Pressure Difference Research Articles

Placental Pathology and Blood Pressure at Age 7: A Longitudinal Discordant Twin Analysis.

Evidence suggests that the intrauterine environment shapes offspring cardiovascular disease risk. Although placental dysfunction may be an important pathophysiologic pathway, numerous parental and pregnancy characteristics that influence offspring blood pressure are strong confounders of the mechanistic role of the placenta in observational analyses of singletons. Therefore, we leverage twin- and sibling-based comparison designs to determine whether placental pathology is associated with offspring blood pressure at age 7 while mitigating major sources of confounding. Data are from pregnant participants and their offspring in the Collaborative Perinatal Project, a longitudinal pregnancy cohort conducted from 1959 to 1965 in the United States. After delivery, placentas were systematically examined for lesions indicative of maternal vascular malperfusion (MVM) and acute inflammation. Blood pressure was assessed at a follow-up research visit when the offspring were 7 years old. Linear fixed-effects models were used to estimate associations between within-twin or sibling discordance in placental pathology and differences in blood pressure at age 7. Overall, 193 twin pairs were eligible for inclusion, and 23.3% had placentas discordant for MVM. In a fixed-effect analysis, a twin with high-grade MVM had a higher systolic blood pressure Z score by 0.56 SDs than their co-twin without MVM (95% CI, 0.06-1.05) or a 5.7-mm Hg difference (95% CI, 0.6-10.8). Associations were consistent in a sensitivity analysis restricted to dichorionic twins and in a secondary analysis of 759 MVM-discordant sibling pairs. Acute placental inflammation was not associated with blood pressure at age 7. MVM in the placenta is associated with higher offspring blood pressure in mid-childhood, independent of parental and pregnancy characteristics that twins have in common. The findings support the role of the placenta and the intrauterine environment in the developmental origins of cardiovascular health.

Effects of salt substitute on urinary electrolytes and blood pressure in a real-world setting—cohort study in Hunan, China

Background and aimsSalt substitute is considered an effective strategy to reduce sodium and increase potassium intake and thereby lower blood pressure in China, but its benefits and risks are uncertain in real-world data. This study is designed to compare the difference in the 1-year efficacy of salt substitute and salt restriction on urinary electrolytes and blood pressure.Methods and resultsA total of 2,929 and 2,071 participants with the 24-h estimated urinary sodium excretion (eUNaE) above 2.36 g/d using salt substitute (SS) and salt restriction (SR) strategies, respectively, were followed for 1 year. Salt substitute users were further divided by potassium chloride (KCl) content (13% vs 25%) and duration (9–11 vs 12 months). The 24-h eUNaE and estimated urinary potassium excretion (eUKE) levels were calculated using the Kawasaki formula from spot urine sample. The SS group (n = 1,897) had lower eUNaE (3.82 ± 1.03 vs 4.05 ± 1.01 g/day, p < 0.01) than the SR group (n = 1,897) after 1 year. Both 13 and 25% KCl substitutes reduced eUNaE versus restriction (p < 0.05). The SS group had a higher eUKE than the SR group (2.09 ± 0.43 vs 1.71 ± 0.62 g/day, p < 0.01). The eUKE was higher with 25% versus 13% KCl substitutes, while the Na/K was lower with 25% versus 13% KCl substitutes (p < 0.05). No significant blood pressure differences occurred between the SS and SR groups (p > 0.05), whereas 25% KCl exposure was related to a lower level of SBP, regardless of whether it was compared with SR or 13% KCl.ConclusionCompared with salt restriction, salt substitute results in more sodium reduction and greater potassium increase. In spite of this, it does not result in better control of blood pressure, especially for the group receiving 13% KCl.

