Molecular Diffusion Rates Research Articles

Catalytic reduction of U(Ⅵ) to U(Ⅳ) using hydrogen as the sole reducing agent

Using hydrogen gas as a sole reducing agent to catalyze the reduction of hexavalent uranium to prepare tetravalent uranium can avoid the problem of pollutant poisoning catalysts caused by hydrazine reducing agents. However, research using only hydrogen as the sole reducing agent is very scarce. Herein, catalyst has been developed for catalytic hydrogen reduction to prepare uranium(Ⅳ) and a systematic study of the influence of process parameters such as catalyst carrier particle size, temperature, pressure, and acidity on the catalytic hydrogen reduction process for the preparation of uranium(Ⅳ) is presented. The effect of catalyst carrier particle size is particularly pronounced due to the differing rates of molecular diffusion. Fine particle-sized catalyst carriers exhibit faster catalytic reaction kinetics. Temperature exhibits an unusual phenomenon in its impact on the reaction process. As temperature increases, the reaction rate decreases, and an upper limit reaction temperature is observed. Furthermore, at excessively high reaction temperatures, an anomalous occurrence of uranium(Ⅳ) formation followed by disappearance was observed. Through an analysis of the reaction mechanism, the underlying reasons for this abnormal phenomenon are elucidated. Additionally, this paper also reveals that reaction rates increase with increasing reaction pressure and decrease with decreasing raw material acidity. Process parameters such as reaction temperature, pressure, and acidity exhibit coupled effects on the reaction process. Different reaction upper limit temperatures are observed under varying pressures and raw material acidities.

Mass transfer of solute in an oscillating flow in a two-dimensional channel

The effective diffusion of a solute in a rectangular two-dimensional channel is experimentally studied. We experimentally examine the effective diffusion of Rhodamine B dissolved in water oscillating in a rectangular Hele–Shaw cell. The concentration of Rhodamine B in water is measured by the intensity of its fluorescence emission. In particular, we consider two problems: (i) effective diffusion of solute in water oscillating in a two-dimensional rectangular channel (Hele–Shaw cell) and (ii) effective diffusion of solute in pores between monosized hard spheres randomly packed in a rectangular Hele–Shaw cell. It is revealed that the rate of solute mass transfer exceeds the molecular diffusion rate in both cases. It has been demonstrated that when water oscillates between parallel walls, diffusion is accelerated by Taylor dispersion with the effective diffusion coefficient Deff exceeding the molecular diffusion coefficient Dm by 1–2 orders of magnitude. The effective diffusion coefficient Deff depends only on the relative amplitude but not on the frequency of the fluid oscillations in the studied range of frequencies and amplitudes. When the fluid oscillates in the pores of the porous medium, solute transport is faster than in the case of Taylor dispersion. Here, the effective diffusion coefficient depends on both the frequency and amplitude of oscillations. The analysis shows that the experimental data obtained at various frequencies and amplitudes of oscillations are consistent with the relation Deff/Dm∼Pe2 (Pe is the Peclet number). We suggest that the enhanced solute mass transfer is associated with the time-averaged fluid flows that arise due to spatial heterogeneity of the amplitude of water oscillations in the pores between randomly packed hard spheres.

Timescales Associated with the Evolution of Reactive Scalar Gradient in Premixed Turbulent Combustion: A Direct Numerical Simulation Analysis

The fractional change in the reaction progress variable gradient depends on the flow normal straining within the flame and also upon the corresponding normal gradients of the reaction rate and its molecular diffusion transport. The statistical behaviours of the normal strain rate and the contributions arising from the normal gradients of the reaction rate and molecular diffusion rate within the flame were analysed by means of a Direct Numerical Simulation (DNS) database of statistically planar turbulent premixed flames ranging from the wrinkled/corrugated flamelets regime to the thin reaction zones regime. The interaction of flame-normal straining with the flame-normal gradient of molecular diffusion rate was found to govern the reactive scalar gradient transport in the preheat zone, where comparable timescales for turbulent straining and molecular diffusion are obtained for small values of Karlovitz numbers. However, the molecular diffusion timescale turns out to be smaller than the turbulent straining timescale for high values of Karlovitz numbers. By contrast, the reaction and hot product zones of the flame remain mostly unaffected by turbulence, and the reactive scalar gradient transport in this zone is determined by the interaction between the flame-normal gradients of molecular diffusion and chemical reaction rates.

