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Reducing the contact time of droplet impacts on surfaces is crucial for various applications including corrosion prevention and anti-icing. This study aims to explore a novel strategy that greatly reduces contact time using a superhydrophobic mesh surface with multiple sets of mutually perpendicular ridges while minimizing the influence of the impacting location. The effects of the impact Weber numbers and ridge spacing on the characteristics of the impact dynamics and contact time are studied experimentally. The experimental results reveal that, for the droplet impact on mesh surfaces, ridges can segment the liquid film into independently multiple-retracting liquid subunits. The retracted subunits provide the upward driving force, which may promote the splashing or pancake bouncing of droplets. At this point, the contact time has a negligible sensitivity for the impacting position and is significantly reduced by up to 68%. Furthermore, the time, dynamic pressure, and energy criteria for triggering splashing and pancake bouncing are proposed theoretically. This work provides an understanding of the mechanism and the design guidelines for effectively reducing the contact time of the impacting droplet on superhydrophobic surfaces.

Bouncing dynamics of a trailing drop off-center impacting a leading drop with varying time intervals and Weber numbers are investigated experimentally. Whether the trailing drop impacts during the spreading or receding process of the leading drop is determined by the time interval. For a short time interval of 0.15 ≤ Δ t * ≤ 0.66, the trailing drop impacts during the spreading of the leading drop, and the drops completely coalesce and rebound; for a large time interval of 0.66 < Δ t * ≤ 2.21, the trailing drop impacts during the receding process, and the drops partially coalesce and rebound. Whether the trailing drop directly impacts the surface or the liquid film of the leading drop is determined by the Weber number. The trailing drop impacts the surface directly at moderate Weber numbers of 16.22 ≤ We ≤ 45.42, while it impacts the liquid film at large Weber numbers of 45.42 < We ≤ 64.88. Intriguingly, when the trailing drop impacts the surface directly or the receding liquid film, the contact time increases linearly with the time interval but independent of the Weber number; when the trailing drop impacts the spreading liquid film, the contact time suddenly increases, showing that the force of the liquid film of the leading drop inhibits the receding of the trailing drop. Finally, a theoretical model of the contact time for the drops is established, which is suitable for different impact scenarios of the successive off-center impact. This study provides a quantitative relationship to calculate the contact time of drops successively impacting a superhydrophobic surface, facilitating the design of anti-icing surfaces.

Tricationic ionic liquid (TIL) electrolytes have been successfully employed in supercapacitors with graphene electrodes, but the low power density of the TILs-based supercapacitors caused by strong cations-anions associations requires enhancement by adding organic solvents to the liquid. In this paper, the role of the solvents acetonitrile (ACN) and ethylene carbonate (EC) on the ion diffusion, the conductivity of the TIL [C 6 (mim) 3 ](Tf 2 N) 3 , and the structures and the capacitances of the electrical double layers (EDLs) in TIL/ACN and TIL/EC electrolytes were probed by molecular dynamics (MD) simulations. The results indicate that adding organic solvents to the liquid significantly reduces interactions between ions, thereby greatly improving the ion diffusion coefficients and the conductivity of the TIL, and the maximum conductivity is found at the 0.55 M TIL/ACN electrolyte concentration. Moreover, the reduced packing of counterions and the strong expulsion of coions near charged electrodes are observed in the organic electrolytes, especially in the TIL/EC electrolyte. Further analyses on EDLs affirm that the asymmetric camel-shaped differential capacitance-voltage ( C - V ) curve in the pure TIL electrolyte is weakly changed by the solvent ACN or EC. Besides, the EDL capacitance in the TIL-based hybrid electrolytes is improved slightly by the organic solvents. Comparing the integral capacitances in TIL/ACN and TIL/EC with different solvent contents, it is found that reducing the solvent polarity may be more beneficial to promote the EDL capacitance. Comprehensively, in this work, the 0.55 M TIL/ACN electrolyte is the optimal choice for the high-performance supercapacitor. Hence, solvating TIL electrolytes in supercapacitors by suitable solvents can effectively enhance the power density without compromising energy density.

