Average Pressure Research Articles

Experimental and numerical investigation on heat transfer analysis of square slotted pin-fin heat sinks

This paper introduces two novel designs of pin-fin heat sink (PHFS), namely the inline slotted pin-fin (ISP) and the V-shaped slotted pin-fin (VSP), to address rapid heat dissipation for one central/graphics processing unit (CPU/GPU) in a single-phase liquid cooling system. Experimental and numerical investigations are conducted to observe the effect of heat transfer for non-slotted and slotted pin-fin heat sinks under different Reynolds numbers (225-720) and heating powers (90-120 W). Parameters such as average wall temperature, Nusselt number, thermal resistance, pressure drop, and hydrothermal performance factor are evaluated. Comparative analyses show that the slotted pin-fin heat sinks exhibit higher Nusselt numbers (Nu) and lower thermal resistance (Rth) levels than that in the non-slotted pin-fin heat sinks, particularly at lower Reynolds numbers. At the Reynolds number 225 and power of 120 W, the inline and V-shaped slotted pin-fin heat sinks experience a 13.98% and 19.69% increase in Nu and a 12.65% and 15.41% reduction in Rth compared to the non-slotted one, respectively. The V-shaped slotted pin-fin heat sink achieves more than 5 ∘C reduction in the maximum wall temperature than the non-slotted one. The slotted structure reduces pressure drop losses by minimizing dead flow areas on one hand. On the other hand, the inclined slots generate vortices behind the fins, increase shear-induced mixing and thus improve the force convection cooling performance.

Continuous positive airway pressure treatment in obstructive sleep apnea syndrome patients with hypertension

Aims: To assess the prevalence and general characteristics of obstructive sleep apnea syndrome in patients with hypertension, investigate the relationship between obstructive sleep apnea syndrome and blood pressure, and the effectiveness of continuous positive pressure ventilation treatment after 1 month in hypertensive patients with obstructive sleep apnea. Methods: Cross-sectional descriptive study with follow-up after 1 month in hypertensive patients treated at the Hue University of Medicine and Pharmacy Hospital with respiratory polygraphy from January 2021 to June 2023. Patients were given history, clinical examination, anthropometric measurements, Lipid profile test, intravenous glucose, Epworth scale assessment, CPAP treatment and re-evaluated after 1 month. Results: 134 patients were registered for the study from 01/2021 to 06/2023. Hypertensive patients with OSAS were 73.13%. BMI in the OSAS (+) group was 22.84 ± 3.04 kg/m2 and was statistically significantly greater than the OSAS (-) group: 22.79 ± 3.07 kg/m2 (p<0.05). Neck circumference in the OSAS (+) group was 37.45 ± 2.44 cm, which was statistically significantly larger than the OSAS (-) group: 36.36 ± 1.57 cm (p<0.05). The rate of loud snoring during sleep and excessive daytime sleepiness in the OSAS patient group was statistically significantly higher than in the group without this syndrome (p<0.05 and p<0.01). The average systolic blood pressure in the OSAS (+) group was 154.79 ± 13.32 mm Hg and was statistically significantly higher than the OSAS (-) group (p<0.01). AHI has a moderate positive correlation with systolic blood pressure (r = 0.45, p<0.01) and diastolic blood pressure (r = 0.34, p<0.01). CPAP treatment improved systolic and diastolic blood pressure and symptoms of excessive daytime sleepiness. Conclusion: There is a relationship between obstructive sleep apnea syndrome and hypertension. CPAP treatment improves blood pressure and daytime sleepiness.

Effect of Cavity Shapes on the Lubrication Performance of High Precision Static and Dynamic Thrust Bearing under Eccentric Load

Abstract The oil cavity shapes, which represent the spatial structures for storing lubricant in static and dynamic thrust bearings, and offset distances, defined as the horizontal distances between the load center and the bearing rotational axis under eccentric loads, directly impact the flow mode of lubricant, pressure, and temperature distribution during bearing operation, so these are the key factors that influence the lubrication performance and the accuracy of bearings. The equations for flow and load capacity of the sector, runway, and double rectangular cavities are derived, and mathematical models are established for different cavities at various tilt positions. Then pressure and temperature fields at different offset distances are analyzed. As the offset distances increase, there is a corresponding increase in the maximum pressures within the sector, runway, and double rectangular cavities by 90.5 kPa, 93.3 kPa, and 30.9 kPa, but average pressures show only minor fluctuations. Concurrently, the maximum temperatures within these cavity shapes are observed to increase by 0.5 K, 0.6 K, and 0.8 K, respectively. The results show that appropriate offset distance can improve the lubrication performance. The runway cavity has the highest load-carrying capacity among the three cavity shapes, while the sector cavity experiences the slightest temperature increase. As the temperature increase in all three cavity shapes is small, the runway cavity exhibits superior performance. The error between simulation and experimental results is less than 10%, which verifies the correctness of the simulation method.

