Sudden Pressure Changes Research Articles

Change-Related Acceleration Effects on Auditory Steady State Response.

Rapid detection of sensory changes is important for survival. We have previously used change-related cortical responses to study the change detection system and found that the generation of a change-related response was based on sensory memory and comparison processes. However, it remains unclear whether change-related cortical responses reflect processing speed. In the present study, we simultaneously recorded the auditory steady-state response (ASSR) and change-related response using magnetoencephalography to investigate the acceleration effects of sensory change events. Overall, 13 healthy human subjects (four females and nine males) completed an oddball paradigm with a sudden change in sound pressure used as the test stimulus, i.e., the control stimulus was a train of 25-ms pure tones at 75 dB for 1,200 ms, whereas the 29th sound at 700 ms of the test stimulus was replaced with a 90-dB tone. Thereafter, we compared the latency of ASSR among four probabilities of test stimulus (0, 25, 75, and 100%). For both the control and test stimulus, stronger effects of acceleration on ASSR were observed when the stimulus was rarer. This finding indicates that ASSR and change-related cortical response depend on physical changes as well as sensory memory and comparison processes. ASSR was modulated without changes in peripheral inputs, and brain areas higher than the primary cortex could be involved in exerting acceleration effects. Furthermore, the reduced latency of ASSR clearly indicated that a new sensory event increased the speed of ongoing sensory processing. Therefore, changes in the latency of ASSR are a sensitive index of accelerated processing.

Horses for courses (or something much smaller!): The design, development and acoustic testing of sub-micron cavitation nucleation agents for biomedical applications

Lipid and protein-shelled microbubbles have been the mainstay of cavitation nucleation strategies for therapeutic applications for several decades. However, a growing number of therapeutic ultrasound applications require nuclei that (i) are significantly smaller in size, in order to overcome a particular biological barrier such as the leaky vasculature of tumours or the stratum corneum; (ii) offer greatly increased cavitation persistence, both during a single extended ultrasound pulse and in terms of extended circulation following intravenous administration; and (iii) have better resilience to sudden ambient pressure changes in order to enable direct injection without nuclei destruction into tissue targets via a needle and syringe. We will review a range of novel cavitation agents currently under development, including sub-micron gas-stabilizing solid particles and nanodroplets, and provide an overview of their known characteristics in terms of acoustic emissions, activation and cavitation thresholds, cavitation persistence, and circulation. Where possible, the relevant performance of these cavitation nucleation agents will be compared to microbubbles for applications ranging from drug delivery to nucleated tissue fractionation.

Application of Coupled Mathematical Model of Wave and Tidal Current in Strong Wind on Muddy Coast of Lianyungang, China

Qi, Q.; Zhu, Z.; Zhang, R., and Liu, L., 2019. Application of coupled mathematical model of wave and tidal current in strong wind on muddy coast of Lianyungang, China. In: Guido-Aldana, P.A. and Mulahasan, S.(eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 220–231. Coconut Creek (Florida), ISSN 0749-0208.In order to accurately simulate the coupled distribution of wave, tidal current and wave-current in muddy sea area under extreme typhoon weather, the advanced Weather Research and Forecasting field model was used to simulate the 10-meter wind speed on the sea surface as the driving wind field of the wave and tidal current. Considering the effect of storm surge, the formation, propagation and attenuation of wind waves in Lianyungang sea area during Typhoon Weipa and Dawei were simulated and reappeared. This paper adopts the three-dimensional tidal current model, considering the factors such as wave-induced nearshore current and the influence of wave on tidal current. There was the anticlockwise circulation circle near the typhoon center, but it was not obvious under the action of gale wind. Due to the sudden change of surface wind and barometric pressure in the sea area, the sea level and the tidal level rose strongly, and the influence of nearshore windblown current was very obvious. The wind-wave-current coupled model could better reflect the hydrodynamic field during typhoon, the changing process of which can provide dynamic conditions for further simulation of river bed erosion and siltation during typhoon.

