Pressure Increment Research Articles

Effects of daily artificial gravity training on orthostatic tolerance following 60-day strict head-down tilt bedrest

PurposeOrthostatic intolerance commonly occurs following immobilization or space flight. We hypothesized that daily artificial gravity training through short-arm centrifugation could help to maintain orthostatic tolerance following head-down tilt bedrest, which is an established terrestrial model for weightlessness.MethodsWe studied 24 healthy persons (eight women; age 33.3 ± 9.0 years; BMI 24.3 ± 2.1 kg/m2) who participated in the 60-days head-down tilt bedrest (AGBRESA) study. They were assigned to 30 min/day continuous or 6 × 5 min intermittent short-arm centrifugation with 1Gz at the center of mass or a control group. We performed head-up tilt testing with incremental lower-body negative pressure until presyncope before and after bedrest. We recorded an electrocardiogram, beat-to-beat finger blood pressure, and brachial blood pressure and obtained blood samples from an antecubital venous catheter. Orthostatic tolerance was defined as time to presyncope. We related changes in orthostatic tolerance to changes in plasma volume determined by carbon dioxide rebreathing.ResultsCompared with baseline measurements, supine and upright heart rate increased in all three groups following head-down tilt bedrest. Compared with baseline measurements, time to presyncope decreased by 323 ± 235 s with continuous centrifugation, by 296 ± 508 s with intermittent centrifugation, and by 801 ± 354 s in the control group (p = 0.0249 between interventions). The change in orthostatic tolerance was not correlated with changes in plasma volume.ConclusionsDaily artificial gravity training on a short-arm centrifuge attenuated the reduction in orthostatic tolerance after 60 days of head-down tilt bedrest.

Mechanically strong and heat-resistant waste poly (ethylene terephthalate) derived by carbon dioxide treatment at ambient temperature

Due to the ever-increasing consumption of poly (ethylene terephthalate) (PET) for the industries of packaging and electronics, the waste non-degradable PET has brought serious ecological pollution. However, the current recovery rate of waste PET is still limited, and the mechanical and heat-resistant properties are too poor to meet the requirements of practical applications. The recycling of waste PET is of practical significance to material/energy saving and environmental protection, contributing to the sustainable development of economy and society. In this work, an innovative method was proposed to fabricate strong and heat-resistant materials by using waste PET bottle flakes via carbon dioxide (CO2) treatment at ambient temperature. The results show that the crystallinity of the PET samples treated by CO2 at 800 psi is increased by 30.6%, the tensile strength and Young's modulus are increased by 21.9% and 20.6%, respectively, compared with untreated samples. Moreover, the dynamic mechanical analysis indicates that the heat-resistant performance of CO2-treated samples is significantly improved, whose storage modulus increased 33.5% and glass transition temperature increased 17.7 °C. Furthermore, aiming to investigate how the CO2-treatment improved the mechanical performance of the waste PET, the sorption-desorption experiments were conducted to examine the sorption kinetics of CO2 in the matrix, combined with the Avrami model employed to analyze the crystallization kinetics of PET under high-pressure CO2. It demonstrates that the enhancement of the tensile strength is ascribed to the transition of crystals from two-dimensional structures to three-dimensional structures with an increment in the CO2 pressure.

Enhanced optoelectronic activity of lead-free halide perovskites KMBr3 (M = Ge, Sn) under hydrostatic pressure

The density functional theory was used to investigate lead-free tin- and germanium-based halide perovskites KMBr3 (M = Sn, Ge) under pressure (0 to 10 GPa). The structural, electronic, optical, and mechanical properties are inquired to determine their potentiality as future photovoltaic materials. The structure shows high accuracy in terms of lattice parameters, which goodly comply with previously reported data. The estimated band gap demonstrates the compounds’ semiconducting nature at zero pressure condition. But the increment of pressure lowers the band gap, improving their conductivity. Furthermore, charge density differences between K-Br and Sn(Ge)-Br are used to determine whether the bonds are ionic or covalent. Besides, the bond length consistently decreases, resulting in stronger bonding under pressure. In addition, the optical functions are improved by pressure, suggesting that these materials could be used in multiple optoelectronic devices operating in the visible and ultraviolet spectrums. Furthermore, the hydrostatic pressure has a prominent effect on the mechanical properties while maintaining stability. The ductile natures as well as the anisotropic behavior get more intensive under applied pressure.

