Microscopic Structural Features Research Articles

Study of the Microstructure Characteristics of Three Different Fine-grained Tailings Sand Samples during Penetration.

This paper explores the microstructural evolution characteristics of tailings sand samples of different types of infiltration failure during the infiltration failure process. The homemade small infiltration deformation instrument is used to test the infiltration failure characteristics of the tailings sand during the infiltration failure process. Evolutionary characteristics of the internal microstructure pores and particle distribution were also studied. Using CT (computerized tomography) technology to establish digital image information, the distribution of the microscopic characteristics of the particle distribution and pore structure after tailing sand infiltration were studied. Microscopic analysis was also performed to analyze the microscopic process of infiltration and destruction, as well as to see the microscopic structural characteristics of the infiltration and destruction of the total tailings. The test results show that there are obvious differences in the microstructure characterization of fluid soil and piping-type infiltration failures. Microstructure parameters have a certain functional relationship with macrofactors. Combining the relationship between macrophysical and mechanical parameters and microstructural parameters, new ideas for future research and the prevention of tailings sand infiltration and failure mechanisms is provided.

New Self‐Organization Route to Tunable Narrowband Optical Filters and Polarizers Demonstrated with ZnO–ZnWO4 Eutectic Composite

AbstractElectromagnetic fields interacting with microscopic structural features in a composite material provide emerging optical properties that surpass those offered by the individual components. However, composite materials can be generally lossy due to the scattering effects induced by inhomogeneities at the interfaces between different compounds. To overcome such problems, complicated and costly manufacturing procedures, such as top‐down approaches, are generally required. In contrast, here ZnO–ZnWO4 eutectic self‐organized composites grown by the micropulling method are considered, displaying sharp and strongly polarized transmission at 397 nm. Such an optical response is notable because it is not observed in either ZnO or ZnWO4 single crystals. The optical response is due to the refractive index matching of the two constituents, which self‐organize into ordered structures via a micropulling down method. The optical behavior reported here can directly lead to applications, such as tunable narrowband filters with bandpass of 3 nm and polarizers, paving the way to a new self‐organization route for manufacturing optical components.

Extended short-range order determines the overall structure of liquid gallium.

Polyvalent metal melts (gallium, tin, bismuth, etc.) have microscopic structural features, which are detected by neutron and X-ray diffraction and which are absent in simple liquids. Based on neutron and X-ray diffraction data and the results of ab initio molecular dynamics simulations for liquid gallium, we examine the structure of this liquid metal at the atomistic level. Time-resolved cluster analysis allows one to reveal that the short-range structural order in liquid gallium is determined by a range of the correlation lengths. This analysis, performed on a set of independent samples corresponding to equilibrium liquid phase, discloses that there are no stable crystalline domains and molecule-like Ga2 dimers typical for crystal phases of gallium. The structure of liquid gallium can be reproduced by the simplified model of the close-packed system of soft quasi-spheres. The results can be applied to analyze the fine structure of other polyvalent liquid metals.

Key aspects for effective mathematical modelling of fractional-diffusion in cardiac electrophysiology: A quantitative study

Microscopic structural features of cardiac tissue play a fundamental role in determining complex spatio-temporal excitation dynamics at the macroscopic level. Recent efforts have been devoted to the development of mathematical models accounting for non-local spatio-temporal coupling able to capture these complex dynamics without the need of resolving tissue heterogeneities down to the micro-scale. In this work, we analyse in detail several important aspects affecting the overall predictive power of these modelling tools and provide some guidelines for an effective use of space-fractional models of cardiac electrophysiology in practical applications. Through an extensive computational study in simplified computational domains, we highlight the robustness of models belonging to different categories, i.e., physiological and phenomenological descriptions, against the introduction of non-locality, and lay down the foundations for future research and model validation against experimental data. A modern genetic algorithm framework is used to investigate proper parameterisations of the considered models, and the crucial role played by the boundary assumptions in the considered settings is discussed. Several numerical results are provided to support our claims.