Evaluación de modelos de turbulencia para el flujo de aire en una tobera plana

En los flujos de gas a velocidades supersónicas se producen ondas de choque, separación del flujo y turbulencia debido a cambios repentinos de la presión. El comportamiento del flujo compresible se puede estudiar mediante equipos experimentales o por métodos numéricos con códigos de la dinámica de fluidos computacional (DFC). En el presente trabajo, el flujo de aire se simula en un dominio computacional 2D con el código ANSYS-Fluent versión 12.1 para la geometría de una tobera plana, utilizando la ecuación de Navier-Stokes de número de Reynolds promedio (NSRP), con el objetivo de evaluar cinco modelos de turbulencia: SST k-ω, k-e estándar, k-ω estándar, k-kl-ω de transición y RSM. Se obtuvieron resultados numéricos de perfiles de presión estática para las paredes de la tobera y de formas de ondas de choque en el campo de flujo, para dos condiciones de relaciones de presión y , los cuales fueron comparados con los datos experimentales del trabajo de Hunter. Se concluye que los resultados numéricos obtenidos con el modelo de turbulencia SST k-ω de Menter (1994) están más ajustados a los datos experimentales de presión estática y de formas de ondas de choque.

Response of the magnetosphere–ionosphere system to sudden changes in solar wind dynamic pressure

The geomagnetic sudden commencement (SC) is a plasma and magnetic field disturbance in the magnetosphere–ionosphere region, which appears as a response of this system to a sudden change in the solar wind dynamic pressures associated with shock and tangential discontinuity of solar wind. As this mechanism seems to be simple, the SC has been widely investigated based on observations in the region from the surface of the Earth to the magnetosphere. A schematic model of the SC was presented by Araki (Solar wind sources of magnetospheric ultra-low-frequency waves. American Geophysical Union, Washington, DC, pp 183–200, 1994), who compiled many observational results and theories related to this phenomenon. Recent advances in supercomputing allow us to present new numerical results including three-dimensional global current systems of the SC which cannot be obtained only by direct observations and theoretical analysis. The simulation study not only confirms the results of a previous model on the initial response of the magnetosphere–ionosphere system to solar wind changes (the preliminary impulse) but also presents new findings on dynamical processes in the magnetosphere–ionosphere system in the period following the initial response (the main impulse). Furthermore, the simulation study reveals the SC sequence in the context of break and recovery of the steady magnetosphere–ionosphere convection system. The transient flow vortex in the flank magnetosphere in the main impulse phase plays an essential role in recovering the convection system. This report describes the SC process from the viewpoint of the state transition of the magnetosphere–ionosphere compound system Tanaka (Space Sci Rev 133:1, https://doi.org/10.1007/s11214-007-9168-4, 2007).

Study on Creep-consolidation Coupling Characteristics of Soil of Deep Foundation Pits in Soft Clay Regions

This paper starts from the mechanism of the coupled effect of consolidation and creep of soft soil, regarding the effect of time, adopting time hardening and Druker-Prager yield criterion coupled creep model, studies the variation law of the excess pore water pressure of soil with time after foundation pit excavation through numerical simulation. The results show that unloading of foundation pit excavation will produce negative excess pore water pressure in the pit bottom and surrounding soil, and the maximum pore water pressure (absolute value) will occur in the center of the foundation pit; after the the excavation completion of the foundation pit, the pore water pressure is continuously dissipated, and the pore pressure of the soil before the pit is dissipated faster, while the soil behind the pit is relatively slow. The excess pore water pressure after dissipation is basically the same as the ultra-static pore pressure when the excavation is completed; due to the impermeability of the underground continuous wall, the pore pressure boundary is very complicated, resulting in a sudden change of the excess pore water pressure behind the wall front wall.

