Pressure Surge Research Articles

Centrifugal Compressor Surge in Innovative Heat Pump: Fluid Dynamic and Vibrational Analysis

Abstract In the current energy scenario, it is necessary to reduce fossil fuel consumption to achieve the far-sighted and stringent decarbonization goals. To date, heat is mainly produced through fossil fuels. Alternatively, electrically driven heat pumps can exploit renewable power to recover environmental and waste heat, offering energy efficient and environmentally friendly heating and cooling for applications ranging from domestic and commercial buildings to process industries. For this reason, they are expected to play a primary role in complementing or displacing natural gas boilers in the residential and industrial sectors in the near future. Centrifugal compressors are already used as prime movers of the working fluid in heat pumps, thanks to their industrial replicability, compact size, affordable costs, and good performance in terms of efficiency and low noise. However, they are subject to instabilities such as surge and stall like any other dynamic compressor and these phenomena develop quite differently than in classic open-loop systems such as gas turbines. In fact, such peculiarity is mainly due to the closed-loop configuration with real gases in two-phase conditions, occurring in typical heat pump cycles. In addition, heat exchangers also contribute to make these phenomena different from what is commonly studied. Compressor surge in closed-loop heat pump systems has received lower attention than other applications by the engineering community, lacking dedicated experimental characterization, and clear exposition of the phenomenon. The aim of this paper is to experimentally investigate the behavior of a centrifugal compressor installed into an innovative close loop heat pump system under stable and unstable conditions from both vibrational and fluid-dynamic points of view. The impact of the main process parameters on the evolution of the instability is shown, highlighting how surge cycles change by varying system operating conditions. The energy contents of surge cycles and pressure fluctuations are highlighted, using data postprocessing techniques such as fast Fourier transform and phase locked average. The vibro-acoustic analysis enrich the comprehension of the phenomena. The experimental results shown in this paper can be a basis for the future development of validated mathematical models of closed-loop heat pumps systems equipped with dynamic compressors operating under stable and unstable operating conditions.

Effect of Nozzle Type on Combustion Characteristics of Ammonium Dinitramide-Based Energetic Propellant

The present study explores the influence of diverse nozzle geometries on the combustion characteristics of ADN-based energetic propellants. The pressure contour maps reveal a rapid initial increase in the average pressure of ADN-based propellants across the three different nozzles. Subsequently, the pressure tapers off gradually as time elapses. Notably, during the crucial initial period of 0–5 μs, the straight nozzle exhibited the most significant pressure surge at 30.2%, substantially outperforming the divergent (6.67%) and combined nozzles (15.5%). The combustion product variation curves indicate that the contents of reactants ADN and CH3OH underwent a steep decline, whereas the product N2O displayed a biphasic behavior, initially rising and subsequently declining. In contrast, the CO2 concentration remained on a steady ascent throughout the entire combustion process, which concluded within 10 μs. Our findings suggest that the straight nozzle facilitated the more expeditious generation of high-temperature and high-pressure combustion gases for ADN-based propellants, expediting reaction kinetics and enhancing combustion efficiency. This is attributed to the reduced intermittent interactions between the nozzle wall and shock waves, which are encountered in the divergent and combined nozzles. In conclusion, the superior combustion characteristics of ADN-based propellants in the straight nozzle, compared to the divergent and combined nozzles, underscore its potential in informing the design of advanced propulsion systems and guiding the development of innovative energetic propellants.

Specification of INF01LE, INF03, and INF04LE infrasound sensors for the observation and detection of destructive geophysical events