Pressure Difference Measuring System for Clean Rooms

This article presents the development and implementation of a pressure difference measuring system tailored for clean rooms, essential in medical facilities to control airflow and reduce nosocomial infections. The study evaluates various pressure sensors, leading to the selection of intelligent sensors that meet specific performance criteria. Key features and operating principles of the system are outlined, including sensor types, measurement techniques, and system architecture. A detailed comparison of sensors such as BMP180 and BMP280 highlights their suitability based on parameters like resolution, power consumption, and communication interfaces. The system’s structure includes dual pressure sensor units connected to a main control unit, enabling real- time pressure monitoring across different room zones. The sensors, equipped with a microcontroller for initial data processing, relay information to the control unit for further analysis and display. Designed with a calibration feature, the system ensures measurement accuracy by allowing recalibration under identical atmospheric conditions. Operating on low voltage, the system provides safe and reliable performance with applications extending to isolation rooms and environments requiring precise pressure regulation. Integrating the measuring system with ventilation systems significantly mitigates the risk of airborne disease transmission, contributing to the maintenance of sterile environments. The article concludes that this cost-effective, intelligent pressure monitoring solution not only enhances safety in healthcare settings but also supports regulatory compliance and improves overall infection control measures in high-risk areas.

Does pre-existing differential pressure have an impact on poroelastic compressibilities?

The existing formulation of quasistatic poroelasticity for saturated porous materials relies on the assumption that differential pressure, defined to be the difference between the confining and liquid pressures, is zero at the reference state. This as- sumption can be problematic in problems involving swelling media, such as clay, and deep underground where pre-existing pore pressure may differ from the total pressure. Here, the quasistatic poroelastic equations are derived from only the conservation of mass for each phase and the Terzaghi effective stress principle for the case when there is a nonzero reference differential pressure. In the process, a dynamic equation for the porosity is derived, and one additional parameter representing a dimensionless reference differential pressure is introduced. Although the form of the quasistatic poroelastic equations remains the same, the poroelastic compressibilities change with the reference state’s nonzero differential pressure. The changes to these compressibil- ities are systematically outlined, and the impact on more specific classes of material are examined. The altered compressibilities imply, among other changes, that the compressional velocity is a function of the pre-existing differential pressure, which is useful to account for in dynamic measurements, but that the dependence is weak for materials with low compressibilities.

Association between youth blood pressure and exposure to pediatric fruit and vegetable prescriptions.

Health impacts of pediatric fruit and vegetable prescription programs (FVPPs) are unclear. This study assessed whether exposure to an FVPP that provided $15 produce prescriptions during pediatric visits was associated with differences in child diet, food security, physical activity, weight status, and blood pressure. This cross-sectional analysis included data from caregiver-child dyads with varying levels of exposure to the FVPP. Dyads completed surveys at pediatric offices. Trained research assistants measured height and weight of children and recorded blood pressure through chart review. Causal inference analyses using propensity score adjustments compared outcomes of exposure groups. 680 dyads enrolled. Youth who received ≥1 prescription (exposed) reported greater physical activity compared to youth who received no prescriptions (unexposed). Blood pressure percentiles were lower among exposed when compared to unexposed youth (63.273 versus 75.060 for SBP; 71.472 versus 77.548 for DBP); and fewer exposed children recorded elevated blood pressure when compared to unexposed (0.141 versus 0.343 for SBP; 0.199 versus 0.344 for DBP; and 0.286 versus 0.531 overall). Similar findings were obtained using duration as a measure of exposure. Youth exposed to the FVPP experienced greater physical activity and healthier blood pressure. Findings may indicate novel health-promoting effects of pediatric FVPPs. When compared to youth with no exposure, youth exposed to a pediatric fruit and vegetable prescription program recorded greater physical activity and healthier blood pressure. Youth with high exposure (≥24 months) to the fruit and vegetable prescription program experienced greater physical activity and healthier blood pressure when compared to youth with low exposure (<24 months). This extends evaluation of pediatric fruit and vegetable prescription programs beyond feasibility and preliminary effectiveness to indicate potential of such programs in positively influencing physical activity and blood pressure of participating youth. Findings indicate novel health-promoting effects of pediatric fruit and vegetable prescription programs.