Study on heat transfer and pressure steady-state characteristics of a floating nozzle under a moving wall

This work considers the flow field as two-dimensional turbulent flow and studies the steady-state properties of heat transfer and the pressure of the suspension nozzle. An adiabatic wall parallel to the moving wall and two slit entrances at either end of the adiabatic wall make up the rectangular flow field. The SST k-ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k - \\omega$$\\end{document} turbulence model is used in the turbulence computation. Both qualitative and quantitative analyses are conducted on the distribution of the flow field, temperature field, local Nusselt number, local pressure coefficient, average Nusselt number, and average pressure coefficient under various combination conditions. The findings indicate that when the suspension nozzle's flow field varies greatly, wall-jet velocity ratio is 0.1. A rise in Jet inclination angle is not helpful for the wall's suspension, and it has minimal effect on the flow field. The flow field is greatly influenced by separation space-slit width ratio. Larger separation space-slit width ratio values are advantageous for the wall's heat transmission but unfavorable for the wall's suspension. The flow field is most influenced by wall-jet velocity ratio. The wall's ability to convey heat is stronger the higher the wall-jet velocity ratio, but its ability to support weight falls.

Improved Design and Economic Estimation of Cold-End Systems for Inland Nuclear Power Plants

Reserve sites for coastal nuclear power plants are gradually being depleted, prompting a shift towards the development of inland nuclear power stations. A new cooling system based on the integration of multiple cooling sources using a hybrid dry–wet cycle is proposed to achieve a balance between energy and water consumption for inland nuclear power stations. Comparative studies among all the available cooling systems were further conducted to analyze the cooling performance and economic viability. The case study results indicate that, in comparison to relative humidity, the cooling performance and circulating water consumption of cooling systems are more susceptible to changes in dry-bulb temperature. In arid and water-scarce regions, a Combined Natural Draft Hybrid Cooling System generally exhibits a monthly average circulating water consumption rate that is more than 270 kg/s lower than that of the natural draft wet cooling system, with an average monthly back pressure reduction of 0.11 kPa. When the dry-bulb temperature exceeds 13 °C, the net profit of wet cooling surpasses that of hybrid cooling. However, this scenario undergoes a reversal as the dry-bulb temperature decreases and local water prices rise. It is emphasized that hybrid cooling demonstrates minimal impact when subjected to changes in environmental conditions, offering extensive regional applicability.

ROLE OF THE MACHINE LEARNING–DERIVED HYPOTENSION INDEX (HPI) TO CONTAIN INTRAOPERATIVE HYPOTENSION DURING TRANSCATHETER EDGE TO EDGE REPAIR PROCEDURES

Abstract Introduction Percutaneous endovascular valvular interventions can result in profound hemodynamic instability, elevated burden of intraoperative hypotension (IOH) and related postoperative complications: ischemic stroke, acute kidney injury and increased mortality. Machine learning(ML),a branch of Artificial intelligence (AI), can analyze large volumes of data, find associations and allowing predictive rather than reactive interventions. The Hypotension Prediction Index (HPI)a ML derived algorithm,provides a unitless number from 0 to 100, that increases accordingly to the risk of developing a hypotensive event (mean arterial pressure – MAP – < 65 mmHg for more than 1 minute) in the following minutes. The aim of this study is to describe IOH in patients undergoing percutaneous valve repair under general anesthesia treated according to an HPI–based hemodynamic guidance (fig.1). Methods Eligible adult patients undergoing transcatheter valve repair procedures (MitraclipTM, TriclipTM)were included in the study. When HPI value exceeded 85,a proactive individualized treatment protocol to prevent hypotension was provided according to the following modalities (fig. 2). Primary outcome measure was TWA–MAP (time weighted average mean arterial pressure)under the threshold of 65 mmHg. Secondary outcomes were number of patients with at least one hypotensive event, number of events per patient,depth and duration of hypotensive events and area under MAP threshold of 65 mmHg (AUT–MAP < 65). Results Twenty–five consecutive patients were prospectively enrolled and treated. During an average monitoring time per patient of 187 ± 31 minutes, the global burden of hypotension, measured as TWA–MAP < 65 mmHg, was 0.12 [0.02, 0.8] mmHg. Two thirds of the patients(16/25) experienced hypotensive events, with a median number of hypotensive events of 1 [0, 3.25] per patient and about 11% of the time spent < 65 mmHg. Each event lasted 4 [1.7, 8.6] minutes with a MAP of 59 [56, 62] mmHg, leading to a total AUT–MAP < 65 mmHg of 20.3 [3.5, 142.2] mmHg x minutes. The majority of hypotensive events occurred after induction of general anesthesia, while hypotension was rare during the procedure (fig. 3). Conclusions HPI algorithm provides accurate and continuous prediction of impending IOH before its occurrence. Machine learning models,as in the case of HPI, could facilitate the physicians to treat IOH which is a potentially modifiable risk factor for major postoperative complications.

