Motion Picture Study of Balata and Hevea Latices. With Observations on Buna-S and Neoprene Latices

1943 ◽  
Vol 16 (3) ◽  
pp. 509-528
Author(s):  
Francis F. Lucas
Keyword(s):  
Large Particle ◽  
Spherical Particles ◽  
Dispersed Particles ◽  
Shaped Particle ◽  
Merging Process ◽  
Common Unit ◽  
Large Spherical Particle ◽  
Mathematical Analyses ◽  
Favorable Conditions ◽  
State Of Tension

Abstract In dispersions of Hevea or balata latex, motion of the particles appears to be controlled by forces acting between particles. The particles are known to have negative charges. It is believed that these charges may not be uniformly distributed over the surface of the particles, and that they fluctuate in intensity. The charges tend to keep the particles separated. Under normal conditions of motion there is no evidence that the particles collide. They approach and recede from one another. Particles differing in size are found associated. A common unit is the doublet, composed of a large particle and an associated small particle acting as a satellite. Particles of varying size seem to have a tendency to form a group or constellation. The motions of a constellation appear to be centered about the largest particle. This particle may have several satellites. Each satellite may have one or more satellites. A large particle is never seen to gyrate about a smaller particle. If the negative charges are nullified, agglomeration takes place. There seems to be some force acting in opposition to that of electrical repulsion. Isolated single particles or units (doublets, triplets, and quads) seem to manifest very little motion. As the concentration of the dispersed particles is increased, the motions appear to be greatly increased. Mathematical analyses based on measurements of the films should provide data which will determine whether this assumption is valid. In dilute dispersions, particle relations can be readily demonstrated, and the particles seem to assume a state of colloidal equilibrium. It appears that the particles were mutually in a state of tension. Motions are slight. Rather concentrated dispersions form chains, groups, and dark interspaces or “holes”. No evidence has been deduced that magnetism plays any part in this grouping arrangement. It is believed that the phenomenon may be fully accounted for on the basis that it is the resultant of forces acting between particles. Time studies show that merging of particles occurs. A simple case may be described as two spherical particles, one larger than the other, in doublet arrangement. The smaller particle may lose its charge, or through some other cause is attracted by the larger particle to which it becomes attached. Through the action of other forces, it appears to be pulled into the larger particle, resulting in an irregularly shaped particle. Ultimately, under favorable conditions, the larger particle completely absorbs the smaller particle and then becomes spherical. During the merging process, however, other particles may be attracted and become attached to this irregular-shaped particle. A common arrangement seems to be a tapering chain of particles, consisting of a large bulbous particle at one end to which have become attached several particles, each succeeding particle somewhat smaller in diameter than its neighbor. In process of merging, these particles are gradually pulled into the large bulbous particle, which ultimately may become a large spherical particle.

Genesis of Tropical Storm Eugene (2005) from Merging Vortices Associated with ITCZ Breakdowns. Part III: Sensitivity to Various Genesis Parameters

2010 ◽  
Vol 67 (6) ◽  
pp. 1745-1758 ◽  
Author(s):  
Chanh Q. Kieu ◽  
Da-Lin Zhang
Keyword(s):  
Boundary Layer ◽  
Potential Vorticity ◽  
Initial Conditions ◽  
Tropical Storm ◽  
Cyclonic Vorticity ◽  
Merging Process ◽  
Continuous Potential ◽  
Frictional Convergence ◽  
Favorable Conditions ◽  
Vortex Merger

Abstract In this study, a series of sensitivity simulations is performed to examine the processes leading to the genesis of Tropical Storm Eugene (2005) from merging vortices associated with the breakdowns of the intertropical convergence zone (ITCZ) over the eastern Pacific. This is achieved by removing or modifying one of the two vortices in the model initial conditions or one physical process during the model integration using the results presented in Parts I and II as a control run. Results reveal that while the ITCZ breakdowns and subsequent poleward rollup (through a continuous potential vorticity supply) provide favorable conditions for the genesis of Eugene, the vortex merger is the most effective process in transforming weak tropical disturbances into a tropical storm. The sensitivity experiments confirm the authors’ previous conclusions that Eugene would not reach its observed tropical storm intensity in the absence of the merger and would become much shorter lived without the potential vorticity supply from the ITCZ. It is found that the merging process is sensitive not only to larger-scale steering flows but also to the intensity of their associated cyclonic circulations and frictional convergence. When one of the vortices is initialized at a weaker intensity, the two vortices bifurcate in track and fail to merge. The frictional convergence in the boundary layer appears to play an important role in accelerating the mutual attraction of the two vortices leading to their final merger. It is also found from simulations with different storm realizations that the storm-scale cyclonic vorticity grows at the fastest rate in the lowest layers, regardless of the merger, because of the important contribution of the convergence associated with the boundary layer friction and latent heating.

