Numerical study of inhibition mechanism of high-pressure hydrogen leakage self-ignition with the addition of ammonia

Hydrogen and ammonia have attracted increasing attention as carbon-free fuels.Ammonia is considered to be an effective energy storage and hydrogen storage medium.However,a small amount of unremoved NH3 is still present in the product during the decomposition of ammonia to produce hydrogen.Therefore,it is very essential to investigate the self-ignition of hydrogen-ammonia mixtures in order to accommodate the various scenarios of hydrogen energy applications.In this paper,the effect of NH3 addition on the self-ignition of high-pressure hydrogen release is numerically investigated.The RNG k-εturbulence model,EDC combustion model,and 213-step detailed NH_(3)/H_(2) combustion mechanism are used.CHEMKIN-Pro programs for zero-dimensional homogeneous and constant volume adiabatic reactor models are used for sensitivity analysis and ignition delay time of the chemical reaction mechanism.The results showed that the minimum burst pressure required for self-ignition increased significantly after the addition of ammonia.The maximum temperature and shock wave intensity inside the tube decreases with increasing ammonia concentration.The ignition delay time and H,HO2,and OH radicals reduce with increasing ammonia concentration.H and HO2 radicals are suggested as indicators for tracking the second and third flame branches,respectively.

Effect of Prone Position in Severe Covid-19 Patients in a Referral Center: A Cohort Retrospective Study

Introduction: Covid-19 is defined as a pandemic disease by WHO, in November 2023, WHO recorded 772.1 million confirmed cases and 6.9 million deaths, including 68,382 confirmed cases and 1426 deaths in Madagascar. The management of severe cases of Covid-19 remains a challenge for the healthcare system in a resource-limited country, due to the consumption of human resources, the shortage of medical resources and the lack of capacity in resource-limited countries. Prone position (PP) improves survival in acute respiratory distress, and numerous studies have shown that during Covid-19, it reduces mortality rates at 28 and 90 days, and increases the number of days without mechanical ventilation. However, data on the beneficial effects of PP remain limited in low-income countries. In this context, our study aims to evaluate the benefits of the prone position for severe Covid-19 patients in a referral center in Madagascar. Method: This is a retrospective cohort study, during the 2nd and 3rd waves of COVID-19, over a period of 11 months in two wards managing COVID-19 cases. We included all patients aged 15 and over with severe forms of COVID-19 who required 6 l/min of oxygen therapy. Results: We enrolled 123 patients, including 40 in the prone position and 83 in the supine position, with a mean age of 60.5 ± 12 years. The prone position (DV) reduced the risk of probable complications of COVID-19 with a strong association in terms of use of respiratory assistance (OR = 0.15;95% CI = 0.05 - 0.47), respiratory deterioration (OR = 0.22;95% CI = 0.09 - 0.58), shock (OR = 0.30;95% CI = 0.11 - 0.79) and hemodynamic instability (OR = 0.33;95% CI = 0.12 - 0.95). Univariate analysis of the effect of prone position on SpO2 showed improvement with significant associations with SpO2 at Day 1- Day 3, D4 - D7, D8 - D14, and persisting even at D15 - D21, D3 and D2 before discharge, and at discharge. In the overall population, the mean length of hospital stay was 22.8 ± 22.1 days, with extremes of 1 and 67 days. Univariate analysis of the effect of the prone position showed a reduction in length of hospital stay with a strong association (p = 0.001) and a mean difference of 14 days. The prone position reduced mortality with a significant association (OR = 0.44;95% CI = 0.20 - 0.98). Conclusion: Awake prone position prevents complications of COVID, improves SPO2 even up to hospital discharge and reduces hospital stay. This practice is simple, less costly and suitable in low income countries.