How to evaluate hydrogen storage properties by Sieverts’ method in the pressure range up to 100 MPa

In order to develop suitable hydrogen storage materials for thermochemical hydrogen compressor using metal hydride, it is necessary to evaluate hydrogen storage properties in high pressure range up to 100 MPa. However, several unexpected issues arose for measuring P-C isotherms up to 100 MPa, which was not observed for the relatively lower pressure range. This led to strange shape of P-C isotherms. In order to solve these, in this paper, we considered the effect of the inner volume of the valve, the pressure increment by a valve operation, and the volume expansion of the sample upon hydrogen absorption. Taken into account these factors, reasonable P-C isotherms were successfully obtained.

Multiobjective and multicondition optimization for a gas–liquid mixed-flow pump based on a three-dimensional inverse design

The mixed-flow pump performs well in transporting gas–liquid mixtures with large flow rates and high inlet gas volume fractions. However, its extensive development is still limited by the operating range and poor overall performance. In this study, a multiobjective and multicondition optimization methodology for improving the gas–liquid flow performance of a mixed-flow pump based on the inverse design is proposed. The impeller blade load is taken as the optimization variable. Moreover, the Euclidean distances of the pressure increment, efficiency, and gas volume fraction in the diffuser are adopted as optimization objectives. Results show that the numerical methodology is verified by the pressure increment and gas distribution obtained in the tests of the original pump. Optimized results demonstrate that the slope of the straight line, the stacking angle at the hub, and the intersection point of the rear parabola and the straight line significantly affect the objectives. The increased load of the first half of the impeller and the reduced load of the second half may improve the comprehensive performance of mixed-flow pumps. The blade length and wrap angle are reduced after optimization, which changes the inlet and outlet angles and deflection of the blade, thereby helping to enhance the cognition of mixed-flow pump performance optimization.

CHANGES ON RIGHT VENTRICULAR DIMENSIONS, FUNCTION, AND PULMONARY CIRCULATION LOADING ACCORDING TO THE DEGREE OF INTERDIALYTIC WEIGHT GAIN IN MAINTENANCE HEMODIALYSIS PATIENTS

Objective: The right ventricle (RV) is a thin-walled cardiac chamber, whose sizing and pressure characteristics are susceptible to altered loading conditions. This study aimed to investigate changes in RV's function, right heart's dimensions, and pulmonary pressures in relation to the degree of fluid accumulation between hemodialysis sessions, evaluated according to the recommended threshold of interdialytic-weight-gain corrected for dry weight (IDWG%). Design and method: Forty-one patients receiving standard thrice-weekly hemodialysis were divided into a higher (> 4.5%) and a lower ( < 4.5%) IDWG% group for the present analysis, according to the recommended higher threshold of IDWG%. All participants underwent a 2-dimensional echocardiographic assessment at the start and the end of the 3-day and the 2-day interdialytic interval in a crossover design. Results: RV systolic pressure (RVSP) increments were more pronounced in the higher compared to the lower IDWG% group (16.43 ± 5.37 vs 14.11 ± 13.38 mmHg respectively, p = 0.015) over the 3-day interval, while changes in RV filling pressures, assessed by RV E/Em did not differ significantly between the two groups (p = 0.84). Significant right heart chambers’ enlargement was observed in both groups and during both intervals, but a more prominent dilatation of inferior vena cava was noted in patients with higher IDWG% (0.44 ± 0.25 vs 0.2 ± 0.31cm, p = 0.014) over the 2-day interval. Conclusions: During the 3-day interdialytic interval, pulmonary circulation is particularly overloaded in patients with fluid accumulation higher that the recommended thresholds, as evidenced by higher RVSP elevations. This finding may add another plausible mechanism for increased cardiovascular morbidity and mortality during the long interval.

