Coagulation Rate Research Articles

Plasma‐Assisted Surface Modification and Heparin Immobilization: Dual‐Functionalized Blood‐Contacting Biomaterials with Improved Hemocompatibility and Antibacterial Features

AbstractThe inferior hemocompatibility or antibacterial properties of blood‐contacting materials and devices are restraining factors that hinder their successful clinical utilization. To highlight these, a plasma‐enhanced modification strategy is favored for surface tailoring of an extensively used biomaterial, polypropylene (PP). The surface activation of the PPs is achieved by oxygen plasma etching and subsequent surface functionalization through amine‐rich precursor mediated coating by plasma glow discharge. After optimum plasma processing parameters are decided, heparin (anticoagulant and antithrombic drug) is either attached or covalently conjugated on the PPs’ surfaces. The aminated films produced at 75 W plasma power with 15 min exposure time are highly hydrophilic (34.72 ± 5.92°) and surface active (65.91 mJ m−2), facilitating high capacity heparin immobilization (≈440 µg cm−2) by covalent linkage. The kinetic‐blood coagulation rate and protein adhesion amount on the plasma‐mediated heparinized PPs are decreased about tenfold and 15‐fold, and platelet adhesion is markedly lowered. In addition, heparinized‐PP surfaces comprise superior antibacterial activity against gram‐positive/‐negative bacteria conveyed particularly by contact‐killing (99%). The heparin‐coating did not cause cytotoxicity on fibroblast cells, instead enhanced their proliferation, as shown by the (3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐Diphenyltetrazolium Bromide) assay. Overall, this simple methodology is highly proficient in becoming a universal strategy for developing dual‐functionalized blood‐contacting materials.

The characters of dissolved organic matters from litter-mimic with the different humification states and their effects on drinking water treatment processes

Dissolved organic matter (DOM) is one kind of the main pollutant in surface water that will cause many problems during drinking water treatment processes. In this study, a simulated humification process of forest litter-mimic was investigated for eight weeks continuously to study the variations in chemical properties such as DOM composition, polysaccharide/protein ratio, average molecular weight, oxidation degree, hydrophilicity, etc., as well as the impact of these variations on the coagulation, ultra−/nanofiltration (UF/NF). Results showed that the removal rate of coagulation (from 67.5 % to 37.0 %) and UF (from 14.4 % to 5.8 %) decreased significantly during the humification process as a function of time, while the removal rate of NF increased from 40.0 % to 72.9 % at first, and then decreased to 47.4 %. This study gave a deep insight into the effect of DOM with different humification ages on the drinking water treatment process with the influence of seasons and vegetation around the water source, which finally aimed to improve drinking water treatment.

Large Eddy Simulation Studies on Effects of Soot Productivity in a Momentum Dominated Strained Diffusion Jet Flames

Abstract The present numerical study is to determine the soot volume fraction, rate of soot nucleation, rate of coagulation, rate of surface growth, and rate of surface oxidation for flame configurations having the fuel mixture composition of C2H4: H2: N2 (63.4: 4.7: 31.9% by mass) along with air. The Brookes–Moss–Hall and OH oxidation radical is coupled with the combustion and P−1 radiation model. The inputs needed for this numerical study to determine soot volume fraction are maintained the same as the earlier experimental conditions. The hyperbolic function in the governing models is interpolated with quadratic upwind interpolation for convective kinetics, diffusion function with second-order upwind in space, and bounded second-order implicit in time. A suitable pressure implicit method for splitting operators, and a pressure–velocity coupler are also incorporated to evaluate pressure to satisfy continuity. The above governing models are solved using the ILU method with a unity Courant–Friedrichs–Lewy number. It is observed that along the axial direction, the flame with 12,900 s−1 shows higher rate of soot nucleation and rate of soot coagulation compared with the flame having lower strain rate. Also, the highest strain rate flame shows the lowest rate of soot surface growth, and also the rate of soot oxidation is the least.

Coagulation Mechanism and Compressive Strength Characteristics Analysis of High-Strength Alkali-Activated Slag Grouting Material.