When an object moves through the atmosphere, it induces pressure fluctuations. If the scale of the object’s movement spans several hundred meters to several kilometers, the period of the pressure fluctuation will range from several seconds to several tens of seconds, determined by the ratio of the scale to the speed of sound. These pressure fluctuations manifest within the frequency range between audible sound (> 20 Hz) and infrasound (< 20 Hz and > 3 mHz). The infrasonic waves, characterized by their low-frequency nature, present a promising avenue for long-distance remote sensing, particularly in the monitoring of geophysical events with the potential for widespread destruction, such as earthquakes and tsunamis. We developed sensors of both membrane and microphone types to monitor infrasound in lower or higher frequency, respectively. These sensors were installed on the Pacific side of Japan to observe infrasound mainly generated by tsunamis. The key advantage lies in the faster propagation speed of Lamb waves (∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document}310 m/s) compared to that of tsunami waves (∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document}200 m/s), making them a valuable precursor for timely detection. By combining with a small MEMS 3-axis accelerometers, this study explores the feasibility of identifying a sudden atmospheric pressure surge within the infrasonic frequency range, following a significant earthquake. The observed surge serves as a crucial indicator of the imminent arrival of large tsunami waves along the shoreline situated between the earthquake’s epicenter and the observation site. The practical implication of this detection methodology is profound, as it could potentially trigger early warning systems, leading to timely and targeted evacuations. These infrasound sensors effectively detected infrasound produced not only by tsunamis but also by volcanic eruptions, meteorite explosions, and so on. This research focuses on the significance of monitoring geophysical events in the infrasound frequency range by demonstrating the development of our infrasound sensors and the natural phenomena captured by these instruments. The study presents observational results based on three types of sensors (INF01LE, INF03, and INF04LE), each exhibiting a flat response within specific frequency ranges: 0.003 to 6.25 Hz, 0.1 to 100 Hz, and 0.1 to 100 Hz, respectively. These sensors have been rigorously tested across various natural phenomena to validate their effectiveness in capturing infrasonic waves. The findings of this research contribute to the growing body of knowledge on infrasonic wave coming from various geophysical disaster perspectives.

Relationships among intensive blood pressure control, morning blood pressure surge and 24-hour blood pressure variability

Abstract Objectives This study aimed to investigate the relationships between cardiovascular outcomes and blood pressure (BP) reduction, 24-hour BP variability (BPV), morning BP surge (MBPS), and visit-to-visit BPV. Methods This study involved 897 participants from the Systolic Blood Pressure International Trial (SPRINT), for whom biochemical and demographic data, medication history, and various blood profile information were collected. Univariate and multivariate linear regression models were used to assess the impact of intensive BP management on 24-hour BPV and the MBPS. Results Among the 897 participants (average age 71.48 ± 9.42 years; 640 males), 453 received intensive treatment. Those in the intensive group were more likely to be on ACE inhibitors, CCBs, or diuretics. This group showed significant reductions in 24-hour systolic and diastolic BP, as well as in both short-term and long-term BPVs, such as average real variability (ARV) and MBPS. The analysis demonstrated strong associations between intensive BP management and improvements in various BPV measures, including systolic ARV, diastolic BP ARV, and cumulative BP loads. A significant correlation was also found between intensive BP lowering and the primary composite outcome of the SPRINT study. Conclusions This study highlighted the significant associations between intensive BP management and reductions in the MBPS and 24-hour BPV, which affect both short-term and long-term health outcomes. The primary benefits of intensive BP control appear to stem from direct BP reduction rather than changes in BPV. However, further extensive randomized controlled trials are needed to confirm these findings.

Neuroprotective agents ineffective in mitigating autonomic dysreflexia following experimental spinal cord injury

Background and objectivesLoss of supraspinal cardiovascular control and secondary damage following spinal cord injury (SCI) lead to cardiovascular dysfunction, where autonomic dysreflexia (AD), triggered by stimuli below the injury, can cause uncontrolled blood pressure (BP) surges, posing severe health risks such as stroke and seizures. While anti-inflammatory neuroprotective agents have been studied for motor recovery, their impact on cardiovascular function remains under investigated. The objective was to assess the efficacy of four clinically approved neuroprotective agents in promoting cardiovascular recovery following SCI. MethodsMale Wistar rats received contusion at the third thoracic spinal segment (T3). Fluoxetine, Glyburide, Valproic acid, and Indomethacin were first administered at 1 h or 6 h post-SCI, and every 12 h for two weeks thereafter. Four weeks following SCI, hemodynamics were measured at rest and during colorectal distension. Locomotor function was assessed prior to SCI and weekly for four weeks after SCI, using the Basso-Beattie-Bresnahan (BBB) locomotor scale. Quantitative comparisons of lesion area were performed. ResultsContrary to the published literature, Indomethacin and Valproic acid resulted in high morbidity and mortality rates 60 % and 40 % respectively) within 2–3 days of administration. Fluoxetine, and Glyburide were well-tolerated. There were no differences in change in systolic BP with colorectal distension compared to control i.e., all experimental groups experienced severe episodes of AD [F(6, 67) = 0.94, p = 0.47]. There was no significant difference in BBB scores in any experimental group compared to control [F(18, 252) = 0.3, p = 0.99]. No between-group differences were observed in tissue sparing at the lesion epicentre [F(6, 422) = 6.98, p = 0.29]. DiscussionDespite promising beneficial effect reported in previous studies, none of the drugs demonstrated improvement in cardiovascular or motor function. Indomethacin and Valproic acid exhibited unexpected high mortality at doses deemed safe in the literature. This emphasizes the necessity for reproducibility studies in pre-clinical research and underscores the importance of publishing null findings to guide future investigations.

