Formation Mechanism Of Structures Research Articles

Laboratory Studies of the Clathrate Hydrate Formation in the Carbon Dioxide-Water Mixtures at Interstellar Conditions.

This study investigates the formation of carbon dioxide clathrate hydrates under conditions simulating interstellar environments, a process of significant astrophysical and industrial relevance. Clathrate hydrates, where gas molecules are trapped within water ice cages, play an essential role in both carbon sequestration strategies and understanding of the behavior of ices in space. We employed a combination of Fourier Transform Infrared (FTIR) spectroscopy, mass spectrometry, temperature-programmed desorption (TPD), and Density Functional Theory (DFT) calculations to explore thin films of H2O:CO2 ice mixtures with varying CO2 concentrations (5-75%) prepared by vapor deposition at temperatures ranging between 11 and 180 K. The study revealed the influence of CO2 concentration and deposition temperature on the formation mechanism of diverse structures, including clathrate hydrates, polyaggregates, and segregated CO2 groups. Spectral features associated with CO2 encapsulation in clathrate hydrates were observed at 2335, 2349, and 3698 cm-1 in the 5 and 15% mixtures after deposition at 11 K and after warming at temperatures above 100 K. The observed increase in CO2 sublimation temperature to 145-155 K and co-condensation of CO2 molecules at 172 K with water molecules at a pressure of 0.5 μTorr can be attributed to the encapsulation of CO2 molecules within the robust hydrogen-bonded framework of the clathrate cages under specific conditions. These findings enhance our understanding of the intricate processes involved in clathrate and hydrate formation in CO2 and H2O mixtures, shedding light on their physical properties and the dependence of their specific characteristics on the formation method.

Spiral and helical formation of passive and active polymers with stiffness heterogeneity in a spherical cavity.

Biomolecules usually adopt ubiquitous circular structures which are important for their functionality. Based on three-dimensional Langevin dynamics simulations, we investigate the conformational change of a polymer confined in a spherical cavity. Both passive and active polymers with either homogeneous or heterogeneous stiffness are analyzed in a comparative manner. For a homogeneous chain, continuous rigidity along the backbone promotes a flat spiral expanding along the cavity surface, while activity-induced softening results in a less-ordered spiral structure. Stiffness heterogeneity basically plays a destructive role in spiral formation. However, as the chain is endowed with activity, the heterogeneity effect depends on the stiffness of the front edge of the chain. As the head is rigid, the flat spiral largely holds, whereas such a structure easily loses as the head is flexible. More intriguingly, a short flexible head induces a distinct compact helix in the interior of the cavity. Under low friction conditions, the prominent inertial effect leads to the break-up of both spiral and helix. In the presence of crowding, the flat spiral close to the surface keeps its stability, while the compact helix inside tends to be dissolved. Our results decipher the significant effects of activity, rigidity, confinement and crowding on modulating polymer conformations, which provides a deeper insight about mechanisms for circular structure formation of biopolymers in crowded environments.

Flow-Sediment Interaction and Formation Mechanism of Sediment Longitudinal Streaky Structures in Rough Channel Flows

Flow-Sediment Interaction and Formation Mechanism of Sediment Longitudinal Streaky Structures in Rough Channel Flows

Self-assembed preparation of wheat germ gliadin and (-)-epigallo-catechin 3-gallate nanoparticles: Structural characterization, formation mechanism and bioactivity

Self-assembed preparation of wheat germ gliadin and (-)-epigallo-catechin 3-gallate nanoparticles: Structural characterization, formation mechanism and bioactivity

Synthesis of triangular lignin photonic crystal nanoparticles: Investigating solvent effects and dialysis optimization.