Bio-Inspired Segmented Flow: Effect of Particle Elongation on the Heat Transfer

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Laura Small ◽  
Fatemeh Hassanipour
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Exchange Process ◽  
Convection Heat Transfer ◽  
Spherical Geometry ◽  
Spherical Particles ◽  
Channel Height ◽  
Segmented Flow ◽  
Heat Transfer Efficiency ◽  
Shaped Particle

This study presents numerical simulations of forced convection heat transfer with parachute-shaped segmented flow. The particles are encapsulated phase-change material flowing with water through a square cross-section duct with iso-flux boundaries. The system is inspired by the gas exchange process in the alveolar capillaries between red blood cells and lung tissue. A numerical model is developed for the motion of elongated encapsulated phase-change particles along a channel in a particulate flow where particle diameters are comparable with the channel height. The heat transfer enhancement for the parachute-shaped particles is compared with that of the spherical particles. Results reveal that the snug movement of the particles has the key role in heat transfer efficiency. The parachute-shaped geometry produces small changes in the heat transfer coefficient compared to a spherical geometry. However, the parachute-shaped particle flow is more robust to changes in particle concentration inside the channel.

Investigation of the Flow Behavior of Participate Filled Fluids

1996 ◽  
Vol 445 ◽  
Author(s):  
T. E. Driscoll ◽  
P. C. Li ◽  
G. L. Lehmann ◽  
E. J. Cotts
Keyword(s):  
Large Particle ◽  
Capillary Flow ◽  
Flow Behavior ◽  
Solid Particles ◽  
Spherical Particles ◽  
Liquid Density ◽  
High Concentration ◽  
Flow Process ◽  
Fluid Mixture ◽  
Underfill Flow

AbstractUnderfill encapsulants, used in direct‐chip‐attachment (DCA) packaging of electronics, consist of an epoxy resin in which a high concentration of solid particles are suspended. As a fluid mixture key features of these encapsulants are their relatively large particle sizes and large particle‐to‐liquid density ratios (ρs/ρ0 ?2.4). Experiments have been conducted to characterize the flow behavior of model mixtures of negatively buoyant, spherical particles suspended in Newtonian liquids. Capillary flow in a parallel surface channel is used to simulate the underfill flow process. The effects of varying the channel spacing, particle size and liquid carrier are reported here. The flow behavior is contrasted with a linear fluid, effective viscosity model. Particle settling appears to be linked to the more complex behavior observed in both our model suspensions and measurements using an actual commercial encapsulant.

scholarly journals The study of the velocity of dispersed particles at different angles of division of a two-phase flow

2019 ◽  
pp. 78-86
Author(s):  
S.A. Shevchenko ◽  
A.F. Shevchenko ◽  
A.P. Tolstopyat ◽  
L.A. Fleyer ◽  
V.I Yeliseyev
Keyword(s):  
Cast Iron ◽  
Flow Separation ◽  
The Other ◽  
Spherical Particles ◽  
Single Particles ◽  
Two Phase ◽  
Injection Process ◽  
Dispersed Particles ◽  
Outflow Velocity ◽  
Air Stream

The aim of this work is to assess the influence of a t-shaped divider (α = 180°) on the speed of movement of spherical particles along the path of a two-nozzle lance in the air stream. Also, comparison with the results of flow separation experiments at smaller angles. The performed studies showed that in the t-shaped divider the reagent particles have a complex trajectory of motion. Part of the particles has an outflow velocity corresponding to other types of divider (7 – 14 m/sec), and the other equilibrium part of the particles is slowed down and has an outflow speed 4 – 5 times lower (1 – 3 m/sec). This is reflected by the bimodal nature of the distribution of the results. In this regard, the transition from single particles to a denser flow (in the case of an increase in the reagent supply intensity) will lead to instability of the injection process, to pulsations and even blocking of the lance. This under conditions of flow into the melt will lead to blockage of the nozzle. This is confirmed by individual attempts to inject granular magnesium through a t-shaped lance in cast iron desulfurization plants. In this case, magnesium was introduced with overestimated flow rates of the transporting gas and an intensity of no more than 5–6 kg/min, which is 5 times less than through a y-shaped two-nozzle lance. In addition, the injection was carried out through one nozzle, since the other in the first seconds of the release of magnesium was clogged. The process proceeded violently and was accompanied by splashes of cast iron from the ladle. It is established that, in comparison with the flow separation angles ( = 30, 60, 90), the t-shaped divider ( = 180) reduces the speed of magnesium and polystyrene particles to a greater extent (by 20 – 50%). In addition, the physical characteristics of the interacting materials, the shape of the particles, the flow rate of the transporting gas, and the length of the nozzle after the divider significantly affect the speed of movement of a solid particle along the path of a two-nozzle lance.

