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.

Surface charge on kaolinites in aqueous suspension

Soil Research ◽  
1976 ◽  
Vol 14 (2) ◽  
pp. 197 ◽  
Author(s):  
MDA Bolland ◽  
AM Posner ◽  
JP Quirk
Keyword(s):  
Surface Charge ◽  
Positive Charge ◽  
Aqueous Suspension ◽  
Isomorphous Substitution ◽  
Ph Values ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Decreasing Ph ◽  
Ph Range ◽  
Exchange Technique

The surface charge of several natural kaolinites was measured in the pH range 3-10 using an exchange technique. The positive charge was found to increase with decreasing pH and sometimes to increase with increasing ionic strength; it occurred on the kaolinites at pH values as high as 9 and 10 and was particularly evident at high ionic strengths. The positive surface charge on kaolinites is thought to be due to exposed alumina such as is found on oxide surfaces. Aluminium was found to dissolve from kaolinite at pH values beiow about 6.5. Aluminium dissolution increased with decreasing pH and time. When the proportion of dissolved aluminium ions balancing negative surface charge was taken into account, the negative and net negative surface charge on kaolinite was concluded to be largely due to pH independent charge resulting from isomorphous substitution, together with some pH dependent charge due to exposed SiOH sites. If Na+ was the index cation, dissolved aluminium ions from the clay replaced some of the Na+ balancing the negative surface charge. However, when Cs+ was the index cation, less Cs+ balancing the negative surface charge on the clay was replaced by dissolved aluminium. As the concentration of either Na+ or Cs+ was increased, less dissolved aluminium replaced the index cation as a counteraction to the negative surface charge.

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.

Electrokinetic properties of Cassiterite

1953 ◽  
Vol 6 (3) ◽  
pp. 278 ◽  
Author(s):  
DJ O'Connor ◽  
AS Buchanan
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Weak Acid ◽  
Surface Conductivity ◽  
Surface Ionization ◽  
Conductivity Measurements ◽  
The Third ◽  
Three Samples ◽  
Negative Surface ◽  
Flotation Collector

Simultaneous ζ-potential and surface conductivity measurements have been made on three samples of cassiterite (SnO2) in water, in solutions of HCl, alkalis, inorganic salts, and the flotation collector reagent sodium cetyl sulphate. It is probable that the intrinsic surface charge of cassiterite in water is negative and that it is due to surface ionization as a very weak acid. Two of the solids possessed a negative surface whilst the positive charge of the third seemed to be due to ionization of a strongly basic impurity. Those samples having a negative charge showed little reaction with sodium cetyl sulphate alone, but appreciable adsorption of cetyl sulphate ion took place in acid solution. On the other hand, the sample with the positive surface reacted with cetyl sulphate ion even in the absence of acid. In all cases adsorption of cetyl sulphate was completely reversible.

Porous Ceramic Materials for Virus Filtration

2011 ◽  
Vol 56 (4) ◽  
pp. 1193-1197
Author(s):  
M. Zalewska ◽  
E. Bobryk ◽  
A. Pędzikiewicz ◽  
M. Szafran
Keyword(s):  
Drinking Water ◽  
Positive Charge ◽  
Porous Ceramic ◽  
Ceramic Materials ◽  
Ceramic Samples ◽  
Preliminary Model ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Virus Filtration ◽  
Porous Ceramic Materials

Porous Ceramic Materials for Virus Filtration The purpose of this study was to design and examine porous ceramic materials on the basis of diatomaceous earth, as well as carrying out preliminary model researches of the purification of drinking water. The conditions, parameters and methods of production of the ceramic samples have been selected on experimental way, in order to characterize them by suitable porosity and tensile strength. The authors have searched such porous ceramic materials, which exhibit positive charge, in contrast to viruses, which have a negative surface charge in pH o drinking water.

scholarly journals Surface Exposure of PEG and Amines on Biodegradable Nanoparticles as a Strategy to Tune Their Interaction with Protein-Rich Biological Media

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1354 ◽  
Author(s):  
Claudia Conte ◽  
Giovanni Dal Poggetto ◽  
Benjamin J. Swartzwelter ◽  
Diletta Esposito ◽  
Francesca Ungaro ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Electrostatic Interactions ◽  
Positive Charge ◽  
Particle Surface ◽  
Molecular Weights ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Body Compartments ◽  
Protein Rich ◽  
The Impact

