A Theory of Electrophoresis of Emulsion Drops in Aqueous Two-Phase Polymer Systems

1981 ◽  
Vol 9 ◽  
Author(s):  
Samuel Levine
Keyword(s):  
Continuous Phase ◽  
Immiscible Liquid ◽  
Ion Distribution ◽  
Two Phase ◽  
Relaxation Effects ◽  
Liquid Phases ◽  
Increase With Increase ◽  
Aqueous Mixture ◽  
Idealised Model ◽  
Two Phases

ABSTRACTTwo immiscible liquid phases form when an aqueous mixture of the electrically neutral polymers dextran and polyethylene glycol are equilibrated at sufficient concentrations. Certain supporting electrolytes which contain sulphate, phosphate or citrate ions partition unequally between the phases, and in their presence, electrophoresis of a drop of one phase suspended in the other is observed, with large mobilities. These mobilities depend linearly on the radius of the drop and the direction of the drop's motion is reversed when the disperse phase and the continuous phase are interchanged. When those ions which produce electrophoresis are present the potential Implied by the direction of electrophoresis is opposite to the Donnan potential observed between the two phases. To explain these results, we postulate an electric dipole layer associated with a mixture of oriented polymer molecules at the surface of a drop. In addition, a potential difference between the interiors of the two phases results from the unequal ion distribution. For the idealised model of a surface layer of point dipoles the inner and outer diffuse layers carry net charges equal in magnitude but opposite in sign. The classical theory of electrophoresis due to Henry, Overbeek and Booth is adapted to the motion of an emulsion drop under an electric field when diffuse ionic layers are present inside and outside the drop. Relaxation effects are treated for the case where the two diffuse layer thicknesses are small compared with the drop radius. An expression is obtained for the electrophoretic mobility of a drop which depends linearly on radius and also shows an increase with increase in salt concentration. The theory presented here is related to the work of Levich.

scholarly journals Estimation of flow velocity for a debris flow via the two-phase fluid model

2015 ◽  
Vol 22 (1) ◽  
pp. 109-116 ◽  
Author(s):  
S. Guo ◽  
P. Xu ◽  
Z. Zheng ◽  
Y. Gao
Keyword(s):  
Debris Flow ◽  
Real World ◽  
Empirical Formula ◽  
Debris Flows ◽  
Fluid Model ◽  
Two Phase ◽  
Liquid Phases ◽  
Two Phases ◽  
Phase Fluid ◽  
Steady Velocity

Abstract. The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate the velocity for a debris flow.

scholarly journals Tiny Bubbles

2009 ◽  
Vol 17 (1) ◽  
pp. 3-5
Author(s):  
Stephen W. Carmichael
Keyword(s):  
Lower Energy ◽  
Critical Role ◽  
Interfacial Area ◽  
Consumer Products ◽  
Phase System ◽  
Two Phase ◽  
Liquid Phases ◽  
Phase Systems ◽  
Two Phases

This is not an article about the song made famous by the late (great) Don Ho. This is about a breakthrough in the understanding of how micrometer-sized bubbles can be stabilized for long periods of time. This can influence the taste, smell, and consistency of consumer products including food and cosmetics.In two-phase systems, which can include air (as bubbles) suspended within a liquid, the structures of the dispersed (bubbles) and continuous (liquid) phases play a critical role in determining the properties of the material. There is also the function of time in that the microstructure of the dispersed phase continuously evolves toward a state of lower energy by minimizing the surface area between the two phases (referred to as the interfacial area). In the long term, this time evolution diminishes the usefulness of two-phase systems. Emilie Dressaire, Rodney Bee, David Bell, Alex Lips, and Howard Stone have devised a way to stabilize a two-phase system for time periods of a year or longer.

scholarly journals Estimation of flow velocity for a debris flow via the two-phase fluid model

2014 ◽  
Vol 1 (1) ◽  
pp. 999-1021
Author(s):  
S. Guo ◽  
P. Xu ◽  
Z. Zheng ◽  
Y. Gao
Keyword(s):  
Debris Flow ◽  
Real World ◽  
Empirical Formula ◽  
Debris Flows ◽  
Fluid Model ◽  
Two Phase ◽  
Liquid Phases ◽  
Two Phases ◽  
Phase Fluid ◽  
Steady Velocity

