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Water drops falling on a deep pool can either coalesce to form a vortex ring or splash, depending on the impact conditions. The transition between coalescence and splashing proceeds via a number of intermediate steps, such as thick and thin jet formation and gas-bubble entrapment. We perform simulations to determine the conditions under which bubble entrapment and jet formation occur. A regime map is established for Weber numbers ranging from 50 to 300 and Froude numbers from 25 to 600. Vortex ring formation is seen for all of the regimes; it is greater for the coalescence regime and less in the case of the thin jet regime.

AbstractObjectiveTo assess efficacy and safety of laughter exercise in patients with symptomatic dry eye disease.DesignNon-inferiority randomised controlled trial.SettingRecruitment was from clinics and community and the trial took place at Zhongshan Ophthalmic Center, Sun Yat-sen University, the largest ophthalmic centre in China, between 18 June 2020 to 8 January 2021.ParticipantsPeople with symptomatic dry eye disease aged 18-45 years with ocular surface disease index scores ranging from 18 to 80 and tear film break-up time of eight seconds or less.InterventionsParticipants were randomised 1:1 to receive laughter exercise or artificial tears (0.1% sodium hyaluronic acid eyedrop, control group) four times daily for eight weeks. The laughter exercise group viewed an instructional video and participants were requested to vocalise the phrases “Hee hee hee, hah hah hah, cheese cheese cheese, cheek cheek cheek, hah hah hah hah hah hah” 30 times per five minute session. Investigators assessing study outcomes were masked to group assignment but participants were unmasked for practical reasons.Main outcome measuresThe primary outcome was the mean change in the ocular surface disease index (0-100, higher scores indicating worse ocular surface discomfort) from baseline to eight weeks in the per protocol population. The non-inferiority margin was 6 points of this index score. Main secondary outcomes included the proportion of patients with a decrease from baseline in ocular surface disease index score of at least 10 points and changes in dry eye disease signs, for example, non-invasive tear break up time at eight weeks.Results299 participants (mean age 28.9 years; 74% female) were randomly assigned to receive laughter exercise (n=149) or 0.1% sodium hyaluronic acid (n=150). 283 (95%) completed the trial. The mean change in ocular surface disease index score at eight weeks was −10.5 points (95% confidence interval (CI) −13.1 to −7.82) in the laughter exercise group and −8.83 (−11.7 to −6.02) in the control group. The upper boundary of the CI for difference in change between groups was lower than the non-inferiority margin (mean difference −1.45 points (95% CI −5.08 to 2.19); P=0.43), supporting non-inferiority. Among secondary outcomes, the laughter exercise was better in improving non-invasive tear break up time (mean difference 2.30 seconds (95% CI 1.30 to 3.30), P<0.001); other secondary outcomes showed no significant difference. No adverse events were noted in either study group.ConclusionsThe laughter exercise was non-inferior to 0.1% sodium hyaluronic acid in relieving subjective symptoms in patients with dry eye disease with limited corneal staining over eight weeks intervention.Trial registrationClinicalTrials.gov NCT04421300.

Dry eye disease (DED) is the most common ocular surface disease, characterized by insufficient production and/or instability of the tear film. Tear substitutes are usually the first line of treatment for patients with DED. Despite the large variety of tear substitutes available on the market, few studies have been performed to compare their performance. There is a need to better understand the specific mechanical and pharmacological roles of each ingredient composing the different formulations. In this review, we describe the main categories of ingredients composing tear substitutes (e.g., viscosity-enhancing agents, electrolytes, osmo-protectants, antioxidants, lipids, surfactants and preservatives) as well as their effects on the ocular surface, and we provide insight into how certain components of tear substitutes may promote corneal wound healing, and/or counteract inflammation. Based on these considerations, we propose an approach to select the most appropriate tear substitute formulations according to the predominant etiological causes of DED.

Effects of eccentricity and horizontal electric field (EH) on the binary‐collision outcomes of water drops are examined using numerically calculated collision characteristics from previous studies and results of simulation experiment conducted by the authors. For a fixed collision kinetic energy (CKE), filament breakups can occur at all values of eccentricity but events of coalescence decrease, and that of sheet breakup increase with increasing eccentricity in absence of EH. However, as EH increases to ∼300 kVm−1 it opposes the variability of the coalescence and sheet breakup events with eccentricity. When EH exceeds ∼300 kVm−1 the collision outcomes might be determined only by the CKE and EH. The calculated value of coalescence efficiency and total number of fragments after a binary collision decreases with an increase in EH. It is argued that an electric field can significantly modify drop size distribution in thunderclouds and needs to be considered for development of precipitation. Plain Language Summary Growth of water drops in clouds is mostly governed by the drop size distribution in them. When two drops collide with each other, they can either coalesce to form a single larger drop, or disintegrate into many smaller drops, or bounce back. These different outcomes after their collisions are mostly determined by whether the collisions are centric where the eccentricity of the collision is zero or grazing where the eccentricity is one or somewhere in between the two extremes. The present study shows that if the collisions occur in presence of a horizontal electric field, it opposes the effect of eccentricity on the outcomes of the collisions. In this study, simultaneous effects of eccentricity and horizontal electric field are examined from numerically calculated collision characteristics from previous studies and utilizing the results of a simulation experiment recently conducted by the authors. Simultaneous effects of eccentricity and electric field on coalescence efficiency and total and spectral size distribution of fragments generated after the collision have also been evaluated. The results suggest that the electric field can significantly modify drop size distribution in thunderclouds and need to be considered for the development of precipitation. Key Points Horizontal electric field opposes the variability of coalescence/sheet breakup of water drops with eccentricity in binary collisions Number of fragments close to small (large) parent drop size decreases (increases) after collisions in the higher horizontal electric field Binary collisions in horizontal electric fields can substantially modify drop size distribution in thunderclouds