Smooth Muscle Mechanosensitivity Generates and Maintains Pressure Gradients Across the Intestine.

The gut, the ureter, or the Fallopian tube all transport biological fluids by generating trains of propagating smooth muscle constrictions collectively known as peristalsis. These tubes connect body compartments at different pressures. We extend here Poiseuille's experiments on liquid flow in inert tubes to an active, mechanosensitive tube: the intestine. We use as a miniature myogenic peristaltic pump model, the fetal chicken gut, and measured the flow and contractile wave propagation as a function of the initially applied pressures and pressure gradients. We dissect the molecular pathways of smooth muscle mechanosensitivity by measuring the force generated by gut rings in different pharmacological conditions. We demonstrate that smooth muscle contractions in response to stretch or pressure is mediated by L-type Ca2+ channels and IP3 receptors. We show that this positive-feedback mechanosensitive behavior can spontaneously generate pressure gradients across gut segments initially subject to equal pressure; this same mechanism tends to stabilize initially applied pressure gradients; it can act jointly or compete with the pressure gradient induced by directional peristaltic waves. We demonstrate that high pressure differentials can reverse the physiological propagation direction of contractile waves imparted by interstitial cell of Cajal pacemaker activity. We find that flow rate increases with tube length, but that the maximum pressure differential generated depends solely on smooth muscle contractile force and on the initial resting pressure applied inside the organ. We provide fundamental mechanical and hydrodynamic insight into the myogenic mechanisms of transport in the gastrointestinal tract. We scale up our results to other human peristaltic organs and discuss their implications for pathophysiology of intestinal obstruction, vesicoureteral reflux and endometriosis.

Numerical investigations on the start-Up characteristics and heat transfer performance of a single-loop oscillating heat pipe with different surface wettable vertical tubes

Abstract The heat transfer performance of an oscillating heat pipe (OHP) was significantly enhanced by changing the inner wall surface wettability and filling ratios. Among the various wettability types, a hybrid surface, where the evaporator and condenser have different wettability, has shown enhancement of heat transfer performance significantly. The effects of different surface wettable vertical tubes are yet to be investigated. Therefore, in the present study, a single-loop OHP with three different surface wettable vertical tubes, namely, alternate wettability OHP (AWOHP) were numerically investigated at different filling ratios of 30%-90%. The different wettability rates of two vertical tubes caused an uneven distribution of slugs and plugs, which generated an unbalanced pressure difference between the tubes, thereby reducing the start-up time by 60-79%. The bulk mean temperature of the left and right adiabatic tubes was investigated to understand the nature of fluid flow. For FRs of 30%-70%, the right tube temperature was always higher than the left tube in AWOHP 3 (hydrophilic left tube, super-hydrophobic right tube), indicating unidirectional circulatory flow, with an occasional change in direction at 70% FR. At lower FR of 30%, AWOHP 2 (super-hydrophilic left tube, super-hydrophobic right tube) exhibited the highest heat transfer performance. In contrast, at higher FRs of 50%-90%, AWOHP 3 exhibited the highest heat transfer performance with conductance (G) of 1075 W/m2K at an FR of 70%, 55% higher than COHP.

Clinical Features of Varicella-Zoster Virus-Associated Anterior Uveitis with or without Ophthalmic Herpes Zoster

