Monitoring film coalescence from aqueous polymeric dispersions using atomic force microscopy: Surface topographic and nano-adhesion studies

The aim of the investigation was to develop the use of topographic and nano-adhesion atomic force microscopy(AFM) studies as a means of monitoring the coalescence of latex particles within films produced from a pharmaceutically relevant aqueous dispersion(Eudragit~?NE30 D). Films were prepared via spin coating and analysed using AFM, initially via tapping mode for topographic assessment followed by force-distance measurements which allowed assessment of site-specific adhesion. The results showed that colloidal particles were clearly observed topographically in freshly prepared samples, with coalescence detected on curing via the disappearance of discernible surface features and a decrease in roughness indices. The effects of temperature and humidity on film curing were also studied, with the former having the most pronounced effect. AFM force measurements showed that the variation in adhesive force reduced with increasing curing time, suggesting a novel method of quantifying the rate of film formation upon curing. It was concluded that the AFM methods outlined in this study may be used as a means of qualitatively and quantitatively monitoring the curing of pharmaceutical films as a function of time and other variables, thereby facilitating rational design of curing protocols.

Atomic Force Microscopy Measurement in the Lignosulfonate/Inorganic Silica System:From Dispersion Mechanism Study to Product Design

Designing and preparing high-performance lignin-based dispersants are crucial steps in realizing the value-added utilization of lignin on an industrial scale.Such process depends heavily on an understanding of the dispersion mechanism of lignin-based dispersants.Here,atomic force microscopy(AFM)is employed to quantitatively investigate the dispersion mechanism of a lignosulfonate/silica(LS/SiO_(2))system under different pH conditions.The results show that the repulsive force between SiO_(2)particles in LS solution is stronger than it is in water,resulting in better dispersion stability.The Derjaguin–Landau–Verwey–Overbeek(DLVO)formula as well as the DLVO formula combined with steric repulsion is utilized for the fitting of the AFM force/distance(F/D)curves between the SiO_(2)probe and substrate in water and in LS solution.Based on these fitting results,electrostatic and steric repulsive forces are respectively calculated,yielding further evidence that LS provides strong steric repulsion between SiO_(2)particles.Further studies indicate that the adsorbance of LS on SiO_(2)(Q),the normalized interaction constant(A),and the characteristic length(L)are the three critical factors affecting steric repulsion in the LS/SiO_(2)system.Based on the above conclusions,a novel quaternized grafted-sulfonation lignin(QAGSL)dispersant is designed and prepared.The QAGSL dispersant exhibits good dispersing performance for SiO_(2)and real cement particles.This work provides a fundamental and quantitative understanding of the dispersion mechanism in the LS/inorganic particle system and provides important guidance for the development of high-performance lignin-based dispersants.

Delta distribution of electronegative plasma predicted by reformed“spring oscillator”dynamic equation with dispersing force

In our relevant paper[Zhao S X(2021)Chin.Phys.B 30055201],a delta distribution of negative ions is given by fluid simulation and preliminarily explained by decomposed anions transport equation.In the present work,first,the intrinsic connection between the electropositive plasma transport equation and spring oscillator dynamic equation is established.Inspired by this similarity,reformed“spring oscillator”equation with dispersing instead of restoring force that gives quasi-delta solution is devised according to the math embodied in the anion equation,which is of potential significance to the disciplines of atomic physics and astronomy as well.For solving the“diffusion confusion”the physics that determines the delta profile within the continuity equation is explored on the basis that recombination loss source term plays the role of drift flux,which is applicable for fluid model of low temperature plasma,but not the ordinary fluid dynamics.Besides,the math and physics revealed in this work predict that the ratio of recombination or attachment(for electrons)frequency versus the species diffusion coefficient is a very important parameter in determining the delta distribution,as it acts as the acceleration of object,according to the reformed oscillator equation.With this theory,the analogous delta profile of electrons density in the famous drift and ambi-polar diffusion heating mechanism of electronegative capacitively coupled plasma is interpreted.

