Littérature scientifique sur le sujet « Mean strain effect »
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Articles de revues sur le sujet "Mean strain effect"
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Guo, Yi, Yun Rong Luo et Qing Yuan Wang. « Mean Strain Effect on the Cyclic Stress-Strain Behavior of Steel Structure Materials Q235 ». Advanced Materials Research 602-604 (décembre 2012) : 430–34. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.430.
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The low cycle fatigue (LCF) behavior of Q235 steel under mean strain control has been investigated. A serious of the strain controlled cyclic loading experiments with several combinations of strain amplitudes and mean strains have been performed. Significant cyclic hardening and mean stress relaxation were observed in all cases. Fractography by scanning electron microscopy (SEM) was used to determine the LCF failure mechanisms and fatigue crack propagation modes of the Q235 steel.
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Ellyin, F. « Effect of Tensile-Mean-Strain on Plastic Strain Energy and Cyclic Response ». Journal of Engineering Materials and Technology 107, no 2 (1 avril 1985) : 119–25. http://dx.doi.org/10.1115/1.3225786.
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Tests have been conducted to determine the effect of tensile-mean-strain on cyclic properties, low cycle fatigue, and total absorbed plastic strain energy to failure of ASTM A-516 Grade 70 carbon low alloy steel. Stable hysteresis loops at half-life are presented for different strain controlled tests. The cyclic properties were determined by a least squares fit technique. The results of tensile-mean-strain are compared with fully-reversed fatigue tests. The absorbed plastic strain energy per cycle was measured and compared with a proposed relationship for non-Masing material behavior. A relationship of the form Wf=KNfα is found to be a good representation of the data. It is observed that the material tends toward a steady-state condition independent of the level of the mean strain provided the fatigue life is greater than one thousand cycles.
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Butler, James P., Hiroshi Miki, Stephanie Squarcia, Rick A. Rogers et John L. Lehr. « Effect of macroscopic deformation on lung microstructure ». Journal of Applied Physiology 81, no 4 (1 octobre 1996) : 1792–99. http://dx.doi.org/10.1152/jappl.1996.81.4.1792.
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Butler, James P., Hiroshi Miki, Stephanie Squarcia, Rick A. Rogers, and John L. Lehr. Effect of macroscopic deformation on lung microstructure. J. Appl. Physiol.81(4): 1792–1799, 1996.—Using an anisotropic theory of diffuse light scattering in lungs, we measured the fractional changes in geometric mean linear intercepts in orthogonal directions when freshly excised rabbit lungs were subjected to isovolume uniaxial strains. Results from the optical technique were compared with morphometric estimates of fractional changes in mean linear intercepts from the same strained and unstrained (control) lobes, with the conclusion that diffuse light scattering is adequate to estimate changes in mean free paths in different directions. We compared optical estimates of fractional changes in mean linear intercepts with the macroscopic strain field measured by displacements of pleural markers; this relationship did not significantly differ from the line of identity. We conclude that the microscopic strain field is closely matched to the macroscopic strain field during uniaxial distortion. This suggests that surface reorientation may not play a large role in the origin of the low shear modulus of the lung, but this cannot be definitively stated without comparison of these experimental results to specific model predictions of the changes in mean linear intercepts in shear deformation.
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IINO, Jun, Hideshi HANAZAKI et Yasuaki KOHAMA. « The Effect of Mean Strain on the Stably Stratified Turbulence. » Transactions of the Japan Society of Mechanical Engineers Series B 67, no 664 (2001) : 3068–75. http://dx.doi.org/10.1299/kikaib.67.3068.
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Scorza, Daniela, Andrea Carpinteri, Giovanni Fortese, Camilla Ronchei, Sabrina Vantadori et Andrea Zanichelli. « Multiaxial fatigue life estimation in low-cycle fatigue regime including the mean stress effect ». MATEC Web of Conferences 165 (2018) : 16002. http://dx.doi.org/10.1051/matecconf/201816516002.
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The goal of the present paper is to discuss the reliability of a strain-based multiaxial Low-Cycle Fatigue (LCF) criterion in estimating the fatigue lifetime of metallic structural components subjected to multiaxial sinusoidal loading with zero and non-zero mean value. Since it is well-known that a tensile mean normal stress reduces the fatigue life of structural components, three different models available in the literature are implemented in the present criterion in order to take into account the above mean stress effect. In particular, such a criterion is formulated in terms of strains by employing the displacement components acting on the critical plane and, then, by defining an equivalent strain related to such a plane. The Morrow model, the Smith-Watson-Topper model and the Manson-Halford model are applied to define such an equivalent strain. The effectiveness of the new formulations is evaluated through comparison with some experimental data reported in the literature, related to biaxial fatigue tests performed on metallic specimens under in-and out-of-phase loadings characterised by non-zero mean stress values.
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Yip, Ming-Chuen, et Yi-Ming Jen. « Mean Strain Effect on Crack Initiation Lives for Notched Specimens Under Biaxial Nonproportional Loading Paths ». Journal of Engineering Materials and Technology 119, no 1 (1 janvier 1997) : 104–12. http://dx.doi.org/10.1115/1.2805962.
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This paper discusses the mean strain effect on the crack initiation lives for notched specimens under biaxial nonproportional loading paths. Elastic-plastic finite element method was used to evaluate the local stresses and strains. Several prediction models related to the mean stress/strain effect were employed to correlate the experimental results with reference fatigue data for smooth specimens. It is found that Fatemi-Socie model gives good prediction for the present research with the assistance of finite element method. The stress behavior in this deflection-controlled tests is discussed in this study, and the failure surfaces are also examined after tests.
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de Beeck, Hanne Op, Lieven J. R. Pauwels et Johan Put. « Schools, strain and offending : Testing a school contextual version of General Strain Theory ». European Journal of Criminology 9, no 1 (janvier 2012) : 52–72. http://dx.doi.org/10.1177/1477370811421646.
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Based on the idea that schools are important socializing settings for adolescents (Gottfredson, 2001), the school contextual version of General Strain Theory (Agnew, 1999) is tested in this article. The main hypothesis of this study is that strain at the school level affects individual offending by creating individual strain. Findings suggest that school contextual effects differ: convincing contextual effects are found for violent offending but not for general offending. Furthermore, although the school mean level of strain does significantly affect individual violent offending, this effect does not proceed by creating individual strain. It is therefore suggested that the school mean level of strain either has a direct effect on violent offending or influences other important individual offending mechanisms such as social learning or lifestyle risks.
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Natesan, Elanghovan, Johan Ahlström, Stefan Eriksson et Christer Persson. « Effects of Temperature on the Evolution of Yield Surface and Stress Asymmetry in A356–T7 Cast Aluminium Alloy ». Materials 14, no 24 (20 décembre 2021) : 7898. http://dx.doi.org/10.3390/ma14247898.
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As the electrification of vehicle powertrains takes prominence to meet stringent emission norms, parts of internal combustion engines like cylinder heads are subjected to an increased number of thermal load cycles. The cost-effective design of such structures subjected to cyclic thermo-mechanical loads relies on the development of accurate material models capable of describing the continuum deformation behaviour of the material. This study investigates the effect of temperature on the evolution of flow stress under cyclic loading in A356-T7 + 0.5% Cu cast aluminium alloy commonly used in modern internal combustion engine cylinder heads. The material exhibits peak stress and flow stress asymmetry with the stress response and flow stress of the material under compressive loading higher than under tension. This peak and flow stress asymmetry decrease with an increase in temperature. To compare this stress asymmetry against conventional steel, cyclic strain-controlled fatigue tests are run on fully pearlitic R260 railway steel material. To study the effect of mean strain on the cyclic mean stress evolution and fatigue behaviour of the alloy, tests with tensile and compressive mean strains of +0.2% and −0.2% are compared against fully reversed (Rε = −1) strain-controlled tests. The material exhibits greater stress asymmetry between the peak tensile and peak compressive stresses for the strain-controlled tests with a compressive mean strain than the tests with an identical magnitude tensile mean strain. The material exhibits mean stress relaxation at all temperatures. Reduced durability of the material is observed for the tests with tensile mean strains at lower test temperatures of up to 150 °C. The tensile mean strains at elevated temperatures do not exhibit such a detrimental effect on the endurance limit of the material.
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Kang, Jidong, Liting Shi, Jie Liang, Babak Shalchi-Amirkhiz et Colin Scott. « The Influence of Specimen Geometry and Strain Rate on the Portevin-Le Chatelier Effect and Fracture in an Austenitic FeMnC TWIP Steel ». Metals 10, no 9 (8 septembre 2020) : 1201. http://dx.doi.org/10.3390/met10091201.
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We studied the Portevin-Le Chatelier effect and fracture behavior of a FeMnC TWIP steel using high speed digital image correlation by varying the specimen geometry (flat vs. round) and test strain rate (0.001 vs. 0.1 s−1). The results show that the mean flow stress, the mean strain hardening rate and the mean strain rate sensitivity parameters are all independent of the specimen geometry and are uncorrelated with the presence or not of Portevin-Le Chatelier (PLC) bands, the type of PLC bands observed or the critical strain for band formation. However, both the fracture strains and stresses and the PLC behavior are highly geometry and/or strain rate dependent. Dynamic strain aging (DSA) and in particular the presence of PLC instabilities appears to play an important but as yet unclear role in promoting premature necking and final fracture.
