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Sample records for accumulated plastic strain

  1. Dislocation accumulation at large plastic strains -- An approach to the theoretical strength of materials

    SciTech Connect

    Embury, J.D. |; Han, K.

    1999-04-01

    The usual method of introducing engineers to the concept of dislocations and their role in plastic flow is to compare an estimate of the theoretical strength of solid (of order {micro}/30 where {micro} is the shear modulus) and the observed strength of either single crystals ({mu}/10{sup 4}) or practical engineering material such as structural steels where the yield stress in shear is of order {mu}/10{sup 3}. However, if one considers the problem in reverse, one can consider the accumulation of dislocations as an important mechanism by which one can produce engineering materials in which the strength level approaches the theoretical strength. If one assumes that the flow stress can be expressed in terms of te mean free path between stored dislocations or as the square root of the global dislocation density, then one can see the influence of dislocation density in a diagrammatic form. It is clear that the strengthening by dislocation accumulation due to large imposed plastic strains represents an important approach both to the development of new, potentially valuable, engineering materials and an important area of basic understanding in terms of the mechanical response of materials close to their theoretical strength. Thus, this article will survey some of the factors which influence dislocation accumulation at large strains and the consequences of such accumulation processes.

  2. Accumulation of plastic strain in Zircaloy-4 at low homologous temperature

    NASA Astrophysics Data System (ADS)

    Matsunaga, Tetsuya; Satoh, Yuhki; Abe, Hiroaki

    2015-10-01

    Time-dependent strain accumulation in Zircaloy-4 was evaluated at 294 K, i.e., homologous temperature (T/Tm, where Tm is the melting temperature) of 0.14, to ascertain the mechanical response in fuel cladding material, even at the time of storage. Although diffusion processes are suppressed, considerable strain accumulation was observed at less than 0.2% offset stress. Transmission electron microscopy and electron backscattered diffraction analyses were used to investigate the dominant microstructural mechanism. Results showed that the heterogeneous dislocation structure generated strain accumulation, where straightly aligned dislocation arrays on the prismatic plane move freely and few deformation twins were formed in the grain interior. Furthermore, few dislocation tangles were observed because the slip systems were limited to one. Therefore, Zircaloy-4 shows weak work-hardening at the low homologous temperature because of the fewer interactions among dislocations, leading to unexpected strain accumulation under constant load conditions.

  3. Strain patterns and strain accumulation along plate margins

    NASA Technical Reports Server (NTRS)

    Savage, J. C.

    1978-01-01

    Observations of strain accumulation along plate margins in Japan, New Zealand, and the United States indicate that: (1) a typical maximum rate of secular strain accumulation is on the order of 0.3 ppm/a, (2) a substantial part of the strain accumulation process can be attributed to slip at depth on the major plate boundary faults, and (3) some plastic deformation in a zone 100 km or more in width is apparently involved in the strain accumulation process.

  4. Computational strain gradient crystal plasticity

    NASA Astrophysics Data System (ADS)

    Niordson, Christian F.; Kysar, Jeffrey W.

    2014-01-01

    A numerical method for viscous strain gradient crystal plasticity theory is presented, which incorporates both energetic and dissipative gradient effects. The underlying minimum principles are discussed as well as convergence properties of the proposed finite element procedure. Three problems of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically oriented face centered cubic crystals are developed in terms of the crystallographic slip parameters. The effect on geometrically necessary dislocation structures introduced by plastic deformation is investigated as a function of the ratio of void radius to plasticity length scale.

  5. Plastic accumulation in the Mediterranean sea.

    PubMed

    Cózar, Andrés; Sanz-Martín, Marina; Martí, Elisa; González-Gordillo, J Ignacio; Ubeda, Bárbara; Gálvez, José Á; Irigoien, Xabier; Duarte, Carlos M

    2015-01-01

    Concentrations of floating plastic were measured throughout the Mediterranean Sea to assess whether this basin can be regarded as a great accumulation region of plastic debris. We found that the average density of plastic (1 item per 4 m2), as well as its frequency of occurrence (100% of the sites sampled), are comparable to the accumulation zones described for the five subtropical ocean gyres. Plastic debris in the Mediterranean surface waters was dominated by millimeter-sized fragments, but showed a higher proportion of large plastic objects than that present in oceanic gyres, reflecting the closer connection with pollution sources. The accumulation of floating plastic in the Mediterranean Sea (between 1,000 and 3,000 tons) is likely related to the high human pressure together with the hydrodynamics of this semi-enclosed basin, with outflow mainly occurring through a deep water layer. Given the biological richness and concentration of economic activities in the Mediterranean Sea, the affects of plastic pollution on marine and human life are expected to be particularly frequent in this plastic accumulation region.

  6. Plastic Accumulation in the Mediterranean Sea

    PubMed Central

    Cózar, Andrés; Sanz-Martín, Marina; Martí, Elisa; González-Gordillo, J. Ignacio; Ubeda, Bárbara; Gálvez, José Á.; Irigoien, Xabier; Duarte, Carlos M.

    2015-01-01

    Concentrations of floating plastic were measured throughout the Mediterranean Sea to assess whether this basin can be regarded as a great accumulation region of plastic debris. We found that the average density of plastic (1 item per 4 m2), as well as its frequency of occurrence (100% of the sites sampled), are comparable to the accumulation zones described for the five subtropical ocean gyres. Plastic debris in the Mediterranean surface waters was dominated by millimeter-sized fragments, but showed a higher proportion of large plastic objects than that present in oceanic gyres, reflecting the closer connection with pollution sources. The accumulation of floating plastic in the Mediterranean Sea (between 1,000 and 3,000 tons) is likely related to the high human pressure together with the hydrodynamics of this semi-enclosed basin, with outflow mainly occurring through a deep water layer. Given the biological richness and concentration of economic activities in the Mediterranean Sea, the affects of plastic pollution on marine and human life are expected to be particularly frequent in this plastic accumulation region. PMID:25831129

  7. Measurement of large strains in ropes using plastic optical fibers

    DOEpatents

    Williams, Jerry Gene; Smith, David Barton; Muhs, Jeffrey David

    2006-02-14

    A method for the direct measurement of large strains in ropes in situ using a plastic optical fiber, for example, perfluorocarbon or polymethyl methacrylate and Optical Time-Domain Reflectometer or other light time-of-flight measurement instrumentation. Protective sheaths and guides are incorporated to protect the plastic optical fiber. In one embodiment, a small rope is braided around the plastic optical fiber to impose lateral compressive forces to restrain the plastic optical fiber from slipping and thus experience the same strain as the rope. Methods are described for making reflective interfaces along the length of the plastic optical fiber and to provide the capability to measure strain within discrete segments of the rope. Interpretation of the data allows one to calculate the accumulated strain at any point in time and to determine if the rope has experienced local damage.

  8. Accumulation and fragmentation of plastic debris in global environments.

    PubMed

    Barnes, David K A; Galgani, Francois; Thompson, Richard C; Barlaz, Morton

    2009-07-27

    One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic products commenced in the 1950s, plastic debris has accumulated in terrestrial environments, in the open ocean, on shorelines of even the most remote islands and in the deep sea. Annual clean-up operations, costing millions of pounds sterling, are now organized in many countries and on every continent. Here we document global plastics production and the accumulation of plastic waste. While plastics typically constitute approximately 10 per cent of discarded waste, they represent a much greater proportion of the debris accumulating on shorelines. Mega- and macro-plastics have accumulated in the highest densities in the Northern Hemisphere, adjacent to urban centres, in enclosed seas and at water convergences (fronts). We report lower densities on remote island shores, on the continental shelf seabed and the lowest densities (but still a documented presence) in the deep sea and Southern Ocean. The longevity of plastic is estimated to be hundreds to thousands of years, but is likely to be far longer in deep sea and non-surface polar environments. Plastic debris poses considerable threat by choking and starving wildlife, distributing non-native and potentially harmful organisms, absorbing toxic chemicals and degrading to micro-plastics that may subsequently be ingested. Well-established annual surveys on coasts and at sea have shown that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing: rather stable, increasing and decreasing trends have all been reported. The average size of plastic particles in the environment seems to be decreasing, and the abundance and global distribution of micro-plastic fragments have increased over the last few decades. However, the environmental consequences of such microscopic debris are still poorly

  9. Accumulation and fragmentation of plastic debris in global environments.

    PubMed

    Barnes, David K A; Galgani, Francois; Thompson, Richard C; Barlaz, Morton

    2009-07-27

    One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic products commenced in the 1950s, plastic debris has accumulated in terrestrial environments, in the open ocean, on shorelines of even the most remote islands and in the deep sea. Annual clean-up operations, costing millions of pounds sterling, are now organized in many countries and on every continent. Here we document global plastics production and the accumulation of plastic waste. While plastics typically constitute approximately 10 per cent of discarded waste, they represent a much greater proportion of the debris accumulating on shorelines. Mega- and macro-plastics have accumulated in the highest densities in the Northern Hemisphere, adjacent to urban centres, in enclosed seas and at water convergences (fronts). We report lower densities on remote island shores, on the continental shelf seabed and the lowest densities (but still a documented presence) in the deep sea and Southern Ocean. The longevity of plastic is estimated to be hundreds to thousands of years, but is likely to be far longer in deep sea and non-surface polar environments. Plastic debris poses considerable threat by choking and starving wildlife, distributing non-native and potentially harmful organisms, absorbing toxic chemicals and degrading to micro-plastics that may subsequently be ingested. Well-established annual surveys on coasts and at sea have shown that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing: rather stable, increasing and decreasing trends have all been reported. The average size of plastic particles in the environment seems to be decreasing, and the abundance and global distribution of micro-plastic fragments have increased over the last few decades. However, the environmental consequences of such microscopic debris are still poorly

  10. Accumulation and fragmentation of plastic debris in global environments

    PubMed Central

    Barnes, David K. A.; Galgani, Francois; Thompson, Richard C.; Barlaz, Morton

    2009-01-01

    One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic products commenced in the 1950s, plastic debris has accumulated in terrestrial environments, in the open ocean, on shorelines of even the most remote islands and in the deep sea. Annual clean-up operations, costing millions of pounds sterling, are now organized in many countries and on every continent. Here we document global plastics production and the accumulation of plastic waste. While plastics typically constitute approximately 10 per cent of discarded waste, they represent a much greater proportion of the debris accumulating on shorelines. Mega- and macro-plastics have accumulated in the highest densities in the Northern Hemisphere, adjacent to urban centres, in enclosed seas and at water convergences (fronts). We report lower densities on remote island shores, on the continental shelf seabed and the lowest densities (but still a documented presence) in the deep sea and Southern Ocean. The longevity of plastic is estimated to be hundreds to thousands of years, but is likely to be far longer in deep sea and non-surface polar environments. Plastic debris poses considerable threat by choking and starving wildlife, distributing non-native and potentially harmful organisms, absorbing toxic chemicals and degrading to micro-plastics that may subsequently be ingested. Well-established annual surveys on coasts and at sea have shown that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing: rather stable, increasing and decreasing trends have all been reported. The average size of plastic particles in the environment seems to be decreasing, and the abundance and global distribution of micro-plastic fragments have increased over the last few decades. However, the environmental consequences of such microscopic debris are still poorly

  11. Plastic Accumulation in the North Atlantic Subtropical Gyre

    NASA Astrophysics Data System (ADS)

    Law, Kara Lavender; Morét-Ferguson, Skye; Maximenko, Nikolai A.; Proskurowski, Giora; Peacock, Emily E.; Hafner, Jan; Reddy, Christopher M.

    2010-09-01

    Plastic marine pollution is a major environmental concern, yet a quantitative description of the scope of this problem in the open ocean is lacking. Here, we present a time series of plastic content at the surface of the western North Atlantic Ocean and Caribbean Sea from 1986 to 2008. More than 60% of 6136 surface plankton net tows collected buoyant plastic pieces, typically millimeters in size. The highest concentration of plastic debris was observed in subtropical latitudes and associated with the observed large-scale convergence in surface currents predicted by Ekman dynamics. Despite a rapid increase in plastic production and disposal during this time period, no trend in plastic concentration was observed in the region of highest accumulation.

  12. Himalayan Strain Accumulation 100 ka Timescales

    NASA Astrophysics Data System (ADS)

    Cannon, J. M.; Murphy, M. A.; Liu, Y.

    2015-12-01

    Crustal scale fault systems and tectonostratigraphic units in the Himalaya can be traced for 2500 km along strike. However regional studies have shown that there is variability in the location and rate of strain accumulation which appears to be driven by Main Himalayan Thrust (MHT) geometry and convergence obliquity. GPS illuminates the modern interseismic strain rate and the historical record of great earthquakes elucidates variations in strain accumulation over 103 years. To connect these patterns with the 106 year structural and thermochronometric geologic record we examine normalized river channel steepness (ksn), a proxy for rock uplift rate, which develops over 104 - 105 years. Here we present a ksn map of the Himalaya and compare it with bedrock geology, precipitation, the historic earthquake record, GPS, seismicity, and seismotectonic models. Our map shows significant along strike changes in the magnitude of channel steepness, the areal extent of swaths of high ksn channels, and their location with respect to the range front. Differences include the juxtaposition of two narrow (30 - 40 km) range parallel belts of high ksn in west Nepal and Bhutan coincident with MHT duplexes and belts of microseismcity, with a single broad (70 km) swath of high ksn and microseismicity in central and eastern Nepal. Separating west and central Nepal a band of low ksn crosses the range coincident with the West Nepal Fault (WNF) and the lowest rate of microseismicity in Nepal. To the west the orogen is obliquely convergent and has less high ksn channels, while the orthogonally convergent region to the east contains the highest concentration of oversteepened channels in the Himalaya supporting the idea that the WNF is a strain partitioning boundary. The syntaxes are characterized by locally high channel steepness surrounded by low to moderate ksn channels consistent with the hypothesis that rapid exhumation within the syntaxes is sustained by an influx of lower crust.

  13. Plastic strain arrangement in copper single crystals in sliding

    SciTech Connect

    Chumaevskii, Andrey V. Lychagin, Dmitry V.; Tarasov, Sergei Yu.

    2014-11-14

    Deformation of tribologically loaded contact zone is one of the wear mechanisms in spite of the fact that no mass loss may occur during this process. Generation of optimal crystallographic orientations of the grains in a polycrystalline materials (texturing) may cause hardening and reducing the deformation wear. To reveal the orientation dependence of an individual gain and simplify the task we use copper single crystals with the orientations of the compression axis along [111] and [110]. The plastic deformation was investigated by means of optical, scanning electron microscopy and EBSD techniques. It was established that at least four different zones were generated in the course of sliding test, such as non-deformed base metal, plastic deformation layer sliding, crystalline lattice reorientation layer and subsurface grain structure layer. The maximum plastic strain penetration depth was observed on [110]-single crystals. The minimum stability of [111]-crystals with respect to rotation deformation mode as well as activation of shear in the sliding contact plane provide for rotation deformation localization below the worn surface. The high-rate accumulation of misorientations and less strain penetration depth was observed on [111]-crystals as compared to those of [110]-oriented ones.

  14. Strain Accumulation in Montenegro Using GPS Measurements

    NASA Astrophysics Data System (ADS)

    Glavatovic, B.; Vucic, L.; D'Agostino, N.; D'Anastasio, E.; Selvaggi, G.

    2011-12-01

    In this work we present the preliminary results of the analysis of GPS measurements collected from continuous stations belonging to networks deployed for both sceintific and societal purposes. The area is particularly interesting in relationship with the large Mw 7.1 earthquake that affected the Montenegro coastal areas in 1979 and the large uncertainties associated with recurrence times of large events and the present-day rate of strain accumulation. The dataset from the MEPOS (Montenegro), MONTEPOS (Montenegro), AGROS (Serbia) and MAKPOS (Macedonia) networks, combined with data from the RING (http://ring.gm.ingv.it) and other continuous GPS networks in the Mediterranean, Eurasian and African regions, has been analyzed using the GIPSY-OASIS II software package and the precise point positioning method [Zumberge et al., 1997]. Carrier phase ambiguities have been successfully resolved across the entire network using an algorithm based on a fixed-point theorem that closely approximates a full-network resolution [Blewitt, 2008]. Satellite orbit and clock parameters, and daily coordinate transformation parameters into ITRF2005 were provided by the Jet Propulsion Laboratory (JPL). ITRF2005 positions were transformed into an Eurasia fixed reference frame by performing daily transformations into a frame that is defined by minimizing the horizontal velocities of 30 stations across the stable part of the Eurasian continent (away from areas affected by glacial isostatic adjustments). Common mode errors for this continental scale frame are further reduced by including an additional 60 stations as far away as Iceland, Eastern Eurasia, and Africa in a daily spatial (7 parameters) filter [D'Anastasio et al., 2008]. We estimate velocities from the continuous GPS time-series using the CATS software package [Williams, 2003] while accounting for annual and semi-annual constituents, simultaneously estimating rate uncertainties given the assumption that the error model is dominated by

  15. Detecting plastic strain distribution by a nonlinear wave mixing method

    NASA Astrophysics Data System (ADS)

    Tang, Guangxin; Liu, Minghe; Jacobs, Laurence J.; Qu, Jianmin

    2013-01-01

    A nonlinear wave mixing method is used to measure the plastic strain distribution in polycrystalline materials. A pair of collinear longitudinal and shear waves is generated. Under the phase matching condition, a resonant shear wave with a difference frequency is generated and propagates towards the shear wave transducer. The amplitude of this resonant shear wave is proportional to the acoustic nonlinearity parameter β, which is known to be related to plastic deformation. By adjusting the two primary waves so that they mix at different locations, the distribution of β can be obtained. This study demonstrates the feasibility of detecting plastic strain distribution in polycrystalline materials by the nonlinear wave mixing technique.

  16. Stress-strain response of plastic waste mixed soil.

    PubMed

    Babu, G L Sivakumar; Chouksey, Sandeep Kumar

    2011-03-01

    Recycling plastic waste from water bottles has become one of the major challenges worldwide. The present study provides an approach for the use plastic waste as reinforcement material in soil. The experimental results in the form of stress-strain-pore water pressure response are presented. Based on experimental test results, it is observed that the strength of soil is improved and compressibility reduced significantly with addition of a small percentage of plastic waste to the soil. The use of the improvement in strength and compressibility response due to inclusion of plastic waste can be advantageously used in bearing capacity improvement and settlement reduction in the design of shallow foundations.

  17. Strain accumulation along the Cascadia subduction zone

    USGS Publications Warehouse

    Murray, M.H.; Lisowski, M.

    2000-01-01

    We combine triangulation, trilateration, and GPS observations to determine horizontal strain rates along the Cascadia subduction zone from Cape Mendocino to the Strait of Juan de Fuca. Shear-strain rates are significantly greater than zero (95% confidence) in all forearc regions (26-167 nanoradians/yr), and are not significant in the arc and backarc regions. The deformation is primarily uniaxial contraction nearly parallel to Juan de Fuca-North America plate convergence (N55??-80??E). The strain rates are consistent with an elastic dislocation model for interseismic slip with a shallow 100-km wide locked zone and a deeper 75-km transition zone along the entire megathrust, except along the central Oregon coast where relatively lower strain rates are consistent with 30-40 km wide locked and transition zones.

  18. High strain rate loading of polymeric foams and solid plastics

    NASA Astrophysics Data System (ADS)

    Dick, Richard D.; Chang, Peter C.; Fourney, William L.

    2000-04-01

    The split-Hopkinson pressure bar (SHPB) provided a technique to determine the high strain rate response for low density foams and solid ABS and polypropylene plastics. These materials are used in the interior safety panels of automobiles and crash test dummies. Because the foams have a very low impedance, polycarbonate bars were used to acquire the strain rate data in the 100 to 1600 l/s range. An aluminum SPHB setup was used to obtain the solid plastics data which covered strain rates of 1000 to 4000 l/s. The curves for peak strain rate versus peak stress for the foams over the test range studied indicates only a slight strain rate dependence. Peak strain rate versus peak stress curves for polypropylene shows a strain rate dependence up to about 1500 l/s. At that rate the solid poly propylene indicates no strain rate dependence. The ABS plastics are strain rate dependent up to 3500 l/s and then are independent at larger strain rates.

  19. Strain hardening and plastic instability properties of austenitic stainless steels after proton and neutron irradiation

    NASA Astrophysics Data System (ADS)

    Byun, T. S.; Farrell, K.; Lee, E. H.; Hunn, J. D.; Mansur, L. K.

    2001-10-01

    Strain hardening and plastic instability properties were analyzed for EC316LN, HTUPS316, and AL6XN austenitic stainless steels after combined 800 MeV proton and spallation neutron irradiation to doses up to 10.7 dpa. The steels retained good strain-hardening rates after irradiation, which resulted in significant uniform strains. It was found that the instability stress, the stress at the onset of necking, had little dependence on the irradiation dose. Tensile fracture stress and strain were calculated from the stress-strain curve data and were used to estimate fracture toughness using an existing model. The doses to plastic instability and fracture, the accumulated doses at which the yield stress reaches instability stress or fracture stress, were predicted by extrapolation of the yield stress, instability stress, and fracture stress to higher dose. The EC316LN alloy required the highest doses for plastic instability and fracture. Plastic deformation mechanisms are discussed in relation to the strain-hardening properties of the austenitic stainless steels.

  20. Strain gradient plasticity theory applied to machining

    NASA Astrophysics Data System (ADS)

    Royer, Raphaël; Laheurte, Raynald; Darnis, Philippe; Gérard, Alain; Cahuc, Olivier

    2011-05-01

    Machining is the most common manufacturing process. A good behaviour law is necessary in the simulation of machining processes (analytical and finite element modeling). Usually, commonly used behaviour laws such as Jonhson-Cook can bring unsatisfactory results especially for high strain and large deformation processes. Significant differences can appear between experimental and simulation results. The aim of this paper is to present the choices made regarding the behaviour law in this context. This study develops a large deformation strain-gradient theoretical framework with hypothesis linked to metal cutting processes. The theoretical framework has the potential of expressing moments at the tool tip as they were observed in experiments. It will be shown that the theory has the capability of interpreting the complex phenomena found in machining and more particularly in high speed machining.

  1. Strain gradient plasticity theory applied to machining

    SciTech Connect

    Royer, Raphael; Laheurte, Raynald; Darnis, Philippe; Gerard, Alain; Cahuc, Olivier

    2011-05-04

    Machining is the most common manufacturing process. A good behaviour law is necessary in the simulation of machining processes (analytical and finite element modeling). Usually, commonly used behaviour laws such as Jonhson-Cook can bring unsatisfactory results especially for high strain and large deformation processes. Significant differences can appear between experimental and simulation results. The aim of this paper is to present the choices made regarding the behaviour law in this context. This study develops a large deformation strain-gradient theoretical framework with hypothesis linked to metal cutting processes. The theoretical framework has the potential of expressing moments at the tool tip as they were observed in experiments. It will be shown that the theory has the capability of interpreting the complex phenomena found in machining and more particularly in high speed machining.

  2. Strain gradient plasticity analysis of elasto-plastic contact between rough surfaces

    NASA Astrophysics Data System (ADS)

    Song, H.; Van der Giessen, E.; Liu, X.

    2016-11-01

    From a microscopic point of view, the real contact area between two rough surfaces is the sum of the areas of contact between facing asperities. Since the real contact area is a fraction of the nominal contact area, the real contact pressure is much higher than the nominal contact pressure, which results in plastic deformation of asperities. As plasticity is size dependent at size scales below tens of micrometers, with the general trend of smaller being harder, macroscopic plasticity is not suitable to describe plastic deformation of small asperities and thus fails to capture the real contact area and pressure accurately. Here we adopt conventional mechanism-based strain gradient plasticity (CMSGP) to analyze the contact between a rigid platen and an elasto-plastic solid with a rough surface. Flattening of a single sinusoidal asperity is analyzed first to highlight the difference between CMSGP and J2 isotropic plasticity. For the rough surface contact, besides CMSGP, pure elastic and J2 isotropic plasticity analysis is also carried out for comparison. In all cases, the contact area A rises linearly with the applied load, but with a different slope which implies that the mean contact pressures are different. CMSGP produces qualitative changes in the distributions of local contact pressures compared with pure elastic and J2 isotropic plasticity analysis, furthermore, bounded by the two.

  3. Constitutive modeling and computational implementation for finite strain plasticity

    NASA Technical Reports Server (NTRS)

    Reed, K. W.; Atluri, S. N.

    1985-01-01

    This paper describes a simple alternate approach to the difficult problem of modeling material behavior. Starting from a general representation for a rate-tpe constitutive equation, it is shown by example how sets of test data may be used to derive restrictions on the scalar functions appearing in the representation. It is not possible to determine these functions from experimental data, but the aforementioned restrictions serve as a guide in their eventual definition. The implications are examined for hypo-elastic, isotropically hardening plastic, and kinematically hardening plastic materials. A simple model for the evolution of the 'back-stress,' in a kinematic-hardening plasticity theory, that is entirely analogous to a hypoelastic stress-strain relation is postulated and examined in detail in modeling finitely plastic tension-torsion test. The implementation of rate-type material models in finite element algorithms is also discussed.

  4. Strain accumulation and rotation in the Eastern California Shear Zone

    USGS Publications Warehouse

    Savage, J.C.; Gan, Weijun; Svarc, J.L.

    2001-01-01

    Although the Eastern California Shear Zone (ECSZ) (strike ???N25??W) does not quite coincide with a small circle drawn about the Pacific-North America pole of rotation, trilateration and GPS measurements demonstrate that the motion within the zone corresponds to right-lateral simple shear across a vertical plane (strike N33??W??5??) roughly parallel to the tangent to that local small circle (strike ???N40??W). If the simple shear is released by slip on faults subparallel to the shear zone, the accumulated rotation is also released, leaving no secular rotation. South of the Garlock fault the principal faults (e.g., Calico-Blackwater fault) strike ???N40??W, close enough to the strike of the vertical plane across which maximum right-lateral shear accumulates to almost wholly accommodate that accumulation of both strain and rotation by right-lateral slip. North of the Garlock fault dip slip as well as strike slip on the principal faults (strike ???N20??W) is required to accommodate the simple shear accumulation. In both cases the accumulated rotation is released with the shear strain. The Garlock fault, which transects the ECSZ, is not offset by north-northwest striking faults nor, despite geological evidence for long-term left-lateral slip, does it appear at the present time to be accumulating left-lateral simple shear strain across the fault due to slip at depth. Rather the motion is explained by right-lateral simple shear across the orthogonal ECSZ. Left-lateral slip on the Garlock fault will release the shear strain accumulating there but would augment the accumulating rotation, resulting in a secular clockwise rotation rate ???80 nrad yr-1 (4.6?? Myr-1).

  5. Rapid intraplate strain accumulation in the New Madrid seismic zone

    USGS Publications Warehouse

    Liu, L.; Zoback, M.D.; Segall, P.

    1992-01-01

    Remeasurement of a triangulation network in the southern part of the New Madrid seismic zone with the Global Positioning System has revealed rapid crustal strain accumulation since the 1950s. This area experienced three large (moment magnitudes >8) earthquakes in 1811 to 1812. The orientation and sense of shear is consistent with right-lateral strike slip motion along a northeast-trending fault zone (as indicated by current seismicity). Detection of crustal strain accumulation may be a useful discriminant for identifying areas where potentially damaging intraplate earthquakes may occur despite the absence of large earthquakes during historic time.

  6. Rapid intraplate strain accumulation in the New Madrid seismic zone

    SciTech Connect

    Liu, L.; Zoback, M.D.; Segall, P. USGS, Menlo Park, CA )

    1992-09-01

    Remeasurement of a triangulation network in the southern part of the New Madrid seismic zone with the Global Positioning System has revealed rapid crustal strain accumulation since the 1950s. This area experienced three large (moment magnitudes greater than 8) earthquakes in 1811 to 1812. The orientation and sense of shear is consistent with right-lateral strike slip motion along a northeast-trending fault zone (as indicated by current seismicity). Detection of crustal strain accumulation may be a useful discriminant for identifying areas where potentially damaging intraplate earthquakes may occur despite the absence of large earthquakes during historic time. 34 refs.

  7. Application Of Elastic Perfectly Plastic Cyclic Analysis To Assessment Of Creep Strain

    SciTech Connect

    Carter, Peter; Jetter, Robert I; Sham, Sam

    2012-01-01

    A cyclic elastic-perfectly plastic analysis method is proposed which provides a conservative estimate to cyclic creep strain accumulation within the ratchet boundary. The method is to check for ratcheting based on an elastic-perfectly material with a temperature-dependent pseudo yield stress defined by temperature, time and stress to give 1% creep strain. It does not require stress classification and is also applicable to a full range of temperature above and below the creep regime. This simplified method could be used as a rapid screening calculation, with full time-dependent creep analysis used if necessary.

  8. Plasticity in bulk metallic glasses investigated via the strain distribution

    SciTech Connect

    Das, Jayanta; Mattern, Norbert; Eckert, Juergen; Bostroem, Magnus; Kvick, Aake; Yavari, Alain Reza; Greer, Alan Lindsay

    2007-09-01

    We measured the atomic-scale elastic strain in order to investigate the yielding of Zr{sub 55}Cu{sub 20}Ni{sub 10}Al{sub 10}Ti{sub 5} and Cu{sub 47.5}Zr{sub 47.5}Al{sub 5} bulk metallic glasses (BMGs) by x-ray synchrotron radiation at room temperature. High resolution strain scanning reveals a deviation from the linear stress-strain relationship at the onset of macroplastic flow. Similar to polycrystalline metals, a saturation of the elastic strain components has been revealed in the case of the ''plastic'' Cu{sub 47.5}Zr{sub 47.5}Al{sub 5} BMG. The results show that the atomic-level elastic strains of the plastic Cu{sub 47.5}Zr{sub 47.5}Al{sub 5} BMG are more homogeneous compared to the 'brittle' Zr{sub 55}Cu{sub 20}Ni{sub 10}Al{sub 10}Ti{sub 5} glass.

  9. Plastic litter accumulation on high-water strandline of urban beaches in Mumbai, India.

    PubMed

    Jayasiri, H B; Purushothaman, C S; Vennila, A

    2013-09-01

    Today, almost every beach on every coastline is threatened by human activities. The inadequate recycling and poor management of waste in developing countries has resulted in considerable quantities of plastic contaminating beaches. Though India has long coastline of 5,420 km along the mainland with 43 % of sandy beaches, data on litter accumulation, particularly the plastics, which are one of the most common and persistent pollutants in marine environment, are scanty. The abundance and distribution of plastic litter was quantitatively assessed in four sandy beaches in Mumbai, India, bimonthly from May 2011 to March 2012. Triplicates of 2 × 2 m (4 m(2)) quadrats were sampled in each beach with a total of 72 quadrats. Overall, average abundance of 11.6 items m(-2) (0.25-282.5 items m(-2)) and 3.24 g m(-2) (0.27-15.53 g m(-2)) plastic litter was recorded in Mumbai beaches. Plastic litter accumulation significantly varied temporally and spatially at p = 0.05. Significantly higher plastic litter accumulation was recorded in Juhu beach. Furthermore, the highest abundance by weight was recorded in November and May numerically. More than 80 % of plastic particles were within the size range of 5-100 mm both by number and weight. Moreover, coloured plastics were predominant with 67 % by number of items and 51 % by weight. Probably, the intense use of beaches for recreation, tourism, and religious activities has increased the potential for plastic contamination in urban beaches in Mumbai.

  10. Plastic litter accumulation on high-water strandline of urban beaches in Mumbai, India.

    PubMed

    Jayasiri, H B; Purushothaman, C S; Vennila, A

    2013-09-01

    Today, almost every beach on every coastline is threatened by human activities. The inadequate recycling and poor management of waste in developing countries has resulted in considerable quantities of plastic contaminating beaches. Though India has long coastline of 5,420 km along the mainland with 43 % of sandy beaches, data on litter accumulation, particularly the plastics, which are one of the most common and persistent pollutants in marine environment, are scanty. The abundance and distribution of plastic litter was quantitatively assessed in four sandy beaches in Mumbai, India, bimonthly from May 2011 to March 2012. Triplicates of 2 × 2 m (4 m(2)) quadrats were sampled in each beach with a total of 72 quadrats. Overall, average abundance of 11.6 items m(-2) (0.25-282.5 items m(-2)) and 3.24 g m(-2) (0.27-15.53 g m(-2)) plastic litter was recorded in Mumbai beaches. Plastic litter accumulation significantly varied temporally and spatially at p = 0.05. Significantly higher plastic litter accumulation was recorded in Juhu beach. Furthermore, the highest abundance by weight was recorded in November and May numerically. More than 80 % of plastic particles were within the size range of 5-100 mm both by number and weight. Moreover, coloured plastics were predominant with 67 % by number of items and 51 % by weight. Probably, the intense use of beaches for recreation, tourism, and religious activities has increased the potential for plastic contamination in urban beaches in Mumbai. PMID:23430068

  11. A polycrystal plasticity model of strain localization in irradiated iron

    NASA Astrophysics Data System (ADS)

    Barton, Nathan R.; Arsenlis, Athanasios; Marian, Jaime

    2013-02-01

    At low to intermediate homologous temperatures, the degradation of structural materials performance in nuclear environments is associated with high number densities of nanometric defects produced in irradiation cascades. In polycrystalline ferritic materials, self-interstitial dislocations loops are a principal signature of irradiation damage, leading to a mechanical response characterized by increased yield strengths, decreased total strain to failure, and decreased work hardening as compared to the unirradiated behavior. Above a critical defect concentration, the material deforms by plastic flow localization, giving rise to strain softening in terms of the engineering stress-strain response. Flow localization manifests itself in the form of defect-depleted crystallographic channels, through which all dislocation activity is concentrated. In this paper, we describe the formulation of a crystal plasticity model for pure Fe embedded in a finite element polycrystal simulator and present results of uniaxial tensile deformation tests up to 10% strain. We use a tensorial damage descriptor variable to capture the evolution of the irradiation damage loop subpopulation during deformation. The model is parameterized with detailed dislocation dynamics simulations of tensile tests up to 1.5% deformation of systems containing various initial densities of irradiation defects. The coarse-grained simulations are shown to capture the essential details of the experimental stress response observed in ferritic alloys and steels. Our methodology provides an effective linkage between the defect scale, of the order of one nanometer, and the continuum scale involving multiple grain orientations.

  12. Linking strain anisotropy and plasticity in copper metallization

    NASA Astrophysics Data System (ADS)

    Murray, Conal E.; Jordan-Sweet, Jean; Priyadarshini, Deepika; Nguyen, Son

    2015-05-01

    The elastic anisotropy of copper leads to significant variation in the x-ray elastic constants (XEC), which link diffraction-based strain measurements to stress. An accurate depiction of the mechanical response in copper thin films requires a determination of an appropriate grain interaction model that lies between Voigt and Reuss limits. It is shown that the associated XEC weighting fraction, x*, between these limits provides a metric by which strain anisotropy can be quantified. Experimental values of x*, as determined by a linear regression scheme of diffraction data collected from multiple reflections, reveal the degree of strain anisotropy and its dependence on plastic deformation induced during in-situ and ex-situ thermal treatments.

  13. Linking strain anisotropy and plasticity in copper metallization

    SciTech Connect

    Murray, Conal E. Jordan-Sweet, Jean; Priyadarshini, Deepika; Nguyen, Son

    2015-05-04

    The elastic anisotropy of copper leads to significant variation in the x-ray elastic constants (XEC), which link diffraction-based strain measurements to stress. An accurate depiction of the mechanical response in copper thin films requires a determination of an appropriate grain interaction model that lies between Voigt and Reuss limits. It is shown that the associated XEC weighting fraction, x*, between these limits provides a metric by which strain anisotropy can be quantified. Experimental values of x*, as determined by a linear regression scheme of diffraction data collected from multiple reflections, reveal the degree of strain anisotropy and its dependence on plastic deformation induced during in-situ and ex-situ thermal treatments.

  14. Determining Recoverable and Irrecoverable Contributions to Accumulated Strain in a NiTiPd High-Temperature Shape Memory Alloy During Thermomechanical Cycling

    NASA Technical Reports Server (NTRS)

    Monroe, J. A.; Karaman, I.; Lagoudas, D. C.; Bigelow, G.; Noebe, R. D.; Padula, S., II

    2011-01-01

    When Ni(29.5)Ti(50.5)Pd30 shape memory alloy is thermally cycled under stress, significant strain can accumulate due to elasticity, remnant oriented martensite and plasticity. The strain due to remnant martensite can be recovered by further thermal cycling under 0 MPa until the original transformation-induced volume change and martensite coefficient of thermal expansion are obtained. Using this technique, it was determined that the 8.15% total accumulated strain after cycling under 200 MPa consisted of 0.38%, 3.97% and 3.87% for elasticity, remnant oriented martensite and creep/plasticity, respectively.

  15. Strain accumulation in southern California, 1973-1980.

    USGS Publications Warehouse

    Savage, J.C.; Prescott, W.H.; Lisowski, M.; King, N.E.

    1981-01-01

    Frequent surveys of seven trilateration networks in southern California over the interval 1973-1980 suggest that a regional increment in strain may have occurred in 1978-1979. Prior to 1978 and after late 1979 the strain accumulation has been predominantly a uniaxial north-south compression. This secular trend was interrupted sometime in 1978-1979 by an increment in both north-south and east-west extension in five of the seven networks. The onset of this change appears to have occurred first in the networks farthest south. The changes occurred without any unusual seismicity within the networks, but the overall seismicity in southern California was unusually low prior to and has been unusually high since the occurrence. The average principal strain rates for the seven networks in the 1973-1980 interval are 0.17 mu strain/yr north- south contraction and 0.08 mu strain/yr east-west extension. Although the observed increment in strain could be related to unidentified systematic error in the measuring system, a careful review of the measurements and comparisons with three other measuring systems reveal no appreciable cumulative systematic error. -Authors

  16. Evolution of plastic anisotropy for high-strain-rate computations

    SciTech Connect

    Schiferl, S.K.; Maudlin, P.J.

    1994-12-01

    A model for anisotropic material strength, and for changes in the anisotropy due to plastic strain, is described. This model has been developed for use in high-rate, explicit, Lagrangian multidimensional continuum-mechanics codes. The model handles anisotropies in single-phase materials, in particular the anisotropies due to crystallographic texture--preferred orientations of the single-crystal grains. Textural anisotropies, and the changes in these anisotropies, depend overwhelmingly no the crystal structure of the material and on the deformation history. The changes, particularly for a complex deformations, are not amenable to simple analytical forms. To handle this problem, the material model described here includes a texture code, or micromechanical calculation, coupled to a continuum code. The texture code updates grain orientations as a function of tensor plastic strain, and calculates the yield strength in different directions. A yield function is fitted to these yield points. For each computational cell in the continuum simulation, the texture code tracks a particular set of grain orientations. The orientations will change due to the tensor strain history, and the yield function will change accordingly. Hence, the continuum code supplies a tensor strain to the texture code, and the texture code supplies an updated yield function to the continuum code. Since significant texture changes require relatively large strains--typically, a few percent or more--the texture code is not called very often, and the increase in computer time is not excessive. The model was implemented, using a finite-element continuum code and a texture code specialized for hexagonal-close-packed crystal structures. The results for several uniaxial stress problems and an explosive-forming problem are shown.

  17. Accumulation of plastic-derived chemicals in tissues of seabirds ingesting marine plastics.

    PubMed

    Tanaka, Kosuke; Takada, Hideshige; Yamashita, Rei; Mizukawa, Kaoruko; Fukuwaka, Masa-aki; Watanuki, Yutaka

    2013-04-15

    We analyzed polybrominated diphenyl ethers (PBDEs) in abdominal adipose of oceanic seabirds (short-tailed shearwaters, Puffinus tenuirostris) collected in northern North Pacific Ocean. In 3 of 12 birds, we detected higher-brominated congeners (viz., BDE209 and BDE183), which are not present in the natural prey (pelagic fish) of the birds. The same compounds were present in plastic found in the stomachs of the 3 birds. These data suggested the transfer of plastic-derived chemicals from ingested plastics to the tissues of marine-based organisms.

  18. Plasticity of Cu nanoparticles: Dislocation-dendrite-induced strain hardening and a limit for displacive plasticity

    PubMed Central

    Albe, Karsten

    2013-01-01

    Summary The plastic behaviour of individual Cu crystallites under nanoextrusion is studied by molecular dynamics simulations. Single-crystal Cu fcc nanoparticles are embedded in a spherical force field mimicking the effect of a contracting carbon shell, inducing pressure on the system in the range of gigapascals. The material is extruded from a hole of 1.1–1.6 nm radius under athermal conditions. Simultaneous nucleation of partial dislocations at the extrusion orifice leads to the formation of dislocation dendrites in the particle causing strain hardening and high flow stress of the material. As the extrusion orifice radius is reduced below 1.3 Å we observe a transition from displacive plasticity to solid-state amorphisation. PMID:23616936

  19. Strain rate insensitive plasticity in aluminum alloy 5083

    SciTech Connect

    Patankar, S.N.; Jen, T.M.

    1998-03-13

    Superplastic forming offers a cost effective means to produce stress free, complex shaped components in one operation with consistency and dimensional accuracy. With the emphasis for light weight structural materials increasing, several aluminum alloys, which include Supral 2004, 7475, 5083 and 8090 have been studied for their superplastic properties with the ultimate objective of using them in automotive and aerospace structures. Among these, non heat treatable 5083 because of its moderate strength, better corrosion resistance, weldability and ability to take surface finishes coupled with its low cost, is preferred for applications involving superplastic forming. Research into the various metallurgical aspects of AA 5083 has been pursued by several groups around the world. In general, development of superplastic alloys has been concerned with grain refinement through elemental additions, recrystallization and thermo-mechanical processing of existing alloys. While the primary role of Mg in 5083 AA is solid solution strengthening many modified Al-Mg alloys have been developed by addition of different elements like Cu, Mn, Zr, etc. in different proportions to AA 5083 with an aim to reduce the tendency of cavitation and improve overall superplastic properties. AA 5083 has been categorized as statically recrystallizing rather than dynamically recrystallizing prior to superplastic deformation that occurs during thermo-mechanical processing. All the studies done so far share one thing and that is the direct dependence of flow stress on the strain. This strain hardening which increases with strain rate is attributed to the grain coarsening that occurs during the deformation of the 5083 alloy. Also found in this alloy is the higher total elongation at lower strain rates. The purpose of this paper is to report and explain the unusual stress strain behavior and strain rate independent plasticity observed in 5083 aluminum alloy.

  20. The amount and accumulation rate of plastic debris on marshes and beaches on the Georgia coast.

    PubMed

    Lee, Richard F; Sanders, Dorothea P

    2015-02-15

    The amount and accumulation rate of plastic debris at 20 sites along the Georgia coast were prepared using data reported by a number of volunteer organizations. The amount of plastic debris at highly visited barrier island beaches and estuarine marshes ranged from 300 to >1000 kg. Relatively large amount of plastics (180-500 kg) were found on less visited barrier island beaches, i.e. Blackbeard, Ossabaw and Cumberland Islands. A follow up monthly or quarterly collection study was carried out on two of the sites, a barrier beach and estuarine marsh, to determine accumulation rate in 8000 m(2) areas. Accumulation rates ranged from 0.18 to 1.28 kg/30 days-8000 m(2) on the barrier island beach and from 0.6 to 1.61 kg/30 days-8000 m(2) at the estuarine marsh site. The major type of plastics, e.g. bottles, food wrappers, plastic fragments, was highly variable at different seasons and sites. The authors recommend consideration of a standardization in reporting plastic debris, with respect to quantitation of debris and sample area.

  1. Quantifying Damage Accumulation During Ductile Plastic Deformation Using Synchrotron Radiation

    SciTech Connect

    Suter, Robert M.; Rollett, Anthony D.

    2015-08-15

    Under this grant, we have developed and demonstrated the ability of near-field High Energy Diffraction Microscopy (nf-HEDM) to map crystal orientation fields over three dimensions in deformed polycrystalline materials. Experimental work was performed at the Advanced Photon Source (APS) at beamline 1-ID. Applications of this new capability to ductile deformation of copper and zirconium samples were demonstrated as was the comparison of the experimental observations to computational plasticity models using a fast Fourier transform based algorithm that is able to handle the large experimental data sets. No such spatially resolved, direct comparison between measured and computed microstructure evolutions had previously been possible. The impact of this work is reflected in numerous publications and presentations as well as in the investments by DOE and DOD laboratories of millions of dollars in applying the technique, developing sophisticated new hardware that allows the technique to be applied to a wide variety of materials and materials problems, and in the use of the technique by other researchers. In essence, the grant facilitated the development of a new form of three dimensional microscopy and its application to technologically critical states of polycrystalline materials that are used throughout the U.S. and world economies. On-going collaborative work is further optimizing experimental and computational facilities at the APS and is pursuing expanded facilities.

  2. Ismetpasa and Destek regions; Creeping or accumulating strain

    NASA Astrophysics Data System (ADS)

    Yavasoglu, Hakan; Alkan, M. Nurullah; Aladogan, Kayhan; Ozulu, I. Murat; Ilci, Veli; Sahin, Murat; Tombus, F. Engin; Tiryakioglu, Ibrahim

    2016-04-01

    The North Anatolian Fault (NAF) is one of the most destructive fault system all over the world. In the last century, many devastating seismic event happened on it and its shear zone (NAFZ). Especially, after the 1999 Izmit and Duzce earthquakes, the earth science studies increase to save human life. To better understand the mechanism of the active fault system, tectonic stress and strain are important phenomena. According to elastic rebound theory, the locked active faults release the accumulated strain abruptly in four periods; interseismic, preseismic, coseismic and postseismic. In the literature, this phase is called the earthquake cycle. On the other hand, there is another scenario (aseismic deformation or creep) to release the strain without any remarkable seismic event. For the creep procedure, the important subject is threshold of the aseismic slip rate. If it is equal or larger than long-term slip rate, the destructive earthquakes will not occur along the fault which has aseismic slip rate. On the contrary, if the creep motion is lower than long-term slip rate along the fault, the fault has potential to produce moderate-to-large size earthquakes. In this study, the regions, Ismetpasa and Destek, have been studied to determine the aseismic deformation using GPS data. The first and second GPS campaigns have been evaluated with GAMIT/GLOBK software. Preliminary results of the project (slip-rate along the NAF in this region and aseismic deformation) will be presented.

  3. Modelling accumulation of marine plastics in the coastal zone; what are the dominant physical processes?

    NASA Astrophysics Data System (ADS)

    Critchell, Kay; Lambrechts, Jonathan

    2016-03-01

    Anthropogenic marine debris, mainly of plastic origin, is accumulating in estuarine and coastal environments around the world causing damage to fauna, flora and habitats. Plastics also have the potential to accumulate in the food web, as well as causing economic losses to tourism and sea-going industries. If we are to manage this increasing threat, we must first understand where debris is accumulating and why these locations are different to others that do not accumulate large amounts of marine debris. This paper demonstrates an advection-diffusion model that includes beaching, settling, resuspension/re-floating, degradation and topographic effects on the wind in nearshore waters to quantify the relative importance of these physical processes governing plastic debris accumulation. The aim of this paper is to prioritise research that will improve modelling outputs in the future. We have found that the physical characteristic of the source location has by far the largest effect on the fate of the debris. The diffusivity, used to parameterise the sub-grid scale movements, and the relationship between debris resuspension/re-floating from beaches and the wind shadow created by high islands also has a dramatic impact on the modelling results. The rate of degradation of macroplastics into microplastics also have a large influence in the result of the modelling. The other processes presented (settling, wind drift velocity) also help determine the fate of debris, but to a lesser degree. These findings may help prioritise research on physical processes that affect plastic accumulation, leading to more accurate modelling, and subsequently management in the future.

  4. Gurson-type elastic-plastic damage model based on strain-rate plastic potential

    NASA Astrophysics Data System (ADS)

    Balan, Tudor; Cazacu, Oana

    2013-12-01

    Ductile damage is generally described by stress-space analytical potentials. In this contribution, it is shown that strain rate potentials, which are exact conjugate of the stress-based potentials, can be equally used to describe the dilatational response of porous metals. This framework is particularly appropriate for porous materials with matrix described by complex yield criteria for which a closed-form expression of the stress-based potential is not available. Illustration of the new approach is done for porous metals containing randomly distributed spherical voids in a von Mises elasto-plastic matrix. Furthermore, a general time integration algorithm for simulation of the mechanical response using this new formulation is developed and implemented in Abaqus/Standard. The proposed model and algorithm are validated with respect to the Abaqus built-in GTN model, which is based on a stress potential, through the simulation of a tensile test on a round bar.

  5. Interseismic Strain Accumulation Across Metropolitan Los Angeles: Puente Hills Thrust

    NASA Astrophysics Data System (ADS)

    Argus, D.; Liu, Z.; Heflin, M. B.; Moore, A. W.; Owen, S. E.; Lundgren, P.; Drake, V. G.; Rodriguez, I. I.

    2012-12-01

    Twelve years of observation of the Southern California Integrated GPS Network (SCIGN) are tightly constraining the distribution of shortening across metropolitan Los Angeles, providing information on strain accumulation across blind thrust faults. Synthetic Aperture Radar Interferometry (InSAR) and water well records are allowing the effects of water and oil management to be distinguished. The Mojave segment of the San Andreas fault is at a 25° angle to Pacific-North America plate motion. GPS shows that NNE-SSW shortening due to this big restraining bend is fastest not immediately south of the San Andreas fault across the San Gabriel mountains, but rather 50 km south of the fault in northern metropolitan Los Angeles. The GPS results we quote next are for a NNE profile through downtown Los Angeles. Just 2 mm/yr of shortening is being taken up across the San Gabriel mountains, 40 km wide (0.05 micro strain/yr); 4 mm/yr of shortening is being taken up between the Sierra Madre fault, at the southern front of the San Gabriel mountains, and South Central Los Angeles, also 40 km wide (0.10 micro strain/yr). We find shortening to be more evenly distributed across metropolitan Los Angeles than we found before [Argus et al. 2005], though within the 95% confidence limits. An elastic models of interseismic strain accumulation is fit to the GPS observations using the Back Slip model of Savage [1983]. Rheology differences between crystalline basement and sedimentary basin rocks are incorporated using the EDGRN/EDCMP algorithm of Wang et al. [2003]. We attempt to place the Back Slip model into the context of the Elastic Subducting Plate Model of Kanda and Simons [2010]. We find, along the NNE profile through downtown, that: (1) The deep Sierra Madre Thrust cannot be slipping faster than 2 mm/yr, and (2) The Puente Hills Thrust and nearby thrust faults (such as the upper Elysian Park Thrust) are slipping at 9 ±2 mm/yr beneath a locking depth of 12 ±5 km (95% confidence limits

  6. Interseismic strain accumulation and anthropogenic motion in metropolitan Los Angeles

    NASA Astrophysics Data System (ADS)

    Argus, Donald F.; Heflin, Michael B.; Peltzer, Gilles; Crampé, FréDeric; Webb, Frank H.

    2005-04-01

    We use global positioning system (GPS) geodesy and synthetic aperture radar (SAR) interferometry to distinguish between interseismic strain accumulation and anthropogenic motion in metropolitan Los Angeles. We establish a relationship between horizontal and vertical seasonal oscillations of the Santa Ana aquifer, use this relationship to infer cumulative horizontal anthropogenic motions from cumulative vertical motions caused by water and oil resource management, and estimate horizontal interseismic velocities corrected for anthropogenic effects. Vertical anthropogenic rates from 1992 to 1999 are slower than 3 mm yr-1 in the Santa Ana and San Gabriel aquifers and faster than 5 mm yr-1 in the Chino aquifer and in many oil fields. Inferred horizontal anthropogenic velocities are faster than 1 mm yr-1 at 18 of 46 GPS sites. Northern metropolitan Los Angeles is contracting, with the 25 km south of the San Gabriel Mountains shortening at 4.5 ± 1 mm yr-1 (95% confidence limits). The thrust fault in an elastic edge dislocation model of the observed strain is creeping at 9 ± 2 mm yr-1 beneath and north of a position 6 ± 2 km deep and 8 ± 8 km north of downtown Los Angeles. The model fault is near the Los Angeles segment of the Puente Hills thrust but south of the Sante Fe Springs segment of the thrust. Disagreement between the 6 km locking depth in the model and the 15 km seismogenic depth inferred from earthquakes suggests that the elastic continuum model may be unsatisfactory; models with different stiffnesses of sedimentary basin and crystalline basement must be investigated.

  7. Interseismic strain accumulation and anthropogenic motion in metropolitan Los Angeles

    NASA Astrophysics Data System (ADS)

    Argus, D. F.; Heflin, M. B.; Peltzer, G.; Crampe, F.; Webb, F. H.

    2005-05-01

    We use global positioning system (GPS) geodesy and synthetic aperture radar (SAR) interferometry to distinguish between interseismic strain accumulation and anthropogenic motion in metropolitan Los Angeles. We establish a relationship between horizontal and vertical seasonal oscillations of the Santa Ana aquifer, use this relationship to infer cumulative horizontal anthropogenic motions from cumulative vertical motions caused by water and oil resource management, and estimate horizontal interseismic velocities corrected for anthropogenic effects. Vertical anthropogenic rates from 1992 to 1999 are slower than 3 mm/yr in the Santa Ana and San Gabriel aquifers and faster than 5 mm/yr in the Chino aquifer and in many oil fields. Inferred horizontal anthropogenic velocities are faster than 1 mm/yr at 18 of 46 GPS sites. Northern metropolitan Los Angeles is contracting, with the 25 km south of the San Gabriel mountains shortening at 4.5 ±1 mm/yr (95% confidence limits). The thrust fault in an elastic edge dislocation model of the observed strain is creeping at 9 ±2 mm/yr beneath and north of a position 6 ±2 km deep and 8 ±8 km north of downtown Los Angeles. The model fault is near the Los Angeles segment of the Puente Hills thrust but south of the Sante Fe Springs segment of the thrust. Disagreement between the 6 km locking depth in the model and the 15 km seismogenic depth inferred from earthquakes suggests that the elastic continuum model may be unsatisfactory; models with different stiffnesses of sedimentary basin and crystalline basement must be investigated.

  8. Features of plastic strain localization at the yield plateau in Hadfield steel single crystals

    NASA Astrophysics Data System (ADS)

    Barannikova, S. A.; Zuev, L. B.

    2008-07-01

    Spatiotemporal distributions of local components of the plastic distortion tensor in Hadfield steel single crystals oriented for single twinning have been studied under active tensile straining conditions using the double-exposure speckle photography technique. Features of the macroscopically inhomogeneous strain localization at the yield plateau are considered. Relations between local components of the plastic distortion tensor in the zone of strain localization are analyzed.

  9. Constraints on accumulated strain near the ETS zone along Cascadia

    NASA Astrophysics Data System (ADS)

    Krogstad, Randy D.; Schmidt, David A.; Weldon, Ray J.; Burgette, Reed J.

    2016-04-01

    Current national seismic hazard models for Cascadia use the zone of episodic tremor and slip (ETS) to denote the lower boundary of the seismogenic zone. Recent numerical models have suggested that an appreciable amount of long-term strain may accumulate at the depth of ETS and questions this assumption. We use uplift rates from leveling campaigns spanning approximately 50-70 yrs in Washington and Oregon to investigate the amount of potential long-term locking near the ETS zone. We evaluate the potential for deeper locking in Cascadia by exploring a range of locking parameters along the subduction zone, including the ETS zone. Of the four east-west leveling profiles studied, three show a reduction in the misfit when secondary locking near the ETS zone is included; however the reduction in misfit values is only statistically significant for one profile. This would suggest that models including a small amount of secondary locking are broadly indistinguishable from models without any secondary locking. If secondary locking is considered, the leveling data allow for locking up to ∼20% of the plate rate near the updip edge of the ETS zone. These results are consistent with, but less resolved, by GPS observations.

  10. Variability of polyploid strains of Candida scottii in accumulation of riboflavin in the medium.

    PubMed

    Imshenetsky, A A; Kondratieva, T F

    1977-01-01

    Polyploid strains of Candida scottii show a higher spontaneous and UV-induced variability in accumulation of riboflavin in the medium than the original haploid strain. UV irradiation affects the formation of variants and induces those which accumulate more riboflavin than any of the most productive variants resulting from spontaneous variability. In the polyploid strains the frequency of plus-variants increases. Therefore, polyploid strains of C. scottii are advantageous for selection processes. PMID:855365

  11. Transformation plasticity at high strain rate in magnesia-partially-stabilized zirconia

    SciTech Connect

    Rogers, W.P. . Dept. of Mechanical Engineering); Nemat-Nasser, S.

    1990-01-01

    Transformation plasticity in magnesia- partially-stabilized zirconia (Mg-PSZ) is studied using a split Hopkinson pressure bar modified for ceramic materials. Axial and transverse strains are measured under uniaxial compressive loading at a strain rate of 250/s. The transformation yield stress is found to increase from 900 MPa under quasi-static loading to 1.2 GPa at high strain rate. Post-yield deformation is characterized by shear and volumetric plastic strains up to 1.2%. During unloading, the axial and transverse plastic strains are partially recovered while the volume is conserved. Axially oriented microcracks are observed but they do not contribute significantly to plastic deformation in Mg-PSZ.

  12. [Dynamic accumulation regulation of curcumin, demethoxycurcumin and bisdemethoxyeurcumin in three strains of curcuma longae rhizome].

    PubMed

    Li, Qing-Miao; Yang, Wen-Yu; Tang, Xue-Mei; Zhang, Mei; Zhou, Xian-Jian; Shu, Guang-Ming; Zhao, Jun-Ning; Fang, Qing-Mao

    2014-06-01

    The paper is aimed to study the dynamic accumulation regulation of curcumin (Cur), demethoxycurcumin (DMC) and bisdemethoxyeurcumin (BDMC) in three strains of Curcuma longa, and provide scientific references for formalized cultivation, timely harvesting, quality control and breeding cultivation of C. longa. The accumulation regulation of the three curcumin derivatives was basically the same in rhizome of three strains. The relative contents decreased along with plant development growing, while the accumulation per hectare increased with plant development growing. The accumulation of curcuminoids per hectare could be taken as the assessment standard for the best harvest time of C. longa. A3 was the best strain in terms of Cur and BDMC content.

  13. Plastic Straining of Iridium Alloy DOP-26 During Cup Sizing Operations

    SciTech Connect

    Ohriner, Evan Keith; Ulrich, George B; Sabau, Adrian S

    2007-09-01

    DOP-26 iridium alloy cups are used for fuel cladding for radioisotope power systems. The cups are deep drawn and recrystallized prior to final fabrication operations. This study characterizes the plastic deformation of cups during a sizing operation following the recrystallization heat treatment. The purpose of the sizing operation is to achieve the specified roundness, diameter, and radius dimensions of the cup. The operation introduces various levels of plastic strain in the cup. Plastic strain can be a cause of inhomogeneous or abnormal grain growth during subsequent exposure to elevated temperature during the service life of the fueled clad. This is particularly true in the case of cups which have irregularities in the cup walls from the deep drawing operations. Diameter and roundness measurements were made on two cups both before and after sizing. Plastic strain levels were calculated using the ABAQUSTM finite element software. The calculated plastic strain levels in both cups were below 0.025, a value shown to be below the critical strain for abnormal grain growth during a simulated service exposure. The calculated maximum plastic strain was found to increase with increased applied sizing load and was not sensitive to the input value for the clearance between the cup and the sizing die. The calculated geometry of the sized cups was in good agreement with the measurements on the finished cups.

  14. Bonding of strain gages to fiber reinforced composite plastic materials

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Hanson, M. P.; Serafini, T. T.

    1970-01-01

    Strain gage is installed during molding of composite and utilizes the adhesive properties of the matrix resin in the composite to bond the strain gage in place. Gages thus embedded provide data at all temperatures that the matrix can withstand.

  15. Prediction of thermal strains in fibre reinforced plastic matrix by discretisation of the temperature exposure history

    NASA Astrophysics Data System (ADS)

    Ngoy, E. K.

    2016-07-01

    Prediction of environmental effects on fibre reinforced plastics habitually is made difficult due to the complex variability of the natural service environment. This paper suggests a method to predict thermal strain distribution over the material lifetime by discretisation of the exposure history. Laboratory results show a high correlation between predicted and experimentally measured strain distribution

  16. Elastic and plastic strain measurement in high temperature environment using laser speckle

    NASA Technical Reports Server (NTRS)

    Chiang, Fu-Pen

    1992-01-01

    Two laser speckle methods are described to measure strain in high temperature environment and thermal strain caused by high temperature. Both are non-contact, non-destructive and remote sensing techniques that can be automated. The methods have different but overlapping ranges of application with one being more suitable for large plastic deformation.

  17. On the homogenization of metal matrix composites using strain gradient plasticity

    NASA Astrophysics Data System (ADS)

    Azizi, Reza; Niordson, Christian F.; Legarth, Brian Nyvang

    2014-04-01

    The homogenized response of metal matrix composites (MMC) is studied using strain gradient plasticity. The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in addition to transverse and longitudinal loading. The analyses are carried out under generalized plane strain condition. Micro-macro homogenization is performed observing the Hill-Mandel energy condition, and overall loading is considered such that the homogenized higher order terms vanish. The results highlight the intrinsic size-effects as well as the effect of fiber volume fraction on the overall response curves, plastic strain distributions and homogenized yield surfaces under different loading conditions. It is concluded that composites with smaller reinforcement size have larger initial yield surfaces and furthermore, they exhibit more kinematic hardening. [Figure not available: see fulltext.

  18. Development of measurement method of work hardeningbehavior in large plastic strain for sheet metal forging

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Nobuo; Yamashita, Tomohiro; Shirakami, Satoshi; kada, Osamu; Yoshida, Tohru; Hiwatashi, Shunji

    2016-08-01

    For the purpose of accuracy improvement of sheet metal forging FE analysis, we have developed a new measurement method of work hardening behavior in large plastic strain by repeatedly performing simple shear test using pre-strained steel sheet. In this method, it is possible to measure work hardening behavior more than equivalent plastic strain 2.0. In addition, it was carried out a comparison between developed method and compression test in order to verify the validity of the results by the developed method. As a result, both results were in good agreement. The validity of developed method has been verified.

  19. Response of Polypmeric Foams and ABS Plastics to High Strain Rate Loading

    NASA Astrophysics Data System (ADS)

    Dick, Richard; Chang, Peter; Fourney, William

    1999-06-01

    The split-Hopkinson pressure bar (SHPB) technique was utilized to obtain high strain rate response data for low-density foams and solid ABS and polypropylene plastics. General Motors provided the materials for this study. These materials are used in the interior panels of automobiles. Because the foams have a very low impedance, polycarbonate bars were used to acquire the strain rate data in the 100 to 1600 per second range. An aluminum SHPB was used to obtain the solid plastics data that covered strain rates of 1000 to 4000 pre second. The experimental data indicate that the foams over the test range are only slightly strain rate dependent while the polypropylene appears to be strain rate independent above 1000 per second and the ABS plastics are strain rate independent above 3000 per second. The projectile length was varied to provide a wide range of induced strains ranging from 10 to 70 per cent for the foams and up to 20 per cent for the plastic materials.

  20. Relationship of trehalose accumulation with ethanol fermentation in industrial Saccharomyces cerevisiae yeast strains.

    PubMed

    Wang, Pin-Mei; Zheng, Dao-Qiong; Chi, Xiao-Qin; Li, Ou; Qian, Chao-Dong; Liu, Tian-Zhe; Zhang, Xiao-Yang; Du, Feng-Guang; Sun, Pei-Yong; Qu, Ai-Min; Wu, Xue-Chang

    2014-01-01

    The protective effect and the mechanisms of trehalose accumulation in industrial Saccharomyces cerevisiae strains were investigated during ethanol fermentation. The engineered strains with more intercellular trehalose achieved significantly higher fermentation rates and ethanol yields than their wild strain ZS during very high gravity (VHG) fermentation, while their performances were not different during regular fermentation. The VHG fermentation performances of these strains were consistent with their growth capacity under osmotic stress and ethanol stress, the key stress factors during VHG fermentation. These results suggest that trehalose accumulation is more important for VHG fermentation of industrial yeast strains than regular one. The differences in membrane integrity and antioxidative capacity of these strains indicated the possible mechanisms of trehalose as a protectant under VHG condition. Therefore, trehalose metabolic engineering may be a useful strategy for improving the VHG fermentation performance of industrial yeast strains.

  1. Relationship of trehalose accumulation with ethanol fermentation in industrial Saccharomyces cerevisiae yeast strains.

    PubMed

    Wang, Pin-Mei; Zheng, Dao-Qiong; Chi, Xiao-Qin; Li, Ou; Qian, Chao-Dong; Liu, Tian-Zhe; Zhang, Xiao-Yang; Du, Feng-Guang; Sun, Pei-Yong; Qu, Ai-Min; Wu, Xue-Chang

    2014-01-01

    The protective effect and the mechanisms of trehalose accumulation in industrial Saccharomyces cerevisiae strains were investigated during ethanol fermentation. The engineered strains with more intercellular trehalose achieved significantly higher fermentation rates and ethanol yields than their wild strain ZS during very high gravity (VHG) fermentation, while their performances were not different during regular fermentation. The VHG fermentation performances of these strains were consistent with their growth capacity under osmotic stress and ethanol stress, the key stress factors during VHG fermentation. These results suggest that trehalose accumulation is more important for VHG fermentation of industrial yeast strains than regular one. The differences in membrane integrity and antioxidative capacity of these strains indicated the possible mechanisms of trehalose as a protectant under VHG condition. Therefore, trehalose metabolic engineering may be a useful strategy for improving the VHG fermentation performance of industrial yeast strains. PMID:24316480

  2. Measurement of Plastic Stress and Strain for Analytical Method Verification (MSFC Center Director's Discretionary Fund Project No. 93-08)

    NASA Technical Reports Server (NTRS)

    Price, J. M.; Steeve, B. E.; Swanson, G. R.

    1999-01-01

    The analytical prediction of stress, strain, and fatigue life at locations experiencing local plasticity is full of uncertainties. Much of this uncertainty arises from the material models and their use in the numerical techniques used to solve plasticity problems. Experimental measurements of actual plastic strains would allow the validity of these models and solutions to be tested. This memorandum describes how experimental plastic residual strain measurements were used to verify the results of a thermally induced plastic fatigue failure analysis of a space shuttle main engine fuel pump component.

  3. Reduced uptake and accumulation of norfloxacin in resistant strains of Neisseria gonorrhoeae isolated in Japan.

    PubMed Central

    Tanaka, M; Fukuda, H; Hirai, K; Hosaka, M; Matsumoto, T; Kumazawa, J

    1994-01-01

    OBJECTIVE--To investigate the alteration of cell permeability toward fluoroquinolones in Neisseria gonorrhoeae, which is a major quinolone-resistance mechanism along with the alteration of DNA gyrase in gram-negative bacteria. The prevalence of fluoroquinolone-resistant N gonorrhoeae strains is rapidly increasing in Japan. MATERIALS AND METHODS--The uptake and accumulation of norfloxacin by gonococcal cells, including six clinical and five World Health Organization (WHO) reference strains, were measured. Of the six clinical strains, two were highly resistant to norfloxacin (MIC 8.0 and 4.0 micrograms/ml), two were moderately resistant (MIC 1.0 and 0.5 microgram/ml), and two were sensitive (MIC 0.063 and 0.004 microgram/ml). All five WHO reference strains were sensitive to norfloxacin (MIC < or = 0.001 to 0.063 microgram/ml). RESULTS--Mean initial norfloxacin uptake in the four resistant strains (104 ng/mg of dry cells) was significantly lower than that in the seven sensitive strains (158 ng/mg of dry cells) (p < 0.05). The mean uptake after 20 minutes was also significantly lower in the four resistant strains (130 ng/mg of dry cells) than in the seven sensitive strains (194 ng/mg of dry cells) (p < 0.05). However, there was no significant difference in mean norfloxacin accumulation after 20 minutes between the four resistant strains (26 ng/mg of dry cells) and the seven sensitive strains (36 ng/mg of dry cells). The accumulation of norfloxacin after 20 minutes was almost zero in two of the four resistant strains, while the remaining two strains accumulated norfloxacin as well as the sensitive strains. CONCLUSIONS--These findings suggest that alteration of bacterial cell permeability is a quinolone-resistance mechanism in N gonorrhoeae isolated in Japan, and that this bacteria may exhibit other mechanisms such as alteration of DNA gyrase. PMID:7959709

  4. The mechanisms of plastic strain accommodation during the high strain rate collapse of corrugated Ni-Al laminate cylinders

    NASA Astrophysics Data System (ADS)

    Olney, K. L.; Chiu, P. H.; Higgins, A.; Serge, M.; Weihs, T. P.; Fritz, G. M.; Stover, A. K.; Benson, D. J.; Nesterenko, V. F.

    2014-09-01

    The Thick-Walled Cylinder method was used on corrugated Ni-Al reactive laminates to examine how their mesostructures accommodate large strain, high strain rate plastic deformation and to examine the potential for intermetallic reaction initiation due to mechanical stimuli. Three main mesoscale mechanisms of large plastic strain accommodation were observed in addition to the bulk distributed uniform plastic flow: (a) the extrusion of wedge-shaped regions into the interior of the cylinder along planes of easy slip provided by angled layers, (b) the development of trans-layer shear bands in the layers with orientation close to radial and (c) the cooperative buckling of neighbouring layers perpendicular to the radius. These mesoscale mechanisms acted to block the development of periodic patterns of multiple, uniformly distributed, shear bands that have been observed in all previously examined solid homogeneous materials and granular materials. The high-strain plastic flow within the shear bands resulted in the dramatic elongation and fragmentation of Ni and Al layers. The quenched reaction between Al and Ni was observed inside these trans-layer shear bands and in a number of the interfacial extruded wedge-shaped regions. The reaction initiated in these spots did not ignite the bulk of the material, demonstrating that these mesostructured Ni-Al laminates are able to withstand high-strain, high-strain rate deformation without reaction. Numerical simulations of the explosively collapsed samples were performed using the digitized geometry of corrugated laminates and predictions of the final, deformed mesostructures agree with the observed deformation patterns.

  5. Transportation and Accumulation of Redox Active Species at the Buried Interfaces of Plasticized Membrane Electrodes.

    PubMed

    Sohail, Manzar; De Marco, Roland; Jarolímová, Zdeňka; Pawlak, Marcin; Bakker, Eric; He, Ning; Latonen, Rose-Marie; Lindfors, Tom; Bobacka, Johan

    2015-09-29

    The transportation and accumulation of redox active species at the buried interface between glassy carbon electrodes and plasticized polymeric membranes have been studied using synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS), near edge X-ray absorption fine structure (NEXAFS), in situ electrochemical Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Ferrocene tagged poly(vinyl chloride) [FcPVC], ferrocene (Fc), and its derivatives together with tetracyanoquinodimethane (TCNQ) doped plasticized polymeric membrane electrodes have been investigated, so as to extend the study of the mechanism of this reaction chemistry to different time scales (both small and large molecules with variable diffusion coefficients) using a range of complementary electrochemical and surface analysis techniques. This study also provides direct spectroscopic evidence for the transportation and electrochemical reactivity of redox active species, regardless of the size of the electrochemically reactive molecule, at the buried interface of the substrate electrode. With all redox dopants, when CA electrolysis was performed, redox active species were undetectable (<1 wt % of signature elements or below the detection limit of SR-XPS and NEXAFS) in the outermost surface layers of the membrane, while a high concentration of redox species was located at the electrode substrate as a consequence of the deposition of the reaction product (Fc(+)-anion complex) at the buried interface between the electrode and the membrane. This reaction chemistry for redox active species within plasticized polymeric membranes may be useful in the fashioning of multilayered polymeric devices (e.g., chemical sensors, organic electronic devices, protective laminates, etc.) based on an electrochemical tunable deposition of redox molecules at the buried substrate electrode beneath

  6. Energetic dislocation interactions and thermodynamical aspects of strain gradient crystal plasticity theories

    NASA Astrophysics Data System (ADS)

    Ertürk, İ.; van Dommelen, J. A. W.; Geers, M. G. D.

    2009-11-01

    This paper focuses on the unification of two frequently used and apparently different strain gradient crystal plasticity frameworks: (i) the physically motivated strain gradient crystal plasticity models proposed by Evers et al. [2004a. Non-local crystal plasticity model with intrinsic SSD and GND effects. Journal of the Mechanics and Physics of Solids 52, 2379-2401; 2004b. Scale dependent crystal plasticity framework with dislocation density and grain boundary effects. International Journal of Solids and Structures 41, 5209-5230] and Bayley et al. [2006. A comparison of dislocation induced back stress formulations in strain gradient crystal plasticity. International Journal of Solids and Structure 43, 7268-7286; 2007. A three dimensional dislocation field crystal plasticity approach applied to miniaturized structures. Philosophical Magazine 87, 1361-1378] (here referred to as Evers-Bayley type models), where a physical back stress plays the most important role and which are further extended here to deal with truly large deformations, and (ii) the thermodynamically consistent strain gradient crystal plasticity model of Gurtin (2002-2008) (here referred to as the Gurtin type model), where the energetic part of a higher order micro-stress is derived from a non-standard free energy function. The energetic micro-stress vectors for the Gurtin type models are extracted from the definition of the back stresses of the improved Evers-Bayley type models. The possible defect energy forms that yield the derived physically based micro-stresses are discussed. The duality of both type of formulations is shown further by a comparison of the micro-boundary conditions. As a result, this paper provides a direct physical interpretation of the different terms present in Gurtin's model.