Model-based closure experiments with optical particle counters for dust-like aerosols

2021 ◽  
Author(s):  
Josef Gasteiger ◽  
Adrian Walser ◽  
Maximilian Dollner ◽  
Marilena Teri ◽  
Bernadett Weinzierl
Keyword(s):  
Size Distribution ◽  
Size Range ◽  
Particle Orientation ◽  
Spherical Particles ◽  
Dust Particles ◽  
Optical Parameters ◽  
Size Distributions ◽  
Scattering Angle ◽  
Desert Dust ◽  
Shaped Particle

<div> <div></div> </div><div><!-- COMO-HTML-CONTENT-START --> <p>The size distribution of desert dust is a central parameter, e.g., for the dust climate effect and the fertilization of oceans and rain forests. The uncertainties of size distribution measurements, however, are large for which the nonsphericity of dust particles is a major reason. Optical particle counters (OPCs) are frequently used for size distribution measurements and possible reasons for uncertainties include (a) the fact that nonspherical dust particles fly with individual orientations through the sampling volume of the OPC while the scattering signals and derived sizes depend on particle orientation, (b) the variability of particle shape, and (c) uncertainties about which definition of particle size is best suited for nonspherical dust.</p> <p>To test the consistency between OPC measurements and independent measurements with other instruments types (e.g., a nephelometer or a lidar) closure experiments can be performed. In such experiments, size distributions derived from OPC measurements are used as input for model calculations of specific optical parameters which then are compared to independent measurements of the same optical parameters (e.g. scattering or backscattering coefficient) of the same aerosol. Deviations have been reported in the literature for desert dust. These deviations may be caused by the particle nonsphericity affecting the derivation of size distributions from OPC as indicated above but may also have other causes, e.g., using a wrong refractive index or assuming spherical particles for calculating the specific optical parameters. So far, the OPC nonsphericity effect has not been investigated in detail. A better understanding of this effect would be helpful for our understanding of size distribution uncertainties and of reasons for deviations in closure experiments.</p> <p>In order to gain insight into the OPC nonsphericity effect, we performed simulations for different combinations of OPCs and instruments measuring specific optical parameters. Irregular dust-like shapes over a wide size range and different refractive indices were considered. Firstly, the deviations of the derived sizes from the original particle sizes were analyzed. Secondly, the derived sizes were used for Mie simulations of the optical parameters and the deviations from those of the original irregularly-shaped particle were calculated. In this respect, e.g., nephelometer responses and lidar-relevant parameters were simulated to reproduce possible closure experiments. These results will be compared to measurement-based closure experiments performed during field campaigns or in a laboratory in order to investigate how well the OPC nonsphericity effect explains observed discrepancies.</p> <p>The simulated closure experiments show, for example, an overestimation of the scattering coefficient at λ=532nm by about 5% to 34% (depending on size range) when using size distributions derived from the DMT CAS instrument (λ=658nm, 4°-12° scattering angle) assuming non-absorbing dust particles. Using the TSI OPS model 3330 (λ=660nm, 30°-150° scattering angle) deviations in the range from -16% to +16% are found.</p> </div>

scholarly journals Identification of the vinculin-binding site in the cytoskeletal protein α-actinin

1994 ◽  
Vol 301 (1) ◽  
pp. 225-233 ◽  
Author(s):  
A McGregor ◽  
A D Blanchard ◽  
A J Rowe ◽  
D R Critchley
Keyword(s):  
Binding Site ◽  
Calcium Binding ◽  
Fusion Proteins ◽  
Spherical Particles ◽  
Sedimentation Equilibrium ◽  
Actin Binding ◽  
Glutathione S Transferase ◽  
Agarose Beads ◽  
Shaped Particle ◽  
Particle Length

