Fraction Of Droplets Research Articles

Fluid dynamics-based distance estimation algorithm for macroscale molecular communication

Many species, from single-cell bacteria to advanced animals, use molecular communication (MC) to share information with each other via chemical signals. Although MC is mostly studied in microscale, new practical applications emerge in macroscale. It is essential to derive an estimation method for channel parameters such as distance for practical macroscale MC systems which include a sprayer emitting molecules as a transmitter (TX) and a sensor as the receiver (RX). Due to the similarity between sneezing/coughing and spraying mechanisms, these practical systems have the potential to be applied in modeling airborne pathogen (viruses, bacteria, etc.) transmission with a MC perspective where an infected human emitting pathogen-laden droplets is considered as a TX. In this paper, a novel approach based on fluid dynamics is proposed for the derivation of the distance estimation in practical MC systems. According to this approach, transmitted molecules are considered as moving and evaporating droplets in the MC channel. With this approach, the Fluid Dynamics-based Distance Estimation (FDDE) algorithm which predicts the propagation distance of the transmitted droplets by updating the diameter of evaporating droplets at each time step is proposed. FDDE algorithm is validated by experimental data. The results reveal that the distance can be estimated by the fluid dynamics approach which introduces novel parameters such as the volume fraction of droplets in a mixture of air and liquid droplets and the beamwidth of the TX. Furthermore, the effect of the evaporation is shown with the numerical results.

Formation of high-entropy alloy by methods of ion-plasma technologies

Multi-element equiatomic single-phase thermodynamically stable substitutional solid solutions (high-entropy alloys) have a unique combination of mechanical, tribological, physical and other properties. The purpose of this research is to develop an ion-plasma method for the formation of high-entropy alloys. A method for the formation of high-entropy alloys has been developed, which consists in the deposition of a multi-element metal plasma on a substrate in a vacuum. Plasma is formed by vacuum-arc plasma-assisted simultaneous independent sputtering of the cathodes of the selected elements. The modes allowing synthesizing thin Ti-Al-Nb-Zr films with a composition close to equiatomic were revealed. The presence of droplet fraction particles of various elemental composition in the films was found. It is shown that the phase composition of the films depends on the concentration of elements in the plasma.

Integration of segmented microflow chemistry and online HPLC/MS analysis on a microfluidic chip system enabling enantioselective analyses at the nanoliter scale.

In this work, we introduce an approach to merge droplet microfluidics with an HPLC/MS functionality on a single chip to analyze the contents of individual droplets. This is achieved by a mechanical rotor-stator interface that precisely positions a microstructured PEEK rotor on a microfluidic chip in a pressure-tight manner. The developed full-body fused silica chip, manufactured by selective laser-induced etching, contained a segmented microflow compartment followed by a packed HPLC channel, which were interconnected by the microfluidic PEEK rotor on the fused silica lid with hair-thin through-holes. This enabled the targeted and leakage-free transfer of 10 nL fractions of droplets as small as 25 nL from the segmented microflow channel into the HPLC compartment that operated at pressures of up to 60 bar. In a proof of concept study, this approach was successfully applied to monitor reactions at the nanoliter scale and to distinguish the formed enantiomers.

The Effect of Curing Temperature on the Morphology and Electro-Optical Properties of a Flexible UV-Cured Polymer Dispersed Liquid Crystal (PDLC)

In this work, the experimental data on flexible PDLC films at the industrial scale and the effect of cure temperature (Tc) on the morphology and electro-optical properties of a UV-cured PDLC system via polymer-induced phase separation (PIPS) method were studied. Under constant UV radiation intebsity and thickness, the morphological parameters such as dimension, number density, and volume fraction of the phase-separated liquid crystal droplets as well as the optical transmissions and switching voltages as a function of cure temperature were determined. The effect of cure temperature on the morphology and electro-optical properties of UV-cured PDLC films were analyzed.