Nonlinear Vibration Analysis of Tubing Strings in Underground Gas Storage Using Multiscale Wavelet Transform

The tubing string exposed to transient flow may undergo nonlinear vibration due to sudden change in pressure in conveying gas. But, the drag on such structures often leads to fatigue failure of the strings that may significantly affect the vibrations through the combined effects of the first sections of gas injection, annulus pressure, the inclined structures, and the large transient flow component. In this paper, the nonlinear vibration analysis of tubing strings in underground gas storage using the multiscale wavelet transform has been studied. The vibration characteristics of strings in the steady gas injection process have been analyzed by numerical simulation. Results of the calculation model are compared to numerical ones reported previously, and the excellent agreement is obtained. The nonlinear vibration experiment of strings in the gas injection process has been studied for discussing the change rules of the string pressure, the wall velocity, and the amplitude in the gas injection process. The results show that the near‐injection port section and the inclined section of strings are the high‐incidence areas of nonlinear vibration of strings in underground gas storage. We also find that significant alteration of the dynamics is due to low‐frequency pressure fluctuation forces on the tubing strings.

고속열차의 터널 진입시 발생하는 압력변화에 대한 수치 해석적 연구

Sudden pressure changes caused by the high-speed train entering the entrance of the tunnel are propagated into the tunnel and spread out around the tunnel in the form of a micro pressure wave at the exit of the tunnel. This phenomenon can cause noise and vibration around the tunnel, causing damage to the surroundings. Analysis of this phenomenon is very difficult, but the development of analytical technology has revealed more phenomena than in the past. In this study, we propose this method of analysis and compare it with the experimental data to show the data with higher reliability.

Osmotically Induced Membrane Fission in Giant Polymer Vesicles: Multilamellarity and Effect of the Amphiphilic Block Lengths.

Amphiphilic block co-polymers are used to form large spherical vesicles. A sudden change in the osmotic pressure across the polymer membrane is used to induce the fission of the polymer vesicle. The membrane area to volume ratio, as expected, is observed to be a parameter suitable to describe the process and even mark the critical points along this transition. The effect of the length of the hydrophobic and hydrophilic chains on the fission process is analyzed. The effects of membrane lamellarity and initial polydispersity are thoroughly analyzed from the experimental data following mathematical models, and the phenomenon of fission in these polymer vesicles is understood via measurements characterizing the membrane, i.e., area stretch modulus.

Contactless Technique for Measuring Blood-Pressure Variability from One Region in Video Plethysmography

Sudden changes in blood pressure are frequently caused by daily events such as exercise, stressful work, and moving between different temperature environments. Sometimes, an abrupt change in blood pressure can endanger human lives. To mitigate such a risk, several studies have previously proposed contactless methods for monitoring changes in blood pressure; however, the number of studies on this issue is insufficient. In previous methods, changes in blood pressure were estimated using the propagation time of the pulse waves obtained from two different skin areas on the basis of an analysis of images from video recordings, which is called a video plethysmogram. However, the relative positional relationship of the two skin areas had to be maintained during the measurement, making the approach restrictive. To solve this problem, in the present study, we propose a new method using the video plethysmogram obtained from only one skin area. In particular, the degree of distortion in the video plethysmogram is calculated as a new index to estimate the blood pressure. On the basis of the results of our experiments with 20 healthy human subjects, we ascertain that the proposed index obtained from the palm area is correlated with the blood-pressure variability as well as the previous approach.

Van der Waals pressure sensors using reduced graphene oxide composites

Reduced graphene oxide (RGO) films intercalated with various polymers were fabricated by reaction-based self-assembly, and their characteristics as vacuum pressure sensors based on van der Waals interactions were studied. At low temperature, the electrical resistances of the samples decrease linearly with increasing vacuum pressure, whereas at high temperature the variation of the electrical resistance shows secondary order curves. Among all samples, the poly vinyl alcohol intercalated RGO shows the highest sensitivity, being almost two times more sensitive than reference RGO. All samples show almost the same signal for repetitive sudden pressure changes, indicating reasonable reproducibility and durability.

Pleural manometry-historical background, rationale for use and methods of measurement.