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Warley, R. L., D. L. Feke et I. Manas-Zloczower. « Transient effects in dynamic modulus measurement of silicone rubber, part 2 : Effect of mean strains and strain history ». Journal of Applied Polymer Science 104, no 4 (2007) : 2197–204. http://dx.doi.org/10.1002/app.25136.
Texte intégralThèses sur le sujet "Mean strain effect"
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Smith, Byron L. « Mean strain effects on the strain life fatigue curve ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA267211.
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Tyagi, P. K. « Linear Instability Of Laterally Strained Constant Pressure Boundary Layer Flows ». Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/265.
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The linear instability of laterally diverging/converging flows is an important aspect towards understanding the laminar-transition process in many viscous flows. In this work the linear instability of constant pressure laterally diverging/converging flow has been investigated.
The laminar velocity field for laterally diverging/converging flows, under the source/sink approximation, has been reduced to two-dimensional flows. This reduction is alternative to the Mangier transformation used earlier. For a constant pressure laterally strained flow, the laminar velocity is found to be governed by the Blasius equation for flow over a flat plate.
The non-parallel linear instability of constant pressure laterally strained flows has been examined. The instability equation is found to be same as that for the Blasius flow. This implies that the stability is same as that for the Blasius flow. A lateral divergence/convergence is shown to alter the Reynolds number from that in a two-dimensional flow. The instability of a laterally converging/diverging flow thus can be obtained from the available results for the Blasius flow by scaling the Reynolds numbers. This leads to the result that while a diverging flow is more unstable than the Blasius flow, a converging flow is more stable. Some additional relevant results are also presented.
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Rutherford, Benjamin Andrew. « Beneficial Tensile Mean Strain Effects on the Fatigue Behavior of Superelastic NiTi ». Thesis, Mississippi State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10266594.
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In this work, beneficial effects of tensile mean strain on fatigue behavior and microstructure of superelastic NiTi (i.e. Nitinol) are studied. Most applications, such as endovascular stents made with NiTi, are subjected to a combination of constant and cyclic loading; thus, understanding the fatigue behavior of NiTi undergoing mean strain loading is necessary. Cyclic strain-controlled fatigue tests are designed to investigate the effects of tensile mean strain on fatigue of superelastic NiTi. Experimental observations show that combinations of large tensile mean strains and small strain amplitudes improve the fatigue life of superelastic NiTi. This behavior arises from reversible, stress-induced phase transformations. The phase transformations cause “stress plateaus” or strain ranges with no change in stress value. Scanning electron microscopy (SEM) of the fracture surfaces of specimens revealed generally short crack growth. Electron backscatter diffraction (EBSD) found the amount of residual martensite to be about ~8%, regardless of loading conditions.
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Warneboldt, Iona. « Multiaxial fatigue design of elastomeric parts using Equivalent Fatigue Loads ». Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2022. http://www.theses.fr/2022ENTA0002.
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Trois étapes sont mises en oeuvre ici : la méthode de localisation, la fonction de dommage matériau et le processus de détermination des chargements équivalents en fatigue (CEF). De nombreux essais de fatigue ont été réalisés (415 au total) pour étudier le comportement en fatigue sous chargement multiaxial relaxant et non relaxant sur des éprouvettes de caoutchouc naturel. La durée de vie et les caractéristiques des fissures sont analysées pour finalement introduire un critère de fatigue approprié basé sur le plan critique et permettant de rendre compte de l'effet de déformation moyenne. Ce critère est généralisé à travers une méthode originale de recherche du plan critique. Pour estimer la réponse mécanique locale (méthode de localisation), une méthode de couplage des axes adaptée à la nature non linéaire des structures élastomères est proposée. Elle est basée sur la décomposition multiplicative des tenseurs du gradient de la déformation. Ces deux étapes sont ensuite mises en oeuvre dans le cadre du processus de détermination du CEF. Pour cela, une méthode d'optimisation globale est ajoutée pour déterminer les chargements simplifiés, induisant partout localement le même endommagement en fatigue dans la structure étudiée que le RLD. Le temps de calcul de cette optimisation est réduit en ne considérant qu'un sous-ensemble de points matériels, les plus endommagés, pour la détermination du CEF. Enfin, la méthode a été testée sur une éprouvette afin de souligner ses capacités et de valider l'approcheThis thesis introduces an Equivalent Fatigue Load (EFL) approach for the multiaxial fatigue design of elastomeric parts. As direct Finite Element Analysis (FEA) calculations of automotive in-service loads (Road Load Data (RLD)) are too expensive, the objective is to derive simplified load blocks as a realistic input for numerical damage calculations. Three streps are applied for this method: the localization method, the material damage function and the EFL determination process. Various fatigue tests have been conducted (415 samples) to study the fatigue behavior of this complex type of relaxing and non-relaxing multiaxial loading on natural rubber specimens. Lifetime and crack features are analyzed to eventually introduce an appropriate critical planebased fatigue measure and to establish a novel mean strain effect model. This criterion is generalized throughout an original critical plane search method. To estimate the local mechanical response (localization method), this thesis identifies an axes-coupling method that is fitted for the nonlinear nature of elastomeric structures. It is based on the multiplicative decomposition of the deformation gradient tensors. These two steps are then implemented in the framework of the EFLdetermination process. For this, a global optimization method is added to determine the simplified load blocks, causing locally the same fatigue behavior in the given structure. The computational costs of this optimization are reduced by only considering a subset of the most damaged material points for EFLdetermination. Finally, the method has been challenged on a specimen to outline its capabilities and to validate the approach
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Shih, Chia-chang, et 施嘉昌. « The mean strain effects on fatigue behaviors and dislocation structures for polycrystalline IF steel ». Thesis, 2009. http://ndltd.ncl.edu.tw/handle/ab2hq6.
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博士國立中山大學
材料與光電科學學系研究所
97
This work is aimed to understand the mechanisms for evolution and reversed evolution of dislocation structure under variable strain amplitudes, using automotive-grade interstitial-free steels (IF steel) under strain ratio (R) = 0 condition. The microstructures were mainly examined by the SEM under BEI/ECCI mode and TEM were used for this study. Near the endurance limit, the dislocation cells smaller than 2μm develop preferably along grain boundaries and triple junctions among the grains. Within grain interiors, it is hardly observed these small dislocation cells and cyclic hardening even at εmax =0.2%. When strain amplitudes were controlled at a range from εmax = 0.25% to 0.6%, a secondary cyclic hardening occurs prior to fatigue failure and less than 2um dislocation cells rapidly developed thoroughly. The secondary hardening rates were found to be directly proportional to the strain amplitudes. For high-low strain fatigue tests, while the maximum strain was decreased from 1.2% to 0.2% or 0.15%, dislocation cells were collapsed first and re-grouped into loop-patch structures due to the gliding behavior of dislocations changing from multiple-slips to single-slip. However, once the strain range is further reduced to 0.1%, dislocation cells would persist, showing no signs of collapse. Moreover, the reversal development of dislocation structures is independent of strain ratio. Furthermore newly developed loop patches are usually confined within dislocation domains with very condensed dislocation cell walls with high boundary misorientation.
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Liao, Lin-wei, et 廖麟偉. « Mean Strain Effects on Cyclic Response and Fatigue Life Prediction for SUS 316 Stainless Steel ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/41546591386819510210.
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碩士國立嘉義大學
生物機電工程學系研究所
99
Applying on the actual engineering project, components are usually subjected to a non-symmetric cyclic stress/strain load. Therefore, this study will examine a main purpose which is mean stress/strain effects on cyclic behavior and fatigue life for 316 Stainless Steel. In this experiment, specimens were subjected to a monotonic tension test and three kinds of cyclic strain load tests, in which, cyclic strain load tests includes fully reversed fatigue test, mean strain 1%fatigue test, and strain ratio 0.5 fatigue test. The experimental result showed that no significant mean stress been found in fully reversed fatigue test. It's easier to produce mean stresses when material subjected to large mean strain and small strain amplitude at the same time, hence reduces the fatigue life. By the damage parameters SWT, and stable strain energy density in tension condition, to estimate the fatigue life, and add a text to judge whether experimental results fit in with Massing's hypothesis. If it does fit, the stable hysteresis loop can be estimated by the double cyclic stress-strain curve. Unfortunately, the result only by the strain ratio 0.5 fatigue test fits Massing's hypothesis. After getting the prediction of fatigue life, in order to confirm the ability of prediction, a value, was obtained by a simple statistical analysis. Finally, result shows that the damage parameter provides a best estimate of fatigue life in this study.
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Chiou, Yung-Chuan, et 邱永川. « Effects of Mean Strain on Cyclic and Fatigue Behavior of AISI 316 and 304 Stainless Steels ». Thesis, 2004. http://ndltd.ncl.edu.tw/handle/73472251118218403173.