The rebound behaviors of multiple droplets simultaneously impacting a superhydrophobic surface were investigated via lattice Boltzmann method (LBM) simulations. Three rebound regions were identified, i.e., an edge-dominating region, a center-dominating region, and an independent rebound region. The occurrence of the rebound regions strongly depends on the droplet spacing and the associated Weber and Reynolds numbers. Three new rebound morphologies, i.e., a pin-shaped morphology, a downward comb-shaped morphology, and an upward comb-shaped morphology, were presented. Intriguingly, in the edge-dominating region, the central droplets experience a secondary wetting process to significantly prolong the contact time. However, in the center-dominating region, the contact time is dramatically shortened because of the strong interactions generated by the central droplets and the central ridges. These findings provide useful information for practical applications such as self-cleaning, anticorrosion, anti-icing, and so forth.

Enantioselective total syntheses of 12 amicoumacin-type natural products are accomplished with a palladium(II)-catalyzed C-H alkylation as the key step to furnish the 3,4-dihydroisocoumarin scaffold. The target chemicals are assembled in a convergent protocol by merging 3,4-dihydroisocoumarin derived amine part with categories of acid segments that are efficiently prepared by chemoselective catalytic oxidation of chiral 1,2-dihydroxyethylfuran-2(5H)-ones. Afterward, the cytotoxicity of amicoumacins on five cancer cell lines and one normal cell line is investigated.

The kinematic time and maximum spreading time for the impact of nanodroplets of different types of fluids on solid surfaces with different wettability are investigated. It shows that the capillary regime still exits for the nanodroplet impact, even if viscous dissipation increases significantly when the droplet size reduces to the nanoscale. By taking into account the influence of liquid types and surface wettability, we first obtain scaling laws of the maximum spreading time for the capillary and viscous regimes. We further propose a universal scaling law by interpolating the scaling laws in the two asymptotic regimes. The universal scaling law is in excellent agreement with molecular dynamics simulations for various liquids and surface wettability.

A novel visible-light-induced 1,4-hydroxysulfonylation of vinyl enynes with sulfonyl chlorides has been established, providing a highly efficient protocol to access multisubstituted sulfonyl allenic alcohols. Control experiments and mechanistic studies disclose that the target products result from sequential reactions of hydroxyl and tosyl radicals, among which chloride anion plays a key role to generate the requisite • OH, thus bridging water and enynes. Moreover, the vinyl pendant is believed to decisively affect the site-selectivity of hydroxyl radical.

In transfer printing, the loaded droplet on the probe has a significant influence on the dispensing resolution. A suitable loading approach for a high-viscous liquid is highly required. Herein, a novel electrostatic loading method is presented, in which the main aim is to control precisely the formation and breaking of a cone-shaped liquid bridge. An experimental device is developed. The influence of electrical and geometric parameters on the feature size of the liquid bridge is investigated in detail. In the formation of the liquid bridge, the increase of voltage or the decrease of the air gap can enhance the electric field intensity, thus reducing the formation period and increasing the initial cone tip diameter of the liquid cone. After the liquid bridge is formed, both the circuit current implying the liquid wetted area on the probe surface and the lifting velocity of the probe are utilized to further regulate the volume of the loaded droplet. Loaded droplets ranging from 60 to 600 pL are obtained via the method with a standard deviation of 4 to 30 pL. Moreover, a dot array is transferred with different loaded droplets. The minimum diameter of the printed dots is about 140 μm with a variation less than 5%. The advantages include the reduced risk of contamination, the droplet-size independent of the size of the probe, and the low cost of the device.

We use the pulse current thermoplastic forming technique based on joule heating to rejuvenate the atomic structure of a La 62 Al 14 Ag 2.34 Ni 10.83 Co 10.83 bulk metallic glass (BMG). The pulse-formed sample exhibits more pronounced β-relaxation than the as-cast one due to the increased free volume. Instead, the sub- T g annealing clearly weakens the β-relaxation and also makes it more isolated from the α-relaxation, showing contributions from free volume and preferred structure. However, both treatments exhibit little influence on the following α-relaxation and high temperature crystallization kinetics. Our results open an effective way to rejuvenate the structure of BMGs and provide an in-depth understanding of the relationship between structural relaxations and crystallization kinetics of BMGs.

