Surface Of Sphere Research Articles

Investigation on the Low‐Frequency Acoustic Performance of Polymer Matrix Composite With Metallic Hollow Spheres Under Different Acoustic Stack Structures

ABSTRACTIn this study, various polymer matrix composites (melamine and flexible polyurethane) combined with 316 L stainless steel hollow spheres were prepared using the casting method. The acoustic properties of the fabricated materials were evaluated under low‐frequency conditions (100–1700 Hz) using an impedance tube. The results indicate that sound absorption and insulation performance are significantly influenced by the incident surface material within this frequency range. Notably, sound waves entering through the polyurethane stainless steel hollow sphere surface yield optimal absorption performance, achieving a maximum sound absorption coefficient of 0.74 at 400 Hz. Conversely, the melamine foam surface provides the best sound absorption at higher frequencies within this range, reaching a coefficient of 0.43 at 1700 Hz. The findings highlight the effective sound absorption and insulation capabilities of the composite materials.

Radiation-Induced Paramagnetic Centers in Meso- and Macroporous Synthetic Opals from EPR and ENDOR Data

The paramagnetic defects and radiation-induced paramagnetic centers (PCs) in silica opals can play a crucial role in determining the magnetic and electronic behavior of materials and serve as local probes of their electronic structure. Systematic investigations of paramagnetic defects are essential for advancing both theoretical and practical aspects of material science. A series of silica opal samples with different geometrical parameters were synthesized and radiation-induced PCs were investigated by means of the conventional and pulsed X- and W-band electron paramagnetic resonance, and 1H/2H Mims electron-nuclear double resonance. Two groups of PCs were distinguished based on their spectroscopic parameters, electron relaxation characteristics, temperature and time stability, localization relative to the surface of silica spheres, and their origin. The obtained data demonstrate that stable radiation-induced E’ PCs can be used as sensitive probes for the hydrogen-containing fillers of the opal pores, for the development of compact radiation monitoring equipment, and for quantum technologies.

Migration of a slip-spin solid spherical particle in a micropolar fluid-filled circular cylindrical tube

A combined study analytically and numerically for the axially symmetric creeping flow due to a slip-spin solid sphere surface moving in a microstructure fluid of micropolar type along the centreline of a circular cylindrical tube is introduced. This investigation was presented under low Reynolds number conditions. A general solution is obtained by superposing the essential solutions in both spherical and cylindrical coordinates to solve the Eringen micropolar field equations. The condition of the microrotation, along with couple stress, is used at the surface of the solid particle; while the microrotation is used at the inner cylindrical surface. Boundary conditions are imposed initially on the inner cylindrical surface using Fourier transforms and subsequently on the outer surface of the solid particle using a collocation technique. This paper aims to study the wall interaction problem of a translating slip-spin solid spherical particle in a micropolar fluid along the centreline of a circular cylindrical tube. The study also investigates the effect of the addition of slip conditions for velocity and microrotation on the surface of a solid particle. There is good convergence in the numerical findings obtained for the normalised hydrodynamic drag force (the tube-corrected factor) applying on the surface of the solid particle for several values of the micropolarity coefficient, slip-spin coefficients, and the ratio between the radius of the solid particle and tube. Regarding the flow of a solid spherical particle along the centreline of a cylindrical tube, our drag findings compare favourably to the solutions found in the literature. We found that the normalised drag force acting on the solid particle monotonically increases with the increase of the particle-to-tube radius ratio and reaches infinity in the limitless, with the increase of the micropolarity coefficient, and with the increase of the slip-spin coefficients for a steady ratio of particle-to-tube radius.

