scholarly journals Drop race: How electrostatic forces influence drop motion

2021 ◽  
Author(s):  
Xiaomei Li ◽  
Pravash Bista ◽  
Amy Stetten ◽  
Henning Bonart ◽  
Maximilian Schür ◽  
...  
Keyword(s):  
Negative Charge ◽  
Equation Of Motion ◽  
Electrostatic Forces ◽  
Tilted Surface ◽  
Novel Approach ◽  
Drop Motion ◽  
Water Drops ◽  
Inclined Planes ◽  
Low Permittivity ◽  
Positively Charged

Abstract Water drops sliding down inclined planes are an everyday phenomenon and are important in many technical applications. Previous understanding is that the motion is mainly dictated by viscous and capillary forces. Here we demonstrate that, in addition to these forces, drops on hydrophobic surfaces are affected by self-generated electrostatic forces. In a novel approach to determine forces on moving drops we imaged their trajectory when sliding down a tilted surface and apply the equation of motion. We found that drop motion on low-permittivity substrates is significantly influenced by electrostatic forces. Sliding drops deposit a negative charge on the surface, which interact with the positively charged drops. We derive an analytical model to describe the force and validate it by numerical computations. The results indicate how to describe and facilitate drop motion in applications, such as in microfluidics, water management on car surfaces, and the creation of sliding drop electrical generators.

On the electric charge collected by water-drops falling through a cloud of electrically charged particles in a vertical electric field

1935 ◽  
Vol 151 (874) ◽  
pp. 665-684 ◽  
Keyword(s):  
Electric Field ◽  
Electric Charge ◽  
Negative Charge ◽  
X Rays ◽  
Vertical Electric Field ◽  
Water Drops ◽  
Cloud Particles ◽  
Large Water ◽  
Electrically Charged ◽  
Positively Charged

The experiments described in this paper are a continuation of work described in a former paper, and have for their object the examination of a mechanism suggested by Wilson in connection with the theory of thunder-clouds. In the former work the interaction of large water-drops with ions produced by X-rays was investigated. In the present work the interaction of large water-drops with electrically charged cloud particles is investigated, and the mechanism suggested by Wilson takes the following form. Consider an uncharged water-drop falling vertically through a cloud of very small water-droplets, each of which has an electric charge either positive or negative. Let there be a vertical electric field which will be taken to be of positive potential gradient so that positively charged cloud particles move down and negatively charged cloud particles move up. The electric field induces equal charges of opposite signs on the upper and lower halves of the drop. In the case considered the upper charge is negative and the lower one positive. A charged cloud particle has a definite small mobility depending on its radius and the charge it carries. Suppose now that the mobility is so small that in strong electric fields, such as occur in thunder-clouds (up to 10,000 volts/cm), the velocity with which the positively charged cloud particles move down is less than the velocity of the falling drop. Under these conditions, those positive cloud particles which are above the drop cannot overtake the drop and so do not reach it, although attracted by the negative charge on its upper half. Those positive cloud particles, which are below and which the drop over-takes, are first repelled by the lower positive charge on the drop before being attracted by the upper negative charge and, since these charges are equal in the neutral drop, these cloud particles do not reach it. Negative cloud particles coming up to meet the falling drop are attracted to its lower positively charged half and give the drop a net negative charge. This destroys the equality of the induced charges, and some of the positive cloud particles which the drop overtakes are now attracted to it. In the presence of equal numbers of positively and negatively charged cloud particles a limiting condition is approached in which the drop collects equal numbers of positive and negative cloud particles per second and has a net negative charge equal to some fraction of the induced charge.

First Principles Investigation of the Stability and the Chemical Behavior of Hydrogen in ThCoH4

2011 ◽  
Vol 66 (3) ◽  
pp. 269-274
Author(s):  
Samir F. Matar
Keyword(s):  
Negative Charge ◽  
Geometry Optimization ◽  
Full Geometry Optimization ◽  
Intermetallic Matrix ◽  
Charge Analysis ◽  
The Stability ◽  
The One ◽  
Site Selective ◽  
Bader Charge Analysis ◽  
Positively Charged

We address the changes in the electronic structure brought by the insertion of hydrogen into ThCo leading to the experimentally observed ThCoH4. Full geometry optimization positions the hydrogen in three sites stabilized in the expanded intermetallic matrix. From a Bader charge analysis, hydrogen is found to be in a narrow iono-covalent (~−0.6) to covalent (~−0.3) bonding which should enable site-selective desorption. The overall chemical picture shows a positively charged Thδ+ with the negative charge redistributed over a complex anion {CoH4}δ− with δ~1.8. Nevertheless this charge transfer remains far from the one in the more ionic hydridocobaltate anion CoH54− in Mg2CoH5, due to the largely electropositive character of Mg.

