scholarly journals Electrostatic charging of wind-blown dust and implications on dust transport

2019 ◽  
Vol 99 ◽  
pp. 02011
Author(s):  
Joseph R. Toth ◽  
Siddharth Rajupet ◽  
Henry Squire ◽  
Blaire Volbers ◽  
Jùn Zhou ◽  
...  
Keyword(s):  
Electric Fields ◽  
High Surface ◽  
Charged Particles ◽  
Volume Ratio ◽  
Dust Storms ◽  
Dust Transport ◽  
Size Dependent ◽  
Surprising Effect ◽  
Electrostatic Charging ◽  
Triboelectric Charging

It is well known that electric fields occur in wind-blown dust, due to the triboelectric charging of particles as they collide. Triboelectric charging, or contact electrification, is a poorly understood and complex phenomenon. It is especially important in granular systems, as the high surface-to-volume ratio can lead to the build-up of large amounts of charge. A particularly surprising effect, which is important in dust systems, is that charge transfer occurs in systems of a single composition, such that there is a particle-size dependent polarity of the particles. Here, we use a combined experimental and theoretical approach to elucidate the electrostatic charging that occurs during dust storms, and the effects of this electrostatic charging on dust transport. We create laboratory-scale wind-blown dust systems, and study the electrostatic charging. We find that larger particles tend to charge positive and to stay at or near the sand bed, while smaller particles tend to charge negative and get lofted to higher elevations. This self-segregating of charged particles would lead to electric fields within a dust storm. Our results show that electric fields then increase the dust transport by more easily lofting charged particles.

scholarly journals The surface tension of surfactant-containing, finite volume droplets

2020 ◽  
Vol 117 (15) ◽  
pp. 8335-8343 ◽  
Author(s):  
Bryan R. Bzdek ◽  
Jonathan P. Reid ◽  
Jussi Malila ◽  
Nønne L. Prisle
Keyword(s):  
Surface Tension ◽  
Finite Volume ◽  
Climate Models ◽  
High Surface ◽  
Finite Size ◽  
Volume Ratio ◽  
Cloud Droplet ◽  
Reaction Rates ◽  
Hygroscopic Growth ◽  
Size Dependent

Surface tension influences the fraction of atmospheric particles that become cloud droplets. Although surfactants are an important component of aerosol mass, the surface tension of activating aerosol particles is still unresolved, with most climate models assuming activating particles have a surface tension equal to that of water. By studying picoliter droplet coalescence, we demonstrate that surfactants can significantly reduce the surface tension of finite-sized droplets below the value for water, consistent with recent field measurements. Significantly, this surface tension reduction is droplet size-dependent and does not correspond exactly to the macroscopic solution value. A fully independent monolayer partitioning model confirms the observed finite-size-dependent surface tension arises from the high surface-to-volume ratio in finite-sized droplets and enables predictions of aerosol hygroscopic growth. This model, constrained by the laboratory measurements, is consistent with a reduction in critical supersaturation for activation, potentially substantially increasing cloud droplet number concentration and modifying radiative cooling relative to current estimates assuming a water surface tension. The results highlight the need for improved constraints on the identities, properties, and concentrations of atmospheric aerosol surfactants in multiple environments and are broadly applicable to any discipline where finite volume effects are operative, such as studies of the competition between reaction rates within the bulk and at the surface of confined volumes and explorations of the influence of surfactants on dried particle morphology from spray driers.

scholarly journals Surface Tension of Surfactant-Containing, Finite Volume Droplets

2020 ◽  
Author(s):  
Bryan Bzdek ◽  
Rachael Miles ◽  
Jussi Malila ◽  
Hallie Boyer ◽  
Jim Walker ◽  
...  
Keyword(s):  
Surface Tension ◽  
Climate Models ◽  
High Surface ◽  
Particle Surface ◽  
Volume Ratio ◽  
Droplet Surface ◽  
Submicron Particles ◽  
Cloud Droplets ◽  
Droplet Shape ◽  
Size Dependent

