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Sample records for dynamic strain aging

  1. Dynamic strain aging in Haynes 282 superalloy

    Directory of Open Access Journals (Sweden)

    Hörnqvist Magnus

    2014-01-01

    Full Text Available Haynes 282 is a newly introduced Ni-based superallony, developed to provide a combination of high-temperature mechanical properties, thermal stability and processability. The present contribution investigates the effect of dynamic strain aging (DSA on the deformation behaviour of Haynes 282 during monotonic and cyclic loading. It is shown that DSA (presumably related to carbon diffusion based on rough estimates of the activation energy completely dominates the development of the stress during cycling at intermediate temperatures, leading to extensive cyclic hardening and serrated yielding. However, no clear effects on the fatigue life or the resulting dislocation structure could be observed. The tensile properties were not severely affected, in spite of the presence of extensive serrated yielding, although a reduction in ductility was observed in the DSA temperature regime. During monotonic loading at lower strain rates indications of an additional DSA mechanism due to substitutional elements were observed.

  2. Dynamic strain aging in magnesium oxide single crystals

    Science.gov (United States)

    Srinivasan, M.; Stoebe, T. G.

    1973-01-01

    Strain rate change transients are considered together with aspects of serrated flow, questions of flow stress and work hardening during dynamic strain aging, and time, temperature, and prestrain dependence of strain aging. On continuing the deformation process after aging for certain periods of time for a particular strain, a subsidiary load drop is sometimes observed in addition to the main yield drops.

  3. Study of dynamic strain aging in dual phase steel

    Energy Technology Data Exchange (ETDEWEB)

    Queiroz, R.R.U. [Instituto Federal de Minas Gerais. Rua Pandia Calogeras, 898, Bauxita, Ouro Preto, MG (Brazil); Cunha, F.G.G. [Department of Metallurgical and Materials Engineering, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627, Pampulha, Belo Horizonte, MG (Brazil); Gonzalez, B.M., E-mail: gonzalez@demet.ufmg.br [Department of Metallurgical and Materials Engineering, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627, Pampulha, Belo Horizonte, MG (Brazil)

    2012-05-01

    Highlights: Black-Right-Pointing-Pointer Characterization of the high temperature mechanical behavior of a dual phase steel. Black-Right-Pointing-Pointer Determination of the effect of dynamic strain aging on the strain hardening rate. Black-Right-Pointing-Pointer Identification of the mechanism associated with dynamic strain aging. Black-Right-Pointing-Pointer The value of the interaction energy carbon-dislocation in ferrite was confirmed. - Abstract: The susceptibility to dynamic strain aging of a dual phase steel was evaluated by the variation of mechanical properties in tension with the temperature and the strain rate. The tensile tests were performed at temperatures varying between 25 Degree-Sign C and 600 Degree-Sign C and at strain rates ranging from 10{sup -2} to 5 Multiplication-Sign 10{sup -4} s{sup -1}. The studied steel presented typical manifestations related to dynamic strain aging: serrated flow (the Portevin-Le Chatelier effect) for certain combinations of temperature and strain rates; the presence of a plateau in the variation of yield stress with temperature; a maximum in the curves of tensile strength, flow stress, and work hardening exponent as a function of temperature; and a minimum in the variation of total elongation with temperature. The determined apparent activation energy values, associated with the beginning of the Portevin-Le Chatelier effect and the maximum in the variation of flow stress with temperature, were 83 kJ/mol and 156 kJ/mol, respectively. These values suggest that the mechanism responsible for dynamic strain aging in the dual phase steel is the locking of dislocations by carbon atoms in ferrite and that the formation of clusters and/or transition carbides and carbide precipitation in martensite do not interfere with the dynamic strain aging process.

  4. DYNAMIC STRAIN AGING BEHAVIOR OF K40S ALLOY

    Institute of Scientific and Technical Information of China (English)

    F.M. Yang; X.F. Sun; H.R. Guan; Z.Q. Hu

    2003-01-01

    The dynamic strain aging behavior during tensile tests of K40S alloy has been investigated in the temperature range of 25-1100℃ with the strain rate range from 10-4to 10-3 s-1. The results show that four different types of serration, identified as A,B, C and E type serration were observed in the temperature range of 300-600℃. The strain exponents for onset of the serrated flow were calculated as 1.21, 2. 79 and 1.61,and the activation energies as 121, 40 and 67kJ/mol for E, B and C type serration respectively. The main mechanism for dynamic strain aging discussed in light of the strain exponent and the activation energy.

  5. Simulation and experimental analyses of dynamic strain aging of a supersaturated age hardenable aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Anjabin, N. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11365-9466 (Iran, Islamic Republic of); Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Karimi Taheri, A. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11365-9466 (Iran, Islamic Republic of); Kim, H.S., E-mail: hskim@postech.ac.kr [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2013-11-15

    In this paper, dynamic strain aging (DSA) behavior in a temperature range of (25–235 °C) and strain rate range of (10{sup −4}–5×10{sup −2} s{sup −1}) was investigated using a supersaturated age hardenable aluminum alloy. It was found that two mechanisms consisted of pinning of solute atoms to mobile dislocations and dynamic precipitation, were responsible for DSA in the testing conditions. The effects of both mechanisms on the macroscopic flow curve were studied using experimental and improved physically based material modeling approaches. It was shown that both phenomena lead to a negative strain rate hardening in the alloy. Dynamic precipitation acting at high temperature results in considerable work hardening and material strengthening. Taking into account these microstructural phenomena, the effects of deformation temperature and strain rate on the macroscopic flow behavior were discussed. The proposed modeling approach could successfully predict the experimental flow curve, possible jerky flow, and the corresponding serration types. Also, the spatial nucleation and propagation of the localized deformation bands along the specimen gauge length were recorded by a digital image correlation method and compared with the proposed model predictions.

  6. Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Chaboche, Jean-Louis [ONERA, DMSM, 29 avenue de la Division Lecerc, F-92320 Chatillon (France); Wang, Qing Yuan [Sichuan University, School of Aeronautics and Astronautics, No. 29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle; Bathias, Claude [Université ParisOuest Nanterre La Défense (France)

    2014-01-01

    Carbon–manganese steel A48 (French standard) is used in steam generator pipes of nuclear reactor pressure vessels at high temperatures (about 200 °C). The steel is sensitive to dynamic strain aging in monotonic tensile test and low cycle fatigue test at certain temperature range and strain rate. Its isotropic hardening behavior observed from experiments has a hardening, softening and hardening evolution with the effect of dynamic strain aging. The isotropic hardening model is improved by coupling the dislocation and dynamic strain aging theory to describe the behavior of A48 at 200 °C.

  7. Analysis of Deformation in Inconel 718 When the Stress Anomaly and Dynamic Strain Aging Coexist

    Science.gov (United States)

    Follansbee, Paul S.

    2016-09-01

    Deformation in Inconel 718 in the presence of combined effects of the stress anomaly and dynamic strain aging is analyzed according to an internal state variable model formulation. The analysis relies on the availability of experimental data in regimes of behavior where both the stress anomaly and dynamic strain aging are absent. A model that introduces two internal state variables—one characterizing interactions of dislocations with solute atoms and one characterizing interaction of dislocations with precipitates—is shown to adequately describe the temperature and strain-rate dependence of the yield stress in several superalloy systems. Strain hardening is then added with a third internal state variable to enable description of the full stress-strain curve. These equations are extrapolated into regimes where the stress anomaly and dynamic strain aging are present to identify signatures of their effects and to compare to similar analyses in a variety of metal systems. Dynamic strain aging in Inconel 718 follows similar trends to those observed previously. The magnitude of the stress anomaly tracks measurements of stress vs test temperature in pure Ni3Al. Several trends in the strain-rate sensitivity of elevated temperature deformation in superalloys are identified based on limited availability of measurements over a wide range of strain rates or tests using strain-rate changes.

  8. Dynamic strain ageing of deformed nitrogen-alloyed AISI 316 stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Ehrnsten, U.; Toivonen, A. [Materials and Structural Integrity, VTT Technical Research Centre of Finland, Kemistintie 3, P.O. Box 1704, FIN-02044 VTT (Finland); Ivanchenko, M.; Nevdacha, V.; Yagozinskyy, Y.; Haenninen, H. [Department of Mechanical Engineering, Helsinki University of Technology Puumiehenkuja 3, P.O. Box 4200, FIN-02015 HUT (Finland)

    2004-07-01

    Intergranular stress corrosion cracking has occurred in BWR environment in non-sensitized, deformed austenitic stainless steel materials. The affecting parameters are so far not fully known, but deformation mechanisms may be decisive. The effect of deformation and nitrogen content on the behaviour of austenitic stainless steels was investigated. The materials were austenitic stainless steels of AISI 316L type with different amounts of nitrogen (0.03 - 0.18%) and they were mechanically deformed 0, 5 and 20%. The investigations are focused on the dynamic strain ageing (DSA) behaviour. A few crack growth rate measurements are performed on nuclear grade AISI 316NG material with different degrees of deformation (0, 5 and 20%). The effects of DSA on mechanical properties of these materials are evaluated based on peaks in ultimate tensile strength and strain hardening coefficient and minimum in ductility in the DSA temperature range. Additionally, internal friction measurements have been performed in the temperature range of -100 to 600 deg. C for determining nitrogen interactions with other alloying elements and dislocations (cold-worked samples). The results show an effect of nitrogen on the stainless steel behaviour, e.g. clear indications of dynamic strain ageing and changes in the internal friction peaks as a function of nitrogen content and amount of deformation. (authors)

  9. Influence of dynamic strain aging on tensile deformation behavior of alloy 617

    Energy Technology Data Exchange (ETDEWEB)

    Ekaputra, I. M. W. [Pukyong National University, Busan (Korea, Republic of); Kim, Woo Gon; Park, Jae Young; Kim, Seon Jin; Kim, Eung Seon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-12-15

    To investigate the dynamic strain aging (DSA) behavior of Alloy 617, high-temperature tensile tests were carried out with strain rates variations of 10{sup -}3{sup /}s, 10{sup -4}/s, and 10{sup -5}/s from 24°C to 950°C. Five flow relationships, Hollomon, Ludwik, Swift, Ludwigson, and Voce, were applied to describe the tensile true stress–strain curves, and the DSA region was defined. In describing the tensile curves, Ludwigson's equation was superior to the other equations, and the DSA region was adequately defined by this equation as plateaus at intermediate temperatures from 200°C to 700°C. It was identified that Alloy 617 is dominated by three types of serrations, known as Types D, A+B, and C. The activation energy values for each serration type were obtained by the Arrhenius equation. By using the obtained activation energy values, the serrated yielding map and the DSA mechanism were drawn and manifested. In addition, the relationship between the tensile strength and strain rate at higher temperatures above 700°C was found to be closely related to the amounts of slip lines. In the scanning electron microscope (SEM) fractographs, there was a significant difference at the low, intermediate, and high temperatures, but almost the same to the three strain rates.

  10. Oxidation assisted intergranular cracking under loading at dynamic strain aging temperatures in Inconel 718 superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Rezende, M.C., E-mail: monica_crezende@hotmail.com [Universidade Federal do Rio de Janeiro, Departamento de Engenharia Metalúrgica e de Materiais, C.P. 68505, Rio de Janeiro 21945-970 (Brazil); Araújo, L.S.; Gabriel, S.B. [Universidade Federal do Rio de Janeiro, Departamento de Engenharia Metalúrgica e de Materiais, C.P. 68505, Rio de Janeiro 21945-970 (Brazil); Dille, J. [Université Libre de Bruxelles, 4MAT Department, Av. F. Roosevelt 50, C.P. 194/03, Brussels (Belgium); Almeida, L.H. de [Universidade Federal do Rio de Janeiro, Departamento de Engenharia Metalúrgica e de Materiais, C.P. 68505, Rio de Janeiro 21945-970 (Brazil)

    2015-09-15

    Highlights: • Mechanical properties are controlled by DSA, precipitation hardening and OAIC. • Between 600 and 700 °C the critical strain for serrations increases with temperature. • This is related to the consumption of matrix elements (especially Nb: for γ′ and γ″). • A reduction in ductility occurs (related to the OAIC) when the DSA is no longer effective. • This reduction is accompanied by an increase in intergranular brittle fracture. - Abstract: It is well established that 718 superalloy exhibits brittle intergranular cracking when deformed under tension at temperatures above 600 °C. This embrittlement effect is related with grain boundary penetration by oxygen (Oxygen Assisted Intergranular Cracking – OAIC). Simultaneously, impacting on its mechanical properties, the precipitation of coherent γ′ and γ″ phases occur above 650 °C and Dynamic Strain Aging (DSA) occurs in the temperature range between 200 and 800 °C. Although literature indicates that OAIC is the mechanism that controls mechanical properties at high temperatures, its interactions with DSA and precipitation are still under discussion. The objective of this work is to investigate the interactions between the embrittlement phenomena (OAIC and DSA) and the hardening mechanism of γ′ and γ″ precipitation on the mechanical properties of an annealed 718 superalloy. Tensile tests were performed at a strain rate of 3.2 × 10{sup −4} s{sup −1} under secondary vacuum, in temperatures ranging from 200 to 800 °C. Fracture surfaces were observed by scanning electron microscopy (SEM) and precipitation by transmission electron microscopy (TEM). The effect of DSA and precipitation on the strength and of OAIC on the ductility was verified.

  11. Modelling of Dynamic Strain Aging with a Dislocation-Based Isotropic Hardening Model and Investigation of Orthogonal Loading

    NARCIS (Netherlands)

    Berisha, B.; Hora, P.; Tong, L.; Wahlen, A.; Boogaard, van den A.H.

    2008-01-01

    Based on experimental results, a dislocation material model describing the dynamic strain aging effect at different temperatures is presented. One and two stage loading tests were performed in order to investigate the influence of the loading direction as well as the temperature influence due to the

  12. A low cycle fatigue model for low carbon manganese steel including the effect of dynamic strain aging

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhi Yong, E-mail: huangzy@scu.edu.cn [Sichuan University, School of Aeronautics and Astronautics, No.29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Wagner, Danièle [Université Paris Ouest Nanterre La Défense (France); Wang, Qing Yuan; Khan, Muhammad Kashif [Sichuan University, School of Aeronautics and Astronautics, No.29 Jiuyanqiao Wangjiang Road, Chengdu 610064 (China); Chaboche, Jean–Louis [ONERA, DMSM, 29 avenue de la Division Lecerc, F-92320, Chatillon (France)

    2016-01-27

    Carbon–manganese steel A48 (French standards) is used in steam generator pipes of the nuclear power plant where it is subjected to the cyclic thermal load. The Dynamic Strain Aging (DSA) influences the mechanical behavior of the steel in low cycle fatigue (LCF) at favorable temperature and strain rate. The peak stress of A48 steel experiences hardening–softening–hardening (HSH) evolution at 200 °C and 0.4% s{sup −1} strain rate in fatigue loading. In this study, isotropic and kinematic hardening rules with DSA effect have been modified. The HSH evolution of cyclic stress associated with cumulative plastic deformation has also been estimated.

  13. Improving tribological performance of gray cast iron by laser peening in dynamic strain aging temperature regime

    Science.gov (United States)

    Feng, Xu; Zhou, Jianzhong; Mei, Yufen; Huang, Shu; Sheng, Jie; Zhu, Weili

    2015-09-01

    A high and stable brake disc friction coefficient is needed for automobile safety, while the coefficient degrades due to elevated temperature during the braking process. There is no better solution except changes in material composition and shape design optimization. In the dynamic strain aging(DSA) temperature regime of gray cast iron, micro-dimples with different dimple depth over diameter and surface area density are fabricated on the material surface by laser peening(LP) which is an LST method. Friction behavior and wear mechanism are investigated to evaluate the effects of surface texturing on the tribological performance of specimens under dry conditions. Through LP impacts assisted by DSA, the friction coefficients of the LPed specimens increase noticeably both at room temperature and elevated temperature in comparison to untreated specimens. Moreover, the coefficient of specimen with dimple depth over diameter of 0.03 and surface area density of 30% is up to 0.351 at room temperature, which dramatically rises up to 1.33 times that of untextured specimen and the value is still up to 0.3305 at 400°C with an increasing ratio of 35% compared to that of untreated specimen. The surface of textured specimen shows better wear resistance compared to untreated specimen. Wear mechanism includes adhesive wear, abrasive wear and oxidation wear. It is demonstrated that LP assisted by DSA can substantially improve wear resistance, raise the friction coefficient as well as its stability of gray cast iron under elevated temperatures. Heat fade and premature wear can be effectively relieved by this surface modification method.

  14. Activated dynamic strain aging of a TRIP590 Steel at 300 °C and low strain rate and relationship to structure

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Y.F., E-mail: shenyf@smm.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China); Wang, P.J.; Liu, Y.D. [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China); Misra, R.D.K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical and Materials Engineering, University of Texas at El Paso, TX 79968 (United States); Zuo, L. [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China)

    2015-10-01

    Transformation-induced plasticity (TRIP) steel was subjected to intercritical annealing and bainite partitioning to elucidate the impact on mechanical properties at temperatures in the range of −70 °C to 300 °C and strain rates of 10{sup −3} to 10{sup −1} s{sup −1} and the behavior related to structure. At temperatures in the range of −70 °C to 150 °C, both the yield strength and tensile strength increased with decrease in the deformation temperature at a constant strain rate. The elongation-to-failure was maximum at room temperature, while the product of strength and ductility was highest at the lowest temperature of −70 °C at various strain rates. Unexpectedly, the serrated flow was observed for specimens tested at 300 °C, which is attributed to dynamic strain aging (DSA), an effect that became more pronounced with decrease in strain rate. The nanosized precipitates facilitated increase in dislocation density during plastic deformation by restraining recovery and annihilation of dislocations, leading to increase in stress with increase in temperature, an effect that decreased with increase in strain rate because of adiabatic heating.

  15. Insights into dynamic strain aging under cyclic creep with reference to strain burst: Some new observations and mechanisms part-II: Microstructural aspects

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Aritra, E-mail: aritra@igcar.gov.in [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 Tamil Nadu (India); Nagesha, A. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 Tamil Nadu (India); Parameswaran, P.; Murugesan, S. [Materials Synthesis and Structural Characterization Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Sandhya, R.; Laha, K. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 Tamil Nadu (India)

    2016-04-13

    Cyclic creep behavior of 316LN austenitic stainless steel (SS) was investigated at 823 K at different combinations of mean stress (σ{sub m}), stress amplitude (σ{sub a}) and stress rate. Characteristic strain bursts were observed being attributed to a pronounced influence of dynamic strain aging (DSA). Detailed microstructural investigation carried out through transmission electron microscope (TEM) revealed that dislocation substructure evolving under a process of strain burst during cyclic creep mainly consists of planar deformation bands. The number density of bands was found to be strongly sensitive to σ{sub m}- σ{sub a}-stress rate combination employed. An important substructural feature found in this study was the formation of microtwins. Either planar slip or twinning was found to dominate the substructure depending on the loading combination, which was demonstrated through a dislocation distribution map. Dislocation substructure was further correlated with evolution of surface relief studied through atomic force microscopy (AFM) and field emission gun-scanning electron microscopy (FEG-SEM), which depicts the formation of slip markings and nucleation of cracks from persistent slip markings during the course of a strain burst. Finally, well-known theoretical models explaining the mechanism of DSA during tensile deformation were suitably modified for load-controlled scenario and the origin of strain burst as a function of σ{sub m} or stress rate was explained based on the same. Dislocation density measurements were carried out for specimens undergoing strain burst during cyclic creep, which was utilized for reconstituting the models.

  16. Microstructure and strain-stress analysis of the dynamic strain aging in inconel 625 at high temperature

    Science.gov (United States)

    Maj, P.; Zdunek, J.; Mizera, J.; Kurzydlowski, K. J.; Sakowicz, B.; Kaminski, M.

    2017-01-01

    Serrated flow is a result of unstable plastic flow, which occurs during tensile and compression tests on some dilute alloys. This phenomenon is referred as the Portevin Le-Chatelier effect (PLC effect). The aim of this research was to investigate and analyze this phenomenon in Inconel 625 solution strengthened superalloy. The tested material was subjected to tensile tests carried out within the temperature range 200-700 °C, with three different strain rates: 0.002 1/s, 0.01/s, and 0.05 1/s and additional compression tests with high deformation speeds of 0.1, 1, and 10 1/s. The tensile strain curves were analyzed in terms of intensity and the observed patterns of serrations Using a modified stress drop method proposed by the authors, the activation energy was calculated with the assumption that the stress drops' distribution is a direct representation of an average solute atom's interaction with dislocations. Subsequently, two models, the standard vacancy diffusion Bilby-Cottrell model and the realistic cross-core diffusion mechanism proposed by Zhang and Curtin, were compared. The results obtained show that the second one agrees with the experimental data. Additional microstructure analysis was performed to identify microstructure elements that may be responsible for the PLC effect. Based on the results, the relationship between the intensity of the phenomenon and the conditions of the tests were determined.

  17. Hardening mechanisms in a dynamic strain aging alloy, Hastelloy X, during isothermal and thermomechanical cyclic deformation

    Science.gov (United States)

    Miner, R. V.; Castelli, M. G.

    1992-01-01

    The relative contributions of the hardening mechanisms in Hastelloy X during cyclic deformation were investigated by conducting isothermal cyclic deformation tests within a total strain range of +/-0.3 pct and at several temperatures and strain rates, and thermomechanical tests within several different temperature limits. The results of the TEM examinations and special constant structure tests showed that the precipitation on dislocations of Cr23C6 contributed to hardening, but only after sufficient time above 500 C. Solute drag alone produced very considerable cyclic hardening. Heat dislocation densities, peaking around 10 exp 11 per sq cm, were found to develop at temperatures producing the greatest cyclic hardening.

  18. Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime

    Directory of Open Access Journals (Sweden)

    Chun Su

    2016-09-01

    Full Text Available As a new treatment process after welding, the process parameters of laser shock peening (LSP in dynamic strain aging (DSA temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution of the surface residual stress of AA6061-T6 welded joints were investigated by using X-ray diffraction technology with the sin2ϕ method and Abaqus software. The fatigue life of the welded joints was estimated by performing tensile fatigue tests. The microstructural evolution in surface and fatigue fractures of the welded joints was presented by means of surface integrity and fracture surface testing. In the DSA temperature regime of AA6061-T6 welded joints, the residual compressive stress was distributed more stably than that of LSP at room temperature. The thermal corrosion resistance and fatigue properties of the welded joints were also improved. The experimental results and numerical analysis were in mutual agreement.

  19. Material property evaluations of bimetallic welds, stainless steel saw fusion lines, and materials affected by dynamic strain aging

    Energy Technology Data Exchange (ETDEWEB)

    Rudland, D.; Scott, P.; Marschall, C.; Wilkowski, G. [Battelle Memorial Institute, Columbus, OH (United States)

    1997-04-01

    Pipe fracture analyses can often reasonably predict the behavior of flawed piping. However, there are material applications with uncertainties in fracture behavior. This paper summarizes work on three such cases. First, the fracture behavior of bimetallic welds are discussed. The purpose of the study was to determine if current fracture analyses can predict the response of pipe with flaws in bimetallic welds. The weld joined sections of A516 Grade 70 carbon steel to F316 stainless steel. The crack was along the carbon steel base metal to Inconel 182 weld metal fusion line. Material properties from tensile and C(T) specimens were used to predict large pipe response. The major conclusion from the work is that fracture behavior of the weld could be evaluated with reasonable accuracy using properties of the carbon steel pipe and conventional J-estimation analyses. However, results may not be generally true for all bimetallic welds. Second, the toughness of austenitic steel submerged-arc weld (SAW) fusion lines is discussed. During large-scale pipe tests with flaws in the center of the SAW, the crack tended to grow into the fusion line. The fracture toughness of the base metal, the SAW, and the fusion line were determined and compared. The major conclusion reached is that although the fusion line had a higher initiation toughness than the weld metal, the fusion-line J-R curve reached a steady-state value while the SAW J-R curve increased. Last, carbon steel fracture experiments containing circumferential flaws with periods of unstable crack jumps during steady ductile tearing are discussed. These instabilities are believed to be due to dynamic strain aging (DSA). The paper discusses DSA, a screening criteria developed to predict DSA, and the ability of the current J-based methodologies to assess the effect of these crack instabilities. The effect of loading rate on the strength and toughness of several different carbon steel pipes at LWR temperatures is also discussed.

  20. Dynamic strain aging precipitation of Mg17Al12 in AZ80 magnesium alloy during multi-directional forging process

    Science.gov (United States)

    Zhu, Q. F.; Wang, G. S.; Wang, X. J.; Liu, F. Z.; Ban, C. Y.; Cui, J. Z.

    2017-05-01

    Dynamic aging precipitation of Mg17Al12 phases in AZ80 magnesium alloy was studied by multi-directional forging (MDF) with decreasing temperatures from 410 to 300 °C. The results show that the morphology of the dynamically precipitated β-Mg17Al12 phases (formed during forging process) exhibited granular shape. During the multi-directional forging process, the inhomogeneous dynamic precipitation of the β-Mg17Al12 phases result in the coexistence of the fine grains (with many granular Mg17Al12 phases) and coarse grains (without Mg17Al12 phases) in the samples. The fine grains (with many granular Mg17Al12 phases) area expands with the decreasing of final forging temperature. The inhomogenous Al content distribution in the Mg matrix leads to the non-uniform dynamic precipitation of the Mg17Al12 phase. These Mg17Al12 phase retards the growth of the DRX grains, which in turns results in the formation fine grains area during the during the MDF process with temperature decreasing.

  1. Experimental evidence for segregation of interstitial impurities to defects in a near α titanium alloy during dynamic strain aging using energy filtered transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Kartik, E-mail: kartik@dmrl.drdo.in [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); School of Engineering Science and Technology, University of Hyderabad, Hyderabad (India); Amrithapandian, S.; Panigrahi, B.K. [Materials Science Group, Indira Gandhi for Centre of Atomic Research, Kalpakkam 603102 (India); Kumar, Vikas [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Bhanu Sankara Rao, K. [Mahatma Gandhi Institute of Technology, Gandipet, Hyderabad 500075 (India); Sundararaman, M. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)

    2015-06-25

    Dynamic strain aging was observed in the temperature range between 300 °C and 500 °C in a near α titanium alloy 834 without Silicon (10.38%Al–0.16%Sn–1.86%Zr–0.37%Nb–0.25%Mo–0.27%C–0.30%O–0.006%N, all in at%) tested in the temperature range from room temperature to 500 °C. Electron microscopic investigation of tensile tested samples in an energy filtered transmission electron microscopy provided direct experimental evidence for segregation of interstitial elements like carbon (C) and nitrogen (N) to lath boundaries and dislocation pile ups. On the basis of these results and the comparison of lattice strain generated by different interstitials in α-Ti, it was concluded that segregation of carbon and nitrogen and not oxygen to defects is responsible for DSA in this alloy.

  2. Beryllium strain under dynamic loading

    Directory of Open Access Journals (Sweden)

    Pushkov Victor

    2015-01-01

    Full Text Available There are some data (not much on dynamic characteristics of beryllium that are important, for example, when estimating construction performance at NPP emergencies. A number of data on stress-strain curves, spall strength, shear strength, fracture and structure responses of shock loaded beryllium have obtained in US and Russian laboratories. For today the model description of this complex metal behavior does not have a reasonable agreement with the experimental data, thus a wider spectrum of experimental data is required. This work presents data on dynamic compression-test diagrams of Russian beryllium. Experiments are performed using Hopkinson bar method (SHPB. Strain rates were ε ∼ 103 s−1.

  3. Experimental investigations concerning the possible effect of dynamic strain ageing on environmentally-assisted cracking of low alloy steels in oxygenated high-temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Roth, A.; Devrient, B. [Framatome ANP GmbH, Erlangen (Germany); Haenninen, H. [Helsinki Univ. of Tech. (Finland); Bruemmer, G. [Hamburgische Electricitaets-Werke AG, Hamburg (Germany); Ilg, U. [EnBW Kraftwerke AG (Germany); Widera, M. [RWE Power AG, Regenerative Stromerzeugung, Essen (Germany); Hofmann, H. [VGB PowerTech e.V., Essen (Germany); Wachter, O. [E.ON Kernkraft GmbH (Germany)

    2003-07-01

    Service experience has revealed cracks due to environmentally-assisted cracking (EAC) in welds of the feedwater piping system of a boiling water reactor (BWR). Two slightly different low alloy steel (LAS) weld filler metals were used in the system of concern, however, only one of them was affected by cracking. To achieve an improved understanding, a laboratory study was initiated to investigate the crack growth behavior of the two relevant weld filler metals in an oxygenated high-temperature water (HTW) environment representing BWR normal water chemistry (NWC) under sequences of cyclic and constant load. Despite the basic similarities in the nominal chemical composition of both weld filler alloys, the crack growth behaviors revealed significant differences. This could not be explained based on the material's sulphur content, which is known to have a pronounced effect on EAC. To elucidate the observed behavior, studies concerning dynamic strain aging (DSA) have been initiated. DSA has been recently suspected to be another parameter that may influence EAC of LAS in HTW. A reasonable coincidence was observed between the susceptibility to DSA exhibited by slow strain rate tensile tests (SSRT) in air and by internal friction measurements with measured free nitrogen contents on the one hand and with the EAC behavior observed in service and in laboratory experiments on the other hand. (orig.)

  4. Diversity and dynamic of lactic acid bacteria strains during aging of a long ripened hard cheese produced from raw milk and undefined natural starter.

    Science.gov (United States)

    Pogačić, Tomislav; Mancini, Andrea; Santarelli, Marcela; Bottari, Benedetta; Lazzi, Camilla; Neviani, Erasmo; Gatti, Monica

    2013-12-01

    The aim of this study was to explore diversity and dynamic of indigenous LAB strains associated with a long ripened hard cheese produced from raw milk and undefined natural starter such as PDO Grana Padano cheese. Samples of milk, curd, natural whey culture and cheeses (2nd, 6th, 9th and 13th months of ripening) were collected from 6 cheese factories in northern Italy. DNA was extracted from each sample and from 194 LAB isolates. tRNA(Ala)-23S rDNA-RFLP was applied to identify isolates. Strain diversity was assessed by (GTG)5 rep-PCR and RAPD(P1)-PCR. Finally, culture-independent LH-PCR (V1-V2 16S-rDNA), was considered to explore structure and dynamic of the microbiota. Grana Padano LAB were represented mainly by Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus delbrueckii, Lactobacillus helveticus and Pediococcus acidilactici, while the structure and dynamic of microbiota at different localities was specific. The strength of this work is to have focused the study on isolates coming from more than one cheese factories rather than a high number of isolates from one unique production. We provided a valuable insight into inter and intraspecies diversity of typical LAB strains during ripening of traditional PDO Grana Padano, contributing to the understanding of specific microbial ecosystem of this cheese.

  5. Strain Aging Behavior in NiAl Microalloyed with Interstitial and Substitutional Solutes

    Science.gov (United States)

    Weaver, M. L.; Noebe R. D.; Kaufman, M. J.

    1997-01-01

    Dynamic strain aging has been investigated in polycrystalline NiAl alloys containing combined additions of interstitial and substitutional impurities. The results indicate that strain aging can be enhanced in polycrystalline alloys containing concentrations of silicon or iron in excess of 0.15 at.% in addition to conventional levels of carbon. This co-doping leads to very dramatic strain aging events, comparable to those typically observed in single crystals. This effect will be discussed with respect to conventional theories of strain aging.

  6. Dynamic strains for earthquake source characterization

    Science.gov (United States)

    Barbour, Andrew J.; Crowell, Brendan W

    2017-01-01

    Strainmeters measure elastodynamic deformation associated with earthquakes over a broad frequency band, with detection characteristics that complement traditional instrumentation, but they are commonly used to study slow transient deformation along active faults and at subduction zones, for example. Here, we analyze dynamic strains at Plate Boundary Observatory (PBO) borehole strainmeters (BSM) associated with 146 local and regional earthquakes from 2004–2014, with magnitudes from M 4.5 to 7.2. We find that peak values in seismic strain can be predicted from a general regression against distance and magnitude, with improvements in accuracy gained by accounting for biases associated with site–station effects and source–path effects, the latter exhibiting the strongest influence on the regression coefficients. To account for the influence of these biases in a general way, we include crustal‐type classifications from the CRUST1.0 global velocity model, which demonstrates that high‐frequency strain data from the PBO BSM network carry information on crustal structure and fault mechanics: earthquakes nucleating offshore on the Blanco fracture zone, for example, generate consistently lower dynamic strains than earthquakes around the Sierra Nevada microplate and in the Salton trough. Finally, we test our dynamic strain prediction equations on the 2011 M 9 Tohoku‐Oki earthquake, specifically continuous strain records derived from triangulation of 137 high‐rate Global Navigation Satellite System Earth Observation Network stations in Japan. Moment magnitudes inferred from these data and the strain model are in agreement when Global Positioning System subnetworks are unaffected by spatial aliasing.

  7. Five challenges in modelling interacting strain dynamics

    DEFF Research Database (Denmark)

    Wikramaratna, Paul S; Kurcharski, Adam; Gupta, Sunetra

    2015-01-01

    Population epidemiological models where hosts can be infected sequentially by different strains have the potential to help us understand many important diseases. Researchers have in recent years started to develop and use such models, but the extra layer of complexity from multiple strains brings...... with it many technical challenges. It is therefore hard to build models which have realistic assumptions yet are tractable. Here we outline some of the main challenges in this area. First we begin with the fundamental question of how to translate from complex small-scale dynamics within a host to useful...... population models. Next we consider the nature of so-called “strain space”. We describe two key types of host heterogeneities, and explain how models could help generate a better understanding of their effects. Finally, for diseases with many strains, we consider the challenge of modelling how immunity...

  8. Spacecraft Dynamic Characterization by Strain Energies Method

    Science.gov (United States)

    Bretagne, J.-M.; Fragnito, M.; Massier, S.

    2002-01-01

    In the last years the significant increase in satellite broadcasting demand, with the wide band communication dawn, has given a great impulse to the telecommunication satellite market. The big demand is translated from operators (such as SES/Astra, Eutelsat, Intelsat, Inmarsat, EuroSkyWay etc.) in an increase of orders of telecom satellite to the world industrials. The largest part of these telecom satellite orders consists of Geostationary platforms which grow more and more in mass (over 5 tons) due to an ever longer demanded lifetime (up to 20 years), and become more complex due to the need of implementing an ever larger number of repeaters, antenna reflectors and feeds, etc... In this frame, the mechanical design and verification of these large spacecraft become difficult and ambitious at the same time, driven by the dry mass limitation objective. By the Finite Element Method (FEM), and on the basis of the telecom satellite heritage of a world leader constructor such as Alcatel Space Industries it is nowadays possible to model these spacecraft in a realistic and confident way in order to identify the main global dynamic aspects such as mode shapes, mass participation and/or dynamic responses. But on the other hand, one of the main aims consists in identifying soon in a program the most critical aspects of the system behavior in the launch dynamic environment, such as possible dynamic coupling between the different subsystems and secondary structures of the spacecraft (large deployable reflectors, thrusters, etc.). To this aim a numerical method has been developed in the frame of the Alcatel SPACEBUS family program, using MSC/Nastran capabilities and it is presented in this paper. The method is based on Spacecraft sub-structuring and strain energy calculation. The method mainly consists of two steps : 1) subsystem modal strain energy ratio (with respect to the global strain energy); 2) subsystem strain energy calculation for each mode according to the base driven

  9. Aging of dynamically stabilized microtubules

    CERN Document Server

    Ebbinghaus, M

    2009-01-01

    The microtubule network, an important part of the cytoskeleton, is constantly remodeled by alternating phases of growth and shrinkage of individual filaments. Plus-end tracking proteins (+TIPs) interact with the microtubule and in many cases alter its dynamics. While it is established that the prototypal CLIP-170 enhances microtubule stability by increasing rescues, the plus-end tracking mechanism is still under debate. We present a model for microtubule dynamics in which a rescue factor is dynamically added to the filament while growing. As a consequence, the filament shows aging behavior which should be experimentally accessible and thus allow one to exclude some hypothesized models of the inclusion of rescue factors at the microtubule plus end. Additionally, we show the strong influence of the cell geometry on the quantitative results.

  10. Nonlinear dynamics of cardiovascular ageing

    Energy Technology Data Exchange (ETDEWEB)

    Shiogai, Y. [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom); Stefanovska, A. [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom); Faculty of Electrical Engineering, University of Ljubljana, Ljubljana (Slovenia); McClintock, P.V.E. [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom)], E-mail: p.v.e.mcclintock@lancaster.ac.uk

    2010-03-15

    The application of methods drawn from nonlinear and stochastic dynamics to the analysis of cardiovascular time series is reviewed, with particular reference to the identification of changes associated with ageing. The natural variability of the heart rate (HRV) is considered in detail, including the respiratory sinus arrhythmia (RSA) corresponding to modulation of the instantaneous cardiac frequency by the rhythm of respiration. HRV has been intensively studied using traditional spectral analyses, e.g. by Fourier transform or autoregressive methods, and, because of its complexity, has been used as a paradigm for testing several proposed new methods of complexity analysis. These methods are reviewed. The application of time-frequency methods to HRV is considered, including in particular the wavelet transform which can resolve the time-dependent spectral content of HRV. Attention is focused on the cardio-respiratory interaction by introduction of the respiratory frequency variability signal (RFV), which can be acquired simultaneously with HRV by use of a respiratory effort transducer. Current methods for the analysis of interacting oscillators are reviewed and applied to cardio-respiratory data, including those for the quantification of synchronization and direction of coupling. These reveal the effect of ageing on the cardio-respiratory interaction through changes in the mutual modulation of the instantaneous cardiac and respiratory frequencies. Analyses of blood flow signals recorded with laser Doppler flowmetry are reviewed and related to the current understanding of how endothelial-dependent oscillations evolve with age: the inner lining of the vessels (the endothelium) is shown to be of crucial importance to the emerging picture. It is concluded that analyses of the complex and nonlinear dynamics of the cardiovascular system can illuminate the mechanisms of blood circulation, and that the heart, the lungs and the vascular system function as a single entity in

  11. Dynamic Strain Conductivity of Compensated Silicon

    Science.gov (United States)

    Zainabidinov, S. Z.; Mamatkarimov, O. O.; Tursunov, I. G.; Tuychiev, U. A.

    In this paper the strain thermal Hall effect has been investigated in initial n-Si(P) and strongly compensated n-Si(Ni) samples of different compensation degree, which have been subject to uniform hydrostatic compression (UHC) under a pulse pressure regime ranging from 0 to 7×108 Pa. An experimental investigation of the strain thermal effect in the n-Si(Ni) sample leads to an essential strain conductivity increase, which is largely controlled by density variations of majority carriers.

  12. A method of measuring dynamic strain under electromagnetic forming conditions.

    Science.gov (United States)

    Chen, Jinling; Xi, Xuekui; Wang, Sijun; Lu, Jun; Guo, Chenglong; Wang, Wenquan; Liu, Enke; Wang, Wenhong; Liu, Lin; Wu, Guangheng

    2016-04-01

    Dynamic strain measurement is rather important for the characterization of mechanical behaviors in electromagnetic forming process, but it has been hindered by high strain rate and serious electromagnetic interference for years. In this work, a simple and effective strain measuring technique for physical and mechanical behavior studies in the electromagnetic forming process has been developed. High resolution (∼5 ppm) of strain curves of a budging aluminum tube in pulsed electromagnetic field has been successfully measured using this technique. The measured strain rate is about 10(5) s(-1), which depends on the discharging conditions, nearly one order of magnitude of higher than that under conventional split Hopkins pressure bar loading conditions (∼10(4) s(-1)). It has been found that the dynamic fracture toughness of an aluminum alloy is significantly enhanced during the electromagnetic forming, which explains why the formability is much larger under electromagnetic forging conditions in comparison with conventional forging processes.

  13. Strain-accelerated dynamics of soft colloidal glasses

    KAUST Repository

    Agarwal, Praveen

    2011-04-11

    We have investigated strain-accelerated dynamics of soft glasses theoretically and experimentally. Mechanical rheology measurements performed on a variety of systems reveal evidence for the speeding-up of relaxation at modest shear strains in both step and oscillatory shear flows. Using the soft glassy rheology (SGR) model framework, we show that the observed behavior is a fundamental, but heretofore unexplored attribute of soft glasses. © 2011 American Physical Society.

  14. Investigation of Strain Aging in the Ordered Intermetallic Compound beta-NiAl. Ph.D. Thesis Final Contractor Report

    Science.gov (United States)

    Weaver, Mark Lovell

    1995-01-01

    The phenomenon of strain aging has been investigated in polycrystalline and single crystal NiAl alloys at temperatures between 300 and 1200 K. Static strain aging studies revealed that after annealing at 1100 K for 7200 s (i.e., 2h) followed by furnace cooling, high purity, nitrogen-doped and titanium-doped polycrystalline alloys exhibited continuous yielding, while conventional-purity and carbon-doped alloys exhibited distinct yield points and Luders strains. Prestraining by hydrostatic pressurization removed the yield points, but they could be reintroduced by further annealing treatments. Yield points could be reintroduced more rapidly if the specimens were prestrained uniaxially rather than hydrostatically, owing to the arrangement of dislocations into cell structures during uniaxial deformation. The time dependence of the strain aging events followed at t(exp 2/3) relationship suggesting that the yield points observed in polycrystalline NiAl were the result of the pinning of mobile dislocations by interstitials, specifically carbon. Between 700 and 800 K, yield stress plateaus, yield stress transients upon a ten-fold increase in strain rate, work hardening peaks, and dips in the strain rate sensitivity (SRS) have been observed in conventional-purity and carbon-doped polycrystals. In single crystals, similar behavior was observed; in conventional-purity single crystals, however, the strain rate sensitivity became negative resulting in serrated yielding, whereas, the strain rate sensitivity stayed positive in high purity and in molybdenum-doped NiAl. These observations are indicative of dynamic strain aging (DSA) and are discussed in terms of conventional strain aging theories. The impact of these phenomena on the composition-structure-property relations are discerned. Finally, a good correlation has been demonstrated between the properties of NiAl alloys and a recently developed model for strain aging in metals and alloys developed by Reed-Hill et al.

  15. Two-strain competition in quasineutral stochastic disease dynamics

    Science.gov (United States)

    Kogan, Oleg; Khasin, Michael; Meerson, Baruch; Schneider, David; Myers, Christopher R.