Abstract. The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate accurately the velocity for a debris flow.

scholarly journals Pseudo-Homogeneous and Heterogeneous Kinetic Models of the NaOH-Catalyzed Methanolysis Reaction for Biodiesel Production

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4192
Author(s):  
Silvia Zabala ◽  
Inés Reyero ◽  
Idoia Campo ◽  
Gurutze Arzamendi ◽  
Luis M. Gandía
Keyword(s):  
Kinetic Models ◽  
Catalyst Deactivation ◽  
Good Description ◽  
Reaction Medium ◽  
Immiscible Liquid ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Heterogeneous Model ◽  
Liquid Phases ◽  
Two Phases

Methanolysis of vegetable oils in the presence of homogeneous catalysts remains the most important process for producing biodiesel. However, there is still a lack of accurate description of the reaction kinetics. This is in part due to the complexity of the reacting system in which a large number of interconnected reactions take place simultaneously. In this work, attention is focused on the biphasic character of the reaction medium, formed by two immiscible liquid phases. The behavior of the phases is investigated regarding their physicochemical properties, mainly density and mutual solubility of the components, as well as composition. In addition, two kinetic models with different level of complexity regarding the biphasic character of the reaction medium have been developed. It has been found that a heterogeneous model considering the presence of the two phases and the distribution of the several compounds between them is indispensable to get a good description of the process in terms of oil conversion and products yields. The model captures the effects of the main variables of an isothermal batch methanolysis process: methanol/oil molar ratio, reaction time and catalyst concentration. Nevertheless, some adjustment is still required as concerns modelling of the saponification reactions and catalyst deactivation.

Kinetics in Heterogeneous Systems

2007 ◽  
Author(s):  
Robert B. Jordan
Keyword(s):  
Liquid Phase ◽  
Mass Transport ◽  
Rate Constant ◽  
Heterogeneous Systems ◽  
Two Phase ◽  
First Order ◽  
Liquid Phases ◽  
Liquid Systems ◽  
The Difference ◽  
Two Phases

In this Chapter, a heterogeneous system is one in which the reactants are present in at least two phases. The discussion will concentrate on two such conditions, two-phase gas/liquid systems and three-phase gas/liquid/solid systems. Chemists tend to favor homogeneous conditions, with the reactants all in one phase, because they provide more controlled and reproducible conditions. However, heterogeneous conditions are often preferred in industrial processes because of the ease of separating the catalyst from the products. In many mechanistic studies, heterogeneity adds a complicating feature to be avoided, but there are times when this cannot be done, or when it happens unexpectedly. In gas/liquid systems, the gas often has limited solubility in the liquid which contains the other reagents. As a consequence, there can be problems of mass transport of the gaseous reactant from the gas to the liquid phase. Mass transport can limit the concentration of the gas in the liquid and/or become a rate-limiting feature of the system. These features can confuse interpretations of product distributions and rate laws. The gas/liquid/solid systems generally involve reactants in the gas and liquid phases and a catalyst as the solid phase. In some cases, the solid may be produced from initially homogeneous conditions, and a question arises as to whether the real catalyst is the original species added or the solid product formed under the reaction conditions. There are further questions about the factors that may control the rate of the catalytic process. In the chemistry laboratory, these systems are most often encountered with the gases H2 or CO reacting with substrate and possibly a catalyst in the liquid phase. For the mechanistic interpretation of kinetic observations, an important factor is the rate of mass transfer of the gas to the liquid phase. The rate of gas absorption into the liquid is typically represented as a first order process, driven by the difference between the saturated gas concentration [G(I)]f and the concentration at any time [G(I)], as given by where kLA is an effective first-order rate constant. This constant is taken as a product of an inherent absorption rate constant, kL, and something related to the surface area of the liquid phase, A.