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博士國立清華大學
動力機械工程學系
92
In this study, author would devote to the effect of the superimposed mean strain on fatigue life and cyclic stress-strain curves. Hence, a series of the strain-controlled cyclic loading experiments with several combinations of strain amplitudes and mean strains have been performed on closed-loop servohydraulic test machines for AISI 316 and 304 stainless steels. In the cyclic stress/strain behavior, a modified expression that describes/predicts the cyclic stress/strain curve under an applied mean strain is developed. Using the modified expression, the effects of superimposed mean strain on the cyclic stress-strain curve can be examined by comparing two descriptive parameters. Furthermore, both of the usual description and the modified expression are identical for cyclic stress-strain curve obtained from completely reversed fatigue test. The damage parameters corresponding to the Smith, Watson and Topper criterion can be extracted from the modified cyclic stress-strain curve (CSSC) expression to predict the fatigue life with mean stress/strain. In addition, based on the two given hypotheses in this study, a simply approach is derived for the determination of the stable mean stress that occurs in strain-controlled tests with an imposed mean strain. The evaluated stable mean stress is applied to fatigue life prediction based on the Morrow mean stress parameter. In theoretical analysis, the whole study of this paper is made in the framework of endochronic theory of plasticity with yield surface. Based on the hypothesis that the stable hysteresis loop exhibits symmetric behavior with respect to the coordinate , an analytical expression is proposed to describe the basic cyclic stress-strain curve obtained from completely reversed constant strain amplitude. And the same time, a set of algebraic equations is developed to express the stress-strain behavior for the tensile branch curve of stable hysteresis loop with a specific mean strain level. Furthermore, according to the symmetric hypothesis, the stable hysteresis loop with a specific mean strain level can be developed. Based on the experimental observation for the stable hysteresis loop with superimposed mean strain, from a viewpoint of the movement of stable hysteresis loop, author explains the effect s of the superimposed mean stress or strain on the fatigue and the cyclic stress-strain curves. And the phenomenon is found that only the plastic strain energy in the tensile part has the obvious effect on fatigue life. According to the observed phenomenon, author assumes that fatigue life is influenced by the magnitude of plastic strain energy in the tensile part. Under the explanation, a new fatigue damaged parameter that takes account of effects of superimposed mean stress/ strain on fatigue life is developed. In the low cyclic fatigue regime, the fatigue parameter based on the plastic strain energy in the tensile part can be applied to predict the fatigue life with superimposed mean stress/ strain. In this study, some important phenomenon concerned the effects of superimposed mean strain on the stable stress-strain behavior are observed and analyzed. And those proposed methods are examined in relation to the stable mean stress evaluation and the two proposed stress-strain correlations based on the endochronic theory of plasticity with yield surface. For AISI 316 and 304 stainless steels, the proposed hypotheses for stable hysteresis loop are acceptable by the experimental observation. Under the condition, the experimental results show the data generated by proposed formulation concerned the stable mean stress is in qualitative agreement with experimental data. Subsequently, a series of experiments for AISI 316/ 304 stainless steels and test data of 1070 Al Alloy have been performed to confirm the validity of the two developed stress-strain correlations. It has been shown that the developed correlations are capable of describing the experimental results of three different metals considered. Furthermore, in prediction of fatigue life with superimposed mean strain, a satisfactory result based on the damaged fatigue parameter of is shown. It is worthy noting that the curve can be directly obtained by modified the standard curve from fully reversed fatigue tests since the magnitude of is equal to a half of the magnitude of .
Livres sur le sujet "Mean strain effect"
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Smith, Byron L. Mean strain effects on the strain life fatigue curve. Monterey, Calif : Naval Postgraduate School, 1993.
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I.H. Badar, M.H. Jaspal*, M.K. Yar, M. Ijaz, A. Khalique, L. Zhang, A. Manzoor, S. Ali, A. Rahman et F. Husnain. Effect of strain and slaughter age on production performance, meat quality and processing characteristics of broilers reared under tropical climatic conditions. Verlag Eugen Ulmer, 2021. http://dx.doi.org/10.1399/eps.2021.326.
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Svedberg, Erika. Militarization and Women : Gendered Militarizations. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190846626.013.263.
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Militarization is defined as a process that fundamentally changes society and all types of relations in it, the formal and institutional as well as the informal and the intimate. In a militarized society, women and men are often affected differently. At its most extreme, militarization results in the disappearance of civil, civilianized space, leaving the civilians with no choice but to live in symbiosis with the military and its war-making. Since the mid-1980s, there has been a steady flow of feminist literature specifically exploring questions on gender and militarization in various disciplines, including International Relations (IR), as well as men and masculinity. The debate between modernists and postmodernists in feminist research of the 1990s questioned the universalizing effects of using the term “woman.” Postmodernists argued that the field should be broadened by introducing the concept of gender and investigating how different structures intersect in creating socioeconomic power relations between women, as well as between women and men, on a global scale. Another strand of thinking implies that it is the gender order of male superiority and female inferiority that drives militarization and war. Some studies on gendered militarization have advanced the idea of a military organization that is democratic, but still has the option of using violent means to defend or to threaten. The question that remains is: in an era dominated by the “War on Terror” and its global ontology of security/insecurity, how we begin to fight militarization without becoming militarized ourselves.
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Hasenkamp, Wendy. Catching the Wandering Mind. Sous la direction de Kalina Christoff et Kieran C. R. Fox. Oxford University Press, 2018. http://dx.doi.org/10.1093/oxfordhb/9780190464745.013.12.
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This chapter considers a form of attention-based meditation as a novel means to gain insight into the mechanisms and phenomenology of spontaneous thought. Focused attention (FA) meditation involves keeping one’s attention on a chosen object, and repeatedly catching the mind when it strays from the object into spontaneous thought. This practice can thus be viewed as a kind of self-caught mind-wandering paradigm, which suggests it may have great utility for research on spontaneous thought. Current findings about the effects of meditation on mind-wandering and meta-awareness are reviewed, and implications for new research paradigms that leverage first-person reporting during FA meditation are discussed. Specifically, research recommendations are made that may enable customized analysis of individual episodes of mind-wandering and their neural correlates. It is hoped that combining detailed subjective reports from experienced meditators with rigorous objective physiological measures will advance the understanding of human consciousness.
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Dutton, George E. Journeys. University of California Press, 2017. http://dx.doi.org/10.1525/california/9780520293434.003.0004.
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This chapter looks at the brief period from 1794 to the summer of 1796, in which the ex-Jesuit community began to explore ways to resolve the crisis in which it found itself. Several short trips to Macao failed to yield any further missionaries for the Padroado Catholics, and so an attempt was made to send two men to Europe to make a direct appeal. Binh conducted a significant and successful fundraising effort among the members of the Padroado community. When the men are finally able to embark for Europe, their mission is turned back after reaching Goa, and its members are beset by pirates on their return voyage, reducing them to rags. The chapter then describes a renewal of this effort, this time led by Binh himself, who, along with three of his companions, set sail for Europe in mid-February of 1796. It describes their five-month journey from Macao through the Straits of Malacca, around the Horn of Africa and to the island of St. Helena. There they transfered to a Portuguese vessel on which they are able to continue their voyage directly to Lisbon, where they arrived in late July of that year.
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French, Nathan S. And God Knows the Martyrs. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190092153.001.0001.
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Jihadi-Salafi narratives of martyrdom-seeking operations are filled with praise for what they label the exemplary self-renunciative acts of their martyrs performed as a model of the earliest traditions of Islam. While many studies evaluate the biographies of these would-be martyrs for evidence of social, psychological, political, or economic strain in an effort to rationalize what are often labeled “suicide bombings,” this book argues that through their legal arguments debating martyrdom-seeking operations, Jihadi-Salafis, including those fighting for al-Qaʿida, ISIS, and their affiliates, craft a theodicy meant to address the suffering and oppression faced by the global Muslim community. Taking as its source material legal arguments (fatwas), texts, pamphlets, magazines, forum posts, videos, and audio files from authors sympathetic to both al-Qaʿida and ISIS on the subjects of martyrdom operations, jurisprudence, and political philosophies, this book reveals that the Jihadi-Salafi legal debates on martyrdom-seeking rearrange the basic objectives (maqāṣid) of the Shariʿa around the principles of maximizing the general welfare (maṣlaḥa) and promoting religion (dīn) above all other concerns—including the preservation of life. This utilitarian turn opens the possibility for formulating a meaningful engagement and critique of Jihadi-Salafi legal interpretation and theories of warfare within a broader, just-war framework. However, as the jurists and propagandists of ISIS demonstrate, this turn also opens the possibility for the utilization of self-renunciative violence as engendering modes of state formation.
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Hill, Felicity. Excommunication in Thirteenth-Century England. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198840367.001.0001.
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Excommunication was the medieval church’s most severe sanction, used against people at all levels of society. It was a spiritual, social, and legal penalty: Excommunication in Thirteenth-Century England offers a fresh perspective on medieval excommunication by taking a multi-dimensional approach to discussion of the sanction. Using England as a case study, the book analyzes the intentions behind excommunication, how it was perceived and received at both national and local level, and the effects it had upon individuals and society. This book uses a thematic structure to argue that our understanding of excommunication should be shaped by how it was received within the community as well as the intentions of canon law and clerics. Challenging assumptions about the inefficacy of excommunication, Hill argues that the sanction remained a useful weapon for the clerical elite. Bringing into dialogue a wide range of source material allows ‘effectiveness’ to be judged within a broader context. The complexity of political communication and action are revealed through public, conflicting, accepted, and rejected excommunications. Excommunication was a means by which political events were communicated down the social strata of medieval society. The book discusses pastoral care, cursing, fears about the afterlife, the implications of social ostracism, manipulations of excommunication in political conflicts, shame and reputation, and mass communication.
