Intra-abdominal pressure monitoring in predicting outcome of patients with severe acute pancreatitis

BACKGROUND: Severe acute pancreatitis (SAP) is a serious disease with many complications, high mortality and poor prognosis. It is characterized by rapid deterioration and poses one of the most difficult challenges in clinical practice. Previous investigations suggest that SAP is one of the main causes of intra-abdominal pressure (IAP) increase. The aim of this study was to evaluate the utility of IAP-monitoring in predicting the severity and prognosis of SAP. METHODS: Eighty-nine patients with SAP who had been treated from February 2001 to December 2005 were studied. Since bladder pressure accurately reflects IAP, we measured it instead of IAP. Bladder pressure was measured at the time of admission and every 12 hours in the course of the disease, 9 consecutive times in all. The APACHE II scores of all patients were obtained within 24 hours after admission. According to a maximum bladder pressure <10 cmH(2)O, all patients were divided into two groups, mildly-elevated and severely-elevated. Mortality and mean APACHE II scores in the two groups were calculated. In addition, the mean bladder pressure and APACHE II scores in survivors were compared with those in deaths. RESULTS: Sixty-eight of the 89 patients were in the severely-elevated group. Mortality and mean APACHE II scores in this group were much higher than those in the mildly-elevated group (mortality, 39.71% vs. 9.52%; mean APACHE II score, 23.15 +/- 7.42 vs. 15.95 +/- 5.35, P<0.01). The mean bladder pressures and APACHE II scores in deaths were significantly greater than those in survivors (mean bladder pressure, 14.1 +/- 3.8 vs. 9.2 +/- 2.3 cmH(2)O, P<0.01; mean APACHE II score, 27.83 +/- 4.87 vs. 18.37 +/- 6.74, P<0.01). CONCLUSION: It is suggested that IAP may be used as a marker of the severity and prognosis of SAP.

Elevated intra-abdominal pressure:A review of current knowledge

Elevated intra-abdominal pressure(IAP)is a known cause of increased morbidity and mortality among critically ill patients.Intra-abdominal hypertension(IAH)and abdominal compartment syndrome can lead to rapid deterioration of organ function and the development of multiple organ failure.Raised IAP affects every system and main organ in the human body.Even marginally sustained IAH results in malperfusion and may disrupt the process of recovery.Yet,despite being so common,this potentially lethal condition often goes unnoticed.In 2004,the World Society of the Abdominal Compartment Syndrome,an international multidisciplinary consensus group,was formed to provide unified definitions,improve understanding and promote research in this field.Simple,reliable and nearly costless standardized methods of non-invasive measurement and monitoring of bladder pressure allow early recognition of IAH and timely optimized management.The correct,structured approach to treatment can have a striking effect and fully restore homeostasis.In recent years,significant progress has been made in this area with the contribution of surgeons,internal medicine specialists and anesthesiologists.Our review focuses on recent advances in order to present the complex underlying pathophysiology and guidelines concerning diagnosis,monitoring and treatment of this life-threatening condition.

The effect of increased intra-abdominal pressure on orbital subarachnoid space width and intraocular pressure