  7. Strain accumulation and rotation in western Nevada, 1993-2000

    USGS Publications Warehouse

    Svarc, J.L.; Savage, J.C.; Prescott, W.H.; Ramelli, A.R.

    2002-01-01

    The positions of 44 GPS monuments in an array extending from the Sierra Nevada at the latitude of Reno to near Austin, Nevada, have been measured several times in the 1993-2000 interval. The western half of the array spans the Walker Lane belt, whereas the eastern half spans the central Nevada seismic zone (CNSZ). The principal strain rates in the Walker Lane belt are 29.6 ?? 5.3 nstrain yr-1 N88.4??E ?? 5.4?? and -12.8 ?? 6.0 nanostrain yr-1 N01.6??W ?? 5.4??, extension reckoned positive, and the clockwise (as seen from above the Earth) rotation rate about a vertical axis is 13.6 ?? 4.0 nrad yr-1. The quoted uncertainties are standard deviations. The motion in the Walker Lane belt can then be represented by a zone striking N35??W subject to 16.8 ?? 4.9 nstrain yr-1 extension perpendicular to it and 19.5 ?? 4.0 nstrain yr-1 right-lateral, simple shear across it. The N35??W strike of the zone is the same as the direction of the local tangent to the small circle drawn about the Pacific-North America pole of rotation. The principal strain rates for the CNSZ are 46.2 ?? 11.0 nstrain yr-1 N49.9??W ?? 6.0?? and -13.6 ?? 6.1 nstrain yr-1 N40.1??E ?? 6.0??, and the clockwise rotation rate about a vertical axis is 20.3 ?? 6.3 nrad yr-1. The motion across the CNSZ can then be represented by a zone striking N12??E subject to 32.6 ?? 11.0 nstrain yr-1 extension perpendicular to it and 25.1 ?? 6.3 nstrain yr-1 right-lateral, simple shear across it. The N12??E strike of the zone is similar to the strikes of the faults (Rainbow Mountain, Fairview Peak, and Dixie Valley) within it.

  8. The strain path dependence of plastic deformation response of AA5754: Experiment and modeling

    SciTech Connect

    Pham, Minh-Son; Hu, Lin; Iadicola, Mark; Creuziger, Adam; Rollett, Anthony D.

    2013-12-16

    This work presents modeling of experiments on a balanced biaxial (BB) pre-strained AA5754 alloy, subsequently reloaded uniaxially along the rolling direction and transverse direction. The material exhibits a complex plastic deformation response during the change in strain path due to 1) crystallographic texture, 2) aging (interactions between dislocations and Mg atoms) and 3) recovery (annihilation and re-arrangement of dislocations). With a BB prestrain of about 5 %, the aging process is dominant, and the yield strength for uniaxially deformed samples is observed to be higher than the flow stress during BB straining. The strain hardening rate after changing path is, however, lower than that for pre-straining. Higher degrees of pre-straining make the dynamic recovery more active. The dynamic recovery at higher strain levels compensates for the aging effect, and results in: 1) a reduction of the yield strength, and 2) an increase in the hardening rate of re-strained specimens along other directions. The yield strength of deformed samples is further reduced if these samples are left at room temperature to let static recovery occur. The synergistic influences of texture condition, aging and recovery processes on the material response make the modeling of strain path dependence of mechanical behavior of AA5754 challenging. In this study, the influence of crystallographic texture is taken into account by incorporating the latent hardening into a visco-plastic self-consistent model. Different strengths of dislocation glide interaction models in 24 slip systems are used to represent the latent hardening. Moreover, the aging and recovery effects are also included into the latent hardening model by considering strong interactions between dislocations and dissolved atom Mg and the microstructural evolution. These microstructural considerations provide a powerful capability to successfully describe the strain path dependence of plastic deformation behavior of AA5754.

  9. Strain accumulation and rotation in western Oregon and southwestern Washington

    USGS Publications Warehouse

    Svarc, J.L.; Savage, J.C.; Prescott, W.H.; Murray, M.H.

    2002-01-01

    Velocities of 75 geodetic monuments in western Oregon and southwestern Washington extending from the coast to more than 300 km inland have been determined from GPS surveys over the interval 1992-2000. The average standard deviation in each of the horizontal velocity components is ??? 1 mm yr-1. The observed velocity field is approximated by a combination of rigid rotation (Euler vector relative to interior North America: 43. 40??N ?? 0.14??, 119.33??W ?? 0.28??, and 0.822 ?? 0.057?? Myr-1 clockwise; quoted uncertainties are standard deviations), uniform regional strain rate (??EE = -7.4 ?? 1.8, ??EN = -3.4 ?? 1.0, and ??NN = -5.0 ?? 0.8 nstrain yr-1, extension reckoned positive), and a dislocation model representing subduction of the Juan de Fuca plate beneath North America. Subduction south of 44.5??N was represented by a 40-km-wide locked thrust and subduction north of 44.5??N by a 75-km-wide locked thrust.

  10. The microstructure origin of large strain plastically deformed SiC nanowires

    NASA Astrophysics Data System (ADS)

    Fu, X.; Jiang, J.; Hu, X.; Yuan, J.; Zhang, Y.; Han, X.; Zhang, Z.

    2008-08-01

    Surprisingly large strain plasticity has been demonstrated for ceramic SiC nanowires through in-situ deformation experiments near room temperature. This article reports a detailed electron energy-loss spectroscopy (EELS) study of deformation-induced localized plastic zones in a bent SiC nanowire. Both the 'red shift' of the plasmon peak and the characteristic fine structure at Si L-edge absorption are consistent with local amorphisation of SiC. The recorded C K-edge fine structure is processed to remove the contribution from the surface amorphous carbon and the extracted C K-edge fine structure has no characteristic sp2-related pre-edge peak and hence is also consistent with amorphous SiC. These results suggest that the large strain plasticity in SiC nanowires is enabled by crystalline-to-amorphous transition.

  11. Dynamic strain aging of the materials characterized by the Peierls plasticity mechanism

    NASA Astrophysics Data System (ADS)

    Petukhov, B. V.

    2016-09-01

    A synergetic model is proposed to describe the influence of dynamic strain aging on the plasticity of materials that is controlled by the Peierls barriers overcome by dislocations. The immobilization of dislocations by the impurities concentrated in the dislocation cores is taken into account. The behavior of calculated deformation curves is studied as a function of the material parameters and the mechanical test conditions.

  12. High Strain Rate Characterization of Plastics and Foams Using Polymeric Split Hopkinson Bar

    NASA Astrophysics Data System (ADS)

    Sawas, Omar; Brar, N. S.

    1997-07-01

    High strain rate and high/low temperature response of engineered plastics and foams is relevant and important for the design and development of fighter aircraft canopies, submarine interiors and automobile exterior and interior systems. The mechanical impedance of conventional split Hopkinson bar materials (aluminum or steel) is extremely large compared to those of plastic or foam specimens. To overcome this difficulty of impedance mismatch we have developed the Polymeric Split Hopkinson Bar (PSHB). A viscoelastic model for cast acrylic bar material, which relates stresses and strains as well as particle velocity and strain, is developed to account for the wave dispersion along the bar. The model is verified by comparing the stress strain data on 1100 aluminum and polycarbonate specimens obtained using PSHB and conventional aluminum SHB. Stress-strain data at a strain rate of 103/s on low strength polyurethane foam (density = 0.57 g/cm3) following this technique show that the foam has a recoverable compressive strain of 0.4 at a stress of 2.9 MPa. High strain rate (2x102-2x103/s) data on polycarbonate, generic elastomer, and styrofoam will also be presented.

  13. A numerical investigation of grain shape and crystallographic texture effects on the plastic strain localization in friction stir weld zones

    NASA Astrophysics Data System (ADS)

    Romanova, V.; Balokhonov, R.; Batukhtina, E.; Shakhidjanov, V.

    2015-10-01

    Crystal plasticity approaches were adopted to build models accounting for the microstructure and texture observed in different friction stir weld zones. To this end, a numerical investigation of crystallographic texture and grain shape effects on the plastic strain localization in a friction stir weld of an aluminum-base alloy was performed. The presence of texture was found to give rise to pronounced mesoscale plastic strain localization.

  14. Factors contributing to plastic strain amplification in slip dominated deformation of magnesium alloys

    NASA Astrophysics Data System (ADS)

    Sinclair, C. W.; Martin, G.; Lebensohn, R. A.

    2015-12-01

    While plastic strains are never distributed uniformly in polycrystals, it has recently been shown experimentally that the distribution can be extremely heterogeneous in magnesium polycrystals even when the deformation is dominated by slip. Here, we attempt to provide insight into the (macroscopic) factors that contribute to this strain amplification and to explain, from a local perspective, the origins of this strain amplification. To do this, full field VPFFT crystal plasticity simulations have been performed under the simplifying assumption that twinning is inoperative. It is shown that the experimentally observed heterogeneity can be reproduced when a sufficiently high anisotropy in slip system strength is assumed. This can be further accentuated by a weakening of the texture.

  15. Explicit mixed strain-displacement finite elements for compressible and quasi-incompressible elasticity and plasticity

    NASA Astrophysics Data System (ADS)

    Cervera, M.; Lafontaine, N.; Rossi, R.; Chiumenti, M.

    2016-09-01

    This paper presents an explicit mixed finite element formulation to address compressible and quasi-incompressible problems in elasticity and plasticity. This implies that the numerical solution only involves diagonal systems of equations. The formulation uses independent and equal interpolation of displacements and strains, stabilized by variational subscales. A displacement sub-scale is introduced in order to stabilize the mean-stress field. Compared to the standard irreducible formulation, the proposed mixed formulation yields improved strain and stress fields. The paper investigates the effect of this enhancement on the accuracy in problems involving strain softening and localization leading to failure, using low order finite elements with linear continuous strain and displacement fields ( P1 P1 triangles in 2D and tetrahedra in 3D) in conjunction with associative frictional Mohr-Coulomb and Drucker-Prager plastic models. The performance of the strain/displacement formulation under compressible and nearly incompressible deformation patterns is assessed and compared to analytical solutions for plane stress and plane strain situations. Benchmark numerical examples show the capacity of the mixed formulation to predict correctly failure mechanisms with localized patterns of strain, virtually free from any dependence of the mesh directional bias. No auxiliary crack tracking technique is necessary.

  16. Absence of strain accumulation in the Shumagin seismic gap, Alaska, 1980-1987 ( USA).

    USGS Publications Warehouse

    Lisowski, M.; Savage, J.C.; Prescott, W.H.; Gross, W.K.

    1988-01-01

    Measurements of the deformation of a trilateration network in the Shumagin seismic gap in the interval 1980-1987 failed to detect any significant strain accumulation (observed extension rate in the direction of plate convergence 0.00 + or - 0.03 mu strain/yr). Dislocation models of the subduction process and measurements at a comparable network at a known seismic subduction zone (Nankai Trough, Japan) suggest that a rate of the order of -0.2 mu strain/yr should have been observed if the main thrust zone beneath the Shumagin Islands were locked. The simplest explanation of the observed absence of strain accumulation in the Shumagin seismic gap is that the main thrust zone beneath the Shumagin Islands is not presently locked. Other possible explanations depend upon very particular circumstances.-Authors

  17. Fusarium proliferatum strains change fumonisin biosynthesis and accumulation when exposed to host plant extracts.

    PubMed

    Górna, Karolina; Pawłowicz, Izabela; Waśkiewicz, Agnieszka; Stępień, Łukasz

    2016-01-01

    Fumonisin concentrations in mycelia and media were studied in liquid Fusarium proliferatum cultures supplemented with host plant extracts. Furthermore, the kinetics of fumonisin accumulation in media and mycelia collected before and after extract addition was analysed as well as the changes in the expression of the FUM1 gene. Fumonisin content in culture media increased in almost all F. proliferatum strains shortly after plant extracts were added. The asparagus extract induced the highest FB level increase and the garlic extract was the second most effective inducer. Fumonisin level decreased constantly until 14th day of culturing, though for some strains also at day 8th an elevated FB level was observed. Pineapple extract induced the highest increase of fum1 transcript levels as well as fumonisin synthesis in many strains, and the peas extract inhibited fungal growth and fumonisin biosynthesis. Moreover, fumonisins were accumulated in mycelia of studied strains and in the respective media. PMID:27268248

  18. Strain accumulation across the Denali fault in the Delta River canyon, Alaska.

    USGS Publications Warehouse

    Savage, J.C.; Lisowski, M.; Prescott, W.H.

    1981-01-01

    Deformation along the Denali fault in the Delta River canyon was determined from geodetic surveys in 1941/1942, 1970, 1975, and 1979. The data were best for the 1975-79 interval; in that period the average strain accumulation was essentially pure right lateral shear at a rate of 0.6+-0.1 murad/a (a is years) (engineering shear) across a vertical plane striking N87oE. The plane of maximum shear is rotated about 30o countercloskwise from the local strike of the Denali fault but closely coincides with the strike of a major linear segment of the fault that begins 50 km farther W. The deformation between 1941-42 and 1970 is consistent with a similar rate of strain accumulation if one removes the coseismic strain step contributed by the 1964 Alaska earthquake. The 1970-75 deformation is poorly defined owing to uncertainties in the 1970 survey, but the strain accumulation during that period is certainly much less than during the 1975-79 interval. The 1975-79 strain accumulation is interpreted by means of a dislocation model which suggests that the Denali fault in the vicinity of the Delta River Canyon behaves as a leaky transform fault.-Authors

  19. An Elastic Plastic Contact Model with Strain Hardening for the LAMMPS Granular Package

    SciTech Connect

    Kuhr, Bryan; Brake, Matthew Robert; Lechman, Jeremy B.

    2015-03-01

    The following details the implementation of an analytical elastic plastic contact model with strain hardening for normal im pacts into the LAMMPS granular package. The model assumes that, upon impact, the co llision has a period of elastic loading followed by a period of mixed elastic plas tic loading, with contributions to each mechanism estimated by a hyperbolic seca nt weight function. This function is implemented in the LAMMPS source code as the pair style gran/ep/history. Preliminary tests, simulating the pouring of pure nickel spheres, showed the elastic/plastic model took 1.66x as long as similar runs using gran/hertz/history.

  20. Effect of hydrogen on plastic strain localization and fracture of steels

    NASA Astrophysics Data System (ADS)

    Nadjozhkin, M. V.; Lunev, A. G.; Li, Yu V.; Barannikova, S. A.

    2016-02-01

    The effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested specimens of low-carbon steels have been studied using a double exposure speckle photography technique. It is found that the mechanical properties of low-carbon steels are affected adversely by hydrogen embrittlement. The deformation diagrams were examined for the deformed samples of low-carbon steels. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation.

  1. On constitutive relations at finite strain - Hypo-elasticity and elasto-plasticity with isotropic or kinematic hardening

    NASA Technical Reports Server (NTRS)

    Atluri, S. N.

    1984-01-01

    Nagtegaal and de Jong (1982) have studied stresses generated by simple finite shear in the case of elastic-plastic and rigid-plastic materials which exhibit anisotropic hardening. They reported that the shear stress is oscillatory in time. It was found that the occurrence of such an 'anomaly' is not restricted to anisotropic plasticity. Similar behavior in finite shear may result even in the case of hypoelasticity and classical isotropic hardening plasticity theory. The present investigation is concerned with the central problem of 'generalizing' with respect to the finite strain case, taking into account the constitutive relations of infinitesimal strain theories of classical plasticity with isotropic or kinematic hardening. The problem of hypoelasticity is also considered. It is shown that current controversies surrounding the choice of stress rate in the finite-strain generalizations of the constitutive relations and the anomalies surrounding kinematic hardening plasticity theory are easily resolvable.

  2. Draft Genome Sequences of Sphingobium sp. Strain TCM1 and Sphingomonas sp. Strain TDK1, Haloalkyl Phosphate Flame Retardant- and Plasticizer-Degrading Bacteria

    PubMed Central

    Abe, Katsumasa; Kasai, Daisuke; Fukuda, Masao; Takahashi, Shouji

    2016-01-01

    Sphingobium sp. strain TCM1 and Sphingomonas sp. strain TDK1 are haloalkyl phosphate flame retardant- and plasticizer-degrading bacteria. We report here the draft genome sequences of these strains to provide insights into the molecular mechanism underlying their degradation ability. PMID:27417843

  3. Evidence of polyethylene biodegradation by bacterial strains from the guts of plastic-eating waxworms.

    PubMed

    Yang, Jun; Yang, Yu; Wu, Wei-Min; Zhao, Jiao; Jiang, Lei

    2014-12-01

    Polyethylene (PE) has been considered nonbiodegradable for decades. Although the biodegradation of PE by bacterial cultures has been occasionally described, valid evidence of PE biodegradation has remained limited in the literature. We found that waxworms, or Indian mealmoths (the larvae of Plodia interpunctella), were capable of chewing and eating PE films. Two bacterial strains capable of degrading PE were isolated from this worm's gut, Enterobacter asburiae YT1 and Bacillus sp. YP1. Over a 28-day incubation period of the two strains on PE films, viable biofilms formed, and the PE films' hydrophobicity decreased. Obvious damage, including pits and cavities (0.3-0.4 μm in depth), was observed on the surfaces of the PE films using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The formation of carbonyl groups was verified using X-ray photoelectron spectroscopy (XPS) and microattenuated total reflectance/Fourier transform infrared (micro-ATR/FTIR) imaging microscope. Suspension cultures of YT1 and YP1 (10(8) cells/mL) were able to degrade approximately 6.1 ± 0.3% and 10.7 ± 0.2% of the PE films (100 mg), respectively, over a 60-day incubation period. The molecular weights of the residual PE films were lower, and the release of 12 water-soluble daughter products was also detected. The results demonstrated the presence of PE-degrading bacteria in the guts of waxworms and provided promising evidence for the biodegradation of PE in the environment.

  4. Strain rate, temperature and representative length scale influence on plasticity and yield stress in copper

    SciTech Connect

    Dupont, Virginie; Germann, Timothy C

    2011-01-18

    Shock compression of materials constitutes a complex process involving high strain rates, elevated temperatures and compression of the lattice. Materials properties are greatly affected by temperature, the representative length scale and the strain rate of the deformation. Experimentally, it is difficult to study the dynamic microscopic mechanisms that affect materials properties following high intensity shock loading, but they can be investigated using molecular dynamics (MD) simulations. Moreover, MD allows a better control over some parameters. We are using MD simulations to study the effect of the strain rate, representative length scale and temperature on the properties of metals during compression. A half-million-atom Cu sample is subjected to strain rates ranging from 10{sup 7} s{sup -1} to 10{sup 12} s{sup -1} at different temperatures ranging from 50K to 1500K. Single crystals as well as polycrystals are investigated. Plasticity mechanisms as well as the evolution of the micro- and macro-yield stress are observed. Our results show that the yield stress increases with increasing strain rate and decreasing temperature. We also show that the strain rate at which the transition between constant and increasing yield stress as a function of the temperature occurs increases with increasing temperature. Calculations at different grain sizes will give an insight into the grain size effect on the plasticity mechanisms and the yield stress.

  5. Analysis of plane-plastic stress problems with axial symmetry in strain-hardening range

    NASA Technical Reports Server (NTRS)

    Wu, M H Lee

    1951-01-01

    A simple method is developed for solving plane-plastic-stress problems with axial symmetry in the strain-hardening range which is based on the deformation theory of plasticity employing the finite-strain concept. The equations defining the problems are first reduced to two simultaneous nonlinear differential equations involving two dependent variables: (a) the octahedral shear strain, and (b) a parameter indicating the ratio of principal stresses. By multiplying the load and dividing the radius by an arbitrary constant, it is possible to solve these problems without iteration for any value of the modified load. The constant is determined by the boundary condition. This method is applied to a circular membrane under pressure, a rotating disk without and with a central hole, and an infinite plate with a circular hole. Two materials, inconel x and 16-25-6, the octahedral shear stress-strain relations of which do not follow the power law, are used. Distributions of octahedral shear strain, as well as of principal stresses and strains, are obtained. These results are compared with the results of the same problems in the elastic range.

  6. Evidence of polyethylene biodegradation by bacterial strains from the guts of plastic-eating waxworms.

    PubMed

    Yang, Jun; Yang, Yu; Wu, Wei-Min; Zhao, Jiao; Jiang, Lei

    2014-12-01

    Polyethylene (PE) has been considered nonbiodegradable for decades. Although the biodegradation of PE by bacterial cultures has been occasionally described, valid evidence of PE biodegradation has remained limited in the literature. We found that waxworms, or Indian mealmoths (the larvae of Plodia interpunctella), were capable of chewing and eating PE films. Two bacterial strains capable of degrading PE were isolated from this worm's gut, Enterobacter asburiae YT1 and Bacillus sp. YP1. Over a 28-day incubation period of the two strains on PE films, viable biofilms formed, and the PE films' hydrophobicity decreased. Obvious damage, including pits and cavities (0.3-0.4 μm in depth), was observed on the surfaces of the PE films using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The formation of carbonyl groups was verified using X-ray photoelectron spectroscopy (XPS) and microattenuated total reflectance/Fourier transform infrared (micro-ATR/FTIR) imaging microscope. Suspension cultures of YT1 and YP1 (10(8) cells/mL) were able to degrade approximately 6.1 ± 0.3% and 10.7 ± 0.2% of the PE films (100 mg), respectively, over a 60-day incubation period. The molecular weights of the residual PE films were lower, and the release of 12 water-soluble daughter products was also detected. The results demonstrated the presence of PE-degrading bacteria in the guts of waxworms and provided promising evidence for the biodegradation of PE in the environment. PMID:25384056

  7. Substructure based modeling of nickel single crystals cycled at low plastic strain amplitudes

    NASA Astrophysics Data System (ADS)

    Zhou, Dong

    In this dissertation a meso-scale, substructure-based, composite single crystal model is fully developed from the simple uniaxial model to the 3-D finite element method (FEM) model with explicit substructures and further with substructure evolution parameters, to simulate the completely reversed, strain controlled, low plastic strain amplitude cyclic deformation of nickel single crystals. Rate-dependent viscoplasticity and Armstrong-Frederick type kinematic hardening rules are applied to substructures on slip systems in the model to describe the kinematic hardening behavior of crystals. Three explicit substructure components are assumed in the composite single crystal model, namely "loop patches" and "channels" which are aligned in parallel in a "vein matrix," and persistent slip bands (PSBs) connected in series with the vein matrix. A magnetic domain rotation model is presented to describe the reverse magnetostriction of single crystal nickel. Kinematic hardening parameters are obtained by fitting responses to experimental data in the uniaxial model, and the validity of uniaxial assumption is verified in the 3-D FEM model with explicit substructures. With information gathered from experiments, all control parameters in the model including hardening parameters, volume fraction of loop patches and PSBs, and variation of Young's modulus etc. are correlated to cumulative plastic strain and/or plastic strain amplitude; and the whole cyclic deformation history of single crystal nickel at low plastic strain amplitudes is simulated in the uniaxial model. Then these parameters are implanted in the 3-D FEM model to simulate the formation of PSB bands. A resolved shear stress criterion is set to trigger the formation of PSBs, and stress perturbation in the specimen is obtained by several elements assigned with PSB material properties a priori. Displacement increment, plastic strain amplitude control and overall stress-strain monitor and output are carried out in the user

  8. Strong strain rate effect on the plasticity of amorphous silica nanowires

    SciTech Connect

    Yue, Yonghai; Zheng, Kun

    2014-06-09

    With electron-beam (e-beam) off, in-situ tensile experiments on amorphous silica nanowires (NWs) were performed inside a transmission electron microscope (TEM). By controlling the loading rates, the strain rate can be adjusted accurately in a wide range. The result shows a strong strain rate effect on the plasticity of amorphous silica NWs. At lower strain rate, the intrinsic brittle materials exhibit a pronounced elongation higher than 100% to failure with obvious necking near ambient temperature. At the strain rate higher than 5.23 × 10{sup −3}/s, the elongation of the NW decreased dramatically, and a brittle fracture feature behavior was revealed. This ductile feature of the amorphous silica NWs has been further confirmed with the in-situ experiments under optical microscopy while the effect of e-beam irradiation could be eliminated.

  9. Elastic-Plastic Strain Acceptance Criteria for Structures Subject to Rapidly Applied Transient Dynamic Loading

    SciTech Connect

    W.R. Solonick

    2003-04-01

    Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on material ductility considerations only and are set as a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local , or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.

  10. Elastic-plastic strain acceptance criterion for structures subject to rapidly applied transient dynamic loading

    SciTech Connect

    Solonick, W.

    1996-11-01

    Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local, or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.

  11. Grain-size-independent plastic flow at ultrahigh pressures and strain rates.

    PubMed

    Park, H-S; Rudd, R E; Cavallo, R M; Barton, N R; Arsenlis, A; Belof, J L; Blobaum, K J M; El-dasher, B S; Florando, J N; Huntington, C M; Maddox, B R; May, M J; Plechaty, C; Prisbrey, S T; Remington, B A; Wallace, R J; Wehrenberg, C E; Wilson, M J; Comley, A J; Giraldez, E; Nikroo, A; Farrell, M; Randall, G; Gray, G T

    2015-02-13

    A basic tenet of material science is that the flow stress of a metal increases as its grain size decreases, an effect described by the Hall-Petch relation. This relation is used extensively in material design to optimize the hardness, durability, survivability, and ductility of structural metals. This Letter reports experimental results in a new regime of high pressures and strain rates that challenge this basic tenet of mechanical metallurgy. We report measurements of the plastic flow of the model body-centered-cubic metal tantalum made under conditions of high pressure (>100  GPa) and strain rate (∼10(7)  s(-1)) achieved by using the Omega laser. Under these unique plastic deformation ("flow") conditions, the effect of grain size is found to be negligible for grain sizes >0.25  μm sizes. A multiscale model of the plastic flow suggests that pressure and strain rate hardening dominate over the grain-size effects. Theoretical estimates, based on grain compatibility and geometrically necessary dislocations, corroborate this conclusion. PMID:25723227

  12. Grain-size-independent plastic flow at ultrahigh pressures and strain rates.

    PubMed

    Park, H-S; Rudd, R E; Cavallo, R M; Barton, N R; Arsenlis, A; Belof, J L; Blobaum, K J M; El-dasher, B S; Florando, J N; Huntington, C M; Maddox, B R; May, M J; Plechaty, C; Prisbrey, S T; Remington, B A; Wallace, R J; Wehrenberg, C E; Wilson, M J; Comley, A J; Giraldez, E; Nikroo, A; Farrell, M; Randall, G; Gray, G T

    2015-02-13

    A basic tenet of material science is that the flow stress of a metal increases as its grain size decreases, an effect described by the Hall-Petch relation. This relation is used extensively in material design to optimize the hardness, durability, survivability, and ductility of structural metals. This Letter reports experimental results in a new regime of high pressures and strain rates that challenge this basic tenet of mechanical metallurgy. We report measurements of the plastic flow of the model body-centered-cubic metal tantalum made under conditions of high pressure (>100  GPa) and strain rate (∼10(7)  s(-1)) achieved by using the Omega laser. Under these unique plastic deformation ("flow") conditions, the effect of grain size is found to be negligible for grain sizes >0.25  μm sizes. A multiscale model of the plastic flow suggests that pressure and strain rate hardening dominate over the grain-size effects. Theoretical estimates, based on grain compatibility and geometrically necessary dislocations, corroborate this conclusion.

  13. Evaluation Of Elastic Strain Accumulation In The Southern Indian Peninsula By GPS-Geodesy

    NASA Astrophysics Data System (ADS)

    Narayanababu, R.; Ec, M.; Tummala, C.

    2004-12-01

    The computed elastic strain accumulation in the southern Indian peninsula from the GPS derived velocity fields of the global network of GPS stations, in and around the Indian plate which includes Maitri, Indian Antarctic Station, show a significant departure from rigid plate behaviour in a manner consistent with the mapped intra plate stress field, observations of deformations and seismicity in the region. Our results of intraplate strain accumulation within Antarctica Plate covering three sites MAIT, CAS1 and DAV1 are 1.8x10-9yr-1, 1.6x10-9yr-1 and 1.1x10-9yr-1, respectively. Similarly, the estimates of interplate strain accumulation between Antarctica and other plates Somalia (SEY1), Africa (HARO), Australia (YAR1), and diffuse plate boundary between India and Australia (COCO) are found to be 1.1x10-9yr-1, 1.0x10-10yr-1, 1.27x10-8yr-1 and 1.18x10-8yr-1, respectively. These estimates are in good agreement with the earlier studies on estimation of global strain rate. The combined GPS and seismic analysis confirm the emergence of diffuse plate boundary between India and Australia and relates to the late Miocene Himalayan uplift. The calculated stress field in the West of the Indian Peninsula has a roughly N-S directed tensional and E-W oriented compressional character and the velocity vectors of all other sites throw a significant insight into the plausible causes of the strain accumulation processes in the Indian Ocean and the northward movement of Indian plate.

  14. Draft Genome Sequence of Arenibacter sp. Strain C-21, an Iodine-Accumulating Bacterium Isolated from Surface Marine Sediment

    PubMed Central

    Ito, Kohei; Nakajima, Nobuyoshi; Yamamura, Shigeki; Tomita, Masaru

    2016-01-01

    Arenibacter sp. strain C-21, isolated from surface marine sediment of Japan, accumulates iodine in the presence of glucose and iodide (I-). We report here the draft genome sequence of this strain to provide insight into the molecular mechanism underlying its iodine-accumulating ability. PMID:27738047

  15. Strain gradient plasticity modeling of the cyclic behavior of laminate microstructures

    NASA Astrophysics Data System (ADS)

    Wulfinghoff, Stephan; Forest, Samuel; Böhlke, Thomas

    2015-06-01

    Two recently proposed Helmholtz free energy potentials including the full dislocation density tensor as an argument within the framework of strain gradient plasticity are used to predict the cyclic elastoplastic response of periodic laminate microstructures. First, a rank-one defect energy is considered, allowing for a size-effect on the overall yield strength of micro-heterogeneous materials. As a second candidate, a logarithmic defect energy is investigated, which is motivated by the work of Groma et al. (2003). The properties of the back-stress arising from both energies are investigated in the case of a laminate microstructure for which analytical as well as numerical solutions are derived. In this context, a new regularization technique for the numerical treatment of the rank-one potential is presented based on an incremental potential involving Lagrange multipliers. The results illustrate the effect of the two energies on the macroscopic size-dependent stress-strain response in monotonic and cyclic shear loading, as well as the arising pile-up distributions. Under cyclic loading, stress-strain hysteresis loops with inflections are predicted by both models. The logarithmic potential is shown to provide a continuum formulation of Asaro's type III kinematic hardening model. Experimental evidence in the literature of such loops with inflections in two-phased FFC alloys is provided, showing that the proposed strain gradient models reflect the occurrence of reversible plasticity phenomena under reverse loading.

  16. A New Fungal Isolate, Penidiella sp. Strain T9, Accumulates the Rare Earth Element Dysprosium

    PubMed Central

    Horiike, Takumi

    2015-01-01

    With an aim to develop a highly efficient method for the recovery of rare earth elements (REEs) by using microorganisms, we attempted to isolate dysprosium (Dy)-accumulating microorganisms that grow under acidic conditions from environmental samples containing high concentrations of heavy metals. One acidophilic strain, T9, which was isolated from an abandoned mine, decreased the concentration of Dy in medium that contained 100 mg/liter Dy to 53 mg/liter Dy after 3 days of cultivation at pH 2.5. The Dy content in the cell pellet of the T9 strain was 910 μg/mg of dry cells. The T9 strain also accumulated other REEs. Based on the results of 28S-D1/D2 rRNA gene sequencing and morphological characterization, we designated this fungal strain Penidiella sp. T9. Bioaccumulation of Dy was observed on the cell surface of the T9 strain by elemental mapping using scanning electron microscopy-energy dispersive X-ray spectroscopy. Our results indicate that Penidiella sp. T9 has the potential to recover REEs such as Dy from mine drainage and industrial liquid waste under acidic conditions. PMID:25710372

  17. A new fungal isolate, Penidiella sp. strain T9, accumulates the rare earth element dysprosium.

    PubMed

    Horiike, Takumi; Yamashita, Mitsuo

    2015-05-01

    With an aim to develop a highly efficient method for the recovery of rare earth elements (REEs) by using microorganisms, we attempted to isolate dysprosium (Dy)-accumulating microorganisms that grow under acidic conditions from environmental samples containing high concentrations of heavy metals. One acidophilic strain, T9, which was isolated from an abandoned mine, decreased the concentration of Dy in medium that contained 100 mg/liter Dy to 53 mg/liter Dy after 3 days of cultivation at pH 2.5. The Dy content in the cell pellet of the T9 strain was 910 μg/mg of dry cells. The T9 strain also accumulated other REEs. Based on the results of 28S-D1/D2 rRNA gene sequencing and morphological characterization, we designated this fungal strain Penidiella sp. T9. Bioaccumulation of Dy was observed on the cell surface of the T9 strain by elemental mapping using scanning electron microscopy-energy dispersive X-ray spectroscopy. Our results indicate that Penidiella sp. T9 has the potential to recover REEs such as Dy from mine drainage and industrial liquid waste under acidic conditions.

  18. A numerical basis for strain-gradient plasticity theory: Rate-independent and rate-dependent formulations

    NASA Astrophysics Data System (ADS)

    Nielsen, K. L.; Niordson, C. F.

    2014-02-01

    A numerical model formulation of the higher order flow theory (rate-independent) by Fleck and Willis [2009. A mathematical basis for strain-gradient plasticity theory - part II: tensorial plastic multiplier. Journal of the Mechanics and Physics of Solids 57, 1045-1057.], that allows for elastic-plastic loading/unloading and the interaction of multiple plastic zones, is proposed. The predicted model response is compared to the corresponding rate-dependent version of visco-plastic origin, and coinciding results are obtained in the limit of small strain-rate sensitivity. First, (i) the evolution of a single plastic zone is analyzed to illustrate the agreement with earlier published results, whereafter examples of (ii) multiple plastic zone interaction, and (iii) elastic-plastic loading/unloading are presented. Here, the simple shear problem of an infinite slab constrained between rigid plates is considered, and the effect of strain gradients, strain hardening and rate sensitivity is brought out. For clarity of results, a 1D model is constructed following a procedure suitable for generalization to 2D and 3D.

  19. The role of dissipation and defect energy in variational formulations of problems in strain-gradient plasticity. Part 2: single-crystal plasticity

    NASA Astrophysics Data System (ADS)

    Reddy, B. D.

    2011-11-01

    Variational formulations are constructed for rate-independent problems in small-deformation single-crystal strain-gradient plasticity. The framework, based on that of Gurtin (J Mech Phys Solids 50: 5-32, 2002), makes use of the flow rule expressed in terms of the dissipation function. Provision is made for energetic and dissipative microstresses. Both recoverable and non-recoverable defect energies are incorporated into the variational framework. The recoverable energies include those that depend smoothly on the slip gradients, the Burgers tensor, or on the dislocation densities (Gurtin et al. J Mech Phys Solids 55:1853-1878, 2007), as well as an energy proposed by Ohno and Okumura (J Mech Phys Solids 55:1879-1898, 2007), which leads to excellent agreement with experimental results, and which is positively homogeneous and therefore not differentiable at zero slip gradient. Furthermore, the variational formulation accommodates a non-recoverable energy due to Ohno et al. (Int J Mod Phys B 22:5937-5942, 2008), which is also positively homogeneous, and a function of the accumulated dislocation density. Conditions for the existence and uniqueness of solutions are established for the various examples of defect energy, with or without the presence of hardening or slip resistance.

  20. Statistics of plastic events in post-yield strain-controlled amorphous solids

    NASA Astrophysics Data System (ADS)

    Dubey, Awadhesh K.; Hentschel, H. George E.; Procaccia, Itamar; Singh, Murari

    2016-06-01

    Amorphous solids yield in strain-controlled protocols at a critical value of the strain. For larger strains the stress and energy display a generic complex serrated signal with elastic segments punctuated by sharp energy and stress plastic drops having a wide range of magnitudes. Here we provide a theory of the scaling properties of such serrated signals taking into account the system-size dependence. We show that the statistics are not homogeneous: they separate sharply to a regime of "small" and "large" drops, each endowed with its own scaling properties. A scaling theory is first derived solely by data analysis, showing a somewhat complex picture. But after considering the physical interpretation one discovers that the scaling behavior and the scaling exponents are in fact very simple and universal.

  1. Comparison of game-farm and wild-strain mallard ducks in accumulation of methylmercury

    USGS Publications Warehouse

    Heinz, G.H.

    1979-01-01

    The accumulation of mercury was compared in game-farm and wild-strain mallard ducks fed a diet containing 0.5 ppm mercury in the form of methylmercury dicyandiamide. There were no significant differences between the two strains in levels of mercury that accumulated in blood, kidney, liver, breast muscle, brain, eggs, or ducklings. Mercury levels in blood were significantly correlated with levels in other tissues and eggs, as were levels in down feathers of ducklings with levels in carcasses of ducklings. The results indicate that game-farm mallards are probably suitable substitutes for wild mallards in toxicological work, that blood samples can be used to estimate levels of mercury in other tissues of adults, and that down feathers are predictive of mercury levels in duckling carcasses.

  2. Draft Genome Sequence of Halomonas sp. HG01, a Polyhydroxyalkanoate-Accumulating Strain Isolated from Peru

    PubMed Central

    Cardinali-Rezende, Juliana; Nahat, Rafael Augusto Teodoro Pereira de Souza; Guzmán Moreno, César Wilber; Carreño Farfán, Carmen Rosa; Silva, Luiziana Ferreira; Taciro, Marilda Keico

    2016-01-01

    Halomonas sp. strain HG01, isolated from a salt mine in Peru, is a halophilic aerobic heterotrophic bacterium accumulating poly-3-hydroxybutyrate and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from different carbon sources. Here, we report the draft genome sequence of this isolate, which was found to be 3,665,487 bp long, with a G+C content of 68%. PMID:26798101

  3. ETS Related Uplift and Strain Accumulation in Northern Cascadia from Tidal Records

    NASA Astrophysics Data System (ADS)

    Alba, S. K.; Weldon, R. J.; Livelybrooks, D.; Schmidt, D. A.; Krogstad, R.

    2011-12-01

    Vertical displacements, uplift rates between events, and net uplift rates spanning the most recent 12 episodic tremor and slip events (ETS) on the northern Cascadia Subduction Zone (between 1997 and 2010) have been determined from hourly water level records from 4 NOAA tide gauges (Neah Bay, Port Angeles, Port Townsend, and Seattle). Dense GPS networks have thus far been the primary means to characterize displacements and inter ETS strain rates associated with ETS that occurred beneath the Olympic Peninsula, WA [McGuire & Segall, 2003; Szeliga et al., 2004; Melbourne et al., 2005; Wang et al., 2008; McCaffrey, 2009; Schmidt & Gao, 2010]. However, GPS generally has poor vertical resolution so we are exploring the use of tidal records are used to improve estimates of vertical deformation and extend the observations to the pre GPS era. Vertical displacements are particularly useful in locating the downdip (and therefore inland) extent of slip, variations in the magnitude of slip on the slip patch, and for determining long term rates that span many ETS cycles. Tidal records were analyzed by removing shared ocean noise so that uncertainties largely depend upon distance to neighboring sites. In northern Cascadia displacements during individual events are on the order of millimeters with near centimeter uncertainties, whereas 12 event average displacements by site are resolved to ~1mm ( -1.19+/-0.95mm at Neah Bay, 2.85+/-0.74mm, Port Angeles, -2.05+/-0.76mm, Port Townsend, and 0.39+/-1.08mm at Seattle), and individual site averages generally agree with displacements inferred from modeling GPS data. The relationship between long term uplift, average vertical displacements during ETS and average uplift which occurs between events can indicate the style and distribution of strain accumulation. Examination of water level trends between events show an interseismic deformation rate approximately equal in magnitude but opposite in sign (although with greater uncertainties). This

  4. Static Strain Aging of Microstructural Constituents in Transformation-Induced-Plasticity Steel

    NASA Astrophysics Data System (ADS)

    Samek, L.; de Moor, E.; Penning, J.; Speer, J. G.; de Cooman, B. C.

    2008-11-01

    A pronounced difference in static strain aging was observed between unstrained and prestrained low-alloy multiphase transformation-induced-plasticity (TRIP) steel. High bake-hardening (BH) values were obtained for prestrained TRIP steel. This aging behavior was shown to be directly related to the multiphase microstructure, by analyzing static strain aging in the ferrite and bainite separately. The ferrite in TRIP steel exhibits very limited strain aging, due to the Cottrell atmosphere formation. The bainite constituent, which contains retained austenite, has a pronounced static strain-aging response in the 2 pct prestrained condition. This is a result of internal stresses generated by the strain-induced martensite and the low-temperature aging of this phase. In the absence of strain-induced martensite, the BH values of TRIP steel are low and are due only to the Cottrell atmosphere formation. The TRIP steel exhibits an intermediate BH response, due to the composite effect of its ferrite and bainite constituents. The influence of the cross-sectional changes and volume changes during tensile tests carried out to determine the BH values is also reviewed.

  5. Plasticity of human Achilles tendon mechanical and morphological properties in response to cyclic strain.

    PubMed

    Arampatzis, Adamantios; Peper, Andreas; Bierbaum, Stefanie; Albracht, Kirsten

    2010-12-01

    The purpose of the current study in combination with our previous published data (Arampatzis et al., 2007) was to examine the effects of a controlled modulation of strain magnitude and strain frequency applied to the Achilles tendon on the plasticity of tendon mechanical and morphological properties. Eleven male adults (23.9 ± 2.2 yr) participated in the study. The participants exercised one leg at low magnitude tendon strain (2.97 ± 0.47%), and the other leg at high tendon strain magnitude (4.72 ± 1.08%) of similar frequency (0.5 Hz, 1s loading, 1s relaxation) and exercise volume (integral of the plantar flexion moment over time) for 14 weeks, 4 days per week, 5 sets per session. The exercise volume was similar to the intervention of our earlier study (0.17 Hz frequency; 3s loading, 3s relaxation) allowing a direct comparison of the results. Before and after the intervention ankle joint moment has been measured by a dynamometer, tendon-aponeurosis elongation by ultrasound and cross-sectional area of the Achilles tendon by magnet resonance images (MRI). We found a decrease in strain at a given tendon force, an increase in tendon-aponeurosis stiffness and tendon elastic modulus of the Achilles tendon only in the leg exercised at high strain magnitude. The cross-sectional area (CSA) of the Achilles tendon did not show any statistically significant (P > 0.05) differences to the pre-exercise values in both legs. The results indicate a superior improvement in tendon properties (stiffness, elastic modulus and CSA) at the low frequency (0.17 Hz) compared to the high strain frequency (0.5 Hz) protocol. These findings provide evidence that the strain magnitude applied to the Achilles tendon should exceed the value, which occurs during habitual activities to trigger adaptational effects and that higher tendon strain duration per contraction leads to superior tendon adaptational responses.

  6. Pseudomonas mutant strains that accumulate androstane and seco-androstane intermediates from bile acids.

    PubMed Central

    Leppik, R A; Sinden, D J

    1987-01-01

    Transposon mutant strains which were affected in bile acid catabolism were isolated from four Pseudomonas spp. Two of the mutant groups isolated were found to accumulate 12 alpha-hydroxyandrosta-1,4-diene-3,17-dione as the major product from deoxycholic acid. Strains in one of these two groups were able to grow on steroids such as chenodeoxycholic acid, which lacks a 12 alpha-hydroxy function, whereas the one member of the second group could not. With chenodeoxycholic acid, this latter strain accumulated a yellow muconic-like derivative, tentatively identified as 3,7-dihydroxy-5,9,17-trioxo-4(5),9(10)-disecoandrosta-1(10)2 -dien-4-oic acid. Members of two further mutant groups accumulated either 12 beta-hydroxyandrosta-1,4-diene-3,17-dione or 3,12 beta-dihydroxy-9(10)-secoandrosta-1,3,5(10)-triene-9,17-dione as the major product from deoxycholic acid. The relationship between the catabolism of m- and p-cresol, 3-ethylphenol and the bile acids was also examined. PMID:3038076

  7. Use of endochronic plasticity for multi-dimensional small and large strain problems

    SciTech Connect

    Hsieh, B J

    1980-04-01

    The endochronic plasticity theory was proposed in its general form by K.C. Valanis. An intrinsic time measure, which is a property of the material, is used in the theory. the explicit forms of the constitutive equation resemble closely those of the classical theory of linear viscoelasticity. Excellent agreement between the predicted and experimental results is obtained for some metallic and non-metallic materials for one dimensional cases. No reference on the use of endochronic plasticity consistent with the general theory proposed by Valanis is available in the open literature. In this report, the explicit constitutive equations are derived that are consistent with the general theory for one-dimensional (simple tension or compression), two-dimensional plane strain or stress and three-dimensional axisymmetric problems.

  8. Monitoring in situ stress/strain behaviour during plastic yielding in polymineralic rocks using neutron diffraction

    NASA Astrophysics Data System (ADS)

    Covey-Crump, S. J.; Schofield, P. F.; Stretton, I. C.; Daymond, M. R.; Knight, K. S.; Tant, J.

    2013-02-01

    Attempts to use rock deformation experiments to examine the elastic and plastic behaviour of polymineralic rocks are hampered by the fact that usually only whole sample properties can be monitored as opposed to the separate contribution of each phase. To circumvent this difficulty, room-temperature, uniaxial compression experiments were performed in a neutron beam-line on a suite of calcite + halite samples with different phase volume proportions. By collecting diffraction data during loading, the elastic strain and hence stress in each phase was determined as a function of load to bulk strains of 1-2%. In all cases, the calcite behaved elastically while the halite underwent plastic yielding. During the fully elastic part of the deformation, the composite elastic properties and the within-phase stresses are well-described both by recent shear lag models and by analyses based on Eshelby's solution for the elastic field around an ellipsoidal inclusion in a homogeneous medium. After the onset of yielding, the halite in situ stress/total strain curve may be reconstructed using the rule of mixtures. At calcite contents of greater than 30%, the in situ halite response may be significantly weaker or stronger than that obtained at lesser calcite contents. The results highlight the potential that such techniques offer for developing an explicitly experimental approach for determining the influence of microstructural variables on the mechanical properties of polymineralic rocks.

  9. Crystal plasticity simulations of microstructure-induced uncertainty in strain concentration near voids in brass

    NASA Astrophysics Data System (ADS)

    Battaile, Corbett C.; Emery, John M.; Brewer, Luke N.; Boyce, Brad L.

    2015-04-01

    The uncertainty in mechanical response near a cylindrical hole in polycrystalline alpha brass was simulated as a function of variations in the crystallographic orientations of the grains near the hole. A total of 4 hole sizes were examined, including the case of a microstructure without a hole, and 45 simulations were performed for each case (yielding 180 simulations total) to acquire statistical data. For a hole larger than the grain size, the deformation resembles the homogenous solution but with perturbations due to the local microstructural environment. For a hole approximately equal to or smaller than the grain size, the deformation deviates substantially from the continuum behaviour, and depends strongly on the local microstructural environment surrounding the hole. Each population of simulations was analysed statistically to determine the effect of micro structural variability on strain localization near each of the four defect sizes. The coefficient of variation in the maximum plastic strain around microstructure-scale holes is about 37%, and the largest values of plastic strain are about twice those in the absence of microstructure. These results have significant implications for analyses of the margin of failure due to defects of this class (e.g. voids or small bolt holes).

  10. Role of Cations in Accumulation and Release of Phosphate by Acinetobacter Strain 210A

    PubMed Central

    van Groenestijn, Johan W.; Vlekke, Gerard J. F. M.; Anink, Désirée M. E.; Deinema, Maria H.; Zehnder, Alexander J. B.

    1988-01-01

    Cells of the strictly aerobic Acinetobacter strain 210A, containing aerobically large amounts of polyphosphate (100 mg of phosphorus per g [dry weight] of biomass), released in the absence of oxygen 1.49 mmol of Pi, 0.77 meq of Mg2+, 0.48 meq of K+, 0.02 meq of Ca2+, and 0.14 meq of NH4+ per g (dry weight) of biomass. The drop in pH during this anaerobic phase was caused by the release of 1.8 protons per PO43− molecule. Cells of Acinetobacter strain 132, which do not accumulate polyphosphate aerobically, released only 0.33 mmol of Pi and 0.13 meq of Mg2+ per g (dry weight) of biomass but released K+ in amounts comparable to those released by strain 210A. Stationary-phase cultures of Acinetobacter strain 210A, in which polyphosphate could not be detected by Neisser staining, aerobically took up phosphate simultaneously with Mg2+, the most important counterion in polyphosphate. In the absence of dissolved phosphate in the medium, no Mg2+ was taken up. Cells containing polyphosphate granules were able to grow in a Mg-free medium, whereas cells without these granules were not. Mg2+ was not essential as a counterion because it could be replaced by Ca2+. The presence of small amounts of K+ was essential for polyphosphate formation in cells of strain 210A. During continuous cultivation under K+ limitation, cells of Acinetobacter strain 210A contained only 14 mg of phosphorus per g (dry weight) of biomass, whereas this element was accumulated in amounts of 59 mg/g under substrate limitation and 41 mg/g under Mg2+ limitation. For phosphate uptake in activated sludge, the presence of K+ seemed to be crucial. PMID:16347788

  11. High-rate Plastic Deformation of Nanocrystalline Tantalum to Large Strains: Molecular Dynamics Simulation

    SciTech Connect

    Rudd, R E

    2009-02-05

    Recent advances in the ability to generate extremes of pressure and temperature in dynamic experiments and to probe the response of materials has motivated the need for special materials optimized for those conditions as well as a need for a much deeper understanding of the behavior of materials subjected to high pressure and/or temperature. Of particular importance is the understanding of rate effects at the extremely high rates encountered in those experiments, especially with the next generation of laser drives such as at the National Ignition Facility. Here we use large-scale molecular dynamics (MD) simulations of the high-rate deformation of nanocrystalline tantalum to investigate the processes associated with plastic deformation for strains up to 100%. We use initial atomic configurations that were produced through simulations of solidification in the work of Streitz et al [Phys. Rev. Lett. 96, (2006) 225701]. These 3D polycrystalline systems have typical grain sizes of 10-20 nm. We also study a rapidly quenched liquid (amorphous solid) tantalum. We apply a constant volume (isochoric), constant temperature (isothermal) shear deformation over a range of strain rates, and compute the resulting stress-strain curves to large strains for both uniaxial and biaxial compression. We study the rate dependence and identify plastic deformation mechanisms. The identification of the mechanisms is facilitated through a novel technique that computes the local grain orientation, returning it as a quaternion for each atom. This analysis technique is robust and fast, and has been used to compute the orientations on the fly during our parallel MD simulations on supercomputers. We find both dislocation and twinning processes are important, and they interact in the weak strain hardening in these extremely fine-grained microstructures.

  12. The role of dissipation and defect energy in variational formulations of problems in strain-gradient plasticity. Part 1: polycrystalline plasticity

    NASA Astrophysics Data System (ADS)

    Reddy, B. D.

    2011-11-01

    A general set of flow laws and associated variational formulations are constructed for small-deformation rate-independent problems in strain-gradient plasticity. The framework is based on the thermodynamically consistent theory due to Gurtin and Anand (J Mech Phys Solids 53:1624-1649, 2005), and includes as variables a set of microstresses which have both energetic and dissipative components. The flow law is of associative type. It is expressed as a normality law with respect to a convex but otherwise arbitrary yield function, or equivalently in terms of the corresponding dissipation function. Two cases studied are, first, an extension of the classical Hill-Mises or J 2 flow law and second, a form written as a linear sum of the magnitudes of the plastic strain and strain gradient. This latter form is motivated by work of Evans and Hutchinson (Acta Mater 57:1675-1688, 2009) and Nix and Gao (J Mech Phys Solids 46:411-425, 1998), who show that it leads to superior correspondence with experimental results, at least for particular classes of problems. The corresponding yield function is obtained by a duality argument. The variational problem is based on the flow rule expressed in terms of the dissipation function, and the problem is formulated as a variational inequality in the displacement, plastic strain, and hardening parameter. Dissipative components of the microstresses, which are indeterminate, are absent from the formulation. Existence and uniqueness of solutions are investigated for the generalized Hill-Mises and linear-sum dissipation functions, and for various combinations of defect energy. The conditions for well-posedness of the problem depend critically on the choice of dissipation function, and on the presence or otherwise of a defect energy in the plastic strain or plastic strain gradient, and of internal-variable hardening.

  13. Strain accumulation across the Coast Ranges at the latitude of San Francisco, 1994-2000

    NASA Astrophysics Data System (ADS)

    Savage, J. C.; Gan, W.; Prescott, W. H.; Svarc, J. L.

    2004-03-01

    A 66-monument geodetic array spanning the Coast Ranges near San Francisco has been surveyed more than eight times by GPS between late 1993 and early 2001. The measured horizontal velocities of the monuments are well represented by uniform, right-lateral, simple shear parallel to N29°W. (The local strike of the San Andreas Fault is ˜N34°W.) The observed areal dilatation rate of 6.9 ± 10.0 nstrain yr-1 (quoted uncertainty is one standard deviation and extension is reckoned positive) is not significantly different from zero, which implies that the observed strain accumulation could be released by strike-slip faulting alone. Our results are consistent with the slip rates assigned by the [2003] to the principal faults (San Gregorio, San Andreas, Hayward-Rodgers Creek, Calaveras-Concord-Green Valley, and Greenville Faults) cutting across the GPS array. The vector sum of those slip rates is 39.8 ± 2.6 mm yr-1 N29.8°W ± 2.8°, whereas the motion across the GPS array (breadth 120 km) inferred from the uniform strain rate approximation is 38.7 ± 1.2 mm yr-1 N29.0°W ± 0.9° right-lateral shear and 0.4 ± 0.9 mm yr-1 N61°E ± 0.9° extension. We interpret the near coincidence of these rates and the absence of significant accumulation of areal dilatation to imply that right-lateral slip on the principal faults can release the accumulating strain; major strain release on reverse faults subparallel to the San Andreas Fault within the Coast Ranges is not required.

  14. Strain accumulation across the Coast Ranges at the latitude of San Francisco, 1994-2000

    USGS Publications Warehouse

    Savage, J.C.; Gan, Weijun; Prescott, W.H.; Svarc, J.L.

    2004-01-01

    A 66-monument geodetic array spanning the Coast Ranges near San Francisco has been surveyed more than eight times by GIPS between late 1993 and early 2001. The measured horizontal velocities of the monuments are well represented by uniform, right-lateral, simple shear parallel to N29??W. (The local strike of the San Andreas Fault is ???N34??W. The observed areal dilatation rate of 6.9 ?? 10.0 nstrain yr-1 (quoted uncertainty is one standard deviation and extension is reckoned positive) is not significantly different from zero, which implies that the observed strain accumulation could be released by strike-slip faulting alone. Our results are consistent with the slip rates assigned by the Working Group on California Earthquake Probabilities [2003] to the principal faults (San Gregorio, San Andreas, Hayward-Rodgers Creek, Calaveras-Concord-Green Valley, and Greenville Faults) cutting across the GPS array. The vector sum of those slip rates is 39.8 ?? 2.6 mm yr-1 N29.8??W ?? 2.8??, whereas the motion across the GPS array (breadth 120 km) inferred from the uniform strain rate approximation is 38.7 ?? 1.2 mm yr-1 N29.0?? ?? 0.9?? right-lateral shear and 0.4 ?? 0.9 mm yr-1 N61??E ?? 0.9?? extension. We interpret the near coincidence of these rates and the absence of significant accumulation of areal dilatation to imply that right-lateral slip on the principal faults can release the accumulating strain; major strain release on reverse faults subparallel to the San Andreas Fault within the Coast Ranges is not required. Copyright 2004 by the American Geophysical union.

  15. Characterization of a S-adenosyl-l-methionine (SAM)-accumulating strain of Scheffersomyces stipitis.

    PubMed

    Križanović, Stela; Butorac, Ana; Mrvčić, Jasna; Krpan, Maja; Cindrić, Mario; Bačun-Družina, Višnja; Stanzer, Damir

    2015-06-01

    S-adenosyl-l-methionine (SAM) is an important molecule in the cellular metabolism of mammals. In this study, we examined several of the physiological characteristics of a SAM-accumulating strain of the yeast Scheffersomyces stipitis (M12), including SAM production, ergosterol content, and ethanol tolerance. S. stipitis M12 accumulated up to 52.48 mg SAM/g dry cell weight. Proteome analyses showed that the disruption of C-24 methylation in ergosterol biosynthesis, a step mediated by C-24 sterol methyltransferase (Erg6p), results in greater SAM accumulation by S. stipitis M12 compared to the wild-type strain. A comparative proteome-wide analysis identified 25 proteins that were differentially expressed by S. stipitis M12. These proteins are involved in ribosome biogenesis, translation, the stress response, ubiquitin-dependent catabolic processes, the cell cycle, ethanol tolerance, posttranslational modification, peroxisomal membrane stability, epigenetic regulation, the actin cytoskeleton and cell morphology, iron and copper homeostasis, cell signaling, and energy metabolism.

  16. Patulin Accumulation In Apples During Storage by Penicillium Expansum and Penicillium Griseofulvum Strains

    PubMed Central

    Welke, Juliane Elisa; Hoeltz, Michele; Dottori, Horacio Alberto; Noll, Isa Beatriz

    2011-01-01

    A part of apples destined to juice production is generally of poor quality. Apples from cold storage or recently harvest (ground harvested or low quality apples) are stored under ambient conditions until they are processed. Since Penicillium expansum and P. griseofulvum are the principal fungal species isolated from stored apples in Brazil, the objective of this study was to investigate the ability of these strains to produce patulin in apples and report the consequences of this type of storage in loss of quality. The toxin was quantified using thin layer chromatography and charge-coupled device camera (TLC-CCD). The rate and quantities that P. expansum and P. griseofulvum can grow and produce patulin are highly dependent on the fungal strain and time. Lesion diameter resulted to be independent of the strain considered. The maximum period of time which apples were kept at cold storage (4 °C) without patulin accumulation was 27 days. When these apples were kept at 25 °C during 3 days, both factors lesion diameter and patulin production increased significantly. These results confirm that time in which apples are taken out from cold storage room before juice production is critical in order to prevent patulin accumulation. PMID:24031618

  17. 20th-Century Strain Accumulation on the Lesser Antilles Megathrust Based on Coral Microatolls

    NASA Astrophysics Data System (ADS)

    Philibosian, B.; Feuillet, N.; Jacques, E.; Weil Accardo, J.; Meriaux, A. S. B.; Guihou, A.; Anglade, A.

    2015-12-01

    The Lesser Antilles subduction zone forms the eastern boundary of the Caribbean plate. The seismic potential of the megathrust remains poorly known, despite the hazard it poses to numerous island populations and its proximity to the Americas. As it has not produced any large earthquakes in modern times, the megathrust has often been assumed to be aseismic. However, historical records of great earthquakes in the 19th century and earlier, which were almost certainly megathrust ruptures, demonstrate that the subduction is not entirely aseismic. Recent occurrences of giant earthquakes in areas where such events were previously thought to be impossible have inspired the geoscience community to re-evaluate the seismic potential of other "low-hazard" subduction zones, such as the Lesser Antilles. Using the method of coral microatoll paleogeodesy developed in Sumatra, we examine 20th-century vertical deformation on the forearc islands of the Lesser Antilles and model the underlying strain accumulation on the megathrust. Our data indicate that the eastern coasts of the forearc islands have been subsiding relative to the arc islands, suggesting that on the time scale of the 20th century, a portion of the megathrust just east of the forearc islands has been locked. Our findings are in contrast to recent GPS-based models that suggest little or no strain accumulation anywhere along the Lesser Antilles megathrust. This discrepancy is potentially explained by the different time scales of measurement, as recent studies elsewhere have indicated that interseismic coupling patterns may vary on decadal time scales and that century-scale or longer records are required to accurately assess seismic potential. The accumulated strain we have detected will likely be released in future earthquakes, uplifting the previously subsiding areas as well as contributing to seismic and potentially to tsunami hazard in the region.

  18. Present-day Block Motions and Strain Accumulation on Active Faults in the Caribbean

    NASA Astrophysics Data System (ADS)

    Symithe, S. J.; Calais, E.; Freed, A. M.

    2014-12-01

    The quasi-frontal subduction of the north and south American plates under the Lesser Antilles and the left and right lateral strike-slip along the northern and southern margins of the Caribbean plate offer the opportunity to study the transition from subduction to strike-slip between major plates. In addition, the segmentation and degree of interplate coupling at the Lesser Antilles subduction is key to our understanding of the earthquake potential of a subduction whose length is similar to the rupture area of the Mw9.0, 2011, Tohoku earthquake in Japan. We used the block modeling approach described in Meade and Loveless (2009) to test the optimal block geometry for the northern, eastern and southern boundaries of the Caribbean plate. We solved for angular velocities for each block/plate and strain accumulation rates for all major faults in the region. Then we calculated the variations in interplate coupling along the subduction plate boundaries using the accumulated strain rates. We tested 11 different block geometries; they are all based on geological evidences unless they are suggested by discrepancies within the GPS and seismological data or by previously published results. We confirm the existence of the micro Gonave plate. The boundary between the Micro-Gonave plate and the Hispaniola crustal block is better suited along the Haitian-Thrust-Belt instead of the Neiba-Matheux fault. The interseismic GPS velocities do not show evidence for a distinct North Lesser Antilles block. We found a totally uncoupled section of the subduction starting from the Puerto-Rico trench to the end of the Lesser Antilles section. All the relative motion of the Caribbean block is lost aseismically along the boundary of that portion of the subduction. While we found strong coupling along the northern Hispaniola section, most of the deformation on this region is being accumulated along intrablock faults with very low strain (~2mm/yr) along the intraplate subduction interface. We also

  19. Strain accumulation in the Shumagin Islands: Results of initial GPS measurements

    NASA Technical Reports Server (NTRS)

    Larson, Kristine M.; Lisowski, Michael

    1994-01-01

    Deformation in the Shumagin seismic gap has been monitored with repeated trilateration (EDM) in the 1980-1987 interval and with the Global Positioning System (GPS) in the 1987-1991 interval. The geodetic network extends for 100-km across the Shumagin Islands to the Alaska Peninsula. Results from the GPS surveys are consistent with those previously reported for the EDM surveys: we failed to detect significant strain accumulation in the N30 deg W direction of plate convergence. Using the method of simultaneous reduction for position and strain rates, we found the average rate of extension in the direction of plate convergence to be -25 +/- 25 nanostrain/yr (nstrain/yr) during the 1987-1991 interval of GPS surveys compared with -20 +/- 15 nstrain/yr during the 1981-1987 interval of complete EDM surveys. We found a marginally significant -26 +/- 12 nstrain/yr extension rate in the 1981-1991 interval covered by the combined EDM and GPS surveys. Strain rates are higher, but not significantly so, in the part of the network closest to the trench. Spatial variation in the deformation is observed in the 1980-1991 average station velocities, where three of the four stations closest to the trench have an arcward velocity of a few mm/yr. The observed strain rates are an order of magnitude lower than the -200 nstrain/yr rate predicted by dislocation models.

  20. Diffusion and accumulation in cultivated vegetable plants of di-(2-ethylhexyl) phthalate (DEHP) from a plastic production factory.

    PubMed

    Du, Q Z; Wang, J W; Fu, X W; Xia, H L

    2010-08-01

    Di-(2-ethylhexyl) phthalate (DEHP) concentrations in the atmosphere and in four vegetable crops including Brassica chinensis L. (bok choy), Brassica campestris L. (field mustard), Vigna unguiculata Walp. (cowpea), and Solanum melongena L. (eggplant) cultivated on land surrounding a plastic production factory were determined. The air DEHP concentrations (means) at the sites 0.2, 0.4, 0.8, and 1.6 km away from the plastic production building were about 9.4-12.8, 5.8-9.6, 1.6-5.0, and 0.04-0.27 microg m(-3) dry weight (DW), respectively. Wind direction is a key factor influencing the measurable DEHP concentration of the air, which was highest in the downwind direction and lowest in the upwind direction, and thus the vegetables accumulated the highest DEHP contents in the downwind direction and the lowest quantities in the upwind direction. The highest DEHP accumulations content of bok choy, field mustard, eggplant, and cowpea were 52.0 +/- 3.1, 43.1 +/- 2.2, 36.2 +/- 2.8, and 19.4 +/- 0.47 mg kg(-1) DW, respectively. Safety estimation on the basis of the daily intake limit referenced by the US Environmental Protection Agency (USEPA) led to the conclusion that eating vegetables cultivated 0.2 km away from the plastic production building is not a food safety problem under normal conditions. A strong positive linear correlation between atmospheric DEHP concentration and DEHP content of the vegetable crops was found. The limits for air DEHP concentration for safe vegetable cultivation are 24.0, 34.8, 40.8, and 82.8 microg m(-3) for bok choy, field mustard, cowpea, and eggplant, respectively, by calculating from the equation of linear regression between air DEHP concentration and vegetable DEHP content.

  1. Diffusion and accumulation in cultivated vegetable plants of di-(2-ethylhexyl) phthalate (DEHP) from a plastic production factory.

    PubMed

    Du, Q Z; Wang, J W; Fu, X W; Xia, H L

    2010-08-01

    Di-(2-ethylhexyl) phthalate (DEHP) concentrations in the atmosphere and in four vegetable crops including Brassica chinensis L. (bok choy), Brassica campestris L. (field mustard), Vigna unguiculata Walp. (cowpea), and Solanum melongena L. (eggplant) cultivated on land surrounding a plastic production factory were determined. The air DEHP concentrations (means) at the sites 0.2, 0.4, 0.8, and 1.6 km away from the plastic production building were about 9.4-12.8, 5.8-9.6, 1.6-5.0, and 0.04-0.27 microg m(-3) dry weight (DW), respectively. Wind direction is a key factor influencing the measurable DEHP concentration of the air, which was highest in the downwind direction and lowest in the upwind direction, and thus the vegetables accumulated the highest DEHP contents in the downwind direction and the lowest quantities in the upwind direction. The highest DEHP accumulations content of bok choy, field mustard, eggplant, and cowpea were 52.0 +/- 3.1, 43.1 +/- 2.2, 36.2 +/- 2.8, and 19.4 +/- 0.47 mg kg(-1) DW, respectively. Safety estimation on the basis of the daily intake limit referenced by the US Environmental Protection Agency (USEPA) led to the conclusion that eating vegetables cultivated 0.2 km away from the plastic production building is not a food safety problem under normal conditions. A strong positive linear correlation between atmospheric DEHP concentration and DEHP content of the vegetable crops was found. The limits for air DEHP concentration for safe vegetable cultivation are 24.0, 34.8, 40.8, and 82.8 microg m(-3) for bok choy, field mustard, cowpea, and eggplant, respectively, by calculating from the equation of linear regression between air DEHP concentration and vegetable DEHP content. PMID:20496185

  2. An Analysis of Strain Accumulation in the Western Part of Black Sea Region in Turkey

    NASA Astrophysics Data System (ADS)

    Deniz, I.; Avsar, N. B.; Deniz, R.; Mekik, C.; Kutoglu, S.

    2014-12-01

    Turkish National Horizontal Control Network (TNHCN) based on the European Datum 1950 (ED50) was used as the principal geodetic network until 2005 in Turkey. Since 2005, Turkish Large Scale Map and Map Information Production Regulation have required that that all the densification points have been produced within the same datum of Turkish National Fundamental GPS Network (TNFGN) put into practise in 2002 and based on International Terrestrial Reference Frame (ITRF). Hence, the common points were produced in both European Datum 1950 (ED50), and TNFGN.It is known that the geological and geophysical information about the network area can be obtained by the evaluation of the coordinate and scale variations in a geodetic network. For one such evaluation, the coordinate variations and velocities of network points, and also the strains are investigated. However, the principal problem in derivation of velocities arises from two different datums. In this context, the computation of velocities using the coordinate data of the ED50 and TNFGN is not accurate and reliable. Likewise, the analysis of strain from the coordinate differences is not reliable. However, due to the fact that the scale of a geodetic network is independent from datum, the strains can be derived from scale variations accurately and reliably.In this study, a test area limited 39.5°-42.0° northern latitudes and 31.0°-37.0° eastern longitudes was chosen. The benchmarks in this test area are composed of 30 geodetic control points derived with the aim of cadastral and engineering applications. We used data mining to investigate the common benchmarks in both reference systems for this area. Accordingly, the ED50 and TNFGN coordinates refer 1954 and 2005, respectively. Thus, it has been investigated the strain accumulation of 51 years in this region. It should be also noted that since 1954, the earthquakes have not registered greater than magnitude 6.0 in the test area. It is a considerable situation for this

  3. Simple structures test for elastic-plastic strain acceptance criterion validation

    SciTech Connect

    Trimble, T.F.; Krech, G.R.

    1997-11-01

    A Simple Structures Test Program was performed where several cantilevered beam and fixed-end beam test specimens (fabricated from HY-80 steel) were subjected to a series of analytically predetermined rapidly applied transient dynamic input loads. The primary objective of the test program was to obtain dynamic nonlinear response for simple structures subjected to these load inputs. Data derived from these tests was subsequently used to correlate to analysis predictions to assess the capability to analytically predict elastic-plastic nonlinear material behavior in structures using typical time-dependent (transient) design methods and the ABAQUS finite element analysis code. The installation of a significant amount of instrumentation on these specimens and post-test measurements enabled the monitoring and recording of strain levels, displacements, accelerations, and permanent set. An assessment of modeling parameters such as the element type and mesh refinement was made using these test results. In addition, currently available material models and the incremental time step procedure used in the transient analyses were evaluated. Comparison of test data to analysis results shows that displacements, accelerations, and peak strain can be predicted with a reasonable level of accuracy using detailed solid models of the tested specimens. Permanent set is overpredicted by a factor of approximately two. However, the accuracy of the prediction of permanent set is being enhanced by updating material modeling in the ABAQUS code to account for effects of strain reversal in oscillatory behavior of dynamically loaded specimens.

  4. Slip distribution, strain accumulation and aseismic slip on the Chaman Fault system

    NASA Astrophysics Data System (ADS)

    Amelug, F.

    2015-12-01

    The Chaman fault system is a transcurrent fault system developed due to the oblique convergence of the India and Eurasia plates in the western boundary of the India plate. To evaluate the contemporary rates of strain accumulation along and across the Chaman Fault system, we use 2003-2011 Envisat SAR imagery and InSAR time-series methods to obtain a ground velocity field in radar line-of-sight (LOS) direction. We correct the InSAR data for different sources of systematic biases including the phase unwrapping errors, local oscillator drift, topographic residuals and stratified tropospheric delay and evaluate the uncertainty due to the residual delay using time-series of MODIS observations of precipitable water vapor. The InSAR velocity field and modeling demonstrates the distribution of deformation across the Chaman fault system. In the central Chaman fault system, the InSAR velocity shows clear strain localization on the Chaman and Ghazaband faults and modeling suggests a total slip rate of ~24 mm/yr distributed on the two faults with rates of 8 and 16 mm/yr, respectively corresponding to the 80% of the total ~3 cm/yr plate motion between India and Eurasia at these latitudes and consistent with the kinematic models which have predicted a slip rate of ~17-24 mm/yr for the Chaman Fault. In the northern Chaman fault system (north of 30.5N), ~6 mm/yr of the relative plate motion is accommodated across Chaman fault. North of 30.5 N where the topographic expression of the Ghazaband fault vanishes, its slip does not transfer to the Chaman fault but rather distributes among different faults in the Kirthar range and Sulaiman lobe. Observed surface creep on the southern Chaman fault between Nushki and north of City of Chaman, indicates that the fault is partially locked, consistent with the recorded M<7 earthquakes in last century on this segment. The Chaman fault between north of the City of Chaman to North of Kabul, does not show an increase in the rate of strain

  5. Estimating Strain Accumulation in the New Madrid and Wabash Valley Seismic Zones

    NASA Astrophysics Data System (ADS)

    Craig, T. J.; Calais, E.

