Brush Height Research Articles

牛场补饲推料装置设计与试验

This paper proposed a supplemental feeding pusher based on beef cattle's auxiliary feeding needs to solve the traditional feeding mode of manual work, labor intensity, and inconsistent manual work standards. Firstly, the conveyed feed particles movement process was established as a motion model and the basis of the design parameters of the screw conveyor was explained. ANSYS static analysis module was used to ensure that the structural parameters of the discharging device were reasonable, ANSYS vibration modal analysis module was used to verify the frame strength and stability. According to the theoretical design of the trial prototype, the control system with STM32F103RE microcontroller as the core was carried out. Finally, the orthogonal test was conducted with the screw shaft speed, sweeping roller brush height, and traveling speed as test factors; different parameters were set to verify the effect of supplemental feeding and pushing, and parameter optimization of the test results was carried out using Design-Expert software. The optional combination of working parameters was determined to be the feeding screw shaft speed 188 r/min, the sweeping roller brush speed 160 r/min, and the work speed 0.26 m/s. The test demonstrated that the residual feed width was 0.73 m, and the transverse coefficient of variation was 14.9%, which could satisfy the needs of auxiliary feeding for beef cattle. This study reduced feed waste and met the cattle feeding needs to the greatest extent, and it could provide a reference for auxiliary feeding machinery.

Study on the Impact of Pole Spacing on Magnetic Flux Leakage Detection under Oversaturated Magnetization.

Magnetic flux leakage (MFL) inspection employs leakage magnetic fields to effectively detect and locate pipeline defects. The spacing between magnetic poles significantly affects the leakage magnetic field strength. While most detectors typically opt for moderate pole spacing for routine detection, this study investigates the propagation characteristics of MFL signals at small pole spacings (under specimen oversaturated magnetization) and their impact on MFL detection. Through finite element simulation and experiments, it reveals a new signal phenomenon in the radial MFL signal By at small pole spacings, the double peak-valley (DPV) phenomenon, characterized by outer and inner peaks and valleys. Theoretical analysis based on the simulation results elucidates the mechanisms for this DPV phenomenon. Based on this, the impact of defect size, pipe wall thickness, and magnetic pole and rigid brush height on MFL signals under small magnetic pole spacings is examined. It is demonstrated that, under a smaller magnetic pole spacing, a potent background magnetic field manifests in the air above the defect. This DPV phenomenon is generated by the magnetic diffusion and compression interactions between the background and defect leakage magnetic fields. Notably, the intensity of the background magnetic field can be mitigated by reducing the height of the rigid brush. In contrast, the pipe wall thickness and magnetic pole height exhibit a negligible influence on the DPV phenomenon. The emergence of the DPV precipitates a reduction in the peak-to-valley difference within the MFL signal, constricting the depth range of detectable defects. However, the presence of DPV increases the identification of defects with smaller opening sizes. These findings reveal the characterization of the MFL signal under small pole spacing, offering a preliminary study on identifying specific defects using unconventional signals. This study provides valuable guidance for MFL detection.

Surface-Initiated Polymerization with an Initiator Gradient: A Monte Carlo Simulation.

Due to the difficulty of accurately characterizing properties such as the molecular weight (Mn) and grafting density (σ) of gradient brushes (GBs), these properties are traditionally assumed to be uniform in space to simplify analysis. Applying a stochastic reaction model (SRM) developed for heterogeneous polymerizations, we explored surface-initiated polymerizations (SIPs) with initiator gradients in lattice Monte Carlo simulations to examine this assumption. An initial exploration of SIPs with 'homogeneously' distributed initiators revealed that increasing σ slows down the polymerization process, resulting in polymers with lower molecular weight and larger dispersity (Đ) for a given reaction time. In SIPs with an initiator gradient, we observed that the properties of the polymers are position-dependent, with lower Mn and larger Đ in regions of higher σ, indicating the non-uniform properties of polymers in GBs. The results reveal a significant deviation in the scaling behavior of brush height with σ compared to experimental data and theoretical predictions, and this deviation is attributed to the non-uniform Mn and Đ.

Effects of Ionic Strength on the Morphology, Scattering, and Mechanical Response of Neurofilament-Derived Protein Brushes.