In accordance with the trans-lamina cribrosa pressure difference theory, decreasing the trans-lamina cribrosa pressure difference can re- lieve glaucomatous optic neuropathy. Increased intracranial pressure can also reduce optic nerve damage in glaucoma patients, and a safe, effective and noninvasive way to achieve this is by increasing the intra-abdominal pressure. The purpose of this study was to observe the changes in orbital subarachnoid space width and intraocular pressure at elevated intra-abdominal pressure. An inflatable abdominal belt was tied to each of 15 healthy volunteers, aged 22-30 years （12 females and 3 males）, at the navel level, without applying pressure to the abdomen, before they laid in the magnetic resonance imaging machine. The baseline orbital subarachnoid space width around the optic nerve was measured by magnetic resonance imaging at 1, 3, 9, and 15 mm behind the globe. The abdominal belt was inflated to increase the pressure to 40 mmHg （1 mmHg = 0.133 kPa）, then the orbital subarachnoid space width was measured every 10 minutes for 2 hours. After removal of the pressure, the measurement was repeated 10 and 20 minutes later. In a separate trial, the intraocular pressure was measured for all the subjects at the same time points, before, during and after elevated intra-abdominal pressure. Results showed that the baseline mean orbital subarachnoid space width was 0.88 ＋ 0.1 mm （range： 0.77-1.05 mm）, 0.77 ＋ 0.11 mm （range： 0.60-0.94 mm）, 0.70 ＋ 0.08 mm （range： 0.62-0.80 ram）, and 0.68 _＋ 0.08 mm （range： 0.57-0.77 mm） at 1, 3, 9, and 15 mm behind the globe, respectively. During the elevated intra-abdominal pressure, the orbital subarachnoid space width increased from the baseline and dilation of the optic nerve sheath was significant at 1, 3 and 9 mm behind the globe. After decompression of the abdominal pressure, the orbital subarachnoid space width normalized and returned to the baseline value. There was no significant difference in the intraocular pressure before, during and after the intra-abdominal pressure elevation. These results verified that the increased intra-abdominal pressure widens the orbital subarachnoid space in this acute trial, but does not alter the intraocular pressure, indicating that intraocular pressure is not affected by rapid increased in- tra-abdominal pressure. This study was registered in the Chinese Clinical Trial Registry （registration number： ChiCTR-ONRC-14004947）.

Noninvasive monitoring of intra-abdominal pressure by measuring abdominal wall tension

BACKGROUND: Noninvasive monitoring of intra-abdominal pressure(IAP) by measuring abdominal wall tension(AWT) was effective and feasible in previous postmortem and animal studies. This study aimed to investigate the feasibility of the AWT method for noninvasively monitoring IAP in the intensive care unit(ICU).METHODS: In this prospective study, we observed patients with detained urethral catheters in the ICU of Shanghai Tenth People's Hospital between April 2011 and March 2013. The correlation between AWT and urinary bladder pressure(UBP) was analyzed by linear regression analysis. The effects of respiratory and body position on AWT were evaluated using the paired samples t test, whereas the effects of gender and body mass index(BMI) on baseline AWT(IAP<12 mm Hg) were assessed using one-way analysis of variance.RESULTS: A total of 51 patients were studied. A significant linear correlation was observed between AWT and UBP(R=0.986, P<0.01); the regression equation was Y=–1.369+9.57X(P<0.01). There were signif icant differences among the different respiratory phases and body positions(P<0.01). However, gender and BMI had no signif icant effects on baseline AWT(P=0.457 and 0.313, respectively).CONCLUSIONS: There was a signif icant linear correlation between AWT and UBP and respiratory phase, whereas body position had signif icant effects on AWT but gender and BMI did not. Therefore, AWT could serve as a simple, rapid, accurate, and important method to monitor IAP in critically ill patients.

Intra-abdominal pressure:Time ripe to revise managementguidelines of acute pancreatitis?

AIM: To systematically review evidence on pathophysiology of intra-abdominal pressure(IAP) in acute pancreatitis(AP) with its clinical correlates. METHODS: Systematic review of available evidence in English literature with relevant medical subject heading terms on Pub Med, Medline and Scopus with further search from open access sources on internet as suggested by articles retrieved. RESULTS: Intra-abdominal hypertension(IAH) is increasingly gaining recognition as a point of specific intervention with potential to alter disease outcome and improve mortality in AP. IAH can be expected in at least 17% of patients presenting with diagnosis of AP to a typical tertiary care hospital(prevalence increasing to 50% in those with severe disease). Abdominal compartment syndrome can be expected in at least 15% patients with severe disease. Recent guidelines on management of AP do not acknowledge utility of surveillance for IAP other than those by Japanese Society of Hepato-BiliaryPancreatic Surgery. We further outline pathophysiologic mechanisms of IAH; understanding of which advances our knowledge and helps to coherently align common observed variations in management related conundrums(such as fluid therapy, nutrition and antibiotic prophylaxis) with potential to further individualize treatment in AP. CONCLUSION: We suggest that IAP be given its due place in future practice guidelines and that recommendations be formed with help of a broader panel with inclusion of clinicians experienced in management of IAH.