Novel analysis of alignment error on spherical Fizeau interferometer and uncertainty evaluation of sphericity calibration system based on random ball test

The National Metrology Institute of Japan (NMIJ) has developed a high-precision sphericity calibration system utilizing a Fizeau interferometer and conducted a thorough evaluation of the system's measurement uncertainty. Generally, there are two principal sources of uncertainty in the measurement outcomes when utilizing a spherical Fizeau interferometer. First, the accuracy of the system is significantly influenced by the prior knowledge of the reference sphere surface's absolute profile. To address this, the study established a straightforward yet effective calibration system for the reference sphere surface using a random ball test method. Second, the system's precision is affected by misalignment aberration, which occurs when there is any lateral or longitudinal displacement of the test sphere from the confocal position relative to the reference sphere. This misalignment can introduce both high-order shape errors (misalignment aberrations) and low-order shape errors (alignment errors). Through analytical consideration of an observation coordinate system on the camera plane, this study delves into misalignment aberrations, suggesting that the impact of misalignment should be determined experimentally for each reference sphere unit due to potential imperfections that may be revealed by misalignment. Furthermore, the study proposes that uncertainties related to misalignment aberrations are theoretically confirmed to be smaller than previous studies by conducting an in-depth uncertainty analysis of the misalignment, with a focus on the observation coordinate system on the camera plane. Notably, the research demonstrates that a measurement uncertainty level of λ/100 is achievable, maintaining a broader tolerance for misalignment than previously reported studies. The uncertainty of calibration of the reference sphere unit's absolute profile was 4.2 nm and the uncertainty of sample measurement was determined to be 4.6 nm with misalignment tolerance of ±λ/10. This advancement marks a stride toward improving the accuracy and reliability of sphericity measurements, offering potential for widespread application in precision engineering and metrology.

Facile Preparation of Raspberry-Like SiO2@Polyurea Microspheres with Tunable Wettability and Their Application for Oil-Water Separation.

Raspberry-like microspheres have been widely used as superhydrophobic materials, photonic crystals, drug carriers, etc. Nevertheless, their preparation methods, usually consisting of multiple steps, are generally time- and energy-consuming. Herein raspberry-like SiO2@polyurea microspheres (SiO2@PUM) are readily prepared via a one-step precipitation polymerization of isophorone diisocyanate in a H2O/acetone mixture with the presence of SiO2 particles. The sphere size, surface roughness, and SiO2 content of SiO2@PUM are easily adjustable by varying the experimental conditions. TEM and SEM observations reveal that the final SiO2@PUM exhibits a core-shell structure, with polyurea (PU) in the core and SiO2 particles as the shell. In the process, the SiO2 particles were initially located on the PUM surface as a monolayer. With the reaction proceeding, the monolayer of SiO2 particles became thicker, forming a thicker layer of SiO2 particles on PUM due to the accumulation of SiO2 particles, leading to a multilayer structure of SiO2 particles on the shell of SiO2@PUM. The formation mechanism of the raspberry-like SiO2@PUM was thoroughly discussed and ascribed to electrostatic attraction between the positively charged PU and negatively charged SiO2 particles. Once dried, SiO2@PUM was superhydrophobic and turned hydrophilic if water-wetted. Using a layer of SiO2@PUM, effective separation with good reusability for a variety of oil-water mixtures was achieved regardless of the oil density and types of oil-water emulsions. This work presents a novel protocol for the preparation of raspberry-like microspheres with tunable wettability via a rapid and green process, and the resulting microspheres are highly effective for the separation of diverse types of oil-water mixtures.

Optimization of CNC turning parameters with different turning tool radii for sphere surface profiles of SUS 304 material based on PVD coating technology applied for industrial arts

Optimization of CNC turning parameters with different turning tool radii for sphere surface profiles of SUS 304 material based on PVD coating technology applied for industrial arts

Transverse vortex-induced vibration of a sphere with the application of Lorentz force at low Reynolds number