Synthesizing nanoparticles with controlled shapes has been highly desirable for nanoparticle assembly research but is fraught with challenges. While the production of traditional spherical lignin nanoparticles (LNPs) has evolved as a solution to address the highly changeable and complex chemical structure of lignin, more complicated geometries with photonic nature are still needed for optical applications. This work represents the first study to fabricate a novel triangular lignin photonic crystal nanoparticle via a green technique that combines solvent shifting and acid precipitation. This new model system has successfully produced LNPs with different structural architectures, ranging from spherical shapes to triangular plates. The structural transformation and formation mechanism of LNPs were investigated through various techniques. The nanotriangles grow depending on the employed solvents with dialysis, which involve controlled nucleation, Ostwald ripening-driven growth, particle coalescence, and geometric optimization. The isolated LNPs displayed excellent hydrophobic properties and remarkable UV-blocking efficiency. Furthermore, they preserved nearly the same zeta potential in aqueous suspensions over 6 months of storage, which is considered highly stable for colloidal systems. Thus, this simple method provides a sustainable and straightforward route for producing triangular LNPs with a wide range of potential applications in sunscreen products.

Slag rim structure and phase formation mechanism in molds during the continuous casting of high-Mn high-Al steel

The slag–steel reaction between low basicity mold flux and high-Mn and high-Al steel results in changes to the composition and properties of the mold flux, forming a slag rim at the meniscus of the mold during continuous casting. In this study, the slag rim was divided into five layers comprising the glass, columnar crystals, fine crystals, coarse crystals, and sinter layers from mold to molten steel based on their morphological features. Compared to the original slag, the Al2O3 content in the slag rim significantly increased and the SiO2 content decreased, thereby increasing the Al2O3/SiO2 mass ratio from 0.05 to 5.52. Phases with high melting points, such as Na2O·CaO·2Al2O3 and LiAlO2, were identified in the slag rim. According to crystallization process calculations using FactSage, these phases were the primary causes of slag rim formation. Thus, new slags with a low O/F mass ratio were subsequently designed to mitigate the generation and growth of Na2O·CaO·2Al2O3. These new compositions reduced the melting point and viscosity, thereby ensuring sufficient fluidity in slags with a high Al2O3/SiO2 mass ratio.

Structural characteristics and mechanism of collaborative environmental governance network of urban agglomerations: perspective of multilevel network

Collaborative environmental governance (CEG) is increasingly advocated to address the environmental risk issues in the integrated development of urban agglomerations. Constructing an effective CEG network from the perspective of interdependent multilevel network plays a vital role in promoting the environmental governance of urban agglomerations. To investigate the structure characteristics and formation mechanism of CEG network, this paper takes the Yangtze River Delta urban agglomeration as the research area, and employes the social network analysis and Exponential Random Graph Model (ERGM) methods to analyze the CEG network, which consists of the collaborative network of cities, relationship network of topics, and affiliation network connecting cities to topics. Research results show that the CEG level in the Yangtze River Delta urban agglomeration continues to improve, while the CEG network is still not in a tightly connected state. For the collaborative network of cities, it presents the small world characteristics and forms a cooperative trend of “central-subcentral-peripheral city.“For the relationship network of topics, the evolution of environmental governance topics is characterized by “from aspect to point.” For the affiliation network connecting cities to topics, as the diversity of environmental governance topics increases among cities, cities within the Yangtze River Delta urban agglomeration tend to share the similar topics. In addition, the interactive triangular structures, star structures, open triangular structures and closed triangular structures in the network can promote the formation of new cooperative relationships in CEG network.

Understanding the Mechanism of Evaporation-Induced Islands during the Formation of Catalyst Layers and Their Influence on the Alkaline Oxidation Evolution Reaction

