细小规格钢丝绳结构伸长研究

残余拉拔应力和捻制应力是钢丝绳在生产捻制过程产生结构伸长的主要原因。制绳钢丝的残余拉拔应力主要有残余拉应力、残余弯曲应力和残余扭转应力。钢丝绳股绳捻制过程中的捻制应力主要有扭转应力、弯曲应力和拉伸应力。以7×3—0.90结构细小钢丝绳为研究对象,将制绳钢丝的直径公差控制在±0.005 mm,中心股的3根钢丝适当加粗为0.16 mm,各股的股间间隙保证在0.01 mm,中心股丝径加粗,破断拉力上升,结构伸长下降。钢丝绳的股捻距一定,随着成品绳捻距的增大,钢丝绳破断拉力上升,结构伸长率下降。当钢丝绳成品捻距一定时,随着股捻距的增大,钢丝绳破断拉力上升,结构伸长率下降。     

The role of geometry on the viscoelastic materials properties: tensile and stress relaxation of the yarn

The time-dependent mechanical behavior of textiles has particular importance. One of such behaviors is stress relaxation. When strain is applied constantly, there is a decreased stress with time in viscoelastic materials, which is called stress relaxation. The aim of this study is to investigate the effect of knot’s geometry (surgeon, square and eight) and the number of knots on the tensile and stress relaxation properties of the polyester yarn. Significant differences were observed for the tensile characteristics of the yarn in the presence of the knot. Generally, the knotted yarns demonstrated lower tensile stress and strain at failure. Moreover, the results revealed that the stress relaxation behavior of the yarn is affected by the number of knots and their geometry. The yarn without knot exhibited the highest stress relaxation percent while the yarn with the surgeon’s knot displayed the least stress relaxation percent. On the other hand, increasing the number of knots led to a decrease in the percentage of yarn stress relaxation.     

Stress and the skin

'The skin is the mirror which reflects the state of the mind.'The skin is the window of the mind.' These have been proverbs since ancient times. It is the topic of this article. Our life became convenient with the information technology these days but too much information often drives us on. We suffer from mental stress rather than physical stress. Since Selye advocated stress reaction, various reactions in the body have been described. Skin is also a target organ of the stress reaction. What the effects of stress are and how stress affects the skin are summarized in this review. Possible use of fragrance for the regulation of the stress reaction is also introduced.     

基于包装结构评价有限元分析在酸奶瓶型优化中的应用

有限元分析用于仿真模拟,普遍应用于固体力学、流体力学、热传导、电磁学等,但在包装结构评价领域应用较少。本试验选择5个酸奶瓶型设计,通过ABAQUS有限元软件分别模拟顶部和侧方压力下的应力分布。试验结果表明:在码垛状态优化设计的2L、2L+B、1R瓶的应力值分别为3.92MPa、2.33MPa、1.8MPa,相对原始设计应力值降低,应力云分布更均匀,抗压能力增强。2L瓶的克重相较最轻,应力集中最低;在运输状态2L瓶的应力值为14.4MPa,2L+B瓶的应力值底部为20.2 MPa,上部为14MPa,应力值降低,应力云分布均匀。1R瓶的应力值为5.32MPa,相对原来的设计应力值未降低,但成本降低。     

The influence of two bar warp-knitted structure on the fabric tensile stress relaxation Part II: (locknit,satin, loop raised)

When strain is applied constantly, there is a decreased stress with time in viscoelastic materials, which is called stress relaxation. During the manufacture and application of clothing and footwear, materials experience various long-lasting deformations, and relaxation process in materials arises. Thus, with theoretical and experimental study of the factors affecting stress relaxation, the ability to design and produce appropriate clothes will be increased. In the first part of this research, we studied the stress relaxation behavior of warp-knitted structures which have longer underlaps in back bar (reverse locknit, three- and four-needle sharkskin, and queens’ cord). Following the previous research, the aim of this study was to investigate the effect of fabric structure, strain percentage, and course density on the stress and stress relaxation of the warp-knitted structures which have longer underlaps in front bar (locknit, three- and four-needle satin, and loop raised). The results reveal that the fabric structure, strain value, and fabric density are important factors affecting the stress and stress relaxation percent of the fabrics. By increasing the strain and the length of underlap in the front guide bar, stress and stress relaxation percent will be increased. Also, fabrics with higher course density show higher stress and stress relaxation percent. Among the mechanical models used to describe the stress relaxation behavior of the fabrics, the three-component Maxwell’s model with parallel-connect nonlinear spring showed the best agreement with the experimental stress relaxation curves of the analyzed fabrics.     