One-pot redox synthesis of graphene from waste graphite of spent lithium ion batteries with peracetic acid assistance

In order to meet increasingly urgent application requirements for energy storage and aviation materials, it is necessary to facilitate the rapid, low-cost, large-scale preparation of high-quality graphene. In this study, reduced graphene oxide (rGO) was prepared from the waste graphite of spent lithium batteries by a one-pot redox reaction using a ternary system contains sulfuric acid, potassium permanganate and peracetic acid. Peroxyacetic acid was first used in the system to effect oxidation and reduction preparation of graphene to avoid additional reduction steps. XRD, XPS, SEM, TEM, FT-IR, and Raman spectroscopy analyses showed that reduced graphene oxide samples synthesized from waste graphite (L-rGO) and commercial graphite (C-rGO) have similar microscopic morphologies and structural characteristics. Therefore, lithium ion battery waste graphite is a good potential resource for the preparation of high-quality rGO. The carbon-to-oxygen ratios of L-rGO and C-rGO were 1.79 and 4.25, respectively, indicating that peracetic acid effectively reduced graphene oxide to rGO. The yield of rGO was calculated to be 61.2%, which means that rGO can be produced on a large scale using this method.

A Multiscale Approach to Studying the High Strain-Rate Deformations of Glass-Fiber-Reinforced Polymer-Matrix Composites

The mechanical properties and failure of composites depend on their microscopic characteristics (constituent properties and microscopic structural features). The continuum theory cannot explain the failure mechanism of composite materials in terms of connecting microscopic damage to the macroscopic fracture. In this paper, a multiscale method combining the High-Fidelity Generalized Method of Cells with ANSYS/LS-DYNA is presented. The method is validated by comparing calculations with experimental results. A nonlinear analysis of glass-fiber-reinforced polymer-matrix composites at high strain rates is performed. The results obtained show that the method presented can be effectively used to predict the mechanical properties of polymer-matrix composites and the increase in stiffness of the composites with growing strain rate.

3D cellular visualization of intact mouse tooth using optical clearing without decalcification

Dental pulp is composed of nerves, blood vessels, and various types of cells and surrounded by a thick and hard enamel-dentin matrix. Due to its importance in the maintenance of tooth vitality, there have been intensive efforts to analyze the complex cellular-level organization of the dental pulp in teeth. Although conventional histologic analysis has provided microscopic images of the dental pulp, 3-dimensional (3D) cellular-level visualization of the whole dental pulp in an intact tooth has remained a technically challenging task. This is mainly due to the inevitable disruption and loss of microscopic structural features during the process of mechanical sectioning required for the preparation of the tooth sample for histological observation. To accomplish 3D microscopic observation of thick intact tissue, various optical clearing techniques have been developed mostly for soft tissue, and their application for hard tissues such as bone and teeth has only recently started to be investigated. In this work, we established a simple and rapid optical clearing technique for intact mouse teeth without the time-consuming process of decalcification. We achieved 3D cellular-level visualization of the microvasculature and various immune cell distributions in the whole dental pulp of mouse teeth under normal and pathologic conditions. This technique could be used to enable diverse research methods on tooth development and regeneration by providing 3D visualization of various pulpal cells in intact mouse teeth.

Fracability Evaluation of Shale of the Wufeng‐Longmaxi Formation in the Changning Area, Sichuan Basin

The fracturing technology for shale gas reservoir is the key to the development of shale gas industrialization. It makes much sense to study the mechanical properties and deformation characteristics of shale, due to its close relationship with the fracability of shale gas reservoir. This paper took marine shale in the Changning area, southern Sichuan Basin of China as the research object. Based on field profile and hand specimen observation, we analyzed the development of natural fractures and collected samples from Wufeng Formation and Longmaxi Formation. Combining with the indoor experiment, we investigated the macroscopic and microscopic structural features and the remarkable heterogeneity of shale samples. Then we illustrated the mechanics and deformation characteristics of shale, through uniaxial compression test and direct shear test. The shale has two types of fracture modes, which depend on the angular relation between loading direction and the bedding plane. Besides, the Wufeng shale has a higher value of brittleness index than the Longmaxi shale, which was calculated using two methods, mechanical parameters and mineral composition. Given the above results, we proposed a fracability evaluation model for shale gas reservoir using the analytic hierarchy process. Four influence factors, brittleness index, fracture toughness, natural fractures and cohesive force, are considered. Finally, under the control of normalized value and weight coefficient of each influence factor, the calculations results indicate that the fracability index of the Wufeng Formation is higher than that of the Longmaxi Formation in Changning area, southern Sichuan Basin.

Metal-Organic Framework Crystal-Assembled Optical Sensors for Chemical Vapors: Effects of Crystal Sizes and Missing-Linker Defects on Sensing Performances.

