Dynamics and controls of ecosystem multiserviceability across the Qingzang Plateau

Ecosystem multiserviceability(EMS),a comprehensive and significant ecological indicator,reflects the capacity of ecosystems to offer multiple services concurrently.Intensified climate change and human activity are continu-ously altering ecosystem functions,services,and EMSs.However,numerous studies have only focused on one or a few ecosystem services,rarely taking into account spatial-temporal distribution and drivers of EMS on behalf of different agencies.We calculated EMS including pastoralist(PA),environmental protection agency(EPA),bio-diversity conservation agency(BCA),and climate change mitigation agency(CCMA)using grassland production,habitat quality,water conservation,and carbon sequestration.Then,the effects of geographical features,climate factors,and human activities on spatial-temporal patterns of EMS were explored.The result indicated that EMS showed a decreasing tendency from the southeast to northwest on the Qingzang Plateau(QZP).Meanwhile,there were no obvious fluctuations in four simulated scenarios(PA,EPA,BCA and CCMA)among different vegetation types during 2000 to 2015.Notably,EMS of all simulated scenarios decreased in the alpine steppe ecosystem,but negligible changes were found in other ecosystems from 2015 to 2020.Moreover,the relative importance of precipitation in annual mean value(from 2000 to 2020)of PA,EPA,BCA and CCMA were 0.13,0.11,0.30 and 0.19,respectively.Overall,precipitation played the dominant role on the dynamics of EMS,followed by elevation and human footprint.Our findings highlighted that understanding the patterns and drivers of EMS could provide a reference for the regional management and maintenance of ecosystem stability on QZP.

Effect of dynamic loading orientation on fracture properties of surrounding rocks in twin tunnels

For expedited transportation,vehicular tunnels are often designed as two adjacent tunnels,which frequently experience dynamic stress waves from various orientations during blasting excavation.To analyze the impact of dynamic loading orientation on the stability of the twin-tunnel,a split Hopkinson pressure bar(SHPB)apparatus was used to conduct a dynamic test on the twin-tunnel specimens.The two tunnels were rotated around the specimen’s center to consider the effect of dynamic loading orientation.LS-DYNA software was used for numerical simulation to reveal the failure properties and stress wave propagation law of the twin-tunnel specimens.The findings indicate that,for a twin-tunnel exposed to a dynamic load from different orientations,the crack initiation position appears most often at the tunnel corner,tunnel spandrel,and tunnel floor.As the impact direction is created by a certain angle(30°,45°,60°,120°,135°,and 150°),the fractures are produced in the middle of the line between the left tunnel corner and the right tunnel spandrel.As the impact loading angle(a)is 90°,the tunnel sustains minimal damage,and only tensile fractures form in the surrounding rocks.The orientation of the impact load could change the stress distribution in the twin-tunnel,and major fractures are more likely to form in areas where the tensile stress is concentrated.

Dynamic mechanical characteristics of deep Jinping marble in complex stress environments

To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain rates and the stress environments in depth significantly affect the mechanical characteristics of rocks.The sensitivity of strain rate to the dynamic strength and deformation modulus shows a negative correlation with depth,indicating that producing penetrative cracks in deep environments is more difficult when damage occurs.The dynamic strength shows a tendency to decrease and then increase slightly,but decreases sharply finally.Transmissivity demonstrates a similar trend as that of strength,whereas reflectivity indicates the opposite trend.Furthermore,two critical depths with high dynamically induced hazard possibilities based on the China Jinping Underground Laboratory(CJPL)were proposed for deep engineering.The first critical depth is 600-900 m,beyond which the sensitivity of rock dynamic characteristics to the strain rate and restraint of circumferential stress decrease,causing instability of surrounding rocks under axial stress condition.The second one lies at 1500-1800 m,where the wave impedance and dynamic strength of deep surrounding rocks drop sharply,and the dissipation energy presents a negative value.It suggests that the dynamic instability of deep surrounding rocks can be divided into dynamic load dominant and dynamic load induced types,depending on the second critical depth.

