Degradation and resynthesis of chlorophyll during increased oxidative stress and prolonged darkness differ between annual and perennial flax(Linum L.)

Among plants,there is considerable variation in lifespan:annuals live less than one year,whereas perennials live for several years,with the longest-living perennial having survived 43,600 years.As proposed by the Disposable Soma Theory,this lifespan variation among plants likely reflects differential investment of limited energy and nutrient resources,with perennials investing more energy and nutrients into biomolecular maintenance compared to annuals in order to ensure persistence over multiple seasons.Such differential investment may be particularly important during periods of exogenous stress,which are known to accelerate biomolecular damage.The present study evaluated this hypothesis using annual and perennial flax(Linum L.)subjected to two exogenous stressors—increased oxidative stress(i.e.,foliar H2O2spraying)and complete prolonged darkness.As chlorophyll has been shown to exhibit degradation in response to changes in environmental conditions,we utilized changes in chlorophyll levels during and after periods of exogenous stress to evaluate our hypotheses.We predicted that i)perennials would exhibit a slower rate of chlorophyll degradation during exposure to exogenous stressors compared to annuals,and ii)perennials would exhibit a faster rate of chlorophyll resynthesis following such exposure compared to annuals.Chlorophyll levels before,during,and after exposure to both exogenous stressors were measured in two separate trails,once using image colour analysis and once using spectrophotometry.While chlorophyll degradation rates in response to oxidative stress did not differ between annuals and perennials,contrary to our predictions,chlorophyll resynthesis rates following such exposure were significantly higher in perennials,as predicted.When plants were subjected to complete prolonged darkness,chlorophyll degradation rates were significantly lower in perennials than annuals,as predicted;however,when plants were subsequently reintroduced to natural photoperiod,chlorophyll resynthesis rates did not consistently differ between annuals and perennials,though they tended to be higher in the latter,as predicted.Overall,our study illuminates that evolutionary transitions between life history strategies in plants have been accompanied by physiological modifications to chlorophyll dynamics that permit perennial species to better maintain chlorophyll levels—and thus photosynthetic energy acquisition-in the face of exogenous stressors,which likely underlies their capacity to survive for multiple growing seasons.Future studies should explore whether other key biomolecules(e.g.,proteins,DNA)are also better maintained in perennial plants,especially in the face of exogenous stress.

Relationship between preoperative psychological stress and shortterm prognosis in elderly patients with femoral neck fracture

BACKGROUND Older adults are at high risk of femoral neck fractures(FNFs).Elderly patients face and adapt to significant psychological burdens,resulting in different degrees of psychological stress response.Total hip replacement is the preferred treatment for FNF in elderly patients;however,some patients have poor postoperative prognoses,and the underlying mechanism is unknown.We speculated that the postoperative prognosis of elderly patients with FNF may be related to preoperative psychological stress.AIM To explore the relationship between preoperative psychological stress and the short-term prognosis of elderly patients with FNF.METHODS In this retrospective analysis,the baseline data,preoperative 90-item Symptom Checklist score,and Harris score within 6 months of surgery of 120 elderly patients with FNF who underwent total hip arthroplasty were collected.We analyzed the indicators of poor short-term postoperative prognosis and the ability of the indicators to predict poor prognosis and compared the correlation between the indicators and the Harris score.RESULTS Anxiety,depression,garden classification of FNF,cause of fracture,FNF reduction quality,and length of hospital stay were independent influencing factors for poor short-term postoperative prognoses in elderly patients with FNF(P<0.05).The areas under the curve for anxiety,depression,and length of hospital stay were 0.742,0.854,and 0.749,respectively.The sensitivities of anxiety,depression,garden classification of FNF,and prediction of the cause of fracture were 0.857,0.786,0.821,and 0.821,respectively.The specificities of depression,FNF quality reduction,and length of hospital stay were the highest at 0.880,0.783,and 0.761,respectively.Anxiety,depression,and somatization scores correlated moderately with Harris scores(r=-0.523,-0.625,and-0.554;all P<0.001).CONCLUSION Preoperative anxiety,depression,and somatization are correlated with poor short-term prognosis in elderly patients with FNF and warrant consideration.

