Stress-driven grain growth

CSIR Research Space (South Africa)

Nabarro, FRN

1998-11-13

Full Text Available of length b (1+ epsilon) is parallel to sigma, embedded in a grain in which the lattice vector b (1+ epsilon) is transverse to sigma. If the embedded grain grows at the expense of its matrix, the source of the stress will do work, and therefore the presence...

Stress state of transversally isotropic body with elliptical crack in the presence of a uniform heat flux at its surface

International Nuclear Information System (INIS)

Podil'chuk, Yu.N.

1995-01-01

An explicit solution of the state thermoelasticity problem is constructed for an infinite transversally isotropic body containing an internal elliptical crack in the isotropy plane. It is assumed that a uniform heat flux is specified at the crack surface and the body is free of external loads. Values of the stress-intensity coefficients depending on the heat flux, the crack dimensions, and the thermoelastic properties of the material are obtained. Note that the analogous problem was considered for an isotropic body. The static thermoelasticity problem for a transversally isotropic body with an internal elliptical crack at whose surface linear temperature variation is specified was solved

On the role of the transformation eigenstrain in the growth or shrinkage of spheroidal isotropic precipitations

International Nuclear Information System (INIS)

Fischer, F.D.; Boehm, H.J.

2005-01-01

The jumps of the strain and stress tensors on the surface of elastic homogeneous or inhomogeneous ellipsoidal inclusions embedded in an elastic matrix are obtained from results reported in the literature. They are used to derive closed-form expressions for the thermodynamic force in such matrix-inclusion systems that are subjected to a generally defined homogeneous transformation eigenstrain. A detailed study is presented for an isotropic spheroidal inclusion in an isotropic matrix in which the most important parameters are the inclusion's aspect ratio α and an eigenstrain triaxiality parameter d-bar. The fluctuations of the thermodynamic force are investigated for a set of specific transformation eigenstrain tensors and are presented for inclusion shapes ranging from disk-like to fiber-like spheroids

Representations for implicit constitutive relations describing non-dissipative response of isotropic materials

Science.gov (United States)

Gokulnath, C.; Saravanan, U.; Rajagopal, K. R.

2017-12-01

A methodology for obtaining implicit constitutive representations involving the Cauchy stress and the Hencky strain for isotropic materials undergoing a non-dissipative process is developed. Using this methodology, a general constitutive representation for a subclass of implicit models relating the Cauchy stress and the Hencky strain is obtained for an isotropic material with no internal constraints. It is shown that even for this subclass, unlike classical Green elasticity, one has to specify three potentials to relate the Cauchy stress and the Hencky strain. Then, a procedure to obtain implicit constitutive representations for isotropic materials with internal constraints is presented. As an illustration, it is shown that for incompressible materials the Cauchy stress and the Hencky strain could be related through a single potential. Finally, constitutive approximations are obtained when the displacement gradient is small.

New criteria for isotropic and textured metals

Science.gov (United States)

Cazacu, Oana

2018-05-01

In this paper a isotropic criterion expressed in terms of both invariants of the stress deviator, J2 and J3 is proposed. This criterion involves a unique parameter, α, which depends only on the ratio between the yield stresses in uniaxial tension and pure shear. If this parameter is zero, the von Mises yield criterion is recovered; if a is positive the yield surface is interior to the von Mises yield surface whereas when a is negative, the new yield surface is exterior to it. Comparison with polycrystalline calculations using Taylor-Bishop-Hill model [1] for randomly oriented face-centered (FCC) polycrystalline metallic materials show that this new criterion captures well the numerical yield points. Furthermore, the criterion reproduces well yielding under combined tension-shear loadings for a variety of isotropic materials. An extension of this isotropic yield criterion such as to account for orthotropy in yielding is developed using the generalized invariants approach of Cazacu and Barlat [2]. This new orthotropic criterion is general and applicable to three-dimensional stress states. The procedure for the identification of the material parameters is outlined. Illustration of the predictive capabilities of the new orthotropic is demonstrated through comparison between the model predictions and data on aluminum sheet samples.

Determine variation of poisson ratios and thermal creep stresses and strain rates in an isotropic disc

Directory of Open Access Journals (Sweden)

Gupta Nishi

2016-01-01

Full Text Available Seth's transition theory is applied to the problem of thermal creep transition stresses and strain rates in a thin rotating disc with shaft having variable density by finite deformation. Neither the yield criterion nor the associated flow rule is assumed here. The results obtained here are applicable to compressible materials. If the additional condition of incompressibility is imposed, then the expression for stresses corresponds to those arising from Tresca yield condition. Thermal effect decreased value of radial stress at the internal surface of the rotating isotropic disc made of compressible material as well as incompressible material and this value of radial stress further much increases with the increase in angular speed. With the introduction of thermal effects, the maximum value of strain rates further increases at the internal surface for compressible materials as compare to incompressible material.

Simulating faults and plate boundaries with a transversely isotropic plasticity model

Science.gov (United States)

Sharples, W.; Moresi, L. N.; Velic, M.; Jadamec, M. A.; May, D. A.

2016-03-01

In mantle convection simulations, dynamically evolving plate boundaries have, for the most part, been represented using an visco-plastic flow law. These systems develop fine-scale, localized, weak shear band structures which are reminiscent of faults but it is a significant challenge to resolve the large- and the emergent, small-scale-behavior. We address this issue of resolution by taking into account the observation that a rock element with embedded, planar, failure surfaces responds as a non-linear, transversely isotropic material with a weak orientation defined by the plane of the failure surface. This approach partly accounts for the large-scale behavior of fine-scale systems of shear bands which we are not in a position to resolve explicitly. We evaluate the capacity of this continuum approach to model plate boundaries, specifically in the context of subduction models where the plate boundary interface has often been represented as a planar discontinuity. We show that the inclusion of the transversely isotropic plasticity model for the plate boundary promotes asymmetric subduction from initiation. A realistic evolution of the plate boundary interface and associated stresses is crucial to understanding inter-plate coupling, convergent margin driven topography, and earthquakes.

Computational modeling for prediction of the shear stress of three-dimensional isotropic and aligned fiber networks.

Science.gov (United States)

Park, Seungman

2017-09-01

Interstitial flow (IF) is a creeping flow through the interstitial space of the extracellular matrix (ECM). IF plays a key role in diverse biological functions, such as tissue homeostasis, cell function and behavior. Currently, most studies that have characterized IF have focused on the permeability of ECM or shear stress distribution on the cells, but less is known about the prediction of shear stress on the individual fibers or fiber networks despite its significance in the alignment of matrix fibers and cells observed in fibrotic or wound tissues. In this study, I developed a computational model to predict shear stress for different structured fibrous networks. To generate isotropic models, a random growth algorithm and a second-order orientation tensor were employed. Then, a three-dimensional (3D) solid model was created using computer-aided design (CAD) software for the aligned models (i.e., parallel, perpendicular and cubic models). Subsequently, a tetrahedral unstructured mesh was generated and flow solutions were calculated by solving equations for mass and momentum conservation for all models. Through the flow solutions, I estimated permeability using Darcy's law. Average shear stress (ASS) on the fibers was calculated by averaging the wall shear stress of the fibers. By using nonlinear surface fitting of permeability, viscosity, velocity, porosity and ASS, I devised new computational models. Overall, the developed models showed that higher porosity induced higher permeability, as previous empirical and theoretical models have shown. For comparison of the permeability, the present computational models were matched well with previous models, which justify our computational approach. ASS tended to increase linearly with respect to inlet velocity and dynamic viscosity, whereas permeability was almost the same. Finally, the developed model nicely predicted the ASS values that had been directly estimated from computational fluid dynamics (CFD). The present

Numerical Analysis of Stress Concentration in Isotropic and Laminated Plates with Inclined Elliptical Holes

Science.gov (United States)

Khechai, Abdelhak; Tati, Abdelouahab; Belarbi, Mohamed Ouejdi; Guettala, Abdelhamid

2018-03-01

The design of high-performance composite structures frequently includes discontinuities to reduce the weight and fastener holes for joining. Understanding the behavior of perforated laminates is necessary for structural design. In the current work, stress concentrations taking place in laminated and isotropic plates subjected to tensile load are investigated. The stress concentrations are obtained using a recent quadrilateral finite element of four nodes with 32 DOFs. The present finite element (PE) is a combination of two finite elements. The first finite element is a linear isoparametric membrane element and the second is a high precision Hermitian element. One of the essential objectives of the current investigation is to confirm the capability and efficiency of the PE for stress determination in perforated laminates. Different geometric parameters, such as the cutout form, sizes and cutout orientations, which have a considerable effect on the stress values, are studied. Using the present finite element formulation, the obtained results are found to be in good agreement with the analytical findings, which validates the capability and the efficiency of the proposed formulation. Finally, to understand the material parameters effect such as the orientation of fibers and degree of orthotropy ratio on the stress values, many figures are presented using different ellipse major to minor axis ratio. The stress concentration values are considerably affected by increasing the orientation angle of the fibers and degree of orthotropy.

Depression of nonlinearity in decaying isotropic turbulence

International Nuclear Information System (INIS)

Kraichnan, R.H.; Panda, R.

1988-01-01

Simulations of decaying isotropic Navier--Stokes turbulence exhibit depression of the normalized mean-square nonlinear term to 57% of the value for a Gaussianly distributed velocity field with the same instantaneous velocity spectrum. Similar depression is found for dynamical models with random coupling coefficients (modified Betchov models). This suggests that the depression is dynamically generic rather than specifically driven by alignment of velocity and vorticity

Crack Tip Creep Deformation Behavior in Transversely Isotropic Materials

International Nuclear Information System (INIS)

Ma, Young Wha; Yoon, Kee Bong

2009-01-01

Theoretical mechanics analysis and finite element simulation were performed to investigate creep deformation behavior at the crack tip of transversely isotropic materials under small scale creep (SCC) conditions. Mechanical behavior of material was assumed as an elastic-2 nd creep, which elastic modulus ( E ), Poisson's ratio (v ) and creep stress exponent ( n ) were isotropic and creep coefficient was only transversely isotropic. Based on the mechanics analysis for material behavior, a constitutive equation for transversely isotropic creep behavior was formulated and an equivalent creep coefficient was proposed under plain strain conditions. Creep deformation behavior at the crack tip was investigated through the finite element analysis. The results of the finite element analysis showed that creep deformation in transversely isotropic materials is dominant at the rear of the crack-tip. This result was more obvious when a load was applied to principal axis of anisotropy. Based on the results of the mechanics analysis and the finite element simulation, a corrected estimation scheme of the creep zone size was proposed in order to evaluate the creep deformation behavior at the crack tip of transversely isotropic creeping materials

Thermal stress state of laminated shells of revolution made of isotropic and linearly orthotropic materials

International Nuclear Information System (INIS)

Savchenko, V.G.

1995-01-01

In this investigation, we will use a cylindrical coordinate system to study the stress state of laminated shells of revolution made of inelastically deforming isotropic materials and elastic materials with linear orthotropy. One of the principal directions of anisotropy coincides with the axis of revolution of the body. The shells will be subjected to nonaxisymmetric loading by body bar K (K Z , K r , K var-phi ) and surface bar t n (t nz , t nr , t nvar-phi ) forces and heating. The level of loading is such that the rheological properties of the materials of the layers are not a factor, although their thermomechanical characteristics depend on temperature. In addition, the loading and heating of the body occur in such a way that simple (or close to simple) deformation processes take place in its isotropic elements. These processes are accompanied by inelastic strains and the formation of unloading regions in which plastic strains having the sign opposite the initial strains develop. It is assumed that the layers of the body are secured to one another without interference and that conditions corresponding to ideal contact prevail at their interfaces

Large Deformation Constitutive Laws for Isotropic Thermoelastic Materials

Energy Technology Data Exchange (ETDEWEB)

Plohr, Bradley J. [Los Alamos National Laboratory; Plohr, Jeeyeon N. [Los Alamos National Laboratory

2012-07-25

We examine the approximations made in using Hooke's law as a constitutive relation for an isotropic thermoelastic material subjected to large deformation by calculating the stress evolution equation from the free energy. For a general thermoelastic material, we employ the volume-preserving part of the deformation gradient to facilitate volumetric/shear strain decompositions of the free energy, its first derivatives (the Cauchy stress and entropy), and its second derivatives (the specific heat, Grueneisen tensor, and elasticity tensor). Specializing to isotropic materials, we calculate these constitutive quantities more explicitly. For deformations with limited shear strain, but possibly large changes in volume, we show that the differential equations for the stress components involve new terms in addition to the traditional Hooke's law terms. These new terms are of the same order in the shear strain as the objective derivative terms needed for frame indifference; unless the latter terms are negligible, the former cannot be neglected. We also demonstrate that accounting for the new terms requires that the deformation gradient be included as a field variable

Stress-induced birefringence in the isotropic phases of lyotropic mixtures

Science.gov (United States)

Fernandes, P. R. G.; Maki, J. N.; Gonçalves, L. B.; de Oliveira, B. F.; Mukai, H.

2018-02-01

In this work, the frequency dependence of the known mechano-optical effect which occurs in the micellar isotropic phases (I ) of mixtures of potassium laurate (KL), decanol (DeOH), and water is investigated in the range from 200 mHz to 200 Hz . In order to fit the experimental data, a model of superimposed damped harmonic oscillators is proposed. In this phenomenological approach, the micelles (microscopic oscillators) interact very weakly with their neighbors. Due to shape anisotropy of the basic structures, each oscillator i (i =1 ,2 ,3 ,...,N ) remains in its natural oscillatory rotational movement around its axes of symmetry with a frequency ω0 i. The system will be in the resonance state when the frequency of the driving force ω reaches a value near ω0 i. This phenomenological approach shows excellent agreement with the experimental data. One can find f ˜2.5 , 9.0, and 4.0 Hz as fundamental frequencies of the micellar isotropic phases I , I1, and I2, respectively. The different micellar isotropic phases I , I1, and I2 that we find in the phase diagram of the KL-DeOH-water mixture are a consequence of possible differences in the intermicellar correlation lengths. This work reinforces the possibilities of technological applications of these phases in devices such as mechanical vibration sensors.

Numerical implementation of a transverse-isotropic inelastic, work-hardening constitutive model

International Nuclear Information System (INIS)

Baladi, G.Y.

1978-01-01

The numerical implementation of a transverse-isotropic inelastic, work-hardening plastic constitutive model is documented. A brief review of the model is presented first to facilitate the understanding of its numerical implementation. This model is formulated in terms of 'pseudo' stress invariants, so that the incremental stress-strain relationship can be readily incorporated into existing finite-difference or infinite-element computer codes. The anisotropic model reduces to its isotropic counterpart without any changes in the mathematical formulation or in the numerical implementation (algorithm) of the model. A typical example of the model and its behavior in uniaxial strain and triaxial compression is presented. (Auth.)

Stress inoculation training supported by physiology-driven adaptive virtual reality stimulation.

Science.gov (United States)

Popović, Sinisa; Horvat, Marko; Kukolja, Davor; Dropuljić, Branimir; Cosić, Kresimir

2009-01-01

Significant proportion of psychological problems related to combat stress in recent large peacekeeping operations underscores importance of effective methods for strengthening the stress resistance of military personnel. Adaptive control of virtual reality (VR) stimulation, based on estimation of the subject's emotional state from physiological signals, may enhance existing stress inoculation training (SIT). Physiology-driven adaptive VR stimulation can tailor the progress of stressful stimuli delivery to the physiological characteristics of each individual, which is indicated for improvement in stress resistance. Therefore, following an overview of SIT and its applications in the military setting, generic concept of physiology-driven adaptive VR stimulation is presented in the paper. Toward the end of the paper, closed-loop adaptive control strategy applicable to SIT is outlined.

A photon-driven micromotor can direct nerve fibre growth

Science.gov (United States)

Wu, Tao; Nieminen, Timo A.; Mohanty, Samarendra; Miotke, Jill; Meyer, Ronald L.; Rubinsztein-Dunlop, Halina; Berns, Michael W.

2012-01-01

Axonal path-finding is important in the development of the nervous system, nerve repair and nerve regeneration. The behaviour of the growth cone at the tip of the growing axon determines the direction of axonal growth and migration. We have developed an optical-based system to control the direction of growth of individual axons (nerve fibres) using laser-driven spinning birefringent spheres. One or two optical traps position birefringent beads adjacent to growth cones of cultured goldfish retinal ganglion cell axons. Circularly polarized light with angular momentum causes the trapped bead to spin. This creates a localized microfluidic flow generating an estimated 0.17 pN shear force against the growth cone that turns in response to the shear. The direction of axonal growth can be precisely manipulated by changing the rotation direction and position of this optically driven micromotor. A physical model estimating the shear force density on the axon is described.

An evaluation on fatigue crack growth in a fine-grained isotropic graphite

International Nuclear Information System (INIS)

Wang Hongtao; Sun Libin; Li Chenfeng; Shi Li; Wang Haitao

2012-01-01

Highlights: ► The propagation of micro- and macro-fatigue cracks in IG-11 graphite was studied. ► The curves of the fatigue crack growth rate versus the SIF range show three stages. ► The fatigue microcrack propagation is very sensitive to graphite's microstructures. ► Graphite's microstructures have no significant impact on fatigue macrocrack growth. ► The fatigue fracture surface indicates the fracture mechanism of the IG-11 graphite. - Abstract: The aim of this paper is to investigate the mechanism of fatigue crack propagation in IG-11 graphite, and determine the crack growth rate in relation to the stress level. Experimental studies were performed at both micro and macro scales. For fatigue microcrack propagation, single-edge-notch specimens were chosen for testing and the fatigue crack growth was measured in situ with a scanning electron microscope. For fatigue macrocrack propagation, CT specimens were used and the fatigue crack growth was measured with a high-accuracy optic microscope. Combining the two groups of experimental results, the following conclusions are derived: (1) The heterogeneous microstructures of the graphite material have significant impact on the fatigue microcrack growth, while their influence on fatigue macrocrack growth is very limited. (2) The relationship between the fatigue crack growth rate and the crack-tip stress intensity factor range can be expressed in the form of Paris formulae, which contains three stages: an initial rising part with a small slope, an abrupt rise with a very large acceleration, and a short final part with a small slope. (3) The fatigue fracture surface of the graphite material contains considerable sliding of leaf-shape graphite flakes combined with small cotton-shape plastic deformations. These sliding traces are approximately aligned at 45°, showing the main cause of the fatigue fracture is the shear stress. There are also a large amount of secondary cracks inside unit cells and on cell walls

Exploring How Weathering Related Stresses and Subcritical Crack Growth May Influence the Size of Sediment Produced From Different Rock Types.

Science.gov (United States)

Eppes, M. C.; Hallet, B.; Hancock, G. S.; Mackenzie-Helnwein, P.; Keanini, R.

2016-12-01

The formation and diminution of rock debris, sediment and soil at and near Earth's surface is driven in large part by in situ, non-transport related, rock cracking. Given the relatively low magnitude stresses that arise in surface and near-surface settings, this production and diminution of granular material is likely strongly influenced and/or driven by subcritical crack growth (Eppes et al., 2016), cracking that occurs under stress loading conditions much lower than a rock's strength as typically measured in the laboratory under rapid loading. Despite a relatively sound understanding of subcritical crack growth through engineering and geophysical studies, its geomorphic and sedimentologic implications have only been minimally explored. Here, based on existing studies, we formulate several hypotheses to predict how weathering-induced stresses combined with the subcritical crack growth properties of rock may influence sediment size distribution. For example, subcritical crack growth velocity (v) can be described by v = CKIn where KI is the mode I (simple opening mode) stress intensity factor, a function of tensile stress at the crack tip and crack length; C is a rock- and environment-dependent constant; and n is material constant, the subcritical crack growth index. Fracture length and spacing in rock is strongly dependent on n, where higher n values result in fewer, more distally spaced cracks (e.g. Olsen, 1993). Thus, coarser sediment might be expected from rocks with higher n values. Weathering-related stresses such as thermal stresses and mineral hydration, however, can disproportionally stress boundaries between minerals with contrasting thermal or chemical properties and orientation, resulting in granular disintegration. Thus, rocks with properties favorable to inducing these stresses might produce sediment whose size is reflective of its constituent grains. We begin to test these hypotheses through a detailed examination of crack and rock characteristics in

Two facets of stress and indirect effects on child diet through emotion-driven eating.

Science.gov (United States)

Tate, Eleanor B; Spruijt-Metz, Donna; Pickering, Trevor A; Pentz, Mary Ann

2015-08-01

Stress has been associated with high-calorie, low-nutrient food intake (HCLN) and emotion-driven eating (EDE). However, effects on healthy food intake remain unknown. This study examined two facets of stress (self-efficacy, perceived helplessness) and food consumption, mediated by EDE. Cross-sectional data from fourth-graders (n=978; 52% female, 28% Hispanic) in an obesity intervention used self-report to assess self-efficacy, helplessness, EDE, fruit/vegetable (FV) intake, and high-calorie/low-nutrient (HCLN) food. Higher stress self-efficacy was associated with higher FV intake, β=.354, pstress perceived helplessness had an indirect effect on HCLN intake through emotion-driven eating, indirect effect=.094, pStress self-efficacy may be more important for healthy food intake and perceived helplessness may indicate emotion-driven eating and unhealthy snack food intake. Obesity prevention programs may consider teaching stress management techniques to avoid emotion-driven eating. Copyright © 2015 Elsevier Ltd. All rights reserved.

An evaluation on fatigue crack growth in a fine-grained isotropic graphite

Energy Technology Data Exchange (ETDEWEB)

Wang Hongtao; Sun Libin [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Li Chenfeng [College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Shi Li [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Wang Haitao, E-mail: wanght@tsinghua.edu.cn [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China)

2012-09-15

Highlights: Black-Right-Pointing-Pointer The propagation of micro- and macro-fatigue cracks in IG-11 graphite was studied. Black-Right-Pointing-Pointer The curves of the fatigue crack growth rate versus the SIF range show three stages. Black-Right-Pointing-Pointer The fatigue microcrack propagation is very sensitive to graphite's microstructures. Black-Right-Pointing-Pointer Graphite's microstructures have no significant impact on fatigue macrocrack growth. Black-Right-Pointing-Pointer The fatigue fracture surface indicates the fracture mechanism of the IG-11 graphite. - Abstract: The aim of this paper is to investigate the mechanism of fatigue crack propagation in IG-11 graphite, and determine the crack growth rate in relation to the stress level. Experimental studies were performed at both micro and macro scales. For fatigue microcrack propagation, single-edge-notch specimens were chosen for testing and the fatigue crack growth was measured in situ with a scanning electron microscope. For fatigue macrocrack propagation, CT specimens were used and the fatigue crack growth was measured with a high-accuracy optic microscope. Combining the two groups of experimental results, the following conclusions are derived: (1) The heterogeneous microstructures of the graphite material have significant impact on the fatigue microcrack growth, while their influence on fatigue macrocrack growth is very limited. (2) The relationship between the fatigue crack growth rate and the crack-tip stress intensity factor range can be expressed in the form of Paris formulae, which contains three stages: an initial rising part with a small slope, an abrupt rise with a very large acceleration, and a short final part with a small slope. (3) The fatigue fracture surface of the graphite material contains considerable sliding of leaf-shape graphite flakes combined with small cotton-shape plastic deformations. These sliding traces are approximately aligned at 45 Degree-Sign , showing the

Sex-driven vulnerability in stress and drug abuse.

Science.gov (United States)

Berry, Alessandra; Raggi, Carla; Borgi, Marta; Cirulli, Francesca

2016-01-01

A growing body of literature shows that a link exists between substance abuse and stress and that the crosstalk of sex hormones with the neuroendocrine system might differently prime vulnerability to drug addiction in male and female subjects. Thus, understanding the neurobiological mechanisms of addiction and the identification of sex-driven determinants in vulnerability to drug abuse may help to better devise and/or implement strategic (pharmacological, behavioural, social) interventions to prevent or face the issue of addiction. Differences between sexes can be found at all stages of life (in both the animal model and human studies) and may account for genetic, epigenetic and environmental/hormonal factors that in turn affect the functionality of the whole organism leading also to a sex-driven differential vulnerability or resilience to non-communicable pathologies. These include the onset and precipitation of stress-related psychiatric disorders as well as "substance-related and addictive disorders" (as defined in the DSM-V). This paper reviews the scientific literature highlighting significant differences in male and female subjects in stress and neuroendocrine function and the implications for sex-dependent differential vulnerability to drug addiction.

Fracture network growth for prediction of fracture characteristics and connectivity in tight reservoir rocks

NARCIS (Netherlands)

Barnhoorn, A.; Cox, S.F.

2012-01-01

Fracturing experiments on very low-porosity dolomite rocks shows a difference in growth of fracture networks by stress-driven fracturing and fluid-driven fracturing. Stress-driven fracture growth, in the absence of fluid pressure, initially forms fractures randomly throughout the rocks followed by

Nonlinear elastic inclusions in isotropic solids

KAUST Repository

Yavari, A.

2013-10-16

We introduce a geometric framework to calculate the residual stress fields and deformations of nonlinear solids with inclusions and eigenstrains. Inclusions are regions in a body with different reference configurations from the body itself and can be described by distributed eigenstrains. Geometrically, the eigenstrains define a Riemannian 3-manifold in which the body is stress-free by construction. The problem of residual stress calculation is then reduced to finding a mapping from the Riemannian material manifold to the ambient Euclidean space. Using this construction, we find the residual stress fields of three model systems with spherical and cylindrical symmetries in both incompressible and compressible isotropic elastic solids. In particular, we consider a finite spherical ball with a spherical inclusion with uniform pure dilatational eigenstrain and we show that the stress in the inclusion is uniform and hydrostatic. We also show how singularities in the stress distribution emerge as a consequence of a mismatch between radial and circumferential eigenstrains at the centre of a sphere or the axis of a cylinder.

Resolved shear stress intensity coefficient and fatigue crack growth in large crystals

Science.gov (United States)

Chen, QI; Liu, Hao-Wen

1988-01-01

Fatigue crack growth in large grain Al alloy was studied. Fatigue crack growth is caused primarily by shear decohesion due to dislocation motion in the crack tip region. The crack paths in the large crystals are very irregular and zigzag. The crack planes are often inclined to the loading axis both in the inplane direction and the thickness direction. The stress intensity factors of such inclined cracks are approximated from the two dimensional finite element calculations. The plastic deformation in a large crystal is highly anisotropic, and dislocation motion in such crystals are driven by the resolved shear stress. The resolved shear stress intensity coefficient in a crack solid, RSSIC, is defined, and the coefficients for the slip systems at a crack tip are evaluated from the calculated stress intensity factors. The orientations of the crack planes are closely related to the slip planes with the high RSSIC values. If a single slip system has a much higher RSSIC than all the others, the crack will follow the slip plane, and the slip plane becomes the crack plane. If two or more slip systems have a high RSSIC, the crack plane is the result of the decohesion processes on these active slip planes.

Bending of Euler-Bernoulli nanobeams based on the strain-driven and stress-driven nonlocal integral models: a numerical approach

Science.gov (United States)

Oskouie, M. Faraji; Ansari, R.; Rouhi, H.

2018-04-01

Eringen's nonlocal elasticity theory is extensively employed for the analysis of nanostructures because it is able to capture nanoscale effects. Previous studies have revealed that using the differential form of the strain-driven version of this theory leads to paradoxical results in some cases, such as bending analysis of cantilevers, and recourse must be made to the integral version. In this article, a novel numerical approach is developed for the bending analysis of Euler-Bernoulli nanobeams in the context of strain- and stress-driven integral nonlocal models. This numerical approach is proposed for the direct solution to bypass the difficulties related to converting the integral governing equation into a differential equation. First, the governing equation is derived based on both strain-driven and stress-driven nonlocal models by means of the minimum total potential energy. Also, in each case, the governing equation is obtained in both strong and weak forms. To solve numerically the derived equations, matrix differential and integral operators are constructed based upon the finite difference technique and trapezoidal integration rule. It is shown that the proposed numerical approach can be efficiently applied to the strain-driven nonlocal model with the aim of resolving the mentioned paradoxes. Also, it is able to solve the problem based on the strain-driven model without inconsistencies of the application of this model that are reported in the literature.

Physiology-driven adaptive virtual reality stimulation for prevention and treatment of stress related disorders.

Science.gov (United States)

Cosić, Kresimir; Popović, Sinisa; Kukolja, Davor; Horvat, Marko; Dropuljić, Branimir

2010-02-01

The significant proportion of severe psychological problems related to intensive stress in recent large peacekeeping operations underscores the importance of effective methods for strengthening the prevention and treatment of stress-related disorders. Adaptive control of virtual reality (VR) stimulation presented in this work, based on estimation of the person's emotional state from physiological signals, may enhance existing stress inoculation training (SIT). Physiology-driven adaptive VR stimulation can tailor the progress of stressful stimuli delivery to the physiological characteristics of each individual, which is indicated for improvement in stress resistance. Following an overview of physiology-driven adaptive VR stimulation, its major functional subsystems are described in more detail. A specific algorithm of stimuli delivery applicable to SIT is outlined.

A New Theory of Non-Linear Thermo-Elastic Constitutive Equation of Isotropic Hyperelastic Materials

Science.gov (United States)

Li, Chen; Liao, Yufei

2018-03-01

Considering the influence of temperature and strain variables on materials. According to the relationship of conjugate stress-strain, a complete and irreducible non-linear constitutive equation of isotropic hyperelastic materials is derived and the constitutive equations of 16 types of isotropic hyperelastic materials are given we study the transformation methods and routes of 16 kinds of constitutive equations and the study proves that transformation of two forms of constitutive equation. As an example of application, the non-linear thermo-elastic constitutive equation of isotropic hyperelastic materials is combined with the natural vulcanized rubber experimental data in the existing literature base on MATLAB, The results show that the fitting accuracy is satisfactory.

Strategic solutions of business innovation-driven growth mainstreaming

OpenAIRE

Smolinska, N. V.

2013-01-01

The method of development of the business innovation capacity and corporate culture level evaluation, that allows identification of this level growth or deterioration within the specific period of time, is the key problem of the article. The data received permit to work out the matrix “the level of corporate culture vs. the level of innovation capacity” of the business in order to reveal the business’ position in this matrix and select the innovation-driven growth strategy of this business....

Deriving the equations of motion of porous isotropic media

International Nuclear Information System (INIS)

Pride, S.R.; Gangi, A.F.; Morgan, F.D.

1992-01-01

The equations of motion and stress/strain relations for the linear dynamics of a two-phase, fluid/solid, isotropic, porous material have been derived by a direct volume averaging of the equations of motion and stress-strain relations known to apply in each phase. The equations thus obtained are shown to be consistent with Biot's equations of motion and stress/strain relations; however, the effective fluid density in the equation of relative flow has an unambiguous definition in terms of the tractions acting on the pore walls. The stress/strain relations of the theory correspond to 'quasistatic' stressing (i.e., inertial effects are ignored). It is demonstrated that using such quasistatic stress/strain relations in the equations of motion is justified whenever the wavelengths are greater than a length characteristic of the averaging volume size. 37 refs., 2 figs

Superfluid H3e in globally isotropic random media

Science.gov (United States)

Ikeda, Ryusuke; Aoyama, Kazushi

2009-02-01

Recent theoretical and experimental studies of superfluid H3e in aerogels with a global anisotropy created, e.g., by an external stress have definitely shown that the A -like phase with an equal-spin pairing in such aerogel samples is in the Anderson-Brinkman-Morel (ABM) (or axial) pairing state. In this paper, the A -like phase of superfluid H3e in globally isotropic aerogel is studied in detail by assuming a weakly disordered system in which singular topological defects are absent. Through calculation of the free energy, a disordered ABM state is found to be the best candidate of the pairing state of the globally isotropic A -like phase. Further, it is found through a one-loop renormalization-group calculation that the coreless continuous vortices (or vortex-Skyrmions) are irrelevant to the long-distance behavior of disorder-induced textures, and that the superfluidity is maintained in spite of lack of the conventional superfluid long-range order. Therefore, the globally isotropic A -like phase at weak disorder is, like in the case with a globally stretched anisotropy, a glass phase with the ABM pairing and shows superfluidity.

Influence of initial stress, irregularity and heterogeneity on Love-type wave propagation in double pre-stressed irregular layers lying over a pre-stressed half-space

Science.gov (United States)

Singh, Abhishek Kumar; Das, Amrita; Parween, Zeenat; Chattopadhyay, Amares

2015-10-01

The present paper deals with the propagation of Love-type wave in an initially stressed irregular vertically heterogeneous layer lying over an initially stressed isotropic layer and an initially stressed isotropic half-space. Two different types of irregularities, viz., rectangular and parabolic, are considered at the interface of uppermost initially stressed heterogeneous layer and intermediate initially stressed isotropic layer. Dispersion equations are obtained in closed form for both cases of irregularities, distinctly. The effect of size and shape of irregularity, horizontal compressive initial stress, horizontal tensile initial stress, heterogeneity of the uppermost layer and width ratio of the layers on phase velocity of Love-type wave are the major highlights of the study. Comparative study has been made to identify the effects of different shapes of irregularity, presence of heterogeneity and initial stresses. Numerical computations have been carried out and depicted by means of graphs for the present study.

Numerical implementation of a transverse-isotropic inelastic, work-hardening constitutive model

International Nuclear Information System (INIS)

Baladi, G.Y.

1977-01-01

This paper documents the numerical implementation of a model, specifically a transverse-isotropic, inelastic, work-hardening constitutive model. A brief overview of the mathematical formulation of the model is presented to facilitate the understanding of its numerical implementation. The model is based on incremental flow theories for materials which have time- and temperature-independent properties and which are capable of undergoing small plastic as well as small elastic strain at each loading increment. In addition, the model is written in terms of 'pseudo' stress invariants so that the incremental anisotropic stress-strain relationship can be readily incorporated into existing finite-difference or finite-element computer codes. The isotropic version of the model is retrieved without any changes in the mathematical formulation or in the numerical implementation (algorithm) of the model. Various methods exist for incorporating inelastic constitutive models into computer programs. The method presented in this paper is appropriate for both finite-difference and finite-element codes, and is applicable for solving static as wall as dynamic problems. This method expresses the material constitutive properties as a matrix of coefficients, C (generalized tangent moduli), which relates incremental stresses to incremental strains. It possesses desirable convergence properties. In either finite-difference or finite-element applications the input quantities are the initial stress components, obtained at the end of the previous strain increment, and the new strain increments. The output quantities are the new values of the stress components

A Finite Element Model for Mixed Porohyperelasticity with Transport, Swelling, and Growth.

Directory of Open Access Journals (Sweden)

Michelle Hine Armstrong

Full Text Available The purpose of this manuscript is to establish a unified theory of porohyperelasticity with transport and growth and to demonstrate the capability of this theory using a finite element model developed in MATLAB. We combine the theories of volumetric growth and mixed porohyperelasticity with transport and swelling (MPHETS to derive a new method that models growth of biological soft tissues. The conservation equations and constitutive equations are developed for both solid-only growth and solid/fluid growth. An axisymmetric finite element framework is introduced for the new theory of growing MPHETS (GMPHETS. To illustrate the capabilities of this model, several example finite element test problems are considered using model geometry and material parameters based on experimental data from a porcine coronary artery. Multiple growth laws are considered, including time-driven, concentration-driven, and stress-driven growth. Time-driven growth is compared against an exact analytical solution to validate the model. For concentration-dependent growth, changing the diffusivity (representing a change in drug fundamentally changes growth behavior. We further demonstrate that for stress-dependent, solid-only growth of an artery, growth of an MPHETS model results in a more uniform hoop stress than growth in a hyperelastic model for the same amount of growth time using the same growth law. This may have implications in the context of developing residual stresses in soft tissues under intraluminal pressure. To our knowledge, this manuscript provides the first full description of an MPHETS model with growth. The developed computational framework can be used in concert with novel in-vitro and in-vivo experimental approaches to identify the governing growth laws for various soft tissues.

A Finite Element Model for Mixed Porohyperelasticity with Transport, Swelling, and Growth.

Science.gov (United States)

Armstrong, Michelle Hine; Buganza Tepole, Adrián; Kuhl, Ellen; Simon, Bruce R; Vande Geest, Jonathan P

2016-01-01

The purpose of this manuscript is to establish a unified theory of porohyperelasticity with transport and growth and to demonstrate the capability of this theory using a finite element model developed in MATLAB. We combine the theories of volumetric growth and mixed porohyperelasticity with transport and swelling (MPHETS) to derive a new method that models growth of biological soft tissues. The conservation equations and constitutive equations are developed for both solid-only growth and solid/fluid growth. An axisymmetric finite element framework is introduced for the new theory of growing MPHETS (GMPHETS). To illustrate the capabilities of this model, several example finite element test problems are considered using model geometry and material parameters based on experimental data from a porcine coronary artery. Multiple growth laws are considered, including time-driven, concentration-driven, and stress-driven growth. Time-driven growth is compared against an exact analytical solution to validate the model. For concentration-dependent growth, changing the diffusivity (representing a change in drug) fundamentally changes growth behavior. We further demonstrate that for stress-dependent, solid-only growth of an artery, growth of an MPHETS model results in a more uniform hoop stress than growth in a hyperelastic model for the same amount of growth time using the same growth law. This may have implications in the context of developing residual stresses in soft tissues under intraluminal pressure. To our knowledge, this manuscript provides the first full description of an MPHETS model with growth. The developed computational framework can be used in concert with novel in-vitro and in-vivo experimental approaches to identify the governing growth laws for various soft tissues.

In-situ observations of stress-induced thin film failures

Energy Technology Data Exchange (ETDEWEB)

Zhao, Z.B., E-mail: zzhao@firstsolar.co [Delphi Research Labs, 51786 Shelby Parkway, Shelby Twp., MI 48315 (United States); Hershberger, J. [Laird Technologies, 4707 Detroit Avenue, Cleveland, Ohio, 44102 (United States); Bilello, J.C. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136 (United States)

2010-02-01

In this work, the failure modes of thin films under thermo-mechanical treatments were observed via in-situ white beam X-ray topography. The in-situ experiments were carried out using an experimental setup on Beamline 2-2 at the Stanford Synchrotron Radiation Laboratory. Magnetron sputtered polycrystalline thin films of Ta and CrN on Si substrates were selected for the present study due to their disparate states of intrinsic residual stresses: the Ta film was anisotropically compressive and the CrN film was isotropically tensile. Under a similar heating-cooling cycle in air, the two types of films exhibited distinct failure modes, which were observed in-situ and in a quasi-real-time fashion. The failures of the samples have been interpreted based on their distinctive growth stress states, superimposed on the additional stress development associated with different forms of thermal instabilities upon heating. These included the formation of oxide for the Ta/Si sample, which led to an increase in compressive stress, and a phase change for the CrN/Si sample, which caused the isotropic stress in the film to become increasingly tensile.

In-situ observations of stress-induced thin film failures

International Nuclear Information System (INIS)

Zhao, Z.B.; Hershberger, J.; Bilello, J.C.

2010-01-01

In this work, the failure modes of thin films under thermo-mechanical treatments were observed via in-situ white beam X-ray topography. The in-situ experiments were carried out using an experimental setup on Beamline 2-2 at the Stanford Synchrotron Radiation Laboratory. Magnetron sputtered polycrystalline thin films of Ta and CrN on Si substrates were selected for the present study due to their disparate states of intrinsic residual stresses: the Ta film was anisotropically compressive and the CrN film was isotropically tensile. Under a similar heating-cooling cycle in air, the two types of films exhibited distinct failure modes, which were observed in-situ and in a quasi-real-time fashion. The failures of the samples have been interpreted based on their distinctive growth stress states, superimposed on the additional stress development associated with different forms of thermal instabilities upon heating. These included the formation of oxide for the Ta/Si sample, which led to an increase in compressive stress, and a phase change for the CrN/Si sample, which caused the isotropic stress in the film to become increasingly tensile.

A model for cell migration in non-isotropic fibrin networks with an application to pancreatic tumor islets.

Science.gov (United States)

Chen, Jiao; Weihs, Daphne; Vermolen, Fred J

2018-04-01

Cell migration, known as an orchestrated movement of cells, is crucially important for wound healing, tumor growth, immune response as well as other biomedical processes. This paper presents a cell-based model to describe cell migration in non-isotropic fibrin networks around pancreatic tumor islets. This migration is determined by the mechanical strain energy density as well as cytokines-driven chemotaxis. Cell displacement is modeled by solving a large system of ordinary stochastic differential equations where the stochastic parts result from random walk. The stochastic differential equations are solved by the use of the classical Euler-Maruyama method. In this paper, the influence of anisotropic stromal extracellular matrix in pancreatic tumor islets on T-lymphocytes migration in different immune systems is investigated. As a result, tumor peripheral stromal extracellular matrix impedes the immune response of T-lymphocytes through changing direction of their migration.

Constitutive modeling of stress-driven grain growth in nanocrystalline metals

KAUST Repository

Gü rses, Ercan; Wafai, Husam; El Sayed, Tamer S.

2013-01-01

the influence of the grain-growth rule on the overall macroscopic response. Finally, the model is shown to provide a good description of the experimentally observed grain-growth-induced relaxation in nc-copper. © 2013 IOP Publishing Ltd.

Isotropic oscillator: spheroidal wave functions

International Nuclear Information System (INIS)

Mardoyan, L.G.; Pogosyan, G.S.; Ter-Antonyan, V.M.; Sisakyan, A.N.

1985-01-01

Solutions of the Schroedinger equation are found for an isotropic oscillator (10) in prolate and oblate spheroidal coordinates. It is shown that the obtained solutions turn into spherical and cylindrical bases of the isotropic oscillator at R→0 and R→ infinity (R is the dimensional parameter entering into the definition of prolate and oblate spheroidal coordinates). The explicit form is given for both prolate and oblate basis of the isotropic oscillator for the lowest quantum states

The isotropic radio background revisited

Energy Technology Data Exchange (ETDEWEB)

Fornengo, Nicolao; Regis, Marco [Dipartimento di Fisica Teorica, Università di Torino, via P. Giuria 1, I–10125 Torino (Italy); Lineros, Roberto A. [Instituto de Física Corpuscular – CSIC/U. Valencia, Parc Científic, calle Catedrático José Beltrán, 2, E-46980 Paterna (Spain); Taoso, Marco, E-mail: fornengo@to.infn.it, E-mail: rlineros@ific.uv.es, E-mail: regis@to.infn.it, E-mail: taoso@cea.fr [Institut de Physique Théorique, CEA/Saclay, F-91191 Gif-sur-Yvette Cédex (France)

2014-04-01

We present an extensive analysis on the determination of the isotropic radio background. We consider six different radio maps, ranging from 22 MHz to 2.3 GHz and covering a large fraction of the sky. The large scale emission is modeled as a linear combination of an isotropic component plus the Galactic synchrotron radiation and thermal bremsstrahlung. Point-like and extended sources are either masked or accounted for by means of a template. We find a robust estimate of the isotropic radio background, with limited scatter among different Galactic models. The level of the isotropic background lies significantly above the contribution obtained by integrating the number counts of observed extragalactic sources. Since the isotropic component dominates at high latitudes, thus making the profile of the total emission flat, a Galactic origin for such excess appears unlikely. We conclude that, unless a systematic offset is present in the maps, and provided that our current understanding of the Galactic synchrotron emission is reasonable, extragalactic sources well below the current experimental threshold seem to account for the majority of the brightness of the extragalactic radio sky.

The isotropic radio background revisited

International Nuclear Information System (INIS)

Fornengo, Nicolao; Regis, Marco; Lineros, Roberto A.; Taoso, Marco

2014-01-01

We present an extensive analysis on the determination of the isotropic radio background. We consider six different radio maps, ranging from 22 MHz to 2.3 GHz and covering a large fraction of the sky. The large scale emission is modeled as a linear combination of an isotropic component plus the Galactic synchrotron radiation and thermal bremsstrahlung. Point-like and extended sources are either masked or accounted for by means of a template. We find a robust estimate of the isotropic radio background, with limited scatter among different Galactic models. The level of the isotropic background lies significantly above the contribution obtained by integrating the number counts of observed extragalactic sources. Since the isotropic component dominates at high latitudes, thus making the profile of the total emission flat, a Galactic origin for such excess appears unlikely. We conclude that, unless a systematic offset is present in the maps, and provided that our current understanding of the Galactic synchrotron emission is reasonable, extragalactic sources well below the current experimental threshold seem to account for the majority of the brightness of the extragalactic radio sky

Linearized holographic isotropization at finite coupling

Energy Technology Data Exchange (ETDEWEB)

Atashi, Mahdi; Fadafan, Kazem Bitaghsir [Shahrood University of Technology, Physics Department (Iran, Islamic Republic of); Jafari, Ghadir [Institute for Research in Fundamental Sciences (IPM), School of Physics, Tehran (Iran, Islamic Republic of)

2017-06-15

We study holographic isotropization of an anisotropic homogeneous non-Abelian strongly coupled plasma in the presence of Gauss-Bonnet corrections. It was verified before that one can linearize Einstein's equations around the final black hole background and simplify the complicated setup. Using this approach, we study the expectation value of the boundary stress tensor. Although we consider small values of the Gauss-Bonnet coupling constant, it is found that finite coupling leads to significant increasing of the thermalization time. By including higher order corrections in linearization, we extend the results to study the effect of the Gauss-Bonnet coupling on the entropy production on the event horizon. (orig.)

On the link between stress field and small-scale hydraulic fracture growth in anisotropic rock derived from microseismicity

Science.gov (United States)

Gischig, Valentin Samuel; Doetsch, Joseph; Maurer, Hansruedi; Krietsch, Hannes; Amann, Florian; Evans, Keith Frederick; Nejati, Morteza; Jalali, Mohammadreza; Valley, Benoît; Obermann, Anne Christine; Wiemer, Stefan; Giardini, Domenico

2018-01-01

To characterize the stress field at the Grimsel Test Site (GTS) underground rock laboratory, a series of hydrofracturing and overcoring tests were performed. Hydrofracturing was accompanied by seismic monitoring using a network of highly sensitive piezosensors and accelerometers that were able to record small seismic events associated with metre-sized fractures. Due to potential discrepancies between the hydrofracture orientation and stress field estimates from overcoring, it was essential to obtain high-precision hypocentre locations that reliably illuminate fracture growth. Absolute locations were improved using a transverse isotropic P-wave velocity model and by applying joint hypocentre determination that allowed for the computation of station corrections. We further exploited the high degree of waveform similarity of events by applying cluster analysis and relative relocation. Resulting clouds of absolute and relative located seismicity showed a consistent east-west strike and 70° dip for all hydrofractures. The fracture growth direction from microseismicity is consistent with the principal stress orientations from the overcoring stress tests, provided that an anisotropic elastic model for the rock mass is used in the data inversions. The σ1 stress is significantly larger than the other two principal stresses and has a reasonably well-defined orientation that is subparallel to the fracture plane; σ2 and σ3 are almost equal in magnitude and thus lie on a circle defined by the standard errors of the solutions. The poles of the microseismicity planes also lie on this circle towards the north. Analysis of P-wave polarizations suggested double-couple focal mechanisms with both thrust and normal faulting mechanisms present, whereas strike-slip and thrust mechanisms would be expected from the overcoring-derived stress solution. The reasons for these discrepancies can be explained by pressure leak-off, but possibly may also involve stress field rotation around the

A record-driven growth process

International Nuclear Information System (INIS)

Godrèche, C; Luck, J M

2008-01-01

We introduce a novel stochastic growth process, the record-driven growth process, which originates from the analysis of a class of growing networks in a universal limiting regime. Nodes are added one by one to a network, each node possessing a quality. The new incoming node connects to the pre-existing node with best quality, that is, with record value for the quality. The emergent structure is that of a growing network, where groups are formed around record nodes (nodes endowed with the best intrinsic qualities). Special emphasis is put on the statistics of leaders (nodes whose degrees are the largest). The asymptotic probability for a node to be a leader is equal to the Golomb–Dickman constant ω = 0.624 329 ..., which arises in problems of combinatorial nature. This outcome solves the problem of the determination of the record breaking rate for the sequence of correlated inter-record intervals. The process exhibits temporal self-similarity in the late-time regime. Connections with the statistics of the cycles of random permutations, the statistical properties of randomly broken intervals, and the Kesten variable are given

Discovery Driven Growth

DEFF Research Database (Denmark)

Bukh, Per Nikolaj

2009-01-01

Anmeldelse af Discovery Driven Growh : A breakthrough process to reduce risk and seize opportunity, af Rita G. McGrath & Ian C. MacMillan, Boston: Harvard Business Press. Udgivelsesdato: 14 august......Anmeldelse af Discovery Driven Growh : A breakthrough process to reduce risk and seize opportunity, af Rita G. McGrath & Ian C. MacMillan, Boston: Harvard Business Press. Udgivelsesdato: 14 august...

In-Situ Characterization of Isotropic and Transversely Isotropic Elastic Properties Using Ultrasonic Wave Velocities

NARCIS (Netherlands)

Pant, S; Laliberte, J; Martinez, M.J.; Rocha, B.

2016-01-01

In this paper, a one-sided, in situ method based on the time of flight measurement of ultrasonic waves was described. The primary application of this technique was to non-destructively measure the stiffness properties of isotropic and transversely isotropic materials. The method consists of

Macroscopic simulation of isotropic permanent magnets

International Nuclear Information System (INIS)

Bruckner, Florian; Abert, Claas; Vogler, Christoph; Heinrichs, Frank; Satz, Armin; Ausserlechner, Udo; Binder, Gernot; Koeck, Helmut; Suess, Dieter

2016-01-01

Accurate simulations of isotropic permanent magnets require to take the magnetization process into account and consider the anisotropic, nonlinear, and hysteretic material behaviour near the saturation configuration. An efficient method for the solution of the magnetostatic Maxwell equations including the description of isotropic permanent magnets is presented. The algorithm can easily be implemented on top of existing finite element methods and does not require a full characterization of the hysteresis of the magnetic material. Strayfield measurements of an isotropic permanent magnet and simulation results are in good agreement and highlight the importance of a proper description of the isotropic material. - Highlights: • Simulations of isotropic permanent magnets. • Accurate calculation of remanence magnetization and strayfield. • Comparison with strayfield measurements and anisotropic magnet simulations. • Efficient 3D FEM–BEM coupling for solution of Maxwell equations.

Mapping of moveout in tilted transversely isotropic media

KAUST Repository

Stovas, A.; Alkhalifah, Tariq Ali

2013-01-01

The computation of traveltimes in a transverse isotropic medium with a tilted symmetry axis tilted transversely isotropic is very important both for modelling and inversion. We develop a simple analytical procedure to map the traveltime function from a transverse isotropic medium with a vertical symmetry axis (vertical transversely isotropic) to a tilted transversely isotropic medium by applying point-by-point mapping of the traveltime function. This approach can be used for kinematic modelling and inversion in layered tilted transversely isotropic media. © 2013 European Association of Geoscientists & Engineers.

Mapping of moveout in tilted transversely isotropic media

KAUST Repository

Stovas, A.

2013-09-09

The computation of traveltimes in a transverse isotropic medium with a tilted symmetry axis tilted transversely isotropic is very important both for modelling and inversion. We develop a simple analytical procedure to map the traveltime function from a transverse isotropic medium with a vertical symmetry axis (vertical transversely isotropic) to a tilted transversely isotropic medium by applying point-by-point mapping of the traveltime function. This approach can be used for kinematic modelling and inversion in layered tilted transversely isotropic media. © 2013 European Association of Geoscientists & Engineers.

Fatigue crack growth behavior under cyclic thermal transient stress

International Nuclear Information System (INIS)

Ueda, Masahiro; Kano, Takashi; Yoshitoshi, Atsushi.

1986-01-01

Thermal fatigue tests were performed using straight pipe specimens subjected to cyclic thermal shocks of liquid sodium, and crack growth behaviors were estimated using striation patterns observed clearly on any crack surface. Crack growth rate under cyclic thermal strain reaches the maximum at one depth, and after that it decreases gradually with crack depth. The peak location of crack growth rate becomes deeper by superposition of constant primary stress. Parallel cracks co-existing in the neighborhood move the peak to shallower location and decrease the maximum crack growth rate. The equivalent stress intensity factor range calculated by Walker's formula is successfully applied to the case of negative stress ratio. Fatigue crack growth rate under cyclic thermal strain agreed well with that under the constant temperature equal to the maximum value in the thermal cycle. Simplified methods for calculating the stress intensity factor and the crack interference factor have been developed. Crack growth behavior under thermal fatigue could be well predicted using numerical analysis results. (author)

Fatigue crack growth behavior under cyclic transient thermal stress

International Nuclear Information System (INIS)

Ueda, Masahiro; Kano, Takashi; Yoshitoshi, Atsushi.

1987-01-01

Thermal fatigue tests were performed using straight pipe specimens subjected to cyclic thermal shocks of liquid sodium, and crack growth behaviors were estimated using striation patterns observed clearly on any crack surface. Crack growth rate under cyclic thermal strain reaches the maximum at one depth, and after that it decreases gradually with crack depth. The peak location of crack growth rate becomes deeper by superposition of constant primary stress. Parallel cracks co-existing in the neighborhood move the peak to shallower location and decrease the maximum crack growth rate. The equivalent stress intensity factor range calculated by Walker's formula is successfully applied to the case of negative stress ratio. Fatigue crack growth rate under cyclic thermal strain agreed well with that under the constant temperature equal to the maximum value in the thermal cycle. Simplified methods for calculating the stress intensity factor and the crack interference factor have been developed. Crack growth behavior under thermal fatigue could be well predicted using numerical analysis results. (author)

Numerical implementation of a transverse-isotropic inelastic, work-hardening constitutive model

International Nuclear Information System (INIS)

Baladi, G.Y.