In this study, the transverse vortex-induced vibration (VIV) of an elastically mounted sphere with the application of a streamwise Lorentz force is investigated through direct numerical simulation. The research parameter range is 300 ≤ Re ≤ 1100 and −0.8 ≤ N ≤ 1, where Re is the Reynolds number and N is the interaction parameter of the Lorentz force. The dependence of sphere responses, forces, and wake structures on Re and N is illustrated in detail. Within this range, two oscillation patterns are identified: VIV and desynchronization. Three wake patterns are identified: two-sided hairpin vortex emerges in the VIV region, while one-sided hairpin vortex and double-threaded wake structures are observed in the desynchronization region. The evolution of these wake patterns is related to the motion of the rear stagnation point (RSP) and separation line (SL) on the sphere surface. A large positive or negative Lorentz force suppresses the motion of RSP and SL, leading to the one-sided hairpin vortex or double-threaded wake structures replacing the two-sided hairpin vortex. Finally, the oscillation patterns are summarized on a map of amplitude response contours in the Re-N space.

Dynamic failures at the metal-glass interface under impact loading

To investigate dynamic fracture behavior in the metal, three metal spheres (e.g., steel sphere, high purity tungsten sphere, and high purity lead sphere) are accelerated by the gas gun devices to impact glass spheres under the critical speed range (i.e., from 70 m/s to 210 m/s). The velocity interferometer system for any reflector (VISAR) devices are employed to measure the particle velocities at the back surface of glass sphere, and high-speed photographs are utilized to capture the failure process at the metal-glass interface. Due to the asynchronous evolutions of stress fields and strain fields in the violent failure process, the results illustrate quite different failure mechanisms from those by the Split Hopkinson Pressure Bar (SHPB) impacting. Fragmentations of the glass sphere are caused mainly by the radial cracks and the lateral cracks around the metal-glass interface and the edges of the sphere with increasing impact velocity. Dynamic failures in the three metal impactors exhibit different modes, e.g., tensile fracture in the steel impactor, shear fracture in the tungsten impactor, and compressed yielding in the lead impactor. The transferring of strain energy releasing is introduced to describe the failure behavior at the metal-glass interface, and a relaxation-diffusion equation of strain energy releasing is then established based on the experimental results and the numeric results by the discrete element method (DEM). The evolutions of failures at the metal-glass interface are discussed. Further investigation is conducted to describe the dynamic fractures in tungsten impactors and steel impactors based on the dimensional analyses, and the quantitative expressions of these strain rate dependent fracture strains and crack width in the metal impactors are obtained. The results are helpful for the profound understanding of the dynamic fracture in the metal structures and the dynamic fragmentations in the brittle material when subjected to impact loading.

Effective quantum gravitational collapse in a polymer framework

We study how the presence of an area gap, different than zero, affects the gravitational collapse of a dust ball. The implementation of such discreteness is achieved through the framework of polymer quantization, a scheme inspired by loop quantum gravity (LQG). We study the collapse using variables which represent the area, in order to impose the non-zero area gap condition. The collapse is analyzed for both the flat and spherical Oppenheimer-Snyder models. In both scenarios the formation of the singularity is avoided, due to the inversion of the velocity at finite values of the sphere surface. This happens due to the presence of a negative pressure, with origins at a quantum level. When the inversion happens inside the black hole event horizon, we achieve a geometry transition to a white hole. When the inversion happens outside the event horizon, we find a new possible astrophysical object. A characterization of such hypothetical object is done. Some constraints on the value for the area gap are also imposed in order to maintain the link with our already established physical theories.

