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Robert G Gilbert - One of the best experts on this subject based on the ideXlab platform.
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Size-Separation characterization of starch and glycogen for biosynthesis–structure–property relationships
Analytical and Bioanalytical Chemistry, 2011Co-Authors: Robert G GilbertAbstract:Starch and glycogen are highly branched polymers of glucose of great importance to humans in managing and mitigating nutrition-related diseases, especially diabetes and obesity, and in industrial uses, for example in food and paper-making. Size-Separation characterization using multiple-detection Size-exclusion chromatography (SEC, also known as gel-permeation chromatography, GPC) is able to furnish substantial amounts of information on the relationships between the biosynthesis, processing, structure, and properties of these biopolymers, and achieves superior characterization for use in industrial product and process improvements. Multi-detector SEC is able to give much more information about structure than simple averages such as total molecular weight or Size; the detailed information yielded by this technique has already given new information on important biosynthesis–structure–property reactions, and has considerable potential in this field in the future. However, it must be used with care to avoid artifacts arising from incomplete dissolution of the substrate and shear scission during Separation. It is also essential in interpreting data to appreciate that this Size-Separation technique can only ever give Size distributions, never true molecular weight distributions. Other Size-Separation techniques, particularly field-flow fractionation, require substantial technical development to be used on undegraded native starches. Figure The three structural levels of glycogen
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Size Separation characterization of starch and glycogen for biosynthesis structure property relationships
Analytical and Bioanalytical Chemistry, 2011Co-Authors: Robert G GilbertAbstract:Starch and glycogen are highly branched polymers of glucose of great importance to humans in managing and mitigating nutrition-related diseases, especially diabetes and obesity, and in industrial uses, for example in food and paper-making. Size-Separation characterization using multiple-detection Size-exclusion chromatography (SEC, also known as gel-permeation chromatography, GPC) is able to furnish substantial amounts of information on the relationships between the biosynthesis, processing, structure, and properties of these biopolymers, and achieves superior characterization for use in industrial product and process improvements. Multi-detector SEC is able to give much more information about structure than simple averages such as total molecular weight or Size; the detailed information yielded by this technique has already given new information on important biosynthesis–structure–property reactions, and has considerable potential in this field in the future. However, it must be used with care to avoid artifacts arising from incomplete dissolution of the substrate and shear scission during Separation. It is also essential in interpreting data to appreciate that this Size-Separation technique can only ever give Size distributions, never true molecular weight distributions. Other Size-Separation techniques, particularly field-flow fractionation, require substantial technical development to be used on undegraded native starches.
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characterization of branched polysaccharides using multiple detection Size Separation techniques
IEEE Journal of Solid-state Circuits, 2010Co-Authors: Francisco Vilaplana, Robert G GilbertAbstract:The structure of branched polysaccharides involves a hierarchy of levels, from the constituent sugars, then the branching pattern, up to the macromolecular architecture, and then supramolecular organization. Finding causal relations between this complex structure/architecture and both (bio)synthetic mechanisms and final properties is needed for understanding the functionality of branched polysaccharides, which is important in fields ranging from improved nutrition and health through to papermaking and pharmaceuticals. The structural complexity makes this task especially challenging. This review focuses on the best current means to obtain reliable branch chain and Size distributions using Size-Separation technologies coupled with number-, mass- and molecular-weight-sensitive detectors. Problems with current technologies are also critically appraised.
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Extracting Physically Useful Information from Multiple-Detection Size-Separation Data for Starch
Biomacromolecules, 2009Co-Authors: Angus Gray-weale, Richard A. Cave, Robert G GilbertAbstract:A method for interpreting multiple-detection Size Separation data of complex branched homopolymers [Konkolewicz, D.; Gilbert, R. G.; Gray-Weale, A. Phys. Rev. Lett. 2007, 98, 238301] is applied to starch. The method, whose application is described in detail, uses the sample’s weight and number distributions over polymer Sizes, along with the molecular weight distribution of the individual branches (or their average degree of polymerization). The branch-length and number Size distributions are used to generate the weight distribution of a hypothetical molecule with the same branch-length and number distributions but where the branches are randomly joined; this reference weight distribution is then compared to the actual one. The method is applied to Size-exclusion chromatography (SEC) data for starch from a particular rice variety, the first time such data have been reported for a native starch. Comparison with the randomly branched reference function shows that the amylopectin component is consistent with...