Stability analysis of intermittently jointed rock slopes based on the stepped failure mode

In practical engineering,due to the noncontinuity characteristics of joints in rock slopes,in addition to plane failure,stepped sliding failure may occur for intermittently jointed rock slopes.Especially for intermittently bedding jointed rock slopes,the correlation and difference in strength parameters between joints and rock bridges,along with the various failure modes and intermittency of rock bridges,contribute to the complexity of stepped failure modes and the unpredictability of failure regions.Based on the upper-bound limit analysis method and multi-sliders step-path failure mode,considering the shear and tensile failure of rock bridges and the weakened relationship between the strength parameters of rock bridges and jointed surfaces,by introducing the modified M-C failure criterion and the formula for calculating the energy consumption of tensile failure of rock bridges,two failure mechanisms are constructed to obtain the safety factor(F_(s))of intermittently jointed rock slopes.The sequential quadratic programming method is used to obtain the optimal upper-bound solution for F_(s).The influence of multiple key parameters(slope height H,horizontal distance L,Slope angleβ,shear strength parameters of the rock bridgeφr and cr,Dimensionless parameter u,weakening coefficients of the internal friction angle and cohesion between the rock bridges and joint surfaces Kφand Kc)on the stability analysis of intermittently jointed rock slopes under the shear failure mode of rock bridges as well as under the tensile failure mode is also explored.The reliability of the failure mechanisms is verified by comparative analysis with theoretical results,numerical results,and landslide cases,and the variation rules of F_(s)with each key parameter are obtained.The results show that F_(s) varies linearly withφr and cr of the rock bridge and with K_(φ)and K_(c),whereas F_(s)changes nonlinearly with H and L.In particular,with the increase in Kφand Kc,Fs increases by approximately 52.78%and 171.02%on average,respectively.For rock bridge tensile failure,F_(s) shows a nonlinearly positive correlation withφr,cr,Kφand Kc.In particular,with the increase in Kφand Kc,Fs increases by approximately 13%and 61.69%on average,respectively.Fs decreases rapidly with increasing slope gradientβand decreasing dimensionless parameterμ.When Kφand Kc are both less than 1.0,the stepped sliding surface occurs more easily than the plane failure surface,especially in the case of tensile failure of the rock bridge.In addition,rock slopes with higher strength parameters,taller heights,and greater weakening coefficients are prone to rock bridge tension failure with lower Fs,and more attention should be given to the occurrence of such accidents in actual engineering.

Effect of vinegar supplementation on patients with esophageal lesions lightly stained with Lugol’s iodine solution:Prospective single-centre trial

BACKGROUND Esophageal chromoendoscopy with iodine solution is important for detecting early esophageal cancer.The effect of routine treatment for lesions lightly stained with Lugol’s iodine solution is limited,and the addition of natural substances to a regular diet is becoming increasingly common.Vinegar has antitumor effects as reported in previous studies.AIM To evaluate whether vinegar supplementation could improve the prognosis of patients with lightly stained esophageal lesions.METHODSThis prospective single-centre trial included consecutive patients with lightly stained lesions between June 2020 and April 2022.Patients in the experimental group received increased amounts of vinegar for 6 months.The primary outcome of the study was the clinical therapeutic effect.Complications related to vinegar ingestion and adverse events were also recorded in detail.RESULTS A total of 166 patients were included in the final analysis.There was no significant difference in the baseline data between the two groups.Intention-to-treat(ITT)analysis demonstrated that the rates at which endoscopic characteristics improved were 33.72%in the experimental group and 20.00%in the conventional group(P=0.007);and the rates at which biopsy pathology improved were 19.77%and 8.75%,respectively(P=0.011).Additional vinegar consumption had a statistically protective effect on the rate at which endoscopic characteristics improved[hazard ratio(HR)_(ITT)=2.183,95%CI:1.183-4.028;HR_(per-protocol(PP))=2.307,95%CI:1.202-4.426]and biopsy pathology improved(HR_(ITT)=2.931,95%CI:1.212-7.089;HR_(PP)=3.320,95%CI:1.295-8.507).No statistically significant effect of increased vinegar consumption on preventing high-grade intraepithelial neoplasia or early cancer was observed(HR_(ITT)=0.382,95%CI:0.079-1.846;HRPP=0.382,95%CI:0.079-1.846).The subgroup analyses indicated that the overall therapeutic improvement of endoscopic characteristics and biopsy pathology seemed more obvious in older(age>60)male patients with small lesions(lesion size≤0.5 cm).Three patients in the experimental group reported acid regurgitation and heartburn.No adverse event during gastroscopy were recorded during follow-up.CONCLUSION A moderately increased ingestion of vinegar could not directly reduce the risk of esophageal cancer in the mucosa dysplasia population,but it improved the endoscopic characteristics and ameliorated the biopsy pathology to a certain extent.Further research is needed to verify the effect of nutritional intervention on precancerous esophageal lesions.

