Segregation Mechanism Research Articles

Segregation of water and gravel using large ball mill device laid roughness bed

This paper presents an experimental approach to study the phenomena of segregating water and gravel using a large ball mill device that reproduces segregation phenomena under debris flow. First, the experiment was conducted in a ball mill device under various conditions: water and gravel mixing, bed velocity, and laid roughness. The occurrence conditions of the segregation phenomena of water and gravel mixing are categorized and compared with each other with and/or without roughness on the bed. Furthermore, the movements after water and gravel mixing in the ball mill device are observed to investigate the segregation mechanism.

Cumulative effect of particle properties on mixing of multi-component mixture in a vibrated packed bed

The effect of particle properties that include shape, size, and density in a vibrated packed bed mixer for binary and ternary mixtures is investigated and mixing is characterized using subdomain mixing index. The mixing behavior can be divided into two different regimes based on the dominant segregation mechanism which is dependent on the theoretically calculated value of the segregation parameter ( Z ). The two different regimes are the percolation and buoyancy control regime. The Z value combines the effect of various physical properties of the particle. The subdomain mixing index value is strongly correlated to the segregation parameter. The results indicate that in a binary mixture decreasing the coarse particle’s density reduces the mixing while decreasing the fine particle’s density enhances the mixing. The extent of segregation behavior for nonspherical particles show shape-induced segregation is not a dominant factor but nonspherical particles show better mixing than spherical particles. • A correlation is developed that can predict dominant segregation mechanisms. • Particle shape-induced segregation is an important secondary factor. • Nonspherical particles show better mixing than spherical particles. • Adding a component to the binary mixture does not always improve mixing. • In a ternary mixture, decreasing the intermediate particles' density reduces mixing.

Action and segregation mechanism of Fe-rich phase in as-cast brass with different Fe contents

Rational recycling of scrap brass is an important link in the global copper supply chain. It is of great significance to clarify the mechanism and tolerance of trace elements in scrap brass. Fe is one of the main trace elements that commonly found in scrap brass. In this study, the effect of Fe on the properties (conductivity and hardness) of brass as cast was investigated in the range of iron content from 0 to 1.2 wt%. The effect of Fe addition on the action and the corresponding segregation mechanism of Fe-rich phase in as-cast brass was reported in this paper. The thermodynamic model of Fe segregation in brass was established. Based on the theoretical analysis, the mechanism of Fe segregation in brass was revealed. This work contributes to a new understanding for the separation behavior of Fe-containing particles in Cu-rich melt. These results may provide theoretical guidance for reasonable regeneration and utilization of scrap brass.

Segregation behaviors of nonmetallic impurities on grain boundary of austenitic steel

Grain boundary (GB) always takes a critical role in the mechanical properties of most engineering materials, and austenitic steel (γ-Fe) is no exception. However, the microscopic mechanism of impurity segregation on γ-Fe GB is still unclear. In this work, we explored the stabilities of eight γ-Fe GBs by density functional theory (DFT) and chose the Σ5 (310) GB as a representative. Here, the separation energy, GB energy, strengthening energy, and theoretical tensile stress of Σ5 (310) GB doped by eight common nonmetallic elements (H, B, C, N, O, Si, P, and S) were analyzed to evaluate the effect of impurities segregation comprehensively. The results show that except for H and Si, impurities of B, C, N, O, P and S all can stabilize Σ5 (310) GB. However, only the B element can strengthen Σ5 (310) GB. Finally, the calculated electron transfer of doped Σ5 (310) GB unveils the superiority of the boron element and the segregation effect of other impurities. This work provides a systematical insight into the effect of impurity doping on Σ5 (310) GB, which will be a useful reference for γ-Fe processing research.