Interaction of a self-expandable stent with the arterial wall in the presence of hypocellular and calcified plaques.

Self-expandable stents manufactured from nitinol alloys are commonly utilized alongside traditional balloon-expandable stents to provide scaffolding to stenosed arteries. However, a significant limitation hampering stent efficacy is restenosis, triggered by neointimal hyperplasia and resulting in the loss of gain in lumen size, post-intervention. In this study, a nonlinear finite element model was developed to simulate stent crimping and expansion and its interaction with the surrounding vessel in the presence of a plaque. The main aim was to determine contact pressures and forces induced at the interface between an artery wall with hypocellular and calcified plaques and an expanded stent. The results demonstrated the drawbacks of plaque calcification, which triggered a sharp contact pressure and radial force surge at the interface as well as a significant rise in von Mises stress within the vessel, potentially leading to rupture and restenosis. A regression line was then established to relate hypocellular and calcified plaques. The adjusted coefficient of determination indicated a good correlation between contact pressures for calcified and hypocellular plaque models. Regarding the directionality of wall properties, contact pressure and force observations were not significantly different between isotropic and anisotropic arteries. Moreover, variations in friction coefficients did not substantially affect the interfacial contact pressures.

Addressing multi-step inverse heat transfer problems via reduced order models in a cooling process for polymer pipes with sparse measurements

In modern polymer pipe extrusion processes with connected post-processing steps, the intermediate cooling and conditioning process is essential for the resulting product quality. In such cases, computationally efficient models are required for real-time process control and optimization. Unfortunately, heat transfer coefficients are rarely known for actual production processes, leading to an inverse heat transfer problem. Existing methods mainly rely on computationally intensive numerical models or on data intensive neural networks. Both are not suitable, if only sparse measurements are available and a fast execution time is required. In contrast to that, we propose to use a proper orthogonal decomposition and project the governing heat equation onto extracted basis functions via the Galerkin method. This leads to an efficient and accurate reduced order model, which can be used for parameter identification and subsequent process control. Regarding the identification, we address the ill-posed problem with well-known relative constraints, l2 regularization and decomposition of coefficients based on the Nusselt number. Simulation and experimental results show that the heat transfer coefficients are consistently identified and robust against initial parameter guesses despite sparse and noisy temperature measurements. Consequently, the proposed method can be efficiently applied in cooling and conditioning processes in polymer extrusion and related applications such as identifying the heat transfer coefficients and thermal resistance in pressurized surge lines of nuclear power plants and brick walls in melting furnaces respectively.

RETRACTION: Augmented venoarteriolar response with ageing is associated with morning blood pressure surge.

RETRACTION: Augmented venoarteriolar response with ageing is associated with morning blood pressure surge.

Daytime actisensitivity predicts nocturnal dipping patterns and morning surge in blood pressure: the Home-Activity ICT-based Japan Ambulatory Blood Pressure Monitoring Prospective study.