    2014-10-01

    We develop a perturbation method for studying quasineutral competition in a broad class of stochastic competition models and apply it to the analysis of fixation of competing strains in two epidemic models. The first model is a two-strain generalization of the stochastic susceptible-infected-susceptible (SIS) model. Here we extend previous results due to Parsons and Quince [Theor. Popul. Biol. 72, 468 (2007), 10.1016/j.tpb.2007.04.002], Parsons et al. [Theor. Popul. Biol. 74, 302 (2008), 10.1016/j.tpb.2008.09.001], and Lin, Kim, and Doering [J. Stat. Phys. 148, 646 (2012), 10.1007/s10955-012-0479-9]. The second model, a two-strain generalization of the stochastic susceptible-infected-recovered (SIR) model with population turnover, has not been studied previously. In each of the two models, when the basic reproduction numbers of the two strains are identical, a system with an infinite population size approaches a point on the deterministic coexistence line (CL): a straight line of fixed points in the phase space of subpopulation sizes. Shot noise drives one of the strain populations to fixation, and the other to extinction, on a time scale proportional to the total population size. Our perturbation method explicitly tracks the dynamics of the probability distribution of the subpopulations in the vicinity of the CL. We argue that, whereas the slow strain has a competitive advantage for mathematically "typical" initial conditions, it is the fast strain that is more likely to win in the important situation when a few infectives of both strains are introduced into a susceptible population.

  16. A population dynamics approach to biological aging

    Science.gov (United States)

    de Almeida, R. M. C.

    A dynamical model for aging in biological population is discussed where asexual reproduction is considered. The maximum life span is inherited from parent to offspring with some random mutations described by a transition matrix, and the fertile period begins at a defined age R. The intra species competition is modeled through a Verhulst-like factor. Discrete time evolution equations are iterated and the transient and asymptotic solutions are obtained. When only bad mutations are taken into account, the stationary solutions are obtained analytically. The results are applied to the Penna model.

  17. TOTAL ANTIOXIDANT ACTIVITY OF SOME BASIDIOMYCETES STRAINS IN GROWTH DYNAMIC

    Directory of Open Access Journals (Sweden)

    O. V. Fedotov

    2016-08-01

    Full Text Available The work is devoted to the study of total antioxidant activity (AOA in the growth dynamics of basidiomycetes strains in their periodic surface cultivation on glucose-peptone medium. Subjects of research are mycelium and culture filtrate (CF from 57 strains, 5 of which are belong to 5 types of Polyporales order, and 52 of which are belong to the 7 types of Agaricales order. In order to study the dynamics of growth used method for determining the weight of absolutely dry biomass accumulation (ADB. Total AOA of mycological material was evaluated by inhibition of lipid peroxidation products accumulation intensity in the model oxidation reaction of Tween-80 by air oxygen. It was found that the most productive in terms of the accumulation of ADB are strains F. velutipes F-610 and P. eryngii P-er. Lowest values of ADB accumulation recorded for strains P. ostreatus P-14 and P-192 and P. citrinopileatus P sіtr. Were selected the most productive strains of Basidiomycetes for the level of total AOA in mycelium and CF. There are strains P. eryngii P-er, P. citrinopileatus P sіtr, P. ostreatus P-035, F. hepatica Fh-08, A. cylindracea 960, P. ostreatus P-081, P-082, P-087, P. citrinopileatus P sіtr. Has not been established the dependence between the growth and the antioxidant activity of the 9- and 12-day fungal cultures. Selected producers of natural antioxidants may be used as biological agents in biotechnology.

  18. Incoherent magnetization dynamics in strain mediated switching of magnetostrictive nanomagnets

    Science.gov (United States)

    Bhattacharya, Dhritiman; Mamun Al-Rashid, Md; D'Souza, Noel; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

    2017-01-01

    Micromagnetic studies of the magnetization change in magnetostrictive nanomagnets subjected to stress are performed for nanomagnets of different sizes. The interplay between demagnetization, exchange and stress anisotropy energies is used to explain the rich physics of size-dependent magnetization dynamics induced by modulating stress anisotropy in planar nanomagnets. These studies have important implications for strain mediated ultralow energy magnetization control in nanomagnets and its application in energy-efficient nanomagnetic computing devices.

  19. Fiber Bragg Gratings, IT Techniques and Strain Gauge Validation for Strain Calculation on Aged Metal Specimens

    Directory of Open Access Journals (Sweden)

    Ander Montero

    2011-01-01

    Full Text Available This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG sensors and infrared thermography (IT techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT techniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural Health Monitoring techniques on real aircraft during their life cycle requires a study of the behaviour of FBG sensors and their wiring under real conditions, before using them for a long time. To simulate aging, specimens were stored in a climate chamber at 70 °C and 90% RH for 60 days. This study is framed within the Structural Health Monitoring (SHM and Non Destructuve Evaluation (NDE research lines, integrated into the avionics area maintained by the Aeronautical Technologies Centre (CTA and the University of the Basque Country (UPV/EHU.

  20. Challenges for ice age dynamics: a dynamical systems perspective

    CERN Document Server

    Crucifix, Michel; Mitsui, Takahito

    2015-01-01

    This chapter is dedicated to the slow dynamics of the climate system, at time scales of one~thousand to one million years. We focus specifically on the phenomenon of ice ages that has characterised the slow evolution of climate over the Quaternary. Ice ages are a form of variability featuring interactions between different large-scale components and processes in the climate system, including ice sheet, deep-ocean and carbon cycle dynamics. This variability is also at least partly controlled by changes in the seasonal and latitudinal incoming solar radiation associated with the combined effects of changes in Earth's orbit shape, precession of equinoxes, and changes in obliquity. A number of possible mechanisms are reviewed in this chapter. We stress that the nature of the interactions between these slow dynamics and faster modes of variability, such as millennium and centennial modes of variability, are still poorly understood. For example, whether the time sequence of ice ages is robustly determined or not by...

  1. Dynamic strain in metallic vs insulating manganite films

    Energy Technology Data Exchange (ETDEWEB)

    Dekker, Martina Cornelia; Oswald, Steffen; Schultz, Ludwig; Doerr, Kathrin [IFW Dresden (Germany)

    2008-07-01

    The use of a ferro- and piezoelectric substrate, PMN-PT(001) (PbMg{sub 1/3}Nb{sub 2/3}O{sub 3}){sub 0.72}(PbTiO{sub 3}){sub 0.28}, allows us to biaxially compress as grown epitaxial films by as much as 0.2%. This reversible dynamic strain process gives a unique insight into the effect of strain on perovskite oxides, eliminating effects such as varying oxygen concentration, which may occur when several substrates with different lattice mismatch are used. We have prepared PLCMO (Pr{sub 1-x}La{sub x}){sub 0.7}Ca{sub 0.3}MnO{sub 3} films on PMN-PT substrates for a range of x values. Around x=0.6, the system exhibits a transition from an insulating to a metallic ground state. We have recorded changes in magnetic moment and transition temperature upon varying x, and compared the effects of dynamic strain on transport behaviour in the metallic and insulating ground states.

  2. Dynamics of Dual Infection with Campylobacter jejuni Strains in Chickens Reveals Distinct Strain-to-Strain Variation in Infection Ecology

    Science.gov (United States)

    Wigley, Paul; Humphrey, Suzanne; Kemmett, Kirsty; Lacharme-Lora, Lizeth; Humphrey, Tom; Williams, Nicola

    2014-01-01

    Although multiple genotypes of Campylobacter jejuni may be isolated from the same commercial broiler flock, little is known about the infection dynamics of different genotypes within individuals or their colonization sites within the gut. Single experimental infections with C. jejuni M1 (sequence type 137, clonal complex 45) and C. jejuni 13126 (sequence type 21, clonal complex 21) revealed that 13126 colonized the ceca at significantly higher levels. The dissemination and colonization sites of the two C. jejuni strains then were examined in an experimental broiler flock. Two 33-day-old broiler chickens were infected with M1 and two with 13126, and 15 birds were left unchallenged. Cloacal swabs were taken postinfection to determine the colonization and shedding of each strain. By 2 days postinfection (dpi), 8/19 birds were shedding M1 whereas none were shedding 13126. At 8 dpi, all birds were shedding both strains. At 18 dpi, liver and cecal levels of each isolate were quantified, while in 10 birds they also were quantified at nine sites throughout the gastrointestinal (GI) tract. 13126 was found throughout the GI tract, while M1 was largely restricted to the ceca and colon. The livers of 7/19 birds were culture positive for 13126 only. These data show that 13126 has a distinctly different infection biology than strain M1. It showed slower colonization of the lower GI tract but was more invasive and able to colonize at a high level throughout the GI tract. The finding that C. jejuni strains have markedly different infection ecologies within the chicken has implications for control in the poultry industry and suggests that the contamination risk of edible tissues is dependent on the isolate involved. PMID:25107966

  3. Atrial strain rate is a sensitive measure of alterations in atrial phasic function in healthy ageing.

    Science.gov (United States)

    Boyd, Anita C; Richards, David A B; Marwick, Thomas; Thomas, Liza

    2011-09-01

    Strain and strain rate measure local deformation of the myocardium and have been used to evaluate phasic atrial function in various disease states. The aim of this study was to define normal values for tissue Doppler-derived atrial strain measurements and examine age-related changes by decade in healthy individuals. Transthoracic echocardiograms were performed on 188 healthy subjects. Tissue Doppler-derived strain and strain rate were measured from the apical four and two-chamber views of the left atrium, and global values were calculated as the mean of all segments. Measurements included peak systolic strain, systolic strain rate, early and late diastolic strain rate. Phasic left atrial volumes and fractions were calculated. Mitral inflow and tissue Doppler imaging were employed to estimate left ventricular diastolic function. A significant reduction in global systolic strain was observed from decade 6. Alterations in atrial strain rate were apparent from decade 5; systolic strain rate and early diastolic strain rate decreased, while late diastolic strain rate increased significantly. Changes in phasic atrial volume and function occurred in conjunction with age-related changes in left ventricular diastolic function. Importantly, age-related changes in global atrial systolic strain rate and early diastolic strain rate occurred a decade before corresponding changes in atrial phasic volume parameters. Atrial strain and strain rate can be used to quantify atrial phasic function and appear to be altered before traditional parameters with ageing. Strain analysis may therefore be more sensitive in detecting subclinical atrial dysfunction with alterations in strain rate parameters observed before traditional parameters.

  4. Dynamic viscoelastic properties of polyvinyl chloride with physical aging

    Science.gov (United States)

    Tian, Fang; Luo, Yingshe; Yin, Shuiping; Wang, Hong; Cao, Chun

    2015-11-01

    The experimental research of dynamic viscoelastic properties of polyvinyl chloride was conducted by the dynamic mechanical analysis method in this paper. And the fitting equation of dynamic modulus of polymers has been presented. Based on the time-aging time equivalent principle, horizontal shift factor and vertical shift factor of aging time are carried out, which proposes a novel method for the research on time-aging time equivalent analysis of dynamic mechanical properties of polymers during physical aging.

  5. Material deformation dynamics at ultrahigh pressures and strain rates

    Science.gov (United States)

    Remington, B. A.; Park, H. S.; Maddox, B. R.; May, M. J.; Pollaine, S. M.; Prisbrey, S. T.; Rudd, R. E.; Hawreliak, J. A.; Perry, T. S.; Comley, A. J.; Wark, J. S.; Meyers, M. A.

    2010-11-01

    Solid-state dynamics experiments at extreme pressures, up to 10 Mbar, and strain rates (1.e6 -1.e8 1/s) are being developed for the NIF laser. The experimental methods are being developed on the Omega laser facility. VISAR measurements establish the ramped, high-pressure conditions. Recovery experiments offer a look at the residual microstructure. Dynamic diffraction measurements allow phase, shear stress (strength), and possibly twin volume fraction and dislocation density to be inferred. Constitutive models for material strength at these conditions by comparing 2D simulations with experiments measuring the Rayleigh-Taylor instability evolution in solid-state samples of vanadium and tantalum. The material deformation likely falls into the phonon drag regime. We estimate of the (microscopic) phonon drag coefficient, by relating to the (macroscopic) effective lattice viscosity.

  6. Emotionality, exploratory behavior, and locomotion in aging inbred strains of mice.

    Science.gov (United States)

    Elias, P K; Elias, M F; Eleftheriou, B E

    1975-01-01

    Two inbred strains of mice, C57BL/6J and DBA/2J, ranging in age from 2 to 38 months, were tested in an open field using the free exploration method. Scores were obtained for locomotor activity, exploratory behavior and emotionality. Strain differences were observed for all three variables. Beginning at late maturity (12 months), locomotor activity decreased with increasing age. Exploratory behavior was at a low level for DBA/2J mice at all ages. For C57BL/6J mice, exploratory behavior decreased significantly between 2 and 6 months and remained stable thereafter. Emotionality remained unchanged with advancing age for both strains of mice.

  7. Young runoff fractions control streamwater age and solute concentration dynamics

    Science.gov (United States)

    Paolo Benettin; Scott W. Bailey; Andrea Rinaldo; Gene E. Likens; Kevin J. McGuire; Gianluca Botter

    2017-01-01

    We introduce a new representation of coupled solute and water age dynamics at the catchment scale, which shows how the contributions of young runoff waters can be directly referenced to observed water quality patterns. The methodology stems from recent trends in hydrologic transport that acknowledge the dynamic nature of streamflow age and explores the use of water age...

  8. Simultaneous measurement of dynamic strain and temperature distribution using high birefringence PANDA fiber Bragg grating

    Science.gov (United States)

    Zhu, Mengshi; Murayama, Hideaki

    2017-04-01

    New approach in simultaneous measurement of dynamic strain and temperature has been done by using a high birefringence PANDA fiber Bragg grating sensor. By this technique, we have succeeded in discriminating dynamic strain and temperature distribution at the sampling rate of 800 Hz and the spatial resolution of 1 mm. The dynamic distribution of strain and temperature were measured with the deviation of 5mm spatially. In addition, we have designed an experimental setup by which we can apply quantitative dynamic strain and temperature distribution to the fiber under testing without bounding it to a specimen.

  9. Material dynamics under extreme conditions of pressure and strain rate

    Energy Technology Data Exchange (ETDEWEB)

    Remington, B A; Allen, P; Bringa, E; Hawreliak, J; Ho, D; Lorenz, K T; Lorenzana, H; Meyers, M A; Pollaine, S W; Rosolankova, K; Sadik, B; Schneider, M S; Swift, D; Wark, J; Yaakobi, B

    2005-09-06

    Solid state experiments at extreme pressures (10-100 GPa) and strain rates ({approx}10{sup 6}-10{sup 8}s{sup -1}) are being developed on high-energy laser facilities, and offer the possibility for exploring new regimes of materials science. These extreme solid-state conditions can be accessed with either shock loading or with a quasi-isentropic ramped pressure drive. Velocity interferometer measurements establish the high pressure conditions. Constitutive models for solid-state strength under these conditions are tested by comparing 2D continuum simulations with experiments measuring perturbation growth due to the Rayleigh-Taylor instability in solid-state samples. Lattice compression, phase, and temperature are deduced from extended x-ray absorption fine structure (EXAFS) measurements, from which the shock-induced {alpha}-{omega} phase transition in Ti and the {alpha}-{var_epsilon} phase transition in Fe are inferred to occur on sub-nanosec time scales. Time resolved lattice response and phase can also be measured with dynamic x-ray diffraction measurements, where the elastic-plastic (1D-3D) lattice relaxation in shocked Cu is shown to occur promptly (< 1 ns). Subsequent large-scale molecular dynamics (MD) simulations elucidate the microscopic dynamics that underlie the 3D lattice relaxation. Deformation mechanisms are identified by examining the residual microstructure in recovered samples. The slip-twinning threshold in single-crystal Cu shocked along the [001] direction is shown to occur at shock strengths of {approx}20 GPa, whereas the corresponding transition for Cu shocked along the [134] direction occurs at higher shock strengths. This slip-twinning threshold also depends on the stacking fault energy (SFE), being lower for low SFE materials. Designs have been developed for achieving much higher pressures, P > 1000 GPa, in the solid state on the National Ignition Facility (NIF) laser.

  10. Yeast Population Dynamics during the Fermentation and Biological Aging of Sherry Wines

    Science.gov (United States)

    Esteve-Zarzoso, B.; Peris-Torán, M. J.; García-Maiquez, E.; Uruburu, F.; Querol, A.

    2001-01-01

    Molecular and physiological analyses were used to study the evolution of the yeast population, from alcoholic fermentation to biological aging in the process of “fino” sherry wine making. The four races of “flor” Saccharomyces cerevisiae (beticus, cheresiensis, montuliensis, and rouxii) exhibited identical restriction patterns for the region spanning the internal transcribed spacers 1 and 2 (ITS-1 and ITS-2) and the 5.8S rRNA gene, but this pattern was different, from those exhibited by non-flor S. cerevisiae strains. This flor-specific pattern was detected only after wines were fortified, never during alcoholic fermentation, and all the strains isolated from the velum exhibited the typical flor yeast pattern. By restriction fragment length polymorphism of mitochondrial DNA and karyotyping, we showed that (i) the native strain is better adapted to fermentation conditions than commercial strains; (ii) two different populations of S. cerevisiae strains are involved in the process of elaboration, of fino sherry wine, one of which is responsible for must fermentation and the other, for wine aging; and (iii) one strain was dominant in the flor population integrating the velum from sherry wines produced in González Byass wineries, although other authors have described a succession of races of flor S. cerevisiae during wine aging. Analyzing all these results together, we conclude that yeast population dynamics during biological aging is a complex phenomenon and differences between yeast populations from different wineries can be observed. PMID:11319081

  11. Polymer Prize Talk: Segmental Dynamics in Polymers : From Cold Melts to Aging and Stressed Glasses

    Science.gov (United States)

    Schweizer, Kenneth

    2008-03-01

    Polymers are excellent glass formers. In the cold molten state they exhibit chemically-specific and strongly non-Arrenhius segmental relaxation which sets the time scale for the generic chain scale dynamics. In the amorphous solid or plastic state the temperature dependence of the alpha relaxation time changes, physical aging emerges, and a rich mechanical response occurs characterized by the dynamic yielding, strain softening and strain hardening processes. We have developed a statistical mechanical theory of activated segmental relaxation in cold melts by combining and extending methods of mode coupling, dynamic density functional and activated hopping theories. The approach is built on the concept of a confining nonequilibrium free energy which quantifies local dynamical constraints and the barrier hopping process. The localizing consequences of interchain caging forces are quantified by the amplitude of nanometer scale density fluctuations (compressibility) and backbone stiffness. Predictions for the kinetic glass and dynamic crossover temperatures, dynamic fragility, and thermal dependence of the segmental relaxation time are consistent with experiments. The theory has been generalized to treat alpha relaxation, physical aging, and nonlinear mechanical properties in the glass. The structural component of density fluctuations become (partially) frozen resulting in a crossover to Arrenhius relaxation. Physical aging is modeled based on a kinetic equation for collective density fluctuations. At intermediate time scales the relaxation time (shear modulus) grows as a power law (logarithmic) function of aging time with a temperature dependent exponent. Applied stress weakens dynamical constraints thereby accelerating relaxation and softening the elastic modulus. A constitutive equation has been constructed from which the temperature dependent dynamic yielding and mechanical response under constant strain rate, constant stress (creep), and other modes of deformation

  12. Effect of various Portland cement paste compositions on early-age strain

    Science.gov (United States)

    Guzzetta, Alana G.

    Early-age strain in paste, mortar, and concrete mixtures was investigated using a new method where the specimen shape was a cone frustum. Strain of the specimen from both the horizontal and vertical directions was captured by height change measurement. The volumetric strain was then calculated as a function of the height change and was plotted versus time. A correlation was found between the slopes of the volumetric strain curve resulting from this test method and the initial setting time of the tested material. An initial evaluation of the repeatability of this innovative test method was conducted. The early-age strain effects of aggregate volume, shrinkage reducing admixture, water-cementitious ratio (w/cm), and partial cement replacement with supplementary cementitious materials were tested and individually compared. From these comparisons, it was observed that ambient temperature, bleed water development, and rheological properties had a significant impact on the volumetric strain results. Data showed increased strain as aggregate volume was reduced and as the w/cm was changed from 0.25 up to 0.50. The addition of shrinkage reducing admixture generally caused an increase in the 36-hour volumetric strain value. In most of the mixtures, cement replacement with 20% fly ash or 10% metakaolin reduced the measured volumetric strain when the w/cm was 0.30. Replacement of cement with 10% silica fume caused an insignificant change in volumetric strain results.

  13. Quantified Facial Soft-tissue Strain in Animation Measured by Real-time Dynamic 3-Dimensional Imaging

    Science.gov (United States)

    Hsu, Vivian M.; Wes, Ari M.; Tahiri, Youssef; Cornman-Homonoff, Joshua

    2014-01-01

    Background: The aim of this study is to evaluate and quantify dynamic soft-tissue strain in the human face using real-time 3-dimensional imaging technology. Methods: Thirteen subjects (8 women, 5 men) between the ages of 18 and 70 were imaged using a dual-camera system and 3-dimensional optical analysis (ARAMIS, Trilion Quality Systems, Pa.). Each subject was imaged at rest and with the following facial expressions: (1) smile, (2) laughter, (3) surprise, (4) anger, (5) grimace, and (6) pursed lips. The facial strains defining stretch and compression were computed for each subject and compared. Results: The areas of greatest strain were localized to the midface and lower face for all expressions. Subjects over the age of 40 had a statistically significant increase in stretch in the perioral region while lip pursing compared with subjects under the age of 40 (58.4% vs 33.8%, P = 0.015). When specific components of lip pursing were analyzed, there was a significantly greater degree of stretch in the nasolabial fold region in subjects over 40 compared with those under 40 (61.6% vs 32.9%, P = 0.007). Furthermore, we observed a greater degree of asymmetry of strain in the nasolabial fold region in the older age group (18.4% vs 5.4%, P = 0.03). Conclusions: This pilot study illustrates that the face can be objectively and quantitatively evaluated using dynamic major strain analysis. The technology of 3-dimensional optical imaging can be used to advance our understanding of facial soft-tissue dynamics and the effects of animation on facial strain over time. PMID:25426394

  14. Quantified Facial Soft-tissue Strain in Animation Measured by Real-time Dynamic 3-Dimensional Imaging.

    Science.gov (United States)

    Hsu, Vivian M; Wes, Ari M; Tahiri, Youssef; Cornman-Homonoff, Joshua; Percec, Ivona

    2014-09-01

    The aim of this study is to evaluate and quantify dynamic soft-tissue strain in the human face using real-time 3-dimensional imaging technology. Thirteen subjects (8 women, 5 men) between the ages of 18 and 70 were imaged using a dual-camera system and 3-dimensional optical analysis (ARAMIS, Trilion Quality Systems, Pa.). Each subject was imaged at rest and with the following facial expressions: (1) smile, (2) laughter, (3) surprise, (4) anger, (5) grimace, and (6) pursed lips. The facial strains defining stretch and compression were computed for each subject and compared. The areas of greatest strain were localized to the midface and lower face for all expressions. Subjects over the age of 40 had a statistically significant increase in stretch in the perioral region while lip pursing compared with subjects under the age of 40 (58.4% vs 33.8%, P = 0.015). When specific components of lip pursing were analyzed, there was a significantly greater degree of stretch in the nasolabial fold region in subjects over 40 compared with those under 40 (61.6% vs 32.9%, P = 0.007). Furthermore, we observed a greater degree of asymmetry of strain in the nasolabial fold region in the older age group (18.4% vs 5.4%, P = 0.03). This pilot study illustrates that the face can be objectively and quantitatively evaluated using dynamic major strain analysis. The technology of 3-dimensional optical imaging can be used to advance our understanding of facial soft-tissue dynamics and the effects of animation on facial strain over time.

  15. Dynamic tensile testing for determining the stress-strain curve at different strain rate

    OpenAIRE

    Mansilla, A; Regidor, A.; García, D.; Negro, A

    2001-01-01

    A detailed discussion of high strain-rate tensile testing is presented. A comparative analysis of different ways to measure stress and strain is made. The experimental stress-strain curves have been suitably interpreted to distinguish between the real behaviour of the material and the influence of the testing methodology itself. A special two sections flat specimen design was performed through FEA computer modelling. The mechanical properties as function of strain rate were experimentally obt...

  16. REVIEW ON RELATIONSHIP BETWEEN DYNAMIC STRAIN AGING AND ENVIRONMENTALLY ASSISTED CRACKING OF STRUCTURAL MATERIALS USED IN NUCLEAR POWER PLANTS%动态应变时效对核电材料环境致裂影响的研究现状与进展

    Institute of Scientific and Technical Information of China (English)

    谭季波; 吴欣强; 韩恩厚

    2012-01-01

    The paper summarized the anomalous deformation characteristics, influencing factors and mechanisms of dynamic strain aging (DSA) in nuclear-grade carbon steels, low alloy steels and austenitic stainless steels. The possible effects of the interaction between DSA and high temperature water on environmentally assisted cracking of structural materials used in nuclear power plants have been discussed. The coming possible research topics and directions are also proposed.%综述了核级碳钢、低合金钢、不锈钢发生动态应变时效(DSA)的反常特征、影响因素及机制,讨论了DSA与高温高压水环境因素的交互作用对核电材料环境致裂的可能影响。指出了当前研究中存在的问题及进一步的研究方向。

  17. Effects of Temperature and Strain Rate on Dynamic Properties of Concrete

    Institute of Scientific and Technical Information of China (English)

    JIA Bin; TAO Junlin; LI Zhengliang; WANG Ruheng; ZHANG Yu

    2008-01-01

    To study the dynamic properties of the concrete subjected to impulsive loading,stress-time curves of concrete in different velocities were measured using split Hopkinson pressure bar (SHPB).Effects of temperature and strain rate on the dynamic yield strength and constitutive relation of the concrete were analyzed.The dynamic mechanical properties of the reinforced concrete are subjected to high strain rates when it is at a relatively low temperature.But with temperature increasing,the temperature softening effect makes the strength of the concrete weaken and the impact toughness of the concrete is saliently relative to strain rate effect.So,strain rate effect,strain hardening and temperature softening work together on the dynamic mechanical capability of concrete and the relation between them is relatively corn plex.

  18. A compositional and dynamic model for face aging.

    Science.gov (United States)

    Suo, Jinli; Zhu, Song-Chun; Shan, Shiguang; Chen, Xilin

    2010-03-01

    In this paper, we present a compositional and dynamic model for face aging. The compositional model represents faces in each age group by a hierarchical And-Or graph, in which And nodes decompose a face into parts to describe details (e.g., hair, wrinkles, etc.) crucial for age perception and Or nodes represent large diversity of faces by alternative selections. Then a face instance is a transverse of the And-Or graph-parse graph. Face aging is modeled as a Markov process on the parse graph representation. We learn the parameters of the dynamic model from a large annotated face data set and the stochasticity of face aging is modeled in the dynamics explicitly. Based on this model, we propose a face aging simulation and prediction algorithm. Inversely, an automatic age estimation algorithm is also developed under this representation. We study two criteria to evaluate the aging results using human perception experiments: 1) the accuracy of simulation: whether the aged faces are perceived of the intended age group, and 2) preservation of identity: whether the aged faces are perceived as the same person. Quantitative statistical analysis validates the performance of our aging model and age estimation algorithm.

  19. Studies on Dynamic Damage Evolution for Pp/pa Polymer Blends Under High Strain Rates

    Science.gov (United States)

    Sun, Zi-Jian; Wang, Li-Li

    The dynamic damage evolution for PP/PA blends with different compatibilizers is studied in high strain rates from two different approaches, namely by determining the unloading elastic modulus of specimen experienced impact deformation and by combining the split Hopkinson pressure bar (SHPB) experimental technique with the back-propagation (BP) neural network. The results obtained by both approaches consistently show that a threshold strain ɛth exists for dynamic damage evolution, and both the damage evolution and ɛth are dependent on strain and strain rate. For non-linear visco-elastic materials, the damage evolution determined by the unloading elastic modulus provides an underestimation of real damage evolution.

  20. Evaluation of static and dynamic contact stresses in simulated granular particles using strain gages

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y.; Shukla, A. (Univ. of Rhode Island, Kingston (United States))

    1993-01-01

    The application of strain gages for the determination of static and dynamic contact loads in granular particles is demonstrated. For experimental convenience, the granular particles are simulated by circular disks fabricated from Homalite-100, a brittle polyester material. Stress field equations in the vicinity of the contact points are carefully evaluated to optimize the relative position of strain gages. The results obtained from strain gages were compared with those obtained using the optical technique of photoelasticity for both static and dynamic problems. Finally, as an example, strain gages are used to study wave propagation in a single chain assembly of disks.

  1. Age-specific labor market dynamics

    NARCIS (Netherlands)

    Gielen, A. C.

    2008-01-01

    One important finding concerns the fact that job separations for older workers constitute mostly a one-way exit out of the labor force, despite the fact that an ageing society calls for an active labor market participation from us all. Also, the allocation of labor for younger workers has shown to b

  2. Age-related greater Achilles tendon compliance is not associated with larger plantar flexor muscle fascicle strains in senior women.

    Science.gov (United States)

    Csapo, R; Malis, V; Hodgson, J; Sinha, S

    2014-04-15

    The aim of the present study was to test the hypothesis that the age-associated decrease of tendon stiffness would necessitate greater muscle fascicle strains to produce similar levels of force during isometric contraction. Greater fascicle strains could force sarcomeres to operate in less advantageous regions of their force-length and force-velocity relationships, thus impairing the capacity to generate strong and explosive contractions. To test this hypothesis, sagittal-plane dynamic velocity-encoded phase-contrast magnetic resonance images of the gastrocnemius medialis (GM) muscle and Achilles tendon (AT) were acquired in six young (YW; 26.1 ± 2.3 yr) and six senior (SW; 76.7 ± 8.3 yr) women during submaximal isometric contraction (35% maximum voluntary isometric contraction) of the plantar flexor muscles. Multiple GM fascicle lengths were continuously determined by automatically tracking regions of interest coinciding with the end points of muscle fascicles evenly distributed along the muscle's proximo-distal length. AT stiffness and Young's modulus were measured as the slopes of the tendon's force-elongation and stress-strain curves, respectively. Despite significantly lower AT stiffness at older age (YW: 120.2 ± 52.3 N/mm vs. SW: 53.9 ± 44.4 N/mm, P = 0.040), contraction-induced changes in GM fascicle lengths were similar in both age groups at equal levels of absolute muscular force (4-5% fascicle shortening in both groups), and even significantly larger in YW (YW: 11-12% vs. SW: 6-8% fascicle shortening) at equal percentage of maximum voluntary contraction. These results suggest that factors other than AT stiffness, such as age-associated changes in muscle composition or fascicle slack, might serve as compensatory adaptations, limiting the degree of fascicle strains upon contraction.

  3. Strain dependent ultrafast carrier dynamics in EuTiO3 films

    Science.gov (United States)

    Li, Zhong-guo; Zhao, Run; Li, Weiwei; Wang, Haiyan; Yang, Hao; Song, Ying-lin

    2014-10-01

    The photocarrier relaxation dynamics of EuTiO3 films have been investigated using femtosecond transient absorption spectroscopy. Two kinds of EuTiO3 films, with and without strain, have been included. In both films, the decay dynamics of 2p-3dt2g transition has a fast (˜2 ps) and slow (ns) components which are independent of the strain. Remarkably, the transient photobleaching of 4f-3dt2g transition is found to be enhanced considerably in the strained film, accompanied with a subnanosecond carrier lifetime. This behavior can be linked to the strain induced band structure modulation. Our results reveal the dynamical interactions in EuTiO3, identifying the critical roles of strain in photo induced phenomena.

  4. Ageing of atrazine in manure amended soils assessed by bioavailability to Pseudomonas sp. strain ADP

    DEFF Research Database (Denmark)

    Glæsner, Nadia; Bælum, Jacob; Strobel, Bjarne W.;

    2014-01-01

    bacteria Pseudomonas sp. strain ADP. Throughout an ageing period of 90 days bioavailability was investigated at days 1, 10, 32, 60 and 90, where ~108 cells g−1 of the ADP strain was inoculated to the 14C-atrazine exposed soil and 14CO2 was collected over 7 days as a measure of mineralized atrazine. Even...... though the bioavailable residue decreased in all of the three soils as time proceeded, we found that ageing occurred faster in the topsoils rich in organic carbon than in subsoil. For one topsoil rich in organic carbon content, Simmelkær, we observed a higher degree of ageing when treated with manure....... Contrarily, sorption experiments showed less sorption to Simmelkær treated with manure than the untreated soil indicating that sorption processes are not the only mechanisms of ageing. The other topsoil low in organic carbon content, Ringe, showed no significant difference in ageing between the manure...

  5. Strain rate and temperature effects on crack initiation of direct aged 718 Alloy

    Directory of Open Access Journals (Sweden)

    Perrais Maxime

    2014-01-01

    Full Text Available During mechanical tests at high temperature in an oxidizing atmosphere, the effects of strain rate on crack initiation are noticeable. This effect is due to a coupling between local mechanical loading and oxidation. Samples were machined in a turbine disk made of direct aged alloy 718. Tests were performed to understand the effect of these couplings on crack initiation and to ensure lifetime is optimized. This study compared the cracking resistance of two different specimen geometries at a given plastic strain and performed quantitative measurement of the mechanical loading conditions inducing crack initiation between 600 ∘C and 650 ∘C. Sample geometries consisted in tensile flat specimens and V-shaped samples. This specific geometry was used to localize strain and damage in the apex of the V and to reach strain rates lower than those possible on standard specimens. Digital image correlation technique was used to provide strain measurements. For each temperature and strain rate, finite element calculations using the identified constitutive law were performed to get a refined level of strain in different areas at the V apex. Tests were stopped after an imposed displacement corresponding to a given plastic strain distribution. SEM observations of the surface of the flat tensile samples revealed no crack initiation. On the contrary, SEM observations at the apex of V specimens for which the level of cumulative strain was close to the level of cumulative strain of flat samples reveal the presence of intergranular damage when the strain rate used was below a given level.

  6. Fiber Bragg grating dynamic strain sensor using an adaptive reflective semiconductor optical amplifier source.

    Science.gov (United States)

    Wei, Heming; Tao, Chuanyi; Zhu, Yinian; Krishnaswamy, Sridhar

    2016-04-01

    In this paper, a reflective semiconductor optical amplifier (RSOA) is configured to demodulate dynamic spectral shifts of a fiber Bragg grating (FBG) dynamic strain sensor. The FBG sensor and the RSOA source form an adaptive fiber cavity laser. As the reflective spectrum of the FBG sensor changes due to dynamic strains, the wavelength of the laser output shifts accordingly, which is subsequently converted into a corresponding phase shift and demodulated by an unbalanced Michelson interferometer. Due to the short transition time of the RSOA, the RSOA-FBG cavity can respond to dynamic strains at high frequencies extending to megahertz. A demodulator using a PID controller is used to compensate for low-frequency drifts induced by temperature and large quasi-static strains. As the sensitivity of the demodulator is a function of the optical path difference and the FBG spectral width, optimal parameters to obtain high sensitivity are presented. Multiplexing to demodulate multiple FBG sensors is also discussed.

  7. DYNAMIC STRAIN MAPPING AND REAL-TIME DAMAGE STATE ESTIMATION UNDER BIAXIAL RANDOM FATIGUE LOADING

    Data.gov (United States)

    National Aeronautics and Space Administration — DYNAMIC STRAIN MAPPING AND REAL-TIME DAMAGE STATE ESTIMATION UNDER BIAXIAL RANDOM FATIGUE LOADING SUBHASISH MOHANTY*, ADITI CHATTOPADHYAY, JOHN N. RAJADAS, AND CLYDE...

  8. Zinc oxide nanoparticle-polymeric thin films for dynamic strain sensing

    OpenAIRE

    2011-01-01

    Piezoelectric transducers are becoming increasingly popular for dynamic strain monitoring due to their small form factors and their ability to generate an electrical voltage drop in response to strain. Although numerous types of piezoelectric thin films have been adopted for strain sensing, it has been shown that piezo-ceramics are expensive, brittle, and can fail during operation, while piezo-polymers possess lower piezoelectricity and mechanical stiffness. Thus, the objective of this study ...

  9. Research on dynamic creep strain and settlement prediction under the subway vibration loading.

    Science.gov (United States)

    Luo, Junhui; Miao, Linchang

    2016-01-01

    This research aims to explore the dynamic characteristics and settlement prediction of soft soil. Accordingly, the dynamic shear modulus formula considering the vibration frequency was utilized and the dynamic triaxial test conducted to verify the validity of the formula. Subsequently, the formula was applied to the dynamic creep strain function, with the factors influencing the improved dynamic creep strain curve of soft soil being analyzed. Meanwhile, the variation law of dynamic stress with sampling depth was obtained through the finite element simulation of subway foundation. Furthermore, the improved dynamic creep strain curve of soil layer was determined based on the dynamic stress. Thereafter, it could to estimate the long-term settlement under subway vibration loading by norms. The results revealed that the dynamic shear modulus formula is straightforward and practical in terms of its application to the vibration frequency. The values predicted using the improved dynamic creep strain formula closed to the experimental values, whilst the estimating settlement closed to the measured values obtained in the field test.

  10. Stress, strain, and structural dynamics an interactive handbook of formulas, solutions, and Matlab toolboxes

    CERN Document Server

    Yang, Bingen

    2005-01-01

    Stress, Strain, and Structural Dynamics is a comprehensive and definitive reference to statics and dynamics of solids and structures, including mechanics of materials, structural mechanics, elasticity, rigid-body dynamics, vibrations, structural dynamics, and structural controls. This text integrates the development of fundamental theories, formulas and mathematical models with user-friendly interactive computer programs, written in the powerful and popular MATLAB. This unique merger of technical referencing and interactive computing allows instant solution of a variety of engineering problems

  11. Combining Facial Dynamics With Appearance for Age Estimation

    NARCIS (Netherlands)

    Dibeklioğlu, H.; Alnajar, F.; Salah, A.A.; Gevers, T.

    2015-01-01

    Estimating the age of a human from the captured images of his/her face is a challenging problem. In general, the existing approaches to this problem use appearance features only. In this paper, we show that in addition to appearance information, facial dynamics can be leveraged in age estimation. We

  12. Aging affects attunement in perceiving length by dynamic touch

    NARCIS (Netherlands)

    Withagen, Rob; Caljouw, Simone R.

    2011-01-01

    Earlier studies have revealed age-dependent differences in perception by dynamic touch. In the present study, we examined whether the capacity to learn deteriorates with aging. Adopting an ecological approach to learning, the authors examined the process of attunement-that is, the changes in what in

  13. Effect of Agave tequilana age, cultivation field location and yeast strain on tequila fermentation process.

    Science.gov (United States)

    Pinal, L; Cornejo, E; Arellano, M; Herrera, E; Nuñez, L; Arrizon, J; Gschaedler, A

    2009-05-01

    The effect of yeast strain, the agave age and the cultivation field location of agave were evaluated using kinetic parameters and volatile compound production in the tequila fermentation process. Fermentations were carried out with Agave juice obtained from two cultivation fields (CF1 and CF2), as well as two ages (4 and 8 years) and two Saccharomyces cerevisiae yeast strains (GU3 and AR5) isolated from tequila fermentation must. Sugar consumption and ethanol production varied as a function of cultivation field and agave age. The production of ethyl acetate, 1-propanol, isobutanol and amyl alcohols were influenced in varying degrees by yeast strain, agave age and cultivation field. Methanol production was only affected by the agave age and 2-phenylethanol was influenced only by yeast strain. This work showed that the use of younger Agave tequilana for tequila fermentation resulted in differences in sugar consumption, ethanol and volatile compounds production at the end of fermentation, which could affect the sensory quality of the final product.

  14. Emotional Dynamics in the Age of Misinformation.

    Science.gov (United States)

    Zollo, Fabiana; Novak, Petra Kralj; Del Vicario, Michela; Bessi, Alessandro; Mozetič, Igor; Scala, Antonio; Caldarelli, Guido; Quattrociocchi, Walter

    2015-01-01

    According to the World Economic Forum, the diffusion of unsubstantiated rumors on online social media is one of the main threats for our society. The disintermediated paradigm of content production and consumption on online social media might foster the formation of homogeneous communities (echo-chambers) around specific worldviews. Such a scenario has been shown to be a vivid environment for the diffusion of false claim. Not rarely, viral phenomena trigger naive (and funny) social responses-e.g., the recent case of Jade Helm 15 where a simple military exercise turned out to be perceived as the beginning of the civil war in the US. In this work, we address the emotional dynamics of collective debates around distinct kinds of information-i.e., science and conspiracy news-and inside and across their respective polarized communities. We find that for both kinds of content the longer the discussion the more the negativity of the sentiment. We show that comments on conspiracy posts tend to be more negative than on science posts. However, the more the engagement of users, the more they tend to negative commenting (both on science and conspiracy). Finally, zooming in at the interaction among polarized communities, we find a general negative pattern. As the number of comments increases-i.e., the discussion becomes longer-the sentiment of the post is more and more negative.

  15. An age-structured population balance model for microbial dynamics

    Directory of Open Access Journals (Sweden)

    Duarte M.V.E.

    2003-01-01

    Full Text Available This work presents an age-structured population balance model (ASPBM for a bioprocess in a continuous stirred-tank fermentor. It relates the macroscopic properties and dynamic behavior of biomass to the operational parameters and microscopic properties of cells. Population dynamics is governed by two time- and age-dependent density functions for living and dead cells, accounting for the influence of substrate and dissolved oxygen concentrations on cell division, aging and death processes. The ASPBM described biomass and substrate oscillations in aerobic continuous cultures as experimentally observed. It is noteworthy that a small data set consisting of nonsegregated measurements was sufficient to adjust a complex segregated mathematical model.

  16. Positive explorers: modeling dynamic control in normal aging.

    Science.gov (United States)

    Glass, Brian D; Osman, Magda

    2017-01-01

    Situations in which there are multiple changes occurring all at once and which demand complex decisions to be made are common throughout life, but little is known about how normal aging influences performance on these types of scenarios. To determine performance differences associated with normal aging, we test older and younger adults in a dynamic control task. The task involves the control of a single output variable over time via multiple and uncertain input controls. The Single Limited Input, Dynamic Exploratory Responses (SLIDER) computational model, is implemented to determine the behavioral characteristics associated with normal aging in a dynamic control task. Model-based analysis demonstrates a unique performance signature profile associated with normal aging. Specifically, older adults exhibit a positivity effect in which they are more influenced by positively valenced feedback, congruent with previous research, as well as enhanced exploratory behavior.