1977-01-01

During the past few decades the dramatic growth of computer technology has been paralleled by an increasing degree of complexity in material constitutive modeling. This paper documents the numerical implementation of one of these models, specifically a transverse-isotropic, inelastic, work-hardening constitutive model which is developed elsewhere by the author. (Auth.)

Mathematical modeling of the crack growth in linear elastic isotropic materials by conventional fracture mechanics approaches and by molecular dynamics method: crack propagation direction angle under mixed mode loading

Science.gov (United States)

Stepanova, Larisa; Bronnikov, Sergej

2018-03-01

The crack growth directional angles in the isotropic linear elastic plane with the central crack under mixed-mode loading conditions for the full range of the mixity parameter are found. Two fracture criteria of traditional linear fracture mechanics (maximum tangential stress and minimum strain energy density criteria) are used. Atomistic simulations of the central crack growth process in an infinite plane medium under mixed-mode loading using Large-scale Molecular Massively Parallel Simulator (LAMMPS), a classical molecular dynamics code, are performed. The inter-atomic potential used in this investigation is Embedded Atom Method (EAM) potential. The plane specimens with initial central crack were subjected to Mixed-Mode loadings. The simulation cell contains 400000 atoms. The crack propagation direction angles under different values of the mixity parameter in a wide range of values from pure tensile loading to pure shear loading in a wide diapason of temperatures (from 0.1 К to 800 К) are obtained and analyzed. It is shown that the crack propagation direction angles obtained by molecular dynamics method coincide with the crack propagation direction angles given by the multi-parameter fracture criteria based on the strain energy density and the multi-parameter description of the crack-tip fields.

Effect of elastic anisotropy of crystal grain on stress intensity factor

Energy Technology Data Exchange (ETDEWEB)

Kamaya, Masayuki [Inst. of Nuclear Safety System Inc., Mihama, Fukui (Japan)

2002-09-01

The stress intensity factor (SIF) is used widely for evaluating integrity of cracked components. Usually, the SIF obtained under isotropic elastic conditions is used for the evaluations. Although, macroscopic elastic behaviors of polycrystal materials can be considered isotropic, each crystal has anisotropic elastic properties. This implies that if the crack size is small and the influence of anisotropic elastic properties on the stress around cracks is significant, the SIF evaluated under anisotropic elastic conditions may differ from the SIF obtained under isotropic elastic conditions. In the present study, the effect of anisotropic elasticity on the SIF was evaluated by using the finite element analysis (FEA). First, the SIF of semi-circular cracks located in a single crystal was evaluated. It was found that the SIF is affected crystal orientation. Secondly, FEA using a polycrystal model was performed. It was found that the change in the SIF was caused by crack tip crystal orientation as well as the deformation constraint from neighboring crystals. Finally, the statistical tendency of change in the SIF caused by the anisotropic elastic properties and the relationship with crack size were examined. The influence of the local SIF on crack growth behavior is also discussed. (author)

Effect of elastic anisotropy of crystal grain on stress intensity factor

International Nuclear Information System (INIS)

Kamaya, Masayuki

2002-01-01

The stress intensity factor (SIF) is used widely for evaluating integrity of cracked components. Usually, the SIF obtained under isotropic elastic conditions is used for the evaluations. Although, macroscopic elastic behaviors of polycrystal materials can be considered isotropic, each crystal has anisotropic elastic properties. This implies that if the crack size is small and the influence of anisotropic elastic properties on the stress around cracks is significant, the SIF evaluated under anisotropic elastic conditions may differ from the SIF obtained under isotropic elastic conditions. In the present study, the effect of anisotropic elasticity on the SIF was evaluated by using the finite element analysis (FEA). First, the SIF of semi-circular cracks located in a single crystal was evaluated. It was found that the SIF is affected crystal orientation. Secondly, FEA using a polycrystal model was performed. It was found that the change in the SIF was caused by crack tip crystal orientation as well as the deformation constraint from neighboring crystals. Finally, the statistical tendency of change in the SIF caused by the anisotropic elastic properties and the relationship with crack size were examined. The influence of the local SIF on crack growth behavior is also discussed. (author)

Soret-driven double diffusive magneto-convection in couple stress liquid

Directory of Open Access Journals (Sweden)

Mishra P.

2012-07-01

Full Text Available The stability analysis of Soret driven double diffusive convection for electrically conducting couple stress liquid is investigated theoretically. The couple stress liquid is confined between two horizontal surfaces and a constant vertical magnetic field is applied across the surfaces. Linear stability analysis is used to investigate the effect of various parameters on the onset of convection. Effect of magnetic field on the onset of convection is presented by means of Chandrasekhar number. The problem is analyzed as a function of Chandrasekhar number (Q, positive and negative Soret parameter (S r and couple stress parameter (C, mainly. The results show that the Q, both positive and negative Sr and C delay the onset of convection. The effect of other parameters is also discussed in paper and shown by graphs.

A necessary condition for dispersal driven growth of populations with discrete patch dynamics.

Science.gov (United States)

Guiver, Chris; Packman, David; Townley, Stuart

2017-07-07

We revisit the question of when can dispersal-induced coupling between discrete sink populations cause overall population growth? Such a phenomenon is called dispersal driven growth and provides a simple explanation of how dispersal can allow populations to persist across discrete, spatially heterogeneous, environments even when individual patches are adverse or unfavourable. For two classes of mathematical models, one linear and one non-linear, we provide necessary conditions for dispersal driven growth in terms of the non-existence of a common linear Lyapunov function, which we describe. Our approach draws heavily upon the underlying positive dynamical systems structure. Our results apply to both discrete- and continuous-time models. The theory is illustrated with examples and both biological and mathematical conclusions are drawn. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Calculation of intensity factors using weight function theory for a transversely isotropic piezoelectric material

International Nuclear Information System (INIS)

Son, In Ho; An, Deuk Man

2012-01-01

In fracture mechanics, the weight function can be used for calculating stress intensity factors. In this paper, a two dimensional electroelastic analysis is performed on a transversely isotropic piezoelectric material with an open crack. A plane strain formulation of the piezoelectric problem is solved within the Leknitskii formalism. Weight function theory is extended to piezoelectric materials. The stress intensity factors and electric displacement intensity factor are calculated by the weight function theory

Influence of initial stress, irregularity and heterogeneity on Love-type ...

Indian Academy of Sciences (India)

The present paper deals with the propagation of Love-type wave in an initially stressed irregular vertically heterogeneous layer lying over an initially stressed isotropic layer and an initially stressed isotropic half- space. Two different types of irregularities, viz., rectangular and parabolic, are considered at the interface.

Static deformation due to a long buried dip-slip fault in an isotropic

Indian Academy of Sciences (India)

Closed-form analytical expressions for the displacements and the stresses at any point of a two-phase medium consisting of a homogeneous, isotropic, perfectly elastic half-space in welded contact with a homogeneous, orthotropic, perfectly elastic half-space due to a dip-slip fault of finite width located at an arbitrary ...

Stress corrosion crack growth in unirradiated zircaloy

International Nuclear Information System (INIS)

Pettersson, K.

1978-10-01

Experimental techniques suitable for the determination of stress corrosion crack growth rates in irradiated Zircaloy tube have been developed. The techniques have been tested on unirradiated. Zircaloy and it was found that the results were in good agreement with the results of other investigations. Some of the results were obtained at very low stress intensities and the crack growth rates observed, gave no indication of the existance of a K sub(ISCC) for iodine induced stress corrosion cracking in Zircaloy. This is of importance both for fuel rod behavior after a power ramp and for long term storage of spent Zircaloy-clad fuel. (author)

Uniaxial stress-driven coupled grain boundary motion in hexagonal close-packed metals: A molecular dynamics study

International Nuclear Information System (INIS)

Zong, Hongxiang; Ding, Xiangdong; Lookman, Turab; Li, Ju; Sun, Jun

2015-01-01

Stress-driven grain boundary (GB) migration has been evident as a dominant mechanism accounting for plastic deformation in crystalline solids. Using molecular dynamics (MD) simulations on a Ti bicrystal model, we show that a uniaxial stress-driven coupling is associated with the recently observed 90° GB reorientation in shock simulations and nanopillar compression measurements. This is not consistent with the theory of shear-induced coupled GB migration. In situ atomic configuration analysis reveals that this GB motion is accompanied by the glide of two sets of parallel dislocation arrays, and the uniaxial stress-driven coupling is explained through a composite action of symmetrically distributed dislocations and deformation twins. In addition, the coupling factor is calculated from MD simulations over a wide range of temperatures. We find that the coupled motion can be thermally damped (i.e., not thermally activated), probably due to the absence of the collective action of interface dislocations. This uniaxial coupled mechanism is believed to apply to other hexagonal close-packed metals

Thermalization vs. isotropization and azimuthal fluctuations

International Nuclear Information System (INIS)

Mrowczynski, Stanislaw

2005-01-01

Hydrodynamic description requires a local thermodynamic equilibrium of the system under study but an approximate hydrodynamic behaviour is already manifested when a momentum distribution of liquid components is not of equilibrium form but merely isotropic. While the process of equilibration is relatively slow, the parton system becomes isotropic rather fast due to the plasma instabilities. Azimuthal fluctuations observed in relativistic heavy-ion collisions are argued to distinguish between a fully equilibrated and only isotropic parton system produced in the collision early stage

Spider Gland Fluids: From Protein-Rich Isotropic Liquid to Insoluble Super Fiber

Science.gov (United States)

2013-09-17

dehydration, methanol treatment, solubilized in ionic liquids and exposed to mechanical stress. Establish the relevant processing conditions for...for liquid-state NMR techniques such as gradient coherence selection , water suppression, and pulsed field gradient self-diffusion measurements. HR...Gln, Ser) including the carbonyl resonances. All the unambiguously assignable 13C isotropic chemical shifts are listed in Tab. 1. The assignment and

Intermetallic Compound Growth and Stress Development in Al-Cu Diffusion Couple

Science.gov (United States)

Mishler, M.; Ouvarov-Bancalero, V.; Chae, Seung H.; Nguyen, Luu; Kim, Choong-Un

2018-01-01

This paper reports experimental observations evidencing that the intermetallic compound phase interfaced with Cu in the Al-Cu diffusion couple is most likely α2-Cu3Al phase, not γ-Cu9Al4 phase as previously assumed, and that its growth to a critical thickness may result in interface failure by stress-driven fracture. These conclusions are made based on an interdiffusion study of a diffusion couple made of a thick Cu plate coated with ˜ 2- μm-thick Al thin film. The interface microstructure and lattice parameter were characterized using scanning electron microscopy and x-ray diffraction analysis. Specimens aged at temperature between 623 K (350°C) and 723 K (450°C) for various hours produced consistent results supporting the main conclusions. It is found that disordered α2-Cu3Al phase grows in a similar manner to solid-state epitaxy, probably owing to its structural similarity to the Cu lattice. The increase in the interface strain that accompanies the α2-Cu3Al phase growth ultimately leads to interface fracture proceeding from crack initiation and growth along the interface. This mechanism provides the most consistent explanation for interface failures observed in other studies.

Space-charge driven emittance growth in a 3D mismatched anisotropic beam

International Nuclear Information System (INIS)

Qiang, J.; Ryne, R.D.; Hofmann, I.

2002-01-01

In this paper we present a 3D simulation study of the emittance growth in a mismatched anisotropic beam. The equipartitioning driven by a 4th order space-charge resonance can be significantly modified by the presence of mismatch oscillation and halo formation. This causes emittance growth in both the longitudinal and transverse directions which could drive the beam even further away from equipartition. The averaged emittance growth per degree freedom follows the upper bound of the 2D free energy limit plus the contributions from equipartitioning

Electrothermal instability growth in magnetically driven pulsed power liners

International Nuclear Information System (INIS)

Peterson, Kyle J.; Sinars, Daniel B.; Yu, Edmund P.; Herrmann, Mark C.; Cuneo, Michael E.; Slutz, Stephen A.; Smith, Ian C.; Atherton, Briggs W.; Knudson, Marcus D.; Nakhleh, Charles

2012-01-01

This paper explores the role of electro-thermal instabilities on the dynamics of magnetically accelerated implosion systems. Electro-thermal instabilities result from non-uniform heating due to temperature dependence in the conductivity of a material. Comparatively little is known about these types of instabilities compared to the well known Magneto-Rayleigh-Taylor (MRT) instability. We present simulations that show electrothermal instabilities form immediately after the surface material of a conductor melts and can act as a significant seed to subsequent MRT instability growth. We also present the results of several experiments performed on Sandia National Laboratories Z accelerator to investigate signatures of electrothermal instability growth on well characterized initially solid aluminum and copper rods driven with a 20 MA, 100 ns risetime current pulse. These experiments show excellent agreement with electrothermal instability simulations and exhibit larger instability growth than can be explained by MRT theory alone.

Residual stress in deuterium implanted nominal copper coatings

International Nuclear Information System (INIS)

Inal, M. Y.; Alam, M.; Peascoe, R. A.; Watkins, T. R.

2000-01-01

The effects of deuterium (D) implantation on the residual stresses in Cu and CuAl 2 phases present in nominal Cu coatings (containing Al) deposited on Al-alloy (Al-6061) substrates were measured using an x-ray diffraction technique. The coatings were deposited by radio frequency magnetron sputtering of a pure Cu target under identical conditions and Al was incorporated in the coatings during growth by diffusion from the substrate. Deuterium was implanted in the coatings at energies of 40 or 40+120 keV with fluences of 1x10 21 , 2x10 21 , or 3x10 21 D + /m 2 . Pole figures of the Cu phase in the coatings prior to and after implantation indicated no effect of implantation on the fibrous texture. Triaxial stress analysis indicated the surface normal stress component to be negligible in Cu and slightly tensile in CuAl 2 under all conditions. Furthermore, under all conditions, the in-plane residual stresses in both phases were found to be compressive and nearly isotropic. The magnitude of the isotropic compressive stress was always higher in CuAl 2 as compared to Cu. The compressive residual stresses in the Cu phase changed only mildly with increasing coating weight, ion energy, and fluence. However, in the CuAl 2 phase the compressive residual stresses changed markedly with increasing ion energy (initial decrease followed by leveling off) and increasing ion fluence (initial decrease followed by an increase), but remained unaffected by increasing coating weight. (c) 2000 American Institute of Physics

Effective stress law for anisotropic elastic deformation

International Nuclear Information System (INIS)

Carroll, M.M.

1979-01-01

An effective stress law is derived analytically to describe the effect of pore fluid pressure on the linearly elastic response of saturated porous rocks which exhibit anisotropy. For general anisotropy the difference between the effective stress and the applied stress is not hydrostatic. The effective stress law involves two constants for transversely isotropic response and three constants for orthotropic response; these constants can be expressed in terms of the moduli of the porous material and of the solid material. These expressions simplify considerably when the anisotropy is structural rather than intrinsic, i.e., in the case of an isotropic solid material with an anisotropic pore structure. In this case the effective stress law involves the solid or grain bulk modulus and two or three moduli of the porous material, for transverse isotropy and orthotropy, respectively. The law reduces, in the case of isotropic response, to that suggested by Geertsma (1957) and by Skempton (1961) and derived analytically by Nur and Byerlee

Growth and physiological responses to water and nutrient stress in ...

African Journals Online (AJOL)

Growth and physiological responses to water and nutrient stress in oil palm. ... changes in growth, physiology and nutrient concentration in response to two watering regimes (well-watered and water-stress conditions) and ... from 32 Countries:.

Interleukin-Driven Insulin-Like Growth Factor Promotes Prostatic Inflammatory Hyperplasia

Science.gov (United States)

Hahn, Alana M.; Myers, Jason D.; McFarland, Eliza K.; Lee, Sanghee

2014-01-01

Prostatic inflammation is of considerable importance to urologic research because of its association with benign prostatic hyperplasia and prostate cancer. However, the mechanisms by which inflammation leads to proliferation and growth remain obscure. Here, we show that insulin-like growth factors (IGFs), previously known as critical developmental growth factors during prostate organogenesis, are induced by inflammation as part of the proliferative recovery to inflammation. Using genetic models and in vivo IGF receptor blockade, we demonstrate that the hyperplastic response to inflammation depends on interleukin-1–driven IGF signaling. We show that human prostatic hyperplasia is associated with IGF pathway activation specifically localized to foci of inflammation. This demonstrates that mechanisms of inflammation-induced epithelial proliferation and hyperplasia involve the induction of developmental growth factors, further establishing a link between inflammatory and developmental signals and providing a mechanistic basis for the management of proliferative diseases by IGF pathway modulation. PMID:25292180

Rocking Rotation of a Rigid Disk Embedded in a Transversely Isotropic Half-Space

Directory of Open Access Journals (Sweden)

Seyed Ahmadi

2014-06-01

Full Text Available The asymmetric problem of rocking rotation of a circular rigid disk embedded in a finite depth of a transversely isotropic half-space is analytically addressed. The rigid disk is assumed to be in frictionless contact with the elastic half-space. By virtue of appropriate Green's functions, the mixed boundary value problem is written as a dual integral equation. Employing further mathematical techniques, the integral equation is reduced to a well-known Fredholm integral equation of the second kind. The results related to the contact stress distribution across the disk region and the equivalent rocking stiffness of the system are expressed in terms of the solution of the obtained Fredholm  integral  equation. When the rigid disk is located on the surface or at the remote boundary, the exact closed-form solutions are presented. For verification purposes, the limiting case of an isotropic half-space is considered and the results are verified with those available in the literature. The jump behavior in the results at the edge of the rigid disk for the case of an infinitesimal embedment is highlighted analytically for the first time. Selected numerical results are depicted for the contact stress distribution across the disk region, rocking stiffness of the system, normal stress, and displacement components along the radial axis. Moreover, effects of anisotropy on the rocking stiffness factor are discussed in detail.

Self-consistent calculation of steady-state creep and growth in textured zirconium

International Nuclear Information System (INIS)

Tome, C.N.; So, C.B.; Woo, C.H.

1993-01-01

Irradiation creep and growth in zirconium alloys result in anisotropic dimensional changes relative to the crystallographic axis in each individual grain. Several methods have been attempted to model such dimensional changes, taking into account the development of intergranular stresses. In this paper, we compare the predictions of several such models, namely the upper-bound, the lower-bound, the isotropic K* self-consistent (analytical) and the fully self-consistent (numerical) models. For given single-crystal creep compliances and growth factors, the polycrystal compliances predicted by the upper- and lower-bound models are unreliable. The predictions of the two self-consistent approaches are usually similar. The analytical isotropic K* approach is simple to implement and can be used to estimate the creep and growth rates of the polycrystal in many cases. The numerical fully self-consistent approach should be used when an accurate prediction of polycrystal creep is required, particularly for the important case of a closed-end internally pressurized tube. In most cases, the variations in grain shape introduce only minor corrections to the behaviour of polycrystalline materials. (author)

Elastic field of approaching dislocation loop in isotropic bimaterial

International Nuclear Information System (INIS)

Wu, Wenwang; Xu, Shucai; Zhang, Jinhuan; Xia, Re; Qian, Guian

2015-01-01

A semi-analytical solution is developed for calculating interface traction stress (ITS) fields due to elastic modulus mismatch across the interface plane of isotropic perfectly bounded bimaterial system. Based on the semi-analytical approaches developed, ITS is used to correct the bulk elastic field of dislocation loop within infinite homogenous medium, and to produce continuous displacement and stress fields across the perfectly-bounded interface. Firstly, calculation examples of dislocation loops in Al–Cu bimaterial system are performed to demonstrate the efficiency of the developed semi-analytical approach; Then, the elastic fields of dislocation loops in twinning Cu and Cu–Nb bimaterial are analyzed; Finally, the effect of modulus mismatch across interface plane on the elastic field of bimaterial system is investigated, it is found that modulus mismatch has a drastic impact on the elastic fields of dislocation loops within bimaterial system. (paper)

Friction stress effects on mode I crack growth predictions

NARCIS (Netherlands)

Chen, Q.; Deshpande, V.S.; Giessen, E. van der; Needleman, A.

2003-01-01

The effect of a lattice friction stress on the monotonic growth of a plane strain mode I crack under small-scale yielding conditions is analyzed using discrete dislocation plasticity. When the friction stress is increased from zero to half the dislocation nucleation stress, the crack tip stress

Parametric study of the deformation of transversely isotropic discs under diametral compression

Directory of Open Access Journals (Sweden)

Christos F. Markides

2017-07-01

Full Text Available The displacement field in a circular disc made of a transversely isotropic material is explored in a parametric manner. The disc is assumed to be loaded by a parabolic distribution of compressive radial stresses along two finite arcs of its periphery in the absence of any tangential (frictional stresses. Advantage is here taken of a recently introduced closed-form analytic solution for the displacement field developed in an orthotropic disc under diametral compression which was achieved adopting the complex potentials technique for rectilinear anisotropic materials as it was formulated in the pioneering work of S.G. Lekhnitskii. The analytic nature of this solution permits thorough, indepth exploration of the influence of some crucial parameters on the qualitative and quantitative characteristics of the deformation of transversely isotropic circular discs compressed between the jaws of the devise suggested by the International Society for Rock Mechanics for the standardized implementation of the Brazilian-disc test. The parameters considered include the anisotropy ratio (i.e., the ratio of the two elastic moduli characterizing the disc material, the angle between the loading axis and the planes of transverse isotropy and the length of the loaded arcs. Strongly non-linear relationships between these parameters and the components of the displacement field are revealed.

Posttraumatic stress disorder and posttraumatic growth in breast cancer patients: a systematic review.

Science.gov (United States)

Koutrouli, Natalia; Anagnostopoulos, Fotios; Potamianos, Gregory

2012-01-01

Breast cancer, potentially a traumatic stressor, may be accompanied by negative outcomes, such as posttraumatic stress disorder or positive changes, such as posttraumatic growth. The authors reviewed 24 studies published from 1990 to 2010 that measured posttraumatic stress disorder and posttraumatic growth in women with breast cancer, in terms of frequency rates, factors associated with posttraumatic stress disorder and posttraumatic growth, and their interrelationships. A relatively small percentage of women experienced posttraumatic stress disorder, while the majority of them reported posttraumatic growth. Age, education, economic status, subjective appraisal of the threat of the disease, treatment, support from significant others, and positive coping strategies were among the most frequently reported factors associated with these phenomena. Moreover, posttraumatic stress disorder and posttraumatic growth were not related. Future research should shed more light on posttraumatic growth and posttraumatic stress disorder among women with breast cancer, the parameters that influence them, and their possible relationship.

Electron Cooling and Isotropization during Magnetotail Current Sheet Thinning: Implications for Parallel Electric Fields

Science.gov (United States)

Lu, San; Artemyev, A. V.; Angelopoulos, V.

2017-11-01

Magnetotail current sheet thinning is a distinctive feature of substorm growth phase, during which magnetic energy is stored in the magnetospheric lobes. Investigation of charged particle dynamics in such thinning current sheets is believed to be important for understanding the substorm energy storage and the current sheet destabilization responsible for substorm expansion phase onset. We use Time History of Events and Macroscale Interactions during Substorms (THEMIS) B and C observations in 2008 and 2009 at 18 - 25 RE to show that during magnetotail current sheet thinning, the electron temperature decreases (cooling), and the parallel temperature decreases faster than the perpendicular temperature, leading to a decrease of the initially strong electron temperature anisotropy (isotropization). This isotropization cannot be explained by pure adiabatic cooling or by pitch angle scattering. We use test particle simulations to explore the mechanism responsible for the cooling and isotropization. We find that during the thinning, a fast decrease of a parallel electric field (directed toward the Earth) can speed up the electron parallel cooling, causing it to exceed the rate of perpendicular cooling, and thus lead to isotropization, consistent with observation. If the parallel electric field is too small or does not change fast enough, the electron parallel cooling is slower than the perpendicular cooling, so the parallel electron anisotropy grows, contrary to observation. The same isotropization can also be accomplished by an increasing parallel electric field directed toward the equatorial plane. Our study reveals the existence of a large-scale parallel electric field, which plays an important role in magnetotail particle dynamics during the current sheet thinning process.

Step driven competitive epitaxial and self-limited growth of graphene on copper surface

Directory of Open Access Journals (Sweden)

Lili Fan

2011-09-01

Full Text Available The existence of surface steps was found to have significant function and influence on the growth of graphene on copper via chemical vapor deposition. The two typical growth modes involved were found to be influenced by the step morphologies on copper surface, which led to our proposed step driven competitive growth mechanism. We also discovered a protective role of graphene in preserving steps on copper surface. Our results showed that wide and high steps promoted epitaxial growth and yielded multilayer graphene domains with regular shape, while dense and low steps favored self-limited growth and led to large-area monolayer graphene films. We have demonstrated that controllable growth of graphene domains of specific shape and large-area continuous graphene films are feasible.

The impact of stress on tumor growth: peripheral CRF mediates tumor-promoting effects of stress

Directory of Open Access Journals (Sweden)

Stathopoulos Efstathios N

2010-09-01

Full Text Available Abstract Introduction Stress has been shown to be a tumor promoting factor. Both clinical and laboratory studies have shown that chronic stress is associated with tumor growth in several types of cancer. Corticotropin Releasing Factor (CRF is the major hypothalamic mediator of stress, but is also expressed in peripheral tissues. Earlier studies have shown that peripheral CRF affects breast cancer cell proliferation and motility. The aim of the present study was to assess the significance of peripheral CRF on tumor growth as a mediator of the response to stress in vivo. Methods For this purpose we used the 4T1 breast cancer cell line in cell culture and in vivo. Cells were treated with CRF in culture and gene specific arrays were performed to identify genes directly affected by CRF and involved in breast cancer cell growth. To assess the impact of peripheral CRF as a stress mediator in tumor growth, Balb/c mice were orthotopically injected with 4T1 cells in the mammary fat pad to induce breast tumors. Mice were subjected to repetitive immobilization stress as a model of chronic stress. To inhibit the action of CRF, the CRF antagonist antalarmin was injected intraperitoneally. Breast tissue samples were histologically analyzed and assessed for neoangiogenesis. Results Array analysis revealed among other genes that CRF induced the expression of SMAD2 and β-catenin, genes involved in breast cancer cell proliferation and cytoskeletal changes associated with metastasis. Cell transfection and luciferase assays confirmed the role of CRF in WNT- β-catenin signaling. CRF induced 4T1 cell proliferation and augmented the TGF-β action on proliferation confirming its impact on TGFβ/SMAD2 signaling. In addition, CRF promoted actin reorganization and cell migration, suggesting a direct tumor-promoting action. Chronic stress augmented tumor growth in 4T1 breast tumor bearing mice and peripheral administration of the CRF antagonist antalarmin suppressed this

The endophytic fungus Piriformospora indica enhances Arabidopsis thaliana growth and modulates Na + /K + homeostasis under salt stress conditions

KAUST Repository

Abdelaziz, Mohamed Ewis

2017-07-13

The mutualistic, endophytic fungus Piriformospora indica has been shown to confer biotic and abiotic stress tolerance to host plants. In this study, we investigated the impact of P. indica on the growth of Arabidopsis plants under normal and salt stress conditions. Our results demonstrate that P. indica colonization increases plant biomass, lateral roots density, and chlorophyll content under both conditions. Colonization with P. indica under salt stress was accompanied by a lower Na+/K+ ratio and less pronounced accumulation of anthocyanin, compared to control plants. Moreover, P. indica colonized roots under salt stress showed enhanced transcript levels of the genes encoding the high Affinity Potassium Transporter 1 (HKT1) and the inward-rectifying K+ channels KAT1 and KAT2, which play key roles in regulating Na+ and K+ homeostasis. The effect of P. indica colonization on AtHKT1;1 expression was also confirmed in the Arabidopsis line gl1-HKT:AtHKT1;1 that expresses an additional AtHKT1;1 copy driven by the native promoter. Colonization of the gl1-HKT:AtHKT1;1 by P. indica also increased lateral roots density and led to a better Na+/K+ ratio, which may be attributed to the observed increase in KAT1 and KAT2 transcript levels. Our findings demonstrate that P. indica colonization promotes Arabidopsis growth under salt stress conditions and that this effect is likely caused by modulation of the expression levels of the major Na+ and K+ ion channels, which allows establishing a balanced ion homeostasis of Na+/K+ under salt stress conditions.

Fatigue Crack Growth Rate and Stress-Intensity Factor Corrections for Out-of-Plane Crack Growth

Science.gov (United States)

Forth, Scott C.; Herman, Dave J.; James, Mark A.

2003-01-01

Fatigue crack growth rate testing is performed by automated data collection systems that assume straight crack growth in the plane of symmetry and use standard polynomial solutions to compute crack length and stress-intensity factors from compliance or potential drop measurements. Visual measurements used to correct the collected data typically include only the horizontal crack length, which for cracks that propagate out-of-plane, under-estimates the crack growth rates and over-estimates the stress-intensity factors. The authors have devised an approach for correcting both the crack growth rates and stress-intensity factors based on two-dimensional mixed mode-I/II finite element analysis (FEA). The approach is used to correct out-of-plane data for 7050-T7451 and 2025-T6 aluminum alloys. Results indicate the correction process works well for high DeltaK levels but fails to capture the mixed-mode effects at DeltaK levels approaching threshold (da/dN approximately 10(exp -10) meter/cycle).

Exchange-Driven Growth with Birth Rate Less Than Death

International Nuclear Information System (INIS)

Lin Zhenquan; Ye Gaoxiang; Ke Jianhong

2005-01-01

We further study the kinetic behavior of the exchange-driven growth with birth and death for the case of birth rate kernel being less than that of death based on the mean-field theory. The symmetric exchange rate kernel is K(k,j) = K'(k,j) = Ikj υ , and the birth and death rates are proportional to the aggregate's size. The long time asymptotic behavior of the aggregate size distribution a k (t) is found to obey a much unusual scaling law with an exponentially growing scaling function Φ(x) = exp (x).

Intra-connected three-dimensionally isotropic bulk negative index photonic metamaterial

International Nuclear Information System (INIS)

Guney, Durdu; Koschny, Thomas; Soukoulis, Costas

2010-01-01

Isotropic negative index metamaterials (NIMs) are highly desired, particularly for the realization of ultra-high resolution lenses. However, existing isotropic NIMs function only two-dimensionally and cannot be miniaturized beyond microwaves. Direct laser writing processes can be a paradigm shift toward the fabrication of three-dimensionally (3D) isotropic bulk optical metamaterials, but only at the expense of an additional design constraint, namely connectivity. Here, we demonstrate with a proof-of-principle design that the requirement connectivity does not preclude fully isotropic left-handed behavior. This is an important step towards the realization of bulk 3D isotropic NIMs at optical wavelengths.

Prediction of residual stress distributions due to surface machining and welding and crack growth simulation under residual stress distribution

International Nuclear Information System (INIS)

Ihara, Ryohei; Katsuyama, JInya; Onizawa, Kunio; Hashimoto, Tadafumi; Mikami, Yoshiki; Mochizuki, Masahito

2011-01-01

Research highlights: → Residual stress distributions due to welding and machining are evaluated by XRD and FEM. → Residual stress due to machining shows higher tensile stress than welding near the surface. → Crack growth analysis is performed using calculated residual stress. → Crack growth result is affected machining rather than welding. → Machining is an important factor for crack growth. - Abstract: In nuclear power plants, stress corrosion cracking (SCC) has been observed near the weld zone of the core shroud and primary loop recirculation (PLR) pipes made of low-carbon austenitic stainless steel Type 316L. The joining process of pipes usually includes surface machining and welding. Both processes induce residual stresses, and residual stresses are thus important factors in the occurrence and propagation of SCC. In this study, the finite element method (FEM) was used to estimate residual stress distributions generated by butt welding and surface machining. The thermoelastic-plastic analysis was performed for the welding simulation, and the thermo-mechanical coupled analysis based on the Johnson-Cook material model was performed for the surface machining simulation. In addition, a crack growth analysis based on the stress intensity factor (SIF) calculation was performed using the calculated residual stress distributions that are generated by welding and surface machining. The surface machining analysis showed that tensile residual stress due to surface machining only exists approximately 0.2 mm from the machined surface, and the surface residual stress increases with cutting speed. The crack growth analysis showed that the crack depth is affected by both surface machining and welding, and the crack length is more affected by surface machining than by welding.

Diffusion tensor magnetic resonance imaging driven growth modeling for radiotherapy target definition in glioblastoma

DEFF Research Database (Denmark)

Jensen, Morten B; Guldberg, Trine L; Harbøll, Anja

2017-01-01

the microscopic tumor cell spread. Gliomas favor spread along the white matter fiber tracts. Tumor growth models incorporating the MRI diffusion tensors (DTI) allow to account more consistently for the glioma growth. The aim of the study was to investigate the potential of a DTI driven growth model to improve...... target definition in glioblastoma (GBM). MATERIAL AND METHODS: Eleven GBM patients were scanned using T1w, T2w FLAIR, T1w + Gd and DTI. The brain was segmented into white matter, gray matter and cerebrospinal fluid. The Fisher-Kolmogorov growth model was used assuming uniform proliferation...

The relationship between the statistics of open ocean currents and the temporal correlations of the wind stress

International Nuclear Information System (INIS)

Bel, Golan; Ashkenazy, Yosef

2013-01-01

We study the statistics of wind-driven open ocean currents. Using the Ekman layer model for the integrated currents, we investigate analytically and numerically the relationship between the wind-stress distribution and its temporal correlations and the statistics of the open ocean currents. We found that temporally long-range correlated winds result in currents whose statistics is proportional to the wind-stress statistics. On the other hand, short-range correlated winds lead to Gaussian distributions of the current components, regardless of the stationary distribution of the winds, and therefore to a Rayleigh distribution of the current amplitude, if the wind stress is isotropic. We found that the second moment of the current speed exhibits a maximum as a function of the correlation time of the wind stress for a non-zero Coriolis parameter. The results were validated using an oceanic general circulation model. (paper)

Three Dimensional Parametric Analyses of Stress Concentration Factor and Its Mitigation in Isotropic and Orthotropic Plate with Central Circular Hole Under Axial In-Plane Loading

Science.gov (United States)

Nagpal, Shubhrata; Jain, Nitin Kumar; Sanyal, Shubhashis

2016-01-01

The problem of finding the stress concentration factor of a loaded rectangular plate has offered considerably analytical difficulty. The present work focused on understanding of behavior of isotropic and orthotropic plate subjected to static in-plane loading using finite element method. The complete plate model configuration has been analyzed using finite element method based software ANSYS. In the present work two parameters: thickness to width of plate (T/A) and diameter of hole to width of plate (D/A) have been varied for analysis of stress concentration factor (SCF) and its mitigation. Plates of five different materials have been considered for complete analysis to find out the sensitivity of stress concentration factor. The D/A ratio varied from 0.1 to 0.7 for analysis of SCF and varied from 0.1 to 0.5 for analyzing the mitigation of SCF. 0.01, 0.05 and 0.1 are considered as T/A ratio for all the cases. The results are presented in graphical form and discussed. The mitigation in SCF reported is very encouraging. The SCF is more sensitive to D/A ratio as compared to T/A.

Separating the Influence of Environment from Stress Relaxation Effects on Dwell Fatigue Crack Growth

Science.gov (United States)

Telesman, Jack; Gabb, Tim; Ghosn, Louis J.

2016-01-01

Seven different microstructural variations of LSHR were produced by controlling the cooling rate and the subsequent aging and thermal exposure heat treatments. Through cyclic fatigue crack growth testing performed both in air and vacuum, it was established that four out of the seven LSHR heat treatments evaluated, possessed similar intrinsic environmental resistance to cyclic crack growth. For these four heat treatments, it was further shown that the large differences in dwell crack growth behavior which still persisted, were related to their measured stress relaxation behavior. The apparent differences in their dwell crack growth resistance were attributed to the inability of the standard linear elastic fracture mechanics (LEFM) stress intensity parameter to account for visco-plastic behavior. Crack tip stress relaxation controls the magnitude of the remaining local tensile stresses which are directly related to the measured dwell crack growth rates. It was hypothesized that the environmentally weakened grain boundary crack tip regions fail during the dwells when their strength is exceeded by the remaining local crack tip tensile stresses. It was shown that the classical creep crack growth mechanisms such as grain boundary sliding did not contribute to crack growth, but the local visco-plastic behavior still plays a very significant role by determining the crack tip tensile stress field which controls the dwell crack growth behavior. To account for the influence of the visco-plastic behavior on the crack tip stress field, an empirical modification to the LEFM stress intensity parameter, Kmax, was developed by incorporating into the formulation the remaining stress level concept as measured by simple stress relaxation tests. The newly proposed parameter, Ksrf, did an excellent job in correlating the dwell crack growth rates for the four heat treatments which were shown to have similar intrinsic environmental cyclic fatigue crack growth resistance.

The experience of acculturative stress-related growth from immigrants’ perspectives

Science.gov (United States)

Kim, Junhyoung; Kim, Hakjun

2013-01-01

Previous literature has mainly focused on the positive effects of stress associated with disability and illness, called stress-related growth. Little research has explored positive changes as a result of acculturative stress among a group of immigrants. In particular, older Asian immigrants may experience a high level of stress related to acculturation because they may face more challenges to adapt to and navigate a new culture. This study was designed to capture the characteristics of stress-related growth associated with acculturative stress. Using in-depth interviews among 13 older Korean immigrants, three main themes associated with the stress-coping strategies were identified: (a) the development of mental toughness, (b) engagement in meaningful activities, and (c) promotion of cultural understanding. These themes indicate that by following the stressful acculturation process, participants developed a better understanding of the new culture, engaged in various leisure activities, and enhanced mental strength. This finding provides information on how immigrants deal with acculturative stress and have positive psychological changes, which results in a sense of happiness and psychological well-being. PMID:24070225

The experience of acculturative stress-related growth from immigrants’ perspectives

Directory of Open Access Journals (Sweden)

Junhyoung Kim

2013-09-01

Full Text Available Previous literature has mainly focused on the positive effects of stress associated with disability and illness, called stress-related growth. Little research has explored positive changes as a result of acculturative stress among a group of immigrants. In particular, older Asian immigrants may experience a high level of stress related to acculturation because they may face more challenges to adapt to and navigate a new culture. This study was designed to capture the characteristics of stress-related growth associated with acculturative stress. Using in-depth interviews among 13 older Korean immigrants, three main themes associated with the stress-coping strategies were identified: (a the development of mental toughness, (b engagement in meaningful activities, and (c promotion of cultural understanding. These themes indicate that by following the stressful acculturation process, participants developed a better understanding of the new culture, engaged in various leisure activities, and enhanced mental strength. This finding provides information on how immigrants deal with acculturative stress and have positive psychological changes, which results in a sense of happiness and psychological well-being.

The tensile deformation behavior of nuclear-grade isotropic graphite posterior to hydrostatic loading

International Nuclear Information System (INIS)

Yoda, S.; Eto, M.

1983-01-01

The effects of prehydrostatic loading on microstructural changes and tensile deformation behavior of nuclear-grade isotropic graphite have been examined. Scanning electron micrographs show that formation of microcracks associated with delamination between basal planes occurs under hydrostatic loading. Hydrostatic loading on specimens results in the decrease in tensile strength and increase in residual strain generated by the applied tensile stress at various levels, indicating that the graphite material is weakened by hydrostatic loading. A relationship between residual strain and applied tensile stress for graphite hydrostatically-loaded at several pressure levels can be approximately expressed as element of= (AP + B) sigmasup(n) over a wide range hydrostatic pressure, where element of, P and sigma denote residual strain, hydrostatic pressure and applied tensile stress, respectively; A, B and n are constant. The effects of prehydrostatic loading on the tensile stress-strain behavior of the graphite were examined in more detail. The ratio of stress after hydrostatic loading to that before hydrostatic loading on the stress-strain relationship remains almost unchanged irrespective of strain. (orig.)

Irradiation creep and growth of zircaloy-4 tubes

International Nuclear Information System (INIS)

Lansiart, S.; Darchis, L.; Pelchat, J.

1990-01-01

The influence of temperature and fast neutron flux on irradiation creep and growth of stress relieved zircaloy-4 pressurized tubes has been derived from experimental irradiations in NaK, performed up to 2.5 10 25 n.m -2 in the temperature range [280, 350] 0 C. A significant influence of temperature on axial growth has been observed: at 280 0 C the elongation can no longer be expressed as a linear function of fluence as for the 350 0 C irradiation temperature; diametral growth, on the other hand, always appears negligible. Irradiation creep obviously depends on temperature too; the diametral strain (including thermal part) has been modelled as a sum of primary and secondary terms, the former being independent of fluence. For the tubing considered it is observed that the ranking of the different batches, with respect to diametral creep resistance, is the same before and under irradiation. Concerning axial creep strain the stress relieved material behaves as does an isotropic tube. This is not the case of recrystallized zircaloy-4 F, which shows a non negligible axial deformation, related to the diametral creep one, even though this diametral irradiation creep strain is strongly reduced comparatively to that of the stress relieved material. The comparison of the two materials growth rates is more complex since their dependence on temperature and flux differs

Lattice Boltzmann model for three-dimensional decaying homogeneous isotropic turbulence

International Nuclear Information System (INIS)

Xu Hui; Tao Wenquan; Zhang Yan

2009-01-01

We implement a lattice Boltzmann method (LBM) for decaying homogeneous isotropic turbulence based on an analogous Galerkin filter and focus on the fundamental statistical isotropic property. This regularized method is constructed based on orthogonal Hermite polynomial space. For decaying homogeneous isotropic turbulence, this regularized method can simulate the isotropic property very well. Numerical studies demonstrate that the novel regularized LBM is a promising approximation of turbulent fluid flows, which paves the way for coupling various turbulent models with LBM

Crack propagation model taking into consideration the local effect of the deviatoric stress and the non-local effect of the isotropic stress

Czech Academy of Sciences Publication Activity Database

Kafka, Vratislav

2011-01-01

Roč. 56, č. 4 (2011), s. 343-358 ISSN 0001-7043 R&D Projects: GA ČR(CZ) GA103/09/2101 Institutional research plan: CEZ:AV0Z20710524 Keywords : crack propagation * nonlocal effect * deviatoric local effect * isotropic nonlocal Subject RIV: BM - Solid Matter Physics ; Magnetism

The endophytic fungus Piriformospora indica enhances Arabidopsis thaliana growth and modulates Na+/K+ homeostasis under salt stress conditions.

Science.gov (United States)

Abdelaziz, Mohamed E; Kim, Dongjin; Ali, Shawkat; Fedoroff, Nina V; Al-Babili, Salim

2017-10-01

The mutualistic, endophytic fungus Piriformospora indica has been shown to confer biotic and abiotic stress tolerance to host plants. In this study, we investigated the impact of P. indica on the growth of Arabidopsis plants under normal and salt stress conditions. Our results demonstrate that P. indica colonization increases plant biomass, lateral roots density, and chlorophyll content under both conditions. Colonization with P. indica under salt stress was accompanied by a lower Na + /K + ratio and less pronounced accumulation of anthocyanin, compared to control plants. Moreover, P. indica colonized roots under salt stress showed enhanced transcript levels of the genes encoding the high Affinity Potassium Transporter 1 (HKT1) and the inward-rectifying K + channels KAT1 and KAT2, which play key roles in regulating Na + and K + homeostasis. The effect of P. indica colonization on AtHKT1;1 expression was also confirmed in the Arabidopsis line gl1-HKT:AtHKT1;1 that expresses an additional AtHKT1;1 copy driven by the native promoter. Colonization of the gl1-HKT:AtHKT1;1 by P. indica also increased lateral roots density and led to a better Na + /K + ratio, which may be attributed to the observed increase in KAT1 and KAT2 transcript levels. Our findings demonstrate that P. indica colonization promotes Arabidopsis growth under salt stress conditions and that this effect is likely caused by modulation of the expression levels of the major Na + and K + ion channels, which allows establishing a balanced ion homeostasis of Na + /K + under salt stress conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

A local isotropic/global orthotropic finite element technique for modeling the crush of wood in impact limiters

International Nuclear Information System (INIS)

Attaway, S.W.; Yoshimura, H.R.

1989-01-01

Wood is often used as the energy absorbing material in impact limiters, because it begins to crush at low strains, then maintains a near constant crush stress up to nearly 60% volume reduction, and then locks up. Hill (Hill and Joseph, 1974) has performed tests that show that wood is an excellent absorber. However, wood's orthotropic behavior for large crush is difficult to model. In the past, analysts have used isotropic foam-like material models for modeling wood. A new finite element technique is presented in this paper that gives a better model of wood crush than the model currently in use. The orthotropic technique is based on locally isotropic, but globally orthotropic (LIGO) (Attaway, 1988) assumptions in which alternating layers of hard and soft crushable material are used. Each layer is isotropic; however, by alternating hard and soft thin layers, the resulting global behavior is orthotropic. In the remainder of this paper, the new technique for modeling orthotropic wood crush will be presented. The model is used to predict the crush behavior for different grain orientations of balsa wood. As an example problem, an impact limiter containing balsa wood as the crushable material is analyzed using both an isotropic model and the LIGO model

Sudden Relaminarization and Lifetimes in Forced Isotropic Turbulence.

Science.gov (United States)

Linkmann, Moritz F; Morozov, Alexander

2015-09-25

We demonstrate an unexpected connection between isotropic turbulence and wall-bounded shear flows. We perform direct numerical simulations of isotropic turbulence forced at large scales at moderate Reynolds numbers and observe sudden transitions from a chaotic dynamics to a spatially simple flow, analogous to the laminar state in wall bounded shear flows. We find that the survival probabilities of turbulence are exponential and the typical lifetimes increase superexponentially with the Reynolds number. Our results suggest that both isotropic turbulence and wall-bounded shear flows qualitatively share the same phase-space dynamics.

Microscopic origins of anisotropic active stress in motor-driven nematic liquid crystals.

Science.gov (United States)

Blackwell, Robert; Sweezy-Schindler, Oliver; Baldwin, Christopher; Hough, Loren E; Glaser, Matthew A; Betterton, M D

2016-03-14

The cytoskeleton, despite comprising relatively few building blocks, drives an impressive variety of cellular phenomena ranging from cell division to motility. These building blocks include filaments, motor proteins, and static crosslinkers. Outside of cells, these same components can form novel materials exhibiting active flows and nonequilibrium contraction or extension. While dipolar extensile or contractile active stresses are common in nematic motor-filament systems, their microscopic origin remains unclear. Here we study a minimal physical model of filaments, crosslinking motors, and static crosslinkers to dissect the microscopic mechanisms of stress generation in a two-dimensional system of orientationally aligned rods. We demonstrate the essential role of filament steric interactions which have not previously been considered to significantly contribute to active stresses. With this insight, we are able to tune contractile or extensile behavior through the control of motor-driven filament sliding and crosslinking. This work provides a roadmap for engineering stresses in active liquid crystals. The mechanisms we study may help explain why flowing nematic motor-filament mixtures are extensile while gelled systems are contractile.

PWSCC Growth Assessment Model Considering Stress Triaxiality Factor for Primary Alloy 600 Components

Directory of Open Access Journals (Sweden)

Jong-Sung Kim

2016-08-01

Full Text Available We propose a primary water stress corrosion cracking (PWSCC initiation model of Alloy 600 that considers the stress triaxiality factor to apply to finite element analysis. We investigated the correlation between stress triaxiality effects and PWSCC growth behavior in cold-worked Alloy 600 stream generator tubes, and identified an additional stress triaxiality factor that can be added to Garud's PWSCC initiation model. By applying the proposed PWSCC initiation model considering the stress triaxiality factor, PWSCC growth simulations based on the macroscopic phenomenological damage mechanics approach were carried out on the PWSCC growth tests of various cold-worked Alloy 600 steam generator tubes and compact tension specimens. As a result, PWSCC growth behavior results from the finite element prediction are in good agreement with the experimental results.

Gravity-driven groundwater flow and slope failure potential: 1. Elastic effective-stress model

Science.gov (United States)

Iverson, Richard M.; Reid, Mark E.

1992-01-01

Hilly or mountainous topography influences gravity-driven groundwater flow and the consequent distribution of effective stress in shallow subsurface environments. Effective stress, in turn, influences the potential for slope failure. To evaluate these influences, we formulate a two-dimensional, steady state, poroelastic model. The governing equations incorporate groundwater effects as body forces, and they demonstrate that spatially uniform pore pressure changes do not influence effective stresses. We implement the model using two finite element codes. As an illustrative case, we calculate the groundwater flow field, total body force field, and effective stress field in a straight, homogeneous hillslope. The total body force and effective stress fields show that groundwater flow can influence shear stresses as well as effective normal stresses. In most parts of the hillslope, groundwater flow significantly increases the Coulomb failure potential Φ, which we define as the ratio of maximum shear stress to mean effective normal stress. Groundwater flow also shifts the locus of greatest failure potential toward the slope toe. However, the effects of groundwater flow on failure potential are less pronounced than might be anticipated on the basis of a simpler, one-dimensional, limit equilibrium analysis. This is a consequence of continuity, compatibility, and boundary constraints on the two-dimensional flow and stress fields, and it points to important differences between our elastic continuum model and limit equilibrium models commonly used to assess slope stability.

The Effect of Creep on the Residual Stresses Generated During Silicon Sheet Growth

Science.gov (United States)

Hutchinson, J. W.; Lambropoulos, J. C.

1984-01-01

The modeling of stresses generated during the growth of thin silicon sheets at high speeds is an important part of the EFG technique since the experimental measurement of the stresses is difficult and prohibitive. The residual stresses which arise in such a growth process lead to serious problems which make thin Si ribbons unsuitable for fabrication. The constitutive behavior is unrealistic because at high temperature (close to the melting point) Si exhibits considerable creep which significantly relaxes the residual stresses. The effect of creep on the residual stresses generated during the growth of Si sheets at high speeds was addressed and the basic qualitative effect of creep are reported.

Stress strain tensors with their application to x-ray stress measurement

International Nuclear Information System (INIS)

Kurita, Masanori

2015-01-01

This paper describes in detail the method of obtaining the formulas of stress-strain tensor that express the directional dependence of stress-strain, that is, how these values change in response to coordinate transformation, and clarifies the preconditions for supporting both formulas. The two conversion formulas are both the second order of tensor, and the formula of strain tensor not only does not use the relational expression of stress and strain at all, but also is obtained completely independently of the formula of stress tensor. Except for the condition that the strain is very small (elastic deformation) in the conversion formula of strain, both formulas unconditionally come into effect. In other words, both formulas hold true even in the isotropic elastic body or anisotropic elastic body. It was shown that the conversion formula of strain can be derived from the conversion formula of stress using the formula of Hooke for isotropic elastic body. From these three-dimensional expressions, the two-dimensional stress-strain coordinate conversion formula that is used for Mohr's stress-strain circle was derived. It was shown that these formulas hold true for three-dimensional stress condition with stress-strain components in the three-axial direction that are not plane stress nor plane strain condition. In addition, as an application case of this theory, two-dimensional and three-dimensional X-ray stress measurements that are effective for residual stress measurement were shown. (A.O.)

Durability-Based Design Criteria for a Quasi-Isotropic Carbon-Fiber-Reinforced Thermoplastic Automotive Composite

Energy Technology Data Exchange (ETDEWEB)

Naus, Dan J [ORNL; Corum, James [ORNL; Klett, Lynn B [ORNL; Davenport, Mike [ORNL; Battiste, Rick [ORNL; Simpson, Jr., William A [ORNL

2006-04-01

This report provides recommended durability-based design properties and criteria for a quais-isotropic carbon-fiber thermoplastic composite for possible automotive structural applications. The composite consisted of a PolyPhenylene Sulfide (PPS) thermoplastic matrix (Fortron's PPS - Ticona 0214B1 powder) reinforced with 16 plies of carbon-fiber unidirectional tape, [0?/90?/+45?/-45?]2S. The carbon fiber was Hexcel AS-4C and was present in a fiber volume of 53% (60%, by weight). The overall goal of the project, which is sponsored by the U.S. Department of Energy's Office of Freedom Car and Vehicle Technologies and is closely coordinated with the Advanced Composites Consortium, is to develop durability-driven design data and criteria to assure the long-term integrity of carbon-fiber-based composite systems for automotive structural applications. This document is in two parts. Part 1 provides design data and correlations, while Part 2 provides the underlying experimental data and models. The durability issues addressed include the effects of short-time, cyclic, and sustained loadings; temperature; fluid environments; and low-energy impacts (e.g., tool drops and kickups of roadway debris) on deformation, strength, and stiffness. Guidance for design analysis, time-independent and time-dependent allowable stresses, rules for cyclic loadings, and damage-tolerance design guidance are provided.

Isotropic nuclear graphites; the effect of neutron irradiation

International Nuclear Information System (INIS)

Lore, J.; Buscaillon, A.; Mottet, P.; Micaud, G.

1977-01-01

Several isotropic graphites have been manufactured using different forming processes and fillers such as needle coke, regular coke, or pitch coke. Their properties are described in this paper. Specimens of these products have been irradiated in the fast reactor Rapsodie between 400 to 1400 0 C, at fluences up to 1,7.10 21 n.cm -2 PHI.FG. The results show an isotropic behavior under neutron irradiation, but the induced dimensional changes are higher than those of isotropic coke graphites although they are lower than those of conventional extruded graphites made with the same coke

Process for the preparation of isotropic petroleum coke

International Nuclear Information System (INIS)

Kegler, W.H.; Huyser, M.E.

