Bibliography on thermal stresses in shells
Hetnarski, R.B.; Keene, F.W. (Rochester Institute of Technology, NY (USA))
1990-01-01
A total of 778 references on the thermal stress behavior of shells are compiled in a bibliography covering the period 1952-1990. The documents included were either originally published in English or had been translated. A general alphabetical listing (by author) with abstracts (where available) is followed by two sections arranged by subject category (under the rubrics geometry and mechanical behavior), an author index, and a list of the journals in which the articles appeared.
Bending stresses in Facetted Glass Shells
Bagger, Anne; Jönsson, Jeppe; Almegaard, Henrik
2008-01-01
A shell structure of glass combines a highly effective structural principle with a material of optimal permeability to light. A facetted shell structure has a piecewise plane geometry, and together the facets form an approximation to a curved surface. A distributed load on a plane-based facetted...... structure will locally cause bending moments in the loaded facets. The bending stresses are dependent on the stiffness of the joints. Approximate solutions are developed to estimate the magnitude of the bending stresses. A FE-model of a facetted glass shell structure is used to validate the expressions...
Stress and vibraton analyses of anisotropic shells of revolution
Noor, Ahmed K.; Peters, Jeanne M.
1988-01-01
An efficient computational strategy is presented for reducing the cost of the stress and free vibration analyses of laminated anisotropic shells of revolution. The analytical formulation is based on a form of the Sanders-Budiansky shell theory including the effects of both the transverse shear deformation and the laminated anisotropic material response. The fundamental unknowns consist of the eight strain components, the eight stress resultants and the five generalized displacements of the shell. Each of the shell variables is expressed in terms of trigonometric functions (Fourier series) in the circumferential co-ordinate, and a three-field mixed finite element model is used for the discretization in the meridional direction. The shell response associated with a range of Fourier harmonics is approximated by a linear combination of a few global approximation vectors, which are generated at a particular value of the Fourier harmonic, within that range. The full equations of the finite element model are solved for only a single Fourier harmonic, and the response corresponding to the other Fourier harmonics is generated using a reduced system of equations with considerably fewer degrees of freedom.
A hybrid-stress solid-shell element for non-linear analysis of piezoelectric structures
SZE; K; Y
2009-01-01
This paper presents eight-node solid-shell elements for geometric non-linear analyze of piezoelectric structures. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger-Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid ele- ment, a hybrid-stress solid-shell element is formulated. The presented finite shell element is able to model arbitrary curved shell structures. Non-linear numerical examples demonstrate the ability of the proposed model to analyze nonlinear piezoelectric devices.
Buckling of un—stiffened cylindrical shell under non—uniform axial compressive stress
宋昌永
2002-01-01
This paper provides a review of recent research advances and trends in the area of stability of unstiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses.Only the more important and interesting aspects of the research,judged from a personal viewpoint,are discussed.They can be crudely classified into four categories:(1) shells subjected to non-uniform loads;(2) shells on discrete supports;(3) shells with intended cutouts/holes;and (4) shells with non-uniform settlements.
Buckling of un-stiffened cylindrical shell under non-uniform axial conpressive stress
宋昌永
2002-01-01
This paper provides a review of recent research advances and trends in the area of stability of un-stiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses. Only the more important and interesting aspects of the research, judged from a personal viewpoint, are discussed. They can be crudely classified into four categories: (1) shells subjected to non-uniform loads; (2) shells on discrete supports; (3) shells with intended cutouts/holes; and (4) shells with non-uniform settlements.
Collapsing spherical null shells in general relativity
S Khakshournia
2011-03-01
Full Text Available In this work, the gravitational collapse of a spherically symmetric null shell with the flat interior and a charged Vaidya exterior spacetimes is studied. There is no gravitational impulsive wave present on the null hypersurface which is shear-free and contracting. It follows that there is a critical radius at which the shell bounces and starts expanding.
Generalized seniority with realistic interactions in open-shell nuclei
Caprio, M A; Cai, K; Constantinou, Ch; Hellemans, V
2014-01-01
Generalized seniority provides a truncation scheme for the nuclear shell model, based on pairing correlations, which offers the possibility of dramatically reducing the dimensionality of the nuclear shell-model problem. Systematic comparisons against results obtained in the full shell-model space are required to assess the viability of this scheme. Here, we extend recent generalized seniority calculations for semimagic nuclei, the Ca isotopes, to open-shell nuclei, with both valence protons and valence neutrons. The even-mass Ti and Cr isotopes are treated in a full major shell and with realistic interactions, in the generalized seniority scheme with one broken proton pair and one broken neutron pair. Results for level energies, orbital occupations, and electromagnetic observables are compared with those obtained in the full shell-model space. We demonstrate that, even for the Ti isotopes, significant benefit would be obtained in going beyond the approximation of one broken pair of each type, while the Cr iso...
Convergence of the Solution to General Viscoelastic Koiter Shell Equations
Fu Shan LI
2007-01-01
By applying the inequality of Korn's type without boundary conditions on a general surface, we prove that the scaled displacement of the two-dimensional linearly viscoelastic Koiter's shell converges to the solution of two-dimensional model system of linearly viscoelastic "membrane" shell.
Generalized synthesis of mesoporous shells on zeolite crystals
Han, Yu
2010-12-30
A simple and generalized synthetic approach is developed for creating mesoporous shells on zeolite crystals. This method allows for the tailoring of thickness, pore size, and composition of the mesoporous shell, and can be applied to zeolites of various structures, compositions, and crystal sizes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Newtonian and General Relativistic Models of Spherical Shells
Vogt, D
2009-01-01
A family of spherical shells with varying thickness is derived by using a simple Newtonian potential-density pair. Then, a particular isotropic form of a metric in spherical coordinates is used to construct a General Relativistic version of the Newtonian family of shells. The matter of these relativistic shells presents equal azimuthal and polar pressures, while the radial pressure is a constant times the tangential pressure. We also make a first study of stability of both the Newtonian and relativistic families of shells.
Stress Analysis of Ellipsoidal Shell with Inner Guide Structure
Wei-Wei Zhang; Xiao-Song Wang; Meng Chen; Shi-Jian Yuan
2014-01-01
In order to overcome stress concentration and increase fatigue life of ellipsoidal shells with inner guide structure, the stress analysis for strength check is very important. Owing to the main sectional profile with ellipsoidal shape, the stress distribution for perfect ellipsoidal shell is firstly conducted based on the theoretical calculation and strain gauges measurement. The experiment results show that the stresses increase gradually from pole region to equatorial plane, but still within elastic range. Secondly, strain gauge measurement for ellipsoidal shells with inner guide structure is conducted. The results show that stresses are concentrated at the vicinity of bottom plate and beyond elastic range, so the structural redesign is needed. Finally based on the analysis mentioned above, a redesigned structure with local thickening is proposed. Experimental research shows that the stress varies more even after structural redesign and within allowable range. Numerical simulation shows that both the deformation and fatigue life after redesign are acceptable.
Stress Resultant Based Elasto-Viscoplastic Thick Shell Model
Pawel Woelke
2012-01-01
Full Text Available The current paper presents enhancement introduced to the elasto-viscoplastic shell formulation, which serves as a theoretical base for the finite element code EPSA (Elasto-Plastic Shell Analysis [1–3]. The shell equations used in EPSA are modified to account for transverse shear deformation, which is important in the analysis of thick plates and shells, as well as composite laminates. Transverse shear forces calculated from transverse shear strains are introduced into a rate-dependent yield function, which is similar to Iliushin's yield surface expressed in terms of stress resultants and stress couples [12]. The hardening rule defined by Bieniek and Funaro [4], which allows for representation of the Bauschinger effect on a moment-curvature plane, was previously adopted in EPSA and is used here in the same form. Viscoplastic strain rates are calculated, taking into account the transverse shears. Only non-layered shells are considered in this work.
Stress Recovery and Error Estimation for Shell Structures
Yazdani, A. A.; Riggs, H. R.; Tessler, A.
2000-01-01
The Penalized Discrete Least-Squares (PDLS) stress recovery (smoothing) technique developed for two dimensional linear elliptic problems is adapted here to three-dimensional shell structures. The surfaces are restricted to those which have a 2-D parametric representation, or which can be built-up of such surfaces. The proposed strategy involves mapping the finite element results to the 2-D parametric space which describes the geometry, and smoothing is carried out in the parametric space using the PDLS-based Smoothing Element Analysis (SEA). Numerical results for two well-known shell problems are presented to illustrate the performance of SEA/PDLS for these problems. The recovered stresses are used in the Zienkiewicz-Zhu a posteriori error estimator. The estimated errors are used to demonstrate the performance of SEA-recovered stresses in automated adaptive mesh refinement of shell structures. The numerical results are encouraging. Further testing involving more complex, practical structures is necessary.
Investigation of stresses in facetted glass shell structures
Bagger, Anne; Jönsson, Jeppe; Wester, Ture
2007-01-01
The typical use of triangular and quadrangular facets in doubly curved facetted shells requires the use of triangulated truss systems or quadrangular truss framing with diagonals or cross tension cabling. In such a structure, the load carrying ability is based on concentrated forces in the framing...... system, while the glass merely serves as a separation of the inside environment from the outside. In this paper facetted glass shell structures with three way vertices, i.e. with three adjoining edges in each vertex are considered, since the load carrying ability of such a structure is achieved primarily...... by in-plane forces in the facets and the transfer of distributed in-plane forces across the joints. It is described how these facets work structurally, specifically how bending moments develop and cause possible stress concentrations in the corners, which are subjected to uplift. Apart from local...
Analysis of stress-strain state of the spherical shallow shell with inclusion
O.B. Kozin
2016-05-01
Full Text Available Development of effective methods of determining the stress-strain state thin-walled structures with inclusions, reinforcements and other stress concentrators is an important task, both from a theoretical and practical point of view, by reason of their great practical application. Aim: The aim of the research is to analyze the elastic-deformed state of a spherical shallow shell. Materials and Methods: In this work, based on the generalized scheme of integral transformations, a constructive method of direct numerical-analytical solutions of boundary value problem of calculating the stress-strain state of a spherical shallow shell with the inclusion in bending is proposed. Results: The results of numerical calculations are presented. Calculations allow predicting the value of deformation of the cylindrical shells structure with reinforcements and determining the optimum parameters for the design or manufacture. The obtained results can be used in determining the strength characteristics of structural elements that consist of composite materials. The article contains comparative analysis of the results and demonstrates the effectiveness of the method for solving this class of problems.
Guang-Xiang Xie; Lei Wang [Anhui University of Science and Technology, Huainan (China)
2008-12-15
The mechanical characteristics of surrounding rock stress shell in longwall mining face were studied, based on the results of in-situ measurement combined with numerical simulation, and the effect of longwall length on mechanical characteristics of surrounding rock stress shell was discovered. The results show that the mechanical characteristics of surrounding rock stress shell are influenced by the length of the face. With an increase of mining face length, the level of concentration of shell stress located in the front face and surrounding rock of roadway is amplified and the three- dimensional stress is focused in the working face. The damage lies in the head entry corner of face and the vertical displacement is reduced but horizontal displacement is enlarged. The dynamic balance of surrounding rock stress shell is improved with rational adjustment of face length. It is effective in protecting the working face and controlling strata behavior. 5 refs., 7 figs.
Stress concentration in a transversely isotropic spherical shell with two circular rigid inclusions
Chekhov, V. N.; Zakora, S. V.
2011-10-01
The refined Timoshenko-type theory that takes into account the transverse shear strains is used to find an analytic solution for the stress state of transversely isotropic shallow spherical shell with two circular rigid inclusions. The case of a shell with closely spaced rigid inclusions of unequal radii under internal pressure is analyzed numerically. The stresses in the shell increase considerably with decrease in the distance between the inclusions and increase in the transverse shear parameter
Enceladus's and Dione's floating ice shells supported by minimum stress isostasy
Beuthe, Mikael; Rivoldini, Attilio; Trinh, Antony
2016-10-01
Enceladus's gravity and shape have been explained in terms of a thick isostatic ice shell floating on a global ocean, in contradiction of the thin shell implied by librations. Here we propose a new isostatic model minimizing crustal deviatoric stress and demonstrate that gravity and shape data predict a 38 ± 4 km thick ocean beneath a 23 ± 4 km thick shell agreeing with—but independent of—libration data. Isostatic and tidal stresses are comparable in magnitude. South polar crust is only 7 ± 4 km thick, facilitating the opening of water conduits and enhancing tidal dissipation through stress concentration. Enceladus's resonant companion, Dione, is in a similar state of minimum stress isostasy. Its gravity and shape can be explained in terms of a 99 ± 23 km thick isostatic shell overlying a 65 ± 30 km thick global ocean, thus providing the first clear evidence for a present-day ocean within Dione.
General Stress Responses in the Honey Bee
Even, Naïla; Devaud, Jean-Marc; Barron, Andrew B.
2012-01-01
The biological concept of stress originated in mammals, where a “General Adaptation Syndrome” describes a set of common integrated physiological responses to diverse noxious agents. Physiological mechanisms of stress in mammals have been extensively investigated through diverse behavioral and physiological studies. One of the main elements of the stress response pathway is the endocrine hypothalamo-pituitary-adrenal (HPA) axis, which underlies the “fight-or-flight” response via a hormonal cascade of catecholamines and corticoid hormones. Physiological responses to stress have been studied more recently in insects: they involve biogenic amines (octopamine, dopamine), neuropeptides (allatostatin, corazonin) and metabolic hormones (adipokinetic hormone, diuretic hormone). Here, we review elements of the physiological stress response that are or may be specific to honey bees, given the economical and ecological impact of this species. This review proposes a hypothetical integrated honey bee stress pathway somewhat analogous to the mammalian HPA, involving the brain and, particularly, the neurohemal organ corpora cardiaca and peripheral targets, including energy storage organs (fat body and crop). We discuss how this system can organize rapid coordinated changes in metabolic activity and arousal, in response to adverse environmental stimuli. We highlight physiological elements of the general stress responses that are specific to honey bees, and the areas in which we lack information to stimulate more research into how this fascinating and vital insect responds to stress. PMID:26466739
Temperature-time distribution and thermal stresses on the RTG fins and shell during water cooling
Turner, R. H.
1983-01-01
Radioisotope thermoelectric generator (RTG) packages designed for space missions generally do not require active cooling. However, the heat they generate cannot remain inside of the launch vehicle bay and requires active removal. Therefore, before the Shuttle bay door is closed, the RTG coolant tubes attached to the heat rejection fins must be filled with water, which will circulate and remove most of the heat from the cargo bay. There is concern that charging a system at initial temperature around 200 C with water at 24 C can cause unacceptable thermal stresses in the RTG shell and fins. A computer model is developed to estimate the transient temperature distribution resulting from such charging. The thermal stresses resulting from the temperature gradients do not exceed the elastic deformation limit for the material. Since the simplified mathematical model for thermal stresses tends to overestimate stresses, it is concluded that the RTG can be cooled by introducing water at 24 C to the initially hot fin coolant tubes while the RTG is in the Shuttle cargo bay.
Temperature-time distribution and thermal stresses on the RTG fins and shell during water cooling
Turner, R. H.
1983-01-01
Radioisotope thermoelectric generator (RTG) packages designed for space missions generally do not require active cooling. However, the heat they generate cannot remain inside of the launch vehicle bay and requires active removal. Therefore, before the Shuttle bay door is closed, the RTG coolant tubes attached to the heat rejection fins must be filled with water, which will circulate and remove most of the heat from the cargo bay. There is concern that charging a system at initial temperature around 200 C with water at 24 C can cause unacceptable thermal stresses in the RTG shell and fins. A computer model is developed to estimate the transient temperature distribution resulting from such charging. The thermal stresses resulting from the temperature gradients do not exceed the elastic deformation limit for the material. Since the simplified mathematical model for thermal stresses tends to overestimate stresses, it is concluded that the RTG can be cooled by introducing water at 24 C to the initially hot fin coolant tubes while the RTG is in the Shuttle cargo bay.
Generalized asymptotic expansions for coupled wavenumbers in fluid-filled cylindrical shells
Kunte, M. V.; Sarkar, Abhijit; Sonti, Venkata R.
2010-12-01
Analytical expressions are found for the coupled wavenumbers in an infinite fluid-filled cylindrical shell using the asymptotic methods. These expressions are valid for any general circumferential order ( n). The shallow shell theory (which is more accurate at higher frequencies) is used to model the cylinder. Initially, the in vacuo shell is dealt with and asymptotic expressions are derived for the shell wavenumbers in the high- and the low-frequency regimes. Next, the fluid-filled shell is considered. Defining a relevant fluid-loading parameter μ, we find solutions for the limiting cases of small and large μ. Wherever relevant, a frequency scaling parameter along with some ingenuity is used to arrive at an elegant asymptotic expression. In all cases, Poisson's ratio ν is used as an expansion variable. The asymptotic results are compared with numerical solutions of the dispersion equation and the dispersion relation obtained by using the more general Donnell-Mushtari shell theory ( in vacuo and fluid-filled). A good match is obtained. Hence, the contribution of this work lies in the extension of the existing literature to include arbitrary circumferential orders ( n).
Vibration and Stability of Thick Simply Supported Shallow Shells Subjected to In-Plane Stresses
MATSUNAGA, H.
1999-08-01
The effects of higher order deformations on natural frequencies and buckling stresses of a thick shallow shell with reactangular planform subjected to uniaxial and biaxial in-plane stresses are studied. Based on the power series expansion of displacement components, a set of fundamental dynamic equations of a two-dimensional higher order shallow shell theory is derived through Hamilton's principle. Several sets of truncated approximate theories which can take into account the complete effects of higher order deformations such as shear deformations with thickness changes and rotatory inertia are applied to solve the vibration and stability problems of a thick shallow shell. Three types of simply supported shallow shells with positive, zero and negative Gaussian curvatures are considered. In order to assure the accuracy of the present theory, convergence properties of the lowest two natural frequencies for the first vibration moder=s=1 are examined in detail. The present results are also compared with those of existing theories. In the case of a simply supported shallow shell, buckling stresses can be calculated from the natural frequencies without in-plane stresses.
Harper, Catherine
2006-01-01
Susie MacMurray's Shell installation manifests in Pallant House Gallery, Chichester, like some pulsing exotica, a heavily-textured wall-paper, darkly decorative, heavily luxurious, broodingly present, with more than a hint of the uncanny or the gothic. A remarkable undertaking by an artist of significance, this work's life-span will be just one year, and then it will disappear, leaving no physical trace, but undoubtedly contributing in a much less tangible way to an already rich layering of n...
Generalized oscillator strengths for some higher valence-shell excitations of krypton atom
2007-01-01
The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ← 4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. (Phys. Rev. A 67 022703 (2003)). The differences between the experimental results and theoretical calculations show that more studies are needed.
Generalized Kolbenstvedt model for electron impact ionization of K-, L- and M-shell atoms
Haque, A.K.F.; Uddin, M.A.; Patoary, M.A.R.; Basak, A.K. [Rajshahi Univ., Dept. of Physics (Bangladesh); Talukder, M.R. [Rajshahi Univ., Dept. of Applied Physics and Electronic Engineering (Bangladesh); Saha, B.C. [Florida A and M Univ., Dept. of Physics (United States); Karim, K.R. [Illinois State Univ., Dept. of Physics, IL (United States); Malik, F.B. [Southern Illinois Univ., Dept. of Physics, IL (United States); Washington Univ., St. Louis, Dept. of Physics, MO (United States)
2007-05-15
The recently modified Kolbenstvedt (MKLV) model, developed for electron impact ionization of the K-shell atomic targets, has been extended to generalize its two parameters in terms of the electronic orbitals nl. The generalized MKLV (GKLV) with two sets of the species independent parameters for the same nl, one set for the ionization of inner orbits and another for the outermost orbit, is found profoundly successful in accounting for the electron impact ionization cross section data of the K, L and M-shell neutral atoms with atomic numbers Z = 1-92 for the incident energies up to 1000 MeV in a consistent manner. (authors)
Bonarski, Jan T; Checa, Antonio G; Rodriguez-Navarro, Alejandro; Tarkowski, Leszek; Wajda, Wojciech
2015-12-06
The microstructures of different groups of molluscs are characterized by preferential orientations of crystallites (texture), leading to a significant anisotropy of the physical properties of the shells. A complementary characteristic, usually neglected, is the distribution of the residual stresses existing within the shell wall. By means of X-ray diffraction, we study the distribution of stresses with thickness in the shell wall of the gastropod Conus marmoreus, which has a microstructure of the crossed-lamellar type. The results revealed an extraordinary texture inhomogeneity and the existence of tensional residual stresses along the shell thickness, the origins of which are unknown. Some of the observed changes in textural parameters and stresses coincide with the transitions between shell layers, although other features are of unknown origin. Our results provide insight into the microstructural regularities that govern the mesoscale construction of shells, such as that of C. marmoreus.
Boundary behaviors for general off-shell amplitudes in Yang-Mills theory
Zhang, Yun; Chen, Gang
2013-07-01
The boundary behavior of amplitudes—the amplitudes’ behavior under a large Britto-Cachazo-Feng-Witten (BCFW) momenta deformation for a pair of legs—in Yang-Mills theory is of great interest recently. In this article we analyze the boundary behavior of off-shell Yang-Mills amplitudes in Feynman gauge. The deformed legs can be either adjacent or nonadjacent. We find that a set of reduced vertices can be used to simplify the analysis and calculation of the boundary behavior of amplitudes. Boundary behavior for amplitudes with adjacent BCFW deformation is read off from the reduced vertices. Then we discover a relationship between a permutation sum with fixed color ordering of the legs and the improved boundary behavior for the off-shell amplitudes with a nonadjacent BCFW momenta deformation. Based on the boundary behavior, we generalize the BCFW recursion relation to calculate general tree-level off-shell amplitudes and analyze the relations between them.
Reissner-Nordstroem thin-shell wormholes with generalized cosmic Chaplygin gas
Sharif, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); Azam, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); University of Education, Division of Science and Technology, Lahore (Pakistan)
2013-09-15
Following Visser's approach (Visser in Phys. Rev. D 39:3182, 1989; Nucl. Phys. B 328:203, 1989; Lorentzian wormholes. AIP Press, New York, 1996) of cut and paste, we construct Reissner-Nordstroem thin-shell wormholes by taking the generalized cosmic Chaplygin gas for the exotic matter located at the wormhole throat. The Darmois-Israel conditions are used to determine the dynamical quantities of the system. The viability of the thin-shell wormholes is explored with respect to radial perturbations preserving the spherical symmetry. We find stable as well as unstable Reissner-Nordstroem thin-shell wormhole solutions depending upon the model parameters. Finally, we compare our results with both generalized and modified Chaplygin gases. (orig.)
Hui Shi
2015-01-01
Full Text Available Effects of curvature upon the vibration characteristics of doubly curved shallow shells are assessed in this paper. Boundary conditions of the shell are generally specified in terms of distributed elastic restraints along the edges. The classical homogeneous boundary supports can be easily simulated by setting the stiffnesses of restraining springs to either zero or infinite. Vibration problems of the shell are solved by a modified Fourier series method that each of the displacements is invariably expressed as a simple trigonometric series which converges uniformly and acceleratedly over the solution domain. All the unknown expansion coefficients are treated equally as a set of independent generalized coordinates and solved using the Rayleigh-Ritz technique. The current method provides a unified solution to the vibration problems of curved shallow shells involving different geometric properties and boundary conditions with no need of modifying the formulations and solution procedures. Extensive tabular and graphical results are presented to show the curvature effects on the natural frequencies of the shell with various boundary conditions.
Dynamic buckling of elastic-plastic cylindrical shells and axial stress waves
徐新生; 苏先樾; 王仁
1995-01-01
The mechanism for bifurcation of elastic-plastic buckling of the semi-infinite cylindrical shell under impacting axial loads is proposed based on the theory of stress wave. Numerical results on three kinds of end supports and step and impulse loads are given.
Enceladus's and Dione's floating ice shells supported by minimum stress isostasy
Beuthe, Mikael; Trinh, Antony
2016-01-01
Enceladus's gravity and shape have been explained in terms of a thick isostatic ice shell floating on a global ocean, in contradiction of the thin shell implied by librations. Here we propose a new isostatic model minimizing crustal deviatoric stress, and demonstrate that gravity and shape data predict a $\\rm{38\\pm4\\,km}$-thick ocean beneath a $\\rm{23\\pm4\\,km}$-thick shell agreeing with -- but independent of -- libration data. Isostatic and tidal stresses are comparable in magnitude. South polar crust is only $7\\pm4\\rm\\,km$ thick, facilitating the opening of water conduits and enhancing tidal dissipation through stress concentration. Enceladus's resonant companion, Dione, is in a similar state of minimum stress isostasy. Its gravity and shape can be explained in terms of a $\\rm{99\\pm23\\,km}$-thick isostatic shell overlying a $\\rm{65\\pm30\\,km}$-thick global ocean, thus providing the first clear evidence for a present-day ocean within Dione.
Harrison, Peter N.; Johnson, Eric R.; Starnes, James H., Jr.
1994-01-01
A mixed method of approximation based on Reissner's variational principle is developed for the linear analysis of interlaminar stresses in laminated composites, with special interest in laminates that contain terminated internal plies (dropped-ply laminates). Two models are derived, one for problems of generalized plane deformation and the other for the axisymmetric response of shells of revolution. A layerwise approach is taken in which the stress field is assumed with an explicit dependence on the thickness coordinate in each layer. The dependence of the stress field on the thickness coordinate is determined such that the three-dimensional equilibrium equations are satisfied by the approximation. The solution domain is reduced to one dimension by integration through the thickness. Continuity of tractions and displacements between layers is imposed. The governing two-point boundary value problem is composed of a system of both differential and algebraic equations (DAE's) and their associated boundary conditions. Careful evaluation of the system of DAE's was required to arrive at a form that allowed application of a one-step finite difference approximation. A two-stage Gauss implicit Runge-Kutta finite difference scheme was used for the solution because of its relatively high degree of accuracy. Patch tests of the two models revealed problems with solution accuracy for the axisymmetric model of a cylindrical shell loaded by internal pressure. Parametric studies of dropped-ply laminate characteristics and their influence on the interlaminar stresses were performed using the generalized plane deformation model. Eccentricity of the middle surface of the laminate through the ply drop-off was found to have a minimal effect on the interlaminar stresses under longitudinal compression, transverse tension, and in-plane shear. A second study found the stiffness change across the ply termination to have a much greater influence on the interlaminar stresses.
Comparative cephalopod shell strength and the role of septum morphology on stress distribution
Robert Lemanis
2016-09-01
Full Text Available The evolution of complexly folded septa in ammonoids has long been a controversial topic. Explanations of the function of these folded septa can be divided into physiological and mechanical hypotheses with the mechanical functions tending to find widespread support. The complexity of the cephalopod shell has made it difficult to directly test the mechanical properties of these structures without oversimplification of the septal morphology or extraction of a small sub-domain. However, the power of modern finite element analysis now permits direct testing of mechanical hypothesis on complete, empirical models of the shells taken from computed tomographic data. Here we compare, for the first time using empirical models, the capability of the shells of extant Nautilus pompilius, Spirula spirula, and the extinct ammonite Cadoceras sp. to withstand hydrostatic pressure and point loads. Results show hydrostatic pressure imparts highest stress on the final septum with the rest of the shell showing minimal compression. S. spirula shows the lowest stress under hydrostatic pressure while N. pompilius shows the highest stress. Cadoceras sp. shows the development of high stress along the attachment of the septal saddles with the shell wall. Stress due to point loads decreases when the point force is directed along the suture as opposed to the unsupported chamber wall. Cadoceras sp. shows the greatest decrease in stress between the point loads compared to all other models. Greater amplitude of septal flutes corresponds with greater stress due to hydrostatic pressure; however, greater amplitude decreases the stress magnitude of point loads directed along the suture. In our models, sutural complexity does not predict greater resistance to hydrostatic pressure but it does seem to increase resistance to point loads, such as would be from predators. This result permits discussion of palaeoecological reconstructions on the basis of septal morphology. We further
Comparative cephalopod shell strength and the role of septum morphology on stress distribution.
Lemanis, Robert; Zachow, Stefan; Hoffmann, René
2016-01-01
The evolution of complexly folded septa in ammonoids has long been a controversial topic. Explanations of the function of these folded septa can be divided into physiological and mechanical hypotheses with the mechanical functions tending to find widespread support. The complexity of the cephalopod shell has made it difficult to directly test the mechanical properties of these structures without oversimplification of the septal morphology or extraction of a small sub-domain. However, the power of modern finite element analysis now permits direct testing of mechanical hypothesis on complete, empirical models of the shells taken from computed tomographic data. Here we compare, for the first time using empirical models, the capability of the shells of extant Nautilus pompilius, Spirula spirula, and the extinct ammonite Cadoceras sp. to withstand hydrostatic pressure and point loads. Results show hydrostatic pressure imparts highest stress on the final septum with the rest of the shell showing minimal compression. S. spirula shows the lowest stress under hydrostatic pressure while N. pompilius shows the highest stress. Cadoceras sp. shows the development of high stress along the attachment of the septal saddles with the shell wall. Stress due to point loads decreases when the point force is directed along the suture as opposed to the unsupported chamber wall. Cadoceras sp. shows the greatest decrease in stress between the point loads compared to all other models. Greater amplitude of septal flutes corresponds with greater stress due to hydrostatic pressure; however, greater amplitude decreases the stress magnitude of point loads directed along the suture. In our models, sutural complexity does not predict greater resistance to hydrostatic pressure but it does seem to increase resistance to point loads, such as would be from predators. This result permits discussion of palaeoecological reconstructions on the basis of septal morphology. We further suggest that the ratio
Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell
Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.
1987-01-01
During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.
Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell
Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.
1987-01-01
During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.
Comparison of local stress values obtained by two measuring methods on blast furnace shell
P. Bigoš
2015-01-01
Full Text Available This paper describes measuring of time behaviour specified for local stress increments on the blast furnace shell that were performed using strain gauge sensors. These results are compared with values obtained by means of the second specific measuring method. There is also presented in this paper a commentary and discussion concerning the measured time behaviour obtained from the both measuring methods. This article presents results from another of experimental analysis series concerning the blast furnace shell in one concrete metallurgical plant.
Stress concentration in a T-type shell joint
Kuznetsov, V. V.; Leviakov, S. V.
A T-joint of thin-walled pipes is considered which is loaded by internal pressure. The stress-strain state of the T-joint is investigated by the finite element method using a geometrically nonlinear formulation. It is shown that calculations based on the linear theory lead to significant errors for pressure levels typical of operating conditions.
General formalism for the stability of thin-shell wormholes in 2 + 1 dimensions
Bejarano, Cecilia [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina); Eiroa, Ernesto F. [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina); Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Simeone, Claudio [Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); IFIBA-CONICET, Buenos Aires (Argentina)
2014-08-15
In this article we theoretically construct circular thin-shell wormholes in a 2 + 1-dimensional spacetime. The construction is symmetric with respect to the throat. We present a general formalism for the study of the mechanical stability under perturbations preserving the circular symmetry of the configurations, adopting a linearized equation of state for the exotic matter at the throat. We apply the formalism to several examples. (orig.)
"Shell Shock": An Entity that Predated Combat-related Posttraumatic Stress Disorder
Ragul Ganesh
2015-01-01
Full Text Available In the last century, numerous soldiers had been diagnosed with various post combat disorders. The terminology that has been utilized to describe such patients include combat fatigue, combat stress reaction, soldier′s heart, effort syndrome, non-ulcer dyspepsia, effects of agent orange and gulf war syndrome. The initial description of such post combat disorder was probably ′shell shock′ which came into vogue during the World War I. The soldiers, undergoing unyielding artillery bombardment, in the trenches suffered persistent symptoms of headache, behavioural changes and memory impairment, and was designated at the time as ′shell shock′. Myers and Mott, independently studied numerous soldiers to elucidate the features and aetiology of the entity. An attempt was made to restrict the usage of the term, but the psychological distress of the soldiers persisted to be addressed in some manner or the other, culminating in the genesis of Post Traumatic Stress Disorder.
Reynolds stress and heat flux in spherical shell convection
Käpylä, P. J.; Mantere, M. J.; Guerrero, G.; Brandenburg, A.; Chatterjee, P.
2011-07-01
Context. Turbulent fluxes of angular momentum and enthalpy or heat due to rotationally affected convection play a key role in determining differential rotation of stars. Their dependence on latitude and depth has been determined in the past from convection simulations in Cartesian or spherical simulations. Here we perform a systematic comparison between the two geometries as a function of the rotation rate. Aims: Here we want to extend the earlier studies by using spherical wedges to obtain turbulent angular momentum and heat transport as functions of the rotation rate from stratified convection. We compare results from spherical and Cartesian models in the same parameter regime in order to study whether restricted geometry introduces artefacts into the results. In particular, we want to clarify whether the sharp equatorial profile of the horizontal Reynolds stress found in earlier Cartesian models is also reproduced in spherical geometry. Methods: We employ direct numerical simulations of turbulent convection in spherical and Cartesian geometries. In order to alleviate the computational cost in the spherical runs, and to reach as high spatial resolution as possible, we model only parts of the latitude and longitude. The rotational influence, measured by the Coriolis number or inverse Rossby number, is varied from zero to roughly seven, which is the regime that is likely to be realised in the solar convection zone. Cartesian simulations are performed in overlapping parameter regimes. Results: For slow rotation we find that the radial and latitudinal turbulent angular momentum fluxes are directed inward and equatorward, respectively. In the rapid rotation regime the radial flux changes sign in accordance with earlier numerical results, but in contradiction with theory. The latitudinal flux remains mostly equatorward and develops a maximum close to the equator. In Cartesian simulations this peak can be explained by the strong "banana cells". Their effect in the
FINITE ELEMENT FOR STRESS-STRAIN STATE MODELING OF TWO-LAYERED AXIALLY SYMMETRIC SHELLS
K. S. Kurochka
2015-07-01
Full Text Available Subject of Research. Computation of composite material designs requires application of numerical methods. The finiteelement method usage is connected with surface approximation problems. Application of volumetric and laminar elements leads to systems with large sizes and a great amount of computation. The objective of this paper is to present an equivalent two-layer mathematical model for evaluation of displacements and stresses of cross-ply laminated cone shells subjected to uniformly distributed load. An axially symmetric element for shell problems is described. Method. Axially symmetric finite element is proposed to be applied in calculations with use of correlation for the inner work of each layer separately. It gives the possibility to take into account geometric and physical nonlinearities and non-uniformity in the layers of the shell. Discrete mathematical model is created on the base of the finite-element method with the use of possible motions principle and Kirchhoff–Love assumptions. Hermite element is chosen as a finite one. Cone shell deflection is considered as the quantity sought for. Main Results. One-layered and two-layered cone shells have been considered for proposed mathematical model verification with known analytical and numerical analytical solutions, respectively. The axial displacements of the two-layered cone are measured with an error not exceeding 5.4 % for the number of finite elements equal to 30. The proposed mathematical model requires fewer nodes to define the finite element meshing of the system and much less computation time. Thereby time for finding solution decreases considerably. Practical Relevance. Proposed model is applicable for computation of multilayered designs under axially symmetric loads: composite high-pressure bottles, cylinder shaped fiberglass pipes, reservoirs for explosives and flammable materials, oil and gas storage tanks.
Thin-shell wormholes with a generalized Chaplygin gas in Einstein-Born-Infeld theory
Eiroa, Ernesto F. [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina); Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Figueroa Aguirre, Griselda [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina)
2012-11-15
We construct spherically symmetric thin-shell wormholes supported by a generalized Chaplygin gas in Born-Infeld electrodynamics coupled to Einstein gravity, and we analyze their stability under radial perturbations. For different values of the Born-Infeld parameter and the charge, we compare the results with those obtained in a previous work for Maxwell electrodynamics. The stability region in the parameter space reduces and then disappears as the value of the Born-Infeld parameter is modified in the sense of a larger departure from Maxwell theory. (orig.)
Liu, Yu-Lei; Zhao, Yang; Dai, Zhong-Min; Chen, Han-Min; Yang, Wei-Jun
2009-06-19
Artemia has attracted much attention for its ability to produce encysted embryos wrapped in a protective shell when subject to extremely harsh environmental conditions. However, what the cyst shell is synthesized from and how the formative process is performed remains, as yet, largely unknown. Over 20 oviparous specifically expressed genes were identified through screening the subtracted cDNA library enriched between oviparous and ovoviviparous Artemia ovisacs. Among them, a shell gland-specifically expressed gene (SGEG) has been found to be involved in the cyst shell formation. Lacking SGEG protein (by RNA interference) caused the cyst shell to become translucent and the chorion layer of the shell to become less compact and pultaceous and to show a marked decrease of iron composition within the shell. The RNA interference induced defective diapause cysts with a totally compromised resistibility to UV irradiation, extremely large temperature differences, osmotic pressure, dryness, and organic solvent stresses. In contrast, the natural cyst would provide adequate protection from all such factors. SGEG contains a 345-bp open reading frame, and its consequentially translated peptide consists of a 33-amino acid residue putative signal peptide and an 81-amino acid residue mature peptide. The results of Northern blotting and in situ hybridization indicate that the gene is specifically expressed in the cells of shell glands during the period of diapause cyst formation of oviparous Artemia. This investigation adds strong insight into the mechanism of cyst shell formation of Artemia and may be applicable to other areas of research in extremophile biology.
STABILITY AND NATURAL VIBRATIONS OF INHOMOGENEOUS SHELLS TAKING INTO ACCOUNT THE STRESS STATE
Bazhenov V.A.
2015-12-01
Full Text Available The work is devoted to the problem of developing a unified methodology based on the efficient numerical analysis of problems of stability and natural vibrations of a wide class of inhomogeneous shells, thin and medium thickness. In problems of its natural vibrations takes into account the presence of a pre-stressed state of the structure from the action of static loads, which significantly affect the spectrum of natural vibrations and allows determining the bifurcation point and the value of the critical force of buckling by dynamic criteria.
Psychological stress and multimorbidity in general practice
Prior, Anders
2017-01-01
Background The number of persons living with multiple chronic conditions (multimorbidity) is rising owing to prolonged life and improved medical treatment. In this context, attention to mental health is essential; psychiatric illness has been associated with impaired quality of chronic care...... and poor prognosis of physical diseases, including increased mortality. However, little is known on the physical consequences of sub‐threshold psychological stress, which is more common than psychiatric disorders in the background population and is highly prevalent in persons with multimorbidity...... embrace poor mental health below the threshold for psychiatric disorders. More research on interventions targeting stress and multimorbidity are warranted....
Transcriptome response to copper heavy metal stress in hard-shelled mussel (Mytilus coruscus).
Xu, Meiying; Jiang, Lihua; Shen, Kang-Ning; Wu, Changwen; He, Guangyuan; Hsiao, Chung-Der
2016-03-01
The hard-shelled mussel (Mytilus coruscus) has considerably one of the most economically important marine shellfish worldwide and considered as a good invertebrate model for ecotoxicity study for a long time. In the present study, we used Illumina sequencing technology (HiSeq2000) to sequence, assemble and annotate the transcriptome of the hard-shelled mussel which challenged with copper pollution. A total of 21,723,913 paired-end clean reads (NCBI SRA database SRX1411195) were generated from HiSeq2000 sequencer and 96,403 contigs (with N50 = 1118 bp) were obtained after de novo assembling with Trinity software. Digital gene expression analysis reveals 1156 unigenes are upregulated and 1681 unigenes are downregulated when challenged with copper. By KEGG pathway enrichment analysis, we found that unigenes in four KEGG pathways (aminoacyl-tRNA biosynthesis, apoptosis, DNA replication and mismatch repair) show significant differential expressed between control and copper treated groups. We hope that the gill transcriptome in copper treated hard-shelled mussel can give useful information to understand how mussel handles with heavy metal stress at molecular level.
Transcriptome response to copper heavy metal stress in hard-shelled mussel (Mytilus coruscus
Meiying Xu
2016-03-01
Full Text Available The hard-shelled mussel (Mytilus coruscus has considerably one of the most economically important marine shellfish worldwide and considered as a good invertebrate model for ecotoxicity study for a long time. In the present study, we used Illumina sequencing technology (HiSeq2000 to sequence, assemble and annotate the transcriptome of the hard-shelled mussel which challenged with copper pollution. A total of 21,723,913 paired-end clean reads (NCBI SRA database SRX1411195 were generated from HiSeq2000 sequencer and 96,403 contigs (with N50 = 1118 bp were obtained after de novo assembling with Trinity software. Digital gene expression analysis reveals 1156 unigenes are upregulated and 1681 unigenes are downregulated when challenged with copper. By KEGG pathway enrichment analysis, we found that unigenes in four KEGG pathways (aminoacyl-tRNA biosynthesis, apoptosis, DNA replication and mismatch repair show significant differential expressed between control and copper treated groups. We hope that the gill transcriptome in copper treated hard-shelled mussel can give useful information to understand how mussel handles with heavy metal stress at molecular level.
Racism-Related Stress, General Life Stress, and Psychological Functioning among Black American Women
Pieterse, Alex L.; Carter, Robert T.; Ray, Kilynda V.
2013-01-01
The relationship between general life stress, perceived racism, and psychological functioning was explored in a sample of 118 Black American women. Findings indicate that racism-related stress was not a significant predictor of psychological functioning when controlling for general life stress. Perceived racism was positively associated with…
Xingzhe Wang; Xiaojing Zheng
2009-01-01
Based on the generalized variational principle of magneto-thermo-elasticity of the ferromagnetic elastic medium, a nonlinear coupling theoretical modeling for a ferromagnetic thin shell is developed. All governing equations and boundary conditions for the ferromagnetic shell are obtained from the variational manipulations on the magnetic scalar potential, temperature and the elastic displacement related to the total energy functional. The multi-field couplings and geometrical nonlinearity of the ferromagnetic thin shell are taken into account in the modeling. The general modeling can be further deduced to existing models of the magneto-elasticity and the thermo-elasticity of a ferromagnetic shell and magneto-thermo-elasticity of a ferromagnetic plate, which axe coincident with the ones in literature.
Born-Infeld Thin-shell Wormholes Supported by Generalized Cosmic Chaplygin Gas
Azam, M
2016-01-01
This paper investigates thin-shell wormholes in Born-Infeld theory supported by generalized Cosmic Chaplygin gas (GCCG). We study their stability via radial perturbations for distinct values of charge and Born-Infeld parameter. The comparison of wormhole solutions corresponding to generalized Chaplygin gas, modified Chaplygin gas with GCCG quation of state is established. It is found that similar type of wormhole solutions exists for small value of charge and Born-Infeld parameter for all type of equation of state, while some extra stable as well as unstable solution are found corresponding to large value of charge and Born-Infeld parameter. Thus, it is concluded that GCCG and large value of charge may responsible for such extra solutions.
Triangular and Fibonacci number patterns driven by stress on core/shell microstructures.
Li, Chaorong; Zhang, Xiaona; Cao, Zexian
2005-08-05
Fibonacci number patterns and triangular patterns with intrinsic defects occur frequently on nonplanar surfaces in nature, particularly in plants. By controlling the geometry and the stress upon cooling, these patterns can be reproduced on the surface of microstructures about 10 micrometers in diameter. Spherules of the Ag core/SiOx shell structure, possessing markedly uniform size and shape, self-assembled into the Fibonacci number patterns (5 by 8 and 13 by 21) or the triangular pattern, depending on the geometry of the primary supporting surface. Under proper geometrical constraints, the patterns developed through self-assembly in order to minimize the total strain energy. This demonstrates that highly ordered microstructures can be prepared simultaneously across large areas by stress engineering.
Krishna, S., E-mail: skrishna.bhu@gmail.com [Physics Department, Centre of Advanced Studies, Banaras Hindu University (BHU), Varanasi-221 005 (India); Shukla, A., E-mail: ashukla038@gmail.com [Physics Department, Centre of Advanced Studies, Banaras Hindu University (BHU), Varanasi-221 005 (India); Malik, R.P., E-mail: rpmalik1995@gmail.com [Physics Department, Centre of Advanced Studies, Banaras Hindu University (BHU), Varanasi-221 005 (India); DST-CIMS, Faculty of Science, BHU-Varanasi-221 005 (India)
2014-12-15
Using the supersymmetric (SUSY) invariant restrictions on the (anti-)chiral supervariables, we derive the off-shell nilpotent symmetries of the general one (0+1)-dimensional N=2 SUSY quantum mechanical (QM) model which is considered on a (1, 2)-dimensional supermanifold (parametrized by a bosonic variable t and a pair of Grassmannian variables θ and θ-bar with θ{sup 2}=(θ-bar){sup 2}=0,θ(θ-bar)+(θ-bar)θ=0). We provide the geometrical meanings to the two SUSY transformations of our present theory which are valid for any arbitrary type of superpotential. We express the conserved charges and Lagrangian of the theory in terms of the supervariables (that are obtained after the application of SUSY invariant restrictions) and provide the geometrical interpretation for the nilpotency property and SUSY invariance of the Lagrangian for the general N=2 SUSY quantum theory. We also comment on the mathematical interpretation of the above symmetry transformations. - Highlights: • A novel method has been proposed for the derivation of N=2 SUSY transformations. • General N=2 SUSY quantum mechanical (QM) model with a general superpotential, is considered. • The above SUSY QM model is generalized onto a (1, 2)-dimensional supermanifold. • SUSY invariant restrictions are imposed on the (anti-)chiral supervariables. • Geometrical meaning of the nilpotency property is provided.
Mohammad, S. Noor
2010-09-01
Semiconductor nanotubes, including carbon nanotubes, have vast potential for new technology development. The fundamental physics and growth kinetics of these nanotubes are still obscured. Various models developed to elucidate the growth suffer from limited applicability. An in-depth investigation of the fundamentals of nanotube growth has, therefore, been carried out. For this investigation, various features of nanotube growth, and the role of the foreign element catalytic agent (FECA) in this growth, have been considered. Observed growth anomalies have been analyzed. Based on this analysis, a new shell model and a general hypothesis have been proposed for the growth. The essential element of the shell model is the seed generated from segregation during growth. The seed structure has been defined, and the formation of droplet from this seed has been described. A modified definition of the droplet exhibiting adhesive properties has also been presented. Various characteristics of the droplet, required for alignment and organization of atoms into tubular forms, have been discussed. Employing the shell model, plausible scenarios for the formation of carbon nanotubes, and the variation in the characteristics of these carbon nanotubes have been articulated. The experimental evidences, for example, for the formation of shell around a core, dipole characteristics of the seed, and the existence of nanopores in the seed, have been presented. They appear to justify the validity of the proposed model. The diversities of nanotube characteristics, fundamentals underlying the creation of bamboo-shaped carbon nanotubes, and the impurity generation on the surface of carbon nanotubes have been elucidated. The catalytic action of FECA on growth has been quantified. The applicability of the proposed model to the nanotube growth by a variety of mechanisms has been elaborated. These mechanisms include the vapor-liquid-solid mechanism, the oxide-assisted growth mechanism, the self
朱卫平; 黄黔
2002-01-01
This is one of the applications of Part (Ⅰ), in which the angular stiffness, and the corresponding stress distributions of U- shaped bellows were discussed.The bellows was divided into protruding sections, concave sections and ring plates for the calculation that the general solution (Ⅰ) with its reduced form to ring plates were used respectively, but the continuity of the surface stresses and the meridian rotations at each joint of the sections were entirely satisfied.The present results were compared with those of the slender ring shell solution proposed earlier by the authors, the standards of the Expansion Joint Manufacturers Association (EJMA), the experiment and the finite element method.It is shown that the governing equation and the general solution (Ⅰ) are very effective.
On Wave Dark Matter, Shells in Elliptical Galaxies, and the Axioms of General Relativity
Bray, Hubert L
2012-01-01
This paper is a sequel to the author's paper entitled "On Dark Matter, Spiral Galaxies, and the Axioms of General Relativity" [arXiv:1004.4016] which explored a geometrically natural axiomatic definition for dark matter modeled by a scalar field satisfying the Einstein-Klein-Gordon wave equations which, after much calculation, was shown to be consistent with the observed spiral and barred spiral patterns in disk galaxies. We give an update on where things stand on this "wave dark matter" model of dark matter (aka scalar field dark matter and boson stars), an interesting alternative to the WIMP model of dark matter, and discuss how it has the potential to help explain the long-observed interleaved shell patterns, also known as ripples, in the images of elliptical galaxies.
P. Bigoš
2012-01-01
Full Text Available This paper deals with installation of strain gauges on the external surface of the blast furnace shell in two rows, whereas there will be defi ned 8 measuring points in every row. The fi nal result is evaluation of data obtained during up to 45 days of the operation. In this papers are commentary and discussions to measured time behaviours. The main purpose of this measuring was investigation of impact of salamander on blast furnace shell expansion after its lay off , cooling and next starting of operation.
Generalized tetany: an unusual complication during dobutamine stress echocardiography.
Abbas, Amr E; Loftis, Rochelle; Lester, Steven J; Crawford, Michael B; Appleton, Christopher P
2002-11-01
Dobutamine stress echocardiography is a frequently used noninvasive method for the evaluation of inducible myocardial ischemia, myocardial viability, and preoperative cardiac risk. Although its clinical safety has been validated, side effects and complications especially with the coadministration of atropine can occur. We report a case of generalized tetany in a 49-year-old woman undergoing dobutamine stress echocardiography.
Stress-driven buckling patterns in spheroidal core/shell structures.
Yin, Jie; Cao, Zexian; Li, Chaorong; Sheinman, Izhak; Chen, Xi
2008-12-09
Many natural fruits and vegetables adopt an approximately spheroidal shape and are characterized by their distinct undulating topologies. We demonstrate that various global pattern features can be reproduced by anisotropic stress-driven buckles on spheroidal core/shell systems, which implies that the relevant mechanical forces might provide a template underpinning the topological conformation in some fruits and plants. Three dimensionless parameters, the ratio of effective size/thickness, the ratio of equatorial/polar radii, and the ratio of core/shell moduli, primarily govern the initiation and formation of the patterns. A distinct morphological feature occurs only when these parameters fall within certain ranges: In a prolate spheroid, reticular buckles take over longitudinal ridged patterns when one or more parameters become large. Our results demonstrate that some universal features of fruit/vegetable patterns (e.g., those observed in Korean melons, silk gourds, ribbed pumpkins, striped cavern tomatoes, and cantaloupes, etc.) may be related to the spontaneous buckling from mechanical perspectives, although the more complex biological or biochemical processes are involved at deep levels.
Stress state of the box shell under the indentation of two inclusions
Vladimir А. Grishin
2015-03-01
Full Text Available Thin-walled structures are widely used in various fields in modern technologies of mechanical engineering, construction, aviation industry, shipbuilding, rocket engineering, oil, gas and other industries. Variety of forms of such structures, various loading conditions and pinning, presence of defects and inhomogeneities lead to wide range of different formulations of the problems of research on strength characteristics of such structures and methods used for this purpose. The characteristic feature of this type of problems is the difficulty of their analytical or numerical solving. Assessment of convergence of numerical method solution requires the ability to compare the numerical results with analytical solution results of the corresponding problem.The research is devoted to solving the problem of stress state of box-shell with rectangular profile and infinite length under the indentation of two symmetrically arranged thin rigid inclusions. The problem is reduced to a system of integral equations. The solution is sought in the space of functions that have nonintegrable singularities using the apparatus of the regularization of divergent integrals. Obtained infinite system of linear algebraic equations is solved by the method of reduction. There are obtained the numerical values of the upsettings of inclusions depending on inclusions length and ratios of geometric dimensions of the cross-section of the shell.
Gillet, Jean-Numa; Meunier, Michel
2005-05-12
Nanocharacterization is essential for nanoengineering of new types of core-shell (c-s) nanoparticles, which can be used to design new devices for photonics, electronics, catalysis, medicine, etc. X-ray photoelectron spectroscopy (XPS) has been widely used to study the elemental composition of the c-s nanoparticles. However, the physical and chemical properties of a c-s nanoparticle dramatically depend on the sizes of its core and shell. We therefore propose a general equation for the XPS intensity of a c-s nanoparticle, which is based on an analytical model. With this equation, XPS can now also be used for nanocharacterization of the core and shell sizes of the c-s nanoparticles (with a diameter smaller than or equal to the XPS probing depth of approximately 10 nm). To validate the new equation with experimental XPS data, we first determine the average shell thickness of a group of c-s nanoparticles by comparing the XPS intensity of reference bare cores to that of the c-s nanoparticles. Then we study the growth kinetics of the cores and shells of another group of c-s nanoparticles where the shells are obtained by oxidation.
Delale, F.; Erdogan, F.
1977-01-01
The problem of a cylindrical shell containing a circumferential through crack is considered by taking into account the effect of transverse shear deformations. The formulation is given for a specially orthotropic material within the confines of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions regarding moment and stress resultants on the crack surface. Consequently, aside from multiplicative constants representing the stress intensity factors, the membrane and bending components of the asymptotic stress fields near the crack tip are found to be identical. The stress intensity factors are calculated separately for a cylinder under a uniform membrane load, and that under a uniform bending moment. Sample results showing the nature of the out-of-plane crack surface displacement and the effect of the Poisson's ratio are presented.
Grassmannian Integral for General Gauge Invariant Off-shell Amplitudes in N=4 SYM
Bork, L V
2016-01-01
In this paper we consider tree-level gauge invariant off-shell amplitudes (Wilson line form factors) in $\\mathcal{N}=4$ SYM with arbitrary number of off-shell gluons or equivalently Wilson line operator insertions. We make a conjecture for the Grassmannian integral representation for such objects and verify our conjecture on several examples. It is remarkable that in our formulation one can consider situation when on-shell particles are not present at all, i.e. we have Grassmannian integral representation for purely off-shell object. In addition we show that off-shell amplitude with arbitrary number of off-shell gluons could be also obtained using quantum inverse scattering method for auxiliary $\\mathfrak{gl}(4|4)$ super spin chain.
Kroon Van Diest, Ashley M; Tartakovsky, Margarita; Stachon, Caitlin; Pettit, Jeremy W; Perez, Marisol
2014-06-01
The purpose of the current study was to expand upon the literature examining the relationship between acculturative stress and eating disorder symptoms among different ethnic groups. Specifically, acculturative stress was explored as a moderator of the relationship between body dissatisfaction and eating disorder symptoms among ethnic minority women. Additionally, the distinction between acculturative stress and general life stress in predicting eating disorder symptoms was assessed. Participants consisted of 247 undergraduate women, all of whom were members of an ethnic minority group including African Americans, Asian Americans, and Latinas. Acculturative stress was found to moderate the relationship between body dissatisfaction and eating disorder symptoms, but only among African American women. Acculturative stress was also found to significantly predict bulimic symptoms above and beyond general life stress among African American, Asian American, and Latina women.