We study the bouncing dynamics of nanodroplets on superhydrophobic surfaces. We show that there are three velocity regimes with different scaling laws of the contact time, τ. Although τ remains constant over a wide velocity range, as seen for macroscale bouncing, we demonstrate that viscosity plays an essential role in nanodroplet bouncing even for low-viscosity fluids. We propose a new scaling τ ∼ ( ρμR 0 4 /γ 2 ) 1/3 = ( R 0 / v 0 ) We 2/3 Re -1/3 to characterize the viscosity effect, which agrees well with the simulated results for water and argon nanodroplets with various radii and hydrophobicities. We also find pancake bouncing of nanodroplets, which is responsible for an abruptly reduced τ in a high-velocity regime.

ε-Poly-l-lysine (ε-PL) consists of 25-35 lysine residues which are linked by an isopeptide bond formed by dehydration condensation of α-carboxyl and ε-amino groups and has good antibacterial activity and broad-spectrum inhibition range. However, there is no clear conclusion about the structure and antibacterial mechanism of ε-PL in aqueous solution. Herein, a high purity of ε-PL was prepared using Amberlite IRC-50 ion-exchange resin. Membrane filtration and dynamic light scattering were used to study the variations of ε-PL aggregation in aqueous solution with pH value. The conformational changes and antibacterial activities of ε-PL and carbamoylated ε-PL in different water environments were studied with circular dichroism (CD) and inhibition zone. The structural changes during the spray-drying process were determined by Fourier transform infrared spectroscopy. The results indicated that the side chain amino charge played a decisive role in the ε-PL conformation and aggregation. ε-PL exhibited the properties of a β-sheet during spray drying from acidic liquids to solids. The cation enhanced the antibacterial activity of ε-PL but did not play a key role. Instead, the backbone of ε-PL might determine the mechanism of ε-PL antibacterial.

In this letter, we successfully explored a cascade Pd/Cu-catalyzed intermolecular C(sp 3 )-H arylation of amides and intramolecular C-N coupling reaction. This method provides a one-pot strategy to synthesize 3,4-2 H-quinolinone with good regioselectivity of C-H arylation and C-N coupling from C-I and C-X bonds from readily available starting materials.

When droplets are placed on hydrophobic textured surfaces, different wetting states Cassie-Baxter (CB) state or Wenzel (W) state may occur depending on materials and structures of surfaces, types and sizes of droplets, thermal fluctuations, and external stimuli. The wetting transition from the CB to the W state and the opposite process have attracted a great deal of attention because of their primary importance for designing and fabricating textured surfaces. In this work, molecular dynamics (MD) simulations are employed to understand the mechanism behind the CB-to-W transition for a nanoscale water film placed on a surface decorated with a single nanogroove when an external electric field is applied. The free energy variation during the transition process is computed on the basis of the restrained MD simulations. Water intrusion into the groove is observed by simulation snapshots, which provides direct evidence for the electric field-induced CB-to-W transition. In the previous experiments, however, only a sharp reduction in the apparent contact angle is employed to judge whether the transition takes place. The free energy curves reveal that there are two energy barriers separating the CB and W states (Δ E 1 ) as well as separating the W and CB states (Δ E 2 ). Owing to the presence of Δ E 1 , although the CB state has a higher free energy than the W state, it cannot spontaneously convert to the W state. When the external energy input exceeds Δ E 1 , the CB-to-W transition can be triggered, otherwise the transition will stop, and the water film will return to the CB state. Moreover, it is found that the maximum of free energy always occurs after the film touches the groove bottom. Thus, the requirement that the film should touch the groove bottom is responsible for the presence of the energy barrier Δ E 1 . Finally, the dependence of the two energy barriers on the electric field strength, groove aspect ratio, and intrinsic contact angle of the groove is also discussed.