1975-01-01

A description is given of a process for preparing isotropic coke from oil residue charge. It includes blowing air into the residue until it reaches a softening temperature of around 49 to 116 deg C, the deferred coking of the residue having undergone blowing at a temperature of around 247 to 640 deg C, at a pressure between around 1.38x10 5 and 1.72x10 6 Pa, and the recovery of isotropic coke with a thermal expansion coefficient ratio under 1.5 approximately. The isotropic coke is used for preparing hexagonal graphite bars for nuclear reactor moderators [fr

Effects of salt-drought stress on growth and physiobiochemical characteristics of Tamarix chinensis seedlings.

Science.gov (United States)

Liu, Junhua; Xia, Jiangbao; Fang, Yanming; Li, Tian; Liu, Jingtao

2014-01-01

The present study was designed to clarify the effects of salinity and water intercross stresses on the growth and physiobiochemical characteristics of Tamarix chinensis seedlings by pots culture under the artificial simulated conditions. The growth, activities of SOD, POD, and contents of MDA and osmotic adjusting substances of three years old seedlings of T. chinensis were studied under different salt-drought intercross stress. Results showed that the influence of salt stress on growth was greater than drought stress, the oxidation resistance of SOD and POD weakened gradually with salt and drought stresses intensified, and the content of MDA was higher under severe drought and mild and moderate salt stresses. The proline contents increased with the stress intensified but only significantly higher than control under the intercross stresses of severe salt-severe drought. It implied that T. chinensis could improve its stress resistance by adjusted self-growth and physiobiochemical characteristics, and the intercross compatibility of T. chinensis to salt and drought stresses can enhance the salt resistance under appropriate drought stress, but the dominant factors influencing the physiological biochemical characteristics of T. chinensis were various with the changing of salt-drought intercross stresses gradients.

Effects of Salt-Drought Stress on Growth and Physiobiochemical Characteristics of Tamarix chinensis Seedlings

Directory of Open Access Journals (Sweden)

Junhua Liu

2014-01-01

Full Text Available The present study was designed to clarify the effects of salinity and water intercross stresses on the growth and physiobiochemical characteristics of Tamarix chinensis seedlings by pots culture under the artificial simulated conditions. The growth, activities of SOD, POD, and contents of MDA and osmotic adjusting substances of three years old seedlings of T. chinensis were studied under different salt-drought intercross stress. Results showed that the influence of salt stress on growth was greater than drought stress, the oxidation resistance of SOD and POD weakened gradually with salt and drought stresses intensified, and the content of MDA was higher under severe drought and mild and moderate salt stresses. The proline contents increased with the stress intensified but only significantly higher than control under the intercross stresses of severe salt-severe drought. It implied that T. chinensis could improve its stress resistance by adjusted self-growth and physiobiochemical characteristics, and the intercross compatibility of T. chinensis to salt and drought stresses can enhance the salt resistance under appropriate drought stress, but the dominant factors influencing the physiological biochemical characteristics of T. chinensis were various with the changing of salt-drought intercross stresses gradients.

Growth, carcase and meat characteristics of stress susceptible and ...

African Journals Online (AJOL)

Growth, carcase and meat characteristics of stress susceptible and stress resistant. South African Landrace gilts. P.H. Heinze*. Animal and Dairy Science Research Institute, Private Bag X2, Irene, 1675Republic of South Africa. G. Mitchell. Department of Physiology, Medical School, University of the Witwatersrand, York ...

Effect of residual stresses on interface crack growth by void expansion mechanism

DEFF Research Database (Denmark)

Tvergaard, Viggo

2006-01-01

Crack growth along an interface between two adjacent elastic-plastic materials in a layered solid is analysed, using special interface elements to represent the fracture process ahead of the crack-tip. These interface elements account for ductile failure by the nucleation and growth of voids to c....... The results show that the value of the T-stress component in the softer material adjacent to the interface crack plays the dominant role, such that a negative value of this stress component gives a significant increase of the interface fracture toughness.......Crack growth along an interface between two adjacent elastic-plastic materials in a layered solid is analysed, using special interface elements to represent the fracture process ahead of the crack-tip. These interface elements account for ductile failure by the nucleation and growth of voids...... to coalescence. In these elements the stress components normal to the interface and the shear stresses are given by equilibrium with the surrounding material, and the stress component tangential to the interface is determined by the requirement of compatibility with the surrounding material in the tangential...

Intrinsic stress evolution during amorphous oxide film growth on Al surfaces

International Nuclear Information System (INIS)

Flötotto, D.; Wang, Z. M.; Jeurgens, L. P. H.; Mittemeijer, E. J.

2014-01-01

The intrinsic stress evolution during formation of ultrathin amorphous oxide films on Al(111) and Al(100) surfaces by thermal oxidation at room temperature was investigated in real-time by in-situ substrate curvature measurements and detailed atomic-scale microstructural analyses. During thickening of the oxide a considerable amount of growth stresses is generated in, remarkably even amorphous, ultrathin Al 2 O 3 films. The surface orientation-dependent stress evolutions during O adsorption on the bare Al surfaces and during subsequent oxide-film growth can be interpreted as a result of (i) adsorption-induced surface stress changes and (ii) competing processes of free volume generation and structural relaxation, respectively

Numerical study of how creep and progressive stiffening affect the growth stress formation in trees

DEFF Research Database (Denmark)

Ormarsson, Sigurdur; Dahlblom, O.; Johansson, M.

2010-01-01

It is not fully understood how much growth stresses affect the final quality of solid timber products in terms of e.g. shape stability. It is for example difficult to predict the internal growth stress field within the tree stem. Growth stresses are progressively generated during the tree growth...... and they are highly influenced by climate, biologic and material related factors. To increase the knowledge of the stress formation a finite element model was created to study how the growth stresses develop during the tree growth. The model is an axisymmetric general plane strain model where material for all new...... annual rings is progressively added to the tree during the analysis. The material model used is based on the theory of small strains (where strains refer to the undeformed configuration which is good approximation for strains less than 4%) where so-called biological maturation strains (growth...

Influence of Hardening Model on Weld Residual Stress Distribution

Energy Technology Data Exchange (ETDEWEB)

Mullins, Jonathan; Gunnars, Jens (Inspecta Technology AB, Stockholm (Sweden))

2009-06-15

This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

Influence of Hardening Model on Weld Residual Stress Distribution

International Nuclear Information System (INIS)

Mullins, Jonathan; Gunnars, Jens

2009-06-01

This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

Rac1 and Cdc42 GTPases regulate shear stress-driven β-catenin signaling in osteoblasts

International Nuclear Information System (INIS)

Wan, Qiaoqiao; Cho, Eunhye; Yokota, Hiroki; Na, Sungsoo

2013-01-01

Highlights: •Shear stress increased TCF/LEF activity and stimulated β-catenin nuclear localization. •Rac1, Cdc42, and RhoA displayed distinct dynamic activity patterns under flow. •Rac1 and Cdc42, but not RhoA, regulate shear stress-driven TCF/LEF activation. •Cytoskeleton did not significantly affect shear stress-induced TCF/LEF activation. -- Abstract: Beta-catenin-dependent TCF/LEF (T-cell factor/lymphocyte enhancing factor) is known to be mechanosensitive and an important regulator for promoting bone formation. However, the functional connection between TCF/LEF activity and Rho family GTPases is not well understood in osteoblasts. Herein we investigated the molecular mechanisms underlying oscillatory shear stress-induced TCF/LEF activity in MC3T3-E1 osteoblast cells using live cell imaging. We employed fluorescence resonance energy transfer (FRET)-based and green fluorescent protein (GFP)-based biosensors, which allowed us to monitor signal transduction in living cells in real time. Oscillatory (1 Hz) shear stress (10 dynes/cm 2 ) increased TCF/LEF activity and stimulated translocation of β-catenin to the nucleus with the distinct activity patterns of Rac1 and Cdc42. The shear stress-induced TCF/LEF activity was blocked by the inhibition of Rac1 and Cdc42 with their dominant negative mutants or selective drugs, but not by a dominant negative mutant of RhoA. In contrast, constitutively active Rac1 and Cdc42 mutants caused a significant enhancement of TCF/LEF activity. Moreover, activation of Rac1 and Cdc42 increased the basal level of TCF/LEF activity, while their inhibition decreased the basal level. Interestingly, disruption of cytoskeletal structures or inhibition of myosin activity did not significantly affect shear stress-induced TCF/LEF activity. Although Rac1 is reported to be involved in β-catenin in cancer cells, the involvement of Cdc42 in β-catenin signaling in osteoblasts has not been identified. Our findings in this study demonstrate

Rac1 and Cdc42 GTPases regulate shear stress-driven β-catenin signaling in osteoblasts

Energy Technology Data Exchange (ETDEWEB)

Wan, Qiaoqiao; Cho, Eunhye [Department of Biomedical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202 (United States); Yokota, Hiroki [Department of Biomedical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202 (United States); Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202 (United States); Na, Sungsoo, E-mail: sungna@iupui.edu [Department of Biomedical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202 (United States)

2013-04-19

Highlights: •Shear stress increased TCF/LEF activity and stimulated β-catenin nuclear localization. •Rac1, Cdc42, and RhoA displayed distinct dynamic activity patterns under flow. •Rac1 and Cdc42, but not RhoA, regulate shear stress-driven TCF/LEF activation. •Cytoskeleton did not significantly affect shear stress-induced TCF/LEF activation. -- Abstract: Beta-catenin-dependent TCF/LEF (T-cell factor/lymphocyte enhancing factor) is known to be mechanosensitive and an important regulator for promoting bone formation. However, the functional connection between TCF/LEF activity and Rho family GTPases is not well understood in osteoblasts. Herein we investigated the molecular mechanisms underlying oscillatory shear stress-induced TCF/LEF activity in MC3T3-E1 osteoblast cells using live cell imaging. We employed fluorescence resonance energy transfer (FRET)-based and green fluorescent protein (GFP)-based biosensors, which allowed us to monitor signal transduction in living cells in real time. Oscillatory (1 Hz) shear stress (10 dynes/cm{sup 2}) increased TCF/LEF activity and stimulated translocation of β-catenin to the nucleus with the distinct activity patterns of Rac1 and Cdc42. The shear stress-induced TCF/LEF activity was blocked by the inhibition of Rac1 and Cdc42 with their dominant negative mutants or selective drugs, but not by a dominant negative mutant of RhoA. In contrast, constitutively active Rac1 and Cdc42 mutants caused a significant enhancement of TCF/LEF activity. Moreover, activation of Rac1 and Cdc42 increased the basal level of TCF/LEF activity, while their inhibition decreased the basal level. Interestingly, disruption of cytoskeletal structures or inhibition of myosin activity did not significantly affect shear stress-induced TCF/LEF activity. Although Rac1 is reported to be involved in β-catenin in cancer cells, the involvement of Cdc42 in β-catenin signaling in osteoblasts has not been identified. Our findings in this study demonstrate

Finite element study of growth stress formation in wood and related distortion of sawn timber

DEFF Research Database (Denmark)

Ormarsson, Sigurdur; Dahlblom, O.; Johansson, M.

2009-01-01

-related stresses in wood (drying distortions) and growth-related stresses (distortions appearing when logs are split up to timber boards by sawing). To get more knowledge on how these distortions can be reduced in wooden products, there is a need for improved understanding of this material behaviour through good...... numerical tools developed from empirical data. A three-dimensional finite element board distortion model developed by Ormarsson (1999) has been extended to include the influence of growth stresses by incorporating a one-dimensional finite element growth stress model developed here. The growth stress model...... is formulated as an axisymmetric general plane strain model where material for all new annual rings is progressively added to the tree during the analysis. The simulation results presented include how stresses are progressively generated during the tree growth, distortions related to the redistribution...

Residual stresses in high temperature corrosion of pure zirconium using elasto-viscoplastic model: Application to the deflection test in monofacial oxidation

Science.gov (United States)

Fettré, D.; Bouvier, S.; Favergeon, J.; Kurpaska, L.

2015-12-01

The paper is devoted to modeling residual stresses and strains in an oxide film formed during high temperature oxidation. It describes the deflection test in isothermal high-temperature monofacial oxidation (DTMO) of pure zirconium. The model incorporates kinetics and mechanism of oxidation and takes into account elastic, viscoplastic, growth and chemical strains. Different growth strains models are considered, namely, isotropic growth strains given by Pilling-Bedworth ratio, anisotropic growth strains defined by Parise and co-authors and physically based model for growth strain proposed by Clarke. Creep mechanisms based on dislocation slip and core diffusion, are used. A mechanism responsible for through thickness normal stress gradient in the oxide film is proposed. The material parameters are identified using deflection tests under 400 °C, 500 °C and 600 °C. The effect of temperature on creep and stress relaxation is analyzed. Numerical sensitivity study of the DTMO experiment is proposed in order to investigate the effects of the initial foil thickness and platinum coating on the deflection curves.

Isotropic compression of cohesive-frictional particles with rolling resistance

NARCIS (Netherlands)

Luding, Stefan; Benz, Thomas; Nordal, Steinar

2010-01-01

Cohesive-frictional and rough powders are the subject of this study. The behavior under isotropic compression is examined for different material properties involving Coulomb friction, rolling-resistance and contact-adhesion. Under isotropic compression, the density continuously increases according

Growth and stress response mechanisms underlying post-feeding regenerative organ growth in the Burmese python.

Science.gov (United States)

Andrew, Audra L; Perry, Blair W; Card, Daren C; Schield, Drew R; Ruggiero, Robert P; McGaugh, Suzanne E; Choudhary, Amit; Secor, Stephen M; Castoe, Todd A

2017-05-02

Previous studies examining post-feeding organ regeneration in the Burmese python (Python molurus bivittatus) have identified thousands of genes that are significantly differentially regulated during this process. However, substantial gaps remain in our understanding of coherent mechanisms and specific growth pathways that underlie these rapid and extensive shifts in organ form and function. Here we addressed these gaps by comparing gene expression in the Burmese python heart, liver, kidney, and small intestine across pre- and post-feeding time points (fasted, one day post-feeding, and four days post-feeding), and by conducting detailed analyses of molecular pathways and predictions of upstream regulatory molecules across these organ systems. Identified enriched canonical pathways and upstream regulators indicate that while downstream transcriptional responses are fairly tissue specific, a suite of core pathways and upstream regulator molecules are shared among responsive tissues. Pathways such as mTOR signaling, PPAR/LXR/RXR signaling, and NRF2-mediated oxidative stress response are significantly differentially regulated in multiple tissues, indicative of cell growth and proliferation along with coordinated cell-protective stress responses. Upstream regulatory molecule analyses identify multiple growth factors, kinase receptors, and transmembrane receptors, both within individual organs and across separate tissues. Downstream transcription factors MYC and SREBF are induced in all tissues. These results suggest that largely divergent patterns of post-feeding gene regulation across tissues are mediated by a core set of higher-level signaling molecules. Consistent enrichment of the NRF2-mediated oxidative stress response indicates this pathway may be particularly important in mediating cellular stress during such extreme regenerative growth.

Entropy-driven crystal formation on highly strained substrates

KAUST Repository

Savage, John R.

2013-05-20

In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropy-driven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substrate-mediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate.

Impact of plant growth promoting bacillus subtilis on growth and physiological parameters of bassia indica (indian bassia) grown udder salt stress

International Nuclear Information System (INIS)

Abeer, H.; Asma, A. H.; Allah, A.; Qarawi, A.; Shalawi, A.; Dilfuza, E.

2015-01-01

In this study, the role of a salt-tolerant plant growth-promoting bacterium (PGPR), Bacillus subtilis, in the alleviation of salinity stress during the growth of Indian bassia (Bassia indica (Wight) A.J. Scott), was studied under ccontrolled growth chamber conditions following seed inoculation. Physiological parameters such as neutral and phospholipids, fatty acid composition as well as photosynthetic pigments, were investigated. Salinity inhibited shoot and root length by 16 and 42 percentage, dry weight by 37 and 23 percentage respectively and negatively affected physiological parameters. Inoculation of unstressed and salt-stressed Indian bassia with B. subtilis significantly improved root and shoot growth, total lipid content, the phospholipid fraction, photosynthetic pigments (chlorophyll a and b and carotenoid contents) and also increased oleic (C 18:1 ), linoleic (C 18:2 ) and linolenic (C 18:3 ) acids in plant leaves compared to uninoculated plants. The salt-tolerant PGPR, B. subtilis could act synergistically to promote the growth and fitness of Indian bassia plants under salt stress by providing an additional supply of an auxin (IAA) and induce salt stress resistance by reducing stress ethylene levels. (author)

Creep Modeling in a Composite Rotating Disc with Thickness Variation in Presence of Residual Stress

Directory of Open Access Journals (Sweden)

Vandana Gupta

2012-01-01

Full Text Available Steady-state creep response in a rotating disc made of Al-SiC (particle composite having linearly varying thickness has been carried out using isotropic/anisotropic Hoffman yield criterion and results are compared with those using von Mises yield criterion/Hill's criterion ignoring difference in yield stresses. The steady-state creep behavior has been described by Sherby's creep law. The material parameters characterizing difference in yield stresses have been used from the available experimental results in literature. Stress and strain rate distributions developed due to rotation have been calculated. It is concluded that the stress and strain distributions got affected from the thermal residual stress in an isotropic/anisotropic rotating disc, although the effect of residual stress on creep behavior in an anisotropic rotating disc is observed to be lower than those observed in an isotropic disc. Thus, the presence of residual stress in composite rotating disc with varying thickness needs attention for designing a disc.

Three-dimensional modelling of thermal stress in floating zone silicon crystal growth

Science.gov (United States)

Plate, Matiss; Krauze, Armands; Virbulis, Jānis

2018-05-01

During the growth of large diameter silicon single crystals with the industrial floating zone method, undesirable level of thermal stress in the crystal is easily reached due to the inhomogeneous expansion as the crystal cools down. Shapes of the phase boundaries, temperature field and elastic material properties determine the thermal stress distribution in the solid mono crystalline silicon during cylindrical growth. Excessive stress can lead to fracture, generation of dislocations and altered distribution of intrinsic point defects. Although appearance of ridges on the crystal surface is the decisive factor of a dislocation-free growth, the influence of these ridges on the stress field is not completely clear. Here we present the results of thermal stress analysis for 4” and 5” diameter crystals using a quasi-stationary three dimensional mathematical model including the material anisotropy and the presence of experimentally observed ridges which cannot be addressed with axis-symmetric models. The ridge has a local but relatively strong influence on thermal stress therefore its relation to the origin of fracture is hypothesized. In addition, thermal stresses at the crystal rim are found to increase for a particular position of the crystal radiation reflector.

The experience of acculturative stress-related growth from immigrants’ perspectives

OpenAIRE

Kim, Junhyoung; Kim, Hakjun

2013-01-01

Previous literature has mainly focused on the positive effects of stress associated with disability and illness, called stressrelated growth. Little research has explored positive changes as a result of acculturative stress among a group of immigrants. In particular, older Asian immigrants may experience a high level of stress related to acculturation because they may face more challenges to adapt to and navigate a new culture. This study was designed to capture the characteristics of stress-...

Interactively variable isotropic resolution in computed tomography

International Nuclear Information System (INIS)

Lapp, Robert M; Kyriakou, Yiannis; Kachelriess, Marc; Wilharm, Sylvia; Kalender, Willi A

2008-01-01

An individual balancing between spatial resolution and image noise is necessary to fulfil the diagnostic requirements in medical CT imaging. In order to change influencing parameters, such as reconstruction kernel or effective slice thickness, additional raw-data-dependent image reconstructions have to be performed. Therefore, the noise versus resolution trade-off is time consuming and not interactively applicable. Furthermore, isotropic resolution, expressed by an equivalent point spread function (PSF) in every spatial direction, is important for the undistorted visualization and quantitative evaluation of small structures independent of the viewing plane. Theoretically, isotropic resolution can be obtained by matching the in-plane and through-plane resolution with the aforementioned parameters. Practically, however, the user is not assisted in doing so by current reconstruction systems and therefore isotropic resolution is not commonly achieved, in particular not at the desired resolution level. In this paper, an integrated approach is presented for equalizing the in-plane and through-plane spatial resolution by image filtering. The required filter kernels are calculated from previously measured PSFs in x/y- and z-direction. The concepts derived are combined with a variable resolution filtering technique. Both approaches are independent of CT raw data and operate only on reconstructed images which allows for their application in real time. Thereby, the aim of interactively variable, isotropic resolution is achieved. Results were evaluated quantitatively by measuring PSFs and image noise, and qualitatively by comparing the images to direct reconstructions regarded as the gold standard. Filtered images matched direct reconstructions with arbitrary reconstruction kernels with standard deviations in difference images of typically between 1 and 17 HU. Isotropic resolution was achieved within 5% of the selected resolution level. Processing times of 20-100 ms per frame

Contact mechanics and friction for transversely isotropic viscoelastic materials

NARCIS (Netherlands)

Mokhtari, Milad; Schipper, Dirk J.; Vleugels, N.; Noordermeer, Jacobus W.M.; Yoshimoto, S.; Hashimoto, H.

2015-01-01

Transversely isotropic materials are an unique group of materials whose properties are the same along two of the principal axes of a Cartesian coordinate system. Various natural and artificial materials behave effectively as transversely isotropic elastic solids. Several materials can be classified

Formation of stacking faults and the screw dislocation-driven growth: a case study of aluminum nitride nanowires.

Science.gov (United States)

Meng, Fei; Estruga, Marc; Forticaux, Audrey; Morin, Stephen A; Wu, Qiang; Hu, Zheng; Jin, Song

2013-12-23

Stacking faults are an important class of crystal defects commonly observed in nanostructures of close packed crystal structures. They can bridge the transition between hexagonal wurtzite (WZ) and cubic zinc blende (ZB) phases, with the most known example represented by the "nanowire (NW) twinning superlattice". Understanding the formation mechanisms of stacking faults is crucial to better control them and thus enhance the capability of tailoring physical properties of nanomaterials through defect engineering. Here we provide a different perspective to the formation of stacking faults associated with the screw dislocation-driven growth mechanism of nanomaterials. With the use of NWs of WZ aluminum nitride (AlN) grown by a high-temperature nitridation method as the model system, dislocation-driven growth was first confirmed by transmission electron microscopy (TEM). Meanwhile numerous stacking faults and associated partial dislocations were also observed and identified to be the Type I stacking faults and the Frank partial dislocations, respectively, using high-resolution TEM. In contrast, AlN NWs obtained by rapid quenching after growth displayed no stacking faults or partial dislocations; instead many of them had voids that were associated with the dislocation-driven growth. On the basis of these observations, we suggest a formation mechanism of stacking faults that originate from dislocation voids during the cooling process in the syntheses. Similar stacking fault features were also observed in other NWs with WZ structure, such as cadmium sulfide (CdS) and zinc oxide (ZnO).

Stability analysis of non-autonomous reaction-diffusion systems: the effects of growing domains

KAUST Repository

Madzvamuse, Anotida; Gaffney, Eamonn A.; Maini, Philip K.

2009-01-01

By using asymptotic theory, we generalise the Turing diffusively-driven instability conditions for reaction-diffusion systems with slow, isotropic domain growth. There are two fundamental biological differences between the Turing conditions on fixed and growing domains, namely: (i) we need not enforce cross nor pure kinetic conditions and (ii) the restriction to activator-inhibitor kinetics to induce pattern formation on a growing biological system is no longer a requirement. Our theoretical findings are confirmed and reinforced by numerical simulations for the special cases of isotropic linear, exponential and logistic growth profiles. In particular we illustrate an example of a reaction-diffusion system which cannot exhibit a diffusively-driven instability on a fixed domain but is unstable in the presence of slow growth. © Springer-Verlag 2009.

Stability analysis of non-autonomous reaction-diffusion systems: the effects of growing domains

KAUST Repository

Madzvamuse, Anotida

2009-08-29

By using asymptotic theory, we generalise the Turing diffusively-driven instability conditions for reaction-diffusion systems with slow, isotropic domain growth. There are two fundamental biological differences between the Turing conditions on fixed and growing domains, namely: (i) we need not enforce cross nor pure kinetic conditions and (ii) the restriction to activator-inhibitor kinetics to induce pattern formation on a growing biological system is no longer a requirement. Our theoretical findings are confirmed and reinforced by numerical simulations for the special cases of isotropic linear, exponential and logistic growth profiles. In particular we illustrate an example of a reaction-diffusion system which cannot exhibit a diffusively-driven instability on a fixed domain but is unstable in the presence of slow growth. © Springer-Verlag 2009.

Cadmium stress in wheat seedlings: growth, cadmium accumulation and photosynthesis

DEFF Research Database (Denmark)

Ci, Dunwei; Jiang, Dong; Wollenweber, Bernd

2010-01-01

parameters were generally depressed by Cd stress, especially under the high Cd concentrations. Cd concentration and accumulation in both shoots and roots increased with increasing external Cd concentrations. Relationships between corrected parameters of growth, photosynthesis and fluorescence and corrected......Seedlings of wheat (Triticum aestivum L.) cultivars Jing 411, Jinmai 30 and Yangmai 10 were exposed to 0, 10, 20, 30, 40 or 50 μM of CdCl2 in a solution culture experiment. The effects of cadmium (Cd) stress on wheat growth, leaf photon energy conversion, gas exchange, and Cd accumulation in wheat...

A test procedure for determining the influence of stress ratio on fatigue crack growth

Science.gov (United States)

Fitzgerald, J. H.; Wei, R. P.

1974-01-01

A test procedure is outlined by which the rate of fatigue crack growth over a range of stress ratios and stress intensities can be determined expeditiously using a small number of specimens. This procedure was developed to avoid or circumvent the effects of load interactions on fatigue crack growth, and was used to develop data on a mill annealed Ti-6Al-4V alloy plate. Experimental data suggest that the rates of fatigue crack growth among the various stress ratios may be correlated in terms of an effective stress intensity range at given values of K max. This procedure is not to be used, however, for determining the corrosion fatigue crack growth characteristics of alloys when nonsteady-state effects are significant.

Effects of Bicarbonate Limitation and Salinity Stress on Growth and ...

African Journals Online (AJOL)

Photosynthetic organisms rarely experience optimal growth conditions in their natural habitat, and at any given time, two or more physical and chemical variables are likely to be suboptimal. The extreme environment of the Great Salt Plains (GSP) results in low algal biomass, such that natural selection is likely driven by ...

The influence of wall stress on AAA growth and biomarkers

NARCIS (Netherlands)

Speelman, L.; Hellenthal, F.A.M.V.I.; Pulinx, B.; Bosboom, E.M.H.; Breeuwer, M.; Sambeek, M.R.; Vosse, van de F.N.; Jacobs, M.J.H.M.; Wodzig, W.K.W.H.; Schurink, G.W.H.

2010-01-01

Objectives This study investigated the relation between abdominal aortic aneurysm (AAA) wall stress, AAA growth rate and biomarker concentrations. With increasing wall stress, more damage may be caused to the AAA wall, possibly leading to progression of the aneurysm and reflection in up- or

Chronic psychosocial stress disturbs long-bone growth in adolescent mice

Directory of Open Access Journals (Sweden)

Sandra Foertsch

2017-12-01

Full Text Available Although a strong association between psychiatric and somatic disorders is generally accepted, little is known regarding the interrelationship between mental and skeletal health. Although depressive disorders have been shown to be strongly associated with osteoporosis and increased fracture risk, evidence from post-traumatic stress disorder (PTSD patients is less consistent. Therefore, the present study investigated the influence of chronic psychosocial stress on bone using a well-established murine model for PTSD. C57BL/6N mice (7 weeks old were subjected to chronic subordinate colony housing (CSC for 19 days, whereas control mice were singly housed. Anxiety-related behavior was assessed in the open-field/novel-object test, after which the mice were euthanized to assess endocrine and bone parameters. CSC mice exhibited increased anxiety-related behavior in the open-field/novel-object test, increased adrenal and decreased thymus weights, and unaffected plasma morning corticosterone. Microcomputed tomography and histomorphometrical analyses revealed significantly reduced tibia and femur lengths, increased growth-plate thickness and reduced mineral deposition at the growth plate, suggesting disturbed endochondral ossification during long-bone growth. This was associated with reduced Runx2 expression in hypertrophic chondrocytes in the growth plate. Trabecular thicknesses and bone mineral density were significantly increased in CSC compared to singly housed mice. Tyrosine hydroxylase expression was increased in bone marrow cells located at the growth plates of CSC mice, implying that local adrenergic signaling might be involved in the effects of CSC on the skeletal phenotype. In conclusion, chronic psychosocial stress negatively impacts endochondral ossification in the growth plate, affecting both longitudinal and appositional bone growth in adolescent mice.

Model and calculation of in situ stresses in anisotropic formations

Energy Technology Data Exchange (ETDEWEB)

Yuezhi, W.; Zijun, L.; Lixin, H. [Jianghan Petroleum Institute, (China)

1997-08-01

In situ stresses in transversely isotropic material in relation to wellbore stability have been investigated. Equations for three horizontal in- situ stresses and a new formation fracture pressure model were described, and the methodology for determining the elastic parameters of anisotropic rocks in the laboratory was outlined. Results indicate significantly smaller differences between theoretically calculated pressures and actual formation pressures than results obtained by using the isotropic method. Implications for improvements in drilling efficiency were reviewed. 13 refs., 6 figs.

Reciprocal Regulation of the TOR Kinase and ABA Receptor Balances Plant Growth and Stress Response.

Science.gov (United States)

Wang, Pengcheng; Zhao, Yang; Li, Zhongpeng; Hsu, Chuan-Chih; Liu, Xue; Fu, Liwen; Hou, Yueh-Ju; Du, Yanyan; Xie, Shaojun; Zhang, Chunguang; Gao, Jinghui; Cao, Minjie; Huang, Xiaosan; Zhu, Yingfang; Tang, Kai; Wang, Xingang; Tao, W Andy; Xiong, Yan; Zhu, Jian-Kang

2018-01-04

As sessile organisms, plants must adapt to variations in the environment. Environmental stress triggers various responses, including growth inhibition, mediated by the plant hormone abscisic acid (ABA). The mechanisms that integrate stress responses with growth are poorly understood. Here, we discovered that the Target of Rapamycin (TOR) kinase phosphorylates PYL ABA receptors at a conserved serine residue to prevent activation of the stress response in unstressed plants. This phosphorylation disrupts PYL association with ABA and with PP2C phosphatase effectors, leading to inactivation of SnRK2 kinases. Under stress, ABA-activated SnRK2s phosphorylate Raptor, a component of the TOR complex, triggering TOR complex dissociation and inhibition. Thus, TOR signaling represses ABA signaling and stress responses in unstressed conditions, whereas ABA signaling represses TOR signaling and growth during times of stress. Plants utilize this conserved phospho-regulatory feedback mechanism to optimize the balance of growth and stress responses. Copyright © 2017 Elsevier Inc. All rights reserved.

Exploiting the bad eating habits of Ras-driven cancers.

Science.gov (United States)

White, Eileen

2013-10-01

Oncogenic Ras promotes glucose fermentation and glutamine use to supply central carbon metabolism, but how and why have only emerged recently. Ras-mediated metabolic reprogramming generates building blocks for growth and promotes antioxidant defense. To fuel metabolic pathways, Ras scavenges extracellular proteins and lipids. To bolster metabolism and mitigate stress, Ras activates cellular self-cannibalization and recycling of proteins and organelles by autophagy. Targeting these distinct features of Ras-driven cancers provides novel approaches to cancer therapy.

X-ray and Moessbauer investigations of isotropic barium ferrites

International Nuclear Information System (INIS)

Kirichok, P.P.; Pashchenko, V.A.; Dem'yaniv, T.O.; Ryabova, G.N.; Lisovskij, A.M.

1984-01-01

Using the methods of X-ray and γ-resonance spectroscopy the crystal chemical and magnetic structure of isotropic barium hexaferrites is studied. compacting pressure the lattice parameter c of ferrite of the BaOx5.7Fe 2 O 3 is decreased and the diffraction line width on its X-ray p attern is increased. Due to increasing the isoststical compacting pressure quadrupole splitting of the γ-resonance absorption spectrum of 57 Fe nuclei in tetrahedral positions 4f 1 and in positions 2a decreases. The sintering temperature growth leads to increasing the lattice parameter c and diffraction line widths and decreasing the effeutive field values and isomeric s hifts on 57 Fe nuclei. Isostatical compacting pressure does not affect the electron configuration of iron ions

Particle-pair relative velocity measurement in high-Reynolds-number homogeneous and isotropic turbulence using 4-frame particle tracking velocimetry

Science.gov (United States)

Dou, Zhongwang; Ireland, Peter J.; Bragg, Andrew D.; Liang, Zach; Collins, Lance R.; Meng, Hui

2018-02-01

The radial relative velocity (RV) between particles suspended in turbulent flow plays a critical role in droplet collision and growth. We present a simple and accurate approach to RV measurement in isotropic turbulence—planar 4-frame particle tracking velocimetry—using routine PIV hardware. It improves particle positioning and pairing accuracy over the 2-frame holographic approach by de Jong et al. (Int J Multiphas Flow 36:324-332; de Jong et al., Int J Multiphas Flow 36:324-332, 2010) without using high-speed cameras and lasers as in Saw et al. (Phys Fluids 26:111702, 2014). Homogeneous and isotropic turbulent flow ({R_λ }=357) in a new, fan-driven, truncated iscosahedron chamber was laden with either low-Stokes (mean St=0.09, standard deviation 0.05) or high-Stokes aerosols (mean St=3.46, standard deviation 0.57). For comparison, DNS was conducted under similar conditions ({R_λ }=398; St=0.10 and 3.00, respectively). Experimental RV probability density functions (PDF) and mean inward RV agree well with DNS. Mean inward RV increases with St at small particle separations, r, and decreases with St at large r, indicating the dominance of "path-history" and "inertial filtering" effects, respectively. However, at small r, the experimental mean inward RV trends higher than DNS, possibly due to the slight polydispersity of particles and finite light sheet thickness in experiments. To confirm this interpretation, we performed numerical experiments and found that particle polydispersity increases mean inward RV at small r, while finite laser thickness also overestimates mean inward RV at small r, This study demonstrates the feasibility of accurately measuring RV using routine hardware, and verifies, for the first time, the path-history and inertial filtering effects on particle-pair RV at large particle separations experimentally.

Crop yield response to water stress imposed at different growth stages

International Nuclear Information System (INIS)

Iqbal, M.; Mahmood Shah, M.; Wisal, M.

1995-01-01

Potato requires sufficient soil moisture and fertilization to produce high yields but the present water resoures are limited compared to the cultivable land, field experiments were conduced from 1991 to 1995 to study relationship between yield and crop water use as a function of water stress imposed at different growth stages. The irrigation treatments involved application of full and stress watering s selectively at four growth stages : Establishment , Flowering Tuber formation and ripening. In full watering, full water requirements of the crop were met, i.e., ET sub a = ET sub m whereas in stress watering about half the amount of full watering was applied, i.e., ET sub a < ET sub m. Changes in moisture content of the soil pre files after irrigation were monitored with the help of neutron moisture probe in order to compute ET sub a by the water balance method. The results obtained showed that the tuber yield was produced by full watering ( T 1) and the lowest by continuous stress watering (T 2). A plot of relative yield against relative evapotranspiration deficit revealed that ripening was the lest sensitive whereas early development followed by flowering the most sensitive growth stage to water stress. The crop water use efficiencies were generally higher in the treatments where a combination of normal and stress watering was applied compared to where all - normal watering s were applied. The traditional irrigation practice resulted in wasteful water application with relatively lower yields, hence the results from this project will have high value for the farming community to get this higher yields with scarce water resources. The studies with labelled fertilizer showed that planting and earthing - up were equally important growth stages of potato for applying fertilizer for its efficient utilization. 3 figs; 25 tabs; 12 refs (Author)

Visualization and computer graphics on isotropically emissive volumetric displays.

Science.gov (United States)

Mora, Benjamin; Maciejewski, Ross; Chen, Min; Ebert, David S

2009-01-01

The availability of commodity volumetric displays provides ordinary users with a new means of visualizing 3D data. Many of these displays are in the class of isotropically emissive light devices, which are designed to directly illuminate voxels in a 3D frame buffer, producing X-ray-like visualizations. While this technology can offer intuitive insight into a 3D object, the visualizations are perceptually different from what a computer graphics or visualization system would render on a 2D screen. This paper formalizes rendering on isotropically emissive displays and introduces a novel technique that emulates traditional rendering effects on isotropically emissive volumetric displays, delivering results that are much closer to what is traditionally rendered on regular 2D screens. Such a technique can significantly broaden the capability and usage of isotropically emissive volumetric displays. Our method takes a 3D dataset or object as the input, creates an intermediate light field, and outputs a special 3D volume dataset called a lumi-volume. This lumi-volume encodes approximated rendering effects in a form suitable for display with accumulative integrals along unobtrusive rays. When a lumi-volume is fed directly into an isotropically emissive volumetric display, it creates a 3D visualization with surface shading effects that are familiar to the users. The key to this technique is an algorithm for creating a 3D lumi-volume from a 4D light field. In this paper, we discuss a number of technical issues, including transparency effects due to the dimension reduction and sampling rates for light fields and lumi-volumes. We show the effectiveness and usability of this technique with a selection of experimental results captured from an isotropically emissive volumetric display, and we demonstrate its potential capability and scalability with computer-simulated high-resolution results.

Effect of Water Deficit Stress on Peach Growth under Commercial Orchard Management Conditions

Directory of Open Access Journals (Sweden)

M. Rahmati

2015-06-01

Full Text Available In order to study the sensitivity of vegetative growth to water deficit stress of a late-maturing peach (Prunus persica L. cv. Elberta under orchard conditions, an experiment was conducted as randomized complete-block design with three treatments and four repetitions in Shahdiran commercial orchard in Mashhad during 2011. Three irrigation treatments including 360 (low stress, 180 (moderate stress and 90 (severe stress m3ha-1week-1 using a drip irrigation system (minimum stem water potential near harvest: -1.2, -1.5 and -1.7 MPa, respectively from the mid-pit hardening stage (12th of June until harvest (23rd of Sep. applied. Predawn, stem and leaf water potentials, leaf photosynthesis, transpiration, stomatal conductance and leaf temperature, the number of new shoots on fruit bearing shoots and vegetative shoots lengths during growing season as well as leaf area at harvest were measured. The results showed that water deficit stress had negative effects on peach tree water status, thereby resulting in decreased leaf gas exchange and tree vegetative growth. As significant decreased assimilate production of tree was resulted from both decreased leaf assimilation rate (until about 23 % and 50 %, respectively under moderate and severe stress conditions compared to low stress conditions and decreased leaf area of tree (until about 57% and 79%, respectively under moderate and severe stress conditions compared to low stress conditions at harvest. The significant positive correlation between leaf water potential and vegetative growth of peach revealed that shoot growth would decrease by 30% and 50% of maximum at leaf water potential of –1.56 and –2.30 MPa, respectively.

Evaluation of stress corrosion crack growth in BWR piping systems

International Nuclear Information System (INIS)

Kassir, M.; Sharma, S.; Reich, M.; Chang, M.T.

1985-05-01

This report presents the results of a study conducted to evaluate the effects of stress intensity factor and environment on the growth behavior of intergranular stress corrosion cracks in type 304 stainless steel piping systems. Most of the detected cracks are known to be circumferential in shape, and initially started at the inside surface in the heat affected zone near girth welds. These cracks grow both radially in-depth and circumferentially in length and, in extreme cases, may cause leakage in the installation. The propagation of the crack is essentially due to the influence of the following simultaneous factors: (1) the action of applied and residual stress; (2) sensitization of the base metal in the heat affected zone adjacent to girth weld; and (3) the continuous exposure of the material to an aggressive environment of high temperature water containing dissolved oxygen and some levels of impurities. Each of these factors and their effects on the piping systems is discussed in detail in the report. The report also evaluates the time required for hypothetical cracks in BWR pipes to propagate to their critical size. The pertinent times are computed and displayed graphically. Finally, parametric study is performed in order to assess the relative influence and sensitivity of the various input parameters (residual stress, crack growth law, diameter of pipe, initial size of defect, etc.) which have bearing on the growth behavior of the intergranular stress corrosion cracks in type 304 stainless steel. Cracks in large-diameter as well as in small-diameter pipes are considered and analyzed. 27 refs., 25 figs., 10 tabs

Nested structures approach in designing an isotropic negative-index material for infrared

DEFF Research Database (Denmark)

Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei

2009-01-01

We propose a new generic approach for designing isotropic metamaterial with nested cubic structures. As an example, a three-dimensional isotropic unit cell design "Split Cube in Cage" (SCiC) is shown to exhibit an effective negative refractive index on infrared wavelengths. We report on the refra......We propose a new generic approach for designing isotropic metamaterial with nested cubic structures. As an example, a three-dimensional isotropic unit cell design "Split Cube in Cage" (SCiC) is shown to exhibit an effective negative refractive index on infrared wavelengths. We report...

A Benzimidazole Proton Pump Inhibitor Increases Growth and Tolerance to Salt Stress in Tomato

Directory of Open Access Journals (Sweden)

Michael J. Van Oosten

2017-07-01

Full Text Available Pre-treatment of tomato plants with micromolar concentrations of omeprazole (OP, a benzimidazole proton pump inhibitor in mammalian systems, improves plant growth in terms of fresh weight of shoot and roots by 49 and 55% and dry weight by 54 and 105% under salt stress conditions (200 mM NaCl, respectively. Assessment of gas exchange, ion distribution, and gene expression profile in different organs strongly indicates that OP interferes with key components of the stress adaptation machinery, including hormonal control of root development (improving length and branching, protection of the photosynthetic system (improving quantum yield of photosystem II and regulation of ion homeostasis (improving the K+:Na+ ratio in leaves and roots. To our knowledge OP is one of the few known molecules that at micromolar concentrations manifests a dual function as growth enhancer and salt stress protectant. Therefore, OP can be used as new inducer of stress tolerance to better understand molecular and physiological stress adaptation paths in plants and to design new products to improve crop performance under suboptimal growth conditions.Highlight: Omeprazole enhances growth of tomato and increases tolerance to salinity stress through alterations of gene expression and ion uptake and transport.

The effects of anxiety and depression on stress-related growth among Chinese army recruits: Resilience and coping as mediators.

Science.gov (United States)

Yu, Yongju; Peng, Li; Liu, Botao; Liu, Yunbo; Li, Min; Chen, Long; Xie, Junrun; Li, Jing; Li, Jiawen

2016-09-01

Stress-related growth can occur after various traumas or stressful events. In order to investigate how anxiety and depression relate to stress-related growth, this study was conducted with 443 Chinese army recruits who had just finished a 3-month recruit training program. Path analyses revealed that resilience and positive/negative coping partially mediated the effect of anxiety on perceived stress-related growth, while negative coping fully mediated the relationship between depression and perceived stress-related growth. Moreover, positive coping partially carried the influence of resilience on perceived stress-related growth. Anxiety and depression may be potential targets for intervention to enhance the development of stress-related growth among Chinese army recruits. © The Author(s) 2015.

Mechanisms of radiation induced creep and growth

International Nuclear Information System (INIS)

Bullough, R.; Wood, M.H.

1980-01-01

Irradiation creep occurs primarily because the applied stress causes the evolving microstructure to respond in an anisotropic fashion to the interstitial and vacancy fluxes. On the other hand, irradiation growth requires the response to be naturally anisotropic in the absence of applied stress. Four fundamental mechanisms of irradiation creep have been conjectured: stress induced preferred absorption (SIPA) of the point defects on the dislocations, stress induced preferred nucleation (SIPN) of point defects in planar aggregates (edge dislocation loops), stress induced climb and glide (SICG) of the dislocation network and stress induced gas driven interstitial deposition (SIGD). These mechanisms will be briefly outlined and commented upon. The contributions made by these mechanisms to the total strain are not, in general, mutually separable and also depend on the prevailing (and changing) microstructure during irradiation. The fundamental mechanism of irradiation growth will be discussed: it is believed to arise by the preferred condensation of point defects and climb of dislocation loops and network on certain crystallographic planes. The preferred absorption and nucleation is thus a consequence of natural crystallographic anisotropy and not due to any external stresses. Again the effectiveness of this mechanism depends on the prevailing microstructure in the material. In this connection will be particularly drawn to the significance of solute trapping, segregation at grain boundaries, dislocation bias for interstitials and transport parameters for an understanding of irradiation growth in materials like zirconium and its alloys; the relevance of recent simulation studies of growth in such materials using electrons to the growth under neutron irradiation will be discussed in detail and a consistent model of growth in these materials will be presented. (orig.)

The revised geometric measure of entanglement for isotropic state

International Nuclear Information System (INIS)

Cao Ya

2011-01-01

Based on the revised geometric measure of entanglement (RGME), we obtain the analytical expression of isotropic state and generalize to n-particle and d-dimension mixed state case. Meantime, we obtain the relation about isotropic state E-tilde sin 2 (ρ) ≤ E re (ρ). The results indicate RGME is an appropriate measure of entanglement. (authors)

Prolactin, thyrotropin, and growth hormone release during stress associated with parachute jumping.

Science.gov (United States)

Noel, G L; Dimond, R C; Earll, J M; Frantz, A G

1976-05-01

Prolactin, growth hormone, and thyrotropin (TSH) release during the stress of parachute jumping has been evaluated in 14 male subjects. Subjects were studied at several times before and immediately after their first military parachute jump. All three hormones had risen significantly 1 to 14 min after the jump, compared to mean levels measured immediately beforehand. Earlier studies of physical exercise by ourselves and others would suggest that emotional stress played a role in producing changes of this magnitude. We conclude that prolactin, TSH, and growth hormone are released in physiologically significant amounts in association with the stress of parachute jumping.

Bacterial exopolysaccharide and biofilm formation stimulate chickpea growth and soil aggregation under salt stress

Directory of Open Access Journals (Sweden)

Aisha Waheed Qurashi

2012-09-01

Full Text Available To compensate for stress imposed by salinity, biofilm formation and exopolysaccharide production are significant strategies of salt tolerant bacteria to assist metabolism. We hypothesized that two previously isolated salt-tolerant strains Halomonas variabilis (HT1 and Planococcus rifietoensis (RT4 have an ability to improve plant growth, These strains can form biofilm and accumulate exopolysacharides at increasing salt stress. These results showed that bacteria might be involved in developing microbial communities under salt stress and helpful in colonizing of bacterial strains to plant roots and soil particles. Eventually, it can add to the plant growth and soil structure. We investigated the comparative effect of exopolysacharide and biofilm formation in two bacterial strains Halomonas variabilis (HT1 and Planococcus rifietoensis (RT4 in response to varying salt stress. We found that biofilm formation and exopolysaccharide accumulation increased at higher salinity. To check the effect of bacterial inoculation on the plant (Cicer arietinum Var. CM-98 growth and soil aggregation, pot experiment was conducted by growing seedlings under salt stress. Inoculation of both strains increased plant growth at elevated salt stress. Weight of soil aggregates attached with roots and present in soil were added at higher salt concentrations compared to untreated controls. Soil aggregation was higher at plant roots under salinity. These results suggest the feasibility of using above strains in improving plant growth and soil fertility under salinity.

The separate roles of subgrains and forest dislocations in the isotropic hardening of type 304 stainless steel

International Nuclear Information System (INIS)

Kassner, M.E.; Miller, A.K.; Sherby, O.D.

1982-01-01

Tests on 304 stainless steel were conducted involving first warm working in torsion, then cold working in torsion, and finally measurement of the elevated-temperature yield strength in compression. These tests permitted separation of the effects of subgrain size and forest dislocation density on the isotropic part of the flow stress. Forest dislocation strengthening appears to dominate in this material. Th results are best fitted by a root-mean-square summation of strength terms representing the contributions of solutes, forest dislocations, and subgrain boundaries. The same equation successfully predicts the flow stress during elevated-temperature transient deformation (under both constant strain rate and variable strain rate) from the transient dislocation substructure

Effect of salt stress on growth, inorganic ion and proline ...

African Journals Online (AJOL)

The inhibitory effect of salt stress in rice is complex and is one of the main reasons for reduction of plant growth and crop productivity. In the present study, the response of rice callus cultivar Khao Dawk Mali 105 (KDML105), commonly known as Thai jasmine rice, to salt stress was examined. Callus cultures of KDML105 rice ...

Bone growth, limb proportions and non-specific stress in archaeological populations from Croatia.

Science.gov (United States)

Pinhasi, R; Timpson, A; Thomas, M; Slaus, M

2014-01-01

The effect of environmental factors and, in particular, non-specific stress on the growth patterns of limbs and other body dimensions of children from past populations is not well understood. This study assesses whether growth of mediaeval and post-mediaeval children aged between 0-11.5 years from Adriatic (coastal) and continental Croatia varies by region and by the prevalence and type of non-specific stress. Dental ages were estimated using the Moorrees, Fanning and Hunt (MFH) scoring method. Growth of long bone diaphyses (femur, tibia, humerus, radius and ulna) was assessed by using a composite Z-score statistic (CZS). Clavicular length was measured as a proxy for upper trunk width, distal metaphyseal width of the femur was measured as a proxy for body mass and upper and lower intra-limb indices were calculated. Differences between sub-sets sampled by (a) region and (b) active vs healed non-specific stress indicators and (c) intra-limb indices were tested by Mann--Whitney U-tests and Analysis of Covariance (ANCOVA). Adriatic children attained larger dimensions-per-age than continental children. Children with healed stress lesions had larger dimensions-per-age than those with active lesions. No inter-regional difference was found in intra-limb indices. These findings highlight the complexity of growth patterns in past populations and indicate that variation in environmental conditions such as diet and differences in the nature of non-specific stress lesions both exert a significant effect on long bone growth.

Restoration of hippocampal growth hormone reverses stress-induced hippocampal impairment

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Caitlin M. Vander Weele

2013-06-01

Full Text Available Though growth hormone (GH is synthesized by hippocampal neurons, where its expression is influenced by stress exposure, its function is poorly characterized. Here, we show that a regimen of chronic stress that impairs hippocampal function in rats also leads to a profound decrease in hippocampal GH levels. Restoration of hippocampal GH in the dorsal hippocampus via viral-mediated gene transfer completely reversed stress-related impairment of two hippocampus-dependent behavioral tasks, auditory trace fear conditioning and contextual fear conditioning, without affecting hippocampal function in unstressed control rats. GH overexpression reversed stress-induced decrements in both fear acquisition and long-term fear memory. These results suggest that loss of hippocampal GH contributes to hippocampal dysfunction following prolonged stress and demonstrate that restoring hippocampal GH levels following stress can promote stress resilience.

Finite element approximation of a new variational principle for compressible and incompressible linear isotropic elasticity

International Nuclear Information System (INIS)

Franca, L.P.; Stenberg, R.

1989-06-01

Stability conditions are described to analyze a variational formulation emanating from a variational principle for linear isotropic elasticity. The variational principle is based on four dependent variables (namely, the strain tensor, augmented stress, pressure and displacement) and is shown to be valid for any compressibility including the incompressible limit. An improved convergence error analysis is established for a Galerkin-least-squares method based upon these four variables. The analysis presented establishes convergence for a wide choice of combinations of finite element interpolations. (author) [pt

Effects of stacking sequence on fracture mechanisms in quasi-isotropic Carbon/epoxy laminates under tensile loading

International Nuclear Information System (INIS)

Hessabi, Z. R.; Majidi, B.; Aghazadeh, J.

2006-01-01

The progress of damage in quasi-isotropic carbon/epoxy laminates under tensile loading has been Investigated microscopically. One significant mode of failure in laminated composites is delamination initiating at free edges. The interlaminar stress in the boundary ply along the free edges of a laminated composite is the main factor to cause delamination. The laminate stacking sequence affects the interlaminar stress distribution and consequently may change the mode of failure. It is of design importance to determine a suitable criterion based on stress analysis to obtain the best stacking sequence. In the present work, tensile properties of six samples with different stacking sequences have been examined. Results showed that stress analysis at distance very close to the free edges is a suitable criterion to predict the initiation of delamination and the stacking sequence of [90/45/0/-45] s , has the highest strength among the others. Furthermore finite element analysis showed that the adjacent ±45 plies cause premature delamination during tensile loading

Stress anisotropy and stress gradient in magnetron sputtered films with different deposition geometries

International Nuclear Information System (INIS)

Zhao, Z.B.; Yalisove, S.M.; Bilello, J.C.

2006-01-01

Mo films were deposited via magnetron sputtering with two different deposition geometries: dynamic deposition (moving substrate) and static deposition (fixed substrate). The residual stress and structural morphologies of these films were investigated, with particular focus on in-plane anisotropy of the biaxial stress and stress gradient across the film thickness. The results revealed that the Mo films developed distinct states of residual stress, which depended on both deposition geometry and film thickness. With the dynamic geometry, the Mo films generally exhibited anisotropic stress. Both the degree of anisotropy and the magnitude of stress varied as functions of film thickness. The variation of stress was linked to the evolution of anisotropic microstructures in the films. The Mo films from the static geometry developed isotropic residual stress, which was more compressive and noticeably larger in magnitude than that of the Mo films from the dynamic geometry. Aside from these disparities, the two types of Mo films (i.e., anisotropic and isotropic) exhibited notably similar trends of stress variation with film thickness. Depth profiling indicated the presence of large stress gradients for the Mo films, irrespective of the deposition geometries. This observation seems to be consistent with the premise that Mo films develop a zone T structure, which is inherently inhomogeneous along the film thickness. Moreover, the largest stress gradient for both types of deposition geometries arises at roughly the same film depth (∼240 nm from substrate), where the stresses sharply transits from highly compressive to less compressive or even tensile. This appears to correspond to the boundary region that separates two distinct stages of microstructural evolution, a feature unique to zone T-type structure

Application of hydraulic fracturing to determine virgin in situ stress state around Waste Isolation Pilot Plant - in situ measurements

International Nuclear Information System (INIS)

Wawersik, W.R.; Stone, C.M.