Post‐Synthetic Ensembling Design of Hierarchically Ordered FAU‐type Zeolite Frameworks for Vacuum Gas Oil Hydrocracking

AbstractZeolites hold importance as catalysts and membranes across numerous industrial processes that produce most of the world's fuels and chemicals. In zeolite catalysis, the rate of molecular diffusion inside the micropore channels defines the catalyst's longevity and selectivity, thereby influencing the catalytic efficiency. Decreasing the diffusion pathlengths of zeolites to the nanoscopic level by fabricating well‐organized hierarchically porous architecture can efficiently overcome their intrinsic mass‐transfer limitations without losing hydrothermal stability. We report a rational post‐synthetic design for synthesizing hierarchically ordered FAU‐type zeolites exhibiting 2D‐hexagonal (P6mm) and 3D‐cubic (Ia d) mesopore channels. The synthesis involves methodical incision of the parent zeolite into unit‐cell level zeolitic fragments by in situ generated base and bulky surfactants. The micellar ensembles formed by these surfactant‐zeolite interactions are subsequently reorganized into various ordered mesophases by tuning the micellar curvature with ion‐specific interactions (Hofmeister effect). Unlike conventional crystallization, which offers poor control over mesophase formation due to kinetic constraints, crystalline mesostructures can be developed under dilute, mild alkaline conditions by controlled reassembly. The prepared zeolites with nanometric diffusion pathlengths have demonstrated excellent yields of naphtha and middle‐distillates in vacuum gas oil hydrocracking with decreased coke deposition.

Post-Synthetic Ensembling Design of Hierarchically Ordered FAU-type Zeolite Frameworks for Vacuum Gas Oil Hydrocracking.

Zeolites hold importance as catalysts and membranes across numerous industrial processes that produce most of the world's fuels and chemicals. In zeolite catalysis, the rate of molecular diffusion inside the micropore channels defines the catalyst's longevity and selectivity, thereby influencing the catalytic efficiency. Decreasing the diffusion pathlengths of zeolites to the nanoscopic level by fabricating well-organized hierarchically porous architecture can efficiently overcome their intrinsic mass-transfer limitations without losing hydrothermal stability. We report a rational post-synthetic design for synthesizing hierarchically ordered FAU-type zeolites exhibiting 2D-hexagonal (P6mm) and 3D-cubic (Ia d) mesopore channels. The synthesis involves methodical incision of the parent zeolite into unit-cell level zeolitic fragments by in situ generated base and bulky surfactants. The micellar ensembles formed by these surfactant-zeolite interactions are subsequently reorganized into various ordered mesophases by tuning the micellar curvature with ion-specific interactions (Hofmeister effect). Unlike conventional crystallization, which offers poor control over mesophase formation due to kinetic constraints, crystalline mesostructures can be developed under dilute, mild alkaline conditions by controlled reassembly. The prepared zeolites with nanometric diffusion pathlengths have demonstrated excellent yields of naphtha and middle-distillates in vacuum gas oil hydrocracking with decreased coke deposition.

Regulating adsorption-desorption through controlled modification of the 2D pores in layered double hydroxides

Selective transport and adsorption in two-dimensional (2D) materials depend on the affinity and molecular size of the adsorbate. However, until now studies have predominantly been restricted to small molecules (<1 nm), limiting their use in drug delivery, catalysis, and agriculture applications, which require the inclusion of larger molecules (∼1–3 nm). In this study, we utilize a simple methodology to modify the interlayer structure of layered doubled hydroxide (LDH). Using benzene sulfonate surfactants of increasing carbon tail length, we induce 2D pores ranging between 1.7–3 nm while maintaining a similar intergallery chemical environment. The synthesized composites were thoroughly characterized by XRD, FTIR, HRTEM, XPS, and ICP. Our findings reveal that the interlayer d-spacing is linearly correlated to the molecular size of the surfactant. Additionally, both the internal diffusion parameter of the Morris-Weber model (Kint), as well as the internal capacity of Methylene Blue (MB) were found to be linearly correlated to the interlayer d-spacing measured by XRD. Moreover, we found that the desorption trend of MB from the modified LDHs correlates with the chemical affinity to the modified LDH surface as well as the amounts of MB adsorbed internally and externally. Overall, the results highlight the potential of LDH-based materials to serve as a promising material platform with a controlled molecular adsorption capacity and diffusion rate.

