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Disperse systems, and emulsions in particular, are currently massively used in fields as varied as food industry, cosmetics, health care and environmentally‐friendly materials. To meet increasingly precise needs or targeted applications, these systems need to be endowed with new functionalities at their interfaces, in addition to their composition and structural properties. However, due to the fragility of drops and the low reactivity of their surface, conventional solid surface chemistry cannot be used for such a purpose. Several specific emulsion interface functionalization techniques have thus been developed for targeted systems and applications, but a general framework has yet to be drawn. In this review, we attempt to present these methods in a unified way through the prism of what we may call “liquid surface chemistry”. We propose to categorize existing methods into drop‐coating strategies, including layer‐by‐layer techniques and polymer coating, with a particular focus on polydopamine, and emulsifier‐carrier approaches involving particles and/or amphiphilic molecules. They are discussed in a transversal way, highlighting the underlying physico‐chemical principles and providing a comparative analysis of their advantages, current limitations and potential for improvement. We also propose future directions and opportunities, involving for instance DNA‐based programmability or artificial intelligence, which could make liquid surface chemistry more versatile and controlled. [ABSTRACT FROM AUTHOR]

The splashes of a highly viscous fluid (glycerol) resulting from its pulsed displacement from a gap between two rapidly approaching disks are studied. It is found that, outside the disks, the splash has the form of a thin film bounded by an annular rim. A physical model of the splash is formulated, and analytical solutions describing its trajectory are given. The calculation results are compared with experimental data. The effects of fluid viscosity, surface tension, and film breakdown are analyzed. It is shown that the key influence on the splash development scenarios is exerted by surface tension of the film connecting the rim to the disks. [ABSTRACT FROM AUTHOR]

The results of experimental studies of the cocombustion of coal–water fuel with fuel oil are presented. According to the results of experimental studies, the efficiency of joint ignition of stationary single droplets of coal–water fuel and fuel oil was substantiated. A decrease in the ignition delay times of fuel droplets was found in comparison with the ignition of only coal–water fuel droplets under identical conditions. A significant decrease in the ignition delay times of coal–water fuel droplets is typical for droplets with sizes of 2 and 3 mm in the entire studied temperature range of the oxidizer (from 873 to 1,273 K) and distances (from 2 to 4 mm) between drops of coal–water fuel and fuel oil. It has been experimentally established that the reduction of ignition delay times is 58 and 70%. For droplets of coal–water fuel with a characteristic size of 1 mm, the changes in ignition delay times are ambiguous. The joint combustion of coal–water fuel and fuel oil affects the ignition of droplets of coal–water fuel, and the characteristic size of which is more than 1 mm. With this method of burning coal–water fuel and fuel oil, the latter acts as a catalyst when igniting coal–water fuel, thereby ensuring a stable combustion of such fuel. The combustion of two-component coal–water fuel together with fuel oil can avoid the problems typical of such fuels: reduce the requirements for spraying devices, solve the problem of low reactivity, increase the completeness of combustion of this fuel, and fully use it in the production of thermal and electrical energy. [ABSTRACT FROM AUTHOR]

The collision of drops of water and elastic liquids with a thin cylinder (fiber) has been studied. Aqueous solutions of polymers were used as elastic liquids, which simulated the rheological behavior of oral fluid—the main carrier of infections by airborne drops. Water as a Newtonian fluid was investigated to identify the elastic effects when comparing the collisions of Newtonian and non-Newtonian fluids—water and polymer solutions. The flight path of the drop and the cylinder axis are mutually perpendicular. Attention is focused on the difference between the collisions of water drops and drops of elastic liquids. In the experiments, the diameter of the drop was 3 mm, and the diameter of the horizontal stainless-steel cylinders was 0.4 and 0.8 mm. Drops were formed by the slow flow of liquid from a vertical stainless-steel capillary with an outer diameter of 0.8 mm, from which the drops were periodically separated under the influence of gravity. The velocity of the drop before the collision was determined by the distance between the end of the capillary and the target (cylinder); in the experiments, this distance was 5, 10, and 20 mm. The velocities of falling drops before impact were estimated in the range of 0.2–0.5 m/s. The collision process was monitored using high-speed video recording methods with frame rates of 240 and 960 Hz. Water and aqueous solutions of polyacrylamide with a molecular weight of 11 million and concentrations of 100 and 1000 ppm were used as test liquids. Experiments have shown that, depending on the height of the drop and the concentration of the polymer, various drop collision scenarios are possible: (1) short-term rebound of the drop from an obstacle, (2) braking and stopping the drop on the obstacle, (3) flow of the drop around a cylindrical obstacle while maintaining continuity and continuing free flight, (4) disintegration of the drop into two secondary drops, each with its own history of subsequent flight. [ABSTRACT FROM AUTHOR]

A mathematical model is constructed for the dynamics of a raindrop moving in a gravity field through an atmosphere containing fine particles, taking into account the processes of relaxation of its velocity and the capture of fine particles. It has been established that the equation of motion of a drop in the problem being posed belongs to the class of singularly perturbed equations, for the integration of which it is necessary to involve special algorithms. In the limiting modes of droplet motion, analytical solutions of the problem are obtained that describe the dependence of the droplet velocity and coordinate on time. In the complete formulation, the solutions of the problem are obtained numerically for different values of the defining parameters. The influence of the droplet size on the parameters of its motion in a concentrated aerodispersed mixture has been studied. The dependences of the limiting volume fraction of the solid component in the composition of the drop and the intensity of the precipitation of particles (washed out by the drop) on the earth's surface on the size of the drop are obtained. A comparison of the calculated, approximate–analytical and experimental dependences of the steady-state rate of fall of a drop on its size has been carried out, and it shows their good agreement. [ABSTRACT FROM AUTHOR]

High-speed video recording was used to trace the matter transfer pattern of a free-falling water drop and of the deformation of the free surface of the target fluid at the intrusive mode when the available potential surface energy (APSE) exceeds the kinetic energy of the drop. The free surface of the unified drop-target fluid system remains convex at the initial submerging stage. The inflowing drop forms a lenticular intrusion in the fluid bulk, which gradually transforms into a vortex ring. A cavity begins to form with a time delay Δt = 10 to 12 ms. The cavity surface includes traditional flat, spherical, cylindrical and conical sections moving at different velocities. The temporal variability of the intrusion and cavity geometry was traced. The drop substance is preserved as individual fibers in the wake of the submerging ring. [ABSTRACT FROM AUTHOR]

