Bat selfies: photographic surveys of flying bats.

The recent pandemic and other environmental concerns have resulted in restrictions on research and surveys involving capture and handling bats. While acoustic surveys have been widely used as an alternative survey method, in this study, we show how photographic surveys can offer an important contribution to study and survey bats. We outline approaches, using high speed flash and automated trip beams to obtain photos of flying bats of sufficient quality for reliable identification of species. We show, through a series of examples of setups and photographs, that photography is effective for surveying bats at a variety of sites, where bats roost, drink, and forage. We note, however, that photographic surveys cannot replace capture in all situations. In addition, although photographing bats is less invasive than capturing them, it can involve disturbance, so we stress the importance of minimizing the impact of such operations on bats. Supplementary Information: The online version contains supplementary material available at 10.1007/s42991-022-00233-7.

Analysis of red blood cells' dynamic status in a simulated blood circulation system using an ultrahigh-speed simultaneous framing optical electronic camera.

Alterations in the morphologic and mechanical properties of red blood cells (RBCs) are considered direct indicators of blood quality. Current measures of characterizing these properties in vivo are limited by the complicated hemodynamic environment. To better evaluate the quality of fresh and stored blood, a new research platform was constructed to evaluate the hemodynamic characteristics of RBCs. The research platform consists mostly of a microfluidic chip, microscope, and ultrahigh-speed simultaneous framing optical electronic camera (USFOEC). The microfluidic chip was designed to simplify the complicated hemodynamic environment. The RBCs were diluted in erythrocyte preservative fluid and infused into the microfluidic channels. After approximately 600× magnification of using the microscope and camera, the RBCs' dynamic images were captured by the USFOEC. Eight sequential and blur-free images were simultaneously captured by the USFOEC system. Results showed that RBC deformation changed with flow velocity and stored RBCs were less sensitive to deformation (Kfresh < Kstored ). The frozen-stored RBCs were better able to sustain hydrodynamic stress (DI49day = 0.128 vs. DIfrozen = 0.118) than cold-stored RBCs but more sensitive to variations in flow speed (K49day = 1626.2 vs. Kfrozen = 1318.2). Results showed that the stored RBCs had worse deformability than fresh RBCs, but frozen-stored RBCs may incur less damage during storage than those stored at merely cold temperatures. This USFOEC imaging system can serve as a platform for direct observation of cell morphological and mechanical properties in a medium similar to a physiologic environment. © 2016 International Society for Advancement of Cytometry.

Dynamic fracture of inorganic glasses by hard spherical and conical projectiles.

In this article, high-speed photographic investigations of the dynamic crack initiation and propagation in several inorganic glasses by the impact of small spherical and conical projectiles are described. These were carried out at speeds of up to approximately 2×10(6) frames s(-1). The glasses were fused silica, 'Pyrex' (a borosilicate glass), soda lime and B(2)O(3). The projectiles were 0.8-2 mm diameter spheres of steel, glass, sapphire and tungsten carbide, and their velocities were up to 340 m s(-1). In fused silica and Pyrex, spherical projectiles' impact produced Hertzian cone cracks travelling at terminal crack velocities, whereas in soda-lime glass fast splinter cracks were generated. No crack bifurcation was observed, which has been explained by the nature of the stress intensity factor of the particle-impact-generated cracks, which leads to a stable crack growth. Crack bifurcation was, however, observed in thermally tempered glass; this bifurcation has been explained by the tensile residual stress and the associated unstable crack growth. A new explanation has been proposed for the decrease of the included angle of the Hertzian cone cracks with increasing impact velocity. B(2)O(3) glass showed dynamic compaction and plasticity owing to impact with steel spheres. Other observations, such as total contact time, crack lengths and response to oblique impacts, have also been explained.

Continuous motion of particles attached to cavitation bubbles.