<p>Surface tension influences the fraction of atmospheric particles that become cloud droplets. Recent field studies have indicated that surfactants, which lower the surface tension of macroscopic solutions, are an important component of aerosol mass. However, the surface tension of activating aerosol particles is still unresolved, with most climate models assuming activating particles have a surface tension equal to that of water. For surfactants to be relevant to particle activation into cloud droplets, multiple parameters must be considered. First, the concentration of surfactant in the initial particle must be sufficiently large that surface tension depression is maintained during activation, despite the dilution that occurs as water condenses onto the particle. Second, the high surface to volume ratio of micron and submicron particles necessitates partitioning a larger fraction of the surfactant molecules to the particle surface than in a typical solution, resulting in a depletion of the bulk concentration and an increase in the surface tension relative to a bulk sample. Third, the timescale for establishing equilibrium at the droplet surface must be known. The interplay of these parameters highlights the necessity of direct measurements of picolitre droplet surface tension.</p><p>This presentation will describe two cutting-edge approaches we have developed to directly measure the surface tension of microscopic droplets. In the first approach, ejection of ~20 µm radius surfactant-containing droplets from a dispenser excites oscillations in droplet shape that can be used to retrieve the droplet surface tension on microsecond timescales. These measurements allow investigation of surfactant partitioning timescales in aerosol and, crucially, test the assumption that droplet surfaces are generally in their equilibrium state. In the second approach, the coalescence of ~8 µm radius droplets is investigated. Coalescence excites droplet shape oscillations which again permit quantification of droplet surface tension. We demonstrate that surfactants can significantly reduce the surface tension of finite sized droplets below the value for water, consistent with recent field measurements. This surface tension reduction is droplet size dependent and does not correspond exactly to the macroscopic solution value. A new monolayer partitioning model confirms the observed size dependent surface tension arises from the high surface-to-volume ratio in finite-sized droplets and enables predictions of aerosol hygroscopic growth. This model, constrained by the laboratory measurements, is consistent with a reduction in critical supersaturation for activation and a 30% increase in cloud droplet number concentration, in line with a radiative cooling effect larger than current estimates assuming a water surface tension by 1 W·m<sup>-2</sup>. The results imply that one single value for surface tension cannot be used to predict the activated aerosol fraction.</p>

Synergism at the Nanoscale

2016 ◽  
pp. 42-77
Author(s):  
Raquel Eugenia Galian ◽  
Julia Pérez-Prieto
Keyword(s):  
Optical Properties ◽  
High Surface ◽  
Organic Ligand ◽  
Volume Ratio ◽  
Colloidal Dispersions ◽  
Organic Ligands ◽  
Organic Media ◽  
Intrinsic Properties ◽  
Smart Systems ◽  
Size Dependent

Photoactive nanoparticles are smart systems that exhibit unique optical properties. In general, their intrinsic properties are size dependent. The degree and type of response to size are both related to their composition. Nanoparticles usually require to be capped with organic ligands in order to be dispersible in an aqueous or organic media, thus leading to nanoparticle colloidal dispersions and enhancing the processability of the material. The organic ligand also plays a key role in their preparation. In addition, the high surface-to-volume ratio of the nanoparticles combined with the affinity of the ligands for the nanoparticle surface can be used to place a large number of functional molecules at their periphery. The purpose of this chapter is to understand the synergism between nanoparticles and organic ligands with regard to their preparation, performance, and applicability.

Surface Stress Effect on the Vibrational Response of Circular Nanoplates With Various Edge Supports

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
R. Ansari ◽  
R. Gholami ◽  
M. Faghih Shojaei ◽  
V. Mohammadi ◽  
S. Sahmani
Keyword(s):  
Differential Equation ◽  
Boundary Conditions ◽  
Surface Stress ◽  
High Surface ◽  
Continuum Theory ◽  
Volume Ratio ◽  
Stress Effect ◽  
Size Dependent ◽  
Surface Stress Effect ◽  
Generalized Differential

The classical continuum theory cannot be directly used to describe the behavior of nanostructures because of their size-dependent attribute. Surface stress effect is one of the most important size dependencies of structures at this submicron size, which is due to the high surface to volume ratio of nanoscale domain. In the present study, the nonclassical governing differential equation together with corresponding boundary conditions are derived using Hamilton's principle, into which the surface energies are incorporated through the Gurtin-Murdoch elasticity theory. The model developed herein contains intrinsic length scales to take the size effect into account and is used to analyze the free vibration response of circular nanoplates including surface stress effect. The generalized differential quadrature (GDQ) method is employed to discretize the governing size-dependent differential equation along with simply supported and clamped boundary conditions. The classical and nonclassical frequencies of circular nanoplates with various edge supports and thicknesses are calculated and are compared to each other. It is found that the influence of surface stress can be different for various circumferential mode numbers, boundary conditions, plate thicknesses, and surface elastic constants.