Low‐Field High‐Resolution PFG‐NMR to Predict the Size Distribution of Inner Droplets in Double Emulsions

AbstractIn double emulsions, the inner and outer droplet size distribution (DSD) determines the quality of the double emulsion and is therefore essential to be measured. Low‐field high‐resolution pulsed‐field gradient nuclear magnetic resonance is used to measure the inner DSD in water‐in‐oil‐in‐water double emulsions. The Gaussian phase distribution approach is employed with a mixture of two normal distributions to predict bimodal inner droplets. This approach allows the prediction of the swelling of inner droplet during storage of double emulsions, and thus to validate a phenomenological population balance model estimating inner droplet swelling. Only a fraction of the inner droplets are found to swell during storage, due to differences in the Laplace pressure, thus leading to the formation of a bimodal size distribution of the inner droplets.Practical Applications: This methodology is useful to predict the evolution of double emulsions during storage, in a wide range of applications, such as food and pharmaceutical products.

Superheated metastable water atomization: fine atomized water plumes diagnostics and disperse characteristics; summary of results, applications in power generation and new techniques.

Complex experimental investigation of superheated flow and dispersion characteristics of sprays in atomizing nozzles of various types is made. The comparative analysis of experimental and calculating investigations of thermo physic and hydro- gas-dynamic flow and disperse characteristics was carried out for various types of spray nozzles. It has shown that the main process, which determine peculiarities of superheated metastable water flow and phase transformation in spray nozzles, is quick (explosive) boiling up. And the optimal variant for superheated water atomization and achieving the most fine spray plumes, which contain mainly submicron droplet fraction, at initial temperature 240°C (and higher) is atomization by means of contracting-expanding nozzles. In such nozzles the explosive boiling is accomplished by quick transformation of foamed liquid into vapor-droplet flow. Diagnostic peculiarities are considered for these optically dense spray plumes; the auxiliary measurement methods were worked out for estimation superheated water high atomization level. The experimental and calculating data dimensionless treatment was made for achieving extremely fine (mainly submicron) superheated water spray. The dimensionless parameter, which determines necessary water (or some other liquids, for example – fuels) superheating level was derived. The possible technical applications of superheated water sprays are described, and up-to-date state of corresponding projects is given.

Evaluation of laser diffraction-based particle size measurements using digital inline holography

The measurements of size distribution of small particles (e.g. dusts, droplets, bubbles, etc) are critical for a broad range of applications in environmental science, public health, industrial manufacturing, etc. Laser diffraction (LD), a widely used method for such applications, depends on model-based inversion with underlying assumptions on particle properties. Furthermore, the presence of sampling biases such as velocity differentials are often overlooked in simple ex-situ calibrations, which introduces as an additional source of error. In contrast, digital inline holography (DIH), a single camera coherent imaging technique, can both measure particle size distributions without the need for a model-based inversion and can directly provide information on the shape characteristics of the particles. In this study, we evaluate the performance of an LD system in characterizing polydisperse droplets produced in a flat fan spray using in-situ DIH based imaging as a reference. The systematic differences in the two techniques are examined. A droplet-trajectory-based correction for the LD-inferred size distributions is proposed to compensate for the observed differences. We validate the correction using NIST standard polydisperse particles undergoing differential settling, and then apply the correction to polydisperse spray droplet measurements. The correction improves agreement between LD and DIH size distributions for droplets over two orders of magnitude, but with LD still underestimating the fraction of droplets at sizes above ∼1 mm. This underestimation is possibly linked to the complex oscillatory and rotational motion of droplets which cannot be faithfully captured by measurement or modelled by the correction algorithm without additional information.

Osteogenic Effect of tsRNA-10277-Loaded Exosome Derived from Bone Mesenchymal Stem Cells on Steroid-Induced Osteonecrosis of the Femoral Head.