Seismic performance of U-shaped spillway retaining wall from shake table tests

A series of large-scale shake table tests were performed to evaluate the seismic behavior of a U-shaped spillway retaining wall. Three test model configurations were employed using different backfill conditions in terms of in-place soil density. Two earthquake records were employed as input motion and scaled in terms of time duration and acceleration amplitude to assess various aspects of seismic response. The test results showed that dynamic wall deflection and wall bending moment generally increased with Peak Ground Acceleration (PGA) amplitude. At peak wall deflection, the seismic earth pressure increment coefficient (ΔKAE) was back-calculated from the measured bending moment along each wall. In addition, the location of ΔKAE along the wall height and the resulting base moment were evaluated and discussed. The results suggested that seismic demands were generally lower up to a PGA of about 0.8 g, compared to the classic Seed and Whitman recommendation for seismic lateral earth pressure and seismic bending moment of retaining walls. Beyond PGA of 0.8 g, test results were in general agreement with the Seed and Whitman solution. Finally, two-dimensional finite element analyses were performed, and the computational results showed overall reasonable agreement with the experimental data.

Implementation of community services of glaucoma counseling in Citra Medika Hospital of Sidoarjo

Background: Glaucoma is a disease attributed to damage to the optic nerve, resulting in decreased visual field and vision function. Glaucoma's main risk factor is the increment of intraocular pressure due to an imbalance of aqueous humor production and secretion. If this condition goes untreated, it will lead to retinal ganglion cell degeneration. These cells are part of the central nervous system, which has cell bodies in the retinal layer and axons in the optic nerve. These cells' degeneration causes cupping, which is the appearance of the optic disc and vision loss. Glaucoma's cause has yet to be identified, and not all factors that cause its progression have been found. Objectives: this community dedication was written to access the society knowledge about glaucoma. Methods: This project entailed counseling the community around Citra Medika Hospital, Sidoarjo. This community service was conducted by co-assistant members of the Faculty of Medicing, Hang Tuah University, Surabaya. It aimed to provide participants with an understanding of glaucoma, including its types, risk factors, and preventive measures. Discussion: The participants in this community outreach were the individuals waiting for their relatives at the eye outpatient installation at Citra Medika Hospital, Sidoarjo. In total, 30% of the participants were male and 70% were female. Conclusion: This community service is expected to increase public awareness of glaucoma. As a result, they may then carry out examinations when they encounter glaucoma-related symptoms.

Hemodynamic changes associated to increments of PEEP in mechanically ventilated patients admitted into the cardiac intensive care unit

Abstract Funding Acknowledgements Type of funding sources: None. Background Current evidence suggests that incremental levels of PEEP generate an increase in right intracavitary pressures, diminishing venous return and consequently lessening left ventricular preload and stroke volume, resulting in a significant decrease of cardiac output. Nonetheless, most studies regarding these interactions have been done in patients requiring mechanical ventilation for non-cardiac disorders or in animals. We studied the effects of incremental levels of PEEP on cardiac intracavitary pressures and hemodynamics in mechanically ventilated patients admitted into the Cardiac Intensive Care Unit. Purpose We aimed to model how increments in PEEP alter cardiac output and other hemodynamic variables in patients with cardiac disfunction. Methods We included 14 mechanically ventilated patients admitted into a Cardiac Intensive Care Unit from 2018 to 2020. Data on intracavitary pressures and hemodynamics were recorded via Swan-Ganz catheterization and echocardiographic imaging. We documented measurements for all variables of interest at three different levels of PEEP: 5cmH2O, 10cmH2O and 15cmH2O. We conducted general descriptive statistics, mean comparison tests for paired data and linear regression models with Stata version 12.0 (StataCorp LP, College Station, TX). Results 7 (50%) patients admitted in the study had cardiogenic shock, 11 (79%) patients were mechanically ventilated in a volume-controlled setting and 3 (21%) were on pressure support ventilation. Seven (50%) patients needed vasoactive drugs during the study. Only 1 (7%) patient required an intra-aortic balloon pump. Seven (50%) patients had a visual left ventricular ejection fraction lesser than 40% and 3 (21%) had a moderate-severe mitral regurgitation. Paired mean testing by groups associated to gains of PEEP revealed statistically significant increments in Mean Pulmonary Artery Pressure (mPAP), Pulmonary Capillary Wedge Pressure (PCWP) and Central Venous Pressure (CVP). Inversely, increments of PEEP were linked to significant decrements in Cardiac Output (CO) [Figure 1 & Table 1]. Conclusions In mechanically ventilated patients admitted into the Cardiac Intensive Care Unit, rises in PEEP are associated to increments in intracavitary cardiac pressures, and inversely, with decrements in cardiac output. Although our findings are statistically significant, we have yet to clarify whether these are clinically meaningful, specifically within PEEP increments of 5 to 10cmH2O, the usual range in clinical practice.