  17. Dynamics of a seismogenic fault subject to variable strain rate

    Directory of Open Access Journals (Sweden)

    M. Dragoni

    2011-06-01

    Full Text Available The behaviour of seismogenic faults is generally investigated under the assumption that they are subject to a constant strain rate. We consider the effect of a slowly variable strain rate on the recurrence times of earthquakes generated by a single fault. To this aim a spring-block system is employed as a low-order analog of the fault. Two cases are considered: a sinusoidal oscillation in the driver velocity and a monotonic change from one velocity value to another. In the first case, a study of the orbit of the system in the state space suggests that the seismic activity of the equivalent fault is organized into cycles that include several earthquakes and repeat periodically. Within each cycle the recurrence times oscillate about an average value equal to the recurrence period for constant strain rate. In the second case, the recurrence time changes gradually from the value before the transition to the value following it. Asymptotic solutions are also given, approximating the case when the amplitude of the oscillation or of the monotonic change is much smaller than the average driver velocity and the period of oscillation or the duration of the transition is much longer than the recurrence times of block motions. If the system is not isolated but is subject to perturbations in stress, the perturbation anticipates or delays the subsequent earthquake. The effects of stress perturbations in the two cases of strain rate oscillations and monotonic change are considered.

  18. Effects of Sex, Strain, and Energy Intake on Hallmarks of Aging in Mice

    DEFF Research Database (Denmark)

    Mitchell, Sarah J.; Madrigal-Matute, Julio; Scheibye-Knudsen, Morten

    2016-01-01

    Calorie restriction (CR) is the most robust non-genetic intervention to delay aging. However, there are a number of emerging experimental variables that alter CR responses. We investigated the role of sex, strain, and level of CR on health and survival in mice. CR did not always correlate...

  19. Local strain-induced band gap fluctuations and exciton localization in aged WS2 monolayers

    Science.gov (United States)

    Krustok, J.; Kaupmees, R.; Jaaniso, R.; Kiisk, V.; Sildos, I.; Li, B.; Gong, Y.

    2017-06-01

    Optical properties of aged WS2 monolayers grown by CVD method on Si/SiO2 substrates are studied using temperature dependent photoluminescence and reflectance contrast spectroscopy. Aged WS2 monolayers have a typical surface roughness about 0.5 nm and, in addition, a high density of nanoparticles (nanocaps) with the base diameter about 30 nm and average height of 7 nm. The A-exciton of aged monolayer has a peak position at 1.951 eV while in as-grown monolayer the peak is at about 24 meV higher energy at room temperature. This red-shift is explained using local tensile strain concept, where strain value of 2.1% was calculated for these nanocap regions. Strained nanocaps have lower band gap energy and excitons will funnel into these regions. At T=10K a double exciton and trion peaks were revealed. The separation between double peaks is about 20 meV and the origin of higher energy peaks is related to the optical band gap energy fluctuations caused by random distribution of local tensile strain due to increased surface roughness. In addition, a wide defect related exciton band XD was found at about 1.93 eV in all aged monolayers. It is shown that the theory of localized excitons describes well the temperature dependence of peak position and halfwidth of the A-exciton band. The possible origin of nanocaps is also discussed.

  20. Strain aging and load relaxation behavior of type 316 stainless steel at room temperature

    Science.gov (United States)

    Hannula, S. P.; Korhonen, M. A.; Li, C. Y.

    1986-10-01

    The strain aging and load relaxation behavior of type 316 stainless steel (SS) at room temperature were studied. It is shown that rapid aging occurs in 316 SS at room temperature to an extent that affects the load relaxation behavior of the material. Qualitatively, the aging behavior was found to agree with those reported earlier for Fe-Ni-C-alloys, and the observed aging characteristics could be explained by using an earlier proposed vacancy-interstitial mechanism. The load relaxation behavior is analyzed in terms of Hart’s state variable model. Effects of strain aging and strain hardening on the load relaxation behavior and the scaling of the relaxation curves are determined. It is shown that aging can be accounted for by a time-dependent change in a model parameter, which is dependent on the mobile dislocation density and the dislocation mobility. In addition, a dependency on plastic state of the same parameter previously held constant was found. It is concluded that this phenomenon, which in 316 SS could be rationalized in terms of increasing forest dislocation density, is likely to be more general, and a provision for it should be made in the state variable theory.

  1. Effect of Temperature and Strain Rate on Dynamic Properties of Low Silicon TRIP Steel

    Institute of Scientific and Technical Information of China (English)

    TIAN Rong; LI Lin; B C De Cooman; WEI Xi-chen; SUN Peng

    2006-01-01

    The dynamic tensile test of 0.11C-0.62Si-1.65Mn TRIP steel was carried out at different strain rates and test temperatures. The results show that both temperature and strain rate affect the retained austenite transformation. At high strain rates, the uniform elongation decreases, whereas the total elongation and energy absorption increase. The tensile strength is less strain rate sensitive. With raising test temperature, the tensile strength is reduced and the mechanical properties generally deteriorate, especially at 110 ℃. However, excellent mechanical properties were obtained at 50 ℃ and 75 ℃.

  2. Dynamics of CRISPR Loci in Microevolutionary Process of Yersinia pestis Strains

    Science.gov (United States)

    Barros, Maria Paloma S.; França, Camila T.; Lins, Rosanny Holanda F. B.; Santos, Milena Danda V.; Silva, Ednaldo J.; Oliveira, Maria Betânia M.; Silveira-Filho, Vladimir M.; Rezende, Antônio M.; Balbino, Valdir Q.; Leal-Balbino, Tereza Cristina

    2014-01-01

    The potential use of CRISPR loci genotyping to elucidate population dynamics and microevolution of 146 Yersinia pestis strains from different biovars and locations was investigated in this work. The majority of strains from the Orientalis biovar presented specific spacer arrays, allowing for the establishment of a CRISPR signature for their respective isolates. Twenty-one new spacers were found in the Y. pestis strains from plague foci in Brazil. Ninety-three (64%) strains were grouped in the G1 genotype, whereas the others were distributed in 35 genotypes. This study allowed observing a microevolutionary process in a group of Y. pestis isolated from Brazil. We also identified specific genotypes of Y. pestis that were important for the establishment of the bacteria in plague foci in Brazil. The data have provided supporting evidence for the diversity and dynamics of CRISPR loci present in the genome of Y. pestis strains from plague foci in Brazil. PMID:25265542

  3. Dynamic strain measurement of hydraulic system pipeline using fibre Bragg grating sensors

    Directory of Open Access Journals (Sweden)

    Qiang Wang

    2016-04-01

    Full Text Available Fatigue failure is a serious problem in hydraulic piping systems installed in the machinery and equipment working in harsh operational conditions. To alleviate this problem, health monitoring of pipes can be conducted by measuring and analysing vibration-induced strain. Fibre Bragg grating is considered as a promising sensing approach for dynamic load monitoring. In this article, dynamic strain measurements based on fibre Bragg grating sensors for small-bore metal pipes have been investigated. The quasi-distributed strain sensing of fibre Bragg grating sensors is introduced. Two comparison experiments were carried out under vibration and impact loads among the methods of electrical strain gauge, piezoelectric accelerometer and fibre Bragg grating sensor. Experimental results indicate that fibre Bragg grating sensor possesses an outstanding ability to resist electromagnetic interference compared with strain gauge. The natural frequency measurement results, captured by fibre Bragg grating sensor, agree well with the modal analysis results obtained from finite element analysis. In addition, the attached fibre Bragg grating sensor brings a smaller impact on the dynamic characteristics of the measured pipe than the accelerometer due to its small size and lightweight. Fibre Bragg grating sensors have great potential for the quasi-distributed measurement of dynamic strain for the dynamic characteristic research and health monitoring of hydraulic system pipeline.

  4. Effect of strain-induced precipitation on dynamic recrystallization in Mg–Al–Sn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, Abu Syed Humaun, E-mail: abu.kabir@mail.mcgill.ca; Sanjari, Mehdi; Su, Jing; Jung, In-Ho; Yue, Stephen

    2014-10-20

    Two different amounts of tin (Sn) were added to a Mg–3 wt% Al binary alloy to form different amounts of precipitates during hot deformation. The thermodynamic modeling software, FactSage{sup ™}, was used to calculate the amounts of Sn to generate the desired relative levels of precipitation. The alloys were deformed at four different temperatures and three different strain rates to generate different amounts of precipitates. The objective was to study the effect of these precipitates on dynamic recrystallization. The results indicated that the formation of strain-induced precipitates is a function of deformation temperature, strain, and strain rate. The findings also revealed that higher amounts of precipitates reduced the volume fraction of dynamic recrystallization and refined the dynamically recrystallized grain size.

  5. Effect of strain field on displacement cascade in tungsten studied by molecular dynamics simulation

    Science.gov (United States)

    Wang, D.; Gao, N.; Wang, Z. G.; Gao, X.; He, W. H.; Cui, M. H.; Pang, L. L.; Zhu, Y. B.

    2016-10-01

    Using atomistic methods, the coupling effect of strain field and displacement cascade in body-centered cubic (BCC) tungsten is directly simulated by molecular dynamics (MD) simulations at different temperatures. The values of the hydrostatic and uniaxial (parallel or perpendicular to primary knock-on atom (PKA) direction) strains are from -2% to 2% and the temperature is from 100 to 1000 K. Because of the annealing effect, the influence of strain on radiation damage at low temperature has been proved to be more significant than that at high temperature. When the cascade proceeds under the hydrostatic strain, the Frenkel Pair (FP) production, the fraction of defect in cluster and the average size of the defect cluster, all increase at tensile state and decrease at compressive state. When the cascade is under uniaxial strain, the effect of strain parallel to PKA direction is less than the effect of hydrostatic strain, while the effect of strain perpendicular to PKA direction can be negligible. Under the uniaxial strain along direction, the SIA and SIA cluster is observed to orientate along the strain direction at tensile state and the uniaxial compressive strain with direction perpendicular to has led to the similar preferred nucleation. All these results indicate that under irradiation, the tensile state should be avoided for materials used in nuclear power plants.

  6. Ageing of atrazine in manure amended soils assessed by bioavailability to Pseudomonas sp. strain ADP.

    Science.gov (United States)

    Glæsner, Nadia; Bælum, Jacob; Strobel, Bjarne W; Jacobsen, Carsten S

    2014-04-01

    Animal manure is applied to agricultural land in areas of high livestock production. In the present study, we evaluated ageing of atrazine in two topsoils with and without addition of manure and in one subsoil. Ageing was assessed as the bioavailability of atrazine to the atrazine mineralizing bacteria Pseudomonas sp. strain ADP. Throughout an ageing period of 90 days bioavailability was investigated at days 1, 10, 32, 60 and 90, where ~10(8) cells g(-1) of the ADP strain was inoculated to the (14)C-atrazine exposed soil and (14)CO2 was collected over 7 days as a measure of mineralized atrazine. Even though the bioavailable residue decreased in all of the three soils as time proceeded, we found that ageing occurred faster in the topsoils rich in organic carbon than in subsoil. For one topsoil rich in organic carbon content, Simmelkær, we observed a higher degree of ageing when treated with manure. Contrarily, sorption experiments showed less sorption to Simmelkær treated with manure than the untreated soil indicating that sorption processes are not the only mechanisms of ageing. The other topsoil low in organic carbon content, Ringe, showed no significant difference in ageing between the manure-treated and untreated soil. The present study illustrates that not simply the organic carbon content influences adsorption and ageing of atrazine in soil but the origin and composition of organic matter plays an important role.

  7. A smile can reveal your age: enabling facial dynamics in age estimation

    NARCIS (Netherlands)

    Dibeklioğlu, H.; Gevers, T.; Salah, A.A.; Valenti, R.; Babaguchi, N.; Aizawa, K.; Smith, J.

    2012-01-01

    Estimation of a person's age from the facial image has many applications, ranging from biometrics and access control to cosmetics and entertainment. Many image-based methods have been proposed for this problem. In this paper, we propose a method for the use of dynamic features in age estimation, and

  8. Experimental study of dynamic mechanical properties of reactive powder concrete under high-strain-rate impacts

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The dynamic mechanical properties of reactive powder concrete subjected to compressive impacts with high strain rates ranging from 10 to 1.1×102 s-1 were investigated by means of SHPB (split-Hopkinson-pressure-bar) tests of the cylindrical specimens with five different steel fiber volumetric fractions.The properties of wave stress transmission,failure,strength,and energy consumption of RPC with varied fiber volumes and impact strain rates were analyzed.The influences of impact strain rates and fiber volumes on those properties were characterized as well.The general forms of the dynamic stress-strain relationships of RPC were modeled based on the experimental data.The investigations indicate that for the plain RPC the stress response is greater than the strain response,showing strong brittle performance.The RPC with a certain volume of fibers sustains higher strain rate impact and exhibits better deformability as compared with the plain RPC.With a constant fiber fraction,the peak compressive strength,corresponding peak strain and the residual strain of the fiber-reinforced RPC rise by varying amounts when the impact strain rate increases,with the residual strain demonstrating the greatest increment.Elevating the fiber content makes trivial contribution to improving the residual deformability of RPC when the impact strain rate is constant.The tests also show that the fiber content affects the peak compressive strength and the peak deformability of RPC in a different manner.With a constant impact strain rate and the fiber fraction less than 1.75%,the peak compressive strength rises with an increasing fiber volume.The peak compressive strength tends to decrease as the fiber volume exceeds 1.75%.The corresponding peak strain,however,incessantly rises with the increasing fiber volume.The total energy Edisp that RPC consumed during the period from the beginning of impacts to the time of residual strains elevates with the fiber volume increment as long as the fiber

  9. Complex systems dynamics in aging: new evidence, continuing questions.

    Science.gov (United States)

    Cohen, Alan A

    2016-02-01

    There have long been suggestions that aging is tightly linked to the complex dynamics of the physiological systems that maintain homeostasis, and in particular to dysregulation of regulatory networks of molecules. This review synthesizes recent work that is starting to provide evidence for the importance of such complex systems dynamics in aging. There is now clear evidence that physiological dysregulation--the gradual breakdown in the capacity of complex regulatory networks to maintain homeostasis--is an emergent property of these regulatory networks, and that it plays an important role in aging. It can be measured simply using small numbers of biomarkers. Additionally, there are indications of the importance during aging of emergent physiological processes, functional processes that cannot be easily understood through clear metabolic pathways, but can nonetheless be precisely quantified and studied. The overall role of such complex systems dynamics in aging remains an important open question, and to understand it future studies will need to distinguish and integrate related aspects of aging research, including multi-factorial theories of aging, systems biology, bioinformatics, network approaches, robustness, and loss of complexity.

  10. Dynamic Mechanical Response of Biomedical 316L Stainless Steel as Function of Strain Rate and Temperature.

    Science.gov (United States)

    Lee, Woei-Shyan; Chen, Tao-Hsing; Lin, Chi-Feng; Luo, Wen-Zhen

    2011-01-01

    A split Hopkinson pressure bar is used to investigate the dynamic mechanical properties of biomedical 316L stainless steel under strain rates ranging from 1 × 10(3) s(-1) to 5 × 10(3) s(-1) and temperatures between 25°C and 800°C. The results indicate that the flow stress, work-hardening rate, strain rate sensitivity, and thermal activation energy are all significantly dependent on the strain, strain rate, and temperature. For a constant temperature, the flow stress, work-hardening rate, and strain rate sensitivity increase with increasing strain rate, while the thermal activation energy decreases. Catastrophic failure occurs only for the specimens deformed at a strain rate of 5 × 10(3) s(-1) and temperatures of 25°C or 200°C. Scanning electron microscopy observations show that the specimens fracture in a ductile shear mode. Optical microscopy analyses reveal that the number of slip bands within the grains increases with an increasing strain rate. Moreover, a dynamic recrystallisation of the deformed microstructure is observed in the specimens tested at the highest temperature of 800°C.

  11. [The dynamics of physical work capacity among ageing truck drivers].

    Science.gov (United States)

    Khurtsilava, O G; Bashkireva, A S; Khavinson, V Kh

    2013-01-01

    The studies of biological age, ageing rate, physical work capacity in professional lorry drivers were conducted. The examination revealed peculiarities of system organization of functions, which determine the physical work capacity levels. Dynamics of the ageing process of professional driver's organism in relation with calendar age and driving experience were shown using the biological age on physical work capacity model. The results point at the premature decrease of the physical work capacity in professional drivers. There was revealed premature contraction of the range of cardio-vascular system adaptive reactions on submaximum physical load in the drivers as compared with control group. It was proved, that premature age-related changes of physiologic indices in drivers are just "risk indicators", while long driving experience is a real risk factor, accelerating the ageing process. The "risk group" with manifestations of accelerating ageing was observed in 40-49-year old drivers with 15-19 years of professional experience. There was demonstrated the expediency of using the following methods for the age rate estimation according to biologic age indices and necessity of prophylactic measures for premature and accelerated ageing prevention among working population.

  12. Work strain in midlife and old age disability: A longitudinal study with 23 years of follow up.

    OpenAIRE

    Ghamari, Vanessa

    2014-01-01

    Increasing parts of the world are facing ageing societies with growing figures of morbidity and disability. Focus of attention for European countries is directed towards prevention of old age impairment. As considerable time is spent at work, preventative psychosocial work environment measures could be entry points for a healthier ageing. The aims of this study are to i) explore the impact of mid-life work strain on old age disability ii) to examine the independent effects of the work strain ...

  13. Determination of a dynamic feeding strategy for recombinant Pichia pastoris strains.

    Science.gov (United States)

    Spadiut, Oliver; Dietzsch, Christian; Herwig, Christoph

    2014-01-01

    The knowledge of certain strain specific parameters of recombinant P. pastoris strains is required to be able to set up a feeding regime for fed-batch cultivations. To date, these parameters are commonly determined either by time-consuming and labor-intensive continuous cultivations or by several, consecutive fed-batch cultivations. Here, we describe a fast method based on batch experiments with methanol pulses to extract certain strain characteristic parameters, which are required to set up a dynamic feeding strategy for P. pastoris strains based on specific substrate uptake rate (q(s)). We further describe in detail the course of actions which have to be taken to obtain the desired dynamics during feeding.

  14. Nanoparticle monolayer-based flexible strain gauge with ultrafast dynamic response for acoustic vibration detection

    Institute of Scientific and Technical Information of China (English)

    Lizhi Yi[1; Weihong Jiao[1; Ke Wu[1; Lihua Qian[1; Xunxing Yu[2; Qi Xia[2; Kuanmin Mao[2; Songliu Yuan[1; Shuai Wang[3; Yingtao Jiang[4

    2015-01-01

    The relatively poor dynamic response of current flexible strain gauges has prevented their wide adoption in portable electronics. In this work, we present a greatly improved flexible strain gauge, where one strip of Au nanoparticle (NP) monolayer assembled on a polyethylene terephthalate film is utilized as the active unit. The proposed flexible gauge is capable of responding to applied stimuli without detectable hysteresis via electron tunneling between adjacent nanoparticles within the Au NP monolayer. Based on experimental quantification of the time and frequency domain dependence of the electrical resistance of the proposed strain gauge, acoustic vibrations in the frequency range of 1 to 20,000 Hz could be reliably detected. In addition to being used to measure musical tone, audible speech, and creature vocalization, as demonstrated in this study, the ultrafast dynamic response of this flexible strain gauge can be used in a wide range of applications, including miniaturized vibratory sensors, safe entrance guard management systems, and ultrasensitive pressure sensors.

  15. Quantitative imaging of heterogeneous dynamics in drying and aging paints.

    Science.gov (United States)

    van der Kooij, Hanne M; Fokkink, Remco; van der Gucht, Jasper; Sprakel, Joris

    2016-09-29

    Drying and aging paint dispersions display a wealth of complex phenomena that make their study fascinating yet challenging. To meet the growing demand for sustainable, high-quality paints, it is essential to unravel the microscopic mechanisms underlying these phenomena. Visualising the governing dynamics is, however, intrinsically difficult because the dynamics are typically heterogeneous and span a wide range of time scales. Moreover, the high turbidity of paints precludes conventional imaging techniques from reaching deep inside the paint. To address these challenges, we apply a scattering technique, Laser Speckle Imaging, as a versatile and quantitative tool to elucidate the internal dynamics, with microscopic resolution and spanning seven decades of time. We present a toolbox of data analysis and image processing methods that allows a tailored investigation of virtually any turbid dispersion, regardless of the geometry and substrate. Using these tools we watch a variety of paints dry and age with unprecedented detail.

  16. Experimental study on structural defect detection by monitoring distributed dynamic strain

    Science.gov (United States)

    Liu, R. M.; Babanajad, S. K.; Taylor, T.; Ansari, F.

    2015-11-01

    A defect detection method of civil structures is studied. In order to complete the task, the proposed detection method is based on the analysis of distributed dynamic strains using Brillouin scattering based fiber optic sensors along large span structures. The current challenges in the detection of localized damage fundamentally include monitoring the dynamic strain as well as eliminating the system noise and the distortion of the changing distributed strain. Due to the capability of Brillouin scattering based methods in distributed monitoring of large structures, Brillouin optical time-domain analysis approach is implemented for assessing damage. In order to highlight the singularity at the damage location, Fourier as well as dual tree complex wavelet transform approaches were conducted. During the processing, the dynamic distributed strain in the time domain was transformed into the frequency domain for extraction of natural and forced frequencies. Then, the data was decomposed, filtered for extraction of crack features and reconstructed. The feasibility of the proposed method is evaluated through an experimental program involving the use of pulse-pre-pump Brillouin optical time domain analysis for the distributed measurement of dynamic strain with 13 Hz sampling speed and detection of simulated cracks in a 15 m long steel beam. The beam mimics a bridge girder with two artificial cracks along its length subjected to free and forced vibrations. The results indicate that the method based on the discontinuities in the strain distribution is applicable in the detection of very small damage as small as 40 micro strains. A crack gauge independently monitored the crack opening displacements during the experiments, and the limit of detected crack openings based on the first appearance of strain singularities was 30 μm.

  17. Dynamic High-Temperature Characterization of an Iridium Alloy in Compression at High Strain Rates

    Energy Technology Data Exchange (ETDEWEB)

    Song, Bo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Experimental Environment Simulation Dept.; Nelson, Kevin [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials Dept.; Lipinski, Ronald J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Nuclear Fuel Cycle Technology Dept.; Bignell, John L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Structural and Thermal Analysis Dept.; Ulrich, G. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Radioisotope Power Systems Program; George, E. P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Radioisotope Power Systems Program

    2014-06-01

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-temperature high-strain-rate performance are needed for understanding high-speed impacts in severe elevated-temperature environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain-rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. Current high-temperature Kolsky compression bar techniques are not capable of obtaining satisfactory high-temperature high-strain-rate stress-strain response of thin iridium specimens investigated in this study. We analyzed the difficulties encountered in high-temperature Kolsky compression bar testing of thin iridium alloy specimens. Appropriate modifications were made to the current high-temperature Kolsky compression bar technique to obtain reliable compressive stress-strain response of an iridium alloy at high strain rates (300 – 10000 s-1) and temperatures (750°C and 1030°C). Uncertainties in such high-temperature high-strain-rate experiments on thin iridium specimens were also analyzed. The compressive stress-strain response of the iridium alloy showed significant sensitivity to strain rate and temperature.

  18. Dynamic tensile fracture of mortar at ultra-high strain-rates

    Energy Technology Data Exchange (ETDEWEB)

    Erzar, B., E-mail: benjamin.erzar@cea.fr; Buzaud, E.; Chanal, P.-Y. [CEA, DAM, GRAMAT, F-46500 Gramat (France)

    2013-12-28

    During the lifetime of a structure, concrete and mortar may be exposed to highly dynamic loadings, such as impact or explosion. The dynamic fracture at high loading rates needs to be well understood to allow an accurate modeling of this kind of event. In this work, a pulsed-power generator has been employed to conduct spalling tests on mortar samples at strain-rates ranging from 2 × 10{sup 4} to 4 × 10{sup 4} s{sup −1}. The ramp loading allowed identifying the strain-rate anytime during the test. A power law has been proposed to fit properly the rate-sensitivity of tensile strength of this cementitious material over a wide range of strain-rate. Moreover, a specimen has been recovered damaged but unbroken. Micro-computed tomography has been employed to study the characteristics of the damage pattern provoked by the dynamic tensile loading.

  19. Note: Dynamic strain field mapping with synchrotron X-ray digital image correlation

    Energy Technology Data Exchange (ETDEWEB)

    Lu, L. [CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027 (China); The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610207 (China); Fan, D.; Luo, S. N., E-mail: sluo@pims.ac.cn [The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610207 (China); Bie, B. X. [The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610207 (China); School of Science, Wuhan University of Technology, Wuhan, Hubei 430070 (China); Ran, X. X.; Qi, M. L., E-mail: qiml@whut.edu.cn [School of Science, Wuhan University of Technology, Wuhan, Hubei 430070 (China); Parab, N.; Sun, J. Z.; Liao, H. J.; Hudspeth, M. C.; Claus, B. [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States); Fezzaa, K.; Sun, T. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Chen, W. [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States); School of Material Science Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Gong, X. L., E-mail: gongxl@ustc.edu.cn [CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027 (China)

    2014-07-15

    We present a dynamic strain field mapping method based on synchrotron X-ray digital image correlation (XDIC). Synchrotron X-ray sources are advantageous for imaging with exceptional spatial and temporal resolutions, and X-ray speckles can be produced either from surface roughness or internal inhomogeneities. Combining speckled X-ray imaging with DIC allows one to map strain fields with high resolutions. Based on experiments on void growth in Al and deformation of a granular material during Kolsky bar/gas gun loading at the Advanced Photon Source beamline 32ID, we demonstrate the feasibility of dynamic XDIC. XDIC is particularly useful for dynamic, in-volume, measurements on opaque materials under high strain-rate, large, deformation.

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

    Science.gov (United States)

    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.

  1. Nucleation mechanisms of dynamic recrystallization in Inconel 625 superalloy deformed with different strain rates

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The effects of strain rates on the hot working characteristics and nucleation mechanisms of dynamic recrystallization (DRX) were studied by optical microscopy and electron backscatter diffraction (EBSD) technique. Hot compression tests were conducted using a Gleeble-1500 simulator at a true strain of 0.7 in the temperature range of 1000 to 1150 °C and strain rate range of 0.01 to 10.00 s-1. It is found that the size and volume fraction of the DRX grains in hot-deformed Inconel 625 superalloy firstly decreas...

  2. A molecular-dynamics study of defects and failure mechanisms in strained heteroepitaxial interfaces

    Science.gov (United States)

    Schiffbauer, Jarrod E.; Bachlechner, Martina E.

    2006-03-01

    The formation and growth of pits and pit-like structures through a delamination-driven mechanism have been observed in the analysis of comprehensive molecular dynamics simulations of a laterally strained Si(111)/Si3N4(0001) interfacial system. These phenomena contribute to the ultimate mechanical failure of the simulated samples. Several factors play a key role the nucleation and growth of the pits including temperature and strain rate. Here we present an overview of the dependence of pit nucleation and morphology on both global and local conditions for a representative range of temperatures and applied strain rates.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. Dynamic strain measurements of marine propellers under non-uniform inflow

    Science.gov (United States)

    Tian, Jin; Croaker, Paul; Zhang, Zhiyi; Hua, Hongxing

    2016-09-01

    An experimental investigation was conducted to determine the dynamic strain characteristics of marine propellers under non-uniform inflow. Two 7-bladed highly skewed model propellers of identical geometries, but different elastic characteristics were tested at various rotational speeds and free stream velocities in the water tunnel. Two kinds of wire mesh wake screens located 400mm upstream of the propeller plane were used to generate four-cycle and six-cycle inflows. A laser doppler velocimetry (LDV) system located 100mm downstream of the wake screen plane was used to measure the axial velocity distributions produced by the wake screens. Strain gauges were bonded onto the propeller blades in different positions. A customized underwater data acquisition system which can record data off-line was used to record the dynamic strain. The results show that the frequency properties of the blade dynamic strain are determined by the harmonics of the inflow and that the stiffness of the propeller has an essential effect on the dynamic strain amplitudes.

  5. Dynamic tensile behavior of AZ31B magnesium alloy at ultra-high strain rates

    Directory of Open Access Journals (Sweden)

    Geng Changjian

    2015-04-01

    Full Text Available The samples having {0001} parallel to extruding direction (ED present a typical true stress–true strain curve with concave-down shape under tension at low strain rate. Ultra-rapid tensile tests were conducted at room temperature on a textured AZ31B magnesium alloy. The dynamic tensile behavior was investigated. The results show that at ultra-high strain rates of 1.93 × 102 s−1 and 1.70 × 103 s−1, the alloy behaves with a linear stress–strain response in most strain range and exhibits a brittle fracture. In this case, {10-12}  extension twinning is basic deformation mode. The brittleness is due to the macroscopic viscosity at ultra-high strain rate, for which the external critical shear stress rapidly gets high to result in a cleavage fracture before large amounts of dislocations are activated. Because {10-12} tension twinning, {10-11} compressive twinning, basal slip, prismatic slip and pyramidal slip have different critical shear stresses (CRSS, their contributions to the degree of deformation are very differential. In addition, Schmid factor plays an important role in the activity of various deformation modes and it is the key factor for the samples with different strain rates exhibit various mechanical behavior under dynamic tensile loading.

  6. Dynamic tensile behaviour and deformational mechanism of C5191 phosphor bronze under high strain rates deformation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Dao-chun [College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Mechanical and Electrical Engineering, Taizhou Vocational & Technical College, Taizhou 318000 (China); Chen, Ming-he, E-mail: meemhchen@nuaa.edu.cn [College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Wang, Lei; Cheng, Hu [College of Mechanical Engineering, Taizhou University, Taizhou 318000 (China)

    2016-01-01

    High speed stamping process is used to high strength and high electrical conductivity phosphor bronze with extremely high strain rates more than 10{sup 3} s{sup −1}. This study on the dynamic tensile behaviour and deformational mechanism is to optimise the high speed stamping processes and improve geometrical precision in finished products. Thus, the tensile properties and deformation behaviour of C5191 phosphor bronze under quasi-static tensile condition at a strain rate of 0.001 s{sup −1} by electronic universal testing machine, and dynamic tensile condition at strain rate of 500, 1000 and 1500 s{sup −1} by split Hopkinson tensile bar (SHTB) apparatus were studied. The effects of strain rate and the deformation mechanism were investigated by means of SEM and TEM. The results showed that the yield strength and tensile strength of C5191 phosphor bronze under high strain rates deformation increased by 32.77% and 11.07% respectively compared with quasi-static condition, the strain hardening index increases from 0.075 to 0.251, and the strength of the material strain rates sensitivity index change from 0.005 to 0.022, which presented a clear sensitive to strain rates. Therefore, it is claimed that the dominant deformation mechanism was changed by the dislocation motion under different strain rates, and the ability of plastic deformation of C5191 phosphor bronze increased due to the number of movable dislocations increased significantly, started multi-line slip, and the soft effect of adiabatic temperature rise at the strain rate ranging from 500 to 1500 s{sup −1}.

  7. The Stochastic Multi-strain Dengue Model: Analysis of the Dynamics

    Science.gov (United States)

    Aguiar, Maíra; Stollenwerk, Nico; Kooi, Bob W.

    2011-09-01

    Dengue dynamics is well known to be particularly complex with large fluctuations of disease incidences. An epidemic multi-strain model motivated by dengue fever epidemiology shows deterministic chaos in wide parameter regions. The addition of seasonal forcing, mimicking the vectorial dynamics, and a low import of infected individuals, which is realistic in the dynamics of infectious diseases epidemics show complex dynamics and qualitatively a good agreement between empirical DHF monitoring data and the obtained model simulation. The addition of noise can explain the fluctuations observed in the empirical data and for large enough population size, the stochastic system can be well described by the deterministic skeleton.

  8. Covariance of dynamic strain responses for structural damage detection

    Science.gov (United States)

    Li, X. Y.; Wang, L. X.; Law, S. S.; Nie, Z. H.

    2017-10-01

    A new approach to address the practical problems with condition evaluation/damage detection of structures is proposed based on the distinct features of a new damage index. The covariance of strain response function (CoS) is a function of modal parameters of the structure. A local stiffness reduction in structure would cause monotonous increase in the CoS. Its sensitivity matrix with respect to local damages of structure is negative and narrow-banded. The damage extent can be estimated with an approximation to the sensitivity matrix to decouple the identification equations. The CoS sensitivity can be calibrated in practice from two previous states of measurements to estimate approximately the damage extent of a structure. A seven-storey plane frame structure is numerically studied to illustrate the features of the CoS index and the proposed method. A steel circular arch in the laboratory is tested. Natural frequencies changed due to damage in the arch and the damage occurrence can be judged. However, the proposed CoS method can identify not only damage happening but also location, even damage extent without need of an analytical model. It is promising for structural condition evaluation of selected components.

  9. The role of telomere dynamics in aging and cancer

    Science.gov (United States)

    Blagoev, Krastan; Goodwin, Edwin

    2006-03-01

    Telomere length changes are far more dynamic than previously thought. In addition to a gradual loss of ˜100 base pairs per telomere in each cell division, losses as well as gains may occur within a single cell cycle. We are investigating how telomere exchange, extension, and deletion affect the proliferative potential of telomerase-negative somatic cells. Experimental techniques are being devised to detect dynamic telomere processes and quantify both the frequency and length changes of each. In parallel, a ``dynamic telomere model'' is being used that incorporates telomere dynamics to study how the telomere size distribution evolves with time. This is an essential step towards understanding the role that telomere dynamics play in the normal aging of tissues and organisms. The model casts light on relationships not otherwise easily explained by a deterministic ``mitotic clock,'' or to what extent the shortest initial telomere determines the onset of senescence. We also expect to identify biomarkers that will correlate with aging better than average telomere length and to shed light on the transition to unlimited growth found in telomerase-negative tumor cells having the ALT (alternative lengthening of telomeres) phenotype, and to evaluate strategies to suppress the growth of these tumors.

  10. The Dynamic Tensile Behavior of Railway Wheel Steel at High Strain Rates

    Science.gov (United States)

    Jing, Lin; Han, Liangliang; Zhao, Longmao; Zhang, Ying

    2016-11-01

    The dynamic tensile tests on D1 railway wheel steel at high strain rates were conducted using a split Hopkinson tensile bar (SHTB) apparatus, compared to quasi-static tests. Three different types of specimens, which were machined from three different positions (i.e., the rim, web and hub) of a railway wheel, were prepared and examined. The rim specimens were checked to have a higher yield stress and ultimate tensile strength than those web and hub specimens under both quasi-static and dynamic loadings, and the railway wheel steel was demonstrated to be strain rate dependent in dynamic tension. The dynamic tensile fracture surfaces of all the wheel steel specimens are cup-cone-shaped morphology on a macroscopic scale and with the quasi-ductile fracture features on the microscopic scale.

  11. Characterization of dynamic three-dimensional strain fields in the canine radius.

    Science.gov (United States)

    Coleman, John C; Hart, Richard T; Owan, Ichiro; Tankano, Yuichi; Burr, David B

    2002-12-01

    This note describes a method to approximate the 3-D mechanical environment of a long bone during a normal daily activity. Our specific goal was to characterize the temporal and spatial strain distributions in the mid-shaft region of the canine radius during gait. Direct measurement of strains along the entire surface of in vivo bone is not feasible, so we employed a combination of experimental measurements and numerical interpolation techniques to approximate the time-varying longitudinal strain distribution. Using standard in vivo strain gauging techniques, we measured dynamic strains at nine locations (three locations on each of three cross sections, data pooled from two experimental animals) on the canine radius during trotting gait. These in vivo strain measurements were then used to approximate the time course of the strain field for the entire radius mid-shaft region using a 3-D numerical interpolation scheme using finite element basis functions. Despite limitations in the present implementation of the method, the results show that there are considerable time-dependent variations in the strain distribution occurring at different transverse sections along the length of the diaphysis with substantial anteroposterior bending and rotation of neutral axis locations during the gait cycle.

  12. Dynamic energy budget approaches for modelling organismal ageing.

    Science.gov (United States)

    van Leeuwen, Ingeborg M M; Vera, Julio; Wolkenhauer, Olaf

    2010-11-12

    Ageing is a complex multifactorial process involving a progressive physiological decline that, ultimately, leads to the death of an organism. It involves multiple changes in many components that play fundamental roles under healthy and pathological conditions. Simultaneously, every organism undergoes accumulative 'wear and tear' during its lifespan, which confounds the effects of the ageing process. The scenario is complicated even further by the presence of both age-dependent and age-independent competing causes of death. Various manipulations have been shown to interfere with the ageing process. Calorie restriction, for example, has been reported to increase the lifespan of a wide range of organisms, which suggests a strong relation between energy metabolism and ageing. Such a link is also supported within the main theories for ageing: the free radical hypothesis, for instance, links oxidative damage production directly to energy metabolism. The Dynamic Energy Budgets (DEB) theory, which characterizes the uptake and use of energy by living organisms, therefore constitutes a useful tool for gaining insight into the ageing process. Here we compare the existing DEB-based modelling approaches and, then, discuss how new biological evidence could be incorporated within a DEB framework.

  13. Dynamical properties of the brain tissue under oscillatory shear stresses at large strain range

    Science.gov (United States)

    Boudjema, F.; Khelidj, B.; Lounis, M.

    2017-01-01

    In this experimental work, we study the viscoelastic behaviour of in vitro brain tissue, particularly the white matter, under oscillatory shear strain. The selective vulnerability of this tissue is the anisotropic mechanical properties of theirs different regions lead to a sensitivity to the angular shear rate and magnitude of strain. For this aim, shear storage modulus (G‧) and loss modulus (G″) were measured over a range of frequencies (1 to 100 Hz), for different levels of strain (1 %, to 50 %). The mechanical responses of the brain matter samples showed a viscoelastic behaviour that depend on the correlated strain level and frequency range and old age sample. The samples have been showed evolution behaviour by increasing then decreasing the strain level. Also, the stiffness anisotropy of brain matter was showed between regions and species.

  14. Observation of a new dynamic recovery mechanism in the high strain regime

    DEFF Research Database (Denmark)

    Yu, Tianbo; Hansen, Niels; Huang, Xiaoxu;

    2014-01-01

    lamellar boundaries connected by triple junctions. Here we report that mechanically assisted triple junction motion is an important mechanism of dynamic recovery, and it replaces two boundaries by one, while maintaining the structural morphology. The observation rationalizes many features of the evolution......Plastic deformation of metals refines the microstructure and increases the strength through work hardening, but this effect of deformation is counterbalanced by dynamic recovery. After deformation to large strains, the microstructure typically shows a lamellar morphology, with finely spaced...

  15. Investment age and dynamic productivity growth in the Spanish food processing industry

    NARCIS (Netherlands)

    Kapelko, Magda; Oude Lansink, A.G.J.M.; Stefanou, S.E.

    2016-01-01

    This article analyzes the relation between investment age, measured as the number of years since investment spike, and dynamic productivity growth and its components, which include dynamic technical change, dynamic inefficiency change, and dynamic scale inefficiency change. The empirical application

  16. Dynamical heterogeneity in aging colloidal glasses of Laponite

    Science.gov (United States)

    Jabbari-Farouji, S.; Zargar, R.; Wegdam, G. H.; Bonn, Daniel

    Glasses behave as solids due to their long relaxation time; however the origin of this slow response remains a puzzle. Growing dynamic length scales due to cooperative motion of particles are believed to be central to the understanding of both the slow dynamics and the emergence of rigidity. Here, we provide experimental evidence of a growing dynamical heterogeneity length scale that increases with increasing waiting time in an aging colloidal glass of Laponite. The signature of heterogeneity in the dynamics follows from dynamic light scattering measurements in which we study both the rotational and translational diffusion of the disk-shaped particles of Laponite in suspension. These measurements are accompanied by simultaneous microrheology and macroscopic rheology experiments. We find that rotational diffusion of particles slows down at a faster rate than their translational motion. Such decoupling of translational and orientational degrees of freedom finds its origin in the dynamic heterogeneity since rotation and translation probe different length scales in the sample. The macroscopic rheology experiments show that the low frequency shear viscosity increases at a much faster rate than both rotational and translational diffusive relaxation times.

  17. Molecular dynamics simulations of the straining of nanoparticle chain aggregates: the case of copper

    Science.gov (United States)

    Dalis, Adamos; Friedlander, Sheldon K.