Protein brushes not only play a key role in the functionality of neurofilaments but also have wide applications in biomedical materials. Here, we investigate the effect of ionic strength on the morphology of protein brushes using continuous-space self-consistent field theory. A coarse-grained multiblock charged macromolecular model is developed to capture the chemical identity of amino acid sequences. For neurofilament heavy (NFH) brushes at pH 2.4, we predict three morphological regimes: swollen brushes, condensed brushes, and coexisting brushes, which consist of both a dense inner layer and a diffuse outer layer. The brush height predicted by our theory is in good agreement with the experimental data for a wide range of ionic strengths. The dramatic height decrease is a result of the electrostatic screening-induced transition from the overlapping state to the isolated state of the coexisting brushes. We also studied the evolution of the scattering and mechanical responses accompanying the morphological change. The oscillation in the reflectivity spectra characterizes the existence and microstructure of the inner condensed layer, whereas the shoulder in the force spectra signifies a swollen morphology.

Photo-Programmable Processes in Bithiophene–Azobenzene Monolayers on Gold Probed via Simulations

In this study, we investigate the structural changes, electronic properties, and charge redistribution within azo-bithiophene (Azo-BT)-chemisorbed monolayers under different light stimuli using the density functional theory and molecular dynamics simulations. We consider two types of switches, Azo-BT and BT-Azo, with different arrangements of the Azo and BT blocks counting from the anchor thiol group. The chemisorbed monolayers of pure cis- and trans-isomers with a surface concentration of approximately 2.7 molecules per nm2 are modeled on a gold surface using the classical all-atom molecular dynamics. Our results reveal a significant shrinkage of the BT-Azo layer under UV illumination, whereas the thicknesses of the Azo-BT layer remain comparable for both isomers. This difference in behavior is attributed to the ordering of the trans-molecules in the layers, which is more pronounced for Azo-BT, leading to a narrow distribution of the inclination angle to the gold surface. Conversely, both layers consisting of cis-switches exhibit disorder, resulting in similar brush heights. To study charge transfer within the immobilized layers, we analyze each snapshot of the layer and calculate the mean charge transfer integrals using Nelsen’s algorithm for a number of interacting neighboring molecules. Combining these integrals with reorganization energies defined for the isolated molecules, we evaluate the charge transfer rates and mobilities for electron and hole hopping within the layers at room temperature based on Marcus’ theory. This research offers new perspectives for the innovative design of electrode surface modifications and provides insights into controlling charge transfer within immobilized layers using light triggers. Additionally, we identify molecular properties that are enhanced via specific molecular design, which contributes to the development of more efficient molecular switches for various electronic applications.

Swelling and shrinking of two opposing polyelectrolyte brushes.

Salt concentration and confinement effects affect the configuration of polyelectrolyte (PE) brushes due to electrostatic interactions. In this work, we develop a new theoretical model to analyze the electrostatics and swelling-shrinking behavior of two opposing PE brushes. By comparing three length scales, i.e., equilibrium brush height, separation distance, and Debye length, we obtain distinct scaling laws for brush height in different regimes. We provide explanations for the anomalous shrinkage of the PE brush with added salt reported in experiments and simulations, the applicability of the homogeneous brush assumption, and the confinement effect on the brush height. Our model can be used to shed light on the configuration and functionalities of PE-grafted interfaces, which play important roles in ion selective membranes and organism lubrication. We also anticipate that our method will be useful to understand the functionalities of other charged soft matter systems, such as hydrogel swelling and colloidal stability.

Morphology of Polymer Brushes in the Presence of Attractive Nanoparticles: Effects of Temperature.

We study the role of temperature on the structure of pure polymer brushes and their mixture with attractive nanoparticles in flat and cylindrical geometries. It has previously been established that the addition of such nanoparticles causes the polymer brush to collapse and the intensity of the collapse depends on the attraction strength, the nanoparticle diameter, and the grafting density. In this work, we carry out molecular dynamics simulation under good solvent conditions to show how the collapse transition is affected by the temperature, for both plane grafted and inside-cylinder grafted brushes. We first examine the pure brush morphology and verify that the brush height is insensitive to temperature changes in both planar and cylindrical geometries, as expected for a polymer brush in a good solvent. On the other hand, for both system geometries, the brush structure in the presence of attractive nanoparticles is quite responsive to temperature changes. Generally speaking, for a given nanoparticle concentration, increasing the temperature causes the brush height to increase. A brush which contracts when nanoparticles are added eventually swells beyond its pure brush height as the system temperature is increased. The combination of two easily controlled external parameters, namely, concentration of nanoparticles in solution and temperature, allows for sensitive and reversible adjustment of the polymer brush height, a feature which could be exploited in designing smart polymer devices.