Effect of intra-abdominal pressure on respiratory function in patients undergoing ventral hernia repair

AIM: To determine the influence of intra-abdominal pressure(IAP) on respiratory function after surgical repair of ventral hernia and to compare two different methods of IAP measurement during the perioperative period. METHODS: Thirty adult patients after elective repair of ventral hernia were enrolled into this prospective study.IAP monitoring was performed via both a balloontipped nasogastric probe [intragastric pressure(IGP), Ci MON, Pulsion Medical Systems, Munich, Germany] and a urinary catheter [intrabladder pressure(IBP), Uno Meter Abdo-Pressure Kit, Uno Medical, Denmark] on five consecutive stages:(1) after tracheal intubation(AI);(2) after ventral hernia repair;(3) at the end of surgery;(4) during spontaneous breathing trial through the endotracheal tube; and(5) at 1 h after tracheal extubation. The patients were in the complete supine position during all study stages.RESULTS: The IAP(measured via both techniques) increased on average by 12% during surgery compared to AI(P < 0.02) and by 43% during spontaneous breathing through the endotracheal tube(P < 0.01). In parallel, the gradient between РаСО2 and Et CO2 [Р(а-et)CO2] rose significantly, reaching a maximum during the spontaneous breathing trial. The PаO2/Fi O2 decreased by 30% one hour after tracheal extubation(P = 0.02). The dynamic compliance of respiratory system reduced intraoperatively by 15%-20%(P < 0.025). At all stages, we observed a significant correlation between IGP and IBP(r = 0.65-0.81, P < 0.01) with a mean bias varying from-0.19 mm Hg(2SD 7.25 mm Hg) to-1.06 mm Hg(2SD 8.04 mm Hg) depending on the study stage. Taking all paired measurements together(n = 133), the median IGP was 8.0(5.5-11.0) mm Hg and the median IBP was 8.8(5.8-13.1) mm Hg. The overall r2 value( n = 30) was 0.76(P < 0.0001). Bland and Altman analysis showed an overall bias for the mean values per patient of 0.6 mm Hg(2SD 4.2 mm Hg) with percentage error of 45.6%. Looking at changes in IAP between the different study stages, we found an excellent concordance coefficient of 94.9% comparing IBP and IGP( n = 117).CONCLUSION: During ventral hernia repair, the IAP rise is accompanied by changes in Р(а-et)CO2 and PаO2/Fi O2-ratio. Estimation of IAP via IGP or IBP demonstrated excellent concordance.

Should we perform decompressive laparotomy during severe acute pancreatitis with intra-abdominal hypertension below 25 mmHg:Only the gut knows

We suggest that during severe acute pancreatitis(SAP)with intra-abdominal hypertension,practitioners should consider decompressive laparotomy,even with intra-abdominal pressure(IAP)below 25 mmHg.Indeed,in this setting,non-occlusive mesenteric ischemia(NOMI)may occur even with IAP below this cutoff and lead to transmural necrosis if abdominal perfusion pressure is not promptly restored.We report our experience of 18 critically ill patients with SAP having undergone decompressive laparotomy of which one third had NOMI while IAP was mostly below 25 mmHg.

