Aggregation Of Suspensions Research Articles

The efficacy of fetal neural cell aggregates and their combination with fetal liver stromal cells to reduce brain damage after intracerebral hemorrhage in rats

Patients with intracerebral hemorrhage have frequent complications and high mortality. There are currently no effective treatments for this disease. We investigated the effect of the use of cryopreserved aggregates of neural cells in combination with fetal liver stromal cells on the reduction of rat brain injury after intracerebral hemorrhage. Methods. Intracerebral hemorrhage (ICH) was modeled in rats by stereotactic administration of 0.2 U of collagenase type IV into the striatum. Neural cell obtained from brain and stromal cells (SCs) – from liver of rat fetuses of 15 dpc. The suspension of neural cell aggregates (NCAs) alone or in combination with fetal liver stromal cells was injected into the lateral ventricle. The level of lipid peroxidation was determined by the thiobarbituric acid test. The degree of brain cells injury after ICH was determined by the activity of lactate dehydrogenase in blood serum. To assess the intensity of adverse factors and the regenerative potential of different variants of cell therapy, the area of the lost striatum in the rat brain and the average distance from the border of the lesion to the nearest neurons were determined. Results. Combined transplantation of NCAs with fetal liver SCs in rats with ICH was found to reduce malonic dialdehyde concentration and lactate dehydrogenase activity more effectively than NCAs alone, indicating inhibition of lipid peroxidation and reduction of cell injury after intracerebral hemorrhage as a result of the addition of SCs. It was shown a significant decrease in the area of lost striatum in both experimental groups. The single administration of NCAs reduced the distance from the lesion border to the nearest neurons the most, indicating the best conditions for survival and/or regeneration of neurons close to the lesion compared to controls. Conclusions. Administration of NCAs, both alone and in combination with fetal liver SCs, reduces the intensity of oxidative stress, preserves the intact striatum tissue, and increases the number of neurons near the brain lesion in intracerebral hemorrhage in rats. The co-transplantation of fetal liver SCs helps to inhibit lipid peroxidation more effectively.

Aggregation and breakup of colloidal particle aggregates in shear flow: A combined Monte Carlo - Stokesian dynamics approach

A method for the simulation of aggregation and breakup processes in colloidal particle suspensions is presented. The method combines a Monte Carlo algorithm to determine, on the basis of probabilistic considerations, the sequence of aggregation and breakup events, and a Discrete Element Method, built in the framework of Stokesian dynamics and contact mechanics, to accurately reproduce them. Liquid-solid suspensions subject to a uniform shear stress are investigated. The model is seen to be able to reproduce the typical dynamic steady state which is observed in colloidal suspensions under severe shearing, in which the effects of aggregation and breakup balance each other. The structural properties of the aggregates and the dynamics of the aggregation and breakup phenomena are characterized in detail. Both fragmentation and erosion are seen to contribute to the breakup process, which is characterized by an exponent similar to the one reported in the literature for compact clusters.

The mechanisms of gravity-constrained aggregation in natural colloidal suspensions

Colloidal settlement in natural aqueous suspensions is effectively compensated by diffusive movement if particles resist aggregation – a state known as colloidal stability. However, if the settling velocity increases upon aggregation, complex structural features emerge from the directional movement induced by gravity. We present a comprehensive modeling study on the evolution of an aggregated three-dimensional structure due to diffusion, surface interactions, and gravity. The systematic investigation of particle geometry and size revealed three mechanisms: (I) aggregation due to spatial confinement of settled particles, (II) aggregation due to differential settling, whereby fast and slow particles collide, (III) inhibition of aggregation due to fractionation of particles with different settling velocity. A 3D visualization tool allowed us to follow the subtle interplay of these mechanisms and the highly dynamic hierarchical self-assembly of aggregates. It revealed how the balance of the different interactions determines the actual rate of aggregation.

A Molecular Communication Detection Method for the Deformability of Erythrocyte Membrane in Blood Vessels.