1985-10-01

Hydraulic fracturing tests were carried out in horizontal drillholes in rock salt in the Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM. It was determined that the virgin in situ stress field is isotropic or nearly isotropic. The inferred magnitude of the isotropic in situ stress falls between bounds of 14.28 MPa and 17.9 MPa for the average breakdown/reopening pressures and driving pressures. The best estimate from instantaneous shut-in pressures is 16.61 MPa. Given some uncertainties about the interpretation of hydraulic fracturing data in salt, all of the foregoing values are in acceptable agreement with an average calculated isotropic in situ stress of 14.9 MPa at an average depth of 657 m below surface. Interpretations of breakdown and reopening pressures are based on finite element analyses of the relaxed stress field around a borehole in salt. This stress field varies little between approximately 50 and 200 days after drilling. The finite element analyses were also used to interpret the observed stable pressure-time signatures with little or no pressure drops during primary breakdown of the salt formation. The conclusion about the isotropic nature of the virgin in situ stress field is supported by observations of the induced fracture patterns. The report includes a comparison of the hydrofrac data in the WIPP with the published results of hydraulic fracturing tests in salt at three other locations. 75 refs., 21 figs., 4 tabs

Stress corrosion and corrosion fatigue crack growth monitoring in metals

International Nuclear Information System (INIS)

Senadheera, T.; Shipilov, S.A.

2003-01-01

Environmentally assisted cracking (including stress corrosion cracking and corrosion fatigue) is one of the major causes for materials failure in a wide variety of industries. It is extremely important to understand the mechanism(s) of environmentally assisted crack propagation in structural materials so as to choose correctly from among the various possibilities-alloying elements, heat treatment of steels, parameters of cathodic protection, and inhibitors-to prevent in-service failures due to stress corrosion cracking and corrosion fatigue. An important step towards understanding the mechanism of environmentally assisted crack propagation is designing a testing machine for crack growth monitoring and that simultaneously provides measurement of electrochemical parameters. In the present paper, a direct current (DC) potential drop method for monitoring crack propagation in metals and a testing machine that uses this method and allows for measuring electrochemical parameters during stress corrosion and corrosion fatigue crack growth are described. (author)

Plant Growth-Promoting Rhizobacteria Enhance Salinity Stress Tolerance in Okra through ROS-Scavenging Enzymes

Directory of Open Access Journals (Sweden)

Sheikh Hasna Habib

2016-01-01

Full Text Available Salinity is a major environmental stress that limits crop production worldwide. In this study, we characterized plant growth-promoting rhizobacteria (PGPR containing 1-aminocyclopropane-1-carboxylate (ACC deaminase and examined their effect on salinity stress tolerance in okra through the induction of ROS-scavenging enzyme activity. PGPR inoculated okra plants exhibited higher germination percentage, growth parameters, and chlorophyll content than control plants. Increased antioxidant enzyme activities (SOD, APX, and CAT and upregulation of ROS pathway genes (CAT, APX, GR, and DHAR were observed in PGPR inoculated okra plants under salinity stress. With some exceptions, inoculation with Enterobacter sp. UPMR18 had a significant influence on all tested parameters under salt stress, as compared to other treatments. Thus, the ACC deaminase-containing PGPR isolate Enterobacter sp. UPMR18 could be an effective bioresource for enhancing salt tolerance and growth of okra plants under salinity stress.

Drought stress, growth and nonstructural carbohydrate dynamics of pine trees in a semi-arid forest.

Science.gov (United States)

Klein, Tamir; Hoch, Günter; Yakir, Dan; Körner, Christian

2014-09-01

In trees exposed to prolonged drought, both carbon uptake (C source) and growth (C sink) typically decrease. This correlation raises two important questions: (i) to what degree is tree growth limited by C availability; and (ii) is growth limited by concurrent C storage (e.g., as nonstructural carbohydrates, NSC)? To test the relationships between drought, growth and C reserves, we monitored the changes in NSC levels and constructed stem growth chronologies of mature Pinus halepensis Miller trees of three drought stress levels growing in Yatir forest, Israel, at the dry distribution limit of forests. Moderately stressed and stressed trees showed 34 and 14% of the stem growth, 71 and 31% of the sap flux density, and 79 and 66% of the final needle length of healthy trees in 2012. In spite of these large reductions in growth and sap flow, both starch and soluble sugar concentrations in the branches of these trees were similar in all trees throughout the dry season (2-4% dry mass). At the same time, the root starch concentrations of moderately stressed and stressed trees were 47 and 58% of those of healthy trees, but never drought there is more than one way for a tree to maintain a positive C balance. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Effect of drought stress on growth, yield and seed quality of tomato (lycopersicon esculentum L.)

International Nuclear Information System (INIS)

Pervez, M.A.; Ayub, C.M.

2009-01-01

Plant growth is seriously affected by abiotic stresses such as drought, salinity or temperature. Drought is one of the most important limiting factors for agricultural crops and vegetable production in particular all around the world. Drought stress during vegetative or early reproductive growth usually reduces yield by reducing the number of seeds, seed size and seed quality. To assess the effect of drought stress on seed yield, seed quality and growth of tomato, the experiment was conducted in green house in plastic pots at Pen-y-Fridd field station, University of Wales, Bangor, U.K. during 2003-2004. Tomato cv. Moneymaker was used as a test crop. There were four treatments i.e. early stress (when first truss has set the fruits), middle stress (when fruits in first truss were fully matured and started changing their colour), late stress (when fruits on first truss were ripened fully), whereas in control no stress was imposed. Analysis of data regarding various attributes (fruit weight and shoot dry weight per plant, number of seeds per fruit, total number of seeds and seed weight per plant and vigour of seed) showed that drought stress had non-significant effect on vigour, quality and yield of tomato seed. Plant height, number of leaves and number of fruits per plant showed significant results toward drought stress signifying drought effects on growth of tomato. (author)

EFFECT OF DROUGHT STRESS ON EARLY GROWTH OF ...

African Journals Online (AJOL)

Ridwan

ABSTRACT. Drought and high temperatures are said to have triggered increased tree mortality and could be linked to the menace of climate change. This research therefore investigated the effect of drought stress on early growth of Adansonia digitata where seedlings were exposed to different watering frequencies (Once ...

Stable solutions of inflation driven by vector fields

Energy Technology Data Exchange (ETDEWEB)

Emami, Razieh [Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Mukohyama, Shinji [Center for Gravitational Physics, Yukawa Institute for Theoretical Physics, Kyoto University, 606-8502, Kyoto (Japan); Namba, Ryo [Department of Physics, McGill University, Montréal, QC, H3A 2T8 (Canada); Zhang, Ying-li, E-mail: iasraziehm@ust.hk, E-mail: shinji.mukohyama@yukawa.kyoto-u.ac.jp, E-mail: namba@physics.mcgill.ca, E-mail: yingli@bao.ac.cn [National Astronomy Observatories, Chinese Academy of Science, Beijing 100012 (China)

2017-03-01

Many models of inflation driven by vector fields alone have been known to be plagued by pathological behaviors, namely ghost and/or gradient instabilities. In this work, we seek a new class of vector-driven inflationary models that evade all of the mentioned instabilities. We build our analysis on the Generalized Proca Theory with an extension to three vector fields to realize isotropic expansion. We obtain the conditions required for quasi de-Sitter solutions to be an attractor analogous to the standard slow-roll one and those for their stability at the level of linearized perturbations. Identifying the remedy to the existing unstable models, we provide a simple example and explicitly show its stability. This significantly broadens our knowledge on vector inflationary scenarios, reviving potential phenomenological interests for this class of models.

Stable solutions of inflation driven by vector fields

International Nuclear Information System (INIS)

Emami, Razieh; Mukohyama, Shinji; Namba, Ryo; Zhang, Ying-li

2017-01-01

Many models of inflation driven by vector fields alone have been known to be plagued by pathological behaviors, namely ghost and/or gradient instabilities. In this work, we seek a new class of vector-driven inflationary models that evade all of the mentioned instabilities. We build our analysis on the Generalized Proca Theory with an extension to three vector fields to realize isotropic expansion. We obtain the conditions required for quasi de-Sitter solutions to be an attractor analogous to the standard slow-roll one and those for their stability at the level of linearized perturbations. Identifying the remedy to the existing unstable models, we provide a simple example and explicitly show its stability. This significantly broadens our knowledge on vector inflationary scenarios, reviving potential phenomenological interests for this class of models.

Functional evolution of leptin of Ochotona curzoniae in adaptive thermogenesis driven by cold environmental stress.

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Jie Yang

Full Text Available BACKGROUND: Environmental stress can accelerate the directional selection and evolutionary rate of specific stress-response proteins to bring about new or altered functions, enhancing an organism's fitness to challenging environments. Plateau pika (Ochotona curzoniae, an endemic and keystone species on Qinghai-Tibetan Plateau, is a high hypoxia and low temperature tolerant mammal with high resting metabolic rate and non-shivering thermogenesis to cope in this harsh plateau environment. Leptin is a key hormone related to how these animals regulate energy homeostasis. Previous molecular evolutionary analysis helped to generate the hypothesis that adaptive evolution of plateau pika leptin may be driven by cold stress. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis, recombinant pika leptin was first purified. The thermogenic characteristics of C57BL/6J mice injected with pika leptin under warm (23±1°C and cold (5±1°C acclimation is investigated. Expression levels of genes regulating adaptive thermogenesis in brown adipose tissue and the hypothalamus are compared between pika leptin and human leptin treatment, suggesting that pika leptin has adaptively and functionally evolved. Our results show that pika leptin regulates energy homeostasis via reduced food intake and increased energy expenditure under both warm and cold conditions. Compared with human leptin, pika leptin demonstrates a superior induced capacity for adaptive thermogenesis, which is reflected in a more enhanced β-oxidation, mitochondrial biogenesis and heat production. Moreover, leptin treatment combined with cold stimulation has a significant synergistic effect on adaptive thermogenesis, more so than is observed with a single cold exposure or single leptin treatment. CONCLUSIONS/SIGNIFICANCE: These findings support the hypothesis that cold stress has driven the functional evolution of plateau pika leptin as an ecological adaptation to the Qinghai-Tibetan Plateau.

Three-dimensional coupled thermoelastodynamic stress and flux induced wave propagation for isotropic half-space with scalar potential functions

Science.gov (United States)

Hayati, Yazdan; Eskandari-Ghadi, Morteza

2018-02-01

An asymmetric three-dimensional thermoelastodynamic wave propagation with scalar potential functions is presented for an isotropic half-space, in such a way that the wave may be originated from an arbitrary either traction or heat flux applied on a patch at the free surface of the half-space. The displacements, stresses and temperature are presented within the framework of Biot's coupled thermoelasticity formulations. By employing a complete representation for the displacement and temperature fields in terms of two scalar potential functions, the governing equations of coupled thermoelasticity are uncoupled into a sixth- and a second-order partial differential equation in cylindrical coordinate system. By virtue of Fourier expansion and Hankel integral transforms, the angular and radial variables are suppressed respectively, and a 6{th}- and a 2{nd}-order ordinary differential equation in terms of depth are received, which are solved readily, from which the displacement, stresses and temperature fields are derived in transformed space by satisfying both the regularity and boundary conditions. By applying the inverse Hankel integral transforms, the displacements and temperature are numerically evaluated to determine the solutions in the real space. The numerical evaluations are done for three specific cases of vertical and horizontal time-harmonic patch traction and a constant heat flux passing through a circular disc on the surface of the half-space. It has been previously proved that the potential functions used in this paper are applicable from elastostatics to thermoelastodynamics. Thus, the analytical solutions presented in this paper are verified by comparing the results of this study with two specific problems reported in the literature, which are an elastodynamic problem and an axisymmetric quasi-static thermoelastic problem. To show the accuracy of numerical results, the solution of this study is also compared with the solution for elastodynamics exists in

Growth recovery in newly arrived international adoptees in Italy: relation to parenting stress.

Science.gov (United States)

Canzi, Elena; Rosnati, Rosa; Miller, Laurie C

2018-04-12

Following initial adversities, most internationally adopted children arrive with significant growth delays. Post-placement recovery has been widely documented, but research about risk or protective factors is still limited. Even less is known about the relationship between growth recovery and the quality of the family environment. 28 children in 26 adoptive families were involved in this longitudinal study. A comprehensive evaluation (including anthropometry, cognitive assessment [using the Leiter International Performance Scale-Revised], and completion by both parents of the Parenting Stress Index - Short Form) was done at arrival of the child, and 1 year later. Results evidenced that on arrival nearly half of children had growth measurements in the normal range. All the children showed a significant recovery in height and weight at 6 and 12 months post-placement. Initial and follow up growth measurements correlated strongly. Growth recovery was related to the age of the child at adoption, the proportion of time the child had resided in institutional care, as well as parenting stress. Results suggested that the higher the parenting stress experienced the less improvements occurred in children: for mothers for height and weight, for fathers for all the growth indicators. Results suggested the critical importance of family factor in influencing children's growth recovery.

On a hierarchical construction of the anisotropic LTSN solution from the isotropic LTSN solution

International Nuclear Information System (INIS)

Foletto, Taline; Segatto, Cynthia F.; Bodmann, Bardo E.; Vilhena, Marco T.

2015-01-01

In this work, we present a recursive scheme targeting the hierarchical construction of anisotropic LTS N solution from the isotropic LTS N solution. The main idea relies in the decomposition of the associated LTS N anisotropic matrix as a sum of two matrices in which one matrix contains the isotropic and the other anisotropic part of the problem. The matrix containing the anisotropic part is considered as the source of the isotropic problem. The solution of this problem is made by the decomposition of the angular flux as a truncated series of intermediate functions and replace in the isotropic equation. After the replacement of these into the split isotropic equation, we construct a set of isotropic recursive problems, that are readily solved by the classic LTS N isotropic method. We apply this methodology to solve problems considering homogeneous and heterogeneous anisotropic regions. Numerical results are presented and compared with the classical LTS N anisotropic solution. (author)

On the solid stress in a fluidized bed

International Nuclear Information System (INIS)

Qassim, R.Y.; Souza, R. de.

1980-09-01

The existence of solid stress in an incipiently gas-fluidized bed is shown by experimental measurement. This stress is shown to have two components: an isotropic pressure and an extra stress which depends on the relative velocity between fluid and solid. Both the solid pressure and the solid extra stress component are found to be of the same order of magnitude as the fluid pressure. (Author) [pt

A crack opening stress equation for fatigue crack growth

Science.gov (United States)

Newman, J. C., Jr.

1984-01-01

A general crack opening stress equation is presented which may be used to correlate crack growth rate data for various materials and thicknesses, under constant amplitude loading, once the proper constraint factor has been determined. The constraint factor, alpha, is a constraint on tensile yielding; the material yields when the stress is equal to the product of alpha and sigma. Delta-K (LEFM) is plotted against rate for 2024-T3 aluminum alloy specimens 2.3 mm thick at various stress ratios. Delta-K sub eff was plotted against rate for the same data with alpha = 1.8; the rates correlate well within a factor of two.

Transgenic tobacco plants constitutively expressing peanut BTF3 exhibit increased growth and tolerance to abiotic stresses.

Science.gov (United States)

Pruthvi, V; Rama, N; Parvathi, M S; Nataraja, K N

2017-05-01

Abiotic stresses limit crop growth and productivity worldwide. Cellular tolerance, an important abiotic stress adaptive trait, involves coordinated activities of multiple proteins linked to signalling cascades, transcriptional regulation and other diverse processes. Basal transcriptional machinery is considered to be critical for maintaining transcription under stressful conditions. From this context, discovery of novel basal transcription regulators from stress adapted crops like peanut would be useful for improving tolerance of sensitive plant types. In this study, we prospected a basal transcription factor, BTF3 from peanut (Arachis hypogaea L) and studied its relevance in stress acclimation by over expression in tobacco. AhBTF3 was induced under PEG-, NaCl-, and methyl viologen-induced stresses in peanut. The constitutive expression of AhBTF3 in tobacco increased plant growth under non stress condition. The transgenic plants exhibited superior phenotype compared to wild type under mannitol- and NaCl-induced stresses at seedling level. The enhanced cellular tolerance of transgenic plants was evidenced by higher cell membrane stability, reactive oxygen species (ROS) scavenging activity, seedling survival and vigour than wild type. The transgenic lines showed better in vitro regeneration capacity on growth media supplemented with NaCl than wild type. Superior phenotype of transgenic plants under osmotic and salinity stresses seems to be due to constitutive activation of genes of multiple pathways linked to growth and stress adaptation. The study demonstrated that AhBTF3 is a positive regulator of growth and stress acclimation and hence can be considered as a potential candidate gene for crop improvement towards stress adaptation. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

Circular High-Q Resonating Isotropic Strain Sensors with Large Shift of Resonance Frequency under Stress

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Hilmi Volkan Demir

2009-11-01

Full Text Available We present circular architecture bioimplant strain sensors that facilitate a strong resonance frequency shift with mechanical deformation. The clinical application area of these sensors is for in vivo assessment of bone fractures. Using a rectangular geometry, we obtain a resonance shift of 330 MHz for a single device and 170 MHz for its triplet configuration (with three side-by-side resonators on chip under an applied load of 3,920 N. Using the same device parameters with a circular isotropic architecture, we achieve a resonance frequency shift of 500 MHz for the single device and 260 MHz for its triplet configuration, demonstrating substantially increased sensitivity.

Predictors of Stress-Related Growth in Parents of Children with ADHD

Science.gov (United States)

Finzi-Dottan, Ricky; Triwitz, Yael Segal; Golubchik, Pavel

2011-01-01

This study was designed to investigate stress-related growth in 71 parents of children with ADHD, compared with 80 parents of non-clinical children. Adopting Tedeschi and Calhoun's (2004) theoretical framework for predicting personal growth, the study investigated the contribution of emotional intelligence (individual characteristics), social…

A priori study of subgrid-scale flux of a passive scalar in isotropic homogeneous turbulence

International Nuclear Information System (INIS)

Chumakov, Sergei

2008-01-01

We perform a direct numerical simulation (DNS) of forced homogeneous isotropic turbulence with a passive scalar that is forced by mean gradient. The DNS data are used to study the properties of subgrid-scale flux of a passive scalar in the framework of large eddy simulation (LES), such as alignment trends between the flux, resolved, and subgrid-scale flow structures. It is shown that the direction of the flux is strongly coupled with the subgrid-scale stress axes rather than the resolved flow quantities such as strain, vorticity, or scalar gradient. We derive an approximate transport equation for the subgrid-scale flux of a scalar and look at the relative importance of the terms in the transport equation. A particular form of LES tensor-viscosity model for the scalar flux is investigated, which includes the subgrid-scale stress. Effect of different models for the subgrid-scale stress on the model for the subgrid-scale flux is studied.

A priori study of subgrid-scale flux of a passive scalar in isotropic homogeneous turbulence.

Science.gov (United States)

Chumakov, Sergei G

2008-09-01

We perform a direct numerical simulation (DNS) of forced homogeneous isotropic turbulence with a passive scalar that is forced by mean gradient. The DNS data are used to study the properties of subgrid-scale flux of a passive scalar in the framework of large eddy simulation (LES), such as alignment trends between the flux, resolved, and subgrid-scale flow structures. It is shown that the direction of the flux is strongly coupled with the subgrid-scale stress axes rather than the resolved flow quantities such as strain, vorticity, or scalar gradient. We derive an approximate transport equation for the subgrid-scale flux of a scalar and look at the relative importance of the terms in the transport equation. A particular form of LES tensor-viscosity model for the scalar flux is investigated, which includes the subgrid-scale stress. Effect of different models for the subgrid-scale stress on the model for the subgrid-scale flux is studied.

Data-Driven Problems in Elasticity

Science.gov (United States)

Conti, S.; Müller, S.; Ortiz, M.

2018-01-01

We consider a new class of problems in elasticity, referred to as Data-Driven problems, defined on the space of strain-stress field pairs, or phase space. The problem consists of minimizing the distance between a given material data set and the subspace of compatible strain fields and stress fields in equilibrium. We find that the classical solutions are recovered in the case of linear elasticity. We identify conditions for convergence of Data-Driven solutions corresponding to sequences of approximating material data sets. Specialization to constant material data set sequences in turn establishes an appropriate notion of relaxation. We find that relaxation within this Data-Driven framework is fundamentally different from the classical relaxation of energy functions. For instance, we show that in the Data-Driven framework the relaxation of a bistable material leads to material data sets that are not graphs.

REDUCED ISOTROPIC CRYSTAL MODEL WITH RESPECT TO THE FOURTH-ORDER ELASTIC MODULI

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O. Burlayenko

2018-04-01

Full Text Available Using a reduced isotropic crystal model the relationship between the fourth-order elastic moduli of an isotropic medium and the independent components of the fourth-order elastic moduli tensor of real crystals of various crystal systems is found. To calculate the coefficients of these relations, computer algebra systems Redberry and Mathematica for working with high order tensors in the symbolic and explicit form were used, in light of the overly complex computation. In an isotropic medium, there are four independent fourth order elastic moduli. This is due to the presence of four invariants for an eighth-rank tensor in the three-dimensional space, that has symmetries over the pairs of indices. As an example, the moduli of elasticity of an isotropic medium corresponding to certain crystals of cubic system are given (LiF, NaCl, MgO, CaF2. From the obtained results it can be seen that the reduced isotropic crystal model can be most effectively applied to high-symmetry crystal systems.

On the skew-symmetric character of the couple-stress tensor

OpenAIRE

Hadjesfandiari, Ali R.

2013-01-01

In this paper, the skew-symmetric character of the couple-stress tensor is established as the result of arguments from tensor analysis. Consequently, the couple-stress pseudo-tensor has a true vectorial character. The fundamental step in this development is that the isotropic couple-stress tensor cannot exist.

A finite-density calculation of the surface tension of isotropic-nematic interfaces

International Nuclear Information System (INIS)

Moore, B.G.; McMullen, W.E.

1992-01-01

The surface tension of the isotropic-nematic interface in a fluid of intermediate-sized hard particles is studied and calculated. The transition from isotropic to nematic is fixed to occur in a continuous fashion by varying the biaxiality of the model particles. A reversal in the preferred orientation of the bulk nematic relative to the isotropic-nematic interface suggests an oblique orientation of the bulk nematic. 32 refs., 8 figs

Increased classical endoplasmic reticulum stress is sufficient to reduce chondrocyte proliferation rate in the growth plate and decrease bone growth.

Directory of Open Access Journals (Sweden)

Louise H W Kung

Full Text Available Mutations in genes encoding cartilage oligomeric matrix protein and matrilin-3 cause a spectrum of chondrodysplasias called multiple epiphyseal dysplasia (MED and pseudoachondroplasia (PSACH. The majority of these diseases feature classical endoplasmic reticulum (ER stress and activation of the unfolded protein response (UPR as a result of misfolding of the mutant protein. However, the importance and the pathological contribution of ER stress in the disease pathogenesis are unknown. The aim of this study was to investigate the generic role of ER stress and the UPR in the pathogenesis of these diseases. A transgenic mouse line (ColIITgcog was generated using the collagen II promoter to drive expression of an ER stress-inducing protein (Tgcog in chondrocytes. The skeletal and histological phenotypes of these ColIITgcog mice were characterised. The expression and intracellular retention of Tgcog induced ER stress and activated the UPR as characterised by increased BiP expression, phosphorylation of eIF2α and spliced Xbp1. ColIITgcog mice exhibited decreased long bone growth and decreased chondrocyte proliferation rate. However, there was no disruption of chondrocyte morphology or growth plate architecture and perturbations in apoptosis were not apparent. Our data demonstrate that the targeted induction of ER stress in chondrocytes was sufficient to reduce the rate of bone growth, a key clinical feature associated with MED and PSACH, in the absence of any growth plate dysplasia. This study establishes that classical ER stress is a pathogenic factor that contributes to the disease mechanism of MED and PSACH. However, not all the pathological features of MED and PSACH were recapitulated, suggesting that a combination of intra- and extra-cellular factors are likely to be responsible for the disease pathology as a whole.

A methodology for interpretation of overcoring stress measurements in anisotropic rock

International Nuclear Information System (INIS)

Hakala, M.; Sjoeberg, J.

2006-11-01

The in situ state of stress is an important parameter for the design of a repository for final disposal of spent nuclear fuel. This report presents work conducted to improve the quality of overcoring stress measurements, focused on the interpretation of overcoring rock stress measurements when accounting for possible anisotropic behavior of the rock. The work comprised: (i) development/upgrading of a computer code for calculating stresses from overcoring strains for anisotropic materials and for a general overcoring probe configuration (up to six strain rosettes with six gauges each), (ii) development of a computer code for determining elastic constants for transversely isotropic rocks from biaxial testing, and (iii) analysis of case studies of selected overcoring measurements in both isotropic and anisotropic rocks from the Posiva and SKB sites in Finland and Sweden, respectively. The work was principally limited to transversely isotropic materials, although the stress calculation code is applicable also to orthotropic materials. The developed computer codes have been geared to work primarily with the Borre and CSIRO HI three-dimensional overcoring measurement probes. Application of the codes to selected case studies, showed that the developed tools were practical and useful for interpreting overcoring stress measurements conducted in anisotropic rock. A quantitative assessment of the effects of anisotropy may thus be obtained, which provides increased reliability in the stress data. Potential gaps in existing data and/or understanding can also be identified. (orig.)

EFFECT OF TWO COMMERCIAL ANTI-STRESS DRUGS ON THE GROWTH OF ARTIFICIALLY INDUCED STRESSED BROILERS

Directory of Open Access Journals (Sweden)

A. Memon, N. A. Qureshi, Mol. Rind, A.A. Solangi and G. Memono1

2001-01-01

Full Text Available The Study was carried out to evaluate the efficacy of anti-stress commercial drugs (Vitasol Super and Vitamionic-33 on growth of stressed broilers, at the Poultry Experimental Station, Sindh Agriculture University Tandojam during August-September, 1998. A-day old 150 chicks were equally housed in three groups that were A, Band C. In group “A” five grams Vitasol Super was added in 40 litres of drinking water, while in group “B” one gram of Vitaminic-33 was added in three litres of drinking water. Group “C” was kept as control, where no anti-stress drug was supplemented in water. Results revealed highly significant difference among weight gain of broilers fed on ration supplemented with different anti-stress drugs. Average weight gain of all groups A, Band C were 1796.50, 1899.80 and 1760.52 gms, respectively. Average feed consumption of different groups were 3830, 3859 and 3818 gms, respectively. Average feed conversion ratio of different groups A, Band C was 2.14, 2.03 and 2.17, respectively. The average dressing percentage of difference groups were 62.10, 64.52 and 61.60. Highly significant difference was observed in weight of internal organs of different groups. The average per kilogram of broilers profit of different groups were Rs. 10.49, 13.81 and 10.95, respectively. The birds of group B, which was, earned maximum profit given Vitaminic-33 (anti-stress drug. It was concluded that anti-stress vitamin (Vitaminic-33 at the rate of 5grams/40 litres of water ad libitum can be successfully used for better growth of broilers

Thermal and Driven Stochastic Growth of Langmuir Waves in the Solar Wind and Earth's Foreshock

Science.gov (United States)

Cairns, Iver H.; Robinson, P. A.; Anderson, R. R.

2000-01-01

Statistical distributions of Langmuir wave fields in the solar wind and the edge of Earth's foreshock are analyzed and compared with predictions for stochastic growth theory (SGT). SGT quantitatively explains the solar wind, edge, and deep foreshock data as pure thermal waves, driven thermal waves subject to net linear growth and stochastic effects, and as waves in a pure SGT state, respectively, plus radiation near the plasma frequency f(sub p). These changes are interpreted in terms of spatial variations in the beam instability's growth rate and evolution toward a pure SGT state. SGT analyses of field distributions are shown to provide a viable alternative to thermal noise spectroscopy for wave instruments with coarse frequency resolution, and to separate f(sub p) radiation from Langmuir waves.

ER stress-induced protein, VIGG, disturbs plant cation homeostasis, which is correlated with growth retardation and robustness to ER stress

International Nuclear Information System (INIS)

Katoh, Hironori; Fujita, Keiko; Takuhara, Yuki; Ogawa, Atsushi; Suzuki, Shunji

2011-01-01

Highlights: → VIGG is an ER stress-induced protein in plant. → We examine the characteristics of VIGG-overexpressing Arabidopsis plants. → VIGG-overexpressing plants reveal growth retardation and robustness to ER stress. → VIGG disturbs cation homeostasis in plant. -- Abstract: VIGG is a putative endoplasmic reticulum (ER) resident protein induced by virus infection and ER stress, and is correlated with fruit quality in grapevine. The present study was undertaken to determine the biological function of VIGG in grapevine. Experiments using fluorescent protein-VIGG fusion protein demonstrated that VIGG is localized in ER and the ER targeting sequence is in the N-terminus. The overexpression of VIGG in Arabidopsis plant led to growth retardation. The rosette leaves of VIGG-overexpressing plants were smaller than those of the control plants and rolled at 42 days after seeding. VIGG-overexpressing plants revealed robustness to ER stress as well as the low expression of ER stress marker proteins, such as the luminal binding proteins. These characteristics of VIGG-overexpressing plants were supported by a microarray experiment that demonstrated the disruption of genes related to ER stress response and flowering, as well as cation mobility, in the plants. Finally, cation homeostasis in the plants was disturbed by the overexpression of VIGG. Taken together, these results suggest that VIGG may disturb cation homeostasis in plant, which is correlated with the robustness to ER stress and growth retardation.

ER stress-induced protein, VIGG, disturbs plant cation homeostasis, which is correlated with growth retardation and robustness to ER stress

Energy Technology Data Exchange (ETDEWEB)

Katoh, Hironori; Fujita, Keiko; Takuhara, Yuki [Laboratory of Fruit Genetic Engineering, The Institute of Enology and Viticulture, University of Yamanashi, Kofu, Yamanashi 400-0005 (Japan); Ogawa, Atsushi [Department of Biological Production, Akita Prefectural University, Shimosinjyou-nakano 241-438, Akita 010-0195 (Japan); Suzuki, Shunji, E-mail: suzukis@yamanashi.ac.jp [Laboratory of Fruit Genetic Engineering, The Institute of Enology and Viticulture, University of Yamanashi, Kofu, Yamanashi 400-0005 (Japan)

2011-02-18

Highlights: {yields} VIGG is an ER stress-induced protein in plant. {yields} We examine the characteristics of VIGG-overexpressing Arabidopsis plants. {yields} VIGG-overexpressing plants reveal growth retardation and robustness to ER stress. {yields} VIGG disturbs cation homeostasis in plant. -- Abstract: VIGG is a putative endoplasmic reticulum (ER) resident protein induced by virus infection and ER stress, and is correlated with fruit quality in grapevine. The present study was undertaken to determine the biological function of VIGG in grapevine. Experiments using fluorescent protein-VIGG fusion protein demonstrated that VIGG is localized in ER and the ER targeting sequence is in the N-terminus. The overexpression of VIGG in Arabidopsis plant led to growth retardation. The rosette leaves of VIGG-overexpressing plants were smaller than those of the control plants and rolled at 42 days after seeding. VIGG-overexpressing plants revealed robustness to ER stress as well as the low expression of ER stress marker proteins, such as the luminal binding proteins. These characteristics of VIGG-overexpressing plants were supported by a microarray experiment that demonstrated the disruption of genes related to ER stress response and flowering, as well as cation mobility, in the plants. Finally, cation homeostasis in the plants was disturbed by the overexpression of VIGG. Taken together, these results suggest that VIGG may disturb cation homeostasis in plant, which is correlated with the robustness to ER stress and growth retardation.

Comparison of three-dimensional isotropic and conventional MR arthrography with respect to the diagnosis of rotator cuff and labral lesions: Focus on isotropic fat-suppressed proton density and VIBE sequences

International Nuclear Information System (INIS)

Park, S.Y.; Lee, I.S.; Park, S.K.; Cheon, S.J.; Ahn, J.M.; Song, J.W.

2014-01-01

Aim: To compare the diagnostic accuracies of three-dimensional (3D) isotropic magnetic resonance arthrography (MRA) using fat-suppressed proton density (PD) or volume interpolated breath-hold examination (VIBE) sequences with that of conventional MRA for the diagnosis of rotator cuff and labral lesions. Materials and methods: Eighty-six patients who underwent arthroscopic surgery were included. 3D isotropic sequences were performed in the axial plane using fat-suppressed PD (group A) in 53 patients and using VIBE (group B) in 33 patients. Reformatted images were obtained corresponding to conventional images, and evaluated for the presence of labral and rotator cuff lesions using conventional and 3D isotropic sequences. The diagnostic performances of each sequence were determined using arthroscopic findings as the standard. Results: Good to excellent interobserver agreements were obtained for both 3D isotropic sequences for the evaluation of rotator cuff and labral lesions. Excellent agreement was found between two-dimensional (2D) and 3D isotropic MRA, except for supraspinatus tendon (SST) tears by both readers and for subscapularis tendon (SCT) tears by reader 2 in group B. 2D MRA and 3D isotropic sequences had high diagnostic performances for rotator and labral tears, and the difference between the two imaging methods was insignificant. Conclusions: The diagnostic performances of 3D isotropic VIBE and PD sequences were similar to those of 2D MRA

Universal stress proteins are important for oxidative and acid stress resistance and growth of Listeria monocytogenes EGD-e in vitro and in vivo.

Directory of Open Access Journals (Sweden)

Christa Seifart Gomes

Full Text Available BACKGROUND: Pathogenic bacteria maintain a multifaceted apparatus to resist damage caused by external stimuli. As part of this, the universal stress protein A (UspA and its homologues, initially discovered in Escherichia coli K-12 were shown to possess an important role in stress resistance and growth in several bacterial species. METHODS AND FINDINGS: We conducted a study to assess the role of three homologous proteins containing the UspA domain in the facultative intracellular human pathogen Listeria monocytogenes under different stress conditions. The growth properties of three UspA deletion mutants (Δlmo0515, Δlmo1580 and Δlmo2673 were examined either following challenge with a sublethal concentration of hydrogen peroxide or under acidic conditions. We also examined their ability for intracellular survival within murine macrophages. Virulence and growth of usp mutants were further characterized in invertebrate and vertebrate infection models. Tolerance to acidic stress was clearly reduced in Δlmo1580 and Δlmo0515, while oxidative stress dramatically diminished growth in all mutants. Survival within macrophages was significantly decreased in Δlmo1580 and Δlmo2673 as compared to the wild-type strain. Viability of infected Galleria mellonella larvae was markedly higher when injected with Δlmo1580 or Δlmo2673 as compared to wild-type strain inoculation, indicating impaired virulence of bacteria lacking these usp genes. Finally, we observed severely restricted growth of all chromosomal deletion mutants in mice livers and spleens as compared to the load of wild-type bacteria following infection. CONCLUSION: This work provides distinct evidence that universal stress proteins are strongly involved in listerial stress response and survival under both in vitro and in vivo growth conditions.

PGPR Potentially Improve Growth of Tomato Plants in Salt-Stressed Environment

Directory of Open Access Journals (Sweden)

Mariam Zameer

2016-06-01

Full Text Available Plant growth promoting rhizobacteria are colonized bacterial species that has the capability to improve plant growth by certain direct and indirect means. Environmental factors including both biotic and abiotic stresses are among the major constraints to crop production. In the current study, the effectiveness of microbial inoculation (Bacillus megaterium for enhancing growth of tomato plants under salt stress conditions has been investigated. Significant improvement in shoot length, root length, leaf surface area, number of leaves, total weight of the shoot and root was observed in tomato plants inoculated with zm7 strain post 15 and 30 days of its application. Zm3, Zm4 and Zm6 strains improved the morphological parameters as compared to the control. Chlorophyll content a, chlorophyll content b, anthocyanin and carotenoid content was increased in tomato plants subjected to Zm7, Zm6 and Zm4 strains. Stress responsive genes; metallothionein and glutothion gene were found highly expressed in Zm7 treated tomato plants as compared to control, untreated plants. Significant correlation of anthocyanin was reported for carotenoids, chlorophyll-b, shoot weight and total weight of seedling while carotenoids were significantly correlated with leaf surface area, root length, chlorophyll-b and anthocyanin. Overall, Zm7 strain proved best for improvement in salt stressed plant’s morphological parameters and biochemical parameters as compared to control, untreated plants.

Critical-like features of stress response in frictional packings

International Nuclear Information System (INIS)

Cakir, Abdullah; Silbert, Leonardo E

2015-01-01

The mechanical response of static, unconfined, overcompressed face centred cubic, granular arrays is studied using large-scale, discrete element method simulations. Specifically, the stress response due to the application of a localised force perturbation—the Green function technique—is obtained in granular packings generated over several orders of magnitude in both the particle friction coefficient and the applied forcing. We observe crossover behaviour in the mechanical state of the system characterised by the changing nature of the resulting stress response. The transition between anisotropic and isotropic stress response exhibits critical-like features through the identification of a diverging length scale that distinguishes the spatial extent of anisotropic regions from those that display isotropic behaviour. A multidimensional phase diagram is constructed that parameterises the response of the system due to changing friction and force perturbations. (paper)

Salt and alkali stresses reduction in wheat by plant growth promoting haloalkaliphilic bacteria

OpenAIRE

Torbaghan, Mehrnoush Eskandari; Lakzian, Amir; Astaraei, Ali Reza; Fotovat, Amir; Besharati, Hossein

2017-01-01

Haloalkaliphilic bacteria have plant growth promoting characteristics that can be used to deal with different environmental stresses. To study the effect of haloalkaliphilic bacteria to reduce salinity and alkalinity stress in wheat, 48 isolates were isolated and grouped into halophiles, alkaliphiles and haloalkaliphiles based on growth characteristics. The ammonia, 3-indole acetic acid and ACC (1-aminocyclopropane-1-carboxylate) deaminase production were studied. Wheat yield was evaluated in...

Isotropic Negative Thermal Expansion Metamaterials.

Science.gov (United States)

Wu, Lingling; Li, Bo; Zhou, Ji

2016-07-13

Negative thermal expansion materials are important and desirable in science and engineering applications. However, natural materials with isotropic negative thermal expansion are rare and usually unsatisfied in performance. Here, we propose a novel method to achieve two- and three-dimensional negative thermal expansion metamaterials via antichiral structures. The two-dimensional metamaterial is constructed with unit cells that combine bimaterial strips and antichiral structures, while the three-dimensional metamaterial is fabricated by a multimaterial 3D printing process. Both experimental and simulation results display isotropic negative thermal expansion property of the samples. The effective coefficient of negative thermal expansion of the proposed models is demonstrated to be dependent on the difference between the thermal expansion coefficient of the component materials, as well as on the circular node radius and the ligament length in the antichiral structures. The measured value of the linear negative thermal expansion coefficient of the three-dimensional sample is among the largest achieved in experiments to date. Our findings provide an easy and practical approach to obtaining materials with tunable negative thermal expansion on any scale.

Diffusion tensor magnetic resonance imaging driven growth modeling for radiotherapy target definition in glioblastoma.

Science.gov (United States)

Jensen, Morten B; Guldberg, Trine L; Harbøll, Anja; Lukacova, Slávka; Kallehauge, Jesper F

2017-11-01

The clinical target volume (CTV) in radiotherapy is routinely based on gadolinium contrast enhanced T1 weighted (T1w + Gd) and T2 weighted fluid attenuated inversion recovery (T2w FLAIR) magnetic resonance imaging (MRI) sequences which have been shown to over- or underestimate the microscopic tumor cell spread. Gliomas favor spread along the white matter fiber tracts. Tumor growth models incorporating the MRI diffusion tensors (DTI) allow to account more consistently for the glioma growth. The aim of the study was to investigate the potential of a DTI driven growth model to improve target definition in glioblastoma (GBM). Eleven GBM patients were scanned using T1w, T2w FLAIR, T1w + Gd and DTI. The brain was segmented into white matter, gray matter and cerebrospinal fluid. The Fisher-Kolmogorov growth model was used assuming uniform proliferation and a difference in white and gray matter diffusion of a ratio of 10. The tensor directionality was tested using an anisotropy weighting parameter set to zero (γ0) and twenty (γ20). The volumetric comparison was performed using Hausdorff distance, Dice similarity coefficient (DSC) and surface area. The median of the standard CTV (CTVstandard) was 180 cm 3 . The median surface area of CTVstandard was 211 cm 2 . The median surface area of respective CTV γ0 and CTV γ20 significantly increased to 338 and 376 cm 2 , respectively. The Hausdorff distance was greater than zero and significantly increased for both CTV γ0 and CTV γ20 with respective median of 18.7 and 25.2 mm. The DSC for both CTV γ0 and CTV γ20 were significantly below one with respective median of 0.74 and 0.72, which means that 74 and 72% of CTVstandard were included in CTV γ0 and CTV γ20, respectively. DTI driven growth models result in CTVs with a significantly increased surface area, a significantly increased Hausdorff distance and decreased overlap between the standard and model derived volume.

Effects of drought stress on growth, solute accumulation and membrane stability of leafy vegetable, huckleberry (Solanum scabrum Mill.).

Science.gov (United States)

Assaha, Dekoum Vincent Marius; Liu, Liyun; Ueda, Akihiro; Nagaoka, Toshinori; Saneoka, Hirofumi

2016-01-01

The present study sought to investigate the factors implicated in growth impairment of huckleberry (a leafy vegetable) under water stress conditions. To achieve this, seedlings of plant were subjected to control, mild stress and severe stress conditions for 30 days. Plant growth, plant water relation, gas exchange, oxidative stress damage, electrolyte leakage rate, mineral content and osmolyte accumulation were measured. Water deficit markedly decreased leaf, stem and root growth. Leaf photosynthetic rate was tremendously reduced by decrease in stomatal conductance under stress conditions. Malondialdehyde (MDA) content markedly increased under mild (82%) and severe (131%) stress conditions, while electrolyte leakage rate (ELR) increased by 59% under mild stress and 3-fold under severe stress. Mineral content in leafwas high in stressed plants, while proline content markedly increased under mild stress (12-fold) and severe stress (15-fold), with corresponding decrease in osmotic potential at full turgor and an increase in osmotic adjustment. These results suggest that maintenance of high mineral content and osmotic adjustment constitute important adaptations in huckleberry under water deficit conditions and that growth depression under drought stress would be mainly caused by increased electrolyte leakage resulting from membrane damage induced by oxidative stress.

Directional statistics-based reflectance model for isotropic bidirectional reflectance distribution functions.

Science.gov (United States)

Nishino, Ko; Lombardi, Stephen

2011-01-01

We introduce a novel parametric bidirectional reflectance distribution function (BRDF) model that can accurately encode a wide variety of real-world isotropic BRDFs with a small number of parameters. The key observation we make is that a BRDF may be viewed as a statistical distribution on a unit hemisphere. We derive a novel directional statistics distribution, which we refer to as the hemispherical exponential power distribution, and model real-world isotropic BRDFs as mixtures of it. We derive a canonical probabilistic method for estimating the parameters, including the number of components, of this novel directional statistics BRDF model. We show that the model captures the full spectrum of real-world isotropic BRDFs with high accuracy, but a small footprint. We also demonstrate the advantages of the novel BRDF model by showing its use for reflection component separation and for exploring the space of isotropic BRDFs.

Role of high-temperature creep stress in thermally grown oxide growth of thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Ogawa, K.; Nakao, Y.; Seo, D.; Miura, H.; Shoji, T. [Tohoku Univ., Sendai (Japan)

2008-07-01

Thermally grown oxide (TGO) grows at the top / bond coating interface of the thermal barrier coating (TBC) in service. It is supposed that the failures of the TBC occur due to thermal stress and the decrease of adhesive strength caused by the TGO growth. Recently, large local stress has been found to change both the diffusion constant of oxygen through an existing oxide and the rate of chemical reaction at the oxide / oxidized material interface. Since high thermal stress occurs in the TBC, the volume expansion of the newly grown oxide, and centrifugal force, the growth rate of the TGO may change depending on not only temperature but also the stress. The aim of this study is to make clear the influence of stress on the growth rate of the TGO quantitatively. As a result, the thickness of the TGO clearly increases with increase of the amplitude of the applied stress and temperature. The increase rate of the TGO thickness is approximately 23% when the applied stress is increased from 0 to 205 MPa at 900 C, and approximately 29% when the stress is increased from 0 to 150 MPa at 950 C. (orig.)

Effect of salt stress on growth and contents of organic and inorganic ...

African Journals Online (AJOL)

Effect of salt stress on growth and contents of organic and inorganic compounds in noni ( Morinda citrifolia L.) ... seedlings at 1, 10, 20, 30 and 40 days of salt stress in a 5 x 2 completely randomized experimental design. ... from 32 Countries:.

Ellipsoidal basis for isotropic oscillator

International Nuclear Information System (INIS)

Kallies, W.; Lukac, I.; Pogosyan, G.S.; Sisakyan, A.N.

1994-01-01

The solutions of the Schroedinger equation are derived for the isotropic oscillator potential in the ellipsoidal coordinate system. The explicit expression is obtained for the ellipsoidal integrals of motion through the components of the orbital moment and Demkov's tensor. The explicit form of the ellipsoidal basis is given for the lowest quantum numbers. 10 refs.; 1 tab. (author)

Constitutive modeling of void-growth-based tensile ductile failures with stress triaxiality effects

KAUST Repository

Mora Cordova, Angel

2014-07-01

In most metals and alloys, the evolution of voids has been generally recognized as the basic failure mechanism. Furthermore, stress triaxiality has been found to influence void growth dramatically. Besides strain intensity, it is understood to be the most important factor that controls the initiation of ductile fracture. We include sensitivity of stress triaxiality in a variational porous plasticity model, which was originally derived from hydrostatic expansion. Under loading conditions rather than hydrostatic deformation, we allow the critical pressure for voids to be exceeded so that the growth due to plasticity becomes dependent on the stress triaxiality. The limitations of the spherical void growth assumption are investigated. Our improved constitutive model is validated through good agreements with experimental data. Its capacity for reproducing realistic failure patterns is also indicated by a numerical simulation of a compact tensile (CT) test. © 2013 Elsevier Inc.

Soft network materials with isotropic negative Poisson's ratios over large strains.

Science.gov (United States)

Liu, Jianxing; Zhang, Yihui

2018-01-31

Auxetic materials with negative Poisson's ratios have important applications across a broad range of engineering areas, such as biomedical devices, aerospace engineering and automotive engineering. A variety of design strategies have been developed to achieve artificial auxetic materials with controllable responses in the Poisson's ratio. The development of designs that can offer isotropic negative Poisson's ratios over large strains can open up new opportunities in emerging biomedical applications, which, however, remains a challenge. Here, we introduce deterministic routes to soft architected materials that can be tailored precisely to yield the values of Poisson's ratio in the range from -1 to 1, in an isotropic manner, with a tunable strain range from 0% to ∼90%. The designs rely on a network construction in a periodic lattice topology, which incorporates zigzag microstructures as building blocks to connect lattice nodes. Combined experimental and theoretical studies on broad classes of network topologies illustrate the wide-ranging utility of these concepts. Quantitative mechanics modeling under both infinitesimal and finite deformations allows the development of a rigorous design algorithm that determines the necessary network geometries to yield target Poisson ratios over desired strain ranges. Demonstrative examples in artificial skin with both the negative Poisson's ratio and the nonlinear stress-strain curve precisely matching those of the cat's skin and in unusual cylindrical structures with engineered Poisson effect and shape memory effect suggest potential applications of these network materials.

Long-term salt stress responsive growth, carbohydrate metabolism ...

African Journals Online (AJOL)

We investigated the long-term responses of tobacco tissues to salt stress, with a particular interest for growth parameters, proline (Pro) accumulation, and carbohydrate metabolism. Exposure of 17-day-old tobacco plants to 0.2 M NaCl was followed by a higher decrease in dry matter in roots than shoots with a decrease of ...

Impact of water stress on growth reserves and re-growth of Themeda ...

African Journals Online (AJOL)

Four water stress treatments (T1 = 0–25%, T2 = 25–50%, T3 = 50–75% and T4 = 75–100% depletion of plant available water) were applied to the plants in pots in a glasshouse. The TNCC declined drastically after severe defoliation over all the water treatments (P < 0.05), in all the plant parts (P < 0.05) and for all the growth ...

Effects of microstructure and residual stress on fatigue crack growth of stainless steel narrow gap welds

International Nuclear Information System (INIS)

Jang, Changheui; Cho, Pyung-Yeon; Kim, Minu; Oh, Seung-Jin; Yang, Jun-Seog

2010-01-01

The effects of weld microstructure and residual stress distribution on the fatigue crack growth rate of stainless steel narrow gap welds were investigated. Stainless steel pipes were joined by the automated narrow gap welding process typical to nuclear piping systems. The weld fusion zone showed cellular-dendritic structures with ferrite islands in an austenitic matrix. Residual stress analysis showed large tensile stress in the inner-weld region and compressive stress in the middle of the weld. Tensile properties and the fatigue crack growth rate were measured along and across the weld thickness direction. Tensile tests showed higher strength in the weld fusion zone and the heat affected zone compared to the base metal. Within the weld fusion zone, strength was greater in the inner weld than outer weld region. Fatigue crack growth rates were several times greater in the inner weld than the outer weld region. The spatial variation of the mechanical properties is discussed in view of weld microstructure, especially dendrite orientation, and in view of the residual stress variation within the weld fusion zone. It is thought that the higher crack growth rate in the inner-weld region could be related to the large tensile residual stress despite the tortuous fatigue crack growth path.

Measurement of stress using synchrotron x-rays

International Nuclear Information System (INIS)

Weidner, Donald J; Li Li

2006-01-01

Stress analysis in polycrystalline materials reveals that stress can vary considerably among different subpopulations of grains. Samples of MgO and mixtures of MgO and spinel have been studied. After the onset of plastic flow, stronger grains or orientations will support more stress than the weaker grains. A grain to grain fabric develops that enables this stress partitioning. The stress partitioning and the resulting fabric can invalidate static measurements of elastic moduli. However, high temperature flow mechanisms reveal a more isotropic strength behaviour resulting in a more uniform variation of stress with orientation

Comparison between isotropic linear-elastic law and isotropic hyperelastic law in the finite element modeling of the brachial plexus.

Science.gov (United States)

Perruisseau-Carrier, A; Bahlouli, N; Bierry, G; Vernet, P; Facca, S; Liverneaux, P

2017-12-01

Augmented reality could help the identification of nerve structures in brachial plexus surgery. The goal of this study was to determine which law of mechanical behavior was more adapted by comparing the results of Hooke's isotropic linear elastic law to those of Ogden's isotropic hyperelastic law, applied to a biomechanical model of the brachial plexus. A model of finite elements was created using the ABAQUS ® from a 3D model of the brachial plexus acquired by segmentation and meshing of MRI images at 0°, 45° and 135° of shoulder abduction of a healthy subject. The offset between the reconstructed model and the deformed model was evaluated quantitatively by the Hausdorff distance and qualitatively by the identification of 3 anatomical landmarks. In every case the Hausdorff distance was shorter with Ogden's law compared to Hooke's law. On a qualitative aspect, the model deformed by Ogden's law followed the concavity of the reconstructed model whereas the model deformed by Hooke's law remained convex. In conclusion, the results of this study demonstrate that the behavior of Ogden's isotropic hyperelastic mechanical model was more adapted to the modeling of the deformations of the brachial plexus. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Isotropic harmonic oscillator plus inverse quadratic potential in N-dimensional spaces

International Nuclear Information System (INIS)

Oyewumi, K.A.; Bangudu, E.A.

2003-01-01

Some aspects of the N-dimensional isotropic harmonic plus inverse quadratic potential were discussed. The hyperradial equation for isotropic harmonic oscillator plus inverse quadratic potential is solved by transformation into the confluent hypergeometric equation to obtain the normalized hyperradial solution. Together with the hyperangular solutions (hyperspherical harmonics), these form the complete energy eigenfunctions of the N-dimensional isotropic harmonic oscillator plus inverse quadratic potential and the energy eigenvalues are also obtained. These are dimensionally dependent. The dependence of radial solution on the dimensions or potential strength and the degeneracy of the energy levels are discussed. (author)

Evaluation of micro fatigue crack growth under equi-biaxial stress by membranous pressure fatigue test

International Nuclear Information System (INIS)

Iida, Satoshi; Abe, Shigeki; Nakamura, Takao; Kamaya, Masayuki

2014-01-01

For preventing nuclear power plant (NPP) accidents, NPPs are required to ensure system safety in long term safe operation under aging degradation. Now, fatigue accumulation is one of major ageing phenomena and are evaluated to ensure safety by design fatigue curve that are based on the results of uniaxial fatigue tests. On the other hand, thermal stress that occurs in piping of actual components is not uniaxial but equi-biaxial. For accurate evaluation, it is required to conform real circumstance. In this study, membranous pressure fatigue test was conducted to simulated equi-biaxial stress. Crack initiation and crack growth were examined by replica investigation. Calculation result of equivalent stress intensity factor shows crack growth under equi-biaxial stress is faster than under uniaxial stress. It is concluded that equi-biaxial fatigue behavior should be considered in the evaluation of fatigue crack initiation and crack growth. (author)

Software development for specific geometry and safe design of isotropic material multicell beams

International Nuclear Information System (INIS)

Tariq, M.M.; Ahmed, M.A.

