High-speed Digital Video Camera Research Articles

The Disintegration of Magnetic Fluid Layer on Liquid and Solid Substrates in Vertical Magnetic Field

The purpose of this work is to experimentally study the process of decomposition of a horizontal layer of a magnetic fluid lying on a liquid non-wettable substrate into an ordered system of drops under the influence of a vertical magnetic field.Methods. In the experiment, the studied liquids in the form of a two-layer system filling a cylindrical glass cuvette were placed on a horizontal platform in the center of the Helmholtz coils connected to a direct current source. The development of magnetic fluid layer free surface instability was monitored using a high-speed digital video camera installed at the top of the coil system.Results. The dependence of the critical strength of the magnetic field on the thickness of the torn layer and the magnetic susceptibility of the magnetic fluid is determined. The obtained experimental data are compared with the results of existing theoretical studies of the instability of the magnetic fluid layer. Compared to the case of a solid substrate, the rupture of the magnetic fluid layer on a liquid substrate occurred at lower values of the critical field strength. In this case, the development of instability of the free surface magnetic fluid layer on a solid substrate occurs at field strengths twice as high as the instability strength of the interface of the layer on a liquid substrate.Conclusion. The use of a liquid substrate makes it possible to break such layers of the magnetic fluid, the deformation of which on a solid substrate is limited only by a periodic perturbation of the surface. The magnitude of the critical strength leading to the disintegration of a continuous magnetic fluid layer on a liquid substrate increases with increasing thickness of this layer. An increase in the magnetic susceptibility of the magnetic fluid leads to a decrease in the critical field strength.

TRPA1/M8 agonists upregulate ciliary beating through the pannexin-1 channel in the human nasal mucosa

BackgroundNasal breathing is important for maintaining physiological respiration. However, airflow in the nasal cavity has an inherent cooling effect and may suppress ciliary beating, an essential frontline defense in the airway. Nasal airflow is thought to be perceived by thermoreceptors for cool temperatures. We herein investigated the effect of the activation of thermosensitive transient receptor potentials (TRPs) for cool/cold temperatures on ciliary beating to search for a compensatory mechanism.MethodsInferior turbinates were collected from patients with chronic hypertrophic rhinitis. Ex vivo ciliary beat frequency (CBF) and ATP release were measured using a high-speed digital video camera and by luciferin-luciferase assay, respectively. Intracellular Ca2+ ([Ca2+]i) imaging of isolated ciliated cells was performed using Fluo-8. The nasal mucosae were also subjected to fluorescence immunohistochemistry and real-time RT-PCR for TRPA1/TRPM8.ResultsCBF was significantly increased by adding either cinnamaldehyde (TRPA1 agonist) or l-menthol (TRPM8 agonist). This increase was inhibited by pannexin-1 blockers, carbenoxolone and probenecid. Cinnamaldehyde and l-menthol also increased the ATP release from the nasal mucosa and [Ca2+]i of isolated ciliated cells. Immunohistochemistry detected TRPA1 and TRPM8 on the epithelial surface including the cilia and in the submucosal nasal glands. Existence of these receptors were confirmed at the transcriptional level by real-time RT-PCR.ConclusionsThese results indicate the stimulatory effect of the activation of TRPA1/TRPM8 on ciliary beating in the nasal mucosa, which would be advantageous to maintain airway mucosal defense against the fall of temperature under normal nasal breathing. This stimulatory effect is likely to be mediated by pannexin-1.

Causal relationship between spatiotemporal parameters of walking and the locomotor rehabilitation index in healthy people.

