Surface charge of erythrocytes and neutrophils is altered in psoriatic patients treated with PUVA.

Clemmer and Beebe have pointed out that surface structures on graphite substrates can be misinterpreted as biopolymer images in STM experiments. We have been using electrochemical methods to react DNA fragments onto gold electrodes for STM and AFM imaging. The adsorbates produced in this way are only homogeneous in special circumstances. Searching an inhomogeneous substrate for ‘desired’ images limits the value of the data. Here, we report on a reversible method for imaging adsorbates. The molecules can be lifted onto and off the substrate during imaging. This leaves no doubt about the validity or statistical significance of the images. Furthermore, environmental effects (such as changes in electrolyte or surface charge) can be investigated easily.

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INFLUENCE OF SURFACE PRETREATMENT ON THE SURFACE CHARGE DENSITY AT THE INTERFACE BETWEEN MCT MBE AND AL3 ALD

Автометрия ◽

10.15372/aut20200506 ◽

2020 ◽

Keyword(s):

Charge Density ◽

Surface Charge ◽

Surface Charge Density ◽

Surface Pretreatment

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Application of Singular Shape Functions for the Surface Charge Approximation in the Boundary Element Method

Elektrichestvo ◽

10.24160/0013-5380-2020-2-48-53 ◽

2020 ◽

Vol 2 (2) ◽

pp. 48-53

Author(s):

Аlexander G. KALIMOV ◽

◽

Sergey A. VAZHNOV ◽

Keyword(s):

Boundary Element Method ◽

Surface Charge ◽

Boundary Element ◽

Shape Functions ◽

Element Method

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Molecular Characterization of the Surface Excess Charge Layer in Droplets

10.26434/chemrxiv.11853405.v2 ◽

2020 ◽

Author(s):

Victor Kwan ◽

Styliani Consta

Keyword(s):

Hydrogen Bonds ◽

Surface Charge ◽

Droplet Size ◽

Chloride Ions ◽

Total Charge ◽

Excess Charge ◽

Surface Excess ◽

High Concentration ◽

Dipole Orientation ◽

Charge Layer

<div>Charged droplets play a central role in native mass spectrometry, atmospheric aerosols and in serving as micro-reactors for accelerating chemical reactions. The surface excess charge layer in droplets has often been associated with distinct chemistry. Using molecular simulations for droplets with Na+ and Cl- ions we have found that this layer is ≈ 1.5−1.7 nm thick and depending on the droplet size it includes 33%-55% of the total number of ions. Here, we examine the eﬀect of droplet size and nature of ions in the structure of the surface excess charge layer by using molecular dynamics. We ﬁnd that in the presence of simple ions the thickness of the surface excess charge layer is invariant not only with respect to droplet size but also with respect to the nature of the simple ions and it is not sensitive to ﬁne details of diﬀerent force ﬁelds used in our simulations.</div><div> In the presence of macroions the excess surface charge layer may extend to 2.0. nm. For the same droplet size, iodide and model hydronium ions show considerably higher concentration than the sodium and chloride ions. <br></div><div>We also ﬁnd that diﬀerences in the average water dipole orientation in the presence of cations and anions in this layer are reﬂected in the charge distributions. Within the surface charge layer, the number of hydrogen bonds reduces gradually relative to the droplet interior where the number of hydrogen bonds is on the average 2.9 for droplets of diameter < 4 nm and 3.5 for larger droplets. The decrease in the number of hydrogen bonds from the interior to the surface is less pronounced in larger droplets. In droplets with diameter < 4 nm and high concentration of ions the charge of the ions is not compensated only by the solvent polarization charge but by the total charge that also includes the other free charge. This ﬁnding shows exceptions to the commonly made assumption that the solvent compensates the charge of the ions in solvents with very high dielectric constant. The study provides molecular insight into the bi-layer droplet structure assumed in the equilibrium partitioning model of C. Enke and assesses critical assumptions of the Iribarne-Thomson model for the ion-evaporation mechanism. <br></div>

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Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells

10.26434/chemrxiv.7851461.v3 ◽

2019 ◽

Author(s):

Valentina Guccini ◽

Annika Carlson ◽

Shun Yu ◽

Göran Lindbergh ◽

Rakel Wreland Lindström ◽

...

Keyword(s):