Extremely low frequency electromagnetic fields promote cognitive function and hippocampal neurogenesis of rats with cerebral ischemia

Extremely low frequency electromagnetic fields(ELF-EMF) can improve the learning and memory impairment of rats with Alzheimer's disease, however, its effect on cerebral ischemia remains poorly understood.In this study, we established rat models of middle cerebral artery occlusion/reperfusion.One day after modeling, a group of rats were treated with ELF-EMF(50 Hz, 1 mT) for 2 hours daily on 28 successive days.Our results showed that rats treated with ELF-EMF required shorter swimming distances and latencies in the Morris water maze test than those of untreated rats.The number of times the platform was crossed and the time spent in the target quadrant were greater than those of untreated rats.The number of BrdU~+/NeuN~+ cells, representing newly born neurons, in the hippocampal subgranular zone increased more in the treated than in untreated rats.Up-regulation in the expressions of Notch1, Hes1, and Hes5 proteins, which are the key factors of the Notch signaling pathway, was greatest in the treated rats.These findings suggest that ELF-EMF can enhance hippocampal neurogenesis of rats with cerebral ischemia, possibly by affecting the Notch signaling pathway.The study was approved by the Institutional Ethics Committee of Sichuan University, China(approval No.2019255A) on March 5, 2019.

Vulnerability and adaptation of an oasis social–ecological system affected by glacier change in an arid region of northwestern China

The Hexi Inland River Basin in an arid region of northwestern China was chosen as the study area for this research. The authors define the vulnerability of an oasis social-ecological system to glacier change; select 16 indicators from natural and socioeconomic systems according to exposure, sensitivity, and adaptive capacity; and construct a vulnerability-assessment indicator system aimed at an inland river basin in the arid region of Northwestern China. Vulnerability of the oasis socialecological system affected by glacier change in the study area is evaluated by Spatial Principal Component Analysis(SPCA) under the circumstance of glacier change. The key factors affecting the vulnerability are analyzed. The vulnerability of the oasis social-ecological system in the Hexi Inland River Basin affected by glacier change is of more than medium grade, accounting for about 48.0% of the total number of counties in the study area. In terms of the spatial pattern of the vulnerability, the oasis economic belt is the most vulnerable. With the rapid development of the area's society and economy, the exposure of the system to glacial changes is significantly increased; and an increase in glacial meltwater is not enough to overcome the impact of increased exposure, which is the main reason for the high vulnerability. Based on the result of the vulnerability analysis and combined with the present industrial structure in the Hexi Inland River Basin, near-,medium-, and long-term adaptation initiatives are put forward in the article.