Experiments have identified two modes of coalescence of a free-falling drop of liquid mixing with a deep target fluid at rest–a slow intrusive mode and a fast impact mode. The influence of the energy transfer and transformation processes on the flow dynamics and structure is analyzed. Experimental planning and data interpretation were carried out subject to the properties of complete solutions to the system of fundamental equations of inhomogeneous fluid mechanics. The transfer of the results to flows in facilities and in the environment is discussed. [ABSTRACT FROM AUTHOR]

Acoustic signals have been studied by coordinated optical and acoustic methods in two modes of a free-falling water drop merging with water. Only the primary sound packet is observed in the intrusive mode at a low drop velocity when a cavity is formed with a delay in the colored wake of the inflowing liquid. The influence of the drop velocity on the parameters of the primary signal was traced in the experiments. The cavity begins to form from the moment of initial contact when the drop velocity is high. The flow pattern becomes more complicated, the drop substance is distributed over the surface of the emerging cavity and growing crown in the form of individual fibers forming linear and reticular structures. The falling section of the primary signal is constituted by a group of pulses with a complex spectral composition. Further, after a pause, one or more low-frequency sound packets are recorded. The spectral portrait of the secondary packets is related to the shape of the detached gas cavity. A smooth axisymmetric cavity radiates a monochromatic packet. A complex-shaped cavity transforming into a gas bubble emits a multi-frequency signal. The duration and amplitudes of the secondary sound signals depend on the rate of transformation of the separated gas cavity into a smooth spheroidal bubble. The parameters of acoustic signals change non-monotonically with increasing velocity of the merging drop. [ABSTRACT FROM AUTHOR]

The merging of a falling drop with a water surface gives rise to a series of hydrodynamic phenomena that differ in time and space scales. Among them, fast unsteady flows are distinguished, in the process of which deformed underwater caverns and gas cavities separated from them are formed. When the surface of the separating gas cavity closes, the formed bubble undergoes volumetric oscillations, which, in turn, generate short acoustic packets propagating under water and in the air. Experimental data are presented in which the sequence of the formation of caverns is traced, and the processes of the formation and detachment of bubbles and accompanying acoustic signals are identified and detailed. In the composition of the sound packets recorded in the water and air environments, there are differences associated with the characteristics of propagation (transient damping at the water-air boundary) and the influence of the transmission functions of the hydrophone and microphone. In the case of detachment, reattachment, and reseparation of an air bubble from successive caverns, the frequency of the emitted signal increases. Despite the highly irregular shape of the emitting bubbles, the emission frequency remains constant, which indicates the volume of the bubble as the governing parameter of acoustic emission. [ABSTRACT FROM AUTHOR]

The transverse impact of a pulsed water microjet on individual cylindrical fibers is studied. The stages of ejection, breakup, and collision of the microjet were recorded by high-speed photography. A significant deceleration of the microjet by the fiber and its splitting into two parts were revealed. The mechanisms of the observed phenomena and the influence of various factors are discussed. [ABSTRACT FROM AUTHOR]

The processes of interaction of liquid droplets with solid surfaces have become of interest to many researchers. The achievements of world science should be used for the development of technologies for spray cooling, metal hardening, inkjet printing, anti-icing surfaces, fire extinguishing, fuel spraying, etc. Collisions of drops with surfaces significantly affect the conditions and characteristics of heat transfer. One of the main areas of research into the interaction of drops with solid surfaces is the modification of the latter. Changes in the hydrophilic and hydrophobic properties of surfaces give the materials various functional properties—increased heat transfer, resistance to corrosion and biofouling, anti-icing, etc. This review paper describes methods for obtaining hydrophilic and hydrophobic surfaces. The features of the interaction of liquid droplets with such surfaces are considered. The existing and possible applications of modified surfaces are discussed, as well as topical areas of research. [ABSTRACT FROM AUTHOR]

When a water drop is placed on a hot solid surface, it either undergoes explosive contact boiling or exhibits a stable state. In the latter case, the drop floats over an insulating layer of vapor generated by rapid vaporization of water at the surface/drop interface; this is known as the Leidenfrost state. Here, we discuss a previously unrecognized steady state in which a water drop "stands" on a hot smooth surface. In this state, the drop stabilizes itself with partial adhesion on the hot surface, leading to unique deformation and rotation behavior reminiscent of Sufi whirling--a form of spinning dance. Our analysis of this standing Leidenfrost state reveals the underlying mechanisms that drive the drop's stable partial adhesion and subsequent deformation with rotation. The heat-transfer efficiency of this standing state is up to 390% greater than that of the traditional floating Leidenfrost state. [ABSTRACT FROM AUTHOR]

The processes of freezing of water droplets sitting on a substrate after exposure to nanosecond spark discharges have been experimentally studied. It has been found that the droplets subjected to spark discharge treatment freeze much earlier than those unexposed to discharges. The analogy of the observed processes with the well-known Mpemba effect is noted. A qualitative explanation is given for the observed effect: rapid freezing is due to hydrated electrons, which are formed upon contact of water with plasma and play the role of crystallization centers. [ABSTRACT FROM AUTHOR]

[Display omitted] The rich variety of patterns induced by evaporating drops containing particles has significant guidance for coating processes, inkjet printing, and nanosemiconductors. However, most existing works construct a uniform pattern by suppressing the coffee ring effect, and establishing the connection between them is still an academic challenge. We report uniform, polygonal, and coffee ring patterns obtained by adjusting the solute concentration that sets in when an ethanol drop with dissolved ibuprofen is deposited on a silicon wafer. Pattern formation involves rich hydrodynamic events: spreading, evaporative instability, dewetting, film formation, and particle deposition. Based on the distinct multiscale properties, this series of patterns is directly connected from the perspective of fractal geometry, which allows us to name them "fractal deposition patterns". A theoretical model considering film stability is established to explain the mechanism behind pattern formation, which is well verified by experiments. This work has presented a unique strategy that can directly connect uniform, polygonal, and coffee ring patterns under the same physics, hoping to provide instructive guidance for practical applications. [ABSTRACT FROM AUTHOR]