Microporous metal-organic frameworks (MOFs) are promising candidate materials for chemical sensing, but the reproducible fabrication of MOF-based sensors with optimized and stable performances remains a significant challenge. Here, we report the fabrication of MOF optical sensors with steady but tunable optical properties via assembling UiO-66 crystals with controllable sizes and missing-linker defects. The well-defined but tunable microscopic and mesoscopic structural features of MOF sensing components greatly facilitate the optimization of device performance. The UiO-66 crystal-assembled sensors display fast response (2.00 s) and short recovery (3.00 s) to ethanol vapor (one of the analytes we tested). Our systematical investigation indicates that the mesoporous features of sensing components contribute greatly to the enhanced sensitivity (by ∼24.6% to the saturated ethanol vapor), response speed (by ∼42.9%), and recovery speed (by ∼59.7%) of the crystal-assembled sensors in comparison to their dense counterpart. The building crystal sizes show a slight influence on the response speed but profound effects on the sensitivity and recovery performances of sensors. The missing-linker defects have obvious beneficial effects on the desorption kinetics of analyte and can cause a faster recovery of sensors.

Microscopic Structural and Dynamic Features in Triphilic Room Temperature Ionic Liquids.

Here we report a thorough investigation of the microscopic and mesoscopic structural organization in a series of triphilic fluorinated room temperature ionic liquids, namely [1-alkyl,3-methylimidazolium][(trifluoromethanesulfonyl)(nonafluorobutylsulfonyl)imide], with alkyl = ethyl, butyl, octyl ([Cnmim][IM14], n = 2, 4, 8), based on the synergic exploitation of X-ray and Neutron Scattering and Molecular Dynamics simulations. This study reveals the strong complementarity between X-ray/neutron scattering in detecting the complex segregated morphology in these systems at mesoscopic spatial scales. The use of MD simulations delivering a very good agreement with experimental data allows us to gain a robust understanding of the segregated morphology. The structural scenario is completed with determination of dynamic properties accessing the diffusive behavior and a relaxation map is provided for [C2mim][IM14] and [C8mim][IM14], highlighting their natures as fragile glass formers.

Morphological changes of parathyroid glands and thymus of rats after correction of induced immunosupression

The aim of the research was to investigate the features of the electron microscopic structure of rats' parathyroid glands and thymus after correction of cyclophosphamide-induced immunosuppression with imunofan.Material and methods. The study was performed on 24 male rats weighing 180±10 g. The animals of the experimental series were injected cyclophosphamide once intramuscularly at a dosage of 200 mg/kg. Immunocorrection was achieved by administering imunofan once a day at 50 mcg/kg for 1, 3, 5, 7, 9 days. The second group consisted of intact rats. The animals were withdrawn from the experiment on 3rd and 30th day after the drugs administration. We studied the ultrastructure of organs in the rats of the control group and after immunostimulation.Results. It was established that on the 3rd day after correction of induced immunosuppression imunofan parathyroid nuclei characterized by uneven surface due to numerous invaginations of nuclear membranes. In separate cells sporadic pyknosis of nuclei is determined. The number of secretory granules decreases, the amount of glycogen and lipid droplets increases. In the thymus characteristic signs of an accidental involution occur. After 30 days after the administration of immunotropic drugs, the number of active dark parathyrocytes increased. In the nucleoli, the predominance of the granular component over the fibrillar component is revealed. Well-developed organelles of protein synthesis were found in the cytoplasm of cells. In the cortex of the thymus, an increased number of plasma cells is observed, a recovery of the population of both lymphoid cells and microenvironment cells, in particular macrophages, is noted. Conclusions. On the 3rd day after the administration of immunotropic drugs, a decrease in the number of secretory granules, pyknosis of nuclei and multiple invaginations of nuclear membranes are revealed in segregated cells. The use of an immunocorrector leads to the development of organelles of protein synthesis and an increase in the number of secretory granules in the cytoplasm of cells on the 30th day after administration of the drugs. In the cortical zone of the thymus there is an active cells proliferation. The dynamics of changes in the electron microscopic structure of rats' parathyroid glands and thymus indicates a high degree of reactivity of the organs in response to the administration of immunotropic drugs.