    2005-07-01

    Previous studies in our laboratory have shown that individual nanoparticle chain aggregates (NCAs) exhibit unusual mechanical behaviour when under strain inside the transmission electron microscope. NCAs made of various materials (e.g. carbon, metal oxides and metals) were strained by as much as 100% under tension. The nanoparticles that compose the chains were 5-10 nm in diameter and the chains of the order of 1 µm in length. Such aggregates are of technological importance in the manufacture of nanocomposite materials (e.g. rubber), aggregate break-up (e.g. sampling diesel emissions) and chemical-mechanical planarization. The goal of this study was to simulate the mechanical behaviour of chain aggregates with morphological properties similar to those of technological interest. Molecular dynamics (MD) and energy minimization computer simulations are employed to investigate, at the atomic scale, the behaviour of short nanoparticle aggregates under strain and to obtain quantitative information on the forces involved in aggregate straining and fracturing. The interaction potential used is that of copper obtained with the embedded atom method (EAM). Two seven-nanoparticle aggregates are studied, one linear and the other kinked. The seven nanoparticles in both aggregates are single crystals and about 2.5 nm in diameter each. The aggregates are strained along their longest dimension, to the breaking point, at strain rates spanning from 2.5 × 107 to 8.0 × 108 s-1 (MD simulations). The linear aggregate yield strain is about 0.1. The kinked aggregate elastic limit is also about 0.1, but only one-third of the stress develops along the straining direction compared to the linear aggregate. The kinked aggregate breaks at a strain of about 0.5, five times higher than the breaking strain of the linear aggregate. The ability of the kinked aggregate to straighten through combined nanoparticle interface sliding and rotation accounts for the extra strain accommodation. Simulation

  18. Molecular dynamics simulations of the straining of nanoparticle chain aggregates: the case of copper.

    Science.gov (United States)

    Dalis, Adamos; Friedlander, Sheldon K

    2005-07-01

    Previous studies in our laboratory have shown that individual nanoparticle chain aggregates (NCAs) exhibit unusual mechanical behaviour when under strain inside the transmission electron microscope. NCAs made of various materials (e.g. carbon, metal oxides and metals) were strained by as much as 100% under tension. The nanoparticles that compose the chains were 5-10 nm in diameter and the chains of the order of 1 µm in length. Such aggregates are of technological importance in the manufacture of nanocomposite materials (e.g. rubber), aggregate break-up (e.g. sampling diesel emissions) and chemical-mechanical planarization. The goal of this study was to simulate the mechanical behaviour of chain aggregates with morphological properties similar to those of technological interest. Molecular dynamics (MD) and energy minimization computer simulations are employed to investigate, at the atomic scale, the behaviour of short nanoparticle aggregates under strain and to obtain quantitative information on the forces involved in aggregate straining and fracturing. The interaction potential used is that of copper obtained with the embedded atom method (EAM). Two seven-nanoparticle aggregates are studied, one linear and the other kinked. The seven nanoparticles in both aggregates are single crystals and about 2.5 nm in diameter each. The aggregates are strained along their longest dimension, to the breaking point, at strain rates spanning from 2.5 × 10(7) to 8.0 × 10(8) s(-1) (MD simulations). The linear aggregate yield strain is about 0.1. The kinked aggregate elastic limit is also about 0.1, but only one-third of the stress develops along the straining direction compared to the linear aggregate. The kinked aggregate breaks at a strain of about 0.5, five times higher than the breaking strain of the linear aggregate. The ability of the kinked aggregate to straighten through combined nanoparticle interface sliding and rotation accounts for the extra strain accommodation

  19. Reflective SOA fiber cavity adaptive laser source for measuring dynamic strains

    Science.gov (United States)

    Wei, Heming; Tao, Chuanyi; Krishnaswamy, Sridhar

    2016-04-01

    Smart sensors based on Optical fiber Bragg gratings (FBGs) are suitable for structural health monitoring of dynamic strains in civil, aerospace, and mechanical structures. In these structures, dynamic strains with high frequencies reveal acoustic emissions cracking or impact loading. It is necessary to find a practical tool for monitoring such structural damages. In this work, we explore an intelligent system based on a reflective semiconductor optical amplifier (RSOA)- FBG composed as a fiber cavity for measuring dynamic strain in intelligent structures. The ASE light emitted from a RSOA laser and reflected by a FBG is amplified in the fiber cavity and coupled out by a 90:10 coupler, which is demodulated by a low frequency compensated Michelson interferometer using a proportional-integral-derivative (PID) controller and is monitored via a photodetector. As the wavelength of the FBG shifts due to dynamic strain, the wavelength of the optical output from the laser cavity shifts accordingly, which is demodulated by the Michelson Interferometer. Because the RSOA has a quick transition time, the RSOA- FBG fiber cavity shows an ability of high frequency response to the FBG reflective spectrum shift, with frequency response extending to megahertz.

  20. Studies on prolactin-secreting cells in aging rats of different strains. I. Alterations in pituitary histology and serum prolactin levels as related to ageing.

    NARCIS (Netherlands)

    Putten, van L.J.A.; Zwieten, van M.J.; Mattheij, J.A.M.; Kemenade, J.A.M.

    1988-01-01

    Serum PRL levels and histologically tumor-free pituitary glands of 91 aging rats of the BN/BiRij strain, the WAG/Rij strain and their F1 hybrid were studied. In rats with pituitary glands without signs of hyperplasia, serum PRL levels were, in comparison to rats of 15-24 months, increased 25-29-mont

  1. Telomere dynamics may link stress exposure and ageing across generations.

    Science.gov (United States)

    Haussmann, Mark F; Heidinger, Britt J

    2015-11-01

    Although exposure to stressors is known to increase disease susceptibility and accelerate ageing, evidence is accumulating that these effects can span more than one generation. Stressors experienced by parents have been reported to negatively influence the longevity of their offspring and even grand offspring. The mechanisms underlying these long-term, cross-generational effects are still poorly understood, but we argue here that telomere dynamics are likely to play an important role. In this review, we begin by surveying the current connections between stress and telomere dynamics. We then lay out the evidence that exposure to stressors in the parental generation influences telomere dynamics in offspring and potentially subsequent generations. We focus on evidence in mammalian and avian studies and highlight several promising areas where our understanding is incomplete and future investigations are critically needed. Understanding the mechanisms that link stress exposure across generations requires interdisciplinary studies and is essential to both the biomedical community seeking to understand how early adversity impacts health span and evolutionary ecologists interested in how changing environmental conditions are likely to influence age-structured population dynamics.

  2. Extracting full-field dynamic strain response of a rotating wind turbine using photogrammetry

    Science.gov (United States)

    Baqersad, Javad; Poozesh, Peyman; Niezrecki, Christopher; Avitabile, Peter

    2015-04-01

    Health monitoring of wind turbines is typically performed using conventional sensors (e.g. strain-gages and accelerometers) that are usually mounted to the nacelle or gearbox. Although many wind turbines stop operating due to blade failures, there are typically few to no sensor mounted on the blades. Placing sensors on the rotating parts of the structure is a challenge due to the wiring and data transmission constraints. Within the current work, an approach to monitor full-field dynamic response of rotating structures (e.g. wind turbine blades or helicopter rotors) is developed and experimentally verified. A wind turbine rotor was used as the test structure and was mounted to a block and horizontally placed on the ground. A pair of bearings connected to the rotor shaft allowed the turbine to freely spin along the shaft. Several optical targets were mounted to the blades and a pair of high-speed cameras was used to monitor the dynamics of the spinning turbine. Displacements of the targets during rotation were measured using three-dimensional point tracking. The point tracking technique measured both rigid body displacement and flexible deformation of the blades at target locations. While the structure is rotating, only flap displacements of optical targets (displacements out of the rotation plane) were used in strain prediction process. The measured displacements were expanded and applied to the finite element model of the turbine to extract full-field dynamic strain on the structure. The proposed approach enabled the prediction of dynamic response on the outer surface as well as within the inner points of the structure where no other sensor could be easily mounted. In order to validate the proposed approach, the predicted strain was compared to strain measured at four locations on the spinning blades using a wireless strain-gage system.

  3. Equivalent Plastic Strain Gradient Plasticity with Grain Boundary Hardening and Comparison to Discrete Dislocation Dynamics

    CERN Document Server

    Bayerschen, E; Wulfinghoff, S; Weygand, D; Böhlke, T

    2015-01-01

    The gradient crystal plasticity framework of Wulfinghoff et al. [53] incorporating an equivalent plastic strain and grain boundary yielding, is extended with additional grain boundary hardening. By comparison to averaged results from many discrete dislocation dynamics (DDD) simulations of an aluminum type tricrystal under tensile loading, the new hardening parameter in the continuum model is calibrated. It is shown that although the grain boundaries (GBs) in the discrete simulations are impenetrable, an infinite GB yield strength corresponding to microhard GB conditions, is not applicable in the continuum model. A combination of a finite GB yield strength with an isotropic bulk Voce hardening relation alone also fails to model the plastic strain profiles obtained by DDD. Instead, a finite GB yield strength in combination with GB hardening depending on the equivalent plastic strain at the GBs is shown to give a better agreement to DDD results. The differences in the plastic strain profiles obtained in DDD simu...

  4. EFFECT OF STRAIN FIELD ON THRESHOLD DISPLACEMENT ENERGY OF TUNGSTEN STUDIED BY MOLECULAR DYNAMICS SIMULATION

    Energy Technology Data Exchange (ETDEWEB)

    Wang, D.; Gao, Ning; Setyawan, Wahyu; Kurtz, Richard J.; Gao, X.; He, W. H.

    2016-03-31

    The influence of hydrostatic strain on point defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten was studied with molecular dynamics simulations. Two different tungsten potentials (Fikar and Juslin) were used. The minimum Ed direction calculated with the Fikar-potential was <100>, but with the Juslin-potential it was <111>. The most stable self-interstitial (SIA) configuration was a <111>-crowdion for both potentials. The stable SIA configuration did not change with applied strain. Varying the strain from compression to tension increased the vacancy formation energy but decreased the SIA formation energy. The SIA formation energy changed more significantly than for a vacancy such that Ed decreased with applied strain from compression to tension.

  5. Pathobiology of aging mice and GEM: background strains and experimental design.

    Science.gov (United States)

    Brayton, C F; Treuting, P M; Ward, J M

    2012-01-01

    The use of induced and spontaneous mutant mice and genetically engineered mice (and combinations thereof) to study cancers and other aging phenotypes to advance improved functional human life spans will involve studies of aging mice. Genetic background contributes to pathology phenotypes and to causes of death as well as to longevity. Increased recognition of expected phenotypes, experimental variables that influence phenotypes and research outcomes, and experimental design options and rationales can maximize the utility of genetically engineered mice (GEM) models to translational research on aging. This review aims to provide resources to enhance the design and practice of chronic and longevity studies involving GEM. C57BL6, 129, and FVB/N strains are emphasized because of their widespread use in the generation of knockout, transgenic, and conditional mutant GEM. Resources are included also for pathology of other inbred strain families, including A, AKR, BALB/c, C3H, C57L, C58, CBA, DBA, GR, NOD.scid, SAMP, and SJL/J, and non-inbred mice, including 4WC, AB6F1, Ames dwarf, B6, 129, B6C3F1, BALB/c,129, Het3, nude, SENCAR, and several Swiss stocks. Experimental strategies for long-term cross-sectional and longitudinal studies to assess causes of or contributors to death, disease burden, spectrum of pathology phenotypes, longevity, and functional healthy life spans (health spans) are compared and discussed.

  6. Influence of tooth profile modification on spur gear dynamic tooth strain

    Science.gov (United States)

    Oswald, Fred B.; Townsend, Dennis P.

    1995-06-01

    This paper presents results of dynamic strain gage measurements performed on the NASA gear-noise rig. The experiments were part of a joint research program between NASA and the U.S. Army Research Laboratory to advance the technology of rotorcraft transmissions. Tests were performed on six sets of low contact ratio spur gears with different tooth profile modifications. Results presented include static and dynamic measurements of gear tooth strain taken over a matrix of operating conditions. The results demonstrate that a well-designed tooth profile modification can significantly reduce dynamic loads in spur gears, especially for gears which operate at high speed and under high torque. The two parabolic modifications tested were not as effective as linear modifications, possibly because the modification zone was too long.

  7. Dynamic tensile stress–strain characteristics of carbon/epoxy laminated composites in through-thickness direction

    Directory of Open Access Journals (Sweden)

    Nakai Kenji

    2015-01-01

    Full Text Available The effect of strain rate up to approximately ε̇ = 102/s on the tensile stress–strain properties of unidirectional and cross-ply carbon/epoxy laminated composites in the through-thickness direction is investigated. Waisted cylindrical specimens machined out of the laminated composites in the through-thickness direction are used in both static and dynamic tests. The dynamic tensile stress–strain curves up to fracture are determined using the split Hopkinson bar (SHB. The low and intermediate strain-rate tensile stress–strain relations up to fracture are measured on an Instron 5500R testing machine. It is demonstrated that the ultimate tensile strength and absorbed energy up to fracture increase significantly, while the fracture strain decreases slightly with increasing strain rate. Macro- and micro-scopic examinations reveal a marked difference in the fracture surfaces between the static and dynamic tension specimens.

  8. Quantified Facial Soft-tissue Strain in Animation Measured by Real-time Dynamic 3-Dimensional Imaging

    Directory of Open Access Journals (Sweden)

    Vivian M. Hsu, MD

    2014-09-01

    Conclusions: This pilot study illustrates that the face can be objectively and quantitatively evaluated using dynamic major strain analysis. The technology of 3-dimensional optical imaging can be used to advance our understanding of facial soft-tissue dynamics and the effects of animation on facial strain over time.

  9. Fractional Dynamics of Network Growth Constrained by Aging Node Interactions.

    Directory of Open Access Journals (Sweden)

    Hadiseh Safdari

    Full Text Available In many social complex systems, in which agents are linked by non-linear interactions, the history of events strongly influences the whole network dynamics. However, a class of "commonly accepted beliefs" seems rarely studied. In this paper, we examine how the growth process of a (social network is influenced by past circumstances. In order to tackle this cause, we simply modify the well known preferential attachment mechanism by imposing a time dependent kernel function in the network evolution equation. This approach leads to a fractional order Barabási-Albert (BA differential equation, generalizing the BA model. Our results show that, with passing time, an aging process is observed for the network dynamics. The aging process leads to a decay for the node degree values, thereby creating an opposing process to the preferential attachment mechanism. On one hand, based on the preferential attachment mechanism, nodes with a high degree are more likely to absorb links; but, on the other hand, a node's age has a reduced chance for new connections. This competitive scenario allows an increased chance for younger members to become a hub. Simulations of such a network growth with aging constraint confirm the results found from solving the fractional BA equation. We also report, as an exemplary application, an investigation of the collaboration network between Hollywood movie actors. It is undubiously shown that a decay in the dynamics of their collaboration rate is found, even including a sex difference. Such findings suggest a widely universal application of the so generalized BA model.

  10. Fractional Dynamics of Network Growth Constrained by Aging Node Interactions

    Science.gov (United States)

    Safdari, Hadiseh; Zare Kamali, Milad; Shirazi, Amirhossein; Khalighi, Moein; Jafari, Gholamreza; Ausloos, Marcel

    2016-01-01

    In many social complex systems, in which agents are linked by non-linear interactions, the history of events strongly influences the whole network dynamics. However, a class of “commonly accepted beliefs” seems rarely studied. In this paper, we examine how the growth process of a (social) network is influenced by past circumstances. In order to tackle this cause, we simply modify the well known preferential attachment mechanism by imposing a time dependent kernel function in the network evolution equation. This approach leads to a fractional order Barabási-Albert (BA) differential equation, generalizing the BA model. Our results show that, with passing time, an aging process is observed for the network dynamics. The aging process leads to a decay for the node degree values, thereby creating an opposing process to the preferential attachment mechanism. On one hand, based on the preferential attachment mechanism, nodes with a high degree are more likely to absorb links; but, on the other hand, a node’s age has a reduced chance for new connections. This competitive scenario allows an increased chance for younger members to become a hub. Simulations of such a network growth with aging constraint confirm the results found from solving the fractional BA equation. We also report, as an exemplary application, an investigation of the collaboration network between Hollywood movie actors. It is undubiously shown that a decay in the dynamics of their collaboration rate is found, even including a sex difference. Such findings suggest a widely universal application of the so generalized BA model. PMID:27171424

  11. Molecular Structure and Dynamics of Water on Pristine and Strained Phosphorene: Wetting and Diffusion at Nanoscale

    Science.gov (United States)

    Zhang, Wei; Ye, Chao; Hong, Linbi; Yang, Zaixing; Zhou, Ruhong

    2016-12-01

    Phosphorene, a newly fabricated two-dimensional (2D) nanomaterial, has emerged as a promising material for biomedical applications with great potential. Nonetheless, understanding the wetting and diffusive properties of bio-fluids on phosphorene which are of fundamental importance to these applications remains elusive. In this work, using molecular dynamics (MD) simulations, we investigated the structural and dynamic properties of water on both pristine and strained phosphorene. Our simulations indicate that the diffusion of water molecules on the phosphorene surface is anisotropic, with strain-enhanced diffusion clearly present, which arises from strain-induced smoothing of the energy landscape. The contact angle of water droplet on phosphorene exhibits a non-monotonic variation with the transverse strain. The structure of water on transverse stretched phosphorene is demonstrated to be different from that on longitudinal stretched phosphorene. Moreover, the contact angle of water on strained phosphorene is proportional to the quotient of the longitudinal and transverse diffusion coefficients of the interfacial water. These findings thereby offer helpful insights into the mechanism of the wetting and transport of water at nanoscale, and provide a better foundation for future biomedical applications of phosphorene.

  12. Dynamic Stress-Strain Behaviour of Steel Fiber Reinforced High-Performance Concrete with Fly Ash

    Directory of Open Access Journals (Sweden)

    Tan Chien Yet

    2012-01-01

    Full Text Available The addition of steel fibers into concrete mix can significantly improve the engineering properties of concrete. The mechanical behaviors of steel fiber reinforced high-performance concrete with fly ash (SFRHPFAC are studied in this paper through both static compression test and dynamic impact test. Cylindrical and cube specimens with three volume fractions of end-hooked steel fibers with volume fraction of 0.5%, 1.0%, and 1.5% (39.25, 78.50, and 117.75 kg/m3 and aspect ratio of 64 are used. These specimens are then tested for static compression and for dynamic impact by split Hopkinson pressure bar (SHPB at strain rate of 30–60 s−1. The results reveal that the failure mode of concrete considerably changes from brittle to ductile with the addition of steel fibers. The plain concrete may fail under low-strain-rate single impact whereas the fibrous concrete can resist impact at high strain rate loading. It is shown that strain rate has great influence on concrete strength. Besides, toughness energy is proportional to the fiber content in both static and dynamic compressions.

  13. Dynamic strain-induced giant electroresistance and erasing effect in ultrathin ferroelectric tunnel-junction memory

    Science.gov (United States)

    Yau, Hei-Man; Xi, Zhongnan; Chen, Xinxin; Wen, Zheng; Wu, Ge; Dai, Ji-Yan

    2017-06-01

    Strain engineering plays a critical role in ferroelectric memories. In this work, we demonstrate dynamic strain modulation on tunneling electroresistance in a four-unit-cell ultrathin BaTi O3 metal/ferroelectric/semiconductor tunnel junction by applying mechanical stress to the device. With an extra compressive strain induced by mechanical stress, which is dynamically applied beyond the lattice mismatch between the BaTi O3 layer and the Nb :SrTi O3 substrate, the ON/OFF current ratio increases significantly up to a record high value of 107, whereas a mechanical erasing effect can be observed when a tensile stress is applied. This dynamic strain engineering gives rise to an efficient modulation of ON/OFF ratio due to the variation of BaTi O3 polarization. This result sheds light on the mechanism of electroresistance in the ferroelectric tunnel junctions by providing direct evidence for polarization-induced resistive switching, and also provides another stimulus for memory state operation.

  14. Effect of genetic strain and gender on age-related changes in body composition of the laboratory rat.

    Data.gov (United States)

    U.S. Environmental Protection Agency — Body composition data for common laboratory strains of rat as a function of age. This dataset is associated with the following publication: Gordon , C., K. Jarema ,...

  15. Nonlinear Strain Measures, Shape Functions and Beam Elements for Dynamics of Flexible Beams

    Energy Technology Data Exchange (ETDEWEB)

    Sharf, I. [University of Victoria, Department of Mechanical Engineering (Canada)

    1999-05-15

    In this paper, we examine several aspects of the development of an explicit geometrically nonlinear beam element. These are: (i) linearization of the displacement field; (ii) the effect of a commonly adopted approximation for the nonlinear Lagrangian strain; and (iii) use of different-order shape functions for discretization. The issue of rigid-body check for a nonlinear beam element is also considered. An approximate check is introduced for an element based on an (approximate) intermediate strain measure. Several numerical examples are presented to support the analysis. The paper concludes with a discussion on the use of explicit nonlinear beam elements for multibody dynamics simulation.

  16. Dynamic Grain Growth in Forsterite Aggregates Experimentally Deformed to High Strain

    Science.gov (United States)

    Kellermann Slotemaker, A.; de Bresser, H.; Spiers, C.; Drury, M.

    2004-12-01

    The dynamics of the outer Earth are largely controlled by olivine rheology. From previous work it has become clear that if olivine rocks are deformed to high strain, substantial weakening may occur before steady state mechanical behaviour is approached. This weakening appears directly related to progressive modification of the grain size distribution through competing effects of dynamic recrystallization and syn-deformational grain growth. However, most of our understanding of these processes in olivine comes from tests on coarse-grained materials that were reduced in grain size during straining by grain size insensitive (dislocation) creep mechanisms. The aim of the present study was to investigate microstructure evolution of fine-grained olivine rocks that coarsen in grain size while deforming by grain size sensitive (GSS) creep. We used fine-grained (~1 μ m) olivine aggregates (i.e., forsterite/Mg2SiO4), containing ~0.5 wt% water and 10 vol% enstatite (MgSiO3). Two types of experiments were carried out: 1) Hot isostatic pressing (HIP) followed by axial compression to varying strains up to a maximum of ~45%, at 600 MPa confining pressure and a temperature of 950°C, 2) HIP treatment without axial deformation. Microstructures were characterized by analyzing full grain size distributions and texture using SEM/EBSD. Our stress-strain curves showed continuous hardening. When samples were temporally unloaded for short time intervals, no difference in flow stress was observed before and after the interruption in straining. Strain rate sensitivity analysis showed a low value of ~1.5 for the stress exponent n. Measured grain sizes show an increase with strain up to a value twice that of the starting value. HIP-only samples showed only minor increase in grain size. A random LPO combined with the low n ~1.5 suggests dominant GSS creep controlled by grain boundary sliding. These results indicate that dynamic grain growth occurs in forsterite aggregates deforming by GSS

  17. DYNAMIC STRENGTH AND STRAIN RATE EFFECTS ON FRACTURE BEHAVIOR OF TUNGSTEN AND TUNGSTEN ALLOYS

    OpenAIRE

    Zurek, A; G. Gray

    1991-01-01

    An investigation of the stress-strain response as a function of strain rate, spall strength, and dynamic fracture behavior of pure W, W-26Re, W-Ni- Fe and W-Ni-Fe-Co has been performed. Spall strength measurements, obtained in symmetric-impact tests, showed an increase in spall strength from 0.4 GPa for pure tungsten to 3.8 GPa for 90W-7Ni-3Fe. Concurrent with the increase in spall strength was a change in fracture mode from cleavage (for pure W) to a mixture of transgranular and intergranula...

  18. Similarity between humans and foams in aging dynamics

    Science.gov (United States)

    Weon, Byung Mook; Stewart, Peter S.

    2014-03-01

    Foams are cellular networks between two immiscible phases. Foams are initially unstable and finally evolve toward a state of lower energy through sequential coalescences of bubbles. In physics, foams are model systems for materials that minimize surface energy. We study coalescence dynamics of clean foams using numerical simulations with a network model. Initial clean foams consist of equally pressurized bubbles and a low fraction of liquid films without stabilizing agents. Aging of clean foams occurs with time as bubbles rapidly coalesce by film rupture and finally evolve toward a new quasi-equilibrium state. Here we find that foam aging is analogous to biological aging: the death rate of bubbles increases exponentially with time, which is similar to the Gompertz mortality law for biological populations. The coalescence evolution of foams is self-similar regardless of initial conditions. The population change of bubbles is well described by a Boltzmann sigmoidal function, indicating that the foam aging is a phase transition phenomenon. This result suggests that foams can be useful model systems for giving insights into biological aging. Suwon 440-746, South Korea.

  19. Dynamic drawing characteristics of preschool and younger school age children

    Directory of Open Access Journals (Sweden)

    Cvetković Andrijana

    2014-01-01

    Full Text Available The main objective of this research is to determine developmental characteristics of dynamic drawings of preschool and younger school age children. The sample consists of 90 typical developed children, aged between 6 and 9. The sample includes 47 (52.2% girls and 43 (47.8% boys from preschool institutions and elementary schools in Pirot and Belgrade. Action representation in dynamic drawings was evaluated using three types of drawings: a man who runs, a man shooting a ball and a man lifting a ball from the floor. We determined that a very small number of the respondents reaches the highest level of graphical representation of figures in motion, and that girl’s achievements are better than boy’s achievements. However, this result is on the border of statistical significance (p=0.052. Also, there is a statistically significant trend of progress to higher levels of action representation (p=0.000 with the increase in chronological age of the respondents.

  20. Evaluation of the dynamic behavior of a Pelton runner based on strain gauge measurements

    Science.gov (United States)

    Mack, Reiner; Probst, Christian

    2016-11-01

    A reliable mechanical design of Pelton runners is very important in the layout of new installations and modernizations. Especially in horizontal machines, where the housing is not embedded into concrete, a rupture of a runner bucket can have severe consequences. Even if a crack in the runner is detected on time, the outage time that follows the malfunction of the runner is shortening the return of investment. It is a fact that stresses caused by the runner rotation and the jet forces are superposed by high frequent dynamic stresses. In case of resonance it even can be the dominating effect that is limiting the lifetime of a runner. Therefore a clear understanding of the dynamic mechanisms is essential for a safe runner design. This paper describes the evaluation of the dynamic behavior of a Pelton runner installed in a model turbine based on strain gauge measurements. Equipped with strain gauges at the root area of the buckets, the time responses of the strains under the influence of various operational parameters were measured. As a result basic theories for the jet bucket excitation were verified and the influence of the water mass was detected by evaluating the frequency shift in case of resonance. Furthermore, the influence of the individual bucket masses onto the dynamic behaviour for different mode shapes got measured.

  1. Field study of age-differentiated strain for assembly line workers in the automotive industry.

    Science.gov (United States)

    Börner, Kerstin; Scherf, Christian; Leitner-Mai, Bianca; Spanner-Ulmer, Birgit

    2012-01-01

    A field study in an automotive supply industry company was conducted to explore age-differentiated strain of assembly line workers. Subjective and objective data from 23 female workers aged between 27 and 57 years were collected at the workplace belt buckle assembly during morning shifts. Subjects with medication or chronic diseases affecting heart rate and breath rate were excluded. For subjective data generation different questionnaires were used. Before the Work Ability Index and the Munich Chronotype Questionnaire were completed by the subjects. Short questionnaires (strain-ratings, NASA-TLX) directly at begin and end of the work were used for obtaining shift-related data. During the whole shift (6 a.m. - 2.45 p.m.) bodily functions were logged with a wireless chest strap. In addition, the motion of the hand-arm-system was recorded for 30 times, 3 minutes each after a fixed time-schedule. First results show that younger subjects need significant less time for assembly (mean = 14.940 s) compared to older subjects (mean = 17.040 s; t(472.026) = -9.278 , p < 0.01).

  2. Aging of medium strength aluminum alloy friction stir welds produced by different process parameter after tensile strain hardening

    Energy Technology Data Exchange (ETDEWEB)

    Cerri, Emanuela, E-mail: emanuela.cerri@unipr.it; Leo, Paola

    2014-10-15

    Effect of tool rotation rate and travel speed on aging of 6082T6 friction stir welds after tensile strain hardening were investigated using Vickers microhardness (HV) measurements and precipitation hardening concepts. Tensile tests were performed at constant strain rate up to natural fracture followed by aging at low and medium temperatures. The results showed that HV measured on strain hardened FSW joints was not very sensitive to travel speeds experienced during FSW process, at constant rotation rate; anyway, strain hardening was very effective on hardness and induce an average increase by 20–25% in the stirred zone (SZ). Strain hardening was also very effective on aging at 200 °C, while it was not at 300 °C. At this temperature, HV assumed uniform values along joint cross section. - Highlights: • FSW joints have been investigated after tensile deformation and aging. • Tensile strain hardening induces a 20–25% HV increment in the stirred zone. • Subsequent aging at 200 °C did not substantially modify hardness profiles. • After aging at 300 °C, HV values were uniform and lower than HV minimum.

  3. Mechanical strain modulates age-related changes in the proliferation and differentiation of mouse adipose-derived stromal cells

    Directory of Open Access Journals (Sweden)

    Chiang Wen-Sheng

    2010-03-01

    Full Text Available Abstract Background Previous studies on the effects of aging in human and mouse mesenchymal stem cells suggest that a decline in the number and differentiation potential of stem cells may contribute to aging and aging-related diseases. In this report, we used stromal cells isolated from adipose tissue (ADSCs of young (8-10 weeks, adult (5 months, and old (21 months mice to test the hypothesis that mechanical loading modifies aging-related changes in the self-renewal and osteogenic and adipogenic differentiation potential of these cells. Results We show that aging significantly reduced the proliferation and increased the adipogenesis of ADSCs, while the osteogenic potential is not significantly reduced by aging. Mechanical loading (10% cyclic stretching, 0.5 Hz, 48 h increased the subsequent proliferation of ADSCs from mice of all ages. Although the number of osteogenic colonies with calcium deposition was increased in ADSCs subjected to pre-strain, it resulted from an increase in colony number rather than from an increase in osteogenic potential after strain. Pre-strain significantly reduced the number of oil droplets and the expression of adipogenic marker genes in adult and old ADSCs. Simultaneously subjecting ADSCs to mechanical loading and adipogenic induction resulted in a stronger inhibition of adipogenesis than that caused by pre-strain. The reduction of adipogenesis by mechanical strain was loading-magnitude dependent: loading with 2% strain only resulted in a partial inhibition, and loading with 0.5% strain could not inhibit adipogenesis in ADSCs. Conclusions We demonstrate that mechanical stretching counteracts the loss of self-renewal in aging ADSCs by enhancing their proliferation and, at the same time, reduces the heightened adipogenesis of old cells. These findings are important for the further study of stem cell control and treatment for a variety of aging related diseases.

  4. Imaging the ageing dynamics of polymer solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Seeland, Marco; Roland, Roesch; Harald, Hoppe [Institute of Physics, Ilmenau University of Technology (Germany)

    2010-07-01

    Nowadays, many attempts are existing on the route towards higher power conversion efficiencies in polymer solar cells. In addition, the lifetimes of such devices play a key role for the market entry as commercial products. To investigate the timescale of degradation processes, we applied long-time stability measurements with devices stored in the dark and under illumination and compare the results with luminescence images. The application of those techniques allows us to investigate the ageing dynamics in our devices consisting of an interpenetrating network of P3HT and PCBM, sandwiched between the ITO/PEDOT:PSS and aluminium electrode.

  5. Lack of evidence for an impairment of tuberoinfundibolar dopaminergic neurons in aged male rats of the Sprague-Dawley strain.

    Science.gov (United States)

    Amoroso, S; Di Renzo, G F; Maurano, F; Maida, P; Taglialatela, M; Annunziato, L

    1987-01-01

    Circulating prolactin (PRL) levels, dopamine (DA) content, in vitro basal and stimulus-evoked endogenous DA release from arcuate-periventricular nuclei median-eminence fragments were studied in young (4 months) and old (24-25 months) male rats of Sprague-Dawley strain. Serum PRL levels did not differ in young and aged animals. In addition DA tissue content, basal and K+- or d-amphetamine evoked endogenous DA release did not show age-related differences. These results suggest that in male rats of the Sprague-Dawley strain the activity of tuberoinfundibular dopaminergic (TIDA) neurons does not change during senescence, unlike what happens in other strains of rats.

  6. Detecting signals of seasonal influenza severity through age dynamics

    DEFF Research Database (Denmark)

    Lee, Elizabeth C.; Viboud, Cécile; Simonsen, Lone

    2015-01-01

    BACKGROUND: Measures of population-level influenza severity are important for public health planning, but estimates are often based on case-fatality and case-hospitalization risks, which require multiple data sources, are prone to surveillance biases, and are typically unavailable in the early...... stages of an outbreak. To address the limitations of traditional indicators, we propose a novel severity index based on influenza age dynamics estimated from routine physician diagnosis data that can be used retrospectively and for early warning. METHODS: We developed a quantitative 'ground truth......' severity benchmark that synthesizes multiple traditional severity indicators from publicly available influenza surveillance data in the United States. Observing that the age distribution of cases may signal severity early in an epidemic, we constructed novel retrospective and early warning severity indexes...

  7. Dynamic recrystallization of electroformed copper liners of shaped charges in high-strain-rate plastic deformation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The microstructures in the electroformed copper liners of shaped charges after high-strain-rate plastic deformation were investigated by transmission electron microscopy (TEM). Meanwhile, the orientation distribution of the grains in the recovered slug was examined by the electron backscattering Kikuchi pattern (EBSP) technique. EBSP analysis illustrated that unlike the as-formed electroformed copper linersof shaped charges the grain orientations in the recovered slug are distributed along randomly all the directions after undergoing heavily strain deformation at high-strain rate. Optical microscopy shows a typical recrystallization structure, and TEM examination reveals dislocation cells existed in the thin foil specimen. These results indicate that dynamic recovery and recrystallization occur during this plastic deformation process, and the associated deformation temperature is considered to be higher than 0.6 times the melting point of copper.

  8. Dynamical scaling for underdamped strain order parameters quenched below first-order phase transitions

    Science.gov (United States)

    Shankaraiah, N.; Dubey, Awadhesh K.; Puri, Sanjay; Shenoy, Subodh R.

    2016-12-01

    In the conceptual framework of phase ordering after temperature quenches below transition, we consider the underdamped Bales-Gooding-type "momentum conserving" dynamics of a 2D martensitic structural transition from a square-to-rectangle unit cell. The one-component or NOP=1 order parameter is one of the physical strains, and the Landau free energy has a triple well, describing a first-order transition. We numerically study the evolution of the strain-strain correlation, and find that it exhibits dynamical scaling, with a coarsening length L (t ) ˜tα . We find at intermediate and long times that the coarsening exponent sequentially takes on respective values close to α =2 /3 and 1 /2 . For deep quenches, the coarsening can be arrested at long times, with α ≃0 . These exponents are also found in 3D. To understand such behavior, we insert a dynamical-scaling ansatz into the correlation function dynamics to give, at a dominant scaled separation, a nonlinear kinetics of the curvature g (t )≡1 /L (t ) . The curvature solutions have time windows of power-law decays g ˜1 /tα , with exponent values α matching simulations, and manifestly independent of spatial dimension. Applying this curvature-kinetics method to mass-conserving Cahn-Hilliard dynamics for a double-well Landau potential in a scalar NOP=1 order parameter yields exponents α =1 /4 and 1 /3 for intermediate and long times. For vector order parameters with NOP≥2 , the exponents are α =1 /4 only, consistent with previous work. The curvature kinetics method could be useful in extracting coarsening exponents for other phase-ordering dynamics.

  9. Dynamic Scaling of Lipofuscin Deposition in Aging Cells

    Science.gov (United States)

    Family, Fereydoon; Mazzitello, K. I.; Arizmendi, C. M.; Grossniklaus, H. E.

    2011-07-01

    Lipofuscin is a membrane-bound cellular waste that can be neither degraded nor ejected from the cell but can only be diluted through cell division and subsequent growth. The fate of postmitotic (non-dividing) cells such as neurons, cardiac myocytes, skeletal muscle fibers, and retinal pigment epithelial cells (RPE) is to accumulate lipofuscin, which as an "aging pigment" has been considered a reliable biomarker for the age of cells. Environmental stress can accelerate the accumulation of lipofuscin. For example, accumulation in brain cells appears to be an important issue connected with heavy consumption of alcohol. Lipofuscin is made of free-radical-damaged protein and fat, whose abnormal accumulation is related to a range of disorders including Type IV mucolipidosis (ML4), Amyotrophic Lateral Sclerosis (ALS), Alzheimer's disease, Parkinson disease, and age-related macular degeneration (AMD) which is the leading cause of blindness beyond the age of 50 years. The study of lipofuscin formation and growth is important, because of their association with cellular aging. We introduce a model of non-equilibrium cluster growth and aggregation that we have developed for studying the formation and growth of lipofuscin. As an example of lipofuscin deposit in a given kind of postmitotic cell, we study the kinetics of lipofuscin growth in a RPE cell. Our results agree with a linear growth of the number of lipofuscin granules with age. We apply the dynamic scaling approach to our model and find excellent data collapse for the cluster size distribution. An unusual feature of our model is that while small particles are removed from the cell the larger ones become fixed and grow by aggregation.

  10. Dynamics of a Class 1 Integron Located on Plasmid or Chromosome in Two Aeromonas spp. Strains

    Science.gov (United States)

    Pérez-Valdespino, Abigail; Lazarini-Martínez, Alfredo; Rivera-González, Alejandro X.; García-Hernández, Normand; Curiel-Quesada, Everardo

    2016-01-01

    Integrons are non-mobile bacterial genetic elements that carry different cassettes conferring antibiotic resistance. Cassettes can excise or integrate by action of an integron-encoded integrase, enabling bacteria to face environmental challenges. In this work, the functionality and dynamics of two integrons carrying the same cassette arrangement (dfrA12–orfF–aadA2), but located on plasmid or chromosome in two different strains were studied. In order to demonstrate the functionality of the Class 1 integrase, circular cassette integration intermediaries were PCR amplified by PCR using extrachromosomal DNA extracted from bacteria grown in the presence or absence of cassette-encoded antibiotics. Circular aadA2 and dfrA12–orfF–aadA2 cassettes were detected in cultures grown either in the presence or absence of antibiotics in both strains. No dfrA12–orfF circular intermediates could be detected under any culture conditions. These results show that both integrons are functional. However, these elements show different dynamics and functionality since the presence of streptomycin led to detectable gene rearrangements in the variable region only in the strain with the plasmid-born integron. In addition, complete integration products were demonstrated using a receptor molecule carrying an empty integron. In this case, integration products were observed in both strains even in the absence of antibiotics, but they were more evident in the strain with the plasmid-located integron when streptomycin was present in the culture medium. This suggests that integrons in the two strains respond differently to streptomycin even though DNA sequences upstream the intI1 gene, including the lexA boxes of both integrons are identical. PMID:27733851

  11. Dynamics of a Class 1 integron located on plasmid or chromosome in two Aeromonas spp. strains

    Directory of Open Access Journals (Sweden)

    Abigail Perez-Valdespino

    2016-09-01

    Full Text Available Integrons are non-mobile bacterial genetic elements that carry different cassettes conferring antibiotic resistance. Cassettes can excise or integrate by action of an integron-encoded integrase, enabling bacteria to face environmental challenges. In this work the functionality and dynamics of two integrons carrying the same cassette arrangement (dfrA12-orfF-aadA2, but located on plasmid or chromosome in two different strains were studied. In order to demonstrate the functionality of the Class 1 integrase, circular cassette integration intermediaries were PCR amplified by PCR using extrachromosomal DNA extracted from bacteria grown in the presence or absence of cassette-encoded antibiotics. Circular aadA2 and dfrA12-orfF-aadA2 cassettes were detected in cultures grown either in the presence or absence of antibiotics in both strains. No dfrA12-orfF circular intermediates could be detected under any culture conditions. These results show that both integrons are functional. However, these elements show different dynamics and functionality since the presence of streptomycin led to detectable gene rearrangements in the variable region only in the strain with the plasmid-born integron. In addition, complete integration products were demonstrated using a receptor molecule carrying an empty integron. In this case integration products were observed in both strains even in the absence of antibiotics, but they were more evident in the strain with the plasmid-located integron when streptomycin was present in the culture medium. This suggests that integrons in the two strains respond differently to streptomycin even though DNA sequences upstream the intI1 gene, including the lexA boxes of both integrons are identical.

  12. Dynamic damage and stress-strain relations of ultra-high performance cementitious composites subjected to repeated impact

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Ultra-high performance cementitious composites (UHPCC) were prepared by replacing 60% of cement with ultra-fine industrial waste powders.The dynamic damage and compressive stress-strain relations of UHPCC were studied using split Hopkinson pressure bar (SHPB).The damage of UHPCC subjected to repeated impact was measured by the ultrasonic pulse velocity method.Results show that the dynamic damage of UHPCC increases linearly with impact times and the abilities of repeated impact resistance of UHPCC are improved with increasing fiber volume fraction.The stress waves on impact were recorded and the average stress,strain and strain rate of UHPCC were calculated based on the wave propagation theory.The effects of strain rate,fibers volume fraction and impact times on the stress-strain relations of UHPCC were studied.Results show that the peak stress and elastic modulus decrease while the strain rate and peak strain increase gradually with increasing impact times.

  13. Dynamic Strain Sensing in a Long-Span Suspension Bridge Using Fiber Bragg Grating Sensors

    Science.gov (United States)

    Zhu, Yinian; Zhu, Yan-Jin; Balogun, Oluwaseyi; Zhu, Songye; Xu, You-Lin; Krishnaswamy, Sridhar

    2011-06-01

    Optical fiber sensors are ideal for monitoring continuous deterioration conditions of civil infrastructure, especially of long-span bridges. Typically, a network of sensors is used to measure the strains or low frequency vibrational response of the structure. In this work, we demonstrate dynamic spectral demodulation of fiber Bragg grating (FBG) sensor responses with a stabilized Michelson interferometer for monitoring mechanical strains in a model of long-span bridge. A series of experiments has been performed, including the measurements of the natural resonant modes of the model bridge, impact response of a bridge member and acoustic emissions in a fractured aluminum bar. The experimental results not only reveal that dynamic spectral demodulation of FBG strain responses at frequencies extending up to about 3.5 MHz is possible, but also suggest that the method may be suitable for monitoring high frequency mechanical strains in civil structures that result from cracking or impact loading, thus providing a tool for local detection of structural damage.

  14. Dynamics of Learning Motivation in Early School Age Children

    Directory of Open Access Journals (Sweden)

    Arkhireyeva T.V.

    2015-08-01

    Full Text Available The paper presents outcomes of a longitudinal study on learning motivation in children of early school age. The aim was to reveal the leading motives in first, second, third and fourth grades and to explore the dynamics of some learning motives in children over the whole period of elementary school. As it was found, the learning activity in the children was mostly motivated by social motives, among which the leading ones were the motives of selfdetermination and wellbeing. As for learning motives, over the course of all four years the children were for the most part motivated by the content of the learning activity, and not by its process. The dynamics of certain social motives of the learning activity varied across the sample, with some going through the periods of increase and decrease and others having a oneway dynamics. The study also revealed a decrease in the motivation rooted in the learning activity itself between the second and third year; at the same time, in the second, third and fourth years the children were more motivated by the content of the learning activity than by its process

  15. Characterizations of Dynamic Strain-induced Transformation in Low Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    Luhan Hao; Mingyue Sun; Namin Xiao; Dianzhong Li

    2012-01-01

    Dynamic strain-induced transformation of the low carbon steel Q(235) at 770℃ and 850℃ leads to fine ferrite grains. The microstructure characterization and mechanism of the fine ferrite grain were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) technique. The results show that strain-induced microstructure is the mixed microstructure of ferrite and pearlite, with cementite randomly distributed on ferrite grain boundaries and the grains interiors. EBSD images of grain boundaries demonstrate that high angle grain boundaries (HAGBs) are dominant in both of the deformation induced microstructures occurring below and above A(e3) , with only a few low angle grain boundaries (LAGBs) existing in the grain interiors. It implies that the dynamic strain-induced transformation (DSIT) happens above and below A(e3) temperature and has the same phase transition mechanisms. The refinement of ferrite is the cooperative effect of DSIT and continuous dynamic recrystallization (CDRX) of ferrite. Besides, DSIT is deemed as an incomplete carbon diffusion phase transition through the analysis of microstructure and the previous simulated results. The strengths of the Q(235) steel with refined ferrite and pearlite structure get doubled than the initial state without treated by DSIT and the residual stress in the refined structure is partly responsible for the ductility loss.