PurposeSteroids are known to inhibit osteogenic differentiation and subsequent bone formation in bone mesenchymal stem cells (BMSCs). However, little is known about the role of BMSC exosomes (Exos) and tRNA-derived small RNAs (tsRNAs) in steroid-induced osteonecrosis of the femoral head (SONFH). The objective of this study was to characterize the tsRNA expression profiles of plasma Exos collected from SONFH patients and healthy individuals using small RNA sequencing and further explore the effect of BMSC Exos carrying specific tsRNAs on osteogenic differentiation.Materials and MethodsBased on insights from small RNA sequencing, five differentially expressed (DE) tsRNAs were selected for quantitative real-time polymerase chain reaction (qRT-PCR). The regulatory networks associated with interactions of the tsRNAs-mRNA-pathways were reconstructed. The osteogenesis and adipogenesis in BMSCs were detected via ALP and oil red O staining methods, respectively.ResultsA total of 345 DE small RNAs were screened, including 223 DE tsRNAs. The DE tsRNAs were enriched in Wnt signaling pathway and osteogenic differentiation. We identified five DE tsRNAs, among which tsRNA-10277 was significantly downregulated in plasma Exos of SONFH patients compared to that in healthy individuals. Dexamethasone-induced BMSCs were associated with an increased fraction of lipid droplets and decreased osteogenic differentiation, whereas BMSC Exos restored the osteogenic differentiation of that. After treatment of tsRNA-10277-loaded BMSC Exos, the lipid droplets and osteogenic differentiation ability were found to be decreased and enhanced in dexamethasone-induced BMSCs, respectively.ConclusionAn altered tsRNA profile might be involved in the pathophysiology of SONFH. tsRNA-10277-loaded BMSC Exos enhanced osteogenic differentiation ability of dexamethasone-induced BMSCs. Our results provide novel insights into the osteogenic effect of BMSC Exos carrying specific tsRNAs on SONFH.

Spectral Radiative Properties of a Liquid n-Octane Droplet in the Midinfrared Region

The optical constants of a liquid hydrocarbon such as liquid n-octane are basic material properties that may be used to evaluate their thermal radiation transfer capabilities. In this study, the ellipsometry method was used to measure the optical constants of liquid n-octane in the midinfrared wavelength range of 2.0–16.0 μm at temperatures of 20, 50, and 80°C. Experimental analyses indicate the significant effect of temperature on the refractive index, although it has little effect on the absorption index. With increasing temperature, the refractive index shows a linear decrease, and reduced density leads to weaker absorption intensities. The radiative properties of n-octane droplets, including the absorption and scattering efficiency factors of single droplets with droplet radii r = 10, 20, 50, and 100 μm and the absorption and scattering coefficients in a droplets-air system of droplet volume fractions fv = 2%, 3%, and 4%, were calculated using Mie theory. The numerical results indicate that, with increasing temperature, the absorption efficiency factor slightly decreases, and the variation trend of the scattering efficiency factor is more complicated. With increasing droplet radius, the absorption efficiency factor increases within the studied wavelength range, except for certain absorption peaks, but the scattering efficiency factor tends to decrease. While the absorption is greater, the scattering is weaker for a given droplet radius. With an increasing volume fraction of n-octane droplets, the absorption and scattering coefficients increase linearly within the studied wavelength range.

Droplet Generation in Standing-Surface-Acoustic-Wave Nebulization at Controlled Air Humidity

Surface-acoustic-wave (SAW) aerosol generators are very promising systems for applications requiring small aerosol sources and adjustable droplet-size distributions at low aerosol flowrates. However, the droplet-generation mechanism by SAW is yet unclear and dedicated experiments are necessary to gain further insights. In this work, the atomization zone is investigated experimentally to gain more insight into the droplet-generation mechanism by SAW. Three regions are observed in the atomization zone showing different acoustofluidic effects, including the formation of liquid films and patterns in a standing SAW (SSAW) wavefield and droplet generation. In addition, the influence of the humidity of surrounding air on the measured droplet-size distribution of the aerosols generated by SSAW is investigated. Therefore, the air humidity is adjusted at constant air temperature in the sophisticated wind-tunnel Turbulent Leipzig Aerosol Cloud Interaction Simulator combined with an optical particle spectrometer with resolution down to the sub-\textmu{}m scale. Besides the humidity influence on the droplet size in the measurement region, water-saturated air allowed us to estimate the initial droplet-size distribution at the atomization zone on the chip surface. This parameter is crucial for the determination of the underlying liquid-film disintegration mechanism, i.e., the droplets' origin. Hereby, a bimodal log-normal droplet-size distribution is obtained. The mean diameter of the main droplet fraction decreases from 7.2 to 5.3 \textmu{}m with increasing relative humidity from 8.6 to 97%, apparently due to evaporation of smaller droplets in unsaturated air. A second peak corresponds to a mean diameter as small as 600 nm at high humidity conditions, which is likely to correspond to a droplet-generation mechanism not reported so far and extremely difficult to measure or visualize with conventional techniques. The droplet-size measurement results from the aerosol spectrometer are compared and validated in respect to existing droplet-generation models with the results of a phase-Doppler anemometry, a high-resolution, nonintrusive local aerosol-measurement technique.