Modelling thermoresponsive polymer brush by mesoscale computer simulations

We consider a functional surface comprising thermoresponsive polymer chains, the material that has found numerous technological and biomedical applications. However, to achieve the required time and length scales for computer modelling of such applications, one is compelled to use coarse-grained mesoscopic modelling approaches. The model used here is based on the previous work [Soto-Figueroa et al., Soft Matter, 8, 1871 (2012)], and it mimics the principal feature of the poly(N-iso-propylacrylamide) (PNIPAM), namely, the rapid change of its hydrophilicity at the lower critical solution temperature (LCST). For the case of an isolated chain, we discuss scaling properties of the radius of gyration, end-to-end distance, various distribution functions, and the density profile of monomers below and above the LCST. For the case of the model thermoresposive brush, we search for the optimum grafting density at which the change in the brush height, upon crossing the LCST, reaches its maximum value. The interpretation of the thermoresponse, in terms of the Alexander-de Gennes blobs and the level of solvation of polymer chains in a brush, is provided.

Electric double layer of spherical pH-responsive polyelectrolyte brushes in an electrolyte solution: A strong stretching theory accounting for excluded volume interaction and mass action law

In this paper, we study the electrostatics of pH-responsive polyelectrolyte-grafted spherical particles by using a strong stretching theory that takes into account the excluded volume interaction and the density of chargeable sites on the polyelectrolyte molecules. Based on free energy formalism, we obtain self-consistent field equations for determining the structure and electrostatics of spherical polyelectrolyte brushes. First, we find that the smaller the radius of the inner core, the longer the height of the polyelectrolyte brush. Then, we also prove that an increase in the excluded volume interaction yields a swelling of the polyelectrolyte brush height. In addition, we demonstrate how the effect of pH, bulk ionic concentration, and lateral separation between adjacent polyelectrolyte chains on the electrostatic properties of a spherical polyelectrolyte brush is affected by the radius of the inner core, the excluded volume interaction, and the chargeable site density.

Free energies of polymer brushes with mobile anchors in a good solvent calculated with the expanded ensemble method

We explore the free energy of “mobile polymer brushes”: The polymer molecules are not chemically bonded to the particle surface but are rather adsorbed by one end. They can desorb to the equilibrium solution and are able to move laterally along the interface. In a good solvent the prevailing forces in the system (apart from the attraction between the adsorbed anchor and the surface) originate from the entropic repulsion between the individual chains. Here we explore the brushes’ free energy and adsorption equilibrium using Brownian Dynamics in conjunction with Expanded Ensembles Monte Carlo simulations that we adapt making it more suitable for polymer brushes. Expanded Ensembles are employed to calculate the excess chemical potential of a polymer chain as a function of the interfacial lateral density, polymer length, and effective exclusion volume of the segment. The thermodynamic properties are related to the structural features, such as brush height, chain radius of gyration, and the in-plane radial distribution function between the chain anchors. Specific attention is paid to the scaling of the excess chemical potential and brush height with the polymer length and interfacial density as well as its influence on the adsorption equilibrium between interface and the bulk polymer solution.

Electrostatic Potential Analysis in Polyelectrolyte Brush-Grafted Microchannels Filled with Polyelectrolyte Dispersion

In this study, the model framework that includes almost all relevant parameters of interest has been developed to quantify the electrostatic potential and charge density occurring in microchannels grafted with polyelectrolyte brushes and simultaneously filled with polyelectrolyte dispersion. The brush layer is described by the Alexander-de Gennes model incorporated with the monomer distribution function accompanying the quadratic decay. Each ion concentration due to mobile charges in the bulk and fixed charges in the brush layer can be determined by multi-species ion balance. We solved 2-dimensional Poisson–Nernst–Planck equations adopted for simulating electric field with ion transport in the soft channel, by considering anionic polyelectrolyte of polyacrylic acid (PAA). Remarkable results were obtained regarding the brush height, ionization, electrostatic potential, and charge density profiles with conditions of brush, dispersion, and solution pH. The Donnan potential in the brush channel shows several times higher than the surface potential in the bare channel, whereas it becomes lower with increasing PAA concentration. Our framework is fruitful to provide comparative information regarding electrostatic interaction properties, serving as an important bridge between modeling and experiments, and is possible to couple with governing equations for flow field.

Programmable Site-Specific Functionalization of DNA Origami with Polynucleotide Brushes.