We analyze different flow regimes of a filament formed by extrusion of a material through a cylindrical die. We deduce that the elongational yield stress of a simple yield stress fluid (i.e., with negligible thixotropy effects) can be determined from the mass of the droplet after filament breakage and an estimation of the critical radius at pinch-off at the solid-liquid regime transition. We demonstrate that such a simple characterization is relevant in a relatively wide range of extrusion velocities, i.e., this velocity slightly affects the drop mass in this range. For the simple yield stress fluids used, Carbopol gel, clay-water paste at different concentrations, and emulsion, covering a large range of yield stress values (50–1000 Pa), the elongational yield stress appears to be equal to the simple shear yield stress times a factor equal to about 1.5 3. As a consequence, this simple test may be used to obtain, almost instantaneously and without sophisticated apparatus (a syringe and a balance are sufficient), a good estimate of the shear yield stress of simple yield stress fluids. In that case, the main source of uncertainty (up to about 20%) is the value of the critical radius at the solid-liquid transition. Finally, we review the operating conditions (material properties and extrusion characteristics) for which we can expect this approach to be valid. [ABSTRACT FROM AUTHOR]

• Protein aggregates were increased significantly under dropping stress at –30 °C. • Poloxamer-188 prevented the aggregation caused by dropping stress at –30 °C. • The cooling rate affected the stability in the frozen state. • Local heat induced by the dropping stress could be a root cause of the aggregation. The formation of protein aggregates, which can be immunogenic and lower the efficacy and safety of protein drugs, has been an issue in biopharmaceutical development for more than a decade. Although protein drugs are often shipped as frozen material, the effect of the accidental dropping of frozen proteins, which can occur during shipping and handling, on the physical stability has not been studied. Here, a frozen Fc fusion protein was subjected to dropping stress and the increase in the aggregate concentration was evaluated. Significant increases in micron-sized aggregates were observed at –30 °C (p ≤ 0.01), but not at –60 °C. Proteins adsorbed on the vial surfaces were not remarkably detached by the action of dropping and were not the primary cause of the increase in micron-sized aggregates. When the vials were dropped, local heat generation occurred and this led to local freeze-thaw stress that induced protein aggregation. Poloxamer-188, which is known to mitigate aggregation caused by freeze-thaw stress, effectively prevented the aggregation caused by the dropping stress in the frozen state at –30 °C. In addition, rapid freezing could suppress the aggregation caused by the dropping stress. The results demonstrated that dropping stress reduced the stability of proteins even in the frozen state, and they provide new insights into the formulation and freezing processes to prevent protein aggregation caused by dropping stress in the frozen state. [Display omitted] [ABSTRACT FROM AUTHOR]

• The wetting of porous surfaces differs from that of dense surfaces due to the liquid's infiltration. • During evaporation, the base of the droplet undergoes three stages: expansion, constant base, and shrinkage. • A theoretical model for the temporal evolution of the contact angle was developed for the second and third stages. This study aims to examine the membrane wetting of a porous cylindrical surface in comparison with dense cylindrical surfaces. Droplets of distilled water, ethyl alcohol, and 35 g/L NaCl solution with an average volume of 5 µl were deposited on a hydrophobic polypropylene (PP) cylindrical membrane with micropores, a dense polypropylene (PP) cylindrical membrane, and a stainless-steel cylinder, to investigate their temporal wettability behavior. The diagnostics consisted of backlight imaging using a high-speed camera. The droplet spreading was characterized in terms of the droplet base length and the droplet contact angle as a function of time. The study found that the temporal evolution of the contact angle of droplets on dense and porous surfaces is connected to the dynamics of the droplet base. The droplet base undergoes three stages: expanding base, constant base, and finally shrinking base. The study found that for a porous PP membrane, the contact angle decreased exponentially in the initial stage and then linearly over time, indicating the initial dominance of absorption followed later by evaporation. In contrast, dense surfaces exhibit a linear decrease in contact angle, emphasizing pure evaporation with no absorption. A theoretical model for the temporal evolution of the contact angle due to evaporation was developed and the model was successful in correlating the experimental data during the second and third stages. The present study also developed simplified linearized correlations for the temporal evolution of droplets for all three stages. The findings for the time-dependent wetting behavior of PP membranes with micropores demonstrated that even hydrophobic porous materials can become wet due to the liquid's infiltration on the hydrophobic porous surface. [ABSTRACT FROM AUTHOR]

• An optimized, explainable machine learning model to predict shape and drag evolution for a freely moving drop in air. • SHAP analysis enables model explainability and identifies key features affecting temporal changes in drop shape and drag. • Uncertainty quantification for drop shape and drag coefficient using the ensemble method. • Development of reduced-feature models guided by the SHAP analysis. Accurately predicting the shape and drag of a moving drop is crucial in many spray applications. However, due to the complex interaction between the drag force and drop shape deformation, accurate prediction of drop shape and drag from Computational Fluid Dynamics (CFD) simulation requires large computational resources and time. A novel data-driven approach using NARXNN (Non-linear Auto Regressive eXogenous input Neural Network) is proposed in this study, which recurrently predicts the drop shape and drag for a given Weber number (We) and Reynolds number (Re), in the sub-critical We regime where there is no drop breakup. The average error in radius and drag coefficient for the test cases, as low as 0.36 % and 0.49 % , respectively, is achieved. Most importantly, SHAP (SHapley Additive exPlanations) analysis is performed to identify important features for the predictions, hence enabling the explainability of the physics involved in the predictions of machine learning (ML) models for drop deformation and the interaction between the drop and gas flows. Global interpretation of SHAP values identifies We and Re as the most important features to predict the drop shape and drag. Based on the SHAP analysis, several reduced-feature models are developed. All the reduced-feature models can predict drop shape and drag coefficient within 4 % average error in radius and drag coefficient for any We and Re combinations within the prescribed parameter space. The ML models developed in this study demonstrate a tremendous computational advantage over the traditional CFD simulations. The drop shape and drag coefficient evolution can be predicted within seconds for a single case, whereas the CFD simulation takes several days to a week on a single processor. [ABSTRACT FROM AUTHOR]

