Average Droplet Research Articles

Mortalidade de Tuta absoluta em função da estrutura do volume depositado por pulverizadores

ABSTRACT: In the scientific toxicity evaluations of insecticides against larvae of Tuta absoluta (Tomato pinworm), a leaf coverage rate of 100 % or very close to this value is sought to guarantee the contact of the insect with the chemical product. However, deposition can change according to the different pesticide application methods used in field productions; consequently, interfering with pest control. From this perspective, this study evaluated the mortality of Tuta absoluta and the deposited volume dispersion on tomato leaflets as a function of droplet sizes and the method of chemical treatment with abamectin. For that purpose, an experiment was conducted in a randomized block design with five treatments and five replications. The treatments consisted of different chemical treatment methods: immersion, hydraulic spraying with three droplet sizes, and pneumatic spraying, in which the following parameters were evaluated: larval mortality, volume retained (deposition), surface density of active ingredient, droplet density, and coverage percentage. The different chemical treatments with abamectin provided larval mortality rates above 90%. Furthermore, the highest mortality values (98% and 95.9%) were associated; respectively, with the sprayings that provided the highest droplet densities: hydraulic spraying with average droplets (181 droplets cm-2) and pneumatic spraying with very fine droplets (256 droplets cm-2), the latter using an application volume 84% lower (80 L ha-1) than the lowest volume recommended by the manufacturer (500 L ha-1).

Rational Design, Synthesis, and Characterization of a Solid Δ9-Tetrahydrocannabinol Nanoformulation Suitable for "Microdosing" Applications.

Background: This article highlights the formulation of a solid Δ9-tetrahydrocannabinol (THC)-loaded ingestible prepared from pure THC distillate. Methods: A THC-containing ethanol-assisted cannabinoid nanoemulsion (EACNE) was created using a solvent displacement technique. Subsequently, the EACNE was converted to a solid powdery material while still retaining its THC potency, a format uniquely suited for "microdosing" applications. Results: EACNE had an average lipid droplet size of ∼190 nm, with a polydispersity index of 0.15, and an average droplet ζ potential of -49±10 mV. The nanoemulsion (NE) was colloidally stable for at least 6 weeks, with no meaningful change in cannabinoid potency over the experimental period, as determined by high-performance liquid chromatography analysis. The EACNE remained stable when subjected to physical stresses such as heat, freeze/thaw cycles, carbonation, dilution to beverage concentrations, high sucrose concentrations, and a pH range between 5 and 8. The microencapsulated EACNE demonstrated limited free-flowing behavior but was freely redispersible in water without any visible phase separation. Conclusions: We report the design, creation, and characterization of a THC NE generated without the use of specialized equipment, such as a microfluidizer or a high-pressure homogenizer. This emulsion could readily be converted to a water-redispersible powder. This embodiment is particularly suited for THC "microdosing," a practice that might decouple the health benefits of THC from its psychotropic effects.

Atomization Characteristics of Hydrogen Peroxide Solutions in Electrostatic Field.

Hydrogen peroxide (H2O2) can be considered as a sterilant or a green propellant. For a common use in industrial application, spray is an effective method to form fine H2O2 droplets. In this paper, electrostatic atomization based on the configuration of needle ring electrodes is proposed to produce H2O2 spray by minimizing its effective surface tension. The breakup performances of H2O2 ligaments can be improved by increasing the electric field intensity, reducing the nozzle size, and adjusting suitable volume flow rate. The smallest average diameter of breakup droplets for 35 wt. % concentration H2O2 solution reached 92.8 μm under optimum operation conditions. The H2O2 concentration significantly influenced the breakup performance owing to the concentration effect on comprehensive physical properties such as density, surface tension, viscosity, and permittivity. The average diameters of breakup droplets decreased with decreasing H2O2 concentration. At 8 wt. % concentration, the average breakup droplet diameter was reduced to 67.4 μm. Finally, electrostatic atomization mechanism of H2O2 solution was analyzed by calculating dimensionless parameters of Re, We, and Oh numbers with the combination of the operation conditions and physical properties for in-depth understanding the breakup behaviors. The calculation showed that the minimum average diameter of breakup droplets was obtained at 8 wt. % concentration at the investigated range of H2O2 concentration, which kept in agreement with the experimental results.

