Pressure Research Articles

A collisional-radiative model for atmospheric-pressure low-temperature air discharges

Plasma-assisted combustion technology has been a hot spot in aero-engines and scramjet-engines. The electron density is a key discharge parameter related to the active-particle density. The latter has been considered playing an important role in the above applications by the kinetic effect. In this work, an atmospheric pressure air plasma collisional-radiative model considering the excited states of atomic nitrogen and oxygen is built based on previous widely kinetic investigations of molecules and radicals, as well as their excited states. The excited states, especially the atomic nitrogen and oxygen states were less investigated in previous works. The emission intensity distributions from the model have a good agreement with those measured in the glide arc plasma with two discharge modes, as well as the microwave plasma. Based on the kinetics of molecular and atomic emitting states, the line-ratio method is presented to determine the electron density. The N2(337 nm)/O(844 nm) and N2(337 nm)/NO(γ) line ratios are used for the glide arc plasma and microwave plasma torch, respectively. Besides, the kinetics of the excited states involved with two line-ratios are also investigated in the two types of discharges. Combined with the atmospheric pressure actinometry method, the kinetic effect of the plasma-assisted combustion can be revealed quantitatively in the future.

Impact of overvoltage on the mode transition of the spark gap switch: from edge breakdown to stochastic breakdown

Abstract Spark gap switch (SGS) is a fundamental but critical component for large-scale pulsed power devices, whose reliable operation is significantly affected by the breakdown characteristics of SGS. It is observed experimentally that, with the increase of overvoltage, the bridging position of the spark channel transits from edge to stochastic center. In this work, the influence of overvoltage on the breakdown process of a parallel-plate SGS with low geometric distortion of static electric field (<13%) between an atmospheric-pressure air gap of 5 mm is investigated by particle-in-cell/Monte Carlo collision simulation. It is found that, under a low overvoltage (ratio of applied voltage U a to static breakdown voltage U 0, U a/U 0 = 1.5), the streamers at the edge first bridge the gap before that in the central region, due to the field enhancement induced by the electrode curvature. Under higher overvoltage (U a/U 0 = 3), the synchronicity between streamers initiating from the center and those from the edge is greatly improved during the inception stage. After the streamers pass the middle of the gap, the field enhancement at the streamer front is more intensified and promotes the generation of fast electrons. These fast electrons rapidly magnify the difference among the propagating streamers by providing abundant seed electrons ahead of the discharge channel, which leads to the randomness of the bridging position. The results in this work demonstrate the relationship between overvoltage and streamer dynamics, which is beneficial for the performance improvement of SGS.

Adaptive servo-ventilation for the treatment of intrathecal baclofen-induced central sleep apnea: A case report.

Baclofen is a common muscle relaxant agent used in a number of neurological disorders acting at central level and potentially causing adverse respiratory events, still largely unknown at therapeutic doses. We present the case of a young woman with spastic tetraparesis secondary to perinatal asphyxia treated with a standard dose of intrathecal baclofen who developed nocturnal symptoms, somnolence and memory loss during the day. Nocturnal cardio-respiratory sleep monitoring showed a high number of central sleep apneas (CSA). The patient was adapted and treated with a positive air pressure device, Adaptative Servo-Ventilator, specific designed to treat CSA particularly in patients with heart failure. The treatment was well tolerated and within few days CSA was reversed. The patient reported a feeling of restful sleep and disappearance of morning tiredness. The efficacy of the treatment was verified with nocturnal cardio-respiratory monitoring after 2 months and complete resolution of all symptoms was also confirmed.