Publications on form in popular music have largely assumed the formal sections germane to pop-rock to be the formal designs of "popular music." But the most popular music of our time--music charting on the Billboard Top-40--has absorbed the influence of electronic dance music (EDM) in a way that has fundamentally changed its formal structure. This results in "Top-40 EDM," a genre defined by collaborations between seasoned EDM producers and A-list pop singers. This article begins by defining EDM's three core formal functions (verse, riser, and drop), and compares them to more familiar functions heard in pop-rock music (verse, prechorus, chorus, and postchorus). Part two draws on de Clercq's (2017) concept of blended formal functions to define Top-40 EDM's most recognizable section, the "riserchorus." Part three examines the larger structure of these tracks, including their "compound AAA" forms, in which each of the song's rotations feature the same formal functions, though presented differently. Finally, the article demonstrates how Top-40 EDM producers regularly combine samples at the end of their tracks, resulting in cumulative hyper-blended sections like "riserchorus-bridge" and "riserchorusdrop." [ABSTRACT FROM AUTHOR]

For the first time, the transfer of the substance of a free-falling drop into a resting target fluid at the stage of formation of a primary cavity was tracked by high-speed video recording. In the experiments, water-diluted drops in a ratio of 1 : 100 ink solution or a saturated solution of baking soda with a diameter of cm fell at a velocity of U = 3.1 m/s into water or a 20% ammonium thiocyanate solution in the splash formation mode. In all experiments, the wall of the growing cavity is pierced by thin fibers containing drop material, which form an intermediate fine-structured layer. After the end of the fiber growth stage with a duration of 7–8 ms and diffusion smoothing of the concentration gradients, a liquid layer of intermediate density with a thickness of 1.5 to 0.7 mm is formed around the growing cavity. The layer is separated by a sharp boundary from the target fluid. A new group of inclined fibrous loops is formed in the wake of the collapsing cavity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermodynamic properties of flat and spherical interfaces from a microscopic model. • Interfacial tensions, profiles of normal and transverse pressure. • Predicted microscopic structure of drops in oil + water + surfactant mixtures. • Curvature dependence of interfacial tension and Tolman length for spherical drops. • Predicted interfacial tensions in water/n-alkane mixtures agree with experiment. The interfacial properties and structure of nonuniform fluids containing complex chainlike molecules and associating species are very much needed in a variety of different fields, including enhanced oil recovery, drug delivery, pharmacy, cosmetics, food processing, etc. Recently, we described the Multilayer Quasichemical Model (MQuM) of a nonuniform fluid that provides a remarkably detailed structural information, including the local concentration and orientation of functional groups of the molecules, the orientation profiles of the chemical bonds in molecular chains and the orientation profiles of the hydrogen bonds in the mixture. In this work, we focus on the description of thermodynamic properties with the aid of MQuM, including the interfacial tension and the profiles of normal and transverse pressures. Before proceeding to more complex systems, a test is performed through comparison with the previously known results from the Scheutjens-Fleer theory for the planar liquid–vapor interface and spherical droplet in one-component fluid of nonpolar monomeric molecules. The model is applied then for planar interfaces between the liquid phases in mixtures of water with n-alkanes of different chain length and for spherical drops in model systems that contain an associating solvent, a nonpolar chain and a nonionic amphiphile. Our theoretical results are compared with experiment, predictions from iSAFT and MD simulation data from the literature. For the spherical droplets, we discuss the model description of the dependence of the interfacial tension on the curvature and estimate the Tolman length. For the planar interface between the equilibrium liquid phases in water – n-alkane mixtures, the interfacial tensions predicted from the model are in good agreement with experiment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermodynamic properties of flat and spherical interfaces from a microscopic model. • Interfacial tensions, profiles of normal and transverse pressure. • Predicted microscopic structure of drops in oil + water + surfactant mixtures. • Curvature dependence of interfacial tension and Tolman length for spherical drops. • Predicted interfacial tensions in water/n-alkane mixtures agree with experiment. The interfacial properties and structure of nonuniform fluids containing complex chainlike molecules and associating species are very much needed in a variety of different fields, including enhanced oil recovery, drug delivery, pharmacy, cosmetics, food processing, etc. Recently, we described the Multilayer Quasichemical Model (MQuM) of a nonuniform fluid that provides a remarkably detailed structural information, including the local concentration and orientation of functional groups of the molecules, the orientation profiles of the chemical bonds in molecular chains and the orientation profiles of the hydrogen bonds in the mixture. In this work, we focus on the description of thermodynamic properties with the aid of MQuM, including the interfacial tension and the profiles of normal and transverse pressures. Before proceeding to more complex systems, a test is performed through comparison with the previously known results from the Scheutjens-Fleer theory for the planar liquid–vapor interface and spherical droplet in one-component fluid of nonpolar monomeric molecules. The model is applied then for planar interfaces between the liquid phases in mixtures of water with n-alkanes of different chain length and for spherical drops in model systems that contain an associating solvent, a nonpolar chain and a nonionic amphiphile. Our theoretical results are compared with experiment, predictions from iSAFT and MD simulation data from the literature. For the spherical droplets, we discuss the model description of the dependence of the interfacial tension on the curvature and estimate the Tolman length. For the planar interface between the equilibrium liquid phases in water – n-alkane mixtures, the interfacial tensions predicted from the model are in good agreement with experiment. [ABSTRACT FROM AUTHOR]

The shape evolution of a subsiding splash of a freely falling drop (the diameter is D = 0.42 cm, and the contact velocity is U = 3.1 m/s) in the mode of active generation of sound packets was traced by high-speed video recording. The shape of the splash is continuously transformed as it spreads. During the formation of the second cavity, the splash base pinches off the depression bottom of the deformed surface of the target fluid. A third cavity is formed when the top of the splash is immersed. A returning droplet, which has previously flown out from the top of the splash and which by its lateral surface is in contact with the walls of the remnant of the third cavity, forms the fourth cavity. The shape of the last cavity is distorted by thin flows that are accelerated by the fast conversion of the available potential surface energy (APSE) when the free surfaces of the merging fluids are eliminated. A rupture in the base of the subsiding splash was observed in all experiments of this series. [ABSTRACT FROM AUTHOR]