Walking speed is a functional vital sign affecting mechanical parameters individually. Further, there is a tendency for pathological gait to occur at slower speeds, which does not always allow for an adequate comparison with normal gait. Therefore, recognizing the influence of spatiotemporal adjustments on healthy gait can broaden our understanding of the applicability of gait quality markers. This study aimed to identify the causal relationship between the stride length-frequency walking ratio index (R_SL/SF) at the self-selected walking speed (SSWS) and optimal walking speed (OWS) and the locomotor rehabilitation index (LRI) in healthy adults. Healthy adults (n = 68) of both sexes aged 20-59 years were included in this study. The SSWS was determined using a 30-m walkway. The OWS and LRI were predicted by equations proposed in the literature. The volunteers walked on the treadmill at speeds corresponding to the OWS and SSWS in two bouts of 60 s each, with a break in between. The spatiotemporal parameters were recorded using a high-speed digital video camera, digitalized, and mathematically processed. Multiple linear regression was applied using the forced regression method. Significant correlations were found between the LRI and R_SL/SF at the SSWS (R = 0.397; p < 0.001) and OWS (R = 0.266; p = 0.014). The regression model showed that 16 % of the variability in the LRI was attributable to the R_SL/SF variability at the SSWS. The average and 95 % confidence interval LRI were 94.7 % (91.6 %-97.8 %). The LRI average is around 95 % for healthy and young adults and the R_SL/SF explained just 16 % of the variance in LRI.

Color contamination matrix property assessment for improvement of colored smoke PIV

A single-camera color PIV system that can acquire PIV data of three separated layers has been redesigned, purposing improvement of wind tunnel applicability. We target smoke image that has particle-per-pixel values higher than unity. The system constitutes of a high-power color-coding illuminator and a digital color high-speed video camera. RGB values in recorded image involves severe color contaminations due to five optical and digital sequences (Fig. 1). To quantify this, a snapshot calibration is proposed to describe the contamination matrix equation (Eq. (1)). Taking the inverse matrix (Eq. (2)) allows in-plane PIV in each color layer to be accurately implemented. We also derive mathematical limits to operate the colored smoke PIV, which is explained by the matrix property (Eq (3)). Feasibility of the proposed method has been demonstrated by application to a turbulent wake behind a Delta wing (Fig. 2) and also to a boundary layer flow along heated chocolate.

Experiments and modeling on cryogenic quenching enhancement by the structured capillary-porous coatings of surface

In the present study, the influence of structured capillary-porous coatings of surface on cryogenic quenching by the falling liquid nitrogen film is investigated. The coating was produced by the directional plasma spraying technique. The cryogenic quenching experiments were performed on high-temperature vertical copper slab with bare surface and on the surfaces with different orientation of coating protrusions. Thermocouples and a high-speed digital video camera were employed to obtain a synchronized data on the temperature-time history of the transient process and the pattern of quench front propagation. The peculiarities of quench front dynamics and heat transfer in the transient process are studied. The created numerical model determines the quench front velocity and the temperature fields in the heater, varying in space and time. The dynamic pattern of quench front propagation obtained numerically satisfactorily correlates with the observed in the experiments one. The heat transfer curves during quenching were determined for different surfaces based on the experimental cooling thermograms and visualization data. The results show that the cooling rate is influenced by the thermal properties of the coating as well as the geometry of the protrusions on the solid surface. The presence of capillary-porous coating significantly affects the dynamics of quenching, which results in the decrease more then threefold of the total quench time. In this way, the structured capillary-porous coating is a method for reducing the time and the total mass of cryogenic fluid required for a quenching process. The effect is due to the fact that the initialization of a quench front on a specimen with the coating occurs at a temperature significantly higher than the thermodynamic limit of a liquid superheat, when a stable solid-liquid contact is thermodynamically impossible. This phenomenon appears as a result of local contacts of the crests of wavy liquid flow at the liquid-vapor interface with the protrusions on the modified surface. The results indicated also the minimum film boiling temperature increase on heat transfer surface coated with capillary-porous layer. This increased temperature caused earlier transition to nucleate boiling, which results in the decrease in the quenching time. The results reliability is confirmed by direct comparison with experimental data on the quench front dynamics, velocity and geometry.

A new high-speed observation system for evaluating the spark location in WEDM of Inconel 718