We investigate the global variation of earthquake stress drops using spectra of about 2000 events of mb ≥ 5.5 between 1990 and 2007. We use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions, based on a convolutional model. The observed P wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near‐source attenuation. Assuming a Brune‐type source model, we estimate corner frequencies and compute stress drops. Stress drop estimates for individual earthquakes range from about 0.3 to 50 MPa, but the median stress drop of about 4 MPa does not vary with moment, implying earthquake self‐similarity over the Mw = 5.2 to 8.3 range of our data. A comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range. While the absolute values of our estimated stress drops depend upon the assumed source model, we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions, which includes an inherent assumption of constant rupture velocity. We find a dependence of median stress drop on focal mechanism, with a factor of 3–5 times higher stress drops for strike‐slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes.

The purpose of this study was to determine the reliability and validity of a portable force plate when analyzing jumping and landing tasks. Subjects performed 3 drop vertical jumps and 3 drop landings on both a standard strain gauge laboratory force plate and a portable force plate. In contrast to typical laboratory installed force plates, the portable 6-component force plate can be easily transported and used onsite at various training or data collection sites and incorporates Hall effect technology. The measured parameters included maximum force and time to maximum force for initial stance of the both tests, maximum takeoff force, and time to maximum takeoff force for the drop vertical jump. The Pearson correlation coefficients for the drop landing and the drop vertical jump for maximum force (r = 0.942, r = 0.940), time to maximum force (r = 0.891, r = 0.920) and for drop jump maximum jumping force (r = 0.971), and time to maximum takeoff force (r = 0.917) were all high and indicate that the force data collected by a resistor-type portable force plate provide similar measures to a standard strain-gauge laboratory force plate. Additionally, the within session reliability of the drop landing and the drop vertical jump measured by the portable force plate showed high interclass correlation coefficients for examined variables of 0.979 and 9.67 for maximum landing force and 0.917 and 0.920 for time to maximum landing force, respectively. The interclass correlation coefficients for the maximum takeoff force and time to maximum takeoff force during the drop vertical jump were 0.991 and 0.86. The results indicate the force and timing measurements from the portable force plate were both valid and reliable. Use of the portable force plate may facilitate methods of force measurement that can be applied out into the field and therefore a valuable tool for on site landing and jump force measurements in a variety of settings for large numbers of subjects.The purpose of this study was to determine the reliability and validity of a portable force plate when analyzing jumping and landing tasks. Subjects performed 3 drop vertical jumps and 3 drop landings on both a standard strain gauge laboratory force plate and a portable force plate. In contrast to typical laboratory installed force plates, the portable 6-component force plate can be easily transported and used onsite at various training or data collection sites and incorporates Hall effect technology. The measured parameters included maximum force and time to maximum force for initial stance of the both tests, maximum takeoff force, and time to maximum takeoff force for the drop vertical jump. The Pearson correlation coefficients for the drop landing and the drop vertical jump for maximum force (r = 0.942, r = 0.940), time to maximum force (r = 0.891, r = 0.920) and for drop jump maximum jumping force (r = 0.971), and time to maximum takeoff force (r = 0.917) were all high and indicate that the force data collected by a resistor-type portable force plate provide similar measures to a standard strain-gauge laboratory force plate. Additionally, the within session reliability of the drop landing and the drop vertical jump measured by the portable force plate showed high interclass correlation coefficients for examined variables of 0.979 and 9.67 for maximum landing force and 0.917 and 0.920 for time to maximum landing force, respectively. The interclass correlation coefficients for the maximum takeoff force and time to maximum takeoff force during the drop vertical jump were 0.991 and 0.86. The results indicate the force and timing measurements from the portable force plate were both valid and reliable. Use of the portable force plate may facilitate methods of force measurement that can be applied out into the field and therefore a valuable tool for on site landing and jump force measurements in a variety of settings for large numbers of subjects.