Analytical Studies of the Cloud Droplet Spectral Dispersion Influence on the First Indirect Aerosol Effect

Atmospheric aerosols （acting as cloud condensation nuclei） can enhance the cloud droplet number concentration and reduce the cloud droplet size, and in turn affect the cloud optical depth, as well as the cloud albedo, and thereby exert a radiative influence on climate （the first indirect aerosol effect）. In this paper, based on various relationships between cloud droplet spectral dispersion （c） and cloud droplet number concentration （Nc）, we analytically derive the corresponding expressions of the cloud radiative forcing induced by changes in the cloud droplet number concentration. Further quantitative evaluation indicates that the cloud radiative forcing induced by aerosols for the different ^-Nc relationships varies from -29.1% to 25.2%, compared to the case without considering spectral dispersion （e = 0）. Our results suggest that an accurate description of e - Nc relationships helps to reduce the uncertainty of the first indirect aerosol effect and advances our scientific understanding of aerosol-cloud-radiation interactions.

Dispersion of Co-poly Carboxylate Superplasticizer Containing Poiyether Side Chain

Free radical co-polymerization was employed to synthesize co-poly carboxylate (PC) su-perplasticizers with different amount of carboxyl and methyl polyethylene glycol (MPEG) side chain. Dispersion ability and retention of PC were compared with one another. The results show that increase of side chain is advantageous to dispersion, but it decreases when amount of MPEG is beyond a certain value which is different with the proportion of carboxyl. If the amount of carboxyl increases, the influence of side chain in copolymer on dispersion diminishes. Polyether side chain is advantageous to retention. And the author explained the mechanism of PC using the theory of steric repulsive force.

Development and evaluation of lafutidine solid dispersion via hot melt extrusion:Investigating drug-polymer miscibility with advanced characterisation

In current study,immediate release solid dispersion(SD)formulation of antiulcer drug lafutidine(LAFT)was developed using hot melt extrusion(HME)technique.Amphiphilic Soluplus
used as a primary solubilizing agent,with different concentrations of selected surfactants like PEG 400,Lutrol F127(LF127),Lutrol F68(LF68)were used to investigate their influence on formulations processing via HME.Prepared amorphous glassy solid dispersion was found to be thermodynamically and physicochemically stable.On the contrary,traces of crystalline LAFT not observed in the extrudates according to differential scanning calorimetry(DSC),X-ray diffraction(XRD),scanning electron microscopy(SEM)and Raman spectroscopy.Raman micro spectrometry had the lowest detection limit of LAFT crystals compared with XRD and DSC.Atomic Force microscopy(AFM)studies revealed drugpolymer molecular miscibility and surface interaction at micro level.1HeCOSY NMR spectroscopy confirmed miscibility and interaction between LAFT and Soluplus
,with chemical shift drifting and line broadening.MD simulation studies using computational modelling showed intermolecular interaction between molecules.Dissolution rate and solubility of LAFT was enhanced remarkably in developed SD systems.Optimized ratio of polymer and surfactants played crucial role in dissolution rate enhancement of LAFT SD.The obtained results suggested that developed LAFT has promising potential for oral delivery and might be an efficacious approach for enhancing the therapeutic potential of LAFT.

Stochastic modeling of subgrid-scale effects on particle motion in forced isotropic turbulence

The subgrid-scale effects on particle motion were investigated in forced isotropic turbulence by DNS and priorLES methods.In the DNS field,the importance of Kolmogorov scaling to preferential accumulation was validated by comparing the radial distribution functions under various particle Stokes numbers.The prior-LES fields were generated by filtering the DNS data.The subgrid-scale Stokes number(StSGS)is a useful tool for determining the effects of subgrid-scale eddies on particle motion.The subgrid-scale eddies tend to accumulate particles with StSGSb 1 and disperse particles with 1 b StSGSb 10.For particles with StSGS?1,the effects of subgrid-scale eddies on particle motion can be neglected.In order to restore the subgrid-scale effects,the Langevin-type stochastic model with optimized parameters was adopted in this study.This model is effective for the particles with StSGS N 1 while has an adverse impact on the particles with StSGSb 1.The results show that the Langevin-type stochastic model tends to smooth the particle distribution in the isotropic turbulence.