Introduction: Low hemoglobin levels are associated with an increased risk of mortality in intensive care (ICU) patients. The underlying reason is due to the limitation in oxygen delivery to the tissues caused by a reduction in the number of oxygen carrying erythrocytes. This study aimed to examine the relationship between hemoglobin drop (DHgb= admission hemoglobin-nadir hemoglobin), nadir hemoglobin levels (NdrHgb; the lowest hemoglobin value during ICU stay) and mortality in COVID ARDS patients admitted to intensive care. Materials and Methods: This was a prospective non-randomized study of consecutive COVID ARDS patients who had at least two determinations of hemoglobin level (the first on admission) separated by 24 hours and an ICU stay <14 days. Admission hemoglobin (AdmHgb), NdrHgb and DHgb levels were analyzed. Data on blood transfusions were also collected. Results: Although high DHgb and low NdrHgb levels were significantly associated with mortality in univariate analysis of patients, this was not sustained in multivariate analysis. The area under the ROC curve (AUC) of DHgb was 0.577, with a cut-off value of 1.9 g/dL, sensitivity and specificity were 50.7%, and 65.2%, respectively. NdrHgb had a cut-off value of 10.7 g/ dL, with an AUC of 0.423, sensitivity and specificity of 50%. Conclusion: Our results showed that DHgb and low NdrHgb levels are both predictive markers for mortality with moderate sensitivity and specifity. We recommend further studies evaluating a simple scoring model based on DHgb and NdrHgb for predicting mortality. [ABSTRACT FROM AUTHOR]

The evolution of the distribution pattern of an ink droplet freely falling on the wavy surface of a liquid is traced by video-recording methods. A system of travelling plane gravity–capillary waves with a frequency of Hz (a wavelength of cm) was created by a vertically oscillating pointed strip. Drops of alizarin ink with diameter cm fell freely from the dispenser and reached contact velocity cm/s in the mode of splash formation. In the phase of primary contact and coalescence, the colored drop spreads in agitated liquid like in a quiet medium with the formation of a cavity with its bottom covered by colored fibers, a crown, and a splash. The growing crown is surrounded by a group of thin radial trickles with vortex heads and separate spots (wakes of earlier returned ejected droplets). Subsequently, the colored liquid on the surface is divided into three independently moving formations: a finely structured area of primary contact of an irregular shape, a submerging vortex ring, and a near-surface vortex dipole. In all components of the flow, the dye is distributed in the form of thin fibers for a long time until the final phase of erosion by residual flows and molecular diffusion processes. The geometry of movement and the general structure of the separated colored areas are traced. [ABSTRACT FROM AUTHOR]

The evolution of the shape of a sequence of cavities accompanying the coalescence a freely falling drop with a liquid at rest is traced by the method of high-speed video recording. The flow is visualized by the dark field method in the side view (the line of sight lies on the free surface), as well as in the LED-based backlight. In the first case, LED sources were installed on top and on the side of the transparent cuvette; in the second case, a spotlight located behind the cuvette was added to the LED sources. For the first time, the high-resolution experimental technique allows registering the bottom oscillations of the secondary cavities and visualizing the groups of gas bubbles, including frozen-in ones, which reproduce the initial shape of the rapidly filling second cavity, which is formed during splash coalescence. The next shallow cavity is formed after the splash top is submerged. The last cavity is formed by a returning drop previously ejected from the top of the splash. An increase in the rate of the collapsing cavity depth is associated with the conversion of the available potential surface energy (APSE) with a decrease in the area of the free surface of the fluid. [ABSTRACT FROM AUTHOR]

We consider a sequence of four variable polynomials by refining Stieltjes's continued fraction for Eulerian polynomials. Using combinatorial theory of Jacobi-type continued fractions and bijections, we derive various combinatorial interpretations in terms of permutation statistics for these polynomials, which include special kinds of descents and excedances in a recent paper of Baril and Kirgizov. As a byproduct, we derive several equidistribution results for permutation statistics, which enables us to confirm and strengthen a recent conjecture of Vajnovszki and also to obtain several companion permutation statistics for two bistatistics in a conjecture of Baril and Kirgizov. [ABSTRACT FROM AUTHOR]

For the first time, the process of merging a drop of ferric chloride solution (concentration 16 and 1%) with a solution of ammonium thiocyanate (20%), including the formation and restructuring of a system of inclined loops on the surface of the cavity, visualized by the products of a chemical reaction, was recorded on video. The brightly colored iron thiocyanate solution formed during the merging of liquids lands into primary contact droplets and groups of subsequent splashes. Fibers containing iron thiocyanate form linear and mesh structures on the walls of the cavity and crown. Ledges and small annular legged vortices are formed at the bottom of the cavity, under the mesh nodes. During the cavity collapse, the ledges extend into inclined loops up to 4.6 mm long, which penetrate into the target fluid. As the flow evolves, the fibers rearrange, forming new structures. Finely colored areas persist for a long time and spread out under the influence of diffusion processes. [ABSTRACT FROM AUTHOR]

The process of disintegration of a drop (water, a saturated solution of ferrous sulfate, or alizarin ink) freely falling into water into fibers is first observed in the vicinity of the confluence line of liquids. Photo and video recording of the evolution of the flow pattern is carried out. At the bottom of the cavity, annular capillary waves covering the confluence area are visualized as well. Thin radial jets (ligaments) transporting droplet matter descending from the pointed crests of the perturbed boundary of the fluid confluence region are traced. In the mode of splash formation, the ligaments continue in the crown, penetrate the veil, and partially penetrate the spikes at the tops of the pointed teeth on its edge. Wakes of the jets colored by the drop substance form linear and reticulated structures deformed by flows and spreading out under the action of diffusion. Sprays, the sequences of gradually growing small droplets, fly out from the tips of the spikes, the size and angular position of which change with time. Additional acceleration of the fluid in the jets is associated with conversion of the available potential energy upon elimination of the free surfaces of the coalesced fluids. [ABSTRACT FROM AUTHOR]