BackgroundDry eye disease (DED) affects more than 14% of the elderly population causing decrease of quality of life, high costs and vision impairment. Current treatments for DED aim at lubricating and controlling inflammation of the ocular surface. Development of novel therapies targeting different pathogenic mechanisms is sought-after. The aim of this study is to evaluate safety and efficacy of recombinant human nerve growth factor (rhNGF) eye drops in patients with DED.MethodsForty consecutive patients with moderate to severe DED were included in a phase IIa, prospective, open label, multiple-dose, clinical trial to receive rhNGF eye drops at 20 µg/mL (Group 1: G1) or at 4 µg/mL (Group 2: G2) concentrations, two times a day in both eyes for 28 days (NCT02101281). The primary outcomes measures were treatment-emerged adverse events (AE), Symptoms Assessment in Dry Eye (SANDE) scale, ocular surface staining and Schirmer test.ResultsOf 40 included patients, 39 completed the trial. Both tested rhNGF eye drop concentrations were safe and well tolerated. Twenty-nine patients experienced at least one AE (14 in G1 and 15 in G2), of which 11 had at least 1 related AE (8 in G1 and 3 in G2). Both frequency and severity of DED symptoms and ocular surface damage showed significant improvement in both groups, while tear function improved only in G1.ConclusionsThe data of this study indicate that rhNGF eye drops in both doses is safe and effective in improving symptoms and signs of DED. Randomised clinical trials are ongoing to confirm the therapeutic benefit of rhNGF in DED.Trial registration number NCT02101281.

Understanding drop size distribution (DSD) variability has important implications for remote sensing and numerical modeling applications. Twelve disdrometer datasets across three latitude bands are analyzed in this study, spanning a broad range of precipitation regimes: light rain, orographic, deep convective, organized midlatitude, and tropical oceanic. Principal component analysis (PCA) is used to reveal comprehensive modes of global DSD spatial and temporal variability. Although the locations contain different distributions of individual DSD parameters, all locations are found to have the same modes of variability. Based on PCA, six groups of points with unique DSD characteristics emerge. The physical processes that underpin these groups are revealed through supporting radar observations. Group 1 (group 2) is characterized by high (low) liquid water content (LWC), broad (narrow) distribution widths, and large (small) median drop diameters D 0 . Radar analysis identifies group 1 (group 2) as convective (stratiform) rainfall. Group 3 is characterized by weak, shallow radar echoes and large concentrations of small drops, indicative of warm rain showers. Group 4 identifies heavy stratiform precipitation. The low latitudes exhibit distinct bimodal distributions of the normalized intercept parameter N w , LWC, and D 0 and are found to have a clustering of points (group 5) with high rain rates, large N w , and moderate D 0 , a signature of robust warm rain processes. A distinct group associated with ice-based convection (group 6) emerges in the midlatitudes. Although all locations exhibit the same covariance of parameters associated with these groups, it is likely that the physical processes responsible for shaping the DSDs vary as a function of location.

Asymmetrical faults in the grid can lead to voltage drops at the grid-connected points, and in serious cases, there is also a risk of cutting the machine. The traditional voltage support strategy is easily affected by the output of the units and cannot support the voltage flexibly. To address the above problems, an optimized strategy for boosting voltage performance is proposed under asymmetrical faults in the power grid. Firstly, the voltage support principle under asymmetrical fault is analyzed, and the voltage support equation is derived. Then, based on the above equations, an optimal voltage support strategy under asymmetrical faults is proposed by taking the operation requirements of grid-connected standard voltage as the objective and considering the peak current and active power fluctuation amplitude as the constraints. Finally, the effectiveness and flexibility of the above strategy are validated by simulation.

Corneal abrasion is a frequent complication in critically ill, intubated patients, potentially leading to visual impairment. This study compares the efficacy of three ocular care methods in preventing corneal abrasion among this vulnerable population. We conducted a randomized controlled trial involving 156 intubated adult patients admitted to the ICU. Participants were randomly allocated to one of three intervention groups (n = 52 per group): (1) polyethylene cover only, (2) polyethylene cover with artificial tear drops, and (3) polyethylene cover with Lubratex eye ointment. One eye per patient was randomly assigned as the control, receiving standard ICU eye care. Daily assessments over five days included a standardized dryness and corneal abrasion checklist, graded strip evaluation of eye dryness, and documentation of corneal abrasion incidence. Data were analyzed using descriptive and inferential statistics (SPSS-18). The incidence of corneal abrasion was significantly lower in the group receiving polyethylene cover with Lubratex eye ointment (4%) compared to the polyethylene cover with artificial tears group (36%, p < 0.001) and the polyethylene cover only group (60%, p < 0.001). The combined application of a polyethylene cover with Lubratex eye ointment effectively prevents corneal abrasion in intubated ICU patients. This method demonstrates superior efficacy compared to polyethylene covers used alone or with artificial tears. We recommend its implementation as standard practice for corneal abrasion prophylaxis in this high-risk population. Trial Registration . This study is registered with the Iranian Registry of Clinical Trials (IRCT201506294736N8) and can be accessed at www.IRCT.ir .