Analysis and Reflection on the Green, Low-Carbon, and Energy-Saving Design of the Super High-Rise Building

Shanghai Tower has become a new landmark of Shanghai. In the current trend advocating green building and energy efficiency, considerations of wind loads and thermal characteristics of the perimeter structure of Shanghai Tower are crucial. This paper conducts comparative simulation studies on the wind environment of Shanghai Tower using Ecotect software, and stress analyses and thermal simulations of the perimeter structure using ANSYS software. The study compared three buildings’ surface wind pressure distributions using models with equal-volume and circular cross-sections. We found that the unique exterior design of the Shanghai Tower results in a more regular and uniform distribution of wind pressure on its surface compared to both circular and square planar models, with a lower average wind pressure value. In addition, the stress analysis results indicate significant differences in deformation and stress distribution between the windward and leeward sides. Enhancing the bending moment detection of the peripheral structure and optimizing the layout of detection points are recommended. Thermal simulation results show excessive heat conduction flux in winter conditions, suggesting optimization using passive energy-saving methods such as light-sensitive thermal insulation materials during winter. This research is a reference for designing other super-tall buildings prioritizing low-carbon energy efficiency and structural safety.

In vitro evaluation of a hybrid negative pressure system for wound therapy.

The objective of this study was to assess whether negative pressure could be maintained accurately and repeatably with a wall-suction-based hybrid negative pressure wound therapy (h-NPWT) system by comparing it with a commercial negative pressure wound therapy (NPWT) device. In vitro experimental study. A commercial NPWT device (control) and three h-NPWT devices, with 0, 3, and 6 meters of additional tubing using the hospital-wall suction (groups 1, 2, and 3 respectively), were applied sequentially to a commercial NPWT dressing on a silicone skin substrate and set to run at a continuous pressure of -125 mmHg. The pressure within the wound space was monitored at 10 second intervals for 24 h. The process was repeated five times for each group. The commercial NPWT device produced an average pressure variance of 3.02 mmHg, and the h-NPWT produced average variances of 4.38, 4.24 and 4.20 mmHg for groups 1, 2 and 3, respectively. All groups produced an average pressure within 0.15 mmHg of -125 mmHg over the 24-hour period, and the h-NPWT systems produced the smallest range with all values remaining within a ±5% variation from -125 mmHg. The h-NPWT system achieved negative pressures that were comparable to those of a commercial control NPWT device. The addition of tubing between the skin substrate and the canister did not affect the pressure applied at the wound site. The h-NPWT device tested in this study can be considered as an alternative for negative wound therapy when a commercial device cannot be used.

Comparison of surgical outcomes between Kahook Dual Blade goniotomy and Trabectome surgery in patients with open-angle glaucoma