Heinrich M Jaeger - One of the best experts on this subject based on the ideXlab platform.
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effect of air on granular Size Separation in a vibrated granular bed
Physical Review E, 2005Co-Authors: Matthias E Mobius, Sidney R Nagel, Xiang Cheng, Greg S. Karczmar, Peter Eshuis, Heinrich M JaegerAbstract:Using high-speed video and magnetic resonance imaging (MRI) we study the motion of a large sphere in a vertically vibrated bed of smaller grains. As previously reported we find a nonmonotonic density dependence of the rise and sink time of the large sphere. We show that air drag causes relative motion between the intruder and the bed during the shaking cycle and is ultimately responsible for the observed density dependence of the risetime. We investigate in detail how the motion of the intruder sphere is influenced by Size of the background particles, initial vertical position in the bed, ambient pressure, and convection. We explain our results in the framework of a simple model and find quantitative agreement in key aspects with numerical simulations to the model equations.
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Intruders in the dust: air-driven granular Size Separation.
Physical Review Letters, 2004Co-Authors: Matthias E Mobius, Sidney R Nagel, Xiang Cheng, Greg S. Karczmar, Heinrich M JaegerAbstract:Using MRI and high-speed video we investigate the motion of a large intruder particle inside a vertically shaken bed of smaller particles. We find a pronounced, nonmonotonic density dependence, with both light and heavy intruders moving faster than those whose density is approximately that of the granular bed. For light intruders, we furthermore observe either rising or sinking behavior, depending on intruder starting height, boundary condition, and interstitial gas pressure. We map out the phase boundary delineating the rising and sinking regimes. A simple model can account for much of the observed behavior and shows how the two regimes are connected by considering pressure gradients across the granular bed during a shaking cycle.
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Size Separation of granular particles
Nature, 2001Co-Authors: Matthias E Mobius, Benjamin E Lauderdale, Sidney R Nagel, Heinrich M JaegerAbstract:Granular media differ from other materials in their response to stirring or jostling — unlike two-fluid systems, bi-disperse granular mixtures will separate according to particle Size when shaken, with large particles rising, a phenomenon termed the 'Brazil-nut effect'1,2,3,4,5,6,7,8. Mounting evidence indicates that differences in particle density affect Size Separation in mixtures of granular particles9,10,11. We show here that this density dependence does not follow a steady trend but is non-monotonic and sensitive to background air pressure. Our results indicate that particle density and interstitial air must both be considered in Size segregation.
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vibration induced Size Separation in granular media the convection connection
Physical Review Letters, 1993Co-Authors: James B Knight, Heinrich M Jaeger, Sidney R NagelAbstract:We have investigated the rise of a single large glass bead through a vibrated cylindrical column of smaller particles and found that vibration-induced Size Separation in this geometry arises from convective processes rather than from local rearrangements as had been proposed previously. A convection cycle, rising in the middle and dropping in a thin stream along the walls of the cell, is responsible for all particle movement. Particles larger than the width of the thin downward convection zone are carried to the top of the column and then trapped, resulting in Size segregation. For a variety of accelerations the position of the rising particle can be scaled onto a single curve.
Sidney R Nagel - One of the best experts on this subject based on the ideXlab platform.
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effect of air on granular Size Separation in a vibrated granular bed
Physical Review E, 2005Co-Authors: Matthias E Mobius, Sidney R Nagel, Xiang Cheng, Greg S. Karczmar, Peter Eshuis, Heinrich M JaegerAbstract:Using high-speed video and magnetic resonance imaging (MRI) we study the motion of a large sphere in a vertically vibrated bed of smaller grains. As previously reported we find a nonmonotonic density dependence of the rise and sink time of the large sphere. We show that air drag causes relative motion between the intruder and the bed during the shaking cycle and is ultimately responsible for the observed density dependence of the risetime. We investigate in detail how the motion of the intruder sphere is influenced by Size of the background particles, initial vertical position in the bed, ambient pressure, and convection. We explain our results in the framework of a simple model and find quantitative agreement in key aspects with numerical simulations to the model equations.