Continuous monitoring of the quantity and quality of groundwater resources is essential due to the excessive dependence of employment on these resources. The present study was conducted with the aim of quantitative and qualitative study of groundwater resources in the villages of centeral part of Bandar Lengeh city. After quantitatively estimating the groundwater balance, taking into account all components of the aquifer inlet and outlet, level hydrogeological maps and groundwater level changes based on the average of the lunar data were at least in GIS software (10.3 version). By quantitative and qualitative monitoring of groundwater resources in the study area, using water quality statistics of 35 wells that were registered by the Regional Water Company during the statistical period of 2003-2018, groundwater curves were drawn and plotted. The results showed that the groundwater balance of Pedlmezan, west Dezhgan and east Dezhgan aquifers were 5.94, 0.64 and 3.24 million cubic meters per year, respectively, and the amount of allowable withdrawal from the mentioned aquifers were 5.60, 0.64 and 0.64 million cubic meters per year, respectively. Annual drop of -0.03, -0.08 and -0.07 meters of water level of Pedlmezan, west Dezhgan and east Dezhgan indicates the favorable conditions of the aquifer water balance. The qualitative results of the basin showed that the average electrical conductivity of Pedlmezan aquifer has decreased from 6935 μs⁄cm in 2007 to 5654 μs⁄cm in 2003. In Dezhgan plain aquifer, it was found that the average electrical conductivity of the aquifer has increased from 7410 μs⁄cm in 1998 to 10424 μs⁄cm in 2007. Decreasing the amount of electrical conductivity in Pedlmezan aquifer and increasing it in Dezhgan basin is directly related to fluctuations in rainfall in the relevant basin in this period. The general result of this research is that the integrated management of water resources and the measures and planning of the regions have maintained the relative balance of water balance in the region, but in order to prevent the reduction of the quality of water resources with high salinity of the basin, the ban on further exploitation of the water resources of the basin should continue. [ABSTRACT FROM AUTHOR]

The effect of a shielding gas on the plasma flow of an electric arc and molten metal is studied. The effect of the shielding gas on the plasma flow of the electric arc of molten metal is simulated, and a mathematical model is developed that describes the flow of the plasma-forming gas inside a device that forms the necessary directions of plasma flows to form a droplet of molten electrode metal of the required size. It is established that the shielding gas and its pressure affect the gas outflow rate and the formation and size of an electrode metal drop. The time of the formation and detachment of the droplet changes at the increase in the pressure of the shielding gas, the higher the gas pressure, the smaller the volume of the droplet. Argon and carbon dioxide have different effects on the plasma flow of the electric arc, the length of the arc, the formation and detachment of the droplet. The process of the droplet formation can be controlled by changing the gas composition, pressure, and gas velocity. It is determined that the gas flow rate increases from 1.2 to 5.2 m/s and the volume of a droplet of molten electrode metal decreases at the increase in the gas flow from 10 to 30 L/min. The droplet volume can be changed on average by 65% depending on the shielding gas. [ABSTRACT FROM AUTHOR]

• Liquid atomization on two counter-rotating wheels was studied experimentally. • Predominant atomization mechanism is by ligament breakup and head droplet pinching. • At same Weber numbers, droplet diameters are lower than for spinning discs and cups. • Liquid impingement point and wheel gap largely affect mass transfer between wheels. • Significant splashing of liquid can occur after impingement due to a hydraulic jump. This paper presents an experimental study of the liquid disintegration process on an atomizer with two counter-rotating wheels by high-speed imaging. The process was investigated for a wide range of wheel rotational speeds, liquid flow rates and impingement positions. Compared to flat disc and cup atomizers operating at similar Weber numbers, proposed atomizer design is capable of producing much finer droplets in the ligament formation mode (mean diameter under 0.15 mm when We = 106) and at a significantly larger liquid throughput. Despite the atomizer gap flow complexity, approximation of mean liquid trajectories with tangent lines proved to be fairly accurate. We were able to identify two main challenges in atomizer operation, namely the occurrence of hydraulic jump upon liquid impingement causing the formation of large droplets, and escaping of the liquid spray through the wheel gap. Nevertheless, both issues can be largely mitigated by optimization of atomizer geometry and operating parameters. [ABSTRACT FROM AUTHOR]

The dynamics of a cavity formed in the intrusive mode of coalescence of a freely falling drop flowing smoothly into a liquid have been traced for the first time by the methods of photo and video registration. The cavity begins to form when the bottom part of the drop submerges, when the fluid coalescence line contracts to the center of the flow, and, simultaneously with the annihilation of the drop surface, the surface of the target liquid is restored. In this case, the orientation of ligaments (thin trickles), formed in the vicinity of the contact line changes. At the initial phase, they are directed outward and distribute the transmitted momentum and energy of the drop over the entire surface of the intrusion. Retraction of the coalescence line holds the transmitted energy and momentum of the drop in the contact patch. If the kinetic energy of the falling drop noticeably exceeds the potential surface energy, the cavity begins to form at the initial contact of the fluids and deepens in the course of the entire coalescence process, capturing the drop matter. [ABSTRACT FROM AUTHOR]

A simple laboratory experiment to measure the surface tension of liquids has been proposed in this work, which is well suited for any undergraduate laboratory demonstration. Burette with modified Tate's law has been found to return surface tension values as good as those obtained using Traube's stalagmometer. Experimental data and error analysis show similar result accuracy. Also, a comparative study brings to notice the exactitude of drop weight method over drop number method, both from stalagmometer and burette. The rate of flow of 11-23 drops per minute has been found to be highly suitable for minimization of errors due to evaporation and satellite drop formation. Angular dependence of surface tension has been proposed numerically and validated for the respective case with the angle of 0° to deviate the least from literature value. The results obtained in this study are synchronous with the established theoretical understanding of the concept. [ABSTRACT FROM AUTHOR]

For the first time, photo and video detection is carried out for all groups of small droplets (splashes) emitted when a drop of cm in diameter falls with a velocity of m/s into a pool with water. In the splash-formation mode, groups of droplets are ejected in echelons first from the tops of spikes on the veil around the primary contact area, then, from the spikes on the edges of the split shells of the crown, and, finally, from the teeth of its chevron. The first splashes fly out radially, and the next move inward around the cavity and vertically upward. The splash sizes grow with time from 0.1 to 1.0 mm. Their velocities decrease from 20 to 1 m/s, and the intervals between groups increase from 50 μs to 2.5 ms until the beginning of smoothing of the crown teeth ( ms). The acceleration of the droplets is facilitated by the conversion of the available potential energy when the free surfaces of the merging droplets are annihilated. [ABSTRACT FROM AUTHOR]