Phonon dispersion relations of crystalline solids based on LAMMPS package

The phonon dispersion relations of crystalline solids play an important role in determining the mechanical and thermal properties of materials.The phonon dispersion relation,as well as the vibrational density of states,is also often used as an indicator of variation of lattice thermal conductivity with the external stress,defects,etc.In this study,a simple and fast tool is proposed to acquire the phonon dispersion relation of crystalline solids based on the LAMMPS package.The theoretical details for the calculation of the phonon dispersion relation are derived mathematically and the computational flow chart is present.The tool is first used to calculate the phonon dispersion relation of graphene with two atoms in the unit cell.Then,the phonon dispersions corresponding to several potentials or force fields,which are commonly used in the LAMMPS package to modeling the graphene,are obtained to compare with that from the DFT calculation.They are further extended to evaluate the accuracy of the used potentials before the molecular dynamics simulation.The tool is also used to calculate the phonon dispersion relation of superlattice structures that contains more than one hundred of atoms in the unit cell,which predicts the phonon band gaps along the cross-plane direction.Since the phonon dispersion relation plays an important role in the physical properties of condensed matter,the proposed tool for the calculation of the phonon dispersion relation is of great significance for predicting and explaining the mechanical and thermal properties of crystalline solids.

A Simple Approach to Compute Interatomic Force Constant for Mono and Diatomic Semiconductors

In this paper, a mathematical relation was found between interatomic Hooke’s force constant and both the bulk modulus and interatomic distance in solid crystals, considering that the forces which have effect on an atom are only those resulted from the neighboring atoms, and the forces are subject to Hooke’s law as the deflections of atoms from their equilibrium positions are very small. This work has been applied on some solid semiconducting crystals of diatomic primitive cell, including crystals of mono-atomic primitive cell automatically, by using linear statistical fitting with computer programming and, then, using mathematical analysis, proceeding from the vibrational dispersion relation of solid linear lattice, these two methods have been used in the process in order to support each other and for the result to be satisfying and reasonable. This is a contribution to the process of using computer programming in physics to facilitate mathematical analyses and obtain the required relations and functions by designing and developing appropriate computer programs in line with the macro and micro natures of materials. The importance of this is in enhancing our understanding of the interatomic actions in cells and of the crystal structure of materials in general and semiconductors in particular, as it is a step of the initial steps to facilitate the process of calculating energies and extracting mathematical relations between correlation energy and temperature as well as between sub-fusion and fusion energies with temperature.

考虑应力梯度的缺口疲劳分散性研究

针对缺口部位的微观结构及尺寸导致的疲劳分散差异较大的问题,为准确预测缺口件的疲劳分散性,以矩形截面缺口件为例,采用宏观Chaboche循环塑性本构模型与细观晶体循环塑性本构模型相结合的有限元子模型方法,并考虑缺口效应,提出了以应力梯度影响因子、等效应力与纵向应变为变量的统计标准差作为疲劳指示因子FIP_(notch)。在不同位移载荷、位移载荷比和缺口直径大小情况下将疲劳指示因子FIP_(notch)与经典的Fatemi-Socie疲劳指示因子FIP FS进行疲劳分散性的比较与分析。结果表明:疲劳指示因子FIP_(notch)均能很好地预测不同位移载荷、位移载荷比和缺口直径下的缺口疲劳分散性,且比经典的FIP FS方法有更高的精度与适用性。