Molecular communication (MC) inspired drug delivery holds considerable promise as a new design for targeted therapy with high efficiency and minimal toxicity. The process of drug delivery can be modelled in a blood flow-based MC system, where nanoparticles (NPs) carry therapeutic agents through the blood vessel channels to the targeted diseased tissue. Most previous studies in the flow-based MC consider a Newtonian fluid with a laminar flow, which ignores the influence of red blood cells (RBCs). However, the nature of blood flow is a complex and non-Newtonian fluid composed of proteins, platelets, plasma and deformable cells, especially RBCs. The ability to change their shapes is essential to the proper functioning of RBCs in the microvasculature. Different shapes of RBCs have a great impact on the performance of blood flow. Changes in the properties and shapes of RBCs are often associated with different diseases, such as sickle cell anemia, diabetes, and malaria. Thus, it is highly important to establish a more realistic blood flow MC model considering the deformable cells. According to our previous study, the motion and adhesion of individual NPs are modelled through the Brownian adhesion dynamics. Subsequently, this paper establishes a particle-cell hybrid model in the flow-based MC, which focuses on the RBC deformation, aggregation, and dispersion in the blood suspension. Based on the state of the RBC deformation and aggregation in the vessels with different flow rates, this paper proposes a novel methodology for detecting the deformability of the cells. The blood state in terms of RBC deformability is determined by the difference in NPs' concentration at the receiving end., this paper sheds some light on the influence of RBCs on the motion of NPs, which provides new insights on the design of targeted drug delivery and the detection of vascular diseases.

Rheological properties of peanut protein isolate aggregation suspension and acid-induced gel

The dynamic rheological properties of peanut protein isolate (PPI) suspension and acid-induced PPI gels were studied. In frequency sweep test, the storage modulus (G′) and the loss modulus (G″) of PPI aggregation suspensions at different concentrations increased with the increase of frequency. The steady state shear flow test showed that PPI aggregation suspension had a thinning behavior of the shear, and the image of steady shear curve fitted the Carreau model. After gel formation, acid-induced PPI gels showed a typical Type I behavior (strain thinning) in strain sweep test, meaning that PPI gel got easily broken down, and there was a very small opportunity for the protein molecules to re-establish the network. Compared with the strain sweep of PPI aggregation suspensions and gels, the range of the storage modulus existed a dramatic difference, which could get about tenfold. As the frequency increased, both elasticity and viscosity increased in frequency sweep test, which indicated that the frequency dependence of the storage modulus increased with the increase of concentration. Keywords: peanut protein isolate (PPI), aggregation suspension, acid-induced PPI gel, dynamic rheological properties DOI: 10.25165/j.ijabe.20211403.6021 Citation: Huang Z G, Wang X Y, Chi S Y, Hua Z, Bi C H. Rheological properties of peanut protein isolate aggregation suspension and acid-induced gel. Int J Agric & Biol Eng, 2021; 14(3): 255–260.

Onsager's variational principle in active soft matter.

Onsagers variational principle (OVP) was originally proposed by Lars Onsager in 1931 [L. Onsager, Phys. Rev., 1931, 37, 405]. This fundamental principle provides a very powerful tool for formulating thermodynamically consistent models. It can also be employed to find approximate solutions, especially in the study of soft matter dynamics. In this work, OVP is extended and applied to the dynamic modeling of active soft matter such as suspensions of bacteria and aggregates of animal cells. We first extend the general formulation of OVP to active matter dynamics where active forces are included as external non-conservative forces. We then use OVP to analyze the directional motion of individual active units: a molecular motor walking on a stiff biofilament and a toy two-sphere microswimmer. Next we use OVP to formulate a diffuse-interface model for an active polar droplet on a solid substrate. In addition to the generalized hydrodynamic equations for active polar fluids in the bulk region, we have also derived thermodynamically consistent boundary conditions. Finally, we consider the dynamics of a thin active polar droplet under the lubrication approximation. We use OVP to derive a generalized thin film equation and then employ OVP as an approximation tool to find the spreading laws for the thin active polar droplet. By incorporating the activity of biological systems into OVP, we develop a general approach to construct thermodynamically consistent models for better understanding the emergent behaviors of individual animal cells and cell aggregates or tissues.