Quantifying the impact of earthquakes and geological factors on spatial heterogeneity of debris-flow prone areas:A case study in the Hengduan Mountains

Understanding the spatial heterogeneity of debris-flow-prone areas holds significant implications for regional risk management, particularly in seismically active regions with geological faults. Despite the significance of this knowledge, a comprehensive quantification of the influence of regional topographical and geological factors on the spatial heterogeneity of debris-flow-prone areas has been lacking. This study selected the Hengduan Mountains, an earthquake-prone region characterized by diverse surface conditions and complex landforms, as a representative study area. An improved units zoning and objective factors identification methodology was employed in earthquake and fault analysis to assess the impact of seismic activity and geological factors on spatial heterogeneity of debrisflow prone areas. Results showed that the application of GIS technology with hydrodynamic intensity and geographical units analysis can effectively analyze debris-flow prone areas. Meanwhile, earthquake and fault zones obviously increase the density of debrisflow prone catchments and make them unevenly distributed. The number of debris-flow prone areas shows a nonlinear variation with the gradual increase of geomorphic factor value. Specifically, the area with 1000 m-2500 m elevation difference, 25°-30° average slope, and 0.13-0.15 land use index is the most favorable conditions for debris-flow occurrence;The average annual rainfall from 600 to 1150 mm and landslides gradient from 16° to 35° are the main causal factors to trigger debris flow. Our study sheds light on the quantification of spatial heterogeneity in debris flow-prone areas in earthquake-prone regions, which can offer crucial support for post-debris flow risk management strategies.

Mathematical Modeling of Peat Self-ignition at Ambient Temperature Oscillations

In the classical formulation, the problem of thermal explosion in a finite volume of the reacting material in the presence of harmonic oscillations of the ambient temperature has been solved. It is shown that in the oscillation periods, commensurate with the adiabatic induction period of thermal explosion, implement a kind of resonance which corresponding with average ambient temperature. At both high and very low frequencies oscillations at ambient temperature, their influence on the critical condition and on the induction period of thermal explosion is negligible. However, at low-frequencies influence of ambient temperature oscillations, even a relatively low amplitude, on critical condition and especially on induction period of thermal explosion, can be very strong.

Rockburst proneness considering energy characteristics and sample shape effects

Accurate prediction of rockburst proneness is one of challenges for assessing the rockburst risk and selecting effective control measures.This study aims to assess rockburst proneness by considering the energy characteristics and qualitative information during rock failure.Several representative rock types in cylindrical and cuboidal sample shapes were tested under uniaxial compression conditions and the failure progress was detected by a high-speed camera.The far-field ejection mass ratio(FEMR)was determined considering the qualitative failure information of the rock samples.The peak-strength energy impact index and the residual elastic energy index were used to quantitatively evaluate the rockburst proneness of both cylindrical and cuboidal samples.Further,the performance of these two indices was analyzed by comparing their estimates with the FEMR.The results show that the accuracy of the residual elastic energy index is significantly higher than that of the peak-strength energy impact index.The residual elastic energy index and the FEMR are in good agreement for both cylindrical and cuboidal rock materials.This is because these two indices can essentially reflect the common energy release mechanism characterized by the mass,ejection velocity,and ejection distance of rock fragments.It suggests that both the FEMR and the residual elastic energy index can be used to accurately measure the rockburst proneness of cylindrical and cuboidal samples based on uniaxial compression test.

Statistical Analysis of Accident Proneness of Drivers

A mathematical model describing the risks of road accidents has been built on the basis of statistical data of drivers’ accident rate. It has been revealed that drivers can be divided by the degree of their accident proneness into four categories with sharply differing probabilities of road accidents. It has been shown that there is a possibility of classification of drivers in accordance with specified categories.

Clinical Nursing for Patients Undergoing Prone-Position Laparoscopic Partial Nephrectomy

Objective:To explore effective nursing strategies for patients undergoing prone-position laparoscopic partial nephrectomy.Methods:A total of 19 patients undergoing prone-position laparoscopic partial nephrectomy were selected,with hospital admission spanning from January 2024 to June 2024.Patients were randomly divided into the study group(n=10)and the control group(n=9).The control group received basic nursing care,while the study group received comprehensive high-quality nursing care.The recovery period,length of hospital stay,complication rates,SCL-90 scores,and nursing quality scores were compared between the two groups.Results:The recovery period and hospital stay were significantly shorter in the study group compared to the control group(P<0.05).The complication rate in the study group was lower than that in the control group(P<0.05).After the nursing intervention,the SCL-90 scores of the study group were lower than those of the control group(P<0.05).Nursing quality scores were higher in the study group than in the control group(P<0.05).Conclusion:Comprehensive high-quality nursing intervention for patients undergoing prone-position laparoscopic partial nephrectomy can shorten the recovery period and hospital stay,reduce the complication rate,improve mental health,and enhance nursing quality,making it suitable for wider application in medical institutions.