Effect of surface wettability of ceramic proppant on oil flow performance in hydraulic fractures

AbstractCeramic proppants are critical products for holding induced fractures open and enhancing hydrogen productivity in low‐permeability reservoirs. Though the effects of proppant size and proppant type on the well productivity have been well studied in the past, the role of the proppant surface wettability in the oil flow performance has not been thoroughly investigated. To help the readers and the industries understand the wetting behavior of ceramic proppants, this research was designed to analyze the effect of the proppant wettability on the flow efficiencies of oil and water under different conditions (for example, various proppant size, water saturation, and waterflooding). Also, it was required to determine the optimal wettability of proppants in the available candidates for the enhancement of oil recovery in the hydraulic fracturing process. Results of the work indicate that the proppant wettability plays an essential role in the productivities of water and oil in tight sandstones. Compared with the same‐size oil‐wet proppants, the mixed‐wet proppants contribute to increasing the oil flow efficiency and reducing the produced volume of water. However, an increased value of proppant size can significantly enhance the oil recovery. Besides, using the oil‐wet proppants, the waterflooding phenomenon can lead to a lower oil recovery than that of the non‐water‐flooded specimen. Based on the findings of the microscopic structural characteristics of the proppant surface, a fluid channel mechanism was proposed to help understand the proppant wettability effect on the flow behaviors of oil and water. This research can provide guidance on the determination of proppants in the designs of hydraulic fracturing operations. These findings can help the reservoir engineers dealing with hydraulic fracturing better design the surface wettability of the proppants, especially for those reservoirs with a multi‐phase flow.

Overview of emulsified viscosity reducer for enhancing heavy oil recovery

Chinese water flooding heavy oil reserves are abundant and the output is increasing year by year, but the heavy oil water flooding recovery rate is low. It is of great significance to improve the heavy oil water flooding recovery rate to improve the development level of heavy oil reservoirs. This paper reviews heavy oil emulsified viscosity reduction technology, emulsified viscosity reduction theory, viscosity reducer flooding microscopic mechanism and structural characteristics of surfactants for heavy oil emulsified viscosity reduction. Meanwhile, the research focus of emulsified viscosity reducer in the future is put forward.

Carrier localization structure combined with current micropaths in AlGaN quantum wells grown on an AlN template with macrosteps

The microscopic structural and optical characteristics of AlGaN-based light-emitting diodes grown on AlN templates with macrosteps were evaluated. Cross-sectional transmission electron microscopy in the high-angle annular dark field scanning mode and microscopic energy dispersive X-ray spectroscopy reveal that the AlGaN cladding layer under the AlGaN quantum wells (QWs) has microscopic compositional modulations originating from the macrosteps at the AlN template surface. The Ga-rich oblique zones in the cladding layer likely behave as current micropaths. These micropaths are connected to the carrier localization structure, which is formed by the modulation of both the well widths and the compositions of the QWs. In-plane spatially-resolved cathodoluminescence (CL) spectroscopy indicated significant inhomogeneity of the CL characteristics: the brighter emission with a lower peak photon energy confirms the existence of the carrier localization structure in the QWs. Carrier localization in the QWs along with the current micropaths in the AlGaN cladding layer appears to increase the external quantum efficiency of AlGaN LEDs.

An architectonic type principle integrates macroscopic cortico-cortical connections with intrinsic cortical circuits of the primate brain.

The connections linking neurons within and between cerebral cortical areas form a multiscale network for communication. We review recent work relating essential features of cortico-cortical connections, such as their existence and laminar origins and terminations, to fundamental structural parameters of cortical areas, such as their distance, similarity in cytoarchitecture, defined by lamination or neuronal density, and other macroscopic and microscopic structural features. These analyses demonstrate the presence of an architectonic type principle. Across species and cortices, the essential features of cortico-cortical connections vary consistently and strongly with the cytoarchitectonic similarity of cortical areas. By contrast, in multivariate analyses such relations were not found consistently for distance, similarity of cortical thickness, or cellular morphology. Gradients of laminar cortical differentiation, as reflected in overall neuronal density, also correspond to regional variations of cellular features, forming a spatially ordered natural axis of concerted architectonic and connectional changes across the cortical sheet. The robustness of findings across mammalian brains allows cross-species predictions of the existence and laminar patterns of projections, including estimates for the human brain that are not yet available experimentally. The architectonic type principle integrates cortical connectivity and architecture across scales, with implications for computational explorations of cortical physiology and developmental mechanisms.