Investigation of the short-term stress distribution in stopes and drifts backfilled with cemented paste backfill

Cemented paste backfill(CPB) is largely used in underground mines worldwide.A key issue associated with application of CPB is to estimate the stresses in backfilled stopes and on barricades.Recent numerical and experimental results show that arching effect is absent shortly after the placement of CPB in stopes.However,stress decreases in barricade drift with increasing distance between the measurement points and drawpoint have also been observed,demonstrating arching effect shortly after the pouring of CPB.To explain these paradoxes,CPB is considered as Bingham fluid having a yield shear stress.Three dimensional analytical solutions are proposed to evaluate the short-term total stresses in backfilled stopes and on barricades,accounting for the CPB's yield shear stress-induced arching effect.Stress diminution due to such arching effect in the backfilled stopes and on barricades is indeed obtained.But the reduction becomes insignificant using typical yield shear stress and stope geometry.More analyses indicate that the typical yield shear stress values do not fully correspond to field conditions where the yield shear stress would increase exponentially due to apparent consolidation(loss of water by drainage,a phenomenon similar to the desiccation of overly saturated fine-grained materials).

Influence of anisotropic stress path and stress history on stiffness of calcareous sands from Western Australia and the Philippines

Investigation of dynamic properties of carbonate/calcareous soils is important in earthquake and offshore engineering as these soils are commonly encountered in large-scale projects related with energy geomechanics and land reclamation.In this study,the stiffness and stiffness anisotropy of two types of calcareous sands(CS)from the Western Australia and the Philippines were examined using bender elements configured in different directions in stress path setups.Stiffness measurements were taken on specimens subjected to constant p’compression/extension and biaxial stress paths and additional tests were performed on three types of silica sands with different geological origins and particle shapes,which were used as benchmark materials in the study.Compared with the three brands of silica sands,the stiffness of the CS was found to be more significantly influenced by anisotropic loading;an important observation of the experimental results was that stress anisotropy had different weighted influences on the stiffness in different directions,thus influencing stiffness anisotropy.Comparisons were made between the specimens subjected to complex loading paths,and respected model parameters as suggested from published expressions in the literature.These comparisons further highlighted that calcareous soils have different responses in terms of stiffness,stiffness anisotropy and loading history,compared with that of silica-based sands.

Effects of short-term heat stress on PSII and subsequent recovery for senescent leaves of Vitis vinifera L. cv. Red Globe

Heat stress occurs frequently in energy-saving sunlight greenhouses(ESSG) at the late growth stage. Three-year delayed cultivation(DC) of the Red Globe cultivar of Vitis vinifera L. was used to clarify the physiological mechanisms of short-term heat stress on PSII and subsequent recovery from heat stress. By November, the photosynthetic function had declined and the fall in transpiration rate(E) with heating time increased the possibility of heat damage. In July, the most obvious increase was in the relative variable fluorescence at J point at 40°C, and in November it changed to K point. The 5 min of heat treatment resulted in a significant increase of the relative variable fluorescence at 0.3 ms(W), and after 10 min of heat treatment, the number of reactive centres per excited cross section(RC/CS), probability that a trapped exciton moves an electron into the electron transport chain beyond Q–(at t=0)(Ψ) and quantum yield of electron transport at t=0(φ) decreased significantly(P<0.05), suggesting that the reaction centre, donor and acceptor side of photosystem II(PSII) were all significantly inhibited(P<0.05) and that the thermal stability of the photosynthetic mechanism was reduced. The inhibition of energy fluxes for senescent leaves in November was earlier and more pronounced than that for healthy leaves, which did not recover from heat stress of more than 15 min after 2 h recovery at room temperature.

Effects of short-term osmotic stress on leaf hydraulic conductivity and ZmPIPs mRNA accumulation in maize seedlings

Plants maintain water balance by varying hydraulic properties, and plasma membrane intrinsic proteins（PIPs） may be involved in this process. Leaf xylem and root hydraulic conductivity and the m RNA contents of four highly expressed Zm PIP genes（Zm PIP1;1, Zm PIP1;2, Zm PIP2;2, and Zm PIP2;5） in maize（Zea mays） seedlings were investigated. Under well-watered conditions, leaf hydraulic conductivity（K_（leaf）） varied diurnally and was correlated with whole-plant hydraulic conductivity. Similar diurnal rhythms of leaf transpiration rate（E）, K_（leaf） and root hydraulic conductivity（K_（root）） in well-watered plants are important for maintaining whole-plant water balance. After 2 h of osmotic stress treatment induced by 10% polyethylene glycol 6000, the K_（root） of stressed plants decreased but K_（leaf） increased, compared with well-watered plants. The m RNA contents of four Zm PIPs were significantly up-regulated in the leaves of stressed plants, especially for Zm PIP1;2. Meanwhile, Zm PIP2;5 was significantly down-regulated in the roots of stressed plants. After 4 h of osmotic stress treatment, the E and leaf xylem water potentials of stressed plants unexpectedly increased. The increase in K_（leaf） and a partial recovery of K_（root） may have contributed to this process. The m RNA content of Zm PIP1;2 but not of the other three genes was up-regulated in roots at this time. In summary, the m RNA contents of these four Zm PIPs associated with K_（leaf） and K_（root） change in maize seedlings during short-term osmotic stress, especially for Zm PIP1;2 and Zm PIP2;5, which may help to further reveal the hydraulic resistance adjustment role of Zm PIPs.