ABSTRACT Purpose This study aimed to investigate the clinical characteristics, diagnostic markers, and treatment outcomes of varicella-zoster virus-associated anterior uveitis (VZV-AU) with and without ophthalmic herpes zoster (herpes zoster ophthalmicus (HZO) and zoster sine herpete (ZSH), respectively). Methods Clinical records of 47 VZV-AU patients (21 ZSH, 26 hZO) were retrospectively reviewed for clinical findings, medication use, and PCR using aqueous humor (AH) results. Results There was no significant difference in age, gender, visual acuity (VA), or intraocular pressure (IOP) between the two groups. At the initial visit, small-to-medium white keratic precipitates (KPs) were significantly more observed in ZSH group than in HZO group, although there was no significant difference in the frequencies of other ocular findings between the two groups. Early antiviral medication use was significantly higher in HZO group (96.2%) than in ZSH group (19.1%). PCR was performed in 85.7% of ZSH and 53.8% of HZO patients. VZV-DNA positivity and viral load were similar between groups. Multivariate analysis revealed a positive correlation between white KPs and VZV viral load in AH. Although the ultimate use of antiviral medication was still less in ZSH group (71.4%), there were no significant differences in VA and IOP at the last visit between the two groups. Conclusion Patients with ZSH had more white KPs and received less early antiviral medication than those with HZO. However, visual outcomes were similar between the two groups. Small-to-medium white KPs were significantly associated with the viral load of VZV in AH, suggesting that they could be an active marker.

Phenotypic Plasticity, Multiple Paternity, and Shell Shape Divergence Across Lake‐Stream Habitats in a Freshwater Mussel Brood (Pyganodon grandis)

ABSTRACT Hydrodynamic forces and their absence appear to exert differential selection pressure on aquatic biodiversity in lake and stream habitats, creating a tight fit between organismal phenotypes and their environments. Ecophenotypic variants may be the result of genetic differentiation or phenotypic plasticity, where a genotype can produce multiple phenotypes dependent on the environment. Freshwater mussels possess a wide degree of morphological variation that frequently covaries with the environment, making them a good system to understand the mechanisms of ecophenotypic variation across hydrological conditions. We designed a two‐year experiment where individuals from the same Pyganodon grandis maternal brood (half and full siblings) were reared at a controlled site and four natural sites involving one lake and three streams. At the end of the experiment, shell shape was quantified for recaptured (N = 70), wild (N = 206), and zoo‐reared (N = 305) mussels. The maternal individual and 46 recaptured mussels were sequenced for genomic single nucleotide polymorphisms to test for multiple paternity and its effect on offspring morphology. Analysis of covariance found significant differences in shell shape between rearing sites, particularly between stream and lake habitats, but no shape differences were detected across the three stream sites. At two of the four sites, the shell shape of recaptured individuals was not significantly different than that of wild populations. Genomic sequencing and parentage analysis identified 11–27 different fathers among recaptured individuals. Yet no genetic differences were present between stream and lake habitats, and there was no paternal effect on shell shape. Taken together, phenotypic plasticity, over genetic differentiation, is identified as the primary mechanism of ecophenotypic variation. Plasticity is likely ubiquitous across freshwater mussels and may be a key adaptation given their high variance in habitat use. Multiple paternity may also play a role in the evolution of phenotypic plasticity, allowing more males from greater distances opportunities for fertilization, thus increasing genetic connectivity. Lastly, phenotypic plasticity and multiple paternity are convenient properties for freshwater mussel conservation and propagation. Multiple fathers increase the genetic variation of propagated broods, while plasticity may provide resilience to the release of stocked individuals across environmental heterogeneity.

Blood pressure measurement and nocturnal dipping patterns are heavily affected by body posture through changes in hydrostatic pressure between the arm and the heart.

Nocturnal blood pressure (BP) shows the highest predictive power for cardiovascular events. However, there is a poor reproducibility of personalized dipping patterns in single individuals. We hypothesize that changes in body position during sleep cause variations in hydrostatic pressure,leading to incorrect BP values and dipping classifications. 26 subjects aged 18-30 years, as well as 25 participants aged 50 years and older underwent ambulatory BP measurements on the left arm, as well as determination of the hydrostatic pressure difference between the cuff and heart level during BP measurement. We observed that the BP measurement cuff was above the heart level (negative hydrostatic pressure) mostly through the night. Laying on the right side revealed the largest hydrostatic pressure difference and maximum incorrect BP measurement, with a mean of -9.61 mmHg during sleep. Correcting for hydrostatic pressure led to reclassification of nocturnal hypertension in 14 subjects (27.5%). Dipping patterns changed in 19 participants (37.3%). In total, 25 subjects (49.0%) changed either their nocturnal hypertension and/or their dipping classification. Our findings underscore the importance of accounting for hydrostatic pressure in ambulatory BP monitoring. Changes in body posture during sleep provide a plausible reason for the variability seen in nocturnal dipping patterns. Further research should focus on incorporating hydrostatic pressure compensation mechanisms in 24-h BP measurement. Limiting the noticeable effect of hydrostatic pressure differences could greatly improve hypertension diagnosis, classification, and treatment monitoring.