Application and Validation of a Multi-block Constitutive Model at Landslides of the Wenchuan Earthquake

A multi-block model and a corresponding computer program have been developed which predict the kinematics of landslides.Furthermore,a unique event for studying different models simulating the triggering and movement of landslides is the 2008Wenchuan earthquake in the mountainous region in Sichuan Province of China,which caused a large number of rapid landslides.The purpose of the paper is two-fold:(a)to propose and incorporate into the multi-block model constitutive relations predicting soil response along slip surfaces,and(b)to apply the multi-block model with the constitutive relations at landslides triggered by the Wenchuan earthquake.The proposed constitutive equations predict the shape of the shear stress-displacement response measured in ring shear tests.In the application,four landslides caused by the Wenchuan earthquake were considered.Only in one of these landslides the shear resistance-displacement response along the slip surface has been measured in laboratory tests.At this landslide,the triggering and movement of the landslide was predicted.In the other landslides,back analyses were performed and it was observed that the multi-block model predicted reasonably well the final configuration of all slides.In addition,as the measured and back-estimated total friction angle of all landslides was less than 180,and the materials along the slip surface were sandy,it is inferred that some,or all of the slip surface during these slides was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.Concluding,the paper(A)proposed and validated a multi-block constitutive model which can be applied to predict the triggering and movement of earthquake-induced slides and(B)by analyzing four landslides of the 2008 Wenchuan earthquake,it concludes that some,or all of the slip surface during these slides,was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.

Microaerobic iron oxidation and carbon assimilation and associated microbial community in paddy soil

Iron oxidation is a prevalent and important biogeochemical process in paddy soil,but little is known about whether and how microbially mediated iron oxidation is coupled with carbon assimilation,particularly under microaerobic conditions.Here,we investigated kinetics of CO_2 assimilation and Fe(Ⅱ)oxidation in an incubation experiment with paddy soil under suboxic conditions,and profiled the associated microbial community using DNA-stable isotope probing and 16S r RNA gene-based sequencing.The results showed that CO_2 assimilation and Fe(II)oxidation in the gradient tubes were predominantly mediated by the microbes enriched in the paddy soil,primarily Azospirillum and Magnetospirillum,as their relative abundances were higher in the^( 13)C heavy fractions compared to^( 12)C heavy fractions.This study provided direct evidence of chemoautotrophic microaerophiles linking iron oxidation and carbon assimilation at the oxic–anoxic interface in the paddy soil ecosystem.

Development of community-based landslide early warning system in the earthquake-affected areas of Nepal Himalaya

In the central Nepal Himalaya,landslides form the major natural hazards annually resulting in many casualties and damage.Structural as well as non-structural measures are in place to minimize the risk of landslide hazard.To reduce the landslide risk,a Landslide Early Warning System(LEWS)as a nonstructural measure has been piloted at Sundrawati village(Kalinchowk rural municipality,Dolakha district)to identify its effectiveness.Intensive discussions with stakeholders,aided by landslide susceptibility map,resulted in a better understanding of surface dynamics and the relationship between rainfall and surface movement.This led to the development of a LEWS comprised of extensometers,soil moisture sensors,rain gauge stations,and solar panels as an energy source that blows siren receiving signals via a micro-controller and interfacing circuit.The data generated through the system is transmitted via a Global System for Mobile Communications(GSM)network to responsible organizations in realtime to circulate the warning to local residents.This LEWS is user-friendly and can be easily operated by a community.The successful pilot early warning system has saved 495 people from 117 households in August 2018.However,landslide monitoring and dissemination of warning information remains a complex process where technical and communications skill should work closely together.

A Study for the Influence of the Location of PCMs Assembly System on Improving Thermal Environment inside Disaster-Relief Temporary Houses

Currently,people pay more and more attention to the transitional resettlement of victims after various natural disasters.There is an urgent need for a large number of temporary houses to resettle the victims after natural disasters.Disaster-relief temporary houses(DTHs)played an important role in the post-disaster resettlement in the past,which can not only be produced on a large scale,but also can be quickly and conveniently erected,which were the main means to solve the problem of transitional resettlement.However,due to their temporary nature,there was no extra energy consuming system installed in the DTHs generally.Hence the indoor thermal environment inside the DTHs was severe in summer.In this study,combined with the field experimental tests of the DTHs in Wenchuan Earthquake and Lushan Earthquake and the experimental study of the full-size DTH,it found that the thermal environment inside the DTH was intolerably high in summer.It had negative impact on victims.In order to improve the thermal environment inside DTHs during post-disaster period which lacked of extra energy resources,this study used the method of combining phase change materials(PCMs)with walls of the DTH to explore its feasibility and effectiveness.The results showed that PCMs could effectively improve the thermal environment inside the DTH in summer.Furthermore,the difference of the composite positions between PCMs and the wall affected the improvement effect.The energy release rate of the PCMs assembly system(PAS)varied according to the positions of the PCMs.