Fig. 9 Freeze fracture electron micrograph of ELimixed phosphoinositides (4:1) liposomes after 10 passes through a0.1 pirn polycarbonate filter. growth, particularly during storage, would be undesirable in most products. Fortunately the tendency of liposomes to aggregate and fuse can be controlled by the inclusion of small amounts of negatively charged lipids such as PS or PG or positively charged amphiphiles such as stearylamine in the formulation. Knowing the number and the sign of charged groups added and the valency and concentration of electrolytes in the me-dium, the magnitude of the electrostatic forces generated by these charged groups can be closely approximated by using the double layer theory. These results can then be correlated with physical stability of liposomes and used to guide formulation efforts. The amount of charged component and ionic conditions in a particular liposome dos-age form can be adjusted to produce a high-enough zeta potential to inhibit close ap-proach of vesicles and prevent their aggregation. In practice it is usually necessary to determine empirically the magnitude of the zeta potential required to prevent aggrega-tion in a particular system. However, once this has been done, it is possible to use the zeta potential as a quality control check to insure that each batch of liposomes contains sufficient charged groups to avoid aggregation during storage.

1998 ◽  
pp. 84-108
Keyword(s):  
Quality Control ◽  
Zeta Potential ◽  
Physical Stability ◽  
Freeze Fracture ◽  
Electron Micrograph ◽  
Electrostatic Forces ◽  
Quality Control Check ◽  
Charged Component ◽  
Fracture Electron ◽  
Positively Charged

A Design Method of Rain Test Device Based on Water Drop Motion Simulation

2013 ◽  
Vol 871 ◽  
pp. 363-368
Author(s):  
Hong Tao Zeng ◽  
Lin Lin Lin ◽  
Cong Feng ◽  
Zhi Huai Xiao
Keyword(s):  
Design Method ◽  
Water Drop ◽  
Electrical Equipment ◽  
Simulation Software ◽  
Test Device ◽  
Rainy Weather ◽  
Drop Motion ◽  
Water Drops ◽  
Motion Characteristics ◽  
Insulation Performance

In order to measure the electric insulation performance of the electrical equipment in rainy weather, its essential to design a rain device to simulate different conditions of rainfall. In this paper, a motion model of raindrop sprayed by the rain device and differential equations describing its motion characteristics are built. Basing on the analysis of water drop motion, a set of simulation software is developed for the selection of rain test device and the analysis of test results. The software can simulate the water drops motion process from nozzle to test equipment, and the simulation results is almost the same with field test, so the simulation software provides the basis for the design of rain test device.

scholarly journals The mechanism of spray electrification: the waterfall effect

2016 ◽  
Author(s):  
James K. Beattie
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Hydrophobic Hydration ◽  
General Phenomenon ◽  
Aqueous Interfaces ◽  
Preferential Adsorption ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Low Permittivity ◽  
Net Positive Charge

Abstract. The waterfall effect describes the separation of charge by splashing at the base of a waterfall. Smaller drops that have a net negative charge are created, while larger drops and/or the bulk maintain overall charge neutrality with a net positive charge. Since it was first described by Lenard (1892) the effect has been confirmed many times, but a molecular explanation has not been available. Application of our fluctuation-correlation model of hydrophobic hydration accounts for the negative charge observed at aqueous interfaces with low permittivity materials. The negative surface charge observed in the waterfall effect is created by the preferential adsorption of hydroxide ions generated from the autolysis of water. On splashing, shear forces generate small negative drops from the surface, leaving a positive charge on the remaining large fragment. The waterfall effect is a manifestation of the general phenomenon of the negative charge at the interface between water and hydrophobic surfaces that is created by the preferential adsorption of hydroxide ions.