Early and concomitant administration of norepinephrine and ilomedin improves microcirculatory perfusion without impairing macrocirculation in an intestinal ischemia-reperfusion injury swine model : a randomized experimental trial.

Intestinal ischemia-reperfusion injury is associated with both macrocirculatory and microcirculatory failure. Association of a vasoconstrictor in combination with a vasodilator such as ilomedin may improve macrocirculation parameters, microcirculation perfusion and reduce endothelial dysfunction. The primary objective was to demonstrate a difference in mean arterial pressure (MAP) after intestinal reperfusion with the concomitant administration of norepinephrine and ilomedin during ischemia compared with traditional hemodynamic treatment strategies (fluid resuscitation and vasopressors only). Secondary objectives were to demonstrate an improvement in peripheral and intestinal microcirculatory perfusion and endothelial dysfunction after intestinal reperfusion using this association. We conducted a randomized preclinical trial in twenty-one large white pigs, in which a 2-hour small bowel ischemia was performed using a segmental mesenteric occlusion model, followed by a 2-hour reperfusion. Pigs were randomized into 3 groups: goal directed fluid therapy, early administration of norepinephrine before reperfusion and early administration of ilomedin and norepinephrine before reperfusion. Macrocirculatory (MAP and Cardiac Index (CI)), microcirculatory (Sublingual with SideStream Dark Field system and intestinal hemoglobin oxygen saturation with hyperspectral imaging (HSI)) measurements and biological analysis (biomarkers of endothelial dysfunction) were performed. There were no significant differences in the MAP (p = 0.499) and the CI (p = 0.659) between the 3 groups. Perfused Vessel Density (PVD) in sublingual microcirculation was significantly higher immediately after reperfusion and 2 hours after reperfusion in the early administration of ilomedin and norepinephrine group compared with the other 2 groups (p < 0.05). Hemoglobin oxygen saturation measured at the intestinal level was significantly higher immediately after reperfusion in the early administration of ilomedin and norepinephrine group compared with the other 2 groups (p < 0.01). There were no significant differences in biomarkers of endothelial dysfunction between the 3 groups. Creatinine, AST and alkaline phosphatases increased significantly 2 hours after reperfusion in the early administration of ilomedin and norepinephrine group compared with baseline (p < 0.05). Early administration of norepinephrine and ilomedin during ischemia improved short-term post-reperfusion sublingual and intestinal microcirculation without worsening macrocirculatory parameters in an intestinal ischemia-reperfusion injury model. However, use of this strategy seemed to worsen both liver and kidney function.

Polymer Capsules with Volatile Organic Compounds as Reference Materials for Controlled Emission.

Encapsulation of volatile organic compounds (VOCs) that could evaporate at a defined rate is of immense interest for application in emission reference materials (ERMs). Polyurethane/polyurea microcapsules with various VOC active ingredients (limonene, pinene, and toluene) were successfully produced by interfacial polymerization with Shirasu porous glass membrane emulsification in a size range between 10 and 50 μm. The effect of surfactant, VOC, monomer(s) type, and ratio has a great effect on the formulation process and morphology of capsules. The type of VOC played a significant role in the encapsulation efficiency. Due to the difference in vapor pressure and VOC/water interfacial tension, the formulation for encapsulation was optimized for each individual VOC. Furthermore, to achieve effective stability of the large droplets/capsules, a combination of ionic and nonionic surfactants was used. Optical and scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), were used to characterize the optimized microcapsules. The results showed that the obtained microcapsules exhibited a spherical shape and core-shell morphology and featured characteristic urethane-urea bonds. The amount of encapsulated VOC ranges between 54 and 7 wt %. The emission tests were performed with the help of the emission test chamber procedure (EN 16516). The limonene-loaded polyurethane/polyurea microcapsules show a change in emission rate of less than 10% within 14 days and can be considered as a potential candidate for use as an ERM.