Optimization of the chemical composition of high molecular weight surfactants used to stabilize polymer dispersions in suspension polymerization of monomers

The possible reasons for the occurrence of emulsion polymerization of a monomer simultaneously with suspension polymerization, namely the formation of polymer particles from a highly dispersed fraction of monomer droplets in the initial emulsion and associates of high molecular weight surfactants, are considered. Data on colloidal solubility of monomer in surfactant associates and data on determination of hydrodynamic radii of high molecular weight surfactant associates are presented. The results obtained can be the basis for the choice of surfactants in suspension polymerization, which ensure the minimum contribution of the highly dispersed fraction of monomer droplets to the formation of polymer-monomer particles.

Vacuum Arcs with Diffuse Cathode Attachment (Review)

The review covers the results of predominantly experimental studies of stationary vacuum arcs with diffuse cathode attachment that burns in vapor of the cathode material with a current density of less than 100 A/cm2. Such discharges are of great interest for a number of technologies that require the formation of high-intensity plasma flows without a droplet fraction. The discharges on cathodes made of graphite, pure metals, and oxides, as well as mixed cathodes, are considered. The specificity of the processes on vacuum arc cathodes is characterized by the ratio of the fluxes of thermally vaporized atoms and thermionic electrons. The review presents the results of studies of cathode materials with an atom-electron ratio of ~10–2 to ~108. Data on the working cathode temperature, the current–voltage characteristic of the discharge, the heat flux from the plasma to the cathode, the plasma parameters, its radiation spectrum, and the ion energy in the cathode jet are presented. Depending on the cathode material, the working temperature ranged from 1.2 to 2.5 kK. An analysis of the features of the charge-transfer processes on various cathodes is also presented.

The effect of curing temperature and time on morphology and Electro-Optical properties of flexible thermoset polymer dispersed liquid crystal (PDLC) films

In this work, we studied the effect of cure temperature (Tc) and cure time (tc) on the morphology and few electro-optical properties of flexible thermoset PDLC systems by Polymer Induced Phase Separation (PIPS) method. Under a constant thickness, we determined the morphological parameters including dimension, number density and volume fraction of phase separated liquid crystal droplets, as well as optical transmissions and switching voltages as a function of cure temperature and cure time. We analyzed the effect of cure temperature and time on morphology and electro-optical properties in the thermoset PDLC films.

Transmission of pathogen-laden expiratory droplets in a coach bus

Droplet dispersion carrying viruses/bacteria in enclosed/crowded buses may induce transmissions of respiratory infectious diseases, but the influencing mechanisms have been rarely investigated. By conducting high-resolution CFD simulations, this paper investigates the evaporation and transport of solid-liquid mixed droplets (initial diameter 10 μm and 50 μm, solid to liquid ratio is 1:9) exhaled in a coach bus with 14 thermal manikins. Five air-conditioning supply directions and ambient relative humidity (RH = 35 % and 95 %) are considered.Results show that ventilation effectiveness, RH and initial droplet size significantly influence droplet transmissions in coach bus. 50 μm droplets tend to evaporate completely within 1.8 s and 7 s as RH = 35 % and 95 % respectively, while 0.2 s or less for 10 μm droplets. Thus 10 μm droplets diffuse farther with wider range than 50 μm droplets which tend to deposit more on surfaces. Droplet dispersion pattern differs due to various interactions of gravity, ventilation flows and the upward thermal body plume. The fractions of droplets suspended in air, deposited on wall surfaces are quantified. This study implies high RH, backward supply direction and passengers sitting at nonadjacent seats can effectively reduce infection risk of droplet transmission in buses. Besides taking masks, regular cleaning is also recommended since 85 %–100 % of droplets deposit on object surfaces.