Abstract Wire electrical discharge machining (WEDM) is a good machining method for nickel-base superalloy, which is a key material in aero-engine, rocket engine and nuclear reactor. Experimental data indicate that the spark location along the thickness direction is usually uneven in WEDM. This phenomenon will be harmful to the usability and reliability of the parts machined by WEDM, especially in aerospace. However, the spark location is very difficult to observe directly with high precision due to the narrow cutting kerf. In view of this situation, a new high-speed observation system is proposed to evaluate the spark location during the continuous discharge process for the first time. The discharge spark, in turn, passes through heat-resistant glass, optical filter, focusing lens and digital high-speed videocamera. A series of image processing methods and centroid methods are utilized to acquire the spark location in this system. It can be observed that the number of discharge sparks of all regions in decreasing order is: middle region, lower region and upper region. The maximal standard deviation (St) of spark location can reach up to 0.137. Thereafter, a group of discharge experiments are carried out to analyze the relations between the process parameters and spark location evenness. An optimal combination of process parameters for even spark location is obtained, which can produce a standard deviation (St) of spark locations as low as 0.039. Eventually, the relation between spark location and machining characteristics is also illustrated. Ra can be decreased by 32.6% without reducing machining efficiency based on the process parameter optimization for even spark location.

Calmodulin Regulates Ciliary Beats in the Human Nasal Mucosa Through Adenylate/Guanylate Cyclases and Protein Kinases A/G

Background: The ciliary beat of the airway epithelium, including the sinonasal epithelium, has a significant role in frontline defense and is thought to be controlled by the level of intracellular Ca²⁺. Involvement of calmodulin and adenylate/guanylate cyclases in the regulation of ciliary beats has been reported, and here we investigated the interrelation between these components of the ciliary beat regulatory pathway. Methods: The inferior turbinates were collected from 29 patients with chronic hypertrophic rhinitis/rhinosinusitis during endoscopic sinonasal surgery. The turbinate mucosa was cut into thin strips, and mucociliary movement was observed under a phase-contrast light microscope equipped with a high-speed digital video camera. Results: The ciliary beat frequency (CBF) was significantly increased by stimulation with 100 μM CALP3 (calmodulin agonist), which was completely suppressed by adding 100 µM SQ22536 (adenylate cyclase inhibitor) and 10 µM ODQ (guanylate cyclase inhibitor) together and by adding 1 µM KT5720 (protein kinase A inhibitor) and 1 µM KT5823 (protein kinase G inhibitor) together. The CBF was significantly increased by stimulation with 10 µM forskolin (adenylate cyclase activator) and 10 µM BAY41-2272 (guanylate cyclase activator) and by stimulation with 100 µM 8-bromo-cAMP (cAMP analog) and 100 µM 8-bromo-cGMP (cGMP analog), which was not changed by adding 1 µM calmidazolium (calmodulin antagonist). Conclusions: These results confirmed that the regulatory pathway of ciliary beats in the human nasal mucosa involves calmodulin, adenylate/guanylate cyclases, and protein kinases A/G and indicate that adenylate/guanylate cyclases and protein kinases A/G act downstream of calmodulin, but not vice versa, and that these cyclases relay calmodulin signaling.

Sparse representation of complex steerable pyramid for machine fault diagnosis by using non-contact video motion to replace conventional accelerometers

Structural health monitoring is vital for ensuring structural safety, avoiding property damage. Contact-type vibration measurement devices, such as accelerometers that provide high-spatial-resolution sensing capacity, cannot be installed on the inspected objects if their surface is hot or inaccessible. In contrast, non-contact-type vibration measurement devices, such as laser vibrometers, are relatively expensive and perform measurements sequentially, which could be time- and labor-intensive when the inspected areas are large. Recently, an alternative non-contact method has been proposed to measure vibration using a high-speed digital-video camera. Due to the continuous advancement in technology, these high-speed cameras are relatively low-cost and have simultaneous measurement capacity with high spatial resolution. To convert the video images captured by the camera to vibration displacement, the key is to use appropriate video signal processing method. For this purpose, phase-based analysis is often used. However, this analysis is time-consuming. Therefore, this paper presents a new processing method by combining the multiple-scale pyramid decomposition method and sparse representation technique. This method can considerably reduce the number of redundant steerable filters, improve the computation efficiency of phase-based video processing and replace the conventional mounted sensors. The experiments indicate that the results obtained by the proposed method for machine shaft fault diagnosis are comparable to those obtained using a physically mounted accelerometer. Hence, the proposed method provides a workable solution to detect abnormal vibrations generated by a structure/machine, with the advantages of no contact and low cost. In the future, this method could be used, for example, to measure the heart and breathing rates of elderly persons without a sensor placed on the body during sleeping.