Multiscale designs of the chitinous nanocomposite of beetle horn towards an enhanced biomechanical functionality

Operating mainly as a type of weapon, the beetle horn develops an impressive mechanical efficiency based on chitinous materials to maximize the injury to opponent and simultaneously minimize the damage to itself and underlying brain under stringent loading conditions. Here the cephalic horn of the beetle Allomyrina dichotoma is probed using multiscale characterization combined with finite element simulations to explore the origins of its biomechanical functionality from the perspective of materials science. The horn is revealed to be highly regulated from the macroscopic shape, geometry, and connection with the body to the meso- and microscopic architecture, moisture content, and chemical and structural characteristics. Varying kinds of gradients are integrated at all length-scales. Such designs are demonstrated to benefit the mechanical performance by mitigating stress concentrations, retarding crack propagation, and modulating local properties to better adapt to stress. Enhanced rigidity, robustness and stability are additionally generated from the constrained flexibility endowed by the nanocomposite plywood structure through the reorientation of chitin nanofibrils within the proteinaceous matrix. These findings shed light on the intriguing materials-design strategies of nature in creating synergy of offence and persistence. They may even offer inspiration for the synthesis of high-performance materials and structures, in particular beams to resist bending and torsion.

Self-Assembled Micellar Structures of Lipopeptides with Variable Number of Attached Lipid Chains Revealed by Atomistic Molecular Dynamics Simulations.

We present atomistic molecular dynamics simulation study of the self-assembly behavior of toll-like agonist lipopeptides (Pam nCSK4) in aqueous solutions. The variable number of hexadecyl lipid chains ( n = 1, 2, 3) per molecule has been experimentally suggested to have remarkable influence on their self-assembled nanostructures. Starting from preassembled spherical or bilayer configurations, the aggregates of lipopeptides, PamCSK4 and Pam2CSK4, which contain peptide sequences CSK4 linked to either mono- or dilipid chains (Pam), evolve into spherical-like micelles within 30 ns, whereas the self-assembled structure of trilipidated lipopeptides, Pam3CSK4, relaxes much slower and reaches an equilibrium state of flattened wormlike micelle with a bilayer packing structure. The geometric shapes and sizes, namely the gyration radii of spherical micelles and thickness of the flattened wormlike micelle, are found to be in good agreement with experimental measurements, which effectively validates the simulation models and employed force fields. Detailed analyses of molecular packing reveal that these self-assembled nanostructures all consist of a hydrophobic core constructed of lipid chains, a transitional layer, and a hydrophilic interfacial layer composed of peptide sequences. The average area per peptide head at the interfaces is found to be nearly constant for all micellar structures studied. The packing parameter of the lipopeptide molecules thus increases with the increase of the number of linked lipid chains, giving rise to the distinct micellar shape transition from spherical-like to flattened wormlike geometry with bilayer stacking, which is qualitatively different from the shape transitions of surfactant micelles induced by variation of concentration or salt type. To facilitate the close-packing of the lipid chains in the hydrophobic core, the lipopeptide molecules typically take the bent conformation with average tilt angles between the peptide sequences and the lipid chains ranging from 110° to 140°. This consequently affects the orientation angles of the lipid chains with respect to the radial or normal direction of the spherical-like or flattened wormlike micelles. In addition, the secondary structures of the peptides may also be altered by the number of lipid chains to which they are linked and the resultant micellar structures. Our simulation results on the microscopic structural features of the lipopeptide nanostructures may provide potential insights into their bioactivities and contribute to the design of bioactive medicines or drug carriers. The force fields built for these lipopeptides and the geometric packing discussions could also be adopted for simulating and understanding the self-assembly behavior of other bioactive amiphiphiles with similar chemical compositions.

Expeller Barrel Dry Heat and Moist Heat Pressure Duration Induce Changes in Canola Meal Protein for Ruminant Utilisation.