Core-shell structure and high rate performance of Ce-doped Li4Ti5O12 for lithium-ion battery anode materials

Lithium titanate (LTO) can be a very promising anode material for lithium-ion batteries (LSBs) due to its inherent ability to inhibit the growth of lithium dendrites as well as its unique “zero-strain” properties. Unfortunately, the low electronic conductivity of LTO leads to serious shortcomings in higher electrochemical demands. In this work, the Ce3+-doped C@Li4Ti5-xCexO12 (x = 0, 0.1, 0.15 and 0.2) anode materials synthesized by the hydrothermal method using carbon spheres as templates showed more significant improvement in both structural and electrochemical properties. The results demonstrate that electronic conductivity, lithium-ion diffusion rate, discharge specific capacity, discharge rate capability, and significant improvement stability of C@Li4Ti5-xCexO12 (x = 0.1, 0.15 and 0.2) electrodes. Among them, C@Li4Ti4.85Ce0.15O12 electrode exhibits the highest initial discharge specific capacity (250.86 mAh/g) at 0.1C, which is 1.28-fold that of C@ Li4Ti5O12 (195.94 mAh/g), and initial discharge capacity from 205.96 mAh/g to 170.39 mAh/g after 500 cycles, corresponding to 82.7 % of the initial stable discharge capacity. The outstanding performance of C@Li4Ti4.85Ce0.15O12 can be attributed to the lower interfacial impedance, higher electronic conductivity, high oxygen vacancy concentration, and moderate amount of Ce3+ doping can enhance the electrochemical activity. In addition, carbon sphere surface defects shown to be effective in improving lithium-ion storage. This work demonstrates that Ce3+ doping is an effective method to improve the electrochemical performance of LTOs and provides a more effective guide for designing and optimizing anode electrode materials for lithium-ion batteries

Thermal analysis of hybrid nano-fluids: Modeling and non-similar solutions

The thermal analysis of hybrid nano-fluids is a significant research area with diverse applications in industries such as paint, electronics, and mechanical engineering. Existing literature provides limited solutions to the governing equations for the flow of these fluids. Modeling and deriving non-similar solutions for these equations pose interesting and challenging mathematical problems. This study focuses on investigating heat transfer in the flow of two types of nano-fluids, specifically Al2O3/H2O micropolar nano-fluid and Al2O3 + Ag/H2O hybrid nano-fluid, near an isothermal sphere. Conservation laws are employed to formulate the mathematical problem, and by normalizing the variables, the governing equations are converted into a set of dimensionless partial differential equations. Non-similar solutions are then obtained using numerical methods. A comparative analysis is carried out to assess the influence of various parameters on different profiles and engineering quantities for both types of nano-fluids. Both linear and rotational velocities fall down near the surface of sphere with rising microstructure in hybrid nanofluid. The micro-rotation parameter rises the temperature profile while reduces the Nusselt number of both traditional Al2O3/water based nanofluid as well as hybrid nanofluid.

The encapsulation of noble metal over metal oxide semiconductor TiO2@Ag for the degradation of sulphur dye in effluent water by photocatalysis and electrochemical water splitting

Metal Oxide Semiconductor - Metal core-shell nanostructure with TiO2 as core and Ag nanoparticles as shell (TiO2@Ag) have been synthesized by a simple, environmentally friendly room temperature wet chemical method. The prepared TiO2@Ag core-shell nanoparticle was characterized by using various analytic techniques. X-ray diffraction analysis confirms the formation of tetragonal bcc structure anatase phase of TiO2 and Face-Centred Cubic structure (fcc) of silver in core-shell nanostructure. Fourier Transform Infrared Spectroscopy (FTIR) study proved the presence of characteristic peaks of both TiO2 and Ag. XPS study revealed the existence Ti4+ and metallic silver in core-shell nanostructure, High - Resolution Transmission Electron Microscopy (HR–TEM) and High - Resolution Scanning Electron Microscopy (HR–SEM) revealed the covering of Ag nanoparticles at the surface of TiO2 spheres. The TiO2@Ag core-shell nanoparticles exhibit a high residual mass of 95.9 % and stability to withstand up to 1000 °C. The prepared TiO2@Ag core-shell nanoparticles as photocatalyst showed enhanced photocatalytic degradation (240 min) of sulphur dye in effluent water with a degradation efficiency of 81 % and capable of employing in wastewater treatment to eliminate toxic elements present in it. In the current study, we have used core-shell nanoparticles prepared using the wet chemical method at room temperature. The prepared core-shell nanoparticles were used to study the photocatalytic degradation of sulphur black dye directly collected from textile effluent water. They were also used for the production of oxygen and hydrogen through the electrolysis process. The synthesized TiO2@Ag core-shell nanoparticles act as effective electrocatalyst for the production of oxygen and hydrogen through oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) using the electrolysis process.