Effects of Altered Intra-abdominal Pressure on the Upper Airway Collapsibility in a Porcine Model

Background： Obstructive sleep apnea is strongly associated with obesity, particularly abdominal obesity common in centrally obese males. Previous studies have demonstrated that intra-abdominal pressure （IAP） is increased in morbid obesity, and tracheal traction forces may influence pharyngeal airway collapsibility. This study aimed to investigate that whether IAP plays a role in the mechanism of upper airway （UA） collapsibility via IAP-related caudal tracheal traction. Methods： An abdominal wall lifting （AWL） system and graded CO2 pneumoperitoneum pressure was applied to four supine, anesthetized Guizhou miniature pigs and its effects on tracheal displacement （TD） and airflow dynamics of UA were studied. Individual run data in 3 min obtained before and after AWL and obtained before and after graded pneumoperitoneum pressure were analyzed. Differences between baseline and AWL/graded pneumoperitoneum pressure data of each pig were examined using a Student＇s t-test or analysis of variance. Results： Application of AWL resulted in decreased IAP and significant caudal TD. The average displacement amplitude was 0.44 mm （P 〈 0.001 ）. There were three subjects showed increased tidal volume （TV） （P 〈 0.01 ） and peak inspiratory airflow （P 〈 0.01 ）; however, the change of flow limitation inspiratory UA resistance （Rua） was not significant. Experimental increased lAP by pneumoperitoneum resulted in significant cranial TD. The average displacement amplitude was 1.07 mm （P 〈 0.001） when lAP was 25 cmH2O compared to baseline. There were three subjects showed reduced Rua while the TV increased （P 〈 0.01 ）. There was one subject had decreased TV and elevated Rua （P 〈 0.001）. Conclusions： Decreased IAP significantly increased caudal TD, and elevated lAP significantly increased cranial TD. However, the mechanism of UA collapsibility appears primarily mediated by changes in lung volume rather than tracheal traction effect. TV plays an independent role in the mechanism of UA collapsibility.

Effect of increased intra-abdominal pressure and decompressive laparotomy on aerated lung volume distribution

Increased intra-abdominal pressure(IAP) is common in intensive care patients,affecting aerated lung volume distribution.The current study deals with the effect of increased IAP and decompressive laparotomy on aerated lung volume distribution.The serial whole-lung computed tomography scans of 16 patients with increased IAP were retrospectively analyzed between July 2006 and July 2008 and compared to controls.The IAP increased from(12.1±2.3) mmHg on admission to(25.2±3.6) mmHg(P<0.01) before decompressive laparotomy and decreased to(14.7±2.8) mmHg after decompressive laparotomy.Mean time from admission to decompressive laparotomy and length of intensive-care unit(ICU) stay were 26 h and 16.2 d,respectively.The percentage of normally aerated lung volume on admission was significantly lower than that of controls(P<0.01).Prior to decompressive laparotomy,the total lung volume and percentage of normally aerated lung were significantly less in patients compared to controls(P<0.01),and the absolute volume of non-aerated lung and percentage of non-aerated lung were significantly higher in patients(P<0.01).Peak inspiratory pressure,partial pressure of carbon dioxide in arterial blood,and central venous pressure were higher in patients,while the ratio of partial pressure of arterial O2 to the fraction of inspired O2(PaO2/FIO2) was decreased relative to controls prior to laparotomy.An approximately 1.8 cm greater cranial displacement of the diaphragm in patients versus controls was observed before laparotomy.The sagittal diameter of the lung at the T6 level was significantly increased compared to controls on admission(P<0.01).After laparotomy,the volume and percentage of non-aerated lung decreased significantly while the percentage of normally aerated lung volume increased significantly(P<0.01).In conclusion,increased IAP decreases total lung volume while increasing non-aerated lung volume.Decompressive laparotomy is associated with resolution of these effects on lung volumes.