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Valenti, Marco. Changing Rural Settlements in the Early Middle Ages in Central and Northern Italy. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198777601.003.0012.
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Archaeological sites of this period reveal the continued existence of a very ruralized society. The countryside, subject to a significant strengthening of economic control, was the primary source of wealth and success for the middle and upper social strata that invested in it. Choosing to optimize the exploitation of agricultural land led defining settlements in a more urban way. Since rural sites were the spaces where the labour force was ‘anchored’, they were often fortified to protect assets. Examples include both large lay and ecclesiastical aristocratic landowners and more local elites all over Italy. In the vast majority of cases we have fortified villages that are, in fact, agricultural holdings (manorial estates). In any context, the signs of material power exercised by a dominant figure include the management and a very pronounced control of activities, goods, foodstuffs, and labour, which find their counterpart in features and topography of rural centres. Settlements where production is aimed at wealth accumulation, often defended even from insiders by separating the spaces of power from those of the peasant masses, are frequently observed archaeologically. This is evidenced by the structural changes taking place both in the villages and in the single residential building types, serving as signs of a significant effort devoted to the centralization of production means (animals, tools, craft-shops), in order to increase what appears to be the main objective of landed elites: managing territorial resources in order to store foodstuffs, not only for personal consumption but also for to sell them in urban markets; in other words, to produce wealth.
Chapitres de livres sur le sujet "Mean strain effect"
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Putra, Teuku Edisah, Husaini et Rauzatul Akmal. « The Effects of Mean Strain on the Fatigue Life of the SAE 1541 Carbon Steel Based on the Strain-Life Approach ». Dans Structural Integrity, 171–83. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-85646-5_13.
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Soudien, Crain, Vijay Reddy et Jaqueline Harvey. « The Impact of COVID-19 on a Fragile Education System : The Case of South Africa ». Dans Primary and Secondary Education During Covid-19, 303–25. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-81500-4_12.
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AbstractThis chapter provides a critical look at what COVID-19 meant for the education sector in South Africa. It documents the path of the pandemic in the education space to understand its effects and the short-term responses of the education system. It begins with the premise that the South African educational system is structurally fragile. Its fragility arises out of the injustices of the apartheid system which disadvantaged schools and learners. It argues that the country has made progress in dealing with this legacy but that the drivers of change, such as improved household incomes, improved access to school materials and better nutrition, have come under strain in recent times. Because of COVID-19, the upward social mobility of low-income communities is growing in precarity while inequalities are exacerbated.
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Northcott, Michael S. « Ecological Hope ». Dans Historical and Multidisciplinary Perspectives on Hope, 215–38. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-46489-9_12.
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Abstract Horkeimer and Adorno, and later Lynn White Jr, blame the anti-animist strain in Western Christianity, its origination of the scientific and industrial revolutions, and the European Enlightenment, as the cultural roots of the ecological crisis. But evidence shows there is no necessary connection between animism and care for other kind. I propose that a more fruitful approach is to reconsider the post-Reformation and scientific eschewal of agency in nonhuman beings and ecosystems such as forests, rivers, and the oceans. Rediscovering the “agency of the others” is also essential as a means to resolve the ecological crisis, since humans alone cannot restore or “save” the Earth from the systemic effects of 200 years of industrial pollution and destruction of resilient biodiverse habitats. Christian eschatological hope has valuable resources for this approach including evidence that in the lives of the saints new friendships were formed between humans and other animals. Analogously, recent developments in ecological restoration and “rewilding” indicate a new peaceable partnership between humans and other kind and, in the light of Christian messianism, and the “theory of hope,” may be said to anticipate a wider ecological reconciliation between humans and other kind.
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Nzengya, Daniel M., et John K. Maguta. « Gendered Vulnerability to Climate Change Impacts in Selected Counties in Kenya ». Dans African Handbook of Climate Change Adaptation, 1–18. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-42091-8_169-1.
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AbstractExtreme climate change events such as frequent and prolonged droughts or floods associated with climate change can be very disruptive to peoples’ livelihoods particularly in rural settings, where people rely on the immediate environment for livelihood. Shocks in the people’s livelihoods can trigger diverse responses that include migration as a coping or adaption strategy. Migration takes many forms depending on the context and resources availability. Very few studies in Kenya have used qualitative analysis to bring up women’s voices in relation to gender, climate change, and migration, especially along hydrological gradient. This chapter presents results of qualitative research conducted from 58 participants in 2018 in three counties in Kenya, namely, Kiambu County, Machakos, and Makueni. The study sought to examine gender perceptions related to climate-induced migration, that is: whether climate change is perceived to be affecting women’s livelihood differently from that of men; examine in what ways experiences of climate induced migration differed for men and women; explore perceptions on the county government efforts to cope with climate-induced migration; and examine perceptions of the role of nongovernmental agencies in helping citizens cope with climate change. From the results obtained on ways in which climate change affected women livelihoods more than men had four themes: (1) women exerted more strain in domestic chores, child/family care, and in the farm labor; (2) women also experienced more time demands. The sources of water and firewood were getting more scarce leading to women travel long distances in search to fetch water and firewood; (3) reduced farm yields, hence inadequate food supply; and (4) the effects of time and strain demands on women was a contributory factor to women poor health and domestic conflicts. Several measures that the county government could take to assist women to cope with climate change-induced migration had five themes which include the following: (1) developing climate change mitigations, and reducing deforestation; (2) increasing water harvesting and storage; (3) develop smart agriculture through the use of drought-resistant crops and drought mitigation education; (4) encourage diversification of livelihoods; and finally (5) providing humanitarian assistance to the most vulnerable populations such as orphans and the very poor. Thirdly, the measures mentioned that NGO’s could take to assist rural communities to cope with climate change-induced migration did not vary significantly from those mentioned for county government, except probably for a new theme of increasing advocacy for climate adaption policies.
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Nzengya, Daniel M., et John Kibe Maguta. « Gendered Vulnerability to Climate Change Impacts in Selected Counties in Kenya ». Dans African Handbook of Climate Change Adaptation, 2045–62. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_169.
Texte intégralRésumé :
AbstractExtreme climate change events such as frequent and prolonged droughts or floods associated with climate change can be very disruptive to peoples’ livelihoods particularly in rural settings, where people rely on the immediate environment for livelihood. Shocks in the people’s livelihoods can trigger diverse responses that include migration as a coping or adaption strategy. Migration takes many forms depending on the context and resources availability. Very few studies in Kenya have used qualitative analysis to bring up women’s voices in relation to gender, climate change, and migration, especially along hydrological gradient. This chapter presents results of qualitative research conducted from 58 participants in 2018 in three counties in Kenya, namely, Kiambu County, Machakos, and Makueni. The study sought to examine gender perceptions related to climate-induced migration, that is: whether climate change is perceived to be affecting women’s livelihood differently from that of men; examine in what ways experiences of climate induced migration differed for men and women; explore perceptions on the county government efforts to cope with climate-induced migration; and examine perceptions of the role of nongovernmental agencies in helping citizens cope with climate change. From the results obtained on ways in which climate change affected women livelihoods more than men had four themes: (1) women exerted more strain in domestic chores, child/family care, and in the farm labor; (2) women also experienced more time demands. The sources of water and firewood were getting more scarce leading to women travel long distances in search to fetch water and firewood; (3) reduced farm yields, hence inadequate food supply; and (4) the effects of time and strain demands on women was a contributory factor to women poor health and domestic conflicts. Several measures that the county government could take to assist women to cope with climate change-induced migration had five themes which include the following: (1) developing climate change mitigations, and reducing deforestation; (2) increasing water harvesting and storage; (3) develop smart agriculture through the use of drought-resistant crops and drought mitigation education; (4) encourage diversification of livelihoods; and finally (5) providing humanitarian assistance to the most vulnerable populations such as orphans and the very poor. Thirdly, the measures mentioned that NGO’s could take to assist rural communities to cope with climate change-induced migration did not vary significantly from those mentioned for county government, except probably for a new theme of increasing advocacy for climate adaption policies.
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Eliseev, Alexander A., Tatiana A. Kalashnikova, Andrey V. Filippov et Evgeny A. Kolubaev. « Material Transfer by Friction Stir Processing ». Dans Springer Tracts in Mechanical Engineering, 169–88. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60124-9_8.