Reject and Resubmit: A Formal Analysis of Gender Differences in Reapplication and Their Contribution to Women’s Presence in Talent Pipelines

A common explanation for women’s underrepresentation in many economic contexts is that women exit talent pipelines at higher rates than men. Recent empirical findings reveal that, in male-dominated selection contexts, women are less likely than men to reapply after being rejected for an opportunity. We examine the conditions under which this gender difference contributes to women’s underrepresentation in talent pipelines over time. We formally model and analyze the population dynamics of a generic selection context, which we then ground using three distinct empirical settings. We show that gender differences in reapplication are an important mechanism of gender segregation in some selection contexts but negligible in others. The extent to which gender differences in reapplication contribute to women’s underrepresentation is driven in part by the rejection rate. Higher rejection rates increase the stock of rejected applicants, which in turn enables gender differences in reapplication to disproportionally reduce women’s representation. The results demonstrate that interactions between individuals’ choices on the supply side and screeners’ behavior on the demand side may have consequences for gender inequality, even if we were able to fully eliminate demand-side biases. We discuss the theoretical and policy implications of our research for understanding women’s underrepresentation in talent pipelines. We also interrogate the effectiveness of common interventions focused on encouraging women to apply for opportunities in male-dominated domains. Supplemental Material: The online appendix is available at https://doi.org/10.1287/orsc.2022.1635 .

The Internal Structure of Io

Io is a differentiated body with a silicate crust and mantle, and an iron-rich core. However, its internal structure, especially that of its mantle, differs from that of other terrestrial bodies, as a result of the intense heat supply by tidal dissipation. The amount and distribution of melt in Io’s interior strongly depend on the composition, as well as the heat and mass transport mechanisms operating at depth and in the near-surface. This article discusses melting processes and the mechanisms of magma segregation inside Io, informed by Earth-based observations and spacecraft measurements, as well as thermo-chemical and thermo-physical modeling.

Shape matters: Competing mechanisms of particle shape segregation.

It is well known that granular mixtures that differ in size or shape segregate when sheared. In the past, two mechanisms have been proposed to describe this effect, and it is unclear if both exist. To settle this question, we consider a bidisperse mixture of spheroids of equal volume in a rotating drum, where the two mechanisms are predicted to act in opposite directions. We present evidence that there are two distinct segregation mechanisms driven by relative overstress. Additionally, we showed that, for nonspherical particles, these two mechanisms (kinetic and gravity) can act in different directions leading to a competition between the effects of the two. As a result, the segregation intensity varies nonmonotonically as a function of aspect ratio (AR), and, at specific points, the segregation direction changes for both prolate and oblate spheroids, explaining the surprising segregation reversal previously reported. Consistent with previous results, we found that the kinetic mechanism is dominant for (almost) spherical particles. Furthermore, for moderate aspect ratios, the kinetic mechanism is responsible for the spherical particles' segregation to the periphery of the drum, and the gravity mechanism plays only a minor role. Whereas, at the extreme values of AR, the gravity mechanism notably increases and overtakes its kinetic counterpart.

Market-based waste segregation and waste bin siting suitability studies using GIS and multi-criteria evaluation in the Kumasi Metropolis

This study examined the readiness and motivation of market women to separate solid waste in the Central Business Districts (CBD) of Kumasi. Multiple non-probability sampling techniques were adopted to sample 156 respondents. The results obtained were analysed using SPSS. From the study, 81.4% of market women were willing to sort their waste provided there are proper infrastructures such as separate waste bins. Also, 85.3% of the women also indicated that training and educating them on the consequences of sorting waste will have a great impact on their attitudes to participate. A Relative Importance Index (RII) assessment of the reasons why waste sorting was done, the highest index (RII = 0.87) was recorded for environmental protection. The second highest order of reason for sorting waste by the women was related to personal hygiene (RII = 0.86) whereas reduce proliferation of landfills recorded (RII = 0.85) as the third highest index. The fourth and fifth reasons were that it will be easier to produce manure from sorted waste and fulfilment to mankind with RII of 0.77 and 0.58 respectively. A spatial multicriteria evaluation was performed to select suitable sites for the waste bins for the CBD. A total of 192 suitable locations were identified for waste bins in the three business districts. It is recommended that proper waste management equipment (colour-coded bins) are provided in the CBD bin as a motivating mechanism for waste segregation.