Caving thickness effects of surrounding rocks macro stress shell evolving characteristics
Guang-xiang Xie; Ke Yang [Anhui University of Science and Technology, Huainan (China). Key Laboratory of Coal Mine Safety and Efficiently Caving of Ministry of Education
2009-06-15
In order to explore the influence of different caving thicknesses on the macro stress shell, (MSS) distribution and evolving characteristics of surrounding rocks in unsymmetrical disposal and fully mechanized top-coal caving (FMTC), based on unsymmetrical disposal characteristics, the analyses of numerical simulation, material simulation and in-situ observation were synthetically applied according to the geological and technical conditions of the 1151(3) working face in Xieqiao Mine. The results show that the stress peak value of the MSS-base and the ratio of MSS-body height to caving thickness are nonlinear and inversely proportional to the caving thickness. The MSS-base width, the MSS-body height, the MSS-base distance to working face wall and the rise distance of MSS-base beside coal pillar are nonlinear and directly proportional to the caving thickness. The characteristics of MSS distribution and its evolving rules of surrounding rocks and the integrated caving thickness effects are obtained. The investigations will provide theoretic references to the surrounding rocks stability control of the working face and roadway, roadway layout, gas extraction and exploitation, and efficiency of caving, etc. 13 refs., 5 figs., 5 tabs.
Principle Generalized Net Model of a Human Stress Reaction
Anthony Shannon
2008-04-01
Full Text Available The present study was aimed at investigating the mechanism of a human stress reaction by means of Generalized Nets (GNs. A principle GN-model of the main structures, organs and systems of the human body taking part in the acute and chronic reaction of the organism to a stress stimulus is generated. A possible application of the GN-model of the human stress reaction for testing the effect of known or newly synthesized pharmacological products as well as of food supplements is discussed.
Zhang, Lingyu; Wang, Tingting; Yang, Lei; Liu, Cong; Wang, Chungang; Liu, Haiyan; Wang, Y Andrew; Su, Zhongmin
2012-09-24
Hollow mesoporous SiO(2) (mSiO(2)) nanostructures with movable nanoparticles (NPs) as cores, so-called yolk-shell nanocapsules (NCs), have attracted great research interest. However, a highly efficient, simple and general way to produce yolk-mSiO(2) shell NCs with tunable functional cores and shell compositions is still a great challenge. A facile, general and reproducible strategy has been developed for fabricating discrete, monodisperse and highly uniform yolk-shell NCs under mild conditions, composed of mSiO(2) shells and diverse functional NP cores with different compositions and shapes. These NPs can be Fe(3)O(4) NPs, gold nanorods (GNRs), and rare-earth upconversion NRs, endowing the yolk-mSiO(2) shell NCs with magnetic, plasmonic, and upconversion fluorescent properties. In addition, multifunctional yolk-shell NCs with tunable interior hollow spaces and mSiO(2) shell thickness can be precisely controlled. More importantly, fluorescent-magnetic-biotargeting multifunctional polyethyleneimine (PEI)-modified fluorescent Fe(3)O(4)@mSiO(2) yolk-shell nanobioprobes as an example for simultaneous targeted fluorescence imaging and magnetically guided drug delivery to liver cancer cells is also demonstrated. This synthetic approach can be easily extended to the fabrication of multifunctional yolk@mSiO(2) shell nanostructures that encapsulate various functional movable NP cores, which construct a potential platform for the simultaneous targeted delivery of drug/gene/DNA/siRNA and bio-imaging.
Recent developments in anisotropic heterogeneous shell theory
Grigorenko, Alexander Ya; Grigorenko, Yaroslav M; Vlaikov, Georgii G
2016-01-01
This volume focuses on the relevant general theory and presents some first applications, namely those based on classical shell theory. After a brief introduction, during which the history and state-of-the-art are discussed, the first chapter presents the mechanics of anisotropic heterogeneous shells, covering all relevant assumptions and the basic relations of 3D elasticity, classical and refined shell models. The second chapter examines the numerical techniques that are used, namely discrete orthogonalization, spline-collocation and Fourier series, while the third highlights applications based on classical theory, in particular, the stress-strain state of shallow shells, non-circular shells, shells of revolution, and free vibrations of conical shells. The book concludes with a summary and an outlook bridging the gap to the second volume.
Kuai, Long; Geng, Baoyou; Wang, Shaozhen; Sang, Yan
2012-07-23
In this work, we utilize the galvanic displacement synthesis and make it a general and efficient method for the preparation of Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells, which consist of multilayer nanoparticles. The method is generally applicable to the preparation of Au-Au, Au-Pd, and Au-Pt core-shell nanostructures with typical porous shells. Moreover, the Au-Au isomeric core-shell nanostructure is reported for the first time. The lower oxidation states of Au(I), Pd(II), and Pt(II) are supposed to contribute to the formation of porous core-shell nanostructures instead of yolk-shell nanostructures. The electrocatalytic ethanol oxidation and oxygen reduction reaction (ORR) performance of porous Au-Pd core-shell nanostructures are assessed as a typical example for the investigation of the advantages of the obtained core-shell nanostructures. As expected, the Au-Pd core-shell nanostructure indeed exhibits a significantly reduced overpotential (the peak potential is shifted in the positive direction by 44 mV and 32 mV), a much improved CO tolerance (I(f)/I(b) is 3.6 and 1.63 times higher), and an enhanced catalytic stability in comparison with Pd nanoparticles and Pt/C catalysts. Thus, porous Au-M (M = Au, Pd, and Pt) core-shell nanostructures may provide many opportunities in the fields of organic catalysis, direct alcohol fuel cells, surface-enhanced Raman scattering, and so forth.
Transgenerational stress memory is not a general response in Arabidopsis.
Ales Pecinka
Full Text Available Adverse conditions can trigger DNA damage as well as DNA repair responses in plants. A variety of stress factors are known to stimulate homologous recombination, the most accurate repair pathway, by increasing the concentration of necessary enzymatic components and the frequency of events. This effect has been reported to last into subsequent generations not exposed to the stress. To establish a basis for a genetic analysis of this transgenerational stress memory, a broad range of treatments was tested for quantitative effects on homologous recombination in the progeny. Several Arabidopsis lines, transgenic for well-established recombination traps, were exposed to 10 different physical and chemical stress treatments, and scored for the number of somatic homologous recombination (SHR events in the treated generation as well as in the two subsequent generations that were not treated. These numbers were related to the expression level of genes involved in homologous recombination and repair. SHR was enhanced after the majority of treatments, confirming previous data and adding new effective stress types, especially interference with chromatin. Compounds that directly modify DNA stimulated SHR to values exceeding previously described induction rates, concomitant with an induction of genes involved in SHR. In spite of the significant stimulation in the stressed generations, the two subsequent non-treated generations only showed a low and stochastic increase in SHR that did not correlate with the degree of stimulation in the parental plants. Transcripts coding for SHR enzymes generally returned to pre-treatment levels in the progeny. Thus, transgenerational effects on SHR frequency are not a general response to abiotic stress in Arabidopsis and may require special conditions.
Itagaki, N.; Matsuno, H.; Suhara, T.
2016-09-01
The antisymmetrized quasi-cluster model (AQCM) is a method to describe transitions from the α cluster wave functions to jj-coupling shell model wave functions. In this model, the cluster-shell transition is characterized by only two parameters: R representing the distance between α clusters and Λ describing the breaking of α clusters. The contribution of the spin-orbit interaction, very important in the jj-coupling shell model, can be taken into account starting with the α cluster model wave function. In this article we show the generality of AQCM by extending the application to heavier regions: various 4N nuclei from 4He to 100Sn. The characteristic magic numbers of the jj-coupling shell model, 28 and 50, are described starting with the α cluster model. The competition of two different configurations is discussed in 20Ne (16O + one quasi-cluster and 12C + two quasi-clusters) and 28Si (pentagon shape of five quasi-clusters and 12C + 16O). Also, we compare the energy curves for the α + 40Ca cluster configuration calculated with and without the α breaking effect in 44Ti.
Generalized non-linear strength theory and transformed stress space
YAO Yangping; LU Dechun; ZHOU Annan; ZOU Bo
2004-01-01
Based on the test data of frictional materials and previous research achievements in this field, a generalized non-linear strength theory (GNST) is proposed. It describes non-linear strength properties on the π-plane and the meridian plane using a unified formula, and it includes almost all the present non-linear strength theories, which can be used in just one material. The shape of failure function of the GNST is a smooth curve between the SMP criterion and the Mises criterion on the π-plane, and an exponential curve on the meridian plane. Through the transformed stress space based on the GNST, the combination of the GNST and various constitutive models using p and q as stress parameters can be realized simply and rationally in three-dimensional stress state.
Charles R. Steele
1995-01-01
Full Text Available Shell structures are indispensable in virtually every industry. However, in the design, analysis, fabrication, and maintenance of such structures, there are many pitfalls leading to various forms of disaster. The experience gained by engineers over some 200 years of disasters and brushes with disaster is expressed in the extensive archival literature, national codes, and procedural documentation found in larger companies. However, the advantage of the richness in the behavior of shells is that the way is always open for innovation. In this survey, we present a broad overview of the dynamic response of shell structures. The intention is to provide an understanding of the basic themes behind the detailed codes and stimulate, not restrict, positive innovation. Such understanding is also crucial for the correct computation of shell structures by any computer code. The physics dictates that the thin shell structure offers a challenge for analysis and computation. Shell response can be generally categorized by states of extension, inextensional bending, edge bending, and edge transverse shear. Simple estimates for the magnitudes of stress, deformation, and resonance in the extensional and inextensional states are provided by ring response. Several shell examples demonstrate the different states and combinations. For excitation frequency above the extensional resonance, such as in impact and acoustic excitation, a fine mesh is needed over the entire shell surface. For this range, modal and implicit methods are of limited value. The example of a sphere impacting a rigid surface shows that plastic unloading occurs continuously. Thus, there are no short cuts; the complete material behavior must be included.
Roemelt, Michael; Neese, Frank
2013-04-11
A spin-adapted configuration interaction with singles method that is based on a restricted open-shell reference function (ROCIS) with general total spin S is presented. All excited configuration state functions (CSFs) are generated with the aid of a spin-free second quantization formalism that only leads to CSFs within the first order interacting space. By virtue of the CSF construction, the formalism involves higher than singly excited determinants but not higher than singly excited configurations. Matrix elements between CSFs are evaluated on the basis of commutator relationships using a symbolic algebra program. The final equations were, however, hand-coded in order to maximize performance. The method can be applied to fairly large systems with more than 100 atoms in reasonable wall-clock times and also parallelizes well. Test calculations demonstrate that the approach is far superior to UHF-based configuration interaction with single excitations but necessarily falls somewhat short of quantitative accuracy due to the lack of dynamic correlation contributions. In order to implicitly account for dynamic correlation in a crude way, the program optionally allows for the use of Kohn-Sham orbitals in combination with a modest downscaling of two-electron integrals (DFT/ROCIS). All two-electron integrals of Kohn-Sham orbitals that appear in the Hamiltonian matrix are reduced by a total of three scaling parameters that are suitable for a wide range of molecules. Test calculations on open-shell organic radicals as well as transition metal complexes demonstrate the wide applicability of the method and its ability to calculate the electronic spectra of large molecular systems.
General pairing interactions and pair truncation approximations for fermions in a single-j shell
Zhao, Y M; Ginocchio, J N; Yoshinaga, N
2003-01-01
We investigate Hamiltonians with attractive interactions between pairs of fermions coupled to angular momentum J. We show that pairs with spin J are reasonable building blocks for the low-lying states. For systems with only a J = Jmax pairing interaction, eigenvalues are found to be approximately integers for a large array of states, in particular for those with total angular momenta I le 2j. For I=0 eigenstates of four fermions in a single-j shell we show that there is only one non-zero eigenvalue. We address these observations using the nucleon pair approximation of the shell model and relate our results with a number of currently interesting problems.
On General Off-Shell Representations of World Line (1D Supersymmetry
Charles F. Doran
2014-02-01
Full Text Available Every finite-dimensional unitary representation of the N-extended world line supersymmetry without central charges may be obtained by a sequence of differential transformations from a direct sum of minimal Adinkras, simple supermultiplets that are identifiable with representations of the Clifford algebra. The data specifying this procedure is a sequence of subspaces of the direct sum of Adinkras, which then opens an avenue for the classification of the continuum of the so-constructed off-shell supermultiplets.
On General Off-Shell Representations of Worldline (1D) Supersymmetry
Doran, Charles F; Iga, Kevin M; Landweber, Gregory D
2014-01-01
Every finite-dimensional unitary representation of the N-extended worldline supersymmetry without central charges may be obtained by a sequence of differential transformations from a direct sum of minimal Adinkras, simple supermultiplets that are identifiable with representations of the Clifford algebra. The data specifying this procedure is a sequence of subspaces of the direct sum of Adinkras, which then opens an avenue for classification of the continuum of so constructed off-shell supermultiplets.
1968-04-01
loading (e. g. shallow shell theory , Geckeler’s approximation for symmetrically loaded shells, etc.) Although the Shear Deformation and Specialized...interest. Included are the Reissner-Meissner equations, Geckeler’s approximations, shallow - shell theory , Donnell’s theory, and others. A. General Shells of
BROWN MH
2008-11-13
Laboratory testing was performed to develop a comprehensive understanding of the corrosivity of the tank wastes stored in Double-Shell Tanks using simulants primarily from Tanks 241-AP-105, 241-SY-103 and 241-AW-105. Additional tests were conducted using simulants of the waste stored in 241-AZ-102, 241-SY-101, 241-AN-107, and 241-AY-101. This test program placed particular emphasis on defining the range of tank waste chemistries that do not induce the onset of localized forms of corrosion, particularly pitting and stress corrosion cracking. This document summarizes the key findings of the research program.
Hansen, Tobias
2015-07-15
This thesis covers two main topics: the tensorial structure of quantum field theory correlators in general spacetime dimensions and a method for computing string theory scattering amplitudes directly in target space. In the first part tensor structures in generic bosonic CFT correlators and scattering amplitudes are studied. To this end arbitrary irreducible tensor representations of SO(d) (traceless mixed-symmetry tensors) are encoded in group invariant polynomials, by contracting with sets of commuting and anticommuting polarization vectors which implement the index symmetries of the tensors. The tensor structures appearing in CFT{sub d} correlators can then be inferred by studying these polynomials in a d + 2 dimensional embedding space. It is shown with an example how these correlators can be used to compute general conformal blocks describing the exchange of mixed-symmetry tensors in four-point functions, which are crucial for advancing the conformal bootstrap program to correlators of operators with spin. Bosonic string theory lends itself as an ideal example for applying the same methods to scattering amplitudes, due to its particle spectrum of arbitrary mixed-symmetry tensors. This allows in principle the definition of on-shell recursion relations for string theory amplitudes. A further chapter introduces a different target space definition of string scattering amplitudes. As in the case of on-shell recursion relations, the amplitudes are expressed in terms of their residues via BCFW shifts. The new idea here is that the residues are determined by use of the monodromy relations for open string theory, avoiding the infinite sums over the spectrum arising in on-shell recursion relations. Several checks of the method are presented, including a derivation of the Koba-Nielsen amplitude in the bosonic string. It is argued that this method provides a target space definition of the complete S-matrix of string theory at tree-level in a at background in terms of a
De Giovanni, Laura N; Guzman, Andrea S; Virgolini, Miriam B; Cancela, Liliana M
2016-12-15
Relapse is a common feature of cocaine addiction. In rodents, it can be elicited by cues, stress or the drug. Restraint stress-induced reinstatement of cocaine-conditioned place preference (CPP) is a useful model to study the mechanisms involved in stress-induced relapse of drug-seeking behavior. There is evidence that the glutamate NMDA receptors are critically involved in drug- and cue-induced reinstatement of seeking behavior and drug-CPP responses. The aim of this study was to investigate the contribution of NMDA receptors within core vs. shell nucleus accumbens (NAc) subregions to restraint stress-induced reinstatement of extinguished cocaine-CPP. After extinction of cocaine-conditioned preference, animals were administered MK 801 systemically or directly into intra-core or intra-shell, and restrained for 30min or left undisturbed in their home-cages. First, we demonstrated that restraint stress-induced reinstatement of extinguished cocaine-CPP depends on the duration of restraint as well as on the context in which it is applied. Second, this effect was blocked by systemic MK 801 administration either before or after restraint. Third, intra-core but not intra-shell administration abrogated the restraint stress-induced reinstatement. These findings show that NMDA receptors within NAc core, but not shell, play a critical role in restraint stress-induced reinstatement of cocaine-CPP.
Jin, Guoyong; Su, Zhu
2015-01-01
This book develops a uniform accurate method which is capable of dealing with vibrations of laminated beams, plates and shells with arbitrary boundary conditions including classical boundaries, elastic supports and their combinations. It also provides numerous solutions for various configurations including various boundary conditions, laminated schemes, geometry and material parameters, which fill certain gaps in this area of reach and may serve as benchmark solutions for the readers. For each case, corresponding fundamental equations in the framework of classical and shear deformation theory are developed. Following the fundamental equations, numerous free vibration results are presented for various configurations including different boundary conditions, laminated sequences and geometry and material properties. The proposed method and corresponding formulations can be readily extended to static analysis.
Stress-strength reliability for general bivariate distributions
Alaa H. Abdel-Hamid
2016-10-01
Full Text Available An expression for the stress-strength reliability R=P(X1
Zeighampour, Hamid; Tadi Beni, Y.
2014-07-01
This work investigated vibrations and instability of double-walled carbon nanotube (DWCNT) conveying fluid by a modified couple stress theory. For this purpose, Donnell's shell model was developed and, using the modified couple stress theory, the equations of motion and corresponding classical and non-classical boundary conditions of DWCNT were obtained through Hamilton's principle. Then, DWCNT with simple-simple and clamped-clamped supports were investigated. The effect of the van der Waals (vdW) forces was considered between the two walls, and the DWCNT surroundings were modeled as a visco-Pasternak foundation. The governing equations of motion and corresponding boundary conditions were discretized through differential quadrature method (DQM), and the vibration problem was solved by using the boundary conditions. The results show that the effects of fluid velocity, stiffness and damping of the visco-Pasternak foundation, nanotube length, and size parameter in the modified couple stress theory are stronger than in the classical theory. Finally, the effect of vdW forces and presence of fluid in the DWCNT examined on the natural frequencies of DWCNT.
Synthesis and stress relaxation of ZnO/Al-doped ZnO core-shell nanowires.
Wang, Hong-Bo; Ma, Fei; Li, Qian-Qian; Dong, Ce-Zhou; Ma, Da-Yan; Wang, Hong-Tao; Xu, Ke-Wei
2013-04-07
Doping nanostructures is an effective method to tune their electrical and photoelectric properties. Taking ZnO nanowires (NWs) as a model system, we demonstrate that atomic layer deposition (ALD) can be adopted for the realization of a doping process by the homo-epitaxial growth of a doped shell on the NW core. The Al-doped ZnO NWs have a layered superlattice structure with dopants mainly occupying the interstitial positions. After annealing, Al(3+) ions diffuse into the ZnO matrix and occupy substitutional locations, which is desirable for dopant activation. The stress accumulated during epitaxial growth is relaxed by the nucleation of dislocations, dislocation dipoles and anti-phase boundaries. We note that the proposed method can be easily adopted for doping different types of nanostructures, and fabricating superlattices and multiple quantum wells on NWs in a controllable way.
Low-Stress Iridium Coatings for Thin-Shell X-Ray Telescopes Project
National Aeronautics and Space Administration — We propose to develop and commercialize a new type of low-stress iridium (Ir) X-ray mirror coating technology that can be used for the construction of...
Lager, J. R.
1975-01-01
A cylindrical shell structure 3.66 m (144 in.) high by 4.57 m (180 in.) diameter was designed using a wide variety of materials and structural concepts to withstand design ultimate combined loading 1225.8 N/cm (700 lb/in.) axial compression and 245.2 N/cm (140 lb/in.) torsion. The overall cylinder geometry and design loading are representative of that expected on a high performance space tug vehicle. The relatively low design load level results in designs that use thin gage metals and fibrous-composite laminates. Fabrication and structural tests of small panels and components representative of many of the candidate designs served to demonstrate proposed fabrication techniques and to verify design and analysis methods. Three of the designs evaluated, honeycomb sandwich with aluminum faceskins, honeycomb sandwich with graphite/epoxy faceskins, and aluminum truss with fiber-glass meteoroid protection layers, were selected for further evaluation.
Studies on Thin-shells and Thin-shell Wormholes
Övgün, Ali
2016-01-01
The study of traversable wormholes is very hot topic for the past 30 years. One of the best possible way to make traversable wormhole is using the thin-shells to cut and paste two spacetime which has tunnel from one region of space-time to another, through which a traveler might freely pass in wormhole throat. These geometries need an exotic matter which involves a stress-energy tensor that violates the null energy condition. However, this method can be used to minimize the amount of the exotic matter. The goal of this thesis study is to study on thin-shell and thin-shell wormholes in general relativity in 2+1 and 3+1 dimensions. We also investigate the stability of such objects.
The oyster genome reveals stress adaptation and complexity of shell formation
Zhang, Guofan; Fang, Xiaodong; Guo, Ximing
2012-01-01
The Pacific oyster Crassostrea gigas belongs to one of the most species-rich but genomically poorly explored phyla, the Mollusca. Here we report the sequencing and assembly of the oyster genome using short reads and a fosmid-pooling strategy, along with transcriptomes of development and stress re...
Stress-energy-momentum of affine-metric gravity generalized Komar superpotential
Giachetta, G
1995-01-01
In case of the Einstein's gravitation theory and its first order Palatini reformulation, the stress-energy-momentum of gravity has been proved to reduce to the Komar superpotential. We generalize this result to the affine-metric theory of gravity in case of general connections and arbitrary Lagrangian densities invariant under general covariant transformations. In this case, the stress-energy-momentum of gravity comes to the generalized Komar superpotential depending on a Lagrangian density in a precise way.
Vanagas Giedrius
2005-06-01
Full Text Available Abstract Background There are number of studies showing that general practice is one of the most stressful workplace among health care workers. Since Baltic States regained independence in 1990, the reform of the health care system took place in which new role and more responsibilities were allocated to general practitioners' in Lithuania. This study aimed to explore the psychosocial stress level among Lithuanian general practitioner's and examine the relationship between psychosocial stress and work characteristics. Methods The cross-sectional study of 300 Lithuanian General practitioners. Psychosocial stress was investigated with a questionnaire based on the Reeder scale. Job demands were investigated with the R. Karasek scale. The analysis included descriptive statistics; interrelationship analysis between characteristics and multivariate logistic regression to estimate odds ratios for each of the independent variables in the model. Results Response rate 66% (N = 197. Our study highlighted highest prevalence of psychosocial stress among widowed, single and female general practitioners. Lowest prevalence of psychosocial stress was among males and older age general practitioners. Psychosocial stress occurs when job demands are high and job decision latitude is low (χ2 = 18,9; p Conclusion One half of respondents suffering from work related psychosocial stress. High psychological workload demands combined with low decision latitude has the greatest impact to stress caseness among GP's. High job demands, high patient load and young age of GP's can be assigned as significant predictors of psychosocial stress among GP's.
Brosschot, Jos F; Verkuil, Bart; Thayer, Julian F
2017-03-01
Based on neurobiological and evolutionary arguments, the generalized unsafety theory of stress (GUTS) hypothesizes that the stress response is a default response, and that chronic stress responses are caused by generalized unsafety (GU), independent of stressors or their cognitive representation. Three highly prevalent conditions are particularly vulnerable to becoming 'compromised' in terms of GU, and carry considerable health risks: Thus, GUTS critically revises and expands stress theory, by focusing on safety instead of threat, and by including risk factors that have hitherto not been attributed to stress.
General engineering ethics and multiple stress of atomic energy engineering
Takeda, Kunihiko [Shibaura Inst. of Tech., Tokyo (Japan)
1999-08-01
The factors, by which the modern engineering ethics has been profoundly affected, were classified to three categories, namely mental blow, the destruction of human function and environment damage. The role of atomic energy engineering in the ethic field has been shown in the first place. It is pointed out that it has brought about the mental blow by the elucidation of universal truth and discipline and the functional disorder by the power supply. However, the direct effect of radiation to the human kinds is only a part of the stresses comparing to the accumulation of the social stress which should be taken into account of by the possibility of disaster and the suspicion of the atomic energy politics. An increase in the multiple stresses as well as the restriction of criticism will place obstacles on the promotion of atomic energy. (author)
A Suggested Stress Analysis Procedure For Nozzle To Head Shell Element Model – A Case Study
Sanket S. Chaudhari
2012-08-01
Full Text Available Stress analysis of pressure vessel has been always a serious and a critical analysis. The paper performs a standard procedure of pressure vessel analysis and validation based on previous papers. It also demonstrates the most critical part and how it affects entire structure. Relevant ASME (ASME, 2004, ASME Boiler and Pressure Vessel Code, Section VIII, Division 2, American Society of Mechanical Engineers, New York norms are produced to explain analysis procedure. WRC (Welding research council methodology is explained to validate finite element analysis work
Shatskii, I. P.; Makoviichuk, N. V.
2011-05-01
The problem of closure of collinear cracks during bending of a shallow shell is considered within the framework of the Kirchhoff theory. Crack closure is described using the model of contact along a line on one of the shell faces. Strain and moment intensity factors and fracture load are studied as functions of shell curvature and defect location, and the distribution of contact forces along the cracks is investigated.
Macian-Sorribes, Hector; Pulido-Velazquez, Manuel; Tilmant, Amaury
2015-04-01
Stochastic programming methods are better suited to deal with the inherent uncertainty of inflow time series in water resource management. However, one of the most important hurdles in their use in practical implementations is the lack of generalized Decision Support System (DSS) shells, usually based on a deterministic approach. The purpose of this contribution is to present a general-purpose DSS shell, named Explicit Stochastic Programming Advanced Tool (ESPAT), able to build and solve stochastic programming problems for most water resource systems. It implements a hydro-economic approach, optimizing the total system benefits as the sum of the benefits obtained by each user. It has been coded using GAMS, and implements a Microsoft Excel interface with a GAMS-Excel link that allows the user to introduce the required data and recover the results. Therefore, no GAMS skills are required to run the program. The tool is divided into four modules according to its capabilities: 1) the ESPATR module, which performs stochastic optimization procedures in surface water systems using a Stochastic Dual Dynamic Programming (SDDP) approach; 2) the ESPAT_RA module, which optimizes coupled surface-groundwater systems using a modified SDDP approach; 3) the ESPAT_SDP module, capable of performing stochastic optimization procedures in small-size surface systems using a standard SDP approach; and 4) the ESPAT_DET module, which implements a deterministic programming procedure using non-linear programming, able to solve deterministic optimization problems in complex surface-groundwater river basins. The case study of the Mijares river basin (Spain) is used to illustrate the method. It consists in two reservoirs in series, one aquifer and four agricultural demand sites currently managed using historical (XIV century) rights, which give priority to the most traditional irrigation district over the XX century agricultural developments. Its size makes it possible to use either the SDP or
["Stress" ulcer--a problem of the general surgeon].
Danelisen, D; Zigić, B; Rac, S
1982-01-01
Contemporary way of living accompanied by everday frustrations, a frequent use of medicaments, an easy application of corticosteroids, complexity of an opeation, so as an increased incidence of polytraumas --those are the factors responsible for an increasing rate of stress ulcus. The rate of 54 verified stress ulcus in the period from 1969-1979 in Regional Medical Centre of Banja Luka, at Surgical Department, are very often indicative of this disease. Thirty eight operatively treated patients are indicative of severity of this disease. The authors are reporting their experiences in resolving this disease by method of vagotomy with partial gastrectomy in comparison to simple sutures of acutely developed ulcus in addition to PS vagotomy. Perforation, which has, usually, been bigger than the chronic ulcus, we had in 31 cases. If the reports of the world authors are reliable, perforation occurs in 5% of cases only, therefore it is clear how many such conditions has remained undetected or treated under various other "working" diagnoses: (DIC, consumer coagulopathy, fibrinolysis, etc.". The stress ulcus is the disease which is a danger to any patient at Surgical Department.
Bandiera, Rino; Petruk, Oleh
2016-06-01
We present an extension of the classical synchrotron emission theory, for the combination of an ordered magnetic field plus a random component. Exact analytical formulae are obtained for a power-law distribution of radiating particles. We also discuss a treatment of the internal Faraday rotation. These results are then applied to discuss some general properties of the structure of the radio emission and polarization from shell-type supernova remnants. To this purpose we have used a thin-layer approximation to model the supernova remnant shell: this approximation does not guarantee the same level of accuracy of numerical simulations, but is adequate to show at least qualitatively how the observed maps are affected by the geometry of the source. Some further considerations are presented on the more general case in which the energy distribution of the emitting particles is not a pure power law.
Caving thickness effects of surrounding rocks macro stress shell evolving characteristics
XIE Guang-xiang; YANG Ke
2009-01-01
In order to explore the influence of different caving thicknesses on the MSS dis-tribution and evolving characteristics of surrounding rocks in unsymmetrical disposal and fully mechanized top-coal caving (FMTC), based on unsymmetrical disposal characteris-tics, the analyses of numerical simulation, material simulation and in-situ observation were synthetically applied according to the geological and technical conditions of the 1151(3) working face in Xieqiao Mine. The results show that the stress peak value of the MSS-base and the ratio of MSS-body height to caving thickness are nonlinear and inversely proportional to the caving thickness. The MSS-base width, the MSS-body height, the MSS-base distance to working face wall and the rise distance of MSS-base beside coal pillar are nonlinear and directly proportional to the caving thickness. The characteristics of MSS distribution and its evolving rules of surrounding rocks and the integrated caving thickness effects are obtained. The investigations will provide lots of theoretic references to the surrounding rocks' stability control of the working face and roadway, roadway layout, gas extraction and exploitation, and efficiency of caving, etc.
Santos, M C; Barros, L; Carolino, E
2010-12-01
To identify occupational stressors and coping resources in a group of physiotherapists, and to analyse interactions between subjective levels of stress, efficacy in stress resolution and coping resources used by these professionals. A sample of 55 physiotherapists working in three general hospitals in Portugal completed the Coping Resources Inventory for Stress, the Occupational Stressors Inventory and two subjective scales for stress and stress resolution. Most physiotherapists perceived that they were moderately stressed (19/55, 35%) or stressed (20/55, 36%) due to work, and reported that their efficacy in stress resolution was moderate (25/54, 46%) or efficient (23/54, 42%). Issues related to lack of professional autonomy, lack of organisation in the hierarchical command chain, lack of professional and social recognition, disorganisation in task distribution and interpersonal conflicts with superiors were identified as the main sources of stress. The most frequently used coping resources were social support, stress monitoring, physical health and structuring. Perceived efficacy in stress resolution was inversely related to perceived level of occupational stress (r=-0.61, P<0.01). Significant correlations were found between several coping resources and the perceived level of stress and efficacy in stress resolution. Associations between problem solving, cognitive restructuring and stress monitoring and both low levels of perceived stress and high levels of perceived efficacy were particularly strong. The importance of identifying stressors and coping resources related to physiotherapists' occupational stress, and the need for the development of specific training programmes to cope with stress are supported. Copyright © 2010 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.
Stress among general practitioners of Kwa-Dukuza, Kwa-Zulu Natal
Indiran Govender
2009-04-01
Full Text Available Background: Stress and burnout are prevalent among the caring professionals, including doctors and nurses. The work-related stress rate among the general working population is 18% whilst among doctors it is around 28%. Stress in general practitioners (GPs can result in multiple negative consequences. Detecting stress early may have positive outcomes for doctors, their families and the people they care for at their practice.Method: A cross-sectional, descriptive study using a self-administered, standardised questionnaire (12-item General Health Questionnaire [GHC] was performed on the 30 general practitioners in Kwa-Dukuza. Confidentiality and anonymity were maintained.Results: 26 of the 30 GPs (87% responded to the survey. 10 GPs (38% were stressed as per the GHQ, six of whom were severely stressed. 22 reported that they felt stressed at work (subjectively.Conclusion: The results indicated that stress among Kwa-Dukuza GPs is slightly higher (38% than found in other studies that indicate a prevalence of 28% among doctors.
Work Related Stress, Burnout, Job Satisfaction and General Health of Nurses
Natasha Khamisa; Brian Oldenburg; Karl Peltzer; Dragan Ilic
2015-01-01
Gaps in research focusing on work related stress, burnout, job satisfaction and general health of nurses is evident within developing contexts like South Africa. This study identified the relationship between work related stress, burnout, job satisfaction and general health of nurses. A total of 1200 nurses from four hospitals were invited to participate in this cross-sectional study (75% response rate). Participants completed five questionnaires and multiple linear regression analysis was us...
MS-on-shell quark mass relation up to four loops in QCD and a general SU(N) gauge group
Marquard, Peter [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Smirnov, Alexander V. [Moscow State Univ. (Russian Federation). Research Computing Center; Smirnov, Vladimir A. [Moscow State Univ. (Russian Federation). Skobeltsyn Inst. of Nuclear Physics; Steinhauser, Matthias; Wellmann, David [Karlsruher Institut fuer Technologie (Germany). Inst. fuer Theoretische Teilchenphysik
2016-06-15
In this paper we compute the relation between heavy quark masses defined in the modified minimal subtraction and on-shell scheme. Detailed results are presented for all coefficients of the SU(N{sub c}) colour factors. The reduction of the four-loop on-shell integrals is performed for a general QCD gauge parameter. Some of the about 380 master integrals are computed analytically, others with high numerical precision based on Mellin-Barnes representations, and the rest numerically with the help of FIESTA. We discuss in detail the precise numerical evaluation of the four-loop master integrals. Updated relations between various short-distance masses and the MS quark mass to next-to-next-to-next-to-leading order accuracy are provided for the charm, bottom and top quark. We discuss the dependence on the renormalization and factorization scale.
Annika Clamor
2015-01-01
Full Text Available Explanatory models ascribe to arousability a central role for the development of psychotic symptoms. Thus, a disposition to hyperarousal (i.e., increased arousal predisposition (AP may serve as an underlying vulnerability indicator for psychosis by interacting with stressors to cause symptoms. In this case, AP, stress-response, and psychotic symptoms should be linked before the development of a diagnosable psychotic disorder. We conducted a cross-sectional online study in a population sample (N=104; Mage=27.7 years, SD=11.2, range 18–70. Participants rated their AP and subclinical psychotic symptoms. Participants reported their stress-levels before and after two stress inductions including an arithmetic and a social stressor. The participants with an increased AP generally felt more stressed. However, AP was not associated with the specific stress-response. As expected, positive psychotic symptoms were significantly associated with AP, but this was not mediated by general stress-levels. Its association to subtle, nonclinical psychotic symptoms supports our assumption that AP could be a vulnerability indicator for psychosis. The trait is easily accessible via a short self-report and could facilitate the identification of people at risk and be a promising target for early stress-management. Further research is needed to clarify its predictive value for stress-responses.
An, Myung In; Choi, Cheol Young
2010-01-01
Changes in water temperature and salinity are responsible for a variety of physiological stress responses in aquatic organisms. Stress induced by these factors was recently associated with enhanced reactive oxygen species (ROS) generation, which caused oxidative damage. In the present study, we investigated the time-related effects of changes in water temperature and salinity on mRNA expression and the activities of antioxidant enzymes (SOD and CAT) and lipid peroxidation (LPO) in the gills and digestive glands of the ark shell, Scapharca broughtonii. To investigate physiological responses, hydrogen peroxide (H(2)O(2)), lysozyme activity, aspartate aminotransferase (AspAT), and alanine aminotransferase (AlaAT) were measured in the hemolymph. Water temperature and salinity changes significantly increased antioxidant enzyme mRNA expression and activity in the digestive glands and gills in a time-dependent manner. H(2)O(2) concentrations increased significantly in the high-temperature and hyposalinity treatments. LPO, AspAT and AlaAT levels also increased significantly in a time-dependent manner, while lysozyme activity decreased. These results suggest that antioxidant enzymes play important roles in reducing oxidative stress in ark shells exposed to changes in water temperature and salinity.
Heron, R J; McKeown, S; Tomenson, J A; Teasdale, E L
1999-09-01
This study was designed to evaluate the effectiveness of stress management training workshops within Zeneca Pharmaceuticals. The study was of cross-sectional design, comparing groups of workshop attendees and non-attendees. In addition, self-rated well-being scores of attendees were compared with results obtained pre-workshop and 2-3 months after the workshop. Employees participating in the study were drawn from the Manufacturing, Research and Development, Sales and Marketing sites of Zeneca Pharmaceuticals located in Cheshire, United Kingdom. Three hundred and ninety persons who had participated in stress management workshops since 1988 were matched for age, gender and department with an equal number of employees who had not attended stress management workshops. Outcome measures included self-rated well-being (as measured by the 30-question General Health Questionnaire), knowledge of company guidance on the management of stress in staff, and an assessment of coping strategies. Subjects who had not attended a stress management workshop were much more likely to have a poor understanding of the principles of management of stress in staff [odds ratio (OR) = 8.3; 95% confidence interval (CI) = 3.3-21.3] and more likely to have poor coping skills (OR = 2.8; CI = 1.3-6.1). However, mean scores for the two measures were similar in attendees and non-attendees. Self-rating of current well-being was strongly associated with the life-events score, but not related to workshop attendance. The study indicates that stress management training workshops reduce the prevalence of employees with a poor understanding of the principles of the management of stress in staff and with poor coping strategies. An improvement in the self-rated well-being observed shortly after the workshop was not sustained.
A surface crack in shells under mixed-mode loading conditions
Joseph, P. F.; Erdogan, F.
1988-01-01
The present consideration of a shallow shell's surface crack under general loading conditions notes that while the mode I state can be separated, modes II and III remain coupled. A line spring model is developed to formulate the part-through crack problem under mixed-mode conditions, and then to consider a shallow shell of arbitrary curvature having a part-through crack located on the outer or the inner surface of the shell; Reissner's transverse shear theory is used to formulate the problem under the assumption that the shell is subjected to all five moment and stress resultants.
Morris, Bethany H; Rottenberg, Jonathan
2015-02-01
Stress-induced anhedonia is associated with depression vulnerability (Bogdan & Pizzagalli, 2006). We investigated stress-induced deficits in reward learning in a depression-vulnerable group with analogue generalized anxiety disorder (GAD, n = 34), and never-depressed healthy controls (n = 41). Utilizing a computerized signal detection task, reward learning was assessed under stressor and neutral conditions. Controls displayed intact reward learning in the neutral condition, and the expected stress-induced blunting. The GAD group as a whole also showed intact reward learning in the neutral condition. When GAD subjects were analyzed as a function of prior depression history, never-depressed GAD subjects showed heightened reward learning in the stressor condition. Better reward learning under stress among GAD subjects predicted lower depression symptoms 1 month later. Robust reward learning under stress may indicate depression resistance among anxious individuals.
Using the stress function in the flow of generalized Newtonian fluids through pipes and slits
Sochi, Taha
2015-01-01
We use a generic and general numerical method to obtain solutions for the flow of generalized Newtonian fluids through circular pipes and plane slits. The method, which is simple and robust can produce highly accurate solutions which virtually match any analytical solutions. The method is based on employing the stress, as a function of the pipe radius or slit thickness dimension, combined with the rate of strain function as represented by the fluid rheological constitutive relation that correlates the rate of strain to stress. Nine types of generalized Newtonian fluids are tested in this investigation and the solutions obtained from the generic method are compared to the analytical solutions which are obtained from the Weissenberg-Rabinowitsch-Mooney-Schofield method. Very good agreement was obtained in all the investigated cases. All the required quantities of the flow which include local viscosity, rate of strain, flow velocity profile and volumetric flow rate, as well as shear stress, can be obtained from ...
Davidovich, E; Pessov, Y; Baniel, A; Ram, D
2015-01-01
To assess self-reported stress during the performance of different procedures in pediatric dentistry, according to the professional experience of the dentists. During the years 2010 to 2011, an anonymous survey was administered by means of an internet link, and by distribution at professional meetings of dentists . No statistically significant differences in stress were reported for maxilla and mandibular procedures. Placement of a rubber dam was rated as the most stressful procedure among dental students. For general practitioners and specialists, injection of local anesthesia to an anxious child was the most stressful procedure, regardless of age, sex, or years of professional experience. A negative correlation was found between years of experience and level of stress for all the procedures surveyed, but not for the use of nitrous oxide. No differences were found between male and female dentists in stress scores for any of the procedures. Higher rates of stress during operative procedures were reported among dental students than among experienced dentists. Anxiety of the pediatric patients, but not the location of the procedure: maxillary or mandibular, affected the dentists' reported level of stress.
Keke eQi
2013-10-01
Full Text Available Orexins are recently found to participate in mediating stress-induced drug relapse. However, the neuroanatomical basis that orexin transmission modulates stress-induced drug seeking remains unknown. The nucleus accumbens shell (NAcSh, best known for its role in appetitive and negative motivation via dopamine receptors, is likely to be the potential important brain area where the orexin system mediates stress-induced drug relapse since the function of dopamine system in the NAcSh can be regulated by orexin transmission. In the present study, a morphine conditioned place preference (CPP model was used to determine whether the two types of orexin receptors would be involved into footshock-induced and/or drug priming-induced CPP reinstatement differentially. The results showed that blockade of orexin-1 or orexin-2 receptor in the NAcSh significantly attenuated stress-induced morphine CPP reinstatement, but neither of the orexin antagonists had any effect on morphine priming-induced reinstatement. These findings indicate that the NAcSh is a brain area through which orexins participate in stress but not drug priming-induced relapse of opioid seeking.
Francesco Tornabene
2017-01-01
Full Text Available The main aim of the present paper is to solve numerically the free vibration problem of sandwich shell structures with variable thickness and made of Functionally Graded Materials (FGMs. Several Higher-order Shear Deformation Theories (HSDTs, defined by a unified formulation, are employed in the study. The FGM structures are characterized by variable mechanical properties due to the through-the-thickness variation of the volume fraction distribution of the two constituents and the arbitrary thickness profile. A four-parameter power law expression is introduced to describe the FGMs, whereas general relations are used to define the thickness variation, which can affect both the principal coordinates of the shell reference domain. A local scheme of the Generalized Differential Quadrature (GDQ method is employed as numerical tool. The natural frequencies are obtained varying the exponent of the volume fraction distributions using higher-order theories based on a unified formulation. The structural models considered are two-dimensional and require less degrees of freedom when compared to the corresponding three-dimensional finite element (FE models, which require a huge number of elements to describe the same geometries accurately. A comparison of the present results with the FE solutions is carried out for the isotropic cases only, whereas the numerical results available in the literature are used to prove the validity as well as accuracy of the current approach in dealing with FGM structures characterized by a variable thickness profile.
朱卫平; 黄黔
2002-01-01
( Ⅱ ) is one of the applications of ( Ⅰ ), in which the angular stiffness, the lateral stiffness and the corresponding stress distributions of Omega-shaped bellows were calculated, and the present results were compared with those of the other theories and experiments. It is shown that the non-homogeneous solution of ( Ⅰ ) can solve the pure bending problem of the bellows by itself, and be more effective than by the theory of slender ring shells; but if a lateral slide of the bellows support exists the non- homogeneous solution will no longer entirely satisfy the boundary conditions of the problem, in this case the homogeneous solution of ( Ⅰ ) should be included, that is to say, the full solution of ( Ⅰ )can meet all the requirements.
Yang, Jerry Zhijian
2014-01-01
Irving and Kirkwood formulism (IK formulism) provides a way to compute continuum mechanics quantities at certain location in terms of molecular variables. To make the approach more practical in computer simulation, Hardy proposed to use a spacial kernel function that couples continuum quantities with atomistic information. To reduce irrational fluctuations, Murdoch proposed to use a temporal kernel function to smooth the physical quantities obtained in Hardy's approach. In this paper, we generalize the original IK formulism to systematically incorporate both spacial and temporal average. The Cauchy stress tensor is derived in this generalized IK formulism (g-IK formulism). Analysis is given to illuminate the connection and difference between g-IK formulism and traditional temporal post-process approach. The relationship between Cauchy stress and first Piola-Kirchhoff stress is restudied in the framework of g-IK formulism. Numerical experiments using molecular dynamics are conducted to examine the analysis res...
SHI Jin-hua
2006-01-01
By summarizing the formation of stress reaction induced by tracheal intubation and method of medicinal control, the recognition of Chinese medicine in treatment of cardiac arrhythmia and hypertension with acupuncture and the clinical application of acupuncture on stress reaction induced by tracheal intubation,it is concluded that the side effects of tracheal intubation are inevitable, even though there are many methods presented for the prevention and treatment for it. In recent years, the functions of acupuncture in anesthesia,especially in regulation of circulatory properties have been developed gradually and have been applied by many physicians in controlling the stress reaction induced by tracheal intubation in general anesthesia. Being a kind of dual-directional and positive regulation and stimulation, acupuncture provides definite and safe effects on controlling the stress reaction induced by tracheal intubation.
Platsidou, Maria; Agaliotis, Ioannis
2017-01-01
The role of empathy in the teaching profession has been vastly investigated in relation to its effect on students, but research on how teachers' empathy affects their own well-being at work is limited. This study investigated empathy and instructional assignment-related stress factors of primary school teachers serving in general or special…
Platsidou, Maria; Agaliotis, Ioannis
2017-01-01
The role of empathy in the teaching profession has been vastly investigated in relation to its effect on students, but research on how teachers' empathy affects their own well-being at work is limited. This study investigated empathy and instructional assignment-related stress factors of primary school teachers serving in general or special…
Lagrangian viscoelastic flow computations using a generalized molecular stress function model
Rasmussen, Henrik K.
2002-01-01
–Sawyers fluid to a fluid described by a generalized molecular stress function (MSF) model allowing the use of dissipative convective constraint release in the constitutive equation. The convergence of the method is demonstrated on the axis-symmetric problem of the inflation of a polymeric membrane only...
General job stress: a unidimensional measure and its non-linear relations with outcome variables.
Yankelevich, Maya; Broadfoot, Alison; Gillespie, Jennifer Z; Gillespie, Michael A; Guidroz, Ashley
2012-04-01
This article aims to examine the non-linear relations between a general measure of job stress [Stress in General (SIG)] and two outcome variables: intentions to quit and job satisfaction. In so doing, we also re-examine the factor structure of the SIG and determine that, as a two-factor scale, it obscures non-linear relations with outcomes. Thus, in this research, we not only test for non-linear relations between stress and outcome variables but also present an updated version of the SIG scale. Using two distinct samples of working adults (sample 1, N = 589; sample 2, N = 4322), results indicate that a more parsimonious eight-item SIG has better model-data fit than the 15-item two-factor SIG and that the eight-item SIG has non-linear relations with job satisfaction and intentions to quit. Specifically, the revised SIG has an inverted curvilinear J-shaped relation with job satisfaction such that job satisfaction drops precipitously after a certain level of stress; the SIG has a J-shaped curvilinear relation with intentions to quit such that turnover intentions increase exponentially after a certain level of stress.
Hwang, Hye-Won; Hyun, Hong-Keun; Kim, Young-Jae; Kim, Jung-Wook; Shin, Teo Jeon
2017-05-01
Stress related to dental treatment can be associated with negative outcomes. Heart rate variability (HRV) is an objective measurement of autonomic nervous system activity. Therefore, HRV was used to identify autonomic nervous system reactions during mesiodens extraction under general anesthesia in children. Electrocardiography was performed with customized software during treatment. HRV parameters were analyzed according to time and frequency domains during each dental procedure (local anesthesia, incision, flap, bone removal, extraction of mesiodens, and suturing). The relations of HRV parameters to age also were determined. Total autonomic nervous system activity decreased markedly after local anesthesia injection. Depending on the responses of sympathetic nerve activity, patients were categorized in a stress group and a nonstress group. The ratio of low-frequency power (LF) to high-frequency power (HF), an indication of sympathetic and parasympathetic balance, increased in the stress group after incision and flap formation. Conversely, the LF/HF ratio decreased during treatment in the nonstress group. However, HR, widely used to evaluate stress responses, did not change statistically during mesiodens extraction in either group. HRV parameters did not differ statistically according to age. The internal stress related to mesiodens extraction can be evaluated more objectively with HRV parameters than with conventional methods. Sympathetic nerve activity in the stress group differed from that in the nonstress group during the treatment procedures. Copyright © 2016 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.
Tarumi, Moto; Kobayashi, Masato; Nakai, Hiromi
2012-11-13
The antisymmetric product of strongly orthogonal geminals (APSG) method is a wave function theory that can effectively treat the static electron correlation. Recently, we proposed the open-shell APSG method using one-electron orbitals for open-shell parts. In this paper, we have extended the perturbation correction to the open-shell APSG calculations through Møller-Plesset-type multiconfiguration perturbation theory (MP-MCPT). Numerical applications demonstrate that the present open-shell MP-MCPT can reasonably reproduce the dissociation energies or equilibrium distances for open-shell systems.
Vićentić Sreten
2010-01-01
Full Text Available Background/Aim. So far, studies of stress have shown that physicians are at a high risk of sickness from psychic and somatic disorders related to professional stress, that can lead to important disturbance of personal, familiar and professional functionating. The aim of this study was to investigate the doctors exposition level to professional stress, to compare stress level in general practitioners (GP group with that in the group of psychiatrists and risk level for the apperance of burnout syndrome. Methods. This cross-section study included subjects recruited by a random sample method. Thirty General Practice doctors and 30 psychiatrists (totally 60 doctors filled the set of 3 questionnaires: Sociodemographics features, General Health Questionnaire (GHQ; Goldberg D, 1991, and Maslach Burnout Inventory (MBI; Maslach C, 1996. Appropriate statistical procedures (Pearson test, t-test, variance analysis in interpretation of the results were used. Results. A total level of psychic distress measured with the GHQ test in both groups of physicians was very low implying their good mental health. A difference in Burnout risk based on MBI test between the groups was statistically significant (χ2 = 4,286; p < 0.05 only at subscale Personal Accomplishment (MBI-PA; it was a consequence of a higher number of GPs with medium burnout risk (13.3 : 0.0%. However, even 35 physicians from the sample were affected with a high burnout risk measured with subscales Emotional Ehausation (MBI-EE and MBI-DP, showing that both groups of physicians had risk for the appearance of burnout syndrome. Conclusion. The obtained results showed a high burnout risk level in both, GPs and psychiatrists, groups. In both groups there was no presence of psychic disorders (anxiety, depression, insomnia, while there was a high level of emotional ehausation and overtension by job, and also a lower total personal accomplishment. Level of exposition to professional stress is higher in GPs
Terakado, Ako; Watanabe, Takako
2012-10-01
This study was conducted to create a questionnaire that measures stress among nurses engaged in palliative care on general wards. Nurses with at least 3 years of experience involved in palliative care on a general ward in six facilities in Japan were the subjects from September 7 to October 4, 2004. A draft questionnaire on stress factors and conditions of stress in nurses engaged in end-of-life care was created, and question items and content meaning were revised to produce 32 question items, with a four-point Likert scale for the responses. Two pretests were conducted. Internal validity was investigated and resulted in 31 question items. Factor analysis using the principal factor method (Varimax rotation) was performed, and Cronbach's coefficient alpha was used to evaluate internal consistency and check reliability. The survey response rate was 94%, with a valid response rate of 98%. Analysis was conducted using responses from 269 participants, of whom 98.9% were female, with a mean age of 35.4 years. The mean length of experience as a nurse was 13.6 years, and the mean length of experience in cancer nursing was 8 years. Results of factor analysis produced eigenvalues of 5.260-1.558 and a cumulative proportion of 58.032%. After two items were deleted, six stress-related factors were identified; their alpha coefficients were 0.753 to 0.912, ensuring high reliability. The questionnaire developed had high internal validity and high reliability, and it can thus serve as a first stage in elucidating stress among nurses engaged in palliative care on general wards.
Li, Xiao-liang; Kang, Yue; Zhang, Xiao-yan; Zhu, Bing-lin; Fang, Wei-huan
2012-06-01
The heat shock cognate protein 70 (Hsc70) is a member of a 70-kDa heat shock protein (HSP70) family that functions as molecular chaperones. In this study, a novel Hsc70 gene from Chinese soft-shelled turtle (Pelodiscus sinensis) (tHsc70) was identified. The tHsc70 full-length complementary DNA (cDNA) is 2272 bp long with a 1941-bp open reading frame (ORF) encoding 646 amino acids. Three characteristic signature regions of the HSP70 family, two major domains of an adenosine triphosphate (ATP)/guanosine triphosphate (GTP) binding domain (ABD), and a substrate-binding domain (SBD) were present in the predicted tHsc70 amino acid sequence. The tHsc70 gene was expressed in Escherichia coli BL21 and the expression product reacted with the anti-Hsc70 mouse monoclonal antibody by Western blotting. Homology analysis revealed that tHsc70 shared identity from 53.9% to 87.7% at the nucleotide level, and 49.1% to 99.5% at the amino acid level with the known Hsc70s. Phylogenetic analysis showed that tHsc70 was clustered together with the Hsc70 gene of another reptile species (Alligator mississippiensis). The tHsc70 was expressed in the liver, lung, heart, and skeletal muscle. The expression patterns of tHsc70 messenger RNA (mRNA) differed among different tissues under different durations of heat stress at 40 °C. Adaptation at 25 °C for 1 h after heat stress was also different among tissues and length of heat stress. Irrespective of different profiles of expression under heat stress, tHsc70 may play roles in protecting turtles from thermal stress.
Work related stress, burnout, job satisfaction and general health of nurses.
Khamisa, Natasha; Oldenburg, Brian; Peltzer, Karl; Ilic, Dragan
2015-01-12
Gaps in research focusing on work related stress, burnout, job satisfaction and general health of nurses is evident within developing contexts like South Africa. This study identified the relationship between work related stress, burnout, job satisfaction and general health of nurses. A total of 1200 nurses from four hospitals were invited to participate in this cross-sectional study (75% response rate). Participants completed five questionnaires and multiple linear regression analysis was used to determine significant relationships between variables. Staff issues are best associated with burnout as well as job satisfaction. Burnout explained the highest amount of variance in mental health of nurses. These are known to compromise productivity and performance, as well as affect the quality of patient care. Issues, such as security risks in the workplace, affect job satisfaction and health of nurses. Although this is more salient to developing contexts it is important in developing strategies and intervention programs towards improving nurse and patient related outcomes.