    2014-12-01

    The mechanical behaviour -- and hence earthquake potential -- of faults in continental interiors is a question of critical importance for the resultant seismic hazard, but no consensus has yet been reached on this controversial topic. The debate has focused on the central and eastern United States, in particular the New Madrid Seismic Zone, struck by three magnitude 7 or greater earthquakes in 1811--1812, and to a lesser extent the Wabash Valley Seismic Zone just to the north. A key aspect of this issue is the rate at which strain is currently accruing on those faults in the plate interior, a quantity that remains debated. Understanding if the present-day strain rates indicate sufficient motion to account for the historical and paleoseismological earthquakes by steady-state fault behaviour, or if strain accumulation is time-dependent in this area, is critical for investigating the causative process driving this seismicity in the plate interior, and how regional strain reflects the interplay between stresses arising from different geological processes. Here we address this issue with an analysis of up to 14 years of continuous GPS data from a network of 200 sites in the central United States centred on the New Madrid and Wabash Valley seismic zones. We find that high-quality sites in these regions show motions that are consistently within the 95% confidence limit of zero deformation relative to a rigid background. These results place an upper bound on regional strain accrual of 0.2 mm/yr and 0.5 mm/yr in the New Madrid and Wabash Valley Seismic Zones, respectively. These results, together with increasing evidence for temporal clustering and spatial migration of earthquake sequences in continental interiors, indicate that either tectonic loading rates or fault properties vary with time in the NMSZ and possibly plate-wide.

  6. Lipid accumulation by oleaginous and non-oleaginous yeast strains in nitrogen and phosphate limitation.

    PubMed

    Kolouchová, Irena; Maťátková, Olga; Sigler, Karel; Masák, Jan; Řezanka, Tomáš

    2016-09-01

    We investigated the possibility of utilizing both oleaginous yeast species accumulating large amounts of lipids (Yarrowia lipolytica, Rhodotorula glutinis, Trichosporon cutaneum, Candida sp.) and traditional biotechnological non-oleaginous ones characterized by high biomass yield (Kluyveromyces polysporus, Torulaspora delbrueckii, Saccharomyces cerevisiae) as potential producers of biofuel-utilizable and nutritionally valuable lipids. The main objective was to increase lipid accumulation by increasing C/P ratio together with higher C/N ratio, while maintaining high biomass yield. The C/N ratio of 30 was found to lead to higher biomass content and the total lipid content increased significantly with higher C/P ratio. With higher ratios of both C/N and C/P, the content of monounsaturated fatty acids (FAs) in cell lipids increased while polyunsaturated FAs decreased. Oleaginous yeast species had a lower proportion of unsaturated FAs (approx. 80 %) than non-oleaginous strains (approx. 90 %). At a C/N ratio of 30 and C/P ratio 1043, T. cutaneum produced a high amount of ω-6 unsaturated linoleic acid, the precursor of some prostaglandins, leukotrienes, and thromboxanes, while Candida sp. and K. polysporus accumulated a high content of palmitoleic acid.

  7. A physical model for strain accumulation in the San Francisco Bay Region

    USGS Publications Warehouse

    Pollitz, F.F.; Nyst, M.

    2005-01-01

    Strain accumulation in tectonically active regions is generally a superposition of the effects of background tectonic loading, steady-state dislocation processes, such as creep, and transient deformation. In the San Francisco Bay region (SFBR), the most uncertain of these processes is transient deformation, which arises primarily in association with large earthquakes. As such, it depends upon the history of faulting and the rheology of the crust and mantle, which together determine the pattern of longer term (decade-scale) post-seismic response to earthquakes. We utilize a set of 102 GPS velocity vectors in the SFBR in order to characterize the strain rate field and construct a physical model of its present deformation. We first perform an inversion for the continuous velocity gradient field from the discrete GPS velocity field, from which both tensor strain rate and rotation rate may be extracted. The present strain rate pattern is well described as a nearly uniform shear strain rate oriented approximately N34??W (140 nanostrain yr-1) plus a N56??E uniaxial compression rate averaging 20 nanostrain yr-1 across the shear zone. We fit the velocity and strain rate fields to a model of time-dependent deformation within a 135-kin-wide, arcuate shear zone bounded by strong Pacific Plate and Sierra Nevada block lithosphere to the SW and NE, respectively. Driving forces are purely lateral, consisting of shear zone deformation imposed by the relative motions between the thick Pacific Plate and Sierra Nevada block lithospheres. Assuming a depth-dependent viscoelastic structure within the shear zone, we account for the effects of steady creep on faults and viscoelastic relaxation following the 1906 San Francisco and 1989 Loma Prieta earthquakes, subject to constant velocity boundary conditions on the edges of the shear zone. Fault creep is realized by evaluating dislocations on the creeping portions of faults in the fluid limit of the viscoelastic model. A priori plate

  8. Slow plastic strain rate compressive flow in binary CoAl intermetallics

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1985-01-01

    Constant-velocity elevated temperature compression tests have been conducted on a series of binary CoAl intermetallics produced by hot extrusion of blended prealloyed powders. The as-extruded materials were polycrystalline, and they retained their nominal 10-micron grain size after being tested between 1100 and 1400 K at strain rates ranging from 2 x 10 to the -4th to 2 x 10 to the -7th per sec. Significant plastic flow was obtained in all cases; while cracking was observed, much of this could be due to failure at matrix-oxide interfaces along extrusion stringers rather than to solely intergranular fracture. A maximum in flow strength occurs at an aluminum-to-cobalt ratio of 0.975, and the stress exponent appears to be constant for aluminum-to-cobalt ratios of 0.85 or more. It is likely that very aluminum-deficient materials deform by a different mechanism than do other compositions.

  9. Numerical implementation of a crystal plasticity model with dislocation transport for high strain rate applications

    NASA Astrophysics Data System (ADS)

    Mayeur, Jason R.; Mourad, Hashem M.; Luscher, Darby J.; Hunter, Abigail; Kenamond, Mark A.

    2016-05-01

    This paper details a numerical implementation of a single crystal plasticity model with dislocation transport for high strain rate applications. Our primary motivation for developing the model is to study the influence of dislocation transport and conservation on the mesoscale response of metallic crystals under extreme thermo-mechanical loading conditions (e.g. shocks). To this end we have developed a single crystal plasticity theory (Luscher et al (2015)) that incorporates finite deformation kinematics, internal stress fields caused by the presence of geometrically necessary dislocation gradients, advection equations to model dislocation density transport and conservation, and constitutive equations appropriate for shock loading (equation of state, drag-limited dislocation velocity, etc). In the following, we outline a coupled finite element–finite volume framework for implementing the model physics, and demonstrate its capabilities in simulating the response of a [1 0 0] copper single crystal during a plate impact test. Additionally, we explore the effect of varying certain model parameters (e.g. mesh density, finite volume update scheme) on the simulation results. Our results demonstrate that the model performs as intended and establishes a baseline of understanding that can be leveraged as we extend the model to incorporate additional and/or refined physics and move toward a multi-dimensional implementation.

  10. New regimes of plastic flow at very high pressures and strain rates

    NASA Astrophysics Data System (ADS)

    Remington, Bruce

    2015-06-01

    Recent progress in understanding solid-state plastic flow at very high pressures and strain rates for high energy density (HED) science will be described. These results are relevant to hypervelocity impacts, space hardware durability, planetary formation dynamics, advanced designs for inertial confinement fusion, and basic HED science. We use high power lasers to study the Rayleigh-Taylor and Richtmyer-Meshkov hydrodynamic instability evolution in the solid state plastic flow regime on the Janus, Omega, and NIF lasers, spanning peak pressures from 10 - 500 GPa (0.1 - 5 Mbar). We are pursuing time resolved diffraction experiments to understand the lattice level dynamics resulting from high rate compression of samples. EXAFS experiments probe the atomic level structure and phase, and provide a volume-averaged temperature. We use the very bright, high time resolution x-ray probe at LCLS to examine the detailed lattice response and time evolution right behind the shock front. And finally, shock driven samples are recovered so that the residual microstructure caused by the shock can be examined by SEM, TEM, and other characterization techniques. An overview of these recent results, with comparisons to theory and simulations, will be given. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  11. Direct synchrotron x-ray measurements of local strain fields in elastically and plastically bent metallic glasses

    DOE PAGES

    Wu, Yuan; Stoica, Alexandru Dan; Ren, Yang; Ma, Dong; Gao, Yanfei F.; Bei, Hongbin

    2015-09-03

    In situ high-energy synchrotron X-ray diffraction was conducted on elastically and plastically bent bulk metallic glass (BMG) thin plates, from which distinct local elastic strain fields were mapped spatially. These directly measured residual strain fields can be nicely interpreted by our stress analysis, and also validate a previously proposed indirect residual-stress-measurement method by relating nanoindentation hardness to residual stresses. Local shear strain variations on the cross sections of these thin plates were found in the plastically bent BMG, which however cannot be determined from the indirect indentation method. As a result, this study has important implications in designing and manipulatingmore » internal strain fields in BMGs for the purpose of ductility enhancement.« less

  12. Direct synchrotron x-ray measurements of local strain fields in elastically and plastically bent metallic glasses

    SciTech Connect

    Wu, Yuan; Stoica, Alexandru Dan; Ren, Yang; Ma, Dong; Gao, Yanfei F.; Bei, Hongbin

    2015-09-03

    In situ high-energy synchrotron X-ray diffraction was conducted on elastically and plastically bent bulk metallic glass (BMG) thin plates, from which distinct local elastic strain fields were mapped spatially. These directly measured residual strain fields can be nicely interpreted by our stress analysis, and also validate a previously proposed indirect residual-stress-measurement method by relating nanoindentation hardness to residual stresses. Local shear strain variations on the cross sections of these thin plates were found in the plastically bent BMG, which however cannot be determined from the indirect indentation method. As a result, this study has important implications in designing and manipulating internal strain fields in BMGs for the purpose of ductility enhancement.

  13. Correlation of data on strain accumulation adjacent to the San Andreas Fault with available models

    NASA Technical Reports Server (NTRS)

    Turcotte, Donald L.

    1986-01-01

    Theoretical and numerical studies of deformation on strike slip faults were performed and the results applied to geodetic observations performed in the vicinity of the San Andreas Fault in California. The initial efforts were devoted to an extensive series of finite element calculations of the deformation associated with cyclic displacements on a strike-slip fault. Measurements of strain accumulation adjacent to the San Andreas Fault indicate that the zone of strain accumulation extends only a few tens of kilometers away from the fault. There is a concern about the tendency to make geodetic observations along the line to the source. This technique has serious problems for strike slip faults since the vector velocity is also along the fault. Use of a series of stations lying perpendicular to the fault whose positions are measured relative to a reference station are suggested to correct the problem. The complexity of faulting adjacent to the San Andreas Fault indicated that the homogeneous elastic and viscoelastic approach to deformation had serious limitations. These limitation led to the proposal of an approach that assumes a fault is composed of a distribution of asperities and barriers on all scales. Thus, an earthquake on a fault is treated as a failure of a fractal tree. Work continued on the development of a fractal based model for deformation in the western United States. In order to better understand the distribution of seismicity on the San Andreas Fault system a fractal analog was developed. The fractal concept also provides a means of testing whether clustering in time or space is a scale-invariant process.

  14. Dependence of Microelastic-plastic Nonlinearity of Martensitic Stainless Steel on Fatigue Damage Accumulation

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.

    2006-01-01

    Self-organized substructural arrangements of dislocations formed in wavy slip metals during cyclic stress-induced fatigue produce substantial changes in the material microelastic-plastic nonlinearity, a quantitative measure of which is the nonlinearity parameter Beta extracted from acoustic harmonic generation measurements. The contributions to Beta from the substructural evolution of dislocations and crack growth for fatigued martensitic 410Cb stainless steel are calculated from the Cantrell model as a function of percent full fatigue life to fracture. A wave interaction factor f(sub WI) is introduced into the model to account experimentally for the relative volume of material fatigue damage included in the volume of material swept out by an interrogating acoustic wave. For cyclic stress-controlled loading at 551 MPa and f(sub WI) = 0.013 the model predicts a monotonic increase in Beta from dislocation substructures of almost 100 percent from the virgin state to roughly 95 percent full life. Negligible contributions from cracks are predicted in this range of fatigue life. However, over the last five percent of fatigue life the model predicts a rapid monotonic increase of Beta by several thousand percent that is dominated by crack growth. The theoretical predictions are in good agreement with experimental measurements of 410Cb stainless steel samples fatigued in uniaxial, stress-controlled cyclic loading at 551 MPa from zero to full tensile load with a measured f(sub WI) of 0.013.

  15. Dependence of microelastic-plastic nonlinearity of martensitic stainless steel on fatigue damage accumulation

    SciTech Connect

    Cantrell, John H.

    2006-09-15

    Self-organized substructural arrangements of dislocations formed during cyclic stress-induced fatigue of metals produce substantial changes in the material microelastic-plastic nonlinearity, a quantitative measure of which is the nonlinearity parameter {beta} extracted from acoustic harmonic generation measurements. The contributions to {beta} from the substructural evolution of dislocations and crack growth for fatigued martensitic 410Cb stainless steel are calculated from the Cantrell model [Proc. R. Soc. London, Ser. A 460, 757 (2004)] as a function of percent full fatigue life to fracture. A wave interaction factor f{sub WI} is introduced into the model to account experimentally for the relative volume of fatigue damage included in the total volume of material swept out by an interrogating acoustic wave. For cyclic stress-controlled loading at 551 MPa and f{sub WI}=0.013 the model predicts a monotonic increase in {beta} from dislocation substructures of almost 100% from the virgin state to roughly 95% full life. Negligible contributions from cracks are predicted in this range of fatigue life. However, during the last 5% of fatigue life the model predicts a rapid monotonic increase of {beta} by several thousand percent that is dominated by crack growth. The theoretical predictions are in good agreement with experimental measurements of 410Cb stainless steel samples fatigued in uniaxial, stress-controlled cyclic loading at 551 MPa from zero to full tensile load with a measured f{sub WI} of 0.013.

  16. Accumulation of a bioactive benzoisochromanequinone compound kalafungin by a wild type antitumor-medermycin-producing streptomycete strain.

    PubMed

    Lü, Jin; He, Qiang; Huang, Luyao; Cai, Xiaofeng; Guo, Wenwen; He, Jing; Zhang, Lili; Li, Aiying

    2015-01-01

    Medermycin and kalafungin, two antibacterial and antitumor antibiotics isolated from different streptomycetes, share an identical polyketide skeleton core. The present study reported the discovery of kalafungin in a medermycin-producing streptomycete strain for the first time. A mutant strain obtained through UV mutagenesis showed a 3-fold increase in the production of this antibiotic, compared to the wild type strain. Heterologous expression experiments suggested that its production was severely controlled by the gene cluster for medermycin biosynthesis. In all, these findings suggested that kalafungin and medermycin could be accumulated by the same streptomycete and share their biosynthetic pathway to some extent in this strain. PMID:25695632

  17. Accumulation of a Bioactive Benzoisochromanequinone Compound Kalafungin by a Wild Type Antitumor-Medermycin-Producing Streptomycete Strain

    PubMed Central

    Lü, Jin; He, Qiang; Huang, Luyao; Cai, Xiaofeng; Guo, Wenwen; He, Jing; Zhang, Lili; Li, Aiying

    2015-01-01

    Medermycin and kalafungin, two antibacterial and antitumor antibiotics isolated from different streptomycetes, share an identical polyketide skeleton core. The present study reported the discovery of kalafungin in a medermycin-producing streptomycete strain for the first time. A mutant strain obtained through UV mutagenesis showed a 3-fold increase in the production of this antibiotic, compared to the wild type strain. Heterologous expression experiments suggested that its production was severely controlled by the gene cluster for medermycin biosynthesis. In all, these findings suggested that kalafungin and medermycin could be accumulated by the same streptomycete and share their biosynthetic pathway to some extent in this strain. PMID:25695632

  18. Accumulation of a bioactive benzoisochromanequinone compound kalafungin by a wild type antitumor-medermycin-producing streptomycete strain.

    PubMed

    Lü, Jin; He, Qiang; Huang, Luyao; Cai, Xiaofeng; Guo, Wenwen; He, Jing; Zhang, Lili; Li, Aiying

    2015-01-01

    Medermycin and kalafungin, two antibacterial and antitumor antibiotics isolated from different streptomycetes, share an identical polyketide skeleton core. The present study reported the discovery of kalafungin in a medermycin-producing streptomycete strain for the first time. A mutant strain obtained through UV mutagenesis showed a 3-fold increase in the production of this antibiotic, compared to the wild type strain. Heterologous expression experiments suggested that its production was severely controlled by the gene cluster for medermycin biosynthesis. In all, these findings suggested that kalafungin and medermycin could be accumulated by the same streptomycete and share their biosynthetic pathway to some extent in this strain.

  19. SPONTANEOUS MUTATION ACCUMULATION IN MULTIPLE STRAINS OF THE GREEN ALGA, CHLAMYDOMONAS REINHARDTII

    PubMed Central

    Morgan, Andrew D; Ness, Rob W; Keightley, Peter D; Colegrave, Nick

    2014-01-01

    Estimates of mutational parameters, such as the average fitness effect of a new mutation and the rate at which new genetic variation for fitness is created by mutation, are important for the understanding of many biological processes. However, the causes of interspecific variation in mutational parameters and the extent to which they vary within species remain largely unknown. We maintained multiple strains of the unicellular eukaryote Chlamydomonas reinhardtii, for approximately 1000 generations under relaxed selection by transferring a single cell every ∼10 generations. Mean fitness of the lines tended to decline with generations of mutation accumulation whereas mutational variance increased. We did not find any evidence for differences among strains in any of the mutational parameters estimated. The overall change in mean fitness per cell division and rate of input of mutational variance per cell division were more similar to values observed in multicellular organisms than to those in other single-celled microbes. However, after taking into account differences in genome size among species, estimates from multicellular organisms and microbes, including our new estimates from C. reinhardtii, become substantially more similar. Thus, we suggest that variation in genome size is an important determinant of interspecific variation in mutational parameters. PMID:24826801

  20. Along-strike Variations in Active Strain Accumulation in the Northwest Himalaya

    NASA Astrophysics Data System (ADS)

    Morell, K. D.; Ahmad, T.; Sandiford, M.; Codilean, A. T.; Fulop, R. H.

    2015-12-01

    The spatial distribution of channel steepness, erosion rate, and physiographic data highlight pronounced along-strike changes in active strain accumulation in the northwest Himalaya. In particular, the data suggest that the mid-crustal ramp of the Main Himalayan Thrust could merge along-strike with an active portion of the Main Boundary Thrust near longitude ~77º E. This along-strike change in active fault geometry also coincides with the lateral termination of both lesser and greater Himalayan sequences, a significant reduction in total shortening within the wedge, and pronounced variations in regional seismicity. Recent activity along extensional structures in the high Himalaya of this same region appears to have led to significant reorganization, modification and capture of the Sutlej River basin, one of the largest Himalayan river systems. Given the recent 2015 Gorkha earthquake along a comparable section ~500-km along strike, these new constraints on active fault architecture could have regional implications for how strain is partitioned along seismogenic faults in the northwest Himalaya.

  1. Spontaneous mutation accumulation in multiple strains of the green alga, Chlamydomonas reinhardtii.

    PubMed

    Morgan, Andrew D; Ness, Rob W; Keightley, Peter D; Colegrave, Nick

    2014-09-01

    Estimates of mutational parameters, such as the average fitness effect of a new mutation and the rate at which new genetic variation for fitness is created by mutation, are important for the understanding of many biological processes. However, the causes of interspecific variation in mutational parameters and the extent to which they vary within species remain largely unknown. We maintained multiple strains of the unicellular eukaryote Chlamydomonas reinhardtii, for approximately 1000 generations under relaxed selection by transferring a single cell every ~10 generations. Mean fitness of the lines tended to decline with generations of mutation accumulation whereas mutational variance increased. We did not find any evidence for differences among strains in any of the mutational parameters estimated. The overall change in mean fitness per cell division and rate of input of mutational variance per cell division were more similar to values observed in multicellular organisms than to those in other single-celled microbes. However, after taking into account differences in genome size among species, estimates from multicellular organisms and microbes, including our new estimates from C. reinhardtii, become substantially more similar. Thus, we suggest that variation in genome size is an important determinant of interspecific variation in mutational parameters. PMID:24826801

  2. Stover Composition in Maize and Sorghum Reveals Remarkable Genetic Variation and Plasticity for Carbohydrate Accumulation.

    PubMed

    Sekhon, Rajandeep S; Breitzman, Matthew W; Silva, Renato R; Santoro, Nicholas; Rooney, William L; de Leon, Natalia; Kaeppler, Shawn M

    2016-01-01

    Carbohydrates stored in vegetative organs, particularly stems, of grasses are a very important source of energy. We examined carbohydrate accumulation in adult sorghum and maize hybrids with distinct phenology and different end uses (grain, silage, sucrose or sweetness in stalk juice, and biomass). Remarkable variation was observed for non-structural carbohydrates and structural polysaccharides during three key developmental stages both between and within hybrids developed for distinct end use in both species. At the onset of the reproductive phase (average 65 days after planting, DAP), a wide range for accumulation of non-structural carbohydrates (free glucose and sucrose combined), was observed in internodes of maize (11-24%) and sorghum (7-36%) indicating substantial variation for transient storage of excess photosynthate during periods of low grain or vegetative sink strength. Remobilization of these reserves for supporting grain fill or vegetative growth was evident from lower amounts in maize (8-19%) and sorghum (9-27%) near the end of the reproductive period (average 95 DAP). At physiological maturity of grain hybrids (average 120 DAP), amounts of these carbohydrates were generally unchanged in maize (9-21%) and sorghum (16-27%) suggesting a loss of photosynthetic assimilation due to weakening sink demand. Nonetheless, high amounts of non-structural carbohydrates at maturity even in grain maize and sorghum (15-18%) highlight the potential for developing dual-purpose (grain/stover) crops. For both species, the amounts of structural polysaccharides in the cell wall, measured as monomeric components (glucose and pentose), decreased during grain fill but remained unchanged thereafter with maize biomass possessing slightly higher amounts than sorghum. Availability of carbohydrates in maize and sorghum highlights the potential for developing energy-rich dedicated biofuel or dual-purpose (grain/stover) crops. PMID:27375668

  3. Stover composition in maize and sorghum reveals remarkable genetic variation and plasticity for carbohydrate accumulation

    DOE PAGES

    Sekhon, Rajandeep S.; Breitzman, Matthew W.; Silva, Renato R.; Santoro, Nicholas; Rooney, William L.; de Leon, Natalia; Kaeppler, Shawn M.

    2016-06-08

    Carbohydrates stored in vegetative organs, particularly stems, of grasses are a very important source of energy. We examined carbohydrate accumulation in adult sorghum and maize hybrids with distinct phenology and different end uses (grain, silage, sucrose or sweetness in stalk juice, and biomass). Remarkable variation was observed for nonstructural carbohydrates and structural polysaccharides during three key developmental stages both between and within hybrids developed for distinct end use in both species. At the onset of the reproductive phase (average 65 days after planting, DAP), a wide range for accumulation of non-structural carbohydrates (free glucose and sucrose combined), was observed inmore » internodes of maize (11-24%) and sorghum (7-36%) indicating substantial variation for transient storage of excess photosynthate during periods of low grain or vegetative sink strength. Remobilization of these reserves for supporting grain fill or vegetative growth was evident from lower amounts in maize (8-19%) and sorghum (9-27%) near the end of the reproductive period (average 95 DAP). At physiological maturity of grain hybrids (average 120 DAP), amounts of these carbohydrates were generally unchanged in maize (9-21%) and sorghum (16-27%) suggesting a loss of photosynthetic assimilation due to weakening sink demand. Nonetheless, high amounts of non-structural carbohydrates at maturity even in grain maize and sorghum (15-18%) highlight the potential for developing dual-purpose (grain/stover) crops. For both species, the amounts of structural polysaccharides in the cell wall, measured as monomeric components (glucose and pentose), decreased during grain fill but remained unchanged thereafter with maize biomass possessing slightly higher amounts than sorghum. In conclusion, availability of carbohydrates in maize and sorghum highlights the potential for developing energy-rich dedicated biofuel or dual-purpose (grain/stover) crops.« less

  4. Stover Composition in Maize and Sorghum Reveals Remarkable Genetic Variation and Plasticity for Carbohydrate Accumulation

    PubMed Central

    Sekhon, Rajandeep S.; Breitzman, Matthew W.; Silva, Renato R.; Santoro, Nicholas; Rooney, William L.; de Leon, Natalia; Kaeppler, Shawn M.

    2016-01-01

    Carbohydrates stored in vegetative organs, particularly stems, of grasses are a very important source of energy. We examined carbohydrate accumulation in adult sorghum and maize hybrids with distinct phenology and different end uses (grain, silage, sucrose or sweetness in stalk juice, and biomass). Remarkable variation was observed for non-structural carbohydrates and structural polysaccharides during three key developmental stages both between and within hybrids developed for distinct end use in both species. At the onset of the reproductive phase (average 65 days after planting, DAP), a wide range for accumulation of non-structural carbohydrates (free glucose and sucrose combined), was observed in internodes of maize (11–24%) and sorghum (7–36%) indicating substantial variation for transient storage of excess photosynthate during periods of low grain or vegetative sink strength. Remobilization of these reserves for supporting grain fill or vegetative growth was evident from lower amounts in maize (8–19%) and sorghum (9–27%) near the end of the reproductive period (average 95 DAP). At physiological maturity of grain hybrids (average 120 DAP), amounts of these carbohydrates were generally unchanged in maize (9–21%) and sorghum (16–27%) suggesting a loss of photosynthetic assimilation due to weakening sink demand. Nonetheless, high amounts of non-structural carbohydrates at maturity even in grain maize and sorghum (15–18%) highlight the potential for developing dual-purpose (grain/stover) crops. For both species, the amounts of structural polysaccharides in the cell wall, measured as monomeric components (glucose and pentose), decreased during grain fill but remained unchanged thereafter with maize biomass possessing slightly higher amounts than sorghum. Availability of carbohydrates in maize and sorghum highlights the potential for developing energy-rich dedicated biofuel or dual-purpose (grain/stover) crops. PMID:27375668

  5. A simple recovery process for biodegradable plastics accumulated in cyanobacteria treated with ionic liquids.

    PubMed

    Kobayashi, Daigo; Fujita, Kyoko; Nakamura, Nobuhumi; Ohno, Hiroyuki

    2015-02-01

    Here, we proposed a simple recovery process for poly(3-hydroxybutyrate) (PHB) accumulated in cyanobacteria by using ionic liquids (ILs), which dissolve cyanobacteria but not PHB. First, we investigated the effects of IL polarity on hydrogen-bonding receipt ability (β value) and hydrogen-bonding donating ability (α value) and evaluated the subsequent dissolution of cyanobacteria. We found that ILs having α values higher than approximately 0.4 and β values of approximately 0.9 were suitable for dissolution of cyanobacteria. In particular, 1-ethyl-3-methylimidazolium methylphosphonate ([C2mim][MeO(H)PO2]) was found to dissolve cyanobacteria components, but not PHB. Thus, we verified that PHB produced in cyanobacteria could be separated and recovered by simple filtering after dissolution of cyanobacteria in [C2mim][MeO(H)PO2]. Using this technique, more than 98 % of PHB was obtained on the filter as residues separated from cyanobacteria. Furthermore, [C2mim][MeO(H)PO2] maintained the ability to dissolve cyanobacteria after a simple recycling procedure.

  6. Starch and lipid accumulation in eight strains of six Chlorella species under comparatively high light intensity and aeration culture conditions.

    PubMed

    Takeshita, Tsuyoshi; Ota, Shuhei; Yamazaki, Tomokazu; Hirata, Aiko; Zachleder, Vilém; Kawano, Shigeyuki

    2014-04-01

    The microalgae family Chlorella species are known to accumulate starch and lipids. Although nitrogen or phosphorous deficiencies promote starch and lipids formation in many microalgae, these deficiencies also limit their growth and productivity. Therefore, the Chlorellaceae strains were attempted to increase starch and lipids productivity under high-light-intensity conditions (600-μmol photons m(-2)s(-1)). The 12:12-h light-dark (LD) cycle conditions elicited more stable growth than the continuous light (LL) conditions, whereas the starch and lipids yields increased in LL conditions. The amount of starch and lipids per cell increased in Chlorella viscosa and Chlorella vulgaris in sulfur-deficient medium, and long-chain fatty acids with 20 or more carbon atoms accumulated in cells grown in sulfur-deficient medium. Accumulation of starch and lipids was investigated in eight strains. The accumulation was strain-dependent, and varied according to the medium and light conditions. Five of the eight Chlorella strains exhibited similar accumulation patterns.

  7. New perspectives in plastic biodegradation.

    PubMed

    Sivan, Alex

    2011-06-01

    During the past 50 years new plastic materials, in various applications, have gradually replaced the traditional metal, wood, leather materials. Ironically, the most preferred property of plastics--durability--exerts also the major environmental threat. Recycling has practically failed to provide a safe solution for disposal of plastic waste (only 5% out of 1 trillion plastic bags, annually produced in the US alone, are being recycled). Since the most utilized plastic is polyethylene (PE; ca. 140 million tons/year), any reduction in the accumulation of PE waste alone would have a major impact on the overall reduction of the plastic waste in the environment. Since PE is considered to be practically inert, efforts were made to isolate unique microorganisms capable of utilizing synthetic polymers. Recent data showed that biodegradation of plastic waste with selected microbial strains became a viable solution.

  8. Plastic ingestion by Flesh-footed Shearwaters (Puffinus carneipes): Implications for fledgling body condition and the accumulation of plastic-derived chemicals.

    PubMed

    Lavers, Jennifer L; Bond, Alexander L; Hutton, Ian

    2014-04-01

    To provide much needed quantitative data on the lethal and sublethal effects of plastic pollution on marine wildlife, we sampled breast feathers and stomach contents from Flesh-footed Shearwater (Puffinus carneipes) fledglings in eastern Australia. Birds with high levels of ingested plastic exhibited reduced body condition and increased contaminant load (p < 0.05). More than 60% of fledglings exceed international targets for plastic ingestion by seabirds, with 16% of fledglings failing these targets after a single feeding (range: 0.13-3.21 g of plastic/feeding). As top predators, seabirds are considered sentinels of the marine environment. The amount of plastic ingested and corresponding damage to Flesh-footed Shearwater fledglings is the highest reported for any marine vertebrate, suggesting the condition of the Australian marine environment is poor. These findings help explain the ongoing decline of this species and are worrying in light of increasing levels of plastic pollution in our oceans.

  9. Strain Accumulation and Release in the South Iceland Seismic Zone (Invited)

    NASA Astrophysics Data System (ADS)

    Arnadottir, T.; Hreinsdottir, S.; Geirsson, H.; Ofeigsson, B.

    2013-12-01

    Iceland is located on the Mid-Atlantic ridge, straddling the plate boundary of the North-American and Eurasian plates. Several active volcanic zones and two main transforms accommodate the plate spreading across the island. In the South, the South Iceland Seismic Zone (SISZ) forms the active plate boundary between the Hengill triple junction in the west, and the Eastern Volcanic Zone. The SISZ translates the E-W left lateral shear at depth by faulting on numerous N-S oriented faults in the brittle crust forming the southern margin of the proposed Hreppar micro-plate in South Iceland. In June 2000 and May 2008, two sets of magnitude 6.5 and 6.0 main shocks struck the SISZ. Both earthquake episodes consisted of a pair of main shocks of similar size rupturing closely spaced faults, where static and dynamic stress changes generated by the first event triggered the second main shock further west. The June 2000 earthquakes occurred in the central part of the SISZ, and the May 2008 events in the western part, close to the Hengill triple junction. Since June 2000 annual GPS measurements have been conducted in a geodetic network in South Iceland and a number of continuous GPS stations have been installed. We report strain rate variations in South Iceland derived from GPS observations during 2000 to 2013. In addition to plate motion, and post-seismic signals, the surface deformation is complicated by magma accumulation under active volcanoes at the eastern border of the SISZ - Hekla, and Eyjafjallajökull - as well as subsidence and contraction in the Hengill area caused by fluid withdrawal for geothermal energy production. We also note an increase in strain rates in the epicentral area of the May 2008 main shocks during 2004 to 2007. Previous studies have indicated that the seismic moment released in the June 2000 and May 2008 earthquakes is only half of the accumulated stress since the last major earthquake sequence in 1896-1912. Thus, magnitude 6-7 events may be expected

  10. Oxidative stress is a mediator for increased lipid accumulation in a newly isolated Dunaliella salina strain.

    PubMed

    Yilancioglu, Kaan; Cokol, Murat; Pastirmaci, Inanc; Erman, Batu; Cetiner, Selim

    2014-01-01

    Green algae offer sustainable, clean and eco-friendly energy resource. However, production efficiency needs to be improved. Increasing cellular lipid levels by nitrogen depletion is one of the most studied strategies. Despite this, the underlying physiological and biochemical mechanisms of this response have not been well defined. Algae species adapted to hypersaline conditions can be cultivated in salty waters which are not useful for agriculture or consumption. Due to their inherent extreme cultivation conditions, use of hypersaline algae species is better suited for avoiding culture contamination issues. In this study, we identified a new halophilic Dunaliella salina strain by using 18S ribosomal RNA gene sequencing. We found that growth and biomass productivities of this strain were directly related to nitrogen levels, as the highest biomass concentration under 0.05 mM or 5 mM nitrogen regimes were 495 mg/l and 1409 mg/l, respectively. We also confirmed that nitrogen limitation increased cellular lipid content up to 35% under 0.05 mM nitrogen concentration. In order to gain insight into the mechanisms of this phenomenon, we applied fluorometric, flow cytometric and spectrophotometric methods to measure oxidative stress and enzymatic defence mechanisms. Under nitrogen depleted cultivation conditions, we observed increased lipid peroxidation by measuring an important oxidative stress marker, malondialdehyde and enhanced activation of catalase, ascorbate peroxidase and superoxide dismutase antioxidant enzymes. These observations indicated that oxidative stress is accompanied by increased lipid content in the green alga. In addition, we also showed that at optimum cultivation conditions, inducing oxidative stress by application of exogenous H2O2 leads to increased cellular lipid content up to 44% when compared with non-treated control groups. Our results support that oxidative stress and lipid overproduction are linked. Importantly, these results also suggest that

  11. Oxidative Stress Is a Mediator for Increased Lipid Accumulation in a Newly Isolated Dunaliella salina Strain

    PubMed Central

    Yilancioglu, Kaan; Cokol, Murat; Pastirmaci, Inanc; Erman, Batu; Cetiner, Selim

    2014-01-01

    Green algae offer sustainable, clean and eco-friendly energy resource. However, production efficiency needs to be improved. Increasing cellular lipid levels by nitrogen depletion is one of the most studied strategies. Despite this, the underlying physiological and biochemical mechanisms of this response have not been well defined. Algae species adapted to hypersaline conditions can be cultivated in salty waters which are not useful for agriculture or consumption. Due to their inherent extreme cultivation conditions, use of hypersaline algae species is better suited for avoiding culture contamination issues. In this study, we identified a new halophilic Dunaliella salina strain by using 18S ribosomal RNA gene sequencing. We found that growth and biomass productivities of this strain were directly related to nitrogen levels, as the highest biomass concentration under 0.05 mM or 5 mM nitrogen regimes were 495 mg/l and 1409 mg/l, respectively. We also confirmed that nitrogen limitation increased cellular lipid content up to 35% under 0.05 mM nitrogen concentration. In order to gain insight into the mechanisms of this phenomenon, we applied fluorometric, flow cytometric and spectrophotometric methods to measure oxidative stress and enzymatic defence mechanisms. Under nitrogen depleted cultivation conditions, we observed increased lipid peroxidation by measuring an important oxidative stress marker, malondialdehyde and enhanced activation of catalase, ascorbate peroxidase and superoxide dismutase antioxidant enzymes. These observations indicated that oxidative stress is accompanied by increased lipid content in the green alga. In addition, we also showed that at optimum cultivation conditions, inducing oxidative stress by application of exogenous H2O2 leads to increased cellular lipid content up to 44% when compared with non-treated control groups. Our results support that oxidative stress and lipid overproduction are linked. Importantly, these results also suggest that

  12. Oxidative stress is a mediator for increased lipid accumulation in a newly isolated Dunaliella salina strain.

    PubMed

    Yilancioglu, Kaan; Cokol, Murat; Pastirmaci, Inanc; Erman, Batu; Cetiner, Selim

    2014-01-01

    Green algae offer sustainable, clean and eco-friendly energy resource. However, production efficiency needs to be improved. Increasing cellular lipid levels by nitrogen depletion is one of the most studied strategies. Despite this, the underlying physiological and biochemical mechanisms of this response have not been well defined. Algae species adapted to hypersaline conditions can be cultivated in salty waters which are not useful for agriculture or consumption. Due to their inherent extreme cultivation conditions, use of hypersaline algae species is better suited for avoiding culture contamination issues. In this study, we identified a new halophilic Dunaliella salina strain by using 18S ribosomal RNA gene sequencing. We found that growth and biomass productivities of this strain were directly related to nitrogen levels, as the highest biomass concentration under 0.05 mM or 5 mM nitrogen regimes were 495 mg/l and 1409 mg/l, respectively. We also confirmed that nitrogen limitation increased cellular lipid content up to 35% under 0.05 mM nitrogen concentration. In order to gain insight into the mechanisms of this phenomenon, we applied fluorometric, flow cytometric and spectrophotometric methods to measure oxidative stress and enzymatic defence mechanisms. Under nitrogen depleted cultivation conditions, we observed increased lipid peroxidation by measuring an important oxidative stress marker, malondialdehyde and enhanced activation of catalase, ascorbate peroxidase and superoxide dismutase antioxidant enzymes. These observations indicated that oxidative stress is accompanied by increased lipid content in the green alga. In addition, we also showed that at optimum cultivation conditions, inducing oxidative stress by application of exogenous H2O2 leads to increased cellular lipid content up to 44% when compared with non-treated control groups. Our results support that oxidative stress and lipid overproduction are linked. Importantly, these results also suggest that

  13. Parametric analysis of plastic strain and force distribution in single pass metal spinning

    SciTech Connect

    Choudhary, Shashank E-mail: mohantejesh93@gmail.com E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Tejesh, Chiruvolu Mohan E-mail: mohantejesh93@gmail.com E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Regalla, Srinivasa Prakash E-mail: mohantejesh93@gmail.com E-mail: ksuresh@hyderabad.bits-pilani.ac.in; Suresh, Kurra E-mail: mohantejesh93@gmail.com E-mail: ksuresh@hyderabad.bits-pilani.ac.in

    2013-12-16

    Metal spinning also known as spin forming is one of the sheet metal working processes by which an axis-symmetric part can be formed from a flat sheet metal blank. Parts are produced by pressing a blunt edged tool or roller on to the blank which in turn is mounted on a rotating mandrel. This paper discusses about the setting up a 3-D finite element simulation of single pass metal spinning in LS-Dyna. Four parameters were considered namely blank thickness, roller nose radius, feed ratio and mandrel speed and the variation in forces and plastic strain were analysed using the full-factorial design of experiments (DOE) method of simulation experiments. For some of these DOE runs, physical experiments on extra deep drawing (EDD) sheet metal were carried out using En31 tool on a lathe machine. Simulation results are able to predict the zone of unsafe thinning in the sheet and high forming forces that are hint to the necessity for less-expensive and semi-automated machine tools to help the household and small scale spinning workers widely prevalent in India.

  14. Developmental and waste reduction plasticity of three black soldier fly strains (Diptera: Stratiomyidae) raised on different livestock manures.

    PubMed

    Zhou, Fen; Tomberlin, Jeffery K; Zheng, Longyu; Yu, Ziniu; Zhang, Jibin

    2013-11-01

    Black soldier flies, Hermetia illucens L., are distributed throughout the temperate and tropic regions of the world and are known an established method for sustainably managing animal wastes. Colonies used to conduct research on the black soldier fly within the past 20 yr have predominately been established from eggs or larvae received from a colony originated from Bacon County, GA. Consequently, little is known about the phenotypic plasticity (i.e., development and waste conversion) across strains from different regions. This study compared the development of three strains of the black soldier fly (Texas; Guangzhou, China; and Wuhan, China) and their ability to reduce dry matter and associated nutrients in swine, dairy, and chicken manure. The Wuhan strain appeared to be more fit. Larvae from Wuhan needed 17.7-29.9% less time to reach the prepupal stage than those from Guangzhou or Texas, respectively. Larvae from Wuhan weighed 14.4-37.0% more than those from Guanghzhou or Texas, respectively. Larvae from the Wuhan strain reduced dry matter 46.0% (swine), 40.1% (dairy), and 48.4% (chicken) more than the Guangzhou strain and 6.9, 7.2, and 7.9% more than the Texas strain. This study demonstrates that phenotypic plasticity (e.g., development and waste conversion) varies across populations of black soldier flies and should be taken into account when selecting and establishing a population as a waste management agent in a given region of the world. PMID:24843926

  15. Developmental and waste reduction plasticity of three black soldier fly strains (Diptera: Stratiomyidae) raised on different livestock manures.

    PubMed

    Zhou, Fen; Tomberlin, Jeffery K; Zheng, Longyu; Yu, Ziniu; Zhang, Jibin

    2013-11-01

    Black soldier flies, Hermetia illucens L., are distributed throughout the temperate and tropic regions of the world and are known an established method for sustainably managing animal wastes. Colonies used to conduct research on the black soldier fly within the past 20 yr have predominately been established from eggs or larvae received from a colony originated from Bacon County, GA. Consequently, little is known about the phenotypic plasticity (i.e., development and waste conversion) across strains from different regions. This study compared the development of three strains of the black soldier fly (Texas; Guangzhou, China; and Wuhan, China) and their ability to reduce dry matter and associated nutrients in swine, dairy, and chicken manure. The Wuhan strain appeared to be more fit. Larvae from Wuhan needed 17.7-29.9% less time to reach the prepupal stage than those from Guangzhou or Texas, respectively. Larvae from Wuhan weighed 14.4-37.0% more than those from Guanghzhou or Texas, respectively. Larvae from the Wuhan strain reduced dry matter 46.0% (swine), 40.1% (dairy), and 48.4% (chicken) more than the Guangzhou strain and 6.9, 7.2, and 7.9% more than the Texas strain. This study demonstrates that phenotypic plasticity (e.g., development and waste conversion) varies across populations of black soldier flies and should be taken into account when selecting and establishing a population as a waste management agent in a given region of the world.

  16. Global Positioning System measurements of strain accumulation across the Imperial Valley, California - 1986-1989

    NASA Technical Reports Server (NTRS)

    Larsen, Shawn; Reilinger, Robert

    1992-01-01

    The Global Positioning System (GPS) data collected in southern California from 1986 to 1989 indicate considerable strain accumulation across the Imperial Valley. Displacements are computed at 29 stations in and near the valley from 1986 to 1988, and at 11 sites from 1988 to 1989. The earlier measurements indicate 5.9 =/- 1.0 cm/yr right-lateral differential velocity across the valley, although the data are heavily influenced by the 1987 Superstition Hills earthquake sequence. Some measurements, especially the east-trending displacements, are suspects for large errors. The 1988 to 1989 GPS displacements are best modeled by 5.2 =/- 0.9 cm/yr of valley crossing deformation, but rates calculated from conventional geodetic measurements (3.4 to 4.3 cm/yr) fit the data nearly as well. There is evidence from GPS and Very Long Base Interferometry (VLBI) observations that the present slip rate along the southern San Andreas fault is smaller than the long-term geologic estimate, suggesting a lower earthquake potential than is currently assumed. Correspondingly, a higher earthquake potential is indicated for the San Jacinto fault. The Imperial Valley GPS sites form part of a 183 station network in southern California and northern Baja California, which spans a cross-section of the North American-Pacific plate boundary.

  17. Dislocation pileup as a representation of strain accumulation on a strike-slip fault

    USGS Publications Warehouse

    Savage, J.C.

    2006-01-01

    The conventional model of strain accumulation on a vertical transform fault is a discrete screw dislocation in an elastic half-space with the Burgers vector of the dislocation increasing at the rate of relative plate motion. It would be more realistic to replace that discrete dislocation by a dislocation distribution, presumably a pileup in which the individual dislocations are in equilibrium. The length of the pileup depends upon the applied stress and the amount of slip that has occurred at depth. I argue here that the dislocation pileup (the transition on the fault from no slip to slip at the full plate rate) occupies a substantial portion of the lithosphere thickness. A discrete dislocation at an adjustable depth can reproduce the surface deformation profile predicted by a pileup so closely that it will be difficult to distinguish between the two models. The locking depth (dislocation depth) of that discrete dislocation approximation is substantially (???30%) larger than that (depth to top of the pileup) in the pileup model. Thus, in inverting surface deformation data using the discrete dislocation model, the locking depth in the model should not be interpreted as the true locking depth. Although dislocation pileup models should provide a good explanation of the surface deformation near the fault trace, that explanation may not be adequate at greater distances from the fault trace because approximating the expected horizontally distributed deformation at subcrustal depths by uniform slip concentrated on the fault is not justified.

  18. Interseismic strain accumulation in south central Chile from GPS measurements, 1996-1999

    NASA Astrophysics Data System (ADS)

    Ruegg, J. C.; Campos, J.; Madariaga, R.; Kausel, E.; de Chabalier, J. B.; Armijo, R.; Dimitrov, D.; Georgiev, I.; Barrientos, S.

    2002-06-01

    Two campaigns of Global Positioning System (GPS) measurements were carried out in the Concepción-Constitución area of Chile in 1996 and 1999. It is very likely that this area is a mature seismic gap, since no subduction earthquake has occurred there since 1835. In 1996, 32 sites were occupied in the range 35°S-37°S, between the Pacific coast of Chile and the Andes near the Chile-Argentina border. In 1999, the network was extended by the installation of 9 new points in the Arauco region whereas 13 points among the 1996 stations were reoccupied. The analysis of this campaign data set, together with the data recorded at eight continuous GPS sites (mostly IGS stations) in South America and surrounding regions, indicates a velocity of about 40 +/- 10 mm/yr in the direction N80-90°S for the coastal sites with respect to stable cratonic South America. This velocity decreases to about 20-25 mm/yr towards the Andes. We interpret this result as reflecting interseismic strain accumulation above the Nazca-South America subduction zone, due to a locked thrust zone extending down to about 60 km depth.

  19. GPS measurements of strain accumulation across the Imperial Valley, California: 1986-1989

    NASA Technical Reports Server (NTRS)

    Larsen, Shawn; Reilinger, Robert

    1989-01-01

    The Global Positioning System (GPS) data collected in southern California from 1986 to 1989 indicate considerable strain accumulation across the Imperial Valley. Displacements are computed at 29 stations in and near the valley from 1986 to 1988, and at 11 sites from 1988 to 1989. The earlier measurements indicate 5.9 +/- 1.0 cm/yr right-lateral differential velocity across the valley, although the data are heavily influenced by the 1987 Superstition Hills earthquake sequence. Some measurements, especially the east-trending displacements, are suspects for large errors. The 1988 to 1989 GPS displacements are best modeled by 5.2 +/- 0.9 cm/yr of valley crossing deformation, but rates calculated from conventional geodetic measurements (3.4 to 4.3 cm/yr) fit the data nearly as well. There is evidence from GPS and Very Long Base Interferometry (VLBI) observations that the present slip rate along the southern San Andreas fault is smaller than the long-term geologic estimate, suggesting a lower earthquake potential than is currently assumed. Correspondingly, a higher earthquake potential is indicated for the San Jacinto fault. The Imperial Valley GPS sites form part of a 183 station network in southern California and northern Baja California, which spans a cross-section of the North American-Pacific plate boundary.

  20. Prediction of the Elastic-Plastic Stress/Strain Response for Injection-Molded Long-Fiber Thermoplastics

    SciTech Connect

    Nguyen, Ba Nghiep; Bapanapalli, Satish K.; Kunc, Vlastimil; Phelps, Jay; Tucker III, Charles L.

    2009-01-26

    This paper proposes a model to predict the elastic-plastic response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the elastic-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber orientation was predicted using the anisotropic rotary diffusion model recently developed by Phelps and Tucker for LFTs. An incremental procedure using the Eshelby’s equivalent inclusion method and the Mori-Tanaka model is proposed to compute the overall stress increment resulting from an overall strain increment for an aligned fiber composite that contains the same fiber volume fraction and length distribution as the actual composite. The incremental response of the later is then obtained from the solution for the aligned fiber composite that is averaged over all possible fiber orientations using the orientation averaging method. Failure during incremental loading is predicted using the Van Hattum-Bernado model. The elastic-plastic and strength prediction model for LFTs was validated against the experimental stress-strain results obtained for long glass fiber/polypropylene specimens.

  1. Texture, residual strain, and plastic deformation around scratches in alloy 600 using synchrotron x-ray Laue micro-diffraction.

    SciTech Connect

    Suominen Fuller, M. L.; Klassen, R. J.; McIntyre, N. S.; Gerson, A. R.; Ramamurthy, S.; King, P. J.; Liu, W.; Univ. of Western Ontario; Univ. of South Australia; Babcock & Wilcox Canada

    2008-01-01

    Deformation around two scratches in Alloy 600 (A600) was studied nondestructively using synchrotron Laue differential aperture X-ray microscopy. The orientation of grains and elastic strain distribution around the scratches were measured. A complex residual deviatoric elastic strain state was found to exist around the scratches. Heavy plastic deformation was observed up to a distance of 20 {micro}m from the scratches. In the region 20-30 {micro}m from the scratches the diffraction spots were heavily streaked and split indicating misoriented dislocation cell structures.

  2. Shock and High Strain Rate Characterization of HTPB with Varying Plasticizer

    NASA Astrophysics Data System (ADS)

    Montaigne, Didier; Neel, Christopher; Gould, Peter; Molek, Christopher; Jordan, Jennifer

    2013-06-01

    Hydroxy-terminated polybutadiene (HTPB) has long been used as a binder in propellants and explosives. However, cured HTPB rubbery polyurethanes have not been characterized in a systematic fashion as function of plasticizer content. In this study, four isocyanate-cured HTPB variants with different amounts of plasticizer have been formulated. The materials were characterized using dynamic mechanical analysis and quasi-static and dynamic compression experiments. Additionally, the shock Hugoniot was measured on the two extremes of the material - no plasticizer and maximum plasticizer. The properties of the HTPB were predicted using the Porter-Gould model for polymers.

  3. Prion Strain Differences in Accumulation of PrPSc on Neurons and Glia Are Associated with Similar Expression Profiles of Neuroinflammatory Genes: Comparison of Three Prion Strains

    PubMed Central

    Carroll, James A.; Striebel, James F.; Rangel, Alejandra; Woods, Tyson; Phillips, Katie; Peterson, Karin E.; Race, Brent; Chesebro, Bruce

    2016-01-01

    Misfolding and aggregation of host proteins are important features of the pathogenesis of neurodegenerative diseases including Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia and prion diseases. In all these diseases, the misfolded protein increases in amount by a mechanism involving seeded polymerization. In prion diseases, host prion protein is misfolded to form a pathogenic protease-resistant form, PrPSc, which accumulates in neurons, astroglia and microglia in the CNS. Here using dual-staining immunohistochemistry, we compared the cell specificity of PrPSc accumulation at early preclinical times post-infection using three mouse scrapie strains that differ in brain regional pathology. PrPSc from each strain had a different pattern of cell specificity. Strain 22L was mainly associated with astroglia, whereas strain ME7 was mainly associated with neurons and neuropil. In thalamus and cortex, strain RML was similar to 22L, but in substantia nigra, RML was similar to ME7. Expression of 90 genes involved in neuroinflammation was studied quantitatively using mRNA from thalamus at preclinical times. Surprisingly, despite the cellular differences in PrPSc accumulation, the pattern of upregulated genes was similar for all three strains, and the small differences observed correlated with variations in the early disease tempo. Gene upregulation correlated with activation of both astroglia and microglia detected in early disease prior to vacuolar pathology or clinical signs. Interestingly, the profile of upregulated genes in scrapie differed markedly from that seen in two acute viral CNS diseases (LaCrosse virus and BE polytropic Friend retrovirus) that had reactive gliosis at levels similar to our prion-infected mice. PMID:27046083

  4. Prion Strain Differences in Accumulation of PrPSc on Neurons and Glia Are Associated with Similar Expression Profiles of Neuroinflammatory Genes: Comparison of Three Prion Strains.

    PubMed

    Carroll, James A; Striebel, James F; Rangel, Alejandra; Woods, Tyson; Phillips, Katie; Peterson, Karin E; Race, Brent; Chesebro, Bruce

    2016-04-01

    Misfolding and aggregation of host proteins are important features of the pathogenesis of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, frontotemporal dementia and prion diseases. In all these diseases, the misfolded protein increases in amount by a mechanism involving seeded polymerization. In prion diseases, host prion protein is misfolded to form a pathogenic protease-resistant form, PrPSc, which accumulates in neurons, astroglia and microglia in the CNS. Here using dual-staining immunohistochemistry, we compared the cell specificity of PrPSc accumulation at early preclinical times post-infection using three mouse scrapie strains that differ in brain regional pathology. PrPSc from each strain had a different pattern of cell specificity. Strain 22L was mainly associated with astroglia, whereas strain ME7 was mainly associated with neurons and neuropil. In thalamus and cortex, strain RML was similar to 22L, but in substantia nigra, RML was similar to ME7. Expression of 90 genes involved in neuroinflammation was studied quantitatively using mRNA from thalamus at preclinical times. Surprisingly, despite the cellular differences in PrPSc accumulation, the pattern of upregulated genes was similar for all three strains, and the small differences observed correlated with variations in the early disease tempo. Gene upregulation correlated with activation of both astroglia and microglia detected in early disease prior to vacuolar pathology or clinical signs. Interestingly, the profile of upregulated genes in scrapie differed markedly from that seen in two acute viral CNS diseases (LaCrosse virus and BE polytropic Friend retrovirus) that had reactive gliosis at levels similar to our prion-infected mice. PMID:27046083

  5. A physical model for strain accumulation in the San Francisco Bay region: Stress evolution since 1838

    USGS Publications Warehouse

    Pollitz, F.; Bakun, W.H.; Nyst, M.

    2004-01-01

    Understanding of the behavior of plate boundary zones has progressed to the point where reasonably comprehensive physical models can predict their evolution. The San Andreas fault system in the San Francisco Bay region (SFBR) is dominated by a few major faults whose behavior over about one earthquake cycle is fairly well understood. By combining the past history of large ruptures on SFBR faults with a recently proposed physical model of strain accumulation in the SFBR, we derive the evolution of regional stress from 1838 until the present. This effort depends on (1) an existing compilation of the source properties of historic and contemporary SFBR earthquakes based on documented shaking, geodetic data, and seismic data (Bakun, 1999) and (2) a few key parameters of a simple regional viscoelastic coupling model constrained by recent GPS data (Pollitz and Nyst, 2004). Although uncertainties abound in the location, magnitude, and fault geometries of historic ruptures and the physical model relies on gross simplifications, the resulting stress evolution model is sufficiently detailed to provide a useful window into the past stress history. In the framework of Coulomb failure stress, we find that virtually all M ??? 5.8 earthquakes prior to 1906 and M ??? 5.5 earthquakes after 1906 are consistent with stress triggering from previous earthquakes. These events systematically lie in zones of predicted stress concentration elevated 5-10 bars above the regional average. The SFBR is predicted to have emerged from the 1906 "shadow" in about 1980, consistent with the acceleration in regional seismicity at that time. The stress evolution model may be a reliable indicator of the most likely areas to experience M ??? 5.5 shocks in the future.

  6. Complex Toxin Profile of French Mediterranean Ostreopsis cf. ovata Strains, Seafood Accumulation and Ovatoxins Prepurification

    PubMed Central

    Brissard, Charline; Herrenknecht, Christine; Séchet, Véronique; Hervé, Fabienne; Pisapia, Francesco; Harcouet, Jocelyn; Lémée, Rodolphe; Chomérat, Nicolas; Hess, Philipp; Amzil, Zouher

    2014-01-01

    Ostreopsis cf. ovata produces palytoxin analogues including ovatoxins (OVTXs) and a putative palytoxin (p-PLTX), which can accumulate in marine organisms and may possibly lead to food intoxication. However, purified ovatoxins are not widely available and their toxicities are still unknown. The aim of this study was to improve understanding of the ecophysiology of Ostreopsis cf. ovata and its toxin production as well as to optimize the purification process for ovatoxin. During Ostreopsis blooms in 2011 and 2012 in Villefranche-sur-Mer (France, NW Mediterranean Sea), microalgae epiphytic cells and marine organisms were collected and analyzed both by LC-MS/MS and hemolysis assay. Results obtained with these two methods were comparable, suggesting ovatoxins have hemolytic properties. An average of 223 μg·kg−1 of palytoxin equivalent of whole flesh was found, thus exceeding the threshold of 30 μg·kg−1 in shellfish recommended by the European Food Safety Authority (EFSA). Ostreopsis cells showed the same toxin profile both in situ and in laboratory culture, with ovatoxin-a (OVTX-a) being the most abundant analogue (~50%), followed by OVTX-b (~15%), p-PLTX (12%), OVTX-d (8%), OVTX-c (5%) and OVTX-e (4%). Ostreopsis cf. ovata produced up to 2 g of biomass per L of culture, with a maximum concentration of 300 pg PLTX equivalent cell−1. Thus, an approximate amount of 10 mg of PLTX-group toxins may be produced with 10 L of this strain. Toxin extracts obtained from collected biomass were purified using different techniques such as liquid-liquid partition or size exclusion. Among these methods, open-column chromatography with Sephadex LH20 phase yielded the best results with a cleanup efficiency of 93% and recovery of about 85%, representing an increase of toxin percentage by 13 fold. Hence, this purification step should be incorporated into future isolation exercises. PMID:24828292

  7. The mechanisms of plastic strain accommodation and post critical behavior of heterogeneous reactive composites subject to dynamic loading

    NASA Astrophysics Data System (ADS)

    Olney, Karl L.

    The dynamic behavior of granular/porous and laminate reactive materials is of interest due to their practical applications; reactive structural components, reactive fragments, etc. The mesostructural properties control meso- and macro-scale dynamic behavior of these heterogeneous composites including the behavior during the post-critical stage of deformation. They heavily influence mechanisms of fragment generation and the in situ development of local hot spots, which act as sites of ignition in these materials. This dissertation concentrates on understanding the mechanisms of plastic strain accommodation in two representative reactive material systems with different heterogeneous mesostructrues: Aluminum-Tungsten granular/porous and Nickel-Aluminum laminate composites. The main focus is on the interpretation of results of the following dynamic experiments conducted at different strain and strain rates: drop weight tests, explosively expanded ring experiments, and explosively collapsed thick walled cylinder experiments. Due to the natural limitations in the evaluation of the mesoscale behavior of these materials experimentally and the large variation in the size scales between the mesostructural level and the sample, it is extremely difficult, if not impossible, to examine the mesoscale behavior in situ. Therefore, numerical simulations of the corresponding experiments are used as the main tool to explore material behavior at the mesoscale. Numerical models were developed to elucidate the mechanisms of plastic strain accommodation and post critical behavior in these heterogeneous composites subjected to dynamic loading. These simulations were able to reproduce the qualitative and quantitative features that were observable in the experiments and provided insight into the evolution of the mechanisms of plastic strain accommodation and post critical behavior in these materials with complex mesotructure. Additionally, these simulations provided a framework to examine

  8. Plastic ingestion by Flesh-footed Shearwaters (Puffinus carneipes): Implications for fledgling body condition and the accumulation of plastic-derived chemicals.

    PubMed

    Lavers, Jennifer L; Bond, Alexander L; Hutton, Ian

    2014-04-01

    To provide much needed quantitative data on the lethal and sublethal effects of plastic pollution on marine wildlife, we sampled breast feathers and stomach contents from Flesh-footed Shearwater (Puffinus carneipes) fledglings in eastern Australia. Birds with high levels of ingested plastic exhibited reduced body condition and increased contaminant load (p < 0.05). More than 60% of fledglings exceed international targets for plastic ingestion by seabirds, with 16% of fledglings failing these targets after a single feeding (range: 0.13-3.21 g of plastic/feeding). As top predators, seabirds are considered sentinels of the marine environment. The amount of plastic ingested and corresponding damage to Flesh-footed Shearwater fledglings is the highest reported for any marine vertebrate, suggesting the condition of the Australian marine environment is poor. These findings help explain the ongoing decline of this species and are worrying in light of increasing levels of plastic pollution in our oceans. PMID:24480381

  9. Auxotroph Accumulation in Deoxyribonucleic Acid Polymeraseless Strains of Escherichia coli K-121

    PubMed Central

    Berg, Claire M.

    1971-01-01

    Spontaneous auxotrophs are found with high frequency in several strains of Escherichia coli K-12 deficient in Kornberg deoxyribonucleic acid polymerase. These include amino acid-, vitamin-, purine-, and pyrimidine-requiring strains. Although this was suggestive evidence that these strains might be mutators, reconstruction experiments demonstrate that auxotrophs possess a selective advantage over prototrophs in the same culture. Thus, despite the high frequency of auxotrophs in polymerase-deficient strains, it is not yet clear whether they have elevated mutation rates. PMID:4934065

  10. Relaxation of the single-slip condition in strain-gradient plasticity

    PubMed Central

    Anguige, Keith; Dondl, Patrick W.

    2014-01-01

    We consider the variational formulation of both geometrically linear and geometrically nonlinear elasto-plasticity subject to a class of hard single-slip conditions. Such side conditions typically render the associated boundary-value problems non-convex. We show that, for a large class of non-smooth plastic distortions, a given single-slip condition (specification of Burgers vectors) can be relaxed by introducing a microstructure through a two-stage process of mollification and lamination. The relaxed model can be thought of as an aid to simulating macroscopic plastic behaviour without the need to resolve arbitrarily fine spatial scales. PMID:25197243

  11. Prediction of the Elastic-Plastic Stress/Strain Response for Injection-Molded Long-Fiber Thermoplastics

    SciTech Connect

    Nguyen, Ba N.; Kunc, Vlastimil; Phelps, Jay H; TuckerIII, Charles L.; Bapanapalli, Satish K

    2009-01-01

    This paper proposes a model to predict the elastic-plastic response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the elastic-plastic behavior obeying the Ramberg-Osgood relation and J-2 deformation theory of plasticity. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber orientation was predicted using an anisotropic rotary diffusion model recently developed for LFTs. An incremental procedure using Eshelby's equivalent inclusion method and the Mori-Tanaka assumption is proposed to compute the overall stress increment resulting from an overall strain increment for an aligned-fiber composite that contains the same fiber volume fraction and length distribution as the actual composite. The incremental response of the latter is then obtained from the solution for the aligned-fiber composite by averaging over all fiber orientations. Failure during incremental loading is predicted using the Van Hattum-Bernado model. The model is validated against the experimental stress-strain results obtained for long-glass-fiber/polypropylene specimens.

  12. Cellular basis of morphological variation and temperature-related plasticity in Drosophila melanogaster strains with divergent wing shapes.

    PubMed

    Torquato, Libéria Souza; Mattos, Daniel; Matta, Bruna Palma; Bitner-Mathé, Blanche Christine

    2014-12-01

    Organ shape evolves through cross-generational changes in developmental patterns at cellular and/or tissue levels that ultimately alter tissue dimensions and final adult proportions. Here, we investigated the cellular basis of an artificially selected divergence in the outline shape of Drosophila melanogaster wings, by comparing flies with elongated or rounded wing shapes but with remarkably similar wing sizes. We also tested whether cellular plasticity in response to developmental temperature was altered by such selection. Results show that variation in cellular traits is associated with wing shape differences, and that cell number may play an important role in wing shape response to selection. Regarding the effects of developmental temperature, a size-related plastic response was observed, in that flies reared at 16 °C developed larger wings with larger and more numerous cells across all intervein regions relative to flies reared at 25 °C. Nevertheless, no conclusive indication of altered phenotypic plasticity was found between selection strains for any wing or cellular trait. We also described how cell area is distributed across different intervein regions. It follows that cell area tends to decrease along the anterior wing compartment and increase along the posterior one. Remarkably, such pattern was observed not only in the selected strains but also in the natural baseline population, suggesting that it might be canalized during development and was not altered by the intense program of artificial selection for divergent wing shapes.

  13. Oil accumulation in the model green alga Chlamydomonas reinhardtii: characterization, variability between common laboratory strains and relationship with starch reserves

    PubMed Central

    2011-01-01

    Background When cultivated under stress conditions, many microalgae species accumulate both starch and oil (triacylglycerols). The model green microalga Chlamydomonas reinhardtii has recently emerged as a model to test genetic engineering or cultivation strategies aiming at increasing lipid yields for biodiesel production. Blocking starch synthesis has been suggested as a way to boost oil accumulation. Here, we characterize the triacylglycerol (TAG) accumulation process in Chlamydomonas and quantify TAGs in various wild-type and starchless strains. Results In response to nitrogen deficiency, Chlamydomonas reinhardtii produced TAGs enriched in palmitic, oleic and linoleic acids that accumulated in oil-bodies. Oil synthesis was maximal between 2 and 3 days following nitrogen depletion and reached a plateau around day 5. In the first 48 hours of oil deposition, a ~80% reduction in the major plastidial membrane lipids occurred. Upon nitrogen re-supply, mobilization of TAGs started after starch degradation but was completed within 24 hours. Comparison of oil content in five common laboratory strains (CC124, CC125, cw15, CC1690 and 11-32A) revealed a high variability, from 2 μg TAG per million cell in CC124 to 11 μg in 11-32A. Quantification of TAGs on a cell basis in three mutants affected in starch synthesis (cw15sta1-2, cw15sta6 and cw15sta7-1) showed that blocking starch synthesis did not result in TAG over-accumulation compared to their direct progenitor, the arginine auxotroph strain 330. Moreover, no significant correlation was found between cellular oil and starch levels among the twenty wild-type, mutants and complemented strains tested. By contrast, cellular oil content was found to increase steeply with salt concentration in the growth medium. At 100 mM NaCl, oil level similar to nitrogen depletion conditions could be reached in CC124 strain. Conclusion A reference basis for future genetic studies of oil metabolism in Chlamydomonas is provided. Results

  14. Study of plastic strain localization mechanisms caused by nonequilibrium transitions in mesodefect ensembles under high-speed loading

    SciTech Connect

    Sokovikov, Mikhail Chudinov, Vasiliy; Bilalov, Dmitry; Oborin, Vladimir; Uvarov, Sergey; Plekhov, Oleg; Naimark, Oleg

    2015-10-27

    The behavior of specimens dynamically loaded during split Hopkinson (Kolsky) bar tests in a regime close to simple shear conditions was studied. The lateral surface of the specimens was investigated in-situ using a high-speed infrared camera CEDIP Silver 450M. The temperature field distribution obtained at different time allowed one to trace the evolution of plastic strain localization. The process of target perforation involving plug formation and ejection was examined using a high-speed infrared camera and a VISAR velocity measurement system. The microstructure of tested specimens was analyzed using an optical interferometer-profiler and a scanning electron microscope. The development of plastic shear instability regions has been simulated numerically.

  15. Analysis of Strains Lacking Known Osmolyte Accumulation Mechanisms Reveals Contributions of Osmolytes and Transporters to Protection against Abiotic Stress

    PubMed Central

    Murdock, Lindsay; Burke, Tangi; Coumoundouros, Chelsea; Culham, Doreen E.; Deutch, Charles E.; Ellinger, James; Kerr, Craig H.; Plater, Samantha M.; To, Eric; Wright, Geordie

    2014-01-01

    Osmolyte accumulation and release can protect cells from abiotic stresses. In Escherichia coli, known mechanisms mediate osmotic stress-induced accumulation of K+ glutamate, trehalose, or zwitterions like glycine betaine. Previous observations suggested that additional osmolyte accumulation mechanisms (OAMs) exist and their impacts may be abiotic stress specific. Derivatives of the uropathogenic strain CFT073 and the laboratory strain MG1655 lacking known OAMs were created. CFT073 grew without osmoprotectants in minimal medium with up to 0.9 M NaCl. CFT073 and its OAM-deficient derivative grew equally well in high- and low-osmolality urine pools. Urine-grown bacteria did not accumulate large amounts of known or novel osmolytes. Thus, CFT073 showed unusual osmotolerance and did not require osmolyte accumulation to grow in urine. Yeast extract and brain heart infusion stimulated growth of the OAM-deficient MG1655 derivative at high salinity. Neither known nor putative osmoprotectants did so. Glutamate and glutamine accumulated after growth with either organic mixture, and no novel osmolytes were detected. MG1655 derivatives retaining individual OAMs were created. Their abilities to mediate osmoprotection were compared at 15°C, 37°C without or with urea, and 42°C. Stress protection was not OAM specific, and variations in osmoprotectant effectiveness were similar under all conditions. Glycine betaine and dimethylsulfoniopropionate (DMSP) were the most effective. Trimethylamine-N-oxide (TMAO) was a weak osmoprotectant and a particularly effective urea protectant. The effectiveness of glycine betaine, TMAO, and proline as osmoprotectants correlated with their preferential exclusion from protein surfaces, not with their propensity to prevent protein denaturation. Thus, their effectiveness as stress protectants correlated with their ability to rehydrate the cytoplasm. PMID:24951793

  16. A physically based model of temperature and strain rate dependent yield in BCC metals: Implementation into crystal plasticity

    NASA Astrophysics Data System (ADS)

    Lim, Hojun; Battaile, Corbett C.; Carroll, Jay D.; Boyce, Brad L.; Weinberger, Christopher R.

    2015-01-01

    In this work, we develop a crystal plasticity finite element model (CP-FEM) that constitutively captures the temperature and strain rate dependent flow stresses in pure BCC refractory metals. This model is based on the kink-pair theory developed by Seeger (1981) and is calibrated to available data from single crystal experiments to produce accurate and convenient constitutive laws that are implemented into a BCC crystal plasticity model. The model is then used to predict temperature and strain rate dependent yield stresses of single and polycrystal BCC refractory metals (molybdenum, tantalum, tungsten and niobium) and compared with existing experimental data. To connect to larger length scales, classical continuum-scale constitutive models are fit to the CP-FEM predictions of polycrystal yield stresses. The results produced by this model, based on kink-pair theory and with origins in dislocation mechanics, show excellent agreement with the Mechanical Threshold Stress (MTS) model for temperature and strain-rate dependent flow. This framework provides a method to bridge multiple length scales in modeling the deformation of BCC metals.

  17. Plastic Stress-strain Relations for 75S-T6 Aluminum Alloy Subjected to Biaxial Tensile Stresses

    NASA Technical Reports Server (NTRS)

    Marin, Joseph; Ulrich, B H; Hughes, W P

    1951-01-01

    In this investigation, the material tested was a 75S-T6 aluminum alloy and the stresses were essentially biaxial and tensile. The biaxial tensile stresses were produced in a specially designed testing machine by subjecting a thin-walled tubular specimen to axial tension and internal pressure. Plastic stress-strain relations for various biaxial stress conditions were obtained using a clip-type SR-4 strain gage. Three types of tests were made: Constant-stress-ratio tests, variable-stress-ratio tests, and special tests. The constant-stress-ratio test results gave control data and showed the influence of biaxial stresses on the yield, fracture, and ultimate strength of the material. By means of the variable-stress-ratio tests, it is possible to determine whether there is any significant difference between the flow and deformation type of theory. Finally, special tests were conducted to check specific assumptions made in the theories of plastic flow. The constant-stress-ratio tests show that the deformation theory based on the octahedral, effective; or significant stress-strain relations is in approximate agreement with the test results. The variable-stress-ratio tests show that both the deformation and flow theory are in equally good agreement with the test results.

  18. Phyllosphere yeasts rapidly break down biodegradable plastics.

    PubMed

    Kitamoto, Hiroko K; Shinozaki, Yukiko; Cao, Xiao-Hong; Morita, Tomotake; Konishi, Masaaki; Tago, Kanako; Kajiwara, Hideyuki; Koitabashi, Motoo; Yoshida, Shigenobu; Watanabe, Takashi; Sameshima-Yamashita, Yuka; Nakajima-Kambe, Toshiaki; Tsushima, Seiya

    2011-11-29

    The use of biodegradable plastics can reduce the accumulation of environmentally persistent plastic wastes. The rate of degradation of biodegradable plastics depends on environmental conditions and is highly variable. Techniques for achieving more consistent degradation are needed. However, only a few microorganisms involved in the degradation process have been isolated so far from the environment. Here, we show that Pseudozyma spp. yeasts, which are common in the phyllosphere and are easily isolated from plant surfaces, displayed strong degradation activity on films made from poly-butylene succinate or poly-butylene succinate-co-adipate. Strains of P. antarctica isolated from leaves and husks of paddy rice displayed strong degradation activity on these films at 30°C. The type strain, P. antarctica JCM 10317, and Pseudozyma spp. strains from phyllosphere secreted a biodegradable plastic-degrading enzyme with a molecular mass of about 22 kDa. Reliable source of biodegradable plastic-degrading microorganisms are now in our hands.