The Energy Consumption Comparison of Temperature Difference-based Defrosting Exit Method and Time-based Defrosting Exit Method with Various Static Pressure Differences

The time-based defrosting exit method(TDEM) has been widely used in cold storage, but the issue of energy consumption has been heavily criticized. In this paper, a temperature difference-based defrosting exit method(TDDEM) is proposed to compare with TDEM. Firstly, a parameter acquisition system of cold storage is constructed, and the experimental setup is conducted to determine the experimental parameters. Subsequentially, the range of defrosting static pressure difference is determined based on pre-frosting experiment, and the defrosting experiment of TDEM and TDDEM are carried out at five various static pressure difference conditions, 16Pa, 14Pa, 12Pa, 10Pa and 8Pa, respectively. The results show that the temperature fluctuations per defrosting events of TDEM are more severe compared to TDDEM, with with average increases of 102.2%, 91.6%, 59.3%, and 46.5%, respectively. Energy consumptions of TDDEM are markedly lower than TDEM, with reductions of 21.4%, 15.7%, 14.09% and 14.59%, respectively. Whether TDEM or TDDEM, the lowest energy consumption is occurred at 10Pa, and highest is 8Pa.

Modeling Investigation on Gas Backflow Performances in Screw Vacuum Pump

Rotor structure has a great influence on the gas backflow in a screw vacuum pump. The characteristics of the gas main flow along the spiral groove of the screw rotor and the gas reverse flow along the tooth-shaped, tooth side, radial, and circumferential clearances are investigated. A new mathematical model of the pumping flow and backflow involved in a flow balance model is proposed to investigate the actions of the shearing force and pressure difference force. The calculated backflow is verified by comparing the experimental measured results. The relationships of the structural parameters of the screw rotor are established. The effects of the rotor parameters, such as pitch, diameter, and compression ratio, on backflow are revealed. The results show that the rotor diameter and compression ratio remain constant and that the influence of pitch on the backflow is slightly weak, with backflow variations of less than 3%, whereas the pitch, rotor length, and compression ratio are constant and the rotor addendum diameter is directly proportional to the backflow. The addendum diameter of rotor #4 is the largest, and its backflow is about 1.5 times larger than that of rotor #1. When the rotor radial sizes and the pitch of the suction end are constant, the compression ratio is inversely proportional to the backflow in the low-pressure region and proportional to the backflow in the high-pressure regions. Therefore, for a vacuum pump operating in low-pressure areas, the use of the compression ratio of 2.2 or higher is favorable for the reduction in backflow.

Experimental Evaluation of Low-Carbon Cement and Its Application to the Oil and Gas Industry

Summary This study initiates a series of tests to examine the application of Type IL cement for well-cementing operations. Type IL cement is a blend of 5–15% limestone with Type I/II Portland cement. This substitution by reducing the amount of CO2 emitted from cement plants can be aligned with sustainability efforts in the cement industry. We first measured the properties of cement slurry made of Type IL cement and compared them with specifications for the well cementing. The properties of hardened cement including the compressive strength and bonding strength were also examined. For compressive strength measurement, both cubic and cylindrical samples were prepared. To measure the bonding strength, the modified pushout test was used. We also investigated the effect of severe environments on the strength reduction of the hardened cement. In addition, the scaled abandonment plugging setup was used to quantify the sealing capabilities of Type IL cement in a well-plugging scenario. To force nitrogen flow through, differential pressure was applied to the system by decreasing the pressure above the plug-in controlled timesteps. We found that Type IL hardened cement offers substantial sealing capabilities compared with data available in the literature, although the leakage rate seems to gradually increase with each increase in differential pressure.

