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1
Yun, Sungchan, Jaeung Kim y Guk Hee Kim. "Dynamic characteristics of ellipsoidal Janus drop impact on a solid surface". Physics of Fluids 34, n.º 10 (octubre de 2022): 102104. http://dx.doi.org/10.1063/5.0118969.
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Impinging Janus drops can be stably produced by adding a high-viscosity drop to a low-viscosity drop. Here, we investigate the dynamic features of bouncing Janus drops on a solid substrate for an exploration of the effects of the viscosity ratio, initial drop shape, and impact velocity on altering the hydrodynamics. Numerical results show that the low-viscosity component evolves into liquid alignment along the principal direction with the help of a preferential flow, thereby resulting in the partial detachment from the mother Janus drops. We establish a regime map of the separation ratio of the drop and discuss how the parameters affect the asymmetry in the bounce and separation behavior. The low-viscosity components can be more likely to be detached from Janus drops as the viscosity ratio, drop's ellipticity, and/or impact velocity increase. This phenomenon is explained by the residence time and breakup of symmetry in the horizontal momentum between the low- and high-viscosity components. The peculiar dynamic characteristics of the Janus drop can provide potential for various applications, such as liquid purification and separation.
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Benilov, E. S. "Dynamics of a drop floating in vapor of the same fluid". Physics of Fluids 34, n.º 4 (abril de 2022): 042104. http://dx.doi.org/10.1063/5.0088421.
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Evaporation of a liquid drop surrounded by either vapor of the same fluid, or vapor and air, is usually attributed to vapor diffusion, which, however, does not apply to the former setting, as pure fluids do not diffuse. The present paper puts forward an additional mechanism, one that applies to both settings. It is shown that disparities between the drop and vapor in terms of their pressure and chemical potential give rise to a flow. Its direction depends on the vapor density and the drop's size. In undersaturated or saturated vapor, all drops evaporate, but in oversaturated (yet thermodynamically stable) vapor, there exists a critical radius: smaller drops evaporate, whereas larger drops act as centers of condensation and grow. The developed model is used to estimate the evaporation time of a drop floating in saturated vapor. It is shown that, if the vapor-to-liquid density ratio is small, so is the evaporative flux; as a result, millimeter-sized water drops at temperatures lower than [Formula: see text] survive for days. If, however, the temperature is comparable (but not necessarily close) to its critical value, such drops evaporate within minutes. Micron-sized drops, in turn, evaporate within seconds for all temperatures between the triple and critical points.
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Ryu, Sangjin, Haipeng Zhang y Carson Emeigh. "The Dark Annulus of a Drop in a Hele-Shaw Cell Is Caused by the Refraction of Light through Its Meniscus". Micromachines 13, n.º 7 (28 de junio de 2022): 1021. http://dx.doi.org/10.3390/mi13071021.
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Knowing the meniscus shape of confined drops is important for understanding how they make first contact and then coalesce. When imaged from the top view by brightfield microscopy, a liquid drop (e.g., corn syrup) confined in a Hele-Shaw cell, surrounded by immiscible liquid (e.g., mineral oil), had a dark annulus, and the width of the annulus decreased with increasing concentration of corn syrup. Since the difference in the annulus width was presumed to be related to the meniscus shape of the drops, three-dimensional images of the drops with different concentrations were obtained using confocal fluorescence microscopy, and their cross-sectional meniscus profile was determined by image processing. The meniscus of the drops remained circular despite varying concentration. Since the refractive index of corn syrup increased with concentration, while the surface tension coefficient between corn syrup and mineral oil remained unchanged, the observed change in the annulus width was then attributed to the refraction of light passing through the drop’s meniscus. As such, a ray optics model was developed, which predicted that the annulus width of the drop would decrease as the refractive index of the drop approached that of the surrounding liquid. Therefore, the dark annulus of the drops in the Hele-Shaw cell was caused by the refraction of light passing through the circular meniscus of the drop.
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Bergemann, Nico, Anne Juel y Matthias Heil. "Viscous drops on a layer of the same fluid: from sinking, wedging and spreading to their long-time evolution". Journal of Fluid Mechanics 843 (16 de marzo de 2018): 1–28. http://dx.doi.org/10.1017/jfm.2018.127.
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We study the axisymmetric spreading of drops deposited on a pre-existing horizontal layer of the same viscous fluid. Using a combination of experiments, numerical modelling based on the axisymmetric free-surface Navier–Stokes equations and scaling analyses, we explore the drops’ behaviour in a regime where the flow is driven by gravitational and/or capillary forces while inertial effects are small. We find that during the early stages of the drops’ evolution there are three distinct spreading behaviours depending on the thickness of the liquid layer. For thin layers the fluid ahead of a clearly defined spreading front is at rest and the overall behaviour resembles that of a drop spreading on a dry substrate. For thicker films, the spreading is characterised by an advancing wedge which is sustained by fluid flow from the drop into the layer. Finally, for thick layers the drop sinks into the layer, accompanied by significant flow within the layer. As the drop keeps spreading, the evolution of its shape becomes self-similar, with a power-law behaviour for its radius and its excess height above the undisturbed fluid layer. We employ lubrication theory to analyse the drop’s ultimate long-term behaviour and show that all drops ultimately enter an asymptotic regime which is reached when their excess height falls below the thickness of the undisturbed layer.
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KUSHNER, JOSEPH, MICHAEL A. ROTHER y ROBERT H. DAVIS. "Buoyancy-driven interactions of viscous drops with deforming interfaces". Journal of Fluid Mechanics 446 (23 de octubre de 2001): 253–69. http://dx.doi.org/10.1017/s0022112001005699.
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Experiments were conducted on the interactions of two different-sized deformable drops moving due to gravity in an immiscible viscous fluid at low Reynolds number. As the drops come close to each other, several interactions are possible: (i) separation of the drops, (ii) capture of the smaller drop behind the larger drop, (iii) breakup of the smaller drop into two or more drops, and (iv) pass-through of one drop through the other, with possible cycle interaction or leap-frogging. The interactions depend on several system parameters, including the drop-to-medium viscosity ratio, the radius ratio of the two drops, the initial horizontal offset of the two drops at large vertical separation, and the gravitational Bond number (which represents the ratio of buoyant forces to interfacial tension forces for the larger drop and describes how much the drops will deform). Experimental analysis was conducted by videotaping trajectories of glycerol–water drops of various compositions falling in castor oil. The results show good agreement with available theoretical results, both for interaction maps and individual trajectories. The results also provide data beyond the present limitations of theoretical algorithms and reveal the new pass-through phenomenon.
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Knyazikhin, Y., R. B. Myneni, A. Marshak, W. J. Wiscombe, M. L. Larsen y J. V. Martonchik. "Small-Scale Drop Size Variability: Impact on Estimation of Cloud Optical Properties". Journal of the Atmospheric Sciences 62, n.º 7 (1 de julio de 2005): 2555–67. http://dx.doi.org/10.1175/jas3488.1.
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Abstract Most cloud radiation models and conventional data processing techniques assume that the mean number of drops of a given radius is proportional to volume. The analysis of microphysical data on liquid water drop sizes shows that, for sufficiently small volumes, this proportionality breaks down; the number of cloud drops of a given radius is instead proportional to the volume raised to a drop size–dependent nonunit power. The coefficient of proportionality, a generalized drop concentration, is a function of the drop size. For abundant small drops the power is unity as assumed in the conventional approach. However, for rarer large drops, it falls increasingly below unity. This empirical fact leads to drop clustering, with the larger drops exhibiting a greater degree of clustering. The generalized drop concentration shows the mean number of drops per cluster, while the power characterizes the occurrence frequency of clusters. With a fixed total number of drops in a cloud, a decrease in frequency of clusters is accompanied by a corresponding increase in the generalized concentration. This initiates a competing process missed in the conventional models: an increase in the number of drops per cluster enhances the impact of rarer large drops on cloud radiation while a decrease in the frequency suppresses it. Because of the nonlinear relationship between the number of clustered drops and the volume, these two opposite tendencies do not necessarily compensate each other. The data analysis suggests that clustered drops likely have a stronger radiative impact compared to their unclustered counterpart; ignoring it results in underestimation of the contribution from large drops to cloud horizontal optical path.
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Gires, Auguste, Ioulia Tchiguirinskaia y Daniel Schertzer. "3D trajectories and velocities of rainfall drops in a multifractal turbulent wind field". Atmospheric Measurement Techniques 15, n.º 19 (14 de octubre de 2022): 5861–75. http://dx.doi.org/10.5194/amt-15-5861-2022.