  19. Facilitated Leaching of Additive-Derived PBDEs from Plastic by Seabirds' Stomach Oil and Accumulation in Tissues.

    PubMed

    Tanaka, Kosuke; Takada, Hideshige; Yamashita, Rei; Mizukawa, Kaoruko; Fukuwaka, Masa-Aki; Watanuki, Yutaka

    2015-10-01

    Our previous study suggested the transfer of polybrominated diphenyl ether (PBDE) flame retardants from ingested plastics to seabirds' tissues. To understand how the PBDEs are transferred, we studied leaching from plastics into digestive fluids. We hypothesized that stomach oil, which is present in the digestive tract of birds in the order Procellariiformes, acts as an organic solvent, facilitating the leaching of hydrophobic chemicals. Pieces of plastic compounded with deca-BDE were soaked in several leaching solutions. Trace amounts were leached into distilled water, seawater, and acidic pepsin solution. In contrast, over 20 times as much material was leached into stomach oil, and over 50 times as much into fish oil (a major component of stomach oil). Analysis of abdominal adipose, liver tissue, and ingested plastics from 18 wild seabirds collected from the North Pacific Ocean showed the occurrence of deca-BDE or hexa-BDEs in both the tissues and the ingested plastics in three of the birds, suggesting transfer from the plastic to the tissues. In birds with BDE209 in their tissues, the dominance of BDE207 over other nona-BDE isomers suggested biological debromination at the meta position. Model calculation of PBDE exposure to birds based on the results of the leaching experiments combined with field observations suggested the dominance of plastic-mediated internal exposure to BDE209 over exposure via prey. PMID:26325685

  20. Facilitated Leaching of Additive-Derived PBDEs from Plastic by Seabirds' Stomach Oil and Accumulation in Tissues.

    PubMed

    Tanaka, Kosuke; Takada, Hideshige; Yamashita, Rei; Mizukawa, Kaoruko; Fukuwaka, Masa-Aki; Watanuki, Yutaka

    2015-10-01

    Our previous study suggested the transfer of polybrominated diphenyl ether (PBDE) flame retardants from ingested plastics to seabirds' tissues. To understand how the PBDEs are transferred, we studied leaching from plastics into digestive fluids. We hypothesized that stomach oil, which is present in the digestive tract of birds in the order Procellariiformes, acts as an organic solvent, facilitating the leaching of hydrophobic chemicals. Pieces of plastic compounded with deca-BDE were soaked in several leaching solutions. Trace amounts were leached into distilled water, seawater, and acidic pepsin solution. In contrast, over 20 times as much material was leached into stomach oil, and over 50 times as much into fish oil (a major component of stomach oil). Analysis of abdominal adipose, liver tissue, and ingested plastics from 18 wild seabirds collected from the North Pacific Ocean showed the occurrence of deca-BDE or hexa-BDEs in both the tissues and the ingested plastics in three of the birds, suggesting transfer from the plastic to the tissues. In birds with BDE209 in their tissues, the dominance of BDE207 over other nona-BDE isomers suggested biological debromination at the meta position. Model calculation of PBDE exposure to birds based on the results of the leaching experiments combined with field observations suggested the dominance of plastic-mediated internal exposure to BDE209 over exposure via prey.

  1. Critical Plastic Strain as a Criterion for Failure in Ballistic Impact Experiments of U/Ti and Ti64 Alloys

    NASA Astrophysics Data System (ADS)

    Herrmann, B.; Favorsky, V.; Zaretsky, E.; Shvarts, D.

    2006-07-01

    Strain localization and failure in U-0.75Ti and Ti-6Al-4V alloys were studied in symmetric (rod-on-rod) and reverse ballistic (disk-on-rod) impact experiments, accompanied by VISAR monitoring of the lateral sample surface velocity. Softly-recovered samples were metallurgically examined, and the experiments were numerically simulated using an AUTODYN™ 2-D code. Satisfactory reproduction of both the measured velocity profiles and the results of metallographic examination of the damage produced by adiabatic shearing were obtained by using the Steinberg-Cochran-Guinan-type constitutive equation (calibrated in preliminary planar impact experiments) and the AUTODYN™ built-in erosion function. A good agreement was found between strains, measured by using natural markers (martensite in U/Ti and texture in Ti64), corresponding to the onset of adiabatic shearing (0.5 - 1.0) and the value of the critical plastic strain used in the simulations as a criterion for triggering the erosion function (0.6 for both alloys). In the case of Ti64 the shearing is finalized by cracking at observed strain values of 1.0 - 1.5, whereas in the U/Ti the shear strain reaches values greater by at least one order of magnitude and is terminated by void growth and coalescence.

  2. Estimation of Material Parameters in Nonlinear Hardening Plasticity Models and Strain Life Curves for CuAg Alloy

    NASA Astrophysics Data System (ADS)

    Srnec Novak, J.; Benasciutti, D.; De Bona, F.; Stanojević, A.; De Luca, A.; Raffaglio, Y.

    2016-03-01

    This work investigates the cyclic response and low-cycle fatigue behaviour of a CuAg alloy used in crystallizer for continuous casting lines. Therefore isothermal strain-based fatigue tests are first performed on CuAg specimens at different temperature levels (20 °C, 250 °C, 300 °C). The evolution of stress-strain loops recorded during the cyclic tests is used for the parameter identification of several nonlinear hardening models (nonlinear kinematic, nonlinear isotropic). Cyclic stress-strain data from experiments are compared with results from numerical simulations with the identified material parameters, showing a satisfying agreement. Critical examination of numerical results from different models is also performed. Finally, the strain- life fatigue curves estimated from experimental data are compared with approximate strain-life equations (Universal Slopes Equation, 10% Rule) which are obtained from simple tensile tests. The material parameters determined in this work can conveniently be used as inputs in a elasto- plastic finite element simulations of a crystallizer.

  3. Influence of Roller Burnishing Parameters on Depletion of Plasticity Reserve

    NASA Astrophysics Data System (ADS)

    Blumenstein, V. Yu; Petrenko, K. P.

    2016-04-01

    Roller burnishing process considerably increases surface quality and service life of machine parts. Efficiency of roller burnishing rises greatly when technological inheritance (TI) is taken into account. Research results of degree of plasticity reserve depletion (DPRD) while roller burnishing are presented. Results obtained made it possible to establish mechanisms of strain accumulation and plasticity reserve depletion according to roller burnishing parameters.

  4. Identification of oleaginous yeast strains able to accumulate high intracellular lipids when cultivated in alkaline pretreated corn stover

    PubMed Central

    Sitepu, Irnayuli R.; Jin, Mingjie; Fernandez, J. Enrique; da Costa Sousa, Leonardo; Balan, Venkatesh; Boundy-Mills, Kyria L.

    2015-01-01

    Microbial oil is a potential alternative to food/plant-derived biodiesel fuel. Our previous screening studies identified a wide range of oleaginous yeast species, using a defined laboratory medium known to stimulate lipid accumulation. In this study, the ability of these yeasts to grow and accumulate lipids was further investigated in synthetic hydrolysate (SynH) and authentic ammonia fiber expansion (AFEX™)-pretreated corn stover hydrolysate (ACSH). Most yeast strains tested were able to accumulate lipids in SynH, but only a few were able to grow and accumulate lipids in ACSH medium. Cryptococcus humicola UCDFST 10-1004 was able to accumulate as high as 15.5 g/L lipids, out of a total of 36 g/L cellular biomass when grown in ACSH, with a cellular lipid content of 40% of cell dry weight. This lipid production is among the highest reported values for oleaginous yeasts grown in authentic hydrolysate. Pre-culturing in SynH media with xylose as sole carbon source enabled yeasts to assimilate both glucose and xylose more efficiently in the subsequent hydrolysate medium. This study demonstrates that ACSH is a suitable medium for certain oleaginous yeasts to convert lignocellullosic sugars to triacylglycerols for production of biodiesel and other valuable oleochemicals. PMID:25052467

  5. Identification of oleaginous yeast strains able to accumulate high intracellular lipids when cultivated in alkaline pretreated corn stover.

    PubMed

    Sitepu, Irnayuli R; Jin, Mingjie; Fernandez, J Enrique; da Costa Sousa, Leonardo; Balan, Venkatesh; Boundy-Mills, Kyria L

    2014-09-01

    Microbial oil is a potential alternative to food/plant-derived biodiesel fuel. Our previous screening studies identified a wide range of oleaginous yeast species, using a defined laboratory medium known to stimulate lipid accumulation. In this study, the ability of these yeasts to grow and accumulate lipids was further investigated in synthetic hydrolysate (SynH) and authentic ammonia fiber expansion (AFEX™)-pretreated corn stover hydrolysate (ACSH). Most yeast strains tested were able to accumulate lipids in SynH, but only a few were able to grow and accumulate lipids in ACSH medium. Cryptococcus humicola UCDFST 10-1004 was able to accumulate as high as 15.5 g/L lipids, out of a total of 36 g/L cellular biomass when grown in ACSH, with a cellular lipid content of 40 % of cell dry weight. This lipid production is among the highest reported values for oleaginous yeasts grown in authentic hydrolysate. Preculturing in SynH media with xylose as sole carbon source enabled yeasts to assimilate both glucose and xylose more efficiently in the subsequent hydrolysate medium. This study demonstrates that ACSH is a suitable medium for certain oleaginous yeasts to convert lignocellullosic sugars to triacylglycerols for production of biodiesel and other valuable oleochemicals.

  6. Accumulation of Amino Acids in Rhizobium sp. Strain WR1001 in Response to Sodium Chloride Salinity

    PubMed Central

    Hua, Sui-Sheng T.; Tsai, Victor Y.; Lichens, Georgia M.; Noma, Amy T.

    1982-01-01

    Rhizobium sp. strain WR1001, isolated from the Sonoran Desert by Eskew and Ting, was found to be able to grow in defined medium containing NaCl up to 500 mM, a concentration approaching that of sea water. Therefore, it is a valuable strain for studying the biochemical basis of salt tolerance. Intracellular free glutamate was found to increase rapidly in response to osmotic stress by NaCl. It accounted for 88% of the amino acid pool when the bacterium was grown in 500 mM NaCl. The role of glutamate dehydrogenase in glutamate biosynthesis was examined in several Rhizobium strains. Both NADH- and NADPH-dependent glutamate dehydrogenase activities in various Rhizobium strains were observed. The range of activity differed considerably depending on the particular strain. KCl (500 mM) did not stimulate glutamate dehydrogenase activity, as reported in a number of bacterial strains by Measures. The low activity of glutamate dehydrogenase in Rhizobium sp. strain WR1001 apparently cannot fulfill a biosynthetic function of glutamate formation in response to medium NaCl concentrations. PMID:16346049

  7. The theory of plasticity in the case of simple loading accompanied by strain-hardening

    NASA Technical Reports Server (NTRS)

    Ilyushin, A A

    1949-01-01

    The author has previously shown that a deformation theory of plasticity is entirely adequate when the loading is simple; that is, when all the applied forces grow in proportion to a single parameter. The author now shows how a general plasticitytheory for any complex loading may be constructed by successively adding quantities of the nature of correction terms to the deformation theory. All of the theories of plasticity so far suggested for the complex loading condition are shown to be special cases of this general theory.

  8. Modeling anisotropic plasticity: Eulerian hydrocode applications of high strain-rate deformation processes

    SciTech Connect

    Clancy, S.P.; Burkett, M.W.; Maudlin, P.J.

    1998-02-01

    Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength are implemented in the two dimensional MESA hydrodynamics code. Quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure are utilized. An associative flow strength formulation incorporating these yield functions is solved using a geometric normal return method. A stretching rod problem is selected to investigate the effects of material anisotropy on a tensile plastic instability (necking). The rod necking rate and topology are compared for MESA simulations performed for both isotropic and anisotropic cases utilizing the elastic-perfectly-plastic and the Mechanical Threshold Stress flow stress models.

  9. Inter-Rifting and Inter-Seismic Strain Accumulation in a Propagating Ridge System: A Geodetic Study from South Iceland

    NASA Astrophysics Data System (ADS)

    Travis, M. E.; La Femina, P. C.; Geirsson, H.

    2012-12-01

    The Mid-Atlantic Ridge, a slow spreading (~19 mm/yr) mid-ocean ridge boundary between the North American and Eurasian plates, is exposed subaerially in Iceland as the result of ridge-hotspot interaction. Plate spreading in Iceland is accommodated along neovolcanic zones comprised of central volcanoes and their fissure swarms. In south Iceland plate motion is partitioned between the Western Volcanic Zone (WVZ) and Eastern Volcanic Zone (EVZ). The EVZ is propagating to the southwest, while the WVZ is dying out from the northeast. Plate motion across both systems has been accommodated by repeated rifting events and fissure eruptions. In this study we investigate whether the WVZ is active and accumulating strain, and how strain is partitioned between the WVZ and EVZ. We also test how strain is accumulating along fissure swarms within the EVZ (i.e. is strain accumulation localized to one fissure swarm, or are multiple systems active?). We use GPS data and elastic block models run using the program DEFNODE to investigate these issues. GPS data are processed using the GIPSY-OASIS II software, and have been truncated to the 2000.5-2011 time period to avoid co-seismic displacement from the two June 2000 South Iceland Seismic Zone earthquakes. We also truncate the time series for sites within 20 km of Eyjafjallajökull to the beginning of 2010 to eliminate deformation associated with the March 2010 eruption of that volcano. We correct for co-seismic displacement from the two May 2008 SISZ earthquakes, inflation at Hekla volcano and the horizontal component of glacial isostatic rebound (GIA). Our best-fit model for inter-rifting and inter-seismic elastic strain accumulation suggests 80-90% of spreading is accommodated in the EVZ with the other 10-20% accommodated by the WVZ. The best-fit location of the EVZ is between Veidivotn and Lakigigar in an area of no Holocene volcanic activity. We suggest the WVZ is only active at Hengill and its associated fissure swarm. Geologic and

  10. Strain accumulation and fluid-rock interaction in a naturally deformed diamictite, Willard thrust system, Utah (USA): Implications for crustal rheology and strain softening

    NASA Astrophysics Data System (ADS)

    Yonkee, W. Adolph; Czeck, Dyanna M.; Nachbor, Amelia C.; Barszewski, Christine; Pantone, Spenser; Balgord, Elizabeth A.; Johnson, Kimberly R.

    2013-05-01

    Structural and geochemical patterns of heterogeneously deformed diamictite in northern Utah (USA) record interrelations between strain accumulation, fluid-rock interaction, and softening processes across a major fault (Willard thrust). Different clast types in the diamictite have varying shape fabrics related to competence contrasts with estimated effective viscosity ratios relative to micaceous matrix of: ˜6 and 8 for large quartzite clasts respectively in the Willard hanging wall and footwall; ˜5 and 2 for less altered and more altered granitic clasts respectively in the hanging wall and footwall; and ˜1 for micaceous clasts that approximate matrix strain. Within the footwall, matrix X-Z strain ratios increase from ˜2 to 8 westward along a distinct deformation gradient. Microstructures record widespread mass transfer, alteration of feldspar to mica, and dislocation creep of quartz within matrix and clasts. Fluid influx along microcracks and mesoscopic vein networks increased westward and led to reaction softening and hydrolytic weakening, in conjunction with textural softening from alignment of muscovite aggregates. Consistent Si, Al, and Ti concentrations between matrix, granitic clasts, and protoliths indicate limited volume change. Mg gain and Na loss reflect alteration of feldspar to phengitic muscovite. Within the hanging wall, strain is overall lower with matrix X-Z strain ratios of ˜2 to 4. Microstructures record mass transfer and dislocation creep concentrated in the matrix. Greater Al and Ti concentrations and lower Si concentrations in matrix indicate volume loss by quartz dissolution. Na gain in granitic clasts reflects albitization. Large granitic clasts have less mica alteration and greater competence compared to smaller clasts. Differences in strain and alteration patterns across the Willard thrust fault suggest overall downward (up-temperature) fluid flow in the hanging wall and upward (down-temperature) fluid flow in the footwall.

  11. Slip-rates along the Chaman fault: Implication for transient strain accumulation and strain partitioning along the western Indian plate margin

    NASA Astrophysics Data System (ADS)

    Ul-Hadi, Shams; Khan, Shuhab D.; Owen, Lewis A.; Khan, Abdul S.; Hedrick, Kathryn A.; Caffee, Marc W.

    2013-11-01

    The Chaman fault in Western Pakistan marks the western collision boundary between the Indian and Eurasian plates and connects the Makran subduction zone to the Himalayan convergence zone. Geomorphic-scale slip-rates along an active strand of the Chaman fault are added to the sporadic data set of this poorly investigated transform system. Field investigations coupled with high-resolution GeoEye-1 satellite data of an alluvial fan surface (Bostankaul alluvial fan) show ~ 1150 m left-lateral offset by the fault since the formation of the alluvial fan surface. A weighted mean 10Be exposure age of 34.8 ± 3 kyr for the Bostankaul alluvial surface yields a slip-rate of 33.3 ± 3.0 mm/yr. This rate agrees with the geologically defined slip-rates along the Chaman fault, but is approximately twice as large as that inferred from the decade-long global positioning system measurements of 18 ± 1 mm/yr. The contrast in geomorphic and geodetic slip-rates along the Chaman fault, like other major intra-continental strike-slip faults, has two major implications: 1) the geodetic rates might represent a period of reduced displacement as compared to the averaged Late Pleistocene rate because of transient variations in rates of elastic strain accumulation; or 2) strain partitioning within the plate boundary zone. While strain partitioning could be the reason of slip-rate variations within the western Indian plate boundary zone, transient strain accumulation could explain contrasting slip-rates along the Chaman fault at this stage in its poorly understood seismic cycle.

  12. An analytical elastic plastic contact model with strain hardening and frictional effects for normal and oblique impacts

    SciTech Connect

    Brake, M. R. W.

    2015-02-17

    Impact between metallic surfaces is a phenomenon that is ubiquitous in the design and analysis of mechanical systems. We found that to model this phenomenon, a new formulation for frictional elastic–plastic contact between two surfaces is developed. The formulation is developed to consider both frictional, oblique contact (of which normal, frictionless contact is a limiting case) and strain hardening effects. The constitutive model for normal contact is developed as two contiguous loading domains: the elastic regime and a transitionary region in which the plastic response of the materials develops and the elastic response abates. For unloading, the constitutive model is based on an elastic process. Moreover, the normal contact model is assumed to only couple one-way with the frictional/tangential contact model, which results in the normal contact model being independent of the frictional effects. Frictional, tangential contact is modeled using a microslip model that is developed to consider the pressure distribution that develops from the elastic–plastic normal contact. This model is validated through comparisons with experimental results reported in the literature, and is demonstrated to be significantly more accurate than 10 other normal contact models and three other tangential contact models found in the literature.

  13. An analytical elastic plastic contact model with strain hardening and frictional effects for normal and oblique impacts

    DOE PAGES

    Brake, M. R. W.

    2015-02-17

    Impact between metallic surfaces is a phenomenon that is ubiquitous in the design and analysis of mechanical systems. We found that to model this phenomenon, a new formulation for frictional elastic–plastic contact between two surfaces is developed. The formulation is developed to consider both frictional, oblique contact (of which normal, frictionless contact is a limiting case) and strain hardening effects. The constitutive model for normal contact is developed as two contiguous loading domains: the elastic regime and a transitionary region in which the plastic response of the materials develops and the elastic response abates. For unloading, the constitutive model ismore » based on an elastic process. Moreover, the normal contact model is assumed to only couple one-way with the frictional/tangential contact model, which results in the normal contact model being independent of the frictional effects. Frictional, tangential contact is modeled using a microslip model that is developed to consider the pressure distribution that develops from the elastic–plastic normal contact. This model is validated through comparisons with experimental results reported in the literature, and is demonstrated to be significantly more accurate than 10 other normal contact models and three other tangential contact models found in the literature.« less

  14. Some new extensions to multi-mechanism models for plastic and viscoplastic material behavior under small strains

    NASA Astrophysics Data System (ADS)

    Wolff, Michael; Bökenheide, Simone; Böhm, Michael

    2016-05-01

    Multi-mechanism models (MM models) have become an important tool for modeling complex material behavior. In particular, two-mechanism models are used. They are applied to model ratcheting in metal plasticity as well as steel behavior during phase transformations. We consider a small-deformation setting. The characteristic trait of multi-mechanism models is the additive decomposition of the inelastic (e.g., plastic or viscoplastic) strain into several parts. These parts are sometimes called mechanisms. In comparison with rheological models, the mechanisms can interact with each other. This leads to new properties and allows to describe important observable effects. Up to now, each mechanism has one kinematic internal variable. As a new feature, we develop multi-mechanism models (in series) with several kinematic variables for each mechanism as well as with several isotropic variables for each flow criterion. We describe this complex situation by three structural matrices which express the mutual relations between mechanisms, flow criteria, kinematic, and isotropic variables. The well-known Chaboche model with a unique inelastic strain and several kinematic variables represents a special case of these general multi-mechanism models. In this work, we also present a matrix-based approach for these new complex MM models. The presented models can form the basis for developing numerical algorithms for simulation and parameter identification.

  15. Poles Apart: Arctic and Antarctic Octadecabacter strains Share High Genome Plasticity and a New Type of Xanthorhodopsin

    PubMed Central

    Vollmers, John; Voget, Sonja; Dietrich, Sascha; Gollnow, Kathleen; Smits, Maike; Meyer, Katja; Brinkhoff, Thorsten; Simon, Meinhard; Daniel, Rolf

    2013-01-01

    The genus Octadecabacter is a member of the ubiquitous marine Roseobacter clade. The two described species of this genus, Octadecabacter arcticus and Octadecabacter antarcticus, are psychrophilic and display a bipolar distribution. Here we provide the manually annotated and finished genome sequences of the type strains O. arcticus 238 and O. antarcticus 307, isolated from sea ice of the Arctic and Antarctic, respectively. Both genomes exhibit a high genome plasticity caused by an unusually high density and diversity of transposable elements. This could explain the discrepancy between the low genome synteny and high 16S rRNA gene sequence similarity between both strains. Numerous characteristic features were identified in the Octadecabacter genomes, which show indications of horizontal gene transfer and may represent specific adaptations to the habitats of the strains. These include a gene cluster encoding the synthesis and degradation of cyanophycin in O. arcticus 238, which is absent in O. antarcticus 307 and unique among the Roseobacter clade. Furthermore, genes representing a new subgroup of xanthorhodopsins as an adaptation to icy environments are present in both Octadecabacter strains. This new xanthorhodopsin subgroup differs from the previously characterized xanthorhodopsins of Salinibacter ruber and Gloeobacter violaceus in phylogeny, biogeography and the potential to bind 4-keto-carotenoids. Biochemical characterization of the Octadecabacter xanthorhodopsins revealed that they function as light-driven proton pumps. PMID:23671678

  16. Poles apart: Arctic and Antarctic Octadecabacter strains share high genome plasticity and a new type of xanthorhodopsin.

    PubMed

    Vollmers, John; Voget, Sonja; Dietrich, Sascha; Gollnow, Kathleen; Smits, Maike; Meyer, Katja; Brinkhoff, Thorsten; Simon, Meinhard; Daniel, Rolf

    2013-01-01

    The genus Octadecabacter is a member of the ubiquitous marine Roseobacter clade. The two described species of this genus, Octadecabacter arcticus and Octadecabacter antarcticus, are psychrophilic and display a bipolar distribution. Here we provide the manually annotated and finished genome sequences of the type strains O. arcticus 238 and O. antarcticus 307, isolated from sea ice of the Arctic and Antarctic, respectively. Both genomes exhibit a high genome plasticity caused by an unusually high density and diversity of transposable elements. This could explain the discrepancy between the low genome synteny and high 16S rRNA gene sequence similarity between both strains. Numerous characteristic features were identified in the Octadecabacter genomes, which show indications of horizontal gene transfer and may represent specific adaptations to the habitats of the strains. These include a gene cluster encoding the synthesis and degradation of cyanophycin in O. arcticus 238, which is absent in O. antarcticus 307 and unique among the Roseobacter clade. Furthermore, genes representing a new subgroup of xanthorhodopsins as an adaptation to icy environments are present in both Octadecabacter strains. This new xanthorhodopsin subgroup differs from the previously characterized xanthorhodopsins of Salinibacter ruber and Gloeobacter violaceus in phylogeny, biogeography and the potential to bind 4-keto-carotenoids. Biochemical characterization of the Octadecabacter xanthorhodopsins revealed that they function as light-driven proton pumps. PMID:23671678

  17. [Coupling effects of partitioning alternative drip irrigation with plastic mulch and nitrogen fertilization on cotton dry matter accumulation and nitrogen use].

    PubMed

    Li, Pei-Ling; Zhang, Fu-Cang

    2013-02-01

    A field experiment with complete combination design was conducted to study the effects of partitioning alternative drip irrigation with plastic mulch and nitrogen fertilization on the dry matter accumulation and nitrogen use efficiency of cotton plant. Three levels of irrigation (260, 200, and 140 mm) and of nitrogen fertilizer (270, 180, and 90 kg.hm-2) were installed. The cotton dry mass was the highest in treatments medium nitrogen/high water and high nitrogen/high water. As compared with that in high nitrogen/high water treatment, the nitrogen use efficiency for dry matter accumulation in medium nitrogen/high water treatment was increased by 34.0% -44.6%, with an average of 34.7% , while the water use efficiency was decreased by 6.4% -10.7%, averagely 10.2%. As for the nitrogen accumulation in cotton plant, the nitrogen use efficiency was the highest in medium nitrogen/high water treatment, and the water use efficiency was the highest in high nitrogen/medium water treatment. Compared with high nitrogen/high water treatment, medium nitrogen/high water treatment increased the nitrogen use efficiency for cotton nitrogen accumulation by 29.0% -41.7%, but decreased the water use efficiency for cotton nitrogen accumulation by 5.5%-14.0%. Among the treatments of coupling water and nitrogen of higher cotton yield, treatment medium nitrogen/high water had the higher cotton nitrogen recovery rate, nitrogen agronomic efficiency, and apparent use efficiency than the treatments high nitrogen/medium water and high nitrogen/high water, but no significant differences were observed in the nitrogen absorption ratio and nitrogen physiological efficiency. Treatment medium nitrogen/high water was most beneficial to the coupling effects of water and nitrogen under partitioning alternate drip irrigation with plastic mulch and nitrogen fertilization.

  18. Observations of strain accumulation across the San Andreas fault near Palmdale, California, with a two-color geodimeter

    USGS Publications Warehouse

    Langbein, J.O.; Linker, M.F.; McGarr, A.; Slater, L.E.

    1982-01-01

    Two-color laser ranging measurements during a 15-month period over a geodetic network spanning the San Andreas fault near Palmdale, California, indicate that the crust expands and contracts aseismically in episodes as short as 2 weeks. Shear strain parallel to the fault has accumulated monotonically since November 1980, but at a variable rate. Improvements in measurement precision and temporal resolution over those of previous geodetic studies near Palmdale have resulted in the definition of a time history of crustal deformation that is much more complex than formerly realized. Copyright ?? 1982 AAAS.

  19. Cesium accumulation of Rhodococcus erythropolis CS98 strain immobilized in hydrogel matrices.

    PubMed

    Takei, Takayuki; Yamasaki, Mika; Yoshida, Masahiro

    2014-04-01

    Agarose gels were superior to calcium-alginate gels for immobilizing Rhodococcus erythropolis CS98 strain to remove cesium from water. Suitable incubation time of the immobilized cells in cesium solutions, cell number in the gels and volume ratio of the cesium solution to the gels for efficient cesium removal were identified.

  20. Selection of microalgae for high CO2 fixation efficiency and lipid accumulation from ten Chlorella strains using municipal wastewater.

    PubMed

    Hu, Xia; Zhou, Jiti; Liu, Guangfei; Gui, Bing

    2016-08-01

    As significant differences in cellular physiology, metabolic potential and genetics occur among strains with morphological similarity, the screening of appropriate microalgae species for effective CO2 fixation and biodiesel production is extremely critical. In this study, ten strains of Chlorella were cultivated in municipal wastewater influent (MWI) and their tolerance for MWI, CO2 fixation efficiency and lipid productivity were assessed. The results showed that the biomass concentrations of four strains (Chlorella vulgaris, Chlorella 64.01, Chlorella regularis var. minima and Chlorella sp.) were significantly higher than other strains. When the cultivation systems were aerated with 10% CO2, Chlorella sp. showed the highest CO2 fixation efficiency (35.51%), while the highest lipid accumulation (58.48%) was observed with C. vulgaris. Scanning electron microscopy images revealed that the cells of both Chlorella sp. and C. vulgaris kept their normal morphologies after 15day batch culture. These findings indicated that Chlorella sp. and C. vulgaris have fairly good tolerance for MWI, and moreover, Chlorella sp. was appropriate for CO2 fixation while C. vulgaris represented the highest potential for producing biodiesel.

  1. Selection of microalgae for high CO2 fixation efficiency and lipid accumulation from ten Chlorella strains using municipal wastewater.

    PubMed

    Hu, Xia; Zhou, Jiti; Liu, Guangfei; Gui, Bing

    2016-08-01

    As significant differences in cellular physiology, metabolic potential and genetics occur among strains with morphological similarity, the screening of appropriate microalgae species for effective CO2 fixation and biodiesel production is extremely critical. In this study, ten strains of Chlorella were cultivated in municipal wastewater influent (MWI) and their tolerance for MWI, CO2 fixation efficiency and lipid productivity were assessed. The results showed that the biomass concentrations of four strains (Chlorella vulgaris, Chlorella 64.01, Chlorella regularis var. minima and Chlorella sp.) were significantly higher than other strains. When the cultivation systems were aerated with 10% CO2, Chlorella sp. showed the highest CO2 fixation efficiency (35.51%), while the highest lipid accumulation (58.48%) was observed with C. vulgaris. Scanning electron microscopy images revealed that the cells of both Chlorella sp. and C. vulgaris kept their normal morphologies after 15day batch culture. These findings indicated that Chlorella sp. and C. vulgaris have fairly good tolerance for MWI, and moreover, Chlorella sp. was appropriate for CO2 fixation while C. vulgaris represented the highest potential for producing biodiesel. PMID:27521939

  2. Comparative analysis of inelastic strain recovery and plastic deformation in a Ti49.1Ni50.9 (at %) alloy under torsion and bending

    NASA Astrophysics Data System (ADS)

    Grishkov, V. N.; Lotkov, A. I.; Baturin, A. A.; Timkin, V. N.; Zhapova, D. Yu.

    2015-10-01

    The paper reports on an experimental study of inelastic strain recovery, due to superelasticity and shape-memory effects, and plastic deformation under torsion and bending in a binary TiNi alloy containing 50.9 at % of Ni. It is found that the material under torsion and bending displays an anomalously high superelasticity of 16.4% and 13.5% and total recovery strain of 24.6% and 16.4% which exceed the theoretical limit of recoverable strain equal to 10.3% in the alloy involved in a cubic B2 to monoclinic B19' phase transformation. The correlation between the high recovery strains and the intensity and mechanisms of plastic deformation with increasing total strain is discussed.

  3. Factors affecting accumulation and degradation of curdlan, trehalose and glycogen in cultures of Cellulomonas flavigena strain KU (ATCC 53703).

    PubMed

    Siriwardana, Lakmal S; Gall, Aaron R; Buller, Clarence S; Esch, Steven W; Kenyon, William J

    2011-03-01

    Cellulomonas flavigena strain KU (ATCC 53703) is a cellulolytic, Gram-positive bacterium which produces large quantities of an insoluble exopolysaccharide (EPS) when grown in minimal media with a high carbon-to-nitrogen (C/N) ratio. Earlier studies proved the EPS is structurally identical to the linear β-1,3-glucan known as curdlan and provided evidence that the EPS functions as a carbon and energy reserve compound. We now report that C. flavigena KU also accumulates two intracellular, glucose-storage carbohydrates under conditions of carbon and energy excess. These carbohydrates were partially purified and identified as the disaccharide trehalose and a glycogen/amylopectin-type polysaccharide. A novel method is described for the sequential fractionation and quantitative determination of all three carbohydrates from culture samples. This fractionation protocol was used to examine the effects of C/N ratio and osmolarity on the accumulation of cellular carbohydrates in batch culture. Increasing the C/N of the growth medium caused a significant accumulation of curdlan and glycogen but had a relatively minor effect on accumulation of trehalose. In contrast, trehalose levels increased in response to increasing osmolarity, while curdlan levels declined and glycogen levels were generally unaffected. During starvation for an exogenous source of carbon and energy, only curdlan and glycogen showed substantial degradation within the first 24 h. These results support the conclusion that extracellular curdlan and intracellular glycogen can both serve as short-term reserve compounds for C. flavigena KU and that trehalose appears to accumulate as a compatible solute in response to osmotic stress.

  4. Inhibition of chlamydiae by primary alcohols correlates with the strain-specific complement of plasticity zone phospholipase D genes.

    PubMed

    Nelson, David E; Crane, Deborah D; Taylor, Lacey D; Dorward, David W; Goheen, Morgan M; Caldwell, Harlan D

    2006-01-01

    Members of the genus Chlamydia are obligate intracellular pathogens that have a unique biphasic developmental cycle and interactions with host cells. Many genes that dictate host infection tropism and, putatively, pathogenic manifestations of disease are clustered in a hypervariable region of the genome termed the plasticity zone (PZ). Comparative genomics studies have determined that an uncharacterized family of PZ genes encoding orthologs of eukaryotic and prokaryotic members of the phospholipase D (PLD) enzyme family varies among chlamydiae. Here, we show that the PZ PLD (pzPLD) of Chlamydia trachomatis are transcribed during both normal and persistent infection and that the corresponding PLD proteins are predominantly localized in reticulate bodies on the inner leaflet of the inclusion membrane. Further, we show that strains of chlamydiae encoding the pzPLD, but not a strain lacking these genes, are inhibited by primary alcohols, potent PLD inhibitors, during growth in HeLa 229 cells. This inhibitory effect is amplified approximately 5,000-fold during recovery from persistent infection. These findings suggest that the chlamydial pzPLD may be important, strain-specific, pathogenesis factors in vivo.

  5. The stress-strain relationships in wood and fiber-reinforced plastic laminae of reinforced glued-laminated wood beams

    NASA Astrophysics Data System (ADS)

    Tingley, Daniel Arthur

    The reinforcement of wood and wood composite structural products to improve their mechanical properties has been in practice for many years. Recently, the use of high-strength fiber-reinforced plastic (FRP) as a reinforcement in such applications has been commercialized. The reinforcement is manufactured using a standard pultrusion process or alternatively a sheet-forming process commonly referred to as "pulforming". The high-modulus fibers are predominately unidirectional, although off-axis fibers are often used to enhance off-axis properties. The fibers used are either of a single type or multiple types, which are called "hybrids". Unidirectional, single, and hybrid fiber FRP physical properties and characteristics were compared to wood. Full-scale reinforced glulams were tested. Aramid-reinforced plastics (ARP) used as tensile reinforcements were found to be superior in strength applications to other types of FRP made with fiber, such as carbon and fiberglass. Carbon/aramid-reinforced plastic (CARP) was shown to be superior in both modulus and strength design situations. Fiberglass was shown to be suitable only in hybrid situations with another fiber such as aramid or carbon and only in limited use situations where modulus was a design criteria. The testing and analysis showed that the global response of reinforced glulam beams is controlled by localized strength variations in the wood such as slope of grain, knots, finger joints, etc. in the tensile zone. The elemental tensile strains in the extreme wood tensile laminae, due to global applied loads, were found to be well below the strain at failure in clear wood samples recovered from the failure area. Two areas affecting the relationship between the wood and the FRP were investigated: compatibility of the wood and FRP materials and interface characteristics between the wood and FRP. The optimum strain value at yield point for an FRP was assessed to be slightly higher than the clear wood value in tension for a

  6. Radiation-induced pulmonary endothelial dysfunction and hydroxyproline accumulation in four strains of mice

    SciTech Connect

    Ward, W.F.; Sharplin, J.; Franko, A.J.; Hinz, J.M. )

    1989-10-01

    C57BL mice exposed to 14 Gy of whole-thorax irradiation develop significant histologic lung fibrosis within 52 weeks, whereas CBA and C3H mice do not exhibit substantial fibrosis during this time. The purpose of the present study was to determine whether this strain-dependent difference in radiation histopathology is associated with genetic differences in pulmonary endothelial metabolic activity or in endothelial radioresponsiveness. C57BL/6J, C57BL/10J, CBA/J, and C3H/HeJ mice were sacrificed 12 weeks after exposure to 0 or 14 Gy of 300-kV X rays to the whole thorax. Lung angiotensin converting enzyme (ACE) activity and plasminogen activator (PLA) activity were measured as indices of pulmonary endothelial function; and lung hydroxyproline (HP) content served as an index of pulmonary fibrosis. Lung ACE and PLA activities in sham-irradiated C57BL/6J and CB57BL/10J mice were only half as high as those in sham-irradiated CBA/J and C3H/HeJ mice. Exposure to 14 Gy of X rays produced a slight but nonsignificant reduction in lung ACE and PLA activity in the C57BL strains, and a significant reduction in the CBA/J and C3H/HeJ mice. Even after 14 Gy, however, lung ACE and PLA activities in CBA/J and C3H/HeJ mice were higher than those in sham-irradiated C57BL/6J and C57BL/10J mice. Lung HP content in all four strains increased significantly after irradiation, but this increase was accompanied by an increase in lung wet weight. As a result, HP concentration (per milligram wet weight) remained constant or increased slightly in both C57BL strains and actually decreased in the CBA/J and C3H/HeJ mice. These data demonstrate significant genetic differences in both intrinsic pulmonary endothelial enzyme activity and endothelial radioresponsiveness among the four strains of mice.

  7. The Effect of transient change in strain rate on plastic flow behaviour of Al-Mg-Si alloy at elevated temperatures

    SciTech Connect

    Petrov, P.; Voronkov, V.; Potapenko, K.; Ivanov, V.

    2011-05-04

    In extrusion forging processes, the abrupt changes in strain rate follows the plastic deformation of a material within the deforming zone. To simulate accurately this effect, the specific experimental investigation of the plastic flow during the transient change in strain rate should be performed. The present paper deals with the investigation of this effect on the flow stress of an Al-Mg-Si alloy during its deformation at 350 deg. C. The investigation consists of two steps. Both steps are connected to the monotonic uniaxial compression loading of a cylindrical specimen. During the first step the flow behaviour of the alloy is investigated at the constant strain rate wihin the range of 0.1-50 s{sup -1} at the temperature range of 350-430 deg. C. During the second step the strain rate is abruptly increased or decreased from its current value at a fixed engineering strain of 17-21%. From the beginning of the test up to the strain of 17-21% the value of the strain rate is constant and equal to either 1 s{sup -1} or 10 s{sup -1}. At the strain of 17-21% the value of a strain rate is either increased to 10 s{sup -1} or decreased to 1 s{sup -1}.The results of the experimental investigations were used to determine the isothermal flow stress-strain curves of the Al-Mg-Si alloy as well as the heat effect of plastic deformation of the alloy. On basis of these curves, the strain rate sensitivity index m as a function of true strain and temperature was determined. This parameter allows to optimize a technological process of hot forging of the aluminium alloy as well as it is very important data for the construction of a phenomenological flow stress model.

  8. Dislocation microstructures and strain-gradient plasticity with one active slip plane

    NASA Astrophysics Data System (ADS)

    Conti, Sergio; Garroni, Adriana; Müller, Stefan

    2016-08-01

    We study dislocation networks in the plane using the vectorial phase-field model introduced by Ortiz and coworkers, in the limit of small lattice spacing. We show that, in a scaling regime where the total length of the dislocations is large, the phase field model reduces to a simpler model of the strain-gradient type. The limiting model contains a term describing the three-dimensional elastic energy and a strain-gradient term describing the energy of the geometrically necessary dislocations, characterized by the tangential gradient of the slip. The energy density appearing in the strain-gradient term is determined by the solution of a cell problem, which depends on the line tension energy of dislocations. In the case of cubic crystals with isotropic elasticity our model shows that complex microstructures may form in which dislocations with different Burgers vector and orientation react with each other to reduce the total self-energy.

  9. Modeling anisotropic plasticity: Eulerian hydrocode applications of high strain-rate deformation processes

    SciTech Connect

    Clancy, S.P.; Burkett, M.W.; Maudlin, P.J.

    1997-05-01

    Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength are implemented in the two-dimensional MESA hydrodynamics code. Quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure are utilized. An associative flow strength formulation incorporating these yield functions is solved using a geometric normal return method. A stretching rod problem is selected to investigate the effects of material anisotropy on a tensile plastic instability (necking). The rod necking rate and topology are compared for MESA simulations performed for both isotropic and anisotropic cases utilizing the Mechanical Threshold Stress flow stress model.

  10. Bulk Nanolayered Composites: Interfacial Influence on Microstructural Evolution at Large Plastic Strains

    SciTech Connect

    Mara, Nathan A.; Carpenter, John S.; Han, Weizhong; Zheng, Shijian; McCabe, Rodney J.; Wang, Jian; Beyerlein, Irene J.

    2012-07-31

    Conclusions are: (1) As-processed ARB material has similar morphology, chemistry as PVD, but different interfacial structure; (2) Density of interfaces AND interfacial structure play a role in determining hardness, an example is twinning in Cu at the {l_brace}112{r_brace}Cu//{l_brace}112{r_brace}Nb interface and higher strength, no twinning in Cu in the {l_brace}111{r_brace}Cu//{l_brace}110{r_brace}Nb interface; and (3) Need to understand effects of processing history to predict the effects on the interfaces we produce - Amount of strain, Strain Path, Annealing.

  11. Interseismic Strain Accumulation at the Northern Costa Rica Seismogenic Zone From Integration of InSAR and GPS

    NASA Astrophysics Data System (ADS)

    Schwartz, S. Y.; Xue, L.

    2012-12-01

    The presence of the Nicoya Peninsula directly above the seismogenic zone in northern Costa Rica has allowed detailed studies of its seismic and aseismic behavior. This segment of the Middle American Trench generates large earthquakes about every 50 years with the last event occurring in 1950. Abundant seismicity, multiple episodes of slow slip and tremor and years of surface deformation have been recorded here between 2000 and 2011, since the first GPS and seismic instruments were installed. Several models of interseismic strain accumulation have been produced using the GPS data. These models reveal different patterns of locking and variations in locking magnitude that range between 50% to 100% of the plate convergence rate. The GPS data provide excellent temporal coverage but relatively sparse spatial coverage and poor quality vertical measurements of ground deformation. To improve on this, we combine InSAR and GPS observations to produce the first interseismic deformation estimates obtained by InSAR at a subduction zone. We use 18 ALOS SAR acquisitions between 2007 and 2011 covering the Nicoya Peninsula and ROI_PAC software to construct 120 interferograms with perpendicular baselines under 1200m. GPS data are used to correct for orbital errors and corrected interferograms are stacked to produce a deformation rate map that strongly resembles a synthetic interferogram constructed using a GPS based interseismic deformation model. To detect accumulated interseismic deformation over a longer time period we use the small baseline subset (SBAS) method to construct InSAR time series. The resulting linear rate map agrees very well with the GPS measurements along two profiles perpendicular to the coast where GPS observations are the densest. Maximum displacements reach ~10-15 mm/yr near the coastline. Future work will integrate these results with GPS observations to obtain a high-resolution strain accumulation model for the Nicoya Peninsula.

  12. Full-Field Strain Measurement On Titanium Welds And Local Elasto-Plastic Identification With The Virtual Fields Method

    SciTech Connect

    Tattoli, F.; Casavola, C.; Pierron, F.; Rotinat, R.; Pappalettere, C.

    2011-01-17

    One of the main problems in welding is the microstructural transformation within the area affected by the thermal history. The resulting heterogeneous microstructure within the weld nugget and the heat affected zones is often associated with changes in local material properties. The present work deals with the identification of material parameters governing the elasto--plastic behaviour of the fused and heat affected zones as well as the base material for titanium hybrid welded joints (Ti6Al4V alloy). The material parameters are identified from heterogeneous strain fields with the Virtual Fields Method. This method is based on a relevant use of the principle of virtual work and it has been shown to be useful and much less time consuming than classical finite element model updating approaches applied to similar problems. The paper will present results and discuss the problem of selection of the weld zones for the identification.

  13. Dual-phase steel sheets under cyclic tension–compression to large strains: Experiments and crystal plasticity modeling

    NASA Astrophysics Data System (ADS)

    Zecevic, Milovan; Korkolis, Yannis P.; Kuwabara, Toshihiko; Knezevic, Marko

    2016-11-01

    In this work, we develop a physically-based crystal plasticity model for the prediction of cyclic tension-compression deformation of multi-phase materials, specifically dual-phase (DP) steels. The model is elasto-plastic in nature and integrates a hardening law based on statistically stored dislocation density, localized hardening due to geometrically necessary dislocations (GNDs), slip-system-level kinematic backstresses, and annihilation of dislocations. The model further features a two level homogenization scheme where the first level is the overall response of a two-phase polycrystalline aggregate and the second level is the homogenized response of the martensite polycrystalline regions. The model is applied to simulate a cyclic tension-compression-tension deformation behavior of DP590 steel sheets. From experiments, we observe that the material exhibits a typical decreasing hardening rate during forward loading, followed by a linear and then a non-linear unloading upon the load reversal, the Bauschinger effect, and changes in hardening rate during strain reversals. To predict these effects, we identify the model parameters using a portion of the measured data and validate and verify them using the remaining data. The developed model is capable of predicting all the particular features of the cyclic deformation of DP590 steel, with great accuracy. From the predictions, we infer and discuss the effects of GNDs, the backstresses, dislocation annihilation, and the two-level homogenization scheme on capturing the cyclic deformation behavior of the material.

  14. Stimulation of pigment accumulation in Anabaena azollae strains: effect of light intensity and sugars.

    PubMed

    Venugopal, V; Prasanna, R; Sood, A; Jaiswal, P; Kaushik, B D

    2006-01-01

    The influence of high light intensity on the growth and pigment accumulating ability of Anabaena azollae was investigated. A. azollae responded positively to high light intensity (6 klx) and was further evaluated at higher intensities (10 and 15 klx), in the presence of glucose, sucrose and jaggery +/- DCMU. Significant enhancement in phycobiliproteins and carotenoids was observed in the sugar supplemented cultures at high light intensities. SDS-PAGE profiles of whole cell proteins revealed the presence of unique bands in such treatments. Sucrose supplementation induced a 30-90 % increase in carotenoids, phycocyanin and phycoerythrin content at 10 klx. Molecular analysis of the stimulatory and interactive role of sugars on pigment enhancement at high light intensity may aid in better exploitation of cyanobacteria as a source of pigments.

  15. Effects of gasket on coupled plastic flow and strain-induced phase transformations under high pressure and large torsion in a rotational diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Feng, Biao; Levitas, Valery I.

    2016-01-01

    Combined plastic flow and strain-induced phase transformations (PTs) under high pressure in a sample within a gasket subjected to three dimensional compression and torsion in a rotational diamond anvil cell (RDAC) are studied using a finite element approach. The results are obtained for the weaker, equal-strength, and stronger high-pressure phases in comparison with low-pressure phases. It is found that, due to the strong gasket, the pressure in the sample is relatively homogenous and the geometry of the transformed zones is mostly determined by heterogeneity in plastic flow. For the equal-strength phases, the PT rate is higher than for the weaker and stronger high-pressure phases. For the weaker high-pressure phase, transformation softening induces material instability and leads to strain and PT localization. For the stronger high-pressure phase, the PT is suppressed by strain hardening during PT. The effect of the kinetic parameter k that scales the PT rate in the strain-controlled kinetic equation is also examined. In comparison with a traditional diamond anvil cell without torsion, the PT progress is much faster in RDAC under the same maximum pressure in the sample. Finally, the gasket size and strength effects are discussed. For a shorter and weaker gasket, faster plastic flow in radial and thickness directions leads to faster PT kinetics in comparison with a longer and stronger gasket. The rates of PT and plastic flows are not very sensitive to the modest change in a gasket thickness. Multiple experimental results are reproduced and interpreted. Obtained results allow one to design the desired pressure-plastic strain loading program in the experiments for searching new phases, reducing PT pressure by plastic shear, extracting kinetic properties from experiments with heterogeneous fields, and controlling homogeneity of all fields and kinetics of PTs.

  16. Modeling anisotropy plasticity : 3D Eulerian hydrocode simulations of high strain rate deformation processes.

    SciTech Connect

    Burkett, M. W.; Clancy, S. P.; Maudlin, P. J.; Holian, K. S.

    2001-01-01

    Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength have been implemented in the three-dimensional Conejo hydrodynamics code. The anisotropic constitutive modeling is posed in an unrotated material frame of reference using the theorem of polar decomposition to obtain rigid body rotation. Continuous quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure were utilized. Simple rectangular shear problems, R-value problems, and Taylor cylinder impact data were used to verify and validate the implementation of the anisotropic model. A stretching rod problem (involving large strain and high strain-rate deformation) was selected to investigate the effects of material anisotropy. Conejo simulations of rod topology were compared for two anisotropic cases.

  17. Modeling Anisotropic Plasticity: 3D Eulerian Hydrocode Simulations of High Strain Rate Deformation Processes

    NASA Astrophysics Data System (ADS)

    Burkett, Michael W.; Clancy, Sean P.; Maudlin, Paul J.; Holian, Kathleen S.

    2002-07-01

    Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength have been implemented in the three-dimensional Conejo hydrodynamics code. The anisotropic constitutive modeling is posed in an unrotated material frame of reference using the theorem of polar decomposition to obtain rigid body rotation. Continuous quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure were utilized. Simple rectangular shear problems, R-Value problems, and Taylor cylinder impact data were used to verify and validate the implementation of the anisotropic model. A stretching rod problem (involving large strain and high strain-rate deformation) was selected to investigate the effects of material anisotropy. Conejo simulations of rod topology were compared for two anisotropic cases.

  18. Modeling Anisotropic Plasticity: 3D Eulerian Hydrocode Simulations of High Strain Rate Deformation Processes

    NASA Astrophysics Data System (ADS)

    Burkett, Michael; Clancy, Sean; Maudlin, Paul; Holian, Kathleen

    2001-06-01

    : Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength has been implemented in the three-dimensional CONEJO hydrodynamics code. CONEJO is an explicit, Eulerian continuum mechanics code that is utilized to predict formation processes associated with material deformation at elevated strain-rates and is a code development project under the Accelerated Strategic Computing Initiative (ASCI) program. Some special features of CONEJO include a high-order advection algorithm, a material interface tracking scheme, and van Leer monotonic advection-limiting. The anisotropic constitutive modeling is posed in an unrotated material frame using the theorem of polar decomposition to describe rigid body rotation. An Euler-Rodrigues description is used to quantify the rigid body rotations. Continuous quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure were utilized. Associative flow formulations incorporating these yield functions were solved using a geometric normal return method. Simple rectangular shear problems, "R-value" problems, and Taylor cylinder impact test data were utilized to verify and validate the implementation of the anisotropic model. A "stretching rod" problem (involving large strain and strain-rate deformation) was selected to investigate the effects of material anisotropy for this deformation process. The rod necking rate and topology was compared for CONEJO simulations using several isotropic and anisotropic descriptions that utilized the Mechanical Threshold Stress (MTS) model.

  19. Enhancement of Biodegradable Plastic-degrading Enzyme Production from Paraphoma-like Fungus, Strain B47-9.

    PubMed

    Sameshima-Yamashita, Yuka; Koitabashi, Motoo; Tsuchiya, Wataru; Suzuki, Ken; Watanabe, Takashi; Shinozaki, Yukiko; Yamamoto-Tamura, Kimiko; Yamazaki, Toshimasa; Kitamoto, Hiroko

    2016-01-01

    To improve the productivity of Paraphoma-like fungal strain B47-9 for biodegradable plastic (BP)-degrading enzyme (PCLE), the optimal concentration of emulsified poly(butylene succinate-co-adipate) (PBSA) in the medium was determined. Emulsified PBSA was consumed as a sole carbon source and an inducer of PCLE production by strain B47-9. Among the various concentrations of emulsified PBSA [0.09-0.9% (w/v)] used in flask cultivation, 0.27% yielded the maximum enzyme activity within a short cultivation period. To evaluate the residual concentration of emulsified PBSA in culture, emulsified PBSA in aliquots of culture supernatant was digested in vitro, and the concentration of released monomerised succinic acid was determined. Regardless of the initial concentration of emulsified PBSA in medium, PCLE activity was detected after residual succinic acid decreased below 0.04 mg/mL in culture broth. Jarfermentation was performed at a 0.27% PBSA concentration. Among the various airflow rates tested, 1 LPM resulted in a PCLE production rate of 1.0 U/mL/day. The enzyme activity in the resulting culture filtrate (4.2 U/2 mL) was shown to degrade commercial BP films (1 × 1 cm, 20 µm thickness) within 8 hours. PMID:26876678

  20. InSAR observations of strain accumulation and fault creep along the Chaman Fault system, Pakistan and Afghanistan

    NASA Astrophysics Data System (ADS)

    Fattahi, Heresh; Amelung, Falk

    2016-08-01

    We use 2004-2011 Envisat synthetic aperture radar imagery and InSAR time series methods to estimate the contemporary rates of strain accumulation in the Chaman Fault system in Pakistan and Afghanistan. At 29 N we find long-term slip rates of 16 ± 2.3 mm/yr for the Ghazaband Fault and of 8 ± 3.1 mm/yr for the Chaman Fault. This makes the Ghazaband Fault one of the most hazardous faults of the plate boundary zone. We further identify a 340 km long segment displaying aseismic surface creep along the Chaman Fault, with maximum surface creep rate of 8.1 ± 2 mm/yr. The observation that the Chaman Fault accommodates only 30% of the relative plate motion between India and Eurasia implies that the remainder is accommodated south and east of the Katawaz block microplate.

  1. Interseismic strain accumulation in seismic gap of south central Chile from GPS measurements

    NASA Astrophysics Data System (ADS)

    Rudloff, A.; Vigny, C.; Ruegg, J. C.; Campos, J.

    2003-04-01

    Three campaigns of Global Positioning System (GPS) measurements were carried out in the Concepcion-Constitucion seismic gap in South Central Chile in 1996, 1999, and 2002. We observed a network of about 40 sites, made of 2 east-west transects roughly perpendicular to the trench ranging from the coastal area to the Argentina border and 1 north-south profile along the coast. Data sets were processed with MIT's GAMIT/GLOBK package. Horizontal velocities have formal uncertainties around 1 to 2 mm/yr in average. Vertical velocities are also determined and have uncertainties around 2 to 5 mm/yr. We find that the convergence between Nazca and South-America plates better matches the pole previously estimated by (Larson et al, 1997) than the Nuvel-1A estimate. Our estimate predicts a convergence of 72 mm/yr at N70 to be compared with Nuvel-1A 80 mm/yr at N79. With respect to stable South America, horizontal velocities decrease from 35 mm/yr on the coast to 14 mm/yr in the Cordillera. Vertical velocities help constraint lithospheric flecture. Partionning of the slightly oblique convergence will be investigated. The gradient of convergent parallel velocities reflects aseismic elastic loading on a zone of about 400 km width. Interestingly enough, this gradient exhibit a linear pattern, marginally compatible with the expected arctangent shape. 70 mm/yr of motion accumulated since the last big event in this area (1835 Earthquake described by Darwin) represent more than 10 m of displacement. Therefore, this area is probably mature for a next large earthquake, the magnitude of which could reach 8.5.

  2. Lead solubilization and accumulation by two strains of Pseudomonas obtained from a contaminated alfisol's effluent in southwestern Nigeria.

    PubMed

    Ekundayo, E O; Killham, K

    2001-10-01

    Two strains of Pseudomonas species (B2 and D5) selected from an array of lead solubilizing and accumulating bacteria obtained from the effluent contaminated soil samples of a battery manufacturing factory were studied. Increase in pH between 4.0 and 6.0 favoured the growth of isolates: Peak log10 cfu mL(-1) values of 7.1, 7.5 and 8.5 were obtained at pH 4, 5 and 6, respectively. Cell bound lead concentrations for B2 (0.34 mg mL(-1)) and D5 (0.30 mg mL(-1)) obtained by direct contact with Pbs were greater than lead concentrations of 0.89 and 0.25 mg mL(-1) for B2 and D5, respectively, obtained in dialyzed cultures. These cell bound lead concentration in undialyzed cultures were also greater than lead concentrations of 0.03 and 0.07 mg mL(-1) for B2 and D5 in culture supernatants. Glucose addition did nor improve lead accumulation in the isolates. Exploitation of such isolates for the biotreatment of lead laden effluent was conducted. PMID:11683230

  3. Lead solubilization and accumulation by two strains of Pseudomonas obtained from a contaminated alfisol's effluent in southwestern Nigeria.

    PubMed

    Ekundayo, E O; Killham, K

    2001-10-01

    Two strains of Pseudomonas species (B2 and D5) selected from an array of lead solubilizing and accumulating bacteria obtained from the effluent contaminated soil samples of a battery manufacturing factory were studied. Increase in pH between 4.0 and 6.0 favoured the growth of isolates: Peak log10 cfu mL(-1) values of 7.1, 7.5 and 8.5 were obtained at pH 4, 5 and 6, respectively. Cell bound lead concentrations for B2 (0.34 mg mL(-1)) and D5 (0.30 mg mL(-1)) obtained by direct contact with Pbs were greater than lead concentrations of 0.89 and 0.25 mg mL(-1) for B2 and D5, respectively, obtained in dialyzed cultures. These cell bound lead concentration in undialyzed cultures were also greater than lead concentrations of 0.03 and 0.07 mg mL(-1) for B2 and D5 in culture supernatants. Glucose addition did nor improve lead accumulation in the isolates. Exploitation of such isolates for the biotreatment of lead laden effluent was conducted.

  4. Dynamic response of Cu4Zr54 metallic glass to high strain rate shock loading: plasticity, spall and atomic-level structures

    SciTech Connect

    Luo, Shengnian; Arman, Bedri; Germann, Timothy C; Cagin, Tahir

    2009-01-01

    We investigate dynamic response of Cu{sub 46}Zr{sub 54} metallic glass under adiabatic planar shock wave loading (one-dimensional strain) wjth molecular dynamics simulations, including Hugoniot (shock) states, shock-induced plasticity and spallation. The Hugoniot states are obtained up to 60 CPa along with the von Mises shear flow strengths, and the dynamic spall strength, at different strain rates and temperatures. The spall strengths likely represent the limiting values achievable in experiments such as laser ablation. For the steady shock states, a clear elastic-plastic transition is identified (e.g., in the shock velocity-particle velocity curve), and the shear strength shows strain-softening. However, the elastic-plastic transition across the shock front displays transient stress overshoot (hardening) above the Hugoniot elastic limit followed by a relatively sluggish relaxation to the steady shock state, and the plastic shock front steepens with increasing shock strength. The local von Mises shear strain analysis is used to characterize local deformation, and the Voronoi tessellation analysis, the corresponding short-range structures at various stages of shock, release, tension and spallation. The plasticity in this glass is manifested as localized shear transformation zones and of local structure rather than thermal origin, and void nucleation occurs preferentially at the highly shear-deformed regions. The Voronoi and shear strain analyses show that the atoms with different local structures are of different shear resistances that lead to shear localization (e.g., the atoms indexed with (0,0,12,0) are most shear-resistant, and those with (0,2,8,1) are highly prone to shear flow). The dynamic changes in local structures are consistent with the observed deformation dynamics.

  5. Interseismic Strain Accumulation in Metropolitan Los Angeles Distinguished from Oil and Water management using InSAR and GPS

    NASA Astrophysics Data System (ADS)

    Argus, D. F.; Agram, P. S.; Rollins, C.; Avouac, J. P.; Barbot, S.

    2015-12-01

    Thesis.InSAR measurements from 1992 to 2012 are detecting deformation due to oil pumping and groundwater changes throughout metropolitan Los Angeles. This is allowing elastic strain build up on blind thrusts beneath the city to be accurately evaluated using GPS. Oil Fields.Pumping and repressurization of oil fields have generated substantial displacement in metropolitan Los Angeles, causing Beverly Hills, downtown, and Whittier to subside at 3-10 mm/yr and Santa Fe Springs and La Mirada to rise at 5-9 mm/yr. Aquifers.Displacements of the Santa Ana and San Gabriel Valley aquifers accumulate in response to sustained changes in groundwater over periods of either drought or heavy precipitation. Santa Ana aquifer has subsided nearly 0.1 m in response to lowering of the groundwater level by about 25 m over the past 18 years. Anthropogenic Vs. Tectonic Motion.We are assessing horizontal motions due to changes groundwater using an empirical relationship established on the basis of seasonal oscillations of Santa Ana aquifer. Anthropogenic horizontal motion is estimated to be proportional to the directional gradient in vertical motion inferred with InSAR. We are finding this rough approximation to be quite useful for evaluating deviations of GPS positions from a constant velocity. We are also constructing Mogi models of volume change in oil fields to evaluate GPS deviations. Earthquake Strain Buildup on Blind Thrust Faults.NNE contraction perpendicular to the big restraining bend in the San Andreas fault is fastest not immediately south of the San Andreas in the San Gabriel Mountains, but instead 50 km south of the fault in northern metropolitan Los Angeles. An elastic model of interseismic strain accumulation fit to GPS data and incorporating a 1D approximation of the rheology of the Los Angeles basin indicates the deep segment of the Puente Hills (-upper Elysian Park) Thrust to be slipping at 9 ±2 mm/yr beneath a locking depth of 12 ±5 km. Please see also our

  6. Fabric Transitions in Quartz via Visco-Plastic Self-Consistent Modelling: Axial Compression and Simple Shear under Constant Strain

    NASA Astrophysics Data System (ADS)

    Morales, L. F. G.; Lloyd, G. E.; Mainprice, D.

    2014-12-01

    Quartz is a common crustal mineral that deforms plastically in a wide range of temperatures and pressures, leading to the development of different types of crystallographic preferred orientation (CPO) patterns. In this contribution we present the results of an extensive modelling of quartz fabric transitions via visco-plastic self- consistent (VPSC) approach. For that, we have performed systematic simulations using different sets of relative critical resolved shear stress of the main quartz slip systems. We have performed these simulations in axial compression and simple shear regimes under constant Von Mises equivalent strain of 100% (γ=1.73), assuming that the aggregates deformed exclusively by dislocation glide. Some of the predicted CPOs patterns are similar to those observed in naturally and experimentally deformed quartz. Nevertheless, some classical CPO patterns usually interpreted as resulting from dislocation glide (e.g. Y-maxima due to prism slip) are clearly not developed in the simulated conditions. In addition we report potentially new preferred orientation patterns that might develop in high temperature conditions, both in axial compression and simple shear. We have demonstrated that CPOs generated under axial compression are usually stronger that those predicted under simple shear, due to the continuous rotation observed in the later simulations. The fabric strength depends essentially on the dominant active slip system, and normally the stronger CPOs result from dominant basal slip in , followed by rhomb and prism [c] slip, whereas prism slip does not produce strong fabrics. The opening angle of quartz [0001] fabric used as a proxy of temperature seems to be reliable for deformation temperatures of ~400°C, when the main slip systems have similar behaviours.

  7. Bounds and estimates for the effect of strain gradients upon the effective plastic properties of an isotropic two-phase composite

    NASA Astrophysics Data System (ADS)

    Fleck, Norman A.; Willis, John R.

    2004-08-01

    Predictions are made for the size effect on strength of a random, isotropic two-phase composite. Each phase is treated as an isotropic, elastic-plastic solid, with a response described by a modified deformation theory version of the Fleck-Hutchinson strain gradient plasticity formulation (Fleck and Hutchinson, J. Mech. Phys. Solids 49 (2001) 2245). The essential feature of the new theory is that the plastic strain tensor is treated as a primary unknown on the same footing as the displacement. Minimum principles for the energy and for the complementary energy are stated for a composite, and these lead directly to elementary bounds analogous to those of Reuss and Voigt. For the case of a linear hardening solid, Hashin-Shtrikman bounds and self-consistent estimates are derived. A non-linear variational principle is constructed by generalising that of Ponte Castañeda (J. Mech. Phys. Solids 40 (1992) 1757). The minimum principle is used to derive an upper bound, a lower estimate and a self-consistent estimate for the overall plastic response of a statistically homogeneous and isotropic strain gradient composite. Sample numerical calculations are performed to explore the dependence of the macroscopic uniaxial response upon the size scale of the microstructure, and upon the relative volume fraction of the two phases.

  8. Lamotrigine attenuates deficits in synaptic plasticity and accumulation of amyloid plaques in APP/PS1 transgenic mice.

    PubMed

    Zhang, Mao-Ying; Zheng, Chuan-Yi; Zou, Ming-Ming; Zhu, Jian-Wei; Zhang, Yan; Wang, Jing; Liu, Chun-Feng; Li, Qi-Fa; Xiao, Zhi-Cheng; Li, Shao; Ma, Quan-Hong; Xu, Ru-Xiang

    2014-12-01

    Hyperactivity and its compensatory mechanisms may causally contribute to synaptic and cognitive deficits in Alzheimer's disease (AD). Blocking the overexcitation of the neural network, with levetiracetam (LEV), a sodium channel blocker applied in the treatment of epilepsy, prevented synaptic and cognitive deficits in human amyloid precursor protein (APP) transgenic mice. This study has brought the potential use of antiepileptic drugs (AEDs) in AD therapy. We showed that the chronic treatment with lamotrigine (LTG), a broad-spectrum AED, suppressed abnormal spike activity, prevented the loss of spines, synaptophysin immunoreactivity, and neurons, and thus attenuated the deficits in synaptic plasticity and learning and memory in APP and presenilin 1 (PS1) mice, which express human mutant APP and PS1. In contrast with LEV, which failed to reduce the generation of amyloid β, the chronic LTG treatment reduced the cleavage of APP by β-secretase and thus the numbers and the size of amyloid plaques in the brains of APP and PS1 mice. Moreover, the levels of brain-derived neurotrophic growth factor (BDNF) and nerve growth factor (NGF) were enhanced in the brains of APP and PS1 mice by the chronic LTG treatment. Therefore, these observations demonstrate that LTG attenuates AD pathology through multiple mechanisms, including modulation of abnormal network activity, reduction of the generation of amyloid beta and upregulation of BDNF and NGF. PMID:25044076

  9. Influence of intense plastic straining on grain refinement, precipitation, and mechanical properties of Al-Cu-Li-Based alloys

    NASA Astrophysics Data System (ADS)

    Salem, H. G.; Goforth, R. E.; Hartwig, K. T.

    2003-05-01

    Grain refinement is one of the major interests when an ultrahigh strength/ductility combination is demanded for ambient and cryogenic temperature applications, especially when superplastic forming (SPF) is involved for the manufacturing of different aerospace structures. Equal-channel angular extrusion (ECAE) is a relatively new metalworking process, which is capable of producing an ultrafine, submicron-grained (SMG) structure by means of intense plastic straining without a change in the shape or dimensions of the worked material. In the current research work, the influence of ECAE processing on the room-temperature mechanical properties of Al-Cu-Li-Mg-Ag-Zr alloys in the T4 and T6 temper conditions is investigated. An ultrafine SMG structure of 0.2 to 0.4 µm was produced for the ECAE-processed alloys from an initial grain size of >100 µm, which is compared with a conventionally processed superplastic Weldalite sheet material with an ˜1.5 µm grain size. The ECAE processing eliminates the precipitation-free zones (PFZs) in the T6 temper condition without the need for prior stretching. A significant improvement in the mechanical properties at room temperature is achieved by ECAE processing in comparison with conventional processing.

  10. Flow Curve Determination at Large Plastic Strain Levels: Limitations of the Membrane Theory in the Analysis of the Hydraulic Bulge Test

    NASA Astrophysics Data System (ADS)

    Lemoine, X.; Iancu, A.; Ferron, G.

    2011-05-01

    Nowadays, an accurate determination of the true stress-strain curve is a key-element for all finite element (FE) forming predictions. Since the introduction of Advanced High Strength Steels (AHSS) for the automotive market, the standard uniaxial tension test suffers the drawback of relatively low uniform elongations. The extrapolation of the uniaxial stress-strain curve up to large strains is not without consequence in forming predictions—especially formability and springback. One of the means to solve this problem is to use experimental tests where large plastic strain levels can be reached. The hydraulic bulge test is one of these tests. The effective plastic strain levels reached in the bulge test are of about 0.7. From an experimental standpoint, the biaxial flow stress is estimated using measurement of fluid pressure, and calculation of thickness and curvature at the pole, via appropriate measurements and assumptions. The biaxial stress at the pole is determined using the membrane equilibrium equation. The analysis proposed in this paper consists of performing "virtual experiments" where the results obtained by means of FE calculations are used as input data for determining the biaxial stress-strain law in agreement with the experimental procedure. In this way, a critical discussion of the experimental procedure can be made, by comparing the "experimental" stress-strain curve (Membrane theory curve) with the "reference" one introduced in the simulations. In particular, the influences of the "(die diameter)/thickness" ratio and of the plastic anisotropy are studied, and limitations of the hydraulic bulge test analysis are discussed.

  11. Interseismic strain accumulation across an active thrust system: an InSAR case study in the Himalaya

    NASA Astrophysics Data System (ADS)

    Grandin, R.; Doin, M.; Ducret, G.; Bollinger, L.; Pinel-Puysségur, B.; Lasserre, C.; Jolivet, R.

    2011-12-01

    The major active thrust system underlying the Himalayan range produces recurrent large earthquakes, posing a significant threat to the densely populated Indo-Gangetic basin. Measuring the interseismic deformation associated with this fault system could provide important constraints on the geometry of the locked faults that are bound to rupture in future great earthquakes. This has so far been considered out of reach of InSAR techniques, due to decorrelation, prominent topographic features, and unfavourable climatic conditions. However, preliminary tests carried out with the archived ASAR data provided by ESA's ENVISAT satellite since 2002 have shown that recent advances in InSAR processing may now allow geodesists to tackle most of these perturbations. In this context, applying these advanced techniques to the case of the Himalayas is both a challenging and necessary task. We will present the methodology and the first results of an InSAR study of interseismic strain accumulation across the Himalayas. Small-baseline processing of ENVISAT data using a combination of ROI_PAC software, NSBAS processing chain and MulSAR technique yields a sufficient number of coherent interferograms to compute a preliminary average velocity map of interseismic uplift. Time-space variations of stratified tropospheric delay observed in these interferogrames are mitigated using a prediction deduced from outputs of the ECMWF global meteorological reanalysis ERA-Interim. Finally, a correction of DEM errors from the wrapped InSAR data set further improves the coherence of interferograms with a large perpendicular baseline. Comparison of the InSAR LOS velocity maps with microseismic activity detected near the transition zone at the base of the seismogenic portion of the Main Himalayan Thrust is expected to provide constraints on the process of elastic strain accumulation during the interseismic period. This will help in understanding the interaction between the construction of topography

  12. Elastic and Inelastic Strain Accumulation Along the Northern and Central Itoigawa-Shizuoka Tectonic Line, Central Japan

    NASA Astrophysics Data System (ADS)

    Teratani, N.; Sagiya, T.; Nishimura, T.; Yarai, H.; Suito, H.

    2014-12-01

    Itoigawa-Shizuoka Tectonic Line (ISTL) in central Japan is one of the most active fault systems in Japan. The Japanese government evaluated a M8 class earthquake may occur at the Gofukuji fault in the central ISTL with a possibility of 14% in the next 30 years. So we analyze GPS data around the northern and the central ISTL to monitor tectonic strain accumulation and to propose a fault model for future earthquake in this area. Along the northern and central ISTL, there exist active faults such as the Kamishiro fault (KF), the East Mathumoto Basin fault (EMBF) and the Gofukuji fault (GF). KF and EMBF are east-dipping reverse faults, and GF is a left-lateral strike slip fault. We analyzed GPS data of 34 campaign sites during 2002-2010 and 55 continuous sites during 1998-2013 to obtain 3-dimentional velocities in the ITRF 2008 reference frame. Around GF, the velocity field represents a typical inter-seismic pattern around a strike slip fault. By applying an elastic dislocation model, we estimate a fault slip rate as 5-7 mm/yr with a locking depth of over 5 km. These parameters are consistent with the seismogenic zone depth and the geological slip rate of GF. On the other hand, for KF and EMBF, we model the deformation pattern with faults in an elastic layer overlying a viscoelastic substratum to represent steady contraction. The modeling result shows KF dips at 30-40 degree and its locking depth is only 2 km, implying that the whole fault is creeping. EMBF dips at 40-50 degree with a locking depth of 2 km. The results indicate that there is ongoing stress accumulation around GF, but KF and EMBF accommodates contraction inelastically. GF at the central ISTL is considered to store strain energy more than 1.000 years and a future major earthquake should occur to release shear stress along the central part. The rupture may continue to the south, but more observation and modeling effect is necessary.

  13. The Lima-Peru seismic gap: a study of inter-seismic strain accumulation from a decade of GPS measurements

    NASA Astrophysics Data System (ADS)

    Norabuena, E. O.; Pollitz, F. F.; Dixon, T. H.