Combining surface-initiated, TdT (terminal deoxynucleotidyl transferase) catalyzed enzymatic polymerization (SI-TcEP) with precisely engineered DNA origami nanostructures (DONs) presents an innovative pathway for the generation of stable, polynucleotide brush-functionalized DNA nanostructures. We demonstrate that SI-TcEP can site-specifically pattern DONs with brushes containing both natural and non-natural nucleotides. The brush functionalization can be precisely controlled in terms of the location of initiation sites on the origami core and the brush height and composition. Coarse-grained simulations predict the conformation of the brush-functionalized DONs that agree well with the experimentally observed morphologies. We find that polynucleotide brush-functionalization increases the nuclease resistance of DONs significantly, and that this stability can be spatially programmed through the site-specific growth of polynucleotide brushes. The ability to site-specifically decorate DONs with brushes of natural and non-natural nucleotides provides access to a large range of functionalized DON architectures that would allow for further supramolecular assembly, and for potential applications in smart nanoscale delivery systems.

Programmable Site‐Specific Functionalization of DNA Origami with Polynucleotide Brushes

AbstractCombining surface‐initiated, TdT (terminal deoxynucleotidyl transferase) catalyzed enzymatic polymerization (SI‐TcEP) with precisely engineered DNA origami nanostructures (DONs) presents an innovative pathway for the generation of stable, polynucleotide brush‐functionalized DNA nanostructures. We demonstrate that SI‐TcEP can site‐specifically pattern DONs with brushes containing both natural and non‐natural nucleotides. The brush functionalization can be precisely controlled in terms of the location of initiation sites on the origami core and the brush height and composition. Coarse‐grained simulations predict the conformation of the brush‐functionalized DONs that agree well with the experimentally observed morphologies. We find that polynucleotide brush‐functionalization increases the nuclease resistance of DONs significantly, and that this stability can be spatially programmed through the site‐specific growth of polynucleotide brushes. The ability to site‐specifically decorate DONs with brushes of natural and non‐natural nucleotides provides access to a large range of functionalized DON architectures that would allow for further supramolecular assembly, and for potential applications in smart nanoscale delivery systems.

Glycopolymer Microarrays with Sub‐Femtomolar Avidity for Glycan Binding Proteins Prepared by Grafted‐To/Grafted‐From Photopolymerizations

AbstractWe report a novel glycan array architecture that binds the mannose‐specific glycan binding protein, concanavalin A (ConA), with sub‐femtomolar avidity. A new radical photopolymerization developed specifically for this application combines the grafted‐from thiol–(meth)acrylate polymerization with thiol–ene chemistry to graft glycans to the growing polymer brushes. The propagation of the brushes was studied by carrying out this grafted‐to/grafted‐from radical photopolymerization (GTGFRP) at >400 different conditions using hypersurface photolithography, a printing strategy that substantially accelerates reaction discovery and optimization on surfaces. The effect of brush height and the grafting density of mannosides on the binding of ConA to the brushes was studied systematically, and we found that multivalent and cooperative binding account for the unprecedented sensitivity of the GTGFRP brushes. This study further demonstrates the ease with which new chemistry can be tailored for an application as a result of the advantages of hypersurface photolithography.

Polymer brush-induced depletion interactions and clustering of membrane proteins

We investigate the effect of mobile polymer brushes on proteins embedded in biological membranes by employing both Asakura-Oosawa type of theoretical model and coarse-grained molecular dynamics simulations. The brush polymer-induced depletion attraction between proteins changes non-monotonically with the size of brush. The depletion interaction, which is determined by the ratio of the protein size to the grafting distance between brush polymers, increases linearly with the brush size as long as the polymer brush height is shorter than the protein size. When the brush height exceeds the protein size, however, the depletion attraction among proteins is slightly reduced. We also explore the possibility of the brush polymer-induced assembly of a large protein cluster, which can be related to one of many molecular mechanisms underlying recent experimental observations of integrin nanocluster formation and signaling.

Sculpting Enzyme-Generated Giant Polymer Brushes.

We present a simple yet versatile method for sculpting ultra-thick, enzyme-generated hyaluronan polymer brushes with light. The patterning mechanism is indirect, driven by reactive oxygen species created by photochemical interactions with the underlying substrate. The reactive oxygen species disrupt the enzyme hyaluronan synthase, which acts as the growth engine and anchor of the end-grafted polymers. Spatial control over the grafting density is achieved through inactivation of the enzyme in an energy density dose-dependent manner, before or after polymerization of the brush. Quantitative variation of the brush height is possible using visible wavelengths and illustrated by the creation of a brush gradient ranging from 0 to 6 μm in height over a length of 56 μm (approximately a 90 nm height increase per micron). Building upon the fundamental insights presented in this study, this work lays the foundation for the flexible and quantitative sculpting of complex three-dimensional landscapes in enzyme-generated hyaluronan brushes.

