Electrostatic force

SUMMARY - Little is known about the possible contribution of electrostatic forces to pollination processes in nature. Earlier studies have shown that plants and pollinating insects possess surface electrical charges and are surrounded by electric fields. Accordingly, these electric fields should be more intense near sharp points on the edges, for example anthers and stigmas in the flowers. One mechanism

An electrolyte local composition model is developed for excess Gibbs energy, which is assumed to be the sum of two contributions, one resulting from long range electrostatic forces between ions and the other from short range forces between all the species. The validity of the model is demonstrated for systems emcompassing the entire range from molecular liquid to fused salt.

In this paper, the response to the first harmonic component (2f) of the electrostatic force in single terminal driven electrostatic comb-drive and parallel-plate drive was used as a signal to extract device parameters, namely, the Q-factor and resonant frequency instead of the fundamental (1f) resonance response. It is shown that the difficulty in motional measurement due to electrical cross-talk (parasitics)

The phenomenon of electrostatic attraction between charged materials has been recognized since early Greek times. Despite its long history, the relative importance of electrostatic forces (compared with non-electrostatic forces) on powder particles is still a subject of debate among today's scientists. In this article, we attempt to present a systematic evaluation of the possible magnitudes of electrostatic forces and van

A conventional method of DNA sequencing can determine up to 1000 base pairs at one time. A long piece of DNA should be cut up into many short DNA fragments that are suitable for DNA sequencing. These DNA fragments, however, lose their order information. If the fragments are prepared from the terminus of the long chromosomal DNA, the reorganization process can be omitted. To achieve this, a single DNA molecule should be fixed with a stretched form, and sequentially cut from the terminus to prepare fragments that keep order information. In this report, a novel stretching and cutting method for single DNA molecules are presented. The method of stretching is based on manipulation and reversible change of globular DNA molecules. The globular DNA can be easily manipulated by electrostatic force, because this transition suppresses breakdown of long DNA molecules due to shear stress accompanied with flow. A single globular DNA molecule was anchored at the tip of needle electrode of tungsten...

Zeta potential measurements of silica-induced protein (SIP) Escherichia coli and quartz showed that the former are positively charged under acidic condition and negatively charged under neutral and alkaline conditions, with an isoelectric point (IEP) at pH 4.5, while the quartz was always negatively charged. Adsorption experiments with bacteria cells on quartz were conducted under different conditions. The results show that at pH values lower than the IEP of the cells, more cells were adsorbed due to electrostatic forces. However, at pH > 4.5, the amount of adsorbed cells decreased as a result of electrostatic repulsion forces. Zeta potentials of quartz showed that at pH 2.5 a significant change in the surface chemistry of quartz occurred after bacterial treatment. The degree of this change was related to the initial SIP E. coli concentration; at 5 × 107 cells/ml the average zeta potential of biotreated quartz shifted from –30 mV to 0 mV and at higher concentrations the zeta potential shifted to the positive direction and reached a similar value to that of the bacterial cells. SIP E. coli showed hydrophobic properties at pH lower than the IEP, with approximately 60% of the cells moving to the organic phase from aqueous phase. Bioflotation of quartz using SIP E. coli alone at pH 2.5 gave approximately 60% recovery because at this pH more bacteria adsorb onto the quartz surface and the bacterial surface is hydrophobic. In anionic flotation of quartz using sodium dodecyl sulfate, SIP E. coli cells act as a surface modifier, with an increase in flotation recovery from 28% to 85%. This is because the bacterial cells confer hydrophobic properties to the quartz and the biotreated quartz is positively charged, so a large amount of the collector was adsorbed and the recovery increased.