Mechanical Performance of Bio-inspired Bidirectional Corrugated Sandwich Pressure Shell Under External Hydrostatic Pressure

This paper aims to enhance the compression capacity of underwater cylindrical shells by adopting the corrugated sandwich structure of cuttlebone.The cuttlebone suffers uniaxial external compression,while underwater cylindrical shells are in a biaxial compressive stress state.To suit the biaxial compressive stress state,a novel bidirectional corrugated sandwich structure is proposed to improve the bearing capacity of cylindrical shells.The static and buckling analysis for the sandwich shell and the unstiffened cylindrical shell with the same volume-weight ratio are studied by numerical simulation.It is indicated that the proposed sandwich shell can effectively reduce the ratio between circumferential and axial stress from 2 to 1.25 and improve the critical buckling load by about 1.63 times.Numerical simulation shows that optimizing and adjusting the structural parameters could significantly improve the advantage of the sandwich shell.Then,the hydrostatic pressure tests for shell models fabricated by 3D printing are carried out.According to the experimental results,the overall failure position of the sandwich shell is at the center part of the sandwich shell.It has been found the average critical load of the proposed sandwich shell models exceeds two times that of the unstiffened shell models.Hence,the proposed bio-inspired bidirectional corrugated sandwich structure can significantly enhance the pressure resistance capability of cylindrical shells.

Effects of seepage pressure on the mechanical behaviors and microstructure of sandstone

Surrounding rocks of underground engineering are subjected to long-term seepage pressure,which can deteriorate the mechanical properties and cause serious disasters.In order to understand the impact of seepage pressure on the mechanical property of sandstone,uniaxial compression tests,P-wave velocity measurements,and nuclear magnetic resonance(NMR)tests were conducted on saturated sandstone samples with varied seepage pressures(i.e.0 MPa,3 MPa,4 MPa,5 MPa,6 MPa,7 MPa).The results demonstrate that the mechanical parameters(uniaxial compressive strength,peak strain,elastic modulus,and brittleness index),total energy,elastic strain energy,as well as elastic strain energy ratio,decrease with increasing seepage pressure,while the dissipation energy and dissipation energy ratio increase.Moreover,as seepage pressure increases,the micro-pores gradually transform into meso-pores and macro-pores.This increases the cumulative porosity of sandstone and decreases P-wave velocity.The numerical results indicate that as seepage pressure rises,the number of tensile cracks increases progressively,the angle range of microcracks is basically from 50-120to 80-100,and as a result,the failure mode transforms to the tensile-shear mixed failure mode.Finally,the effects of seepage pressure on mechanical properties were discussed.The results show that decrease in the effective stress and cohesion under the action of seepage pressure could lead to deterioration of strength behaviors of sandstone.

Emulsifying property,antioxidant activity,and bitterness of soybean protein isolate hydrolysate obtained by Corolase PP under high hydrostatic pressure

Enzymatic hydrolysis of proteins can enhance their emulsifying properties and antioxidant activities.However,the problem related to the hydrolysis of proteins was the generation of the bitter taste.Recently,high hydrostatic pressure(HHP)treatment has attracted much interest and has been used in several studies on protein modification.Hence,the study aimed to investigate the effects of enzymatic hydrolysis by Corolase PP under different pressure treatments(0.1,100,200,and 300 MPa for 1-5 h at 50℃)on the emulsifying property,antioxidant activity,and bitterness of soybean protein isolate hydrolysate(SPIH).As observed,the hydrolysate obtained at 200 MPa for 4 h had the highest emulsifying activity index(47.49 m^(2)/g)and emulsifying stability index(92.98%),and it had higher antioxidant activities(44.77%DPPH free radical scavenging activity,31.12%superoxide anion radical scavenging activity,and 61.50%copper ion chelating activity).At the same time,the enhancement of emulsion stability was related to the increase of zeta potential and the decrease of mean particle size.In addition,the hydrolysate obtained at 200 MPa for 4 h had a lower bitterness value and showed better palatability.This study has a broad application prospect in developing food ingredients and healthy foods.