Rashba-induced spin texture and spin-layer-locking effects in the antiferromagnetic CrI3 bilayer

The antiferromagnetic (AFM) CrI3 bilayer is a particularly interesting representative of van der Waals 2D semiconductors, which are currently being studied for their magnetism and for their potential in spintronics. Using ab initio density-functional theory calculations, we investigate the spin texture in momentum space of the states of the (doubly degenerate) highest valence band of the AFM CrI3 bilayer with Cr-spin moments perpendicular to the layers. We find the existence, in the main central part of the Brillouin zone, of a Rashba in-plane spin texture of opposite signs on the two layers, resulting from the intrinsic local electric fields acting on each layer. To study the layer segregation of the wavefunctions, we apply a small electric field that splits the degenerate states according to their layer occupancy. We find that the wavefunctions of the highest valence band are layer-segregated, belonging to only one of the two layers with opposite in-plane spin textures, and the segregation occurs over nearly the whole Brillouin zone. The corresponding layer locking of the in-plane-canted spin is related to the separation in energy of the highest AFM band from the rest of the valence bands. We explain how the band interactions destroy the layer locking at the K, K′, and Γ points. Furthermore, we compare the layer locking of the in-plane-canted spin in our AFM bilayer system with the hidden spin polarization in centrosymmetric nonmagnetic materials, pointing out the differences in segregation mechanisms and their consequences for the layer locking. We note that a similar Rashba effect with layer locking of in-plane-canted spin could occur in other van der Waals AFM bilayers with strong spin–orbit coupling and an isolated energy band.

Early developmental plasticity enables the induction of an intermediate extraembryonic cell state

Two fundamental elements of pre-implantation embryogenesis are cells' intrinsic self-organization program and their developmental plasticity, which allows embryos to compensate for alterations in cell position and number; yet, these elements are still poorly understood. To be able to decipher these features, we established culture conditions that enable the two fates of blastocysts' extraembryonic lineages-the primitive endoderm and the trophectoderm-to coexist. This plasticity emerges following the mechanisms of the first lineage segregation in the mouse embryo, and it manifests as an extended potential for extraembryonic chimerism during the pre-implantation embryogenesis. Moreover, this shared state enables robust assembly into higher-order blastocyst-like structures, thus combining both the cell fate plasticity and self-organization features of the early extraembryonic lineages.

Chemical compaction and fluid segregation in piston cylinder experiments

Fluid segregation is a ubiquitous process in deep-seated rocks, mainly driven by buoyancy and gravitational compaction, which occur in drained systems until permeability decreases and the system become practically undrained. The mechanism and rate of fluid segregation following this stage are poorly constrained, despite the importance of these factors for fluid distribution and the physical and chemical properties in the Earth. To this end, we performed sintering experiments of quartzite, with H2O–CO2 fluids of 1.9%–18.0% added volume fraction using a piston-cylinder apparatus at 900°C under nominally isotropic pressure of 1 GPa. The subsequent chemical redistribution of silica and fluids resulted in capsule-scale fluid segregation (CFS) and the formation of dense quartzite (∼0.3%) within 192 h in pure H2O systems. Comparative experiments showed that dissolution/precipitation was not caused by the temperature gradient. Instead, we considered the fluid pressure difference within the experimental capsule between fluid-rich and fluid-poor domains caused by the different response against small pressure oscillation during experiments. Fluid-rich rock is elastically “soft” (i.e., having larger Skempton's coefficient) compared to fluid-poor rock to increase pore fluid pressure under a compressional stress change. Therefore, more silica dissolves in fluid-rich domains with higher solubility, while it precipitates in fluid-poor domains through diffusive transport, expanding porosity contrast. This chemical compaction in the capsule scale is effective as long as elasticity dominates matrix viscosity because the pressure difference relaxes with time. The calculated relaxation time of quartzite at the experimental condition was comparable to the intervals of the oil pressure addition which produced stress change. A one-dimensional model for porosity evolution showed that time-averaged SiO2 diffusivity during CFS was much larger than the grain boundary diffusivity of tightly sintered quartz aggregates, but was comparable to the diffusivity of SiO2 in aqueous fluid with ∼0.1 vol% fluid fraction. During metamorphism where the fluid pressure difference may be maintained for longer duration, the spontaneous silica cementation may play a role for formation of syn-metamorphic veins and control of the amount of pore fluids transported to deep Earth.