A micro–macro constitutive model for rock considering breakage effects

The paper proposes a three-scale binary medium-based constitutive model on the basis of the meso structures and micro components to describe the elasto-plastic mechanical behavior of mudstone samples.Based on the breakage mechanism of geomaterials,mudstone samples are considered as two different materials(bonded and frictional elements)at mesoscales.From micro to meso scales,given the similar but different mineralogy composition and porosity of the bonded and frictional elements at microscale,as well as their separate mechanical characteristics,different homogenization methods are adopted to obtain their respective meso mechanical properties.At the mesoscale,in view of the unique meso structures and the continuous material transformation,the extended self-consistent scheme(SCS)is improved to be adaptable to elasto-plastic composites with varying meso components.With the consideration of the evolution form of the breakage ratio under the external loading being given based on the assumed strength distribution of the meso bonded elements,the mechanical relations between meso and macro scales are established.Finally,on the basis of the mean-field method and combined with the critical mechanical connections between different scales,the micro-meso-macro constitutive model for mudstone samples are proposed.The model validation shows that,with a few model parameters,the proposed model can well reflect the stress and deformation features of mudstone samples with complex micro-components.

Comparative Experimental Study on Heat Transfer Characteristics of Building Exterior Surface at High and Low Altitudes

The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are scarce.Therefore,the authors propose a modified measurement method based on the heat balance of a model building,and use the same model building to measure its external surface heat transfer coefficient under outdoor conditions in Chengdu city,China at an altitude of 520 m and Daocheng city at an altitude of 3750 m respectively.The results show that the total heat transfer coefficient(h_(t))of building surface in high-altitude area is reduced by 34.48%.The influence of outdoor wind speed on the convective heat transfer coefficient(h_(c))in high-altitude area is not as significant as that in low-altitude area.The fitting relation between convection heat transfer coefficient and outdoor wind speed is also obtained.Under the same heating power,the average temperature rise of indoor and outdoor air at highaltitude is 41.9%higher than that at low altitude,and the average temperature rise of inner wall is 25.8%higher than that at low altitude.It shows that high-altitude area can create a more comfortable indoor thermal environment than low-altitude area under the same energy consumption condition.It is not appropriate to use the heat transfer characteristics of the exterior surface of buildings in low-altitude area for building energy saving design and related heating equipment selection and system terminal matching design in high-altitude area.

Factors contributing to the oxygen concentration over the Qinghai-Tibetan Plateau and its contribution rate calculation

A decline in atmospheric oxygen concentration is projected in the 21st century given the background of global warming.The Qinghai-Tibetan Plateau is located at a high altitude,and thus,it faces a hypoxia challenge;however,knowledge of the factors contributing to its atmospheric oxygen concentration is still lacking.Here,we conducted joint observations of ecosystem oxygen production and carbon sinks and near-surface atmospheric oxygen concentrations on the Qinghai-Tibetan Plateau and meteorological elements at Beijing Fangshan Station.Using seasonal differences and statistical methods,we calculated the relative contribution rates of vegetation to changes in atmospheric oxygen concentration.Our results indicate that solar radiation,atmospheric humidity,and ecosystem oxygen consumption and production have a significant impact on the atmospheric oxygen concentration,and the impact shows temporal and spatial differences.Vegetation significantly impacts the oxygen concentration,with a contribution rate of 16.7%–24.5%,which is underestimated in existing research.Our findings provide important insights into the factors that influence atmospheric oxygen concentration and highlight the contribution of vegetation.To better understand the oxygen dynamics of the Qinghai-Tibetan Plateau,we recommend further field observations of soil respiration and vegetation photosynthesis to clarify the contributions of carbon storage,carbon sinks and other factors to the near-surface atmospheric oxygen concentration.