Fuel Cells ◽

Fuel Cell ◽

Surface Charge ◽

Proton Exchange Membrane ◽

Membrane Surface ◽

Proton Exchange ◽

Membrane Thickness ◽

Fuel Cell Performance ◽

Cellulose Nanofibres ◽

Exchange Membrane

The performance of thin carboxylated cellulose nanofiber-based (CNF) membranes as proton exchange membranes in fuel cells has been measured in-situ as a function of CNF surface charge density (600 and 1550 µmol g<sup>-1</sup>), counterion (H<sup>+</sup>or Na<sup>+</sup>), membrane thickness and fuel cell relative humidity (RH 55 to 95 %). The structural evolution of the membranes as a function of RH as measured by Small Angle X-ray scattering shows that water channels are formed only above 75 % RH. The amount of absorbed water was shown to depend on the membrane surface charge and counter ions (Na<sup>+</sup>or H<sup>+</sup>). The high affinity of CNF for water and the high aspect ratio of the nanofibers, together with a well-defined and homogenous membrane structure, ensures a proton conductivity exceeding 1 mS cm<sup>-1</sup>at 30 °C between 65 and 95 % RH. This is two orders of magnitude larger than previously reported values for cellulose materials and only one order of magnitude lower than Nafion 212. Moreover, the CNF membranes are characterized by a lower hydrogen crossover than Nafion, despite being ≈ 30 % thinner. Thanks to their environmental compatibility and promising fuel cell performance the CNF membranes should be considered for new generation proton exchange membrane fuel cells.<br>

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Evaluation of Soil Surface Charge Using the Back-Titration Technique

Soil Science Society of America Journal ◽

10.2136/sssaj2004.0082 ◽

2004 ◽

Vol 68 (1) ◽

pp. 82 ◽

Cited By ~ 7

Author(s):

Ying Ge ◽

William Hendershot

Keyword(s):

Surface Charge ◽

Soil Surface ◽

Back Titration ◽

Titration Technique

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Effect of Polyphosphate on Removal of Endocrine-Disrupting Chemicals of Nonylphenol and Bisphenol-A by Activated Carbons

Water Quality Research Journal ◽

10.2166/wqrj.2005.052 ◽

2005 ◽

Vol 40 (4) ◽

pp. 484-490 ◽

Cited By ~ 5

Author(s):

Keun J. Choi ◽

Sang G. Kim ◽

Chang W. Kim ◽

Seung H. Kim

Keyword(s):

Activated Carbon ◽

Bisphenol A ◽

Surface Charge ◽

Activated Carbons ◽

Endocrine Disrupting Chemicals ◽

Dipole Interaction ◽

High Affinity ◽

Calcium Polyphosphate ◽

Endocrine Disrupting ◽

Positively Charged

Abstract This study examined the effect of polyphosphate on removal of endocrine-disrupting chemicals (EDCs) such as nonylphenol and bisphenol-A by activated carbons. It was found that polyphosphate aided in the removal of nonylphenol and bisphenol- A. Polyphosphate reacted with nonylphenol, likely through dipole-dipole interaction, which then improved the nonylphenol removal. Calcium interfered with this reaction by causing competition. It was found that polyphosphate could accumulate on carbon while treating a river. The accumulated polyphosphate then aided nonylphenol removal. The extent of accumulation was dependent on the type of carbon. The accumulation occurred more extensively with the wood-based used carbon than with the coal-based used carbon due to the surface charge of the carbon. The negatively charged wood-based carbon attracted the positively charged calcium-polyphosphate complex more strongly than the uncharged coal-based carbon. The polyphosphate-coated activated carbon was also effective in nonylphenol removal. The effect was different depending on the type of carbon. Polyphosphate readily attached onto the wood-based carbon due to its high affinity for polyphosphate. The attached polyphosphate then improved the nonylphenol removal. However, the coating failed to attach polyphosphate onto the coal-based carbon. The nonylphenol removal performance of the coal-based carbon remained unchanged after the polyphosphate coating.

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Surface charge and extracellular polymer of sludge in the anaerobic degradation process

Water Science & Technology ◽

10.2166/wst.1996.0565 ◽

1996 ◽

Vol 34 (5-6) ◽

pp. 309-316 ◽

Cited By ~ 20

Author(s):

X. S. Jia ◽

Herbert H. P. Fang ◽

H. Furumai

Keyword(s):

Surface Charge ◽

Growth Phase ◽

Anaerobic Degradation ◽

Degradation Process ◽

Anaerobic Sludge ◽

Batch Experiments ◽

High Substrate Concentration ◽

Negative Surface ◽

Negative Surface Charge ◽

Extracellular Polymer

Changes of surface charge and extracellular polymer (ECP) content were investigated in batch experiments for three anaerobic sludges, each of which had been enriched at 35°C and pH 639-7.3 for more than 40 batches using propionate, butyrate and glucose, individually, as the sole substrate. Results showed that both ECP and the negative surface charge were dependent on the growth phase of microorganisms. They increased at the beginning of all batches when the microorganisms were in the prolific-growth phase, having high substrate concentration and food-to-microorganisms ratio. Both later gradually returned to their initial levels when the microorganisms were in the declined-growth phase, as the substrate became depleted. The negative surface charge increased linearly with the total-ECP content in all series with slopes of 0.0187, 0.0212 and 0.0157 meq/mg-total-ECP for sludge degrading propionate, butyrate and glucose, respectively. The change of surface charge for the first two sludges was mainly due to the increase of proteinaceous fraction of ECP; but, for glucose-degrading sludge, that could be due to the increases of both proteinaceous and carbohydrate fractions of ECP. The negative-charged nature of anaerobic sludge implies that cations should be able to promote granulation of anaerobic sludge.

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