Genome-wide association and transcriptome studies reveal the segregation mechanism of mantle markings in three-way cross hybrid abalone

Trait separation which often appears in shellfish progeny, has been commercially used in shellfish breeding projects. A three-way cross hybrid abalone was produced with heterosis in growth performance and thermal tolerance, and with segregation in mantle marking. However, the inheritance mechanism of mantle marking is unclear. In this study, mantle marking was demonstrated to be a qualitative trait, following simple Mendelian inheritance, through inheritance pattern analysis of the presence of black markings on the mantle in five families of three-way cross of hybrid abalone. Thermal tolerance of abalone was assessed by the Arrhenius breakpoint temperature (ABT) of cardiac performance and a correlation between mantle marking and thermal tolerance of abalone was verified. A genome-wide association study (GWAS) for mantle marking was conducted using 603,067 high-quality single nucleotide polymorphisms (SNPs) derived from 57 individuals with mantle markings (Y group) and 58 individuals without mantle markings (N group). A total of 493 SNPs that were significantly (p < 2.32E–07) associated with mantle markings were mainly distributed on chromosome 15. In the potential significantly associated region, 80 genes, including pigmentation-related genes PTPRT, PTPRC, PNCA, and CALM4 were annotated. Transcriptome analysis of the two groups showed that the expression levels of these genes (PTPRT, DDT-b, ATOX1, SLC6A3, and GSTO1) were significantly different, and they may play important roles in the formation of mantle markings in the three-way cross hybrid abalone. Overall, our data provide valuable information for deciphering the phenotype differences of mantle marking in three-way cross hybrid abalone and help in the molecular marker-assisted breeding in abalone.

High‐resolution stable isotopic signals of ground ice indicate freeze–thaw history in permafrost on the northeastern Qinghai–Tibet Plateau

AbstractUnderstanding the mechanism of formation of ground ice and the freeze–thaw history of permafrost is essential when assessing the future of permafrost in a changing climate. High‐resolution ground ice records, integrating stable isotopes (δ18O, d‐excess, and δ13C), hydrochemistry (EC and pH) data, and cryostratigraphy at a depth of 4.8 m from two contrasting permafrost profiles (P‐1, P‐2) in the Source Area of the Yellow River (SAYR) on the northeastern Qinghai–Tibet Plateau (QTP), were investigated. The results suggested significant depth variations in the stable isotopes and hydrochemistry of the ground ice. The near‐surface ground ice (NSGI) and deep‐layer ground ice (DLGI) were characterized in terms of variations in stable isotopes and known modern active layer data. By synthesizing the measured δ18O and the modeled isotopic fractionation processes during freezing, we suggest that both the NSGI and DLGI in P‐1 were mainly formed by the segregation mechanism during permafrost aggradation. The NSGI in P‐2, however, exhibited quick freezing origins compared with the predominant ice segregation processes for the DLGI. By combining the evolution of various stable isotopes and hydrochemistry with 14C age data, four historical freeze–thaw stages were identified. Specifically, one thawing–refreezing stage (2.8–2.2 m), one freezing aggradation stage (2.2–1.6 m), and two permafrost aggradation–degradation cycle stages (4.8–2.8 m; 1.6–0.7 m) were differentiated, which emphasize the importance of climate‐induced freeze–thaw transitions and differing permafrost aggradation processes on ground ice formation and resultant isotope hydrochemical behaviors. This study is the first to use high‐resolution data in ground ice to interpret the freeze–thaw history of permafrost in the SAYR. These findings are important for further understanding of past permafrost evolution and projected future permafrost degradation trends on the QTP, and provide an alternative method to explore permafrost history.