Ambulatory blood pressure (BP) is influenced by physical activity and the BP response to physical activity (actisensitivity) differs between individuals. This study investigated associations between daytime actisensitivity and nighttime BP dipping status and morning BP surge. Twenty-four-hour ambulatory BP monitoring (ABPM) with simultaneously monitored physical activity using a multisensor all-in-one device (TM-2441; A&D Company) was performed at baseline in HI-JAMP study participants. Those with complete BP measurements and complete physical activity monitoring data were included in this analysis. Actisensitivity was calculated as the slope of the regression line between daytime SBP and log-transformed physical activity over a 5 min period before each BP reading. Hyper and negative reactivity were defined as actisensitivity greater than 90th and less than 10th percentile, respectively. Data from 2692 individuals (mean age 69.9 ± 11.9 years; mean BMI 24.8 ± 4.1 kg/m2, 53.6% men) were analyzed. Those with hyper reactivity had a high prevalence of the extreme dipper pattern of nighttime BP and exaggerated morning BP surge; those with negative reactivity had higher nighttime BP and a riser pattern of nighttime BP. Results remained significant after adjusting for 24-h physical activity. Differences in diurnal BP variability based on actisensitivity were augmented in individuals aged at least 75 years. This study is the first to investigate associations between actisensitivity and 24-h ambulatory BP profiles using an all-in-one multisensor device in a large real-world population. The associations seen between either hyper or negative actisensitivity and abnormal diurnal BP variability, especially in the elderly, could contribute to increased cardiovascular event risk. University Hospital Medical Information Network Clinical Trials Registry, UMIN000029151 (HI-JAMP study).

A CASE REPORT: PHEOCHROMOCYTOMA-INDUCED HYPERTENSION IN A 65-YEAR-OLD PATIENT – AN ANESTHESIOLOGIST’S PERSPECTIVE

Pheochromocytoma is a rare adrenal gland tumor that produces excessive amounts of adrenaline and noradre­naline, leading to a surge in blood pressure. This condi­tion often goes undiagnosed due to its infrequency and diverse symptom presentation, surgery is considered as the definitive treatment. We report a 65-year-old male patient, initially referred to an endocrinologist for further evaluation of a mass in the right kidney discovered via Magnetic Resonance Imaging (MRI), leading to a diagno­sis of pheochromocytoma. Following a successful surgi­cal procedure and peri-operative period, the patient was discharged and advised to return to the hospital 1 month after the surgery and every 1 year for regular follow-ups.

Abstract MP01: Clinical Characteristics of Morning Blood Pressure Surge in Patients with Autonomic Failure

Autonomic failure (AF) is characterized by orthostatic hypotension (OH), but most of these patients also have nocturnal supine hypertension (SH), which has been associated with end-organ damage, pressure natriuresis, and worsening of daytime OH. About 30% of patients with SH, however, have a preserved nocturnal BP dipping that is likely associated with a morning BP surge (MBPS). To determine the pattern of MBPS and its association with dipping, natriuresis, and morning OH, we studied 92 AF patients (67±1 yr, 59% males; 32 multiple system atrophy and 60 peripheral autonomic failure [pAF]). Patients were studied off BP medications and placed on a low monoamine, caffeine-free diet containing 150 mEq/d sodium and 70 mEq/d potassium. Nocturnal BP was assessed every 2 hours from 8pm-8am, followed by a 10-minute standing test. Urine was collected for 24 hours and divided into two 12-hour periods. As expected, we found that dipping (systolic BP [SBP] fall ≥10% during nighttime sleep [12am-6am] from baseline [8pm to 10pm]) occurred in 33% of patients, with an average decrease of 35±5 mmHg at 4am. The MBPS (SBP increase at 8am from the average of 3 nighttime SBPs centered on the lowest one) was 10±2 mmHg (range -83 to 77 mmHg; MBPS≥ 20 mmHg, 23%). MBPS was negatively correlated with the magnitude of dipping (r=-0.328, p&lt;0.001; dippers 18±3 vs. nondippers 6±3 mmHg; p=0.010) and mean nighttime SBP (r=-0.230, p=0.028). The night-to-day ratio of sodium (r=-0.417, p=0.002) and urine (r=-0.292, p=0.037) excretion was also negatively correlated with MBPS, indicating that patients with greater MBPS had decreased natriuresis during the night compared to the day. In the morning, a greater MBPS was associated with a larger SBP drop on standing (r=-0.242, p=0.034). No associations were found between MBPS and age, sex, history of essential hypertension, or the underlying diagnosis of AF. To assess the hemodynamic mechanisms of the MBPS, we studied 17 AF patients (67±2 yr, 14 males, all pAF). We found that MBPS (13±5 mmHg, range -18 to 56 mmHg) was associated with an increase in systemic vascular resistance (SVR, r=0.777, p=0.01) and a higher augmentation index (Aix@75, r=0.516, p=0.049). In conclusion, a subset of AF patients had a preserved dipping pattern and an MBPS despite severe impairment of BP regulation. MBPS was associated with increased SVR, lower nighttime SBP, and lower night-to-day natriuresis, but the higher supine SBP in the morning was associated with worse OH.