Coalescence-induced droplet self-jumping on superhydrophobic surfaces has received extensive attentions over the past decade because of its potential applications ranging from anti-icing materials to self-sustained condensers, in which a higher jumping velocity v j is always expected and favorable. However, the previous studies have shown that there is a velocity limit with v j ≤ 0.23 u ic for microscale droplets and v j ≤ 0.127 u ic for nanoscale droplets, where u ic is referred to as the inertial-capillary velocity. Here, we show that the jumping velocity can be significantly increased by patterning a single groove, ridge, or more hydrophobic strip, whose size is comparable with the radius of coalescing droplets, on a superhydrophobic surface. We implement molecular dynamics simulations to investigate the coalescence of two equally sized nanodroplets (8.0 nm in radius) on these surfaces. We found that a maximum v j = 0.23 u ic is achieved on the surface with a 1.6 nm high and 5.9 nm wide ridge, which is 1.81 times higher than the nanoscale velocity limit. We also demonstrate that the presence of groove, ridge, and strip alters coalescence dynamics of droplets, leading to a significantly shortened coalescence time which remarkably reduces viscous dissipation during coalescence; thus, we believe that the present approach is also effective for microscale droplet jumping.

Coalescence-induced self-propelled jumping of droplets on superhydrophobic surfaces has potential applications for condensation heat transfer enhancement, anti-icing, self-cleaning, antidew, and so forth. However, most of the previous studies focused on two identical droplets which are not commonly encountered in the nature. In this work, coalescence-induced jumping phenomena of two unequal-sized droplets on superhydrophobic surfaces were investigated theoretically and numerically. First, by introducing modified inertial-capillary velocity (u ic * ) and Ohnesorge number (Oh*) with consideration of radius ratio (r*) of two coalescing droplets, we proposed a generalized inertial-capillary scaling law for the jumping velocity of coalesced droplets, which is expected to be applicable for both two identical droplets and two unequal-sized droplets coalescing on superhydrophobic surfaces. Subsequently, we employed molecular dynamics simulations to investigate the coalescence-induced jumping process of two unequal-sized nanodroplets. Our simulations showed that the dimensionless jumping velocity (v j /u ic * ) well follows the generalized inertial-capillary scaling law with v j /u ic * ≈ 0.127 in a specific Oh* range; however, it rapidly reduces and finally vanishes when the radius ratio of large droplet to small droplet is larger than a certain threshold value. Our simulations also revealed that nonjumping of two unequal-sized droplets with a very large radius ratio is due to that the larger droplet swallows the small one, so that the liquid bridge has no chance to impact the solid surface, and hence the "liquid bridge impacting substrate" mechanism fails in this circumstance.

When an electric field with various strengths is applied to two adjacent conducting droplets, the droplets may completely coalesce, partially coalesce, or bounce off one another. To reveal an atom-scale mechanism of coalescence or non-coalescence, dynamic behaviors of two conducting nanodroplets at a homogeneous electric field are studied via molecular dynamics simulations in this work. The results show that there is a critical field strength and a critical cone angle above which the two droplets partially coalesce or bounce off. Charge transfer between the two droplets is observed when the droplets are brought into contact. The partial coalescence and the bounce-off of the two droplets at strong field strengths are found to be due to the high charge transfer rate, which leads to the breakup of the coalescing droplet at different locations.

Ultrastructural observations, combined with proteomic and comparative genomic analyses, were applied to interpret the differences in protein composition and oil-body characteristics of mature seed of two Brassica napus lines with high and low oil contents of 55.19% and 36.49%, respectively. The results showed that oil bodies were arranged much closer in the high than in the low oil content line, and differences in cell size and thickness of cell walls were also observed. There were 119 and 32 differentially expressed proteins (DEPs) of total and oil-body proteins identified. The 119 DEPs of total protein were mainly involved in the oil-related, dehydration-related, storage and defense/disease, and some of these may be related to oil formation. The DEPs involved with dehydration-related were both detected in total and oil-body proteins for high and low oil lines and may be correlated with the number and size of oil bodies in the different lines. Some genes that corresponded to DEPs were confirmed by quantitative trait loci (QTL) mapping analysis for oil content. The results revealed that some candidate genes deduced from DEPs were located in the confidence intervals of QTL for oil content. Finally, the function of one gene that coded storage protein was verified by using a collection of Arabidopsis lines that can conditionally express the full length cDNA from developing seeds of B. napus.

Hydrodynamic models are generally applied to describe the dynamic wetting of newtonian or non-newtonian fluids on a solid surface. Conversely, the molecular-kinetic paradigm is only utilized for spreading newtonian fluids while considering the movement of a contact line as a molecular hopping process. This study extended the molecular-kinetic paradigm to the wetting behavior of non-newtonian fluids, while assuming there are n fluid components at the contact line regime interacting simultaneously with a solid surface during front movement. The limiting cases of the derived model at slow and fast moving speeds were discussed. Moreover, the derived model was validated based on dynamic contact angle data of three carboxymethylcellulose (CMC) aqueous solutions measured using the force-balance method. Best-fit parameters were used to interpret the wetting dynamics of CMC solutions.