Microbubble-mediated therapeutic gene or drug delivery is a promising strategy for various cardiovascular diseases (CVDs), but the efficiency and precision need to be improved. Here, we propose a cavitation bubble-driven drug delivery strategy that can be applied to CVDs. A bubble-pulse-driving theory was proposed, and the formula of time-averaged thrust driven by bubble pulses was derived. The continuous motion of particles propelled by cavitation bubbles in the ultrasonic field is investigated experimentally by high-speed photography. The cavitation bubbles grow and collapse continuously, and generate periodic pulse thrust to drive the particles to move in the liquid. Particles attached to bubbles will move in various ways, such as ejection, collision, translation, rotation, attitude variation, and circular motion. The cavity attached to the particle is a relatively large cavitation bubble, which does not collapse to the particle surface, but to the axis of the bubble perpendicular to the particle surface. The cavitation bubble expands spherically and collapses asymmetrically, which makes the push on the particle generated by the bubble expansion greater than the pull on the particle generated by the bubble collapse. The time-averaged force of the cavitation bubble during its growth and collapse is the cavitation-bubble-driven force that propels the particle. Both the cavitation-bubble-driven force and the primary Bjerknes force act in the same position on the particle surface, but in different directions. In addition to the above two forces, particles are also affected by the mass force acting on the center of mass and the motion resistance acting on the surface, so the complex motion of particles can be explained.

Theoretical and Experimental Studies of the Shock-Compressed Gas Parameters in the Welding Gap.

This work is devoted to the study of the processes that take place in the welding gap during explosive welding (EW). In the welding gap, when plates collide, a shock-compressed gas (SCG) region is formed, which moves at supersonic speed and has a high temperature that can affect the quality of the weld joint. Therefore, this work focuses on a detailed study of the parameters of the SCG. A complex method of determining the SCG parameters included: determination of the detonation velocity using electrical contact probes, ceramic probes, and an oscilloscope; calculation of the SCG parameters; high-speed photography of the SCG region; measurement of the SCG temperature using optical pyrometry. As a result, it was found that the head front of the SCG region moved ahead of the collision point at a velocity of 3000 ± 100 m/s, while the collision point moved with a velocity of 2500 m/s. The calculation of the SCG temperature showed that the gas was heated up to 2832 K by the shock compression, while the measured temperature was in the range of 4100-4400 K. This is presumably due to the fact that small metal particles that broke off from the welded surfaces transferred their heat to the SCG region. Thus, the results of this study can be used to optimize the EW parameters and improve the weld joint quality.

Investigation of factors enhancing droplets spreading on leaves with burrs.

Introduction: Spread effect is one of the aspects on deposition quality evaluation of pesticide droplets. It could be affected by many factors such as the microstructure of the target plant leaf surface, physical features of the droplets, and the concentration of spray additives. Methods: In this study, using a high-speed photography system, 2.3% glyphosate ammonium salt solution with different concentration of the additive was applied to investigate the impact process of single droplet deposition on the plant leaf surface with burrs. Effect of droplet sizes and velocities on spreading area and dynamic deposition procedure was analyzed using image processing programs. Results: The diffusion factor in the process of droplet spreading was changed over time. The occurrence of bubbles in the droplets was observed in the results. With the bubble generation, the droplet diameter expands and a better diffusion effect is obtained. As a result, better spreading effect was obtained as the droplet diameter was expanded with the generation of bubbles. The significant effects of each physical property of droplets on droplet spreading and the interaction effects between the influencing factors were analyzed. A significant correlation was found between additive concentration, droplet impact velocity, droplet diameters and droplet spreading area. All interactions of concentration:velocity, concentration:diameter, velocity:diameter, and concentration:velocity:diameter had a significant effect on the spreading area of droplets. The study of the factors influencing the process of pesticide droplet impact on the leaf surface contributes to the efficient use of pesticides. Thus, the consumption of pesticides and the resulting impact on the environment can be reduced.

Investigation on the cavitation bubble collapse and the movement characteristics near spherical particles based on Weiss theorem.

In this paper, the cavitation bubble dynamics near two spherical particles of the same size are investigated theoretically and experimentally. According to the Weiss theorem, the flow characteristics and the Kelvin impulse are obtained and supported by the sufficient experimental data. In terms of the initial bubble position, the bubble size and the distance between the two particles, the collapse morphology and the movement characteristics of the bubble are revealed in detail. The main findings include: (1) Based on a large number of experimental results, it is found that the Kelvin impulse theoretical model established in this paper can effectively predict the movement characteristics of the cavitation bubble near two particles of the same size. (2) When the initial bubble position is gradually away from the particles along the horizontal symmetry axis near two particles of the same size, the movement distance of the bubble centroid in the first period increases first and then decreases. (3) When the initial position of the bubble centroid is at the asymmetric position near the two particles, the movement direction of the bubble centroid is biased towards the particle closer to the bubble, but not towards the center of this particle.