Two-phase fuel droplet burning in weightlessness

Using multicomponent and multi-phase fuels is one of the methods for increasing effectiveness of rocket engines. In developing different compositions one should guarantee a stable fuel burning process in weightlessness. The present study is aimed at developing physical and mathematical models, allowing to consider the effect of multiphase fuel (hydrocarbon liquid + solid combustible material) on the conditions of ignition and modes of propagation of combustion in poly-dispersed non-uniform mixtures. In this case, the combustion of different droplet fractions occurs in different modes: the volatile fraction evaporates and burns in the gas-phase mode, and the solid fuel fraction reacts with the oxidizer in the heterogeneous mode. The effect of the presence of a solid fraction in droplets reacting in a heterogeneous regime on the evaporation rate of the volatile fuel component is studied. The effect of tightness due to the presence of other drops on the evaporation rate of each drop is taken into account. The results of computational modeling of flame propagation during ignition of poly-dispersed mixture of liquid hydrocarbon fuel droplets with solid fine carbon particles are presented.

Protein Binding to Lipid Droplets with Altered Ratios of Surface Phospholipids

Alcoholic Fatty Liver Disease (AFLD) is characterized by an increase in lipid droplets in the liver after acute ingestion of alcohol. Previous experiments with a rat model of AFLD show hepatic lipid droplets contain altered levels of the predominant classes of phospholipids. Specifically, hepatic lipid droplets from AFLD rats were found with lower amounts of phosphatidylcholine (PC) relative to phosphatidylethanolamine (PE). Our experiments aim to determine if the altered phospholipid composition of AFLD lipid droplets causes differences in the numbers or types of lipid droplet‐associated proteins. We selected proteins based on their membrane binding motifs and roles in lipid droplet homeostasis. AML12 cells cultured in choline‐deficient media simulate the altered phospholipid composition of AFLD lipid droplets. We isolated lipid droplets from AML12 cells cultured with and without choline and examined proteins of interest by SDS‐PAGE and western blotting. We found equivalent levels of rab18 and lanosterol synthase in lipid droplet fractions from cells grown with and without choline. Alternatively, perilipin 1, perilipin 2, and CIDE‐C are predominantly found in lipid droplet fractions from cells grown without choline (with lower ratios of PC:PE). The proteins that are most influenced by lipid droplet surface composition are all predicted to associate with lipid droplets through amphipathic alpha helices. By evaluating how altered phospholipid monolayer composition affects the binding of lipid droplet proteins, we seek to further elucidate the biochemical pathways that contribute to AFLD.Support or Funding InformationThis research was supported by St. Olaf College and the TRIO McNair Scholars Program.

Development of a computational method to quantify the partitioning of polycyclic aromatic hydrocarbons in seawater into dissolved and droplet forms

The ecological risk and potential injury from polycyclic aromatic hydrocarbons (PAHs) from spilled crude oil in water is dependent on whether they are dissolved or associated with droplets/particles. Using oil collected from the Deepwater Horizon incident, laboratory experiments were conducted to develop a computational method to determine the physical state of PAHs in sampled seawater and compare these to results from methods designed to physically separate dissolved and droplet oil used during the spill. The analytical results were used to develop a method to calculate droplet/particulate concentrations from unfractionated water samples based on oil composition and allocation of minimally soluble oil components to the droplet fraction. The computational method is less labor-intensive and costly than field fractionation and can be used to optimize the use of previously collected data. The results also showed that physical separation can result in insoluble high-molecular-weight PAHs being present in the filtrate (i.e., the “dissolved” fraction), potentially leading to an overestimate of dissolved components.

Surfactant-Stabilized Spontaneous 3-(Trimethoxysilyl) Propyl Methacrylate Nanoemulsions.