Efficient cooling of heat-generating equipment components is a crucial problem for many industrial sectors. This problem is traditionally solved by using liquid sprayers with low cooling efficiency (because of drop recoil). Electric sprayers were proposed for implementation into industry to avoid recoil of fragmented charged drops because of electrical attraction that provided a dense precipitate of drops on a heated conducting surface and further efficient cooling due to liquid evaporation. Fundamental physical laws are used to formulate a mathematical model (in analytical form) and to obtain a practically useful solution to the fragmentation of a test drop by inertial, electric-field, and surface-tension forces. Results of numerical and graphical simulation of this process are given. [ABSTRACT FROM AUTHOR]

Thin liquid or gas films are everywhere in nature, from foams to submillimetric bubbles at a free surface, and their rupture leaves a collection of small drops and bubbles. However, the mechanisms at play responsible for the bursting of these films is still in debate. The present study thus aims at understanding the drainage dynamics of the thin air film squeezed by gravity between a millimetric droplet and a smooth solid or a liquid thin film. Solving coupled lubrication equations and analyzing the dominant terms in the solid- and liquid-film cases, we explain why the drainage is much faster in the liquid-film case, leading often to a shorter coalescence time, as observed in recent experiments. [ABSTRACT FROM AUTHOR]

Combined high-resolution optic and acoustic methods are used for the first time to synchronously detect the fine structure of processes initiated by submersion of a freely falling water drop in a tank with degassed liquid. The emphasis is on analyzing the evolution of the fine structure of flow pattern, the accompanying capillary waves, and the amplitude–frequency characteristics of sound packets. The sequence of acoustic signals includes a shock pulse, which is caused by the initial contact of the drop with the surface of the liquid at rest, and a series of consecutive sound packets. The shock pulse being reliably reproduced in experiments has a complex structure, which includes short segments of high-frequency oscillations and longer segments of low-frequency oscillations. The number of emitted sound packets and their parameters vary in an arbitrary way from one experiment to another while the size of drop and the distance of fall remain invariable. A series of experiments reveals cases of single and secondary packet emission with different spectral compositions of packets, as well as cases of their total absence. Analysis of data is performed with allowance for the effect of the "double layer", which replaces the coalescence surface of liquids and retains the disturbances caused by transformation of available potential surface energy to other forms, such as thermal energy, pressure disturbance, and energy of fine currents actively affecting the gas cavities. [ABSTRACT FROM AUTHOR]

We show that the Euler equations describing the unsteady potential flow of a two-dimensional deep fluid with a free surface in the absence of gravity and surface tension can be integrated exactly under a special choice of boundary conditions at infinity. We assume that the fluid surface at infinity is unperturbed, while the velocity increase is proportional to distance and inversely proportional to time. This means that the fluid is compressed according to a self-similar law. We consider perturbations of a self-similarly compressible fluid and show that their evolution can be accurately described analytically after a conformal map of the fluid surface to the lower half-plane and the introduction of two arbitrary functions analytic in this half-plane. If one of these functions is equal to zero, then the solution can be written explicitly. In the general case, the solution appears to be a rapidly converging series whose terms can be calculated using recurrence relations. [ABSTRACT FROM AUTHOR]

The patterns of mass transfer of aqueous-ink-solution drops of 0.2 and 0.5 cm in diameter which fall freely into vegetable oil are investigated by means of macrophoto and high-speed video techniques over the range of the height of fall from 25 to 65 cm. The double layer formed by the contacting surfaces affects the flow pattern in the drop submerging phase. In this layer a part of the available potential surface energy of fluids is converted into other forms. The geometries of the chevron consisting of oil and the drop mass distribution pattern over the inner crown surface turn out to be similar in the initial flow phase. With time, the cavity and splash shapes and the drop mass distribution patterns that depend on time and the distance of drop fall (drop contact velocity) differ significantly. With the beginning of collapse, the ink-free regions (so-called voids) and outlined by thin filaments of drop matter are formed on the inner crown surface. Then, the filaments disintegrate into fine droplets. The geometry of splashes including those reaching the maximum height over the parameter range considered is traced. [ABSTRACT FROM AUTHOR]

We employ three-dimensional numerical simulations to explore the impact dynamics of non-spherical drops in a deep liquid pool by varying the aspect ratios (A r) and Weber numbers (We). We observe that when a non-spherical drop is gently placed on a liquid pool, it exhibits a partial coalescence phenomenon and the emergence of a daughter droplet for A r > 0. 67. In contrast to the prolate (A r < 1) and spherical drops (A r = 1) , an oblate (A r > 1) drop with a high aspect ratio encapsulates air in a ring-like bubble within the pool and emerges a liquid column that undergoes Rayleigh–Plateau capillary instability, leading to the formation of two daughter droplets with complex shapes. When the parent drop is impacted with finite velocity, our observations indicate that increasing the Weber number leads to elevated crater heights on the free surface for all aspect ratios. A prolate drop produces a less pronounced wave swell and exhibits a prolonged impact duration owing to its negligible impact area. Conversely, an oblate drop generates a much wider wave swell than spherical and prolate drops. We analyze the relationship between rim formation dynamics and the kinetic and surface energies of the system. Finally, we establish an analogy by comparing the dynamics of a freely falling non-spherical drop, undergoing topological oscillations during its descent from a height, with the impact dynamics of parent drops of various shapes striking the liquid surface with an equivalent velocity. Our investigation involving non-spherical drops contrasts the extensive studies conducted by various researchers on the impact of a parent spherical drop just above the free surface of a liquid pool. [Display omitted] • We investigate the coalescence dynamics of non-spherical drops. • Beyond a critical aspect ratio, the drop undergoes partial coalescence. • Oblate drops encapsulate ring-like air bubbles and form two daughter droplets. • Oblate drops produce a broader wave swell than spherical and prolate drops. • The interplay of the kinetic and surface energies of the system is analysed. [ABSTRACT FROM AUTHOR]

