Size effects on dynamics of nanodroplets in binary head-on collisions

Head-on collision dynamics of 10, 50 and 100 nm droplets are investigated in vacuum by molecular dynamics, involving 35,858, 4,506,410 and 36,051,466 molecules, respectively. A variety of droplet collision dynamics are observed, such as coalescence, hole formation and shattering, as a function of the Weber number. It is found for the first time that the collision and reflexive separation can occur in the nanodroplet regime when the droplet diameter reaches 100 nm but not for 10 or 50 nm droplets. The size effect in droplet collisions is studied based on the analysis of stretching factors, energy dissipation and collision outcomes for droplets of different diameters. The kinetic energy dissipation due to the atomic interactions at nanoscales is identified to significantly influence the occurrence or otherwise of reflexive separation. Through quantitative analysis of the evolution of the internal structure of the 100 nm nanodroplets collision at the Weber number of 277, it is revealed for the first time that molecules from both parent nanodroplets have penetrated the full length of the merged nanodroplet in the direction of collision, due to a combination of molecular mixing and internal currents. Consequently, all three child nanodroplets have molecules from both parent nanodroplets, contrary to the perception gained from common imaging techniques. The results show that the dynamics, outcomes and mechanisms of nanodroplet collisions have both similarities and differences compared with their micro- and macro-counterparts

Regimes of Head-On Collisions of Equal-Sized Binary Droplets

Through molecular dynamics simulations, head-on collision processes of two identical droplets with a diameter of 10.9 nm are elaborately scrutinized over a wide range of impact Weber numbers (from 6.7 to 1307) both in vacuum and in an ambient of nitrogen gas. As the impact Weber number exceeds a certain critical value, a hole or multiple holes in apparently random locations are observed in the disklike structure formed by two colliding droplets. We name this a new "hole regime" of droplet collisions, which has not yet been reported in previous studies. As the impact Weber number increases, the number of holes increases. The hole or holes may disappear unless a second critical impact Weber number is exceeded, when the merged droplet is likely to experience dramatic shattering. It is also found that the existence of ambient gas provides a "cushion effect" which resists droplet deformation, thus delaying or even preventing the appearance of hole formation and shattering regimes. Moreover, increasing ambient pressure suppresses hole formation. A model based on energy balance is proposed to predict droplet behaviors, which provides a more accurate estimate of the maximum spreading factor compared to previous models. Finally, we further extend the current nanoscale droplet collision regime map and analyze the similarities and dissimilarities between nano- and macroscale droplet collision. Our study extends the current understanding on nanodroplet collisions

Protective effect of WY14643 in hepatic ischemia/reperfusion injury via suppressing the activation of TLR4/NF-KB P65 signal pathway.

Background: Hepatic ischemia/reperfusion (I/R) injury is a disaster common critical event which frequently occurs in a variety of clinical scenarios. To investigate the protective effect of Wy14643 (WY) precondition against hepatic ischemia/ reperfusion (I/R) injury in rats and its potential mechanism.Methods: Thirty Sprague–Dawley male rats weighing 220-250 g were randomly divided into three groups (n=10) including the sham-operated +saline group (Sham), the ischemic-reperfusion+ vehicle (IRI), and the WY14643 preconditioning group (WY). The three groups were pretreated with saline, ethanol and WY, at 1 h before ischemia with a concentration of 10 mg/kg , respectively. Hepatic ischemia-reperfusion (I/R) was induced by clamping blood supply to the left lateral and median lobes of the liver for 90 min. Blood samples and liver tissues were obtained at the end of 4h reperfusion. The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were measured. The histological changes of hepatic tissues were examanied by HE staining. The expression of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) were detected by ELISA and RT-PCR. Moreover, the expression of TLR-4 , IκΒ-α, Myd88, p65 and PPAR-α were detected by western blotting.Result: After 4 h reperfusion, compared with the IRI group, the liver dysfunction (ALT, AST and LDH), damage score, the expression of TNF-α , IL-6, and IL-1β, the protein expression level of TLR4, Myd88, the phosphorylation level of IκB-α and p65 in the WY group was significantly decreased (all P<0.05); while the protein expression of IκB-α was increased (P<0.05) with no difference in the expression of p65 (P>0.05) .Conclusion: Wy14643 precondition could protect liver againest I/R injury and the protective effect is associated with suppressing inflammation by reducing the activation of TLR-4/NF-κB signaling.Key words: hepatic ischemia reperfusion injury; inflammation; Wy14643; TLR-4/NF-κ