Penstock pipe’s hydraulic design for the mini hydropower plant at Besai Kemu, Bukit Kemuning, Lampung, Indonesia

Abstract Hydropower, as a renewable energy source, holds significant potential for electricity generation. However, optimizing the design of hydropower penstocks to ensure efficient energy conversion remains a complex challenge. This study aims to address this gap by investigating the optimal hydraulic calculations for designing a penstock system in Lampung, Indonesia, thereby contributing to the understanding of micro hydropower engineering. The research adopts an explanatory methodology, utilizing a case study approach in Bukit Kemuning, Lampung, Indonesia. Design data collection at the research site and relevant hydraulic design indicators from literature serve as the foundation for conducting comprehensive hydraulic calculations. The study focuses on key parameters such as penstock dimensions, power generation capacity, and energy loss assessments to inform the design process. The analysis reveals a flow rate of 11 m3/s and a flow velocity of 2.43 m/s, resulting in a targeted power output of 3234 Kilowatts. The findings underscore the critical role of key elevation parameters and design considerations in optimizing the penstock system for efficient electricity generation. Detailed calculations elucidate the determination of penstock dimensions, the evaluation of energy losses, and the consideration of surge pressure velocity to ensure system resilience. To withstand high water pressure, the research advocates for penstock pipes with specific dimensions: two pipes, each 116 m in length, with a diameter of 2.4 m and a cross-sectional area of 4.52 m2 requiring a thickness of 10 mm. The study identifies pressure reduction factors, including head loss due to penstock friction (0.169 m), friction losses (0.1635 m), and water hammer reaching 2 bar with an acceleration of 88.03 m/s2. The net head after turbulent and friction losses is determined to be 30 m. This study highlights the importance of tailored design strategies in effectively harnessing hydropower resources, offering valuable insights for micro hydropower projects globally.

Comparative Analysis of Water Hammer Performance in Different Pipe Parameters with FSI

Water hammer (WH) is a critical phenomenon in fluid-filled piping systems that can lead to severe pressure surges and structural damage. The characteristics of the pipe material, geometry, and support conditions play a crucial role in the fluid–structure interaction (FSI) during WH events. This study investigates the impact of various pipe parameters, including material, length, thickness, and diameter, on the WH behavior using an FSI-based numerical approach. A comprehensive computational model was developed based on the algorithm presented in Delft Hydraulics Benchmark Problem (A) to simulate the WH phenomenon in pipes made of different materials, such as steel, copper, ductile iron, PPR (polypropylene random copolymer), and GRP (glass-reinforced plastic). This study examines the influence of pipe parameters on WH performance in pipelines, utilizing FSI to analyze the phenomenon. The results show that the pipe material has a significant influence on the pressure wave speed, stress wave propagation, and the overall system response during WH. Pipes with lower modulus of elasticity, such as PPR and GRP, exhibit lower pressure wave speeds but higher stress wave speeds compared with steel pipes. Increasing the elastic modulus, pipe wall thickness, length, and diameter enhances the pipe’s stiffness and impacts the timing, magnitude of pressure surges, and the likelihood of cavitation. The findings of this study provide valuable insights into the design and mitigation of WH in piping systems.

Prognostic value of morning blood pressure surge in chronic kidney disease.

This was a retrospective study. This study investigated the occurrence of a composite endpoints (cardiovascular and cerebrovascular events, end-stage renal disease, and death) in 153 patients (aged≥18years) with a diagnosis of in chronic kidney disease (CKD). Based on morning blood pressure surge (MBPS) defined as ≥35mm Hg, patients were divided into two groups: with MBPS (n=50) and without MBPS (n=103). All patients were followed up for at least 1year. Baseline demographic, laboratory and follow-up data were collected. The clinical characteristics of the two groups were compared. The relationships between MBPS and endpoint events were analyzed using the Kaplan-Meier method and Cox regression model. In total, 153 patients (mean age 41.8years; 56.86% males) were included in this study. During the follow-up period (mean 4.3years), 34 endpoint events occurred. After adjustment for the covariates, the risk of cardiovascular and cerebrovascular events, end-stage renal disease and death remained significantly higher in patients with MBPS (hazard ratio [HR] and 95% confidence interval [CI] 3.124 [1.096-9.130]]) Among the other variables, systolic blood pressure, and night-time and daytime pulse pressures remained significantly associated with outcome in patients of CKD (1.789 [1.205-2.654], 1.710 [1.200-2.437], and 1.318 [1.096-1.586], respectively]. In conclusions, MBPS was identified as an independent prognostic factor for composite endpoint events (cardiovascular and cerebrovascular events, end-stage renal disease and death) patients with chronic kidney disease patients.