Nanoemulsions are a versatile means to create a variety of consumer products and complex materials. Producing nanoemulsions with a high volume fraction of the dispersed phase is generally limited to mechanically intensive processes, such as high-pressure homogenization, and often results in polydisperse droplet size distributions. Low-energy methods, such as spontaneous emulsification, can produce monodispersed droplets, but the volume fraction of the dispersed phase is usually much lower. Here, we report on the spontaneous emulsification of 3-(trimethoxysilyl) propyl methacrylate (TPM) into an alkaline aqueous phase (pH > 10.0) that contains surfactants (Tween 20, sodium dodecyl sulfate (SDS), or cetyltrimethylammonium bromide (CTAB)). The nanoemulsions are monodisperse with droplet diameters that range between 15 and 500 nm. The small droplet size is due to the presence of surfactants that stabilize the droplets against coalescence. The spontaneous emulsion process can produce emulsions with a dispersed volume fraction of up to 10% in CTAB solutions and up to 30% using Tween 20 and SDS. After the emulsification process, the TPM droplets can be polymerized to produce nanoparticles. Using dynamic light scattering and scanning electron microscopy, we characterize the relationship between the surfactant concentration and the size of the droplets in the nanoemulsions. We find that the droplet diameter is primarily determined by the molar ratio of oil to surfactant. We also find that the pH in the aqueous phase also modulates the droplet diameter when using an ionic surfactant. This work expands the spontaneous emulsification of TPM in the absence of stabilizing particles to the nanoscale while producing one of the highest volume fractions of nanoemulsion droplets obtained via a low-energy mechanism.

A Preliminary Model for the Migration of Sulfide Droplets in a Magmatic Conduit and the Significance of Volatiles

Abstract A close relationship between Ni–Cu–(PGE) sulfide deposits and magmatic conduit systems has been widely accepted, but our present understanding still rests on empirical inductions that sulfide liquids are entrained during magma ascent and aggregated at hydrodynamic traps such as the opening of a conduit into a larger magma body. In this contribution, a preliminary quantitative model for the dynamics of mm-scale sulfide droplets in a vertical magmatic conduit is developed, examining such limiting parameters as the size, transport velocity and the magmas’ maximum carrying capacity for sulfide droplets. Addition of numerous dense sulfide droplets significantly reduces magma buoyancy and rapidly increases the bulk viscosity, and the resulting pressure gradient in the propagating conduit dyke restricts the maximum volume fraction of droplets that can be carried by ascending magma. For sulfide droplets alone, the maximum carrying capacity is low, but it will be improved dramatically by the addition of volatiles which reduces the density and viscosity of silicate melt. Potential volatile degassing during decompression further facilitates sulfide entrainment by reducing bulk magma density, and the formation of buoyant compound vapour-sulfide liquid bubble drops also greatly enhances the carrying capacity. The breakdown of compound drops by detachment of parts of the vapour bubble or sulfide droplet may occur at low pressure, which liberates sulfide liquids from rising compound drops, potentially to collect in traps in the conduit system. When sulfide-laden magma flows through a widening conduit, many droplets can be captured by the re-circulation flow just downstream of the expanding section, followed by sulfide liquid accumulation and enhanced chemical interaction via diffusive exchange with the recirculating magma, potentially resulting in an economic, high-tonnage ore body. We apply our models to the emplacement of sulfide-rich magmatic suspensions at Noril’sk and show that the disseminated mineralization in intrusions could have formed when magmas carrying re-suspended sulfide liquid entrained from pre-existing sulfide accumulations in the conduit system reached their limiting sulfide carrying capacity as dictated by buoyancy and were deflected into blind sills flanking the principal conduit for flood basalt volcanism.

Generation of gas-metal plasma of arc low-pressure discharges and investigation of the deposition mode of wear-resistant nitride coatings

The modes of gas-metal plasma generation are investigated at independent and combined operation of plasma generators of the different construction. The dependences of an ion current on a collector on the current of the arc discharge of plasma sources, on the pressure and on the composition of working gas in the wide ranges of parameters are obtained. The distributions of metal and nitride coatings growth rate along vacuum chamber radius at the use of the system of magnetic plasma flow separation from droplet fraction are revealed. The service properties of the plasma sources of different type are defined. The parameter ranges for the optimum modes of ZrN and ZrNbN coating deposition by vacuum arc plasma-assistance method are revealed. The parameters of gas-metal plasma at simultaneous functioning the different type plasma sources are measured.