Objective: To compare the medium-term therapeutic effects of Kahook Dual Blade (KDB) goniotomy and Trabectome surgery in the treatment of patients with primary open-angle glaucoma (POAG). Methods: This study was a non-randomized prospective interventional controlled clinical study. POAG patients who underwent KDB goniotomy or Trabectome surgery at Beijing Tongren Hospital from May 2017 to April 2022 were enrolled. The definition of successful surgery was postoperative average intraocular pressure (IOP)≤21 mmHg (1 mmHg=0.133 kPa) and IOP decrease≥20%. Follow-up visits were conducted on the 1st day, 1st week, 1st, 3rd and 6th month after surgery. The IOP value, the number of IOP-lowering medications, the proportion of surgical success (average IOP≤21 mmHg at 6 months), and complications were evaluated. Statistical methods included independent sample t-test, Mann-Whitney rank sum test, χ2 test, repeated measures two-factor analysis of variance, Bonferroni, Friedman M test, Wilcoxon, and Log-rank. The Kaplan-Meier method was used to calculate the cumulative success rate of each group. Results: Seventeen male patients (17 eyes) and 10 female patients (10 eyes) were included. The mean age was (39.9±17.7) years old. There were 11 patients in the KDB group and 16 patients in the Trabectome group. There was no significant difference in clinical baseline conditions between the two groups (P>0.05). The IOPs in the KDB and Trabectome groups at postoperative 1 week [(16.6±6.3) and (16.4±4.1) mmHg) and 6 months [(17.8±5.3) and (19.9±4.4) mmHg) were lower than those before surgery [(25.1±9.3) and (27.4±9.1) mmHg) (all P<0.05). There was no significant difference in the overall IOP between groups (P>0.05). The IOP reduction rates in the KDB and Trabectome groups were 23.4% and 19.0%, with no significant difference (P=0.674). The numbers of IOP-lowering medications used in the KDB and Trabectome groups at 3 months [2.0 (1.0, 4.0) and 2.0 (1.0, 2.3)] and 6 months [2.0 (0.0, 4.0) and 2.0 (1.0, 3.0)] after surgery were not significantly different from those before surgery [4.0 (2.0, 4.0) and 3.0 (2.0, 4.0)] (both P>0.05). There was no statistical significance in the overall number of IOP-lowering medications used between the two groups (P>0.05). There was also no statistically significant difference in the proportion of patients with an IOP decrease of≥20% and the proportion of patients whose mean postoperative IOP was≤21 mmHg (all P>0.05). The proportions of IOP≤21 mmHg in the KDB group and the Trabectome group at 6 months after surgery were 81.8% and 68.8% (P>0.05). Serious intraoperative or postoperative complications occurred in neither group. Conclusions: Both KDB trabeculotomy and Trabectome surgery can effectively reduce IOP and have a good safety profile in treating POAG, with the same number of IOP-lowering medications.

Reservoir Quality Under the Control of Gravity Flows in the C7 Member of Yanchang Formation in the Jinghe Oilfield, Ordos Basin, China

The late Triassic sandstone reservoir in the C7 member of the Jinghe oilfield southern Ordos basin is a typical deep-water gravity flow tight oil reservoir. Sedimentary microfacies, physical properties, and petrographic analysis were being examined for quality determination. Pore structure and physical properties data together combined with, thin sections, and scanning electron microscope and core images were used to identify factors controlling reservoir physical properties. The depositional system under debates of different gravity flows including debris flow, seismite slumping, and turbidity flows. Among which sandy debris flow facies shows a better distribution of porosity and permeability followed by seismite-slump, where turbidity facies are the poorest. The petrophysical analysis shows that the study oil interval is a typical tight sandstone reservoir with an average porosity of 9% and permeability average being 0.025mD. The rock classification criteria of the C7 sandstone reveal the sub-categories of lithic feldspar sandstone and feldspar lithic sandstone. Average quartz sandstone contents of 48.25%, average feldspar sandstone content being 25%, and lithic fragments content of 29%. The formation lithology comprises mostly fine-grained sandstone and small pore size, which disclose that the porosity-permeability distribution increases proportional to the average and median pore throat radius, and decreases with average and median pressure. The microfacies distribution shows that the depositional facies controlled physical properties. The sandstone primary pores are affected by the mineral composition of quartz, feldspar, illite, smectite, kaolinite, calcite, and dolomite. Features such as dissolved pores and intergranular pore filling by feldspar, silky-like aggregates of illite-smectite intergranular pore filling and most diagenetic minerals influenced the sandstone pores beside the compaction.