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Abstract. Weather radars measure rainfall in altitude, whereas hydro-meteorologists are mainly interested in rainfall at ground level. During their fall, drops are advected by the wind, which affects the location of the measured field. The governing equation of a rain drop's motion relates the acceleration to the forces of gravity and buoyancy along with the drag force. It depends non-linearly on the instantaneous relative velocity between the drop and the local wind, which yields complex behaviour. Here, the drag force is expressed in a standard way with the help of a drag coefficient expressed as a function of the Reynolds number. Corrections accounting for the oblateness of drops greater than 1–2 mm are suggested and validated through a comparison of the retrieved “terminal fall velocity” (i.e. without wind) with commonly used relationships in the literature. An explicit numerical scheme is then implemented to solve this equation for a 3+1D turbulent wind field, and hence analyse the temporal evolution of the velocities and trajectories of rain drops during their fall. It appears that multifractal features of the input wind are simply transferred to the drop velocity with an additional fractional integration whose level depends on the drop size, and a slight time shift. Using an actual high-resolution 3D sonic anemometer and a scale invariant approach to simulate realistic fluctuations of wind in space, trajectories of drops of various sizes falling form 1500 m are studied. For a strong wind event, drops located within a radar gate in altitude during 5 min are spread on the ground over an area of the size of a few kilometres. The spread for drops of a given diameter is found to cover a few radar pixels. Consequences on measurements of hydro-meteorological extremes that are needed to improve the resilience of urban areas are discussed.
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Carrier, Odile, Noushine Shahidzadeh-Bonn, Rojman Zargar, Mounir Aytouna, Mehdi Habibi, Jens Eggers y Daniel Bonn. "Evaporation of water: evaporation rate and collective effects". Journal of Fluid Mechanics 798 (9 de junio de 2016): 774–86. http://dx.doi.org/10.1017/jfm.2016.356.
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We study the evaporation rate from single drops as well as collections of drops on a solid substrate, both experimentally and theoretically. For a single isolated drop of water, in general the evaporative flux is limited by diffusion of water through the air, leading to an evaporation rate that is proportional to the linear dimension of the drop. Here, we test the limitations of this scaling law for several small drops and for very large drops. We find that both for simple arrangements of drops, as well as for complex drop size distributions found in sprays, cooperative effects between drops are significant. For large drops, we find that the onset of convection introduces a length scale of approximately 20 mm in radius, below which linear scaling is found. Above this length scale, the evaporation rate is proportional to the surface area.
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Fallah, Kayvan, Moahammad Rahni, Alireza Mohammadzadeh y Mohammad Najafi. "Drop formation in cross-junction micro-channel, using lattice Boltzmann method". Thermal Science 22, n.º 2 (2018): 909–19. http://dx.doi.org/10.2298/tsci160322230f.
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Drop formation in cross-junction micro-channels is numerically studied using the lattice Boltzmann method with pseudo-potential model. To verify the simulation, the results are compared to previous numerical and experimental data. Furthermore, the effects of capillary number, flow rate ratio, contact angle, and viscosity ratio on the flow patterns, drop length, and interval between drops are investigated and highlighted. The results show that the drop forming process has different regimes, namely, jetting, drop, and squeezing regimes. Also, it is shown that increasing in the flow rate ratio in the squeezing regime causes increment in drop length and decrement in drops interval distance. On the other hand, the drops length and the interval between the generated drops increase as contact angle increases. Also, the drop length and distance between drops is solely affected by viscosity ratio.
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Anjos, Gustavo R. "Numerical Investigation of Two-Phase Flows in Corrugated Channel with Single and Multiples Drops". Fluids 6, n.º 1 (31 de diciembre de 2020): 13. http://dx.doi.org/10.3390/fluids6010013.
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This work aims at investigating numerically the effects of channel corrugation in two-phase flows with single and multiples drops subject to buoyancy-driven motion. A state-of-the-art model is employed to accurately compute the dynamics of the drop’s interface deformation using a modern moving frame/moving mesh technique within the arbitrary Lagrangian–Eulerian framework, which allows one to simulate very large domains. The results reveal a complex and interesting dynamics when more than one drop is present in the system, leading eventually in coalescence due to the amplitude of the corrugated sinusoidal channel and distance between drops.
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Zabarankin, Michael. "Small deformation theory for two leaky dielectric drops in a uniform electric field". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, n.º 2233 (enero de 2020): 20190517. http://dx.doi.org/10.1098/rspa.2019.0517.
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A small deformation theory for two non-identical spherical drops freely suspended in an ambient fluid and subjected to a uniform electric field is presented. The three phases are assumed to be leaky dielectric (slightly conducting) viscous incompressible fluids and the nonlinear effects of inertia and surface charge convection are neglected. The deformed shapes of the drops are linearized with respect to the electric capillary number that characterizes the balance between the electric stress and the surface tension. When the two drops are sufficiently far apart, their deformed shapes are predicted by Taylor’s small deformation theory—depending on Taylor’s discriminating function, the drops may become prolate, oblate or remain spherical. When the two drops get closer to each other, in addition to becoming prolate/oblate, they start translating and developing an egg shape. (Since there is no net charge, the centre of mass of the two drops remains stationary.) The extent of each of these ‘modes’ of deformation depends on the distance between the drops’ centres and on drop-to-ambient fluid ratios of electric conductivities, dielectric constants and viscosities. The predictions of the small deformation theory for two drops perfectly agree with the existing results of two-drop dynamics simulation based on a boundary-integral equation approach. Moreover, while previous works observed only three types of behaviour for two identical drops—the drops may either become prolate or oblate and move towards each other or become prolate and move away from each other—the small deformation theory predicts that non-identical drops may, in fact, become oblate and move away from each other when the drop-to-ambient fluid conductivity ratios are reciprocal and the drop-to-ambient fluid viscosity ratios are sufficiently large. The presented theory also readily yields an analytical insight into the interplay among different modes of drop deformation and can be used to guide the selection of the phases’ electromechanical properties for two-drop dynamics simulations.
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BAYGENTS, J. C., N. J. RIVETTE y H. A. STONE. "Electrohydrodynamic deformation and interaction of drop pairs". Journal of Fluid Mechanics 368 (10 de agosto de 1998): 359–75. http://dx.doi.org/10.1017/s0022112098001797.
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The motion of two drops in a uniform electric field is considered using the leaky dielectric model. The drops are assumed to have no native charge and a dielectrophoretic effect favours translation of the drops toward one another. However, circulatory flows that stem from electrohydrodynamic stresses may either act with or against this dielectrophoretic effect. Consequently, both prolate and oblate drop deformations may be generated and significant deformation occurs near drop contact owing to enhancement of the local electric field. For sufficiently widely spaced drops, electrohydrodynamic flows dominate direct electrical interactions so drops may be pushed apart, though closely spaced drops almost always move together as a result of the electrical interaction or deformation.
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Manga, Michael y H. A. Stone. "Buoyancy-driven interactions between two deformable viscous drops". Journal of Fluid Mechanics 256 (noviembre de 1993): 647–83. http://dx.doi.org/10.1017/s0022112093002915.
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Time-dependent interactions between two buoyancy-driven deformable drops are studied in the low Reynolds number flow limit for sufficiently large Bond numbers that the drops become significantly deformed. The first part of this paper considers the interaction and deformation of drops in axisymmetric configurations. Boundary integral calculations are presented for Bond numbers ℬ = Δρga2/σ in the range 0.25 ≤ ℬ < ∞ and viscosity ratios λ in the range 0.2 ≤ λ ≤ 20. Specifically, the case of a large drop following a smaller drop is considered, which typically leads to the smaller drop coating the larger drop for ℬ [Gt ] 1. Three distinct drainage modes of the thin film of fluid between the drops characterize axisymmetric two-drop interactions: (i) rapid drainage for which the thinnest region of the film is on the axis of symmetry, (ii) uniform drainage for which the film has a nearly constant thickness, and (iii) dimple formation. The initial mode of film drainage is always rapid drainage. As the separation distance decreases, film flow may change to uniform drainage and eventually to dimpled drainage. Moderate Bond numbers, typically ℬ = O(10) for λ = O(1), enhance dimple formation compared to either much larger or smaller Bond numbers. The numerical calculations also illustrate the extent to which lubrication theory and analytical solutions in bipolar coordinates (which assume spherical drop shapes) are applicable to deformable drops.The second part of this investigation considers the 'stability’ of axisymmetric drop configurations. Laboratory experiments and two-dimensional boundary integral simulations are used to study the interactions between two horizontally offset drops. For sufficiently deformable drops, alignment occurs so that the small drop may still coat the large drop, whereas for large enough drop viscosities or high enough interfacial tension, the small drop will be swept around the larger drop. If the large drop is sufficiently deformable, the small drop may then be ‘sucked’ into the larger drop as it is being swept around the larger drop. In order to explain the alignment process, the shape and translation velocities of widely separated, nearly spherical drops are calculated using the method of reflections and a perturbation analysis for the deformed shapes. The perturbation analysis demonstrates explicitly that drops will tend to be aligned for ℬ > O(d/a) where d is the separation distance between the drops.