Clinical, ultrasonographic, and functional outcomes after obstetric anal sphincter injury primary repair: A single-center experience.

To present clinical and instrumental sequelae after obstetric anal sphincter injuries (OASIS), evaluating correlations between intrapartum severity of lesions, postpartum symptoms, and sonographic and manometric findings; outcomes during subsequent deliveries were also evaluated. This retrospective study evaluated all consecutive women who sustained an OASIS between 2015 and 2020. Postpartum symptoms, anorectal manometry (ARM), and three-dimensional endoanal ultrasonography (3D-EAUS) were analyzed. A total of 107 women underwent OASIS primary repair; 84 (78.5%) of them were asymptomatic after 1 month. The presence and severity of symptoms showed a great correlation with instrumental outcomes in terms of maximum resting pressure, squeeze pressure increment (SPI), circumferential extension of defect for both external anal sphincter (EAS) and internal anal sphincter (IAS), and EAS, IAS and total Starck scores. There was a significant correlation between ARM and 3D-EAUS findings, with the exception of SPI, for which the abnormalities were not predictable based on EAUS results. Both ARM and EAUS findings after OASIS are directly related to each other, and associated with symptoms. These instrumental tools may be useful for OASIS assessment and counseling.

Numerical investigation of gas–liquid two-phase performance in a mixed-flow pump by using a modified drag force model

As key devices to lift deep-sea oil and gas, mixed-flow pumps can transport multiphase flow with high inlet gas volume fraction (IGVF). Performance parameters of mixed-flow pumps may be disturbed by the complex flow and gas–liquid distribution under various conditions that need an accurate two-phase flow numerical methodology for prediction. In this work, the gas–liquid mixed flow performance of a mixed-flow pump is investigated based on the modified drag force model, which considers the bubble deformation at high IGVF. The effects of the IGVF on pressure increment and gas phase distribution are explored. The influences of flow rate and rotational speed are studied as well. Experiments are conducted to obtain performance parameters and gas–liquid distribution images. The results show that performance parameters and gas–liquid distribution predicted in simulations are consistent with those obtained in experiments. The pressure increment of the mixed-flow pump is decreased as the IGVF and flow rate increase. Especially when IGVF increases from 5% to 15%, the pressure increment drops sharply, which is the surging phenomenon. The increased speed may improve the performance. The evolution of gas phase distribution is deeply analyzed to improve the understanding of gas–liquid flow characteristics in mixed-flow pumps.

Satellite Study of the <i>E. huxleyi Phenomenon</i> in the Barents, Norwegian, and Greenland Seas in 2003–2021: Temporal Dynamics of the Bloom Areal Extent, Inorganic Carbon Production and CО2 Partial Pressure in Surface Water

Based on satellite data, E. huxleyi bloom contouring, quantification of particulate inorganic carbon (PIC) production and increment of CO2 partial pressure, (pCO2) in surface water were performed. 18-year (2003–2021) time series of these variables are obtained for the Norwegian, Greenland and Barents seas. The bloom areas in the North Atlantic–Arctic water are the lowest in the Greenland Sea varying from 10×103 km2 to (20–40)×103 km2. In the Norwegian and Barents Seas they reach in some years (60–80)×103 km2 and (500–600)×103 km2, respectively. The total PIC content within E. huxleyi blooms rarely exceeds in the Greenland and Norwegian seas 12–14 kilotons and 40 kilotons, respectively. In the Barents Sea, in some years, it can be up to 550 kilotons. The highest level of pCO2 within E. huxleyi blooms in surface waters in the Barents Sea was ~350 µatm. In the Norwegian Sea, pCO2 in surface waters within the E. huxleyi bloom was also close to 350 µatm, but most often it remained about 250 µatm. In the Greenland Sea there were only four years of relatively enhanced pCO2 (up to 250 µatm), otherwise remaining below the level of confident determination by our method. As E. huxleyi blooms are generally very extensive, occur throughout the entire World Oceans (and hence in sum occur all year around), this phenomenon has a potential to both decrease to some degree the role of the World Oceans as sinkers of atmospheric CO2, and affect the carbonate counter pump.