Experimental study of seepage characteristics of single rock fracture based on stress states and stress history

Through seepage tests under different loading and unloading confining pressures and different hydraulic gradients,the authors studied the effects of stress states and stress history on fracture permeability evolution for single granite fracture and sandstone fracture. The results show that there exists a linear relationship between the seepage discharge and osmotic pressure in sandstone fissure under each level of confining pressure. With the increasing in the confining pressure,the permeability of the fracture decreases,but the decreasing rate is changeing. During the unloading process,the fracture seepage velocity cannot be fully recovered to the size of the loading process. Therefore,in the unloading process of the confining pressure,the recovery of fracture permeability shows obvious hysteresis effects. The flow rate of the fracture remains unchanged during five cycles of loading and unloading processes of the confining pressure. In each cycle,the evolution character of the flow rate with the confining pressure remains unchanged. These experiments show that the seepage characteristics of sandstone and granite fractures are not the same under the same stress state.

Influence of excavation beneath existing building on dynamic impedances of underpinning pile considering stress history

The addition of basement beneath existing building changes the underpinning pile from fully embedded to partially embedded,and thus influences the mechanical properties of pile.In the past,scholars paid attention to the change in the bearing capacity of pile but neglected the difference of dynamic characteristics before and after construction,and potential changes in stress history of remaining soil are also ignored.In this work,a calculation model is built to investigate the influence of excavation on dynamic impedance of underpinning pile considering the effect of stress history.The soil is simulated by the dynamic Winkler foundation,which is characterized by springs and dashpots.Properties of remaining soil after excavation are updated to consider the effect of stress history through modifying the initial shear modulus and related parameters.The dynamic impedance of pile after excavation is obtained based on the transfer matrix method.The parameter study is carried out to evaluate the dynamic impedance with various excavation depths,considering or ignoring stress history effect,and various element lengths.The results show that shallow soil plays an important role to dynamic impedance,and overestimated dynamic impedance is obtained if not considering the stress history effect.

Application of Ambient Stress Parameters to Short-Term Prediction of the 2004, M_S5.0 Shuangbai, Yunnan Earthquake

Based on the data recorded by the regional digital seismic network of Yunnan and using new methods, the short-term variations of the ambient stress field of Yunnan and its adjacent areas are monitored in real time. With the in-depth analyses of the spatial-temporal evolution of the ambient stress field prior to the 2004, Shuangbai M_S5.0 earthquake, concrete procedures for predicting the three elements of the earthquake are presented.

Biological Analysis and Response to Low Phosphate Stress of Phosphate Transporter Family 1 (PHT1) Genes in Solanum tuberosum L.

Inorganic phosphate(Pi)is one of the main nutrients necessary for plant growth.Phosphate transporters mediate the acquisition,transport and recycling of phosphate,which is essential for plant growth and development.Although PHT1 has been reported in many plants at home and abroad,it is rarely studied in potato.Therefore,it is of great significance to study the PHT1 family members in order to understand the molecular response mechanism of potato in low phosphate state.In this study,a total of 6 potato PHT1 genes were identified and isolated.It was found that after the expression of different members of potato PHT1 gene,there were certain differences in amino acids and proteins,and the transmembrane domains ranged from 6 to 12.The difference in the secondary and tertiary protein structure of potato PHT1 also led to a difference in protein morphology.In addition,the expression of the PHT1 gene in potato increased obviously during 3~9 h of Pi deficiency stress.Overall,the expression levels of different genes in roots,stems and leaves are distinctly different,but the expression levels of the StPHT1;6 and StPHT1;10 genes are very high in roots,stems and leaves,indicating that these two genes may participate in the absorption of Pi in potato and play a role in Pi translocation.These two genes play a major role in the regulation of expression under short-term Pi deficiency stress.Our results provide an important reference for further understanding the evolution and function of potato phosphate transporters,and have important significance for improving the ability of potato to tolerate low Pi.