Design, assembly and testing of an upgraded aeroacoustics wind tunnel facility

The Aeroacoustics Laboratory in the Department of Aerospace Engineering at Penn State currently serves several areas of experimental research. Most notable in the laboratory is the Anechoic Chamber of which the Aeroacoustics Wind Tunnel is an integral part. In recent years the dominant areas of research have included model aircraft exhaust jets and model rotors for helicopter applications involving detailed noise experiments. In the jet noise area, the applications have included aircraft in both flyover and take-off configurations. In the flyover application the air flow surrounding the exhaust jet has a significant effect on the radiated noise and must be simulated to produce experimental results that will be most useful in preliminary design of noise suppression applications. The Aeroacoustics Wind Tunnel at Penn State serves the purpose for this simulation. During aircraft take-off, the aircraft airspeed is in a range exceeding 250 ft per second, or Mach number of over M = 0.22. In the years preceding 2022, the velocity of the free jet flow of the Penn State facility was limited to less than 200 ft/sec. This paper reports on a project to design upgrades to the existing wind tunnel to improve the test section flow velocity to values closer to the 250 ft/sec target. The approach began with a preliminary design of the return flow ducting to convert the open jet, open return wind tunnel to a closed return tunnel. The concept is to make use of the flow energy in the exhaust of the tunnel to boost the input energy to the inlet fan that drives the flow to the test section. An integral part of the preliminary design involved making use of an upgraded flow analysis computer code to predict the gain in test section velocity of the new facility. For the available horsepower of two fans in the facility, the configurations of the existing and upgraded wind tunnel were entered into this analysis code based on a quasi-one-dimensional formulation. The code included empirical data formulated to include the various shapes of the components of the tunnels. The relative flow velocities in each section used simple incompressible continuity to calculate all velocities in the component sections. The average dynamic pressure in each section is calculated from the flow (constant) density and the velocity squared. Each section had a non-dimensional pressure loss parameter calculated from empirical data (from the relevant literature). The basic code (using the Excel algorithms) was based on a predictor-corrector concept in which the calculation was initialized with the estimated velocity and pressure of the flow at the entrance to the test section. The loss in each following section is estimated to determine the loss in the total pressure and the cumulated loss compared to the gains made at the two fans in the circuit. The initial guess is adjusted based on the total pressure value at the end of the circuit. During the related experiments, measurements of the total and dynamic pressure were performed at several joints between sections and compared to the values predicted in the analysis code. Various settings of the horsepower of the drive fans were used and the results were compared to flow measurements for the tunnel configurations (predominantly for the open return and closed return tunnel setups available before and after the upgrade project.) Results of the analysis and experiments are presented and analyzed together with the remaining activities planned for the coming months.

Changes in the state of matter of KCIO4 to improve thermal and combustion properties of Al/MoO3 nanothermite

To improve the thermal and combustion properties of nanothermites, a design theory of changing the state of matter and structural state of the reactants during reaction was proposed. The Al/MoO3/KClO4 (Kp) nanothermite was prepared and the Al/MoO3 nanothermite was used as a control. SEM and XRD were used to characterize the nanothermites; DSC was used to test thermal properties; and constant volume and open combustion tests were performed to examine their combustion performance. Phase and morphology characterization of the combustion products were performed to reveal the mechanism of the aluminothermic reaction. The results show that the Al/MoO3/Kp nanothermite exhibited excellent thermal properties, with a total heat release of 1976 J·g− 1, increasing by approximately 33% of 1486 J·g− 1 of the Al/MoO3 nanothermite, and activation energy of 269.66 kJ·mol− 1, which demonstrated higher stability than the Al/MoO3 nanothermite (205.64 kJ·mol− 1). During the combustion test, the peak pressure of the Al/MoO3/Kp nanothermite was 0.751 MPa, and the average pressure rise rate was 25.03 MPa·s− 1, much higher than 0.188 MPa and 6.27 MPa·s− 1 of the Al/MoO3 nanothermite. The combustion products of Al/MoO3 nanothermite were Al2O3, MoO, and Mo, indicating insufficient combustion and incomplete reaction, whereas, the combustion products of Al/MoO3/Kp nanothermite were Al2O3, MoO, and KCl, indicating complete reaction. Their “coral-like” morphology was the effect of reactants solidifying after melting during the combustion process. The characterization of reactants and pressure test during combustion reveals the three stages of aluminothermic reaction in thermites. The excellent thermal and combustion performance of Al/MoO3/Kp nanothermite is attributed to the melt and decomposition of Kp into O2 in the third stage. This study provides new ideas and guidance for the design of high-performance nanothermites.

Clinical Effects of Sildenafil in the Treatment of Congenital Heart Disease with Pulmonary Hypertension

Objective: To analyze the improvement of mean pulmonary arterial pressure and oxygenation index as well as the therapeutic effect of sildenafil treatment in patients with congenital heart disease and pulmonary arterial hypertension. Methods: A total of 104 patients with congenital heart disease and pulmonary arterial hypertension were recruited from February 2023 to January 2024 and grouped into study and control groups using a randomized numerical table, with 52 patients in each group. The study group received sildenafil treatment, while the control group received conventional treatment. The therapeutic effects of both groups were analyzed and compared. Results: The study group had an average pulmonary arterial pressure of 26.23 ± 2.16 mmHg, an oxygenation index of 241.63 ± 4.86, and a total effective treatment rate of 98.08%, which was significantly better than the control group (P &lt; 0.05). Conclusion: By implementing sildenafil treatment for patients with congenital heart disease and pulmonary hypertension, the mean pulmonary artery pressure and oxygenation index of the patients improved significantly, and the effective rate of treatment increased significantly.