Reservoir quality evaluation of the Narimba Formation in Bass Basin,Australia:Implications from petrophysical analysis,sedimentological features,capillary pressure and wetting fluid saturation

The evaluation of reservoir quality was accomplished on the Late Paleocene to Early Eocene Narimba Formation in Bass Basin,Australia.This study involved combination methods such as petrophysical analysis,petrography and sedimentological studies,reservoir quality and fluid flow units from derivative parameters,and capillary pressure and wetting fluid saturation relationship.Textural and diagenetic features are affecting the reservoir quality.Cementation,compaction,and presence of clay minerals such as kaolinite are found to reduce the quality while dissolution and secondary porosity are noticed to improve it.It is believed that the Narimba Formation is a potential reservoir with a wide range of porosity and permeability.Porosity ranges from 3.1%to 25.4%with a mean of 15.84%,while permeability ranges between 0.01 mD and 510 mD,with a mean of 31.05 mD.Based on the heterogenous lithology,the formation has been categorized into five groups based on permeability variations.Group I showed an excellent to good quality reservoir with coarse grains.The impacts of both textural and diagenetic features improve the reservoir and producing higher reservoir quality index(RQI)and flow zone indicators(FZI)as well as mostly mega pores.The non-wetting fluid migration has the higher possibility to flow in the formation while displacement pressure recorded as zero.Group II showed a fair quality reservoir with lower petrophysical properties in macro pores.The irreducible water saturation is increasing while the textural and digenetic properties are still enhancing the reservoir quality.Group III reflects lower quality reservoir with mostly macro pores and higher displacement pressure.It may indicate smaller grain size and increasing amount of cement and clay minerals.Group IV,and V are interpreted as a poor-quality reservoir that has lower RQI and FZI.The textural and digenetic features are negatively affecting the reservoir and are leading to smaller pore size and pore throat radii(r35)values to be within the range of macro,meso-,micro-,and nano pores.The capillary displacement pressure curves of the three groups show increases reaching the maximum value of 400 psia in group V.Agreement with the classification of permeability,r35 values,and pore type can be used in identifying the quality of reservoir.

An adaptive physics-informed deep learning method for pore pressure prediction using seismic data

Accurate prediction of formation pore pressure is essential to predict fluid flow and manage hydrocarbon production in petroleum engineering.Recent deep learning technique has been receiving more interest due to the great potential to deal with pore pressure prediction.However,most of the traditional deep learning models are less efficient to address generalization problems.To fill this technical gap,in this work,we developed a new adaptive physics-informed deep learning model with high generalization capability to predict pore pressure values directly from seismic data.Specifically,the new model,named CGP-NN,consists of a novel parametric features extraction approach(1DCPP),a stacked multilayer gated recurrent model(multilayer GRU),and an adaptive physics-informed loss function.Through machine training,the developed model can automatically select the optimal physical model to constrain the results for each pore pressure prediction.The CGP-NN model has the best generalization when the physicsrelated metricλ=0.5.A hybrid approach combining Eaton and Bowers methods is also proposed to build machine-learnable labels for solving the problem of few labels.To validate the developed model and methodology,a case study on a complex reservoir in Tarim Basin was further performed to demonstrate the high accuracy on the pore pressure prediction of new wells along with the strong generalization ability.The adaptive physics-informed deep learning approach presented here has potential application in the prediction of pore pressures coupled with multiple genesis mechanisms using seismic data.

The regulation of ferrocene-based catalysts on heat transfer in highpressure combustion of ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum composite propellants