Data augmentation for bias correction in mapping PM_(2.5) based on satellite retrievals and ground observations

As most air quality monitoring sites are in urban areas worldwide,machine learning models may produce substantial estimation bias in rural areas when deriving spatiotemporal distributions of air pollutants.The bias stems from the issue of dataset shift,as the density distributions of predictor variables differ greatly between urban and rural areas.We propose a data-augmentation approach based on the multiple imputation by chained equations(MICE-DA)to remedy the dataset shift problem.Compared with the benchmark models,MICE-DA exhibits superior predictive performance in deriving the spatiotemporal distributions of hourly PM2.5 in the megacity(Chengdu)at the foot of the Tibetan Plateau,especially for correcting the estimation bias,with the mean bias decreasing from-3.4µg/m3 to-1.6µg/m3.As a complement to the holdout validation,the semi-variance results show that MICE-DA decently preserves the spatial autocorrelation pattern of PM2.5 over the study area.The essence of MICE-DA is strengthening the correlation between PM2.5 and aerosol optical depth(AOD)during the data augmentation.Consequently,the importance of AOD is largely enhanced for predicting PM2.5,and the summed relative importance value of the two satellite-retrieved AOD variables increases from 5.5%to 18.4%.This study resolved the puzzle that AOD exhibited relatively lower importance in local or regional studies.The results of this study can advance the utilization of satellite remote sensing in modeling air quality while drawing more attention to the common dataset shift problem in data-driven environmental research.

Application of modified discontinuous deformation analysis to dynamic modelling of the Baige landslide in the Jinsha River

Accurate dynamic modeling of landslides could help understand the movement mechanisms and guide disaster mitigation and prevention.Discontinuous deformation analysis(DDA)is an effective approach for investigating landslides.However,DDA fails to accurately capture the degradation in shear strength of rock joints commonly observed in high-speed landslides.In this study,DDA is modified by incorporating simplified joint shear strength degradation.Based on the modified DDA,the kinematics of the Baige landslide that occurred along the Jinsha River in China on 10 October 2018 are reproduced.The violent starting velocity of the landslide is considered explicitly.Three cases with different violent starting velocities are investigated to show their effect on the landslide movement process.Subsequently,the landslide movement process and the final accumulation characteristics are analyzed from multiple perspectives.The results show that the violent starting velocity affects the landslide motion characteristics,which is found to be about 4 m/s in the Baige landslide.The movement process of the Baige landslide involves four stages:initiation,high-speed sliding,impact-climbing,low-speed motion and accumulation.The accumulation states of sliding masses in different zones are different,which essentially corresponds to reality.The research results suggest that the modified DDA is applicable to similar high-level rock landslides.

ICF通用组合在临床应用中的评估者间和评估者内信度研究

目的:探讨ICF通用组合在临床功能评估中的评估者间和评估者内信度,为其临床应用提供依据。方法:来自21个省份、50家医院康复医学科、神经内科、心内科、呼吸科和骨科的4784例患者参与了本研究,其中康复科患者776例。患者在入院时、住院中期、出院3个时间点接受同一名评估者的ICF通用组合功能评估,以进行评估者内信度分析。康复科患者同时接受2名评估者的评估,以进行评估者间信度分析。组内相关系数(ICC)检验评估者间信度和评估者内信度。结果:ICF通用组合的7个条目中除了d850有报酬的就业的ICC为0.40外,其他类目及总分的ICC都在0.70—0.95之间,评估者间信度佳。ICF通用组合的7个类目在入院和住院中期两个时间点之间的ICC要高于入院和出院两个时间点之间的ICC,评估者内信度佳。结论:除了d850有报酬的就业,ICF通用组合的其他条目及总分评估者间信度良好。ICF通用组合的评估者内信度良好。