  16. Solid Dynamic Models for Analysis of Stress and Strain in Human Hearts

    Directory of Open Access Journals (Sweden)

    Qiu Guan

    2012-01-01

    Full Text Available This paper proposes a solid model based on four-dimensional trivariate B-spline for strain and stress analysis of ventricular myocardium. With a series of processing steps in the four-dimensional medical images, the feature points of ventricular inner and outer wall are obtained. A B-spline surface is then used to build the dynamic deformation model of the myocardial walls. With such a surface model, a hexahedron control mesh can be constructed by sweeping the cloud data, and the ventricular solid model is built by fitting the trivariate B-spline parameters. Based on these models, a method of isogeometric analysis can be applied to calculate the stress and strain continuously distributed in the ventricle. The model is represented smoothly in the cylindrical coordinate system and is easy to measure myocardium dynamics for finding abnormal motion. Experiments are carried out for comparing the stress and strain distribution. It is found that the solid model can determine ventricular dynamics which can well reflect the deformation distribution in the heart and imply early clues of cardiac diseases.

  17. Bonding dynamics of compliant microbump during ultrasonic bonding investigated by using Si strain gauge

    Science.gov (United States)

    Iwanabe, Keiichiro; Nakadozono, Kenichi; Senda, Yousuke; Asano, Tanemasa

    2016-06-01

    The bonding dynamics of a cone-shaped microbump during ultrasonic bonding are investigated by in situ measurements of the strain generated in a substrate using a piezoresistance strain sensor. The strain sensor is composed of a pair of p- and n-type piezoresistance gauges to extract strain components in the ultrasonic vibration along the plane parallel to the substrate surface and along the direction perpendicular to the surface. Flip-chip bonding is performed at room-temperature. The time evolution of the strain generated in the substrate according to the load-up of pressing force and application of ultrasonic vibration is clearly detected. The softening of the bump metal during the application of ultrasonic vibration is clearly observed. Results of a comparative study between the bonding of a cone-shaped microbump and that of a flat-top microbump suggest mechanical stress concentration near the top end of the cone-shaped microbump, which results in the transformation of the crystal texture of the bump from grains to fine crystallites.

  18. Mechanical Characterization of Brain Tissue in Compression at Dynamic Strain Rates

    CERN Document Server

    Rashid, Badar; Gilchrist, Michael; 10.1016/j.jmbbm.2012.01.022

    2013-01-01

    Traumatic brain injury (TBI) occurs when local mechanical load exceeds certain tolerance levels for brain tissue. Extensive research has been done previously for brain matter experiencing compression at quasistatic loading; however, limited data is available to model TBI under dynamic impact conditions. In this research, an experimental setup was developed to perform unconfined compression tests and stress relaxation tests at strain rates < 90/s. The brain tissue showed a stiffer response with increasing strain rates, showing that hyperelastic models are not adequate. Specifically, the compressive nominal stress at 30% strain was 8.83 +/- 1.94, 12.8 +/- 3.10 and 16.0 +/- 1.41 kPa (mean +/- SD) at strain rates of 30, 60 and 90/s, respectively. Relaxation tests were also conducted at 10%-50% strain with the average rise time of 10 ms, which can be used to derive time dependent parameters. Numerical simulations were performed using one-term Ogden model with initial shear modulus mu_0 = 6.06 +/- 1.44, 9.44 +/-...

  19. Evolution of carbon distribution and mechanical properties during the static strain ageing of heavily drawn pearlitic steel wires

    Energy Technology Data Exchange (ETDEWEB)

    Lamontagne, A. [Univ Lyon, INSA Lyon, MATEIS – UMR CNRS 5510, Bât. St Exupéry, 25 Avenue Jean Capelle, F-69621 Villeurbanne Cedex (France); Massardier, V., E-mail: veronique.massardier@insa-lyon.fr [Univ Lyon, INSA Lyon, MATEIS – UMR CNRS 5510, Bât. St Exupéry, 25 Avenue Jean Capelle, F-69621 Villeurbanne Cedex (France); Sauvage, X. [University of Rouen, GPM, UMR CNRS 6634, BP 12, Avenue de l’Université, 76801 Saint-Etienne du Rouvray (France); Kléber, X. [Univ Lyon, INSA Lyon, MATEIS – UMR CNRS 5510, Bât. St Exupéry, 25 Avenue Jean Capelle, F-69621 Villeurbanne Cedex (France); Mari, D. [Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, Station 3, Lausanne CH-1015 (Switzerland)

    2016-06-14

    The static strain ageing of heavily cold-drawn pearlitic steel wires was investigated using both global techniques and local techniques (Atom Probe Tomography (APT)), in order to highlight how the cold-drawn destabilized microstructure returns to a more stable state during post-drawing treatments between 20 °C and 150 °C. The global techniques (thermoelectric power, differential scanning calorimetry) clearly showed that ageing occurs in three successive ageing stages and is due to a redistribution of the carbon atoms coming from the strain-induced cementite dissolution. The first ageing stage was unambiguously attributed to the carbon segregation to the defects, while the second and third stages were interpreted as being due to the precipitation of intermediate carbides (2nd stage) and cementite (3rd stage). The true strain was not found to significantly affect the ageing kinetics and mechanisms but appeared to play a role in the amount of carbon atoms involved in the different ageing stages. APT analyses confirmed that ageing is governed by the carbon depletion of strain-induced supersaturated ferrite. The strengthening mechanisms associated with the different ageing stages were also discussed.

  20. Interaction of mouse splenocytes and macrophages with bacterial strains in vitro : the effect of age in the immune response

    NARCIS (Netherlands)

    Van Beek, A. A.; Hoogerland, J. A.; Belzer, C.; De Vos, P.; De Vos, W. M.; Savelkoul, H. F. J.; Leenen, P. J. M.

    2016-01-01

    Probiotics influence the immune system, both at the local and systemic level. Recent findings suggest the relation between microbiota and the immune system alters with age. Our objective was to address direct effects of six bacterial strains on immune cells from young and aged mice: Lactobacillus pl

  1. Interaction of mouse splenocytes and macrophages with bacterial strains in vitro: the effect of age in the immune response

    NARCIS (Netherlands)

    Beek, van A.A.; Hoogerland, Joanne; Belzer, C.; Vos, de P.; Vos, de W.M.; Savelkoul, H.F.J.; Leenen, P.J.

    2016-01-01

    Probiotics influence the immune system, both at the local and systemic level. Recent findings suggest the relation between microbiota and the immune system alters with age. Our objective was to address direct effects of six bacterial strains on immune cells from young and aged mice: Lactobacillus pl

  2. Static and dynamic strain energy release rates in toughened thermosetting composite laminates

    Science.gov (United States)

    Cairns, Douglas S.

    1992-01-01

    In this work, the static and dynamic fracture properties of several thermosetting resin based composite laminates are presented. Two classes of materials are explored. These are homogeneous, thermosetting resins and toughened, multi-phase, thermosetting resin systems. Multi-phase resin materials have shown enhancement over homogenous materials with respect to damage resistance. The development of new dynamic tests are presented for composite laminates based on Width Tapered Double Cantilevered Beam (WTDCB) for Mode 1 fracture and the End Notched Flexure (ENF) specimen. The WTDCB sample was loaded via a low inertia, pneumatic cylinder to produce rapid cross-head displacements. A high rate, piezo-electric load cell and an accelerometer were mounted on the specimen. A digital oscilloscope was used for data acquisition. Typical static and dynamic load versus displacement plots are presented. The ENF specimen was impacted in three point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions were determined analytically and experimentally. The test results for Mode 1 fracture are relatively insensitive to strain rate effects for the laminates tested in this study. The test results from Mode 2 fracture indicate that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. While the static fracture properties of the homogeneous systems may be relatively high, the apparent Mode 2 dynamic critical strain energy release rate drops significantly. The results indicate that static Mode 2 fracture testing is inadequate for determining the fracture performance of composite structures subjected to conditions such as low velocity impact. A good correlation between the basic Mode 2 dynamic fracture properties and the performance is a combined material/structural Compression After Impact (CAI) test is found. These results underscore the importance of

  3. Effect of aging and oxidation on strain hardening behaviour of a nickel-free high nitrogen austenitic stainless steel

    Science.gov (United States)

    Karthik, B.; Veerababu, R.; Satyanarayana, D. V. V.

    2016-05-01

    Effect of aging and oxidation on strain hardening behaviour of a nickel-free high nitrogen austenitic stainless steel has been investigated using room temperature tensile tests and TEM. The alloy in both oxidised and unoxidised conditions exhibits a transition in flow behaviour that can be described best by the Ludwigson flow relationship as evident from the lowest values of the sum of residual squares, χ 2, of the fit. The transition in macroscopic flow behaviour with strain has been correlated to change in deformation mechanism from planar slip in the low strain regime (LSR) to deformation twinning and slip in the high strain regime (HSR) in solution treated (ST) condition of the alloy. However, the LSR of the alloy aged for longer times (>100 h) is characterized by the formation of dislocation tangles, while the HSR is marked by the formation of well-defined finer dislocation cell structure. This difference in deformation sub-structures in low and high strain regimes between ST and long term aged samples has been correlated to the change in stacking fault energy due to the precipitation of Cr2N and σ-phases. Further, the alloy in ST condition exhibits the highest strain hardening rate, which then progressively decreases with aging time.

  4. Effects of Finish Cooling Temperature on Tensile Properties After Thermal Aging of Strain-Based API X60 Linepipe Steels

    Science.gov (United States)

    Sung, Hyo Kyung; Lee, Dong Ho; Shin, Sang Yong; Lee, Sunghak; Ro, Yunjo; Lee, Chang Sun; Hwang, Byoungchul

    2015-09-01

    Two types of strain-based American Petroleum Institute (API) X60 linepipe steels were fabricated at two finish cooling temperatures, 673 K and 723 K (400 °C and 450 °C), and the effects of the finish cooling temperatures on the tensile properties after thermal aging were investigated. The strain-based API X60 linepipe steels consisted mainly of polygonal ferrite (PF) or quasi-polygonal ferrite and the volume fraction of acicular ferrite increased with the increasing finish cooling temperature. In contrast, the volume fractions of bainitic ferrite (BF) and secondary phases decreased. The tensile properties before and after thermal aging at 473 K and 523 K (200 °C and 250 °C) were measured. The yield strength, ultimate tensile strength, and yield ratio increased with the increasing thermal aging temperature. The strain hardening rate in the steel fabricated at the higher finish cooling temperature decreased rapidly after thermal aging, probably due to the Cottrell atmosphere, whereas the strain hardening rate in the steel fabricated at the lower finish cooling temperature changed slightly after thermal aging. The uniform elongation and total elongation decreased with increasing thermal aging temperature, probably due to the interactions between carbon atoms and dislocations. The uniform elongation decreased rapidly with the decreasing volume fractions of BF and martensite and secondary phases. The yield ratio increased with the increasing thermal aging temperature, whereas the strain hardening exponent decreased. The strain hardening exponent of PL steel decreased rapidly after thermal aging because of the large number of mobile dislocations between PF and BF or martensite or secondary phases.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Anomalous strain effect on the thermal conductivity of borophene: a reactive molecular dynamics study

    Science.gov (United States)

    Mortazavi, Bohayra; Le, Minh-Quy; Rabczuk, Timon; Pereira, Luiz Felipe C.

    2017-09-01

    Borophene, an atomically thin, corrugated, crystalline two-dimensional boron sheet, has been recently synthesized. Here we investigate mechanical properties and lattice thermal conductivity of borophene using reactive molecular dynamics simulations. We performed uniaxial tensile strain simulations at room temperature along in-plane directions, and found 2D elastic moduli of 188 N m-1 and 403 N m-1 along zigzag and armchair directions, respectively. This anisotropy is attributed to the buckling of the borophene structure along the zigzag direction. We also performed non-equilibrium molecular dynamics to calculate the lattice thermal conductivity. Considering its size-dependence, we predict room-temperature lattice thermal conductivities of 75.9 ± 5.0 W m-1 K-1 and 147 ± 7.3 W m-1 K-1, respectively, and estimate effective phonon mean free paths of 16.7 ± 1.7 nm and 21.4 ± 1.0 nm for the zigzag and armchair directions. In this case, the anisotropy is attributed to differences in the density of states of low-frequency phonons, with lower group velocities and possibly shorten phonon lifetimes along the zigzag direction. We also observe that when borophene is strained along the armchair direction there is a significant increase in thermal conductivity along that direction. Meanwhile, when the sample is strained along the zigzag direction there is a much smaller increase in thermal conductivity along that direction. For a strain of 8% along the armchair direction the thermal conductivity increases by a factor of 3.5 (250%), whereas for the same amount of strain along the zigzag direction the increase is only by a factor of 1.2 (20%). Our predictions are in agreement with recent first principles results, at a fraction of the computational cost. The simulations shall serve as a guide for experiments concerning mechanical and thermal properties of borophene and related 2D materials.

  7. PRINCIPAL COMPONENT DECOMPOSITION BASED FINITE ELEMENT MODEL UPDATING FOR STRAIN-RATE-DEPENDENCE NONLINEAR DYNAMIC PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    GUO Qintao; ZHANG Lingmi; TAO Zheng

    2008-01-01

    Thin wall component is utilized to absorb impact energy of a structure. However, the dynamic behavior of such thin-walled structure is highly non-linear with material, geometry and boundary non-linearity. A model updating and validation procedure is proposed to build accurate finite element model of a frame structure with a non-linear thin-walled component for dynamic analysis. Design of experiments (DOE) and principal component decomposition (PCD) approach are applied to extract dynamic feature from nonlinear impact response for correlation of impact test result and FE model of the non-linear structure. A strain-rate-dependent non-linear model updating method is then developed to build accurate FE model of the structure. Computer simulation and a real frame structure with a highly non-linear thin-walled component are employed to demonstrate the feasibility and effectiveness of the proposed approach.

  8. Growth plate cartilage shows different strain patterns in response to static versus dynamic mechanical modulation.

    Science.gov (United States)

    Kaviani, Rosa; Londono, Irene; Parent, Stefan; Moldovan, Florina; Villemure, Isabelle

    2016-08-01

    Longitudinal growth of long bones and vertebrae occurs in growth plate cartilage. This process is partly regulated by mechanical forces, which are one of the underlying reasons for progression of growth deformities such as idiopathic adolescent scoliosis and early-onset scoliosis. This concept of mechanical modulation of bone growth is also exploited in the development of fusionless treatments of these deformities. However, the optimal loading condition for the mechanical modulation of growth plate remains to be identified. The objective of this study was to evaluate the effects of in vitro static versus dynamic modulation and of dynamic loading parameters, such as frequency and amplitude, on the mechanical responses and histomorphology of growth plate explants. Growth plate explants from distal ulnae of 4-week-old swines were extracted and randomly distributed among six experimental groups: baseline ([Formula: see text]), control ([Formula: see text]), static ([Formula: see text]) and dynamic ([Formula: see text]). For static and dynamic groups, mechanical modulation was performed in vitro using an Indexed CartiGen bioreactor. A stress relaxation test combined with confocal microscopy and digital image correlation was used to characterize the mechanical responses of each explant in terms of peak stress, equilibrium stress, equilibrium modulus of elasticity and strain pattern. Histomorphometrical measurements were performed on toluidine blue tissue sections using a semi-automatic custom-developed MATLAB toolbox. Results suggest that compared to dynamic modulation, static modulation changes the strain pattern of the tissue and thus is more detrimental for tissue biomechanics, while the histomorphological parameters are not affected by mechanical modulation. Also, under dynamic modulation, changing the frequency or amplitude does not affect the biomechanical response of the tissue. Results of this study will be useful in finding optimal and non-damaging parameters

  9. Pore-pressure sensitivities to dynamic strains: observations in active tectonic regions

    Science.gov (United States)

    Barbour, Andrew J.

    2015-01-01

    Triggered seismicity arising from dynamic stresses is often explained by the Mohr-Coulomb failure criterion, where elevated pore pressures reduce the effective strength of faults in fluid-saturated rock. The seismic response of a fluid-rock system naturally depends on its hydro-mechanical properties, but accurately assessing how pore-fluid pressure responds to applied stress over large scales in situ remains a challenging task; hence, spatial variations in response are not well understood, especially around active faults. Here I analyze previously unutilized records of dynamic strain and pore-pressure from regional and teleseismic earthquakes at Plate Boundary Observatory (PBO) stations from 2006 through 2012 to investigate variations in response along the Pacific/North American tectonic plate boundary. I find robust scaling-response coefficients between excess pore pressure and dynamic strain at each station that are spatially correlated: around the San Andreas and San Jacinto fault systems, the response is lowest in regions of the crust undergoing the highest rates of secular shear strain. PBO stations in the Parkfield instrument cluster are at comparable distances to the San Andreas fault (SAF), and spatial variations there follow patterns in dextral creep rates along the fault, with the highest response in the actively creeping section, which is consistent with a narrowing zone of strain accumulation seen in geodetic velocity profiles. At stations in the San Juan Bautista (SJB) and Anza instrument clusters, the response depends non-linearly on the inverse fault-perpendicular distance, with the response decreasing towards the fault; the SJB cluster is at the northern transition from creeping-to-locked behavior along the SAF, where creep rates are at moderate to low levels, and the Anza cluster is around the San Jacinto fault, where to date there have been no statistically significant creep rates observed at the surface. These results suggest that the strength

  10. A distributed optical fiber sensing system for dynamic strain measurement based on artificial reflector

    Science.gov (United States)

    Sun, Zhenhong; Shan, Yuanyuan; Li, Yanting; Zhang, Yixin; Zhang, Xuping

    2016-10-01

    Phase sensitive optical time domain reflectometry (Φ-OTDR) has been widely used in many applications for its distributed sensing ability on weak disturbance all along the sensing fiber. However, traditional Φ-OTDR cannot make quantitative measurement on the external disturbance due to the randomly distributed position and reflectivity of scatters within the optical fiber. Recently, some methods have been proposed to realize quantitative measurement of dynamic strain. In these literatures, the fiber with or without FBGs in practice was easily damaged and with difficulty of maintenance. PZT is employed to generate strain event in the fiber. There is a large gap compared with the real detecting environment, which will not reveal the full performance of the sensing system. In this paper, a distributed optical fiber sensing (DOFS) system for dynamic strain measurement based on artificial reflector is proposed and demonstrated experimentally. The fiber under test (FUT) is composed by four 20-meter long single mode optical fiber patch cords (OFPCs), which are cascaded with ferrule contactor/physical contact (FC/PC) connectors via fiber flanges. The fiber facet of FC/PC connector forms an artificial reflector. When the interval between the two reflectors is changed, the phase of the interference signal will also be changed. A symmetric 3×3 coupler with table-look-up scheme is introduced to discriminate the phase change through interference intensity. In our experiment, the center 10m section of the second OFPC is attached to the bottom of an aluminum alloy plate. An ordinary loudspeaker box was located on the top of the aluminum alloy plate. The dynamic strain generated by the loudspeaker box is transmitted from the aluminum alloy plate to the OFPC. Experimental results show that the proposed method has a good frequency response characteristic up to 3.2 kHz and a linear intensity response of R2=0.9986 while the optical probe pulse width and repetition rate were 100ns

  11. The dynamic Virtual Fields Method on rubbers at medium and high strain rates

    Directory of Open Access Journals (Sweden)

    Yoon Sung-Ho

    2015-01-01

    Full Text Available Elastomeric materials are widely used for energy absorption applications, often experiencing high strain rate deformations. The mechanical characterization of rubbers at high strain rates presents several experimental difficulties, especially associated with achieving adequate signal to noise ratio and static stress equilibrium, when using a conventional technique such as the split Hopkinson pressure bar. In the present study, these problems are avoided by using the dynamic Virtual Fields Method (VFM in which acceleration fields, clearly generated by the non-equilibrium state, are utilized as a force measurement with in the frame work of the principle of virtual work equation. In this paper, two dynamic VFM based techniques are used to characterise an EPDM rubber. These are denoted as the linear and nonlinear VFM and are developed for (respectively medium (drop-weight and high (gas-gun strain-rate experiments. The use of the two VFMs combined with high-speed imaging analysed by digital imaging correlation allows the identification of the parameters of a given rubber mechanical model; in this case the Ogden model is used.

  12. Prediction of dynamic strains on a monopile offshore wind turbine using virtual sensors

    Science.gov (United States)

    Iliopoulos, A. N.; Weijtjens, W.; Van Hemelrijck, D.; Devriendt, C.

    2015-07-01

    The monitoring of the condition of the offshore wind turbine during its operational states offers the possibility of performing accurate assessments of the remaining life-time as well as supporting maintenance decisions during its entire life. The efficacy of structural monitoring in the case of the offshore wind turbine, though, is undermined by the practical limitations connected to the measurement system in terms of cost, weight and feasibility of sensor mounting (e.g. at muddline level 30m below the water level). This limitation is overcome by reconstructing the full-field response of the structure based on the limited number of measured accelerations and a calibrated Finite Element Model of the system. A modal decomposition and expansion approach is used for reconstructing the responses at all degrees of freedom of the finite element model. The paper will demonstrate the possibility to predict dynamic strains from acceleration measurements based on the aforementioned methodology. These virtual dynamic strains will then be evaluated and validated based on actual strain measurements obtained from a monitoring campaign on an offshore Vestas V90 3 MW wind turbine on a monopile foundation.

  13. Effects of strain rate on the hot deformation behavior and dynamic recrystallization in China low activation martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Yuanyuan [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Chen, Xizhang, E-mail: kernel.chen@gmail.com [School of Mechanical and Electrical Engineering, Wenzhou University, Wenzhou 325035 (China); Madigan, Bruce [Montana Tech, Butte, MT (United States); Cao, Hongyan [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Konovalov, Sergey [Center for Collective Use Material Science, Siberian State Industrial University, Novokuznetsk (Russian Federation)

    2016-02-15

    Graphical abstract: - Highlights: • Average grain sizes of 1.8 μm are observed at strain rate of 10 s{sup −1}. • Peak stress value increased, but strain decreased with increasing of strain rate. • A catenuliform recrystallized occurred at a strain rate of 5 s{sup −1}. • DRX effect improved with increasing of deformation amounts. - Abstract: To investigate the effects of strain rate on dynamic recrystallization (DRX) behavior on China low activation martensitic steel, hot uniaxial compression tests with strain rates ranging from 0.1 s{sup −1} to 10 s{sup −1} and deformations amounts of 40% and 70% where conducted. The true stress–true strain curves were analyzed for the occurrence of DRX under the different strain rates and compressive deformation amounts. The steel microstructures were examined and linked to the observed stress-strain diagrams to study DRX. Results show that DRX was responsible for refining the grain structure over a wide range of strain rates under 70% deformation. However, significant DRX occurred only at the relatively low strain rate of 0.1 s{sup −1} under 40% deformation. The original elongated microstructure of the rolled plate from which the specimens were taken was replaced by dynamic recrystallization grains. At 70% deformation, the average grain size was 4.2 μm at a strain rate of 0.1 s{sup −1}, 2.5 μm at a strain rate of 5 s{sup −1}, 1.8 μm at a strain rate of 10 s{sup −1}. In conclusion, with increasing strain rate, the recrystallized grain size decreased and the peak stress increased.

  14. Effect of Strain Field on Threshold Displacement Energy of Tungsten Studied by Molecular Dynamics Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dong; Gao, Ning; Setyawan, W.; Kurtz, R. J.; Wang, Zhi-Guang; Gao, Xing; He, Wen-Hao; Pang, Li-Long

    2016-09-01

    The influence of strain field on defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten (W) has been studied with molecular dynamics simulations. Two different W potentials (Fikar and Juslin) were compared and the results indicate that the connection distance and selected function linking the short-range and long-range portions of the potentials affects the threshold displacement energy and its direction-specific values. The minimum Ed direction calculated with the Fikar-potential is <100> and with the Juslin-potential is <111>. Nevertheless, the most stable self-interstitial configuration is found to be a <111>-crowdion for both potentials. This stable configuration does not change with applied strain. Varying the strain from compression to tension increases the vacancy formation energy but decreases the self-interstitial formation energy. The formation energy of a self-interstitial changes more significantly than a vacancy such that Ed decreases with applied hydrostatic strain from compression to tension.

  15. Calibration of nonlocal strain gradient shell model for buckling analysis of nanotubes using molecular dynamics simulations

    Science.gov (United States)

    Mehralian, Fahimeh; Tadi Beni, Yaghoub; Karimi Zeverdejani, Mehran

    2017-09-01

    The present paper is concerned with the applicability of nonlocal strain gradient theory for axial buckling analysis of nanotubes. The first order shear deformation theory with the von Kármán geometrical nonlinearity is utilized to establish theoretical formulations. The governing equations and boundary conditions are derived using the minimum potential energy principle. As main purpose of this study, the small length scale parameters are calibrated for the axial buckling problem of carbon nanotubes (CNTs) using molecular dynamics (MDs) simulations. Further the influences of different geometrical and material parameters, such as length and thickness ratio as well as small length scale parameters on the buckling response of nanotubes are studied. It is indicated that the effect of small length scale parameters on the critical buckling load becomes more prominent by increasing thickness and decreasing length ratio. Moreover, the calibrated small length scale parameters presented herein would be useful for the purpose of applying the nonlocal strain gradient theory for the analysis of nanotubes. The calibrated nonlocal strain gradient theory presented herein should be useful for researchers who are using the nonlocal strain gradient shell theories for analysis of micro/nanotubes.

  16. Molecular dynamics study of strain-induced diffusivity of nitrogen in pure iron nanocrystalline

    Science.gov (United States)

    Mohammadzadeh, Roghayeh; Razmara, Naiyer; Razmara, Fereshteh

    2016-12-01

    In the present study, the self-diffusion process of nitrogen in pure iron nanocrystalline under strain conditions has been investigated by Molecular Dynamics (MD). The interactions between particles are modeled using Modified Embedded Atom Method (MEAM). Mean Square Displacement (MSD) of nitrogen in iron structure under strain is calculated. Strain is applied along [ 11 2 ¯ 0 ] and [ 0001 ] directions in both tensile and compression conditions. The activation energy and pre-exponential diffusion factor for nitrogen diffusion is comparatively high along [ 0001 ] direction of compressed structure of iron. The strain-induced diffusion coefficient at 973 K under the compression rate of 0.001 Å/ps along [ 0001 ] direction is about 6.72E-14 m2/s. The estimated activation energy of nitrogen under compression along [ 0001 ] direction is equal to 12.39 kcal/mol. The higher activation energy might be due to the fact that the system transforms into a more dense state when compressive stress is applied.

  17. Highly dynamically evolved intermediate-age open clusters

    CERN Document Server

    Piatti, Andrés E; Sampedro, Laura M

    2016-01-01

    We present a comprehensive UBVRI and Washington CT1T2 photometric analysis of seven catalogued open clusters, namely: Ruprecht 3, 9, 37, 74, 150, ESO 324-15 and 436-2. The multi-band photometric data sets in combination with 2MASS photometry and Gaia astrometry for the brighter stars were used to estimate their structural parameters and fundamental astrophysical properties. We found that Ruprecht 3 and ESO 436-2 do not show self-consistent evidence of being physical systems. The remained studied objects are open clusters of intermediate-age (9.0 < log(t yr-1) < 9.6), of relatively small size (r_cls ~ 0.4 - 1.3 pc) and placed between 0.6 and 2.9 kpc from the Sun. We analized the relationships between core, half-mass, tidal and Jacoby radii as well as half-mass relaxation times to conclude that the studied clusters are in an evolved dynamical stage. The cluster masses obtained by summing those of the observed cluster stars resulted to be ~ 10-15 per cent of the masses of open clusters of similar age locat...

  18. Highly dynamically evolved intermediate-age open clusters

    Science.gov (United States)

    Piatti, Andrés E.; Dias, Wilton S.; Sampedro, Laura M.

    2017-04-01

    We present a comprehensive UBVRI and Washington CT1T2 photometric analysis of seven catalogued open clusters, namely: Ruprecht 3, 9, 37, 74, 150, ESO 324-15 and 436-2. The multiband photometric data sets in combination with 2MASS photometry and Gaia astrometry for the brighter stars were used to estimate their structural parameters and fundamental astrophysical properties. We found that Ruprecht 3 and ESO 436-2 do not show self-consistent evidence of being physical systems. The remained studied objects are open clusters of intermediate age (9.0 ≤ log(t yr-1) ≤ 9.6), of relatively small size (rcls ∼ 0.4-1.3 pc) and placed between 0.6 and 2.9 kpc from the Sun. We analysed the relationships between core, half-mass, tidal and Jacoby radii as well as half-mass relaxation times to conclude that the studied clusters are in an evolved dynamical stage. The total cluster masses obtained by summing those of the observed cluster stars resulted to be ∼10-15 per cent of the masses of open clusters of similar age located closer than 2 kpc from the Sun. We found that cluster stars occupy volumes as large as those for tidally filled clusters.

  19. Dynamic strain estimation for fatigue assessment of an offshore monopile wind turbine using filtering and modal expansion algorithms

    Science.gov (United States)

    Maes, K.; Iliopoulos, A.; Weijtjens, W.; Devriendt, C.; Lombaert, G.

    2016-08-01

    Offshore wind turbines are exposed to continuous wind and wave excitation. The monitoring of high periodic strains at critical locations is important to assess the remaining lifetime of the structure. At some critical locations below the water level, direct measurements of the strains are not feasible. Response estimation techniques can then be used to estimate the strains from a limited set of response measurements and a system model. This paper compares a Kalman filtering algorithm, a joint input-state estimation algorithm, and a modal expansion algorithm, for the estimation of dynamic strains in the tower of an offshore monopile wind turbine. The algorithms make use of a model of the structure and a limited number of response measurements for the prediction of the strain responses. The strain signals obtained from the response estimation algorithms are compared to the actual measured strains in the tower.

  20. The Rule of Dynamic Strain to Near Source Aftershock Distribution of the 2014, Mw 6.0, Napa (California) Earthquake

    Science.gov (United States)

    Emolo, A.; De Matteis, R.; Convertito, V.

    2015-12-01

    The 2014 Napa was recognized as a right-lateral strike-slip fault. About 400 aftershocks occurred, mainly in the near-source range, in the two months after the earthquake. They mostly occurred between 8 and 11 km depth interesting an area of about 10 km2 north-northwest-trending with respect to the mainshock hypocenter. However, the aftershock distribution was not able to constrain the mainshock fault plane. Since Parsons et al. (2014) have shown that Coulomb static stress change does not completely explain near-source aftershock distribution, we explore whether dynamic strain transfer, enhanced by source directivity, contributed to trigger the aftershock sequence. Indeed, dynamic strain transfer triggering attributes enhanced failure probabilities to increased shear stresses or strains, to permeability changes and maybe to fault weakening. In this respect, we observe that a single inverse power law fits the decay of aftershock density as function of distance from the fault plane, suggesting that dynamic stress/strain might have played a role in the aftershocks triggering. To test this hypothesis, we used Peak-Ground Velocities (PGVs) as a proxy for peak-dynamic strain/stress field, accounting for both fault finiteness and source directivity. We first use a point source to retrieve the best parameters of the directivity function from the inversion of the PGVs. Next, the same PGVs are used to jointly infer the surface fault projection and the dominant horizontal rupture direction. Finally, we map the peak-dynamic strain/stress, modified by source geometry and directivity, to resolve the relationship between the aftershocks location and the areas of large dynamic strain values. Thus, we believe that dynamic strain/stress actually contributed to the Napa aftershock distribution. Our results may help to better constrain the Napa causative fault and complement Coulomb static stress change to identify areas that will be more likely affected by aftershocks.

  1. Long-gauge FBGs interrogated by DTR3 for dynamic distributed strain measurement of helicopter blade model

    Science.gov (United States)

    Nishiyama, M.; Igawa, H.; Kasai, T.; Watanabe, N.

    2014-05-01

    In this paper, we describe characteristics of distributed strain sensing based on a Delayed Transmission/Reflection Ratiometric Reflectometry (DTR3) scheme with a long-gauge Fiber Bragg Grating (FBG), which is attractive to dynamic structural deformation monitoring such as a helicopter blade and an airplane wing. The DTR3 interrogator using the longgauge FBG has capability of detecting distributed strain with 50 cm spatial resolution in 100 Hz sampling rate. We evaluated distributed strain sensing characteristics of the long-gauge FBG attached on a 5.5 m helicopter blade model in static tests and free vibration dynamic tests.

  2. Serotypes and patterns of antibiotic resistance in strains causing invasive pneumococcal disease in children less than 5 years of age.

    Directory of Open Access Journals (Sweden)

    Chunfeng Liu

    Full Text Available OBJECTIVE: The serotypes and patterns of antibiotic resistance of Streptococcus pneumoniae (S. pneumoniae strains that cause invasive pneumococcal disease (IPD in infants were analyzed to provide guidance for clinical disease prevention and treatment. METHODS: The clinical features of confirmed IPD were evaluated in 61 patients, less than 5 years of age, who were admitted to our hospital between January 2009 and December 2011. The serotypes and antibiotic resistance of strains of S.pneumoniae were determined using the capsular swelling method and the E-test. RESULTS: A total of 61 invasive strains were isolated. The serotype distribution of those isolates were 19A (41.0%, 14 (19.7%, 19F (11.5%, 23F (9.8%, 8 (4.9%, 9V (4.9%, 1 (3.3%, and 4, 6B, and 20 (each 1.6%. The percentage of S. pneumoniae strains resistant to erythromycin, clindamycin, and cotrimoxazole were 100%, 86.9%, and 100%, respectively. The percentage of S. pneumoniae strains resistant to penicillin, amoxicillin/clavulanic acid, cefuroxime, ceftriaxone, cefotaxime, cefepime, and meropenem were 42.6%, 18.0%, 82.0%, 18.0%, 13.1%, 13.1%, and 36.1%, respectively. The percentage of multidrug-resistant strains was 95.6%. Strains of all serotypes isolated in this study were highly resistant to erythromycin, cotrimoxazole, and clindamycin. Strains with serotype 19A had the highest rates of resistance. CONCLUSIONS: Serotype 19A strains were most frequently isolated from children with IPD treated in our hospital. The strains causing IPD are highly resistant to antibiotics.

  3. Strain rate dependent deformation and failure behavior of laser welded DP780 steel joint under dynamic tensile loading

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang, E-mail: liuyang@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Dong, Danyang, E-mail: dongdanyang@mail.neu.edu.cn [College of Science, Northeastern University, Shenyang 110819 (China); Wang, Lei, E-mail: wanglei@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Chu, Xi, E-mail: chuxi.ok@163.com [College of Science, Northeastern University, Shenyang 110819 (China); Wang, Pengfei, E-mail: wpf1963871400@163.com [College of Science, Northeastern University, Shenyang 110819 (China); Jin, Mengmeng, E-mail: 24401878@163.com [College of Science, Northeastern University, Shenyang 110819 (China)

    2015-03-11

    Laser welded DP steel joints are used widely in the automotive industry for weight reduction. Understanding the deformation and fracture behavior of the base metal (BM) and its welded joint (WJ), especially at high strain rates, is critical for the design of vehicle structures. This paper is concerned with the effects of strain rate on the tensile properties, deformation and fracture behavior of the laser welded DP780 steel joint. Quasi-static and dynamic tensile tests were performed on the WJ and BM of the DP780 steel using an electromechanical universal testing machine and a high-speed tensile testing machine over a wide range of strain rate (0.0001–1142 s{sup −1}). The microstructure change and microhardness distribution of the DP780 steel after laser welding were examined. Digital image correlation (DIC) and high-speed photography were employed for the strain measurement of the DP780 WJ during dynamic tensile tests. The DP780 WJ is a heterogeneous structure with hardening in fusion zone (FZ) and inner heat-affected zone (HAZ), and softening in outer HAZ. The DP780 BM and WJ exhibit positive strain rate dependence on the YS and UTS, which is smaller at lower strain rates and becomes larger with increasing strain rate, while ductility in terms of total elongation (TE) tends to increase under dynamic loading. Laser welding leads to an overall reduction in the ductility of the DP780 steel. However, the WJ exhibits a similar changing trend of the ductility to that of the BM with respect to the strain rate over the whole strain rate range. As for the DP780 WJ, the distance of tensile failure location from the weld centerline decreases with increasing strain rate. The typical ductile failure characteristics of the DP780 BM and WJ do not change with increasing strain rate. DIC measurements reveal that the strain localization starts even before the maximum load is attained in the DP780 WJ and gradual transition from uniform strains to severely localized strains

  4. Molecular dynamics simulation of materials response to high strain-rate loading

    Energy Technology Data Exchange (ETDEWEB)

    Belak, J

    1999-07-22

    A molecular dynamics (MD) analysis of conservation of momentum through a shock front is presented. The MD model uses a non-traditional boundary condition that allows simulation in the reference frame of the shock front. Higher order terms proportional to gradients in the density are shown to be non-negligible at the shock front. The simulation is used to study the sequence of thermodynamic states during shock loading. Melting is observed in the simulations, though above the thermodynamic melt curve as is common in homogeneous simulations of melting. High strain-rate tensile loading is applied to the growth of nanoscale voids in copper. Void growth is found to occur by plasticity mechanisms with dislocations emerging from the void surface. [molecular dynamics, shock loading, conservation of momentum, shock melting, void growth

  5. A general procedure for estimating dynamic displacements using strain measurements and operational modal analysis

    Science.gov (United States)

    Skafte, Anders; Aenlle, Manuel L.; Brincker, Rune

    2016-02-01

    Measurement systems are being installed in more and more civil structures with the purpose of monitoring the general dynamic behavior of the structure. The instrumentation is typically done with accelerometers, where experimental frequencies and mode shapes can be identified using modal analysis and used in health monitoring algorithms. But the use of accelerometers is not suitable for all structures. Structures like wind turbine blades and wings on airplanes can be exposed to lightning, which can cause the measurement systems to fail. Structures like these are often equipped with fiber sensors measuring the in-plane deformation. This paper proposes a method in which the displacement mode shapes and responses can be predicted using only strain measurements. The method relies on the newly discovered principle of local correspondence, which states that each experimental mode can be expressed as a unique subset of finite element modes. In this paper the technique is further developed to predict the mode shapes in different states of the structure. Once an estimate of the modes is found, responses can be predicted using the superposition of the modal coordinates weighted by the mode shapes. The method is validated with experimental tests on a scaled model of a two-span bridge installed with strain gauges. Random load was applied to simulate a civil structure under operating condition, and strain mode shapes were identified using operational modal analysis.

  6. Optimal Reference Strain Structure for Studying Dynamic Responses of Flexible Rockets

    Science.gov (United States)

    Tsushima, Natsuki; Su, Weihua; Wolf, Michael G.; Griffin, Edwin D.; Dumoulin, Marie P.

    2017-01-01

    In the proposed paper, the optimal design of reference strain structures (RSS) will be performed targeting for the accurate observation of the dynamic bending and torsion deformation of a flexible rocket. It will provide the detailed description of the finite-element (FE) model of a notional flexible rocket created in MSC.Patran. The RSS will be attached longitudinally along the side of the rocket and to track the deformation of the thin-walled structure under external loads. An integrated surrogate-based multi-objective optimization approach will be developed to find the optimal design of the RSS using the FE model. The Kriging method will be used to construct the surrogate model. For the data sampling and the performance evaluation, static/transient analyses will be performed with MSC.Natran/Patran. The multi-objective optimization will be solved with NSGA-II to minimize the difference between the strains of the launch vehicle and RSS. Finally, the performance of the optimal RSS will be evaluated by checking its strain-tracking capability in different numerical simulations of the flexible rocket.

  7. Strategy Dependent Swimming Dynamics Change among a Predatory Algae Species with Different Strains

    Science.gov (United States)

    Katz, Joseph; Sheng, Jian; Malkiel, Edwin; Adolf, Jason; Place, Allen

    2008-11-01

    Digital holographic microscopic cinematography is used for measuring the 3D, time resolved, swimming behavior of toxic and non-toxic strains the marine dinoflagellate Karlodinium veneficum. We focus on the response of predators of the same species, but with different predation strategy, to the presence of prey, Storeatula major. Experiments are performed in a 3x3 mm cuvette, at densities extending to 100,000 cells/ml. Holograms are recorded at 60fps and at 20X magnification. In each case, we simultaneously track 200-500 cells in the 3mm deep sample, at a spatial resolution of 0.4x0.4x2 μm. We show that responses are largely dependent on the predation strategy. K. veneficum 2064, a toxic mixotroph, slows down and decreases the helix radius and clusters around the prey. Conversely, MD5, a non-toxic, autotrophic-like strain is completely oblivious to prey. Strain 1974, which is toxic and twice as motile, shows heterotrophic-like responses with characteristics of an active hunter. Also, on going spectral analysis of the 3-D motion provides quantitative insight on the swimming dynamics of microorganisms.

  8. Sex-, age- and strain-related quantities of muscalure on the cuticula of the housefly (Musca domestica)

    NARCIS (Netherlands)

    Noorman, N; denOtter, CJ; Sommeijer, MJ; Francke, PJ

    1997-01-01

    Muscalure, (Z)-9-tricosene, is the major component of the cuticular contact sex pheromone of female houseflies, Musca domestica. By means of gas chromatography the relative amounts of muscalure were determined on female and male houseflies of different sex, age and strain. Females and males of mixed

  9. Brillouin optical time domain reflectometry for fast detection of dynamic strain incorporating double-edge technique

    CERN Document Server

    Shangguan, Mingjia; Xia, Haiyun; Qiu, Jiawei; Shentu, Guoliang; Dou, Xiankang; Zhang, Qiang; Pan, Jian-wei

    2016-01-01

    For the first time, a direct detection BOTDR is demonstrated for distributed dynamic strain sensing incorporating double-edge technique, time-division multiplexing technique and upconversion technique. The double edges are realized by using the transmission curve and reflection curve of an all-fiber Fabry-Perot interferometer (FPI). Benefiting from the low loss of the fiber at, the time-division multiplexing technique is performed to realize the double-edge technique by using only a single-channel FPI and only one piece of a detector. In order to detect the weak spontaneous Brillouin backscattering signal efficiently, a fiber-coupled upconversion detector is adopted to upconvert the backscattering signal at 1548.1 nm to 863 nm, which is detected by a Si-APD finally. In the experiment, dynamic strain disturbance up to 1.9m{\\epsilon} over 1.5 km of polarization maintaining fiber is detected at a sampling rate of 30 Hz. An accuracy of 30{\\mu}{\\epsilon} and spatial resolution of 0.6 m is realized.