Peculiarities of the initialization and dynamics of the quench front on an extremely overheated plate cooled by a falling film of a cryogenic fluid

Quenching is a generally accepted term for the process of rapid cooling of a solid body that is superheated above the temperature of the thermodynamic limit of a liquid superheat. The paper presents the results of computational experiments simulating the quenching of a high-temperature vertical copper plate by a gravitationally flowing film of liquid nitrogen. The peculiarities of the initialization and dynamics of the quench front in the transition process are investigated. The initial temperature of the test sample was higher than the Leidenfrost temperature and even higher than the critical temperature, which excluded the possibility of long-term stable liquid-solid contact. An improved numerical model of quenching is implemented, which assumes at the time of the quench front initialization an unsteady local contact of the liquid with the extremely overheated surface in the vicinity of the upper boundary of the heater. A dynamic pattern of the running quench front was obtained numerically, which satisfactorily correlates with that observed in cryogenic experiments by the high-speed digital video camera. The reliability of the results obtained numerically is confirmed by direct comparison with experimental data on the velocity and the shape of the quench front.

Appropriate Neck Flexion Without Head-hitting Decreases The Thrown Player’S Risk Of Brain Injury In Judo

PURPOSE: Judo is one of the worldwide sports and its competitive athletic events have been held in Olympic Games. Serious brain injuries, however, have been occasionally noted in judo practices and/or competitions. Since the patterns and severities of brain injuries largely depend on the kinematics of the thrown players, it is essential to investigate the mechanism of brain injury from the biomechanical viewpoint in popular throwing techniques. The aim of this study is to evaluate the brain injury criterion (BrIC), an indicator of brain injury, with measuring the presence or absence of head-hitting on the anthropomorphic test device (ATD) in judo throwing technique Ouchi-gari. METHODS: A male judo expert (thrower) threw an ATD for 6 times by Ouchi-gari with or without head-hitting, respectively. The ATD with a straight neck component necessarily hit the occipital region on the mat, whereas an angled component was designed for preventing the ATD’s head-hitting. A 3-axis angular rate sensor, mounted in the gravity center of the ATD’s head, assessed head axial angular velocity in each trial. To evaluate the ATD’s head impact quantitatively, we calculated the BrIC from the head axial angular velocity. High-speed digital video cameras also recorded the kinematics of the ATD’s whole body during trials. RESULTS: In all trials, the largest angular velocities were recorded in the phase of the initial head (with head-hitting) or back (without head-hitting) contacting to the mat. The peak BrIC values of ATD ranged from 0.94 to 2.27 (with head-hitting) and 0.54 to 0.91 (without head-hitting). The average BrIC value with head-hitting (1.62 ± 0.22, mean ± S.E.) trials was significantly higher than those without head-hitting (0.73 ± 0.08) trials (p<0.05). Four out of six trials with head-hitting scored BrIC values larger than 1.0, which implies the human tolerance limit for serious brain injury. However, BrIC values were less than 1.0 in all other trials without head-hitting. CONCLUSIONS: These results suggested that thrown player’s break-fall technique, with appropriate neck flexion to avoid head-hitting, decreases the BrIC value effectively and the risk of serious brain injuries in judo.

Comparative visualized investigation of impact-driven high-speed liquid jets injected in submerged water and in ambient air

This paper is a comparative study on the characteristics of high-speed liquid jets injected in surrounding water and air using shadowgraph technique. One of the main objectives is to investigate the effects of liquid’s physical properties, used to generate the high-speed liquid jets, on jet generation’s characteristics. Moreover, comparative investigations on effects of those liquid jets after injected in water and air are reported. The high-speed liquid jets were generated by the impact of a projectile launched by a horizontal single-stage power gun. The impact-driven high-speed liquid jets were visualized by shadowgraph technique and images were recorded by a high-speed digital video camera. The process of impact-driven high-speed liquid jet injection in air and water, oblique shock waves, jet-induced shock waves, shock waves propagation, the bubble behavior, bubble collapse-induced rebound shock waves and bubble cloud regeneration were clearly observed. It was found that different properties of liquid (surface tension and kinematic viscosity) affect the jet maximum velocity and shape of the jet. Bubble behaviors were only found for the jet injected in water. From the shadowgraph images, it is found that the maximum average jet velocity, expansion and contraction velocities of bubble in axial direction increase when the value of the multiplied result of surface tension by kinematic viscosity increases. Therefore, surface tension and kinematic viscosity are the significant physical properties that affect characteristics of high-speed liquid jets.