2011-01-01

Comparison of analytical results with finite element results for analysis of isotropic material multicell beams subjected to free torsion case is the main idea of this paper. Progress in the fundamentals and applications of advanced materials and their processing technologies involves costly experiments and prototype testing for reliability. The software development for design analysis of structures with advanced materials is a low cost but challenging research. Multicell beams have important industrial applications in the aerospace and automotive sectors. This paper explains software development to test different materials in design of a multicell beam. Objective of this paper is to compute the torsional loading of multicell beams of isotropic materials for safe design in both symmetrical and asymmetrical geometries. Software has been developed in Microsoft Visual Basic. Distribution of Saint Venant shear flows, shear stresses, factors of safety, volume, mass, weight, twist, polar moment of inertia and aspect ratio for free torsion in multicell beam have been calculated using this software. The software works on four algorithms, these are, Specific geometry algorithm, material selection algorithm, factor of safety algorithm and global algorithm. User can specify new materials analytically, or choose a pre-defined material from the list, which includes, plain carbon steels, low alloy steels, stainless steels, cast irons, aluminum alloys, copper alloys, magnesium alloys, titanium alloys, precious metals and refractory metals. Although this software is restricted to multicell beam comprising of three cells, however future versions can have ability to address more complicated shapes and cases of multicell beams. Software also describes nomenclature and mathematical formulas applied to help user understand the theoretical background. User can specify geometry of multicell beam for three rectangular cells. Software computes shear flows, shear stresses, safety factors

Validity of the isotropic thermal conductivity assumption in supercell lattice dynamics

Science.gov (United States)

Ma, Ruiyuan; Lukes, Jennifer R.

2018-02-01

Superlattices and nano phononic crystals have attracted significant attention due to their low thermal conductivities and their potential application as thermoelectric materials. A widely used expression to calculate thermal conductivity, presented by Klemens and expressed in terms of the relaxation time by Callaway and Holland, originates from the Boltzmann transport equation. In its most general form, this expression involves a direct summation of the heat current contributions from individual phonons of all wavevectors and polarizations in the first Brillouin zone. In common practice, the expression is simplified by making an isotropic assumption that converts the summation over wavevector to an integral over wavevector magnitude. The isotropic expression has been applied to superlattices and phononic crystals, but its validity for different supercell sizes has not been studied. In this work, the isotropic and direct summation methods are used to calculate the thermal conductivities of bulk Si, and Si/Ge quantum dot superlattices. The results show that the differences between the two methods increase substantially with the supercell size. These differences arise because the vibrational modes neglected in the isotropic assumption provide an increasingly important contribution to the thermal conductivity for larger supercells. To avoid the significant errors that can result from the isotropic assumption, direct summation is recommended for thermal conductivity calculations in superstructures.

3D geometrically isotropic metamaterial for telecom wavelengths

DEFF Research Database (Denmark)

Malureanu, Radu; Andryieuski, Andrei; Lavrinenko, Andrei

2009-01-01

of the unit cell is not infinitely small, certain geometrical constraints have to be fulfilled to obtain an isotropic response of the material [3]. These conditions and the metal behaviour close to the plasma frequency increase the design complexity. Our unit cell is composed of two main parts. The first part...... is obtained in a certain bandwidth. The proposed unit cell has the cubic point group of symmetry and being repeatedly placed in space can effectively reveal isotropic optical properties. We use the CST commercial software to characterise the “cube-in-cage” structure. Reflection and transmission spectra...

Mathematical Model of Growth Factor Driven Haptotaxis and Proliferation in a Tissue Engineering Scaffold

KAUST Repository

Pohlmeyer, J. V.

2013-01-29

Motivated by experimental work (Miller et al. in Biomaterials 27(10):2213-2221, 2006, 32(11):2775-2785, 2011) we investigate the effect of growth factor driven haptotaxis and proliferation in a perfusion tissue engineering bioreactor, in which nutrient-rich culture medium is perfused through a 2D porous scaffold impregnated with growth factor and seeded with cells. We model these processes on the timescale of cell proliferation, which typically is of the order of days. While a quantitative representation of these phenomena requires more experimental data than is yet available, qualitative agreement with preliminary experimental studies (Miller et al. in Biomaterials 27(10):2213-2221, 2006) is obtained, and appears promising. The ultimate goal of such modeling is to ascertain initial conditions (growth factor distribution, initial cell seeding, etc.) that will lead to a final desired outcome. © 2013 Society for Mathematical Biology.

THE PROPAGATION OF NEUTRINO-DRIVEN JETS IN WOLF-RAYET STARS

Energy Technology Data Exchange (ETDEWEB)

Nagakura, Hiroki, E-mail: hiroki@heap.phys.waseda.ac.jp [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, JapanAND (Japan); Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)

2013-02-20

We numerically investigate the jet propagation through a rotating collapsing Wolf-Rayet star with detailed central engine physics constructed based on the neutrino-driven collapsar model. The collapsing star determines the evolution of the mass accretion rate, black hole mass, and spin, all of which are important ingredients for determining the jet luminosity. We reveal that neutrino-driven jets in rapidly spinning Wolf-Rayet stars are capable of breaking out from the stellar envelope, while those propagating in slower rotating progenitors fail to break out due to insufficient kinetic power. For progenitor models with successful jet breakouts, the kinetic energy accumulated in the cocoon could be as large as {approx}10{sup 51} erg and might significantly contribute to the luminosity of the afterglow emission or to the kinetic energy of the accompanying supernova if nickel production takes place. We further analyze the post-breakout phase using a simple analytical prescription and conclude that the relativistic jet component could produce events with an isotropic luminosity L {sub p(iso)} {approx} 10{sup 52} erg s{sup -1} and isotropic energy E {sub j(iso)} {approx} 10{sup 54} erg. Our findings support the idea of rapidly rotating Wolf-Rayet stars as plausible progenitors of GRBs, while slowly rotational ones could be responsible for low-luminosity or failed GRBs.

Stress and strain provide positional and directional cues in development.

Directory of Open Access Journals (Sweden)

Behruz Bozorg

2014-01-01

Full Text Available The morphogenesis of organs necessarily involves mechanical interactions and changes in mechanical properties of a tissue. A long standing question is how such changes are directed on a cellular scale while being coordinated at a tissular scale. Growing evidence suggests that mechanical cues are participating in the control of growth and morphogenesis during development. We introduce a mechanical model that represents the deposition of cellulose fibers in primary plant walls. In the model both the degree of material anisotropy and the anisotropy direction are regulated by stress anisotropy. We show that the finite element shell model and the simpler triangular biquadratic springs approach provide equally adequate descriptions of cell mechanics in tissue pressure simulations of the epidermis. In a growing organ, where circumferentially organized fibers act as a main controller of longitudinal growth, we show that the fiber direction can be correlated with both the maximal stress direction and the direction orthogonal to the maximal strain direction. However, when dynamic updates of the fiber direction are introduced, the mechanical stress provides a robust directional cue for the circumferential organization of the fibers, whereas the orthogonal to maximal strain model leads to an unstable situation where the fibers reorient longitudinally. Our investigation of the more complex shape and growth patterns in the shoot apical meristem where new organs are initiated shows that a stress based feedback on fiber directions is capable of reproducing the main features of in vivo cellulose fiber directions, deformations and material properties in different regions of the shoot. In particular, we show that this purely mechanical model can create radially distinct regions such that cells expand slowly and isotropically in the central zone while cells at the periphery expand more quickly and in the radial direction, which is a well established growth pattern

Stress and strain provide positional and directional cues in development.

Science.gov (United States)

Bozorg, Behruz; Krupinski, Pawel; Jönsson, Henrik

2014-01-01

The morphogenesis of organs necessarily involves mechanical interactions and changes in mechanical properties of a tissue. A long standing question is how such changes are directed on a cellular scale while being coordinated at a tissular scale. Growing evidence suggests that mechanical cues are participating in the control of growth and morphogenesis during development. We introduce a mechanical model that represents the deposition of cellulose fibers in primary plant walls. In the model both the degree of material anisotropy and the anisotropy direction are regulated by stress anisotropy. We show that the finite element shell model and the simpler triangular biquadratic springs approach provide equally adequate descriptions of cell mechanics in tissue pressure simulations of the epidermis. In a growing organ, where circumferentially organized fibers act as a main controller of longitudinal growth, we show that the fiber direction can be correlated with both the maximal stress direction and the direction orthogonal to the maximal strain direction. However, when dynamic updates of the fiber direction are introduced, the mechanical stress provides a robust directional cue for the circumferential organization of the fibers, whereas the orthogonal to maximal strain model leads to an unstable situation where the fibers reorient longitudinally. Our investigation of the more complex shape and growth patterns in the shoot apical meristem where new organs are initiated shows that a stress based feedback on fiber directions is capable of reproducing the main features of in vivo cellulose fiber directions, deformations and material properties in different regions of the shoot. In particular, we show that this purely mechanical model can create radially distinct regions such that cells expand slowly and isotropically in the central zone while cells at the periphery expand more quickly and in the radial direction, which is a well established growth pattern in the meristem.

Grain boundary cavity growth under applied stress and internal pressure

International Nuclear Information System (INIS)

Mancuso, J.F.

1977-08-01

The growth of grain boundary cavities under applied stress and internal gas pressure was investigated. Methane gas filled cavities were produced by the C + 4H reversible CH4 reaction in the grain boundaries of type 270 nickel by hydrogen charging in an autoclave at 500 0 C with a hydrogen pressure of either 3.4 or 14.5 MPa. Intergranular fracture of nickel was achieved at a charging temperature of 300 0 C and 10.3 MPa hydrogen pressure. Cavities on the grain boundaries were observed in the scanning electron microscope after fracture. Photomicrographs of the cavities were produced in stereo pairs which were analyzed so as to correct for perspective distortion and also to determine the orientational dependence of cavity growth under an applied tensile stress

Stress generation by myosin minifilaments in actin bundles

International Nuclear Information System (INIS)

Dasanayake, Nilushi L; Carlsson, Anders E

2013-01-01

Forces and stresses generated by the action of myosin minifilaments are analyzed in idealized computer-generated actin bundles, and compared to results for isotropic actin networks. The bundles are generated as random collections of actin filaments in two dimensions with constrained orientations, crosslinked and attached to two fixed walls. Myosin minifilaments are placed on actin filament pairs and allowed to move and deform the network so that it exerts forces on the walls. The vast majority of simulation runs end with contractile minifilament stress, because minifilaments rotate into energetically stable contractile configurations. This process is aided by the bending and stretching of actin filaments, which accomodate minifilament rotation. Stresses for bundles are greater than those for isotropic networks, and antiparallel filaments generate more tension than parallel filaments. The forces transmitted by the actin network to the walls of the simulation cell often exceed the tension in the minifilament itself. (paper)

Frictionless contact of a rigid punch indenting a transversely isotropic elastic layer

Directory of Open Access Journals (Sweden)

Rajesh Patra

2016-03-01

Full Text Available This article is concerned with the study of frictionless contact between a rigid punch and a transversely isotropic elastic layer. The rigid punch is assumed to be axially symmetric and is being pressed towards the layer by an applied concentrated load. The layer is resting on a rigid base and is assumed to be ufficiently thick in comparison with the amount of indentation by the rigid punch. The relationship between the applied load $P$ and the contact area is obtained by solving the mathematically formulated problem through use of Hankel transform of different order. Effect of indentation on the distribution of normal stress at the surface as well as the relationship between the applied load and the area of contact have been shown graphically.

The effect of fiber microstructure on evolution of residual stresses in silicon carbide/titanium aluminide composites

Science.gov (United States)

Pindera, Marek-Jerzy; Freed, Alan D.

1992-01-01

This paper examines the effect of the morphology of the SCS6 silicon carbide fiber on the evolution of residual stresses in SiC/Ti composites. A micromechanics model based on the concentric cylinder concept is presented which is used to calculate residual stresses in a SiC/Ti composite during axisymmetric cooling by a spatially uniform temperature change. The silicon carbide fiber is modeled as a layered material with five distinct transversely isotropic and orthotropic, elastic layers, whereas the titanium matrix is taken to be isotropic, with temperature-dependent elastoplastic properties. The results arc compared with those obtained based on the assumption that the silicon carbide fiber is isotropic and homogeneous.

A study on fatigue crack growth model considering high mean loading effects based on structural stress

International Nuclear Information System (INIS)

Kim, Jong Sung; Kim, Cheol; Jin, Tae Eun; Dong, P.

2004-01-01

The mesh-insensitive structural stress procedure by Dong is modified to apply to the welded joints with local thickness variation and inarguable shear/normal stresses along local discontinuity surface. In order to make use of the structural stress based K solution for fatigue correlation of welded joints, a proper crack growth model needs to be developed. There exist some significant discrepancies in inferring the slope or crack growth exponent in the conventional Paris law regime. Two-stage crack growth model was not considered since its applications are focused upon the fatigue behavior in welded joints in which the load ratio effects are considered negligible. In this paper, a two-stage crack growth law considering high mean loading is proposed and proven to be effective in unifying the so-called anomalous short crack growth data

Kinetic Behavior of Exchange-Driven Growth with Catalyzed-Birth Processes

Science.gov (United States)

Wang, Hai-Feng; Lin, Zhen-Quan; Kong, Xiang-Mu

2006-12-01

Two catalyzed-birth models of n-species (n>=2) aggregates with exchange-driven growth processes are proposed and compared. In the first one, the exchange reaction occurs between any two aggregates Amk and Amj of the same species with the rate kernels Km(k,j) = Kmkj (m = 1,2,...,n, n>=2), and aggregates of An species catalyze a monomer-birth of Al species (l = 1,2,...,n-1) with the catalysis rate kernel Jl(k,j) = Jlkjυ. The kinetic behaviors are investigated by means of the mean-field theory. We find that the evolution behavior of aggregate-size distribution alk(t) of Al species depends crucially on the value of the catalysis rate parameter υ: (i) alk(t) obeys the conventional scaling law in the case of υ0. In the second model, the mechanism of monomer-birth of An-species catalyzed by Al species is added on the basis of the first model, that is, the aggregates of Al and An species catalyze each other to cause monomer-birth. The kinetic behaviors of Al and An species are found to fall into two categories for the different υ: (i) growth obeying conventional scaling form with υ0.

Growth Stresses in Thermally Grown Oxides on Nickel-Based Single-Crystal Alloys

Science.gov (United States)

Rettberg, Luke H.; Laux, Britta; He, Ming Y.; Hovis, David; Heuer, Arthur H.; Pollock, Tresa M.

2016-03-01

Growth stresses that develop in α-Al2O3 scale that form during isothermal oxidation of three Ni-based single crystal alloys have been studied to elucidate their role in coating and substrate degradation at elevated temperatures. Piezospectroscopy measurements at room temperature indicate large room temperature compressive stresses in the oxides formed at 1255 K or 1366 K (982 °C or 1093 °C) on the alloys, ranging from a high of 4.8 GPa for René N4 at 1366 K (1093 °C) to a low of 3.8 GPa for René N5 at 1255 K (982 °C). Finite element modeling of each of these systems to account for differences in coefficients of thermal expansion of the oxide and substrate indicates growth strains in the range from 0.21 to 0.44 pct at the oxidation temperature, which is an order of magnitude higher than the growth strains measured in the oxides on intermetallic coatings that are typically applied to these superalloys. The magnitudes of the growth strains do not scale with the parabolic oxidation rate constants measured for the alloys. Significant spatial inhomogeneities in the growth stresses were observed, due to (i) the presence of dendritic segregation and (ii) large carbides in the material that locally disrupts the structure of the oxide scale. The implications of these observations for failure during cyclic oxidation, fatigue cycling, and alloy design are considered.

Fatigue crack growth in 2024-T3 aluminum under tensile and transverse shear stresses

Science.gov (United States)

Viz, Mark J.; Zehnder, Alan T.

1994-01-01

The influence of transverse shear stresses on the fatigue crack growth rate in thin 2024-T3 aluminum alloy sheets is investigated experimentally. The tests are performed on double-edge cracked sheets in cyclic tensile and torsional loading. This loading generates crack tip stress intensity factors in the same ratio as the values computed for a crack lying along a lap joint in a pressurized aircraft fuselage. The relevant fracture mechanics of cracks in thin plates along with the details of the geometrically nonlinear finite element analyses used for the test specimen calibration are developed and discussed. Preliminary fatigue crack growth data correlated using the fully coupled stress intensity factor calibration are presented and compared with fatigue crack growth data from pure delta K(sub I)fatigue tests.

Growth and nitrogen metabolism changes in NaCl-stressed tobacco ...

African Journals Online (AJOL)

Growth and nitrogen metabolism changes in NaCl-stressed tobacco (Nicotiana rustica L. var. Souffi) seedlings. Chokri Zaghdoud, Houda Maâroufi-Dguimi, Youssef Ouni, Mokhtar Guerfel, Houda Gouia, Kamel-Eddine Negaz, Ali Ferchichi, Mohamed Debouba ...

Time-dependent analytical thermal model to investigate thermally induced stresses in quasi-CW-pumped laser rods

CSIR Research Space (South Africa)

Bernhardi, EH

2008-01-01

Full Text Available that determines the temperature and the thermally induced stresses in isotropic rods is presented. Even though the model is developed for isotropic rods, it is shown that it can also be used to accurately estimate the thermal effects in anisotropic rods...

Profit-driven and demand-driven investment growth and fluctuations in different accumulation regimes

OpenAIRE

Giovanni Dosi; Mauro Sodini; Maria Enrica Virgillito

2013-01-01

The main task of this work is to develope a model able to encompass, at the same time, Keynesian, demand-driven, and Marxian, profit-driven determinants of fluctuations. Our starting point is the Goodwin's model (1967), rephrased in discrete time and extended by means of a coupled dynamics structure. The model entails the combined interaction of a demand effect, which resembles a rudimentary first approximation to an accelerator, and of a hysteresis effect in wage formation in turn affecting ...

The Impact of Urban Growth and Climate Change on Heat Stress in an Australian City

Science.gov (United States)

Chapman, S.; Mcalpine, C. A.; Thatcher, M. J.; Salazar, A.; Watson, J. R.

2017-12-01

Over half of the world's population lives in urban areas. Most people will therefore be exposed to climate change in an urban environment. One of the climate risks facing urban residents is heat stress, which can lead to illness and death. Urban residents are at increased risk of heat stress due to the urban heat island effect. The urban heat island is a modification of the urban environment and increases temperatures on average by 2°C, though the increase can be much higher, up to 8°C when wind speeds and cloud cover are low. The urban heat island is also expected to increase in the future due to urban growth and intensification, further exacerbating urban heat stress. Climate change alters the urban heat island due to changes in weather (wind speed and cloudiness) and evapotranspiration. Future urban heat stress will therefore be affected by urban growth and climate change. The aim of this study was to examine the impact of urban growth and climate change on the urban heat island and heat stress in Brisbane, Australia. We used CCAM, the conformal cubic atmospheric model developed by the CSIRO, to examine temperatures in Brisbane using scenarios of urban growth and climate change. We downscaled the urban climate using CCAM, based on bias corrected Sea Surface Temperatures from the ACCESS1.0 projection of future climate. We used Representative Concentration Pathway (RCP) 8.5 for the periods 1990 - 2000, 2049 - 2060 and 2089 - 2090 with current land use and an urban growth scenario. The present day climatology was verified using weather station data from the Australian Bureau of Meteorology. We compared the urban heat island of the present day with the urban heat island with climate change to determine if climate change altered the heat island. We also calculated heat stress using wet-bulb globe temperature and apparent temperature for the climate change and base case scenarios. We found the urban growth scenario increased present day temperatures by 0.5°C in the

Precession of elastic waves in vibrating isotropic spheres and transversely isotropic cylinders subjected to inertial rotation

CSIR Research Space (South Africa)

Joubert, S

2006-05-01

Full Text Available and Manufacturing TRANSVERSELY ISOTROPIC CYLINDER - 1 φ φ r z a x y Ω P P O u v w z ( )1 1 1 2 1 1 rrr rz rr zr r zrz zz rz u r r z r v r r z r w r r z r ϕ ϕϕ ϕϕ ϕϕ ϕ ϕ σσ σ σ σ ρ ϕ σσ σ σ ρ ϕ σσ σ σ ρ ϕ... ∂ ∂ ∂ + + + − = ∂ ∂ ∂ ∂∂ ∂ + + + = ∂ ∂ ∂ ∂∂ ∂ + + + = ∂ ∂ ∂ && && && 6 CSIR Material Science and Manufacturing TRANSVERSELY ISOTROPIC CYLINDER - 2 ( )1 1 1 2 1 1 rrr rz rr zr r zrz zz rz u r r z r v r r z r w r r z r ϕ ϕϕ ϕϕ ϕϕ ϕ ϕ σσ σ σ σ ρ ϕ σσ σ σ ρ ϕ σσ σ σ ρ ϕ...

Effect of applied environmental stress on growth, photosynthesis, carbon allocation, and hydrocarbon production in Euphorbia lathyris

International Nuclear Information System (INIS)

Taylor, S.E.; Calvin, M.

1988-01-01

Photosynthetic activity was reduced by salinity stress, but is was found to be less sensitive than growth. Salinity stress also caused changes in the concentrations of specific cations. Moderate water stress had little effect on growth, but large changes in hydrocarbon production were still observed. Carbon allocation experiments with radiolabeled carbon indicated that carbon for latex production was supplied by nearby leaves, with some translocation down the stem also occurring

water stress mediated changes in growth, physiology and secondary metabolites of desi ajwain (trachyspermum ammi l.)

International Nuclear Information System (INIS)

Azhar, N.; Hussain, B.; Abbasi, K.Y.

2011-01-01

Biotic and abiotic stresses exert a considerable influence on the production of several secondary metabolites in plants; water stress is one of the most important abiotic stress factors. This study was carried out to elucidate the effect of drought stress on growth, physiology and secondary metabolite production in desi ajwain (Trachyspermum ammi L.). Plants were grown in pots and three drought levels (100%, 80% and 60%) of field capacity were created. The experiment was laid out in complete randomized design (CRD) with three replicates. Data on growth, physiological and biochemical parameters were recorded and analyzed statistically. Physiological parameters like transpiration rate and stomatal conductance decreased concentration increased. The photosynthetic rate showed significantly with increasing water stress levels, but internal CO/sub 2/ non-significant reduction from 100% field capacity to 80% field capacity but increased at 60% field capacity. Growth parameters including plant height, herb fresh and dry weights were reduced significantly with increasing stress levels, while total phenolic contents and chlorophyll contents increased under water stress conditions. These results suggest that cultivation of medicinal plants like desi ajwain under drought stress could enhance the production of secondary metabolites. (author)

A ghrelin-growth hormone axis drives stress-induced vulnerability to enhanced fear.

Science.gov (United States)

Meyer, R M; Burgos-Robles, A; Liu, E; Correia, S S; Goosens, K A

2014-12-01

Hormones in the hypothalamus-pituitary-adrenal (HPA) axis mediate many of the bodily responses to stressors, yet there is no clear relationship between the levels of these hormones and stress-associated mental illnesses such as posttraumatic stress disorder (PTSD). Therefore, other hormones are likely to be involved in this effect of stress. Here we used a rodent model of PTSD in which rats repeatedly exposed to a stressor display heightened fear learning following auditory Pavlovian fear conditioning. Our results show that stress-related increases in circulating ghrelin, a peptide hormone, are necessary and sufficient for stress-associated vulnerability to exacerbated fear learning and these actions of ghrelin occur in the amygdala. Importantly, these actions are also independent of the classic HPA stress axis. Repeated systemic administration of a ghrelin receptor agonist enhanced fear memory but did not increase either corticotropin-releasing factor (CRF) or corticosterone. Repeated intraamygdala infusion of a ghrelin receptor agonist produced a similar enhancement of fear memory. Ghrelin receptor antagonism during repeated stress abolished stress-related enhancement of fear memory without blunting stress-induced corticosterone release. We also examined links between ghrelin and growth hormone (GH), a major downstream effector of the ghrelin receptor. GH protein was upregulated in the amygdala following chronic stress, and its release from amygdala neurons was enhanced by ghrelin receptor stimulation. Virus-mediated overexpression of GH in the amygdala was also sufficient to increase fear. Finally, virus-mediated overexpression of a GH receptor antagonist was sufficient to block the fear-enhancing effects of repeated ghrelin receptor stimulation. Thus, ghrelin requires GH in the amygdala to exert fear-enhancing effects. These results suggest that ghrelin mediates a novel branch of the stress response and highlight a previously unrecognized role for ghrelin and

Growth, stress, and defects of heteroepitaxial diamond on Ir/YSZ/Si(111)

Science.gov (United States)

Gallheber, B.-C.; Fischer, M.; Mayr, M.; Straub, J.; Schreck, M.

2018-06-01

Basic understanding of the fundamental processes in crystal growth as well as the structural quality of diamond synthesized by chemical vapour deposition on iridium surfaces has reached a high level for samples with (001) orientation. Diamond deposition on the alternative (111) surface is generally more challenging but of appreciable technological interest, too. In the present work, heteroepitaxy of diamond on Ir/YSZ/Si(111) with different off-axis angles and directions has been studied. During the growth of the first microns, strong and complex intrinsic stress states were rapidly formed. They restricted the range of suitable temperatures in this study to values between 830 °C and 970 °C. At low-stress conditions, the maximum growth rates were about 1 μm/h. They facilitated long-time processes which yielded pronounced structural improvements with minimum values of 0.08° for the azimuthal mosaic spread, 4 × 107 cm-2 for the dislocation density and 1.8 cm-1 for the Raman line width. This refinement is even faster than on (001) growth surfaces. It indicates substantial differences between the two crystal directions in terms of merging of mosaic blocks and annihilation of dislocations. Crystals with a thickness of up to 330 μm have been grown. The correlation of photoluminescence and μ-Raman tomograms with topography data also revealed fundamental differences in the off-axis growth between (001) and (111) orientation. Finally, the analysis of the microscopic structures at the growth surface provided the base for a model that can conclusively explain the intriguing reversal of stress tensor anisotropy caused by a simple inversion in sign of the off-axis angle.

Chronic water stress reduces tree growth and the carbon sink of deciduous hardwood forests.

Science.gov (United States)

Brzostek, Edward R; Dragoni, Danilo; Schmid, Hans Peter; Rahman, Abdullah F; Sims, Daniel; Wayson, Craig A; Johnson, Daniel J; Phillips, Richard P

2014-08-01

Predicted decreases in water availability across the temperate forest biome have the potential to offset gains in carbon (C) uptake from phenology trends, rising atmospheric CO2 , and nitrogen deposition. While it is well established that severe droughts reduce the C sink of forests by inducing tree mortality, the impacts of mild but chronic water stress on forest phenology and physiology are largely unknown. We quantified the C consequences of chronic water stress using a 13-year record of tree growth (n = 200 trees), soil moisture, and ecosystem C balance at the Morgan-Monroe State Forest (MMSF) in Indiana, and a regional 11-year record of tree growth (n > 300 000 trees) and water availability for the 20 most dominant deciduous broadleaf tree species across the eastern and midwestern USA. We show that despite ~26 more days of C assimilation by trees at the MMSF, increasing water stress decreased the number of days of wood production by ~42 days over the same period, reducing the annual accrual of C in woody biomass by 41%. Across the deciduous forest region, water stress induced similar declines in tree growth, particularly for water-demanding 'mesophytic' tree species. Given the current replacement of water-stress adapted 'xerophytic' tree species by mesophytic tree species, we estimate that chronic water stress has the potential to decrease the C sink of deciduous forests by up to 17% (0.04 Pg C yr(-1) ) in the coming decades. This reduction in the C sink due to mesophication and chronic water stress is equivalent to an additional 1-3 days of global C emissions from fossil fuel burning each year. Collectively, our results indicate that regional declines in water availability may offset the growth-enhancing effects of other global changes and reduce the extent to which forests ameliorate climate warming. © 2014 John Wiley & Sons Ltd.

Isotropic blackbody cosmic microwave background radiation as evidence for a homogeneous universe.

Science.gov (United States)

Clifton, Timothy; Clarkson, Chris; Bull, Philip

2012-08-03

The question of whether the Universe is spatially homogeneous and isotropic on the largest scales is of fundamental importance to cosmology but has not yet been answered decisively. Surprisingly, neither an isotropic primary cosmic microwave background (CMB) nor combined observations of luminosity distances and galaxy number counts are sufficient to establish such a result. The inclusion of the Sunyaev-Zel'dovich effect in CMB observations, however, dramatically improves this situation. We show that even a solitary observer who sees an isotropic blackbody CMB can conclude that the Universe is homogeneous and isotropic in their causal past when the Sunyaev-Zel'dovich effect is present. Critically, however, the CMB must either be viewed for an extended period of time, or CMB photons that have scattered more than once must be detected. This result provides a theoretical underpinning for testing the cosmological principle with observations of the CMB alone.

Cotton growth potassium deficiency stress is influenced by photosynthetic apparatus and root system

International Nuclear Information System (INIS)

Hussain, Z.U.; Arshad, M.

2010-01-01

Due to rapid depletion of soil potassium (K) and increasing cost of K fertilizers in Pakistan, the K-use efficient crop genotypes become very important for agricultural sustain ability. However, limited research has been done on this important issue particularly in cotton, an important fibre crop. We studied the growth and biomass production of three cotton genotypes (CIM-506, NIAB- 78 and NIBGE-2) different in K-use efficiency in a K-deficient solution culture. Genotypes differed significantly for biomass production, absolute growth rates (shoot, root, leaf, total), leaf area, mean leaf area and relative growth rate of leaf under K deficiency stress, besides specific leaf area. The relative growth rate (shoot, root, total) did not differ significantly, except for leaf. For all these characters, NIBGE-2 was the best performer followed by NIAB-78 and CIM-506. Shoot dry weight was significantly related with (in decreasing order of significance): mean leaf area, leaf dry weight, leaf area, root dry weight, absolute growth rate of shoot, absolute growth rate of root, absolute growth rate total, absolute growth rate root, relative growth rate leaf, relative growth rate total and relative growth rate shoot. Hence, the enhanced biomass accumulation of cotton genotypes under K deficiency stress is related to their efficient photosynthetic apparatus and root system, appeared to be the most important morphological markers while breeding for K-use efficient cotton genotypes.(author)

On Rayleigh waves in a thinly layered laminated thermoelastic medium with stress couples under initial stresses

Directory of Open Access Journals (Sweden)

Pijush Pal Roy

1988-01-01

Full Text Available A study is made of the propagation of Rayleigh waves in a thinly layered laminated thermoelastic medium under deviatoric, hydrostatic, and couple stresses. The frequency equation of the Rayleigh waves is obtained. The phase velocity of the Rayleigh waves depends on the initial stress, deviatoric stress, and the couple stress. The laminated medium is first replaced by an equivalent anisotropic thermoelastic continuum. The corresponding thermoelastic coefficients (after deformation are derived in terms of initially isotropic thermoelastic coefficients (before deformation of individual layers. Several particular cases are discussed for the determination of the displacement fields with or without the effect of the couple stress.

The isotropic Universe

International Nuclear Information System (INIS)

Raine, D.J.

1981-01-01

This introduction to contemporary ideas in cosmology differs from other books on the 'expanding Universe' in its emphasis on physical cosmology and on the physical basis of the general theory of relativity. It is considered that the remarkable degree of isotropy, rather than the expansion, can be regarded as the central observational feature of the Universe. The various theories and ideas in 'big-bang' cosmology are discussed, providing an insight into current problems. Chapter headings are: quality of matter; expanding Universe; quality of radiation; quantity of matter; general theory of relativity; cosmological models; cosmological tests; matter and radiation; limits of isotropy; why is the Universe isotropic; singularities; evolution of structure. (U.K.)

Growth on Alpha-Ketoglutarate Increases Oxidative Stress Resistance in the Yeast Saccharomyces cerevisiae

Directory of Open Access Journals (Sweden)

Maria Bayliak

2017-01-01

Full Text Available Alpha-ketoglutarate (AKG is an important intermediate in cell metabolism, linking anabolic and catabolic processes. The effect of exogenous AKG on stress resistance in S. cerevisiae cells was studied. The growth on AKG increased resistance of yeast cells to stresses, but the effects depended on AKG concentration and type of stressor. Wild-type yeast cells grown on AKG were more resistant to hydrogen peroxide, menadione, and transition metal ions (Fe2+ and Cu2+ but not to ethanol and heat stress as compared with control ones. Deficiency in SODs or catalases abolished stress-protective effects of AKG. AKG-supplemented growth led to higher values of total metabolic activity, level of low-molecular mass thiols, and activities of catalase and glutathione reductase in wild-type cells compared with the control. The results suggest that exogenous AKG may enhance cell metabolism leading to induction of mild oxidative stress. It turn, it results in activation of antioxidant system that increases resistance of S. cerevisiae cells to H2O2 and other stresses. The presence of genes encoding SODs or catalases is required for the expression of protective effects of AKG.

Spatial and temporal patterns of chickpea genotypes (Cicer arietinum L. root growth under waterlogging stress

Directory of Open Access Journals (Sweden)

ali ganjali

2009-06-01

Full Text Available The dynamic of root growth of chickpea genotypes; including Rupali (Desi and Flip 97-530 (Kabuli were evaluated under waterlogging stress in a Glasshouse experiment at CSIRO, Perth, WA. during 2005. Root growth boxes (0.1×0.24×1.0 m with one wall of glass were used as experimental units. Data were analyzed based on Randomized Complete Block Design with three replications. Waterlogging was induced when the first root reached 50cm. The water level was maintained on the soil surface for 12 days. After that, waterlogging was finished by draining the root growth boxes. In soil profile, root growth rate were calculated based on recorded information on transparent films during growing season. There was positive and strong linear correlation between the root traits that were measured in soil (direct measurment and transparent films (indirect measurment. Decay and death of roots caused a severe decrease on root growth rate during waterlogging, but root growth rate was sharply increased at the end of recovery period on 0-40 cm layer of soil surface. In both genotypes, spatial and temporal patterns of the root growth were different. Root growth rate was highest on distinc time for each layer of soil profile. In both genotypes, RLD decreased with increasing soil depth. Results showed that more distribution of root system on upper soil layers (0-40 cm is a strategy for chickpea plants, and so, soil management is very important on this layer. In stress and non stress environments, Flip 97-530 showed better root characteristics than the Rupali during growing season, so this genotype is probably more tolerate to water logging stress.

Growth of marine yeast on different strength of stress solutes

Digital Repository Service at National Institute of Oceanography (India)

Gupta, R.

tested against the stress solutes NaCl (0-16%), potassium chloride (KCl) and sodium sulphate (Na sub(2) SO sub(4)) at 0.4%, 4% and 8% concentrations. D. hansenii and D. marama were the most versatile isolates exhibiting excellent growth in all...

A theoretical insight into H accumulation and bubble formation by applying isotropic strain on the W-H system under a fusion environment

Science.gov (United States)

Han, Quan-Fu; Liu, Yue-Lin; Zhang, Ying; Ding, Fang; Lu, Guang-Hong

2018-04-01

The solubility and bubble formation of hydrogen (H) in tungsten (W) are crucial factors for the application of W as a plasma-facing component under a fusion environment, but the data and mechanism are presently scattered, indicating some important factors might be neglected. High-energy neutron-irradiated W inevitably causes a local strain, which may change the solubility of H in W. Here, we performed first-principles calculations to predict the H solution behaviors under isotropic strain combined with temperature effect in W and found that the H solubility in interstitial lattice can be promoted/impeded by isotropic tensile/compressive strain over the temperature range 300-1800 K. The calculated H solubility presents good agreement with the experiment. Together, our previous results of anisotropic strain, except for isotropic compression, both isotropic tension and anisotropic tension/compression enhance H solution so as to reveal an important physical implication for H accumulation and bubble formation in W: strain can enhance H solubility, resulting in the preliminary nucleation of H bubble that further causes the local strain of W lattice around H bubble, which in turn improves the H solubility at the strained region that promotes continuous growth of the H bubble via a chain-reaction effect in W. This result can also interpret the H bubble formation even if no radiation damage is produced in W exposed to low-energy H plasma.

An Isotropic Light Sensor for Measurements of Visible Actinic Flux in Clouds

NARCIS (Netherlands)

Hage, J.C.H. van der; Roode, S.R. de

1999-01-01

A low-cost isotropic light sensor is described consisting of a spherical diffuser connected to a single photodiode by a light conductor. The directional response to light is isotropic to a high degree. The small, lightweight, and rugged construction makes this instrument suitable not only for

Growth Following Adversity: Positive Psychological Perspectives on Posttraumatic Stress

Directory of Open Access Journals (Sweden)

Stephen Joseph

2009-12-01

Full Text Available The impact of traumatic events is well documented within the clinical psychology literature where it is recognized that people who experience traumatic events may go on to develop posttraumatic stress disorder (PTSD. At first glance one might ask what the relevance of positive psychology is to the study of trauma. But a number of literatures and philosophies throughout human history have conveyed the idea that there is personal gain to be found in suffering. The observation that stressful and traumatic events can provoke positive psychological changes is also contained in the major religions of Buddhism, Christianity, Hinduism, Islam, and Judaism. Within existential philosophy and humanistic psychology it has also been recognized that positive changes can come about as a result of suffering. But it is only within the last decade that the topic of growth following adversity has become a focus for empirical work. In this paper I will provide an overview of the subject and the research we have conducted at the Centre for Trauma, Resilience, and Growth (CTRG.

Effects of transverse temperature field nonuniformity on stress in silicon sheet growth

Science.gov (United States)

Mataga, P. A.; Hutchinson, J. W.; Chalmers, B.; Bell, R. O.; Kalejs, J. P.

1987-01-01

Stress and strain rate distributions are calculated using finite element analysis for steady-state growth of thin silicon sheet temperature nonuniformities imposed in the transverse (sheet width) dimension. Significant reductions in residual stress are predicted to occur for the case where the sheet edge is cooled relative to its center provided plastic deformation with high creep rates is present.

Effect of stress ratio and frequency on fatigue crack growth rate of ...

Indian Academy of Sciences (India)

Effect of stress ratio and frequency on the fatigue crack propagation of 2618 aluminium alloy–silicon carbide composite were investigated at ambient temperature. With the first set of specimens, the fatigue crack growth rates were studied at three frequencies of 1 Hz, 5 Hz and 10 Hz at a stress ratio of 0.1 whereas the effects ...

Calculated isotropic Raman spectra from interacting H2-rare-gas pairs

International Nuclear Information System (INIS)

Gustafsson, M; Głaz, W; Bancewicz, T; Godet, J-L; Maroulis, G; Haskapoulos, A

2014-01-01

We report on a theoretical study of the H 2 -He and H 2 -Ar pair trace-polarizability and the corresponding isotropic Raman spectra. The conventional quantum mechanical approach for calculations of interaction-induced spectra, which is based on an isotropic interaction potential, is employed. This is compared with a close-coupling approach, which allows for inclusion of the full, anisotropic potential. It is established that the anisotropy of the potential plays a minor role for these spectra. The computed isotropic collision-induced Raman intensity, which is due to dissimilar pairs in H 2 -He and H 2 -Ar gas mixtures, is comparable to the intensities due to similar pairs (H 2 -H 2 , He-He, and Ar-Ar), which have been studied previously

Plant growth regulators ameliorate or exacerbate abiotic and biotic stress effects on Zea mays kernel weight in a genotype-specific manner

OpenAIRE

Wang, Yishi; Stutts, Lauren; Stapleton, Ann

2016-01-01

Plant growth regulators have documented roles in plant responses to single stresses. In combined-stress environments, plants display novel genetic architecture for growth traits and the response to growth regulators is unclear. We investigated the role of plant growth regulators in combined-stress responses in Zea mays. Twelve maize inbreds were exposed to all combinations of the following stressors: drought, nitrogen, and density stress. Chemical treatments were utilized to alter balances of...

Separating the Influence of Environment from Stress Relaxation Effects on Dwell Fatigue Crack Growth in a Nickel-Base Disk Alloy

Science.gov (United States)

Telesman, J.; Gabb, T. P.; Ghosn, L. J.

2016-01-01

Both environmental embrittlement and crack tip visco-plastic stress relaxation play a significant role in determining the dwell fatigue crack growth (DFCG) resistance of nickel-based disk superalloys. In the current study performed on the Low Solvus High Refractory (LSHR) disk alloy, the influence of these two mechanisms were separated so that the effects of each could be quantified and modeled. Seven different microstructural variations of LSHR were produced by controlling the cooling rate and the subsequent aging and thermal exposure heat treatments. Through cyclic fatigue crack growth testing performed both in air and vacuum, it was established that four out of the seven LSHR heat treatments evaluated, possessed similar intrinsic environmental resistance to cyclic crack growth. For these four heat treatments, it was further shown that the large differences in dwell crack growth behavior which still persisted, were related to their measured stress relaxation behavior. The apparent differences in their dwell crack growth resistance were attributed to the inability of the standard linear elastic fracture mechanics (LEFM) stress intensity parameter to account for visco-plastic behavior. Crack tip stress relaxation controls the magnitude of the remaining local tensile stresses which are directly related to the measured dwell crack growth rates. It was hypothesized that the environmentally weakened grain boundary crack tip regions fail during the dwells when their strength is exceeded by the remaining local crack tip tensile stresses. It was shown that the classical creep crack growth mechanisms such as grain boundary sliding did not contribute to crack growth, but the local visco-plastic behavior still plays a very significant role by determining the crack tip tensile stress field which controls the dwell crack growth behavior. To account for the influence of the visco-plastic behavior on the crack tip stress field, an empirical modification to the LEFM stress

Mechanical and electronic properties of monolayer and bilayer phosphorene under uniaxial and isotropic strains.

Science.gov (United States)

Hu, Ting; Han, Yang; Dong, Jinming

2014-11-14

The mechanical and electronic properties of both the monolayer and bilayer phosphorenes under either isotropic or uniaxial strain have been systematically investigated using first-principles calculations. It is interesting to find that: 1) Under a large enough isotropic tensile strain, the monolayer phosphorene would lose its pucker structure and transform into a flat hexagonal plane, while two inner sublayers of the bilayer phosphorene could be bonded due to its interlayer distance contraction. 2) Under the uniaxial tensile strain along a zigzag direction, the pucker distance of each layer in the bilayer phosphorene can exhibit a specific negative Poisson's ratio. 3) The electronic properties of both the monolayer and bilayer phosphorenes are sensitive to the magnitude and direction of the applied strains. Their band gaps decrease more rapidly under isotropic compressive strain than under uniaxial strain. Also, their direct-indirect band gap transitions happen at the larger isotropic tensile strains compared with that under uniaxial strain. 4) Under the isotropic compressive strain, the bilayer phosphorene exhibits a transition from a direct-gap semiconductor to a metal. In contrast, the monolayer phosphorene initially has the direct-indirect transition and then transitions to a metal. However, under isotropic tensile strain, both the bilayer and monolayer phosphorene show the direct-indirect transition and, finally, the transition to a metal. Our numerical results may open new potential applications of phosphorene in nanoelectronics and nanomechanical devices by external isotropic strain or uniaxial strain along different directions.

Effects of salt stress on tillering nodes to the growth of winter wheat (Triticum aestivum L.)

International Nuclear Information System (INIS)

Qiong, Y.; Yuan, G.; Zhixia, X.; Xiaojing, L.

2016-01-01

In monsoon climate regions, the tillering nodes of winter wheat can be stressed by high salt accumulation on the soil surface in spring, thereby leading to salt-induced damage. To understand whether tillering nodes could be stressed by salinity and to estimate its effects on the growth of winter wheat under salt stress, the tillering nodes of two wheat cultivars, H-4589 (salt-sensitive) and J-32 (salt-tolerant), were treated with salinity to investigate the physiological and biochemical changes in seedling growth. The results indicated that salt stress on tillering nodes significantly reduced plant height and shoot dry weight; increased Na+ accumulation, soluble sugar and proline in both H-4589 and J-32; which demonstrated remarkable effects on the growth of winter wheat when the tillering nodes were under salt stress. Furthermore, equivalent Na+ accumulations were discovered in two cultivars when tillering nodes were under salt stress, while remarkably different Na+ accumulations were discovered in two cultivars when roots were under salt stress. Based on the results from anatomic analyses, we speculated that no anatomic differences in tillering nodes between two cultivars could give reason to the equivalent Na+ accumulations in two cultivars when tillering nodes were under salt stress; and more lignified endodermis in primary roots as well as larger reduction of lateral root number in salt-tolerant cultivars which contributed to preventing Na+ influx could explain the remarkably lower Na+ accumulation in salt-tolerant cultivar when roots were under salt stress. All of these results indicated that the tillering nodes could mediate Na+ influx from the environment leading to salt-induced damage to the growth of winter wheat. (author)

Fracture analysis of a transversely isotropic high temperature superconductor strip based on real fundamental solutions

Science.gov (United States)

Gao, Zhiwen; Zhou, Youhe

2015-04-01

Real fundamental solution for fracture problem of transversely isotropic high temperature superconductor (HTS) strip is obtained. The superconductor E-J constitutive law is characterized by the Bean model where the critical current density is independent of the flux density. Fracture analysis is performed by the methods of singular integral equations which are solved numerically by Gauss-Lobatto-Chybeshev (GSL) collocation method. To guarantee a satisfactory accuracy, the convergence behavior of the kernel function is investigated. Numerical results of fracture parameters are obtained and the effects of the geometric characteristics, applied magnetic field and critical current density on the stress intensity factors (SIF) are discussed.

Isotropic quantum walks on lattices and the Weyl equation

Science.gov (United States)

D'Ariano, Giacomo Mauro; Erba, Marco; Perinotti, Paolo

2017-12-01

We present a thorough classification of the isotropic quantum walks on lattices of dimension d =1 ,2 ,3 with a coin system of dimension s =2 . For d =3 there exist two isotropic walks, namely, the Weyl quantum walks presented in the work of D'Ariano and Perinotti [G. M. D'Ariano and P. Perinotti, Phys. Rev. A 90, 062106 (2014), 10.1103/PhysRevA.90.062106], resulting in the derivation of the Weyl equation from informational principles. The present analysis, via a crucial use of isotropy, is significantly shorter and avoids a superfluous technical assumption, making the result completely general.

Comparative study of drought and salt stress effects on germination and seedling growth of pea

Directory of Open Access Journals (Sweden)

Petrović Gordana

2016-01-01

Full Text Available Seed germination is first critical and the most sensitive stage in the life cycle of plants compromise the seedlings establishment. Salt and drought tolerance testing in initial stages of plant development is of vital importance, because the seed with more rapid germination under salt or water deficit conditions may be expected to achieve a rapid seedling establishment, resulting in higher yields. The aim of this study was to determine whether the pea seed germination and seedling growth were inhibited by the salt toxicity and osmotic effect during the seedling development, and also identification of the sensitive seedling growth parameters in response to those stresses. Based on the obtained results, pea has been presented to be more tolerant to salt than water stress during germination and early embryo growth. Investigated cultivars showed greater susceptibility to both abiotic stresses when it comes growth parameters compared to seed germination. [Projekat Ministarstva nauke Republike Srbije, br. TR-31024 i br. TR-31022

Abscisic acid regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin.

Science.gov (United States)

Rowe, James H; Topping, Jennifer F; Liu, Junli; Lindsey, Keith

2016-07-01

Understanding the mechanisms regulating root development under drought conditions is an important question for plant biology and world agriculture. We examine the effect of osmotic stress on abscisic acid (ABA), cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We integrate experimental data to construct hormonal crosstalk networks to formulate a systems view of root growth regulation by multiple hormones. Experimental analysis shows: that ABA-dependent and ABA-independent stress responses increase under osmotic stress, but cytokinin responses are only slightly reduced; inhibition of root growth under osmotic stress does not require ethylene signalling, but auxin can rescue root growth and meristem size; osmotic stress modulates auxin transporter levels and localization, reducing root auxin concentrations; PIN1 levels are reduced under stress in an ABA-dependent manner, overriding ethylene effects; and the interplay among ABA, ethylene, cytokinin and auxin is tissue-specific, as evidenced by differential responses of PIN1 and PIN2 to osmotic stress. Combining experimental analysis with network construction reveals that ABA regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Growth and Development Temperature Influences Level of Tolerance to High Light Stress 1

Science.gov (United States)

Steffen, Kenneth L.; Palta, Jiwan P.

1989-01-01

The influence of growth and development temperature on the relative tolerance of photosynthetic tissue to high light stress at chilling temperatures was investigated. Two tuber-bearing potato species, Solanum tuberosum L. cv Red Pontiac and Solanum commersonii were grown for 4 weeks, at either 12 or 24°C with 12 hours of about 375 micromoles per second per square meter of photosynthetically active radiation. Paired leaf discs were cut from directly across the midvein of leaflets of comparable developmental stage and light environment from each species at each growth temperature treatment. One disc of each pair was exposed to 1°C and about 1000 micromoles per second per square meter photosynthetically active radiation for 4 hours, and the other disc was held at 1°C in total darkness for the same duration. Photosynthetic tissue of S. tuberosum, developed at 12°C, was much more tolerant to high light and low temperature stress than tissue developed under 24°C conditions. Following the high light treatment, 24°C-grown S. tuberosum tissue demonstrated light-limited and light-saturated rates that were approximately 50% of their paired dark controls. In contrast, the 12°C-grown tissue from S. tuberosum that was subjected to the light stress showed only a 18 and 6% reduction in light-limited and light-saturated rates of photosynthetic oxygen evolution, respectively. Tissue from 24°C-grown S. commersonii was much less sensitive to the light stress than was tissue from S. tuberosum grown under the same conditions. The results presented here demonstrate that: (a) acclimation of S. tuberosum to lower temperature growth conditions with a constant light environment, results in the increased capacity of photosynthetic tissue to tolerate high light stress at chilling temperature and (b) following growth and development at relatively high temperatures S. commersonii, a frost- and heat-tolerant wild species, has a much greater tolerance to the high light stress at chilling

Impact of interaction range and curvature on crystal growth of particles confined to spherical surfaces

Science.gov (United States)

Paquay, Stefan; Both, Gert-Jan; van der Schoot, Paul

2017-07-01

When colloidal particles form a crystal phase on a spherical template, their packing is governed by the effective interaction between them and the elastic strain of bending the growing crystal. For example, if growth commences under appropriate conditions, and the isotropic crystal that forms reaches a critical size, growth continues via the incorporation of defects to alleviate elastic strain. Recently, it was experimentally found that, if defect formation is somehow not possible, the crystal instead continues growing in ribbons that protrude from the original crystal. Here we report on computer simulations in which we observe both the formation of ribbons at short interaction ranges and packings that incorporate defects if the interaction is longer-ranged. The ribbons only form above some critical crystal size, below which the nucleus is disk-shaped. We find that the scaling of the critical crystal size differs slightly from the one proposed in the literature, and we argue that this is because the actual morphology transition is caused by the competition between line tension and elastic stress, rather than the competition between chemical potential and elastic stress.

Stochastic isotropic hyperelastic materials: constitutive calibration and model selection

Science.gov (United States)

Mihai, L. Angela; Woolley, Thomas E.; Goriely, Alain

2018-03-01

Biological and synthetic materials often exhibit intrinsic variability in their elastic responses under large strains, owing to microstructural inhomogeneity or when elastic data are extracted from viscoelastic mechanical tests. For these materials, although hyperelastic models calibrated to mean data are useful, stochastic representations accounting also for data dispersion carry extra information about the variability of material properties found in practical applications. We combine finite elasticity and information theories to construct homogeneous isotropic hyperelastic models with random field parameters calibrated to discrete mean values and standard deviations of either the stress-strain function or the nonlinear shear modulus, which is a function of the deformation, estimated from experimental tests. These quantities can take on different values, corresponding to possible outcomes of the experiments. As multiple models can be derived that adequately represent the observed phenomena, we apply Occam's razor by providing an explicit criterion for model selection based on Bayesian statistics. We then employ this criterion to select a model among competing models calibrated to experimental data for rubber and brain tissue under single or multiaxial loads.

Longitudinal cross-lagged relationships between mindfulness, posttraumatic stress symptoms, and posttraumatic growth in adolescents following the Yancheng tornado in China.

Science.gov (United States)

An, Yuanyuan; Yuan, Guangzhe; Zhang, Na; Xu, Wei; Liu, Zhen; Zhou, Feng

2018-08-01

Treatment of posttraumatic stress symptoms and facilitation of posttraumatic growth are two encouraging areas of research, yet little is understood about the relationships between trait mindfulness, posttraumatic stress symptoms, and posttraumatic growth. Previous work suggests the linkages among these variables, but most studies have been conducted in adult samples. The aim of this study was to examine longitudinal cross-lagged relationships between mindfulness, posttraumatic stress symptoms, and posttraumatic growth among adolescent survivors of the 2016 Jiangsu tornado in China. Data was collected at two secondary schools located in Yancheng city, where the severe catastrophic damage occurred during the tornado. The sample included 247 adolescent survivors (59.5% girls) aged 12-14 years who were directly affected by the tornado. Participants self-reported their trait mindfulness, posttraumatic stress symptoms, and posttraumatic growth at two time points: 6-month (T1) and 9-month post-tornado (T2; attrition rate 17.4%). Cross-lagged structural equation modelling analyses were conducted. Results showed that posttraumatic stress symptoms at T1 significantly predicted reduced trait mindfulness at T2 but not posttraumatic growth; trait mindfulness at T1 did not significantly predict posttraumatic stress symptoms nor posttraumatic growth at T2; and posttraumatic growth at T1 did not predict trait mindfulness nor posttraumatic stress symptoms at T2. These findings suggested that posttraumatic stress symptoms may negatively influence the development of trait mindfulness in disaster-affected adolescents in China, and that posttraumatic growth may have unique implications for this young population which was not associated with posttraumatic stress symptoms or trait mindfulness. Copyright © 2018 Elsevier B.V. All rights reserved.

Work satisfaction and posttraumatic growth 1 year after the 2008 Wenchuan earthquake: the perceived stress as a moderating factor.