scholarly journals Two-Dimensional Nanomaterials for Gas Sensing Applications: The Role of Theoretical Calculations

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 851 ◽  
Author(s):  
Yamei Zeng ◽  
Shiwei Lin ◽  
Ding Gu ◽  
Xiaogan Li
Keyword(s):  
Electric Fields ◽  
Gas Sensing ◽  
Theoretical Calculations ◽  
High Surface ◽  
Volume Ratio ◽  
Two Dimensional ◽  
Sensing Properties ◽  
Sensing Applications ◽  
Gas Sensing Properties ◽  
2D Nanomaterials

Two-dimensional (2D) nanomaterials have attracted a large amount of attention regarding gas sensing applications, because of their high surface-to-volume ratio and unique chemical or physical gas adsorption capabilities. As an important research method, theoretical calculations have been massively applied in predicting the potentially excellent gas sensing properties of these 2D nanomaterials. In this review, we discuss the contributions of theoretical calculations in the study of the gas sensing properties of 2D nanomaterials. Firstly, we elaborate on the gas sensing mechanisms of 2D layered nanomaterials, such as the traditional charge transfer mechanism, and a standard for distinguishing between physical and chemical adsorption, from the perspective of theoretical calculations. Then, we describe how to conduct a theoretical analysis to explain or predict the gas sensing properties of 2D nanomaterials. Thirdly, we discuss three important methods that have been applied in order to improve the gas sensing properties, that is, defect functionalization (vacancy, edge, grain boundary, and doping), heterojunctions, and electric fields. Among these strategies, theoretical calculations play a very important role in explaining the mechanisms underlying the enhanced gas sensing properties. Finally, we summarize both the advantages and limitations of the theoretical calculations, and present perspectives for further research on the 2D nanomaterials-based gas sensors.

Impact of dust and sand storms on the aviation operation and assessment of conditions for their occurrence at aerodromes in European Russia

2020 ◽  
Vol 4 ◽  
pp. 78-95
Author(s):  
A.R. Ivanova ◽  
◽  
E.N. Skriptunova ◽  
N.I. Komasko ◽  
A.A. Zavialova ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Dust Storms ◽  
European Russia ◽  
Air Transport ◽  
Review Of Literature ◽  
Dust Transport ◽  
Air Masses ◽  
The Past ◽  
Sand Storm ◽  
The Impact

A review of literature on the impact of dust and sand storms on the air transport operation is presented. Observational data on dust storms at the aerodromes of European Russia for the period of 2001-2019 are analyzed. The seasonal variations in dust transport episodes at aerodromes and its relationship with visibility changes are discussed. The characteristics of dusty air masses and advection are given. It is concluded that the frequency of dust transfer episodes for the aerodromes under study has decreased over the past five years, except for Gumrak aerodrome (Volgograd). Keywords: dust storm, sand storm, aviation, visibility, seasonal variations, aerodrome оf European Russia

scholarly journals Electrospun Nanofibers for Sensing and Biosensing Applications—A Review

2021 ◽  
Vol 22 (12) ◽  
pp. 6357
Author(s):  
Kinga Halicka ◽  
Joanna Cabaj
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Toxic Metal ◽  
Volume Ratio ◽  
Electrospun Nanofibers ◽  
Clinical Diagnostics ◽  
Loading Capacity ◽  
Electrospun Nanofiber ◽  
Sensing Platforms ◽  
Different Types

Sensors and biosensors have found applications in many areas, e.g., in medicine and clinical diagnostics, or in environmental monitoring. To expand this field, nanotechnology has been employed in the construction of sensing platforms. Because of their properties, such as high surface area to volume ratio, nanofibers (NFs) have been studied and used to develop sensors with higher loading capacity, better sensitivity, and faster response time. They also allow to miniaturize designed platforms. One of the most commonly used techniques of the fabrication of NFs is electrospinning. Electrospun NFs can be used in different types of sensors and biosensors. This review presents recent studies concerning electrospun nanofiber-based electrochemical and optical sensing platforms for the detection of various medically and environmentally relevant compounds, including glucose, drugs, microorganisms, and toxic metal ions.

scholarly journals Study of the geometry of open channels in a layer-bed-type microfluidic immobilized enzyme reactor

2021 ◽  
Author(s):  
Cynthia Nagy ◽  
Robert Huszank ◽  
Attila Gaspar
Keyword(s):  
Immobilized Enzyme ◽  
High Surface ◽  
Volume Ratio ◽  
Volumetric Flow Rate ◽  
Enzyme Reactor ◽  
Channel Pattern ◽  
Immobilized Enzyme Reactor ◽  
Split Flow ◽  
Parallel Streams ◽  
Enzymatic Microreactors