THE EFFECT OF PROCOAGULANT PHOSPHOLIPID VESICLES WITH NET POSITIVE CHARGE ON THE ACTIVITY OF PROTHROMBINASE

1987 ◽  
Author(s):  
J Rosing ◽  
H Speijer ◽  
J W P Govers-Riemslag ◽  
R F A Zwaal
Keyword(s):  
Vitamin K ◽  
Negative Charge ◽  
Positive Charge ◽  
Coagulation Factor ◽  
Phospholipid Vesicles ◽  
Electrostatic Model ◽  
Acidic Phospholipid ◽  
Positively Charged ◽  
Net Positive Charge ◽  
Prothrombin Activation

It is generally thought that procoagulant phospholipid surfaces that promote the activation of vitamin K-dependent coagulation factors should have a net negative charge in order to promote calcium-dependent binding of the enzymes (FVIIa, FIXa and FXa) and substrates (prothrombin and FX) of the coagulation factor-activating complexes. Two models have been proposed to explain calcium-mediated association of vitamin K-dependent proteins with phospholipid: a) an electrostatic model, in which a positively-charged protein-calcium complex is attracted by a negatively-charged phospholipid surface and b) a chelation model in which a coordination complex is formed between calcium ions, γ-carboxyglutamic acids of the proteins and negatively-charged membrane phospholipids. To study the effect of the electrostatic potential of phospholipid vesicles on their activity in the pro-thrombinase complex the net charge of vesicles was varied by introduction of varying amounts of positively-charged stearylamine in the membrane surface. Introduction of 0-15 mole% stearylamine in phospholipid vesicles that contained 5 mole% phosphatidylseri-ne (PS) hardly affected their activity in prothrombin activation. Electrophoretic analysis showed that vesicles with > 5 mole% stearylamine had a net positive charge. The procoagulant activity of vesicles that contained phosphatidic acid, phosphatidylglyce-rol, phosphatidylinositol or phosphatidyl-glactate (PLac) as acidic phospholipid was much more effected by incorporation of stearylamine. Amounts of stearylamine that compensated the negative charge of acidic phospholipid caused considerable inhibition of the activity of the latter vesicles in prothrombin activation. The comparison of vesicles containing PS and PLac as acidic phospholipid is of special interest. PS and PLac only differ by the presence of NH+ 3-group in the serine moiety of PS. Thus, in spite of the fact that vesicles with PLac are more negatively charged than vesicles with PS, they are less procoagulant. Our results show that a) although procoagulant membranes have to contain acidic phospholipids there is no requirement for a net negative charge, b) the amino group of phosphatidylserine has an important function in the interaction of procoagulant membranes with vitamin K-dependent proteins and c) the chelation model can satisfactorily explain calcium-mediated lipid-protein association.

scholarly journals The Position of Solid Carbon Dioxide in the Triboelectric Series

2019 ◽  
Vol 72 (8) ◽  
pp. 633 ◽  
Author(s):  
Jinyang Zhang ◽  
Simone Ciampi
Keyword(s):  
Carbon Dioxide ◽  
Negative Charge ◽  
Plastic Material ◽  
Indirect Evidence ◽  
Liquid Carbon ◽  
Solid Carbon Dioxide ◽  
Dry Ice ◽  
First Time ◽  
Charge Sign ◽  
Positively Charged

The process of releasing liquid carbon dioxide from a fire extinguisher is accompanied by a strong static charging of the plastic material making up the extinguisher discharge horn. Firefighters often report an electric shock when operating CO2 extinguishers, but the origin of this electrostatic hazard is largely unknown. Here, we begin to investigate this phenomenon, and test the hypothesis of plastic samples being tribocharged on contact with rapidly flowing solid CO2. Using Faraday pail measurements, we show that non-conductive polymers gain a net static charge when brought in and out of contact with dry ice (solid CO2). These measurements of charge sign and magnitude give indirect evidence helping to place solid CO2 for the first time on the triboelectric series. Polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE), and polyvinyl chloride (PVC) samples acquire a negative charge when rubbed against dry ice, whereas poly(methyl methacrylate) (PMMA), glass, and nylon surfaces become positively charged. Therefore, we suggest the position of dry ice in the triboelectric series to be close to that of materials with stable cations and unstable anions, possibly locating it between PMMA and PVC.

scholarly journals Structural requirements for the utilization of ascorbate analogues in the prolyl 4-hydroxylase reaction