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AbstractMechanical surface hardening processes have long been of interest to science and technology. Today, surface modification technologies have reached a new level. One of them is friction stir processing that refines the grain structure of the material to a submicrocrystalline state. Previously, the severe plastic deformation occurring during processing was mainly described from the standpoint of temperature and deformation, because the process is primarily thermomechanical. Modeling of friction stir welding and processing predicted well the heat generation in a quasi-liquid medium. However, the friction stir process takes place in the solid phase, and therefore the mass transfer issues remained unresolved. The present work develops the concept of adhesive-cohesive mass transfer during which the rotating tool entrains the material due to adhesion, builds up a transfer layer due to cohesion, and then leaves it behind. Thus, the transfer layer thickness is a clear criterion for the mass transfer effectiveness. Here we investigate the effect of the load on the transfer layer and analyze it from the viewpoint of the friction coefficient and heat generation. It is shown that the transfer layer thickness increases with increasing load, reaches a maximum, and then decreases. In so doing, the average moment on the tool and the temperature constantly grow, while the friction coefficient decreases. This means that the mass transfer cannot be fully described in terms of temperature and strain. The given load dependence of the transfer layer thickness is explained by an increase in the cohesion forces with increasing load, and then by a decrease in cohesion due to material overheating. The maximum transfer layer thickness is equal to the feed to rotation rate ratio and is observed at the axial load that causes a stress close to the yield point of the material. Additional plasticization of the material resulting from the acoustoplastic effect induced by ultrasonic treatment slightly reduces the transfer layer thickness, but has almost no effect on the moment, friction coefficient, and temperature. The surface roughness of the processed material is found to have a similar load dependence.
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Abioja, M. O., et J. A. Abiona. « Impacts of Climate Change to Poultry Production in Africa : Adaptation Options for Broiler Chickens ». Dans African Handbook of Climate Change Adaptation, 275–96. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_111.
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AbstractGlobal climate change poses a great threat to poultry production. Greenhouse gases (GHGs) are released through both natural and anthropogenic sources into the atmosphere. Though poultry production contributes little to the release of GHGs, the subsector has been shown to be greatly affected by climate change and global warming. Poultry production as a major subsector of agriculture has provided the teeming population with a supply of needed animal protein in terms of meat and egg production all over the world. It is yet a major global employer of labor. Though it occupies a vantage position in meeting human needs, it is being threatened by climate change, especially in Africa where necessary structure to tackle the menace is nonexistent. Broiler chickens that are reared mainly for chicken meat cannot tolerate the high ambient temperature that prevails mostly in the tropical environment. Chickens are homeotherms that homeostatically regulate core body temperature within a narrow range. Elevated ambient temperature above thermal comfort zone, such as envisaged in climate change scenarios, will trigger series of neuroendocrine modulations that are detrimental to the welfare and productivity in broiler chickens. Such birds are said to be undergoing heat stress (HS). Negative effects of HS include reduced feed consumption, growth rate, feed digestion and efficiency, immunity, welfare, and survivability. Various adaptive measures that could be harnessed by broiler farmers, ranging from housing, feeding, watering, stocking, breeding for thermo-tolerant strains, thermal conditioning, use of phytochemicals, and much more, are reviewed upon in this chapter.
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Huang, Lihong, et Saiki Lucy Cheah. « The Young Environmental Citizens in Nordic Countries : Their Concerns, Values, Engagement, and Intended Future Actions ». Dans IEA Research for Education, 123–46. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66788-7_6.
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AbstractThis chapter presents an analysis of students’ concerns, values, engagement, and intended future participation on environmental issues in relation to their home socioeconomic background, gender, and migrant status. Analyzing IEA International Civic and Citizenship Education Study (ICCS) 2016 data of Nordic countries, we first present descriptions of student responses to all questions related to environmental issues and compare Nordic results with European and international averages. Then, we construct a composite score of student environmental citizenship for investigating its relationship with student background factors such as gender, migrant status, and home socioeconomic status through comparing means between student groups with different background characteristics. Lastly, we apply factorial ANOVA analysis method to examine the effect sizes of student background factors and the interactions between them on youth environmental citizenship in the four countries. The results show that there are both similarities and small variations in elements of student environmental citizenship among the Nordic countries and in comparison with their European and international peers. Nordic students stand out as the concerned environmental citizens while they are somehow lower than their European and international peers in engagement, values, and intended participation of environmental citizenship. We find that student environmental citizenship is socially divided in all Nordic countries as it differs significantly between students from different socioeconomic strata and genders. Although not all differences of student environmental citizenship by migrant status are statistically significant among the Nordic countries, we find some significant influence of migrant status interaction with socioeconomic statuses and genders.
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« Mean Stress ». Dans Fatigue and Durability of Structural Materials, 75–103. ASM International, 2006. http://dx.doi.org/10.31399/asm.tb.fdsm.t69870075.
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Abstract This chapter discusses the concept of mean stress and explains how it is used in fatigue analysis and design. It begins by examining the stress-strain response of test samples subjected to cyclic forces and strains, noting important features and what they reveal about materials and their fatigue behaviors. It then discusses the challenge of developing hysteresis loops for complex loading patterns and accounting for effects such as ratcheting and stress relaxation. The sections that follow provide a summary of the various ways mean stress is described in the literature and the methods used to calculate or predict its effect on the fatigue life of machine components. The discussion also sheds light on why tensile mean stress is detrimental to both fatigue life and ductility, while compressive mean stress is highly beneficial.
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KOMOTORI, J., et M. SHIMIZU. « Grain Size Effect in Low Cycle Fatigue of Steel Under Mean Strain ». Dans Proceedings of The 7th International Conference On Fracture (ICF7), 1213–20. Elsevier, 1989. http://dx.doi.org/10.1016/b978-0-08-034341-9.50135-2.
Texte intégralActes de conférences sur le sujet "Mean strain effect"
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Kamaya, Masayuki. « Influence of Mean Strain on Fatigue Life of Stainless Steel (Effect of Constant and Ratcheting Mean Strain) ». Dans ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28279.
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The influence of mean strain on fatigue life was investigated for Type 316 stainless steel at room temperature in ambient environment. Two types of mean strain were simulated in the fatigue tests: constant and increasing (ratcheting) mean strains. In order to apply the constant mean strain, prestraining was induced prior to fatigue tests. Although the stress amplitudes became larger due to the prestraining, fatigue lives were almost the same as those obtained using non-prestrained specimens for the same strain range. Change in the maximum peak stress and stress amplitude due to the prestraining had little influence on the fatigue life. It was shown that the mean strain showed little influence on the fatigue life under the same strain range. The ratcheting mean strain was observed during the fatigue tests under mean stress. The fatigue life was reduced by applying the mean stress for the same strain range. The degree of the reduction was increased with the magnitude of the ratcheting mean strain. It was deduced that the increasing mean strain enhanced the crack mouth opening and increased the effective strain range. It was concluded that the ratcheting mean strain reduced the fatigue life for the same strain range, and the reduction in fatigue life could be predicted conservatively by assuming the crack mouth was never closed during the fatigue tests.
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Nolting, A. E., et D. L. Duquesnay. « The Effect of Mean Stress and Mean Strain on Fatigue Damage Following Overloads ». Dans SAE 2003 World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States : SAE International, 2003. http://dx.doi.org/10.4271/2003-01-0910.
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Watanabe, Shin-ichi, Koh-ichi Imamura, Osamu Watanabe et Akihiro Matsuda. « Effect of Strain Amplitudes and Mean Strain Values on Fatigue Life at Elevated Temperature ». Dans ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97867.
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This paper shows randomness effects of loading amplitude and mean value of displacement-controlled loading history for perforated plates made of SUS304 stainless steel at elevated temperature of 550°C. Under the random wave of strain amplitude, the fracture behavior at elevated temperature environment is clarified by measuring the load-deflection curve at all cycles. The data of experiments were evaluated by Miner’s rule, which has been established as an evaluation method for load variation problem. Number of cycles to fracture is compared to show the good agreement with the Best Fit Fatigue curve (BFF). Peak count method also was used in calculating frequency of the strain in order to evaluate Miner’s rule, and the local strain concentration is calculated based on Stress Redistribution Locus (SRL) method. The other object of this study is to evaluate effect of mean value of strain in loading diagram on fatigue life. The mean strain were used for the cases of R = −0.0, −0.2, −0.4, −0.8 and −1.0. The crack length is measured by using photographs with the CCD video camera at a constant frequency. From the measurement, it is found that the number of cycles to failure is reduced when the absolute of value of mean strain is decreased. And cracks develop at both sides around the hole, but the growth of each crack may not be symmetric. By using these inelastic strain amplitude and crack initiation cycle, the experimented results are shown at the present study.
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Chaise, T., et D. Ne´lias. « Multi-Impact Simulation : Effect of the Covering Rate on the Mean Plastic Strain Profiles ». Dans STLE/ASME 2010 International Joint Tribology Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ijtc2010-41065.
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Multi-impact modeling is a challenge in the simulation of processes such as shot peening, with its variants laser peening and ultrasonic peening, or cold spray. Shot peening is commonly used to induce compressive stresses in machine elements subject to fatigue. The large number of impacts involved in the process implies consequent computation time to obtain representative results. In this paper, we present a new approach to model shot peening by using a semi-analytical method that accounts for plasticity. The numerical efficiency of the code along with the use of a small representative area allows reduction in the computation time. It is also possible to observe, with a small number of impacts, the effect of several coverage rates. Thus the improving efficiency of the process with increasing covering rate can be observed as well as potential saturation effect when the covering rate is too high.