  10. Brillouin optical time domain reflectometry for fast detection of dynamic strain incorporating double-edge technique

    Science.gov (United States)

    Shangguan, Mingjia; Wang, Chong; Xia, Haiyun; Shentu, Guoliang; Dou, Xiankang; Zhang, Qiang; Pan, Jian-wei

    2017-09-01

    For the first time, to the best of our knowledge, a direct detection Brillouin optical time-domain reflectometry (BOTDR) is demonstrated for fast distributed dynamic strain sensing incorporating double-edge technique, time-division multiplexing technique and upconversion technique. In order to guarantee the robust stability of the system, the double-edge technique is implemented by using a convert single-channel FPI and a fiber-coupled upconversion single-photon detector, incorporating a time-division multiplexing method. The upconversion single-photon detector is adopted to upconvert the backscattering photons from 1548.1 nm to 863 nm, which is subsequently detected by a Silicon avalanche photodiode (Si-APD). In the experiment, dynamic strain disturbance up to 1.9 mε over 1.5 km of a polarization maintaining fiber is detected at a sampling rate of 30 Hz. An accuracy of ± 30 με and spatial resolution of 0.6 m are realized.

  11. Study of coherence strain of GP II zones in an aged aluminum composite

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Rivera, J.L., E-mail: jose.hernandez@cimav.edu.mx [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, C.P. 31109, Chihuahua (Mexico); Stuttgart Center for Electron Microscopy, Max Planck Institute for Intelligent Systems (formerly Max Planck Institute for Metals Research), Heisenbergstrase 3, 70569 Stuttgart (Germany); Rivera, J.J. Cruz [Facultad de Ingenieria-Instituto de Metalurgia, Universidad Autonoma de San Luis Potosi, Sierra Leona 550, Lomas 2a seccion, C.P. 78210, San Luis Potosi (Mexico); Koch, C.T. [Department of Physics, Ulm University, 86069 Ulm (Germany); Stuttgart Center for Electron Microscopy, Max Planck Institute for Intelligent Systems (formerly Max Planck Institute for Metals Research), Heisenbergstrase 3, 70569 Stuttgart (Germany); Oezdoel, V.B. [Stuttgart Center for Electron Microscopy, Max Planck Institute for Intelligent Systems (formerly Max Planck Institute for Metals Research), Heisenbergstrase 3, 70569 Stuttgart (Germany); Martinez-Sanchez, R. [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, C.P. 31109, Chihuahua (Mexico)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Precipitation sequence was changed in 2024 Al alloy. Black-Right-Pointing-Pointer Image artifacts ought to the mask size and shape increased the real strain value. Black-Right-Pointing-Pointer The strain distribution around experimental GP area was non uniform and more complex than reference. Black-Right-Pointing-Pointer The origin of this strain distribution are related to mechanisms by which GP precipitates lose coherence. - Abstract: Strain mapping using the geometric phase analysis (GPA) technique was applied to Al-GP II (Guinier-Preston) nanoscale precipitates, using both high resolution transmission electron microscopy (HRTEM) micrographs as well as the exit wave function (EWF) obtained by focal series reconstruction. The experimental strain results were compared with strain maps obtained from an atomic model which consisted of an Al supercell containing a GP II precipitate. It was built as a reference from literature data. The experimental results demonstrate a complex strain distribution and larger fluctuations than the reference strain maps. These differences were found to be partly a consequence of image artifacts produced by the technique as well as complex microstructural events which were present at the development stage studied.

  12. Regional Groundwater Processes and Flow Dynamics from Age Tracer Data

    Science.gov (United States)

    Morgenstern, Uwe; Stewart, Mike K.; Matthews, Abby

    2016-04-01

    Age tracers are now used in New Zealand on regional scales for quantifying the impact and lag time of land use and climate change on the quantity and quality of available groundwater resources within the framework of the National Policy Statement for Freshwater Management 2014. Age tracers provide measurable information on the dynamics of groundwater systems and reaction rates (e.g. denitrification), essential for conceptualising the regional groundwater - surface water system and informing the development of land use and groundwater flow and transport models. In the Horizons Region of New Zealand, around 200 wells have tracer data available, including tritium, SF6, CFCs, 2H, 18O, Ar, N2, CH4 and radon. Well depths range from shallower wells in gravel aquifers in the Horowhenua and Tararua districts, and deeper wells in the aquifers between Palmerston North and Wanganui. Most of the groundwater samples around and north of the Manawatu River west of the Tararua ranges are extremely old (>100 years), even from relatively shallow wells, indicating that these groundwaters are relatively disconnected from fresh surface recharge. The groundwater wells in the Horowhenua tap into a considerably younger groundwater reservoir with groundwater mean residence time (MRT) of 10 - 40 years. Groundwater along the eastern side of the Tararua and Ruahine ranges is significantly younger, typically groundwater recharge rates, as deduced from groundwater depth and MRT, are extremely low in the central coastal area, consistent with confined groundwater systems, or with upwelling of old groundwater close to the coast. Very low vertical recharge rates along the Manawatu River west of the Manawatu Gorge indicate upwelling groundwater conditions in this area, implying groundwater discharge into the river is more likely here than loss of river water into the groundwater system. High recharge rates observed at several wells in the Horowhenua area and in the area east of the Tararua and

  13. Studies on Stress-Strain Curves of Aged Composite Solid Rocket Propellants

    Directory of Open Access Journals (Sweden)

    Himanshu Shekhar

    2012-03-01

    Full Text Available Mechanical property evaluation of composite solid rocket propellants is used as a quick quality control tool for propellant development and production. However, stress-strain curves from uni-axial tensile testing can be utilised to assess the shelf-life of propellants also. Composite propellants (CP of two varieties cartridge-loaded (CLCP and case-bonded (CBCP are utilized in rocket and missile applications. Both classes of propellants were evaluated for mechanical properties namely tensile strength, modulus and percentage elongation using specimens conforming to ASTM D638 type IV at different ageing time. Both classes of propellants show almost identical variation in various mechanical properties with time. Tensile strength increases with time for both classes of propellants and percentage elongation reduces. Initial modulus is also found to decrease with time. Tensile strength is taken as degradation criteria and it is observed that CLCP has slower degradation rate than CBCP. This is because of two facts–(i higher initial tensile strength of CLCP (1.39 MPa compared to CBCP (0.665 MPa and (ii lower degradation rate of CLCP (0.0014 MPa/day with respect to CBCP (0.0025 MPa/day. For the studied composite propellants, a degradation criterion in the form of percentage change in tensile strength is evaluated and shelf life for different degradation criteria is tabulated for quick reference.Defence Science Journal, 2012, 62(2, pp.90-94, DOI:http://dx.doi.org/10.14429/dsj.62.773

  14. Nanoscale Structure, Dynamics, and Aging Behavior of Metallic Glass Thin Films.

    Science.gov (United States)

    Burgess, J A J; Holt, C M B; Luber, E J; Fortin, D C; Popowich, G; Zahiri, B; Concepcion, P; Mitlin, D; Freeman, M R

    2016-08-08

    Scanning tunnelling microscopy observations resolve the structure and dynamics of metallic glass Cu100-xHfx films and demonstrate scanning tunnelling microscopy control of aging at a metallic glass surface. Surface clusters exhibit heterogeneous hopping dynamics. Low Hf concentration films feature an aged surface of larger, slower clusters. Argon ion-sputtering destroys the aged configuration, yielding a surface in constant fluctuation. Scanning tunnelling microscopy can locally restore the relaxed state, allowing for nanoscale lithographic definition of aged sections.

  15. Nanoscale Structure, Dynamics, and Aging Behavior of Metallic Glass Thin Films

    Science.gov (United States)

    Burgess, J. A. J.; Holt, C. M. B.; Luber, E. J.; Fortin, D. C.; Popowich, G.; Zahiri, B.; Concepcion, P.; Mitlin, D.; Freeman, M. R.

    2016-01-01

    Scanning tunnelling microscopy observations resolve the structure and dynamics of metallic glass Cu100−xHfx films and demonstrate scanning tunnelling microscopy control of aging at a metallic glass surface. Surface clusters exhibit heterogeneous hopping dynamics. Low Hf concentration films feature an aged surface of larger, slower clusters. Argon ion-sputtering destroys the aged configuration, yielding a surface in constant fluctuation. Scanning tunnelling microscopy can locally restore the relaxed state, allowing for nanoscale lithographic definition of aged sections. PMID:27498698

  16. Automated data-based damage localization under ambient vibration using local modal filters and dynamic strain measurements: Experimental applications

    Science.gov (United States)

    Tondreau, Gilles; Deraemaeker, Arnaud

    2014-12-01

    This paper deals with the experimental application of modal filters for automated damage localization using dynamic strain measurements. Previously developed for damage detection, the extension of modal filtering to damage localization consists in splitting a very large network of dynamic strain sensors into several independent local sensor networks. An efficient signal processing coupled to control charts allows a fully automated data-based damage localization once the modal filters are initialized. The method is tested experimentally on a small clamped-free steel plate and a 3.78 m long steel I-beam, both instrumented with a network of cheap piezoelectric patches to measure the dynamic strains. A removable damage is introduced at different positions by means of a small removable damage device. For both applications, the method can successfully detect and locate all damage cases considered, showing the potentiality of the method for field applications.

  17. Dynamic behaviour and shock-induced martensite transformation in near-beta Ti-5553 alloy under high strain rate loading

    Directory of Open Access Journals (Sweden)

    Wang Lin

    2015-01-01

    Full Text Available Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy with alpha/beta phases exhibits various strain rate hardening effects, both failure through adiabatic shear band. Ti-5553 alloy with Widmannstatten microstructure exhibit more obvious strain rate hardening effect, lower critical strain rate for ASB nucleation, compared with the alloy with Bimodal microstructures. Under dynamic compression, shock-induced beta to alpha” martensite transformation occurs.

  18. Evaluation of Dynamic Deformation Behaviors in Metallic Materials under High Strain-Rates Using Taylor Bar Impact Test

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Kyung Oh; Shin, Hyung Seop [Andong National Univ., Andong (Korea, Republic of)

    2016-09-15

    To ensure the reliability and safety of various mechanical systems in accordance with their high-speed usage, it is necessary to evaluate the dynamic deformation behavior of structural materials under impact load. However, it is not easy to understand the dynamic deformation behavior of the structural materials using experimental methods in the high strain-rate range exceeding 10{sup 4} s{sup -1}. In this study, the Taylor bar impact test was conducted to investigate the dynamic deformation behavior of metallic materials in the high strain-rate region, using a high-speed photography system. Numerical analysis of the Taylor bar impact test was performed using AUTODYN S/W. The results of the analysis were compared with the experimental results, and the material behavior in the high strain-rate region was discussed.

  19. Dynamical heterogeneity in aging colloidal glasses of Laponite

    NARCIS (Netherlands)

    Jabbari-Farouji, S.; Zargar, R.; Wegdam, G.H.; Bonn, D.

    2012-01-01

    Glasses behave as solids due to their long relaxation time; however the origin of this slow response remains a puzzle. Growing dynamic length scales due to cooperative motion of particles are believed to be central to the understanding of both the slow dynamics and the emergence of rigidity. Here, w

  20. Strain energy analysis of screw dislocations in 4H-SiC by molecular dynamics

    Science.gov (United States)

    Kawamura, Takahiro; Mizutani, Mitsutoshi; Suzuki, Yasuyuki; Kangawa, Yoshihiro; Kakimoto, Koichi

    2016-03-01

    We simulated screw dislocations with the Burgers vector parallel to the [0001] direction in 4H-SiC by a classical molecular dynamics method. A stable structure of an extended dislocation generated by the dissociation of a screw dislocation was identified by calculating the strain energy caused by dislocation cores and stacking faults. As a result, we conclude that the most expected structure of the extended dislocation is made of partial dislocations with the Burgers vector b = 1/2c + 1/2c (c is equal to the thickness of one period in the c-axis direction of 4H-SiC) and the stacking fault that is parallel to the a-plane, and that the distance between the dislocation cores is less than about 44 Å.

  1. Nonlocal strain gradient theory calibration using molecular dynamics simulation based on small scale vibration of nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mehralian, Fahimeh [Mechanical Engineering Department, Shahrekord University, Shahrekord (Iran, Islamic Republic of); Tadi Beni, Yaghoub, E-mail: tadi@eng.sku.ac.ir [Faculty of Engineering, Shahrekord University, Shahrekord (Iran, Islamic Republic of); Karimi Zeverdejani, Mehran [Mechanical Engineering Department, Shahrekord University, Shahrekord (Iran, Islamic Republic of)

    2017-06-01

    Featured by two small length scale parameters, nonlocal strain gradient theory is utilized to investigate the free vibration of nanotubes. A new size-dependent shell model formulation is developed by using the first order shear deformation theory. The governing equations and boundary conditions are obtained using Hamilton's principle and solved for simply supported boundary condition. As main purpose of this study, since the values of two small length scale parameters are still unknown, they are calibrated by the means of molecular dynamics simulations (MDs). Then, the influences of different parameters such as nonlocal parameter, scale factor, length and thickness on vibration characteristics of nanotubes are studied. It is also shown that increase in thickness and decrease in length parameters intensify the effect of nonlocal parameter and scale factor.

  2. Direct measurement of the correlated dynamics of the protein-backbone and proximal waters of hydration in mechanically strained elastin

    CERN Document Server

    Sun, Cheng; Huang, Jiaxin; Boutis, Gregory S

    2011-01-01

    We report on the direct measurement of the correlation times of the protein backbone carbons and proximal waters of hydration in mechanically strained elastin by nuclear magnetic resonance methods. The experimental data indicate a decrease in the correlation times of the carbonyl carbons as the strain on the biopolymer is increased. These observations are in good agreement with short 4ns molecular dynamics simulations of (VPGVG)3, a well studied mimetic peptide of elastin. The experimental results also indicate a reduction in the correlation time of proximal waters of hydration with increasing strain applied to the elastomer. A simple model is suggested that correlates the increase in the motion of proximal waters of hydration to the increase in frequency of libration of the protein backbone that develops with increasing strain. Together, the reduction in the protein entropy accompanied with the increase in entropy of the proximal waters of hydration with increasing strain, support the notion that the source ...

  3. Linking water age and solute dynamics in streamflow at the Hubbard Brook Experimental Forest, NH, USA

    Science.gov (United States)

    Paolo Benettin; Scott W. Bailey; John L. Campbell; Mark B. Green; Andrea Rinaldo; Gene E. Likens; Kevin J. McGuire; Gianluca Botter

    2015-01-01

    We combine experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is here applied to...

  4. Dynamic simulation for tempo-spatial distribution of strain energy density in inhomogeneous stratified crust

    Institute of Scientific and Technical Information of China (English)

    CHEN Yu-kun; NIE Yong-an

    2000-01-01

    Through simulating the research on dynamic variations of strain energy density (SED) in seismogenic model with hard inclusion, the authors have gained further knowledge to such problems as the process of earthquake preparation, initial rupture, conditions of the initial rupture and fracture propagation direction, etc. Results of the research show that SED (strain energy density) in soft inclusion is very high during the initial period of earthquake preparation. And the increment of SED in the soft area decreases at the later stage of the process. Meanwhile, the increment increases quickly in hard inclusion and in the intersection zone of the inclusion with an erecting fault, where the increment of SED is maximum. Thus, the intersection zone between hard inclusion with larger elastic modulus and erecting fault becomes the place where the initial rupture or earthquake occurs. The fracture in the end part of the hard inclusion spreads along a direction nearly vertical to the erecting fault, so the theoretical fracture direction is consistent with that calculated by digital simulation.

  5. Transmission dynamics of Bartonella sp. strain OE 1-1 in Sundevall's jirds (Meriones crassus).

    Science.gov (United States)

    Morick, Danny; Krasnov, Boris R; Khokhlova, Irina S; Gottlieb, Yuval; Harrus, Shimon

    2013-02-01

    A high prevalence of Bartonella infection is found in many natural systems; however, the transmission dynamics leading to observations of these infections is not fully understood. The capability of Xenopsylla ramesis fleas to serve as competent vectors of Bartonella sp. OE 1-1 (a strain closely related to the zoonotic Bartonella elizabethae) to Meriones crassus jirds was investigated. Naïve X. ramesis fleas were placed for 72 h on naïve jirds or jirds that were either experimentally or naturally infected with Bartonella sp. strain OE 1-1, after which they were placed on naïve jirds. Postfeeding, 69 to 100% of the fleas collected from each Bartonella-positive jird contained Bartonella DNA, and all naïve jirds became positive for Bartonella sp. OE 1-1 after infestation with the infected fleas. In addition, maternal transmission of Bartonella sp. OE 1-1 in jirds was tested by mating 5 Bartonella-positive and 5 naïve female jirds with 10 naïve male jirds in the absence of fleas. Fifteen offspring were delivered by each group. Cultures of blood drawn from all offspring on days 35 and 47 postdelivery were found to be negative for Bartonella. A single spleen sample from the offspring of a Bartonella-positive mother was found molecularly positive for Bartonella sp. OE 1-1. This study demonstrates that X. ramesis fleas are competent vectors of Bartonella sp. OE 1-1 to M. crassus jirds and indicates that maternal transmission is probably not the major transmission route from female jirds to their offspring. We suggest that the dynamics of Bartonella sp. OE 1-1 in the M. crassus jird population in nature is mostly dependent on its vectors.

  6. Dynamics of cell proliferation in the adult dentate gyrus of two inbred strains of mice

    Science.gov (United States)

    Hayes, N. L.; Nowakowski, R. S.

    2002-01-01

    The output potential of proliferating populations in either the developing or the adult nervous system is critically dependent on the length of the cell cycle (T(c)) and the size of the proliferating population. We developed a new approach for analyzing the cell cycle, the 'Saturate and Survive Method' (SSM), that also reveals the dynamic behaviors in the proliferative population and estimates of the size of the proliferating population. We used this method to analyze the proliferating population of the adult dentate gyrus in 60 day old mice of two inbred strains, C57BL/6J and BALB/cByJ. The results show that the number of cells labeled by exposure to BUdR changes dramatically with time as a function of the number of proliferating cells in the population, the length of the S-phase, cell division, the length of the cell cycle, dilution of the S-phase label, and cell death. The major difference between C57BL/6J and BALB/cByJ mice is the size of the proliferating population, which differs by a factor of two; the lengths of the cell cycle and the S-phase and the probability that a newly produced cell will die within the first 10 days do not differ in these two strains. This indicates that genetic regulation of the size of the proliferating population is independent of the genetic regulation of cell death among those newly produced cells. The dynamic changes in the number of labeled cells as revealed by the SSM protocol also indicate that neither single nor repeated daily injections of BUdR accurately measure 'proliferation.'.

  7. Microstructure and annealing behavior of a modified 9Cr-1Mo steel after dynamic plastic deformation to different strains

    DEFF Research Database (Denmark)

    Zhang, Zhenbo; Mishin, Oleg; Tao, N.R.;

    2015-01-01

    The microstructure, hardness and tensile properties of a modified 9Cr-1Mo steel processed by dynamic plastic deformation (DPD) to different strains (0.5 and 2.3) have been investigated in the as-deformed and annealed conditions. It is found that significant structural refinement and a high level...... of strength can be achieved by DPD to a strain of 2.3, and that the microstructure at this strain contains a large fraction of high angle boundaries. The ductility of the DPD processed steel is however low. Considerable structural coarsening of the deformed microstructure without pronounced recrystallization...

  8. Verification of new model for calculation of critical strain for the initialization of dynamic recrystallization using laboratory rolling

    Directory of Open Access Journals (Sweden)

    R. Fabík

    2009-10-01

    Full Text Available This paper presents a new model for calculation of critical strain for initialization of dynamic recrystallization. The new model reflects the history of forming in the deformation zone during rolling. In this region of restricted deformation, the strain rate curve for the surface of the strip exhibits two peaks. These are the two reasons why the onset of dynamic recrystallization DRX near the surface of the rolled part occurs later than in theory during strip rolling. The present model had been used in a program for simulation of forming processes with the aid of FEM and a comparison between the physical experiment and a mathematical model had been drawn.

  9. Ultrasonic slow dynamics to probe concrete aging and damage

    Science.gov (United States)

    Larose, E.; Tremblay, N.; Payan, C.; Garnier, V.; Rossetto, V.

    2013-01-01

    The stiffness of concrete experiences a drop immediately after a moderate mechanical solicitation. Then the stiffness rises back logarithmically toward its initial value. This Slow Dynamics behavior has been probed by macroscopic quantities averaged over the sample volume, including resonant frequency. This article presents a different approach based on diffuse acoustic wave spectroscopy, a technique that is directly sensitive to the details of the sample structure. The parameters of the dynamics are found to depend on mechanical and thermal damage of the medium. Results confirm that slow dynamics can be used onsite to assess the level of damage of a given structure.

  10. Dynamics of pre-strained bi-material elastic systems linearized three-dimensional approach

    CERN Document Server

    Akbarov, Surkay D

    2015-01-01

    This book deals with dynamics of pre-stressed or pre-strained bi-material elastic systems consisting of stack of pre-stressed layers, stack of pre-stressed layers and pre-stressed half space (or half plane), stack of pre-stressed layers as well as absolute rigid foundation, pre-stressed compound solid and hollow cylinders and pre-stressed sandwich hollow cylinders. The problems considered in the book relate to the dynamics of a moving and oscillating moving load, forced vibration caused by linearly located or point located time-harmonic forces acting to the foregoing systems. Moreover, a considerable part of the book relate to the problems regarding the near surface, torsional and axisymmetric longitudinal waves propagation and dispersion in the noted above bi-material elastic systems. The book carries out the investigations within the framework of the piecewise homogeneous body model with the use of the Three-Dimensional Linearized Theory of Elastic Waves in Initially Stressed Bodies.

  11. Ultraslow dynamics and stress relaxation in the aging of a soft glassy system

    OpenAIRE

    Ramos, Laurence; Cipelletti, Luca

    2001-01-01

    We use linear rheology and multispeckle dynamic light scattering (MDLS) to investigate the aging of a gel composed of multilamellar vesicles. Light scattering data indicate rearrangement of the gel through an unusual ultraslow ballistic motion. A dramatic slowdown of the dynamics with sample age $t_{w}$ is observed for both rheology and MDLS, the characteristic relaxation time scaling as $t_{w}^{\\mu}$. We find the same aging exponent $\\mu =0.78$ for both techniques, suggesting that they probe...

  12. The large shear strain dynamic behaviour of in-vitro porcine brain tissue and a silicone gel model material.

    Science.gov (United States)

    Brands, D W; Bovendeerd, P H; Peters, G W; Wismans, J S

    2000-11-01

    The large strain dynamic behaviour of brain tissue and silicone gel, a brain substitute material used in mechanical head models, was compared. The non-linear shear strain behaviour was characterised using stress relaxation experiments. Brain tissue showed significant shear softening for strains above 1% (approximately 30% softening for shear strains up to 20%) while the time relaxation behaviour was nearly strain independent. Silicone gel behaved as a linear viscoelastic solid for all strains tested (up to 50%) and frequencies up to 461 Hz. As a result, the large strain time dependent behaviour of both materials could be derived for frequencies up to 1000 Hz from small strain oscillatory experiments and application of Time Temperature Superpositioning. It was concluded that silicone gel material parameters are in the same range as those of brain tissue. Nevertheless the brain tissue response will not be captured exactly due to increased viscous damping at high frequencies and the absence of shear softening in the silicone gel. For trend studies and benchmarking of numerical models the gel can be a good model material.

  13. Dynamic changes in mouse hematopoietic stem cell numbers during aging

    NARCIS (Netherlands)

    de Haan, G; Van Zant, G

    1999-01-01

    To address the fundamental question of whether or not stem cell populations age, we performed quantitative measurements of the cycling status and frequency of hematopoietic stem cells in long-lived C57BL/6 (B6) and short-lived DBA/2 (DBA) mice at different developmental and aging stages. The frequen

  14. Aging dynamics in ferroelectric deuterated potassium dihydrogen phosphate

    Science.gov (United States)

    Hecht, Rachel; Cieszymski, Samuel F.; Colla, Eugene V.; Weissman, M. B.

    2017-09-01

    Anomalously large dielectric aging is found in the high-susceptibility plateau ferroelectric regime of nominally ˜95 % deuterated potassium dihydrogen phosphate (DKDP). Much less aging is found in nondeuterated KDP throughout most of its plateau region. Optical images of the DKDP domain structure show no dramatic change during aging. Small changes in electric field restore the preaged susceptibility, but the previous aging almost recovers after returning to a respective aging field. Susceptibility vs field can show memory of at least two prior aging fields. Aging effects are not fully erased even by brief heating above the Curie point, indicating a role for diffusion of hydrogen to the domain walls, leaving changes in disorder that can survive temporary absence of domain walls. Asymmetrical nonlinear susceptibility develops for fields slightly above or below a prior aging field and during field sweeps, with the dependence of the second-harmonic magnitude on sweep rate giving a characteristic time comparable to the time for hydrogen to diffuse a domain-wall width.

  15. Strain-specific estimation of epidemic success provides insights into the transmission dynamics of tuberculosis

    Science.gov (United States)

    Rasigade, Jean-Philippe; Barbier, Maxime; Dumitrescu, Oana; Pichat, Catherine; Carret, Gérard; Ronnaux-Baron, Anne-Sophie; Blasquez, Ghislaine; Godin-Benhaim, Christine; Boisset, Sandrine; Carricajo, Anne; Jacomo, Véronique; Fredenucci, Isabelle; Pérouse de Montclos, Michèle; Flandrois, Jean-Pierre; Ader, Florence; Supply, Philip; Lina, Gérard; Wirth, Thierry

    2017-01-01

    The transmission dynamics of tuberculosis involves complex interactions of socio-economic and, possibly, microbiological factors. We describe an analytical framework to infer factors of epidemic success based on the joint analysis of epidemiological, clinical and pathogen genetic data. We derive isolate-specific, genetic distance-based estimates of epidemic success, and we represent success-related time-dependent concepts, namely epidemicity and endemicity, by restricting analysis to specific time scales. The method is applied to analyze a surveillance-based cohort of 1,641 tuberculosis patients with minisatellite-based isolate genotypes. Known predictors of isolate endemicity (older age, native status) and epidemicity (younger age, sputum smear positivity) were identified with high confidence (P tuberculosis can be gained from active surveillance data. PMID:28349973

  16. DYNAMICS OF PIKE (ESOX LUCIUS LINNAEUS, 1758 AGE STRUCTURE IN THE DNIEPER LOWER REACHES IN CONNECTION WITH FISHING

    Directory of Open Access Journals (Sweden)

    K. Geina

    2015-03-01

    Full Text Available Purpose. To analyze the dynamics of pike (Esox luceus Linnaeus, 1758 age structure of the Dnieper lower reaches in conditions of the modification of fishing pressure. Methodology. An analysis of fishing situation has been performed based on data of official fishery statistics. Fish sampling was done at control-observation posts of the Institute of Fisheries of the NAAS of Ukraine and directly in the fishery. Juvenile fish yield was determined using a complex of fry fishing gears using a stationary net-station. Field and cameral processing of the material was performed using generally accepted methods. Findings. A retrospective analysis of the situation in the Dnieper-Bug lower reach system clearly indicates on the presence of continuous tendency of catch decline of representative of native fish fauna – pike. With relatively uniform indices of the “yield” of its juveniles before Dnieper flow impoundment and in conditions of present time, its commercial catches significantly dropped. The dynamics of pike current age structure indicates on an increase of relative density of age groups, which form the recruitment of the commercial portion of the population (1-1+ and a decrease of importance of the component of the right side of age series. A discrepancy between the observed changes of the age group and commercial harvest quantities indicates on increased human pressure on this species. Originality. For the first, we analyzed the dynamics of fish juvenile “yield” and age structure of pike commercial stock of the Dnieper lower reaches in the river flow transformation process. Practical value. A decrease of the ichthyomass of piscivorous fishes in the Dnieper lower reaches results in changes of fish populations of littoral biotopes towards the prevalence of the dominance of coarse species that lead to a deterioration of forage availability for a number of valuable commercial species. An increase of the number of pike can regulate the strain

  17. Full-field dynamic strain prediction on a wind turbine using displacements of optical targets measured by stereophotogrammetry

    Science.gov (United States)

    Baqersad, Javad; Niezrecki, Christopher; Avitabile, Peter

    2015-10-01

    Health monitoring of rotating structures (e.g. wind turbines and helicopter blades) has historically been a challenge due to sensing and data transmission problems. Unfortunately mechanical failure in many structures initiates at components on or inside the structure where there is no sensor located to predict the failure. In this paper, a wind turbine was mounted with a semi-built-in configuration and was excited using a mechanical shaker. A series of optical targets was distributed along the blades and the fixture and the displacement of those targets during excitation was measured using a pair of high speed cameras. Measured displacements with three dimensional point tracking were transformed to all finite element degrees of freedom using a modal expansion algorithm. The expanded displacements were applied to the finite element model to predict the full-field dynamic strain on the surface of the structure as well as within the interior points. To validate the methodology of dynamic strain prediction, the predicted strain was compared to measured strain by using six mounted strain-gages. To verify if a simpler model of the turbine can be used for the expansion, the expansion process was performed both by using the modes of the entire turbine and modes of a single cantilever blade. The results indicate that the expansion approach can accurately predict the strain throughout the turbine blades from displacements measured by using stereophotogrammetry.

  18. Molecular and serological diversity of Neisseria meningitidis carrier strains isolated from Italian students aged 14 to 22 years.

    Science.gov (United States)

    Gasparini, Roberto; Comanducci, Maurizio; Amicizia, Daniela; Ansaldi, Filippo; Canepa, Paola; Orsi, Andrea; Icardi, Giancarlo; Rizzitelli, Emanuela; De Angelis, Gabriella; Bambini, Stefania; Moschioni, Monica; Comandi, Sara; Simmini, Isabella; Boccadifuoco, Giueseppe; Brunelli, Brunella; Giuliani, Marzia Monica; Pizza, Mariagrazia; Panatto, Donatella

    2014-06-01

    Neisseria meningitidis is an obligate human commensal that commonly colonizes the oropharyngeal mucosa. Carriage is age dependent and very common in young adults. The relationships between carriage and invasive disease are not completely understood. In this work, we performed a longitudinal carrier study in adolescents and young adults (173 subjects). Overall, 32 subjects (18.5%) had results that were positive for meningococcal carriage in at least one visit (average monthly carriage rate, 12.1%). Only five subjects tested positive at all four visits. All meningococcal isolates were characterized by molecular and serological techniques. Multilocus sequence typing, PorA typing, and sequencing of the 4CMenB vaccine antigens were used to assess strain diversity. The majority of positive subjects were colonized by capsule null (34.4%) and capsular group B strains (28.1%), accounting for 23.5% and 29.4% of the total number of isolates, respectively. The fHbp and nhba genes were present in all isolates, while the nadA gene was present in 5% of the isolates. The genetic variability of the 4CMenB vaccine antigens in this collection was relatively high compared with that of other disease-causing strain panels. Indications about the persistence of the carriage state were limited to the time span of the study. All strains isolated from the same subject were identical or cumulated minor changes over time. The expression levels and antigenicities of the 4CMenB vaccine antigens in each strain were analyzed by the meningococcal antigen typing system (MATS), which revealed that expression can change over time in the same individual. Future analysis of antigen variability and expression in carrier strains after the introduction of the MenB vaccine will allow for a definition of its impact on nasopharyngeal/oropharyngeal carriage.

  19. Calculation of the effect of inertia on the dynamic viscosity of dilute emulsions in a pure straining motion

    NARCIS (Netherlands)

    Oosterbroek, M.; Tropper, R.; Mellema, J.

    1980-01-01

    The dynamic viscosity of a dilute emulsion is calculated for a pure straining motion. The emulsion consists of almost spherical drops of a Newtonian fluid immersed in another Newtonian fluid. The oscillating velocity field of the flow is derived from the Navier-Stokes equation, in which the linear

  20. Comparative assessment of erbium fiber ring lasers and reflective SOA linear lasers for fiber Bragg grating dynamic strain sensing.

    Science.gov (United States)

    Wei, Heming; Krishnaswamy, Sridhar

    2017-05-01

    Fiber Bragg grating (FBG) dynamic strain sensors using both an erbium-based fiber ring laser configuration and a reflective semiconductor optical amplifier (RSOA)-based linear laser configuration are investigated theoretically and experimentally. Fiber laser models are first presented to analyze the output characteristics of both fiber laser configurations when the FBG sensor is subjected to dynamic strains at high frequencies. Due to differences in the transition times of erbium and the semiconductor (InP/InGaAsP), erbium-doped fiber amplifier (EDFA)- and RSOA-based fiber lasers exhibit different responses and regimes of stability when the FBG is subjected to dynamic strains. The responses of both systems are experimentally verified using an adaptive photorefractive two-wave mixing (TWM) spectral demodulation technique. The experimental results show that the RSOA-FBG fiber linear cavity laser is stable and can stably respond to dynamic strains at high frequencies. An example application using a multiplexed TWM interferometer to demodulate multiple FBG sensors is also discussed.

  1. Mechanisms of pit formation at strained crystalline Si(111)/Si3N4(0001) interfaces: Molecular-dynamics simulations

    Science.gov (United States)

    Bachlechner, Martina E.; Srivastava, Deepak; Owens, Eli T.; Schiffbauer, Jarrod; Anderson, Jonas T.; Burky, Melissa R.; Ducatman, Samuel C.; Gripper, Adam M.; Guffey, Eric J.; Ramos, Fernando Serrano

    2006-08-01

    Molecular-dynamics simulations of the crystalline silicon-silicon nitride interfaces are performed to investigate the mechanical failure mechanisms at the interfaces under external strain. At 8% applied tensile strain, parallel to the interface, regular crack initiation and propagation in silicon nitride and dislocation emission and propagation in silicon are observed. At larger 16% strain, however, the formation of a pit similar to that in experiments with lattice-mismatched systems is observed. The simulation results suggest the primary mechanism of pit formation is interaction of a local compressional pinch of the film at the interface with the close proximity to the arrival of a dislocation at the interface in the highly strained silicon.

  2. Correlations between the ages of Alnus host species and the genetic diversity of associated endosymbiotic Frankia strains from nodules

    Institute of Scientific and Technical Information of China (English)

    DAI Yumei; ZHANG Chenggang; XIONG Zhi; ZHANG Zhongze

    2005-01-01

    Nodule samples were collected from four alder species: Alnus nepalensis, A. sibirica, A. tinctoria and A. mandshurica growing in different environments on Gaoligong Mountains,Yunnan Province of Southwest China and on Changbai Mountains, Jilin Province of Northeast China. PCR-RFLP analysis of the IGS between nifD and nifK genes was directly applied to uncultured Frankia strains in the nodules. A total of 21 restriction patterns were obtained. The Frankia population in the nodules of A. nepalensis had the highest genetic diversity among all four Frankia populations; by contrast, the population in the nodules of A. mandshurica had the lowest degree of divergence; the ones in the nodules of A. sibirica and A. tinctoria were intermediate. A dendrogram, which was constructed based on the genetic distance between the restriction patterns, indicated that Frankia strains from A. sibirica and A. tinctoria had a close genetic relationship. Frankia strains from A. nepalensis might be the ancestor of Frankia strains infecting other Alnus species. From these results and the inference of the ages of Alnus host species, it is deduced that there was a co-evolution between Alnus and its microsymbiont Frankia in China.

  3. Associations between strain, herd size, age at first calving, culling reason and lifetime performance characteristics in Holstein-Friesian cows.

    Science.gov (United States)

    Adamczyk, K; Makulska, J; Jagusiak, W; Węglarz, A

    2017-02-01

    Cow longevity and lifetime performance traits are good indicators of breeding effectiveness and animal welfare. They are also interrelated with the economics of dairy herd. Unfortunately, a high milk yield is often associated with deteriorated cow health and fertility and, consequently, with an increased culling rate. This situation, observed also in the Polish population of Holstein-Friesian cattle, inspired us to undertake a study on the associations between some factors and lifetime performance characteristics. The data set consisted of the records on 135 496 cows, including 131 526 of the Black and White strain (BW), and 3970 of the Red and White strain (RW) covered by performance recording and culled in 2012. It was found that cows of the BW strain and those from the largest herds (>100 cows) reached higher lifetime and mean daily energy-corrected milk (ECM) yields than cows of the RW strain and those from smaller herds culled at a similar age. Cows youngest at first calving (indicates that heifers can be bred even when they are younger than 15 to 16 months with no significant negative effect on their later performance. Infertility and reproduction problems (39.6%) and udder diseases (15.5%) constituted the most frequent reasons for cow culling. Cow longevity and lifetime productivity were considerably affected by the interactions between the studied factors.

  4. Language in the aging brain: the network dynamics of cognitive decline and preservation.

    Science.gov (United States)

    Shafto, Meredith A; Tyler, Lorraine K

    2014-10-31

    Language is a crucial and complex lifelong faculty, underpinned by dynamic interactions within and between specialized brain networks. Whereas normal aging impairs specific aspects of language production, most core language processes are robust to brain aging. We review recent behavioral and neuroimaging evidence showing that language systems remain largely stable across the life span and that both younger and older adults depend on dynamic neural responses to linguistic demands. Although some aspects of network dynamics change with age, there is no consistent evidence that core language processes are underpinned by different neural networks in younger and older adults.

  5. Mathematically modelling the dynamics of cholesterol metabolism and ageing.

    Science.gov (United States)

    Morgan, A E; Mooney, K M; Wilkinson, S J; Pickles, N A; Mc Auley, M T

    2016-07-01

    Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the UK. This condition becomes increasingly prevalent during ageing; 34.1% and 29.8% of males and females respectively, over 75 years of age have an underlying cardiovascular problem. The dysregulation of cholesterol metabolism is inextricably correlated with cardiovascular health and for this reason low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) are routinely used as biomarkers of CVD risk. The aim of this work was to use mathematical modelling to explore how cholesterol metabolism is affected by the ageing process. To do this we updated a previously published whole-body mathematical model of cholesterol metabolism to include an additional 96 mechanisms that are fundamental to this biological system. Additional mechanisms were added to cholesterol absorption, cholesterol synthesis, reverse cholesterol transport (RCT), bile acid synthesis, and their enterohepatic circulation. The sensitivity of the model was explored by the use of both local and global parameter scans. In addition, acute cholesterol feeding was used to explore the effectiveness of the regulatory mechanisms which are responsible for maintaining whole-body cholesterol balance. It was found that our model behaves as a hypo-responder to cholesterol feeding, while both the hepatic and intestinal pools of cholesterol increased significantly. The model was also used to explore the effects of ageing in tandem with three different cholesterol ester transfer protein (CETP) genotypes. Ageing in the presence of an atheroprotective CETP genotype, conferring low CETP activity, resulted in a 0.6% increase in LDL-C. In comparison, ageing with a genotype reflective of high CETP activity, resulted in a 1.6% increase in LDL-C. Thus, the model has illustrated the importance of CETP genotypes such as I405V, and their potential role in healthy ageing. Copyright © 2016 Elsevier Ireland Ltd. All

  6. Effect of cooling rate after hot rolling and of multistage strain aging on the drawability of low-carbon-steel wire rod

    Science.gov (United States)

    Taheri, A. Karimi; Maccagno, T. M.; Jonas, J. J.

    1995-05-01

    Tensile testing was used to simulate the multistage strain aging occurring in low-C steel during the relatively short intervals between dies in a multiple-die wire-drawing machine. The effects were examined of three simulated post-hot-rolling cooling rates and three thermal treatments on the strain-aging susceptibility of a high- and a low-N steel. This was measured by applying a 6 pct tensile strain, followed by aging at either 65° or 100 °C for 20 seconds, and then pulling the specimen to failure at room temperature. Increases in flow stress and decreases in the elongation to fracture both indicated high susceptibility to strain aging. It was found that the nitrogen content, the cooling rate from the hot-rolling temperature to about 300 °C, as well as the cooling rate below 300 °C, all have dramatic effects on the strain-aging behavior. Moreover, multistage strain aging is more severe than single-stage strain aging. The implications of these observations on increasing the drawability of low-carbon-steel wire are discussed.

  7. On the dynamics of the age structure, dependency, and consumption

    Science.gov (United States)

    Hock, Heinrich

    2013-01-01

    We examine the effects of population aging due to declining fertility and rising elderly life expectancy on consumption possibilities in the presence of intergenerational transfers. Our analysis is based on a highly tractable continuous-time overlapping generations model in which the population is divided into three groups (youth dependents, workers, and elderly dependents) and lifecourse transitions take place in a probabilistic fashion. We show that the consumption-maximizing response to greater longevity in highly developed countries is an increase in fertility. However, with larger transfer payments, the actual fertility response will likely be the opposite, leading to further population aging. PMID:24353374

  8. Firm age, business cycles and aggregate labor market dynamics

    NARCIS (Netherlands)

    P. Sedláček

    2011-01-01

    Job creation and destruction rates fall with a firm's age, young businesses have higher exit rates, conditional on survival they grow faster and given their employment shares they create relatively more jobs than older firms. In fact, recent studies show that the well established negative relationsh

  9. Quantitative imaging of heterogeneous dynamics in drying and aging paints

    NARCIS (Netherlands)

    Kooij, Van Der Hanne M.; Fokkink, Remco; Gucht, Van Der Jasper; Sprakel, Joris

    2016-01-01

    Drying and aging paint dispersions display a wealth of complex phenomena that make their study fascinating yet challenging. To meet the growing demand for sustainable, high-quality paints, it is essential to unravel the microscopic mechanisms underlying these phenomena. Visualising the governing

  10. Optimal Dynamic Advertising Strategy Under Age-Specific Market Segmentation

    Science.gov (United States)

    Krastev, Vladimir

    2011-12-01

    We consider the model proposed by Faggian and Grosset for determining the advertising efforts and goodwill in the long run of a company under age segmentation of consumers. Reducing this model to optimal control sub problems we find the optimal advertising strategy and goodwill.