Simple SummaryCanola meal, a by-product of oil production from canola seed, is a source of protein commonly incorporated into dairy and feedlot rations. Processing conditions and pressure treatments can alter the quality of protein in canola meal. In this study, the impact of expeller dry heat and moist heat pressure duration time on general nutritional properties, in vitro protein degradability, Maillard reaction product formation, and molecular and microscopic structural characteristics of canola meal were investigated. Increased dry heat temperature rapidly increased digestible protein and non-protein nitrogen content, and constricted amide II secondary structure. Increased moist heat pressure treatment duration promoted browning, and the conversion of protein to more intermediately and slowly degradable forms. Dry heat and moist heat pressure affected meal protein solubility and protein and lipid-related functional groups. Moist heat pressure fragmented canola meal into enzyme-resistant aggregates with crevices containing oil bodies. Induced changes may impact the supply of protein and amino acids and subsequently the yield and composition (protein and lipid) of milk produced by dairy cows. These findings benefit producers of canola meal by further describing the effects of processing and treatment conditions on protein characteristics, particularly those which affect the production potential of ruminants fed canola meal as a source of protein.To improve the protein nutritional quality of canola (Brassica napus L.) meal, further investigation of the effects of processing conditions and post-production treatments is desirable. The impact of barrel dry heat temperature (20 °C (cold press) and 100 °C (expeller)) and moist heat pressure (MHP) duration time on general nutritional properties, Maillard reaction product (MRP) formation, in vitro protein degradability, and molecular and microscopic structural characteristics of canola meals were investigated. Increased MHP duration reduced (p < 0.05) dry matter, soluble protein, rapidly degradable protein, yellowness (early MRP), whiteness (late MRPs), absorbance at 294 nm (intermediate MRPs), and amide I; and increased (p < 0.05) non-protein N, neutral detergent fibre, neutral detergent insoluble crude protein (CP), intermediately and slowly degradable protein, in vitro effective CP degradability, redness, degree of colour change, and browning. Increased dry heat temperature reduced (p < 0.01) CP and rapidly degradable protein, constricted amide II, reduced (p < 0.05) protein solubility in 0.5% KOH and increased (p < 0.05) acid-detergent fibre and intermediate MRPs. Browning index and redness exhibited potential as rapid indicators of effective CP degradability and soluble protein, respectively. Dry heat and MHP altered (p < 0.05) lipid-related functional groups. Dry heat affected napin solubility, and MHP altered cruciferin and napin solubility. Application of MHP induced the formation of proteolysis-resistant protein aggregates with crevices containing oil bodies. Induced changes may impact the supply of proteins and amino acids and subsequently the yield and composition (protein and lipid) of milk produced by dairy cows.

Rotational dynamics of polyatomic ions in aqueous solutions: From continuum model to mode-coupling theory, aided by computer simulations.

Due to the presence of the rotational mode and the distributed surface charges, the dynamical behavior of polyatomic ions in water differs considerably from those of the monatomic ions. However, their fascinating dynamical properties have drawn scant attention. We carry out theoretical and computational studies of a series of well-known polyatomic ions, namely, sulfate, nitrate, and acetate ions. All three ions exhibit different rotational diffusivity, with that of the nitrate ion being considerably larger than the other two. They all defy the hydrodynamic laws of size dependence. Study of the local structure around the ions provides valuable insight into the origin of these differences. We carry out a detailed study of the rotational diffusion of these ions by extensive computer simulation and by using the theoretical approaches of the dielectric friction developed by Fatuzzo-Mason (FM) and Nee-Zwanzig (NZ), and subsequently generalized by Alavi and Waldeck. A critical element of the FM-NZ theory is the decomposition of the total rotational friction, ζRot, into Stokes and dielectric parts. The study shows a dominant role of dielectric friction in the sense that if the ions are made neutral, the nature of diffusion changes and the values become much larger. Our analyses further reveal that the decomposition of total friction into the Stokes and dielectric friction breaks down for sulfate ions but remains semi-quantitatively valid for nitrate and acetate ions. We discuss the relationship between translational and rotational dielectric friction on rigid spherical ions. We develop a self-consistent mode-coupling theory (SC-MCT) formalism that could provide a unified view of rotational friction of polyatomic ions in polar medium. Our SC-MCT shows that the breakdown can be attributed to the change in the microscopic structural features. The mode-coupling theory helps in elucidating the role of coupling between translational and rotational motion of these ions. In fact, these two motions self-consistently determine the value of each other. The reference interaction site model-based MCT suggests an interesting relation between the torque-torque and the force-force time correlation function with the proportionality constant being determined by the geometry and the charge distribution of the polyatomic molecule. We point out several parallelisms between the theories of translational and rotation friction calculations of ions in polar liquids.

Universality of microscopic structural and dynamic features in liquid alkali metals near the melting point

The assumption proposed in [U. Balucani et al., Phys. Rev. B 47, 3011 (1993)] that the space and time dependences of the characteristics of the microscopic structure and dynamics for the group of liquid alkali metals are reduced to a common general form through scaling transformations has been discussed. It has been found that such description is possible when scale units are (i) the effective size of a particle corresponding, in particular, to the experimentally measured position of the main peak in the static structure factor, (ii) the characteristic time scale of the thermal mean free path of the particle, and (iii) the parameters of the “liquid”–“crystal” phase separation (in particular, the melting temperature). This conclusion follows directly from the comparative analysis of experimental data on X-ray diffraction, as well as on the inelastic neutron and X-ray scattering data. This work develops the ideas proposed in [A. V. Mokshin et al., J. Chem. Phys. 121, 7341 (2004)].