Effect of pH, ionic strength, and freezing treatment on a colloidal suspension of egg white aggregates

• pH and ionic strength effected egg white suspensions under frozen condition. • Number of egg white aggregates decreased during freezing process. • Surface characteristic was modified by freezing, pH, and ionic strength. • Modification of egg white aggregation affected foam stability. Characteristics of protein colloidal suspensions can be modified by freezing treatment. In this study, different colloidal suspensions of egg white aggregates (with different pH levels and ionic strengths) were frozen for several days, after which the colloidal suspensions were analyzed by a tunable resistive pulse sensing device to detect changes in particle characteristics. The average particle diameter in suspension increased with an enhancement in ionic strength. Particle number concentration decreased during five days of freezing treatment. The same colloidal suspensions were also analyzed using a small-angle X-ray scattering device. The results indicate that the inner structure was influenced by pH but did not change during the freezing process. The stability of foam made from frozen-thawed suspensions also increased with the enhancement of ionic strength. Based on these results, it appears that by controlling pH levels, ionic strength, and freezing time, the characteristics of egg white aggregates can be modified by freezing.

A biomimetic model of 3D fluid extracellular macromolecular crowding microenvironment fine-tunes ovarian cancer cells dissemination phenotype

An early fundamental step in ovarian cancer progression is the dissemination of cancer cells through liquid environments, one of them being cancer ascites accumulated in the peritoneal cavity. These biological fluids are highly crowded with a high total macromolecule concentration. This biophysical property of fluids is widely used in tissue engineering for a few decades now, yet is largely underrated in cancer biomimetic models. To unravel the role of fluids extracellular macromolecular crowding (MMC), we exposed ovarian cancer cells (OCC) to high molecular weight inert polymer solutions. High macromolecular composition of extracellular liquid presented a differential effect: i) it impeded non-adherent OCC aggregation in suspension and, decreased their adhesion; ii) it promoted adherent OCC migration by decreasing extracellular matrix deposition. Besides, there seemed to be a direct link between the extracellular MMC and intracellular processes, especially the actin cytoskeleton organization and the nucleus morphology. In conclusion, extracellular fluid MMC orients OCC dissemination phenotype. Integrating MMC seems crucial to produce more relevant mimetic 3D in vitro fluid models to study ovarian dissemination but also to screen drugs.

Rheological properties and fractal-rheology analysis of peanut protein isolate suspension

This study focuses on the non-linear rheological property and microstructure of peanut protein isolate (PPI) aggregation suspension. The impact of higher harmonics (I3 and I5) on fundamental stress wave during large amplitude oscillatory shear test was studied. Rheological test show that storage modulus G′ and loss modulus G″ increased with increasing PPI concentration. The non-linear viscoelastic properties of PPI suspension with different concentration were investigated. Using confocal laser-scanning microscopy method, this research explored the microstructure of PPI suspension as well as the fractal dimensions. The new critical strain indirect method combined with Wu-Morbidelli model to calculate the fractal dimension (2.9225) is very close to the actual fractal dimension (2.9206). Fourier Transform Rheology was adopted to get the new critical strain for fractal dimension calculation, which was proved to be feasible. Keywords: peanut protein isolate suspension, rheological property, microstructure, fractal analysis DOI: 10.25165/j.ijabe.20201306.5717 Citation: Bi C H, Chi S Y, Hua Z, Li D, Huang Z G, Liu Y. Rheological properties and fractal-rheology analysis of peanut protein isolate suspension. Int J Agric & Biol Eng, 2020; 13(6): 220–226.