Advances in the Use of Prone Cardiopulmonary Resuscitation During Spinal Surgery in the Prone Position

Spinal surgery is usually performed in the prone position, which is a longer and more difficult procedure and is prone to complications such as circulatory dysfunction and stress injuries. Among them, stress injury is the main complication of prone spine surgery, but the reasons for stress injury in prone spine surgery are not clear, and whether prone cardiopulmonary resuscitation (CPR) can be used needs to be further verified. Supine cardiopulmonary resuscitation is commonly used in posterior spinal surgery, retroperitoneal surgery, and so on, which can effectively improve the patient’s hypoxemia. Such surgeries require a high level of anesthetic management, and cardiopulmonary resuscitation is necessary if a patient in a prone position experiences cardiac arrest. In the process of cardiopulmonary resuscitation, supine cardiopulmonary resuscitation is often used, especially for some obese patients, if they are immediately changed to the supine position, it takes up more time, there may be wound infection, and there is a possibility of missing the optimal rescue and resuscitation time. Based on this, this paper reviews the use of prone-position cardiopulmonary resuscitation for spinal surgery in the prone position.

Effect of Prone Position Ventilation in Patients with Severe Craniocerebral Injury Complicated with Pulmonary Infection

Objective:To investigate the effects of prone ventilation in patients with severe traumatic brain injury combined with pulmonary infection.Methods:A total of 100 patients with severe traumatic brain injury combined with pulmonary infection in the hospital were randomly divided into a prone ventilation group and a conventional ventilation group,with 50 patients in each group.The Glasgow Coma Scale(GCS)score,APACHE II score,sputum culture results,oxygenation indicators,and prognosis were compared between the two groups.Data were processed using SPSS 25.0 statistical software,and t-tests and chi-square tests were used to compare continuous and categorical variables,respectively.Results:The experimental group showed better oxygenation indicators,a lower positive rate of sputum cultures,and reduced intracranial pressure compared to the control group(all P<0.05).Multivariate Cox regression analysis indicated that GCS score,APACHE II score,and prone ventilation were independent risk factors affecting patient prognosis(all P<0.05).Conclusion:Prone ventilation can improve oxygenation,reduce the risk of pulmonary infection,and decrease intracranial pressure in patients with severe traumatic brain injury combined with pulmonary infection,thereby improving patient prognosis.GCS score and APACHE II score can serve as important indicators for prognostic evaluation.

Error-prone PCR致哈茨木霉几丁质酶突变的条件优化

运用Error-prone PCR对哈茨木霉几丁质酶基因(Chit42)进行人工突变。在常规PCR基础上,通过提高体系中Mg2+浓度,适当加入一定浓度Mn2+,调节四种dNTP(dATP、dGTP、dCTP、dGTP)浓度,得到产生明显突变效果的试验条件。在Error-prone PCR中,使用5.0 mmol·L-1Mg2+,0.5 mmol·L-1Mn2+,0.04 mmol·L-1dATP和dGTP,1.5 mmol·L-1dTTP和dCTP进行扩增后,随机挑选10个克隆测序,累积13 370个碱基,检测到57个突变,平均突变率为0.4%。为产生优良突变株、酶分子定向进化奠定基础。