For the first time, the evolution of the spreading pattern of a fallen water drop over the surface of a cavity and a crown in a deep layer of oil has been traced by high-resolution video and photography. At the stage of active drop submergence, the double layer formed by the contacting surfaces of immiscible fluids is the most rapid component of the flow. Droplets containing both fluids fly out from the tops of the spikes on the edge of the crown. The water covering the inner surface of the cavity and the crown flows unevenly downwards after submergence of the drop. Isolated anhydrous areas, voids, are formed on the surface of the crown and are separated by narrow bands of water, which eventually break up into separate drops. The bulk of the water unevenly submerges to the bottom of the cavity and, at its collapses, remains in the bulk of the liquid in the form of individual fragments, gradually tightening into smooth droplets. The regularities of the temporal changes in the splash height and in the shape of the cavity section are revealed. [ABSTRACT FROM AUTHOR]

Atypical central neurocytoma with extracranial metastases is a rare variant of benign central neurocytoma (CN). No definitive course of treatment exists for atypical CN. We report a unique case of atypical CN with concomitant pituitary macroadenoma and subsequent metastases to the spine. The patient received craniospinal radiation therapy. Close-follow up post tumor-resection may be advised to monitor for drop metastases. To the best of our knowledge, this is the only case reported of atypical CN with drop metastases to the spine concomitant with pathological-proven pituitary macroadenoma. [ABSTRACT FROM AUTHOR]

With a purpose for textile material coating applications, a process of spraying the polymer flow is considered. The equipment for determining the polymer drop size is designed. The formulas for estimating the size of polymer droplets are validated. For controlling and measuring the polymer drop size in real time, the multi-frequency phase method is suggested to be used. Classification is needed to find a category, within which the measurement will be done. Photos of various particles are obtained while experiments of spraying polymers are conducted. The sizes of those particles are determined. It is ascertained with the laser measurement and the corresponding software that when polymer drops get onto a textile material, they cool rapidly. The quality of the material is maintained. For properly spraying the polymer, the pressure of 6 MPa and the nozzle diameter of 2 mm are sufficient. The structure of the textile material along with the coating is maintained best with these parameters. [ABSTRACT FROM AUTHOR]

• Spreading dynamics of a sessile viscoelastic drop on a horizontal surface is studied. • Simplified Phan–Thien–Tanner model represents the rheology of the viscoelastic drop. • Theoretical results are validated with our experimental results. • Elastic nature of the viscoelastic fluids reduces the spreading rate of the drop. We study the spreading dynamics of a sessile viscoelastic drop on a horizontal surface, where a simplified Phan–Thien–Tanner (sPTT) model is considered to represent the rheology of viscoelastic drop. We have adopted a macroscopic approach to obtain the temporal evolution of the spreading drop, while to establish the efficacy of the theoretical model, we have validated the results obtained from the mathematical formulation with the experimental results for both the Newtonian (Si-oil) and viscoelastic (PDMS and aqueous solution of CMC and glycerin) drops. Following the framework of Seaver–Berg approximation, the spherical shape of the drop is assumed as a cylindrical disk here. We observe from this study that an increment in the elasticity of the fluid enhances the velocity gradient and increases the viscous dissipation in the drop volume, leading to a reduction in the spreading rate. [ABSTRACT FROM AUTHOR]

The phenomenon of drop formation at a single plain hole and a single nozzle hole in a plate submerged in a quiescent continuous phase is studied by carrying out numerical simulations. Phase-field method has been used for tracking the evolution of the interface between the drop phase and the continuous phase. The computational approach used in the numerical simulations is validated using the data reported in literature. The validated computational approach is then used for parametric analysis to understand the effects of various independent variables on the phenomenon of drop formation. For identical conditions, the drops formed at a nozzle hole are found to be smaller than the drops formed at a plain hole. The drop detachment time is more for a plain hole than for a nozzle hole. The drop detachment height is, however, more for a nozzle hole than for a plain hole. Correlations to estimate drop diameter for both types of holes are presented. [ABSTRACT FROM AUTHOR]

Direct Numerical Simulations have been performed to study the droplet spreading behaviour on a spherical surface. A coupled immersed boundary and volume of fluid method is used to represent the gas-liquid-solid interactions. The contact area of the droplet on the surface is recorded in order to fit the initial spreading with a power-law representation, using the contact-angle and interface curvature as fitting parameters. Small viscous droplets are used to reduce interfacial oscillations as well as low drop velocities to reduce impact forces. A decrease of spreading area with increasing curvature is observed. Moreover, the model shows good agreement compared to equilibrium states. A strong contact-angle dependence is found for the pre-factor of the power law, which is expected, and a linear decrease was found in the exponent for increasing curvature of the surface. Unlabelled Image • The spreading dynamics change with increasing surface curvature. • Two spreading regimes become apparent at increased curvatures and make the fitting of the power law impossible. • Due to the reduced spreading area for increased curvatures, droplet oscillations are more pronounced. • Less viscous spreading occurs at higher surface curvatures. [ABSTRACT FROM AUTHOR]

The simultaneous uptake of residential photovoltaic (PV) systems and electric vehicles (EVs) can lead to contrasting voltage problems (i.e. voltage rise and drop) in low‐voltage (LV) networks throughout the day. While solutions that directly manage these technologies can be effective in mitigating their impacts, they affect or require interactions with customers. A more practical alternative for distribution network operators (DNOs) is, therefore, to manage voltages using only network assets. For this purpose, two advanced methods to control on‐load tap changer fitted transformers, owned and operated by DNOs, are proposed: a rule‐based control method that only requires monitoring from remote points and a three‐phase optimal power flow‐based control method that requires full observability and adopts a simple – yet effective – forecasting to cater for future uncertainties. The performance of the proposed methods is thoroughly assessed within a stochastic approach on a real UK LV network considering realistic 1 min resolution demand, PV, and EV profiles. Results show that both methods are effective in managing contrasting voltage problems caused by both PV systems and EVs. While the optimisation method leads to the lowest number of tap changes, the rule‐based method, given its limited observability requirement, could be considered a practical interim solution. [ABSTRACT FROM AUTHOR]