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Kamaya, Masayuki. « Mean Stress Effect on Fatigue Properties of Type 316 Stainless Steel : Part I — In High-Temperature Air Environment ». Dans ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65135.
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The mean stress effect on the fatigue life of Type 316 stainless steel was investigated at 325°C in air. It was shown that the fatigue life was extended by applying the mean stress under the same stress amplitude. Increase in the maximum peak stress by applying the mean stress induced additional plastic strain and this hardened the material. The strain range of the hardened material was relatively small for the same stress amplitude, and this extended the fatigue life for a given stress amplitude. On the other hand, the fatigue life was shortened by the mean stress for the same strain range. The mean stress increased the effective strain range due to an increase in the minimum peak stress. Also, the mean stress induced ratcheting strain during the fatigue test and this accelerated crack mouth opening. The enhanced crack mouth opening accelerated the crack growth and shortened the fatigue life for a given strain range.
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Kamaya, Masayuki. « Mean Stress Effect on Fatigue Properties of Type 316 Stainless Steel : Part II — In PWR Primary Water Environment ». Dans ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65136.
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The mean stress effect on the fatigue life of Type 316 stainless steel was investigated at 325°C in simulated PWR primary water. It was shown that, as shown in high-temperature air environment, the fatigue life was extended by applying the mean stress under the same stress amplitude. An increase in the maximum peak stress by applying the mean stress induced additional plastic strain and this hardened the material. On the other hand, the fatigue life was shortened by the mean stress for the same strain range. The ratcheting strain caused by applying mean stress accelerated crack mouth opening and reduced fatigue life. It was also shown that the fatigue life in the simulated PWR primary water was shorter than that in air even without the mean stress. The magnitude of the reduction depended on the strain range. The reduction in fatigue life was the maximum when the strain range was 0.6%. The environmental effect disappeared when the effective strain was less than 0.4%.
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Li, Leilei, Bingjun Gao, Junhua Dong et Xu Chen. « Experimental Study on Cryogenic Ratcheting of Pre-Strain Austenitic Stainless Steel SS304 ». Dans ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-93192.
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Abstract Austenitic stainless steel SS304 is often used as the inner container of the Liquefied Natural Gas (LNG) semitrailer tank. Due to excellent cryogenic ductility and strain-hardening effect, pre-strain of austenitic stainless steel is practicable and conducive to achieve lightweight design of this kind of transporting vehicle. In the present work, we focus on the cryogenic ratcheting of pre-strain austenitic stainless steel SS304. The SS304 specimens were cut from as received plates and butt welded plates which are all pre-strained 8% and 12%. With CARE electronic universal testing machine, ratcheting experiments are performed at both ambient temperature and 110K with different mean stresses and stress amplitudes. Ratcheting strains increase with the mean stress and stress amplitude under cryogenic temperature, but much smaller than that at ambient temperature. And it would quickly get shakedown after ratcheting in a few cycles due to the rapid γ-α′ phase transformation under cryogenic temperature. The cryogenic ratcheting strain generally reduces with the pre-strain amount for both parent material specimens and welded specimens. Compared with parent material specimens, weld specimens yield much smaller cryogenic ratcheting strain due to the hardening effect of welding induced initial ferrite with less slipping system.
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Fatinah, T. S., K. S. Basaruddin, A. S. Abd Rahman et M. S. Abdul Majid. « Effect of mean stress and amplitude stress on mechanical stress-strain response of chopped strand mat (CSM) composite under cyclic load ». Dans 3RD ELECTRONIC AND GREEN MATERIALS INTERNATIONAL CONFERENCE 2017 (EGM 2017). Author(s), 2017. http://dx.doi.org/10.1063/1.5002288.
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Yoshii, Kan, et Toshiyuki Meshii. « Reconsidering the Effect of Stress Biaxiality on Pipe Burst (Effect of Axial Loading on the Onset of Plastic Instability) ». Dans ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28141.
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Pipe failure under internal pressure loading is understood as due to the onset of plastic instability. Law et al. [1] extended the Considere’s construction [2], which predicts the onset of plastic instability for tensile test specimen, so that it can predict the onset of plastic instability, and thus burst of pipes under internal pressure. They noted that “It is important to note that the reduced stress and strain where instability occurs is not a result of the biaxial stress state, but of the vessel geometry where increased stress comes from both increased inner diameter and reduced wall thickness” [1]. However, they intrinsically assumed that the cylinder plane that experiences instability is in plane strain state. Considering the fact that power plant pipes are often subjected to axial force from sources such as thermal expansion/contraction or fixing, the effect of deviation from the plane strain conditions should be considered. For this purpose, the onset of plastic instability of the elastic-plastic internally pressurized 1) 2D plane strain pipe, 2) 3D pipe and 3) 3D pipe additionally subjected to axial force, were compared. The results showed that the onset of plastic instability could be monitored at the pressure when pRm−σθt > 0 for all the cases. Here, Rm, σθ, and t are the current mean radius, circumferential stress at mean radius and thickness at pressure p. However, the strain at this instability pressure showed non-negligible change due to presence of axial loading. On this meaning, the biaxiality affected the onset of plastic instability.
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Kamaya, Masayuki. « Mean Stress Correction of S45C Carbon Steel Based on Crack Growth Concept ». Dans ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21822.
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Abstract Influence of the mean stress on fatigue life and fatigue limit was investigated for carbon steel. Uni-axial fatigue tests were conducted under stress and strain-controlled conditions at room temperature. The fatigue life and fatigue limit were reduced by applying the mean stress for the same stress amplitude. The fatigue life exhibited a better correlation with the strain range than the stress amplitude did. Increase in strain range caused by applying the mean stress correlated well with the decrease in the fatigue life. It was assumed that the mean stress effect on the fatigue life was brought about by the change in crack growth rate caused by applying the mean stress. The mean stress enhanced crack mouth opening and accelerated the crack growth. The reduction in the fatigue limit was also brought about by the same effect. It was shown that the effective strain range gave good prediction of fatigue life and fatigue limit with and without the mean stress.
Rapports d'organisations sur le sujet "Mean strain effect"
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Cahaner, Avigdor, Sacit F. Bilgili, Orna Halevy, Roger J. Lien et Kellye S. Joiner. effects of enhanced hypertrophy, reduced oxygen supply and heat load on breast meat yield and quality in broilers. United States Department of Agriculture, novembre 2014. http://dx.doi.org/10.32747/2014.7699855.bard.
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Original objectivesThe objectives of this project were to evaluate the growth performance, meat yield and quality attributes of broiler strains widely differing in their genetic potential under normal temperature vs. warm temperature (short and long-term) conditions. Strain differences in breast muscle accretion rate, metabolic responses under heat load and, gross and histopathological changes in breast muscle under thermal load was also to be characterized. BackgroundTremendous genetic progress has been made in broiler chicken growth rate and meat yield since the 1950s. Higher growth rate is driven by higher rates of feed intake and metabolism, resulting in elevated internal heat production. Hot rearing conditions negatively affect broiler growth by hindering dissipation of heat and may lead to a lethal elevation in body temperature. To avoid heat-induced mortality, broilers reduce feed intake, leading to depressed growth rate, lower weight gain, reduce breast meat yield and quality. Thus, the genetic potential of contemporary commercial broilers (CCB) is not fully expressed under hot conditions. Major conclusions, solutions, and achievementsResearch conducted in Israel focused on three broiler strains – CCB, Featherless, Feathered sibs (i.e., sharing similar genetic background). Complimentary research trials conducted at Auburn utilized CCB (Cobb 500, Cobb 700, Ross 308, Ross 708), contrasting their performance to slow growing strains. Warm rearing conditions consistently reduced feed intake, growth rate, feed efficiency, body weight uniformity and breast muscle yield, especially pronounced with CCB and magnified with age. Breast meat quality was also negatively affected, as measured by higher drip loss and paler meat color. Exposure to continuous or short-term heat stress induced respiratory alkalosis. Breast muscle histomorphometrics confirmed enhanced myofiber hypertrophy in CCB. Featherless broilers exhibited a significant increase in blood-vessel density under warm conditions. Rapid growth and muscle accretion rate was correlated to various myopathies (white striping, woody and necrotic) as well as to increases in plasma creatinekinase levels. Whether the trigger(s) of muscle damage is loss of cellular membrane integrity due to oxidative damage or tissue lactate accumulation, or to loss of inter-compartmental cation homeostasis is yet to be determined. Based on genome-wide single-nucleotide polymorphism array genotyping, identification of the gene with the recessive mutation Scaleless (sc) facilitated the development a dCAPS assay to discriminate between sc carrier (sc/+) and non-carrier (+/+) individuals. ImplicationsThis project confirmed that featherless broiler strains grow efficiently with high yield and quality of breast meat, even under warm rearing conditions that significantly depress the overall performance of CCB. Therefore, broiler meat production in hot regions and climates can be substantially improved by introducing the featherless gene into contemporary commercial broiler stocks. This approach has become more feasible with the development of dCAPS assay. A novel modification of the PCR protocol (using whole blood samples instead of extracted DNA) may contribute to the efficient development of commercial featherless broiler strains. Such strains will allow expansion of the broiler meat production in developing countries in warm climates, where energy intensive environmental control of rearing facilities are not economical and easily achievable.