Role of coal ash morphology and composition in delivery and transport of trace metals in the aquatic environment

Fly ash is predominately the inorganic byproduct of coal combustion for electrical power generation. It is composed of aluminosilicates with Fe, Mg, K, and Ca forming submicron to 100 μm spheres and amorphous particles. During combustion trace elements are incorporated into the heterogenous fine particles that can pose risks to the environment and human health. This study combines optical, rock magnetic, and geochemical analyses of fly ash originating from Appalachian coal to develop an integrated suite of environmental coal ash tracers. The non-magnetic portion of power plant fly ash has higher abundance of clear spheres and clear amorphous particles, combined with enrichment of As, B, Th, Ba, Li, Se, Cd, Pb, and Tl. The magnetic fraction is enriched in opaque and orange spheres and Cu, U, V, Mo, Cr, Ni, and Co. Plerospheres occur in either fraction. We investigated ash-bearing fluvial sediment from Emory-Clinch River system that was impacted by the instantaneous TVA spill in 2008 and Hyco Lake in North Carolina that was contaminated by chronic releases of fly ash since 1964. Five years after the TVA spill, most ash in the riverbed reflects one population with trace element concentrations proportional to percent total ash. This relationship does not hold for As and Se, volatile elements associated with the outer surface of clear spheres, which are affected by river transport. At Hyco Lake, small clear and opaque spheres correlate with trace elements released from storage ponds. The combination of trace elements, fly ash morphology and rock magnetism provides a powerful set of tools to assess the distribution of ash and potential impact on the environment. We conclude that dispersal of fly ash to the aquatic environment, especially small clear and opaque spheres, should be avoided in favor of dry landfills.

Compressive failure of thermally strengthened glass spheres — Why are Prince Rupert's drops so strong?

This paper aims to elucidate the exceptional high strength of Prince Rupert's Drops (PRDs). PRDs are idealized as thermally strengthened Glass Spheres (SGSs), and their compressive failure mechanisms are investigated experimentally and numerically. The distributions of residual stress within SGS specimens are quantitatively characterized using an integrated photo-elastic method. Uniaxial compression tests conducted on these specimens reveal that the compressive residual stress present on the sphere's surface significantly enhances its strength. High-speed video images demonstrate that SGSs fail at the equatorial region, in contrast to annealed glass spheres (AGS) which typically fracture near the Hertzian contact zone. Numerical simulations suggest that the residual stress mitigates the maximum principal stress on the surface of SGSs, thereby impeding the development of flaws on the surface of the specimens. Ultimately, failure of SGS specimens under pressure occurs due to the “squeezing” effect, in contrast to AGSs which commonly fail due to contact indentation.

Monson’s sphere in Chinese young adult females with individual normal occlusion: a preliminary study using digital models

BackgroundThis study investigated the characteristics of Monson’s sphere in Chinese young adult females with individual normal occlusion to provide a reference for oral rehabilitation in prosthodontic and orthodontic treatments.MethodsPoints at the dental cusps and incisal edges were selected from 51 digital mandibular dental models of Chinese young adult females (aged 18–22 years) with individual normal occlusion. Monson’s spheres were fitted to the selected points based on the least-squares principle and the radii were calculated. The deviation of each selected point from its relative spherical surface was also calculated. The radii and deviations of these points were examined using conventional descriptive statistics and distributions of the most deviated points inside and outside the spheres were analyzed.ResultsThe mean radius of Monson’s sphere in Chinese young adult females was 79.60 ± 14.13 mm. The deviation of each selected point from its relative sphere surface was 0.38 ± 0.30 mm. The maximum deviations inside and outside the sphere were 0.93 ± 0.25 mm and 0.95 ± 0.30 mm, respectively. The most deviated points outside the spheres were mainly distributed at the distolingual cusps of the mandibular second permanent molars (31.37%), while those inside the spheres were mainly distributed at the mesiolingual cusps of the mandibular first permanent molars (45.10%).ConclusionsThe radius of Monson’s sphere in Chinese young adult females was smaller than the classic four-inch value suggested by Monson. Deviation was observed from all selected points to their Monson’s sphere surface, with the most deviated points distributed primarily in the molar region.