原油-CO_(2)相互作用机理分子动力学模拟研究

CO_(2)的众多驱油机理已经被广泛认同,但受油藏因素影响,不同油藏条件下CO_(2)驱的效果差异较大。因此,需要进一步深化研究CO_(2)与原油的微观相互作用机理,明确不同油藏条件下CO_(2)的驱油方式,最大限度挖潜CO_(2)驱的潜力。利用分子动力学模拟方法研究了组分、温度、压力对油滴-CO_(2)相互作用的影响。求取动力学参数,量化表征油滴-CO_(2)间的相互作用,厘清了不同条件下二者的微观相互作用规律。模拟结果显示,色散力是主导CO_(2)-烷烃分子相互作用的主要作用能,二者相互作用主要包含两方面:一是CO_(2)分子克服烷烃分子间的位阻作用向油滴内部溶解扩散,二是CO_(2)分子对油滴外层分子的萃取吸引作用。随着烷烃分子链长减小、温度降低和压力增加,油滴溶解度参数和CO_(2)配位数增加,油滴外层分子的弯曲度减小,二者的相互作用增强。研究结果认为,在温度较低、压力较高的轻质和中轻质油藏中,应尽可能地实现CO_(2)混相驱和近混相驱,在温度较高、压力较低的中质和重质油藏中,应充分发挥CO_(2)非混相驱的溶解降黏、膨胀原油体积和补充能量的优势。研究结果能够为室内研究和现场实施CO_(2)驱油提供理论指导。

Probing the effect of Young's modulus on the plugging performance of micro-nano-scale dispersed particle gels

The effect of mechanical strength of the dispersed particle gel(DPG)on its macro plugging performance is significant,however,little study has been reported.In this paper,DPG particles with different mechanical strengths were obtained by mechanical shearing of bulk gels prepared with different formula.Young’s moduli of DPG particles on the micro and nano scales were measured by atomic force microscope for the first time.The mapping relationship among the formula of bulk gel,the Young’s moduli of the DPG particles and the final plugging performance were established.The results showed that when the Young’s moduli of the DPG particles increased from 82 to 328 Pa,the plugging rate increased significantly from 91.46%to 97.10%due to the distinctly enhanced stacking density and strength at this range.While when the Young’s moduli of the DPG particles surpassed 328 Pa,the further increase of plugging rate with the Young’s moduli of the DPG particles became insignificant.These results indicated that the improvement of plugging rate was more efficient by adjusting the Young’s moduli of the DPG particles within certain ranges,providing guidance for improving the macroscopic application properties of DPG systems in reservoir heterogeneity regulation.

数字经济对我国服务业集聚空间格局的重塑——基于区域与行业异质性的分析

数字经济正在成为重塑服务业集聚空间格局的重要力量。从集聚力和分散力视角并结合技术成本约束,构建数字经济影响服务业集聚的理论框架,进而从区域、行业以及双重异质性方面实证检验数字经济对服务业集聚的影响。结果显示,区域异质性下,数字经济显著提升了东部、南方、北方地区的服务业集聚水平,而对中西部地区服务业集聚水平的作用为负;行业异质性下,数字经济与消费性和生产性服务业集聚存在显著正向关系,而与公共性服务业集聚存在显著负向关系;双重异质性下,区域和行业的交互特征使数字经济对相应服务业集聚的影响呈现出较大不同。进一步分析表明,数字经济通过需求赋能和创新赋能影响了服务业集聚的空间格局,这一影响的异质性与行业对需求和创新的偏好相关。据此提出,在通过数字经济的需求和创新赋能效应助力服务业集聚的空间格局优化时,政府也须着力改善地区间的“数字鸿沟”问题,进而缩小数字经济下服务业集聚效益的区域差异。

Atomic dispersion of bulk/nano metals to atomic-sites catalysts and their application in thermal catalysis

Supported metal-group materials are commonly utilized as state-of-the-art catalysts in industry.Atomic-sites catalysts(ASCs)have attracted increasing attention in catalysis owing to their 100%atom efficiency and unique catalytic performances toward various reactions.In particular,atomic dispersion of bulk and nano metals has become the focus of research and development in the synthesis of ASCs.Over the past decade,burgeoning interests have been paid to atomic dispersion in ASCs and their applications in catalysis.However,to the best of our knowledge,the systematic summary and analysis of atomic dispersion were rarely reported.In this review,recently developed ASCs by atomic dispersion were discussed in terms of synthetic atmosphere,driving force,applications in thermal catalytic reactions.Perspectives related to challenges and directions as well as design strategies of ASCs in atomic dispersion were also provided.