Natural fibers as promising core materials of vacuum insulation panels

To reduce energy consumption in buildings, this paper investigates the feasibility of using natural fibers as cost-effective, environmentally sustainable core materials for vacuum insulation panels (VIPs). First, a comprehensive experimental study was conducted for 10 potential natural fiber candidates. The thermal conductivities of the 10 natural fiber mats at various vacuum pressures were measured; their compression and morphology properties were quantified. In addition, an analytical model was used to explore the major factors that influence the thermal conductivity of natural fibers as a function of internal air pressure. Results show that recycled cotton, kapok, and bamboo fibers are ideal candidates for VIP core materials; at <0.05 Pa, their thermal conductivities varied between 2 and 4 mW/(m⋅K). Furthermore, for some fibers, thermal conductivity was inversely proportional to fiber density. For the selection of fiber materials for VIP cores, the ideal fiber candidate has a small fiber diameter and a low fiber mat density. Based on thermal measurements, even though the internal air pressure of 5 Pa was enough to attain the minimum thermal conductivity, obtaining internal air pressure below 5 Pa is recommended for prolonged service life, considering small leaks of VIP package barrier films and potential off-gassing from fibers. The simulation results predicting the effective thermal conductivities matched the experimental results well. These findings indicate that natural fiber–based VIPs have the potential to be a sustainable, inexpensive alternative to the current technologies in building insulation materials.

Rapid-response, low-detection-limit, positive-negative air pressure sensing: GaN chips integrated with hydrophobic PDMS films

Despite the importance of positive and negative pressure sensing in numerous domains, the availability of a single sensing unit adept at handling this dual task remains highly limited. This study introduces a compact optical device capable of swiftly and precisely detecting positive and negative pressures ranging from −35 kPa to 35 kPa. The GaN chip, which serves as a core component of the device, is monolithically integrated with light-emitting and light-detecting elements. By combining a deformable PDMS film coated with a hydrophobic layer, the chip can respond to changes in optical reflectance induced by pressure fluctuations. The integrated sensing device has low detection limits of 4.3 Pa and −7.8 Pa and fast response times of 0.14 s and 0.22 s for positive and negative pressure variations, respectively. The device also demonstrates adaptability in capturing distinct human breathing patterns. The proposed device, characterized by its compactness, responsiveness, and ease of operation, holds promise for a variety of pressure-sensing applications.

Unveiling the enigmatic connection: Belly dancer's dyskinesia as an unusual manifestation of normal pressure hydrocephalus: A case report.

Normal pressure hydrocephalus is rarely associated with Belly dancer's dyskinesia and seizure. Belly dancer's dyskinesia (BDD) is characterized by bilateral, sluggish, involuntary, repetitive, and rhythmic motions of the anterior abdominal wall. We present a rare case of a 78-year-old man diagnosed with normal pressure hydrocephalus associated with BDD and seizure who presented with left-sided weakness of the body and abnormal body movements.

Normal pressure hydrocephalus treatment: is it time to rethink?

Normal pressure hydrocephalus treatment: is it time to rethink?

The effectiveness of various CSF diversion surgeries in idiopathic normal pressure hydrocephalus: a systematic review and meta-analysis

Idiopathic normal pressure hydrocephalus (iNPH) is commonly treated using cerebrospinal fluid (CSF) diversion procedures, most commonly ventriculoperitoneal (VP) but also lumboperitoneal (LP), ventriculoatrial (VA) shunting, and endoscopic third-ventriculostomy (ETV). Despite the prevalence of these interventions and recent advancements in iNPH diagnostic processes, there is limited up-to-date evidence regarding surgical outcomes. A systematic review and meta-analysis were conducted to analyse the effects of CSF diversion surgeries among iNPH patients. The primary outcome was efficacy of the CSF diversion procedure, defined as symptomatic improvement, and secondary outcomes included surgical complications. Several major databases were searched for original studies from inception up to June 4, 2024, which were evaluated using random-effects meta-analyses, meta-regression, and influence analyses. This study was registered with PROSPERO: CRD42023458526. Out of the 1963 studies screened, 54 were included in this review, and 4811 patients were pooled. Overall, more than 74% of patients experienced improvement after surgical treatment (95% CI: 70-78%). VP shunting demonstrated an efficacy of 75% (95% CI 70-79%), VA shunting at 75% (95% CI: 70-80%), and LP shunting at 70% (95% CI: 52-83%). ETV had a success rate of 69% (95% CI: 58-78%). Gait improvement was high at 72% (95% CI: 67-77%), while urinary and cognitive dysfunction each improved in approximately 50% of patients. The efficacy of surgery did not increase between 2005 and 2024 (p=0.54). Complications occurred in 20.6% of cases, with a surgery revision rate of 15.1%. This meta-analysis found that the overall efficacy of CSF diversion procedures for iNPH remained unchanged from 2005 to 2024, with 74% of cases showing improvement. No procedure was found to be clearly superior, and only half of the patients saw improvements in urinary and cognitive dysfunction. The stagnant efficacy over time and frequent complications highlight the need for improved patient selection criteria to best identify those most likely to benefit from CSF shunting. None for this study.