On metallic-type asteroid rotation moving in magnetic field (introducing magnetic second-grade YORP effect)

A novel physical effect has been found to be illuminated of being physically self-consistent to take into account in further calculating the dynamics of magnetically-induced asteroid rotation, surface of which has mostly a conducting structure (whereas such mostly metallic-formed asteroid is assumed to be moving in an external magnetic field of planet but in the meantime to be orbiting preferably outside its sphere of effective attraction). The last condition of asteroid surface's having conducting structure means the existence of the applied external torques stemming from the physical interactions between external magnetic field and iron asteroid itself (including long-term effect due to torques stemming from arising eddy-currents on metallic surface of asteroid). Such eddy-currents should heat the conducting surface of asteroid with further non-uniformly re-directing the heat flow from surface of asteroid into outer space via fluxes of thermal photons which carry momentum (in orthogonal direction to the surface which is in most cases far from the ideal surface of sphere). This leads by taking into account the overall outcome of heat flow (from the non-ideal surface of asteroid) to a kind of long-term magnetic second-grade YORP effect. System of Euler equations for aforementioned dynamics of asteroid magnetic rotation has been investigated in regard to existence of semi-analytical solution. Various perturbations (such as collisions, YORP effect) may destabilize the rotation of asteroid deviating it from the current spin state, whereas the electric(eddy)current-induced dissipation of energy reduces kinetic one of asteroid spin. So, dynamics of the asteroid rotation should result in a spinning about maximal-inertia axis with the proper spin state corresponding to minimal energy with a fixed angular momentum.

Carbon/copper oxide electrode materials with high atomic utilization constructed by in-situ induced growth strategy of nano metal-organic frameworks

Carbon/metal composites derived from metal-organic frameworks (MOFs) have attracted widespread attention due to their excellent electronic conductivity, adjustable porosity, and outstanding stability. However, traditional synthesis methods are limited by the dense stereo geometry and large crystal grain size of MOFs, resulting in many metals active sites are buried in the carbon matrix. While the common strategy involves incorporating additional dispersed media into material, this leads to a decrease in practical metal content. In this study, nanosized copper-metal-organic frameworks (Cu-MOFs) are in-situ grown on surface of carbon spheres by pre-anchoring copper ions, and the hybrid composite of porous carbon/copper oxide with high copper atom utilization rate is prepared through activation and pyrolysis methods. This strategy effectively addresses the issue of insufficient exposure of metal sites, and the obtained composite material exhibits high effective copper atom utilization rate, large specific surface area (2052.3 m2·g−1), diverse pore structure, outstanding specific capacity (1076.5F·g−1 at 0.5 A·g−1), and excellent cycle stability. Furthermore, this highly atom-economical universal method has positive significance in application fields of catalysis, energy storage, and adsorption.