Subatmospheric pleural pressure (Ppl), which is approximately -3 to -5 cmH2O at functional residual capacity (FRC) makes pleura a unique organ in the human body. The negative Ppl is critical for maintaining the lungs in a properly inflated state and for proper blood circulation within the thorax. Significant and sudden pleural pressure changes associated with major pleural pathologies, as well as therapeutic interventions may be associated with life-threatening complications. The pleural pressure may show two different values depending on the measurement method applied. These are called pleural liquid pressure and pleural surface pressure. It should also be realized that there are significant differences in pleural pressure distribution in pneumothorax and pleural effusion. In pneumothorax, the pressure is the same throughout the pleural space, while in pleural effusion there is a vertical gradient of approximately 1 cm H2O/cm in the pleural pressure associated with the hydrostatic pressure of the fluid column. Currently, two main methods of pleural pressure measurement are used: simple water manometers and electronic systems. The water manometers are conceptually simple, cheap and user-friendly but they only allow the estimation of the mean values of pleural pressure. The electronic systems for pleural pressure measurement are based on pressure transducers. Their major advantages include precise measurements of instantaneous pleural pressure and the ability to display and to store a large amount of data. The paper presents principles and details of pleural pressure measurement as well as the rationale for its use.

Modeling of conductivity relaxation in oxide ceramics taking account of concentration dependent chemical diffusivities and surface exchange coefficients

Conductivity relaxation of disk-shaped ceramic samples upon a sudden change of the oxygen partial pressure of the surrounding gas phase has been simulated by application of a three-dimensional finite element model. The geometry is based on a homogeneous cylindrical specimen with a diameter of 10mm and a thickness of 0.1mm, where four peripheral line contacts are attached to the sample in accordance with the van der Pauw method. Both the chemical diffusion coefficient and the chemical surface exchange coefficient are assumed to vary with the oxygen non-stoichiometry during the oxygen exchange reaction (oxidation or reduction). The alteration of the oxygen non-stoichiometry as well as the relaxation of the electrical conductivity are calculated simultaneously. The modeling of conductivity relaxation curves is applied to the SOFC cathode material La0.4Sr0.6FeO3−δ (LSF) at 900°C. The simulation of conductivity relaxation curves can be performed for arbitrary oxygen partial pressure changes. The present modeling approach allows the interpretation of significant differences between oxidation and reduction steps owing to the concentration (non-stoichiometry) dependence of the kinetic parameters.

Experimental study on the motion of a flexible hose net used for fish-harvesting in a set-net fishery

In a set-net fishery, a leader net and the related nets guide migratory fish into a box chamber net. Many workers have to visit the set-net and haul the box chamber net for harvesting almost every day, while the net-hauling operation in the early morning is dangerous. An automated net-hauling system using a flexible hose net has been proposed as a manpower-saving measure in such operation. The hose net comprises the brick forms of flexible hoses and is installed on the water bottom below the box chamber net. Compressed air is injected from one edge of the hose net to haul the box chamber net gradually, resulting in cornering fish in the other edge. The purpose of the present study is to observe the motion of the hose net and to analyze its formation in water current. Water tank testing was carried out using a 1/100 scale model of a set-net and a hose net. As a result, the middle part of the hose net was steep enough to corner fish in the end of the box chamber net. The two-dimensional formation of the hose net could be approximated by a catenary curve, while a part of the hose net including air inside was likely to have stiffness. The stiffness of the hose including air inside should be taken into account in the following water tank testing. The experimental results will provide the benchmark for the validation of the numerical model, which will be developed in the future. In addition, numerical analysis as well as water tank testing will reveal the tension on the hose net and mooring ropes for the basic design of the hose net in the future. For realizing the prototype of the hose net, special care should be taken for the explosion of air with decreasing pressure in the floating operation and for the leakage of air through the pinholes, which may be generated by sudden change in water pressure on the flexible hoses and their connectors.