Pathophysiology of Normal Pressure Hydrocephalus

The current perspective for the pathophysiology of normal pressure hydrocephalus is focusing on stiffness of the central nervous tissue, especially on a type of cerebrovascular disorder. Rigid intracranial vessels and tissues derived by either vascular risk factors or aging may lead into impaired dynamics of the cerebrospinal fluid such as increased pulsatility and decreased absorption of the cerebrospinal fluid. Enlarged ventricle may result in a decrease of blood perfusion in brain parenchyma, and in turn global hypoxia and neuro-inflammation along with a breakdown of the blood-brain-barrier. Deterioration of the glymphatic pathway, the crucial disposal pathway of the waste product of the brain, also might contribute to the irreversible injury of the nervous tissue by deposition of abnormal toxic proteins including amyloid beta. Of note, the pathophysiology of the normal pressure hydrocephalus is moving to a type of cerebrovascular disorder instead of the etiology of idiopathic.

HEART RATE VARIABILITY IN OFFSPRING OF NORMOTENSIVE AND HYPERTENSIVE PARENTS: A COMPARATIVE STUDY

Objective: This study aims to evaluate the differences in heart rate variability (HRV), a biomarker of autonomic nervous system, between offspring of normotensive and hypertensive parents to understand the genetic predisposition of autonomic dysfunction. Methods: This study was a cross-sectional observational study.Two groups of healthy adults, offspring of parents with hypertension (n = 50) and offspring of parents with normal blood pressure (n = 50). Short-term HRV was measured using 5-minute electrocardiogram (ECG). HRV indices such as time and frequency domainwere measured. Data were compared by using independent t-tests, with p &lt; 0.05 being considered as statistically significant. Results:The offspring of parents with hypertension showed significantly lower HRV, with SDNN (30.5 ± 8.2 ms) compared to offspring of parents with normal blood pressure (45.2 ± 7.1 ms, p &lt; 0.001). RMSSD also was significantly lower in offspring of hypertensive group. Low-frequency (LF) power was higher in offspring of parents with hypertension,while high-frequency (HF) power was significantly reduced in them compared to the normotensive group. The LF:HF ratio was higher in offspring of parents with hypertension (2.80 ± 0.85) compared to the normotensive group (1.40 ± 0.60, p &lt; 0.001), indicating sympathovagal imbalance. Conclusion: Offspring of parents with hypertension hadlower HRV, suggesting autonomic dysfunction even in the absence of clinical hypertension. These findings emphasize the potential role of genetic predisposition in the early onset of autonomic dysregulation Further studies are required to understand mechanisms contributing to these differences in HRV.

Design player robot badminton-based microcontroller

Robots are one of the technologies that is currently advancing quickly. Generally speaking, a robot's movement is similar to that of an automobile; it can only move forward, backward, left, and right. Because the movement is controlled by these movements, it is thought that the robot's movement is extremely restricted to the left and right directions. solely with the front wheels. As a result, a robot was developed in this study that can control sliding motions to the left and right utilizing omniwheels on its front and back wheels. Badminton is a sport involving rackets that is played by two people or two opposing pairs. Robotic badminton players are employed as a substitute for human trainers in the training process, particularly for service and drive motions. With the use of a wireless joystick, the robot's ATMega 8535 microprocessor controls both the robot's direction of motion and the movement of its racket. Using a double acting pneumatic cylinder that requires 7 bar of air pressure, the robot service arm uses the compressor's air pressure. The average time it takes for the racket to strike the ball at 7 bar of wind pressure is 00:5.2 seconds. The time it takes for the ball to fall onto the racket in the absence of wind pressure is 00:28 seconds on average. A difference value of 00:22.7 seconds is acquired, and this value will be utilized as the programming reference delay. The robot encounters a slope with an average angle change of 7º when moving forward, an average angle change of 10º when moving backward, an average angle change of 5.2º when moving right, and an average angle change of 3º when moving left. The uneven field surface causes the robot to move at a slope, which modifies the speed of the motor on the wheels