    2013-05-01

    The Peruvian subduction zone between the Mendaña Fracture zone and Arica, northern Chile, has been source of large megathrust earthquakes since historical to present times, The two last major events affecting the southern segment corresponds to Arequipa 2001 (Mw 8.3) and Pisco 2007 (Mw 8.1). A noteworthy event is the Lima 1746 earthquake with an assigned magnitude of Mw 8.5 and which is assumed to have broken several km of the seismogenic zone off Lima. The great shock was followed by a devastating tsunami that destroyed the main port of Callao, killing about 99 percent of its population. This extreme event was followed by quiescence of a few hundred years until the XX century when the Lima subduction zone was broken again by the earthquakes of May 1940 (Mw 8.0), October 1966 (Mw 8.0) and Lima 1974 (Mw 8.0). The broken areas overlap partially with the estimated area of the 1746 earthquake and put the region in a state of seismic gap representing a major hazard for Lima city - Peru's capital and its about 9 million of inhabitants. Our study reports the interseismic strain accumulation derived from a decade of GPS measurement at 11 geodetic monuments including one measurement in an island 80 km offshore and models variations of coupling along the plate interface.

  14. Effect of constitutive equations on qualitative behavior of solutions in the vicinity of bi-material interfaces at large plastic strains

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sergei; Goldstein, Robert

    2016-11-01

    The main objective of the present paper is to compare, by means of a problem permitting a closed-form solution, qualitative behavior of solutions based on three models of strain hardening plasticity and two models of viscoplasticity. The elastic portion of the strain tensor is neglected. The study focuses on the solution behavior near frictional interfaces. The solution behavior essentially depends on the model chosen. Such features of the solutions as nonexistence and singularity are emphasized. The key constitutive parameter that divides all the models considered into two groups is the saturation stress. In particular, under certain conditions no solution satisfying the regime of sticking exists for the models that involve the saturation stress. Qualitative comparison with numerous experimental observations is made. It is concluded that models with a saturation stress, including the models considered in the present paper, may be capable of describing the generation of a narrow layer of severe plastic deformation in the vicinity of frictional interfaces.

  15. The Effects of Light, Temperature, and Nutrition on Growth and Pigment Accumulation of Three Dunaliella salina Strains Isolated from Saline Soil

    PubMed Central

    Wu, Zhe; Duangmanee, Promchup; Zhao, Pu; Juntawong, Niran; Ma, Chunhong

    2016-01-01

    Background: Developing algal industries in saline-alkali areas is necessary. However, suitable strains and optimal production conditions must be studied before widespread commercial use. Objectives: The effects of light, temperature, KNO3, and CO(NH2)2 on beta-carotene and biomass accumulation were compared and evaluated in order to provide scientific guidance for commercial algal production in northeastern Thailand. Materials and Methods: An orthogonal design was used for evaluating optimal conditions for the algal production of three candidate Dunaliella salina strains (KU XI, KU 10 and KU 31) which were isolated from saline soils and cultured in the column photobioreactor. Results: The optimal light and temperature for algae growth were 135.3 μmol m-2 s-1 and 22°C, while the conditions of 245.6 μmol m-2 s-1 and 22°C induced the highest level of beta-carotene production (117.99 mg L-1). The optimal concentrations of KNO3, CO(NH2)2, and NaHCO3 for algae growth were 0.5 g L-1, 0.36 g L-1, and 1.5 g L-1, respectively, while 0, 0.12 g L-1 and 1.5 g L-1 were best suited for beta-carotene accumulation. The highest beta-carotene rate per cell appeared with the highest light intensity (12.21 pg) and lowest temperature (12.47 pg), and the lowest total beta-carotene content appeared at the lowest temperature (15°C). There was not a significant difference in biomass accumulation among the three Dunaliella strains; however, the beta-carotene accumulation of KU XI was higher than that of the other two strains. Conclusions: Light and temperature were both relevant factors that contributed to the growth and beta-carotene accumulation of the three D. salina strains, and NaHCO3 had significantly positive effects on growth. The degree of impact of the different factors on cell growth was temperature > NaHCO3 > light intensity > KNO3 > CO (NH2)2 > strains; the impact on beta-carotene accumulation was temperature > light intensity > KNO3 > CO (NH2)2 > strains > NaHCO3 PMID

  16. Measurement of interseismic strain accumulation in the Southern Andes (25°-35°S) using Envisat SAR data

    NASA Astrophysics Data System (ADS)

    Ducret, G.; Doin, M. P.; Grandin, R.; Socquet, A.; Vigny, C.; Métois, M.; Béjar-Pizzaro, M.

    2012-04-01

    The Chilean subduction zone is one of the most active in the world. The Nazca plate subducts under the South America plate with a velocity around 7 cm/year. Along-strike and along-dip variations of interseismic coupling suggest that the subduction interface is divided into segments. Rupture of one or several consecutive segments may produce earthquakes of magnitude greater than 8.0. However, the definition of the segmentation in the particular case of the Chilean subduction and its relation to earthquake nucleation in general is a debated topic. We focus on an area extending over 1000 km in latitude, located between Taltal (~25°S) and Constitution (~35°S), which has been accumulating tectonic strain since the mid-20th century. Three main earthquakes occurred in the last decade around the boundaries of this segment : the 1995 Antogagasta (M=8.1) and the 2007 Tocopilla (M=7.7) earthquakes to the North and the 2010 Maule (M=8.8) earthquake to the South. A few seismic swarms occurred in recent years : the episode of Valparaiso (~33°S) in 1985, the Puntaqui (~30°S) crisis in 1997, and the swarms in the Copiapo (~27°S) region in 1973 and 2006. The 25-35°S part of the subduction zone experiences since 38 years a background seismicity (given by USGS catalog), that is mainly located along the plate interface and less frequently within the overriding plate. The seismicity rate is varying from South to North with a maximum seismicity located around La Serena area (~30°S). There, the coupling distribution is constrained by an important GPS dataset that indicate a lower coupling (less than 60%) compared with areas further North and South. Similarly, GPS data suggest that the Copiapo area also corresponds to a local minimum of coupling. However the GPS network is too sparse further North to constrain coupling variations between 28° and 25°S. We use InSAR (Interferometric Synthetic Aperture Radar) to provide additional insights on interseismic strain accumulation and the

  17. ROS accumulation and oxidative damage to cell structures in Saccharomyces cerevisiae wine strains during fermentation of high-sugar-containing medium.

    PubMed

    Landolfo, Sara; Politi, Huguette; Angelozzi, Daniele; Mannazzu, Ilaria

    2008-06-01

    To further elucidate the impact of fermentative stress on Saccharomyces cerevisiae wine strains, we have here evaluated markers of oxidative stress, oxidative damage and antioxidant response in four oenological strains of S. cerevisiae, relating these to membrane integrity, ethanol production and cell viability during fermentation in high-sugar-containing medium. The cells were sampled at different fermentation stages and analysed by flow cytometry to evaluate membrane integrity and accumulation of reactive oxygen species (ROS). At the same time, catalase and superoxide dismutase activities, trehalose accumulation, and protein carbonylation and degradation were measured. The results indicate that the stress conditions occurring during hypoxic fermentation in high-sugar-containing medium result in the production of ROS and trigger an antioxidant response. This involves superoxide dismutase and trehalose for the protection of cell structures from oxidative damage, and protein catabolism for the removal of damaged proteins. Cell viability, membrane integrity and ethanol production depend on the extent of oxidative damage to cellular components. This is, in turn, related to the 'fitness' of each strain, which depends on the contribution of individual cells to ROS accumulation and scavenging. These findings highlight that the differences in individual cell resistances to ROS contribute to the persistence of wine strains during growth under unfavourable culture conditions, and they provide further insights into our understanding of yeast behaviour during industrial fermentation.

  18. A multi-scale model of dislocation plasticity in α-Fe: Incorporating temperature, strain rate and non-Schmid effects

    SciTech Connect

    Lim, H.; Hale, L. M.; Zimmerman, J. A.; Battaile, C. C.; Weinberger, C. R.

    2015-01-05

    In this study, we develop an atomistically informed crystal plasticity finite element (CP-FE) model for body-centered-cubic (BCC) α-Fe that incorporates non-Schmid stress dependent slip with temperature and strain rate effects. Based on recent insights obtained from atomistic simulations, we propose a new constitutive model that combines a generalized non-Schmid yield law with aspects from a line tension (LT) model for describing activation enthalpy required for the motion of dislocation kinks. Atomistic calculations are conducted to quantify the non-Schmid effects while both experimental data and atomistic simulations are used to assess the temperature and strain rate effects. The parameterized constitutive equation is implemented into a BCC CP-FE model to simulate plastic deformation of single and polycrystalline Fe which is compared with experimental data from the literature. This direct comparison demonstrates that the atomistically informed model accurately captures the effects of crystal orientation, temperature and strain rate on the flow behavior of siangle crystal Fe. Furthermore, our proposed CP-FE model exhibits temperature and strain rate dependent flow and yield surfaces in polycrystalline Fe that deviate from conventional CP-FE models based on Schmid's law.

  19. A multi-scale model of dislocation plasticity in α-Fe: Incorporating temperature, strain rate and non-Schmid effects

    DOE PAGES

    Lim, H.; Hale, L. M.; Zimmerman, J. A.; Battaile, C. C.; Weinberger, C. R.

    2015-01-05

    In this study, we develop an atomistically informed crystal plasticity finite element (CP-FE) model for body-centered-cubic (BCC) α-Fe that incorporates non-Schmid stress dependent slip with temperature and strain rate effects. Based on recent insights obtained from atomistic simulations, we propose a new constitutive model that combines a generalized non-Schmid yield law with aspects from a line tension (LT) model for describing activation enthalpy required for the motion of dislocation kinks. Atomistic calculations are conducted to quantify the non-Schmid effects while both experimental data and atomistic simulations are used to assess the temperature and strain rate effects. The parameterized constitutive equationmore » is implemented into a BCC CP-FE model to simulate plastic deformation of single and polycrystalline Fe which is compared with experimental data from the literature. This direct comparison demonstrates that the atomistically informed model accurately captures the effects of crystal orientation, temperature and strain rate on the flow behavior of siangle crystal Fe. Furthermore, our proposed CP-FE model exhibits temperature and strain rate dependent flow and yield surfaces in polycrystalline Fe that deviate from conventional CP-FE models based on Schmid's law.« less

  20. Three hen strains fed photoisomerized trans,trans CLA-rich soy oil exhibit different yolk accumulation rates and source-specific isomer deposition.

    PubMed

    Shinn, Sara E; Gilley, Alex D; Proctor, Andrew; Anthony, Nicholas B

    2015-04-01

    Most CLA chicken feeding trials used cis,trans (c,t) and trans,cis (t,c) CLA isomers to produce CLA-rich eggs, while reports of trans,trans (t,t) CLA enrichment in egg yolks are limited. The CLA yolk fatty acid profile changes and the 10-12 days of feeding needed for maximum CLA are well documented, but there is no information describing CLA accumulation during initial feed administration. In addition, no information on CLA accumulation rates in different hen strains is available. The aim of this study was to determine a mathematical model that described yolk CLA accumulation and depletion in three hen strains by using t,t CLA-rich soybean oil produced by photoisomerization. Diets of 30-week Leghorns, broilers, and jungle fowl were supplemented with 15% CLA-rich soy oil for 16 days, and eggs were collected for 32 days. Yolk fatty acid profiles were measured by GC-FID. CLA accumulation and depletion was modeled by both quadratic and piecewise regression analysis. A strong quadratic model was proposed, but it was not as effective as piecewise regression in describing CLA accumulation and depletion. Broiler hen eggs contained the greatest concentration of CLA at 3.2 mol/100 g egg yolk, then jungle fowl at 2.9 mol CLA, and Leghorns at 2.3 mol CLA. The t,t CLA isomer levels remained at 55% of total yolk CLA during CLA feeding. However, t-10,c-12 (t,c) CLA concentration increased slightly during CLA accumulation and was significantly greater than c-9,t-11 CLA. Jungle fowl had the smallest increase in yolk saturated fat with CLA yolk accumulation.

  1. The Effect of Single Crystal Elastic and Plastic Anisotropy on Strain Heterogeneity: Comparison of Olivine to Other Common Minerals

    NASA Astrophysics Data System (ADS)

    Cline, C. J., II; Burnley, P. C.

    2013-12-01

    In order to extrapolate the rheological behavior of polycrystalline earth materials to conditions and timescales that are unachievable in a laboratory setting, some sort of model is required. Numerical models are particularly appealing for this task but for these models to provide a sound platform for extrapolation they must be based on a complete understanding of all deformation mechanics that are operating in the real material. In a simplified description these mechanics can be thought of as having three components 1) the individual grains, 2) the grain boundaries and 3) the macroscopic aggregate response, which can be thought of as the interaction of the other two components within the polycrystal. Traditionally, the aggregate response is thought to represent the summed or average behavior of all individual grains deforming under the influence of the macroscopic stress tensor but; recent work within our lab using finite element models (FEM) has shown that local stress fields within the aggregate are not representative of the macroscopic stress tensor and can vary in both direction and magnitude. These variations in the stress tensor produce a pattern similar to force chains that are observed in deformation experiments on granular materials; and appear to be a direct consequence of stress percolation which is controlled by the anisotropy of the elastic and plastic strengths of the individual grains. To test this hypothesis we will conduct a suite of deformation experiments utilizing multiple monomineralic polycrystals that have a range of single crystal anisotropies. In order to infer the direction of stress acting on each grain and reconstruct the total modulation of stress direction throughout the sample, we have chosen materials that form microstructures that are sensitive to stress direction, such as deformation twins and kink bands. This experimental technique will allow for a direct comparison between the single crystal anisotropy of a material and the

  2. Deformation mechanism study of a hot rolled Zr-2.5Nb alloy by transmission electron microscopy. I. Dislocation microstructures in as-received state and at different plastic strains

    SciTech Connect

    Long, Fei; Daymond, Mark R. Yao, Zhongwen

    2015-03-07

    Thin foil dog bone samples prepared from a hot rolled Zr-2.5Nb alloy have been deformed by tensile deformation to different plastic strains. The development of slip traces during loading was observed in situ through SEM, revealing that deformation starts preferentially in certain sets of grains during the elastic-plastic transition region. TEM characterization showed that sub-grain boundaries formed during hot rolling consisted of screw 〈a〉 dislocations or screw 〈c〉 and 〈a〉 dislocations. Prismatic 〈a〉 dislocations with large screw or edge components have been identified from the sample with 0.5% plastic strain. Basal 〈a〉 and pyramidal 〈c + a〉 dislocations were found in the sample that had been deformed with 1.5% plastic strain, implying that these dislocations require larger stresses to be activated.

  3. Analysis of the Plasticity-Enhancing Mechanisms in 12 pctMn Austeno-ferritic Steel by In Situ Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Lee, Sangwon; Woo, Wanchuck; De Cooman, Bruno C.

    2014-12-01

    The tensile behavior of ductile ultra-high strength Fe-12 pctMn-0.3 pctC-2 pctAl austeno-ferritic steel was studied by in situ neutron diffraction measurement of the elastic lattice strains, dislocation density, stacking fault probability, and strain-induced transformation kinetics. Micro-yielding was observed in austenite, and the plastic deformation of ferrite remained very limited throughout the deformation. The analysis identified three contributions to the strain hardening: twinning-induced plasticity, transformation-induced plasticity, and the accumulation of a high density of geometrically necessary dislocations accommodating the strain mismatch at the phase boundaries.

  4. Distributions of energy storage rate and microstructural evolution in the area of plastic strain localization during uniaxial tension of austenitic steel

    NASA Astrophysics Data System (ADS)

    Oliferuk, W.; Maj, M.

    2015-08-01

    The presented work is devoted to an experimental determination of the energy storage rate in the area of strain localization. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. The results of experiments have shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. To interpret the decrease of the energy storage rate in terms of micro-mechanisms, microstructural observations using Transmission Electron Microscopy (TEM) and Electron Back Scattered Diffraction (EBSC) were performed. On the basis of microstructural studies it is believed that a 0 value of energy storage rate corresponds to the state in which only two dominant components of the texture appear, creating conditions for crystallographic shear banding.

  5. Crustal strain accumulation on Southern Basin and Range Province faults modulated by distant plate boundary earthquakes? Evidence from geodesy, seismic imaging, and paleoseismology

    NASA Astrophysics Data System (ADS)

    Bennett, R. A.; Shirzaei, M.; Broermann, J.; Spinler, J. C.; Holland, A. A.; Pearthree, P.

    2014-12-01

    GPS in Arizona reveals a change in the pattern of crustal strain accumulation in 2010 and based on viscoelastic modeling appears to be associated with the distant M7.2 El Mayor-Cucapah (EMC) earthquake in Baja California, Mexico. GPS data collected between 1999 and 2009 near the Santa Rita normal fault in SE Arizona reveal a narrow zone of crustal deformation coincident with the fault trace, delineated by W-NW facing Pleistocene fault scarps of heights 1 to 7 m. The apparent deformation zone is also seen in a preliminary InSAR interferogram. Total motion across the zone inferred using an elastic block model constrained by the pre-2010 GPS measurements is ~1 mm/yr in a sense consistent with normal fault motion. However, continuous GPS measurements throughout Arizona reveal pronounced changes in crustal velocity following the EMC earthquake, such that the relative motion across the Santa Rita fault post-2010 is negligible. Paleoseismic evidence indicates that mapped Santa Rita fault scarps were formed by two or more large magnitude (M6.7 to M7.6) surface rupturing normal-faulting earthquakes 60 to 100 kyrs ago. Seismic refraction and reflection data constrained by deep (~800 m) well log data provide evidence of progressive, possibly intermittent, displacement on the fault through time. The rate of strain accumulation observed geodetically prior to 2010, if constant over the past 60 to 100 kyrs, would imply an untenable minimum slip rate deficit of 60 to 100 m since the most recent earthquake. One explanation for the available geodetic, seismic, and paleoseismic evidence is that strain accumulation is modulated by viscoelastic relaxation associated with frequent large magnitude earthquakes in the Salton Trough region, episodically inhibiting the accumulation of elastic strain required to generate large earthquakes on the Santa Rita and possibly other faults in the Southern Basin and Range. An important question is thus for how long the postseismic velocity changes

  6. Plastic-Strain-Amplitude Dependence of Dislocation Structures in Cyclically Deformed <112>-Oriented Cu-7 at. pct Al Alloy Single Crystals

    NASA Astrophysics Data System (ADS)

    Li, X. W.; Peng, N.; Wu, X. M.; Wang, Z. G.

    2014-08-01

    Dislocation structures in Cu-7 at. pct Al alloy single crystals cyclically deformed at different plastic strain amplitudes were investigated by transmission electron microscope (TEM) and compared with the results of Cu single crystals. It is found that the plastic strain amplitude γ pl has an obvious effect on the slip deformation mode, and consequently on the cyclic hardening behavior of Cu-7 at. pct Al alloy single crystals with an intermediate stacking fault energy. For instance, a high slip planarity ( i.e., only formation of planar-slip bands) contributes to the occurrence of a gentle cyclic hardening with a much lower saturation stress at a low γ pl of 4.5 × 10-4. A mixed planar/wavy-slip mode ( e.g., persistent Lüder's bands/wall-like microstructures) at an intermediate γ pl of 2.2 × 10-3 causes an obvious cyclic hardening up to a comparable saturation stress to that for the Cu single crystal. In contrast, the deformation mode is dominated by wavy slip ( e.g., ill-defined dislocation cells and walls) at the highest γ pl of 7.2 × 10-3, causing that its cyclic hardening curve is quite similar to that for the Cu single crystal; in this case, a slightly higher saturation stress level than that for the Cu single crystal is reached due to the additional solid solution strengthening.

  7. Elastic-plastic-brittle transitions and avalanches in disordered media.

    PubMed

    Kale, Sohan; Ostoja-Starzewski, Martin

    2014-01-31

    A spring lattice model with the ability to simulate elastic-plastic-brittle transitions in a disordered medium is presented. The model is based on bilinear constitutive law defined at the spring level and power-law-type disorder introduced in the yield and failure limits of the springs. The key parameters of the proposed model effectively control the disorder distribution, significantly affecting the stress-strain response, the damage accumulation process, and the fracture surfaces. The model demonstrates a plastic strain avalanche behavior for perfectly plastic as well as hardening materials with a power-law distribution, in agreement with the experiments and related models. The strength of the model is in its generality and ability to interpolate between elastic-plastic hardening and elastic-brittle transitions.

  8. Interrogation of the Substrate Profile and Catalytic Properties of the Phosphotriesterase from Sphingobium sp. Strain TCM1: An Enzyme Capable of Hydrolyzing Organophosphate Flame Retardants and Plasticizers.

    PubMed

    Xiang, Dao Feng; Bigley, Andrew N; Ren, Zhongjie; Xue, Haoran; Hull, Kenneth G; Romo, Daniel; Raushel, Frank M

    2015-12-29

    The most familiar organophosphorus compounds are the neurotoxic insecticides and nerve agents. A related group of organophosphorus compounds, the phosphotriester plasticizers and flame retardants, has recently become widely used. Unlike the neurotoxic phosphotriesters, the plasticizers and flame retardants lack an easily hydrolyzable bond. While the hydrolysis of the neurotoxic organophosphates by phosphotriesterase enzymes is well-known, the lack of a labile bond in the flame retardants and plasticizers renders them inert to typical phosphotriesterases. A phosphotriesterase from Sphingobium sp. strain TCM1 (Sb-PTE) has recently been reported to catalyze the hydrolysis of organophosphorus flame retardants. This enzyme has now been expressed in Escherichia coli, and the activity with a wide variety of organophosphorus substrates has been characterized and compared to the activity of the well-known phosphotriesterase from Pseudomonas diminuta (Pd-PTE). Structure prediction suggests that Sb-PTE has a β-propeller fold, and homology modeling has identified a potential mononuclear manganese binding site. Sb-PTE exhibits catalytic activity against typical phosphotriesterase substrates such as paraoxon, but unlike Pd-PTE, Sb-PTE is also able to effectively hydrolyze flame retardants, plasticizers, and industrial solvents. Sb-PTE can hydrolyze both phosphorus-oxygen bonds and phosphorus-sulfur bonds, but not phosphorus-nitrogen bonds. The best substrate for Sb-PTE is the flame retardant triphenyl phosphate with a kcat/Km of 1.7 × 10(6) M(-1) s(-1). Quite remarkably, Sb-PTE is also able to hydrolyze phosphotriesters with simple alcohol leaving groups such as tributyl phosphate (kcat/Km = 40 M(-1) s(-1)), suggesting that this enzyme could be useful for the bioremediation of a wide variety of organophosphorus compounds.

  9. Project Hotspot: Linear accumulation rates of late Cenozoic basalt at Kimama, Idaho, and implications for crustal strain and subsidence rates of the central Snake River Plain

    NASA Astrophysics Data System (ADS)

    Rodgers, D. W.; Potter, K. E.; Shervais, J. W.; Champion, D. E.; Duncan, R. A.

    2013-12-01

    Project Hotspot's Kimama drill hole on the Snake River Plain, Idaho recovered a 1912 m thick section of basalt core that ranges in age from ~700 ka to at least 6.14 Ma, based on five 40Ar/39Ar analyses and twenty paleomagnetic age assignments. Fifty-four flow groups comprising 510 individual flows were defined, yielding an average recurrence interval of ~11,400 years between flows. Age-depth analysis indicate that, over thicknesses >150 m and age spans >500 k.y., accumulation rates were constant at 30 m/100 k.y. The existence and persistence of this linear accumulation rate for greater than 5 m.y. documents an external tectonic control on eruption dynamics. One conceptual model relates accumulation rates to horizontal crustal strain, such that far-field extension rate controls the periodicity of dikes that feed basalt flows. In this model, each of the 54 flow groups would have a deep-seated, relatively wide (1-10m) dike that branches upward into a network of narrow (10-100 cm) dikes feeding individual lava flows. Assuming an east-west lateral lava flow extent of up to 50 km, the Kimama data record a steady-state crustal strain rate of 10-9 to 10-10 y-1. This rate is comparable to modern, decadal strain rates measured with GPS in the adjacent Basin & Range province, but exceeds decadal strain rates of zero measured in the eastern Snake River Plain. Linear accumulation rates also provide insight into basalt subsidence history. In this model, the middle-upper crust subsides due to the added weight of lava flows, the added weight of mid-crustal sills/dikes, and thermal contraction in the wake of the Yellowstone hot spot. Isostatic compensation would occur in the (nearly) molten lower crust. Assuming constant surface elevation and a basalt density of 2.6 g/cm3, the lava flow weight would account for 87% of the burial through time, yielding a steady-state "tectonic" subsidence rate of 4 m/100 k.y. attributed to the driving forces of mid-crustal injection and/or thermal

  10. Plastic response and correlations in athermally sheared amorphous solids

    NASA Astrophysics Data System (ADS)

    Puosi, F.; Rottler, J.; Barrat, J.-L.

    2016-09-01

    The onset of irreversible deformation in low-temperature amorphous solids is due to the accumulation of elementary events, consisting of spatially and temporally localized atomic rearrangements involving only a few tens of atoms. Recently, numerical and experimental work addressed the issue of spatiotemporal correlations between these plastic events. Here, we provide further insight into these correlations by investigating, via molecular dynamics (MD) simulations, the plastic response of a two-dimensional amorphous solid to artificially triggered local shear transformations. We show that while the plastic response is virtually absent in as-quenched configurations, it becomes apparent if a shear strain was previously imposed on the system. Plastic response has a fourfold symmetry, which is characteristic of the shear stress redistribution following the local transformation. At high shear rate we report evidence for a fluctuation-dissipation relation, connecting plastic response and correlation, which seems to break down if lower shear rates are considered.

  11. Resolving Mechanical Response of Plastic Bonded Explosives at High Strain-Rate Using Split Hopkinson Pressure Bar

    NASA Astrophysics Data System (ADS)

    Joshi, Vasant S.; Lee, Richard J.

    2002-07-01

    The mechanical properties of two explosives (PBXN-110 and PBXW-128) were determined using a split-Hopkinson pressure bar at strain rates between 103 /s and 104 /s. The stress-strain data for 1, 2 and 3-wave analysis were compared to determine when stress equalization was achieved in the test samples. PBXN-110 behaved similar to conventional Hopkinson bar samples, i.e., stress equalization was maintained for most of the loading cycle. Stress equalization was not achieved until late in the loading cycle for PBXW-128. This behavior eventually terminates during the compression process yielding a uniform response.

  12. InSAR time-series constraints on inter-seismic strain accumulation and creep distribution along North Anatolian and Chaman Faults

    NASA Astrophysics Data System (ADS)

    Havazli, E.; Fattahi, H.; Amelung, F.

    2013-12-01

    In many aspects, the San Andreas and the North Anatolian fault zones show many similarities. They are similarly right-lateral, strike-slip faults, at the same time, are transforms. However, they vary in the maximum amount of lateral displacement and show different topographic features. The maximum offset is nearly 300 km along the San Andreas Fault whereas it is approximately 85-90 km along the North Anatolian Fault. In recent years, interseismic crustal velocities and strains have been determined for North Anatolian Fault Zone through repeated measurements using the Global Positioning System and satellite radar interferometry. The Chaman Fault in Pakistan and Afghanistan is the only major fault along the western India-Eurasia plate boundary zone and probably accommodates the entire relative plate motion of 30-35 mm/yr. Recent GPS and InSAR studies on the Chaman fault yield slip rates of 18 × 1 mm/yr. The inconsistency in geologic, geodetic and seismic slip rates along the Chaman Fault need investigations to better understand the geodynamic responses of the Indo-Asia collision along its western boundary. We use InSAR time-series analysis using archived and new SAR imagery to constrain strain accumulation across the North Anatolian Fault and Chaman Faults. We expect a relative accuracy of InSAR measurements better than 1 mm/yr over 100 km, made possible by recent advances in flattening residual, orbital error and atmospheric correction strategies [Fattahi & Amelung, 2013]. After validation of the technique in Southern San Andreas Fault, using GPS observations, we apply the same InSAR time-series approach to constrain strain accumulation across the North Anatolian and Chaman Faults. We will use the InSAR data to establish the first-order fault properties of the Chaman and North Anatolian Faults (creep distribution, locking depth) using analytical two-dimensional elastic strain accumulation models along different transects across the faults. Our preliminary results

  13. Optimization of macroelement concentrations, pH and osmolarity for triacylglycerol accumulation in Rhodococcus opacus strain PD630

    PubMed Central

    2013-01-01

    The refinement of biodiesel or renewable diesel from bacterial lipids has a great potential to make a contribution for energy production in the future. This study provides new data concerning suitable nutrient concentrations for cultivation of the Gram-positive Rhodococcus opacus PD630, which is able to accumulate large amounts of lipids during nitrogen limitation. Enhanced concentrations of magnesium have been shown to increase the final optical density and the lipid content of the cells. Elevated phosphate concentrations slowed down the onset of the accumulation phase, without a clear effect on the final optical density and the cell’s lipid content. A robust growth of R. opacus was possible in the presence of ammonium concentrations of up to 1.4 g l-1 and sucrose concentrations of up to 240 g l-1, with an optimum regarding growth and lipid storage observed in the range of 0.2 to 0.4 g l-1 ammonium and 20 to 40 g l-1 sucrose, respectively. Moreover, R. opacus showed tolerance to high salt concentrations. PMID:23855965

  14. Strain accumulation in the New Madrid and Wabash Valley seismic zones from 14 years of continuous GPS observation

    NASA Astrophysics Data System (ADS)

    Craig, Timothy J.; Calais, Eric

    2014-12-01

    The mechanical behavior—and hence earthquake potential—of faults in continental interiors is an issue of critical importance for the resultant seismic hazard, but no consensus has yet been reached on this controversial topic. The debate has focused on the central and eastern United States, in particular, the New Madrid Seismic Zone, struck by four magnitude 7 or greater earthquakes in 1811-1812, and to a lesser extent the Wabash Valley Seismic Zone just to the north. A key aspect of this issue is the rate at which strain is currently accruing on those plate interior faults, a quantity that remains debated. Here we address this issue with an analysis of up to 14.6 years of continuous GPS data from a network of 200 sites in the central United States centered on the New Madrid and Wabash Valley seismic zones. We find that the high-quality sites in these regions show motions that are consistently within the 95% confidence limit of zero deformation. These results place an upper bound on strain accrual on faults of 0.2 mm/yr and 0.6 mm/yr in the New Madrid and Wabash Valley Seismic Zones, respectively. For the New Madrid region, where a paleoseismic record is available for the past ˜5000 years, we argue that strain accrual—if any—does not permit the 500-900 year repeat time of paleo-earthquakes observed in the Upper Mississippi Embayment. These results, together with increasing evidence for temporal clustering and spatial migration of earthquake sequences in continental interiors, indicate that either tectonic loading rates or fault properties vary with time in the New Madrid Seismic Zone and possibly plate wide.

  15. Effect of severe plastic deformation on microstructure and mechanical properties of magnesium and aluminium alloys in wide range of strain rates

    NASA Astrophysics Data System (ADS)

    Skripnyak, Vladimir; Skripnyak, Evgeniya; Skripnyak, Vladimir; Vaganova, Irina; Skripnyak, Nataliya

    2013-06-01

    Results of researches testify that a grain size have a strong influence on the mechanical behavior of metals and alloys. Ultrafine grained HCP and FCC metal alloys present higher values of the spall strength than a corresponding coarse grained counterparts. In the present study we investigate the effect of grain size distribution on the flow stress and strength under dynamic compression and tension of aluminium and magnesium alloys. Microstructure and grain size distribution in alloys were varied by carrying out severe plastic deformation during the multiple-pass equal channel angular pressing, cyclic constrained groove pressing, and surface mechanical attrition treatment. Tests were performed using a VHS-Instron servo-hydraulic machine. Ultra high speed camera Phantom V710 was used for photo registration of deformation and fracture of specimens in range of strain rates from 0,01 to 1000 1/s. In dynamic regime UFG alloys exhibit a stronger decrease in ductility compared to the coarse grained material. The plastic flow of UFG alloys with a bimodal grain size distribution was highly localized. Shear bands and shear crack nucleation and growth were recorded using high speed photography.

  16. Relationship between Nitrite Reduction and Active Phosphate Uptake in the Phosphate-Accumulating Denitrifier Pseudomonas sp. Strain JR 12

    PubMed Central

    Barak, Yoram; van Rijn, Jaap

    2000-01-01

    Phosphate uptake by the phosphate-accumulating denitrifier Pseudomonas sp. JR12 was examined with different combinations of electron and carbon donors and electron acceptors. Phosphate uptake in acetate-supplemented cells took place with either oxygen or nitrate but did not take place when nitrite served as the final electron acceptor. Furthermore, nitrite reduction rates by this denitrifier were shown to be significantly reduced in the presence of phosphate. Phosphate uptake assays in the presence of the H+-ATPase inhibitor N,N′-dicyclohexylcarbodiimide (DCCD), in the presence of the uncoupler carbonyl cyanide 3-chlorophenylhydrazone (CCCP), or with osmotic shock-treated cells indicated that phosphate transport over the cytoplasmic membrane of this bacterium was mediated by primary and secondary transport systems. By examining the redox transitions of whole cells at 553 nm we found that phosphate addition caused a significant oxidation of a c-type cytochrome. Based on these findings, we propose that this c-type cytochrome serves as an intermediate in the electron transfer to both nitrite reductase and the site responsible for active phosphate transport. In previous studies with this bacterium we found that the oxidation state of this c-type cytochrome was significantly higher in acetate-supplemented, nitrite-respiring cells (incapable of phosphate uptake) than in phosphate-accumulating cells incubated with different combinations of electron donors and acceptors. Based on the latter finding and results obtained in the present study it is suggested that phosphate uptake in this bacterium is subjected to a redox control of the active phosphate transport site. By means of this mechanism an explanation is provided for the observed absence of phosphate uptake in the presence of nitrite and inhibition of nitrite reduction by phosphate in this organism. The implications of these findings regarding denitrifying, phosphate removal wastewater plants is discussed. PMID

  17. A simplified method for elastic-plastic-creep structural analysis

    NASA Technical Reports Server (NTRS)

    Kaufman, A.

    1985-01-01

    A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

  18. A simplified method for elastic-plastic-creep structural analysis

    NASA Technical Reports Server (NTRS)

    Kaufman, A.

    1984-01-01

    A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

  19. Construction of a Vibrio cholerae prototype vaccine strain O395-N1-E1 which accumulates cell-associated cholera toxin B subunit.

    PubMed

    Rhie, Gi-eun; Jung, Hae-Mi; Kim, Bong Su; Mekalanos, John J

    2008-10-01

    Because of its production and use in Vietnam, the most widely used oral cholera vaccine consists of heat- or formalin-killed Vibrio cholerae whole cells (WC). An earlier version of this type of vaccine called whole cell-recombinant B subunit vaccine (BS-WC) produced in Sweden also contained the B subunit of cholera toxin (CTB). Both WC and BS-WC vaccines produced moderate levels of protection in field trials designed to evaluate their cholera efficacy. V. cholerae cells in these vaccines induce antibacterial immunity, and CTB contributes to the vaccine's efficacy presumably by stimulating production of anti-toxin neutralizing antibody. Although more effective than the WC vaccine, the BS-WC vaccine has not been adopted for manufacture by developing world countries primarily because the CTB component is difficult to manufacture and include in the vaccine in the doses needed to induce significant immune responses. We reasoned this was a technical problem that might be solved by engineering strains of V. cholerae that express cell-associated CTB that would co-purify with the bacterial cell fraction during the manufacture of WC vaccine. Here we report that construction of a V. cholerae O1 classical strain, O395-N1-E1, that has been engineered to accumulate CTB in the periplasmic fraction by disrupting the epsE gene of type II secretion pathway. O395-N1-E1 induces anti-CTB IgG and vibriocidal antibodies in mice immunized with two doses of formalin killed whole cells. Intraperitoneal immunization of mice with O395-N1-E1 induced a significantly higher anti-CTB antibody response compared to that of the parental strain, O395-N1. Our results suggest that this prototype cholera vaccine candidate strain may assist in preparing improved and inexpensive oral BS-WC cholera vaccine without the need to purify CTB separately. PMID:18582519

  20. Effect of intense plastic straining on microstructure and mechanical properties of an Al-Mg-Sc alloy

    NASA Astrophysics Data System (ADS)

    Kaibyshev, R.; Avtokratova, E.; Sitdikov, O.

    2010-07-01

    An Al-5%Mg-0.18%Mn-0.2%Sc-0.08%Zr-0.002%Be was subjected to equal-channel angular extrusion up to true strains of ~3 and ~8, that resulted in the formation of partially recrystallized and fully recrystallized structure, respectively. It was shown that the alloy with partially recrystallized structure exhibits highest strength and ductility. The material with fully recrystallized structure showed lowest fatigue crack growth rate and highest value of fracture toughness. Reasons of this unusual effect of microstructure on crack propagation resistance under fatigue are discussed.

  1. [Study of the Accumulation of Rec A from Bacillus subtilis in the Mitochondria of a Recombinant Strain of the Yeast Yarrowia lipolytica].

    PubMed

    Isakova, E P; Deryabina, Y I; Leonovich, O A; Zylkova, M V; Biriukova, Iu K

    2016-01-01

    No eukaryotic species has a system for homologous DNA recombination of the mitochondrial genome. We report on an integrative genetic systembased on the pQ-SRUS construct that allows the expression of the RecA recombinase from Bacillus subtilis and its transportation to mitochondria of Yarrowia lipolytica. The targeting of recombinant RecA to mitochondria is provided by leader sequences (5'-UTR and 3-UTR) derived from the SOD2 gene mRNA, which exhibit affinity to the outer mitochondrial membrane and provides cotranslational import of RecA to the inner space of mitochondria. The accumulation of RecA in mitochondria of the Y. lipolytica recombinant strain bearing the pQ-SRUS construct has been shown by immunoblotting of purified mitochondrial preparations.

  2. Differential accumulation of poly(A)+ RNA between virulent and double-stranded RNA-induced hypovirulent strains of Cryphonectria (Endothia) parasitica.

    PubMed Central

    Powell, W A; Van Alfen, N K

    1987-01-01

    The double-stranded RNA responsible for transmissible hypovirulence in Cryphonectria (Endothia) parasitica was found to affect the accumulation of specific poly(A)+ RNA. Using differential hybridization techniques, two genes were isolated, Vir1 and Vir2, which were specifically expressed as poly(A)+ RNAs in the virulent cells. The highly expressed RNA sequences from these genes were not found in total RNA isolated from either American or European hypovirulent strains, although the genes were present in their genomes. Other virulence- and hypovirulence-specific RNA sequences were also detected. One isolated hypovirulence-specific RNA sequence was expressed in both virulent and hypovirulent cells, but in a two- to fourfold-higher concentration in the hypovirulent cells. The results show that hypovirulence is associated with concurrent changes in a few highly expressed poly(A)+ RNAs, which suggests a specific effect of the double-stranded RNA on fungal gene expression. Images PMID:2446118

  3. [Study of the Accumulation of Rec A from Bacillus subtilis in the Mitochondria of a Recombinant Strain of the Yeast Yarrowia lipolytica].

    PubMed

    Isakova, E P; Deryabina, Y I; Leonovich, O A; Zylkova, M V; Biriukova, Iu K

    2016-01-01

    No eukaryotic species has a system for homologous DNA recombination of the mitochondrial genome. We report on an integrative genetic systembased on the pQ-SRUS construct that allows the expression of the RecA recombinase from Bacillus subtilis and its transportation to mitochondria of Yarrowia lipolytica. The targeting of recombinant RecA to mitochondria is provided by leader sequences (5'-UTR and 3-UTR) derived from the SOD2 gene mRNA, which exhibit affinity to the outer mitochondrial membrane and provides cotranslational import of RecA to the inner space of mitochondria. The accumulation of RecA in mitochondria of the Y. lipolytica recombinant strain bearing the pQ-SRUS construct has been shown by immunoblotting of purified mitochondrial preparations. PMID:27266246

  4. The French neurotropic vaccine strain of yellow fever virus accumulates mutations slowly during passage in cell culture.

    PubMed

    Holbrook, M R; Li, L; Suderman, M T; Wang, H; Barrett, A D

    2000-08-01

    This study of the yellow fever French neurotropic vaccine strain from the Institut Pasteur (FNV-IP) demonstrates that this viral genome is not as stable as that of the 17D-204 vaccine virus. FNV-IP was plaque-purified three times and then passaged eight times in Vero cells. Viral populations from the second and eighth passage post purification were sequenced and compared to the published sequences of FNV-IP. The passage-2 viral population had 31 nucleotide and nine amino acid changes compared to the parental virus while the passage-8 virus had six additional nucleotide changes encoding a single amino acid substitution. The plaque-purified virus also had two sequence deletions in the 3'-noncoding region. The plaque purification resulted in selection of a passage-2 virus that had a mouse LD(50) of 20 pfu/ml, 67-fold greater than parental FNV-IP which had an LD(50) of 0.3 pfu/ml. Subsequent passage in Vero cells resulted in a passage-8 virus which had increased neurovirulence with an LD(50) of 3.2 pfu/ml. The only amino acid difference between the passage-2 and passage-8 viruses was at amino acid 638 of NS5 which lies within domain V of the RNA-dependent-RNA polymerase. Overall, these data indicate that FNV-IP virus has an inherently less stable genome than 17D vaccine virus and a variable viral population.

  5. Escherichia coli rimM and yjeQ null strains accumulate immature 30S subunits of similar structure and protein complement

    PubMed Central

    Leong, Vivian; Kent, Meredith; Jomaa, Ahmad; Ortega, Joaquin

    2013-01-01

    Assembly of the Escherichia coli 30S ribosomal subunits proceeds through multiple parallel pathways. The protein factors RimM, YjeQ, RbfA, and Era work in conjunction to assist at the late stages of the maturation process of the small subunit. However, it is unclear how the functional interplay between these factors occurs in the context of multiple parallel pathways. To understand how these factors work together, we have characterized the immature 30S subunits that accumulate in ΔrimM cells and compared them with immature 30S subunits from a ΔyjeQ strain. The cryo-EM maps obtained from these particles showed that the densities representing helices 44 and 45 in the rRNA were partially missing, suggesting mobility of these motifs. These 30S subunits were also partially depleted in all tertiary ribosomal proteins, particularly those binding in the head domain. Using image classification, we identified four subpopulations of ΔrimM immature 30S subunits differing in the amount of missing density for helices 44 and 45, as well as the amount of density existing in these maps for the underrepresented proteins. The structural defects found in these immature subunits resembled those of the 30S subunits that accumulate in the ΔyjeQ strain. These findings are consistent with an “early convergency model” in which multiple parallel assembly pathways of the 30S subunit converge into a late assembly intermediate, as opposed to the mature state. Functionally related factors will bind to this intermediate to catalyze the last steps of maturation leading to the mature 30S subunit. PMID:23611982

  6. Bacterial production of the biodegradable plastics polyhydroxyalkanoates.

    PubMed

    Urtuvia, Viviana; Villegas, Pamela; González, Myriam; Seeger, Michael

    2014-09-01

    Petroleum-based plastics constitute a major environmental problem due to their low biodegradability and accumulation in various environments. Therefore, searching for novel biodegradable plastics is of increasing interest. Microbial polyesters known as polyhydroxyalkanoates (PHAs) are biodegradable plastics. Life cycle assessment indicates that PHB is more beneficial than petroleum-based plastics. In this report, bacterial production of PHAs and their industrial applications are reviewed and the synthesis of PHAs in Burkholderia xenovorans LB400 is described. PHAs are synthesized by a large number of microorganisms during unbalanced nutritional conditions. These polymers are accumulated as carbon and energy reserve in discrete granules in the bacterial cytoplasm. 3-hydroxybutyrate and 3-hydroxyvalerate are two main PHA units among 150 monomers that have been reported. B. xenovorans LB400 is a model bacterium for the degradation of polychlorobiphenyls and a wide range of aromatic compounds. A bioinformatic analysis of LB400 genome indicated the presence of pha genes encoding enzymes of pathways for PHA synthesis. This study showed that B. xenovorans LB400 synthesize PHAs under nutrient limitation. Staining with Sudan Black B indicated the production of PHAs by B. xenovorans LB400 colonies. The PHAs produced were characterized by GC-MS. Diverse substrates for the production of PHAs in strain LB400 were analyzed.

  7. Comparison of methods for quantitating Salmonella enterica Typhimurium and Heidelberg strain attachment to reusable plastic shipping container coupons and preliminary assessment of sanitizer efficacy.

    PubMed

    Shi, Zhaohao; Baker, Christopher A; Lee, Sang In; Park, Si Hong; Kim, Sun Ae; Ricke, Steven C

    2016-09-01

    Salmonella serovars, one of the leading contributors to foodborne illness and are especially problematic for foods that are not cooked before consumption, such as fresh produce. The shipping containers that are used to transport and store fresh produce may play a role in cross contamination and subsequent illnesses. However, methods for quantitatively attached cells are somewhat variable. The overall goal of this study was to compare conventional plating with molecular methods for quantitating attached representative strains for Salmonella Typhimurium and Heidelberg on reusable plastic containers (RPC) coupons, respectively. We attached Salmonella enterica serovar Typhimurium ATCC 14028 and serovar Heidelberg SL486 (parent and an antibiotic resistant marker strain) to plastic coupons (2.54 cm(2)) derived from previously used shipping containers by growing for 72 h in tryptic soy broth. The impact of the concentration of sanitizer on log reductions between unsanitized and sanitized coupons was evaluated by exposing attached S. Typhimurium cells to 200 ppm and 200,000 ppm sodium hypochlorite (NaClO). Differences in sanitizer effectiveness between serovars were also evaluated with attached S. Typhimurium compared to attached S. Heidelberg populations after being exposed to 200 ppm peracetic acid (PAA). Treatment with NaClO caused an average of 2.73 ± 0.23 log CFU of S. Typhimurium per coupon removed with treatment at 200 ppm while 3.36 ± 0.54 log CFU were removed at 200,000 ppm. Treatment with PAA caused an average of 2.62 ± 0.15 log CFU removed for S. Typhimurium and 1.41 ± 0.17 log CFU for S. Heidelberg (parent) and 1.61 ± 0.08 log CFU (marker). Lastly, scanning electron microscopy (SEM) was used to visualize cell attachment and coupon surface topography. SEM images showed that remaining attached cell populations were visible even after sanitizer application. Conventional plating and qPCR yielded similar levels of enumerated bacterial populations

  8. Comparison of methods for quantitating Salmonella enterica Typhimurium and Heidelberg strain attachment to reusable plastic shipping container coupons and preliminary assessment of sanitizer efficacy.

    PubMed

    Shi, Zhaohao; Baker, Christopher A; Lee, Sang In; Park, Si Hong; Kim, Sun Ae; Ricke, Steven C

    2016-09-01

    Salmonella serovars, one of the leading contributors to foodborne illness and are especially problematic for foods that are not cooked before consumption, such as fresh produce. The shipping containers that are used to transport and store fresh produce may play a role in cross contamination and subsequent illnesses. However, methods for quantitatively attached cells are somewhat variable. The overall goal of this study was to compare conventional plating with molecular methods for quantitating attached representative strains for Salmonella Typhimurium and Heidelberg on reusable plastic containers (RPC) coupons, respectively. We attached Salmonella enterica serovar Typhimurium ATCC 14028 and serovar Heidelberg SL486 (parent and an antibiotic resistant marker strain) to plastic coupons (2.54 cm(2)) derived from previously used shipping containers by growing for 72 h in tryptic soy broth. The impact of the concentration of sanitizer on log reductions between unsanitized and sanitized coupons was evaluated by exposing attached S. Typhimurium cells to 200 ppm and 200,000 ppm sodium hypochlorite (NaClO). Differences in sanitizer effectiveness between serovars were also evaluated with attached S. Typhimurium compared to attached S. Heidelberg populations after being exposed to 200 ppm peracetic acid (PAA). Treatment with NaClO caused an average of 2.73 ± 0.23 log CFU of S. Typhimurium per coupon removed with treatment at 200 ppm while 3.36 ± 0.54 log CFU were removed at 200,000 ppm. Treatment with PAA caused an average of 2.62 ± 0.15 log CFU removed for S. Typhimurium and 1.41 ± 0.17 log CFU for S. Heidelberg (parent) and 1.61 ± 0.08 log CFU (marker). Lastly, scanning electron microscopy (SEM) was used to visualize cell attachment and coupon surface topography. SEM images showed that remaining attached cell populations were visible even after sanitizer application. Conventional plating and qPCR yielded similar levels of enumerated bacterial populations

  9. Three-dimensional modeling of plastic deformation flow during ECAP

    SciTech Connect

    Budilov, I. N.; Alexandrov, I. V.; Beyerlein, Irene J.; Lukaschuk, Y. V.; Zhernakov, V. S.

    2004-01-01

    Plastic flow during equal-channel angular pressing (ECAP) of a copper billet is analyzed in this paper using three-dimensional finite element. The influence of the outer die radius and friction coefficient on the homogeneity in the accumulated plastic strain distribution is investigated. An increase in either outer radius or friction conditions was found to decrease the size of the steady-state region and increase heterogeneity in the final strain distribution from top to bottom and from side to side. Recent investigations have clearly demonstrated the great potential of the severe plastic deformation (SPD) methods, particularly by means of equal-channel angular pressing (ECAP), for ultra-fine grain refinement in various metals and alloys. One of the biggest challenges faced is the fabrication of larger and larger bulk ECAP samples with a uniform desired microstructure, e.g. equiaxed ultra-fine grains, and hence outstanding mechanical properties characteristic of such SPD materials. The degree of homogeneity depends on a myriad of processing and material variables. Numerical methods, such as finite elements (FE), have been an important tool in simulating the ECAP process and exploring the large ECAP parameter space, such as the pressing route and number of passes, die channel intersection angle, outer radius of the die, friction coefficient, pressing rate, material deformation response, and backpressure, e.g. Studying the effects of several factors simultaneously, however, can potentially lead to ambiguous conclusions about the regularities in the plastic flow, regularities in the material fill status, or the final distributions of accumulated total plastic strain. Thus more systematic studies using FE coupled with theoretical considerations are needed. Also, most of the FE studies found in the literature are two-dimensional analyses, and therefore cannot make conclusions regarding the influence of the confined character of plastic deformation on plastic flow in

  10. Our plastic age.

    PubMed

    Thompson, Richard C; Swan, Shanna H; Moore, Charles J; vom Saal, Frederick S

    2009-07-27

    Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production. In this Theme Issue of Philosophical Transactions of the Royal Society, we describe current and future trends in usage, together with the many benefits that plastics bring to society. At the same time, we examine the environmental consequences resulting from the accumulation of waste plastic, the effects of plastic debris on wildlife and concerns for human health that arise from the production, usage and disposal of plastics. Finally, we consider some possible solutions to these problems together with the research and policy priorities necessary for their implementation.

  11. Our plastic age

    PubMed Central

    Thompson, Richard C.; Swan, Shanna H.; Moore, Charles J.; vom Saal, Frederick S.

    2009-01-01

    Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production. In this Theme Issue of Philosophical Transactions of the Royal Society, we describe current and future trends in usage, together with the many benefits that plastics bring to society. At the same time, we examine the environmental consequences resulting from the accumulation of waste plastic, the effects of plastic debris on wildlife and concerns for human health that arise from the production, usage and disposal of plastics. Finally, we consider some possible solutions to these problems together with the research and policy priorities necessary for their implementation. PMID:19528049

  12. Our plastic age.

    PubMed

    Thompson, Richard C; Swan, Shanna H; Moore, Charles J; vom Saal, Frederick S

    2009-07-27

    Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production. In this Theme Issue of Philosophical Transactions of the Royal Society, we describe current and future trends in usage, together with the many benefits that plastics bring to society. At the same time, we examine the environmental consequences resulting from the accumulation of waste plastic, the effects of plastic debris on wildlife and concerns for human health that arise from the production, usage and disposal of plastics. Finally, we consider some possible solutions to these problems together with the research and policy priorities necessary for their implementation. PMID:19528049

  13. Purification, characterization, and cloning of the gene for a biodegradable plastic-degrading enzyme from Paraphoma-related fungal strain B47-9.

    PubMed

    Suzuki, Ken; Noguchi, Masako Tsujimoto; Shinozaki, Yukiko; Koitabashi, Motoo; Sameshima-Yamashita, Yuka; Yoshida, Shigenobu; Fujii, Takeshi; Kitamoto, Hiroko K

    2014-05-01

    Paraphoma-related fungal strain B47-9 secreted a biodegradable plastic (BP)-degrading enzyme which amounted to 68 % (w/w) of the total secreted proteins in a culture medium containing emulsified poly(butylene succinate-co-adipate) (PBSA) as sole carbon source. The gene for this enzyme was found to be composed of an open reading frame consisting of 681 nucleotides encoding 227 amino acids and two introns. Southern blot analysis showed that this gene exists as a single copy. The deduced amino acid sequence suggested that this enzyme belongs to the cutinase (E.C.3.1.1.74) family; thus, it was named P araphoma-related fungus cutinase-like enzyme (PCLE). It degraded various types of BP films, such as poly(butylene succinate), PBSA, poly(butylene adipate-co-terephthalate), poly(ε-caprolactone), and poly(DL-lactic acid). It has a molecular mass of 19.7 kDa, and an optimum pH and temperature for degradation of emulsified PBSA of 7.2 and 45 °C, respectively. Ca(2+) ion at a concentration of about 1.0 mM markedly enhanced the degradation of emulsified PBSA. PMID:24384748

  14. Purification, characterization, and cloning of the gene for a biodegradable plastic-degrading enzyme from Paraphoma-related fungal strain B47-9.

    PubMed

    Suzuki, Ken; Noguchi, Masako Tsujimoto; Shinozaki, Yukiko; Koitabashi, Motoo; Sameshima-Yamashita, Yuka; Yoshida, Shigenobu; Fujii, Takeshi; Kitamoto, Hiroko K

    2014-05-01

    Paraphoma-related fungal strain B47-9 secreted a biodegradable plastic (BP)-degrading enzyme which amounted to 68 % (w/w) of the total secreted proteins in a culture medium containing emulsified poly(butylene succinate-co-adipate) (PBSA) as sole carbon source. The gene for this enzyme was found to be composed of an open reading frame consisting of 681 nucleotides encoding 227 amino acids and two introns. Southern blot analysis showed that this gene exists as a single copy. The deduced amino acid sequence suggested that this enzyme belongs to the cutinase (E.C.3.1.1.74) family; thus, it was named P araphoma-related fungus cutinase-like enzyme (PCLE). It degraded various types of BP films, such as poly(butylene succinate), PBSA, poly(butylene adipate-co-terephthalate), poly(ε-caprolactone), and poly(DL-lactic acid). It has a molecular mass of 19.7 kDa, and an optimum pH and temperature for degradation of emulsified PBSA of 7.2 and 45 °C, respectively. Ca(2+) ion at a concentration of about 1.0 mM markedly enhanced the degradation of emulsified PBSA.

  15. Stochastic approach to plasticity and yield in amorphous solids

    NASA Astrophysics Data System (ADS)

    Hentschel, H. G. E.; Jaiswal, Prabhat K.; Procaccia, Itamar; Sastry, Srikanth

    2015-12-01

    We focus on the probability distribution function (PDF) P (Δ γ ;γ ) where Δ γ are the measured strain intervals between plastic events in a athermal strained amorphous solids, and γ measures the accumulated strain. The tail of this distribution as Δ γ →0 (in the thermodynamic limit) scales like Δ γη . The exponent η is related via scaling relations to the tail of the PDF of the eigenvalues of the plastic modes of the Hessian matrix P (λ ) which scales like λθ, η =(θ -1 )/2 . The numerical values of η or θ can be determined easily in the unstrained material and in the yielded state of plastic flow. Special care is called for in the determination of these exponents between these states as γ increases. Determining the γ dependence of the PDF P (Δ γ ;γ ) can shed important light on plasticity and yield. We conclude that the PDF's of both Δ γ and λ are not continuous functions of γ . In slowly quenched amorphous solids they undergo two discontinuous transitions, first at γ =0+ and then at the yield point γ =γ Y to plastic flow. In quickly quenched amorphous solids the second transition is smeared out due to the nonexisting stress peak before yield. The nature of these transitions and scaling relations with the system size dependence of <Δ γ > are discussed.

  16. Stochastic approach to plasticity and yield in amorphous solids.

    PubMed

    Hentschel, H G E; Jaiswal, Prabhat K; Procaccia, Itamar; Sastry, Srikanth

    2015-12-01

    We focus on the probability distribution function (PDF) P(Δγ;γ) where Δγ are the measured strain intervals between plastic events in a athermal strained amorphous solids, and γ measures the accumulated strain. The tail of this distribution as Δγ→0 (in the thermodynamic limit) scales like Δγ(η). The exponent η is related via scaling relations to the tail of the PDF of the eigenvalues of the plastic modes of the Hessian matrix P(λ) which scales like λ(θ), η=(θ-1)/2. The numerical values of η or θ can be determined easily in the unstrained material and in the yielded state of plastic flow. Special care is called for in the determination of these exponents between these states as γ increases. Determining the γ dependence of the PDF P(Δγ;γ) can shed important light on plasticity and yield. We conclude that the PDF's of both Δγ and λ are not continuous functions of γ. In slowly quenched amorphous solids they undergo two discontinuous transitions, first at γ=0(+) and then at the yield point γ=γ(Y) to plastic flow. In quickly quenched amorphous solids the second transition is smeared out due to the nonexisting stress peak before yield. The nature of these transitions and scaling relations with the system size dependence of 〈Δγ〉 are discussed.

  17. The strain accumulation studies between India and Antarctica in the Southern Indian Peninsula with GPS/GNSS-Geodesy by geodetically tying the two continents

    NASA Astrophysics Data System (ADS)

    Narayana Babu, R. N.; EC, M.

    2011-12-01

    Two global networks (IND and ANT) have been chosen that geodetically connect the two continents to holistically understand the geodynamical and crustal deformation processes in the south of Indian peninsula between India and Antarctica,. Since the baseline length between HYDE, India and MAIT, Antarctica is more than 10,000 km, it is mandatory to form these two different networks to improve the accuracy of the baseline measurements by GPS and so the IGS Station at Diego Garcia (DGAR) is chosen as the common station between the two networks. 13 years of data from 1997 to 2010 were used. By these global networks' analyses, the stations HYDE and MAIT are geodetically tied through DGAR. Very long baselines have been estimated from HYDE and also from Kerguelen (KERG) to other chosen IGS stations in and around India and Antarctica. Our analysis and results using ANT network show an increase in the baseline lengths between Kerguelen in Antarctic plate and other stations such as SEY1, DGAR and COCO and shortening of baseline lengths between HYDE in Indian plate and all these above stations using IND network. The analysis using ANT network also shows lengthening of baselines from Kerguelen to the sites Yaragadee (YAR1) and Tidbinbilla (TID2) in Australian plate; and Seychelles (SEY1) in Male plate, COCO in the diffuse plate boundary between India and Australia and DGAR in Capricorn plate at the rates of 5.3cm/yr, 3.8cm/yr, 5.6mm/yr, 3.03 cm/yr and 5.5 cm/yr respectively. The high rate of movement of COCO Island in comparison to Seychelles could be the result of excessive strain accumulation due to the Indo-Australia diffuse plate boundary forces acting upon this region. The estimated elastic strain accumulation shows an increasing trend of 1.27x 10-8 yr-1 in the south of Indian peninsula. Our results show the precision of approximately 3-4mm (North), 5-6 mm (East), and 10-12mm (vertical) for the estimation of site coordinates. These results provide new information on the

  18. Geodetic Tying of Antarctica and India With 10 Years of Continuous GPS Measurements for Geodynamical and Strain Accumulation Studies in the South of Indian Peninsula

    NASA Astrophysics Data System (ADS)

    Ec, M.; N, R.

    2008-12-01

    To holistically understand the geodynamical and crustal deformation processes between India and Antarctica, two global networks (IND and ANT) have been chosen. The objective is to geodetically connect the two continents. The IGS Station at Diego Garcia (DGAR) is the common station between the two networks. 10 years of data from 1997 to 2007 were used. By these global networks' analyses, the stations HYDE in India and MAIT at Antarctica are geodetically tied through the station DGAR. Very long baselines have been estimated from HYDE and also from Kerguelen (KERG) to other chosen IGS stations in and around India and Antarctica. Our analysis and results using ANT network show an increase in the baseline lengths between Kerguelen in Antarctic plate and other stations such as SEY1, DGAR and COCO and shortening of baseline lengths between HYDE in Indian plate and all these above stations using IND network. The analysis using ANT network also shows lengthening of baselines from Kerguelen to the sites Yaragadee (YAR1) and Tidbinbilla (TID2) in Australian plate; and Seychelles (SEY1) in Male plate, COCO in the diffuse plate boundary between India and Australia and DGAR in Capricorn plate at the rates of 5.3cm/yr, 3.8cm/yr, 5.6mm/yr, 3.03 cm/yr and 5.5 cm/yr respectively. The high rate of movement of COCO Island in comparison to Seychelles could be the result of excessive strain accumulation due to the Indo-Australia diffuse plate boundary forces acting upon this region. The estimated elastic strain accumulation shows an increasing trend of 1.27x 10-8 yr-1 in the south of Indian peninsula. Our results show the precision of approximately 3-4mm (North), 5-6 mm (East), and 10-12mm (vertical) for the estimation of site coordinates. These results provide new information on the direction and rate of Indian plate motion, the driving mechanisms of Indian plate and intraplate seismicity of the Indian Ocean on the whole.

  19. Shear-wave Velocity Structure and Inter-Seismic Strain Accumulation in the Up-Dip Region of the Cascadia Subduction Zone: Similarities to Tohoku?

    NASA Astrophysics Data System (ADS)

    Collins, J. A.; McGuire, J. J.; Wei, M.

    2013-12-01

    the measured compliances in this frequency band using a genetic algorithm that solves for the S-wave velocity, P-wave velocity, and density in a layered structure. By including constraints on the Vp distribution from active-source studies, these parameters appear well constrained down to about 4 km depth from our dataset. There is a clear difference in observed compliance values between stations close to the deformation front (~10 km) and those further up the continental slope (~30-40 km) indicating a region of unconsolidated, high-porosity sediment similar to the off-Tohoku region. The low S-wave velocities and high Vp/Vs ratios in the up-dip region correspond to unconsolidated high-porosity sediments. We calculated the effect of this material property contrast on the inter-seismic strain accumulation in the up-dip region of the subduction zone using a finite element model and find that the sediments can increase the amount of inter-seismic strain accumulated in the up-dip region by >100% relative to a homogenous elastic model.

  20. Elevated temperature differentially affects virulence, VirB protein accumulation, and T-pilus formation in different Agrobacterium tumefaciens and Agrobacterium vitis strains.

    PubMed

    Baron, C; Domke, N; Beinhofer, M; Hapfelmeier, S

    2001-12-01

    That gene transfer to plant cells is a temperature-sensitive process has been known for more than 50 years. Previous work indicated that this sensitivity results from the inability to assemble a functional T pilus required for T-DNA and protein transfer to recipient cells. The studies reported here extend these observations and more clearly define the molecular basis of this assembly and transfer defect. T-pilus assembly and virulence protein accumulation were monitored in Agrobacterium tumefaciens strain C58 at different temperatures ranging from 20 degrees C to growth-inhibitory 37 degrees C. Incubation at 28 degrees C but not at 26 degrees C strongly inhibited extracellular assembly of the major T-pilus component VirB2 as well as of pilus-associated protein VirB5, and the highest amounts of T pili were detected at 20 degrees C. Analysis of temperature effects on the cell-bound virulence machinery revealed three classes of virulence proteins. Whereas class I proteins (VirB2, VirB7, VirB9, and VirB10) were readily detected at 28 degrees C, class II proteins (VirB1, VirB4, VirB5, VirB6, VirB8, VirB11, VirD2, and VirE2) were only detected after cell growth below 26 degrees C. Significant levels of class III proteins (VirB3 and VirD4) were only detected at 20 degrees C and not at higher temperatures. Shift of virulence-induced agrobacteria from 20 to 28 or 37 degrees C had no immediate effect on cell-bound T pili or on stability of most virulence proteins. However, the temperature shift caused a rapid decrease in the amount of cell-bound VirB3 and VirD4, and VirB4 and VirB11 levels decreased next. To assess whether destabilization of virulence proteins constitutes a general phenomenon, levels of virulence proteins and of extracellular T pili were monitored in different A. tumefaciens and Agrobacterium vitis strains grown at 20 and 28 degrees C. Levels of many virulence proteins were strongly reduced at 28 degrees C compared to 20 degrees C, and T-pilus assembly did

  1. Accumulate repeat accumulate codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative channel coding scheme called 'Accumulate Repeat Accumulate codes' (ARA). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes, thus belief propagation can be used for iterative decoding of ARA codes on a graph. The structure of encoder for this class can be viewed as precoded Repeat Accumulate (RA) code or as precoded Irregular Repeat Accumulate (IRA) code, where simply an accumulator is chosen as a precoder. Thus ARA codes have simple, and very fast encoder structure when they representing LDPC codes. Based on density evolution for LDPC codes through some examples for ARA codes, we show that for maximum variable node degree 5 a minimum bit SNR as low as 0.08 dB from channel capacity for rate 1/2 can be achieved as the block size goes to infinity. Thus based on fixed low maximum variable node degree, its threshold outperforms not only the RA and IRA codes but also the best known LDPC codes with the dame maximum node degree. Furthermore by puncturing the accumulators any desired high rate codes close to code rate 1 can be obtained with thresholds that stay close to the channel capacity thresholds uniformly. Iterative decoding simulation results are provided. The ARA codes also have projected graph or protograph representation that allows for high speed decoder implementation.

  2. Plastic Surgery

    MedlinePlus

    ... How Can I Help a Friend Who Cuts? Plastic Surgery KidsHealth > For Teens > Plastic Surgery Print A ... her forehead lightened with a laser? What Is Plastic Surgery? Just because the name includes the word " ...

  3. Time series analysis of strain accumulation along the Haiyuan fault (Gansu, China) over the 1993-2009 period, from ERS and ENVISAT InSAR data

    NASA Astrophysics Data System (ADS)

    Jolivet, Romain; Lasserre, Cecile; Doin, Marie-Pierre; Guillaso, Stéphane; Cavalié, Olivier; Peltzer, Gilles; Sun, Jianbao; Rong, Dailu; Shen, Zheng-Kang; Xu, Xiwei

    2010-05-01

    We use SAR interferometry to measure the strain accumulation along the left-lateral Haiyuan fault system (HFS), that marks the north-eastern boundary of the tibetan plateau. The last major earthquakes that occured along the HFS are the M~8 1920 Haiyuan earthquake (strike-slip mechanism) and the Ml=8-8.3 1927 Gulang earthquake that ruptured a thrust fault system. No large earthquake is reported on the central section of the HFS, the "Tianzhu seismic gap", since ~1000 years. We first analyze the complete ENVISAT SAR data archive along 4 descending and 2 ascending tracks for the 2003-2009 period and construct an InSAR-based mean Line-Of-Sight (LOS) velocity map around the HFS from the eastern end of the Qilian shan (102° E), to the west, to the Liupan shan (106° E), to the east. Data are processed using a small baseline chain type. For each track, all radar images are coregistrated to a single master and interferograms are produced using a local adaptative range filtering. Residual orbital and atmospheric delays are jointly inverted and corrected for each unwrapped interferogram. Atmospheric corrections are validated using the ERA40 global atmospheric model (ECMWF). The interferograms series on each track are then inverted to obtain the increments of LOS radar delays between acquisition dates, adapting the Lopez-Quiroz et al. 2009 time series analysis. The obtained LOS mean velocity maps show a dominant left-lateral motion across the fault with along-strike variations: some fault sections are locked at shallow depth while others are creeping and local vertical movements are observed (subsidence in the "Jingtai" pull-apart basin). For various fault slip rates imposed below 20 km (4-10 mm/yr), we model the shallow velocity by inverting the mean LOS velocity maps for both strike-slip and dip-slip motion on vertical, 5km x 2.5km discretized patches, using a least-square method with an appropriate degree of smoothing. The fault geometry follows the surface trace of the

  4. Enabling Strain Hardening Simulations with Dislocation Dynamics

    SciTech Connect

    Arsenlis, A; Cai, W

    2006-12-20

    Numerical algorithms for discrete dislocation dynamics simulations are investigated for the purpose of enabling strain hardening simulations of single crystals on massively parallel computers. The algorithms investigated include the /(N) calculation of forces, the equations of motion, time integration, adaptive mesh refinement, the treatment of dislocation core reactions, and the dynamic distribution of work on parallel computers. A simulation integrating all of these algorithmic elements using the Parallel Dislocation Simulator (ParaDiS) code is performed to understand their behavior in concert, and evaluate the overall numerical performance of dislocation dynamics simulations and their ability to accumulate percents of plastic strain.

  5. The plasticity of global proteome and genome expression analyzed in closely related W3110 and MG1655 strains of a well-studied model organism, Escherichia coli-K12.

    PubMed

    Vijayendran, Chandran; Polen, Tino; Wendisch, Volker F; Friehs, Karl; Niehaus, Karsten; Flaschel, Erwin

    2007-03-10

    The use of Escherichia coli as a model organism has provided a great deal of basic information in biomolecular sciences. Examining trait differences among closely related strains of the same species addresses a fundamental biological question: how much diversity is there at the single species level? The main aim of our research was to identify significant differences in the activities of groups of genes between two laboratory strains of an organism closely related in genome structure. We demonstrate that despite strict and controlled growth conditions, there is high plasticity in the global proteome and genome expression in two closely related E. coli K12 sub-strains (W3110 and MG1655), which differ insignificantly in genome structure. The growth patterns of these two sub-strains were very similar in a well-equipped bioreactor, and their genome structures were shown to be almost identical by DNA microarray. However, detailed profiling of protein and gene expression by 2-dimensional gel electrophoresis and microarray analysis showed many differentially expressed genes and proteins, combinations of which were highly correlated. The differentially regulated genes and proteins belonged to the following functional categories: genes regulated by sigma subunit of RNA polymerase (RpoS), enterobactin-related genes, and genes involved in central metabolism. Genes involved in central cell metabolism - the glycolysis pathway, the tricarboxylic acid cycle and the glyoxylate bypass - were differentially regulated at both the mRNA and proteome levels. The strains differ significantly in central metabolism and thus in the generation of precursor metabolites and energy. This high plasticity probably represents a universal feature of metabolic activities in closely related species, and has the potential to reveal differences in regulatory networks. We suggest that unless care is taken in the choice of strains for any validating experiment, the results might be misleading. PMID

  6. The plasticity of global proteome and genome expression analyzed in closely related W3110 and MG1655 strains of a well-studied model organism, Escherichia coli-K12.

    PubMed

    Vijayendran, Chandran; Polen, Tino; Wendisch, Volker F; Friehs, Karl; Niehaus, Karsten; Flaschel, Erwin

    2007-03-10

    The use of Escherichia coli as a model organism has provided a great deal of basic information in biomolecular sciences. Examining trait differences among closely related strains of the same species addresses a fundamental biological question: how much diversity is there at the single species level? The main aim of our research was to identify significant differences in the activities of groups of genes between two laboratory strains of an organism closely related in genome structure. We demonstrate that despite strict and controlled growth conditions, there is high plasticity in the global proteome and genome expression in two closely related E. coli K12 sub-strains (W3110 and MG1655), which differ insignificantly in genome structure. The growth patterns of these two sub-strains were very similar in a well-equipped bioreactor, and their genome structures were shown to be almost identical by DNA microarray. However, detailed profiling of protein and gene expression by 2-dimensional gel electrophoresis and microarray analysis showed many differentially expressed genes and proteins, combinations of which were highly correlated. The differentially regulated genes and proteins belonged to the following functional categories: genes regulated by sigma subunit of RNA polymerase (RpoS), enterobactin-related genes, and genes involved in central metabolism. Genes involved in central cell metabolism - the glycolysis pathway, the tricarboxylic acid cycle and the glyoxylate bypass - were differentially regulated at both the mRNA and proteome levels. The strains differ significantly in central metabolism and thus in the generation of precursor metabolites and energy. This high plasticity probably represents a universal feature of metabolic activities in closely related species, and has the potential to reveal differences in regulatory networks. We suggest that unless care is taken in the choice of strains for any validating experiment, the results might be misleading.