考虑硬化历史的圆筒形件二次拉深极限拉深比的解析模型

以圆筒形件二次拉深成形为例,基于主应力法和板料弯曲理论,考虑材料硬化历史、壁厚比t_(min)/t_(max)、凹模圆角半径和摩擦因数的影响,建立了一种预测圆筒形件二次拉深极限拉深比的解析模型,并对SUS304不锈钢板料进行了拉深试验验证。结果表明:解析模型的预测值与试验结果吻合较好;考虑硬化历史的解析模型与未考虑硬化历史的模型相比二次拉深极限拉深比相差约10%;摩擦因数、凹模圆角半径对二次拉深极限拉深比有显著影响,摩擦因数越大,二次拉深极限拉深比越小;凹模圆角半径越大,二次拉深极限拉深比越大。

远场水下爆炸冲击作用下重力坝动力稳定性的简化时程分析方法

高坝大库的抗爆与防护是国防安全的重要研究课题。该文针对远场水下爆炸冲击作用下混凝土重力坝的稳定安全评价问题,研究了远场水下爆炸冲击波的传播及其与坝体的相互作用过程;基于波动理论和平面波假设,建立了重力坝爆炸动应力场的简化理论计算模型,最终建议了一种远场水下爆炸冲击波作用下重力坝动力稳定性的简化时程分析方法;同时结合工程实际,采用该方法对某混凝土重力坝的动力稳定性进行了分析。结果表明:在远场爆炸冲击荷载作用下,重力坝的稳定安全系数呈现出先增后减再增并最终保持恒定的变化规律;下游坝面反射形成的拉伸波与剪切波的共同作用是导致建基面稳定安全系数降低的主要原因。

主应力轴旋转条件下初始应力状态对冻结黏土动力特性的影响试验研究

为了揭示主应力轴旋转条件下初始应力状态对冻结黏土动力特性的影响,利用冻土空心圆柱仪实现了纯主应力轴旋转的圆形应力路径,在圆形应力路径基础上开展了一系列室内空心扭剪试验,研究了初始应力状态对冻结黏土累积塑性应变、应力-应变滞回圈和动模量的影响。结果表明:纯主应力轴旋转条件下试样承受的初始应力越大时,冻结黏土空心圆柱试样的累积塑性应变发展速率越快,产生的最终累积塑性应变也相对较大。另外,发现纯主应力旋转条件下随着初始应力的增大,冻结黏土试样轴向应力-应变和剪切应力-应变滞回曲线倾斜度增大,冻结黏土试样的轴向回弹模量和剪切模量也增大,且不同循环应力比下轴向回弹模量和剪切模量与静偏应力比之间呈线性关系。研究结果有助于完善寒区工程和人工冻结工程设计理论。

Psychiatric outcomes in outpatients affected by long COVID:A link between mental health and persistence of olfactory complaint

BACKGROUND Anosmia was one of the main symptoms of coronavirus disease 2019(COVID-19).A psychiatric history(i.e.,depression)may be an independent contributor to the risk of COVID-19 diagnosis,and COVID-19 survivors appear to have an increased risk of neuropsychiatric sequelae(bidirectional association).AIM To compare the rate of psychiatric disorder among post-COVID patients without anosmia vs patients with persistent olfactory complaints.METHODS We conducted a prospective case control study from March 2020 to May 2021.Patients recruited at the ENT department of Nice University Hospital had a subjective olfactory complaint(visual analogue scale)for over 6 wk and a molecular or CT-proven severe acute respiratory syndrome coronavirus 2 diagnosis confirmed by serology.Post-COVID patients without persistent olfactory disorders were recruited at the university hospital infectiology department.Psychiatric medical histories were collected by a psychiatrist during the assessments.RESULTS Thirty-four patients with post-COVID-19 olfactory complaints were included in the first group of the study.Fifty percent of the patients were female(n=17).The group’s mean age was 40.5±12.9 years.The control group included 32 participants,of which 34.4%were female(n=11),and had a mean age of 61.2±12.2 years.The rate of psychiatric disorder among post-COVID patients with olfactory complaints was significatively higher(41.7%)than among patients without(18.8%)(χ2=5.9,P=0.015).CONCLUSION The presence of a psychiatric history may constitute a potential risk factor for the development of long COVID due to persistent anosmia.It therefore seems important to establish reinforced health monitoring after a COVID 19 infection in at-risk patients.Further prospective,translational,and collaborative studies are needed to extrapolate these results to the general population.

