A critical evaluation of short columns for estimating the attachment efficiency of engineered nanomaterials in natural soils

Short, saturated packed columns are used frequently to estimate the attachment efficiency (α) of engineered nanomaterials (ENMs) in relatively homogeneous porous media, but a combined experimental and theoretical approach to...

Nanoparticle affinity for natural soils: a functional assay for determining particle attachment efficiency in complex systems

Few standardized methods and reference systems have been established for evaluating the behavior of engineered nanomaterials in complex media like natural soils.

Effect of Comminution Methods on Low-Rank Coal Bubble–Particle Attachment/Detachment: Implications for Flotation

The floatability of fine low-rank coal particles can be greatly influenced by their morphological characteristics, such as shape and surface roughness. In this study, the attachment efficiency and detachment amplitude of fine low-rank coal particles produced by various comminution methods onto/from the bubble surface were investigated using homemade bubble–particle wrap angle and bubble–particle attachment/detachment testing systems. Results showed that the length–diameter ratio of rod-milled products was smaller than that of crushed products. The wrap angle of particles obtained by the crushed method was larger than that obtained by the rod-milled method, i.e., particles with greater length–diameter ratio showed higher attachment efficiency onto the bubble surface. Meanwhile, particles with greater length–diameter ratio exhibited a larger detachment amplitude, which suggests that it is more difficult to be detached from the bubble surface. However, rod-milled products showed lower attachment onto the bubble surface. The flotation test confirmed that the floatability ratio of crushed products was higher than that of rod-milled products, consistent with evidence from experimental analyses. This study provides a fundamental understanding of particle shapes for low-rank coal flotation by a novel research method combining the attachment efficiency and detachment amplitude of bubble–particle combinations.

Cytotoxic Effect of Chitosan Nanoparticles on Normal Human Dental Pulp Cells

Introduction: Recent in vitro studies have shown that chitosan nanoparticles could enhance the antimicrobial activity of several dental materials. However, the biocompatibility of these nanoparticles with normal human cells is still controversial. The aim of this study was to evaluate the potential toxicity of various sizes and concentrations of chitosan nanoparticles cultured with normal human dental pulp cells. Methods: Normal human dental pulp cells were derived from human dental pulp tissues and cultured with (50-67) nm and (318-350) nm chitosan nanoparticles in concentrations: 0.2 mg/mL, 0.5 mg/mL, 1 mg/mL, and 2 mg/mL as study groups, and 0 mg/mL as a control. The cell attachment efficiency for each group was assessed at 16 hours. The proliferation rate and cell viability were evaluated at days 7 and 14. Both, attachment efficiency and proliferation rate were assessed by measuring the optical density of crystal violet stained cells. The cell viability was determined by the activity of the mitochondrial dehydrogenase enzyme. Statistical analysis was performed using One-Way ANOVA and post hoc Tukey test. Results: All concentrations of the (50-67) nm group significantly reduced cell attachment efficiency in comparison with the control (p<0.01) and with the (318-350) nm group (p<0.01). All concentrations of both groups, (50-67) nm and (318-350) nm, significantly reduced cell proliferation and cell viability compared to the control in dose-dependent and size-associated manners. (p<0.01). Conclusion: Chitosan nanoparticles exhibit a cytotoxic effect on normal human dental pulp cells

A model sensitivity analysis to determine the most important physicochemical properties driving environmental fate and exposure of engineered nanoparticles

Sensitivity analyses indicate attachment efficiency and transformation rate constant are most important in modeling environmental fate of engineered nanoparticles.

The Similarity of the Action of Franklin and ESE Lightning Rods under Natural Conditions

In the lightning rods categorized as ESE an intermittent voltage impulse is applied to the lightning rod to modulate the electric field at its tip in an attempt to speed up the initiation of a connecting leader from the lightning rod when it is under the influence of a down coming stepped leader. In this paper it is shown that due to the stepping nature of the down coming stepped leader, there is a natural modulation of the electric field at the tip of any lightning rod exposed to the lightning stepped leaders and this modulation is much more intense than any artificial modulation that is possible under practical conditions. Based on the results it is claimed that artificial modulation of the electric field at the tip of lightning rods by applying voltage pulses to it is an unnecessary endeavor because the nature itself has endowed the tip of the lightning rod with a modulating electric field. Thus, as far as the effectiveness of artificial modulation of the tip electric field is concerned, there could be no difference in the lightning attachment efficiency between ESE and Franklin lightning rods.