Seismic coefficients for pseudo-static analysis of wrap-faced GRS walls with nonlinear soil fills

Pseudo-static seismic design procedure for Geosynthetic Reinforced Soil (GRS) walls includes the selection of a suitable horizontal seismic coefficient for external and internal stability analysis. The present guidelines for the seismic design of GRS walls have been mostly adopted from studies performed on conventional retaining walls. Hence, it is required to study the seismic response of GRS walls. In the present study, a finite element (FE) model of a wrap-faced GRS wall was developed in OpenSees. It was analysed for multiple earthquake time histories to study the variability in earthquake characteristics. The shaking level was also varied from 0.12g to 0.48g to consider the nonlinear response of backfill soil. The acceleration response and dynamic earth pressure increment in the wall were observed to increase with the shaking level but at a lower rate for higher shaking levels. The reinforcement force increments under seismic loading also showed a similar response. The internal failure plane in the GRS wall was slightly inclined, although not completely aligned with Rankine's active failure plane. Seismic coefficients are recommended for wrap-faced GRS walls as a function of PHA. The coefficients were calibrated using the maximum earth pressure and reinforcement forces obtained from FE analysis. The effect of reinforcement stiffness is also incorporated in the recommendation for internal stability analysis. A seismic coefficient greater than PHA is suggested at low shaking levels. It is in direct contrast to many previous studies as the coefficients are calibrated considering the maximum force demand in the GRS wall. Force-based designs need to consider the applicability of maximum earth pressure and reinforcement forces in the GRS wall, which can cause either external or internal instability in the wall. While at higher PHAs, the seismic coefficient should be almost constant to provide reliable estimates of earth pressure and reinforcement forces.

DFT Insights into Noble Gold-Based Compound Li5AuP2: Effect of Pressure on Physical Properties.

In this study, the Li5AuP2 compound is investigated in detail due to the unique chemical properties of gold that are different from other metals. Pressure is applied to the compound from 0 to 25 GPa to reveal its structural, mechanical, electronic, and dynamical properties using density functional theory (DFT). Within this pressure range, the compound is optimized with a tetragonal crystal structure, making it mechanically and dynamically stable above 18 GPa and resulting in an increment of bulk, shear, and Young's moduli of Li5AuP2. Pressure application, furthermore, changes the brittle or ductile nature of the compound. The anisotropic elastic and sound wave velocities are visualized in three dimensions. The thermal properties of the Li5AuP2 compound are obtained, including enthalpy, free energy, entropy × T, heat capacity, and Debye temperature. The electronic properties of the Li5AuP2 compound are studied using the Perdew-Burke-Ernzerhof (PBE) and Heyd-Scuseria-Ernzerhof (HSE) functionals. The pressure increment is found to result in higher band gap values. The Mulliken and bond overlap populations are also determined to reveal the chemical nature of this compound. The optical properties, such as dielectric functions, refractive index, and energy loss function of the Li5AuP2 compound, are established in detail. To our knowledge, this is the first attempt to study this compound in such detail, thus, making the results obtained here beneficial for future studies related to the chemistry of gold.

Flow Pressure Characteristics of the Ahmed Glaucoma Valve and Possible Effect of Entrapped Air in the Tube.

The purpose of this study was to assess the pressure characteristics of the Ahmed Glaucoma Valve (AGV) and possible effects of air trapped in the tube. Physiologic saline was pumped through 17 AGVs using a syringe infusion pump, and the flow pressure was measured by a set of pressure transducers. During the infusion at a rate of 2µL/minute, the pressure measurement was repeated twice in each AGV to determine the repriming pressures with/without air (1µL) in the tube. After a pressure surge occurred during the initial priming, the pressure decreased suddenly and then became constant. The repriming pressure, determined as the peak pressure before valve opening, was significantly (P < 0.0001, paired t-test) higher with air (26.5 ± 6.8 mm Hg) than without air (12.1 ± 3.8 mm Hg), whereas the constant pressures after repriming was equivalent between with (10.6 ± 3.7 mm Hg) and without (10.4 ± 2.9 mm Hg) air conditions (P = 0.68). Air in the AGV tube causes increased repriming pressure of about two-fold compared to repriming without air. This pressure increment caused by air in the capillary-sized tube might occur because of the effects of viscosity pressure and capillary pressure. To ensure stable surgical results, surgeons are advised to not allow air to remain in the tube. Pars plana tube insertion of the AGV combined with gas tamponade surgery may result in higher-than-expected intraocular pressure. Conversely, injection of air/gas can avoid postoperative hypotony when the AGV is implanted in eyes with a high risk of hypotony.