“Advocates for Each Other”: The creation and evaluation of a pragmatic peer navigation program for black patients in primary care with uncontrolled hypertension

BackgroundBlack individuals in the U.S. and in our primary care clinic experience worse control of blood pressure compared to White individuals. ObjectiveTo address this inequity, our objectives were to (1) elicit from patients and community members their ideas for barriers and facilitators to blood pressure control; and (2) use their input to design and pilot a navigator program for Black patients in our clinic to improve blood pressure management. Patient involvementWe conducted three focus groups with 27 individuals and identified two main areas of need that informed the peer navigator program: (1) community-based services and (2) skill development for hypertension self-management. MethodsPeer navigators from the Black community called participants at least monthly for 6–12 months and connected them with medical and social services. Available blood pressure data was used as the primary outcome to measure change pre- to post-peer navigation program. ResultsAmong 499 eligible patients in the clinic, 53 (10.6%) enrolled in the peer navigation program. For those with baseline and follow-up blood pressure data, mean systolic blood pressure decreased from 155.9 to 142.4 mmHg after the program (change of −13.6, 95% CI −24.7 to −2.4) for the enrolled patients (N = 17) and from 139.1 to 137.1 mmHg (change of −2.5, −4.8 to 1.9) for unenrolled, comparison patients (N = 183). DiscussionThis community-informed peer navigation program to support Black patients with uncontrolled hypertension led to a 11.1 mmHg greater decrease in average systolic blood pressure for enrolled patients compared to the comparison group. However, the enrolled group started with a significantly higher systolic blood pressure at baseline with more room for improvement. While this study was conducted during the pandemic years, low uptake of this program needs to be addressed in expansion efforts. Practical valueClinic-based peer navigation for hypertension improved blood pressure control and was highly regarded by the subset of enrolled patients. Increasing uptake and sustainable funding for non-billable clinic roles remain areas of need. FundingGrant from the Pacific Hospital Preservation & Development Authority.

The Role of Blood Pressure Control in Prevention of Hematoma After Blepharoplasty.

Hematoma formation after blepharoplasty is serious and potentially vision-threatening, with hypertension being the primary risk factor. The aim of this paper is to assess perioperative blood pressure trends and rates of complication in patients undergoing a strict blood pressure protocol designed to keep perioperative systolic blood pressure below 120 mmHg. A retrospective chart review was performed of 32 patients undergoing face lift with conomitant blepharoplasty from January 2015 to July 2018. For each patient blood pressure readings obtained before, during, and after surgery were reviewed. Two-sample one-tail T-tests were performed, and p values less than 0.05 were considered statistically significant. The mean systolic blood pressure (SBP) for all patients was highest intraoperatively. Patients with known hypertension had higher mean SBPs than patients without hypertension across all phases of care, with a statistically significant difference in immediate preoperative SBP (p=0.05). Males had a higher average blood pressure immediately postoperatively (p=0.05). A previous diagnosis of hypertension in females was associated with a higher immediate preoperative SBP (p=0.07) as well as age over 65 (p=0.07). The overall rate of complications was 37.5%. No patients experienced hematoma. This study demonstrated that keeping blood pressure below 120 mmHg after surgery was an effective method of preventing hematoma after blepharoplasty, even in patients concurrently on anti-coagulative medications. Special attention to blood pressure control should be shown to patients with known risk factors such as a previous diagnosis of hypertension, male sex, or age greater than 65. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Cross-dimensional multi-physics model and two-phase mass-transport enhancement for the hydrogen peroxide-based fuel cell