Advancements in anode development substantially reduce the cost and enhance the performance of water electrolysis. The strategic configuration of nano-sized catalyst materials on anode supports is a pivotal factor in the expansion of the production of catalyst layers and has a significant influence on their electrochemical performance [1–3]. Therefore, it is essential to understand the structure formation mechanisms during electrode fabrication. This contribution aims to explore the inherent drying mechanisms in the coating process and their subsequent influence on the morphological evolution of anodes, ultimately establishing a linkage between these morphological changes and electrochemical performance and stability metrics. The initial phase of the study involved a detailed characterization of commercial nickel cobalt oxide nanoparticles via advanced analytical techniques, including transmission electron microscopy and energy-dispersive X-ray spectroscopy [4]. Subsequently, a stable ink was formulated by dispersing the catalyst alongside a binder in a solvent, which was then uniformly applied to a conductive nickel plate utilizing an ultrasonic spray coater. Prior to application, the catalyst inks underwent optimization based on the Hansen solubility parameters of catalyst materials [5, 6] and subsequent visualization of their stability and dispersibility characteristics through transmittogram analysis [7]. The drying process of the coating was conducted at two distinct temperatures, 50 °C and 150 °C, to investigate the effect of temperature on solvent evaporation. Morphological and structural analyses of the anodes were subsequently performed using scanning electron microscopy (SEM), laser scanning microscopy (LSM), and atomic force microscopy (AFM), providing insight into the alterations induced by the drying process. The analyses conducted in this study elucidate significant modifications in the morphology of the layer structures attributable to variations in drying temperatures as illustrated in Figure 1. Specifically, lower temperature resulted in reduced evaporation rates that facilitated the formation of larger, isolated regions/islands on the anode support. These are indicative of a non-uniform coating distribution. In contrast, a higher temperature promoted rapid evaporation, resulting in a quite homogeneous distribution of smaller islands accompanied by the emergence of voids within the anode layer. Electrochemical analysis revealed that these morphological changes are of vital importance: they govern the wetting behaviour and the dynamics of bubble formation which are important for the electrochemical performance and durability of the catalyst layers. Moreover, the insights gleaned from this study are instrumental in identifying optimal configurations of catalyst layer structures, i.e., features that should be maintained during scale-up. In conclusion, this study significantly advances the field by revealing novel principles governing the design and optimization of electrode structures for the oxygen evolution reaction. In particular, the complicated relationship between drying temperatures and morphological evolution, which significantly influences electrochemical performance is explained.

Regulatory mechanism of blending additives on interface interaction and phase separation of the heterogeneous braid-reinforced hollow fiber membranes

The exfoliation of the polymer layer from the reinforcement material is the key challenge for applying braid-reinforced hollow fiber membranes (BR HFMs). In this work, a mixed amphiphilic additive system was constructed and adopted in BR HFMs preparation by non-solvent induced phase separation (NIPS). The effect of the mixed system on the state of the casting solution and phase inversion process, the interaction between the casting solution and the braid material, together with the structure and filtration performance was studied. The role of the mixed system on the interface coordination and membrane structure formation mechanisms was elucidated. The results showed that both the composition of the mixed amphiphilic additives and the interaction time between the casting solution and braid material threw much light on the interface coordination and membrane formation. The interfacial compatibility of the casting solution and braid material was obviously improved, resulting in the enhancement of the binding force between the braid and PVDF membrane layer. The permeation flux and anti-exfoliation performance were simultaneously improved with the proper addition of the mixed amphiphilic additives. The stability of the BR HFMs was primarily testified by filtration of real sludge suspension solution with back-washing operation.

Boundary sources of velocity gradient tensor and its invariants

The present work elucidates the boundary behaviors of the velocity gradient tensor (A≡∇u) and its principal invariants (P, Q, R) for compressible flow interacting with a stationary rigid wall. First, it is found that the boundary value of A exhibits an inherent physical structure being compatible with the normal-nilpotent decomposition, where both the strain-rate and rotation-rate tensors contain the physical contributions from the spin component of the vorticity. Second, we derive the kinematic and dynamical forms of the boundary A flux from which the known boundary fluxes can be recovered by applying the symmetric–antisymmetric decomposition. Then, we obtain the explicit expression of the boundary Q flux as a result of the competition among the boundary fluxes of squared dilatation, enstrophy and squared strain-rate. Importantly, we find that both the coupling between the spin and surface pressure gradient, and the spin-curvature quadratic interaction (sw·K·sw), are not responsible for the generation of the boundary Q flux, although they contribute to both the boundary fluxes of enstrophy and squared strain-rate. Moreover, we prove that the boundary R flux must vanish on a stationary rigid wall. Finally, the boundary fluxes of the principal invariants of the strain-rate and rotation-rate tensors are also discussed. It is revealed that the boundary flux of the third invariant of the strain-rate tensor is proportional to the wall-normal derivative of the vortex stretching term (ω·D·ω), which serves as a source term accounting for the spatiotemporal evolution rate of the wall-normal enstrophy flux. As an example, several relevant surface quantities to the surface curvature are calculated based on global skin friction and surface pressure measurements in a flow over a National Advisory Committee for Aeronautics Fundamental Aeronautics Investigates The Hill model. These theoretical results provide a unified description of boundary vorticity and vortex dynamics, which could be valuable in understanding the formation mechanisms of complex near-wall coherent structures and the boundary sources of flow noise.

