Sedimentation

Bernhardt, Claus

doi:10.1007/978-94-011-1238-3_5

Cited by 12 publications

(7 citation statements)

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“…A 10-times diluted suspension was transferred to a 17 ml thin walled polyallomer tube and centrifugated at 29,000 rpm (135,293 × g ) for 19 h at 20°C; 500 μl of supernatant were taken from the surface of the liquid. According to centrifugation theory the maximum particle diameter in the supernatant was below 1 nm [ 17 ]. The supernatant was analyzed by ICP-MS using dissolution in acid as before.…”

Section: Methodsmentioning

confidence: 99%

Distribution of silver in rats following 28 days of repeated oral exposure to silver nanoparticles or silver acetate

et al. 2011

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BackgroundThe study investigated the distribution of silver after 28 days repeated oral administration of silver nanoparticles (AgNPs) and silver acetate (AgAc) to rats. Oral administration is a relevant route of exposure because of the use of silver nanoparticles in products related to food and food contact materials.ResultsAgNPs were synthesized with a size distribution of 14 ± 4 nm in diameter (90% of the nanoparticle volume) and stabilized in aqueous suspension by the polymer polyvinylpyrrolidone (PVP). The AgNPs remained stable throughout the duration of the 28-day oral toxicity study in rats. The organ distribution pattern of silver following administration of AgNPs and AgAc was similar. However the absolute silver concentrations in tissues were lower following oral exposure to AgNPs. This was in agreement with an indication of a higher fecal excretion following administration of AgNPs. Besides the intestinal system, the largest silver concentrations were detected in the liver and kidneys. Silver was also found in the lungs and brain. Autometallographic (AMG) staining revealed a similar cellular localization of silver in ileum, liver, and kidney tissue in rats exposed to AgNPs or AgAc.Using transmission electron microscopy (TEM), nanosized granules were detected in the ileum of animals exposed to AgNPs or AgAc and were mainly located in the basal lamina of the ileal epithelium and in lysosomes of macrophages within the lamina propria. Using energy dispersive x-ray spectroscopy it was shown that the granules in lysosomes consisted of silver, selenium, and sulfur for both AgNP and AgAc exposed rats. The diameter of the deposited granules was in the same size range as that of the administered AgNPs. No silver granules were detected by TEM in the liver.ConclusionsThe results of the present study demonstrate that the organ distribution of silver was similar when AgNPs or AgAc were administered orally to rats. The presence of silver granules containing selenium and sulfur in the intestinal wall of rats exposed to either of the silver forms suggests a common mechanism of their formation. Additional studies however, are needed to gain further insight into the underlying mechanisms of the granule formation, and to clarify whether AgNPs dissolve in the gastrointestinal system and/or become absorbed and translocate as intact nanoparticles to organs and tissues.

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Section: Methodsmentioning

confidence: 99%

Distribution of silver in rats following 28 days of repeated oral exposure to silver nanoparticles or silver acetate

et al. 2011

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“…Therefore, the critical (or lowest) particle size for which Brownian motion remains dominant can be obtained by equating the shift produced by Brownian motion to that produced by the gravity-induced sedimentation. In a polydisperse system, such limiting particle size allows identifying threshold value for particles behaving as “colloids” or as settling units. − Einstein derived the translational motion of particles undergoing Brownian diffusion as where x̅ is the shift due to Brownian motion at a certain time t and D is the Einstein’s diffusion coefficient. In the case of spheres, and under laminar flow, particles diffuse according to the Stokes–Einstein equation where k B is the Boltzman’s constant (1.38 × 10 –16 g cm 2 /s 2 K), T is the temperature in K, η is the viscosity of the medium, and R is the radius of the particles.…”

Section: Results and Discussionmentioning

confidence: 99%

Particulate Coatings via Evaporation-Induced Self-Assembly of Polydisperse Colloidal Lignin on Solid Interfaces

et al. 2018

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Polydisperse smooth and spherical biocolloidal particles were suspended in aqueous media and allowed to consolidate via evaporation-induced self-assembly. The stratification of the particles at the solid–air interface was markedly influenced, but not monotonically, by the drying rate. Cross-sectional imaging via electron microscopy indicated a structured coating morphology that was distinctive from that obtained by using particles with a mono- or bimodal distribution. Segregation patterns were found to derive from the interplay of particle diffusion, interparticle forces, and settling dynamics. Supporting our experimental findings, computer simulations showed an optimal drying rate for achieving maximum segregation. Overall, stratified coatings comprising nano- and microparticles derived from lignin are expected to open opportunities for multifunctional structures that can be designed and predicted on the basis of experimental Péclet numbers and computational order.

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“…Migration of a particle from r 1 to r 2 in a centrifuge is described by the sedimentation equation , ln nobreak0em.25em⁡ r 2 r 1 = 2 R 2 normalΔ ρ 9 η ω 2 t where R is the particle radius, Δρ is the difference between the density of the particle and the density of the surrounding liquid, η is the suspension viscosity, ω is the angular frequency of the rotor, and t is the duration of centrifugation. The term (2 R 2 Δρ)/9η is known as the sedimentation coefficient.…”

Section: Resultsmentioning

confidence: 99%

Large-Scale Inhomogeneities in Solutions of Low Molar Mass Compounds and Mixtures of Liquids: Supramolecular Structures or Nanobubbles?

2013

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In textbooks, undersaturated solutions of low molar mass compounds and mixtures of freely miscible liquids are considered as homogeneous at larger length scales exceeding appreciably dimensions of individual molecules. However, growing experimental evidence reveals that it is not the case. Large-scale structures with sizes on the order of 100 nm are present in solutions and mixtures used in everyday life and research practice, especially in aqueous systems. These mesoscale inhomogeneities are long-lived, and (relatively slow) kinetics of their formation can be monitored upon mixing the components. Nevertheless, the nature of these structures and mechanisms behind their formation are not clear yet. Since it was previously suggested that these can be nanobubbles stabilized by adsorbed solute at the gas/solvent interface, we devote the current study to addressing this question. Static and dynamic light scattering was used to investigate solutions and mixtures prepared at ordinary conditions (equilibrated with air at 1 atm), prepared with degassed solvent, and solutions and mixtures degassed after formation of large structures. The behavior of large structures in strong gravitational centrifugal fields was also investigated. Systems from various categories were chosen for this study: aqueous solutions of an inorganic ionic compound (MgSO4), organic ionic compound (citric acid), uncharged organic compound (urea), and a mixture of water with organic solvent freely miscible with water (tert-butyl alcohol). Obtained results show that these structures are not nanobubbles in all cases. Visualization of large-scale structures via nanoparticle tracking analysis is presented. NTA results confirm conclusions from our previous light scattering work.

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Sedimentation

Cited by 12 publications

References 0 publications

Distribution of silver in rats following 28 days of repeated oral exposure to silver nanoparticles or silver acetate

Distribution of silver in rats following 28 days of repeated oral exposure to silver nanoparticles or silver acetate

Particulate Coatings via Evaporation-Induced Self-Assembly of Polydisperse Colloidal Lignin on Solid Interfaces

Large-Scale Inhomogeneities in Solutions of Low Molar Mass Compounds and Mixtures of Liquids: Supramolecular Structures or Nanobubbles?

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