β-Ga2O3 solar-blind deep-ultraviolet photodetector based on a four-terminal structure with or without Zener diodes

A four-terminal photodetector was fabricated on the (2⎯⎯⎯012¯01)-dominant β-Ga2O3 thin film which was deposited in a plasma-assisted molecular beam epitaxy system. The suitability of this film for solar-blind DUV detection was proved by its transmission spectra. Moreover, the device operating in a specific voltage-current mode can accurately detect the DUV radiation both qualitatively and quantitatively. Accordingly, a dark/photo voltage ratio of 15 was achieved, which is comparable to that of previously-reported β-Ga2O3 interdigital metal-semiconductor-metal photoconductor. More importantly, the aperture ratio of our proposed device exceeds 80%, nearly doubling that of the conventional interdigital metal-semiconductor-metal devices including photoconductor and Schottky-type photodiode, which can intensively benefit the detection efficiency. Furthermore, it was found the dark/photo voltage ratio was nearly trebled with the assistance of two Zener diodes, and further enhancement can be expected by increasing the operating current and/or adopting Zener diodes with smaller Zener voltage. Therefore, this work provides a promising alternative for solar-blind DUV detection.published_or_final_versio

Channel discord and distortion

Discord, originally notable as a signature of bipartite quantum correlation, in fact can be nonzero classically, i.e. arising from noisy measurements by one of the two parties. Here we redefine classical discord to quantify channel distortion, in contrast to the previous restriction of classical discord to a state, and we then show a monotonic relationship between classical (channel) discord and channel distortion. We show that classical discord is equivalent to (doubly stochastic) channel distortion by numerically discovering a monotonic relation between discord and total-variation distance for a bipartite protocol with one party having a noiseless channel and the other party having a noisy channel. Our numerical method includes randomly generating doubly stochastic matrices for noisy channels and averaging over a uniform measure of input messages. Connecting discord with distortion establishes discord as a signature of classical, not quantum, channel distortion

Bounce regime of droplet collisions: A molecular dynamics study

Droplet collisions have complex dynamics, which can lead to many different regimes of outcomes. The head-on collision and bounce back regime has been observed in previous experiments but numerical simulations using macro- or mesoscale approaches have difficulties reproducing the phenomena, because the interfacial regions are not well resolved. Previous molecular dynamics (MD) simulations have not reproduced the bounce regime either but have reported the coalescence and/or shattering regimes. To scrutinize the dynamics and mechanisms of binary collisions especially the interfacial regions, head-on collision processes of two identical nano-droplets with various impact velocities both in vacuum and in an ambient of nitrogen gas are investigated by MD simulations. With the right combination of the impact velocity and ambient pressure, the head-on collision and bounce back phenomenon is successfully reproduced. The bounce phenomena are mainly attributed to the “cushion effect” of the in-between nitrogen molecules and evaporated water molecules from the two nano-droplets. The analysis has verified and also extended the current gas film theory for the bounce regime through including the effects of evaporated water molecules (vapour). Some similarities and some dissimilarities between nanoscale and macro-/meso-/microscale droplet collisions have been observed. The study provides unprecedented insight into the interfacial regions between two colliding droplets

Stepwise pH control to promote synergy of chemical and biological processes for augmenting short-chain fatty acid production from anaerobic sludge fermentation

This is the author accepted manuscriptAlthough sludge-converted short-chain fatty acids (SCFAs) are promising feedstocks for biorefineries, it remains challenging to maximise SCFA production by enhancing synergies between chemical/biological hydrolysis and acidogenesis processes while employing a balanced composition of microbial communities to counteract methanogenesis. Herein, stepwise control of fermentation pH and chemical/microbiological composition analysis of fermented sludge were used to probe the underlying mechanisms of SCFA production. Fermentation at pH 11 during the first three days promoted both chemical and microbial hydrolysis of sludge proteins and provided a niche for Anaerobrancaceae sp. to transform soluble protein into SCFAs. When pH was decreased from 11 to 9, Acinetobacter, Proteiniborus, Proteiniclasticum, and other acetogens became predominant and stayed significantly more active than during first-stage fermentation at pH 11, which benefited the acidification of hydrolysed substrates. Further assays indicated that early-stage sludge fermentation at pH 11 decreased the total amount of methanogenic archaea and hence reduced the amount of SCFAs consumed for methane production. Thus, the use of stepwise pH control for sludge fermentation allowed one to establish process synergies, facilitate chemical and biological hydrolysis, inhibit methanogens, and promote the growth of acidifying bacterial communities, which resulted in efficient SCFA production from sludge.Royal Society Newton International Fellowshi