应力路径对盐城粉质黏土动剪切模量影响试验研究

沿海地区地下土常受到地震、施工、波浪等各种动力作用的影响。为了研究应力路径对粉质黏土动力特性的影响,选取盐城地区不同深度的粉质黏土原状样进行循环应力路径下的共振柱试验。结果表明:应力历史对土动力参数响应的影响显著,加卸载路径间土的最大动剪切模量Gmax和动剪切模量G之间有明显差异;在围压0~80 kPa时,Gmax快速上升,变异性减小;地质年代和埋深对土动力学参数的变化起重要作用。随着埋深增加,各应力路径下Gmax和围压变化时G的差异不断扩大,当地质年代发生变化时,G显著增加;根据试验提出最大动剪切模量与围压间的拟合关系式并提供不同应力历史粉质黏土的拟合结果,为盐城以及相关沿海地区的工程设计和施工提供参考。

土的压缩模量与变形模量的理论关系

在实际工程中经常用到土的变形模量,由于测试变形模量需要花费较多的时间和费用,故常常通过压缩模量来估算变形模量,但这种估算有很大争议。本文首先指出长期公认的变形模量与压缩模量间的关系式E_(0)=βE_(s)中存在的问题,然后重新推导了它们的关系式E_(0)=β′E_(s),考虑到土的结构性、应力历史条件以及土体扰动,最后建立了一种新的变形模量与压缩模量的关系式E_(0)=αE_(s)。

航天工研院超高层空中大堂的结构设计与分析

超高层建筑航天工研院在21层设置了空中大堂,为实现镂空轻巧创意,配合玻璃幕墙竖向风格,结构采用钢吊杆悬挂空中大堂的楼盖。采用弹性屈曲分析法对穿层柱、穿层墙的稳定性进行了研究;采用PMM屈服球对穿层柱的正截面承载力进行了验算;采用弹塑性时程分析法对穿层墙的承载力进行了复核;采用行走激励振动响应分析法对空中大堂悬挂楼板进行了舒适度分析;采用应力分析方法对悬挂楼板的承载力性能进行了评定;采用性能化设计方法对悬吊空中大堂的钢吊杆的承载力进行了验算;采用弹塑性时程分析方法对吊挂梁进行了承载力验算。结果表明:穿层柱、穿层墙的稳定性满足规范要求;悬挂楼板的自振频率及竖向加速度满足舒适度要求;钢吊杆的选型合理可靠;穿层柱、穿层墙、悬挂楼板、钢吊杆及吊挂梁的承载力均能满足既定的抗震性能目标要求;采用的结构方案不仅较好地实现建筑创意,而且空中大堂的结构设计安全可靠,合理可行。

广州某旧改项目超限分析与设计

某旧改项目有地下2层,主要包括6栋48层超高层住宅、2栋41层高层住宅,为钢筋混凝土剪力墙结构体系。针对超高层结构各超限项和结构薄弱处,该项目采取了抗震性能设计,通过各项分析,完善计算,实现结构性能目标。具体而言,采用YJK和MIDAS软件进行多遇地震对比分析,结果显示主要结构指标都在规范允许范围;采用SAUSAGE进行弹塑性时程分析,结果表明该结构在罕遇地震作用下各项指标表现良好,耗能机制合理;通过YJK软件楼板温度影响分析显示,大底板地下室楼板配筋时应考虑温度应力作用。

厦门裕景中心1号酒店塔楼超限结构设计研究

厦门裕景中心项目主体为框架—剪力墙结构,平面呈S形,上部结构的5~7层中间部分设置转换桁架用于支撑上方11层钢结构,存在细腰、扭转不规则、偏心布置、托柱转换、底盘高度超限等多项不规则情况。该项目为续建工程,上部荷载较原来有所增加,需重新复核基础承载力,并基于抗震性能设计,设置合理的抗震性能目标,通过罕遇地震下的动力弹塑性时程分析,找出薄弱部位,从而提出可行加强措施。最后,分析交叉桁架节点应力及小震中震下转换桁架的传力途径,确保达到中震性能目标。

基于非线性时程的750kV构架抗震性能分析

750kV变电构架是我国西北地区变电工程最核心的构筑物。文中采用通用有限元分析软件SAP2000,对某位于抗震设防烈度8度区的750kV格构式构架的抗震性能开展非线性时程分析。研究结果表明,750kV构架整体抗震性能可达到性能要求,构架梁柱杆件主材均满足抗震承载力要求,仅在罕遇地震作用下,部分柱腹杆应力比超限,建议采取增大该处杆件截面等加强措施,以增强750kV构架的抗震性能。