  11. Age structured dynamical model for an endangered lizard Eulamprus leuraensis

    Science.gov (United States)

    Supriatna, A. K.; Rachmadani, Q.; Ilahi, F.; Anggriani, N.; Nuraini, N.

    2014-02-01

    The Blue Mountains Water Skink, Eulamprus leuraensis, is listed as an endangered species under the IUCN Red List. This lizard species has a typical characteristic of growth with a low fecundity. It is known that the offspring quality may decline with maternal age of the parents despite they can grow rapidly from neonatal size to adult size within two to three years. It is also believed that low adult survival rates and specialization on rare and fragmented type of habitat are the main cause leading to the endangered status of the lizard. A mathematical model with age structure for Eulamprus leuraensis, taking into account the variation of survival rate in each structure and the declining of offspring quality with respect to maternal age is considered here. Stable coexistence of non-trivial equilibriumis shown. It is also shown that an endangered status is due to combination oflow reproductive output and low rates of adult survival. Further, understanding the age structure within populations can facilitate efective management of the endangered species.

  12. Ab-initio study of dynamical properties of two dimensional MoS2 under strain

    Directory of Open Access Journals (Sweden)

    Himadri Soni

    2015-10-01

    Full Text Available In this paper, we report the biaxial strain induced modifications in the phonon dispersion curves of monolayer MoS2 using first principles calculations in the framework of density functional perturbation theory. We have used the ultrasoft psedopotentials and the exchange correlation energies have been approximated by the local density approximation. There are significant changes in the phonon dispersion curves under strain. A systematic decrease in the optical phonon modes is observed with strain percentage. The longitudinal and transverse acoustic phonon modes of monolayer MoS2 show linear dependency for both without and with strain cases. However, the out of plane acoustic mode (ZA which behaves quadratically with wave vector k- turns linear under strain. We have also linked ripple in single layer (SL MoS2 by ZA mode with strain using shell elasticity theory. The strain induced softening of linear behaviour of ZA mode with strain indicates the absence of rippling under strain. At a very high strain there is a possibility of structural phase transition as the ZA mode at zone centre turns imaginary above 15% strain. Our results indicate a close relationship between the morphology and properties enabling the device tailoring and bandgap engineering in SL-MoS2 by manipulating the strain.

  13. The impact of nitrogen starvation on the dynamics of triacylglycerol accumulation in nine microalgae strains

    NARCIS (Netherlands)

    Breuer, G.; Lamers, P.P.; Martens, D.E.; Draaisma, R.B.; Wijffels, R.H.

    2012-01-01

    Microalgae-derived lipids are an alternative to vegetable and fossil oils, but lipid content and quality vary among microalgae strains. Selection of a suitable strain for lipid production is therefore of paramount importance. Based on published results for 96 species, nine strains were selected to

  14. Acanthamoeba polyphaga strain age and method of cyst production influence the observed efficacy of therapeutic agents and contact lens disinfectants.

    Science.gov (United States)

    Hughes, Reanne; Heaselgrave, Wayne; Kilvington, Simon

    2003-10-01

    The effects of age in culture and the type of medium used for induction of Acanthamoeba polyphaga (Ros) cysts on susceptibilities to polyhexamethylene biguanide (PHMB; 3 micro g/ml), chlorhexidine digluconate (30 micro g/ml), myristamidopropyl dimethylamine (20 micro g/ml), H(2)O(2) (3%), and two multipurpose contact lens solutions (MPS-1 and MPS-2, based on 1 micro g of PHMB per ml) were examined. Strain Ros-02 was cryopreserved on isolation in 1991, while strain Ros-91 had been in continuous axenic culture. Significant differences in susceptibilities to the disinfectants were found depending on the medium used for cyst preparation and the age of the test strain, with Ros-02 generally being more resistant. For example, the killing of Ros-91 cysts produced from an axenic culture of trophozoites in the presence of 50 mM MgCl(2) by MPS-2 was 4 logs, but the killing of Ros-02 by MPS-2 was only 2 logs (P < 0.05) and killing of both strains with cysts obtained from monoxenic cultures with Escherichia coli was only 1 log (P < 0.001). Assays repeated with different batches of the various cyst types gave consistent results. A batch of Ros-91 cysts stored at 4 degrees C and tested over an 8-week period with MPS-1 showed progressively increasing susceptibility to disinfection, although there was no loss of viability during storage (P < 0.01). These observations have important implications for the standardization and interpretation of Acanthamoeba disinfectant and therapeutic agent testing.

  15. Artificial insemination of individually caged broiler breeders. 1. Reproductive performance of males in relation to age and strain of females.

    Science.gov (United States)

    Ansah, G A; Crober, D C; Buckland, R B; Sefton, A E; Kennedy, B W

    1980-02-01

    Studies were conducted to evaluate the reproductive capacity of male broiler breeders used for artificial insemination over an extended period and mated to females of six strains. Biweekly determinations were made of semen volume, semen concentration, and spermatozoal motility for each of the 47 males caged individually from their 39th to 63rd week of age. The percent fertility, duration of fertility, and percent hatchability were determined at five-week intervals (periods) using three young and three force-molted broiler female strains. With young female strains, the mean percent fertility for a 7-day collection of eggs following a single insemination (1 to 7 days) ranged from 95.7 to 81.1 over six consecutive periods. The mean duration of fertility (days) and the mean percent hatchability of fertile eggs was 13.3 and 13.0, and 92.5 and 84.9 respectively, for the first two periods. With force-molted hens, the mean percent fertility (1 to 7 days) ranged between 97.2 and 86.0 over the first three periods, and the mean duration of fertility and the mean percent hatchability was 13.2 and 12.8, and 91.5 and 84.1, respectively, for the first two periods. Fertility of eggs collected for 10 days following a single insemination was slightly but consistently lower than fertility over 7 days for both female groups. Significant differences among males and between periods existed for each semen trait. The effects of male, young female strain and period on fertility and duration of fertility were significant. Hatchability was significantly affected by period only. No male by female strain interaction existed for percent fertility or hatchability. A significant male by period interaction existed for percent fertility, semen volume and concentration. The results obtained are considered to support the feasibility of maintaining broiler breeders in cages and the use of artificial insemination (AI) to produce broiler hatching eggs.

  16. Suppression of repeated adiabatic shear banding by dynamic large strain extrusion machining

    Science.gov (United States)

    Cai, S. L.; Dai, L. H.

    2014-12-01

    High speed machining (HSM) is an advanced production technology with great future potential. Chip serration or segmentation is a commonly observed phenomenon during high speed machining of metals, which is found to be ascribed to a repeated shear band formation fueled by thermo-plastic instability occurring within the primary shear zone. The occurrence of serrated chips leads to the cutting force fluctuation, decreased tool life, degradation of the surface finish and less accuracy in machine parts during high speed machining. Hence, understanding and controlling serrated chip formation in HSM are extremely important. In this work, a novel dynamic large strain extrusion machining (DLSEM) technique is developed for suppressing formation of serrated chips. The systematic DLSEM experiments of Ti-6Al-4V and Inconel 718 alloy with varying degrees of imposed extrusion constraint were carried out. It is found that there is a prominent chip morphology transition from serrated to continuous state and shear band spacing decreases with the constraint degree increasing. In order to uncover underlying mechanism of the imposed extrusion constraint suppressing repeated adiabatic shear banding in DLSEM, new theoretical models are developed where the effects of extrusion constraint, material convection due to chip flow and momentum diffusion during shear band propagation are included. The analytical expressions for the onset criterion of adiabatic shear band and shear band spacing in DLSEM are obtained. The theoretical predictions are in agreement with the experimental results.

  17. Finite strain formulation of viscoelastic damage model for simulation of fabric reinforced polymers under dynamic loading

    Directory of Open Access Journals (Sweden)

    Treutenaere S.

    2015-01-01

    Full Text Available The use of fabric reinforced polymers in the automotive industry is growing significantly. The high specific stiffness and strength, the ease of shaping as well as the great impact performance of these materials widely encourage their diffusion. The present model increases the predictability of explicit finite element analysis and push the boundaries of the ongoing phenomenological model. Carbon fibre composites made up various preforms were tested by applying different mechanical load up to dynamic loading. This experimental campaign highlighted the physical mechanisms affecting the initial mechanical properties, namely intra- and interlaminar matrix damage, viscoelasticty and fibre failure. The intralaminar behaviour model is based on the explicit formulation of the matrix damage model developed by the ONERA as the given damage formulation correlates with the experimental observation. Coupling with a Maxwell-Wiechert model, the viscoelasticity is included without losing the direct explicit formulation. Additionally, the model is formulated under a total Lagrangian scheme in order to maintain consistency for finite strain. Thus, the material frame-indifference as well as anisotropy are ensured. This allows reorientation of fibres to be taken into account particularly for in-plane shear loading. Moreover, fall within the framework of the total Lagrangian scheme greatly makes the parameter identification easier, as based on the initial configuration. This intralaminar model thus relies upon a physical description of the behaviour of fabric composites and the numerical simulations show a good correlation with the experimental results.

  18. Strain-Mediated Interfacial Dynamics during Au–PbS Core–Shell Nanostructure Formation

    KAUST Repository

    Niu, Kai-Yang

    2016-05-23

    An understanding of the hierarchical nanostructure formation is of significant importance for the design of advanced functional materials. Here, we report the in situ study of lead sulfide (PbS) growth on gold (Au) nanorod seeds using liquid cell transmission electron microscopy (TEM). By tracking the formation dynamics of Au-PbS core-shell nanoparticles, we found the preferential heterogeneous nucleation of PbS on the ends of a Au nanorod prior to the development of a complete PdS shell. During PbS shell growth, drastic sulfidation of Au nanorod was observed, leading to large volume shrinkage (up to 50%) of the initial Au nanorod seed. We also captured intriguing wavy interfacial behavior, which can be explained by our DFT calculation results that the local strain gradient at the core-shell interface facilitates the mass transport and mediates reversible phase transitions of Au ↔ Au2S during the PbS shell growth. © 2016 American Chemical Society.

  19. Effects of age, sex, and treatment on weight-loss dynamics in overweight people

    National Research Council Canada - National Science Library

    Rojo-Tirado, Miguel A; Benito, Pedro J; Atienza, David; Rincon, Emiliano; Calderon, Francisco J

    2013-01-01

    The objective of this work was to evaluate how sex, age, and the kind of treatment followed affect weight loss in overweight men and women, as well as to develop an explanation for the evolution of weight-loss dynamics...

  20. Static and dynamic strain coupling behaviour of ferroic and multiferroic perovskites from resonant ultrasound spectroscopy.

    Science.gov (United States)

    Carpenter, M A

    2015-07-08

    Resonant ultrasound spectroscopy (RUS) provides a window on the pervasive influence of strain coupling at phase transitions in perovskites through determination of elastic and anelastic relaxations across wide temperature intervals and with the application of external fields. In particular, large variations of elastic constants occur at structural, ferroelectric and electronic transitions and, because of the relatively long interaction length provided by strain fields in a crystal, Landau theory provides an effective formal framework for characterizing their form and magnitude. At the same time, the Debye equations provide a robust description of dynamic relaxational processes involving the mobility of defects which are coupled with strain. Improper ferroelastic transitions driven by octahedral tilting in KMnF3, LaAlO3, (Ca,Sr)TiO3, Sr(Ti,Zr)O3 and BaCeO3 are accompanied by elastic softening of tens of % and characteristic patterns of acoustic loss due to the mobility of twin walls. RUS data for ferroelectrics and ferroelectric relaxors, including BaTiO3, (K,Na)NbO3,Pb(Mg1/3Nb2/3)O3 (PMN), Pb(Sc1/2Ta1/2)O3 (PST), (Pb(Zn1/3Nb2/3)O3)0.955(PbTiO3)0.045 (PZN-PT) and (Pb(In1/2Nb1/2)O3)0.26(Pb(Mg1/3Nb2/3)O3)0.44(PbTiO3)0.30 (PIN-PMN-PT) show similar patterns of softening and attenuation but also have precursor softening associated with the development of polar nano regions. Defect-induced ferroelectricity occurs in KTaO3, without the development of long range ordering. By way of contrast, spin-lattice coupling is much more variable in strength, as reflected in a greater range of softening behaviour for Pr0.48Ca0.52MnO3 and Sm0.6Y0.4MnO3 as well as for the multiferroic perovskites EuTiO3,BiFeO3, Bi0.9Sm0.1FeO3, Bi0.9Nd0.1FeO3, (BiFeO3)0.64(CaFeO2.5)0.36, (Pb(Fe0.5Ti0.5)O3)0.4(Pb(Zr0.53Ti0.47)O3)0.6. A characteristic feature of transitions in which there is a significant Jahn-Teller component is softening as the transition point is approached from above, as illustrated by

  1. Static and dynamic strain coupling behaviour of ferroic and multiferroic perovskites from resonant ultrasound spectroscopy

    Science.gov (United States)

    Carpenter, M. A.

    2015-07-01

    Resonant ultrasound spectroscopy (RUS) provides a window on the pervasive influence of strain coupling at phase transitions in perovskites through determination of elastic and anelastic relaxations across wide temperature intervals and with the application of external fields. In particular, large variations of elastic constants occur at structural, ferroelectric and electronic transitions and, because of the relatively long interaction length provided by strain fields in a crystal, Landau theory provides an effective formal framework for characterizing their form and magnitude. At the same time, the Debye equations provide a robust description of dynamic relaxational processes involving the mobility of defects which are coupled with strain. Improper ferroelastic transitions driven by octahedral tilting in KMnF3, LaAlO3, (Ca,Sr)TiO3, Sr(Ti,Zr)O3 and BaCeO3 are accompanied by elastic softening of tens of % and characteristic patterns of acoustic loss due to the mobility of twin walls. RUS data for ferroelectrics and ferroelectric relaxors, including BaTiO3, (K,Na)NbO3,Pb(Mg1/3Nb2/3)O3 (PMN), Pb(Sc1/2Ta1/2)O3 (PST), (Pb(Zn1/3Nb2/3)O3)0.955(PbTiO3)0.045 (PZN-PT) and (Pb(In1/2Nb1/2)O3)0.26(Pb(Mg1/3Nb2/3)O3)0.44(PbTiO3)0.30 (PIN-PMN-PT) show similar patterns of softening and attenuation but also have precursor softening associated with the development of polar nano regions. Defect-induced ferroelectricity occurs in KTaO3, without the development of long range ordering. By way of contrast, spin-lattice coupling is much more variable in strength, as reflected in a greater range of softening behaviour for Pr0.48Ca0.52MnO3 and Sm0.6Y0.4MnO3 as well as for the multiferroic perovskites EuTiO3,BiFeO3, Bi0.9Sm0.1FeO3, Bi0.9Nd0.1FeO3, (BiFeO3)0.64(CaFeO2.5)0.36, (Pb(Fe0.5Ti0.5)O3)0.4(Pb(Zr0.53Ti0.47)O3)0.6. A characteristic feature of transitions in which there is a significant Jahn-Teller component is softening as the transition point is approached from above, as illustrated by

  2. Strain- and age-dependent hippocampal neuron sodium currents correlate with epilepsy severity in Dravet syndrome mice.

    Science.gov (United States)

    Mistry, Akshitkumar M; Thompson, Christopher H; Miller, Alison R; Vanoye, Carlos G; George, Alfred L; Kearney, Jennifer A

    2014-05-01

    Heterozygous loss-of-function SCN1A mutations cause Dravet syndrome, an epileptic encephalopathy of infancy that exhibits variable clinical severity. We utilized a heterozygous Scn1a knockout (Scn1a(+/-)) mouse model of Dravet syndrome to investigate the basis for phenotype variability. These animals exhibit strain-dependent seizure severity and survival. Scn1a(+/-) mice on strain 129S6/SvEvTac (129.Scn1a(+/-)) have no overt phenotype and normal survival compared with Scn1a(+/-) mice bred to C57BL/6J (F1.Scn1a(+/-)) that have severe epilepsy and premature lethality. We tested the hypothesis that strain differences in sodium current (INa) density in hippocampal neurons contribute to these divergent phenotypes. Whole-cell voltage-clamp recording was performed on acutely-dissociated hippocampal neurons from postnatal days 21-24 (P21-24) 129.Scn1a(+/-) or F1.Scn1a(+/-) mice and wild-type littermates. INa density was lower in GABAergic interneurons from F1.Scn1a(+/-) mice compared to wild-type littermates, while on the 129 strain there was no difference in GABAergic interneuron INa density between 129.Scn1a(+/-) mice and wild-type littermate controls. By contrast, INa density was elevated in pyramidal neurons from both 129.Scn1a(+/-) and F1.Scn1a(+/-) mice, and was correlated with more frequent spontaneous action potential firing in these neurons, as well as more sustained firing in F1.Scn1a(+/-) neurons. We also observed age-dependent differences in pyramidal neuron INa density between wild-type and Scn1a(+/-) animals. We conclude that preserved INa density in GABAergic interneurons contributes to the milder phenotype of 129.Scn1a(+/-) mice. Furthermore, elevated INa density in excitatory pyramidal neurons at P21-24 correlates with age-dependent onset of lethality in F1.Scn1a(+/-) mice. Our findings illustrate differences in hippocampal neurons that may underlie strain- and age-dependent phenotype severity in a Dravet syndrome mouse model, and emphasize a contribution

  3. Aging dynamics in interacting many-body systems

    CERN Document Server

    Sanders, Lloyd P; Lizana, Ludvig; Fogelmark, Karl; Metzler, Ralf; Ambjörnsson, Tobias

    2013-01-01

    Low-dimensional, complex systems are often characterized by logarithmically slow dynamics. We study the generic motion of a labeled particle in an ensemble of identical diffusing particles with hardcore interactions in a strongly disordered, one-dimensional environment. Each particle in this single file is trapped for a random waiting time $\\tau$ with power law distribution $\\psi(\\tau)\\simeq\\tau^{-1- \\alpha}$, such that the $\\tau$ values are independent, local quantities for all particles. From scaling arguments and simulations, we find that for the scale-free waiting time case $02$ we recover Harris law $\\simeq t^{1/2}$.

  4. Metal and nutrient dynamics on an aged intensive green roof.

    Science.gov (United States)

    Speak, A F; Rothwell, J J; Lindley, S J; Smith, C L

    2014-01-01

    Runoff and rainfall quality was compared between an aged intensive green roof and an adjacent conventional roof surface. Nutrient concentrations in the runoff were generally below Environmental Quality Standard (EQS) values and the green roof exhibited NO3(-) retention. Cu, Pb and Zn concentrations were in excess of EQS values for the protection of surface water. Green roof runoff was also significantly higher in Fe and Pb than on the bare roof and in rainfall. Input-output fluxes revealed the green roof to be a potential source of Pb. High concentrations of Pb within the green roof soil and bare roof dusts provide a potential source of Pb in runoff. The origin of the Pb is likely from historic urban atmospheric deposition. Aged green roofs may therefore act as a source of legacy metal pollution. This needs to be considered when constructing green roofs with the aim of improving pollution remediation.

  5. Laser-induced novel patterns: As smart strain actuators for new-age dental implant surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Celen, Serap, E-mail: serap.celen@ege.edu.tr [Ege University, Faculty of Engineering, Mechanical Engineering Department, Izmir, 35100 (Turkey); Oezden, Hueseyin [Ege University, Faculty of Engineering, Mechanical Engineering Department, Izmir, 35100 (Turkey)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer It is time for that paradigm shift and for an exploration of novel surfaces. Black-Right-Pointing-Pointer We developed novel 3D smart surfaces as strain actuators by nanosecond laser pulse energies. Black-Right-Pointing-Pointer We analyzed these smart surface morphologies using FEM. Black-Right-Pointing-Pointer We estimated their internal stiffness values which play a great role on stress shielding effect. Black-Right-Pointing-Pointer We gave the optimum operation parameters. - Abstract: Surface morphologies of titanium implants are of crucial importance for long-term mechanical adaptation for following implantation. One major problem is the stress shielding effect which originates from the mismatch of the bone and the implant elasticity. It is time for a paradigm shift and for an exploration of novel smart surfaces to prevent this problem. Several surface treatment methods have traditionally been used to modify the surface morphology of titanium dental implants. The laser micro-machining can be considered as a unique and promising, non-contact, no media, contamination free, and flexible treatment method for modifying surface properties of materials in the biomedical industry. The aim of the present study is two folds; to develop novel 3D smart surfaces which can be acted as strain actuators by nanosecond laser pulse energies and irradiation strategies. And analyze these smart surface morphologies using finite element methods in order to estimate their internal stiffness values which play a great role on stress shielding effect. Novel 3D smart strain actuators were prepared using an ytterbium fiber laser ({lambda} = 1060 nm) with 200-250 ns pulse durations on commercial pure titanium dental implant material specimen surfaces and optimum operation parameters were suggested.

  6. Effects of age, hemoglobin type and parasite strain on IgG recognition of Plasmodium falciparum-infected erythrocytes in Malian children.

    Directory of Open Access Journals (Sweden)

    Amir E Zeituni

    Full Text Available BACKGROUND: Naturally-acquired antibody responses to antigens on the surface of Plasmodium falciparum-infected red blood cells (iRBCs have been implicated in antimalarial immunity. To profile the development of this immunity, we have been studying a cohort of Malian children living in an area with intense seasonal malaria transmission. METHODOLOGY/PRINCIPAL FINDINGS: We collected plasma from a sub-cohort of 176 Malian children aged 3-11 years, before (May and after (December the 2009 transmission season. To measure the effect of hemoglobin (Hb type on antibody responses, we enrolled age-matched HbAA, HbAS and HbAC children. To quantify antibody recognition of iRBCs, we designed a high-throughput flow cytometry assay to rapidly test numerous plasma samples against multiple parasite strains. We evaluated antibody reactivity of each plasma sample to 3 laboratory-adapted parasite lines (FCR3, D10, PC26 and 4 short-term-cultured parasite isolates (2 Malian and 2 Cambodian. 97% of children recognized ≥1 parasite strain and the proportion of IgG responders increased significantly during the transmission season for most parasite strains. Both strain-specific and strain-transcending IgG responses were detected, and varied by age, Hb type and parasite strain. In addition, the breadth of IgG responses to parasite strains increased with age in HbAA, but not in HbAS or HbAC, children. CONCLUSIONS/SIGNIFICANCE: Our assay detects both strain-specific and strain-transcending IgG responses to iRBCs. The magnitude and breadth of these responses varied not only by age, but also by Hb type and parasite strain used. These findings indicate that studies of acquired humoral immunity should account for Hb type and test large numbers of diverse parasite strains.

  7. Identification of the mechanisms responsible for static strain ageing in heavily drawn pearlitic steel wires

    Science.gov (United States)

    Lamontagne, A.; Kleber, X.; Massardier-Jourdan, V.; Mari, D.

    2014-08-01

    The microstructural changes occurring during drawing and ageing in pearlitic steel wires have been studied using the thermoelectric power (TEP) measurements combined with atom probe tomography (APT) and differential scanning calorimetry (DSC). APT analysis confirmed that cementite dissolution occurs during the cold-drawing process. The high sensitivity of TEP to solute atoms allowed two ageing mechanisms to be identified, both related to a redistribution of carbon atoms. The complementary use of tensile tests and DSC confirmed these results.

  8. Influence of three bacteria strains on the population dynamics of Tisbe holothuriae (Copepoda, Harpacticoida)

    Science.gov (United States)

    Guérin, J.-P.; Rieper-Kirchner, M.

    1991-12-01

    , carried out with animals bearing a large coefficient of inbreeding (0.375), the results concerning the maximum number of egg-sacs are good (10) as are the mean number of descendants per female (294: the highest number of the seven experiments). These results indicate that genetic factors involved in the reduction of descendants in ageing laboratory cultures can be suppressed to a certain extent by nutritional factors. The poor results obtained with Helgo 21 and NCMB 308 alone must be considered with caution: after a period of adaptation with an alimentary complement, these strains could perhaps permit an interesting production of copepods.

  9. Microstructure and annealing behavior of a modified 9Cr-1Mo steel after dynamic plastic deformation to different strains

    Science.gov (United States)

    Zhang, Z. B.; Mishin, O. V.; Tao, N. R.; Pantleon, W.

    2015-03-01

    The microstructure, hardness and tensile properties of a modified 9Cr-1Mo steel processed by dynamic plastic deformation (DPD) to different strains (0.5 and 2.3) have been investigated in the as-deformed and annealed conditions. It is found that significant structural refinement and a high level of strength can be achieved by DPD to a strain of 2.3, and that the microstructure at this strain contains a large fraction of high angle boundaries. The ductility of the DPD processed steel is however low. Considerable structural coarsening of the deformed microstructure without pronounced recrystallization takes place during annealing of the low-strain and high-strain samples for 1 h at 650 °C and 600 °C, respectively. Both coarsening and partial recrystallization occur in the high-strain sample during annealing at 650 °C for 1 h. For this sample, it is found that whereas coarsening alone results in a loss of strength with only a small gain in ductility, coarsening combined with pronounced partial recrystallization enables a combination of appreciably increased ductility and comparatively high strength.

  10. Microstructure and annealing behavior of a modified 9Cr−1Mo steel after dynamic plastic deformation to different strains

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.B.; Mishin, O.V. [Danish-Chinese Center for Nanometals, Section for Materials Science and Advanced Characterization, Department of Wind Energy, Technical University of Denmark, Risø Campus, 4000 Roskilde (Denmark); Sino-Danish Center for Education and Research (China); Sino-Danish Center for Education and Research (Denmark); Tao, N.R. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, Shenyang 110016 (China); Sino-Danish Center for Education and Research (China); Sino-Danish Center for Education and Research (Denmark); Pantleon, W., E-mail: pawo@dtu.dk [Section for Materials and Surface Engineering, Department of Mechanical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby (Denmark); Sino-Danish Center for Education and Research (China); Sino-Danish Center for Education and Research (Denmark)

    2015-03-15

    The microstructure, hardness and tensile properties of a modified 9Cr−1Mo steel processed by dynamic plastic deformation (DPD) to different strains (0.5 and 2.3) have been investigated in the as-deformed and annealed conditions. It is found that significant structural refinement and a high level of strength can be achieved by DPD to a strain of 2.3, and that the microstructure at this strain contains a large fraction of high angle boundaries. The ductility of the DPD processed steel is however low. Considerable structural coarsening of the deformed microstructure without pronounced recrystallization takes place during annealing of the low-strain and high-strain samples for 1 h at 650 °C and 600 °C, respectively. Both coarsening and partial recrystallization occur in the high-strain sample during annealing at 650 °C for 1 h. For this sample, it is found that whereas coarsening alone results in a loss of strength with only a small gain in ductility, coarsening combined with pronounced partial recrystallization enables a combination of appreciably increased ductility and comparatively high strength.

  11. Dynamical Processes in Ageing, Gene Regulation and Communication

    DEFF Research Database (Denmark)

    Bendtsen, Kristian Moss

    project we constructed a mathematical model and showed that if DNA damage is primarily caused by geno-toxic agents, it would be advantageous for cells to have a fragile DNA repair mechanism. The second part of my Ph.D. thesis covers gene regulation. In the first project we show how RNA polymerase can...... be used as a transcription factor. This requires that promoter regions overlap, which 15% of promoters in E.coli do. In the second project I analyse a negative auto regulated transcription motif coupled to a positive auto regulation transcription motif. I find that a general feature of this motif...... players develop favourite communication partners. We observed how this dynamic caused a communication network to form. By quantifying the information flow in this network, we were able to shown how that the network functions as an anti-exploration mechanism against "information leeches"....

  12. Molecular dynamics simulation of temperature and strain rate effects on the elastic properties of bimetallic Pd-Pt nanowires

    Science.gov (United States)

    Sankaranarayanan, Subramanian K. R. S.; Bhethanabotla, Venkat R.; Joseph, Babu

    2007-10-01

    Molecular dynamics simulation is used to investigate the mechanical properties of infinitely long, cylindrical bimetallic Pd-Pt nanowires, with an approximate diameter of 1.4nm and two different compositions (25% and 50% Pt). The nanowires are subjected to uniaxial tensile strain along the [001] axis with varying strain rates of 0.05%ps-1 , and 5.0%ps-1 , at simulation temperatures of 50 and 300K , to study the effects of strain rates and thermal conditions on the deformation characteristics and mechanical properties of the nanowire. The deformation and rupture mechanism of these nanowires is explored in detail. Comparisons to the behavior exhibited by pure Pd and Pt nanowires of similar diameter are also made. The effect of lattice mismatch on the observed deformation modes in bimetallic nanowires is also discussed. Our simulations indicate that Pd-Pt alloy nanowires of various compositions, with little lattice mismatch between Pd and Pt atoms, undergo similar deformation and rupture upon uniaxial stretching. It is found that yielding and fracture mechanisms depend on the applied strain rate as well as atomic arrangement and temperature. At low temperature and strain rate, where crystal order and stability are highly preserved, the calculated stress-strain response of pure Pt and Pd as well as Pd-Pt alloy nanowires showed clear periodic, stepwise dislocation-relaxation behavior. Crystalline to amorphous transformation takes place at high strain rates (5%ps-1) , with amorphous melting detected at 300K . Deformation of nanowires at higher strain rates and low temperature, where the superplasticity characteristic is significantly enhanced, results in the development of a multishell helical structure. Mechanical properties of the alloy nanowires are significantly different from those of bulk phase and are dictated by the applied strain rate, temperature, alloy composition, as well as the structural rearrangement associated with nanowire elongation. We find that Young

  13. In-Situ Nuclear Magnetic Resonance Investigation of Strain, Temperature, and Strain-Rate Variations of Deformation-Induced Vacancy Concentration in Aluminum

    NARCIS (Netherlands)

    Linga Murty, K.; Detemple, K.; Kanert, O.; Hosson, J.Th.M. De

    1998-01-01

    Critical strain to serrated flow in solid solution alloys exhibiting dynamic strain aging (DSA) or Portevin–LeChatelier effect is due to the strain-induced vacancy production. Nuclear magnetic resonance (NMR) techniques can be used to monitor in situ the dynamical behavior of point and line defects

  14. Ageing dynamics of translational and rotational diffusion in a colloidal glass

    Energy Technology Data Exchange (ETDEWEB)

    Jabbari-Farouji, Sara [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018XE Amsterdam (Netherlands); Eiser, Erika [van' t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam (Netherlands); Wegdam, Gerard H [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018XE Amsterdam (Netherlands); Bonn, Daniel [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018XE Amsterdam (Netherlands)

    2004-10-20

    We study the dynamics of translational and rotational diffusion during the ageing of a colloidal glass of Laponite using polarized and depolarized dynamic light scattering. The dynamics are qualitatively similar between the two degrees of freedom. The short-time diffusion is independent of the time elapsed since the sample preparation. The intermediate- and long-time diffusion, on the other hand, slows down by several orders of magnitude during the ageing. The slowing down of the rotational diffusion is found to be much faster than that of the translational diffusion. (letter to the editor)

  15. Large Scale 3-D Dislocation Dynamics and Atomistic Simulations of Flow and Strain-Hardening Behavior of Metallic Micropillars

    Science.gov (United States)

    Rao, Satish

    2015-03-01

    Experimental studies show strong strengthening effects for micrometer-scale FCC as well as two-phase superalloy crystals, even at high initial dislocation densities. This talk shows results from large-scale 3-D discrete dislocation simulations (DDS) used to explicitly model the deformation behavior of FCC Ni (flow stress and strain-hardening) as well as superalloy microcrystals for diameters ranging from 1 - 20 microns. The work shows that two size-sensitive athermal hardening processes, beyond forest and precipitation hardening, are sufficient to develop the dimensional scaling of the flow stress, stochastic stress variation, flow intermittency and, high initial strain-hardening rates, similar to experimental observations for various materials. In addition, 3D dislocation dynamics simulations are used to investigate strain-hardening characteristics and dislocation microstructure evolution with strain in large 20 micron size Ni microcrystals (bulk-like) under three different loading axes: 111, 001 and 110. Three different multi-slip loading axes, , and , are explored for shear strains of ~0.03 and final dislocation densities of ~1013/m2. The orientation dependence of initial strain hardening rates and dislocation microstructure evolution with strain are discussed. The simulated strain hardening results are compared with experimental data under similar loading conditions from bulk single-crystal Ni. Finally, atomistic simulation results on the operation of single arm sources in Ni bipillars with a large angle grain boundary is discussed. The atomistic simulation results are compared with experimental mechanical behavior data on Cu bipillars with a similar large angle grain boundary. This work was supported by AFOSR (Dr. David Stargel), and by a grant of computer time from the DOD High Performance Computing Modernization Program, at the Aeronautical Systems Center/Major Shared Resource Center.

  16. Chromosomal Copy Number Variation in Saccharomyces pastorianus Is Evidence for Extensive Genome Dynamics in Industrial Lager Brewing Strains.

    Science.gov (United States)

    van den Broek, M; Bolat, I; Nijkamp, J F; Ramos, E; Luttik, M A H; Koopman, F; Geertman, J M; de Ridder, D; Pronk, J T; Daran, J-M

    2015-09-01

    Lager brewing strains of Saccharomyces pastorianus are natural interspecific hybrids originating from the spontaneous hybridization of Saccharomyces cerevisiae and Saccharomyces eubayanus. Over the past 500 years, S. pastorianus has been domesticated to become one of the most important industrial microorganisms. Production of lager-type beers requires a set of essential phenotypes, including the ability to ferment maltose and maltotriose at low temperature, the production of flavors and aromas, and the ability to flocculate. Understanding of the molecular basis of complex brewing-related phenotypic traits is a prerequisite for rational strain improvement. While genome sequences have been reported, the variability and dynamics of S. pastorianus genomes have not been investigated in detail. Here, using deep sequencing and chromosome copy number analysis, we showed that S. pastorianus strain CBS1483 exhibited extensive aneuploidy. This was confirmed by quantitative PCR and by flow cytometry. As a direct consequence of this aneuploidy, a massive number of sequence variants was identified, leading to at least 1,800 additional protein variants in S. pastorianus CBS1483. Analysis of eight additional S. pastorianus strains revealed that the previously defined group I strains showed comparable karyotypes, while group II strains showed large interstrain karyotypic variability. Comparison of three strains with nearly identical genome sequences revealed substantial chromosome copy number variation, which may contribute to strain-specific phenotypic traits. The observed variability of lager yeast genomes demonstrates that systematic linking of genotype to phenotype requires a three-dimensional genome analysis encompassing physical chromosomal structures, the copy number of individual chromosomes or chromosomal regions, and the allelic variation of copies of individual genes.

  17. The Development of Even-Aged Plantation Forests: An Exercise in Forest Stand Dynamics

    Science.gov (United States)

    Wilson, E. R.; Leslie, A. D.

    2008-01-01

    In this paper we present a field-based practical exercise that allows students in forestry, ecology and natural resources to develop their understanding of forest stand dynamics. The exercise involves measurement of key tree growth parameters in four even-aged, single-species plantation stands of different age but occupying sites with similar soil…

  18. Age-independent seismic anisotropy under oceanic plates explained by strain history in the asthenosphere

    Science.gov (United States)

    Hedjazian, Navid; Garel, Fanny; Davies, D. Rhodri; Kaminski, Edouard

    2017-02-01

    The depth of the oceanic lithosphere-asthenosphere boundary (LAB), as inferred from shear wave velocities, increases with lithospheric age, in agreement with models of cooling oceanic lithosphere. On the other hand, the distribution of radial anisotropy under oceanic plates is almost age-independent. In particular, radial anisotropy shows a maximum positive gradient at a depth of ∼70 km, which, if used as a proxy, indicates an age-independent LAB depth. These contrasting observations have fueled a controversy on the seismological signature of the LAB. To better understand the discrepancy between these observations, we model the development of lattice preferred orientation (LPO) in upper mantle crystal aggregates and predict the seismic anisotropy produced by plate-driven mid-ocean ridge flows. The model accounts for the progressive cooling of the lithosphere with age and can incorporate both diffusion and dislocation creep deformation mechanisms. We find that an age-independent distribution of radial anisotropy is the natural consequence of these simple flows. The depth and strength of anisotropy is further controlled by the deformation regime - dislocation or diffusion creep - experienced by crystals during their ascent towards, and subsequent motion away from, the ridge axis. Comparison to surface wave tomography models yield constraints on rheological parameters such as the activation volume. Although not excluded, additional mechanisms proposed to explain some geophysical signatures of the LAB, such as the presence of partial melt or changes in water content, are not required to explain the radial anisotropy proxy. Our prediction, that the age-independent radial anisotropy proxy marks the transition to flow-induced asthenospheric anisotropy, provides a way to reconcile thermal, mechanical and seismological views of the LAB.

  19. Age Dimension Homeostasis of Physiological Systems, a Slow Dynamics Model in Biology

    Science.gov (United States)

    Kurachi, K.; Yasui, M.; Isobe, T.; Suenaga, E.; Kurachi, S.

    2006-05-01

    Throughout the life span, complex physiological systems are regulated by specific age related mechanisms, thus maintaining the age axis homeostasis. Our efforts for understanding the underlying mechanisms began about a decade ago, successfully discovering the very fist such a mechanism, we called the ASE/AIE-mediated age-related regulatory mechanism of gene expression. This mechanism can explain the major feature of the age-related increase profile of blood coagulation activity. Global analyses of the mouse liver genes and proteins revealed heir highly dynamic and complex age-related regulation, suggesting the existence of several major phases over the life span. These studies facilitate a systematic investigation into the regulatory mechanisms of age-axis homeostasis, a slow dynamics system of the complex biological systems.

  20. Irregularity in dengue fever epidemics: difference between first and secondary infections drives the rich dynamics more than the detailed number of strains

    CERN Document Server

    Aguiar, Maíra; Stollenwerk, Nico

    2011-01-01

    Different extensions of the classical single-strain SIR model for the host population, motivated by modeling dengue fever epidemiology, have reported a rich dynamic structure including deterministic chaos which was able to explain the large fluctuations of disease incidences. A comparison between the basic two-strain dengue model, which already captures differences between primary and secondary infections, with the four-strain dengue model, that introduces the idea of competition of multiple strains in dengue epidemics shows that the difference between first and secondary infections drives the rich dynamics more than the detailed number of strains to be considered in the model structure. Chaotic dynamics were found to happen at the same parameter region of interest, for both the two and the four-strain models, able to explain the fluctuations observed in empirical data and showing a qualitatively good agreement between empirical data and model simulation. Since the law of parsimony favors the simplest of two ...

  1. The basic approach to age-structured population dynamics models, methods and numerics

    CERN Document Server

    Iannelli, Mimmo

    2017-01-01

    This book provides an introduction to age-structured population modeling which emphasises the connection between mathematical theory and underlying biological assumptions. Through the rigorous development of the linear theory and the nonlinear theory alongside numerics, the authors explore classical equations that describe the dynamics of certain ecological systems. Modeling aspects are discussed to show how relevant problems in the fields of demography, ecology, and epidemiology can be formulated and treated within the theory. In particular, the book presents extensions of age-structured modelling to the spread of diseases and epidemics while also addressing the issue of regularity of solutions, the asymptotic behaviour of solutions, and numerical approximation. With sections on transmission models, non-autonomous models and global dynamics, this book fills a gap in the literature on theoretical population dynamics. The Basic Approach to Age-Structured Population Dynamics will appeal to graduate students an...

  2. Dynamic analysis of a hepatitis B model with three-age-classes

    Science.gov (United States)

    Zhang, Suxia; Zhou, Yicang

    2014-07-01

    Based on the fact that the likelihood of becoming chronically infected is dependent on age at primary infection Kane (1995) [2], Edmunds et al. (1993) [3], Medley et al. (2001) [4], and Ganem and Prince (2004) [6], we formulate a hepatitis B transmission model with three age classes. The reproduction number, R0 is defined and the dynamical behavior of the model is analyzed. It is proved that the disease-free equilibrium is globally stable if R01. The unique endemic equilibrium and its global stability is obtained in a special case. Simulations are also conducted to compare the dynamical behavior of the model with and without age classes.

  3. Wettability of Sanded and Aged Fast-growing Poplar Wood Surfaces: II. Dynamic Wetting Models

    OpenAIRE

    Zhiyong Qin; Qian Zhang; Qiang Gao; Shifeng Zhang; Jianzhang Li

    2014-01-01

    The dynamic wettability of adhesive on sanded and aged wood surfaces was measured using the sessile drop method. Four different models were used to evaluate and compare the wetting process. It was shown that the wettability of freshly sanded wood and aged wood both decreased compared to the control wood. There was no evidence of change in wettability with increasing grit number. Aging reduced the wettability of the wood surface. The coefficients of determination (R2) for all four models were ...

  4. [Age-related dynamics of the motion reaction in school children].

    Science.gov (United States)

    Makarenko, M V; Petrenko, Iu O; Baĭda, O H; Men'shykh, O E

    2009-01-01

    We studied functional state of the central nervous system of boys and girls aged from 7 to 17 years old. Peculiarities of age-dependent dynamics of functional level of the central nervous system, stability of the reactions, levels of functional possibilities were described. The age-dependent periods of strengthening and weakening of correlation between the indexes of motive reaction and the criteria of the functional state of central nervous system were determined.

  5. Determination of the acoustoelastic coefficient for surface acoustic waves using dynamic acoustoelastography: an alternative to static strain.

    Science.gov (United States)

    Ellwood, R; Stratoudaki, T; Sharples, S D; Clark, M; Somekh, M G

    2014-03-01

    The third-order elastic constants of a material are believed to be sensitive to residual stress, fatigue, and creep damage. The acoustoelastic coefficient is directly related to these third-order elastic constants. Several techniques have been developed to monitor the acoustoelastic coefficient using ultrasound. In this article, two techniques to impose stress on a sample are compared, one using the classical method of applying a static strain using a bending jig and the other applying a dynamic stress due to the presence of an acoustic wave. Results on aluminum samples are compared. Both techniques are found to produce similar values for the acoustoelastic coefficient. The dynamic strain technique however has the advantages that it can be applied to large, real world components, in situ, while ensuring the measurement takes place in the nondestructive, elastic regime.