Using low-speed sedimentation equilibrium we have established that vinculin binds to alpha-actinin with a Kd of 1.3 x 10(-5) M. Electron microscopy of negatively stained preparations of vinculin revealed spherical particles (diameter 11.2 nm; S.D. 1.7 nm, n = 21), whereas alpha-actinin appeared as a rod-shaped particle (length 33 nm; S.D. 3.3 nm, n = 23). Mixtures of the two proteins contained both ‘lollipop’- and ‘dumbell’-shaped particles which we interpret as either one or two spherical vinculin molecules associated with the ends of the alpha-actinin rod. We have further defined the vinculin-binding site in alpha-actinin using 125I-vinculin and a gel-blot assay in which proteolytic fragments of alpha-actinin and fragments of alpha-actinin expressed in Escherichia coli were resolved by SDS/PAGE and blotted to nitrocellulose. 125I-vinculin bound to polypeptides derived from the spectrin-like repeat region of alpha-actinin, but did not bind to the actin-binding domain. Binding was inhibited by a 100-fold molar excess of unlabelled vinculin. Using a series of glutathione S-transferase fusion proteins we have mapped the vinculin-binding site to a region toward the C-terminal end of the molecule (alpha-actinin residues 713-749). 125I-vinculin also bound to fusion proteins containing this sequence which had been immobilized on glutathione-agarose beads. The vinculin-binding site is localized in a highly conserved region of the molecule close to the first of two EF-hand calcium-binding motifs.

Theoretical Analysis of Cylindrical Microparticle Photophoresis in a Perpendicular Optical Field with Thermal Stress Slip Model

2012 ◽  
Vol 28 (1) ◽  
pp. 113-121 ◽  
Author(s):  
P.-Y. Tzeng ◽  
C.-H. Liu ◽  
W.-K. Li ◽  
C.-Y. Soong
Keyword(s):  
Thermal Stress ◽  
Theoretical Analysis ◽  
Slip Flow ◽  
Optical Field ◽  
Spherical Particles ◽  
Asymmetric Distribution ◽  
Shaped Particle ◽  
Slip Flow Regime ◽  
Long Cylinder ◽  
The Continuum

ABSTRACTThe present study is concerned with a theoretical analysis of the photophoresis of a microsized long cylinder in a perpendicular optical field. Different from previous studies of photophoresis, thermal stress slip usually neglected is taken into account in the analysis. The gaseous fluid relative to the microparticle in photophoretic motion falls into slip-flow regime. Asymmetric distribution of the absorbed heat energy within the particle becomes the driving force for photophoretic motion of the cylinder-shaped particle. By evaluating heat source function distributions at various conditions, the study focuses on the effects of particle size and optical properties on the energy distribution and the resultant influences on the photophoresis. The photophoretic mobility is developed by the slip flow model with consideration of thermal stress slip. The results reveal that the photophoretic mobility decreases with the increase of particle thermal conductivity (k*) and increases with Knudsen number (Kn). The thermal stress slip effect on photophoretic velocity is more noticeable at high Kn, but disappears at the continuum limit. A long cylinder-shaped particle has higher photophoretic velocity than a spherical particle at low k*, while the situation reverses at high k*. With thermal stress slip considered, the critical condition for crossing of the photophoretic velocity curves of cylindrical and spherical particles is mildly influenced by Kn.

scholarly journals Occurrence of Petunia Vein-Clearing Virus in the U.S.A.

Plant Disease ◽  
1998 ◽  
Vol 82 (2) ◽  
pp. 262-262 ◽  
Author(s):  
B. E. L. Lockhart ◽  
D.-E. Lesemann
Keyword(s):  
Petunia Hybrida ◽  
Virus Isolate ◽  
Leaf Size ◽  
Uranyl Acetate ◽  
Spherical Particles ◽  
Serological Relationship ◽  
Vein Clearing ◽  
Double Stranded Dna ◽  
Tentative Member ◽  
Favorable Conditions

Petunia vein-clearing virus (PVCV), a tentative member of the caulimovirus group of plant pararetroviruses, was first identified in petunia (Petunia hybrida Vilm.) in Germany in the hybrid cv. Himmelröschen (1). A similar virus was recently identified in Minnesota in the petunia cv. Fantasy Pink grown from seed in commercial greenhouses. This virus has spherical particles 46 to 47 nm in diameter in preparations negatively stained with 1% uranyl acetate or sodium phosphotungstate, pH 7.0, and which contain a double-stranded DNA genome approximately 7.3 kb in size. The virus was shown by immunoelectron microscopy (IEM) to be closely related serologically to PVCV. No serological relationship to any other caulimoviruses was detected. Like PVCV, which is transmitted only by seed and grafting, the Minnesota virus isolate was not transmitted by mechanical inoculation to petunia or any other indicator plant. Symptoms associated with infection by PVCV in cv. Fantasy Pink consisted of mild vein clearing to severe vein yellowing, and reduction in leaf size and internode length. Symptoms were most frequently expressed when plants were under water and nutrient stress. Vigorously growing plants usually showed no symptoms, and no virions were detected by IEM in partially purified extracts from such plants. This suggests that infection of petunia hybrids by seed-borne PVCV may possibly be more widespread, but may go unnoticed because virus-induced symptoms may not be elicited in plants growing under favorable conditions. References: (1) D. Lesemann and R. Casper. Phytopathology 63:1118, 1973.

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