In deep coal mining, grouting reinforcement and water blockage are the most effective means for reinforcing the rock mass of extremely broken coal. However, traditional cement grouting materials are not suitable for use in complex strata because of their insufficient early mechanical strength and slow setting time. This study innovatively proposes using alkali-activated grouting material to compensate for the shortcomings of traditional grouting materials and strengthen the reinforcement of extremely unstable broken coal and rock mass. The alkali-activated grouting material was prepared using slag as raw material combined with sodium hydroxide and liquid sodium silicate activation. The compressive strength of specimens cured for 1 d, 3 d, and 28 d was regularly measured and the condensation behavior was analyzed. Using X-ray diffraction and scanning electron microscopy, formation behavior of mineral crystals and microstructure characteristics were further analyzed. The results showed that alkali-activated slag grouting material features prompt and high strength and offers the advantages of rapid setting and adjustable setting time. With an increase in sodium hydroxide content, the compressive strength first increased (maximum increase was 21.1%) and then decreased, while the setting time continued to shorten. With an increase in liquid sodium silicate level, the compressive strength increased significantly (and remained unchanged, maximum increase was 35.9%), while the setting time decreased significantly (and remained unchanged). X-ray diffraction analysis identified the formation of aluminosilicate minerals as the main reason for the excellent mechanical properties and accelerated coagulation rate.

Coagulation rate coefficients for fractal-like agglomerates in the diffusive and ballistic limits

Predicting agglomeration dynamics in aerosol or colloidal systems requires accurate models for the agglomerate collision rate. In the present work, numerical simulations cover the ballistic and the diffusive collision regimes as limiting cases and are used to derive coagulation rate coefficients for a large number of agglomerate sizes and morphologies. The simulations account for both the translational and rotational motion of agglomerates and allow for the monitoring of individual collision events. The results suggest that the power law suffices to characterize the clusters’ morphologies and that representative collision radii of agglomerates are mainly controlled by two parameters: (i) the radius of gyration, Rg, and (ii) the morphology characterized by the fractal dimension Df. Collision radii for the diffusive regime are up to 10% above the corresponding ballistic results and cluster rotation also increases the effective collision radius. The latter effect can lead to differences of up to 16% in the diffusive regime. In contrast, interpenetration effects, i.e. a small cluster passing through a larger cluster without collision, are less pronounced in the diffusive limit. The results provide strong correlations between collision radii and key parameters for both regimes such that improved analytical expressions for the coagulation rate coefficients can be suggested. Compared to existing models for the ballistic and diffusive regimes, the proposed correlations offer reduced complexity across an extended range of the relevant parameter space.

Clinical Application of a Safe Blood Sampling Device with an Indwelling Needle.

Background The traditional indwelling needle catheter is hard and can only complete one puncture at a time. The safety and indwelling needle catheter is soft, with a large lumen, with high success rate of blood collection, and one puncture completes two operations, so it is of important value and significance to study the new safety and indwelling needle. To explore the clinical utility of a novel blood collection device with indwelling needle for blood collection among pediatric patients. Methods A total of 300 children who were admitted to the children's hospital from March to June 2020 were selected and randomly divided into the control group (148) and the observation group (152). The control group received venipuncture using regular needles for infusion and blood collection. For the observation group, a modified indwelling needle device was used for the procedures. Comparisons were made between the two devices in five aspects: blood sample quality, operation time, needlestick incidence, related complications, and patient satisfaction. Results There was no significant difference in coagulation rate between the two groups, but slightly lower overall hemolysis incidence in the observation group. The unqualified rate of blood specimens collected in the observation group was 10.0% lower than that in the control group (P < 0.05). Shorter operation time, lower incidence of needlestick injuries, and improved satisfaction were observed in the group using the novel blood collection device. Conclusions This modified blood collection device is superior to the regular venipuncture needle, in terms of safety, efficiency, and patient satisfaction; thus, it has potential for broad clinical applications for infusion and blood collection.

Effect of pH value on the coagulation kinetics of phenol formaldehyde resin dispersion

Phenol-formaldehyde resin (PFR) has been synthesized in a reaction catalyzed with NaOH. The molecular structures of PFR were investigated using Fourier transform infrared spectroscopy (FTIR) and high performance liquid chromatography-mass spectrometry (HPLC-MS). In this study, the size of PFR aggregates were measured by a dynamic light scattering technique (DLS) in order to elucidate the dispersion performance of PFR dispersed in water. The coagulation behavior of the PFR aggregates with various pH values, valences and concentrations of H+ were investigated using DLS. The highest coagulation rate (ddt) at different pH values followed the order of: acidic > alkaline, which can be explained by the effects of electrostatic repulsion at protonation states of phenolic –OH groups. The coagulation phenomenon appeared at pH values less than 7. The fractal dimension df ≈ 2.1 could be determined for reaction-linked colloid aggregation (RLCA) when pH < 7. These results indicated that PFR had a coagulation behavior which could be exploited in enhanced oil recovery (EOR) processes.