Error-prone PCR获得EPSP酶突变基因提高水稻的草甘膦抗性

将通过Error-prone PCR方法获得的表达水稻EPSP酶突变基因epsp102和未经修饰的水稻epsp基因分别导入籼稻恢复系明恢86,获得转化克隆84个和109个。对T1、T2代转基因水稻三叶期和分蘖期喷施草甘膦,各选出4个对草甘膦高抗性的T3代材料,进行分子鉴定。对其中的3个株系进行农艺性状考察,并各选1个株系作为父本与其他优良恢复系进行杂交,进一步考察epsp和epsp102基因在不同遗传背景下的抗性和农艺性状表现。Southern结果显示:epsp的整合拷贝数为2～3拷贝,epsp102拷贝数为1～2拷贝。萌发种子、三叶期及分蘖期对草甘膦抗性检测显示:转基因萌发种子对草甘膦的抗性提高15倍;三叶期对草甘膦的抗性提高3～4倍。分蘖期剂量效应检测结果显示:非转基因对照在施0.1倍以上的致死剂量农达时,植株显著失水,而转基因株系水分生理正常。两地两季的农艺性状考察显示:与对照相比转基因株系的穗数明显增多,转基因株系ep-3和ep102-20结实率和单株重与对照没有显著差异;以ep-3和ep102-20作父本,与4个恢复系杂交的F2代对草甘膦的抗性没有降低,两个组合的结实率显著增加,SK/ep-3组合结实率显著下降,其余组合的结实率与对照持平。

基于射波刀Xsight spine prone tracking模式治疗脊柱肿瘤患者的摆位准确性分析

目的:射波刀脊柱肿瘤治疗提供了两种追踪模式,即脊柱追踪系统(Xsight spine tracking,XST)和俯卧位脊柱追踪系统(Xsight spine prone tracking,XSPT)。本研究通过比较两种脊柱追踪模式的摆位误差,评估射波刀采用XSPT模式治疗脊柱肿瘤患者的摆位准确性。方法:回顾性分析2020年7月至2021年6月在北京大学第三医院行射波刀治疗的腰骶脊柱肿瘤患者18例,分别采用仰卧位(真空垫固定)和俯卧位(热塑体网与俯卧板固定)进行CT模拟定位。按照XST与XSPT两种追踪方式设计治疗计划,治疗中分别记录两种体位脊柱追踪的摆位修正误差,平移修正为进出、左右、升降方向,角度修正为顺时针-逆时针旋转、仰俯、倾斜。同时采集俯卧位治疗模式下同步呼吸追踪的相关误差。两种追踪模式的摆位修正误差参数通过配对t检验方法进行分析,比较两组修正误差的差异。同时分析俯卧位同步呼吸相关误差,评估呼吸模型的预测准确性。结果:升降方向仰卧位修正误差为(0.18±0.16)mm,俯卧位为(0.31±0.26)mm,差异具有统计学意义(P<0.05);进出方向仰卧位修正误差为(0.27±0.24)mm,俯卧位为(0.50±0.40)mm,差异具有统计学意义(P<0.05)。俯卧位呼吸模型相关误差左右、进出和升降的平均值分别为(0.21±0.11)mm、(0.41±0.38)mm和(0.68±0.42)mm。结论:治疗中受呼吸运动的影响,相比于仰卧位定位方式,俯卧位在升降与进出方向摆位误差相对较大,但俯卧位治疗方式具有同步呼吸追踪系统,且该系统可以实现治疗过程中呼吸动度的实时修正。俯卧位脊柱追踪模式的一致性与准确性同样能够满足临床治疗需求。

Rockburst proneness criteria for rock materials:Review and new insights

To review the rockburst proneness(or tendency)criteria of rock materials and compare the judgment accuracy of them,twenty criteria were summarized,and their judgment accuracy was evaluated and compared based on the laboratory tests on fourteen types of rocks.This study begins firstly by introducing the twenty rockburst proneness criteria,and their origins,definitions,calculation methods and grading standards were summarized in detail.Subsequently,to evaluate and compare the judgment accuracy of the twenty criteria,a series of laboratory tests were carried out on fourteen types of rocks,and the rockburst proneness judgment results of the twenty criteria for the fourteen types of rocks were obtained accordingly.Moreover,to provide a unified basis for the judgment accuracy evaluation of above criteria,a classification standard(obtained according to the actual failure results and phenomena of rock specimen)of rockburst proneness in laboratory tests was introduced.The judgment results of the twenty criteria were compared with the judgment results of this classification standard.The results show that the judgment results of the criterion based on residual elastic energy(REE)index are completely consistent with the actual rockburst proneness,and the other criteria have some inconsistent situations more or less.Moreover,the REE index is based on the linear energy storage law and defined in form of a difference value and considered the whole failure process,and these superior characteristics ensure its accuracy.It is believed that the criterion based on REE index is comparatively more accurate and scientific than other criteria,and it can be recommended to be applied to judge the rockburst proneness of rock materials.