Unveiling the future reservoir of anti-cancer molecule—Combretastatin A4 from callus and cell aggregate suspension culture of flame creeper (Combretum microphyllum): growth, exudation and elicitation studies

Combretastatin A4 (CA4), a natural stilbenoid molecule, has currently gained noticeable prominence for holding outstanding anti-angiogenic and selective vascular-targeting competency combined with renowned potential to prevent tumour metastasis. Efficacious preclinical insights against several types of cancer revealed better druggability potentials of specialized derivative(s) of this molecule. Considering such therapeutic significance and scanty natural availability, the competence of callus and compact cell aggregates (CCA)—suspension cultures of Combretum microphyllum had been explored revealing their untouched potentials as effective production alternatives for CA4. The CCA-suspension culture accumulated the highest amount of the CA4 (2.29 ± 0.04 mg/g DW) at 12 weeks cultivation period, which was 2.26 fold higher over that in 3 years old in-vivo plant leaves (1.01 ± 0.05 mg/g DW). In comparison, the calli (grown with TDZ) showed 1.89 fold lesser yield of CA4 (1.21 ± 0.05 mg/g DW) than the CCA-suspension culture. Exudation of CA4 in CCA-suspension cultures was evident throughout culture duration with the highest level (70.03%) at the maximum production phase. Compared to untreated control CCA-suspension culture, methyl-jasmonate (MeJ) elicitation first time ascertained 2.26 fold improvement of CA4 yield with noticeable stimulation of exudation. Observably, the longer duration (48hrs) and the higher dose (200 µm) of MeJ treatment proved optimum for the maximum enhancement of CA4 yield in CCA-suspension cultures. Present findings unveiled an unprecedented avenue towards fulfilling the rising commercial requirement of CA4 for future anti-cancer drug development processes through strategic implementation of in-vitro cultures options in C. microphyllum including MeJ elicitation and exudation. First report of a leading anti-cancer molecule- Combretastatin A4 synthesis in Combretum microphyllum through calli and compact cell aggregate-suspension cultures with promising yield improvement benefits through exudation and MeJ elicitation.

Distribution and Diversity of Coccolithophores in Surface Sediments of the Northern Red Sea: Coccolith Accumulation in Brine Pools and Observation of Productivity

A quantitative analysis of coccoliths is presented in 18 core-top samples ranging between 26° N and 21° N and covering two major deep brine pools in the northern part of the Red Sea. Non-brine sites are characterized by rich coccoliths that may reach up to 3.31 × 109 coccoliths/g made by 22 species, whereas brine sites of Shaban and Kebrit Deeps with additional two non-brine sites are characterized by a decline in coccoliths/g (3.25 × 108 coccoliths/g), Shannon diversity, CaCO3 (%), and high TOC (%). Carbonate dissolution, inferred by qualitative observation and quantitative indices, was only observed at one brine site GeoB7828 in Kebrit Deep. This suggests that the decline in coccolith assemblages may not entirely be attributed to carbonate dissolution. The major decline, however, is probably related to the suspension of fecal pellets and marine aggregates containing delicate coccolith shields within a nepheloid layer and subsequently grazed by zooplankters in which reduced the numbers of coccolith that reached the bottom of the brine sites, or alternatively a deep-sea flow current that carried and remobilized some suspended particles outside the brine pool. Latitudinal fluctuations of eutrophic/oligotrophic coccoliths suggest profound trophic changes in the photic zone in the northern part of the Red Sea. C. braarudii, a valuable nutrient-indicator species is here reported for the first time, along with G. oceanica, H. carteri as well as biogenic opal dominating the assemblage between 26° N and 24° N, suggesting elevated nutrient conditions and supporting recent high chl-a records, whereas areas between 21° N and 23° N lie under oligotrophic conditions due to the presence of U. sibogae, U. tenuis, R. clavigera, F. profunda, and S. pulchra.

Global 5-methylcytosine and physiological changes are triggers of indirect somatic embryogenesis in Coffea canephora.