Extraction

2015 ◽  
Author(s):  
Roger G. Harrison ◽  
Paul W. Todd ◽  
Scott R. Rudge ◽  
Demetri P. Petrides
Keyword(s):  
Organic Solvent ◽  
Scale Up ◽  
Pharmaceutical Products ◽  
Immiscible Liquid ◽  
The Other ◽  
Soluble Form ◽  
Separation And Purification ◽  
High Concentration ◽  
Liquid Phases ◽  
Two Phases

Extraction is a process in which two phases come into contact with the objective of transferring a solute or particle from one phase to the other. For the separation and purification of biological products, the phases are most commonly immiscible liquids, and the solute is in soluble form. In certain instances, however, one phase is a liquid and the other phase is a solid; the extraction of caffeine from coffee beans is one example. Although most extractions in biotechnology involve the transfer of soluble bioproducts, organelles and cells have at times been transferred between phases. An organic solvent is often used as the extracting liquid when the solute to be extracted is stable in the organic solvent, typical examples being low molecular weight antibiotics. It is usually not feasible to extract proteins with organic solvents, since proteins are often denatured or degraded as a result of contact with the organic solvent. Proteins can often be successfully extracted by means of two immiscible liquid phases that consist of solutions of two water-soluble but incompatible polymers, or one polymer plus a high concentration of certain salts. Extraction usually comes early in the purification process for a bioproduct and typically would precede a high-resolution step such as chromatography. Extraction is often advantageous because it can bring about a significant reduction in volume and/or can separate the desired product from cells or cell debris. It is desirable to reduce the volume as soon as possible in the process, since large volumes typically lead to large costs. The extractions of interest in the purification of biotechnological and pharmaceutical products are mainly liquid-to-liquid, and this is the emphasis in this chapter. The basic definitions and principles of extraction are developed first, followed by an explanation of scale-up and design procedures for the extractors most commonly used for bioproducts. After completing this chapter, the reader should be able to do the following: • Define and use key constants such as the partition coefficient, solvent-to-feed ratio, and extraction factor. • Explain the factors that affect the partitioning of biomolecules.

Phase Inversion in Two-Phase Liquid Systems

1992 ◽  
Vol 57 (7) ◽  
pp. 1419-1423
Author(s):  
Jindřich Weiss
Keyword(s):  
Interfacial Tension ◽  
Phase Inversion ◽  
Continuous Phase ◽  
Considerable Effect ◽  
Weak Dependence ◽  
Dispersed Phase ◽  
Two Phase ◽  
Liquid Systems ◽  
Phase Liquid

New data on critical holdups of dispersed phase were measured at which the phase inversion took place. The systems studied differed in the ratio of phase viscosities and interfacial tension. A weak dependence was found of critical holdups on the impeller revolutions and on the material contactor; on the contrary, a considerable effect of viscosity was found out as far as the viscosity of continuous phase exceeded that of dispersed phase.

A Lightweight Formalism for Reference Lifetimes and Borrowing in Rust

2021 ◽  
Vol 43 (1) ◽  
pp. 1-73
Author(s):  
David J. Pearce
Keyword(s):  
Memory Management ◽  
Programming Model ◽  
Type System ◽  
Control Flow ◽  
Two Phase ◽  
Type Checking ◽  
Strong Focus ◽  
Reference Implementation ◽  
Two Phases ◽  
Complex Features

Rust is a relatively new programming language that has gained significant traction since its v1.0 release in 2015. Rust aims to be a systems language that competes with C/C++. A claimed advantage of Rust is a strong focus on memory safety without garbage collection. This is primarily achieved through two concepts, namely, reference lifetimes and borrowing . Both of these are well-known ideas stemming from the literature on region-based memory management and linearity / uniqueness . Rust brings both of these ideas together to form a coherent programming model. Furthermore, Rust has a strong focus on stack-allocated data and, like C/C++ but unlike Java, permits references to local variables. Type checking in Rust can be viewed as a two-phase process: First, a traditional type checker operates in a flow-insensitive fashion; second, a borrow checker enforces an ownership invariant using a flow-sensitive analysis. In this article, we present a lightweight formalism that captures these two phases using a flow-sensitive type system that enforces “ type and borrow safety .” In particular, programs that are type and borrow safe will not attempt to dereference dangling pointers. Our calculus core captures many aspects of Rust, including copy- and move-semantics, mutable borrowing, reborrowing, partial moves, and lifetimes. In particular, it remains sufficiently lightweight to be easily digested and understood and, we argue, still captures the salient aspects of reference lifetimes and borrowing. Furthermore, extensions to the core can easily add more complex features (e.g., control-flow, tuples, method invocation). We provide a soundness proof to verify our key claims of the calculus. We also provide a reference implementation in Java with which we have model checked our calculus using over 500B input programs. We have also fuzz tested the Rust compiler using our calculus against 2B programs and, to date, found one confirmed compiler bug and several other possible issues.