Insight into the behavior of colloidal gas aphron (CGA) fluids at elevated pressures: An experimental study

Recently, colloidal gas aphron (CGA) fluids technology has been employed to drill depleted oil and gas reservoirs. Almost all reported experience on CGA fluids were conducted at ambient conditions, and little attention has been paid on the behavior of CGAs at high pressures which is more close to real conditions. In this study, high pressure experiments were conducted by using High Pressure Microscope cell to visualize/monitor the behavior of CGAs at elevated pressures. Single bubble behavior and bubble size distribution (BSD) of CGAs were investigated under different scenarios of pressure change. Results of experiments revealed that BSD of CGAs is controlled by the path of pressure changes, and sudden pressure change affects BSD less than stepwise changes in pressure. The pressure-volume product of bubbles, as a new criterion for analysis of single bubble behavior was introduced. The behavior of pressure-volume product for a single bubble shows significant loss of air via diffusion through tri-layer film into the bulk phase during compression as well as a hysteretic behavior during compression and decompression processes. Monitoring single bubble behavior at elevated pressures revealed that CGAs meet three distinct regions with time: first, they exhibited a sharp reduction in bubble size (region I), then became stable with minimum change in bubble diameter (region II), and finally, the size of bubbles decreased suddenly and after a short time they were collapsed (region III). Observations which showed aphrons were survived at pressures as high as 2000psig may support the idea for field applications of CGAs as drilling fluids. Results of this work may provide thorough insight into behavior of CGA fluids at elevated pressures.

Basic Methods for the Study of Reproductive Ecology of Fish in Aquaria.

Captive-rearing observations are valuable for revealing aspects of fish behavior and ecology when continuous field investigations are impossible. Here, a series of basic techniques are described to enable observations of the reproductive behavior of a wild-caught gobiid fish, as a model, kept in an aquarium. The method focuses on three steps: collection, transport, and observations of reproductive ecology of a substrate spawner. Essential aspects of live fish collection and transport are (1) preventing injury to the fish, and (2) careful acclimation to the aquarium. Preventing harm through injuries such as scratches or a sudden change of water pressure is imperative when collecting live fish, as any physical damage is likely to negatively affect the survival and later behavior of the fish. Careful acclimation to aquaria decreases the incidence death and mitigates the shock of transport. Observations during captive rearing include (1) the identification of individual fish and (2) monitoring spawned eggs without negative effects to the fish or eggs, thereby enabling detailed investigation of the study species' reproductive ecology. The subcutaneous injection of a visible implant elastomer (VIE) tag is a precise method for the subsequent identification of individual fish, and it can be used with a wide size range of fish, with minimal influence on their survival and behavior. If the study species is a substrate spawner that deposits adhesive eggs, an artificial nest site constructed from polyvinyl chloride (PVC) pipe with the addition of a removable waterproof sheet will facilitate counting and monitoring the eggs, lessening the investigator's influence on the nest-holding and egg-guarding behavior of the fish. Although this basic method entails techniques that are seldom mentioned in detail in research articles, they are fundamental for undertaking experiments that require the captive rearing of a wild fish.

Numerical simulations (2D) on the influence of pre-existing local structures and seismic source characteristics in earthquake-volcano interactions

Earthquake triggering of hydrothermal and volcanic systems is ubiquitous, but the underlying processes driving these systems are not well-understood. We numerically investigate the influence of seismic wave interaction with volcanic systems simulated as a trapped, high-pressure fluid reservoir connected to a fluid-filled fault system in a 2-D poroelastic medium. Different orientations and earthquake magnitudes are studied to quantify dynamic and static stress, and pore pressure changes induced by a seismic event. Results show that although the response of the system is mainly dominated by characteristics of the radiated seismic waves, local structures can also play an important role on the system dynamics. The fluid reservoir affects the seismic wave front, distorts the static overpressure pattern induced by the earthquake, and concentrates the kinetic energy of the incoming wave on its boundaries. The static volumetric stress pattern inside the fault system is also affected by the local structures. Our results show that local faults play an important role in earthquake-volcanic systems dynamics by concentrating kinetic energy inside and acting as wave-guides that have a breakwater-like behavior. This generates sudden changes in pore pressure, volumetric expansion, and stress gradients. Local structures also influence the regional Coulomb yield function. Our results show that local structures affect the dynamics of volcanic and hydrothermal systems, and should be taken into account when investigating triggering of these systems from nearby or distant earthquakes.