We investigate the adhesion mechanism of aluminum spheres on a silicon substrate. Aluminum particles in the size range of 60-1500 nm were deposited onto a silicon substrate. It was found that aluminum particles underwent plastic deformation rather than elastic deformation because of van der Waals interactions. A finite element model developed recently is also used to analyze our results. Because the MP model was proposed to describe plastic deformation based on an analysis of metal microcontacts, our results prove the correctness of the MP model from its origin and basis of arguments.

Human bcl-2 gene is an apoptosis-related oncogene containing a GC-rich sequence which is located upstream from P1 promoter and has the potential to form G-quadruplex structures. However, the regulatory role of the quadruplex and the effect of its ligands on bcl-2 have not been clarified. Here, we demonstrated that the G-quadruplex structure was disrupted when partial mutation of G --> A was made, resulting in a 2-fold increase in basal transcriptional activity of bcl-2 promoter. Quindoline derivatives, the highly active G-quadruplex ligands developed by our group, could significantly suppress bcl-2 transcriptional activation but had less effect on mutated bcl-2 transcription. These results provided direct evidence that G-quadruplex structure formed in bcl-2 promoter region could function as a transcriptional repressor element, and G-quadruplex specific ligands could regulate the transcription of bcl-2 through stabilization of quadruplex structure. The results further indicated that quindoline derivatives could induce apoptosis of HL-60 tumor cells.

Recently, the scope of the investigation of the deformation mechanism extended to the micrometer and submicrometer regimes. The sphere-substrate contact method was usually used because it is rather difficult to make two micrometer or submicrometer spheres contact each other precisely. Here, we used the sphere-sphere contact method via a novel, simple process to investigate the deformation of spheres. The silica particle size ranges from 400 to 900 nm. Traditionally, the harder the particle, the smaller both the contact radius and the adhesion force. Therefore, it is widely accepted that silica particles should undergo elastic deformation, but we found that silica particles underwent plastic deformation rather than elastic deformation because of van der Waals interaction. The contact radii were observed by scanning electron microscopy (SEM).

A series of 5-N-methyl quindoline (cryptolepine) derivatives (2a- x) as telomeric quadruplex ligands was synthesized and evaluated. The designed ligands possess a positive charge at the 5- N position of the aromatic quindoline scaffold. The quadruplex binding of these compounds was evaluated by circular dichroism (CD) spectroscopy, fluorescence resonance energy transfer (FRET) melting assay, polymerase chain reaction (PCR) stop assay, nuclear magnetic resonance (NMR), and molecular modeling studies. Introduction of a positive charge not only significantly improved the binding ability but also induced the selectivity toward antiparallel quadruplex, whereas the nonmethylated derivatives tended to stabilize hybrid-type quadruplexes. NMR and molecular modeling studies revealed that the ligands stacked on the external G-quartets and the positively charged 5- N atom could contribute to the stabilizing ability. Long-term exposure of human cancer cells to 2r showed a remarkable cessation in population growth and cellular senescence phenotype and accompanied by a shortening of the telomere length.

Stabilization of G-quadruplex structures in the promoter region of certain oncogenes is an emerging field in anticancer drug design. Human c-myc gene is one of these oncogenes, and G-quadruplexes have been proven to be the transcriptional controller of this gene. In the present study, the interaction of quindoline derivatives with G-quadruplexes in c-myc was investigated. The experimental results indicated that these derivatives have the ability to induce/stabilize the G-quadruplexes in c-myc, which lead to down-regulation of the c-myc in the Hep G2 cell line. It was found that derivatives with terminal amino groups in their side chains would selectively bind to the isomers with the double nucleotide loops in the absence of K+. Molecular modeling studies revealed the binding mode between the derivatives and the G-quadruplexes is end-stacking at the 3'-position, and the positively charged side chain on the quindoline derivatives may contribute to the selectivity to certain loop isomers of topological quadruplexes as well as the improved stabilization action.