Invited review: From heat stress to disease—Immune response and candidate genes involved in cattle thermotolerance

Heat stress implies unfavorable effects on primary and functional traits in dairy cattle and, in consequence, on the profitability of the whole production system. The increasing number of days with extreme hot temperatures suggests that it is imperative to detect the heat stress status of animals based on adequate measures. However, confirming the heat stress status of an individual is still challenging, and, in consequence, the identification of novel heat stress biomarkers, including molecular biomarkers, remains a very relevant issue. Currently, it is known that heat stress seems to have unfavorable effects on immune system mechanisms, but this information is of limited use in the context of heat stress phenotyping. In addition, there is a lack of knowledge addressing the molecular mechanisms linking the relevant genes to the observed phenotype. In this review, we explored the potential molecular mechanisms explaining how heat stress affects the immune system and, therefore, increases the occurrence of immune-related diseases in cattle. In this regard, 2 relatively opposite hypotheses are under focus: the immunosuppressive action of cortisol, and the proinflammatory effect of heat stress. In both hypotheses, the modulation of the immune response during heat stress is highlighted. Moreover, it is possible to link candidate genes to these potential mechanisms. In this context, immune markers are very valuable indicators for the detection of heat stress in dairy cattle, broadening the portfolio of potential biomarkers for heat stress.     

乳酸菌的热胁迫研究进展

乳酸菌和其他自由生活的微生物一样,在发酵及食品加工、贮藏过程中经常暴露于各种环境胁迫条件下,包括饥饿胁迫、渗透压胁迫以及热胁迫等,增加胁迫抗性是提高生物量及代谢产物积累的有效策略。热胁迫可能是自然界及工业应用中微生物所面临的最常见压力。目前研究表明来自不同生境的乳酸菌通过基因表达的快速变化对温度的突然升高做出反应,从而导致热休克蛋白的蛋白质水平升高。热休克蛋白在进化过程中具有高度保守性,在正常条件下,其有助于受体调节,细胞骨架稳定及蛋白质的折叠、组装、运输、降解。在热胁迫条件下,其功能变得尤为重要。综述了乳酸菌的热胁迫耐受机制及不同乳酸菌的热胁迫反应,为研究乳酸菌热胁迫应答机制提供一定的理论借鉴,有利于乳酸菌的工业化应用。     

预应力钢丝的应力腐蚀

长期以来 ,冷拉预应力钢丝的应力腐蚀问题并未引起人们的足够重视。从产生应力腐蚀的机理出发 ,分析产生应力腐蚀的诸多原因 ,指出影响应力腐蚀开裂的 4个因素 ,使用中预应力钢丝的应力腐蚀情况与钢材的冶金状态、持续拉伸应力、时间的连续性和环境状况息息相关。提出降低钢丝应力腐蚀的对应措施 ,并介绍美国标准中关于“氢脆敏感性试验”的方法 ,以评价钢丝应力腐蚀开裂倾向     

烟草盐胁迫与耐盐相关基因的研究进展

盐胁迫是非生物胁迫中的重点研究领域，在盐胁迫下，植物体内通过激发抗盐基因的表达来增强植物的耐盐能力。本文介绍了烟草耐盐胁迫的作用机制，从离子转运、渗透调节、抗氧化性、信号传导与表达调控、保护细胞免受胁迫伤害等5个方面系统地综述了烟草耐盐相关基因的研究进展，并对未来烟草盐胁迫的研究方向进行了展望。      

Gelatin Photoelasticity: A New Technique for Measuring Stress Distributions in Gels During Penetration Testing

The birefringence observed in polarized light on subjecting gelatin gels to stress has been employed as a novel means of examining stress distributions set up during penetration testing. Two types of information are contained in the observed patterns: maximum shear stress magnitudes can be assessed from the isochromatic patterns, and stress directions can be constructed from the isoclinic patterns. Relative shear stress magnitudes can be estimated directly, and absolute shear stress magnitudes can be calculated provided the fringe constant of the gel is measured under carefully controlled experimental conditions. Information on stress directions is generally of lesser value.     