Simultaneous observations of traveling convection vortices: Ionosphere‐thermosphere coupling

AbstractWe present simultaneous observations of magnetosphere‐ionosphere‐thermosphere coupling over Svalbard during a traveling convection vortex (TCV) event. Various spaceborne and ground‐based instruments made coordinated measurements, including magnetometers, particle detectors, an all‐sky camera, European Incoherent Scatter (EISCAT) Svalbard Radar, Super Dual Auroral Radar Network (SuperDARN), and SCANning Doppler Imager (SCANDI). The instruments recorded TCVs associated with a sudden change in solar wind dynamic pressure. The data display typical features of TCVs including vortical ionospheric convection patterns seen by the ground magnetometers and SuperDARN radars and auroral precipitation near the cusp observed by the all‐sky camera. Simultaneously, electron and ion temperature enhancements with corresponding density increase from soft precipitation are also observed by the EISCAT Svalbard Radar. The ground magnetometers also detected electromagnetic ion cyclotron waves at the approximate time of the TCV arrival. This implies that they were generated by a temperature anisotropy resulting from a compression on the dayside magnetosphere. SCANDI data show a divergence in thermospheric winds during the TCVs, presumably due to thermospheric heating associated with the current closure linked to a field‐aligned current system generated by the TCVs. We conclude that solar wind pressure impulse‐related transient phenomena can affect even the upper atmospheric dynamics via current systems established by a magnetosphere‐ionosphere‐thermosphere coupling process.

Infrasound detection of meteors

Meteorites that penetrate the atmosphere generate infrasound waves of very low frequency content. These waves can be detected even at large distances. In this study, we analyzed the infrasound waves produced by three meteors.The October 7, 2008 TC3 meteor fell over the north Sudan Nubian Desert, the February 15, 2013 Russian fireball, and the February 6, 2016 Atlantic meteor near to the Brazil coast.The signals of these three meteors were detected by the infrasound sensors of the International Monitoring System (IMS) of the Comprehensive Test Ban Treaty Organization (CTBTO). The progressive Multi Channel Technique is applied to the signals in order to locate these infrasound sources. Correlation of the recorded signals in the collocated elements of each array enables to calculate the delays at the different array element relative to a reference one as a way to estimate the azimuth and velocity of the coming infrasound signals. The meteorite infrasound signals show a sudden change in pressure with azimuth due to its track variation at different heights in the atmosphere. Due to movement of the source, a change in azimuth with time occurs. Our deduced locations correlate well with those obtained from the catalogues of the IDC of the CTBTO.

Role of Steam Explosion on Enzymatic Digestibility, Xylan Extraction, and Lignin Release of Lignocellulosic Biomass

This work studies the contribution of each step of the steam explosion (residence time and sudden decompression) of wheat straw. Raw wheat straw and wheat straw with different degrees of xylan extraction were subjected to a steam explosion without residence time at 160, 180, 200, or 220 °C, in order to identify the individual contribution of the sudden pressure change upon enzymatic digestibility, xylan extraction, and lignin release. In addition, the contribution of the residence time of the biomass in the reactor before the explosion was estimated using pretreated biomass prepared by autohydrolysis at 180–220 °C with a residence time of up to 56 min. Results show that steam explosion alone does not have significant effects on digestibility, xylan extraction, or lignin release of raw wheat straw. For autohydrolyzed biomass, steam explosion of 200 °C and above increases glucose release after 72 h of enzymatic hydrolysis at an enzymatic dose of 22 mg protein/g substrate. Digestibility at several enzymatic ...