ICF通用组合在中国人群临床应用中的效度研究

目的:探讨ICF通用组合在中国人群临床功能评估中的结构效度,为其临床应用提供依据。方法:采用ICF通用组合功能评估量表,于入院和出院时两个时间点对来自全国21个省份和自治区50家医院康复医学科、神经内科或脑外科、心血管科、呼吸科和骨科4510名患者进行评估。所得数据用于评价ICF通用组合在临床功能评估中的结构效度。结果:"d850有报酬的就业"不适用于NRS评分,缺失值较大。除去此项,患者出院时ICF通用组合评分(15.25±13.48)分,低于入院时(23.76±15.15)分,差异有显著性意义(P<0.001)。探索性因子分析结果表明,抽取特征根>1的公因子共有2个,累积贡献率为78.018%。采用结构方程模型方法,拟合了"b130能量和驱力功能"、"b152情感功能"、"b280痛感"、"d230执行日常事务"、"d450步行"、"d455到处移动"关系模型,结构方程模型调整的拟合优度指数RMSEA=0.026,NFI=0.999,CFI=0.999,AGFI=0.994,模型较好的拟合了数据。结论:ICF通用组合能反映出、入院时患者的不同功能状态且其结构效度良好,是一种临床上有效的测量患者功能状态的工具。

Stiffness of individual quadriceps muscle assessed using ultrasound shear wave elastography during passive stretching

Background: Until recently it has not been possible to isolate the mechanical behavior of individual muscles during passive stretching. Muscle shear modulus(an index of muscle stiffness) measured using ultrasound shear wave elastography can be used to estimate changes in stiffness of an individual muscle. The aims of the present study were(1) to determine the shear modulus—knee angle relationship and the slack angle of the vastus medialis oblique(VMO), rectus femoris(RF), and vastus lateralis(VL) muscles;(2) to determine whether this differs between the muscles.Methods: Nine male rowers took part in the study. The shear modulus of VMO, RF, and VL muscles was measured while the quadriceps was passively stretched at 3°/s. The relationship between the muscle shear modulus and knee angle was plotted as shear modulus—knee angle curve through which the slack angle of each muscle was determined.Results: The shear modulus of RF was higher than that of VMO and VL when the muscles were stretched over 54°(all p < 0.01). No significant difference was found between the VMO and VL(all p > 0.05). The slack angle was similar among the muscles: 41.3°± 10.6°, 44.3°± 9.1°, and 44.3°± 5.6° of knee flexion for VMO, RF, and VL, respectively(p = 0.626).Conclusion: This is the first study to experimentally determine the muscle mechanical behavior of individual heads of the quadriceps during passive stretching. Different pattern of passive tension was observed between mono-and bi-articular muscles. Further research is needed to determine whether changes in muscle stiffness are muscle-specific in pathological conditions or after interventions such as stretching protocols.

Spatial memory enhances the evacuation efficiency of virtual pedestrians under poor visibility condition

Spatial memory is a critical navigation support tool for disoriented evacuees during evacuation under adverse environ-mental conditions such as dark or smoky conditions. Owing to the complexity of memory, it is challenging to understand the effect of spatial memory on pedestrian evacuation quantitatively. In this study, we propose a simple method to quan- titatively represent the evacuee＇s spatial memory about the emergency exit, model the evacuation of pedestrians under the guidance of the spatial memory, and investigate the effect of the evacuee＇s spatial memory on the evacuation from theoretical and physical perspectives. The result shows that （i） a good memory can significantly assist the evacuation of pedestrians under poor visibility conditions, and the evacuation can always succeed when the degree of the memory exceeds a threshold （φ〉 0.5）; （ii） the effect of memory is superior to that of ＂follow-the-crowd＂ under the same environmental conditions; （iii） in the case of multiple exits, the difference in the degree of the memory between evacuees has a significant effect （the greater the difference, the faster the evacuation） for the evacuation under poor visibility conditions. Our study provides a new quantitative insight into the effect of spatial memory on crowd evacuation under poor visibility conditions.