Science.gov (United States)

Xu, Jiuping; Wu, Wei

2014-06-01

This study investigated the role of perceived stress as a possible moderating factor between posttraumatic growth (PTG) and work satisfaction. A stratified random sampling strategy was used to survey 2080 adult survivors of the 2008 Sichuan earthquake. The Posttraumatic Growth Inventory, the Job Satisfaction Index Scale and the Perceived Stress Scale were used in the assessment of the posttraumatic growth, work satisfaction and perceived stress respectively, and hierarchical multiple regression analyses were used for the analysis. The findings highlight work satisfaction as an important factor in both the prediction of posttraumatic growth and for its moderating effect on perceived stress. Some demographic characteristics, such as gender, education level, and housing condition were found to also affect the survivors' posttraumatic growth. This conclusion indicates that managers should pay closer attention to their employees' psychological state after a disaster and medical practitioners should consider survivors' work status and perceived stress when dispensing mental health care. Copyright © 2014 Elsevier Inc. All rights reserved.

Effect of plant growth hormones and abiotic stresses on germination ...

African Journals Online (AJOL)

Phosphatases are widely found in plants having intracellular and extracellular activities. Phosphatases are believed to be important for phosphorous scavenging and remobilization in plants, but its role in adaptation to abiotic stresses and growth hormones at germination level has not been critically evaluated. To address ...

Effect of Salicylic Acid on the Growth and Physiological Characteristics of Maize under Stress Conditions

International Nuclear Information System (INIS)

Manzoor, K.; Ilyas, N.; Batool, N.; Arshad, M.; Ahmad, B.

2015-01-01

Salicylic acid (SA) is a naturally occurring signaling molecule and growth regulator that enhances plant growth particularly in stress conditions. The present study was planned to evaluate the effects of different levels of SA on maize growth under drought and salt stress conditions. An experiment was conducted to test the morphological, physiological and biochemical changes in two cultivar of maize D-1184 and TG-8250. Varying levels of salicylic acid, i.e. 5mM, 10mM and 15mM were applied through foliar method. Exogenous applications of salicylic acid were done after 20 days of germination of the maize plants. Salicylic acid significantly affects root and shoot dry matter under drought and salt stress. Foliar application of SA significantly increased proline concentration (11 percentage and 12 percentage), amino acid accumulation (25 percentage and 18 percentage), relative water (17 percentage and 14 percentage) and Chlorophyll content. Overall, it can be concluded that SA at lower concentration is effective to minimize the effect of stress conditions. Maize cultivar TG-8250 showed better tolerance under drought and salt stress condition as compared to D-1184 cultivar. (author)

Torsional vibration of a pipe pile in transversely isotropic saturated soil

Science.gov (United States)

Zheng, Changjie; Hua, Jianmin; Ding, Xuanming

2016-09-01

This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot's poroelastic theory and the constitutive relations of the transversely isotropic medium, the dynamic governing equations of the outer and inner transversely isotropic saturated soil layers are derived. The Laplace transform is used to solve the governing equations of the outer and inner soil layers. The dynamic torsional response of the pipe pile in the frequency domain is derived utilizing 1D elastic theory and the continuous conditions at the interfaces between the pipe pile and the soils. The time domain solution is obtained by Fourier inverse transform. A parametric study is conducted to demonstrate the influence of the anisotropies of the outer and inner soil on the torsional dynamic response of the pipe pile.

Design methodology of single-feed compact near-isotropic antenna design

KAUST Repository

Su, Zhen

2017-06-07

The abundance of mobile wireless devices is giving rise to a new paradigm known as Internet of Things. In this paradigm, wireless devices will be everywhere and communicating with each other. Since they will be oriented randomly in the environment, they should be able to communicate equally in all directions in order to have stable communication link. Hence, compact near isotropic antennas are required, which can enable orientation insensitive communication. In this paper, we propose a simple design methodology to design a compact near-isotropic wire antenna based on equal vector potentials. As a proof of concept, a quarter wavelength monopole antennas has been designed that is wrapped on a 3D-printed box keeping the vector potentials in three orthogonal different directions equal. By optimizing the dimension of the antenna arms, a nearly isotropic radiation pattern is thus achieved. The results show that the antenna has a maximum gain of 2.2dBi at 900 MHz with gain derivation of 9.4dB.

Human population growth offsets climate-driven increase in woody vegetation in sub-Saharan Africa

DEFF Research Database (Denmark)

Brandt, Martin Stefan; Rasmussen, Kjeld; Peñuelas, Josep

2017-01-01

The rapidly growing human population in sub-Saharan Africa generates increasing demand for agricultural land and forest products, which presumably leads to deforestation. Conversely, a greening of African drylands has been reported, but this has been difficult to associate with changes in woody...... an increase in woody cover largely in drylands, and 11% had a decrease (2,150,000 km2), mostly in humid zones. Increases in woody cover were associated with low population growth, and were driven by increases in CO2 in the humid zones and by increases in precipitation in drylands, whereas decreases in woody...... cover were associated with high population growth. The spatially distinct pattern of these opposing trends reflects, first, the natural response of vegetation to precipitation and atmospheric CO2, and second, deforestation in humid areas, minor in size but important for ecosystem services...

Mechanical metamaterials at the theoretical limit of isotropic elastic stiffness

Science.gov (United States)

Berger, J. B.; Wadley, H. N. G.; McMeeking, R. M.

2017-02-01

A wide variety of high-performance applications require materials for which shape control is maintained under substantial stress, and that have minimal density. Bio-inspired hexagonal and square honeycomb structures and lattice materials based on repeating unit cells composed of webs or trusses, when made from materials of high elastic stiffness and low density, represent some of the lightest, stiffest and strongest materials available today. Recent advances in 3D printing and automated assembly have enabled such complicated material geometries to be fabricated at low (and declining) cost. These mechanical metamaterials have properties that are a function of their mesoscale geometry as well as their constituents, leading to combinations of properties that are unobtainable in solid materials; however, a material geometry that achieves the theoretical upper bounds for isotropic elasticity and strain energy storage (the Hashin-Shtrikman upper bounds) has yet to be identified. Here we evaluate the manner in which strain energy distributes under load in a representative selection of material geometries, to identify the morphological features associated with high elastic performance. Using finite-element models, supported by analytical methods, and a heuristic optimization scheme, we identify a material geometry that achieves the Hashin-Shtrikman upper bounds on isotropic elastic stiffness. Previous work has focused on truss networks and anisotropic honeycombs, neither of which can achieve this theoretical limit. We find that stiff but well distributed networks of plates are required to transfer loads efficiently between neighbouring members. The resulting low-density mechanical metamaterials have many advantageous properties: their mesoscale geometry can facilitate large crushing strains with high energy absorption, optical bandgaps and mechanically tunable acoustic bandgaps, high thermal insulation, buoyancy, and fluid storage and transport. Our relatively simple

The Arabidopsis PLAT domain protein1 promotes abiotic stress tolerance and growth in tobacco

Czech Academy of Sciences Publication Activity Database

Hyun, T.K.; Albacete, A.; van der Graaff, E.; Eom, S. H.; Großkinsky, D.K.; Böhm, H.; Janschek, U.; Rim, Y.; Ali, W.; Kim, S.Y.; Roitsch, Thomas

2015-01-01

Roč. 24, č. 4 (2015), s. 651-663 ISSN 0962-8819 Institutional support: RVO:67179843 Keywords : Abiotic stress * Biotic stress * Plant growth * AtPLAT1 gene * Tobacco Subject RIV: EH - Ecology, Behaviour Impact factor: 2.054, year: 2015

On the Anisotropic Nature of MRI-driven Turbulence in Astrophysical Disks

DEFF Research Database (Denmark)

Murphy, Gareth; Pessah, Martin E.

2015-01-01

-periodic way on timescales comparable to ∼10 inverse angular frequencies, motivating the temporal analysis of its anisotropy. We introduce a 3D tensor invariant analysis to quantify and classify the evolution of the anisotropy of the turbulent flow. This analysis shows a continuous high level of anisotropy......, with brief sporadic transitions toward two- and three-component isotropic turbulent flow. This temporal-dependent anisotropy renders standard shell averaging especially when used simultaneously with long temporal averages, inadequate for characterizing MRI-driven turbulence. We propose an alternative way...

The suite of analytical benchmarks for neutral particle transport in infinite isotropically scattering media

International Nuclear Information System (INIS)

Kornreich, D.E.; Ganapol, B.D.

1997-01-01

The linear Boltzmann equation for the transport of neutral particles is investigated with the objective of generating benchmark-quality evaluations of solutions for homogeneous infinite media. In all cases, the problems are stationary, of one energy group, and the scattering is isotropic. The solutions are generally obtained through the use of Fourier transform methods with the numerical inversions constructed from standard numerical techniques such as Gauss-Legendre quadrature, summation of infinite series, and convergence acceleration. Consideration of the suite of benchmarks in infinite homogeneous media begins with the standard one-dimensional problems: an isotropic point source, an isotropic planar source, and an isotropic infinite line source. The physical and mathematical relationships between these source configurations are investigated. The progression of complexity then leads to multidimensional problems with source configurations that also emit particles isotropically: the finite line source, the disk source, and the rectangular source. The scalar flux from the finite isotropic line and disk sources will have a two-dimensional spatial variation, whereas a finite rectangular source will have a three-dimensional variation in the scalar flux. Next, sources emitting particles anisotropically are considered. The most basic such source is the point beam giving rise to the Green's function, which is physically the most fundamental transport problem, yet may be constructed from the isotropic point source solution. Finally, the anisotropic plane and anisotropically emitting infinite line sources are considered. Thus, a firm theoretical and numerical base is established for the most fundamental neutral particle benchmarks in infinite homogeneous media

Gamma-secretase inhibitor treatment promotes VEGF-A-driven blood vessel growth and vascular leakage but disrupts neovascular perfusion.

Directory of Open Access Journals (Sweden)

Mattias Kalén

Full Text Available The Notch signaling pathway is essential for normal development due to its role in control of cell differentiation, proliferation and survival. It is also critically involved in tumorigenesis and cancer progression. A key enzyme in the activation of Notch signaling is the gamma-secretase protein complex and therefore, gamma-secretase inhibitors (GSIs--originally developed for Alzheimer's disease--are now being evaluated in clinical trials for human malignancies. It is also clear that Notch plays an important role in angiogenesis driven by Vascular Endothelial Growth Factor A (VEGF-A--a process instrumental for tumor growth and metastasis. The effect of GSIs on tumor vasculature has not been conclusively determined. Here we report that Compound X (CX, a GSI previously reported to potently inhibit Notch signaling in vitro and in vivo, promotes angiogenic sprouting in vitro and during developmental angiogenesis in mice. Furthermore, CX treatment suppresses tumor growth in a mouse model of renal carcinoma, leads to the formation of abnormal vessels and an increased tumor vascular density. Using a rabbit model of VEGF-A-driven angiogenesis in skeletal muscle, we demonstrate that CX treatment promotes abnormal blood vessel growth characterized by vessel occlusion, disrupted blood flow, and increased vascular leakage. Based on these findings, we propose a model for how GSIs and other Notch inhibitors disrupt tumor blood vessel perfusion, which might be useful for understanding this new class of anti-cancer agents.

Effect of progressive drought stress on growth, leaf gas exchange, and antioxidant production in two maize cultivars.

Science.gov (United States)

Anjum, Shakeel Ahmad; Tanveer, Mohsin; Ashraf, Umair; Hussain, Saddam; Shahzad, Babar; Khan, Imran; Wang, Longchang

2016-09-01

Drought stress is one of the major environmental factors responsible for reduction in crop productivity. In the present study, responses of two maize cultivars (Rung Nong 35 and Dong Dan 80) were examined to explicate the growth, yield, leaf gas exchange, leaf water contents, osmolyte accumulation, membrane lipid peroxidation, and antioxidant activity under progressive drought stress. Maize cultivars were subjected to varying field capacities (FC) viz., well-watered (80 % FC) and drought-stressed (35 % FC) at 45 days after sowing. The effects of drought stress were analyzed at 5, 10, 15, 20, ad 25 days after drought stress (DAS) imposition. Under prolonged drought stress, Rung Nong 35 exhibited higher reduction in growth and yield as compared to Dong Dan 80. Maize cultivar Dong Dan 80 showed higher leaf relative water content (RWC), free proline, and total carbohydrate accumulation than Run Nong 35. Malondialdehyde (MDA) and superoxide anion were increased with prolongation of drought stress, with higher rates in cultivar Run Nong 35 than cultivar Dong Dan 80. Higher production of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) and glutathione reductase (GR) resulted in improved growth and yield in Dong Dan 80. Overall, the cultivar Dong Dan 80 was better able to resist the detrimental effects of progressive drought stress as indicated by better growth and yield due to higher antioxidant enzymes, reduced lipid peroxidation, better accumulation of osmolytes, and maintenance of tissue water contents.

Effects of alkali stress on growth, free amino acids and carbohydrates metabolism in Kentucky bluegrass (Poa pratensis).

Science.gov (United States)

Zhang, Pingping; Fu, Jinmin; Hu, Longxing

2012-10-01

Soil alkalization is one of the most prominent adverse environmental factors limiting plant growth, while alkali stress affects amino acids and carbohydrates metabolism. The objective of this study was conducted to investigate the effects of alkali stress on growth, amino acids and carbohydrates metabolism in Kentucky bluegrass (Poa pratensis). Seventy-day-old plants were subjected to four pH levels: 6.0 (control), 8.0 (low), 9.4 (moderate) and 10.3 (severe) for 7 days. Moderate to severe alkali stress (pH >9.4) caused a significant decline in turf quality and growth rate in Kentucky bluegrass. Soluble protein was unchanged in shoots, but decreased in roots as pH increased. The levels of amino acids was kept at the same level as control level at 4 days after treatment (DAT) in shoots, but greater at 7 DAT, when plants were subjected to severe (pH 10.3) alkali stress. The alkali stressed plants had a greater level of starch, water soluble carbohydrate and sucrose content, but lower level of fructose and glucose. Fructan and total non-structural carbohydrate (TNC) increased at 4 DAT and decreased at 7 DAT for alkali stressed plants. These results suggested that the decrease in fructose and glucose contributed to the growth reduction under alkali stress, while the increase in amino acids, sucrose and storage form of carbohydrate (fructan, starch) could be an adaptative mechanism in Kentucky bluegrass under alkali stress.

Cytokinin-producing, plant growth-promoting rhizobacteria that confer resistance to drought stress in Platycladus orientalis container seedlings.

Science.gov (United States)

Liu, Fangchun; Xing, Shangjun; Ma, Hailin; Du, Zhenyu; Ma, Bingyao

2013-10-01

One of the proposed mechanisms through which plant growth-promoting rhizobacteria (PGPR) enhance plant growth is the production of plant growth regulators, especially cytokinin. However, little information is available regarding cytokinin-producing PGPR inoculation on growth and water stress consistence of forest container seedlings under drought condition. This study determined the effects of Bacillus subtilis on hormone concentration, drought resistance, and plant growth under water-stressed conditions. Although no significant difference was observed under well-watered conditions, leaves of inoculated Platycladus orientalis (oriental thuja) seedlings under drought stress had higher relative water content and leaf water potential compared with those of noninoculated ones. Regardless of water supply levels, the root exudates, namely sugars, amino acids and organic acids, significantly increased because of B. subtilis inoculation. Water stress reduced shoot cytokinins by 39.14 %. However, inoculation decreased this deficit to only 10.22 %. The elevated levels of cytokinins in P. orientalis shoot were associated with higher concentration of abscisic acid (ABA). Stomatal conductance was significantly increased by B. subtilis inoculation in well-watered seedlings. However, the promoting effect of cytokinins on stomatal conductance was hampered, possibly by the combined action of elevated cytokinins and ABA. B. subtilis inoculation increased the shoot dry weight of well-watered and drought seedlings by 34.85 and 19.23 %, as well as the root by 15.445 and 13.99 %, respectively. Consequently, the root/shoot ratio significantly decreased, indicative of the greater benefits of PGPR on shoot growth than root. Thus, inoculation of cytokinin-producing PGPR in container seedlings can alleviate the drought stress and interfere with the suppression of shoot growth, showing a real potential to perform as a drought stress inhibitor in arid environments.

Fracture analysis of a transversely isotropic high temperature superconductor strip based on real fundamental solutions

International Nuclear Information System (INIS)

Gao, Zhiwen; Zhou, Youhe

2015-01-01

Highlights: • We studied fracture problem in HTS based on real fundamental solutions. • When the thickness of HTS strip increases the SIF decrease. • A higher applied field leads to a larger stress intensity factor. • The greater the critical current density is, the smaller values of the SIF is. - Abstract: Real fundamental solution for fracture problem of transversely isotropic high temperature superconductor (HTS) strip is obtained. The superconductor E–J constitutive law is characterized by the Bean model where the critical current density is independent of the flux density. Fracture analysis is performed by the methods of singular integral equations which are solved numerically by Gauss–Lobatto–Chybeshev (GSL) collocation method. To guarantee a satisfactory accuracy, the convergence behavior of the kernel function is investigated. Numerical results of fracture parameters are obtained and the effects of the geometric characteristics, applied magnetic field and critical current density on the stress intensity factors (SIF) are discussed

Comparative Effects of Salt Stress and Extreme pH Stress Combined on Glycinebetaine Accumulation, Photosynthetic Abilities and Growth Characters of Two Rice Genotypes

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Suriyan CHA-UM

2009-12-01

Full Text Available Glycinebetaine (Glybet accumulation, photosynthetic efficiency and growth performance in indica rice cultivated under salt stress and extreme pH stress were investigated. Betaine aldehyde dehydrogenase (BADH activity and Glybet accumulation in the seedlings of salt-tolerant and salt-sensitive rice varieties grown under saline and acidic conditions peaked after treatment for 72 h and 96 h, respectively, and were higher than those grown under neutral pH and alkaline salt stress. A positive correlation was found between BADH activity and Glybet content in both salt-tolerant (r2 = 0.71 and salt-sensitive (r2 = 0.86 genotypes. The chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids contents in the stressed seedlings significantly decreased under both acidic and alkaline stresses, especially in the salt-sensitive genotype. Similarly, the maximum quantum yield of PSII (Fv/Fm, photon yield of PSII (ΦPSII, non-photochemical quenching (NPQ and net photosynthetic rate (Pn in the stressed seedlings were inhibited, leading to overall growth reduction. The positive correlations between chlorophyll a content and Fv/Fm, total chlorophyll content and ΦPSII, ΦPSII and Pn as well as Pn and leaf area in both salt-tolerant and salt-sensitive genotypes were found. Saline acidic and saline alkaline soils may play a key role affecting vegetative growth prior to the reproductive stage in rice plants.

High-pressure crystal structure of elastically isotropic CaTiO3 perovskite under hydrostatic and non-hydrostatic conditions.

Science.gov (United States)

Zhao, Jing; Ross, Nancy L; Wang, Di; Angel, Ross J

2011-11-16

The structural evolution of orthorhombic CaTiO3 perovskite has been studied using high-pressure single-crystal x-ray diffraction under hydrostatic conditions up to 8.1 GPa and under a non-hydrostatic stress field formed in a diamond anvil cell (DAC) up to 4.7 GPa. Under hydrostatic conditions, the TiO6 octahedra become more tilted and distorted with increasing pressure, similar to other 2:4 perovskites. Under non-hydrostatic conditions, the experiments do not show any apparent difference in the internal structural variation from hydrostatic conditions and no additional tilts and distortions in the TiO6 octahedra are observed, even though the lattice itself becomes distorted due to the non-hydrostatic stress. The similarity between the hydrostatic and non-hydrostatic cases can be ascribed to the fact that CaTiO3 perovskite is nearly elastically isotropic and, as a consequence, its deviatoric unit-cell volume strain produced by the non-hydrostatic stress is very small; in other words, the additional octahedral tilts relevant to the extra unit-cell volume associated with the deviatoric unit-cell volume strain may be totally neglected. This study further addresses the role that three factors--the elastic properties, the crystal orientation and the pressure medium--have on the structural evolution of an orthorhombic perovskite loaded in a DAC under non-hydrostatic conditions. The influence of these factors can be clearly visualized by plotting the three-dimensional distribution of the deviatoric unit-cell volume strain in relation to the cylindrical axis of the DAC and indicates that, if the elasticity of a perovskite is nearly isotropic as it is for CaTiO3, the other two factors become relatively insignificant.

High-pressure crystal structure of elastically isotropic CaTiO3 perovskite under hydrostatic and non-hydrostatic conditions

International Nuclear Information System (INIS)

Zhao Jing; Ross, Nancy L; Wang, Di; Angel, Ross J

2011-01-01

The structural evolution of orthorhombic CaTiO 3 perovskite has been studied using high-pressure single-crystal x-ray diffraction under hydrostatic conditions up to 8.1 GPa and under a non-hydrostatic stress field formed in a diamond anvil cell (DAC) up to 4.7 GPa. Under hydrostatic conditions, the TiO 6 octahedra become more tilted and distorted with increasing pressure, similar to other 2:4 perovskites. Under non-hydrostatic conditions, the experiments do not show any apparent difference in the internal structural variation from hydrostatic conditions and no additional tilts and distortions in the TiO 6 octahedra are observed, even though the lattice itself becomes distorted due to the non-hydrostatic stress. The similarity between the hydrostatic and non-hydrostatic cases can be ascribed to the fact that CaTiO 3 perovskite is nearly elastically isotropic and, as a consequence, its deviatoric unit-cell volume strain produced by the non-hydrostatic stress is very small; in other words, the additional octahedral tilts relevant to the extra unit-cell volume associated with the deviatoric unit-cell volume strain may be totally neglected. This study further addresses the role that three factors-the elastic properties, the crystal orientation and the pressure medium-have on the structural evolution of an orthorhombic perovskite loaded in a DAC under non-hydrostatic conditions. The influence of these factors can be clearly visualized by plotting the three-dimensional distribution of the deviatoric unit-cell volume strain in relation to the cylindrical axis of the DAC and indicates that, if the elasticity of a perovskite is nearly isotropic as it is for CaTiO 3 , the other two factors become relatively insignificant. (paper)

The Isotropic Radio Background and Annihilating Dark Matter

Energy Technology Data Exchange (ETDEWEB)

Hooper, Dan [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Belikov, Alexander V. [Institut d' Astrophysique (France); Jeltema, Tesla E. [Univ. of California, Santa Cruz, CA (United States); Linden, Tim [Univ. of California, Santa Cruz, CA (United States); Profumo, Stefano [Univ. of California, Santa Cruz, CA (United States); Slatyer, Tracy R. [Princeton Univ., Princeton, NJ (United States)

2012-11-01

Observations by ARCADE-2 and other telescopes sensitive to low frequency radiation have revealed the presence of an isotropic radio background with a hard spectral index. The intensity of this observed background is found to exceed the flux predicted from astrophysical sources by a factor of approximately 5-6. In this article, we consider the possibility that annihilating dark matter particles provide the primary contribution to the observed isotropic radio background through the emission of synchrotron radiation from electron and positron annihilation products. For reasonable estimates of the magnetic fields present in clusters and galaxies, we find that dark matter could potentially account for the observed radio excess, but only if it annihilates mostly to electrons and/or muons, and only if it possesses a mass in the range of approximately 5-50 GeV. For such models, the annihilation cross section required to normalize the synchrotron signal to the observed excess is sigma v ~ (0.4-30) x 10^-26 cm^3/s, similar to the value predicted for a simple thermal relic (sigma v ~ 3 x 10^-26 cm^3/s). We find that in any scenario in which dark matter annihilations are responsible for the observed excess radio emission, a significant fraction of the isotropic gamma ray background observed by Fermi must result from dark matter as well.

Growth rate regulated genes and their wide involvement in the Lactococcus lactis stress responses

Directory of Open Access Journals (Sweden)

Redon Emma

2008-07-01

Full Text Available Abstract Background The development of transcriptomic tools has allowed exhaustive description of stress responses. These responses always superimpose a general response associated to growth rate decrease and a specific one corresponding to the stress. The exclusive growth rate response can be achieved through chemostat cultivation, enabling all parameters to remain constant except the growth rate. Results We analysed metabolic and transcriptomic responses of Lactococcus lactis in continuous cultures at different growth rates ranging from 0.09 to 0.47 h-1. Growth rate was conditioned by isoleucine supply. Although carbon metabolism was constant and homolactic, a widespread transcriptomic response involving 30% of the genome was observed. The expression of genes encoding physiological functions associated with biogenesis increased with growth rate (transcription, translation, fatty acid and phospholipids metabolism. Many phages, prophages and transposon related genes were down regulated as growth rate increased. The growth rate response was compared to carbon and amino-acid starvation transcriptomic responses, revealing constant and significant involvement of growth rate regulations in these two stressful conditions (overlap 27%. Two regulators potentially involved in the growth rate regulations, llrE and yabB, have been identified. Moreover it was established that genes positively regulated by growth rate are preferentially located in the vicinity of replication origin while those negatively regulated are mainly encountered at the opposite, thus indicating the relationship between genes expression and their location on chromosome. Although stringent response mechanism is considered as the one governing growth deceleration in bacteria, the rigorous comparison of the two transcriptomic responses clearly indicated the mechanisms are distinct. Conclusion This work of integrative biology was performed at the global level using transcriptomic analysis

Cyanobacteria-mediated phenylpropanoids and phytohormones in rice (Oryza sativa) enhance plant growth and stress tolerance.

Science.gov (United States)

Singh, Dhananjaya P; Prabha, Ratna; Yandigeri, Mahesh S; Arora, Dilip K

2011-11-01

Phenylpropanoids, flavonoids and plant growth regulators in rice (Oryza sativa) variety (UPR 1823) inoculated with different cyanobacterial strains namely Anabaena oryzae, Anabaena doliolum, Phormidium fragile, Calothrix geitonos, Hapalosiphon intricatus, Aulosira fertilissima, Tolypothrix tenuis, Oscillatoria acuta and Plectonema boryanum were quantified using HPLC in pot conditions after 15 and 30 days. Qualitative analysis of the induced compounds using reverse phase HPLC and further confirmation with LC-MS/MS showed consistent accumulation of phenolic acids (gallic, gentisic, caffeic, chlorogenic and ferulic acids), flavonoids (rutin and quercetin) and phytohormones (indole acetic acid and indole butyric acid) in rice leaves. Plant growth promotion (shoot, root length and biomass) was positively correlated with total protein and chlorophyll content of leaves. Enzyme activity of peroxidase and phenylalanine ammonia lyase and total phenolic content was fairly high in rice leaves inoculated with O. acuta and P. boryanum after 30 days. Differential systemic accumulation of phenylpropanoids in plant leaves led us to conclude that cyanobacterial inoculation correlates positively with plant growth promotion and stress tolerance in rice. Furthermore, the study helped in deciphering possible mechanisms underlying plant growth promotion and stress tolerance in rice following cyanobacterial inoculation and indicated the less explored avenue of cyanobacterial colonization in stress tolerance against abiotic stress.

STRESSED STATE OF ROCKY SUBSOIL IN THE VICINITY OF A CIRCULAR SECTION HYDRAULIC ENGINEERING TUNNEL TAKING INTO ACCOUNT THE ANISOTROPY OF THE GROUND MEDIUM

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D. T. Bautdinov

2016-01-01

Full Text Available Objectives. The aim of this study consists ina parametric analysis of the stress state of transversely isotropic rocky ground in the vicinity of a circular cross-sectional hydraulic tunnel taking into account the dead load of the subsoil medium under various relations of the elastic characteristics of the subsoil environment in orthogonal directions and at different angles of inclination of the plane of isotropy. Methods. A transversely isotropic medium model (a special case of an anisotropic medium is applied, in which the subsoil in one plane has the characteristics of an isotropic medium (isotropic plane but in a perpendicular direction – in contradistinction to the characteristics of an isotropic medium.The angle of isotropic planar inclination models the oblique bedding of subsoil layers. Results. The determination of tangential stresses on the contour generation allows the strength of the subsoil medium to be estimated at different depths of emplacement. The calculation of extensive hydraulic engineering tunnels, constructed in strong, transversely isotropic rocky ground, is reduced to a problem of plane strain elasticity theory for a transversely isotropic medium surrounding the tunnel construction. Since the solution of this problem cannot be achieved using analytical methods, the analysis of the stress state was carried out by finite element method using the ANSYS software complex. The type and size of the finite element appropriate for the calculation were pre-identified based on solutions to the task of verification. For the verificatory task, the Kirsch problem was adopted. Conclusion.When designing underground structures, it is necessary to determine the physical and mechanical properties of rocky soils in greater detail and to pay special attention to the elastic characteristics. The absence of tensile stresses in the upper section of development with some relations of the moduli of deformation and Poisson's ratios benefit the

Effects of root radius, stress, crack growth and rate on fracture instability

Energy Technology Data Exchange (ETDEWEB)

McClintock, F A

1965-01-01

Of various criteria for fracture at the root of a notch, the energy, local stress, and displacement criteria have limited validity. More appropriate is the history of both stress and strain over a small region ahead of the crack, as required for fracture by the coalescence of holes. Expressions are given for crack initiation, growth, and subsequent instability in anti-plane strain of a nonhardening material. Instability is shown to depend primarily on those strain increments arising from crack growth at constant load rather than on those from increasing load at constant crack length. Thus final instability conditions are similar for single and double- ended cracks, round notches, and cracks cut under constant load. Round notches may give instability, restabilization and final instability. The growth and coalescence of holes in front of a crack in a linearly viscous material is studied for both tensile and anti-plant-strain cracks. The absence of residual strain eliminates instability, but the crack continually accelerates. (26 refs.)

Plant Growth Promoting Rhizobacteria in Amelioration of Salinity Stress: A Systems Biology Perspective

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Gayathri Ilangumaran

2017-10-01

Full Text Available Salinity affects plant growth and is a major abiotic stress that limits crop productivity. It is well-understood that environmental adaptations and genetic traits regulate salinity tolerance in plants, but imparting the knowledge gained towards crop improvement remain arduous. Harnessing the potential of beneficial microorganisms present in the rhizosphere is an alternative strategy for improving plant stress tolerance. This review intends to elucidate the understanding of salinity tolerance mechanisms attributed by plant growth promoting rhizobacteria (PGPR. Recent advances in molecular studies have yielded insights into the signaling networks of plant–microbe interactions that contribute to salt tolerance. The beneficial effects of PGPR involve boosting key physiological processes, including water and nutrient uptake, photosynthesis, and source-sink relationships that promote growth and development. The regulation of osmotic balance and ion homeostasis by PGPR are conducted through modulation of phytohormone status, gene expression, protein function, and metabolite synthesis in plants. As a result, improved antioxidant activity, osmolyte accumulation, proton transport machinery, salt compartmentalization, and nutrient status reduce osmotic stress and ion toxicity. Furthermore, in addition to indole-3-acetic acid and 1-aminocyclopropane-1-carboxylic acid deaminase biosynthesis, other extracellular secretions of the rhizobacteria function as signaling molecules and elicit stress responsive pathways. Application of PGPR inoculants is a promising measure to combat salinity in agricultural fields, thereby increasing global food production.

Hybrid determination of mixed-mode stress intensity factors on discontinuous finite-width plate by finite element and photoelasticity

International Nuclear Information System (INIS)

Baek, Tae Hyun; Chen, Lei; Hong, Dong Pyo

2011-01-01

For isotropic material structure, the stress in the vicinity of crack tip is generally much higher than the stress far away from it. This phenomenon usually leads to stress concentration and fracture of structure. Previous researches and studies show that the stress intensity factor is one of most important parameter for crack growth and propagation. This paper provides a convenient numerical method, which is called hybrid photoelasticity method, to accurately determine the stress field distribution in the vicinity of crack tip and mixed-mode stress intensity factors. The model was simulated by finite element method and isochromatic data along straight lines far away from the crack tip were calculated. By using the isochromatic data obtained from finite element method and a conformal mapping procedure, stress components and photoelastic fringes in the hybrid region were calculated. To easily compare calculated photoelastic fringes with experiment results, the fringe patterns were reconstructed, doubled and sharpened. Good agreement shows that the method presented in this paper is reliable and convenient. This method can then directly be applied to obtain mixed mode stress intensity factors from the experimentally measured isochromatic data along the straight lines

Morpho-Physiological Responses of Maize to Drought Stress at Different Growth Stages in Northern Semi-Arid Region of Fars

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R. Hemati

2014-04-01

Full Text Available In order to evaluate morpho-physiological responses of hybrid corn KSC750 to water stress at various stages of growth, a field experiment was conducted at the Pasargad region (northwest Fars in 2010. The experiment carried out as a randomized complete block design, with 3 replications. In this study, corn growth period was divided into three phases: the establishment of plant to tasseling (phase I, tasseling to dough development (phase II and dough development to ripening (phase III. Treatments were consisted of control, irrigation cut off after dough development, water stress of 75 percent of FC during vegetative phase and after dough development, water stress of 75 percent of FC during whole growth phase, water stress of 50 percent of FC during vegetative stage and after dough development and water stress of 50 percent of FC during whole growth phase. Results showed that mild drought stress (75% FC at vegetative phase was not significantly effected growth and yield of corn. However, application of drought stress during the whole growth period significantly reduced morphological parameters as well as yield and yield components. Based on these results, flowering and grain filling stages were identified as more sensitive stages to drought stress in corn. Moreover, irrigation cut off after dough development terminated to a satisfactory yield. The results indicated that, overall, under Pasargad region and similar agro climatic conditions, it would be possible to save water to 75 percentage of corn water requirement through application of deficit irrigation after dough development stage.

On the influence of abiotic stress conditions on growth of barley and bean and their predisposition for pathogens

Energy Technology Data Exchange (ETDEWEB)

Oerke, E.C.; Schoenbeck, F.

1986-01-01

Shorttime changes of environmental conditions stressed barley and bean and affected plant growth and their predisposition for various pathogens. Moderate stress intensities as low or high temperatures, water or light deficits, increased the susceptibility to Erysiphe graminis var. hordei or Uromyces phaseoli and reduced disease level of spot blotch caused by Cochliobolus sativus, respectively. There was only little effect on plant growth in that case. Intensive stress as a result of combinations of unfavorable environmental conditions or longtime continuance of moderate stress reduced the plant growth and turned the predisposing effect to the opposite: after the treatment, plants were more resistent to diseases caused by biotrophic fungi, whereas there was increased susceptibility to the perthotrophic fungus. High intensities of fertilization acted as an additional stress and intensified the plant reaction to environmental alterations. The variation of the predisposition is discussed in relation to stress intensity.

Growth stress buildup in ion beam sputtered Mo thin films and comparative study of stress relaxation upon thermal annealing or ion irradiation

International Nuclear Information System (INIS)

Debelle, A.; Abadias, G.; Michel, A.; Jaouen, C.; Pelosin, V.

2007-01-01

In an effort to address the understanding of the origin of growth stress in thin films deposited under very energetic conditions, the authors investigated the stress state and microstructure of Mo thin films grown by ion beam sputtering (IBS) as well as the stress relaxation processes taking place during subsequent thermal annealing or ion irradiation. Different sets of samples were grown by varying the IBS deposition parameters, namely, the energy E 0 and the flux j of the primary ion beam, the target-to-sputtering gas mass ratio M 1 /M 2 as well as film thickness. The strain-stress state was determined by x-ray diffraction using the sin 2 ψ method and data analyzed using an original stress model which enabled them to correlate information at macroscopic (in terms of stress) and microscopic (in terms of defect concentration) levels. Results indicate that these refractory metallic thin films are characterized by a high compressive growth stress (-2.6 to -3.8 GPa), resulting from the creation of a large concentration (up to ∼1.4%) of point or cluster defects, due to the atomic peening mechanism. The M 1 /M 2 mass ratio enables tuning efficiently the mean deposited energy of the condensing atoms; thus, it appears to be the more relevant deposition parameter that allows modifying both the microstructure and the stress level in a significant way. The growth stress comes out to be highly unstable. It can be easily relaxed either by postgrowth thermal annealing or ion irradiation in the hundred keV range at very low dose [<0.1 dpa (displacement per atom)]. It is shown that thermal annealing induces deleterious effects such as oxidation of the film surface, decrease of the film density, and in some cases adhesion loss at the film/substrate interface, while ion irradiation allows controlling the stress level without generating any macroscopic damage

The response of leaves to heat stress in tomato plants with source-sink modulated by growth regulators

Directory of Open Access Journals (Sweden)

Zofia Starck

2014-01-01

Full Text Available The response to heat stress was investigated in heat-sensitive, Roma V. F. and heat-tolerant, Robin, cultivars whose fruit growth was stimulated by NOA + GA3 , or NOA + GA3 + zeatin. The treated plants were compared with untreated control plant. In each of these series half of the plants were subjected to one or three cycles of heat stress. A single cycle of 38°/25°C day and night did not significantly affect either the respiration rate or chlorophyll content. In PGR-untreated intact cv. Roma, heat stress inhibited starch formation during the day and strongly depressed night export from the blades. High temperature depressed the night transport less in plants having a higher sink demand of fruits in plant treated with PGR. In this case the amount of substances available for export was much higher and both sugars and starch were more intensively remobilized at night. In intact Robin plants, PGR and heat stress much less affected sugar and starch content. High temperature diminished noctural starch remobilization only in the NOA + GA3 series. Leaf disc growth was evaluated as a measure of response to heat stress after elimination of the direct effect of fruit demands. One cycle of high temperature did not negatively affect the growth of leaf discs; it even caused thermal low growth activation in both cultivars. Three cycles of heat stress depressed leaf disc growth after short-term stimulation, especially in Roma plants. Immediately after 3-day heat stress, there was no response of discs to GA3 or zeatin added to the solution on which the discs were floated. Leaf disc growth of Robin control and NOA + GA3 series was very similar in plants from optimal temperature conditions. High temperature inhibited only disc growth of the NOA + GA3 series owing to depression of starch break-down, diminishing the pool of sugars. In contrast, leaf discs of Roma cv. excided from NOA + GA3 treated plants from the optimal temperature series, grew more intensively

Efficient anisotropic wavefield extrapolation using effective isotropic models

KAUST Repository

Alkhalifah, Tariq Ali; Ma, X.; Waheed, Umair bin; Zuberi, Mohammad

2013-01-01

Isotropic wavefield extrapolation is more efficient than anisotropic extrapolation, and this is especially true when the anisotropy of the medium is tilted (from the vertical). We use the kinematics of the wavefield, appropriately represented

Acoustic reflection log in transversely isotropic formations

Science.gov (United States)

Ronquillo Jarillo, G.; Markova, I.; Markov, M.

2018-01-01

We have calculated the waveforms of sonic reflection logging for a fluid-filled borehole located in a transversely isotropic rock. Calculations have been performed for an acoustic impulse source with the characteristic frequency of tens of kilohertz that is considerably less than the frequencies of acoustic borehole imaging tools. It is assumed that the borehole axis coincides with the axis of symmetry of the transversely isotropic rock. It was shown that the reflected wave was excited most efficiently at resonant frequencies. These frequencies are close to the frequencies of oscillations of a fluid column located in an absolutely rigid hollow cylinder. We have shown that the acoustic reverberation is controlled by the acoustic impedance of the rock Z = Vphρs for fixed parameters of the borehole fluid, where Vph is the velocity of horizontally propagating P-wave; ρs is the rock density. The methods of waveform processing to determine the parameters characterizing the reflected wave have been discussed.

From current-driven to neoclassically driven tearing modes.

Science.gov (United States)

Reimerdes, H; Sauter, O; Goodman, T; Pochelon, A

2002-03-11

In the TCV tokamak, the m/n = 2/1 island is observed in low-density discharges with central electron-cyclotron current drive. The evolution of its width has two distinct growth phases, one of which can be linked to a "conventional" tearing mode driven unstable by the current profile and the other to a neoclassical tearing mode driven by a perturbation of the bootstrap current. The TCV results provide the first clear observation of such a destabilization mechanism and reconcile the theory of conventional and neoclassical tearing modes, which differ only in the dominant driving term.

Direct uptake of canopy rainwater causes turgor-driven growth spurts in the mangrove Avicennia marina.

Science.gov (United States)

Steppe, Kathy; Vandegehuchte, Maurits W; Van de Wal, Bart A E; Hoste, Pieter; Guyot, Adrien; Lovelock, Catherine E; Lockington, David A

2018-03-17

Mangrove forests depend on a dense structure of sufficiently large trees to fulfil their essential functions as providers of food and wood for animals and people, CO2 sinks and protection from storms. Growth of these forests is known to be dependent on the salinity of soil water, but the influence of foliar uptake of rainwater as a freshwater source, additional to soil water, has hardly been investigated. Under field conditions in Australia, stem diameter variation, sap flow and stem water potential of the grey mangrove (Avicennia marina (Forssk.) Vierh.) were simultaneously measured during alternating dry and rainy periods. We found that sap flow in A. marina was reversed, from canopy to roots, during and shortly after rainfall events. Simultaneously, stem diameters rapidly increased with growth rates up to 70 μm h-1, which is about 25-75 times the normal growth rate reported in temperate trees. A mechanistic tree model was applied to provide evidence that A. marina trees take up water through their leaves, and that this water contributes to turgor-driven stem growth. Our results indicate that direct uptake of freshwater by the canopy during rainfall supports mangrove tree growth and serve as a call to consider this water uptake pathway if we aspire to correctly assess influences of changing rainfall patterns on mangrove tree growth.

Considerations of ion temperature gradient driven turbulence

International Nuclear Information System (INIS)

Cowley, S.C.; Kulsrud, R.M.

1991-02-01

The ion temperature gradient driven instability is considered in this paper. Physical pictures are presented to clarify the nature of the instability. The saturation of a single eddy is modeled by a simple nonlinear equation. We show that eddies which are elongated in the direction of the temperature gradient are the most unstable and have the highest saturation amplitudes. In a sheared magnetic field, such elongated eddies twist with the field lines. This structure is shown to be alternative to the usual Fourier mode picture in which the mode is localized around the surface where k parallel = 0. We show how these elongated twisting eddies, which are an integral part of the ''ballooning mode'' structure, could survive in a torus. The elongated eddies are shown to be unstable to secondary instabilities that are driven by the large gradients in the long eddy. We argue that this mechanism isotropizes ion temperature gradient turbulence. We further argue that the ''mixing length'' is set by this nonlinear process, not by a linear eigenmode width. 17 refs., 6 figs

Magnetoelastic shear wave propagation in pre-stressed anisotropic media under gravity

Science.gov (United States)

Kumari, Nirmala; Chattopadhyay, Amares; Singh, Abhishek K.; Sahu, Sanjeev A.

2017-03-01

The present study investigates the propagation of shear wave (horizontally polarized) in two initially stressed heterogeneous anisotropic (magnetoelastic transversely isotropic) layers in the crust overlying a transversely isotropic gravitating semi-infinite medium. Heterogeneities in both the anisotropic layers are caused due to exponential variation (case-I) and linear variation (case-II) in the elastic constants with respect to the space variable pointing positively downwards. The dispersion relations have been established in closed form using Whittaker's asymptotic expansion and were found to be in the well-agreement to the classical Love wave equations. The substantial effects of magnetoelastic coupling parameters, heterogeneity parameters, horizontal compressive initial stresses, Biot's gravity parameter, and wave number on the phase velocity of shear waves have been computed and depicted by means of a graph. As a special case, dispersion equations have been deduced when the two layers and half-space are isotropic and homogeneous. The comparative study for both cases of heterogeneity of the layers has been performed and also depicted by means of graphical illustrations.

Growth and physiological responses of some Capsicum frutescens varieties to copper stress

Science.gov (United States)

Jadid, Nurul; Maziyah, Rizka; Nurcahyani, Desy Dwi; Mubarokah, Nilna Rizqiyah

2017-06-01

Copper (Cu) is an essential micronutrient participating in various physiological processes. However, excessive uptake of this micronutrient could potentially affect plant growth and development as well as plant productivity. In this present work, growth and physiological responses of some Capsicum frustescens varieties to Cu stress were determined. Three C. frutescens varieties used in this work were var. Bara, CF 291, and Genie. In addition, these varieties were treated with different concentration of Cu (0, 30, 70, and 120 ppm). The growth and physiological responses measured in this work included plant height, root length, malondialdehyde (MDA), and chlorophyll. The result showed that all varieties tested relatively displayed plant growth reduction including plant height and root length. Likewise, an increase of MDA level, a major bioindicator for oxidative damage was also found in all varieties following exposure to elevated Cu concentration. Finally, the chlorophyll content was also affected indicated by a decreased amount of chlorophyll, especially in var. CF291. The overall results demonstrated that elevated Cu concentration might decrease C. frutescens productivity where among the three varieties tested, var CF 291 seemed to be the most sensitive varieties to Cu stress.

Growth responses of NaCl stressed rice (Oryza sativa L.) plants ...

African Journals Online (AJOL)

GREGORY

2010-09-27

Sep 27, 2010 ... Growth responses of NaCl stressed rice (Oryza sativa. L.) plants ... 2008), which is a real threat to human's food security. Existed situation may ..... content and composition of essential oil and minerals in black cumin. (Nigella ...

Pre-disposition and epigenetics govern variation in bacterial survival upon stress.

Directory of Open Access Journals (Sweden)

Ming Ni

Full Text Available Bacteria suffer various stresses in their unpredictable environment. In response, clonal populations may exhibit cell-to-cell variation, hypothetically to maximize their survival. The origins, propagation, and consequences of this variability remain poorly understood. Variability persists through cell division events, yet detailed lineage information for individual stress-response phenotypes is scarce. This work combines time-lapse microscopy and microfluidics to uniformly manipulate the environmental changes experienced by clonal bacteria. We quantify the growth rates and RpoH-driven heat-shock responses of individual Escherichia coli within their lineage context, stressed by low streptomycin concentrations. We observe an increased variation in phenotypes, as different as survival from death, that can be traced to asymmetric division events occurring prior to stress induction. Epigenetic inheritance contributes to the propagation of the observed phenotypic variation, resulting in three-fold increase of the RpoH-driven expression autocorrelation time following stress induction. We propose that the increased permeability of streptomycin-stressed cells serves as a positive feedback loop underlying this epigenetic effect. Our results suggest that stochasticity, pre-disposition, and epigenetic effects are at the source of stress-induced variability. Unlike in a bet-hedging strategy, we observe that cells with a higher investment in maintenance, measured as the basal RpoH transcriptional activity prior to antibiotic treatment, are more likely to give rise to stressed, frail progeny.

Endoplasmic reticulum stress disrupts placental morphogenesis: implications for human intrauterine growth restriction.

Science.gov (United States)

Yung, Hong Wa; Hemberger, Myriam; Watson, Erica D; Senner, Claire E; Jones, Carolyn P; Kaufman, Randal J; Charnock-Jones, D Stephen; Burton, Graham J

2012-12-01

We recently reported the first evidence of placental endoplasmic reticulum (ER) stress in the pathophysiology of human intrauterine growth restriction. Here, we used a mouse model to investigate potential underlying mechanisms. Eif2s1(tm1RjK) mice, in which Ser51 of eukaryotic initiation factor 2 subunit alpha (eIF2α) is mutated, display a 30% increase in basal translation. In Eif2s1(tm1RjK) placentas, we observed increased ER stress and anomalous accumulation of glycoproteins in the endocrine junctional zone (Jz), but not in the labyrinthine zone where physiological exchange occurs. Placental and fetal weights were reduced by 15% (97 mg to 82 mg, p growth factor for placental development; indeed, activity in the Pdk1-Akt-mTOR pathways was decreased in Eif2s1(tm1RjK) placentas, indicating loss of Igf2 signalling. Furthermore, we observed premature differentiation of trophoblast progenitors at E9.5 in mutant placentas, consistent with the in vitro results and with the disproportionate development of the labyrinth and Jz seen in placentas at E18.5. Similar disproportion has been reported in the Igf2-null mouse. These results demonstrate that ER stress adversely affects placental development, and that modulation of post-translational processing, and hence bioactivity, of secreted growth factors contributes to this effect. Placental dysmorphogenesis potentially affects fetal growth through reduced exchange capacity. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Isotropic events observed with a borehole array in the Chelungpu fault zone, Taiwan.

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Ma, Kuo-Fong; Lin, Yen-Yu; Lee, Shiann-Jong; Mori, Jim; Brodsky, Emily E

2012-07-27

Shear failure is the dominant mode of earthquake-causing rock failure along faults. High fluid pressure can also potentially induce rock failure by opening cavities and cracks, but an active example of this process has not been directly observed in a fault zone. Using borehole array data collected along the low-stress Chelungpu fault zone, Taiwan, we observed several small seismic events (I-type events) in a fluid-rich permeable zone directly below the impermeable slip zone of the 1999 moment magnitude 7.6 Chi-Chi earthquake. Modeling of the events suggests an isotropic, nonshear source mechanism likely associated with natural hydraulic fractures. These seismic events may be associated with the formation of veins and other fluid features often observed in rocks surrounding fault zones and may be similar to artificially induced hydraulic fracturing.

Finite amplitude, horizontal motion of a load symmetrically supported between isotropic hyperelastic springs.

Science.gov (United States)

Beatty, Millard F; Young, Todd R

2012-03-01

The undamped, finite amplitude horizontal motion of a load supported symmetrically between identical incompressible, isotropic hyperelastic springs, each subjected to an initial finite uniaxial static stretch, is formulated in general terms. The small amplitude motion of the load about the deformed static state is discussed; and the periodicity of the arbitrary finite amplitude motion is established for all such elastic materials for which certain conditions on the engineering stress and the strain energy function hold. The exact solution for the finite vibration of the load is then derived for the classical neo-Hookean model. The vibrational period is obtained in terms of the complete Heuman lambda-function whose properties are well-known. Dependence of the period and hence the frequency on the physical parameters of the system is investigated and the results are displayed graphically.

A mathematical model for IL-6-mediated, stem cell driven tumor growth and targeted treatment

Science.gov (United States)

Nör, Jacques Eduardo

2018-01-01

Targeting key regulators of the cancer stem cell phenotype to overcome their critical influence on tumor growth is a promising new strategy for cancer treatment. Here we present a modeling framework that operates at both the cellular and molecular levels, for investigating IL-6 mediated, cancer stem cell driven tumor growth and targeted treatment with anti-IL6 antibodies. Our immediate goal is to quantify the influence of IL-6 on cancer stem cell self-renewal and survival, and to characterize the subsequent impact on tumor growth dynamics. By including the molecular details of IL-6 binding, we are able to quantify the temporal changes in fractional occupancies of bound receptors and their influence on tumor volume. There is a strong correlation between the model output and experimental data for primary tumor xenografts. We also used the model to predict tumor response to administration of the humanized IL-6R monoclonal antibody, tocilizumab (TCZ), and we found that as little as 1mg/kg of TCZ administered weekly for 7 weeks is sufficient to result in tumor reduction and a sustained deceleration of tumor growth. PMID:29351275

Stress-inducible expression of an F-box gene TaFBA1 from wheat enhanced the drought tolerance in transgenic tobacco plants without impacting growth and development

Directory of Open Access Journals (Sweden)

Xiangzhu Kong

2016-09-01

Full Text Available E3 ligase plays an important role in the response to many environment stresses in plants. In our previous study, constitutive overexpression of an F-box protein gene TaFBA1 driven by 35S promoter improved the drought tolerance in transgenic tobacco plants, but the growth and development in transgenic plants was altered in normal conditions. In this study, we used stress-inducible promoter RD29A instead of 35S promoter, as a results, the stress-inducible transgenic tobacco plants exhibit a similar phenotype with WT plants. However, the drought tolerance of the transgenic plants with stress-inducible expressed TaFBA1 was enhanced. The improved drought tolerance of transgenic plants was indicated by their higher seed germination rate and survival rate, greater biomass and photosynthesis than those of WT under water stress, which may be related to their greater water retention capability and osmotic adjustment. Moreover, the transgenic plants accumulated less reactive oxygen species (ROS, kept lower MDA content and membrane leakage under water stress, which may be related to their higher levels of antioxidant enzyme activity and upregulated gene expression of some antioxidant enzymes. These results suggest that stress induced expression of TaFBA1 confers drought tolerance via the improved water retention and antioxidative compete abilibty. Meanwhile, this stress-inducible expression strategy by RD29A promoter can minimize the unexpectable effects by 35S constitutive promoter on phenotypes of the transgenic plants.

Stress-Inducible Expression of an F-box Gene TaFBA1 from Wheat Enhanced the Drought Tolerance in Transgenic Tobacco Plants without Impacting Growth and Development.

Science.gov (United States)

Kong, Xiangzhu; Zhou, Shumei; Yin, Suhong; Zhao, Zhongxian; Han, Yangyang; Wang, Wei

2016-01-01

E3 ligase plays an important role in the response to many environment stresses in plants. In our previous study, constitutive overexpression of an F-box protein gene TaFBA1 driven by 35S promoter improved the drought tolerance in transgenic tobacco plants, but the growth and development in transgenic plants was altered in normal conditions. In this study, we used stress-inducible promoter RD29A instead of 35S promoter, as a results, the stress-inducible transgenic tobacco plants exhibit a similar phenotype with wild type (WT) plants. However, the drought tolerance of the transgenic plants with stress-inducible expressed TaFBA1 was enhanced. The improved drought tolerance of transgenic plants was indicated by their higher seed germination rate and survival rate, greater biomass and photosynthesis than those of WT under water stress, which may be related to their greater water retention capability and osmotic adjustment. Moreover, the transgenic plants accumulated less reactive oxygen species, kept lower MDA content and membrane leakage under water stress, which may be related to their higher levels of antioxidant enzyme activity and upregulated gene expression of some antioxidant enzymes. These results suggest that stress induced expression of TaFBA1 confers drought tolerance via the improved water retention and antioxidative compete ability. Meanwhile, this stress-inducible expression strategy by RD29A promoter can minimize the unexpectable effects by 35S constitutive promoter on phenotypes of the transgenic plants.