Work Related Stress, Burnout, Job Satisfaction and General Health of Nurses
Natasha Khamisa
2015-01-01
Full Text Available Gaps in research focusing on work related stress, burnout, job satisfaction and general health of nurses is evident within developing contexts like South Africa. This study identified the relationship between work related stress, burnout, job satisfaction and general health of nurses. A total of 1200 nurses from four hospitals were invited to participate in this cross-sectional study (75% response rate. Participants completed five questionnaires and multiple linear regression analysis was used to determine significant relationships between variables. Staff issues are best associated with burnout as well as job satisfaction. Burnout explained the highest amount of variance in mental health of nurses. These are known to compromise productivity and performance, as well as affect the quality of patient care. Issues, such as security risks in the workplace, affect job satisfaction and health of nurses. Although this is more salient to developing contexts it is important in developing strategies and intervention programs towards improving nurse and patient related outcomes.
Sunita Deswal
2013-01-01
Full Text Available The aim of this paper is to study magneto-thermoelastic interactions in an initially stressed isotropic homogeneous half-space in the context of fractional order theory of generalized thermoelasticity. State space formulation with the Laplace transform technique is used to obtain the general solution, and the resulting formulation is applied to the ramp type increase in thermal load and zero stress. Solutions of the problem in the physical domain are obtained by using a numerical method of the Laplace inverse transform based on the Fourier expansion technique, and the expressions for the displacement, temperature, and stress inside the half-space are obtained. Numerical computations are carried out for a particular material for illustrating the results. Results obtained for the field variables are displayed graphically. Some comparisons have been shown in figures to present the effect of fractional parameter, ramp parameter, magnetic field, and initial stress on the field variables. Some particular cases of special interest have been deduced from the present investigation.
VIRTUAL MASS EFFECT ON CONSTRAINED OSCILLATION OF OPEN SHELLS
Mr. Oleg Ye. Sysoyev Doctor of Engineering, Professor, the Civil construction and Architecture Department, Dean of the Cadastre and Civil construction faculty, Komsomolsk-on-Amur State Technical University (Russia, Komsomolsk-on-Amur. E-mail: fks@knastu.ru.
2016-09-01
Full Text Available In the laboratory of constructions of Komsomolsk-on-Amur State Technical University (KnAGTU an experiment has been carried on. The aim of the experiment was to identify patterns of influence of magnitude of fluctuations in the virtual mass on constrained oscillation of open shells. Constrained oscillation of curved and open-shell carrying the virtual mass was measured with the help of induction accelerometers. Steel shell is pin supported along the edges, rectangular in the plan. Pin supported open shells along both sides, as the most frequently used in the construction have not yet been investigated. The calculation was made based on the general equation of oscillation of a shell, as well as Donnell - Mushtari - Vlasov equations. In the theoretical calculation, assumptions about the flatness were not taken into account. But it seemed that the magnitude of the stresses from bending moments are comparable in magnitude to the stress of the effort. In consequence, substantial increase in the differentiation was obtained. As a result, values of theoretical constrained oscillation of a shell were obtained. We compared the theoretical and analytical data.
Morey, R.A.; Dunsmoor, J E; Haswell, C C; Brown, V M; Vora, A; Weiner, J.; Stjepanovic, D; Wagner, H R; ,; Brancu, Mira; Marx, Christine E.; Naylor, Jennifer C.; Van Voorhees, Elizabeth; Taber, Katherine H.; Beckham, Jean C.
2015-01-01
Fear conditioning is an established model for investigating posttraumatic stress disorder (PTSD). However, symptom triggers may vaguely resemble the initial traumatic event, differing on a variety of sensory and affective dimensions. We extended the fear-conditioning model to assess generalization of conditioned fear on fear processing neurocircuitry in PTSD. Military veterans (n=67) consisting of PTSD (n=32) and trauma-exposed comparison (n=35) groups underwent functional magnetic resonance ...
Hombergh, P. van den; Kunzi, B.; Elwyn, G.; Doremalen, J.H.M. van; Akkermans, R.P.; Grol, R.P.T.M.; Wensing, M.J.P.
2009-01-01
BACKGROUND: The impact of high physician workload and job stress on quality and outcomes of healthcare delivery is not clear. Our study explored whether high workload and job stress were associated with lower performance in general practices in the Netherlands. METHODS: Secondary analysis of data fr
Analysis of laminated composite shells under internal pressure
Yuan, F. G.
1991-01-01
A closed form solution is presented that predicts the response of filament wound composite shells subjected to internal pressure. The material of the shell is assumed to be general cylindrically anisotropic. Based on the theory of cylindrical anisotropic elasticity coupled differential equations are developed using Lekhnitskii's stress function approach. Two composite systems, graphite/epoxy and glass/epoxy, are selected to demonstrate the influence of degree of material anisotropy and fiber orientations on the axial and induced twisting deformation. Detailed stress distributions of (45) off-axis unidirectional and (45/-45)s symmetric angle-ply fiber-reinforced laminated shells are shown to illustrate the effect of radius-to-thickness ratio and stacking sequence.
THERMAL RESIDUAL STRESSES OF FUNCTIONALLY GRADED PIEZOELECTRIC SHELLS%功能梯度压电材料壳体热残余应力
舒小平
2012-01-01
Thermal residual phenomenon occurs in functionally graded (FG) piezoelectric structures when workpieces are-cooling and affects their strength. A FG piezoelectric hollow sphere or circular cylinder was divided to a number of layers through its thickness like a composite laminate, each layer with constant material properties. According to the interfacial continuity conditions, a recursive relation was built and the explicit thermal residual solutions with piezothermoelastic coupling were deduced. The solutions were suitable for both multi-layered and continuous FG piezoelectric shells. The solutions are exact for multi-layered FG piezoelectric shells, and approximate for continuous FG piezoelectric shells and converge to the exact solutions when the number of layers increases. The solutions also hold for FG piezoelectric coatings on a substrate. This method is independent of the distribution functions of material properties through thickness and shows its adaptability. The factors to affect thermal residual stresses and interfacial strength were discussed. The thermal residual stresses of a sphere with double curvatures are much bigger than those of a cylinder.%功能梯度压电材料结构成型冷却后会出现热残余现象,影响结构强度.借鉴复合材料层合结构的研究方法,将功能梯度压电材料球壳和圆柱壳沿厚度分为若干层,各层视为均匀材料,根据层间连续条件导出递推关系,得到显式的力—电—热多场耦合热残余解.统一了多层功能梯度压电材料壳体和连续功能梯度压电材料壳体热残余解.对于前者,其解为精确解；对于后者,其解为渐近解,随层数增加而收敛于精确解.其解也适用于功能梯度压电材料涂层.该方法对材料性能的变化方式(函数)没有要求,适应性强.并讨论影响热残余应力和界面强度的因素,球壳因双曲率的影响,热残余应力显著大于柱壳.
Zhen Chen
2016-01-01
Full Text Available Accelerated degradation test (ADT has been widely used to assess highly reliable products’ lifetime. To conduct an ADT, an appropriate degradation model and test plan should be determined in advance. Although many historical studies have proposed quite a few models, there is still room for improvement. Hence we propose a Nonlinear Generalized Wiener Process (NGWP model with consideration of the effects of stress level, product-to-product variability, and measurement errors for a higher estimation accuracy and a wider range of use. Then under the constraints of sample size, test duration, and test cost, the plans of constant-stress ADT (CSADT with multiple stress levels based on the NGWP are designed by minimizing the asymptotic variance of the reliability estimation of the products under normal operation conditions. An optimization algorithm is developed to determine the optimal stress levels, the number of units allocated to each level, inspection frequency, and measurement times simultaneously. In addition, a comparison based on degradation data of LEDs is made to show better goodness-of-fit of the NGWP than that of other models. Finally, optimal two-level and three-level CSADT plans under various constraints and a detailed sensitivity analysis are demonstrated through examples in this paper.
Lu, Chang-Qin; Du, Dan-Yang; Xu, Xiao-Min
2016-10-02
The aim of this research is to verify the two-dimensional challenge-hindrance stressor framework in the Chinese context, and investigate the moderating effect of general self-efficacy in the stress process. Data were collected from 164 Chinese employee-supervisor dyads. The results demonstrated that challenge stressors were positively related to job performance while hindrance stressors were negatively related to job performance. Furthermore, general self-efficacy strengthened the positive relationship between challenge stressors and job performance, whereas the attenuating effect of general self-efficacy on the negative relationship between hindrance stressors and job performance was nonsignificant. These findings qualify the two-dimensional challenge-hindrance stressor framework, and support the notion that employees with high self-efficacy benefit more from the positive effect of challenge stressors in the workplace. By investigating the role of an individual difference variable in the challenge-hindrance stressor framework, this research provides a more accurate picture of the nature of job stress, and enhances our understanding of the job stressor-job performance relationship.
Zhao, Guanghui; Peng, Xiaomen; Li, Hongping; Wang, Jianzhi; Zhou, Lincheng; Zhao, Tianqi; Huang, Zhihao; Jiang, Haifei
2015-05-01
FexOy@FexOy/C nanoparticles with a soap-bubble-like shell have been synthesized, and the materials exhibit excellent Fenton catalytic performance. More importantly, FexOy@FexOy/C nanoparticles as catalysts and precursors could catalyze organic dye molecules to form iron oxide@organic dye polymer core-shell nanospheres.
Generalized Phenomenological Cyclic Stress-Strain-Strength Characterization of Granular Media.
1984-09-02
following special form of the general hypoelastic equation to model the behavior of granular media: dij = [a0 dem + a3 "pq d pq] 6ij + 1 dcij + C 2 dem...Phenomitno ogical I C.yclic Stress-Strain-Strength Characterization f Granular M~dia !RSO%.hL APT’.OR(S) M._McVay,_D._Seereeram,_P.__Linton andD... Granular Medi a, Vollow Cylinder. Cyclic Triaxial Test, Plasticity, Prediction Expanding Cavity LClic CTC rests ISTAAC? fCoom w mz_’-. ,f_.V,,A6’V "d
Lau, Ying; Tha, Pyai Htun; Wong, Daniel Fu Keung; Wang, Yuqiong; Wang, Ying; Yobas, Piyanee Klainin
2016-02-01
Few studies have examined different perceptions of stress or explored the positive aspects of well-being among pregnant Chinese women, so there is a need to explore these phenomena in order to fill the research gap. The aim of this study was to examine the relationships among the different perceptions of stress, coping styles, and general well-being using a structural equation modeling approach. We examined a hypothetical model among 755 pregnant Chinese women based on the integration of theoretical models. The Perceived Stress Scale (PSS), the Trait Coping Styles Questionnaire (TCSQ), and the General Well-Being Schedule (GWB) were used to measure perceived stress, coping styles, and general well-being, respectively. A structural equation model showed that positive and negative perceptions of stress significantly influenced positive and negative coping styles, respectively. Different perceptions of stress were significantly associated with general well-being, but different coping styles had no significant effects on general well-being. The model had a good fit to the data (IFI = 0.910, TLI = 0.904, CFI = 0.910, and RMSEA = 0.038). Different perception of stress was able to predict significant differences in coping styles and general well-being.
A circumferential crack in a cylindrical shell under tension.
Duncan-Fama, M. E.; Sanders, J. L., Jr.
1972-01-01
A closed cylindrical shell under uniform internal pressure has a slit around a portion of its circumference. Linear shallow shell theory predicts inverse square-root-type singularities in certain of the stresses at the crack tips. This paper reports the computed strength of these singularities for different values of a dimensionless parameter based on crack length, shell radius and shell thickness.
Modeling the carbon isotope composition of bivalve shells (Invited)
Romanek, C.
2010-12-01
The stable carbon isotope composition of bivalve shells is a valuable archive of paleobiological and paleoenvironmental information. Previous work has shown that the carbon isotope composition of the shell is related to the carbon isotope composition of dissolved inorganic carbon (DIC) in the ambient water in which a bivalve lives, as well as metabolic carbon derived from bivalve respiration. The contribution of metabolic carbon varies among organisms, but it is generally thought to be relatively low (e.g., organism and high (>90%) in the shells from terrestrial organisms. Because metabolic carbon contains significantly more C-12 than DIC, negative excursions from the expected environmental (DIC) signal are interpreted to reflect an increased contribution of metabolic carbon in the shell. This observation contrasts sharply with modeled carbon isotope compositions for shell layers deposited from the inner extrapallial fluid (EPF). Previous studies have shown that growth lines within the inner shell layer of bivalves are produced during periods of anaerobiosis when acidic metabolic byproducts (e.g., succinic acid) are neutralized (or buffered) by shell dissolution. This requires the pH of EPF to decrease below ambient levels (~7.5) until a state of undersaturation is achieved that promotes shell dissolution. This condition may occur when aquatic bivalves are subjected to external stressors originating from ecological (predation) or environmental (exposure to atm; low dissolved oxygen; contaminant release) pressures; normal physiological processes will restore the pH of EPF when the pressure is removed. As a consequence of this process, a temporal window should also exist in EPF at relatively low pH where shell carbonate is deposited at a reduced saturation state and precipitation rate. For example, EPF chemistry should remain slightly supersaturated with respect to aragonite given a drop of one pH unit (6.5), but under closed conditions, equilibrium carbon isotope
Funke, R; Eichler, A; Distler, J; Golub, Y; Kratz, O; Moll, G H
2016-12-16
Because chronic stress is an important risk factor for anxiety states and depressive disorders, we studied hypothalamus-pituitary-adrenal (HPA) axis and sympathetic system activity via changes in cortisol and alpha amylase activity levels in pediatric generalized anxiety disorder (GAD) patients (n = 26) with comorbid depression and a healthy comparison group (n = 26). Morning plasma cortisol and diurnal profiles of salivary cortisol and salivary alpha amylase (sAA) activity were assessed, also reactivity of HPA-axis, sAA activity, and heart rate following a psychosocial stressor (Trier Social Stress Test for children). GAD patients with comorbid depression showed increased morning plasma and salivary cortisol levels, ameliorating throughout in-patient treatment, and higher sAA activity in their diurnal profile. Both HPA and sympathetic activity positively correlated with the severity of anxiety and depression. We also demonstrated a blunted HPA and sympathetic response to acute stress in patients. This pattern of neuroendocrine and sympathetic changes seems to be distinct from the one previously reported in pediatric patients with only social anxiety or depressive disorders. We propose morning plasma and saliva cortisol levels as potential physiological indicators for supporting the evaluation of symptoms' severity and treatment progress in children with GAD and comorbid depressive disorder.
Masoud Samadzadeh
2013-12-01
Full Text Available During the past few years, there have been tremendous efforts on measuring the effects of different factors such as work stress, general heath quality, etc. on performance of employees. In this paper, we present an empirical investigation to study the effects of work stress, general health, organizational intelligence and job satisfaction on employee performance. The proposed study of this paper uses two questionnaires where one is associated with general heath quality (GHQ with 20 questions and the other one consists of 12 questions, which is associated with work stress. The study chooses a sample of 144 employees from 222 people who worked for one of Islamic Azad University in Iran. Cronbach alphas for work stress, general health, organizational intelligence, job satisfaction and organizational performance are 0.911, 0.895, 0.795, 0.863 and, 0.864, respectively. The results indicate that job satisfaction has the highest influence on organizational performance followed by other factors.
Durham, Tory A; Elhai, Jon D; Fine, Thomas H; Tamburrino, Marijo; Cohen, Gregory; Shirley, Edwin; Chan, Philip K; Liberzon, Israel; Galea, Sandro; Calabrese, Joseph R
2015-07-30
The present study investigated symptom relations between two highly comorbid disorders--posttraumatic stress disorder (PTSD) and generalized anxiety disorder (GAD)--by exploring their underlying dimensions. Based on theory and prior empirical research it was expected that the dysphoria factor of PTSD would be more highly related to GAD. As part of a longitudinal project of mental health among Ohio National Guard Soldiers, 1266 subjects were administered the Posttraumatic Stress Disorder Checklist (PCL) and Generalized Anxiety Disorder-7 scale (GAD-7). Confirmatory factor analyses (CFAs) were conducted to examine two models of PTSD and to determine which PTSD factors were more related to the GAD factor. The results indicate that the GAD factor was significantly more highly correlated with PTSD's dysphoria factor than with all other PTSD factors, including PTSD's reexperiencing factor, avoidance factor, and hyperarousal factor. Results indicate GAD was not significantly more highly correlated with numbing than most other factors of PTSD. The results are consistent with prior research. Implications of the results are discussed in regards to PTSD in DSM-5, comorbidity and diagnostic specificity.
Influence of Transverse Shear on an Axial Crack in a Cylindrical Shell
Krenk, Steen
1978-01-01
. The asymptotic membrane and bending stress fields ahead of the crack are found to be self similar. Stress intensity factors are given as a function of the shell parameter for various values of the ratio shell radius to shell thickness. Considerable differences from 8th order shell theory results are found...... for the bending stresses, while the membrane stresses of the 8th order theory seems to be a lower limit reached for very thin shells....
Herrou, Julien; Willett, Jonathan W.; Czyz, Daniel M.; Babnigg, Gyorgy; Kim, Youngchang; Crosson, Sean
2017-03-01
Brucella abortus sigma(E1) is an EcfG family sigma factor that regulates the transcription of dozens of genes in response to diverse stress conditions and is required for maintenance of chronic infection in a mouse model. A putative ATP-binding cassette transporter operon, bab1_0223-bab1_0226, is among the most highly activated gene sets in the sigma(E1) regulon. The proteins encoded by the operon resemble quaternary ammonium-compatible solute importers but are most similar in sequence to the broadly conserved YehZYXW system, which remains largely uncharacterized. Transcription of yehZYXW is activated by the general stress sigma factor sigma(S) in Enterobacteriaceae, which suggests a functional role for this transport system in bacterial stress response across the classes Alphaproteobacteria and Gammaproteobacteria. We present evidence that B. abortus YehZYXW does not function as an importer of known compatible solutes under physiological conditions and does not contribute to the virulence defect of a sigma(E1)- null strain. The sole in vitro phenotype associated with genetic disruption of this putative transport system is reduced growth in the presence of high Li+ ion concentrations. A crystal structure of B. abortus YehZ revealed a class II periplasmic binding protein fold with significant structural homology to Archaeoglobus fulgidus ProX, which binds glycine betaine. However, the structure of the YehZ ligand-binding pocket is incompatible with high-affinity binding to glycine betaine. This is consistent with weak measured binding of YehZ to glycine betaine and related compatible solutes. We conclude that YehZYXW is a conserved, stress-regulated transport system that is phylogenetically and functionally distinct from quaternary ammonium-compatible solute importers
Hauk, Mateusz; Chodkiewicz, Jan
2013-06-01
The purpose of this study was to analyze the role of general and occupational stress in the relationship between workaholism (recognized in two ways: as addiction and as behavioral tendency) and the intensity of work-family and family-work conflict. The study included 178 working people. The survey was conducted at three stages - half a year before a holiday, right after the holiday and half a year after the holiday. The Excessive Work Involvement Scale (SZAP) by Golińska for the measurement of workaholism recognized as addiction; The Scale of Workaholism as Behavioral Tendencies (SWBT) by Mudrack and Naughton as adapted by Dudek et al for the measurement of workaholism as behavioral tendency; the Perceived Stress Scale by Cohen et al., as adapted by Juczyński for the measurement of general stress; the Scale of Occupational Stress by Stanton in the adaptation of Dudek and Hauk for measurement of occupational stress; the Scale of Work-Family Conflict WFC/FWC by Netemeyer et al. with the Polish adaptation of A.M. Zalewska. Workaholism was measured once - before a holiday, the explained and intervening variables (the level of conflicts and stress, respectively) were measured at three stages. To test the mediating role of general and occupational stress, hierarchical regression analysis as well as the method of bootstrapping were applied. Our results indicate that general stress is an important mediator of the relationship between workaholism recognized as an addiction and work-family conflicts. Occupational stress turned out to be the only mediator in the relationship between workaholism (recognized as an addiction) and the work-family conflict, noted exclusively in the first stage of the study. Both general and occupational stress were not significant mediators in the relationship between workaholism recognized as a behavioral tendency and the conflicts described.
Almegaard, Henrik
2004-01-01
A new statical and conceptual model for membrane shell structures - the stringer system - has been found. The principle was first published at the IASS conference in Copenhagen (OHL91), and later the theory has been further developed (ALMO3)(ALMO4). From the analysis of the stringer model it can...... be concluded that all membrane shells can be described by a limited number of basic configurations of which quite a few have free edges....
Work Related Stress: Application of a Special Study to the General Business Community.
Gallagher, Denise M.; And Others
There has been much recent attention given to stress and the negative side effects associated with excessive stress. Employers need to recognize the effect that stress can have on the productivity and attitudes of their employees. To examine work-related stress and to develop stress management strategies, a study was conducted of flight attendants…
Plate shell structures of glass
Bagger, Anne
. This modelling technique is used to model a plate shell structure with a span of 11.5 meters in the FE software \\textsc{Abaqus}. The structure is analyzed with six different connection details with varying stiffness characteristics, to investigate the influence of these characteristics on the structural effects...... University, a script has been developed for an automated generation of a given plate shell geometry and a corresponding finite element (FE) model. A suitable FE modelling technique is proposed, suggesting a relatively simple method of modelling the connection detail's stiffness characteristics....... Based on these investigations, and FE analysis of other plate shell models, the structural behaviour is described. Possible methods of estimating the stresses in a given plate shell structure are proposed. The non-linear behaviour of a plate shell structure is investigated for varying parameters...
Yongcheng Yao
2014-08-01
Full Text Available Objectives: This study aims at exploring associations of general self-efficacy (GSE, workplace violence and doctors' work-related attitudes. Material and Methods: In this study a cross-sectional survey design was applied. Questionnaires were administrated to 758 doctors working in 9 hospitals of Zhengzhou, Henan province, China, between June and October 2010. General information on age, gender, and years of working was collected, and the doctors' experience and witnessing workplace violence, job satisfaction, job initiative, occupational stress as well as GSE were measured. General linear regression analysis was performed in association analyses. Results: Both experiencing and witnessing workplace violence were significantly positively correlated with the level of occupational stress but significantly negatively correlated with job satisfaction, job initiative, and GSE. General self-efficacy significantly modified relationships between both experiencing and witnessing workplace violence with occupational stress (β = 0.49 for experiencing violence; β = 0.43 for witnessing violence; p 0.05. The levels of occupational stress declined significantly with the increase of GSE, while job satisfaction increased significantly along with its increase. The effects of GSE on occupational stress and job satisfaction weakened as the frequency of violence increased. Conclusions: The findings suggest that GSE can modify effects of workplace violence on health care workers' stress and job satisfaction. Enhancing GSE in combination with stress reduction may lead to facilitating health care workers' recovery from workplace violence, and thereby improving their work-related attitudes.
Yao, Yongcheng; Wang, Wei; Wang, Faxuan; Yao, Wu
2014-06-01
This study aims at exploring associations of general self-efficacy (GSE), workplace violence and doctors' work-related attitudes. In this study a cross-sectional survey design was applied. Questionnaires were administrated to 758 doctors working in 9 hospitals of Zhengzhou, Henan province, China, between June and October 2010. General information on age, gender, and years of working was collected, and the doctors' experience and witnessing workplace violence, job satisfaction, job initiative, occupational stress as well as GSE were measured. General linear regression analysis was performed in association analyses. Both experiencing and witnessing workplace violence were significantly positively correlated with the level of occupational stress but significantly negatively correlated with job satisfaction, job initiative, and GSE. General self-efficacy significantly modified relationships between both experiencing and witnessing workplace violence with occupational stress (β = 0.49 for experiencing violence; β = 0.43 for witnessing violence; p 0.05). The levels of occupational stress declined significantly with the increase of GSE, while job satisfaction increased significantly along with its increase. The effects of GSE on occupational stress and job satisfaction weakened as the frequency of violence increased. The findings suggest that GSE can modify effects of workplace violence on health care workers' stress and job satisfaction. Enhancing GSE in combination with stress reduction may lead to facilitating health care workers' recovery from workplace violence, and thereby improving their work-related attitudes.
Ersan, Nilüfer; Fişekçioğlu, Erdoğan; Dölekoğlu, Semanur; Oktay, İnci; İlgüy, Dilhan
2017-02-06
The aims of this study were to identify sources of stress among clinical students and to evaluate the students' perceived levels of stress, general self-efficacy and effective coping strategies in a private dental school environment. The study group consisted of 130 undergraduate clinical dental students in a Turkish private dental school, during the academic year 2014-2015. The students were surveyed using modified version of the dental environment stress (DES) survey, the perceived stress scale, the general self-efficacy scale (G-SES) and the brief coping scale. Age, sex, year of study, history of psychiatric treatment and factors that affected the choice of dentistry were also recorded. Final year and female clinical dental students, who were found to be the most stressful students, had moderate to high perceived stress scores. Total and 'Faculty and administration' related DES scores increased with the year of study. Stressors related to 'Workload' and 'Clinical training' affected females more than males. G-SES scores were higher in male students and students, who had no history of psychiatric treatment. The most and the least common coping strategies were 'Planning' and 'Substance abuse', respectively. 'Religion' was found to be one of the main coping strategies. Stress factors affecting Turkish clinical dental students studying at private dental school differed from the previously reported stress factors affecting students studying at a governmental dental school. Advanced year and female students experienced more stress than the other students.
The crack problem in a specially orthotropic shell with double curvature
Delale, F.; Erdogan, F.
1982-01-01
The crack problem of a shallow shell with two nonzero curvatures is considered. It is assumed that the crack lies in one of the principal planes of curvature and the shell is under Mode I loading condition. The material is assumed to be specially orthotropic. After giving the general formulation of the problem the asymptotic behavior of the stress state around the crack tip is examined. The analysis is based on Reissner's transverse shear theory. Thus, as in the bending of cracked plates, the asymptotic results are shown to be consistent with that obtained from the plane elasticity solution of crack problems. Rather extensive numerical results are obtained which show the effect of material orthotropy on the stress intensity factors in cylindrical and spherical shells and in shells with double curvature. Other results include the stress intensity factors in isotropic toroidal shells with positive or negative curvature ratio, the distribution of the membrane stress resultant outside the crack, and the influence of the material orthotropy on the angular distribution of the stresses around the crack tip.
Analysis of reinforced concrete shells with transverse shear forces
Schulz, Mauro
2013-01-01
This research investigates the simultaneous effect of in-plane and transverse loads in reinforced concrete shells. The infinitesimal shell element is divided into layers (with triaxial behavior) that are analyzed according to the smeared rotating crack approach. The set of internals forces includes the derivatives of the in-plane components. The corresponding generalized strains are determined using an extension of the equivalent section method, valid for shells. The formulation yields through-the-thickness distributions of stresses and strains and the spatial orientation of the concrete struts. Although some simplifications are necessary to establish a practical first-order approximation, higher-order solutions could be developed. Despite the fact that constitutive matrices are not symmetric, because of the tension-softening formulation, the equilibrium and compatibility conditions are satisfied, the stiffness derivatives are explicitly calculated and the algorithms show good convergence. The formulation pre...
Steudte-Schmiedgen, Susann; Wichmann, Susann; Stalder, Tobias; Hilbert, Kevin; Muehlhan, Markus; Lueken, Ulrike; Beesdo-Baum, Katja
2017-01-01
Studies investigating cortisol secretion in patients with generalized anxiety disorder (GAD) have reported heterogeneous findings. Further, current knowledge on the specificity of endocrine changes for GAD and/or comorbid major depression (MD) is limited. Hence, the current study investigated long-term integrated cortisol secretion, as indexed by hair cortisol concentrations (HCC), and experimentally-induced cortisol stress reactivity in relation to GAD, MD and their comorbidity. Carefully characterized groups of 17 GAD patients including 8 with comorbid MD (GAD-MD), 12 MD patients and 21 healthy controls were recruited. Alongside psychometric data, HCC (N = 43) and salivary cortisol stress reactivity in response to the Trier Social Stress Test (N = 45) were determined. Findings revealed that MD patients exhibited lower HCC compared to controls and GAD patients, with no differences between the latter two groups. Interestingly, when the GAD group was separated into two groups based on MD comorbidity, lower HCC in MD patients were found compared to controls and GAD-noMD patients, but did not show differences when compared to GAD-MD patients. No HCC differences were seen between GAD-MD or GAD-noMD patients and healthy controls. No TSST group differences emerged. Our findings suggest MD to be related to long-term attenuation in cortisol secretion. While no group differences emerged between patients with GAD, neither with nor without MD, and controls, the current results provide tentative evidence that MD determines long-term endocrine changes, with pure GAD showing a distinct pattern. Future studies are needed to confirm our findings in larger samples of pure and comorbid groups.
Klusák J.
2009-12-01
Full Text Available The study of bi-material notches becomes a topical problem as they can model efficiently geometrical or material discontinuities. When assessing crack initiation conditions in the bi-material notches, the generalized stress intensity factors H have to be calculated. Contrary to the determination of the K-factor for a crack in an isotropic homogeneous medium, for the ascertainment of the H-factor there is no procedure incorporated in the calculation systems. The calculation of these fracture parameters requires experience. Direct methods of estimation of H-factors need choosing usually length parameter entering into calculation. On the other hand the method combining the application of the reciprocal theorem (Ψ-integral and FEM does not require entering any length parameter and is capable to extract the near-tip information directly from the far-field deformation.
Local well-posedness to inhomogeneous Ericksen-Leslie system with general Leslie stress tensor
Gong, Huajun; Li, Jinkai; Xu, Chen
2017-02-01
In this paper, we establish the local well-posedness of strong solutions to the Cauchy problem of the density-dependent liquid crystal system, with general Leslie stress tensor, in R^3. By using a biharmonic regularization argument, and making full use of the property of the intrinsic cancellation of the regularized system, we are able to overcome the difficulties caused by the high-order coupling terms, establish some appropriate a priori estimates, which are independent of the regularized parameter, and consequently obtain a strong solution to the original liquid crystal system, by letting the regularization parameter go to zero. The main advantage of the biharmonic regularization is that it does not destroy the property of the intrinsic cancellation of the original system.
Lee, Joyce; Daffern, Michael; Ogloff, James R P; Martin, Trish
2015-02-01
In their daily work, mental health nurses (MHN) are often exposed to stressful events, including patient-perpetrated aggression and violence. Personal safety and health concerns, as well as concern for the physical and psychological well-being of patients, dominate; these concerns have a profound impact on nurses. This cross-sectional study explored and compared the psychological well-being of 196 hospital-based MHN (97 forensic and 99 mainstream registered psychiatric nurses or psychiatric state enrolled nurses). The aim was to examine exposure to inpatient aggression and work stress, and identify factors contributing to the development of post-traumatic stress reactions and general distress. Multiple regression analyses indicated that working in a mainstream setting is associated with increased work stress; however, mainstream and forensic nurses experienced similar psychological well-being. As a group, 14-17% of mainstream and forensic nurses met the diagnostic criteria for post-traumatic stress disorder, and 36% scored above the threshold for psychiatric caseness. A tentative model of post-traumatic stress and general distress in nurses was developed, illustrating the impact of aggression and stress on well-being. The present study affirms that mental health nursing is a challenging and stressful occupation. Implications for organizations, managers, and individual nurses are discussed.
The transverse shear deformation behaviour of magneto-electro-elastic shell
Albarody, Thar M. Badri; Al-Kayiem, Hussain H. [UniversitiTeknologi PETRONAS, Perak (Malaysia); Faris, Waleed [International Islamic University Malaysia, Perak (Malaysia)
2016-01-15
Compared to the large number of possible magneto-electro-elastic shell theories, very few exact solutions determining the in-plane stresses, electric displacements and magnetic inductions are possible. While, solving the magneto-electro-elastic shell equations in terms of thermo-magneto-electro-elastic generalized field functions on arbitrary domains and for general conditions exactly are not always possible. In the present work, a linear version of magneto-electro-elastic shell with simply supported boundary conditions, solved exactly, provided that the lamination scheme is cross-ply or anti-symmetric angle-ply laminates. The exact solution that introduced herein can measure the in-plane stresses, electric displacements and magnetic inductions. It also allow for an accurate and usually elegant and conclusive investigation of the various sensations in a shell structure. However, it is important for micro-electro-mechanical shell applications to have an approach available that gives the transverse shear deformation Behaviour for cases that cannot examine experimentally. An investigated examples were accompanied and noteworthy conclusions were drawn which highlight the issues of the implementation of the exact solution, implication of the effects of the material properties, lay-ups of the constituent layers, and shell parameters on the static Behaviour.
Biomechanics of turtle shells: how whole shells fail in compression.
Magwene, Paul M; Socha, John J
2013-02-01
Turtle shells are a form of armor that provides varying degrees of protection against predation. Although this function of the shell as armor is widely appreciated, the mechanical limits of protection and the modes of failure when subjected to breaking stresses have not been well explored. We studied the mechanical properties of whole shells and of isolated bony tissues and sutures in four species of turtles (Trachemys scripta, Malaclemys terrapin, Chrysemys picta, and Terrapene carolina) using a combination of structural and mechanical tests. Structural properties were evaluated by subjecting whole shells to compressive and point loads in order to quantify maximum load, work to failure, and relative shell deformations. The mechanical properties of bone and sutures from the plastral region of the shell were evaluated using three-point bending experiments. Analysis of whole shell structural properties suggests that small shells undergo relatively greater deformations before failure than do large shells and similar amounts of energy are required to induce failure under both point and compressive loads. Location of failures occurred far more often at sulci than at sutures (representing the margins of the epidermal scutes and the underlying bones, respectively), suggesting that the small grooves in the bone created by the sulci introduce zones of weakness in the shell. Values for bending strength, ultimate bending strain, Young's modulus, and energy absorption, calculated from the three-point bending data, indicate that sutures are relatively weaker than the surrounding bone, but are able to absorb similar amounts of energy due to higher ultimate strain values. Copyright © 2012 Wiley Periodicals, Inc.
2008-01-01
Based on Lazarus and Folkman’s theory about stress and coping, this research aimed at answering questions related to how nurses, who work in two specialized units of a general hospital, evaluate their working environment, their health and how they manage with stressing situations. In the unit of infectious diseases, the nurses’ evaluation of their working environment did not surpass the limits of what is considered as acceptable. In the unit of hematological alterations, the results showed hi...
Nilsen, Cecilie Bræin
2016-01-01
Aim: 1) To investigate prevalence of posttraumatic stress disorder (PTSD) and symptoms of posttraumatic stress (PTSS) in a general intensive care patient population, and risk factors for post ICU-PTSD/PTSS. 2) To investigate how instruments and loss to follow-up could influence the prevalence of PTSD/PTSS in this patient population. Background: Studies have found a wide variance of PTSD/PTSS in this patient population. A number of risk factors were associated with developing post-ICU ...
Britto, Eliane da Silva; Carvalho, Ana Maria Pimenta
2003-12-01
Based on Lazarus and Folkman's theory about stress and coping, this research aimed at answering questions related to how nurses, who work in two specialized units of a general hospital, evaluate their working environment, their health and how they manage with stressing situations. In the unit of infectious diseases, the nurses' evaluation of their working environment did not surpass the limits of what is considered as acceptable. In the unit of hematological alterations, the results showed higher stress levels. In both units, the evaluation of their health was considered as satisfactory and the coping strategies were similar.
Liu, Xiaoguang; Wu, Yan; Chen, Yuanyuan; Xu, Fang; Halliday, Nigel; Gao, Kexiang; Chan, Kok Gan; Cámara, Miguel
2016-04-01
The σ(S) subunit RpoS of RNA polymerase functions as a master regulator of the general stress response in Escherichia coli and related bacteria. RpoS has been reported to modulate biocontrol properties in the rhizobacterium Serratia plymuthica IC1270. However, the role of RpoS in the stress response and biofilm formation in S. plymuthica remains largely unknown. Here we studied the role of RpoS from an endophytic S. plymuthica G3 in regulating these phenotypes. Mutational analysis demonstrated that RpoS positively regulates the global stress response to acid or alkaline stresses, oxidative stress, hyperosmolarity, heat shock and carbon starvation, in addition to proteolytic and chitinolytic activities. Interestingly, rpoS mutations resulted in significantly enhanced swimming motility, biofilm formation and production of the plant auxin indole-3-acetic acid (IAA), which may contribute to competitive colonization and environmental fitness for survival. These findings provide further insight into the strain-specific role of RpoS in the endophytic strain G3 of S. plymuthica, where it confers resistance to general stresses encountered within the plant environment. The heterogeneous functionality of RpoS in rhizosphere and endophytic S. plymuthica populations may provide a selective advantage for better adaptation to various physiological and environmental stresses.
The Lamé equation in shell membrane theory
Schief, W. K.; Szereszewski, A.; Rogers, C.
2007-07-01
A classical nonlinear shell membrane system has recently been demonstrated to have underlying integrable structure. Here, a wide class of corresponding parallel membranes is shown to be generated via a Schrödinger equation of Lamé type. This class is characterized by the existence of a multiplicity of stress distributions for a given membrane geometry. A variety of viable membrane geometries such as generalized Dupin cyclides are constructed explicitly together with the associated one-parameter families of stress resultants. A Lax pair which encapsulates both the Gauss-Mainardi-Codazzi and constrained equilibrium equations is also recorded.
Alastalo, Hanna
2013-01-01
Experienced stress in childhood might have been so severe that it has effects throughout the life course. It has been suggested that early life stress may extend consequences on psychological and physical well-being. Previous findings focusing upon consequences of early life stress are however limited and mostly based upon retrospective studies. Still little is known about the consequences of early life stress, such as war separation on physical health from a longitudinal aspect. This th...
Functional ecological genomics to demonstrate general and specific responses to abiotic stress
Roelofs, D.; Aarts, M.G.M.; Schat, H.; Straalen, van N.M.
2008-01-01
1. Stress is a major component of natural selection in soil ecosystems. The most prominent abiotic stress factors in the field are temperature extremes (heat, cold), dehydration (drought), high salinity and specific toxic compounds such as heavy metals. Organisms are able to deal with these stresses
Schibalski, J V; Müller, M; Ajdacic-Gross, V; Vetter, S; Rodgers, S; Oexle, N; Corrigan, P W; Rössler, W; Rüsch, N
2017-04-01
It is unclear whether mental illness stigma affects individuals with subthreshold syndromes outside clinical settings. We therefore investigated the role of different stigma variables, including stigma-related stress and shame reactions, for avoidant stigma coping among members of the general population with elevated symptom levels. Based on a representative population survey, general stress resilience, stigma variables, shame about having a mental illness as well as avoidant stigma coping (secrecy and social withdrawal) were assessed by self-report among 676 participants with elevated symptom levels. Stigma variables and resilience were examined as predictors of avoidant stigma coping in a path model. Increased stigma stress was predicted by lower general stress resilience as well as by higher levels of perceived stigma, group identification and perceived legitimacy of discrimination. More shame was associated with higher perceived legitimacy. Lower resilience as well as more perceived stigma, group identification and perceived legitimacy predicted avoidant coping. Stigma stress partly mediated effects of resilience, perceived stigma and group identification on avoidant coping; shame partly mediated effects of perceived legitimacy on coping. Stigma stress and shame were also directly and positively related to avoidant stigma coping. Analyses were adjusted for symptoms, neuroticism and sociodemographic variables. Stigma may affect a larger proportion of the population than previously thought because stigma variables predicted secrecy and withdrawal among members of the general population with elevated, but overall mild symptom levels. Avoidant stigma coping likely has harmful effects, potentially exacerbating pre-existing psychological distress and undermining social networks. This highlights the need to reduce public stigma as well as to support individuals with subthreshold syndromes in their coping with stigma stress and shame reactions. Copyright © 2017
Modeling Technique and Stress Analysis of the Main Gear Box Shell%汽车主减速器壳体的建模技术和应力分析
关锋
2015-01-01
利用Pro/E软件建立汽车主减速器壳体的三维模型，然后将其导入ANSYS中，建立有限元力学模型。通过ANSYS分析计算，得到主减速器壳体应力大小和分布图形，分析结果为结构优化提供了理论依据。%The 3D solid model of the main gear box shell is built by using the Pro/E software, and the finite element analyzing is then established after importing the model into ANSYS. Through the ANSYS, the stress intensity and distribution graph of the main gear box shell are acquired. The analysis results may provide a theoretical basis for its structural optimization design.
Herrou, Julien; Willett, Jonathan W.; Czyż, Daniel M.; Babnigg, Gyorgy; Kim, Youngchang; Crosson, Sean; Stock, Ann M.
2016-12-19
Herrou, Julien; Rotskoff, Grant; Luo, Yun; Roux, Benoît; Crosson, Sean
2012-05-22
α-Proteobacteria uniquely integrate features of two-component signal transduction (TCS) and alternative sigma factor (σ) regulation to control transcription in response to general stress. The core of this regulatory system is the PhyR protein, which contains a σ-like (SL) domain and a TCS receiver domain. Aspartyl phosphorylation of the PhyR receiver in response to stress signals promotes binding of the anti-σ factor, NepR, to PhyR-SL. This mechanism, whereby NepR switches binding between its cognate σ factor and phospho-PhyR (PhyR∼P), controls transcription of the general stress regulon. We have defined the structural basis of the PhyR∼P/NepR interaction in Caulobacter crescentus and characterized the effect of aspartyl phosphorylation on PhyR structure by molecular dynamics simulations. Our data support a model in which phosphorylation of the PhyR receiver domain promotes its dissociation from the PhyR-SL domain, which exposes the NepR binding site. A highly dynamic loop-helix region (α3-α4) of the PhyR-SL domain plays an important role in PhyR∼P binding to NepR in vitro, and in stress-dependent activation of transcription in vivo. This study provides a foundation for understanding the protein-protein interactions and protein structural dynamics that underpin general stress adaptation in a large and metabolically diverse clade of the bacterial kingdom.
李磊鑫; 刘勇; 陈炉云
2016-01-01
文章重点研究了焊接残余应力对环肋圆柱壳水下声辐射的影响。通过运用热弹塑性有限元法数值模拟环肋圆柱壳对接焊接过程，得到厚板环形焊缝的三维残余应力场和应变场，然后对含有残余应力的环肋圆柱壳动力特性进行研究，并运用有限元法和边界元法分析了低频激励下其水下声辐射的特点。研究结果表明焊接残余应力对环肋圆柱壳声辐射有较明显的影响，不仅使声辐射功率曲线和外场声压曲线向低频移动，而且使在大部分激励频率上含有焊接残余应力结构的声辐射功率和外场声压均大于无焊接残余应力结构。%This paper focuses on the influence of welding residual stress on underwater acoustic radiation of ring stiffened cylindrical shell. The thermal elastic-plastic finite element method is used to simulate ring stiffened cylindrical shell butt welding process and to calculate the three-dimensional welding-induced residual stress and strain field. And the dynamic characteristic of ring stiffened cylindrical shell with residu-al stress is investigated. Finally, its acoustic radiation is solved by combining direct boundary element method with finite element method. The results show that residual stress has a significant impact on underwater a-coustic radiation of ring stiffened cylindrical shell under low frequency excitation. It makes acoustic radia-tion power and sound pressure curve integrally move toward lower frequency, and makes acoustic radiation power and sound pressure increase at most excitation frequencies comparing with structure without residual stress.
Ho, Chiu Man; Okada, Nobuchika
2014-01-01
Supersymmetry does not dictate the way we should quantize the fields in the supermultiplets, and so we have the freedom to quantize the Standard Model (SM) particles and their superpartners differently. We propose a generalized quantization scheme under which a particle can only appear off-shell, while its contributions to quantum corrections are exactly the same as those in the usual quantum field theory. We apply this quantization scheme solely to the sparticles in the $R$-parity preserving...
Romelsjö, A; Hasin, D; Hilton, M
1992-01-01
The relationship between 15 measures of stressful working conditions and high alcohol consumption (35 g 100% ethanol per day or more for men and 25 g or more for women) was studied, using cross-sectional data from a general population survey of 1344 males and 1494 females; the ages 25-64 years...... increased odds ratios were lower when subjects with an alcohol diagnosis at inpatient care during 1980-84 were excluded in the analyses. On the whole, our findings are not conclusive. The strong, but imprecise associations between stressful working conditions and severe alcohol problems, are however......-adjusted odds ratios, were positive and some were negative when high alcohol consumption was the endpoint, but there was a clear variation by sex and social class. Generally the positive associations were stronger among male non-manual employees. Among males, there was a clear association between stressful...
Ebstrup, Jeanette Frost; Eplov, Lene Falgaard; Pisinger, Charlotta
2011-01-01
of neuroticism, extroversion, openness, agreeableness, and conscientiousness, and to explore the role of general self-efficacy (GSE). A population-based cross-sectional study was conducted at the Research Centre for Prevention and Health, Denmark, in 2006-2008. Men and women (N=3471) aged 18-69, were randomly......-significant - whilst neuroticism had a positive association. The associations with agreeableness and openness became positive and significant, respectively, when GSE was included. All five personality-stress models were mediated by GSE, with extroversion and conscientiousness having the strongest mediating effect....... The strongest stress-association was found for neuroticism. GSE was shown to change the impact and interpretation of the personality dimensions on perceived stress. These results indicate that GSE is an important factor to consider in the link between personality and perceived stress....
Nygaard, Egil; Jensen, Tine K.; Dyb, Grete
2012-01-01
The aim of this study was to evaluate the structure of posttraumatic stress reaction factors and their relation to general mental health problems in Norwegian children exposed to the tsunami on December 26, 2004. A total of 133 children and adolescents (ages 6-17) were interviewed 10 months posttsunami using the UCLA PTSD Reaction Index, and 104…
Nannapaneni, P.; Hertwig, F.; Depke, M.; Hecker, M.; Mader, U.; Volker, U.; Steil, L.; Hijum, S.A.F.T. van
2012-01-01
The structure of the SigB-dependent general stress regulon of Bacillus subtilis has previously been characterized by proteomics approaches as well as DNA array-based expression studies. However, comparing the SigB targets published in three previous major transcriptional profiling studies it is obvi
Jun, Won Hee; Lee, Gyungjoo
2017-05-30
To compare anger, anger expression, life stress and social support among female students at a nursing university and a general university and to examine factors affecting anger in each group. University students typically experience constant stress resulting from factors like academic requirements, personal relationships and career decisions; this tends to promote anger. Particularly, nursing students' anger can negatively affect the quality of care that they provide, and also their mental health. Therefore, anger management of nursing students is very important in the training and development of future nurses. Nursing education needs to confirm factors associated with anger of nursing students compared with general university students to develop specific intervention programs for decreasing their anger levels. A descriptive, cross-sectional design was used. Participants were 286 female students (146 from a nursing university and 140 from a general university); they completed self-report surveys examining anger, anger expression, life stress and social support. A stepwise multiple regression analysis was done to identify factors affecting anger. Data were collected from 15 May-10 June 2016. In the stepwise multiple regression analysis, we entered three anger expression factors, eight life stress factors and social support as explanatory variables; factors affecting anger among nursing students were anger-out and same-sex peer relationship stress. In general university students, anger-out, anger-control and anger-in were identified as factors affecting anger. Becoming proficient in beneficial anger expression techniques and reducing stress from same-sex peer relationships will reduce anger among female nursing students. © 2017 John Wiley & Sons Ltd.
Job Stress of Medical Staffs in General Hospital%综合医院一线医务人员工作应激调查
王玉林; 刘碧英; 王锐
2003-01-01
Objective: To explore the job stress status of medical staffs in general hospital. Methods: A total of 201 medical staffs were sampled from a general hospital in Changsha City, Hunan Province, and their job stress levels were evaluated by the Medical Job Stress Invemory. Results:The subjects from internal medicine department showed silgnificantIy higher job stress level than those from surgical departmem;and the doctors group showed higher stress level in the interpersonal subscale than the nurses group. Condusion:It is important to pay attention to medical staff''s job stress and job burnout in order to improve their mental health levels.
On the Calculation of Shallow Shells
Ambartsumyan, S. A.
1956-01-01
This paper considers a sufficiently thin shallow shell of nonzero Gaussian curvature. It also presents a system of symmetrically constructed differential equations, constructed by the mixed method through the stress function and the displpacement function.
School-Related Stress, School Support, and Somatic Complaints: A General Population Study.
Torsheim, Torbjorn; Wold, Bente
2001-01-01
Examined relationship between school-related stress, social support, and somatic complaints among Norwegian adolescents. Found that students with high levels of school-related stress had a higher odds ratio for weekly headache, abdominal pain, backache, dizziness, and coexisting somatic complaints. For social support, associations were weaker, but…
司剑钧
2014-01-01
Liangshui tunnel on Lanzhou-Chongqing railway is located in soft rock of carbon phyllite.The rock has extra-high ground stress,with the maximum horizontal principal stress ranging from 6.5 MPa to 11.3 MPa.In the early stage of the tunnel construction,serious deformation occurred to the primary support structure,which resulted in distorted and fractured steel arches,instability of the support structure and interference of the primary support structure into the lining clearance.Therefore,the distorted primary support structure had to be dismantled and even cracks occurred to the secondary lining at local positions.In the paper,double-shell primary support experiment and double-shell secondary lining experiment are made,so as to solve the above-mentioned problems.In the experiments,the primary support deformation,the surrounding rock pressure,the contact pressure,the steel arch stress,the steel bar stress and the concrete stress are studied.Conclusions drawn are as follows:1 )The deformation of the double-shell primary support is relatively small,the stress of the shotcrete,steel arches,secondary lining concrete and secondary lining steel bars have not exceeded the allowable stresses of these materials,and the double-shell primary support works well;2 )Due to the adoption of the double-shell primary support,the steel bar binding process can be reduced,no additional lining formwork jumbos are needed,the construction organization is more convenient,and construction efficiency is relatively high.%兰渝铁路两水隧道洞身主要通过炭质千枚岩软岩地层，隧道为极高地应力状态，最大水平主应力值为6．5～11．3 MPa。施工前期，隧道初期支护结构变形较大，部分钢拱架扭曲、断裂，支护结构失稳，初期支护结构侵入衬砌净空，拆换拱情况频繁发生，局部地段二次衬砌开裂。针对前期施工中出现的问题，分别开展双层初期支护和双层衬砌试验，对试验段初期支护
Vanhoudt, Nathalie, E-mail: nvanhoud@sckcen.be [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Hasselt University, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Cuypers, Ann [Hasselt University, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Horemans, Nele [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Remans, Tony; Opdenakker, Kelly; Smeets, Karen [Hasselt University, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Bello, Daniel Martinez [Hasselt University, Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Agoralaan Building D, 3590 Diepenbeek (Belgium); Havaux, Michel [Commissariat a l' Energie Atomique (CEA)/Cadarache, Direction des Sciences du Vivant, Departement d' Ecophysiologie Vegetale et de Microbiologie, Laboratoire d' Ecophysiologie de la Photosynthese, 13108 Saint-Paul-lez-Durance (France); Wannijn, Jean; Van Hees, May [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium); Vangronsveld, Jaco [Hasselt University, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek (Belgium); Vandenhove, Hildegarde [Belgian Nuclear Research Center (SCK-CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol (Belgium)
2011-06-15
The cellular redox balance seems an important modulator under heavy metal stress. While for other heavy metals these processes are well studied, oxidative stress related responses are also known to be triggered under uranium stress but information remains limited. This study aimed to further unravel the mechanisms by which plants respond to uranium stress. Seventeen-day-old Arabidopsis thaliana seedlings, grown on a modified Hoagland solution under controlled conditions, were exposed to 0, 0.1, 1, 10 and 100 {mu}M uranium for 1, 3 and 7 days. While in Part I of this study oxidative stress related responses in the roots were discussed, this second Part II discusses oxidative stress related responses in the leaves and general conclusions drawn from the results of the roots and the leaves will be presented. As several responses were already visible following 1 day exposure, when uranium concentrations in the leaves were negligible, a root-to-shoot signaling system was suggested in which plastids could be important sensing sites. While lipid peroxidation, based on the amount of thiobarbituric acid reactive compounds, was observed after exposure to 100 {mu}M uranium, affecting membrane structure and function, a transient concentration dependent response pattern was visible for lipoxygenase initiated lipid peroxidation. This transient character of uranium stress responses in leaves was emphasized by results of lipoxygenase (LOX2) and antioxidative enzyme transcript levels, enzyme capacities and glutathione concentrations both in time as with concentration. The ascorbate redox balance seemed an important modulator of uranium stress responses in the leaves as in addition to the previous transient responses, the total ascorbate concentration and ascorbate/dehydroascorbate redox balance increased in a concentration and time dependent manner. This could represent either a slow transient response or a stable increase with regard to plant acclimation to uranium stress
SPSM and its application in cylindrical shells
NIE Wu; ZHOU Su-lian; PENG Hui
2008-01-01
In naval architectures, the structure of prismatic shell is used widely. But there is no suitable method to analyze this kind of structure. Stiffened prismatic shell method (SPSM) presented in this paper, is one of the harmonic semi-analytic methods. Theoretically, strong stiffened structure can be analyzed economically and accurately. SPSM is based on the analytical solution of the governing differential equations for orthotropic cylindrical shells. In these differential equations, the torsional stiffness, bending stiffness and the exact position of each stiffener are taken into account with the Heaviside singular function. An algorithm is introduced, in which the actions of stiffeners on shells are replaced by external loads at each stiffener position. Stiffened shells can be computed as non-stiffened shells. Eventually, the displacement solution of the equations is acquired by the introduction of Green function. The stresses in a corrugated transverse bulkhead without pier base of an oil tanker are computed by using SPSM.
Early crisis intervention to patients with acute stress disorder in general hospital.
Andoh, Hidehiro; Yamamoto, Kenji; Ichimura, Atsushi; Sato, Shinko; Teraoka, Naoko; Ozono, Hiroko; Kushino, Nobuhisa; Maruyama, Manabu; Matsumoto, Hideo; Yamazaki, Kosuke
2003-04-01
This report presents 2 patients who were diagnosed to have acute stress disorder (ASD), received early psychiatric intervention (crisis intervention as a short-term psychotherapy), and subsequently had good outcome. Encounter with an event that causes psychological trauma may induce post-traumatic stress disorder (PTSD). However, the 2 patients described here have shown no particular mental symptoms for more than 2 years after the event and are leading normal lives. Psychological debriefing as a group used to be regarded as effective for the prevention of PTSD, but early identification of the stress-related disorder and intensive treatment of individual patients is recently considered to be more necessary. Both of the 2 patients presented here showed good outcome, and early crisis intervention in individual patients is suggested to be effective for the treatment of stress-related disorders and prevention of PTSD.
Patterning of the turtle shell.