Research on Panel Flutter Considering the Effect of Convective Active Cooling

The aeroelastic characteristics of the panel under the action of coolant are obviously different from the flutter characteristics of the traditional panel. In order to solve this problem, the dynamics model of the panel flutter was established in this paper based on von Karman’s large deformation theory and the Kirchhoff–Love hypothesis. The panel dynamics equations were discretized into constant differential equations with finite degrees of freedom by Galerkin’s method, and solved by the fourth Runge–Kutta method in the time domain. The nonlinear modified piston theory was used to predict the unsteady aerodynamic loads, and the accuracy of the flutter analysis model was verified. On this basis, the effects of the head-panel pressure of coolant, the pressure drop ratio, the coolant injection direction, and the inertial resistance and viscous resistance on panel stability and flight stability were investigated, respectively. The results showed that reducing the pressure drop ratio, and reducing or increasing the head-panel pressure (valuing away from the freestream pressure) can improve the critical dynamic pressure when bifurcation occurs. At M∞=5.0, the pressure drop ratio causes a 22.1% increment in the critical dynamic pressure. The influence of the coolant injection direction on the panel bifurcation is mainly influenced by the head-panel pressure. The inertial resistance slows down the convergence process of the panel response, increases the limit cycle amplitude, and reduces the critical dynamic pressure of the panel, while the viscous resistance plays the opposite role. Based on these conclusions, this paper finally proposes the suppression method of panel fluttering from head-panel pressure, inertial resistance, viscous resistance, etc.

Defecatory disorders in patients with type 1 diabetes and chronic constipation.

Chronic constipation (CC) may be caused by defecatory disorders (DDs) and associated with reduced rectal sensation. Among patients with type 1 diabetes (T1D) and CC (T1DCC patients), the prevalence of DDs and reduced rectal sensation is unknown. We sought to compare complications of T1D, anorectal dysfunction, and CC symptoms, among T1DCC patients with versus without a DD. Anorectal pressures at rest and during squeeze and evacuation, as well as rectal sensation and rectal balloon expulsion time (BET) were measured with high-resolution anorectal manometry in 114 consecutive T1DCC patients. Thirty-seven patients (32%) had prolonged BET, suggestive of a DD. Complications of T1D included peripheral neuropathy (n = 67, 59%), retinopathy (n = 42, 37%), and nephropathy (n = 26, 23%). Among these complications, only retinopathy was associated with, that is, more prevalent in patients with normal (45%) than prolonged BET (19%). Compared with patients with normal BET, patients with prolonged BET had a lower rectal pressure (mean [SD], 32 [23] mm Hg vs. 23 [19] mm Hg, p = 0.03), greater anal pressure (91 [23] mm Hg vs. 68 [36] mm Hg, p < 0.001), and lower rectoanal gradient (-67 [30] mm Hg vs. -36 [32] mm Hg, p < 0.0001) during evacuation. Anal resting pressure and anal squeeze increment were below normal in 14 (13%) and 32 (29%) of patients and one or more rectal sensory thresholds were above normal in 34 (30%) patients; these abnormalities affected similar proportions in the normal and prolonged BET cohorts. Among T1DCC patients, 37 (32%) had prolonged BET, which was associated with anorectal pressures indicative of a DD but was not associated with reduced rectal sensation, suggesting that DDs are more likely explained by abdomino-anal dyscoordination than visceral disturbance.