The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxylterminated polybutadiene/aluminum(AP/HTPB/Al)composite propellants under high pressures is a crucial step for its application in high-pressure solid rocket motors.In this work,the combustion characteristics of AP/HTPB/Al composite propellants containing ferrocene-based catalysts were investigated,including the burning rate,thermal behavior,the local heat transfer,and temperature profile in the range of 7-28 MPa.The results showed that the exponent breaks were still observed in the propellants after the addition of positive catalysts(Ce-Fc-MOF),the burning rate inhibitor((Ferrocenylmethyl)trimethylammonium bromide,Fc Br)and the mixture of Fc Br/catocene(GFP).However,the characteristic pressure has increased,and the exponent decreased from 1.14 to 0.66,0.55,and 0.48 when the addition of Ce-FcMOF,Fc Br and Fc Br/GFP in the propellants.In addition,the temperature in the first decomposition stage was increased by 7.50℃ and 11.40℃ for the AP/Fc Br mixture and the AP/Fc Br/GFP mixture,respectively,compared to the pure AP.On the other hand,the temperature in the second decomposition stage decreased by 48.30℃ and 81.70℃ for AP/Fc Br and AP/Fc Br/GFP mixtures,respectively.It was also found that Fc Br might generate ammonia to cover the AP surface.In this case,a reaction between the methyl in Fc Br and perchloric acid caused more ammonia to appear at the AP surface,resulting in the suppression of ammonia desorption.In addition,the coarse AP particles on the quenched surface were of a concave shape relative to the binder matrix under low and high pressures when the catalysts were added.In the process,the decline at the AP/HTPB interface was only exhibited in the propellant with the addition of Ce-Fc-MOF.The ratio of the gas-phase temperature gradient of the propellants containing catalysts was reduced significantly below and above the characteristic pressure,rather than 3.6 times of the difference in the blank propellant.Overall,the obtained results demonstrated that the pressure exponent could be effectively regulated and controlled by adjusting the propellant local heat and mass transfer under high and low pressures.

Driving pressure in mechanical ventilation:A review

Driving pressure(ΔP)is a core therapeutic component of mechanical ventilation(MV).Varying levels ofΔP have been employed during MV depending on the type of underlying pathology and severity of injury.However,ΔP levels have also been shown to closely impact hard endpoints such as mortality.Considering this,conducting an in-depth review ofΔP as a unique,outcome-impacting therapeutic modality is extremely important.There is a need to understand the subtleties involved in making sureΔP levels are optimized to enhance outcomes and minimize harm.We performed this narrative review to further explore the various uses ofΔP,the different parameters that can affect its use,and how outcomes vary in different patient populations at different pressure levels.To better utilizeΔP in MV-requiring patients,additional large-scale clinical studies are needed.

Lateral earth pressure of granular backfills on retaining walls with expanded polystyrene geofoam inclusions under limited surcharge loading

Existing studies have focused on the behavior of the retaining wall equipped with expanded polystyrene(EPS)geofoam inclusions under semi-infinite surcharge loading rather than limited surcharge loading.In this paper,the failure mode and the earth pressure acting on the rigid retaining wall with EPS geofoam inclusions and granular backfills(henceforth referred to as EPS-wall),under limited surcharge loading are investigated through two-and three-dimensional model tests.The testing results show that different from the sliding of almost all the backfill in the EPS-wall under semi-infinite surcharge loading,only an approximately triangular backfill slides in the wall under limited surcharge loading.The distribution of the lateral earth pressure on the EPS-wall under limited surcharge loading is non-linear,and the distribution changes from the increase of the wall depth to the decrease with the increase of the limited surcharge loading.An approach based on the force equilibrium of a differential element is developed to predict the lateral earth pressure behind the EPS-wall subjected to limited surcharge loading,and its performance was fully validated by the three-dimensional model tests.