Impact of the coagulation of dust particles on Mars during the 2018 global dust storm

Coagulation of particles occurs when two particles collide and stick together. In the Martian atmosphere, coagulation of dust would increase the dust effective particle size, as small particles accrete to larger particles. Murphy et al. (1990) concluded that Brownian coagulation of dust in the Martian atmosphere was not significant, due to the low dust particle mixing ratios, while Montmessin et al. (2002) and Fedorova et al. (2014) showed that it mostly involves dust particle radii smaller than 0.1 μm. However, the effects of coagulation have never been explored in 3D, during a global dust storm, and in presence of larger numbers of small particles. Here we revisit this issue by using the NASA Ames Mars Global Climate Model (MGCM) to investigate the temporal and spatial changes in dust particle sizes during the 2018 global dust storm due to dust coagulation and the overall impact of these processes on Mars' climate. Our parameterization for dust coagulation includes the effect of Brownian motion, Brownian diffusion enhancement, and gravitational collection. We show that Brownian motion and Brownian diffusion enhancement dominate gravitational collection. Coagulation has a significant impact during the global storm, with coagulation rates increased by a factor of 10 compared to non-storm conditions. The mean effective particle radius can be increased by a factor of up to 2 due to coagulation, leading to a 20 K colder atmosphere above 30 km altitude. Overall, our parameterization improves the representation of the decay phase of the storm relative to MCS dust observations. Coagulation also remains a significant process affecting dust outside the storm period if large numbers of submicron-sized particles are involved. As coagulation removes the small sub-micron particles within a relatively short time, it may therefore be possible, in GCMs, to lift larger amounts of submicron-sized particles from the surface without excess dust buildup in the atmosphere, thus improving the agreement with some of the observations without diverging from the observed column opacities.

Zeolite fly ash-enhanced coagulation treatment of oil recovery wastewater from polymer flooding.

Herein, an enhanced coagulation model is proposed in which zeolite is used as a crystal nucleus to promote flocs. The zeolite is prepared from fly ash by microwave-assisted hydrothermal synthesis. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and specific surface area and pore size analysis (BET) characterization confirmed the successful synthesis of ZFA, and improved the surface properties. Thus, the adsorption capacity of ZFA as crystal nucleus was improved, which enabled it to achieve better results in the process of enhanced coagulation. Compared with those of conventional coagulation, the oil content and SS removal rate of ZFA-enhanced coagulation increased by 85% and 44%, respectively. Compared with that of CFA-enhanced coagulation, the oil removal efficiency increased by 4%, and the SS removal efficiency increased by 9%. The optimal conditions of ZFA-enhanced coagulation were as follows: ZFA dosage of 100mg/L, pH value of 5-8, ZFA particle size range of 60-75μm, temperature of 40-50 ℃, and precipitation time of 30min.

Brownian coagulation of like-charged aerosol particles

In this study we explore the role of Brownian coagulation on bidisperse like-charged spherical particles interacting via non-continuum hydrodynamics interactions. It is well established in the existing literature that van der Waals interactions enhance the coagulation rate. However, the role of near-field attractive electrostatic forces on the pair interactions of like-charged aerosols is relatively less explored. We have found that electrostatic interactions enhance the coagulation rate between like-charged Brownian particles while interacting through non-continuum hydrodynamics.

Hemostatic cotton based on biocompatible poly(vinyl alcohol)/soluble starch-fish skin collagen composites

Fish skin collagen has attracted a wide range of attention in the field of hemostatic materials due to its excellent biocompatibility and hemostatic performance. In this work, the hemostatic cotton based on poly(vinyl alcohol)/soluble starch-fish skin collagen (PVA/SS-FSC) composites was prepared by solvent displacement followed by lyophilization. The experimental results showed that the PVA/SS enabled the composite material to have 3-D porous structures. When compounding with FSC, PVA/SS-FSC(1) composite cotton (mass ratio 1:1:1) possessed 3-D porous structures, good water absorption, and no cytotoxicity or hemolytic properties. In vitro and in vivo experiments demonstrated that the PVA/SS-FSC(1) hemostatic cotton accelerated the coagulation rate, reduced blood loss, and improved the hemostatic efficiency. Furthermore, arterial hemostasis tests in rats confirmed that the PVA/SS-FSC(1) hemostatic cotton afforded a shorter hemostasis time (64 ± 7 s) and lower blood loss (323 ± 38 mg) compared with commercial hemostatic gauze (210 ± 12 s and 840 ± 41 mg, respectively), thus indicating promising applications in rapid wound hemostasis.