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Ryu, Sangjin, Haipeng Zhang y Udochukwu John Anuta. "A Review on the Coalescence of Confined Drops with a Focus on Scaling Laws for the Growth of the Liquid Bridge". Micromachines 14, n.º 11 (31 de octubre de 2023): 2046. http://dx.doi.org/10.3390/mi14112046.
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The surface–tension-driven coalescence of drops has been extensively studied because of the omnipresence of the phenomenon and its significance in various natural and engineering systems. When two drops come into contact, a liquid bridge is formed between them and then grows in its lateral dimensions. As a result, the two drops merge to become a bigger drop. The growth dynamics of the bridge are governed by a balance between the driving force and the viscous and inertial resistances of involved liquids, and it is usually represented by power–law scaling relations on the temporal evolution of the bridge dimension. Such scaling laws have been well-characterized for the coalescence of unconfined or freely suspended drops. However, drops are often confined by solid or liquid surfaces and thus are a different shape from spheres, which affects their coalescence dynamics. As such, the coalescence of confined drops poses more complicated interfacial fluid dynamics challenges compared to that of unconfined drops. Although there have been several studies on the coalescence of confined drops, they have not been systematically reviewed in terms of the properties and geometry of the confining surface. Thus, we aim to review the current literature on the coalescence of confined drops in three categories: drop coalescence on a solid surface, drop coalescence on a deformable surface, and drop coalescence between two parallel surfaces with a small gap (i.e., Hele-Shaw cell), with a focus on power–law scaling relations, and to suggest challenges and outlooks for future research on the phenomena.
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Encarnación Escobar, José M., Jaap Nieland, Arie van Houselt, Xuehua Zhang y Detlef Lohse. "Marangoni puffs: dramatically enhanced dissolution of droplets with an entrapped bubble". Soft Matter 16, n.º 18 (2020): 4520–27. http://dx.doi.org/10.1039/d0sm00093k.
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We present a curious effect observed during the dissolution process of water-immersed long-chain alcohol drops with an entrapped bubble. When the drop-water interface and the air bubble contact each other, a rapid cyclic motion that accelerates the drop's dissolution is found. We name this eye-catching phenomenon puffing.
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Zhang, Xiaoguang y Robert H. Davis. "The rate of collisions due to Brownian or gravitational motion of small drops". Journal of Fluid Mechanics 230 (septiembre de 1991): 479–504. http://dx.doi.org/10.1017/s0022112091000861.
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A dilute dispersion containing drops of one fluid dispersed in a second, immiscible fluid is considered. The drops are sufficiently small that inertia is negligible and that they remain spherical. Two drops of different size are in relative motion due to either Brownian diffusion or gravitational sedimentation. When the drops become close, they interact with each other owing to hydrodynamic disturbances and van der Waals attractions, and, under favourable conditions, they will collide with each other and coalesce. The rate at which two drops collide is predicted by solving the diffusion equation for Brownian coalescence, and by using a trajectory analysis to follow the relative motion of pairs of drops for gravity-induced coalescence.The emphasis of our analysis is on the effects of drop interactions on their collision rate, and these are described by the collision efficiency. Since the hydrodynamic resistance to the drop relative motion reduces with a decreasing ratio of the viscosities of the drop fluid and the surrounding fluid, the collision efficiency increases with decreasing viscosity ratio. A qualitative difference in the collision behaviour of viscous drops from that of rigid spheres is demonstrated; finite collision rates for drops are predicted even in the absence of attractive forces, provided that drop deformation is negligible, whereas rigid particles with smooth surfaces will not come into contact in a fluid continuum unless an attractive force is present which is able to overcome the lubrication forces resisting the relative motion. Hydrodynamic interactions between two spherical drops are accounted for exactly by determining the two-sphere relative mobility functions from previous solutions for two drops moving along and normal to their line of centres. These solutions are based on the method of reflections for widely separated drops, lubrication theory for drops in near-contact, and bispherical coordinates for general separations. The hydrodynamic interactions have a greater effect on reducing the rate of gravity collisions than the rate of Brownian collisions.
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Jensen, Jørgen B. y Alison D. Nugent. "Condensational Growth of Drops Formed on Giant Sea-Salt Aerosol Particles". Journal of the Atmospheric Sciences 74, n.º 3 (9 de febrero de 2017): 679–97. http://dx.doi.org/10.1175/jas-d-15-0370.1.
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Abstract The most basic aspect of cloud formation is condensational growth onto cloud condensation nuclei (CCN). As such, condensational growth of cloud drops is often assumed to be a well-understood process described by the drop growth equation. When this process is represented in models, CCN activate into cloud drops at cloud base, and it is often assumed that drops consist of pure water or that the hygroscopic contribution after drop activation is small because of the inclusion of only small CCN. Drop growth rate in adiabatic ascent in such models is proportional to supersaturation and assumed to be inversely proportional to the drop radius, thereby making the drop spectrum narrow with altitude. However, the present study demonstrates that drop growth on giant sea-salt aerosol particles (GCCN; dry radius 0.5 m) behaves differently. For typical marine stratocumulus updrafts and for drops grown on GCCN with sizes m, these drops typically remain concentrated salt solutions. Because of this, their condensational growth is accelerated, and they rapidly attain precipitation drop sizes through condensation only. Additionally, drops formed on GCCN may also grow by condensation in cloudy downdrafts. The strong effect of condensation on GCCN is important when carried through to calculating rain-rate contribution as a function of aerosol size. GCCN larger than 2 m account for most of the rainfall rate in the modeled precipitating marine stratocumulus.
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Choi, WooSeok y Sungchan Yun. "Characterizing the Bounce and Separation Dynamics of Janus Drop on Macrotextured Surface". Polymers 14, n.º 12 (8 de junio de 2022): 2322. http://dx.doi.org/10.3390/polym14122322.
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Janus drops are thermodynamically stable when a high-viscosity fluid is imposed on a low-viscosity fluid. To understand physical mechanisms in Janus drop impact on macrotextured surfaces, several challenges in finding parameters or strategies still remain. Here, this study investigates the asymmetric bounce and separation of impinging Janus drops on non-wettable surfaces decorated with a macroridge to explore the effect of the drop size, viscosity ratio, and ridge size on the dynamics. Through numerical simulations, we determine the threshold Weber number, above which separation occurs, by varying drop diameters and viscosity ratios of the Janus drops. We investigate the initial bouncing directions of separated drops as a function of the impact velocity and viscosity ratio. We also predict how the separation efficiency is affected by the ridge’s height and width. The asymmetric impact dynamics of Janus drops on macrotextured surfaces can provide new strategies to control drop bouncing in applications, such as liquid separation and purification.
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Marshak, Alexander, Yuri Knyazikhin, Michael L. Larsen y Warren J. Wiscombe. "Small-Scale Drop-Size Variability: Empirical Models for Drop-Size-Dependent Clustering in Clouds". Journal of the Atmospheric Sciences 62, n.º 2 (1 de febrero de 2005): 551–58. http://dx.doi.org/10.1175/jas-3371.1.
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Abstract By analyzing aircraft measurements of individual drop sizes in clouds, it has been shown in a companion paper that the probability of finding a drop of radius r at a linear scale l decreases as lD(r), where 0 ≤ D(r) ≤ 1. This paper shows striking examples of the spatial distribution of large cloud drops using models that simulate the observed power laws. In contrast to currently used models that assume homogeneity and a Poisson distribution of cloud drops, these models illustrate strong drop clustering, especially with larger drops. The degree of clustering is determined by the observed exponents D(r). The strong clustering of large drops arises naturally from the observed power-law statistics. This clustering has vital consequences for rain physics, including how fast rain can form. For radiative transfer theory, clustering of large drops enhances their impact on the cloud optical path. The clustering phenomenon also helps explain why remotely sensed cloud drop size is generally larger than that measured in situ.
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Moláček, Jan y John W. M. Bush. "Drops bouncing on a vibrating bath". Journal of Fluid Mechanics 727 (28 de junio de 2013): 582–611. http://dx.doi.org/10.1017/jfm.2013.279.