Measurement of morphological changes of pear leaves in airflow based on high-speed photography.

The morphological changes of leaves under the airflow have a significant effect on the deposition of pesticide droplets on the leaves, but the wind-induced vibration of the leaves is complicated to measure. In this study, an aerodynamic test of the pear leaf was conducted in the wind tunnel, and binocular high-speed photography was used to record the deformation and vibration of the leaves under various airflow velocities. Experiments showed that air velocity (v) had a significant effect on the morphological response of the leaf. As v increased, the leaf was in three states, including static deformation, low-frequency vibration, and reconfiguration of airfoil steady state. The mutation from one state to another occurred at the critical velocity of vcr1 and vcr2 . By tracking the leaf marker point, various morphological parameters were calculated, including the bending angle of the petiole, the wind deflection angle, and the twist angle of leaves under different air velocities. When vcr1 ≤v ≤vcr2 , the parameters changed periodically. When v< vcr1 , the petiole and the leaf bent statically, and the bending angle of the petiole and the wind deflection angle of the leaf gradually increased. When v >vcr2 , the morphology of the leaf and the petiole was stable. Besides, this study tracked and measured the wind deflection area of leaf, which was consistent with the theoretical calculation results. The measurement of the leaf morphological parameters can reflect the morphological changes of leaves under airflow, thus providing a basis for the decision-making of air-assisted spray airflow.

Theoretical investigation and experimental support for the cavitation bubble dynamics near a spherical particle based on Weiss theorem and Kelvin impulse.

In the present paper, the laser-induced cavitation bubble dynamics near a fixed spherical particle is comprehensively investigated based on the Weiss theorem, the Kelvin impulse theory and the high-speed photography experiment. Firstly, the applicability range of the theoretical model in the time and the space is statistically obtained based on sufficient experimental results. Then, the in-depth theoretical analysis is carried out in terms of the liquid flow field and the bubble Kelvin impulse with the corresponding experimental results as the reasonable support. In addition, the theoretical prediction model of the bubble movement is established and experimentally fitted from the analytic expression of the Kelvin impulse. Through our research, it is found that: (1) the applicability range of the Kelvin impulse theory for the bubble near the spherical particle is approximately the dimensionless distance between the bubble and particle (γ) greater than 0.50. (2) The effect of the particle on the liquid velocity between the bubble and the particle is mainly manifested in the form of the image bubble, which always causes the liquid velocity in this region to be significantly lower than other surrounding regions. (3) The average movement velocity of the bubble centroid can be reasonably predicted by establishing a directly proportional function between the Kelvin impulse and the velocity with the relationship constant (α) equal to 3.57×10-6 ± 1.63×10-7 kg.

Experimental investigation of dynamic mechanical characteristics of inhomogeneous composite coal-sandstone combination for coalbed methane development.

In deep resource exploitation, the coal seam and the strata are jointly loaded, forming a systematic combined structure that can have a significant effect on coalbed methane (CBM) development. Therefore, to understand the deformation and damage characteristics due to blasting load of the complex and real ground conditions, the 50 mm split Hopkinson pressure bar (SHPB) was used to study the dynamic performance and energy changes of coal-sandstone combination and sandstone-coal combination as inhomogeneous materials. In addition, high-speed photographic equipment was employed to determine the damage failure mechanisms. The results showed that the dynamic compressive strength and failure strains of two combinations showed polynomial relationships with increasing strain rates. The strain rate effects and likenesses of the two combinations' energy and energy rates were substantial. Furthermore, for the coal-sandstone combination, the initial damage fractures occurred at the end face near the bar, and at the interface for the sandstone-coal combination. Eventually, the improved constitutive model based on the ZWT was significantly consistent with the two combinations. The related theory can perform an effective and practical role in the mining of coal rocks under complex ground conditions for CBM development.

Circular motion of submillimeter-sized acoustic bubbles attached to a boundary by high-speed image analysis.