Mixing intensification in an acoustofluidic micromixer aided with micro-pillars

In this work, we present an acoustofluidic micromixer that employs the combination of acoustic waves and micro-pillars to achieve enhanced mixing performance. We have shown that micro-pillars can generate micro-vortices, which lead to intense stretching and folding of the fluid trapped inside the micromixer and subsequently result in the formation of lamellar structures consisting of layers of the stretched fluids having steep concentration gradients between them. High concentration gradients coupled with the increased interfacial area result in higher rates of molecular diffusion. A numerical study is conducted, testing the performance of micro-pillars of three different designs in comparison to a simple rectangular acoustofluidic micromixer without any micro-pillars. The performance of the device in terms of improving the reaction kinetics of a chemical process has also been analyzed. For wide aspect ratio microchannels, our acoustofluidic micromixer helps in achieving rapid and homogeneous mixing while maintaining a high throughput.

Interfacial interaction behavior of recycled asphalt pavement: Molecular dynamics simulation

Recycling waste asphalt mixture (WAM) to prepare recycled asphalt pavement (RAP) is an important measure to handle road construction waste. Asphalt-aggregate interface (AAI) and matrix-aged asphalt interface (MAI), as weak interfaces in RAP, interface interaction behavior directly affects the road performance of RAP. In this paper, molecular models of asphalt and aggregate were constructed. Molecular dynamics simulation was used to analyze and evaluate the interaction behavior of the AAI and the MAI in RAP. The mean square displacement (MSD), relative concentration function (RCP), and radial distribution function (RDF) were used to quantitatively analyse the interface interaction behavior. The research results are as follows: For the AAI, the temperature, the aging level of asphalt, and chemical composition of aggregates will affect the interaction behavior of the AAI. Increasing temperature accelerates the diffusion of asphalt on the surface of aggregate. However, the increase of the aging level of asphalt and the alkalinity of aggregate will decrease the interaction rate of asphalt on the surface of aggregate. For the MAI, the temperature and the ratio of filler-asphalt (RFA) significantly affect the interaction behavior of the MAI. The molecular diffusion rate of matrix asphalt and aged asphalt increases significantly with the increasing temperature. The addition of filler will decrease the diffusion rate of asphalt, and the diffusion rate decreases with the increase of RFA. This article comprehensively and systematically studies and evaluates the effect of various factors on the interface interaction behavior. The results provide guidance for improving the adhesion ability of AAI and enhancing the degree of incorporation of MAI.

Resolving Molecular Size and Homologues with a Self-Assembled Metal–Organic Framework Photonic Crystal Detector

Traditional environmental photonic sensing based on the balanced reflection of a photonic structure can hardly be applied to distinguish molecular size and homologues, since the refractive index change introduced by these analytes can be too similar to be unambiguously distinguished. Here, a sensing method based on the pore size selectivity and organics adsorption–desorption capacity of self-assembled ZIF-8 photonics crystal is demonstrated, which can tell apart different molecular sizes, homologues, and organics with similar structures and physical properties. Specificity is improved by the inherent relationships between the pore size of ZIF-8 metal–organic frameworks and the associated molecular diffusion rates in the pores, so that the combination of the observed peak shift and recovery time are unique to each analyte. Using this method, selective detection of molecular size is also demonstrated in the case of linear vs cyclic molecules, since only the former can penetrate inside the ZIF-8 pores to induce a large wavelength shift. The reflection peak shift caused by the linear molecules was found to be about 30–40 nm, an order of magnitude larger compared to those for the cyclic molecules. A relationship between the diffusion rate of linear molecules in ZIF-8 pore and the recovery time of photonic crystal reflective peak is further established, linking the recovery time and the linear molecular diffusion coefficient. Finally, different linear molecules are identified by their associated recovery time to detect homologues or organics with similar refractive index.

Epidural Pulsation Accelerates the Drainage of Brain Interstitial Fluid.

Unhindered transportation of substances in the brain extracellular space (ECS) is essential for maintaining brain function. Regulation of transportation is a novel strategy for treating ECS blockage-related brain diseases, but few techniques have been developed to date. In this study, we established a novel approach for accelerating the drainage of brain interstitial fluid (ISF) in the ECS using minimally invasive surgery, in which a branch of the external carotid artery is separated and implanted epidurally (i.e., epidural arterial implantation [EAI]) to promote a pulsation effect on cerebrospinal fluid (CSF) in the frontoparietal region. Tracer-based magnetic resonance imaging was used to evaluate the changes in ISF drainage in rats 7 and 15 days post-EAI. The drainage of the traced ISF from the caudate nucleus to ipsilateral cortex was significantly accelerated by EAI. Significant increases in the volume fraction of the ECS and molecular diffusion rate were demonstrated using the DECS-mapping technique, which may account for the mechanisms underlying the changes in brain ISF. This study provides a novel perspective for encephalopathy treatment via the brain ECS.