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Shani, Moshe, et C. P. Emerson. Genetic Manipulation of the Adipose Tissue via Transgenesis. United States Department of Agriculture, avril 1995. http://dx.doi.org/10.32747/1995.7604929.bard.
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The long term goal of this study was to reduce caloric and fat content of beef and other red meats by means of genetic modification of the animal such that fat would not be accumulated. This was attempted by introducing into the germ line myogenic regulatory genes that would convert fat tissue to skeletal muscle. We first determined the consequences of ectopic expression of the myogenic regulatory gene MyoD1. It was found that deregulation of MyoD1 did not result in ectopic skeletal muscle formation but rather led to embryonic lethalities, probably due to its role in the control of the cell cycle. This indicated that MyoD1 should be placed under stringent control to allow survival. Embryonic lethalities were also observed when the regulatory elements of the adipose-specific gene adipsin directed the expression of MyoD1 or myogenin cDNAs, suggesting that these sequences are probably not strong enough to confer tissue specificity. To determine the specificity of the control elements of another fat specific gene (adipocyte protein 2-aP2), we fused them to the bacterial b-galactosidase reporter gene and established stable transgenic strains. The expression of the reporter gene in none of the strains was adipose specific. Each strain displayed a unique pattern of expression in various cell lineages. Most exciting results were obtained in a transgenic strain in which cells migrating from the ventro-lateral edge of the dermomyotome of developing somites to populate the limb buds with myoblasts were specifically stained for lacZ. Since the control sequences of the adipsin or aP2 genes did not confer fat specificity in transgenic mice we have taken both molecular and genetic approaches as an initial effort to identify genes important in the conversion of a multipotential cell such as C3H10T1/2 cell to adipoblast. Several novel adipocyte cell lines have been established that differ in the expression of transcription factors of the C/EBP family known to be markers for adipocyte differentiation. These studies revealed that one of the genetic programming changes which occur during 10T1/2 conversion from multipotential cell to a committed adipoblast is the ability to linduce C/EBPa gene expression. It is expected that further analysis of this gene would identify elements which regulate this lineage-specific expression. Such elements might be good candidates in future attempts to convert adipoblasts to skeletal muscle cells in vivo.
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Groeneveld, Andrew, et C. Crane. Advanced cementitious materials for blast protection. Engineer Research and Development Center (U.S.), avril 2023. http://dx.doi.org/10.21079/11681/46893.
Texte intégralRésumé :
Advanced cementitious materials, commonly referred to as ultra-high performance concretes (UHPCs), are developing rapidly and show promise for civil infrastructure and protective construction applications. Structures exposed to blasts experience strain rates on the order of 102 s-1 or more. While a great deal of research has been published on the durability and the static properties of UHPC, there is less information on its dynamic properties. The purpose of this report is to (1) compile existing dynamic property data—including compressive strength, tensile strength, elastic modulus, and energy absorption—for six proprietary and research UHPCs and (2) implement a single-degree-of-freedom (SDOF) model for axisymmetric UHPC panels under blast loading as a means of comparing the UHPCs. Although simplified, the model allows identification of key material properties and promising materials for physical testing. Model results indicate that tensile strength has the greatest effect on panel deflection, with unit weight and elastic modulus having a moderate effect. CEMTECmultiscale® deflected least in the simulation. Lafarge Ductal®, a commonly available UHPC in North America, performed in the middle of the five UHPCs considered.
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Mevarech, Moshe, Jeremy Bruenn et Yigal Koltin. Virus Encoded Toxin of the Corn Smut Ustilago Maydis - Isolation of Receptors and Mapping Functional Domains. United States Department of Agriculture, septembre 1995. http://dx.doi.org/10.32747/1995.7613022.bard.
Texte intégralRésumé :
Ustilago maydis is a fungal pathogen of maize. Some strains of U. maydis encode secreted polypeptide toxins capable of killing other susceptible strains of U. maydis. Resistance to the toxins is conferred by recessive nuclear genes. The toxins are encoded by genomic segments of resident double-strande RNA viruses. The best characterized toxin, KP6, is composed of two polypeptides, a and b, which are not covalently linked. It is encoded by P6M2 dsRNA, which has been cloned, sequenced and expressed in a variety of systems. In this study we have shown that the toxin acts on the membranes of sensitive cells and that both polypeptides are required for toxin activity. The toxin has been shown to function by creating new pores in the cell membrane and disrupting ion fluxes. The experiments performed on artificial phospholipid bilayers indicated that KP6 forms large voltage-independent, cation-selective channels. Experiments leading to the resolution of structure-function relationship of the toxin by in vitro analysis have been initiated. During the course of this research the collaboration also yielded X-ray diffracion data of the crystallized a polypeptide. The effect of the toxin on the pathogen has been shown to be receptor-mediated. A potential receptor protein, identified in membrane fractions of sensitive cells, was subjected to tryptic hydrolysis followed by amino-acid analysis. The peptides obtained were used to isolate a cDNA fragment by reverse PCR, which showed 30% sequence homology to the human HLA protein. Analysis of other toxins secreted by U. maydis, KP1 and KP4, have demonstrated that, unlike KP6, they are composed of a single polypeptide. Finally, KP6 has been expressed in transgenic tobacco plants, indicating that accurate processing by Kex2p-like activity occurs in plants as well. Using tobacco as a model system, we determined that active antifungal toxins can be synthesized and targeted to the outside of transgenic plant cells. If this methodology can be applied to other agronomically crop species, then U. maydis toxins may provide a novel means for biological control of pathogenic fungi.
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Granot, David, Scott Holaday et Randy D. Allen. Enhancing Cotton Fiber Elongation and Cellulose Synthesis by Manipulating Fructokinase Activity. United States Department of Agriculture, 2008. http://dx.doi.org/10.32747/2008.7613878.bard.
Texte intégralRésumé :
a. Objectives (a) Identification and characterization of the cotton fiber FRKs; (b) Generating transgenic cotton plants overproducing either substrate inhibited tomato FRK or tomato FRK without substrate inhibition; (c) Generating transgenic cotton plants with RNAi suppression of fiber expressed FRKs; (d) Generating Arabidopsis plants that over express FRK1, FRK2, or both genes, as additional means to assess the contribution of FRK to cellulose synthesis and biomass production. b. Background to the topic: Cellulose synthesis and fiber elongation are dependent on sugar metabolism. Previous results suggested that FRKs (fructokinase enzymes that specifically phosphorylate fructose) are major players in sugar metabolism and cellulose synthesis. We therefore hypothesized that increasing fructose phosphorylation may enhance fiber elongation and cellulose synthesis in cotton plants. Accordinlgy, the objectives of this research were: c. Major conclusions and achievements: Two cotton FRKs expressed in fibers, GhFRK2 and GhFRK3, were cloned and characterized. We found that GhFRK2 enzyme is located in the cytosol and GhFRK3 is located within plastids. Both enzymes enable growth on fructose (but not on glucose) of hexose kinase deficient yeast strain, confirming the fructokinase activity of the cloned genes. RNAi constructs with each gene were prepared and sent to the US collaborator to generate cotton plants with RNAi suppression of these genes. To examine the effect of FRKs using Arabidopsis plants we generated transgenic plants expressing either LeFRK1 or LeFRK2 at high level. No visible phenotype has been observed. Yet, plants expressing both genes simultaneously are being created and will be tested. To test our hypothesis that increasing fructose phosphorylation may enhance fiber cellulose synthesis, we generated twenty independent transgenic cotton plant lines overexpressing Lycopersicon (Le) FRK1. Transgene expression was high in leaves and moderate in developing fiber, but enhanced FRK activity in fibers was inconsistent between experiments. Some lines exhibited a 9-11% enhancement of fiber length or strength, but only one line tested had consistent improvement in fiber strength that correlated with elevated FRK activity in the fibers. However, in one experiment, seed cotton mass was improved in all transgenic lines and correlated with enhanced FRK activity in fibers. When greenhouse plants were subjected to severe drought during flowering and boll development, no genotypic differences in fiber quality were noted. Seed cotton mass was improved for two transgenic lines but did not correlate with fiber FRK activity. We conclude that LeFRK1 over-expression in fibers has only a small effect on fiber quality, and any positive effects depend on optimum conditions. The improvement in productivity for greenhouse plants may have been due to better structural development of the water-conducting tissue (xylem) of the stem, since stem diameters were larger for some lines and the activity of FRK in the outer xylem greater than observed for wild-type plants. We are testing this idea and developing other transgenic cotton plants to understand the roles of FRK in fiber and xylem development. We see the potential to develop a cotton plant with improved stem strength and productivity under drought for windy, semi-arid regions where cotton is grown. d. Implications, scientific and agricultural: FRKs are probably bottle neck enzymes for biomass and wood synthesis and their increased expression has the potential to enhance wood and biomass production, not only in cotton plants but also in other feed and energy renewable plants.