Mapping Pressure Surge Source in Urban Water Networks: Integrating Low‐ and High‐Frequency Pressure Data With an Illustrative Real Case Study

AbstractThis paper introduces a novel methodology that integrates low‐ and high‐frequency pressure monitoring in the parts of the urban water distribution network characterized by the largest number of repairing operations. This integrated approach aims to pinpoint the source and characterize potentially dangerous pressure variations. The actual behavior of a real operational water distribution network is considered as an example to verify the effectiveness of the proposed methodology. The analysis of the acquired pressure signals allows for mapping frequent pressure surges and identifying their source in the functioning conditions of a big user. Notwithstanding these pressure variations are not overly large, according to the literature, their near‐continuous nature poses a risk of inducing pipe breaks, and then leakage, due to fatigue. The proposed method integrating routine low‐frequency measurements with targeted high‐frequency surveys provides a cost‐effective, proactive management strategy.

Numerical modeling of cavity collapse water hammer in pipeline systems: Internal mechanisms and influential factors of transient flow and secondary pressure rise dynamics

This study explores the dynamics of pressure wave propagation and cavitation in pressurized pipelines during and after the rapid closure of the pipeline's end ball valve, utilizing a three-dimensional computational fluid dynamics approach with the method of characteristics, validated against Bergant and Simpson's experimental data of three degrees of cavitation. It innovatively examines transient pressure dynamics through both energy transformation and wave propagation perspectives, focusing on the phases of water column separation and coalescence, and the dynamics of flow interruption bubbles. The research delves into the detailed mechanisms of pressure wave propagation and further assesses the effects of physical factors. Key findings include: (1) As initial inlet velocities increase, cavitation starts earlier, extends further, and intensifies, with higher final volume fractions near the valve, indicating that higher velocities exacerbate cavitation. Higher inlet velocities also correlate with more intricate and expansive vortex formations. (2) Secondary pressure surges in water hammer result from the superposition of two-stage positive pressure waves. Initially, positive pressure waves within the conduit reflect twice from air pockets and the upstream boundary, remaining positive. Subsequently, they interact with secondary positive pressure waves reflected by the valve, causing a secondary pressure surge. (3) The fluid flow is laterally symmetry in the pipe cross section, except for minor local asymmetrical spikes in areas with vapor bubbles. Velocity discrepancies are notable near the pipe walls due to vapor accumulation, primarily on the upper wall due to buoyancy. This accumulation may narrow the flow area, possibly accelerating the water passing by. (4) Lower flow velocities, downward inclines, and slower valve closures diminish secondary pressure rise amplitudes in water hammer events, while reduced static heads intensify cavitation despite lessening pulse amplitudes. These findings offer valuable insights for the design and operational guidance of complex hydraulic systems during transient processes in urban water supplies.

POD–ANN as digital twins for surge line thermal stratification

This paper describes a hybrid proper orthogonal decomposition (POD) and artificial neural network (ANN) strategy to construct digital twins of a pressurizer surge line under thermal stratification conditions. The one-way coupled conjugate heat transfer and thermal stress analysis was conducted by use of parametric modeling and the introduction of the inverse distance weighted interpolation for the grid mapping, which allows for the mapped grids to have the same number of nodes regardless of variations of surge line geometries. A snapshot-based POD was utilized to obtain truncated lower-order modes and the full-order system response was projected onto these modes with reduced state coefficients. Then the ANN was employed to establish a surrogate model between the five chosen design variables of interest and the reduced state coefficients, resulting in a surrogate-assisted digital twin for a pressurizer surge line. Prediction of fluid–structure interface temperature and thermal stress distribution was thus achieved in an in-line real-time manner for a wide range of parameter variations. We publicly share all code implementations, and we believe that our efforts open a door for the digital twining of thermo–fluid–structure interaction problems

Psychological distress, forced awakening, and morning blood pressure surge.