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Intruders in the dust: air-driven granular Size Separation.
Physical Review Letters, 2004Co-Authors: Matthias E Mobius, Sidney R Nagel, Xiang Cheng, Greg S. Karczmar, Heinrich M JaegerAbstract:Using MRI and high-speed video we investigate the motion of a large intruder particle inside a vertically shaken bed of smaller particles. We find a pronounced, nonmonotonic density dependence, with both light and heavy intruders moving faster than those whose density is approximately that of the granular bed. For light intruders, we furthermore observe either rising or sinking behavior, depending on intruder starting height, boundary condition, and interstitial gas pressure. We map out the phase boundary delineating the rising and sinking regimes. A simple model can account for much of the observed behavior and shows how the two regimes are connected by considering pressure gradients across the granular bed during a shaking cycle.
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Size Separation of granular particles
Nature, 2001Co-Authors: Matthias E Mobius, Benjamin E Lauderdale, Sidney R Nagel, Heinrich M JaegerAbstract:Granular media differ from other materials in their response to stirring or jostling — unlike two-fluid systems, bi-disperse granular mixtures will separate according to particle Size when shaken, with large particles rising, a phenomenon termed the 'Brazil-nut effect'1,2,3,4,5,6,7,8. Mounting evidence indicates that differences in particle density affect Size Separation in mixtures of granular particles9,10,11. We show here that this density dependence does not follow a steady trend but is non-monotonic and sensitive to background air pressure. Our results indicate that particle density and interstitial air must both be considered in Size segregation.
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vibration induced Size Separation in granular media the convection connection
Physical Review Letters, 1993Co-Authors: James B Knight, Heinrich M Jaeger, Sidney R NagelAbstract:We have investigated the rise of a single large glass bead through a vibrated cylindrical column of smaller particles and found that vibration-induced Size Separation in this geometry arises from convective processes rather than from local rearrangements as had been proposed previously. A convection cycle, rising in the middle and dropping in a thin stream along the walls of the cell, is responsible for all particle movement. Particles larger than the width of the thin downward convection zone are carried to the top of the column and then trapped, resulting in Size segregation. For a variety of accelerations the position of the rising particle can be scaled onto a single curve.
Arshad Kudrolli - One of the best experts on this subject based on the ideXlab platform.
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Size Separation in vibrated granular matter
Reports on Progress in Physics, 2004Co-Authors: Arshad KudrolliAbstract:We review recent developments in Size Separation in vibrated granular materials. Motivated by a need in industry to handle granular materials efficiently and a desire to make fundamental advances in non-equilibrium physics, experimental and theoretical investigations have shown Size Separation to be a complex phenomenon. Large particles in a vibrated granular system normally rise to the top. However, they may also sink to the bottom or show other patterns, depending on subtle variations in physical conditions. While Size ratio is a dominant factor, particle-specific properties such as density, inelasticity and friction can play an important role. The nature of the energy input, boundary conditions and interstitial air have also been shown to be significant factors in determining spatial distributions. The presence of convection can enhance mixing or lead to Size Separation. Experimental techniques including direct visualization and magnetic resonance imaging are being used to investigate these properties. Molecular dynamics and Monte Carlo simulation techniques have been developed to probe Size Separation. Analytical methods such as kinetic theory are being used to study the interplay between particle Size and density in the vibro-fluidized regime, and geometric models have been proposed to describe Size Separation for deep beds. Besides discussing these studies, we will also review the impact of inelastic collisions and friction on the density and velocity distributions to gain a deeper appreciation of the non-equilibrium nature of the system. While a substantial number of studies have been performed, considerable work is still required to achieve a firm description of the phenomena.
Lixin Wu - One of the best experts on this subject based on the ideXlab platform.
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flexible single layer ionic organic inorganic frameworks towards precise nano Size Separation
Nature Communications, 2016Co-Authors: Shan Wang, Ding Zhou, Hao Zhang, Bao Li, Lixin WuAbstract:Membranes composed of ionic frameworks offer applications in nano-Size Separation thanks to their highly regular pores. Here, the authors devise such a system composed of polyoxometalates and organic pseudorotaxanes, and demonstrate their ability to separate mixed Sized CdTe quantum dots.