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AbstractWe present the results of a combined experimental and theoretical investigation of millimetric droplets bouncing on a vertically vibrating fluid bath. We first characterize the system experimentally, deducing the dependence of the droplet dynamics on the system parameters, specifically the drop size, driving acceleration and driving frequency. As the driving acceleration is increased, depending on drop size, we observe the transition from coalescing to vibrating or bouncing states, then period-doubling events that may culminate in either walking drops or chaotic bouncing states. The drop’s vertical dynamics depends critically on the ratio of the forcing frequency to the drop’s natural oscillation frequency. For example, when the data describing the coalescence–bouncing threshold and period-doubling thresholds are described in terms of this ratio, they collapse onto a single curve. We observe and rationalize the coexistence of two non-coalescing states, bouncing and vibrating, for identical system parameters. In the former state, the contact time is prescribed by the drop dynamics; in the latter, by the driving frequency. The bouncing states are described by theoretical models of increasing complexity whose predictions are tested against experimental data. We first model the drop–bath interaction in terms of a linear spring, then develop a logarithmic spring model that better captures the drop dynamics over a wider range of parameter space. While the linear spring model provides a faster, less accurate option, the logarithmic spring model is found to be more accurate and consistent with all existing data.
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Yagi-Yaguchi, Yukari, Takashi Kojima, Kazunari Higa, Murat Dogru, Osama MA Ibrahim, Takahiko Shimizu, Kazuo Tsubota y Jun Shimazaki. "The Effects of 3% Diquafosol Sodium Eye Drops on Tear Function and the Ocular Surface of Cu, Zn-Superoxide Dismutase-1 (Sod1) Knockout Mice Treated with Antiglaucoma Eye Medications". Diagnostics 10, n.º 1 (1 de enero de 2020): 20. http://dx.doi.org/10.3390/diagnostics10010020.
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Anti-glaucoma eye drop treatment often induces dry eyes and can lead to poor medication adherence. This study aimed to investigate the effects of 3% diquafosol sodium eye drops on tear function and the ocular surface epithelium in Sod1−/− mice after treatment with anti-glaucoma eye drops. The mice were divided into four groups: group 1, control group; group 2, anti-glaucoma eye drop; group 3, anti-glaucoma eye drops followed by a secretagogue eye drop (3% diquafosol); and group 4, simultaneous anti-glaucoma and secretagogue eye drop. Mice underwent assessments of tear quantity, tear film breakup time, and vital staining score. Mice in groups 3 and 4 showed significantly better tear stability and lower corneal staining scores than mice in group 2 after eye drop instillations (p < 0.05). Mice in group 4 showed significantly better tear stability, lower corneal staining scores, and higher goblet cell densities than those in group 1 after eye drop instillations (p < 0.05). The conjunctival epithelium showed stratification and abundance of Muc5AC-positive goblet cells in group 4, whereas thinning with desquamation was observed with a few goblet cells in group 2. Thus, simultaneous administration of 3% diquafosol sodium eye drops with topical anti-glaucoma drops showed favorable effects on tear stability and the corneal epithelium against the ocular surface toxicity inflicted by the anti-glaucoma eye drops.
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Kopiyka, O. K., V. V. Kalinchak, A. S. Chernenko y M. O. Ivanov. "Theoretical and experimental study of heat and mass transfer, evaporation and ignition drops of monoatomic ethanol/butanol binary mixture in cold air". Physics of Aerodisperse Systems, n.º 61 (9 de diciembre de 2023): 70–88. http://dx.doi.org/10.18524/0367-1631.2023.61.291121.
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The study evaporation process results of lower alcohols' single drops (ethanol, butanol and their binary mixtures) with an initial droplet size of 1.5-2.5 mm in air at room temperature and atmospheric pressure are presented. To describe the heat and mass transfer of the fuel mixture's drops with different initial composition, prognostic evaluation of dynamics' changes fuels drops size, composition and temperature during their evaporation are proposed. Taking into account the temperature dependence of the heat of vaporization, an analytical dependence for evaluating the drop surface temperature of one-component evaporating fuels is proposed. Comparative analysis of the calculated model's data allowed to suggest a possible evaporation mechanism of multi-component fuel mixtures droplets and to explain some peculiarities in the behavior of the main characteristics this process. It is shown that the thermocouple wires qualitatively affects the behavior with time of temperature and droplet size. Formula for the drop's temperature during evaporation into account the influence of thermocouple are presented.
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Magalhães Barbosa Felisberto, Michelle y Alvaro Vianna Novaes de Carvalho Teixeira. "SIMULATION OF A PERFECT DIELECTRIC DROP IN ELECTRO-OSMOTIC FLOW OF AN ELECTROLYTE THROUGH A MICROCHANNEL". Journal of Engineering and Exact Sciences 3, n.º 3 (22 de marzo de 2017): 294–319. http://dx.doi.org/10.18540/jcecvl3iss3pp294-319.
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This research uses a computational fluid dynamic model to simulate motion and deformation of a dielectric drop in electrolyte solution in a microchannel. Wall charge density, the Debye-Hückel parameter and the Weber number are varied for uncharged, positively and negatively charged drop interfaces. Drop flow and deformation were analysed and the effects of charge distribution, electric field and permittivity jump were discussed. For a positively charged channel wall, negatively charged drops moved faster and positively charged drops moved slower than an uncharged drop. This effect increased for a higher We. Vortex flow was observed inside the drop. For a low surface tension, the drops were elongated due to electric forces acting on its surface with the charged drops deforming more than the uncharged one. When the permittivity component of the force was removed, the drop had a horizontal deformation that was sufficiently high to cause the negatively charged drop to break up.
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PIGEONNEAU, FRANCK y FRANÇOIS FEUILLEBOIS. "Collision of drops with inertia effects in strongly sheared linear flow fields". Journal of Fluid Mechanics 455 (25 de marzo de 2002): 359–86. http://dx.doi.org/10.1017/s002211200100742x.
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The relative motion of drops in shear flows is responsible for collisions leading to the creation of larger drops. The collision of liquid drops in a gas is considered here. The drops are small enough for the Reynolds number to be low (negligible fluid motion inertia), yet large enough for the Stokes number to be possibly of order unity (non-negligible inertia in the motion of drops). Possible concurrent effects of Van der Waals attractive forces and drop inertia are taken into account.General expressions are first presented for the drag forces on two interacting drops of different sizes embedded in a general linear flow field. These expressions are obtained by superposition of solutions for the translation of drops and for steady drops in elementary linear flow fields (simple shear flows, pure straining motions). Earlier solutions adapted to the case of inertialess drops (by Zinchenko, Davis and coworkers) are completed here by the solution for a simple shear flow along the line of centres of the drops. A solution of this problem in bipolar coordinates is provided; it is consistent with another solution obtained as a superposition of other elementary flow fields.The collision efficiency of drops is calculated neglecting gravity effects, that is for strongly sheared linear flow fields. Results are presented for the cases of a simple linear shear flow and an axisymmetric pure straining motion. As expected, the collision efficiency increases with the Stokes numbers, that is with drop inertia. On the other hand, the collision efficiency in a simple shear flow becomes negligible below some value of the ratio of radii, regardless of drop inertia. The value of this threshold increases with decreasing Van der Waals forces. The concurrence between drop inertia and attractive van der Waals forces results in various anisotropic shapes of the collision cross-section. By comparison, results for the collision efficiency in an axisymmetric pure straining motion are more regular. This flow field induces axisymmetric sections of collision and strong inertial effects resulting in collision efficiencies larger than unity. Effects of van der Waals forces only appear when one of the drops has a very low Stokes number.
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Kilic, O., H. M. Ozturk y E. Ata. "Tropicamide eye drops reduce clozapine-induced hypersalivation: A case report". European Psychiatry 33, S1 (marzo de 2016): S543—S544. http://dx.doi.org/10.1016/j.eurpsy.2016.01.2009.