  7. Effect of material inhomogeneity on the cyclic plastic deformation behavior at the microstructural level: micromechanics-based modeling of dual-phase steel

    NASA Astrophysics Data System (ADS)

    Paul, Surajit Kumar

    2013-07-01

    The microstructure of dual-phase (DP) steels typically consists of a soft ferrite matrix with dispersed islands of hard martensite phase. Due to the composite effect of ferrite and martensite, DP steels exhibit a unique combination of strain hardening, strength and ductility. A microstructure-based micromechanical modeling approach is adopted in this work to capture the tensile and cyclic plastic deformation behavior of DP steel. During tensile straining, strain incompatibility between the softer ferrite matrix and the harder martensite phase arises due to a difference in the flow characteristics of these two phases. Microstructural-level inhomogeneity serves as the initial imperfection, triggering strain incompatibility, strain partitioning and finally shear band localization during tensile straining. The local deformation in the ferrite phase is constrained by adjacent martensite islands, which locally results in stress triaxiality development in the ferrite phase. As the martensite distribution varies within the microstructure, the stress triaxiality also varies in a band within the microstructure. Inhomogeneous stress and strain distribution within the softer ferrite phase arises even during small tensile straining because of material inhomogeneity. The magnitude of cyclic plastic deformation within the softer ferrite phase also varies according to the stress distribution in the first-quarter cycle tensile loading. Accumulation of tensile/compressive plastic strain with number of cycles is noted in different locations within the ferrite phase during both symmetric stress and strain controlled cycling. The basic mode of cyclic plastic deformation in an inhomogeneous material is cyclic strain accumulation, i.e. ratcheting. Microstructural inhomogeneity results in cyclic strain accumulation in the aggregate DP material even in symmetric stress cycling.

  8. Killing of Schistosoma mansoni sporocysts by Biomphalaria glabrata hemolymph in vitro: alteration of hemocyte behavior after poly-L-lysine treatment of plastic, and the kinetics of killing by different host strains.

    PubMed

    Boehmler, A M; Fryer, S E; Bayne, C J

    1996-04-01

    Behavior of hemocytes of the gastropod mollusc Biomphalaria glabrata was markedly changed on plastic by treatment of the substrate with 0.1 mg/ml poly-L-lysine compared to behavior on untreated plastic. On lysine, the cells showed minimal spreading, moved significantly faster, and formed aggregates. Cell-mediated cytotoxicity (CMC) assays were set up on the modified and untreated substrates to compare the killing capacities of B. glabrata hemocytes against Schistosoma mansoni sporocysts. Hemolymph from 1316-R1 (resistant) snails showed higher killing in lysine-treated wells; no significant difference in sporocyst mortality was observed in MO (susceptible) hemolymph between treated and untreated wells. The CMC assays on poly-L-lysine-treated plastic were used to compare the kinetics of parasite killing in hemolymph from 2 susceptible (MO, MRLc) and 2 resistant (1316-R1, 10R2) host strains. Marked differences could be observed between the two resistant snail strains, suggesting different mechanisms of parasite recognition, killing, or both.

  9. Time series and MinTS analysis of strain accumulation along the Haiyuan fault (Gansu, China) over the 2003-2010 period, from ENVISAT InSAR data

    NASA Astrophysics Data System (ADS)

    Jolivet, R.; Lasserre, C.; Lin, N.; Simons, M.; Doin, M.; Hetland, E. A.; Muse, P.; Peltzer, G.; Jianbao, S.; Dailu, R.

    2010-12-01

    We use SAR interferometry to measure the strain accumulation along the left-lateral Haiyuan fault system (hereafter HFS), that marks the north-eastern boundary of the tibetan plateau. The last major earthquakes that occured along the HFS are the M~8 1920 Haiyuan earthquake (strike-slip mechanism) and the Ml=8-8.3 1927 Gulang earthquake that ruptured a thrust fault system. There has been no known large earthquake on the central section of the HFS, the “Tianzhu seismic gap”, in the last ~1000 years. We first analyze the complete ENVISAT SAR data archive along three descending and two ascending tracks for the 2003-2009 period and construct an InSAR-based mean line-of-sight (LOS) velocity map around the HFS from the eastern end of the Qilian Shan (102° E), to the west, to the Liupan Shan (106° E), to the east. We empirically correct our interferograms for propagation delays associated with changes on the stratified atmospheric structure. We then estimate the mean LOS velocity for each track using a time series analysis which reveals the existence of a 40 km long creeping segment located at the western end of the 1920 rupture. Extending from the Jingtai pull-apart basin, which shows a 2-3 mm/yr subsidence rate, to the Mao Mao Shan, the creep rate is estimated to reach 8 mm/yr locally and is higher than the long term loading rate of the Haiyuan fault, estimated geodetically at 5±1 mm/yr. The surface extension of the creeping segment is colocated with strong micro- and moderate seismic activity. We also explore the possibility of transient creep during the 2003-2010 time period, using a SBAS style, smoothed, time series analysis and the Multiscale Interferometric Time Series method (MinTS, CalTech, see Hetland et al. 2010 AGU abstract). While classic time series methods are based on a pixel-by-pixel approach and do not consider spatial data covariances, due to residual atmospheric noise, the wavelet decomposition of each interferograms and the time inversion in the

  10. Assessment of Creep Strain Distribution Across Base Metal of 316LN Austenitic Stainless Steel Weld Joint by an EBSD-Based Parameter

    NASA Astrophysics Data System (ADS)

    Vijayanand, V. D.; Ganesan, V.; Ganesh Kumar, J.; Parameswaran, P.; Naveena; Laha, K.

    2015-11-01

    Electron backscatter diffraction (EBSD) analysis has been used to estimate the accumulated strain in base metal region of 316LN austenitic stainless steel weld joints, creep tested at 923 K (650 °C), and at stresses of 175 and 225 MPa. The variation in strength of weld metal, heat-affected zone (HAZ), and base metal-induced stress and strain gradients across the weld joint under creep exposure. Finite element analysis (FEA) of von-Mises stress distribution across the joint has been carried out on incorporating strength of different constituents of the joint, derived by miniature specimen testing techniques. The FEA simulations revealed preferential accumulation of von-Mises stress in the base metal region near to HAZ. The variation in accumulated plastic strain across the base metal has been estimated using a `crystal deformation' ( C d) parameter which quantifies the orientation spread within a grain. This parameter was obtained by EBSD analysis carried out using a scanning electron microscope. The trend in variation of accumulated plastic strain across the base metal accounted well with the von-Mises stress variation, which causes plastic deformation. The plastic strain in the base metal in both the stress levels was found to accumulate preferentially near to the HAZ and reduced steadily toward the ridge at the end of specimen. Transmission electron microscopic study has been carried out to substantiate the findings of the EBSD investigation.

  11. Elastic And Plastic Deformations In Butt Welds

    NASA Technical Reports Server (NTRS)

    Verderaime, V.

    1992-01-01

    Report presents study of mathematical modeling of stresses and strains, reaching beyond limits of elasticity, in bars and plates. Study oriented toward development of capability to predict stresses and resulting elastic and plastic strains in butt welds.

  12. Plastic Jellyfish.

    ERIC Educational Resources Information Center

    Moseley, Christine

    2000-01-01

    Presents an environmental science activity designed to enhance students' awareness of the hazards of plastic waste for wildlife in aquatic environments. Discusses how students can take steps to reduce the effects of plastic waste. (WRM)

  13. Inelastic Strain Analysis of Solder Joint in NASA Fatigue Specimen

    NASA Technical Reports Server (NTRS)

    Dasgupta, Abhijit; Oyan, Chen

    1991-01-01

    The solder fatigue specimen designed by NASA-GSFC/UNISYS is analyzed in order to obtain the inelastic strain history during two different representative temperature cycles specified by UNISYS. In previous reports (dated July 25, 1990, and November 15, 1990), results were presented of the elastic-plastic and creep analysis for delta T = 31 C cycle, respectively. Subsequent results obtained during the current phase, from viscoplastic finite element analysis of the solder fatigue specimen for delta T = 113 C cycle are summarized. Some common information is repeated for self-completeness. Large-deformation continuum formulations in conjunction with a standard linear solid model is utilized for modeling the solder constitutive creep-plasticity behavior. Relevant material properties are obtained from the literature. Strain amplitudes, mean strains, and residual strains (as well as stresses) accumulated due to a representative complete temperature cycle are obtained as a result of this analysis. The partitioning between elastic strains, time-independent inelastic (plastic) strains, and time-dependent inelastic (creep) strains is also explicitly obtained for two representative cycles. Detailed plots are presented for two representative temperature cycles. This information forms an important input for fatigue damage models, when predicting the fatigue life of solder joints under thermal cycling

  14. Fracture toughness of shape memory alloy actuators: effect of transformation-induced plasticity

    NASA Astrophysics Data System (ADS)

    Jape, Sameer; Solomou, Alexandros; Baxevanis, Theocharis; Lagoudas, Dimitris C.

    2016-04-01

    Numerical analysis of static cracks in a plane strain center-cracked infinite medium shape memory alloy (SMA) panel subjected to cyclic thermal variations and a constant mechanical load is conducted using the finite element method. In solid-state SMA actuators, permanent changes in the material's microstructure in the form of dislocations are caused during cyclic thermomechanical loading, leading to macroscopic irreversible strains, known as transformation induced plastic (TRIP) strains. The influence of these accumulated TRIP strains on mechanical fields close to the crack tip is investigated in the present paper. Virtual crack growth technique (VCCT) in ABAQUS FEA suite is employed to calculate the crack tip energy release rate and crack is assumed to be stationary (or static) so that the crack tip energy release rate never reaches the material specific critical value. Increase in the crack tip energy release rate is observed during cooling and its relationship with accumulation of TRIP due to cyclic transformation is studied.

  15. Morphological study of elastic-plastic-brittle transitions in disordered media.

    PubMed

    Kale, Sohan; Ostoja-Starzewski, Martin

    2014-10-01

    We use a spring lattice model with springs following a bilinear elastoplastic-brittle constitutive behavior with spatial disorder in the yield and failure thresholds to study patterns of plasticity and damage evolution. The elastic-perfectly plastic transition is observed to follow percolation scaling with the correlation length critical exponent ν≈1.59, implying the universality class corresponding to the long-range correlated percolation. A quantitative analysis of the plastic strain accumulation reveals a dipolar anisotropy (for antiplane loading) which vanishes with increasing hardening modulus. A parametric study with hardening modulus and ductility controlled through the spring level constitutive response demonstrates a wide spectrum of behaviors with varying degree of coupling between plasticity and damage evolution. PMID:25375508

  16. Characterization of Strain-Induced Precipitation in Inconel 718 Superalloy

    NASA Astrophysics Data System (ADS)

    Calvo, Jessica; Penalva, Mariluz; Cabrera, José María

    2016-06-01

    Inconel 718 presents excellent mechanical properties at high temperatures, as well as good corrosion resistance and weldability. These properties, oriented to satisfy the design requirements of gas turbine components, depend on microstructural features such as grain size and precipitation. In this work, precipitation-temperature-time diagrams have been derived based on a stress relaxation technique and the characterization of precipitates by scanning electron microscopy. By using this methodology, the effect of strain accumulation during processing on the precipitation kinetics can be determined. The results show that the characteristics of precipitation are significantly modified when plastic deformation is applied, and the kinetics are slightly affected by the amount of total plastic deformation.

  17. Characterization of Strain-Induced Precipitation in Inconel 718 Superalloy

    NASA Astrophysics Data System (ADS)

    Calvo, Jessica; Penalva, Mariluz; Cabrera, José María

    2016-08-01

    Inconel 718 presents excellent mechanical properties at high temperatures, as well as good corrosion resistance and weldability. These properties, oriented to satisfy the design requirements of gas turbine components, depend on microstructural features such as grain size and precipitation. In this work, precipitation-temperature-time diagrams have been derived based on a stress relaxation technique and the characterization of precipitates by scanning electron microscopy. By using this methodology, the effect of strain accumulation during processing on the precipitation kinetics can be determined. The results show that the characteristics of precipitation are significantly modified when plastic deformation is applied, and the kinetics are slightly affected by the amount of total plastic deformation.

  18. Accumulate-Repeat-Accumulate-Accumulate-Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Sam; Thorpe, Jeremy

    2004-01-01

    Inspired by recently proposed Accumulate-Repeat-Accumulate (ARA) codes [15], in this paper we propose a channel coding scheme called Accumulate-Repeat-Accumulate-Accumulate (ARAA) codes. These codes can be seen as serial turbo-like codes or as a subclass of Low Density Parity Check (LDPC) codes, and they have a projected graph or protograph representation; this allows for a high-speed iterative decoder implementation using belief propagation. An ARAA code can be viewed as a precoded Repeat-and-Accumulate (RA) code with puncturing in concatenation with another accumulator, where simply an accumulator is chosen as the precoder; thus ARAA codes have a very fast encoder structure. Using density evolution on their associated protographs, we find examples of rate-lJ2 ARAA codes with maximum variable node degree 4 for which a minimum bit-SNR as low as 0.21 dB from the channel capacity limit can be achieved as the block size goes to infinity. Such a low threshold cannot be achieved by RA or Irregular RA (IRA) or unstructured irregular LDPC codes with the same constraint on the maximum variable node degree. Furthermore by puncturing the accumulators we can construct families of higher rate ARAA codes with thresholds that stay close to their respective channel capacity thresholds uniformly. Iterative decoding simulation results show comparable performance with the best-known LDPC codes but with very low error floor even at moderate block sizes.

  19. Growth and (137)Cs uptake and accumulation among 56 Japanese cultivars of Brassica rapa, Brassica juncea and Brassica napus grown in a contaminated field in Fukushima: Effect of inoculation with a Bacillus pumilus strain.

    PubMed

    Djedidi, Salem; Kojima, Katsuhiro; Ohkama-Ohtsu, Naoko; Bellingrath-Kimura, Sonoko Dorothea; Yokoyama, Tadashi

    2016-06-01

    Fifty six local Japanese cultivars of Brassica rapa (40 cultivars), Brassica juncea (10 cultivars) and Brassica napus (6 cultivars) were assessed for variability in growth and (137)Cs uptake and accumulation in association with a Bacillus pumilus strain. Field trial was conducted at a contaminated farmland in Nihonmatsu city, in Fukushima prefecture. Inoculation resulted in different responses of the cultivars in terms of growth and radiocesium uptake and accumulation. B. pumilus induced a significant increase in shoot dry weight in 12 cultivars that reached up to 40% in one B. rapa and three B. juncea cultivars. Differences in radiocesium uptake were observed between the cultivars of each Brassica species. Generally, inoculation resulted in a significant increase in (137)Cs uptake in 22 cultivars, while in seven cultivars it was significantly decreased. Regardless of plant cultivar and bacterial inoculation, the transfer of (137)Cs to the plant shoots (TF) varied by a factor of up to 5 and it ranged from to 0.011 to 0.054. Five inoculated cultivars, showed enhanced shoot dry weights and decreased (137)Cs accumulations, among which two B. rapa cultivars named Bitamina and Nozawana had a significantly decreased (137)Cs accumulation in their shoots. Such cultivars could be utilized to minimize the entry of radiocesium into the food chain; however, verifying the consistency of their radiocesium accumulation in other soils is strongly required. Moreover, the variations in growth and radiocesium accumulation, as influenced by Bacillus inoculation, could help selecting well grown inoculated Brassica cultivars with low radiocesium accumulation in their shoots.

  20. Growth and (137)Cs uptake and accumulation among 56 Japanese cultivars of Brassica rapa, Brassica juncea and Brassica napus grown in a contaminated field in Fukushima: Effect of inoculation with a Bacillus pumilus strain.

    PubMed

    Djedidi, Salem; Kojima, Katsuhiro; Ohkama-Ohtsu, Naoko; Bellingrath-Kimura, Sonoko Dorothea; Yokoyama, Tadashi

    2016-06-01

    Fifty six local Japanese cultivars of Brassica rapa (40 cultivars), Brassica juncea (10 cultivars) and Brassica napus (6 cultivars) were assessed for variability in growth and (137)Cs uptake and accumulation in association with a Bacillus pumilus strain. Field trial was conducted at a contaminated farmland in Nihonmatsu city, in Fukushima prefecture. Inoculation resulted in different responses of the cultivars in terms of growth and radiocesium uptake and accumulation. B. pumilus induced a significant increase in shoot dry weight in 12 cultivars that reached up to 40% in one B. rapa and three B. juncea cultivars. Differences in radiocesium uptake were observed between the cultivars of each Brassica species. Generally, inoculation resulted in a significant increase in (137)Cs uptake in 22 cultivars, while in seven cultivars it was significantly decreased. Regardless of plant cultivar and bacterial inoculation, the transfer of (137)Cs to the plant shoots (TF) varied by a factor of up to 5 and it ranged from to 0.011 to 0.054. Five inoculated cultivars, showed enhanced shoot dry weights and decreased (137)Cs accumulations, among which two B. rapa cultivars named Bitamina and Nozawana had a significantly decreased (137)Cs accumulation in their shoots. Such cultivars could be utilized to minimize the entry of radiocesium into the food chain; however, verifying the consistency of their radiocesium accumulation in other soils is strongly required. Moreover, the variations in growth and radiocesium accumulation, as influenced by Bacillus inoculation, could help selecting well grown inoculated Brassica cultivars with low radiocesium accumulation in their shoots. PMID:26986237

  1. Plasticity effects in hydraulic fracturing

    SciTech Connect

    Medlin, W.L.; Masse, L.

    1986-09-01

    The importance of reservoir rock plasticity in fracturing operations has been investigated by laboratory experiments and field results. A Lagrangian formulation for crack propagation provided the basis for the laboratory experiments. A simple crack propagation experiment showed that plasticity effects can be observed and that the importance of plasticity depends on the relative magnitudes of surface energy and energy dissipated in plastic deformation of a reservoir rock. The latter can be evaluated by laboratory measurements of a plasticity coefficient, ..cap alpha.., which comes out of the Lagrangian analysis. To measure ..cap alpha.., the authors developed a triaxial system for applying tensile stress to rock cores under confining pressure at strain rates characteristic of fracturing operations. Strain gauges mounted on each core were used with a servo-controlled press to apply strain at a linear rate between 10/sup -4/ and 10/sup -6/ seconds /sup -1/ and to obtain stress/strain data to the point of tensile failure. To distinguish between plasticity and nonlinear elastic phenomena, the authors also obtained strain hysteresis data.

  2. Accumulate-Repeat-Accumulate-Accumulate Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Samuel; Thorpe, Jeremy

    2007-01-01

    Accumulate-repeat-accumulate-accumulate (ARAA) codes have been proposed, inspired by the recently proposed accumulate-repeat-accumulate (ARA) codes. These are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. ARAA codes can be regarded as serial turbolike codes or as a subclass of low-density parity-check (LDPC) codes, and, like ARA codes they have projected graph or protograph representations; these characteristics make it possible to design high-speed iterative decoders that utilize belief-propagation algorithms. The objective in proposing ARAA codes as a subclass of ARA codes was to enhance the error-floor performance of ARA codes while maintaining simple encoding structures and low maximum variable node degree.

  3. Microbial uptake and accumulation of (/sup 14/C Carbofuran) 1,3-dihydro-2,2-dimethyl-7 benzofuranylmethyl carbamate in twenty fungal strains isolated by miniecosystem studies

    SciTech Connect

    Arunachalam, K.D.; Lakshmanan, M.

    1988-07-01

    Studies have amply demonstrated that members of the microbial world vary widely in their response to pesticides and that several factors may influence the toxicity of pesticides. Similarly, the microbial tolerance of pesticides may be affected by growth conditions, physiological conditions of cells and various stress factors which might exist in natural population. The pesticides are incorporated into microorganisms by an active or passive accumulation mechanism. Most observations of pesticide accumulation within the cells were recorded with chlorinated hydrocarbons. It was found that not only live bacterial cells, but autoclaved cells also, show a similar uptake of pesticides. Since aquatic microorganisms and plankton in freshwater and marine environments are an important nutrient source for a broad spectrum of aquatic filter-feeding organisms, their accumulation of pesticides can constitute a hazardous link in the food chain to fish and higher vertebrates.

  4. X-ray Laue micro diffraction and neutron diffraction analysis of residual elastic strains and plastic deformation in a 1% uniaxial tensile tested nickel alloy 600 sample

    SciTech Connect

    Chao, Jing; Mark, Alison; Fuller, Marina; Barabash, Rozaliya; McIntyre, Stewart; Holt, Richard A.; Klassen, Robert; Liu, W.

    2009-01-01

    The magnitude and distribution of elastic strain for a nickel alloy 600 (A600) sample that had been subjected to uniaxial tensile stress were measured by micro Laue diffraction (MLD) and neutron diffraction techniques. For a sample that had been dimensionally strained by 1%, both MLD and neutron diffraction data indicated that the global residual elastic strain was on the order of 10{sup -4}, however the micro-diffraction data indicated considerable grain-to-grain variability amongst individual components of the residual strain tensor. A more precise comparison was done by finding those grains in the MLD map that had appropriate oriented in the specific directions matching those used in the neutron measurements and the strains were found to agree within the uncertainty. Large variations in strain values across the grains were noted during the MLD measurements which are reflected in the uncertainties. This is a possible explanation for the large uncertainty in the average strains measured from multiple grains during neutron diffraction.

  5. Plastic flow and failure in HY100, HY130 and AF1410 alloy steels under high strain rate and impact loading conditions

    NASA Astrophysics Data System (ADS)

    Rajendran, A. M.; Last, H. R.; Garrett, R. K., Jr.

    1995-03-01

    This report presents the results from impact experiments, constitutive/failure modeling, and metallurgical failure analyses for three steels: HY100, HY130, and AF1410. The main objectives of this effort are: (1) to obtain fundamental engineering data in terms of stress-strain curves up to failure at different temperatures and strain rates, (2) to evaluate the observed differences in the macroscopic behaviors through microscopic metallurgical studies, and (3) to describe the flow and failure behaviors using already available material strength and spall models. The high strain rate and impact experiments considered are the split Hopkinson bar (SHB) and the planar plate impact tests, respectively. In addition, the baseline data include quasi-static (QS) tests at low strain rates. The QS and SHB data provide stress-strain curves at different strain rates and temperatures. The experimental data illustrate the effects of two important loading parameters (strain rate and temperature) on the flow and failure behaviors of HY100, HY130, and AF1410 steels.

  6. The Pan-Genome of the Animal Pathogen Corynebacterium pseudotuberculosis Reveals Differences in Genome Plasticity between the Biovar ovis and equi Strains

    PubMed Central

    Soares, Siomar C.; Silva, Artur; Trost, Eva; Blom, Jochen; Ramos, Rommel; Carneiro, Adriana; Ali, Amjad; Santos, Anderson R.; Pinto, Anne C.; Diniz, Carlos; Barbosa, Eudes G. V.; Dorella, Fernanda A.; Aburjaile, Flávia; Rocha, Flávia S.; Nascimento, Karina K. F.; Guimarães, Luís C.; Almeida, Sintia; Hassan, Syed S.; Bakhtiar, Syeda M.; Pereira, Ulisses P.; Abreu, Vinicius A. C.; Schneider, Maria P. C.; Miyoshi, Anderson

    2013-01-01

    Corynebacterium pseudotuberculosis is a facultative intracellular pathogen and the causative agent of several infectious and contagious chronic diseases, including caseous lymphadenitis, ulcerative lymphangitis, mastitis, and edematous skin disease, in a broad spectrum of hosts. In addition, Corynebacterium pseudotuberculosis infections pose a rising worldwide economic problem in ruminants. The complete genome sequences of 15 C. pseudotuberculosis strains isolated from different hosts and countries were comparatively analyzed using a pan-genomic strategy. Phylogenomic, pan-genomic, core genomic, and singleton analyses revealed close relationships among pathogenic corynebacteria, the clonal-like behavior of C. pseudotuberculosis and slow increases in the sizes of pan-genomes. According to extrapolations based on the pan-genomes, core genomes and singletons, the C. pseudotuberculosis biovar ovis shows a more clonal-like behavior than the C. pseudotuberculosis biovar equi. Most of the variable genes of the biovar ovis strains were acquired in a block through horizontal gene transfer and are highly conserved, whereas the biovar equi strains contain great variability, both intra- and inter-biovar, in the 16 detected pathogenicity islands (PAIs). With respect to the gene content of the PAIs, the most interesting finding is the high similarity of the pilus genes in the biovar ovis strains compared with the great variability of these genes in the biovar equi strains. Concluding, the polymerization of complete pilus structures in biovar ovis could be responsible for a remarkable ability of these strains to spread throughout host tissues and penetrate cells to live intracellularly, in contrast with the biovar equi, which rarely attacks visceral organs. Intracellularly, the biovar ovis strains are expected to have less contact with other organisms than the biovar equi strains, thereby explaining the significant clonal-like behavior of the biovar ovis strains. PMID:23342011

  7. Suppressor Mutations in the Study of Photosystem I Biogenesis: sll0088 Is a Previously Unidentified Gene Involved in Reaction Center Accumulation in Synechocystis sp. Strain PCC 6803

    PubMed Central

    Yu, Jianping; Shen, Gaozhong; Wang, Tao; Bryant, Donald A.; Golbeck, John H.; McIntosh, Lee

    2003-01-01

    In previous work, some members of our group isolated mutant strains of Synechocystis sp. strain PCC 6803 in which point mutations had been inserted into the psaC gene to alter the cysteine residues to the FA and FB iron-sulfur clusters in the PsaC subunit of photosystem I (J. P. Yu, I. R. Vassiliev, Y. S. Jung, J. H. Golbeck, and L. McIntosh, J. Biol. Chem. 272:8032-8039, 1997). These mutant strains did not grow photoautotrophically due to suppressed levels of chlorophyll a and photosystem I. In the results described here, we show that suppressor mutations produced strains that are capable of photoautotrophic growth at moderate light intensity (20 μmol m−2 s−1). Two separate suppressor strains of C14SPsaC, termed C14SPsaC-R62 and C14SPsaC-R18, were studied and found to have mutations in a previously uncharacterized open reading frame of the Synechocystis sp. strain PCC 6803 genome named sll0088. C14SPsaC-R62 was found to substitute Pro for Arg at residue 161 as the result of a G482→C change in sll0088, and C14SPsaC-R18 was found to have a three-amino-acid insertion of Gly-Tyr-Phe following Cys231 as the result of a TGGTTATTT duplication at T690 in sll0088. These suppressor strains showed near-wild-type levels of chlorophyll a and photosystem I, yet the serine oxygen ligand to FB was retained as shown by the retention of the S ≥ 3/2 spin state of the [4Fe-4S] cluster. The inactivation of sll0088 by insertion of a kanamycin resistance cartridge in the primary C14SPsaC mutant produced an engineered suppressor strain capable of photoautotrophic growth. There was no difference in psaC gene expression or in the amount of PsaC protein assembled in thylakoids between the wild type and an sll0088 deletion mutant. The sll0088 gene encodes a protein predicted to be a transcriptional regulator with sequence similarities to transcription factors in other prokaryotic and eukaryotic organisms, including Arabidopsis thaliana. The protein contains a typical helix

  8. Post-irradiation plastic deformation in bcc Fe grains investigated by means of 3D dislocation dynamics simulations

    NASA Astrophysics Data System (ADS)

    Gururaj, K.; Robertson, C.; Fivel, M.

    2015-04-01

    Post-irradiation tensile straining is investigated by means of three-dimensional dislocation dynamics simulations adapted to body centred cubic Fe. Namely, 1 μm Fe grains are strained at various temperatures in the 100-300 K range, in absence and in presence of radiation-induced defect dispersions. The defect-induced hardening is consistent with the disperse barrier effect up to 5 ×1021m-3 loops and is weakly dependent on the straining temperature. The dislocation-loops interaction rate augments with the accumulated plastic strain, loop density and strength; while it is mainly independent of the number of active slip systems and thermally activated screw dislocation mobility. An additional, radiation-induced hardening mechanism known as dislocation "decoration" is also implemented and tested for comparison. Those results show that the plastic flow localisation transition depends on the total yield point rise rather than on the lone, dispersed loop density. The simulation results are then rationalized through an original micro-mechanical model relating the grain-scale stress-strain behaviour to dislocation sub-structure formation and spreading. That model combines strain dependent and strain independent hardening mechanisms, which both contribute to the associated stress-strain response and plastic flow spreading.

  9. Cultivar-Dependent Transcript Accumulation in Wheat Roots Colonized by Pseudomonas fluorescens Q8r1-96 Wild Type and Mutant Strains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In Triticum aestivum L. (wheat), the root-colonizing bacterium Pseudomonas fluorescens strain Q8r1-96 produces the antifungal metabolite 2,4-diacetylphloroglucinol (DAPG), suppresses damage caused by soilborne root pathogens, and modulates multiple stress or defense pathways in wheat roots. To test...

  10. Plastics Technology.

    ERIC Educational Resources Information Center

    Barker, Tommy G.

    This curriculum guide is designed to assist junior high schools industrial arts teachers in planning new courses and revising existing courses in plastics technology. Addressed in the individual units of the guide are the following topics: introduction to production technology; history and development of plastics; safety; youth leadership,…

  11. The Effect of Cold Plastic Straining of Submicrocrystalline and Coarse-Grained Titanium on the Temperature Behavior of Flow Stress in the Stage of Microplastic Deformation

    NASA Astrophysics Data System (ADS)

    Dudarev, E. F.; Pochivalova, G. P.; Kolobov, Yu. R.; Bakach, G. P.; Skosyrskii, A. B.; Zhorovkov, M. F.; Goraynov, А. А.

    2013-10-01

    The results of an experimental investigation of the effect of mechanical-thermal treatment of submicrocrystalline and coarse-grained titanium on the deformation behavior in the stage of microplastic deformation at room and elevated temperatures are reported. The structural factors giving rise to the flowstress changes in the stage of microplastic deformation as a result of mechanical-thermal treatment are discussed. The general tendencies and special features of the effect of annealing and testing temperatures on the deformation behavior and flow stress in the first and second stages of microplastic deformation of submicrocrystalline and coarse-grained titanium subjected to large plastic deformation at 295 K are clarified.

  12. Characterization of plant-growth-promoting effects and concurrent promotion of heavy metal accumulation in the tissues of the plants grown in the polluted soil by Burkholderia strain LD-11.

    PubMed

    Huang, Gui-Hai; Tian, Hui-Hui; Liu, Hai-Ying; Fan, Xian-Wei; Liang, Yu; Li, You-Zhi

    2013-01-01

    Plant-growth-promoting (PGP) bacteria especially with the resistance to multiple heavy metals are helpful to phytoremediation. Further development of PGP bacteria is very necessary because of the extreme diversity of plants, soils, and heavy metal pollution. A Burkholderia sp. strain, numbered LD-11, was isolated, which showed resistances to multiple heavy metals and antibiotics. It can produce indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase and siderophores. Inoculation with the LD-11 improved germination of seeds of the investigated vegetable plants in the presence of Cu, promoted elongation of roots and hypocotyledonary axes, enhanced the dry weights of the plants grown in the soils polluted with Cu and/or Pb, and increased activity of the soil urease and the rhizobacteria diversity. Inoculation with the LD-11 significantly enhanced Cu and/or Pb accumulation especially in the roots of the plants grown in the polluted soils. Notably, LD-11 could produce siderophores in the presence of Cu. Conclusively, the PGP effects and concurrent heavy metal accumulation in the plant tissues results from combined effects of the above-mentioned multiple factors. Cu is an important element that represses production of the siderophore by the bacteria. Phytoremediation by synergistic use of the investigated plants and the bacterial strain LD-11 is a phytoextraction process. PMID:23819291

  13. Characterization of plant-growth-promoting effects and concurrent promotion of heavy metal accumulation in the tissues of the plants grown in the polluted soil by Burkholderia strain LD-11.

    PubMed

    Huang, Gui-Hai; Tian, Hui-Hui; Liu, Hai-Ying; Fan, Xian-Wei; Liang, Yu; Li, You-Zhi

    2013-01-01

    Plant-growth-promoting (PGP) bacteria especially with the resistance to multiple heavy metals are helpful to phytoremediation. Further development of PGP bacteria is very necessary because of the extreme diversity of plants, soils, and heavy metal pollution. A Burkholderia sp. strain, numbered LD-11, was isolated, which showed resistances to multiple heavy metals and antibiotics. It can produce indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase and siderophores. Inoculation with the LD-11 improved germination of seeds of the investigated vegetable plants in the presence of Cu, promoted elongation of roots and hypocotyledonary axes, enhanced the dry weights of the plants grown in the soils polluted with Cu and/or Pb, and increased activity of the soil urease and the rhizobacteria diversity. Inoculation with the LD-11 significantly enhanced Cu and/or Pb accumulation especially in the roots of the plants grown in the polluted soils. Notably, LD-11 could produce siderophores in the presence of Cu. Conclusively, the PGP effects and concurrent heavy metal accumulation in the plant tissues results from combined effects of the above-mentioned multiple factors. Cu is an important element that represses production of the siderophore by the bacteria. Phytoremediation by synergistic use of the investigated plants and the bacterial strain LD-11 is a phytoextraction process.

  14. Cyclic hardening in copper described in terms of combined monotonic and cyclic stress-strain curves

    SciTech Connect

    Chandler, H.D. . School of Mechanical Engineering)

    1995-01-01

    Hardening of polycrystalline copper subjected to tension-compression loading cycles in the plastic region is discussed with reference to changes in flow stress determined from equations describing dislocation glide. It is suggested that hardening is as a result of the accumulation of strain on a monotonic stress-strain curve. On initial loading, the behavior is monotonic. On stress reversal, a characteristic cyclic stress-strain curve is followed until the stress reaches a value in reverse loading corresponding to the maximum attained during the preceding half cycle. Thereafter, the monotonic path is followed until strain reversal occurs at completion of the half cycle. Repetition of the process results in cyclic hardening. Steady state cyclic behavior is reached when a stress associated with the monotonic stress-strain curve is reached which is equal to the stress associated with the cyclic stress-strain curve corresponding to the imposed strain amplitude.

  15. Switches in the mode of transmission select for or against a poorly aphid-transmissible strain of potato virus Y with reduced helper component and virus accumulation.

    PubMed

    Legavre, T; Maia, I G; Casse-Delbart, F; Bernardi, F; Robaglia, C

    1996-07-01

    A poorly aphid-transmissible potato virus Y (PVY-PAT) variant emerged after several cycles of mechanical transmission of an initially aphid-transmissible (AT) isolate. Sequence analysis of the N-terminal region of the helper component-proteinase (HC-Pro) gene revealed a Lys to Glu change at a position previously found to abolish the HC-Pro aphid transmission activity in several potyviruses. Two cycles of aphid transmission allowed the virus population to evolve towards an AT form (PVY-ATnew) where a Glu to Lys change was observed. PVY-PAT produced lower amounts of coat protein and the accumulation of its HC-Pro in infected plants decreased from 7 to 28 days post-inoculation, as compared to PVY-ATnew. RT-PCR and restriction analysis showed that the two virus populations co-existed in the PVY-AT isolate and that the AT form was counter-selected during mechanical transmission. These observations suggest that the Lys to Glu substitution leads to decreased stability of HC-Pro resulting in poor transmissions by aphids, and further strengthen the idea that HC-Pro is involved in the accumulation of potyvirus in infected plants.

  16. Effect of Plastic Pre-straining on Residual Stress and Composition Profiles in Low-Temperature Surface-Hardened Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Bottoli, Federico; Christiansen, Thomas L.; Winther, Grethe; Somers, Marcel A. J.

    2016-08-01

    The present work deals with the evaluation of the residual stress profiles in expanded austenite by applying grazing incidence X-ray diffraction (GI-XRD) combined with successive sublayer removal. Annealed and deformed ( ɛ eq=0.5) samples of stable stainless steel EN 1.4369 were nitrided or nitrocarburized. The residual stress profiles resulting from the thermochemical low-temperature surface treatment were measured. The results indicate high-residual compressive stresses of several GPa's in the nitrided region, while lower-compressive stresses are produced in the carburized case. Plastic deformation in the steel prior to thermochemical treatment has a hardly measurable influence on the nitrogen-rich zone, while it has a measurable effect on the stresses and depth of the carbon-rich zone.

  17. The contribution of remotely triggered displacement events to the long-term strain accumulation along the Atacama Fault System, N-Chile

    NASA Astrophysics Data System (ADS)

    Victor, P.; Schurr, B.; Sobiesiak, M.; Ewiak, O.; Oncken, O.

    2012-12-01

    The Atacama Fault System (AFS) in N-Chile is an active trench-parallel fault system, located above approximately the down-dip end of coupling of the north Chilean subduction zone. The average long-term displacement rate for the last 100 000 - 10 000 years ranges between 0.2 and 0.3 mm/yr as determined by various methods and authors. The mode of displacement accumulation through time for this type of fault is not well understood. Surface ruptures along individual segments of the main fault scarp unambiguously reveal that the AFS has seismically ruptured several times during its past, but recurrence intervals are at least one order of magnitude longer than the megathrust earthquake cycle of the underlying subduction interface. Nevertheless these trench parallel fault systems bear a potential of unexpected large seismic ruptures as demonstrated by prominent examples like the Kobe Earthquak in 1995 and Denali Earthquake in 2002. The aim of this study is to quantify the relative proportion of aseismic and seismic slip through time and to investigate the impact of subduction zone earthquakes on the slip behavior of the AFS. Since 2008 we continuously monitor four active fault segments of the AFS with an array of 11 creepmeter stations, two of them co-located with Broadband seismometers. The displacement across the fault is continuously monitored with 2 samples/min with a resolution of 1μm. The displacement time series reveals that no continuous creep can be detected for 10 of the 11 stations. Instead we observe sudden displacement events correlated in time with far field megathrust earthquakes or local earthquakes on the plate interface or in the overriding crust. The most prominent event recorded on the creepmeters was the Mw=8.8 Maule earthquake in 2010 located 1500km to 1800km away from the creepmeter array. All of the stations showed a triggered sudden displacement event 6-8 min after the main shock. Correlation with seismological data from a nearby IPOC station

  18. Plastic hinge modeling of structures

    NASA Astrophysics Data System (ADS)

    Maruthayappan, Ramakrishnan

    1994-07-01

    The rapid changes taking place in vehicle design has resulted in a great variety of vehicles having different structural configurations. The behavior of such structures under impact or crash conditions demand an efficient modeling of the system. Since a vehicle crash is a dynamic phenomenon exhibiting complex interaction between structural and inertial forces, the model should be able to predict the transient deformations which range from small strain elastic deformations to large strain plastic deformations. Among various formulations and modeling techniques available, the plastic hinge theory offers a simple, realistic and a computationally efficient model. This thesis explores and applies the plastic hinge modeling technique to some simple structures ranging from an elementary cantilever beam to a torque box representing a passenger compartment. The nonlinear static and dynamic behavior of a general aviation seat model for different load cases have been predicted using this theory. A detailed study and application of nonlinear finite element technique has also been performed. A comparative study of the responses yielded by plastic hinge model and finite element model demonstrates the effectiveness and accuracy of the plastic hinge model in predicting the behavior of the structures reliably. This thesis also studies and predicts the dynamics of mechanical systems using plastic hinges modeled with flexible and rigid bodies with contact-impact and plastic deformation.

  19. Plastics recycling: challenges and opportunities

    PubMed Central

    Hopewell, Jefferson; Dvorak, Robert; Kosior, Edward

    2009-01-01

    Plastics are inexpensive, lightweight and durable materials, which can readily be moulded into a variety of products that find use in a wide range of applications. As a consequence, the production of plastics has increased markedly over the last 60 years. However, current levels of their usage and disposal generate several environmental problems. Around 4 per cent of world oil and gas production, a non-renewable resource, is used as feedstock for plastics and a further 3–4% is expended to provide energy for their manufacture. A major portion of plastic produced each year is used to make disposable items of packaging or other short-lived products that are discarded within a year of manufacture. These two observations alone indicate that our current use of plastics is not sustainable. In addition, because of the durability of the polymers involved, substantial quantities of discarded end-of-life plastics are accumulating as debris in landfills and in natural habitats worldwide. Recycling is one of the most important actions currently available to reduce these impacts and represents one of the most dynamic areas in the plastics industry today. Recycling provides opportunities to reduce oil usage, carbon dioxide emissions and the quantities of waste requiring disposal. Here, we briefly set recycling into context against other waste-reduction strategies, namely reduction in material use through downgauging or product reuse, the use of alternative biodegradable materials and energy recovery as fuel. While plastics have been recycled since the 1970s, the quantities that are recycled vary geographically, according to plastic type and application. Recycling of packaging materials has seen rapid expansion over the last decades in a number of countries. Advances in technologies and systems for the collection, sorting and reprocessing of recyclable plastics are creating new opportunities for recycling, and with the combined actions of the public, industry and governments it

  20. Plastics recycling: challenges and opportunities.

    PubMed

    Hopewell, Jefferson; Dvorak, Robert; Kosior, Edward

    2009-07-27

    Plastics are inexpensive, lightweight and durable materials, which can readily be moulded into a variety of products that find use in a wide range of applications. As a consequence, the production of plastics has increased markedly over the last 60 years. However, current levels of their usage and disposal generate several environmental problems. Around 4 per cent of world oil and gas production, a non-renewable resource, is used as feedstock for plastics and a further 3-4% is expended to provide energy for their manufacture. A major portion of plastic produced each year is used to make disposable items of packaging or other short-lived products that are discarded within a year of manufacture. These two observations alone indicate that our current use of plastics is not sustainable. In addition, because of the durability of the polymers involved, substantial quantities of discarded end-of-life plastics are accumulating as debris in landfills and in natural habitats worldwide. Recycling is one of the most important actions currently available to reduce these impacts and represents one of the most dynamic areas in the plastics industry today. Recycling provides opportunities to reduce oil usage, carbon dioxide emissions and the quantities of waste requiring disposal. Here, we briefly set recycling into context against other waste-reduction strategies, namely reduction in material use through downgauging or product reuse, the use of alternative biodegradable materials and energy recovery as fuel. While plastics have been recycled since the 1970s, the quantities that are recycled vary geographically, according to plastic type and application. Recycling of packaging materials has seen rapid expansion over the last decades in a number of countries. Advances in technologies and systems for the collection, sorting and reprocessing of recyclable plastics are creating new opportunities for recycling, and with the combined actions of the public, industry and governments it

  1. Plastics recycling: challenges and opportunities.

    PubMed

    Hopewell, Jefferson; Dvorak, Robert; Kosior, Edward

    2009-07-27

    Plastics are inexpensive, lightweight and durable materials, which can readily be moulded into a variety of products that find use in a wide range of applications. As a consequence, the production of plastics has increased markedly over the last 60 years. However, current levels of their usage and disposal generate several environmental problems. Around 4 per cent of world oil and gas production, a non-renewable resource, is used as feedstock for plastics and a further 3-4% is expended to provide energy for their manufacture. A major portion of plastic produced each year is used to make disposable items of packaging or other short-lived products that are discarded within a year of manufacture. These two observations alone indicate that our current use of plastics is not sustainable. In addition, because of the durability of the polymers involved, substantial quantities of discarded end-of-life plastics are accumulating as debris in landfills and in natural habitats worldwide. Recycling is one of the most important actions currently available to reduce these impacts and represents one of the most dynamic areas in the plastics industry today. Recycling provides opportunities to reduce oil usage, carbon dioxide emissions and the quantities of waste requiring disposal. Here, we briefly set recycling into context against other waste-reduction strategies, namely reduction in material use through downgauging or product reuse, the use of alternative biodegradable materials and energy recovery as fuel. While plastics have been recycled since the 1970s, the quantities that are recycled vary geographically, according to plastic type and application. Recycling of packaging materials has seen rapid expansion over the last decades in a number of countries. Advances in technologies and systems for the collection, sorting and reprocessing of recyclable plastics are creating new opportunities for recycling, and with the combined actions of the public, industry and governments it

  2. Non-Saccharomyces and Saccharomyces strains co-fermentation increases acetaldehyde accumulation: effect on anthocyanin-derived pigments in Tannat red wines.

    PubMed

    Medina, Karina; Boido, Eduardo; Fariña, Laura; Dellacassa, Eduardo; Carrau, Francisco

    2016-07-01

    During fermentation, Saccharomyces cerevisiae releases into the medium secondary metabolic products, such as acetaldehyde, able to react with anthocyanins, producing more stable derived pigments. However, very limited reports are found about non-Saccharomyces effects on grape fermentation. In this study, six non-Saccharomyces yeast strains, belonging to the genera Metschnikowia and Hanseniaspora, were screened for their effect on red wine colour and wine-making capacity under pure culture conditions and mixed with Saccharomyces. An artificial red grape must was prepared, containing a phenolic extract of Tannat grapes that allows monitoring changes of key phenol parameters during fermentation, but without skin solids in the medium. When fermented in pure cultures, S. cerevisiae produced higher concentrations of acetaldehyde and vitisin B (acetaldehyde reaction-dependent) compared to M. pulcherrima M00/09G, Hanseniaspora guillermondii T06/09G, H. opuntiae T06/01G, H. vineae T02/05F and H. clermontiae (A10/82Fand C10/54F). However, co-fermentation of H. vineae and H. clermontiae with S. cerevisiae resulted in a significantly higher concentration of acetaldehyde compared with the pure S. cerevisiae control. HPLC-DAD-MS analysis confirmed an increased formation of vitisin B in co-fermentation treatments when compared to pure Saccharomyces fermentation, suggesting the key role of acetaldehyde. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26888345

  3. Non-Saccharomyces and Saccharomyces strains co-fermentation increases acetaldehyde accumulation: effect on anthocyanin-derived pigments in Tannat red wines.

    PubMed

    Medina, Karina; Boido, Eduardo; Fariña, Laura; Dellacassa, Eduardo; Carrau, Francisco

    2016-07-01

    During fermentation, Saccharomyces cerevisiae releases into the medium secondary metabolic products, such as acetaldehyde, able to react with anthocyanins, producing more stable derived pigments. However, very limited reports are found about non-Saccharomyces effects on grape fermentation. In this study, six non-Saccharomyces yeast strains, belonging to the genera Metschnikowia and Hanseniaspora, were screened for their effect on red wine colour and wine-making capacity under pure culture conditions and mixed with Saccharomyces. An artificial red grape must was prepared, containing a phenolic extract of Tannat grapes that allows monitoring changes of key phenol parameters during fermentation, but without skin solids in the medium. When fermented in pure cultures, S. cerevisiae produced higher concentrations of acetaldehyde and vitisin B (acetaldehyde reaction-dependent) compared to M. pulcherrima M00/09G, Hanseniaspora guillermondii T06/09G, H. opuntiae T06/01G, H. vineae T02/05F and H. clermontiae (A10/82Fand C10/54F). However, co-fermentation of H. vineae and H. clermontiae with S. cerevisiae resulted in a significantly higher concentration of acetaldehyde compared with the pure S. cerevisiae control. HPLC-DAD-MS analysis confirmed an increased formation of vitisin B in co-fermentation treatments when compared to pure Saccharomyces fermentation, suggesting the key role of acetaldehyde. Copyright © 2016 John Wiley & Sons, Ltd.

  4. Dislocation Modeling and Comparison With GPS Data to Assess Possible Elastic Strain Accumulation in the Central Lesser Antilles: New Constraints From the NSF REU Site in Dominica Between 2001 and 2007

    NASA Astrophysics Data System (ADS)

    Staisch, L.; Styron, R. H.; James, S.; Turner, H. L.; Ashlock, A.; Cavness, C. L.; Collier, X.; Fauria, K.; Feinstein, R.; Murphy, R.; Williams, B.; Mattioli, G. S.; Jansma, P. E.; Cothren, J.

    2007-12-01

    The Caribbean, North and South American plates are converging at a rate of 2 cm/yr in the central region of the Lesser Antilles arc. Here we report high-precision GPS data in concert with forward modeling of a simplified subduction zone geometry to assess strain accumulation for the Lesser Antilles trench. We are able to constrain both vertical and horizontal surface deformation from campaign and continuous GPS observations from 28 geodetic benchmarks located in Guadeloupe, Dominica and Aves Island. Precise station positions were estimated with GIPSY-OASIS II using an absolute point positioning strategy and final, precise orbits, clocks, earth orientation parameters, and x-files. All position estimates were updated to ITRF05 and a revised Caribbean Euler pole was used to place our observations in a CAR-fixed frame. Surface displacements for each site were estimated over 2-7 years. CAR-fixed velocities are projected onto a 500 kilometer transect from the LA trench to Aves Island and compared to calculated displacements for 88 different subduction models. Finite dislocations within an elastic half-space with variable parameters such as angle of the subducting slab, the downdip extent of the locked zone, and percentage of plate interface locking were investigated. Other parameters, such as trench length and slip remained constant. Using a chi-squared, best-fit statistical criterion, the GPS data constrain the subduction interface to a 75 kilometer downdip extent, a 10° dip angle, and near 50% locking. This implies that the subduction zone offshore Dominica is in an interseismic state, thus accumulating strain and causing small westward and upward displacement of the Lesser Antilles relative to the stable Caribbean interior.

  5. Plastic condoms.

    PubMed

    1968-01-01

    Only simple equipment, simple technology and low initial capital investment are needed in their manufacture. The condoms can be made by people who were previously unskilled or only semi-skilled workers. Plastic condoms differ from those made of latex rubber in that the nature of the plastic film allows unlimited shelf-life. Also, the plastic has a higher degree of lubricity than latex rubber; if there is a demand for extra lubrication in a particular market, this can be provided. Because the plastic is inert, these condoms need not be packaged in hermetically sealed containers. All these attributes make it possible to put these condoms on the distributors' shelves in developing countries competitively with rubber condoms. The shape of the plastic condom is based on that of the lamb caecum, which has long been used as luxury-type condom. The plastic condom is made from plastic film (ethylene ethyl acrilate) of 0.001 inch (0.0254 mm.) thickness. In addition, a rubber ring is provided and sealed into the base of the condom for retention during coitus. The advantage of the plastic condom design and the equipment on which it is made is that production can be carried out either in labour-intensive economy or with varying degrees of mechanization and automation. The uniform, finished condom if made using previously untrained workers. Training of workers can be done in a matter of hours on the two machines which are needed to produce and test the condoms. The plastic film is provided on a double wound roll, and condom blanks are prepared by means of a heat-sealing die on the stamping machine. The rubber rings are united to the condom blanks on an assembly machine, which consists of a mandrel and heat-sealing equipment to seal the rubber ring to the base of the condom. Built into the assembly machine is a simple air-testing apparatus that can detect the smallest pinhole flaw in a condom. The manufacturing process is completed by unravelling the condom from the assembly

  6. Interseismic strain accumulation measured by GPS in the seismic gap between Constitución and Concepción in Chile

    NASA Astrophysics Data System (ADS)

    Ruegg, J. C.; Rudloff, A.; Vigny, C.; Madariaga, R.; de Chabalier, J. B.; Campos, J.; Kausel, E.; Barrientos, S.; Dimitrov, D.

    2009-06-01

    The Concepción-Constitución area [35-37°S] in South Central Chile is very likely a mature seismic gap, since no large subduction earthquake has occurred there since 1835. Three campaigns of global positioning system (GPS) measurements were carried out in this area in 1996, 1999 and 2002. We observed a network of about 40 sites, including two east-west transects ranging from the coastal area to the Argentina border and one north-south profile along the coast. Our measurements are consistent with the Nazca/South America relative angular velocity (55.9°N, 95.2°W, 0.610°/Ma) discussed by Vigny et al. (2008, this issue) which predicts a convergence of 68 mm/year oriented 79°N at the Chilean trench near 36°S. With respect to stable South America, horizontal velocities decrease from 45 mm/year on the coast to 10 mm/year in the Cordillera. Vertical velocities exhibit a coherent pattern with negative values of about 10 mm/year on the coast and slightly positive or near zero in the Central Valley or the Cordillera. Horizontal velocities have formal uncertainties in the range of 1-3 mm/year and vertical velocities around 3-6 mm/year. Surface deformation in this area of South Central Chile is consistent with a fully coupled elastic loading on the subduction interface at depth. The best fit to our data is obtained with a dip of 16 ± 3°, a locking depth of 55 ± 5 km and a dislocation corresponding to 67 mm/year oriented 78°N. However in the northern area of our network the fit is improved locally by using a lower dip around 13°. Finally a convergence motion of about 68 mm/year represents more than 10 m of displacement accumulated since the last big interplate subduction event in this area over 170 years ago (1835 earthquake described by Darwin). Therefore, in a worst case scenario, the area already has a potential for an earthquake of magnitude as large as 8-8.5, should it happen in the near future.

  7. Improved hardening theory for cyclic plasticity.

    NASA Technical Reports Server (NTRS)

    Vos, R. G.; Armstrong, W. H.

    1973-01-01

    A temperature-dependent version of a combined hardening theory, including isotropic and kinematic hardening, is presented within the framework of recent plasticity formulations. This theory has been found to be especially useful in finite-element analysis of aerospace vehicle engines under conditions of large plastic strain and low-cycle fatigue.

  8. Electromagnetic bonding of plastics to aluminum

    NASA Technical Reports Server (NTRS)

    Sheppard, A. T.; Silbert, L.

    1980-01-01

    Electromagnetic curing is used to bond strain gage to aluminum tensile bar. Electromagnetic energy heats only plastic/metal interface by means of skin effect, preventing degradation of heat-treated aluminum. Process can be easily applied to other metals joined by high-temperature-curing plastic adhesives.

  9. Cosmetic Plastic Surgery Statistics

    MedlinePlus

    2014 Cosmetic Plastic Surgery Statistics Cosmetic Procedure Trends 2014 Plastic Surgery Statistics Report Please credit the AMERICAN SOCIETY OF PLASTIC SURGEONS when citing statistical data or using ...

  10. Plastics Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 16 units to consider for use in a tech prep competency profile for the occupation of plastics technician. All the units listed will not necessarily apply to every situation or tech prep consortium, nor will all the competencies within each unit be appropriate. Several units appear within each specific occupation and would…

  11. Structural features of plastic deformation in bulk metallic glasses

    SciTech Connect

    Scudino, S. Shakur Shahabi, H.; Stoica, M.; Kühn, U.; Kaban, I.; Escher, B.; Eckert, J.; Vaughan, G. B. M.

    2015-01-19

    Spatially resolved strain maps of a plastically deformed bulk metallic glass (BMG) have been created by using high-energy X-ray diffraction. The results reveal that plastic deformation creates a spatially heterogeneous atomic arrangement, consisting of strong compressive and tensile strain fields. In addition, significant shear strain is introduced in the samples. The analysis of the eigenvalues and eigenvectors of the strain tensor indicates that considerable structural anisotropy occurs in both the magnitude and direction of the strain. These features are in contrast to the behavior observed in elastically deformed BMGs and represent a distinctive structural sign of plastic deformation in metallic glasses.

  12. Accumulate Repeat Accumulate Coded Modulation

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative coded modulation scheme called 'Accumulate Repeat Accumulate Coded Modulation' (ARA coded modulation). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes that are combined with high level modulation. Thus at the decoder belief propagation can be used for iterative decoding of ARA coded modulation on a graph, provided a demapper transforms the received in-phase and quadrature samples to reliability of the bits.

  13. Plastic bronchitis.

    PubMed

    Singhi, Anil Kumar; Vinoth, Bharathi; Kuruvilla, Sarah; Sivakumar, Kothandam

    2015-01-01

    Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics. They are ominous with poor prognosis. Sometimes, infection or airway reactivity may provoke cast bronchitis as a two-step insult on a vulnerable vascular bed. In such instances, aggressive management leads to longer survival. This report of cast bronchitis discusses its current understanding. PMID:26556975

  14. A variational approach for a nonlinear one-dimensional damage-elasto-plastic second-gradient continuum model

    NASA Astrophysics Data System (ADS)

    Placidi, Luca

    2016-03-01

    A one-dimensional displacement second-gradient damage continuum theory has been already presented within the framework of a variational approach. Damage is associated with strain concentration. Therefore, not only non-local effects of displacement second-gradient modelling should be considered in a comprehensive model, but also any plastic effects. The aim of this paper is therefore to extend such a model to plasticity. The action is intended to depend not only with respect to first and second gradient of displacement field and to a scalar damage field, but also to further two internal variables, i.e. the accumulated plastic tension and the accumulated plastic compression. A constitutive prescription on the stiffness is given in terms of the scalar damage parameter in a usual way, i.e. as in many other works, it is prescribed to decrease as far as the damage increases. On the other hand, the microstructural material length (i.e. the square of the constitutive function in front of the squared displacement second-gradient term in the action functional) is prescribed to increase as far as the damage increases, being this last assumption connected to the interpretation that a damage state induces a microstructure in the continuum and that such a microstructure is more important as far as the damage increases. Initial damage threshold and yield stresses are naturally introduced in the action in front of linear terms, respectively, of damage and plastic internal variables. The hardening matrix is also introduced in a natural way as the coefficient matrix in front of the quadratic terms of the two plastic internal variables. At a given value of damage and plastic parameters, the behaviour is referred to second-gradient linear elastic material. However, the damage and plastic evolutions make the model not only nonlinear, but also inelastic. The second principle of thermodynamics is considered by assuming that the scalar damage and plastic parameters do not decrease their

  15. New Class of Plastic Bulk Metallic Glass

    SciTech Connect

    Chen, L. Y.; Jiang, Q. K.; Wang, X. D.; Cao, Q. P.; Zeng, Y. W.; Jiang, J. Z.; Fu, Z. D.; Zhang, S. L.; Zhang, G. Q.; Hao, X. P.; Wang, B. Y.; Franz, H.; Liu, Y. G.; Xie, H. S.

    2008-02-22

    An intrinsic plastic Cu{sub 45}Zr{sub 46}Al{sub 7}Ti{sub 2} bulk metallic glass (BMG) with high strength and superior compressive plastic strain of up to 32.5% was successfully fabricated by copper mold casting. The superior compressive plastic strain was attributed to a large amount of randomly distributed free volume induced by Ti minor alloying, which results in extensive shear band formation, branching, interaction and self-healing of minor cracks. The mechanism of plasticity presented here suggests that the creation of a large amount of free volume in BMGs by minor alloying or other methods might be a promising new way to enhance the plasticity of BMGs.

  16. Up-cycling of PET (polyethylene terephthalate) to the biodegradable plastic PHA (polyhydroxyalkanoate).

    PubMed

    Kenny, Shane T; Runic, Jasmina Nikodinovic; Kaminsky, Walter; Woods, Trevor; Babu, Ramesh P; Keely, Chris M; Blau, Werner; O'Connor, Kevin E

    2008-10-15

    The conversion of the petrochemical polymer polyethylene terephthalate (PET) to a biodegradable plastic polyhydroxyal-kanoate (PHA) is described here. PET was pyrolised at 450 degrees C resulting in the production of a solid, liquid, and gaseous fraction. The liquid and gaseous fractions were burnt for energy recovery, whereas the solid fraction terephthalic acid (TA) was used as the feedstock for bacterial production of PHA. Strains previously reported to grow on TA were unable to accumulate PHA. We therefore isolated bacteria from soil exposed to PET granules at a PET bottle processing plant From the 32 strains isolated, three strains capable of accumulation of medium chain length PHA (mclPHA) from TA as a sole source of carbon and energy were selected for further study. These isolates were identified using 16S rDNA techniques as P. putida (GO16), P. putida (GO19), and P. frederiksbergensis (GO23). P. putida GO16 and GO19 accumulate PHA composed predominantly of a 3-hydroxydecanoic acid monomer while P. frederiksbergensis GO23 accumulates 3-hydroxydecanoic acid as the predominant monomer with increased amounts of 3-hydroxydodecanoic acid and 3-hydroxydodecenoic acid compared to the other two strains. PHA was detected in all three strains when nitrogen depleted below detectable levels in the growth medium. Strains GO16 and GO19 accumulate PHA at a maximal rate of approximately 8.4 mg PHA/l/h for 12 h before the rate of PHA accumulation decreased dramatically. Strain GO23 accumulates PHA at a lower maximal rate of 4.4 mg PHA/l/h but there was no slow down in the rate of PHA accumulation over time. Each of the PHA polymers is a thermoplastic with the onset of thermal degradation occurring around 308 degrees C with the complete degradation occurring by 370 degrees C. The molecular weight ranged from 74 to 123 kDa. X-ray diffraction indicated crystallinity of the order of 18-31%. Thermal analysis shows a low glass transition (-53 degrees C) with a broad melting

  17. Heat accumulator

    SciTech Connect

    Bracht, A.

    1981-09-29

    A heat accumulator comprises a thermally-insulated reservoir full of paraffin wax mixture or other flowable or meltable heat storage mass, heat-exchangers immersed in the mass, a heat-trap connected to one of the heat-exchangers, and a heat user connected to the other heat-exchanger. Pumps circulate fluids through the heat-trap and the heat-using means and the respective heat-exchangers, and a stirrer agitates and circulates the mass, and the pumps and the stirrer and electric motors driving these devices are all immersed in the mass.

  18. The Application of Strain Range Partitioning Method to Torsional Creep-Fatigue Interaction

    NASA Technical Reports Server (NTRS)

    Zamrik, S. Y.

    1975-01-01

    The method of strain range partitioning was applied to a series of torsional fatigue tests conducted on tubular 304 stainless steel specimens at 1200 F. Creep strain was superimposed on cycling strain, and the resulting strain range was partitioned into four components; completely reversed plastic shear strain, plastic shear strain followed by creep strain, creep strain followed by plastic strain and completely reversed creep strain. Each strain component was related to the cyclic life of the material. The damaging effects of the individual strain components were expressed by a linear life fraction rule. The plastic shear strain component showed the least detrimental factor when compared to creep strain reversed by plastic strain. In the latter case, a reduction of torsional fatigue life in the order of magnitude of 1.5 was observed.

  19. On the plasticity event in metallic glass

    NASA Astrophysics Data System (ADS)

    Liu, Weidong; Ruan, Haihui; Zhang, Liangchi

    2013-03-01

    Based on a systematic molecular dynamics analysis, this study reveals that plastic deformation of metallic glass is not through a uniform configuration change but via many localized plasticity events. These events are manifested by the atomic clusters of high kinetic energy and high strain rate, emerging even in the elastic deformation regime. The life of such a plasticity event is on the order of 10-12 s, during which the distribution of kinetic energy follows a power law. The study shows that yielding in metallic glass occurs at the sudden surge point of the number of plasticity events. In the steady plastic deformation regime, the continuous nucleation and annihilation of the plastic events lead to a steady flow stress and stabilized total potential energy.

  20. Modeling Near-Crack-Tip Plasticity from Nano- to Micro-Scales

    NASA Technical Reports Server (NTRS)

    Glaessgen, Edward H.; Saether, Erik; Hochhalter, Jake D.; Yamakov, Vesselin I.

    2010-01-01

    Several efforts that are aimed at understanding the plastic deformation mechanisms related to crack propagation at the nano-, meso- and micro-length scales including atomistic simulation, discrete dislocation plasticity, strain gradient plasticity and crystal plasticity are discussed. The paper focuses on discussion of newly developed methodologies and their application to understanding damage processes in aluminum and its alloys. Examination of plastic mechanisms as a function of increasing length scale illustrates increasingly complex phenomena governing plasticity

  1. Microplate Technique for Determining Accumulation of Metals by Algae

    PubMed Central

    Hassett, James M.; Jennett, J. Charles; Smith, James E.

    1981-01-01

    A microplate technique was developed to determine the conditions under which pure cultures of algae removed heavy metals from aqueous solutions. Variables investigated included algal species and strain, culture age (11 and 44 days), metal (mercury, lead, cadmium, and zinc), pH, effects of different buffer solutions, and time of exposure. Plastic, U-bottomed microtiter plates were used in conjunction with heavy metal radionuclides to determine concentration factors for metal-alga combinations. The technique developed was rapid, statistically reliable, and economical of materials and cells. Results (expressed as concentration factors) were in reasonably good agreement with literature values. All species of algae studied removed mercury from solution. Green algae proved better at accumulating cadmium than did blue-green algae. No alga studied removed zinc, perhaps because cells were maintained in the dark during the labeling period. Chlamydomonas sp. proved superior in ability to remove lead from solution. PMID:16345764

  2. Attenuated Escherichia coli strains expressing the colonization factor antigen I (CFA/I) and a detoxified heat-labile enterotoxin (LThK63) enhance clearance of ETEC from the lungs of mice and protect mice from intestinal ETEC colonization and LT-induced fluid accumulation.

    PubMed

    Byrd, Wyatt; Boedeker, Edgar C

    2013-03-15

    Although enterotoxigenic Escherichia coli (ETEC) infections are important causes of infantile and traveler's diarrhea there is no licensed vaccine available for those at-risk. Our goal is to develop a safe, live attenuated ETEC vaccine. We used an attenuated E. coli strain (O157:H7, Δ-intimin, Stx1-neg, Stx2-neg) as a vector (ZCR533) to prepare two vaccine strains, one strain expressing colonization factor antigen I (ZCR533-CFA/I) and one strain expressing CFA/I and a detoxified heat-labile enterotoxin (ZCR533-CFA/I+LThK63) to deliver ETEC antigens to mucosal sites in BALB/c mice. Following intranasal and intragastric immunization with the vaccine strains, serum IgG and IgA antibodies were measured to the CFA/I antigen, however, only serum IgG antibodies were detected to the heat-labile enterotoxin. Intranasal administration of the vaccine strains induced respiratory and intestinal antibody responses to the CFA/I and LT antigens, while intragastric administration induced only intestinal antibody responses with no respiratory antibodies detected to the CFA/I and LT antigens. Mice immunized intranasally with the vaccine strains showed enhanced clearance of wild-type (wt) ETEC bacteria from the lungs. Mice immunized intranasally and intragastrically with the vaccine strains were protected from intestinal colonization following oral challenge with ETEC wt bacteria. Mice immunized intragastrically with the ZCR533-CFA/I+LThK63 vaccine strain had less fluid accumulate in their intestine following challenge with ETEC wt bacteria or with purified LT as compared to the sham mice indicating that the immunized mice were protected from LT-induced intestinal fluid accumulation. Thus, mice intragastrically immunized with the ZCR533-CFA/I+LThK63 vaccine strain were able to effectively neutralize the activity of the LT enterotoxin. However, no difference in intestinal fluid accumulation was detected in the mice immunized intranasally with the vaccine strain as compared to the sham

  3. Benthic plastic debris in marine and fresh water environments.

    PubMed

    Corcoran, Patricia L

    2015-08-01

    This review provides a discussion of the published literature concerning benthic plastic debris in ocean, sea, lake, estuary and river bottoms throughout the world. Although numerous investigations of shoreline, surface and near-surface plastic debris provide important information on plastic types, distribution, accumulation, and degradation, studies of submerged plastic debris have been sporadic in the past and have become more prominent only recently. The distribution of benthic debris is controlled mainly by combinations of urban proximity and its association with fishing-related activities, geomorphology, hydrological conditions, and river input. High density plastics, biofouled products, polymers with mineral fillers or adsorbed minerals, and plastic-metal composites all have the potential to sink. Once deposited on the bottoms of water basins and channels, plastics are shielded from UV light, thus slowing the degradation process significantly. Investigations of the interactions between benthic plastic debris and bottom-dwelling organisms will help shed light on the potential dangers of submerged plastic litter.

  4. Benthic plastic debris in marine and fresh water environments.

    PubMed

    Corcoran, Patricia L

    2015-08-01

    This review provides a discussion of the published literature concerning benthic plastic debris in ocean, sea, lake, estuary and river bottoms throughout the world. Although numerous investigations of shoreline, surface and near-surface plastic debris provide important information on plastic types, distribution, accumulation, and degradation, studies of submerged plastic debris have been sporadic in the past and have become more prominent only recently. The distribution of benthic debris is controlled mainly by combinations of urban proximity and its association with fishing-related activities, geomorphology, hydrological conditions, and river input. High density plastics, biofouled products, polymers with mineral fillers or adsorbed minerals, and plastic-metal composites all have the potential to sink. Once deposited on the bottoms of water basins and channels, plastics are shielded from UV light, thus slowing the degradation process significantly. Investigations of the interactions between benthic plastic debris and bottom-dwelling organisms will help shed light on the potential dangers of submerged plastic litter. PMID:26129903

  5. Elastic-plastic analysis of AS4/PEEK composite laminate using a one-parameter plasticity model

    NASA Technical Reports Server (NTRS)

    Sun, C. T.; Yoon, K. J.

    1992-01-01

    A one-parameter plasticity model was shown to adequately describe the plastic deformation of AS4/PEEK (APC-2) unidirectional thermoplastic composite. This model was verified further for unidirectional and laminated composite panels with and without a hole. The elastic-plastic stress-strain relations of coupon specimens were measured and compared with those predicted by the finite element analysis using the one-parameter plasticity model. The results show that the one-parameter plasticity model is suitable for the analysis of elastic-plastic deformation of AS4/PEEK composite laminates.

  6. The role of cyclic plastic zone size on fatigue crack growth behavior in high strength steels

    NASA Astrophysics Data System (ADS)

    Korda, Akhmad A.; Miyashita, Y.; Mutoh, Y.

    2015-09-01

    The role of cyclic plastic zone in front of the crack tip was studied in high strength steels. Estimated plastic zone size would be compared with actual observation. Strain controlled fatigue tests of the steels were carried out to obtain cyclic stress-strain curves for plastic zone estimation. Observations of plastic zone were carried out using in situ SEM fatigue crack growth tests under a constant-ΔK. Hard microstructures in structural steels showed to inhibit the extent of plastic deformation around the crack tip. The rate of crack growth can be correlated with the size of plastic zone. The smaller the plastic zone size, the slower the fatigue crack growth.

  7. Long-term sorption of metals is similar among plastic types: implications for plastic debris in aquatic environments.

    PubMed

    Rochman, Chelsea M; Hentschel, Brian T; Teh, Swee J

    2014-01-01

    Concerns regarding plastic debris and its ability to accumulate large concentrations of priority pollutants in the aquatic environment led us to quantify relationships between different types of mass-produced plastic and metals in seawater. At three locations in San Diego Bay, we measured the accumulation of nine targeted metals (aluminum, chromium, manganese, iron, cobalt, nickel, zinc, cadmium and lead) sampling at 1, 3, 6, 9 and 12 months, to five plastic types: polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), and polypropylene (PP). Accumulation patterns were not consistent over space and time, and in general all types of plastic tended to accumulate similar concentrations of metals. When we did observe significant differences among concentrations of metals at a single sampling period or location in San Diego Bay, we found that HDPE typically accumulated lesser concentrations of metals than the other four polymers. Furthermore, over the 12-month study period, concentrations of all metals increased over time, and chromium, manganese, cobalt, nickel, zinc and lead did not reach saturation on at least one plastic type during the entire 12-month exposure. This suggests that plastic debris may accumulate greater concentrations of metals the longer it remains at sea. Overall, our work shows that a complex mixture of metals, including those listed as priority pollutants by the US EPA (Cd, Ni, Zn and Pb), can be found on plastic debris composed of various plastic types. PMID:24454866

  8. Long-Term Sorption of Metals Is Similar among Plastic Types: Implications for Plastic Debris in Aquatic Environments

    PubMed Central

    Rochman, Chelsea M.; Hentschel, Brian T.; Teh, Swee J.

    2014-01-01

    Concerns regarding plastic debris and its ability to accumulate large concentrations of priority pollutants in the aquatic environment led us to quantify relationships between different types of mass-produced plastic and metals in seawater. At three locations in San Diego Bay, we measured the accumulation of nine targeted metals (aluminum, chromium, manganese, iron, cobalt, nickel, zinc, cadmium and lead) sampling at 1, 3, 6, 9 and 12 months, to five plastic types: polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), and polypropylene (PP). Accumulation patterns were not consistent over space and time, and in general all types of plastic tended to accumulate similar concentrations of metals. When we did observe significant differences among concentrations of metals at a single sampling period or location in San Diego Bay, we found that HDPE typically accumulated lesser concentrations of metals than the other four polymers. Furthermore, over the 12-month study period, concentrations of all metals increased over time, and chromium, manganese, cobalt, nickel, zinc and lead did not reach saturation on at least one plastic type during the entire 12-month exposure. This suggests that plastic debris may accumulate greater concentrations of metals the longer it remains at sea. Overall, our work shows that a complex mixture of metals, including those listed as priority pollutants by the US EPA (Cd, Ni, Zn and Pb), can be found on plastic debris composed of various plastic types. PMID:24454866

  9. Degradation of Oxo-Biodegradable Plastic by Pleurotus ostreatus

    PubMed Central

    da Luz, José Maria Rodrigues; Paes, Sirlaine Albino; Nunes, Mateus Dias; da Silva, Marliane de Cássia Soares; Kasuya, Maria Catarina Megumi

    2013-01-01

    Growing concerns regarding the impact of the accumulation of plastic waste over several decades on the environmental have led to the development of biodegradable plastic. These plastics can be degraded by microorganisms and absorbed by the environment and are therefore gaining public support as a possible alternative to petroleum-derived plastics. Among the developed biodegradable plastics, oxo-biodegradable polymers have been used to produce plastic bags. Exposure of this waste plastic to ultraviolet light (UV) or heat can lead to breakage of the polymer chains in the plastic, and the resulting compounds are easily degraded by microorganisms. However, few studies have characterized the microbial degradation of oxo-biodegradable plastics. In this study, we tested the capability of Pleurotus ostreatus to degrade oxo-biodegradable (D2W) plastic without prior physical treatment, such as exposure to UV or thermal heating. After 45 d of incubation in substrate-containing plastic bags, the oxo-biodegradable plastic, which is commonly used in supermarkets, developed cracks and small holes in the plastic surface as a result of the formation of hydroxyl groups and carbon-oxygen bonds. These alterations may be due to laccase activity. Furthermore, we observed the degradation of the dye found in these bags as well as mushroom formation. Thus, P. ostreatus degrades oxo-biodegradable plastics and produces mushrooms using this plastic as substrate. PMID:23967057

  10. Degradation of oxo-biodegradable plastic by Pleurotus ostreatus.

    PubMed

    da Luz, José Maria Rodrigues; Paes, Sirlaine Albino; Nunes, Mateus Dias; da Silva, Marliane de Cássia Soares; Kasuya, Maria Catarina Megumi

    2013-01-01

    Growing concerns regarding the impact of the accumulation of plastic waste over several decades on the environmental have led to the development of biodegradable plastic. These plastics can be degraded by microorganisms and absorbed by the environment and are therefore gaining public support as a possible alternative to petroleum-derived plastics. Among the developed biodegradable plastics, oxo-biodegradable polymers have been used to produce plastic bags. Exposure of this waste plastic to ultraviolet light (UV) or heat can lead to breakage of the polymer chains in the plastic, and the resulting compounds are easily degraded by microorganisms. However, few studies have characterized the microbial degradation of oxo-biodegradable plastics. In this study, we tested the capability of Pleurotus ostreatus to degrade oxo-biodegradable (D2W) plastic without prior physical treatment, such as exposure to UV or thermal heating. After 45 d of incubation in substrate-containing plastic bags, the oxo-biodegradable plastic, which is commonly used in supermarkets, developed cracks and small holes in the plastic surface as a result of the formation of hydroxyl groups and carbon-oxygen bonds. These alterations may be due to laccase activity. Furthermore, we observed the degradation of the dye found in these bags as well as mushroom formation. Thus, P. ostreatus degrades oxo-biodegradable plastics and produces mushrooms using this plastic as substrate.