Investigation of Liquid Droplet Flow Behavior in a Vertical Nozzle Chamber

Abstract This study aims to better understand the aluminum oxide agglomerates breakup mechanism, consequently determining the best solution for the solid rocket motor (SRM) nozzle erosion problem. Two-phase air-water flow experimental investigation was conducted as a substitute for liquid aluminum agglomerates and exhaust combustion gases. The results show that increasing the exhaust air velocity enhances the droplet's breakup tendency to reduce the average diameter and increase droplet numbers per the testing channel volume. Numerical models were constructed and validated using the experimental results. The percentage error in the droplets’ average diameter and the number is between 6 and 15% and 8 and 18%, respectively. Furthermore, the effect of reducing the liquid surface tension was studied. The results showed that it facilitates water bodies’ separation from the interface surface, because of the reduced bounding forces between surface’s molecules, which enhances the breakup process (0.5–17% increase in the droplets’ average diameter and 4–100% increase in its number) and reduces the droplets impact on the nozzle walls, hence reducing the SRM nozzle erosion problem.

Microexplosive Fragmentation of a Group of Inhomogeneous Fuel Droplets

We have experimentally studied the process of microexplosive fragmentation of two-component (diesel fuel–water) liquid droplets heated in a high-temperature gas medium. The experiment involved a group of 10–30 droplets falling down in a tubular muffle furnace. The delay times of microexplosion were studied and it was established that integral characteristics of the process significantly depend on the relative arrangement of droplets in the group. Limiting distances between droplets (within an average initial droplet radius of 8–10) are established for which the microexplosion characteristics are close to those observed in experiments with single droplets.

IMPROVED CIPROFLOXACIN PENETRATION IN GOAT EYES USING COMPLEXATION TECHNIQUE

Objective: The objective of the present work was to improve the retention and penetration of ciprofloxacin (CF) ion pair entrapped within submicron emulsion (SE) in goat eyes and characterize the SE for improvement of ocular activity. The developed delivery system resulted with prolonged drug release as compared to the conventional dosage form.
 Methods: SE prepared by high-energy emulsification and sonication to obtain uniform globule size. Ion-pair complex is prepared by precipitation method.
 Results: Average internal droplets size of the optimized formulation was 0.300 μm, pH of the optimized formulation was 6.4±0.7 (average of three determinations) and viscosity 3.2±0.3 cP suitable for ocular use. Entrapment was 92.12%. In vitro drug release pattern in dialysis membrane showed sustain release of CF, a cumulative percent release of CF was found 77% in 10 h. Scanning electron microscopy showed spherical shape and size within 1 μm. In vitro release in goat eyes was found 35.86 % for optimized formulation compared to market, 26.83% in 60 min.
 Conclusion: Developed optimized formulation can be a good candidate for ocular drug delivery in severe ocular infections where frequent dosing required such as endophthalmitis, corneal ulcer, and penetrating trauma.

Abstract ID: 88 Quantum versus classical Monte Carlo simulation of low energy electron transport in condensed media

Purpose Monte Carlo simulations are being applied to study radiation interactions and energy deposition on sub-micron length scales within cells, e.g., DNA, in diverse contexts across medical physics. While these classical trajectory Monte Carlo simulations ignore the quantum wave nature of the electron, quantum effects may become non-negligible as electron energy decreases below 1 keV, with electron wavelength becoming considerable relative to the size of biological targets. This work investigates quantum mechanical (QM) treatments of low energy electron transport in condensed media and compares results with those from the corresponding classical trajectory Monte Carlo (MC) model. Methods For QM calculations, a simplified model of electron transport in water is developed consisting of a plane wave (representing an electron) incident on a collection of ∼103 point scatterers (molecules) representing a water droplet. Scatterer positions are random but are constrained by a minimum scatterer-to-scatterer separation, dmin, in some simulations. Cross sections for isotropic elastic and inelastic (absorption) interactions are varied. QM calculations involve numerically solving the system of ∼103 coupled equations for the electron wavefield incident on each scatterer. Results are averaged over 105 droplets with different point scatterer positions but otherwise same parameters (incident electron energy, cross sections). Average QM droplet incoherent cross sections and scattering event densities are compared with analogues computed within the corresponding classical MC model, and estimates of relative errors on MC results are computed. Results Relative errors on MC results vary with electron wavelength, droplet shape and structure (dmin), and interaction cross section. Relative errors on droplet differential cross sections generally differ from errors on scattering event density. The introduction of inelastic scatter generally increases relative errors (compared to calculations with the same elastic scatter cross section) with some exceptions (e.g. longer wavelength, relatively large inelastic cross section). Accounting for structure (non-zero dmin) enhances differences between QM and MC results. Conclusions The quantum wave nature of electrons may be non-negligible for simulations of electron transport within small-scale biological targets. Future work will involve the development of more realistic models of electron transport in condensed media.