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IntroductionClozapine-induced sialorrhea (CIS) is a common, treatment-limiting and stigmatizing side effect. All systemic agents that are used for hypersalivation may increase clozapine side effects such as blood pressure changes, constipation, or arrythmias. Oral application of topical anti-muscarinic agents may be a low side effect option for treatment of CIS.ObjectiveThe aim of this case report was to propose an off-label treatment of tropicamide drops to CIS and to stimulate further investigation.Case reportA 33-year-old male inpatient with schizophrenia has been on clozapine 800 mg and amisulpride 600 mg/day. His drooling was occasional and severe as drool drips off his chin during the day and night. Wet area over the pillow, visual analog scale (VAS), the short form of health survey (SF-36), UKU side effect rating scale, scale for the assessment of negative symptoms (SANS), scale for the assessment of positive symptoms (SAPS) were applied at baseline and in one-week intervals. Oral application of one drop of tropicamide % 0.5 (5 mg/mL) to left and one drop to right side before going to bed in the first week and two drops to each side were administered subsequently. Informed consent was given by the patient.ResultsNo psychological, neurological, autonomic and other side effects were observed associated with tropicamide. On VAS, the patient rated hypersalivation 5/7 at baseline, 4/7 after one drop each, 3/7 after two drops each.ConclusionsThe reduction of CIS by oral use of tropicamide eye drops is promising and should be explored with randomized controlled trials.Disclosure of interestThe authors have not supplied their declaration of competing interest.
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GUIDO, S. y M. SIMEONE. "Binary collision of drops in simple shear flow by computer-assisted video optical microscopy". Journal of Fluid Mechanics 357 (25 de febrero de 1998): 1–20. http://dx.doi.org/10.1017/s0022112097007921.
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The collision of two equi-sized drops immersed in an immiscible liquid phase undergoing a shear flow in a parallel plate apparatus has been investigated over a range of capillary numbers. The drops were observed along the vorticity direction of shear flow by video enhanced contrast optical microscopy. Images of the colliding drops were processed by image analysis techniques. The distance Δy between the drop centres along the velocity gradient direction was measured as a function of time during approach, collision and separation of the two drops. It was found that Δy increases irreversibly after collision, thus providing a mechanism for drop dispersion in a concentrated system. Drop shape evolution during collision was characterized by measuring a deformation parameter and the angle made by the drop major axis with respect to the velocity gradient direction. The extent of the near-contact region when the drops are sliding on each other was also estimated. Coalescence was a rare event and was observed in the extensional quadrant of the shear flow. The experimental results show good agreement with numerical simulations recently reported in the literature.
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Clamp, P. J. "Expansile properties of otowicks: an in vitro study". Journal of Laryngology & Otology 122, n.º 7 (julio de 2008): 687–90. http://dx.doi.org/10.1017/s0022215108002661.
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AbstractObjective:To determine the expansile and absorptive properties of the expandable ear wick when tested with commonly prescribed ear drop preparations.Design:This in vitro study assessed wick expansion and absorption of drops when different ear drop preparations were applied. Nine commonly used ear drop preparations were tested (Gentisone HC, Sofradex, Otomize, Betnesol, Exocin, Canesten, Locorten-Vioform, EarCalm and ichthammol glycerin) with a standard expandable ear wick.Main outcome measures:Weight, length and width of otowick following exposure to ear drops.Results:There was a marked difference in the absorption and expansion of the otowick when different drops were used. This corresponded to the aqueous or oil base of each preparation. All aqueous ear drop preparations (i.e. Gentisone HC, Sofradex, Otomize, Betnesol, Exocin and EarCalm) produced similar rates of absorption into, and expansion of, the otowick. The oil-based ear drop preparations (i.e. Canesten, Locorten-Vioform and ichthammol glycerin) failed to expand the wick and showed poor rates of absorption into the wick.Conclusion:Expandable ear wicks should only be used in conjunction with aqueous ear drops. When using expandable otowicks as an adjunct to treating fungal otitis externa, acetic acid ear drops should be prescribed, as all other anti-fungal drops are oil-based.
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PREMNATH, KANNAN N. y JOHN ABRAHAM. "LATTICE BOLTZMANN SIMULATIONS OF DROP–DROP INTERACTIONS IN TWO-PHASE FLOWS". International Journal of Modern Physics C 16, n.º 01 (enero de 2005): 25–44. http://dx.doi.org/10.1142/s0129183105006930.
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In this paper, three-dimensional computations of drop–drop interactions using the lattice Boltzmann method (LBM) are reported. The LBM multiphase flow model employed is evaluated for single drop problems and binary drop interactions. These include the verification of Laplace–Young relation for static drops, drop oscillations, and drop deformation and breakup in simple shear flow. The results are compared with experimental data, analytical solutions and numerical solutions based on other computational methods, as applicable. Satisfactory agreement is shown. Initial studies of drop–drop interactions involving the head-on collisions of drops in quiescent medium and off-center collision of drops in the presence of ambient shear flow are considered. As expected, coalescence outcome is observed for the range of parameters studied.
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Manga, Michael. "Dynamics of drops in branched tubes". Journal of Fluid Mechanics 315 (25 de mayo de 1996): 105–17. http://dx.doi.org/10.1017/s0022112096002352.
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The flow of two-dimensional deformable drops through branching (bifurcating) tubes is studied numerically using a boundary integral formulation. The undeformed drop diameter is assumed to be less than the tube diameter. Capillary numbers between 10−2 and 1 are considered. Flow in the branching tube is characterized by the fraction of fluid which enters each of the two downstream branches. The likelihood of drops entering the high-flow-rate branch increases as (i) the viscosity ratio between the drops and suspending fluid decreases, (ii) the capillary number increases, and (iii) the drop size increases. Hydrodynamic interactions between the suspended drops increase the number of drops which enter the low-flow-rate branch. The implications of these results for dispersion processes and local transport are explored. The disturbance flow created by drops passing over ‘dead-end’ pores or cavities results in fluid transfer between the pore and the free stream; suspensions may then be effective in improving the ‘cleaning’ of porous materials.
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Behera, Nalinikanta, Shubhadeep Mandal y Suman Chakraborty. "Electrohydrodynamic settling of drop in uniform electric field: beyond Stokes flow regime". Journal of Fluid Mechanics 881 (24 de octubre de 2019): 498–523. http://dx.doi.org/10.1017/jfm.2019.744.
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The electrohydrodynamics of a weakly conducting buoyant drop under the combined influence of gravity and a uniform electric field is studied computationally, focusing on the inertia-dominated regime. Numerical simulations are performed for both perfectly dielectric and leaky dielectric drops over a wide range of dimensionless parameters to explore the interplay of fluid inertia and electrical stress to govern the drop shape and charge convection. For perfectly dielectric drops, the fluid inertia alters the drop shape and the deformation behaviour of the drop follows a non-monotonic path. The drop shape at steady state exhibits the transition from oblate to prolate shape on increasing the electric field strength, in sharp contrast to the cases concerning the Stokes flow regime. Similar behaviour is also obtained for leaky dielectric drops for certain fluid properties. For leaky dielectric drops, the fluid inertia also affects the convective transport of charges at the drop surface and thereby alters the drop dynamics. Unlike the Stokes flow regime, where surface charge convection has little effect on the settling speed, the same modifies the drop settling speed quite significantly in the finite inertial regime depending on the combination of electrical conductivity ratio and permittivity ratio. For oblate drops at low capillary number, charge convection alters drop shape, while keeping the nature of deformation unaltered. However, for relatively large capillary number, the oblate drop transforms into a dimpled shape due to charge convection. For all cases, an interesting fact is noticed that under the combined action of electric and inertial forces, the resultant deformation is less than the summation of the deformations caused by individual effects, when inertial effects are strong. These results are likely to provide deep insights into the interplay of various nonlinearities towards altering electrohydrodynamic settling of drops and bubbles.
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Alhashem, Abdulwahab, Mosab Alrahmani y Hosny Abou-Ziyan. "Effect of Surface Renewal on the Drop Size Distribution in Dropwise Condensation within a Hybrid Surface". Applied Sciences 14, n.º 5 (27 de febrero de 2024): 1931. http://dx.doi.org/10.3390/app14051931.
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The description of liquid drop growth and drop distribution are two key models in evaluating the thermal performance of dropwise condensation (DWC) heat transfer. The drop size distribution describes the growth process of small drops by direct condensation and large drops by coalescence. The present work investigates the effect of surface renewal and coalescence intensities of DWC within a hybrid surface. Additionally, it examines the validity of the current empirical expression of the drop size distribution that is developed for DWC without considering surface renewal and coalescence intensities. The simulation work illustrates the drop growth process and surface renewal as drops depart and merge with neighboring film regions. The simulation results show that in hybrid DWC, the area fraction occupied by drops (f) lies between 0.28 to 0.296 for the ratio of maximum drop diameter to DWC region width (RD) from 0.125 to 1 and a total temperature drop (∆T) of 2, 4, and 8 ℃. Thus, the drop population is less sensitive to RD, and an average f of 0.288 is generalized. On the other hand, the surface renewal for DWC within the hybrid surface shows improvement for RD > 0.5 with the highest enhancement of 64 to 85% taking place at RD = 1, mainly due to the merging effect. In addition, results for drop size distribution profiles of DWC within the hybrid surface are characterized by a lower population of large drops and a higher population of small drops than full DWC. Additionally, the constant exponent (n) in the literature’s empirical expression is replaced by a polynomial series as a function of drop effective and maximum radii. The impact of surface renewal on coalescence intensity is presented in a relatively steeper slope on the logarithmic scale.