The response of soft tissue cells to Ti implants is modulated by blood-implant interactions.

Titanium-based dental implants have been highly optimized to enhance osseointegration, but little attention has been given to the soft tissue-implant interface, despite being a major contributor to long term implant stability. This is strongly linked to a lack of model systems that enable the reliable evaluation of soft tissue-implant interactions. Current in vitro platforms to assess these interactions are very simplistic, thus suffering from limited biological relevance and sensitivity to varying implant surface properties. The aim of this study was to investigate how blood-implant interactions affect downstream responses of different soft tissue cells to implants in vitro, thus taking into account not only the early events of blood coagulation upon implantation, but also the multicellular nature of soft tissue. For this, three surfaces (smooth and hydrophobic; rough and hydrophobic; rough and hydrophilic with nanostructures), which reflect a wide range of implant surface properties, were used to study blood-material interactions as well as cell-material interactions in the presence and absence of blood. Rough surfaces stimulated denser fibrin network formation compared to smooth surfaces and hydrophilicity accelerated the rate of blood coagulation compared to hydrophobic surfaces. In the absence of blood, smooth surfaces supported enhanced attachment of human gingival fibroblasts and keratinocytes, but limited changes in gene expression and cytokine production were observed between surfaces. In the presence of blood, rough surfaces supported enhanced fibroblast attachment and stimulated a stronger anti-inflammatory response from macrophage-like cells than smooth surfaces, but only smooth surfaces were capable of supporting long-term keratinocyte attachment and formation of a layer of epithelial cells. These findings indicate that surface properties not only govern blood-implant interactions, but that this can in turn also significantly modulate subsequent soft tissue cell-implant interactions.

Modeling particle-particle binary coagulation rate constants for spherical aerosol particles at high volume fractions using Langevin Dynamics simulations

Effect of volume-fraction and particle-particle hydrodynamic interactions on the coagulation rate of particles are investigated. Particle coagulation is modeled using Langevin Dynamics (LD) based trajectory simulations of N mono-sized spherical particles in a periodic domain. The extended Kirkwood-Risemann approach (J. Fluid Mechanics 855, 535 (2018)) is invoked to compute particle-particle hydrodynamic interactions whose effect is parameterized as a function of the momentum Knudsen number (Kn). The results are summarized as a model for coagulation rate constant (βij) that depends on the diffusive Knudsen number (KnD) used in prior work to parameterize coagulation in the dilute regime (Aerosol Sci. Tech. 45, 1499 (2011)), Kn and particle volume-fraction ηv. In the absence of hydrodynamic interactions, it is observed that the coagulation rate constant in the continuum limit for mass transfer (KnD→0) is significantly enhanced by a factor of ∼80 at ηv∼0.3 due to particle crowding. While considering hydrodynamic interactions for ηv≥0.05, we use a screening distance around each particle that scales inversely with ηv beyond which the contribution of farther neighbors is neglected owing to the rapid decay of hydrodynamic interactions with distance. We also present new LD calculations of βij and elucidate the dependence of the same on Kn1 and the particle radii ratio θr for the coagulation of two particles in the dilute limit ηv→0. It is observed that the reduction of βij becomes significant as Kn1→0: at the lowest momentum Knudsen number considered (Kn1=0.1): βij is reduced by a factor of ∼10 for equally sized particles (θr=0.5). At high KnD,Kn1, the particle size disparity is not significant, and it is seen that βij matches hard sphere predictions, indicating the insignificant contributions by hydrodynamic interactions. A series of animations of 2-particle simulations are presented as part of the Supplemental Information to illustrate the role of hydrodynamic interactions in particle coagulation. Computational results are summarized as regressions for convenient incorporation into particle/droplet growth sectional models.