Complications associated with prone positioning in elective spinal surgery

Complications associated with prone surgical positioning during elective spine surgery have the potential to cause serious patient morbidity.Although many ofthese complications remain uncommon,the range of possible morbidities is wide and includes multiple organ systems.Perioperative visual loss(POVL)is a well described,but uncommon complication that may occur due to ischemia to the optic nerve,retina,or cerebral cortex.Closed-angle glaucoma and amaurosis have been reported as additional etiologies for vision loss following spinal surgery.Peripheral nerve injuries,such as those caused by prolonged traction to the brachial plexus,are more commonly encountered postoperative events.Myocutaneous complications including pressure ulcers and compartment syndrome may also occur after prone positioning,albeit rarely.Other uncommon positioning complications such as tongue swelling resulting in airway compromise,femoral artery ischemia,and avascular necrosis of the femoral head have also been reported.Many of these are well-understood and largely avoidable through thoughtful attention to detail.Other complications,such as POVL,remain incompletely understood and thus more difficult to predict or prevent.Here,the current literature on the complications of prone positioning for spine surgery is reviewed to increase awareness of the spectrum of potential complications and to inform spine surgeons of strategies to minimize the risk of prone patient morbidity.

Efficacy of prone position in acute respiratory distress syndrome patients: A pathophysiology-based review

Acute respiratory distress syndrome(ARDS) is a syndrome with heterogeneous underlying pathological processes. It represents a common clinical problem in intensive care unit patients and it is characterized by high mortality. The mainstay of treatment for ARDS is lung protective ventilation with low tidal volumes and positive end-expiratory pressure sufficient for alveolar recruitment. Prone positioning is a supplementary strategy available in managing patients with ARDS. It was first described 40 years ago and it proves to be in alignment with two major ARDS pathophysiological lung models; the "sponge lung"- and the "shape matching"-model. Current evidence strongly supports that prone positioning has beneficial effects on gas exchange, respiratory mechanics, lung protection and hemodynamics as it redistributes transpulmonary pressure, stress and strain throughout the lung and unloads the right ventricle. The factors that individually influence the time course of alveolar recruitment and the improvement in oxygenation during prone positioning have not been well characterized. Although patients' response to prone positioning is quite variable and hard to predict, large randomized trials and recent meta-analyses show that prone position in conjunction with a lung-protective strategy, when performed early and in sufficient duration, may improve survival in patients with ARDS. This pathophysiology-based review and recent clinical evidence strongly support the use of prone positioning in the early management of severe ARDS systematically and not as a rescue maneuver or a last-ditch effort.

Mechanical properties and rockburst proneness of phyllite under uniaxial compression

To investigate the influence of the bedding angle,β,on the mechanical properties and rockburst proneness,uniaxial compression tests were conducted using cylindrical phyllite specimens with different bedding angles.According to the results,the peak stress,peak strain,cumulative acoustic emission counts,and potential energy of the elastic strain exhibited a U-shaped change trend.With an increase in β from 0°to 90°,the failure mode transformed from tensile splitting failure along the bedding plane to shear slip failure along the weak bedding plane.Finally,the failure mode evolved into a tensile splitting failure across the bedding plane.When β=15°,30°,and 45°,the phyllite specimens exhibited strong,slight,and moderate rockburst proneness,with strong,slight,and moderate shear slip rockbursts,respectively.When β=0°,60°,75°,and 90°,the phyllite specimens had extremely strong rockburst proneness,and an extremely strong strain rockburst occurred.