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Bayareh, M. y S. Mortazavi. "Equilibrium Position of a Buoyant Drop in Couette and Poiseuille Flows at Finite Reynolds Numbers". Journal of Mechanics 29, n.º 1 (16 de octubre de 2012): 53–58. http://dx.doi.org/10.1017/jmech.2012.109.
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AbstractThe equilibrium position of a deformable drop in Couette and Poiseuille flows is investigated numerically by solving the full Navier-Stokes equations using a finite difference/front tracking method. The objective of this work is to study the motion of a non-neutrally buoyant drop in Couette and Poiseuille flows with different density ratios at finite Reynolds numbers. Couette flow: The equilibrium position of the lighter drops is higher than the heavier drops at each particle Reynolds number. Also, the equilibrium position height increases with increasing the Reynolds number at a fixed density ratio. At this equilibrium distance from the wall, the migration velocity is zero, while the velocity of the drop in the flow direction and rotational velocity of the drop is finite. It is observed that the equilibrium position is independent of the initial position of the drops and depends on the density ratio and the shear Reynolds number. Poiseuille flow: When the drop is slightly buoyant, it moves to an equilibrium position between the wall and the centerline. The equilibrium position is close to the centerline if the drop lags the fluid but close to the wall if the drop leads the fluid. As the Reynolds number increases, the equilibrium position of lighter drops moves slightly closer to the wall and the equilibrium position of heavier drops moves towards the centerline.
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Pozrikidis, C. "Inviscid drops with internal circulation". Journal of Fluid Mechanics 209 (diciembre de 1989): 77–92. http://dx.doi.org/10.1017/s0022112089003046.
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The shape of a moving inviscid axisymmetric drop is considered as a function of surface tension and of the intensity of the internal circulation. In a frame of reference moving with the drop, the drop is modelled as a region of diffused vorticity which is bounded by a vortex sheet, and is imbedded in streaming flow. First, an asymptotic analysis is performed for a slightly non-spherical drop whose circulation is very close to that required for the spherical shape. The results indicate that steady drop shapes may exist at all but a number of distinct values of the Weber number, the lowest two of which are 4.41 and 6.15. For highly deformed drops, the problem is formulated as an integral equation for the shape of the drop, and for the strength of the bounding vortex sheet. A numerical procedure is developed for solving this equation, and numerical calculations are performed for Weber numbers between 0 and 4.41. Limiting members in the computed family of solutions contain spherical drops, and inviscid bubbles with vanishing circulation. Computed new shapes include saucer-like shapes with a rounded main body and an elongated tip. The relationship between inviscid drops and drops moving at large Reynolds numbers is discussed.
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Aderkas, Patrick von y Cathy Leary. "Ovular secretions in the micropylar canal of larches (Larix kaempferi and L. x eurolepis)". Canadian Journal of Botany 77, n.º 4 (28 de septiembre de 1999): 531–36. http://dx.doi.org/10.1139/b99-014.
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In Larix kaempferi (Lamb.) Carr. and L. × eurolepis A. Henry, a secretion fills the micropylar canal of the ovule during a period of archegonial development that ranges from central cell stage until fertilization. Dissection of the ovuliferous scales caused excess fluid to be exuded from the micropylar canal, forming a drop at the tip of the micropyle. This drop was collected, and its production was quantified. Drop volume was recorded, and the percentage of ovules with drops was counted. The maximum volume of 217 nL far exceeded the volume of the micropyle, which ranged between 18 ± 8 and 28 ± 7 nL (mean ± SD). Removal of drops resulted in further drops being secreted. No drops were produced in ovules that had aborted megagametophyte development.Key words: Larix, micropylar secretions, ovule development.
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Na, Kyeong Ik, Won June Lee, Youn Joo Choi y Sung Pyo Park. "Prescribing trends of glaucoma medication in Korea from 2007 to 2020: A nationwide population-based study". PLOS ONE 19, n.º 7 (11 de julio de 2024): e0305619. http://dx.doi.org/10.1371/journal.pone.0305619.
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Purpose Investigating long-term trends in glaucoma medication. Methods All patients diagnosed with glaucoma and prescribed glaucoma eye drops between 2007 and 2020 in Korea’s Health Insurance Review and Assessment Service database participated in this study. A weight was assigned to each prescription using the reciprocal of the total number of prescriptions received by the individual in that year. The number of patients who received each type of glaucoma eye drop prescription was calculated by summing the weights for each year. Results During the study period, prostaglandin analog eye drop monotherapy was the most frequently given type of glaucoma eye drop prescription. Until 2008, the second most frequently given type of glaucoma eye drop prescription was beta blocker eye drop monotherapy; thereafter, it changed to carbonic anhydrase inhibitor/beta blocker fixed-combination eye drop monotherapy. The prescription proportion of single-ingredient glaucoma eye drops decreased (-1.290%/year, P < 0.001), whereas that of fixed-combination glaucoma eye drops increased (1.291%/year, P < 0.001). The number of glaucoma eye drops prescribed per patient remained constant (-0.00030/year, P = 0.167) with an average of 1.302, while the number of active ingredients prescribed per patient increased (0.01737/year, P < 0.001) from 1.659 in 2007 to 1.896 in 2020. Conclusion Over 14 years, there was no change in the number of glaucoma eye drops prescribed to individual patients in Korea. However, the number of active ingredients prescribed increased owing to the increased prescription of fixed-combination eye drops. The current trends in glaucoma medication are expected to help establish future treatment strategies.
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Tokay, Ali, Walter A. Petersen, Patrick Gatlin y Matthew Wingo. "Comparison of Raindrop Size Distribution Measurements by Collocated Disdrometers". Journal of Atmospheric and Oceanic Technology 30, n.º 8 (1 de agosto de 2013): 1672–90. http://dx.doi.org/10.1175/jtech-d-12-00163.1.
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Abstract An impact-type Joss–Waldvogel disdrometer (JWD), a two-dimensional video disdrometer (2DVD), and a laser optical OTT Particle Size and Velocity (PARSIVEL) disdrometer (PD) were used to measure the raindrop size distribution (DSD) over a 6-month period in Huntsville, Alabama. Comparisons indicate event rain totals for all three disdrometers that were in reasonable agreement with a reference rain gauge. In a relative sense, hourly composite DSDs revealed that the JWD was more sensitive to small drops (<1 mm), while the PD appeared to severely underestimate small drops less than 0.76 mm in diameter. The JWD and 2DVD measured comparable number concentrations of midsize drops (1–3 mm) and large drops (3–5 mm), while the PD tended to measure relatively higher drop concentrations at sizes larger than 2.44 mm in diameter. This concentration disparity tended to occur when hourly rain rates and drop counts exceeded 2.5 mm h−1 and 400 min−1, respectively. Based on interactions with the PD manufacturer, the partially inhomogeneous laser beam is considered the cause of the PD drop count overestimation. PD drop fall speeds followed the expected terminal fall speed relationship quite well, while the 2DVD occasionally measured slower drops for diameters larger than 2.4 mm, coinciding with events where wind speeds were greater than 4 m s−1. The underestimation of small drops by the PD had a pronounced effect on the intercept and shape of parameters of gamma-fitted DSDs, while the overestimation of midsize and larger drops resulted in higher mean values for PD integral rain parameters.
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Jeong, Seong Ju, Brian W. Stump y Heather R. DeShon. "Stress Drop Variations of Induced Earthquakes near the Dallas–Fort Worth Airport, Texas". Seismic Record 2, n.º 2 (1 de abril de 2022): 68–77. http://dx.doi.org/10.1785/0320220003.
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Abstract We estimate stress drops for injection-induced earthquakes near the Dallas–Fort Worth Airport in the Fort Worth basin (FWB), Texas, to investigate source properties in response to fluid injection. The stress drops for the Airport sequence show three unique characteristics compared to those estimated for other earthquake sequences in the FWB: (1) stress drops have lower mean and median values; (2) stress drops increase with moment magnitude; and (3) stress drops increase in size over the first 1.5 km in radial distance from the injection point. The low stress drop Airport events occurred shortly after the initiation of injection near a fault within hundreds of meters of the well. Pore pressure perturbations in the Airport area are 1 order of magnitude lower than those from the other sequences, suggesting that absolute pore pressure changes may not be the main factors of stress drop variations. We suggest that the low stress drop events may be related to transition from aseismic slip to seismic rupture previously observed in laboratory and field experiments.