  11. Plastic Deformations in Complex Plasmas

    SciTech Connect

    Durniak, C.; Samsonov, D.

    2011-04-29

    Complex plasmas are macroscopic model systems of real solids and liquids, used to study underdamped dynamics and wave phenomena. Plastic deformations of complex plasma crystals under slow uniaxial compression have been studied experimentally and numerically. It is shown that the lattice becomes locally sheared and that this strain is relaxed by shear slips resulting in global uniform compression and heat generation. Shear slips generate pairs of dislocations which move in opposite directions at subsonic speeds.

  12. Texture evolution of an Fe–Ni alloy sheet produced by cross accumulative roll bonding

    SciTech Connect

    Azzeddine, Hiba; Tirsatine, Kamel; Baudin, Thierry; Helbert, Anne-Laure; Brisset, François; Bradai, Djamel

    2014-11-15

    The texture evolution in an Fe–36%Ni (wt.%) alloy, severely deformed to a true strain of 4.8 by cross accumulative roll bonding, was investigated using X-ray diffraction and a visco-plastic self-consistent simulation. At the surface, the C component ((100)<011>) exhibited a strong continuous strengthening from cycles 1 to 5. At the mid-thickness region, the texture evolution appeared to be cyclic due to the cyclic nature of the imposed deformation. A copper-type texture was observed even after cycles, whereas a new major texture component named H ((012)<22{sup ¯}1>) was formed after odd cycles, with several other minor ones belonging to a (210) fiber. A significant change in the plastic anisotropy was introduced by cross accumulative roll bonding processing. - Highlight: • The texture after CARB is characterized by a typical C shear component near the surface. • The texture evolution in the mid thickness of samples seen to be cyclic • VPSC model reproduced the experimental texture in the early CARB cycle. • The CARB process can reduce the plastic anisotropy of the sheet.

  13. Endothelial Plasticity: Shifting Phenotypes through Force Feedback

    PubMed Central

    Krenning, Guido; Barauna, Valerio G.; Krieger, José E.; Harmsen, Martin C.; Moonen, Jan-Renier A. J.

    2016-01-01

    The endothelial lining of the vasculature is exposed to a large variety of biochemical and hemodynamic stimuli with different gradients throughout the vascular network. Adequate adaptation requires endothelial cells to be highly plastic, which is reflected by the remarkable heterogeneity of endothelial cells in tissues and organs. Hemodynamic forces such as fluid shear stress and cyclic strain are strong modulators of the endothelial phenotype and function. Although endothelial plasticity is essential during development and adult physiology, proatherogenic stimuli can induce adverse plasticity which contributes to disease. Endothelial-to-mesenchymal transition (EndMT), the hallmark of endothelial plasticity, was long thought to be restricted to embryonic development but has emerged as a pathologic process in a plethora of diseases. In this perspective we argue how shear stress and cyclic strain can modulate EndMT and discuss how this is reflected in atherosclerosis and pulmonary arterial hypertension. PMID:26904133

  14. Plastic debris in the open ocean.

    PubMed

    Cózar, Andrés; Echevarría, Fidel; González-Gordillo, J Ignacio; Irigoien, Xabier; Ubeda, Bárbara; Hernández-León, Santiago; Palma, Alvaro T; Navarro, Sandra; García-de-Lomas, Juan; Ruiz, Andrea; Fernández-de-Puelles, María L; Duarte, Carlos M

    2014-07-15

    There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean.

  15. Plastic debris in the open ocean

    PubMed Central

    Cózar, Andrés; Echevarría, Fidel; González-Gordillo, J. Ignacio; Irigoien, Xabier; Úbeda, Bárbara; Hernández-León, Santiago; Palma, Álvaro T.; Navarro, Sandra; García-de-Lomas, Juan; Ruiz, Andrea; Fernández-de-Puelles, María L.; Duarte, Carlos M.

    2014-01-01

    There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean. PMID:24982135

  16. A phase-field model for ductile fracture at finite strains and its experimental verification

    NASA Astrophysics Data System (ADS)

    Ambati, Marreddy; Kruse, Roland; De Lorenzis, Laura

    2016-01-01

    In this paper, a phase-field model for ductile fracture previously proposed in the kinematically linear regime is extended to the three-dimensional finite strain setting, and its predictions are qualitatively and quantitatively compared with several experimental results, both from ad-hoc tests carried out by the authors and from the available literature. The proposed model is based on the physical assumption that fracture occurs when a scalar measure of the accumulated plastic strain reaches a critical value, and such assumption is introduced through the dependency of the phase-field degradation function on this scalar measure. The proposed model is able to capture the experimentally observed sequence of elasto-plastic deformation, necking and fracture phenomena in flat specimens; the occurrence of cup-and-cone fracture patterns in axisymmetric specimens; the role played by notches and by their size on the measured displacement at fracture; and the sequence of distinct cracking events observed in more complex specimens.

  17. Factors influencing the detection of beach plastic debris.

    PubMed

    Lavers, Jennifer L; Oppel, Steffen; Bond, Alexander L

    2016-08-01

    Marine plastic pollution is a global problem with considerable ecological and economic consequences. Quantifying the amount of plastic in the ocean has been facilitated by surveys of accumulated plastic on beaches, but existing monitoring programmes assume the proportion of plastic detected during beach surveys is constant across time and space. Here we use a multi-observer experiment to assess what proportion of small plastic fragments is missed routinely by observers, and what factors influence the detection probability of different types of plastic. Detection probability across the various types of plastic ranged from 60 to 100%, and varied considerably by observer, observer experience, and biological material present on the beach that could be confused with plastic. Blue fragments had the highest detection probability, while white fragments had the lowest. We recommend long-term monitoring programmes adopt survey designs accounting for imperfect detection or at least assess the proportion of fragments missed by observers. PMID:27363010

  18. The application of 'strain range partitioning method' to torsional creep-fatigue interaction

    NASA Technical Reports Server (NTRS)

    Zamrik, S. Y.; Bilir, O. G.

    1975-01-01

    The method of strain range partitioning was applied to a series of torsional fatigue tests conducted on tubular 304 stainless steel specimens at 1200 F (649 C). Creep strain was superimposed on cycling strain, and the resulting strain range was partitioned into four components; completely reversed plastic shear strain followed by creep strain, creep strain followed by plastic strain and completely reversed creep strain. Each strain component was related to the cyclic life of the material. The paper describes the experimental procedure used to achieve strain partitioning and the torsional test results are compared to those obtained from axial tests. The damaging effects of the individual strain components were expressed by a linear life fraction rule. The shear strain plastic component showed the least detrimental factor when compared to creep strain reversal by plastic strain. In the latter case, a reduction of torsional fatigue life in the order of magnitude of 1.5 was observed.

  19. Plasticity in Ultra Fine Grained Materials

    SciTech Connect

    Koslowski, Marisol

    2015-04-15

    Understanding the mechanisms of deformation of nanocrystalline (nc) materials is critical to the design of micro and nano devices and to develop materials with superior fracture strength and wear resistance for applications in new energy technologies. In this project we focused on understanding the following plastic deformation processes described in detail in the following sections: 1. Plastic strain recovery (Section 1). 2. Effect of microstructural variability on the yield stress of nc metals (Section 2). 3. The role of partial and extended full dislocations in plastic deformation of nc metals (Section 3).

  20. Volume dilatation in a polycarbonate blend at varying strain rates

    NASA Astrophysics Data System (ADS)

    Hiermaier, S.; Huberth, F.

    2012-05-01

    Impact loaded polymers show a variety of strain-rate dependent mechanical properties in their elastic, plastic and failure behaviour. In contrast to purely crystalline materials, the volume of polymeric materials can significantly change under irreversible deformations. In this paper, uni-axial tensile tests were performed in order to measure the dilatation in the Polycarbonate-Acrylnitril-Butadien-Styrol (PC-ABS) Bayblend T65. The accumulation of dilatation was measured at deformation speeds of 0.1 and 500 [ mm/ s]. Instrumented with a pair of two high-speed cameras, volume segments in the samples were observed. The change in volume was quantified as relation between the deformed and initial volumes of the segments. It was observed that the measured dilatations are of great significance for the constitutive models. This is specifically demonstrated through comparisons of stress-strain relations derived from the two camera-perspectives with isochoric relations based on single-surface observations of the same experiments.

  1. Ensembles of gliding grain boundary dislocations in ultrafine grained materials produced by severe plastic deformation

    SciTech Connect

    Nazarov, A.A.

    1997-10-15

    Severe plastic deformation which is now widely used to produce an ultrafine grained (UFG) structure in metals and alloys necessarily leads to the accumulation of interfacial dislocations which arise due to the incompatibilities of strains of neighbor misorientated areas. The most important result of the dislocation storage at grain boundaries (GBs) and associated internal stresses is the fragmentation which at extremely large strains is usually followed by the formation of a very fine highly misorientated granular structure. After deformation the UFG structure must preserve residual dislocation arrays in GBs, since recovery at room temperature is not enough to provide their annihilation. Recently, a hypothesis has been put forward that the internal stresses induced by these arrays are the origin of a number of fundamental properties of UFG materials different from those of coarse grained ones. The author suggested that, in addition, the nonequilibrium dislocation ensembles in GBs were characterized by disordered distribution of dislocations. Thus, three main sources of internal stresses can exist in UFG materials prepared by severe plastic deformation: (1) disordered sessile EGBD arrays, (2) excess density of sessile EGBDs, that is junction disclinations, and (3) arrays of tangential EGBDs. Each of these components can contribute to the experimentally observed elastic strain, excess GB energy and volume expansion in UFG materials.

  2. The effects of plasticity in adhesive fracture

    NASA Technical Reports Server (NTRS)

    Chang, M. D.; Devries, K. L.; Williams, M. L.

    1973-01-01

    An energy-balance analysis is presented for adhesive failure in end loaded cantilever beams. The analysis includes the effects of input work, stored strain energy, dissipated plastic energy, and specific adhesive surface energy. Experimental results obtained with 6061-T6 aluminum are presented as evidence for the validity of the approach.-

  3. Geodetic strain measurements in Washington.

    USGS Publications Warehouse

    Savage, J.C.; Lisowski, M.; Prescott, W.H.

    1981-01-01

    Two new geodetic measurements of strain accumulation in the state of Washington for the interval 1972-1979 are reported. Near Seattle the average principal strain rates are 0.07 + or - 0.03 mu strain/yr N19oW and -0.13 + or - 0.02 mu strain/yr N71oE, and near Richland (south central Washington) the average principal strain rates are -0.02 + or - 0.01 mu strain/yr N36oW and -0.04 + or - 0.01 mu strain/yr N54oE. Extension is taken as positive, and the uncertainties quoted are standard deviations. A measurement of shear strain accumulation (dilation not determined) in the epoch 1914- 1966 along the north coast of Vancouver Island by the Geodetic Survey of Canada indicates a marginally significant accumulation of right-lateral shear (0.06 + or - 0.03 mu rad/yr) across the plate boundary (N40oW strike). Although there are significant differences in detail, these strain measurements are roughly consistent with a crude dislocation model that represents subduction of the Juan de Fuca plate. The observed accumulation of strain implies that large, shallow, thrust earthquakes should be expected off the coast of Washington and British Columbia. However, this conclusion is not easily reconciled with either observations of elevation change along the Washington coast or the focal mechanism solutions for shallow earthquakes in Washington. -Authors

  4. Periodontal Plastic Surgery

    MedlinePlus

    ... Dental Implants Dentures Direct Bonding Implants versus Bridges Orthodontics and Aligners Periodontal Plastic Surgery Porcelain Crowns Porcelain ... Dental Implants Dentures Direct Bonding Implants versus Bridges Orthodontics and Aligners Periodontal Plastic Surgery Porcelain Crowns Porcelain ...

  5. Plasticity and Geotechnics

    NASA Astrophysics Data System (ADS)

    Yu, Hai-Sui

    Plasticity and Geotechnics is the first attempt to summarize and present, in one volume, the major developments achieved to date in the field of plasticity theory for geotechnical materials and its applications to geotechnical analysis and design.

  6. Plastic Surgery for Teenagers

    MedlinePlus

    ... or severe acne and scarring. Teens frequently gain self-esteem and confidence when their physical problems are corrected. ... art as a helpful index of anxiety and self-esteem with plastic surgery. Plastic and Reconstructive Surgery 2002. ...

  7. Plastic casting resin poisoning

    MedlinePlus

    Epoxy poisoning; Resin poisoning ... Epoxy and resin can be poisonous if they are swallowed or their fumes are breathed in. ... Plastic casting resins are found in various plastic casting resin products.

  8. Ear Plastic Surgery

    MedlinePlus

    ... Meeting Calendar Find an ENT Doctor Near You Ear Plastic Surgery Ear Plastic Surgery Patient Health Information ... they may improve appearance and self-confidence. Can Ear Deformities Be Corrected? Formation of the ear during ...

  9. Plastic encapsulated parts

    SciTech Connect

    Castillo, T.

    1994-10-01

    Plastic semiconductor packages were characterized as possible alternatives for canned devices, which are susceptible to internal shorts caused by conductive particles. Highly accelerated stress testing (HAST) as well as electrical and mechanical testing were conducted on plastic technology devices.

  10. Tomorrow's Plastic World

    ERIC Educational Resources Information Center

    Macdonald, Averil

    2005-01-01

    Far from being just cheap packaging materials, plastics may be the materials of tomorrow. Plastic can conduct electricity, and this opens up a host of high-tech possibilities in the home and in energy generation. These possibilities are discussed here along with how plastic can be recycled and perhaps even grown.

  11. Processing of plastics

    PubMed Central

    Spaak, Albert

    1975-01-01

    An overview is given of the processing of plastic materials from the handling of polymers in the pellet and powder form to manufacturing of a plastic fabricated product. Various types of equipment used and melt processing ranges of various polymer formulations to make the myriad of plastic products that are commercially available are discussed. PMID:1175556

  12. Plastics in Building.

    ERIC Educational Resources Information Center

    Skeist, Irving, Ed.

    The evaluation and use of plastics in the construction industry are explained. The contributors offer extensive, timely, and thoroughly researched data on the chemistry, properties, functions, engineering behavior, and specific applications of plastics to building requirements. The major subjects discussed in depth are--(1) the role of plastics in…

  13. A multiscale gradient-dependent plasticity model for size effects

    NASA Astrophysics Data System (ADS)

    Lyu, Hao; Taheri-Nassaj, Nasrin; Zbib, Hussein M.

    2016-06-01

    The mechanical behaviour of polycrystalline material is closely correlated to grain size. In this study, we investigate the size-dependent phenomenon in multi-phase steels using a continuum dislocation dynamic model coupled with viscoplastic self-consistent model. We developed a dislocation-based strain gradient plasticity model and a stress gradient plasticity model, as well as a combined model, resulting in a theory that can predict size effect over a wide range of length scales. Results show that strain gradient plasticity and stress gradient plasticity are complementary rather than competing theories. The stress gradient model is dominant at the initial strain stage, and is much more effective for predicting yield strength than the strain gradient model. For larger deformations, the strain gradient model is dominant and more effective for predicting size-dependent hardening. The numerical results are compared with experimental data and it is found that they have the same trend for the yield stress. Furthermore, the effect of dislocation density at different strain stages is investigated, and the findings show that the Hall-Petch relation holds for the initial strain stage and breaks down for higher strain levels. Finally, a power law to describe the size effect and the transition zone between the strain gradient and stress gradient dominated regions is developed.

  14. Stored Energy of Plastic Deformation in Tube Bending Processes

    NASA Astrophysics Data System (ADS)

    Śloderbach, Z.; Pająk, J.

    2013-03-01

    The paper presents an aproximate analytic method for determination of the stored energy of plastic deformation during cold bending of metal tubes at bending machines. Calculations were performed for outer points of the tube layers subjected to tension and compression (the points of maximum strains). The percentage of stored energy related to the plastic strain work was determined and the results were presented in graphs. The influence and importance of the stored energy of plastic deformation on the service life of pipeline bends are discussed.

  15. Probing incipient plasticity by indenting colloidal glasses

    NASA Astrophysics Data System (ADS)

    Rahmani, Y.; Koopman, R.; Denisov, D.; Schall, P.

    2013-01-01

    Glasses are lucrative engineering materials owing to their superior mechanical properties such as high strength and large elastic strain. A central question concerns incipient plasticity - the onset of permanent deformation - that is central to their relaxation, aging, yield and fracture. Here, we use an analogue of nano-indentation performed on a colloidal glass to obtain direct images of the incipient plasticity, allowing us to elucidate the onset of permanent deformation. We visualize the microscopic strain by following distorted nearest neighbor configurations, and observe a surprising hierarchical structure of deformation: at the onset of irreversible deformation, the strain acquires a robust fractal structure, and we measure its fractal dimension. These results give direct evidence that the onset of permanent deformation has the hallmarks of a critical point, in agreement with recent theoretical works.

  16. Biodegradability of Plastics

    PubMed Central

    Tokiwa, Yutaka; Calabia, Buenaventurada P.; Ugwu, Charles U.; Aiba, Seiichi

    2009-01-01

    Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed. PMID:19865515

  17. Biodegradability of plastics.

    PubMed

    Tokiwa, Yutaka; Calabia, Buenaventurada P; Ugwu, Charles U; Aiba, Seiichi

    2009-08-26

    Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.

  18. Strain limit criteria to predict failure

    SciTech Connect

    Flanders, H.E.

    1995-12-31

    In recent years extensive effort has been expended to qualify existing structures for conditions that are beyond the original design basis. Determination of the component failure load is useful for this type of evaluation. This paper presents criteria based upon strain limits to predict the load at failure. The failure modes addressed are excessive plastic deformations, localized plastic strains, and structural instability. The effects of analytical method sophistication, as built configurations, material properties degradation, and stress state are addressed by the criteria.

  19. Antioxidant enzymes activities of Burkholderia spp. strains-oxidative responses to Ni toxicity.

    PubMed

    Dourado, M N; Franco, M R; Peters, L P; Martins, P F; Souza, L A; Piotto, F A; Azevedo, R A

    2015-12-01

    Increased agriculture production associated with intense application of herbicides, pesticides, and fungicides leads to soil contamination worldwide. Nickel (Ni), due to its high mobility in soils and groundwater, constitutes one of the greatest problems in terms of environmental pollution. Metals, including Ni, in high concentrations are toxic to cells by imposing a condition of oxidative stress due to the induction of reactive oxygen species (ROS), which damage lipids, proteins, and DNA. This study aimed to characterize the Ni antioxidant response of two tolerant Burkholderia strains (one isolated from noncontaminated soil, SNMS32, and the other from contaminated soil, SCMS54), by measuring superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione S-transferase (GST) activities. Ni accumulation and bacterial growth in the presence of the metal were also analyzed. The results showed that both strains exhibited different trends of Ni accumulation and distinct antioxidant enzymes responses. The strain from contaminated soil (SCMS54) exhibited a higher Ni biosorption and exhibited an increase in SOD and GST activities after 5 and 12 h of Ni exposure. The analysis of SOD, CAT, and GR by nondenaturing PAGE revealed the appearance of an extra isoenzyme in strain SCMS54 for each enzyme. The results suggest that the strain SCMS54 isolated from contaminated soil present more plasticity with potential to be used in soil and water bioremediation.

  20. Antioxidant enzymes activities of Burkholderia spp. strains-oxidative responses to Ni toxicity.

    PubMed

    Dourado, M N; Franco, M R; Peters, L P; Martins, P F; Souza, L A; Piotto, F A; Azevedo, R A

    2015-12-01

    Increased agriculture production associated with intense application of herbicides, pesticides, and fungicides leads to soil contamination worldwide. Nickel (Ni), due to its high mobility in soils and groundwater, constitutes one of the greatest problems in terms of environmental pollution. Metals, including Ni, in high concentrations are toxic to cells by imposing a condition of oxidative stress due to the induction of reactive oxygen species (ROS), which damage lipids, proteins, and DNA. This study aimed to characterize the Ni antioxidant response of two tolerant Burkholderia strains (one isolated from noncontaminated soil, SNMS32, and the other from contaminated soil, SCMS54), by measuring superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione S-transferase (GST) activities. Ni accumulation and bacterial growth in the presence of the metal were also analyzed. The results showed that both strains exhibited different trends of Ni accumulation and distinct antioxidant enzymes responses. The strain from contaminated soil (SCMS54) exhibited a higher Ni biosorption and exhibited an increase in SOD and GST activities after 5 and 12 h of Ni exposure. The analysis of SOD, CAT, and GR by nondenaturing PAGE revealed the appearance of an extra isoenzyme in strain SCMS54 for each enzyme. The results suggest that the strain SCMS54 isolated from contaminated soil present more plasticity with potential to be used in soil and water bioremediation. PMID:26289332

  1. Elasto-plastic contact between rollers

    NASA Astrophysics Data System (ADS)

    Chu, Kunliang; Li, Penghui

    1991-12-01

    Knowledge of the three-dimensional contact stress between roller and rolling road for a strain- hardening material in an elasto-plastic state is limited, to say the least. Mathematical analyses of stress for this problem meet with extreme difficulties. Therefore, experimental approaches are desirable. The experimental elasto-plastic stress analysis method proposed by A. R. Hunter is extended in this investigation. The model material is epoxy resin, which exhibits a frozen nonlinear effective stress-strain behavior similar to that of bearing steel when subjected to a thermal cycle whose maximum temperature is significantly less than the critical temperature of the material. This effective stress-strain curve and an effective birefringence- stress curve were obtained by subjecting uniaxial tensile specimens to constant stress and the appropriate thermal cycle. Then the model was subjected to the same thermal cycle and a uniform distributed load that would develop a plastic zone. The stress distributions on the contact surface and the plastic-zone expansion law were obtained from photomechanical analysis of the slices removed from the model. Several important conclusions were summed up that would greatly improve the roller bearing design.

  2. Materials response to large plastic deformation

    SciTech Connect

    Stout, M.G.; Hecker, S.S.

    1982-01-01

    Strain hardening at large plastic strains cannot be inferred from small-strain tensile tests. Most metals and alloys at room temperature do not reach steady state saturation at strain levels of 3 to 5. Typically, some disturbing influence offsets the balance between dislocation generation and annihilation. The most prominent of these appears to be texture formation. However, grain size, second-phase particles, and deformation on shear bands are also important. The effect on hardening of most of these features depends on geometry (or deformation mode) and, hence, no single intrinsic hardening curve can be expected at large strains. It should be noted that high material purity and a torsional deformation mode favor saturation. 42 references, 15 figures.

  3. Waste plastics liquefaction technology

    SciTech Connect

    Machidori, Hideki; Ikawa, Hironori

    1996-12-31

    Plastics are now indispensable not only in industries but for daily life because of their excellent convenience. Only in Japan, about 12.25 million tons of plastics were produced in 1993. On the other hand, the production of waste plastics in the form of industrial and municipal wastes reached 7.56 million tons in the same year. A greater part of the produced waste plastics are now disposed of by incineration and landfill. The incineration would however generate detrimental substances from burned-up plastics and emit them into the exhaust gas, while the landfill would reduce rapidly the residual capacity of the final repositories. Under the circumstances, the Law for the Promotion of Sorted Collection and Recommercialization of Plastics Containers and Packages is to be enforced in 2000 in Japan. Waste plastics liquefaction technology has become high-lighted and is presupposed to employ for the treatment of waste plastics other than PET bottles in the law for the reason that relatively wide variety of waste plastics can be processed in quantity by this technology. The Kubota Corporation has made R and D efforts relating to the plastics liquefaction technology for more than 4 years, and it is now entering the stage of its commercialization.

  4. How Plastics Work

    NASA Astrophysics Data System (ADS)

    Bloomfield, Louis

    2013-03-01

    We encounter plastics every day, but despite their widespread use, amazing range of properties, and basic scientific underpinnings, most physicists--like most people--know relatively little about plastics. In contrast to hard crystalline and amorphous solids (e.g., metals, salts, ceramics, and glasses), we take plastics for granted, select them carelessly, and examine them more closely only on a need-to-know basis. By ignoring plastics until we need them, however, we risk not knowing what we don't know and using the wrong ones. To repurpose a familiar advertisement, ``there's a plastic for that.'' This talk will review some of the basic physics and science of plastics. It will examine the roles of temperature, order, intermolecular forces, entanglements, and linkages in plastics, and how those issues affect the properties of a given plastic. We'll stop along the way to recognize a few of the more familiar plastics, natural and synthetic, and explain some of their mechanical, chemical, and optical properties. The talk will conclude by explaining the remarkable properties of a plastic that has been largely misunderstood since its discovery 70 years ago: Silly Putty.

  5. The evolution of γ-Mg17Al12 intermetallic compound during accumulative back extrusion and subsequent ageing treatment

    NASA Astrophysics Data System (ADS)

    Maghsoudi, M. H.; Zarei-Hanzaki, A.; Abedi, H. R.; Shamsolhodaei, A.

    2015-11-01

    Accumulative back extrusion (ABE) processing, as a novel severe plastic deformation (SPD) method, has been recently justified to be capable of modifying the microstructural characteristics of alloys. In line to its ongoing researches, the present work has been planned to study the evolution of γ-Mg17Al12 intermetallic phase during ABE and subsequent ageing treatment in a high Al-bearing Mg-Al-Zn alloy. The behaviour of γ intermetallic has been systematically examined as following points of view: (i) strain-temperature-dependent morphology changes, (ii) strain-induced dissolution, and (iii) re-ageing behaviour as a function of time and temperature. Aiming to analyse the morphology of eutectic γ compound with respect to the strain and temperature, 2D projections of effective diameter, shape factor and globularity have been made in strain/temperature graphs. The processing conditions (strain and temperature) corresponding to the desired and undesired morphologies are introduced and microstructurally explained through underlying plasticity mechanisms, i.e., 'necking-thinning-particle separation' and 'brittle fragmentation.' The former mechanism is suggested to be in relation with partial strain-induced dissolution of eutectic γ phase, leading to generation of a supersaturated solid solution. This has resulted to the observation of 'off-stoichiometry' phenomena in Mg17Al12 phase and has been justified through dislocation-assisted deformation mechanism at elevated temperature. Surprisingly, a unique re-ageing behaviour has been found for the obtained solid solutions, where a modified kinetics and morphology of γ phase precipitation were characterized. The altered precipitation behaviour is attributed to the specific defect structure achieved by SPD acting as fast diffusion channel for Al solutes.

  6. Cutting Edge Geometry Effect on Plastic Deformation of Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Korovin, G. I.; Filippov, A. V.; Proskokov, A. V.; Gorbatenko, V. V.

    2016-04-01

    The paper presents experimental studies of OT4 titanium alloy machining with cutting edges of various geometry parameters. Experiments were performed at a low speed by the scheme of free cutting. Intensity of plastic shear strain was set for defining of cutting edge geometry effect on machining. Images of chip formed are shown. Estimation of strain magnitude was accomplished with digital image correlation method. Effect of rake angle and cutting edge angle has been studied. Depth of deformed layer and the area of the plastic strain is determine. Results showed that increasing the angle of the cutting edge inclination results in a change the mechanism of chip formation.

  7. Oxidation of Molecular Hydrogen by a Chemolithoautotrophic Beggiatoa Strain

    PubMed Central

    2016-01-01

    ABSTRACT A chemolithoautotrophic strain of the family Beggiatoaceae, Beggiatoa sp. strain 35Flor, was found to oxidize molecular hydrogen when grown in a medium with diffusional gradients of oxygen, sulfide, and hydrogen. Microsensor profiles and rate measurements suggested that the strain oxidized hydrogen aerobically when oxygen was available, while hydrogen consumption under anoxic conditions was presumably driven by sulfur respiration. Beggiatoa sp. 35Flor reached significantly higher biomass in hydrogen-supplemented oxygen-sulfide gradient media, but hydrogen did not support growth of the strain in the absence of reduced sulfur compounds. Nevertheless, hydrogen oxidation can provide Beggiatoa sp. 35Flor with energy for maintenance and assimilatory purposes and may support the disposal of internally stored sulfur to prevent physical damage resulting from excessive sulfur accumulation. Our knowledge about the exposure of natural populations of Beggiatoaceae to hydrogen is very limited, but significant amounts of hydrogen could be provided by nitrogen fixation, fermentation, and geochemical processes in several of their typical habitats such as photosynthetic microbial mats and submarine sites of hydrothermal fluid flow. IMPORTANCE Reduced sulfur compounds are certainly the main electron donors for chemolithoautotrophic Beggiatoaceae, but the traditional focus on this topic has left other possible inorganic electron donors largely unexplored. In this paper, we provide evidence that hydrogen oxidation has the potential to strengthen the ecophysiological plasticity of Beggiatoaceae in several ways. Moreover, we show that hydrogen oxidation by members of this family can significantly influence biogeochemical gradients and therefore should be considered in environmental studies. PMID:26896131

  8. Theory of radial X-ray Diffraction from a Polycrystalline Sample Undergoing Plastic Deformation

    SciTech Connect

    S Karato

    2011-12-31

    Theory of lattice strain in a polycrystalline aggregate under deviatoric stress is extended to include the influence of ongoing plastic deformation. When deviatoric stress is applied to a polycrystalline material at high temperatures (or above the yield stress), applied macroscopic stress is redistributed to individual grains by plastic deformation according to their orientations with respect to the macroscopic stress and plastic anisotropy of a given crystal. This microstress causes elastic deformation of individual grains that can be measured by x-ray diffraction. Consequently, the observed lattice strain depends on two material properties, viscosity (plasticity) and elastic compliance as well as the applied macroscopic stress and the stress-strain distribution among various grains. The influence of plastic deformation on lattice strain is analyzed using an anisotropic and nonlinear power-law constitutive relationship. In this model, the dependence of inferred macroscopic stress on the crystallographic orientation of diffraction plane (hkl) comes from elastic and plastic anisotropy of a crystal. In many materials, plastic anisotropy dominates over elastic anisotropy. This explains the observed large dependence of inferred stress on the diffraction plane and means that the determination of elastic anisotropy is difficult when plastic deformation occurs with anisotropic plasticity. When elastic anisotropy is known, plastic anisotropy of single crystal and/or stress-strain distribution in a deformed polycrystal can be determined from radial x-ray diffraction using the present model. Some examples are presented using the data on MgO.

  9. Selection and screening of microbial consortia for efficient and ecofriendly degradation of plastic garbage collected from urban and rural areas of Bangalore, India.

    PubMed

    Skariyachan, Sinosh; Megha, M; Kini, Meghna Niranjan; Mukund, Kamath Manali; Rizvi, Alya; Vasist, Kiran

    2015-01-01

    Industrialization and urbanization have led to massive accumulation of plastic garbage all over India. The persistence of plastic in soil and aquatic environment has become ecological threat to the metropolitan city such as Bangalore, India. Present study investigates an ecofriendly, efficient and cost-effective approach for plastic waste management by the screening of novel microbial consortia which are capable of degrading plastic polymers. Plastic-contaminated soil and water samples were collected from six hot spots of urban and rural areas of Bangalore. The plastic-degrading bacteria were enriched, and degradation ability was determined by zone of clearance method. The percentage of polymer degradation was initially monitored by weight loss method, and the main isolates were characterized by standard microbiology protocols. These isolates were used to form microbial consortia, and the degradation efficiency of the consortia was compared with individual isolate and known strains obtained from the Microbial Type Culture Collection (MTCC) and Gene Bank, India. One of the main enzymes responsible for polymer degradation was identified, and the biodegradation mechanism was hypothesized by bioinformatics studies. From this study, it is evident that the bacteria utilized the plastic polymer as a sole source of carbon and showed 20-50% weight reduction over a period of 120 days. The two main bacteria responsible for the degradation were microbiologically characterized to be Pseudomonas spp. These bacteria could grow optimally at 37 °C in pH 9.0 and showed 35-40% of plastic weight reduction over 120 days. These isolates were showed better degradation ability than known strains from MTCC. The current study further revealed that the microbial consortia formulated by combining Psuedomonas spp. showed 40 plastic weight reduction over a period of 90 days. Further, extracellular lipase, one of the main enzymes responsible for polymer degradation, was identified. The

  10. Selection and screening of microbial consortia for efficient and ecofriendly degradation of plastic garbage collected from urban and rural areas of Bangalore, India.

    PubMed

    Skariyachan, Sinosh; Megha, M; Kini, Meghna Niranjan; Mukund, Kamath Manali; Rizvi, Alya; Vasist, Kiran

    2015-01-01

    Industrialization and urbanization have led to massive accumulation of plastic garbage all over India. The persistence of plastic in soil and aquatic environment has become ecological threat to the metropolitan city such as Bangalore, India. Present study investigates an ecofriendly, efficient and cost-effective approach for plastic waste management by the screening of novel microbial consortia which are capable of degrading plastic polymers. Plastic-contaminated soil and water samples were collected from six hot spots of urban and rural areas of Bangalore. The plastic-degrading bacteria were enriched, and degradation ability was determined by zone of clearance method. The percentage of polymer degradation was initially monitored by weight loss method, and the main isolates were characterized by standard microbiology protocols. These isolates were used to form microbial consortia, and the degradation efficiency of the consortia was compared with individual isolate and known strains obtained from the Microbial Type Culture Collection (MTCC) and Gene Bank, India. One of the main enzymes responsible for polymer degradation was identified, and the biodegradation mechanism was hypothesized by bioinformatics studies. From this study, it is evident that the bacteria utilized the plastic polymer as a sole source of carbon and showed 20-50% weight reduction over a period of 120 days. The two main bacteria responsible for the degradation were microbiologically characterized to be Pseudomonas spp. These bacteria could grow optimally at 37 °C in pH 9.0 and showed 35-40% of plastic weight reduction over 120 days. These isolates were showed better degradation ability than known strains from MTCC. The current study further revealed that the microbial consortia formulated by combining Psuedomonas spp. showed 40 plastic weight reduction over a period of 90 days. Further, extracellular lipase, one of the main enzymes responsible for polymer degradation, was identified. The

  11. Plasticized phenolphthalein polycarbonate

    NASA Technical Reports Server (NTRS)

    Harrison, E. S.

    1976-01-01

    Phenolphthalein polycarbonate was successfully plasticized with polychlorinated biphenyls (e.g., Aroclor 1231) or tricresyl phosphate and cast from tetrahydrofuran to give clear films without loss of fire resistance. At loadings of 20 to 30 percent plasticizer the Tg was lowered to approximately 100 C which would render phenolphthalein polycarbonate easily moldable. Although these materials had some mechanical integrity as shown by their film forming ability, the room temperature toughness of the plasticized polymer was not significantly improved over unmodified polymer.

  12. Plasticity and Geomechanics

    NASA Astrophysics Data System (ADS)

    Davis, R. O.; Selvadurai, A. P. S.

    2002-11-01

    Plasticity and Geomechanics is a concise introduction to the general subject of plasticity with a particular emphasis on applications in geomechanics. Derived from the authors' lecture notes, this book is written with students firmly in mind. Excessive use of mathematical methods is avoided and, where possible, physical interpretations are given for important concepts. The authors present a clear introduction to the complex ideas and concepts of plasticity and demonstrate how this developing subject is of critical importance to geomechanics and geotechnical engineering.

  13. Plasticity and Geomechanics

    NASA Astrophysics Data System (ADS)

    Davis, R. O.; Selvadurai, A. P. S.

    2005-08-01

    Plasticity and Geomechanics is a concise introduction to the general subject of plasticity with a particular emphasis on applications in geomechanics. Derived from the authors' lecture notes, this book is written with students firmly in mind. Excessive use of mathematical methods is avoided and, where possible, physical interpretations are given for important concepts. The authors present a clear introduction to the complex ideas and concepts of plasticity and demonstrate how this developing subject is of critical importance to geomechanics and geotechnical engineering.

  14. Plastics and health risks.

    PubMed

    Halden, Rolf U

    2010-01-01

    By 2010, the worldwide annual production of plastics will surpass 300 million tons. Plastics are indispensable materials in modern society, and many products manufactured from plastics are a boon to public health (e.g., disposable syringes, intravenous bags). However, plastics also pose health risks. Of principal concern are endocrine-disrupting properties, as triggered for example by bisphenol A and di-(2-ethylhexyl) phthalate (DEHP). Opinions on the safety of plastics vary widely, and despite more than five decades of research, scientific consensus on product safety is still elusive. This literature review summarizes information from more than 120 peer-reviewed publications on health effects of plastics and plasticizers in lab animals and humans. It examines problematic exposures of susceptible populations and also briefly summarizes adverse environmental impacts from plastic pollution. Ongoing efforts to steer human society toward resource conservation and sustainable consumption are discussed, including the concept of the 5 Rs--i.e., reduce, reuse, recycle, rethink, restrain--for minimizing pre- and postnatal exposures to potentially harmful components of plastics.

  15. The plastics waste problem

    SciTech Connect

    Rowatt, R.J.

    1993-01-01

    Post-consumer plastic is a symptom of the municipal solid waste (MSW) problem, not the cause. Yet the U.S. public sees plastic as a major contributor to the waste stream. Two-thirds say the environmental risks of using plastics outweigh the benefits and that they favor mandatory recycling programs in their community; more than four-fifths think recycling can substantially reduce the amount of solid waste and decry the presence of nonbiodegradable plastics in landfills. Given this perception, the author reviews solid waste management issues and examines the contributions that resin producers can make.

  16. Coatings For Plastic Optics

    NASA Astrophysics Data System (ADS)

    Schaffer, Robert W.

    1983-11-01

    Over the past decade there has been a tremendous surge of interest in the use of plastic optical elements to supplement or replace glass optics. While the technology of molding and polishing plastic optics has been the chief interest, there has been increasing need for precision coatings for these elements. In some instances these coatings are as critical as the elements themselves. In this paper we will describe the difficulties incurred in coating plastic and some of the many coatings presently available today despite the difficulties encountered. We will then cover the durability aspects of these coatings and lastly, point out some areas to consider when evaluating using plastic instead of glass.

  17. Multi-scale plasticity modeling: Coupled discrete dislocation and continuum crystal plasticity

    NASA Astrophysics Data System (ADS)

    Wallin, M.; Curtin, W. A.; Ristinmaa, M.; Needleman, A.

    A hierarchical multi-scale model that couples a region of material described by discrete dislocation plasticity to a surrounding region described by conventional crystal plasticity is presented. The coupled model is aimed at capturing non-classical plasticity effects such as the long-range stresses associated with a density of geometrically necessary dislocations and source limited plasticity, while also accounting for plastic flow and the associated energy dissipation at much larger scales where such non-classical effects are absent. The key to the model is the treatment of the interface between the discrete and continuum regions, where continuity of tractions and displacements is maintained in an average sense and the flow of net Burgers vector is managed via "passing" of discrete dislocations. The formulation is used to analyze two plane strain problems: (i) tension of a block and (ii) crack growth under mode I loading with various sizes of the discrete dislocation plasticity region surrounding the crack tip. The computed crack growth resistance curves are nearly independent of the size of the discrete dislocation plasticity region for region sizes ranging from 30 μm×30 μm to 10 μm×5 μm. The multi-scale model can reduce the computational time for the mode I crack analysis by a factor of 14 with little or no loss of fidelity in the crack growth predictions.

  18. Material Properties Test to Determine Ultimate Strain and True Stress-True Strain Curves for High Yield Steels

    SciTech Connect

    K.R. Arpin; T.F. Trimble

    2003-04-01

    This testing was undertaken to develop material true stress-true strain curves for elastic-plastic material behavior for use in performing transient analysis. Based on the conclusions of this test, the true stress-true strain curves derived herein are valid for use in elastic-plastic finite element analysis for structures fabricated from these materials. In addition, for the materials tested herein, the ultimate strain values are greater than those values cited as the limits for the elastic-plastic strain acceptance criteria for transient analysis.

  19. Strain rate change transients during cyclic deformation of copper

    SciTech Connect

    Kaschner, G.C.; Gibeling, J.C.

    1996-12-15

    In the present study, the authors have undertaken to apply the strain rate change method to mechanically probe the mechanisms of cyclic deformation in copper. The goals of this work were twofold: to carefully explore differences in results obtained under conventional displacement control with those recorded under plastic strain control and to apply the formalism for monotonic deformation described above to cyclic deformation. To achieve these goals, it has been necessary to utilize computed-variable servo-hydraulic control to develop a new test technique incorporating strain rate change tests performed during low cycle fatigue. Plastic strain is used as the control variable to ensure a constant plastic strain rate between pre-determined plastic strain limits.

  20. Strain incompatibility and residual strains in ferroelectric single crystals

    PubMed Central

    Pramanick, A.; Jones, J. L.; Tutuncu, G.; Ghosh, D.; Stoica, A. D.; An, K.

    2012-01-01

    Residual strains in ferroelectrics are known to adversely affect the material properties by aggravating crack growth and fatigue degradation. The primary cause for residual strains is strain incompatibility between different microstructural entities. For example, it was shown in polycrystalline ferroelectrics that residual strains are caused due to incompatibility between the electric-field-induced strains in grains with different crystallographic orientations. However, similar characterization of cause-effect in multidomain ferroelectric single crystals is lacking. In this article, we report on the development of plastic residual strains in [111]-oriented domain engineered BaTiO3 single crystals. These internal strains are created due to strain incompatibility across 90° domain walls between the differently oriented domains. The average residual strains over a large crystal volume measured by in situ neutron diffraction is comparable to previous X-ray measurements of localized strains near domain boundaries, but are an order of magnitude lower than electric-field-induced residual strains in polycrystalline ferroelectrics. PMID:23226595

  1. Reinforced plastics durability

    SciTech Connect

    Pritchard, G.

    1999-01-01

    Written especially for first-time users of reinforced plastics. The book offers substantial introductory information with key concepts. Chapters examine the long-term threats to the integrity of reinforced plastics: outdoor weathering, solvent/water attack, high temperatures, and repetitive stress.

  2. Coatings for plastic glazing

    SciTech Connect

    Not Available

    1993-05-01

    This article describes how, as a replacement for glass, coated thermoplastic polymers can reduce cost and weight and increase occupant retention and design flexibility. Advances in transparent protective coatings have increased the potential for successful use of plastics in automotive applications. Originally, plastic materials were considered replacements for metals but, with proven performance, the utility of plastics is expanding beyond metal displacement. Now, transparent plastics are being considered as a potential replacement for glass. Driving this approach are many of the same reasons that plastics were first considered as alternatives to metals--cost, weight, design flexibility, and CAFE requirements. Glass has good optical properties, abrasion and chemical resistance, and outdoor durability, but it is also heavy, breakable, and expensive to form into intricate shapes. Although most clear plastics offer good optical properties, moldability, toughness, and cost benefits, their primary limitation is poor surface resistance to abrasion, scratching, chemicals, and the outdoor environment. In many cases, clear protective coatings can minimize these limitations. The potential advantages and disadvantages of plastic vs glass in automotive applications are given. Transparent plastic materials available for consideration as replacements for automotive glazing are listed.

  3. Detecting plastics in seedcotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The US cotton industry wants to increase market share and value by supplying pure cotton. Removing contamination requires developing a means to detect plastics in seedcotton. This study was conducted to determine if Ion Mobility Spectrometry (IMS) could be used to find small amounts of plastic in ...

  4. A model of grain refinement and strengthening of Al alloys due to cold severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Qiao, Xiao Guang; Gao, Nong; Starink, Marco J.

    2012-02-01

    This paper presents a model which quantitatively predicts grain refinement and strength/hardness of Al alloys after very high levels of cold deformation through processes including cold rolling, equal channel angular pressing (ECAP), multiple forging (MF), accumulative roll bonding (ARB) and embossing. The model deals with materials in which plastic deformation is exclusively due to dislocation movement within grains, which is in good approximation the case for many metallic alloys at low temperature, for instance aluminium alloys. In the early stages of deformation, the generated dislocations are stored in grains and contribute to overall strength. With increase in strain, excess dislocations form and/or move to new cell walls/grain boundaries and grains are refined. We examine this model using both our own data as well as the data in the literature. It is shown that grain size and strength/hardness are predicted to a good accuracy.

  5. A computer program for cyclic plasticity and structural fatigue analysis

    NASA Technical Reports Server (NTRS)

    Kalev, I.

    1980-01-01

    A computerized tool for the analysis of time independent cyclic plasticity structural response, life to crack initiation prediction, and crack growth rate prediction for metallic materials is described. Three analytical items are combined: the finite element method with its associated numerical techniques for idealization of the structural component, cyclic plasticity models for idealization of the material behavior, and damage accumulation criteria for the fatigue failure.

  6. Nonlinear plastic modes in disordered solids.

    PubMed

    Gartner, Luka; Lerner, Edan

    2016-01-01

    We propose a theoretical framework within which a robust micromechanical definition of precursors to plastic instabilities, often termed soft spots, naturally emerges. They are shown to be collective displacements (modes) z[over ̂] that correspond to local minima of a barrier function b(z[over ̂]), which depends solely on inherent structure information. We demonstrate how some heuristic searches for local minima of b(z[over ̂]) can a priori detect the locus and geometry of imminent plastic instabilities with remarkable accuracy, at strains as large as γ_{c}-γ∼10^{-2} away from the instability strain γ_{c}. Our findings suggest that the a priori detection of the entire field of soft spots can be effectively carried out by a systematic investigation of the landscape of b(z[over ̂]). PMID:26871014

  7. Nonlinear plastic modes in disordered solids

    NASA Astrophysics Data System (ADS)

    Gartner, Luka; Lerner, Edan

    2016-01-01

    We propose a theoretical framework within which a robust micromechanical definition of precursors to plastic instabilities, often termed soft spots, naturally emerges. They are shown to be collective displacements (modes) z ̂ that correspond to local minima of a barrier function b (z ̂) , which depends solely on inherent structure information. We demonstrate how some heuristic searches for local minima of b (z ̂) can a priori detect the locus and geometry of imminent plastic instabilities with remarkable accuracy, at strains as large as γc-γ ˜10-2 away from the instability strain γc. Our findings suggest that the a priori detection of the entire field of soft spots can be effectively carried out by a systematic investigation of the landscape of b (z ̂) .

  8. Plastic deformation of polycrystalline zirconium carbide

    NASA Technical Reports Server (NTRS)

    Darolia, R.; Archbold, T. F.

    1976-01-01

    The compressive yield strength of arc-melted polycrystalline zirconium carbide has been found to vary from 77 kg per sq mm at 1200 C to 19 kg per sq mm at 1800 C. Yield drops were observed with plastic strain-rates greater than 0.003/sec but not with slower strain rates. Strain-rate change experiments yielded values for the strain-rate sensitivity parameter m which range from 6.5 at 1500 C to 3.8 at 1800 C, and the product dislocation velocity stress exponent times T was found to decrease linearly with increasing temperature. The deformation rate results are consistent with the Kelly-Rowcliffe model in which the diffusion of carbon assists the motion of dislocations.

  9. Track recording plastic compositions

    NASA Technical Reports Server (NTRS)

    Tarle, Gregory (Inventor)

    1983-01-01

    Improved nuclear track recording plastic compositions are provided which exhibit greatly decreased surface roughness when etched to produce visible tracks of energetic nuclear particles which have passed into and/or through said plastic. The improved compositions incorporate a small quantity of a phthalic acid ester into the major plastic component which is derived from the polymerization of monomeric di-ethylene glycol bis allyl carbonate. Di-substituted phthalic acid esters are preferred as the added component, with the further perference that the ester substituent has a chain length of 2 or more carbon atoms. The inclusion of the phthalic acid ester to an extent of from about 1-2% by weight of the plastic compositions is sufficient to drastically reduce the surface roughness ordinarily produced when the track recording plastic is contacted by etchants.

  10. Natural Strain

    NASA Technical Reports Server (NTRS)

    Freed, Alan D.

    1997-01-01

    Logarithmic strain is the preferred measure of strain used by materials scientists, who typically refer to it as the "true strain." It was Nadai who gave it the name "natural strain," which seems more appropriate. This strain measure was proposed by Ludwik for the one-dimensional extension of a rod with length l. It was defined via the integral of dl/l to which Ludwik gave the name "effective specific strain." Today, it is after Hencky, who extended Ludwik's measure to three-dimensional analysis by defining logarithmic strains for the three principal directions.

  11. Constitutive modeling of cyclic plasticity and creep, using an internal time concept

    NASA Technical Reports Server (NTRS)

    Watanabe, O.; Atluri, S. N.

    1986-01-01

    Using the concept of an internal time as related to plastic strains, a differential stress-strain relation for elastoplasticity is rederived, such that (1) the concept of a yield-surface is retained; (2) the definitions of elastic and plastic processes are analogous to those in classical plasticity theory; and (3) its computational implementation, via a 'tangent-stiffness' finite element method and a 'generalized-midpoint-radial-return' stress-integration algorithm, is simple and efficient. Also, using the concept of an internal time, as related to both the inelastic strains as well as the Newtonian time, a constitutive model for creep-plasticity interaction, is discussed. The problem of modeling experimental data for plasticity and creep, by the present analytical relations, as accurately as desired, is discussed. Numerical examples which illustrate the validity of the present relations are presented for the cases of cyclic plasticity and creep.

  12. 77 FR 54930 - Carlyle Plastics and Resins, Formerly Known as Fortis Plastics, A Subsidiary of Plastics...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-06

    ... Employment and Training Administration Carlyle Plastics and Resins, Formerly Known as Fortis Plastics, A... determination was published in the Federal Register on Monday, July 23, 2012 (77 FR 43123). ] At the request of... plastic parts. New information shows that Fortis Plastics is now called Carlyle Plastics and Resins....

  13. Plastic Surgery for Ethnic Patients

    MedlinePlus

    ... Briefing Papers > Plastic Surgery for Ethnic Patients Briefing Paper: Plastic Surgery for Ethnic Patients More than 3. ... 2067-2071. Share Related Links Plastic Surgery Briefing Papers Menu Cosmetic Reconstructive Patient Safety Before & After Find ...

  14. Engineering of surface microstructure transformations using high rate severe plastic deformation in machining

    NASA Astrophysics Data System (ADS)

    Abolghasem, Sepideh

    Engineering surface structures especially at the nanometer length-scales can enable fundamentally new multifunctional property combinations, including tunable physical, mechanical, electrochemical and biological responses. Emerging manufacturing paradigms involving Severe Plastic Deformation (SPD), for manipulating final microstructure of the surfaces are unfortunately limited by poorly elucidated process-structure-performance linkages, which are characterized by three central variables of plasticity: strain, strain-rate and temperature that determine the resulting Ultrafine Grained (UFG) microstructure. The challenge of UFG surface engineering, design and manufacturing can be overcome if and only if the mappings between the central variables and the final microstructure are delineated. The objective of the proposed document is to first envision a phase-space, whose axes are parameterized in terms of the central variables of SPD. Then, each point can correspond to a unique microstructure, characterized by its location on this map. If the parametrization and the population of the datasets are accurately defined, then the mapping is bijective where: i) realizing microstructure designs can be reduced to simply one of tuning process parameters falling within the map s desired subspaces. And, inversely, ii) microstructure prediction is directly possible by merely relating the measured/calculated thermomechanics at each point in the deformation zone to the corresponding spot on the maps. However, the analytic approach to establish this map first requires extensive datasets, where the microstructures are accurately measured for a known set of strain, strain-rate and temperature of applied SPD. Although such datasets do not exist, even after the empirical data is accumulated, there is a lack of formalized statistical outlines in relating microstructural characteristic to the process parameters in order to build the mapping framework. Addressing these gaps has led to this

  15. Strain engineered high reflectivity DBRs in the deep UV

    NASA Astrophysics Data System (ADS)

    Franke, A.; Hoffmann, M. P.; Hernandez-Balderrama, L.; Kaess, F.; Bryan, I.; Washiyama, S.; Bobea, M.; Tweedie, J.; Kirste, R.; Gerhold, M.; Collazo, R.; Sitar, Z.

    2016-02-01

    The maximum achievable reflectivity of current III-nitride Bragg reflectors in the UV-C spectral range is limited due to plastic relaxation of thick multilayer structures. Cracking due to a large mismatch of the thermal expansion and lattice constants between AlxGa1-xN/AlyGa1-yN alloys of different composition and the substrate at the heterointerface is the common failure mode. Strain engineering and strain relaxation concepts by the growth on a strain reduced Al0.85Ga0.15N template and the implementation of low temperature interlayers is demonstrated. A significant enhancement of the maximum reflectivity above 97% at a resonance wavelength of 270 nm due to an increase of the critical thickness of our AlN/Al0.65Ga0.35N DBRs to 1.45 μm (25.5 pairs) prove their potential. By comparing the growth of identical Bragg reflectors on different pseudo-templates, the accumulated mismatch strain energy in the DBR, not the dislocation density provided by the template/substrate, was identified to limit the critical thickness. To further enhance the reflectivity low temperature interlays were implemented into the DBR to partially relief the misfit strain. Relaxation is enabled by the nucleation of small surface domains facilitating misfit dislocation injection and glide. Detailed structural and optical investigations will be conducted to prove the influence of the LT-AlN interlayers on the strain state, structural integrity and reflectivity properties. Coherent growth and no structural and optical degradation of the Bragg mirror properties was observed proving the fully applicability of the relaxation concept to fabricate thick high reflectivity DBR and vertical cavity laser structures.

  16. Elastic-plastic finite-element analyses of thermally cycled single-edge wedge specimens

    NASA Technical Reports Server (NTRS)

    Kaufman, A.

    1982-01-01

    Elastic-plastic stress-strain analyses were performed for single-edge wedge alloys subjected to thermal cycling in fluidized beds. Three cases (NASA TAZ-8A alloy under one cycling condition and 316 stainless steel alloy under two cycling conditions) were analyzed by using the MARC nonlinear, finite-element computer program. Elastic solutions from MARC showed good agreement with previously reported solutions that used the NASTRAN and ISO3DQ computer programs. The NASA TAZ-8A case exhibited no plastic strains, and the elastic and elastic-plastic analyses gave identical results. Elastic-plastic analyses of the 316 stainless steel alloy showed plastic strain reversal with a shift of the mean stresses in the compressive direction. The maximum equivalent total strain ranges for these cases were 13 to 22 percent greater than that calculated from elastic analyses.

  17. Plasticity characteristics obtained through hardness measurement

    SciTech Connect

    Milman, Y.V.; Galanov, B.A.; Chugunova, S.I. )

    1993-09-01

    A characteristic of material plasticity [delta][sub H] is proposed. [delta][sub H] is determined as a part of plastic deformation in the total deformation during indentation. The following analytic expressions for the elastic deformation [epsilon][sub e] and for the total deformation [epsilon] on the contact area indenter-specimen in the direction of loading force are obtained, [epsilon][sub e] = 1.08(1 [minus] v [minus] 2v[sup 2])H[sub V/E], [epsilon] [approx] 0.076, where H[sub V] is the Vickers hardness, E is Young's modulus, v is the Poisson ratio, and [delta][sub H] = 1 [minus] ([epsilon][sub e]/[epsilon]). The [delta][sub H] value is calculated for various crystalline materials at different temperatures and in different structural states. [delta][sub H] is consistent with the concept of plasticity established before, and to characterize the influence of temperature, alloying and strain hardening on plasticity. The necessary condition for revealing ductility at tension and bending is [delta][sub H] [>=] 0.9. [delta][sub H] can be used as a plasticity characteristic of brittle materials.

  18. Plastic flow of polycrystalline materials

    NASA Astrophysics Data System (ADS)

    Langer, James

    Leo Kadanoff had a long interest in fluid flows, especially fingering instabilities. This interest was one example of his insatiable curiosity about simple, fundamentally important, and often multidisciplinary phenomena. Here is an example of another class of such phenomena that I had hoped to show him this year. The experts in polycrystalline solid mechanics have insisted for decades that their central problem - dislocation-mediated strain hardening - is intrinsically unsolvable. I think they're wrong. My colleagues and I have made progress recently in theories of both amorphous and polycrystalline plasticity by introducing an effective disorder temperature as a dynamical variable in our equations of motion. In this way, we have been able to describe how the densities of flow defects or dislocations evolve in response to external forcing, and thus to develop theories that promise to become as predictive, and full of surprises, as the laws of fluid flow. For Kadanoff session.

  19. Monitoring the abundance of plastic debris in the marine environment

    PubMed Central

    Ryan, Peter G.; Moore, Charles J.; van Franeker, Jan A.; Moloney, Coleen L.

    2009-01-01

    Plastic debris has significant environmental and economic impacts in marine systems. Monitoring is crucial to assess the efficacy of measures implemented to reduce the abundance of plastic debris, but it is complicated by large spatial and temporal heterogeneity in the amounts of plastic debris and by our limited understanding of the pathways followed by plastic debris and its long-term fate. To date, most monitoring has focused on beach surveys of stranded plastics and other litter. Infrequent surveys of the standing stock of litter on beaches provide crude estimates of debris types and abundance, but are biased by differential removal of litter items by beachcombing, cleanups and beach dynamics. Monitoring the accumulation of stranded debris provides an index of debris trends in adjacent waters, but is costly to undertake. At-sea sampling requires large sample sizes for statistical power to detect changes in abundance, given the high spatial and temporal heterogeneity. Another approach is to monitor the impacts of plastics. Seabirds and other marine organisms that accumulate plastics in their stomachs offer a cost-effective way to monitor the abundance and composition of small plastic litter. Changes in entanglement rates are harder to interpret, as they are sensitive to changes in population sizes of affected species. Monitoring waste disposal on ships and plastic debris levels in rivers and storm-water runoff is useful because it identifies the main sources of plastic debris entering the sea and can direct mitigation efforts. Different monitoring approaches are required to answer different questions, but attempts should be made to standardize approaches internationally. PMID:19528052

  20. Natural Strain

    NASA Technical Reports Server (NTRS)

    Freed, Alan D.

    1995-01-01

    The purpose of this paper is to present a consistent and thorough development of the strain and strain-rate measures affiliated with Hencky. Natural measures for strain and strain-rate, as I refer to them, are first expressed in terms of of the fundamental body-metric tensors of Lodge. These strain and strain-rate measures are mixed tensor fields. They are mapped from the body to space in both the Eulerian and Lagrangian configurations, and then transformed from general to Cartesian fields. There they are compared with the various strain and strain-rate measures found in the literature. A simple Cartesian description for Hencky strain-rate in the Lagrangian state is obtained.

  1. Elastic-plastic analysis of the SS-3 tensile specimen

    SciTech Connect

    Majumdar, S.

    1998-09-01

    Tensile tests of most irradiated specimens of vanadium alloys are conducted using the miniature SS-3 specimen which is not ASTM approved. Detailed elastic-plastic finite element analysis of the specimen was conducted to show that, as long as the ultimate to yield strength ratio is less than or equal to 1.25 (which is satisfied by many irradiated materials), the stress-plastic strain curve obtained by using such a specimen is representative of the true material behavior.

  2. Strain concentration factor as a function of strain in a design application

    SciTech Connect

    Smith, R.E.

    1981-01-01

    This paper presents results for a detailed inelastic finite element analysis for a part of the Clinch River Breeder Reactor Control Rod Drive Mechanism. The analysis results indicate that plastic strain concentration factors may in fact be less than corresponding elastic strain concentration factors for nominal strains as low as .2%. This is particularly insightful in that it is presently common practice to approximate inelastic strain concentration factors as the square of the elastic concentration factors. The paper also examines Neuber's relation for predicting strain concentration factors and looks at the variation in the strain concentration factor through the cross-section of the component analyzed.

  3. A Dynamic Discrete Dislocation Plasticity Method for the Dimulation of Plastic Relaxation under Shock Loading

    NASA Astrophysics Data System (ADS)

    Gurrutxaga-Lerma, Benat; Sutton, Adrian; Eakins, Daniel; Balint, Daniel; Dini, Daniele

    2013-06-01

    This talk intends to offer some insight as to how Discrete Dislocation Plasticity (DDP) can be adapted to simulate plastic relaxation processes under weak shock loading and high strain rates. In those circumstances, dislocations are believed to be the main cause of plastic relaxation in crystalline solids. Direct simulation of dislocations as the dynamic agents of plastic relaxation in those cases remains a challenge. DDP, where dislocations are modelled as discrete discontinuities in elastic continuum media, is often unable to adequately simulate plastic relaxation because it treats dislocation motion quasi-statically, thus neglecting the time-dependent nature of the elastic fields and assuming that they instantaneously acquire the shape and magnitude predicted by elastostatics. Under shock loading, this assumption leads to several artefacts that can only be overcome with a fully time-dependent formulation of the elastic fields. In this talk one of such formulations for the creation, annihilation and arbitrary motion of straight edge dislocations will be presented. These solutions are applied in a two-dimensional model of time-dependent plastic relaxation under shock loading, and some relevant results will be presented. EPSRC CDT in Theory and Simulation of Materials

  4. Shape-Shifting Plastic

    SciTech Connect

    2015-05-20

    A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature

  5. A Plastic Menagerie

    ERIC Educational Resources Information Center

    Hadley, Mary Jane

    2010-01-01

    Bobble heads had become quite popular, depicting all sorts of sports figures, animals, and even presidents. In this article, the author describes how her fourth graders made bobble head sculptures out of empty plastic drink bottles. (Contains 1 online resource.)

  6. Mechanical plasticity of cells

    NASA Astrophysics Data System (ADS)

    Bonakdar, Navid; Gerum, Richard; Kuhn, Michael; Spörrer, Marina; Lippert, Anna; Schneider, Werner; Aifantis, Katerina E.; Fabry, Ben

    2016-10-01

    Under mechanical loading, most living cells show a viscoelastic deformation that follows a power law in time. After removal of the mechanical load, the cell shape recovers only incompletely to its original undeformed configuration. Here, we show that incomplete shape recovery is due to an additive plastic deformation that displays the same power-law dynamics as the fully reversible viscoelastic deformation response. Moreover, the plastic deformation is a constant fraction of the total cell deformation and originates from bond ruptures within the cytoskeleton. A simple extension of the prevailing viscoelastic power-law response theory with a plastic element correctly predicts the cell behaviour under cyclic loading. Our findings show that plastic energy dissipation during cell deformation is tightly linked to elastic cytoskeletal stresses, which suggests the existence of an adaptive mechanism that protects the cell against mechanical damage.

  7. Recycle plastics into feedstocks

    SciTech Connect

    Kastner, H.; Kaminsky, W.

    1995-05-01

    Thermal cracking of mixed-plastics wastes with a fluidized-bed reactor can be a viable and cost-effective means to meet mandatory recycling laws. Strict worldwide environmental statutes require the hydrocarbon processing industry (HPI) to develop and implement product applications and technologies that reuse post-consumer mixed-plastics waste. Recycling or reuse of plastics waste has a broad definition. Recycling entails more than mechanical regranulation and remelting of polymers for film and molding applications. A European consortium of academia and refiners have investigated if it is possible and profitable to thermally crack plastics into feedstocks for refining and petrochemical applications. Development and demonstration of pyrolysis methods show promising possibilities of converting landfill garbage into valuable feedstocks such as ethylene, propylene, BTX, etc. Fluidized-bed reactor technologies offer HPI operators a possible avenue to meet recycling laws, conserve raw materials and yield a profit. The paper describes thermal cracking for feedstocks and pyrolysis of polyolefins.

  8. Dreaming in plastic

    NASA Astrophysics Data System (ADS)

    Korzhov, Marianna; Andelman, David; Shikler, Rafi

    2008-07-01

    Plastic is one of the most versatile materials available. It is cheap, flexible and easy to process, and as a result it is all around us - from our computer keyboards to the soles of our shoes. One of its most common applications is as an insulating coating for electric wires; indeed, plastic is well known for its insulating characteristics. It came as something of a surprise, therefore, when in the late 1970s a new generation of plastics was discovered that displayed exactly the opposite behaviour - the ability to conduct electricity. In fact, plastics can be made with a whole range of conductivities - there are polymer materials that behave like semiconductors and there are those that can conduct as well as metals. This discovery sparked a revolution in the electronics community, and three decades of research effort is now yielding a range of stunning new applications for this ubiquitous material.

  9. Cortical plasticity and rehabilitation.

    PubMed

    Moucha, Raluca; Kilgard, Michael P

    2006-01-01

    The brain is constantly adapting to environmental and endogenous changes (including injury) that occur at every stage of life. The mechanisms that regulate neural plasticity have been refined over millions of years. Motivation and sensory experience directly shape the rewiring that makes learning and neurological recovery possible. Guiding neural reorganization in a manner that facilitates recovery of function is a primary goal of neurological rehabilitation. As the rules that govern neural plasticity become better understood, it will be possible to manipulate the sensory and motor experience of patients to induce specific forms of plasticity. This review summarizes our current knowledge regarding factors that regulate cortical plasticity, illustrates specific forms of reorganization induced by control of each factor, and suggests how to exploit these factors for clinical benefit.

  10. Trehalose accumulation enhances tolerance of Saccharomyces cerevisiae to acetic acid.

    PubMed

    Yoshiyama, Yoko; Tanaka, Koichi; Yoshiyama, Kohei; Hibi, Makoto; Ogawa, Jun; Shima, Jun

    2015-02-01

    Trehalose confers protection against various environmental stresses on yeast cells. In this study, trehalase gene deletion mutants that accumulate trehalose at high levels showed significant stress tolerance to acetic acid. The enhancement of trehalose accumulation can thus be considered a target in the breeding of acetic acid-tolerant yeast strains.

  11. Laser cutting plastic materials

    SciTech Connect

    Van Cleave, R.A.

    1980-08-01

    A 1000-watt CO/sub 2/ laser has been demonstrated as a reliable production machine tool for cutting of plastics, high strength reinforced composites, and other nonmetals. More than 40 different plastics have been laser cut, and the results are tabulated. Applications for laser cutting described include fiberglass-reinforced laminates, Kevlar/epoxy composites, fiberglass-reinforced phenolics, nylon/epoxy laminates, ceramics, and disposable tooling made from acrylic.

  12. Nonlinear analysis of AS4/PEEK thermoplastic composite laminate using a one parameter plasticity model

    NASA Technical Reports Server (NTRS)

    Sun, C. T.; Yoon, K. J.

    1990-01-01

    A one-parameter plasticity model was shown to adequately describe the orthotropic plastic deformation of AS4/PEEK (APC-2) unidirectional thermoplastic composite. This model was verified further for unidirectional and laminated composite panels with and without a hole. The nonlinear stress-strain relations were measured and compared with those predicted by the finite element analysis using the one-parameter elastic-plastic constitutive model. The results show that the one-parameter orthotropic plasticity model is suitable for the analysis of elastic-plastic deformation of AS4/PEEK composite laminates.

  13. T-cell clones expressing different T-cell receptors accumulate in the brains of dying and surviving mice after peripheral infection with far eastern strain of tick-borne encephalitis virus.

    PubMed

    Fujii, Yoshiki; Hayasaka, Daisuke; Kitaura, Kazutaka; Takasaki, Tomohiko; Suzuki, Ryuji; Kurane, Ichiro

    2011-08-01

    Tick-borne encephalitis virus (TBEV), a representative acute central nervous system disease-inducible virus, is known to elicit dose-independent mortality in a mouse model. We previously reported that subcutaneous infection with a wide range of TBEV Oshima strain challenge doses (10(2)-10(6) PFU) produced an approximately 50% mortality rate. However, the factors playing critical roles in mortality and severity remain unclear. In this study, we distinguished surviving and dying mice by their degree of weight loss after TBEV infection, and investigated qualitative differences in brain-infiltrating T cells between each group by analyzing T-cell receptor (TCR) repertoire and complementary determining region 3 (CDR3) sequences. TCR repertoire analysis revealed that the expression levels of VA8-1, VA15-1, and VB8-2 families were increased in brains derived from both surviving and dying mice. CDR3 amino acid sequence characteristics differed between each group. In dying mice, high frequencies of VA15-1/AJ12 and VB8-2/BJ1.1 gene usage were observed. While in surviving mice, high frequencies of VA8-1/AJ15 or VA8-1/AJ23 gene usage were observed. VB8-2/BJ2.7 gene usage and short CDR3 were observed frequently in both surviving and dying mice. However, no differences in T-cell activation markers and apoptosis-related genes were observed between these groups using quantitative real-time PCR analysis. These results suggest that TBEV-infection severity may be involved in antigen specificity, but not in the number or activation level of brain-infiltrating T cells.

  14. BOOK REVIEW: Introduction to Computational Plasticity

    NASA Astrophysics Data System (ADS)

    Hartley, P.

    2006-04-01

    . Chapter two introduces one of several yield criteria, that normally attributed to von Mises (though historians of mechanics might argue over who was first to develop the theory of yielding associated with strain energy density), and its two or three-dimensional representation as a yield surface. The expansion of the yield surface during plastic deformation, its translation due to kinematic hardening and the Bauschinger effect in reversed loading are described with a direct link to the material stress-strain curve. The assumption, that the increment of strain is normal to the yield surface, the normality principle, is introduced. Uniaxial loading of an elastic-plastic material is used as an example in which to develop expressions to describe increments in stress and strain. The full presentation of numerous expressions, tensors and matrices with a clear explanation of their development, is a recurring, and commendable, feature of the book, which provides an invaluable introduction for those new to the subject. The chapter moves on from time-independent behaviour to introduce viscoplasticity and creep. Chapter three takes the theories of deformation another stage further to consider the problems associated with large deformation in which an important concept is the separation of the phenomenon into material stretch and rotation. The latter is crucial to allow correct measures of strain and stress to be developed in which the effects of rigid body rotation do not contribute to these variables. Hence, the introduction of 'objective' measures for stress and strain. These are described with reference to deformation gradients, which are clearly explained; however, the introduction of displacement gradients passes with little comment, although velocity gradients appear later in the chapter. The interpretation of different strain measures, e.g. Green--Lagrange and Almansi, is covered briefly, followed by a description of the spin tensor and its use in developing the objective

  15. The Need for Plastics Education.

    ERIC Educational Resources Information Center

    Society of Plastics Engineers, Inc., Stamford, CT.

    In view of a lack of trained personnel in the industry, the Plastics Education Foundation proposes that educators (1) add more plastics programs, (2) establish plastics engineering degrees at appropriate 4-year institutions, (3) add plastics processing technology to current engineering curricula, and (4) interest younger students in courses and/or…

  16. Ectoine accumulation in Brevibacterium epidermis.

    PubMed

    Onraedt, Annelies; De Muynck, Cassandra; Walcarius, Bart; Soetaert, Wim; Vandamme, Erick

    2004-10-01

    As a halotolerant bacterial species, Brevibacterium epidermis DSM 20659 can grow at relatively high salinity, tolerating up to 2 M NaCl. It synthesizes ectoine and the intracellular content increases with the medium salinity, with a maximum of 0.14 g ectoine/g CDW at 1 M NaCl. Sugar-stressed cells do not synthesize ectoine. Ectoine synthesis is also affected by the presence of external osmolytes. Added betaine is taken up and completely replaced ectoine, while L-proline is only temporarily accumulated after which ectoine is synthesized. The strain can metabolize ectoine; L-glutamate is a better carbon source for ectoine synthesis than L-aspartate.