The circular motion of submillimeter-sized bubbles attached to a boundary in an 18.5 kHz ultrasonic field are investigated experimentally by high-speed photography and image analysis. It is found that the vibration of gas bubbles with diameters of 0.2-0.4 mm is between spherical radial vibration and regular surface fluctuation. Different from the circular motion of suspended bubbles in water, the circular motion of gas bubbles attached to a boundary presents some new characteristics. These bubbles attached to a boundary (wandering bubbles) will rotate around a fixed bubble array (holding bubbles). Both the wondering bubbles and holding bubbles are "degas" bubbles. The primary Bjerknes force acting on wandering bubbles in the acoustic wave field and the secondary Bjerknes force between the wandering bubbles and the holding bubbles strongly affects the circular motion. The circling and residence behavior of gas bubbles is described and analyzed in detail, which is helpful to understand and improve industrial applications such as ultrasonic cleaning, sonochemical treatment, aeration and cavitation reduction.

Mechanism and dynamics of hydrodynamic-acoustic cavitation (HAC).

Bubble clusters in hydrodynamic cavitation, acoustic cavitation and hydrodynamic-acoustic cavitation (HAC) are investigated via high-speed photography. By introducing a cavitation state variable, a method for cavitation characterization is proposed. The periodic characteristics and intensity distributions of hydrodynamic cavitation, acoustic cavitation and HAC are quantitatively analyzed using this method. It is found that the range of HAC is evidently widened and the strength of HAC is significantly enhanced compared with hydrodynamic cavitation or acoustic cavitation. Furthermore, we developed a preliminary physical model describing the dynamics of a cavitation bubble in HAC and proposed a mechanism to explain the enhancement of the intensity in HAC.

High-speed photographic observation of the sonication of a rabbit carotid artery filled with microbubbles by 20-kHz low frequency ultrasound.

The aim of this study is to assess the physical damage of cavitation effects induced by low frequency ultrasound and microbubbles (MBs) to an in vitro vessel. A rabbit carotid artery filled with SonoVue MBs and methylene blue was irradiated with 20-kHz ultrasound, and the results were recorded by high-speed photography at 3000 frames per second. The carotid artery filled with MBs experienced a slight tremor during ultrasonication. Six intermittent blue flow events occurred in two places on the artery wall during the 5-s process. The duration of each leakage event was 90-360ms with an average of 200ms. Hematoxylin-eosin (H-E) staining demonstrated the separation of the carotid artery elastic membrane, local blood vessel wall defects and hole formation, and the surface of the ruptured area was rough and irregular. Another carotid artery was filled with a 0.9% NaCl solution and methylene blue as a control and irradiated with 20-kHz ultrasound. No blue liquid flow was seen, and no holes in the vessel were observed. H-E staining revealed intact vascular endothelial cells and smooth muscles with no vascular wall defects. Low-frequency ultrasound combined with MBs can cause a vessel to rupture and holes to form in a short time. High-speed photography is useful for observing transient changes caused by the effects of ultrasound cavitation on an in vitro vessel.

Using Small-scale Blast Tests and Numerical Modelling to Trace the Origin of Fines Generated in Blasting.

Waste fines from rock breakage often negatively influence economics and environment. The Austrian Science Fund (FWF) sponsors a project to investigate the cause of the fines by studying blast fragmentation throughout small-scale blast tests and numerical simulations. The tests include blast-loading confined granite and mortar cylinders by detonating cord with 6, 12, and 20 g/m of PETN. The blast-driven dynamic cracking at the end face of the cylinder opposite to the initiation point is filmed with a high-speed camera. The filming is followed up by an analysis of surface and internal crack systems and sieving of the blasted cylinders to quantify the amount of fine material created. The numerical simulations cover the blast fragmentation of a mortar cylinder. These simulations use Finite and Discrete Element Methods (FEM, DEM) with explicit time integration. The model cylinders are loaded by a pressure evolution acting on the borehole wall. Both methods produce realistic crack patterns, consisting of through-going radial cracks with crack intersections around a crushed zone at the borehole. Furthermore, the DEM models have also yielded realistic fragment size distributions (FSD). The paper covers the present progress of the ongoing project and related future work.