Microstructure and mechanical properties of V–Cr–Zr alloy with carbide and oxide strengthening

A comparative study of the effectiveness of carbide and oxide types of strengthening of V–Cr–Zr alloy was carried out by means of a comprehensive certification of structural-phase state parameters and measuring the mechanical properties characteristics. It has been shown that the use of chemical-heat treatment contributes to a significant increase in the thermal stability of the microstructure and mechanical properties of V–Cr–Zr alloy in comparison with carbide strengthening under the conditions of thermomechanical treatment. A controlled increase in the volume fraction of fine particles based on ZrO2, along with an increase in the concentration of oxygen in the solid solution, leads to a decrease in the rate of oxides coagulation and an increase in the thermal stability of high disperse heterophase structure. These effects contribute to the retention of high defect structural states with nonzero values of crystal lattice curvature even after high-temperature (0.67 Tmelt) anneals. The high efficiency of dispersion and substructural strengthening is a consequence of blocking dislocation slip by fine particles stabilized by oxygen in a solid solution.

Enhanced Performance of Natural Polymer Coagulants for Dye Removal from Wastewater: Coagulation Kinetics, and Mathematical Modelling Approach

This study explores the potentials of Brachystegia eurycoma coagulant (BEC) and Vigna subterranean coagulant (VSC) as natural organic polymers (NOPs) for the decolourisation of Crystal Ponceau 6R (AR 44) in wastewater. Materials characterisation studies were done on the precursors. A detailed kinetics study was employed. The decolourisation procedures were evaluated through time-dependent reduction in the concentration of particles, with the variation of the independent parameters. The proximate analysis showed protein contents of 19.77% and 18.15% for BEC and VSC, respectively. The functional test showed the presence of –OH, N–H, and C=H. The surface morphological study revealed some rough surfaces, different pores sizes, and compact-net structures. The order of removal efficiency was VSC > BEC with an optimum of 88.8% and 73.3%, respectively. The values of the coagulation rate constant (K) and coagulation order (α) obtained for BEC and VSC were 6.38 × 10− 4 L mg− 1 min− 1, 1.8 and 4.03 × 10− 3 L mg− 1 min− 1, 1.9, respectively. The coagulation time, T ag of 31.35 and 26.96 min for BEC and VSC, respectively, disclosed quick coagulation. The coagulation-flocculation kinetics demonstrated that the process conforms to the pseudo-second-order model with R 2 >0.997, suggesting that the rate-controlling mechanism is governed by chemisorption. In the mass transfer study, experimental data were well predicted by the cross-validation test, with a percentage mean relative deviation modulus (M%) of 3.26 and 2.54 for BEC and VSC, respectively. These coagulants added meaningful progress in wastewater treatment by coagulation-flocculation while displaying significant adsorption features. Likewise, the usage of kinetics studies and particle behaviour modelling should be a prerequisite in water treatment processes.

Intricate relations among particle collision, relative motion and clustering in turbulent clouds: computational observation and theory

Abstract. Considering turbulent clouds containing small inertial particles, we investigate the effect of particle collision, in particular collision–coagulation, on particle clustering and particle relative motion. We perform direct numerical simulation (DNS) of coagulating particles in isotropic turbulent flow in the regime of small Stokes number (St=0.001–0.54) and find that, due to collision–coagulation, the radial distribution functions (RDFs) fall off dramatically at scales r∼d (where d is the particle diameter) to small but finite values, while the mean radial component of the particle relative velocity (MRV) increases sharply in magnitude. Based on a previously proposed Fokker–Planck (drift-diffusion) framework, we derive a theoretical account of the relationship among particle collision–coagulation rate, RDF and MRV. The theory includes contributions from turbulent fluctuations absent in earlier mean-field theories. We show numerically that the theory accurately accounts for the DNS results (i.e., given an accurate RDF, the theory could produce an accurate MRV). Separately, we also propose a phenomenological model that could directly predict MRV and find that it is accurate when calibrated using fourth moments of the fluid velocities. We use the model to derive a general solution of RDF. We uncover a paradox: the past empirical success of the differential version of the theory is theoretically unjustified. We see a further shape-preserving reduction of the RDF (and MRV) when the gravitational settling parameter (Sg) is of order O(1). Our results demonstrate strong coupling between RDF and MRV and imply that earlier isolated studies on either RDF or MRV have limited relevance for predicting particle collision rate.