Inhibition of turbulent methane/air premixed bunsen flames by dimethyl methylphosphonate

There is little knowledge about the inhibition efficiency of dimethyl methylphosphonate (DMMP) against turbulent flames, in which vortices of different sizes corrugate and stretch the flame front. This study is to investigate the performance and the mechanism of DMMP in inhibiting turbulent methane/air premixed Bunsen flames. Several important parameters are chosen to characterize the combustion of the flames, including flame brush height, flame brush thickness and turbulent burning velocity. It is found that the flame brush expands both horizontally and vertically with the increase of turbulent intensity. For all the flames, the centerline mean flame brush thickness increases linearly with flame height. Turbulent burning velocity decreases monotonically with the increasing of DMMP addition. However, the normalized turbulent burning velocity increases with the normalized turbulent intensity. Compared with the performance in laminar premixed flames, the inhibition efficiency depends on the turbulent intensity. For low-intensity turbulent flames, the inhibition efficiency is higher than that in laminar premixed flames, but the relative inhibition efficiency decreases with DMMP addition. This can be attributed to the relative size of the vortices and the flame front thickness: when the Kolmogorov length scale is less than the preheat zone thickness but greater than the reaction zone thickness, vortices reduce the burning velocity; when the Kolmogorov length scale is less than the reaction zone thickness, vortices facilitate the combustion. The trend is opposite in high-intensity turbulent flames, which is mainly attributed to the generating of the flame pockets in the flame tips.

Cyclic Polyethylene Glycol as Nanoparticle Surface Ligand.

Cyclic polymers behave different than linear polymers due to the lack of end groups and smaller coil dimensions. Herein, we demonstrate that cyclic polyethylene glycol (PEG) can be used as an alternative of classical linear PEG ligands for gold nanoparticle (AuNP) stabilization. We observed that the brush height of cyclic PEG on AuNPs of diameter 4.4 and 13.2 nm increases identically as that of linear brushes with (Nσ1/2)0.7 (N, number of monomers in a chain and σ, grafting density) and that cyclic brushes are more stretched than their linear analogues when compared to their unperturbed dimensions. Such structural effect and the reduced footprint diameter in cyclic brushes with the entire chain in a concentrated polymer brush regime explains the distinct response of NPs to ionic strength and temperature, respectively, compared to linear analogues. These experiments are an important step in understanding the effect of polymer brush topology on colloidal properties.

Effects of graft locations on dispersion behavior of polymer-grafted nanorods: A molecular dynamics simulation study

In this paper, we present the effects of graft locations on the dispersion behavior of polymer-grafted nanorods using molecular dynamics simulations. Four graft locations of chains on nanorods, i.e., end-grafted, quarter-grafted, middle-grafted and uniformly grafted, are specially designed, and the effects of graft locations are examined in both sparsely grafted case and densely grafted case. Simulation results show that the end-grafted nanorods exhibit the poorest dispersion in the matrix, whilst the body-grafted (quarter-grafted and middle-grafted) ones show the best dispersion. At low grafting density in the mushroom regime, the middle-grafted disperse slightly better than the quarter-grafted, whereas at high grafting density in the brush regime, the situation is reversed. By analyzing the conformations of graft chains (mushroom height and brush height) and the behavior of grafted nanorods, it is inferred that the inter-rod cohesive energy provides a great contribution to the dispersion, as reflected by the significant role of the center region of nanorods. In general, a dense and wide coverage of the center/middle region of nanorods by graft chains can effectively improve the nanorod dispersion. This work is expected to provide some guidance on controlling and improving the dispersion of nanorods in polymer nanocomposites.

Organic solvent filtration by brush membranes: Permeability, selectivity and fouling correlate with degree of SET-LRP grafting

A novel surface modification technique for polyimide membranes, their characterization and organic solvent filtration performance is described. The process involves treating crosslinked polyimide support membranes with surface initiators followed by Single Electron Transfer - Living Radical Polymerization (SET-LRP) with three alkyl methacrylates. Proof of grafting is established using ATR-FTIR, XPS and FESEM. The degree of grafting (DG) and brush height were a function of monomer type and polymerization time and provide a unifying basis for correlating selectivity and permeability. The permeability of these composite membranes, evaluated with 6 organic solvents (alcohols), correlated with solvent properties and can be tailored with DG. Filtration performance was assessed by measuring the selectivity and fouling of the organic dye Rose Bengal (RB) in ethanol. The polarized wall concentration increased with DG, whereas the RB sieving coefficient decreased with DG. Flux decline during RB filtration was best described by pore blocking and by heterogeneous and Langmuir sorption models. These studies provide a basis for designing polymeric membranes comprising branched brush selective layers with defined microstructure not possible with the widely popular phase inversion process.