Indirect somatic embryogenesis (ISE) establishment for Coffea species started in the 1970s. Since then, intraspecific variations in the morphogenic pathway have been reported, even in the common environmental condition in vitro. Several authors have suggested that these variations are the result of genetic, epigenetic, and/or physiological events, highlighting the need for investigations to know the causes. Along these lines, this study aimed to investigate and describe, for the first time, the global 5-methylcytosine and physiological changes that occur in the cells of the aggregate suspensions of Coffea canephora during proliferation and somatic embryo regeneration steps. The cell proliferation step was characterized by increase in cell mass in all subcultures; relatively low mean values of global 5-methylcytosine (5-mC%), abscisic acid (ABA), and indole-3-acetic acid (IAA); high mean value of 1-aminocyclopropane-1-carboxylic acid (ACC, an ethylene precursor); and increase followed by decrease in spermidine (Spd, a polyamine) level. Therefore, these epigenetic and physiologic aspects promoted the cell proliferation, which is fundamental for ISE. In turn, the somatic embryo regeneration was correlated with global 5-mC% and physiological changes. The competence acquisition, determination, and cell differentiation steps were marked by increases in mean values of 5-mC%, IAA and ABA, and decreases in ACC and Spd, evincing that these changes are the triggers for regeneration and maturation of somatic embryos. Therefore, dynamic and coordinated epigenetic and physiologic changes occur in the cells of the aggregate suspensions during the C. canephora ISE in liquid system.

Highly crystalline MAPbI3 perovskite grain formation by irreversible poor-solvent diffusion aggregation, for efficient solar cell fabrication

Energy efficient synthesis providing high quality crystalline thin films are highly desired in many applications. Here we devise a non-toxic solvent approach for production of highly crystalline MAPbI 3 perovskite by exploiting diffusion aggregation processes. Isopropanol solution based methylammonium lead triiodide (MAPbI 3 ) is used in this context, where the crystal growth initiation starts in an unstable suspension far from equilibrium and the subsequent crystallization is driven by the solubility parameters. The crystal formation is monitored by scanning transmission electron microscope (STEM), observing small crystallization centers growing as time evolves to large grains with high crystal purity. Energy dispersive X-ray spectroscopy (EDS) in STEM mode revealed a Pb rich core-shell structure in newly formed grains. Nano-beam Electron Diffraction (NBED) scan defined PbI 2 crystallites in the Pb rich shell with a single crystal MAPbI 3 core in newly formed grains. After a week stirring, the same aggregated suspension exhibited grains with only single crystal MAPbI 3 structure. The NBED analysis shows a kinetically slow transition from a core shell structure to a single crystal grain. This research presents an impactful insight on the factors that may cause sub-stoichiometric grain boundary effects which can influence the solar cell performance. In addition, the structure, morphology and optical properties of the perovskite grains have been presented. A powder of highly crystalline particles was subsequently prepared by evaporation of the solvent in a low-vacuum oven. Thin film MAPbI 3 solar cells were fabricated by dissolving the powder and applying it in a classical fabrication route. The MAPbI 3 solar cells gave a champion efficiency of 20% (19.9%) and an average efficiency at approximately 17% with low hysteresis effects. Here a strategy to manufacture the material structure without toxic solvents is highlighted. The single-crystal growth devised here opens both for shelf storage of materials as well as a more flexible manufacturing of devices. The process can likely be extended to other fields, where the intermediate porous framework and large surface area would be beneficial for battery or super capacitor materials. • A non-toxic solvent approach for production of high quality MAPbI 3 perovskite grains. • Nano-beam electron diffraction scan on PbI 2 crystallites and single crystal MAPbI 3 grains. • The porous framework of grains and large surface area would be beneficial for energy storage. • Low hysteresis effects and high efficiency for the perovskite solar cells.