Mannose 2, 3, 4, 5, 6-O-pentasulfate (MPS): a partial activator of human heparin cofactor II with anticoagulation potential

Thromboembolic diseases are a major cause of mortality in human and the currently available anticoagulants are associated with various drawbacks, therefore the search for anticoagulants that have better safety profile is highly desirable. Compounds that are part of the dietary routine can be modified to possibly increase their anticoagulant potential. We show mannose 2,3,4,5,6-O-pentasulfate (MPS) as a synthetically modified form of mannose that has appreciable anticoagulation properties. An in silico study identified that mannose in sulfated form can bind effectively to the heparin-binding site of antithrombin (ATIII) and heparin cofactor II (HCII). Mannose was sulfated using a simple sulfation strategy-involving triethylamine-sulfur trioxide adduct. HCII and ATIII were purified from human plasma and the binding analysis using fluorometer and isothermal calorimetry showed that MPS binds at a unique site. A thrombin inhibition analysis using the chromogenic substrate showed that MPS partially enhances the activity of HCII. Further an assessment of in vitro blood coagulation assays using human plasma showed that the activated partial thromboplastin time (APTT) and prothrombin time (PT) were prolonged in the presence of MPS. A molecular dynamics simulation analysis of the HCII-MPS complex showed fluctuations in a N-terminal loop and the cofactor binding site of HCII. The results indicate that MPS is a promising lead due to its effect on the in vitro coagulation rate. Communicated by Ramaswamy H. Sarma

Diamond particles aggregation in aqueous electrolytes with multivalent ions

In this article certain features of the electro-orientation effect are used to study the kinetics of coagulation in diamond colloidal dispersions. The results of a study of the influence of multivalent ions on the formation of paired aggregates from diamond particles in colloidal systems are presented. A technique was developed for studying the rate of coagulation at the early stages, using the relaxation dependences of electro-optical effects. The effect of aqueous electrolytes on the rate of formation of paired aggregates from diamond particles has been studied. It is shown that the rate of formation of paired aggregates at the isoelectric point is consistent with the theory of rapid coagulation. Based on electro-optical studies of the polarizability anisotropy of individual particles and paired aggregates from them, it was assumed that the polarizability anisotropy of a paired aggregate is lower than the polarizability anisotropy of an individual particle with volume and shape close to that of an aggregate. The rates of coagulation of colloidal systems of diamond and graphite with the same particle number concentration and size are compared. It is shown that at the isoelectric point the coagulation period of graphite colloid is five times shorter than the coagulation period of diamond colloid.

Drag and lift forces acting on linear and irregular agglomerates formed by spherical particles

Nano- and micrometer particles tend to stick together to form agglomerates in the presence of attractions. An accurate calculation of the drag and lift forces on an agglomerate is a key step for predicting the sedimentation rate, the coagulation rate, the diffusion coefficient, and the mobility of the agglomerate. In this work, particle-resolved direct numerical simulation is used to calculate the drag and lift forces acting on linear and irregular agglomerates formed by spherical particles. For linear agglomerates, the drag coefficient CD follows the sine squared function of the incident angle. The ratio between CD of a linear agglomerate and that for a sphere increases with the agglomerate size, and the increasing rate is a function of the Reynolds number and the incident angle. Based on this observation, explicit expressions are proposed for CD of linear agglomerates at two reference incident angles, 60° and 90°, from which CD at any incident angle can be predicted. A new correlation is also proposed to predict the lift coefficient CL for linear agglomerates. The relative errors for the drag and lift correlations are ∼2.3% and ∼4.3%, respectively. The drag coefficient for irregular agglomerates of arbitrary shape is then formulated based on the sphericity and the crosswise sphericity of agglomerates with a relative error of ∼4.0%. Finally, the distribution of the lift coefficient for irregular agglomerates is presented, which is non-Gaussian and strongly depends on the structure. The mean values and the standard deviations of CL can be well correlated with the Reynolds number.

The symmetric coalescent and Wright–Fisher models with bottlenecks

We define a new class of Ξ-coalescents characterized by a possibly infinite measure over the nonnegative integers. We call them symmetric coalescents since they are the unique family of exchangeable coalescents satisfying a symmetry property on their coagulation rates: they are invariant under any transformation that consists of moving one element from one block to another without changing the total number of blocks. We illustrate the diversity of behaviors of this family of processes by introducing and studying a one parameter subclass, the (β,S)-coalescents. We also embed this family in a larger class of Ξ-coalescents arising as the limit genealogies of Wright–Fisher models with bottlenecks. Some convergence results rely on a new Skorokhod type metric, that induces the Meyer–Zheng topology, which allows us to study the scaling limit of non-Markovian processes using standard techniques.