Correlation between subretinal tissue plasminogen activator and air injection rates with pressure in a retina mimicking model

By investigating the correlation between the injection rate and pressure of subretinal tissue plasminogen activator (tPA) and air using a standard Viscous Fluid Control (VFC) system with a 38-gauge cannula, we aimed to establish guidelines for stable injections. We fabricated a retina mimicking model (RMM) with 0.25% agarose solution and an aluminum plate, and substituted submacular hemorrhage (SMH) and tPA with blood-mimicking fluid (BMF) and balanced salt solution (BSS), respectively. The diameter of the pre-bleb mimicking SMH in RMM was 1.30 ± 0.16 cm, increasing to 1.98 ± 0.24 cm and 1.83 ± 0.22 cm after bleb propagation with BSS and air, respectively. BSS injection rates were 2.86 ± 0.04 µl/sec, 6.74 ± 0.48 µl/sec and 8.55 ± 0.16 µl/sec at 8, 12, and 16 psi, respectively. Air injection rates were 37.98 ± 3.11 µl/sec, 79.01 ± 5.13 µl/sec and 156.06 ± 13.72 µl/sec at 2, 3 and 4 psi, respectively. By experimenting with different pressures in the RMM, we found 12 psi to be the minimum for proper BSS injection and 2 psi for air. These findings provide crucial parameters for safer surgery to prevent irreversible damage.

Evaluation of Machine Learning Application on the Prediction of Particulate Matter Concentrations in Small/Medium-Sized City

Objectives:In this study, Machine Learning (ML) algorithms were evaluated to predict the concentration of particulate matter (PM10 and PM2.5) using air quality and meteorological data in small/medium-sized city.Methods:ML models, including Multiple Linear Regression (MLR), Decision Tree Regression (DTR), Random Forest (RF), Extreme Gradient Boosting (XGB), Light Gradient Boosting Machine (LGB), were used to predict PM10 and PM2.5 concentrations. Five air quality variables, including NO2, SO2, CO, PM10 and PM2.5, and seven meteorological variables, including temperature, humidity, vapor pressure, wind speed, precipitation, local atmospheric pressure, and sea-level atmosphere pressure, were collected from three air quality monitoring stations and one meteorological observatory from 2017 to 2022. A total of 52,583 sets of data were used for ML. The prediction accuracies of the applied ML models were evaluated using the Root Mean Squared Error (RMSE), Mean Absolute Error (MAE), and Coefficient of determination (R2).Results and Discussion:Higher ML performance was obtained when using the data including PM10 and PM2.5 compared to the data excluding these variables. Among five different ML models, the XGB model showed the highest accuracy in predicting PM10 and PM2.5 one hour in the future. However, poorer performance was obtained as the predicted period increased from one hour to 72 hours.Conclusion:The application of ML algorithms for the short-term prediction of PM10 and PM2.5 was successful in this study. However, more input variables and deep learning algorithms are needed for long-term prediction of PM10 and PM2.5.

Effect of steam curing regime on the mechanical properties, drying shrinkage, and microstructure of mortar in high-altitude areas with low air pressure

Low air pressure in plateau regions impacts the microstructure and macroscopic properties of cement-based materials by altering water transport. However, the efficiency of steam curing, a frequently-used curing approach, under these conditions has been inadequately studied. This work compares the effects of steam curing on the mechanical properties, drying shrinkage, and microstructure of cement-based materials at low air pressure. Results show that low air pressure decreases the compressive strength and increases the drying shrinkage of steam-cured mortar due to reduced hydration and increased total pore volume. Optimally, a steam curing temperature of 40°C to 60°C minimizes thermal damage, and a pre-curing time of 3 hours yields the best mechanical properties and drying shrinkage. Additionally, a field case confirms the effectiveness of the proposed steam curing regime; the demolding strength of precast beams meets engineering standards, and drying shrinkage fluctuates significantly with daily temperature changes. Notably, a 25.30 % difference in 90-day drying shrinkage between steam-cured and non-steam-cured specimens underscores the necessity of steam curing in high-altitude areas. These findings are crucial for optimizing steam curing practices in low-pressure environments.