The direct liquid fuel cell utilizing hydrogen peroxide as an oxidant is considered to be the promising energy conversion technology, owing to its superior energy density and theoretical voltage. In the hydrogen peroxide-based fuel cells, the ever-changing two-phase mass transport and multi-component reaction processes resulting from the hydrogen peroxide self-decomposition exerts a pivotal influence on their performance. In this work, taken hydrogen peroxide self-decomposition into account, a cross-dimensional multi-physics model for the hydrogen peroxide-based fuel cell was proposed and developed to clarify the complex mechanisms of transports and reactions. In this ingeniously developed model, the multi-component reaction in the porous electrode is elucidated by a two-dimensional (2D) sub-model, the two-phase mass transport in the flow field is captured by a three-dimensional (3D) sub-model, and the one-dimensional (1D) correlation equation is served as a bridge between them. The uneven distribution of gas–liquid volume, velocity and current density and their relationships in fuel cell with serpentine flow field and dot matrix flow field were thus achieved. Furthermore, a novel gradient dot matrix flow field was developed to match the two-phase mass transport and multi-component reaction processes of hydrogen peroxide-based fuel cell. It is found that the continuously increasing pressure and velocity along flow path is balanced by the gradient-downsized ribs and the formation of large-volume oxygen bubbles is prevented by the gradient-densified ribs, achieving obviously uniformized current density distribution. Moreover, the gradient dot matrix flow field enables 54 % higher average hydrogen peroxide coverage contents (49 %) and 86 % lower average pressure drop (172 Pa) compared to the serpentine flow field, yielding 6.3 % higher peak power density (210 mW cm−2) and ultra-low extra pump power in fuel cell. This work will make contribution towards gaining profound insights into the intricate mechanisms underlying mass and charge transport, and offering invaluable guidance for the flow field design for the hydrogen peroxide-based fuel cells.

Effect of the early diastolic blood pressure response to the head-up tilt test on the recurrence of benign paroxysmal positional vertigo.

Otolith organ acts complementarily with the autonomic nervous system to maintain blood pressure. However, the effect of blood pressure variability in the autonomic nervous system on otolith organ has not yet been determined. This study aimed to verify the hypothesis that blood pressure variability in the autonomic nervous system affects the recurrence of benign paroxysmal positional vertigo (BPPV), which is the most common disease of the vestibular organs, by using the head-up tilt test (HUTT). This study included 432 patients diagnosed with idiopathic BPPV. The follow-up period for all patients was 12 months. Age, sex, hypertension, diabetes and recurrence were analyzed. The HUTT parameters were divided into a group of patients whose average diastolic blood pressure increased in the upright position compared to supine position during the HUTT (DBP1) and a group of patients whose average diastolic blood pressure decreased in the upright position compared to supine position during the HUTT (DBP2). Model selection, general loglinear analysis, and logit loglinear analysis were performed using a hierarchically progressing loglinear analysis. In summary, the group with increased average diastolic blood pressure (DBP1) showed a higher tendency for BPPV recurrence compared to the group with decreased diastolic blood pressure (DBP2) in the upright position during the HUTT, although the difference was not statistically significant (p = 0.080). However, in males, the DBP1 group demonstrated a significantly higher recurrence rate of BPPV than the DBP2 group during the HUTT (95% CI, -20.021 to -16.200; p < 0.001). It is presumed that poor autonomic nervous system response through vestibulosympathetic reflex maintains elevated diastolic blood pressure in the upright position during the HUTT. This variability is assumed to affect the recurrence of BPPV.

Explorative study on lower inflection point dynamics during cardiopulmonary resuscitation: Potential implications for airway management

IntroductionIn patients undergoing cardiopulmonary resuscitation (CPR) after an Out-of-Hospital Cardiac Arrest (OHCA), intrathoracic airway closure can impede ventilation, adversely affecting patient outcomes. This explorative study investigates the evolution of intrathoracic airway closure by analyzing the lower inflection point (LIP) during the inspiration phase of CPR, aiming to identify the potential thresholds for alveolar recruitment. Methods and materialsEleven OHCA patients undergoing CPR with endotracheal intubation and manual bag ventilation were included. Flow and pressure measurements were obtained using Sensirion SFM3200AW and Wika CPT2500 sensors attached to the endotracheal tube, connected to a Surface Go Tablet for data collection. Flow data was analyzed in Microsoft Excel, while pressure data was processed using the Wika USBsoft2500 application. Analysis focused on the inspiration phase of the first 6–8 breaths, with an additional 2 breaths recorded and analyzed at the end of CPR. ResultsAcross the cohort, the median tidal volume was 870.00 ml (mL), average flow was 31.90 standard liters per minute (slm), and average pressure was 17.21 cmH2O. The calculated average LIP was 31.47 cmH2O. Most cases (72.7%) exhibited a negative trajectory in LIP evolution during CPR, with 2 cases (18.2%) showing a positive trajectory and 1 case remaining inconclusive. The average LIP in the first 8 breaths was significantly higher than in the last 2 breaths (p = 0.018). No significant correlation was found between average LIP and return of spontaneous circulation (ROSC), compression depth, frequency, or end-tidal CO2 (EtCO2). However, a significant negative correlation was observed between the average LIP of the last 2 breaths and CPR duration (p = 0.023). Validation: LIP calculation in low-flow ventilations using the novel mathematical method yielded values consistent with those reported in the literature. Discussion/conclusionThese explorative data demonstrate a predominantly negative trajectory in LIP evolution during CPR, suggesting potential challenges in maintaining airway patency. Limitations include a small sample size and sensor recording issues. Further research is warranted to explore the evolution of LIP and its implications for personalized ventilation strategies in CPR.