Acoustic power dependences of sonoluminescence and bubble dynamics.

The decreasing effect of sonoluminescence (SL) in water at high acoustic powers was investigated in relation to bubble dynamics and acoustic emission spectra. The intensity of SL was measured in the power range of 1-18W at 83.8kHz for open-end (free liquid surface and film-covered surface) and fixed-end boundaries of sound fields. The power dependence of the SL intensity showed a maximum and then decrease to zero for all the boundaries. Similar results were obtained for sonochemiluminescence in luminol solution. The power dependence of the SL intensity was strongly correlated with the bubble dynamics captured by high-speed photography at 64kfps. In the low-power range where the SL intensity increases, bubble streamers were observed and the population of streaming bubbles increased with the power. At powers after SL maximum occurred, bubble clusters came into existence. Upon complete SL reduction, only bubble clusters were observed. The subharmonic in the acoustic emission spectra increased markedly in the region where bubble clusters were observed. Nonspherical oscillations of clustering bubbles may make a major contribution to the subharmonic.

Objective measures of laryngeal imaging: what have we learned since Dr. Paul Moore.

Dr. Paul Moore pioneered the use of high-speed cinematography for observation of normal and abnormal vocal fold vibrations during phonation. His analysis of the glottal area waveform, opening and closing speed index, and open quotient from the high-speed films were labor intensive but relevant today. With advances in digital image capture and automated image extraction techniques, stroboscopy and high-speed images of vocal fold vibration may be analyzed with objective measures. Digital high-speed image capture in color is now clinically practical at high resolution. Digital kymography now allows analysis of the vibratory waveform from each vocal fold. Serial capture and comparison can document changes in vibratory function with treatment. Quantification of vocal fold vibration using such techniques is now practical. This is a review of vocal fold vibration capture and analysis techniques since Dr. Moore.

Acoustic emission monitoring from a lab scale high shear granulator--a novel approach.

A new approach to the monitoring of granulation processes using passive acoustics together with precise control over the granulation process has highlighted the importance of particle-particle and particle-bowl collisions in acoustic emission. The results have shown that repeatable acoustic results could be obtained but only when a spray nozzle water addition system was used. Acoustic emissions were recorded from a transducer attached to the bowl and an airborne transducer. It was found that the airborne transducer detected very little from the granulation and only experienced small changes throughout the process. The results from the bowl transducer showed that during granulation the frequency content of the acoustic emission shifted towards the lower frequencies. Results from the discrete element model indicate that when larger particles are used the number of collisions the particles experience reduces. This is a result of the volume conservation methodology used in this study, therefore larger particles results in less particles. These simulation results coupled with previous theoretical work on the frequency content of an impacting sphere explain why the frequency content of the acoustic emissions reduces during granule growth. The acoustic system used was also clearly able to identify when large over-wetted granules were present in the system, highlighting its benefit for detecting undesirable operational conditions. High-speed photography was used to study if visual changes in the granule properties could be linked with the changing acoustic emissions. The high speed photography was only possible towards the latter stages of the granulation process and it was found that larger granules produced a higher magnitude of acoustic emission across a broader frequency range.

Darwin's bee-trap: The kinetics of Catasetum, a new world orchid.

The orchid genera Catasetum employs a hair-trigger activated, pollen release mechanism, which forcibly attaches pollen sacs onto foraging insects in the New World tropics. This remarkable adaptation was studied extensively by Charles Darwin and he termed this rapid response "sensitiveness." Using high speed video cameras with a frame speed of 1000 fps, this rapid release was filmed and from the subsequent footage, velocity, speed, acceleration, force and kinetic energy were computed.

A Study of Instantaneous Biological Effects of Blast Waves with High-speed Photography / 第三军医大学学报

The instantaneous changes of the body cavities under the impact of blast waves were studied in three dogs. The changes were recorded with the high-speed photography of three different speeds (563, 1526, and 6526 frames/second). It was demonstrated that there was an 11.7% reduction on average of the body cavities due to compression after 0.777 kg/cm2 of overpressure was received.In correlation with the authors' previous research work and with the relevant literature, it is believed that the 11.7% reduction is likely related to the severe pulmonary injury which is resulted from the abrupt disturbance of hemodynamics after blast wave impact.