Meteotsunami Impact in Indonesia Due to the Shockwave of the Hunga Tonga Volcanic Eruption on January 15, 2022

This paper presents the impact of a meteotsunami resulting from the shockwave of the underwater volcanic eruption of Hunga Tonga­–Hunga Ha'apai (HTHH) on January 15, 2022.The tsunami was detected in various locations in Indonesia through a network of water level sensors monitored by the Meteorology, Climatology, and Geophysics Agency (BMKG). The tsunami wave heights varied significantly and exhibited a non-linear relationship with the distance from the volcano. The heights of detected tsunami ranged from 2.8 to 22.6 cm, with the highest recorded at the water level sensor south of Java Island. The heights of waves are believed influenced by Proudman resonance in the Indian Ocean waters beside the local amplification effect. The average period of the tsunami waves was approximately 40 minutes, exceeding five days. The tsunami was triggered by the coupling effect between the shockwave with a velocity of 312 m/s and the sea surface. The air pressure anomalies due to the shockwave ranging from 1.2 to 2.2 hPa. Throughout Indonesian waters, this meteotsunami phenomenon did not have a significant impact.

Optimizing Precipitation Forecasting and Agricultural Water Resource Allocation Using the Gaussian-Stacked-LSTM Model

Our study investigates the use of machine learning models for daily precipitation prediction using data from 56 meteorological stations in Jilin Province, China. We evaluate Stacked Long Short-Term Memory (LSTM), Transformer, and Support Vector Regression (SVR) models, with Stacked-LSTM showing the best performance in terms of accuracy and stability, as measured by the Root Mean Square Error (RMSE). To improve robustness, Gaussian noise was introduced, particularly enhancing predictions for zero-precipitation days. Key predictors identified through variable attribution analysis include temperature, dew point, prior precipitation, and air pressure. Additionally, we demonstrate the practical benefits of precipitation forecasts in optimizing water resource allocation. A prediction-based strategy outperforms equal distribution in managing resources efficiently, as shown in a case study using 2022 Beidahu data. Overall, our research advances precipitation forecasting through deep learning and offers valuable insights for water resource management.

A prospective cohort study investigating the association between type 2 diabetes and subsequent cardiovascular events in patients with different blood pressure, HbA1c, and lipid levels.

Globally, there has been a steady increase in the prevalence of type 2 diabetes, and the risk of cardiovascular disease has increased. The relationship between diabetes and the incidence of cardiovascular disease (CVD) at different blood pressure, glycated haemoglobin A1c (HbA1c), and lipid levels remains uncertain. This study aimed to investigate these associations within a population-based cohort. We analysed data from the Guiyang subcentre of the China Cardiometabolic Disease and Cancer Cohort Study, which enrolled participants aged 40 years and older between 2011 and 2012. Subsequently, a follow-up visit was conducted during 2014-2016 to assess incident CVD events. The analysis included a cohort of 7197 adults, of whom 590 were diagnosed with diabetes. Among all the participants, the CVD events linked to diabetes had a multivariable adjusted hazard ratio of 2.37 [95% confidence intervals (CI): 1.38-4.08]. Patients with diabetes had a greater risk of experiencing CVD events if they had high blood pressure [hazard ratios (HR): 1.24, 95% CI: 1.39-4.21] and high lipid levels (HR: 2.19, 95% CI: 1.29-3.70) compared to people with normal blood pressure (HR: 1.23, 95% CI: 0.54-2.82) and lipid levels (HR: 1.26, 95% CI: 0.47-3.41). Our analysis revealed a significant association between diabetes and an increased risk of subsequent CVD events, which can be mitigated through optimal management of the metabolic profile of cardiovascular risk factors.

Design of Positive Pressure Re-Acceleration Assisted Seeding Mechanism for Corn Based on CFD-EDEM Gas-Solid Coupling Simulation