Lining failure performance of highway tunnels induced by the drainage system deterioration

Lining cracks and water leakage induced by tunnel drainage system deterioration occurred frequently, which have seriously influenced the durability of operation tunnels. In this paper, a series of model experiments and numerical simulations were performed to investigate the hydro-mechanical damage mechanism of the lining under the drainage system deterioration and groundwater height variation conditions. By combining model tests and numerical simulation, the seepage field distribution, the mechanical characteristics, and the failure evolution of the lining were conducted. Results reveal that the water pressure behind the tunnel lining increases as the drainage system deterioration, especially at the tunnel foot. The higher the groundwater height, the greater the water pressure increment with the blockage process. Furthermore, the internal force abruptly changes at the tunnel foot with the drainage system deterioration, and the maximum tensile stress on the lining foot outside reaches the damage strength of 2 MPa when the groundwater height exceeds 30 m, whereas the maximum compressive stress has not reached the compressive damage strength. Finally, micro-cracks under tension occur at the outside of the lining foot for the groundwater height of 30 m, and the lining foot is destroyed with the groundwater uplift to 40 m. In the case of tunnel drainage system deterioration, the high groundwater heights exceeding 30 m will affect the safety of the highway tunnel's foot.

Relationship of Bern Score, Spinal Elastance, and Opening Pressure in Patients With Spontaneous Intracranial Hypotension.

Existing tools to diagnose spontaneous intracranial hypotension (SIH), namely spinal opening pressure (OP) and brain MRI, have limited sensitivity. We investigated whether evaluation of brain MRI using the Bern score, combined with calculated craniospinal elastance, would aid in diagnosing SIH and provide insight into its pathophysiology. A retrospective chart review was performed of patients who underwent brain MRI and pressure-augmented dynamic CT myelography (dCTM) for suspicion of SIH. Two blinded neuroradiologists assigned Bern scores for each brain MRI. OP and incremental pressure changes after intrathecal saline infusion were recorded to calculate craniospinal elastance. The relationship between Bern score, OP, and elastance and whether a leak was found were analyzed. Seventy-two consecutive dCTMs were performed in 53 patients. Twelve CSF-venous fistulae, 2 ruptured meningeal diverticula, 2 dural defects, and 1 dural bleb were found (17/53, 32%). Among patients with imaging-proven CSF leak/fistula, OP was normal in all but 1 patient and was not significantly different in those with a leak compared with those without (15.1 vs 13.6 cm H2O, p = 0.24, A = 0.40). The average Bern score in individuals with a leak was significantly higher than that in those without (5.35 vs 1.85, p < 0.001, A = 0.85), even when excluding pachymeningeal enhancement from the score (3.77 vs 1.57, p = 0.001, A = 0.78). The average elastance in those with a leak was higher than that in those without, but this difference was not statistically significant (2.05 vs 1.20 mL/cm H2O, p = 0.19, A = 0.40). Increased elastance was significantly associated with an increased Bern score (95% CI -0.55 to 0.12, p < 0.01) and was significantly associated with venous distention, pachymeningeal enhancement, prepontine narrowing, and subdural collections, but not a narrowed mamillopontine or suprasellar distance. OP is not an effective predictor for diagnosing CSF leak and if used in isolation would result in misdiagnosis of 94% of patients in our cohort. The Bern score was associated with a higher diagnostic yield of dCTM. Elastance was significantly associated with certain components of the Bern score.

Comparative study on heat extraction performance of three enhanced geothermal systems

Enhanced geothermal systems (EGSs) in this study are classified as fracturing-EGS (F-EGS), pipe-EGS (P-EGS) and excavation-EGS (E-EGS) according to reservoir stimulation strategies. However, the heat extraction performances of three EGSs employing different stimulation strategies are not fully understood. Here, we define the region where the pore pressure increment calculated by a hydraulic fracturing process is higher than rock tensile strength as the stimulation region for establishing a more accurate F-EGS model, and then compare three geothermal systems to select a appropriate reservoir stimulation strategy. We find that the F-EGS model assuming an entire stimulated region significantly exaggerates the heat extraction results. The optimal conditions for P-EGS are low injection rates and short operation times, which is suiTablefor seasonal heating or multi-energy co-generation projects including a thermal recovery phase. Theoretically, E-EGS has better geothermal extraction performance than F-EGS based on existing model assumptions, but its construction feasibility and economics need further exploration. H2O is more suiTableas a heat exchange fluid in E-EGS than supercritical CO2. This study provides a reference for geothermal mining simulation and reservoir stimulation strategy selection.