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R. Hogg

Bio: R. Hogg is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Mixing (physics) & Diffusion (business). The author has an hindex of 4, co-authored 4 publications receiving 1788 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a quantitative theory is presented which describes the kinetics of coagulation of colloidal systems containing more than one dispersed species, using the linear (Debye-Huckel) approximation for low surface potentials.
Abstract: A quantitative theory is presented which describes the kinetics of coagulation of colloidal systems containing more than one dispersed species. A general expression has been derived to describe the potential energy of interaction between dissimilar spherical colloidal particles, using the linear (Debye-Huckel) approximation for low surface potentials. An overall stability ratio has been defined which takes into account the possibility of interactions between like, as well as unlike, particles in the system. The errors introduced by the use of the linear approximation have been assessed in terms of their effects on the stability ratio, and found to be quite small. The theory has been used to describe the behaviour of a hypothetical system under various conditions.

1,734 citations

Journal ArticleDOI
TL;DR: In this paper, a quantitative theory is presented which describes the mixing of two identical powders in a horizontal barrel mixer, and it is proposed that when two components are loaded end-to-end in a simple barrel mixers, mixing can occur only by diffusion.

96 citations

Journal ArticleDOI
TL;DR: In this article, a quantitative theory is developed to describe mixing in particulate systems in which one component is present only as a trace quantity, and theoretical expressions are derived to predict the rates of mixing of essentially identical components both as spherical or as angular particles.

22 citations

Journal ArticleDOI
01 Jan 1966-Nature
TL;DR: In this article, the authors considered the mechanism whereby particle motion about the mixer axis results in diffusion along the axis and showed that if regions of high concentration of one component remain, then such an aggregate may be too small to be segmented by the action of the mixer in a finite time and diffusion out of the aggregate must take place before final mixing can occur.
Abstract: IN the mixing of participate materials it is often stated that the underlying mechanism of the process is the diffusion of the components one into another, which implies a random motion of the particles. Implicit in this assumption is that diffusion, as described by Fick's Laws, results from agitation of the particles by the rotation of the mixer. However, the mechanism whereby particle motion about the mixer axis results in diffusion along the axis has not been considered. It is important to consider this question, since previous investigations1,2 have suggested that final intimate particle–particle contact can only proceed through diffusion. If, during the mixing process, regions of high concentration of one component remain, then such an aggregate may be too small to be segmented by the action of the mixer in a finite time, and diffusion out of the aggregate must take place before final mixing can occur.

17 citations


Cited by
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Journal ArticleDOI
TL;DR: The atomic force microscope (AFM) is not only used to image the topography of solid surfaces at high resolution but also to measure force-versus-distance curves as discussed by the authors, which provide valuable information on local material properties such as elasticity, hardness, Hamaker constant, adhesion and surface charge densities.

3,281 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present theories describing colloid mobilization, deposition, and transport, laboratory experiments in model systems designed to test these theories, and applications of these theories to colloid-facilitated transport experiments in natural groundwater systems.

1,145 citations

ReportDOI
01 Sep 1970
TL;DR: In this article, a distinct sequence of sorption of different bacterial types has been observed both on glass slides and electron microscope grids immersed in seawater for periods of up to 24 hours.
Abstract: : A distinct sequence of sorption of different bacterial types has been observed both on glass slides and electron microscope grids immersed in seawater for periods of up to 24 hours. A comparison of the bacterial groups initially attracted to a surface with those subsequently adhering firmly to the surface suggests a selective irreversible sorption of certain groups of marine bacteria. Firm adhesion of bacteria in the short time periods considered does not involve pili or holdfast structures. The ability to produce extracellular polymeric fibrils may be important in such selective sorption. Two phases in the process of sorption of marine bacteria to surfaces have been defined as (a) an instantaneous reversible phase, and (b) a time-dependent irreversible phase. Reversible sorption of the non-motile Achromobacter sp. strain R8 decreases to zero as the electrolyte concentration decreases, or as the thickness of the electrical double-layer increases. The electrolyte concentration at which all bacteria are repelled from the glass surface depends on the valency of the electrolyte. The reversible phase of sorption is interpreted in terms of the balance between the electrical double-layer repulsion energies at different electrolyte concentrations and the van der Waals attractive energies. The rotational motion of the motile Pseudomonas sp. strain R3 at a liquid-glass interface is considered in terms of the concept of reversible sorption.

922 citations

Journal ArticleDOI
TL;DR: In this paper, the reverse phase is interpreted in terms of the balance between the electrical double-layer repulsion energies at different electrolyte concentrations and the van der Waals attractive energies.
Abstract: Summary: The sorption of two marine bacteria to surfaces involved an instantaneous reversible phase, and a time-dependent irreversible phase. Reversible sorption of the non-motile Achromobacter strain R8 decreased to zero as the electrolyte concentration decreased, or as the thickness of the electrical double-layer increased. The electrolyte concentration at which all bacteria were repelled from the glass surface depended on the valency of the cation. The reversible phase is interpreted in terms of the balance between the electrical double-layer repulsion energies at different electrolyte concentrations and the van der Waals attractive energies. Even at the electrolyte concentration of seawater, the bacteria probably are held at a small distance from the glass surface by a repulsion barrier. Reversible sorption often led to rotational motion of the motile Pseudomonas sp. strain R3 at a liquid-glass interface. Pseudomonas R3 produced polymeric fibrils in artificial seawater; these may be concerned in the irreversible sorption of the bacteria to surfaces. Sorption and polymer production were stimulated by 7 mg./l. glucose but higher levels inhibited irreversible sorption. Omission of Ca2+ and Mg2+ from the artificial seawater prevented growth, polymer production, and sorption to surfaces by Pseudomonas R3.

918 citations

Journal ArticleDOI
TL;DR: The factors that determine NP colloidal stability, the various efforts to stabilize NP in biological media, the methods to characterize NP colloid stability in situ, and a discussion regarding NP interactions with cells are examined.
Abstract: Nanomaterials are finding increasing use for biomedical applications such as imaging, diagnostics, and drug delivery. While it is well understood that nanoparticle (NP) physico-chemical properties can dictate biological responses and interactions, it has been difficult to outline a unifying framework to directly link NP properties to expected in vitro and in vivo outcomes. When introduced to complex biological media containing electrolytes, proteins, lipids, etc., nanoparticles (NPs) are subjected to a range of forces which determine their behavior in this environment. One aspect of NP behavior in biological systems that is often understated or overlooked is aggregation. NP aggregation will significantly alter in vitro behavior (dosimetry, NP uptake, cytotoxicity), as well as in vivo fate (pharmacokinetics, toxicity, biodistribution). Thus, understanding the factors driving NP colloidal stability and aggregation is paramount. Furthermore, studying biological interactions with NPs at the nanoscale level requires an interdisciplinary effort with a robust understanding of multiple characterization techniques. This review examines the factors that determine NP colloidal stability, the various efforts to stabilize NP in biological media, the methods to characterize NP colloidal stability in situ, and provides a discussion regarding NP interactions with cells.

733 citations