A smoothed particle hydrodynamics study on effect of coarse aggregate on self-compacting concrete flows

Coarse aggregates increase inhomogeneity and alter rheological properties of self-compacting concrete. In this work, the effect of coarse aggregates on self-compacting concrete is studied by considering its pipe flow. Self-compacting concrete is modelled as suspension of coarse aggregates in cement mortar and a two-phase Smoothed Particle Hydrodynamics (SPH) model is employed. Cement mortar, a yield-stress fluid, is modelled by fluid SPH particles, while each coarse aggregate is represented by a group of solid SPH particles, which moves as a rigid body. Simulation results show that, at the same volume fractions, the flow rate is higher for larger coarse aggregates, that is up to 24% in the investigated cases. Both effective yield stress and effective plastic viscosity of the concretes increase with the coarse aggregate content. Effective yield stress is smaller for bigger coarse aggregates. The reduction in effective yield stress is a consequence of bigger averaged gap between larger coarse aggregates through which the cement mortar flows.

Microstructure evolution based particle chain model for shear yield stress of magnetorheological fluids

To predict the shear stress of magnetorheological fluids (MRFs) under magnetic field and shear flows, a meso-microscale shear model is proposed based on the entire course of particle aggregates and chains. For this purpose, a systematic study on the microstructure evolution and rheological properties of MRFs is conducted by using molecular dynamics simulations. An efficient chain identification technique is introduced to count the number of particle chains within the suspension system. From the perspective of particle-level simulations, the microstructured behavior of MRFs involving particle aggregation and internal structure evolution of magnetorheological suspensions are addressed. Shear properties of MRFs derived by the proposed model are studied, and model verification by comparison with previous experimental data and predictions of the existing structural viscosity model is included as well. It is revealed that the proposed meso-microscale shear model exhibits satisfactory accuracy and efficiency for describing the rheological properties of MRFs. Besides, the critical factors linked with rheological properties of MRFs such as magnetic field strength, particle volume fraction and shear rate, are analyzed, further demonstrating the applicability of the proposed model in design and optimization of MRFs.

Stability and characterization of mixture of three particle system containing ZnO-CuO nanoparticles and clay

The aim of this study was to understand heteroaggregation of mixture of ZnO and CuO nanoparticles (NPs) with clay, for the first time as per the authors' knowledge. Aggregation studies of mixture of ZnO and CuO nanoparticles with clay was done (ionic strength =5 mM; pH 7; nanoparticles concentration = 0.1 mg/L, 1 mg/L, 10 mg/L; Clay concentration = 1, 10, and 100 mg/L and HA concentration = 0.1,1, and 10 mg/L as total organic carbon). Critical coagulation concentration (CCC) and attachment efficiency values of suspensions with ZnO: CuO ratio = 0.1, 1, 10 were also determined. Aggregation and liquid portions of mixture suspension at equal mass ratio were characterized for size, zeta potential (ZP), metal and ion contents, pH and conductivity. Results indicated that CCC was found to be 120.7 mM for ZnO: CuO ratio 10 and 1144 mM for ZnO: CuO ratio 1. Values of attachment efficiency were obtained to be 0.9 and 0.8 for these two ZnO:CuO ratio. At natural water ionic strength (IS) condition, aggregate rate constant of mixture of particles ranged from 0.281 to 8.63 nm/min for 10 mg/L NP concentration. Aggregation in suspension containing mixture of particles was found to be affected by NP concentration, clay concentration, and humic acid (p < 0.05). During a 1-h aggregation study, 2.67 mg Cu metal/g aggregate and 0.38 mg Zn/g aggregate were found in aggregates of 5 mM suspension. Overall, this study provided information on aggregation characterization of mixture of metal oxide nanoparticles (ZnO and CuO) in HA and clay presence, which is useful in understanding aggregation formation and in characterizing exposure dose for environmental risk assessment. More detailed information on a three -particle system with natural colloids is required for predicting their fate in aquatic system and defining risk.