Isotropic transmission of magnon spin information without a magnetic field.

Science.gov (United States)

Haldar, Arabinda; Tian, Chang; Adeyeye, Adekunle Olusola

2017-07-01

Spin-wave devices (SWD), which use collective excitations of electronic spins as a carrier of information, are rapidly emerging as potential candidates for post-semiconductor non-charge-based technology. Isotropic in-plane propagating coherent spin waves (magnons), which require magnetization to be out of plane, is desirable in an SWD. However, because of lack of availability of low-damping perpendicular magnetic material, a usually well-known in-plane ferrimagnet yttrium iron garnet (YIG) is used with a large out-of-plane bias magnetic field, which tends to hinder the benefits of isotropic spin waves. We experimentally demonstrate an SWD that eliminates the requirement of external magnetic field to obtain perpendicular magnetization in an otherwise in-plane ferromagnet, Ni 80 Fe 20 or permalloy (Py), a typical choice for spin-wave microconduits. Perpendicular anisotropy in Py, as established by magnetic hysteresis measurements, was induced by the exchange-coupled Co/Pd multilayer. Isotropic propagation of magnon spin information has been experimentally shown in microconduits with three channels patterned at arbitrary angles.

Scanning anisotropy parameters in horizontal transversely isotropic media

KAUST Repository

Masmoudi, Nabil; Stovas, Alexey; Alkhalifah, Tariq Ali

2016-01-01

in reservoir characterisation, specifically in terms of fracture delineation. We propose a travel-time-based approach to estimate the anellipticity parameter η and the symmetry axis azimuth ϕ of a horizontal transversely isotropic medium, given an inhomogeneous

Wave propagation in isotropic- or composite-material piping conveying swirling liquid

International Nuclear Information System (INIS)

Chen, T.L.C.; Bert, C.W.

1977-01-01

An analysis is presented for the propagation of free harmonic waves in a thin-walled, circular cylindrical shell of orthotropic or isotropic material conveying a swirling flow. The shell motion is modeled by using the dynamic orthotropic version of the Sanders improved first-approximation linear shell theory and the fluid forces are described by using inviscid incompressible flow theory. Frequency spectra are presented for pipes made of isotropic material and composite materials of current engineering interest. (Auth.)

Isotropic Optical Mouse Placement for Mobile Robot Velocity Estimation

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Sungbok Kim

2014-06-01

Full Text Available This paper presents the isotropic placement of multiple optical mice for the velocity estimation of a mobile robot. It is assumed that there can be positional restriction on the installation of optical mice at the bottom of a mobile robot. First, the velocity kinematics of a mobile robot with an array of optical mice is obtained and the resulting Jacobian matrix is analysed symbolically. Second, the isotropic, anisotropic and singular optical mouse placements are identified, along with the corresponding characteristic lengths. Third, the least squares mobile robot velocity estimation from the noisy optical mouse velocity measurements is discussed. Finally, simulation results for several different placements of three optical mice are given.

The effects of extraversion, social support on the posttraumatic stress disorder and posttraumatic growth of adolescent survivors of the Wenchuan earthquake.

Science.gov (United States)

Jia, Xuji; Ying, Liuhua; Zhou, Xiao; Wu, Xinchun; Lin, Chongde

2015-01-01

The aim of this study was to examine the relationships among extraversion, social support, posttraumatic stress disorder and posttraumatic growth among adolescent survivors of the Wenchuan earthquake. Six hundred thirty-eight participants were selected from the survivors of the 2008 Wenchuan earthquake. Participants completed four main questionnaires, including the Extraversion Subscale, the Social Support Scale, the Child PTSD Symptom Scale, and the Posttraumatic Growth Inventory. A bivariate correlation analysis revealed significant correlations among extraversion, social support, posttraumatic stress disorder and posttraumatic growth. Extraversion had significant indirect effects on posttraumatic stress disorder (β = -.037, p posttraumatic growth (β = .077, p posttraumatic growth and a nonsignificant direct effect on posttraumatic stress disorder. Social support fully mediates the relationship between extraversion and posttraumatic stress disorder and partially mediates the relationship between extraversion and posttraumatic growth. Psychological interventions and care for survivors of the earthquake should include the various functions and sources of social support and how they serve to benefit individuals.

Investigation into the temperature dependence of isotropic- nematic phase transition of Gay- Berne liquid crystals

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A Avazpour

2014-12-01

Full Text Available Density functional approach was used to study the isotropic- nematic (I-N transition and calculate the values of freezing parameters of the Gay- Berne liquid crystal model. New direct and pair correlation functions of a molecular fluid with Gay- Berne pair potential were used. These new functions were used in density functional theory as input to calculate the isotropic- nematic transition densities for elongation at various reduced temperatures. It was observed that the isotropic- nematic transition densities increase as the temperature increases. It was found that the new direct correlation function is suitable to study the isotropic- nematic transition of Gay- Berne liquids. Comparison to other works showed qualitative agreement

Adaptation of BAp crystal orientation to stress distribution in rat mandible during bone growth

Energy Technology Data Exchange (ETDEWEB)

Nakano, T; Fujitani, W; Ishimoto, T [Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871 (Japan); Umakoshi, Y [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaragi, 305-0471 (Japan)], E-mail: nakano@mat.eng.osaka-u.ac.jp

2009-05-01

Biological apatite (BAp) c-axis orientation strongly depends on stress distribution in vivo and tends to align along the principal stress direction in bones. Dentulous mandible is subjected to a complicated stress condition in vivo during chewing but few studies have been carried out on the BAp c-axis orientation; so the adaptation of BAp crystal orientation to stress distribution was examined in rat dentulous mandible during bone growth and mastication. Female SD rats 4 to 14 weeks old were prepared, and the bone mineral density (BMD) and BAp crystal orientation were analyzed in a cross-section of mandible across the first molar focusing on two positions: separated from and just under the tooth root on the same cross-section perpendicular to the mesiodistal axis. The degree of BAp orientation was analyzed by a microbeam X-ray diffractometer using Cu-K{alpha} radiation equipped with a detector of curved one-dimensional PSPC and two-dimensional PSPC in the reflection and transmission optics, respectively. BMD quickly increased during bone growth up to 14 weeks, although it was independent of the position from the tooth root. In contrast, BAp crystal orientation strongly depended on the age and the position from the tooth root, even in the same cross-section and direction, especially along the mesiodistal and the biting axes. With increased biting stress during bone growth, the degree of BAp orientation increased along the mesiodistal axis in a position separated from the tooth root more than that near the tooth root. In contrast, BAp preferential alignment clearly appeared along the biting axis near the tooth root. We conclude that BAp orientation rather than BMD sensitively adapts to local stress distribution, especially from the chewing stress in vivo in the mandible.

Modified stress intensity factor as a crack growth parameter applicable under large scale yielding conditions

International Nuclear Information System (INIS)

Yasuoka, Tetsuo; Mizutani, Yoshihiro; Todoroki, Akira

2014-01-01

High-temperature water stress corrosion cracking has high tensile stress sensitivity, and its growth rate has been evaluated using the stress intensity factor, which is a linear fracture mechanics parameter. Stress corrosion cracking mainly occurs and propagates around welded metals or heat-affected zones. These regions have complex residual stress distributions and yield strength distributions because of input heat effects. The authors previously reported that the stress intensity factor becomes inapplicable when steep residual stress distributions or yield strength distributions occur along the crack propagation path, because small-scale yielding conditions deviate around those distributions. Here, when the stress intensity factor is modified by considering these distributions, the modified stress intensity factor may be used for crack growth evaluation for large-scale yielding. The authors previously proposed a modified stress intensity factor incorporating the stress distribution or yield strength distribution in front of the crack using the rate of change of stress intensity factor and yield strength. However, the applicable range of modified stress intensity factor for large-scale yielding was not clarified. In this study, the range was analytically investigated by comparison with the J-integral solution. A three-point bending specimen with parallel surface crack was adopted as the analytical model and the stress intensity factor, modified stress intensity factor and equivalent stress intensity factor derived from the J-integral were calculated and compared under large-scale yielding conditions. The modified stress intensity was closer to the equivalent stress intensity factor when compared with the stress intensity factor. If deviation from the J-integral solution is acceptable up to 2%, the modified stress intensity factor is applicable up to 30% of the J-integral limit, while the stress intensity factor is applicable up to 10%. These results showed that

Scalar properties of transversely isotropic tuff from images of orthogonal cross sections

International Nuclear Information System (INIS)

Berge, P.A.; Berryman, J.G.; Blair, S.C.; Pena, C.

1997-01-01

Image processing methods have been used very effectively to estimate physical properties of isotropic porous earth materials such as sandstones. Anisotropic materials can also be analyzed in order to estimate their physical properties, but additional care and a larger number of well-chosen images of cross sections are required to obtain correct results. Although low-symmetry anisotropic media present difficulties for two-dimensional image processing methods, geologic materials are often transversely isotropic. Scalar properties of porous materials such as porosity and specific surface area can be determined with only minor changes in the analysis when the medium is transversely isotropic rather than isotropic. For example, in a rock that is transitively isotropic due to thin layers or beds, the overall porosity may be obtained by analyzing images of cross sections taken orthogonal to the bedding planes, whereas cross sections lying within the bedding planes will determine only the local porosity of the bed itself. It is known for translationally invariant anisotropic media that the overall specific surface area can be obtained from radial averages of the two-point correlation function in the full three-dimensional volume. Layered materials are not translationally invariant in the direction of the layering, but we show nevertheless how averages of cross sections may be used to obtain the specific surface area for a transversely isotropic rock. We report values of specific surface area obtained for thin sections of Topopah Spring Tuff from Yucca Mountain, Nevada. This formation is being evaluated as a potential host rock for geologic disposal of nuclear waste. Although the present work has made use of thin sections of tuff for the images, the same methods of analysis could also be used to simplify quantitative analysis of three-dimensional volumes of pore structure data obtained by means of x-ray microtomography or other methods, using only a few representative cross

Crack initiation and growth in welded structures

International Nuclear Information System (INIS)

Assire, A.

2000-01-01

This work concerns the remaining life assessment of a structure containing initial defects of manufacturing. High temperature crack initiation and growth are studied for austenitic stainless steels, and defect assessment methods are improved in order to take into account welded structures. For these one, the probability to have a defect is significant. Two kinds of approaches are commonly used for defect assessment analysis. Fracture mechanics global approach with an energetic criterion, and local approach with a model taking into account the physical damage mechanism. For both approaches mechanical fields (stress and strain) have to be computed everywhere within the structure. Then, Finite Element computation is needed. The first part of the thesis concerns the identification of non linear kinematic and isotropic constitutive models. A pseudo-analytical method is proposed for a 'Two Inelastic Strain' model. This method provides a strategy of identification with a mechanical meaning, and this enables to associate each parameter to a physical phenomenon. Existing identifications are improved for cyclic plasticity and creep on a large range of stress levels. The second part concerns high temperature crack initiation and growth in welded structures. Finite Element analysis on plate and tube experimental configuration enable to understand the phenomenons of interaction between base metal and weld metal under mechanical and thermal loading. Concerning global approach, criteria based on C* parameter (Rice integral for visco-plasticity) are used. Finite Element computations underline the fact that for a defect located in the weld metal, C* values strongly depend on the base metal creep strain rate, because widespread visco-plasticity is located in both metals. A simplified method, based on the reference stress approach, is proposed and validated with Finite Element results. Creep crack growth simplified assessment is a quite good validation of the experimental results

Rhizospheric salt tolerant bacteria improving plant growth in single and mixed culture inoculations under NaCl stress (abstract)

International Nuclear Information System (INIS)

Afrasayab, S.; Hasnain, S.

2005-01-01

Salt tolerant bacterial strains isolated from rhizosphere of Mazus plant (inhabitant of salt range) were used singly (ST -1; ST -2; ST -3; ST -4) and in mixed combinations (ST -1,3,4; ST -2,3,4) to improve the growth to Tricticum aestivum in the pot experiments. Growth and yield of T. aestivum var. Inqlab-91 plants exposed to NaCl stress (0.75% NaCl) was markedly affected. Na/sup +//K/sup +/ ratios in shoots and roots were profoundly increased under NaCl stress. Bacterial inoculations improved plant growth under salt stress. Bacterial combinations ST - 1,3,4 and ST -2,3,4 were more effective in stimulating growth and showed prominent results as compared to their pure cultures. Mono and mixed bacterial inoculations improved yield parameters of wheat. ST -1,3,4 mixed culture inoculation maximally improved yield under salt stress. Generally bacterial inoculations resulted in increase in Na/sup +//K/sup +/ ratios in shoots and roots under salt free and salt stress conditions. Overall ST -1,3,4 mixed inoculation yielded promising results under NaCl stress, hence 168 rRNA gene sequence analysis of its pure cultures was obtained for their identification to genus level. (author)

first principles derivation of a stress function for axially symmetric

African Journals Online (AJOL)

HOD

governing partial differential equations of linear isotropic elasticity were reduced to the solution of the biharmonic ... The stress function was then applied to solve the axially symmetric ..... [1] Borg S.K.: Fundamentals of Engineering Elasticity,.

Hydraulic Fracture Growth in a Layered Formation based on Fracturing Experiments and Discrete Element Modeling

Science.gov (United States)

Yushi, Zou; Xinfang, Ma; Tong, Zhou; Ning, Li; Ming, Chen; Sihai, Li; Yinuo, Zhang; Han, Li

2017-09-01

Hydraulic fracture (HF) height containment tends to occur in layered formations, and it significantly influences the entire HF geometry or the stimulated reservoir volume. This study aims to explore the influence of preexisting bedding planes (BPs) on the HF height growth in layered formations. Laboratory fracturing experiments were performed to confirm the occurrence of HF height containment in natural shale that contains multiple weak and high-permeability BPs under triaxial stresses. Numerical simulations were then conducted to further illustrate the manner in which vertical stress, BP permeability, BP density(or spacing), pump rate, and fluid viscosity control HF height growth using a 3D discrete element method-based fracturing model. In this model, the rock matrix was considered transversely isotropic and multiple BPs can be explicitly represented. Experimental and numerical results show that the vertically growing HF tends to be limited by multi-high-permeability BPs, even under higher vertical stress. When the vertically growing HF intersects with the multi-high-permeability BPs, the injection pressure will be sharply reduced. If a low pumping rate or a low-viscosity fluid is used, the excess fracturing fluid leak-off into the BPs obviously decreases the rate of pressure build up, which will then limit the growth of HF. Otherwise, a higher pumping rate and/or a higher viscosity will reduce the leak-off time and fluid volume, but increase the injection pressure to drive the HF to grow and to penetrate through the BPs.

Topography-specific isotropic tunneling in nanoparticle monolayer with sub-nm scale crevices.

Science.gov (United States)

Wang, Guisheng; Jiao, Weihong; Yi, Lizhi; Zhang, Yuejiao; Wu, Ke; Zhang, Chao; Lv, Xianglong; Qian, Lihua; Li, Jianfeng; Yuan, Songliu; Chen, Liang

2016-10-07

Material used in flexible devices may experience anisotropic strain with identical magnitude, outputting coherent signals that tend to have a serious impact on device reliability. In this work, the surface topography of the nanoparticles (NPs) is proposed to be a parameter to control the performance of strain gauge based on tunneling behavior. In contrast to anisotropic tunneling in a monolayer of spherical NPs, electron tunneling in a monolayer of urchin-like NPs actually exhibits a nearly isotropic response to strain with different loading orientations. Isotropic tunneling of the urchin-like NPs is caused by the interlocked pikes of these urchin-like NPs in a random manner during external mechanical stimulus. Topography-dependent isotropic tunneling in two dimensions reported here opens a new opportunity to create highly reliable electronics with superior performance.

Cosmic acceleration driven by mirage inhomogeneities

Energy Technology Data Exchange (ETDEWEB)

Galfard, Christophe [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce road, Cambridge CB3 0WA (United Kingdom); Germani, Cristiano [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce road, Cambridge CB3 0WA (United Kingdom); Kehagias, Alex [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece)

2006-03-21

A cosmological model based on an inhomogeneous D3-brane moving in an AdS{sub 5} x S{sub 5} bulk is introduced. Although there are no special points in the bulk, the brane universe has a centre and is isotropic around it. The model has an accelerating expansion and its effective cosmological constant is inversely proportional to the distance from the centre, giving a possible geometrical origin for the smallness of a present-day cosmological constant. Besides, if our model is considered as an alternative of early-time acceleration, it is shown that the early stage accelerating phase ends in a dust-dominated FRW homogeneous universe. Mirage-driven acceleration thus provides a dark matter component for the brane universe final state. We finally show that the model fulfils the current constraints on inhomogeneities.

Isotropic Broadband E-Field Probe

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Béla Szentpáli

2008-01-01

Full Text Available An E-field probe has been developed for EMC immunity tests performed in closed space. The leads are flexible resistive transmission lines. Their influence on the field distribution is negligible. The probe has an isotropic reception from 100 MHz to 18 GHz; the sensitivity is in the 3 V/m–10 V/m range. The device is an accessory of the EMC test chamber. The readout of the field magnitude is carried out by personal computer, which fulfils also the required corrections of the raw data.

Stress corrosion crack growth rate in dissimilar metal welds

International Nuclear Information System (INIS)

Fernandez, M. P.; Lapena, J.; Lancha, A. M.; Perosanz, F. J.; Navas, M.

2000-01-01

Dissimilar welds, used to join different sections in light water reactors, are potentially susceptible to stress corrosion cracking (SCC) in aqueous mediums characteristic of nuclear plants. However, the study of these The ma has been limited to evaluating the weld material susceptibility in these mediums. Little scarce data are available on crack growth rates due, fundamentally, to inadequate testing techniques. In order to address this lack of information the crack growth rate at the interface of ferritic SA 533 B-1 alloy and alloy I-82, in a dissimilar weld (SA533B-1/I-82/316L), was studied. Experiments were conducted in water at 288 degree centigrade, 8 ppm of O 2 and 1 μS/cm conductivity. (Author) 33 refs

New model for surface fracture induced by dynamical stress

OpenAIRE

Andersen, J. V.; Lewis, L. J.

1997-01-01

We introduce a model where an isotropic, dynamically-imposed stress induces fracture in a thin film. Using molecular dynamics simulations, we study how the integrated fragment distribution function depends on the rate of change and magnitude of the imposed stress, as well as on temperature. A mean-field argument shows that the system becomes unstable for a critical value of the stress. We find a striking invariance of the distribution of fragments for fixed ratio of temperature and rate of ch...

Sex-specific impact of prenatal stress on growth and reproductive parameters of guinea pigs.

Science.gov (United States)

Schöpper, Hanna; Klaus, Teresa; Palme, Rupert; Ruf, Thomas; Huber, Susanne

2012-12-01

Body condition and reproductive maturation are parameters of reproductive success that are influenced by sexual hormones rising in the circulation during the time of puberty. Various endocrine systems can be programmed by conditions experienced during early life. Stress for instance is supposed to be capable of influencing fetal development, leading to adjustments of offspring's later physiology. We examined whether prenatal stress (induced by exposure to strobe light) during early- to mid-gestation was capable of affecting later reproductive parameters in guinea pigs (Cavia aperea f. porcellus). Therefore, we measured the levels of testosterone and progesterone from the age of day 12-124 in prenatally stressed (PS, n = 20) and unaffected control animals (n = 24). Furthermore, we determined the timing of puberty and growth. Body weight development revealed significantly faster growth in PS females compared to control animals. The onset of first estrus was slightly earlier in PS females, however not significantly so. Cycle lengths and levels of progesterone differed between groups over the course of time with higher progesterone levels and more constant cycles among PS females compared to control females who displayed marked differences between first and subsequent cycles. Levels of testosterone did not differ between groups. We conclude that prenatal stress accelerates growth and maturity in females, but not in males.

Kinetic Behavior of Exchange-Driven Growth with Catalyzed-Birth Processes

International Nuclear Information System (INIS)

Wang Haifeng; Lin Zhenquan; Kong Xiangmu

2006-01-01

Two catalyzed-birth models of n-species (n≥2) aggregates with exchange-driven growth processes are proposed and compared. In the first one, the exchange reaction occurs between any two aggregates A m k and A m j of the same species with the rate kernels K m (k,j) = K m kj (m = 1,2,...,n, n≥2), and aggregates of A n species catalyze a monomer-birth of A l species (l = 1,2,...,n-1) with the catalysis rate kernel J l (k,j) = J l kj υ . The kinetic behaviors are investigated by means of the mean-field theory. We find that the evolution behavior of aggregate-size distribution a l k (t) of A l species depends crucially on the value of the catalysis rate parameter υ: (i) a l k (t) obeys the conventional scaling law in the case of υ≤0, (ii) a l k (t) satisfies a modified scaling form in the case of υ>0. In the second model, the mechanism of monomer-birth of A n -species catalyzed by A l species is added on the basis of the first model, that is, the aggregates of A l and A n species catalyze each other to cause monomer-birth. The kinetic behaviors of A l and A n species are found to fall into two categories for the different υ: (i) growth obeying conventional scaling form with υ≤0, (ii) gelling at finite time with υ>0.

An isotropic suspension system for a biaxial accelerometer using electroplated thick metal with a HAR SU-8 mold

International Nuclear Information System (INIS)

Lee, Jin Seung; Lee, Seung S

2008-01-01

In this paper, a novel approach is developed to design an isotropic suspension system using thick metal freestanding micro-structures combining bulk micro-machining with electroplating based on a HAR SU-8 mold. An omega-shape isotropic suspension system composed of circular curved beams that have free switching of imaginary boundary conditions is proposed. This novel isotropic suspension design is not affected by geometric dimensional parameters and always achieves matching stiffness along the principle axes of elasticity. Using the finite element method, the isotropic suspension system was compared with an S-shaped meandering suspension system. In order to realize the suggested isotropic suspension system, a cost-effective fabrication process using electroplating with the SU-8 mold was developed to avoid expensive equipment and materials such as deep reactive-ion etching (DRIE) or a silicon-on-insulator (SOI) wafer. The fabricated isotropic suspension system was verified by electromagnetic actuation experiments. Finally, a biaxial accelerometer with isotropic suspension system was realized and tested using a vibration generator system. The proposed isotropic suspension system and the modified surface micro-machining technique based on electroplating with an SU-8 mold can contribute towards minimizing the system size, simplifying the system configuration, reducing the system price of and facilitating mass production of various types of low-cost sensors and actuators

Stress analysis in curved composites due to thermal loading

Science.gov (United States)

Polk, Jared Cornelius

Many structures in aircraft, cars, trucks, ships, machines, tools, bridges, and buildings, consist of curved sections. These sections vary from straight line segments that have curvature at either one or both ends, segments with compound curvatures, segments with two mutually perpendicular curvatures or Gaussian curvatures, and segments with a simple curvature. With the advancements made in multi-purpose composites over the past 60 years, composites slowly but steadily have been appearing in these various vehicles, compound structures, and buildings. These composite sections provide added benefits over isotropic, polymeric, and ceramic materials by generally having a higher specific strength, higher specific stiffnesses, longer fatigue life, lower density, possibilities in reduction of life cycle and/or acquisition cost, and greater adaptability to intended function of structure via material composition and geometry. To be able to design and manufacture a safe composite laminate or structure, it is imperative that the stress distributions, their causes, and effects are thoroughly understood in order to successfully accomplish mission objectives and manufacture a safe and reliable composite. The objective of the thesis work is to expand upon the knowledge of simply curved composite structures by exploring and ascertaining all pertinent parameters, phenomenon, and trends in stress variations in curved laminates due to thermal loading. The simply curved composites consist of composites with one radius of curvature throughout the span of the specimen about only one axis. Analytical beam theory, classical lamination theory, and finite element analysis were used to ascertain stress variations in a flat, isotropic beam. An analytical method was developed to ascertain the stress variations in an isotropic, simply curved beam under thermal loading that is under both free-free and fixed-fixed constraint conditions. This is the first such solution to Author's best knowledge

Isotropic gates and large gamma detector arrays versus angular distributions

International Nuclear Information System (INIS)

Iacob, V.E.; Duchene, G.

1997-01-01

Angular information extracted from in-beam γ ray measurements are of great importance for γ ray multipolarity and nuclear spin assignments. In our days large Ge detector arrays became available allowing the measurements of extremely weak γ rays in almost 4π sr solid angle (e.g., EUROGAM detector array). Given the high detector efficiency it is common for the mean suppressed coincidence multiplicity to reach values as high as 4 to 6. Thus, it is possible to gate on particular γ rays in order to enhance the relative statistics of a definite reaction channel and/or a definite decaying path in the level scheme of the selected residual nucleus. As compared to angular correlations, the conditioned angular distribution spectra exhibit larger statistics because in the latter the gate-setting γ ray may be observed by all the detectors in the array, relaxing somehow the geometrical restrictions of the angular correlations. Since the in-beam γ ray emission is anisotropic one could inquire that gate setting as mentioned above, based on anisotropic γ ray which would perturb the angular distributions in the unfolded events. As our work proved, there is no reason to worry about this if the energy gate runs over the whole solid angle in an ideal 4π sr detector, i.e., if the gate is isotropic. In real quasi 4π sr detector arrays the corresponding quasi isotropic gate preserves the angular properties of the unfolded data, too. However extraction of precise angular distribution coefficient especially a 4 , requires the consideration of the deviation of the quasi isotropic gate relative to the (ideal) isotropic gate

The use of Stress Tensor Discriminator Faults in separating heterogeneous fault-slip data with best-fit stress inversion methods. II. Compressional stress regimes

Science.gov (United States)

Tranos, Markos D.

2018-02-01

Synthetic heterogeneous fault-slip data as driven by Andersonian compressional stress tensors were used to examine the efficiency of best-fit stress inversion methods in separating them. Heterogeneous fault-slip data are separated only if (a) they have been driven by stress tensors defining 'hybrid' compression (R constitute a necessary discriminatory tool for the establishment and comparison of two compressional stress tensors determined by a best-fit stress inversion method. The best-fit stress inversion methods are not able to determine more than one 'real' compressional stress tensor, as far as the thrust stacking in an orogeny is concerned. They can only possibly discern stress differences in the late-orogenic faulting processes, but not between the main- and late-orogenic stages.

The effect of plant growth-promoting rhizobacteria on asparagus seedlings and germinating seeds subjected to water stress under greenhouse conditions.

Science.gov (United States)

Liddycoat, Scott M; Greenberg, Bruce M; Wolyn, David J

2009-04-01

Plant growth-promoting rhizobacteria (PGPR) can have positive effects on vigour and productivity, especially under stress conditions. In asparagus (Asparagus officinalis L.) field culture, seeds are planted in high-density nurseries, and 1-year-old crowns are transplanted to production fields. Performance can be negatively affected by water stress, transplant shock, and disease pressure on wounded roots. PGPR inoculation has the potential to alleviate some of the stresses incurred in the production system. In this study, the effects of PGPR (Pseudomonas spp.) treatment were determined on 3-week-old greenhouse-grown seedlings and germinating seeds of 2 asparagus cultivars. The pots were irrigated to a predetermined level that resulted in optimum growth or the plants were subjected to drought or flooding stress for 8 weeks. The cultivars responded differently to PGPR: single inoculations of seedlings enhanced growth of 'Guelph Millennium' under optimum conditions and 'Jersey Giant' seedlings under drought stress. Seed inoculations with PGPR resulted in a positive response only for 'Guelph Millennium', for which both single or multiple inoculations enhanced plant growth under drought stress.

Effect of membrane and through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity

International Nuclear Information System (INIS)

Yoo, Yeon-Sik

2003-11-01

This study clarified the effect of a membrane and a through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity due to irregularity of crack surface. Each stress component relates to fatigue crack growth behavior directly in general and thus the wild-used K I solutions are anticipated to give good evaluation results on it. Meanwhile, it is necessary to notify that surface irregularity for coolant leakage assessment is made by stress history in nature. Surface irregularity is known to be largely classified into the following two aspects: surface roughness due to continuous crack opening and closure behavior and surface turnover due to cyclic bending stress dominance. Therefore, the deterministic parameters on resistance of coolant leakage by surface irregularity are considered to be not only stress history but crack opening behavior. (author)

Depth migration in transversely isotropic media with explicit operators

Energy Technology Data Exchange (ETDEWEB)

Uzcategui, Omar [Colorado School of Mines, Golden, CO (United States)

1994-12-01

The author presents and analyzes three approaches to calculating explicit two-dimensional (2D) depth-extrapolation filters for all propagation modes (P, SV, and SH) in transversely isotropic media with vertical and tilted axis of symmetry. These extrapolation filters are used to do 2D poststack depth migration, and also, just as for isotropic media, these 2D filters are used in the McClellan transformation to do poststack 3D depth migration. Furthermore, the same explicit filters can also be used to do depth-extrapolation of prestack data. The explicit filters are derived by generalizations of three different approaches: the modified Taylor series, least-squares, and minimax methods initially developed for isotropic media. The examples here show that the least-squares and minimax methods produce filters with accurate extrapolation (measured in the ability to position steep reflectors) for a wider range of propagation angles than that obtained using the modified Taylor series method. However, for low propagation angles, the modified Taylor series method has smaller amplitude and phase errors than those produced by the least-squares and minimax methods. These results suggest that to get accurate amplitude estimation, modified Taylor series filters would be somewhat preferred in areas with low dips. In areas with larger dips, the least-squares and minimax methods would give a distinctly better delineation of the subsurface structures.

Thinner regions of intracranial aneurysm wall correlate with regions of higher wall shear stress: a 7.0 tesla MRI

Science.gov (United States)

Blankena, Roos; Kleinloog, Rachel; Verweij, Bon H.; van Ooij, Pim; ten Haken, Bennie; Luijten, Peter R.; Rinkel, Gabriel J.E.; Zwanenburg, Jaco J.M.

2016-01-01

Purpose To develop a method for semi-quantitative wall thickness assessment on in vivo 7.0 tesla (7T) MRI images of intracranial aneurysms for studying the relation between apparent aneurysm wall thickness and wall shear stress. Materials and Methods Wall thickness was analyzed in 11 unruptured aneurysms in 9 patients, who underwent 7T MRI with a TSE based vessel wall sequence (0.8 mm isotropic resolution). A custom analysis program determined the in vivo aneurysm wall intensities, which were normalized to signal of nearby brain tissue and were used as measure for apparent wall thickness (AWT). Spatial wall thickness variation was determined as the interquartile range in AWT (the middle 50% of the AWT range). Wall shear stress was determined using phase contrast MRI (0.5 mm isotropic resolution). We performed visual and statistical comparisons (Pearson’s correlation) to study the relation between wall thickness and wall shear stress. Results 3D colored AWT maps of the aneurysms showed spatial AWT variation, which ranged from 0.07 to 0.53, with a mean variation of 0.22 (a variation of 1.0 roughly means a wall thickness variation of one voxel (0.8mm)). In all aneurysms, AWT was inversely related to WSS (mean correlation coefficient −0.35, P<0.05). Conclusions A method was developed to measure the wall thickness semi-quantitatively, using 7T MRI. An inverse correlation between wall shear stress and AWT was determined. In future studies, this non-invasive method can be used to assess spatial wall thickness variation in relation to pathophysiologic processes such as aneurysm growth and –rupture. PMID:26892986

[Effect of exogenous sucrose on growth and active ingredient content of licorice seedlings under salt stress conditions].

Science.gov (United States)

Liu, Fu-zhi; Yang, Jun

2015-11-01

Licorice seedlings were taken as experimental materials, an experiment was conducted to study the effects of exogenous sucrose on growth and active ingredient content of licorice seedlings under NaCl stress conditions. The results of this study showed that under salt stress conditions, after adding a certain concentration of exogenous sucrose, the licorice seedlings day of relative growth rate was increasing, and this stress can be a significant weakening effect, indicating that exogenous sucrose salt stress-relieving effect. The total flavonoids and phenylalanine ammonia lyase (PAL) activity were significantly increased, the exogenous sucrose can mitigated the seedling roots under salt stress, the licorice flavonoid content in the enhanced growth was largely due to the activity of PAL an increased, when the concentration of exogenous sucrose wae 10 mmol x L(-1), PAL activity reaching a maximum, when the concentration of exogenous sucrose was 15 mmol x L(-1), PAL activity turned into a downward trend, the results indicating that this mitigation has concentration effect. After applying different concentrations of exogenous sugar, the contents of liquiritin changes with the change of flavonoids content was similar. After applying different concentrations of exogenous sucrose, the content of licorice acid under salt stress was higher than the levels were not reached during salt stress, the impact of exogenous sucrose concentration gradient of licorice acid accumulation was not obvious.

Micromechanical combined stress analysis: MICSTRAN, a user manual

Science.gov (United States)

Naik, R. A.

1992-01-01

Composite materials are currently being used in aerospace and other applications. The ability to tailor the composite properties by the appropriate selection of its constituents, the fiber and matrix, is a major advantage of composite materials. The Micromechanical Combined Stress Analysis (MICSTRAN) code provides the materials engineer with a user-friendly personal computer (PC) based tool to calculate overall composite properties given the constituent fiber and matrix properties. To assess the ability of the composite to carry structural loads, the materials engineer also needs to calculate the internal stresses in the composite material. MICSTRAN is a simple tool to calculate such internal stresses with a composite ply under combined thermomechanical loading. It assumes that the fibers have a circular cross-section and are arranged either in a repeating square or diamond array pattern within a ply. It uses a classical elasticity solution technique that has been demonstrated to calculate accurate stress results. Input to the program consists of transversely isotropic fiber properties and isotropic matrix properties such as moduli, Poisson's ratios, coefficients of thermal expansion, and volume fraction. Output consists of overall thermoelastic constants and stresses. Stresses can be computed under the combined action of thermal, transverse, longitudinal, transverse shear, and longitudinal shear loadings. Stress output can be requested along the fiber-matrix interface, the model boundaries, circular arcs, or at user-specified points located anywhere in the model. The MICSTRAN program is Windows compatible and takes advantage of the Microsoft Windows graphical user interface which facilitates multitasking and extends memory access far beyond the limits imposed by the DOS operating system.

Investigating source processes of isotropic events

Science.gov (United States)

Chiang, Andrea

This dissertation demonstrates the utility of the complete waveform regional moment tensor inversion for nuclear event discrimination. I explore the source processes and associated uncertainties for explosions and earthquakes under the effects of limited station coverage, compound seismic sources, assumptions in velocity models and the corresponding Green's functions, and the effects of shallow source depth and free-surface conditions. The motivation to develop better techniques to obtain reliable source mechanism and assess uncertainties is not limited to nuclear monitoring, but they also provide quantitative information about the characteristics of seismic hazards, local and regional tectonics and in-situ stress fields of the region . This dissertation begins with the analysis of three sparsely recorded events: the 14 September 1988 US-Soviet Joint Verification Experiment (JVE) nuclear test at the Semipalatinsk test site in Eastern Kazakhstan, and two nuclear explosions at the Chinese Lop Nor test site. We utilize a regional distance seismic waveform method fitting long-period, complete, three-component waveforms jointly with first-motion observations from regional stations and teleseismic arrays. The combination of long period waveforms and first motion observations provides unique discrimination of these sparsely recorded events in the context of the Hudson et al. (1989) source-type diagram. We examine the effects of the free surface on the moment tensor via synthetic testing, and apply the moment tensor based discrimination method to well-recorded chemical explosions. These shallow chemical explosions represent rather severe source-station geometry in terms of the vanishing traction issues. We show that the combined waveform and first motion method enables the unique discrimination of these events, even though the data include unmodeled single force components resulting from the collapse and blowout of the quarry face immediately following the initial

Evaluation of rice genotypes to salt stress in different growth stages ...

African Journals Online (AJOL)

Tolerant genotypes were tested in young seedling stage in hydroponic system and then reproductive stage in 2010. Results show that vegetative growth was less affected by salt stress comparison to reproductive stage. Na and Na-K ratio in tolerant genotypes were lower than suspectible genotypes in salt condition in ...

Suppression of cancer growth in mice by adeno-associated virus vector-mediated IFN-beta expression driven by hTERT promoter.

Science.gov (United States)

He, Ling Feng; Wang, Yi Gang; Xiao, Tian; Zhang, Kang Jiang; Li, Gong Chu; Gu, Jin Fa; Chu, Liang; Tang, Wen Hao; Tan, Wen-Song; Liu, Xin Yuan

2009-12-28

Adeno-associated virus (AAV) has rapidly become a promising gene delivery vehicle for its excellent advantages of non-immunogenic, low pathogenicity and long-term gene expression in vivo. However, a major obstacle in development of effective AAV vector is the lack of tissue specificity, which caused low efficiency of AAV transfer to target cells. The application of human telomerase reverse transcriptase (hTERT) promoter is a prior targeting strategy for AAV in cancer gene therapy as hTERT activity is transcriptionally upregulated in most cancer cells. In the present work, we investigated whether AAV-mediated human interferon beta (IFN-beta) gene driven by hTERT promoter could specifically express in tumor cells and suppress tumor cell growth. Our data demonstrated that hTERT promoter-driven IFN-beta expression was the tumor-specific, decreased the cell viability of tumor cells but not normal cells, and induced tumor cell apoptosis via activation of caspase pathway and release of cytochrome c. AAV-mediated IFN-beta expression driven by hTERT promoter significantly suppressed the growth of colorectal cancer and lung cancer xenograft in mice and resulted in tumor cells death in vivo. These data suggested that AAVs in combination with hTERT-mediated IFN-beta expression could exert potential antitumor activity and provide a novel targeting approach to clinical gene therapy of varieties of cancers.

Estimation of transversely isotropic material properties from magnetic resonance elastography using the optimised virtual fields method.

Science.gov (United States)

Miller, Renee; Kolipaka, Arunark; Nash, Martyn P; Young, Alistair A

2018-03-12

Magnetic resonance elastography (MRE) has been used to estimate isotropic myocardial stiffness. However, anisotropic stiffness estimates may give insight into structural changes that occur in the myocardium as a result of pathologies such as diastolic heart failure. The virtual fields method (VFM) has been proposed for estimating material stiffness from image data. This study applied the optimised VFM to identify transversely isotropic material properties from both simulated harmonic displacements in a left ventricular (LV) model with a fibre field measured from histology as well as isotropic phantom MRE data. Two material model formulations were implemented, estimating either 3 or 5 material properties. The 3-parameter formulation writes the transversely isotropic constitutive relation in a way that dissociates the bulk modulus from other parameters. Accurate identification of transversely isotropic material properties in the LV model was shown to be dependent on the loading condition applied, amount of Gaussian noise in the signal, and frequency of excitation. Parameter sensitivity values showed that shear moduli are less sensitive to noise than the other parameters. This preliminary investigation showed the feasibility and limitations of using the VFM to identify transversely isotropic material properties from MRE images of a phantom as well as simulated harmonic displacements in an LV geometry. Copyright © 2018 John Wiley & Sons, Ltd.

A novel transgenic mouse model of growth plate dysplasia reveals that decreased chondrocyte proliferation due to chronic ER stress is a key factor in reduced bone growth

Directory of Open Access Journals (Sweden)

Benedetta Gualeni

2013-11-01

Disease mechanisms leading to different forms of chondrodysplasia include extracellular matrix (ECM alterations and intracellular stress resulting in abnormal changes to chondrocyte proliferation and survival. Delineating the relative contribution of these two disease mechanisms is a major challenge in understanding disease pathophysiology in genetic skeletal diseases and a prerequisite for developing effective therapies. To determine the influence of intracellular stress and changes in chondrocyte phenotype to the development of chondrodysplasia, we targeted the expression of the G2320R mutant form of thyroglobulin to the endoplasmic reticulum (ER of resting and proliferating chondrocytes. Previous studies on this mutant protein have shown that it induces intracellular aggregates and causes cell stress and death in the thyroid gland. The expression and retention of this exogenous mutant protein in resting and proliferating chondrocytes resulted in a chronic cell stress response, growth plate dysplasia and reduced bone growth, without inducing any alterations to the architecture and organization of the cartilage ECM. More significantly, the decreased bone growth seemed to be the direct result of reduced chondrocyte proliferation in the proliferative zone of growth plates in transgenic mice, without transcriptional activation of a classical unfolded protein response (UPR or apoptosis. Overall, these data show that mutant protein retention in the ER of resting and proliferative zone chondrocytes is sufficient to cause disrupted bone growth. The specific disease pathways triggered by mutant protein retention do not necessarily involve a prototypic UPR, but all pathways impact upon chondrocyte proliferation in the cartilage growth plate.

Rate of fatigue crack growth in residual stress fields of welded titanium joints with different contents of embrittling impurities

International Nuclear Information System (INIS)

Troshchenko, V.T.; Pokrovskij, V.V.; Yarusevich, V.L.; Mikhajlov, V.I.; Sher, V.A.

1990-01-01

Resistance to fatigue crack growth (FCG) has been studied in welded joints of structural titanium alloys contaminated by embrittling impurities. Besides, effect of crack closing has been taken into account what makes it possible to determine the effective coefficient of the stress intensity. The rate of fatigue crack growth is proved to considerably depend on the value and direction of residual stresses. The rate dependence of FCG in welded joints of structural titanium alloys on the swing of effective coefficient of stress intensity is invariant to the value and direction of weld residual stresses

Polarity driven simultaneous growth of free-standing and lateral GaAsP epitaxial nanowires on GaAs (001) substrate

International Nuclear Information System (INIS)

Sun, Wen; Xu, Hongyi; Guo, Yanan; Gao, Qiang; Hoe Tan, Hark; Jagadish, Chennupati; Zou, Jin

2013-01-01

Simultaneous growth of 〈111〉 B free-standing and ±[110] lateral GaAsP epitaxial nanowires on GaAs (001) substrates were observed and investigated by electron microscopy and crystallographic analysis. It was found that the growth of both free-standing and lateral ternary nanowires via Au catalysts was driven by the fact that Au catalysts prefer to maintain low-energy (111) B interfaces with surrounding GaAs(P) materials: in the case of free-standing nanowires, Au catalysts maintain (111) B interfaces with their underlying GaAsP nanowires; while in the case of lateral nanowires, each Au catalyst remain their side (111) B interfaces with the surrounding GaAs(P) material during the lateral nanowire growth

A facilitator of leisure activities for stress-related growth experience among middle-aged Korean women with depression.

Science.gov (United States)

Kim, Junhyoung; Kim, Jung-Hyun

2014-01-01

Leisure may serve as a coping resource following negative life events that facilitate positive changes. Previous studies on leisure have mainly focused on stress-related growth among individuals living in Western cultures. This study aimed to capture the role of leisure involvement as a facilitator of stress-related growth among middle-aged Korean women with depression. Three main themes were identified as an outcome of participation in leisure activities: (a) strengthening meaningful relationships, (b) improving positive emotions, and (c) facilitating personal strength. By participating in leisure activities, individuals with depression may develop the ability to cope with stress and experience positive changes.

Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

International Nuclear Information System (INIS)

Kamaya, Masayuki

2013-01-01

The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth was almost the same regardless of the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)

A 3D printed dual GSM band near isotropic on-package antenna

KAUST Repository

Zhen, Su

2017-10-25

In this paper, we propose an on-package dual band monopole antenna with near-isotropic radiation pattern for GSM mobile applications. The proposed antenna is well matched for both GSM 900 and 1800 bands and provides decent gain for both the bands (1.67 and 3.27 dBi at 900 MHz and 1800 MHz respectively). The antenna is printed with silver ink on a 3D printed polymer based package. The package houses the GSM electronics and the battery. By optimizing the antenna arms width and length, a near-isotropic radiation pattern is achieved. Unlike the published isotropic antennas which are either single band or large in size, the proposed antenna covers both GSM bands with required bandwidth and is only half wavelength long. The design is low cost and highly suitable for various GSM applications such as localization, in additional to conventional communication applications.

A program to calculate pulse transmission responses through transversely isotropic media

Science.gov (United States)

Li, Wei; Schmitt, Douglas R.; Zou, Changchun; Chen, Xiwei

2018-05-01

We provide a program (AOTI2D) to model responses of ultrasonic pulse transmission measurements through arbitrarily oriented transversely isotropic rocks. The program is built with the distributed point source method that treats the transducers as a series of point sources. The response of each point source is calculated according to the ray-tracing theory of elastic plane waves. The program could offer basic wave parameters including phase and group velocities, polarization, anisotropic reflection coefficients and directivity patterns, and model the wave fields, static wave beam, and the observed signals for pulse transmission measurements considering the material's elastic stiffnesses and orientations, sample dimensions, and the size and positions of the transmitters and the receivers. The program could be applied to exhibit the ultrasonic beam behaviors in anisotropic media, such as the skew and diffraction of ultrasonic beams, and analyze its effect on pulse transmission measurements. The program would be a useful tool to help design the experimental configuration and interpret the results of ultrasonic pulse transmission measurements through either isotropic or transversely isotropic rock samples.

Effects of NaCl stress on seed germination, early seedling growth ...

African Journals Online (AJOL)

Effects of salt stress on seed germination, early seedling growth and some physiological characteristics were evaluated for four cauliflower species in seven treatments of salinity including 0 (control), 34, 68, 102, 136, 170 and 204 mM NaCl in a three replicated randomized completely block design (RCBD). This result shows ...

Mutually catalyzed birth of population and assets in exchange-driven growth

Science.gov (United States)

Lin, Zhenquan; Ke, Jianhong; Ye, Gaoxiang

2006-10-01

We propose an exchange-driven aggregation growth model of population and assets with mutually catalyzed birth to study the interaction between the population and assets in their exchange-driven processes. In this model, monomer (or equivalently, individual) exchange occurs between any pair of aggregates of the same species (population or assets). The rate kernels of the exchanges of population and assets are K(k,l)=Kkl and L(k,l)=Lkl , respectively, at which one monomer migrates from an aggregate of size k to another of size l . Meanwhile, an aggregate of one species can yield a new monomer by the catalysis of an arbitrary aggregate of the other species. The rate kernel of asset-catalyzed population birth is I(k,l)=Iklμ [and that of population-catalyzed asset birth is J(k,l)=Jklν ], at which an aggregate of size k gains a monomer birth when it meets a catalyst aggregate of size l . The kinetic behaviors of the population and asset aggregates are solved based on the rate equations. The evolution of the aggregate size distributions of population and assets is found to fall into one of three categories for different parameters μ and ν : (i) population (asset) aggregates evolve according to the conventional scaling form in the case of μ⩽0 (ν⩽0) , (ii) population (asset) aggregates evolve according to a modified scaling form in the case of ν=0 and μ>0 ( μ=0 and ν>0 ), and (iii) both population and asset aggregates undergo gelation transitions at a finite time in the case of μ=ν>0 .

Effects of cadmium stress on growth and amino acid metabolism in two Compositae plants.

Science.gov (United States)

Zhu, Guangxu; Xiao, Huayun; Guo, Qingjun; Zhang, Zhongyi; Zhao, Jingjing; Yang, Dan

2018-08-30

Cadmium, a high toxic heavy metal, is one of the most serious contaminants in soil and a potential threat to plant growth and human health. Amino acid metabolism has the central role in heavy metal stress resistance of plants. In this paper, a pot experiment was carried out to study the effects of different concentrations of cadmium (0, 3, 6, 12, 30 mg kg -1 ) on the growth, Cd accumulation and amino acid metabolism in two Compositae plants (Ageratum conyzoides L. and Crassocephalum crepidioides). The results showed that under cadmium stress, C. crepidioides accumulated more Cd in its shoot and was tolerant to Cd, whereas its low Cd-accumulating relative, A. conyzoides, suffered reduced growth. The Cd content in the aerial part of C. crepidioides exceeded the threshold of Cd-hyperaccumulator. Furthermore, the bioaccumulation factor (BCF) and biological transfer factor (BTF) values for Cd in C. crepidioides were > 1. Thus, C. crepidioides can be regarded as Cd-hyperaccumulator. The comparison between both studied plants indicated that Cd stress resulted in a differential but coordinated response of amino acid levels, which are playing a significant role in plant adaptation to Cd stress. Glu, Gln, Asp, Asn, Gaba, Val and Ala dominated the major amino acids. Higher Cd tolerance and Cd accumulation in C. crepidioides was associated with greater accumulation of free amino acids, especially for Gln and Asn, in C. crepidioides than in A. conyzoides. Copyright © 2018 Elsevier Inc. All rights reserved.

A two-dimensional continuum model of biofilm growth incorporating fluid flow and shear stress based detachment

KAUST Repository

Duddu, Ravindra

2009-05-01

We present a two-dimensional biofilm growth model in a continuum framework using an Eulerian description. A computational technique based on the eXtended Finite Element Method (XFEM) and the level set method is used to simulate the growth of the biofilm. The model considers fluid flow around the biofilm surface, the advection-diffusion and reaction of substrate, variable biomass volume fraction and erosion due to the interfacial shear stress at the biofilm-fluid interface. The key assumptions of the model and the governing equations of transport, biofilm kinetics and biofilm mechanics are presented. Our 2D biofilm growth results are in good agreement with those obtained by Picioreanu et al. (Biotechnol Bioeng 69(5):504-515, 2000). Detachment due to erosion is modeled using two continuous speed functions based on: (a) interfacial shear stress and (b) biofilm height. A relation between the two detachment models in the case of a 1D biofilm is established and simulated biofilm results with detachment in 2D are presented. The stress in the biofilm due to fluid flow is evaluated and higher stresses are observed close to the substratum where the biofilm is attached. © 2008 Wiley Periodicals, Inc.

Temperature-dependent study of isotropic-nematic transition for a Gay-Berne fluid using density-functional theory

International Nuclear Information System (INIS)

Singh, Ram Chandra

2007-01-01

We have used the density-functional theory to study the effect of varying temperature on the isotropic-nematic transition of a fluid of molecules interacting via the Gay-Berne intermolecular potential. The nematic phase is found to be stable with respect to isotropic phase in the temperature range 0.80≤T*≤1.25. Pair correlation functions needed as input information in density-functional theory is calculated using the Percus-Yevick integral equation theory. We find that the density-functional theory is good for studying the isotropic-nematic transition in molecular fluids if the values of the pair-correlation functions in the isotropic phase are known accurately. We have also compared our results with computer simulation results wherever they are available

Ponderomotive force effects on temperature-gradient-driven instabilities

International Nuclear Information System (INIS)

Sundaram, A.K.; Hershkowitz, N.

1992-01-01

The modification of temperature-gradient-driven instabilities due to the presence of nonuniform radio-frequency fields near the ion cyclotron frequency is investigated in the linear regime. Employing the fluid theory, it is shown that the induced field line compression caused by ion cyclotron range of frequencies (ICRF) fields makes the net parallel compressibility positive, and thus provides a stabilizing influence on the ion-temperature-gradient-driven mode for an appropriately tailored profile of radio-frequency (rf) pressure. Concomitantly, the radial ponderomotive force generates an additional contribution via coupling between the perturbed fluid motion and the equilibrium ponderomotive force and this effect plays the role of dissipation to enhance or decrease the growth of temperature-gradient-driven modes depending upon the sign of rf pressure gradients. For decreased growth of temperature-gradient-driven instabilities, the plasma density gradients and rf pressure gradients must have opposite signs while enhancement in growth arises when both gradients have the same sign. Finally, the kinetic effects associated with these modes are briefly discussed

Phenotypic indications of FtsZ inhibition in hok/sok-induced bacterial growth changes and stress response.

Science.gov (United States)

Chukwudi, Chinwe Uzoma; Good, Liam

2018-01-01

The hok/sok locus has been shown to enhance the growth of bacteria in adverse growth conditions such as high temperature, low starting-culture densities and antibiotic treatment. This is in addition to their well-established plasmid-stabilization effect via post-segregational killing of plasmid-free daughter cells. It delays the onset of growth by prolonging the lag phase of bacterial culture, and increases the rate of exponential growth when growth eventually begins. This enables the cells adapt to the prevailing growth conditions and enhance their survival in stressful conditions. These effects functionally complement defective SOS response mechanism, and appear analogous to the growth effects of FtsZ in the SOS pathway. In this study, the role of FtsZ in the hok/sok-induced changes in bacterial growth and cell division was investigated. Morphologic studies of early growth-phase cultures and cells growing under temperature stress showed elongated cells typical of FtsZ inhibition/deficiency. Both ftsZ silencing and over-expression produced comparable growth effects in control cells, and altered the growth changes observed otherwise in the hok/sok + cells. These changes were diminished in SOS-deficient strain containing mutant FtsZ. The involvement of FtsZ in the hok/sok-induced growth changes may be exploited as drug target in host bacteria, which often propagate antibiotic resistance elements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization of the E.coli proteome and its modifications during growth and ethanol stress

Directory of Open Access Journals (Sweden)

Boumediene eSoufi

2015-02-01

Full Text Available We set out to provide a resource to the microbiology community especially with respect to systems biology based endeavors. To this end, we generated a comprehensive dataset monitoring the changes in protein expression, copy number, and post translational modifications in a systematic fashion during growth and ethanol stress in E.coli. We utilized high-resolution mass spectrometry combined with the Super-SILAC approach. In a single experiment, we have identified over 2,300 proteins, which represent approximately 88% of the estimated expressed proteome of E. coli and estimated protein copy numbers using the Intensity Based Absolute Quantitation (IBAQ. The dynamic range of protein expression spanned up to six orders of magnitude, with the highest protein copy per cell estimated at approximately 300,000. We focused on the proteome dynamics involved during stationary phase growth. A global up-regulation of proteins related to stress response was detected in later stages of growth. We observed the down-regulation of the methyl directed mismatch repair system containing MutS and MutL of E. coli growing in long term growth cultures, confirming that higher incidence of mutations presents an important mechanism in the increase in genetic diversity and stationary phase survival in E.coli. During ethanol stress, known markers such as alcohol dehydrogenase and aldehyde dehydrogenase were induced, further validating the dataset. Finally, we performed unbiased protein modification detection and revealed changes of many known and unknown protein modifications in both experimental conditions.