This study proposes a positive pressure re-acceleration assisted seeding mechanism and analyzes the motion mechanism of corn seeds during the seeding process. By employing the CFD-EDEM gas-solid coupling simulation analysis method, the fluid characteristics, initial ejection velocity of seeds, seed dropping time difference, and sowing position difference in the seeding mechanism under different structural parameters of the air pressure valve body were investigated. The optimal structural parameters of the air pressure valve body were determined (nozzle gap c = 0.6 mm, throat constriction diameter d = 16 mm, and throat constriction length l = 44 mm). A multi-factor experimental method was used to explore the effects of airflow pressure, forward speed during sowing, and sowing distance on sowing performance, aiming to identify the optimal working parameters for the positive pressure re-acceleration seeding mechanism. High-speed camera technology was used to record and analyze the seed movement process. The results indicate that an increase in positive pressure within the seed guide tube shortens the sowing time of corn seeds, reduces the coefficient of variation of seed dropping time difference, and effectively improves the consistency of sowing distance. The optimal parameters are a forward speed of 8 km/h, sowing distance of 20 cm, airflow pressure of 10 kPa, with a sowing distance coefficient of variation of 7.56%, and a seed dropping time difference coefficient of variation of 5.35%.

Research on the influencing factors of the difference in warming rates between the east, west and central regions of North America during the 21st century

Temperature in North America (NA) is a significant focus of current climate change research. This study focuses on various climate variables and employs linear regression and correlation coefficient analysis to examine the factors influencing the differences in warming rates across the eastern, western, and central regions of NA in the 21st century, as well as the correlations between these factors and temperature. Results indicate that NA temperatures are rising with notable regional variations in warming rates. Under the influence of cloud cover, the impact of precipitation on warming rates is relatively minor, whereas radiation significantly affects warming rates. Additionally, sea level pressure influences wind patterns, thereby significantly impacting warming rates. This study highlights the complexity of regional climate dynamics in NA and provides deep insights into regional climate differences.

Effect of DASH vs. Mediterranean diet on metabolic syndrome and cardiometabolic profile in adults with high normal blood pressure or grade 1 hypertension: the DASH-MedDiet randomized controlled trial

Abstract Background Lifestyle interventions are recommended as the first-line treatment to control metabolic syndrome components and improve cardiometabolic profile. However, studies directly comparing the effects of the Dietary Approaches to Stop Hypertension (DASH) vs. the Mediterranean diet (MedDiet) on metabolic syndrome prevalence and cardiometabolic risk factors are currently lacking. Purpose We aimed to assess the effects of a 3-month intensive dietary intervention implementing salt restriction either alone or on top of the DASH and MedDiet compared to no/ minimal intervention on metabolic syndrome prevalence and cardiometabolic profile in never drug-treated adults with high normal blood pressure (BP) or grade 1 hypertension. Methods We randomly assigned individuals to the control group (CG, n = 60), salt restriction group (SRG, n = 60), DASH diet with salt restriction group (DDG, n = 60), or MedDiet with salt restriction group (MDG, n = 60). All patients were followed monthly for 3 months in individual sessions coordinated by the clinical dietician. For the patients of all four study groups, the goal was to maintain the initial body weight unchanged. Patients in the CG received general advice on dietary principles for BP control. For the patients in all three intervention groups, the goal was to limit sodium intake to 2,000 mg/ day (equivalent to 5,0g salt/ day). In addition, patients in the DDG and the MDG received an individualized dietary plan with six daily sample menus to facilitate the adoption of the assigned dietary pattern. Anthropometric indices, dietary intake, office BP, and fasting blood samples were evaluated pre- and post-intervention. Results According to the intention-to-treat analysis, at 3 months post-intervention, the DDG and the MDG had lower odds ratio (OR) (95% CI) of metabolic syndrome [0.29 (0.12, 0.72), and 0.15 (0.06, 0.41), respectively] compared to the CG. Moreover, the MDG had lower odds of elevated BP levels compared to both the DDG and the SRG [0.08 (0.03, 0.19), and 0.13 (0.05, 0.34), respectively], and lower odds of metabolic syndrome compared to the SRG [0.25 (0.09, 0.67)]. In addition, the DDG and the MDG had lower odds of elevated fasting glucose compared to both the CG and the SRG, whereas the study groups did not differ regarding the odds of elevated waist circumference, elevated triglycerides, and reduced HDL- cholesterol. Regarding cardiometabolic indices, total and LDL-cholesterol, fasting glucose, HbA1c, and systolic/ diastolic BP were reduced in all three intervention groups compared to the CG. Conclusions On a background of salt restriction, the MedDiet was superior in BP reduction, but the DASH and MedDiet reduced the prevalence of metabolic syndrome to the same extent.