The potential of direct air capture using adsorbents in cold climates.

Global warming threatens the entire planet, and solutions such as direct air capture (DAC) can be used to meet net-zero goals and go beyond. This study investigates using DAC in a 5-step temperature vacuum swing adsorption (TVSA) cycle with adsorbents' Li-X and Na-X, readily available industrial zeolites, to capture and concentrate CO2 from air in cold climates. From this study, we report that Na-X in cold conditions has the highest known CO2 adsorption capacity in air of 2.54mmol/g. This combined with Na-X's low CO2 heat of adsorption, and fast uptake-rate in comparison to other benchmark materials, allowed for Na-X operating in cold conditions to have the lowest reported DAC operating energy of 1.1 MWh/tonCO2. These findings from this study show the promise of this process in cold climates of Canada, Alaska, Greenland, and Antarctica to be part of the solution to global warming.

A model of algal‐virus population dynamics reveals underlying controls on material transfer

AbstractThe influence of viruses on nutrient cycles and energy transfer in aquatic systems is important, yet still being determined. We developed a dynamic model to capture the population dynamics of algal hosts and their viruses. The model was fitted to literature data of population dynamics during laboratory one‐step infection experiments. Model parameters that underlie population dynamics were quantified in diverse algal groups, covering 7 different algal classes, 14 different host genera, and 32 different virus genotypes. The hypothesis that trade‐offs exist between traits that underlie population dynamics was evaluated. We report a possible virus size‐dependent trade‐off between the rate at which viruses can initiate infection, and the efficiency of carbon transfer from hosts to viruses upon lysis. We hypothesize that slower rates of infection in large viruses, due to slower rates of molecular diffusion, are compensated by enhanced utilization of host resources. Our approach provides a quantitative trait‐framework for understanding and quantifying virus activity in diverse natural communities.

Loss of α6β4 Integrin-Mediated Hemidesmosomes Promotes Prostate Epithelial Cell Migration by Stimulating Focal Adhesion Dynamics.

Epithelial cell adhesion is mediated by actin cytoskeleton-linked focal adhesions (FAs) and intermediate filament-associated hemidesmosomes (HDs). HDs are formed by α6β4-integrins and mediate stable anchoring to the extracellular matrix (ECM) while FAs containing β1-integrins regulate cell migration. Loss of HDs has been reported in various cancers such as prostate cancer where it correlates with increased invasive migration. Here we have studied cell migration properties and FA dynamics in genetically engineered prostate epithelial cell lines with intact or disrupted HDs. Disruption of HDs by depleting α6- or β4-integrin expression promoted collective cell migration and modulated migratory activity. Dynamic analysis of fluorescent protein-tagged FA marker proteins revealed faster FA assembly and disassembly kinetics in HD-depleted cells. FRAP analysis showed that loss of HDs correlated with faster diffusion rates of focal adhesion kinase (FAK) and vinculin in and out of FAs. These data suggest that loss of α6β4-mediated HDs promote cell migration and FA assembly dynamics by influencing the molecular diffusion rates of FAK.

IVIM Imaging of Paraspinal Muscles Following Moderate and High-Intensity Exercise in Healthy Individuals.

Background:Quantification of the magnitude and spatial distribution of muscle blood flow changes following exercise may improve our understanding of the effectiveness of various exercise prescriptions. Intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) is a technique that quantifies molecular diffusion and microvascular blood flow, and has recently gained momentum as a method to evaluate a muscle’s response to exercise. It has also been shown to predict responses to exercise-based physical therapy in individuals with low back pain. However, no study has evaluated the sensitivity of IVIM-MRI to exercise of varying intensity in humans. Here, we aimed to evaluate IVIM signal changes of the paraspinal muscles in response to moderate and high intensity lumbar extension exercise in healthy individuals.Methods:IVIM data were collected in 11 healthy volunteers before and immediately after a 3-min bout of moderate and high-intensity resisted lumbar extension. IVIM data were analyzed to determine the average perfusion fraction (f), pseudo-diffusion coefficient (D*), and diffusion coefficient (D) in the bilateral paraspinal muscles. Changes in IVIM parameters were compared between the moderate and high intensity exercise bouts.Results:Exercise increased all IVIM parameters, regardless of intensity (p < 0.003). Moderate intensity exercise resulted in a 11.2, 19.6, and 3.5% increase in f, D* and D, respectively. High intensity exercise led to a similar increase in f (12.2%), but much greater changes in D* (48.6%) and D (7.9%).Conclusion:IVIM parameter increases suggest that both the moderate and high-intensity exercise conditions elicited measurable changes in blood flow (increased f and D*) and extravascular molecular diffusion rates (increased D), and that there was a dose-dependence of exercise intensity on D* and D.