Stress concentration at notches

CERN Document Server

Savruk, Mykhaylo P

2017-01-01

This book compiles solutions of linear theory of elasticity problems for isotropic and anisotropic bodies with sharp and rounded notches. It contains an overview of established and recent achievements, and presents the authors’ original solutions in the field considered with extensive discussion. The volume demonstrates through numerous, useful examples the effectiveness of singular integral equations for obtaining exact solutions of boundary problems of the theory of elasticity for bodies with cracks and notches. Incorporating analytical and numerical solutions of the problems of stress concentrations in solid bodies with crack-like defects, this volume is ideal for scientists and PhD students dealing with the problems of theory of elasticity and fracture mechanics. Stands as a modern and extensive compendium of solutions to the problems of linear theory of elasticity of isotropic and anisotropic bodies with sharp and rounded notches; Adopts a highly reader-friendly layout of tables, charts, approximation ...

Predictors of Posttraumatic Stress and Posttraumatic Growth in Childhood Cancer Survivors

Czech Academy of Sciences Publication Activity Database

Koutná, Veronika; Jelínek, Martin; Blatný, Marek; Kepák, T.

2017-01-01

Roč. 9, č. 3 (2017), s. 1-11, č. článku 26. ISSN 2072-6694 R&D Projects: GA ČR(CZ) GAP407/11/2421 Institutional support: RVO:68081740 Keywords : posttraumatic stress * posttraumatic growth * benefit finding * childhood cancer survivors Subject RIV: AN - Psychology OBOR OECD: Psychology (including human - machine relations)

Phase-field-crystal model for magnetocrystalline interactions in isotropic ferromagnetic solids

Science.gov (United States)

Faghihi, Niloufar; Provatas, Nikolas; Elder, K. R.; Grant, Martin; Karttunen, Mikko

2013-09-01

An isotropic magnetoelastic phase-field-crystal model to study the relation between morphological structure and magnetic properties of pure ferromagnetic solids is introduced. Analytic calculations in two dimensions were used to determine the phase diagram and obtain the relationship between elastic strains and magnetization. Time-dependent numerical simulations in two dimensions were used to demonstrate the effect of grain boundaries on the formation of magnetic domains. It was shown that the grain boundaries act as nucleating sites for domains of reverse magnetization. Finally, we derive a relation for coercivity versus grain misorientation in the isotropic limit.

Bell inequalities stronger than the Clauser-Horne-Shimony-Holt inequality for three-level isotropic states

International Nuclear Information System (INIS)

Ito, Tsuyoshi; Imai, Hiroshi; Avis, David

2006-01-01

We show that some two-party Bell inequalities with two-valued observables are stronger than the CHSH inequality for 3x3 isotropic states in the sense that they are violated by some isotropic states in the 3x3 system that do not violate the CHSH inequality. These Bell inequalities are obtained by applying triangular elimination to the list of known facet inequalities of the cut polytope on nine points. This gives a partial solution to an open problem posed by Collins and Gisin. The results of numerical optimization suggest that they are candidates for being stronger than the I 3322 Bell inequality for 3x3 isotropic states. On the other hand, we found no Bell inequalities stronger than the CHSH inequality for 2x2 isotropic states. In addition, we illustrate an inclusion relation among some Bell inequalities derived by triangular elimination

Computations of Quasiconvex Hulls of Isotropic Sets

Czech Academy of Sciences Publication Activity Database

Heinz, S.; Kružík, Martin

2017-01-01

Roč. 24, č. 2 (2017), s. 477-492 ISSN 0944-6532 R&D Projects: GA ČR GA14-15264S; GA ČR(CZ) GAP201/12/0671 Institutional support: RVO:67985556 Keywords : quasiconvexity * isotropic compact sets * matrices Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 0.496, year: 2016 http://library.utia.cas.cz/separaty/2017/MTR/kruzik-0474874.pdf

Constitutive modeling of void-growth-based tensile ductile failures with stress triaxiality effects

KAUST Repository

Mora Cordova, Angel; Liu, Jinxing; El Sayed, Tamer S.

2014-01-01

In most metals and alloys, the evolution of voids has been generally recognized as the basic failure mechanism. Furthermore, stress triaxiality has been found to influence void growth dramatically. Besides strain intensity, it is understood

Geometrical considerations in analyzing isotropic or anisotropic surface reflections.

Science.gov (United States)

Simonot, Lionel; Obein, Gael

2007-05-10

The bidirectional reflectance distribution function (BRDF) represents the evolution of the reflectance with the directions of incidence and observation. Today BRDF measurements are increasingly applied and have become important to the study of the appearance of surfaces. The representation and the analysis of BRDF data are discussed, and the distortions caused by the traditional representation of the BRDF in a Fourier plane are pointed out and illustrated for two theoretical cases: an isotropic surface and a brushed surface. These considerations will help characterize either the specular peak width of an isotropic rough surface or the main directions of the light scattered by an anisotropic rough surface without misinterpretations. Finally, what is believed to be a new space is suggested for the representation of the BRDF, which avoids the geometrical deformations and in numerous cases is more convenient for BRDF analysis.

Suppression of magnetic islands by rf-driven currents

International Nuclear Information System (INIS)

Reiman, A.H.

1982-06-01

The quasilinear theory for the saturation of nonlinear tearing modes is modified to include rf driven currents. It is shown that the presence of lower hybrid driven currents can strongly suppress the growth of magnetic islands

Effects of Consolidation Stress State on Normally Consolidated Clay

DEFF Research Database (Denmark)

Lade, Poul V.

2000-01-01

The effect of consolidation stress state on the stress-strain and strength characteristics has been studied from experiments on undisturbed block samples of a natural, normally consolidated clay known as San Francisco Bay Mud. The results of experiments on K0-consolidated, hollow cylinder specimens...... and on isotropically consolidated, cubical specimens, both tested in triaxial compression and extension, clearly showed the influence of the undisturbed fabric as well as the effect of the initial consolidation stress states. While the K0-consolidated specimens appeared to retain their original fabric and exhibit...

Effect of T-stress on crack growth along an interface between ductile and elastic solids

DEFF Research Database (Denmark)

Tvergaard, Viggo

2003-01-01

For crack growth along an interface joining an elastic-plastic solid to an elastic substrate the effect of a non-singular stress component in the crack growth direction in the elastic-plastic solid is investigated. Conditions of small scale yielding are assumed, and due to the mismatch of elastic...

Cantilever surface stress sensors with single-crystalline silicon piezoresistors

DEFF Research Database (Denmark)

Rasmussen, Peter Andreas; Hansen, Ole; Boisen, Anja

2005-01-01

We present a cantilever with piezoresistive readout optimized for measuring the static deflection due to isotropic surface stress on the surface of the cantilever [Sens. Actuators B 79(2-3), 115 (2001)]. To our knowledge nobody has addressed the difference in physical regimes, and its influence o...

Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

International Nuclear Information System (INIS)

Kamaya, Masayuki

2013-01-01

The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth did not depend on the heat transfer coefficient and only slightly depended on the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)

An Antibody That Locks HER3 in the Inactive Conformation Inhibits Tumor Growth Driven by HER2 or Neuregulin

Energy Technology Data Exchange (ETDEWEB)

Garner, Andrew P.; Bialucha, Carl U.; Sprague, Elizabeth R.; Garrett, Joan T.; Sheng, Qing; Li, Sharon; Sineshchekova, Olga; Saxena, Parmita; Sutton, Cammie R.; Chen, Dongshu; Chen, Yan; Wang, Huiqin; Liang, Jinsheng; Das, Rita; Mosher, Rebecca; Gu, Jian; Huang, Alan; Haubst, Nicole; Zehetmeier, Carolin; Haberl, Manuela; Elis, Winfried; Kunz, Christian; Heidt, Analeah B.; Herlihy, Kara; Murtie, Joshua; Schuller, Alwin; Arteaga, Carlos L.; Sellers, William R.; Ettenberg, Seth A. (Novartis)

2013-08-08

HER2/HER3 dimerization resulting from overexpression of HER2 or neuregulin (NRG1) in cancer leads to HER3-mediated oncogenic activation of phosphoinositide 3-kinase (PI3K) signaling. Although ligand-blocking HER3 antibodies inhibit NRG1-driven tumor growth, they are ineffective against HER2-driven tumor growth because HER2 activates HER3 in a ligand-independent manner. In this study, we describe a novel HER3 monoclonal antibody (LJM716) that can neutralize multiple modes of HER3 activation, making it a superior candidate for clinical translation as a therapeutic candidate. LJM716 was a potent inhibitor of HER3/AKT phosphorylation and proliferation in HER2-amplified and NRG1-expressing cancer cells, and it displayed single-agent efficacy in tumor xenograft models. Combining LJM716 with agents that target HER2 or EGFR produced synergistic antitumor activity in vitro and in vivo. In particular, combining LJM716 with trastuzumab produced a more potent inhibition of signaling and cell proliferation than trastuzumab/pertuzumab combinations with similar activity in vivo. To elucidate its mechanism of action, we solved the structure of LJM716 bound to HER3, finding that LJM716 bound to an epitope, within domains 2 and 4, that traps HER3 in an inactive conformation. Taken together, our findings establish that LJM716 possesses a novel mechanism of action that, in combination with HER2- or EGFR-targeted agents, may leverage their clinical efficacy in ErbB-driven cancers.

Seeing is believing : communication performance under isotropic teleconferencing conditions

NARCIS (Netherlands)

Werkhoven, P.J.; Schraagen, J.M.C.; Punte, P.A.J.

2001-01-01

The visual component of conversational media such as videoconferencing systems communicates important non-verbal information such as facial expressions, gestures, posture and gaze. Unlike the other cues, selective gaze depends critically on the configuration of cameras and monitors. Under isotropic

Exogenous 5-Aminolevulenic Acid Promotes Antioxidative Defence System, Photosynthesis and Growth in Soybean against Cold Stress

Directory of Open Access Journals (Sweden)

Elahe MANAFI

2015-12-01

Full Text Available In the present study, the possibility of enhancing cold stress tolerance of young soybean plants (Glycine max [L.] Merr by exogenous application of 5-aminolevulinic acid (ALA was investigated. ALA was applied at various concentrations (0, 0.3, 0.6 and 0.9 mM by seed priming and foliar application method. After ALA treatment, the plants were subjected to cold stress at 10 ± 0.5 °C for 72 h. Cold stress significantly decreased plant growth, relative water content, chlorophyll, photosynthesis and stomatal conductivity, while it increased electrolyte leakage and proline accumulation. ALA at low concentrations (0.3 mM protected plants against cold stress, enhancing plant height, shoot fresh and dry weight, chlorophyll content, photosynthesis, stomatal conductivity as well as relative water content. Increase of electrolyte leakage was also prevented by 0.6 mM ALA. ALA also enhanced superoxide dismutase and catalase activities at 0.6 mM concentration especially under cold stress conditions. Proline increased with increasing in ALA concentration under both temperature conditions. In most cases, application of ALA by spraying method was better than seed priming method. Results showed that ALA, which is considered as an endogenous plant growth regulator, can be used effectively to protect soybean plants from the damaging effects of cold stress, by enhancing the activity of antioxidative enzymes, protecting cell membrane against reactive oxygen species and finally by promoting chlorophyll synthesis, leading to more intense photosynthesis and more carbon fixation, without any adverse effect on the plant growth.

Development of a 10 m quasi-isotropic strand assembled from 2G wires

Science.gov (United States)

Kan, Changtao; Wang, Yinshun; Hou, Yanbing; Li, Yan; Zhang, Han; Fu, Yu; Jiang, Zhe

2018-03-01

Quasi-isotropic strands made of second generation (2G) high temperature superconducting (HTS) wires are attractive to applications of high-field magnets at low temperatures and power transmission cables at liquid nitrogen temperature in virtue of their high current carrying capability and well mechanical property. In this contribution, a 10 m length quasi-isotropic strand is manufactured and successfully tested in liquid nitrogen to verify the feasibility of an industrial scale production of the strand by the existing cabling technologies. The strand with copper sheath consists of 72 symmetrically assembled 2G wires. The uniformity of critical properties of long quasi-isotropic strands, including critical current and n-value, is very important for their using. Critical currents as well as n-values of the strand are measured every 1 m respectively and compared with the simulation results. Critical current and n-value of the strand are calculated basing on the self-consistent model solved by the finite element method (FEM). Effects of self-field on the critical current and n-value distributions in wires of the strand are analyzed in detail. The simulation results show good agreement with the experimental data and the 10 m quasi-isotropic strand has good critical properties uniformity.

An experimental study on the effects of compressive stress on the fatigue crack growth of low-alloy steel

International Nuclear Information System (INIS)

Jones, D.P.; Hoppe, R.G.; James, B.A.

1993-01-01

A series of fatigue crack growth rate tests was conducted in order to study effects of negative stress ratio on fatigue crack growth rate of low-alloy steel in air. Four-point bend specimens were used to simulate linear stress distributions typical of pressure vessel applications. This type of testing adds to knowledge on negative stress ratio effects for low-alloy steels obtained in the past from uniform tension-compression tests. Applied bending stress range was varied over twice the yield strength. Load control was used for tests for which the stress range was less than twice the yield strength and deflection control was used for the higher stress range tests. Crack geometries were both short and long fatigue cracks started at notches and tight fatigue cracks for which crack closure could occur over the full crack face. Results are presented in terms of the stress intensity factor ratio R = K MIN /K MAX . The negative R-ratio test results were correlated to an equation of the form da/dN = C[ΔK/(A-R)] n , where A, C, and n are curve fitting parameters. It was found that effects of negative R-ratio on fatigue crack growth rates for even the high stress range tests could be bounded by correlating the above equation to only positive R-ratio test results and extending the resulting equation into the negative R-ratio regime

Acoustic carpet invisibility cloak with two open windows using multilayered homogeneous isotropic material

International Nuclear Information System (INIS)

Ren Chun-Yu; Xiang Zhi-Hai; Cen Zhang-Zhi

2011-01-01

We present a method for designing an open acoustic cloak that can conceal a perturbation on flat ground and simultaneously meet the requirement of communication and matter interchange between the inside and the outside of the cloak. This cloak can be constructed with a multilayered structure and each layer is an isotropic and homogeneous medium. The design scheme consists of two steps: firstly, we apply a conformal coordinate transformation to obtain a quasi-perfect cloak with heterogeneous isotropic material; then, according to the profile of the material distribution, we degenerate this cloak into a multilayered-homogeneous isotropic cloak, which has two open windows with negligible disturbance on its invisibility performance. This may greatly facilitate the fabrication and enhance the applicability of such a carpet-type cloak. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Induced piezoelectricity in isotropic biomaterial.

Science.gov (United States)

Zimmerman, R L

1976-01-01

Isotropic material can be made to exhibit piezoelectric effects by the application of a constant electric field. For insulators, the piezoelectric strain constant is proportional to the applied electric field and for semiconductors, an additional out-of-phase component of piezoelectricity is proportional to the electric current density in the sample. The two induced coefficients are proportional to the strain-dependent dielectric constant (depsilon/dS + epsilon) and resistivity (drho/dS - rho), respectively. The latter is more important at frequencies such that rhoepsilonomega less than 1, often the case in biopolymers.Signals from induced piezoelectricity in nature may be larger than those from true piezoelectricity. PMID:990389

How Isotropic is the Universe?

Science.gov (United States)

Saadeh, Daniela; Feeney, Stephen M; Pontzen, Andrew; Peiris, Hiranya V; McEwen, Jason D

2016-09-23

A fundamental assumption in the standard model of cosmology is that the Universe is isotropic on large scales. Breaking this assumption leads to a set of solutions to Einstein's field equations, known as Bianchi cosmologies, only a subset of which have ever been tested against data. For the first time, we consider all degrees of freedom in these solutions to conduct a general test of isotropy using cosmic microwave background temperature and polarization data from Planck. For the vector mode (associated with vorticity), we obtain a limit on the anisotropic expansion of (σ_{V}/H)_{0}Universe is strongly disfavored, with odds of 121 000:1 against.

Growth and Physiological Responses of Phaseolus Species to Salinity Stress

Directory of Open Access Journals (Sweden)

J. S. Bayuelo-Jiménez

2012-01-01

Full Text Available This paper reports the changes on growth, photosynthesis, water relations, soluble carbohydrate, and ion accumulation, for two salt-tolerant and two salt-sensitive Phaseolus species grown under increasing salinity (0, 60 and 90 mM NaCl. After 20 days exposure to salt, biomass was reduced in all species to a similar extent (about 56%, with the effect of salinity on relative growth rate (RGR confined largely to the first week. RGR of salt-tolerant species was reduced by salinity due to leaf area ratio (LAR reduction rather than a decline in photosynthetic capacity, whereas unit leaf rate and LAR were the key factors in determining RGR on salt-sensitive species. Photosynthetic rate and stomatal conductance decreased gradually with salinity, showing significant reductions only in salt-sensitive species at the highest salt level. There was little difference between species in the effect of salinity on water relations, as indicated by their positive turgor. Osmotic adjustment occurred in all species and depended on higher K+, Na+, and Cl− accumulation. Despite some changes in soluble carbohydrate accumulation induced by salt stress, no consistent contributions in osmotic adjustment could be found in this study. Therefore, we suggest that tolerance to salt stress is largely unrelated to carbohydrate accumulation in Phaseolus species.

Stress-related hormonal alterations, growth and pelleted starter intake in pre-weaning Holstein calves in response to thermal stress.

Science.gov (United States)

López, E; Mellado, M; Martínez, A M; Véliz, F G; García, J E; de Santiago, A; Carrillo, E

2018-04-01

This study aimed to investigate the effect of heat stress and month of birth on growth performance, pelleted starter intake, and stress-related hormones in Holstein calves. Birth weight and growth records, representing 4735 Holstein calves from a large commercial dairy herd in northern Mexico (25° N; 22.3 °C mean annual temperature) from 2013 to 2015, were analyzed. Temperature-humidity index (THI) at calving, season of birth, and month of birth were the independent variables, whereas growth traits were the dependent variables. Increased THI at birth from  85 units was associated with a decrease in birth weight from 39.3 to 38.7 kg. Calves subjected to high THI (> 75 units) at calving showed lesser (P calves born with THI calves born in the fall was about 70 g less (P calves delivered in winter months. Plasma triiodothyronine and tetraiodothyronine levels were lower (1.02 ± 0.21 and 48 ± 7.9 ng/mL, respectively; P calves born in summer (59 ± 40 ng/mL) than calves born in winter (20 ± 28 ng/mL). Pelleted starter intake 1 week before weaning was lowest (P calves. Thus, environmental management of the newborn calf during hot spring and summer months is warranted to optimize pelleted starter intake and calf growth rates.

Scanning anisotropy parameters in horizontal transversely isotropic media

KAUST Repository

Masmoudi, Nabil

2016-10-12

The horizontal transversely isotropic model, with arbitrary symmetry axis orientation, is the simplest effective representative that explains the azimuthal behaviour of seismic data. Estimating the anisotropy parameters of this model is important in reservoir characterisation, specifically in terms of fracture delineation. We propose a travel-time-based approach to estimate the anellipticity parameter η and the symmetry axis azimuth ϕ of a horizontal transversely isotropic medium, given an inhomogeneous elliptic background model (which might be obtained from velocity analysis and well velocities). This is accomplished through a Taylor\\'s series expansion of the travel-time solution (of the eikonal equation) as a function of parameter η and azimuth angle ϕ. The accuracy of the travel time expansion is enhanced by the use of Shanks transform. This results in an accurate approximation of the solution of the non-linear eikonal equation and provides a mechanism to scan simultaneously for the best fitting effective parameters η and ϕ, without the need for repetitive modelling of travel times. The analysis of the travel time sensitivity to parameters η and ϕ reveals that travel times are more sensitive to η than to the symmetry axis azimuth ϕ. Thus, η is better constrained from travel times than the azimuth. Moreover, the two-parameter scan in the homogeneous case shows that errors in the background model affect the estimation of η and ϕ differently. While a gradual increase in errors in the background model leads to increasing errors in η, inaccuracies in ϕ, on the other hand, depend on the background model errors. We also propose a layer-stripping method valid for a stack of arbitrary oriented symmetry axis horizontal transversely isotropic layers to convert the effective parameters to the interval layer values.

Impacts of priming with silicon on the growth and tolerance of maize plants to alkaline stress

Directory of Open Access Journals (Sweden)

ِArafat eAbdel Latef

2016-03-01

Full Text Available Silicon (Si has been known to augment plant defense against biotic and abiotic pressures. Maize (Zea maize L. is classified as a Si accumulator and is relatively susceptible to alkaline stress. In this work, grains of maize were grown in pots and exposed to various concentrations of Na2CO3 (0, 25, 50 and 75 mM with or without 1.5 mM Si in the form of sodium metasilicate Na2O3Si.5H2O for 25 days. Alkaline-stressed plants showed a decrease in growth parameters, leaf relative water content (LRWC, and the contents of photosynthetic pigments, soluble sugars, total phenols and potassium ion (K+, as well as potassium/sodium ion (K+/Na+ ratio. By contrast, alkaline stress increased the contents of soluble proteins, total free amino acids, proline, Na+ and malondialdehyde (MDA, as well as the activities of superoxide dismutase (SOD, catalase (CAT and peroxidase (POD in stressed plants. On the other hand, application of Si by grain priming improved growth of stressed plants, which was accompanied by the enhancement in LRWC, levels of photosynthetic pigments, soluble sugars, soluble proteins, total free amino acids, K+ and activities of SOD, CAT and POD enzymes. Furthermore, Si supplement resulted in a decrease in the contents of proline, MDA and Na+, which together with enhanced K+ level led to a favorable adjustment of K+/Na+ ratio, in stressed plants relative to plants treated with alkaline stress alone. Taken together, these results indicate that Si plays a pivotal role in alleviating the negative effects of alkaline stress on the maize growth by improving water status, enhancing photosynthetic pigments, accumulating osmoprotectants rather than proline, activating the antioxidant machinery, and maintaining the balance of K+/Na+. Thus, our findings demonstrate that seed priming with Si is an efficient strategy that can be used to boost tolerance of maize plants to alkaline stress.

SIMULATION OF THE stress-strain state of excavation BOUNDARIES in fractured massifs

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Nizomov Dzhahongir Nizomovich

2012-07-01

Any limiting process, namely, if or and any results are in line with the isotropic medium. The proposed algorithm and calculation pattern may be used to research the concentrated stresses alongside the boundaries of hydrotechnical engineering facilities.

Higher gradient expansion for linear isotropic peridynamic materials

Czech Academy of Sciences Publication Activity Database

Šilhavý, Miroslav

2017-01-01

Roč. 22, č. 6 (2017), s. 1483-1493 ISSN 1081-2865 Institutional support: RVO:67985840 Keywords : peridynamics * higher-grade theories * non-local elastic-material model * representation theorems for isotropic functions Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 2.953, year: 2016 http:// journals .sagepub.com/doi/10.1177/1081286516637235

Higher gradient expansion for linear isotropic peridynamic materials

Czech Academy of Sciences Publication Activity Database

Šilhavý, Miroslav

2017-01-01

Roč. 22, č. 6 (2017), s. 1483-1493 ISSN 1081-2865 Institutional support: RVO:67985840 Keywords : peridynamics * higher-grade theories * non-local elastic-material model * representation theorems for isotropic functions Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 2.953, year: 2016 http://journals.sagepub.com/doi/10.1177/1081286516637235

Magnetic and structural investigation of growth induced magnetic anisotropies in Fe50Co50 thin films

Directory of Open Access Journals (Sweden)

Neri I.

2013-01-01

Full Text Available In this paper, we investigate the magnetic properties of Fe50 Co50 polycrystalline thin films, grown by dc-magnetron sputtering, with thickness (t ranging from 2.5 nm up to 100 nm. We focused on the magnetic properties of the samples to highlight the effects of possible intrinsic stress that may develop during growth, and their dependence on film thickness. Indeed, during film deposition, due to the growth technique and growth conditions, a metallic film may display an intrinsic compressive or tensile stress. In our case, due to the Fe50Co50 magnetolastic properties, this stress may in its turn promote the development of magnetic anisotropies. Samples magnetic properties were monitored with a SQUID magnetometer and a magneto–optic Kerr effect apparatus, using both an in–plane and an out–of–plane magnetic field. Magnetoresistance measurements were collected, as well, to further investigate the magnetic behavior of the samples. Indications about the presence of intrinsic stress were obtained accessing samples curvature with an optical profilometer. For t ≤ 20 nm, the shape of the in-plane magnetization loops is squared and coercivity increases with t, possibly due to fact that, for small t values, the grain size grows with t. The magnetoresistive response is anisotropic in character. For t > 20 nm, coercivity smoothly decreases, the approach to saturation gets slower and the shape of the whole loop gets less and less squared. The magnetoresistive effect becomes almost isotropic and its intensity increases of about one order of magnitude. These results suggest that the magnetization reorientation process changes for t > 20 nm, and are in agreement with the progressive development of an out-of-plane easy axis. This hypothesis is substantiated by profilometric analysis that reveals the presence of an in-plane compressive stress.

CCN2/CTGF is required for matrix organization and to protect growth plate chondrocytes from cellular stress.

Science.gov (United States)

Hall-Glenn, Faith; Aivazi, Armen; Akopyan, Lusi; Ong, Jessica R; Baxter, Ruth R; Benya, Paul D; Goldschmeding, Roel; van Nieuwenhoven, Frans A; Hunziker, Ernst B; Lyons, Karen M

2013-08-01

CCN2 (connective tissue growth factor (CTGF/CCN2)) is a matricellular protein that utilizes integrins to regulate cell proliferation, migration and survival. The loss of CCN2 leads to perinatal lethality resulting from a severe chondrodysplasia. Upon closer inspection of Ccn2 mutant mice, we observed defects in extracellular matrix (ECM) organization and hypothesized that the severe chondrodysplasia caused by loss of CCN2 might be associated with defective chondrocyte survival. Ccn2 mutant growth plate chondrocytes exhibited enlarged endoplasmic reticula (ER), suggesting cellular stress. Immunofluorescence analysis confirmed elevated stress in Ccn2 mutants, with reduced stress observed in Ccn2 overexpressing transgenic mice. In vitro studies revealed that Ccn2 is a stress responsive gene in chondrocytes. The elevated stress observed in Ccn2-/- chondrocytes is direct and mediated in part through integrin α5. The expression of the survival marker NFκB and components of the autophagy pathway were decreased in Ccn2 mutant growth plates, suggesting that CCN2 may be involved in mediating chondrocyte survival. These data demonstrate that absence of a matricellular protein can result in increased cellular stress and highlight a novel protective role for CCN2 in chondrocyte survival. The severe chondrodysplasia caused by the loss of CCN2 may be due to increased chondrocyte stress and defective activation of autophagy pathways, leading to decreased cellular survival. These effects may be mediated through nuclear factor κB (NFκB) as part of a CCN2/integrin/NFκB signaling cascade.

ISOTROPIC LUMINOSITY INDICATORS IN A COMPLETE AGN SAMPLE

International Nuclear Information System (INIS)

Diamond-Stanic, Aleksandar M.; Rieke, George H.; Rigby, Jane R.

2009-01-01

The [O IV] λ25.89 μm line has been shown to be an accurate indicator of active galactic nucleus (AGN) intrinsic luminosity in that it correlates well with hard (10-200 keV) X-ray emission. We present measurements of [O IV] for 89 Seyfert galaxies from the unbiased revised Shapley-Ames (RSA) sample. The [O IV] luminosity distributions of obscured and unobscured Seyferts are indistinguishable, indicating that their intrinsic AGN luminosities are quite similar and that the RSA sample is well suited for tests of the unified model. In addition, we analyze several commonly used proxies for AGN luminosity, including [O III] λ5007 A, 6 cm radio, and 2-10 keV X-ray emission. We find that the radio luminosity distributions of obscured and unobscured AGNs show no significant difference, indicating that radio luminosity is a useful isotropic luminosity indicator. However, the observed [O III] and 2-10 keV luminosities are systematically smaller for obscured Seyferts, indicating that they are not emitted isotropically.

The Space-Time Continuum as a Transversely Isotropic Material and the Meaning of the Temporal Coordinate

International Nuclear Information System (INIS)

Christov, C. I.

2010-01-01

A transversely isotropic elastic continuum is considered in four dimensions, three of which are isotropic, and the properties of the material change only related to the fourth dimension. The model employs two dilational and three shear Lame coefficients. The isotropic dilational coefficient is assumed to be much larger than the second dilational coefficient, and the three shear coefficients. This amounts to a material that is virtually incompressible in the three isotropic dimensions. The first and third shear coefficients are positive, while the second shear coefficient is assumed to be negative. As a result, in the equations of elastic equilibrium, the second derivatives of the displacement with respect to the fourth coordinate enter with negative sign. This makes the equations hyperbolic, with a fourth dimension opposing to the other three. The hyperbolic nature of the fourth dimension allows to be interpreted as time.

Self-confinement of finite dust clusters in isotropic plasmas.

Science.gov (United States)

Miloshevsky, G V; Hassanein, A

2012-05-01

Finite two-dimensional dust clusters are systems of a small number of charged grains. The self-confinement of dust clusters in isotropic plasmas is studied using the particle-in-cell method. The energetically favorable configurations of grains in plasma are found that are due to the kinetic effects of plasma ions and electrons. The self-confinement phenomenon is attributed to the change in the plasma composition within a dust cluster resulting in grain attraction mediated by plasma ions. This is a self-consistent state of a dust cluster in which grain's repulsion is compensated by the reduced charge and floating potential on grains, overlapped ion clouds, and depleted electrons within a cluster. The common potential well is formed trapping dust clusters in the confined state. These results provide both valuable insights and a different perspective to the classical view on the formation of boundary-free dust clusters in isotropic plasmas.

Immunoreactive cortisone in droppings reflect stress levels, diet and growth rate of gull-billed tern chicks.

Science.gov (United States)

Albano, Noelia; Santiago-Quesada, Francisco; Masero, José A; Sánchez-Guzmán, Juan M; Möstl, Erich

2015-03-01

Blood levels of corticosterone have been traditionally analyzed to assess stress levels in birds; however, measuring steroid hormone metabolites in feces and droppings has gained much interest as a noninvasive technique successfully used for such purposed in vertebrates. Diet may affect these fecal metabolite levels (e.g., due to nutritional stress), however, this variable has not been taken into account in studies with chicks despite the great dietary flexibility of many avian species. In this study, we addressed for the first time this key issue and validated the technique in wild gull-billed tern chicks (Gelochelidon nilotica). Several enzyme immunoassays were used to determine the most appropriate test to measure the stress response. Subsequently, we performed an experiment in captivity to assess adrenocortical activity in gull-billed tern chicks fed with two diets: piscivorous vs. insectivorous. Finally, the relation between the chicks' growth rate and excreted immunoreactive glucocorticoid metabolites (EGMs) was also evaluated. We found the immunoreactive cortisone metabolites to be a good index of stress (as being an index of adrenocortical reactivity) in chicks of this species. Fish-fed chicks had higher levels of cortisone metabolites when comparing both concentration and total daily excreted metabolites. Within each treatment diet, cortisone metabolite levels and growth rates were negatively correlated. These findings suggest that the diet should be considered when using this technique for comparative purposes and highlight the trade-off between stress levels and chicks growth rates. Copyright © 2015 Elsevier Inc. All rights reserved.

Sterically controlled mechanochemistry under hydrostatic pressure

Science.gov (United States)

Yan, Hao; Yang, Fan; Pan, Ding; Lin, Yu; Hohman, J. Nathan; Solis-Ibarra, Diego; Li, Fei Hua; Dahl, Jeremy E. P.; Carlson, Robert M. K.; Tkachenko, Boryslav A.; Fokin, Andrey A.; Schreiner, Peter R.; Galli, Giulia; Mao, Wendy L.; Shen, Zhi-Xun; Melosh, Nicholas A.

2018-02-01

Mechanical stimuli can modify the energy landscape of chemical reactions and enable reaction pathways, offering a synthetic strategy that complements conventional chemistry. These mechanochemical mechanisms have been studied extensively in one-dimensional polymers under tensile stress using ring-opening and reorganization, polymer unzipping and disulfide reduction as model reactions. In these systems, the pulling force stretches chemical bonds, initiating the reaction. Additionally, it has been shown that forces orthogonal to the chemical bonds can alter the rate of bond dissociation. However, these bond activation mechanisms have not been possible under isotropic, compressive stress (that is, hydrostatic pressure). Here we show that mechanochemistry through isotropic compression is possible by molecularly engineering structures that can translate macroscopic isotropic stress into molecular-level anisotropic strain. We engineer molecules with mechanically heterogeneous components—a compressible (‘soft’) mechanophore and incompressible (‘hard’) ligands. In these ‘molecular anvils’, isotropic stress leads to relative motions of the rigid ligands, anisotropically deforming the compressible mechanophore and activating bonds. Conversely, rigid ligands in steric contact impede relative motion, blocking reactivity. We combine experiments and computations to demonstrate hydrostatic-pressure-driven redox reactions in metal-organic chalcogenides that incorporate molecular elements that have heterogeneous compressibility, in which bending of bond angles or shearing of adjacent chains activates the metal-chalcogen bonds, leading to the formation of the elemental metal. These results reveal an unexplored reaction mechanism and suggest possible strategies for high-specificity mechanosynthesis.

Mechanical properties of the collagen network in human articular cartilage as measured by osmotic stress technique

NARCIS (Netherlands)

Basser, P.J.; Schneiderman, R.; Bank, R.A.; Wachtel, E.; Maroudas, A.

1998-01-01

We have used an isotropic osmotic stress technique to assess the swelling pressures of human articular cartilage over a wide range of hydrations in order to determine from these measurements, for the first time, the tensile stress in the collagen network, P(c), as a function of hydration. Osmotic

Effects of drought and salt stresses on growth characteristics of euhalophyte Suaeda salsa in coastal wetlands

Science.gov (United States)

Jia, Jia; Huang, Chen; Bai, Junhong; Zhang, Guangliang; Zhao, Qingqing; Wen, Xiaojun

2018-02-01

The pot experiment was carried out in the Yellow River Delta to investigate the effects of drought and salt stresses on growth characteristics of Suaeda salsa, and to reveal the role of nitrogen (N) application in alleviation effects of drought and salt stresses on Suaeda salsa in coastal wetlands. In this study, plants were exposed to two water contents treatments (i.e., 14% and 26% water content), four salinity treatments (i.e., 2 g/kg, 4 g/kg, 6 g/kg, and 8 g/kg NaCl) and two N application treatments (i.e., 0 and 200 N mg/kg) in field conditions. Growth characteristics of Suaeda salsa were assessed as fresh weight, dry weight, height, total nitrogen (TN) and total carbon (TC). Our results showed that fresh weight, dry weight and height of Suaeda salsa promoted at lower salinity treatments but reduced at higher salinity treatments, while TN and TC contents kept stable with increasing salinity levels. Drought stress diminished the fresh weight, dry weight and height of Suaeda salsa, whereas enhanced TN contents. Under the interactive stresses of drought and salt, fresh weight and dry weight showed slight increases at lower salinity treatments, whereas decreases at higher salinity treatments. N application promoted the fresh weight, dry weight and TN contents other than the height and TC contents of Suaeda salsa. The interaction between N application and salt stress exhibited a significant influence on the fresh weight and dry weight of Suaeda salsa, whereas no significant interaction between N application and drought stress was observed. These findings of this study suggested that higher salinity, drought and the interaction of drought and higher salinity would retard the growth of Suaeda salsa, whereas N application could only mitigate the deleterious effects of salt stress on Suaeda salsa.

Fibroblast growth factor 21 and its novel association with oxidative stress

Directory of Open Access Journals (Sweden)

Miguel Ángel Gómez-Sámano

2017-04-01

Full Text Available Fibroblast growth factor 21 (FGF21 is an endocrine-member of the FGF family. It is synthesized mainly in the liver, but it is also expressed in adipose tissue, skeletal muscle, and many other organs. It has a key role in glucose and lipid metabolism, as well as in energy balance. FGF21 concentration in plasma is increased in patients with obesity, insulin resistance, and metabolic syndrome. Recent findings suggest that such increment protects tissue from an increased oxidative stress environment. Different types of physical stress, such as strenuous exercising, lactation, diabetic nephropathy, cardiovascular disease, and critical illnesses, also increase FGF21 circulating concentration. FGF21 is now considered a stress-responsive hormone in humans. The discovery of an essential response element in the FGF21 gene, for the activating transcription factor 4 (ATF4, involved in the regulation of oxidative stress, and its relation with genes such as NRF2, TBP-2, UCP3, SOD2, ERK, and p38, places FGF21 as a key regulator of the oxidative stress cell response. Its role in chronic diseases and its involvement in the treatment and follow-up of these diseases has been recently the target of new studies. The diminished oxidative stress through FGF21 pathways observed with anti-diabetic therapy is another clue of the new insights of this hormone.

Seismic sensitivity of normal-mode coupling to Lorentz stresses in the Sun

Science.gov (United States)

Hanasoge, Shravan M.

2017-09-01

Understanding the governing mechanism of solar magnetism remains an outstanding challenge in astrophysics. Seismology is the most compelling technique to infer the internal properties of the Sun and stars. Waves in the Sun, nominally acoustic, are sensitive to the emergence and cyclical strengthening of magnetic field, evidenced by measured changes in resonant oscillation frequencies that are correlated with the solar cycle. The inference of internal Lorentz stresses from these measurements has the potential to significantly advance our appreciation of the dynamo. Indeed, seismological inverse theory for the Sun is well understood for perturbations in composition, thermal structure and flows but, is not fully developed for magnetism, owing to the complexity of the ideal magnetohydrodynamic (MHD) equation. Invoking first-Born perturbation theory to characterize departures from spherically symmetric hydrostatic models of the Sun and applying the notation of generalized spherical harmonics, we calculate sensitivity functions of seismic measurements to the general time-varying Lorentz stress tensor. We find that eigenstates of isotropic (I.e. acoustic only) background models are dominantly sensitive to isotropic deviations in the stress tensor and much more weakly than anisotropic stresses (and therefore challenging to infer). The apple cannot fall far from the tree.

Isotropic cosmic expansion and the Rubin-Ford effect

International Nuclear Information System (INIS)

Fall, S.M.; Jones, B.J.T.

1976-01-01

It is shown that the Rubin-Ford data (Astrophys. J. Lett. 183:L111 (1973)), often taken as evidence for large scale anisotropic cosmic expansion, probably only reflect the inhomogeneous distribution of galaxies in the region of the sample. The data presented are consistent with isotropic expansion, an unperturbed galaxy velocity field, and hence a low density Universe. (author)

Effect of drought stress on early growth of Adansonia digitata (L.) in ...

African Journals Online (AJOL)

Drought and high temperatures are said to have triggered increased tree mortality and could be linked to the menace of climate change. This research therefore investigated the effect of drought stress on early growth of Adansonia digitata where seedlings were exposed to different watering frequencies (Once daily, after 3, ...

A simple mechanical model for the isotropic harmonic oscillator

International Nuclear Information System (INIS)

Nita, Gelu M

2010-01-01

A constrained elastic pendulum is proposed as a simple mechanical model for the isotropic harmonic oscillator. The conceptual and mathematical simplicity of this model recommends it as an effective pedagogical tool in teaching basic physics concepts at advanced high school and introductory undergraduate course levels.

Magnetization reversal processes of isotropic permanent magnets with various inter-grain exchange interactions

Directory of Open Access Journals (Sweden)

Hiroshi Tsukahara

2017-05-01

Full Text Available We performed a large-scale micromagnetics simulation on a supercomputing system to investigate the properties of isotropic nanocrystalline permanent magnets consisting of cubic grains. In the simulation, we solved the Landau–Lifshitz–Gilbert equation under a periodic boundary condition for accurate calculation of the magnetization dynamics inside the nanocrystalline isotropic magnet. We reduced the inter-grain exchange interaction perpendicular and parallel to the external field independently. Propagation of the magnetization reversal process is inhibited by reducing the inter-grain exchange interaction perpendicular to the external field, and the coercivity is enhanced by this restraint. In contrast, when we reduce the inter-grain exchange interaction parallel to the external field, the coercivity decreases because the magnetization reversal process propagates owing to dipole interaction. These behaviors show that the coercivity of an isotropic permanent magnet depends on the direction of the inter-grain exchange interaction.

Effect of Nitrogen Nutritional Stress on Some Growth Parameters of Zea mays L. and Vigna unguiculata (L. Walp.

Directory of Open Access Journals (Sweden)

Akinbode Foluso OLOGUNDUDU

2013-02-01

Full Text Available This study investigated the responses of maize (Zea mays L. and cowpea (Vigna unguiculata L. Walp. seedlings growth parameters to nitrogen nutritional stress. This was with a view to determining whether nitrogen nutritional stress would retard or enhance maize and cowpea growth, partly, wholly or not at all through its effect on biomass accumulation and some morphological parameters. Germination of seeds was done using treated sand in sixty plastic pots. A group of the seedlings was nutrient stressed by administering 200 ml of complete nutrient solution minus nitrogen (-N while the other groups were fed with five times (X5N and ten times (X10N the optimal concentration of nitrogen and the last regime was fed with full nutrient solution (FN. The effects of optimal concentration and nitrogen stress on the growth rates (as measured by their fresh and dry weight were studied. The result of the growth analysis showed that there was increase in shoot height with supraoptimal concentrations of nitrogen treatments (X10N and X5N while there was a decrease in shoot height with minus nitrogen (-N regimes. The observed higher biomass (dry matter yield under the FN regimes in both Zea mays and Vigna unguiculata were attributed to optimal nutrient assimilation rate.

A halotolerant Enterobacter sp. displaying ACC deaminase activity promotes rice seedling growth under salt stress.

Science.gov (United States)

Sarkar, Anumita; Ghosh, Pallab Kumar; Pramanik, Krishnendu; Mitra, Soumik; Soren, Tithi; Pandey, Sanjeev; Mondal, Monohar Hossain; Maiti, Tushar Kanti

2018-01-01

Agricultural productivity is proven to be hampered by the synthesis of reactive oxygen species (ROS) and production of stress-induced ethylene under salinity stress. One-aminocyclopropane-1-carboxylic acid (ACC) is the direct precursor of ethylene synthesized by plants. Bacteria possessing ACC deaminase activity can use ACC as a nitrogen source preventing ethylene production. Several salt-tolerant bacterial strains displaying ACC deaminase activity were isolated from rice fields, and their plant growth-promoting (PGP) properties were determined. Among them, strain P23, identified as an Enterobacter sp. based on phenotypic characteristics, matrix-assisted laser desorption ionization-time of flight mass spectrometry data and the 16S rDNA sequence, was selected as the best-performing isolate for several PGP traits, including phosphate solubilization, IAA production, siderophore production, HCN production, etc. Enterobacter sp. P23 was shown to promote rice seedling growth under salt stress, and this effect was correlated with a decrease in antioxidant enzymes and stress-induced ethylene. Isolation of an acdS mutant strain enabled concluding that the reduction in stress-induced ethylene content after inoculation of strain P23 was linked to ACC deaminase activity. Copyright © 2017 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

The membrane tethered transcription factor EcbZIP17 from finger millet promotes plant growth and enhances tolerance to abiotic stresses.

Science.gov (United States)

Ramakrishna, Chopperla; Singh, Sonam; Raghavendrarao, Sangala; Padaria, Jasdeep C; Mohanty, Sasmita; Sharma, Tilak Raj; Solanke, Amolkumar U

2018-02-01

The occurrence of various stresses, as the outcome of global climate change, results in the yield losses of crop plants. Prospecting of genes in stress tolerant plant species may help to protect and improve their agronomic performance. Finger millet (Eleusine coracana L.) is a valuable source of superior genes and alleles for stress tolerance. In this study, we isolated a novel endoplasmic reticulum (ER) membrane tethered bZIP transcription factor from finger millet, EcbZIP17. Transgenic tobacco plants overexpressing this gene showed better vegetative growth and seed yield compared with wild type (WT) plants under optimal growth conditions and confirmed upregulation of brassinosteroid signalling genes. Under various abiotic stresses, such as 250 mM NaCl, 10% PEG6000, 400 mM mannitol, water withdrawal, and heat stress, the transgenic plants showed higher germination rate, biomass, primary and secondary root formation, and recovery rate, compared with WT plants. The transgenic plants exposed to an ER stress inducer resulted in greater leaf diameter and plant height as well as higher expression of the ER stress-responsive genes BiP, PDIL, and CRT1. Overall, our results indicated that EcbZIP17 improves plant growth at optimal conditions through brassinosteroid signalling and provide tolerance to various environmental stresses via ER signalling pathways.

Effects of molecular elongation on liquid crystalline phase behaviour: isotropic-nematic transition

Science.gov (United States)

Singh, Ram Chandra; Ram, Jokhan

2003-08-01

We present the density-functional approach to study the isotropic-nematic transitions and calculate the values of freezing parameters of the Gay-Berne liquid crystal model, concentrating on the effects of varying the molecular elongation, x0. For this, we have solved the Percus-Yevick integral equation theory to calculate the pair-correlation functions of a fluid the molecules of which interact via a Gay-Berne pair potential. These results have been used in the density-functional theory as an input to locate the isotropic-nematic transition and calculate freezing parameters for a range of length-to-width parameters 3.0⩽ x0⩽4.0 at reduced temperatures 0.95 and 1.25. We observed that as x0 is increased, the isotropic-nematic transition is seen to move to lower density at a given temperature. We find that the density-functional theory is good to study the freezing transitions in such fluids. We have also compared our results with computer simulation results wherever they are available.

Absence of surface stress change during pentacene thin film growth on the Si(111)-(7 x 7) surface: a buried reconstruction interface

International Nuclear Information System (INIS)

Kury, P; Horn von Hoegen, M; Heringdorf, F-J Meyer zu; Roos, K R

2008-01-01

We use high-resolution surface stress measurements to monitor the surface stress during the growth of pentacene (C 22 H 14 ) on the (7x7) reconstructed silicon (111) surface. No significant change in the surface stress is observed during the pentacene growth. Compared to the changes in the surface stress observed for Si and Ge deposition on the Si(111)-(7x7) surface, the insignificant change in the surface stress observed for the pentacene growth suggests that the pentacene molecules of the first adsorbate layer, although forming strong covalent bonds with the Si adatoms, do not alter the structure of the (7x7) reconstruction. The (7x7) reconstruction remains intact and, with subsequent deposition of pentacene, eventually becomes buried under the growing film. This failure of the pentacene to affect the structure of the reconstruction may represent a fundamental difference between the growth of organic thin films and that of inorganic thin films on semiconductor surfaces

Edge preserving smoothing and segmentation of 4-D images via transversely isotropic scale-space processing and fingerprint analysis

International Nuclear Information System (INIS)

Reutter, Bryan W.; Algazi, V. Ralph; Gullberg, Grant T; Huesman, Ronald H.

2004-01-01

Enhancements are described for an approach that unifies edge preserving smoothing with segmentation of time sequences of volumetric images, based on differential edge detection at multiple spatial and temporal scales. Potential applications of these 4-D methods include segmentation of respiratory gated positron emission tomography (PET) transmission images to improve accuracy of attenuation correction for imaging heart and lung lesions, and segmentation of dynamic cardiac single photon emission computed tomography (SPECT) images to facilitate unbiased estimation of time-activity curves and kinetic parameters for left ventricular volumes of interest. Improved segmentation of lung surfaces in simulated respiratory gated cardiac PET transmission images is achieved with a 4-D edge detection operator composed of edge preserving 1-D operators applied in various spatial and temporal directions. Smoothing along the axis of a 1-D operator is driven by structure separation seen in the scale-space fingerprint, rather than by image contrast. Spurious noise structures are reduced with use of small-scale isotropic smoothing in directions transverse to the 1-D operator axis. Analytic expressions are obtained for directional derivatives of the smoothed, edge preserved image, and the expressions are used to compose a 4-D operator that detects edges as zero-crossings in the second derivative in the direction of the image intensity gradient. Additional improvement in segmentation is anticipated with use of multiscale transversely isotropic smoothing and a novel interpolation method that improves the behavior of the directional derivatives. The interpolation method is demonstrated on a simulated 1-D edge and incorporation of the method into the 4-D algorithm is described

Weak convergence to isotropic complex [Formula: see text] random measure.

Science.gov (United States)

Wang, Jun; Li, Yunmeng; Sang, Liheng

2017-01-01

In this paper, we prove that an isotropic complex symmetric α -stable random measure ([Formula: see text]) can be approximated by a complex process constructed by integrals based on the Poisson process with random intensity.

Oxidation of Fe–22Cr Coated with Co3O4: Microstructure Evolution and the Effect of Growth Stresses

DEFF Research Database (Denmark)

Hansson, Anette Nørgaard; Burriel, Monica; Garcia, Gemma

2007-01-01

The oxidation behavior of a commercially available Fe–22Cr alloy coated with a Co3O4 layer by metal organic—chemical vapor deposition was investigated in air with 1% H2O at 1,173 K and compared to the oxidation behavior of the non-coated alloy. The oxide morphology was examined with X......-ray diffraction, electron microscopy, and energy dispersive X-ray spectroscopy. Cr2O3 developed in between the Co3O4 coating and the alloy, while alloying elements of the substrate were incorporated into the coating. Particular attention was devoted to possible sources of growth stresses and the effect...... of the growth stresses on microstructure evolution in the scales that developed on the non-coated and the coated Fe–22Cr alloy. Microstructural features suggested that scale spallation on coated Fe–22Cr occurred as a result of superimposing thermal stresses during cooling onto the growth stresses, that had...

Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states

Science.gov (United States)

Wåhlander, Martin; Nilsson, Fritjof; Carlmark, Anna; Gedde, Ulf W.; Edmondson, Steve; Malmström, Eva

2016-08-01

We demonstrate a novel route to synthesise hydrophobic matrix-free composites of polymer-grafted graphene oxide (GO) showing isotropic or nematic alignment and shape-memory effects. For the first time, a cationic macroinitiator (MI) has been immobilised on anionic GO and subsequently grafted with hydrophobic polymer grafts. Dense grafts of PBA, PBMA and PMMA with a wide range of average graft lengths (MW: 1-440 kDa) were polymerised by surface-initiated controlled radical precipitation polymerisation from the statistical MI. The surface modification is designed similarly to bimodal graft systems, where the cationic MI generates nanoparticle repulsion, similar to dense short grafts, while the long grafts offer miscibility in non-polar environments and cohesion. The state-of-the-art dispersions of grafted GO were in the isotropic state. Transparent and translucent matrix-free GO-composites could be melt-processed directly using only grafted GO. After processing, birefringence due to nematic alignment of grafted GO was observed as a single giant Maltese cross, 3.4 cm across. Permeability models for composites containing aligned 2D-fillers were developed, which were compared with the experimental oxygen permeability data and found to be consistent with isotropic or nematic states. The storage modulus of the matrix-free GO-composites increased with GO content (50% increase at 0.67 wt%), while the significant increases in the thermal stability (up to 130 °C) and the glass transition temperature (up to 17 °C) were dependent on graft length. The tuneable matrix-free GO-composites with rapid thermo-responsive shape-memory effects are promising candidates for a vast range of applications, especially selective membranes and sensors.We demonstrate a novel route to synthesise hydrophobic matrix-free composites of polymer-grafted graphene oxide (GO) showing isotropic or nematic alignment and shape-memory effects. For the first time, a cationic macroinitiator (MI) has been

Induced surface stress at crystal surfaces

International Nuclear Information System (INIS)

Dahmen, K.

2002-05-01

Changes of the surfaces stress Δτ (s) can be studied by observing the bending of thin crystalline plates. With this cantilever method one can gain the induced change of surface stress Δτ (s) from the bending of plates with the help of elasticity theory. For elastic isotropic substrates the relevant relations are known. Here the relations are generalized to elastic anisotropic crystals with a C 2v - Symmetry. The equilibrium shapes of crystalline plates oriented along the (100)-, (110)-, or (111)-direction which are clamped along one edge are calculated with a numeric method under the load of a homogeneous but pure isotropic or anisotropic surface stress. The results can be displayed with the dimensionality, so that the effect of clamping can be described in a systematic way. With these tabulated values one can evaluate cantilever experiments exactly. These results are generalized to cantilever methods for determining magnetoelastic constants. It is shown which magnetoelastic constants are measured in domains of thin films with ordered structures. The eigenshape and the eigenfrequency of plates constraint through a clamping at one side are calculated. These results give a deeper understanding of the elastic anisotropy. The induced surface stress of oxygen on the (110)-surface of molybdenum is measured along the principle directions Δτ [001] and Δτ [ anti 110] . The anisotropy of the surface stress is found for the p(2 x 2)-reconstruction. Lithium induces a tensile surface stress on the Molybdenum (110)-surface up to a coverage of Θ = 0, 3 monolayer. For a higher coverage the induced stress drops and reaches a level of less than -1, 2 N/m at one monolayer. It is shown, that cobalt induces a linear increasing stress with respect to the coverage on the (100)-surface of copper with a value of 2, 4GPa. The copper (100)-surface is bombarded with accelerated ions in the range between 800-2200 eV. The resulting induced compressive stress (Δτ (s) < 0) of the order

Study of open systems with molecules in isotropic liquids