Cracking in asphalt materials

This chapter provides a comprehensive review of both laboratory characterization and modelling of bulk material fracture in asphalt mixtures. For the purpose of organization, this chapter is divided into a section on laboratory tests and a section on models. The laboratory characterization section is further subdivided on the basis of predominant loading conditions (monotonic vs. cyclic). The section on constitutive models is subdivided into two sections, the first one containing fracture mechanics based models for crack initiation and propagation that do not include material degradation due to cyclic loading conditions. The second section discusses phenomenological models that have been developed for crack growth through the use of dissipated energy and damage accumulation concepts. These latter models have the capability to simulate degradation of material capacity upon exceeding a threshold number of loading cycles.Peer ReviewedPostprint (author's final draft

Investigation of ethanol oxidation over aluminum nanoparticle using ReaxFF molecular dynamics simulation

Aluminum nanoparticles are an effective and economical additive for producing energetic fuels. In the present study, the state of the art ReaxFF molecular dynamics (MD) simulation has been used to uncover the detailed mechanisms of ethanol oxidation over aluminum nanoparticles with different oxidation states. The MD results reveal the dynamics process of ethanol oxidation reactions at nanoscales. The presence of aluminum nanoparticles is found to reduce the initial temperature of ethanol oxidation to 324 K. It is also found that compared to ethanol, oxygen molecules are more easily adsorbed on aluminum surfaces. Moreover, different oxidation states of aluminum nanoparticles influence the initial ethanol reactions on the nanoparticles’ surfaces. OH-abstraction is more commonly observed on pure aluminum nanoparticles while H-abstraction prevails on aluminum nanoparticles with oxide. The separated H atom from hydroxyl forms bonds with Al and O atom on aluminum nanoparticles surrounded by thin and thick oxide layers, respectively. Adsorptive dissociation of ethanol is hindered by the oxide layer surrounding the aluminum nanoparticle. Gas products like H2O and CO resulting from ethanol oxidation on aluminum nanoparticles with the thick oxide layer are observed while almost all the C, H and O atoms in ethanol diffuse into the nanoparticles without or with the thin oxide layer. For ethanol dissociation, a higher temperature is required than adsorption. In addition, the rate of ethanol dissociation increases with rising reaction temperatures. The activation energy for ethanol adsorptive dissociation is found to be 4.58 kcal/mol on the aluminum nanoparticle with the thin oxide layer, which is consistent with results from much more expensive DFT calculations

Suppression of esophageal tumor growth and chemoresistance by directly targeting the PI3K/AKT pathway

Esophageal cancer is the sixth most common cause of cancer-related deaths worldwide. Novel therapeutic intervention is urgently needed for this deadly disease. The functional role of PI3K/AKT pathway in esophageal cancer is little known. In this study, our results from 49 pairs of human esophageal tumor and normal specimens demonstrated that AKT was constitutively active in the majority (75.5%) of esophageal tumors compared with corresponding normal tissues. Inhibition of the PI3K/AKT pathway with specific inhibitors, wortmannin and LY294002, significantly reduced Bcl-xL expression, induced caspase-3-dependent apoptosis, and repressed cell proliferation and tumor growth in vitro and in vivo without obvious toxic effects. Moreover, significantly higher expression level of p-AKT was observed in fluorouracil (5-FU)-resistant esophageal cancer cells. Inactivation of PI3K/AKT pathway markedly increased the sensitivity and even reversed acquired resistance of esophageal cancer cells to chemotherapeutic drugs in vitro. More importantly, the resistance of tumor xenografts derived from esophageal cancer cells with acquired 5-FU resistance to chemotherapeutic drugs was significantly abrogated by wortmannin treatment in animals. In summary, our data support PI3K/AKT as a valid therapeutic target and strongly suggest that PI3K/AKT inhibitors used in conjunction with conventional chemotherapy may be a potentially useful therapeutic strategy in treating esophageal cancer patients.published_or_final_versio