Cytogenetic techniques in current biomedical research. PART III: numerical alterations of human karyotype

Numerical abnormalities of karyotype are the result of genome mutations. Unlike gene and chromosomal abnormalities, genome mutations do not disrupt the structure of DNA or chromosomes. The cause of numerical changes in the karyotype is a violation of the mechanism of chromosome segregation during meiosis or mitosis. Like other mutations, genome mutations are a natural mechanism for increasing of genetic diversity in offspring. At the same time, humans usually have negative effects of any numerical deviations from the norm, for this reason, cytogenetic examination of aneuploidies is an important diagnostic tool in medical genetics.A change in the number of sex chromosomes is usually not lethal. The spectrum of detected deviations in the carrier is from inconstant impairment of reproduction but a normal phenotype to malformations of some internal organs, infertility and severe intellectual disabilities. Aneuploidies of autosomes are always a threat to life and health. Only autosomal trisomies on chromosomes 13, 18, 21 and 22 are compatible with live birth, there are solitary reports of the birth of children with polyploidies. At the same time, the prognosis of life is relatively favorable only in the case of trisomy 21, leading to the formation of Down syndrome. Other aneuploidies usually lead to spontaneous termination of pregnancy in the early stages and are discovered in samples of abortion material.In this regard, cytogenetic analysis of chromosomal aneuploidies is used to establish the genetic cause of anomalies and malformations in the postnatal period, delays in speech and psychomotor development, reproduction disorders in adults. Of particular importance is the cytogenetic analysis of the karyotype of embryos in the prenatal period. The proposed lecture analyzes the mechanism of formation of genomic mutations and their diversity. The possible medical consequences of the presence of various types of aneuploidies are considered. To the reader attention is offered syndromes associated with a change in the number of chromosomes in the karyotype. The description is illustrated by real images of patient karyotypes.The lecture is aimed primarily at students of medical and biological specialties, young specialists who plan to use cytogenetic research methods in their practical activities, and doctors who are faced with the need to analyze and interpret the results of cytogenetic analysis. To assimilate the material under discussion, it is recommended to familiarize yourself with the previous lecture of the cycle.

Microstructure and mechanical properties of laser DED produced crack-free Al 7075 alloy: Effect of process parameters and heat treatment

Laser directed energy deposition (DED) is an attractive additive manufacturing (AM) technique to fabricate high-strength Al 7075 alloy components for various applications. However, its poor weldability and easy occurrence of cracks during the highly non-equilibrium process have limited the adoption of this material for AM. In this research, various DED process conditions were employed to fabricate crack-free Al 7075 samples, and double aging combined with solution treatment was performed on the as-built materials thanks to the precipitation hardening nature of Al 7075. The influences of DED process parameters and heat treatment on microstructure and mechanical properties were investigated. It was found that the setting of laser power at 280 W and scanning speed at 500 mm/min led to crack-free material deposition with the highest density among all conditions investigated. Compared with the as-built Al 7075, the average micro-hardness of the alloy increased from 91.73 to 144.91 HV, and the ultimate tensile strength increased from 233.18 to 342.16 MP after heat treatment. Meanwhile, it was discovered that mass Cu elements are segregated at grain boundaries (GBs) for the as-built material. The existence of Al2Cu phase at GBs is believed to effectively mitigate the hot cracking, and the coherent strengthening mechanism of Cu segregation to the Al GBs is discussed. In addition, it was shown that Mg and Zn contents increased at the GBs after heat treatment, which tend to form precipitated phases and lead to the improved mechanical properties for DED produced Al 7075.

The influence of strain on phase stability in mixed-halide perovskites

<h2>Summary</h2> Lead halide perovskites are at the forefront of semiconductor research because of the tremendous efficiency increase of the corresponding devices together with low-cost fabrication. In sharp contrast with conventional semiconductors (e.g., silicon), they exhibit a soft and disordered lattice that directly affects their optoelectronic properties, making them particularly susceptible to strain. This perspective highlights the most common strategies to manipulate strain in lead halide perovskites at different length scales, focusing on how compressive and tensile strain affect ion migration and thereby undesired phase segregation in mixed-halide perovskites. We emphasize the role of the reduced unit cell volume and the polarizability of the lattice in the suppression of phase segregation. Finally, we highlight some of the most puzzling questions about the phase segregation mechanism, we propose targeted experiments for filling the gap in understanding, and we discuss the potential of using the apparent weaknesses of this class of materials (softness and phase segregation) as a strength.

