in the binding pose. [ABSTRACT FROM AUTHOR]

Epitaxial BiFeO 3 film shows excellent ferroelectric properties, which is not only studied extensively in magnetoelectric modulation but also shows good tribological performance. In our experiment, we find that the surface of BiFeO 3 film can be more lubricant with the application of bias voltages or stress through the AFM probe with a reduction (up to ∼40%) of the friction between the sample and the probe tip. Based on the Prandtl-Tomlinson model, the mechanism of the dry lubrication on BiFeO 3 film originates from the reduction of van der Waals force between sample surface and probe tip. The findings here could be advantageously used in promoting the performance and durability of Micro/Nano Electromechanical devices based on ferroelectric thin films. [ABSTRACT FROM AUTHOR]

Abstract The catalytic dehydrogenation of organic hydrides on transition metal surfaces is of fundamental importance to hydrogen storage technologies based on organic hydrides. Density functional theory (DFT) calculations were performed to study the dehydrogenation of both trans - and cis -decalin on flat Pt(111) and stepped Pt(211) surfaces. Considering that long-range van der Waals (vdW) forces play an important role in the adsorption and reaction of large organic molecules on metal surfaces, a recently developed vdW-inclusive method (optB88-vdW) was adopted in the computational procedure for accurate adsorption results. It revealed that the adsorption energies of decalin on Pt(111) and Pt(211) have little difference due to the dominant role of vdW forces during adsorption instead of chemical interaction. The possible dehydrogenation pathways of decalin on Pt(211) and Pt(111) are found to be clearly dependent on the isomeric molecular structures of decalin and the metal crystal facets. The dehydrogenation is more favourable for cis -decalin than for trans -decalin when on Pt(211) compared to on Pt(111). Taking the Gibbs free energy calculated for the experimental conditions (500 K, 1 atm) as the descriptor, it was observed that the energy barrier for the desorption of reaction product (naphthalene) is much higher than that of every elementary dehydrogenation step. Therefore, desorption of naphthalene is critical in determining the dehydrogenation reaction rate, especially on stepped Pt surfaces. Graphical abstract Image 1 Highlights • Decalin dehydrogenation mechanisms on Pt(111) and Pt(211) are studied by DFT method. • vdW forces are predominant during decalin adsorption on Pt surfaces. • Reaction pathway is dependent on decalin isomer structure and Pt surface. • Desorption of naphthalene may determine the reaction rate, especially on Pt(211). • Low temperature and Pt step atoms favour tetralin dehydrogenation instead of desorption. [ABSTRACT FROM AUTHOR]

Variations in roughness on a surface spawn variations in adhesion force between the surface and any particles that contact the surface. To fully characterize the adhesion that will be exhibited when a particle contacts any location on the surface, it is desirable to map the surface with nanoscale detail. Since it is impractical to make nanoscale roughness measurements over the entirety of a surface with a characteristic dimension on the order of centimeters, a relationship between the number of surface measurements and the likely variation in the expected adhesion force is similarly desirable. In this work, the predicted van der Waals force was used to describe the particle adhesion force. The bootstrap statistical method was employed to estimate the error associated with the predicted mean adhesion force between a smooth spherical particle and a rough surface as a function of the number of locations on the surface where the roughness was measured. Specifically, 40 atomic force microscope (AFM) topographical scans (5 × 5 μm) were taken of three different surfaces and used as model surface inputs to an existing van der Waals adhesion force simulator. The simulator described the expected adhesion force resulting from 1200 contacts between the smooth, spherical particle (10 μm diameter) and random locations on each scanned area. After analyzing the results using the bootstrap method, it was determined that the adhesion between the particle and 10-15 scanned areas (out of 40) optimizes the accuracy of the predicted adhesion with respect to the researcher’s labor. [ABSTRACT FROM AUTHOR]

• The interaction forces between soil particles at different restoration stages were quantitatively evaluated. • The charge properties of soil particle surface were altered during revegetation. • Electrostatic repulsive and van der Waals attractive forces were enhanced during revegetation. • The net repulsive force declined and thus soil erosion resistance increased during revegetation. Vegetation restoration is a valid way to improve soil erosion resistance by enhancing the stability of soil aggregates. Past studies have shown that the net force (the sum of electrostatic, hydration, and van der Waals forces) between soil particles had crucial effects on the stability of soil aggregates. However, little is known about the influence of vegetation restoration on the net force and soil erosion resistance, which hinders our quantitative understanding of this process at the particle to particle level. In this study, to quantitatively analyze the influence of vegetation restoration on soil net force and their relationship with aggregate stability and erosion resistance, we collected soil samples from four different restoration stages (including farmland, grassland, shrubland, and forest), then used Na+-saturated soil aggregates (1 to 5 mm model aggregates) to conduct our experiments. The stability of soil aggregates and erosion resistance were tested through the wet sieving method and rainfall simulation experiments. Our results indicated that the soil net force was repulsive and decreased with vegetation restoration. The stability of soil aggregates and erosion resistance increased with vegetation restoration. With the decrease of electrolyte concentration, the net force and splash erosion rate both first increased (from 1 to 10−2 mol L−1) then remained stable (from 10−2 to 10−4 mol L−1), while the soil aggregate stability first decreased (from 1 to 10−2 mol L−1) then remained stable (from 10−2 to 10−4 mol L−1). The experimental results of soil aggregate stability and splash erosion rate changing with electrolyte concentration could be well explained by soil net force. Moreover, the rate of splash erosion and the stability of soil aggregates showed a significantly negative linear relationship (P < 0.01). Overall, the results indicated that the vegetation restoration process could reduce the net repulsive force of soil particles and thus increase the stability of soil aggregates and erosion resistance. These findings provided quantitative information about the mechanistic understanding of vegetation restoration improving soil erosion resistance. [ABSTRACT FROM AUTHOR]