Tunneling nanotubes (TNTs): An essential yet overlooked modality of inter-cellular communication

Tunneling nanotubes (TNTs) are open membranous protrusions that allow direct communication between distant cells. Recent research has revealed their significant biological roles, prompting a reassessment of many physiological and pathological processes, especially in the nervous system where TNT properties could play a key physiological role. TNT-like connections have been observed in the developing brain and are implicated in neurodegenerative diseases, brain cancers, as well as in other diseases, underscoring their importance in pathophysiological events. This review covers the key features of TNTs, including their structural properties, formation mechanisms, and detection challenges. We also explore their functions, focusing on the nervous system. The discovery of TNTs may lead to a reconsideration of brain function as a physically connected neuronal network, as proposed by Golgi, complementing Cajal's theory of neurons as separate entities.

In-situ preparation and performance of weather resistant laminated anti-fire glass using the micro-nano multilayer K2O·nSiO2-based material

We describe a low-cost method for the synthesis of weather resistant K2O·nSiO2-based anti-fire material with micro-nano multilayer structure, which was significant for application in the high-altitude and high-latitude regions. Here, the low-temperature stable cold-resistant (LTSCR), low-temperature reversible cold-resistant (LTRCR) and low-temperature irreversible cold-resistant (LTICR) K2O·nSiO2-based laminated anti-fire glass were prepared via an in-situ reaction using a high solid content and low viscosity SiO2 sol (HSLV SiO2 sol, 60 wt%, 24.3 mPa s ± 1.2 mPa s). The morphological, mechanical, optical, anti-rheological, cold resistant, thermal insulation and UV resistant performances were systematically characterized. The homogeneous structure and micro-nano multilayer structure were clearly shown in scanning electron microscopy (SEM) micrographs. The structure formation, foaming, subsidence process and weather resistant mechanisms were further investigated in detail. The significant differences appeared in the LTSCR and LTRCR K2O·nSiO2-based anti-fire materials during subsidence dynamics analysis. Combined with morphological and Tg analysis, the micro-nano multilayer reinforcement in the insulating layer was the key to enhance the strength of the K2O·nSiO2-based material, and sponge-like pores prolonged the anti-fire time in the event of a fire. The low-temperature-withstanding performance was tested at extreme-cold environment, the LTSCR K2O·nSiO2-based laminated anti-fire glass didn't freeze for more than 18 h at −60 ± 1 °C. The UV resistance performance was more than 2000h due to the reinforcements with the micro-nano multilayer structure. This work also provides a new routine for synthesizing high-quality anti-fire glass with different shapes, including curved surfaces.

Structure Formation Through Magnetohydrodynamical Instabilities in Primordial Disks

The shear flow instabilities under the presence of magnetic fields in the primordial disk can greatly facilitate the formation of density structures that serve as seeds prior to the onset of the gravitational Jeans instability. We evaluate the effects of the Parker, magnetorotational and kinematic dynamo instabilities by comparing the properties of these instabilities. We calculate the mass spectra of coagulated density structures by the above mechanism in the radial direction for an axisymmetric magnetohydrodynamic (MHD) torus equilibrium and power density profile models. Our local three-dimensional MHD simulation indicates that the coupling of the Parker and magnetorotational instability creates spiral arms and gas blobs in an accretion disk, reinforcing the theory and model. Such a mechanism for the early structure formation may be tested in a laboratory. The recent progress in experiments involving shear flows in rotating tokamak, field reversed configuration (FRC) and laser plasmas may become a key element to advance in nonlinear studies.