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Yuan, Xiao Fang, Jing Yin Li y Bin Zhang. "Effects of Surface Tension on Drop Impact on a Horizontal Rotating Disk". Applied Mechanics and Materials 268-270 (diciembre de 2012): 1084–93. http://dx.doi.org/10.4028/www.scientific.net/amm.268-270.1084.
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The impact processes of water and ethanol drops on a rotating horizontal aluminum disk were recorded and analyzed using a high-speed digital camera together with an image analysis program. The angular velocities of the disk were altered to study the effect of surface tension of drops on drop impact processes. The experimental results show that a lower surface tension will result in a higher tangential spread factor and a lower receding rate during the receding stage, for the drop impinging and depositing on a rotating disk. In addition, a lower surface tension of the drop tends to promote the occurrence of splash. The experimental results further verify a proposed correlation of splash-deposition boundary for drops impinging on a rotating disk. Both drops, though they have a quite different surface tension, experience four stages, with two new stages different from those of drops impinging on stationary surfaces. Their tangential spreading factors both increase obviously with the tangential velocity at the impact point, while their radial spreading factors vary a little.
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Walls, Daniel J., Eckart Meiburg y Gerald G. Fuller. "The shape evolution of liquid droplets in miscible environments". Journal of Fluid Mechanics 852 (7 de agosto de 2018): 422–52. http://dx.doi.org/10.1017/jfm.2018.535.
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Miscible liquids often come into contact with one another in natural and technological situations, commonly as a drop of one liquid present in a second, miscible liquid. The shape of a liquid droplet present in a miscible environment evolves spontaneously in time, in a distinctly different fashion than drops present in immiscible environments, which have been reported previously. We consider drops of two classical types, pendant and sessile, in building upon our prior work with miscible systems. Here we present experimental findings of the shape evolution of pendant drops along with an expanded study of the spreading of sessile drops in miscible environments. We develop scalings considering the diffusion of mass to group volumetric data of the evolving pendant drops and the diffusion of momentum to group leading-edge radial data of the spreading sessile drops. These treatments are effective in obtaining single responses for the measurements of each type of droplet, where the volume of a pendant drop diminishes exponentially in time and the leading-edge radius of a sessile drop grows following a power law of $t^{1/2}$ at long times. A complementary numerical approach to compute the concentration and velocity fields of these systems using a simplified set of governing equations is paired with our experimental findings.
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AHMED, KAFEEL, DON McCALLUM y DEREK F. SHELDON. "MULTIPHASE MICRO-DROP INTERACTION IN INKJET PRINTING OF 3D STRUCTURES FOR TACTILE MAPS". Modern Physics Letters B 19, n.º 28n29 (20 de diciembre de 2005): 1699–702. http://dx.doi.org/10.1142/s0217984905010256.
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Ink-jet technology is a novel method for rapid deposition of accurately measured material with high precision. Consequently it has been used for applications such as, deposition of light emitting polymers and more recently for fabricating 3D objects and micro-mechanical structures. Ink-jet technology is also being applied to produce tactile maps for the visually impaired. The efficiency of the tactile maps, as outlined by psychophysical and cartographic studies of haptics, depends on its 3D features. To comprehend and control these features, detailed understanding of interaction amongst micro-drops, which are typically 50μm in diameter, is imperative. Multiphase interaction takes place between each liquid drop at impact with liquid or solid cured drops (deposited previously) and the solid substrate in an envelop of air. The behavior of micro-drops with regards to surface tension, drop coalescence among liquid and solid drops, drop impact kinetics, wettability, surface energy and drop spread has been analyzed using a computational model.
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Wang, Yaru y Changhong Wang. "Novel Eye Drop Delivery Systems: Advance on Formulation Design Strategies Targeting Anterior and Posterior Segments of the Eye". Pharmaceutics 14, n.º 6 (27 de mayo de 2022): 1150. http://dx.doi.org/10.3390/pharmaceutics14061150.
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Eye drops are the most common and convenient route of topical administration and the first choice of treatment for many ocular diseases. However, the ocular bioavailability of traditional eye drops (i.e., solutions, suspensions, and ointments) is very low because of ophthalmic physiology and barriers, which greatly limits their therapeutic effect. Over the past few decades, many novel eye drop delivery systems, such as prodrugs, cyclodextrins, in situ gels, and nanoparticles, have been developed to improve ophthalmic bioavailability. These novel eye drop delivery systems have good biocompatibility, adhesion, and propermeation properties and have shown superior performance and efficacy over traditional eye drops. Therefore, the purpose of this review was to systematically present the research progress on novel eye drop delivery systems and provide a reference for the development of dosage form, clinical application, and commercial transformation of eye drops.
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Schneider, J., Mike Tokach, Steve Dritz, J. Nelssen, Joel DeRouchey y Robert Goodband. "Determining the accuracy of gestation feed drops". Journal of Swine Health and Production 16, n.º 6 (1 de noviembre de 2008): 298–303. http://dx.doi.org/10.54846/jshap/552.
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Objective: To determine the accuracy of three different types of gestation feed drops. Materials and methods: Econo, Accu, and Ultra feed drops (Automated Production Systems, Assumption, Illinois) were attached to feed lines at three angles (90°, 75°, and 60°). Feed was collected and weighed at settings of 2, 4, 6, 8, and 10 lb (0.9, 1.8, 2.7, 3.6, and 4.65 kg) for the Econo and Accu feed drops and 2, 4, 6, and 8 lb for the Ultra feed drops. Results: There was a drop type × angle × feed level interaction (P < .01) for the feed settings versus the actual amount dropped. At 90°, the relationship between the feeder setting (x) and actual quantity of feed dropped was best described by the regression equation (1.156x + 0.244) for the Econo, (1.010x + 0.072) for the Accu, and (1.009x + 0.231) for the Ultra feed drops. At 75°, the regression equations were (1.014x – 0.139) for the Econo, (0.997x + 0.057) for the Accu, and (1.005x + 0.156) for the Ultra feed drops. At 60°, the regression equations were (0.689x – 0.076) for the Econo, (0.989x – 0.249) for the Accu, and (0.951x + 0.026) for the Ultra feed drops. Implications: The type of feed drop and its angle relative to the feed line influences the amount of feed dispensed at a feeder setting. The Accu and Ultra feed drops more accurately dispense the correct amount of feed than the Econo feed drops.
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Planchette, C., H. Hinterbichler, M. Liu, D. Bothe y G. Brenn. "Colliding drops as coalescing and fragmenting liquid springs". Journal of Fluid Mechanics 814 (3 de febrero de 2017): 277–300. http://dx.doi.org/10.1017/jfm.2016.852.
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A universal modelling approach of drop fragmentation after head-on drop collisions is presented. In this approach, the colliding drops are seen as liquid springs that coalesce, compress and relax, leading the merged drop to break up if it reaches a critical aspect ratio. Combining energetic balance of the compression and relaxation phases with a Rayleigh-like criterion, we deduce the fragmentation threshold velocity for the collision of two and three drops of the same liquid and of two drops of immiscible liquids. Predictions and experimental results obtained for these three kinds of collisions using various liquids and drop sizes are found to be in good agreement over a wide domain whose boundaries are discussed.
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Moss, AJ y TW Green. "Erosive effects of the large water drops (gravity drops) that fall from plants". Soil Research 25, n.º 1 (1987): 9. http://dx.doi.org/10.1071/sr9870009.
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A large proportion of rainfall, intercepted by plants, is released again as large 'gravity drops', averaging about 5 mm in diameter. Almost all raindrops are considerably finer, and less erosive, than these large drops, and such conversions can thus result in increased drop erosivity. Because all are large, fall height provides the major control of gravity-drop erosivity. Experimental studies demonstrated that erosivity rose rapidly over the first 2 m of free fall, and it was found that only drops released from less than 0.3 m above the soil surface had small-to-negligible erosivity. Conversion of some 15-20% of a fine, artificial rain to gravity drops by a small tree branch, held only 0.8 m, above a shallow water flow, more than tripled the transport rate of medium sand.
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HA, JONG-WOOK y SEUNG-MAN YANG. "Deformation and breakup of Newtonian and non-Newtonian conducting drops in an electric field". Journal of Fluid Mechanics 405 (25 de febrero de 2000): 131–56. http://dx.doi.org/10.1017/s0022112099007223.