Carbonated polymeric nanofluids for enhanced oil recovery from sandstone reservoir

Polymeric nanoparticle (NP) suspensions are colloidal suspensions where NPs (size ≤ 100 nm) are suspended in the polymer-enhanced base fluid, mainly water. Compared to water or sole polymer solutions, they exhibit superior rheological, mass transfer, and heat tolerance attributes. While the use of polymeric NP suspensions as injection fluids for enhanced oil recovery has been explored in past studies, their use as carrier fluids for CO2-loaded (carbonated) water injection has not been explored to date. Thus, this study explores the use of polymeric NP suspensions prepared using SiO2, ZnO, and TiO2 nanoparticles of varying concentration for CO2 loading and their use as carbonated fluids for enhanced oil recovery from sand-packs mimicking a sandstone reservoir. It was observed that the use of nanoparticles improved CO2 absorption in the base fluid, water by a significant margin (≈8–23%). The inclusion of salt (3 wt% NaCl) induced aggregation in NP suspensions and reduced their CO2 loading capacity. When used for flooding, the carbonated polymeric NP suspensions exhibited superior oil mobilization than their non-carbonated peers resulting in more oil produced even at a higher temperature and salinity (additional 12–20% of OOIP). Increasing temperature reduced the loading (absorption) of CO2 and oil recovery effectiveness of the polymeric NP suspensions while salt majorly impacted oil recovery efficiency under the investigated conditions. Based on the results obtained in this study, the use of 0.1 wt% SiO2 NPs has been recommended as the ideal concentration for use in carbonated water injection.

Hydrodynamic influence on the aggregation of colloids with short-range depletion potential in dilute suspensions

We numerically study the effect of hydrodynamics on colloid aggregation in dilute suspensions using inertial coupling, a type of immersed boundary method. Some previous studies found that hydrodynamics affects the equilibrium cluster shape. Comparing to Langevin dynamics and Monte Carlo simulations we find instead no statistically relevant difference in the formed cluster structure due to hydrodynamic effects, only a slowing down. Time correlation studies find two timescales: a short one faster than the single particle diffusion time, and a longer exponential decay of several diffusion times.

Particles, protists, and zooplankton in glacier-influenced coastal Svalbard waters

Glacier retreat is an eminent consequence of exacerbating climate change. In the Svalbard archipelago, most of the glaciers are discharging fresh and turbid waters directly to the sea, substantially impacting the coastal Arctic marine ecosystems. This study attempted to characterise the environmental conditions (hydrography, turbidity, marine aggregates) in the glacial-influenced waters and relate them to the abundance and species composition of protists and zooplankton. The study was conducted in the summer of 2016 in two Svalbard fjords (Wijdefjorden and Rijpfjorden) as well as in coastal waters close to glacier terminations on two islands (Nordaustlandet and Edgeøya). Well-recognised gradients in seawater salinity, turbidity, and particle aggregates that spread from glacier fronts towards open waters were not directly associated with the corresponding horizontal gradients in plankton communities. However, the studied environmental parameters explained the high overall variability in protists and zooplankton abundance (70 and 62% of explained variation, respectively). Different vertical distribution patterns and composition of plankton and marine aggregates were observed between fjords compared to open sea island locations suggesting different origin and transport of pelagic organisms and aggregate suspensions among study locations. The results do not support the hypothesis of synchronised horizontal change in environmental and biological components, which indicates that the relation between glacier meltwaters and plankton dynamics is a derivative of complex interactions driven by several physical and ecological processes that occur at different spatiotemporal scales. Nevertheless, this investigation provides new data pertaining to particle and plankton concentrations and structure in coastal waters near glaciers, which is essential for further understanding of the future coastal Arctic ecosystems functioning under rapid glacier retreat caused by climate change.

Influence of particle dispersion on the viscosity change in highly-concentrated cement suspensions: An experimental correlation

Fresh concrete is a concentrated suspension of Portland cement and aggregates. Cement-based materials show a fluid-to-solid transition incorporating water, which allows us to cast and place a structure in field. Ease of construction requires a lower viscosity of cement-based materials, and it could be achieved by cement particle dispersion in water. In this study, a laser backscattering measurement identifies the cement dispersion in in situ samples, and their size distribution are parametrized using the occurrence rate of a Poisson process. The cement dispersion is unaffected by external shearing intensity while the concentration (or water-to-cement ratio) or the use of dispersant alters its degree. Finally, associating the dispersion measurement with the microstructural state determined by their viscosity curves makes it clear how the cement viscosity decreases.