Development of new gas analytical technique for infrared spectroscopy combined with differential pressure measurements.

A new gas analytical technique for infrared laser spectroscopy combined with differential pressure measurement (IR-DP) is developed. The basic idea of this technique is that the absorption process of molecules by laser irradiation is monitored as the pressure enhancement in a gas cell by use of a differential pressure gauge. The system is composed of a tunable IR laser system, sample cell, differential pressure gauge, and data accumulation system. Using this system, the measurements of the IR absorption spectra for cyclohexane (50 ppm) and ammonia (100 ppm) are demonstrated. By comparison of the current IR-DP spectra with conventional Fourier-transform infrared spectra, the spectral resolution is found to be about 3cm-1, reflecting the laser resolution. Furthermore, the estimated pressure enhancement based on a simple model is consistent with the experimental results. These results suggest that the newly developed IR-DP technique is one of a powerful tool for trace gas detection.

Relationship between asymmetry of transverse sinus and difference in intraocular pressure Based on MRV imaging examination

Transverse sinus asymmetry refers to the inconsistencies in the shape structure, size or blood flow of the intracranial transverse sinus. Intraocular pressure difference refers to the obvious difference in intraocular pressure between the two eyes. Transversal sinus asymmetry may be correlated with intraocular pressure difference, but the mechanism of correlation is still unclear. To investigate the relationship between transverse sinus asymmetry and IOP differences based on MRV examination, and to explore the possible mechanism. Patients with transverse sinus asymmetry were selected and examined using the MRV technique. At the same time, the patients' IOP was measured using standard methods of IOP measurement. Correlation analysis and statistical methods were used to evaluate the association between transverse sinus asymmetry and IOP differences. There was a statistically significant distinction observed between groups I and V (Z=6.78, P<0.01). Significant variations were also noted in the intraocular pressures across all groups, encompassing the average measurements of the right eye and left eye, along with the variance between the two (right eye: F=15.43, P<0.01; left eye: F=4.62, P=0.002; variance between eyes: F=41.79, P<0.01). The asymmetry of the transverse sinus exhibited a negative relationship with the intraocular pressure of the right eye (r=0.51, P<0.01) and the difference between the pressures of the two eyes (r=0.79, P<0.01); no significant association was found between the asymmetry and the left eye's intraocular pressure. In conclusion, a certain correlation exists between the intraocular pressures of the left and right eyes and the morphology of the transverse sinus. When the transverse sinus is thicker on one side, the corresponding drainage veins are thicker, resulting in lower intraocular pressure on that same side.

Mitigation of train-tunnel aerodynamics through active airflow control at front and rear noses: Impact of slit area

As railway transportation advances toward higher speeds, traditional passive measures may struggle to meet the stringent aerodynamic criteria in tunnels, necessitating the exploration of novel active flow control techniques. This study employs three-dimensional, compressible, unsteady Reynolds-averaged Navier–Stokes simulations to investigate the aerodynamic effects of the suction and blowing slit area (S) positioned on the front and rear noses of the train. The results indicate that suction and blowing activation is particularly effective in alleviating pressure on the narrower side of the tunnel. Specifically, with a 4 m2 slit, the original 4.8% pressure difference between symmetrical points on the train body is fully eliminated. The influence of suction and blowing on the positive pressures is confined to the front and rear noses where the slits are located. Notably, only suction at the front nose mitigates pressure gradients, while blowing at the rear is unrelated. The peak-to-peak pressure (ΔP) on both the train surface and tunnel wall exhibits a linear decline, with reductions of 17.4% and 16.6%, respectively, as S increases from 0 to 4 m2. Similarly, the slipstreams on both sides of the tunnel decrease linearly with increasing slit area: with u/Umax = −0.008S + 0.24 for the near side, and u/Umin = 0.014S − 0.265 for the far side. Additionally, expanding the slit area further boosts the stability and safety of the train during tunnel exit by reducing lateral forces and rolling moments, while also decreasing overall drag, thereby partially compensating for the energy input. Although the maximum lift on the head car increases with slit area, the lift on the tail car initially rises and then decreases, helping to mitigate instability upon tunnel exit. Overall, the hybrid suction and blowing technique offers promising potential for enhancing the tunnel aerodynamics in the future.