Nanoparticles (NPs) based on amphiphilic block copolymers of polyethylene glycol (PEG) and biodegradable polyesters are of particular current interest in drug nanodelivery due to their easily manipulated properties. The interaction of these NPs with biological environments is highly influenced by shell features, which drive biological identity after administration. To widen the strategies available for tuning particle surface chemistry, here we developed a panel of amine-bearing PEGylated NPs with a poly(ε-caprolactone) (PCL) core for the delivery of lipophilic drugs, and investigated the impact of NP modifications on their interaction with abundant circulating proteins (human serum albumin—HSA—and mucin), as well as their transport through biological barriers (artificial mucus—AM, extracellular matrix—ECM). We prepared NPs based on a diamino-terminated PCL (amine-NPs) and its mixture with PEG-PCL copolymers (amine/PEG-NPs) at different PEG molecular weights by nanoprecipitation, as well as corresponding NPs of PEG-PCL (PEG-NPs). The presence of an amine-bearing polymer resulted in NPs with a net positive charge and a zeta potential dependent on the length of PEG in the copolymer. Amine/PEG-NPs had a larger fixed aqueous layer thickness as compared to PEG-NPs, suggesting that PEG conformation is affected by the presence of positive charges. In general, amine-bearing NPs promptly interacted with the dysopsonic protein HSA, due to electrostatic interactions, and lose stability, thereby undergoing time-related aggregation. On the other hand, amine/PEG-NPs interaction with mucin induced switching to a negative surface charge but did not alter the quality of the dispersion. The transport kinetics of NPs through a layer of artificial mucus and tumor extracellular matrix was studied by means of fluorescent NPs based upon FRET. Amine/PEG-NPs did not cross the ECM, but they were promptly transported through the AM, with swifter transport noted at increasing MWs of PEG in the copolymer. Finally, we demonstrated that all the different NP types developed in this study are internalized by human monocytes and, despite the positive charge, they did not induce a measurable inflammatory effect. In conclusion, we showed that the concurrent presence of both PEG and amine groups on NP surface is a promising strategy for directing their interaction with body compartments. While PEG-NPs are confirmed for their capacity to cross ECM-like compartments, amine/PEG-NPs are revealed as a powerful platform to widen the arsenal of nanotools available for overcoming mucus-covered epithelia.

scholarly journals Enforced expression of phosphatidylinositol 4-phosphate 5-kinase homolog alters PtdIns(4,5)P2 distribution and the localization of small G-proteins

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yanbo Yang ◽  
Miriam Park ◽  
Masashi Maekawa ◽  
Gregory D. Fairn
Keyword(s):  
Plasma Membrane ◽  
Surface Charge ◽  
Electrostatic Interactions ◽  
Negative Charge ◽  
Anionic Charge ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Polybasic Domains ◽  
Phosphatidylinositol 4 ◽  
Hydrolysis Of

Abstract The generation of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) by phosphatidylinositol 4-phosphate 5-kinases (PIP5Ks) is essential for many functions including control of the cytoskeleton, signal transduction, and endocytosis. Due to its presence in the plasma membrane and anionic charge, PtdIns(4,5)P2, together with phosphatidylserine, provide the inner leaflet of the plasma membrane with a negative surface charge. This negative charge helps to define the identity of the plasma membrane, as it serves to recruit or regulate a multitude of peripheral and membrane proteins that contain polybasic domains or patches. Here, we determine that the phosphatidylinositol 4-phosphate 5-kinase homolog (PIPKH) alters the subcellular distribution of PtdIns(4,5)P2 by re-localizing the three PIP5Ks to endomembranes. We find a redistribution of the PIP5K family members to endomembrane structures upon PIPKH overexpression that is accompanied by accumulation of PtdIns(4,5)P2 and phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3). PIP5Ks are targeted to membranes in part due to electrostatic interactions; however, the interaction between PIPKH and PIP5K is maintained following hydrolysis of PtdIns(4,5)P2. Expression of PIPKH did not impair bulk endocytosis as monitored by FM4-64 uptake but did result in clustering of FM4-64 positive endosomes. Finally, we demonstrate that accumulation of polyphosphoinositides increases the negative surface charge of endosomes and in turn, leads to relocalization of surface charge probes as well as the polycationic proteins K-Ras and Rac1.

Charges on the surfaces of two chlorites

Clay Minerals ◽  
1981 ◽  
Vol 16 (4) ◽  
pp. 347-359 ◽  
Author(s):  
Angela A. Jones
Keyword(s):  
Surface Charge ◽  
Surface Area ◽  
Negative Charge ◽  
Total Surface Area ◽  
Acid System ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Ph Dependent ◽  
Positively Charged

AbstractTwo chlorites, sheridanite and clinochlore, have been examined to determine their surface charge characteristics. In order to increase their surface area and to produce a measurable surface charge, the chlorites were treated with 10−3m, 10−2m, and 10−1m HCl in 10−2m MgCl2 solutions. These treatments are shown not to alter the crystallinity of the chlorites and to produce a small pH-dependent negative charge which is not directly related to the total surface area. The clinochlore, (Si6.13Al1.84)(Al1.53FeIII0.53FeII0.18Mg9.52)O20(OH)16, is more readily attacked by the acids than the sheridanite, (Si5.43Al2.55)(Al2.90FeII0.05Mg8.86)O20(OH)16, and also produces material with greater surface area and pH-dependent, negative, surface charge. It is concluded that: (i) isomorphous substitutions in the lattice are not reflected in a permanent surface charge; (ii) the observed surface charge arises not only at the edges of the particles but also at points where the chlorite is predisposed to attack by acids; (iii) in the chlorite-acid system used, anions—probably mainly silicate—block positively charged sites.