A 3D cellular automata ore stockpile model – Part 1: Simulation of size segregation

This paper describes a 3D cellular automaton (CA) for modelling ore pile formation that incorporates size segregation due to surface stratification. Ore stockpiles and bins are essential in mining operations as a buffer between the mine and the mineral processing plant, and their operation plays an important role in the overall performance of the downstream equipment. Size segregation can occur if the feed size to the pile varies over time or due to a variety of segregation mechanisms occurring in the pile itself. In particular,it can occur as a result of percolation stratification within surface flows. The structure of the newly developed CA model is described, and the simulated surface profile and size segregation response is validated through a series of laboratory-scale piles for characterizing the segregation potential of the feed particles. It is found that the model adequately describes the segregation behaviour at a range of model scales where coarse particles roll to the outside of the pile and fine particles are concentrated around the centre of the pile. Moreover, it is found that the model is sufficiently fast to use in real-time applications such as dynamic process control and digital twins.

Towards the modeling of the interplay between radiation induced segregation and sink microstructure

Excess point defects created by irradiation in metallic alloys diffuse and annihilate at sinks available in the microstructure, such as grain boundaries, dislocations, or point defect clusters. Fluxes of defects create fluxes of alloying elements, leading to local changes of composition near the sinks and to a modification of the properties of the materials. The direction and the amplitude of this radiation-induced segregation, its tendency to produce an enrichment or a depletion of solute, depend on a set of transport coefficients that are very difficult to measure experimentally. The understanding of radiation-induced segregation phenomena has, however, made significant progress in recent years, thanks to the modeling at different scales of diffusion and segregation mechanisms. We review here these different advances and try to identify the key scientific issues that limit the development of predictive models, applicable to real alloys. The review addresses three main issues: the calculation of the transport coefficients from ab initio calculations, the modeling of segregation kinetics at static point defects sinks—mainly by kinetic Monte Carlo or diffusion-reaction models—and the more challenging task of modeling the dynamic interplay between radiation-induced segregation and sink microstructure evolution, especially when this evolution results from annihilation of point defects. From this overview of the current state-of-the-art in this field, we discuss still-open questions and guidelines for what constitutes, in our opinion, the desirable future works on this topic.

Investigation of local process in granular segregation based on discrete element method

The phenomenon of granular size segregation under vibration has plagued researchers due to the unsteady and high particle number concentration. Discrete element method (DEM) is employed to simulate the process of intruder rising through small background particles from the bottom to the top in a cylindrical container. To describe the segregation level during this process, a segregation evaluation parameter, α, is introduced. It is found that the granular process can be divided into two stages according to the evaluation of α, an initial stage (IS) and a stable intermediate stage (SIS). For a better understanding of the segregation process in these different stages, a new viewpoint focused on the local processes is presented in this article. The segregation mechanism is clarified through numerical simulation of local processes and reference to previous research results.

Reversible Phase Segregation and Amorphization of Mixed-Halide Perovskite Nanocrystals in Glass Matrices.

Mixed-halide perovskites have attracted great attention in applications of lighting and photovoltaic devices due to their excellent properties. Understanding the phase segregation mechanism of mixed-halide perovskite has significance for suppressing the performance degradation of optoelectronic devices. Herein, we investigate the mixed-halide perovskite nanocrystals (NCs) in isolation from the external factors (oxygen, moisture, and pressure) using glass encapsulation, which shows excellent photostability against phase segregation. By monitoring the structural evolution of the NCs in glass matrices, the coexisting phase segregation and amorphization of mixed-halide perovskites are observed in real-time. The results show that thermal-induced local temperature increase plays a dominant role in the phase segregation of mixed-halide perovskite NCs. The recovery process is driven by the spontaneous crystallization of the amorphous mixed-halide phase. The clarified dynamic equilibrium process between the compositional segregation (mixing) and structural disorder (order) gives us a better insight into the reversible phase segregation mechanism of mixed-halide perovskite.