Design of Mn-based nanozymes with multiple enzyme-like activities for identification/quantification of glyphosate and green transformation of organophosphorus

A Mn-based nanozyme, Mn-uNF/Si, with excellent alkali phosphatase-like activity was designed by in-situ growth of ultrathin Mn-MOF on the surface of silicon spheres, and implemented as an effective solid Lewis-Brønsted acid catalyst for broad-spectrum dephosphorylation. H218O-mediated GC-MS studies confirmed the cleavage sites and the involvement of H2O in the new bonds. DRIFT NH3-IR and in-situ ATR-FTIR confirmed the coexistence of Lewis-Brønsted acid sites and the adjustment of adsorption configurations at the interfacial sites. In addition, a green transformation route of “turning waste into treasure” was proposed for the first time (“OPs→PO43−→P food additive”) using edible C. reinhardtii as a transfer station. By alkali etching of Mn-uNF/Si, a nanozyme Mn-uNF with laccase-like activity was obtained. Intriguingly, glyphosate exhibits a laccase-like fingerprint-like response (+,−) of Mn-uNF, and a non-enzyme amplified sensor was thus designed, which shows a good linear relationship with Glyp in a wide range of 0.49–750 μM, with a low LOD of 0.61 μM, as well as high selectivity and anti-interference ability under the co-application of phosphate fertilizers and multiple pesticides. This work provides a controllable methodology for the design of bifunctional nanozymes, which sheds light on the highly efficient green transformation of OPs, and paves the way for the selective recognition and quantification of glyphosate. Mechanistically, we also provided deeper insights into the structure-activity relationship at the atomic scale.

Scalar curvature for metric spaces: Defining curvature for quantum gravity without coordinates

Geometrical properties of spacetime are difficult to study in nonperturbative approaches to quantum gravity like causal dynamical triangulations (CDT), where one uses simplicial manifolds to define the gravitational path integral, instead of Riemannian manifolds. In particular, in CDT one only relies on two mathematical tools, a distance measure and a volume measure. In this paper, we define a notion of scalar curvature, for metric spaces endowed with a volume measure or a random walk, without assuming nor using notions of tensor calculus. Furthermore, we directly define the Ricci scalar, without the need of defining and computing the Riemann or the Ricci tensor . For this, we make use of quantities, like the surface of a geodesic sphere, or the return probability of scalar diffusion processes, that can be computed in these metric spaces, as in a Riemannian manifold, where they receive scalar curvature contributions. Our definitions recover the classical results of scalar curvature when the sets are Riemannian manifolds. We propose two methods to compute the scalar curvature in these spaces, and we compare their features in natural implementations in discrete spaces. The defined generalized scalar curvatures are easily implemented on discrete spaces, like graphs. We present the results of our definitions on random triangulations of a 2D sphere and plane. Additionally, we show the results of our generalized scalar curvatures on the quantum geometries of 2D CDT, where we find that all our definitions indicate a flat ground state of the gravitational path integral. Published by the American Physical Society 2024

Novel PEI/Zein core–shell composite as mixed-mode stationary phase for high performance liquid chromatography

Based on the adhesion of polyethyleneimine (PEI), a novel PEI/zein co-modified core-shell stationary phase (PEI/Zein@SiO2) was prepared by doping zein to form a composite modification layer. The stationary phase achieved effective separation of nucleosides, bases and antibiotics in hydrophilic interaction mode on account of the hydrophilic groups of composite coating. With the hydrophobicity of zein, the flavones could be separated in reversed-phase mode. In short, the separation and analysis of hydrophilic/hydrophobic compounds were accomplished excellently by the PEI/Zein@SiO2 column with mixed double mode. The prepared chromatographic stationary phase not only avoided the dissolution of zein, but also covered the strong adsorption of some analytes caused by silica hydroxyl groups on the surface of silica spheres. The morphological structure and specific surface area of the material were reflected by various characterization techniques. Hydrophilic/hydrophobic compounds were used as tested analytes to research separation performance and retention mechanisms of PEI/Zein@SiO2 column. The stability and reproducibility of the PEI/Zein@SiO2 stationary phase were satisfied. Therefore, the modification of zein could improve the separation selectivity of stationary phase effectively for complex samples, which had the potential to be one of the significant potential application materials in stationary phase packing.