Effect of hydrophobic modification of hydroxypropyl methylcellulose on silicone oil emulsions

ABSTRACTTo study the effect of hydrophobic modification of the emulsifier on the relationship between emulsion stability and polymer emulsifier concentration, silicone oil emulsions were prepared using hydroxypropyl methylcellulose (original HPMC) and HPMC stearoxy ether (hydrophobic HPMC) at concentrations around their overlap concentrations. Both HPMC types completely emulsified the silicone oil. However, the volume fraction of silicone oil in the emulsion prepared using hydrophobic HPMC was less than that that by the original HPMC, and the average oil droplet size in the former emulsion was less than that in the latter emulsion. Increasing HPMC concentration led to increase in both the amount of adsorbed polymer emulsifier and the storage moduli in the linear region, irrespective of which HPMC was used. Stress-strain sweep curves obtained by a rheo-optical method showed that emulsions stabilized by the hydrophobic HPMC flowed slowly, even beyond the yield stress, whereas emulsions prepared using the original HPMC flowed quickly beyond the yield stress. The storage moduli of the emulsions prepared by the hydrophobic HPMC were larger than those prepared using the original HPMC.

Optically isotropic liquid crystal mixtures and their application to high-performance liquid crystal devices

Optically isotropic liquid crystal (OILC) mixtures utilising polymerisation-induced phase separation in mixtures of prepolymers and liquid crystals (LCs) have been made and their overall electro-optic performances have been tested by applying an in-plane electric field for flexible display application. Excellent transparent films with a LC to prepolymer weight ratio of 42:58 are achieved and confirmed by SEM images. The average LC droplet size inside the polymer matrix is 215 nm. Consequently, an in-plane driven LC device with a crossed polariser shows a very high contrast ratio over 1000 comparable to the conventional nematic in-plane switching cell, wide viewing angle, a low threshold voltage of 8.2 V, hysteresis free and fast response time. The proposed LC device is free from an alignment layer and the rubbing process and its dark state is not disturbed by mechanical pressure, which can open its application to flexible liquid crystal displays.

Effect of Urethane Acrylate Oligomer and UV Curing Temperature on Electro-Optical Property of Polymer-Dispersed Liquid Crystal

Polymer-dispersed liquid crystal (PDLC) films were prepared by photopolymerization after substituting the reactive diluent monomer 2-ethylhexyl acrylate with an aliphatic urethane acrylate (UA) oligomer in a conventional pre-polymer (PN393). The effects of UA concentration and UV curing temperature on the PDLC films’ physical properties were examined. The average LC droplet size decreased with increasing UA concentration. The driving voltage decreased by 30% and the response time increased by 26%. The PDLC films with 30 wt% of UA showed the lowest driving voltage and the highest contrast ratio when the LC pre-polymer mixture was UV-cured slightly above the nematic-isotropic coexistence temperature.

Ultrasonic Scattering Measurements of Dispersed Oil Droplets in the Presence of Gas

ABSTRACT To help minimize the effects of oil spills on marine environments, chemical dispersants are used to disperse the oil in the water column so the oil can be consumed by naturally occurring bacteria. During the Deepwater Horizon incident, 1.1 million gallons of dispersant were injected directly into the flowing plume of oil and natural gas over 1500 meters deep. Dispersant's main effect is to decrease the surface tension at the oil-water interface causing the oil to form droplets smaller than ~70 microns so they can remain in the water column. Currently the efficacy of aerial applied dispersants on surface slicks is determined by measuring the droplet size decrease using a Laser In-Situ Scattering Transmissometer (LISST) or by detecting the oil in the water column using fluorometers. LISST instruments are limited to dilute mixtures, below ~500 ppm, because the LISST signal saturates for concentrated mixtures, and their windows can become occluded by oil and biofilms. Fluorometers only measure oil concentration; thus they cannot distinguish between naturally dispersed oil droplets, which can float back to the surface, from chemically dispersed oil droplets, which will remain in the water column to be naturally biodegraded. When gas is present as was the case in the Deepwater Horizon incident where it was estimated that the plume consisted of ~22% natural gas, the LISST cannot distinguish between oil droplets and gas bubbles and thus is not able to track the effectiveness of dispersants in the presence of gas. Acoustic measurements overcome the problems associated with the LISST and fluorometers and are ideal for applications subsurface near a blowout and for low ppm levels expected for surface slicks. One of the key features of the sound wave propagating through the water is the scattering at the interface between the water and object. In previous work we showed the proof of concept to measure the average oil droplet size using acoustic. We used the resonance behavior of the gas bubbles to identify them and separate their contribution to the measured acoustic scattering for various oil and dispersant combinations . We developed acoustic scattering and resonance measurements to track the size of oil droplets in the presence of gas during subsurface releases at SINTEF and in Ohmsett's large wave tank.