On the Estimation of the Surface Elevation of Regular and Irregular Waves Using the Velocity Field of Bubbles

This paper describes a new set of experiments focused on estimating time series of the free surface elevation of water (FSEW) from velocities recorded by submerged air bubbles under regular and irregular waves using a low-cost non-intrusive technique. The main purpose is to compute wave heights and periods using time series of velocities recorded at any depth. The velocities were taken from the tracking of a bubble curtain with only one high-speed digital video camera and a bubble generator. These experiments eliminate the need of intrusive instruments while the methodology can also be applied if the free surface is not visible or even if only part of the depth can be recorded. The estimation of the FSEW was successful for regular waves and reasonably accurate for irregular waves. Moreover, the algorithm to reconstruct the FSEW showed better results for larger wave amplitudes.

Dynamic fracture development in a multiply cracked solid

We have been studying the collective, global behaviour of multiple cracks in solid materials and its connection with each individual, local crack motion. Here, by using a high-speed digital video camera, we examine fracture evolution in a two-dimensional, initially linear elastic rectangular polycarbonate specimen where sets of cracks are prepared and uniaxial tensile strain with a prescribed constant rate is externally applied. We trace local fracture development around every individual crack, and simultaneously, we obtain global stress-strain curves and physical properties like tensile strength of the specimens. By knowing the global characteristics, then, we concentrate our attention to more local, secondary and further fractures caused by the extending main or primary fracture and reversely its influence on the global nature of the multiply cracked specimens. For various different distribution patterns and values of density of initial cracks, we observe the dynamic evolution of the primary fracture and the fracture-induced waves, as well as the generation of the subsidiary fracture. We find that after a total split of the specimen into two by the propagation of the primary fracture, the secondary fracture may be initiated and propagated at a distance from the primary fracture. That is, fracture propagation may jump in multiply cracked solids even without additional external loading. Moreover, in our observations, the secondary fracture moves into the direction opposite to the primary one, and is once arrested and then resumes its propagation with some delay. The secondary and further fractures, or a cluster of fractures, are obviously not owing to additional external energy, but by dynamic waves produced upon enlargement of the primary fracture. The development of the secondary and further fractures in a specimen may be concealed in the global stress-strain relation but may rather appear in a global pattern of dynamic wave radiation such as doublet or a cluster of ruptures in the solid Earth, namely, earthquakes.

Biomechanical Analysis of the Head Movements of a Person Thrown by the Judo Technique 'Seoi-nage'.

The present study examined the kinematics and biomechanical parameters of the head of a person thrown forward by the judo technique ‘Seoi-nage’. A judo expert threw an anthropomorphic test device (the POLAR dummy) five times. Kinematics data were obtained with a high-speed digital video camera. Linear and angular accelerations of the head were measured by accelerometers mounted at the center of gravity of the dummy’s head. When Seoi-nage was performed, the dummy fell forward accompanied by contacting the anterior parietal regions of the head to the tatami, and the linear and angular accelerations of most axes reached peak values when the head contacted the tatami. Peak resultant linear and angular accelerations were 20.3 ± 9.8 G and 1890.1 ± 1151.9 rad/s2, respectively (means ± standard deviation). Peak values in linear and angular acceleration did not significantly differ between the three directional axes. Absolute angular accelerations in all axes observed in Seoi-nage were high and the resultant value was approximately equal to the already reported in Ouchi-gari, one of the predominant techniques causing judo-related acute subdural hematoma. However, the remarkable increase of linear acceleration in the longitudinal direction and/or angular acceleration in the sagittal plane, as previously reported in techniques being thrown backward (i.e., Ouchi-gari and Osoto-gari), was not detected. The likely mechanism of acute subdural hematoma caused by Seoi-nage is that a large angular acceleration causes large strains and deformations of the brain surface and subsequent rupture of cortical vessels.

Calmodulin and protein kinases A/G mediate ciliary beat response in the human nasal epithelium.