Moustakas-Verho, Jacqueline E; Cebra-Thomas, Judith; Gilbert, Scott F
2017-08-01
Interest in the origin and evolution of the turtle shell has resulted in a most unlikely clade becoming an important research group for investigating morphological diversity in developmental biology. Many turtles generate a two-component shell that nearly surrounds the body in a bony exoskeleton. The ectoderm covering the shell produces epidermal scutes that form a phylogenetically stable pattern. In some lineages, the bones of the shell and their ectodermal covering become reduced or lost, and this is generally associated with different ecological habits. The similarity and diversity of turtles allows research into how changes in development create evolutionary novelty, interacting modules, and adaptive physiology and anatomy. Copyright © 2017 Elsevier Ltd. All rights reserved.
Transcription of Satellite III non-coding RNAs is a general stress response in human cells
Valgardsdottir, Rut; Chiodi, Ilaria; Giordano, Manuela; Rossi, Antonio; Bazzini, Silvia; Ghigna, Claudia; Riva, Silvano; Biamonti, Giuseppe
2008-01-01
In heat-shocked human cells, heat shock factor 1 activates transcription of tandem arrays of repetitive Satellite III (SatIII) DNA in pericentromeric heterochromatin. Satellite III RNAs remain associated with sites of transcription in nuclear stress bodies (nSBs). Here we use real-time RT-PCR to study the expression of these genomic regions. Transcription is highly asymmetrical and most of the transcripts contain the G-rich strand of the repeat. A low level of G-rich RNAs is detectable in unstressed cells and a 104-fold induction occurs after heat shock. G-rich RNAs are induced by a wide range of stress treatments including heavy metals, UV-C, oxidative and hyper-osmotic stress. Differences exist among stressing agents both for the kinetics and the extent of induction (>100- to 80.000-fold). In all cases, G-rich transcripts are associated with nSBs. On the contrary, C-rich transcripts are almost undetectable in unstressed cells and modestly increase after stress. Production of SatIII RNAs after hyper-osmotic stress depends on the Tonicity Element Binding Protein indicating that activation of the arrays is triggered by different transcription factors. This is the first example of a non-coding RNA whose transcription is controlled by different transcription factors under different growth conditions. PMID:18039709
Deswal, Sunita; Kalkal, Kapil Kumar; Sheoran, Sandeep Singh
2016-09-01
A mathematical model of fractional order two-temperature generalized thermoelasticity with diffusion and initial stress is proposed to analyze the transient wave phenomenon in an infinite thermoelastic half-space. The governing equations are derived in cylindrical coordinates for a two dimensional axi-symmetric problem. The analytical solution is procured by employing the Laplace and Hankel transforms for time and space variables respectively. The solutions are investigated in detail for a time dependent heat source. By using numerical inversion method of integral transforms, we obtain the solutions for displacement, stress, temperature and diffusion fields in physical domain. Computations are carried out for copper material and displayed graphically. The effect of fractional order parameter, two-temperature parameter, diffusion, initial stress and time on the different thermoelastic and diffusion fields is analyzed on the basis of analytical and numerical results. Some special cases have also been deduced from the present investigation.
Monzon, M. D.; Marrero, M. D.; Benitez, A. N.; Hernandez, P. M.
2005-07-01
This study deals with a research field started at the LFI (Laboratorio de Fabricacion Integrada) of the ULPGC (Universidad de Las Palmas de Gran Canaria). Its aim is to analyse and propose improvements in the electroformed nickel cores manufacture. The main application of these cores is to be used as plastic injection molds. It has been considered an important part of this study taking under consideration internal stresses that appear in the nickel electroformed core. These stresses play a determinant role towards reaching a dimensional and resistant quality standard of the shells, which will be later transformed into cores. The investigation includes not only a theoretic study but also an experimental one. the testing method has the remarkable advantage of a wide industrial application because of its simplicity, low cost and reproducibility of the electrolytic bath actual conditions. (Author) 7 refs.
NIF Double Shell outer-shell experiments
Merritt, E. C.; Montgomery, D. S.; Kline, J. L.; Daughton, W. S.; Wilson, D. C.; Dodd, E. S.; Renner, D. B.; Cardenas, T.; Batha, S. H.
2016-10-01
At the core of the Double Shell concept is the kinetic energy transfer from the outer shell to the inner shell via collision. This collision sets both the implosion shape of the inner shell, from imprinting of the shape of the outer shell, as well as the maximum energy available to compress the DT fuel. Therefore, it is crucial to be able to control the time-dependent shape of the outer shell, such that the outer shell is nominally round at the collision time. We present the experiment results from our sub-scale ( 1 MJ) NIF outer-shell only shape tuning campaign, where we vary shape by changing a turn-on time delay between the same pulse shape on the inner and outer cone beams. This type of shape tuning is unique to this platform and only possible since the Double Shell design uses a single-shock drive (4.5 ns reverse ramp pulse). The outer-shell only targets used a 5.75 mm diameter standard near-vacuum NIF hohlraum with 0.032 mg/cc He gas fill, and a Be capsule with 0.4% uniform Cu dopant, with 242 um thick ablator. We also present results from a third outer-shell only shot used to measure shell trajectory, which is critical in determining the shell impact time. This work conducted under the auspices of the U.S. DOE by LANL under contract DE-AC52-06NA25396.
Suldo, Shannon M; Shaunessy, Elizabeth; Thalji, Amanda; Michalowski, Jessica; Shaffer, Emily
2009-01-01
Navigating puberty while developing independent living skills may render adolescents particularly vulnerable to stress, which may ultimately contribute to mental health problems (Compas, Orosan, & Grant, 1993; Elgar, Arlett, & Groves, 2003). The academic transition to high school presents additional challenges as youth are required to interact with a new and larger peer group and manage greater academic expectations. For students enrolled in academically rigorous college preparatory programs, such as the International Baccalaureate (IB) program, the amount of stress perceived may be greater than typical (Suldo, Shaunessy, & Hardesty, 2008). This study investigated the environmental stressors and psychological adjustment of 162 students participating in the IB program and a comparison sample of 157 students in general education. Factor analysis indicated students experience 7 primary categories of stressors, which were examined in relation to students' adjustment specific to academic and psychological functioning. The primary source of stress experienced by IB students was related to academic requirements. In contrast, students in the general education program indicated higher levels of stressors associated with parent-child relations, academic struggles, conflict within family, and peer relations, as well as role transitions and societal problems. Comparisons of correlations between categories of stressors and students' adjustment by curriculum group reveal that students in the IB program reported more symptoms of psychopathology and reduced academic functioning as they experienced higher levels of stress, particularly stressors associated with academic requirements, transitions and societal problems, academic struggles, and extra-curricular activities. Applied implications stem from findings suggesting that students in college preparatory programs are more likely to (a) experience elevated stress related to academic demands as opposed to more typical adolescent
Le Page, Yvon; Saxe, Paul
2002-03-01
A symmetry-general approach for the least-squares, therefore precise, extraction of elastic coefficients for strained materials is reported. It analyzes stresses calculated ab initio for properly selected strains. The problem, its implementation, and its solution strategy all differ radically from a previous energy-strain approach that we published last year, but the normal equations turn out to be amenable to the same constrainment scheme that makes both approaches symmetry general. The symmetry considerations governing the automated selection of appropriately strained models and their Cartesian systems are detailed. The extension to materials under general stress is discussed and implemented. VASP was used for ab initio calculation of stresses. A comprehensive range of examples includes a triclinic material (kyanite) and simple materials with a range of symmetries at zero pressure, MgO under hydrostatic pressure, Ti4As3 under [001] uniaxial strain, and Si under [001] uniaxial stress. The MgO case agrees with recent experimental work including elastic coefficients as well as their first and second derivatives. The curves of elastic coefficients for Si show a gradual increase in the 33 compliance coefficient, leading to a collapse of the material at -11.7 GPa, compared with -12.0 GPa experimentally. Interpretation of results for Be using two approximations [local density (LDA), generalized gradient (GGA)], two approaches (stress strain and energy strain), two potential types (projector augmented wave and ultrasoft), and two quantum engines (VASP and ORESTES) expose the utmost importance of the cell data used for the elastic calculations and the lesser importance of the other factors. For stiffness at relaxed cell data, differences are shown to originate mostly in the considerable overestimation of the residual compressive stresses at x-ray cell data by LDA, resulting in a smaller relaxed cell, thus larger values for diagonal stiffness coefficients. The symmetry
Stiffeners in variational-difference method for calculating shells with complex geometry
Ivanov Vyacheslav Nikolaevich
2014-05-01
equated to zero in order to minimize the total potential energy. As an example a parabolic-sinusoidal shell with a stiffened hole is analyzed. It is shown that ribs have generally beneficial effect to the zone of the opening: cause a reduction in a modulus of a stress, but an eccentricity affects differently, so material properties and design solutions should be taken into account in an analysis.
A. M. Abd-Alla
2011-01-01
Full Text Available The surface waves propagation in generalized magneto-thermo-viscoelastic granular medium subjected to continuous boundary conditions has been investigated. In addition, it is also subjected to thermal boundary conditions. The solution of the more general equations are obtained for thermoelastic coupling. The frequency equation of Rayleigh waves is obtained in the form of a determinant containing a term involving the coefficient of friction of a granular media which determines Rayleigh waves velocity as a real part and the attenuation coefficient as an imaginary part, and the effects of rotation, magnetic field, initial stress, viscosity, and gravity field on Rayleigh waves velocity and attenuation coefficient of surface waves have been studied in detail. Dispersion curves are computed numerically for a specific model and presented graphically. Some special cases have also been deduced. The results indicate that the effect of rotation, magnetic field, initial stress, and gravity field is very pronounced.
Romelsjö, A; Hasin, D; Hilton, M
1992-01-01
The relationship between 15 measures of stressful working conditions and high alcohol consumption (35 g 100% ethanol per day or more for men and 25 g or more for women) was studied, using cross-sectional data from a general population survey of 1344 males and 1494 females; the ages 25-64 years...... in metropolitan Stockholm in 1984. In a longitudinal component of the study, hospitalization and mortality with alcohol-related diagnosis was assessed during 1984-90, and also the association between previous experience of unemployment and high alcohol consumption. Some of the associations, expressed as age......-adjusted odds ratios, were positive and some were negative when high alcohol consumption was the endpoint, but there was a clear variation by sex and social class. Generally the positive associations were stronger among male non-manual employees. Among males, there was a clear association between stressful...
Jones, Rupert CM; Chung, Man C; Berger, Zoë; Campbell, John L.
2007-01-01
Reported prevalence of myocardial infarction-related post-traumatic stress disorder (PTSD) varies from 0 to 25%. PTSD after myocardial infarction may affect quality of life, cardiovascular outcomes, and health service usage. Of 164 patients with previous myocardial infarction, 111 participated in the study and 36 had PTSD, giving a prevalence of 32%; the lowest possible estimate being 22%. PTSD was associated with significantly worse general health than that of individuals without PTSD. Preva...
2013-01-01
Purpose: We aimed to clarify whether personality traits and work-related attitudes affect job stress among medical care professionals. Methods: Subjects were 455 nurses (59 males, 396 females) working in general hospitals. Seven dimensions of personality traits, i.e., novelty seeking (NS), harm avoidance (HA), reward dependence (RD), persistence (P), self-directedness (SD), cooperativeness (C) and selftranscendence (ST), were assessed by using the Temperament Character Inventory-125. A 15-ite...
Istrate, Nicolae; Lindner, John
2014-03-01
We design an Earth-like artificial gravity field using the Darmois-Israel junction conditions of general relativity to connect the flat spacetime outside an infinitesimally thin cylinder to the curved spacetime inside. In the calculation of extrinsic curvature, our construction exploits Earth's weak gravity, which implies similar inside and outside curvatures, to approximate the unit normal inside by the negative unit normal outside. The stress-energy distribution on the cylinder's sides includes negative energy density.
... diabetes. Shopdiabetes.org: Your Stress-Free System for Family Dinners! - 2017-03-book-oclock-scramble.html Shopdiabetes.org Your Stress-Free System for Family Dinners! A year of delicious meals to help prevent ...
... sudden negative change, such as losing a job, divorce, or illness Traumatic stress, which happens when you ... stress, so you can avoid more serious health effects. NIH: National Institute of Mental Health
The parasite-stress theory may be a general theory of culture and sociality.
Fincher, Corey L; Thornhill, Randy
2012-04-01
In the target article, we presented the hypothesis that parasite-stress variation was a causal factor in the variation of in-group assortative sociality, cross-nationally and across the United States, which we indexed with variables that measured different aspects of the strength of family ties and religiosity. We presented evidence supportive of our hypothesis in the form of analyses that controlled for variation in freedom, wealth resources, and wealth inequality across nations and the states of the USA. Here, we respond to criticisms from commentators and attempt to clarify and expand the parasite-stress theory of sociality used to fuel our research presented in the target article.
Thermal stress response of General Purpose Heat Source (GPHS) aeroshell material
Grinberg, I. M.; Hulbert, L. E.; Luce, R. G.
1980-01-01
A thermal stress test was conducted to determine the ability of the GPHS aeroshell 3 D FWPF material to maintain physical integrity when exposed to a severe heat flux such as would occur from prompt reentry of GPHS modules. The test was performed in the Giant Planetary Facility at NASA's Ames Research Center. Good agreement was obtained between the theoretical and experimental results for both temperature and strain time histories. No physical damage was observed in the test specimen. These results provide initial corroboration both of the analysis techniques and that the GPHS reentry member will survive the reentry thermal stress levels expected.
Isogeometric shell formulation based on a classical shell model
Niemi, Antti
2012-09-04
This paper constitutes the first steps in our work concerning isogeometric shell analysis. An isogeometric shell model of the Reissner-Mindlin type is introduced and a study of its accuracy in the classical pinched cylinder benchmark problem presented. In contrast to earlier works [1,2,3,4], the formulation is based on a shell model where the displacement, strain and stress fields are defined in terms of a curvilinear coordinate system arising from the NURBS description of the shell middle surface. The isogeometric shell formulation is implemented using the PetIGA and igakit software packages developed by the authors. The igakit package is a Python package used to generate NURBS representations of geometries that can be utilised by the PetIGA finite element framework. The latter utilises data structures and routines of the portable, extensible toolkit for scientific computation (PETSc), [5,6]. The current shell implementation is valid for static, linear problems only, but the software package is well suited for future extensions to geometrically and materially nonlinear regime as well as to dynamic problems. The accuracy of the approach in the pinched cylinder benchmark problem and present comparisons against the h-version of the finite element method with bilinear elements. Quadratic, cubic and quartic NURBS discretizations are compared against the isoparametric bilinear discretization introduced in [7]. The results show that the quadratic and cubic NURBS approximations exhibit notably slower convergence under uniform mesh refinement as the thickness decreases but the quartic approximation converges relatively quickly within the standard variational framework. The authors future work is concerned with building an isogeometric finite element method for modelling nonlinear structural response of thin-walled shells undergoing large rigid-body motions. The aim is to use the model in a aeroelastic framework for the simulation of flapping wings.
Stress-related mental disorders with sick leave: a minimal intervention in general practice
Bakker, I.M.
2007-01-01
1. Introduction As stated in chapter 1, this study is carried out because patients and their care-givers have much to gain by the development and implementation of effective care for patients on sick leave having stress-related mental disorders (SMDs). Most people having SMDs with sick leave consult
Oral manifestations of stress-related disorders in the general population of Ludhiana
Damanpreet Kaur
2016-01-01
Full Text Available Introduction: Oral diseases associated with psychological disorders have long been known in medicine. Emotional as well as psychological factors may act as significant risk factors in the initiation and progression of oromucosal diseases. Aims and Objectives: The aim of this study was to determine a correlation between stress and development of certain oral conditions such as lichen planus, myofacial pain dysfunction syndrome, xerostomia, bruxism, aphthous ulcers, and burning mouth syndrome. Materials and Methods: An observational comparative study was conducted among patients reporting to the Department of Oral Medicine and Radiology. A total of 130 patients gave a positive history of oral lesions, out of which 62 were stress related and the other 68 patients served as the control group (oral lesions with no history of stress. All these patients were subjected to routine systemic and oral examination. The results obtained were statistically compared using P value, t-test, and Chi-square test. Results: It was found that lichen planus and burning mouth syndrome were more common in females and myofacial pain dysfunction syndrome was prevalent in males. Xerostomia was found to increase with age. Conclusion: It was concluded that, though the etiology of most oral lesions is not known, the role of stress and other psychogenic factors cannot be ruled out in their occurrence.
Stress-related mental disorders with sick leave: a minimal intervention in general practice
Bakker, I.M.
2007-01-01
1. Introduction As stated in chapter 1, this study is carried out because patients and their care-givers have much to gain by the development and implementation of effective care for patients on sick leave having stress-related mental disorders (SMDs). Most people having SMDs with sick leave consult
Vahdat Haji Hoseinlou
2015-08-01
Conclusion: Based on the results of this study, parasitic infection (intestinal protozoa as a stressor factor can increase serum cortisol concentration. In addition, intestinal protozoa was reduced immune system sensitivity and function. It seems that the neutrophil to lymphocyte ratio can be a potential useful parameters for evaluating the stress system activity and function in patients infected with the intestinal protozoa.
Cook-Cottone, Catherine
2004-01-01
Childhood, in our culture, does not preclude exposure to trauma. Sexual abuse, physical abuse, natural disaster, urban violence, school violence, and terrorism result in significant numbers of children with posttraumatic stress disorder (PTSD) symptomatology. Many factors contribute to symptomatic expression, with some children showing few effects…
Quantum corrected Schwarzschild thin-shell wormhole
Jusufi, Kimet [State University of Tetovo, Physics Department, Tetovo (Macedonia, The Former Yugoslav Republic of)
2016-11-15
Recently, Ali and Khalil (Nucl Phys B, 909, 173-185, 2016), based on Bohmian quantum mechanics, derived a quantum corrected version of the Schwarzschild metric. In this paper, we construct a quantum corrected Schwarzschild thin-shell wormhole (QSTSW) and investigate the stability of this wormhole. First we compute the surface stress at the wormhole throat by applying the Darmois-Israel formalism to the modified Schwarzschild metric and show that exotic matter is required at the throat to keep the wormhole stable. We then study the stability analysis of the wormhole by considering phantom-energy for the exotic matter, generalized Chaplygin gas (GCG), and the linearized stability analysis. It is argued that quantum corrections can affect the stability domain of the wormhole. (orig.)
Quantum corrected Schwarzschild thin-shell wormhole
Jusufi, Kimet
2016-11-01
Recently, Ali and Khalil (Nucl Phys B, 909, 173-185, 2016), based on Bohmian quantum mechanics, derived a quantum corrected version of the Schwarzschild metric. In this paper, we construct a quantum corrected Schwarzschild thin-shell wormhole (QSTSW) and investigate the stability of this wormhole. First we compute the surface stress at the wormhole throat by applying the Darmois-Israel formalism to the modified Schwarzschild metric and show that exotic matter is required at the throat to keep the wormhole stable. We then study the stability analysis of the wormhole by considering phantom-energy for the exotic matter, generalized Chaplygin gas (GCG), and the linearized stability analysis. It is argued that quantum corrections can affect the stability domain of the wormhole.
Quantum Corrected Schwarzschild Thin Shell Wormhole
Jusufi, Kimet
2016-01-01
Recently, Ali and Khalil \\cite{ahmed}, based on the Bohmian quantum mechanics derived a quantum corrected version of the Schwarzschild metric. In this paper, we construct a quantum corrected Schwarzschild thin shell wormhole (QSTSW) and investigate the stability of this wormhole. First we compute the surface stress at the wormhole throat by applying the Darmois-Israel formalism to the modified Schwarzschild metric and show that exotic matter is required at the throat to keep the wormhole stable. We then study the stability analysis of the wormhole by considering phantom-energy for the exotic matter, generalized Chaplygin gas (GCG), and the linearized stability analysis. It is argued that, quantum corrections can affect the stability domain of the wormhole.
Bockers, Estelle; Roepke, Stefan; Michael, Lars; Renneberg, Babette; Knaevelsrud, Christine
2016-02-01
Posttraumatic stress disorder (PTSD) and interpersonal traumatization are frequently associated with trauma-related guilt and shame. However, research on generalized guilt and shame in PTSD is lacking. The aim of this study was to investigate generalized explicit and implicit guilt and shame in interpersonal traumatization and PTSD. Interpersonally traumatized women either with PTSD (n = 28) or without PTSD (n = 32) and 32 nontraumatized women completed the Test of Self-Conscious Affect-3 and the Implicit Association Test to measure explicit and implicit guilt and shame. Explicit guilt and shame were significantly higher in women with PTSD than in traumatized women without PTSD. Traumatized women without PTSD showed significantly higher levels of explicit guilt and shame than nontraumatized women did. PTSD was associated with implicit guilt but not implicit shame. In addition to trauma-related guilt and shame, generalized explicit guilt and shame and implicit guilt seem to play a crucial role in PTSD.
Spherical thin-shell wormholes and modified Chaplygin gas
Sharif, M.; Azam, M., E-mail: msharif.math@pu.edu.pk, E-mail: azammath@gmail.com [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan)
2013-05-01
The purpose of this paper is to construct spherical thin-shell wormhole solutions through cut and paste technique and investigate the stability of these solutions in the vicinity of modified Chaplygin gas. The Darmois-Israel formalism is used to formulate the stresses of the surface concentrating the exotic matter. We explore the stability of the wormhole solutions by using the standard potential method. We conclude that there exist more stable as well as unstable solutions than the previous study with generalized Chaplygin gas [19].
Mixed isoparametric finite element models of laminated composite shells
Noor, A. K.; Andersen, C. M.
1977-01-01
Mixed shear-flexible isoparametric elements are presented for the stress and free vibration analysis of laminated composite shallow shells. Both triangular and quadrilateral elements are considered. The 'generalized' element stiffness, consistent mass, and consistent load coefficients are obtained by using a modified form of the Hellinger-Reissner mixed variational principle. Group-theoretic techniques are used in conjunction with computerized symbolic integration to obtain analytic expressions for the stiffness, mass and load coefficients. A procedure is outlined for efficiently handling the resulting system of algebraic equations. The accuracy of the mixed isoparametric elements developed is demonstrated by means of numerical examples, and their advantages over commonly used displacement elements are discussed.
Akbar, S; Price, C W
1996-10-24
In the bacterium Bacillus subtilis (Bs), the alternative transcription factor sigma B is activated by environmental stresses to control the expression of a large set of unlinked genes. However, the range of physiological functions mediated by these sigma B-controlled genes is presently unknown. We report here that the newly identified gene csbB is under the dual control of a sigma B-dependent and a sigma B-independent promoter. The predicted product of csbB is a 329 residue protein containing two potential membrane-spanning segments in its C-terminal region, leading us to speculate that one class of sigma B-controlled genes acts to modify the cell envelope as part of the general stress response.
Burke, F J Trevor; Crisp, Russell J; James, Ali; Mackenzie, Louis; Thompson, Owen; Pal, A; Sands, Peter; Palin, William M
2017-06-01
This paper evaluates the five year clinical evaluation of restorations formed in a low shrinkage stress resin composite material (3M ESPE Filtek Silorane, Seefeld, Germany) and placed in the general dental practices of five members of the PREP Panel, a group of UK practice-based researchers. Results indicated satisfactory performance of the material under evaluation, other than for marginal staining, which affected 60% of the restorations evaluated after five years, albeit with less than 10% of the circumference of the restorations being affected. The low shrinkage stress material, Filtek Silorane™, demonstrated good clinical performance in the majority of parameters which were assessed at five years. Copyright© 2017 Dennis Barber Ltd.
Priestley, Jessica R C; Buelow, Matthew W; McEwen, Scott T; Weinberg, Brian D; Delaney, Melanie; Balus, Sarah F; Hoeppner, Carlyn; Dondlinger, Lynn; Lombard, Julian H
2013-09-01
We investigated the effect of suppressing plasma angiotensin II (ANG II) levels on arteriolar relaxation in the hamster cheek pouch. Arteriolar diameters were measured via television microscopy during short-term (3-6days) high salt (HS; 4% NaCl) diet and angiotensin converting enzyme (ACE) inhibition with captopril (100mg/kg/day). ACE inhibition and/or HS diet eliminated endothelium-dependent arteriolar dilation to acetylcholine, endothelium-independent dilation to the NO donor sodium nitroprusside, the prostacyclin analogs carbacyclin and iloprost, and the KATP channel opener cromakalim; and eliminated arteriolar constriction during KATP channel blockade with glibenclamide. Scavenging of superoxide radicals and low dose ANG II infusion (25ng/kg/min, subcutaneous) reduced oxidant stress and restored arteriolar dilation in arterioles of HS-fed hamsters. Vasoconstriction to topically-applied ANG II was unaffected by HS diet while arteriolar responses to elevation of superfusion solution PO2 were unaffected (5% O2, 10% O2) or reduced (21% O2) by HS diet. These findings indicate that sustained exposure to low levels of circulating ANG II leads to widespread dysfunction in endothelium-dependent and independent vascular relaxation mechanisms in cheek pouch arterioles by increasing vascular oxidant stress, but does not potentiate O2- or ANG II-induced constriction of arterioles in the distal microcirculation of normotensive hamsters. Copyright © 2013 Elsevier Inc. All rights reserved.
Nemeth, Michael P.
2010-01-01
A comprehensive development of nondimensional parameters and equations for nonlinear and bifurcations analyses of quasi-shallow shells, based on the Donnell-Mushtari-Vlasov theory for thin anisotropic shells, is presented. A complete set of field equations for geometrically imperfect shells is presented in terms general of lines-of-curvature coordinates. A systematic nondimensionalization of these equations is developed, several new nondimensional parameters are defined, and a comprehensive stress-function formulation is presented that includes variational principles for equilibrium and compatibility. Bifurcation analysis is applied to the nondimensional nonlinear field equations and a comprehensive set of bifurcation equations are presented. An extensive collection of tables and figures are presented that show the effects of lamina material properties and stacking sequence on the nondimensional parameters.
Aas, Monica; Steen, Nils E; Agartz, Ingrid; Aminoff, Sofie R; Lorentzen, Steinar; Sundet, Kjetil; Andreassen, Ole A; Melle, Ingrid
2012-08-15
Schizophrenia spectrum and bipolar disorder are characterized by high levels of childhood trauma as well as of cognitive dysfunction. Our aim is to investigate the association between these two factors in the largest study in the literature so far. A total of 406 patients with schizophrenia spectrum- or bipolar disorders were recruited from a catchment area based organization in Oslo, Norway. Information about early life stress was obtained using the Childhood Trauma Questionnaire (CTQ). Cognitive function was assessed through a comprehensive and standardized neuropsychological test battery. Physical abuse, sexual abuse and physical neglect were significantly associated with reduced scores on working memory and executive function scales (p=0.04 to pIntelligence (WASI) (p=0.059 to pdisorders, in particular working memory and executive function as well as general cognition. Moreover, these dysfunctions seem to be driven by underlying deficits in general cognitive tasks as measured by the WASI.
Left ventricular wall stress compendium.
Zhong, L; Ghista, D N; Tan, R S
2012-01-01
Left ventricular (LV) wall stress has intrigued scientists and cardiologists since the time of Lame and Laplace in 1800s. The left ventricle is an intriguing organ structure, whose intrinsic design enables it to fill and contract. The development of wall stress is intriguing to cardiologists and biomedical engineers. The role of left ventricle wall stress in cardiac perfusion and pumping as well as in cardiac pathophysiology is a relatively unexplored phenomenon. But even for us to assess this role, we first need accurate determination of in vivo wall stress. However, at this point, 150 years after Lame estimated left ventricle wall stress using the elasticity theory, we are still in the exploratory stage of (i) developing left ventricle models that properly represent left ventricle anatomy and physiology and (ii) obtaining data on left ventricle dynamics. In this paper, we are responding to the need for a comprehensive survey of left ventricle wall stress models, their mechanics, stress computation and results. We have provided herein a compendium of major type of wall stress models: thin-wall models based on the Laplace law, thick-wall shell models, elasticity theory model, thick-wall large deformation models and finite element models. We have compared the mean stress values of these models as well as the variation of stress across the wall. All of the thin-wall and thick-wall shell models are based on idealised ellipsoidal and spherical geometries. However, the elasticity model's shape can vary through the cycle, to simulate the more ellipsoidal shape of the left ventricle in the systolic phase. The finite element models have more representative geometries, but are generally based on animal data, which limits their medical relevance. This paper can enable readers to obtain a comprehensive perspective of left ventricle wall stress models, of how to employ them to determine wall stresses, and be cognizant of the assumptions involved in the use of specific models.
Multiple shells in IRC+10216: shell properties
Mauron, N.; Huggins, P. J.
2000-07-01
We report on the properties of the multiple shells in the circumstellar envelope of IRC+10216, using deep optical imaging, including data from the Hubble Space Telescope. The intensity profiles confirm the presence of thin ( ~ 0farcs5 -3'' ec), limb-brightened shells in the envelope, seen in stellar and ambient Galactic light scattered by dust. The shells are spaced at irregular intervals of ~ 5'' ec-20'' ec, corresponding to time scales of 200-800 yr, although intervals as short as ~ 1'' ec (40 yr) are seen close to the star. The location of the main shells shows a good correlation with high-resolution, molecular line maps of the inner envelope, indicating that the dust and gas are well coupled. The shell/intershell density contrast is typically ~ 3, and we find that the shells form the dominant mass component of the circumstellar envelope. The shells exhibit important evolutionary effects: the thickness increases with increasing radius, with an effective dispersion velocity of 0.7 km s-1 and there is evidence for shell interactions. Despite the presence of bipolar structure close to the star, the global shell pattern favors a roughly isotropic, episodic mass loss mechanism, with a range of time scales. Based on observations made with the Canada-France-Hawaii telescope, operated by CNRS, NRCC and UH, and on dearchived observations made with the NASA/ESA Hubble Space Telescope, operated by AURA Inc., under NASA contract NAS5-26555
Yamaguchi, Yoshie
2010-01-01
The purpose of this study was to identify the current status of operations at community general support centers which provide coordination for elderly care and the correlation of personal traits, work environment and the occupational stress of the staff. Subjects of the study were 251 staff members of community general support centers. The current status of operations at the community general support centers and the personal traits, work environment, effort-remuneration imbalance model (ERI) and general health questionnaire (GHQ) were surveyed. The initial analysis involved a comparison by a chi-square test on: The effort-remuneration ratio (E/R ratio) of personal traits and work environment, risk of over-commitment (OC), and GHQ score. To explore the correlation between the E/R ratio of the three GHQ groups (low, middle and high score groups) and the OC value, one-way analysis of variance was performed. Out of the four basic functions of the community general support centers, 22.0% of the respondents noted that "establishment of a regional, comprehensive/multi-tiered service network" was functioning, and 50.4% of respondents noted that "comprehensive and continuous care management" was functioning. The average effort score was 15.5 +/- 5.3, approximately double the average value of preceding studies. Significant differences found in GHQ scores were related to working hours (pworking hours of 50 h or more" (OR: 10.38, 95% CI: 2.52-42.70), "Unstable employment" (OR: 2.75, 95% CI: 1.22-6.21) and "Anxiety related to task content" (OR: 17.04, 95% CI: 3.57-81.24). Items observed to have significant correlation with OC value risk factors were: "Weekly working hours of 50 h or more" (OR: 8.04, 95% CI: 1.99-32.41) and "Anxiety related to task content" (OR: 4.60, 95% CI: 2.04-10.37). We conclude that the basic functions of the community general support centers are not presently very functional. The stress levels of the community general support center staff are high and
Collip, Dina; Wigman, Johanna T. W.; Myin-Germeys, Inez; Jacobs, Nele; Derom, Catherine; Thiery, Evert; Wichers, Marieke; van Os, Jim
2013-01-01
Subclinical psychotic experiences at the level of the general population are common, forming an extended psychosis phenotype with clinical psychosis. Persistence of subclinical experiences is associated with transition to later mental disorder. Increased daily life stress reactivity is considered an
A theory of latticed plates and shells
Pshenichnon, Gi
1993-01-01
The book presents the theory of latticed shells as continual systems and describes its applications. It analyses the problems of statics, stability and dynamics. Generally, a classical rod deformation theory is applied. However, in some instances, more precise theories which particularly consider geometrical and physical nonlinearity are employed. A new effective method for solving general boundary value problems and its application for numerical and analytical solutions of mathematical physics and reticulated shell theory problems is described. A new method of solving the shell theory's nonli
Industrial mixing techniques for Hanford double-shell tanks
Daymo, E.A.
1997-09-01
Jet mixer pumps are currently the baseline technology for sludge mobilization and mixing in one-million gallon double-shell tanks at the Hanford and Savannah River Sites. Improvements to the baseline jet mixer pump technology are sought because jet mixer pumps have moving parts that may fail or require maintenance. Moreover, jet mixers are relatively expensive, they heat the waste, and, in some cases, may not mobilize enough of the sludge. This report documents a thorough literature search for commercially available applicable mixing technologies that could be used for double-shell tank sludge mobilization and mixing. Textbooks, research articles, conference proceedings, mixing experts, and the Thomas Register were consulted to identify applicable technologies. While there are many commercial methods that could be used to mobilize sludge or mix the contents of a one-million gallon tank, few will work given the geometrical constraints (e.g., the mixer must fit through a 1.07-m-diameter riser) or the tank waste properties (e.g., the sludge has such a high yield stress that it generally does not flow under its own weight). Pulsed fluid jets and submersible Flygt mixers have already been identified at Hanford and Savannah River Sites for double-shell tank mixing applications. While these mixing technologies may not be applicable for double-shell tanks that have a thick sludge layer at the bottom (since too many of these mixers would need to be installed to mobilize most of the sludge), they may have applications in tanks that do not have a settled solids layer. Retrieval projects at Hanford and other U.S. Department of Energy sites are currently evaluating the effectiveness of these mixing techniques for tank waste applications. The literature search did not reveal any previously unknown technologies that should be considered for sludge mobilization and mixing in one-million gallon double-shell tanks.
Boron Stress Activates the General Amino Acid Control Mechanism and Inhibits Protein Synthesis
Uluisik, Irem; Kaya, Alaattin; Fomenko, Dmitri E.; Karakaya, Huseyin C.; Carlson, Bradley A.; Gladyshev, Vadim N.; Koc, Ahmet
2011-01-01
Boron is an essential micronutrient for plants, and it is beneficial for animals. However, at high concentrations boron is toxic to cells although the mechanism of this toxicity is not known. Atr1 has recently been identified as a boron efflux pump whose expression is upregulated in response to boron treatment. Here, we found that the expression of ATR1 is associated with expression of genes involved in amino acid biosynthesis. These mechanisms are strictly controlled by the transcription factor Gcn4 in response to boron treatment. Further analyses have shown that boron impaired protein synthesis by promoting phosphorylation of eIF2α in a Gcn2 kinase dependent manner. The uncharged tRNA binding domain (HisRS) of Gcn2 is necessary for the phosphorylation of eIF2α in the presence of boron. We postulate that boron exerts its toxic effect through activation of the general amino acid control system and inhibition of protein synthesis. Since the general amino acid control pathway is conserved among eukaryotes, this mechanism of boron toxicity may be of general importance. PMID:22114689
Boron stress activates the general amino acid control mechanism and inhibits protein synthesis.
Irem Uluisik
Full Text Available Boron is an essential micronutrient for plants, and it is beneficial for animals. However, at high concentrations boron is toxic to cells although the mechanism of this toxicity is not known. Atr1 has recently been identified as a boron efflux pump whose expression is upregulated in response to boron treatment. Here, we found that the expression of ATR1 is associated with expression of genes involved in amino acid biosynthesis. These mechanisms are strictly controlled by the transcription factor Gcn4 in response to boron treatment. Further analyses have shown that boron impaired protein synthesis by promoting phosphorylation of eIF2α in a Gcn2 kinase dependent manner. The uncharged tRNA binding domain (HisRS of Gcn2 is necessary for the phosphorylation of eIF2α in the presence of boron. We postulate that boron exerts its toxic effect through activation of the general amino acid control system and inhibition of protein synthesis. Since the general amino acid control pathway is conserved among eukaryotes, this mechanism of boron toxicity may be of general importance.
徐明瑜; 谭文长
2001-01-01
The velocity field of generalized second order fluid with fractional anomalous diffusion caused by a plate moving impulsively in its own plane is investigated and the anomalous diffusion problems of the stress field and vortex sheet caused by this process are studied. Many previous and classical results can be considered as particular cases of this paper, such as the solutions of the fractional diffusion equations obtained by Wyss; the classical Rayleigh' s time-space similarity solution; the relationship between stress field and velocity field obtained by Bagley and co-worker and Podlubny' s results on the fractional motion equation of a plate. In addition, a lot of significant results also are obtained. For example, the necessary condition for causing the vortex sheet is that the time fractional diffusion index β must be greater than that of generalized second order fluid α; the establishment of the vorticity distribution function depends on the time history of the velocity profile at a given point, and the time history can be described by the fractional calculus.
Keller, Hanne Dauer
2015-01-01
Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....
Keller, Hanne Dauer
2015-01-01
Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....
Radell, Milen L; Beck, Kevin D; Gilbertson, Mark W; Myers, Catherine E
2017-01-01
Post-traumatic stress disorder (PTSD) can develop following exposure to a traumatic event. Re-experiencing, which includes intrusive memories or flashbacks of the trauma, is a core symptom cluster of PTSD. From an associative learning perspective, this cluster may be attributed to cues associated with the trauma, which have come to elicit symptoms in a variety of situations encountered in daily life due to a tendency to overgeneralize. Consistent with this, prior studies have indicated that both individuals with clinically diagnosed with PTSD, and those with self-reported symptoms who may not meet full diagnostic criteria, show changes in generalization. Building on prior research, the current study examined whether PTSD symptom burden, but also gender, veteran status, and combat experience-all associated with PTSD vulnerability-modulate learning and generalization in a computer-based task. Participants were presented with stimulus compounds consisting of a foreground and background that could be predictive of reward, punishment or no outcome. Learning was followed by a generalization test where these components were recombined to form novel configurations. An interaction between PTSD symptom burden and gender was found where females with more severe PTSD symptoms showed no evidence of sensitivity to the background. This result is consistent with increased generalization, and may indicate a decrease in the ability to process cue configurations leading to re-experiencing in a variety of situations. Further work is indicated to help elucidate the cognitive processes driving gender differences that may confer vulnerability to PTSD.
Beck, Kevin D.; Gilbertson, Mark W.; Myers, Catherine E.
2017-01-01
Post-traumatic stress disorder (PTSD) can develop following exposure to a traumatic event. Re-experiencing, which includes intrusive memories or flashbacks of the trauma, is a core symptom cluster of PTSD. From an associative learning perspective, this cluster may be attributed to cues associated with the trauma, which have come to elicit symptoms in a variety of situations encountered in daily life due to a tendency to overgeneralize. Consistent with this, prior studies have indicated that both individuals with clinically diagnosed with PTSD, and those with self-reported symptoms who may not meet full diagnostic criteria, show changes in generalization. Building on prior research, the current study examined whether PTSD symptom burden, but also gender, veteran status, and combat experience–all associated with PTSD vulnerability–modulate learning and generalization in a computer-based task. Participants were presented with stimulus compounds consisting of a foreground and background that could be predictive of reward, punishment or no outcome. Learning was followed by a generalization test where these components were recombined to form novel configurations. An interaction between PTSD symptom burden and gender was found where females with more severe PTSD symptoms showed no evidence of sensitivity to the background. This result is consistent with increased generalization, and may indicate a decrease in the ability to process cue configurations leading to re-experiencing in a variety of situations. Further work is indicated to help elucidate the cognitive processes driving gender differences that may confer vulnerability to PTSD. PMID:28196108
[Effect of local sustained stress on general oxygen consumption in belt conveyer workers].
Nakamura, E; Taguchi, S; Fujiki, Y; Kanetaka, A; Nagata, H
1984-09-01
The modern mechanization and rationalization of production procedures have recently reduced the intensity of work in most factories. However, it has been pointed out that monotonous inactive work and/or co-operative work can in some sense impose stronger mental and physical stresses which may induce ill health in workers. In this study, assuming the assembly and adjustment of videotape-recorders on a belt conveyor to be representative of monotonous inactive and co-operative work, changes in oxygen consumption, heart rate, blood pressure, body temperature, critical flicker fusion and subjective symptoms of fatigue throughout a workday have been followed for six female workers engaged in this type of work. The main results obtained were as follows: The average oxygen consumption of six workers was 230 ml/min, almost unchanged during the work. The belt conveyor work indicated the metabolic rate of 0.3 in terms of relative metabolic rate. The net daily energy expenditure due to the work was only about 100 kcal. The average heart rate during assembly and adjustment were respectively, about 1.4 and 1.2 times the average heart rate at rest. The blood pressure and the rate of oxygen removal increased slightly as the work progressed in assembly work, but did not increase at all in adjustment work. The critical flicker fusion and body temperature showed little change during the work.
Al Ansari, Mohammed S.
1999-01-01
A simplified method for the design of paraboloid shell footing base on the displacement of the shell's crown where the column axial load is transferred to the footing has been developed. A case study was presented to demonstrate the use of the proposed method and to illustrate its capabilities. The results of the proposed method confirm the ability of the shell model in determining accurate and practical results for the design of paraboloid shell footing. Base on the analytical results of thi...
Jensen, Line Skov; Lova, Lotte; Hansen, Zandra Kulikovsky; Schønemann, Emilie; Larsen, Line Lyngby; Colberg Olsen, Maria Sophia; Juhl, Nadja; Magnussen, Bogi Roin
2012-01-01
Stress er en tilstand som er meget omdiskuteret i samfundet, og dette besværliggør i en vis grad konkretiseringen af mulige løsningsforslag i bestræbelsen på at forebygge den såkaldte folkesygdom. Hovedkonklusionen er, at selv om der bliver gjort meget for at forebygge, er der ikke meget der aktivt kan sættes i værk for at reducere antallet af stressramte, før en fælles forståelse af stressårsager og effektiv stresshåndtering er fremlagt. Problemformuleringen er besvaret gennem en undersø...
A peridynamic theory for linear elastic shells
Chowdhury, Shubhankar Roy; Roy, Debasish; Reddy, J N
2015-01-01
A state-based peridynamic formulation for linear elastic shells is presented. The emphasis is on introducing, possibly for the first time, a general surface based peridynamic model to represent the deformation characteristics of structures that have one physical dimension much smaller than the other two. A new notion of curved bonds is exploited to cater for force transfer between the peridynamic particles describing the shell. Starting with the three dimensional force and deformation states, appropriate surface based force, moment and several deformation states are arrived at. Upon application on the curved bonds, such states beget the necessary force and deformation vectors governing the motion of the shell. Correctness of our proposal on the peridynamic shell theory is numerically assessed against static deformation of spherical and cylindrical shells and flat plates.
general equilibrium equations derived for shallow shells are expressed in terms of the stresses and deviations corresponding to the equivalent sandwich model. The radial displacement as well as the meridional, circumferential and membrane shear stresses are expressed by finite Fourier series for each face of the sandwich model. A closed form solution is found for the multilobed deformation rates and for the critical time as well. A numerical integration of the deformation rates shows, for a given cylinder, that the multilobed creep buckling deformations grow much faster
Incremental deformation analysis of shell and corrugated diaphragm based on arbitrary configuration
Xuefeng He; Jue Zhang; Huijun Chen; Jing Fang
2005-01-01
With respect to an arbitrary configuration of a deformed structure, two sets of incremental equations are proposed for the deformation analysis of revolution shells and diaphragms loaded by both lateral pressures and the initial stresses produced in manufacturing. These general equations can be reduced to the simplified Koiter's Reissner-Meissner-Reissner (RMR) equations and the simplified Reissner's equations, when the initial stresses are set to zero.They can also be deduced to the total Lagrange form or the updated Lagrange form, respectively, as the structure is specified as the un-deformed or the former-deformed configurations. These incremental equations can be easily transformed into finite difference forms and solved by common numerical solvers of ordinary differential equations. Some numerical examples are presented to show the applications of the incremental equations to the deep shell of revolution and the corrugated diaphragms used in microelectronical mechanical system (MEMS). The results are in good agreement with those from finite element method (FEM).
On the Flutter of Cylindrical Shells and Panels Moving in a Flow of Gas
Stepanov, R. D.
1958-01-01
The equations of shells are taken in the form of the general technical theory of shallow shells and shells of medium length. The aerodynamic forces acting on a shell are taken into account only as forces of excess pressure according to the formula proposed by A.A. Iliushin in reference 3.
Sar, Vedat; Alioğlu, Firdevs; Akyüz, Gamze
2014-01-01
This study sought to determine the prevalence of experiences of possession and paranormal phenomena (PNP) in the general population and their possible relations to each other and to traumatic stress and dissociation. The study was conducted on a representative female sample recruited from a town in central eastern Turkey. The Dissociative Disorders Interview Schedule, the posttraumatic stress disorder (PTSD) and borderline personality disorder sections of the Structured Clinical Interviews for DSM-IV Axis-I and Personality Disorders, and the Childhood Abuse and Neglect Questionnaire were administered to 628 women. Of these, 127 (20.2%) women reported at least 1 type of PNP and 13 (2.1%) women reported possession. Women with a dissociative disorder reported all types of possession and PNP (except telepathy) more frequently than those without. Whereas women with a trauma history in childhood and adulthood or PTSD reported possession more frequently than those without, PNP were associated with childhood trauma only. Factor analysis yielded 4 dimensions: possession by and/or contact with nonhuman entities, extrasensory communications, possession by a human entity, and precognition. These factors correlated with number of secondary features of dissociative identity disorder and Schneiderian symptoms. Latent class analysis identified 3 groups. The most traumatized group, with predominantly dissociative and trauma-related disorders, had the highest scores on all factors. Notwithstanding their presence in healthy individuals, possession and PNP were associated with trauma and dissociation in a subgroup of affected participants. Both types of experience seem to be normal human capacities of experiencing that may be involved in response to traumatic stress. Given the small numbers, this study should be considered preliminary.
Lee, Seul; Oh, HyunSoo; Suh, YeonOk; Seo, WhaSook
2017-03-01
To develop and examine a relocation stress intervention programme tailored for the family caregivers of patients scheduled for transfer from a surgical intensive care unit to a general ward. Family relocation stress syndrome has been reported to be similar to that exhibited by patients, and investigators have emphasised that nurses should make special efforts to relieve family relocation stress to maximise positive contributions to the well-being of patients by family caregivers. A nonequivalent control group, nonsynchronised pretest-post-test design was adopted. The study subjects were 60 family caregivers of patients with neurosurgical or general surgical conditions in the surgical intensive care unit of a university hospital located in Incheon, South Korea. Relocation stress and family burden were evaluated at three times, that is before intervention, immediately after transfer and four to five days after transfer. This relocation stress intervention programme was developed for the family caregivers based on disease characteristics and relocation-related needs. In the experimental group, relocation stress levels significantly and continuously decreased after intervention, whereas in the control group, a slight nonsignificant trend was observed. Family burden levels in the control group increased significantly after transfer, whereas burden levels in the experimental group increased only marginally and nonsignificantly. No significant between-group differences in relocation stress or family burden levels were observed after intervention. Relocation stress levels of family caregivers were significantly decreased after intervention in the experimental group, which indicates that the devised family relocation stress intervention programme effectively alleviated family relocation stress. The devised intervention programme, which was tailored to disease characteristics and relocation-related needs, may enhance the practicality and efficacy of relocation stress
Composite shell spacecraft seat
Barackman, Victor J. (Inventor); Pulley, John K. (Inventor); Simon, Xavier D. (Inventor); McKee, Sandra D. (Inventor)
2008-01-01
A two-part seat (10) providing full body support that is specific for each crew member (30) on an individual basis. The two-part construction for the seat (10) can accommodate many sizes and shapes for crewmembers (30) because it is reconfigurable and therefore reusable for subsequent flights. The first component of the two-part seat construction is a composite shell (12) that surrounds the crewmember's entire body and is generically fitted to their general size in height and weight. The second component of the two-part seat (10) is a cushion (20) that conforms exactly to the specific crewmember's entire body and gives total body support in more complex environment.
Ono K
2017-02-01
Full Text Available Kotaro Ono,1 Yoshikazu Takaesu,1 Yukiei Nakai,2 Akiyoshi Shimura,1 Yasuyuki Ono,1 Akiko Murakoshi,1 Yasunori Matsumoto,1 Hajime Tanabe,3 Ichiro Kusumi,2 Takeshi Inoue1 1Department of Psychiatry, Tokyo Medical University, Tokyo, 2Department of Psychiatry, Hokkaido University Graduate School of Medicine, Hokkaido, 3Department of Clinical Human Sciences, Graduate school of Humanities and Social Sciences, Shizuoka University, Shizuoka, Japan Background: Recent studies have suggested that the interactions among several factors affect the onset, progression, and prognosis of major depressive disorder. This study investigated how childhood abuse, neuroticism, and adult stressful life events interact with one another and affect depressive symptoms in the general adult population. Subjects and methods: A total of 413 participants from the nonclinical general adult population completed the Patient Health Questionnaire-9, the Child Abuse and Trauma Scale, the neuroticism subscale of the shortened Eysenck Personality Questionnaire – Revised, and the Life Experiences Survey, which are self-report scales. Structural equation modeling (Mplus version 7.3 and single and multiple regressions were used to analyze the data. Results: Childhood abuse, neuroticism, and negative evaluation of life events increased the severity of the depressive symptoms directly. Childhood abuse also indirectly increased the negative appraisal of life events and the severity of the depressive symptoms through enhanced neuroticism in the structural equation modeling. Limitations: There was recall bias in this study. The causal relationship was not clear because this study was conducted using a cross-sectional design. Conclusion: This study suggested that neuroticism is the mediating factor for the two effects of childhood abuse on adulthood depressive symptoms and negative evaluation of life events. Childhood abuse directly and indirectly predicted the severity of depressive symptoms
Derivation of a poroelastic flexural shell model
Mikelic, Andro
2015-01-01
In this paper we investigate the limit behavior of the solution to quasi-static Biot's equations in thin poroelastic flexural shells as the thickness of the shell tends to zero and extend the results obtained for the poroelastic plate by Marciniak-Czochra and Mikeli\\'c. We choose Terzaghi's time corresponding to the shell thickness and obtain the strong convergence of the three-dimensional solid displacement, fluid pressure and total poroelastic stress to the solution of the new class of shell equations. The derived bending equation is coupled with the pressure equation and it contains the bending moment due to the variation in pore pressure across the shell thickness. The effective pressure equation is parabolic only in the normal direction. As additional terms it contains the time derivative of the middle-surface flexural strain. Derivation of the model presents an extension of the results on the derivation of classical linear elastic shells by Ciarlet and collaborators to the poroelastic shells case. The n...
Unconstrained Finite Element for Geometrical Nonlinear Dynamics of Shells
Humberto Breves Coda
2009-01-01
Full Text Available This paper presents a positional FEM formulation to deal with geometrical nonlinear dynamics of shells. The main objective is to develop a new FEM methodology based on the minimum potential energy theorem written regarding nodal positions and generalized unconstrained vectors not displacements and rotations. These characteristics are the novelty of the present work and avoid the use of large rotation approximations. A nondimensional auxiliary coordinate system is created, and the change of configuration function is written following two independent mappings from which the strain energy function is derived. This methodology is called positional and, as far as the authors' knowledge goes, is a new procedure to approximated geometrical nonlinear structures. In this paper a proof for the linear and angular momentum conservation property of the Newmark algorithm is provided for total Lagrangian description. The proposed shell element is locking free for elastic stress-strain relations due to the presence of linear strain variation along the shell thickness. The curved, high-order element together with an implicit procedure to solve nonlinear equations guarantees precision in calculations. The momentum conserving, the locking free behavior, and the frame invariance of the adopted mapping are numerically confirmed by examples.
Mohammad Zamani Nejad
2014-01-01
Full Text Available Using disk form multilayers, a semi-analytical solution has been derived for determination of displacements and stresses in a rotating cylindrical shell with variable thickness under uniform pressure. The thick cylinder is divided into disk form layers form with their thickness corresponding to the thickness of the cylinder. Due to the existence of shear stress in the thick cylindrical shell with variable thickness, the equations governing disk layers are obtained based on first-order shear deformation theory (FSDT. These equations are in the form of a set of general differential equations. Given that the cylinder is divided into n disks, n sets of differential equations are obtained. The solution of this set of equations, applying the boundary conditions and continuity conditions between the layers, yields displacements and stresses. A numerical solution using finite element method (FEM is also presented and good agreement was found.
Stress Concentration Analysis of Reinforced Cylindrical Shells with Large Opening%圆柱壳大开孔补强的应力集中分析
舒斌; 胡刚义; 肖伟; 张元盛
2011-01-01
Combined with practical engineering, stress concentration on the reinforcement of pressure hull of submarine with large opening was studied.Different forms of reinforcement were investigated by the Finite Element Method (FEM) and rules of thumb.Models were constructed and the stress concentration factors were worked out.By comparing and analyzing the results from these two methods, it shows that the bending hoop stress of opening where lies in maximum hoop membrane stress cannot be ignored when the opening stiffened by coaming.The calculations also prove effective in reinforcement of structural design of large openings.%针对潜艇耐压壳体上大开孔补强处的应力集中现象,结合工程实际问题,采用规范和有限元法对潜艇耐压壳体上大开孔不同补强形式进行了研究,建立了相应的模型,并求出了应力集中系数.通过对两种方法的计算结果进行分析比较,发现当围壁加强时,最大周向应力处的弯曲应力不容忽视.结果说明,用有限单元法进行大开孔补强结构设计是合理、有效的,是对规范计算的完善和补充.
Thermoelastic bending of locally heated orthotropic shells
Shevchenko, V. P.; Gol'tsev, A. S.