Structure formation mechanism of pectin-soy protein isolate gels: Unraveling the role of peach pectin fractions

This study investigated the macro & micro properties of the composite gels formed by soy protein isolate (SPI) and peach pectin fractions: water-soluble pectin (WSP), chelator-soluble pectin (CSP), and sodium carbonate soluble pectin (NSP). Specially, the interaction between pectin fractions and SPI was studied to explain the formation mechanism of the composite gels. WSP, as a high methoxyl pectin, exhibited rich branching (sugar ratio B = 3.10). CSP, as a low methoxyl pectin, depicted a high linearity. NSP, with low linearity (sugar ratio A = 6.14), contained numerous side chains. Due to the strong interaction between pectin fractions and SPI, the new composites with excellent dense network microstructures were formed, accompanied by increased apparent viscosity, higher G′ and G′′, and reduced particle size. XRD and FT-IR analysis highlighted the modifications in gel structures. SEM-dispersive X-ray spectroscopy observed elemental distribution and framework composition in pectin-SPI gels. Hydrophobic interaction was the most important chemical force in pectin-SPI binding. Molecular docking results indicated that galacturonic acid in pectin bound more strongly to 7S than to 11S, with tighter hydrogen bonds. Notably, WSP-SPI showed the lowest turbidity, indicating enhanced solubility and particle dispersion, which helped prevent aggregation. CSP-SPI demonstrated the highest G′ and G′′, ascribing to the high linearity and abundant carboxyl groups in CSP. NSP-SPI showed the highest apparent viscosity and irregular structure. Overall, the texture properties of pectin-SPI gels were driven by pectin's structure properties, which would provide new and valuable information for texture control in gel formulation.

The ultra-low friction mechanism of diamond film by in-situ forming of graphene sheet on sliding interface

In the present study, a novel process of in-situ fabrication of graphene sheets on ultrananocrystalline diamond (UNCD) film with aid of Au layer catalyst was designed. An in-situ ultra strong CC bonds are formed in the graphene-diamond interface under the action of heating, which can decrease the friction coefficient of the film. Besides, the friction-induced formation of graphene nano-scrolls play a pivotal role in achieving an exceptionally low friction coefficient of 0.025 for annealed Au/UNCD film. The potential structural formation mechanisms and frictional mechanisms have been discussed in detail. The achievement in this work provides a novel insight into the in-situ fabrication of graphene-diamond structure in mechanical fields with outstanding low friction coefficient and anti-wear performance.

Dominant and genome-wide formation of DNA:RNA hybrid G-quadruplexes in living yeast cells

Guanine-rich DNA forms G-quadruplexes (G4s) that play a critical role in essential cellular processes. Previous studies have mostly focused on intramolecular G4s composed of four consecutive guanine tracts (G-tracts) from a single strand. However, this structural form has not been strictly confirmed in the genome of living eukaryotic cells. Here, we report the formation of hybrid G4s (hG4s), consisting of G-tracts from both DNA and RNA, in the genome of living yeast cells. Analysis of Okazaki fragment syntheses and two other independent G4-specific detections reveal that hG4s can efficiently form with as few as a single DNA guanine-guanine (GG) tract due to the participation of G-tracts from RNA. This finding increases the number of potential G4-forming sites in the yeast genome from 38 to 587,694, a more than 15,000-fold increase. Interestingly, hG4s readily form and even dominate at G4 sites that are theoretically capable of forming the intramolecular DNA G4s (dG4s) by themselves. Compared to dG4s, hG4s exhibit broader kinetics, higher prevalence, and greater structural diversity and stability. Most importantly, hG4 formation is tightly coupled to transcription through the involvement of RNA, allowing it to function in a transcription-dependent manner. Overall, our study establishes hG4s as the overwhelmingly dominant G4 species in the yeast genome and emphasizes a renewal of the current perception of the structural form, formation mechanism, prevalence, and functional role of G4s in eukaryotic genomes. It also establishes a sensitive and currently the only method for detecting the structural form of G4s in living cells.