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In this article, we considered experimentally the deformation and breakup of Newtonian and non-Newtonian conducting drops in surrounding fluid subjected to a uniform electric field. First, we examined three distinctive cases of Newtonian-fluid pairs with different relative conductivities, namely highly conducting drops, conducting drops and slightly conducting drops. The results on the Newtonian fluids demonstrated that when the conductivity of the drop is very large relative to that of the surrounding fluid, the deformation response of such highly conducting drops is described well by the electrohydrostatic theory, especially with regard to the prediction of the critical point. Specifically, when the ratio of drop to continuous-phase resistivity, R, was less than 10−5, the electrohydrostatic theory was quite satisfactory. Then, the non-Newtonian effect on the drop deformation and breakup was studied for highly conducting drops which satisfied the condition R < O(10−5). The highly conducting drop became stable in a weak or moderate field strength when either the drop or the continuous phase was non-Newtonian. On the other hand, when both the phases were non-Newtonian, more complicated responses were observed depending on the ratio of zero-shear-rate viscosities. Although the effects of the rheological properties are minimal on all features away from the critical conditions for breakup or prior to the instability, the non-Newtonian properties have a significant influence during drop burst, which is accompanied by large velocities and velocity gradients. In particular, when the ratio of the zero-shear-rate viscosity of the drop to that of the ambient fluid was much larger than unity, non-Newtonian properties of the drop phase enhanced the drop stability. Conversely, the elasticity of the continuous phase deteriorated the drop stability. Meanwhile if the zero-shear-rate viscosity ratio was much smaller than unity, the elasticity of the continuous phase produced a stabilizing effect. The effects of resistivity and viscosity ratios on the breakup modes were also investigated. When at least one of the two contiguous phases possessed considerable non-Newtonian properties, tip streaming appeared.
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Phimmasene, Soukvilay, Kittipong Tonmitra, Apirat Siritaratiwat y Arkom Kaewrawang. "Environmental Study on the Behavior of Water Drops with Circular Resin Insulator Material under DC Electric Field Stress". Advanced Materials Research 979 (junio de 2014): 111–14. http://dx.doi.org/10.4028/www.scientific.net/amr.979.111.
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The influence of damages on the insulator’s surface in the distribution system is investigated in this paper. The circular resin is used as the specimen under high voltage direct current (HVDC) between the electrodes with diameter of 2 mm and distance between both electrodes are 35 mm. There are three cases in the experiment and it was tested in environmental condition under dry surface, single droplet and double droplets. The HVDC had been applied to the electrodes, the level of applied were 5, 10, 15, 20, 25, 30 and 35 kV. The results show that the arc occurs rapidly in the case of single and double drops with compared to dry surface. The movements of the water drop of the single and doubles are pretty similar, but the arc occurs quickly in the double drop in comparison with single drop owing to double drops stretch to each other. The double drops take a lower voltage on stretching, whereas the single drop takes higher because the double drops have much more densities than single drop. Besides, the double drops act as a bridge allow the electrical field generated from both electrodes pulled them resulting in arcing easily. In conclusion, the droplets on the surfaces cause the leakage current and it has an effect on the stability of the distribution system.
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Yin, Zhaohua y Qiaohong Li. "Thermocapillary migration and interaction of drops: two non-merging drops in an aligned arrangement". Journal of Fluid Mechanics 766 (4 de febrero de 2015): 436–67. http://dx.doi.org/10.1017/jfm.2015.10.
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AbstractA numerical study on the interaction of two spherical drops in thermocapillary migration in microgravity is presented. Unequal drop sizes in the axisymmetric model lead to strong drop interaction if the leading drop is smaller. The effect of the ratio of the two drop radii, their initial distance apart, and non-dimensional numbers on the interaction is studied in the case of non-merging drops in detail. The Marangoni number adopted in this paper is fairly large (around 100) so as to reveal the phenomena of real flows. As a result, the heat wake behind the leading drop plays an important role in drop interaction, and obviously different final drop distances and transient migration processes are observed for various sets of non-dimensional numbers. The influence of drop deformation on drop interaction is also investigated for relatively large capillary number (up to 0.2). Finally, some simulations are performed to explain the phenomena of drop interaction in previous experiments, and some suggestions for future experiments are also provided.
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LYUBIMOV, D. V., V. V. KONOVALOV, T. P. LYUBIMOVA y I. EGRY. "Small amplitude shape oscillations of a spherical liquid drop with surface viscosity". Journal of Fluid Mechanics 677 (27 de abril de 2011): 204–17. http://dx.doi.org/10.1017/jfm.2011.76.
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The analysis of surface oscillations of liquid drops allows measurements of the surface tension and viscosity of the liquid. For small oscillations of spherical drops with a free surface, classical formulae by Rayleigh and Lamb relate these quantities to the frequency and damping of the oscillations. In many cases, however, the drop's surface is covered by a surface film, typically an oxide layer or a surfactant, exhibiting a rheological behaviour different from the bulk fluid. It is the purpose of this paper to investigate how such surface properties influence the oscillation spectrum of a spherical drop. For small bulk shear viscosity, the cases of small, finite and large surface viscosities are discussed, and the onset of aperiodic motion as a function of the surface parameters is also derived.
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Sun, Jing Mei, Xian Fu Wei y Bei Qing Huang. "Influence of the Viscosity of Edible Ink to Piezoelectric Ink-Jet Printing Drop State". Applied Mechanics and Materials 200 (octubre de 2012): 676–80. http://dx.doi.org/10.4028/www.scientific.net/amm.200.676.
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Piezoelectric Inkjet Printing is the main ink-jet printing at present, and drop state will have great influence to ink-jet printing quality, so the ink-jet drop state of edible ink is researched based on piezoelectric inkjet printing. The viscosity of the ink is adjusted by the way of adding different levels of resin, and then the samples which have different viscosity are got. Drop state is observed through drops observatory which installs Spectra Polaris nozzle (35pl), then the speed, volume, tail length and roundness of the drops are measured at certain moment in order to evaluate the influence of viscosity to ink-jet drop state. The result shows that viscosity has big influence to ink-jet drop state, when the viscosity becomes larger, the speed of drops becomes smaller, the variation of volume is not so obvious, the tail length of drops becomes smaller and roundness becomes larger accordingly, until the viscosity is 10mPa•s, the tail length is the smallest and roundness is the biggest, the drop state is the best , when viscosity is bigger than 10mPa•s, the tail length will become bigger and roundness smaller.
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Müllertz, Olivia, Anne Hedengran, Zaynab Ahmad Mouhammad, Josefine Freiberg, Richárd Nagymihály, Jette Jacobsen, Susan Weng Larsen et al. "Impact of benzalkonium chloride-preserved and preservative-free latanoprost eye drops on cultured human conjunctival goblet cells upon acute exposure and differences in physicochemical properties of the eye drops". BMJ Open Ophthalmology 6, n.º 1 (diciembre de 2021): e000892. http://dx.doi.org/10.1136/bmjophth-2021-000892.
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ObjectiveTo investigate the short-term impact on human conjunctival goblet cell (GC) survival and mucin release of acute exposure to benzalkonium chloride (BAK) preserved and preservative-free (PF) 0.005% (w/v) latanoprost (LT) eye drops, and to compare the eye drops’ physicochemical properties.Methods and analysisPrimary GC cultures were established from human conjunctival donor tissue. The impact of eye drops on GC survival was assessed using a lactate dehydrogenase assay. Mucin release was evaluated through mucin-specific immunostaining. pH value, osmolality, drop mass and surface tension for all LT eye drops were measured.ResultsAfter application with PF-LT for 30 min (min), the GC survival was maintained compared with control (p=0.9941), while all BAK-LT eye drops reduced survival with approximately 30% (p<0.02). Following application with PF-LT for 30 min, mucin was found around the GC nucleus, as seen in the vehicle control, indicating no secretion. In contrast, BAK-LT caused diffuse staining of mucin, similar to the secretagogue histamine, indicating stimulation of secretion. The pH value of the BAK-LT and PF-LT eye drops were 6.0–6.9 and 6.8, respectively. The osmolality was 258–288 mOsm/kg for the BAK-LT eye drops and 276 for PF-LT eye drops. The mean drop mass was 26–31 mg for the BAK-LT eye drops and 30 mg for PF-LT. The surface tension was lower for all BAK-LT eye drops (31.1–32.1 mN/m) compared with PF-LT (42 mN/m).ConclusionPF-LT compared with various branded and generic LT preparations containing BAK are less cytotoxic when applied to cultured GCs.