Morning blood pressure surge (MBPS) has been recognized as an independent predictor of cardiovascular disease events. Psychological distress, including anxiety, depression, and perceived stress, and behavioral risk factors, such as poor sleep quality, have been associated with increased MBPS. Elevations in sympathetic activity induced by forced awakening may also contribute to further increases in MBPS. Yet, no examination of the interrelationships among psychological distress, sleep quality, awakening mode (natural vs. forced awakenings), and MBPS has been undertaken. This pilot study aimed: (1) to examine if MBPS differs by awakening mode and (2) to investigate whether psychological distress is associated with MBPS difference between natural and forced awakenings, independent of sleep quality. Thirty-two healthy adults were included in this cross-sectional study. Blood pressure was measured using a beat-to-beat blood pressure monitor over two nights, consisting of one night of natural awakening and one night of forced awakening. Psychological distress and sleep quality were assessed using questionnaires. We conducted paired t-tests (aim 1) and multiple linear regressions (aim 2). MBPS was significantly greater during forced awakening compared with natural awakening. In addition, the MBPS difference between natural and forced awakenings was significantly greater in participants with higher anxiety levels, independent of sleep quality. We found that augmentation of MBPS by forced awakening was significantly greater in individuals who reported higher anxiety levels. Additional research is needed to examine the potential impacts of forced awakening and anxiety on MBPS in a larger sample of individuals at risk for cardiovascular disease.

Blood pressure changes during ketamine infusion for the treatment of depression

ObjectiveThis study aimed to examine blood pressure changes during ketamine infusion for depression and exploring the factors associated with these changes. MethodThis study is a retrospective chart-review of patients with depression undergoing ketamine infusion at Yale Psychiatry Hospital during a 7-year period. Blood pressure (BP) was recorded every 10 min during the infusion. Surges in systolic and diastolic blood pressure (SBP, DBP), along with severe hypertension events, were analyzed in relation to patient demographics. ResultsA total of 138 patients received a total of 2342 infusions. SBP and DBP peaked at 40 min after the start of the infusion with a mean change of 16.0 (SD: 11.2) and 11.0 mmHg (SD: 8.45) respectively. Severe hypertension was observed in 17 patients (12.5%) and 23 infusion sessions (0.98%), occuring more frequently during the first three infusions (43.4%). Age (OR = 1.04 [1.02,1.05], p-value <0.001) was significantly associated with a surge in SBP and all patients with a past medical history of hypertension experienced a BP surge during their infusions. ConclusionKetamine infusions can cause significant blood pressure increases, particularly in older and hypertensive patients, highlighting the need for careful cardiovascular monitoring to mitigate risks during treatment.

The impact of forced awakening on morning blood pressure surge

BackgroundPoor sleep quality can cause an increase in morning blood pressure surge (MBPS), an independent risk factor of cardiovascular disease (CVD) events. Awakening induced by external factors such as alarm clocks, may also contribute to increased MBPS. ObjectivesTo (1) compare the MBPS and sleep quality parameters between natural and forced awakenings and (2) examine the potential impact of forced awakening on MBPS, independent of sleep quality. MethodsThirty-two healthy adults participated in this pilot study, which included one night of natural awakening and one night of forced awakening (i.e., sleep was interrupted by an alarm after five hours). Objective and self-reported sleep quality parameters were measured using a multisensory wristband and sleep diaries, respectively, and beat-to-beat blood pressure variability was assessed using a continuous blood pressure monitor. Analyses included a paired t-test (objective 1) and linear mixed models (objective 2). ResultsParticipants predominantly consisted of young, healthy, and highly educated Asian adults. During the night of sleep with forced awakening, significantly higher MBPS, lower objective wakefulness after sleep onset, and lower self-reported sleep latency were observed, compared to the night with natural awakening. Forced awakening was significantly associated with increased MBPS after controlling for age, sex, mean arterial pressure, and sleep quality. ConclusionsForced awakening may significantly increase MBPS, consequently heightening the risk of CVD events. Study findings should be validated in a larger sample. Further research is also warranted to examine the impact of forced awakening on MBPS in individuals with CVD.