Hard Particle Mask Electrochemical Machining of Micro-Textures

The efficient and cost-effective preparation of masks has always been a challenging issue in mask-based electrochemical machining. In this paper, an electrochemical machining process of micro-textures is proposed using hard particle masks such as titanium and zirconia particles. Numerical simulations were conducted to analyze the formation mechanisms of micro-protrusion structures with insulating and conductive hard particle masks, followed by experimental verification of the process. The results indicate that when the hard particles are electrically insulating, metal material preferentially dissolves at the center of the particle gap, and the dissolution then expands over time in depth and towards the particle contact points. Conversely, using the conductive particles as the masks, such as titanium particles, dissolution initially occurs in a ring region centered at the contact point between the hard particle and the anode, with a radius approximately one-quarter of the chosen particle’s diameter (200 μm), and then continues to expand outward.

The growth mechanism and optical properties of flower-like porous Gd2O2S:Er3+/Yb3+ phosphor

The self-assembly mechanism of porous materials has always been a hot topic and a challenging issue in research. What factors induce the self-assembly process, and how is the temperature sensing performance related to it? Innovatively, in this paper, Gd2O2S:Er3+/Yb3+ phosphors with different morphologies were synthesized, and elucidated the formation mechanism of flower-like structures through relevant theorems, formulas, and experiments, proposing that polar molecules and dipole-dipole interactions guide the synergistic effect of van der Waals forces and hydrogen bonding, which ultimately induces the self-assembly of spherical structures into flower-like ones. In addition, four representative intermediates were selected to investigate their luminescence and temperature sensing properties. The results show that the flower-like sample can respond more effectively to changes in ambient temperature because of its rich pore structures, and thus exhibit better temperature sensing performance. In-depth research on the self-assembly mechanism of materials helps to predict and regulate their properties, and the unique characteristics of flower-like sample provide new ideas for material selection in the field of high-precision temperature measurement.

Asymmetric Dust Accumulation of the PDS 70 Disk Revealed by ALMA Band 3 Observations

The PDS 70 system, hosting two planets within its disk, is an ideal target for examining the effect of planets on dust accumulation, growth, and ongoing planet formation. Here, we present high-resolution (0.″07 = 8 au) dust continuum observations of the PDS 70 disk in ALMA Band 3 (3.0 mm). While previous Band 7 observations showed a dust ring with slight asymmetry, our Band 3 observations reveal a more prominent asymmetric peak in the northwest direction, where the intensity is 2.5 times higher than in other directions and the spectral index is at the local minimum with α SED ∼ 2.2. This indicates that a substantial amount of dust is accumulated both radially and azimuthally in the peak. We also detect point-source emission around the stellar position in the Band 3 image, which is likely to be free–free emission. We constrain the eccentricity of the outer ring to be e < 0.04 from the position of the central star and the outer ring. From the comparison with numerical simulations, we constrain the mass of PDS 70c to be less than 4.9 MJupiter if the gas turbulence strength α turb = 10−3. Then, we discuss the formation mechanism of the disk structures and further planet formation scenarios in the disk.

Starch-related structural basis and enzymatic mechanism of the different appearances of soft rice

To investigate the fine starch structure characteristics and formation mechanism of high-quality appearance soft rice, two high-quality and low-quality soft rice varieties (HA-SR and LA-SR, respectively) were selected. Differences in appearance quality, fine starch structure, and activity of key enzymes involved in starch synthesis during the grain-filling stage were compared. The results showed that compared with LA-SR, HA-SR were less chalky, more transparent, had larger starch grains, a lower content of shorter chains (DP 6–24), a higher content of longer chains (DP ≥ 25), lower relative crystallinity, fewer ordered structures, more amorphous structures and larger thicknesses of semi-crystalline lamellae. In terms of amylase activity during the grain-filling stage, the AGPase and GBSS activities of HA-SR were higher, and the SBE activity of HA-SR was lower compared to LA-SR. In conclusion, higher AGPase activity can produce a higher filling rate resulting in fuller starch grain in soft rice. Fuller starch grains reduce the chalkiness of soft rice. Higher AGPase and GBSS activities and lower SBE activity can result in soft rice with more long-branched and less short-branched amylopectin. Thus, soft rice has lower relative crystallinity and less ordered structure. These structures may facilitate reduce grain chalkiness and improve grain transparency.