真菌中氧胁迫调控因子AP-1研究进展

氧化应激是细胞应激反应的一种,在所有生物中都是保守进化的。应激反应的调控包括转录、翻译和翻译后修饰,决定生物体是否适应、存活、或者死亡。酵母中b-ZIP型激活蛋白(Yap)家族包括8个成员,Yap1是酵母Yap家族中首先发现的成员,具有DNA结合结构域和转录激活活性,在细胞的氧化应激中发挥着必不可少的作用。在氧化压力下,Yap1的活性增加。本文对近年来AP-1转录因子在真菌中的主要研究进展进行了综述,重点介绍了AP-1作为主要的氧化应激调节器参与的生物学应激反应、致病性及产生真菌毒素等,并介绍了AP-1在铁代谢、钴毒性、DNA损伤、耐药性中的功能。     

A 100-Year Review: Stress physiology including heat stress

Stress is an external event or condition that places a strain on a biological system. The animal response to a stress involves the expenditure of energy to remove or reduce the impact of the stress. This increases maintenance requirements of the animal and results in loss of production. The biological response to stress is divided into acute and chronic phases, with the acute phase lasting hours to a few days and the chronic phase lasting several days to weeks. The acute response is driven by homeostatic regulators of the nervous and endocrine systems and the chronic phase by homeorhetic regulators of the endocrine system. Both responses involve alterations in energy balance and metabolism. Thermal environment affects all animals and therefore represents the largest single stressor in animal production. Other types of stressors include housing conditions, overcrowding, social rank, disease, and toxic compounds. “Acclimation” to a stress is a phenotypic response developed by the animal to an individual stressor within the environment. However, under natural conditions, it is rare for only one environmental variable to change over time. “Acclimatization” is the process by which an animal adapts to several stressors within its natural environment. Acclimation is a homeorhetic process that takes several weeks to occur and occurs via homeorhetic, not homeostatic, mechanisms. It is a phenotypic change that disappears when the stress is removed. When the stress is severe and not relieved by acclimatization or management changes, the animal is considered chronically stressed and is susceptible to increased incidence of disease and poor health. Milk yield and reproduction are extremely sensitive to stress because of the high energy and protein demands of lactation and the complexity of the reproductive process and multiple organs that are involved. Improvements in protection of animals against stress require improved education of producers to recognize stress and methods for estimating degree of stress on animals.     

三点弯曲工况下复合材料层合板的应力变化

为研究三点弯曲工况下复合材料层合板的应力问题,基于连续介质损伤力学以及Hashin失效准则,建立复合材料层合板三点弯曲有限元模型。模拟三点弯曲成形过程,讨论成形过程中应力分布及变化规律。结果表明:0°铺层应力值始终高于90°铺层,下表面的应力值小于上表面,但下表面的应力值达到最大值的时间要早于上表面;沿X轴方向,越接近压头位置,上下表面的应力差越小,在板料端部上下表面应力值相等;沿Y轴方向,上下表面的应力值变化幅度较小,上下表面的应力差基本保持不变。     

基于FEM的滑动螺旋副螺纹牙根应力计算及PDS仿真分析

目前,滑动螺旋副螺纹牙根应力的分析计算仍然是基于材料力学悬臂梁理论和假设的计算方法,与精确解有较大的差距.利用有限元分析软件ANSYS 10.0对5种型号梯形螺纹牙根应力进行了有限元分析,得出了等效正应力等值分布图.用数学工具软件MATLAB 7.0分析了螺纹牙根应力随几何尺寸的变化规律.借助于ANSYS10.0中的Monto-Carlo模拟方法对螺纹牙根应力进行了弯曲强度可靠性概率有限元计算.以最大弯曲等效正应力为随机输出参数,得出了最大等效正应力大于指定值的概率、随机响应结果相对于随机输入参数的灵敏度值、最大等效正应力柱状图、输出参数相对于最重要输入参数的散点图以及输入参数与输出参数之间的相关系数.     

基于有限元法易拉罐跌落过程力学性能分析

为了研究在不同跌落高度、不同跌落方式下易拉罐的应力分布及应力-时间曲线变化情况,基于有限元法对易拉罐在跌落过程中的力学性能进行了分析。结果表明:随着跌落高度的增加,易拉罐与地面接触部位的应力逐渐增大,且应力分布区域呈扩大状态。跌落方式不同,易拉罐所受应力、应力分布区域不同,易拉罐所受应力区域的大小与易拉罐跌落角度的大小并不成正比关系。     

Kimchi suppresses 7-ketocholesterol-induced endoplasmic reticulum stress in macrophages

The oxidation of low-density lipoproteins (oxLDL) is considered as a key step in the development of atherosclerosis. Oxysterols such as 7-ketocholesterol (7-KC) have been reported to be partially responsible for the cytotoxicity of oxLDL and induce endoplasmic reticulum (ER) stress which eventually causes apoptosis. We aimed to investigate whether ER stress is induced by 7-KC and can be prevented by the kimchi methanol extract (KME) in RAW264.7 macrophage cells. ER stress induced by 7-KC was characterized by the activation of ER stress markers (GRP78, CHOP, and ATF6). ER stress could aggravate macrophage apoptosis, as assessed by caspase-3 activity. ER stress and apoptosis were inhibited by the KME and glutathione (GSH). We conclude that 7-KC causes aberrant ER stress and apoptosis, all of which are inhibited by KME and GSH. The inhibitory expression of ER stress markers highlights its new protective role against oxLDL-induced ER stress, apoptosis, and subsequent atherosclerosis.     