Aerodynamic instability of brush seals in gas turbine engines based on a fluid-structure interaction method

By brush seal, we mean a type of mechanical seal that uses a large number of closely packed, thin, and flexible bristles to create an outstanding seal between rotating and stationary components in gas turbine engines. However, at high levels of swirling and pressured environments in engines, bristles of brush seals tend to circumferentially slip, which leads to reduced sealing performance and seal failure. In this paper, the effects of upstream–downstream pressure differences Δp (0.2–0.5 MPa), downstream static pressure (0.1–1.0 MPa), and the coverage of bristles by a front plate (0%–90%) on the mechanical characteristics and deflections of bristles of a brush seal at highly swirling inlet were investigated based on a two-way fluid-structure coupling method. A key criterion for bristle instability, based on a simplified two-dimensional (2D) theoretical analysis, is obtained from the fluid-structure coupling simulations. The results indicate that a fundamental reason for the bristle circumferential slip is the ratio of the normal to the axial aerodynamic forces (Fn/Fax) acting on the first row of bristles. When this ratio exceeds 0.9, the bristles will slip circumferentially. The effects of the pressure differential across the seal, the downstream pressure, inlet swirl velocity, and front plate coverage of the bristles on bristle stability can all be explained through their influences on this force ratio. At relatively low outlet static pressure of 0.1 MPa, upstream bristles slip when the inlet swirl is in the range of 230–300 m/s and the bristle slip instability is more likely to occur at higher pressure difference conditions. However, at high downstream pressures, Fn/Fax declines with the growth of Δp, contributing to the stability tendency. With the constant Δp, the value of Fn/Fax significantly increases as the downstream pressure rises, and the critical swirl velocity required to trigger bristle slip is considerably reduced. Additionally, the front plate shields a part of the bristles away from pressure gradient in axial direction but leads to outward radial flow upstream of the bristle pack, thereby increasing the Fn/Fax. Thus, front plate does not offer protection to bristles under high inlet swirl conditions, on the contrary, it may cause early slip of the bristles.

Dual effects of pressure difference for long-wave stratified flow in horizontal microchannels

In this work, the linear stability analysis combining with energy balance theory is performed to clarify the suppressing and boosting long-wave instabilities driven by pressure difference in horizontal microchannels as well as its corresponding physical meanings. It is found that, for a specific fluid combination, there exists a certain relative liquid film thickness (hN,c) at which the disturbance work done by interfacial shear stress over unit wavelength (denoted by ISS) is exactly equal to the total viscous dissipation rate over unit wavelength within both phase bulk flows (denoted by DIStot). When the liquid film thickness (hN) exceeds hN,c, ISS is smaller than DIStot, indicating that the initial disturbance energy cannot be replenished from the primary flow until its completely disappear due to the viscosity dissipation. Conversely, ISS is larger than DIStot, indicating that the initial disturbance can acquire energy from the primary flow and grow up. The strength of suppressing and boosting effect can be influenced by liquid film thickness, flow rate, and channel height. However, the demarcation of the dual effects remains unchanged. An analytical expression of hN,c with respect to the viscosity ratio is established by means of long-wave approximation method, which matches well with the numerical results. The energy balance mechanisms revealed in the present study provide a new insight into the wave mode in the confined space and help the design of microfluidic systems.