1994 ◽  
Vol 300 (1) ◽  
pp. 75-79 ◽  
Author(s):  
G Tschank ◽  
J Sanders ◽  
K H Baringhaus ◽  
F Dallacker ◽  
K I Kivirikko ◽  
...  
Keyword(s):  
Negative Charge ◽  
Substrate Inhibition ◽  
Side Chain ◽  
Structural Requirements ◽  
Response Behaviour ◽  
Structural Analogues ◽  
Microsomal Hydroxylation ◽  
Ring Position ◽  
Charged Group ◽  
Positively Charged

The ability of structural analogues of ascorbate to serve as substitutes for this reducing agent in the prolyl 4-hydroxylase reaction was studied. In experiments using the purified enzyme, variations of the compounds′ side chain were compatible with co-substrate activity. The presence of very large hydrophobic substituents or a positively charged group caused an increase in the observed Km values. A negative charge and smaller modifications did not change the affinity to the enzyme when compared with L-ascorbate. 6-Bromo-6-deoxy-L-ascorbate had a lower Km than the physiological reductant. Substitution at the -OH group in ring position 3 prevented binding to the enzyme. The same pattern of activity was observed when the full and uncoupled prolyl 4-hydroxylase reactions were studied. The Vmax. values with all compounds were similar. The reaction of microsomal prolyl 4-hydroxylase was supported by D-isoascorbate, O6-tosyl-L-ascorbate and 5-deoxy-L-ascorbate, giving the same dose-response behaviour as L-ascorbate itself. Again, 6-bromo-6-deoxy-L-ascorbate gave a lower Km and a similar Vmax. value. L-Ascorbic acid 6-carboxylate produced substrate inhibition at concentrations above 0.3 mM. The Km and Vmax. values calculated from concentrations up to 0.2 mM were similar to those of L-ascorbate. The enzyme activity observed with 6-amino-6-deoxy-L-ascorbate was very low in the microsomal hydroxylation system. The calculated Vmax. value was lower than that of L-ascorbate, suggesting a restriction of the access of this compound to the enzyme.

scholarly journals The polarity of thunderclouds

1932 ◽  
Vol 138 (834) ◽  
pp. 205-229 ◽  
Keyword(s):  
South Africa ◽  
Negative Charge ◽  
Upper Atmosphere ◽  
Positive Polarity ◽  
The Earth ◽  
Positively Charged

The mechanism of the maintenance of the negative charge upon the surface of the earth has long been sought. C. T. R. Wilson has made the suggestion that the activity of thunderstorms of positive polarity—positively charged above and negatively charged below—will serve to separate positive and negative charges, by carrying negative charges to the earth and positive charges to the upper atmosphere. Experiments carried out by him during and subse­quent to 1916 indicated the presence of clouds predominantly of positive polarity, and similar experiments carried out by Schonland and Craib, in South Africa, gave similar conclusions. Appleton, Watt and Herd made observations on the form of atmospherics, and came to the conclusion that the thunderclouds which were the seat of the disturbances producing atmospherics were of positive polarity.

Grown from lithium flux, the ErCo5Si3.17silicide is a combination of disordered derivatives of the UCo5Si3and Yb6Co30P19structure types

2015 ◽  
Vol 71 (6) ◽  
pp. 506-510
Author(s):  
Andrij Stetskiv ◽  
Beata Rozdzynska-Kielbik ◽  
Renata Misztal ◽  
Volodymyr Pavlyuk
Keyword(s):  
Electronic Structure ◽  
Negative Charge ◽  
Electronic Structure Calculations ◽  
Trigonal Prismatic Coordination ◽  
A Site ◽  
Derivatives Of ◽  
Structure Calculations ◽  
Trigonal Prismatic ◽  
Positively Charged

A ternary hexaerbium triacontacobalt enneakaidecasilicide, ErCo5Si3.17, crystallizes as a combination of disordered variants of the hexagonal UCo5Si3(P63/m) and Yb6Co30P19(P-6) structure types and is closely related to the Sc6Co30Si19and Ce6Rh30Si19types. The Er, Co and three of the Si atoms occupy sites ofm.. symmetry and a fourth Si atom occupies a site of -6.. symmetry. The environment of the Er atom is a 21-vertex pseudo-Frank–Kasper polyhedron. Trigonal prismatic coordination is observed for the Si atoms. The Co atoms are enclosed in heavily deformed cuboctahedra and 11-vertex polyhedra. Crystallochemistry analysis and the data from electronic structure calculations (TB–LMTO–ASA) suggest that the Er atoms form positively charged cations which compensate the negative charge of the [Co12Si9]m−polyanions.

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