Study on SBS modifier of bio-oil/sulfur compound under dry modification mode

To solve the problem of poor modification effect caused by insufficient swelling of SBS modifier in asphalt mixture under dry modification mode, the crosslinking reaction among bio-oil, sulfur, and SBS was used to prepare an efficient dry modifier to improve the road performance of dry modified asphalt mixture. At the micro level, the molecular models of asphalt, mineral, and compound SBS modifier were established. The basic properties of the compound-modified asphalt and the interaction between the compound-modified asphalt and mineral were predicted by four indexes, namely, microviscosity, relative distribution concentration, mean square displacement, and adhesion work. Macroscopically, the compound modifier was prepared by using bio-oil, sulfur, and SBS, and the reaction time was determined. The modification effect of the compound dry modifier was verified by a basic performance test of the asphalt and asphalt mixture. On the micro level, bio-oil/sulfur compound matched the SBS molecules in the asphalt model after determining that microscopic viscosity was higher than that in the common SBS model. The complex model matched the SBS asphalt in ore material on the surface in terms of the molecular diffusion rate, and adhesion effect also improved the SBS model in terms of predicting whether the complex matches dry process modification effect was superior to that of the common SBS modified agent. At the macro level, the reaction time of the compound modified agent was 30 min, and the prediction conclusion of molecular simulation was verified by the asphalt and asphalt mixture test. The penetration degree, softening point, ductility and aging indexes of the complex dry modified asphalt meet the standards of the wet modified asphalt in The Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004). The indexes of high temperature rutting resistance, ultimate flexural strain and residual strength ratio of freezing-thawing splitting also reach the standard of wet-modified asphalt mixture.

Study on the Adhesion Force between Wax Crystal Particles and Hydrate Particles.

In this work, to solve the problem of pipeline blockage caused by the accumulation of hydrate particles and wax particles and to explore the interaction characteristics of adhesive force between gas hydrate particles and wax particles as well as droplets, a high-pressure triaxial mobile device was used to measure the adhesion strength between cyclopentane hydrate particles and different commonly seen phases in the pipeline, including cyclopentane hydrate particles themselves, liquid droplets, and wax crystal particles. These experiments were conducted at different temperatures. The results showed that the adhesion between hydrate and wax particles was decreased with the increase in temperature; this is because the wax is amorphous, the heat absorbed when the temperature rises only increases its average kinetic energy, and the stronger the kinetic energy, the lower its viscosity, resulting in reduced adhesion between particles. Meanwhile, this adhesion was also affected by the concentration of wax. As the wax concentration increased from 1 to 5.32 wt % and then to 8.14 wt %, the adhesion between hydrate and wax particles was first decreased and then increased. This was because when the wax crystal concentration was below 5 wt %, a higher wax molecule concentration meant a more hydrophobic surface, which restricted the formation of a capillary liquid bridge between particles and thus reduced the interforce between wax crystal particles and hydrate particles. When the wax crystal concentration was between 5 and 8 wt %, the change of hydrophobicity was no longer the dominating factor, the increase in wax concentration blocked the hydrate molecular diffusion path, which caused a higher hydrate viscosity, therefore leading to a decreased hydrate molecular diffusion rate and a reduced conversion rate of the liquid bridge in hydrates, the lower conversion rate could subsequently lead to the increasing size of micropores in the hydrate shell, and adhesion between particles was increased.