Inkjet printing as a possible route to study confined crystal structures

Inkjet printing is a technique for the precise deposition of liquid droplets in the pL-volume range in well-defined patterns. Previous studies have shown that inkjet printing is attractive in polymer technology since it permits the controlled deposition of functional polymer surfaces. We suggest that the technique might also be useful for studying crystallization, in particular confined crystallization. Inkjet printing is a non-contact deposition method with minimal risk of contamination, which allows the exact deposition of both polymer solutions and polymer melts. This paper demonstrates the possibility of utilizing the technique to create surfaces where polymer chains form isolated small structures. These structures were confined by both the low polymer content in each droplet and the time constraint on crystal formation that arose as the result of the rapid solvent evaporation from the pL-sized droplets. In theory, inkjet printing enables the exact deposition of systems with as few as a single polymer chain in the average droplet. With appropriate instrumentation, the versatile inkjet technology can be utilized to create whole surfaces covered with polymer structures formed by the crystallization of small, dilute and rapidly evaporating droplets. 110pL droplets of a 10−6gL−1 poly(ε-caprolactone) solution in 1-butanol have been deposited and studied by atomic force microscopy. Small structures of ca. 10nm thickness and ca. 50nm diameter also seemed to exhibit crystalline features. Some of the small structures had unusual rectangular forms whilst others were interpreted to be early precursors to six-sided single crystals previously observed for poly(ε-caprolactone). The unusual forms observed may have resulted from the entrapment of crystal structures into metastable phases, due to the limited amount of polymer material present and the rapid evaporation of the droplets.

Cross-Flow Microfiltration of Industrial Oily Wastewater: Experimental and Theoretical Consideration

Microfiltration of industrial oily wastewater was performed using polyamide membrane. A rectangular cross flow membrane cell was used for the experiments. Effects of different operating parameters such as transmembrane pressure drop and Reynolds numbers on the steady state permeate flux and oil rejection was investigated in detail. Initial oil concentration in the industrial oil-water emulsion was found to be 192 mg/L with average oil droplet range size 0.01 to 47 µm. The treated industrial oily water was characterized in terms of electrical conductivity, total dissolved solids (TDS), and chemical oxygen demand (COD). It was observed that the steady state permeate flux increased with transmembrane pressure drop and Reynolds numbers. The oil concentration in permeate was found to be around 4.5 mg/L, after treatment, which was lower than the permissible discharge limit. The results showed that microfiltration was an efficient and ecologically suited technology for the treatment of industrial oily wastewater. The cross flow velocity was considered in both laminar and turbulent regimes. A model was proposed by combining of Brownian diffusion and shear-induced diffusion to predict the steady state permeate flux data at different Reynolds numbers and different transmembrane pressure drops.

Fluctuations and Luck in Droplet Growth by Coalescence

After the initial rapid growth by condensation, further growth of a cloud droplet is punctuated by coalescence events. Such a growth process is essentially stochastic. Yet, computational approaches to this problem dominate and transparent quantitative theory remains elusive. The stochastic coalescence problem is revisited and it is shown, via simple back-of-the-envelope results, that regardless of the initial size, the fastest one-in-a-million droplets, required for warm rain initiation, grow about 10 times faster than the average droplet. While approximate, the development presented herein is based on a realistic expression for the rate of coalescence. The results place a lower bound on the relative velocity of neighboring droplets, necessary for warm rain initiation. Such velocity differences may arise from a variety of physical mechanisms. As an example, turbulent shear is considered and it is argued that even in the most pessimistic case of a cloud composed of single-sized droplets, rain can still for...