Possible roles of vacuolar H+-ATPase and mitochondrial function in tolerance to air-drying stress revealed by genome-wide screening of Saccharomyces cerevisiae deletion strains

Yeasts used in bread making are exposed to air-drying stress during dried yeast production processes. To clarify the genes required for air-drying tolerance, we performed genome-wide screening using the complete deletion strain collection of diploid Saccharomyces cerevisiae. The screening identified 278 gene deletions responsible for air-drying sensitivity. These genes were classified based on their cellular function and on the localization of their gene products. The results showed that the genes required for air-drying tolerance were frequently involved in mitochondrial functions and in connection with vacuolar H(+)-ATPase, which plays a role in vacuolar acidification. To determine the role of vacuolar acidification in air-drying stress tolerance, we monitored intracellular pH. The results showed that intracellular acidification was induced during air-drying and that this acidification was amplified in a deletion mutant of the VMA2 gene encoding a component of vacuolar H(+)-ATPase, suggesting that vacuolar H(+)-ATPase helps maintain intracellular pH homeostasis, which is affected by air-drying stress. To determine the effects of air-drying stress on mitochondria, we analysed the mitochondrial membrane potential under air-drying stress conditions using MitoTracker. The results showed that mitochondria were extremely sensitive to air-drying stress, suggesting that a mitochondrial function is required for tolerance to air-drying stress. We also analysed the correlation between oxidative-stress sensitivity and air-drying-stress sensitivity. The results suggested that oxidative stress is a critical determinant of sensitivity to air-drying stress, although ROS-scavenging systems are not necessary for air-drying stress tolerance.     

酿酒酵母SOD1、SOD2基因缺失对胁迫耐受性的影响

以sod1Δ、sod2Δ、sod1Δsod2Δ酿酒酵母基因缺失菌株为遗传材料,采用休止细胞梯度生长法,分析SOD1和SOD2基因缺失对高温、乙醇毒性、高渗透压、高盐、乙酸毒性及营养饥饿胁迫条件耐受性的影响。结果显示,与野生型菌株相比,sod1Δ菌株对高温、高渗透压和乙酸胁迫的耐受性降低;sod2Δ菌株耐受性无明显变化;sod1Δsod2Δ双缺失菌株对高温、乙醇毒性、乙酸毒性、高渗透压和高盐的耐受性均下降,表明酵母超氧化物歧化酶基因与多种胁迫耐受性密切相关。     

Tensile behavior of staple fiber yarns part II: model validation

The theoretical models of tensile behavior of staple fiber yarns derived in Part I of this work are compared and validated with experimental results. It is observed that the stress–strain curve of yarn always lies under the stress–strain curve of fiber. The well-known Gégauff’s theory is found to overestimate fiber stress utilization in yarn. The partial generalization of helical model by taking fiber orientation into account results in satisfactory agreement with the experimental results. Clearly, fiber orientation plays an important role in deciding the fiber stress utilization in yarns. The lower is the variability of fiber direction in relation to the corresponding helical direction of fibers, the higher is the fiber stress utilization in yarn.     

Have we underestimated the impact of pre-slaughter stress on meat quality in ruminants?

Stress is the inevitable consequence of the process of transferring animals from farm to slaughter. The effects of chronic stress on muscle glycogen depletion and the consequent dark cutting condition have been well documented. However, there has been little examination of the consequences of acute stress immediately pre-slaughter on ruminant meat quality. New evidence is emerging to show that non pH-mediated effects on meat quality can occur through pre-slaughter stress in cattle and sheep. This paper reviews the general aspects of pre-slaughter stress in the pre-slaughter context. It then examines the impacts of pre-slaughter stressors on ruminant carcass and meat quality and considers remedial strategies for remediating and preventing pre-slaughter stress. Further quantification of the biological costs of pre-slaughter stress and the consequences to meat quality is required.