Rock burst proneness prediction by acoustic emission test during rock deformation

Rock burst is a severe disaster in mining and underground engineering,and it is important to predict the rock burst risk for minimizing the loss during the constructing process.The rock burst proneness was connected with the acoustic emission(AE) parameter in this work,which contributes to predicting the rock burst risk using AE technique.Primarily,a rock burst proneness index is proposed,and it just depends on the heterogeneous degree of rock material.Then,the quantificational formula between the value of rock burst proneness index and the accumulative AE counts in rock sample under uniaxial compression with axial strain increases is developed.Finally,three kinds of rock samples,i.e.,granite,limestone and sandstone are tested about variation of the accumulative AE counts under uniaxial compression,and the test data are fitted well with the theoretic formula.

An enriched environment improves cognitive performance in mice from the senescence-accelerated prone mouse 8 strain Role of upregulated neurotrophic factor expression in the hippocampus

In this study,we examined 3-month-old female mice from the senescence-accelerated prone mouse 8 strain and age-matched homologous normal aging female mice from the senescence accelerated-resistant mouse 1 strain.Mice from each strain were housed in an enriched environment（including a platform,running wheels,tunnel,and some toys）or a standard environment for 3 months.The mice housed in the enriched environment exhibited shorter escape latencies and a greater percentage of time in the target quadrant in the Morris water maze test,and they exhibited reduced errors and longer latencies in step-down avoidance experiments compared with mice housed in the standard environment.Correspondently,brain-derived neurotrophic factor mRNA and protein ex- pression in the hippocampus was significantly higher in mice housed in the enriched environment compared with those housed in the standard environment,and the level of hippocampal brain-derived neurotrophic factor protein was positively correlated with the learning and memory abilities of mice from the senescence-accelerated prone mouse 8 strain.These results suggest that an enriched environment improved cognitive performance in mice form the senescence-accelerated prone mouse 8 strain by increasing brain-derived neurotrophic factor expression in the hippocampus.

Experiments on rockburst proneness of pre-heated granite at different temperatures: Insights from energy storage, dissipation and surplus

Many underground engineering projects show that rockburst can occur in rocks at great depth and high temperature, and temperature is a critical factor affecting the intensity of rockburst. In general, temperature can affect the energy storage, dissipation, and surplus in rock. To explore the influence of temperature on the energy storage and dissipation characteristics and rockburst proneness, the present study has carried out a range of the uniaxial compression(UC) and single-cyclic loading-unloading uniaxial compression(SCLUC) tests on pre-heated granite specimens at 20℃-700℃. The results demonstrate that the rockburst proneness of pre-heated granite initially increases and subsequently decreases with the increase of temperature. The temperature of 300℃ has been found to be the threshold for rockburst proneness. Meanwhile, it is found that the elastic strain energy density increases linearly with the total input strain energy density for the pre-heated granites, confirming that the linear energy property of granite has not been altered by temperature. According to this inherent property, the peak elastic strain energy of pre-heated granites can be calculated accurately. On this basis, utilising the residual elastic energy index, the rockburst proneness of pre-heated granite can be determined quantitatively. The obtained results from high to low are: 317.9 k J/m^(3)(300℃), 264.1 k J/m^(3)(100℃), 260.6 k J/m^(3)(20℃), 235.5 k J/m^(3)(500℃), 158.9 k J/m^(3)(700℃), which are consistent with the intensity of actual rockburst for specimens. In addition, the relationship between temperature and energy storage capacity(ESC) of granite was discussed, revealing that high temperature impairs ESC of rocks, which is essential for reducing the rockburst proneness. This study provides some new insights into the rockburst proneness evaluation in high-temperature rock engineering.

Prediction method of rock burst proneness based on rough set and genetic algorithm

A new method based on rough set theory and genetic algorithm was proposedto predict the rock burst proneness. Nine influencing factors were first selected, and then,the decision table was set up. Attributes were reduced by genetic algorithm. Rough setwas used to extract the simplified decision rules of rock burst proneness. Taking the practical engineering for example, the rock burst proneness was evaluated and predicted bydecision rules. Comparing the prediction results with the actual results, it shows that theproposed method is feasible and effective.