Mucociliary clearance of the airway epithelium is an essential function for mucosal defense. We recently proposed a hypothetical mechanism of ciliary beat regulation, in which the pannexin-1 (Panx1)-P2X7 unit serves as an oscillator generating a periodic increase in intracellular Ca2+ ([Ca2+ ]i ). In the present study, we examined the localization of Panx1 and P2X7 at the ultrastructural level, and investigated the regulatory pathway subsequent to [Ca2+ ]i increase. The inferior turbinate mucosa was collected from patients with chronic hypertrophic rhinitis during endoscopic sinonasal surgery. The mucosa was examined by transmission immunoelectron microscopy for Panx1 and P2X7. Alternatively, the mucosa was cut into thin strips, and ciliary beat frequency (CBF) was measured under a phase-contrast light microscope with a high-speed digital video camera. In immunoelectron microscopy, immunoreactivities for Panx1 and P2X7 were localized along the plasma membrane of the entire length of the cilia. CBF was significantly increased by stimulation with 100 µM acetylcholine (Ach). The Ach-induced CBF increase was significantly inhibited by calmidazolium (calmodulin antagonist), SQ22536 (adenylate cyclase inhibitor), ODQ (guanylate cyclase inhibitor), KT5720 (protein kinase A inhibitor), and KT5823 (protein kinase G inhibitor). Fluorodinitrobenzene (creatine kinase inhibitor) completely inhibited the ciliary beat in a time- and dose-dependent manner. These results indicate that Panx1 and P2X7 coexist at the cilia of the human nasal epithelial cells and that the ciliary beat is regulated by calmodulin, adenylate/guanylate cyclases and protein kinases A/G, and crucially depends on creatine kinase.

The Effects of Water Flow Rate On The Air Entrainment Process From Vertical Plunging Water Jet With Downcomer

This study is intended to research the characteristics of bubbles produced by the phenomenon of air entrainment. This phenomenon is used in the Jameson cell, a flotation system used to separate valuable minerals from impurities. This process has proven successful in providing high separation efficiency. However, the characteristics of hydrodynamic bubbles and water entrainment have not been widely described. Research was set up in the form of a water loop consisting of a pump, flow meter, nozzle, downcomer, and water box. Data collection is done by using a digital camera and a high-speed digital video camera with a backlighting system. The resulting image is processed with software to obtain quantitative data. Results indicate that increasing the water flow rate also causes the ratio of air to water to increase (air entrainment).Air Entrainment is natural phenomenon air carried out as a result of a fluid jet stream. Mass transfer deepens penetration because a high jet speed produces bubbles and tends to force those bubbles towards the flow. Increasing the water flow rate will expand the surface roughness to produce more bubbles. Thus, it can be concluded that there are three phenomena that will affect whether or not the discharge will increase the air entrainment process: depth of bubble penetration, area of bubble dispersion, and air entrainment rate.

The Effect of Direct Head Impact in Judo on Internal of Cervical Spine

PURPOSE: Judo is one of the popular combat sports, which is played worldwide and organized even in the Olympic Games. Serious neck injuries, however, have been occasionally noted in judo trainings and/or competitions. Since the pattern and severity of neck injuries largely depend on the kinematic motion of the thrown player, it is essential to investigate the mechanisms of neck injury from biomechanical view point in various different throwing techniques. Thus, the aim of this study was to evaluate a predictive indicator of cervical spine injury, neck injury criterion (Nij) with direct head impact by Judo throwing techniques using an anthropomorphic test device (ATD). METHODS: Two male judo experts (thrower) repeatedly threw the ATD for 5 times by Seoi-nage (Seoi), Osoto-gari (Osoto) and Ouchi-gari (Ouchi) techniques to make ATD's head hit directly to the mat. A 6-axis load cell (force transducer), mounted in the ATD’s cervical spine, assessed neck axial force and bending moment in each trial. To evaluate the the ATD’s neck load quantitatively, we calculated the Nij value from the neck axial force and bending moment. Kinematic data of the ATD’s whole body were also recorded during trials, using high-speed digital video cameras. RESULTS: In all trials, the largest neck loads were observed at the phase of the head contact to the mat. The peak Nij values of ATD ranged from 0.63 to 1.60 (Seoi), 0.54 to 0.58 (Osoto) and 0.19 to 0.29 (Ouchi). The average Nij value in Seoi (1.03±0.19, mean±S.E.) trials was significantly higher than those in Osoto (0.56±0.01) and Ouchi (0.24±0.02) trials (p<0.05, respectively). In three out of five tests, Nij value in Seoi trial exceeded 1.0 implying the real human tolerance limit for neck loading. However, in other two trials (Osoto and Ouchi), Nij values were less than 1.0. CONCLUSIONS: When thrown forward, the judo player might be accompanied with a direct contact of parietal and/or frontal regions of the head to the mat and suffered from neck injuries. Judo throwing technique, Seoi, has higher risk of serious neck injuries than the other techniques thrown backward including Osoto and Ouchi.