Composite droplets with core/shell morphologies prepared from HDPE/PS/PMMA ternary blends by twin‐screw extrusion

AbstractTernary blends of PS and PMMA in a PE matrix were prepared by twin‐screw extrusion to investigate the core/shell encapsulation phenomenon in the composite droplet. The PS was found to encapsulate the PMMA to form composite droplets within the PE matrix as expected from the spreading coefficient theory. The effects of dispersed phase concentration, viscosity ratio, feeding sequence and twin‐screw operating conditions were investigated. The blend morphology was observed by scanning electron microscopy after selective extraction of either PS or PMMA, and average core and composite droplet diameters were determined by image analysis. Although it is known that the structure of composite droplet blends can be substantially altered through control of the volume fraction of the components in the dispersed phase, this study demonstrates that blends with a 1:1 composite droplet volume fraction are relatively stable to large variations in the minor phase viscosities and processing conditions. Twin‐screw extrusion thus provides a highly robust technique for the melt processing of blends possessing composite droplet morphologies. Polym. Eng. Sci. 44:749–759, 2004. © 2004 Society of Plastics Engineers.

Some characteristics of electrospark deposition

Abstract The paper deals with some characteristics of electrospark deposition. A relevant device and the process are described, the material transfer is shown schematically, and the average droplet...

Evidence of flexoelectricity in polymer-dispersed liquid crystals

The linear electro-optic response of polymer-dispersed liquid crystal films has been studied. Micrometer-sized droplets of a cyanobiphenyl mixture (E7) were formed in a Norland Optical Adhesive 65 photopolymer by photopolymerization-induced phase separation. Samples with various average nematic droplet sizes were systematically investigated. The temperature dependence of the first-harmonic electro-optic spectra was obtained. Peculiar peaks and double peaks in the phase spectra were found at temperatures close to the clearing point. Samples with narrow distributions of droplet sizes were characterized by a double peak of the amplitude spectra in the low-frequency range. A flexoelectric origin of the first-harmonic spectra in confined nematic systems is discussed.

Climate sensitivity to cloud optical properties

A radiative’convective model was developed to investigate the sensitivity of climate to cloud optical properties and the related feedback processes. This model demonstrates that the Earth’s surface temperature increases with cloud optical depth when the clouds are very thin but decreases with cloud optical depth when the cloud shortwave (solar) radiative forcing is larger than the cloud longwave (terrestrial) radiative forcing. When clouds are included in the model, the magnitude of the greenhouse effect due to a doubling of the CO2 concentration varies with the cloudoptical depth: the thicker the clouds, the weaker the greenhouse warming. In addition, a small variation in the cloud droplet size has a larger impact on the equilibrium state temperature in the lower atmosphere than the warming caused by a doubling of the CO2 concentration: a 2% increase in the average cloud droplet size per degree increase in temperature doubles the warming caused by the doubling of the CO2 concentration. These findings suggest that physically reliable correlations between the cloud droplet size and macrophysical meteorological variables such as temperature, wind and water vapor fields are needed on a global climate scale to assess the climate impact of increases in greenhouse gases.

Cloud properties inferred from bimodal aerosol number distributions

Nonprecipitating clouds leave a distinctive fingerprint on the aerosol particles that cycle through them by segregating aerosol particles into two populations, those which are incorporated into cloud droplets and those which are not. This leads to a bimodal or double-peaked character in the aerosol number distribution. If some reasonable assumptions are made, cloud microphysical properties can be inferred from the bimodal aerosol distributions. We have collected over 1700 bimodal distributions from five stations in North America and inferred cloud droplet concentration and maximum supersaturation in the clouds which processed the aerosol particles. Average cloud droplet concentrations are 100–200 cm−3 at “background” stations, while at the polluted site, cloud droplet concentrations were as high as 3000 cm−3. Inferred values of maximum supersaturation ranged from 0.3% at clean sites to 0.1% at the polluted site. Cloud droplet concentration and maximum supersaturation were usually inversely correlated. Cloud droplet concentration and geometric mean diameter of the cloud-processed mode in the aerosol number distribution were also inversely correlated. These two relationships can be understood by comparison with a simple model of cloud activation.

The effects of entrainment on the growth of droplets in continental cumulus clouds

In this paper data are presented from aircraft passes through continental cumulus clouds obtained during the Cooperative Convective Precipitation Experiment. The effect of evaporation of liquid water from the cloud following the entrainment of free tropospheric air is to totally remove a fraction of the droplets of all sizes rather than partially evaporate most of the droplets. Supersaturations in the cloud are found on average to be considerably higher than those predicted for an adiabatic cloud and the supersaturation is not closely tied to the vertical wind. These observations are found to have a number of important consequences for cloud droplet growth: 1. The average lifetime of individual droplets is considerably less than the age of the cloud and is not expected to exceed about five minutes. This has important consequences for the oxidation of SO2 to sulphate. 2. Statistically favoured droplets that avoid evaporation are observed to grow much larger than average droplets and to sizes larger than would occur at the same altitude in an adiabatic cloud.