2007-03-01
The thermoelastic bending of locally heated orthotropic shells is studied using the classical theory of thermoelasticity of thin shallow orthotropic shells and the method of fundamental solutions. Linear distribution of temperature over thickness and the Newton's law of cooling are assumed. Numerical analysis is carried out for orthotropic shells of arbitrary Gaussian curvature made of a strongly anisotropic material. The behavior of thermal forces and moments near the zone of local heating is studied for two areas of thermal effect: along a coordinate axis and along a circle of unit radius. Generalized conclusions are drawn
Ono, Kotaro; Takaesu, Yoshikazu; Nakai, Yukiei; Shimura, Akiyoshi; Ono, Yasuyuki; Murakoshi, Akiko; Matsumoto, Yasunori; Tanabe, Hajime; Kusumi, Ichiro; Inoue, Takeshi
2017-01-01
Background Recent studies have suggested that the interactions among several factors affect the onset, progression, and prognosis of major depressive disorder. This study investigated how childhood abuse, neuroticism, and adult stressful life events interact with one another and affect depressive symptoms in the general adult population. Subjects and methods A total of 413 participants from the nonclinical general adult population completed the Patient Health Questionnaire-9, the Child Abuse and Trauma Scale, the neuroticism subscale of the shortened Eysenck Personality Questionnaire – Revised, and the Life Experiences Survey, which are self-report scales. Structural equation modeling (Mplus version 7.3) and single and multiple regressions were used to analyze the data. Results Childhood abuse, neuroticism, and negative evaluation of life events increased the severity of the depressive symptoms directly. Childhood abuse also indirectly increased the negative appraisal of life events and the severity of the depressive symptoms through enhanced neuroticism in the structural equation modeling. Limitations There was recall bias in this study. The causal relationship was not clear because this study was conducted using a cross-sectional design. Conclusion This study suggested that neuroticism is the mediating factor for the two effects of childhood abuse on adulthood depressive symptoms and negative evaluation of life events. Childhood abuse directly and indirectly predicted the severity of depressive symptoms. PMID:28243100
Haugland, Trude; Veenstra, Marijke; Vatn, Morten H; Wahl, Astrid K
2013-01-01
The purpose of the study was to evaluate changes in general self-efficacy, health related quality of life (HRQoL), and stress among patients with neuroendocrine tumors (NET) following a multidisciplinary educational intervention. Forty-one patients were enrolled in this exploratory pilot study. A total of 37 patients completed the full 26-week intervention based on the principles of self-efficacy. General self-efficacy was measured by the General Self-Efficacy Scale, HRQoL was measured with the SF-36, and stress was measured with the Impact of Event Scale. Mixed effect models were used to evaluate changes in general self-efficacy, mental and physical components of HRQoL, and stress adjusting for demographic and clinical variables. Results showed significant improvements in patients' general self-efficacy (β = 0.71; P stress (β = -2.10, P = 0.008). Findings suggest that patients with NET have the capacity to improve their ability to cope with their disease, problem-solve, improve their physical status, and reduce their stress following an educational intervention based on the principles of self-efficacy. These preliminary data provide a basis for future randomized controlled trials to test interventions to improve HRQoL for patients with NET.
Trude Haugland
2013-01-01
Full Text Available The purpose of the study was to evaluate changes in general self-efficacy, health related quality of life (HRQoL, and stress among patients with neuroendocrine tumors (NET following a multidisciplinary educational intervention. Forty-one patients were enrolled in this exploratory pilot study. A total of 37 patients completed the full 26-week intervention based on the principles of self-efficacy. General self-efficacy was measured by the General Self-Efficacy Scale, HRQoL was measured with the SF-36, and stress was measured with the Impact of Event Scale. Mixed effect models were used to evaluate changes in general self-efficacy, mental and physical components of HRQoL, and stress adjusting for demographic and clinical variables. Results showed significant improvements in patients’ general self-efficacy (β = 0.71; P<0.05, physical component scores of HRQoL (β = 3.09; P<0.01, and stress (β=-2.10, P=0.008. Findings suggest that patients with NET have the capacity to improve their ability to cope with their disease, problem-solve, improve their physical status, and reduce their stress following an educational intervention based on the principles of self-efficacy. These preliminary data provide a basis for future randomized controlled trials to test interventions to improve HRQoL for patients with NET.
Stochastic Analysis of Cylindrical Shell
Grzywiński Maksym
2014-06-01
Full Text Available The paper deals with some chosen aspects of stochastic structural analysis and its application in the engineering practice. The main aim of the study is to apply the generalized stochastic perturbation techniques based on classical Taylor expansion with a single random variable for solution of stochastic problems in structural mechanics. The study is illustrated by numerical results concerning an industrial thin shell structure modeled as a 3-D structure.
Au/SiO2/QD core/shell/shell nanostructures with plasmonic-enhanced photoluminescence
Yang, Ping; Kawasaki, Kazunori; Ando, Masanori; Murase, Norio
2012-09-01
A sol-gel method has been developed to fabricate Au/SiO2/quantum dot (QD) core-shell-shell nanostructures with plasmonic-enhanced photoluminescence (PL). Au nanoparticle (NP) was homogeneously coated with a SiO2 shell with adjusted thickness through a Stöber synthesis. When the toluene solution of hydrophobic CdSe/ZnS QDs was mixed with partially hydrolyzed 3-aminopropyltrimethoxysilane (APS) sol, the ligands on the QDs were replaced by a thin functional SiO2 layer because the amino group in partially hydrolyzed APS has strong binding interaction with the QDs. Partially hydrolyzed APS plays an important role as a thin functional layer for the transfers of QDs to water phase and the subsequent connection to aqueous SiO2-coated Au NPs. Although Au NPs were demonstrated as efficient PL quenchers when the SiO2 shell on the Au NPs is thin (less than 5 nm), we found that precise control of the spacing between the Au NP core and the QD shell resulted in QDs with an enhancement of 30 % of PL efficiency. The Au/SiO2/QD core/shell/shell nanostructures also reveal strong surface plasmon scattering, which makes the Au/SiO/QD core-shell-shell nanostructures an excellent dual-modality imaging probe. This technology can serve as a general route for encapsulating a variety of discrete nanomaterials because monodispersed nanostructures often have a similar surface chemistry.
Foreman, Robert; Fiebig, Aretha; Crosson, Sean
2012-06-01
A conserved set of regulators control the general stress response in Caulobacter crescentus, including σ(T), its anti-σ factor NepR, the anti-anti-σ factor PhyR, and the transmembrane sensor kinase PhyK. We report that the soluble histidine kinase LovK and the single-domain response regulator LovR also function within the C. crescentus general stress pathway. Our genetic data support a model in which LovK-LovR functions upstream of σ(T) by controlling the phosphorylation state and thus anti-anti-σ activity of PhyR. Transcription of lovK and lovR is independently activated by stress through a mechanism that requires sigT and phyR. Conversely, lovK and lovR function together to repress transcription of the general stress regulon. Concordant with a functional role of the LovK-LovR two-component system as a negative regulator of the general stress pathway, lovK-lovR-null mutants exhibit increased cell survival after osmotic stress, while coordinate overexpression of lovK and lovR attenuates cell survival relative to that of the wild type. Notably, lovK can complement the transcriptional and cell survival defects of a phyK-null mutant when lovR is deleted. Moreover, in this same genetic background, σ(T)-dependent transcription is activated in response to osmotic stress. This result suggests that flavin-binding LOV (light, oxygen, or voltage) histidine kinases are competent to perceive cytoplasmic signals in addition to the environmental signal blue light. We conclude that the PhyK-PhyR and LovK-LovR two-component signaling systems coordinately regulate stress physiology in C. crescentus.
The dorsal shell wall structure of Mesozoic ammonoids
Gregor Radtke
2017-03-01
Full Text Available The study of pristine preserved shells of Mesozoic Ammonoidea shows different types of construction and formation of the dorsal shell wall. We observe three major types: (i The vast majority of Ammonoidea, usually planispirally coiled, has a prismatic reduced dorsal shell wall which consists of an outer organic component (e.g., wrinkle layer, which is the first layer to be formed, and the subsequently formed dorsal inner prismatic layer. The dorsal mantle tissue suppresses the formation of the outer prismatic layer and nacreous layer. With the exception of the outer organic component, secretion of a shell wall is omitted at the aperture. A prismatic reduced dorsal shell wall is always secreted immediately after the hatching during early teleoconch formation. Due to its broad distribution in (planispiral Ammonoidea, the prismatic reduced dorsal shell wall is probably the general state. (ii Some planispirally coiled Ammonoidea have a nacreous reduced dorsal shell wall which consists of three mineralized layers: two prismatic layers (primary and secondary dorsal inner prismatic layer and an enclosed nacreous layer (secondary dorsal nacreous layer. The dorsal shell wall is omitted at the aperture and was secreted in the rear living chamber. Its layers are a continuation of an umbilical shell doubling (reinforcement by additional shell layers that extends towards the ventral crest of the preceding whorl. The nacreous reduced dorsal shell wall is formed in the process of ontogeny following a prismatic reduced dorsal shell wall. (iii Heteromorph and some planispirally coiled taxa secrete a complete dorsal shell wall which forms a continuation of the ventral and lateral shell layers. It is formed during ontogeny following a prismatic reduced dorsal shell wall or a priori. The construction is identical with the ventral and lateral shell wall, including a dorsal nacreous layer. The wide distribution of the ability to form dorsal nacre indicates that it is
Nonsymmetric Dynamical Thin-Shell Wormhole
Svitek, O
2016-01-01
The thin-shell wormhole created using the Darmois--Israel formalism applied to Robinson--Trautman family of spacetimes is presented. The stress energy tensor created on the throat is interpreted in terms of two dust streams and it is shown that asymptotically this wormhole settles to the Schwarzschild wormhole with throat on the horizon.
Calculation of tubular joints as compound shells
Golovanov, A. I.
A scheme for joining isoparametric finite shell elements with a bend in the middle surface is described. A solution is presented for the problem of the stress-strain state of a T-joint loaded by internal pressure. A refined scheme is proposed for calculating structures of this kind with allowance for the stiffness of the welded joint.
Tselishchev, M. F.; Plotnikov, P. N.; Brodov, Yu. M.
2015-11-01
Rolling the tube sheet of a heat exchanger with U-shaped tubes, as exemplified by the vapor cooler GP-24, was simulated. The simulation was performed using the finite element method with account of elas- tic-plastic properties of the tube and tube sheet materials. The simulation consisted of two stages; at the first stage, maximum and residual contact stress in the conjunction of a separate tube and the tube sheet was determined using the "equivalent sleeve" model; at the second stage, the obtained contact stress was applied to the hole surface in the tube sheet. Thus, different tube rolling sequences were simulated: from the center to the periphery of the tube sheet and from the periphery to the center along a spiral line. The studies showed that the tube rolling sequence noticeably influences the value of the tube sheet residual deflection for the same rolling parameters of separate tubes. Residual deflection of the tube sheet in different planes was determined. It was established that the smallest residual deflection corresponds to the tube rolling sequence from the periphery to the center of the tube sheet. The following dependences were obtained for different rolling sequences: maximum deformation of the tube sheet as a function of the number of rolled tubes, residual deformation of the tube sheet along its surface, and residual deflection of the tube sheet as a function of the rotation angle at the periphery. The preferred sequence of tube rolling for minimizing the tube sheet deformation is indicated.
Sochi, Taha
2015-01-01
We investigate the possibility that the spatial dependency of stress in generalized Newtonian flow systems is a function of the applied pressure field and the conduit geometry but not of the fluid rheology. This possibility is well established for the case of a one-dimensional flow through simply connected regions, specifically tubes of circular uniform cross sections and plane thin slits. If it can also be established for the more general case of generalized Newtonian flow through non-circular or multiply connected geometries, such as the two-dimensional flow through conduits of rectangular or elliptical cross sections or the flow through annular circular pipes, then analytical or semi-analytical or highly accurate numerical solutions; regarding stress, rate of strain, velocity profile and volumetric flow rate; for these geometries can be obtained from the stress function, which can be easily obtained from the Newtonian case, in combination with the constitutive rheological relation for the particular non-Ne...
Cho, H. T.; Hu, B. L.
2012-09-01
We calculate the expectation values of the stress-energy bitensor defined at two different spacetime points x, x‧ of a massless, minimally coupled scalar field with respect to a quantum state at finite temperature T in a flat N-dimensional spacetime by means of the generalized zeta-function method. These correlators, also known as the noise kernels, give the fluctuations of energy and momentum density of a quantum field which are essential for the investigation of the physical effects of negative energy density in certain spacetimes or quantum states. They also act as the sources of the Einstein-Langevin equations in stochastic gravity which one can solve for the dynamics of metric fluctuations as in spacetime foams. In terms of constitutions these correlators are one rung above (in the sense of the correlation—BBGKY or Schwinger-Dyson—hierarchies) the mean (vacuum and thermal expectation) values of the stress-energy tensor which drive the semiclassical Einstein equation in semiclassical gravity. The low- and the high-temperature expansions of these correlators are also given here: at low temperatures, the leading order temperature dependence goes like TN while at high temperatures they have a T2 dependence with the subleading terms exponentially suppressed by e-T. We also discuss the singular behavior of the correlators in the x‧ → x coincident limit as was done before for massless conformal quantum fields. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical in honour of Stuart Dowker’s 75th birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’.
Mechanical stability of cylindrical thin-shell wormholes
Sharif, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); Azam, M. [University of Education, Division of Science and Technology, Lahore (Pakistan)
2013-04-15
In this paper, we apply the cut and paste procedure to the charged black string for the construction of a thin-shell wormhole. We consider the Darmois-Israel formalism to determine the surface stresses of the shell. We take the Chaplygin gas to deal with the matter distribution on shell. The radial perturbation approach (preserving the symmetry) is used to investigate the stability of static solutions. We conclude that stable static solutions exist both for uncharged and charged black string thin-shell wormholes for particular values of the parameters. (orig.)
Lindgren, Jonathan
2016-12-01
We study collisions of massive pointlike particles in three dimensional anti-de Sitter space, generalizing the work on massless particles in [1]. We show how to construct exact solutions corresponding to the formation of either a black hole or a conical singularity from the collision of an arbitrary number of massive particles that fall in radially and collide at the origin of AdS. No restrictions on the masses or the angular and radial positions from where the particles are released, are imposed. We also consider the limit of an infinite number of particles, obtaining novel timelike thin shell spacetimes. These thin shells have an arbitrary mass distribution as well as a non-trivial embedding where the radial location of the shell depends on the angular coordinate, and we analyze these shells using the junction formalism of general relativity. We also consider the massless limit and find consistency with earlier results, as well as comment on the stress-energy tensor modes of the dual CFT.
Lindgren, Jonathan [Theoretische Natuurkunde, Vrije Universiteit Brussel, and the International Solvay Institutes,Pleinlaan 2, B-1050 Brussels (Belgium); Physique Théorique et Mathématique, Université Libre de Bruxelles,Campus Plaine C.P. 231, B-1050 Bruxelles (Belgium)
2016-12-13
We study collisions of massive pointlike particles in three dimensional anti-de Sitter space, generalizing the work on massless particles in http://dx.doi.org/10.1088/0264-9381/33/14/145009. We show how to construct exact solutions corresponding to the formation of either a black hole or a conical singularity from the collision of an arbitrary number of massive particles that fall in radially and collide at the origin of AdS. No restrictions on the masses or the angular and radial positions from where the particles are released, are imposed. We also consider the limit of an infinite number of particles, obtaining novel timelike thin shell spacetimes. These thin shells have an arbitrary mass distribution as well as a non-trivial embedding where the radial location of the shell depends on the angular coordinate, and we analyze these shells using the junction formalism of general relativity. We also consider the massless limit and find consistency with earlier results, as well as comment on the stress-energy tensor modes of the dual CFT.
Lindgren, Jonathan
2016-01-01
We study collisions of massive pointlike particles in three dimensional anti-de Sitter space, generalizing the work on massless particles in [1]. We show how to construct exact solutions corresponding to the formation of either a black hole or a conical singularity from the collision of an arbitrary number of massive particles that fall in radially and collide at the origin of AdS. No restrictions on the masses or the angular and radial positions from where the particles are released, are imposed. We also consider the limit of an infinite number of particles, obtaining novel timelike thin shell spacetimes. These thin shells have an arbitrary mass distribution as well as a non-trivial embedding where the radial location of the shell depends on the angular coordinate, and we analyze these shells using the junction formalism of general relativity. We also consider the massless limit and find consistency with earlier results, as well as comment on the stress-energy tensor modes of the dual CFT.
STRESS ANALYSIS AND BURST PRESSURE DETERMINATION OF TWO LAYER COMPOUND PRESSURE VESSEL
HARERAM LOHAR
2013-02-01
Full Text Available Multilayer pressure vessel is designed to work under high-pressure condition. This paper introduces the stress analysis and the burst pressure calculation of a two-layer shrink fitted pressure vessel. In the shrink-fitting problems, considering long hollow cylinders, the plane strain hypothesis can be regarded as more natural. Generally hoops stress distribution is non-linear and sharply reduced toward the outer surface. By shrink fitting concentric shells towards the inner shells are placed in residual compression so that the initial compressive hoop stress must be relieved by internal pressure before hoop tensile stress are developed. Therefore the maximum hoop stress will be reduced, resulting more burst pressure. The analytical results of stress distribution and burst pressure is calculated and validated by ANSYS Workbench results.
Zhao G
2017-04-01
Full Text Available Guoliang Zhao, Xiaoyue Yin, Ya Li, Jianlin Shao Department of Anesthesiology, The First Affiliated Hospital of Kunming Medical University, Kunming, People’s Republic of China Purpose: The study aimed to assess the combined effects of parecoxib with three different doses of remifentanil and its effect on the stress and cough responses following tracheal extubation under general anesthesia.Methods: A total of 120 patients with American Society of Anesthesiologists (ASA scores of I or II, undergoing selective thyroidectomy with total intravenous anesthesia (propofol-remifentanil and tracheal intubation, were randomly allocated to be treated with an intravenous injection of parecoxib and a continuous infusion of remifentanil at 0.1 μg/kg/min (R1, 0.2 μg/kg/min (R2, 0.3 μg/kg/min (R3, or an isotonic saline injection (the control group. Hemodynamic vital signs, emergence time, extubation time, sedation-agitation scale (SAS score, pain visual analog scale (VAS score, occurrence of coughing, and side effects were recorded before surgery and during the peri-extubation period. The vital signs included blood pressure (BP, heart rate (HR, respiratory rate (R, and peripheral arterial oxygen saturation (SPO2.Results: BP, HR, the occurrence rate of coughing, and extubation awareness decreased with the dose of remifentanil, and the differences among the groups were significant (P < 0.05. Emergence and extubation time increased with the dose of remifentanil, and the differences among the groups were significant (P < 0.05. The occurrence rates of respiratory depression and bradycardia in group R3 were significantly higher than those in other groups (P < 0.05. SAS and VAS were lowest in group R3, and the differences among the groups were significant (P < 0.05. BP, HR, SAS, and VAS increased with time in the remifentanil groups.Conclusion: The combined use of parecoxib and a moderate dose of remifentanil can effectively suppress the stress and coughing
Writuparna Das
2015-01-01
Full Text Available Background: Laparoscopy though minimally invasive produces significant hemodynamic surge and neuroendocrine stress response. Though general anesthesia (GA is the conventional technique, now-a-days, regional anesthesia has been accepted for laparoscopic diagnostic procedures, and its use is also being extended to laparoscopic surgeries. Objective: The aim was to compare the hemodynamic surge and neuroendocrine stress response during laparoscopic cholecystectomy (LC under GA and spinal anesthesia (SA in American Society of Anesthesiologists (ASA PS 1 patients. Materials and Methods: Thirty ASA physical status I patients, aged 18-65 years were randomly allocated into two equal groups of 15 each. Group A received GA with controlled ventilation. Patients were preoxygenated for 5 min with 100/5 oxygen, premedicated with midazolam 0.03 mg/kg intravenous (i.v, fentanyl 2 mcg/kg i.v; induction was done with thiopentone 3-5 mg/kg i.v; intubation was achieved after muscle relaxation with 0.5 mg/kg atracurium besylate i.v. Anesthesia was maintained with 1-2% sevoflurane and N2O:O2 (60:40 and intermittent i.v injection of atracurium besylate. Group B SA with 0.5% hyperbaric bupivacaine and 25 μg fentanyl along with local anesthetic instillation in the subdiaphragmatic space. Mean arterial pressure, heart rate (HR, oxygen saturation, end tidal carbon-dioxide were recorded. Venous blood was collected for cortisol assay before induction and 30 min after pneumoperitoneum. All data were collected in Microsoft excel sheet and statistically analyzed using SPSS software version 16 (SPSS Inc., Chicago, IL, USA. All numerical data were analyzed using Student′s t-test and paired t-test. Any value <0.05 was taken as significant. Results: Mean arterial pressure and mean HR and postpneumoperitoneum cortisol level were lower in group B than group A though the difference was not statistically significant in hemodynamic parameters but significant in case of cortisol
LI Lian-He; FAN Tian-You
2006-01-01
@@ The stress potential function theory for plane elasticity of icosahedral quasicrystals is developed. By introducing stress functions, huge numbers of basic equations involving elasticity of icosahedral quasicrystals are reduced to a single partial differential equation of the 12th order.
1995-01-01
In 1988 Zheng Haigen, a seaman with the Towboat Company of the Shanghai Salvage Bureau, began collecting spiral shells. Today he has more than 600 in his collection. The most valuable are the rare parrot shell and a shell whose spirals wind counter-clockwise. In 1991 a miniature conch with a diameter of 0.31 millimeters that he found buried in tons of sand made the Guinness Book of World Records.
Tang, Yi-Lei
2015-01-01
The idea that the new particles invented in some models beyond the standard model can appear only inside the loops is attractive. In this paper, we fill these loops with off-shell tachyons, leading to a solution of the zero results of the loop diagrams involving the off-shell non-tachyonic particles. We also calculate the Passarino-Veltman $A_0^o$ and $B_0^o$ of the off-shell tachyons.
NONLINEAR THEORY OF DYNAMIC STABILITY FOR LAMINATED COMPOSITE CYLINDRICAL SHELLS
周承倜; 王列东
2001-01-01
Hamilton Principle was uaed to derive the general governing equations of nonlinear dynamic stability for laminated cylindrical shells in which, factors of nonlinear large deflection, transverse shear and longitudinal inertia force were concluded. Equations were solved by variational method. Analysis reveals that under the action of dynamic load,laminated cylindrical shells will fall into a state of parametric resonance and enter into the dynamic unstable region that causes dynamic instability of shells. Laminated shells of three typical composites were computed: i.e. T300/5 208 graphite epoxy E-glass epoxy, and ARALL shells. Results show that all factors will induce important influence for dynamic stability of laminated shells. So, in research of dynamic stability for laminated shells, to consider these factors is important.
Symmetries and deformations in the spherical shell model
Van Isacker, P.; Pittel, S.
2016-02-01
We discuss symmetries of the spherical shell model that make contact with the geometric collective model of Bohr and Mottelson. The most celebrated symmetry of this kind is SU(3), which is the basis of Elliott’s model of rotation. It corresponds to a deformed mean field induced by a quadrupole interaction in a single major oscillator shell N and can be generalized to include several major shells. As such, Elliott’s SU(3) model establishes the link between the spherical shell model and the (quadrupole component of the) geometric collective model. We introduce the analogue symmetry induced by an octupole interaction in two major oscillator shells N-1 and N, leading to an octupole-deformed solution of the spherical shell model. We show that in the limit of large oscillator shells, N\\to ∞ , the algebraic octupole interaction tends to that of the geometric collective model.
Altenbach, Holm
2011-01-01
In this volume, scientists and researchers from industry discuss the new trends in simulation and computing shell-like structures. The focus is put on the following problems: new theories (based on two-dimensional field equations but describing non-classical effects), new constitutive equations (for materials like sandwiches, foams, etc. and which can be combined with the two-dimensional shell equations), complex structures (folded, branching and/or self intersecting shell structures, etc.) and shell-like structures on different scales (for example: nano-tubes) or very thin structures (similar
Numerical Study of the Mechanical Response of Turtle Shell
Wei Zhang; Chengwei Wu; Chenzhao Zhang; Zhen Chen
2012-01-01
The turtle shell is an amazing structure optimized through the long-term evolution by nature.This paper reports the mechanical response of the shell (Red-ear turtle) to static and dynamic loads,respectively.It is found that the turtle shell under a compressive load yields the maximum vertical displacement at the rear end,but the vertical displacement at the front end is only half of that at the rear end.The maximum horizontal displacement of the shell also occurs at the rear end.It is believed that such a deformation pattern is helpful for protecting the turtle's internal organs and its head.The principal stress directions in the inside surface of the shell under a compressive load are almost the same as those of the biofiber distribution in the inside surface,which results in the strong bending resistance of the turtle shell.
Sycz, Gabriela; Carrica, Mariela Carmen; Tseng, Tong-Seung; Bogomolni, Roberto A; Briggs, Winslow R; Goldbaum, Fernando A; Paris, Gastón
2015-01-01
Brucella is the causative agent of the zoonotic disease brucellosis, and its success as an intracellular pathogen relies on its ability to adapt to the harsh environmental conditions that it encounters inside the host. The Brucella genome encodes a sensor histidine kinase containing a LOV domain upstream from the kinase, LOVHK, which plays an important role in light-regulated Brucella virulence. In this report we study the intracellular signaling pathway initiated by the light sensor LOVHK using an integrated biochemical and genetic approach. From results of bacterial two-hybrid assays and phosphotransfer experiments we demonstrate that LOVHK functionally interacts with two response regulators: PhyR and LovR, constituting a functional two-component signal-transduction system. LOVHK contributes to the activation of the General Stress Response (GSR) system in Brucella via PhyR, while LovR is proposed to be a phosphate-sink for LOVHK, decreasing its phosphorylation state. We also show that in the absence of LOVHK the expression of the virB operon is down-regulated. In conclusion, our results suggest that LOVHK positively regulates the GSR system in vivo, and has an effect on the expression of the virB operon. The proposed regulatory network suggests a similar role for LOVHK in other microorganisms.
Hämmig, Oliver; Brauchli, Rebecca; Bauer, Georg F
2012-05-31
Effort-reward imbalance (ERI) and work-life imbalance (WLI) are recognised risk factors for work stress and burnout but have not been investigated conjointly so far and compared with each other in this regard. The present cross-sectional study provides initial evidence by studying associations of ERI and WLI with general stress and burnout simultaneously. The study was based on survey data collected in 2007 among the personnel of a large public hospital in the canton of Zurich covering a random sample of 502 employees of all professions and positions. Prevalence rates, correlation coefficients, standardised regression coefficients and odds ratios were calculated as measures of association. Concerning the main research question and relating to the entire study sample, WLI was found to be more strongly associated with general stress and burnout than ERI. As stratified analyses with regard to burnout have shown, this applied especially to nursing, technical care and emergency staffs who account for more than three fifths of the study population. But for other professional categories like physicians, therapists and medical-technical personnel the opposite of a stronger association of ERI with burnout was found. Results also suggested that general stress plays a (rather minor) mediating role in the relationships between ERI and burnout and particularly between WLI and burnout. For the prevention of chronic stress and burnout one should consider both high efforts put into work as well as all job demands that are competing and interfering with family responsibilities or other private activities should be considered.
A Method for Quantifying, Visualising, and Analysing Gastropod Shell Form.
Liew, Thor-Seng; Schilthuizen, Menno
2016-01-01
Quantitative analysis of organismal form is an important component for almost every branch of biology. Although generally considered an easily-measurable structure, the quantification of gastropod shell form is still a challenge because many shells lack homologous structures and have a spiral form that is difficult to capture with linear measurements. In view of this, we adopt the idea of theoretical modelling of shell form, in which the shell form is the product of aperture ontogeny profiles in terms of aperture growth trajectory that is quantified as curvature and torsion, and of aperture form that is represented by size and shape. We develop a workflow for the analysis of shell forms based on the aperture ontogeny profile, starting from the procedure of data preparation (retopologising the shell model), via data acquisition (calculation of aperture growth trajectory, aperture form and ontogeny axis), and data presentation (qualitative comparison between shell forms) and ending with data analysis (quantitative comparison between shell forms). We evaluate our methods on representative shells of the genera Opisthostoma and Plectostoma, which exhibit great variability in shell form. The outcome suggests that our method is a robust, reproducible, and versatile approach for the analysis of shell form. Finally, we propose several potential applications of our methods in functional morphology, theoretical modelling, taxonomy, and evolutionary biology.
A Method for Quantifying, Visualising, and Analysing Gastropod Shell Form
Liew, Thor-Seng; Schilthuizen, Menno
2016-01-01
Quantitative analysis of organismal form is an important component for almost every branch of biology. Although generally considered an easily-measurable structure, the quantification of gastropod shell form is still a challenge because many shells lack homologous structures and have a spiral form that is difficult to capture with linear measurements. In view of this, we adopt the idea of theoretical modelling of shell form, in which the shell form is the product of aperture ontogeny profiles in terms of aperture growth trajectory that is quantified as curvature and torsion, and of aperture form that is represented by size and shape. We develop a workflow for the analysis of shell forms based on the aperture ontogeny profile, starting from the procedure of data preparation (retopologising the shell model), via data acquisition (calculation of aperture growth trajectory, aperture form and ontogeny axis), and data presentation (qualitative comparison between shell forms) and ending with data analysis (quantitative comparison between shell forms). We evaluate our methods on representative shells of the genera Opisthostoma and Plectostoma, which exhibit great variability in shell form. The outcome suggests that our method is a robust, reproducible, and versatile approach for the analysis of shell form. Finally, we propose several potential applications of our methods in functional morphology, theoretical modelling, taxonomy, and evolutionary biology. PMID:27280463
Liyakhath
2014-11-01
Full Text Available : BACKGROUND: Tracheal extubation and emergence is associated with significant haemodynamic alterations and is poorly tolerated by patients with co-morbid conditions. We compared the efficacy of fentanyl and dexmedetomidine in mitigating haemodynamic stress response and assessed extubation quality in study groups. MATERIALS AND METHODS: One fifty patients of either sex, ASA grade I & II normotensive patients, aged 18-55 years undergoing elective surgeries under general anaesthesia were randomized into 3 equal groups. Anaesthetic technique was standardized. 10 minutes prior to extubation, patients in Group N, F and D received intravenous bolus infusion of 0.9% normal Saline, Fentanyl 1μg /kg and Dexmedetomidine 1μg /kg respectively over 10 minutes period. Heart Rate (HR, Systolic BP (SBP, Diastolic BP (DBP and Mean Arterial Pressure (MAP were noted at extubation, 2, 4, 6, 8, 10 min and at regular interval thereafter for a period of two hours. Extubation quality was evaluated on 5-point extubation quality scale [ scale 1 = no coughing, 2 = smooth extubation, minimal coughing (1 or 2 times, 3 = moderate coughing (3 or 4 times, 4 = severe coughing (5-10 times and straining, 5 = poor extubation, very uncomfortable (laryngospasm and coughing >10 times]. Ramsay sedation score and Aldrete’s recovery score were recorded. Any adverse events, use of rescue drugs and postoperative analgesics were noted. RESULTS: All the measured haemodynamic parameters were significantly elevated at extubation and at various points of observation in normal saline group than fentanyl and dexmedetomidine group (p=0.000. Tachycardia response was seen in 84% patients in group N, compared to 36% and 8% in group F & D respectively (p=0.000. Statistically significant hypertensive response was noticed in 43(86% patients of group N, 9(18% of group F and 3(6% of group D (p=0.000. Duration of tachycardia and hypertensive response was significantly longer in control group. Three
M.P. Hengartner (Michael P.); D. van der Linden (Dimitri); L. Bohleber (Laura); A. von Wyl (Agnes)
2017-01-01
textabstractWe conducted an online survey including 306 participants aged 18-64years to assess the general factor of personality (GFP) and Big Five personality traits in relation to individual stress and coping reactions following a shooting emergency alarm at a Swiss university campus. Although the
Jae S. Ahn
2015-01-01
Full Text Available We introduce higher-order cylindrical shell element based on ESL (equivalent single-layer theory for the analysis of laminated composite shells. The proposed elements are formulated by the dimensional reduction technique from three-dimensional solid to two-dimensional cylindrical surface with plane stress assumption. It allows the first-order shear deformation and considers anisotropic materials due to fiber orientation. The element displacement approximation is established by the integrals of Legendre polynomials with hierarchical concept to ensure the C0-continuity at the interface between adjacent elements as well as C1-continuity at the interface between adjacent layers. For geometry mapping, cylindrical coordinate is adopted to implement the exact mapping of curved shell configuration with a constant curvature with respect to any direction in the plane. The verification and characteristics of the proposed element are investigated through the analyses of three cylindrical shell problems with different shapes, loadings, and boundary conditions.
Dina Collip
Full Text Available Subclinical psychotic experiences at the level of the general population are common, forming an extended psychosis phenotype with clinical psychosis. Persistence of subclinical experiences is associated with transition to later mental disorder. Increased daily life stress reactivity is considered an endophenotype for psychotic disorders. We examined, in a longitudinal framework, whether baseline momentary assessment markers of stress reactivity would predict persistence of subclinical psychotic experiences over time. In a general population sample of female twins (N = 566, the Experience Sampling Method (ESM; repetitive random sampling of momentary emotions, psychotic experiences and context was used to assess (emotional and psychotic daily life stress reactivity. Persistence of subclinical psychotic experiences was based on the Community Assessment of Psychic Experiences (CAPE, assessed three times over 14 months post-baseline. It was investigated whether baseline daily life emotional and psychotic stress reactivity predicted persistence of psychotic experiences over time. Higher levels of emotional stress reactivity (a decrease in positive and an increase in negative affect in response to stress, and increased psychotic reactivity to daily stress was found in individuals with persistent psychotic experiences over time compared to individuals with transient psychotic experiences. The results suggest that markers of daily life stress reactivity may predict "macro-level" persistence of normally transient expression of psychotic liability over time. Linking daily life markers of altered reactivity in terms of emotions and psychotic experiences to longitudinal persistence of psychotic experiences, associated with increased risk of transition to overt mental disorder, may contribute to earlier and more accurate diagnosis of risk.
2010-01-01
... Standards for Grades of Pistachio Nuts in the Shell § 51.2540 General. (a) Compliance with the provisions of.... (b) These standards are applicable to pistachio nuts in the shell which may be in a natural,...
W.A.Nishshanka
2015-08-01
Full Text Available Abstract Stress is a state of emotional cognitive behavioral and physical reactions to unfavorable situations and is characterized by high levels of arousal distress and feelings of not coping. It has major behavioral and health implications. Stress has a special significance in health care where the workers experience both psychosocial and physical stress. As front-line health care workers who are in the wards for twenty four hours a day Nursing Officers are at high risk of stress due to their enormous responsibilities. In the ward setting they act as the link between the physicians patients and the community.
Shalev, Idan; Moffitt, Terrie E.; Braithwaite, Antony W.; Danese, Andrea; Fleming, Nicholas I.; Goldman-Mellor, Sidra; Harrington, HonaLee; Houts, Renate M.; Israel, Salomon; Poulton, Richie; Robertson, Stephen P.; Sugden, Karen; Williams, Benjamin; Caspi, Avshalom
2013-01-01
There is evidence that persistent psychiatric disorders lead to age-related disease and premature mortality. Telomere length has emerged as a promising biomarker in studies that test the hypothesis that internalizing psychiatric disorders are associated with accumulating cellular damage. We tested the association between the persistence of internalizing disorders (depression, generalized anxiety disorder and post-traumatic stress disorder) and leukocyte telomere length (LTL) in the prospective-longitudinal Dunedin Study (N=1037). Analyses showed that the persistence of internalizing disorders across repeated assessments from ages 11 to 38 years predicted shorter LTL at age 38 years in a dose-response manner, specifically in men (β= −.137, 95% CI: −.232, −.042, p=.005). This association was not accounted for by alternative explanatory factors, including childhood maltreatment, tobacco smoking, substance dependence, psychiatric medication use, poor physical health, or low socioeconomic status. Additional analyses using DNA from blood collected at two time points (ages 26 and 38 years) showed that LTL erosion was accelerated among men who were diagnosed with internalizing disorder in the interim (β= −.111, 95% CI: −.184, −.037, p=.003). No significant associations were found among women in any analysis, highlighting potential sex differences in internalizing-related telomere biology. These findings point to a potential mechanism linking internalizing disorders to accelerated biological aging in the first half of the life course, particularly in men. Because internalizing disorders are treatable, the findings suggest the hypothesis that treating psychiatric disorders in the first half of the life course may reduce the population burden of age-related disease, and extend health expectancy. PMID:24419039
Kalnay, E.; Atlas, R.
1986-01-01
Instantaneous and 15-day time-averaged fields of surface wind, wind stress, curl of the wind stress, and wind divergence are presented. These fields are derived from the Goddard Laboratory for Atmospheres four-dimensional analysis/forecast cycle, for the period September 6-30, 1978, using conventional data, satellite temperature soundings, cloud-track winds, and subjectively dealiased Seasat scatterometer winds.
Cylindrical shell buckling through strain hardening
Bandyopadhyay, K.; Xu, J.; Shteyngart, S. [Brookhaven National Lab., Upton, NY (United States); Gupta, D. [USDOE, Germantown, MD (United States)
1995-04-01
Recently, the authors published results of plastic buckling analysis of cylindrical shells. Ideal elastic-plastic material behavior was used for the analysis. Subsequently, the buckling analysis program was continued with the realistic stress-strain relationship of a stainless steel alloy which does not exhibit a clear yield point. The plastic buckling analysis was carried out through the initial stages of strain hardening for various internal pressure values. The computer program BOSOR5 was used for this purpose. Results were compared with those obtained from the idealized elastic-plastic relationship using the offset stress level at 0.2% strain as the yield stress. For moderate hoop stress values, the realistic stress-grain case shows a slight reduction of the buckling strength. But, a substantial gain in the buckling strength is observed as the hoop stress approaches the yield strength. Most importantly, the shell retains a residual strength to carry a small amount of axial compressive load even when the hoop stress has exceeded the offset yield strength.
Greco,Salvatore; Mesiar, Radko; Rindone, Fabio
2014-01-01
Aggregation functions on [0,1] with annihilator 0 can be seen as a generalized product on [0,1]. We study the generalized product on the bipolar scale [–1,1], stressing the axiomatic point of view. Based on newly introduced bipolar properties, such as the bipolar increasingness, bipolar unit element, bipolar idempotent element, several kinds of generalized bipolar product are introduced and studied. A special stress is put on bipolar semicopulas, bipolar quasi-copulas and bipolar copulas.
Greco, Salvatore; Mesiar, Radko; Rindone, Fabio
2014-01-01
Aggregation functions on [0,1] with annihilator 0 can be seen as a generalized product on [0,1]. We study the generalized product on the bipolar scale [–1,1], stressing the axiomatic point of view. Based on newly introduced bipolar properties, such as the bipolar increasingness, bipolar unit element, bipolar idempotent element, several kinds of generalized bipolar product are introduced and studied. A special stress is put on bipolar semicopulas, bipolar quasi-copulas and bipolar copulas.
Engineered inorganic core/shell nanoparticles
Mélinon, Patrice, E-mail: patrice.melinon@univ-lyon1.fr [Institut Lumière matière Université Claude Bernard Lyon 1 et CNRS et OMNT, Domaine Scientifique de la Doua, Bâtiment Léon Brillouin, 43 Boulevard du 11 Novembre 1918, F 69622 Villeurbanne (France); Begin-Colin, Sylvie [IPCMS et OMNT, 23 rue du Loess BP 43, 67034 STRASBOURG Cedex 2 (France); Duvail, Jean Luc [IMN UMR 6502 et OMNT Campus Sciences : 2 rue de la Houssinire, BP32229, 44322 Nantes Cedex3 (France); Gauffre, Fabienne [SPM et OMNT : Institut des sciences chimiques de Rennes - UMR 6226, 263 Avenue du General Leclerc, CS 74205, 35042 RENNES Cedex (France); Boime, Nathalie Herlin [IRAMIS-NIMBE, Laboratoire Francis Perrin (CEA CNRS URA 2453) et OMNT, Bat 522, CEA Saclay, 91191 Gif sur Yvette Cedex (France); Ledoux, Gilles [Institut Lumière Matière Université Claude Bernard Lyon 1 et CNRS et OMNT, Domaine Scientifique de la Doua, Bâtiment Alfred Kastler 43 Boulevard du 11 Novembre 1918 F 69622 Villeurbanne (France); Plain, Jérôme [Universit de technologie de Troyes LNIO-ICD, CNRS et OMNT 12 rue Marie Curie - CS 42060 - 10004 Troyes cedex (France); Reiss, Peter [CEA Grenoble, INAC-SPrAM, UMR 5819 CEA-CNRS-UJF et OMNT, Grenoble cedex 9 (France); Silly, Fabien [CEA, IRAMIS, SPEC, TITANS, CNRS 2464 et OMNT, F-91191 Gif sur Yvette (France); Warot-Fonrose, Bénédicte [CEMES-CNRS, Université de Toulouse et OMNT, 29 rue Jeanne Marvig F 31055 Toulouse (France)
2014-10-20
It has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed.
Theory of elastic thin shells solid and structural mechanics
Gol'Denveizer, A L; Dryden, H L
1961-01-01
Theory of Elastic Thin Shells discusses the mathematical foundations of shell theory and the approximate methods of solution. The present volume was originally published in Russian in 1953, and remains the only text which formulates as completely as possible the different sets of basic equations and various approximate methods of shell analysis emphasizing asymptotic integration. The book is organized into five parts. Part I presents the general formulation and equations of the theory of shells, which are based on the well-known hypothesis of the preservation of the normal element. Part II is
Gravitational collapse of a cylindrical null shell in vacuum
S. Khakshournia
2008-03-01
Full Text Available Barrabès-Israel null shell formalism is used to study the gravitational collapse of a thin cylindrical null shell in vacuum. In general the lightlike matter shell whose history coincides with a null hypersurface is characterized by a surface energy density. In addition, a gravitational impulsive wave is present on this null hypersurface whose generators admit both the shear and expansion. In the case of imposing the cylindrical flatness the surface energy-momentum tensor of the matter shell on the null hypersurface vanishes and the null hyper- surface is just the history of the gravitational wave .
Off-shell BCJ Relation in Nonlinear Sigma Model
Chen, Gang; Liu, Hanqing
2016-01-01
We investigate relations among tree-level off-shell currents in nonlinear sigma model. Under Cayley parametrization, we propose and prove a general revised BCJ relation for even-point currents. Unlike the on-shell BCJ relation, the off-shell one behaves quite differently from Yang-Mills theory although the algebraic structure is the same. After performing the permutation summation in the revised BCJ relation, the sum is non-vanishing, instead, it equals to the sum of sub-current products with the BCJ coefficients under a specific ordering, which is presented by an explicit formula. Taking on-shell limit, this identity is reduced to the on-shell BCJ relation, and thus provides the full off-shell correspondence of tree-level BCJ relation in nonlinear sigma model.
Yong, Ee Hou; Nelson, David R; Mahadevan, L
2013-10-25
On microscopic scales, the crystallinity of flexible tethered or cross-linked membranes determines their mechanical response. We show that by controlling the type, number, and distribution of defects on a spherical elastic shell, it is possible to direct the morphology of these structures. Our numerical simulations show that by deflating a crystalline shell with defects, we can create elastic shell analogs of the classical platonic solids. These morphologies arise via a sharp buckling transition from the sphere which is strongly hysteretic in loading or unloading. We construct a minimal Landau theory for the transition using quadratic and cubic invariants of the spherical harmonic modes. Our approach suggests methods to engineer shape into soft spherical shells using a frozen defect topology.
Hankin, Benjamin L; Barrocas, Andrea L; Young, Jami F; Haberstick, Brett; Smolen, Andrew
2015-02-28
No research with youth has investigated whether measured genetic risk interacts with stressful environment (G⁎E) to explain engagement in non-suicidal self-injury (NSSI). Two independent samples of youth were used to test the a priori hypothesis that the Transporter-Linked Polymorphic Region (5-HTTLPR) would interact with chronic interpersonal stress to predict NSSI. We tested this hypothesis with children and adolescents from United States public schools in two independent samples (N׳s=300 and 271) using identical procedures and methods. They were interviewed in person with the Self-Injurious Thoughts and Behaviors Interview to assess NSSI engagement and with the UCLA Chronic Stress Interview to assess interpersonal stress. Buccal cells were collected for genotyping of 5-HTTLPR. For both samples, ANOVAs revealed the hypothesized G*E. Specifically, short carriers who experienced severe interpersonal stress exhibited the highest level of NSSI engagement. Replicated across two independent samples, results provide the first demonstration that youth at high genetic susceptibility (5-HTTLPR) and high environmental exposure (chronic interpersonal stress) are at heightened risk for NSSI. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
Molla Jafar, Hamdam; Salabifard, Seddigheh; Mousavi, Seyedeh Maryam; Sobhani, Zahra
2015-09-28
Admission to university is a very sensitive period of life for efficient, active, and young workforces in any country, and it is mostly associated with many changes in social and human relationships. These changes lead to anxiety in students. Moreover, humans need certain functions in order to adaptively deal with different life situations and challenges. By training stress management, these functions can help human acquire the required abilities. The present study was aimed at investigating the effectiveness of stress management training in anxiety, psychological hardiness, and general self-efficacy among university students. The study was a quasi-experimental intervention (pretest-posttest-follow-up) including a control group, it was a fundamental applied study. The statistical population consisted of all students of Islamic Azad University, Karaj, Iran. Convenient sampling was employed to select 30 students who were divided into an experimental group (n=15) and a control group (n=15). Before stress management training, both groups filled out Beck Anxiety Inventory, Long and Goulet scale of psychological hardiness, and General Self-efficacy Scale (GSE-10). Afterwards, the experimental group was provided with stress management training. And after the experiment, the abovementioned questionnaires and scales were responded by the two groups. Finally the collected data were analyzed and compared using one-way MANOVA. The results of MANOVA indicated that there was a significant difference between the two groups in terms of anxiety, hardiness, and general self-efficacy (pstress management among university students cause anxiety to drop; moreover, it enhances their psychological hardiness and self-efficacy. In regard with the role and importance of stress management, training this skill should be included in educational plans of university.
Miner, Patricia; Shimonova, Lyudmila; Khaimov, Arthur; Borukhova, Yaffa; Ilyayeva, Ester; Ranaldi, Robert; Bodnar, Richard J
2012-03-14
Food intake is significantly increased following administration of agonists of GABA and opioid receptors into the nucleus accumbens shell (NACs) and ventral tegmental area (VTA). GABA-A or GABA-B receptor antagonist pretreatment within the VTA or NACs differentially affects mu-opioid agonist-induced feeding elicited from the same site. Correspondingly, general or selective opioid receptor antagonist pretreatment within the VTA or NACs differentially affects GABA agonist-induced feeding elicited from the same site. Regional interactions have been evaluated in feeding studies by administering antagonists in one site prior to agonist administration in a second site. Thus, opioid antagonist-opioid agonist and GABA antagonist-GABA agonist feeding interactions have been identified between the VTA and NACs. However, pretreatment with GABA-A or GABA-B receptor antagonists in the VTA failed to affect mu opioid agonist-induced feeding elicited from the NACs, and correspondingly, these antagonists administered in the NACs failed to affect mu opioid-induced feeding elicited from the VTA. To evaluate whether regional and reciprocal VTA and NACs feeding interactions occur for opioid receptor modulation of GABA agonist-mediated feeding, the present study examined whether feeding elicited by the GABA-B agonist, baclofen microinjected into the NACs was dose-dependently blocked by pretreatment with general (naltrexone: NTX), mu (beta-funaltrexamine: BFNA), kappa (nor-binaltorphamine: NBNI) or delta (naltrindole: NTI) opioid antagonists in the VTA, and correspondingly, whether VTA baclofen-induced feeding was dose-dependently blocked by NACs pretreatment with NTX, BFNA, NBNI or NTI in rats. Bilateral pairs of cannulae aimed at the VTA and NACs were stereotaxically implanted in rats, and their food intakes were assessed following vehicle and baclofen (200 ng) in each site. Baclofen produced similar magnitudes of increased food intake following VTA and NACs treatment. Baclofen
Dai, Hui-Hui
2011-01-01
A polymer network can imbibe water, forming an aggregate called hydrogel, and undergo large and inhomogeneous deformation with external mechanical constraint. Due to the large deformation, nonlinearity plays a crucial role, which also causes the mathematical difficulty for obtaining analytical solutions. Based on an existing model for equilibrium states of a swollen hydrogel with a core-shell structure, this paper seeks analytical solutions of the deformations by perturbation methods for three cases, i.e. free-swelling, nearly free-swelling and general inhomogeneous swelling. Particularly for the general inhomogeneous swelling, we introduce an extended method of matched asymptotics to construct the analytical solution of the governing nonlinear second-order variable-coefficient differential equation. The analytical solution captures the boundary layer behavior of the deformation. Also, analytical formulas for the radial and hoop stretches and stresses are obtained at the two boundary surfaces of the shell, ma...
Active elastic thin shell theory for cellular deformations
Berthoumieux, Hélène; Maître, Jean-Léon; Heisenberg, Carl-Philipp; Paluch, Ewa K.; Jülicher, Frank; Salbreux, Guillaume
2014-06-01
We derive the equations for a thin, axisymmetric elastic shell subjected to an internal active stress giving rise to active tension and moments within the shell. We discuss the stability of a cylindrical elastic shell and its response to a localized change in internal active stress. This description is relevant to describe the cellular actomyosin cortex, a thin shell at the cell surface behaving elastically at a short timescale and subjected to active internal forces arising from myosin molecular motor activity. We show that the recent observations of cell deformation following detachment of adherent cells (Maître J-L et al 2012 Science 338 253-6) are well accounted for by this mechanical description. The actin cortex elastic and bending moduli can be obtained from a quantitative analysis of cell shapes observed in these experiments. Our approach thus provides a non-invasive, imaging-based method for the extraction of cellular physical parameters.
Jouven, Xavier; Schwartz, Peter J; Escolano, Sylvie; Straczek, Céline; Tafflet, Muriel; Desnos, Michel; Empana, Jean Philippe; Ducimetière, Pierre
2009-07-01
The aim of this study involves the early identification, among apparently healthy individuals, of those at high risk for sudden cardiac death. We tested the hypothesis that individuals who respond to mild mental stress in preparation for exercise test with the largest heart rate increases might be at highest risk. Data from 7746 civil servants participating in the Paris Prospective Study I, followed-up for 23 years, allowed to compare heart rate changes between rest and mild mental stress (preparation prior to an exercise test) between subjects who suffered sudden cardiac death (n = 81), non-sudden (n = 129) coronary death, or death from any cause (n = 1306). The mean heart rate increase during mild mental stress was 8.9 +/- 10.8 b.p.m. Risk of sudden cardiac death increased progressively with heart rate increase during mental stress and the relative risk of the third vs. the first tertile was 2.09 (95% confidence interval, 1.13-3.86) after adjustment for confounders. This relationship was not observed for non-sudden coronary death. An important heart rate increase produced by a mild mental stress predicts long-term risk for sudden cardiac death. Heart rate changes before an exercise test may provide a simple tool for risk stratification.
Multi-Shell Hollow Nanogels with Responsive Shell Permeability.
Schmid, Andreas J; Dubbert, Janine; Rudov, Andrey A; Pedersen, Jan Skov; Lindner, Peter; Karg, Matthias; Potemkin, Igor I; Richtering, Walter
2016-03-17
We report on hollow shell-shell nanogels with two polymer shells that have different volume phase transition temperatures. By means of small angle neutron scattering (SANS) employing contrast variation and molecular dynamics (MD) simulations we show that hollow shell-shell nanocontainers are ideal systems for controlled drug delivery: The temperature responsive swelling of the inner shell controls the uptake and release, while the thermoresponsive swelling of the outer shell controls the size of the void and the colloidal stability. At temperatures between 32 °C shell. Computer simulations showed, that temperature induced switching of the permeability of the inner shell allows for the encapsulation in and release of molecules from the cavity.
Evolution of Luminescence with Shell's Thickness in Colloidal CdSe/CdS Core/Shell Quantum Dots
LIANG Da-Shun; SHEN Li; WANG Zhi-Bing; CUI Yi-Ping; ZHANG Jia-Yu; YE Yong-Hong
2008-01-01
@@ We synthesize colloidal CdSe/CdS core/shell quantum clots with different shell thicknesses, and there are five samples including CdSe core dots, and CdSe/CdS core/shell dots with 1-4 CdS layers.X-ray diffraction and Raman measurements indicate that the stress in CdSe core becomes stronger with the increasing shell thickness, and the optical measurements show that when the shell becomes thicker, the photoluminescence quantum yield is enhanced, and the radiative decay is also expedited.The temperature-dependent optical spectra are measured.The relation between the microstructure and the optical properties is discussed.
Horizon Shells and BMS-like Soldering Transformations
Blau, Matthias
2015-01-01
We revisit the theory of null shells in general relativity, with a particular emphasis on null shells placed at horizons of black holes. We study in detail the considerable freedom that is available in the case that one solders two metrics together across null hypersurfaces (such as Killing horizons) for which the induced metric is invariant under translations along the null generators. In this case the group of soldering transformations turns out to be infinite dimensional, and these solderings create non-trivial horizon shells containing both massless matter and impulsive gravitational wave components. We also rephrase this result in the language of Carrollian symmetry groups. To illustrate this phenomenon we discuss in detail the example of shells on the horizon of the Schwarzschild black hole (with equal interior and exterior mass), uncovering a rich classical structure at the horizon and deriving an explicit expression for the general horizon shell energy-momentum tensor. In the special case of BMS-like ...
Fracture mechanics analyses of partial crack closure in shell structures
Zhao, Jun
2007-12-01
This thesis presents the theoretical and finite element analyses of crack-face closure behavior in shells and its effect on the stress intensity factor under a bending load condition. Various shell geometries, such as spherical shell, cylindrical shell containing an axial crack, cylindrical shell containing a circumferential crack and shell with double curvatures, are all studied. In addition, the influence of material orthotropy on the crack closure effect in shells is also considered. The theoretical formulation is developed based on the shallow shell theory of Delale and Erdogan, incorporating the effect of crack-face closure at the compressive edges. The line-contact assumption, simulating the crack-face closure at the compressive edges, is employed so that the contact force at the closure edges is introduced, which can be translated to the mid-plane of the shell, accompanied by an additional distributed bending moment. The unknown contact force is computed by solving a mixed-boundary value problem iteratively, that is, along the crack length, either the normal displacement of the crack face at the compressive edges is equal to zero or the contact pressure is equal to zero. It is found that due to the curvature effects crack closure may not always occur on the entire length of the crack, depending on the direction of the bending load and the geometry of the shell. The crack-face closure influences significantly the magnitude of the stress intensity factors; it increases the membrane component but decreases the bending component. The maximum stress intensity factor is reduced by the crack-face closure. The significant influence of geometry and material orthotropy on rack closure behavior in shells is also predicted based on the analytical solutions. Three-dimensional FEA is performed to validate the theoretical solutions. It demonstrates that the crack face closure occurs actually over an area, not on a line, but the theoretical solutions of the stress intensity
Single-shell tank riser resistance to ground test plan
Kiewert, L.R.
1996-03-11
This Test Procedure provides the general directions for conducting Single-Shell Tank Riser to Earth Measurements which will be used by engineering as a step towards providing closure for the Lightning Hazard Issue.
Thin-shell wormholes in Einstein-Born-Infeld theory
Eiroa, Ernesto F
2015-01-01
We construct spherically symmetric thin-shell wormholes with a generalized Chaplygin gas at the throat, in Born-Infeld electrodynamics coupled to Einstein gravity. We analyze their stability under radial perturbations.
Nonlinear Elastic Deformation of Thin Composite Shells of Discretely Variable Thickness
Lutskaya, I. V.; Maksimyuk, V. A.; Storozhuk, E. A.; Chernyshenko, I. S.
2016-11-01
A method for analyzing the stress-strain state of nonlinear elastic orthotropic thin shells with reinforced holes and shells of discretely variable thickness is developed. The reference surface is not necessarily the midsurface. The constitutive equations are derived using Lomakin's theory of anisotropic plasticity. The methods of successive approximations and variational differences are used. The Kirchhoff-Love hypotheses are implemented using Lagrange multipliers. The method allows analyzing the stress-strain state of shells with arbitrarily varying thickness and ribbed shells. The numerical results are presented in the form of tables and analyzed
Some shell formulations, in view of their applicability to finite elements
Debongnie, Jean-François
1986-01-01
Surface geometry and shell geometry, in the frame of general tensor calculus. Fundamentals of the theory of thin shells. Expressing strains from curvilinear components of the displacements. Applicability of the preceeding theory to finite elements. Expressing strains from the cartesian components of the displacements. Moderate rotation theory (curvilinear components). Moderate rotation theory (cartesian components). Quasi-plane and almost-plane shells. Shells with shearing strains (cartesian ...
Deffayet, C; Esposito-Farèse, G
2009-01-01
We extend to curved backgrounds all flat-space scalar field models that obey purely second-order equations, while maintaining their second-order dependence on both field and metric. This extension simultaneously restores to second order the, originally higher derivative, stress-tensors as well. The process is transparent and uniform for all dimensions.
Rousakis, Aris; Vlassis, Arsenios; Vlanti, Anna;
2013-01-01
-sensing pathway, the target of rapamycin (TOR). We also demonstrated that the GCN-2 and TOR signaling pathways converge on the PHA-4/FoxA transcription factor and its downstream target genes to ensure survival of the whole organism under a multitude of stress conditions, such as nutrient scarcity or environmental...
Stesses in tank shell with shape deformation
Kowalski, Dariusz
2003-01-01
In the paper are shown the results of measurements of stress state in the real tank. The tests were performed with the utilisation of electroresistant tensometry methods. The object of the tests was a vertical tank with nominal capacity of 12.000 m3 and a floating roof. The tank had been operated incessantly for almost 40 years. The shape deformation of the shell generating line was very large. This deformation fluctuated in the range from –170 to +150mm. The measurements of the stress state ...
From shell logs to shell scripts
Jacobs, Nico; Blockeel, Hendrik
2001-01-01
Analysing the use of a Unix command shell is one of the classic applications in the domain of adaptive user interfaces and user modelling. Instead of trying to predict the next command from a history of commands, we automatically produce scripts that automate frequent tasks. For this we use an ILP association rule learner. We show how to speedup the learning task by dividing it into smaller tasks, and the need for a preprocessing phase to detect frequent subsequences in the data. We illustrat...
Liochev, Stefan I
2015-07-20
Aging and oxidative stress are complex phenomena, and their understanding is of enormous theoretical and practical significance. Numerous hypotheses and theories that attempt to explain these phenomena have been developed. These hypotheses and theories compete with each other, with each claiming to be the correct one, while significantly contradicting each other. It is important to develop a maximally correct theory that may then trigger significant practical breakthroughs. None of these theories is entirely correct or close enough to the truth. However, most of them contain many correct elements (CE). Finding these CE is possible by analysis of these theories. Once the CE are found, they can be merged by synthesis in a better new theory. An analysis of some of the theories of aging followed by synthesis is attempted.
Corrasion of a remoulded cohesive bed by saltating littorinid shells
Amos, C. L.; Sutherland, T. F.; Cloutier, D.; Patterson, S.
2000-07-01
along the rounded outer lip of the aperture (measured to be 0.5% of the nominal cross-sectional area of the shell). T increased with shell mass ( Mg) and current speed ( Uy). Below 0.29 m s -1, T0.35 m s -1, T> τo where τo is the fluid-induced shear stress. The total erosion rate ( Etot= Es+ Eo) was compared to the excess total bed shear stress ( τtot- τcrit) and found to be linearly related in the form: E tot=0.010 [τ tot-τ crit] gm -2 s -1. Es appeared to be in linear continuity with Eo if the impact area was set to 0.05% of the estimated shell nominal cross-sectional area.
Lee, M. C.; Kendall, J. M., Jr.; Bahrami, P. A.; Wang, T. G.
1986-01-01
Fluid-dynamic and capillary forces can be used to form nearly perfect, very small spherical shells when a liquid that can solidify is passed through an annular die to form an annular jet. Gravity and certain properties of even the most ideal materials, however, can cause slight asymmetries. The primary objective of the present work is the control of this shell formation process in earth laboratories rather than space microgravity, through the development of facilities and methods that minimize the deleterious effects of gravity, aerodynamic drag, and uncontrolled cooling. The spherical shells thus produced can be used in insulation, recyclable filter materials, fire retardants, explosives, heat transport slurries, shock-absorbing armor, and solid rocket motors.
Hamza, Alex V.; Biener, Juergen; Wild, Christoph; Woerner, Eckhard
2016-11-01
A novel method for fabricating diamond shells is introduced. The fabrication of such shells is a multi-step process, which involves diamond chemical vapor deposition on predetermined mandrels followed by polishing, microfabrication of holes, and removal of the mandrel by an etch process. The resultant shells of the present invention can be configured with a surface roughness at the nanometer level (e.g., on the order of down to about 10 nm RMS) on a mm length scale, and exhibit excellent hardness/strength, and good transparency in the both the infra-red and visible. Specifically, a novel process is disclosed herein, which allows coating of spherical substrates with optical-quality diamond films or nanocrystalline diamond films.
Zhang, Wei; Duan, Guangfeng; Xu, Qin; Jia, Zhaobao; Bai, Zhengyang; Liu, Weizhi; Pan, Xiao; Tian, Wenhua
2015-11-01
After the Wenchuan earthquake, a large number of studies have focused on postearthquake psychological disorders among survivors; however, most of these studies were conducted within a relatively short period. This study was conducted to examine the symptoms of posttraumatic stress disorder (PTSD) and general psychiatric morbidity among adult survivors 3 years after the Wenchuan earthquake, China. Through a multistage systematic sampling approach, a cross-sectional survey of 360 participants, 18 years or older, was conducted. The prevalence of PTSD and general psychiatric morbidity was 10.3% and 20.6%, respectively. Multivariate analysis revealed significant predictors for PTSD, including female gender and having felt guilt concerning someone's death or injury. Significant predictors for general psychiatric morbidity included unmarried status and having been in serious danger. These results suggest that mental health services should be continuously available to earthquake survivors.
Svalbonas, V.
1973-01-01
A procedure for the structural analysis of stiffened shells of revolution is presented. A digital computer program based on the Love-Reissner first order shell theory was developed. The computer program can analyze orthotropic thin shells of revolution, subjected to unsymmetric distributed loading or concentrated line loads, as well as thermal strains. The geometrical shapes of the shells which may be analyzed are described. The shell wall cross section can be a sheet, sandwich, or reinforced sheet or sandwich. General stiffness input options are also available.
Lourenço, Rogério F; Kohler, Christian; Gomes, Suely L
2011-06-01
The extracytoplasmic function sigma factor σ(T) is the master regulator of general stress response in Caulobacter crescentus and controls the expression of its paralogue σ(U). In this work we showed that PhyR and NepR act, respectively, as positive and negative regulators of σ(T) expression and function. Biochemical data also demonstrated that NepR directly binds σ(T) and the phosphorylated form of PhyR. We also described the essential role of the histidine kinase gene CC3474, here denominated phyK, for expression of σ(T)-dependent genes and for resistance to stress conditions. Additionally, in vivo evidence of PhyK-dependent phosphorylation of PhyR is presented. This study also identified a conserved cysteine residue (C95) located in the periplasmic portion of PhyK that is crucial for the function of the protein. Furthermore, we showed that PhyK, PhyR and σ(T) regulate the same set of genes and that σ(T) apparently directly controls most of its regulon. In contrast, σ(U) seems to have a very modest contribution to the expression of a subset of σ(T)-dependent genes. In conclusion, this report describes the molecular mechanism involved in the control of general stress response in C. crescentus.
Ram Chandra Saxena
2012-01-01
Full Text Available A randomized, double-blind, placebo-controlled study was conducted to evaluate the efficacy of OciBest, an extract of Ocimum tenuiflorum Linn. in symptomatic control of general stress. The participants received either placebo (n=79 or OciBest (n=71; 1200 mg of actives per day for six weeks. The severity of stress-related symptoms was self-evaluated by patients at weeks 0, 2, 4 and 6 of the trial period using a symptom rating scale. After six weeks of intervention, scores of symptoms such as forgetfulness, sexual problems of recent origin, frequent feeling of exhaustion, and frequent sleep problems of recent origin decreased significantly (P≤0.05 in OciBest group as compared with placebo group. Also, the total symptom scores of OciBest group revealed significant reduction (P≤0.05 as compared to placebo group. The overall improvement in OciBest group was found to be 1.6 times or 39% more in the control of general stress symptoms with respect to placebo. No adverse events were reported during the study. The findings revealed that OciBest was found to be effective and well tolerated by all the patients over the six weeks of study period.
Zahra Lak
2013-01-01
Full Text Available Aim: The purpose of this study was to investigate the effectiveness of cognitive–behavioral stress management on reduction of anxiety among addicts with GAD. Method: The design of the study is experimental with pretest -posttest and control group. The population of the study was all addicts with GAD in Tehran self-referred centers that scored the most points in GAD-7 test. 24 addicts were allocated into experimental group (N=12 and control group (N=12. The cognitive-behavioral stress management was demonstrated in 10 weekly sessions on the experimental group while there was no psychological treatment for the control group. DASS-21 questionnaire and GAD-7 questionnaire were completed by both groups before and after program. The data was analyzed using covariance. Results: There were no significant differences in anxiety between two groups before intervention. Results of this study demonstrated that cognitive –behavioral stress management led to significant decrease in anxiety in experimental group. Conclusion: Regarding to effectiveness of cognitive-behavioral stress management on anxiety, it may also be used as a supplement method decreasing generalized anxiety disorder among addicts.
Hengartner, Michael P; van der Linden, Dimitri; Bohleber, Laura; von Wyl, Agnes
2017-02-01
We conducted an online survey including 306 participants aged 18-64 years to assess the general factor of personality (GFP) and Big Five personality traits in relation to individual stress and coping reactions following a shooting emergency alarm at a Swiss university campus. Although the emergency eventually turned out to be a false alarm, various witnesses showed pronounced distress owing to a vast police operation. The GFP structure was replicated using two alternative modelling approaches. Neuroticism related substantially to acute fear and traumatic distress as well as to more enduring maladaptive coping. Agreeableness was negatively associated with the coping strategy of medication use, whereas both agreeableness and conscientiousness related positively to social activity following the emergency. The GFP related moderately to peri-traumatic distress and showed a substantial negative association with medication use and a strong positive association with social activity. In conclusion, both the GFP and Big Five traits significantly moderate stress responses following a stressful life event. The GFP predominantly relates to socially adaptive coping, whereas in particular neuroticism accounts for acute stress reactions such as fear and traumatic distress. These findings support the notion that personality influences how persons react in the face of adversity. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Shear correction factors for layered plates and shells
Gruttmann, F.; Wagner, W.
2016-10-01
In this paper layered composite shells subjected to static loading are considered. The theory is based on a multi-field functional, where the associated Euler-Lagrange equations include besides the global shell equations formulated in stress resultants, the local in-plane equilibrium in terms of stresses and a constraint which enforces the correct shape of warping through the thickness. Within representative volume elements warping displacements are interpolated with layerwise cubic functions in thickness direction and constant shape throughout the reference surface. Elimination of warping and Lagrange parameters by static condensation leads to a material matrix for the stress resultants and to shear correction factors for layered plates and shells. For linear elasticity the computation can be done once in advance. The condensed material matrix is used in displacement based elements along with the enhanced strain method or in mixed hybrid elements with the usual 5 or 6 nodal degrees of freedom. This allows standard geometrical boundary conditions and the elements are applicable also to shell intersection problems. The interlaminar shear stresses are evaluated via the constitutive law by back substitution of the eliminated parameters. The computed transverse shear stresses are automatically continuous at the layer boundaries and zero at the outer surfaces. Furthermore, the integrals of the shear stresses coincide exactly with the shear forces without introduction of further constraints.
Shear correction factors for layered plates and shells
Gruttmann, F.; Wagner, W.
2017-01-01
In this paper layered composite shells subjected to static loading are considered. The theory is based on a multi-field functional, where the associated Euler-Lagrange equations include besides the global shell equations formulated in stress resultants, the local in-plane equilibrium in terms of stresses and a constraint which enforces the correct shape of warping through the thickness. Within representative volume elements warping displacements are interpolated with layerwise cubic functions in thickness direction and constant shape throughout the reference surface. Elimination of warping and Lagrange parameters by static condensation leads to a material matrix for the stress resultants and to shear correction factors for layered plates and shells. For linear elasticity the computation can be done once in advance. The condensed material matrix is used in displacement based elements along with the enhanced strain method or in mixed hybrid elements with the usual 5 or 6 nodal degrees of freedom. This allows standard geometrical boundary conditions and the elements are applicable also to shell intersection problems. The interlaminar shear stresses are evaluated via the constitutive law by back substitution of the eliminated parameters. The computed transverse shear stresses are automatically continuous at the layer boundaries and zero at the outer surfaces. Furthermore, the integrals of the shear stresses coincide exactly with the shear forces without introduction of further constraints.
Nazemi, Sanaz; Pourfath, Mahdi; Soleimani, Ebrahim Asl; Kosina, Hans
2016-04-01
Due to their tunable properties, silicon nano-crystals (NC) are currently being investigated. Quantum confinement can generally be employed for size-dependent band-gap tuning at dimensions smaller than the Bohr radius (˜5 nm for silicon). At the nano-meter scale, however, increased surface-to-volume ratio makes the surface effects dominant. Specifically, in Si-SiO2 core-shell semiconductor NCs the interfacial transition layer causes peculiar electronic and optical properties, because of the co-existence of intermediate oxidation states of silicon (Sin+, n = 0-4). Due to the presence of the many factors involved, a comprehensive understanding of the optical properties of these NCs has not yet been achieved. In this work, Si-SiO2 NCs with a diameter of 1.1 nm and covered by amorphous oxide shells with thicknesses between 2.5 and 4.75 Å are comprehensively studied, employing density functional theory calculations. It is shown that with increased oxide shell thickness, the low-energy part of the optical transition spectrum of the NC is red shifted and attenuated. Moreover, the absorption coefficient is increased in the high-energy part of the spectrum which corresponds to SiO2 transitions. Structural examinations indicate a larger compressive stress on the central silicon cluster with a thicker oxide shell. Examination of the local density of states reveals the migration of frontier molecular orbitals from the oxide shell into the silicon core with the increase of silica shell thickness. The optical and electrical properties are explained through the analysis of the density of states and the spatial distribution of silicon sub-oxide species.
BOWOOSS: bionic optimized wood shells with sustainability
Pohl, Göran
2011-04-01
In architecture, shell construction is used for the most efficient, large spatial structures. Until now the use of wood rather played a marginal role, implementing those examples of architecture, although this material offers manifold advantages, especially against the background of accelerating shortage of resources and increasing requirements concerning the energy balance. Regarding the implementation of shells, nature offers a wide range of suggestions. The focus of the examinations is on the shells of marine plankton, especially of diatoms, whose richness in species promises the discovery of entirely new construction principles. The project is targeting at transferring advantageous features of these organisms on industrial produced, modular wood shell structures. Currently a transfer of these structures in CAD - models is taking place, helping to perform stress analysis by computational methods. Micro as well as macro structures are the subject of diverse consideration, allowing to draw the necessary conclusions for an architectural design. The insights of these tests are the basis for the development of physical models on different scales, which are used to verify the different approaches. Another important aim which is promoted in the project is to enhance the competitiveness of timber construction. Downsizing of the prefabricated structural elements leads to considerable lower transportation costs as abnormal loads can be avoided as far as possible and means of transportation can be loaded with higher efficiency so that an important contribution to the sustainability in the field of architecture can also be made.
Sensitivity analysis for the dynamic response of viscoplastic shells of revolution
Kulkarni, Makarand; Noor, Ahmed K.
1995-01-01
A computational procedure is presented for evaluating the sensitivity coefficients of the dynamic axisymmetric response of viscoplastic shells of revolution. The analytical formulation is based on Reissner's large deformation shell theory with the effects of transverse shear deformation, rotatory inertia and moments turning around the normal to the middle surface included. The material model is chosen to be isothermal viscoplasticity, and an associated flow rule is used with a von Mises effective stress. A mixed formulation is used with the fundamental unknowns consisting of six stress resultants, three generalized displacements and three velocity components. Spatial discretization is performed using finite elements, with discontinuous stress resultants across element interfaces. The temporal integration is performed by using an explicit central difference scheme (leap-frog method) with an implicit constitutive update. The sensitivity coefficients are evaluated using a direct differentiation approach. Numerical results are presented for a spherical cap subjected to step loading, and a circular plate subjected to impulsive loading. The sensitivity coefficients are generated by evaluating the derivatives of the response quantities with respect to thickness, mass density, Young's modulus, and two of the material parameters characterizing the viscoplastic response. Time histories of the response and sensitivity coefficients are presented, along with spatial distributions of these quantities at selected times.
Computer analysis of shells of revolution using asymptotic results
Steele, C. R.; Ranjan, G. V.; Goto, C.; Pulliam, T. H.
1979-01-01
It is suggested that asymptotic results for the behavior of thin shells can be incorporated in a general computer code for the analysis of a complex shell structure. The advantage when compared to existing finite difference or finite element codes is a substantial reduction in computational labor with the capability of working to a specified level of accuracy. A reduction in user preparation time and dependance on user judgment is also gained, since mesh spacing can be internally generated. The general theory is described in this paper, as well as the implementation in the computer code FAST 1 (Functional Algorithm for Shell Theory) for the analysis of the general axisymmetric shell structure with axisymmetric loading.
A cylindrical shell with an axial crack under skew-symmetric loading.
Yuceoglu, U.; Erdogan, F.
1973-01-01
The skew-symmetric problem for a cylindrical shell containing an axial crack is considered. It is assumed that the material has a special orthotropy - namely, that the shear modulus may be evaluated from the measured Young's moduli and Poisson ratios and is not an independent material constant. The problem is solved within the confines of an eighth-order linearized shallow shell theory. As numerical examples, the torsion of an isotropic cylinder and that of a specially orthotropic cylinder (titanium) are considered. The membrane and bending components of the stress intensity factor are calculated and are given as functions of a dimensionless shell parameter. In the torsion problem for the axially cracked cylinder the bending effects appear to be much more significant than that found for the circumferentially cracked cylindrical shell. Also, as the shell parameter increases, unlike the results found in the pressurized shell, the bending stresses around crack ends do not change sign.
Sauviac, Laurent; Bruand, Claude
2014-07-01
The EcfG-type sigma factor RpoE2 is the regulator of the general stress response in Sinorhizobium meliloti. RpoE2 activity is negatively regulated by two NepR-type anti-sigma factors (RsiA1/A2), themselves under the control of two anti-anti-sigma factors (RsiB1/B2) belonging to the PhyR family of response regulators. The current model of RpoE2 activation suggests that in response to stress, RsiB1/B2 are activated by phosphorylation of an aspartate residue in their receiver domain. Once activated, RsiB1/B2 become able to interact with the anti-sigma factors and release RpoE2, which can then associate with the RNA polymerase to transcribe its target genes. The purpose of this work was to identify and characterize proteins involved in controlling the phosphorylation status of RsiB1/B2. Using in vivo approaches, we show that the putative histidine kinase encoded by the rsiC gene (SMc01507), located downstream from rpoE2, is able to both positively and negatively regulate the general stress response. In addition, our data suggest that the negative action of RsiC results from inhibition of RsiB1/B2 phosphorylation. From these observations, we propose that RsiC is a bifunctional histidine kinase/phosphatase responsible for RsiB1/B2 phosphorylation or dephosphorylation in the presence or absence of stress, respectively. Two proteins were previously proposed to control PhyR phosphorylation in Caulobacter crescentus and Sphingomonas sp. strain FR1. However, these proteins contain a Pfam:HisKA_2 domain of dimerization and histidine phosphotransfer, whereas S. meliloti RsiC harbors a Pfam:HWE_HK domain instead. Therefore, this is the first report of an HWE_HK-containing protein controlling the general stress response in Alphaproteobacteria.
On-Shell Diagrams for N = 8 Supergravity Amplitudes
Heslop, Paul
2016-01-01
We define recursion relations for N = 8 supergravity amplitudes using a generalization of the on-shell diagrams developed for planar N = 4 super-Yang-Mills. Although the recursion relations generically give rise to non-planar on-shell diagrams, we show that at tree-level the recursion can be chosen to yield only planar diagrams, the same diagrams occurring in the planar N = 4 theory. This implies non-trivial identities for non-planar diagrams as well as interesting relations between the N = 4 and N = 8 theories. We show that the on-shell diagrams of N = 8 supergravity obey equivalence relations analogous to those of N = 4 super-Yang-Mills, and we develop a systematic algorithm for reading off Grassmannian integral formulae directly from the on-shell diagrams. We also show that the 1-loop 4-point amplitude of N = 8 supergravity can be obtained from on-shell diagrams.
Incorporation of hazelnut shell and husk in MDF production.
Cöpür, Yalçin; Güler, Cengiz; Taşçioğlu, Cihat; Tozluoğlu, Ayhan
2008-10-01
Hazelnut shell and husk (Coryllus arellana L.) is an abundant agricultural residue in Turkey and investigating the possibilities of utilizing husk and shell in panel production might help to overcome the raw material shortage that the panel industry is facing. The aim of this work was to investigate the possibilities of utilizing hazelnut shell and husk in medium density fiberboard (MDF) production. To produce general purpose fiberboards, fiber-husk and fiber-shell mixtures at various percentages were examined in this study. The results indicated that panels could be produced utilizing hazelnut husk up to 20% addition without falling below the properties required in the standards. Shell addition was restricted up to 10%, because higher addition levels diminished the elastic modulus and internal bond strength below the acceptable level.
Thin-shell wormholes constrained by cosmological observations
Wang, Deng; Meng, Xin-He
2017-09-01
We investigate the thin-shell wormholes constrained by cosmological observations for the first time in the literature. Without loss of generality, we study the thin-shell wormholes in ωCDM model and analyze their stability under perturbations preserving the symmetry. Firstly, we constrain the ωCDM model using a combination of Union 2.1 SNe Ia data, the latest H(z) data and CMB data. Secondly, we use the constrained dark energy equation of state (EoS) ω which lies in [ - 1 . 05 , - 0 . 89 ] to investigate thin-shell wormholes generated by various black hole spacetimes. We find that the stable Schwarzschild and Reinssner-Nordström thin-shell wormholes constrained by cosmological observations do not exist. In addition, the method we developed can be applied in exploring the stable thin-shell wormholes from any black hole spacetime in the framework of any cosmological theory.
Simulation for double shell pinch
Wang Gang-Hua; Hu Xi-Jing; Sun Cheng-Wei
2004-01-01
Basic shock phenomena are presented in a composite pinch, a hybrid of the Z-pinch. The successive transfer of current within the plasma structure is demonstrated by our calculations. Properties of the shock wave are described.The current distribution between the two shells after the outer shell hitting the inner shell is also discussed.
Temporal structures in shell models
Okkels, F.
2001-01-01
The intermittent dynamics of the turbulent Gledzer, Ohkitani, and Yamada shell-model is completely characterized by a single type of burstlike structure, which moves through the shells like a front. This temporal structure is described by the dynamics of the instantaneous configuration of the shell...
Recent Advances in Shell Evolution with Shell-Model Calculations
Utsuno, Yutaka; Tsunoda, Yusuke; Shimizu, Noritaka; Honma, Michio; Togashi, Tomoaki; Mizusaki, Takahiro
2014-01-01
Shell evolution in exotic nuclei is investigated with large-scale shell-model calculations. After presenting that the central and tensor forces produce distinctive ways of shell evolution, we show several recent results: (i) evolution of single-particle-like levels in antimony and cupper isotopes, (ii) shape coexistence in nickel isotopes understood in terms of configuration-dependent shell structure, and (iii) prediction of the evolution of the recently established $N=34$ magic number towards smaller proton numbers. In any case, large-scale shell-model calculations play indispensable roles in describing the interplay between single-particle character and correlation.
Kopey, B.V.; Kopey, L.B. [Ivano-Frankivsk State Technical Oil and Gas University (Ukraine); Maksymuk, A.V.; Shcherbyna, N.M. [National Ukrainian Academy of Sciences (Ukraine)
1998-12-31
The methods of calculation of contact stresses during cylinder shell tube - steel bandage interaction are presented. Tymoshenko`s generalized theory of shells serves as a basis for investigating steel head to fiberglass sucker rod joint strength. This theory allows to consider mechanical performance of composite materials. The problem is reduced to solving Fredholm integral equation of second degree. The numeric analysis is performed. Several joints of composite body with steel head are proposed. The full-size sucker rod fatigue tests are performed to determine the fatigue limit under the bending and axial cyclic loads in the medium of oil well fluids. (orig.)
Semenyuk, N. P.; Trach, V. M.; Zhukova, N. B.; Vlasuk, D. S.
2015-05-01
The nonlinear deformation and stability of composite shells are estimated by using the Timoshenko-Mindlin theory of anisotropic shells. The resolving system of equations is presented in a mixed form in displacements, forces, and moments. For its derivation, a modified version of the generalized Hu-Washizu variational principle formulated in rates for a quasi-static problem is used. However, instead of differentiation with respect to time, displacements, stresses, and loads are assumed to depend on a parameter, for which it is advisable to take the length of the arc of equilibrium states, as demonstrated in some studies. On variation of this parameter, the shell-load system can occur either at regular or singular points. A boundary value problem is formulated in the form of a normal system of differential equations in the derivatives of displacements, forces, and moments. In the separation of variables, the Fourier series are used in a complex form. The boundary value problem is solved by the Godunov discrete orthogonalization method in the field of complex numbers. Then, the Cauchy problem is solved by using known methods. Using the methodology developed, an analysis of the influence of composite properties and parameters of the layered structures on the form of the equilibrium curves of cylindrical shells is carried out. The mechanical characteristics of the initial elementary layers of the reinforced material are determined by the micromechanics methods developed by Eshelby, Mori-Tanaka, and Vanin.
2010-01-01
... 7 Agriculture 2 2010-01-01 2010-01-01 false Split shell. 51.2002 Section 51.2002 Agriculture... Standards for Grades of Filberts in the Shell 1 Definitions § 51.2002 Split shell. Split shell means a shell... of the shell, measured in the direction of the crack....
Titia Feldmann, C.; Bensing, J.; Ruijter, Arie de
Objective: To confront the views of refugee patients and general practitioners in the Netherlands, focusing on medically unexplained physical symptoms (MUPS). Methods: The study is based on in depth interviews with refugees from Afghanistan (n = 36) and Somalia (n = 30). Additionally,
Kuyper, L.S.
2011-01-01
Previous studies show that lesbian, gay and bisexual (LGB) individuals report more health problems than heterosexual individuals. However, several important gaps remain in the knowledge regarding the explanations for these health differences. In general, there is a lack of differentiation between
Kuyper, L.S.
2011-01-01
Previous studies show that lesbian, gay and bisexual (LGB) individuals report more health problems than heterosexual individuals. However, several important gaps remain in the knowledge regarding the explanations for these health differences. In general, there is a lack of differentiation between su
Titia Feldmann, C.; Bensing, J.; Ruijter, Arie de
2007-01-01
Objective: To confront the views of refugee patients and general practitioners in the Netherlands, focusing on medically unexplained physical symptoms (MUPS). Methods: The study is based on in depth interviews with refugees from Afghanistan (n = 36) and Somalia (n = 30). Additionally, semistructured
Feldmann, C.T.; Bensing, J.M.; Ruijter, A. de
2007-01-01
Objective: To confront the views of refugee patients and general practitioners in the Netherlands, focusing on medically unexplained physical symptoms (MUPS). Methods: The study is based on in depth interviews with refugees from Afghanistan (n=36) and Somalia (n=30). Additionally, semi-structured in
Insights from the Shell Proteome: Biomineralization to Adaptation.
Arivalagan, Jaison; Yarra, Tejaswi; Marie, Benjamin; Sleight, Victoria A; Duvernois-Berthet, Evelyne; Clark, Melody S; Marie, Arul; Berland, Sophie
2017-01-01
Bivalves have evolved a range of complex shell forming mechanisms that are reflected by their incredible diversity in shell mineralogy and microstructures. A suite of proteins exported to the shell matrix space plays a significant role in controlling these features, in addition to underpinning some of the physical properties of the shell itself. Although, there is a general consensus that a minimum basic protein tool kit is required for shell construction, to date, this remains undefined. In this study, the shell matrix proteins (SMPs) of four highly divergent bivalves (The Pacific oyster, Crassostrea gigas; the blue mussel, Mytilus edulis; the clam, Mya truncata, and the king scallop, Pecten maximus) were analyzed in an identical fashion using proteomics pipeline. This enabled us to identify the critical elements of a "basic tool kit" for calcification processes, which were conserved across the taxa irrespective of the shell morphology and arrangement of the crystal surfaces. In addition, protein domains controlling the crystal layers specific to aragonite and calcite were also identified. Intriguingly, a significant number of the identified SMPs contained domains related to immune functions. These were often are unique to each species implying their involvement not only in immunity, but also environmental adaptation. This suggests that the SMPs are selectively exported in a complex mix to endow the shell with both mechanical protection and biochemical defense. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
Core-Shell Nanoparticle-Enhanced Raman Spectroscopy.
Li, Jian-Feng; Zhang, Yue-Jiao; Ding, Song-Yuan; Panneerselvam, Rajapandiyan; Tian, Zhong-Qun
2017-03-08
Core-shell nanoparticles are at the leading edge of the hot research topics and offer a wide range of applications in optics, biomedicine, environmental science, materials, catalysis, energy, and so forth, due to their excellent properties such as versatility, tunability, and stability. They have attracted enormous interest attributed to their dramatically tunable physicochemical features. Plasmonic core-shell nanomaterials are extensively used in surface-enhanced vibrational spectroscopies, in particular, surface-enhanced Raman spectroscopy (SERS), due to the unique localized surface plasmon resonance (LSPR) property. This review provides a comprehensive overview of core-shell nanoparticles in the context of fundamental and application aspects of SERS and discusses numerous classes of core-shell nanoparticles with their unique strategies and functions. Further, herein we also introduce the concept of shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) in detail because it overcomes the long-standing limitations of material and morphology generality encountered in traditional SERS. We then explain the SERS-enhancement mechanism with core-shell nanoparticles, as well as three generations of SERS hotspots for surface analysis of materials. To provide a clear view for readers, we summarize various approaches for the synthesis of core-shell nanoparticles and their applications in SERS, such as electrochemistry, bioanalysis, food safety, environmental safety, cultural heritage, materials, catalysis, and energy storage and conversion. Finally, we exemplify about the future developments in new core-shell nanomaterials with different functionalities for SERS and other surface-enhanced spectroscopies.
Webster, Nicole B; Palmer, A Richard
2016-02-01
Gastropod shell sculpture offers a novel tool for studying morphological patterning. Existing shell features may be manipulated experimentally to test how alteration affects subsequent shell growth and form. Axial sculpture occurs in many gastropod groups, and spacing of sculpture may be regular or irregular. But how gastropods control sculpture placement during shell growth is unknown. We studied the growth and positioning of axial lamellae in the muricid Nucella lamellosa, and compared these to the superficially similar axial varices seen in other muricids. First, we tested whether the feeding rate had any effect on the rate of addition or positioning of new lamellae. Second, we tested what effect previous shell sculpture had on lamellar placement, and shell growth in general, by removing all shell sculpture and allowing snails to grow over the "shaved" shell surface. Lamellar growth appeared to be relatively plastic; spacing was highly variable both within and among individual snails, and 1-2 weeks were required to complete the addition of a new lamella. Body growth rate was the primary determinant of lamellar growth; past lamellae had no effect on placement of new lamellae or rate of shell length increase. Feeding rate and body size affected only growth in shell length, and had no direct effect on spacing or on the rate of addition of new lamellae. The growth of axial lamellae in N. lamellosa differed from that of varices by exhibiting neither a) regular spacing nor b) a growth hiatus after completion of a lamella. Significantly, despite the obvious impediment of previous sculpture to future shell growth, removal of this sculpture had no observable effect on the rate of body growth or on any aspect of subsequent lamellar growth.
Interface Fracture in Adhesively Bonded Shell Structures
Jensen, Henrik Myhre
2007-01-01
Two methods for the prediction of crack propagation through the interface of adhesively bonded shells are discussed. One is based on a fracture mechanics approach; the other is based on a cohesive zone approach. Attention is focussed on predicting the shape of the crack front and the critical...... stress required to propagate the crack under quasi-static conditions. The fracture mechanical model is theoretically sound and it is accurate and numerically stable. The cohesive zone model has some advantages over the fracture mechanics based model. It is easier to generalise the cohesive zone model...... to take into account effects such as plastic deformation in the adhering shells, and to take into account effects of large local curvatures of the interface crack front. The comparison shows a convergence of the results based on the cohesive zone model towards the results based on a fracture mechanics...
Nuclear level density: Shell-model approach
Sen'kov, Roman; Zelevinsky, Vladimir
2016-06-01
Knowledge of the nuclear level density is necessary for understanding various reactions, including those in the stellar environment. Usually the combinatorics of a Fermi gas plus pairing is used for finding the level density. Recently a practical algorithm avoiding diagonalization of huge matrices was developed for calculating the density of many-body nuclear energy levels with certain quantum numbers for a full shell-model Hamiltonian. The underlying physics is that of quantum chaos and intrinsic thermalization in a closed system of interacting particles. We briefly explain this algorithm and, when possible, demonstrate the agreement of the results with those derived from exact diagonalization. The resulting level density is much smoother than that coming from conventional mean-field combinatorics. We study the role of various components of residual interactions in the process of thermalization, stressing the influence of incoherent collision-like processes. The shell-model results for the traditionally used parameters are also compared with standard phenomenological approaches.
Large deformation of liquid capsules enclosed by thin shells immersed in the fluid
Le, Duc-Vinh; Tan, Zhijun
2010-06-01
The deformation of a liquid capsule enclosed by a thin shell in a simple shear flow is studied numerically using an implicit immersed boundary method. We present a thin-shell model for computing the forces acting on the shell middle surface during the deformation within the framework of the Kirchhoff-Love theory of thin shells. This thin-shell model takes full account of finite-deformation kinematics which allows thickness stretching as well as large deflections and bending strains. For hyperelastic materials, the plane-stress assumption is used to compute the hydrostatic pressure and the incompressibility condition yields the thickness strain component and the corresponding change in the thickness. The stresses developing over the cross-section of the shell are integrated over the thickness to yield the stress and moment resultants which are then used to compute the forces acting on the shell middle surface. The immersed boundary method is employed for calculating the hydrodynamics and fluid-structure interaction effects. The location of the thin shell is updated implicitly using the Newton-Krylov method. The present numerical technique has been validated by several examples including an inflation of a spherical shell and deformations of spherical and oblate spheroidal capsules in the shear flow.
Asymptotic analysis of laminated plates and shallow shells
Skoptsov, K. A.; Sheshenin, S. V.
2011-02-01
It was noted long ago [1] that the material strength theory develops both by improving computational methods and by widening the physical foundations. In the present paper, we develop a computational technique based on asymptotic methods, first of all, on the homogenization method [2, 3]. A modification of the homogenization method for plates periodic in the horizontal projection was proposed in [4], where the bending of a homogeneous plate with periodically repeating inhomogeneities on its surface was studied. A more detailed asymptotic analysis of elastic plates periodic in the horizontal projection can be found, e.g., in [5, 6]. In [6], three asymptotic approximations were considered, local problems on the periodicity cell were obtained for them, and the solvability of these problems was proved. In [7], it was shown that the techniques developed for plates periodic in the horizontal projection can also be used for laminated plates. In [7], this was illustrated by an example of asymptotic analysis of an isotropic plate symmetric with respect to the midplane. In what follows, these methods are generalized to the case of combined bending and extension of a longitudinal laminated plate up to the third approximation, which permits finding all components of the stress tensor. The study of the plate behavior is based on the method of homogenization of the three-dimensional problem of linear elasticity and does not use any hypotheses. It turns out that the Kirchhoff-Love hypothesis for the entire packet of layers is simply a consequence of the method in the zeroth approximation, and the bending stresses corresponding to the classical theory of laminated plates [8] are obtained in the first approximation. The successive approximations describe the behavior of the normal and the stress more precisely. In the present paper, the results obtained in [7] are refined, and the asymptotic solution is compared with the direct analysis of a laminated plate by the finite
Horizon shells and BMS-like soldering transformations
Blau, Matthias; O'Loughlin, Martin
2016-03-01
We revisit the theory of null shells in general relativity, with a particular emphasis on null shells placed at horizons of black holes. We study in detail the considerable freedom that is available in the case that one solders two metrics together across null hypersurfaces (such as Killing horizons) for which the induced metric is invariant under translations along the null generators. In this case the group of soldering transformations turns out to be infinite dimensional, and these solderings create non-trivial horizon shells containing both massless matter and impulsive gravitational wave components. We also rephrase this result in the language of Carrollian symmetry groups. To illustrate this phenomenon we discuss in detail the example of shells on the horizon of the Schwarzschild black hole (with equal interior and exterior mass), uncovering a rich classical structure at the horizon and deriving an explicit expression for the general horizon shell energy-momentum tensor. In the special case of BMS-like soldering supertranslations we find a conserved shell-energy that is strikingly similar to the standard expression for asymptotic BMS supertranslation charges, suggesting a direct relation between the physical properties of these horizon shells and the recently proposed BMS supertranslation hair of a black hole.
Horizon shells and BMS-like soldering transformations
Blau, Matthias [Albert Einstein Center for Fundamental Physics,Institute for Theoretical Physics, University of Bern,Sidlerstrasse 5, 3012 Bern (Switzerland); O’Loughlin, Martin [University of Nova Gorica,Vipavska 13, 5000 Nova Gorica (Slovenia)
2016-03-07
We revisit the theory of null shells in general relativity, with a particular emphasis on null shells placed at horizons of black holes. We study in detail the considerable freedom that is available in the case that one solders two metrics together across null hypersurfaces (such as Killing horizons) for which the induced metric is invariant under translations along the null generators. In this case the group of soldering transformations turns out to be infinite dimensional, and these solderings create non-trivial horizon shells containing both massless matter and impulsive gravitational wave components. We also rephrase this result in the language of Carrollian symmetry groups. To illustrate this phenomenon we discuss in detail the example of shells on the horizon of the Schwarzschild black hole (with equal interior and exterior mass), uncovering a rich classical structure at the horizon and deriving an explicit expression for the general horizon shell energy-momentum tensor. In the special case of BMS-like soldering supertranslations we find a conserved shell-energy that is strikingly similar to the standard expression for asymptotic BMS supertranslation charges, suggesting a direct relation between the physical properties of these horizon shells and the recently proposed BMS supertranslation hair of a black hole.
Bhavani Muthukrishnan
2016-06-01
Full Text Available BACKGROUND The stress response to surgery is characterised by increased secretion of pituitary hormones and activation of the sympathetic nervous system. The changes triggered by the stress response are short-lived and well tolerated by normal healthy patients belonging to ASA 1 and 2. In patients with other comorbidities like myocardial ischaemia, renal insufficiency, uncontrolled diabetes, liver disease and cerebrovascular diseases, these changes can be life threatening. The recognition of the factors which initiate the stress response can be considered for modification in the preoperative period itself. Various anaesthetic techniques and pain management strategies have been put into use to control the stress response. AIM To study the rise in serum cortisol levels during surgery after administering oral pregabalin as a premedicant. SETTINGS AND DESIGN A Prospective Randomised Placebo Controlled Study. MATERIALS AND METHODS All consented patients were aged between 18 and 50 years belonging to ASA 1 & 2 undergoing elective surgical procedures under general anaesthesia of duration between 30 minutes and 180 minutes. Group A received oral placebo, Group B oral pregabalin 150 mg 60-90 minutes before surgery with sips of water. They were randomly allocated to a particular group using computer generated numbers. The ward staff nurse administered the drug kept in sealed envelopes. Both the patients and the person administering anaesthesia were unaware of the group. STATISTICAL ANALYSIS The results were analysed using SPSS Version 17 software with the help of the statistician. The students’ paired t-test was used to compare the mean change in the cortisol levels in the two groups. RESULTS There was a significant [p < 0.01] reduction in the intraoperative cortisol levels after premedication with pregabalin. There was an increase in serum cortisol levels after extubation in both the groups which was statistically significant (p < 0.01. CONCLUSION
A novel approach to thin-shell wormholes and applications
Lobo, Francisco S N; Martín-Moruno, Prado; Montelongo-García, Nadiezhda; Visser, Matt
2015-01-01
A novel framework is presented that can be adapted to a wide class of generic spherically symmetric thin-shell wormholes. By using the Darmois--Israel formalism, we analyze the stability of arbitrary spherically symmetric thin-shell wormholes to linearized perturbations around static solutions. We demonstrate in full generality that the stability of the wormhole is equivalent to choosing suitable properties for the exotic material residing on the wormhole throat. As an application, we consider the thin-shell variant of the Ellis wormhole for the cases of a vanishing momentum flux and non-zero external fluxes.
2012-08-01
possibilities that heretofore have not been investigated, namely, “rigid bodies” [7]. Another need for the use of these techniques is in multi-patch NURBS meshes... techniques is completely satisfactory in all cases. Even if they can be used successfully in certain situations they can give rise to reduced critical...condition which is violated at the patch boundaries. The C0 boundaries between patches behave like piano hinges for thin shell formulations, and
van Marwijk Harm WJ
2006-05-01
Full Text Available Abstract Background The main aims of this paper are to describe the setting and design of a Minimal Intervention in general practice for Stress-related mental disorders in patients on Sick leave (MISS, as well as to ascertain the study complies with the requirements for a cluster randomised controlled trial (RCT. The potential adverse consequences of sick leave due to Stress-related Mental Disorders (SMDs are extensive, but often not recognised. Since most people having SMDs with sick leave consult their general practitioner (GP at an early stage, a tailored intervention given by GPs is justified. We provide a detailed description of the MISS; that is more accurate assessment, education, advice and monitoring to treat SMDs in patients on sick leave. Our hypothesis is that the MISS will be more effective compared to the usual care, in reducing days of sick leave of these patients. Methods The design is a pragmatic RCT. Randomisation is at the level of GPs. They received the MISS-training versus no training, in order to compare the MISS vs. usual care at patient level. Enrolment of patients took place after screening in the source population, that comprised 20–60 year old primary care attendees. Inclusion criteria were: moderately elevated distress levels, having a paid job and sick leave for no longer than three months. There is a one year follow up. The primary outcome measure is lasting full return to work. Reduction of SMD- symptoms is one of the secondary outcome measures. Forty-six GPs and 433 patients agreed to participate. Discussion In our study design, attention is given to the practical application of the requirements for a pragmatic trial. The results of this cluster RCT will add to the evidence about treatment options in general practice for SMDs in patients on sick leave, and might contribute to a new and appropriate guideline. These results will be available at the end of 2006.
Shell model calculations of 109Sb in the sdgh shell
Dikmen, E.; Novoselsky, A.; Vallieres, M.
2001-12-01
The energy spectra of the antimony isotope 109Sb in the sdgh shell are calculated in the nuclear shell model approach by using the CD-Bonn nucleon-nucleon interaction. The modified Drexel University parallel shell model code (DUPSM) was used for the calculations with maximum Hamiltonian dimension of 762 253 of 5.14% sparsity. The energy levels are compared to the recent experimental results. The calculations were done on the Cyborg Parallel Cluster System at Drexel University.
Multi-Shell Shell Model for Heavy Nuclei
Sun, Yang; Wu, Cheng-Li
2003-01-01
Performing a shell model calculation for heavy nuclei has been a long-standing problem in nuclear physics. Here we propose one possible solution. The central idea of this proposal is to take the advantages of two existing models, the Projected Shell Model (PSM) and the Fermion Dynamical Symmetry Model (FDSM), to construct a multi-shell shell model. The PSM is an efficient method of coupling quasi-particle excitations to the high-spin rotational motion, whereas the FDSM contains a successful t...
A particular thin-shell wormhole
Övgün, A.; Sakalli, I.
2017-01-01
Using a black hole with scalar hair, we construct a scalar thin-shell wormhole ( TSW) in 2+1 dimensions by applying the Visser cut and paste technique. The surface stress, which is concentrated at the wormhole throat, is determined using the Darmois-Israel formalism. Using various gas models, we analyze the stability of the TSW. The stability region is changed by tuning the parameters l and u. We note that the obtained TSW originating from a black hole with scalar hair could be more stable with a particular value of the parameter l, but it still requires exotic matter.
Stability of the Shallow Axisymmetric Parabolic-Conic Bimetallic Shell by Nonlinear Theory
M. Jakomin; Kosel, F.
2011-01-01
In this contribution, we discuss the stress, deformation, and snap-through conditions of thin, axi-symmetric, shallow bimetallic shells of so-called parabolic-conic and plate-parabolic type shells loaded by thermal loading. According to the theory of the third order that takes into account the balance of forces on a deformed body, we present a model with a mathematical description of the system geometry, displacements, stress, and thermoelastic deformations. The equations are based on the lar...
Anaesthetic and other treatments of shell shock: World War I and beyond.
McKenzie, A G
2012-03-01
Post-traumatic stress disorder (PTSD) is an important health risk factor for military personnel deployed in modern warfare. In World War I this condition (then known as shell shock or 'neurasthenia') was such a problem that 'forward psychiatry' was begun by French doctors in 1915. Some British doctors tried general anaesthesia as a treatment (ether and chloroform), while others preferred application of electricity. Four British 'forward psychiatric units' were set up in 1917. Hospitals for shell shocked soldiers were also established in Britain, including (for officers) Craiglockhart War Hospital in Edinburgh; patients diagnosed to have more serious psychiatric conditions were transferred to the Royal Edinburgh Asylum. Towards the end of 1918 anaesthetic and electrical treatments of shell shock were gradually displaced by modified Freudian methods psychodynamic intervention. The efficacy of 'forward psychiatry' was controversial. In 1922 the War Office produced a report on shell shock with recommendations for prevention of war neurosis. However, when World War II broke out in 1939, this seemed to have been ignored. The term 'combat fatigue' was introduced as breakdown rates became alarming, and then the value of pre-selection was recognised. At the Maudsley Hospital in London in 1940 barbiturate abreaction was advocated for quick relief from severe anxiety and hysteria, using i.v. anaesthetics: Somnifaine, paraldehyde, Sodium Amytal. 'Pentothal narcosis' and 'narco-analysis' were adopted by British and American military psychiatrists. However, by 1945 medical thinking gradually settled on the same approaches that had seemed to be effective in 1918. The term PTSD was introduced in 1980. In the UK the National Institute for Health and Clinical Excellence (NICE) guidelines for management (2005) recommend trauma-focussed Cognitive Behavioural Therapy and consideration of antidepressants.
Multi-shell effective interactions
Tsunoda, Naofumi; Hjorth-Jensen, Morten; Otsuka, Takaharu
2013-01-01
Background: Effective interactions, either derived from microscopic theories or based on fitting selected properties of nuclei in specific mass regions, are widely used inputs to shell-model studies of nuclei. Until recently, most shell-model calculations have been confined to a single oscillator shell. Recent interest in nuclei away from the stability line, requires however larger shell-model spaces. Since the derivation of microscopic effective interactions has been limited to degenerate model spaces, there are both conceptual and practical limits to present shell-model calculations that utilize such interactions. Purpose: The aim of this work is to present a novel microscopic method to calculate effective interactions for the nuclear shell model. Its main difference from existing theories is that it can be applied not only to degenerate model spaces but also to non-degenerate model spaces. Methods: The formalism is presented in the form of many-body perturbation theory based on the recently developed Exten...
Shell Biorefinery: Dream or Reality?
Chen, Xi; Yang, Huiying; Yan, Ning
2016-09-12
Shell biorefinery, referring to the fractionation of crustacean shells into their major components and the transformation of each component into value-added chemicals and materials, has attracted growing attention in recent years. Since the large quantities of waste shells remain underexploited, their valorization can potentially bring both ecological and economic benefits. This Review provides an overview of the current status of shell biorefinery. It first describes the structural features of crustacean shells, including their composition and their interactions. Then, various fractionation methods for the shells are introduced. The last section is dedicated to the valorization of chitin and its derivatives for chemicals, porous carbon materials and functional polymers. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Wrinkling of Pressurized Elastic Shells
Vella, Dominic
2011-10-01
We study the formation of localized structures formed by the point loading of an internally pressurized elastic shell. While unpressurized shells (such as a ping-pong ball) buckle into polygonal structures, we show that pressurized shells are subject to a wrinkling instability. We study wrinkling in depth, presenting scaling laws for the critical indentation at which wrinkling occurs and the number of wrinkles formed in terms of the internal pressurization and material properties of the shell. These results are validated by numerical simulations. We show that the evolution of the wrinkle length with increasing indentation can be understood for highly pressurized shells from membrane theory. These results suggest that the position and number of wrinkles may be used in combination to give simple methods for the estimation of the mechanical properties of highly pressurized shells. © 2011 American Physical Society.
Iofa, Mikhail Z
2016-01-01
Geometry of the spacetime with a spherical shell embedded in it is studied in two coordinate systems - in Kodama-Schwarzschild coordinates and in Gaussian normal coordinates. We consider transformations between the coordinate systems as in the 4D spacetime so as at the surface $\\S$ swept in the spacetime by the spherical shell. Extrinsic curvatures of the surface swept by the shell are calculated in both coordinate systems. Applications to the Israel junction conditions are discussed.
Shell effects in nuclear magnetization
Kondratyev, V.N.; Maruyama, Toshiki; Chiba, Satoshi [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan)
2000-08-01
The magnetization of nuclei in strong magnetic fields associated with magnetars' is considered within the shell model. It is demonstrated that the magnetic field gives rise to a phase-shift of the shell-oscillations in nuclear masses shifting significantly the nuclear magic numbers of the iron region towards smaller mass numbers. Shell-effects are found to result in anomalies of the nuclear magnetization. Such anomalies resemble the behavior associated with a phase transition. (author)
Anjan Das
2013-07-01
Full Text Available Context: Laryngoscopy and endotracheal intubation is associated detrimental hemodynamic changes like rise in blood pressure (BP, heart rate (HR leading to adverse cardiological outcome specially in susceptible individuals. Aims: To compare the blood pressure (BP and heart rate (HR changes during laryngoscopy and endotracheal intubation as well as to evaluate the preoperative sedation status between oral clonidine and oral midazolam as premedication for the patients undergoing general anesthesia (GA. Settings and Design: Fifty patients between 18 and 60 years of age of either sex of American Society of Anesthesiologists (ASA Grade I and II undergoing GA were randomly divided into two equal groups of 25 patients each. Group-C patients received clonidine 4 mcg/kg orally and Group-M patients received 0.5 mg/kg midazolam orally as premedication. Material s and Methods: After measuring baseline hemodynamic parameters patients of both groups received premedication. Preoperative sedation was assessed 2 hr after premedication administration. Standard anesthetic technique was followed. Hemodynamic (HR, BP parameters were noted baseline, immediately after laryngoscopy and intubation and 5 min after intubation to observe the stress response. Results and Statistical Analysis: A significant difference in pre-operative sedation between two groups (P < 0.05 and midazolam (group M produced significantly better sedation than clonidine (group C. Laryngoscopic stress response in group C was still at a lower level than baseline values and significantly (P < 0.005 less than group M. Conclusions: Oral midazolam is more effective in producing preoperative sedation than oral clonidine while on the contrary oral clonidine is more efficacious in reducing laryngoscopic stress response than oral midazolam. Laryngoscopy and intubation was better controlled by oral clonidine than midazolam.
Kaiser, Marie; Kuwert, Philipp; Braehler, Elmar; Glaesmer, Heide
2015-10-01
At the end of World War II and during the first decade after the war, roughly 200,000 children were fathered in intimate contacts between German women and foreign soldiers. The experiences of these German occupation children (GOC) have been so far described in case reports and from historical perspective only. Research on psychosocial consequences of growing up as a GOC has been missing so far. This study examined traumatic experiences, posttraumatic stress disorder, somatization, and depression in GOC (N = 146) using self-report instruments: Posttraumatic Diagnostic Scale and Patient Health Questionnaire. Findings have then been compared with a representative birth cohort-matched sample from the German general population (N = 977). German occupation children showed significantly higher prevalence rates of most traumatic experiences, higher point prevalence rates of full and partial posttraumatic stress disorder, depression, and somatization than the control group. In summary, GOC often grew up under difficult conditions (e.g., poverty, single mothers, and stigmatization). Even decades later, they showed higher rates of different mental disorders and higher comorbidity. These findings underline the complex and long-term impact of their burdened social, financial, and familial conditions. The results underpin the importance of conceptualizing occupation children as a vulnerable group in postconflict settings.
Plate shell structures of glass
Bagger, Anne
to their curved shape. A plate shell structure maintains a high stiffness-to-weight ratio, while facilitating the use of plane structural elements. The study focuses on using laminated glass panes for the load bearing facets. Various methods of generating a plate shell geometry are suggested. Together with Ghent......, such as facet size, imperfections, and connection characteristics. The critical load is compared to that of a similar, but smoothly curved, shell structure. Based on the investigations throughout the study, a set of guidelines for the structural design of plate shells of glass is proposed....
Kahre, Melinda A.; Hollingsworth, Jeffery
2012-01-01
The dust cycle is a critically important component of Mars' current climate system. Dust is present in the atmosphere of Mars year-round but the dust loading varies with season in a generally repeatable manner. Dust has a significant influence on the thermal structure of the atmosphere and thus greatly affects atmospheric circulation. The dust cycle is the most difficult of the three climate cycles (CO2, water, and dust) to model realistically with general circulation models. Until recently, numerical modeling investigations of the dust cycle have typically not included the effects of couplings to the water cycle through cloud formation. In the Martian atmosphere, dust particles likely provide the seed nuclei for heterogeneous nucleation of water ice clouds. As ice coats atmospheric dust grains, the newly formed cloud particles exhibit different physical and radiative characteristics. Thus, the coupling between the dust and water cycles likely affects the distributions of dust, water vapor and water ice, and thus atmospheric heating and cooling and the resulting circulations. We use the NASA Ames Mars GCM to investigate the effects of radiatively active water ice clouds on surface stress and the potential for dust lifting. The model includes a state-of-the-art water ice cloud microphysics package and a radiative transfer scheme that accounts for the radiative effects of CO2 gas, dust, and water ice clouds. We focus on simulations that are radiatively forced by a prescribed dust map, and we compare simulations that do and do not include radiatively active clouds. Preliminary results suggest that the magnitude and spatial patterns of surface stress (and thus dust lifting potential) are substantial influenced by the radiative effects of water ice clouds.
2010-01-01
... 7 Agriculture 2 2010-01-01 2010-01-01 false Shell. 51.2289 Section 51.2289 Agriculture Regulations... Standards for Shelled English Walnuts (Juglans Regia) Definitions § 51.2289 Shell. Shell means the outer shell and/or the woody partition from between the halves of the kernel, and any fragments of either....
INITIATION OF SHELL MOTION ON SAND BEDS: AN EXPERIMENTAL STUDY
Subhasish DEY; Alok KUMAR
2002-01-01
Experimental study on initiation of bivalve shell motion on a horizontal sand bed, under a unidirectional flow of water, is presented. Experiments were carried out in a flume with three types of bivalve shells,namely Coquina Clam, Cross-barred Chione and Ponderous Ark, to test the condition for initiation of motion. The shape parameters of bivalve shells are defined appropriately. Experiments were conducted in a flume with a horizontal bed, and the critical shear stresses were estimated using Vanoni's side-wall correction. The characteristic parameters affecting the initiation of shell motion on a horizontal bed in rough-turbulent regime identified based on the physical reasoning and dimensional analysis are the Shields parameter (nondimensional critical shear stress), nondimensional competent mean velocity,nondimensional sand roughness, nondimensional flow depth and shape parameter. Equations of Shields parameter and nondimensional competent mean velocity for the initial movement of shells on a horizontal sand bed with convex upward and downward conditions are obtained using experimental data.
Internal resonance of axially moving laminated circular cylindrical shells
Wang, Yan Qing; Liang, Li; Guo, Xing Hui
2013-11-01
The nonlinear vibrations of a thin, elastic, laminated composite circular cylindrical shell, moving in axial direction and having an internal resonance, are investigated in this study. Nonlinearities due to large-amplitude shell motion are considered by using Donnell's nonlinear shallow-shell theory, with consideration of the effect of viscous structure damping. Differently from conventional Donnell's nonlinear shallow-shell equations, an improved nonlinear model without employing Airy stress function is developed to study the nonlinear dynamics of thin shells. The system is discretized by Galerkin's method while a model involving four degrees of freedom, allowing for the traveling wave response of the shell, is adopted. The method of harmonic balance is applied to study the nonlinear dynamic responses of the multi-degrees-of-freedom system. When the structure is excited close to a resonant frequency, very intricate frequency-response curves are obtained, which show strong modal interactions and one-to-one-to-one-to-one internal resonance phenomenon. The effects of different parameters on the complex dynamic response are investigated in this study. The stability of steady-state solutions is also analyzed in detail.
Rose, Cheryl A.; Young, Richard D.; Starnes, James H., Jr.
1999-01-01
Results of a geometrically nonlinear finite element parametric study to determine curvature correction factors or "bulging factors" that account for increased stresses due to curvature for longitudinal cracks in unstiffened pressurized cylindrical shells are presented. Geometric parameters varied in the study include the shell radius, the shell wall thickness, and the crack length. The major results are presented in graphs of the bulging factor as a function of the applied load and as a function of geometric parameters that include the shell radius, the shell thickness and the crack length. The computed bulging factors are compared with solutions based on linear shallow shell theory, and with semi-empirical solutions that approximately account for the nonlinear deformation in the vicinity of the crack. The effect of biaxial loads on the computed bulging factors is also discussed.
XU; Mingyu(
2001-01-01
generalized fractional calculus, J. Comput.Appl. Math., 2000, 118(1): 241－259.
Sun, Xiaolian; Li, Dongguo; Guo, Shaojun; Zhu, Wenlei; Sun, Shouheng
2016-02-01
Using a modified seed-mediated method, we synthesized core/shell Au/FePt nanoparticles (NPs) with Au sizes of 4, 7, and 9 nm and the FePt shell was controlled to have similar FePt compositions and 0.5, 1, and 2 nm thickness. We studied both core and shell effects on electrochemical and electrocatalytic properties of the Au/FePt NPs, and found that the Au core did change the redox chemistry of the FePt shell and promoted its electrochemical oxidation of methanol. The catalytic activity was dependent on the FePt thicknesses, but not much on the Au core sizes, and the 1 nm FePt shell was found to be the optimal thickness for catalyzing methanol oxidation in 0.1 M HClO4 + 0.1 M methanol, offering not only high activity (1.19 mA cm(-2) at 0.5 V vs. Ag/AgCl), but also enhanced stability. Our studies demonstrate a general approach to the design and tuning of shell catalysis in the core/shell structure to achieve optimal catalysis for important electrochemical reactions.
The computer in shell stability analysis
Almroth, B. O.; Starnes, J. H., Jr.
1975-01-01
Some examples in which the high-speed computer has been used to improve the static stability analysis capability for general shells are examined. The fundamental concepts of static stability are reviewed with emphasis on the differences between linear bifurcation buckling and nonlinear collapse. The analysis is limited to the stability of conservative systems. Three examples are considered. The problem of cylinders subjected to bending loads is used as an example to illustrate that a simple structure can have a sufficiently complicated nonlinear behavior to require a computer analysis for accurate results. An analysis of the problems involved in the modeling of stiffening elements in plate and shell structures illustrates the necessity that the analyst recognizes all important deformation modes. The stability analysis of the Skylab structure indicates the size of problems that can be solved with current state-of-the-art capability.
Young, Richard D.; Rose, Cheryl A.; Starnes, James H., Jr.
2000-01-01
Results of a geometrically nonlinear finite element parametric study to determine curvature correction factors or bulging factors that account for increased stresses due to curvature for longitudinal and circumferential cracks in unstiffened pressurized cylindrical shells are presented. Geometric parameters varied in the study include the shell radius, the shell wall thickness, and the crack length. The major results are presented in the form of contour plots of the bulging factor as a function of two nondimensional parameters: the shell curvature parameter, lambda, which is a function of the shell geometry, Poisson's ratio, and the crack length; and a loading parameter, eta, which is a function of the shell geometry, material properties, and the applied internal pressure. These plots identify the ranges of the shell curvature and loading parameters for which the effects of geometric nonlinearity are significant. Simple empirical expressions for the bulging factor are then derived from the numerical results and shown to predict accurately the nonlinear response of shells with longitudinal and circumferential cracks. The numerical results are also compared with analytical solutions based on linear shallow shell theory for thin shells, and with some other semi-empirical solutions from the literature, and limitations on the use of these other expressions are suggested.
Multi-Shell Shell Model for Heavy Nuclei
Sun, Y; Sun, Yang; Wu, Cheng-Li
2003-01-01
Performing a shell model calculation for heavy nuclei has been a long-standing problem in nuclear physics. Here we propose one possible solution. The central idea of this proposal is to take the advantages of two existing models, the Projected Shell Model (PSM) and the Fermion Dynamical Symmetry Model (FDSM), to construct a multi-shell shell model. The PSM is an efficient method of coupling quasi-particle excitations to the high-spin rotational motion, whereas the FDSM contains a successful truncation scheme for the low-spin collective modes from the spherical to the well-deformed region. The new shell model is expected to describe simultaneously the single-particle and the low-lying collective excitations of all known types, yet keeping the model space tractable even for the heaviest nuclear systems.
薛明德; 王和慧; 陈伟; 黄克智
1999-01-01
The stress analysis based on the theory of a thin shell is carried out for cylindrical shells with normally intersecting nozzles subjected to external moment loads on the ends of shells with a large diameter ratio （ρ0≤0.8）. Instead of the Donnell shallow shell equation, the modified Morley equation, which is applicable to ρ0 （R/T）1/2（?）1, is used for the analysis of the shell with cutout. The solution in terms of displacement function for the nozzle with a nonplanar end is based on the Goldenveizer equation. The boundary forces and displacements at the intersection are all transformed from Gaussian coordinates （α, β） on the shell, or Gaussian coordinates （ζ, θ） on the nozzle into three-dimensional cylindrical coordinates （ρ, θ, z）. Their expressions on the intersecting curve are periodic functions of θ and expanded in Fourier series. Every harmonic of Fourier coefficients of boundary forces and displacements are obtained by numerical quadrature. The results obtained are in agreement with
Kukudzhanov, S. N.
2008-10-01
We study the natural vibrations and the dynamic stability of nearly cylindrical orthotropic shells of revolution subjected to meridional forces uniformly distributed over the shell ends. We consider shells of medium length for which the shape of the midsurface generatrix is described by a parabolic function. Using the theory of shallow shells, we obtain the resolving equation for the vibrations of the corresponding prestressed shell. In the isotropic case, this equation differs from the well-known equation [1] by an additional term, which can be of the same order as the other terms taken into account. We consider shells of both positive and negative Gaussian curvature. We assumed that the shell ends are freely supported. The formulas and universal curves describing the dependence of the minimum frequency, the wave generation shape, and the dynamic instability domain boundaries on the orthotropy parameters, the preliminary stress, the Gaussian curvature, and the amplitude of the shell deviation from the cylinder are given in dimensionless form. We find that in the case of prestresses the orthotropy parameters and the shell deviation from the cylinder (of the order of thickness) can significantly change the least frequencies, the wave generation shape, and the dynamic instability domain boundaries of the corresponding prestressed orthotropic cylindrical shell. In this case, we note that for convex shells under preliminary compression the influence of the elastic parameter in the axial direction is stronger than the influence of the elastic parameter in the circular direction, while the situation is opposite in the case of concave shells. In the case of preliminary extension, the leading role of any orthotropy parameter can vary depending on the value of the preliminary stress and the Gaussian curvature.
1949-01-01
In part I of this study a survey has veen given of what Dutch authors have written since 1870, when capital punishment was abolished, on subjects concerning the general preventive effect of punishment. This historical survey ends where, during the years 1940-1945, under the stress of the occupation
Transverse shear effect in a circumferentially cracked cylindrical shell
Delale, F.; Erdogan, F.
1979-01-01
The objectives of the paper are to solve the problem of a circumferentially-cracked cylindrical shell by taking into account the effect of transverse shear, and to obtain the stress intensity factors for the bending moment as well as the membrane force as the external load. The formulation of the problem is given for a specially orthotropic material within the framework of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions as to moment and stress resultants on the crack surface. The effect of Poisson's ratio on the stress intensity factors and the nature of the out-of-plane displacement along the edges of the crack, i.e., bulging, are also studied.
Shell Trumpets from Western Mexico
Robert Novella
1991-11-01
Full Text Available Marine shells have been used as musical instruments in almost all parts of the world (Izikowitz 1935, including Mesoamerica, where large univalves, also called conch shells in the literature, had a utilitarian function as trumpets. Their use is well documented in most cultural areas of Mesoamerica, as in Western Mexico, through their various occurrences in archaeological contexts and museums collections.
Shell model and spectroscopic factors
Poves, P. [Madrid Univ. Autonoma and IFT, UAM/CSIC, E-28049 (Spain)
2007-07-01
In these lectures, I introduce the notion of spectroscopic factor in the shell model context. A brief review is given of the present status of the large scale applications of the Interacting Shell Model. The spectroscopic factors and the spectroscopic strength are discussed for nuclei in the vicinity of magic closures and for deformed nuclei. (author)
Biomineralisation in Mollusc shells
Dauphin, Y.; Cuif, J. P.; Salomé, M.; Williams, C. T.
2009-04-01
The main components of Mollusc shells are carbonate minerals: calcite and aragonite. ACC is present in larval stages. Calcite and aragonite can be secreted simultaneously by the mantle. Despite the small number of varieties, the arrangement of the mineral components is diverse, and dependant upon the taxonomy. They are also associated with organic components much more diverse, the diversity of which reflects the large taxonomic diversity. From TGA analyses, the organic content (water included) is high (>5% in some layers). The biomineralisation process is not a passive precipitation process, but is strongly controlled by the organism. The biological-genetic control is shown by the constancy of the arrangement of the layers, the mineralogy and the microstructure in a given species. Microstructural units (i.e. tablets, prisms etc.) have shapes that do not occur in non-biogenic counterparts. Nacreous tablets, for example, are flattened on their crystallographic c axis, which is normally the axis of maximum growth rate for non-biogenic aragonite. Morever, their inner structure is species-specific: the arrangements of nacreous tablets in Gastropoda - Cephalopoda, and in Bivalvia differ, and the inner arrangement of the nacreous tablets is different in ectocochlear and endocochlear Cephalopoda. The organic-mineral ratios also differ in the various layers of a shell. Differences in chemical composition also demonstrates the biological-genetic control: for example, aragonite has a low Sr content unknown in non-biogenic samples; two aragonitic layers in a shell have different Sr and Mg contents, S is higher in calcitic layers. Decalcification releases soluble (SOM) and insoluble (IOM) organic components. Insoluble components form the main part of the intercrystalline membranes, and contain proteins, polysaccharides and lipids. Soluble phases are present within the crystals and the intercrystalline membranes. These phases are composed of more or less glycosylated proteins
Anastasides, Nicole; Beck, Kevin D; Pang, Kevin C H; Servatius, Richard J; Gilbertson, Mark W; Orr, Scott P; Myers, Catherine E
2015-01-01
One interpretation of re-experiencing symptoms in post-traumatic stress disorder (PTSD) is that memories related to emotional information are stored strongly, but with insufficient specificity, so that stimuli which are minimally related to the traumatic event are sufficient to trigger recall. If so, re-experiencing symptoms may reflect a general bias against encoding background information during a learning experience, and this tendency might not be limited to learning about traumatic or even autobiographical events. To test this possibility, we administered a discrimination-and-transfer task to 60 Veterans (11.2% female, mean age 54.0 years) self-assessed for PTSD symptoms in order to examine whether re-experiencing symptoms were associated with increased generalization following associative learning. The discrimination task involved learning to choose the rewarded object from each of six object pairs; each pair differed in color or shape but not both. In the transfer phase, the irrelevant feature in each pair was altered. Regression analysis revealed no relationships between re-experiencing symptoms and initial discrimination learning. However, re-experiencing symptom scores contributed to the prediction of transfer performance. Other PTSD symptom clusters (avoidance/numbing, hyperarousal) did not account for significant additional variance. The results are consistent with an emerging interpretation of re-experiencing symptoms as reflecting a learning bias that favors generalization at the expense of specificity. Future studies will be needed to determine whether this learning bias may pre-date and confer risk for, re-experiencing symptoms in individuals subsequently exposed to trauma, or emerges only in the wake of trauma exposure and PTSD symptom development.
Hwang, Yong Seok; Levitas, Valery I
2016-10-19
The external surface of metallic particles is usually covered by a thin and strong oxide shell, which significantly affects superheating and melting of particles. The effects of geometric parameters and heating rate on characteristic melting and superheating temperatures and melting behavior of aluminum nanoparticles covered by an oxide shell were studied numerically. For this purpose, the multiphysics model that includes the phase field model for surface melting, a dynamic equation of motion, a mechanical model for stress and strain simulations, interface and surface stresses, and the thermal conduction model including thermoelastic and thermo-phase transformation coupling as well as transformation dissipation rate was formulated. Several nontrivial phenomena were revealed. In comparison with a bare particle, the pressure generated in a core due to different thermal expansions of the core and shell and transformation volumetric expansion during melting, increases melting temperatures with the Clausius-Clapeyron factor of 60 K GPa(-1). For the heating rates Q ≤ 10(9) K s(-1), melting temperatures (surface and bulk start and finish melting temperatures, and maximum superheating temperature) are independent of Q. For Q ≥ 10(12) K s(-1), increasing Q generally increases melting temperatures and temperature for the shell fracture. Unconventional effects start for Q ≥ 10(12) K s(-1) due to kinetic superheating combined with heterogeneous melting and geometry. The obtained results are applied to shed light on the initial stage of the melt-dispersion-mechanism of the reaction of Al nanoparticles. Various physical phenomena that promote or suppress melting and affect melting temperatures and temperature of the shell fracture for different heating-rate ranges are summarized in the corresponding schemes.
Reckziegel, P; Boufleur, N; Barcelos, R C S; Benvegnú, D M; Pase, C S; Muller, L G; Teixeira, A M; Zanella, R; Prado, A C P; Fett, R; Block, J M; Burger, M E
2011-09-01
The present study evaluated the role of pecan nut (Carya illinoensis) shells aqueous extract (AE) against oxidative damage induced by cigarette smoke exposure (CSE) and behavioral parameters of smoking withdrawal. Mice were passively exposed to cigarette smoke for 3 weeks (6, 10, and 14 cigarettes/day) and orally treated with AE (25 g/L). CSE induced lipid peroxidation in brain and red blood cells (RBC), increased catalase (CAT) activity in RBC, and decreased plasma ascorbic acid levels. AE prevented oxidative damage and increased antioxidant defenses of mice exposed to cigarette smoke. In addition, AE reduced the locomotor activity and anxiety symptoms induced by smoking withdrawal, and these behavioral parameters showed a positive correlation with RBC lipid peroxidation. Our results showed the beneficial effects of this by-product of the pecan industry, indicating its usefulness in smoking cessation.
Suresh, Patricia
2013-03-01
To measure and compare the perceived levels of job-related stress and stressors of newly qualified nurses and fourth-year student nurses in the clinical environment and to explore the participants\\' views on stress and stressors.
Isogeometric shell discretizations for flexible multibody dynamics
Goyal, Anmol, E-mail: goyal@mathematik.uni-kl.de; Doerfel, Michael R., E-mail: michael.doerfel@web.de; Simeon, Bernd, E-mail: simeon@mathematik.uni-kl.de; Vuong, Anh-Vu, E-mail: vuong@mathematik.uni-kl.de [Technische Universitaet Kaiserslautern, Felix Klein Zentrum fuer Mathematik, FB Mathematik (Germany)
2013-08-01
This work aims at including nonlinear elastic shell models in a multibody framework. We focus our attention to Kirchhoff-Love shells and explore the benefits of an isogeometric approach, the latest development in finite element methods, within a multibody system. Isogeometric analysis extends isoparameteric finite elements to more general functions such as B-splines and NURBS (Non-Uniform Rational B-Splines) and works on exact geometry representations even at the coarsest level of discretizations. Using NURBS as basis functions, high regularity requirements of the shell model, which are difficult to achieve with standard finite elements, are easily fulfilled. A particular advantage is the promise of simplifying the mesh generation step, and mesh refinement is easily performed by eliminating the need for communication with the geometry representation in a CAD (Computer-Aided Design) tool. Target applications are wind turbine blades and twist beam rear suspensions. First numerical examples demonstrate an impressive convergence behavior of the isogeometric approach even for a coarse mesh, while offering substantial savings with respect to the number of degrees of freedom.
Leading singularities and off-shell conformal integrals
Drummond, James; Duhr, Claude; Eden, Burkhard; Heslop, Paul; Pennington, Jeffrey; Smirnov, Vladimir A.
2013-08-29
The three-loop four-point function of stress-tensor multiplets in N=4 super Yang-Mills theory contains two so far unknown, off-shell, conformal integrals, in addition to the known, ladder-type integrals. In our paper we evaluate the unknown integrals, thus obtaining the three-loop correlation function analytically. The integrals have the generic structure of rational functions multiplied by (multiple) polylogarithms. We use the idea of leading singularities to obtain the rational coefficients, the symbol — with an appropriate ansatz for its structure — as a means of characterising multiple polylogarithms, and the technique of asymptotic expansion of Feynman integrals to obtain the integrals in certain limits. The limiting behaviour uniquely fixes the symbols of the integrals, which we then lift to find the corresponding polylogarithmic functions. The final formulae are numerically confirmed. Furthermore, we develop techniques that can be applied more generally, and we illustrate this by analytically evaluating one of the integrals contributing to the same four-point function at four loops. This example shows a connection between the leading singularities and the entries of the symbol.
Vacuum thin shell solutions in five-dimensional Lovelock gravity
Garraffo, C; Gravanis, E; Willison, S
2010-01-01
Junction conditions for vacuum solutions in five-dimensional Einstein-Gauss-Bonnet gravity are studied. We focus on those cases where two spherically symmetric regions of space-time are joined in such a way that the induced stress tensor on the junction surface vanishes. So a spherical vacuum shell, containing no matter, arises as a boundary between two regions of the space-time. Such solutions are a generalized kind of spherically symmetric empty space solutions, described by metric functions of the class $C^0$. New global structures arise with surprising features. In particular, we show that vacuum spherically symmetric wormholes do exist in this theory. These can be regarded as gravitational solitons, which connect two asymptotically (Anti) de-Sitter spaces with different masses and/or different effective cosmological constants. We prove the existence of both static and dynamical solutions and discuss their (in)stability under perturbations that preserve the symmetry. This leads us to discuss a new type of...
Dynamic stability of simply supported composite cylindrical shells under partial axial loading
Dey, Tanish; Ramachandra, L. S.
2015-09-01
The parametric vibration of a simply supported composite circular cylindrical shell under periodic partial edge loadings is discussed in this article. Donnell's nonlinear shallow shell theory considering first order shear deformation theory is used to model the shell. The applied partial edge loading is represented in terms of a Fourier series and stress distributions within the cylindrical shell are determined by prebuckling analysis. The governing equations of the dynamic instability of shells are derived in terms of displacements (u-v-w) and rotations (φx, φθ). Employing the Galerkin and Bolotin methods the dynamic instability regions are computed. Using the expression for the stress function derived in this paper, the pre-buckling stresses in the cylindrical shell due to partial loading can be calculated explicitly. Numerical results are presented to show the influence of radius-to-thickness ratio, different partial edge loading distributions and shear deformation on the dynamic instability regions. The linear and nonlinear responses in the stable and unstable regions are presented to bring out the characteristic features of the dynamic instability regions, such as the existence of beats, its dependence on forcing frequency and effect of nonlinearity on the response. The effect of dynamic load amplitude on the nonlinear response is also studied. It is found that for higher values of dynamic loading, the shell exhibits chaotic behavior.
A quadrilateral shell element with degree of freedom to represent thickness-stretch
Yamamoto, Takeki; Yamada, Takahiro; Matsui, Kazumi
2017-04-01
This paper presents a quadrilateral shell element incorporating thickness-stretch, and demonstrates its performance in small and large deformation analyses for hyperelastic material and elastoplastic models. In terms of geometry, the proposed shell element is based on the formulation of the MITC4 shell element, with additional degrees of freedom to represent thickness-stretch. To consider the change in thickness, we introduce a displacement variation to the MITC4 shell element, in the thickness direction. After the thickness direction is expressed in terms of the director vectors that are defined at each midsurface node, additional nodes are placed along the thickness direction from the bottom surface to the top surface. The thickness-stretch is described by the movement of these additional nodes. The additional degrees of freedom are used to compute the transverse normal strain without assuming the plane stress condition. Hence, the three dimensional constitutive equation can be employed in the proposed formulation without any modification. By virtue of not imposing the plane stress condition, the surface traction is evaluated at the surface where the traction is applied, whereas it is assessed at the midsurface for conventional shell elements. Several numerical examples are presented to examine the fundamental performance of the proposed shell element. In particular, the proposed approach is capable of evaluating the change in thickness and the stress distribution when the effect of the surface traction is included. The behavior of the proposed shell element is compared with that of solid elements.
Putwain, David William
2011-01-01
High stakes examinations have been identified as a significant source of stress for secondary school students; however, there is little data accounting for, and explaining, the experiences of examination stress. This study aimed to further the understanding of examination stress in secondary school students by conducting interviews with 34…
Hasin, Deborah S.; Shmulewitz, Dvora; Stohl, Malka; Greenstein, Eliana; Aivadyan, Christina; Morita, Kara; Saha, Tulshi; Aharonovich, Efrat; Jung, Jeesun; Zhang, Haitao; Nunes, Edward V.; Grant, Bridget F.
2016-01-01
Background Little is known about the procedural validity of lay-administered, fully-structured assessments of depressive, anxiety and post-traumatic stress (PTSD) disorders in the general population as determined by comparison to clinical re-appraisal, and whether this differs between current regular substance abusers and others. We evaluated the procedural validity of the Alcohol Use Disorder and Associated Disabilities Interview Schedule, DSM-5 Version (AUDADIS-5) assessment of these disorders through clinician re-interviews. Methods Test-retest design among respondents from the National Epidemiologic Survey on Alcohol and Related Conditions-III (NESARC-III): (264 current regular substance abusers, 447 others). Clinicians blinded to AUDADIS-5 results administered the semi-structured Psychiatric Research Interview for Substance and Mental Disorders, DSM-5 version (PRISM-5). AUDADIS-5/PRISM-5 concordance was indicated by kappa (κ) for diagnoses and intraclass correlation coefficients (ICC) for dimensional measures (DSM-5 symptom or criterion counts). Results were compared between current regular substance abusers and others. Results AUDADIS-5 and PRISM-5 concordance for DSM-5 depressive disorders, anxiety disorders and PTSD was generally fair to moderate (κ =0.24–0.59), with concordance on dimensional scales much better (ICC=0.53–0.81). Concordance differed little between regular substance abusers and others. Conclusions AUDADIS-5/PRISM-5 concordance indicated procedural validity for the AUDADIS-5 among substance abusers and others, suggesting that AUDADIS-5 diagnoses of DSM-5 depressive, anxiety and PTSD diagnoses are informative measures in both groups in epidemiologic studies. The stronger concordance on dimensional measures supports the current movement towards dimensional psychopathology measures, suggesting that such measures provide important information for research in the NESARC-III and other datasets, and possibly for clinical purposes as well. PMID
Herod, S M; Dettmer, A M; Novak, M A; Meyer, J S; Cameron, J L
2011-01-01
Stress-induced reproductive dysfunction is a relatively common cause of infertility in women. In response to everyday life stress, some individuals readily develop reproductive dysfunction (i.e., they are stress sensitive), whereas others are more stress resilient. Female cynomolgus monkeys, when exposed to mild combined psychosocial and metabolic stress (change in social environment + 20% reduced calorie diet), can be categorized as stress sensitive (SS; they rapidly become anovulatory in response to stress), medium stress resilient (MSR; they slowly become anovulatory in response to prolonged stress), or highly stress resilient (HSR; they maintain normal menstrual cycles in response to stress). In this study, we examined whether increased sensitivity to stress-induced reproductive dysfunction is associated with elevated adrenal axis activity by measuring 1) the diurnal release of ACTH and cortisol, 2) ACTH and cortisol in response to an acute psychological stress, 3) the percent suppression of cortisol in response to dexamethasone negative feedback, 4) the diurnal release of ACTH and cortisol following exposure to mild psychosocial and metabolic stress, 5) the concentration of cortisol in hair, and 6) adrenal weight. SS monkeys (n = 5) did not differ from MSR (n = 5) or HSR (n = 7) monkeys in any measurement of baseline HPA axis activity or the integrated measurements of chronic HPA axis activity. However, MSR + SS monkeys (n = 10) did secrete more cortisol than HSR monkeys during the daytime hours (1000-1800) following exposure to a novel social environment and reduced diet. We conclude that increased activity of the HPA axis is unlikely to be the primary mechanism causing increased sensitivity to stress-induced reproductive dysfunction.
MicroShell Minimalist Shell for Xilinx Microprocessors
Werne, Thomas A.
2011-01-01
MicroShell is a lightweight shell environment for engineers and software developers working with embedded microprocessors in Xilinx FPGAs. (MicroShell has also been successfully ported to run on ARM Cortex-M1 microprocessors in Actel ProASIC3 FPGAs, but without project-integration support.) Micro Shell decreases the time spent performing initial tests of field-programmable gate array (FPGA) designs, simplifies running customizable one-time-only experiments, and provides a familiar-feeling command-line interface. The program comes with a collection of useful functions and enables the designer to add an unlimited number of custom commands, which are callable from the command-line. The commands are parameterizable (using the C-based command-line parameter idiom), so the designer can use one function to exercise hardware with different values. Also, since many hardware peripherals instantiated in FPGAs have reasonably simple register-mapped I/O interfaces, the engineer can edit and view hardware parameter settings at any time without stopping the processor. MicroShell comes with a set of support scripts that interface seamlessly with Xilinx's EDK tool. Adding an instance of MicroShell to a project is as simple as marking a check box in a library configuration dialog box and specifying a software project directory. The support scripts then examine the hardware design, build design-specific functions, conditionally include processor-specific functions, and complete the compilation process. For code-size constrained designs, most of the stock functionality can be excluded from the compiled library. When all of the configurable options are removed from the binary, MicroShell has an unoptimized memory footprint of about 4.8 kB and a size-optimized footprint of about 2.3 kB. Since MicroShell allows unfettered access to all processor-accessible memory locations, it is possible to perform live patching on a running system. This can be useful, for instance, if a bug is
Greenhouse Effect: Temperature of a Metal Sphere Surrounded by a Glass Shell and Heated by Sunlight
Nguyen, Phuc H.; Matzner, Richard A.
2012-01-01
We study the greenhouse effect on a model satellite consisting of a tungsten sphere surrounded by a thin spherical, concentric glass shell, with a small gap between the sphere and the shell. The system sits in vacuum and is heated by sunlight incident along the "z"-axis. This development is a generalization of the simple treatment of the…
New Variational Techniques for Acoustic Radiation and Scattering From Elastic Shell Structures
1993-12-20
in structural dynamics When the mechanical energy functions are very complicated, as in the case of a doubly curved-shell, determination of the...Investigator, Professor and Woodruff Chair, School of Mechanical Enginneering , Georgia Institute of Technology. 2. Allan D. Pierce, Co-Principal...5 1. General Implementation of SVP for Bodies of Revolution ........ 7 2. Structural Dynamics for Plates and Shells
[Development of a ballistic furnace for shell production]. Annual report 1998
Cook, R; Isakov, A I
1998-12-31
During the fourth contract year, the authors continued to develop Ballistic technology of shell formation. A new upgraded version of Ballistic Furnace with longer hot zone (1.56m) and cooling one (1.2m) had been finally assembled, and a lot of shell formation experiments had been carried out. The change of the Ballistic Furnace configuration has led to significant changing in operational conditions suitable for shells production. They had found optimal operational conditions for some grades of initial granules giving them high yield of good shells. Serious attention was paid on initial granules preparation. In the experiments some unexpected results were obtained--first of all it was a strong influence of temperature profile, an initial granule velocity and a trajectory angle on good quality shells yield. Those observations made them consider some additional physical phenomena (initial granule defragmentation and gas convection inside hot zone) to explain good shell formation. Appropriate estimations of the velocity of possible convectional gas currents in the hot zone, strength of formed shells, thermal stress in an initial granule caused by its fast heating in the ballistic furnace etc. were made. Good quality shells up to 2mm in diameters with high yield were produced. Although a production of good quality shells in diameter range > 1.8 mm stays an easy job, their experience led them to declare that Ballistic technology hasn't reach its boundaries, and future development will allow them to obtain perfect results.
Surface corrections to the shell-structure of the moment of inertia
Gorpinchenko, D V; Bartel, J; Blocki, J P
2015-01-01
The moment of inertia for nuclear collective rotations is derived within a semiclassical approach based on the Inglis cranking and the Strutinsky shell-correction methods, improved by surface corrections within the non-perturbative periodic-orbit theory. For adiabatic (statistical-equilibrium) rotations it was approximated by the generalized rigid-body moment of inertia accounting for the shell corrections of the particle density. An improved phase-space trace formula allows to express the shell components of the moment of inertia more accurately in terms of the free-energy shell correction with their ratio evaluated within the extended Thomas-Fermi effective-surface approximation.
Buckling analysis of stringer-stiffened laminated cylindrical shells with nonuniform eccentricity
Sadeghifar, M. [Islamic Azad University, Department of Mechanical Engineering, Nowshahr Branch, Nowshahr (Iran, Islamic Republic of); Bagheri, M. [Sattari Air University, Faculty of Aerospace Engineering, Tehran (Iran, Islamic Republic of); Jafari, A.A. [K.N. Toosi University of Technology, Faculty of Mechanical Engineering, Tehran (Iran, Islamic Republic of)
2011-07-15
In this study, the influence of nonuniformity of eccentricity of stringers on the general axial buckling load of stiffened laminated cylindrical shells with simply supported end conditions is investigated. The critical loads are calculated using Love's First-order Shear Deformation Theory and solved using the Rayleigh-Ritz procedure. The effects of the shell length-to-radius ratio, shell thickness-to-radius ratio, number of stringers, and stringers depth-to-width ratio on the buckling load of nonuniformly eccentric shells, are examined. The research demonstrates that an appropriate nonuniform distribution of eccentricity of stringers leads the buckling load to increase significantly. (orig.)
Da-Yong Lin; Yan-Xin Liu; Qian Li
2016-01-01
Objective:To investigate the effect of general anesthesia on stress response and inflammatory cytokines in elderly patients undergoing abdominal surgery under the guidance of Narcotrend. Methods:A total of 150 elderly patients with abdominal surgery in our hospital from January 2015 to December 2015 were randomly divided into three groups: D0, D2 and E2 group, each 50 cases. With different depth of anesthesia, the stress response indexes COR, ACTH, CRP and ET-1, the inflammatory factors IL-6 and TNF-α before anesthesia, postoperative 1 h and postoperative 1 d were compared.Results:The differences of Cor, ACTH, CRP and ET-1 in the three groups D0, D2 and E2 were all statistically significant (P<0.05); the differences of Cor, ACTH and CRP at each time point were also statistically significant (P<0.05), Cor in D0 and D2 group were significantly increased postoperative 1 h and 1 d (P<0.05), ACTH in D0, D2 and E2 group were significantly increased postoperative 1 h and 1 d (P<0.05), CRP in D0 group was significantly increased postoperative 1 h and 1 d (P<0.05); The increase amplitude of Cor in D0 and D2 group at each time point was higher than in E2 group (P<0.05), the increase amplitude of ACTH in D2 group at each time point was lower than in D0 and E2 group (P<0.05), the increase amplitude of CRP in D0 group at each time point was higher than in D2 and E2 group (P<0.05), ET-1 in D0 and D2 group had no changes at each time point, while the decrease amplitude of ET-1 in E2 group at each time point was significantly higher than in D0 and D2 group (P<0.05). The differences of IL-6 and TNF-α in the three groups D0, D2 and E2 were all statistically significant (P<0.05); the differences of IL-6 and TNF-α at each time point were also statistically significant (P<0.05), IL-6 and TNF-α in D0 group were significantly increased postoperative 1 h and 1 d (P < 0.05); the increase amplitude of IL-6 and TNF-α in D0 group at each time point was higher than in D2 and E2 group (P<0
Xian-Ze Meng
2012-01-01
Full Text Available Introduction. Posttraumatic stress disorder (PTSD is accompanied by poor general psychological status (GPS. In the present study, we investigated the effects of a Chinese herbal formula on GPS in earthquake survivors with PTSD. Methods. A randomized, double-blind, placebo-controlled trial compared a Chinese herbal formula, Xiao-Tan-Jie-Yu-Fang (XTJYF, to placebo in 2008 Sichuan earthquake survivors with PTSD. Patients were randomized into XTJYF (n=123 and placebo (n=122 groups. Baseline-to-end-point score changes in the three global indices of the Symptom Checklist-90-Revised (SCL-90-R and rates of response in the SCL global severity index (GSI were the primary endpoints. A subanalysis of the nine SCL factors and the sleep quality score were secondary endpoints. Results and Discussion. Compared to placebo, the XTJYF group was significantly improved in all three SCL global indices (P = 0.001~0.028. More patients in the XTJYF group reported “much improved” than the placebo group (P = 0.001. The XTJYF group performed significantly better than control in five out of nine SCL factors (somatization, obsessive-compulsive behavior, depression, anxiety, and hostility (P = 0.001~0.036, and in sleep quality score (P<0.001. XTJYF produced no serious adverse events. These findings suggest that XTJYF may be an effective and safe treatment option for improving GPS in patients with PTSD.
Effects of asymmetry on the strength of the chelonian shell: a comparison of three species.
Rivera, Gabriel; Stayton, C Tristan
2013-08-01
A major focus of the field of organismal biology is to understand how morphology impacts performance. Although the functional implications of certain aspects of shape have been widely examined, the functional implications of a related parameter, symmetry, remain mostly unknown. We used finite-element models to examine the effects of turtle shell asymmetry on shell strength across three morphologically distinct emydid species. The goals of this study were to: 1) test the hypothesis that increased asymmetry (independent of differences in shape) is associated with increased stress levels for a given load, and thus with weaker shells, 2) ascertain how asymmetry and the position of load application interact to influence shell strength, and 3) determine how interspecific differences in shape influence the effect of asymmetry. We found that increased asymmetry does produce higher stresses for both midline and non-midline loads. Non-midline loads produce slightly larger and more variable stresses. Species-specific shell shape can mitigate the effects of asymmetry; stronger shapes are potentially more resistant to the negative effects of asymmetry. Our findings indicate that changes in asymmetry associated with relatively small changes in shape can have as much of an effect on stress incurred by the shell as the changes in shape themselves. Copyright © 2013 Wiley Periodicals, Inc.
Stability of the Regular Hayward Thin-Shell Wormholes
M. Sharif
2016-01-01
Full Text Available The aim of this paper is to construct regular Hayward thin-shell wormholes and analyze their stability. We adopt Israel formalism to calculate surface stresses of the shell and check the null and weak energy conditions for the constructed wormholes. It is found that the stress-energy tensor components violate the null and weak energy conditions leading to the presence of exotic matter at the throat. We analyze the attractive and repulsive characteristics of wormholes corresponding to ar>0 and ar<0, respectively. We also explore stability conditions for the existence of traversable thin-shell wormholes with arbitrarily small amount of fluid describing cosmic expansion. We find that the space-time has nonphysical regions which give rise to event horizon for 0
The secondary buckling transition: wrinkling of buckled spherical shells.
Knoche, Sebastian; Kierfeld, Jan
2014-07-01
We theoretically explain the complete sequence of shapes of deflated spherical shells. Decreasing the volume, the shell remains spherical initially, then undergoes the classical buckling instability, where an axisymmetric dimple appears, and, finally, loses its axisymmetry by wrinkles developing in the vicinity of the dimple edge in a secondary buckling transition. We describe the first axisymmetric buckling transition by numerical integration of the complete set of shape equations and an approximate analytic model due to Pogorelov. In the buckled shape, both approaches exhibit a locally compressive hoop stress in a region where experiments and simulations show the development of polygonal wrinkles, along the dimple edge. In a simplified model based on the stability equations of shallow shells, a critical value for the compressive hoop stress is derived, for which the compressed circumferential fibres will buckle out of their circular shape in order to release the compression. By applying this wrinkling criterion to the solutions of the axisymmetric models, we can calculate the critical volume for the secondary buckling transition. Using the Pogorelov approach, we also obtain an analytical expression for the critical volume at the secondary buckling transition: The critical volume difference scales linearly with the bending stiffness, whereas the critical volume reduction at the classical axisymmetric buckling transition scales with the square root of the bending stiffness. These results are confirmed by another stability analysis in the framework of Donnel, Mushtari and Vlasov (DMV) shell theory, and by numerical simulations available in the literature.
Deshev, Hristo
2008-01-01
Targeted at professionals who handle a lot of repetitive tasks, this title serves as not only a tutorial, but also a reference. It shows how PowerShell can help professionals script most system administration tasks and reduce their burden.
Menon, Vinith
2013-01-01
Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. A practical, hands-on tutorial approach that explores the concepts of PowerShell in a friendly manner, taking an adhoc approach to each topic.If you are an administrator who is new to PowerShell or are looking to get a good grounding in these new features, this book is ideal for you. It's assumed that you will have some experience in PowerShell and Windows Server, as well being familiar with the PowerShell command-line.
Standardized CSR and climate performance: why is Shell willing, but Hydro reluctant?; Shell; Hydro
Boasson, Elin Lerum; Wettestad, Joergen
2007-06-15
This report aims to contribute to the ongoing discussion concerning whether CSR merely serves to streamline company rhetoric or also has an influence on actual efforts. We discuss the tangible effects of CSR instruments on the climate-related rules and performances of the two different oil companies Hydro and Shell. First we explore whether similar CSR instruments lead to similar climate-related rules and practices in the two companies. Both Hydro and Shell adhere to the Global Compact (GC), the Global Reporting Initiative (GRI), the Carbon Disclosure Project (CDP) and the Global Gas Flaring Reduction Public-Private Partnership (GGFR). The report concludes that the GC has not rendered any tangible effects in either of the companies. Concerning the other instruments, Hydro has only followed the instrument requirements that fit their initial approach, and refrained from all deviating requirements. Shell has been more malleable, but we have noted few effects on the actual emissions and business portfolio resulting from the instrument adherence. Second, we assess how the differing results of the similar CSR portfolio may be explained. The reluctant attitude of the leaders in Hydro and the strong CSR motivation of Shell's executives result in significant differences. Hydro executives are able to constrain the effects of the instrument adherence. With Shell we note the opposite pattern: Its leaders promoted the instruments to be translated into internal rules, but a general lack of hierarchical structures hinders them from governing the conduct of various sub-organisations. The very diversity of the Shell culture helps to explain why the efforts of its executives have resulted in limited impact. The strength of the Hydro culture makes the corporation resistant to the instruments. Moreover, Hydro is strikingly shielded by virtue of its strong position in Norway. In contrast, Shell is more strongly affected by the global field of petroleum and the global field of CSR
Ovgun, A.
2016-11-01
We construct a rotating thin-shell wormhole using a Myers-Perry black hole in five dimensions, using the Darmois-Israel junction conditions. The stability of the wormhole is analyzed under perturbations. We find that exotic matter is required at the throat of the wormhole to keep it stable. Our analysis shows that stability of the rotating thin-shell wormhole is possible if suitable parameter values are chosen.
NONE
2013-02-15
Shell has been using scenario planning for four decades. During that time these scenarios have helped the company and governments across the world to make better strategic choices. Scenarios provide lenses that help see future prospects more clearly, make richer judgments and be more sensitive to uncertainties. Discover how the Shell Scenarios team has helped guide decision makers at major moments in history and get a peek at the team future focus, including the intricate relationship between energy, water and food.
Ovgun, A
2016-01-01
In this article, we construct rotating thin shell wormhole using a Myers-Perry black hole in five dimensions. The stability of the wormhole is analyzed under perturbations follows from the Darmois-Israel junction conditions. We find that it required exotic matter at the throat to keep throat of wormhole stable. Our analysis shows that the stability of the rotating thin-shell wormhole is available with choosing suitable values of parameters.
Stellar Populations of Shell Galaxies
Carlsten, S; Zenteno, A
2016-01-01
We present a study of the inner (out to $\\sim$1 R$_{\\mathrm{eff}}$) stellar populations of 9 shell galaxies. We derive stellar population parameters from long slit spectra by both analyzing the Lick indices of the galaxies and by fitting Single Stellar Population model spectra to the full galaxy spectra. The results from the two methods agree reasonably well. Many of the shell galaxies in our sample appear to have lower central $\\mathrm{Mg}_{2}$ index values than non-shell galaxies of the same central velocity dispersion, which is likely due to a past interaction event. Our shell galaxy sample shows a relation between central metallicity and velocity dispersion that is consistent with previous samples of non-shell galaxies. Analyzing the metallicity gradients in our sample, we find an average metallicity gradient of -0.16$\\pm$0.10 dex per decade in radius. We compare this with formation models to constrain the merging history of shell galaxies. We argue that our galaxies likely have undergone major mergers in...
Thin elastic shells with variable thickness for lithospheric flexure of one-plate planets
Beuthe, Mikael
2007-01-01
Planetary topography can either be modeled as a load supported by the lithosphere, or as a dynamical effect due to lithospheric flexure caused by mantle convection. In both cases the response of the lithosphere to external forces can be calculated with the theory of thin elastic plates or shells. On one-plate planets the spherical geometry of the lithospheric shell plays an important role in the flexure mechanism. So far the equations governing the deformations and stresses of a spherical shell have only been derived under the assumption of a shell of constant thickness. However local studies of gravity and topography data suggest large variations in the thickness of the lithosphere. In this article we obtain the scalar flexure equations governing the deformations of a thin spherical shell with variable thickness or variable Young's modulus. The resulting equations can be solved in succession, except for a system of two simultaneous equations, the solutions of which are the transverse deflection and an associ...
A Systematic Analysis for Shells of Revolution with Nonsymmetric Loads.
EDGE EFFECT SOLUTIONS. However, a ystematic technique for evaluating the arbitrary constant for each harmonic of loading from the boundary conditions has been lacking. The solutions, including the particular solutions for surface loads and temperature effects, the deformations for the membrane solutions, and the curvature changes for the inextensional deformation, are presented in what may be their simplest form for the shell of arbitrary meridian. The relative order of magnitude of the contribution of each solution to the various stresses and displacements is
无
2001-01-01
Under certain conditions, the dynamic equatioins of membrane shells and the dynamic equations of flexural shells are obtained from dynamic equations of Koiter shells by the method of asymptotic analysis.
Transient impact responses of laminated composite cylindrical shells
无
2011-01-01
The generalized ray method(GRM) has been successfully used to study the transient elastic wave transmitting in the beams,planar trusses,space frames and infinite layered media.In this letter,the GRM is extended to investigate the early short time transient responses of laminated composite cylindrical shells under impact load.By using the Laplace transformation and referring to the boundary conditions,the ray groups transmitting in the finite laminated cylindrical shells under the shock load are obtained ...
Problems with tunneling of thin shells from black holes
Borun D Chowdhury
2008-01-01
It is shown that exp(−2 Im($\\int p dr$)) is not invariant under canonical transformations in general. Specifically for shells tunneling out of black holes, this quantity is not invariant under canonical transformations. It can be interpreted as the transmission coefficient only in the cases in which it is invariant under canonical transformations. Although such cases include alpha decay, they do not include the tunneling of shells from black holes. The simplest extension to this formula which is invariant under canonical transformations is proposed. However, it is shown that this gives half the correct temperature for black holes.
Ion Structure Near a Core-Shell Dielectric Nanoparticle
Ma, Manman; Gan, Zecheng; Xu, Zhenli
2017-02-01
A generalized image charge formulation is proposed for the Green's function of a core-shell dielectric nanoparticle for which theoretical and simulation investigations are rarely reported due to the difficulty of resolving the dielectric heterogeneity. Based on the formulation, an efficient and accurate algorithm is developed for calculating electrostatic polarization charges of mobile ions, allowing us to study related physical systems using the Monte Carlo algorithm. The computer simulations show that a fine-tuning of the shell thickness or the ion-interface correlation strength can greatly alter electric double-layer structures and capacitances, owing to the complicated interplay between dielectric boundary effects and ion-interface correlations.
L-shell radiative transition rates by selective synchrotron ionization
Bonetto, R D [Centro de Investigacion y Desarrollo en Ciencias Aplicadas Dr. Jorge J. Ronco, CONICET-UNLP, Calle 47 No. 257-Cc 59 (1900) La Plata (Argentina); Carreras, A C [Facultad de Matematica, AstronomIa y FIsica, Universidad Nacional de Cordoba, Ciudad Universitaria (5000) Cordoba (Argentina); Trincavelli, J [Facultad de Matematica, AstronomIa y FIsica, Universidad Nacional de Cordoba, Ciudad Universitaria (5000) Cordoba (Argentina); Castellano, G [Facultad de Matematica, AstronomIa y FIsica, Universidad Nacional de Cordoba, Ciudad Universitaria (5000) Cordoba (Argentina)
2004-04-14
Relative L-shell radiative transition rates were obtained for a number of decays in Gd, Dy, Er, Yb, Hf, Ta and Re by means of a method for refining atomic and experimental parameters involved in the spectral analysis of x-ray irradiated samples. For this purpose, pure samples were bombarded with monochromatic synchrotron radiation tuning the incident x-ray energy in order to allow selective ionization of the different atomic shells. The results presented are compared to experimental and theoretical values published by other authors. A good general agreement was found and some particular discrepancies are discussed.
Charged thin-shell gravastars in noncommutative geometry
Övgün, Ali; Banerjee, Ayan; Jusufi, Kimet
2017-08-01
In this paper we construct a charged thin-shell gravastar model within the context of noncommutative geometry. To do so, we choose the interior of the nonsingular de Sitter spacetime with an exterior charged noncommutative solution by cut-and-paste technique and apply the generalized junction conditions. We then investigate the stability of a charged thin-shell gravastar under linear perturbations around the static equilibrium solutions as well as the thermodynamical stability of the charged gravastar. We find the stability regions, by choosing appropriate parameter values, located sufficiently close to the event horizon.
Faster radial strain relaxation in InAs-GaAs core-shell heterowires
Kavanagh, Karen L. [Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Saveliev, Igor; Blumin, Marina; Ruda, Harry E. [Centre for Advanced Nanotechnology, University of Toronto, 170 College Street, Toronto, Ontario M5S 3E4 (Canada); Swadener, Greg [Mechanical Engineering and Design, Aston University, Aston Triangle, Birmingham B4 7ET (United Kingdom)
2012-02-15
The structure of wurtzite and zinc blende InAs-GaAs (001) core-shell nanowires grown by molecular beam epitaxy on GaAs (001) substrates has been investigated by transmission electron microscopy. Heterowires with InAs core radii exceeding 11 nm, strain relax through the generation of misfit dislocations, given a GaAs shell thickness greater than 2.5 nm. Strain relaxation is larger in radial directions than axial, particularly for shell thicknesses greater than 5.0 nm, consistent with molecular statics calculations that predict a large shear stress concentration at each interface corner.
Osredkar Joško
2012-05-01
Full Text Available The human organism is exposed to the influence of various forms of stress, either physical, psychological or chemical, which all have in common that they may adversely affect our body. A certain amount of stress is always present and somehow directs, promotes or inhibits the functioning of the human body. Unfortunately, we are now too many and too often exposed to excessive stress, which certainly has adverse consequences. This is especially true for a particular type of stress, called oxidative stress. All aerobic organisms are exposed to this type of stress because they produce energy by using oxygen. For this type of stress you could say that it is rather imperceptibly involved in our lives, as it becomes apparent only at the outbreak of certain diseases. Today we are well aware of the adverse impact of radicals, whose surplus is the main cause of oxidative stress. However, the key problem remains the detection of oxidative stress, which would allow us to undertake timely action and prevent outbreak of many diseases of our time. There are many factors that promote oxidative stress, among them are certainly a fast lifestyle and environmental pollution. The increase in oxidative stress can also trigger intense physical activity that is directly associated with an increased oxygen consumption and the resulting formation of free radicals. Considering generally positive attitude to physical activity, this fact may seem at first glance contradictory, but the finding has been confimed by several studies in active athletes. Training of a top athlete daily demands great physical effort, which is also reflected in the oxidative state of the organism. However, it should be noted that the top athletes in comparison with normal individuals have a different defense system, which can counteract the negative effects of oxidative stress. Quite the opposite is true for irregular or excessive physical activity to which the body is not adapted.
Excitation Potentials and Shell Corrections for the Elements Z2=20 to Z2=30
Andersen, H.H.; Sørensen, H.; Vadja, P.
1969-01-01
Excitation potentials and shell corrections for the elements Z 2=20 to Z2=30 are evaluated from experimental stopping-power data for 5-12-MeV protons and deuterons. Use is made of Walske's K- and L-shell corrections and shell corrections calculated by Bonderup (1967) on the basis of the Thomas-Fe...... are found by means of Bonderup's shell corrections. Within the Z2 interval treated here, it is found that I/Z2 increases with increasing Z2, contrary to the general trend through the periodic system of elements......Excitation potentials and shell corrections for the elements Z 2=20 to Z2=30 are evaluated from experimental stopping-power data for 5-12-MeV protons and deuterons. Use is made of Walske's K- and L-shell corrections and shell corrections calculated by Bonderup (1967) on the basis of the Thomas...
Black hole entropy off-shell vs on-shell
Frolov, V P; Zelnikov, A I
1996-01-01
Different methods of calculation of quantum corrections to the thermodynamical characteristics of a black hole are discussed and compared. The relation between on-shell and off-shell approaches is established. The off-shell methods are used to explicitly demonstrate that the thermodynamical entropy S^{TD} of a black hole, defined by the first thermodynamical law, differs from the statistical-mechanical entropy S^{SM}, determined as S^{SM}=-\\mbox{Tr}(\\hat{\\rho}^H\\ln\\hat{\\rho}^H) for the density matrix \\hat{\\rho}^H of a black hole. It is shown that the observable thermodynamical black hole entropy can be presented in the form S^{TD}=\\pi {\\bar r}_+^2+S^{SM}-S^{SM}_{Rindler}. Here {\\bar r}_+ is the radius of the horizon shifted because of the quantum backreaction effect, and S^{SM}_{Rindler} is the statistical-mechanical entropy calculated in the Rindler space.
Curvature effects in thin magnetic shells.
Gaididei, Yuri; Kravchuk, Volodymyr P; Sheka, Denis D
2014-06-27
A magnetic energy functional is derived for an arbitrary curved thin shell on the assumption that the magnetostatic effects can be reduced to an effective easy-surface anisotropy; it can be used for solving both static and dynamic problems. General static solutions are obtained in the limit of a strong anisotropy of both signs (easy-surface and easy-normal cases). It is shown that the effect of the curvature can be treated as the appearance of an effective magnetic field, which is aligned along the surface normal for the case of easy-surface anisotropy and is tangential to the surface for the case of easy-normal anisotropy. In general, the existence of such a field excludes the solutions that are strictly tangential or strictly normal to the surface. As an example, we consider static equilibrium solutions for a cone surface magnetization.
Shell shock, trauma, and the First World War: the making of a diagnosis and its histories.