Experimental study on droplet flow of falling film between horizontal tubes

Droplet flow is one of the most significant flow patterns in horizontal tubes falling film flow, which is widely observed in industrial equipment. Flow visualization of water/ethanol/30% glycerol-water solution falling in 8/23/38 mm tube spacing using high-resolution and high-speed digital video camera is presented here. The image edges detection algorithm of Sobel is developed to quantify falling distance and velocity for each frame of a sequence. The results illustrate that the droplet flow between tubes can be divided into the following four processes: droplet formation, droplet falling, droplet impact, neck break and retraction. The “escape length” is proposed in droplet formation process. The falling process can be divided into three stages according to the appearance and break of liquid neck. The droplet in different tube spacing displays different falling stages, which affect the processes of droplet impact and neck break and retraction eventually. The droplets falling velocity increases linearly with the falling distance in the first and second stages of falling process. The increase of viscosity can retard the droplets falling and the decrease of surface tension can predate the appearance of the droplet detaching. In addition, a new correlation has been suggested to predict the primary droplet diameter. When 9mm < s < 15 mm and 25ms < τa < 40 ms, there is a phenomenon of ``liquid globule rebound".

Decreased ciliary beat responsiveness to acetylcholine in the nasal polyp epithelium.

We investigated the difference in ciliary beat responsiveness to acetylcholine in ex vivo and the difference in the expressions of associated molecules (M1/M3 muscarinic receptors, pannexin-1 and P2X7 purinergic receptor) between the nasal polyp and turbinate mucosa. Laboratorial study. Nasal polyp and inferior turbinate were collected from patients with hypertrophic rhinitis and/or nasal polyp during endoscopic sinonasal surgery. The mucosa was cut into thin strips, and ciliary movement was observed under a phase-contrast light microscope equipped with a high-speed digital video camera. The samples were also examined by scanning electron microscopy, fluorescence immunohistochemistry, and quantitative reverse transcription-polymerase chain reaction. Cilia were well preserved in both tissues at the ultrastructural level. The baseline ciliary beat frequency (CBF) was not different between the two tissues. The CBF of the turbinate was significantly increased by stimulation with acetylcholine (P<0.001), but that of the polyp was not. The ratio of the acetylcholine-stimulated CBF to the baseline CBF was significantly lower in the polyp than in the turbinate (P<0.001). Immunohistochemical study revealed that immunoreactivities for M3, pannexin-1 and P2X7 were weaker in the polyp than in the turbinate. The mRNA expressions of M1, M3 and P2X7 were significantly lower and that of pannexin-1 tended to be lower in the polyp than in the turbinate. These results indicate that ciliary beat responsiveness to acetylcholine is decreased in the nasal polyp. This may be explained by the decreased expressions of M3, P2X7 and probably pannexin-1 in this tissue.

An experimental study of the mechanical and fracturing behavior in PMMA specimen containing multiple 3D embedded flaws under uniaxial compression

This paper studies the mechanical and fracture behavior of poly methyl methacrylate (PMMA) specimens containing multiple embedded flaws, under uniaxial compression. The initiation, propagation, coalescence of cracks, and failure of specimens are captured by a high-speed digital video camera system. Six types of cracks and three modes of crack coalescence are captured in the PMMA specimens. The experimental observations show that the effects of the flaw angle on crack propagation and coalescence are stronger than the non-overlapping length. Furthermore, the peak strength and crack initiation stress show regular change with increasing in the flaw angle and the non-overlapping length.