  6. Universality and extremal aging for dynamics of spin glasses on sub-exponential time scales

    CERN Document Server

    Arous, G Ben

    2010-01-01

    We consider Random Hopping Time (RHT) dynamics of the Sherrington - Kirkpatrick (SK) model and p-spin models of spin glasses. For any of these models and for any inverse temperature we prove that, on time scales that are sub-exponential in the dimension, the properly scaled clock process (time-change process) of the dynamics converges to an extremal process. Moreover, on these time scales, the system exhibits aging like behavior which we called extremal aging. In other words, the dynamics of these models ages as the random energy model (REM) does. Hence, by extension, this confirms Bouchaud's REM-like trap model as a universal aging mechanism for a wide range of systems which, for the first time, includes the SK model.

  7. Viscoplastic behavior of zirconium alloys in the temperatures range 20 deg C - 400 deg C: characterization and modeling of strain ageing phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Graff, St

    2006-10-15

    The anomalous strain rate sensitivity of zirconium alloys over the temperatures range 20-600 C has been widely reported in the literature. This unconventional behavior is related to the existence of strain ageing phenomenon which results from the combined action of thermally activated diffusion of foreign atoms to and along dislocation cores and the long range of dislocations interactions. The important role of interstitial and substitutional atoms in zirconium alloys, responsible for strain ageing and the lack of information about the domain where strain ageing is active have not been yet adequately characterized because of the multiplicity of alloying elements and chemical impurities. The aim of this work is to characterize experimentally the range of temperatures and strain rates where strain ageing is active on the macroscopic and mesoscopic scales. We propose also a predictive approach of the strain ageing effects, using the macroscopic strain ageing model suggested by McCormick (McCormick, 1988; Zhang et al., 2000). Specific zirconium alloys were elaborated starting from a crystal bar of zirconium with 2.2 wt% hafnium and very low oxygen content (80 wt ppm), called ZrHf. Another substitutional atom was added to the solid solution under the form of 1 wt% niobium. Some zirconium alloys were doped with oxygen, others were not. All of them were characterized by various mechanical tests (standard tensile tests, tensile tests with strain rate changes, relaxation tests with unloading). The experimental results were compared with those for the standard oxygen doped zirconium alloy (1300 wt ppm) studied by Pujol (Pujol, 1994) and called Zr702. The following experimental evidences of the age-hardening phenomena were collected and then modeled: 1) low and/or negative strain rate sensitivity around 200-300 C, 2) creep arrest at 200 C, 3) relaxation arrest at 200 C and 300 C, 4) plastic strain heterogeneities observed in laser extensometry on the millimeter scale

  8. Tracing the dynamic life story of a Bronze Age Female.

    Science.gov (United States)

    Frei, Karin Margarita; Mannering, Ulla; Kristiansen, Kristian; Allentoft, Morten E; Wilson, Andrew S; Skals, Irene; Tridico, Silvana; Nosch, Marie Louise; Willerslev, Eske; Clarke, Leon; Frei, Robert

    2015-05-21

    Ancient human mobility at the individual level is conventionally studied by the diverse application of suitable techniques (e.g. aDNA, radiogenic strontium isotopes, as well as oxygen and lead isotopes) to either hard and/or soft tissues. However, the limited preservation of coexisting hard and soft human tissues hampers the possibilities of investigating high-resolution diachronic mobility periods in the life of a single individual. Here, we present the results of a multidisciplinary study of an exceptionally well preserved circa 3.400-year old Danish Bronze Age female find, known as the Egtved Girl. We applied biomolecular, biochemical and geochemical analyses to reconstruct her mobility and diet. We demonstrate that she originated from a place outside present day Denmark (the island of Bornholm excluded), and that she travelled back and forth over large distances during the final months of her life, while consuming a terrestrial diet with intervals of reduced protein intake. We also provide evidence that all her garments were made of non-locally produced wool. Our study advocates the huge potential of combining biomolecular and biogeochemical provenance tracer analyses to hard and soft tissues of a single ancient individual for the reconstruction of high-resolution human mobility.

  9. Intraobserver reproducibility of parameters of standard and 2D speckle tracking echocardiography, dynamics of global longitudinal strain I in patients with acute primary anterior STEMI

    Science.gov (United States)

    Kercheva, M.; Ryabova, T.; Ryabov, V.; Karpov, R.

    2015-11-01

    The aim of this study was to assess the intraobserver reproducibility of parameters of standard and 2 dimensional speckle tracking echocardiography, dynamics of global longitudinal strain in patients with acute primary anterior STEMI. The study included 24 patients, mean age 58.46±10.2. Echocardiography with 2D speckle tracking imaging was performed on the 1st (T1), 7th (T2), 14th days (T3) after STEMI («Vivid E9»). Analysis of echocardiographic images was performed offline at the different periods by the two independent observers (EchoPac) - experienced and inexperienced. In order to assess the agreement between standard and 2D speckle tracking echocardiography, a correlation analysis (Pearson correlation, Spearman's rank correlation coefficient) and Bland-Altman analysis were undertaken. The 23 patients had urgent reperfusion therapy, 6 patients underwent primary PCI, 16 patients - PCI after successful fibrinolysis (68%). GLS and WMSI had the best intraobsever reproducibility. Dynamics of EDV LV, ESV LV, EF LV was without significant differences. Nevertheless, it was found positive dynamic of GLS: - 12.65±3.53 (T1), -13.61±3.81 (T2), -14.27±4.1 (T3), pspeckle-tracking and standard echocardiography was revealed in GLS and WMSI. The modern management of STEMI patients limits adverse postinfarction remodeling and preserves of global left ventricular contractility detected by the EF LV. However, GLS had the positive dynamics and improved to the 14th day.

  10. Space-resolved diffusing wave spectroscopy measurements of the macroscopic deformation and the microscopic dynamics in tensile strain tests

    Science.gov (United States)

    Nagazi, Med-Yassine; Brambilla, Giovanni; Meunier, Gérard; Marguerès, Philippe; Périé, Jean-Noël; Cipelletti, Luca

    2017-01-01

    We couple a laser-based, space-resolved dynamic light scattering apparatus to a universal traction machine for mechanical extensional tests. We perform simultaneous optical and mechanical measurements on polyether ether ketone, a semi-crystalline polymer widely used in the industry. Due to the high turbidity of the sample, light is multiply scattered by the sample and the diffusing wave spectroscopy (DWS) formalism is used to interpret the data. Space-resolved DWS yields spatial maps of the sample strain and of the microscopic dynamics. An excellent agreement is found between the strain maps thus obtained and those measured by a conventional stereo-digital image correlation technique. The microscopic dynamics reveals both affine motion and plastic rearrangements. Thanks to the extreme sensitivity of DWS to displacements as small as 1 nm, plastic activity and its spatial localization can be detected at an early stage of the sample strain, making the technique presented here a valuable complement to existing material characterization methods.

  11. Monitoring of in vitro dynamics of Acanthamoeba strains isolated from infected eyes as a useful tool in keratitis management.

    Science.gov (United States)

    Chomicz, Lidia; Padzik, Marcin; Szaflik, Jacek P; Nahorski, Wacław L; Kryczka, Tomasz; Szaflik, Jerzy

    2014-11-01

    Free-living amoebae of Acanthamoeba genus are ubiquitous in various parts of the world. Some species of these amoebozoans present a serious risk to human health as the causative agents of vision-threatening diseases, Acanthamoeba keratitis. Correct diagnosis requires both a clinical examination of the cornea and amoebic form identification in affected eyes. Despite advances in pharmacotherapy, the infection is difficult to diagnose and to threat. Population dynamics of five different Acanthamoeba strains cultured in vitro under bacteria-free condition in BSC medium, was monitored in terms of diagnostic and therapeutic management. The range of protozoan number in the exponential growth phase, the morpho-physiological status of amoeba forms and their ability to multiply were evaluated. Results of the studies revealed that early and continued monitoring of the strains maintained in an axenic culture showed correlation between the dynamics of cultivated amoebae and the course of the disease, differences in response to pharmacotherapy and the surgical management efficacy. Concluding, the in vitro monitoring of dynamics of Acanthamoeba strains isolated from infected corneas may be important not only for proper diagnosis but also as a useful tool in keratitis management and therapeutic prognosis.

  12. Pulmonary neuroendocrine cell hyperplasia: identification, diagnostic criteria and incidence in untreated ageing rats of different strains.

    Science.gov (United States)

    Haworth, Richard; Woodfine, Jennie; McCawley, Sean; Pilling, Andrew M; Lewis, David J; Williams, Tom C

    2007-08-01

    Pulmonary Neuroendocrine Cells (PNEC) are found as clusters called neuroepithelial bodies (NEB) or as single cells scattered in the respiratory epithelium. Pulmonary neuroendocrine cell hyperplasia is recorded in humans and experimentally manipulated rodents. The objectives of this work were to identify the optimal immunohistochemical markers for PNEC in the rat for use on paraffin-embedded, formalin-fixed material and to provide the first comparative incidence of PNEC hyperplasia in untreated 2-year-old rats of different strains. Calcitonin-gene related peptide (CGRP) and protein G product 9.5 (PGP9.5) antibodies identified PNEC consistently and selectively. In contrast, PNEC did not express chromogranin-A or S-100. PNEC hyperplasia was defined as foci of PNEC with greater than 40 nuclei, excluding overlying respiratory epithelium and submucosal PNEC. PNEC hyperplasia was observed at low incidence (0-7%) in untreated 2-year-old Sprague-Dawley, Han Wistar and Wistar rats but not Fischer 344 rats. This is the first report of spontaneous PNEC hyperplasia in rats. The cause of this hyperplasia is unknown, but experimental models that induce PNEC hyperplasia by causing bronchiolar cell injury are discussed. PNEC neoplasia in the rat is unreported in the literature and was not observed in animals examined in this study.

  13. Study on Relation Between Dynamic Pattern of Regional Vertical Strain Rate and Several Strong Earthquakes such as Lijiang (Ms7. 0) and Menyuan (Ms6.4) Earthquakes

    Institute of Scientific and Technical Information of China (English)

    Wang Shuangxu; Jiang Zaisen; Zhang Xi; Chen Bing

    2000-01-01

    Making use of the method of obtaining regional vertical strain rate from regional preciseleveling data and gaining dynamic pattern combining with deformation data on spanningfaults, the regional vertical strain dynamic evolution characteristics of several moderatelystrong earthquakes such as Lijiang ( Ms 7.0) and Menyuan ( Ms 6.4) earthquakes occurredin crustal deformation monitoring areas located in the western Yunnan and Qilianshan-Hexiregion. Based on the above-mentioned facts, by studying the time-space nonhomogeneity andstrain energy accumulation status, some criteria for judging the medium- and short-termstrong seismic risk regions according to the regional vertical strain rate dynamic informationare proposed.

  14. A general procedure for estimating dynamic displacements using strain measurements and operational modal analysis

    DEFF Research Database (Denmark)

    Skafte, Anders; Aenlle, Manuel L.; Brincker, Rune

    2016-01-01

    measuring the in-plane deformation. This paper proposes a method in which the displacement mode shapes and responses can be predicted using only strain measurements. The method relies on the newly discovered principle of local correspondence, which states that each experimental mode can be expressed....... The method is validated with experimental tests on a scaled model of a two-span bridge installed with strain gauges. Random load was applied to simulate a civil structure under operating condition, and strain mode shapes were identified using operational modal analysis....

  15. Aging synaptic mitochondria exhibit dynamic proteomic changes while maintaining bioenergetic function.

    Science.gov (United States)

    Stauch, Kelly L; Purnell, Phillip R; Fox, Howard S

    2014-04-01

    Aging correlates with a progressive impairment of mitochondrial homeostasis and is an influential factor for several forms of neurodegeneration. However, the mechanisms underlying age-related alterations in synaptosomal mitochondria, a neuronal mitochondria population highly susceptible to insults and critical for brain function, remain incompletely understood. Therefore this study investigates the synaptic mitochondrial proteomic and bioenergetic alterations that occur with age. The utilization of a state of the art quantitative proteomics approach allowed for the comparison of protein expression levels in synaptic mitochondria isolated from 5 (mature), 12 (old), and 24 (aged) month old mice. During the process of aging we find that dynamic proteomic alterations occur in synaptic mitochondria. Despite direct (mitochondrial DNA deletions) and indirect (increased antioxidant protein levels) signs of mitochondrial damage in the aged mice, there was an overall maintenance of mitochondrial function. Therefore the synaptic mitochondrial proteomic changes that occur with aging correlate with preservation of synaptic mitochondrial function.

  16. Origin of end-of-aging and subaging scaling behavior in glassy dynamics

    DEFF Research Database (Denmark)

    Sibani, Paolo; Kenning, Gregory G.

    2010-01-01

    the field change. The response curve obtained for different values of $t_w$ are  usually collapsed using  values of  $\\mu$  slightly below  one, a scaling behavior generally known as \\emph{sub-aging}.    Recent spin glass Thermoremanent Magnetization experiments have  shown that  the value of $\\mu......-aging and end of aging behavior in glassy dynamics. The mechanism  combines real  and configuration space properties of the  state produced by the initial thermal quench which initiates the aging process....

  17. Experimental modal analysis and dynamic strain fiber Bragg gratings for structural health monitoring of composite antenna sub-reflector

    Science.gov (United States)

    Panopoulou, A.; Fransen, S.; Gomez-Molinero, V.; Kostopoulos, V.

    2013-09-01

    The objective of this work is to develop a new structural health monitoring system for composite aerospace structures based on dynamic response strain measurements and experimental modal analysis techniques. Fiber Bragg grating (FBG) optical sensors were used for monitoring the dynamic response of the composite structure. The structural dynamic behavior has been numerically simulated and experimentally verified by means of vibration testing. The hypothesis of all vibration tests was that actual damage in composites reduces their stiffness and produces an eigenfrequency shifting to lower values in the same sense as mass increase produces. Thus, damage was simulated by slightly varying locally the mass of the structure at different zones. The correlation between the simulated damage and the loss of stiffness was analytically defined. Experimental modal analysis based on the strain responses was conducted and the extracted strain mode shapes were the input for the damage detection expert system. A feed-forward back propagation neural network was the core of the damage detection system. The features-input to the neural network consisted of the strain mode shapes, extracted from the experimental modal analysis. Dedicated training and validation activities were carried out based on the experimental results. The system showed high reliability, confirmed by the ability of the neural network to recognize the size and the position of damage on the structure. The experiments were performed on a real structure i.e. a lightweight antenna sub-reflector, manufactured and tested at EADS CASA ESPACIO. An integrated FBG sensor network, based on the advantage of multiplexing, was mounted on the structure with optimum topology. Numerical simulation was used as a support tool at all the steps of the work. Potential applications for the proposed system are during ground qualification extensive tests of space structures and during the mission as modal analysis tool on board, being able

  18. Motor unit discharge rate in dynamic movements of the aging soleus

    DEFF Research Database (Denmark)

    Kallio, Jouni; Søgaard, Karen; Avela, Janne

    2014-01-01

    % in concentric (CON) and eccentric (ECC) contractions. Soleus intramuscular EMG was recorded with bipolar fine-wire electrodes and decomposed to individual trains of motor unit discharges. In ISO the MUDR increased with each force level from 40 to 100% MVC. In dynamic contractions the descriptive analysis showed......Aging is related to a variety of changes at the muscular level. It seems that the age-related changes in motor unit activation are muscle- and intensity dependent. The purpose of this study was to examine the motor unit discharge rate (MUDR) in both isometric and dynamic contractions of the aging...... a higher MUDR in CON compared to ISO or ECC. The difficulties of recording single motor units in dynamic contractions, especially in the elderly is discussed....

  19. The role of neuromuscular changes in aging and knee osteoarthritis on dynamic postural control.

    Science.gov (United States)

    Takacs, Judit; Carpenter, Mark G; Garland, S Jayne; Hunt, Michael A

    2013-04-01

    Knee osteoarthritis (OA) is a chronic joint condition, with 30% of those over the age of 75 exhibiting severe radiographic disease. Nearly 50% of those with knee OA have experienced a fall in the past year. Falls are a considerable public health concern, with a high risk of serious injury and a significant socioeconomic impact. The ability to defend against a fall relies on adequate dynamic postural control, and alterations in dynamic postural control are seen with normal aging. Neuromuscular changes associated with aging may be responsible for some of these alterations in dynamic postural control. Even greater neuromuscular deficits, which may impact dynamic postural control and the ability to defend against a fall, are seen in people with knee OA. There is little evidence to date on how knee OA affects the ability to respond to and defend against falls and the neuromuscular changes that contribute to balance deficits. As a result, this review will: summarize the key characteristics of postural responses to an external perturbation, highlight the changes in dynamic postural control seen with normal aging, review the neuromuscular changes associated with aging that have known and possible effects on dynamic postural control, and summarize the neuromuscular changes and balance problems in knee OA. Future research to better understand the role of neuromuscular changes in knee OA and their effect on dynamic postural control will be suggested. Such an understanding is critical to the successful creation and implementation of fall prevention and treatment programs, in order to reduce the excessive risk of falling in knee OA.

  20. Myocardial Strain Imaging with High-Performance Adaptive Dynamic Grid Interpolation Method

    Science.gov (United States)

    Shuhui Bu,; Makoto Yamakawa,; Tsuyoshi Shiina,

    2010-07-01

    The accurate assessment of local myocardial strain is important for diagnosing ischemic heart diseases because decreased myocardial motion often appears in the early stage. Calculating the spatial derivation of displacement is a necessary step in the strain calculation, but the numerical calculation is extremely sensitive to noise. Commonly used smoothing methods are the moving-average and median filters; however, these methods have a trade-off between spatial resolution and accuracy. A novel smoothing/fitting method is proposed for overcoming this problem. In this method, the detected displacement vectors are discretized at mesh nodes, and virtual springs are connected between adjacent nodes. By controlling the elasticity of the virtual springs, misdetected displacements are fitted without the above problem. Further improvements can be achieved by applying a Kalman filter for position tracking, and then calculating the strain from the accumulated displacement vectors. From the simulation results, we conclude that the proposed method improves the accuracy and spatial resolution of the strain images.

  1. An explicit finite element formulation for dynamic strain localization and damage evolution in metals

    Energy Technology Data Exchange (ETDEWEB)

    Mourad, Hashem M [Los Alamos National Laboratory; Bronkhorst, Curt A [Los Alamos National Laboratory; Addessio, Francis L [Los Alamos National Laboratory

    2010-12-16

    An explicit finite element formulation, used to study the behavior and failure mechanisms of metallic materials under high strain rate loading, is presented. The formulation is based on the assumed-strain approach of Fish and Belytschko [1988], which allows localization bands to be embedded within an element, thereby alleviating mesh sensitivity and reducing the required computational effort. The behavior of the material outside localization bands (and of the virgin material prior to the onset of strain localization) is represented using a Gurson-type coupled plasticity-damage model based on the work of Johnson and Addessio [1988]. Assuming adiabatic conditions, the response of the localization band material is represented by a set of constitutive equations for large elasticviscoplastic deformations in metals at high strain rates and high homologous temperatures (see Brown et al. [1989]). Computational results are compared to experimental data for different metallic alloys to illustrate the advantages of the proposed modeling strategy.

  2. Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions

    Directory of Open Access Journals (Sweden)

    Soo Yeol Lee

    2015-11-01

    Full Text Available We investigated the evolution of the strain fields around a fatigued crack tip between the steady- and overloaded-fatigue conditions using a nondestructive neutron diffraction technique. The two fatigued compact-tension specimens, with a different fatigue history but an identical applied stress intensity factor range, were used for the direct comparison of the crack tip stress/strain distributions during in situ loading. While strains behind the crack tip in the steady-fatigued specimen are irrelevant to increasing applied load, the strains behind the crack tip in the overloaded-fatigued specimen evolve significantly under loading, leading to a lower driving force of fatigue crack growth. The results reveal the overload retardation mechanism and the correlation between crack tip stress distribution and fatigue crack growth rate.

  3. Mathematical Model of Three Age-Structured Transmission Dynamics of Chikungunya Virus

    Science.gov (United States)

    Agusto, Folashade B.; Easley, Shamise; Freeman, Kenneth; Thomas, Madison

    2016-01-01

    We developed a new age-structured deterministic model for the transmission dynamics of chikungunya virus. The model is analyzed to gain insights into the qualitative features of its associated equilibria. Some of the theoretical and epidemiological findings indicate that the stable disease-free equilibrium is globally asymptotically stable when the associated reproduction number is less than unity. Furthermore, the model undergoes, in the presence of disease induced mortality, the phenomenon of backward bifurcation, where the stable disease-free equilibrium of the model coexists with a stable endemic equilibrium when the associated reproduction number is less than unity. Further analysis of the model indicates that the qualitative dynamics of the model are not altered by the inclusion of age structure. This is further emphasized by the sensitivity analysis results, which shows that the dominant parameters of the model are not altered by the inclusion of age structure. However, the numerical simulations show the flaw of the exclusion of age in the transmission dynamics of chikungunya with regard to control implementations. The exclusion of age structure fails to show the age distribution needed for an effective age based control strategy, leading to a one size fits all blanket control for the entire population. PMID:27190548

  4. Anomalous carrier dynamics in bilayer graphene in presence of mechanical strain: A theoretical study

    Science.gov (United States)

    Enamullah

    2016-05-01

    One of the optical response of charge carriers in bilayer graphene, anomalous Rabi oscillation is investigated theoretically in presence of mechanical strain. Rabi oscillation in extreme non-resonance regime is known as anomalous Rabi oscillation, has been predicted theoretically in single layer graphene by new technique known as asymptotic rotating wave approximation. In this article, we have shown a strong dependence of anomalous Rabi oscillations of charge carriers on the mechanical strain near the vanishing point of conduction and valance band.

  5. The accuracy of seismic estimates of dynamic strains: an evaluation using strainmeter and seismometer data from Piñon Flat Observatory, California

    Science.gov (United States)

    Gomberg, Joan S.; Agnew, Duncan Carr

    1996-01-01

    The dynamic strains associated with seismic waves may play a significant role in earthquake triggering, hydrological and magmatic changes, earthquake damage, and ground failure. We determine how accurately dynamic strains may be estimated from seismometer data and elastic-wave theory by comparing such estimated strains with strains measured on a three-component long-base strainmeter system at Pin??on Flat, California. We quantify the uncertainties and errors through cross-spectral analysis of data from three regional earthquakes (the M0 = 4 ?? 1017 N-m St. George, Utah; M0 = 4 ?? 1017 N-m Little Skull Mountain, Nevada; and M0 = 1 ?? 1019 N-m Northridge, California, events at distances of 470, 345, and 206 km, respectively). Our analysis indicates that in most cases the phase of the estimated strain matches that of the observed strain quite well (to within the uncertainties, which are about ?? 0.1 to ?? 0.2 cycles). However, the amplitudes are often systematically off, at levels exceeding the uncertainties (about 20%); in one case, the predicted strain amplitudes are nearly twice those observed. We also observe significant ?????? strains (?? = tangential direction), which should be zero theoretically; in the worst case, the rms ?????? strain exceeds the other nonzero components. These nonzero ?????? strains cannot be caused by deviations of the surface-wave propagation paths from the expected azimuth or by departures from the plane-wave approximation. We believe that distortion of the strain field by topography or material heterogeneities give rise to these complexities.

  6. Dynamics of a stochastic multi-strain SIS epidemic model driven by Lévy noise

    Science.gov (United States)

    Chen, Can; Kang, Yanmei

    2017-01-01

    A stochastic multi-strain SIS epidemic model is formulated by introducing Lévy noise into the disease transmission rate of each strain. First, we prove that the stochastic model admits a unique global positive solution, and, by the comparison theorem, we show that the solution remains within a positively invariant set almost surely. Next we investigate stochastic stability of the disease-free equilibrium, including stability in probability and pth moment asymptotic stability. Then sufficient conditions for persistence in the mean of the disease are established. Finally, based on an Euler scheme for Lévy-driven stochastic differential equations, numerical simulations for a stochastic two-strain model are carried out to verify the theoretical results. Moreover, numerical comparison results of the stochastic two-strain model and the deterministic version are also given. Lévy noise can cause the two strains to become extinct almost surely, even though there is a dominant strain that persists in the deterministic model. It can be concluded that the introduction of Lévy noise reduces the disease extinction threshold, which indicates that Lévy noise may suppress the disease outbreak.

  7. Dynamics of climate-based malaria transmission model with age-structured human population

    Science.gov (United States)

    Addawe, Joel; Pajimola, Aprimelle Kris

    2016-10-01

    In this paper, we proposed to study the dynamics of malaria transmission with periodic birth rate of the vector and an age-structure for the human population. The human population is divided into two compartments: pre-school (0-5 years) and the rest of the human population. We showed the existence of a disease-free equilibrium point. Using published epidemiological parameters, we use numerical simulations to show potential effect of climate change in the dynamics of age-structured malaria transmission. Numerical simulations suggest that there exists an asymptotically attractive solution that is positive and periodic.

  8. New compliant strain gauges for self-sensing dynamic deformation of flapping wings on miniature air vehicles

    Science.gov (United States)

    Wissman, James; Perez-Rosado, Ariel; Edgerton, Alex; Levi, Benjamin M.; Karakas, Zeynep N.; Kujawski, Mark; Philipps, Alyssa; Papavizas, Nicholas; Fallon, Danielle; Bruck, Hugh A.; Smela, Elisabeth

    2013-08-01

    Over the past several years there has been an increasing interest in the development of miniature air vehicles (MAVs) with flapping wings. To allow these MAVs to adjust to changes in wind direction and to maximize their efficiency, it is desirable to monitor the deformation of the wing during flight. This paper presents a step in this direction, demonstrating the measurement of strain on the surface of the wing using minimally invasive compliant piezoresistive sensors. The strain gauges consisted of latex mixed with electrically conducting exfoliated graphite, and they were applied by spray coating. To calibrate the gauges, both static and dynamic testing up to 10 Hz were performed using cantilever structures. In tension the static sensitivity was a linear 0.4 Ω μɛ-1 and the gauge factor was 28; in compression, the gauge factor was -5. Although sensitivities in tension and compression differed by a factor of almost six, this was not reflected in the dynamic data, which followed the strain reversibly with little distortion. There was no attenuation with frequency, indicating a sufficiently small time constant for this application. The gauges were thin, compliant, and light enough to measure, without interference, deformations due to shape changes of the flexible wing associated with generating lift and thrust. During flapping the resistance closely tracked the generated thrust, measured on a test stand, with both signals tracing figure-8 loops as a function of wing position throughout each cycle.

  9. [Dynamics of parasite communities in an age series of Arctic Cisco Coregonus migratorius (Georgi, 1775)].

    Science.gov (United States)

    Dugarov, Zh N; Pronin, N M

    2013-01-01

    Parasite communities of Arctic cisco from Chivyrkui Bay of Lake Baikal have been analyzed at levels of a host individual (infracommunity), a individual age group of a host-(assemblages of infracommunities), and a host population (component community). Significant positive correlations of parameters of species richness (number of parasite species, Margalef and Menhinick indices) with the age of Arctic cisco were recorded only at the level of parasite inffacommunities. The absence of linear positive correlations between the parameters of species richness and the age of Arctic cisco at the level of assemblages of parasite infracommunities were revealed for the first time for fish of Lake Baikal. The peculiarity of the dynamics of parasite communities of. Arctic cisco is determined by specific features of the host physiology and ecology, primarily by the age dynamics of the feeding spectrum.

  10. Evaluation of acrylamide-removing properties of two Lactobacillus strains under simulated gastrointestinal conditions using a dynamic system.

    Science.gov (United States)

    Rivas-Jimenez, L; Ramírez-Ortiz, K; González-Córdova, A F; Vallejo-Cordoba, B; Garcia, H S; Hernandez-Mendoza, A

    2016-09-01

    The aim of this study was to evaluate the capability of Lactobacillus reuteri NRRL 14171 and Lactobacillus casei Shirota to remove dietary acrylamide (AA) under simulated gastrointestinal conditions using a dynamic system. The effects of different AA levels or bacteria concentration on toxin removal by Lactobacillus strains were assessed. Thereafter, AA-removing capability of bacteria strains under either fasting or postprandial simulated gastrointestinal conditions was evaluated. Commercial potato chips were analyzed for their AA content, and then used as a food model. Average AA content (34,162μg/kg) in potato chips exceeded by ca. 34-fold the indicative values recommended by the EU. Toxin removal ability was dependent on AA content and bacterial cell concentration. A reduction on bacterial viability was observed in the food model and at the end of both digestive processes evaluated. However, bacteria survived in enough concentrations to remove part of the toxin (32-73%). Both bacterial strains were able to remove AA under different simulated gastrointestinal conditions, being L. casei Shirota the most effective (ca. 70% removal). These findings confirmed the risk of potato chips as dietary AA exposure for consumers, and that strains of the genus Lactobacillus could be employed to reduce the bioavailability of dietary AA.

  11. Dynamic Strength and Accumulated Plastic Strain Development Laws and Models of the Remolded Red Clay under Long-Term Cyclic Loads: Laboratory Test Results

    Directory of Open Access Journals (Sweden)

    Li Jian

    2015-09-01

    Full Text Available The dynamic strength and accumulated plastic strain are two important parameters for evaluating the dynamic response of soil. As a special clay, the remolded red clay is often used as the high speed railway subgrade filling, but studies on its dynamic characteristics are few. For a thorough analysis of the suitability of the remolded red clay as the subgrade filling, a series of long-term cyclic load triaxial test under different load histories are carried out. Considering the influence of compactness, confining pressure, consolidation ratio, vibration frequency and dynamic load to the remolded red clay dynamic property, the tests obtain the development curves of the dynamic strength and accumulated plastic strain under different test conditions. Then, through curve fitting method, two different hyperbolic models respectively for the dynamic strength and accumulated plastic strain are built, which can match the test datum well. By applying the dynamic strength model, the critical dynamic strength of the remolded red clay are gained. Meanwhile, for providing basic datum and reference for relevant projects, all key parameters for the dynamic strength and accumulated plastic strain of the remolded red clay are given in the paper.

  12. Mitochondrial activity and dynamics changes regarding metabolism in ageing and obesity.

    Science.gov (United States)

    López-Lluch, Guillermo

    2017-03-01

    Mitochondria play an essential role in ageing and longevity. During ageing, a general deregulation of metabolism occurs, affecting molecular, cellular and physiological activities in the organism. Dysfunction of mitochondria has been associated with ageing and age-related diseases indicating their importance in the maintenance of cell homeostasis. Three major nutritional sensors, mTOR, AMPK and Sirtuins are involved in the control of mitochondrial physiology. These nutritional sensors control mitochondrial biogenesis, dynamics by regulating fusion and fission processes, and turnover through mito- and autophagy. Apart of the known factors involved in fusion, OPA1 and mitofusins, and fission, DRP1 and FIS1, emerging factors such as prohibitins and sestrins can play important functions in mitochondrial dynamics regulation. Mitochondria is also affected by sexual hormones that suffer drastic changes during ageing. The recent literature demonstrates the complex interaction between nutritional sensors and mitochondrial homeostasis in the physiology of adipose tissue and in the accumulation of fat in other organs such as muscle and liver. In this article, the role of mitochondrial homeostasis in ageing and age-dependent fat accumulation is revised. This review highlights the importance of mitochondria in the accumulation of fat during ageing and related diseases such as obesity, metabolic syndrome or type 2 diabetes mellitus. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  13. Size-dependent dynamic pull-in instability of vibrating electrically actuated microbeams based on the strain gradient elasticity theory

    Science.gov (United States)

    Sedighi, Hamid M.

    2014-02-01

    This paper presents the impact of vibrational amplitude on the dynamic pull-in instability and fundamental frequency of actuated microbeams by introducing the second order frequency-amplitude relationship. The nonlinear governing equation of microbeam predeformed by an electric force including the fringing field effect, based on the strain gradient elasticity theory is considered. The predicted results of the strain gradient elasticity theory are compared with the outcomes that arise from the classical and modified couple stress theory. The influences of basic nondimensional parameters on the pull-in instability as well as the natural frequency are investigated by a powerful asymptotic approach namely the Parameter Expansion Method (PEM). It is demonstrated that two terms in series expansions are sufficient to produce an acceptable solution of the microstructure. The phase portrait of the microstructure shows that by increasing the actuation voltage parameter, the stable center point loses its stability and coalesces with unstable saddle node.

  14. Application of a PVDF-based stress gauge in determining dynamic stress-strain curves of concrete under impact testing

    Science.gov (United States)

    Meng, Yi; Yi, Weijian

    2011-06-01

    Polyvinylidene fluoride (PVDF) piezoelectric material has been successfully applied in many engineering fields and scientific research. However, it has rarely been used for direct measurement of concrete stresses under impact loading. In this paper, a new PVDF-based stress gauge was developed to measure concrete stresses under impact loading. Calibrated on a split Hopkinson pressure bar (SHPB) with a simple measurement circuit of resistance strain gauges, the PVDF gauge was then used to establish dynamic stress-strain curves of concrete cylinders from a series of axial impact testing on a drop-hammer test facility. Test results show that the stress curves measured by the PVDF-based stress gauges are more stable and cleaner than that of the stress curves calculated with the impact force measured from a load cell.

  15. Static and Dynamic Strain Monitoring of Reinforced Concrete Components through Embedded Carbon Nanotube Cement-Based Sensors

    Directory of Open Access Journals (Sweden)

    Antonella D’Alessandro

    2017-01-01

    Full Text Available The paper presents a study on the use of cement-based sensors doped with carbon nanotubes as embedded smart sensors for static and dynamic strain monitoring of reinforced concrete (RC elements. Such novel sensors can be used for the monitoring of civil infrastructures. Because they are fabricated from a structural material and are easy to utilize, these sensors can be integrated into structural elements for monitoring of different types of constructions during their service life. Despite the scientific attention that such sensors have received in recent years, further research is needed to understand (i the repeatability and accuracy of sensors’ behavior over a meaningful number of sensors, (ii testing configurations and calibration methods, and (iii the sensors’ ability to provide static and dynamic strain measurements when actually embedded in RC elements. To address these research needs, this paper presents a preliminary characterization of the self-sensing capabilities and the dynamic properties of a meaningful number of cement-based sensors and studies their application as embedded sensors in a full-scale RC beam. Results from electrical and electromechanical tests conducted on small and full-scale specimens using different electrical measurement methods confirm that smart cement-based sensors show promise for both static and vibration-based structural health monitoring applications of concrete elements but that calibration of each sensor seems to be necessary.

  16. Population dynamics and genetic diversity of C4 strains of human enterovirus 71 in Mainland China, 1998-2010.

    Directory of Open Access Journals (Sweden)

    Dawei Guan

    Full Text Available BACKGROUND: Since 1997, several countries within the Asian Pacific region have been affected by one or more massive outbreaks of Hand Foot and Mouth Disease (HFMD. Virus typing experiments revealed that these outbreaks were caused by strains of human enterovirus 71 (EV71 belonging to several different, recently emerged subgenogroups. In mainland China, a different situation was observed. The first outbreak, localized in Shangdong Province, was reported in 2007, and was followed by a wide-spread outbreak in mainland China in 2008. Since then, numbers of reported HFMD cases have been persistently high. METHODOLOGY/PRINCIPAL FINDINGS: To gain insight in the epidemiological behavior of EV71 in China, we studied genetic diversity and EV71 population dynamics to address whether the increase in number of reported EV71 infections reflects a real increase in viral spread or is just the result of increased awareness and surveillance. We used systematically collected VP1 gene sequences of 257 EV71 strains collected in Guangdong province from 2008 to 2010 as part of HFMD surveillance activities, and supplemented them with 305 GenBank EV71 reference stains collected in China from 1998 to 2010. All isolates from Guangdong Province belonged to subgenogroup C4. Viral population dynamics indicated that the increased reporting of HFMD in China since 2007 reflects a real increase in viral spread and continued replacement of viral lineages through time. Amino acid sequence comparisons revealed substitution of amino acid in residues 22, 145 and 289 through time regularly with the VP1 gene of EV71 strains isolated in mainland China from 1998 to 2010. CONCLUSIONS: EV71 strains isolated in mainland China mainly belonged to subgenogroup C4. There was exponential growth of the EV71 virus population in 2007 and 2008. There was amino acid substitution through time regularly with the VP1 gene which possibly increased viral spread and/or ability of the virus to circulate

  17. Dynamics of the chemical composition and productivity of composts for the cultivation of Agaricus bisporus strains

    Directory of Open Access Journals (Sweden)

    Meire Cristina Nogueira de Andrade

    2013-12-01

    Full Text Available Two compost formulations based on oat straw (Avena sativa and brachiaria (Brachiaria sp. were tested for the cultivation of three Agaricus bisporus strains (ABI-07/06, ABI-05/03, and PB-1. The experimental design was a 2 x 3 factorial scheme (composts x strains with 6 treatments and 8 repetitions (boxes containing 12 kg of compost. The chemical characterization of the compost (humidity, organic matter, carbon, nitrogen, pH, raw protein, ethereal extract, fibers, ash, cellulose, hemicellulose, and lignin before and after the cultivation of A. bisporus and the production (basidiomata mass, productivity, and biological efficiency were evaluated. Data were submitted to variance analysis, and averages were compared by means of the Tukey's test. According to the results obtained, the chemical and production characteristics showed that the best performances for the cultivation of A. bisporus were presented by the compost based on oat and the strain ABI-07/06.

  18. Dynamics of the chemical composition and productivity of composts for the cultivation of Agaricus bisporus strains.

    Science.gov (United States)

    de Andrade, Meire Cristina Nogueira; de Jesus, João Paulo Furlan; Vieira, Fabrício Rocha; Viana, Sthefany Rodrigues Fernandes; Spoto, Marta Helena Fillet; de Almeida Minhoni, Marli Teixeira

    2013-12-01

    Two compost formulations based on oat straw (Avena sativa) and brachiaria (Brachiaria sp.) were tested for the cultivation of three Agaricus bisporus strains (ABI-07/06, ABI-05/03, and PB-1). The experimental design was a 2 × 3 factorial scheme (composts × strains) with 6 treatments and 8 repetitions (boxes containing 12 kg of compost). The chemical characterization of the compost (humidity, organic matter, carbon, nitrogen, pH, raw protein, ethereal extract, fibers, ash, cellulose, hemicellulose, and lignin) before and after the cultivation of A. bisporus and the production (basidiomata mass, productivity, and biological efficiency) were evaluated. Data were submitted to variance analysis, and averages were compared by means of the Tukey's test. According to the results obtained, the chemical and production characteristics showed that the best performances for the cultivation of A. bisporus were presented by the compost based on oat and the strain ABI-07/06.

  19. A parametric study on the dynamic behavior of porous bronze at various strain rates

    Science.gov (United States)

    Zhang, Yue; Hu, Jianxing; Lei, Jianyin; Wang, Zhihua; Zhao, Longmao

    2016-10-01

    An experimental investigation on the porous bronze at various strain rates is firstly carried out in this study to explore the effects of relative density and strain rate in the mechanical behavior. Furthermore, a multi-parameter constitutive model of describing the rate-dependent behavior for porous bronze is developed. The parameters in the constitutive model are density dependent, and the specific forms of these parameters as functions of relative density are obtained. It can be concluded from the test results and constitutive model that the high relative density leads to increase in yield strength and energy absorption capacity of the materials and the strain rate also has positive effects on the yield strength and energy absorption capacity of porous bronze.

  20. Ageing shocks and short-run regional labour market dynamics in a spatial panel VAR approach

    DEFF Research Database (Denmark)

    Mitze, Timo; Schmidt, Torben Dall; Rauhut, Daniel

    2017-01-01

    Using a flexible spatial panel VAR model for a small-scale labour market system, we investigate the dynamic interdependences between changes in the demographic structure and the labour market performance of a regional economy. With a particular focus on ageing shocks, we describe an increase...

  1. The dispersion of age differences between partners and the asymptotic dynamics of the HIV epidemic.

    Science.gov (United States)

    d'Albis, Hippolyte; Augeraud-Véron, Emmanuelle; Djemai, Elodie; Ducrot, Arnaud

    2012-01-01

    In this paper, the effect of a change in the distribution of age differences between sexual partners on the dynamics of the HIV epidemic is studied. In a gender- and age-structured compartmental model, it is shown that if the variance of the distribution is small enough, an increase in this variance strongly increases the basic reproduction number. Moreover, if the variance is large enough, the mean age difference barely affects the basic reproduction number. We, therefore, conclude that the local stability of the disease-free equilibrium relies more on the variance than on the mean.

  2. THE LEVEL AND AGE DYNAMICS OF SPORTS ACHIEVEMENTS OF ATHLETES-VETERANS OF THE HAMMER THROW

    Directory of Open Access Journals (Sweden)

    Ivanova Natalya Dmitrievna

    2013-03-01

    Full Text Available The article presents the records of the world and Russian athletes veterans in the hammer throw, starting with the age group 35-39 years and up to age group 100-104 years, and a comparison of the records of veterans subject to an age factor and of the high scores of athletes in the current sports. The aim of the work is to analyze the level and dynamics of the records of the world and Russian athletes, veterans in the hammer throw in each five-year group starting with the age group 35-39 years and up to age group 100-104 years. The novelty of the work consists in comparison of the records of the world and Russia in the hammer throw active athletes and records of veterans with the amendment to the age factor. Analysis of the level and age dynamics of sports achievements of domestic and foreign athletes-throwers older age groups. In the course of the research it is established, that in the throwing hammer, decreasing absolute (without regard to the age factor results, which is largely due to the natural age-related changes in the organism of athletes. Records of the world athletes-veterans compared with the records of active athletes and the transition from each of the five-year group in the following, decline on average in men by 10,0%, among women by 19,3%, in spite of the fact that the weight of the shells in the hammer throw with age decreases. Presented the reasons for the backwardness of Russian athletes older than 35 years of foreign veterans.

  3. Heart wall motion analysis by dynamic 3D strain rate imaging from tissue Doppler echocardiography

    Science.gov (United States)

    Hastenteufel, Mark; Wolf, Ivo; de Simone, Raffaele; Mottl-Link, Sibylle; Meinzer, Hans-Peter

    2002-04-01

    The knowledge about the complex three-dimensional (3D) heart wall motion pattern, particular in the left ventricle, provides valuable information about potential malfunctions, e.g., myocardial ischemia. Nowadays, echocardiography (cardiac ultrasound) is the predominant technique for evaluation of cardiac function. Beside morphology, tissue velocities can be obtained by Doppler techniques (tissue Doppler imaging, TDI). