WorldWideScience

Sample records for surface asperities indented

  1. Asperity interaction in adhesive contact of metallic rough surfaces

    International Nuclear Information System (INIS)

    Sahoo, Prasanta; Banerjee, Atanu

    2005-01-01

    The analysis of adhesive contact of metallic rough surfaces considering the effect of asperity interaction is the subject of this investigation. The micro-contact model of asperity interactions developed by Zhao and Chang (2001 Trans. ASME: J. Tribol. 123 857-64) is combined with the elastic plastic adhesive contact model developed by Chang et al (1988 Trans. ASME: J. Tribol. 110 50-6) to consider the asperity interaction and elastic-plastic deformation in the presence of surface forces simultaneously. The well-established elastic adhesion index and plasticity index are used to consider the different contact conditions. Results show that asperity interaction influences the load-separation behaviour in elastic-plastic adhesive contact of metallic rough surfaces significantly and, in general, adhesion is reduced due to asperity interactions

  2. Asperity Interaction and Substrate Deformation in Statistical Summation Models of Contact Between Rough Surfaces

    NARCIS (Netherlands)

    Vakis, Antonis I.

    A method is proposed to account for asperity interaction and bulk substrate deformation in models that utilize statistical summation of asperity forces to characterize contact between rough surfaces. Interaction deformations of noncontacting asperities are calculated based on the probability that

  3. Direct Observation of Asperity Deformation of Specimen with Random Rough Surface in Upsetting Process

    DEFF Research Database (Denmark)

    Azushima, A.; Kuba, S.; Tani, S.

    2004-01-01

    The trapping behavior of liquid lubricant and contact behavior of asperities at the workpiece-tool interface during upsetting and indentation are observed directly using a compression subpress which consists of a transparent die made of sapphire, a microscope with a CCD camera and a video system....

  4. Elastic layer under axisymmetric indentation and surface energy effects

    Science.gov (United States)

    Intarit, Pong-in; Senjuntichai, Teerapong; Rungamornrat, Jaroon

    2018-04-01

    In this paper, a continuum-based approach is adopted to investigate the contact problem of an elastic layer with finite thickness and rigid base subjected to axisymmetric indentation with the consideration of surface energy effects. A complete Gurtin-Murdoch surface elasticity is employed to consider the influence of surface stresses. The indentation problem of a rigid frictionless punch with arbitrary axisymmetric profiles is formulated by employing the displacement Green's functions, derived with the aid of Hankel integral transform technique. The problem is solved by assuming the contact pressure distribution in terms of a linear combination of admissible functions and undetermined coefficients. Those coefficients are then obtained by employing a collocation technique and an efficient numerical quadrature scheme. The accuracy of proposed solution technique is verified by comparing with existing solutions for rigid indentation on an elastic half-space. Selected numerical results for the indenters with flat-ended cylindrical and paraboloidal punch profiles are presented to portray the influence of surface energy effects on elastic fields of the finite layer. It is found that the presence of surface stresses renders the layer stiffer, and the size-dependent behavior of elastic fields is observed in the present solutions. In addition, the surface energy effects become more pronounced with smaller contact area; thus, the influence of surface energy cannot be ignored in the analysis of indentation problem especially when the indenter size is very small such as in the case of nanoindentation.

  5. Disturbance induced by surface preparation on instrumented indentation test

    International Nuclear Information System (INIS)

    Li, Yugang; Kanouté, Pascale; François, Manuel

    2015-01-01

    Surface preparation, which may induce considerable sample disturbance, plays an important role in instrumented indentation test (IIT). In this study, the sample disturbance (mainly divided into residual stresses and plastic strain) induced by the surface preparation process of instrumented indentation test specimens were investigated with both experimental tests and numerical simulations. Grazing incidence X-ray diffractions (GIXRD) and uniaxial tensile tests were conducted for characterizing the residual stresses and high plastic strain in the top surface layers of a carefully mechanically polished indentation sample, which, in the present work, is made of commercially pure titanium. Instrumented indentation tests and the corresponding finite element simulations were performed as well. For comparison, a reference sample (carefully mechanically polished & electrolytically polished) which represents the raw material was prepared and tested. Results showed that a careful mechanical polishing procedure can effectively reduce the level of residual stresses induced by this process. However, the high plastic strain in the surface region imposed by the polishing process is significant. The induced plastic strain can affect a depth up to 5 µm, which is deeper than the maximum penetration depth h max (3 µm) used for the instrumented indentation tests. In the near surface layer (in the range of depth about 350 nm), the plastic strain levels are fairly high. In the very top layer, the plastic strain was even estimated to reach more than 60%. The simultaneous use of indentation tests and numerical simulations showed that the existence of high plastic strain in the surface region will make the load vs depth (P–h) curve shift upwards, the contact hardness (H) increase and the contact stiffness (S) decrease

  6. Asperity interaction in elastic-plastic contact of rough surfaces in presence of adhesion

    International Nuclear Information System (INIS)

    Sahoo, Prasanta; Banerjee, Atanu

    2005-01-01

    This paper presents an analysis of the effect of asperity interaction in elastic-plastic contact of rough surfaces in the presence of adhesion. The micro-contact model of asperity interactions, developed by Zhao and Chang (2001 Trans. ASME: J. Tribol. 123 857-64), is integrated into the elastic-plastic contact model developed by Roy Chowdhury and Ghosh (1994 Wear 174 9-19) to allow the asperity interaction and elastic-plastic deformation in the presence of surface forces to be considered simultaneously. The well-established elastic and plastic adhesion indices are used to consider the different conditions that arise as a result of varying load and material parameters. Results show that asperity interaction influences the loading-unloading behaviour in elastic-plastic adhesive contact of rough surfaces and in general asperity interactions reduce the effect of surface forces

  7. Metallography of the indented aluminium sheet fracture surfaces

    International Nuclear Information System (INIS)

    Khan, M.A.; Qaiser, S.; Haq, A.U.; Atkins, A.G.

    1997-01-01

    It was experimentally observed that indentation of aluminium sheet samples with a sharp tool leads the off cut metal into a flare out-curvature, whose shape depends upon the geometry of the tool, applied force, displacement, material properties etc. The crack initiation, crack propagation and fracture surfaces were studied. Type grain, fibers, cut marks and voids were analyzed on optical and scanning electron microscopes to see how these were produced,. and their relationship to the material inherent properties, since this phenomenon has hot been studied so far. The sharp tool angles were responsible for the plastic flow. Plastic work per volume, fracture toughness and deformation area of the indented material. The metallographic information provided details of sheet metal deformation, and failure into the particular shapes represented on the fracture surfaces. (author)

  8. Elastic-plastic adhesive contact of rough surfaces using n-point asperity model

    International Nuclear Information System (INIS)

    Sahoo, Prasanta; Mitra, Anirban; Saha, Kashinath

    2009-01-01

    This study considers an analysis of the elastic-plastic contact of rough surfaces in the presence of adhesion using an n-point asperity model. The multiple-point asperity model, developed by Hariri et al (2006 Trans ASME: J. Tribol. 128 505-14) is integrated into the elastic-plastic adhesive contact model developed by Roy Chowdhury and Ghosh (1994 Wear 174 9-19). This n-point asperity model differs from the conventional Greenwood and Williamson model (1966 Proc. R. Soc. Lond. A 295 300-19) in considering the asperities not as fixed entities but as those that change through the contact process, and hence it represents the asperities in a more realistic manner. The newly defined adhesion index and plasticity index defined for the n-point asperity model are used to consider the different conditions that arise because of varying load, surface and material parameters. A comparison between the load-separation behaviour of the new model and the conventional one shows a significant difference between the two depending on combinations of mean separation, adhesion index and plasticity index.

  9. Adhesive friction for elastic-plastic contacting rough surfaces considering asperity interaction

    International Nuclear Information System (INIS)

    Sahoo, Prasanta

    2006-01-01

    The paper describes a theoretical study of adhesive friction at the contact between rough surfaces taking asperity interaction into consideration and using an elastic-plastic model of contact deformation that is based on an accurate finite element analysis of an elastic-plastic single asperity contact. The micro-contact model of asperity interactions, developed by Zhao and Chang, is integrated into the improved elastic-plastic rough surface adhesive contact analysis to consider the adhesive friction behaviour of rough surfaces. The model considers a large range of interference values from fully elastic through elastic-plastic to fully plastic regimes of contacting asperities. Two well-established adhesion indices are used to consider different conditions that arise as a result of varying load, surface and material parameters. Results are obtained for the coefficient of friction against applied load for various combinations of these parameters. The results show that the coefficient of friction depends strongly on the applied load for the no-interaction case while it becomes insensitive to the load for interaction consideration. Moreover, the inclusion of elastic-plastic asperities further reduces the friction coefficient

  10. Ra and the average effective strain of surface asperities deformed in metal-working processes

    DEFF Research Database (Denmark)

    Bay, Niels; Wanheim, Tarras; Petersen, A. S

    1975-01-01

    Based upon a slip-line analysis of the plastic deformation of surface asperities, a theory is developed determining the Ra-value (c.l.a.) and the average effective strain in the surface layer when deforming asperities in metal-working processes. The ratio between Ra and Ra0, the Ra-value after...... and before deformation, is a function of the nominal normal pressure and the initial slope γ0 of the surface asperities. The last parameter does not influence Ra significantly. The average effective strain View the MathML sourcege in the deformed surface layer is a function of the nominal normal pressure...... and γ0. View the MathML sourcege is highly dependent on γ0, View the MathML sourcege increasing with increasing γ0. It is shown that the Ra-value and the strain are hardly affected by the normal pressure until interacting deformation of the asperities begins, that is until the limit of Amonton's law...

  11. Influence of the Molecular Adhesion Force on the Indentation Depth of a Particle into the Wafer Surface in the CMP Process

    Directory of Open Access Journals (Sweden)

    Zhou Jianhua

    2014-01-01

    Full Text Available By theoretical calculation, the external force on the particle conveyed by pad asperities and the molecular adhesion force between particle and wafer are compared and analyzed quantitatively. It is confirmed that the molecular adhesion force between particle and wafer has a great influence on the chemical mechanical polishing (CMP material removal process. Considering the molecular adhesion force between particle and wafer, a more precise model for the indentation of a particle into the wafer surface is developed in this paper, and the new model is compared with the former model which neglected the molecular adhesion force. Through theoretical analyses, an approach and corresponding critical values are applied to estimate whether the molecular adhesion force in CMP can be neglected. These methods can improve the precision of the material removal model of CMP.

  12. Surface asperity evolution and microstructure analysis of Al 6061T5 alloy in a quasi-static cold uniaxial planar compression (CUPC)

    International Nuclear Information System (INIS)

    Li, Hejie; Jiang, Zhengyi; Wei, Dongbin; Gao, Xingjian; Xu, Jianzhong; Zhang, Xiaoming

    2015-01-01

    Highlights: • We used AFM and EBSD to analyses the surface asperity flattening process. • Analysis of the influence of deformation rate on the surface asperity flattening. • Investigation of the effect of lubrication on microstructure development. • Deformation rate influence the generation of orientation components obviously. - Abstract: In a quasi-static cold uniaxial planar compression, surface asperity evolution and microstructure analysis of Al 6061T5 alloy are carried out by employing Atomic Force Microscope (AFM) and Electron Backscattered Diffraction (EBSD) methods. Strain rate affects the surface asperity evolution obviously. While lubrication can hinder the surface asperity flattening by constraining the surface localized deformation. Lubrication can accelerate the crystallization in CUPC process. It also impedes the activation of some orientation components by hindering the activation of related slip systems in light metal Al alloy

  13. Surface asperity evolution and microstructure analysis of Al 6061T5 alloy in a quasi-static cold uniaxial planar compression (CUPC)

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hejie, E-mail: hejiel2003@gmail.com [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Jiang, Zhengyi, E-mail: jiang@uow.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Wei, Dongbin [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); School of Electrical, Mechanical and Mechatronic Systems, University of Technology, Sydney, NSW 2007 (Australia); Gao, Xingjian [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Xu, Jianzhong; Zhang, Xiaoming [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang, Liaoning 110004 (China)

    2015-08-30

    Highlights: • We used AFM and EBSD to analyses the surface asperity flattening process. • Analysis of the influence of deformation rate on the surface asperity flattening. • Investigation of the effect of lubrication on microstructure development. • Deformation rate influence the generation of orientation components obviously. - Abstract: In a quasi-static cold uniaxial planar compression, surface asperity evolution and microstructure analysis of Al 6061T5 alloy are carried out by employing Atomic Force Microscope (AFM) and Electron Backscattered Diffraction (EBSD) methods. Strain rate affects the surface asperity evolution obviously. While lubrication can hinder the surface asperity flattening by constraining the surface localized deformation. Lubrication can accelerate the crystallization in CUPC process. It also impedes the activation of some orientation components by hindering the activation of related slip systems in light metal Al alloy.

  14. Assessment of surface caking of powders using the ball indentation method.

    Science.gov (United States)

    Chen, Qinqin; Zafar, Umair; Ghadiri, Mojtaba; Bi, Jinfeng

    2017-04-15

    Powder caking is a ubiquitous problem, which could significantly decrease product quality and lead to economic losses. Hence it is important to know the conditions under which it occurs. The caking behaviour of three powder materials (PVP, HPC and CaHPO 4 ) has been investigated by the ball indentation method (BIM) as affected by relative humidity (RH), temperature and time. The resistance to powder flow, as indicated by the hardness is measured by a ball indenting the powder bed surface. The surface hardness increases with increasing RH and temperature, indicating caking of the powder bed. Moreover, the temperature and RH show a coupled effect on powder caking. Irreversible caking is formed in PVP and HPC at 75% RH; the particles coalesce and the volume of powder bed is significantly reduced with time. However, the caking of CaHPO 4 is reversible. To examine the caking mechanism of PVP and HPC, the critical glass transition RH is determined at 25°C and 45°C. The values are 63% and 53% RH for PVP and 61% and 50% RH for HPC, respectively. The glass transition moisture content in the ball indentation experiments is comparable with that determined by the dynamic vapor sorption measurement. BIM could be a fast and effective method for the assessment of powder surface caking. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Comparison of the aerodynamics of bridge cables with helical fillets and a pattern-indented surface

    DEFF Research Database (Denmark)

    Kleissl, K.; Georgakis, C.T.

    2012-01-01

    In this paper, the aerodynamics of bridge cables with helical fillets and a pattern-indented surface are examined. To this end, an extensive wind-tunnel test campaign was undertaken to measure the static force coefficients about the critical Reynolds number region, with varying relative cable...... cable was found to have a much slower flow transition for near normal flow and relatively large lift force components for the yawed positions. Flow visualizations confirmed the existence of specific flow structures which are often associated with the presence of lower drag or large lift forces...

  16. On the distinction between instrumented indentation technique and x-ray diffraction method in nondestructive or semi-nondestructive surface stress measurement

    International Nuclear Information System (INIS)

    Okano, Shigetaka; Kanamaru, Daisuke; Ihara, Ryohei; Mochizuki, Masahito

    2016-01-01

    In this study, the effect of machined surface layer on stress measurement by means of instrumented indentation technique and X-ray diffraction method was comparatively investigated through the use of three weld specimens of low-carbon austenitic stainless steel with different machined surface layers; as-cutout, mechanically-polished and electrolytically-polished specimens. Tensile and compressive stresses exist respectively in the machined surface layer of as-cutout and mechanically-polished specimens. Meanwhile, no stress and no machined surface layer exist in electrolytically-polished specimen. Tungsten Inert Gas (TIG) bead-on-plate welding was performed under the same welding heat input condition to introduce the residual stress into these three specimens. Against these three specimens, firstly the X-ray diffraction method was applied, then the instrumented indentation technique was applied and finally the stress relief technique was applied to measure the distributions of residual stress after welding. Based on a comparison between these stress measurement results, the instrumented indentation technique was in good agreement with the stress relief technique rather than the X-ray diffraction method, even though both machined surface layer and penetration of indenter had almost the same depths. That is why it can be considered that the instrumented indentation technique measures the residual stress in deeper areas of material surface than penetration depth of indenter. A distinction between the instrumented indentation technique and X-ray diffraction method in surface stress measurement was thus clarified from a viewpoint of measurement depth. (author)

  17. Application of reference point indentation for micro-mechanical surface characterization of calcium silicate based dental materials.

    Science.gov (United States)

    Antonijević, Djordje; Milovanović, Petar; Riedel, Christoph; Hahn, Michael; Amling, Michael; Busse, Björn; Djurić, Marija

    2016-04-01

    The objective of this study was to elucidate micromechanical properties of Biodentine and two experimental calcium silicate cements (CSCs) using Reference Point Indentation (RPI). Biomechanical characteristics of the cement type and the effects of a radiopacifier, liquid components, acid etching treatment and bioactivation in simulated body fluid (SBF) were investigated by measuring the microhardness, average unloading slope (Avg US) and indentation distance increase (IDI). Biodentine had a greater microhardness than the experimental CSCs, while the Avg US and IDI values were not significantly different among investigated materials. There was a statistically significant difference in microhardness and IDI values between pure CSCs and radiopacified cements (p calcium chloride and CSCs' immersion in SBF are beneficial for CSCs' micromechanical performance, while the addition of radiopacifiers and acid etching treatment weaken the CSCs' surface. Application of RPI aids with the characterization of micromechanical properties of synthetic materials' surfaces.

  18. Drag penalty due to the asperities in the substrate of super-hydrophobic and liquid infused surfaces

    Science.gov (United States)

    Garcia Cartagena, Edgardo J.; Arenas, Isnardo; Leonardi, Stefano

    2017-11-01

    Direct numerical simulations of two superposed fluids in a turbulent channel with a textured surface made of pinnacles of random height have been performed. The viscosity ratio between the two fluids are N =μo /μi = 50 (μo and μi are the viscosities of outer and inner fluid respectively) mimicking a super-hydrophobic surface (water over air) and N=2.5 (water over heptane) resembling a liquid infused surface. Two set of simulations have been performed varying the Reynolds number, Reτ = 180 and Reτ = 390 . The interface between the two fluids is flat simulating infinite surface tension. The position of the interface between the two fluids has been varied in the vertical direction from the base of the substrate (what would be a rough wall) to the highest point of the roughness. Drag reduction is very sensitive to the position of the interface between the two fluids. Asperities above the interface induce a large form drag and diminish considerably the drag reduction. When the mean height of the surface measured from the interface in the outer fluid is greater than one wall unit, k+ > 1 , the drag increases with respect to a smooth wall. Present results provide a guideline to the accuracy required in manufacturing super-hydrophobic and liquid infused surfaces. This work was supported under ONR MURI Grants N00014-12-0875 and N00014-12- 1-0962, Program Manager Dr. Ki-Han Kim. Numerical simulations were performed on the Texas Advanced Computer Center.

  19. Optimization of the Conditions for Extraction of Serine Protease from Kesinai Plant (Streblus asper Leaves Using Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Md. Zaidul Islam Sarker

    2011-11-01

    Full Text Available Response surface methodology (RSM using a central composite design (CCD was employed to optimize the conditions for extraction of serine protease from kesinai (Streblus asper leaves. The effect of independent variables, namely temperature (42.5,47.5, X1, mixing time (2–6 min, X2, buffer content (0–80 mL, X3 and buffer pH (4.5–10.5, X4 on specific activity, storage stability, temperature and oxidizing agent stability of serine protease from kesinai leaves was investigated. The study demonstrated that use of the optimum temperature, mixing time, buffer content and buffer pH conditions protected serine protease during extraction, as demonstrated by low activity loss. It was found that the interaction effect of mixing time and buffer content improved the serine protease stability, and the buffer pH had the most significant effect on the specific activity of the enzyme. The most desirable conditions of 2.5 °C temperature, 4 min mixing time, 40 mL buffer at pH 7.5 was established for serine protease extraction from kesinai leaves.

  20. Residual stresses around Vickers indents

    International Nuclear Information System (INIS)

    Pajares, A.; Guiberteau, F.; Steinbrech, R.W.

    1995-01-01

    The residual stresses generated by Vickers indentation in brittle materials and their changes due to annealing and surface removal were studied in 4 mol% yttria partially stabilized zirconia (4Y-PSZ). Three experimental methods to gain information about the residual stress field were applied: (i) crack profile measurements based on serial sectioning, (ii) controlled crack propagation in post indentation bending tests and (iii) double indentation tests with smaller secondary indents located around a larger primary impression. Three zones of different residual stress behavior are deduced from the experiments. Beneath the impression a crack free spherical zone of high hydrostatic stresses exists. This core zone is followed by a transition regime where indentation cracks develop but still experience hydrostatic stresses. Finally, in an outward third zone, the crack contour is entirely governed by the tensile residual stress intensity (elastically deformed region). Annealing and surface removal reduce this crack driving stress intensity. The specific changes of the residual stresses due to the post indentation treatments are described and discussed in detail for the three zones

  1. Kanto Asperity Project -Background and Outline-

    Science.gov (United States)

    Kobayashi, R.; Yamamoto, Y.; Sato, T.; Shishikura, M.; Curewitz, D.

    2009-12-01

    The Kanto region (Tokyo and the surrounding area) is one of the most densely populated urban areas in the world and has been devastated by repeated great earthquakes. This region is located at an island arc-island arc collision zone and a zone where Pacific and Philippine Sea plates are subducting. Great earthquakes along the Sagami trough, where the Philippine Sea slab is subducting, have repeatedly occurred. The 1703 Genroku and 1923 (Taisho) Kanto earthquakes caused severe damages in the metropolitan area. The recurrence periods of Taisho- and Genroku-type earthquakes are about 200-400 and 2000 years, respectively (e.g., Earthquake Research Committee, 2004). Many studies on the asperities along the Sagami trough have been carried out. Two asperities of the 1923 Kanto earthquake are located around the western part of Kanagawa prefecture (the base of the Izu peninsula) and around the Miura peninsula. An additional asperity of the 1703 Genroku earthquake is located the southern part of the Boso Peninsula. Slow slip events have also repeatedly occurred in an area adjacent to the asperities of the great earthquakes, off Boso peninsula (e.g., Ozawa et al 2007). In the cases of Nankai and Cascadia, slow slip events occur at deeper levels than the asperities, in a transition zone between the asperity and a region of steady slip. In contrast, slow slip events in the Kanto region have occurred at relatively shallow depths, at the same level as the asperity, raising the possibiltiy of friction controlled by different conditions (materials, fluid, or surface roughness) to those (temperature and pressure) encountered at Nankai and Cascadia. Deep seismic profiling have been carried out since the Special Project for Earthquake Disaster Mitigation in Urban areas (DaiDaiToku) (2002-2006). These profiling successfully presented a new image of the upper surface of the Philippine Sea slab (Sato et al. 2005), which is shallower than the previous models. This profiling also presents

  2. Mechanical characterization and single asperity scratch behaviour of dry zinc and manganese phosphate coatings

    NARCIS (Netherlands)

    Ernens, D.; de Rooij, M. B.; Pasaribu, H. R.; van Riet, E.J.; van Haaften, W.M.; Schipper, D. J.

    The goal of this study is to characterise the mechanical properties of zinc and manganese phosphate coatings before and after running in. The characterization is done with nano-indentation to determine the individual crystal hardness and single asperity scratch tests to investigate the deformation

  3. Rock Joint Asperities and Mechanical Strength of Concrete

    Science.gov (United States)

    Ficker, Tomáš; Komárková, Tereza

    2017-10-01

    Mechanical interactions between concrete foundations of large civil engineering structures (tunnels, bridges or dams) and the asperity surfaces of rock masses represent a useful topic for investigation. It is obvious that such large objects exert huge pressures on bedrocks and this might result in surprising variations of mechanical properties of the materials used in foundations. The present contribution evaluates possible changes of the compressive strength of concrete caused by the invasive acting of asperity-like needles penetrating into the volume of this material. The experimental arrangement simulates mechanical interactions between sharp asperities of bedrocks and the cement-based materials placed in the foundations of large civil engineering structures.

  4. Effect of 3D fractal dimension on contact area and asperity interactions in elastoplastic contact

    Directory of Open Access Journals (Sweden)

    Abdeljalil Jourani

    2016-05-01

    Full Text Available Few models are devoted to investigate the effect of 3D fractal dimension Ds on contact area and asperity interactions. These models used statistical approaches or two-dimensional deterministic simulations without considering the asperity interactions and elastic–plastic transition regime. In this study, a complete 3D deterministic model is adopted to simulate the contact between fractal surfaces which are generated using a modified two-variable Weierstrass–Mandelbrot function. This model incorporates the asperity interactions and considers the different deformation modes of surface asperities which range from entirely elastic through elastic-plastic to entirely plastic contact. The simulations reveal that the elastoplastic model is more appropriate to calculate the contact area ratio and pressure field. It is also shown that the influence of the asperity interactions cannot be neglected, especially at lower fractal dimension Ds and higher load.

  5. Analysis of indentation creep

    Science.gov (United States)

    Don S. Stone; Joseph E. Jakes; Jonathan Puthoff; Abdelmageed A. Elmustafa

    2010-01-01

    Finite element analysis is used to simulate cone indentation creep in materials across a wide range of hardness, strain rate sensitivity, and work-hardening exponent. Modeling reveals that the commonly held assumption of the hardness strain rate sensitivity (mΗ) equaling the flow stress strain rate sensitivity (mσ...

  6. Transient effects in friction fractal asperity creep

    CERN Document Server

    Goedecke, Andreas

    2013-01-01

    Transient friction effects determine the behavior of a wide class of mechatronic systems. Classic examples are squealing brakes, stiction in robotic arms, or stick-slip in linear drives. To properly design and understand mechatronic systems of this type, good quantitative models of transient friction effects are of primary interest. The theory developed in this book approaches this problem bottom-up, by deriving the behavior of macroscopic friction surfaces from the microscopic surface physics. The model is based on two assumptions: First, rough surfaces are inherently fractal, exhibiting roughness on a wide range of scales. Second, transient friction effects are caused by creep enlargement of the real area of contact between two bodies. This work demonstrates the results of extensive Finite Element analyses of the creep behavior of surface asperities, and proposes a generalized multi-scale area iteration for calculating the time-dependent real contact between two bodies. The toolset is then demonstrated both...

  7. Crystal plasticity study of single crystal tungsten by indentation tests

    International Nuclear Information System (INIS)

    Yao, Weizhi

    2012-01-01

    Owing to its favorable material properties, tungsten (W) has been studied as a plasma-facing material in fusion reactors. Experiments on W heating in plasma sources and electron beam facilities have shown an intense micro-crack formation at the heated surface and sub-surface. The cracks go deep inside the irradiated sample, and often large distorted areas caused by local plastic deformation are present around the cracks. To interpret the crack-induced microscopic damage evolution process in W, one needs firstly to understand its plasticity on a single grain level, which is referred to as crystal plasticity. In this thesis, the crystal plasticity of single crystal tungsten (SCW) has been studied by spherical and Berkovich indentation tests and the finite element method with a crystal plasticity model. Appropriate values of the material parameters included in the crystal plasticity model are determined by fitting measured load-displacement curves and pile-up profiles with simulated counterparts for spherical indentation. The numerical simulations reveal excellent agreement with experiment. While the load-displacement curves and the deduced indentation hardness exhibit little sensitivity to the indented plane at small indentation depths, the orientation of slip directions within the crystals governs the development of deformation hillocks at the surface. It is found that several factors like friction, indentation depth, active slip systems, misoriented crystal orientation, misoriented sample surface and azimuthal orientation of the indenter can affect the indentation behavior of SCW. The Berkovich indentation test was also used to study the crystal plasticity of SCW after deuterium irradiation. The critical load (pop-in load) for triggering plastic deformation under the indenter is found to depend on the crystallographic orientation. The pop-in loads decrease dramatically after deuterium plasma irradiation for all three investigated crystallographic planes.

  8. Cable indenter aging monitor

    International Nuclear Information System (INIS)

    Shook, T.A.; Gardner, J.B.

    1988-07-01

    This project was undertaken to develop a hand-held, nondestructive test device to assess the aged condition of electrical cable by in situ measurement of mechanical properties of polymeric jackets and insulations. The device is an indenter similar to those used to make hardness measurements. Comparison of measurements made on installed cables with previous measurements serving as baseline aging/mechanical property data will determine the state of aging of the field cables. Such a device will be valuable in nuclear and fossil plant life extension programs. Preliminary laboratory tests on cables covered with ethylene propylene rubber (EPR) and chlorosulfated polyethylene (CSPE) point to the measurement of the rate of force increase resulting from constant rate deformation as having the best correlation with progressive thermal aging. This first phase of the work has demonstrated the technical feasibility of the method. A second phase will include the generation of additional groundwork data and the design of the portable indenter for in situ plant measurements

  9. Blunt indentation of core graphite

    International Nuclear Information System (INIS)

    Hartley, M.; McEnaney, B.

    1996-01-01

    Blunt indentation experiments were carried out on unoxidized and thermally oxidised IM1-24 graphite as a model to simulate local point stresses acting on graphite moderator bricks. Blunt indentation of unoxidized graphite initiates cracks close to the region of maximum tensile stress at the edge of the indentation. Cracks propagate and converge to form a cone of material. Failure is catastrophic, typically forming three pieces of graphite and ejecting the cone referred to above. The failure mode under indentation loading for highly oxidised graphite (weigh loss > 40%) is different from that for the unoxidized graphite. There is no longer a distinct crack path, the indentation is much deeper than in the case of the unoxidized graphite, and there is a region of crushed debris beneath the indentation, producing a crater-like structure. The reduction in the compressive fracture stress, σ cf , under indentation loading with increasing fractional weight loss on oxidation, x, can be fitted to σ cf /σ 0 = exp-[5.2x] where σ 0 is the compressive fracture stress of the unoxidized graphite. This indicates that the effect of thermal oxidation on indentation fracture stress is more severe than the effects of radiolytic oxidation on conventional strengths of nuclear graphites. (author). 8 refs, 12 figs

  10. Single asperity abrasion of coated nodular cast iron

    NARCIS (Netherlands)

    Masen, Marc Arthur; de Rooij, Matthias B.; Schipper, Dirk J.; Adachi, K.; Kato, K.

    2007-01-01

    In the sliding contact between a rigid indenter and a softer deforming surface, a wear scar is formed in the softer surface. This wear scar consists of a groove flanked by two shoulders, where part of the material from the groove is transferred to these shoulders and the rest is actually removed

  11. Characteristics of Asperity Damage and Its Influence on the Shear Behavior of Granite Joints

    Science.gov (United States)

    Meng, Fanzhen; Zhou, Hui; Wang, Zaiquan; Zhang, Chuanqing; Li, Shaojun; Zhang, Liming; Kong, Liang

    2018-02-01

    Surface roughness significantly affects the shear behavior of rock joints; thus, studies on the asperity damage characteristics and its influence on the shear behavior of joints are extremely important. In this paper, shear tests were conducted on tensile granite joints; asperity damage was evaluated based on acoustic emission (AE) events; and the influence of asperity damage on joint shear behavior was analyzed. The results indicated that the total AE events tended to increase with normal stress. In addition, the asperity damage initiation shear stress, which is defined as the transition point from slow growth to rapid growth in the cumulative events curve, was approximately 0.485 of the peak shear strength regardless of the normal stress. Moreover, 63-85% of the AE events were generated after the peak shear stress, indicating that most of the damage occurred in this stage. Both the dilation and the total AE events decreased with shear cycles because of the damage inflicted on asperities during the previous shear cycle. Two stages were observed in the normal displacement curves under low normal stress, whereas three stages (compression, dilation and compression again) were observed at a higher normal stress; the second compression stage may be caused by tensile failure outside the shear plane. The magnitude of the normal stress and the state of asperity are two important factors controlling the post-peak stress drop and stick-slip of granite joints. Serious deterioration of asperities will stop stick-slip from recurring under the same normal stress because the ability to accumulate energy is decreased. The AE b-value increases with the number of shear cycles, indicating that the stress concentration inside the fault plane is reduced because of asperity damage; thus, the potential for dynamic disasters, such as fault-slip rockbursts, will be decreased.

  12. Inflammation induced by Bothrops asper venom.

    Science.gov (United States)

    Teixeira, Catarina; Cury, Yara; Moreira, Vanessa; Picolo, Gisele; Chaves, Fernando

    2009-07-01

    Inflammation is a major characteristic of envenomation by snakes from viperine and crotaline species. Bothrops asper snake venom elicits, among other alterations, a pronounced inflammatory response at the site of injection both in humans and experimental animals. This review describes the current status of our understanding of the inflammatory reaction, including pain, triggered by Bothrops asper venom. The experimental studies on the action of this venom as well as the complex network of chemical mediators involved are summarized. Moreover, aspects of the molecular mechanisms orchestrating this important response to envenomation by Bothrops asper are presented. Considering that isolated toxins are relevant tools for understanding the actions of the whole venom, studies dealing with the mechanisms of inflammatory and nociceptive properties of phospholipases A(2), a metalloproteinase and serine-proteases isolated from Bothrops asper venom are also described.

  13. Micromechanics of pseudo-single-asperity friction: Effects of nanometer-scale roughness

    Science.gov (United States)

    Li, Qunyang

    Nanometer-scale roughness on a solid surface has significant effects on friction, since inter-surface forces operate predominantly within a nanometer-scale gap distance in frictional contact. This thesis presents two novel atomic force microscope friction experiments, each using a gold surface sliding against a flat mica surface as the representative friction system. A diamagnetic lateral force calibrator (D-LFC) was invented to enable the accurate quantitative force measurements. In one of the experiment, a disk-shaped single nano-asperity of gold was used to measure the molecular level frictional behavior. The adhesive friction stress was measured to be 264 MPa and the molecular friction factor 0.0108 for a direct gold-mica contact in 30% humid air. The capillary force from the condensed water meniscuses was found to play an important role in magnifying the contact pressure to plastically deform the nano-asperities leading to the dramatic evolution of frictional responses. In the second experiment, the frictional response of a micrometer-scale asperity with nanometer-scale roughness exhibited a pseudo-single-asperity frictional behavior. However, the apparent friction stress, 40.5 MPa, fell well below the Hurtado-Kim model prediction for a smooth-single-asperity friction, exhibiting an apparent size-scale dependence of the friction stress. An interfacial roughness (IR) layer model was then developed to investigate the effects of roughness on pseudo-single-asperity friction. The model calculation shows that the nanometer-scale surface roughness is the major mechanism that explains the apparent size-scale dependence of the friction observed in the experiments. Furthermore, the analysis shows that the apparent friction stress as well as the apparent pressure-dependent fiction factor relies on the surface roughness. Both experimental and theoretical results suggest that the evolution status of surface roughness is one of the important internal variables for the

  14. [Chemical constituents of Dipsacus asper].

    Science.gov (United States)

    Wang, Qiang; Liu, Er-Wei; Han, Li-Feng; Zhang, Yi

    2013-07-01

    To study the chemical constituents of Dipsacus asper, chromatographic methods such as D101 macroporous resin, silica gel, octadecylsilyl (ODS) column chromatographic techniques and preparative HPLC were used, and five compounds were isolated from 70% (v/v) ethanol extract of the plant. By using spectroscopic techniques including 1H NMR, 13C NMR, 1H-1H COSY, HSQC, HMBC and TOF-MS, the compounds were identified as 3beta-hydroxy-24-nor-urs-4 (23), 12-dien-28-oic acid (1), ursolic acid (2), oleanolic acid (3), 3-O-alpha-L-rhamnosyl(1 --> 3)-beta-D-glucopyranosyl (1 --> 3)-alpha-L-rhamnosyl (1 --> 2)-alpha-L-arabinopyranosyl hederagenin 28-O-beta-D-glucopyranosyl (1 --> 6)-beta-D-glucopyranosyl ester (4), 3-O-[beta-D-xylopyranosyl (1 --> 4)-beta-D-glucopyranosyl (1 --> 4)] [alpha-L-rhamnosyl(1 --> 3)]-beta-D-glucopyranosyl (1 --> 3)-alpha-L-rhamnosyl(1 --> 2)-alpha-L-arabinopyranosyl hederagenin (5), separately. Among them, 1 is a new compound, and 2 is isolated from this plant for the first time.

  15. Numerical Modeling Describing the Effects of Heterogeneous Distributions of Asperities on the Quasi-static Evolution of Frictional Slip

    Science.gov (United States)

    Selvadurai, P. A.; Parker, J. M.; Glaser, S. D.

    2017-12-01

    A better understanding of how slip accumulates along faults and its relation to the breakdown of shear stress is beneficial to many engineering disciplines, such as, hydraulic fracture and understanding induced seismicity (among others). Asperities forming along a preexisting fault resist the relative motion of the two sides of the interface and occur due to the interaction of the surface topographies. Here, we employ a finite element model to simulate circular partial slip asperities along a nominally flat frictional interface. Shear behavior of our partial slip asperity model closely matched the theory described by Cattaneo. The asperity model was employed to simulate a small section of an experimental fault formed between two bodies of polymethyl methacrylate, which consisted of multiple asperities whose location and sizes were directly measured using a pressure sensitive film. The quasi-static shear behavior of the interface was modeled for cyclical loading conditions, and the frictional dissipation (hysteresis) was normal stress dependent. We further our understanding by synthetically modeling lognormal size distributions of asperities that were randomly distributed in space. Synthetic distributions conserved the real contact area and aspects of the size distributions from the experimental case, allowing us to compare the constitutive behaviors based solely on spacing effects. Traction-slip behavior of the experimental interface appears to be considerably affected by spatial clustering of asperities that was not present in the randomly spaced, synthetic asperity distributions. Estimates of bulk interfacial shear stiffness were determined from the constitutive traction-slip behavior and were comparable to the theoretical estimates of multi-contact interfaces with non-interacting asperities.

  16. A method to separate and quantify the effects of indentation size, residual stress and plastic damage when mapping properties using instrumented indentation

    International Nuclear Information System (INIS)

    Hou, X D; Jennett, N M

    2017-01-01

    Instrumented indentation is a convenient and increasingly rapid method of high resolution mapping of surface properties. There is, however, significant untapped potential for the quantification of these properties, which is only possible by solving a number of serious issues that affect the absolute values for mechanical properties obtained from small indentations. The three most pressing currently are the quantification of: the indentation size effect (ISE), residual stress, and pile-up and sink-in—which is itself affected by residual stress and ISE. Hardness based indentation mapping is unable to distinguish these effects. We describe a procedure that uses an elastic modulus as an internal reference and combines the information available from an indentation modulus map, a hardness map, and a determination of the ISE coefficient (using self-similar geometry indentation) to correct for the effects of stress, pile up and the indentation size effect, to leave a quantified map of plastic damage and grain refinement hardening in a surface. This procedure is used to map the residual stress in a cross-section of the machined surface of a previously stress free metal. The effect of surface grinding is compared to milling and is shown to cause different amounts of work hardening, increase in residual stress, and surface grain size reduction. The potential use of this procedure for mapping coatings in cross-section is discussed. (paper)

  17. A method to separate and quantify the effects of indentation size, residual stress and plastic damage when mapping properties using instrumented indentation

    Science.gov (United States)

    Hou, X. D.; Jennett, N. M.

    2017-11-01

    Instrumented indentation is a convenient and increasingly rapid method of high resolution mapping of surface properties. There is, however, significant untapped potential for the quantification of these properties, which is only possible by solving a number of serious issues that affect the absolute values for mechanical properties obtained from small indentations. The three most pressing currently are the quantification of: the indentation size effect (ISE), residual stress, and pile-up and sink-in—which is itself affected by residual stress and ISE. Hardness based indentation mapping is unable to distinguish these effects. We describe a procedure that uses an elastic modulus as an internal reference and combines the information available from an indentation modulus map, a hardness map, and a determination of the ISE coefficient (using self-similar geometry indentation) to correct for the effects of stress, pile up and the indentation size effect, to leave a quantified map of plastic damage and grain refinement hardening in a surface. This procedure is used to map the residual stress in a cross-section of the machined surface of a previously stress free metal. The effect of surface grinding is compared to milling and is shown to cause different amounts of work hardening, increase in residual stress, and surface grain size reduction. The potential use of this procedure for mapping coatings in cross-section is discussed.

  18. Indentation Depth Dependent Mechanical Behavior in Polymers

    OpenAIRE

    Alisafaei, Farid; Han, Chung-Souk

    2015-01-01

    Various experimental studies have revealed size dependent deformation of materials at micro and submicron length scales. Among different experimental methods, nanoindentation testing is arguably the most commonly applied method of studying size effect in various materials where increases in the hardness with decreasing indentation depth are usually related to indentation size effects. Such indentation size effects have been observed in both metals and polymers. While the indentation size effe...

  19. Reference point indentation is not indicative of whole mouse bone measures of stress intensity fracture toughness.

    Science.gov (United States)

    Carriero, Alessandra; Bruse, Jan L; Oldknow, Karla J; Millán, José Luis; Farquharson, Colin; Shefelbine, Sandra J

    2014-12-01

    Bone fragility is a concern for aged and diseased bone. Measuring bone toughness and understanding fracture properties of the bone are critical for predicting fracture risk associated with age and disease and for preclinical testing of therapies. A reference point indentation technique (BioDent) has recently been developed to determine bone's resistance to fracture in a minimally invasive way by measuring the indentation distance increase (IDI) between the first and last indentations over cyclic indentations in the same position. In this study, we investigate the relationship between fracture toughness KC and reference point indentation parameters (i.e. IDI, total indentation distance (TID) and creep indentation distance (CID)) in bones from 38 mice from six types (C57Bl/6, Balb, oim/oim, oim/+, Phospho1(-/-) and Phospho1 wild type counterpart). These mice bone are models of healthy and diseased bone spanning a range of fracture toughness from very brittle (oim/oim) to ductile (Phospho1(-/-)). Left femora were dissected, notched and tested in 3-point bending until complete failure. Contralateral femora were dissected and indented in 10 sites of their anterior and posterior shaft surface over 10 indentation cycles. IDI, TID and CID were measured. Results from this study suggest that reference point indentation parameters are not indicative of stress intensity fracture toughness in mouse bone. In particular, the IDI values at the anterior mid-diaphysis across mouse types overlapped, making it difficult to discern differences between mouse types, despite having extreme differences in stress intensity based toughness measures. When more locations of indentation were considered, the normalised IDIs could distinguish between mouse types. Future studies should investigate the relationship of the reference point indentation parameters for mouse bone in other material properties of the bone tissue in order to determine their use for measuring bone quality. Copyright © 2014

  20. Diffusive versus Displacive Contact Plasticity of Nanoscale Asperities: Temperature- and Velocity-Dependent Strongest Size.

    Science.gov (United States)

    Guo, Wei; Wang, Zhao; Li, Ju

    2015-10-14

    We predict a strongest size for the contact strength when asperity radii of curvature decrease below 10 nm. The reason for such strongest size is found to be correlated with the competition between the dislocation plasticity and surface diffusional plasticity. The essential role of temperature is calculated and illustrated in a comprehensive asperity size-strength-temperature map taking into account the effect of contact velocity. Such a map should be essential for various phenomena related to nanoscale contacts such as nanowire cold welding, self-assembly of nanoparticles and adhesive nanopillar arrays, as well as the electrical, thermal, and mechanical properties of macroscopic interfaces.

  1. [Study on identification of wild Dipsacus asper and cultivated Dipsacus asper at different growth years by organization structure].

    Science.gov (United States)

    Yang, Jun; Peng, Hua-Sheng; Xuan, Yan; Qu, Jie

    2012-12-01

    To study the regular pattern of growing development and the structural changes of the main root of Dipsacus asper; Find the basis for distinguishing between wild and cultivated Dipsacus asper as well as identifying cultivated Dipsacus asper at different growth years. Continuous sectional sampling and histological observation was conducted on the main roots of annual and biennial cultivated Dipsacus asper and on the main roots of bolting and non-bolting plants of wild Dipsacus asper; Histological observation was carried out respectively on the main roots of one to four-year-old cultivated Dipsacus asper. It was discovered for the first time that there was structure of growth rings in the main roots of Dipsacus asper. And the ways in which the vessels of the growth rings were arranged differed between wild and cultivated Dipsacus asper, the vessels of growth rings in wild Dipsacus asper were arranged tangentially while those in cultivated Dipsacus asper were arranged as clusters. Pith existed in the upper part of roots of wild Dipsacus asper,while it was not found in the cultivated ones, and this could be adopted as a preliminary method to distinguish the wild Dipsacus asper from cultivatedone. The structures of growth rings in each main root were in consistency from top to bottom, and the thickening of roots mainly depended on the growth of xylem in the first year. There were particular relations and regular patterns between the structure of main roots of one to four-year-old cultivated Dipsacus asper and the ages of their growth, which could serve as the primary basis for identifying their growth years. Methods to distinguish wild Dipsacus asper from cultivated ones at different ages by organization structure are established, which could provide the basis for identification of the medicinal material of Dipsacus asper.

  2. Asperity Degradation and Damage in the Direct Shear Test: A Hybrid FEM/DEM Approach

    Science.gov (United States)

    Karami, A.; Stead, D.

    2008-04-01

    This paper investigates the processes of joint surface damage and near-surface intact rock tensile failure using a hybrid FEM/DEM code. Selected Barton and Choubey JRC profiles were simulated in direct shear tests and the surface damage mechanisms investigated in terms of joint surface wear or tensile fracturing of intact rock along the joint plane. Shear strength and displacement profiles for each joint profile are numerically simulated. Numerical results agree closely with published experimental observations. Furthermore, results show that dilation along the joint is controlled dominantly by the joint surface geometry and the applied normal stress. Significant dilation is expected to occur where there is a large asperity provided the applied normal stress is low. In this case, joint surface damage is limited to surface wear. In contrast, when the applied normal stress is high, dilation will be low and damage is composed of both surface wear and asperity breakage through near-joint-surface intact rock tensile failure. Local joint dilation angles vary in proportion to the magnitude of the dilation. Several joint profiles with different geometrical configurations were simulated within a slope and the possible modes of joint surface damage were investigated. It was found that due to low normal stresses acting on the joint surfaces within a slope the dominant mode of joint surface damage is by yielding and surface wear of asperities.

  3. Application of Indenting Method for Calculation of Activation Energy

    International Nuclear Information System (INIS)

    Kim, Jong-Seog; Kim, Tae-Ryong

    2006-01-01

    For the calculation of activation energy of cable materials, we used to apply the break-elongation test in accordance with ASTM D412(Stand Test Methods for Rubber Properties in Tension). For the cable jacket and insulation which have regular thickness, break-elongation test had been preferred since it showed linear character in the activation energy curve. But, for the cable which has irregular thickness or rugged surface of cable inside, break-elongation test show scattered data which can not be used for the calculation of activation energy. It is not easy to prepare break-elongation specimen for the cable smaller than 13mm diameter in accordance with ASTM D412. In the cases of above, we sometime use TGA method which heat the specimen from 50 .deg. C to 700 .deg. C at heating rates of 10, 15, 20 .deg. C/min. But, TGA is suspected for the representative of natural aging in the plant since it measure the weight decreasing rate during burning which may have different aging mechanism with that of natural aging. To solve above problems, we investigated alternatives such as indenter test. Indenter test is very convenient since it does not ask for a special test specimen as the break-elongation test does. Regular surface of cable outside is the only requirement of indenter test. Experience of activation energy calculation by using the indenter test is described herein

  4. Competing indentation deformation mechanisms in glass using different strengthening methods

    Directory of Open Access Journals (Sweden)

    Jian Luo

    2016-11-01

    Full Text Available Chemical strengthening via ion exchange, thermal tempering, and lamination are proven techniques for strengthening of oxide glasses. For each of these techniques, the strengthening mechanism is conventionally ascribed to the linear superposition of the compressive stress profile on the glass surface. However, in this work we use molecular dynamics simulations to reveal the underlying indentation deformation mechanism beyond the simple linear superposition of compressive and indentation stresses. In particular, the plastic zone can be dramatically different from the commonly assumed hemispherical shape, which leads to a completely different stress field and resulting crack system. We show that the indentation-induced fracture is controlled by two competing mechanisms: the compressive stress itself and a potential reduction in free volume that can increase the driving force for crack formation. Chemical strengthening via ion exchange tends to escalate the competition between these two effects, while thermal tempering tends to reduce it. Lamination of glasses with differential thermal expansion falls in between. The crack system also depends on the indenter geometry and the loading stage, i.e., loading vs. after unloading. It is observed that combining thermal tempering or high free volume content with ion exchange or lamination can impart a relatively high compressive stress and reduce the driving force for crack formation. Therefore, such a combined approach might offer the best overall crack resistance for oxide glasses.

  5. Cathodoluminescence study of vickers indentations in magnesium ...

    African Journals Online (AJOL)

    Vickers diamond pyramid indentations made in single crystal of magnesium oxide (MgO) were examined in an environmental scanning electron microscope interfaced with an AVS-2000 spectrophotometer for luminescence. Three distinct zones around the indentations were identified to exhibit cathodoluminescence, which ...

  6. Indentation of Ellipsoidal and Cylindrical Elastic Shells

    KAUST Repository

    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.

  7. Influence of strain gradients on lattice rotation in nano-indentation experiments: A numerical study

    KAUST Repository

    Demiral, Murat

    2014-07-01

    In this paper the texture evolution in nano-indentation experiments was investigated numerically. To achieve this, a three-dimensional implicit finite-element model incorporating a strain-gradient crystal-plasticity theory was developed to represent accurately the deformation of a body-centred cubic metallic material. A hardening model was implemented to account for strain hardening of the involved slip systems. The surface topography around indents in different crystallographic orientations was compared to corresponding lattice rotations. The influence of strain gradients on the prediction of lattice rotations in nano-indentation was critically assessed. © 2014 Elsevier B.V..

  8. Determination of the Mechanical Properties of Plasma-Sprayed Hydroxyapatite Coatings Using the Knoop Indentation Technique

    Science.gov (United States)

    Hasan, Md. Fahad; Wang, James; Berndt, Christopher

    2015-06-01

    The microhardness and elastic modulus of plasma-sprayed hydroxyapatite coatings were evaluated using Knoop indentation on the cross section and on the top surface. The effects of indentation angle, testing direction, measurement location and applied load on the microhardness and elastic modulus were investigated. The variability and distribution of the microhardness and elastic modulus data were statistically analysed using the Weibull modulus distribution. The results indicate that the dependence of microhardness and elastic modulus on the indentation angle exhibits a parabolic shape. Dependence of the microhardness values on the indentation angle follows Pythagoras's theorem. The microhardness, Weibull modulus of microhardness and Weibull modulus of elastic modulus reach their maximum at the central position (175 µm) on the cross section of the coatings. The Weibull modulus of microhardness revealed similar values throughout the thickness, and the Weibull modulus of elastic modulus shows higher values on the top surface compared to the cross section.

  9. Micro and macro contact mechanics for interacting asperities

    Indian Academy of Sciences (India)

    The motivation for modelling the asperities at micro scales comes from the preliminary results obtained from photoelastic experiments. Numerical results are presented based on the analytical results available for Hertzian contacts. The motivation for modelling the asperities at macro scales comes from the results available ...

  10. Micro and macro contact mechanics for interacting asperities

    Indian Academy of Sciences (India)

    The motivation for modelling the asperities at micro scales comes from the pre- liminary results obtained from photoelastic experiments. Numerical results ... deciding the severity of contact stresses. The sur- face roughness leads to interlocking of asperities at micro scale resulting in friction between. ∗. For correspondence.

  11. Chemical composition of Dipsacus asper Wallich ex Candolle ...

    African Journals Online (AJOL)

    Purpose: To evaluate the larvicidal activity of the essential oil of Dipsacus asper Wallich ex Candolle. (Dipsacaceae) roots against the ... Keywords: Dipsacus asper, Aedes aegypti, Culex pipiens pallens, Essential oil, Larvicidal activity,. Caryophyllene .... moistened filter paper was kept in the cage for oviposition of A. aegypti ...

  12. Contact stiffness of randomly rough surfaces.

    Science.gov (United States)

    Pohrt, Roman; Popov, Valentin L

    2013-11-21

    We investigate the contact stiffness of an elastic half-space and a rigid indenter with randomly rough surface having a power spectrum C2D(q)proportional q(-2H-2), where q is the wave vector. The range of H[symbol: see text] is studied covering a wide range of roughness types from white noise to smooth single asperities. At low forces, the contact stiffness is in all cases a power law function of the normal force with an exponent α. For H > 2, the simple Hertzian behavior is observed . In the range of 0 dimensional contact mechanics and the method of dimensionality reduction (MDR). The influence of the long wavelength roll-off is investigated and discussed.

  13. Standard practice for instrumented indentation testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This practice defines the basic steps of Instrumented Indentation Testing (IIT) and establishes the requirements, accuracies, and capabilities needed by an instrument to successfully perform the test and produce the data that can be used for the determination of indentation hardness and other material characteristics. IIT is a mechanical test that measures the response of a material to the imposed stress and strain of a shaped indenter by forcing the indenter into a material and monitoring the force on, and displacement of, the indenter as a function of time during the full loading-unloading test cycle. 1.2 The operational features of an IIT instrument, as well as requirements for Instrument Verification Annex A1), Standardized Reference Blocks (Annex A2) and Indenter Requirements (Annex A3) are defined. This practice is not intended to be a complete purchase specification for an IIT instrument. 1.3 With the exception of the non-mandatory Appendix X4, this practice does not define the analysis necessary...

  14. A simple model for indentation creep

    Science.gov (United States)

    Ginder, Ryan S.; Nix, William D.; Pharr, George M.

    2018-03-01

    A simple model for indentation creep is developed that allows one to directly convert creep parameters measured in indentation tests to those observed in uniaxial tests through simple closed-form relationships. The model is based on the expansion of a spherical cavity in a power law creeping material modified to account for indentation loading in a manner similar to that developed by Johnson for elastic-plastic indentation (Johnson, 1970). Although only approximate in nature, the simple mathematical form of the new model makes it useful for general estimation purposes or in the development of other deformation models in which a simple closed-form expression for the indentation creep rate is desirable. Comparison to a more rigorous analysis which uses finite element simulation for numerical evaluation shows that the new model predicts uniaxial creep rates within a factor of 2.5, and usually much better than this, for materials creeping with stress exponents in the range 1 ≤ n ≤ 7. The predictive capabilities of the model are evaluated by comparing it to the more rigorous analysis and several sets of experimental data in which both the indentation and uniaxial creep behavior have been measured independently.

  15. Mechanical characterization of soft materials using transparent indenter testing system and finite element simulation

    Science.gov (United States)

    Xuan, Yue

    Background. Soft materials such as polymers and soft tissues have diverse applications in bioengineering, medical care, and industry. Quantitative mechanical characterization of soft materials at multiscales is required to assure that appropriate mechanical properties are presented to support the normal material function. Indentation test has been widely used to characterize soft material. However, the measurement of in situ contact area is always difficult. Method of Approach. A transparent indenter method was introduced to characterize the nonlinear behaviors of soft materials under large deformation. This approach made the direct measurement of contact area and local deformation possible. A microscope was used to capture the contact area evolution as well as the surface deformation. Based on this transparent indenter method, a novel transparent indentation measurement systems has been built and multiple soft materials including polymers and pericardial tissue have been characterized. Seven different indenters have been used to study the strain distribution on the contact surface, inner layer and vertical layer. Finite element models have been built to simulate the hyperelastic and anisotropic material behaviors. Proper material constants were obtained by fitting the experimental results. Results.Homogeneous and anisotropic silicone rubber and porcine pericardial tissue have been examined. Contact area and local deformation were measured by real time imaging the contact interface. The experimental results were compared with the predictions from the Hertzian equations. The accurate measurement of contact area results in more reliable Young's modulus, which is critical for soft materials. For the fiber reinforced anisotropic silicone rubber, the projected contact area under a hemispherical indenter exhibited elliptical shape. The local surface deformation under indenter was mapped using digital image correlation program. Punch test has been applied to thin films of

  16. The difference of phase distributions in silicon after indentation with Berkovich and spherical indenters

    International Nuclear Information System (INIS)

    Zarudi, I.; Zhang, L.C.; Cheong, W.C.D.; Yu, T.X.

    2005-01-01

    This study analyses the microstructure of monocrystalline silicon after indentation with a Berkovich and spherical indenter. Transmission electron microscopy on cross section view samples was used to explore the detailed distributions of various phases in the subsurfaces of indented silicon. It was found that an increase of the P max would promote the growth of the crystalline R8/BC8 phase at the bottom of the deformation zone. Microcracks were always generated in the range of the P max studied. It was also found that the deformation zones formed by the Berkovich and spherical indenters have very different phase distribution characteristics. A molecular dynamics simulation and finite element analysis supported the experimental observations and suggested that the distribution of the crystalline phases in the transformation zone after indentation was highly stress-dependent

  17. Indentation of aluminium foam at low velocity

    Directory of Open Access Journals (Sweden)

    Shi Xiaopeng

    2015-01-01

    Full Text Available The indentation behaviour of aluminium foams at low velocity (10 m/s ∼ 30 m/s was investigated both in experiments and numerical simulation in this paper. A flat-ended indenter was used and the force-displacement history was recorded. The Split Hopkinson Pressure bar was used to obtain the indentation velocity and forces in the dynamic experiments. Because of the low strength of the aluminium foam, PMMA bar was used, and the experimental data were corrected using Bacon's method. The energy absorption characteristics varying with impact velocity were then obtained. It was found that the energy absorption ability of aluminium foam gradually increases in the quasi-static regime and shows a significant increase at ∼10 m/s velocity. Numerical simulation was also conducted to investigate this process. A 3D Voronoi model was used and models with different relative densities were investigated as well as those with different failure strain. The indentation energy increases with both the relative density and failure strain. The analysis of the FE model implies that the significant change in energy absorption ability of aluminium foam in indentation at ∼10 m/s velocity may be caused by plastic wave effect.

  18. Analysis of the equivalent indenter concept used to extract Young’s modulus from a nano-indentation test: some new insights into the Oliver–Pharr method

    DEFF Research Database (Denmark)

    Andriollo, Tito; Thorborg, Jesper; Hattel, Jesper Henri

    2017-01-01

    's elastic solution which is formally valid only for indentation into a flat surface. This allows for formulating the problem of extracting Young's modulus from the unloading curve as an optimization problem. However, it is proved that the latter does not have a unique solution, due to the particular...

  19. SIFAT MEKANIS BAMBU BETUNG (Dendrocalamus asper

    Directory of Open Access Journals (Sweden)

    Fengky S. Yoresta

    2016-08-01

    Full Text Available Penelitian ini bertujuan mendapatkan nilai kekakuan dan kekuatan lentur maksimum bambu betung (Dendrocalamus asper dengan posisi kulit bambu yang berbeda, serta untuk menentukan nilai kekuatan tarik sejajar serat bambu betung. Kekakuan, kekuatan lentur maksimum, dan kekuatan tarik sejajar serat berturut-turut dinyatakan dalam MOE (modulus of elastcity, MOR (modulus of rupture, dan σtr// (maximum tensile strength. Bambu betung yang berumur +­ 4 tahun digunakan dalam penelitian ini. Sepuluh spesimen uji masing-masing digunakan untuk pengujian lentur dengan posisi kulit bambu di serat atas/daerah tekan, di serat bawah/daerah tarik, dan pengujian tarik sejajar serat. Pengujian dilaboratorium dilakukan berdasarkan ASTM D143-05. Hasil penelitian menunjukkan bahwa posisi kulit bambu mempengaruhi nilai MOE dan MOR. Bambu dengan posisi kulit di serat atas/daerah tekan cenderung memiliki nilai MOE dan MOR lebih tinggi dibandingkan bambu dengan posisi kulit di serat bawah/daerah tarik. Bambu dengan posisi kulit di serat atas memiliki nilai MOE = 62118,90 kg/cm2dan MOR = 826,36 kg/cm2, sedangkan bambu dengan posisi kulit di serat bawah memiliki nilai MOE = 51563,20 kg/cm2dan MOR = 633,38 kg/cm2. Kekuatan tarik sejajar serat bambu diperoleh sebesar 2309,00 kg/cm2. Kata Kunci: Kekakuan, Kekuatan Lentur, MOE, MOR, Kekuatan Tarik

  20. Site-controlled fabrication of silicon nanotips by indentation-induced selective etching

    Science.gov (United States)

    Jin, Chenning; Yu, Bingjun; Liu, Xiaoxiao; Xiao, Chen; Wang, Hongbo; Jiang, Shulan; Wu, Jiang; Liu, Huiyun; Qian, Linmao

    2017-12-01

    In the present study, the indentation-induced selective etching approach is proposed to fabricate site-controlled pyramidal nanotips on Si(100) surface. Without any masks, the site-controlled nanofabrication can be realized by nanoindentation and post etching in potassium hydroxide (KOH) solution. The effect of indentation force and etching time on the formation of pyramidal nanotips was investigated. It is found that the height and radius of the pyramidal nanotips increase with the indentation force or etching time, while long-time etching can lead to the collapse of the tips. The formation of pyramidal tips is ascribed to the anisotropic etching of silicon and etching stop of (111) crystal planes in KOH aqueous solution. The capability of this fabrication method was further demonstrated by producing various tip arrays on silicon surface by selective etching of the site-controlled indent patterns, and the maximum height difference of these tips is less than 10 nm. The indentation-induced selective etching provides a new strategy to fabricate well site-controlled tip arrays for multi-probe SPM system, Si nanostructure-based sensors and high-quality information storage.

  1. Comparison of Isolated Indentation and Grid Indentation Methods for HVOF Sprayed Cermets

    Science.gov (United States)

    Nohava, Jiří; Haušild, Petr; Houdková, Šárka; Enžl, Radek

    2012-06-01

    This paper compares the results of two approaches of instrumented indentation for characterization of mechanical properties of HVOF coatings. Three types of HVOF sprayed coatings (Cr3C2-NiCr, WC-Co, (Ti, Mo)(C,N)-NiCo) were investigated by the means of isolated nanoindentation and grid indentation methods. The results of the isolated indentation revealed hardness and elastic modulus of the individual phases in very good agreement with the corresponding bulk material. The grid indentation method, based on statistical evaluation of a large number of indentations, was influenced by the carbide-matrix interface, which gave rise to a third peak apart from the two peaks corresponding to the carbides and metallic matrix. As a consequence, the bimodal Gaussian fit was insufficient and a trimodal fit had to be used. The results extracted from low load grid nanoindentations were quite close to the results of isolated indentations whereas higher load grid nanoindentation revealed overall properties of the coating.

  2. Microhardness with depth sensing indentation. Instruments methods and applications; Mesure de durete submicronique instrumentee. Methode et applications

    Energy Technology Data Exchange (ETDEWEB)

    Poissonnet, S

    1999-07-01

    The study of applied surface layer or modified layers lead to the development of depth sensing indentation instruments in which measurements of penetration depth replaces optical measurements of surface impressions and sub-micron hardness may be determined. Indentation curves, depth-load, of elastoplastic materials give informations about plasticity and elasticity. After a description of the micro-indentation techniques we show few applications. Irradiation effects are measured in different materials like hafnium diboride, stainless steel or kapton. Hardness in oxide formed on metal study give informations. All these examples show that the nano-indentation is a powerful mean in the physical studies of materials because of a good statistic may be obtained and we have access to thin samples and to small phases. (author)

  3. Indentation of elastically soft and plastically compressible solids

    DEFF Research Database (Denmark)

    Needleman, A.; Tvergaard, Viggo; Van der Giessen, E.

    2015-01-01

    The effect of soft elasticity, i.e., a relatively small value of the ratio of Young's modulus to yield strength and plastic compressibility on the indentation of isotropically hardening elastic-viscoplastic solids is investigated. Calculations are carried out for indentation of a perfectly sticking...... the ratio of nominal indentation hardness to yield strength. A linear relation is found between the nominal indentation hardness and the logarithm of the ratio of Young's modulus to yield strength, but with a different coefficient than reported in previous studies. The nominal indentation hardness decreases...

  4. Indentation modulus and hardness of viscoelastic thin films by atomic force microscopy: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Passeri, D., E-mail: daniele.passeri@uniroma1.it [Dipartimento di Energetica, Universita di Roma ' La Sapienza' , Via A. Scarpa 16, 00161 Roma (Italy); Bettucci, A.; Biagioni, A.; Rossi, M.; Alippi, A. [Dipartimento di Energetica, Universita di Roma ' La Sapienza' , Via A. Scarpa 16, 00161 Roma (Italy); Tamburri, E. [Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma ' Tor Vergata' , Via della Ricerca Scientifica, 00133 Roma (Italy); Lucci, M.; Davoli, I. [Dipartimento di Fisica, Universita di Roma ' Tor Vergata' , Via della Ricerca Scientifica, 00133 Roma (Italy); Berezina, S. [Department of Physics, University of Zilina, 01026, Univerzitna 1 Zilina (Slovakia)

    2009-11-15

    We propose a nanoindentation technique based on atomic force microscopy (AFM) that allows one to deduce both indentation modulus and hardness of viscoelastic materials from the force versus penetration depth dependence, obtained by recording the AFM cantilever deflection as a function of the sample vertical displacement when the tip is pressed against (loading phase) and then removed from (unloading phase) the surface of the sample. Reliable quantitative measurements of both indentation modulus and hardness of the investigated sample are obtained by calibrating the technique through a set of different polymeric samples, used as reference materials, whose mechanical properties have been previously determined by standard indentation tests. By analyzing the dependence of the cantilever deflection versus time, the proposed technique allows one to evaluate and correct the effect of viscoelastic properties of the investigated materials, by adapting a post-experiment data processing procedure well-established for standard depth sensing indentation tests. The technique is described in the case of the measurement of indentation modulus and hardness of a thin film of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate), deposited by chronoamperometry on an indium tin oxide (ITO) substrate.

  5. A Comparison of Quasi-Static Indentation Testing to Low Velocity Impact Testing

    Science.gov (United States)

    Nettles, Alan T.; Douglas, Michael J.

    2001-01-01

    The need for a static test method for modeling low-velocity foreign object impact events to composites would prove to be very beneficial to researchers since much more data can be obtained from a static test than from an impact test. In order to examine if this is feasible, a series of static indentation and low velocity impact tests were carried out and compared. Square specimens of many sizes and thickness were utilized to cover the array of types of low velocity impact events. Laminates with a n/4 stacking sequence were employed since this is by the most common type of engineering laminate. Three distinct flexural rigidities under two different boundary conditions were tested in order to obtain damage due to large deflections, contact stresses and both to examine if the static indentation-impact comparisons are valid under the spectrum of damage modes that can be experienced. Comparisons between static indentation and low velocity impact tests were based on the maximum applied transverse load. The dependent parameters examined included dent depth, back surface crack length, delamination area and to a limited extent, load-deflection behavior. Results showed that no distinct differences could be seen between the static indentation tests and the low velocity impact tests, indicating that static indentation can be used to represent a low velocity impact event.

  6. Polarity influence on the indentation punching of thin {111} GaAs foils at elevated temperatures

    International Nuclear Information System (INIS)

    Patriarche, G; Largeau, L; Riviere, J P; Bourhis, E Le

    2005-01-01

    Thin {111} GaAs substrates were deformed by a Vickers indenter at 350 deg. C-370 deg. C under loads ranging between 0.4 and 1.9 N. Optical microscopy and interferometry were used to observe the indented and opposite faces of the thin foils and hence to investigate the plastic flow through the samples. Attention was paid to the polarity (A or B) of the specimen surface, as GaAs is known to show a large difference between α and β dislocations mobilities. A model considering the influence of polarity is proposed to describe the material flow throughout thin samples

  7. Characterization of Rockwell hardness indenter Tip using image processing and optical profiler and evaluation of measurement uncertainty

    Directory of Open Access Journals (Sweden)

    Moona G.

    2014-01-01

    Full Text Available Hardness is a measure of the resistance of a material to be penetrated and eroded by sharp projections of other materials such as diamond. The process of creating sharp projections on any test surface is known as indentation. Hardness measurement of any material is the result of a complex process of deformation during indentation. The indenter tip geometry, which includes radius of curvature at the tip and tip angle, affects the hardness measurement by influencing the nature of the penetration process on the test surface, because every indenter deforms the specimen surface with a different geometry. The controlled indenter geometry can improve the consistency of hardness measurement. In this paper we report the estimation of two important geometrical parameters, radius of curvature and tip angle of a Rockwell indenter by using a simple method of image processing and compare the results with those obtained with a traceable 3D optical profiler. Evaluation of uncertainty in measuremts is carried out as per ISO guidelines (ISO-GUM and a detailed uncertainty budget is presented. The tip angle estimted is 119.95 degree. The radius of curvature is estimted to be 199.96 ± 0.80μm by image analysis which agrees well with the value estimated by using optical profiler i.e. 199.12 μm.

  8. Evaluation of hot hardness, creep, fatigue and fracture properties of zirconia ceramics by an indentation technique

    International Nuclear Information System (INIS)

    Kutty, T.R.G.; Ganguly, C.; Upadhyaya, D.D.

    1996-01-01

    Zirconia ceramics have wide range engineering applications at room and elevated temperatures. For understanding the mechanical behaviour, the indentation technique was adapted for quick evaluation of hot hardness, creep, fatigue and fracture properties. A Vicker's diamond indentor with 10 N load was employed for hot hardness and creep measurement up to 1300 deg. The fatigue data were evaluated at room temperature by repeated indentation with a constant load (10-2500N) at the same location for a dwell time of 5s until it resulted in the formation of a lateral chip on the sample surface. Thus, the number of cycles for chip formation at a specific indentation load was obtained. The fracture toughness was evaluated at room temperature with a load of 300N using a Vicker's diamond indentor. The results of hot hardness, creep, fatigue, and fracture data ol 3Y-TZP and Mg-PSZ are discussed along with their microstructural features. (authors)

  9. Rebound indentation problem for a viscoelastic half-space and axisymmetric indenter - Solution by the method of dimensionality reduction

    Science.gov (United States)

    Argatov, Ivan I.; Popov, Valentin L.

    2016-08-01

    The method of dimensionality reduction (MDR) is extended for the axisymmetric frictionless unilateral Hertz-type contact problem for a viscoelastic half-space and an arbitrary axisymmetric rigid indenter under the assumption that an arbitrarily evolving in time circular contact area remains singly connected during the whole process of indentation. In particular, the MDR is applied to study in detail the so-called rebound indentation problem, where the contact radius has a single maximum. It is shown that the obtained closed-form analytical solution for the rebound indentation displacement (recorded in the recovery phase, when the contact force vanishes) does not depend on the indenter shape.

  10. Quantitative Hardness Measurement by Instrumented AFM-indentation.

    Science.gov (United States)

    Caron, Arnaud

    2016-11-22

    In this work, a combination of amplitude-modulated non-contact atomic force microscopy and atomic force spectroscopy is applied for instrumented hardness measurements on an Au(111) surface with atomistic resolution of single plasticity events. A careful experimental procedure is described that includes the force sensor selection, its calibration, the calibration of the cantilever deflection detection system, and the minimization of instrumental drift for accurate and reproducible force-distance measurements. Also, a method for the data analysis is presented that allows the extraction of force-penetration curves from recorded force-distance curves. A typical curve displays a clear elastic deformation regime up to the first plasticity event, or pop-in, with a length in the range of one to two Burger's vectors. Later plasticity events exhibit the same magnitude. The work of plasticity is further extracted from the measurements. Finally, the hardness is determined in combination with the indentation curve using non-contact atomic force microscopy images of the remaining indents.

  11. Analysis of Indentation-Derived Power-Law Creep Response

    Science.gov (United States)

    Martinez, Nicholas J.; Shen, Yu-Lin

    2016-03-01

    The use of instrumented indentation to characterize power-law creep is studied by computational modeling. Systematic finite element analyses were conducted to examine how indentation creep tests can be employed to retrieve the steady-state creep parameters pertaining to regular uniaxial loading. The constant indentation load hold and constant indentation-strain-rate methods were considered, first using tin (Sn)-based materials as a model system. The simulated indentation-strain rate-creep stress relations were compared against the uniaxial counterparts serving as model input. It was found that the constant indentation-strain-rate method can help establish steady-state creep, and leads to a more uniform behavior than the constant-load hold method. An expanded parametric analysis was then performed using the constant indentation-strain-rate method, taking into account a wide range of possible power-law creep parameters. The indentation technique was found to give rise to accurate stress exponents, and a certain trend for the ratio between indentation strain rate and uniaxial strain rate was identified. A contour-map representation of the findings serves as practical guidance for determining the uniaxial power-law creep response based on the indentation technique.

  12. The influence of abrasive body dimensions on single asperity wear

    NARCIS (Netherlands)

    Woldman, M.; van der Heide, Emile; Tinga, Tiedo; Masen, Marc Arthur

    2013-01-01

    This work focuses on the relation between the properties of abrasive bodies and the wear they cause. By performing single asperity scratch tests to simulate abrasive wear, the wear process takes place in a controlled environment, allowing the properties of the abrasive body to be isolated and

  13. A mechanistic understanding of the wear coefficient: From single to multiple asperities contact

    Science.gov (United States)

    Frérot, Lucas; Aghababaei, Ramin; Molinari, Jean-François

    2018-05-01

    Sliding contact between solids leads to material detaching from their surfaces in the form of debris particles, a process known as wear. According to the well-known Archard wear model, the wear volume (i.e. the volume of detached particles) is proportional to the load and the sliding distance, while being inversely proportional to the hardness. The influence of other parameters are empirically merged into a factor, referred to as wear coefficient, which does not stem from any theoretical development, thus limiting the predictive capacity of the model. Based on a recent understanding of a critical length-scale controlling wear particle formation, we present two novel derivations of the wear coefficient: one based on Archard's interpretation of the wear coefficient as the probability of wear particle detachment and one that follows naturally from the up-scaling of asperity-level physics into a generic multi-asperity wear model. As a result, the variation of wear rate and wear coefficient are discussed in terms of the properties of the interface, surface roughness parameters and applied load for various rough contact situations. Both new wear interpretations are evaluated analytically and numerically, and recover some key features of wear observed in experiments. This work shines new light on the understanding of wear, potentially opening a pathway for calculating the wear coefficient from first principles.

  14. Laser treatment of boron carbide surfaces: Metallurgical and morphological examinations

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsilbas@kfupm.edu.sa; Karatas, C.

    2014-08-01

    Highlights: • Dense layer with fine grains is formed at surface. • Irregular shaped grains and dendrites are formed below dense layer. • Assisting gas forms nitride species (BN and BC{sub 2}N) at surface. • Fracture toughness of treated surface reduces because of high hardness. • Residual stress is compressive and the maximum residual stress is about 0.9 GPa. - Abstract: Laser treatment of B{sub 4}C tile surfaces is carried out under high pressure nitrogen assisting gas environment. Morphological and metallurgical changes in the laser treated layer are examined by incorporating scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. Microhardness and fracture toughness of the laser treated surface are determined from the indentation data. Residual stress formed at the treated surface is obtained by using X-ray diffraction technique. It is found that laser treated surface is free from large scale asperities including cracks and voids; however, some locally scattered shallow cavities with 1.5–2 μm widths are formed at the surface because of high temperature processing. Dense layer, consisting of fine grains, and formation of nitride species (BN and BC{sub 2}N) enhance microhardness and lower fracture toughness at the surface. Residual stress formed in the treated layer is compressive and the maximum residual stress is in the order of −0.9 GPa.

  15. Material Flow Analysis in Indentation by Two-Dimensional Digital Image Correlation and Finite Elements Method.

    Science.gov (United States)

    Bermudo, Carolina; Sevilla, Lorenzo; Castillo López, Germán

    2017-06-21

    The present work shows the material flow analysis in indentation by the numerical two dimensional Finite Elements (FEM) method and the experimental two-dimensional Digital Image Correlation (DIC) method. To achieve deep indentation without cracking, a ductile material, 99% tin, is used. The results obtained from the DIC technique depend predominantly on the pattern conferred to the samples. Due to the absence of a natural pattern, black and white spray painting is used for greater contrast. The stress-strain curve of the material has been obtained and introduced in the Finite Element simulation code used, DEFORM™, allowing for accurate simulations. Two different 2D models have been used: a plain strain model to obtain the load curve and a plain stress model to evaluate the strain maps on the workpiece surface. The indentation displacement load curve has been compared between the FEM and the experimental results, showing a good correlation. Additionally, the strain maps obtained from the material surface with FEM and DIC are compared in order to validate the numerical model. The Von Mises strain results between both of them present a 10-20% difference. The results show that FEM is a good tool for simulating indentation processes, allowing for the evaluation of the maximum forces and deformations involved in the forming process. Additionally, the non-contact DIC technique shows its potential by measuring the superficial strain maps, validating the FEM results.

  16. Progressive evolution of microfabrics in high-temperature indentation creep experiments

    Science.gov (United States)

    Wassmann, S.; Dorner, D.; Stoeckhert, B.

    2014-12-01

    Microfabrics of natural rocks as well as of those deformed in laboratory experiments are studied post-mortem, the history of fabric evolution being inferred from a finite state. This is a major drawback when being interested in modification of fabrics related to progressive deformation. Here we present a novel approach to analyze and compare fabrics in different stages of evolution, taking spatial position to mimic a time series. Using this approach, evolution in time can be investigated on one sample deformed in a single indentation creep test. Such experiments at high temperatures and atmospheric pressure provide information on mechanical properties of rock-forming minerals as well as on microfabrics developed during inhomogeneous deformation underneath the indenter. Using a conventional creep apparatus, a cylindrical alumina indenter, 2 mm in diameter, is driven by a dead load into the flat surface of a specimen. A penetration depth of 1 mm is typically reached after hours to days, depending on material, applied temperature, and load. Previous experiments on natural, polycrystalline anhydrite carried out at temperatures between 700°C and 920 °C yield a stress exponent of 3.9 indicating deformation in the dislocation creep regime, consistent with microstructural observations (Dorner et al., 2014; Solid Earth). Within a cone-shaped region in front of the indenter, the original microfabric appears entirely unaffected. The neutral cone is mantled by highly deformed shear zones. During progressive indentation this structure of undeformed cone and shear zones propagates into the specimen. Thus, for a homogeneous starting material, serial sections of the deformed specimen normal to the indenter axis provide insight into fabrics in distinct stages of evolution. Microfabrics developed at different distance in front of the approaching indenter can be taken to represent a time series. A disadvantage of the technique is that the history of shear zone deformation is

  17. Indentation Behavior of Permanently Densified Oxide Glasses

    DEFF Research Database (Denmark)

    Bechgaard, Tobias Kjær; Januchta, Kacper; Kapoor, Saurabh

    -induced changes in density, structure, and indentation behavior of a range of oxide glasses, including silicates, borates, and phosphates. The effect of compression on the structure is analyzed through both Raman and NMR spectroscopy, while the mechanical properties are investigated using Vickers micro......Hot isostatic compression can be used as a post treatment method to tune the properties of glass materials as well as to obtain improved understanding of the pressure-induced structural changes and densification mechanisms, e.g., during sharp contact loading. Here, we review the pressure...... number distribution of network formers, the number of non-bridging oxygens, and the packing efficiency in the glasses....

  18. On size-effects in single crystal wedge indentation

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2012-01-01

    Wedge indentation in single crystals is studied numerically, with emphasis on size-effects on the micron scale. Under the assumption of a perfectly sharp wedge indenter, a linear relationship between indentation force and indentation depth would be predicted from conventional theories lacking con...... are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. The finite element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles.......Wedge indentation in single crystals is studied numerically, with emphasis on size-effects on the micron scale. Under the assumption of a perfectly sharp wedge indenter, a linear relationship between indentation force and indentation depth would be predicted from conventional theories lacking...... constitutive length parameters to model sizeeffects. The problem is studied numerically using a strain gradient crystal visco-plasticity theory formulated along the lines proposed by Fleck andWillis (2009). It is shown how the force-indentation relation is affected due to size-dependence in the material. Size-effects...

  19. Indentation and Observation of Anisotropic Soft Tissues Using an Indenter Device

    Directory of Open Access Journals (Sweden)

    Parinaz ASHRAFI

    2015-01-01

    Full Text Available Soft tissues of human body have complex structures and different mechanical behaviors than those of traditional engineering materials. There is a great urge to understand tissue behavior of human body. Experimental data is needed for improvement of soft tissue modeling and advancement in implants and prosthesis, as well as diagnosis of diseases. Mechanical behavior and responses change when tissue loses its liveliness and viability. One of the techniques for soft tissue testing is indentation, which is applied on live tissue in its physiological environment. Indentation affords several advantages over other types of tests such as uniaxial tension, biaxial tension, and simple shear and suction, thus it is of interest to develop new indentation techniques from which more valid data can be extracted. In this study a new indenter device was designed and constructed. Displacement and force rate cyclic loading, and relaxation experiments were conducted on human arm. The in-vivo force rate controlled cyclic loading test method which is novel is compared with the traditional displacement controlled cyclic loading tests. Anisotropic behavior of tissue cannot be determined by axisymmetric tips, therefore ellipsoid tips were used for examining anisotropy and inplane material direction of bulk soft tissues

  20. Macro-scale approach for rough frictionless multi-indentation on a viscoelastic half-space

    OpenAIRE

    DUBOIS, Guillaume; CESBRON, Julien; YIN, Hai Ping; ANFOSSO LEDEE, Fabienne

    2011-01-01

    This paper deals with the numerical study of frictionless viscoelastic tyre/road contact. The present macro-scale approach takes into account both the viscoelastic behaviour of the tyre and the roughness of the road surface by solving the contact problem between a rough multi-indentation surface and a viscoelastic half-space. The method relies on the fact that a viscoelastic solution can be instantaneously reduced to an elastic solution. A simplified description of viscoelastic material behav...

  1. Residual stress evaluation in brittle coatings using indentation technique combined with in-situ bending

    International Nuclear Information System (INIS)

    Futakawa, Masatoshi; Steinbrech, R.W.; Tanabe, Yuji; Hara, Toshiaki

    2000-01-01

    The indentation crack length approach was adopted and further elaborated to evaluate residual stress and toughness of the brittle coatings: two kinds of glass coatings on steel. The influence of the residual stress on indentation cracking was examined in as-received coating condition and by in-situ superimposing a counteracting tensile stress. For purpose of providing reference toughness values stress-free pieces of separated coating material have also been examined. Thus results of the two complementary sets of experiments were assumed to prove self-consistently toughness and residual stress data of the coating. In particular, the in-situ bending of specimen in combination with the indentation test allowed us to vary deliberately the residual stress situation in glass coating. Thus experiments which utilized the combination of bending test and micro-indentation were introduced as a method to provide unambiguous information about residual compressive stress. Toughness and residual compressive stress of glass coatings used in this study were 0.46-0.50 MPa·m 1/2 and 94-111 MPa, respectively. Furthermore, a thermoelastic calculation of the residual compressive stress was performed and it is found that the value of residual compressive stress at coating surface of specimen was 90-102 MPa. (author)

  2. Articular cartilage response to a sliding load using two different-sized spherical indenters1.

    Science.gov (United States)

    Schätti, Oliver R; Colombo, Vera; Torzilli, Peter A; Gallo, Luigi M

    2018-01-01

    Cartilage surface contact geometry influences the deformational behavior and stress distribution throughout the extracellular matrix (ECM) under load. To test the correlation between the mechanical and cellular response of articular cartilage when loaded with two different-sized spherical indenters under dynamic reciprocating sliding motion. Articular cartilage explants were subjected to a reciprocating sliding load using a 17.6 mm or 30.2 mm spherical ball for 2000 cycles at 10 mm/s and 4 kg axial load. Deformation of the cartilage was recorded and contact parameters were calculated according to Hertzian theory. After mechanical loading cartilage samples were collected and analyzed for ECM collagen damage, gene regulation and proteoglycan (PG) loss. Significantly higher ECM deformation and strain and lower dynamic effective modulus were found for explants loaded with the smaller diameter indenter whereas contact radius and stress remained unaffected. Also, the 17.6 mm indenter increased PG loss and significantly upregulated genes for ECM proteins and enzymes as compared to the 30.2 mm indenter. Sliding loads that increase ECM deformation/strain were found to induce enzyme-mediated catabolic processes in articular cartilage explants. These observations provide further understanding of how changes in cartilage contact mechanics under dynamic conditions can affect the cellular response.

  3. Epidemiological, clinical and therapeutic aspects of Bothrops asper bites.

    Science.gov (United States)

    Otero-Patiño, Rafael

    2009-12-01

    Bothrops asper inflicts the majority of snakebites in Central America and in the northern regions of South America, mostly affecting young agricultural workers in rural settings. This species is capable of provoking severe envenomings associated with local and systemic manifestations. The main clinical features are: local edema, ecchymoses, blisters, dermonecrosis, myonecrosis, defibrinogenation, thrombocytopenia, systemic bleeding, hypotension and renal alterations. In addition, soft-tissue infection, acute renal failure, compartmental syndrome, central nervous system hemorrhage and, in pregnant women, abortion, fetal wastage and abruptio placentae have been described as complications. Intravenous administration of antivenom constitutes the mainstay in the therapy. Antivenoms composed of either whole IgG or F(ab')(2) fragments, manufactured in Brazil, Colombia, Costa Rica and Mexico, have been tested in controlled clinical trials, and rational protocols for antivenom administration have been developed. In addition to antivenom therapy, a number of ancillary interventions are recommended in the treatment of B. asper bites.

  4. Nucleation at hardness indentations in cold rolled Al

    DEFF Research Database (Denmark)

    Xu, C.L.; Zhang, Yubin; Wu, G.L.

    2015-01-01

    Nucleation of recrystallization near hardness indentations has been investigated in slightly cold rolled high purity aluminium. Samples were cold rolled to 12% and 20% reductions in thickness and indentations were done with two different loads (500 g and 2000 g). The samples were annealed at 300 ...

  5. A new curved fault model and method development for asperities of the 1703 Genroku and 1923 Kanto earthquakes

    Science.gov (United States)

    Kobayashi, R.; Koketsu, K.

    2008-12-01

    Great earthquakes along the Sagami trough, where the Philippine Sea slab is subducting, have repeatedly occurred. The 1703 Genroku and 1923 (Taisho) Kanto earthquakes (M 8.2 and M 7.9, respectively) are known as typical ones, and cause severe damages in the metropolitan area. The recurrence periods of Genroku- and Taisho-type earthquakes inferred from studies of wave cut terraces are about 200-400 and 2000 years, respectively (e.g., Earthquake Research Committee, 2004). We have inferred the source process of the 1923 Kanto earthquake from geodetic, teleseismic, and strong motion data (Kobayashi and Koketsu, 2005). Two asperities of the 1923 Kanto earthquake are located around the western part of Kanagawa prefecture (the base of the Izu peninsula) and around the Miura peninsula. After we adopted an updated fault plane model, which is based on a recent model of the Philippine Sea slab, the asperity around the Miura peninsula moves to the north (Sato et al., 2005). We have also investigated the slip distribution of the 1703 Genroku earthquake. We used crustal uplift and subsidence data investigated by Shishikura (2003), and inferred the slip distribution by using the same geometry of the fault as the 1923 Kanto earthquake. The peak of slip of 16 m is located the southern part of the Boso peninsula. Shape of the upper surface of the Philippine Sea slab is important to constrain extent of the asperities well. Sato et al. (2005) presented the shape in inland part, but less information in oceanic part except for the Tokyo bay. Kimura (2006) and Takeda et al. (2007) presented the shape in oceanic part. In this study, we compiled these slab models, and planed to reanalyze the slip distributions of the 1703 and 1923 earthquakes. We developed a new curved fault plane on the plate boundary between the Philippine Sea slab and inland plate. The curved fault plane was divided into 56 triangle subfaults. Point sources for the Green's function calculations are located at centroids

  6. Phylogeography of the Central American lancehead Bothrops asper (SERPENTES: VIPERIDAE.

    Directory of Open Access Journals (Sweden)

    Mónica Saldarriaga-Córdoba

    Full Text Available The uplift and final connection of the Central American land bridge is considered the major event that allowed biotic exchange between vertebrate lineages of northern and southern origin in the New World. However, given the complex tectonics that shaped Middle America, there is still substantial controversy over details of this geographical reconnection, and its role in determining biogeographic patterns in the region. Here, we examine the phylogeography of Bothrops asper, a widely distributed pitviper in Middle America and northwestern South America, in an attempt to evaluate how the final Isthmian uplift and other biogeographical boundaries in the region influenced genealogical lineage divergence in this species. We examined sequence data from two mitochondrial genes (MT-CYB and MT-ND4 from 111 specimens of B. asper, representing 70 localities throughout the species' distribution. We reconstructed phylogeographic patterns using maximum likelihood and Bayesian methods and estimated divergence time using the Bayesian relaxed clock method. Within the nominal species, an early split led to two divergent lineages of B. asper: one includes five phylogroups distributed in Caribbean Middle America and southwestern Ecuador, and the other comprises five other groups scattered in the Pacific slope of Isthmian Central America and northwestern South America. Our results provide evidence of a complex transition that involves at least two dispersal events into Middle America during the final closure of the Isthmus.

  7. Phylogeography of the Central American lancehead Bothrops asper (SERPENTES: VIPERIDAE).

    Science.gov (United States)

    Saldarriaga-Córdoba, Mónica; Parkinson, Christopher L; Daza, Juan M; Wüster, Wolfgang; Sasa, Mahmood

    2017-01-01

    The uplift and final connection of the Central American land bridge is considered the major event that allowed biotic exchange between vertebrate lineages of northern and southern origin in the New World. However, given the complex tectonics that shaped Middle America, there is still substantial controversy over details of this geographical reconnection, and its role in determining biogeographic patterns in the region. Here, we examine the phylogeography of Bothrops asper, a widely distributed pitviper in Middle America and northwestern South America, in an attempt to evaluate how the final Isthmian uplift and other biogeographical boundaries in the region influenced genealogical lineage divergence in this species. We examined sequence data from two mitochondrial genes (MT-CYB and MT-ND4) from 111 specimens of B. asper, representing 70 localities throughout the species' distribution. We reconstructed phylogeographic patterns using maximum likelihood and Bayesian methods and estimated divergence time using the Bayesian relaxed clock method. Within the nominal species, an early split led to two divergent lineages of B. asper: one includes five phylogroups distributed in Caribbean Middle America and southwestern Ecuador, and the other comprises five other groups scattered in the Pacific slope of Isthmian Central America and northwestern South America. Our results provide evidence of a complex transition that involves at least two dispersal events into Middle America during the final closure of the Isthmus.

  8. Phylogeography of the Central American lancehead Bothrops asper (SERPENTES: VIPERIDAE)

    Science.gov (United States)

    Parkinson, Christopher L.; Daza, Juan M.; Wüster, Wolfgang

    2017-01-01

    The uplift and final connection of the Central American land bridge is considered the major event that allowed biotic exchange between vertebrate lineages of northern and southern origin in the New World. However, given the complex tectonics that shaped Middle America, there is still substantial controversy over details of this geographical reconnection, and its role in determining biogeographic patterns in the region. Here, we examine the phylogeography of Bothrops asper, a widely distributed pitviper in Middle America and northwestern South America, in an attempt to evaluate how the final Isthmian uplift and other biogeographical boundaries in the region influenced genealogical lineage divergence in this species. We examined sequence data from two mitochondrial genes (MT-CYB and MT-ND4) from 111 specimens of B. asper, representing 70 localities throughout the species’ distribution. We reconstructed phylogeographic patterns using maximum likelihood and Bayesian methods and estimated divergence time using the Bayesian relaxed clock method. Within the nominal species, an early split led to two divergent lineages of B. asper: one includes five phylogroups distributed in Caribbean Middle America and southwestern Ecuador, and the other comprises five other groups scattered in the Pacific slope of Isthmian Central America and northwestern South America. Our results provide evidence of a complex transition that involves at least two dispersal events into Middle America during the final closure of the Isthmus. PMID:29176806

  9. Isolation from a polyvalent antivenom of antibodies to a myotoxin in Bothrops asper snake venom

    OpenAIRE

    Lomonte, Bruno; Mata, Eugenia; Gutiérrez, José María

    1985-01-01

    Antibodies against Bothrops asper rmyotoxin were purified from a polyvalent antivenom by affinity chromatography . These antibodies neutralized most of the myotoxic activity of crude B. asper venom, as judged by histologic evaluation of skeletal muscle and determination of plasma creatine kinase levels in mice. When tested by immunoelectrophoresis, purified antibodies formed two superimposed bands of precipitation against an homogenous by SDS-PAGE analysis) preparation of B. asper myotoxin...

  10. AFM indentation study of breast cancer cells

    International Nuclear Information System (INIS)

    Li, Q.S.; Lee, G.Y.H.; Ong, C.N.; Lim, C.T.

    2008-01-01

    Mechanical properties of individual living cells are known to be closely related to the health and function of the human body. Here, atomic force microscopy (AFM) indentation using a micro-sized spherical probe was carried out to characterize the elasticity of benign (MCF-10A) and cancerous (MCF-7) human breast epithelial cells. AFM imaging and confocal fluorescence imaging were also used to investigate their corresponding sub-membrane cytoskeletal structures. Malignant (MCF-7) breast cells were found to have an apparent Young's modulus significantly lower (1.4-1.8 times) than that of their non-malignant (MCF-10A) counterparts at physiological temperature (37 deg. C), and their apparent Young's modulus increase with loading rate. Both confocal and AFM images showed a significant difference in the organization of their sub-membrane actin structures which directly contribute to their difference in cell elasticity. This change may have facilitated easy migration and invasion of malignant cells during metastasis

  11. Analytical method for establishing indentation rolling resistance

    Science.gov (United States)

    Gładysiewicz, Lech; Konieczna, Martyna

    2018-01-01

    Belt conveyors are highly reliable machines able to work in special operating conditions. Harsh environment, long distance of transporting and great mass of transported martials are cause of high energy usage. That is why research in the field of belt conveyor transportation nowadays focuses on reducing the power consumption without lowering their efficiency. In this paper, previous methods for testing rolling resistance are described, and new method designed by authors was presented. New method of testing rolling resistance is quite simple and inexpensive. Moreover it allows to conduct the experimental tests of the impact of different parameters on the value of indentation rolling resistance such as core design, cover thickness, ambient temperature, idler travel frequency, or load value as well. Finally results of tests of relationship between rolling resistance and idler travel frequency and between rolling resistance and idler travel speed was presented.

  12. Nano indentation of particulate and polymer films

    International Nuclear Information System (INIS)

    Akram, Aisha

    2001-01-01

    A detailed knowledge of the formation and rupture mechanisms of agglomerates is essential when seeking to model equipment designed to produce and process such agglomerated particulate solids. In the work to be described the nano-indentation of two-dimensional agglomerate films was carried out in order to establish a means of identifying the generic breakage mechanisms of agglomerated systems. Data analysis techniques are developed that enable the individual inter-particle junction strengths to be calculated for a model system consisting of rather mono-dispersed colloidal silica particles (20-24 nm diameter) bound with a poly(methyl methacrylate). Applied load and penetration depth data in the range (10 mN and 500 nm respectively) are provided as a function of loading time during a continuous loading. It is argued that these data enable the sequence of the discrete binder bridge failures to be observed thus giving a quantitative indication of the breakage mechanism of this agglomerate system as well as reflect the agglomerate structure. The secondary objective of this work was to produce a range of agglomerates with different mechanical properties, without changing the type and amount of binder or prime particles used in the system. This was achieved by altering the mechanical properties of the binder, poly(methyl methacrylate), by the use of a variety of solvents. From data obtained using nano-indentation on thin films of the treated polymer, brittle and ductile forms of poly(methyl methacrylate) could be distinguished. These trends are reflected, to some degree, in the mechanical response of the agglomerated layers. (author)

  13. Collective behavior of asperities as a model for friction and adhesion

    Science.gov (United States)

    Hulikal, Srivatsan

    Understanding friction and adhesion in static and sliding contact of surfaces is important in numerous physical phenomena and technological applications. Most surfaces are rough at the microscale, and thus the real area of contact is only a fraction of the nominal area. The macroscopic frictional and adhesive response is determined by the collective behavior of the population of evolving and interacting microscopic contacts. This collective behavior can be very different from the behavior of individual contacts. It is thus important to understand how the macroscopic response emerges from the microscopic one. In this thesis, we develop a theoretical and computational framework to study the collective behavior. Our philosophy is to assume a simple behavior of a single asperity and study the collective response of an ensemble. Our work bridges the existing well-developed studies of single asperities with phenomenological laws that describe macroscopic rate-and-state behavior of frictional interfaces. We find that many aspects of the macroscopic behavior are robust with respect to the microscopic response. This explains why qualitatively similar frictional features are seen for a diverse range of materials. We first show that the collective response of an ensemble of one-dimensional independent viscoelastic elements interacting through a mean field reproduces many qualitative features of static and sliding friction evolution. The resulting macroscopic behavior is different from the microscopic one: for example, even if each contact is velocity-strengthening, the macroscopic behavior can be velocity-weakening. The framework is then extended to incorporate three-dimensional rough surfaces, long- range elastic interactions between contacts, and time-dependent material behaviors such as viscoelasticity and viscoplasticity. Interestingly, the mean field behavior dominates and the elastic interactions, though important from a quantitative perspective, do not change the

  14. Micro and macro contact mechanics for interacting asperities

    Indian Academy of Sciences (India)

    This eye gives the location of the maximum shear stress mentioned ... However, the fringe order shows that magnitude of stress level is lower than that of Hertzian eye. The slight tilting of the fringes with respect to the horizontal is ... (1966) discussed the indentation of homogenous hollow cylinder with punches of different.

  15. Finite element simulation of Reference Point Indentation on bone.

    Science.gov (United States)

    Idkaidek, Ashraf; Agarwal, Vineet; Jasiuk, Iwona

    2017-01-01

    Reference Point Indentation (RPI) is a novel technique aimed to assess bone quality. Measurements are recorded by the BioDent instrument that applies multiple indents to the same location of cortical bone. Ten RPI parameters are obtained from the resulting force-displacement curves. Using the commercial finite element analysis software Abaqus, we assess the significance of the RPI parameters. We create an axisymmetric model and employ an isotropic viscoelastic-plastic constitutive relation with damage to simulate indentations on a human cortical bone. Fracture of bone tissue is not simulated for simplicity. The RPI outputs are computed for different simulated test cases and then compared with experimental results, measured using the BioDent, found in literature. The number of cycles, maximum indentation load, indenter tip radius, and the mechanical properties of bone: Young׳s modulus, compressive yield stress, and viscosity and damage constants, are varied. The trends in the RPI parameters are then investigated. We find that the RPI parameters are sensitive to the mechanical properties of bone. An increase in Young׳s modulus of bone causes the force-displacement loading and unloading slopes to increase and the total indentation distance (TID) to decrease. The compressive yield stress is inversely proportional to a creep indentation distance (CID1) and the TID. The viscosity constant is proportional to the CID1 and an average of the energy dissipated (AvED). The maximum indentation load is proportional to the TID, CID1, loading and unloading slopes, and AvED. The damage parameter is proportional to the TID, but it is inversely proportional to both the loading and unloading slopes and the AvED. The value of an indenter tip radius is proportional to the CID1 and inversely proportional to the TID. The number of load cycles is inversely proportional to an average of a creep indentation depth (AvCID) and the AvED. The indentation distance increase (IDI) is strongly

  16. Influence of the indenter tip defect in classical indentation: Application to the hardness determination of DLC thin films

    Energy Technology Data Exchange (ETDEWEB)

    Benarioua, Y. [Département de Génie Mécanique, Faculté de Technologies, Université de M' Sila, BP 166, M’Sila 28000 (Algeria); Roudet, F. [Univ. Lille, FRE 3723-LML – Laboratoire de Mécanique de Lille, F-59000 Lille (France); Chicot, D., E-mail: didier.chicot@univ-lille1.fr [Univ. Lille, FRE 3723-LML – Laboratoire de Mécanique de Lille, F-59000 Lille (France)

    2016-04-26

    For an accurate determination of the materials hardness, instrumented indentation test is undoubtedly the most adequate technique compared to the classical one. However, numerous laboratories or industries have no access to such instrumented device. Consequently, they have no other alternative methods that the use of classical indentation test. However, this technique can lead to wrong interpretation because it does not allow considering the indenter tip defect. In this paper, we suggest to introduce the indenter tip defect into the classical hardness calculation. The proposed methodology is validated on a diamond like-carbon thin film deposited onto a tungsten carbide. Firstly, the truncated indenter tip defect length is estimated from the indentation size effect observed for the substrates which is attributed to the influence of the indenter tip defect. As a result, the tip defect is found to have the same value independently of the tested samples. Afterwards, the tip defect length is introduced into the composite hardness computation and the model of Jönsson and Hogmark is applied to predict film hardness. As a main result, the film hardness is found equal to 37.3 GPa independently of the film thickness and in a good accordance with literature data regarding the diamond hybridization sp3/sp2 ratio.

  17. Protective effect of Dracontium dubium against Bothrops asper venom.

    Science.gov (United States)

    Caro, Daneiva; Ocampo, Yanet; Castro, Jenny; Barrios, Lia; Salas, Rubén; Franco, Luis A

    2017-05-01

    In Colombia, Bothrops asper is responsible for 70-90% of ophidians accidents reported annually. Envenoming occurs mainly in rural areas where both antivenom and health centers are scarce. Thus, patients are frequently treated by local healers that employ medicinal herbs; including several species belonging to Dracontium genus. In this work, we evaluated the neutralizing activity of Dracontium dubium Kunth against the lethal, inflammatory, coagulant and hemolytic effects produced by B. asper venom. Mice treated with D. dubium extract (500 and 1000μg/g, ip), survived to the administration of lethal doses of venom, with remarkable recovery of macroscopic and histology damage. Furthermore, D. dubium exerted a significant inhibition of inflammatory damage promoted by paw injection of B. asper venom. Such activity might be related to the inhibition of macrophage activation and NO production, as demonstrated using LPS-stimulated RAW 264.7 cells. Moreover, the extract of D. dubium remarkably diminished the indirect hemolytic effect of snake venom. On the other hand, no substantial differences were observed in clotting time of plasma incubated with venom when compared to extract treated plasma. Noteworthy, D. dubium extract did not alter the electrophoretic pattern of venom before the assays. Phytochemistry screening revealed the presence of phenolic compounds, flavonoids, tannins and steroids/triterpenoids, which might explain the bioactivity of the extract. Our results, provides strong evidence that support the employment of D. dubium in folk medicine. Further studies are needed to isolate and identify the metabolites responsible for the activity, in order to provide a useful and accessible treatment for snakebite envenoming in low-income rural areas. Copyright © 2017. Published by Elsevier Masson SAS.

  18. Indentation and needle insertion properties of the human eye.

    Science.gov (United States)

    Matthews, A; Hutnik, C; Hill, K; Newson, T; Chan, T; Campbell, G

    2014-07-01

    Characterization of the biomechanical properties of the human eye has a number of potential utilities. One novel purpose is to provide the basis for development of suitable tissue-mimicking material. The purpose of this study was to determine the indentation and needle insertion characteristics on human eye globes and tissue strips. An indenter assessed the elastic response of human eye globes and tissue strips under increasing compressive loads. Needle insertion determined the force (N) needed to penetrate various areas of the eye wall. The results demonstrated that globes underwent slightly greater indentation at the midline than at the central cornea, and corneal strips indented twofold more than scleral strips, although neither difference was significant (P=0.400 and P=0.100, respectively). Significant differences were observed among various areas of needle insertion (Phuman eye construct with potential utility as a model for use in ophthalmology research and surgical teaching.

  19. Non-destructive test of steel structures by conical indentation

    Directory of Open Access Journals (Sweden)

    Beskopylny Alexey

    2017-01-01

    Full Text Available The problem of mechanical properties measurement of steel structures by non-destructive method of impact cone indentation is considered. The method is based on analytical solution and experimental data of a problem of impact indentation by cone into elastic-plastic half-space. Non-destructive dynamic indentation method is one of more efficient for mechanical properties assessment because of compact instrument that makes it possible of measuring at any point of structure. The scheme of impact indentation was considered and the problem of elastic-plastic impact is solved. The device with a computer way of information processing was created and tested for determining the characteristics of the existing structures. The method was adopted and tested on bridge structures, butt welded joints, civil engineering structures and others.

  20. A New Iridoid Glycoside from the Roots of Dipsacus asper

    Directory of Open Access Journals (Sweden)

    Zhonglin Yang

    2012-02-01

    Full Text Available A new iridoid glycoside, named loganic acid ethyl ester (1, together with five known compounds: chlorogenic acid (2, caffeic acid (3, loganin (4, cantleyoside (5 and syringaresinol-4′,4′′-O-bis-β-D-glucoside (6 were isolated from the roots of Dipsacus asper. The structure of compound 1 was elucidated on the basis of detailed spectroscopic analyses. Lignan is isolated from Dipsacaceae species for the first time. Compounds 1, 4 and 5 had moderate neuroprotective effects against the Aβ25–35 induced cell death in PC12 cells.

  1. Effect of viscoplastic material parameters on polymer indentation

    DEFF Research Database (Denmark)

    Tvergaard, V; Needleman, A

    2012-01-01

    The effect of material parameters characterizing viscoplastic flow on the indentation response of polymers is investigated using three-dimensional finite element analyses and a one-dimensional expanding spherical cavity model. The polymer is characterized by a finite strain elastic...... variations considered, it is found that two material stress parameters characterizing the plastic flow resistance have the largest effect on the value of the indentation hardness although variations in other material parameters can lead to significant variations....

  2. Evaluation for rheological constitutive relations, using the indentation technique

    Science.gov (United States)

    Fang, Lei

    1992-01-01

    A simple experimental method of determining the rheological constitutive relations is proposed. The method relies upon an analysis of the frictionless contact of a rigid spherical indenter and the rheological materials. The proposal addresses problems in two fields: rheological constitutive models and contact mechanics. It attempts to evaluate the rheological constitutive relations using an indentation technique. A systematic, optimization-based material parameter/function indentation model is proposed. The identification algorithm is based on a modified Marquardt-Levenberg method. A new integral constitutive equation for viscoelastic materials is derived. The derivation is carried out so that a damage function is included in the model in a relatively convenient form. Inclusion of damage effects makes this constitutive equation considerably more general than the widely accepted K-BKZ integral model. The single-step and double-step stress relaxation indentation experiments on asphalt materials were performed. The K-BKZ, Wagner, and nonlinear Volterra models were evaluated. It is demonstrated that the new integral constitutive model shows a very good agreement with the experimental data. The idea of damage function is introduced not only to have a better fit of data, but the damage (or irreversibility) is observed experimentally. Also, the creep indentation tests on composites were presented. A multiaxial theory of creep deformation for particle-strengthened metal matrix composites (Zhu-Weng Theory) was evaluated. The goal of the proposed research is to develop the indentation technique for use in basic mechanical studies. From the indentation test, material response is measured. The data are used in conjunction with the material parameter identification model to optimally back calculate the constitutive relations. indentation test and other experiment method demonstrates the viability of the proposed approach.

  3. Assessing strain mapping by electron backscatter diffraction and confocal Raman microscopy using wedge-indented Si

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Lawrence H.; Vaudin, Mark D.; Stranick, Stephan J.; Stan, Gheorghe; Gerbig, Yvonne B.; Osborn, William; Cook, Robert F., E-mail: robert.cook@nist.gov

    2016-04-15

    The accuracy of electron backscatter diffraction (EBSD) and confocal Raman microscopy (CRM) for small-scale strain mapping are assessed using the multi-axial strain field surrounding a wedge indentation in Si as a test vehicle. The strain field is modeled using finite element analysis (FEA) that is adapted to the near-indentation surface profile measured by atomic force microscopy (AFM). The assessment consists of (1) direct experimental comparisons of strain and deformation and (2) comparisons in which the modeled strain field is used as an intermediate step. Direct experimental methods (1) consist of comparisons of surface elevation and gradient measured by AFM and EBSD and of Raman shifts measured and predicted by CRM and EBSD, respectively. Comparisons that utilize the combined FEA–AFM model (2) consist of predictions of distortion, strain, and rotation for comparison with EBSD measurements and predictions of Raman shift for comparison with CRM measurements. For both EBSD and CRM, convolution of measurements in depth-varying strain fields is considered. The interconnected comparisons suggest that EBSD was able to provide an accurate assessment of the wedge indentation deformation field to within the precision of the measurements, approximately 2×10{sup −4} in strain. CRM was similarly precise, but was limited in accuracy to several times this value. - Highlights: • We map strain by electron backscatter diffraction and confocal Raman microscopy. • The test vehicle is the multi-axial strain field of wedge-indented silicon. • Strain accuracy is assessed by direct experimental intercomparison. • Accuracy is also assessed by atomic force microscopy and finite element analyses. • Electron diffraction measurements are accurate; Raman measurements need refinement.

  4. Quasi-static indentation modelling of aluminium specimen using finite element analysis

    OpenAIRE

    Mayank Nirbhay; Mahima Dua; Anurag Dixit; Satpal Sharma; R.K. Misra

    2017-01-01

    The influence of different types of rigid hemispherical and conical indenters on a rectangular specimen of aluminium has been investigated, in the small indenter test. A 3-D finite-element FE model was used to carry out the computation of the elastic-plastic solution of different rigid hemispherical and conical indenters. Three hemispherical-headed and four conical-headed indenters were designed and developed for testing. FE software ABAQUS® has been used to determine the load vs. indenter-di...

  5. Plastic Indentation Analysis Used in Study of Colliding Robotic Elements

    Directory of Open Access Journals (Sweden)

    Florina Carmen Ciornei

    2014-06-01

    Full Text Available In robotic system there are frequent situations when on the robotic parts percutions develop. The impact plastic imprints are unique source of data remaining after collision, but complications occur in the analysis and the work models a general impact and presents the manner of processing the experimental data. The paper presents the characteristics occurring in the analysis of the indentation remnant after the oblique impact between a free falling ball and the surface of an inclined metallic prism. A series of difficulties arise while trying to approximate the collision’s imprint profile with a parabola having oblique symmetry axis. Both these impediments and the manner of surmounting them are presented. Finally, the impasse that takes place in the actual analysis of an imprint profile is presented. A first method of surpassing this aspect uses the intrinsic characteristics of osculating circle in a point of the profile is applicable only for smooth signals. The second proposed method is applied to the real signal and provides fine results.

  6. Finite Element Modelling of Elastic-Plastic Contact of Rough Surfaces

    OpenAIRE

    Abdo, Jamil; Haneef, Danish; Al-Shabibi, Abdullah

    2010-01-01

    The contact area and contact load of an elastic-plastic micro-contact was calculated. The ultimate stress asperity is embedded at a critical depth within the actual surface asperities. The finite element solution is used to define the limit at which failure is to occur. The present model is more accurate than the previous models since it accounts for the net elasticplastic by subtracting the plastic portion that reached the ultimate-stress asperity limit. Comparisons of the present model with...

  7. On the use of Raman spectroscopy and instrumented indentation for characterizing damage in machined carbide ceramics

    Science.gov (United States)

    Groth, Benjamin Peter

    Machining is a necessary post-processing step in the manufacturing of many ceramic materials. Parts are machined to meet specific dimensions, with tight tolerances, not attainable from forming alone, as well as to achieve a desired surface finish. However, the machining process is very harsh, often employing the use of high temperatures and pressures to achieve the wanted result. In the case of silicon carbide, a material with extremely high hardness and stiffness, machining is very difficult and requires machining conditions that are highly aggressive. This can leave behind residual stresses in the surface of the material, cause unwanted phase transformations, and produce sub-surface deformation that can lead to failure. This thesis seeks to determine the effect of various machining conditions on the Raman spectra and elastic properties of sintered silicon carbide materials. Sample sets examined included hot-pressed silicon carbide tiles with four different surface finishes, as well as "ideal" single crystal silicon carbide wafers. The surface finishes studied were as follows: an as-pressed finish; a grit blast finish; a harsh rotary ground finish; and a mirror polish. Each finish imparts a different amount, as well as type, of deformation to the sample and are each utilized for a specific application. The sample surfaces were evaluated using a combination of Raman spectroscopy, for phase identification and stress analysis, and nanoindentation, for obtaining elastic properties and imparting uniform controlled deformation to the samples. Raman spectroscopy was performed over each sample surface using 514- and 633-nm wavelength excitation, along with confocal and non-confocal settings to study depth variation. Surfaces stresses were determined using peak shift information extracted from Raman spectra maps, while other spectral variations were used to compare levels of machining damage. Elastic modulus, hardness, and plastic work of indentation maps were generated

  8. Giant panda׳s tooth enamel: Structure, mechanical behavior and toughening mechanisms under indentation.

    Science.gov (United States)

    Weng, Z Y; Liu, Z Q; Ritchie, R O; Jiao, D; Li, D S; Wu, H L; Deng, L H; Zhang, Z F

    2016-12-01

    The giant panda׳s teeth possess remarkable load-bearing capacity and damage resistance for masticating bamboos. In this study, the hierarchical structure and mechanical behavior of the giant panda׳s tooth enamel were investigated under indentation. The effects of loading orientation and location on mechanical properties of the enamel were clarified and the evolution of damage in the enamel under increasing load evaluated. The nature of the damage, both at and beneath the indentation surfaces, and the underlying toughening mechanisms were explored. Indentation cracks invariably were seen to propagate along the internal interfaces, specifically the sheaths between enamel rods, and multiple extrinsic toughening mechanisms, e.g., crack deflection/twisting and uncracked-ligament bridging, were active to shield the tips of cracks from the applied stress. The giant panda׳s tooth enamel is analogous to human enamel in its mechanical properties, yet it has superior hardness and Young׳s modulus but inferior toughness as compared to the bamboo that pandas primarily feed on, highlighting the critical roles of the integration of underlying tissues in the entire tooth and the highly hydrated state of bamboo foods. Our objective is that this study can aid the understanding of the structure-mechanical property relations in the tooth enamel of mammals and further provide some insight on the food habits of the giant pandas. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Dynamic mechanical response of brain tissue in indentation in vivo, in situ and in vitro.

    Science.gov (United States)

    Prevost, Thibault P; Jin, Guang; de Moya, Marc A; Alam, Hasan B; Suresh, Subra; Socrate, Simona

    2011-12-01

    Characterizing the dynamic mechanical properties of brain tissue is deemed important for developing a comprehensive knowledge of the mechanisms underlying brain injury. The results gathered to date on the tissue properties have been mostly obtained in vitro. Learning how these results might differ quantitatively from those encountered in vivo is a critical step towards the development of biofidelic brain models. The present study provides novel and unique experimental results on, and insights into, brain biorheology in vivo, in situ and in vitro, at large deformations, in the quasi-static and dynamic regimes. The nonlinear dynamic response of the cerebral cortex was measured in indentation on the exposed frontal and parietal lobes of anesthetized porcine subjects. Load-unload cycles were applied to the tissue surface at sinusoidal frequencies of 10, 1, 0.1 and 0.01 Hz. Ramp-relaxation tests were also conducted to assess the tissue viscoelastic behavior at longer times. After euthanasia, the indentation test sequences were repeated in situ on the exposed cortex maintained in its native configuration within the cranium. Mixed gray and white matter samples were subsequently excised from the superior cortex to be subjected to identical indentation test segments in vitro within 6-7 h post mortem. The main response features (e.g. nonlinearities, rate dependencies, hysteresis and conditioning) were measured and contrasted in vivo, in situ and in vitro. The indentation response was found to be significantly stiffer in situ than in vivo. The consistent, quantitative set of mechanical measurements thereby collected provides a preliminary experimental database, which may be used to support the development of constitutive models for the study of mechanically mediated pathways leading to traumatic brain injury. Copyright © 2011 Acta Materialia Inc. All rights reserved.

  10. Microindentation deformation of lithium dihydrogen phosphate single crystals: Microhardness measurement and indentation size effect

    Energy Technology Data Exchange (ETDEWEB)

    Iurchenko, Anton [Institute for Single Crystals, National Academy of Sciences of Ukraine, Lenin Avenue 60, 61001 Kharkiv (Ukraine); Borc, Jarosław, E-mail: j.borc@pollub.pl [Department of Applied Physics, Lublin University of Technology, ul. Nadbystrzycka 38, 20-618 Lublin (Poland); Sangwal, Keshra [Department of Applied Physics, Lublin University of Technology, ul. Nadbystrzycka 38, 20-618 Lublin (Poland); Voronov, Alexei [Institute for Single Crystals, National Academy of Sciences of Ukraine, Lenin Avenue 60, 61001 Kharkiv (Ukraine)

    2016-02-15

    The Vickers microhardness H{sub V} of the (110) and (111) as-grown faces of lithium dihydrogen phosphate (LDP) crystals was investigated as a function of applied load P. The microhardness H{sub V} of the two faces increases with load P i.e. reverse indentation size effect (reverse ISE) and the hardness of the (110) face is somewhat lower than that of the (111) face but this difference is not easily recognized for these planes due to large scatter in the data. The origin of observed ISE was analyzed using different approaches. It was found that: (1) Hays–Kendall's and Begley–Hutchinson's relations do not explain the origin of reverse ISE but Meyer's law describes the reverse ISE satisfactorily and its constants provide a link between ISE and formation of radial cracks with applied indentation load P, (2) reverse ISE is associated with tensile surface stresses, (3) despite its failure to explain reverse ISE, Begley–Hutchinson's relation is reliable to obtain load-independent hardness H{sub 0}, is 2337 MPa for LDP, and (4) the value of fracture toughness K{sub C} of LDP crystals lies between 4.7 and 12 MPa m{sup 1/2}. The load-independent hardness H{sub 0} of LDP is higher by a factor of 1.5 than that reported for undoped KDP and ADP crystals whereas its fracture toughness K{sub C} is higher by factor of about 20 than that of undoped KDP crystals. - Highlights: • Vickers indentations on the (110) and (111) faces of LDP crystals were made. • The microhardness H{sub V} was investigated as a function of applied load P. • Reverse indentation size effect was observed. • Fracture toughness K{sub C} from the radial cracks was calculated.

  11. Control with anionic polyacrylamide of runoff and erosion induced by irrigation on Alentejo soils: surface and sprinkler irrigation (center pivot Controlo do escorrimento e da erosão em solos do Alentejo com poliacrilamidas aniónicas: rega de superfície e por aspersão (rampas rotativas

    Directory of Open Access Journals (Sweden)

    F. L. Santos

    2009-01-01

    Full Text Available Most of the Mediterranean soils in Southern Portugal, now being converted to irrigation, were under rain-fed agriculture, in areas of sensitive soils, eroded or with high potential for erosion. The particular characteristic of these soils is its rapidly permeable A-horizon overlaying a B-horizon of very low permeability. Such fact leads to low infiltration of the applied irrigation water and, consequently high limitations to irrigation. Therefore for these soils to be under irrigation it is important to adopt soil and water conservation practices and correctly manage the irrigation systems, hoping that these practices will favour agriculture yields and preserve the environment by reducing runoff, preventing soil loss and enhancing the infiltration of applied water. One of the strategies that can be used to achieve such goals and also help to improve the soil physical properties is the use of soil conditioners, particularly the anionic polyacrylamide (PAM. Encouraging results have been obtained in the irrigated soils of Southern Portugal with their use being able to stabilize soil surface structure and curb irrigation-induced erosion in surface irrigation as well as in sprinkler irrigated fields. Since 1997, studies of anionic polyacrylamide (PAM application have been conducted on field experiments, under surface irrigation and on contour and slopping furrows, and also with pressurized irrigation (center pivot and sprinkler simulators, as well as in more controlled laboratory studies, to test the PAM usefulness in controlling erosion and enhancing infiltration of irrigated soils. Several methodologies of applying PAM have been tested (direct application to the soil surface, in water suspension and later applied to furrows and pressurized systems through the irrigation water, and in multiple and/or single applications as well as several application rates and timing. The results have been conclusive and in most of the studied soils PAM application

  12. Finite element analysis of the cyclic indentation of bilayer enamel

    Science.gov (United States)

    Jia, Yunfei; Xuan, Fu-zhen; Chen, Xiaoping; Yang, Fuqian

    2014-04-01

    Tooth enamel is often subjected to repeated contact and often experiences contact deformation in daily life. The mechanical strength of the enamel determines the biofunctionality of the tooth. Considering the variation of the rod arrangement in outer and inner enamel, we approximate enamel as a bilayer structure and perform finite element analysis of the cyclic indentation of the bilayer structure, to mimic the repeated contact of enamel during mastication. The dynamic deformation behaviour of both the inner enamel and the bilayer enamel is examined. The material parameters of the inner and outer enamel used in the analysis are obtained by fitting the finite element results with the experimental nanoindentation results. The penetration depth per cycle at the quasi-steady state is used to describe the depth propagation speed, which exhibits a two-stage power-law dependence on the maximum indentation load and the amplitude of the cyclic load, respectively. The continuous penetration of the indenter reflects the propagation of the plastic zone during cyclic indentation, which is related to the energy dissipation. The outer enamel serves as a protective layer due to its great resistance to contact deformation in comparison to the inner enamel. The larger equivalent plastic strain and lower stresses in the inner enamel during cyclic indentation, as calculated from the finite element analysis, indicate better crack/fracture resistance of the inner enamel.

  13. Spatial and Temporal Clustering in a Simple Earthquake Asperity Model

    Science.gov (United States)

    Tiampo, K. F.; Kazemian, J.; Dominguez, R.; Klein, W.

    2016-12-01

    Natural earthquake fault systems are highly heterogeneous in space, the result of inhomogeneities that are a function of the variety of materials of different strengths. However, despite their inhomogeneous nature, real faults are often modeled as spatially homogeneous systems. Here we present a simple earthquake fault model based on the Olami-Feder-Christensen (OFC) and Rundle-Jackson-Brown (RJB) cellular automata models with long-range interactions that incorporates asperities, or stronger sites, into the lattice (Rundle and Jackson, 1977; Olami et al., 1992). These asperity cells are significantly stronger than the surrounding lattice sites but eventually rupture when the applied stress reaches their higher threshold stress. The introduction of these spatial heterogeneities results in spatial and temporal clustering in the model similar to that seen in natural fault systems. We observe sequences of activity that begin with a gradually accelerating number of larger events, or foreshocks, prior to a large event, followed by a tail of decreasing activity, or aftershocks. These recurrent large events occur at regular intervals and the characteristic time between events and their magnitude are a function of the stress dissipation parameter. The relative length of the foreshock to aftershock sequence depends on the amount of stress dissipation in the system. This work provides further evidence that the spatial and temporal patterns observed in natural seismicity are strongly influenced by the underlying physical properties and are not solely the result of a simple cascade mechanism. We find that the scaling depends not only on the amount of damage, but also on the spatial distribution of that damage (Dominguez et al., 2011; Kazemian et al., 2014). Here we compare the modeled sequences to those of natural earthquake sequences from California and around the world in order to investigate the interplay between cascade dynamics and spatial structure.

  14. Spherical Indentation Techniques for Creep Property Evaluation Considering Transient Creep

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Dongkyu; Kim, Minsoo; Lee, Hyungyil [Sogang Univ., Seoul, (Korea, Republic of); Lee, Jin Haeng [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-11-15

    Creep through nanoindentations has attracted increasing research attention in recent years. Many studies related to indentation creep tests, however, have simply focused on the characteristics of steady-state creep, and there exist wide discrepancies between the uniaxial test and the indentation test. In this study, we performed a computational simulation of spherical indentations, and we proposed a method for evaluating the creep properties onsidering transient creep. We investigated the material behavior with variation of creep properties and expressed it using regression equations for normalized variables. We finally developed a program to evaluate the creep properties considering transient creep. By using the proposed method, we successfully obtained creep exponents with an average error less than 1.1 and creep coefficients with an average error less than 2.3 from the load-depth curve.

  15. Spherical Indentation Techniques for Creep Property Evaluation Considering Transient Creep

    International Nuclear Information System (INIS)

    Lim, Dongkyu; Kim, Minsoo; Lee, Hyungyil; Lee, Jin Haeng

    2013-01-01

    Creep through nanoindentations has attracted increasing research attention in recent years. Many studies related to indentation creep tests, however, have simply focused on the characteristics of steady-state creep, and there exist wide discrepancies between the uniaxial test and the indentation test. In this study, we performed a computational simulation of spherical indentations, and we proposed a method for evaluating the creep properties onsidering transient creep. We investigated the material behavior with variation of creep properties and expressed it using regression equations for normalized variables. We finally developed a program to evaluate the creep properties considering transient creep. By using the proposed method, we successfully obtained creep exponents with an average error less than 1.1 and creep coefficients with an average error less than 2.3 from the load-depth curve

  16. Master-slave robotic system for needle indentation and insertion.

    Science.gov (United States)

    Shin, Jaehyun; Zhong, Yongmin; Gu, Chengfan

    2017-12-01

    Bilateral control of a master-slave robotic system is a challenging issue in robotic-assisted minimally invasive surgery. It requires the knowledge on contact interaction between a surgical (slave) robot and soft tissues. This paper presents a master-slave robotic system for needle indentation and insertion. This master-slave robotic system is able to characterize the contact interaction between the robotic needle and soft tissues. A bilateral controller is implemented using a linear motor for robotic needle indentation and insertion. A new nonlinear state observer is developed to online monitor the contact interaction with soft tissues. Experimental results demonstrate the efficacy of the proposed master-slave robotic system for robotic needle indentation and needle insertion.

  17. Single-asperity contributions to multi-asperity wear simulated with molecular dynamics

    International Nuclear Information System (INIS)

    Eder, S J; Cihak-Bayr, U; Bianchi, D

    2016-01-01

    We use a molecular dynamics approach to simulate the wear of a rough ferrite surface due to multiple hard, abrasive particles under variation of normal pressure, grinding direction, and particle geometry. By employing a clustering algorithm that incorporates some knowledge about the grinding process such as the main grinding direction, we can break down the total wear volume into contributions from the individual abrasive particles in a time-resolved fashion. The resulting analysis of the simulated grinding process allows statements on wear particle generation, distribution, and stability depending on the initial topography, the grinding angle, the normal pressure, as well as the abrasive shape and orientation with respect to the surface. (paper)

  18. Indentation in the Right Ventricle by an Incomplete Pericardium on 3-Dimensional Reconstructed Computed Tomography

    Directory of Open Access Journals (Sweden)

    Hak Ju Kim

    2017-08-01

    Full Text Available We report the case of a 17-year-old girl who presented with an indentation in the right ventricle caused by an incomplete pericardium on preoperative 3-dimensional reconstructed computed tomography. She was to undergo surgery for a partial atrioventricular septal defect and secundum atrial septal defect. Preoperative electrocardiography revealed occasional premature ventricular beats. We found the absence of the left side of the pericardium intraoperatively, and this absence caused strangulation of the diaphragmatic surface of the right ventricle. After correcting the lesion, the patient’s rhythm disturbances improved.

  19. Primeiro registro de Bothriurus asper Pocock (Scorpiones, Bothriuridae no Distrito Federal, Brasil First record of Bothriurus asper Pocock (Scorpiones, Bothriuridae in Federal District, Brazil

    Directory of Open Access Journals (Sweden)

    Paulo C. Motta

    2006-03-01

    Full Text Available Dez indivíduos do escorpião Bothriurus asper Pocock, 1893, conhecido de alguns estados do nordeste brasileiro, foram encontrados em áreas urbanas próximas à Brasília, Distrito Federal. Provavelmente, esta espécie foi introduzida pela atividade humana.Ten individuals of the scorpion Bothriurus asper Pocock, 1893 from states of Northeast Brazil was found in urban areas near Brasília, Federal District. This species was probably introduced by human activity.

  20. Inhibition of myotoxic activity of Bothrops asper myotoxin II by the anti-trypanosomal drug suramin.

    Science.gov (United States)

    Murakami, Mário T; Arruda, Emerson Z; Melo, Paulo A; Martinez, Ana B; Calil-Eliás, Sabrińa; Tomaz, Marcelo A; Lomonte, Bruno; Gutiérrez, José M; Arni, Raghuvir K

    2005-07-15

    Suramin, a synthetic polysulfonated compound, developed initially for the treatment of African trypanosomiasis and onchocerciasis, is currently used for the treatment of several medically relevant disorders. Suramin, heparin, and other polyanions inhibit the myotoxic activity of Lys49 phospholipase A2 analogues both in vitro and in vivo, and are thus of potential importance as therapeutic agents in the treatment of viperid snake bites. Due to its conformational flexibility around the single bonds that link the central phenyl rings to the secondary amide backbone, the symmetrical suramin molecule binds by an induced-fit mechanism complementing the hydrophobic surfaces of the dimer and adopts a novel conformation that lacks C2 symmetry in the dimeric crystal structure of the suramin-Bothrops asper myotoxin II complex. The simultaneous binding of suramin at the surfaces of the two monomers partially restricts access to the nominal active sites and significantly changes the overall charge of the interfacial recognition face of the protein, resulting in the inhibition of myotoxicity.

  1. Rigid indented cylindrical cathode for X-ray tube

    Science.gov (United States)

    Hudgens, Claude R.

    1985-01-01

    A cathode assembly for a vacuum tube includes a wire filament, a straight bular anode parallel to and surrounding the wire filament, and insulating spacers for rigidly fastening the filament with respect to the anode, and with one side of the anode indented or flattened such that only one portion of the anode is heated to emitting temperatures by the filament.

  2. Image analysis of moving seeds in an indented cylinder

    DEFF Research Database (Denmark)

    Buus, Ole; Jørgensen, Johannes Ravn

    2010-01-01

    inspection in seed cleaning equipment. A prototype of an indented cylinder will be constructed. To make it more dynamic, the cylinder itself will be manufactured using 3D printing technology. The input will come either from 3D scans of existing cylinders or by defining their topology using parametric B...

  3. Indentation fatigue in silicon nitride, alumina and silicon carbide ...

    Indian Academy of Sciences (India)

    Unknown

    ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 µm and. 25 µm, and a sintered silicon ... the sintered silicon carbide was found out to be linked to its previous thermal history. Keywords. Indentation fatigue .... This presence of a grain size effect in the RIF behaviour of the ...

  4. Hardness and elasticity of abrasive particles measured by instrumented indentation

    Czech Academy of Sciences Publication Activity Database

    Hvizdoš, P.; Zeleňák, Michal; Hloch, Sergej

    2016-01-01

    Roč. 8, č. 1 (2016), s. 869-871 ISSN 1805-0476 Institutional support: RVO:68145535 Keywords : abrasive * garnet * hardness * elasticity * instrumental indentation Subject RIV: JQ - Machines ; Tools http://www.mmscience.eu/content/file/archives/MM_Science_201601.pdf

  5. Buckling of Single-Crystal Silicon Nanolines under Indentation

    Directory of Open Access Journals (Sweden)

    Min K. Kang

    2008-01-01

    Full Text Available Atomic force microscope-(AFM- based indentation tests were performed to examine mechanical properties of parallel single-crystal silicon nanolines (SiNLs of sub-100-nm line width, fabricated by a process combining electron-beam lithography and anisotropic wet etching. The SiNLs have straight and nearly atomically flat sidewalls, and the cross section is almost perfectly rectangular with uniform width and height along the longitudinal direction. The measured load-displacement curves from the indentation tests show an instability with large displacement bursts at a critical load ranging from 480 μN to 700 μN. This phenomenon is attributed to a transition of the buckling mode of the SiNLs under indentation. Using a set of finite element models with postbuckling analyses, we analyze the indentation-induced buckling modes and investigate the effects of tip location, contact friction, and substrate deformation on the critical load of mode transition. The results demonstrate a unique approach for the study of nanomaterials and patterned nanostructures via a combination of experiments and modeling.

  6. Prediction of Indentation Behavior of Superelastic TiNi

    Science.gov (United States)

    Neupane, Rabin; Farhat, Zoheir

    2014-09-01

    Superelastic TiNi shape memory alloys have been extensively used in various applications. The great interest in TiNi alloys is due to its unique shape memory and superelastic effects, along with its superior wear and dent resistance. Assessment of mechanical properties and dent resistance of superelastic TiNi is commonly performed using indentation techniques. However, the coupling of deformation and reversible martensitic transformation of TiNi under indentation conditions makes the interpretation of results challenging. An attempt is made to enhance current interpretation of indentation data. A load-depth curve is predicted that takes into consideration the reversible martensitic transformation. The predicted curve is in good agreement with experimental results. It is found in this study that the elastic modulus is a function of indentation depth. At shallow depths, the elastic modulus is high due to austenite dominance, while at high depths, the elastic modulus drops as the depth increases due to austenite to martensite transition, i.e., martensite dominance. It is also found that TiNi exhibits superior dent resistance compared to AISI 304 steel. There is two orders of magnitude improvement in dent resistance of TiNi in comparison to AISI 304 steel.

  7. Indentation fatigue in silicon nitride, alumina and silicon carbide ...

    Indian Academy of Sciences (India)

    Repeated indentation fatigue (RIF) experiments conducted on the same spot of different structural ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 m and 25 m, and a sintered silicon carbide (SSiC) are reported. The RIF experiments were conducted using a Vicker's ...

  8. Application of the method of dimensionality reduction to simulate the fretting wear of anisotropic indenter

    Science.gov (United States)

    Dmitriev, A. I.

    2015-10-01

    In the paper we consider the fretting wear of two contacting bodies (indenter and half-space). Due to heterogeneity the indenter in contact area can have different mechanical properties. With an increasing number of cycles, the wear profile tends towards a limiting shape, in which no further wear occurs. Nonlinear dependence between final wear volume and indenter shear modulus was found. In accordance with our results the soft indenter provides less wear volume under fretting wear.

  9. Residual stress estimation of ceramic thin films by X-ray diffraction and indentation techniques

    International Nuclear Information System (INIS)

    Atar, Erdem; Sarioglu, Cevat; Demirler, Ugur; Sabri Kayali, E.; Cimenoglu, Huseyin

    2003-01-01

    The residual stresses in ceramic thin films obtained by the indentation method have been found to be three times higher than those of the X-ray diffraction method. This discrepancy can be eliminated by setting the geometrical factor for the Vickers pyramid indenter to 1 in the relevant equation of the indentation method

  10. Teknologi Ukir Krawangan pada Bambu Betung (Dendrocalamus Asper

    Directory of Open Access Journals (Sweden)

    Edi Eskak

    2016-04-01

    Full Text Available ABSTRAKBambu betung (dendrocalamus asper merupakan jenis bambu besar dan berbuluh tebal yang di Indonesia potensinya masih cukup melimpah. Bambu betung memiliki kesulitan dalam pengerjaan ukir. Pelaksanaan kegiatan ujicoba pembuatan aksesoris interior dengan teknik ukir krawangan pada bambu betung ini, prosesnya terdiri dari: persiapan bahan (pemotongan, pengawetan dan pengeringan, perancangan desain produk (sumber inspirasi, sketsa alternatif dan gambar kerja, serta pembuatan produk (meliputi: pembentukan global/awal, pembuatan krawangan, pengukiran dan finishing. Dari hasil penelitian menunjukkan bahwa teknik pelobangan (krawangan dengan bor 4 kali lobang kemudian diteruskan dengan gergaji hand jigsaw didapatkan kecepatan rata-rata (4 x 5.1 + 20 = 40,4 detik untuk ukuran lubang 3 – 4 cm, tebal 1,5 cm bentuk variasi lurus lengkung, pada kondisi bambu setengah basah (magel. Ini berarti 5 kali lebih cepat dari pada pemahatan manual (209.1 detik, serta hasil yang didapat lebih rapi dan lebih bersih. Kondisi terbaik untuk pembuatan krawangan adalah kondisi setengah basah (magel yaitu kadar air bambu 30-60%. Kata kunci : bambu betung, ukir krawangan, aksesoris interior.ABSTRACTDendrocalamus Asper (Betung Bamboo is a type of bamboo with thick culm wall, which is have good potential in Indonesia but the utilization still relatively abundant. Betung Bamboo also has a weakness and difficulty in carving, that will be investigated to find a solution from this study. In the implementation of pilot activities to the manufacture of interior accessories krawangan on Betung bamboo carving techniques, the process consists of: preparation of materials (cutting, curing and drying, the design ofthe product design (the source of inspiration, sketches and working drawings alternative, and manufacturing products (including : the formation of global / scratch, making krawangan, carving and finishing. Fromthe results showed that the holling technique (krawangan with

  11. Present coupling along the Peruvian subduction asperity that devastated Lima while breaking during the 1746 earthquake

    Science.gov (United States)

    Cavalié, O.; Chlieh, M.; Villegas Lanza, J. C.

    2017-12-01

    Subduction zone are particularly prone to generating large earthquakes due to its wide lateral extension. In order to understand where, and possibly when, large earthquakes will occur, interseismic deformation observation is a key information because it allows to map asperities that accumulate stress on the plate interface. South American subduction is one of the longest worldwide, running all along the west coast of the continent. Combined with the relatively fast convergence rate between the Nazca plate and the South American continent, Chile and Peru experience regularly M>7.5 earthquakes. In this study, we focused on the Peruvian subduction margin and more precisely on the Central segment containing Lima where the seismic risk is the highest in the country due the large population that lives in the Peruvian capital. On the Central segment (10°S and 15°S), we used over 50 GPS interseismic measurements from campaign and continuous sites, as well as InSAR data to map coupling along the subduction interface. GPS data come from the Peruvian GPS network and InSAR data are from the Envisat satellite. We selected two tracks covering the central segment (including Lima) and with enough SAR image acquisitions between 2003 and 2010 to get a robust deformation estimation. GPS and InSAR data show a consistent tectonic signal with a maximum of surface displacement by the coast: the maximum horizontal velocities from GPS is about 20 mm and InSAR finds 12-13 mm in the LOS component. In addition, InSAR reveals lateral variations along the coast: the maximum motion is measured around Lima (11°S) and fades on either side. By inverting the geodetic data, we were able to map the coupling along the segment. It results in a main asperity where interseismic stress is loading. However, compared the previous published models based on GPS only, the coupling in the central segment seems more heterogeneous. Finally, we compared the deficit of seismic moment accumulating in the

  12. Tribology. Mechanisms of antiwear tribofilm growth revealed in situ by single-asperity sliding contacts.

    Science.gov (United States)

    Gosvami, N N; Bares, J A; Mangolini, F; Konicek, A R; Yablon, D G; Carpick, R W

    2015-04-03

    Zinc dialkyldithiophosphates (ZDDPs) form antiwear tribofilms at sliding interfaces and are widely used as additives in automotive lubricants. The mechanisms governing the tribofilm growth are not well understood, which limits the development of replacements that offer better performance and are less likely to degrade automobile catalytic converters over time. Using atomic force microscopy in ZDDP-containing lubricant base stock at elevated temperatures, we monitored the growth and properties of the tribofilms in situ in well-defined single-asperity sliding nanocontacts. Surface-based nucleation, growth, and thickness saturation of patchy tribofilms were observed. The growth rate increased exponentially with either applied compressive stress or temperature, consistent with a thermally activated, stress-assisted reaction rate model. Although some models rely on the presence of iron to catalyze tribofilm growth, the films grew regardless of the presence of iron on either the tip or substrate, highlighting the critical role of stress and thermal activation. Copyright © 2015, American Association for the Advancement of Science.

  13. Influence of the molecular structure on indentation size effect in polymers

    International Nuclear Information System (INIS)

    Han, Chung-Souk

    2010-01-01

    Size dependent deformation of polymers has been observed by various researchers in various experimental settings including micro beam bending, foams and indentation testing. Here in this article the indentation size effect in polymers is examined which manifests itself in increased hardness at decreasing indentation depths. Based on previously suggested rationale of size dependent deformation and depth dependent hardness model the depth dependent hardness of various polymers are analyzed. It is found that polymers containing aromatic rings in their molecular structure exhibit depth dependent hardness above the micron length scale. For polymers not containing aromatic rings polymers the indentation size effect starts at smaller indentation depths if they are present at all.

  14. Asperity characteristics of the Olami-Feder-Christensen model of earthquakes

    International Nuclear Information System (INIS)

    Kawamura, Hikaru; Yamamoto, Takumi; Kotani, Takeshi; Yoshino, Hajime

    2010-01-01

    Properties of the Olami-Feder-Christensen (OFC) model of earthquakes are studied by numerical simulations. The previous study indicated that the model exhibited 'asperity'-like phenomena, i.e., the same region ruptures many times near periodically [T. Kotani et al., Phys. Rev. E 77, 010102(R) (2008)]. Such periodic or characteristic features apparently coexist with power-law-like critical features, e.g., the Gutenberg-Richter law observed in the size distribution. In order to clarify the origin and the nature of the asperity-like phenomena, we investigate here the properties of the OFC model with emphasis on its stress distribution. It is found that the asperity formation is accompanied by self-organization of the highly concentrated stress state. Such stress organization naturally provides the mechanism underlying our observation that a series of asperity events repeat with a common epicenter site and with a common period solely determined by the transmission parameter of the model. Asperity events tend to cluster both in time and in space.

  15. Full-Field Indentation Damage Measurement Using Digital Image Correlation

    Directory of Open Access Journals (Sweden)

    Elías López-Alba

    2017-07-01

    Full Text Available A novel approach based on full-field indentation measurements to characterize and quantify the effect of contact in thin plates is presented. The proposed method has been employed to evaluate the indentation damage generated in the presence of bending deformation, resulting from the contact between a thin plate and a rigid sphere. For this purpose, the 3D Digital Image Correlation (3D-DIC technique has been adopted to quantify the out of plane displacements at the back face of the plate. Tests were conducted using aluminum thin plates and a rigid bearing sphere to evaluate the influence of the thickness and the material behavior during contact. Information provided by the 3D-DIC technique has been employed to perform an indirect measurement of the contact area during the loading and unloading path of the test. A symmetrical distribution in the contact damage region due to the symmetry of the indenter was always observed. In the case of aluminum plates, the presence of a high level of plasticity caused shearing deformation as the load increased. Results show the full-field contact damage area for different plates’ thicknesses at different loads. The contact damage region was bigger when the thickness of the specimen increased, and therefore, bending deformation was reduced. With the proposed approach, the elastic recovery at the contact location was quantified during the unloading, as well as the remaining permanent indentation damage after releasing the load. Results show the information obtained by full-field measurements at the contact location during the test, which implies a substantial improvement compared with pointwise techniques.

  16. Characterization of Rubbers from Spherical Punch - Plate Indentation Tests

    Directory of Open Access Journals (Sweden)

    Florina Carmen Ciornei

    2016-12-01

    Full Text Available Rubber plates with different compositions and hardness were tested by continuous indentation, using a spherical punch and hysteretic phenomenon was evidenced. The experimental data interpolation with polynomial functions is accurate and permits estimation of the lost work during loading cycles. The interpolation by power law functions is more convenient by using less parameters and having a form accepted in literature. From the rubbers tested, two were considered to present good damping properties.

  17. Extraordinary Indentation Strain Stiffening Produces Superhard Tungsten Nitrides

    Science.gov (United States)

    Lu, Cheng; Li, Quan; Ma, Yanming; Chen, Changfeng

    2017-09-01

    Transition-metal light-element compounds are a class of designer materials tailored to be a new generation of superhard solids, but indentation strain softening has hitherto limited their intrinsic load-invariant hardness to well below the 40 GPa threshold commonly set for superhard materials. Here we report findings from first-principles calculations that two tungsten nitrides, hP4-WN and hP 6 -WN2 , exhibit extraordinary strain stiffening that produces remarkably enhanced indentation strengths exceeding 40 GPa, raising exciting prospects of realizing the long-sought nontraditional superhard solids. Calculations show that hP4-WN is metallic both at equilibrium and under indentation, marking it as the first known intrinsic superhard metal. An x-ray diffraction pattern analysis indicates the presence of hP4-WN in a recently synthesized specimen. We elucidate the intricate bonding and stress response mechanisms for the identified structural strengthening, and the insights may help advance rational design and discovery of additional novel superhard materials.

  18. Extrinsic stretching narrowing and anterior indentation of the rectosigmoid junction

    International Nuclear Information System (INIS)

    Schulman, A.; Fataar, S.

    1979-01-01

    Thirty-five cases of extrinsic narrowing or anterior indentation of the rectosigmoid junction (RSJ) have been studied. The RSJ lies directly behind the pouch of Douglas which is a favoured site for peritoneal metastasis, abscess and endometriosis. Any space-occupying lesion of sufficient size at this site will indent the anterior aspects of the RSJ. Causes include distension or tumour of the ileum or sigmoid colon, gross ascites (when the patient is erect), and tumours below the pelvic peritonium, such as gynaecological neoplasm and internal iliac artery aneurysm. When a desmoplastic metastasis in the pouch of Douglas infiltrates the outer layers of the RSJ, the fibrosis produces an eccentric shortening on its anterior aspect, which in turn causes a pleating of the mucosa with the folds radiating towards the shortened area. This is also seen with primary pelvic carcinomas directly adherent to the rectum, endometriosis with repeated bleeding and increasing eccentric, submucosal fibrosis, and chronic abscess in the pouch of Douglas. Not all extrinsic narrowing of the RSJ are pathological. One case of anterior indentation followed operation for rectal prolapse. Ten additional cases showed narrowing due to a technical artefact air-distended colon rising into the upper abdomen to cause stretching at the RSJ. As with ascites, this narrowing due to 'high-rise sigmoid' disappeared when the patients became recumbent and the colonic air redistributed. (author)

  19. Relationship between thin-film bond strength as measured by a scratch test, and indentation hardness for bonding agents.

    Science.gov (United States)

    Kusakabe, Shusuke; Rawls, H Ralph; Hotta, Masato

    2016-03-01

    To evaluate thin-film bond strength between a bonding agent and human dentin, using a scratch test, and the characteristics and accuracy of measurement. One-step bonding agents (BeautiBond; Bond Force; Adper Easy Bond; Clearfil tri-S Bond) and two-step bonding agents (Cleafil SE Bond; FL-Bond II) were investigated in this study. Flat dentin surfaces were prepared for extracted human molars. The dentin surfaces were ground and bonding agents were applied and light cured. The thin-film bond strength test of the specimens was evaluated by the critical load at which the coated bonding agent failed and dentin appeared. The scratch mark sections were then observed under a scanning electron microscope. Indentation hardness was evaluated by the variation in depth under an applied load of 10gf. Data were compared by one-way ANOVA with the Scheffé's post hoc multiple comparison test (pstrength and indentation hardness were analyzed using analysis of correlation and covariance. The thin-film bond strength of two-step bonding agents were found to be significantly higher than that of one-step bonding agents with small standard deviations. Scratch marks consistently showed adhesive failure in the vicinity of the bonding agent/dentin interface. The indentation hardness showed a trend that two-step bonding agents have greater hardness than one-step bonding agents. A moderately significant correlation (r(2)=0.31) was found between thin-film bond strength and indentation hardness. Thin-film bond strength test is a valid and reliable means of evaluating bond strength in the vicinity of the adhesive interface and is more accurate than other methods currently in use. Further, the thin-film bond strength is influenced by the hardness of the cued bonding agent. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. Static Indentation Load Capacity of the Superelastic 60NiTi for Rolling Element Bearings

    Science.gov (United States)

    DellaCorte, Christopher; Moore, Lewis E., III; Clifton, Joshua S.

    2012-01-01

    The nickel-rich, binary nickel-titanium alloys, such as 60NiTi (60Ni-40Ti by wt%), are emerging as viable materials for use in mechanical components like rolling element bearings and gears. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (approx.100 GPa). These properties result in the potential to endure extremely high indentation loads such as those encountered in bearings, gears and other mechanical components. In such applications, quantifying the load that results in permanent deformation that can affect component performance and life is important. In this paper, the static load capacity is measured by conducting indentation experiments in which 12.7 mm diameter balls made from the ceramic Si3N4 are pressed into highly polished, hardened 60NiTi flat plates. Hertz stress calculations are used to estimate contact stress. The results show that the 60NiTi surface can withstand an approximately 3400 kN load before significant denting (>0.6 microns deep) occurs. This load capacity is approximately twice that of high performance bearing steels suggesting that the potential exists to make highly resilient bearings and components from such materials.

  1. The analgesics morphine and tramadol do not alter the acute toxicity induced by Bothrops asper snake venom in mice

    OpenAIRE

    Gutiérrez, José María; Herrera Arias, Cristina

    2014-01-01

    Analgesics tramadol and morphine were used in mice injected with Bothrops asper venom. Analgesics did not alter the acute toxicity of B. asper venom in mice. Precautionary (prophylactic) analgesia should be introduced routinely in Toxinology. UCR::Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP)

  2. Analysis of the equivalent indenter concept used to extract Young’s modulus from a nano-indentation test: some new insights into the Oliver–Pharr method

    DEFF Research Database (Denmark)

    Andriollo, Tito; Thorborg, Jesper; Hattel, Jesper Henri

    2017-01-01

    on an equivalent conical indenter whose semi-apical angle depends on the ratio between residual and total penetration. Specifically, this angle tends to 90° when the material exhibits extensive inelastic deformation, whereas it reduces to the one characteristic of the real indenter for a perfectly elastic material...

  3. Assessment of the Local Residual Stresses of 7050-T7452 Aluminum Alloy in Microzones by the Instrumented Indentation with the Berkovich Indenter

    Science.gov (United States)

    He, M.; Huang, C. H.; Wang, X. X.; Yang, F.; Zhang, N.; Li, F. G.

    2017-10-01

    The local residual stresses in microzones are investigated by the instrumented indentation method with the Berkovich indenter. The parameters required for determination of residual stresses are obtained from indentation load-penetration depth curves constructed during instrumented indentation tests on flat square 7050-T7452 aluminum alloy specimens with a central hole containing the compressive residual stresses generated by the cold extrusion process. The force balance system with account of the tensile and compressive residual stresses is used to explain the phenomenon of different contact areas produced by the same indentation load. The effect of strain-hardening exponent on the residual stress is tuned-off by application of the representative stress σ_{0.033} in the average contact pressure assessment using the Π theorem, while the yield stress value is obtained from the constitutive function. Finally, the residual stresses are calculated according to the proposed equations of the force balance system, and their feasibility is corroborated by the XRD measurements.

  4. The Effect of Indenter Ball Radius on the Static Load Capacity of the Superelastic 60NiTi for Rolling Element Bearings

    Science.gov (United States)

    DellaCorte, Christopher; Moore, Lewis E., III; Clifton, Joshua S.

    2014-01-01

    Static load capacity is a critical design parameter for rolling element bearings used in space mechanisms because of the potential for Brinell (surface dent) damage due to shock and vibration loading events during rocket launch. Brinell damage to bearing raceways can lead to torque variations (noise) and reduced bearing life. The growing use of ceramic rolling elements with high stiffness in hybrid bearings exacerbates the situation. A new family of hard yet resilient materials based upon nickel-titanium is emerging to address such bearing challenges. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (approx. 100 GigaPascals) and has been shown to endure higher indentation loads than conventional and high performance steel. Indentation load capacity has been reported for relatively large (12.7 millimeters diameter) ceramic (Si3N4) indenter balls pressed against flat plates of 60NiTi. In order to develop damage load threshold criteria applicable to a wide range of bearing designs and sizes, the effects of indenter ball radius and the accuracy of interpolation of the Hertz contact stress relations for 60NiTi must be ascertained. In this paper, results of indentation tests involving ceramic balls ranging from 6.4 to 12.7 mm in diameter and highly polished 60NiTi flat plates are presented. When the resulting dent depth data for all the indenter ball sizes are normalized using the Hertz equations, the data (dent depth versus stress) are comparable. Thus when designing bearings made from 60NiTi, the Hertz stress relations can be applied with relative confidence over a range of rolling element sizes and internal geometries.

  5. On the relationship between indentation hardness and modulus, and the damage resistance of biological materials.

    Science.gov (United States)

    Labonte, David; Lenz, Anne-Kristin; Oyen, Michelle L

    2017-07-15

    The remarkable mechanical performance of biological materials is based on intricate structure-function relationships. Nanoindentation has become the primary tool for characterising biological materials, as it allows to relate structural changes to variations in mechanical properties on small scales. However, the respective theoretical background and associated interpretation of the parameters measured via indentation derives largely from research on 'traditional' engineering materials such as metals or ceramics. Here, we discuss the functional relevance of indentation hardness in biological materials by presenting a meta-analysis of its relationship with indentation modulus. Across seven orders of magnitude, indentation hardness was directly proportional to indentation modulus. Using a lumped parameter model to deconvolute indentation hardness into components arising from reversible and irreversible deformation, we establish criteria which allow to interpret differences in indentation hardness across or within biological materials. The ratio between hardness and modulus arises as a key parameter, which is related to the ratio between irreversible and reversible deformation during indentation, the material's yield strength, and the resistance to irreversible deformation, a material property which represents the energy required to create a unit volume of purely irreversible deformation. Indentation hardness generally increases upon material dehydration, however to a larger extent than expected from accompanying changes in indentation modulus, indicating that water acts as a 'plasticiser'. A detailed discussion of the role of indentation hardness, modulus and toughness in damage control during sharp or blunt indentation yields comprehensive guidelines for a performance-based ranking of biological materials, and suggests that quasi-plastic deformation is a frequent yet poorly understood damage mode, highlighting an important area of future research. Instrumented

  6. A dual triangular pyramidal indentation technique based on FEA solutions for Material property evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Minsoo; Hyun, Hong Chul [Sogana Univ., Seoul (Korea, Republic of); Lee, Jin Haeng; Lee, Hyungyil [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-01-15

    In this study, we suggest a method for material property evaluation by dual triangular pyramidal indenters using the reverse analysis. First, we demonstrated that load displacement curves of conical and triangular pyramidal indenters are different for the same material. For this reason, an independent research on the triangular pyramidal indenter is needed. From FE indentation analyses on various materials, we then investigated the relationships among material properties, indentation parameters and load displacement curves. From this, we established property evaluation formula using dual triangular pyramidal indenters having two different half included angles. The approach provides the values of elastic modulus, yield strength and strain hardening exponent within an average error of 3% for various materials.

  7. The role of the skin microrelief in the contact behaviour of human skin: contact between the human finger and regular surface textures

    NARCIS (Netherlands)

    van Kuilenburg, Julien; Masen, Marc Arthur; van der Heide, Emile

    2013-01-01

    The friction behaviour of the human fingerpad as a function of asperity geometry was investigated experimentally. Surface textures consisting of evenly distributed spherically tipped asperities were used for in vivo testing. Using analytical expressions, a multi-scale model was developed to explain

  8. Indentation size effect of Y-TZP dental ceramics.

    Science.gov (United States)

    Majić Renjo, Marijana; Ćurković, Lidija; Štefančić, Sanja; Ćorić, Danko

    2014-12-01

    The purpose of this study was to investigate and analyze the indentation size effect (ISE) in Vickers hardness of monolithic yttria partially stabilized zirconia (Y-TZP) dental ceramics without and with the addition of dental dye A3. The ISE is analyzed using the Mayer law, a proportional specimen resistance (PSR) model and a modified proportional specimen resistance (MPSR) model. Two samples of Y-TZP dental ceramics, trade names BruxZir (provided by Glidewell Laboratories, CA, USA), were investigated. The first sample was polished Y-TZP and the second sample was polished Y-TZP with the addition of dental dye A3, by VITA Classical Shade Guide. The Vickers hardness was measured under the following loads: 0.49N, 0.98N, 1.96N, 4.90, 9.81N and 29.42N. Thirty indentations were made on each sample, under each load. Relationships between the applied load, F, and the resulting indentation size, d, have been analyzed by the Mayer law, the PSR model and the MPSR model. The Meyer index (n) for both Y-TZP dental ceramics is less than 2, which indicates that hardness is dependent on test loads. The PSR model and the MPSR model were used to calculate "true" Vickers hardness or load-independent hardness. All applied mathematical models are suitable for the data analysis, which is confirmed with high correlation coefficients, but the best correlation between measured values and mathematical models was achieved with the MPSR model with a correlation coefficient of 0.9999. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. EVALUATION OF METALLIC MATERIALS PLASTICITY BY DYNAMIC INDENTATION METHOD

    Directory of Open Access Journals (Sweden)

    V. A. Rudnitsky

    2017-01-01

    Full Text Available The method of plasticity test of metallic materials realized by means of a dynamic dimpling of material by a spherical tip is offered. The measured value of plasticity is defined by a ratio of plastic and complete deformations in the formed indentation which considers influence of an elastic modulus of material. The dependence connecting plasticity and dynamic hardness of materials is received. Experiments on metals from 70 to 380 GPA having an elastic modulus and hardness up to 62 HRC are made.

  10. Optical measuring system for the geometrical parameters of Rockwell and Vickers diamond hardness indenters

    Science.gov (United States)

    Zhang, Liqiong; Cui, Yuanyuan; Zhang, Feng

    2017-11-01

    Hardness testing is widely used for characterizing the mechanical properties of materials. However, the measured hardness values in hardness measurements are strongly influenced by the geometrical parameters of diamond hardness indenters. In the most severe case, the geometrical error of the diamond indenter, Rockwell hardness measurements in particular, leads to be about 50% hardness measurement uncertainty. It has been generally recognized for many years that the geometry of diamond indenters must be calibrated or verified before use to correct the hardness value for each indenter and improve the hardness measurement uncertainty. The contact-based calibration methods and the contactless based optical measuring methods are two typical ways to calibrate the geometrical form of an indenter at present. The contact-based calibration methods characterized by large measurement range of tens of mm with nanometer resolution, has a time-consuming measurement process, the contactless based optical measuring methods have become a general trend. In this work, an optical measuring system, which employs the combination of an interferometric microscope and a profile projection technique, is presented to measure and calibrate the geometrical parameters of Rockwell and Vickers diamond hardness indenters in National Institute of Metrology of China. Initial experiments demonstrated that the angle and axis angle measurement of indenter are achieved with accuracy of 0.1°, the straightness deviation of Rockwell indenters is less than 2μm, the radius measurement uncertainty of the tip of Rockwell indenters is better than 5μm.

  11. Requirements for investigating the temperature-dependent fracture behavior of irradiated materials by indentation

    Energy Technology Data Exchange (ETDEWEB)

    Sacksteder, Irène, E-mail: irene.sacksteder@kit.edu [Karlsruhe Institute of Technology, Institute for Applied Materials, Eggenstein-Leopoldshafen (Germany); Hostettler, Simon [Synton-MDP Inc., Nidau (Switzerland); Charbonneau, Grégoire; Albinski, Bartlomiej; Schneider, Hans-Christian [Karlsruhe Institute of Technology, Institute for Applied Materials, Eggenstein-Leopoldshafen (Germany)

    2013-10-15

    Highlights: • A custom-made indenter is designed for indentations at high temperature. • The instrumented indentation technique at high temperature will be used to investigate temperature dependent fracture mechanisms in structural materials. • A finite-element based model has been validated with a view to predict crack initiation and propagation in Eurofer97 and tungsten-like materials. -- Abstract: The instrumented indentation technique is an interesting testing tool to examine temperature-dependent fracture mechanisms. It is planned to be used to generate cracks at defined temperatures in hard and brittle metallic materials. The present study describes the properties needed for the use of a new type of indenter operating at high temperature. The indenter was designed to meet mechanical and thermal requirements and other constraints relating to the operation of functional units of the indentation instrument. Additionally, a finite element model has been built with a view to predict indentation induced cracks in Eurofer97 and tungsten. The model has been validated both with the theory of Hertz and experimentally by comparison with indentation curves.

  12. Progress in Indentation Study of Materials via Both Experimental and Numerical Methods

    Directory of Open Access Journals (Sweden)

    Mao Liu

    2017-10-01

    Full Text Available Indentation as a method to characterize materials has a history of more than 117 years. However, to date, it is still the most popular way to measure the mechanical properties of various materials at microscale and nanoscale. This review summarizes the background and the basic principle of processing by indentation. It is demonstrated that indentation is an effective and efficient method to identify mechanical properties, such as hardness, Young’s modulus, etc., of materials at smaller scale, when the traditional tensile tests could not be applied. The review also describes indentation process via both experimental tests and numerical modelling in recent studies.

  13. Ontogenetic variability of Bothrops atrox and Bothrops asper snake venoms from Colombia.

    Science.gov (United States)

    Saldarriaga, Mónica María; Otero, Rafael; Núñez, Vitelbina; Toro, Maria Fabiola; Díaz, Abel; Gutiérrez, José María

    2003-09-15

    The lancehead snakes Bothrops asper and Bothrops atrox inflict 70-90% of the 3000 bites reported every year in Colombia. In this work, the venoms of B. atrox from Meta (Villavicencio, 33 specimens) and B. asper from Antioquia (San Carlos, 45 specimens), all of them born in captivity, were obtained at different ages (0-6 months; 1, 2 and 3-years old) and compared in terms of their pharmacological and immunochemical characteristics. A conspicuous ontogenetic variability was observed in venom samples from both species. Venoms from newborn and juvenile specimens showed higher lethal, hemorrhagic, edema-forming and coagulant activities, whereas venoms from 3-year old specimens showed higher indirect hemolytic, i.e. phospholipase A2 activity, being more significant in the case of B. asper. SDS-polyacrylamide gel electrophoresis of whole venom for both species evidenced a predominance of high mol. mass bands in the venoms from specimens of asper of <6 months and in those from 3-year old specimens. Venom of adult specimens showed a higher number of peaks with indirect hemolytic activity than venom of newborn specimens. Polyvalent antivenom produced in Costa Rica recognized all the bands of both venoms from specimens at all ages tested, when assayed by Western blotting.

  14. Snake venomics of the lancehead pitviper Bothrops asper: geographic, individual, and ontogenetic variations.

    Science.gov (United States)

    Alape-Girón, Alberto; Sanz, Libia; Escolano, José; Flores-Díaz, Marietta; Madrigal, Marvin; Sasa, Mahmood; Calvete, Juan J

    2008-08-01

    We report the comparative proteomic characterization of the venoms of adult and newborn specimens of the lancehead pitviper Bothrops asper from two geographically isolated populations from the Caribbean and the Pacific versants of Costa Rica. The crude venoms were fractionated by reverse-phase HPLC, followed by analysis of each chromatographic fraction by SDS-PAGE, N-terminal sequencing, MALDI-TOF mass fingerprinting, and collision-induced dissociation tandem mass spectrometry of tryptic peptides. The two B. asper populations, separated since the late Miocene or early Pliocene (8-5 mya) by the Guanacaste Mountain Range, Central Mountain Range, and Talamanca Mountain Range, contain both identical and different (iso)enzymes from the PLA 2, serine proteinase, and SVMP families. Using a similarity coefficient, we estimate that the similarity of venom proteins between the two B. asper populations may be around 52%. Compositional differences between venoms among different geographic regions may be due to evolutionary environmental pressure acting on isolated populations. To investigate venom variability among specimens from the two B. asper populations, the reverse-phase HPLC protein profiles of 15 venoms from Caribbean specimens and 11 venoms from snakes from Pacific regions were compared. Within each B. asper geographic populations, all major venom protein families appeared to be subjected to individual variations. The occurrence of intraspecific individual allopatric variability highlights the concept that a species, B. asper in our case, should be considered as a group of metapopulations. Analysis of pooled venoms of neonate specimens from Caribbean and Pacific regions with those of adult snakes from the same geographical habitat revealed prominent ontogenetic changes in both geographical populations. Major ontogenetic changes appear to be a shift from a PIII-SVMP-rich to a PI-SVMP-rich venom and the secretion in adults of a distinct set of PLA 2 molecules than in

  15. Effects of Bothrops asper snake venom on lymphatic vessels: insights into a hidden aspect of envenomation.

    Science.gov (United States)

    Mora, Javier; Mora, Rodrigo; Lomonte, Bruno; Gutiérrez, José María

    2008-01-01

    Envenomations by the snake Bothrops asper represent a serious medical problem in Central America and parts of South America. These envenomations concur with drastic local tissue pathology, including a prominent edema. Since lymph flow plays a role in the maintenance of tissue fluid balance, the effect of B. asper venom on collecting lymphatic vessels was studied. B. asper venom was applied to mouse mesentery, and the effects were studied using an intravital microscopy methodology coupled with an image analysis program. B. asper venom induced a dose-dependent contraction of collecting lymphatic vessels, resulting in a reduction of their lumen and in a halting of lymph flow. The effect was reproduced by a myotoxic phospholipase A(2) (PLA(2)) homologue isolated from this venom, but not by a hemorrhagic metalloproteinase or a coagulant thrombin-like serine proteinase. In agreement with this, treatment of the venom with fucoidan, a myotoxin inhibitor, abrogated the effect, whereas no inhibition was observed after incubation with the peptidomimetic metalloproteinase inhibitor Batimastat. Moreover, fucoidan significantly reduced venom-induced footpad edema. The myotoxic PLA(2) homologue, known to induce skeletal muscle necrosis, was able to induce cytotoxicity in smooth muscle cells in culture and to promote an increment in the permeability to propidium iodide in these cells. Our observations indicate that B. asper venom affects collecting lymphatic vessels through the action of myotoxic PLA(2)s on the smooth muscle of these vessels, inducing cell contraction and irreversible cell damage. This activity may play an important role in the pathogenesis of the pronounced local edema characteristic of viperid snakebite envenomation, as well as in the systemic biodistribution of the venom, thus representing a potential therapeutical target in these envenomations.

  16. Thrombelastographic characterization of the thrombin-like activity of Crotalus simus and Bothrops asper venoms.

    Science.gov (United States)

    Nielsen, Vance G; Boyer, Leslie V; Redford, Daniel T; Ford, Paul

    2017-04-01

    : Annually, thousands suffer venomous snake-bite from Crotalus simus and Bothrops asper vipers in central and South America. The goals of the present study were to generally characterize the thrombin-like effects of venom from these snakes in human plasma with viscoelastic methods. Human plasma was exposed to the venom of three different C. simus subspecies and venoms obtained from B. asper vipers located in three different locations in Mexico. To characterize the factor X-activating and thrombin-like activity of these venoms, plasma (normal or factor XIII deficient) was pretreated with a variety of additives (e.g., heparin) in the absence or presence of calcium prior to exposure to 2.0 μg/ml of each viper's venom. These profiles were compared with plasma without venom that had contact activation of coagulation. Coagulation kinetics were determined with thrombelastography. All venoms had thrombin-like activity, with C. s. simus creating a slow growing, weak clot that was likely mediated by metalloproteinases. In contrast, B. asper venoms had rapid onset of coagulation and a high velocity of thrombus growth. Further, B. asper venom activity was calcium-independent, activated prothrombin, activated factor XIII, and independently polymerized fibrinogen. The viscoelastic methods used were able to differentiate subspecies of C. simus and specimens of B. asper, and provide insight into the mechanisms by which the venoms acted on plasma. These methods may be useful in the profiling of similar venoms and perhaps can assist in the assessment of interventions designed to treat envenomation (e.g., antivenom).

  17. Effects of Bothrops asper snake venom on lymphatic vessels: insights into a hidden aspect of envenomation.

    Directory of Open Access Journals (Sweden)

    Javier Mora

    Full Text Available Envenomations by the snake Bothrops asper represent a serious medical problem in Central America and parts of South America. These envenomations concur with drastic local tissue pathology, including a prominent edema. Since lymph flow plays a role in the maintenance of tissue fluid balance, the effect of B. asper venom on collecting lymphatic vessels was studied.B. asper venom was applied to mouse mesentery, and the effects were studied using an intravital microscopy methodology coupled with an image analysis program. B. asper venom induced a dose-dependent contraction of collecting lymphatic vessels, resulting in a reduction of their lumen and in a halting of lymph flow. The effect was reproduced by a myotoxic phospholipase A(2 (PLA(2 homologue isolated from this venom, but not by a hemorrhagic metalloproteinase or a coagulant thrombin-like serine proteinase. In agreement with this, treatment of the venom with fucoidan, a myotoxin inhibitor, abrogated the effect, whereas no inhibition was observed after incubation with the peptidomimetic metalloproteinase inhibitor Batimastat. Moreover, fucoidan significantly reduced venom-induced footpad edema. The myotoxic PLA(2 homologue, known to induce skeletal muscle necrosis, was able to induce cytotoxicity in smooth muscle cells in culture and to promote an increment in the permeability to propidium iodide in these cells.Our observations indicate that B. asper venom affects collecting lymphatic vessels through the action of myotoxic PLA(2s on the smooth muscle of these vessels, inducing cell contraction and irreversible cell damage. This activity may play an important role in the pathogenesis of the pronounced local edema characteristic of viperid snakebite envenomation, as well as in the systemic biodistribution of the venom, thus representing a potential therapeutical target in these envenomations.

  18. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    International Nuclear Information System (INIS)

    Ahn, Taehong; Lee, Sung Bo; Han, Heung Nam; Park, Kyungtae

    2013-01-01

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite

  19. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Taehong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Sung Bo; Han, Heung Nam [Seoul National Univ., Seoul (Korea, Republic of); Park, Kyungtae [Hanbat National Univ., Daejeon (Korea, Republic of)

    2013-05-15

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite.

  20. Quasi-Static Indentation Analysis of Carbon-Fiber Laminates.

    Energy Technology Data Exchange (ETDEWEB)

    Briggs, Timothy [Sandia National Lab. (SNL-CA), Livermore, CA (United States); English, Shawn Allen [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Nelson, Stacy Michelle [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2015-12-01

    A series of quasi - static indentation experiments are conducted on carbon fiber reinforced polymer laminates with a systematic variation of thicknesses and fixture boundary conditions. Different deformation mechanisms and their resulting damage mechanisms are activated b y changing the thickn ess and boundary conditions. The quasi - static indentation experiments have been shown to achieve damage mechanisms similar to impact and penetration, however without strain rate effects. The low rate allows for the detailed analysis on the load response. Moreover, interrupted tests allow for the incremental analysis of various damage mechanisms and pr ogressions. The experimentally tested specimens are non - destructively evaluated (NDE) with optical imaging, ultrasonics and computed tomography. The load displacement responses and the NDE are then utilized in numerical simulations for the purpose of model validation and vetting. The accompanying numerical simulation work serves two purposes. First, the results further reveal the time sequence of events and the meaning behind load dro ps not clear from NDE . Second, the simulations demonstrate insufficiencies in the code and can then direct future efforts for development.

  1. Influence of indenter geometry on the frictional sliding resistance of tooth enamel

    Directory of Open Access Journals (Sweden)

    M.V. Swain

    2017-12-01

    Full Text Available Indentation force-displacement and sliding scratch resistance measurements have been conducted on orangutan tooth enamel. Tests were made with a corner-cube (CC, Berkovich, as well as spherical (nominally 1 μm and 5 μm radius indenters. Indentation loads ranged from 100 to 5000 μN and were also made on fused silica to calibrate the indenter tips. The frictional force as a function of sliding distance was measured with the atomic force microscope (AFM option on the indenter system as well as using a high precision AFM and scanning electron microscope (SEM. The frictional resistance was found to be almost constant with indenter load for the CC and Berkovich indenters; for the CC, it depended upon the orientation of the sliding indenter. For the spherical indenters, the 1 μm showed a sharp increase in frictional resistance with increasing load whereas for the 5 μm tip there was minimal change. Observations of the resultant scratches showed ploughing/cutting with the sharp indenters and a transition from an “ironing” like deformation for all the 5 μm tests and for the low load 1 μm tip with ploughing at the heaviest load. In the case of the sharp tips a “metallic” like discontinuous swarf removal process was evident. It was found that the frictional resistance force scaled with the effective rake angle of the indenter tips. Implications of the current observations for understanding tooth wear are considered.

  2. Study of indentation induced cracks in MoSi2-reaction bonded SiC ...

    Indian Academy of Sciences (India)

    Mo melt into a preform of commercial SiC and petroleum coke powder. The infiltrated sample had a density > 92% of the theoretical density (TD) and microstructurally contained SiC, MoSi2, residual Si and unreacted C. The material was tested for indentation fracture toughness at room temperature with a Vicker's indenter ...

  3. Indentations and Starting Points in Traveling Sales Tour Problems: Implications for Theory

    Science.gov (United States)

    MacGregor, James N.

    2012-01-01

    A complete, non-trivial, traveling sales tour problem contains at least one "indentation", where nodes in the interior of the point set are connected between two adjacent nodes on the boundary. Early research reported that human tours exhibited fewer such indentations than expected. A subsequent explanation proposed that this was because…

  4. A novel sample preparation method to avoid influence of embedding medium during nano-indentation

    Science.gov (United States)

    Yujie Meng; Siqun Wang; Zhiyong Cai; Timothy M. Young; Guanben Du; Yanjun Li

    2012-01-01

    The effect of the embedding medium on the nano-indentation measurements of lignocellulosic materials was investigated experimentally using nano-indentation. Both the reduced elastic modulus and the hardness of nonembedded cell walls were found to be lower than those of the embedded samples, proving that the embedding medium used for specimen preparation on cellulosic...

  5. Temperature-dependent indentation behavior of transformation-toughened zirconia-based ceramics

    Science.gov (United States)

    Tikare, Veena; Heuer, Arthur H.

    1991-01-01

    Indentation behavior of Ce-TZP, Y-TZP, and Mg-PSZ between room temperature and 1300 C was investigated. Hardness decreased with increasing temperature for all three materials, but indentation cracking increased with increasing temperature. The opposing temperature dependences are discussed in terms of dislocation and transformation plasticity.

  6. Crystallographic Analysis of Nucleation at Hardness Indentations in High-Purity Aluminum

    DEFF Research Database (Denmark)

    Xu, Chaoling; Zhang, Yubin; Lin, Fengxiang

    2016-01-01

    Nucleation at Vickers hardness indentations has been studied in high-purity aluminum cold-rolled 12 pct. Electron channeling contrast was used to measure the size of the indentations and to detect nuclei, while electron backscattering diffraction was used to determine crystallographic orientation...

  7. Mechanical properties study of particles reinforced aluminum matrix composites by micro-indentation experiments

    Directory of Open Access Journals (Sweden)

    Yuan Zhanwei

    2014-04-01

    Full Text Available By using instrumental micro-indentation technique, the microhardness and Young’s modulus of SiC particles reinforced aluminum matrix composites were investigated with micro-compression-tester (MCT. The micro-indentation experiments were performed with different maximum loads, and with three loading speeds of 2.231, 4.462 and 19.368 mN/s respectively. During the investigation, matrix, particle and interface were tested by micro-indentation experiments. The results exhibit that the variations of Young’s modulus and microhardness at particle, matrix and interface were highly dependent on the loading conditions (maximum load and loading speed and the locations of indentation. Micro-indentation hardness experiments of matrix show the indentation size effects, i.e. the indentation hardness decreased with the indentation depth increasing. During the analysis, the effect of loading conditions on Young’s modulus and microhardness were explained. Besides, the elastic–plastic properties of matrix were analyzed. The validity of calculated results was identified by finite element simulation. And the simulation results had been preliminarily analyzed from statistical aspect.

  8. Determining the Elastic Modulus of Compliant Thin Films Supported on Substrates from Flat Punch Indentation Measurements

    Science.gov (United States)

    M.J. Wald; J.M. Considine; K.T. Turner

    2013-01-01

    Instrumented indentation is a technique that can be used to measure the elastic properties of soft thin films supported on stiffer substrates, including polymer films, cellulosic sheets, and thin layers of biological materials. When measuring thin film properties using indentation, the effect of the substrate must be considered. Most existing models for determining the...

  9. Nanoindentation hardness measurements using real-shape indenters: application to extremely hard and elastic materials

    Science.gov (United States)

    Martínez, E.; Esteve, J.

    We study the technique of nanoindentation hardness measurement applied to extremely hard and elastic thin films. We do the study with the aid of Hertz's solutions for elastic contacts. The effect of different apical angles in ideally sharp conical diamond indenters is analyzed. In addition, the blunt tip shape of practical diamond indenters is discussed. The area function of the tip of real indenters is deduced from experimental nanoindentation measurements performed with these indenters on fused quartz. Triangular-base pyramidal indenters with Berkovich and cube corner geometries are considered. Theoretical hardness values applying Hertz's and Oliver and Pharr's methods of analysis are obtained and compared with the experimental data deduced from nanoindentation measurements performed on very hard and elastic ta-C films. The theoretical analysis shows a necessary dependence of the calculated hardness values with the apical angle of the indenter in totally elastic materials and to some extent in elastoplastic materials. Moreover, when the indenter tip is blunt or when there are inaccuracies in the measured area function of the indenter tip, hardness values decrease for very small penetration depths. Besides, in these films, because of their very small thickness, measured hardness values also decrease for measurements with penetration depths larger than a fraction of film thickness, due to the effects of the softer substrate.

  10. Quasi-static indentation modelling of aluminium specimen using finite element analysis

    Directory of Open Access Journals (Sweden)

    Mayank Nirbhay

    2017-03-01

    Full Text Available The influence of different types of rigid hemispherical and conical indenters on a rectangular specimen of aluminium has been investigated, in the small indenter test. A 3-D finite-element FE model was used to carry out the computation of the elastic-plastic solution of different rigid hemispherical and conical indenters. Three hemispherical-headed and four conical-headed indenters were designed and developed for testing. FE software ABAQUS® has been used to determine the load vs. indenter-displacement curves, reaction forces, deformation contours and Von-Mises stresses. The FE model was validated by comparing the results with the experimental data received from the Hertz Contact Theory and was found to be in reasonably good agreement.

  11. Natural history of the terciopelo Bothrops asper (Serpentes: Viperidae) in Costa Rica.

    Science.gov (United States)

    Sasa, Mahmood; Wasko, Dennis K; Lamar, William W

    2009-12-01

    The terciopelo Bothrops asper is the only lancehead species widely distributed in the humid lowlands of Middle America and northwestern South America. Its large body size, relative abundance and cryptic habits contribute to the high incidence of snakebites induced by this species throughout its distribution. The terciopelo plays an important role in ecosystems, both as prey and as a generalist predator. Diet comprises a great variety of prey items, including some species that are considered nuisances. B. asper, as other lancehead species, exhibits a notable ontogenetic shift in diet, consuming ectotherms (mainly frogs and lizards) when young, and increasingly incorporating birds, rodents, and other small mammals with maturity. Adult terciopelos also consume large anurans, especially when endothermic prey availability is low. Using radiotelemetry we determined home range and movement patterns from 28 individual B. asper at La Selva Biological Station, Costa Rica. Overall home range estimates are relatively small compared with other pitvipers, averaging between 3.71ha and 5.95ha; home range size did not differ between males and females. Movement patterns are largely aseasonal and consist of short (50 m) movements to new foraging areas. Habitat use is related to prey availability and therefore to foraging strategy. Our data support a strong preference for areas near swamps by both sexes. Reproduction in B. asper is highly seasonal, and--apparently--biannual. Reproductive cycles in Costa Rica are tightly related to rainfall patterns. Therefore, the timing of breeding differs between populations in the Caribbean and Pacific lowlands. Bothrops asper is adapted to areas with low levels of disturbance along the agricultural frontier, and consequently it is not rare to find it in or near human dwellings. However, despite popular belief, no evidence supports a purported increase in population density of this species in Costa Rica. Despite human persecution and substantial

  12. Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope

    DEFF Research Database (Denmark)

    Jensen, Carsten P.

    Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope......Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope...

  13. Sensing inhomogeneous mechanical properties of human corneal Descemet's membrane with AFM nano-indentation.

    Science.gov (United States)

    Di Mundo, Rosa; Recchia, Giuseppina; Parekh, Mohit; Ruzza, Alessandro; Ferrari, Stefano; Carbone, Giuseppe

    2017-10-01

    The paper describes a highly space-resolved characterization of the surface mechanical properties of the posterior human corneal layer (Descemet's membrane). This has been accomplished with Atomic Force Microscopy (AFM) nano-indentation by using a probe with a sharp tip geometry. Results indicate that the contact with this biological tissue in liquid occurs with no (or very low) adhesion. More importantly, under the same operating conditions, a broad distribution of penetration depth can be measured on different x-y positions of the tissue surface, indicating a high inhomogeneity of surface stiffness, not yet clearly reported in the literature. An important contribution to such inhomogeneity should be ascribed to the discontinuous nature of the collagen/proteoglycans fibers matrix tissue, as can be imaged by AFM when the tissue is semi-dry. Using classical contact mechanics calculations adapted to the specific geometry of the tetrahedral tip it has been found that the elastic modulus E of the material in the very proximity of the surface ranges from 0.23 to 2.6 kPa. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Evaluation of antivenoms in the neutralization of hyperalgesia and edema induced by Bothrops jararaca and Bothrops asper snake venoms

    OpenAIRE

    Picolo, G.; Chacur, M.; Gutiérrez, J.M.; Teixeira, C.F.P.; Cury, Y.

    2002-01-01

    Neutralization of hyperalgesia induced by Bothrops jararaca and B. asper venoms was studied in rats using bothropic antivenom produced at Instituto Butantan (AVIB, 1 ml neutralizes 5 mg B. jararaca venom) and polyvalent antivenom produced at Instituto Clodomiro Picado (AVCP, 1 ml neutralizes 2.5 mg B. aspar venom). The intraplantar injection of B. jararaca and B. asper venoms caused hyperalgesia, which peaked 1 and 2 h after injection, respectively. Both venoms also induced edema with a simil...

  15. Evaluation of antivenoms in the neutralization of hyperalgesia and edema induced by Bothrops jararaca and Bothrops asper snake venoms.

    Science.gov (United States)

    Picolo, G; Chacur, M; Gutiérrez, J M; Teixeira, C F P; Cury, Y

    2002-10-01

    Neutralization of hyperalgesia induced by Bothrops jararaca and B. asper venoms was studied in rats using bothropic antivenom produced at Instituto Butantan (AVIB, 1 ml neutralizes 5 mg B. jararaca venom) and polyvalent antivenom produced at Instituto Clodomiro Picado (AVCP, 1 ml neutralizes 2.5 mg B. aspar venom). The intraplantar injection of B. jararaca and B. asper venoms caused hyperalgesia, which peaked 1 and 2 h after injection, respectively. Both venoms also induced edema with a similar time course. When neutralization assays involving the independent injection of venom and antivenom were performed, the hyperalgesia induced by B. jararaca venom was neutralized only when bothropic antivenom was administered iv 15 min before venom injection, whereas edema was neutralized when antivenom was injected 15 min or immediately before venom injection. On the other hand, polyvalent antivenom did not interfere with hyperalgesia or edema induced by B. asper venom, even when administered prior to envenomation. The lack of neutralization of hyperalgesia and edema induced by B. asper venom is not attributable to the absence of neutralizing antibodies in the antivenom, since neutralization was achieved in assays involving preincubation of venom and antivenom. Cross-neutralization of AVCP or AVIB against B. jararaca and B. asper venoms, respectively, was also evaluated. Only bothropic antivenom partially neutralized hyperalgesia induced by B. asper venom in preincubation experiments. The present data suggest that hyperalgesia and edema induced by Bothrops venoms are poorly neutralized by commercial antivenoms even when antibodies are administered immediately after envenomation.

  16. Evaluation of antivenoms in the neutralization of hyperalgesia and edema induced by Bothrops jararaca and Bothrops asper snake venoms

    Directory of Open Access Journals (Sweden)

    Picolo G.

    2002-01-01

    Full Text Available Neutralization of hyperalgesia induced by Bothrops jararaca and B. asper venoms was studied in rats using bothropic antivenom produced at Instituto Butantan (AVIB, 1 ml neutralizes 5 mg B. jararaca venom and polyvalent antivenom produced at Instituto Clodomiro Picado (AVCP, 1 ml neutralizes 2.5 mg B. aspar venom. The intraplantar injection of B. jararaca and B. asper venoms caused hyperalgesia, which peaked 1 and 2 h after injection, respectively. Both venoms also induced edema with a similar time course. When neutralization assays involving the independent injection of venom and antivenom were performed, the hyperalgesia induced by B. jararaca venom was neutralized only when bothropic antivenom was administered iv 15 min before venom injection, whereas edema was neutralized when antivenom was injected 15 min or immediately before venom injection. On the other hand, polyvalent antivenom did not interfere with hyperalgesia or edema induced by B. asper venom, even when administered prior to envenomation. The lack of neutralization of hyperalgesia and edema induced by B. asper venom is not attributable to the absence of neutralizing antibodies in the antivenom, since neutralization was achieved in assays involving preincubation of venom and antivenom. Cross-neutralization of AVCP or AVIB against B. jararaca and B. asper venoms, respectively, was also evaluated. Only bothropic antivenom partially neutralized hyperalgesia induced by B. asper venom in preincubation experiments. The present data suggest that hyperalgesia and edema induced by Bothrops venoms are poorly neutralized by commercial antivenoms even when antibodies are administered immediately after envenomation.

  17. Enhancement of Friction against a Rough Surface by a Ridge-Channel Surface Microstructure.

    Science.gov (United States)

    Bai, Ying; Hui, Chung-Yuen; Levrard, Benjamin; Jagota, Anand

    2015-07-14

    We report on a study of the sliding friction of elastomeric surfaces patterned with ridges and channels (and unstructured flat controls), against both smooth and roughened spherical indenters. Against the smooth spherical indenter, all of the structured surfaces have highly reduced sliding friction due to the reduction in actual area of contact. Against roughened spherical indenters, however, the sliding force for structured samples can be up to 50% greater than that of an unstructured flat control. The mechanism of enhanced friction against a rough surface is due to a combination of increased actual area of contact, interlocking between roughness and the surface structure, and attendant dynamic instabilities that dissipate energy.

  18. Reversible posterior leukoencephalopathy in a venomous snake (Bothrops asper) bite victim.

    Science.gov (United States)

    Delgado, Miguel E; Del Brutto, Oscar H

    2012-03-01

    An 18-year-old man developed posterior reversible leukoencephalopaty after being bitten by a venomous snake (Bothrops asper). It is possible that this previously unrecognized neurological complication of snake bite envenoming occurred as the result of endothelial dysfunction induced by the venom of the offending snake. This pathogenetic mechanism has also been implicated as the cause of cerebral infarctions in snake bite victims. Alternatively, the leukoencephalopathy might have been a complication of antivenom therapy.

  19. Reversible Posterior Leukoencephalopathy in a Venomous Snake (Bothrops asper) Bite Victim

    OpenAIRE

    Delgado, Miguel E.; Del Brutto, Oscar H.

    2012-01-01

    An 18-year-old man developed posterior reversible leukoencephalopaty after being bitten by a venomous snake (Bothrops asper). It is possible that this previously unrecognized neurological complication of snake bite envenoming occurred as the result of endothelial dysfunction induced by the venom of the offending snake. This pathogenetic mechanism has also been implicated as the cause of cerebral infarctions in snake bite victims. Alternatively, the leukoencephalopathy might have been a compli...

  20. Studies on the venom proteome of Bothrops asper: perspectives and applications.

    Science.gov (United States)

    Alape-Girón, Alberto; Flores-Díaz, Marietta; Sanz, Libia; Madrigal, Marvin; Escolano, José; Sasa, Mahmood; Calvete, Juan J

    2009-12-01

    Bothrops asper is responsible for the vast majority of snakebite accidents in Central America and several studies have demonstrated that specific toxic and enzymatic activities of its venom vary with the geographic origin and age of the specimens. Variability in venom proteins and enzymes between specimens from the Caribbean and the Pacific versants of Costa Rica has been reported since 1964. Recently, we performed a comparative proteomic characterization of the venoms from one population of each versant. Proteins belonging to several families, including disintegrin, phospholipases A(2), serine proteinases, C-type lectins, CRISP, l-amino acid oxidase, and Zn(2+)-dependent metalloproteinases show a variable degree of relative occurrence in the venoms of both populations. The occurrence of prominent differences in the protein profile between venoms from adults and newborns, and among venom samples from individual specimens of the same region or developmental stage, further demonstrated the existence of geographic, ontogenetic and individual variability in the venom proteome of this species. These findings provide new insights towards understanding the biology of B. asper, contribute to a deeper understanding of the pathology induced by its venom and underscore the importance of the use of venoms pooled from specimens from both regions for producing antivenom exhibiting the broadest cross-reactivity. Furthermore, knowledge of the protein composition of B. asper venom paves the way for detailed future structure-function studies of individual toxins as well as for the development of new protocols to study the reactivity of therapeutic antivenoms.

  1. Analysis of ray trajectories of flexural waves propagating over generalized acoustic black hole indentations

    Science.gov (United States)

    Huang, Wei; Ji, Hongli; Qiu, Jinhao; Cheng, Li

    2018-03-01

    An Acoustic Black Hole (ABH) indentation embedded in thin-walled structures has been proved remarkably useful for broadband flexural wave focalization, in which the phase velocity of the flexural waves and the refractive index of the media undergo gradual changes from the outside towards the center of the indentation. A generalized two-dimensional ABH indentation can be defined by three geometric parameters: a power index, an extra thickness and a radius of a plateau at the indentation center. The dependence of the energy focalization on these parameters as well as the energy focalization process is of paramount importance for the understanding and design of effective ABH indentations. This work aims at investigating the energy focalization characteristics of flexural waves in such generalized ABH indentations. The calculation of the flexural ray trajectories is conducted to reveal and analyze the wave propagation features through numerical integration of the eikonal equation from the Geometric Acoustics Approximation (GAA). The theoretical results are verified by both experiment using wave visualization technique based on laser acoustic scanning method and finite element (FE) simulations. Finally, the influence of the geometric parameters on the flexural wave focalization characteristics in ABH indentations is discussed in detail.

  2. Indentation versus Rolling: Dependence of Adhesion on Contact Geometry for Biomimetic Structures.

    Science.gov (United States)

    Moyle, Nichole; He, Zhenping; Wu, Haibin; Hui, Chung-Yuen; Jagota, Anand

    2018-04-03

    Numerous biomimetic structures made from elastomeric materials have been developed to produce enhancement in properties such as adhesion, static friction, and sliding friction. As a property, one expects adhesion to be represented by an energy per unit area that is usually sensitive to the combination of shear and normal stresses at the crack front but is otherwise dependent only on the two elastic materials that meet at the interface. More specifically, one would expect that adhesion measured by indentation (a popular and convenient technique) could be used to predict adhesion hysteresis in the more practically important rolling geometry. Previously, a structure with a film-terminated fibrillar geometry exhibited dramatic enhancement of adhesion by a crack-trapping mechanism during indentation with a rigid sphere. Roughly isotropic structures such as the fibrillar geometry show a strong correlation between adhesion enhancement in indentation versus adhesion hysteresis in rolling. However, anisotropic structures, such as a film-terminated ridge-channel geometry, surprisingly show a dramatic divergence between adhesion measured by indentation versus rolling. We study this experimentally and theoretically, first comparing the adhesion of the anisotropic ridge-channel structure to the roughly isotropic fibrillar structure during indentation with a rigid sphere, where only the isotropic structure shows adhesion enhancement. Second, we examine in more detail the anomalous anisotropic film-terminated ridge-channel structure during indentation with a rigid sphere versus rolling to show why these structures show a dramatic adhesion enhancement for the rolling case and no adhesion enhancement for indentation.

  3. Comment on 'Axisymmetric indentation of an incompressible elastic thin film'

    Energy Technology Data Exchange (ETDEWEB)

    Chadwick, Richard S [Section on Auditory Mechanics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892 (United States)

    2005-04-07

    It is shown that a recent method based on the asymptotic inversion of Hankel transforms for indentation of thin films (Yang F Q 2003 J. Phys. D: Appl. Phys. 36 50) provides a non-unique solution for the case of frictionless contact between the film and the substrate. In addition to the solution given by Yang, another one exists having zero hydrostatic stress that results in half the force acting on the indenter for the same indentation. A more rigorous asymptotic method (Chadwick R S 2002 SIAM J. Appl. Math. 62 1520) singles out the smaller force solution as the correct one. (comment)

  4. Direct measurement of asperity contact growth in quartz at hydrothermal conditions

    Science.gov (United States)

    Beeler, Nicholas M.; Hickman, Stephen H.

    2015-01-01

    Earthquake recurrence requires interseismic fault restrengthening which results from solid state deformation in room-temperature friction and indentation experiments. In contrast exhumed fault zones show solution-transport processes such as pressure solution and contact overgrowths influence fault zone properties . In the absence of fluid flow, overgrowths are driven by gradients in surface curvature where material is dissolved, diffuses, and precipitates at the contact without convergence normal to the contact. To determine the rate of overgrowth for quartz, we conducted single contact experiments in an externally heated pressure vessel. Convergence was continuously monitored using reflected-light interferometry through a long-working-distance microscope. Contact normal force was constant with an initial effective normal stress of 1.7 MPa, temperature was between 350 and 530{degree sign}C, and water pressure was constant at 150 MPa. Two control experiments were conducted: one dry at 425{degree sign}C and one bi-material (sapphire) at 425{degree sign}C and 150 MPa water pressure. No contact growth or convergence was observed in the controls. For wet single-phase contacts, growth was initially rapid and then decreased with time. No convergence was observed. Fluid inclusions indicate that the contact is not uniformly wetted. The contact is bounded by small regions of high aperture, reflecting local free-face dissolution as the source for the overgrowth. The apparent activation energy is ~125 kJ/mol. Extrapolation predicts rates of contact area increase orders of magnitude faster than in dry, room-temperature and hydrothermal friction experiments, suggesting that natural strength recovery near the base of the seismogenic zone could be dominated by contact overgrowth.

  5. Indentation size effects in the nano- and micro-hardness of a Fe-based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Xu, F., E-mail: xufu@xtu.edu.cn; Ding, Y.H.; Deng, X.H.; Zhang, P.; Long, Z.L.

    2014-10-01

    Hardness of a Fe-based bulk metallic glass (BMG) was evaluated by both atomic force microscopy (AFM) nanoindentation (nano-hardness) and instrumented indentation with a traditional indenter setup (micro-hardness) under different maximum loads at room temperature. The nano-hardness and the micro-hardness were found to be comparable. For both of the indentation methods, indentation size effect (ISE) is detected as increase in hardness with decrease in indentation peak load. It is proposed that strain rate dependent softening, loading history and the lag between free volume creation and mechanical softening should be responsible for the ISE in this BMG. Furthermore, ISE is found to be more significant in AFM nanoindentation than in instrumented indentation. This can be explained by taking into account the effect of exerted peak load and the face angle of the indenter in a qualitative manner.

  6. Finite Element Bond Modeling for Indented Wires in Pretensioned Concrete Crossties

    Science.gov (United States)

    2016-04-12

    Indented wires have been increasingly employed by : concrete crosstie manufacturers to improve the bond between : prestressing steel reinforcements and concrete, as bond can : affect several critical performance measures, including transfer : length,...

  7. Experimental validation of the new modular application of the upper bound theorem in indentation.

    Directory of Open Access Journals (Sweden)

    Carolina Bermudo

    Full Text Available Nowadays, thanks to the new manufacturing processes, indentation is becoming an essential part of the new arising processes such as the Incremental Forming Processes. This work presents the experimental validation of the analytical model developed for an indentation-based process. The analytical model is originated from the Upper Bound Theorem application by means of its new modular distribution. The modules considered are composed of two Triangular Rigid Zones each. The experimental validation is performed through a series of indentation tests with work-pieces of annealed aluminium EN AW-2030 and punches of steel AISI 304, under plane strain conditions. The results are compared with the ones obtained from the application of this new modular distribution of the Upper Bound Theorem, showing a good approximation and suitability of the model developed for an indentation-based process.

  8. Experimental Validation of the New Modular Application of the Upper Bound Theorem in Indentation

    Science.gov (United States)

    Bermudo, Carolina; Martín, Francisco; Martín, María Jesús; Sevilla, Lorenzo

    2015-01-01

    Nowadays, thanks to the new manufacturing processes, indentation is becoming an essential part of the new arising processes such as the Incremental Forming Processes. This work presents the experimental validation of the analytical model developed for an indentation-based process. The analytical model is originated from the Upper Bound Theorem application by means of its new modular distribution. The modules considered are composed of two Triangular Rigid Zones each. The experimental validation is performed through a series of indentation tests with work-pieces of annealed aluminium EN AW-2030 and punches of steel AISI 304, under plane strain conditions. The results are compared with the ones obtained from the application of this new modular distribution of the Upper Bound Theorem, showing a good approximation and suitability of the model developed for an indentation-based process. PMID:25826738

  9. Aqueous humour dynamics in anterior chamber under influence of cornea indentation

    Science.gov (United States)

    Zuhaila, I.; Jiann, L. Y.; Sharidan, S.; Fitt, A.

    2017-04-01

    The existing temperature different between the cornea and the pupil induces the aqueous humour (AH) to circulate in the anterior chamber (AC). The buoyancy forces produced by the temperature gradient has driven the AH to flow. Previous studies have shown that cornea indentation changes the structure of the AC. This imply that the cornea indentation may change the fluid flow behaviour in the AC. A mathematical model of AH flow has been developed in order to analyse the fluid mechanics concerning the indentation of the cornea. Naiver-Stokes equations is used to describe the flow of AH in the AC. The governing equations have been solved numerically using finite element method. The results show that the cornea indentation has slow down the circulation the AH in the AC.

  10. Spherical indentation of a freestanding circular membrane revisited: Analytical solutions and experiments

    Science.gov (United States)

    Jin, Congrui; Davoodabadi, Ali; Li, Jianlin; Wang, Yanli; Singler, Timothy

    2017-03-01

    Due to the development of novel micro-fabrication techniques to produce ultra-thin materials and increasing interest in thin biological membranes, in recent years, the mechanical characterization of thin films has received a significant amount of attention. To provide a more accurate solution for the relationship among contact radius, load and deflection, the fundamental and widely applicable problem of spherical indentation of a freestanding circular membrane have been revisited. The work presented here significantly extends the previous contributions by providing an exact analytical solution to the governing equations of Föppl-Hecky membrane indented by a frictionless spherical indenter. In this study, experiments of spherical indentation has been performed, and the exact analytical solution presented in this paper is compared against experimental data from existing literature as well as our own experimental results.

  11. Experimental validation of the new modular application of the upper bound theorem in indentation.

    Science.gov (United States)

    Bermudo, Carolina; Martín, Francisco; Martín, María Jesús; Sevilla, Lorenzo

    2015-01-01

    Nowadays, thanks to the new manufacturing processes, indentation is becoming an essential part of the new arising processes such as the Incremental Forming Processes. This work presents the experimental validation of the analytical model developed for an indentation-based process. The analytical model is originated from the Upper Bound Theorem application by means of its new modular distribution. The modules considered are composed of two Triangular Rigid Zones each. The experimental validation is performed through a series of indentation tests with work-pieces of annealed aluminium EN AW-2030 and punches of steel AISI 304, under plane strain conditions. The results are compared with the ones obtained from the application of this new modular distribution of the Upper Bound Theorem, showing a good approximation and suitability of the model developed for an indentation-based process.

  12. Flat indentation of a viscoelastic polymer film on a rigid substrate

    International Nuclear Information System (INIS)

    Choi, Seung Tae; Lee, Seung Ryoon; Earmme, Youn Young

    2008-01-01

    A systematic method of flat indentation was developed to measure the elastic and viscoelastic properties of polymer films. A flat indentation problem on an elastic film perfectly bonded to a rigid substrate was revisited, from which the relationship between the applied force and the penetration depth was obtained in a simple form. Application of the elastic-viscoelastic correspondence principle converts the force-depth relationship for elastic films to the Laplace transform of that for viscoelastic films. Indentation experiments with a flat diamond tip were performed on polymer films (SU-8 and NR4-8000P). Analysis of the measured data with the viscoelastic force-depth relationship provides the shear moduli, Poisson's ratios, and relaxation moduli of these films. Viscoplastic deformations produced in the films that underwent the flat indentation process were quantified by measuring the residual deformation after unloading with an atomic force microscope

  13. Neuroprotective effect of the methanolic extract of Hibiscus asper leaves in 6-hydroxydopamine-lesioned rat model of Parkinson's disease.

    Science.gov (United States)

    Hritcu, Lucian; Foyet, Harquin Simplice; Stefan, Marius; Mihasan, Marius; Asongalem, Acha Emmanuel; Kamtchouing, Pierre

    2011-09-01

    While the Hibiscus asper Hook.f. (Malvaceae) is a traditional herb largely used in tropical region of the Africa as vegetable, potent sedative, tonic and restorative, anti-inflammatory and antidepressive drug, there is very little scientific data concerning the efficacy of this. The antioxidant and antiapoptotic activities of the methanolic extract of Hibiscus asper leaves (50 and 100 mg/kg) were assessed using superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) specific activities, total glutathione (GSH) content, malondialdehyde (MDA) level (lipid peroxidation) and DNA fragmentation assays in male Wistar rats subjected to unilateral 6-hydroxydopamine (6-OHDA)-lesion. In 6-OHDA-lesioned rats, methanolic extract of Hibiscus asper leaves showed potent antioxidant and antiapoptotic activities. Chronic administration of the methanolic extract (50 and 100 mg/kg, i.p., daily, for 7 days) significantly increased antioxidant enzyme activities (SOD, GPX and CAT), total GSH content and reduced lipid peroxidation (MDA level) in rat temporal lobe homogenates, suggesting antioxidant activity. Also, DNA cleavage patterns were absent in the 6-OHDA-lesioned rats treated with methanolic extract of Hibiscus asper leaves, suggesting antiapoptotic activity. Taken together, our results suggest that the methanolic extract of Hibiscus asper leaves possesses neuroprotective activity against 6-OHDA-induced toxicity through antioxidant and antiapoptotic activities in Parkinson's disease model. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  14. Puncture mechanics of soft elastomeric membrane with large deformation by rigid cylindrical indenter

    Science.gov (United States)

    Liu, Junjie; Chen, Zhe; Liang, Xueya; Huang, Xiaoqiang; Mao, Guoyong; Hong, Wei; Yu, Honghui; Qu, Shaoxing

    2018-03-01

    Soft elastomeric membrane structures are widely used and commonly found in engineering and biological applications. Puncture is one of the primary failure modes of soft elastomeric membrane at large deformation when indented by rigid objects. In order to investigate the puncture failure mechanism of soft elastomeric membrane with large deformation, we study the deformation and puncture failure of silicone rubber membrane that results from the continuous axisymmetric indentation by cylindrical steel indenters experimentally and analytically. In the experiment, effects of indenter size and the friction between the indenter and the membrane on the deformation and puncture failure of the membrane are investigated. In the analytical study, a model within the framework of nonlinear field theory is developed to describe the large local deformation around the punctured area, as well as to predict the puncture failure of the membrane. The deformed membrane is divided into three parts and the friction contact between the membrane and indenter is modeled by Coulomb friction law. The first invariant of the right Cauchy-Green deformation tensor I1 is adopted to predict the puncture failure of the membrane. The experimental and analytical results agree well. This work provides a guideline in designing reliable soft devices featured with membrane structures, which are present in a wide variety of applications.

  15. Technical and practical improvements in arthroscopic indentation technique for diagnostics of articular cartilage softening.

    Science.gov (United States)

    Timonen, M A; Töyräs, J; Aula, A S; Karjalainen, J P; Riekkinen, O; Jurvelin, J S

    2011-01-01

    Indentation measurements have been proposed to serve as sensitive in vivo diagnostics of cartilage degeneration. However, practical difficulties have hindered the use of quantitative indentation techniques during routine arthroscopies. In this study we modified the previously commercial indentation technique by designing software for quality control of manual indentations. With the modifications, our aim was to introduce more rapid and less erroneous measurements, as well as more automatic and objective analyses. The performance of the technique was tested in situ using six bovine medial tibial plateaus. All measurements were conducted by three operators. The intraoperator reproducibility was reasonable (CV%  = 7.1%) and the interoperator reproducibility was good (intraclass correlation coefficient  = 0.976). Further, the novel technique was tested by a single operator using 10 bovine medial tibial plateaus. The indentation stiffness values determined with the arthroscopic instrument correlated significantly with the dynamic (r = 0.823) and equilibrium (r = 0.752) moduli as well as tissue water (r =  -0.830) and hydroxyproline (r = 0.776) contents. To conclude, the novel measurement technique showed good reproducibility and was found to give valuable information on cartilage properties. Most importantly, the measurements and analyses were more straightforward and automatic than those introduced in the original indentation approach.

  16. Indentation Size Effect on Ag Nanoparticle-Modified Graphene/Sn-Ag-Cu Solders

    Science.gov (United States)

    Xu, L. Y.; Zhang, S. T.; Jing, H. Y.; Wang, L. X.; Wei, J.; Kong, X. C.; Han, Y. D.

    2018-01-01

    This paper presents the results for the indentation size effect (ISE) on the creep stress exponent and hardness of 0.03 wt.% Ag-modified graphene nanosheet Sn-Ag-Cu solder alloys, using constant loading/holding and multi-cycle (CMC) loading methods, respectively. At each maximum load, with increasing indentation depth, the creep exponent first decreased and then increased. At the same strain rate, the stress exponent also showed the same tendency, increasing as the indentation depth (peak load) increased and then decreased. The hardness was measured continuously with increasing indentation depth by the CMC loading method. The hardness did not exhibit a decrease as the indentation depth increased, which differs from the classical description of the ISE. After an initial decrease, the hardness then increased and finally decreased as the indentation depth increased. This study reviews the existing theories and formulations describing ISE with hardening effects. The experimental results fit well with the empirical formulation. The phenomenon of ISE accompanied by hardening effects has been explained physically via the interaction between geometrically necessary dislocations and grain boundaries.

  17. Quasi-Plastic Deformation of WC-Co Composites Loaded with a Spherical Indenter

    Science.gov (United States)

    Zhang, Haibo; Fang, Zhigang Zak; Belnap, J. Daniel

    2007-03-01

    The quasi-plastic deformation behavior of cemented tungsten carbide (WC-Co) materials was studied using Hertzian indentation techniques. The indentation stress-strain curves of three WC-10 wt pct Co alloys with different hardness values demonstrate that WC-Co alloys exhibit “quasi-plasticity” behavior under indentation load and the increase of indentation stress vs indentation strain bears similarity to “strain hardening” in ductile metals. The analysis of the subsurface indentation damage shows that the mechanisms of the quasi-plastic deformation of WC-Co material are the formation of microcracks. Microcracks were found at heavily damaged areas in all three alloys, and the number of microcracks was higher for the sample with the higher apparent quasi-plasticity. The threshold stress values for the onset of quasi-plastic deformation and formation of ring cracks were determined and used to evaluate the brittleness index of these materials. The correlation of the brittleness index with hardness values gives insight with regard to the brittle or quasi-plastic responses of WC-Co materials.

  18. Method to determine the optimal constitutive model from spherical indentation tests

    Directory of Open Access Journals (Sweden)

    Tairui Zhang

    2018-03-01

    Full Text Available The limitation of current indentation theories was investigated and a method to determine the optimal constitutive model through spherical indentation tests was proposed. Two constitutive models, the Power-law and the Linear-law, were used in Finite Element (FE calculations, and then a set of indentation governing equations was established for each model. The load-depth data from the normal indentation depth was used to fit the best parameters in each constitutive model while the data from the further loading part was compared with those from FE calculations, and the model that better predicted the further deformation was considered the optimal one. Moreover, a Yang’s modulus calculation model which took the previous plastic deformation and the phenomenon of pile-up (or sink-in into consideration was also proposed to revise the original Sneddon-Pharr-Oliver model. The indentation results on six materials, 304, 321, SA508, SA533, 15CrMoR, and Fv520B, were compared with tensile ones, which validated the reliability of the revised E calculation model and the optimal constitutive model determination method in this study. Keywords: Optimal constitutive model, Spherical indentation test, Finite Element calculations, Yang’s modulus

  19. Evaluation of sinking-in and cracking behavior of soda-lime glass under varying angle of trigonal pyramid indenter

    Directory of Open Access Journals (Sweden)

    Satoshi Yoshida

    2016-12-01

    Full Text Available It is well known that glass undergoes elastic and inelastic deformation under a sharp diamond indenter. Although brittle or less-brittle behavior of glass must be connected with such mechanical responses of glass under the indenter, there has been limited research on in-situ deformation behavior of glass during the loading and unloading indentation cycle. This is because most indentation tests were conducted using a commercial hardness tester for which this information is not available. In this study, the in-situ sinking-in region of glass during indentation test is determined using a custom-designed indentation microscope with trigonal pyramid indenters having different tip angles. It is found that both the shape of contact region and the amount of sinking-in are affected by indenter geometries, and that the projected contact region of the glass sample under Berkovich indenter is not a regular triangle, but a concave triangle with bowed-in edges. This is due to the larger amount of sinking-in under the face than under the ridge of indenter. It is also found that these deformation behaviors of glass are inseparably linked with contact damage or cracking in glass.

  20. Comparison of the indentation and elasticity of E. coli and its spheroplasts by AFM

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, C.J. [Genome Science and Technology, University of Tennessee, Knoxville, TN 37932 (United States); Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6123 (United States); Venkataraman, S.; Retterer, S.T. [Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6123 (United States); Allison, D.P. [Genome Science and Technology, University of Tennessee, Knoxville, TN 37932 (United States); Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37932 (United States); Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6123 (United States); Agilent Technologies, Tempe, AZ 85282 (United States); Doktycz, M.J. [Genome Science and Technology, University of Tennessee, Knoxville, TN 37932 (United States); Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6123 (United States)], E-mail: doktyczmj@ornl.gov

    2007-10-15

    Atomic force microscopy (AFM) provides a unique opportunity to study live individual bacteria at the nanometer scale. In addition to providing accurate morphological information, AFM can be exploited to investigate membrane protein localization and molecular interactions on the surface of living cells. A prerequisite for these studies is the development of robust procedures for sample preparation. While such procedures are established for intact bacteria, they are only beginning to emerge for bacterial spheroplasts. Spheroplasts are useful research models for studying mechanosensitive ion channels, membrane transport, lipopolysaccharide translocation, solute uptake, and the effects of antimicrobial agents on membranes. Furthermore, given the similarities between spheroplasts and cell wall-deficient (CWD) forms of pathogenic bacteria, spheroplast research could be relevant in biomedical research. In this paper, a new technique for immobilizing spheroplasts on mica pretreated with aminopropyltriethoxysilane (APTES) and glutaraldehyde is described. Using this mounting technique, the indentation and cell elasticity of glutaraldehyde-fixed and untreated spheroplasts of E. coli in liquid were measured. These values are compared to those of intact E. coli. Untreated spheroplasts were found to be much softer than the intact cells and the silicon nitride cantilevers used in this study.

  1. Effect of double ion implantation and irradiation by Ar and He ions on nano-indentation hardness of metallic alloys

    Science.gov (United States)

    Dayal, P.; Bhattacharyya, D.; Mook, W. M.; Fu, E. G.; Wang, Y.-Q.; Carr, D. G.; Anderoglu, O.; Mara, N. A.; Misra, A.; Harrison, R. P.; Edwards, L.

    2013-07-01

    In this study, the authors have investigated the combined effect of a double layer of implantation on four different metallic alloys, ODS steel MA957, Zircaloy-4, Ti-6Al-4V titanium alloy and stainless steel 316, by ions of two different species - He and Ar - on the hardening of the surface as measured by nano-indentation. The data was collected for a large number of indentations using the Continuous Stiffness Method or "CSM" mode, applying the indents on the implanted surface. Careful analysis of the data in the present investigations show that the relative hardening due to individual implantation layers can be used to obtain an estimate of the relative hardening effect of a combination of two separate implanted layers of two different species. This combined hardness was found to lie between the square root of the sum of the squares of individual hardening effects, (ΔHA2 + ΔHB2)0.5 as the lower limit and the sum of the individual hardening effects, (ΔHA + ΔHB) as the upper limit, within errors, for all depths measured. The hardening due to irradiation by different species of ions was calculated by subtracting the average hardness vs. depth curve of the un-irradiated or "virgin" material from that of the irradiated material. The combined hardening of the irradiated samples due to Ar and He irradiation was found to be described well by an approximate upper bound given by the simple linear sum of the individual hardening (L) and a lower bound given by the square root of the sum of the squares (R) of the individual hardening effects due to Ar and He irradiation along the full depth of the indentation. The peak of the combined hardness of Ar and He irradiated material appears at the depth predicted by both the R and the L curves, in all samples. The combined hardness increase due to Ar and He irradiation lies near the upper limit (L curve) for the ODS steel MA957, somewhere in between L and R curves for Zircaloy-4, and near the R curve for the stainless steel 316

  2. Alternate approach for calculating hardness based on residual indentation depth: Comparison with experiments

    Science.gov (United States)

    Ananthakrishna, G.; K, Srikanth

    2018-03-01

    It is well known that plastic deformation is a highly nonlinear dissipative irreversible phenomenon of considerable complexity. As a consequence, little progress has been made in modeling some well-known size-dependent properties of plastic deformation, for instance, calculating hardness as a function of indentation depth independently. Here, we devise a method of calculating hardness by calculating the residual indentation depth and then calculate the hardness as the ratio of the load to the residual imprint area. Recognizing the fact that dislocations are the basic defects controlling the plastic component of the indentation depth, we set up a system of coupled nonlinear time evolution equations for the mobile, forest, and geometrically necessary dislocation densities. Within our approach, we consider the geometrically necessary dislocations to be immobile since they contribute to additional hardness. The model includes dislocation multiplication, storage, and recovery mechanisms. The growth of the geometrically necessary dislocation density is controlled by the number of loops that can be activated under the contact area and the mean strain gradient. The equations are then coupled to the load rate equation. Our approach has the ability to adopt experimental parameters such as the indentation rates, the geometrical parameters defining the Berkovich indenter, including the nominal tip radius. The residual indentation depth is obtained by integrating the Orowan expression for the plastic strain rate, which is then used to calculate the hardness. Consistent with the experimental observations, the increasing hardness with decreasing indentation depth in our model arises from limited dislocation sources at small indentation depths and therefore avoids divergence in the limit of small depths reported in the Nix-Gao model. We demonstrate that for a range of parameter values that physically represent different materials, the model predicts the three characteristic

  3. Design of Fab-based chimeric antibodies against Bothrops asper toxins

    DEFF Research Database (Denmark)

    M. Haack, Aleksander; B. Hallgren, Malte; U. W. Friis, Rasmus

    Snakebite is one of the world’s most neglected tropical diseases, with an estimated 5 million bites per year, resulting in about 125.000 deaths. The only current treatment for snakebite envenoming is antiserum derived from the blood of immunized mammals(typically horses). These antisera are expen...... are expensive to produce and carry a high risk of causing hyper-allergic reactions in human recipients due to their heterologous origin. Here we report the discovery of chimeric scFvs against Bothrops asper toxins....

  4. Isolation and Functional Characterization of an Acidic Myotoxic Phospholipase A2 from Colombian Bothrops asper Venom

    OpenAIRE

    Posada Arias, Silvia; Rey-Suárez, Paola; Pereáñez J, Andrés; Acosta, Cristian; Rojas, Mauricio; Delazari dos Santos, Lucilene; Ferreira Jr, Rui Seabra; Núñez, Vitelbina

    2017-01-01

    Myotoxic phospholipases A2 (PLA2) are responsible for many clinical manifestations in envenomation by Bothrops snakes. A new myotoxic acidic Asp49 PLA2 (BaCol PLA2) was isolated from Colombian Bothrops asper venom using reverse-phase high performance liquid chromatography (RP-HPLC). BaCol PLA2 had a molecular mass of 14,180.69 Da (by mass spectrometry) and an isoelectric point of 4.4. The complete amino acid sequence was obtained by cDNA cloning (GenBank accession No. MF319968) and revealed a...

  5. Inhibition of the toxic effects of Bothrops asper venom by pinostrobin, a flavanone isolated from Renealmia alpinia (Rottb.) MAAS.

    Science.gov (United States)

    Gómez-Betancur, Isabel; Benjumea, Dora; Patiño, Arley; Jiménez, Nora; Osorio, Edison

    2014-09-29

    Renealmia alpinia has been traditionally used to treat snakebites by indigenous Embera-Katíos tribes belonging to the regions of Antioquia and Chocó, Colombia, and it has been shown to inhibit the enzymatic and biological activities of Bothrops venoms and their purified phospholipase A2 (PLA2) toxins. In addition to its common local usage against snakebites, Renealmia alpinia is commonly used to treat pain. To evaluate the inhibitory ability of pinostrobin, the main compound in the dichloromethane extract of Renealmia alpinia, on the toxic effects of Bothrops asper venom through in vitro and in vivo models and to evaluate its activity against pain and edema. Pinostrobin was isolated from the dichloromethane extract of Renealmia alpinia leaves. The protective properties of the extract and of pinostrobin against the indirect hemolytic, coagulant and proteolytic effects of Bothrops asper venom were evaluated in vitro, and the anti-hemorrhagic and anti-inflammatory activity were evaluated in vivo. Renealmia alpinia extract significantly inhibited the proteolytic activity and indirect hemolytic activity of Bothrops asper venom at a venom:extract ratio of 1:20. Moreover, the present data demonstrate that pinostrobin may mitigate some venom-induced local tissue damage due to hemorrhagic effects, and the compound is also responsible for the analgesic and anti-inflammatory activity of the extract from Renealmia alpinia. This is the first report to describe pinostrobin in the species Renealmia alpinia and its properties in vitro against Bothrops asper venom. Our studies of the activity of Renealmia alpinia against the venom of Bothrops asper have confirmed that this species possesses inhibitory effects against Bothrops asper venom in both in vitro and in vivo models and that these effects may be due to pinostrobin, supporting the traditional usage of the plant. Additionally, pinostrobin may be responsible for the anti-hemorrhagic and analgesic activity (peripheral

  6. Study of the immune response by antibodies against the Bothrops asper venom for the elaboration of a antiophidic vaccine for bovines

    International Nuclear Information System (INIS)

    Gonzalez Rojas, Katherine

    2014-01-01

    Active immunization has determined against Bothrops asper snake venom (tested in murine and bovine models) a induced response by antibody able to prevent in immunized animals. A coagulopathy or death is developed after of be administered with adequate doses of poison. The amount of B. asper venom has defined the poisoning induced in bovine and murine models. The plasmatic concentration of equine antibodies against B. asper venom is specified to prevent coagulopathy and lethality induced by this venom in murine and bovine models. Murine and bovine models have verified the active immunization reached in a concentration of antibodies against B. asper venom equal or greater to the maximum concentration achieved by intravenous administration of antivenoms from equine origin. The concentration of antibodies induced by the active immunization is evaluated against B. asper venom to prevent the development of coagulopathy and lethality induced by the venom in murine and bovine models [es

  7. First record of Porocephalus cf. clavatus (Pentastomida: Porocephalida as a parasite on Bothrops asper (Squamata: Viperidae in Costa Rica

    Directory of Open Access Journals (Sweden)

    G. Alvarado

    Full Text Available Abstract Pentastomids are parasites that infect respiratory cavities of vertebrates, they are pretty common but poorly known in wildlife veterinary. A Bothrops asper snake (Garman, 1884 was captured in the Caribbean region of Costa Rica and had its lung infested with pentastomids, identified as ca Porocephalus clavatus (Wyman, 1845. This represents the first record of Porocephalus (Humboldt, 1812 on B. asper as well as P. cf. clavatus in Costa Rica. Further studies are needed to clarify their taxonomic position, images and scanning electron microscopy photographs (SEM of the specimens are given.

  8. First record of Porocephalus cf. clavatus (Pentastomida: Porocephalida) as a parasite on Bothrops asper (Squamata: Viperidae) in Costa Rica.

    Science.gov (United States)

    Alvarado, G; Sánchez-Monge, A

    2015-11-01

    Pentastomids are parasites that infect respiratory cavities of vertebrates, they are pretty common but poorly known in wildlife veterinary. A Bothrops asper snake (Garman, 1884) was captured in the Caribbean region of Costa Rica and had its lung infested with pentastomids, identified as ca Porocephalus clavatus (Wyman, 1845). This represents the first record of Porocephalus (Humboldt, 1812) on B. asper as well as P. cf. clavatus in Costa Rica. Further studies are needed to clarify their taxonomic position, images and scanning electron microscopy photographs (SEM) of the specimens are given.

  9. Multipoint contact modeling of nanoparticle manipulation on rough surface

    Energy Technology Data Exchange (ETDEWEB)

    Zakeri, M., E-mail: m.zakeri@tabrizu.ac.ir; Faraji, J.; Kharazmi, M. [University of Tabriz, School of Engineering Emerging Technologies (Iran, Islamic Republic of)

    2016-12-15

    In this paper, the atomic force microscopy (AFM)-based 2-D pushing of nano/microparticles investigated on rough substrate by assuming a multipoint contact model. First, a new contact model was extracted and presented based on the geometrical profiles of Rumpf, Rabinovich and George models and the contact mechanics theories of JKR and Schwartz, to model the adhesion forces and the deformations in the multipoint contact of rough surfaces. The geometry of a rough surface was defined by two main parameters of asperity height (size of roughness) and asperity wavelength (compactness of asperities distribution). Then, the dynamic behaviors of nano/microparticles with radiuses in range of 50–500 nm studied during their pushing on rough substrate with a hexagonal or square arrangement of asperities. Dynamic behavior of particles were simulated and compared by assuming multipoint and single-point contact schemes. The simulation results show that the assumption of multipoint contact has a considerable influence on determining the critical manipulation force. Additionally, the assumption of smooth surfaces or single-point contact leads to large error in the obtained results. According to the results of previous research, it anticipated that a particles with the radius less than about 550 nm start to slide on smooth substrate; but by using multipoint contact model, the predicted behavior changed, and particles with radii of smaller than 400 nm begin to slide on rough substrate for different height of asperities, at first.

  10. Isolation and Functional Characterization of an Acidic Myotoxic Phospholipase A2 from Colombian Bothrops asper Venom

    Science.gov (United States)

    Posada Arias, Silvia; Rey-Suárez, Paola; Pereáñez J, Andrés; Acosta, Cristian; Rojas, Mauricio; Ferreira Jr, Rui Seabra; Núñez, Vitelbina

    2017-01-01

    Myotoxic phospholipases A2 (PLA2) are responsible for many clinical manifestations in envenomation by Bothrops snakes. A new myotoxic acidic Asp49 PLA2 (BaCol PLA2) was isolated from Colombian Bothrops asper venom using reverse-phase high performance liquid chromatography (RP-HPLC). BaCol PLA2 had a molecular mass of 14,180.69 Da (by mass spectrometry) and an isoelectric point of 4.4. The complete amino acid sequence was obtained by cDNA cloning (GenBank accession No. MF319968) and revealed a mature product of 124 amino acids with Asp at position 49. BaCol PLA2 showed structural homology with other acidic PLA2 isolated from Bothrops venoms, including a non-myotoxic PLA2 from Costa Rican B. asper. In vitro studies showed cell membrane damage without exposure of phosphatidylserine, an early apoptosis hallmark. BaCol PLA2 had high indirect hemolytic activity and moderate anticoagulant action. In mice, BaCol PLA2 caused marked edema and myotoxicity, the latter seen as an increase in plasma creatine kinase and histological damage to gastrocnemius muscle fibers that included vacuolization and hyalinization necrosis of the sarcoplasm. PMID:29072602

  11. Experimental pathology of local tissue damage induced by Bothrops asper snake venom.

    Science.gov (United States)

    Gutiérrez, José María; Rucavado, Alexandra; Chaves, Fernando; Díaz, Cecilia; Escalante, Teresa

    2009-12-01

    Envenomations by Bothrops asper are often associated with complex and severe local pathological manifestations, including edema, blistering, dermonecrosis, myonecrosis and hemorrhage. The pathogenesis of these alterations has been investigated at the experimental level. These effects are mostly the consequence of the direct action of zinc-dependent metalloproteinases (SVMPs) and myotoxic phospholipases A(2) (PLA(2)s). SVMPs induce hemorrhage, blistering, dermonecrosis and general extracellular matrix degradation, whereas PLA(2)s induce myonecrosis and also affect lymphatic vessels. In addition, the prominent vascular alterations leading to hemorrhage and edema may contribute to ischemia and further tissue necrosis. The mechanisms of action of SVMPs and PLA(2)s are discussed in detail in this review. Venom-induced tissue damage plays also a role in promoting bacterial infection. A prominent inflammatory reaction develops as a consequence of these local pathological alterations, with the synthesis and release of abundant mediators, resulting in edema and pain. However, whether inflammatory cells and mediators contribute to further tissue damage is not clear at present. Muscle tissue regeneration after venom-induced pathological effects is often impaired, thus resulting in permanent tissue loss and dysfunction. SVMP-induced microvessel damage is likely to be responsible of this poor regenerative outcome. Antivenoms are only partially effective in the neutralization of B. asper-induced local effects, and the search for novel toxin inhibitors represents a potential avenue for improving the treatment of this serious aspect of snakebite envenomation.

  12. Biochemistry and toxicology of toxins purified from the venom of the snake Bothrops asper.

    Science.gov (United States)

    Angulo, Yamileth; Lomonte, Bruno

    2009-12-01

    The isolation and study of individual snake venom components paves the way for a deeper understanding of the pathophysiology of envenomings--thus potentially contributing to improved therapeutic modalities in the clinical setting--and also opens possibilities for the discovery of novel toxins that might be useful as tools for dissecting cellular and molecular processes of biomedical importance. This review provides a summary of the different toxins that have been isolated and characterized from the venom of Bothrops asper, the snake species causing the majority of human envenomings in Central America. This venom contains proteins belonging to at least eight families: metalloproteinase, serine proteinase, C-type lectin-like, L-amino acid oxidase, disintegrin, DC-fragment, cystein-rich secretory protein, and phospholipase A(2). Some 25 venom proteins within these families have been isolated and characterized. Their main biochemical properties and toxic actions are described, including, in some cases, their possible relationships to the pathologic effects induced by B. asper venom.

  13. Experimental pathophysiology of systemic alterations induced by Bothrops asper snake venom.

    Science.gov (United States)

    Gutiérrez, José María; Escalante, Teresa; Rucavado, Alexandra

    2009-12-01

    Moderate and severe envenomations by the snake Bothrops asper provoke systemic alterations, such as systemic bleeding, coagulopathy, hypovolemia, hemodynamic instability and shock, and acute renal failure. Systemic hemorrhage is a typical finding of these envenomations, and is primarily caused by the action of P-III snake venom metalloproteinases (SVMPs). This venom also contains a thrombin-like serine proteinase and a prothrombin-activating P-III SVMP, both of which cause defibrin(ogen)ation. Thrombocytopenia, predominantly induced by a C-type lectin-like protein, and platelet hypoaggregation, caused by the two defibrin(ogen)ating enzymes, also contribute to hemostatic disturbances, which potentiate the systemic bleeding induced by hemorrhagic SVMPs. Cardiovascular disturbances leading to shock are due to the combined effects of hemorrhagic toxins, other venom components that increase vascular permeability, the action of hypotensive agents in the venom and of endogenous mediators, and the potential cardiotoxic effect of some toxins. Renal alterations are likely to be caused by direct cytotoxicity of venom components in the kidney, and by renal ischemia resultant from hypovolemia and hypoperfusion. Lethality induced by B. asper venom is the consequence of several combined effects among which the action of P-III SVMPs is especially relevant.

  14. Isolation and Functional Characterization of an Acidic Myotoxic Phospholipase A₂ from Colombian Bothrops asper Venom.

    Science.gov (United States)

    Posada Arias, Silvia; Rey-Suárez, Paola; Pereáñez J, Andrés; Acosta, Cristian; Rojas, Mauricio; Delazari Dos Santos, Lucilene; Ferreira, Rui Seabra; Núñez, Vitelbina

    2017-10-26

    Myotoxic phospholipases A₂ (PLA₂) are responsible for many clinical manifestations in envenomation by Bothrops snakes. A new myotoxic acidic Asp49 PLA₂ (BaCol PLA₂) was isolated from Colombian Bothrops asper venom using reverse-phase high performance liquid chromatography (RP-HPLC). BaCol PLA₂ had a molecular mass of 14,180.69 Da (by mass spectrometry) and an isoelectric point of 4.4. The complete amino acid sequence was obtained by cDNA cloning (GenBank accession No. MF319968) and revealed a mature product of 124 amino acids with Asp at position 49. BaCol PLA₂ showed structural homology with other acidic PLA₂ isolated from Bothrops venoms, including a non-myotoxic PLA₂ from Costa Rican B. asper . In vitro studies showed cell membrane damage without exposure of phosphatidylserine, an early apoptosis hallmark. BaCol PLA₂ had high indirect hemolytic activity and moderate anticoagulant action. In mice, BaCol PLA₂ caused marked edema and myotoxicity, the latter seen as an increase in plasma creatine kinase and histological damage to gastrocnemius muscle fibers that included vacuolization and hyalinization necrosis of the sarcoplasm.

  15. Isolation and Functional Characterization of an Acidic Myotoxic Phospholipase A2 from Colombian Bothrops asper Venom

    Directory of Open Access Journals (Sweden)

    Silvia Posada Arias

    2017-10-01

    Full Text Available Myotoxic phospholipases A2 (PLA2 are responsible for many clinical manifestations in envenomation by Bothrops snakes. A new myotoxic acidic Asp49 PLA2 (BaCol PLA2 was isolated from Colombian Bothrops asper venom using reverse-phase high performance liquid chromatography (RP-HPLC. BaCol PLA2 had a molecular mass of 14,180.69 Da (by mass spectrometry and an isoelectric point of 4.4. The complete amino acid sequence was obtained by cDNA cloning (GenBank accession No. MF319968 and revealed a mature product of 124 amino acids with Asp at position 49. BaCol PLA2 showed structural homology with other acidic PLA2 isolated from Bothrops venoms, including a non-myotoxic PLA2 from Costa Rican B. asper. In vitro studies showed cell membrane damage without exposure of phosphatidylserine, an early apoptosis hallmark. BaCol PLA2 had high indirect hemolytic activity and moderate anticoagulant action. In mice, BaCol PLA2 caused marked edema and myotoxicity, the latter seen as an increase in plasma creatine kinase and histological damage to gastrocnemius muscle fibers that included vacuolization and hyalinization necrosis of the sarcoplasm.

  16. Plasticity under rough surface contact and friction

    NARCIS (Netherlands)

    Sun, F.

    2016-01-01

    The ultimate objective of this work is to gain a better understanding of the plastic behavior of rough metal surfaces under contact loading. Attention in this thesis focuses on the study of single and multiple asperities with micrometer scale dimensions, a scale at which plasticity is known to be

  17. Evaluation of the degradation characteristics of CF-8A cast stainless steel using EDS and nano-indentation

    International Nuclear Information System (INIS)

    Baek, Seung; Koo, Jae Mean; Seok, Chang Sung

    2004-01-01

    Cast austenitic stainless steel piping pump, valve casings, and elbows are susceptible to reductions in toughness and ductility because of long term exposure at the operating temperatures in LWR(Light Water Reactor). In this paper, we have measured the material properties of long term aged CF-8A cast stainless steel, accelerated aging at 400 .deg. C. These studies have been carried out using indentation tests(automated ball indentation and nano-indentation) and EDS(Energy Dispersive Spectroscopy). The fracture toughness of Cf-8A cast stainless steel was also determined by using standard fracture toughness and automated ball indentation

  18. Influence of heat treatment and indenter tip material on depth sensing hardness tests at high temperatures of fusion relevant materials

    International Nuclear Information System (INIS)

    Bredl, Julian; Dany, Manuel; Albinski, Bartlomiej; Schneider, Hans-Christian; Kraft, Oliver

    2015-01-01

    Highlights: • Operation of a custom-made indentation device designed for test temperatures up to 650 °C and a remote handled operation in a Hot Cell. • Instrumented indentation and conventional hardness testing of unirradiated MANET II and EUROFER. • Comparison of diamond and sapphire as indenter tip materials. - Abstract: The instrumented indentation is a suitable method for testing of even small neutron-irradiated specimens. From the continuously recorded indentation depth and the indentation force, it is possible to deduce mechanical parameters of the tested material. In this paper, a brief description of the high temperature device is given and representative results are presented. In the study, unirradiated steels are investigated by instrumented indentation at temperatures up to 500 °C. It is shown that the hardness is highly depending on the testing-temperature and can be correlated to the results of conventional tensile testing experiments. A not negligible influence of the indenter tip material is observed. The results show the functionality of the high-temperature indentation device.

  19. Evaluation of deformation and fracture characteristics of nuclear reactor materials using ball indentation test technique

    International Nuclear Information System (INIS)

    Byun, T. S.; Hong, J. H.; Lee, B. S.; Park, D. G.; Kim, J. H.; Oh, Y. J.; Yoon, J. H.; Chi, S. H.; Kuk, I. H.; Kwon, D. I.; Lee, J. H.

    1998-05-01

    The present report describes the automated ball indentation test techniques and the results of their applications. The ball indentation test technique is an innovative method for evaluating the key mechanical properties from the indentation load-depth data. In the 1st chapter, the existing technique for evaluating basic deformation (tensile) properties is described in detail, and also the application result of the technique is presented. The through-thickness variations of mechanical properties in SA 508 C1.3 reactor pressure vessel steels were measured using an automated ball indentation (ABI) technique. In the 2nd chapter, a method under development, which is similar to that in the 1st chapter, is new method is based on the theoretical solutions rather than experimental relationships. The result of the application showed that the stress-strain curves of various metals were successfully determined with the method. In the 3rd chapter, a new theoretical model was proposed to estimate the fracture toughness of ferritic steels in the transition temperature region. The key concept of the model is that the indention energy to a critical load is related to the fracture energy of the material. The theory was applied to the reactor pressure vessel (RPV) base and weld metals. (author). 24 refs., 3 tabs., 6 figs

  20. Atomic mechanism of shear localization during indentation of a nanostructured metal

    International Nuclear Information System (INIS)

    Sansoz, F.; Dupont, V.

    2007-01-01

    Shear localization is an important mode of deformation in nanocrystalline metals. However, it is very difficult to verify the existence of local shear planes in nanocrystalline metals experimentally. Sharp indentation techniques may provide novel opportunities to investigate the effect of shear localization at different length scales, but the relationship between indentation response and atomic-level shear band formation has not been fully addressed. This paper describes an effort to provide direct insight on the mechanism of shear localization during indentation of nanocrystalline metals from atomistic simulations. Molecular statics is performed with the quasi-continuum method to simulate the indentation of single crystal and nanocrystalline Al with a sharp cylindrical probe. In the nanocrystalline regime, two grain sizes are investigated, 5 nm and 10 nm. We find that the indentation of nanocrystalline metals is characterized by serrated plastic flow. This effect seems to be independent of the grain size. Serration in nanocrystalline metals is found to be associated with the formation of shear bands by sliding of aligned interfaces and intragranular slip, which results in deformation twinning

  1. Method to determine the optimal constitutive model from spherical indentation tests

    Science.gov (United States)

    Zhang, Tairui; Wang, Shang; Wang, Weiqiang

    2018-03-01

    The limitation of current indentation theories was investigated and a method to determine the optimal constitutive model through spherical indentation tests was proposed. Two constitutive models, the Power-law and the Linear-law, were used in Finite Element (FE) calculations, and then a set of indentation governing equations was established for each model. The load-depth data from the normal indentation depth was used to fit the best parameters in each constitutive model while the data from the further loading part was compared with those from FE calculations, and the model that better predicted the further deformation was considered the optimal one. Moreover, a Yang's modulus calculation model which took the previous plastic deformation and the phenomenon of pile-up (or sink-in) into consideration was also proposed to revise the original Sneddon-Pharr-Oliver model. The indentation results on six materials, 304, 321, SA508, SA533, 15CrMoR, and Fv520B, were compared with tensile ones, which validated the reliability of the revised E calculation model and the optimal constitutive model determination method in this study.

  2. Indentation Size Effects in Single Crystal Copper as Revealed by Synchrotron X-ray Microdiffraction

    Energy Technology Data Exchange (ETDEWEB)

    Feng, G.; Budiman, A. S.; Nix, W. D.; Tamura, N.; Patel, J. R.

    2007-11-19

    The indentation size effect (ISE) has been observed in numerous nanoindentation studies on crystalline materials; it is found that the hardness increases dramatically with decreasing indentation size - a 'smaller is stronger' phenomenon. Some have attributed the ISE to the existence of strain gradients and the geometrically necessary dislocations (GNDs). Since the GND density is directly related to the local lattice curvature, the Scanning X-ray Microdiffraction ({mu}SXRD) technique, which can quantitatively measure relative lattice rotations through the streaking of Laue diffractions, can used to study the strain gradients. The synchrotron {mu}SXRD technique we use - which was developed at the Advanced Light Source (ALS), Berkeley Lab - allows for probing the local plastic behavior of crystals with sub-micrometer resolution. Using this technique, we studied the local plasticity for indentations of different depths in a Cu single crystal. Broadening of Laue diffractions (streaking) was observed, showing local crystal lattice rotation due to the indentation-induced plastic deformation. A quantitative analysis of the streaking allows us to estimate the average GND density in the indentation plastic zones. The size dependence of the hardness, as found by nanoindentation, will be described, and its correlation to the observed lattice rotations will be discussed.

  3. 'In vitro' assessment to instrumented indentation hardness tests in enamel of bovine teeth, before and after dental bleaching by laser

    International Nuclear Information System (INIS)

    Britto Junior, Francisco Meira

    2004-01-01

    The laser enamel bleaching is a common used procedure due to its satisfactory esthetic results. The possible changes on the dental structures caused by the bleaching technique are of great importance. The enamel superficial microhardness changes through instrumented indentation hardness on bovine teeth were analyzed in this present study. The samples were divided in two halves, one being the control and the other irradiated with a diode laser (808 nm) or with a Nd:YAG laser (1064 nm) to activate the Whiteness HP bleaching gel (hydrogen peroxide at 35%). It was possible to conclude that there was a statistical significant increase on the enamel superficial microhardness (Group I, sample 1 and Group II, sample 1) despite this increase did not seem to indicate a concern regarding the enamel surface resistance change. There was not a significant statistical change on the enamel microhardness on the other samples. The final conclusion is that there was no superficial enamel morphological change after these treatments. (author)

  4. The 2014, MW6.9 North Aegean Earthquake: Seismic and Geodetic Evidence for Coseismic Slip on Persistent Asperities

    Science.gov (United States)

    Konca, Ali Ozgun; Cetin, Seda; Karabulut, Hayrullah; Reilinger, Robert; Dogan, Ugur; Ergintav, Semih; Cakir, Ziyadin; Tari, Ergin

    2018-02-01

    We report that asperities with the highest coseismic slip in the 2014 of MW6.9 North Aegean Earthquake persisted through the interseismic, coseismic and immediate postseismic periods. We use GPS and seismic data to obtain the source model of the 2014 earthquake, which is located on the western extension of the North Anatolian Fault (NAF). The earthquake ruptured a bilateral, 90 km strike-slip fault with three slip patches; one asperity located west of the hypocenter and two to the east with a rupture duration of 40 s. Relocated pre-earthquake seismicity and aftershocks show that zones with significant coseismic slip were relatively quiet during both the 7-years of interseismic and the 3-month aftershock periods, while the surrounding regions generated significant seismicity during both the interseismic and postseismic periods. We interpret the unusually long fault length and source duration, and distribution of pre- and post-mainshock seismicity as evidence for a rupture of asperities that persisted through strain accumulation and coseismic strain release in a partially coupled fault zone. We further suggest that the association of seismicity with fault creep may characterize the adjacent Izmit, Marmara Sea and Saros segments of the NAF. Similar behavior has been reported for sections of the San Andreas Fault, and some large subduction zones, suggesting that the association of seismicity with creeping fault segments, and rapid re-locking of asperities may characterize many large earthquake faults.

  5. Mechanical evaluation of five flowable resin composites by the dynamic micro-indentation method.

    Science.gov (United States)

    Hirayama, Satoshi; Iwai, Hirotoshi; Tanimoto, Yasuhiro

    2014-01-01

    Measurement of the strength of brittle materials, such as resin composites, is extremely difficult. Micro-indentation hardness testing is a convenient way of investigating the mechanical properties of a small volume of material. In this study, the mechanical properties of five commercially available flowable resin composites were investigated by the dynamic micro-indentation method. Additionally, the effects of inorganic-filler content on the dynamic hardness and elastic modulus of flowable composites obtained by this method were investigated. The weight percentages of the inorganic fillers in the resin composites were determined by the ashing technique. The results indicate that the mechanical properties of flowable composites are affected by not only the filler content but also the properties of the resin matrix. In conclusion, the dynamic micro-indentation method is a useful technique for determining the mechanical behavior of dental resin composites as brittle material.

  6. Using the ultrasound and instrumented indentation techniques to measure the elastic modulus of engineering materials

    International Nuclear Information System (INIS)

    Meza, J. M.; Franco, E. E.; Farias, M. C. M.; Buiochi, F.; Souza, R. M.; Cruz, J.

    2008-01-01

    Currently, the acoustic and nano indentation techniques are two of the most used techniques for materials elastic modulus measurement. In this article fundamental principles and limitations of both techniques are shown and discussed. Last advances in nano indentation technique are also reviewed. an experimental study in ceramic, metallic, composite and single crystals was also done. Results shown that ultrasonic technique is capable to provide results in agreement with those reported in literature. However, ultrasonic technique does not allow measuring the elastic modulus of some small samples and single crystals. On the other hand, the nano indentation technique estimates the elastic modulus values in reasonable agreement with those measured by acoustic methods, particularly in amorphous materials, while in some policristaline materials some deviation from expected values was obtained. (Author) 29 refs

  7. Derivation of tensile flow characteristics for austenitic materials from instrumented indentation technique

    International Nuclear Information System (INIS)

    Lee, K-W; Kim, K-H; Kim, J-Y; Kwon, D

    2008-01-01

    In this study, a method for deriving the tensile flow characteristics of austenitic materials from an instrumented indentation technique is presented along with its experimental verification. We proposed a modified algorithm for austenitic materials that takes their hardening behaviour into account. First, the true strain based on sine function instead of tangent function was adapted. It was proved that the sine function shows constant degrees of hardening which is a main characteristic of the hardening of austenitic materials. Second, a simple and linear constitutive equation was newly suggested to optimize indentation flow curves. The modified approach was experimentally verified by comparing tensile properties of five austenitic materials from uniaxial tensile test and instrumented indentation tests

  8. Analysis of the Indented Cylinder by the use of Computer Vision

    DEFF Research Database (Denmark)

    Buus, Ole Thomsen

    The research summarised in this PhD thesis took advantage of methods from computer vision to experimentally analyse the sorting/separation ability of a specific type of seed sorting device – known as an “indented cylinder”. The indented cylinder basically separates incoming seeds into two sub......-groups: (1) “long” seeds and (2) “short” seeds (known as length-separation). The motion of seeds being physically manipulated inside an active indented cylinder was analysed using various computer vision methods. The data from such analyses were used to create an overview of the machine’s ability to separate...... all the complexities related to that as well. The project arrived at a number of results of high scientific and practical value to the area of applied computer vision and seed processing and agricultural technology in general. The results and methodologies were summarised in one conference paper...

  9. Rediscovery of the enigmatic fungus-farming ant "Mycetosoritis" asper Mayr (Hymenoptera: Formicidae): Implications for taxonomy, phylogeny, and the evolution of agriculture in ants.

    Science.gov (United States)

    Sosa-Calvo, Jeffrey; Ješovnik, Ana; Vasconcelos, Heraldo L; Bacci, Mauricio; Schultz, Ted R

    2017-01-01

    We report the rediscovery of the exceedingly rarely collected and enigmatic fungus-farming ant species Mycetosoritis asper. Since the description of the type specimen in 1887, only four additional specimens are known to have been added to the world's insect collections. Its biology is entirely unknown and its phylogenetic position within the fungus-farming ants has remained puzzling due to its aberrant morphology. In 2014 we excavated and collected twenty-one colonies of M. asper in the Floresta Nacional de Chapecó in Santa Catarina, Brazil. We describe here for the first time the male and larva of the species and complement the previous descriptions of both the queen and the worker. We describe, also for the first time, M. asper biology, nest architecture, and colony demographics, and identify its fungal cultivar. Molecular phylogenetic analyses indicate that both M. asper and M. clorindae are members of the genus Cyphomyrmex, which we show to be paraphyletic as currently defined. More precisely, M. asper is a member of the Cyphomyrmex strigatus group, which we also show to be paraphyletic with respect to the genus Mycetophylax. Based on these results, and in the interest of taxonomic stability, we transfer the species M. asper, M. clorindae, and all members of the C. strigatus group to the genus Mycetophylax, the oldest available name for this clade. Based on ITS sequence data, Mycetophylax asper practices lower agriculture, cultivating a fungal species that belongs to lower-attine fungal Clade 2, subclade F.

  10. Abrasive wear between rough surfaces in deep drawing

    NARCIS (Netherlands)

    Masen, Marc Arthur; de Rooij, Matthias B.

    2004-01-01

    In tribology, many surface contact models are based on the assumption that surfaces are composed of a collection of small asperities of which the tips are equally sized and spherically shaped and have some kind of statistical height distribution. This approach was used in 1966 by Greenwood and

  11. Elastic modulus of claystone evaluated by nano-/micro-indentation tests and meso-compression tests

    Directory of Open Access Journals (Sweden)

    Christophe Auvray

    2017-02-01

    Full Text Available Toarcian claystone such as that of the Callovo-Oxfordian is a qualified multiphase material. The claystone samples tested in this study are composed of four main mineral phases: silicates (clay minerals, quartz, feldspars, micas (≈86%, sulphides (pyrite (≈3%, carbonates (calcite, dolomite (≈10% and organic kerogen (≈1%. Three sets of measurements of the modulus of deformability were compared as determined in (i nano-indentation tests with a constant indentation depth of 2 μm, (ii micro-indentation tests with a constant indentation depth of 20 μm, and (iii meso-compression tests with a constant displacement of 200 μm. These three experimental methods have already been validated in earlier studies. The main objective of this study is to demonstrate the influence of the scaling effect on the modulus of deformability of the material. Different frequency distributions of the modulus of deformability were obtained at the different sample scales: (i in nano-indentation tests, the distribution was spread between 15 GPa and 90 GPa and contained one peak at 34 GPa and another at 51 GPa; (ii in the micro-indentation tests, the distribution was spread between 25 GPa and 60 GPa and displayed peaks at 26 GPa and 37 GPa; and (iii in the meso-compression tests, a narrow frequency distribution was obtained, ranging from 25 GPa to 50 GPa and with a maximum at around 35 GPa.

  12. Postcollisional cooling history of the Eastern and Southern Alps and its linkage to Adria indentation

    Science.gov (United States)

    Heberer, Bianca; Reverman, Rebecca Lee; Fellin, Maria Giuditta; Neubauer, Franz; Dunkl, István; Zattin, Massimiliano; Seward, Diane; Genser, Johann; Brack, Peter

    2017-07-01

    Indentation of rigid blocks into rheologically weak orogens is generally associated with spatiotemporally variable vertical and lateral block extrusion. The European Eastern and Southern Alps are a prime example of microplate indentation, where most of the deformation was accommodated north of the crustal indenter within the Tauern Window. However, outside of this window only the broad late-stage exhumation pattern of the indented units as well as of the indenter itself is known. In this study we refine the exhumational pattern with new (U-Th-Sm)/He and fission-track thermochronology data on apatite from the Karawanken Mountains adjacent to the eastern Periadriatic fault and from the central-eastern Southern Alps. Apatite (U-Th-Sm)/He ages from the Karawanken Mountains range between 12 and 5 Ma and indicate an episode of fault-related exhumation leading to the formation of a positive flower structure and an associated peripheral foreland basin. In the Southern Alps, apatite (U-Th-Sm)/He and fission-track data combined with previous data also indicate a pulse of mainly Late Miocene exhumation, which was maximized along thrust systems, with highly differential amounts of displacement along individual structures. Our data contribute to mounting evidence for widespread Late Miocene tectonic activity, which followed a phase of major exhumation during strain localization in the Tauern Window. We attribute this exhumational phase and more distributed deformation during Adriatic indentation to a major change in boundary conditions operating on the orogen, likely due to a shift from a decoupled to a coupled system, possibly enhanced by a shift in convergence direction.

  13. Effect of Properties and Turgor Pressure on the Indentation Response of Plant Cells

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Needleman, Alan

    2018-01-01

    The indentation of plant cells by a conical indenter is modeled. The cell wall is represented as a spherical shell consisting of a relatively stiff thin outer layer and a softer thicker inner layer. The state of the interior of the cell is idealized as a specified turgor pressure. Attention...... is restricted to axisymmetric deformations, and the wall material is characterized as a viscoelastic solid with different properties for the inner and outer layers. Finite deformation, quasi-static calculations are carried out. The effects of outer layer stiffness, outer layer thickness, turgor pressure...

  14. Strain gradient effects in periodic flat punch indenting at small scales

    DEFF Research Database (Denmark)

    Nielsen, Kim Lau; Niordson, Christian Frithiof; Hutchinson, J. W.

    2014-01-01

    Experiments on soft polycrystalline aluminum have yielded evidence that, besides the required punch load, both the size and shape of imprinted features are affected by the scale of the set-up, e.g. substantial details are lost when the characteristic length is on the order of 10μm. The objective...... of this work is to clarify the role played by strain gradients on this issue, and to shed light on the underlying mechanisms. For this, indentation by a periodic array of flat punch indenters is considered, and a gradient enhanced material model that allows for a numerical investigation of the fundamentals...

  15. Sub-micron indent induced plastic deformation in copper and irradiated steel

    International Nuclear Information System (INIS)

    Robertson, Ch.

    1999-01-01

    In this work we aim to study the indent induced plastic deformation. For this purpose, we have developed a new approach, whereby the indentation curves provides the mechanical behaviour, while the deformation mechanisms are observed thanks to Transmission Electron Microscopy (TEM). In order to better understand how an indent induced dislocation microstructure forms, numerical modeling of the indentation process at the scale of discrete dislocations has been worked out as well. Validation of this modeling has been performed through direct comparison of the computed microstructures with TEM micrographs of actual indents in pure Cu (001]. Irradiation induced modifications of mechanical behaviour of ion irradiated 316L have been investigated, thanks to the mentioned approach. An important hardening effect was reported from indentation data (about 50%), on helium irradiated 316L steel. TEM observations of the damage zone clearly show that this behaviour is associated with the presence of He bubbles. TEM observations of the indent induced plastic zone also showed that the extent of the plastic zone is strongly correlated with hardness, that is to say: harder materials gets a smaller plastic zone. These results thus clearly established that the selected procedure can reveal any irradiation induced hardening in sub-micron thick ion irradiated layers. The behaviour of krypton irradiated 316L steel is somewhat more puzzling. In one hand indeed, a strong correlation between the defect cluster size and densities on the irradiation temperature is observed in the 350 deg. C - 600 deg. C range, thanks to TEM observations of the damage zone. On the other hand, irradiation induced hardening reported from indentation data is relatively small (about 10%) and shows no dependence upon the irradiation temperature (within the mentioned range). In addition, it has been shown that the reported hardening vanishes following appropriate post-irradiation annealing, although most of the TEM

  16. Pressure ulcers, indentation marks and pain from cervical spine immobilization with extrication collars and headblocks : An observational study

    NARCIS (Netherlands)

    Ham, Wietske H W; Schoonhoven, Lisette; Schuurmans, Marieke J; Leenen, Luke P H

    OBJECTIVES: To describe the occurrence and severity of pressure ulcers, indentation marks and pain from the extrication collar combined with headblocks. Furthermore, the influence of time, injury severity and patient characteristics on the development of pressure ulcers, indentation marks and pain

  17. Pressure ulcers, indentation marks and pain from cervical spine immobilization with extrication collars and headblocks: An observational study

    NARCIS (Netherlands)

    Ham, W.H.; Schoonhoven, L.; Schuurmans, M.J.; Leenen, L.P.

    2016-01-01

    OBJECTIVES: To describe the occurrence and severity of pressure ulcers, indentation marks and pain from the extrication collar combined with headblocks. Furthermore, the influence of time, injury severity and patient characteristics on the development of pressure ulcers, indentation marks and pain

  18. A contribution to understanding the results of instrumented indentation on thermal spray coatings - Case study on Al2O3 and stainless steel

    Czech Academy of Sciences Publication Activity Database

    Nohava, J.; Mušálek, Radek; Matějíček, Jiří; Vilémová, Monika

    2014-01-01

    Roč. 240, February (2014), s. 243-249 ISSN 0257-8972 R&D Projects: GA ČR(CZ) GAP108/12/1872; GA ČR(CZ) GPP108/12/P552 Institutional support: RVO:61389021 Keywords : Thermal spray coating * Instrumented indentation * Al2O3 * Stainless steel * Scale effect Subject RIV: JK - Corrosion ; Surface Treatment of Materials Impact factor: 1.998, year: 2014 http://www. science direct.com/ science /article/pii/S0257897213011869#

  19. Evaluation by instrumented indentation of the damage caused by gamma radiation on polymeric materials; Avaliacao por indentacao instrumentada dos danos causados pela radiacao gama em materiais polimericos

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, M.P.; Azevedo, E.C.; Miquelin, C.A.; Soboll, D.S., E-mail: helunica@yahoo.com.b [Universidade Tecnologica Federal do Parana (DAFIS/UTFPR), Curitiba, PR (Brazil). Dept. Academico de Fisica

    2010-07-01

    Several materials with densities close to water are used as phantoms in dosimetry. Such materials are damaged because they are exposed to radiation, the surface layers suffer the largest changes. This damage can be assessed by instrumented indentation. This paper investigates the variations in hardness and elastic modulus of samples of polymethyl-methacrylate, polyvinyl chloride, polyacetal and polypropylene before and after being irradiated with gamma radiation dose 500 Gy, using a Nanoindeter XP, with applied loads between 1 mN and 400 mN. The results are discussed correlating the variations in the mechanical properties of polymers with their applications. (author)

  20. Simulation of the long-term behaviour of a fault with two asperities

    Directory of Open Access Journals (Sweden)

    M. Dragoni

    2010-12-01

    Full Text Available A system made of two sliding blocks coupled by a spring is employed to simulate the long-term behaviour of a fault with two asperities. An analytical solution is given for the motion of the system in the case of blocks having the same friction. An analysis of the phase space shows that orbits can reach a limit cycle only after entering a particular subset of the space. There is an infinite number of different limit cycles, characterized by the difference between the forces applied to the blocks or, as an alternative, by the recurrence pattern of block motions. These results suggest that the recurrence pattern of seismic events produced by the equivalent fault system is associated with a particular stress distribution which repeats periodically. Admissible stress distributions require a certain degree of inhomogeneity, which depends on the geometry of fault system. Aperiodicity may derive from stress transfers from neighboring faults.

  1. Ecology of litterfall production of giant bamboo Dendrocalamus asper in a watershed area

    Directory of Open Access Journals (Sweden)

    A.G. Toledo Bruno

    2017-12-01

    Full Text Available Giant bamboo Dendrocalamus asper is recommended in environmental and livelihood programs in the Philippines due to its various ecological, economic and social benefits. However, there are limited data on the ecology of giant bamboo litterfall production, which contributes to soil nutrient availability. Bamboo also contributed in carbon sequestration. The study was conducted within the Taganibong Watershed in Bukidnon, Philippines. Nine litterfall traps measuring 1mx1m were established within the giant bamboo stand in the study area. Results show that giant bamboo litterfall is dominated by leaves. Biological characteristics of bamboo litterfall do no not influence litterfall production but temperature, wind speed and humidity correlate with the amount of litterfall. Findings of the study further revealed that fresh giant bamboo tissue contains high carbon content and the soil in the bamboo stand has higher organic matter than the open clearing. These data indicate the role of giant bamboo in carbon sequestration and soil nutrient availability.

  2. Dano cavitacional em revestimentos depositados por aspersão termica a chama

    OpenAIRE

    Paulo Villani Marques

    1996-01-01

    Resumo: Quantias elevadas são gastas anualmente na manutenção de turbinas hidráulicas usadas na geração de energia elétrica por causa do ataque cavitacional. Avaliou-se a aplicabilidade de revestimentos metálicos e cerâmicos depositados sobre aço carbono por aspersão térmica a chama na manutenção destes equipamentos em função de sua resistência à erosão por cavitação. Foram realizados ensaios de dureza, rugosidade, ensaio acelerado de cavitação induzida por vibração ultra-sônica, adesão (traç...

  3. Brain antioxidant markers, cognitive performance and acetylcholinesterase activity of rats: efficiency of Sonchus asper

    Directory of Open Access Journals (Sweden)

    Khan Rahmat

    2012-05-01

    Full Text Available Abstract Background Sonchus asper (SA is traditionally used as a folk medicine to treat mental disorders in Pakistan. The aim of this study was to investigate the effect of polyphenolic rich methanolic fraction of SA on cognitive performance, brain antioxidant activities and acetylcholinesterase activity in male rats. Methods 30 male Sprague–Dawley rats were equally divided into three groups in this study. Animals of group I (control received saline (vehicle, group II received SA (50 mg/kg body weight (b.w., and group III treated with SA (100 mg/kg b.w., orally in dimethyl sulphoxide (DMSO for 7 days. The effect of SA was checked on rat cognitive performance, brain antioxidatant and acetylcholinesterase activities. Evaluation of learning and memory was assessed by a step-through a passive avoidance test on day 6 after two habituation trials and an initial acquisition trial on day 5. Antioxidant potential was determined by measuring activities of superoxide dismutase (SOD, catalase (CAT, contents of thiobarbituric acid reactive substances (TBARS and reduced glutathione (GSH in whole-brain homogenates. Acetylcholinesterase (AChE activity was determined by the colorimetric method. Results Results showed that 100 mg/kg b.w., SA treated rats exhibited a significant improvement in learning and memory (step-through latency time. SA administration reduced lipid peroxidation products and elevated glutathione levels in the SA100-treated group. Furthermore, salt and detergent soluble AChE activity was significantly decreased in both SA-treated groups. Short-term orally supplementation of SA showed significant cognitive enhancement as well as elevated brain antioxidant enzymes and inhibited AChE activity. Conclusion These findings stress the critical impact of Sonchus asper bioactive components on brain function.

  4. Deformation and strain distribution in plasma sprayed nickel-aluminum coating loaded by a spherical indenter

    Czech Academy of Sciences Publication Activity Database

    Prchlík, L.; Písačka, Jan; Sampath, S.

    2003-01-01

    Roč. 360, 1-2 (2003), s. 264-274 ISSN 0921-5093 R&D Projects: GA AV ČR KSK1010104 Keywords : indentation, stress-strain relationship, plasma spray Subject RIV: JJ - Other Materials Impact factor: 1.365, year: 2003

  5. Determination of the individual phase properties from the measured grid indentation data

    Czech Academy of Sciences Publication Activity Database

    Haušild, P.; Materna, A.; Kocmanová, L.; Matějíček, Jiří

    2016-01-01

    Roč. 31, č. 22 (2016), s. 3538-3548 ISSN 0884-2914 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Composite * Tungsten * Steel * indentation Subject RIV: JI - Composite Materials Impact factor: 1.673, year: 2016 http://dx. doi . org /10.1557/jmr.2016.375

  6. Assessment with indentation techniques of the local mechanical behavior of joints in polymer parts

    Czech Academy of Sciences Publication Activity Database

    Lach, R.; Hutař, Pavel; Veselý, P.; Nezbedová, E.; Knésl, Zdeněk; Koch, T.; Bierogel, C.; Grellmann, W.

    2013-01-01

    Roč. 58, 11-12 (2013), s. 900-905 ISSN 0032-2725 R&D Projects: GA ČR GC101/09/J027 Institutional support: RVO:68081723 Keywords : weld ed joints * weld lines * microindentation techniques * nanoindentation techniques * hardness * indentation modulus Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.617, year: 2013

  7. Interference of lithospheric folding in western Central Asia by simultaneous Indian and Arabian plate indentation

    NARCIS (Netherlands)

    Smit, J.W.H.; Cloetingh, S.A.P.L.|info:eu-repo/dai/nl/069161836; Burov, E.; Tesauro, M.; Sokoutis, D.|info:eu-repo/dai/nl/298809214; Kaban, M.

    2013-01-01

    Large-scale intraplate deformation of the crust and the lithosphere in Central Asia as a result of the indentation of India has been extensively documented. In contrast, the impact of continental collision between Arabia and Eurasia on lithosphere tectonics in front of the main suture zone, has

  8. Interference of lithospheric folding in Central Asia by simultaneous Indian and Arabian plate indentation

    NARCIS (Netherlands)

    Smit, J.H.W.; Cloetingh, S.A.P.L.; Burov, E.; Tesauro, M.; Sokoutis, D.; Kaban, M.K.

    2013-01-01

    Large-scale intraplate deformation of the crust and the lithosphere in Central Asia as a result of the indentation of India has been extensively documented. In contrast, the impact of continental collision between Arabia and Eurasia on lithosphere tectonics in front of the main suture zone, has

  9. Indentation creep of heterogeneous blends poly(ethylene terephthalate)/impact modifier

    Czech Academy of Sciences Publication Activity Database

    Kolařík, Jan; Pegoretti, A.

    2004-01-01

    Roč. 23, č. 1 (2004), s. 113-121 ISSN 0142-9418 R&D Projects: GA ČR GA106/00/1307 Institutional research plan: CEZ:AV0Z4050913 Keywords : indentation creep * thermoplastics * polymer blends Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.199, year: 2004

  10. Mechanical properties of gray and white matter brain tissue by indentation.

    Science.gov (United States)

    Budday, Silvia; Nay, Richard; de Rooij, Rijk; Steinmann, Paul; Wyrobek, Thomas; Ovaert, Timothy C; Kuhl, Ellen

    2015-06-01

    The mammalian brain is composed of an outer layer of gray matter, consisting of cell bodies, dendrites, and unmyelinated axons, and an inner core of white matter, consisting primarily of myelinated axons. Recent evidence suggests that microstructural differences between gray and white matter play an important role during neurodevelopment. While brain tissue as a whole is rheologically well characterized, the individual features of gray and white matter remain poorly understood. Here we quantify the mechanical properties of gray and white matter using a robust, reliable, and repeatable method, flat-punch indentation. To systematically characterize gray and white matter moduli for varying indenter diameters, loading rates, holding times, post-mortem times, and locations we performed a series of n=192 indentation tests. We found that indenting thick, intact coronal slices eliminates the common challenges associated with small specimens: it naturally minimizes boundary effects, dehydration, swelling, and structural degradation. When kept intact and hydrated, brain slices maintained their mechanical characteristics with standard deviations as low as 5% throughout the entire testing period of five days post mortem. White matter, with an average modulus of 1.89 5kPa ± 0.592 kPa, was on average 39% stiffer than gray matter, pmatter and responded less rapidly to mechanical loading. Understanding the rheological differences between gray and white matter may have direct implications on diagnosing and understanding the mechanical environment in neurodevelopment and neurological disorders. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Crystalline cellulose elastic modulus predicted by atomistic models of uniform deformation and nanoscale indentation

    Science.gov (United States)

    Xiawa Wu; Robert J. Moon; Ashlie Martini

    2013-01-01

    The elastic modulus of cellulose Iß in the axial and transverse directions was obtained from atomistic simulations using both the standard uniform deformation approach and a complementary approach based on nanoscale indentation. This allowed comparisons between the methods and closer connectivity to experimental measurement techniques. A reactive...

  12. Measurement of time-dependent adhesion between a polymer film and a flat indenter tip

    International Nuclear Information System (INIS)

    Choi, S T; Lee, S R; Earmme, Y Y

    2008-01-01

    We revisited an elasticity problem of flat indentation on an elastic film bonded to a rigid substrate and obtained the force-depth relation in a simple form. With the obtained force-depth relation, Kendall's elastic equilibrium theory of adhesion was extended to the adhesion between a flat tip and a compressible elastic film. Thus, the thermodynamic work of adhesion at the moment of debonding of a flat tip from an elastic film was expressed in terms of pull-off force, elastic constants and geometric parameters. It is worth noting that the obtained relation for elastic films is still valid for viscoelastic films if viscoelastic losses are limited to the process zone of debonding. This makes it possible to study the time-dependent adhesion of viscoelastic polymer films. Indentation experiments with a flat diamond tip were performed on SU-8 films, and the results verified that the extended form of Kendall's theory correctly compensates the effect of the finite thickness of the films on the work of adhesion. The indentation results also showed that the work of adhesion is strongly dependent on the unloading velocity of the tip, while indentation depth and dwell time have only minor effects on the work of adhesion

  13. Mechanical damage in a lithium-ion pouch cell under indentation loads

    Science.gov (United States)

    Luo, Hailing; Xia, Yong; Zhou, Qing

    2017-07-01

    The short circuit of lithium-ion batteries induced by mechanical abuse is a great concern in electric vehicle design. It remains a challenge to fully understand the nature of the mechanical damage process with the aim of improving battery crash safety. The present paper investigates the evolution of the damage process for a lithium-ion pouch cell under indentation by loading the cell to various force levels. A significant inflection point on the force-indentation curve is observed before the force peak. Post-mortem examinations indicate that the characteristic change in the local slope of the curve is related to the change occurring at the local interfaces, including three phenomena - formation of tight adhesion on the anode-separator interfaces, delamination in the separators and decoating of graphite particles from the anodes. Analysis of the fracture sequence at the onset of short circuit clearly shows that the number of short-circuited electrode pairs is equal to the number of anode layers adhered with delaminated separator material before fracture occurs. The experimental study in the present paper implies that the inflection point on the force-indentation curve may be an indicator of damage initiation inside pouch cells under indentation.

  14. A Progressive Damage Model for Predicting Permanent Indentation and Impact Damage in Composite Laminates

    Science.gov (United States)

    Ji, Zhaojie; Guan, Zhidong; Li, Zengshan

    2017-10-01

    In this paper, a progressive damage model was established on the basis of ABAQUS software for predicting permanent indentation and impact damage in composite laminates. Intralaminar and interlaminar damage was modelled based on the continuum damage mechanics (CDM) in the finite element model. For the verification of the model, low-velocity impact tests of quasi-isotropic laminates with material system of T300/5228A were conducted. Permanent indentation and impact damage of the laminates were simulated and the numerical results agree well with the experiments. It can be concluded that an obvious knee point can be identified on the curve of the indentation depth versus impact energy. Matrix cracking and delamination develops rapidly with the increasing impact energy, while considerable amount of fiber breakage only occurs when the impact energy exceeds the energy corresponding to the knee point. Predicted indentation depth after the knee point is very sensitive to the parameter μ which is proposed in this paper, and the acceptable value of this parameter is in range from 0.9 to 1.0.

  15. Pagurus Asper H. Milne Edwards, 1848, a subjective synonym of Clibanarius longitarsus (De Haan, 1849) and reversal of precedence (Crustacea: Decapoda: Anomura: Diogenidae).

    Science.gov (United States)

    Low, Martyn E Y; Rahayu, Dwi Listyo

    2014-06-04

    The species-group name Pagurus longitarsus was proposed by De Haan (1849: 211, pl. 50, fig. 3) for a species of hermit crab collected from Japan (see Yamaguchi & Baba 1993: 272, 273). Dana (1852b: 464) transferred Pagurus longitarsus to the genus Clibanarius Dana, 1852 (first established in Dana 1852a). Dana (1852b: 464) also suggested that Pagurus longitarsus De Haan, 1849, and Pagurus asper H. Milne Edwards, 1848, were possibly synonymous by listing "Pagurus asper ? Edwards, Ann. des Sci. Nat., 1848(3), v. [sic] 62" in the synonymy of Pagurus longitarsus De Haan, 1849. Fize & Serène (1955: 72) repeated Dana's (1852b: 464) opinion regarding the synonymy Pagurus longitarsus and Pagurus asper. McLaughlin (2002: 399) and McLaughlin et al. (2010: 20) also considered Pagurus longitarsus De Haan, 1849, and Pagurus asper H. Milne Edwards, 1848, to be possibly conspecific, but considered Clibanarius longitarsus (De Haan, 1849), to be the valid name.

  16. First-principles calculation of the indentation strength of FeB4

    Science.gov (United States)

    Li, Bing; Sun, Hong; Chen, Changfeng

    2014-07-01

    A recent experiment [H. Y. Gou et al., Phys. Rev. Lett. 111, 157002 (2013), 10.1103/PhysRevLett.111.157002] reported a measured Vickers hardness of over 60 GPa for FeB4, placing it as a superhard material far above all other similar ultrahard transition-metal borides, such as ReB2,WB4, and especially CrB4, which has the same crystalline structure as that of FeB4 but a much lower measured Vickers hardness of around 23 GPa. This result, however, is contradicted by theoretical calculations that predict a smaller shear modulus for FeB4 than that of CrB4, indicating that FeB4 is softer than CrB4. Here we report first-principles calculations that aim to understand the stress response of FeB4 under indentation loadings and examine whether there exists a strain-stiffening effect that might enhance the indentation strength. Our results show that there is no strain stiffening in FeB4; instead, the normal pressure beneath the indenter drives a lateral structural expansion which further stretches and weakens the boron-boron and boron-iron bonds in addition to that caused by the shear deformation in Vickers indentation tests. This effect leads to a considerably reduced strength of FeB4, producing an ideal (i.e., an upper bound) indentation strength of 17 GPa that is lower than that (27 GPa) predicted for CrB4. The present results suggest that FeB4 is unlikely to be superhard and further experimental investigation is needed to clarify this issue.

  17. Identification of the crushing behavior of brittle foam: From indentation to oedometric tests

    Science.gov (United States)

    Bouterf, A.; Adrien, J.; Maire, E.; Brajer, X.; Hild, F.; Roux, S.

    2017-01-01

    Compaction of the core of plasterboard is one of the limiting phenomena for its mechanical performance. This mechanism is studied herein in an indentation test. A cylinder made of foamed gypsum is indented in situ in an X-ray lab tomograph with a sphere of millimeter radius. The reported experiments show that foamed plaster displays a sharp transition between an undamaged state (with linear elastic behavior) and a compacted state with collapsed porosity under the indenter. Tomographic acquisitions of the sample under load associated with a global version of Digital Volume Correlation allow displacement fields to be measured at different load levels. However, because of the heterogeneous nature of the indentation test, a fine spatial resolution of the displacement fields is required to measure the strains at the crushing limit. A dedicated procedure exploiting computed displacement fields within the digital volume correlation procedure is utilized. It allows for the quantification of stress fields that are post-processed to identify the crushing criterion. It is shown that this analysis is very consistent with more macroscopic oedometric tests. Last, predictions of a Mohr-Coulomb model are compared with macroscopic and microscopic data. It is shown that despite the fact that this model reproduces very well the load-displacement response of the indentation test, a poorer prediction of the experimental crushed zone is observed. In particular, the transition between compacted plaster and its pristine state is not captured by the model, which predicts a very progressive transition rather than an abrupt one. The same conclusions are drawn for a crushable foam model when compared with experimental evidence of an in situ oedometric test.

  18. Modeling ramp-hold indentation measurements based on Kelvin-Voigt fractional derivative model

    Science.gov (United States)

    Zhang, Hongmei; zhe Zhang, Qing; Ruan, Litao; Duan, Junbo; Wan, Mingxi; Insana, Michael F.

    2018-03-01

    Interpretation of experimental data from micro- and nano-scale indentation testing is highly dependent on the constitutive model selected to relate measurements to mechanical properties. The Kelvin-Voigt fractional derivative model (KVFD) offers a compact set of viscoelastic features appropriate for characterizing soft biological materials. This paper provides a set of KVFD solutions for converting indentation testing data acquired for different geometries and scales into viscoelastic properties of soft materials. These solutions, which are mostly in closed-form, apply to ramp-hold relaxation, load-unload and ramp-load creep-testing protocols. We report on applications of these model solutions to macro- and nano-indentation testing of hydrogels, gastric cancer cells and ex vivo breast tissue samples using an atomic force microscope (AFM). We also applied KVFD models to clinical ultrasonic breast data using a compression plate as required for elasticity imaging. Together the results show that KVFD models fit a broad range of experimental data with a correlation coefficient typically R 2  >  0.99. For hydrogel samples, estimation of KVFD model parameters from test data using spherical indentation versus plate compression as well as ramp relaxation versus load-unload compression all agree within one standard deviation. Results from measurements made using macro- and nano-scale indentation agree in trend. For gastric cell and ex vivo breast tissue measurements, KVFD moduli are, respectively, 1/3-1/2 and 1/6 of the elasticity modulus found from the Sneddon model. In vivo breast tissue measurements yield model parameters consistent with literature results. The consistency of results found for a broad range of experimental parameters suggest the KVFD model is a reliable tool for exploring intrinsic features of the cell/tissue microenvironments.

  19. Mechanical behavior of biopolymer composite coatings on plastic films by depth-sensing indentation - A nanoscale study.

    Science.gov (United States)

    Rovera, Cesare; Cozzolino, Carlo A; Ghaani, Masoud; Morrone, Davide; Olsson, Richard T; Farris, Stefano

    2018-02-15

    Fundamental physical behaviors of materials at the nanoscale level are crucial when local aspects govern the macroscale performance of nanocomposites, e.g., interface and surface phenomena. Because of the increasing interest in biopolymer nanocomposite coatings for many different applications (e.g., optical devices, displays/screens, and packaging), this work investigates the potential of nanoindentation as a method for clarifying the interplay between distinct phases (i.e., organic and inorganic) at local level in thin biopolymer films loaded with nanoparticles. The nanomechanical features of pullulan nanocomposite coatings laid on polyethylene terephthalate (PET) were quantified in terms of elastic modulus (E), hardness (H), and creep (C) through an instrumented indentation test composed of a loading-holding-unloading cycle. Colloidal silica (CS) and cellulose nanocrystals (CNCs) were used as spherical and rod-like nanoparticles, respectively. An overall reinforcing effect was shown for all nanocomposite coatings over the pristine (unfilled) pullulan coating. A size effect was also disclosed for the CS-loaded surfaces, with the highest E value recorded for the largest particles (8.19 ± 0.35 GPa) and the highest H value belonging to the smallest ones (395.41 ± 25.22 MPa). Comparing CS and CNCs, the addition of spherical nanoparticles had a greater effect on the surface hardness than cellulose nanowhiskers (353.50 ± 83.52 MPa and 321.36 ± 43.26 MPa, respectively). As for the elastic modulus, the addition of CS did not provide any improvement over both the bare and CNC-loaded pullulan coatings, whereas the coating including CNCs exhibited higher E values (p coatings were the best performing in terms of C properties, with an average indentation depth of 16.5 ± 1.85 nm under a load of ∼190 μN. These results are discussed in terms of local distribution gradients, surface chemistry of nanoparticles, and how nanoparticle

  20. The Possible Decapitation of a Megathrust Indenter: Evidence from Imaging of Time-dependent Microseismic Structures before and after the 2012 Mw 7.6 Nicoya, Costa Rica

    Science.gov (United States)

    Newman, A. V.; Yao, D.; Kyriakopoulos, C.; Moore-Driskell, M. M.; Hobbs, T. E.; Peng, Z.; Schwartz, S. Y.; Protti, M.; Gonzalez, V.

    2016-12-01

    We normally view the subduction megathrust surface as a constant structure throughout the seismic cycle, with the elastic loading, microseismicity, and slip occurring along it. However, using small events recorded from a uniquely dense seismic network directly over the active megathrust below Nicoya, Costa Rica, we find two different seismogenic structures with near exclusive time-dependent behavior immediately in the region of maximum coseismic slip. Microseismicity recorded at intervals between 1999 and 2009 showed an elevated topographic indenter beneath central Nicoya, and associated with a suture marking transition between Cocos-Nazca Spreading Center and East-Pacific Rise crusts [Kyriakopoulos et al., JGR 2015]. This indenter is located as a focus of interseismic locking and coseismic rupture [Feng et al., JGR 2012; Yue et al., JGR 2013; Protti et al., Nat. Geosc. 2014; Xue et al., JGR 2015; Kyriakopoulos & Newman, JGR 2016]. However, aftershocks recorded in the months following an MW 7.6 earthquake in 2012 define an entirely different structure about 5 km deeper and differing only in the area of maximum coseismic slip. The location of seismicity switches entirely between these faults from the shallow indenter structure beforehand to the deeper and near-linear feature after. To improve our imaging of the behavior and associated slab structure, we perform a detailed joint seismic relocation and tomographic inversion using TomoDD [Zhang and Thurber, PAGEOPH 2003]. We analyze the new locations relative to the imaged slab geometry, and compare automated formulations of the interfaces using the Maximum Seismicity Method [Kyriakopoulos et al., 2015], with data existing before and after the earthquake. Lastly, we show the sensitivity of using either surface in models for fault slip from regional GPS. We hypothesize that the bifurcated fault structure signifies either active decapitation of the indenter, possibly along the crust-mantle interface of the downgoing slab

  1. An optical coherence tomography (OCT)-based air jet indentation system for measuring the mechanical properties of soft tissues

    Science.gov (United States)

    Huang, Yan-Ping; Zheng, Yong-Ping; Wang, Shu-Zhe; Chen, Zhong-Ping; Huang, Qing-Hua; He, Yong-Hong

    2009-01-01

    A novel noncontact indentation system with the combination of an air jet and optical coherence tomography (OCT) was presented in this paper for the quantitative measurement of the mechanical properties of soft tissues. The key idea of this method is to use a pressure-controlled air jet as an indenter to compress the soft tissue in a noncontact way and utilize the OCT signals to extract the deformation induced. This indentation system provides measurement and mapping of tissue elasticity for small specimens with high scanning speed. Experiments were performed on 27 silicone tissue-mimicking phantoms with different Young's moduli, which were also measured by uniaxial compression tests. The regression coefficient of the indentation force to the indentation depth (N mm-1) was used as an indicator of the stiffness of tissue under air jet indentation. Results showed that the stiffness coefficients measured by the current system correlated well with the corresponding Young's moduli obtained by conventional mechanical testing (r = 0.89, p < 0.001). Preliminary in vivo tests also showed that the change of soft tissue stiffness with and without the contraction of the underlying muscles in the hand could be differentiated by the current measurement. This system may have broad applications in tissue assessment and characterization where alterations of mechanical properties are involved, in particular with the potential of noncontact micro-indentation for tissues.

  2. The topography of a continental indenter: The interplay between crustal deformation, erosion, and base level changes in the eastern Southern Alps

    Science.gov (United States)

    Heberer, B.; Prasicek, G.; Neubauer, F.; Hergarten, S.

    2017-01-01

    Abstract The topography of the eastern Southern Alps (ESA) reflects indenter tectonics causing crustal shortening, surface uplift, and erosional response. Fluvial drainages were perturbed by Pleistocene glaciations that locally excavated alpine valleys. The Late Miocene desiccation of the Mediterranean Sea and the uplift of the northern Molasse Basin led to significant base level changes in the far field of the ESA and the Eastern Alps (EA), respectively. Among this multitude of mechanisms, the processes that dominate the current topographic evolution of the ESA and the ESA‐EA drainage divide have not been identified. We demonstrate the expected topographic effects of each mechanism in a one‐dimensional model and compare them with observed channel metrics. We find that the normalized steepness index increases with uplift rate and declines from the indenter tip in the northwest to the foreland basin in the southeast. The number and amplitude of knickpoints and the distortion in longitudinal channel profiles similarly decrease toward the east. Changes in slope of χ‐transformed channel profiles coincide spatially with the Valsugana‐Fella fault linking crustal stacking and uplift induced by indenter tectonics with topographic evolution. Gradients in χ across the ESA‐EA drainage divide imply an ongoing, north directed shift of the Danube‐ESA watershed that is most likely driven by a base level rise in the northern Molasse basin. We conclude that the regional uplift pattern controls the geometry of ESA‐EA channels, while base level changes in the far field control the overall architecture of the orogen by drainage divide migration. PMID:28344912

  3. An Instrumented Macro-Indentation Method for Determining the Mechanical Properties of Coconut Shell (Coco Nucifera of Cameroon)

    OpenAIRE

    Njeugna, E.; Ganou, M.B.K.; Ndapeu, D.; Foba, J.N.T.; Sikame , N.R.T.; Huisken , P.W.M.

    2016-01-01

    International audience; An instrumented macro-indentation test was used to determine the viscoelastic parameters and hardness of the shell of Coco Nucifera from Cameroon in order to promote their use in the manufacture of abrasives. Samples measuring 10 mm x 10 mm x 3 mm were cut out from the bottom of the fruit, close to the natural indentations (the eye) of an approximately round-shaped fruit. The indentation load ranged from 50 to 500 N with an increment of 50 N. A comparator with digital ...

  4. Biochemical characterization and pharmacological properties of a phospholipase A2 myotoxin inhibitor from the plasma of the snake Bothrops asper.

    Science.gov (United States)

    Lizano, S; Lomonte, B; Fox, J W; Gutiérrez, J M

    1997-01-01

    A protein that neutralizes the biological activities of basic phospholipase A2 (PLA2) myotoxin isoforms from the venom of the snake Bothrops asper was isolated from its blood by affinity chromatography with Sepharose-immobilized myotoxins. Biochemical characterization of this B. asper myotoxin inhibitor protein (BaMIP) indicated a subunit molecular mass of 23-25 kDa, an isoelectric point of 4, and glycosylation. Gel-filtration studies revealed a molecular mass of 120 kDa, suggesting that BaMIP possesses an oligomeric structure composed of five 23-25 kDa subunits. Functional studies indicated that BaMIP inhibits the PLA2 activity of B. asper basic myotoxins I and III, as well as the myotoxicity and edema-forming activity in vivo and cytolytic activity in vitro towards cultured endothelial cells, of all four myotoxin isoforms (I-IV) tested. Sequence analysis of the first 63 amino acid residues from the N-terminus of BaMIP indicated more than 65% sequence similarity to the PLA2 inhibitors isolated from the blood of the crotalid snakes Trimeresurus flavoviridis and Agkistrodon blomhoffii siniticus. These inhibitors also share sequences similar to the carbohydrate-recognition domains of human and rabbit cellular PLA2 receptors, suggesting a common domain evolution among snake plasma PLA2 inhibitors and mammalian PLA2 receptors. Despite this similarity, this is the first description of a natural anti-myotoxic factor from snake blood. PMID:9307037

  5. Isolation of bothrasperin, a disintegrin with potent platelet aggregation inhibitory activity, from the venom of the snake Bothrops asper.

    Science.gov (United States)

    Pinto, Adrián; Angulo, Yamileth; Jiménez, Rafael; Lomonte, Bruno

    2003-03-01

    The venom of Bothrops asper induces severe coagulation disturbances in accidentally envenomed humans. However, only few studies have been conducted to identify components that interact with the hemostatic system in this venom. In the present work, we fractionated B. asper venom in order to investigate the possible presence of inhibitors of platelet aggregation. Using a combination of gel filtration, anion-exchange chromatography, and reverse-phase high performance liquid chromatography, we isolated an acidic protein which shows a single chain composition, with a molecular mass of approximately 8 kDa, estimated by SDS-polyacrylamide gel electrophoresis. Its N-terminal sequence has high similarity to disintegrins isolated from different snake venoms, which are known to bind to cellular integrins such as the GPIIb/IIIa fibrinogen receptor on platelets. The purified protein exerted potent aggregation inhibitory activity on ADP-stimulated human platelets in vitro, with an estimated IC50 of 50 nM. This biological activity, together with the biochemical characteristics observed, demonstrate that the protein isolated from B. asper venom is a disintegrin, hereby named "bothrasperin". This is the first disintegrin isolated from Central American viperid snake species.

  6. Bothrops asper envenoming in cattle: Clinical features and management using equine-derived whole IgG antivenom.

    Science.gov (United States)

    Rodríguez, C; Estrada, R; Herrera, M; Gómez, A; Segura, Á; Vargas, M; Villalta, M; León, G

    2016-01-01

    Snakebite envenoming is an important problem in the livestock industry in Costa Rica. Of the 22 species of venomous snakes in the country, Bothrops asper is involved in most animal envenomings. Envenomation is typically characterised by swelling and bleeding at the bite site, coagulopathy, systemic haemorrhage, and, in some cases, death. The aims of the present study were to describe the clinical manifestations of B. asper envenomation in cattle and to evaluate the treatment efficacy of antivenom administration. The clinical effects of naturally occurring envenomation were reproduced experimentally in cattle by giving an intramuscular injection of either 10 mg or 50 mg venom to replicate mild and severe envenomings, respectively. Intravenous antivenom given 6 h after experimental venom injection controlled the symptoms; a dose of 120 mL was found to be appropriate for moderate and 200 mL for severe naturally occurring envenomings. Although administration of antivenom within the first 6 h following a snakebite prevented systemic effects, it did not reduce the extent of swelling at the bite site. Delayed administration of antivenom was not effective in saving naturally envenomed animals. The results indicate that, when promptly administered, antivenom constitutes an effective treatment for B. asper snakebite envenomation in cattle.

  7. Isolation of bothrasperin, a disintegrin with potent platelet aggregation inhibitory activity, from the venom of the snake Bothrops asper

    International Nuclear Information System (INIS)

    Pinto, A.; Angulo, Y.; Jimenez, R.; Lomonte, B.

    2003-01-01

    The venom of Bothrops asper induces severe coagulation disturbances in accidentally envenomed humans. However, only few studies have been conducted to identify components that interact with the hemostatic system in this venom. In the present work, we fractionated B. asper venom in order to investigate the possible presence of inhibitors of platelet aggregation. Using a combination of gel filtration, anion-exchange chromatography, and reverse-phase high performance liquid chromatography, we isolated an acidic protein which shows a single chain composition, with a molecular mass of ∼8 kDa, estimated by SDS-polyacrylamide gel electrophoresis. Its N-terminal sequence has high similarity to disintegrins isolated from different snake venoms, which are known to bind to cellular integrins such as the GPIIb/IIIa fibrinogen receptor on platelets. The purified protein exerted potent aggregation inhibitory activity on ADP-stimulated human platelets in vitro, with an estimated IC 50 of 50 nM. This biological activity, together with the biochemical characteristics observed, demonstrate that the protein isolated from B. asper venom is a disintegrin, hereby named bothrasperin. This is the first disintegrin isolated from Central American viperid snake species. (Author)

  8. Prevention of hepatorenal toxicity with Sonchus asper in gentamicin treated rats

    Directory of Open Access Journals (Sweden)

    Khan Muhammad R

    2011-11-01

    Full Text Available Abstract Background Sonchus asper possesses antioxidant capacity and is used in liver and kidney disorders. We have investigated the preventive effect of methanolic extract of Sonchus asper (SAME on the gentamicin induced alterations in biochemical and morphological parameters in liver and kidneys of Sprague-Dawley male rat. Methods Acute oral toxicity studies were performed for selecting the therapeutic dose of SAME. 30 Sprague-Dawley male rats were equally divided into five groups with 06 animals in each. Group I received saline (0.5 ml/kg bw; 0.9% NaCl while Group II administered with gentamicin 0.5 ml (100 mg/kg bw; i.p. for ten days. Animals of Group III and Group IV received gentamicin and SAME 0.5 ml at a dose of 100 mg/kg bw and 200 mg/kg bw, respectively while Group V received only SAME at a dose of 200 mg/kg bw. Biochemical parameters including aspartate transaminase (AST, alanine transaminase (ALT, alkaline phosphatase (ALP, lactate dehydrogenase (LDH, γ-glutamyltransferase (γ-GT, total cholesterol, triglycerides, total protein, albumin, creatinine, blood urea nitrogen (BUN, total bilirubin and direct bilirubin were determined in serum collected from various groups. Urinary out puts were measured in each group and also assessed for the level of protein and glucose. Lipid peroxides (TBARS, glutathione (GSH, DNA injuries and activities of antioxidant enzymes; catalase (CAT, peroxidase (POD and superoxide dismutase (SOD were determined in liver and renal samples. Histopathological studies of liver and kidneys were also carried out. Results On the basis of acute oral toxicity studies, 2000 mg/kg bw did not induce any toxicity in rats, 1/10th of the dose was selected for preventive treatment. Gentamicin increased the level of serum biomarkers; AST, ALT, ALP, LDH, γ-GT, total cholesterol, triglycerides, total protein, albumin, creatinine, BUN, total and direct bilirubin; as were the urinary level of protein, glucose, and urinary output

  9. Development of 3d micro-nano hybrid patterns using anodized aluminum and micro-indentation

    International Nuclear Information System (INIS)

    Shin, Hong Gue; Kwon, Jong Tae; Seo, Young Ho; Kim, Byeong Hee

    2008-01-01

    We developed a simple and cost-effective method of fabricating 3D micro-nano hybrid patterns in which micro-indentation is applied on the anodized aluminum substrate. Nano-patterns were formed first on the aluminum substrate, and then micro-patterns were fabricated by deforming the nano-patterned aluminum substrate. Hemispherical nano-patterns with a 150 nm-diameter on an aluminum substrate were fabricated by anodizing and alumina removing process. Then, micro-pyramid patterns with a side-length of 50 μm were formed on the nano-patterns using micro-indentation. To verify 3D micro-nano hybrid patterns, we replicated 3D micro-nano hybrid patterns by a hot-embossing process. 3D micro-nano hybrid patterns may be used in nano-photonic devices and nano-biochips applications

  10. Experimental tests of the impact of selected parameters on the indentation rolling resistances

    Science.gov (United States)

    Woźniak, Dariusz; Gładysiewicz, Lech; Konieczna, Martyna

    2018-01-01

    Belt conveyors are main part of transporting systems in mines and in many other branches of industry. During conveyor belt works different types of resistances are generated. Indentation rolling resistance is the most significant component of the resistances from the perspective of energy losses and it cause the biggest costs as well. According to latest state of analyses and measurements it is well known that theoretical rolling resistance were underestimated in comparison with the measured in-situ one. In this paper new method for determination indentation rolling resistance is presented. The authors compared theoretically and experimentally established damping factors. The relation between these two values enabled to obtain more precise equation for damping function. This function is one of the most important component in calculation of the rolling resistance. In new theoretical model value of rolling resistance is nearly twice higher than this used so far.

  11. Constitutive modeling of porcine liver in indentation using 3D ultrasound imaging.

    Science.gov (United States)

    Jordan, P; Socrate, S; Zickler, T E; Howe, R D

    2009-04-01

    In this work we present an inverse finite-element modeling framework for constitutive modeling and parameter estimation of soft tissues using full-field volumetric deformation data obtained from 3D ultrasound. The finite-element model is coupled to full-field visual measurements by regularization springs attached at nodal locations. The free ends of the springs are displaced according to the locally estimated tissue motion, and the normalized potential energy stored in all springs serves as a measure of model-experiment agreement for material parameter optimization. We demonstrate good accuracy of estimated parameters and consistent convergence properties on synthetically generated data. We present constitutive model selection and parameter estimation for perfused porcine liver in indentation, and demonstrate that a quasilinear viscoelastic model with shear modulus relaxation offers good model-experiment agreement in terms of indenter displacement (0.19 mm RMS error) and tissue displacement field (0.97 mm RMS error).

  12. CONTACT STRESSES IN A TRANSVERSELY ISOTROPIC SOLID CYLINDER LATERALLY COMPRESSED BY AN INDENTER

    Directory of Open Access Journals (Sweden)

    Ahmet YAPICI

    2004-03-01

    Full Text Available In this study, an elastostatic contact problem for a laterally compressed transversely isotropic cylinder subjected to radial compression through a circumferential rigid indenter is considered. The extent of the contact region and the stress distribution are sought. It is assumed that the contact between the cylinder and the rigid indenter is frictionless and only compressive normal tractions can be transmitted through the interface. Due to the geometry of the configuration, Fourier transform techniques are chosen. The problem is reduced to a singular integral equation. It is reduced to linear algebraic equation system by using Gauss Chebyshev Integration Formulae and is solved by using Gauss Elimination method. E glass and barium titanate are used as a transversely isotropic materials. The stress analysis is performed for different contact area, punch radiuses and cylinder radiuses. The obtained results are shown in figures.

  13. Construction of stess-strain curves for brittle materials by indentation in a wide temperature range

    Directory of Open Access Journals (Sweden)

    Milman Yu.V.

    2007-01-01

    Full Text Available A test method procedure for constructing stress-strain curves by indentation of brittle and low plastic materials under temperature ranging from 20 to 900°C was developed recently by Yu. Milman, B. Galanov et al. According to this test method procedure stress-strain curves σ - Є for Si, Ge, SiC, TiB2 and WC/Co hard alloy were constructed in the above temperature region and mechanical parameters such as elastic point, σe, yield stress, σs, etc. were extracted by using the measurement results obtained by a set of trihedral pyramid indenters with different angles at the tip, γ1, ranging from 45 to 85°C.

  14. Effects of self-affine surface roughness on the friction coefficient of rubbers in the presence of a liquid interlayer

    NARCIS (Netherlands)

    Palasantzas, G; De Hosson, JTM

    2004-01-01

    In this article, we investigate how the friction coefficient is affected by the presence of a liquid layer in between a self-affine rough surface and a sliding rubber surface. The liquid layer will reduce energy dissipation from the small surface asperities and cavities of lateral sizes smaller than

  15. Comparison of cyclic and impact-based reference point indentation measurements in human cadaveric tibia.

    Science.gov (United States)

    Karim, Lamya; Van Vliet, Miranda; Bouxsein, Mary L

    2018-01-01

    Although low bone mineral density (BMD) is strongly associated with increased fracture risk, up to 50% of those who suffer fractures are not detected as high-risk patients by BMD testing. Thus, new approaches may improve identification of those at increased risk for fracture by in vivo assessment of altered bone tissue properties, which may contribute to skeletal fragility. Recently developed reference point indentation (RPI) allows for assessment of cortical bone indentation properties in vivo using devices that apply cyclic loading or impact loading, but there is little information available to assist with interpretation of RPI measurements. Our goals were to use human cadaveric tibia to determine: 1) the associations between RPI variables, cortical bone density, and morphology; 2) the association between variables obtained from RPI systems using cyclic, slow loading versus a single impact load; and 3) age-related differences in RPI variables. We obtained 20 human tibia and femur pairs from female donors (53-97years), measured total hip BMD using dual-energy X-ray absorptiometry, assessed tibial cortical microarchitecture using high-resolution peripheral quantitative computed tomography (HR-pQCT), and assessed cortical bone indentation properties at the mid-tibial diaphysis using both the cyclic and impact-based RPI systems (Biodent and Osteoprobe, respectively, Active Life Scientific, Santa Barbara, CA). We found a few weak associations between RPI variables, BMD, and cortical geometry; a few weak associations between measurements obtained by the two RPI systems; and no age-related differences in RPI variables. Our findings indicate that in cadaveric tibia from older women RPI measurements are largely independent of age, femoral BMD, and cortical geometry. Furthermore, measurements from the cyclic and impact loading RPI devices are weakly related to each other, indicating that each device reflects different aspects of cortical bone indentation properties

  16. Mechanical properties of orthodontic wires derived by instrumented indentation testing (IIT) according to ISO 14577.

    Science.gov (United States)

    Zinelis, Spiros; Al Jabbari, Youssef S; Gaintantzopoulou, Marianna; Eliades, George; Eliades, Theodore

    2015-01-01

    The aim of this study was the characterization of mechanical properties of representative types of orthodontic wires employing instrumented indentation testing (IIT) according to ISO 14577. Segments were cut from ten wires. The first six are made of stainless steel (SS), two are made of Ni-Ti, and the last two are made of titanium molybdenum alloys (TMA). Then, the Martens hardness (HM), the Vickers hardness (HVIT) based on indentation hardness (H IT), the indentation modulus (E IT), the ratio of elastic to total work (η IT), and the traditional Vickers hardness (HV1) were measured by IIT. The results were statistically analyzed by one-way ANOVA followed by Student-Newman-Keuls (SNK) test at a = 0.05. The HVIT and HV1 data were analyzed by paired t test (a = 0.05). SS wires showed the highest hardness followed by TMA and Ni-Ti alloys. However, all wires showed significantly lower HVIT compared to corresponding HV1, a finding probably appended to elastic recovery around the indentation. E IT for all wires tested was determined much lower than the nominal values of the corresponding alloys due to the implication of residual stress field at the slope of unloading curve. Elastic to total work ratio was ranged from 45.8 to 64.4 % which is higher than that expected for ductile alloys (<30 %). The products tested illustrated significant differences in their mechanical properties. Although IIT provides reliable data for hardness and elastic index of materials tested, the intense residual stress field developed during the manufacturing process significantly affects the determination of modulus of elasticity.

  17. Method of determining elastic and plastic mechanical properties of ceramic materials using spherical indenters

    Science.gov (United States)

    Adler, Thomas A.

    1996-01-01

    The invention pertains a method of determining elastic and plastic mechanical properties of ceramics, intermetallics, metals, plastics and other hard, brittle materials which fracture prior to plastically deforming when loads are applied. Elastic and plastic mechanical properties of ceramic materials are determined using spherical indenters. The method is most useful for measuring and calculating the plastic and elastic deformation of hard, brittle materials with low values of elastic modulus to hardness.

  18. Nuclear Weapon Yield Determination through Nano Indentation of Thermally Degraded Automobile Paint

    Science.gov (United States)

    2011-03-01

    detonation from a test device used in Operation Teapot (dashed lines) (Plum, 1958) ...............13 8. Agilent Nano Indenter G200...2 . (Bauer, 2010) also measured the spectral output of the AXTS and compared it to that measured in Operation Teapot . As shown in Figure 7, the...800, 1200, and 1800 W (solid lines) over the spectral output at 4 different times after detonation of a test device used in Operation Teapot (dashed

  19. Effect of ion irradiation and indentation depth on the kinetics of deformation during micro-indentation of Zr-2.5%Nb pressure tube material at 25 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Bose, B. [Department of Mechanical and Materials Engineering, Faculty of Engineering, University of Western Ontario, London, Ontario, N6A 5B9 (Canada); Klassen, R.J., E-mail: rklassen@eng.uwo.c [Department of Mechanical and Materials Engineering, Faculty of Engineering, University of Western Ontario, London, Ontario, N6A 5B9 (Canada)

    2010-04-01

    Micro-indentation creep tests were performed at 25 deg. C on radial-normal samples cut from Zr-2.5Nb CANDU pressure tube material in both the as-fabricated condition and after irradiation with 8.5 MeV Zr{sup +} ions. The average indentation stress, and hence the yield stress, was found to increase with decreasing indentation depth and with increasing levels of ion irradiation. The activation energy of the indentation creep rate and hence the, activation energy of the obstacles that limit the rate of dislocation glide, was independent of indentation depth but increased from DELTAG{sub 0} = 0.185 to 0.215 mub{sup 3} with increasing ion irradiation damage. The magnitude of the activation energy indicates that ion irradiation introduces a new type of obstacle into the microstructure which reduces the low temperature indentation creep rate of Zr-2.5Nb pressure tubes. This is supported by TEM images showing that Zr{sup +} ion irradiation produces small, nanometer size, dislocation loops which act as obstacles to dislocation glide and thus influence both the yield stress and the activation energy of the low-temperature thermal creep of Zr-2.5Nb pressure tube material. These findings suggest that neutron irradiation will have similar effect upon yield stress and low-temperature thermal creep as the Zr{sup +} ion irradiation since both create similar crystallographic defects in Zr-2.5Nb pressure tubes.

  20. Evaluation of anti-Bothrops asper venom activity of ethanolic extract of Brownea rosademonte leaves.

    Science.gov (United States)

    Salazar, Marcos; Chérigo, Lilia; Acosta, Hildaura; Otero, Rafael; Martínez-Luis, Sergio

    2014-12-01

    Significant inhibition of the coagulant and hemorrhagic effects of Bothrops asper venom was demonstrated by ethanolic extract prepared from the leaves of Brownea rosademonte. In vitro experiments preincubating 5.5 mg of extract kg-1 b.m. for 30 min with a minimum hemorrhagic dose of venom (273.8 ± 16.1 μg of venom kg-1 b.m.) lowered the hemorrhagic activity of the venom alone in CD-1 mice by 51.5 ± 2.6 %. Additionally, 1.7 mg extract L-1 plasma prolonged 5.1 times the plasma coagulation time. Fractionation of the extract led to the isolation of two compounds: ononitol (1) and quercetrin (2). The structure of compounds 1 and 2 was established by spectroscopic analyses, including APCI-HRMS and NMR (1H, 13C, HSQC, HMBC and COSY). A quercetrin concentration of 0.11 μmol L-1 prolonged the plasma coagulation time 2.6 times demonstrating that this compound was one of the active constituents of the Brownea rosademonte extract.

  1. Asperity break after 12 years: The Mw6.4 2015 Lefkada (Greece) earthquake

    Science.gov (United States)

    Sokos, E.; Zahradník, J.; Gallovič, F.; Serpetsidaki, A.; Plicka, V.; Kiratzi, A.

    2016-06-01

    The Mw6.4 earthquake sequence of 2015 in western Greece is analyzed using seismic data. Multiple point source modeling, nonlinear slip patch, and linear slip inversions reveal a coherent rupture image with directivity toward the southwest and several moment release episodes, reflected in the complex aftershock distribution. The key feature is that the 2015 earthquake ruptured a strong asperity, which was left unbroken in between two large subevents of the Mw6.2 Lefkada doublet in 2003. This finding and the well-analyzed Cephalonia earthquake sequence of 2014 provide strong evidence of segmentation of the major dextral Cephalonia-Lefkada Transform Fault (CTF), being related to extensional duplex transform zones. We propose that the duplexes extend farther to the north and that the CTF runs parallel to the western coast of Lefkada and Cephalonia Islands, considerably closer to the inhabited islands than previously thought. Generally, this study demonstrates faulting complexity across short time scales (earthquake doublets) and long time scales (seismic gaps).

  2. Evaluation of anti-Bothrops asper venom activity of ethanolic extract of Brownea rosademonte leaves

    Directory of Open Access Journals (Sweden)

    Salazar Marcos

    2014-12-01

    Full Text Available Significant inhibition of the coagulant and hemorrhagic effects of Bothrops asper venom was demonstrated by ethanolic extract prepared from the leaves of Brownea rosademonte. In vitro experiments preincubating 5.5 mg of extract kg-1 b.m. for 30 min with a minimum hemorrhagic dose of venom (273.8 ± 16.1 μg of venom kg-1 b.m. lowered the hemorrhagic activity of the venom alone in CD-1 mice by 51.5 ± 2.6 %. Additionally, 1.7 mg extract L-1 plasma prolonged 5.1 times the plasma coagulation time. Fractionation of the extract led to the isolation of two compounds: ononitol (1 and quercetrin (2. The structure of compounds 1 and 2 was established by spectroscopic analyses, including APCI-HRMS and NMR (1H, 13C, HSQC, HMBC and COSY. A quercetrin concentration of 0.11 μmol L-1 prolonged the plasma coagulation time 2.6 times demonstrating that this compound was one of the active constituents of the Brownea rosademonte extract.

  3. Atomic force microscopy indentation of fluorocarbon thin films fabricated by plasma enhanced chemical deposition at low radio frequency power

    International Nuclear Information System (INIS)

    Sirghi, L.; Ruiz, A.; Colpo, P.; Rossi, F.

    2009-01-01

    Atomic force microscopy (AFM) indentation technique is used for characterization of mechanical properties of fluorocarbon (CF x ) thin films obtained from C 4 F 8 gas by plasma enhanced chemical vapour deposition at low r.f. power (5-30 W) and d.c. bias potential (10-80 V). This particular deposition method renders films with good hydrophobic property and high plastic compliance. Commercially available AFM probes with stiff cantilevers (10-20 N/m) and silicon sharpened tips (tip radius < 10 nm) are used for indentations and imaging of the resulted indentation imprints. Force depth curves and imprint characteristics are used for determination of film hardness, elasticity modulus and plasticity index. The measurements show that the decrease of the discharge power results in deposition of films with decreased hardness and stiffness and increased plasticity index. Nanolithography based on AFM indentation is demonstrated on thin films (thickness of 40 nm) with good plastic compliance.

  4. A phenomenological method of mechanical properties definition of reactor pressure vessels (RPV) steels VVER according to the ball indentation diagram

    International Nuclear Information System (INIS)

    Bakirov, M. B.; Potapov, V.V.; Massoud, J.P.

    2002-01-01

    This work presents specimen-free methods of a standard uniaxial tension diagram construction and RPV (reactor pressure vessel) steels VVER strength properties definition out of a continuous ball indentation diagram. A similarity phenomenon of uniaxial tension strain curves at a hardening area and an area of a ball indentation constitutes the ground of the methods. The methods are developed on the basis of the uniform graphic representation of elasto-plastic strain processes by indentation and tension and with the reception of the unified yield curve at a hardening area. The calculation results on the phenomenological method conducted for a wide range of RPV steels conditions of nuclear reactors have shown a good precision as far as strain curves construction by the uniaxial tension out of the elasto-plastic indentation diagram is concerned. (authors)

  5. Quantitative Imaging of the Stress/Strain Fields and Generation of Macroscopic Cracks from Indents in Silicon

    Directory of Open Access Journals (Sweden)

    Brian K. Tanner

    2017-11-01

    Full Text Available The crack geometry and associated strain field around Berkovich and Vickers indents on silicon have been studied by X-ray diffraction imaging and micro-Raman spectroscopy scanning. The techniques are complementary; the Raman data come from within a few micrometres of the indentation, whereas the X-ray image probes the strain field at a distance of typically tens of micrometres. For example, Raman data provide an explanation for the central contrast feature in the X-ray images of an indent. Strain relaxation from breakout and high temperature annealing are examined and it is demonstrated that millimetre length cracks, similar to those produced by mechanical damage from misaligned handling tools, can be generated in a controlled fashion by indentation within 75 micrometres of the bevel edge of 200 mm diameter wafers.

  6. Crack formation mechanisms during micro and macro indentation of diamond-like carbon coatings on elastic-plastic substrates

    DEFF Research Database (Denmark)

    Thomsen, N.B.; Fischer-Cripps, A.C.; Swain, M.V.

    1998-01-01

    of cracking and the fracture mechanisms taking place. In the study various diamond-like carbon (DLC) coatings deposited onto stainless steel and tool steel were investigated. Results primarily for one DLC system will be presented here. (C) 1998 Published by Elsevier Science S.A. All rights reserved.......In the present study crack formation is investigated on both micro and macro scale using spherical indenter tips. in particular, systems consisting of elastic coatings that are well adhered to elastic-plastic substrates are studied. Depth sensing indentation is used on the micro scale and Rockwell...... indentation on the macro scale. The predominant driving force for coating failure and crack formation during indentation is plastic deformation of the underlying substrate. The aim is to relate the mechanisms creating both delamination and cohesive cracking on both scales with fracture mechanical models...

  7. Fracture Characteristics of Dlc on Silicon Using Nano-Indentation and Fea

    Science.gov (United States)

    Baek, Seung; Seok, Chang-Sung

    In this study, using the nano and micro-indentation tests and finite element analysis (FEA), we investigated the fracture behaviors of diamond like carbon (DLC) on silicon in indentation state. Diamond like carbon coating of 3μm and 1.5μm thickness were deposited on polished (100) single crystal silicon substrates by radio frequency plasma assisted chemical vapor deposition (RF-PACVD), respectively. Fracture toughness of DLC films was calculated from the measured lengths of the cracks formed by nano and micro-indentation on each sample. We used various equations such as Lawn's and Liang's equation to calculate the fracture toughness. The effective fracture toughnesses of these DLC films were 1.2 ~1.3 MPam0.5, calculated by Lawn's and Liang's equations. The true fracture toughness of DLC on silicon, excluding the portion of fracture toughness due to a substrate, was determined to be 4.0~5.1MPam0.5. DLC films with crack initiation and propagation were analyzed by finite element method.

  8. A novel numerical framework for self-similarity in plasticity: Wedge indentation in single crystals

    Science.gov (United States)

    Juul, K. J.; Niordson, C. F.; Nielsen, K. L.; Kysar, J. W.

    2018-03-01

    A novel numerical framework for analyzing self-similar problems in plasticity is developed and demonstrated. Self-similar problems of this kind include processes such as stationary cracks, void growth, indentation etc. The proposed technique offers a simple and efficient method for handling this class of complex problems by avoiding issues related to traditional Lagrangian procedures. Moreover, the proposed technique allows for focusing the mesh in the region of interest. In the present paper, the technique is exploited to analyze the well-known wedge indentation problem of an elastic-viscoplastic single crystal. However, the framework may be readily adapted to any constitutive law of interest. The main focus herein is the development of the self-similar framework, while the indentation study serves primarily as verification of the technique by comparing to existing numerical and analytical studies. In this study, the three most common metal crystal structures will be investigated, namely the face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close packed (HCP) crystal structures, where the stress and slip rate fields around the moving contact point singularity are presented.

  9. Ultrawide band gaps in beams with double-leaf acoustic black hole indentations.

    Science.gov (United States)

    Tang, Liling; Cheng, Li

    2017-11-01

    Band gaps in conventional phononic crystals (PCs) are attractive for applications such as vibration control, wave manipulation, and sound absorption. Their practical implementations, however, are hampered by several factors, among which the large number of cells required and their impractically large size to ensure the stopbands at reasonably low frequencies are on the top of the list. This paper reports a type of beam carved inside with two double-leaf acoustic black hole indentations. By incorporating the local resonance effect and the Bragg scattering effect generated by a strengthening stud connecting the two branches of the indentations, ultrawide band gaps are achieved. Increasing the length of the stud or reducing the residual thickness of the indentation allows the tuning of the band gaps to significantly enlarge the band gaps, which can exceed 90% of the entire frequency range of interest. Experimental results show that with only three cells, the proposed beam allows considerable vibration energy attenuation within an ultra-broad frequency range including the low frequency range, which conventional PCs can hardly reach. Meanwhile, the proposed configuration also enhances the structural integrity, thus pointing at promising applications in vibration control and a high performance wave filter design.

  10. TEM in situ cube-corner indentation analysis using ViBe motion detection algorithm

    Science.gov (United States)

    Yano, K. H.; Thomas, S.; Swenson, M. J.; Lu, Y.; Wharry, J. P.

    2018-04-01

    Transmission electron microscopic (TEM) in situ mechanical testing is a promising method for understanding plasticity in shallow ion irradiated layers and other volume-limited materials. One of the simplest TEM in situ experiments is cube-corner indentation of a lamella, but the subsequent analysis and interpretation of the experiment is challenging, especially in engineering materials with complex microstructures. In this work, we: (a) develop MicroViBE, a motion detection and background subtraction-based post-processing approach, and (b) demonstrate the ability of MicroViBe, in combination with post-mortem TEM imaging, to carry out an unbiased qualitative interpretation of TEM indentation videos. We focus this work around a Fe-9%Cr oxide dispersion strengthened (ODS) alloy, irradiated with Fe2+ ions to 3 dpa at 500 °C. MicroViBe identifies changes in Laue contrast that are induced by the indentation; these changes accumulate throughout the mechanical loading to generate a "heatmap" of features in the original TEM video that change the most during the loading. Dislocation loops with b = ½ identified by post-mortem scanning TEM (STEM) imaging correspond to hotspots on the heatmap, whereas positions of dislocation loops with b = do not correspond to hotspots. Further, MicroViBe enables consistent, objective quantitative approximation of the b = ½ dislocation loop number density.

  11. Characterization of Adhesion in Pressure Sensitive Adhesives with a Spherical Indenter

    Science.gov (United States)

    Crosby, Alfred; Shull, Kenneth R.

    1997-03-01

    A combination of interfacial effects and bulk viscoelastic behavior controls the performance of pressure sensitive adhesives. We have studied these issues using commercially available adhesive transfer tapes. Using a spherical indenter, these experiments measure the displacement of the indenter into the adhesive as a function of the applied normal contact force. With the assumption of linear elastic behavior under small displacements, accepted theories of this contact problem are used to approximate the contact area and calculate a plateau modulus from the loading data. Fracture mechanics approaches based on linear elasticity also allow us to calculate the energy release rate (i.e. driving force for adhesive failure) from the load/displacement relationship measured during unloading. To alleviate uncertainty in the calculation of the plateau modulus and energy release rate for thicknesses not within the ranges of accepted theories, a finite element model simulates the behavior of the polymer layer upon loading and pull-off of the indenter. Future work will include modeling the adhesive with a viscoelastic constitutive model and characterizing the effects of geometry, substrate material, and loading rate on the adhesive properties.

  12. Fragmentation of copper current collectors in Li-ion batteries during spherical indentation

    International Nuclear Information System (INIS)

    Wang, Hsin; Watkins, Thomas R.; Simunovic, Srdjan; Bingham, Philip R.; Allu, Srikanth; Turner, John A.

    2017-01-01

    Large, areal, brittle fracture of copper current collector foils was observed by 3D x-ray computed tomography (XCT) of a spherically indented Li-ion cell. This fracture was hidden and non-catastrophic to a degree because the graphite layers deformed plastically, and held the materials together so that the cracks in the foils could not be seen under optical and electron microscopy. 3D XCT on the indented cell showed “mud cracks” within the copper layer. The cracking of copper foils could not be immediately confirmed when the cell was opened for post-mortem examination. However, an X-ray radiograph on a single foil of the Cu anode showed clearly that the copper foil had broken into multiple pieces similar to the brittle cracking of a ceramic under indentation. This new failure mode of anodes on Li-ion cell has very important implications on the behavior of Li-ion cells under mechanical abuse conditions. Furthermore, the fragmentation of current collectors in the anode must be taken into consideration for the electrochemical responses which may lead to capacity loss and affect thermal runaway behavior of the cells.

  13. Mechanical indentation improves cerebral blood oxygenation signal quality of functional near-infrared spectroscopy (fNIRS) during breath holding

    Science.gov (United States)

    Vogt, William C.; Romero, Edwin; LaConte, Stephen M.; Rylander, Christopher G.

    2013-03-01

    Functional near-infrared spectroscopy (fNIRS) is a well-known technique for non-invasively measuring cerebral blood oxygenation, and many studies have demonstrated that fNIRS signals can be related to cognitive function. However, the fNIRS signal is attenuated by the skin, while scalp blood content has been reported to influence cerebral oxygenation measurements. Mechanical indentation has been shown to increase light transmission through soft tissues by causing interstitial water and blood flow away from the compressed region. To study the effects of indentation on fNIRS, a commercial fNIRS system with 16 emitter/detector pairs was used to measure cerebral blood oxygenation at 2 Hz. This device used diffuse reflectance at 730 nm and 850 nm to calculate deoxy- and oxy-hemoglobin concentrations. A borosilicate glass hemisphere was epoxied over each sensor to function as both an indenter and a lens. After placing the indenter/sensor assembly on the forehead, a pair of plastic bands was placed on top of the fNIRS headband and strapped to the head to provide uniform pressure and tightened to approx. 15 N per strap. Cerebral blood oxygenation was recorded during a breath holding regime (15 second hold, 15 second rest, 6 cycles) in 4 human subjects both with and without the indenter array. Results showed that indentation increased raw signal intensity by 85 +/- 35%, and that indentation increased amplitude of hemoglobin changes during breath cycles by 313% +/- 105%. These results suggest that indentation improves sensing of cerebral blood oxygenation, and may potentially enable sensing of deeper brain tissues.

  14. Determination of local constitutive properties of titanium alloy matrix in boron-modified titanium alloys using spherical indentation

    International Nuclear Information System (INIS)

    Sreeranganathan, A.; Gokhale, A.; Tamirisakandala, S.

    2008-01-01

    The constitutive properties of the titanium alloy matrix in boron-modified titanium alloys are different from those of the corresponding unreinforced alloy due to the microstructural changes resulting from the addition of boron. Experimental and finite-element analyses of spherical indentation with a large penetration depth to indenter radius ratio are used to compute the local constitutive properties of the matrix alloy. The results are compared with that of the corresponding alloy without boron, processed in the same manner

  15. Indentation analysis of nano-particle using nano-contact mechanics models during nano-manipulation based on atomic force microscopy

    International Nuclear Information System (INIS)

    Daeinabi, Khadijeh; Korayem, Moharam Habibnejad

    2011-01-01

    Atomic force microscopy is applied to measure intermolecular forces and mechanical properties of materials, nano-particle manipulation, surface scanning and imaging with atomic accuracy in the nano-world. During nano-manipulation process, contact forces cause indentation in contact area between nano-particle and tip/substrate which is considerable at nano-scale and affects the nano-manipulation process. Several nano-contact mechanics models such as Hertz, Derjaguin–Muller–Toporov (DMT), Johnson–Kendall–Roberts–Sperling (JKRS), Burnham–Colton–Pollock (BCP), Maugis–Dugdale (MD), Carpick–Ogletree–Salmeron (COS), Pietrement–Troyon (PT), and Sun et al. have been applied as the continuum mechanics approaches at nano-scale. In this article, indentation depth and contact radius between tip and substrate with nano-particle for both spherical and conical tip shape during nano-manipulation process are analyzed and compared by applying theoretical, semiempirical, and empirical nano-contact mechanics models. The effects of adhesion force, as the main contrast point in different nano-contact mechanics models, on nano-manipulation analysis is investigated for different contact radius, and the critical point is discussed for mentioned models.

  16. Study of the Tool Geometry Influence in Indentation for the Analysis and Validation of the New Modular Upper Bound Technique

    Directory of Open Access Journals (Sweden)

    Carolina Bermudo

    2016-07-01

    Full Text Available Focusing on incremental bulk metal forming processes, the indentation process is gaining interest as a fundamental part of these kinds of processes. This paper presents the analysis of the pressure obtained in indentation under the influence of different punch geometries. To this end, an innovative Upper Bound Theorem (UBT based solution is introduced. This new solution can be easily applied to estimate the necessary force that guarantees plastic deformation by an indentation process. In this work, we propose an accurate analytical approach to analyse indentation under different punches. The new Modular Upper Bound (MUB method presents a simpler and faster application. Additionally, its complexity is not considerably increased by the addition of more Triangular Rigid Zones. In addition, a two-dimensional indentation model is designed and implemented using the Finite Element Method (FEM. The comparison of the two methods applied to the indentation process analysed—the new Modular Upper Bound technique and the Finite Element Method—reveal close similarities, the new Modular Upper Bound being more computationally efficient.

  17. Hardening Effect Analysis by Modular Upper Bound and Finite Element Methods in Indentation of Aluminum, Steel, Titanium and Superalloys

    Science.gov (United States)

    Bermudo, Carolina; Sevilla, Lorenzo; Martín, Francisco; Trujillo, Francisco Javier

    2017-01-01

    The application of incremental processes in the manufacturing industry is having a great development in recent years. The first stage of an Incremental Forming Process can be defined as an indentation. Because of this, the indentation process is starting to be widely studied, not only as a hardening test but also as a forming process. Thus, in this work, an analysis of the indentation process under the new Modular Upper Bound perspective has been performed. The modular implementation has several advantages, including the possibility of the introduction of different parameters to extend the study, such as the friction effect, the temperature or the hardening effect studied in this paper. The main objective of the present work is to analyze the three hardening models developed depending on the material characteristics. In order to support the validation of the hardening models, finite element analyses of diverse materials under an indentation are carried out. Results obtained from the Modular Upper Bound are in concordance with the results obtained from the numerical analyses. In addition, the numerical and analytical methods are in concordance with the results previously obtained in the experimental indentation of annealed aluminum A92030. Due to the introduction of the hardening factor, the new modular distribution is a suitable option for the analysis of indentation process. PMID:28772914

  18. Determining interfacial properties of submicron low-k films on Si substrate by using wedge indentation technique

    Science.gov (United States)

    Yeap, Kong Boon; Zeng, Kaiyang; Jiang, Haiyan; Shen, Lu; Chi, Dongzhi

    2007-06-01

    This article presents studies on using a wedge indentation technique to determine interfacial adhesion properties of low-k dielectric films, namely, methyl-silsesquioxane (MSQ) and black diamond (BD™)films, both on a Si substrate. Interfacial crack initiation and propagation processes in the MSQ/Si system are studied by using focused-ion-beam sectioning of the indentation impressions created by wedge tips with 90° and 120° of inclusion angles, respectively. Furthermore, the indentation induced stress is found to be proportional to the ratio of the indentation volume and the interface delamination crack volume for both plane strain and nonplane strain cases. With this analysis, the interface toughness of the MSQ/Si and BD/Si system, in terms of the strain energy release rate, is determined. The interface toughness for the MSQ/Si system is found to be a value of 1.89±0.28J/m2 for the 90° wedge tip indentation and 1.92±0.08J/m2 for the 120° wedge tip indentation. In addition, using the 120° wedge tip, the interface toughnesses of the BD films on the Si substrate with 200 and 500nm thicknesses are found to be the values of 6.62±1.52 and 6.35±2.27J/m2, respectively.

  19. OPPORTUNITY ESTIMATION OF OPTICAL METHOD APPLICATION IN PROBLEM OF KINEMATIC CHARACTERISTICS REGISTRATION OF DYNAMIC INDENTING PROCESS

    Directory of Open Access Journals (Sweden)

    Evgeniya I. Ivanova

    2017-07-01

    Full Text Available Subject of Research. A stereoscopic method of technical vision is proposed for recording the kinematic characteristics of the dynamic indentation process in determining the physico-mechanical properties of materials. The proposed method makes it possible to determine the values of the indenter motion speed with high accuracy. Method. The method is based on the use of two high-speed video cameras immovably fixed on one flat platform. Cameras allow for synchronous recording of the indentation process. The objectives and orientation of cameras in the stereo system provide intersection of the visual fields and the required depth of the image space field. Measurement of the movement speed is performed by triangulation method. The distance between the conjugate points of the recorded object on the stereo images is inversely proportional to the distance between the pair of cameras and the corresponding point of the object in the three-dimensional space. Based on the analysis of images obtained by spatially separated cameras, the coordinates of the object point are determined. Main Results. The experimental setup consisted of two high-speed monochrome camcorders Evercam 4000-32-M, rigidly fixed through stereo. Synchronous recording was kept at a speed of 4000 frames/s with a resolution of 1280 × 860 pixels. The indenter was made in the form of a steel ball with a mass of 230 g with a diameter of 38 mm and fell onto an aluminum disk 10 mm thick from a height of 310 mm. Video images from cameras were transferred to a personal computer for processing. The analysis of the obtained data was carried out in the MATLAB system with the help of a specially written software module. The sensitivity of the proposed method made it possible to determine confidently the values of the maximum approach speed of a steel ball equal to 2.39 m/s and a rebound velocity of 1.2 m/s. The random component of the method error did not exceed 2.5%. Practical Relevance. The

  20. Proteomic and functional profiling of the venom of Bothrops ayerbei from Cauca, Colombia, reveals striking interspecific variation with Bothrops asper venom.

    Science.gov (United States)

    Mora-Obando, Diana; Guerrero-Vargas, Jimmy Alexander; Prieto-Sánchez, Rodrigo; Beltrán, José; Rucavado, Alexandra; Sasa, Mahmood; Gutiérrez, José María; Ayerbe, Santiago; Lomonte, Bruno

    2014-01-16

    Bothrops ayerbei, a pitviper inhabiting the Patía River's basin (Valle Alto del Río Patía) in the Southwestern Department of Cauca, Colombia, was considered as a variant form of Bothrops asper prior to being proposed as a new species in 2010, on the basis of subtle morphological differences. This study reports the proteomic and functional profiling of B. ayerbei venom. Its most striking feature is an almost complete absence (0.7%) of phospholipases A2 (PLA2), which is in contrast to the high proportion of these enzymes (25.3%) in the venom of B. asper from Cauca, as well as in other species of Bothrops. The predominant proteins in B. ayerbei venom are metalloproteinases (53.7%), in agreement with its higher hemorrhagic and lethal activities compared to B. asper venom. Moreover, the negligible content of PLA2s in B. ayerbei venom correlates with its weaker myotoxic effect, in contrast to B. asper venom, here shown to contain abundant Asp49- and Lys49-type PLA2s responsible for its strong myotoxic activity. Other components identified in B. ayerbei venom include bradykinin-potentiating-like peptides and proteins belonging to the C-type lectin/lectin-like, serine proteinase, l-amino acid oxidase, disintegrin, cysteine-rich secretory protein, nerve growth factor, and phosphodiesterase families. The venom composition of B. ayerbei resembles that of neonate specimens of B. asper, which shows a predominance of metalloproteinases, with only low amounts of PLA2s. Therefore, the present findings suggest that the expression of venom proteins in B. ayerbei, in contrast to B. asper, might retain a marked 'paedomorphic' condition. Altogether, the proteomic and toxicological characterization of the venom of B. ayerbei here reported argues in favor of its taxonomical separation from B. asper in Cauca, Colombia. B. ayerbei, a pitviper found in Cauca, Colombia, had been considered as a variant form of B. asper, but was recently described as a new species on the basis of subtle

  1. Fracture Toughness Evaluation of a Ni2MnGa Alloy Through Micro Indentation Under Magneto-Mechanical Loading

    Science.gov (United States)

    Goanţă, Viorel; Ciocanel, Constantin

    2017-12-01

    Ni2MnGa is a ferromagnetic alloy that exhibits the shape memory effect either induced by an externally applied magnetic field or mechanical stress. Due to the former, the alloy is commonly called magnetic shape memory alloy or MSMA. The microstructure of the MSMA consists of tetragonal martensite variants (three in the most general case) that are characterized by a magnetization vector which is aligned with the short side of the tetragonal unit cell. Exposing the MSMA to a magnetic field causes the magnetization vector to rotate and align with the external field, eventually leading to variant reorientation. The variant reorientation is observed macroscopically in the form of recoverable strain of up to 6% [1, 2]. As the magnetic field induced reorientation happens instantaneously [1, 3], MSMAs are suitable for fast actuation, sensing, or power harvesting applications. However, actuation applications are limited by the maximum actuation stress of the material that is about 3.5MPa at approximately 2 to 3% reorientation strain. During MSMA fatigue magneto-mechanical characterization studies [4, 5] it was observed that cracks nucleate and grow on the surface of material samples, after a relatively small number of cycles, leading to loss in material performance. This triggered the need for understanding the mechanisms that govern crack nucleation and growth in MSMAs, as well as the nature of the material, i.e. ductile or brittle. The experimental study reported in this paper was carried out to determine material's fracture toughness, the predominant crack growth directions, and the orientation of the cracks relative to the mechanical loading direction and to the material's microstructure. A fixture has been developed to allow Vickers micro indentation of 3mm by 3mm by 20mm Ni2MnGa samples exposed to different levels of magnetic field and/or mechanical stress. Using the measured characteristics of the impression generated during micro indentation, the lengths of

  2. Lachesis stenophrys venom reduces the equine antibody response towards Bothrops asper venom used as co-immunogen in the production of polyspecific snake antivenom.

    Science.gov (United States)

    Arroyo, Cynthia; Solano, Sergio; Herrera, María; Segura, Álvaro; Estrada, Ricardo; Vargas, Mariángela; Villalta, Mauren; Gutiérrez, José María; León, Guillermo

    2015-09-01

    The anti-bothropic activity of an antivenom prepared from the plasma of horses immunized with Bothrops asper venom (anti-B antivenom) was compared with a similar formulation produced from the plasma of horses immunized with a mixture of B. asper and Lachesis stenophrys venoms (anti-BL antivenom). Likewise, a comparison between the anti-lachesic activity of the anti-BL antivenom and a similar formulation prepared from horses immunized only with L. stenophrys venom (anti-L antivenom) was performed. The anti-BL antivenom had lower concentration of anti-bothropic antibodies than the anti-B antivenom. This difference was associated to a lower response towards all components of B. asper venom, but particularly towards some D49-phospholipases A2 (PLA2s) and PIII-metalloproteinases. Consequently, the anti-BL antivenom was less effective neutralizing lethal, coagulant, defibrinogenating, PLA2, and myotoxic activities of B. asper venom. On the other hand, anti-BL and anti-L antivenoms showed similar concentration of anti-lachesic antibodies, and similar capacity to recognize the HPLC fractions of L. stenophrys venom and to neutralize lethal, coagulant, proteolytic, hemorrhagic, PLA2 and myotoxic activities induced by this venom. It is concluded that, when used as co-immunogens, the venom of L. stenophrys reduces the antibody response towards B. asper venom, whereas the latter does not affect the anti-lachesic response. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. [Evaluation of the inhibitory effect of extracts from leaves of Renealmia alpinia Rottb. Maas (Zingiberaceae) on the venom of Bothrops asper (mapaná)].

    Science.gov (United States)

    Patiño, Arley Camilo; López, Jéssica; Aristizábal, Mónica; Quintana, Juan Carlos; Benjumea, Dora

    2012-09-01

    Traditional medicine is an invaluable source of research into new medicines as a supplement for the treatment of snakebite, considered as a serious public health problem worldwide. The extracts of the medicinal plant, Renealmia alpina, have been used traditionally by indigenous people of Chocó (Colombia) against Bothrops asper snakebite, a snake responsible for the majority of snakebite accidents in Colombia. The ability of extracts of R. alpinia leaves was tested for its ability to neutralize the hemorrhagic, coagulant and proteolytic effects of the snakebite venom of B. asper. The acute toxicity tests and analgesic activity of R. alpina were evaluated in vivo. In addition, tests were undertaken in in vitro conditions to demonstrate inhibition of coagulant, haemolytic and proteolytic activity of the B. asper venom. Results. Renealmia alpinia extracts had no toxic effects in experimental animals and also provided analgesic and antiophidian effects and protection against the lethal effects of the venom of B. asper. Renealmia. alpinia was an effective therapeutic alternative in association with antivenom treatment in the event of a B. asper snakebite accident. It was demonstrated to protect against the lethal effects and provided analgesic properties as well.

  4. Neutralization of venom-induced hemorrhage by equine antibodies raised by immunization with a plasmid encoding a novel P-II metalloproteinase from the lancehead pitviper Bothrops asper.

    Science.gov (United States)

    Arce-Estrada, Viviana; Azofeifa-Cordero, Gabriela; Estrada, Ricardo; Alape-Girón, Alberto; Flores-Díaz, Marietta

    2009-01-14

    In this work, the cDNA encoding a novel P-II type metalloproteinase from Bothrops asper venom glands was cloned, sequenced and used for DNA immunization of animals with accelerated DNA-coated tungsten microparticles and the helius Gene Gun system. Specific antibodies against B. asper venom antigens were induced in mice co-immunized with the plasmid encoding the P-II metalloproteinase together with an expression plasmid encoding the murine IL-2. Similarly, specific antibodies against B. asper venom antigens were also induced in a horse co-immunized with the plasmid encoding the P-II metalloproteinase, together with a plasmid encoding the equine IL-6. The equine antibodies induced by immunization with the P-II metalloproteinase encoding plasmid cross react with several proteins of B. asper, Crotalus durissus durissus, and Lachesis stenophrys venoms in western blot, demonstrating antigenic similarity between the cloned metalloproteinase and other metalloproteinases present in these venoms. Furthermore, the equine antibodies induced by immunization with the P-II metalloproteinase encoding plasmid completely neutralized the hemorrhagic activity of the whole B. asper venom and partially the hemorrhagic activity of C. durissus durissus venom. The neutralizing ability of the produced antibodies raises, for the first time, the possibility of developing therapeutic antivenoms in horses by DNA immunization using tungsten microparticles.

  5. Surface toughness of silicon nitride bioceramics: I, Raman spectroscopy-assisted micromechanics.

    Science.gov (United States)

    Pezzotti, Giuseppe; Enomoto, Yuto; Zhu, Wenliang; Boffelli, Marco; Marin, Elia; McEntire, Bryan J

    2016-02-01

    Indentation micro-fracture is revisited as a tool for evaluating the surface toughness of silicon nitride (Si3N4) bioceramics for artificial joint applications. Despite being unique and practical from an experimental perspective, a quantitative assessment of surface fracture toughness using this method is challenging. An improved method has been developed, consisting of coupling indentation with confocal (spatially resolved) Raman piezo-spectroscopy. Empowered by the Raman microprobe, the indentation micro-fracture method was found to be capable of providing reliable surface toughness measurements in silicon nitride biomaterials. In designing the microstructures of bioceramic bearing couples for improved tribological performance, surface toughness must be considered as a fundamentally different and distinct parameter from bulk toughness. The coupling of indention crack opening displacements (COD) with local stress field assessments by spectroscopy paves the way to reliably compare the structural properties of bioceramics and to quantitatively monitor their evolution during environmental exposure. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Fracture toughness measurements of LPS-SiC: a comparison of the indentation technique and the SEVNB method

    Directory of Open Access Journals (Sweden)

    Kurt Strecker

    2005-06-01

    Full Text Available Many methods are currently used to measure the fracture toughness of ceramic materials. Methods based on crack-length measurements of cracks introduced into the sample surface by the Vicker's indentor have the advantage that they are easy to use, but are very unreliable due to subcritical crack growth and the difficulty in determining the exact length of the cracks. Furthermore, depending on the crack shape there are many equations to calculate K Ic. Other methods like the Chevron Notch or Single Edge Pre-cracked Beam (SEPB are often difficult to execute or expensive. The simple and inexpensive Single-Edge-V-Notched Beam (SEVNB on the other hand gives reliable values of fracture toughness of ceramic materials. In this method a saw cut is tapered to a sharp V-notch using a razor blade sprinkled with diamond paste. Thus, it is possible to introduce a sharp crack with a notch width of less than 20 micrometers, necessary to conduct valid tests. In this investigation, fracture toughness measurements on LPS-SiC materials carried out by the indentation technique and the SEVNB method have been compared.

  7. Indentation studies on Y[sub 2]O[sub 3]-stabilized ZrO[sub 2]; 2: Toughness determination from stable growth of indentation-induced cracks

    Energy Technology Data Exchange (ETDEWEB)

    Dransmann, G.W.; Steinbrech, R.W. (Inst. fuer Reaktorwerkstoffe, Juelich (Germany)); Pajares, A.; Guiberteau, F. (Univ. de Extremadura, Badajoz (Spain). Facultad de Ciencias); Dominguez-Rodriguez, A. (Univ. de Sevilla (Spain). Dept. de Fisic Materia Condensada); Heuer, A.H. (Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering)

    1994-05-01

    Stable indentation cracks were grown in four-point bend tests to study the fracture toughness of two Y[sub 2]O[sub 3]-stabilized ZrO[sub 2] ceramics containing 3 and 4 mol% Y[sub 2]O[sub 3]. By combining microscopic in situ stable crack growth observations at discrete stresses with crack profile measurements, the dependence of toughness on crack extension was determined from crack extension plots, which graphically separate the crack driving residual stress intensity and applied stress intensity factors. Both materials exhibit steeply rising R-curves, with a plateau toughness of 4.5 and 3.1 MPa[center dot]m[sup 1/2] for the 3- and 4-mol% materials, respectively. The magnitude of the plateau toughness reflects the fraction of tetragonal grain contributing to transformation toughening.

  8. Source parameters of microearthquakes on an interplate asperity off Kamaishi, NE Japan over two earthquake cycles

    Science.gov (United States)

    Uchida, Naoki; Matsuzawa, Toru; Ellsworth, William L.; Imanishi, Kazutoshi; Shimamura, Kouhei; Hasegawa, Akira

    2012-01-01

    We have estimated the source parameters of interplate earthquakes in an earthquake cluster off Kamaishi, NE Japan over two cycles of M~ 4.9 repeating earthquakes. The M~ 4.9 earthquake sequence is composed of nine events that occurred since 1957 which have a strong periodicity (5.5 ± 0.7 yr) and constant size (M4.9 ± 0.2), probably due to stable sliding around the source area (asperity). Using P- and S-wave traveltime differentials estimated from waveform cross-spectra, three M~ 4.9 main shocks and 50 accompanying microearthquakes (M1.5–3.6) from 1995 to 2008 were precisely relocated. The source sizes, stress drops and slip amounts for earthquakes of M2.4 or larger were also estimated from corner frequencies and seismic moments using simultaneous inversion of stacked spectral ratios. Relocation using the double-difference method shows that the slip area of the 2008 M~ 4.9 main shock is co-located with those of the 1995 and 2001 M~ 4.9 main shocks. Four groups of microearthquake clusters are located in and around the mainshock slip areas. Of these, two clusters are located at the deeper and shallower edge of the slip areas and most of these microearthquakes occurred repeatedly in the interseismic period. Two other clusters located near the centre of the mainshock source areas are not as active as the clusters near the edge. The occurrence of these earthquakes is limited to the latter half of the earthquake cycles of the M~ 4.9 main shock. Similar spatial and temporal features of microearthquake occurrence were seen for two other cycles before the 1995 M5.0 and 1990 M5.0 main shocks based on group identification by waveform similarities. Stress drops of microearthquakes are 3–11 MPa and are relatively constant within each group during the two earthquake cycles. The 2001 and 2008 M~ 4.9 earthquakes have larger stress drops of 41 and 27 MPa, respectively. These results show that the stress drop is probably determined by the fault properties and does not change

  9. Bothrops asper and Bothrops jararaca snake venoms trigger microbicidal functions of peritoneal leukocytes in vivo.

    Science.gov (United States)

    Zamuner, S R; Gutiérrez, J M; Muscará, M N; Teixeira, S A; Teixeira, C F

    2001-10-01

    Venoms from snakes of the genus Bothrops cause pronounced local effects in the victims. These alterations result not only from the direct toxic action of venom components, but also from the prominent inflammatory reaction associated with these envenomations. In this study we investigated the ability of Bothrops asper (BaV) and Bothrops jararaca (BjV) venoms to induce cellular influx and microbicidal functions in leukocytes. BaV and BjV (5 microg/animal) caused a long lasting infiltration of leukocytes (3-48 h) when injected into mouse peritoneal cavity. Both venoms increased phagocytosis and production of hydrogen peroxide (H2O2) by polymorphonuclear (PMN) and mononuclear (MN) peritoneal leukocytes. In addition, nitric oxide (NO) production by macrophages was also enhanced after the venom injections. This effect was inhibited by treating animals with L-NAME and aminoguanidine, thus suggesting the induction of iNOS synthesis by the venoms. Western blot analysis confirmed the expression of iNOS in macrophages. BaV and BjV injection led to increased levels of IFN-gamma at the site of inflammation. Since IFN-gamma is an effective inducer of iNOS expression, an indirect action of the venoms on iNOS expression can be proposed. A marked formation of nitrotyrosine-containing proteins was also observed in macrophage homogenates. Based on these results, we suggest that reactive oxygen and nitrogen-derived species are involved in the pathogenesis of the local tissue damage characteristic of Bothrops sp envenomations.

  10. DELIGNIFIKASI BAMBU PETUNG (DENDROCALAMUS ASPER DENGAN EKSTRAK ABU JERAMI PADI DAN KAYU

    Directory of Open Access Journals (Sweden)

    Endah Sulistiawati

    2012-10-01

    Full Text Available Kebutuhan tekstil di Indonesia terus meningkat seiring dengan bertambahnya jumlah penduduk. Selama ini pemenuhan tekstil sebagian besar diimpor dari beberapa negara, antara lain: India, China, dan Jepang. Di sisi lain, Indonesia merupakan negara agraris, dengan limbah pertanian yang melimpah. Juga tanaman bambu tumbuh subur dan banyak terdapat di negeri ini. Keunggulan serat tekstil bambu adalah bersifat antiseptik, tahan terhadap mikroba. Penelitian ini merupakan salah satu langkah dalam pembuatan serat tekstil alami dari bambu petung (Dendrocalamus asper dan limbah pertanian yaitu abu jerami padi dan kayu, yaitu tahap delignifikasi. Tujuan penelitian ini mencari waktu perendaman bambu dalam ekstrak abu yang memberikan hasil terbaik. Bambu dipotong dan dibelah tipis, berukuran panjang 15 cm, setebal 0,5 mm. Mula-mula sampel bambu ditimbang (antara 12 sampai 57 gram, lalu direndam dalam ekstrak abu (jerami padi dan kayu sebanyak 500 ml dalam sebuah botol berkapasitas 600 ml dan ditutup. Perendaman dilakukan pada suhu kamar. Waktu perendaman bervariasi dari 4 jam hingga 80 jam. Setelah perendaman selesai, hasil disaring. Sampel filtrat dititrasi untuk diketahui konsentrasi alkali aktifnya. Bambu yang telah direndam lalu dikeringkan menggunakan oven pada suhu 110ºC sampai berat tetap. Selisih berat antara bambu awal dan akhir (kering dihitung, dan dianggap sebagai lignin yang terdegradasi. Dari penelitian dapat disimpulkan bahwa perendaman menggunakan ekstrak abu jerami padi memberikan hasil yang lebih baik dari pada ekstrak abu kayu, karena pengurangan berat padatan lebih besar. Hasil yang tertinggi pada perendaman menggunakan ekstrak abu jerami padi selama 76 jam, dengan selisih berat (basis kering mencapai 44,5%.

  11. Great earthquakes and slow slip events along the Sagami trough and outline of the Kanto Asperity Project

    Science.gov (United States)

    Kobayashi, R.; Yamamoto, Y.; Sato, T.; Shishikura, M.; Ito, H.; Shinohara, M.; Kawamura, K.; Shibazaki, B.

    2010-12-01

    The Kanto region is one of the most densely populated urban areas in the world. Complicated plate configurations are due to T-T-T type triple junction, island arc-island arc collision zone, and very shallow angle between axis of the Sagami trough and subducting direction. Great earthquakes along the Sagami trough have repeatedly occurred. The 1703 Genroku and 1923 (Taisho) Kanto earthquakes caused severe damages in the Tokyo metropolitan area. Intriguingly slow slip events have also repeatedly occurred in an area adjacent to the asperities of the great earthquakes, off Boso peninsula (e.g., Ozawa et al 2007). In the cases of the Nankai and Cascadia subduction zones, slow slip events occur at deeper levels than the asperity, in a transition zone between the asperity and a region of steady slip. In contrast, slow slip events in the Kanto region have occurred at relatively shallow depths, at the same level as the asperity, raising the possibility of friction controlled by different conditions to those (temperature and pressure) encountered at Nankai and Cascadia. We focus on three different types of seismic events occurring repeatedly at the almost same depth of the seismogenic zone along the Sagami trough (5-20 km) (1) The 1923 M~7.9 Taisho earthquake, located in Sagami Bay. Maximum slip is about 6 m, the recurrence interval is 200-400 yr, and the coupling rate is 80-100% (“coupling rates” = “slip amounts during earthquakes or slow-slip events” / [“rate of motion of the Philippine Sea Plate” - “recurrence interval”]) . (2) The 1703 M~8.2 Genroku earthquake, located in Sagami Bay, but also extending to the southern part of Boso Peninsula. Maximum slip is 15-20 m, the recurrence interval is ~2000 yr, and the coupling rate at the southern part of the Boso Peninsula is 10-30%. (3) Boso slow-slip events, located southeast of Boso Peninsula. Maximum slip is 15-20 cm over ~10 days, the recurrence interval is 5-6 yr, and the coupling rate is 70

  12. Isolation of bothrasperin, a disintegrin with potent platelet aggregation inhibitory activity, from the venom of the snake Bothrops asper

    Directory of Open Access Journals (Sweden)

    Adrián Pinto

    2003-03-01

    Full Text Available The venom of Bothrops asper induces severe coagulation disturbances in accidentally envenomed humans. However, only few studies have been conducted to identify components that interact with the hemostatic system in this venom. In the present work, we fractionated B. asper venom in order to investigate the possible presence of inhibitors of platelet aggregation. Using a combination of gel filtration, anion-exchange chromatography, and reverse-phase high performance liquid chromatography, we isolated an acidic protein which shows a single chain composition, with a molecular mass of ~8 kDa, estimated by SDS-polyacrylamide gel electrophoresis. Its N-terminal sequence has high similarity to disintegrins isolated from different snake venoms, which are known to bind to cellular integrins such as the GPIIb/IIIa fibrinogen receptor on platelets. The purified protein exerted potent aggregation inhibitory activity on ADP-stimulated human platelets in vitro, with an estimated IC50 of 50 nM. This biological activity, together with the biochemical characteristics observed, demonstrate that the protein isolated from B. asper venom is a disintegrin, hereby named "bothrasperin". This is the first disintegrin isolated from Central American viperid snake species.El veneno de la serpiente Bothrops asper induce graves alteraciones de la coagulación en los humanos accidentalmente envenenados. Sin embargo, se han realizado pocos estudios para identificar los componentes del veneno que interactúan con el sistema hemostático. En el presente trabajo, fraccionamos el veneno de B. asper para investigar la posible presencia de inhibidores de la agregación plaquetaria. Empleando una combinación de técnicas cromatográficas (filtración en gel, intercambio aniónico y cromatografía líquida de alto desempeño en fase reversa, aislamos una proteína acídica de cadena simple, con una masa molecular de ~8 kDa, estimada mediante electroforesis en gel de poliacrilamida con

  13. Poor regenerative outcome after skeletal muscle necrosis induced by Bothrops asper venom: alterations in microvasculature and nerves.

    Science.gov (United States)

    Hernández, Rosario; Cabalceta, Carmen; Saravia-Otten, Patricia; Chaves, Alessandra; Gutiérrez, José María; Rucavado, Alexandra

    2011-01-01

    Viperid snakebite envenoming is characterized by prominent local tissue damage, including muscle necrosis. A frequent outcome of such local pathology is deficient skeletal muscle regeneration, which causes muscle dysfunction, muscle loss and fibrosis, thus provoking permanent sequelae that greatly affect the quality of life of patients. The causes of such poor regenerative outcome of skeletal muscle after viperid snakebites are not fully understood. A murine model of muscle necrosis and regeneration was adapted to study the effects of the venom and isolated toxins of Bothrops asper, the medically most important snake in Central America. Gastrocnemius muscle was injected with either B. asper venom, a myotoxic phospholipase A(2) (Mtx), a hemorrhagic metalloproteinase (SVMP), or saline solution. At various time intervals, during one month, tissue samples were collected and analyzed by histology, and by immunocytochemical and immunohistochemical techniques aimed at detecting muscle fibers, collagen, endothelial cells, myoblasts, myotubes, macrophages, TUNEL-positive nuclei, and axons. A successful regenerative response was observed in muscle injected with Mtx, which induces myonecrosis but does not affect the microvasculature. In contrast, poor regeneration, with fibrosis and atrophic fibers, occurred when muscle was injected with venom or SVMP, both of which provoke necrosis, microvascular damage leading to hemorrhage, and poor axonal regeneration. The deficient skeletal muscle regeneration after injection of B. asper venom is likely to depend on the widespread damage to the microvasculature, which affects the removal of necrotic debris by phagocytes, and the provision of nutrients and oxygen required for regeneration. In addition, deficient axonal regeneration is likely to contribute to the poor regenerative outcome in this model.

  14. Poor regenerative outcome after skeletal muscle necrosis induced by Bothrops asper venom: alterations in microvasculature and nerves.

    Directory of Open Access Journals (Sweden)

    Rosario Hernández

    Full Text Available BACKGROUND: Viperid snakebite envenoming is characterized by prominent local tissue damage, including muscle necrosis. A frequent outcome of such local pathology is deficient skeletal muscle regeneration, which causes muscle dysfunction, muscle loss and fibrosis, thus provoking permanent sequelae that greatly affect the quality of life of patients. The causes of such poor regenerative outcome of skeletal muscle after viperid snakebites are not fully understood. METHODOLOGY/PRINCIPAL FINDINGS: A murine model of muscle necrosis and regeneration was adapted to study the effects of the venom and isolated toxins of Bothrops asper, the medically most important snake in Central America. Gastrocnemius muscle was injected with either B. asper venom, a myotoxic phospholipase A(2 (Mtx, a hemorrhagic metalloproteinase (SVMP, or saline solution. At various time intervals, during one month, tissue samples were collected and analyzed by histology, and by immunocytochemical and immunohistochemical techniques aimed at detecting muscle fibers, collagen, endothelial cells, myoblasts, myotubes, macrophages, TUNEL-positive nuclei, and axons. A successful regenerative response was observed in muscle injected with Mtx, which induces myonecrosis but does not affect the microvasculature. In contrast, poor regeneration, with fibrosis and atrophic fibers, occurred when muscle was injected with venom or SVMP, both of which provoke necrosis, microvascular damage leading to hemorrhage, and poor axonal regeneration. CONCLUSIONS/SIGNIFICANCE: The deficient skeletal muscle regeneration after injection of B. asper venom is likely to depend on the widespread damage to the microvasculature, which affects the removal of necrotic debris by phagocytes, and the provision of nutrients and oxygen required for regeneration. In addition, deficient axonal regeneration is likely to contribute to the poor regenerative outcome in this model.

  15. Contact problem for a solid indenter and a viscoelastic half-space described by the spectrum of relaxation and retardation times

    Science.gov (United States)

    Stepanov, F. I.

    2018-04-01

    The mechanical properties of a material which is modeled by an exponential creep kernel characterized by a spectrum of relaxation and retardation times are studied. The research is carried out considering a contact problem for a solid indenter sliding over a viscoelastic half-space. The contact pressure, indentation depth of the indenter, and the deformation component of the friction coefficient are analyzed with respect to the case of half-space material modeled by single relaxation and retardation times.

  16. Snake venomics and antivenomics of Bothrops colombiensis, a medically important pitviper of the Bothrops atrox-asper complex endemic to Venezuela: Contributing to its taxonomy and snakebite management.

    Science.gov (United States)

    Calvete, Juan J; Borges, Adolfo; Segura, Alvaro; Flores-Díaz, Marietta; Alape-Girón, Alberto; Gutiérrez, José María; Diez, Nardy; De Sousa, Leonardo; Kiriakos, Demetrio; Sánchez, Eladio; Faks, José G; Escolano, José; Sanz, Libia

    2009-03-06

    The taxonomic status of the medically important pitviper of the Bothrops atrox-asper complex endemic to Venezuela, which has been classified as Bothrops colombiensis, remains incertae cedis. To help resolving this question, the venom proteome of B. colombiensis was characterized by reverse-phase HPLC fractionation followed by analysis of each chromatographic fraction by SDS-PAGE, N-terminal sequencing, MALDI-TOF mass fingerprinting, and collision-induced dissociation tandem mass spectrometry of tryptic peptides. The venom contained proteins belonging to 8 types of families. PI Zn(2+)-metalloproteinases and K49 PLA(2) molecules comprise over 65% of the venom proteins. Other venom protein families comprised PIII Zn(2+)-metalloproteinases (11.3%), D49 PLA(2)s (10.2%), l-amino acid oxidase (5.7%), the medium-sized disintegrin colombistatin (5.6%), serine proteinases (1%), bradykinin-potentiating peptides (0.8%), a DC-fragment (0.5%), and a CRISP protein (0.1%). A comparison of the venom proteomes of B. colombiensis and B. atrox did not support the suggested synonymy between these two species. The closest homologues to B. colombiensis venom proteins appeared to be toxins from B. asper. A rough estimation of the similarity between the venoms of B. colombiensis and B. asper indicated that these species share approximately 65-70% of their venom proteomes. The close kinship of B. colombiensis and B. asper points at the ancestor of B. colombiensis as the founding Central American B. asper ancestor. This finding may be relevant for reconstructing the natural history and cladogenesis of Bothrops. Further, the virtually indistinguishable immunological crossreactivity of a Venezuelan ABC antiserum (raised against a mixture of B. colombiensis and Crotalus durissus cumanensis venoms) and the Costa Rican ICP polyvalent antivenom (generated against a mixture of B. asper, Crotalus simus, and Lachesis stenophrys venoms) towards the venoms of B. colombiensis and B. asper, supports this

  17. Chirality and grain boundary effects on indentation mechanical properties of graphene coated on nickel foil.

    Science.gov (United States)

    Yan, Yuping; Lv, Jiajiang; Liu, Sheng

    2018-04-20

    We investigate chirality and grain boundary (GB) effects on indentation mechanical properties of graphene coated on nickel foil using molecular dynamics simulations. The models of graphene with different chirality angles, different numbers of layers and tilt GBs were established. It was found that the chirality angle of few-layer graphene had a significant effect on the load bearing capacity of graphene/nickel systems, and this turns out to be more significant when the number of layers is greater than one. The enhancement to the contact stiffness, elastic capacity and the load bearing capacity of graphene with tilt GBs was lower than that of pristine graphene.

  18. Dislocation sources and slip band nucleation from indents on silicon wafers

    International Nuclear Information System (INIS)

    Wittge, J.; Danilewsky, A.N.; Allen, D.

    2010-01-01

    The nucleation of dislocations at controlled indents in silicon during rapid thermal annealing has been studied by in situ X-ray diffraction imaging (topography). Concentric loops extending over pairs of inclined {111} planes were formed, the velocities of the inclined and parallel segments being almost equal. Following loss of the screw segment from the wafer, the velocity of the inclined segments almost doubled, owing to removal of the line tension of the screw segments. The loops acted as obstacles to slip band propagation. (orig.)

  19. Chirality and grain boundary effects on indentation mechanical properties of graphene coated on nickel foil

    Science.gov (United States)

    Yan, Yuping; Lv, Jiajiang; Liu, Sheng

    2018-04-01

    We investigate chirality and grain boundary (GB) effects on indentation mechanical properties of graphene coated on nickel foil using molecular dynamics simulations. The models of graphene with different chirality angles, different numbers of layers and tilt GBs were established. It was found that the chirality angle of few-layer graphene had a significant effect on the load bearing capacity of graphene/nickel systems, and this turns out to be more significant when the number of layers is greater than one. The enhancement to the contact stiffness, elastic capacity and the load bearing capacity of graphene with tilt GBs was lower than that of pristine graphene.

  20. Mechanical properties of bovine cortical bone based on the automated ball indentation technique and graphics processing method.

    Science.gov (United States)

    Zhang, Airong; Zhang, Song; Bian, Cuirong

    2018-02-01

    Cortical bone provides the main form of support in humans and other vertebrates against various forces. Thus, capturing its mechanical properties is important. In this study, the mechanical properties of cortical bone were investigated by using automated ball indentation and graphics processing at both the macroscopic and microstructural levels under dry conditions. First, all polished samples were photographed under a metallographic microscope, and the area ratio of the circumferential lamellae and osteons was calculated through the graphics processing method. Second, fully-computer-controlled automated ball indentation (ABI) tests were performed to explore the micro-mechanical properties of the cortical bone at room temperature and a constant indenter speed. The indentation defects were examined with a scanning electron microscope. Finally, the macroscopic mechanical properties of the cortical bone were estimated with the graphics processing method and mixture rule. Combining ABI and graphics processing proved to be an effective tool to obtaining the mechanical properties of the cortical bone, and the indenter size had a significant effect on the measurement. The methods presented in this paper provide an innovative approach to acquiring the macroscopic mechanical properties of cortical bone in a nondestructive manner. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Continuous FEM simulation of the nanoindentation. Actual indenter tip geometries, material elastoplastic deformation laws and universal hardness

    Energy Technology Data Exchange (ETDEWEB)

    Bouzakis, K.D.; Michailidis, N.; Hadjiyiannis, S.; Skordaris, G. [Mechanical Engineering Dept., Aristoteles Univ. of Thessaloniki (Greece); Erkens, G. [CemeCon AG, Wuerselen (Germany)

    2002-09-01

    The precise knowledge of materials mechanical properties is always a core issue in every technical application. Through a developed finite elements method (FEM) continuous simulation of the nanoindentation, the applied force course versus the penetration depth is adequately simulated during the loading and unloading phases of this test, and the corresponding material stress-strain curves, as well as the universal hardness, are stepwise defined. Furthermore, the actual tip geometries of various indenters are approached and through equivalent magnitudes described. The results show that the defined material elastoplastic deformation characteristics are independent of the indenter type, as Vickers or Berkovich, since the existing indenter tip form deviations from their ideal geometry are considered. Furthermore, using the developed FEM-based nanoindentation simulation, the influence of the indenter tip geometry on the defined constitutive laws and the universal hardness is sufficiently elucidated. Various materials stress-strain curves and universal hardness courses versus the indentation depth, determined by means of the developed procedure, are presented. (orig.)

  2. FE simulation of the indentation deformation of SiC modified vinylester composites in respect to their abrasive wear performance

    Directory of Open Access Journals (Sweden)

    2008-10-01

    Full Text Available The abrasive sliding friction and wear behaviours of silicon carbide (SiC filled vinylester (VE composites were investigated. The average grain size of the incorporated SiC particles was varied, holding the volume content of them in every case at 16 vol%. Mechanical properties (hardness, compression modulus, yield stress of the filled and neat VE were determined. The tribological properties were investigated in block (composite – on – ring (steel test configuration. The steel counter bodies were covered with abrasive papers of different graining. Coefficient of friction (COF and specific wear rate of the VE + SiC composites were determined. It was observed that the wear resistance increases with increasing average filler grain size and with decreasing abrasiveness of the counter surface. The COF of the VE + SiC composites is independent of the size of the incorporated particles, but it is strongly influenced by the abrasiveness of the counter body. The worn surfaces of the VE + SiC systems were analysed in scanning electron microscope (SEM to deduce the typical wear mechanisms. The size effect of the SiC filler particles onto the abrasive wear characteristics was investigated by assuming that the roughness peaks of the abrasive paper and the indenter of the microhardness test cause similar micro scaled contact deformations in the composites. Therefore FE method was used to simulate the micro scaled deformation process in the VE + SiC systems during microindentation tests. The FE results provided valuable information on how to explain the size effect of the incorporated SiC filler.

  3. Venom of Bothrops asper from Mexico and Costa Rica: intraspecific variation and cross-neutralization by antivenoms.

    Science.gov (United States)

    Segura, Alvaro; Herrera, María; Villalta, Mauren; Vargas, Mariángela; Uscanga-Reynell, Alfredo; de León-Rosales, Samuel Ponce; Jiménez-Corona, María Eugenia; Reta-Mares, José Francisco; Gutiérrez, José María; León, Guillermo

    2012-01-01

    Bothrops asper is the species that induces the highest incidence of snakebite envenomation in southern Mexico, Central America and parts of northern South America. The intraspecies variability in HPLC profile and toxicological activities between the venoms from specimens collected in Mexico (Veracruz) and Costa Rica (Caribbean and Pacific populations) was investigated, as well as the cross-neutralization by antivenoms manufactured in these countries. Venoms differ in their HPLC profiles and in their toxicity, since venom from Mexican population showed higher lethal and defibrinogenating activities, whereas those from Costa Rica showed higher hemorrhagic and in vitro coagulant activities. In general, antivenoms were more effective in the neutralization of homologous venoms. Overall, both antivenoms effectively neutralized the various toxic effects of venoms from the two populations of B. asper. However, antivenom raised against venom from Costa Rican specimens showed a higher efficacy in the neutralization of defibrinogenating and coagulant activities, thus highlighting immunochemical differences in the toxins responsible for these effects associated with hemostatic disturbances in snakebite envenoming. These observations illustrate how intraspecies venom variation may influence antivenom neutralizing profile. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. Impact of regional variation in Bothrops asper snake venom on the design of antivenoms: integrating antivenomics and neutralization approaches.

    Science.gov (United States)

    Gutiérrez, José María; Sanz, Libia; Flores-Díaz, Marietta; Figueroa, Lucía; Madrigal, Marvin; Herrera, María; Villalta, Mauren; León, Guillermo; Estrada, Ricardo; Borges, Adolfo; Alape-Girón, Alberto; Calvete, Juan J

    2010-01-01

    Intraspecific snake venom variations have implications in the preparation of venom pools for the generation of antivenoms. The impact of such variation in the cross-reactivity of antivenoms against Bothrops asper venom was assessed by comparing two commercial and four experimental antivenoms. All antivenoms showed similar immunorecognition pattern toward the venoms from adult and neonate specimens. They completely immunodepleted most P-III snake venom metalloproteinases (SVMPs), l-amino acid oxidases, serine proteinases, DC fragments, cysteine-rich secretory proteins (CRISPs), and C-type lectin-like proteins, and partially immunodepleted medium-sized disintegrins, phospholipases A(2) (PLA(2)s), some serine proteinases, and P-I SVMPs. Although all antivenoms abrogated the lethal, hemorrhagic, coagulant, proteinase, and PLA(2) venoms activities, monospecific experimental antivenoms were more effective than the polyspecific experimental antivenom. In addition, the commercial antivenoms, produced in horses subjected to repeated immunization cycles, showed higher neutralization than experimental polyspecific antivenom, produced by a single round of immunization. Overall, a conspicuous pattern of cross-neutralization was evident for all effects by all antivenoms, and monospecific antivenoms raised against venom from the Caribbean population were effective against venom from the Pacific population, indicating that geographic variations in venom proteomes of B. asper from Costa Rica do not result in overt variations in immunological cross-reactivity between antivenoms.

  5. Role of nitric oxide in the local and systemic pathophysiological effects induced by Bothrops asper snake venom in mice.

    Science.gov (United States)

    Chaves, F; Teixeira, C F P; Gutiérrez, J M

    2006-06-01

    To assess the role of nitric oxide in the most relevant local and systemic manifestations in mice injected with the venom of the snake Bothrops asper. Mice were pretreated with nitric oxide synthase inhibitors, and the modifications of the pathological effects induced by the venom were tested. Inhibition of NO synthesis did not affect acute local myonecrosis and hemorrhage in muscle tissue upon intramuscular injection of venom. Local footpad edema was reduced in mice pretreated with the NO synthase inhibitor L-NAME, and a reduction in the extent of inflammatory infiltrate in muscle tissue was observed after envenomation in mice pretreated with L-NAME and aminoguanidine. The most pronounced effect of NOS inhibition by L-NAME was an increment in the lethal activity of the venom, when injected by the intraperitoneal route. Nitric oxide does not seem to play a significant role in the local acute pathological alterations (hemorrhage and myonecrosis) induced by B. asper venom in mice, although it contributes to edema and inflammatory infiltrate. Nitric oxide exerts a protective role in the systemic pathophysiological manifestations leading to lethality.

  6. Phenotypic differences in a cryptic predator: factors influencing morphological variation in the terciopelo Bothrops asper (Garman, 1884; Serpentes: Viperidae).

    Science.gov (United States)

    Saldarriaga-Córdoba, Mónica María; Sasa, Mahmood; Pardo, Rodrigo; Méndez, Marco Antonio

    2009-12-01

    The terciopelo Bothrops asper, is a cryptic lancehead pitviper widely distributed in humid environments of Middle America and the north-western portion of South America. Throughout its extensive distribution range, the terciopelo exhibits great morphological variation in external characters, a situation that has complicated its proper separation from other related species. In this paper, we analyzed the phenotypic variation of B. asper based in a sample of 514 specimens from nine distinct physiographic regions. Univariate and multivariate analyses demonstrated great phenotypic differentiation among most pre-established groups, and the pattern is fairly congruent between sexes. However, no correspondence was observed between morphological variation and molecular divergence, inferred from mDNA sequences, between individuals representing the physiographical regions under study. Geographic variation in the number of interrictals, ventral scales, subcaudal scales and dorsal blotches was positively correlated with latitude and number of dry months, but inversely related with precipitation. However, other variables do not exhibit such an effect. The observed relationships between scale counts and environmental variables are explained in terms of selective pressures to improve water balance along the distributional range of the species.

  7. Sub-micron indent induced plastic deformation in copper and irradiated steel; Deformation plastique induite par l'essai d'indentation submicronique, dans le cuivre et l'acier 316L irradie

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Ch

    1999-07-01

    In this work we aim to study the indent induced plastic deformation. For this purpose, we have developed a new approach, whereby the indentation curves provides the mechanical behaviour, while the deformation mechanisms are observed thanks to Transmission Electron Microscopy (TEM). In order to better understand how an indent induced dislocation microstructure forms, numerical modeling of the indentation process at the scale of discrete dislocations has been worked out as well. Validation of this modeling has been performed through direct comparison of the computed microstructures with TEM micrographs of actual indents in pure Cu (001]. Irradiation induced modifications of mechanical behaviour of ion irradiated 316L have been investigated, thanks to the mentioned approach. An important hardening effect was reported from indentation data (about 50%), on helium irradiated 316L steel. TEM observations of the damage zone clearly show that this behaviour is associated with the presence of He bubbles. TEM observations of the indent induced plastic zone also showed that the extent of the plastic zone is strongly correlated with hardness, that is to say: harder materials gets a smaller plastic zone. These results thus clearly established that the selected procedure can reveal any irradiation induced hardening in sub-micron thick ion irradiated layers. The behaviour of krypton irradiated 316L steel is somewhat more puzzling. In one hand indeed, a strong correlation between the defect cluster size and densities on the irradiation temperature is observed in the 350 deg. C - 600 deg. C range, thanks to TEM observations of the damage zone. On the other hand, irradiation induced hardening reported from indentation data is relatively small (about 10%) and shows no dependence upon the irradiation temperature (within the mentioned range). In addition, it has been shown that the reported hardening vanishes following appropriate post-irradiation annealing, although most of the TEM

  8. Finite Element Analysis of Aluminum Honeycombs Subjected to Dynamic Indentation and Compression Loads

    Directory of Open Access Journals (Sweden)

    A.S.M. Ayman Ashab

    2016-03-01

    Full Text Available The mechanical behavior of aluminum hexagonal honeycombs subjected to out-of-plane dynamic indentation and compression loads has been investigated numerically using ANSYS/LS-DYNA in this paper. The finite element (FE models have been verified by previous experimental results in terms of deformation pattern, stress-strain curve, and energy dissipation. The verified FE models have then been used in comprehensive numerical analysis of different aluminum honeycombs. Plateau stress, σpl, and dissipated energy (EI for indentation and EC for compression have been calculated at different strain rates ranging from 102 to 104 s−1. The effects of strain rate and t/l ratio on the plateau stress, dissipated energy, and tearing energy have been discussed. An empirical formula is proposed to describe the relationship between the tearing energy per unit fracture area, relative density, and strain rate for honeycombs. Moreover, it has been found that a generic formula can be used to describe the relationship between tearing energy per unit fracture area and relative density for both aluminum honeycombs and foams.

  9. Depth-sensing nano-indentation on a myelinated axon at various stages

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Wei-Chin; Liao, Jiunn-Der [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Lin, Chou-Ching K [Department of Neurology, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Ju, Ming-Shaung, E-mail: jdliao@mail.ncku.edu.tw [Department of Mechanical Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)

    2011-07-08

    A nano-mechanical characterization of a multi-layered myelin sheath structure, which enfolds an axon and plays a critical role in the transmission of nerve impulses, is conducted. Schwann cells co-cultured in vitro with PC12 cells for various co-culture times are differentiated to form a myelinated axon, which is then observed using a transmission electron microscope. Three major myelination stages, with distinct structural characteristics and thicknesses around the axon, can be produced by varying the co-culture time. A dynamic contact module and continuous depth-sensing nano-indentation are used on the myelinated structure to obtain the load-on-sample versus measured displacement curve of a multi-layered myelin sheath, which is used to determine the work required for the nano-indentation tip to penetrate the myelin sheath. By analyzing the harmonic contact stiffness versus the measured displacement profile, the results can be used to estimate the three stages of the multi-layered structure on a myelinated axon. The method can also be used to evaluate the development stages of myelination or demyelination during nerve regeneration.

  10. Effect of processing on fracture toughness of silicon carbide as determined by Vickers indentations

    Science.gov (United States)

    Dannels, Christine M.; Dutta, Sunil

    1989-01-01

    Several alpha-SiC materials were processed by hot isostatic pressing (HIPing) and by sintering an alpha-SiC powder containing boron and carbon. Several beta-SiC materials were processed by HIPing a beta-SiC powder with boron and carbon additions. The fracture toughnesses K(sub 1c) of these beta- and alpha-SiC materials were estimated from measurements of Vickers indentations. The three formulas used to estimate K(sub 1c) from the indentation fracture patterns resulted in three ranges of K(sub 1c) estimates. Furthermore, each formula measured the effects of processing differently. All three estimates indicated that fine-grained HIPed alpha-SiC has a higher K(sub 1c) than coarsed-grained sintered alpha-SiC. Hot isostatically pressed beta-SiC, which had an ultrafine grain structure, exhibited a K(sub 1c) comparable to that of HIPed alpha-SiC.

  11. A study on the evaluation of material degradation using ball indentation method

    International Nuclear Information System (INIS)

    Kim, Jeong Pyo; Seok, Chang Sung; Ahn, Ha Neul

    2000-01-01

    As huge energy transfer systems like a nuclear power plant, steam power plant and petrochemical plant are operated for a long time, mechanical properties are changed by degradation. The life time of the systems can be affected by the mechanical properties. BI(Ball Indentation) test has a potential to replace conventional fracture tests like a uniaxial tensile test, fracture toughness test, hardness test and so on. In this paper, we would like to present the aging evaluation technique by the BI method. The four classes of the thermally aged 1Cr-1Mo-0.25V specimens were prepared using an artificially accelerated aging method. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed. The results of the BI tests were in good agreement with fracture characteristics by a standard fracture test method. The IDE(Indentation Deformation Energy) of a BI technique as a new parameter for evaluating a degradation was suggested and the new IDE parameter clearly depicts the degradation degree

  12. Experimental creep behavior of porcine liver under indentation with laparoscopic grasper for MIS applications

    Directory of Open Access Journals (Sweden)

    Cheng-mo Cai

    2017-06-01

    Full Text Available Mechanical response of soft tissues behaved disparate due to fast and large deformation during surgical grasping, so there is a need for experimental databases of biomechanical characteristics of soft tissue under the contact of MIS tool, which are more useful for designing new surgical instruments, training inexperienced surgeons, improving surgical simulations and developing surgical robotics system. A novel indentation test to simulate the real-time surgical operation condition was present in this paper. The creep behavior of porcine liver in vitro was studied under uniaxial indentation by using MIS grasper. The nominal stress between the grasper and the liver was 0.02 to 0.1 MPa, the loading velocity was 1 to 3 mm/s, and the holding time was 300 s to simulate clamping tissue operation. Results showed that the creep process of the liver during 300 s of duration can be divided into three stages: loading stage I, transition creep stage II and steady creep stage III. The creep characteristic of liver behaves time-dependent, load-dependent and strongly loading velocity-dependent due to its nonlinear viscoelastic characteristics and hysteresis characteristics. These creep behavior might also be associated with the deformation, migration and biochemical reaction of the liver cells. The phenomenological model derived in this paper may describe the creep behavior of the liver. The results would provide experimental databases and phenomenological models for investigating biomechanical characteristics of soft tissue under the contact of MIS tool.

  13. The indentation of pressurized elastic shells: from polymeric capsules to yeast cells

    KAUST Repository

    Vella, D.

    2011-08-10

    Pressurized elastic capsules arise at scales ranging from the 10 m diameter pressure vessels used to store propane at oil refineries to the microscopic polymeric capsules that may be used in drug delivery. Nature also makes extensive use of pressurized elastic capsules: plant cells, bacteria and fungi have stiff walls, which are subject to an internal turgor pressure. Here, we present theoretical, numerical and experimental investigations of the indentation of a linearly elastic shell subject to a constant internal pressure. We show that, unlike unpressurized shells, the relationship between force and displacement demonstrates two linear regimes. We determine analytical expressions for the effective stiffness in each of these regimes in terms of the material properties of the shell and the pressure difference. As a consequence, a single indentation experiment over a range of displacements may be used as a simple assay to determine both the internal pressure and elastic properties of capsules. Our results are relevant for determining the internal pressure in bacterial, fungal or plant cells. As an illustration of this, we apply our results to recent measurements of the stiffness of baker\\'s yeast and infer from these experiments that the internal osmotic pressure of yeast cells may be regulated in response to changes in the osmotic pressure of the external medium.

  14. Stress Mapping in Glass-to-Metal Seals using Indentation Crack Lengths.

    Energy Technology Data Exchange (ETDEWEB)

    Strong, Kevin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Buchheit, Thomas E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Diebold, Thomas Wayne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Newton, Clay S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bencoe, Denise N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Stavig, Mark E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jamison, Ryan Dale [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-08-01

    Predicting the residual stress which develops during fabrication of a glass-to-metal compression seal requires material models that can accurately predict the effects of processing on the sealing glass. Validation of the predictions requires measurements on representative test geometries to accurately capture the interaction between the seal materials during a processing cycle required to form the seal, which consists of a temperature excursion through the glass transition temperature of the sealing glass. To this end, a concentric seal test geometry, referred to as a short cylinder seal, consisting of a stainless steel shell enveloping a commercial sealing glass disk has been designed, fabricated, and characterized as a model validation test geometry. To obtain data to test/validate finite element (FE) stress model predictions of this geometry, spatially-resolved residual stress was calculated from the measured lengths of the cracks emanating from radially positioned Vickers indents in the glass disk portion of the seal. The indentation crack length method is described, and the spatially-resolved residual stress determined experimentally are compared to FE stress predictions made using a nonlinear viscoelastic material model adapted to inorganic sealing glasses and an updated rate dependent material model for 304L stainless steel. The measurement method is a first to achieve a degree of success for measuring spatially resolved residual stress in a glass-bearing geometry and a favorable comparison between measurements and simulation was observed.

  15. Stress Mapping in Glass-to-Metal Seals using Indentation Crack Lengths

    Energy Technology Data Exchange (ETDEWEB)

    Buchheit, Thomas E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Component & Systems Analysis; Strong, Kevin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Material Mechanics and Tribology; Newton, Clay S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Material Mechanics and Tribology; Diebold, Thomas Wayne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Material Mechanics and Tribology; Bencoe, Denise N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Electronic, Optical and Nano; Stavig, Mark E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Organic Materials Science; Jamison, Ryan Dale [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Transportation System Analysis

    2017-08-01

    Predicting the residual stress which develops during fabrication of a glass-to-metal compression seal requires material models that can accurately predict the effects of processing on the sealing glass. Validation of the predictions requires measurements on representative test geometries to accurately capture the interaction between the seal materials during a processing cycle required to form the seal, which consists of a temperature excursion through the glass transition temperature of the sealing glass. To this end, a concentric seal test geometry, referred to as a short cylinder seal, consisting of a stainless steel shell enveloping a commercial sealing glass disk has been designed, fabricated, and characterized as a model validation test geometry. To obtain data to test/validate finite element (FE) stress model predictions of this geometry, spatially-resolved residual stress was calculated from the measured lengths of the cracks emanating from radially positioned Vickers indents in the glass disk portion of the seal. The indentation crack length method is described, and the spatially-resolved residual stress determined experimentally are compared to FE stress predictions made using a nonlinear viscoelastic material model adapted to inorganic sealing glasses and an updated rate dependent material model for 304L stainless steel. The measurement method is a first to achieve a degree of success for measuring spatially resolved residual stress in a glass-bearing geometry and a favorable comparison between measurements and simulation was observed.

  16. Measurement of diabetic wounds with optical coherence tomography-based air-jet indentation system and a material testing system.

    Science.gov (United States)

    Choi, M-C; Cheung, K-K; Ng, G Y-F; Zheng, Y-P; Cheing, G L-Y

    2015-11-01

    Material testing system is a conventional but destructive method for measuring the biomechanical properties of wound tissues in basic research. The recently developed optical coherence tomography-based air-jet indentation system is a non-destructive method for measuring these properties of soft tissues in a non-contact manner. The aim of the study was to examine the correlation between the biomechanical properties of wound tissues measured by the two systems. Young male Sprague-Dawley rats with streptozotocin-induced diabetic were wounded by a 6 mm biopsy punch on their hind limbs. The biomechanical properties of wound tissues were assessed with the two systems on post-wounding days 3, 7, 10, 14, and 21. Wound sections were stained with picro-sirius red for analysis on the collagen fibres. Data obtained on the different days were charted to obtain the change in biomechanical properties across the time points, and then pooled to examine the correlation between measurements made by the two devices. Qualitative analysis to determine any correlation between indentation stiffness measured by the air-jet indentation system and the orientation of collagen fibres. The indentation stiffness is significantly negatively correlated to the maximum load, maximum tensile stress, and Young's modulus by the material testing system (all p<0.05). The orientation of collagen changes with the indentation stiffness over time. Our findings support the use of optical coherence tomography-based air-jet indentation system to evaluate the biomechanical properties of wounds in a non-contact manner. It is a potential clinical device to examine the biomechanical properties of chronic wounds in vivo in a repeatable manner.

  17. Analytical/Empirical Study on Indentation Behavior of Sandwich Plate with Foam Core and Composite Face Sheets

    Directory of Open Access Journals (Sweden)

    Soheil Dariushi

    2017-07-01

    Full Text Available Sandwich structures are widely used in aerospace, automobile, high speed train and civil applications. Sandwich structures consist of two thin and stiff skins and a thick and light weight core. In this study, the obligatory mandate of a sandwich plate contact constitutes a flexible foam core and composite skins with a hemispherical rigid punch has been studied by an analytical/empirical method. In sandwich structures, calculation of force distribution under the punch nose is complicated, because the core is flexible and the difference between the modulus of elasticity of skin and core is large. In the present study, an exponential correlation between the contact force and indentation is proposed. The coefficient and numerical exponent were calculated using the experimental indentation results. A model based on a high-order sandwich panel theory was used to study the bending behavior of sandwich plate under hemispherical punch load. In the first method, the force distribution under the punch nose was calculated by the proposed method and multiplied to deformation of related point in the loading area to calculate the potential energy of the external loads. In the second method, the punch load was modeled as a point force and multiplied to deformation of maximum indented point. The results obtained from the two methods were compared with the experimental results. Indentation and bending tests were carried out on sandwich plates with glass/epoxy skins and a styrene/acrylonitrile foam core. In the bending test, a simply support condition was set and in the indentation test the sandwich specimens were put on a rigid support. Indeed, in this position the punch movement was equal the indentation. The comparison between the analytical and experimental results showed that the proposed method significantly improved the accuracy of analysis.

  18. Combined effect of electric field and residual stress on propagation of indentation cracks in a PZT-5H ferroelectric ceramic

    International Nuclear Information System (INIS)

    Huang, H.Y.; Chu, W.Y.; Su, Y.J.; Qiao, L.J.; Gao, K.W.

    2005-01-01

    The combined effect of electric field and residual stress on propagation of unloaded indentation cracks in a PZT-5 ceramic has been studied. The results show that residual stress itself is too small to induce delayed propagation of the indentation cracks in silicon oil. If applied constant electric field is larger than 0.2 kV/cm, the combined effect of electric field and residual stress can cause delayed propagation of the indentation crack after passing an incubation time in silicon oil, but the crack will arrest after propagating for 10-30 μm because of decrease of the resultant stress intensity factor induced by the field and residual stress with increasing the crack length. The threshold electric field for delayed propagation of the indentation crack in silicon oil is E DP = 0.2 kV/cm. If the applied electric field is larger than 5.25 kV/cm, combined effect of the electric field and residual stress can cause instant propagation of the indentation crack, and under sustained electric field, the crack which has propagated instantly can propagate continuously, until arrest at last. The critical electric field for instant propagation of the indentation crack is E P = 5.25 kV/cm. If the applied electric field is larger than 12.6 kV/cm, the microcracks induced by the electric field initiate everywhere, grow and connect in a smooth specimen, resulting in delayed failure, even without residual stress. The threshold electric field for delayed failure of a smooth specimen in silicon oil is E DF = 12.6 kV/cm and the critical electric field for instant failure is E F = 19.1 kV/cm

  19. Identification of the material properties of Al 2024 alloy by means of inverse analysis and indentation tests

    International Nuclear Information System (INIS)

    Moy, Charles K.S.; Bocciarelli, Massimiliano; Ringer, Simon P.; Ranzi, Gianluca

    2011-01-01

    Highlights: → Identification of mechanical properties by indentation test and inverse analysis. → Pile-up height is also considered as experimental information. → Inverse problem results to be well posed also in the case of mystical materials. → 2024 Al alloy samples prepared using different age-hardening treatments are studied. - Abstract: This paper outlines an inverse analysis approach aimed at the identification of the mechanical properties of metallic materials based on the experimental results obtained from indentation tests. Previous work has shown the ill-posed nature of the inverse problem based on the load-penetration curve when dealing with mystical materials, which exhibit identical indentation curves even if possessing different yield and strain-hardening properties. For this reason, an additional measurement is used in the present study as input for the inverse analysis which consists of the maximum pile-up height measured after the indentation test. This approach lends itself for practical applications as the load-penetration curve can be easily obtained from commonly available micro-indenters while the pile-up present at the end of the test can be measured by different instruments depending on the size of the indented area, for example by means of an atomic force microscope or a laser profilometer. The inverse analysis procedure consists of a batch deterministic approach, and conventional optimization algorithms are employed for the minimization of the discrepancy norm. The first part of the paper outlines how the inclusion of both the maximum height of the pile-up and the indentation curve in the input data of the inverse analysis leads to a well-defined inverse problem using parameters of mystical materials. The approach is then applied to real experimental data obtained from three sets of 2024 Al alloy samples prepared using different age-hardening treatments. The accuracy of the identification process is validated against the mechanical

  20. Application Of Holographic Interferometry For Investigation Of Microroughness Of Engineering Surfaces

    Science.gov (United States)

    Lech, Marek; Mruk, Irena; Stupnicki, Jacek

    1985-01-01

    The paper describes an improved immersion method of holographic interferometry /IMHI/ adjusted for studies of roughness of engineering surfaces. Special optical arrangement, with two types of immersion cells and adequate technique of preparing transparent replicas reproducting with high fidelity details of differently machined surfaces was elaborated. It permits to obtain the contour maps of the surface asperities with intervals between the planes of succesive contour lines within a range of 1 μm. The results obtained for some engineering surfaces are given.

  1. Geographical variability of the venoms of four populations of Bothrops asper from Panama: Toxicological analysis and neutralization by a polyvalent antivenom.

    Science.gov (United States)

    Vélez, Sara María; Salazar, Marcos; Acosta de Patiño, Hildaura; Gómez, Leandra; Rodriguez, Abdiel; Correa, David; Saldaña, Julio; Navarro, Deyvi; Lomonte, Bruno; Otero-Patiño, Rafael; Gutiérrez, José María

    2017-06-15

    Bothrops asper is the medically most important venomous snake in Central America. In Panama, the country having the highest incidence of snakebites in Latin America, B. asper is widely distributed throughout the country and is responsible for the vast majority of snakebites. This study was performed to analyze whether there are variations in the toxicological profile and in some biochemical parameters between the venoms of B. asper from four different regions in Panama. The venoms showed a similar profile of lethal, hemorrhagic, in vitro coagulant, defibrinogenating, edema-forming, myotoxic and indirect hemolytic activities, with subtle quantitative variations between samples of some regions. The venoms also had similar SDS-PAGE patterns and reverse phase HPLC profiles. A polyvalent antivenom manufactured in Costa Rica, and regularly used in Panama, was effective in the neutralization of lethal activity of the venoms of the four populations, with Mean Effective Doses (ED 50 ) ranging from 5.98 to 9.72 mg venom/mL antivenom. In agreement, a widespread pattern of cross-reactivity between this antivenom and the four venoms was observed by immunoblotting. Overall, results highlight the lack of marked differences between the venoms of the various populations of B. asper in Panama, and that the antivenom from Costa Rica is effective in neutralizing lethality. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Finite element method analysis of surface roughness transfer in micro flexible rolling

    Directory of Open Access Journals (Sweden)

    Qu Feijun

    2016-01-01

    Full Text Available Micro flexible rolling aims to fabricate submillimeter thick strips with varying thickness profile, where the surface quality of products is mainly determined by initial workpiece surface roughness and subsequent surface asperity flattening process, which is affected by process parameters during rolling. This paper shows a 3D finite element model for flexible rolling of a 250 μm thick workpiece with reduction of 20 to 50%, and rolling phase with thinner thickness indicates a better ability to decrease the surface roughness. Four types of initial workpiece surface roughness are studied in the simulation, and the influences of process parameters, such as friction coefficient, rolling speed and roll gap adjusting speed, on surface asperity flattening of workpieces with different initial surface roughness have been numerically investigated and analysed.

  3. Comparing damage from low-velocity impact and quasi-static indentation in automotive carbon/epoxy and glass/polyamide-6 laminates

    NARCIS (Netherlands)

    Spronk, S.W.F.; Kersemans, M.; Gilabert, F. A.; Sevenois, R.D.B.; Garoz, D.; Kassapoglou, C.; Van Paepegem, W.

    2018-01-01

    The results of a low-velocity impact programme on both carbon/epoxy and glass/polyamide-6 composite laminates are compared to the results of quasi-static indentation. Cross-ply and quasi-isotropic stacking sequences are impacted and quasi-static indentation tests are performed up to the same

  4. Determination of the mechanical and physical properties of cartilage by coupling poroelastic-based finite element models of indentation with artificial neural networks

    NARCIS (Netherlands)

    Arbabi, Vahid; Pouran, B; Campoli, Gianni; Weinans, Harrie; Zadpoor, Amir A

    2016-01-01

    One of the most widely used techniques to determine the mechanical properties of cartilage is based on indentation tests and interpretation of the obtained force-time or displacement-time data. In the current computational approaches, one needs to simulate the indentation test with finite element

  5. Neutrophils do not contribute to local tissue damage, but play a key role in skeletal muscle regeneration, in mice injected with Bothrops asper snake venom.

    Science.gov (United States)

    Teixeira, C F P; Zamunér, S R; Zuliani, J P; Fernandes, C M; Cruz-Hofling, M A; Fernandes, I; Chaves, F; Gutiérrez, J M

    2003-10-01

    Local tissue damage induced by crotaline snake venoms includes edema, myonecrosis, hemorrhage, and an inflammatory response associated with a prominent cellular infiltrate. The role of neutrophils in the local tissue damage induced by Bothrops asper snake venom and by myotoxin I, a phospholipase A2 isolated from this venom, was investigated. Male Swiss mice were pretreated with either an antimouse granulocyte rat monoclonal immunoglobulin G (IgG) antibody or with isotype-matched control antibody. No significant differences in these local effects were observed between mice pretreated with antigranulocyte antibodies and those receiving control IgG. Moreover, myotoxicity induced by B. asper myotoxin I was similar in neutrophil-depleted and control mice. The role of neutrophils in the process of skeletal muscle regeneration was also assessed. Muscle regeneration was assessed by quantifying the muscle levels of creatine kinase and by morphometric histological analysis of the area comprised by regenerating cells in damaged regions of skeletal muscle. Mice depleted of neutrophils and then injected with B. asper venom showed a more deficient regenerative response than mice pretreated with control IgG. Moreover, a drastic difference in the regenerative response was observed in mice injected with myotoxin I, because animals pretreated with control IgG showed a successful regeneration, whereas those depleted of neutrophils had abundant areas of necrotic tissue that had not been removed 7 days after injection, associated with reduced contents of creatine kinase. It is concluded that (1) neutrophils do not play a significant role in the acute local pathological alterations induced by the venom of B. asper, and (2) neutrophils play a prominent role in the process of skeletal muscle regeneration after injection of B. asper venom and myotoxin I, probably related to the phagocytosis of necrotic material and the recruitment of other inflammatory cells, two events directly associated

  6. Influence of loading path and precipitates on indentation creep behavior of wrought Mg–6 wt% Al–1 wt% Zn magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nautiyal, Pranjal [Discipline of Mechanical Engineering, Indian Institute of Information Technology, Design & Manufacturing, Jabalpur, Madhya Pradesh 482005 (India); Department of Applied Mechanics, Indian Institute of Technology, Delhi 110016 (India); Jain, Jayant [Department of Applied Mechanics, Indian Institute of Technology, Delhi 110016 (India); Agarwal, Arvind, E-mail: agarwala@fiu.edu [Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174 (United States)

    2016-01-05

    This study reports the effect of loading path and precipitates on indentation induced creep behavior of AZ61 magnesium alloy. Indentation creep tests were performed on solution-treated and peak-aged extruded AZ61 magnesium alloy, and Atomic Force Microscopy (AFM) investigations were carried out to study deformation mechanisms. Twinning is the dominant creep mechanism for indentation along the extrusion direction (ED) in solution-treated alloy. A combination of slip and twinning appears to be the prominent mechanisms for indentation creep perpendicular to ED. Creep flow is arrested for indentation perpendicular to ED, due to slip–twin interactions. Influence of precipitates on creep deformation was also studied. Aged specimen exhibited higher creep resistance than solution-treated specimen. Unlike solution-treated specimens, twinning was not observed in aged alloy. Creep in aged specimen was attributed to slip.

  7. Mapping residual stress fields from Vickers hardness indents using Raman microprobe spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sparks, R.G.; Enloe, W.S.; Paesler, M.A.

    1988-12-01

    Micro-Raman spectroscopy is used to map the residual stress fields in the vicinity of Vickers hardness indents. Both 514.5 and 488.0 nm, light is used to excite the effect and the resulting shifted and broadened Raman peaks are analyzed using computer deconvolution. Half-wave plates are used to vary the orientation of the incident later light`s polarization state with respect to crystal orientation. The Raman scattered light is then analyzed for polarization dependences which are indicative of the various components of the Raman scattering tensor. Such studies can yield valuable information about the orientation of stress components in a well known stress field. The results can then be applied to the determination of stress components in machined semiconductor materials.

  8. Indentation studies on Y2O3-stabilized ZrO2

    International Nuclear Information System (INIS)

    Dransmann, G.W.; Steinbrech, R.W.; Pajares, A.; Guiberteau, F.; Dominguez-Rodriguez, A.; Heuer, A.H.

    1994-01-01

    Stable indentation cracks were grown in four-point bend tests to study the fracture toughness of two Y 2 O 3 -stabilized ZrO 2 ceramics containing 3 and 4 mol% Y 2 O 3 . By combining microscopic in situ stable crack growth observations at discrete stresses with crack profile measurements, the dependence of toughness on crack extension was determined from crack extension plots, which graphically separate the crack driving residual stress intensity and applied stress intensity factors. Both materials exhibit steeply rising R-curves, with a plateau toughness of 4.5 and 3.1 MPa·m 1/2 for the 3- and 4-mol% materials, respectively. The magnitude of the plateau toughness reflects the fraction of tetragonal grain contributing to transformation toughening

  9. A Numerical Framework for Self-Similar Problems in Plasticity: Indentation in Single Crystals

    DEFF Research Database (Denmark)

    Juul, Kristian Jørgensen; Niordson, Christian Frithiof; Nielsen, Kim Lau

    A new numerical framework specialized for analyzing self-similar problems in plasticity is developed. Self-similarity in plasticity is encountered in a number of different problems such as stationary cracks, void growth, indentation etc. To date, such problems are handled by traditional Lagrangian...... procedures that may be associated with severe numerical difficulties relating to sufficient discretization, moving contact points, etc. In the present work, self-similarity is exploited to construct the numerical framework that offers a simple and efficient method to handle self-similar problems in history...... dependent materials. The procedure allows for focusing the mesh only in regions of interest giving highly detailed results in fractions of the time compared to traditional frameworks. The framework is not limited to a specific constitutive law and may be applied to a wide range of material models...

  10. Microstructure of AZ31 Magnesium Alloy deformed by indentation-flattening compound deformation technology

    Science.gov (United States)

    Wang, Minghao; Wang, Zhongtang; Yu, Xiaolin

    2018-03-01

    Characteristic of indentation-flattening compound deformation technology (IFCDT) is discussed, and the parameters of IFCDT are defined. Performance of magnesium alloy AZ31 sheet deformed by IFCDT is researched. The effect of IFCDT coefficient, temperature and reduction ratio on the microstructure of magnesium alloy sheet is analyzed. The research results show that the volume fraction of the twin crystal decreases gradually and the average grain size increases with increasing of coefficient of IFCDT. With increase of the reduction ratio, the volume fraction of the twin crystal gradually increases, and the average grain size also increases. With increase of deformation temperature, the volume fraction of the twin crystal decreases gradually, and the twin crystal grain size increases.

  11. Representative Stress-Strain Curve by Spherical Indentation on Elastic-Plastic Materials

    Directory of Open Access Journals (Sweden)

    Chao Chang

    2018-01-01

    Full Text Available Tensile stress-strain curve of metallic materials can be determined by the representative stress-strain curve from the spherical indentation. Tabor empirically determined the stress constraint factor (stress CF, ψ, and strain constraint factor (strain CF, β, but the choice of value for ψ and β is still under discussion. In this study, a new insight into the relationship between constraint factors of stress and strain is analytically described based on the formation of Tabor’s equation. Experiment tests were performed to evaluate these constraint factors. From the results, representative stress-strain curves using a proposed strain constraint factor can fit better with nominal stress-strain curve than those using Tabor’s constraint factors.

  12. Mechanical evaluation of linear friction welds in titanium alloys through indentation experiments

    International Nuclear Information System (INIS)

    Corzo, M.; Casals, O.; Alcala, J.; Mateo, A.; Anglada, M.

    2005-01-01

    This article shows the results of a project that focuses on the characterization of the weld interface region of dissimilar joints between titanium alloys for aeronautical applications, specifically Ti-6Al-2Sn-4Zr-6Mo with Ti-6Al-4V, and Ti-6Al-2Sn-4Zr-6Mo with Ti-6Al-2Sn-4Zr-2Mo. The uniaxial flow stress and hardening response of the material containing the weld were analyzed following the finite elements simulations and mathematical formulations to correlate hardness and the amount of pile-up and sinking-in phenomena around sharp indenters with uniaxial mechanical properties. This allows to accurately stablishing the influence that welding process has on the mechanical response of the parts. Tests performed on these friction-welded specimens showed that the fine grained microstructures in the welds exhibited better properties than the base materials. (Author) 12 refs

  13. Mechanical properties of cancer cells depend on number of passages: Atomic force microscopy indentation study

    Science.gov (United States)

    Dokukin, Maxim E.; Guz, Natalia V.; Sokolov, Igor

    2017-08-01

    Here we investigate one of the key questions in cell biology, if the properties of cell lines depend on the number of passages in-vitro. It is generally assumed that the change of cell properties (phenotypic drift) is insignificant when the number of passages is low (cell body and parameters of the pericellular brush layer from indentation force curves, which are recorded by means of atomic force microscopy (AFM). Using this method, we tested the change of the cell properties of human cancer breast epithelial cell line, MCF-7 (ATCC® HTB-22™), within the passages between 2 and 10. In contrast to the previous expectations, we observed a substantial transient change of the elastic modulus of the cell body during the first four passages (up to 4 times). The changes in the parameters of the pericellular coat were less dramatic (up to 2 times) but still statistically significant.

  14. On the origin of the mixed alkali effect on indentation in silicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Mauro, J. C.

    2014-01-01

    The compositional scaling of Vickers hardness (Hv) in mixed alkali oxide glasses manifests itself as a positive deviation from linearity as a function of the network modifier/modifier ratio, with a maximum deviation at the ratio of 1:1. In this work, we investigate the link between the indentation...... deformation processes (elastic deformation, plastic deformation, and densification) and Hv in two mixed sodium–potassium silicate glass series. We show that the mixed alkali effect in Hv originates from the nonlinear scaling of the resistance to plastic deformation. We thus confirm a direct relation between...... the resistance to plastic flow and Hv in mixed modifier glasses. Furthermore, we find that the mixed alkali effect also manifests itself as a positive deviation from linearity in the compositional scaling of density for glasses with high alumina content. This trend could be linked to a compaction of the network...

  15. Indentation recovery in GdPO4 and observation of deformation twinning

    Directory of Open Access Journals (Sweden)

    Taylor M. Wilkinson

    2016-09-01

    Full Text Available A series of nanoindentation tests on both single and polycrystalline specimens of a monazite rare-earth orthophosphate, GdPO4, revealed frequent observation of anomalous unloading behavior with a large degree of recovery, where previously this behavior had only been observed in xenotime-structure rare-earth orthophosphates. An indentation site in the polycrystalline sample was examined using TEM to identify the deformation mechanism responsible for recovery. The presence of a twin along the (100 orientation, along with a series of stacking faults contained within the deformation site, provide evidence that the mechanism of recovery in GdPO4 is the collapse of deformation twins during unloading.

  16. Fractal characteristics of an asphaltene deposited heterogeneous surface

    International Nuclear Information System (INIS)

    Amin, J. Sayyad; Ayatollahi, Sh.; Alamdari, A.

    2009-01-01

    Several methods have been employed in recent years to investigate homogeneous surface topography based on image analysis, such as AFM (atomic force microscopy) and SEM (scanning electron microscopy). Fractal analysis of the images provides fractal dimension of the surface which is used as one of the most common surface indices. Surface topography has generally been considered to be mono-fractal. On the other hand, precipitation of organic materials on a rough surface and its irregular growth result in morphology alteration and converts a homogeneous surface to a heterogeneous one. In this case a mono-fractal description of the surface does not completely describe the nature of the altered surface. This work aims to investigate the topography alteration of a glass surface as a result of asphaltene precipitation and its growth at various pressures using a bi-fractal approach. The experimental results of the deposited surfaces were clearly indicating two regions of micro- and macro-asperities namely, surface types I and II, respectively. The fractal plots were indicative of bi-fractal behavior and for each surface type one fractal dimension was calculated. The topography information of the surfaces was obtained by two image analyses, AFM and SEM imaging techniques. Results of the bi-fractal analysis demonstrated that topography alteration in surface type II (macro-asperities) is more evident than that in surface type I (micro-asperities). Compared to surface type II, a better correlation was observed between the fractal dimensions inferred from the AFM images (D A ) and those of the SEM images (D S ) in surface type I.

  17. Indentation theory on a half-space of transversely isotropic multi-ferroic composite medium: sliding friction effect

    Science.gov (United States)

    Wu, F.; Wu, T.-H.; Li, X.-Y.

    2018-03-01

    This article aims to present a systematic indentation theory on a half-space of multi-ferroic composite medium with transverse isotropy. The effect of sliding friction between the indenter and substrate is taken into account. The cylindrical flat-ended indenter is assumed to be electrically/magnetically conducting or insulating, which leads to four sets of mixed boundary-value problems. The indentation forces in the normal and tangential directions are related to the Coulomb friction law. For each case, the integral equations governing the contact behavior are developed by means of the generalized method of potential theory, and the corresponding coupling field is obtained in terms of elementary functions. The effect of sliding on the contact behavior is investigated. Finite element method (FEM) in the context of magneto-electro-elasticity is developed to discuss the validity of the analytical solutions. The obtained analytical solutions may serve as benchmarks to various simplified analyses and numerical codes and as a guide for future experimental studies.

  18. Probing the structure and mechanical properties of the graphite nodules in ductile cast irons via nano-indentation

    DEFF Research Database (Denmark)

    Andriollo, Tito; Fæster, Søren; Winther, Grethe

    2018-01-01

    was characterized via 3D computed tomography. From the recorded load vs. penetration curves, the spatial variation of the maximum indenter penetration hmax and of the reduced Young's modulus E* was determined. It was observed that the pattern of hmax presents features which, statistically, cannot be explained...

  19. Influence of tip indentation on the adhesive behavior of viscoelastic polydimethylsiloxane networks studied by atomic force microscopy

    NARCIS (Netherlands)

    Pickering, J.P.; Vancso, Gyula J.

    2001-01-01

    A commercial atomic force microscope (AFM) outfitted with a custom control and data acquisition system was used to investigate the adhesive nature of a viscoelastic polydimethylsiloxane (PDMS) network. Due to the complex dependence of the adhesion of this sample on factors such as indentation,

  20. Assessment of metalloproteinase inhibitors clodronate and doxycycline in the neutralization of hemorrhage and coagulopathy induced by Bothrops asper snake venom.

    Science.gov (United States)

    Rucavado, Alexandra; Henríquez, Mónica; García, Jonielle; Gutiérrez, José María

    2008-12-01

    Snake venom metalloproteinases (SVMPs) play a prominent role in the local and systemic manifestations of viperid snakebite envenomations. Thus, the possibility of using metalloproteinase inhibitors in the treatment of these envenomations is a promising therapeutic alternative. This study assessed the ability of two metalloproteinase inhibitors, the biphosphonate clodronate and the tetracycline doxycycline, to inhibit proteolytic, hemorrhagic, coagulant and defibrinogenating effects of Bothrops asper venom. Both compounds were able to inhibit these activities, at concentrations in the mM range, when incubated with venom prior to testing. However, when inhibition of hemorrhage was assessed in assays involving independent injection of venom and drug, inhibition was poor, even when these compounds were injected immediately after envenomation. These findings support the concept that the effectiveness of compounds, such as clodronate and doxycycline, whose inhibitory action on SVMPs is based on zinc chelation alone, is limited, and stress the view that more specific molecules are required for an effective inhibition of SVMPs in vivo.

  1. Edema induced by Bothrops asper (Squamata: Viperidae) snake venom and its inhibition by Costa Rican plant extracts.

    Science.gov (United States)

    Badilla, Beatriz; Chaves, Fernando; Mora, Gerardo; Poveda, Luis J

    2006-06-01

    We tested the capacity of leaf (Urera baccifera, Loasa speciosa, Urtica leptuphylla, Chaptalia nutans, and Satureja viminea) and root (Uncaria tomentosa) extracts to inhibit edema induced by Bothrops asper snake venom. Edema-forming activity was studied plethysmographically in the rat hind paw model. Groups of rats were injected intraperitoneally with various doses of each extract and, one hour later, venom was injected subcutaneously in the right hind paw. Edema was assessed at various time intervals. The edematogenic activity was inhibited in those animals that received an injection U. tomentosa, C. nutans or L. speciosa extract. The extract of U. baccifera showed a slight inhibition of the venom effect. Extract from S. viminea and, to a lesser extent that of U. leptuphylla, induced a pro-inflammatory effect, increasing the edema at doses of 250 mg/kg at one and two hours.

  2. Edema induced by Bothrops asper (Squamata: Viperidae snake venom and its inhibition by Costa Rican plant extracts

    Directory of Open Access Journals (Sweden)

    Beatriz Badilla

    2006-06-01

    Full Text Available We tested the capacity of leaf (Urera baccifera, Loasa speciosa, Urtica leptuphylla, Chaptalia nutans, and Satureja viminea and root (Uncaria tomentosa extracts to inhibit edema induced by Bothrops asper snake venom. Edema-forming activity was studied plethysmographically in the rat hind paw model. Groups of rats were injected intraperitoneally with various doses of each extract and, one hour later, venom was injected subcutaneously in the right hind paw. Edema was assessed at various time intervals. The edematogenic activity was inhibited in those animals that received an injection U. tomentosa, C. nutans or L. speciosa extract. The extract of U. baccifera showed a slight inhibition of the venom effect. Extract from S. viminea and, to a lesser extent that of U. leptuphylla, induced a pro-inflammatory effect, increasing the edema at doses of 250 mg/kg at one and two hours. Rev. Biol. Trop. 54(2: 245-252. Epub 2006 Jun 01.Se investigó la capacidad de los extractos de las hojas de Urera baccifera, Loasa speciosa, Urtica leptuphylla, Chaptalia nutans, Satureja viminea y de la raíz de Uncaria tomentosa para inhibir el edema inducido por el veneno de Bothrops asper por métodos pletismométricos. Los grupos de ratas fueron inyectados intraperitonealmente con varias dosis de cada extracto y una hora mas tarde se inyectó veneno por vía subcutánea en la pata trasera derecha de la rata. Se evaluó el edema en distintos intervalos de tiempo. Los resultados muestran que la actividad edematogénica fue inhibida en los animales que recibieron los extractos de raíz de U. tomentosa, hojas de C. nutans y L. speciosa. Los extractos de hojas de U. baccifera mostraron leve inhibición del efecto del veneno. El extracto de hojas de S. viminea y en menor grado el de U. leptuphylla indujeron un efecto pro inflamatorio.

  3. Intramuscular administration of antivenoms in experimental envenomation by Bothrops asper: comparison between Fab and IgG.

    Science.gov (United States)

    Chaves, Fernando; Loría, Gilbert D; Salazar, Adriana; Gutiérrez, José María

    2003-02-01

    The efficacy of intramuscular (im) administration of sheep Fab and IgG antivenoms was assessed in a mouse experimental model of envenomation by Bothrops asper, in order to test if the more rapid absorption of Fab improves neutralization. Both antivenoms were adjusted to have a similar neutralizing potency in assays involving preincubation of venom and antivenom. Neither antivenom was effective in neutralizing lethality, nor in prolonging the time of death, in mice injected with either 3, 2 or 1.5 LD(50)s of venom by the intraperitoneal (ip) route, in experiments in which antivenoms were administered im immediately after envenomation. Antivenoms were effective in the neutralization of defibrinating activity, even if treatment was performed 30 min after envenomation, with no differences between IgG and Fab. Regarding neutralization of local effects, i.e. myonecrosis and hemorrhage, im administration of antivenoms at a site distant from the venom-injection site was completely ineffective in reducing the extent of local tissue damage. However, partial neutralization of these effects was achieved if antivenoms were administered im at the same site of venom injection, provided treatment was performed immediately after envenomation. Fab antivenom was slightly more effective than IgG antivenom in the neutralization of myotoxicity under these conditions, although a similar efficacy was observed between these antivenoms regarding neutralization of hemorrhagic effect. Our observations do not evidence major differences in the neutralizing ability of Fab and IgG antivenoms when applied by the im route, and do not support the hypothesis that im administration of Fab antivenoms constitutes an effective alternative to treat B. asper envenomations.

  4. Muscle Tissue Damage Induced by the Venom of Bothrops asper: Identification of Early and Late Pathological Events through Proteomic Analysis.

    Directory of Open Access Journals (Sweden)

    Cristina Herrera

    2016-04-01

    Full Text Available The time-course of the pathological effects induced by the venom of the snake Bothrops asper in muscle tissue was investigated by a combination of histology, proteomic analysis of exudates collected in the vicinity of damaged muscle, and immunodetection of extracellular matrix proteins in exudates. Proteomic assay of exudates has become an excellent new methodological tool to detect key biomarkers of tissue alterations for a more integrative perspective of snake venom-induced pathology. The time-course analysis of the intracellular proteins showed an early presence of cytosolic and mitochondrial proteins in exudates, while cytoskeletal proteins increased later on. This underscores the rapid cytotoxic effect of venom, especially in muscle fibers, due to the action of myotoxic phospholipases A2, followed by the action of proteinases in the cytoskeleton of damaged muscle fibers. Similarly, the early presence of basement membrane (BM and other extracellular matrix (ECM proteins in exudates reflects the rapid microvascular damage and hemorrhage induced by snake venom metalloproteinases. The presence of fragments of type IV collagen and perlecan one hour after envenoming suggests that hydrolysis of these mechanically/structurally-relevant BM components plays a key role in the genesis of hemorrhage. On the other hand, the increment of some ECM proteins in the exudate at later time intervals is likely a consequence of the action of endogenous matrix metalloproteinases (MMPs or of de novo synthesis of ECM proteins during tissue remodeling as part of the inflammatory reaction. Our results offer relevant insights for a more integrative and systematic understanding of the time-course dynamics of muscle tissue damage induced by B. asper venom and possibly other viperid venoms.

  5. Bothrops asper snake venom and its metalloproteinase BaP-1 activate the complement system. Role in leucocyte recruitment.

    Science.gov (United States)

    Farsky, S H; Gonçalves, L R; Gutiérrez, J M; Correa, A P; Rucavado, A; Gasque, P; Tambourgi, D V

    2000-01-01

    The venom of the snake Bothrops asper, the most important poisonous snake in Central America, evokes an inflammatory response, the mechanisms of which are not well characterized. The objectives of this study were to investigate whether B. asper venom and its purified toxins--phospholipases and metalloproteinase--activate the complement system and the contribution of the effect on leucocyte recruitment. In vitro chemotaxis assays were performed using Boyden's chamber model to investigate the ability of serum incubated with venom and its purified toxins to induce neutrophil migration. The complement consumption by the venom was evaluated using an in vitro haemolytic assay. The importance of complement activation by the venom on neutrophil migration was investigated in vivo by injecting the venom into the peritoneal cavity of C5-deficient mice. Data obtained demonstrated that serum incubated with crude venom and its purified metalloproteinase BaP-1 are able to induce rat neutrophil chemotaxis, probably mediated by agent(s) derived from the complement system. This hypothesis was corroborated by the capacity of the venom to activate this system in vitro. The involvement of C5a in neutrophil chemotaxis induced by venom-activated serum was demonstrated by abolishing migration when neutrophils were pre-incubated with antirat C5a receptor antibody. The relevance of the complement system in in vivo leucocyte mobilization was further demonstrated by the drastic decrease of this response in C5-deficient mice. Pre-incubation of serum with the soluble human recombinant complement receptor type 1 (sCR 1) did not prevent the response induced by the venom, but abolished the migration evoked by metalloproteinase-activated serum. These data show the role of the complement system in bothropic envenomation and the participation of metalloproteinase in the effect. Also, they suggest that the venom may contain other component(s) which can cause direct activation of C5a. PMID:11200361

  6. Immunochemical and biological characterization of monoclonal antibodies against BaP1, a metalloproteinase from Bothrops asper snake venom.

    Science.gov (United States)

    Fernandes, I; Assumpção, G G; Silveira, C R F; Faquim-Mauro, E L; Tanjoni, I; Carmona, A K; Alves, M F M; Takehara, H A; Rucavado, A; Ramos, O H P; Moura-da-Silva, A M; Gutiérrez, J M

    2010-11-01

    BaP1 is a P-I class of Snake Venom Metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomations by Bothrops asper, a medically-important species in Central America and parts of South America. Six monoclonal antibodies (MoAb) against BaP1 (MABaP1) were produced and characterized regarding their isotype, dissociation constant (K(d)), specificity and ability to neutralize BaP1-induced hemorrhagic and proteolytic activity. Two MABaP1 are IgM, three are IgG1 and one is IgG2b. The K(d)s of IgG MoAbs were in the nM range. All IgG MoAbs recognized conformational epitopes of BaP1 and B. asper venom components but failed to recognize venoms from 27 species of Viperidae, Colubridae and Elapidae families. Clone 7 cross-reacted with three P-I SVMPs tested (moojeni protease, insularinase and neuwiedase). BaP1-induced hemorrhage was totally neutralized by clones 3, 6 and 8 but not by clone 7. Inhibition of BaP1 enzymatic activity on a synthetic substrate by MABaP1 was totally achieved by clones 3 and 6, and partially by clone 8, but not by clone 7. In conclusion, these neutralizing MoAbs against BaP1 may become important tools to understand structure-function relationships of BaP1 and the role of P-I class SVMP in snakebite envenomation. (c) 2010 Elsevier Ltd. All rights reserved.

  7. Muscle Tissue Damage Induced by the Venom of Bothrops asper: Identification of Early and Late Pathological Events through Proteomic Analysis.

    Science.gov (United States)

    Herrera, Cristina; Macêdo, Jéssica Kele A; Feoli, Andrés; Escalante, Teresa; Rucavado, Alexandra; Gutiérrez, José María; Fox, Jay W

    2016-04-01

    The time-course of the pathological effects induced by the venom of the snake Bothrops asper in muscle tissue was investigated by a combination of histology, proteomic analysis of exudates collected in the vicinity of damaged muscle, and immunodetection of extracellular matrix proteins in exudates. Proteomic assay of exudates has become an excellent new methodological tool to detect key biomarkers of tissue alterations for a more integrative perspective of snake venom-induced pathology. The time-course analysis of the intracellular proteins showed an early presence of cytosolic and mitochondrial proteins in exudates, while cytoskeletal proteins increased later on. This underscores the rapid cytotoxic effect of venom, especially in muscle fibers, due to the action of myotoxic phospholipases A2, followed by the action of proteinases in the cytoskeleton of damaged muscle fibers. Similarly, the early presence of basement membrane (BM) and other extracellular matrix (ECM) proteins in exudates reflects the rapid microvascular damage and hemorrhage induced by snake venom metalloproteinases. The presence of fragments of type IV collagen and perlecan one hour after envenoming suggests that hydrolysis of these mechanically/structurally-relevant BM components plays a key role in the genesis of hemorrhage. On the other hand, the increment of some ECM proteins in the exudate at later time intervals is likely a consequence of the action of endogenous matrix metalloproteinases (MMPs) or of de novo synthesis of ECM proteins during tissue remodeling as part of the inflammatory reaction. Our results offer relevant insights for a more integrative and systematic understanding of the time-course dynamics of muscle tissue damage induced by B. asper venom and possibly other viperid venoms.

  8. Bothrops asper snake venom and its metalloproteinase BaP–1 activate the complement system. Role in leucocyte recruitment

    Directory of Open Access Journals (Sweden)

    Sandra H. P. Farsky

    2000-01-01

    Full Text Available The venom of the snake Bothrops asper, the most important poisonous snake in Central America, evokes an inflammatory response, the mechanisms of which are not well characterized. The objectives of this study were to investigate whether B. asper venom and its purified toxins – phospholipases and metalloproteinase – activate the complement system and the contribution of the effect on leucocyte recruitment. In vitro chemotaxis assays were performed using Boyden's chamber model to investigate the ability of serum incubated with venom and its purified toxins to induce neutrophil migration. The complement consumption by the venom was evaluated using an in vitro haemolytic assay. The importance of complement activation by the venom on neutrophil migration was investigated in vivo by injecting the venom into the peritoneal cavity of C5-deficient mice. Data obtained demonstrated that serum incubated with crude venom and its purified metalloproteinase BaP–1 are able to induce rat neutrophil chemotaxis, probably mediated by agent(s derived from the complement system. This hypothesis was corroborated by the capacity of the venom to activate this system in vitro. The involvement of C5a in neutrophil chemotaxis induced by venom-activated serum was demonstrated by abolishing migration when neutrophils were pre-incubated with antirat C5a receptor antibody. The relevance of the complement system in in vivo leucocyte mobilization was further demonstrated by the drastic decrease of this response in C5-deficient mice. Pre-incubation of serum with the soluble human recombinant complement receptor type 1 (sCR 1 did not prevent the response induced by the venom, but abolished the migration evoked by metalloproteinase-activated serum. These data show the role of the complement system in bothropic envenomation and the participation of metalloproteinase in the effect. Also, they suggest that the venom may contain other component(s which can cause direct activation

  9. Effects of cementation surface modifications on fracture resistance of zirconia

    Science.gov (United States)

    Srikanth, Ramanathan; Kosmac, Tomaz; Bona, Alvaro Della; Yin, Ling; Zhang, Yu

    2015-01-01

    Objectives To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Methods Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 mm or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2 mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Results Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. Significance While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. PMID:25687628

  10. Effects of cementation surface modifications on fracture resistance of zirconia.

    Science.gov (United States)

    Srikanth, Ramanathan; Kosmac, Tomaz; Della Bona, Alvaro; Yin, Ling; Zhang, Yu

    2015-04-01

    To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Finite element method analysis of surface roughness transfer in micro flexible rolling

    OpenAIRE

    Qu Feijun; Xie Haibo; Jiang Zhengyi

    2016-01-01

    Micro flexible rolling aims to fabricate submillimeter thick strips with varying thickness profile, where the surface quality of products is mainly determined by initial workpiece surface roughness and subsequent surface asperity flattening process, which is affected by process parameters during rolling. This paper shows a 3D finite element model for flexible rolling of a 250 μm thick workpiece with reduction of 20 to 50%, and rolling phase with thinner thickness indicates a better ability to...

  12. Comparison between IgG and F(ab′)2 polyvalent antivenoms: neutralization of systemic effects induced by Bothrops asper venom in mice, extravasation to muscle tissue, and potential for induction of adverse reactions

    OpenAIRE

    León Montero, Guillermo; Monge Monge, María; Rojas Umaña, Ermila; Lomonte, Bruno; Gutiérrez, José María

    2001-01-01

    Whole IgG and F(ab′)2 equine-derived polyvalent (Crotalinae) antivenoms, prepared from the same batch of hyperimmune plasma, were compared in terms of neutralization of the lethal and defibrinating activities induced by Bothrops asper venom, their ability to reach the muscle tissue compartment in envenomated mice, and their potential for the induction of adverse reactions. Both preparations were adjusted to the same potency against the lethal effect of B. asper venom in experiments involving ...

  13. Influence of surface roughness skewness on rolling contact fatigue life

    Science.gov (United States)

    Akamatsu, Yoshinobu; Tsushima, Noriyuki; Goto, Toshihide; Hibi, Kenji

    1992-10-01

    This paper evaluates the effects of randomly distributed small indentations, or pits, on the lubricating properties when operating under these mixed or boundary lubrication conditions. Rings and needle rollers were textured with randomly distributed small indentations, or pits, for evaluation. Skewness (Sk) was used as a measure of surface finish to characterize the degree to which the material of these modified parts was above the mean line, a positive value, or below the mean line, a negative value. Fatigue life tests were conducted on these rolling elements, whose skewness ranged from -1.2 to -2.0, under mixed or boundary lubrication conditions. Test results showed rolling bearing fatigue life to increase with a decrease in skewness as related to the depth, width, and distribution of the surface indentations, or pits, on the parts.

  14. Influence of substrate microstructure and surface finish on cracking and delamination response of TiN-coated cemented carbides

    OpenAIRE

    Yang, Jing; Odén, Magnus; Johansson-Joesaar, Mats P.; Llanes, L.

    2016-01-01

    The cracking and delamination of TiN-coated hardmetals (WC-Co cemented carbides) when subjected to Brale indentation were studied. Experimental variables were substrate microstructure related to low (6 wt% Co) and medium (13 wt% Co) binder content, and surface finishes associated with grinding and polishing stages before film deposition. Brale indentation tests were conducted on both coated and uncoated hardmetals. Emphasis has been placed on assessing substrate microstructure and subsurface ...

  15. Post-collisional deformation of the Anatolides and motion of the Arabian indenter: A paleomagnetic analysis

    International Nuclear Information System (INIS)

    Piper, J; Tatar, O; Gursoy, H; Mesci, B L; Kocbulut, F; Huang, B

    2008-01-01

    In the Anatolides of Turkey the neotectonic (post collisional) phase of deformation embraces the period since final closure of the southern arm of Neotethys in mid-Miocene times. The Arabian Shield indenter has continued to deform into the weak Anatolian accretionary collage resulting from subduction of this ocean by a combination of differential movement relative to the African Plate and counterclockwise (CCW) rotation. Much of resulting deformation has been accommodated by slip along major transforms comprising the North Anatolian Fault Zone (NAFZ), the East Anatolian Fault Zone (EAFZ) and the northward extension of the Dead Sea Fault Zone (DSFZ) but has also been distributed as differential block rotations through the zone of weak crust in between. Facets of this deformation comprise crustal thickening and uplift to produce the Anatolian Plateau, establishment of transform faults and tectonic escape as Arabia has continued to impinge into the Anatolian collage. Paleomagnetic analysis of this deformation is facilitated by the widespread distribution of neotectonic volcanism and graben infills, and rotations relative to the Eurasian reference frame are recognised on two scales. Rapid rotation (up to 5 0 /10,000 years) of small fault blocks is identified between master faults along the intracontinental transforms but deformation does not extend away from these zones and shows that seismogenic upper crust is decoupled from a lower continental lithosphere undergoing continuum deformation. The broad area of weak accreted crust between the transforms is dissected into large fault blocks which exhibit much lower rotation rates (mostly 0 /100,000 years) that vary systematically across the Anatolides. Large CCW rotations near the Arabian indenter diminish westwards to become zero then CW near the limit of tectonic escape in western Turkey. The view that the collage has rotated anticlockwise as a single plate, either uniformly or episodically, during the Neotectonic era is

  16. Preparación toxoide a partir de la fracción hemorrágica del veneno de Bothrops asper (serpiente de América Central y del Sur) (Toxoid preparation from hemorrhagic fraction of the venom from Bothrops asper (snake from Central and South America).

    Science.gov (United States)

    Rodríguez-Acosta, A; Aguilar, I; Girón, M E

    1993-01-01

    A technique is described for preparing a toxoid from the hemorrhagic fraction of the Bothrops asper venom. This method conserves a high degree of immunogenicity although it eliminates lethal effects. None of the animals vaccinated with the toxoid from this fraction had hemorrhagic lesions after they were injected the venom from the hemorrhagic fraction.

  17. Relationship between the frequency magnitude distribution and the visibility graph in the synthetic seismicity generated by a simple stick-slip system with asperities.

    Directory of Open Access Journals (Sweden)

    Luciano Telesca

    Full Text Available By using the method of the visibility graph (VG the synthetic seismicity generated by a simple stick-slip system with asperities is analysed. The stick-slip system mimics the interaction between tectonic plates, whose asperities are given by sandpapers of different granularity degrees. The VG properties of the seismic sequences have been put in relationship with the typical seismological parameter, the b-value of the Gutenberg-Richter law. Between the b-value of the synthetic seismicity and the slope of the least square line fitting the k-M plot (relationship between the magnitude M of each synthetic event and its connectivity degree k a close linear relationship is found, also verified by real seismicity.

  18. Inhibitory properties of the anti-bothropic complex from Didelphis albiventris serum on toxic and pharmacological actions of metalloproteases and myotoxins from Bothrops asper venom.

    Science.gov (United States)

    Trento, E P; Garcia, O S; Rucavado, A; França, S C; Batalini, C; Arantes, E C; Giglio, J R; Soares, A M

    2001-12-01

    Anti-bothropic complex (ABC) was isolated from the serum of the South American opossum (Didelphis albiventris) by single-step affinity chromatography using a Sepharose-immobilized metalloprotease (BaP1) from Bothrops asper as the binding protein. Biochemical characterization of ABC showed the presence of two glycosylated subunits of 43 and 45 kDa, respectively, with an isoelectric point asper venom. In addition to the anti-hemorrhagic and anti-proteolytic activities, ABC also showed anti-myotoxic, anti-lethal, and anti-edematogenic effects against myotoxic phospholipases A(2) isolated from the same venom. Moreover, it had inhibitory effects on the phospholipase A(2) activity of the crude venom as well as the isolated venom phospholipases A(2).

  19. Biochemical characterization, action on macrophages, and superoxide anion production of four basic phospholipases A2 from Panamanian Bothrops asper snake venom.

    Science.gov (United States)

    Rueda, Aristides Quintero; Rodríguez, Isela González; Arantes, Eliane C; Setúbal, Sulamita S; Calderon, Leonardo de A; Zuliani, Juliana P; Stábeli, Rodrigo G; Soares, Andreimar M

    2013-01-01

    Bothrops asper (Squamata: Viperidae) is the most important venomous snake in Central America, being responsible for the majority of snakebite accidents. Four basic PLA2s (pMTX-I to -IV) were purified from crude venom by a single-step chromatography using a CM-Sepharose ion-exchange column (1.5 × 15 cm). Analysis of the N-terminal sequence demonstrated that pMTX-I and III belong to the catalytically active Asp49 phospholipase A2 subclass, whereas pMTX-II and IV belong to the enzymatically inactive Lys49 PLA2s-like subclass. The PLA2s isolated from Panama Bothrops asper venom (pMTX-I, II, III, and IV) are able to induce myotoxic activity, inflammatory reaction mainly leukocyte migration to the muscle, and induce J774A.1 macrophages activation to start phagocytic activity and superoxide production.

  20. Biochemical Characterization, Action on Macrophages, and Superoxide Anion Production of Four Basic Phospholipases A2 from Panamanian Bothrops asper Snake Venom

    Directory of Open Access Journals (Sweden)

    Aristides Quintero Rueda

    2013-01-01

    Full Text Available Bothrops asper (Squamata: Viperidae is the most important venomous snake in Central America, being responsible for the majority of snakebite accidents. Four basic PLA2s (pMTX-I to -IV were purified from crude venom by a single-step chromatography using a CM-Sepharose ion-exchange column (1.5 × 15 cm. Analysis of the N-terminal sequence demonstrated that pMTX-I and III belong to the catalytically active Asp49 phospholipase A2 subclass, whereas pMTX-II and IV belong to the enzymatically inactive Lys49 PLA2s-like subclass. The PLA2s isolated from Panama Bothrops asper venom (pMTX-I, II, III, and IV are able to induce myotoxic activity, inflammatory reaction mainly leukocyte migration to the muscle, and induce J774A.1 macrophages activation to start phagocytic activity and superoxide production.

  1. Vibrotactile perception thresholds at the sole of the foot: effects of contact force and probe indentation.

    Science.gov (United States)

    Gu, Cheng; Griffin, Michael J

    2012-05-01

    When using vibrotactile thresholds to investigate neuropathy in the fingers, the indentation of a vibrating probe, and the force applied to a static surround around a vibrating probe, affect thresholds. This study was designed to investigate the effects on vibrotactile perception thresholds at the sole of the foot of probe indentation (i.e. height of a vibrating probe relative to a static surround) and the force applied to the static surround. Thresholds at 20 Hz (expected to be mediated by the NP I channel) and at 160 Hz (expected to be mediated by the Pacinian channel) were obtained at the hallux (i.e. greater toe) and the ball of the foot on 14 healthy subjects. In one condition, the height of the vibrating probe was varied to 0, 1, 2, 3, and 4 mm above a static surround with 4-N force applied to the surround. In a second condition, the force applied to the surround was varied to 1, 2, 3, 4, 5, and 6 N while using a probe height of 1mm. Thresholds at 20 Hz decreased with increasing probe height from 0 to 1 mm but showed no significant variation between 2, 3, and 4mm at either the hallux or the ball of the foot. Thresholds at 160 Hz decreased with increasing probe height from 0 to 4 mm at both the hallux and the ball of the foot. Thresholds at 20 Hz obtained with 1-N surround force were higher than thresholds obtained with 2 N, but there was no significant difference with surround forces from 2 to 6 N at either the hallux or the ball of the foot. Thresholds at 160 Hz were unaffected by variations in surround force at the ball of the foot but tended to decrease with increasing force at the hallux. It is concluded that a vibrating probe flush with a static surround, and a surround force in the range 2-4 N, are appropriate when measuring vibrotactile thresholds at the hallux and the ball of the foot with a 6-mm diameter contactor and a 2-mm gap to the static surround. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

  2. Characterization of aspercetin, a platelet aggregating component from the venom of the snake Bothrops asper which induces thrombocytopenia and potentiates metalloproteinase-induced hemorrhage.

    Science.gov (United States)

    Rucavado, A; Soto, M; Kamiguti, A S; Theakston, R D; Fox, J W; Escalante, T; Gutiérrez, J M

    2001-04-01

    Thrombocytopenia occurs in a number of patients bitten by Bothrops asper, a species responsible for the majority of snakebites in Central America and southern Mexico. In this work we describe the isolation of a new platelet-aggregating protein, named aspercetin, from the venom of B. asper, which induces thrombocytopenia in mice. Isolation was carried out by a combination of ion-exchange chromatography on DEAE-Sepharose and affinity chromatography on Affi-Gel Blue. Aspercetin is a disulfide-linked heterodimer, with a pI of 4.5 and a molecular mass of 29,759 Da, detemined by MALDI-ESI mass spectrometry. N-terminal sequence shows homology with a number of venom proteins which belong to the C-type lectin family. Aspercetin has functional similarities with botrocetin, from B. jararaca venom, since it induces platelet aggregation only in the presence of plasma or purified von Willebrand factor. Aspercetin-mediated platelet aggregation results from the interaction of von Willebrand factor with platelet receptor GPIb. Aspercetin lacks anticoagulant effect and does not agglutinate erythrocytes, in contrast with other representatives of the C-type lectin family isolated from snake venoms. Moreover, aspercetin is not lethal, nor does it induce myonecrosis, hemorrhage and edema. When injected intravenously or intramuscularly in mice it induces a rapid, dose-dependent drop in platelet counts and prolongs the bleeding time, suggesting that it may play a role in the thrombocytopenia that develops in a number of B. asper envenomations. Moreover, mice injected intravenously with aspercetin and then receiving an intradermal injection of B. asper hemorrhagic metalloproteinase BaP1 develop a larger hemorrhagic lesion than mice receiving only BaP1. This suggests that aspercetin, by reducing platelet numbers, may

  3. Snake venomics and antivenomics of Bothrops colombiensis, a medically important pitviper of the Bothrops atrox-asper complex endemic to Venezuela: Contributing to its taxonomy and snakebite management

    OpenAIRE

    Calvete, Juan J.; Borges, Adolfo; Segura Ruiz, Álvaro; Flores Díaz, Marietta; Alape Girón, Alberto; Gutiérrez, José María; Diez, Nardy; De Sousa, Leonardo; Kiriakos, Demetrio; Sánchez, Eladio; Faks, José G.; Escolano, José; Sanz, Libia

    2009-01-01

    The taxonomic status of the medically important pitviper of the Bothrops atrox-asper complex endemic to Venezuela, which has been classified as Bothrops colombiensis, remains incertae cedis. To help resolving this question, the venom proteome of B. colombiensis was characterized by reverse-phase HPLC fractionation followed by analysis of each chromatographic fraction by SDS-PAGE, N-terminal sequencing, MALDI-TOF mass fingerprinting, and collision-induced dissociation tandem mass spectrometry ...

  4. In Vitro Antiplasmodial Activity of Phospholipases A2 and a Phospholipase Homologue Isolated from the Venom of the Snake Bothrops asper

    OpenAIRE

    Castillo, Juan; Vargas, Leidy; Segura, Cesar; Gutiérrez, José; Pérez, Juan

    2012-01-01

    The antimicrobial and antiparasite activity of phospholipase A2 (PLA2) from snakes and bees has been extensively explored. We studied the antiplasmodial effect of the whole venom of the snake Bothrops asper and of two fractions purified by ion-exchange chromatography: one containing catalytically-active phospholipases A2 (PLA2) (fraction V) and another containing a PLA2 homologue devoid of enzymatic activity (fraction VI). The antiplasmodial effect was assessed on in vitro cultures of Plasmod...

  5. Immunoglobulin G and F(ab')2 polyvalent antivenoms do not differ in their ability to neutralize hemorrhage, edema and myonecrosis induced by Bothrops asper (terciopelo) snake venom

    OpenAIRE

    León Montero, Guillermo; Rojas Céspedes, Gustavo; Lomonte, Bruno; Gutiérrez, José María

    1997-01-01

    The ability of whole immunoglobulin G (IgG) and F(ab')2 polyvalent (Crotalinae) antivenoms to neutralize the hemorrhagic, edema-forming and myotoxic activities of Bothrops asper venom was studied. Both antivenoms were adjusted to the same neutralizing potency against lethal and hemorrhagic activities in experiments where venom and antivenoms were incubated before injection. Thus, in these experimental conditions, differences in the neutralizing ability in experiments involving independent inj...

  6. Neutralizing activities of ethanolic extracts of six plants traditionally used in Guatemala as antidotes for the envenomation caused by the snake Bothrops asper

    Directory of Open Access Journals (Sweden)

    Patricia Saravia-Otten

    2015-07-01

    Full Text Available Many plants are reported to be used in Guatemalan traditional medicine as antidotes against various effects of the snakebite; however, very few attempts have been made to evaluate their neutralizing capacity in controlled experiments. Six plants (Acacia hindsii, Cissampelos pareira; Hamelia patens, Piper peltatum, Sansevieria hyacinthoides and Aristolochia maxima were evaluated in vitro for their ability to neutralize phospholipase A2(PLA2 and proteolytic effects of the venom of Bothrops asper, the snake responsible for approximately half of the snakebite envenomations in Central America. These effects are indicatives of the ability of B. asper venom to produce myotoxicity, hemorrhage and inflammation. Plants were collected, dried and extracted by maceration with ethanol. After pre-incubation of several amounts of each extract with a challenge dose of venom, S. hyacinthoides demonstrated a low neutralizing capacity (< DE 50 of the PLA2 effect (13.90 ± 6.41%; C. pareira (32.98 ± 5.51% and P. peltatum (24.52 ± 7.45% neutralized less than 50% of the proteolytic effect. The results suggest that neither of the tested plants should be used individually to treat the main effects of B. asper envenomation. However, the three low-active extracts might be potentiated when used in mixtures composed of several plants, as prepared by traditional healers. Given the complexity of the venom components and the multiple pathologic effects produced by B. asper envenomation, more tests are required to fully investigate the ability of this plants to neutralize the coagulant, fibrin(ogenolytic, edematizing and myotoxic effects of the venom.

  7. Effect of the metalloproteinase inhibitor batimastat in the systemic toxicity induced by Bothrops asper snake venom: understanding the role of metalloproteinases in envenomation.

    Science.gov (United States)

    Rucavado, Alexandra; Escalante, Teresa; Gutiérrez, José María

    2004-03-15

    The peptidomimetic hydroxamate metalloproteinase inhibitor batimastat (BB-94) was assessed for its ability to neutralize the systemic effects (lethality, hemorrhage and coagulopathy) induced by the venom of Bothrops asper, the most important snake from a medical standpoint in Central America. Batimastat inhibited lethality when a venom challenge dose of two LD(50)s was used by intraperitoneal and intravenous routes, with ED(50)s of 250 and 22 microM, respectively. With a challenge dose of three LD(50)s, lethality was not abrogated, but a conspicuous and dose-dependent delay in the time of death was observed in mice injected with mixtures of venom plus batimastat. Upon incubation with 500 microM batimastat, venom LD(50) increased 2.86-fold (intraperitoneal route) and 2.37-fold (intravenous route), when compared with LD(50) of venom alone. Batimastat also inhibited the hemorrhagic effect induced by venom in the lungs after intravenous injection. Moreover, batimastat exerted a significant inhibition of in vitro coagulant and in vivo defibrinogenating effects of venom, evidencing that metalloproteinases play a key role in the coagulopathy characteristic of B. asper envenomation. The remaining uninhibited coagulant effect is due to serine proteinases, i.e. thrombin-like enzymes, since this effect was completely abrogated by the combination of batimastat and PMSF. Our results stress the view that metalloproteinases play a relevant role in the systemic pathophysiology of B. asper envenomation and that metalloproteinase inhibitors may become a therapeutic alternative in this pathology.

  8. Role of TNF-alpha, IL-1beta and IL-6 in the local tissue damage induced by Bothrops asper snake venom: an experimental assessment in mice.

    Science.gov (United States)

    Chaves, Fernando; Teixeira, Catarina F P; Gutiérrez, José María

    2005-02-01

    The role of the cytokines TNF-alpha, IL-1beta and IL-6 in the acute local pathological effects induced by Bothrops asper snake venom was assessed in mice. Intramuscular injection of this venom induced increments in IL-1beta and IL-6 in muscle, but no elevations of TNF-alpha were detected. Pentoxifylline (PTX), a methylxanthine derivative that inhibits the synthesis of TNF-alpha, and antibodies against these three cytokines were used to assess the role of these cytokines in venom-induced effects. As a control, PTX pretreatment was effective at abrogating lethality and serum TNF-alpha increments in mice subjected to endotoxemia induced by injection of Escherichia coli lipopolysaccharide, although it did not affect the increment in IL-1beta and IL-6 in such endotoxic model. PTX failed to reduce lethality, hemorrhage, myonecrosis, dermonecrosis and edema induced by B. asper venom. Moreover, pretreatment with anti-cytokine antibodies was also ineffective at reducing venom-induced myonecrosis and hemorrhage. It is concluded that TNF-alpha, IL-1beta and IL-6 do not have a significant role in the pathogenesis of the acute local pathological effects induced by B. asper venom in mice, although this does not exclude the possibility that these cytokines play a role in other aspects of venom-induced local pathology, as well as in the reparative and regenerative responses that take place after the onset of tissue damage.

  9. In Vitro Antiplasmodial Activity of Phospholipases A2 and a Phospholipase Homologue Isolated from the Venom of the Snake Bothrops asper

    Directory of Open Access Journals (Sweden)

    Juan Carlos Alarcón Pérez

    2012-12-01

    Full Text Available The antimicrobial and antiparasite activity of phospholipase A2 (PLA2 from snakes and bees has been extensively explored. We studied the antiplasmodial effect of the whole venom of the snake Bothrops asper and of two fractions purified by ion-exchange chromatography: one containing catalytically-active phospholipases A2 (PLA2 (fraction V and another containing a PLA2 homologue devoid of enzymatic activity (fraction VI. The antiplasmodial effect was assessed on in vitro cultures of Plasmodium falciparum. The whole venom of B. asper, as well as its fractions V and VI, were active against the parasite at 0.13 ± 0.01 µg/mL, 1.42 ± 0.56 µg/mL and 22.89 ± 1.22 µg/mL, respectively. Differences in the cytotoxic activity on peripheral blood mononuclear cells between the whole venom and fractions V and VI were observed, fraction V showing higher toxicity than total venom and fraction VI. Regarding toxicity in mice, the whole venom showed the highest lethal effect in comparison to fractions V and VI. These results suggest that B. asper PLA2 and its homologue have antiplasmodial potential.

  10. Active immunization of cattle with a bothropic toxoid does not abrogate envenomation by Bothrops asper venom, but increases the likelihood of survival.

    Science.gov (United States)

    Herrera, María; González, Katherine; Rodríguez, Carlos; Gómez, Aarón; Segura, Álvaro; Vargas, Mariángela; Villalta, Mauren; Estrada, Ricardo; León, Guillermo

    2017-03-01

    This study assessed the protective effect of active immunization of cattle to prevent the envenomation induced by B. asper venom. Two groups of oxen were immunized with a bothropic toxoid and challenged by an intramuscular injection of either 10 or 50 mg B. asper venom, to induce moderate or severe envenomations, respectively. Non-immunized oxen were used as controls. It was found that immunized oxen developed local edema similar to those observed in non-immunized animals. However, systemic effects were totally prevented in immunized oxen challenged with 10 mg venom, and therefore antivenom treatment was not required. When immunized oxen were challenged with 50 mg venom, coagulopathy was manifested 3-16 h later than in non-immunized oxen, demonstrating a delay in the onset of systemic envenomation. In these animals, active immunization did not eliminate the need for antivenom treatment, but increased the time lapse in which antivenom administration is still effective. All experimentally envenomed oxen completely recovered after a week following venom injection. Our results suggest that immunization of cattle with a bothropic toxoid prevents the development of systemic effects in moderate envenomations by B. asper, but does not abrogate these effects in severe envenomation. Copyright © 2016 International Alliance for Biological Standardization. Published by Elsevier Ltd. All rights reserved.

  11. In vitro antiplasmodial activity of phospholipases A2 and a phospholipase homologue isolated from the venom of the snake Bothrops asper.

    Science.gov (United States)

    Castillo, Juan Carlos Quintana; Vargas, Leidy Johana; Segura, Cesar; Gutiérrez, José María; Pérez, Juan Carlos Alarcón

    2012-12-14

    The antimicrobial and antiparasite activity of phospholipase A(2) (PLA(2)) from snakes and bees has been extensively explored. We studied the antiplasmodial effect of the whole venom of the snake Bothrops asper and of two fractions purified by ion-exchange chromatography: one containing catalytically-active phospholipases A(2) (PLA(2)) (fraction V) and another containing a PLA(2) homologue devoid of enzymatic activity (fraction VI). The antiplasmodial effect was assessed on in vitro cultures of Plasmodium falciparum. The whole venom of B. asper, as well as its fractions V and VI, were active against the parasite at 0.13 ± 0.01 µg/mL, 1.42 ± 0.56 µg/mL and 22.89 ± 1.22 µg/mL, respectively. Differences in the cytotoxic activity on peripheral blood mononuclear cells between the whole venom and fractions V and VI were observed, fraction V showing higher toxicity than total venom and fraction VI. Regarding toxicity in mice, the whole venom showed the highest lethal effect in comparison to fractions V and VI. These results suggest that B. asper PLA(2) and its homologue have antiplasmodial potential.

  12. UHPLC-MS/MS quantification combined with chemometrics for the comparative analysis of different batches of raw and wine-processed Dipsacus asper.

    Science.gov (United States)

    Tao, Yi; Du, Yingshan; Su, Dandan; Li, Weidong; Cai, Baochang

    2017-04-01

    A rapid and sensitive ultra-high performance liquid chromatography with tandem mass spectrometry approach was established for the simultaneous determination of 4-caffeoylquinic acid, loganic acid, chlorogenic acid, loganin, 3,5-dicaffeoylquinic acid, dipsacoside B, asperosaponin VI, and sweroside in raw and wine-processed Dipsacus asper. Chloramphenicol and glycyrrhetinic acid were employed as internal standards. The proposed approach was fully validated in terms of linearity, sensitivity, precision, repeatability as well as recovery. Intra- and interassay variability for all analytes were 2.8-4.9 and 1.7-4.8%, respectively. The standard addition method determined recovery rates for each analytes (96.8-104.6%). In addition, the developed approach was applied to 20 batches of raw and wine-processed samples of Dipsacus asper. Principle component analysis and partial least squares-discriminate analysis revealed a clear separation between the raw group and wine-processed group. After wine-processing, the contents of loganic acid, chlorogenic acid, dipsacoside B, and asperosaponin VI were upregulated, while the contents of 3,5-dicaffeoylquinic acid, 4-caffeoylquinic acid, loganin, and sweroside were downregulated. Our results demonstrated that ultra-high performance liquid chromatography with tandem mass spectrometry quantification combined with chemometrics is a viable method for quality evaluation of the raw Dipsacus asper and its wine-processed products. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. G protein regulator 1 (GPR-1) localizes to cortical sites of artificial mechanical indentation in Caenorhabditis elegans zygotes.

    Science.gov (United States)

    Bringmann, Henrik

    2012-10-01

    Cytokinesis and spindle positioning require the cortical force regulator G Protein Regulator 1/2 (GPR-1/2). GPR-1/2 is thought to localize to sites of cortical force generation. Does GPR-1/2 also act as a sensor for mechanical stimulation? I mechanically stimulated the cortex by indenting it with a glass needle and observed the cortical localization of a YFP::GPR-1 transgene. I found that cortical YFP::GPR-1 accumulated at the site of mechanical indentation. This phenomenon occurred on most of the cortical areas except the site of prospective cytokinesis furrow formation. This result suggests that GPR-1/2 can sense mechanical properties of the cortex, which may be important for GPR-1/2 function regulating spindle positioning and cytokinesis. Copyright © 2012 Wiley Periodicals, Inc.

  14. The varieties of surface alteration

    International Nuclear Information System (INIS)

    Kelly, R.

    1984-01-01

    Four aspects of ion-beam modification are reviewed: structural changes, in which crystalline phases are converted to amorphous, amorphous phases are converted to crystalline, or ordered crystalline forms evolve to random crystalline forms; topographical changes, which include the development of facets on flat surfaces, the development of cliffs at grain boundaries, the development of ripples on obliquely bombarded surfaces, and the evolution of blunt asperities, foreign particles, or vertical surfaces into cones or pyramids; bombardment-induced electronic changes, which include the consequences of chemical changes due to the composition of the incident beam, carrier injection due to energy deposition, chemical changes due to recoil implantation, and chemical changes due to preferential sputtering; and compositional changes, which in binary alloys consist mainly of a preferential loss of the component with the lower surface binding energy or larger size. 122 refs.; 32 figs.; 9 tabs

  15. Effect of Echinacea purpurea (Asteraceae aqueous extract on antibody response to Bothrops asper venom and immune cell response

    Directory of Open Access Journals (Sweden)

    Fernando Chaves

    2007-03-01

    Full Text Available The effect of aqueous extract of Echinacea purpurea roots on the murine antibody response to Bothrops asper snake venom in vivo was studied. Three groups were used. Group #1, baseline control, was treated with snake venom plus PBS. Group #2 was treated with snake venom plus sodium alginate as adjuvant (routine method used at Instituto Clodomiro Picado, and group #3 or experimental group, was treated with snake venom plus aqueous extract of E. purpurea root as adjuvant. In all groups, the first inoculation was done with Freund’s complete adjuvant (FCA. By the time of the second bleeding, mice in group #3 showed a remarkable increment in the level of anti-venom antibodies compared with those in groups #1 or #2. In vitro immune cell proliferation as a response to aqueous extract of E. purpurea root was studied using human lymphocytes activated with different lectins (Con A, PHA and PWM. In all cases, increase in percentage of lymphoproliferation was greater when E. purpurea root extract was used in addition to individual lectins. Rev. Biol. Trop. 55 (1: 113-119. Epub 2007 March. 31.Se estudió in vivo, el efecto del extracto acuoso de las raíces de Echinacea purpurea en la respuesta de los anticuerpos murinos al veneno de la serpiente Bothrops asper. El grupo 1 control, fue tratado con el veneno y PBS. El grupo 2 con veneno y alginato de sodio (método utilizado en el Instituto Clodomiro Picado, y el grupo 3 o experimental, con veneno y extracto acuoso de las raíces de E. purpurea. En todos los grupos, la primera inmunización fue hecha con FCA (Freund’s Complete Adjuvant. En las muestras correspondientes a la segunda sangría, los ratones del grupo 3 mostraron un marcado incremento en el nivel de anticuerpos, en comparación con los ratones de los otros grupos. También se determinó la proliferación de células inmunes in vitro, como respuesta al extracto acuoso de la raíz de E. purpurea, utilizando linfocitos humanos activados con

  16. Comparative study of rock salt deformation by indentation and acoustic emission methods

    Science.gov (United States)

    Filimonov, Y.; Traskine, V.; Skvortsova, Z.

    2003-04-01

    Experimental studies of rock salt deformation and failure are of a great interest in the context of the problem of radioactive waste management, as well as for better understanding salt tectonics structures. Laboratory tests with acoustic emission (AE) measurement performed on natural specimens of rock salt under uniaxial compression loading have shown that the AE hit rate is considerably higher (up to five times) in the specimens deformed at a higher loading rate. The cumulative number of AE hits, on the contrary, are larger in the specimens deformed with a lower speed. The shape of the AE vs stress curve is loading rate-dependent too. The indentation tests made with a spherical indentor, i.e. under progressively decreasing stress and strain rate, on synthetic NaCl single crystals in brine demonstrate a transition from dislocation motion limited stage (observed in brine, in air or in a neutral liquid) to the pressure solution stage (observed only in brine). Both methods evidence approximately similar values for the transition rates.

  17. Non-integer viscoelastic constitutive law to model soft biological tissues to in-vivo indentation.

    Science.gov (United States)

    Demirci, Nagehan; Tönük, Ergin

    2014-01-01

    During the last decades, derivatives and integrals of non-integer orders are being more commonly used for the description of constitutive behavior of various viscoelastic materials including soft biological tissues. Compared to integer order constitutive relations, non-integer order viscoelastic material models of soft biological tissues are capable of capturing a wider range of viscoelastic behavior obtained from experiments. Although integer order models may yield comparably accurate results, non-integer order material models have less number of parameters to be identified in addition to description of an intermediate material that can monotonically and continuously be adjusted in between an ideal elastic solid and an ideal viscous fluid. In this work, starting with some preliminaries on non-integer (fractional) calculus, the "spring-pot", (intermediate mechanical element between a solid and a fluid), non-integer order three element (Zener) solid model, finally a user-defined large strain non-integer order viscoelastic constitutive model was constructed to be used in finite element simulations. Using the constitutive equation developed, by utilizing inverse finite element method and in vivo indentation experiments, soft tissue material identification was performed. The results indicate that material coefficients obtained from relaxation experiments, when optimized with creep experimental data could simulate relaxation, creep and cyclic loading and unloading experiments accurately. Non-integer calculus viscoelastic constitutive models, having physical interpretation and modeling experimental data accurately is a good alternative to classical phenomenological viscoelastic constitutive equations.

  18. Evaluation of flow properties in the weldments of vanadium alloys using a novel indentation technique

    Energy Technology Data Exchange (ETDEWEB)

    Gubbi, A.N.; Rowcliffe, A.F.; Lee, E.H.; King, J.F.; Goodwin, G.M. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Automated Ball Indentation (ABI) testing, was successfully employed to determine the flow properties of the fusion zone, heat affected zone (HAZ), and base metal of the gas tungsten arc (GTA) and electron beam (EB) welds of the V-4Cr-4Ti (large heat no. 832665) and the V-5Cr-5Ti (heat 832394) alloys. ABI test results showed a clear distinction among the properties of the fusion zone, HAZ, and base metal in both GTA and EB welds of the two alloys. GTA and EB welds of both V-4Cr-4Ti and V-5Cr-5Ti alloys show strengthening of both the fusion zone and the HAZ (compared to base metal) with the fusion zone having higher strength than the HAZ. These data correlate well with the Brinell hardness. On the other hand, GTA welds of both alloys, after a post-weld heat treatment of 950{degrees}C for 2 h, show a recovery of the properties to base metal values with V-5Cr-5Ti showing a higher degree of recovery compared to V-4Cr-4Ti. These measurements correlate with the reported recovery of the Charpy impact properties.

  19. Controlling Density and Modulus in Auxetic Foam Fabrications—Implications for Impact and Indentation Testing

    Directory of Open Access Journals (Sweden)

    Olly Duncan

    2018-02-01

    Full Text Available Foams are commonly used for cushioning in protective sporting equipment. Volumetrically compressing open-cell polyurethane foam buckles cell ribs creating a re-entrant structure—set by heating then cooling—which can impart auxetic behaviour. Theoretically, auxetic materials improve impact protection by increasing indentation resistance and energy absorption, potentially reducing sporting injuries and burdens on individuals, health services and national economies. In previous work, auxetic foam exhibited ~3 to ~8 times lower peak force (compared to its conventional counterpart under impacts adopted from tests used to certify protective sporting equipment. Increases to the foam’s density and changes to stress/strain relationships (from fabrication mean Poisson’s ratio’s contribution to reduced peak forces under impact is unclear. This work presents a simple fabrication method for foam samples with comparable density and linear stress/strain relationship, but different Poisson’s ratios ranging between 0.1 and −0.3, an important step in assessing the Poisson’s ratio’s contribution to impact force attenuation.

  20. Evaluation of material degradation of 1Cr-1Mo-0.25V steel using ball Indentation method

    International Nuclear Information System (INIS)

    Seok, Chang Sung; Koo, Jae Mean; Kim, Jeong Pyo

    2004-01-01

    The BI (Ball Indentation) method has the potential to assess the mechanical properties and to replace conventional fracture tests. In this study, the effect of aging on mechanical behavior of 1Cr-1Mo-0.25V steels procured by isothermal aging heat-treatment at four different aging times in the range of 0∼1820 hours at 630 .deg. C, were investigated using BI system

  1. Nano-indentation creep properties of the S2 cell wall lamina and compound corner middle lamella [abstract

    Science.gov (United States)

    Joseph E. Jakes; Charles R. Frihart; James F. Beecher; Donald S. Stone

    2010-01-01

    Bulk wood properties are derived from an ensemble of processes taking place at the micron-scale, and at this level the properties differ dramatically in going from cell wall layers to the middle lamella. To better understand the properties of these micron-scaled regions of wood, we have developed a unique set of nano-indentation tools that allow us to measure local...

  2. Anti-icing performance of superhydrophobic surfaces

    Science.gov (United States)

    Farhadi, S.; Farzaneh, M.; Kulinich, S. A.

    2011-05-01

    This article studies the anti-ice performance of several micro/nano-rough hydrophobic coatings with different surface chemistry and topography. The coatings were prepared by spin-coating or dip coating and used organosilane, fluoropolymer or silicone rubber as a top layer. Artificially created glaze ice, similar to the naturally accreted one, was deposited on the nanostructured surfaces by spraying supercooled water microdroplets (average size ˜80 μm) in a wind tunnel at subzero temperature (-10 °C). The ice adhesion strength was evaluated by spinning the samples in a centrifuge at constantly increasing speed until ice delamination occurred. The results show that the anti-icing properties of the tested materials deteriorate, as their surface asperities seem to be gradually broken during icing/de-icing cycles. Therefore, the durability of anti-icing properties appears to be an important point for further research. It is also shown that the anti-icing efficiency of the tested superhydrophobic surfaces is significantly lower in a humid atmosphere, as water condensation both on top and between surface asperities takes place, leading to high values of ice adhesion strength. This implies that superhydrophobic surfaces may not always be ice-phobic in the presence of humidity, which can limit their wide use as anti-icing materials.

  3. Influence of the surface quality due to a hole derived in initial material processing of cold sheets with drawing

    OpenAIRE

    Cvetkov, Slavco; Kocov, Atanas

    2010-01-01

    A research was performed about the influence of the surface quality due to a hole derived in initial material processing of cold-rolled steel sheets with drawing. This influence was researched through the surface quality obtained bu the type of preparation of the hole surface without prejudice to the precise measurement of the achieved quality (asperity). the aim is to indicate how the type of manufacturing the holes can improve the workability of cold-rolled sheets and help solve technical p...

  4. Approche statistique pour identifier les propriétés mécaniques des phases individuelles á partir de données d'indentation

    Czech Academy of Sciences Publication Activity Database

    Čech, J.; Haušild, P.; Materna, A.; Matějíček, Jiří

    2017-01-01

    Roč. 105, č. 1 (2017), č. článku 105. ISSN 0032-6895. [Indentation 2016. Lille, 12.10.2016-14.10.2016] R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Nanoindentation * interface * composites * grid indentation * statistical distribution Subject RIV: JI - Composite Materials OBOR OECD: Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics https://doi.org/10.1051/mattech/2016041

  5. A phospholipase A₂ from Bothrops asper snake venom activates neutrophils in culture: expression of cyclooxygenase-2 and PGE₂ biosynthesis.

    Science.gov (United States)

    Moreira, Vanessa; Gutiérrez, José María; Amaral, Rafaela Bacci; Lomonte, Bruno; Purgatto, Eduardo; Teixeira, Catarina

    2011-02-01

    In this study, the production of prostaglandin E₂ (PGE₂) and up-regulation in cyclooxygenase (COX) pathway induced by a phospholipase A₂ (PLA₂), myotoxin-III (MT-III), purified from Bothrops asper snake venom, in isolated neutrophils were investigated. The arachidonic acid (AA) production and the participation of intracellular PLA₂s (cytosolic PLA₂ and Ca(2+)-independent PLA₂) in these events were also evaluated. MT-III induced COX-2, but not COX-1 gene and protein expression in neutrophils and increased PGE₂ levels. Pretreatment of neutrophils with COX-2 and COX-1 inhibitors reduced PGE₂ production induced by MT-III. Arachidonyl trifluoromethyl ketone (AACOCF₃), an intracellular PLA₂ inhibitor, but not bromoenol lactone (BEL), an iPLA₂ inhibitor, suppressed the MT-III-induced AA and PGE₂ release. In conclusion, MT-III directly stimulates neutrophils inducing COX-2 mRNA and protein expression followed by production of PGE₂. COX-2 isoform is preeminent over COX-1 for production of PGE₂ stimulated by MT-III. PGE₂ and AA release by MT-III probably is related to cPLA₂ activation. Copyright © 2010 Elsevier Ltd. All rights reserved.

  6. Isolation and characterization of a serine proteinase with thrombin-like activity from the venom of the snake Bothrops asper

    Directory of Open Access Journals (Sweden)

    A.V Pérez

    2008-01-01

    Full Text Available A serine proteinase with thrombin-like activity was isolated from the venom of the Central American pit viper Bothrops asper. Isolation was performed by a combination of affinity chromatography on aminobenzamidine-Sepharose and ion-exchange chromatography on DEAE-Sepharose. The enzyme accounts for approximately 0.13% of the venom dry weight and has a molecular mass of 32 kDa as determined by SDS-PAGE, and of 27 kDa as determined by MALDI-TOF mass spectrometry. Its partial amino acid sequence shows high identity with snake venom serine proteinases and a complete identity with a cDNA clone previously sequenced from this species. The N-terminal sequence of the enzyme is VIGGDECNINEHRSLVVLFXSSGFL CAGTLVQDEWVLTAANCDSKNFQ. The enzyme induces clotting of plasma (minimum coagulant dose = 4.1 µg and fibrinogen (minimum coagulant dose = 4.2 µg in vitro, and promotes defibrin(ogenation in vivo (minimum defibrin(ogenating dose = 1.0 µg. In addition, when injected intravenously in mice at doses of 5 and 10 µg, it induces a series of behavioral changes, i.e., loss of the righting reflex, opisthotonus, and intermittent rotations over the long axis of the body, which closely resemble the `gyroxin-like' effect induced by other thrombin-like enzymes from snake venoms.

  7. Effect of Echinacea purpurea (Asteraceae) aqueous extract on antibody response to Bothrops asper venom and immune cell response.

    Science.gov (United States)

    Chaves, Fernando; Chacón, Mauricio; Badilla, Beatriz; Arévalo, Carolina

    2007-03-01

    The effect of aqueous extract of Echinacea purpurea roots on the murine antibody response to Bothrops asper snake venom in vivo was studied. Three groups were used. Group #1, baseline control, was treated with snake venom plus PBS. Group #2 was treated with snake venom plus sodium alginate as adjuvant (routine method used at Instituto Clodomiro Picado), and group #3 or experimental group, was treated with snake venom plus aqueous extract ofE. purpurea root as adjuvant. In all groups, the first inoculation was done with Freund's complete adjuvant (FCA). By the time of the second bleeding, mice in group #3 showed a remarkable increment in the level of anti-venom antibodies compared with those in groups #1 or #2. In vitro immune cell proliferation as a response to aqueous extract of E. purpurea root was studied using human lymphocytes activated with different lectins (Con A, PHA and PWM). In all cases, increase in percentage of lymphoproliferation was greater when E. purpurea root extract was used in addition to individual lectins.

  8. Isolation and characterization of a serine proteinase with thrombin-like activity from the venom of the snake Bothrops asper.

    Science.gov (United States)

    Pérez, A V; Rucavado, A; Sanz, L; Calvete, J J; Gutiérrez, J M

    2008-01-01

    A serine proteinase with thrombin-like activity was isolated from the venom of the Central American pit viper Bothrops asper. Isolation was performed by a combination of affinity chromatography on aminobenzamidine-Sepharose and ion-exchange chromatography on DEAE-Sepharose. The enzyme accounts for approximately 0.13% of the venom dry weight and has a molecular mass of 32 kDa as determined by SDS-PAGE, and of 27 kDa as determined by MALDI-TOF mass spectrometry. Its partial amino acid sequence shows high identity with snake venom serine proteinases and a complete identity with a cDNA clone previously sequenced from this species. The N-terminal sequence of the enzyme is VIGGDECNINEHRSLVVLFXSSGFL CAGTLVQDEWVLTAANCDSKNFQ. The enzyme induces clotting of plasma (minimum coagulant dose = 4.1 microg) and fibrinogen (minimum coagulant dose = 4.2 microg) in vitro, and promotes defibrin(ogen)ation in vivo (minimum defibrin(ogen)ating dose = 1.0 microg). In addition, when injected intravenously in mice at doses of 5 and 10 microg, it induces a series of behavioral changes, i.e., loss of the righting reflex, opisthotonus, and intermittent rotations over the long axis of the body, which closely resemble the ;gyroxin-like' effect induced by other thrombin-like enzymes from snake venoms.

  9. Inflammation induced by Bothrops asper venom: release of proinflammatory cytokines and eicosanoids, and role of adhesion molecules in leukocyte infiltration.

    Science.gov (United States)

    Zamuner, Stella Regina; Zuliani, Juliana Pavan; Fernandes, Cristina Maria; Gutiérrez, José Maria; de Fátima Pereira Teixeira, Catarina

    2005-12-01

    Bothrops asper venom (BaV) causes systemic and local effects characterized by an acute inflammatory reaction with accumulation of leukocytes and release of endogenous mediators. In this study, the effects of BaV on the release of the cytokines IL-1, IL-6 and TNF-alpha and the eicosanoids LTB4 and TXA2 in the peritoneal cavity of mice were analyzed. We also investigated the participation of beta2 integrin chain, l-selectin, LFA-1, ICAM-1 and PECAM-1 adhesion molecules in the BaV-induced leukocyte accumulation. Levels of proinflammatory cytokines IL-6 and TNF-alpha, as well as eicosanoids LTB4 and TXA2 were significantly increased after BaV injection (250 microg/kg), whereas no increment in IL-1 was observed. Anti-mouse l-selectin, LFA-1, ICAM-1, PECAM-1 and beta2 integrin chain monoclonal antibodies resulted in a reduction of neutrophil accumulation induced by BaV injection compared with isotype-matched control injected animals. These data suggest that BaV is able to induce the activation of leukocytes and endothelium to express adhesion molecules involved in the recruitment of neutrophils into the inflammed site. Furthermore, these results showed that BaV induces the release of cytokines and eicosanoids in the local of the venom injection; these inflammatory mediators may be important for the initiation and amplification of the inflammatory reaction characteristic from Bothrops sp envenomation.

  10. Neutralization of Bothrops asper venom by antibodies, natural products and synthetic drugs: contributions to understanding snakebite envenomings and their treatment.

    Science.gov (United States)

    Lomonte, Bruno; León, Guillermo; Angulo, Yamileth; Rucavado, Alexandra; Núñez, Vitelbina

    2009-12-01

    Interest in studies on the neutralization of snake venoms and toxins by diverse types of inhibitors is two-fold. From an applied perspective, results enclose the potential to be translated into useful therapeutic products or procedures, to benefit patients suffering from envenomings. From a basic point of view, on the other hand, neutralizing agents may be used as powerful dissecting tools to determine the relative role of toxins within the context of the overall pathology induced by a venom, or to increase our understanding on the molecular mechanisms by which toxins exert their harmful actions upon particular targets. The venom of the snake Bothrops asper has been the subject of a number of experimental studies addressing its neutralization by antibodies, as well as by non-immunologic inhibitors, including natural products derived from plants or animals, or synthetic drugs. As summarized in the present review, neutralization studies on this venom and some of its isolated toxins have contributed to a better understanding of envenomings by this species, and their treatment. In addition, such studies have provided valuable knowledge on the mechanisms of action and the relative functional importance of particular toxins of this venom, especially in the case of its myotoxic phospholipases A(2) and hemorrhagic metalloproteinases.

  11. Comparison of the adjuvant activity of aluminum hydroxide and calcium phosphate on the antibody response towards Bothrops asper snake venom.

    Science.gov (United States)

    Olmedo, Hidekel; Herrera, María; Rojas, Leonardo; Villalta, Mauren; Vargas, Mariángela; Leiguez, Elbio; Teixeira, Catarina; Estrada, Ricardo; Gutiérrez, José María; León, Guillermo; Montero, Mavis L

    2014-01-01

    The adjuvanticity of aluminum hydroxide and calcium phosphate on the antibody response in mice towards the venom of the snake Bothrops asper was studied. It was found that, in vitro, most of the venom proteins are similarly adsorbed by both mineral salts, with the exception of some basic phospholipases A2, which are better adsorbed by calcium phosphate. After injection, the adjuvants promoted a slow release of the venom, as judged by the lack of acute toxicity when lethal doses of venom were administered to mice. Leukocyte recruitment induced by the venom was enhanced when it was adsorbed on both mineral salts; however, venom adsorbed on calcium phosphate induced a higher antibody response towards all tested HPLC fractions of the venom. On the other hand, co-precipitation of venom with calcium phosphate was the best strategy for increasing: (1) the capacity of the salt to couple venom proteins in vitro; (2) the venom ability to induce leukocyte recruitment; (3) phagocytosis by macrophages; and (4) a host antibody response. These findings suggest that the chemical nature is not the only one determining factor of the adjuvant activity of mineral salts.

  12. Effect of core thickness differences on post-fatigue indentation fracture resistance of veneered zirconia crowns.

    Science.gov (United States)

    Alhasanyah, Abdulrahman; Vaidyanathan, Tritala K; Flinton, Robert J

    2013-07-01

    Despite the excellent esthetics of veneered zirconia crowns, the incidence of chipping and fracture of veneer porcelain on zirconia crowns has been recognized to be higher than in metal ceramic crowns. The objective of this investigation was to study the effect of selected variations in core thickness on the post-fatigue fracture resistance of veneer porcelain on zirconia crowns. Zirconia crowns for veneering were prepared with three thickness designs of (a) uniform 0.6-mm thick core (group A), (b) extra-thick 1.7 mm occlusal core support (group B), and (c) uniform 1.2-mm thick core (group C). The copings were virtually designed and milled by the CAD/CAM technique. Metal ceramic copings (group D) with the same design as in group C were used as controls. A sample size of N = 20 was used for each group. The copings were veneered with compatible porcelain and fatigue tested under a sinusoidal loading regimen. Loading was done with a 200 N maximum force amplitude under Hertzian axial loading conditions at the center of the crowns using a spherical tungsten carbide indenter. After 100,000 fatigue cycles, the crowns were axially loaded to fracture and maximum load levels before fracture was recorded. One-way ANOVA (P crowns. Extra-thick occlusal core support for porcelain veneer may significantly reduce the veneer chipping and fracture of zirconia crowns. This is suggested as an important consideration in the design of copings for zirconia crowns. © 2013 by the American College of Prosthodontists.

  13. Characterizing viscoelastic properties of breast cancer tissue in a mouse model using indentation.

    Science.gov (United States)

    Qiu, Suhao; Zhao, Xuefeng; Chen, Jiayao; Zeng, Jianfeng; Chen, Shuangqing; Chen, Lei; Meng, You; Liu, Biao; Shan, Hong; Gao, Mingyuan; Feng, Yuan

    2018-03-01

    Breast cancer is one of the leading cancer forms affecting females worldwide. Characterizing the mechanical properties of breast cancer tissue is important for diagnosis and uncovering the mechanobiology mechanism. Although most of the studies were based on human cancer tissue, an animal model is still describable for preclinical analysis. Using a custom-build indentation device, we measured the viscoelastic properties of breast cancer tissue from 4T1 and SKBR3 cell lines. A total of 7 samples were tested for each cancer tissue using a mouse model. We observed that a viscoelastic model with 2-term Prony series could best describe the ramp and stress relaxation of the tissue. For long-term responses, the SKBR3 tissues were stiffer in the strain levels of 4-10%, while no significant differences were found for the instantaneous elastic modulus. We also found tissues from both cell lines appeared to be strain-independent for the instantaneous elastic modulus and for the long-term elastic modulus in the strain level of 4-10%. In addition, by inspecting the cellular morphological structure of the two tissues, we found that SKBR3 tissues had a larger volume ratio of nuclei and a smaller volume ratio of extracellular matrix (ECM). Compared with prior cellular mechanics studies, our results indicated that ECM could contribute to the stiffening the tissue-level behavior. The viscoelastic characterization of the breast cancer tissue contributed to the scarce animal model data and provided support for the linear viscoelastic model used for in vivo elastography studies. Results also supplied helpful information for modeling of the breast cancer tissue in the tissue and cellular levels. Copyright © 2018 Elsevier Ltd. All rights reserved.

  14. Estimation of Apple Volume and Its Shape Indentation Using Image Processing Technique and Neural Network

    Directory of Open Access Journals (Sweden)

    M Jafarlou

    2014-04-01

    Full Text Available Physical properties of agricultural products such as volume are the most important parameters influencing grading and packaging systems. They should be measured accurately as they are considered for any good system design. Image processing and neural network techniques are both non-destructive and useful methods which are recently used for such purpose. In this study, the images of apples were captured from a constant distance and then were processed in MATLAB software and the edges of apple images were extracted. The interior area of apple image was divided into some thin trapezoidal elements perpendicular to longitudinal axis. Total volume of apple was estimated by the summation of incremental volumes of these elements revolved around the apple’s longitudinal axis. The picture of half cut apple was also captured in order to obtain the apple shape’s indentation volume, which was subtracted from the previously estimated total volume of apple. The real volume of apples was measured using water displacement method and the relation between the real volume and estimated volume was obtained. The t-test and Bland-Altman indicated that the difference between the real volume and the estimated volume was not significantly different (p>0.05 i.e. the mean difference was 1.52 cm3 and the accuracy of measurement was 92%. Utilizing neural network with input variables of dimension and mass has increased the accuracy up to 97% and the difference between the mean of volumes decreased to 0.7 cm3.

  15. Effect of Surface Roughness on Hydrodynamic Bearings

    Science.gov (United States)

    Majumdar, B. C.; Hamrock, B. J.

    1981-01-01

    A theoretical analysis on the performance of hydrodynamic oil bearings is made considering surface roughness effect. The hydrodynamic as well as asperity contact load is found. The contact pressure was calculated with the assumption that the surface height distribution was Gaussian. The average Reynolds equation of partially lubricated surface was used to calculate hydrodynamic load. An analytical expression for average gap was found and was introduced to modify the average Reynolds equation. The resulting boundary value problem was then solved numerically by finite difference methods using the method of successive over relaxation. The pressure distribution and hydrodynamic load capacity of plane slider and journal bearings were calculated for various design data. The effects of attitude and roughness of surface on the bearing performance were shown. The results are compared with similar available solution of rough surface bearings. It is shown that: (1) the contribution of contact load is not significant; and (2) the hydrodynamic and contact load increase with surface roughness.

  16. Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A₂ myotoxins--distinct mechanisms of action.

    Science.gov (United States)

    Fernández, Julián; Caccin, Paola; Koster, Grielof; Lomonte, Bruno; Gutiérrez, José M; Montecucco, Cesare; Postle, Anthony D

    2013-08-01

    Bothrops snakes are the major cause of ophidian envenomings in Latin America. Their venom contains myotoxins that cause prominent muscle damage, which may lead to permanent disability. These toxins include myotoxins Mt-I and Mt-II, which share the phospholipase A₂ (PLA₂) fold, but Mt-II lacks enzymatic activity because the essential active site Asp49 is replaced by Lys. Both myotoxins cause sarcolemma alterations, with Ca²⁺ entry and loss of ATP and K⁺ from muscle cells, but the molecular lesions at the basis of their cellular action are not known, particularly the role of phospholipid hydrolysis. Here we tested their PLA₂ activity in vivo, and evaluated the hypothesis that Ca²⁺-activated endogenous PLA₂s may be involved in the action of Mt-II. The time course of phospholipid hydrolysis by Mt-I and Mt-II in myotubes in culture and in tibialis anterior mouse muscles was determined. Mt-I rapidly hydrolyzed phosphatidylcholine and phosphatidylethanolamine but not phosphatidylserine, but no phospho-lipids were hydrolyzed in the presence of Mt-II. Whole Bothrops asper venom induced a higher extent of phospholipid hydrolysis than Mt-I alone. These results demonstrate in vivo PLA₂ activity of Mt-I for the first time, and indicate that it acts only on the external monolayer of the sarcolemma. They also exclude activation of endogenous PLA₂s in the action of Mt-II, implying that plasma membrane disruption by this toxin does not depend on phospholipid hydrolysis. Therefore, both Bothrops myotoxins induce Ca²⁺ entry and release of ATP and cause myonecrosis, but through different biochemical mechanisms. © 2013 FEBS.

  17. N-terminal domain of Bothrops asper Myotoxin II Enhances the Activity of Endothelin Converting Enzyme-1 and Neprilysin.

    Science.gov (United States)

    Smith, A Ian; Rajapakse, Niwanthi W; Kleifeld, Oded; Lomonte, Bruno; Sikanyika, Nkumbu L; Spicer, Alexander J; Hodgson, Wayne C; Conroy, Paul J; Small, David H; Kaye, David M; Parkington, Helena C; Whisstock, James C; Kuruppu, Sanjaya

    2016-03-02

    Neprilysin (NEP) and endothelin converting enzyme-1 (ECE-1) are two enzymes that degrade amyloid beta in the brain. Currently there are no molecules to stimulate the activity of these enzymes. Here we report, the discovery and characterisation of a peptide referred to as K49-P1-20, from the venom of Bothrops asper which directly enhances the activity of both ECE-1 and NEP. This is evidenced by a 2- and 5-fold increase in the Vmax of ECE-1 and NEP respectively. The K49-P1-20 concentration required to achieve 50% of maximal stimulation (AC50) of ECE-1 and NEP was 1.92 ± 0.07 and 1.33 ± 0.12 μM respectively. Using BLITZ biolayer interferometry we have shown that K49-P1-20 interacts directly with each enzyme. Intrinsic fluorescence of the enzymes change in the presence of K49-P1-20 suggesting a change in conformation. ECE-1 mediated reduction in the level of endogenous soluble amyloid beta 42 in cerebrospinal fluid is significantly higher in the presence of K49-P1-20 (31 ± 4% of initial) compared with enzyme alone (11 ± 5% of initial; N = 8, P = 0.005, unpaired t-test). K49-P1-20 could be an excellent research tool to study mechanism(s) of enzyme stimulation, and a potential novel drug lead in the fight against Alzheimer's disease.

  18. Efecto inhibitorio de extractos de Renealmia alpinia Rottb. Maas (Zingiberaceae sobre el veneno de Bothrops asper (mapaná

    Directory of Open Access Journals (Sweden)

    Arley Camilo Patiño

    2012-03-01

    Full Text Available Introducción. La medicina tradicional es una invaluable fuente de investigación de nuevos remedioscomo complemento para el tratamiento del accidente ofídico, considerado como un grave problema desalud pública a nivel mundial. Objetivo. Este trabajo de investigación pretende comprobar la capacidad de neutralizar los efectoshemorrágicos, coagulantes y proteolíticos, de los extractos de hojas de Renealmia alpinia, usadatradicionalmente por los indígenas del Chocó (Colombia contra la mordedura de la serpiente Bothropsasper, causante de la gran mayoría de los accidentes ofídicos en nuestro país. Materiales y métodos. Se llevaron a cabo ensayos de toxicidad aguda y de actividad analgésica in vivo de R. alpinia. Además, se hicieron ensayos in vitro sobre inhibición de las actividades coagulante,hemolítica y proteolítica del veneno de Resultados. El presente estudio demuestra que R. alpinia no produce efectos tóxicos en animales deexperimentación; además, presenta efectos analgésicos in vivo y antiofídicos in vitro, y protege contralos efectos letales del veneno de B. asper, in vivo. Conclusión. Renealmia alpinia puede ser una buena alternativa terapéutica como complemento altratamiento con antiveneno en el accidente ofídico, por sus efectos analgésicos y antiofídicos. doi: http://dx.doi.org/10.7705/biomedica.v32i3.591

  19. Isolation of an acidic phospholipase A2 from the venom of the snake Bothrops asper of Costa Rica: biochemical and toxicological characterization.

    Science.gov (United States)

    Fernández, Julián; Gutiérrez, José María; Angulo, Yamileth; Sanz, Libia; Juárez, Paula; Calvete, Juan J; Lomonte, Bruno

    2010-03-01

    Phospholipases A(2) (PLA(2)) are major components of snake venoms, exerting a variety of relevant toxic actions such as neurotoxicity and myotoxicity, among others. Since the majority of toxic PLA(2)s are basic proteins, acidic isoforms and their possible roles in venoms are less understood. In this study, an acidic enzyme (BaspPLA(2)-II) was isolated from the venom of Bothrops asper (Pacific region of Costa Rica) and characterized. BaspPLA(2)-II is monomeric, with a mass of 14,212 +/- 6 Da and a pI of 4.9. Its complete sequence of 124 amino acids was deduced through cDNA and protein sequencing, showing that it belongs to the Asp49 group of catalytically active enzymes. In vivo and in vitro assays demonstrated that BaspPLA(2)-II, in contrast to the basic Asp49 counterparts present in the same venom, lacks myotoxic, cytotoxic, and anticoagulant activities. BaspPLA(2)-II also differed from other acidic PLA(2)s described in Bothrops spp. venoms, as it did not show hypotensive and anti-platelet aggregation activities. Furthermore, this enzyme was not lethal to mice at intravenous doses up to 100 microg (5.9 microg/g), indicating its lack of neurotoxic activity. The only toxic effect recorded in vivo was a moderate induction of local edema. Therefore, the toxicological characteristics of BaspPLA(2)-II suggest that it does not play a key role in the pathophysiology of envenomings by B. asper, and that its purpose might be restricted to digestive functions. Immunochemical analyses using antibodies raised against BaspPLA(2)-II revealed that acidic and basic PLA(2)s form two different antigenic groups in B. asper venom. Copyright (c) 2009 Elsevier Masson SAS. All rights reserved.

  20. A correlation between micro- and nano-indentation on materials irradiated by high-energy heavy ions

    Science.gov (United States)

    Yang, Yitao; Zhang, Chonghong; Ding, Zhaonan; Su, Changhao; Yan, Tingxing; Song, Yin; Cheng, Yuguang

    2018-01-01

    Hardness testing is an efficient means of assessing the mechanical properties of materials due to the small sampling volume requirement. Previous studies have established the correlation between flow stress and Vickers hardness. However, the damage layer produced by ions irradiation with low energy is too thin to perform Vickers hardness test, which is usually measured by nano-indentation. Therefore, it is necessary to correlate the Vickers hardness and nano-hardness for the convenience of assessing mechanical properties of materials under irradiation. In this study, various materials (pure nickel, nickel base alloys and oxide dispersion strengthened steel) were irradiated with high-energy heavy ions to different damage levels. After irradiation, micro- and nano-indentation were performed to characterize the change in hardness. Due to indentation size effect (ISE), the hardness was dependent of load or depth. Therefore, Nix-Gao model was used to obtain the hardness without ISE (Hv0 and Hnano_0). The determined Hv0 was plotted as a function of the corresponding Hnano_0, then a good linear relation was found between Vickers hardness and nano-hardness, and a coefficient was determined to be 81.0 ± 10.5, namely, Hv 0 = 81.0Hnano _ 0 (Hv0 with unit of kgf/mm2, Hnano_0 with unit of GPa). This correlation was based on the data from various materials, therefore it was independent of materials. Based on the established correlation and nano-indentation results, the change fraction in yield stress of Inconel 718 and pure Ni with ion irradiation was compared with that with neutron irradiation. The data of Inconel 718 with heavy ion irradiation was in good agreement with the data with neutron irradiation, which was a good demonstration for the validation of the established correlation. However, a distinctive difference in change fraction of yield stress was seen for pure Ni under heavy ion irradiation and neutron irradiation, which was attributed to the difference in samples

  1. Evolution and environmental degradation of superhydrophobic aspen and black locust leaf surfaces

    Science.gov (United States)

    Tranquada, George Christopher

    The current study is focused on the characterization of four natural leaf species (quaking, bigtooth and columnar european aspen as well as black locust) possessing a unique dual-scale cuticle structure composed of micro- and nano-scale asperities, which are able to effectively resist wetting (superhydrophobic), characteristic of The Lotus Effect. Scanning Electron Microscopy (SEM) was used to track the growth and evolution of their distinctive nano-scale epicuticular wax (ECW) morphologies over one full growing season. In addition, the stability of their superhydrophobic property was tested in various environments. It was determined that the long-term stability of these surfaces is tentatively linked to various environmental stress factors. Specifically, a combination of high temperature and humidity caused the degradation of nanoscale asperities and loss of the superhydrophobic property. The dual-scale surface structure was found to provide a suitable template for the design of future superhydrophobic engineering materials.

  2. Crystallization and preliminary X-ray diffraction analysis of suramin, a highly charged polysulfonated napthylurea, complexed with a myotoxic PLA2 from Bothrops asper venom.

    Science.gov (United States)

    Murakami, Mário T; Gava, Lisandra M; Zela, Sandro P; Arruda, Emerson Z; Melo, Paulo A; Gutierrez, José M; Arni, Raghuvir K

    2004-12-01

    Suramin is a highly charged polysulfonated napthylurea that interferes in a number of physiologically relevant processes such as myotoxicity, blood coagulation and several kinds of cancers. This synthetic compound was complexed with a myotoxic Lys49 PLA(2) from Bothrops asper venom and crystallized by the hanging-drop vapor diffusion method at 18 degrees C. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit cell parameters a=49.05, b=63.84 and c=85.67 angstroms. Diffraction data was collected to 1.78 angstroms.

  3. Biochemical Characterization, Action on Macrophages, and Superoxide Anion Production of Four Basic Phospholipases A 2 from Panamanian Bothrops asper Snake Venom

    OpenAIRE

    Rueda, Aristides Quintero; Rodr?guez, Isela Gonz?lez; Arantes, Eliane C.; Set?bal, Sulamita S.; Calderon, Leonardo de A.; Zuliani, Juliana P.; St?beli, Rodrigo G.; Soares, Andreimar M.

    2012-01-01

    Bothrops asper (Squamata: Viperidae) is the most important venomous snake in Central America, being responsible for the majority of snakebite accidents. Four basic PLA2s (pMTX-I to -IV) were purified from crude venom by a single-step chromatography using a CM-Sepharose ion-exchange column (1.5 × 15 cm). Analysis of the N-terminal sequence demonstrated that pMTX-I and III belong to the catalytically active Asp49 phospholipase A2 subclass, whereas pMTX-II and IV belong to the enzymatically inac...

  4. Material, Mechanical, and Tribological Characterization of Laser-Treated Surfaces

    Science.gov (United States)

    Yilbas, Bekir Sami; Kumar, Aditya; Bhushan, Bharat; Aleem, B. J. Abdul

    2014-10-01

    Laser treatment under nitrogen assisting gas environment of cobalt-nickel-chromium-tungsten-based superalloy and high-velocity oxygen-fuel thermal spray coating of nickel-chromium-based superalloy on carbon steel was carried out to improve mechanical and tribological properties. Superalloy surface was preprepared to include B4C particles at the surface prior to the laser treatment process. Material and morphological changes in the laser-treated samples were examined using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction (XRD) analysis. Residual stresses present at the surface region of the laser-treated layer were determined from the XRD data. The microhardness of the laser-treated surface was measured by indentation tests. Fracture toughness of the coating surfaces before and after laser treatment were also measured using overload indentation tests. Macrowear and macrofriction characterization were carried out using pin-on-disk tests.

  5. Effects of Mn addition on the microstructure and indentation creep behavior of the hot dip Zn coating

    International Nuclear Information System (INIS)

    Wang, Youbin; Zeng, Jianmin

    2015-01-01

    Highlights: • Mn addition could significantly refine the grain of the Zn coating. • Twins could be observed in the Zn coatings. • The stress exponent of the Zn coating increases with Mn addition. • The creep process of the Zn coating is dominated by dislocation climb and twins. - Abstract: The Zn coatings with different Mn additions were prepared by hot dip process, and the effects of the Mn addition on the microstructure and indentation creep behavior of the coatings were investigated through scanning electron microscope and constant-load holding indentation technique at the room temperature. Some twins can be observed in the microstructure of Zn coating, which may account for the formation of the large thermal misfit stress between the zinc coating and the steel substrate. The amount of twin microstructure in the Zn coating decreases with the Mn addition. It is also found that Mn addition could induce MnZn 13 phases to precipitate along the grain boundary and significantly refine the grains of Zn coatings. The steady-state stress of the Zn coating could be improved by Mn addition. The creep stress exponent values are in the range of 14–46 and increases with Mn addition. The creep process of the Zn coating is dominated by dislocation climb and twin formation

  6. Change detection technique for muscle tone during static stretching by continuous muscle viscoelasticity monitoring using wearable indentation tester.

    Science.gov (United States)

    Okamura, Naomi; Kobayashi, Yo; Sugano, Shigeki; Fujie, Masakatsu G

    2017-07-01

    Static stretching is widely performed to decrease muscle tone as a part of rehabilitation protocols. Finding out the optimal duration of static stretching is important to minimize the time required for rehabilitation therapy and it would be helpful for maintaining the patient's motivation towards daily rehabilitation tasks. Several studies have been conducted for the evaluation of static stretching; however, the recommended duration of static stretching varies widely between 15-30 s in general, because the traditional methods for the assessment of muscle tone do not monitor the continuous change in the target muscle's state. We have developed a method to monitor the viscoelasticity of one muscle continuously during static stretching, using a wearable indentation tester. In this study, we investigated a suitable signal processing method to detect the time required to change the muscle tone, utilizing the data collected using a wearable indentation tester. By calculating a viscoelastic index with a certain time window, we confirmed that the stretching duration required to bring about a decrease in muscle tone could be obtained with an accuracy in the order of 1 s.

  7. Time-dependent adhesion of a polydimethylsiloxane (PDMS) elastomer film to a flat indenter tip characterized using a cohesive-zone law

    Science.gov (United States)

    Trong Mai, Nghia; Choi, Seung Tae; Chung, Koo-Hyun; Ryoon Lee, Seung; Shin, Dong Kil; Earmme, Youn Young

    2014-04-01

    The work of adhesion between a polydimethylsiloxane (PDMS) elastomer film and a flat diamond tip was measured by instrumented indentation. The results showed that the apparent work of adhesion between the tip and the PDMS film increases with increasing dwell time and retreating velocity; on the other hand, the indentation depth has no significant effect on adhesion. The indentation experiment was analysed with viscoelastic finite element simulations with rate-dependent cohesive elements, from which the time evolution of adhesion was quantitatively implemented into a rate-dependent cohesive-zone law. This article was originally published with errors. This version has been corrected. Please see Erratum (http://dx.doi.org/10.1080/09500839.2014.909179).

  8. Blister formation and skin damage induced by BaP1, a haemorrhagic metalloproteinase from the venom of the snake Bothrops asper.

    Science.gov (United States)

    Rucavado, A; Núñez, J; Gutiérrez, J M

    1998-01-01

    Blister formation and skin damage can be induced by BaP1, a haemorrhagic metalloproteinase from the venom of the snake Bothrops asper. Pathological changes in the skin were investigated after intramuscular injections of Bothrops asper haemorrhagic metalloproteinase BaP1. Blisters developed within the first hour, with separation of epidermis from the dermal-epidermal junction, whereas acantholysis of epithelial cells was not observed. After the third hour there was ulceration with formation of a proteinaceous scab and inflammatory infiltrate. By 7 to 14 days there was evidence of a regenerative process in dermis and epidermis. Haemorrhage occurred in both dermis and hypodermis as a consequence of BaP1 injection, together with damage of sebaceous glands and an inflammatory reaction in which enlarged macrophages were the predominant cell type. Zymography assays showed the presence of several endogenous metalloproteinases in the exudate, skin homogenates and plasma. In addition, BaP1 was detected in exudates and plasma by immunoblotting. This technique also demonstrated the presence of components immunologically related to laminin and collagen type IV in exudates. It is suggested that BaP1, and probably endogenous matrix metalloproteinases, degrade some protein components at the dermal-epidermal junction, inducing the formation of blisters. PMID:9797720

  9. Comparative study of the efficacy and safety of two polyvalent, caprylic acid fractionated [IgG and F(ab')2] antivenoms, in Bothrops asper bites in Colombia.

    Science.gov (United States)

    Otero-Patiño, Rafael; Segura, Alvaro; Herrera, María; Angulo, Yamileth; León, Guillermo; Gutiérrez, José María; Barona, Jacqueline; Estrada, Sebastián; Pereañez, Andrés; Quintana, Juan Carlos; Vargas, Leidy J; Gómez, Juan Pablo; Díaz, Abel; Suárez, Ana María; Fernández, Jorge; Ramírez, Patricia; Fabra, Patricia; Perea, Monica; Fernández, Diego; Arroyo, Yobana; Betancur, Dalila; Pupo, Lady; Córdoba, Elkin A; Ramírez, C Eugenio; Arrieta, Ana Berta; Rivero, Alcides; Mosquera, Diana Carolina; Conrado, Nectty Lorena; Ortiz, Rosina

    2012-02-01

    The efficacy and safety of two polyvalent horse-derived antivenoms in Bothrops asper envenomings were tested in a randomized, double-blind, clinical trial performed in Colombia. Both antivenoms were manufactured from the same pool of hyperimmune plasma. Antivenom A was made of F(ab')2 fragments, generated by pepsin digestion and caprylic acid precipitation, whereas antivenom B consisted of whole IgG molecules produced by caprylic acid precipitation followed by ion-exchange chromatography. Besides the different nature of the active substance, antivenom B had higher protein concentration, slightly higher turbidity and aggregate content. No significant differences were observed in the efficacy of antivenoms. Both halted local and systemic bleeding (P = 0.40) within 6-12 h of treatment in 100% of the cases, and restored blood coagulation (P = 0.87) within 6-24 h in 84.7% of patients, and within 48 h in all of them, in agreement with restoration of plasma fibrinogen concentration. Venom concentrations in serum dropped significantly (P asper envenomings in Colombia. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. Thrombocytopenia and platelet hypoaggregation induced by Bothrops asper snake venom. Toxins involved and their contribution to metalloproteinase-induced pulmonary hemorrhage.

    Science.gov (United States)

    Rucavado, Alexandra; Soto, Mónica; Escalante, Teresa; Loría, Gilbert D; Arni, Raghuvir; Gutiérrez, José María

    2005-07-01

    Thrombocytopenia and platelet dysfunction occur in patients bitten by Bothrops sp snakes in Latin America. An experimental model was developed in mice to study the effects of B. asper venom in platelet numbers and function. Intravenous administration of this venom induces rapid and prominent thrombocytopenia and ex vivo platelet hypoaggregation. The drop in platelet numbers was primarily due to aspercetin, a protein of the C-type lectin family which induces von Willebrand factor-mediated platelet aggregation/agglutination. In addition, the effect of class P-III hemorrhagic metalloproteinases on the microvessel wall also contributes to thrombocytopenia since jararhagin, a P-III metalloproteinase, reduced platelet counts. Hypoaggregation was associated with the action of procoagulant and defibrin(ogen)ating proteinases jararacussin-I (a thrombin-like serine proteinase) and basparin A (a prothrombin activating metalloproteinase). At the doses which induced hypoaggregation, these enzymes caused defibrin(ogen)ation, increments in fibrin(ogen) degradation products and D-dimer and prolongation of the bleeding time. Incubation of B. asper venom with batimastat and alpha2-macroglobulin abrogated the hypoaggregating activity, confirming the role of venom proteinases in this effect. Neither aspercetin nor the defibrin(ogen)ating and hypoaggregating components induced hemorrhage upon intravenous injection. However, aspercetin, but not the thrombin-like or the prothrombin-activating proteinases, potentiated the hemorrhagic activity of two hemorrhagic metalloproteinases in the lungs.

  11. Extracts of Renealmia alpinia (Rottb.) MAAS Protect against Lethality and Systemic Hemorrhage Induced by Bothrops asper Venom: Insights from a Model with Extract Administration before Venom Injection.

    Science.gov (United States)

    Patiño, Arley Camilo; Quintana, Juan Carlos; Gutiérrez, José María; Rucavado, Alexandra; Benjumea, Dora María; Pereañez, Jaime Andrés

    2015-04-30

    Renealmia alpinia (Rottb.) MAAS, obtained by micropropagation (in vitro) and wild forms have previously been shown to inhibit some toxic activities of Bothrops asper snake venom if preincubated before injection. In this study, assays were performed in a murine model in which extracts were administered for three days before venom injection. R. alpinia extracts inhibited lethal activity of B. asper venom injected by intraperitoneal route. Median Effective Dose (ED50) values were 36.6 ± 3.2 mg/kg and 31.7 ± 5.4 mg/kg (p > 0.05) for R. alpinia wild and in vitro extracts, respectively. At a dose of 75 mg/kg, both extracts totally inhibited the lethal activity of the venom. Moreover, this dose prolonged survival time of mice receiving a lethal dose of venom by the intravenous route. At 75 mg/kg, both extracts of R. alpinia reduced the extent of venom-induced pulmonary hemorrhage by 48.0% (in vitro extract) and 34.7% (wild extract), in agreement with histological observations of lung tissue. R. alpinia extracts also inhibited hemorrhage in heart and kidneys, as evidenced by a decrease in mg of hemoglobin/g of organ. These results suggest the possibility of using R. alpinia as a prophylactic agent in snakebite, a hypothesis that needs to be further explored.

  12. Extracts of Renealmia alpinia (Rottb. MAAS Protect against Lethality and Systemic Hemorrhage Induced by Bothrops asper Venom: Insights from a Model with Extract Administration before Venom Injection

    Directory of Open Access Journals (Sweden)

    Arley Camilo Patiño

    2015-04-01

    Full Text Available Renealmia alpinia (Rottb. MAAS, obtained by micropropagation (in vitro and wild forms have previously been shown to inhibit some toxic activities of Bothrops asper snake venom if preincubated before injection. In this study, assays were performed in a murine model in which extracts were administered for three days before venom injection. R. alpinia extracts inhibited lethal activity of B. asper venom injected by intraperitoneal route. Median Effective Dose (ED50 values were 36.6 ± 3.2 mg/kg and 31.7 ± 5.4 mg/kg (p > 0.05 for R. alpinia wild and in vitro extracts, respectively. At a dose of 75 mg/kg, both extracts totally inhibited the lethal activity of the venom. Moreover, this dose prolonged survival time of mice receiving a lethal dose of venom by the intravenous route. At 75 mg/kg, both extracts of R. alpinia reduced the extent of venom-induced pulmonary hemorrhage by 48.0% (in vitro extract and 34.7% (wild extract, in agreement with histological observations of lung tissue. R. alpinia extracts also inhibited hemorrhage in heart and kidneys, as evidenced by a decrease in mg of hemoglobin/g of organ. These results suggest the possibility of using R. alpinia as a prophylactic agent in snakebite, a hypothesis that needs to be further explored.

  13. Early Afterslip of the 2015 Mw8.2 Illapel, Chile Megathrust Earthquake: Overlapping Slip Regions Challenge the Fixed Asperity Model

    Science.gov (United States)

    Barnhart, W. D.; Murray, J. R.; Briggs, R. W.; Gomez, F. G.; Miles, C.; Svarc, J. L.; Riquelme, S.; Stressler, B.

    2016-12-01

    Great subduction earthquakes are thought to rupture portions of the megathrust where interseismic coupling is high and velocity-weakening frictional behavior is dominant, releasing elastic deformation accrued over a seismic cycle. Conversely, post-seismic afterslip is often assumed to occur primarily in regions of velocity-strengthening frictional characteristics that may correlate with lower interseismic coupling. However, it remains unclear if fixed frictional properties of the subduction interface, co-seismic or aftershock-induced stress redistribution, or other factors control the spatial distribution of afterslip. We use InSAR and GPS observations to map the distribution of co-seismic slip of the 2015 Mw 8.3 Illapel, Chile earthquake and afterslip within the first 38 days following the earthquake. We find that afterslip overlaps the co-seismic slip area and propagates along-strike into regions inferred by other studies to be of high or moderate interseismic coupling. A simple partitioning of the subduction interface into regions of fixed frictional properties, or asperities, cannot reconcile our geodetic observations. Instead, stress heterogeneities, either pre-existing or induced by the earthquake, likely provide the primary control on the afterslip distribution for this subduction zone earthquake. These results contribute to a growing body of evidence that some megathrust faults are not characterized by spatially or temporally fixed asperities; rather, velocity weakening zones conducive to seismogenic rupture may migrate and change characteristics within the time spans of a single co-seismic/post-seismic earthquake sequence.

  14. Roughness analysis of graphite surfaces of casting elements

    Directory of Open Access Journals (Sweden)

    M. Wieczorowski

    2010-01-01

    Full Text Available In the paper profilometric measurements of graphite casting elements were described. Basic topics necessary to assess roughness of their surfaces and influence of asperities on various properties related to manufacturing and use were discussed. Stylus profilometer technique of surface irregularities measurements including its limits resulting from pickup geometry and its contact with measured object were ana-lyzed. Working principle of tactile profilometer and phenomena taking place during movement of a probe on a measured surface were shown. One of the important aspects is a flight phenomenon, which means movement of a pickup without contact with a surface during inspection resulting from too high scanning speed. results of comparison research for graphite elements of new and used mould and pin composing a set were presented. Using some surface roughness, waviness and primary profile parameters (arithmetical mean of roughness profile heights Ra, biggest roughness profile height Rz, maximum primary profile height Pt as well as maximum waviness profile height Wt a possibility of using surface asperities parameters as a measure of wear of chill graphite elements was proved. The most often applied parameter is Ra, but with a help of parameters from W and P family it was shown, that big changes occur not only for roughness but also for other components of surface irregularities.

  15. Crystal structure of a phospholipase A2from Bothrops asper venom: Insights into a new putative "myotoxic cluster".

    Science.gov (United States)

    Salvador, Guilherme H M; Dos Santos, Juliana I; Lomonte, Bruno; Fontes, Marcos R M

    2017-02-01

    Snake venoms from the Viperidae and Elapidae families often have several phospholipases A 2 (PLA 2 s), which may display different functions despite having a similar structural scaffold. These proteins are considered an important target for the development of drugs against local myotoxic damage because they are not efficiently neutralized by conventional serum therapy. PLA 2 s from these venoms are generally divided into two classes: (i) catalytic PLA 2 s (or Asp49-PLA 2 s) and (ii) non-catalytic PLA 2 -like toxins (or Lys49-PLA 2 s). In many Viperidae venoms, a subset of the basic Asp49-PLA 2 s displays some functional and structural characteristics of PLA 2 -like proteins and group within the same phylogenetic clade, but their myotoxic mechanism is still largely unknown. In the present study, we have crystallized and solved the structure of myotoxin I (MT-I), a basic myotoxic Asp49-PLA 2 isolated from Bothrops asper venom. The structure presents a dimeric conformation that is compatible with that of previous dimers found for basic myotoxic Asp49-PLA 2 s and Lys49-PLA 2 s and has been confirmed by other biophysical and bioinformatics techniques. This arrangement suggests a possible cooperative action between both monomers to exert myotoxicity via two different sites forming a putative membrane-docking site (MDoS) and a putative membrane disruption site (MDiS). This mechanism would resemble that proposed for Lys49-PLA 2 s, but the sites involved appear to be situated in a different region. Thus, as both sites are close to one another, they form a "myotoxic cluster", which is also found in two other basic myotoxic Asp49-PLA 2 s from Viperidae venoms. Such arrangement may represent a novel structural strategy for the mechanism of muscle damage exerted by the group of basic, Asp49-PLA 2 s found in viperid snake venoms. Copyright © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  16. Comparison of several innovative bridge cable surface modifications

    DEFF Research Database (Denmark)

    Kleissl, Kenneth; Georgakis, Christos T.

    Over the last two decades, several bridge cable manufacturers have introduced surface modifications on the high-density polyethylene (HDPE) sheathing that is installed for the protection of inner cable strands or wires. The modifications are based on research undertaken predominantly in Europe...... and Japan, with two different prevailing systems: HDPE tubing fitted with helical fillets and tubing with pattern-indented surfaces. In the US and Europe, helical fillets dominate, whilst pattern indented sur-faces are more common in Asia, particularly for long-span cable-stayed bridges. Research......-span bridges can now produce more than 50% of the overall horizontal load on the bridge (Gimsing and Georgakis, 2012). Recently, the authors presented a comprehensive comparative study of the aerodynamic performance of these existing cable surface modifications (Kleissl and Georgakis, 2011, 2012...

  17. West-directed thrusting south of the eastern Himalayan syntaxis indicates clockwise crustal flow at the indenter corner during the India-Asia collision

    Science.gov (United States)

    Haproff, Peter J.; Zuza, Andrew V.; Yin, An

    2018-01-01

    Whether continental deformation is accommodated by microplate motion or continuum flow is a central issue regarding the nature of Cenozoic deformation surrounding the eastern Himalayan syntaxis. The microplate model predicts southeastward extrusion of rigid blocks along widely-spaced strike-slip faults, whereas the crustal-flow model requires clockwise crustal rotation along closely-spaced, semi-circular right-slip faults around the eastern Himalayan syntaxis. Although global positioning system (GPS) data support the crustal-flow model, the surface velocity field provides no information on the evolution of the India-Asia orogenic system at million-year scales. In this work, we present the results of systematic geologic mapping across the northernmost segment of the Indo-Burma Ranges, located directly southeast of the eastern Himalayan syntaxis. Early research inferred the area to have experienced either right-slip faulting accommodating northward indentation of India or thrusting due to the eastward continuation of the Himalayan orogen in the Cenozoic. Our mapping supports the presence of dip-slip thrust faults, rather than strike-slip faults. Specifically, the northern Indo-Burma Ranges exposes south- to west-directed ductile thrust shear zones in the hinterland and brittle fault zones in the foreland. The trends of ductile stretching lineations within thrust shear zones and thrust sheets rotate clockwise from the northeast direction in the northern part of the study area to the east direction in the southern part of the study area. This clockwise deflection pattern of lineations around the eastern Himalayan syntaxis mirrors the clockwise crustal-rotation pattern as suggested by the crustal-flow model and contemporary GPS velocity field. However, our finding is inconsistent with discrete strike-slip deformation in the area and the microplate model.

  18. Comparison of the effect of Crotalus simus and Crotalus durissus ruruima venoms on the equine antibody response towards Bothrops asper venom: implications for the production of polyspecific snake antivenoms.

    Science.gov (United States)

    Dos-Santos, Maria Cristina; Arroyo, Cynthia; Solano, Sergio; Herrera, María; Villalta, Mauren; Segura, Alvaro; Estrada, Ricardo; Gutiérrez, José María; León, Guillermo

    2011-02-01

    Antivenoms are preparations of immunoglobulins purified from the plasma of animals immunized with snake venoms. Depending on the number of venoms used during the immunization, antivenoms can be monospecific (if venom from a single species is used) or polyspecific (if venoms from several species are used). In turn, polyspecific antivenoms can be prepared by purifying antibodies from the plasma of animals immunized with a mixture of venoms, or by mixing antibodies purified from the plasma of animals immunized separately with single venom. The suitability of these strategies to produce polyspecific antibothropic-crotalic antivenoms was assessed using as models the venoms of Bothrops asper, Crotalus simus and Crotalus durissus ruruima. It was demonstrated that, when used as co-immunogen, C. simus and C. durissus ruruima venoms exert a deleterious effect on the antibody response towards different components of B. asper venom and in the neutralization of hemorrhagic and coagulant effect of this venom when compared with a monospecific B. asper antivenom. Polyspecific antivenoms produced by purifying immunoglobulins from the plasma of animals immunized with venom mixtures showed higher antibody titers and neutralizing capacity than those produced by mixing antibodies purified from the plasma of animals immunized separately with single venom. Thus, despite the deleterious effect of Crotalus sp venoms on the immune response against B. asper venom, the use of venom mixtures is more effective than the immunization with separate venoms for the preparation of polyspecific bothropic-crotalic antivenoms. Copyright © 2010 Elsevier Ltd. All rights reserved.

  19. Structural imprints at the front of the Chocó-Panamá indenter: Field data from the North Cauca Valley Basin, Central Colombia

    Science.gov (United States)

    Suter, F.; Sartori, M.; Neuwerth, R.; Gorin, G.

    2008-11-01

    synthetic and antithetic Riedels and is (sub)-perpendicular to the active Romeral Fault System. It is proposed that the continued movement of the Chocó-Panamá Indenter may be responsible for the 060-oriented right-lateral distributed shear strain, and may have closed the northern part of the Cauca Valley, thereby forming the Cauca Valley Basin. Conjugate extensional faults observed at surface in the flat-lying sediments of the Zarzal Formation and Quindío-Risaralda volcaniclastic Fan are associatedwith soft-sediment deformations. These faults are attributed to lateral spreading of the superficial layers during earthquakes and testify to the continuous tectonic activity from Pleistocene to Present. Finally, results presented here bring newinformation about the understanding of the seismic hazard in this area: whereas the Romeral Fault Systemwas so far thought to be themost likely source of earthquakes, themore recent cross-cutting fault systems described herein are another potential hazard to be considered.

  20. Mechanical Anisotropy and Pressure Induced Structural Changes in Piroxicam Crystals Probed by In Situ Indentation and Raman Spectroscopy

    Science.gov (United States)

    Manimunda, Praveena; Hintsala, Eric; Asif, Syed; Mishra, Manish Kumar

    2017-01-01

    The ability to correlate mechanical and chemical characterization techniques in real time is both lacking and powerful tool for gaining insights into material behavior. This is demonstrated through use of a novel nanoindentation device equipped with Raman spectroscopy to explore the deformation-induced structural changes in piroxicam crystals. Mechanical anisotropy was observed in two major faces ( 0bar{1}1 ) and (011), which are correlated to changes in the interlayer interaction from in situ Raman spectra recorded during indentation. The results of this study demonstrate the considerable potential of an in situ Raman nanoindentation instrument for studying a variety of topics, including stress-induced phase transformation mechanisms, mechanochemistry, and solid state reactivity under mechanical forces that occur in molecular and pharmaceutical solids.

  1. Indenter portable equipment. Measurement of the recovery time for the non-destructive power cable ageing evaluation

    International Nuclear Information System (INIS)

    Dinu, E.; Cepisca, C.; Puiu, D.; Gyongyosi, T.; Corbescu, B.; Deloreanu, G.

    2016-01-01

    Have been sampled 5 cable sections with 4 m long, HXH FE 180 E90; 3x 25 mm type. Samples have been thermal accelerating aged (by Loule Lenz effect); the equivalent operation time in NPP being of 0, 10, 20, 30 and 40 years. The recovery time (TR) is an indicator of the viscoelastic properties of the material. This parameter has been shown to be very sensitive to degradation resulting from thermal ageing and/or irradiation for a variety of materials tested to date (PVC, XLPE, EPR and CSPE). TR increase with insulation material degradation. The TR measurement has been incorporated into a recently developed portable indenter. Therefore, this technique can be used for on-site measurements. The results are useful to identify, model and manage the power cable material ageing phenomenon in the NPP. (authors)

  2. Evaluation of degradation due to ageing of the power cables with pvc insulation and jacket. Development of the indentation test

    International Nuclear Information System (INIS)

    Puiu, D.; Gyongyosi, T.; Dinu, E.

    2010-01-01

    The environmental conditions (temperature, radiation) from NPP lead to the ageing of the organic components of the power cable. The effective evaluation of the degradation due to ageing of the cable components, at the observation time, requires knowledge of some electrical and mechanical parameters, useful to characterize the cable condition. In order to develop a non-destructive method for evaluation of degradation due to ageing of the NPP power cables, an experimental device was made able to establish the compressive modulus in power cable components (jacket and insulation). The paper contains a description of the experimental device (indentation device), the working method for determination the compressive modulus values, results and conclusions. The paper presents original contributions in the development of the non-destructive method and of its application area being dedicated to the specialists working in research and technological engineering. (authors)

  3. Load and depth sensing indentation as a tool to monitor a gradient in the mechanical properties across a polymer coating: A study of physical and chemical aging effects

    NARCIS (Netherlands)

    Boersma, A.; Soloukhin, V.A.; Brokken-Zijp, J.C.M.; With, G. de

    2004-01-01

    Load and depth sensing indentation has been used to characterize the elastic modulus and hardness of various polycarbonate films. This analytical technique is shown to be extremely suitable for the determination of gradients in these mechanical properties. Furthermore, it is demonstrated that such a

  4. Lower nanometer-scale size limit for the deformation of a metallic glass by shear transformations revealed by quantitative AFM indentation

    Directory of Open Access Journals (Sweden)

    Arnaud Caron

    2015-08-01

    Full Text Available We combine non-contact atomic force microscopy (AFM imaging and AFM indentation in ultra-high vacuum to quantitatively and reproducibly determine the hardness and deformation mechanisms of Pt(111 and a Pt57.5Cu14.7Ni5.3P22.5 metallic glass with unprecedented spatial resolution. Our results on plastic deformation mechanisms of crystalline Pt(111 are consistent with the discrete mechanisms established for larger scales: Plasticity is mediated by dislocation gliding and no rate dependence is observed. For the metallic glass we have discovered that plastic deformation at the nanometer scale is not discrete but continuous and localized around the indenter, and does not exhibit rate dependence. This contrasts with the observation of serrated, rate-dependent flow of metallic glasses at larger scales. Our results reveal a lower size limit for metallic glasses below which shear transformation mechanisms are not activated by indentation. In the case of metallic glass, we conclude that the energy stored in the stressed volume during nanometer-scale indentation is insufficient to account for the interfacial energy of a shear band in the glassy matrix.

  5. Atrito e desgaste de recobrimentos de PET, politeraftalato de etileno, pós-consumo processados por aspersão térmica Friction and wear of a thermal sprayed PET - poly(ethylene teraphthalate coating

    Directory of Open Access Journals (Sweden)

    Rogério A. X. Nunes

    2007-09-01

    Full Text Available A aspersão térmica envolve processos de recobrimentos que podem utilizar materiais cerâmicos, poliméricos, metálicos ou misturas destes. O material a ser depositado é fundido total ou parcialmente. As partículas aquecidas são aceleradas e projetadas em direção a uma superfície devidamente preparada, onde se formam camadas com estrutura lamelar. Os efeitos das variáveis do processo de aspersão, pressão dos gases de combustão, taxa de alimentação e gás de arraste no transporte do material, sobre a resistência ao desgaste e atrito de filmes PET foram investigados. Os recobrimentos de PET foram caracterizados através do desgaste micro-abrasivo, utilizando o ensaio de caloteste, e da medida dos coeficientes de atrito, com o ensaio de pino-sobre-disco. Os valores do coeficiente de desgaste abrasivo e do coeficiente de atrito dos recobrimentos são comparados com os valores da garrafa PET utilizada como referência. Os coeficientes de desgaste encontrados foram similares aos valores de garrafas PET da ordem de 10-5. As análises estatísticas dos resultados deste trabalho indicam que os efeitos das interações das três variáveis, pressão dos gases de combustão, taxa de alimentação e gás de arraste foram significativos para o coeficiente de desgaste e não significativos para o coeficiente de atrito.The thermal spray technique involves coating processes that can use ceramic, polymers, metallic materials or a blend of these. The material to be deposited is melted totally or partially, where the heated particles are accelerated and projected toward a prepared surface forming layers with a lamellar structure. The effect of the spray process parameters such as, combustion pressure, feed rate and carrier gas, on the wear resistance and friction of PET films was evaluated. The PET coatings were characterized by measuring the wear coefficient through the calowear type testing and the friction coefficients using pin-on-disk testing

  6. Increments in cytokines and matrix metalloproteinases in skeletal muscle after injection of tissue-damaging toxins from the venom of the snake Bothrops asper

    Directory of Open Access Journals (Sweden)

    Alexandra Rucavado

    2002-01-01

    Full Text Available Envenomations by the snake Bothrops asper are characterized by prominent local tissue damage (i.e. myonecrosis, blistering, hemorrhage and edema. Various phospholipases A2 and metalloproteinases that induce local pathological alterations have been purified from this venom. Since these toxins induce a conspicuous inflammatory response, it has been hypothesized that inflammatory mediators may contribute to the local pathological alterations described. This study evaluated the local production of cytokines and matrix metalloproteinases (MMPs as a consequence of intramuscular injections of an Asp-49 myotoxic phospholipase A2 (myotoxin III (MT-III and a P-I type hemorrhagic metalloproteinase (BaP1 isolated from B. asper venom. Both enzymes induced prominent tissue alterations and conspicuous increments in interleukin (IL-1β, IL-6 and a number of MMPs, especially gelatinase MMP-9, rapidly after injection. In contrast, no increments in tumor necrosis factor-α (TNF-α and interferon-γ were detected. In agreement, MT-III and BaP1 did not induce the synthesis of TNF-α by resident peritoneal macrophages in vitro. Despite the conspicuous expression of latent forms of MMPs in muscle, evidenced by zymography, there were no increments in activated MMP-2 and only a small increase in activated MMP-9, as detected by a functional enzymatic assay. This suggests that MMP activity was regulated by a highly controlled activation of latent forms and, probably, by a concomitant synthesis of MMP inhibitors. Since no hemorrhage nor dermonecrosis were observed after injection of MT-III, despite a prominent increase in MMP expression, and since inflammatory exudate did not enhance hemorrhage induced by BaP1, it is suggested that endogenous MMPs released in the tissue are not responsible for the dermonecrosis and hemorrhage characteristic of B. asper envenomation. Moreover, pretreatment of mice with the peptidomimetic MMP inhibitor batimastat did not reduce myotoxic nor

  7. Rupture behaviors of the 2010 Jiashian and 2016 Meinong Earthquakes: Implication for interaction of two asperities on the Chishan Transfer Fault Zone in SW Taiwan.

    Science.gov (United States)

    Jian, P. R.; Hung, S. H.; Chen, Y. L.; Meng, L.; Tseng, T. L.

    2017-12-01

    After about 45 years of seismic quiescence, southwest Taiwan was imperiled by two strong earthquakes, the 2010 Mw 6.2 Jiashian and deadly 2016 Mw 6.4 Meinong earthquakes in the last decade. The focal mechanisms and their aftershock distributions imply that both events occurred on NW-SE striking, shallow-dipping fault planes but at different depths of 21 and 16 km, respectively. Here we present the MUSIC back projection images using high-frequency P- and sP-waves recorded in the European and Australian seismic networks, the directivity analysis using global teleseismic P waves and relocated aftershocks to characterize the rupture behaviors of the two mainshocks and explore the potential connection between them. The results for the Meinong event indicate a unilateral, subhorizontal rupture propagating NW-ward 17 km and lasting for 6-7 s [Jian et al., 2017]. For the Jiashian event, the rupture initiated at a greater depth of 21 km and then propagated both NW-ward and up-dip ( 16o) on the fault plane, with a shorter rupture length of 10 km and duration of 4-5 s. The up-dip propagation is corroborated by the 3-D directivity analysis that leads to the widths of P-wave pulses increasing linearly with the directivity parameter. Moreover, relocation of aftershocks reveals that the Jiashian sequence is confined in a NW-SE elongated zone extending 15 km and 5 km shallower than the hypocenter. The Meinong aftershock sequence shows three clusters: one surrounding the mainshock hypocenter, another one distributed northwestern and deeper (>20 km) off the rupture plane beneath Tainan, and the other distant shallow-focus one (<10 km) beneath the southern Central Mountain Range. As evidenced by similar focal mechanism, rupture behaviors, as well as the spatial configuration of the mainshock rupture zones and aftershock distributions, we attribute the Jiashian and Meinong earthquakes to two asperities on a buried oblique fault that has been reactivated recently, the NW-SE striking

  8. Indentation Behavior and Mechanical Properties of Tungsten/Chromium co-Doped Bismuth Titanate Ceramics Sintered at Different Temperatures.

    Science.gov (United States)

    Xie, Shaoxiong; Xu, Jiageng; Chen, Yu; Tan, Zhi; Nie, Rui; Wang, Qingyuan; Zhu, Jianguo

    2018-03-27

    A sort of tungsten/chromium(W/Cr) co-doped bismuth titanate (BIT) ceramics (Bi₄Ti 2.95 W 0.05 O 12.05 + 0.2 wt % Cr₂O₃, abbreviate to BTWC) are ordinarily sintered between 1050 and 1150 °C, and the indentation behavior and mechanical properties of ceramics sintered at different temperatures have been investigated by both nanoindentation and microindentation technology. Firstly, more or less Bi₂Ti₂O₇ grains as the second phase were found in BTWC ceramics, and the grain size of ceramics increased with increase of sintering temperatures. A nanoindentation test for BTWC ceramics reveals that the testing hardness of ceramics decreased with increase of sintering temperatures, which could be explained by the Hall-Petch equation, and the true hardness could be calculated according to the pressure-state-response (PSR) model considering the indentation size effect, where the value of hardness depends on the magnitude of load. While, under the application of microsized Vickers, the sample sintered at a lower temperature (1050 °C) gained four linearly propagating cracks, however, they were observed to shorten in the sample sintered at a higher temperature (1125 °C). Moreover, both the crack deflection and the crack branching existed in the latter. The hardness and the fracture toughness of BTWC ceramics presented a contrary variational tendency with increase of sintering temperatures. A high sintering tends to get a lower hardness and a higher fracture toughness, which could be attributed to the easier plastic deformation and the stronger crack inhibition of coarse grains, respectively, as well as the toughening effect coming from the second phase.

  9. Diffusion processes in bombardment-induced surface topography

    International Nuclear Information System (INIS)

    Robinson, R.S.

    1984-01-01

    The bombardment of surfaces with moderate energy ions can lead to the development of various micron-sized surface structures. These structures include ridges, ledges, flat planes, pits and cones. The causal phenomena in the production of these features are sputtering, ion reflection, redeposition of sputtered material, and surface diffusion of both impurity and target-atom species. The authors concentrate on the formation of ion bombardment-induced surface topography wherein surface diffusion is a dominant process. The most thoroughly understood aspect of this topography development is the generation of cone-like structures during sputtering. The formation of cones during sputtering has been attributed to three effects. These are: (1) the presence of asperities, defects, or micro-inclusions in the surface layers, (2) the presence of impurities on the surfaces, and (3) particular crystal orientations. (Auth.)

  10. Characterization of Thermochemically Surface-Hardened Titanium by Light Optical Microscopy

    DEFF Research Database (Denmark)

    Gammeltoft-Hansen, Niklas; Munch, Steffen S.; Jellesen, Morten Stendahl

    2017-01-01

    Thermochemically treated titanium grades 2 and 5 were investigated by light optical microscopy and hardness indentation. Gaseous oxidation in oxygen and N2O containing atmospheres resulted in a diffusion zone of oxygen in solid solution in titanium with a hardness up to 1000 HV. A surface scale...

  11. Bothrops asper metalloproteinase BaP1 is inhibited by alpha(2)-macroglobulin and mouse serum and does not induce systemic hemorrhage or coagulopathy.

    Science.gov (United States)

    Escalante, Teresa; Rucavado, Alexandra; Kamiguti, Aura S; Theakston, R David G; Gutiérrez, José María

    2004-02-01

    The ability of the P-I metalloproteinase BaP1, isolated from the venom of the snake Bothrops asper, to induce systemic bleeding, thrombocytopenia and defibrinogenation was assessed in an experimental mouse model. Intravenous administration of BaP1 caused neither systemic bleeding nor any evidence of pathology in lungs, kidneys, liver, heart and brain. Moreover, there were no alterations in the whole blood clotting time or in platelet numbers. In addition, BaP1 did not inhibit collagen-induced platelet aggregation in vitro. Proteolytic and hemorrhagic activities of BaP1 were readily inhibited by the plasma proteinase inhibitor, alpha(2)-macroglobulin, and normal mouse serum also inhibited hemorrhage. Such inhibition may explain why BaP1 induces multiple local tissue-damaging effects, but is largely devoid of systemic toxicity.

  12. Perda de cargas em peças de sistemas de irrigação por aspersão convencional

    OpenAIRE

    Ailton de Almeida

    1995-01-01

    Resumo: As instalações de irrigação por aspersão são constituídas por tubulações portáteis com engate rápido e peças especiais tais como curvas duplas, hidrante de linha, derivação para a lateral e tês entre outras. O projetista dificilmente consegue determinar corretamente a perda de carga localizada nas peças especiais em aço zincado com engate rápido. Um estudo experimental foi conduzido no Laboratório de Hidráulica, ensaiandopeás especiais em tubulações de 0,100 e 0,125m. Como resultado d...

  13. Hyperalgesia induced by Asp49 and Lys49 phospholipases A2 from Bothrops asper snake venom: pharmacological mediation and molecular determinants.

    Science.gov (United States)

    Chacur, M; Longo, I; Picolo, G; Gutiérrez, J M; Lomonte, B; Guerra, J L; Teixeira, C F P; Cury, Y

    2003-05-01

    The ability of Lys49 and Asp49 phospholipases A(2) (PLA(2)), from Bothrops asper snake venom, to cause hyperalgesia was investigated in rats, using the paw pressure test. Intraplantar injection of both toxins (5-20 micro g/paw) caused hyperalgesia, which peaked 1h after injections. Incubation of both proteins with heparin, prior to their injection, partially reduced this response. Chemical modification of Asp49 PLA(2) with p-bromophenacyl bromide (p-BPB), which abrogates its PLA(2) activity, also abolished hyperalgesia. Intraplantar injection of a synthetic peptide corresponding to the C-terminal sequence 115-129 of Lys49 PLA(2), caused hyperalgesia of similar time course, but varying magnitude, than that induced by the native protein. In contrast, a homologous peptide derived from the Asp49 PLA(2) did not show any nociceptive effect. Hyperalgesia induced by both PLA(2)s was blocked by the histamine and serotonin receptor antagonists promethazine and methysergide, respectively, by the bradykinin B(2) receptor antagonist HOE 140 and by antibodies to tumor necrosis factor alfa (TNFalpha) and interleukin 1 (IL-1). Pretreatment with guanethidine, atenolol, prazosin and yohimbine, inhibitors of sympathomimetic amines, or with indomethacin, inhibitor of the cyclo-oxygenase pathway, reduced Lys49 PLA(2)-induced hyperalgesia without interfering with the nociceptive activity of Asp49 PLA(2). The hyperalgesic response to both myotoxins was not modified by pretreatment with celecoxib, an inhibitor of the cyclo-oxygenase type II, by zileuton, an inhibitor of the lipoxygenase pathway or by N(g)-methyl-L-arginine (LNMMA), an inhibitor of nitric oxide synthase. These results suggest that Asp49 and Lys49 PLA(2)s are important hyperalgesic components of B. asper venom, and that Lys49 and Asp49 PLA(2)s exert their algogenic actions through different molecular mechanisms.

  14. Characterization of 'basparin A,' a prothrombin-activating metalloproteinase, from the venom of the snake Bothrops asper that inhibits platelet aggregation and induces defibrination and thrombosis.

    Science.gov (United States)

    Loría, Gilbert D; Rucavado, Alexandra; Kamiguti, Aura S; Theakston, R David G; Fox, Jay W; Alape, Alberto; Gutiérrez, José María

    2003-10-01

    A prothrombin activator, named 'basparin A,' was isolated from the venom of the crotaline snake Bothrops asper, the species responsible for the majority of snakebite cases in Central America. It is an acidic (pI 5.4), 70kDa, single chain P-III metalloproteinase comprising, in addition to the metalloproteinase domain, disintegrin-like, and high-cysteine domains. Basparin A is a glycoprotein displaying immunological cross-reactivity with BaH1, a P-III hemorrhagic metalloproteinase isolated from the same venom. It activates prothrombin through the formation of meizothrombin, without requiring additional cofactors; it is, therefore, a class A snake venom prothrombin activator. In contrast with most venom metalloproteinases, it does not degrade components of the extracellular matrix. Apart from its clotting activity, basparin A inhibits collagen-dependent platelet aggregation in vitro, an effect that does not depend on proteolytic activity. Clotting activity on human plasma is not abrogated by the plasma proteinase inhibitors alpha(2) macroglobulin and murinoglobulin, whereas activity is completely inhibited by Costa Rican polyvalent (Crotalinae) anti-venom. Basparin A does not induce local tissue alterations, such as hemorrhage, myonecrosis, and edema, in mice. Moreover, it does not induce systemic hemorrhage, thrombocytopenia nor prolongation of the bleeding time following intravenous administration. At low doses, the only observed effect induced by basparin A, when injected intravenously or intramuscularly into mice, is defibrin(ogen)ation. At higher doses, intravenous administration resulted in sudden death due to numerous occluding thrombi in pulmonary vessels. Basparin A is likely to play an important role in the coagulopathy associated with B. asper envenoming.

  15. Contributions of the snake venoms of Bothrops asper, Crotalus simus and Lachesis stenophrys to the paraspecificity of the Central American polyspecific antivenom (PoliVal-ICP).

    Science.gov (United States)

    Solano, Gabriela; Gómez, Aarón; Corrales, Greivin; Chacón, Danilo; Estrada, Ricardo; León, Guillermo

    2018-03-15

    PoliVal-ICP antivenom is produced from plasma of horses immunized toward the venoms of Bothrops asper, Crotalus simus and Lachesis stenophrys. The antibody response induced by these venoms confers PoliVal-ICP the capacity to neutralize the venoms of the most important Central American viperids, including not only homologous venoms (i.e., venoms used as immunogen), but many heterologous venoms (i.e., venoms not used as immunogen). In this work, the individual contributions of homologous venoms to the paraspecificity of PoliVal-ICP were inferred from the capacity of experimental monospecific antivenoms toward venoms of B. asper (anti-Ba), C. simus (anti-Cs) and L. stenophrys (anti-Ls), and an experimental polyspecific antivenom (anti-Ba/Cs/Ls) to neutralize the lethality induced by different venoms in mice. It was found that all antivenoms neutralized their corresponding homologous venoms. Moreover, the anti-Ba antivenom cross-neutralized the venoms of Agkistrodon howardgloydi, Atropoides picadoi, Bothriechis lateralis, Bothriechis supraciliaris and Porthidium ophryomegas; the anti-Cs antivenom cross-neutralized the venoms of B. lateralis, B. supraciliaris, Cerrophidion sasai and Porthidium nasutum; and the anti-Ls antivenom cross-neutralized the venoms of B. lateralis, B. supraciliaris, C. sasai and Lachesis melanocephala. All venoms neutralized by any monospecific antivenom were also neutralized by the anti-Ba/Cs/Ls antivenom. Venoms of Atropoides mexicanus, Bothriechis nigroviridis and Bothriechis schlegelii were not neutralized by any experimental antivenom, thus explaining the limitations of PoliVal-ICP to neutralize these venoms. Consequently, an enlargement of the neutralization scope of PoliVal-ICP could be achieved by including these venoms in the group of those used as immunogens. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Food resources influence spatial ecology, habitat selection, and foraging behavior in an ambush-hunting snake (Viperidae: Bothrops asper): an experimental study.

    Science.gov (United States)

    Wasko, Dennis K; Sasa, Mahmood

    2012-06-01

    Prey availability affects many aspects of predators' life history and is considered a primary factor influencing individuals' decisions regarding spatial ecology and behavior, but few experimental data are currently available. Snakes may represent ideal model organisms relative to other animal groups for addressing such resource dependency, due to a presumably more direct link between food resources and many aspects of behavior and natural history. We experimentally investigated the relationship between food intake and spatial behavior in a population of the snake Bothrops asper in a Costa Rican lowland rainforest. Six adult snakes were allowed to forage naturally while six were offered supplemental food in the field, with both groups monitored using radiotelemetry. Mean home range size did not differ between groups presumably due to small sample size, but supplementally fed snakes demonstrated altered patterns of macro- and microhabitat selection, shorter and less frequent movements, and increased mass acquisition. Fed snakes also devoted less time to foraging efforts, instead more frequently remaining inactive and utilizing shelter. Because snakes were always fed in situ and not at designated feeding stations, observed shifts in habitat selection are not explained by animals simply moving to areas of higher food availability. Rather, B. asper may have moved to swamps in order to feed on amphibians when necessary, but remained in preferred forest habitat when food was otherwise abundant. The strong behavioral and spatiotemporal responses of snakes in this population may have been influenced by an overall scarcity of mammalian prey during the study period. Copyright © 2012 Elsevier GmbH. All rights reserved.

  17. Identification of linear B-cell epitopes on myotoxin II, a Lys49 phospholipase A₂ homologue from Bothrops asper snake venom.

    Science.gov (United States)

    Lomonte, Bruno

    2012-10-01

    Knowledge on toxin immunogenicity at the molecular level can provide valuable information for the improvement of antivenoms, as well as for understanding toxin structure-function relationships. The aims of this study are two-fold: first, to identify the linear B-cell epitopes of myotoxin II from Bothrops asper snake venom, a Lys49 phospholipase A₂ homologue; and second, to use antibodies specifically directed against an epitope having functional relevance in its toxicity, to probe the dimeric assembly mode of this protein in solution. Linear B-cell epitopes were identified using a library of overlapping synthetic peptides spanning its complete sequence. Epitopes recognized by a rabbit antiserum to purified myotoxin II, and by three batches of a polyvalent (Crotalidae) therapeutic antivenom (prepared in horses immunized with a mixture of B. asper, Crotalus simus, and Lachesis stenophrys venoms) were mapped using an enzyme-immunoassay based on the capture of biotinylated peptides by immobilized streptavidin. Some of the epitopes identified were shared between the two species, whereas others were unique. Differences in epitope recognition were observed not only between the two species, but also within the three batches of equine antivenom. Epitope V, located at the C-terminal region of this protein, is known to be relevant for toxicity and neutralization. Affinity-purified rabbit antibodies specific for this site were able to immunoprecipitate myotoxin II, suggesting that the two copies of epitope V are simultaneously available to antibody binding, which would be compatible with the mode of dimerization known as "conventional" dimer. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Ultraestructura de bambúes del género Dendrocalamus (Poaceae: Bambusoideae cultivados en Costa Rica IV: Dendrocalamus asper, clones Taiwán y Tailandia

    Directory of Open Access Journals (Sweden)

    Mayra Montiel

    2006-06-01

    Full Text Available El análisis ultraestructural de los clones taiwanés y tailandés de Dendrocalamus asper, realizado al microscopio electrónico de barrido, mostró que el clon de Taiwán tiene estomas de bajo domo en la lámina foliar, mientras que el de Tailandia tiene estomas de alto domo; las acumulaciones de cera cuticular en el clon de Taiwán son de dos formas (cuatro en el de Tailandia. La distribución de los tejidos vasculares es igual en ambos, así como los tejidos que los rodean. Sería difícil identificar estos clones por la observación macroscópica o microscópica de las brácteas del culmo, pues no presentan diferencias significativas: una identificación fiable requiere considerar la ultraestructura de los estomas y las acumulaciones de cera cuticular.An ultraestructural analysis of the Taiwan and Thailand clones of Dendrocalamus asper made with the scanning electron microscope showed that the Taiwan clone had low dome stomata while the Thailand clone has high dome stomata in the leaf lamina. Cuticular wax accumulations in the Taiwan clone has two shapes, against four in the Thailand clone. Both have the same distribution of vascular and surrounding tissues. Macroscopic or microscopic observation of culm bracts are not recommended to differentiate these clones: a reliable identification requires observation of the ultrastructure of stomata and cuticular wax accumulations. Rev. Biol. Trop. 54(Suppl. 2: 65-75. Epub 2006 Dec. 01.

  19. An Observation of Repeating Events at local asperities during a Laboratory Stick-slip Experiment of a Saw-cut Cylindrical Lucite Sample

    Science.gov (United States)

    Gu, C.; Mighani, S.; Prieto, G. A.; Mok, U.; Evans, J. B.; Hager, B. H.; Toksoz, M. N.

    2017-12-01

    Repeating earthquakes have been found in subduction zones and interpreted as repeated ruptures of small local asperities. Repeating earthquakes have also been found in oil/gas fields, interpreted as the reactivation of pre-existing faults due to fluid injection/extraction. To mimic the fault rupture of a fault with local asperities, we designed a "stick-slip" experiment using a saw-cut cylindrical Lucite sample, which had sharp localized ridges parallel to the strike of the fault plane. The sample was subjected to conventional triaxial loading with a constant confining pressure of 10 MPa. The axial load was then increased to 6 MPa at a constant rate of 0.12 MPa/sec until the sliding occurred along the fault plane. Ultrasonic acoustic emissions (AEs) were monitored with eight PZT sensors. Two cycles of AEs were detected with the occurrence rate that decreased from the beginning to the end of each cycle, while the relative magnitudes increased. Correlation analysis indicated that these AEs were clustered into two groups - those with frequency content between 200-300kHz and a second group with frequency content between 10-50kHz. The locations of the high-frequency events, with almost identical waveforms, show that these events are from the sharp localized ridges on the saw-cut plane. The locations of the low-frequency events show an approaching process to the high-frequency events for each cycle. In this single experiment, there was a correlation of the proximity of the low-frequency events with the subsequent triggering of large high-frequency repeating events.

  20. Crustal structure around the asperity regions of large earthquakes along the southernmost Kuril trench revealed by two Airgun-OBS seismic profilings

    Science.gov (United States)

    Machida, Y.; Takanami, T.; Murai, Y.; Amamiya, S.; Nishimura, Y.; Shinohara, M.; McHizuki, K.; Yamada, T.; Nakahigashi, K.; Kuwano, A.; Kanazawa, T.; Hino, R.; Azuma, R.

    2007-12-01

    In the southeast off Hokkaido, Japan, large earthquakes have occurred repeatedly with temporal and spatial regularities along the Kuril trench due to the subduction of Pacific plate at a rate of 80 mm/year (DeMets et al., 1990) [e.g. the 1952 Tokachi-oki earthquake (Mw=8.2), the 1973 Nemuro-oki earthquake (Mw=7.8) and the 2003 Tokachi-oki earthquake (Mw=8.2)]. It is considered that the next large earthquake will occur at the source region of the 1973 Nemuro-oki earthquake in the near future because a low seismic activity has been found in the off shore region of the Nemuro peninsula. In order to clarify the relation between asperity and the recurrence of large earthquake, it is necessary to determine a detailed crustal structure running across the two asperities of the 2003 Tokachi-oki earthquake and 1973 Nemuro-oki earthquake. Therefore we conducted a wide-angle survey across the coseismic rupture areas of the 2003 Tokachi-oki and 1973 Nemuro-oki earthquakes and the afterslip area of the 2003 Tokachi-oki earthquake parallel (profile-A) and perpendicular (profile-B) to the Kuril trench using Ocean Bottom Seismometers (OBSs). In profile-A, 19 OBSs were deployed at a spacing of about 10km and three 25 liter air-guns were fired every 90 seconds which corresponds to a shot interval of about 230m. In profile-B, 11 OBSs were deployed at a spacing of about 11km and two 25 liter airguns were fired every 60 seconds which corresponds to a shot interval of about 150m. In this presentation, we report on the crustal structure using the data obtained in the profile A and B and compare our results with past researches around this region. This study is founded by the Ministry of Education, Culture, Sports, Science and Technology, Japan.

  1. Neutralización del efecto hemorrágico inducido por veneno de Bothrops asper (Serpentes: Viperidae por extractos de plantas tropicales

    Directory of Open Access Journals (Sweden)

    Oscar Castro

    1999-09-01

    Full Text Available Se evaluó la capacidad de extractos orgánicos de 48 especies de plantas costarricenses para neutralizar la actividad hemorrágica del veneno de la serpiente Bothrops asper (terciopelo. Los extractos se evaluaron mediante un bioensayo basado en inyecciones intradérmicas de veneno en ratones, o de mezclas veneno-extracto, seguidas de la cuantificación macroscópica de la hemorragia. Se observó una inhibición total de la hemorragia con los extractos etanólico, de acetato de etilo y acuoso de Bursera simaruba, Clusia torresii, C. palmana, Croton draco, Persea americana, Phoebe brenesii, Pimenta dioica, Sapindus saponaria, Smilax cuculmeca y Virola koschnyi. El análisis químico de estos extractos permitió identificar catequinas, flavonas, antocianinas y taninos condensados, los cuales podrían jugar un papel en la inhibición del efecto hemorrágico debido a la capacidad de quelar el ion zinc requerido por las metaloproteinasas hemorrágicas para su acción.Organic extracts representing 48 species included in 30 families of Costa Rican tropical plants were evaluated for their ability to neutralize hemorrhagic activity induced by the venom of the snake Bothrops asper. A bioassay in mice was used, based on intradermal injection of either venom or venom-extract mixtures followed by the measurement of hemorrhagic areas. Total inhibition of hemorrhage was observed with the ethanolic, ethyl acetate and aquous extracts of Bursera simaruba, Clusia torresii, C. palmana, Croton draco, Persea americana, Phoebe brenesii, Pimenta dioica, Sapindus saponaria, Smilax cuculmeca and Virola koschnyi. Chemical analysis of these extracts identified catequines, flavones, anthocyanines and condensated tannins, which may be responsible for the inhibitory effect observed, probably owing to the chelation of the zinc required for the catalytic activity of venom’s hemorrhagic metalloproteinases.

  2. Effect of resin and type of surface treatment on the flexural strength of cracked feldspathic porcelain

    Directory of Open Access Journals (Sweden)

    Kermanshah Hamid

    2015-05-01

    Full Text Available Background and Aims: Porcelain restorations are often ground for clinical adjustment and this removes the surface glaze layer and introduces flaws that can grow in wet environments due to stress-corrosion, reduce the strength of porcelain and limit restoration lifetime. The aim of this study was to introduce some surface treatment methods to control the flaws of ceramic restorations external surface and improve their strength.   Materials and Methods: 40 feldspathic discs were prepared and divided into 4 groups (n=10: not indented (group 1 and others indented by vickers with 29.4 N and received different treatments: no treatment (group 2, polished (group 3 and polished-silane-resin (group 4. Biaxial flexural strength of discs was tested after water storage. Data were analyzed using one-way ANOVA .   Results: The mean flexural strength of specimens in group 1 (134.49±12.60, 2 (94.81±15.41, 3 (89.20±16.22 and 4 (80.67±12.01 were measured. Group 1 (not indented revealed significantly higher strength (P<0.001 than that of indented groups (2, 3 and 4 . There was no significant difference between group 2 (no treatment and 3 or 4 (treated and between treatment methods (3 and 4 (P=0.136.   Conclusion: The strength of porcelains is dependent on presence of cracks. With the limitations of this study, none of the treatment methods could strengthen the cracked ceramic.

  3. Electrochemical testing of laser treated bronze surface

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [Dept. of Mechanical Engineering, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261 (Saudi Arabia); Toor, Ihsan-ul-Haq; Malik, Jahanzaib; Patel, F. [Dept. of Mechanical Engineering, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261 (Saudi Arabia); Karatas, C. [Engineering Faculty, Hacettepe University, Ankara (Turkey)

    2013-06-25

    Highlights: ► Laser treated surface is free from asperities. ► Laser treated layer extends uniformly below the surface with a thickness in the order of 40 μm. ► Presence of Cu{sub 3}N nitrides is evident from X-ray diffractogram. ► Dendritic structure is formed below the surface due to relatively slower cooling rates as compared to that at the surface. ► The corrosion current density for the laser treated surface is much less than that of the as-received surface. -- Abstract: Electrochemical testing of laser treated bronze surface is carried out and corrosion resistance of the surface is assessed. Morphological and metallurgical changes in the laser treated layer are examined using scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. The pit sites formed at the surface are analyzed using scanning electron microscope. It is found that laser treatment improves the corrosion resistance of the treated surface. Fine grains are formed in the surface region of the laser treated layer, which are attributed to the large cooling rates from the surface.

  4. Model of Nanostructuring Burnishing by a Spherical Indenter Taking into Consideration Plastic Deformations

    Science.gov (United States)

    Lyashenko, Ya. A.; Popov, V. L.

    2018-01-01

    A dynamic model of the nanostructuring burnishing of a surface of metallic details taking into consideration plastic deformations has been suggested. To describe the plasticity, the ideology of dimension reduction method supplemented with the plasticity criterion is used. The model considers the action of the normal burnishing force and the tangential friction force. The effect of the coefficient of friction and the periodical oscillation of the burnishing force on the burnishing kinetics are investigated.

  5. Application of laser interferometry for assessment of surface residual stress by determination of stress-free state

    International Nuclear Information System (INIS)

    Kim, Dong Won; Kwon, Dong Il; Lee, Nak Kyu; Choi, Tae Hoon; Na, Kyoung Hoan

    2003-01-01

    The total relaxed stress in annealing and the thermal strain/stress were obtained from the identification of the residual stress-free state using Electronic Speckle Pattern Interferometry (ESPI). The residual stress fields in case of both single and film/substrate systems were modeled using the thermo-elastic theory and the relationship between relaxed stresses and displacements. We mapped the surface residual stress fields on the indented bulk Cu and the 0.5 μm Au film by ESPI. In indented Cu, the normal and shear residual stress are distributed over -1.7 GPa to 700 MPa and -800 GPa to 600 MPa respectively around the indented point and in deposited Au film on Si wafer, the tensile residual stress is uniformly distributed on the Au film from 500 MPa to 800 MPa. Also we measured the residual stress by the X-Ray Diffractometer (XRD) for the verification of above residual stress results by ESPI

  6. Semianalytical Solution for the Deformation of an Elastic Layer under an Axisymmetrically Distributed Power-Form Load: Application to Fluid-Jet-Induced Indentation of Biological Soft Tissues

    Directory of Open Access Journals (Sweden)

    Minhua Lu

    2017-01-01

    Full Text Available Fluid-jet-based indentation is used as a noncontact excitation technique by systems measuring the mechanical properties of soft tissues. However, the application of these devices has been hindered by the lack of theoretical solutions. This study developed a mathematical model for testing the indentation induced by a fluid jet and determined a semianalytical solution. The soft tissue was modeled as an elastic layer bonded to a rigid base. The pressure of the fluid jet impinging on the soft tissue was assumed to have a power-form function. The semianalytical solution was verified in detail using finite-element modeling, with excellent agreement being achieved. The effects of several parameters on the solution behaviors are reported, and a method for applying the solution to determine the mechanical properties of soft tissues is suggested.

  7. The interrelationship of microstructure and hardness of human coronal dentin using reference point indentation technique and micro-Raman spectroscopy.

    Science.gov (United States)

    Seyedmahmoud, Rasoul; McGuire, Jacob D; Wang, Yong; Thiagarajan, Ganesh; Walker, Mary P

    2017-10-01

    The aim of this paper is to determine the interrelationship between the microstructure - in terms of chemical composition and crystallinity - to the microhardness of coronal dentin. Dentin microhardness was tested by a novel reference point indenter and compared to the traditional Knoop hardness method. Micro-Raman spectroscopy was used to determine the chemical composition and crystallinity of dentin. From the occlusal groove to the border of the coronal pulp chamber, dentin hardness decreased from superficial dentin (SD) to deep dentin (DD). Mineral/organic matrix ratios (phosphate/CH and phosphate/amide I) also decreased from SD to DD; however, this change was significant (Pmicro-Raman spectroscopy. We hypothesize that the decrease in hardness from superficial to deep dentin can potentially be explained by decreased mineral content and increased carbonate content, which is also associated with decreased crystallinity. Collectively, there is a positive association between dentin hardness and mineral content and a negative association between dentin hardness and carbonate content. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. Elastic properties of indium nitrides grown on sapphire substrates determined by nano-indentation: In comparison with other nitrides

    Directory of Open Access Journals (Sweden)

    Ichiro Yonenaga

    2015-07-01

    Full Text Available The hardness of wurtzite indium nitride (α-InN films of 0.5 to 4 μm in thickness was measured by the nano-indentation method at room temperature. After investigation of crystalline quality by x-ray diffraction, the hardness and Young’s modulus were determined to be 8.8 ± 0.4 and 184 ± 5 GPa, respectively, for the In (0001- and N ( 000 1 ̄ -growth faces of InN films. The bulk and shear moduli were then derived to be 99 ± 3 and 77 ± 2 GPa, respectively. The Poisson’s ratio was evaluated to be 0.17 ± 0.03. The results were examined comprehensively in comparison with previously reported data of InN as well as those of other nitrides of aluminum nitride and gallium nitride. The underlying physical process determining the moduli and hardness was examined in terms of atomic bonding and dislocation energy of the nitrides and wurtzite zinc oxide.

  9. Evaluation of the indenter modulus (IM) method in the international round robin test about the cable condition monitoring

    International Nuclear Information System (INIS)

    Kajimura, Yuusaku

    2016-01-01

    In order to ensure the reliability and safety of nuclear power plants, the diagnosis of cable aging is important. The Institute of Nuclear Safety System (INSS) has been developing the indenter modulus (IM) method for more than a dozen years. Its usefulness was demonstrated in the research project 'Assessment of cable aging for nuclear power plant' by the Japan Nuclear Energy Safety Organization in 2009. Furthermore, INSS participated in the IAEA Coordinated Research Project in 2013 to 2015, measuring and acquiring data of insulation materials of cables and cable jackets with insulation which had been never measured before by INSS. The main results are as follows. (1) The IM method is useful for new materials (for example, crosslinked polyolefins) which had never been measured before by INSS. (2) The IM method is also applicable to evaluation of cable jackets with insulation made of such materials as chlorosulfonated polyethylene. Therefore, the IM method is evaluated to be useful and applicable for most cable materials except those which have a high IM value initially and which have a small change in IM value during aging. (author)

  10. Novel attributes of AlGaN/AlN/GaN/SiC HEMTs with the multiple indented channel

    Science.gov (United States)

    Orouji, Ali A.; Ghaffari, Majid

    2015-11-01

    In this paper, a high performance AlGaN/AlN/GaN/SiC High Electron Mobility Transistor (HEMT) with the multiple indented channel (MIC-HEMT) is proposed. The main focus of the proposed structure is based on reduction of the space around the gate, stop of the spread of the depletion region around the source-drain, and decrement of the thickness of the channel between the gate and drain. Therefore, the breakdown voltage increases, meanwhile the elimination of the gate depletion layer extension to source/drain decreases the gate-source and gate-drain capacitances. The optimized results reveal that the breakdown voltage and the drain saturation current increase about 178% and 46% compared with a conventional HEMT (C-HEMT), respectively. Therefore, the maximum output power density is improved by factor 4.1 in comparison with conventional one. Also, the cut-off frequency of 25.2 GHz and the maximum oscillation frequency of 92.1 GHz for the MIC-HEMT are obtained compared to 13 GHz and 43 GHz for that of the C-HEMT and the minimum figure noise decreased consequently of reducing the gate-drain and gate-source capacitances by about 42% and 40%, respectively. The proposed MIC-HEMT shows a maximum stable gain (MSG) exceeding 24.1 dB at 3.1 GHz which the greatest gain is yet reported for HEMTs, showing the potential of this device for high power RF applications.

  11. Correlating confocal microscopy and atomic force indentation reveals metastatic cancer cells stiffen during invasion into collagen I matrices

    Science.gov (United States)

    Staunton, Jack R.; Doss, Bryant L.; Lindsay, Stuart; Ros, Robert

    2016-01-01

    Mechanical interactions between cells and their microenvironment dictate cell phenotype and behavior, calling for cell mechanics measurements in three-dimensional (3D) extracellular matrices (ECM). Here we describe a novel technique for quantitative mechanical characterization of soft, heterogeneous samples in 3D. The technique is based on the integration of atomic force microscopy (AFM) based deep indentation, confocal fluorescence microscopy, finite element (FE) simulations and analytical modeling. With this method, the force response of a cell embedded in 3D ECM can be decoupled from that of its surroundings, enabling quantitative determination of the elastic properties of both the cell and the matrix. We applied the technique to the quantification of the elastic properties of metastatic breast adenocarcinoma cells invading into collagen hydrogels. We found that actively invading and fully embedded cells are significantly stiffer than cells remaining on top of the collagen, a clear example of phenotypical change in response to the 3D environment. Treatment with Rho-associated protein kinase (ROCK) inhibitor significantly reduces this stiffening, indicating that actomyosin contractility plays a major role in the initial steps of metastatic invasion.

  12. Correlating confocal microscopy and atomic force indentation reveals metastatic cancer cells stiffen during invasion into collagen I matrices.

    Science.gov (United States)

    Staunton, Jack R; Doss, Bryant L; Lindsay, Stuart; Ros, Robert

    2016-01-27

    Mechanical interactions between cells and their microenvironment dictate cell phenotype and behavior, calling for cell mechanics measurements in three-dimensional (3D) extracellular matrices (ECM). Here we describe a novel technique for quantitative mechanical characterization of soft, heterogeneous samples in 3D. The technique is based on the integration of atomic force microscopy (AFM) based deep indentation, confocal fluorescence microscopy, finite element (FE) simulations and analytical modeling. With this method, the force response of a cell embedded in 3D ECM can be decoupled from that of its surroundings, enabling quantitative determination of the elastic properties of both the cell and the matrix. We applied the technique to the quantification of the elastic properties of metastatic breast adenocarcinoma cells invading into collagen hydrogels. We found that actively invading and fully embedded cells are significantly stiffer than cells remaining on top of the collagen, a clear example of phenotypical change in response to the 3D environment. Treatment with Rho-associated protein kinase (ROCK) inhibitor significantly reduces this stiffening, indicating that actomyosin contractility plays a major role in the initial steps of metastatic invasion.

  13. An elevated-temperature depth-sensing instrumented indentation apparatus for investigating thermo-mechanical behaviour of thermal barrier coatings

    Science.gov (United States)

    Qu, Zhaoliang; Yu, Miao; Liu, Yanchao; Xu, Baosheng; He, Rujie; Pei, Yongmao; Zhao, Hongwei; Fang, Daining

    2017-04-01

    In our study, an elevated-temperature depth-sensing instrumented indentation apparatus was designed and developed to investigate thermo-mechanical response of thermal barrier coatings (TBCs). A furnace was used to heat the test region up to 1600 °C and a heat protection design was proposed to protect electronic devices from high temperature environment. Load was applied by a precise loading motor and a piezoelectric actuator in high (0-440 N) and low (0-40 N) load ranges, respectively. A loading shielding scheme was designed to protect the low load sensor during the high loading process. In order to obtain reliable test data, the as-developed apparatus was calibrated at room and elevated temperatures. It is found that the developed apparatus was suitable to obtain the intended data. After that, two typical TBCs were tested from 600 to 1500 °C, and the load-depth curves were presented to show the main functions and usability of the measuring system.

  14. Cross-reactivity and cross-immunomodulation between venoms of the snakes Bothrops asper, Crotalus simus and Lachesis stenophrys, and its effect in the production of polyspecific antivenom for Central America.

    Science.gov (United States)

    Arroyo, Cynthia; Solano, Sergio; Segura, Álvaro; Herrera, María; Estrada, Ricardo; Villalta, Mauren; Vargas, Mariángela; Gutiérrez, José María; León, Guillermo

    2017-11-01

    A mixture of the venoms of Bothrops asper, Crotalus simus and Lachesis stenophrys is used as immunogen to produce the polyspecific Central American antivenom (PoliVal-ICP). In this work, we studied the ability of each of these venoms to modulate the antibody response induced by the other two venoms included in the immunization mixture. For that, equine monospecific, bispecific and polyspecific antivenoms were prepared and compared regarding their ability to neutralize the phospholipase A 2 , coagulant and lethal activities of each venom, and their anti-venom antibodies concentration. Results indicate that there is low cross-reactivity and cross-neutralization between venoms of B. asper, C. simus and L. stenophrys, hence justifying the use of all of them as immunogens for the production of the Central American antivenom. It was also found that the venom of B. asper reduces the anti-crotalic response while the venom of C. simus does not affect the anti-bothropic response. On the other hand, the venoms of B. asper and C. simus increase the anti-lachesic response, and L. stenoprhys venom reduced both the anti-bothropic and anti-crotalic responses. On the basis of these results, the immunization strategy can be adjusted by preventing or taking advantage of cross-immunomodulation between venoms, in order to maximize the antibody response towards all venoms. Immune responses can be improved by injecting horses with several immunogen mixtures, composed by one or two of the three venoms, and administering them at different times during the immunization, eventually generating a high titer against the three venoms. Our results suggest that addressing the issue of immunomodulation by venoms might improve antivenom manufacture worldwide. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. A neutralizing recombinant single chain antibody, scFv, against BaP1, A P-I hemorrhagic metalloproteinase from Bothrops asper snake venom.

    Science.gov (United States)

    Castro, J M A; Oliveira, T S; Silveira, C R F; Caporrino, M C; Rodriguez, D; Moura-da-Silva, A M; Ramos, O H P; Rucavado, A; Gutiérrez, J M; Magalhães, G S; Faquim-Mauro, E L; Fernandes, I

    2014-09-01

    BaP1 is a P-I class snake venom metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomings by Bothrops asper, a medically important snake species in Central America and parts of South and North America. The main treatment for these accidents is the passive immunotherapy using antibodies raised in horses. In order to obtain more specific and batch-to-batch consistent antivenons, recombinant antibodies are considered a good option compared to animal immunization. We constructed a recombinant single chain variable fragment (scFv) from a monoclonal antibody against BaP1 (MABaP1) formerly secreted by a hybridoma clone. This recombinant antibody was cloned into pMST3 vector in fusion with SUMO protein and contains VH and VL domains linked by a flexible (G4S)3 polypeptide (scFvBaP1). The aim of this work was to produce scFvBaP1 and to evaluate its potential concerning the neutralization of biologically important activities of BaP1. The cytoplasmic expression of this construct was successfully achieved in C43 (DE3) bacteria. Our results showed that scFvBaP1-SUMO fusion protein presented an electrophoretic band of around 43 kDa from which SUMO alone corresponded to 13.6 kDa, and only the scFv was able to recognize BaP1 as well as the whole venom by ELISA. In contrast, neither an irrelevant scFv anti-LDL nor its MoAb partner recognized it. BaP1-induced fibrinolysis was significantly neutralized by scFvBaP1, but not by SUMO, in a concentration-dependent manner. In addition, scFvBaP1, as well as MaBaP1, completely neutralized in vivo hemorrhage, muscle necrosis, and inflammation induced by the toxin. Docking analyses revealed possible modes of interaction of the recombinant antibody with BaP1. Our data showed that scFv recognized BaP1 and whole B. asper venom, and neutralized biological effects of this SVMP. This scFv antibody can be used for understanding the molecular mechanisms of neutralization of SVMPs, and for exploring the potential of

  16. Surface shape memory in polymers

    Science.gov (United States)

    Mather, Patrick

    2012-02-01

    Many crosslinked polymers exhibit a shape memory effect wherein a permanent shape can be prescribed during crosslinking and arbitrary temporary shapes may be set through network chain immobilization. Researchers have extensively investigated such shape memory polymers in bulk form (bars, films, foams), revealing a multitude of approaches. Applications abound for such materials and a significant fraction of the studies in this area concern application-specific characterization. Recently, we have turned our attention to surface shape memory in polymers as a means to miniaturization of the effect, largely motivated to study the interaction of biological cells with shape memory polymers. In this presentation, attention will be given to several approaches we have taken to prepare and study surface shape memory phenomenon. First, a reversible embossing study involving a glassy, crosslinked shape memory material will be presented. Here, the permanent shape was flat while the temporary state consisted of embossed parallel groves. Further the fixing mechanism was vitrification, with Tg adjusted to accommodate experiments with cells. We observed that the orientation and spreading of adherent cells could be triggered to change by the topographical switch from grooved to flat. Second, a functionally graded shape memory polymer will be presented, the grading being a variation in glass transition temperature in one direction along the length of films. Characterization of the shape fixing and recovery of such films utilized an indentation technique that, along with polarizing microscopy, allowed visualization of stress distribution in proximity to the indentations. Finally, very recent research concerning shape memory induced wrinkle formation on polymer surfaces will be presented. A transformation from smooth to wrinkled surfaces at physiological temperatures has been observed to have a dramatic effect on the behavior of adherent cells. A look to the future in research and

  17. Exploring the elasticity and adhesion behavior of cardiac fibroblasts by atomic force microscopy indentation

    Energy Technology Data Exchange (ETDEWEB)

    Codan, B.; Del Favero, G. [Department of Engineering and Architecture, University of Trieste (Italy); Martinelli, V. [Department of Engineering and Architecture, University of Trieste (Italy); International Center for Genetic Engineering and Biotechnology, Trieste (Italy); Long, C.S.; Mestroni, L. [University of Colorado Cardiovascular Institute, University of Colorado Denver, Aurora, CO (United States); Sbaizero, O., E-mail: sbaizero@units.it [Department of Engineering and Architecture, University of Trieste (Italy)

    2014-07-01

    AFM was used to collect the whole force–deformation cell curves. They provide both the elasticity and adhesion behavior of mouse primary cardiac fibroblasts. To confirm the hypothesis that a link exists between the membrane receptors and the cytoskeletal filaments causing therefore changing in both elasticity and adhesion behavior, actin-destabilizing Cytochalsin D was administrated to the fibroblasts. From immunofluorescence observation and AFM loading/unloading curves, cytoskeletal reorganization as well as a change in the elasticity and adhesion was indeed observed. Elasticity of control fibroblasts is three times higher than that for fibroblasts treated with 0.5 μM Cytochalasin. Moreover, AFM loading–unloading curves clearly show the different mechanical behavior of the two different cells analyzed: (i) for control cells the AFM cantilever rises during the dwell time while cells with Cytochalasin fail to show such an active resistance; (ii) the maximum force to deform control cells is quite higher and as far as adhesion is concern (iii) the maximum separation force, detachment area and the detachment process time are much larger for control compared to the Cytochalasin treated cells. Therefore, alterations in the cytoskeleton suggest that a link must exist between the membrane receptors and the cytoskeletal filaments beneath the cellular surface and inhibition of actin polymerization has effects on the whole cell mechanical behavior as well as adhesion. - Highlights: • The whole AFM force–deformation cell curves were analyzed. • They provide information on both the elasticity and adhesion behavior. • Actin-destabilizing Cytochalasin D was administrated to the fibroblasts. • Change in elasticity and adhesion was ascribed to cytoskeletal reorganization. • A link exists between the membrane receptors and the cytoskeletal filaments.

  18. Ice friction: The effects of surface roughness, structure, and hydrophobicity

    Science.gov (United States)

    Kietzig, Anne-Marie; Hatzikiriakos, Savvas G.; Englezos, Peter

    2009-07-01

    The effect of surface roughness, structure, and hydrophobicity on ice friction is studied systematically over a wide range of temperature and sliding speeds using several metallic interfaces. Hydrophobicity in combination with controlled roughness at the nanoscale is achieved by femtosecond laser irradiation to mimic the lotus effect on the slider's surface. The controlled roughness significantly increases the coefficient of friction at low sliding speeds and temperatures well below the ice melting point. However, at temperatures close to the melting point and relatively higher speeds, roughness and hydrophobicity significantly decrease ice friction. This decrease in friction is mainly due to the suppression of capillary bridges in spite of the presence of surface asperities that facilitate their formation. Finally, grooves oriented in the sliding direction also significantly decrease friction in the low velocity range compared to scratches and grooves randomly distributed over a surface.

  19. [INVITED] Laser treatment of Inconel 718 alloy and surface characteristics

    Science.gov (United States)

    Yilbas, B. S.; Ali, H.; Al-Aqeeli, N.; Karatas, C.

    2016-04-01

    Laser surface texturing of Inconel 718 alloy is carried out under the high pressure nitrogen assisting gas. The combination of evaporation and melting at the irradiated surface is achieved by controlling the laser scanning speed and the laser output power. Morphological and metallurgical changes in the treated surface are analyzed using the analytical tools including optical, electron scanning, and atomic force microscopes, energy dispersive spectroscopy, and X-ray diffraction. Microhardnes and friction coefficient of the laser treated surface are measured. Residual stress formed in the surface region is determined from the X-ray diffraction data. Surface hydrophobicity of the laser treated layer is assessed incorporating the sessile drop method. It is found that laser treated surface is free from large size asperities including cracks and the voids. Surface microhardness increases significantly after the laser treatment process, which is attributed to the dense layer formation at the surface under the high cooling rates, dissolution of Laves phase in the surface region, and formation of nitride species at the surface. Residual stress formed is compressive in the laser treated surface and friction coefficient reduces at the surface after the laser treatment process. The combination of evaporation and melting at the irradiated surface results in surface texture composes of micro/nano-poles and pillars, which enhance the surface hydrophobicity.

  20. Self-cleaning efficiency of artificial superhydrophobic surfaces.

    Science.gov (United States)

    Bhushan, Bharat; Jung, Yong Chae; Koch, Kerstin

    2009-03-03

    The hierarchical structured surface of the lotus (Nelumbo nucifera, Gaertn.) leaf provides a model for the development of biomimetic self-cleaning surfaces. On these water-repellent surfaces, water droplets move easily at a low inclination of the leaf and collect dirt particles adhering to the leaf surface. Flat hydrophilic and hydrophobic, nanostructured, microstructured, and hierarchical structured superhydrophobic surfaces were fabricated, and a systematic study of wettability and adhesion properties was carried out. The influence of contact angle hysteresis on self-cleaning by water droplets was studied at different tilt angles (TA) of the specimen surfaces (3 degrees for Lotus wax, 10 degrees for n-hexatriacontane, as well as 45 degrees for both types of surfaces). At 3 degrees and 10 degrees TA, no surfaces were cleaned by moving water applied onto the surfaces with nearly zero kinetic energy, but most particles were removed from hierarchical structured surfaces, and a certain amount of particles were captured between the asperities of the micro- and hierarchical structured surfaces. After an increase of the TA to 45 degrees (larger than the tilt angles of all structured surfaces), as usually used for industrial self-cleaning tests, all nanostructured surfaces were cleaned by water droplets moving over the surfaces followed by hierarchical and microstructures. Droplets applied onto the surfaces with some pressure removed particles residues and led to self-cleaning by a combination of sliding and rolling droplets. Geometrical scale effects were responsible for superior performance of nanostructured surfaces.

  1. Effects of Bothrops asper snake venom on the expression of cyclooxygenases and production of prostaglandins by peritoneal leukocytes in vivo, and by isolated neutrophils and macrophages in vitro.

    Science.gov (United States)

    Moreira, Vanessa; Gutiérrez, José María; Amaral, Rafaela Bacci; Zamunér, Stella Regina; Teixeira, Catarina de Fátima Pereira

    2009-01-01

    In this study, the ability of Bothrops asper snake venom (BaV) to increase the production of prostaglandins PGE(2) and PGD(2) was assessed in a mouse model in vivo and in inflammatory cells in vitro. In addition, the expressions of COX-1 and COX-2 were assessed. BaV induced an increment in the in vivo synthesis of PGE(2) and PGD(2), together with an enhanced expression of COX-2, but not of COX-1. However, enzymatic activities of COX-1 and COX-2 were increased. Incubation of isolated macrophages and neutrophils with a sub-cytotoxic concentration of BaV in vitro resulted in increased release of PGE(2) and PGD(2) by macrophages and PGE(2) by neutrophils, concomitantly with an increment in the expression of COX-2, but not of COX-1 by both cell types. Our results demonstrate the ability of BaV to promote the expression of COX-2 and to induce the synthesis of proinflammatory prostaglandins. Macrophages and neutrophils may be important targets for this venom under in vivo situation.

  2. A Lys49 phospholipase A(2) homologue from Bothrops asper snake venom induces proliferation, apoptosis and necrosis in a lymphoblastoid cell line.

    Science.gov (United States)

    Mora, Rodrigo; Valverde, Berta; Díaz, Cecilia; Lomonte, Bruno; Gutiérrez, José María

    2005-04-01

    Lys49 phospholipase A(2) homologues are abundant in viperid snake venoms. These proteins have substitutions at the calcium-binding loop and catalytic center which render them enzymatically inactive; however, they display a series of toxic activities, particularly cytotoxicity upon various cell lines in vitro. In this study we explored whether myotoxin II (MT-II), a Lys49 phospholipase A(2) homologue from the venom of the snake Bothrops asper, is capable of inducing various effects in a single cell type, using the lymphoblastoid B cell line CRL-8062 as a model. Cells were incubated with varying concentrations of MT-II for 24 and 48 h, time intervals that are more prolonged than the usual incubation times previously used in the characterization of this toxin. Results indicate that MT-II induces proliferation at low concentrations (0.5-5.0 microg/mL). Apoptosis was predominant at higher toxin levels (5-25 microg/mL), whereas necrosis, associated with overt plasma membrane disruption, occurred at concentrations > or =25 microg/mL, and was the predominant effect at higher MT-II concentrations (50 microg/mL). It is concluded that a single phospholipase A(2) homologue can induce markedly different effects on a single cell line, depending on the concentration used, an observation that may have implications for the action of this type of venom component in vivo.

  3. Inflammatory events induced by Lys-49 and Asp-49 phospholipases A2 isolated from Bothrops asper snake venom: role of catalytic activity.

    Science.gov (United States)

    Zuliani, Juliana P; Fernandes, Cristina M; Zamuner, Stella R; Gutiérrez, José M; Teixeira, Catarina F P

    2005-03-01

    The inflammatory events induced in the peritoneal cavity of mice by two PLA2s isolated from Bothrops asper snake venom were investigated. MT-III, an Asp-49 catalytically active enzyme and MT-II, a catalytically inactive Lys-49 variant induced increase in vascular permeability. Inhibition of enzymatic activity of MT-III with p-bromophenacyl bromide reduced this effect. MT-III induced a larger neutrophil infiltrate than MT-II. This activity was significantly reduced after inhibition of catalytic activity. Reduction in the number of neutrophils was observed when antibodies against L-selectin, CD18 or LFA-1 were used, suggesting the involvement of these adhesion molecules in the effects of both PLA2s. There was no effect with antibodies against ICAM-1 and PECAM-1. Increase in the levels of LTB4 and TXA2, as well as of IL-1, IL-6 and TNF-alpha, were observed in the peritoneal exudates induced by MT-III. MT-II did not enhance levels of eicosanoids but increased those of cytokines. It is concluded that both PLA2s induce inflammatory events in this model. Since MT-III exerts a stronger proinflammatory effect, the enzymatic phospholipid hydrolysis may be relevant for these phenomena. However, the fact that MT-II induced inflammation suggests that molecular regions distinct from the catalytic site elicit inflammatory events perhaps by interacting with specific cell membrane acceptors.

  4. Study of the design and analytical properties of the lethality neutralization assay used to estimate antivenom potency against Bothrops asper snake venom.

    Science.gov (United States)

    Solano, Gabriela; Segura, Alvaro; Herrera, María; Gómez, Aarón; Villalta, Mauren; Gutiérrez, José María; León, Guillermo

    2010-09-01

    The lethality neutralization assay performed in mice is the standard recommended by the World Health Organization to estimate antivenom potency. The interpretation of its results without considering its analytical capacity may lead to erroneous conclusions. Therefore, laboratories that manufacture or control antivenoms must demonstrate the appropriateness of their models. A study of the method used at Instituto Clodomiro Picado, Costa Rica, to estimate the potency of antivenoms against Bothrops asper snake venom was performed. Results show that venom doses ranging from 2 to 6 Median Lethal Doses (LD50) are appropriate to be used as challenge in this test. Variables such as the injection route, number of mice used per venom/antivenom level, and weight of the animals are critical in the estimation of the Median Effective Dose (ED50), whereas incubation time is not. The assay has an acceptable selectivity, linearity, and limits of detection and quantification. Accuracy of the lethality neutralization assay, expressed as percentage recovery, was between 71% and 127%. Intermediate precision, expressed as relative standard deviation, was < or = 17%. It is concluded that the analytical characteristics of this assay are adequate enough to prove product compliance and to have statistical control over an industrial line of antivenom serial production. Copyright 2010 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.

  5. A Lys49-PLA2 myotoxin of Bothrops asper triggers a rapid death of macrophages that involves autocrine purinergic receptor signaling.

    Science.gov (United States)

    Tonello, F; Simonato, M; Aita, A; Pizzo, P; Fernández, J; Lomonte, B; Gutiérrez, J M; Montecucco, C

    2012-07-05

    Lys49-PLA(2) myotoxins, an important component of various viperid snake venoms, are a class of PLA(2)-homolog proteins deprived of catalytic activity. Similar to enzymatically active PLA(2) (Asp49) and to other classes of myotoxins, they cause severe myonecrosis. Moreover, these toxins are used as tools to study skeletal muscle repair and regeneration, a process that can be very limited after snakebites. In this work, the cytotoxic effect of different myotoxins, Bothrops asper Lys49 and Asp49-PLA(2), Notechis scutatus notexin and Naja mossambica cardiotoxin, was evaluated on macrophages, cells that have a key role in muscle regeneration. Only the Lys49-myotoxin was found to trigger a rapid asynchronous death of mouse peritoneal macrophages and macrophagic cell lines through a process that involves ATP release, ATP-induced ATP release and that is inhibited by various purinergic receptor antagonists. ATP leakage is induced also at sublytical doses of the Lys49-myotoxin, it involves Ca(2+) release from intracellular stores, and is reduced by inhibitors of VSOR and the maxi-anion channel. The toxin-induced cell death is different from that caused by high concentration of ATP and appears to be linked to localized purinergic signaling. Based on present findings, a mechanism of cell death is proposed that can be extended to other cytolytic proteins and peptides.

  6. Purification and partial characterization of phospholipases A2 from Bothrops asper (barba amarilla snake venom from Chiriguaná (Cesar, Colombia

    Directory of Open Access Journals (Sweden)

    J. Ramírez-Avila

    2004-01-01

    Full Text Available Components with phospholipase A2 activity were isolated by gel filtration and cationic exchange chromatography from the venom of Bothrops asper snakes from Chiriguaná, Colombia (9°22´N; 73°37´W. Five fractions were obtained by the gel filtration, and PLA2 activity was found in fraction 3 (F3. In the cationic exchange chromatography, F3 showed eight components with PLA2 activity. Six of these components appeared as one band in polyacrylamide gel electrophoresis (SDS-PAGE. Fractions II and VII exhibited an optimal activity at pH 9 and 52ºC. The optimum calcium concentration for fraction II was 48 mM and for fraction VII, 384 mM. Both fractions showed thermal stability. Fraction II was stable at pH values between 2.5 and 9, and fraction VII, between 2.5 and 8. The Michaelis Menten constant (K M was 3.5x10-3 M for fraction II and 1.6x10-3 M for fraction VII. The molecular weight was 16,000 Dalton for fraction II and 17,000 Dalton for fraction VII. Both isoenzymes did not show any toxic activity (DL50 at 5.3 and 4 µg/g. The two fractions showed different kinetic constant (K M, calcium requirement, and substrate specificity for haemolytic activity.

  7. The lethality test used for estimating the potency of antivenoms against Bothrops asper snake venom: pathophysiological mechanisms, prophylactic analgesia, and a surrogate in vitro assay.

    Science.gov (United States)

    Chacón, Francisco; Oviedo, Andrea; Escalante, Teresa; Solano, Gabriela; Rucavado, Alexandra; Gutiérrez, José María

    2015-01-01

    The potency of antivenoms is assessed by analyzing the neutralization of venom-induced lethality, and is expressed as the Median Effective Dose (ED50). The present study was designed to investigate the pathophysiological mechanisms responsible for lethality induced by the venom of Bothrops asper, in the experimental conditions used for the evaluation of the neutralizing potency of antivenoms. Mice injected with 4 LD50s of venom by the intraperitoneal route died within ∼25 min with drastic alterations in the abdominal organs, characterized by hemorrhage, increment in plasma extravasation, and hemoconcentration, thus leading to hypovolemia and cardiovascular collapse. Snake venom metalloproteinases (SVMPs) play a predominat role in lethality, as judged by partial inhibition by the chelating agent CaNa2EDTA. When venom was mixed with antivenom, there was a venom/antivenom ratio at which hemorrhage was significantly reduced, but mice died at later time intervals with evident hemoconcentration, indicating that other components in addition to SVMPs also contribute to plasma extravasation and lethality. Pretreatment with the analgesic tramadol did not affect the outcome of the neutralization test, thus suggesting that prophylactic (precautionary) analgesia can be introduced in this assay. Neutralization of lethality in mice correlated with neutralization of in vitro coagulant activity in human plasma. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. PENGUJIAN SIFAT FISIS-MEKANIS DAN NONDESTRUKTIF METODE GELOMBANG SUARA PAPAN WOL SEMEN BERKERAPATAN SEDANG-TINGGI BAMBU BETUNG (DENDROCALAMUS ASPER

    Directory of Open Access Journals (Sweden)

    Lina Karlinasari

    2012-04-01

    Full Text Available Cement board is a composite wood product has advantages such as fire resistance, termite, water resistant, and has good sound insulation properties. Bamboo is suitable material that can be used as a raw material of cement board. The objectove of this study was to determine the physical-mechanical properties of wool cement boards from betung bamboo (Dendrocalamus asper in various densities. Mechanical testing included nondestructive testing performed using the sound waves velocity method (stress wave velocity. The material used was particles of wool/ excelsior dimensions. The adhesive used was Portland cement type I by the ratio of bamboo: cement: water 1:2:1. Target board densities were 0.5 g/cm3; 0.8 g/cm3; and 1.0 g/cm3. The results showed the higher density of the board the higher mechanical properties of boards. The difference density cement board was more influential on mechanical properties (MOE, MOR, SW board compared with those physical properties. Nondestrcutive testing using sound waves velocity method can be used to predict mechanical bending properties of wool cement board of betung bamboo as indicated by the close relationship between the parameter estimators (dynamic MOE and static testing value (MOE and MOR.

  9. Phase shift reflectometry for sub-surface defect detection

    Science.gov (United States)

    Asundi, Anand; Lei, Huang; Eden, Teoh Kang Min; Sreemathy, Parthasarathy; May, Watt Sook

    2012-11-01

    Phase Shift Reflectometry has recently been seen as a novel alternative to interferometry since it can provide warpage measurement over large areas with no need for large optical components. To confirm its capability and to explore the use of this method for sub-surface defect detection, a Chinese magic mirror is used. This bronze mirror which dates back to the Chinese Han Dynasty appears at first sight to be an ordinary convex mirror. However, unlike a normal mirror, when illuminated by a beam of light, an image is formed onto a screen. It has been hypothesized that there are indentations inside the mirror which alter the path of reflected light rays and hence the reflected image. This paper explores various methods to measure these indentations. Of the methods test Phase Shift Reflectometry (PSR) was found suitable to be the most suitable both in terms of the sensitivity and the field of view.

  10. Evaluación biológica preliminar de extractos vegetales utilizados en la medicina tradicional de la Sierra Nevada deSanta Marta contra el veneno de la Bothrops asper

    Directory of Open Access Journals (Sweden)

    Willinton Barranco Pérez

    2013-10-01

    Full Text Available Title: Preliminary biological evaluation of plants extracts used in the Sierra Nevada de Santa Marta against the snake Bothrops asper venom.ResumenLa mordedura de serpientes constituye un problema de salubridad importante en muchos países tropicales y subtropicales, con un estimado de 2,5 millones de personas envenenadas cada año. En Colombia las especies Bothropsasper y Bothropsatrox son las causantes del 70 al 90 % de los accidentes registrados. Se estima que el 60% de estos accidentes son inicialmente tratados por curanderos tradicionales utilizando plantas medicinales en diferentes preparaciones. Este estudio evaluó la capacidad inhibitoria de cinco especies contra el efecto proteolítico y hemolítico indirecto inducido por el veneno de B. asper en ensayos in vitro.Las especies, que fueron seleccionadas de acuerdo a su uso en la medicina tradicional por parte de las comunidades campesinas de la Sierra Nevada de Santa Marta, fueron, Aristolochia máxima, Cissampelospareira, Equisetumbogotense, Mucunacfpruriens y una especie de la familia Asteraceae. La planta E. bogotense mostró los mayores porcentaje de inhibición contra la actividad de las fosfolipasas A2(42,29 %, así como la mayor precipitación de las proteínas en un rango de masas moleculares de 28,2 y 94,43 KDa. Al fraccionar el extracto de E. bogotense se obtuvieron cinco fracciones, las cuales presentaron un porcentaje de inhibición de 36,6 ± 1,07 a 46,1 ± 13,6. Adicionalmente se detectaron por métodos cualitativos núcleos como, alcaloides, esteroides y/o triterpenos, taninos, cumarinas y leucoantocianidinas. En estudio se reporta la actividad antiofídica en ensayos in vitro de la especie E. bogotense contra el veneno de la especie B.asper. (DUAZARY 2012 No. 2, 140 - 150AbstractIn Colombia the species Bothrops asper and Bothrops atrox are responsible for 70 to 90% of the snakebite accidents. Around 60% of these injuries are initially treated by traditional healers; they

  11. Three-dimensional measuring technique for surface topography using a light-sectioning microscope.

    Science.gov (United States)

    Xia, Linglin; Chen, Peifeng; Wang, Ying; Zhou, Le; Luo, Xi

    2012-03-10

    Three-dimensional (3D) surface topographic analysis, measurement, and assessment techniques have raised great interest not only among researchers but also among industrial users. Many industrial processes and applications are directly influenced by the small-scale roughness of surface finishes. This paper describes the development and implementation of a noncontact, three-dimensional, microtopography measuring system. The instrument is formed by combining a modified light-sectioning microscope subsystem with a computer subsystem. In particular, optical system characteristics of the light-sectioning microscope are investigated, and a textured steel sheet is measured to demonstrate good practical outcomes. Details of measuring processes and image processing algorithms are provided, such as procedures for measurement, image edge extraction, and 3D topography reconstruction. After the 3D topography of the measured surface has been reconstructed, the topography field description parameters are calculated. A standard roughness block was used for calibration of the surface microtopography measuring system. Results obtained showed the measurement method output has good agreement with the actual asperity (unevenness or roughness) of the surface. The computer subsystem is used to process and control asperity measurements and image generation, and for image acquisition and presentation.

  12. Effect of surface pattern on the adhesive friction of elastomers.

    Science.gov (United States)

    Wu-Bavouzet, Fanny; Cayer-Barrioz, Juliette; Le Bot, Alain; Brochard-Wyart, Françoise; Buguin, Axel

    2010-09-01

    We present experimental results for the friction of a flat surface against a hexagonally patterned surface, both being made of PolyDiMethylSiloxane. We simultaneously measure forces of range 10 mN and observe the contact under sliding velocities of about 100 μm/s. We observe adhesive friction on three different pattern heights (80, 310, and 2100 nm). Two kinds of contacts have been observed: the flat surface is in close contact with the patterned one (called intimate contact, observed for 80 nm) or only suspended on the tops on the asperities (called laid contact, observed for 2100 nm). In the range of velocities used, the contact during friction is similar to the static one. Furthermore, our experimental system presents a contact transition during friction for h=310 nm.

  13. A new theory for the static contact between rough, unmated surfaces in non-elastically deforming rock and its implications for rock friction

    Science.gov (United States)

    Stesky, R. M.; Hannan, S. S.

    The closure behavior of fractures in marble and alabaster is markedly different from that in quartzite. The aperture decreases considerably more under normal stress and remains permanently reduced, for the same ratio of normal stress to unconfined compressive strength. Also, a larger permanent relative contact area develops between the surfaces of marble and alabaster than it does between surfaces of quartzite. The permanent contact area increases at an increasing rate with normal stress in marble and alabaster, unlike the nearly linear increase in quartzite. The failure of surface asperities of calcite and gypsum during closure accounts for these differences. We modeled this process by considering the surfaces to consist of paraboloids lying on a flat plane and having a range of initial heights. Closure occurs by pressing a plane rigid surface against the 'hills', flattening their peaks, keeping the base area of the hills constant. To allow for a changing resistance to deformation, the contact stress is assumed to vary linearly with the shortening strain, to a first approximation. This model was tested against measurements of fracture closure and contact area of rough surfaces of calcite marble with a known initial height distribution of surface peaks. The fit to the data is quite good. In all cases, the model shows that closure is accompanied by a decrease in contact strength of deforming asperities, suggested also by the cataclastic deformation observed petrographically. The number of contact spots and the total length of contact seen in profile are also reasonably well modeled. These results have important implications for our understanding of frictional strength of fractures. The overall resistance to shear along rough surfaces depends upon the product of the shear strength and true area of the contacts, both of which are affected by normal stress. Application of this model approach shows that the initial frictional resistance of some fractures in ductile

  14. Indentation Damage in Ceramics.

    Science.gov (United States)

    1987-05-30

    resistance have finer grain sizes (cf. A999 and Vistal ). Most interesting, however, is the quantitative correlation between grinding resistance and...a 0.1 3 4.3 2.2 Vistal I a 0.1 20 4.1 1.7 Vistal 1, a 0.1 40 4.6 1.5 Glass-ceramic Pyroceram c - 1.5 2.3 2.0 Macor C _ 13 2.3 1.0 a. Coors Porcelain

  15. Comparison of irradiated 15Kh2MFA material mechanical properties using conventional testing methods and innovative approach of small punch testing (SPT) and automated ball indentation (ABIT)

    Science.gov (United States)

    Kopriva, R.; Petelova, P.; Eliasova, I.; Kytka, M.; Culek, M.

    2017-02-01

    Article describes two innovative testing methods - Small Punch Testing (SPT) and Automated Ball Indentation Test (ABIT) - which are based on the determination and evaluation of material properties from miniaturized testing specimens. These methods are very promising due to minimum material needed for testing and also in case of testing highly irradiated materials of components that are not included in standard surveillance programs. The test results were obtained for reactor pressure vessel (RPV) base material 15Ch2MFA in both states - initial unirradiated and irradiated. Subsequently results were compared with standard tensile tests to prove applicability of these testing methods for the evaluation of degradation of irradiated structural materials of nuclear power plants.

  16. Amino acid sequence and crystal structure of BaP1, a metalloproteinase from Bothrops asper snake venom that exerts multiple tissue-damaging activities

    Science.gov (United States)

    Watanabe, Leandra; Shannon, John D.; Valente, Richard H.; Rucavado, Alexandra; Alape-Girón, Alberto; Kamiguti, Aura S.; Theakston, R. David G.; Fox, Jay W.; Gutiérrez, José María; Arni, Raghuvir K.

    2003-01-01

    BaP1 is a 22.7-kD P-I-type zinc-dependent metalloproteinase isolated from the venom of the snake Bothrops asper, a medically relevant species in Central America. This enzyme exerts multiple tissue-damaging activities, including hemorrhage, myonecrosis, dermonecrosis, blistering, and edema. BaP1 is a single chain of 202 amino acids that shows highest sequence identity with metalloproteinases isolated from the venoms of snakes of the subfamily Crotalinae. It has six Cys residues involved in three disulfide bridges (Cys 117–Cys 197, Cys 159–Cys 181, Cys 157–Cys 164). It has the consensus sequence H142E143XXH146XXGXXH152, as well as the sequence C164I165M166, which characterize the “metzincin” superfamily of metalloproteinases. The active-site cleft separates a major subdomain (residues 1–152), comprising four α-helices and a five-stranded β-sheet, from the minor subdomain, which is formed by a single α-helix and several loops. The catalytic zinc ion is coordinated by the Nɛ2 nitrogen atoms of His 142, His 146, and His 152, in addition to a solvent water molecule, which in turn is bound to Glu 143. Several conserved residues contribute to the formation of the hydrophobic pocket, and Met 166 serves as a hydrophobic base for the active-site groups. Sequence and structural comparisons of hemorrhagic and nonhemorrhagic P-I metalloproteinases from snake venoms revealed differences in several regions. In particular, the loop comprising residues 153 to 176 has marked structural differences between metalloproteinases with very different hemorrhagic activities. Because this region lies in close proximity to the active-site microenvironment, it may influence the interaction of these enzymes with physiologically relevant substrates in the extracellular matrix. PMID:14500885

  17. Inflammatory effects of BaP1 a metalloproteinase isolated from Bothrops asper snake venom: leukocyte recruitment and release of cytokines.

    Science.gov (United States)

    Fernandes, Cristina Maria; Zamuner, Stella Regina; Zuliani, Juliana Pavan; Rucavado, Alexandra; Gutiérrez, José Maria; Teixeira, Catarina de Fátima Pereira

    2006-04-01

    The inflammatory events induced by BaP1, a 22.7 kDa metalloproteinase isolated from Bothrops asper snake venom, were studied. BaP1 i.p. injection in mice induced a marked inflammatory cell infiltrate into peritoneal cavity of animals with predominance of neutrophils in the early phase followed by mononuclear cells in the late period. Inhibition of enzymatic activity of BaP1 by chelation with EDTA resulted in a drastic reduction of this effect. In addition, BaP1 induced a significant increase of blood neutrophil numbers before its accumulation in peritoneal cavity, thus suggesting a stimulatory action of BaP1 on mechanisms of cell mobilization from bone marrow reserve compartments. A reduction in the number of neutrophils was observed in the exudate when antibodies against LECAM-1, CD18 and LFA-1 were used, suggesting the involvement of these adhesion molecules in the effects of BaP1. In contrast, there was no effect with antibodies against ICAM-1 and PECAM-1. Moreover, a conspicuous increment in the levels of IL-1 and TNF-alpha, but not of LTB4, was observed in peritoneal washes collected from mice injected with BaP1. It is concluded that BaP1 induces in vivo a marked leukocyte influx, which parallels an increased number of these cells in the blood, and is associated to the expression of specific leukocyte adhesion molecules and release of chemotactic inflammatory cytokines. Since BaP1 is a P-I class metalloproteinase, these results indicate that the proteolytic domain of metalloproteinases per se can trigger specific inflammatory events.

  18. Signaling pathways involved in zymosan phagocytosis induced by two secreted phospholipases A2isolated from Bothrops asper snake venom in macrophages.

    Science.gov (United States)

    Zuliani, Juliana Pavan; Gutiérrez, José María; Teixeira, Catarina

    2018-03-03

    Phagocytosis, a process involved in host defense, requires coordination of a variety of signaling reactions. MT-II, a catalytically-inactive Lys49-PLA 2 ¸ and MT-III, an active Asp49-PLA 2 isolated from Bothrops asper snake venom, activate phagocytosis in macrophages. In this study the signal pathways mediating zymosan phagocytosis, focusing in lipidic second messengers, were investigated. Macrophages collected from male Swiss mouse peritoneum were obtained 96h after i.p. injection of thioglycollate. Phagocytosis was evaluated with non-opsonized zymosan in the presence or absence of specific inhibitors. Data showed that both venom PLA 2 s increased phagocytosis. Zileuton, Etoricoxib, PACOCF 3 (5-LO, COX-2 and iPLA 2 inhibitors, respectively), as well as WEB2170 (PAF receptor antagonist) significantly reduced phagocytosis induced by both venom PLA 2 s. However, Indomethacin (COX-1/COX-2 inhibitor) and Montelukast (CysL receptor antagonist) did not affect the toxins-induced phagocytosis. Moreover, while PACOCF3 (iPLA 2 inhibitor), reduced the phagocytosis induced by MT-II and MT-III, AACOCF 3 (cPLA 2 inhibitor) significantly reduced the MT-II, but not MT-III-induced phagocytosis. These data suggest the effect of both sPLA 2 s depends on iPLA 2 and that the effect of MT-II depends on activation of cPLA 2 . COX-2 and 5-LO-derived metabolites as well as PAF are involved in the signaling events required for phagocytosis induced by both venom sPLA 2 s. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Neutralization of the edema-forming, defibrinating and coagulant effects of Bothrops asper venom by extracts of plants used by healers in Colombia.

    Science.gov (United States)

    Núñez, V; Otero, R; Barona, J; Saldarriaga, M; Osorio, R G; Fonnegra, R; Jiménez, S L; Díaz, A; Quintana, J C

    2004-07-01

    We determined the neutralizing activity of 12 ethanolic extracts of plants against the edema-forming, defibrinating and coagulant effects of Bothrops asper venom in Swiss Webster mice. The material used consisted of the leaves and branches of Bixa orellana (Bixaceae), Ficus nymphaeifolia (Moraceae), Struthanthus orbicularis (Loranthaceae) and Gonzalagunia panamensis (Rubiaceae); the stem barks of Brownea rosademonte (Caesalpiniaceae) and Tabebuia rosea (Bignoniaceae); the whole plant of Pleopeltis percussa (Polypodiaceae) and Trichomanes elegans (Hymenophyllaceae); rhizomes of Renealmia alpinia (Zingiberaceae), Heliconia curtispatha (Heliconiaceae) and Dracontium croatii (Araceae), and the ripe fruit of Citrus limon (Rutaceae). After preincubation of varying amounts of each extract with either 1.0 microg venom for the edema-forming effect or 2.0 microg venom for the defibrinating effect, the mixture was injected subcutaneously (sc) into the right foot pad or intravenously into the tail, respectively, to groups of four mice (18-20 g). All extracts (6.2-200 microg/mouse) partially neutralized the edema-forming activity of venom in a dose-dependent manner (58-76% inhibition), with B. orellana, S. orbicularis, G. panamensis, B. rosademonte, and D. croatii showing the highest effect. Ten extracts (3.9-2000 microg/mouse) also showed 100% neutralizing ability against the defibrinating effect of venom, and nine prolonged the coagulation time induced by the venom. When the extracts were administered either before or after venom injection, the neutralization of the edema-forming effect was lower than 40% for all extracts, and none of them neutralized the defibrinating effect of venom. When they were administered in situ (sc at the same site 5 min after venom injection), the neutralization of edema increased for six extracts, reaching levels up to 64% for C. limon.

  20. Amino acid sequence and crystal structure of BaP1, a metalloproteinase from Bothrops asper snake venom that exerts multiple tissue-damaging activities.

    Science.gov (United States)

    Watanabe, Leandra; Shannon, John D; Valente, Richard H; Rucavado, Alexandra; Alape-Girón, Alberto; Kamiguti, Aura S; Theakston, R David G; Fox, Jay W; Gutiérrez, José María; Arni, Raghuvir K

    2003-10-01

    BaP1 is a 22.7-kD P-I-type zinc-dependent metalloproteinase isolated from the venom of the snake Bothrops asper, a medically relevant species in Central America. This enzyme exerts multiple tissue-damaging activities, including hemorrhage, myonecrosis, dermonecrosis, blistering, and edema. BaP1 is a single chain of 202 amino acids that shows highest sequence identity with metalloproteinases isolated from the venoms of snakes of the subfamily Crotalinae. It has six Cys residues involved in three disulfide bridges (Cys 117-Cys 197, Cys 159-Cys 181, Cys 157-Cys 164). It has the consensus sequence H(142)E(143)XXH(146)XXGXXH(152), as well as the sequence C(164)I(165)M(166), which characterize the "metzincin" superfamily of metalloproteinases. The active-site cleft separates a major subdomain (residues 1-152), comprising four alpha-helices and a five-stranded beta-sheet, from the minor subdomain, which is formed by a single alpha-helix and several loops. The catalytic zinc ion is coordinated by the N(epsilon 2) nitrogen atoms of His 142, His 146, and His 152, in addition to a solvent water molecule, which in turn is bound to Glu 143. Several conserved residues contribute to the formation of the hydrophobic pocket, and Met 166 serves as a hydrophobic base for the active-site groups. Sequence and structural comparisons of hemorrhagic and nonhemorrhagic P-I metalloproteinases from snake venoms revealed differences in several regions. In particular, the loop comprising residues 153 to 176 has marked structural differences between metalloproteinases with very different hemorrhagic activities. Because this region lies in close proximity to the active-site microenvironment, it may influence the interaction of these enzymes with physiologically relevant substrates in the extracellular matrix.