Evidence that alteration of charge modifies proximal tubular shunt pathway permselectivity

1989 ◽  
Vol 257 (6) ◽  
pp. F1079-F1086
Author(s):  
S. W. Weinstein ◽  
S. M. Jones ◽  
R. J. Weinstein
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Paracellular Pathway ◽  
Disulfonic Acid ◽  
Physiological Control ◽  
Membrane Charge ◽  
Cation Permeability ◽  
Diffusive Permeability ◽  
Proximal Tubular ◽  
Net Positive Charge

Experiments were performed to test the hypothesis that membrane charge is an important determinant of paracellular pathway ion permselectivity in the proximal tubule. Net negative charge in or around the paracellular pathway should favor cation permeability; net positive charge should favor anion permeability. Therefore compounds such as amiloride and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), capable of changing net membrane charge, should predictably change the diffusive permselectivity of the paracellular pathway to anions and cations. In the first group of experiments amiloride, a compound capable of increasing net positive membrane charge, inhibited cation and enhanced anion diffusive permeability. In a second group of experiments, SITS, a compound capable of increasing net negative membrane charge, inhibited anion and enhanced cation diffusive permeability. The effects of amiloride and SITS were symmetrical; the lumen-to-bath and the bath-to-lumen diffusion potentials were not significantly different in magnitude. In addition these effects were completely and rapidly reversible. Our results suggest that amiloride increases net positive charge, and SITS increases net negative charge within the paracellular pathway. The most likely site for the actions of SITS and amiloride is the tight junction because the effects of the inhibitors were symmetrical. Both compounds act at low concentrations and reversibly such that removal of the inhibitor rapidly reverses its effects. We propose, on the basis of the ease with which these alterations in charge and thus paracellular pathway permselectivity occurred, that the permselectivity of this pathway may not be fixed and constant for any given proximal tubular segment. In fact, permselectivity may vary and thus serve as an important physiological control mechanism for proximal tubular solute and water reabsorption.

Surface charge in some New Zealand soils measured at typical ionic strength

Soil Research ◽  
1992 ◽  
Vol 30 (3) ◽  
pp. 331 ◽  
Author(s):  
RL Parfitt
Keyword(s):  
New Zealand ◽  
Ionic Strength ◽  
Negative Charge ◽  
Positive Charge ◽  
Appreciable Amount ◽  
Surface Charges ◽  
Ph Values ◽  
Soil Solutions ◽  
Negative Surface ◽  
Allophanic Soil

The positive and negative surface charges of some New Zealand soils used for horticulture were measured at different pH values using 0.002 M CaCl2 solutions, Which have a similar ionic strength to soil solutions in New Zealand. The surface negative charge increased with pH for all soil samples including those containing mica and smectite. This behaviour was mainly due to the presence of organic matter and allophane both of which had an appreciable amount of variable negative charge. Allophanic soil B horizons had a higher positive charge than that of the Oxidic soils, which was less than 1 cmol kg-1 at pH 5.

Reduction of Fe(III) in griffithite

Clay Minerals ◽  
2000 ◽  
Vol 35 (4) ◽  
pp. 625-634 ◽  
Author(s):  
P. Komadel ◽  
J. Madejová ◽  
D. A. Laird ◽  
Y. Xia ◽  
J. W. Stucki
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Sodium Dithionite ◽  
Basic Rock ◽  
Octahedral Sheet ◽  
Bicarbonate Buffer ◽  
Structural Differences ◽  
Trioctahedral Smectite ◽  
Net Positive Charge

AbstractGriffithite is a trioctahedral smectite with dioctahedral domains, found in the <2 μm fraction of weathered basic rock from Griffith Park, California, USA. Crystalline admixtures (albite, calcite, quartz and maghemite) are concentrated in the 0.2 – 2 μm fraction, while the <0.06 μm fraction contains only trace amounts of other minerals. Griffithite is primarily an Fe–rich saponite with negative charge located in the tetrahedral sheets. The octahedral occupancy is ∼91%, and ∼26% of the octahedra contain trivalent atoms imparting a net positive charge to the octahedral sheet. Medium levels of Fe(III) reduction in griffithite, up to 60% of total Fe, can be achieved by adding solid sodium dithionite to clay dispersions in a citrate–bicarbonate buffer. By contrast >90% reduction of Fe(III) to Fe(II) is achieved in nontronites using the same method. The lower reducibility of Fe(III) in griffithite relative to nontronites may be due to structural differences between griffithite and nontronites, such as a more negative tetrahedral charge and a positive octahedral charge.

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