Evaluation of tubal patency based on peak injection pressure in four-dimensional hysterosalpingo-contrast sonography among infertile females: a preliminary study.

Although the application of four-dimensional hysterosalpingo-contrast sonography (4D-HyCoSy) has relatively good diagnostic accuracy for assessing the patency of the fallopian tubes, the evaluation process mainly relies on morphological findings of the fallopian tubes and pelvic cavity. The purpose of this study was to explore the relationship of peak injection pressure during 4D-HyCoSy and tubal patency to provide a quantitative indicator for the evaluation of fallopian tube patency. This study included infertile patients who underwent 4D-HyCoSy and laparoscopic chromopertubation (LC) between 2020 and 2022, with LC serving as the reference test for assessing tubal patency. For the HyCoSy procedure, the ultrasound contrast agent was injected automatically using a liquid injection machine, and real-time pressure values were recorded. Patients were classified based on tubal patency status in LC as bilaterally patent, unilaterally patent, or bilaterally nonpatent. The average peak injection pressure and contrast agent volume of different groups were compared. Receiver operating characteristic (ROC) curve analysis was employed to determine the cutoff value. A total of 268 infertile patients were enrolled in the study. With LC as the standard examination, the sensitivity and specificity of 4D-HyCoSy in diagnosing nonpatent fallopian tubes were 91.1% and 95.1%, respectively. In general, peak injection pressure was observed to gradually increase as tubal patency decreased (P<0.001), with average peak injection pressures of 233.5±66.3, 338.8±99.8, and 469.6±63.1 mmHg in the bilaterally patent, unilaterally patent, and bilaterally nonpatent groups, respectively. The volume of contrast agent used in patients in the bilaterally nonpatent group was significantly lower than that in the other two groups (P<0.01), with average volumes of 22.7±6.3, 24.3±9.3, and 18.9±9.2 mL, respectively. When one fallopian tube was patent, the area under the curve (AUC) for distinguishing obstruction from patency of the other fallopian tube was 0.827, with a sensitivity of 79.8% and a specificity of 74.3% (cutoff value: 254.3 mmHg). Similarly, when one fallopian tube was nonpatent, the AUC was 0.866, with a sensitivity of 90.6% and a specificity of 78.3% (cutoff value: 401.3 mmHg). Peak injection pressure during 4D-HyCoSy demonstrates promising diagnostic performance in evaluating fallopian tube patency in infertile patients.

Experimental study on pulsed pneumatic pre-fracturing grouting in sandy and clayey-silty hydrate-bearing sediments

Clayey-silty hydrate reservoirs in the South China Sea (SCS) are characterized by low permeability, poor strength, and weak cementation. In order to improve the injection effect of reservoir stimulation by high-viscosity grout, this paper proposes a pulsed pneumatic pre-fracturing grouting technology to enhance the injectability of grout and improve overall conductivity of hydrate-bearing sediments. In the pulsed pneumatic fracturing experiment, increasing the frequency ƒ results in higher average pneumatic pressure σavg and maximum pneumatic pressure σmax, maintaining elevated pneumatic pressure levels that reduce local soil strength and improve fracturing effectiveness. In addition, the fracture extension range is positively correlated with the pressure and frequency. In a pulsed pneumatic pre-fracturing grouting experiment, this technology outperformed the conventional fracturing grouting. At frequencies of 2.5 Hz, 5 Hz, and 10 Hz, the total extension distance of the grout consolidation body increases by 3.28, 4.43, and 4.71, respectively. Meanwhile, the total weight of the grout consolidation body increased by factors of 1.94, 2.45, and 3.57. Additionally, under high-frequency fracture initiation condition (10 Hz), the average thickness of the grout consolidation body doubled compared to that under low-frequency condition (2.5 Hz). In conclusion, the pulsed pneumatic pre-fracturing grouting technology significantly improved the injectability of high-viscosity grout and the effectiveness of grouting stimulation in sandy and clayey-silty hydrate-bearing sediments.