Loughran, Tracey
2012-01-01
During the First World War, thousands of soldiers were treated for "shell shock," a condition which encompassed a range of physical and psychological symptoms. Shell shock has most often been located within a "genealogy of trauma," and identified as an important marker in the gradual recognition of the psychological afflictions caused by combat. In recent years, shell shock has increasingly been viewed as a powerful emblem of the suffering of war. This article, which focuses on Britain, extends scholarly analyses which question characterizations of shell shock as an early form of post-traumatic stress disorder. It also considers some of the methodological problems raised by recasting shell shock as a wartime medical construction rather than an essentially timeless manifestation of trauma. It argues that shell shock must be analyzed as a diagnosis shaped by a specific set of contemporary concerns, knowledges, and practices. Such an analysis challenges accepted understandings of what shell shock "meant" in the First World War, and also offers new perspectives on the role of shell shock in shaping the emergence of psychology and psychiatry in the early part of the twentieth century. The article also considers what relation, if any, might exist between intellectual and other histories, literary approaches, and perceptions of trauma as timeless and unchanging.
Shell-model calculations for p-shell hypernuclei
Millener, D. J.
2012-01-01
The interpretation of hypernuclear gamma-ray data for p-shell hypernuclei in terms of shell-model calculations that include the coupling of Lambda- and Sigma-hypernuclear states is briefly reviewed. Next, Lambda 8Li, Lambda 8Be, and Lambda 9Li are considered, both to exhibit features of Lambda-Sigma coupling and as possible source of observed, but unassigned, hypernuclear gamma rays. Then, the feasibility of measuring the ground-state doublet spacing of Lambda 10Be, which, like Lambda 9Li, co...
Summary compilation of shell element performance versus formulation.
Heinstein, Martin Wilhelm; Hales, Jason Dean (Idaho National Laboratory, Idaho Falls, ID); Breivik, Nicole L.; Key, Samuel W. (FMA Development, LLC, Great Falls, MT)
2011-07-01
This document compares the finite element shell formulations in the Sierra Solid Mechanics code. These are finite elements either currently in the Sierra simulation codes Presto and Adagio, or expected to be added to them in time. The list of elements are divided into traditional two-dimensional, plane stress shell finite elements, and three-dimensional solid finite elements that contain either modifications or additional terms designed to represent the bending stiffness expected to be found in shell formulations. These particular finite elements are formulated for finite deformation and inelastic material response, and, as such, are not based on some of the elegant formulations that can be found in an elastic, infinitesimal finite element setting. Each shell element is subjected to a series of 12 verification and validation test problems. The underlying purpose of the tests here is to identify the quality of both the spatially discrete finite element gradient operator and the spatially discrete finite element divergence operator. If the derivation of the finite element is proper, the discrete divergence operator is the transpose of the discrete gradient operator. An overall summary is provided from which one can rank, at least in an average sense, how well the individual formulations can be expected to perform in applications encountered year in and year out. A letter grade has been assigned albeit sometimes subjectively for each shell element and each test problem result. The number of A's, B's, C's, et cetera assigned have been totaled, and a grade point average (GPA) has been computed, based on a 4.0-system. These grades, combined with a comparison between the test problems and the application problem, can be used to guide an analyst to select the element with the best shell formulation.
Transition Strength Sums and Quantum Chaos in Shell Model States
Kota, V K B; Kar, K; Gómez, J M G; Retamosa, J
2000-01-01
For the embedded Gaussian orthogonal ensemble (EGOE) of random matrices, the strength sums generated by a transition operator acting on an eigenstate vary with the excitation energy as the ratio of two Gaussians. This general result is compared to exact shell model calculations, with realistic interactions, of spherical orbit occupancies and Gamow-Teller strength sums in some $(ds)$ and $(fp)$ shell examples. In order to confirm that EGOE operates in the chaotic domain of the shell model spectrum, calculations are carried out using two different interpolating hamiltonians generating order-chaos transitions. Good agreement is obtained in the chaotic domain of the spectrum, and strong deviations are observed as nuclear motion approaches a regular regime (transition strength sums appear to follow the Dyson's $\\Delta_3$ statistic). More importantly, they shed new light on the newly emerging understanding that in the chaotic domain of isolated finite interacting many particle systems smoothed densities (they inclu...
Acoustic resonances in two dimensional radial sonic crystals shells
Torrent, Daniel
2010-01-01
Radial sonic crystals (RSC) are fluidlike structures infinitely periodic along the radial direction. They have been recently introduced and are only possible thanks to the anisotropy of specially designed acoustic metamaterials [see Phys. Rev. Lett. {\\bf 103} 064301 (2009)]. We present here a comprehensive analysis of two-dimensional RSC shells, which consist of a cavity defect centered at the origin of the crystal and a finite thickness crystal shell surrounded by a fluidlike background. We develop analytic expressions demonstrating that, like for other type of crystals (photonic or phononic) with defects, these shells contain Fabry-Perot like resonances and strongly localized modes. The results are completely general and can be extended to three dimensional acoustic structures and to their photonic counterparts, the radial photonic crystals.
Acoustic resonances in two-dimensional radial sonic crystal shells
Torrent, Daniel; Sánchez-Dehesa, José
2010-07-01
Radial sonic crystals (RSC) are fluidlike structures infinitely periodic along the radial direction that verify the Bloch theorem and are possible only if certain specially designed acoustic metamaterials with mass density anisotropy can be engineered (see Torrent and Sánchez-Dehesa 2009 Phys. Rev. Lett. 103 064301). A comprehensive analysis of two-dimensional (2D) RSC shells is reported here. A given shell is in fact a circular slab with a central cavity. These finite crystal structures contain Fabry-Perot-like resonances and modes strongly localized at the central cavity. Semi-analytical expressions are developed to obtain the quality factors of the different resonances, their symmetry features and their excitation properties. The results reported here are completely general and can be extended to equivalent 3D spherical shells and to their photonic counterparts.
Off-shell superconformal nonlinear sigma-models in three dimensions
Kuzenko, Sergei M; Tartaglino-Mazzucchelli, Gabriele; von Unge, Rikard
2010-01-01
We develop superspace techniques to construct general off-shell N=1,2,3,4 superconformal sigma-models in three space-time dimensions. The most general N=3 and N=4 superconformal sigma-models are constructed in terms of N=2 chiral superfields. Several superspace proofs of the folklore statement that N=3 supersymmetry implies N=4 are presented both in the on-shell and off-shell settings. We also elaborate on (super)twistor realisations for (super)manifolds on which the three-dimensional N-extended superconformal groups act transitively and which include Minkowski space as a subspace.
2010-01-01
... Standards for Grades of Shelled Pistachio Nuts § 51.2555 General. (a) Compliance with the provisions of.... (b) These standards are applicable to raw, roasted, salted or salted/roasted pistachio kernels....
Lee, Thomas; Schill, Mark E; Tanasovski, Tome
2011-01-01
Here's the complete guide to Windows PowerShell 2.0 for administrators and developers Windows PowerShell is Microsoft's next-generation scripting and automation language. This comprehensive volume provides the background that IT administrators and developers need in order to start using PowerShell automation in exciting new ways. It explains what PowerShell is, how to use the language, and specific ways to apply PowerShell in various technologies. Windows PowerShell is Microsoft's standard automation tool and something that every Windows administrator will eventually have to understand; this b
Shell Models of Magnetohydrodynamic Turbulence
Plunian, Franck; Frick, Peter
2012-01-01
Shell models of hydrodynamic turbulence originated in the seventies. Their main aim was to describe the statistics of homogeneous and isotropic turbulence in spectral space, using a simple set of ordinary differential equations. In the eighties, shell models of magnetohydrodynamic (MHD) turbulence emerged based on the same principles as their hydrodynamic counter-part but also incorporating interactions between magnetic and velocity fields. In recent years, significant improvements have been made such as the inclusion of non-local interactions and appropriate definitions for helicities. Though shell models cannot account for the spatial complexity of MHD turbulence, their dynamics are not over simplified and do reflect those of real MHD turbulence including intermittency or chaotic reversals of large-scale modes. Furthermore, these models use realistic values for dimensionless parameters (high kinetic and magnetic Reynolds numbers, low or high magnetic Prandtl number) allowing extended inertial range and accu...
R. L. Verma
1989-01-01
Full Text Available This paper datails the design and implementation of an AI-based diagnostic shell. The shell has a user-interface which takes in the complaint and aids the user throughout the consultation. The 'expert knowledge' is acquired and encoded in the form of 'IF-THEN' rules, The control mechanism routes through the rules chaining first backwards to identify a fault and then forwards to confirm it.Explanation facilities have been provided to enable the user query the reason for any question asked, a facility to go back and re-answer any previous question, and a trace and explanation of the path of reasoning.This shell was developed and first used for the diagnosis of a digital exchange. It was then applied for the fault-finding of the moving target indicator used in the radar.
Asymptotic safety goes on shell
Benedetti, Dario
2012-01-01
It is well known in quantum field theory that the off-shell effective action depends on the gauge choice and field parametrization used in calculating it. Nevertheless, the typical scheme in which the scenario of asymptotically safe gravity is investigated is an off-shell version of the functional renormalization group equation. Working with the Einstein-Hilbert truncation as a test bed, we develop a new scheme for the analysis of asymptotically safe gravity in which the on-shell part of the effective action is singled out and we show that the beta function for the essential coupling has no explicit gauge dependence. In order to reach our goal, we introduce several technical novelties, including a different decomposition of the metric fluctuations, a new implementation of the ghost sector and a new cut-off scheme. We find a nontrivial fixed point, with a value of the cosmological constant that is independent of the gauge-fixing parameters.
Delta Shell: Integrated Modeling by Example
Donchyts, G.; Jagers, B.; Baart, F.; Geer, P. V.
2011-12-01
We present the integrated modeling environment Delta Shell. It supports the full workflow of integrated environmental modeling: setup, configuration, simulation, analysis and reporting of results. Many components of the environment can be reused independently, allowing development of scientific, geospatial and other applications focused on data analysis, editing, visualization and storage. One of the unique features is that the Delta Shell environment integrates models from many different fields, such as hydrodynamics, hydrology, morphology, ecology, water quality, geospatial and decision support systems. This integration is possible due to flexible general data types, lightweight model coupling framework, the plugin system and the inclusion of a number of high quality open source components. Here we will use the open source morphological model XBeach as an example showing how to integrate models into the Delta Shell environment. Integration of XBeach adds a graphical interface which can be used to make testing coastal safety for complicated coastal areas easier. By using this example, we give an overview of the modeling framework and its possibilities. To increase the usability, the model is integrated with a coastal profile data set covering the whole coast of the Netherlands. This gives the end user a system to easily use the model for scanning the safety of the Dutch coast. The reuse of the components of the environment individually or combined is encouraged. They are available as separate components and have minimal or no dependencies on other components. This includes libraries to work with scientific multidimensional data, geospatial data (in particular geospatial coverages: values of some quantities defined on a spatial domain), editors, visualisation of time-dependent data and the modeling framework (projects, data linking, workflow management, model integration). Most components and the XBeach example are available as open source.
Horváth, Krisztián; Felinger, Attila
2015-08-14
The applicability of core-shell phases in preparative separations was studied by a modeling approach. The preparative separations were optimized for two compounds having bi-Langmuir isotherms. The differential mass balance equation of chromatography was solved by the Rouchon algorithm. The results show that as the size of the core increases, larger particles can be used in separations, resulting in higher applicable flow rates, shorter cycle times. Due to the decreasing volume of porous layer, the loadability of the column dropped significantly. As a result, the productivity and economy of the separation decreases. It is shown that if it is possible to optimize the size of stationary phase particles for the given separation task, the use of core-shell phases are not beneficial. The use of core-shell phases proved to be advantageous when the goal is to build preparative column for general purposes (e.g. for purification of different products) in small scale separations.
Prevalence of anisotropic shell growth in rare earth core-shell upconversion nanocrystals.
Zhang, Chao; Lee, Jim Yang
2013-05-28
Through a series of carefully executed experiments, we discovered the prevalence of anisotropic shell growth in many upconversion NaREF4 systems caused by a combination of factors: selective adsorption of ligands on the core surface due to the core crystal structure, ligand etching, and the lattice mismatch between core and shell components. This could lead to incomplete shell formation in core-shell nanocrystals under certain conditions. Shell growth is always faster in the a and b crystallographic directions than in the c direction. In the case of a larger lattice mismatch between the core and shell, shell growth only occurs in the a and b directions resulting in an oblong core-shell structure. These findings are useful for rationalizing shell-dependent emission properties, understanding the emission mechanisms in complex core-shell nanostructures, and for creating accurate models of core-shell designs for multifunctionality and optimal performance in applications.
Stability of facetted translation shells
Almegaard, Henrik; Vanggaard, Ole
2004-01-01
This article is discussing the spatial stability i.e. rigidity of double curved shell surfaces under different support conditions. It is based upon a method developed by Henrik Almegaard, as part of the theory concerning the stringer system (ALM04a).......This article is discussing the spatial stability i.e. rigidity of double curved shell surfaces under different support conditions. It is based upon a method developed by Henrik Almegaard, as part of the theory concerning the stringer system (ALM04a)....
Learning Shell scripting with Zsh
Festari, Gaston
2014-01-01
A step-by-step tutorial that will teach you, through real-world examples, how to configure and use Zsh and its various features. If you are a system administrator, developer, or computer professional involved with UNIX who are looking to improve on their daily tasks involving the UNIX shell, ""Learning Shell Scripting with Zsh"" will be great for you. It's assumed that you have some familiarity with an UNIX command-line interface and feel comfortable with editors such as Emacs or vi.
Effect of a cylindrical thin-shell of matter on the electrostatic self-force on a charge
Rubin de Celis, Emilio [Universidad de Buenos Aires y IFIBA, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2016-02-15
The electrostatic self-force on a point charge in cylindrical thin-shell space-times is interpreted as the sum of a bulk field and a shell field. The bulk part corresponds to a field sourced by the test charge placed in a space-time without the shell. The shell field accounts for the discontinuity of the extrinsic curvature κ{sup p}{sub q}. An equivalent electric problem is stated, in which the effect of the shell of matter on the field is reconstructed with the electric potential produced by a non-gravitating charge distribution of total image charge Q, to interpret the shell field in both the interior and exterior regions of the space-time. The self-force on a point charge q in a locally flat geometry with a cylindrical thin-shell of matter is calculated. The charge is repelled from the shell if κ{sup p}{sub q} = κ < 0 (ordinarymatter) and attracted toward the shell if κ > 0 (exotic matter). The total image charge is zero for exterior problems, while for interior problems Q/q = κr{sub e}, with re the external radius of the shell. The procedure is general and can be applied to interpret self-forces in other space-times with shells, e.g., for locally flat wormholes we found Q{sub -+}{sup wh}/q = -1/(κ{sub wh}r{sub ±}). (orig.)
Design of a stabilizing shell for KTX
You, Wei [CAS Key Laboratory of Geospace Environment, Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Li, Hong, E-mail: honglee@ustc.edu.cn [CAS Key Laboratory of Geospace Environment, Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Tan, Mingsheng; Lu, Mingjian; Wu, Yanqi; Mao, Wenzhe; Bai, Wei; Tu, Cui; Luo, Bing; Li, Zichao; Adil, Yolbarsop; Hu, Jintong [CAS Key Laboratory of Geospace Environment, Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Song, Yuntao; Yang, Qingxi; Zhang, Ping [Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026 (China); Xie, Jinlin; Lan, Tao; Liu, Adi [CAS Key Laboratory of Geospace Environment, Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Ding, Weixing [CAS Key Laboratory of Geospace Environment, Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095 (United States); Xiao, Chijin [CAS Key Laboratory of Geospace Environment, Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Department of Physics and Engineering Physics, University of Saskatchewan, SK S7 N 5N2 (Canada); and others
2016-10-15
The conductive shell in reversed field pinch devices plays an important role in controlling plasma and in suppressing MHD instabilities. The shell in the Keda torus experiment reversed field pinch (KTX-RFP) device includes a 6-mm stainless steel vacuum chamber and a 1.5-mm stabilizing copper shell. This stabilizing shell has both poloidal and toroidal gaps to allow a coupling of electromagnetic energy to the plasma. Nevertheless, any gaps in this shell generate error fields. A 3D electromagnetic field model has been used to study effects of the gap on the shell. Using off-center current filaments instead of the distributed plasma current density, numerical analyses render the induced current distribution on the stabilizing shell and the resultant error field distribution at a specific frequency. From the analyses and comparisons of different configurations for the stabilizing shell, a suitable shell design is chosen consisting of three sections: one primary shell, two poloidal shield shells, and two toroidal shield shells. Moreover, the time evolution of the magnetic field inside and outside the stabilizing shell was obtained for this design and the dependence of the magnetic field penetration time on mode number and location has been investigated.
付科; 张林洪; 邢万鹏
2012-01-01
In order to accurately define and understand the Bishop's stress, the definition framework of generalized effective stress is put forward by considering the shortcomings of constitutive model of unsaturated soil. And then it compares with the traditional definition framework of the Bishop's stress. Finally, the matric suction, cementation action and hardening process are discussed.%为更好地定义和理解毕肖普(Bishop)应力,针对非饱和土本构模型有效应力研究中存在的问题,提出 了广义有效应力定义框架,并与传统Bishop应力定义框架做了比较,探讨了基质吸力、粘固作用、硬化过程.
Unique morphology and gradient arrangement of nacre's platelets in green mussel shells
Xu, Jun; Zhang, Gangsheng, E-mail: zhanggs@gxu.edu.cn
2015-07-01
Nacre has long served as a classic model in biomineralization and the synthesis of biomimetic materials. However, the morphology and arrangement of its basic building blocks, the aragonite platelets, are still under hot debate. In this study, using a field emission scanning electron microscope (SEM), a high-resolution transmission electron microscope (HRTEM), and an X-ray diffractometer (XRD), we investigate the platelets at the edges and centers of green mussel shells. We find that 1) flat and curved platelets coexist in green mussel shells; 2) the immature platelets at the shell edge are aggregates of aragonite nanoparticles, whereas the immature ones at the shell center are single crystals; and 3) the morphology and thickness of the platelets exhibit a gradient arrangement. Based on these findings, we hypothesize that the gradient in the thickness and curvature of the platelets may probably result from the difference in growth rate between the edge and the center of the shell and from the gradient in compressive stress imposed by the closing of the shells by the adductor muscles or the withdrawal of the periostracum by the mantle. We expect that the presented results will shed new light on the formation mechanisms of natural composite materials. - Highlights: • Flat and curved platelets coexist in green mussel shells. • The immature platelets at the shell edge consist of aragonite nanoparticles. • The immature platelets at the shell center are single crystals. • The morphology and thickness of platelets exhibit a gradient arrangement. • The gradient arrangement of platelets may result from the stress gradient.
Generalized derivations and general relativity
Heller, M; Pysiak, L; Sasin, W
2013-01-01
We construct differential geometry (connection, curvature, etc.) based on generalized derivations of an algebra A. Such a derivation, introduced by Bresar in 1991, is given by a linear mapping u: A -> A such that there exists a usual derivation d of A satisfying the generalized Leibniz rule u(a b) = u(a) b + a d(b) for all a,b in A. The generalized geometry "is tested" in the case of the algebra of smooth functions on a manifold. We then apply this machinery to study the generalized general relativity. We define the Einstein-Hilbert action and deduce from it Einstein's field equations. We show that for a special class of metrics containing, besides the usual metric components, only one non-zero term, the action reduces to O'Hanlon action that is a Brans-Dicke action with potential and with the parameter \\omega equal to zero. We also show that the generalized Einstein equations (with zero energy-stress tensor) are equivalent to those of the Kaluza-Klein theory satisfying a "modified cylinder condition" and hav...
Method and apparatus for an inflatable shell
Johnson, Christopher J. (Inventor)
2012-01-01
A method of assembling an inflatable shell of a structure comprises folding a plurality of shell sections about a set of fold lines and integrating the plurality of shell sections together with one another to form the shell. In another embodiment, an inflatable shell comprises a plurality of shell sections, each shell section having two pairs of fold lines for folding into stowage comprising a first gore section having a plurality of first gore panels layered and collectively folded about at a first set of fold lines. Each layer of the first gore panels and second gore panels are configured such that, once the first gore panel and second gore panel are attached to one another at the respective side edges of each panel, the lines of attachment forming a second set of fold lines for the shell section. A system and method for fabricating gore panels is also disclosed.
Statistical mechanics of thin spherical shells
Kosmrlj, Andrej
2016-01-01
We explore how thermal fluctuations affect the mechanics of thin amorphous spherical shells. In flat membranes with a shear modulus, thermal fluctuations increase the bending rigidity and reduce the in-plane elastic moduli in a scale-dependent fashion. This is still true for spherical shells. However, the additional coupling between the shell curvature, the local in-plane stretching modes and the local out-of-plane undulations, leads to novel phenomena. In spherical shells thermal fluctuations produce a radius-dependent negative effective surface tension, equivalent to applying an inward external pressure. By adapting renormalization group calculations to allow for a spherical background curvature, we show that while small spherical shells are stable, sufficiently large shells are crushed by this thermally generated "pressure". Such shells can be stabilized by an outward osmotic pressure, but the effective shell size grows non-linearly with increasing outward pressure, with the same universal power law expone...
Shell Global Solutions Ready to Benefit China
无
2008-01-01
@@ Thanks to rising oil prices, Global oil giant Royal Dutch Shell has made huge profits - $9 billion - last quarter. Yet the oil giant's main profits come from the exploration of crude oil. Shell Global Solution (SGS),a unit of Shell, is also focusing on providing advanced technology to help Shell's petroleum-related industry segments and its third-party customers to deal with the high price of fossil fuel.
Euclidean Approach for Entropy of Black Shells
S., J Robel Arenas
2016-01-01
We introduce the concept of black shell, consisting on a massive thin spherical shell contracting toward its gravitational radius from the point of view of an external observer far from the shell, in order to effectively model the gravitational collapse. Considering complementary description of entanglement entropy of a black shell and according to Gibbons-Hawking Euclidean approach, we calculate the Bekenstein-Hawking entropy retrieving horizon integral and discarding boundary at infinity.
Evidence for variable crystallinity in bivalve shells
Jacob, D. E.; Wehrmeister, U.
2012-04-01
Bivalve shells are used as important palaeoclimate proxy archives and monitor regional climate variations. The shells mostly exist of two crystalline polymorphic phases of calcium carbonate calcite (rombohedric) and aragonite (orthorhombic). Calcite is the most stable polymorph at standard conditions, whereas vaterite (hexagonal) is the least stable and only rarely found in these structures. Shells are characterized by organized structures and several micro architectures of mollusc shell structures have been identified: Nacre shows different types: columnar and bricked forms and consists of composite inorganic- organic at the nano-scale. They are well known to display a "brick and mortar" structure. By AFM and FIB/TEM methods it could be shown, that its nanostructure consists of the structures in the range of 50 - 100 nm [1, 2]. These structures are vesicles, consisting of CaCO3 and are individually coated by a membrane. Most probably, the mantle epithelian cells of the bivalve extrude CaCO3 vesicles. By Raman spectroscopic investigations the crystalline CaCO3 polymorphs calcite, aragonite and vaterite, as well as ACC were determined. For some species (Diplodon chilensis patagonicus, Hyriopsis cumingii) pure ACC (i.e. not intermingled with a crystalline phase) could be identified. The presence of an amorphous phase is generally deduced from the lack of definite lattice modes, whereas a broad Raman band in this region is to observe. In most of the cultured pearls (Pinctada maxima and genus Hyriopsis) the ν1-Raman band of ACC clearly displays an asymmetric shape and splits into two different bands according to a nanocrystalline and an amorphous fraction. The FWHMs of most of the crystalline fractions are too high for well crystallized materials and support the assumption of nanocrystalline calcium carbonate polymorph clusters in ACC. They are primarily composed of amorphous calcium carbonate (ACC) which is later transformed into a crystalline modification [3
Hybrid Semiloof elements for plates and shells based upon a modified Hu-Washizu principle
Pian, T. H. H.; Sumihara, K.
1984-01-01
Hybrid SemiLoof elements for plates and shells are developed based upon modified Hu-Washizu principle. In the new version of the assumed stress hybrid formulation the equilibrium equations are satisfied through the introduction of internal displacement parameters as Lagrange multipliers. The inversion of the resulting H-matrices is simplified particularly when the stresses are expressed in terms of natural coordinates. A 24-DOF triangular element and a 32-DOF quadrilateral element based on shallow shell theory are derived and evaluated.
Shell theorem for spontaneous emission
Kristensen, Philip Trøst; Mortensen, Jakob Egeberg; Lodahl, Peter;
2013-01-01
and therefore is given exactly by the dipole approximation theory. This surprising result is a spontaneous emission counterpart to the shell theorems of classical mechanics and electrostatics and provides insights into the physics of mesoscopic emitters as well as great simplifications in practical calculations....
Observability inequalities for thin shells
柴树根; 姚鹏飞
2003-01-01
We consider the exact controllability problem from boundary for thin shells. Under some check-able geometric assumptions on the middle surface, we establish the observability inequalities via the Bochnertechnique for the Dirichlet control and the Neumann control problems. We also give several examples to verifythe geometric assumptions.
Shell morphology of core-shell latexes based on conductive polymers
Huijs, F.M; Vercauteren, F.F.; de Ruiter, B.; Kalicharan, D; Hadziioannou, G
Core-shell latexes with a conductive shell can be used to prepare transparent conducting layers. We have focussed on the relation between the conducting polymer content and the shell morphology and on its influence on conductivity. At low polypyrrole (PPy) concentrations the shell has a smooth
On Perturbation Solutions for Axisymmetric Bending Boundary Values of a Deep Thin Spherical Shell
Rong Xiao
2014-01-01
Full Text Available On the basis of the general theory of elastic thin shells and the Kirchhoff-Love hypothesis, a fundamental equation for a thin shell under the moment theory is established. In this study, the author derives Reissner’s equation with a transverse shear force Q1 and the displacement component w. These basic unknown quantities are derived considering the axisymmetry of the deep, thin spherical shell and manage to constitute a boundary value question of axisymmetric bending of the deep thin spherical shell under boundary conditions. The asymptotic solution is obtained by the composite expansion method. At the end of this paper, to prove the correctness and accuracy of the derivation, an example is given to compare the numerical solution by ANSYS and the perturbation solution. Meanwhile, the effects of material and geometric parameters on the nonlinear response of axisymmetric deep thin spherical shell under uniform external pressure are also analyzed in this paper.
Sargsyan S.H.
2014-03-01
Full Text Available In the present paper, the system of equations of three-dimensional micropolar theory of elasticity, written down for thin shell as singularly perturbed with small geometric parameter system, is analyzed asymptotically: the internal iteration process and boundary layers are constructed, their interaction is studied, boundary conditions are obtained for each of them. Then, the main specific properties of the asymptotic solution accepting as hypotheses, general applied theory of micropolar elastic thin shells is constructed and it is shown that the constructed theory is asymptotically correct. Passing from the micropolar theory of thin shells to the classical theory, it is shown, that this applied classical theory of thin shells, when transverse shifts are taken into account, is asymptotically correct theory in relation to the other corrected theories of thin shells.
Restoration of the N=82 Shell Gap from Direct Mass Measurements of $^{132,134}$Sn
Dworschak, M; Blaum, K; Delahaye, P; George, S; Hager, U; Herfurth, F; Herlert, A; Kellerbauer, A G; Kluge, H J; Lunney, D; Schweikhard, L; Yazidjian, C
2008-01-01
A high-precision direct Penning trap mass measurement has revealed a 0.5-MeV deviation of the binding energy of $^{134}$Sn from the currently accepted value. The corrected mass assignment of this neutron-rich nuclide restores the neutron-shell gap at N=82, previously considered to be a case of “shell quenching.” In fact, the new shell gap value for the short-lived $^{132}$Sn is larger than that of the doubly-magic $^{48}$Ca which is stable. The N=82 shell gap has considerable impact on fission recycling during the $r$ process. More generally, the new finding has important consequences for microscopic mean-field theories which systematically deviate from the measured binding energies of closed-shell nuclides.
刘燊; 李丹丹; 张林
2015-01-01
This paper investigated 300 undergraduates in questionnaire to examine the effects of general self-efficacy and regulatory emotional self-efficacy on stress resilience. The results showed that there were significantly positive correlations between general self-efficacy, regulatory emotional self-efficacy and stress resilience; and regulatory emotional self-efficacy completely mediated the relationship between general self-efficacy and stress resilience.%运用问卷调查法，以300名大学生为研究对象，探讨一般自我效能感和情绪调节自我效能感对大学生心理弹性的影响。研究发现：一般自我效能感与情绪调节自我效能感、心理弹性之间均有显著的正相关，情绪调节自我效能感与心理弹性之间有显著的正相关；情绪调节自我效能感在一般自我效能感对心理弹性的影响之间具有完全中介作用。
21 CFR 886.3800 - Scleral shell.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Scleral shell. 886.3800 Section 886.3800 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Prosthetic Devices § 886.3800 Scleral shell. (a) Identification. A scleral shell is...
Shell China Promotes Localization of Employees
无
2008-01-01
@@ Shell China Limited's Executive Chairman Lim Haw Kuang is unquestionably an effective reformer for the Beijing-based company. He localized Shell China Limited's leadership team with Chinese employees going from zero to a majority in three years, and engineered the turnaround of Shell's business in China.
7 CFR 983.29 - Shelled pistachios.
2010-01-01
... 7 Agriculture 8 2010-01-01 2010-01-01 false Shelled pistachios. 983.29 Section 983.29 Agriculture... and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE PISTACHIOS GROWN IN CALIFORNIA, ARIZONA, AND NEW MEXICO Definitions § 983.29 Shelled pistachios. Shelled pistachios means...
Shell Expands Polystyrene Joint Venture in China
无
1997-01-01
@@ Shell China Ltd. and Shell China Holdings BV, both wholly owned subsidiaries and part of the Royal Dutch/Shell Group of Companies, have signed a joint-venture agreement with Jinling Petrochemical Corporation (JPC) on October 17, 1997, in Nanjing, the East China's Jiangsu Province.
Protein profiles of hatchery egg shell membrane
Background: Eggshells, which consist largely of calcareous outer shell and shell membranes, constitute a significant part of poultry hatchery waste. The shell membranes (ESM) not only contain proteins that originate from egg whites but also from the developing embryos and different contaminants of m...
Effective Finite Elements for Shell Analysis.
1984-02-20
conjunction with a shallow shell theory . It 2 should be noteJ that contrary to the results of earlier investigators [12,19], use of a shallow shell theory in...the inadequacy of the shallow shell theory for the relatively deep element emerging from such a coarse mesh. A considerable improvement is obtained
Stability of the Regular Hayward Thin-Shell Wormholes
Sharif, M
2016-01-01
The aim of this paper is to construct regular Hayward thin-shell wormholes and analyze their stability. We adopt Israel formalism to calculate surface stresses of the shell and check the null and weak energy conditions for the constructed wormholes. It is found that the stress-energy tensor components violate the null and weak energy conditions leading to the presence of exotic matter at the throat. We analyze the attractive and repulsive characteristics of wormholes corresponding to $a^r>0$ and $a^r<0$, respectively. We also explore stability conditions for the existence of traversable thin-shell wormholes with arbitrarily small amount of fluids describing cosmic expansion. We find that the spacetime has non-physical regions which give rise to event horizon for $0
Vibrations of cantilevered circular cylindrical shells Shallow versus deep shell theory
Lee, J. K.; Leissa, A. W.; Wang, A. J.
1983-01-01
Free vibrations of cantilevered circular cylindrical shells having rectangular planforms are studied in this paper by means of the Ritz method. The deep shell theory of Novozhilov and Goldenveizer is used and compared with the usual shallow shell theory for a wide range of shell parameters. A thorough convergence study is presented along with comparisons to previously published finite element solutions and experimental results. Accurately computed frequency parameters and mode shapes for various shell configurations are presented. The present paper appears to be the first comprehensive study presenting rigorous comparisons between the two shell theories in dealing with free vibrations of cantilevered cylindrical shells.
Mechanics of couple-stress fluid coatings
Waxman, A. M.
1982-01-01
The formal development of a theory of viscoelastic surface fluids with bending resistance - their kinematics, dynamics, and rheology are discussed. It is relevant to the mechanics of fluid drops and jets coated by a thin layer of immiscible fluid with rather general rheology. This approach unifies the hydrodynamics of two-dimensional fluids with the mechanics of an elastic shell in the spirit of a Cosserat continuum. There are three distinct facets to the formulation of surface continuum mechanics. Outlined are the important ideas and results associated with each: the kinematics of evolving surface geometries, the conservation laws governing the mechanics of surface continua, and the rheological equations of state governing the surface stress and moment tensors.
Ridgely, Charles T.
2010-01-01
Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…
Ridgely, Charles T.
2010-01-01
Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…
Nonlinear Finite Element Analysis of a General Composite Shell
1988-12-01
linked to the main program before execution. Isubroutine upress(t,pa,pb,iunit, ielt ,x,y,z,live,press) c c Pressure distribution subroutine for c...then compiled and linked to the main program before execution. I SUBROUTINE UPRESS(T,PA,PB,IUNIT, IELT ,X,Y,Z,LIVE,PRESS) C c Pressure distribution...I ELSE NIELT- IELT -52 IF ((NIELT.LE. 2) +.OR.(NIELT.GE. 5.AND.NIELT.LE. 8) +.OR.(NIELT.EQ. 55) +.OR.(NIELT.EQ. 13) +.OR.(NIELT.GE. 57.AND.NIELT.LE. 59
3D CENTRAL LINE EXTRACTION OF FOSSIL OYSTER SHELLS
A. Djuricic
2016-06-01
Full Text Available Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare fossils. This saves manpower in relation to current documentation practice and makes the fragile specimens more available for paleontological analysis and public education. In this study, high resolution orthophoto (0.5 mm and digital surface models (1 mm are used to define fossil boundaries that are then used as an input to automatically extract fossil length information via central lines. In general, central lines are widely used in geosciences as they ease observation, monitoring and evaluation of object dimensions. Here, the 3D central lines are used in a novel paleontological context to study fossilized oyster shells with photogrammetric and LiDAR-obtained 3D point cloud data. 3D central lines of 1121 Crassostrea gryphoides oysters of various shapes and sizes were computed in the study. Central line calculation included: i Delaunay triangulation between the fossil shell boundary points and formation of the Voronoi diagram; ii extraction of Voronoi vertices and construction of a connected graph tree from them; iii reduction of the graph to the longest possible central line via Dijkstra’s algorithm; iv extension of longest central line to the shell boundary and smoothing by an adjustment of cubic spline curve; and v integration of the central line into the corresponding 3D point cloud. The resulting longest path estimate for the 3D central line is a size parameter that can be applied in oyster shell age determination both in paleontological and biological applications. Our investigation evaluates ability and performance of the central line method to measure shell sizes accurately by comparing automatically extracted central lines with manually collected reference data used in paleontological analysis. Our results show that the automatically obtained central line length overestimated the manually collected reference by 1.5% in the test set, which
D Central Line Extraction of Fossil Oyster Shells
Djuricic, A.; Puttonen, E.; Harzhauser, M.; Mandic, O.; Székely, B.; Pfeifer, N.
2016-06-01
Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare fossils. This saves manpower in relation to current documentation practice and makes the fragile specimens more available for paleontological analysis and public education. In this study, high resolution orthophoto (0.5 mm) and digital surface models (1 mm) are used to define fossil boundaries that are then used as an input to automatically extract fossil length information via central lines. In general, central lines are widely used in geosciences as they ease observation, monitoring and evaluation of object dimensions. Here, the 3D central lines are used in a novel paleontological context to study fossilized oyster shells with photogrammetric and LiDAR-obtained 3D point cloud data. 3D central lines of 1121 Crassostrea gryphoides oysters of various shapes and sizes were computed in the study. Central line calculation included: i) Delaunay triangulation between the fossil shell boundary points and formation of the Voronoi diagram; ii) extraction of Voronoi vertices and construction of a connected graph tree from them; iii) reduction of the graph to the longest possible central line via Dijkstra's algorithm; iv) extension of longest central line to the shell boundary and smoothing by an adjustment of cubic spline curve; and v) integration of the central line into the corresponding 3D point cloud. The resulting longest path estimate for the 3D central line is a size parameter that can be applied in oyster shell age determination both in paleontological and biological applications. Our investigation evaluates ability and performance of the central line method to measure shell sizes accurately by comparing automatically extracted central lines with manually collected reference data used in paleontological analysis. Our results show that the automatically obtained central line length overestimated the manually collected reference by 1.5% in the test set, which is deemed
Converting Multi-Shell and Diffusion Spectrum Imaging to High Angular Resolution Diffusion Imaging.
Yeh, Fang-Cheng; Verstynen, Timothy D
2016-01-01
Multi-shell and diffusion spectrum imaging (DSI) are becoming increasingly popular methods of acquiring diffusion MRI data in a research context. However, single-shell acquisitions, such as diffusion tensor imaging (DTI) and high angular resolution diffusion imaging (HARDI), still remain the most common acquisition schemes in practice. Here we tested whether multi-shell and DSI data have conversion flexibility to be interpolated into corresponding HARDI data. We acquired multi-shell and DSI data on both a phantom and in vivo human tissue and converted them to HARDI. The correlation and difference between their diffusion signals, anisotropy values, diffusivity measurements, fiber orientations, connectivity matrices, and network measures were examined. Our analysis result showed that the diffusion signals, anisotropy, diffusivity, and connectivity matrix of the HARDI converted from multi-shell and DSI were highly correlated with those of the HARDI acquired on the MR scanner, with correlation coefficients around 0.8~0.9. The average angular error between converted and original HARDI was 20.7° at voxels with signal-to-noise ratios greater than 5. The network topology measures had less than 2% difference, whereas the average nodal measures had a percentage difference around 4~7%. In general, multi-shell and DSI acquisitions can be converted to their corresponding single-shell HARDI with high fidelity. This supports multi-shell and DSI acquisitions over HARDI acquisition as the scheme of choice for diffusion acquisitions.
Converting Multi-Shell and Diffusion Spectrum Imaging to High Angular Resolution Diffusion Imaging
Yeh, Fang-Cheng; Verstynen, Timothy D.
2016-01-01
Multi-shell and diffusion spectrum imaging (DSI) are becoming increasingly popular methods of acquiring diffusion MRI data in a research context. However, single-shell acquisitions, such as diffusion tensor imaging (DTI) and high angular resolution diffusion imaging (HARDI), still remain the most common acquisition schemes in practice. Here we tested whether multi-shell and DSI data have conversion flexibility to be interpolated into corresponding HARDI data. We acquired multi-shell and DSI data on both a phantom and in vivo human tissue and converted them to HARDI. The correlation and difference between their diffusion signals, anisotropy values, diffusivity measurements, fiber orientations, connectivity matrices, and network measures were examined. Our analysis result showed that the diffusion signals, anisotropy, diffusivity, and connectivity matrix of the HARDI converted from multi-shell and DSI were highly correlated with those of the HARDI acquired on the MR scanner, with correlation coefficients around 0.8~0.9. The average angular error between converted and original HARDI was 20.7° at voxels with signal-to-noise ratios greater than 5. The network topology measures had less than 2% difference, whereas the average nodal measures had a percentage difference around 4~7%. In general, multi-shell and DSI acquisitions can be converted to their corresponding single-shell HARDI with high fidelity. This supports multi-shell and DSI acquisitions over HARDI acquisition as the scheme of choice for diffusion acquisitions. PMID:27683539
Torrefaction of pomaces and nut shells.
Chiou, Bor-Sen; Valenzuela-Medina, Diana; Bilbao-Sainz, Cristina; Klamczynski, Artur K; Avena-Bustillos, Roberto J; Milczarek, Rebecca R; Du, Wen-Xian; Glenn, Greg M; Orts, William J
2015-02-01
Apple, grape, olive, and tomato pomaces as well as almond and walnut shells were torrefied at different temperatures and times in a muffle furnace. The fiber content and thermal stability of the raw byproducts were examined and the moisture and ash contents, elemental composition, and gross calorific values of the raw and torrefied samples were characterized. Response surface methodology and a central composite design were used to examine the effects of temperature and time on mass and energy yields of the torrefied byproducts. Raw apple pomace had the highest hemicellulose content, whereas raw grape pomace had the highest lignin content. Raw tomato pomace had the highest gross calorific value because of its high carbon content. Temperature had a larger effect on mass and energy yields than time. Grape pomace generally had the highest mass and energy yields. Also, energy yields of the byproducts could be predicted from mass loss values.
Making electromagnetic wavelets: II. Spheroidal shell antennas
Kaiser, Gerald [Center for Signals and Waves, 3803 Tonkawa Trail 2, Austin, TX (United States)
2005-01-14
In the companion paper, a charge-current distribution was obtained for radiating electromagnetic wavelets. However, it cannot be realized because of two drawbacks: (a) it requires the existence of magnetic charges, and (b) the charge-current distribution, which is concentrated on a spheroidal surface S{sub {alpha}}, is too singular for practical implementation. Both of these difficulties are resolved here. The first is resolved by using Hertz vectors to generate a charge-current distribution on S{sub {alpha}} due solely to bound electric charges. The second is resolved by replacing S{sub {alpha}} with a spheroidal shell of finite thickness. This generalizes the usual boundary conditions on an interface between electromagnetic media by allowing the transition to be gradual.
Vibration analysis of ring-stiffened cross-ply laminated cylindrical shells
Wang, Rong-Tyai; Lin, Zung-Xian
2006-08-01
This work presents the formulation of governing equations for a symmetric cross-ply laminated cylindrical shell with a circumferential stiffener. Two kinds of the circumferential stiffeners are considered: outer ring and inner ring. The effects of rotatory inertia and transverse shearing strain of both the cross-ply laminated shell and stiffener are considered. Further, the warping effect of stiffener also is included. An analytic method is presented to obtain the modal frequencies and their corresponding mode shape functions of the ring-stiffened laminated shell. The orthogonality of two distinct sets of mode shape functions is shown. The effects of inner ring and outer ring on modal frequencies of the ring-stiffened laminated shell are compared. Further, the effect of ply arrangement on modal frequencies of the ring-stiffened shell also is studied. The forced vibration of the ring-stiffened laminated shell due to a concentrated transient force is examined. The stress distributions in the plies of the ring-stiffened laminated shell due to the transient force are investigated.
Phifer-Rixey, M; Heckman, M; Trussell, G C; Schmidt, P S
2008-07-01
Clines can signal spatially varying selection and therefore have long been used to investigate the role of environmental heterogeneity in maintaining genetic variation. However, clinal patterns alone are not sufficient to reject neutrality or to establish the mechanism of selection. Indirect, inferential methods can be used to address neutrality and mechanism, but fully understanding the adaptive significance of clinal variation ultimately requires a direct approach. Ecological model systems such as the rocky intertidal provide a useful context for direct experimentation and can serve as a complement to studies in more traditional genetic model systems. In this study, we use indirect and direct approaches to investigate the role of environmental heterogeneity in the maintenance of shell colour polymorphism in the flat periwinkle snail, Littorina obtusata. We document replicated clines in shell colour morph frequencies over thermal gradients at two spatial scales, contrasting with patterns at previously reported microsatellite loci. In addition, experimental results demonstrate that that shell colour has predictable effects on shell temperature and that these differences in temperature, in turn, coincide with patterns of survivorship under episodic thermal stress. Direct manipulation of shell colour revealed that shell colour, and not a correlated character, was the target of selection. Our study provides evidence that spatially varying selection via thermal regime contributes to the maintenance of shell colour phenotype variation in L. obtusata in the sampled areas of the Gulf of Maine.
Rabenhorst, Greg A.
2011-01-01
The current study is designed to investigate the mediating effects of work-related stress on the relationship between mentoring functions (i.e., career support, psychosocial support, and role modeling) and measures of job attitude (i.e., job satisfaction and organizational commitment). Mentoring is widely used as a means of assisting in the new…
Boelen, Paul A.; Huntjens, Rafaele J. C.; van den Hout, Marcel A.
2014-01-01
Reduced memory specificity is associated with depression, post-traumatic stress disorder (PTSD), and some other forms of psychopathology. Reduced memory specificity is also associated with reduced specificity of envisioned future events. Research in this area has mostly relied on cue-word methods th
Rabenhorst, Greg A.
2011-01-01
The current study is designed to investigate the mediating effects of work-related stress on the relationship between mentoring functions (i.e., career support, psychosocial support, and role modeling) and measures of job attitude (i.e., job satisfaction and organizational commitment). Mentoring is widely used as a means of assisting in the new…
Nuclear Level Density: Shell Model vs Mean Field
Sen'kov, Roman
2015-01-01
The knowledge of the nuclear level density is necessary for understanding various reactions including those in the stellar environment. Usually the combinatorics of Fermi-gas plus pairing is used for finding the level density. Recently a practical algorithm avoiding diagonalization of huge matrices was developed for calculating the density of many-body nuclear energy levels with certain quantum numbers for a full shell-model Hamiltonian. The underlying physics is that of quantum chaos and intrinsic thermalization in a closed system of interacting particles. We briefly explain this algorithm and, when possible, demonstrate the agreement of the results with those derived from exact diagonalization. The resulting level density is much smoother than that coming from the conventional mean-field combinatorics. We study the role of various components of residual interactions in the process of thermalization, stressing the influence of incoherent collision-like processes. The shell-model results for the traditionally...
Pro Bash Programming Scripting the Linux Shell
Johnson, Chris FA
2010-01-01
The bash shell is a complete programming language, not merely a glue to combine external Linux commands. By taking full advantage of shell internals, shell programs can perform as snappily as utilities written in C or other compiled languages. And you will see how, without assuming Unix lore, you can write professional bash 4.0 programs through standard programming techniques. *Complete bash coverage*Teaches bash as a programming language*Helps you master bash 4.0 features What you'll learn*Use the shell to write new utilities and accomplish most programming tasks.*Use shell parameter expansio
Design aids for stiffened composite shells with cutouts
Sahoo, Sarmila
2017-01-01
This book focuses on the free vibrations of graphite-epoxy laminated composite stiffened shells with cutout both in terms of the natural frequencies and mode shapes. The dynamic analysis of shell structures, which may have complex geometry and arbitrary loading and boundary conditions, is solved efficiently by the finite element method, even including cutouts in shells. The results may be readily used by practicing engineers dealing with stiffened composite shells with cutouts. Several shell forms viz. cylindrical shell, hypar shell, conoidal shell, spherical shell, saddle shell, hyperbolic paraboloidal shell and elliptic paraboloidal shell are considered in the book. The dynamic characteristics of stiffened composite shells with cutout are described in terms of the natural frequency and mode shapes. The size of the cutouts and their positions with respect to the shell centre are varied for different edge constraints of cross-ply and angle-ply laminated composite shells. The effects of these parametric variat...
Shell Model Depiction of Isospin Mixing in sd Shell
Lam, Yi Hua; Smirnova, Nadya A. [CENBG (CNRS/IN2P3 - Universite Bordeaux 1) Chemin du Solarium, 33175 Gradignan (France); Caurier, Etienne [IPHC, IN2P3-CNRS et Universite Louis Pasteur, 67037 Strasbourg (France)
2011-11-30
We constructed a new empirical isospin-symmetry breaking (ISB) Hamiltonian in the sd(1s{sub 1/2}, 0d{sub 5/2} and 0d{sub 3/2}) shell-model space. In this contribution, we present its application to two important case studies: (i){beta}-delayed proton emission from {sup 22}Al and (ii) isospin-mixing correction to superallowed 0{sup +}{yields}0{sup +}{beta}-decay ft-values.
Analytic Solution to Shell Boundary – Value Problems
Yu. I. Vinogradov
2015-01-01
Full Text Available Object of research is to find analytical solution to the shell boundary – value problems, i.e. to consider the solution for a class of problems concerning the mechanics of hoop closed shells strain.The objective of work is to create an analytical method to define a stress – strain state of shells under non-axisymmetric loading. Thus, a main goal is to derive the formulas – solutions of the linear ordinary differential equations with variable continuous coefficients.The partial derivative differential equations of mechanics of shells strain by Fourier's method of variables division are reduced to the system of the differential equations with ordinary derivatives. The paper presents the obtained formulas to define solutions of the uniform differential equations and received on their basis formulas to define a particular solution depending on a type of the right parts of the differential equations.The analytical algorithm of the solution of a boundary task uses an approach to transfer the boundary conditions to the randomly chosen point of an interval of changing independent variable through the solution of the canonical matrix ordinary differential equation with the subsequent solution of system of algebraic equations for compatibility of boundary conditions at this point. Efficiency of algorithm is based on the fact that the solution of the ordinary differential equations is defined as the values of Cauchy – Krylova functions, which meet initial arbitrary conditions.The results of researches presented in work are useful to experts in the field of calculus mathematics, dealing with solution of systems of linear ordinary differential equations and creation of effective analytical computing methods to solve shell boundary – value problems.
CHEN Meixia; LUO Dongping; PENG Xu; LUO Bin
2004-01-01
The characteristics of vibration and sound radiation from a double shell with the outer shell coated with viscoelastic layer are systematically studied. The shell's motion funcby three-dimensional Navier equations, whose displacement solutions are expressed by Taylor expansion along the layer thickness. The continuity conditions of displacement and stress between the shell and the layers are used in obtaining the vibration equations. The effects of layer thickness, modulus of elasticity, the loss factor, and the hydro-compressibility on the structural acoustic characteristic are discussed in detail. It showed that the higher the modulus of elasticity is, or the thinner the thickness of layer is, or the smaller the loss factor is, the higher the sound radiation power is.
Pressure Shell Approach to Integrated Environmental Protection
Kennedy, Kriss J.
2011-01-01
The next generation of exploration mission human systems will require environmental protection such as radiation protection that is effective and efficient. In order to continue human exploration, habitat systems will require special shells to protect astronauts from hostile environments. The Pressure Shell Approach to integrated environmental (radiation) protection is a multi-layer shell that can be used for multifunctional environmental protection. Self-healing, self-repairing nano technologies and sensors are incorporated into the shell. This shell consists of multiple layers that can be tailored for specific environmental protection needs. Mainly, this innovation focuses on protecting crew from exposure to micrometeorites, thermal, solar flares, and galactic cosmic ray (GCR) radiation. The Pressure Shell Approach consists of a micrometeoroid and secondary ejecta protection layer; a thin, composite shell placed in between two layers that is non-structural; an open cavity layer that can be filled with water, regolith, or polyethylene foam; a thicker composite shell that is a structural load bearing that is placed between two layers; and a bladder coating on the interior composite shell. This multi-layer shell creates an effective radiation protection system. Most of its layers can be designed with the materials necessary for specific environments. In situ materials such as water or regolith can be added to the shell design for supplemental radiation protection.
Turbine blade with spar and shell
Davies, Daniel O [Palm City, FL; Peterson, Ross H [Loxahatchee, FL
2012-04-24
A turbine blade with a spar and shell construction in which the spar and the shell are both secured within two platform halves. The spar and the shell each include outward extending ledges on the bottom ends that fit within grooves formed on the inner sides of the platform halves to secure the spar and the shell against radial movement when the two platform halves are joined. The shell is also secured to the spar by hooks extending from the shell that slide into grooves formed on the outer surface of the spar. The hooks form a serpentine flow cooling passage between the shell and the spar. The spar includes cooling holes on the lower end in the leading edge region to discharge cooling air supplied through the platform root and into the leading edge cooling channel.
Indentation of Ellipsoidal and Cylindrical Elastic Shells
Vella, Dominic
2012-10-01
Thin shells are found in nature at scales ranging from viruses to hens\\' eggs; the stiffness of such shells is essential for their function. We present the results of numerical simulations and theoretical analyses for the indentation of ellipsoidal and cylindrical elastic shells, considering both pressurized and unpressurized shells. We provide a theoretical foundation for the experimental findings of Lazarus etal. [following paper, Phys. Rev. Lett. 109, 144301 (2012)PRLTAO0031-9007] and for previous work inferring the turgor pressure of bacteria from measurements of their indentation stiffness; we also identify a new regime at large indentation. We show that the indentation stiffness of convex shells is dominated by either the mean or Gaussian curvature of the shell depending on the pressurization and indentation depth. Our results reveal how geometry rules the rigidity of shells. © 2012 American Physical Society.
Chih Chiang Hong
2017-03-01
Full Text Available A model is presented for functionally-graded material (FGM, thick, circular cylindrical shells under an unsteady supersonic flow, following first-order shear deformation theory (FSDT with varied shear correction coefficients. Some interesting vibration results of the dynamics are calculated by using the generalized differential quadrature (GDQ method. The varied shear correction coefficients are usually functions of FGM total thickness, power law index, and environment temperature. Two parametric effects of the environmental temperature and FGM power law index on the thermal stress and center deflection are also presented. The novelty of the paper is that the maximum flutter value of the center deflection amplitude can be predicted and occurs at a high frequency of applied heat flux for a supersonic air flow.
Shell structure and orbit bifurcations in finite fermion systems
Magner, A. G., E-mail: magner@kinr.kiev.ua; Yatsyshyn, I. S. [National Academy of Sciences of Ukraine, Institute for Nuclear Research (Ukraine); Arita, K. [Nagoya Institute of Technology, Department of Physics (Japan); Brack, M. [University of Regensburg, Institute for Theoretical Physics (Germany)
2011-10-15
We first give an overview of the shell-correction method which was developed by V.M. Strutinsky as a practicable and efficient approximation to the general self-consistent theory of finite fermion systems suggested by A.B. Migdal and collaborators. Then we present in more detail a semiclassical theory of shell effects, also developed by Strutinsky following original ideas of M.C. Gutzwiller. We emphasize, in particular, the influence of orbit bifurcations on shell structure. We first give a short overview of semiclassical trace formulae, which connect the shell oscillations of a quantum system with a sum over periodic orbits of the corresponding classical system, in what is usually called the 'periodic orbit theory'. We then present a case study in which the gross features of a typical double-humped nuclear fission barrier, including the effects of mass asymmetry, can be obtained in terms of the shortest periodic orbits of a cavity model with realistic deformations relevant for nuclear fission. Next we investigate shell structures in a spheroidal cavity model which is integrable and allows for far-going analytical computation. We show, in particular, how period-doubling bifurcations are closely connected to the existence of the so-called 'superdeformed' energy minimum which corresponds to the fission isomer of actinide nuclei. Finally, we present a general class of radial power-law potentials which approximate well the shape of a Woods-Saxon potential in the bound region, give analytical trace formulae for it and discuss various limits (including the harmonic oscillator and the spherical box potentials).