scholarly journals XCOVNet: Chest X-ray Image Classification for COVID-19 Early Detection Using Convolutional Neural Networks

2021 ◽  
Author(s):  
Vishu Madaan ◽  
Aditya Roy ◽  
Charu Gupta ◽  
Prateek Agrawal ◽  
Anand Sharma ◽  
...  
Keyword(s):  
Image Classification ◽  
Second Phase ◽  
Two Phase ◽  
X Ray ◽  
The Neural Network ◽  
Rapid Spread ◽  
Chest X Ray ◽  
Polymerase Chain ◽  
Two Phases ◽  
Active Patients

AbstractCOVID-19 (also known as SARS-COV-2) pandemic has spread in the entire world. It is a contagious disease that easily spreads from one person in direct contact to another, classified by experts in five categories: asymptomatic, mild, moderate, severe, and critical. Already more than 66 million people got infected worldwide with more than 22 million active patients as of 5 December 2020 and the rate is accelerating. More than 1.5 million patients (approximately 2.5% of total reported cases) across the world lost their life. In many places, the COVID-19 detection takes place through reverse transcription polymerase chain reaction (RT-PCR) tests which may take longer than 48 h. This is one major reason of its severity and rapid spread. We propose in this paper a two-phase X-ray image classification called XCOVNet for early COVID-19 detection using convolutional neural Networks model. XCOVNet detects COVID-19 infections in chest X-ray patient images in two phases. The first phase pre-processes a dataset of 392 chest X-ray images of which half are COVID-19 positive and half are negative. The second phase trains and tunes the neural network model to achieve a 98.44% accuracy in patient classification.

scholarly journals Two-Phase Turbulence Statistics from High Fidelity Dispersed Droplet Flow Simulations in a Pressurized Water Reactor (PWR) Sub-Channel with Mixing Vanes

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 72
Author(s):  
Nadish Saini ◽  
Igor A. Bolotnov
Keyword(s):  
Continuous Phase ◽  
System Level ◽  
Data Repository ◽  
High Fidelity ◽  
Turbulence Statistics ◽  
Two Phase ◽  
Pressurized Water ◽  
Droplet Dynamics ◽  
High Resolution Data ◽  
Spacer Grids

In the dispersed flow film boiling regime (DFFB), which exists under post-LOCA (loss-of-coolant accident) conditions in pressurized water reactors (PWRs), there is a complex interplay between droplet dynamics and turbulence in the surrounding steam. Experiments have accredited particular significance to droplet collision with the spacer-grids and mixing vane structures and their consequent positive feedback to the heat transfer recorded in the immediate downstream vicinity. Enabled by high-performance computing (HPC) systems and a massively parallel finite element-based flow solver—PHASTA (Parallel Hierarchic Adaptive Stabilized Transient Analysis)—this work presents high fidelity interface capturing, two-phase, adiabatic simulations in a PWR sub-channel with spacer grids and mixing vanes. Selected flow conditions for the simulations are informed by the experimental data found in the literature, including the steam Reynolds number and collision Weber number (Wec={40,80}), and are characteristic of the DFFB regime. Data were collected from the simulations at an unprecedented resolution, which provides detailed insights into the continuous phase turbulence statistics, highlighting the effects of the presence of droplets and the comparative effect of different Weber numbers on turbulence in the surrounding steam. Further, axial evolution of droplet dynamics was analyzed through cross-sectionally averaged quantities, including droplet volume, surface area and Sauter mean diameter (SMD). The downstream SMD values agree well with the existing empirical correlations for the selected range of Wec. The high-resolution data repository from the simulations herein is expected to be of significance to guide model development for system-level thermal hydraulic codes.

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