  17. Amphibious fishes: evolution and phenotypic plasticity.

    PubMed

    Wright, Patricia A; Turko, Andy J

    2016-08-01

    Amphibious fishes spend part of their life in terrestrial habitats. The ability to tolerate life on land has evolved independently many times, with more than 200 extant species of amphibious fishes spanning 17 orders now reported. Many adaptations for life out of water have been described in the literature, and adaptive phenotypic plasticity may play an equally important role in promoting favourable matches between the terrestrial habitat and behavioural, physiological, biochemical and morphological characteristics. Amphibious fishes living at the interface of two very different environments must respond to issues relating to buoyancy/gravity, hydration/desiccation, low/high O2 availability, low/high CO2 accumulation and high/low NH3 solubility each time they traverse the air-water interface. Here, we review the literature for examples of plastic traits associated with the response to each of these challenges. Because there is evidence that phenotypic plasticity can facilitate the evolution of fixed traits in general, we summarize the types of investigations needed to more fully determine whether plasticity in extant amphibious fishes can provide indications of the strategies used during the evolution of terrestriality in tetrapods. PMID:27489213

  18. Extractable/leachable substances from plastic materials used as pharmaceutical product containers/devices.

    PubMed

    Jenke, Dennis

    2002-01-01

    A review is provided related to the accumulation of organic and inorganic leachable substances from DEHP-plasticized PVC, polyolefin and various other related pharmaceutical plastic packaging materials. The review considers both the identification of such leachables as well as their reported levels in actual and simulated pharmaceutical products.

  19. Plastic instabilities in statically and dynamically loaded spherical vessels

    SciTech Connect

    Duffey, Thomas A; Rodriguez, Edward A

    2010-01-01

    Significant changes were made in design limits for pressurized vessels in the 2007 version of the ASME Code (Section VIII, Div. 3) and 2008 and 2009 Addenda. There is now a local damage-mechanics based strain-exhaustion limit as well as the well-known global plastic collapse limit. Moreover, Code Case 2564 (Section VIII, Div. 3) has recently been approved to address impulsively loaded vessels. It is the purpose of this paper to investigate the plastic collapse limit as it applies to dynamically loaded spherical vessels. Plastic instabilities that could potentially develop in spherical shells under symmetric loading conditions are examined for a variety of plastic constitutive relations. First, a literature survey of both static and dynamic instabilities associated with spherical shells is presented. Then, a general plastic instability condition for spherical shells subjected to displacement controlled and impulsive loading is given. This instability condition is evaluated for six plastic and visco-plastic constitutive relations. The role of strain-rate sensitivity on the instability point is investigated. Calculations for statically and dynamically loaded spherical shells are presented, illustrating the formation of instabilities as well as the role of imperfections. Conclusions of this work are that there are two fundamental types of instabilities associated with failure of spherical shells. In the case of impulsively loaded vessels, where the pulse duration is short compared to the fundamental period of the structure, one instability type is found not to occur in the absence of static internal pressure. Moreover, it is found that the specific role of strain-rate sensitivity on the instability strain depends on the form of the constitutive relation assumed.

  20. Phase-field slip-line theory of plasticity

    NASA Astrophysics Data System (ADS)

    Freddi, Francesco; Royer-Carfagni, Gianni

    2016-09-01

    A variational approach to determine the deformation of an ideally plastic substance is proposed by solving a sequence of energy minimization problems under proper conditions to account for the irreversible character of plasticity. The flow is driven by the local transformation of elastic strain energy into plastic work on slip surfaces, once that a certain energetic barrier for slip activation has been overcome. The distinction of the elastic strain energy into spherical and deviatoric parts is used to incorporate in the model the idea of von Mises plasticity and isochoric plastic strain. This is a "phase field model" because the matching condition at the slip interfaces is substituted by the evolution of an auxiliary phase field that, similar to a damage field, is unitary on the elastic phase and null on the yielded phase. The slip lines diffuse in bands, whose width depends upon a material length-scale parameter. Numerical experiments on representative problems in plane strain give solutions with noteworthy similarities with the results from classical slip-line field theory, but the proposed model is much richer because, accounting for elastic deformations, it can describe the formation of slip bands at the local level, which can nucleate, propagate, widen and diffuse by varying the boundary conditions. In particular, the solution for a long pipe under internal pressure is very different from the one obtainable from the classical macroscopic theory of plasticity. For this case, the location of the plastic bands may be an insight to explain the premature failures that are sometimes encountered during the manufacturing process. This practical example enhances the importance of this new theory based on the mathematical sciences.

  1. Solution of elastic-plastic stress analysis problems by the p-version of the finite element method

    NASA Technical Reports Server (NTRS)

    Szabo, Barna A.; Actis, Ricardo L.; Holzer, Stefan M.

    1993-01-01

    The solution of small strain elastic-plastic stress analysis problems by the p-version of the finite element method is discussed. The formulation is based on the deformation theory of plasticity and the displacement method. Practical realization of controlling discretization errors for elastic-plastic problems is the main focus. Numerical examples which include comparisons between the deformation and incremental theories of plasticity under tight control of discretization errors are presented.

  2. Plasticity Effects in Dynamically Loaded Nickel Aluminide Bicrystals

    SciTech Connect

    Loomis, E; Swift, D; McNaney, J; Lorenzana, H; Peralta, P

    2008-12-02

    Elastic and plastic anisotropy are believed to play large roles in the dynamic deformation of many materials at the grain-level. More importantly to polycrystalline materials is how velocity and stress perturbations are transmitted across interfaces in anisotropic materials. Very little work has been done in this area even though it is important for understanding shock/grain boundary interactions. Therefore, experiments have been performed using nanosecond laser shocks of grown Nickel Aluminide bicrystals at tens of GPa. Velocity histories were measured along a line on the back (free) surface of the bicrystals and used to characterize the material behavior. Unstable plastic flow in <100> grains was seen to occur when loaded above 700 m/s free surface velocity. Flow stresses in <111> and <100> grains were measured to be 2.9 and 3.3 GPa, respectively. Calculations were performed based on anisotropic elasticity and dislocation motion on primary slip systems to measure plastic flow properties where plastic strain-rates on the order of 10{sup 6} s{sup -1} were calculated using the experimental velocity histories. Definitive evidence of plastic wave scattering at the grain boundary was not observed experimentally; however, behavior across the grain boundary has been measured. The observations show that a smooth transition occurs between the elastic precursors in both grains as well as the plastic waves (when plastic flow is evident). An anisotropic elastic-plastic wave scattering model has been developed to explain the mechanisms affecting shock/grain boundary interactions.

  3. Elastic-plastic models for multi-site damage

    NASA Technical Reports Server (NTRS)

    Actis, Ricardo L.; Szabo, Barna A.

    1994-01-01

    This paper presents recent developments in advanced analysis methods for the computation of stress site damage. The method of solution is based on the p-version of the finite element method. Its implementation was designed to permit extraction of linear stress intensity factors using a superconvergent extraction method (known as the contour integral method) and evaluation of the J-integral following an elastic-plastic analysis. Coarse meshes are adequate for obtaining accurate results supported by p-convergence data. The elastic-plastic analysis is based on the deformation theory of plasticity and the von Mises yield criterion. The model problem consists of an aluminum plate with six equally spaced holes and a crack emanating from each hole. The cracks are of different sizes. The panel is subjected to a remote tensile load. Experimental results are available for the panel. The plasticity analysis provided the same limit load as the experimentally determined load. The results of elastic-plastic analysis were compared with the results of linear elastic analysis in an effort to evaluate how plastic zone sizes influence the crack growth rates. The onset of net-section yielding was determined also. The results show that crack growth rate is accelerated by the presence of adjacent damage, and the critical crack size is shorter when the effects of plasticity are taken into consideration. This work also addresses the effects of alternative stress-strain laws: The elastic-ideally-plastic material model is compared against the Ramberg-Osgood model.

  4. Experimental and Computational Investigations of Strain Localization in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Bharathula, Ashwini

    non-localized contributions at low strains. Moreover, the magnitude of strain bursts was found to decrease with decrease in specimen size. Furthermore, Weibull statistical analysis was performed to investigate the effect of specimen size on yield strength in this metallic glass. It was revealed that the dispersion in strengths increases dramatically with decrease in sample size, attributed to the size distribution of the defects responsible for shear banding. The findings are crucial in designing systems which promote plasticity in metallic glasses by suppressing the shear-band instability and also in direct application of these materials for structural purposes as small components in micro- and nano-scale systems. On the computational front, Molecular Dynamics (MD) simulations have been employed to generate Zr-Cu metallic glass structures. In order to analyze and better understand and visualize the concepts of "free" volume and flow defects in metallic glasses, an electron density model was developed as an upgrade to the traditional hard sphere approaches. Simple tension and shear modes of deformation were simulated using MD in Zr-Cu system, and role of open volume in deformation was studied using the electron density model. In uniaxial tension simulations, effect of temperature and deformation rate is examined, and the process of accumulation of free volume to the point of catastrophic failure is visualized using the Electron Density model. In shear simulations, we find that the as-quenched glass structures undergo homogeneous deformation and do not exhibit any strain localization. However, it is found that by incorporating a cylindrical void in the glass structure as a source of "free" volume, it is possible to induce strain localization. It was found that a critical void diameter of 8A was required to successfully initialize strain localization in this system.

  5. Real-time, high-resolution study of nanocrystallization and fatigue cracking in a cyclically strained metallic glass.

    PubMed

    Wang, Cheng-Cai; Mao, Yun-Wei; Shan, Zhi-Wei; Dao, Ming; Li, Ju; Sun, Jun; Ma, Evan; Suresh, Subra

    2013-12-01

    Metallic glasses (MGs) exhibit greater elastic limit and stronger resistance to plastic deformation than their crystalline metal counterparts. Their capacity to withstand plastic straining is further enhanced at submicrometer length scales. For a range of microelectromechanical applications, the resistance of MGs to damage and cracking from thermal and mechanical stress or strain cycling under partial or complete constraint is of considerable scientific and technological interest. However, to our knowledge, no real-time, high-resolution transmission electron microscopy observations are available of crystallization, damage, and failure from the controlled imposition of cyclic strains or displacements in any metallic glass. Here we present the results of a unique in situ study, inside a high-resolution transmission electron microscope, of glass-to-crystal formation and fatigue of an Al-based MG. We demonstrate that cyclic straining progressively leads to nanoscale surface roughening in the highly deformed region of the starter notch, causing crack nucleation and formation of nanocrystals. The growth of these nanograins during cyclic straining impedes subsequent crack growth by bridging the crack. In distinct contrast to this fatigue behavior, only distributed nucleation of smaller nanocrystals is observed with no surface roughening under monotonic deformation. We further show through molecular dynamics simulation that these findings can be rationalized by the accumulation of strain-induced nonaffine atomic rearrangements that effectively enhances diffusion through random walk during repeated strain cycling. The present results thus provide unique insights into fundamental mechanisms of fatigue of MGs that would help shape strategies for material design and engineering applications. PMID:24255113

  6. Unified creep-plasticity model for halite

    SciTech Connect

    Krieg, R. D.

    1980-11-01

    There are two national energy programs which are considering caverns in geological salt (NaCl) as a storage repository. One is the disposal of nuclear wastes and the other is the storage of oil. Both short-time and long-time structural deformations and stresses must be predictable for these applications. At 300K, the nominal initial temperature for both applications, the salt is at 0.28 of the melting temperature and exhibits a significant time dependent behavior. A constitutive model has been developed which describes the behavior observed in an extensive set of triaxial creep tests. Analysis of these tests showed that a single deformation mechanism seems to be operative over the stress and temperature range of interest so that the secondary creep data can be represented by a power of the stress over the entire test range. This simple behavior allowed a new unified creep-plasticity model to be applied with some confidence. The resulting model recognizes no inherent difference between plastic and creep strains yet models the total inelastic strain reasonably well including primary and secondary creep and reverse loadings. A multiaxial formulation is applied with a back stress. A Bauschinger effect is exhibited as a consequence and is present regardless of the time scale over which the loading is applied. The model would be interpreted as kinematic hardening in the sense of classical plasticity. Comparisons are made between test data and model behavior.

  7. Chemo-Plasticity of Clays Subjected to Stress and Flow of a Single Contaminant

    NASA Astrophysics Data System (ADS)

    Hueckel, T.

    1997-01-01

    Isothermal chemo-elasto-plasticity of clays is discussed, to describe strains induced in clay by permeation of it with a low dielectric constant organic contaminant, in the presence of stress. The strain is crucial in controlling permeability changes in chemically affected clay barriers of landfills and impoundments. The theory encompasses chemical softening or yield surface reduction, coefficient of chemical reversible expansion or contraction due to mass concentration increase, as well as chemical sensitivity of bulk plastic modulus. The experiments on chemistry and stress dependent permeability of Sarnia clay performed by Fernandez and Quigley (1985, 1991) are interpreted using this model. The numerical representations of the chemo-plastic softening function and the chemo-elastic strain function, as well as plastic bulk modulus sensitivity to concentration are evaluated for dioxane and ethanol. Specific requirements for the tests for chemo-plastic behavior of clays are discussed.

  8. Multiscale Plastic Deformation Near a Fatigue Crack from Diffraction

    SciTech Connect

    Sun, Yinan; Barabash, Rozaliya; Choo, H.; Liaw, Peter K; Lu, Yulin; Brown, Donald; Ice, Gene E

    2007-01-01

    The plastic behavior of an annealed HASTELLOY C-22HS alloy, a face-centered cubic (FCC), nickel-based superalloy, was examined by in-situ neutron-diffraction measurements at room temperature. Both monotonic-tension and low-cycle-fatigue experiments were conducted. Monotonic-tension straining and cyclic-loading deformation were studied as a function of stress. The plastic behavior during deformation is discussed in light of the relationship between the stress and dislocation-density evolution. The calculated dislocation-density evolution within the alloy reflects the strain hardening and cyclic hardening/softening. Experimentally determined lattice strains are compared to verify the hardening mechanism at selected stress levels for tension and cyclic loadings. Combined with calculations of the dislocation densities, the neutron-diffraction experiments provide direct information about the strain and cyclic hardening of the alloy.

  9. The plasticity of clays

    USGS Publications Warehouse

    Group, F.F.

    1905-01-01

    (1) Sand injures plasticity little at first because the grains are suspended in a plastic mass. It is only when grains are abundant enough to come in contact with their neighbors, that the effect becomes serious, and then both strength and amount of possible flow are injured. (2) Certain rare organic colloids increase the plasticity by rendering the water viscous. (3) Fineness also tends to increase plasticity. (4) Plane surfaces (plates) increase the amount of possible flow. They also give a chance for lubrication by thinner films, thus increasing the friction of film, and the strength of the whole mass. The action of plates is thus twofold ; but fineness may be carried to such an extent as to break up plate-like grains into angular fragments. The beneficial effects of plates are also decreased by the fact that each is so closely surrounded by others in the mass. (5) Molecular attraction is twofold in increasing plasticity. As the attraction increases, the coherence and strength of the mass increase, and the amount of possible deformation before crumbling also increases. Fineness increases this action by requiring more water. Colloids and crystalloids in solution may also increase the attraction. It is thus seen to be more active than any other single factor.

  10. Effect of Intensive Plastic Deformation on Microstructure and Mechanical Properties of Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Rakhadilov, Bauyrzhan; Uazyrkhanova, Gulzhaz; Myakinin, Alexandr; Uazyrkhanova, Zhuldyz

    2016-08-01

    In work it was studied the influence of intensive plastic deformation on structure and mechanical properties of aluminum alloys. Intensive plastic deformation was carried out by using equal-channel angular extrusion. It is shown that the most efficient angle of intersection of the channels is the angle of Φ=120°, which ensures defect-free parts at the highest possible level of accumulated strain (e=8). It is established that the intensive milling grain structures in aluminum alloys AMG6 and AMC occurs at ECAE-12 passes, while the intersection angle of the channels of 120°. After ECAE-12 in aluminum alloys the grain refinement reaches to the size of ∼⃒1.0-1.5 gm. It is determined that as a result of equal channel angular pressing, the microhardness of alloy AMG6 increases almost 4 times in comparison with the initial state, the microhardness of alloy AMC increases by almost 4.5 times in comparison with the initial state. It is shown that ECAE-12 mass loss is reduced to 5.4 and 5.6 mg, which shows an increase in wear-resistance of aluminum alloys AMG6 and AMC 13-14 %.

  11. Plastic condom developed.

    PubMed

    1992-01-01

    A prototype plastic condom that is expected to be at least as strong as latex, less likely to fail, and more comfortable to use has been designed by researchers at North Carolina-based Family Health International (FHI). The National Institutes of Health has granted the nonprofit medical research organization $1.3 million to conduct tests that will include clinical trials involving volunteer couples to examine the condom/s safety, efficacy in preventing pregnancy, and acceptability among users. Researchers hope the tests, expected to take about 4 years, will show that the plastic condom can be stored for years without weakening, whereas latex loses strength with time. In addition, FHI claims the plastic condom can be used with any kind of lubricant, while Latex is limited to water-based or silicone lubricants. Latex condoms lose up to 90% of their strength when used with oil-based lubricants such as hand lotion, according to studies.

  12. Consumer hazards of plastics.

    PubMed Central

    Wiberg, G S

    1976-01-01

    The modern consumer is exposed to a wide variety of plastic and rubber products in his day to day life: at home, work, school, shopping, recreation and play, and transport. A large variety of toxic sequellae have resulted from untoward exposures by many different routes: oral, dermal, inhalation, and parenteral. Toxic change may result from the plastic itself, migration of unbound components and additives, chemical decomposition or toxic pyrolysis products. The type of damage may involve acute poisoning, chronic organ damage, reproductive disorders, and carcinogenic, mutagenic and teratogenic episodes. Typical examples for all routes are cited along with the activites of Canadian regulatory agencies to reduce both the incidence and severity of plastic-induced disease. PMID:1026409

  13. Adaptation without Plasticity.

    PubMed

    Del Mar Quiroga, Maria; Morris, Adam P; Krekelberg, Bart

    2016-09-27

    Sensory adaptation is a phenomenon in which neurons are affected not only by their immediate input but also by the sequence of preceding inputs. In visual cortex, for example, neurons shift their preferred orientation after exposure to an oriented stimulus. This adaptation is traditionally attributed to plasticity. We show that a recurrent network generates tuning curve shifts observed in cat and macaque visual cortex, even when all synaptic weights and intrinsic properties in the model are fixed. This demonstrates that, in a recurrent network, adaptation on timescales of hundreds of milliseconds does not require plasticity. Given the ubiquity of recurrent connections, this phenomenon likely contributes to responses observed across cortex and shows that plasticity cannot be inferred solely from changes in tuning on these timescales. More broadly, our findings show that recurrent connections can endow a network with a powerful mechanism to store and integrate recent contextual information. PMID:27681421

  14. Strain rate and temperature dependent mechanical behavior of nanocrystalline gold

    NASA Astrophysics Data System (ADS)

    Karanjgaokar, Nikhil J.

    by about 50% due to the extended temperature gradient along the specimen gauge section that causes plastic strain localization. On the contrary, the microheater based uniform heating method results in uniform temperature and strain fields during tensile experiments and was more suited for experiments at elevated temperatures. This uniform heating method was applied to annealed Au films with average grain size of 64 nm and for strain rates 10-5-10 s-1 , and temperatures 298-383 K. Activation volume calculations based on the combined temperature and strain rate experimental results pointed to two rate limiting mechanisms of inelastic deformation: Creep-driven and dislocation-mediated plasticity, with the transition occurring at increasing strain rates for increasing temperatures. The activation volume for the creep-dominated regime increased monotonically from 6.4b3 to 29.5b3 between 298 and 383 K, signifying GB diffusion processes and dislocation-mediated creep, respectively. The trends in the dislocationmediated plasticity regime followed an abnormally decreasing trend in the activation volume values with temperature, which was explained by a model for thermally activated dislocation depinning. Furthermore, the experimental data allowed us to evaluate the hardening behavior for Au films and model it using a linear hardening law and exponential relationships for the state variable and the saturation stress. The creep response of nanocrystalline Au films with 40 nm grain size was also obtained experimentally in an effort to assess its contribution to the overall mechanical response under uniaxial tension. Unusually high primary creep rates (3.3 x 10-8 to 2.7 x 10-7 s-1) and steady state creep rates (5.5 x 10-9 - 1.1 x 10-8 s-1) were measured with the primary creep regime lasting up to 5-6 hr for some stress amplitudes. A non-linear model based on the kinetics of thermal activation was applied to model the creep behavior of Au films, which captured very well the effect

  15. Local strain and damage mapping in single trabeculae during three-point bending tests.

    PubMed

    Jungmann, R; Szabo, M E; Schitter, G; Tang, Raymond Yue-Sing; Vashishth, D; Hansma, P K; Thurner, P J

    2011-05-01

    The use of bone mineral density as a surrogate to diagnose bone fracture risk in individuals is of limited value. However, there is growing evidence that information on trabecular microarchitecture can improve the assessment of fracture risk. One current strategy is to exploit finite element analysis (FEA) applied to 3D image data of several mm-sized trabecular bone structures obtained from non-invasive imaging modalities for the prediction of apparent mechanical properties. However, there is a lack of FE damage models, based on solid experimental facts, which are needed to validate such approaches and to provide criteria marking elastic-plastic deformation transitions as well as microdamage initiation and accumulation. In this communication, we present a strategy that could elegantly lead to future damage models for FEA: direct measurements of local strains involved in microdamage initiation and plastic deformation in single trabeculae. We use digital image correlation to link stress whitening in bone, reported to be correlated to microdamage, to quantitative local strain values. Our results show that the whitening zones, i.e. damage formation, in the presented loading case of a three-point bending test correlate best with areas of elevated tensile strains oriented parallel to the long axis of the samples. The average local strains along this axis were determined to be (1.6±0.9)% at whitening onset and (12±4)% just prior to failure. Overall, our data suggest that damage initiation in trabecular bone is asymmetric in tension and compression, with failure originating and propagating over a large range of tensile strains. PMID:21396601

  16. A new technique for detecting colored macro plastic debris on beaches using webcam images and CIELUV.

    PubMed

    Kataoka, Tomoya; Hinata, Hirofumi; Kako, Shin'ichiro

    2012-09-01

    We have developed a technique for detecting the pixels of colored macro plastic debris (plastic pixels) using photographs taken by a webcam installed on Sodenohama beach, Tobishima Island, Japan. The technique involves generating color references using a uniform color space (CIELUV) to detect plastic pixels and removing misdetected pixels by applying a composite image method. This technique demonstrated superior performance in terms of detecting plastic pixels of various colors compared to the previous method which used the lightness values in the CIELUV color space. We also obtained a 10-month time series of the quantity of plastic debris by combining a projective transformation with this technique. By sequential monitoring of plastic debris quantity using webcams, it is possible to clean up beaches systematically, to clarify the transportation processes of plastic debris in oceans and coastal seas and to estimate accumulation rates on beaches.

  17. Plastic pollution in five urban estuaries of KwaZulu-Natal, South Africa.

    PubMed

    Naidoo, Trishan; Glassom, David; Smit, Albertus J

    2015-12-15

    Monitoring plastic concentrations in estuaries is vital in assessing the magnitude of terrestrial inputs to oceanic environments. Data on plastics ≤ 5 mm in estuaries are scant. This study determined microplastic levels within five estuaries along the Durban coastline and on intervening beaches. Plastics were isolated from estuarine sediment, beach sediment and the surface water of each estuary and characterised. Sediment at the Bayhead area of Durban harbour had the highest average plastic concentrations (745.4 ± 129.7 particles per 500 ml) and an attenuating concentration trend away from the city centre was found. Prevailing south to north longshore drift was hypothesised to result in plastic accumulation on the northern shores of beaches with estuarine effluents, however, this was not found. Fragments composed the largest percent of plastics (59%) found in Bayhead, whereas fibres dominated other estuaries with proportions ranging from 38% of total plastics in the uMgeni estuary to 66% in the Mdloti.

  18. Plastic pollution in five urban estuaries of KwaZulu-Natal, South Africa.

    PubMed

    Naidoo, Trishan; Glassom, David; Smit, Albertus J

    2015-12-15

    Monitoring plastic concentrations in estuaries is vital in assessing the magnitude of terrestrial inputs to oceanic environments. Data on plastics ≤ 5 mm in estuaries are scant. This study determined microplastic levels within five estuaries along the Durban coastline and on intervening beaches. Plastics were isolated from estuarine sediment, beach sediment and the surface water of each estuary and characterised. Sediment at the Bayhead area of Durban harbour had the highest average plastic concentrations (745.4 ± 129.7 particles per 500 ml) and an attenuating concentration trend away from the city centre was found. Prevailing south to north longshore drift was hypothesised to result in plastic accumulation on the northern shores of beaches with estuarine effluents, however, this was not found. Fragments composed the largest percent of plastics (59%) found in Bayhead, whereas fibres dominated other estuaries with proportions ranging from 38% of total plastics in the uMgeni estuary to 66% in the Mdloti. PMID:26476863

  19. Molecular Signaling in Muscle Plasticity

    NASA Technical Reports Server (NTRS)

    Epstein, Henry F.

    1999-01-01

    Extended spaceflight under microgravity conditions leads to significant atrophy of weight-bearing muscles. Atrophy and hypertrophy are the extreme outcomes of the high degree of plasticity exhibited by skeletal muscle. Stimuli which control muscle plasticity include neuronal, hormonal, nutritional, and mechanical inputs. The mechanical stimulus for muscle is directly related to the work or exercise against a load performed. Little or no work is performed by weight-bearing muscles under microgravity conditions. A major hypothesis is that focal adhesion kinase (FAK) which is associated with integrin at the adherens junctions and costa meres of all skeletal muscles is an integral part of the major mechanism for molecular signaling upon mechanical stimulation in all muscle fibers. Additionally, we propose that myotonic protein kinase (DMPK) and dystrophin (DYSTR) also participate in distinct mechanically stimulated molecular signaling pathways that are most critical in type I and type II muscle fibers, respectively. To test these hypotheses, we will use the paradigms of hindlimb unloading and overloading in mice as models for microgravity conditions and a potential exercise countermeasure, respectively, in mice. We expect that FAK loss-of-function will impair hypertrophy and enhance atrophy in all skeletal muscle fibers whereas DYSTR and DMPK loss-of-function will have similar but more selective effects on Type IT and Type I fibers, respectively. Gene expression will be monitored by muscle-specific creatine kinase M promoter-reporter construct activity and specific MRNA and protein accumulation in the soleus (type I primarily) and plantaris (type 11 primarily) muscles. With these paradigms and assays, the following Specific Project Aims will be tested in genetically altered mice: 1) identify the roles of DYSTR and its pathway; 2) evaluate the roles of the DMPK and its pathway; 3) characterize the roles of FAK and its pathway and 4) genetically analyze the mechanisms

  20. Finite-element formulations for problems of large elastic-plastic deformation

    NASA Technical Reports Server (NTRS)

    Mcmeeking, R. M.; Rice, J. R.

    1975-01-01

    An Eulerian finite element formulation is presented for problems of large elastic-plastic flow. The method is based on Hill's variational principle for incremental deformations, and is ideally suited to isotropically hardening Prandtl-Reuss materials. Further, the formulation is given in a manner which allows any conventional finite element program, for 'small strain' elastic-plastic analysis, to be simply and rigorously adapted to problems involving arbitrary amounts of deformation and arbitrary levels of stress in comparison to plastic deformation moduli. The method is applied to a necking bifurcation analysis of a bar in plane-strain tension. The paper closes with a unified general formulation of finite element equations, both Lagrangian and Eulerian, for large deformations, with arbitrary choice of the conjugate stress and strain measures. Further, a discussion is given of other proposed formulations for elastic-plastic finite element analysis at large strain, and the inadequacies of some of these are commented upon.

  1. Floating plastic debris in the Central and Western Mediterranean Sea.

    PubMed

    Ruiz-Orejón, Luis F; Sardá, Rafael; Ramis-Pujol, Juan

    2016-09-01

    In two sea voyages throughout the Mediterranean (2011 and 2013) that repeated the historical travels of Archduke Ludwig Salvator of Austria (1847-1915), 71 samples of floating plastic debris were obtained with a Manta trawl. Floating plastic was observed in all the sampled sites, with an average weight concentration of 579.3 g dw km(-2) (maximum value of 9298.2 g dw km(-2)) and an average particle concentration of 147,500 items km(-2) (the maximum concentration was 1,164,403 items km(-2)). The plastic size distribution showed microplastics (<5 mm) in all the samples. The most abundant particles had a surface area of approximately 1 mm(2) (the mesh size was 333 μm). The general estimate obtained was a total value of 1455 tons dw of floating plastic in the entire Mediterranean region, with various potential spatial accumulation areas. PMID:27540696

  2. Deformation fields near a steady fatigue crack with anisotropic plasticity

    SciTech Connect

    Gao, Yanfei

    2015-11-30

    In this work, from finite element simulations based on an irreversible, hysteretic cohesive interface model, a steady fatigue crack can be realized if the crack extension exceeds about twice the plastic zone size, and both the crack increment per loading cycle and the crack bridging zone size are smaller than the plastic zone size. The corresponding deformation fields develop a plastic wake behind the crack tip and a compressive residual stress field ahead of the crack tip. In addition, the Hill’s plasticity model is used to study the role of plastic anisotropy on the retardation of fatigue crack growth and the elastic strain fields. It is found that for Mode-I cyclic loading, an enhanced yield stress in directions that are inclined from the crack plane will lead to slower crack growth rate, but this retardation is insignificant for typical degrees of plastic anisotropy. Furthermore, these results provide key inputs for future comparisons to neutron and synchrotron diffraction measurements that provide full-field lattice strain mapping near fracture and fatigue crack tips, especially in textured materials such as wrought or rolled Mg alloys.

  3. Deformation fields near a steady fatigue crack with anisotropic plasticity

    DOE PAGES

    Gao, Yanfei

    2015-11-30

    In this work, from finite element simulations based on an irreversible, hysteretic cohesive interface model, a steady fatigue crack can be realized if the crack extension exceeds about twice the plastic zone size, and both the crack increment per loading cycle and the crack bridging zone size are smaller than the plastic zone size. The corresponding deformation fields develop a plastic wake behind the crack tip and a compressive residual stress field ahead of the crack tip. In addition, the Hill’s plasticity model is used to study the role of plastic anisotropy on the retardation of fatigue crack growth andmore » the elastic strain fields. It is found that for Mode-I cyclic loading, an enhanced yield stress in directions that are inclined from the crack plane will lead to slower crack growth rate, but this retardation is insignificant for typical degrees of plastic anisotropy. Furthermore, these results provide key inputs for future comparisons to neutron and synchrotron diffraction measurements that provide full-field lattice strain mapping near fracture and fatigue crack tips, especially in textured materials such as wrought or rolled Mg alloys.« less

  4. Biodegradable foam plastics based on castor oil.

    PubMed

    Wang, Hong Juan; Rong, Min Zhi; Zhang, Ming Qiu; Hu, Jing; Chen, Hui Wen; Czigány, Tibor

    2008-02-01

    In this work, a simple but effective approach was proposed for preparing biodegradable plastic foams with a high content of castor oil. First of all, castor oil reacted with maleic anhydride to produce maleated castor oil (MACO) without the aid of any catalyst. Then plastic foams were synthesized through free radical initiated copolymerization between MACO and diluent monomer styrene. With changes in MACO/St ratio and species of curing initiator, mechanical properties of MACO foams can be easily adjusted. In this way, biofoams with comparable compressive stress at 25% strain as commercial polyurethane (PU) foams were prepared, while the content of castor oil can be as high as 61 wt %. The soil burial tests further proved that the castor oil based foams kept the biodegradability of renewable resources despite the fact that some petrol-based components were introduced. PMID:18163578

  5. Biodegradable foam plastics based on castor oil.

    PubMed

    Wang, Hong Juan; Rong, Min Zhi; Zhang, Ming Qiu; Hu, Jing; Chen, Hui Wen; Czigány, Tibor

    2008-02-01

    In this work, a simple but effective approach was proposed for preparing biodegradable plastic foams with a high content of castor oil. First of all, castor oil reacted with maleic anhydride to produce maleated castor oil (MACO) without the aid of any catalyst. Then plastic foams were synthesized through free radical initiated copolymerization between MACO and diluent monomer styrene. With changes in MACO/St ratio and species of curing initiator, mechanical properties of MACO foams can be easily adjusted. In this way, biofoams with comparable compressive stress at 25% strain as commercial polyurethane (PU) foams were prepared, while the content of castor oil can be as high as 61 wt %. The soil burial tests further proved that the castor oil based foams kept the biodegradability of renewable resources despite the fact that some petrol-based components were introduced.

  6. Intrinsic plasticity: an emerging player in addiction.

    PubMed

    Kourrich, Saïd; Calu, Donna J; Bonci, Antonello

    2015-03-01

    Exposure to drugs of abuse, such as cocaine, leads to plastic changes in the activity of brain circuits, and a prevailing view is that these changes play a part in drug addiction. Notably, there has been intense focus on drug-induced changes in synaptic excitability and much less attention on intrinsic excitability factors (that is, excitability factors that are remote from the synapse). Accumulating evidence now suggests that intrinsic factors such as K+ channels are not only altered by cocaine but may also contribute to the shaping of the addiction phenotype.

  7. Plastic waste in the marine environment: A review of sources, occurrence and effects.

    PubMed

    Li, W C; Tse, H F; Fok, L

    2016-10-01

    This review article summarises the sources, occurrence, fate and effects of plastic waste in the marine environment. Due to its resistance to degradation, most plastic debris will persist in the environment for centuries and may be transported far from its source, including great distances out to sea. Land- and ocean-based sources are the major sources of plastic entering the environment, with domestic, industrial and fishing activities being the most important contributors. Ocean gyres are particular hotspots of plastic waste accumulation. Both macroplastics and microplastics pose a risk to organisms in the natural environment, for example, through ingestion or entanglement in the plastic. Many studies have investigated the potential uptake of hydrophobic contaminants, which can then bioaccumulate in the food chain, from plastic waste by organisms. To address the issue of plastic pollution in the marine environment, governments should first play an active role in addressing the issue of plastic waste by introducing legislation to control the sources of plastic debris and the use of plastic additives. In addition, plastics industries should take responsibility for the end-of-life of their products by introducing plastic recycling or upgrading programmes.

  8. Plastic waste in the marine environment: A review of sources, occurrence and effects.

    PubMed

    Li, W C; Tse, H F; Fok, L

    2016-10-01

    This review article summarises the sources, occurrence, fate and effects of plastic waste in the marine environment. Due to its resistance to degradation, most plastic debris will persist in the environment for centuries and may be transported far from its source, including great distances out to sea. Land- and ocean-based sources are the major sources of plastic entering the environment, with domestic, industrial and fishing activities being the most important contributors. Ocean gyres are particular hotspots of plastic waste accumulation. Both macroplastics and microplastics pose a risk to organisms in the natural environment, for example, through ingestion or entanglement in the plastic. Many studies have investigated the potential uptake of hydrophobic contaminants, which can then bioaccumulate in the food chain, from plastic waste by organisms. To address the issue of plastic pollution in the marine environment, governments should first play an active role in addressing the issue of plastic waste by introducing legislation to control the sources of plastic debris and the use of plastic additives. In addition, plastics industries should take responsibility for the end-of-life of their products by introducing plastic recycling or upgrading programmes. PMID:27232963

  9. Does a tradeoff exist between morphological and physiological root plasticity? A comparison of grass growth forms

    NASA Astrophysics Data System (ADS)

    Derner, Justin D.; Briske, David D.

    1999-09-01

    A series of experiments were conducted to evaluate the potential tradeoff between morphological and physiological root plasticity in caespitose and rhizomatous grass growth forms in semi-arid and mesic communities. Morphological and physiological root plasticity were evaluated with in-growth cores and excised root assays, respectively. The rhizomatous grass in the semi-arid community was the only species to display significant physiological root plasticity, but all species possessed the capacity to proportionally increase 15N uptake with increasing concentrations of ( 15NH 4) 2SO 4 solution. Neither the caespitose nor the rhizomatous grass displayed morphological root plasticity in response to nitrogen addition in the mesic community. In contrast, significant morphological root plasticity occurred in species of both growth forms in the semi-arid community. These data suggest that the compact architecture and the ability to accumulate nutrients in soils directly beneath caespitose grasses did not increase selection pressure for physiological root plasticity at the expense of morphological root plasticity and that the coarse grained foraging strategy and low density of large diameter roots did not increase morphological root plasticity at the expense of physiological root plasticity in rhizomatous grasses. These preliminary data suggest that 1) a high maximum uptake rate for nitrogen in these perennial grasses may minimize the expression of physiological root plasticity, 2) morphological and physiological root plasticity may represent complimentary, rather than alternative, foraging strategies, and 3) the expression of root plasticity may be strongly influenced by abiotic variables within specific habitats.

  10. Megacell phenotype and its relation to metabolic alterations in transketolase deficient strain of Bacillus pumilus.

    PubMed

    Srivastava, Rajesh K; Jaiswal, Richa; Panda, Dulal; Wangikar, Pramod P

    2009-04-01

    Fermentation with transketolase (tkt) deficient strain of Bacillus is the only reported industrially viable process for production of D-ribose, a commercially important pentose sugar. In addition to direct effects of tkt deficiency, the mutation in non-oxidative part of pentose phosphate pathway (PPP) is known to display several unexpected physiological characteristics such as decreased ability to utilize D-glucose, altered carbon catabolite repression, lack of motility, etc. Here we demonstrate the morphological plasticity of tkt deficient strain of Bacillus pumilus ATCC 21951 and its possible relation with D-ribose productivity, a measure of carbon flux through PPP. The bacilli divide normally in nutrient rich media such as Luria-Bertani (LB) broth while showing cell elongation of up to 20-fold without a visible septum accompanied by moderate to high extracellular D-ribose accumulation in glucose-rich media. The cells stained with DAPI (4'-6-diamidino-2-phenylindole) and anti FtsZ antibody showed nucleoid separation and Z-ring formation in LB broth but not in glucose-rich media. FtsZ protein is known to localize at the future division site forming a ring, called Z-ring, at an early stage in cytokinesis. The strain experiences inhibition or delay in Z-ring formation resulting in cell elongation, possibly due to its altered cell membrane composition resulting from tkt deficiency. We hypothesize that the lack of PPP intermediates may have two effects on the strain: (i) altered the cell membrane leading to delay in Z-ring formation and cell elongation; and (ii) induction of genes of the oxidative part of PPP resulting in D-ribose accumulation. Nutrient rich media such as LB broth may alleviate these metabolite deficiencies thereby restoring normal cell division and inhibiting excessive D-ribose accumulation. The D-ribose productivity and cell elongation may therefore be co-morbid. The results have implications in designing optimal media and monitoring strategy based

  11. Effect of dynamic strain rate on micro-indentation properties of pure aluminum

    NASA Astrophysics Data System (ADS)

    Yamada, Hiroyuki; Hotta, Midori; Kami, Tsuyoshi; Ogasawara, Nagahisa; Chen, Xi

    2015-09-01

    Indentation is widely used to investigate the elastic and plastic properties of mechanical materials, which includes the strain rate sensitivity. The indentation exhibits an inhomogeneous strain distribution in contrast to compression and tensile tests with homogeneous deformation. Thus, the strain rate of the indentation may form the inhomogeneous distribution. Therefore, the effect of strain rate distribution of the indentation on pure aluminum with respect to the strain rate dependence of strength in order to clarify the effect of the strain rate on the indentation technique. First, the numerical simulation was established using the Cowper-Symonds equation as the dynamic constitutive equation. Secondary, the strain rate distribution was calculated from the equivalent plastic strain distribution. The strain rate distribution was quite different from the strain distribution, which showed that the strain rate at the crater rim was higher than that beneath the indenter. Finally, we try to perform the averaging of strain rate distribution in order to make an index of strain rate in the indentation. The average of strain rate distribution was calculated using the equivalent plastic strain above a boundary value that is the critical strain and the representative strain. There is correlation between the average strain rate and the loading curvature, which shows that the average strain rate can express as the representative of strain rate for the indentation technique.

  12. Localized Plastic Deformation in Colloidal Micropillars

    NASA Astrophysics Data System (ADS)

    Strickland, Daniel; Hor, Jyo Lyn; Ortiz, Carlos; Lee, Daeyeon; Gianola, Daniel

    When driven beyond yield, many amorphous solids exhibit concentrated regions of large plastic strain referred to as shear bands. Shear bands are the result of localized, cooperative rearrangements of particles known as shear transformations (STs). STs are dilatory: their operation results in an increase of free volume and local softening that leads to spatially concentrated plasticity. However, the evolution of STs into a macroscopic shear band remains poorly understood. To study the process, we perform compression experiments on amorphous colloidal micropillars. The micropillars, which are composed of fluorescent 3 μm PMMA particles, are made freestanding so that shear banding instabilities are not suppressed by confining boundaries. During compression, we observe strong localization of strain in a band of the pillar. As deformation proceeds, the sheared region continues to dilate until it reaches the colloidal glass transition, at which point dilation terminates. We quantify a length scale by measuring the extent of spatial correlations in strain. This length scale decreases gradually with increasing dilation and becomes static beyond the glass transition. Our results reinforce the idea of yield as a stress-induced glass transition in amorphous solids.

  13. Strain to failure of pressurized thick wall cylinders

    SciTech Connect

    Priddy, T.G.; Roach, D.P.

    1989-01-01

    The determination of the fully plastic response and pressure limit of a highly pressurized vessel is of considerable importance in design. The plastic-strain response during and following autofrettage operations, in comparison with the limiting strain condition, is of special interest. This paper presents the results of an analysis method for thick wall, high pressure, cylinders where the effective plastic strain distribution through the thickness is the material response variable of primary interest. The limiting value of this effective plastic strain depends on the level of tensile-stress triaxiality which also varies through the thickness. This strain-to-failure criterion is used to predict the complete pressure versus strain response and the maximum pressure for test cylinders. A simple model of effective-stress versus effective plastic strain is employed. This model is quantified by data taken from uniaxial, tension, true-stress-strain curves and from the fracture zone of the tensile specimen. A sample calculation is included and, in a companion paper, a series of burst tubes having properties ranging from brittle to ductile are compared with this analytical method. 21 refs., 5 figs., 2 tabs.

  14. Plasticity Tool for Predicting Shear Nonlinearity of Unidirectional Laminates Under Multiaxial Loading

    NASA Technical Reports Server (NTRS)

    Wang, John T.; Bomarito, Geoffrey F.

    2016-01-01

    This study implements a plasticity tool to predict the nonlinear shear behavior of unidirectional composite laminates under multiaxial loadings, with an intent to further develop the tool for use in composite progressive damage analysis. The steps for developing the plasticity tool include establishing a general quadratic yield function, deriving the incremental elasto-plastic stress-strain relations using the yield function with associated flow rule, and integrating the elasto-plastic stress-strain relations with a modified Euler method and a substepping scheme. Micromechanics analyses are performed to obtain normal and shear stress-strain curves that are used in determining the plasticity parameters of the yield function. By analyzing a micromechanics model, a virtual testing approach is used to replace costly experimental tests for obtaining stress-strain responses of composites under various loadings. The predicted elastic moduli and Poisson's ratios are in good agreement with experimental data. The substepping scheme for integrating the elasto-plastic stress-strain relations is suitable for working with displacement-based finite element codes. An illustration problem is solved to show that the plasticity tool can predict the nonlinear shear behavior for a unidirectional laminate subjected to multiaxial loadings.

  15. Strengthening Mechanisms in Nanostructured Al/SiCp Composite Manufactured by Accumulative Press Bonding

    NASA Astrophysics Data System (ADS)

    Amirkhanlou, Sajjad; Rahimian, Mehdi; Ketabchi, Mostafa; Parvin, Nader; Yaghinali, Parisa; Carreño, Fernando

    2016-10-01

    The strengthening mechanisms in nanostructured Al/SiCp composite deformed to high strain by a novel severe plastic deformation process, accumulative press bonding (APB), were investigated. The composite exhibited yield strength of 148 MPa which was 5 and 1.5 times higher than that of raw aluminum (29 MPa) and aluminum-APB (95 MPa) alloys, respectively. A remarkable increase was also observed in the ultimate tensile strength of Al/SiCp-APB composite, 222 MPa, which was 2.5 and 1.2 times greater than the obtained values for raw aluminum (88 MPa) and aluminum-APB (180 MPa) alloys, respectively. Analytical models well described the contribution of various strengthening mechanisms. The contributions of grain boundary, strain hardening, thermal mismatch, Orowan, elastic mismatch, and load-bearing strengthening mechanisms to the overall strength of the Al/SiCp microcomposite were 64.9, 49, 6.8, 2.4, 5.4, and 1.5 MPa, respectively. Whereas Orowan strengthening mechanism was considered as the most dominating strengthening mechanism in Al/SiCp nanocomposites, it was negligible for strengthening the microcomposite. Al/SiCp nanocomposite showed good agreement with quadratic summation model; however, experimental results exhibited good accordance with arithmetic and compounding summation models in the microcomposite. While average grain size of the composite reached 380 nm, it was less than 100 nm in the vicinity of SiC particles as a result of particle-stimulated nucleation mechanism.

  16. Gradient Plasticity Model and its Implementation into MARMOT

    SciTech Connect

    Barker, Erin I.; Li, Dongsheng; Zbib, Hussein M.; Sun, Xin

    2013-08-01

    The influence of strain gradient on deformation behavior of nuclear structural materials, such as boby centered cubic (bcc) iron alloys has been investigated. We have developed and implemented a dislocation based strain gradient crystal plasticity material model. A mesoscale crystal plasticity model for inelastic deformation of metallic material, bcc steel, has been developed and implemented numerically. Continuum Dislocation Dynamics (CDD) with a novel constitutive law based on dislocation density evolution mechanisms was developed to investigate the deformation behaviors of single crystals, as well as polycrystalline materials by coupling CDD and crystal plasticity (CP). The dislocation density evolution law in this model is mechanism-based, with parameters measured from experiments or simulated with lower-length scale models, not an empirical law with parameters back-fitted from the flow curves.

  17. Comparisons of FEM Approaches Modelling the Metal Plastic Behaviour

    SciTech Connect

    Habraken, A. M.; Gerday, A. F.; Diouf, B.; Duchene, L.

    2007-04-07

    Simple phenomenological laws (e.g. classical Hill 1948 quadratic law) are compared to more complex laws based on crystal plasticity through various numerical simulations: mechanical tests of ECAE materials, nanoindentation of titanium alloys and copper, and large strain torsion of copper bars. Taking into consideration the complexity of the investigated processes, the numerical results present rather good agreements with experimental observations.

  18. Plastic debris in the coastal environment: The invincible threat? Abundance of buried plastic debris on Malaysian beaches.

    PubMed

    Fauziah, S H; Liyana, I A; Agamuthu, P

    2015-09-01

    Studies on marine debris have gained worldwide attention since many types of debris have found their way into the food chain of higher organisms. Thus, it is crucial that more focus is given to this area in order to curb contaminations in sea food. This study was conducted to quantify plastic debris buried in sand at selected beaches in Malaysia. Marine debris was identified according to size range and distribution, and this information was related to preventive actions to improve marine waste issues. For the purpose of this study, comparison of plastic waste abundance between a recreational beach and fish-landing beaches was also carried out, since the different beach types represent different activities that produce debris. Six beaches along the Malaysian coastline were selected for this study. The plastic types in this study were related to the functions of the beach. While recreational beaches have abundant quantities of plastic film, foamed plastic including polystyrene, and plastic fragment, fish-landing beaches accumulated line and foamed plastic. A total of 2542 pieces (265.30 g m(-2)) of small plastic debris were collected from all six beaches, with the highest number from Kuala Terengganu, at 879 items m(-2) on Seberang Takir Beach, followed by Batu Burok Beach with 780 items m(-2). Findings from studies of Malaysian beaches have provided a clearer understanding of the distribution of plastic debris. This demonstrates that commitments and actions, such as practices of the 'reduce, reuse, recycle' (3R) approach, supporting public awareness programmes and beach clean-up activities, are essential in order to reduce and prevent plastic debris pollution.

  19. Plastic debris in the coastal environment: The invincible threat? Abundance of buried plastic debris on Malaysian beaches.

    PubMed

    Fauziah, S H; Liyana, I A; Agamuthu, P

    2015-09-01

    Studies on marine debris have gained worldwide attention since many types of debris have found their way into the food chain of higher organisms. Thus, it is crucial that more focus is given to this area in order to curb contaminations in sea food. This study was conducted to quantify plastic debris buried in sand at selected beaches in Malaysia. Marine debris was identified according to size range and distribution, and this information was related to preventive actions to improve marine waste issues. For the purpose of this study, comparison of plastic waste abundance between a recreational beach and fish-landing beaches was also carried out, since the different beach types represent different activities that produce debris. Six beaches along the Malaysian coastline were selected for this study. The plastic types in this study were related to the functions of the beach. While recreational beaches have abundant quantities of plastic film, foamed plastic including polystyrene, and plastic fragment, fish-landing beaches accumulated line and foamed plastic. A total of 2542 pieces (265.30 g m(-2)) of small plastic debris were collected from all six beaches, with the highest number from Kuala Terengganu, at 879 items m(-2) on Seberang Takir Beach, followed by Batu Burok Beach with 780 items m(-2). Findings from studies of Malaysian beaches have provided a clearer understanding of the distribution of plastic debris. This demonstrates that commitments and actions, such as practices of the 'reduce, reuse, recycle' (3R) approach, supporting public awareness programmes and beach clean-up activities, are essential in order to reduce and prevent plastic debris pollution. PMID:26092255

  20. Plastics in Perspective.

    ERIC Educational Resources Information Center

    Bergandine, David R.; Holm, D. Andrew

    The materials in this curriculum supplement, developed for middle school or high school science classes, present solid waste problems related to plastics. The set of curriculum materials is divided into two units to be used together or independently. Unit I begins by comparing patterns in solid waste from 1960 to 1990 and introducing methods for…

  1. Hydrodynamic Elastic Magneto Plastic

    1985-02-01

    The HEMP code solves the conservation equations of two-dimensional elastic-plastic flow, in plane x-y coordinates or in cylindrical symmetry around the x-axis. Provisions for calculation of fixed boundaries, free surfaces, pistons, and boundary slide planes have been included, along with other special conditions.

  2. Strain Gage

    NASA Technical Reports Server (NTRS)

    1995-01-01

    HITEC Corporation developed a strain gage application for DanteII, a mobile robot developed for NASA. The gage measured bending forces on the robot's legs and warned human controllers when acceptable forces were exceeded. HITEC further developed the technology for strain gage services in creating transducers out of "Indy" racing car suspension pushrods, NASCAR suspension components and components used in motion control.

  3. Neurodegeneration with Brain Iron Accumulation

    MedlinePlus

    ... Diversity Find People About NINDS NINDS Neurodegeneration with Brain Iron Accumulation Information Page Synonym(s): Hallervorden-Spatz Disease, ... done? Clinical Trials Organizations What is Neurodegeneration with Brain Iron Accumulation? Neurodegeneration with brain iron accumulation (NBIA) ...

  4. Experimental assessment of unvalidated assumptions in classical plasticity theory.

    SciTech Connect

    Brannon, Rebecca Moss; Burghardt, Jeffrey A.; Bauer, Stephen J.; Bronowski, David R.

    2009-01-01

    This report investigates the validity of several key assumptions in classical plasticity theory regarding material response to changes in the loading direction. Three metals, two rock types, and one ceramic were subjected to non-standard loading directions, and the resulting strain response increments were displayed in Gudehus diagrams to illustrate the approximation error of classical plasticity theories. A rigorous mathematical framework for fitting classical theories to the data, thus quantifying the error, is provided. Further data analysis techniques are presented that allow testing for the effect of changes in loading direction without having to use a new sample and for inferring the yield normal and flow directions without having to measure the yield surface. Though the data are inconclusive, there is indication that classical, incrementally linear, plasticity theory may be inadequate over a certain range of loading directions. This range of loading directions also coincides with loading directions that are known to produce a physically inadmissible instability for any nonassociative plasticity model.

  5. Plastids and Carotenoid Accumulation.

    PubMed

    Li, Li; Yuan, Hui; Zeng, Yunliu; Xu, Qiang

    2016-01-01

    Plastids are ubiquitously present in plants and are the organelles for carotenoid biosynthesis and storage. Based on their morphology and function, plastids are classified into various types, i.e. proplastids, etioplasts, chloroplasts, amyloplasts, and chromoplasts. All plastids, except proplastids, can synthesize carotenoids. However, plastid types have a profound effect on carotenoid accumulation and stability. In this chapter, we discuss carotenoid biosynthesis and regulation in various plastids with a focus on carotenoids in chromoplasts. Plastid transition related to carotenoid biosynthesis and the different capacity of various plastids to sequester carotenoids and the associated effect on carotenoid stability are described in light of carotenoid accumulation in plants. PMID:27485226

  6. Plastids and Carotenoid Accumulation.

    PubMed

    Li, Li; Yuan, Hui; Zeng, Yunliu; Xu, Qiang

    2016-01-01

    Plastids are ubiquitously present in plants and are the organelles for carotenoid biosynthesis and storage. Based on their morphology and function, plastids are classified into various types, i.e. proplastids, etioplasts, chloroplasts, amyloplasts, and chromoplasts. All plastids, except proplastids, can synthesize carotenoids. However, plastid types have a profound effect on carotenoid accumulation and stability. In this chapter, we discuss carotenoid biosynthesis and regulation in various plastids with a focus on carotenoids in chromoplasts. Plastid transition related to carotenoid biosynthesis and the different capacity of various plastids to sequester carotenoids and the associated effect on carotenoid stability are described in light of carotenoid accumulation in plants.

  7. Elastic-plastic behavior of non-woven fibrous mats

    NASA Astrophysics Data System (ADS)

    Silberstein, Meredith N.; Pai, Chia-Ling; Rutledge, Gregory C.; Boyce, Mary C.

    2012-02-01

    Electrospinning is a novel method for creating non-woven polymer mats that have high surface area and high porosity. These attributes make them ideal candidates for multifunctional composites. Understanding the mechanical properties as a function of fiber properties and mat microstructure can aid in designing these composites. Further, a constitutive model which captures the membrane stress-strain behavior as a function of fiber properties and the geometry of the fibrous network would be a powerful design tool. Here, mats electrospun from amorphous polyamide are used as a model system. The elastic-plastic behavior of single fibers are obtained in tensile tests. Uniaxial monotonic and cyclic tensile tests are conducted on non-woven mats. The mat exhibits elastic-plastic stress-strain behavior. The transverse strain behavior provides important complementary data, showing a negligible initial Poisson's ratio followed by a transverse:axial strain ratio greater than -1:1 after an axial strain of 0.02. A triangulated framework has been developed to emulate the fibrous network structure of the mat. The micromechanically based model incorporates the elastic-plastic behavior of single fibers into a macroscopic membrane model of the mat. This representative volume element based model is shown to capture the uniaxial elastic-plastic response of the mat under monotonic and cyclic loading. The initial modulus and yield stress of the mat are governed by the fiber properties, the network geometry, and the network density. The transverse strain behavior is linked to discrete deformation mechanisms of the fibrous mat structure including fiber alignment, fiber bending, and network consolidation. The model is further validated in comparison to experiments under different constrained axial loading conditions and found to capture the constraint effect on stiffness, yield, post-yield hardening, and post-yield transverse strain behavior. Due to the direct connection between

  8. Plastics for Elementary School Children

    ERIC Educational Resources Information Center

    Hanson, Jack

    1977-01-01

    Describes three plastics projects (which involve making a styrene fishing bobber, an acrylic salad fork and spoon set, and acetate shrink art) designed to provide elementary level students an opportunity to work with plastics and to learn about careers in plastics production and distribution. (TA)

  9. Seabirds and floating plastic debris.

    PubMed

    Cadée, Gerhard C

    2002-11-01

    80% of floating plastic debris freshly washed ashore on a Dutch coast showed peckmarks made by birds at sea. They either mistake these debris for cuttlebones or simply test all floating objects. Ingestion of plastic is deleterious for marine organisms. It is urgent to set measures to plastic litter production.

  10. Chimpanzee accumulative stone throwing.

    PubMed

    Kühl, Hjalmar S; Kalan, Ammie K; Arandjelovic, Mimi; Aubert, Floris; D'Auvergne, Lucy; Goedmakers, Annemarie; Jones, Sorrel; Kehoe, Laura; Regnaut, Sebastien; Tickle, Alexander; Ton, Els; van Schijndel, Joost; Abwe, Ekwoge E; Angedakin, Samuel; Agbor, Anthony; Ayimisin, Emmanuel Ayuk; Bailey, Emma; Bessone, Mattia; Bonnet, Matthieu; Brazolla, Gregory; Buh, Valentine Ebua; Chancellor, Rebecca; Cipoletta, Chloe; Cohen, Heather; Corogenes, Katherine; Coupland, Charlotte; Curran, Bryan; Deschner, Tobias; Dierks, Karsten; Dieguez, Paula; Dilambaka, Emmanuel; Diotoh, Orume; Dowd, Dervla; Dunn, Andrew; Eshuis, Henk; Fernandez, Rumen; Ginath, Yisa; Hart, John; Hedwig, Daniela; Ter Heegde, Martijn; Hicks, Thurston Cleveland; Imong, Inaoyom; Jeffery, Kathryn J; Junker, Jessica; Kadam, Parag; Kambi, Mohamed; Kienast, Ivonne; Kujirakwinja, Deo; Langergraber, Kevin; Lapeyre, Vincent; Lapuente, Juan; Lee, Kevin; Leinert, Vera; Meier, Amelia; Maretti, Giovanna; Marrocoli, Sergio; Mbi, Tanyi Julius; Mihindou, Vianet; Moebius, Yasmin; Morgan, David; Morgan, Bethan; Mulindahabi, Felix; Murai, Mizuki; Niyigabae, Protais; Normand, Emma; Ntare, Nicolas; Ormsby, Lucy Jayne; Piel, Alex; Pruetz, Jill; Rundus, Aaron; Sanz, Crickette; Sommer, Volker; Stewart, Fiona; Tagg, Nikki; Vanleeuwe, Hilde; Vergnes, Virginie; Willie, Jacob; Wittig, Roman M; Zuberbuehler, Klaus; Boesch, Christophe

    2016-01-01

    The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites.

  11. Chimpanzee accumulative stone throwing

    PubMed Central

    Kühl, Hjalmar S.; Kalan, Ammie K.; Arandjelovic, Mimi; Aubert, Floris; D’Auvergne, Lucy; Goedmakers, Annemarie; Jones, Sorrel; Kehoe, Laura; Regnaut, Sebastien; Tickle, Alexander; Ton, Els; van Schijndel, Joost; Abwe, Ekwoge E.; Angedakin, Samuel; Agbor, Anthony; Ayimisin, Emmanuel Ayuk; Bailey, Emma; Bessone, Mattia; Bonnet, Matthieu; Brazolla, Gregory; Buh, Valentine Ebua; Chancellor, Rebecca; Cipoletta, Chloe; Cohen, Heather; Corogenes, Katherine; Coupland, Charlotte; Curran, Bryan; Deschner, Tobias; Dierks, Karsten; Dieguez, Paula; Dilambaka, Emmanuel; Diotoh, Orume; Dowd, Dervla; Dunn, Andrew; Eshuis, Henk; Fernandez, Rumen; Ginath, Yisa; Hart, John; Hedwig, Daniela; Ter Heegde, Martijn; Hicks, Thurston Cleveland; Imong, Inaoyom; Jeffery, Kathryn J.; Junker, Jessica; Kadam, Parag; Kambi, Mohamed; Kienast, Ivonne; Kujirakwinja, Deo; Langergraber, Kevin; Lapeyre, Vincent; Lapuente, Juan; Lee, Kevin; Leinert, Vera; Meier, Amelia; Maretti, Giovanna; Marrocoli, Sergio; Mbi, Tanyi Julius; Mihindou, Vianet; Moebius, Yasmin; Morgan, David; Morgan, Bethan; Mulindahabi, Felix; Murai, Mizuki; Niyigabae, Protais; Normand, Emma; Ntare, Nicolas; Ormsby, Lucy Jayne; Piel, Alex; Pruetz, Jill; Rundus, Aaron; Sanz, Crickette; Sommer, Volker; Stewart, Fiona; Tagg, Nikki; Vanleeuwe, Hilde; Vergnes, Virginie; Willie, Jacob; Wittig, Roman M.; Zuberbuehler, Klaus; Boesch, Christophe

    2016-01-01

    The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites. PMID:26923684

  12. Chimpanzee accumulative stone throwing.

    PubMed

    Kühl, Hjalmar S; Kalan, Ammie K; Arandjelovic, Mimi; Aubert, Floris; D'Auvergne, Lucy; Goedmakers, Annemarie; Jones, Sorrel; Kehoe, Laura; Regnaut, Sebastien; Tickle, Alexander; Ton, Els; van Schijndel, Joost; Abwe, Ekwoge E; Angedakin, Samuel; Agbor, Anthony; Ayimisin, Emmanuel Ayuk; Bailey, Emma; Bessone, Mattia; Bonnet, Matthieu; Brazolla, Gregory; Buh, Valentine Ebua; Chancellor, Rebecca; Cipoletta, Chloe; Cohen, Heather; Corogenes, Katherine; Coupland, Charlotte; Curran, Bryan; Deschner, Tobias; Dierks, Karsten; Dieguez, Paula; Dilambaka, Emmanuel; Diotoh, Orume; Dowd, Dervla; Dunn, Andrew; Eshuis, Henk; Fernandez, Rumen; Ginath, Yisa; Hart, John; Hedwig, Daniela; Ter Heegde, Martijn; Hicks, Thurston Cleveland; Imong, Inaoyom; Jeffery, Kathryn J; Junker, Jessica; Kadam, Parag; Kambi, Mohamed; Kienast, Ivonne; Kujirakwinja, Deo; Langergraber, Kevin; Lapeyre, Vincent; Lapuente, Juan; Lee, Kevin; Leinert, Vera; Meier, Amelia; Maretti, Giovanna; Marrocoli, Sergio; Mbi, Tanyi Julius; Mihindou, Vianet; Moebius, Yasmin; Morgan, David; Morgan, Bethan; Mulindahabi, Felix; Murai, Mizuki; Niyigabae, Protais; Normand, Emma; Ntare, Nicolas; Ormsby, Lucy Jayne; Piel, Alex; Pruetz, Jill; Rundus, Aaron; Sanz, Crickette; Sommer, Volker; Stewart, Fiona; Tagg, Nikki; Vanleeuwe, Hilde; Vergnes, Virginie; Willie, Jacob; Wittig, Roman M; Zuberbuehler, Klaus; Boesch, Christophe

    2016-01-01

    The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites. PMID:26923684

  13. Accumulation of swimming bacteria near an interface

    NASA Astrophysics Data System (ADS)

    Tang, Jay; Li, Guanglai

    2012-11-01

    Microbes inhabit planet earth over billions of years and have adapted to diverse physical environment of water, soil, and particularly at or near interfaces. We focused our attention on the locomotion of Caulobacter crescentus, a singly flagellated bacterium, at the interface of water/solid or water/air. We measured the distribution of a forward swimming strain of C. crescentus near a surface using a three-dimensional tracking technique based on dark field microscopy and found that the swimming bacteria accumulate heavily within a micrometer from the surface. We attribute this accumulation to frequent collisions of the swimming cells with the surface, causing them to align parallel to the surface as they continually move forward. The extent of accumulation at the steady state is accounted for by balancing alignment caused by these collisions with rotational Brownian motion of the micrometer-sized bacteria. We performed a simulation based on this model, which reproduced the measured results. Additional simulations demonstrate the dependence of accumulation on swimming speed and cell size, showing that longer and faster cells accumulate more near a surface than shorter and slower ones do. The overarching goal of our study is to describe interfacial microbial behavior through detailed analysis of their motion. We acknowledge support by NSF PHY 1058375.

  14. Mapping microscale strain heterogeneity during creep deformation

    NASA Astrophysics Data System (ADS)

    Quintanilla Terminel, A.; Evans, J.

    2013-12-01

    We use a new technique combining microfabrication technology and compression tests to map the strain field at a micrometric scale in polycrystalline materials. This technique allows us to map local strain while measuring macroscopic strain and rheological properties, and provides insight into the relative contribution of various plasticity mechanisms under varying creep conditions. The micro-strain mapping technique was applied to Carrara Marble under different deformation regimes, at 300 MPa and temperatures ranging from 200 to 700 °C. At 600 °C, strain of 10%, and strain rate of 3e-5s-1, the local strain at twin and grain boundaries is up to 5 times greater than the average sample strain. At these conditions, strains averaged across a particular grain may vary by as much as 100%, but the strain field becomes more homogeneous with increasing strain. For example, for the analyzed experiments, the average wavelength of the strain heterogeneity is 70 micrometers at 10% strain, but increases to 110 micrometers at 20%. For a strain of 10%, heterogeneity is increased at slower strain rate (at 1e-5s-1). This increase seems to be associated with a more important role of twin boundary and grain boundary migration. As expected, twin densities are markedly greater at the lower temperature, though it is still unclear whether the relative twin volume is greater. However, twin strains are still important at 600 °C and accommodate an average of 14 % of the total strain at 10% deformation and a strain rate of 3e-5s-1.

  15. Strain accumulation across the Prince William Sound asperity, Southcentral Alaska

    USGS Publications Warehouse

    Savage, James C.; Svarc, Jerry L.; Lisowski, Michael

    2015-01-01

    The surface velocities predicted by the conventional subduction model are compared to velocities measured in a GPS array (surveyed in 1993, 1995, 1997, 2000, and 2004) spanning the Prince William Sound asperity. The observed velocities in the comparison have been corrected to remove the contributions from postseismic (1964 Alaska earthquake) mantle relaxation. Except at the most seaward monument (located on Middleton Island at the seaward edge of the continental shelf, just 50 km landward of the deformation front in the Aleutian Trench), the corrected velocities qualitatively agree with those predicted by an improved, two-dimensional, back slip, subduction model in which the locked megathrust coincides with the plate interface identified by seismic refraction surveys, and the back slip rate is equal to the plate convergence rate. A better fit to the corrected velocities is furnished by either a back slip rate 20% greater than the plate convergence rate or a 30% shallower megathrust. The shallow megathrust in the latter fit may be an artifact of the uniform half-space Earth model used in the inversion. Backslip at the plate convergence rate on the megathrust mapped by refraction surveys would fit the data as well if the rigidity of the underthrust plate was twice that of the overlying plate, a rigidity contrast higher than expected. The anomalous motion at Middleton Island is attributed to continuous slip at near the plate convergence rate on a postulated, listric fault that splays off the megathrust at depth of about 12 km and outcrops on the continental slope south-southeast of Middleton Island.

  16. Strain localization in the middle- to upper continental crust: examples from the Patos and Pernambuco shear zones (Borborema Province, NE Brazil)

    NASA Astrophysics Data System (ADS)

    Viegas, G.; Archanjo, C. J.; Hollanda, M. H.; Vauchez, A. R.

    2014-12-01

    The accommodation of deformation in the Earth's lithosphere typically results in a heterogeneous distribution of strain in the continental crust, which is a function of effective pressure, temperature and strain rate at different structural levels. In Northeast Brazil, the Borborema Province is characterized by an interconnected, crustal-scale shear zone system associated with a widespread granitic plutonism. Two of the most prominent structures of this system, the Patos and Pernambuco shear zones, are characterized by ~ 600 km long E-W striking mylonite belts in which strain localization processes are observed either in association with partial melting in the Patos strike-slip fault, or as zones of overprinting brittle-ductile deformation in the Pernambuco shear zone. Deformation mechanisms are distinct across the Patos shear zone, mainly marked by crystalline plasticity and diffusion creep in the high-temperature northern border, magmatic flow in the central region and dislocation creep coupled with microfracturing in the southern sector. The Espinho Branco migmatite (~ 565 Ma) acts as a weak rheological layer that accumulates strain in the northern portion of the fault. Alternatively, the absence of partial melting and the dominant cataclastic/plastic flow regime lead to grain-size sensitive strain localization at the southern border. The Pernambuco shear zone was nucleated at the vicinities of two granitoid batholiths at c.a. 588 Ma. Low-temperature mylonites adjacent to the batholiths show several microstructures indicating coeval activity of brittle-ductile deformation. Recent zircon U-Pb (SHRIMP) data on these mylonites yielded mean ages of ~ 539 Ma, suggesting successive events of thermal input and shearing within the structure. These features suggest that strain localization processes exert an important control on the rheology of the continental lithosphere; the accommodation of deformation in the middle crust is mainly attained by the presence of weak

  17. BOOK REVIEW: Introduction to Computational Plasticity

    NASA Astrophysics Data System (ADS)

    Hartley, P.

    2006-04-01

    . Chapter two introduces one of several yield criteria, that normally attributed to von Mises (though historians of mechanics might argue over who was first to develop the theory of yielding associated with strain energy density), and its two or three-dimensional representation as a yield surface. The expansion of the yield surface during plastic deformation, its translation due to kinematic hardening and the Bauschinger effect in reversed loading are described with a direct link to the material stress-strain curve. The assumption, that the increment of strain is normal to the yield surface, the normality principle, is introduced. Uniaxial loading of an elastic-plastic material is used as an example in which to develop expressions to describe increments in stress and strain. The full presentation of numerous expressions, tensors and matrices with a clear explanation of their development, is a recurring, and commendable, feature of the book, which provides an invaluable introduction for those new to the subject. The chapter moves on from time-independent behaviour to introduce viscoplasticity and creep. Chapter three takes the theories of deformation another stage further to consider the problems associated with large deformation in which an important concept is the separation of the phenomenon into material stretch and rotation. The latter is crucial to allow correct measures of strain and stress to be developed in which the effects of rigid body rotation do not contribute to these variables. Hence, the introduction of 'objective' measures for stress and strain. These are described with reference to deformation gradients, which are clearly explained; however, the introduction of displacement gradients passes with little comment, although velocity gradients appear later in the chapter. The interpretation of different strain measures, e.g. Green--Lagrange and Almansi, is covered briefly, followed by a description of the spin tensor and its use in developing the objective

  18. Evidence of concurrent local adaptation and high phenotypic plasticity in a polar microeukaryote.

    PubMed

    Rengefors, Karin; Logares, Ramiro; Laybourn-Parry, Johanna; Gast, Rebecca J

    2015-05-01

    Here we investigated whether there is evidence of local adaptation in strains of an ancestrally marine dinoflagellate to the lacustrine environment they now inhabit (optimal genotypes) and/or if they have evolved phenotypic plasticity (a range of phenotypes). Eleven strains of Polarella glacialis were isolated and cultured from three different environments: the polar seas, a hyposaline and a hypersaline Antarctic lake. Local adaptation was tested by comparing growth rates of lacustrine and marine strains at their own and reciprocal site conditions. To determine phenotypic plasticity, we measured the reaction norm for salinity. We found evidence of both, limited local adaptation and higher phenotypic plasticity in lacustrine strains when compared with marine ancestors. At extreme high salinities, local lake strains outperformed other strains, and at extreme low salinities, strains from the hyposaline lake outperformed all other strains. The data suggest that lake populations may have evolved higher phenotypic plasticity in the lake habitats compared with the sea, presumably due to the high temporal variability in salinity in the lacustrine systems. Moreover, the interval of salinity tolerance differed between strains from the hyposaline and hypersaline lakes, indicating local adaptation promoted by different salinity.

  19. Strain balanced quantum posts

    SciTech Connect

    Alonso-Alvarez, D.; Alen, B.; Ripalda, J. M.; Llorens, J. M.; Taboada, A. G.; Briones, F.; Roldan, M. A.; Hernandez-Saz, J.; Hernandez-Maldonado, D.; Herrera, M.; Molina, S. I.

    2011-04-25

    Quantum posts are assembled by epitaxial growth of closely spaced quantum dot layers, modulating the composition of a semiconductor alloy, typically InGaAs. In contrast with most self-assembled nanostructures, the height of quantum posts can be controlled with nanometer precision, up to a maximum value limited by the accumulated stress due to the lattice mismatch. Here, we present a strain compensation technique based on the controlled incorporation of phosphorous, which substantially increases the maximum attainable quantum post height. The luminescence from the resulting nanostructures presents giant linear polarization anisotropy.

  20. Emergence of stable interfaces under extreme plastic deformation

    PubMed Central

    Beyerlein, Irene J.; Mayeur, Jason R.; Zheng, Shijian; Mara, Nathan A.; Wang, Jian; Misra, Amit

    2014-01-01

    Atomically ordered bimetal interfaces typically develop in near-equilibrium epitaxial growth (bottom-up processing) of nanolayered composite films and have been considered responsible for a number of intriguing material properties. Here, we discover that interfaces of such atomic level order can also emerge ubiquitously in large-scale layered nanocomposites fabricated by extreme strain (top down) processing. This is a counterintuitive result, which we propose occurs because extreme plastic straining creates new interfaces separated by single crystal layers of nanometer thickness. On this basis, with atomic-scale modeling and crystal plasticity theory, we prove that the preferred bimetal interface arising from extreme strains corresponds to a unique stable state, which can be predicted by two controlling stability conditions. As another testament to its stability, we provide experimental evidence showing that this interface maintains its integrity in further straining (strains > 12), elevated temperatures (> 0.45 Tm of a constituent), and irradiation (light ion). These results open a new frontier in the fabrication of stable nanomaterials with severe plastic deformation techniques. PMID:24616514