AbstractThis paper aims at studying open channel geometries in a layer-bed-type immobilized enzyme reactor with computer-aided simulations. The main properties of these reactors are their simple channel pattern, simple immobilization procedure, regenerability, and disposability; all these features make these devices one of the simplest yet efficient enzymatic microreactors. The high surface-to-volume ratio of the reactor was achieved using narrow (25–75 μm wide) channels. The simulation demonstrated that curves support the mixing of solutions in the channel even in strong laminar flow conditions; thus, it is worth including several curves in the channel system. In the three different designs of microreactor proposed, the lengths of the channels were identical, but in two reactors, the liquid flow was split to 8 or 32 parallel streams at the inlet of the reactor. Despite their overall higher volumetric flow rate, the split-flow structures are advantageous due to the increased contact time. Saliva samples were used to test the efficiencies of the digestions in the microreactors. Graphical abstract

scholarly journals A Review on Biosensors and Recent Development of Nanostructured Materials-Enabled Biosensors

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1109
Author(s):  
Varnakavi. Naresh ◽  
Nohyun Lee
Keyword(s):  
High Surface ◽  
Three Dimensional ◽  
Biological Response ◽  
Volume Ratio ◽  
Recent Decade ◽  
Disease Diagnosis ◽  
Electrical Signal ◽  
Detection Sensitivity ◽  
Wide Range ◽  
Color Tunability

A biosensor is an integrated receptor-transducer device, which can convert a biological response into an electrical signal. The design and development of biosensors have taken a center stage for researchers or scientists in the recent decade owing to the wide range of biosensor applications, such as health care and disease diagnosis, environmental monitoring, water and food quality monitoring, and drug delivery. The main challenges involved in the biosensor progress are (i) the efficient capturing of biorecognition signals and the transformation of these signals into electrochemical, electrical, optical, gravimetric, or acoustic signals (transduction process), (ii) enhancing transducer performance i.e., increasing sensitivity, shorter response time, reproducibility, and low detection limits even to detect individual molecules, and (iii) miniaturization of the biosensing devices using micro-and nano-fabrication technologies. Those challenges can be met through the integration of sensing technology with nanomaterials, which range from zero- to three-dimensional, possessing a high surface-to-volume ratio, good conductivities, shock-bearing abilities, and color tunability. Nanomaterials (NMs) employed in the fabrication and nanobiosensors include nanoparticles (NPs) (high stability and high carrier capacity), nanowires (NWs) and nanorods (NRs) (capable of high detection sensitivity), carbon nanotubes (CNTs) (large surface area, high electrical and thermal conductivity), and quantum dots (QDs) (color tunability). Furthermore, these nanomaterials can themselves act as transduction elements. This review summarizes the evolution of biosensors, the types of biosensors based on their receptors, transducers, and modern approaches employed in biosensors using nanomaterials such as NPs (e.g., noble metal NPs and metal oxide NPs), NWs, NRs, CNTs, QDs, and dendrimers and their recent advancement in biosensing technology with the expansion of nanotechnology.

scholarly journals Water uptake of various electrospun nonwovens

2020 ◽  
Vol 6 (3) ◽  
pp. 155-158
Author(s):  
Katharina Wulf ◽  
Volkmar Senz ◽  
Thomas Eickner ◽  
Sabine Illner
Keyword(s):  
Contact Angle ◽  
Surface Modification ◽  
Water Absorption ◽  
Water Uptake ◽  
Biomedical Applications ◽  
High Surface ◽  
Volume Ratio ◽  
Polymer Composition ◽  
Water Wetting ◽  
Morphology Changes

AbstractIn recent years, nanofiber based materials have emerged as especially interesting for several biomedical applications, regarding their high surface to volume ratio. Due to the superficial nano- and microstructuring and the different wettability compared to nonstructured surfaces, the water absorption is an important parameter with respect to the degradation stability, thermomechanic properties and drug release properties, depending on the type of polymer [1]. In this investigation, the water absorption of different non- and plasma modified biostable nanofiber nonwovens based on polyurethane, polyester and polyamide were analysed and compared. Also, the water absorption by specified water wetting, the contact angle and morphology changes were examined. The results show that the water uptake is highly dependent on the surface modification and the polymer composition itself and can therefore be partially changed.

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