Scalar gradient and flame propagation statistics of a flame-resolved laboratory-scale turbulent stratified burner simulation

A bluff-body stabilised turbulent jet flame burning in a stratified mode of combustion for fuel-lean methane/air mixtures is investigated by a flame-resolved simulation. A tabulated chemistry approach based on premixed flamelet generated manifolds (PFGM) accounts for thermochemistry. The computations are performed for a grid-resolution of 100 µm, sufficient to resolve the thermal flame thickness. The look-up table is generated with a mixture-averaged diffusivity assumption and the preferential diffusion fluxes are included in the simulation, using an efficient method without increasing the dimensionality of the manifold. The predicted mean and RMS quantities are found to be in good agreement with the experiment. The investigation focuses on the comparison of the combustion behaviour of the upstream locations close to the inlet with weak mixture fraction gradients to the downstream locations away from the inlet with strong mixture fraction gradients. Statistical analysis of the diffusion terms within the flame revealed that the preferential diffusion remains significant near the inlet, in the recirculation zone over the bluff-body. The structure of the stratified flame in downstream locations is statistically analysed in terms of displacement speed and scalar gradients by comparing against the corresponding quantities in upstream locations with weak mixture fraction gradients. It is shown that the displacement speed is statistically different between the flames under weak or strong mixture fraction gradients due to the influence of molecular diffusion and reaction rate components. However, increased curvature effects and cross-dissipation component also play a role. Finally, scalar dissipation and cross-dissipation rates of the mixture fraction fluctuation and the reaction progress variable fluctuation within the flame-brush are investigated, and their closure approaches are discussed.

Fabrication of PCDTBT Conductive Network via Phase Separation.

Poly[N-9′-hepta-decanyl-2,7-carbazole-alt-5-5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) is a stable semiconducting polymer with high rigidity in its molecular chains, which makes it difficult to organize into an ordered structure and affects the device performance. Here, a PCDTBT network consisting of aggregates and nanofibers in thin films was fabricated through the phase separation of mixed PCDTBT and polyethylene glycol (PEG). Using atomic force microscopy (AFM), the effect of the blending conditions (weight ratio, solution concentration, and molecular weight) and processing conditions (substrate temperature and solvent) on the resulting phase-separated morphologies of the blend films after a selective washing procedure was studied. It was found that the phase-separated structure’s transition from an island to a continuous structure occurred when the weight ratio of PCDTBT/PEG changed from 2:8 to 7:3. Increasing the solution concentration from 0.1 to 3.0 wt% led to an increase in both the height of the PCDTBT aggregate and the width of the nanofiber. When the molecular weight of the PEG was increased, the film exhibited a larger PCDTBT aggregate size. Meanwhile, denser nanofibers were found in films prepared using PCDTBT with higher molecular weight. Furthermore, the electrical characteristics of the PCDTBT network were measured using conductive AFM. Our findings suggest that phase separation plays an important role in improving the molecular chain diffusion rate and fabricating the PCDTBT network.

Study on the Adhesion Performance of Asphalt-Calcium Silicate Hydrate Gel Interface in Semi-Flexible Pavement Materials Based on Molecular Dynamics.

The interface between an asphalt binder and a calcium silicate hydrate (C-S-H) gel is a weak point of semi-flexible pavement material. In this study, the adhesion performance of asphalt-C-S-H gel interface in semi-flexible pavements at a molecular scale has been investigated. Molecular dynamics (MD) simulations were applied to establish three asphalt binders: 70# asphalt binder (the penetration is 70 mm), PG76-22 modified asphalt binder (a kind of asphalt binder that can adapt to the highest temperature of 76 °C and the lowest temperature of −22 °C), and S-HV asphalt binder (super high viscosity). The effects of different temperatures and SBS modifier contents on interfacial adhesion were explored. The obtained results showed that temperature variations had little effect on the adhesion work of the asphalt-C-S-H gel interface. It was also found that by increasing the content of SBS modifier, the adhesion work of the asphalt-C-S-H gel interface was increased. The molecular weight of each component was found to be an important factor affecting its molecular diffusion rate. The addition of SBS modifier could regulate the adsorption of aromatics by C-S-H gel in the four components of asphalt binder and improve the adsorption of resins by C-S-H gel.

Nanoscale Catalyst Chemotaxis Can Drive the Assembly of Functional Pathways.

Recent experiments demonstrate molecular chemotaxis or altered diffusion rates of enzymes in the presence of their own substrates. We show here an important implication, namely, that if a nanoscale catalyst A produces a small-molecule ligand product L which is the substrate of another catalyst B, the two catalysts will attract each other. We explore this nonequilibrium producer recruitment force (ProRec) in a reaction–diffusion model. The predicted cat–cat association will be the strongest when A is a fast producer of L and B is a tight binder to it. ProRec is a force that could drive a mechanism (the catpath mechanism) by which catalysts could become spatially localized into functional pathways, such as in the biochemical networks in cells, which can achieve complex goals.