Study on the Influence of Radial Pressurization on Anchoring Performance of Bolts

Supporting soft rock roadways in coal mines has long posed a formidable challenge. Addressing issues such as the formation of soft rock strata, poor fracture development, limited tolerance, and the frequent and severe damage sustained by conventional bolts due to their low elongation and bearing capacity, this study employs bottom expansion and filling technology. It combines theoretical analysis with booster bolt pull-out tests to scrutinize the radial stress distribution of bolts under extrusion forces. Moreover, it conducts a comparative analysis of bolt bearing characteristics under varying radial pressurization conditions, delving into the impact of radial directional increases in compressive stress on bolt anchoring performance.

Possible Relevance of the Allende Meteorite Conditions in Prebiotic Chemistry: An Insight into the Chondrules and Organic Compounds

The study of the mineral and organic content of the Allende meteorite is important for our understanding of the molecular evolution of the universe as well as the ancient Earth. Previous studies have characterized the magnetic minerals present in ordinary and carbonaceous chondrites, providing information on the evolution of magnetic fields. The interaction of organic compounds with magnetic minerals is a possible source of chemical diversity, which is crucial for molecular evolution. Carbon compounds in meteorites are of great scientific interest for a variety of reasons, such as their relevance to the origins of chirality in living organisms. This study presents the characterization of organic and mineral compounds in the Allende meteorite. The structural and physicochemical characterization of the Allende meteorite was accomplished through light microscopy, powder X-ray diffraction with complementary Rietveld refinement, Raman and infrared spectroscopy, mass spectrometry, scanning electron microscopy, and atomic force microscopy using magnetic signal methods to determine the complex structure and the interaction of organic compounds with magnetic Ni-Fe minerals. The presence of Liesegang-like patterns of chondrules in fragments of the Allende structure may also be relevant to understanding how the meteorite was formed. Other observations include the presence of magnetic materials and nanorod-like solids with relatively similar sizes as well as the heterogeneous distribution of carbon in chondrules. Signals observed in the Raman and infrared spectra resemble organic compounds such as carbon nanotubes and peptide-like molecules that have been previously reported in other meteorites, making the Mexican Allende meteorite a feasible sample for the study of the early Earth and exoplanetary bodies.

压力扩散型锚杆支护效应的研究分析

随着煤矿矿井开采深度及长度的延伸,对锚杆的锚固支护效果要求也逐渐提高,压力扩散型锚杆可有效地提高锚杆的支护效果。采用有限元仿真的形式建立巷道掘进的支护模型,对压力扩散型锚杆的支护效应进行分析,并与常规应用的拉力型锚杆进行对比分析。应用结果表明,压力扩散型锚杆的轴力作用相对于拉力型锚杆有轻微减小,而对位移的控制效应可减小14.5%,可有效地提高锚杆支护的效果,对于煤矿的支护安全具有重要的作用。

氨基磺酸系陶瓷分散剂在黑泥/水界面的吸附分散作用

氨基磺酸系陶瓷分散剂(ASP)与木质素磺酸钙(木钙)、萘磺酸盐甲醛缩合物(fdn)及磺化丙酮甲醛缩合物(saf)相比具有明显分散降黏效果。测定了四种分散剂在黑泥表面的吸附等温线及其对黑泥颗粒表面Zeta电位的影响,结果表明ASP既有较大的饱和吸附量,又能提高黑泥颗粒的Zeta电位,通过静电排斥和空间位阻协同作用表现出优良的分散性能。通过加入脲、氯化钠及柠檬酸钠研究了ASP在黑泥/水界面的吸附作用力,发现吸附过程的主导作用力是络合作用,同时氢键吸附也是重要的吸附作用力。

纳米SiO_2水溶液制备、改性及应用性能研究

采用硅单质法制备了低成本高固含量的纳米 Si O2 水溶液 ,并进行表面处理。结果表明 :两亲性和核 -壳型纳米Si O2 在水中分散稳定 ,Si O2 /聚丙烯酸酯涂膜的附着力、柔韧性和耐冲击性提高 ;纳米 Si O2 用量增大 ,对乳液的成膜温度影响较小 ,但涂膜硬度增大 ,膜柔韧性好 ,回粘温度和热分解温度升高 ,具有更好的防尘性和耐热性。