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Ohad, Itzhak, et Himadri Pakrasi. Role of Cytochrome B559 in Photoinhibition. United States Department of Agriculture, décembre 1995. http://dx.doi.org/10.32747/1995.7613031.bard.
Texte intégralRésumé :
The aim of this research project was to obtain information on the role of the cytochrome b559 in the function of Photosystem-II (PSII) with special emphasis on the light induced photo inactivation of PSII and turnover of the photochemical reaction center II protein subunit RCII-D1. The major goals of this project were: 1) Isolation and sequencing of the Chlamydomonas chloroplast psbE and psbF genes encoding the cytochrome b559 a and b subunits respectively; 2) Generation of site directed mutants and testing the effect of such mutation on the function of PSII under various light conditions; 3) To obtain further information on the mechanism of the light induced degradation and replacement of the PSII core proteins. This information shall serve as a basis for the understanding of the role of the cytochrome b559 in the process of photoinhibition and recovery of photosynthetic activity as well as during low light induced turnover of the D1 protein. Unlike in other organisms in which the psbE and psbF genes encoding the a and b subunits of cytochrome b559, are part of an operon which also includes the psbL and psbJ genes, in Chlamydomonas these genes are transcribed from different regions of the chloroplast chromosome. The charge distribution of the derived amino-acid sequences of psbE and psbF gene products differs from that of the corresponding genes in other organisms as far as the rule of "positive charge in" is concerned relative to the process of the polypeptide insertion in the thylakoid membrane. However, the sum of the charges of both subunits corresponds to the above rule possibly indicating co-insertion of both subunits in the process of cytochrome b559 assembly. A plasmid designed for the introduction of site-specific mutations into the psbF gene of C. reinhardtii. was constructed. The vector consists of a DNA fragment from the chromosome of C. reinhardtii which spans the region of the psbF gene, upstream of which the spectinomycin-resistance-conferring aadA cassette was inserted. This vector was successfully used to transform wild type C. reinhardtii cells. The spectinomycin resistant strain thus obtained can grow autotrophically and does not show significant changes as compared to the wild-type strain in PSII activity. The following mutations have been introduced in the psbF gene: H23M; H23Y; W19L and W19. The replacement of H23 involved in the heme binding to M and Y was meant to permit heme binding but eventually alter some or all of the electron transport properties of the mutated cytochrome. Tryptophane W19, a strictly conserved residue, is proximal to the heme and may interact with the tetrapyrole ring. Therefore its replacement may effect the heme properties. A change to tyrosine may have a lesser affect on the potential or electron transfer rate while a replacement of W19 by leucine is meant to introduce a more prominent disturbance in these parameters. Two of the mutants, FW19L and FH23M have segregated already and are homoplasmic. The rest are still grown under selection conditions until complete segregation will be obtained. All mutants contain assembled and functional PSII exhibiting an increased sensitivity of PSII to the light. Work is still in progress for the detailed characterization of the mutants PSII properties. A tobacco mutant, S6, obtained by Maliga and coworkers harboring the F26S mutation in the b subunit was made available to us and was characterized. Measurements of PSII charge separation and recombination, polypeptide content and electron flow indicates that this mutation indeed results in light sensitivity. Presently further work is in progress in the detailed characterization of the properties of all the above mutants. Information was obtained demonstrating that photoinactivation of PSII in vivo initiates a series of progressive changes in the properties of RCII which result in an irreversible modification of the RCII-D1 protein leading to its degradation and replacement. The cleavage process of the modified RCII-D1 protein is regulated by the occupancy of the QB site of RCII by plastoquinone. Newly synthesized D1 protein is not accumulated in a stable form unless integrated in reassembled RCII. Thus the degradation of the irreversibly modified RCII-D1 protein is essential for the recovery process. The light induced degradation of the RCII-D1 protein is rapid in mutants lacking the pD1 processing protease such as in the LF-1 mutant of the unicellular alga Scenedesmus obliquus. In this case the Mn binding site of PSII is abolished, the water oxidation process is inhibited and harmful cation radicals are formed following light induced electron flow in PSII. In such mutants photo-inactivation of PSII is rapid, it is not protected by ligands binding at the QB site and the degradation of the inactivated RCII-D1 occurs rapidly also in the dark. Furthermore the degraded D1 protein can be replaced in the dark in absence of light driven redox controlled reactions. The replacement of the RCII-D1 protein involves the de novo synthesis of the precursor protein, pD1, and its processing at the C-terminus end by an unknown processing protease. In the frame of this work, a gene previously isolated and sequenced by Dr. Pakrasi's group has been identified as encoding the RCII-pD1 C-terminus processing protease in the cyanobacterium Synechocystis sp. PCC 6803. The deduced sequence of the ctpA protein shows significant similarity to the bovine, human and insect interphotoreceptor retinoid-binding proteins. Results obtained using C. reinhardtii cells exposes to low light or series of single turnover light flashes have been also obtained indicating that the process of RCII-D1 protein turnover under non-photoinactivating conditions (low light) may be related to charge recombination in RCII due to back electron flow from the semiquinone QB- to the oxidised S2,3 states of the Mn cluster involved in the water oxidation process.
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Wideman, Jr., Robert F., Nicholas B. Anthony, Avigdor Cahaner, Alan Shlosberg, Michel Bellaiche et William B. Roush. Integrated Approach to Evaluating Inherited Predictors of Resistance to Pulmonary Hypertension Syndrome (Ascites) in Fast Growing Broiler Chickens. United States Department of Agriculture, décembre 2000. http://dx.doi.org/10.32747/2000.7575287.bard.
Texte intégralRésumé :
Background PHS (pulmonary hypertension syndrome, ascites syndrome) is a serious cause of loss in the broiler industry, and is a prime example of an undesirable side effect of successful genetic development that may be deleteriously manifested by factors in the environment of growing broilers. Basically, continuous and pinpointed selection for rapid growth in broilers has led to higher oxygen demand and consequently to more frequent manifestation of an inherent potential cardiopulmonary incapability to sufficiently oxygenate the arterial blood. The multifaceted causes and modifiers of PHS make research into finding solutions to the syndrome a complex and multi threaded challenge. This research used several directions to better understand the development of PHS and to probe possible means of achieving a goal of monitoring and increasing resistance to the syndrome. Research Objectives (1) To evaluate the growth dynamics of individuals within breeding stocks and their correlation with individual susceptibility or resistance to PHS; (2) To compile data on diagnostic indices found in this work to be predictive for PHS, during exposure to experimental protocols known to trigger PHS; (3) To conduct detailed physiological evaluations of cardiopulmonary function in broilers; (4) To compile data on growth dynamics and other diagnostic indices in existing lines selected for susceptibility or resistance to PHS; (5) To integrate growth dynamics and other diagnostic data within appropriate statistical procedures to provide geneticists with predictive indices that characterize resistance or susceptibility to PHS. Revisions In the first year, the US team acquired the costly Peckode weigh platform / individual bird I.D. system that was to provide the continuous (several times each day), automated weighing of birds, for a comprehensive monitoring of growth dynamics. However, data generated were found to be inaccurate and irreproducible, so making its use implausible. Henceforth, weighing was manual, this highly labor intensive work precluding some of the original objectives of using such a strategy of growth dynamics in selection procedures involving thousands of birds. Major conclusions, solutions, achievements 1. Healthy broilers were found to have greater oscillations in growth velocity and acceleration than PHS susceptible birds. This proved the scientific validity of our original hypothesis that such differences occur. 2. Growth rate in the first week is higher in PHS-susceptible than in PHS-resistant chicks. Artificial neural network accurately distinguished differences between the two groups based on growth patterns in this period. 3. In the US, the unilateral pulmonary occlusion technique was used in collaboration with a major broiler breeding company to create a commercial broiler line that is highly resistant to PHS induced by fast growth and low ambient temperatures. 4. In Israel, lines were obtained by genetic selection on PHS mortality after cold exposure in a dam-line population comprising of 85 sire families. The wide range of PHS incidence per family (0-50%), high heritability (about 0.6), and the results in cold challenged progeny, suggested a highly effective and relatively easy means for selection for PHS resistance 5. The best minimally-invasive diagnostic indices for prediction of PHS resistance were found to be oximetry, hematocrit values, heart rate and electrocardiographic (ECG) lead II waves. Some differences in results were found between the US and Israeli teams, probably reflecting genetic differences in the broiler strains used in the two countries. For instance the US team found the S wave amplitude to predict PHS susceptibility well, whereas the Israeli team found the P wave amplitude to be a better valid predictor. 6. Comprehensive physiological studies further increased knowledge on the development of PHS cardiopulmonary characteristics of pre-ascitic birds, pulmonary arterial wedge pressures, hypotension/kidney response, pulmonary hemodynamic responses to vasoactive mediators were all examined in depth. Implications, scientific and agricultural Substantial progress has been made in understanding the genetic and environmental factors involved in PHS, and their interaction. The two teams each successfully developed different selection programs, by surgical means and by divergent selection under cold challenge. Monitoring of the progress and success of the programs was done be using the in-depth estimations that this research engendered on the reliability and value of non-invasive predictive parameters. These findings helped corroborate the validity of practical means to improve PHT resistance by research-based programs of selection.