Pressure generation under deformation in a large-volume press

Deformation can change the transition pathway of materials under high pressure,thus significantly affects physical and chemical properties of matters.However,accurate pressure calibration under deformation is challenging and thereby causes relatively large pressure uncertainties in deformation experiments,resulting in the synthesis of complex multiphase materials.Here,pressure generations of three types of deformation assemblies were well calibrated in a Walker-type largevolume press(LVP)by electrical resistance measurements combined with finite element simulations(FESs).Hard Al_(2)O_(3) or diamond pistons in shear and uniaxial deformation assemblies significantly increase the efficiency of pressure generation compared with the conventional quasi-hydrostatic assembly.The uniaxial deformation assembly using flat diamond pistons possesses the highest efficiency in these deformation assemblies.This finding is further confirmed by stress distribution analysis based on FESs.With this deformation assembly,we found shear can effectively promote the transformation of C60 into diamond under high pressure and realized the synthesis of phase-pure diamond at relatively moderate pressure and temperature conditions.The present developed techniques will help improve pressure efficiencies in LVP and explore the new physical and chemical properties of materials under deformation in both science and technology.

At-rest lateral earth pressure of compacted expansive soils:Experimental investigations and prediction approach

This paper presents experimental studies on a compacted expansive soil,from Nanyang,China for investigating the at-rest lateral earth pressureσL of expansive soils.The key studies include(i)relationships between theσL and the vertical stressσV during soaking and consolidation,(ii)the influences of initial dry densityρd0 and moisture content w 0 on the vertical and lateral swelling pressures at no swelling strain(i.e.σV0 andσL0),and(iii)evolution of theσL during five long-term wetting-drying cycles.Experimental results demonstrated that the post-soakingσL-σV relationships are piecewise linear and their slopes in the passive state(σL>σV)and active state(σL<σV)are similar to that of the consolidationσL-σV relationships in the normal-and over-consolidated states,respectively.The soakingσL-σV relationships converge to the consolidationσL-σV relationships at a thresholdσV where the interparticle swelling is restrained.TheσL0 andσV0 increase monotonically withρd0;however,they show increasing-then-decreasing trends with the w 0.The extent of compaction-induced swelling anisotropy,which is evaluated byσL0/σV0,reduces with an increase in the compaction energy and molding water content.TheσL reduces over moisture cycles and the stress relaxation in theσL during soaking is observed.An approach was developed to predict the at-rest soakingσL-σV relationships,which requires conventional consolidation and shear strength properties and one measurement of theσL-σV relationships during soaking.The proposed approach was validated using the results of three different expansive soils available in the literature.

The effectiveness of physical activity interventions on blood pressure in children and adolescents:A systematic review and network meta-analysis

Background:High blood pressure(BP)is a major contributor to mortality and cardiovascular diseases.Despite the known benefits of exercise for reducing BP,it is crucial to identify the most effective physical activity(PA)intervention.This systematic review and network meta-analysis(NMA)aimed to evaluate the available evidence on the effectiveness of various PA interventions for reducing BP and to determine their hierarchy based on their impact on BP.Methods:A search of PubMed,SPORTDiscus,PsycINFO,Web of Science,CINAHL,Cochrane,and Eric databases was conducted up to December 2022 for this systematic review and NMA.Randomized controlled trials and quasi-experimental studies targeting healthy children and adolescents aged 6-12 years old were included in this study.Only studies that compared controlled and intervention groups using PA or exercise as the major influence were included.We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)guidelines.Three independent investigators performed the literature screening,data extraction,and risk of bias assessment.We used Bayesian arm-based NMA to synthesize the data.The primary outcomes were systolic BP and diastolic BP.We calculated the mean differences(MDs)in systolic BP and diastolic BP before and after treatment.Mean treatment differences were estimated using NMA and random-effect models.Results:We synthesized 27 studies involving 15,220 children and adolescents.PA combined with nutrition and behavior change was the most effective intervention for reducing both systolic BP and diastolic BP(MD=-8.64,95%credible interval(95%CI):-11.44 to-5.84;MD=-6.75,95%CI:-10.44 to-3.11),followed by interventions with multiple components(MD=-1.39,95%CI:-1.94 to-0.84;MD=-2.54,95%CI:-4.89 to-0.29).Conclusion:Our findings suggest that PA interventions incorporating nutrition and behavior change,followed by interventions with multiple components,are most effective for reducing both systolic BP and diastolic BP in children and adolescents.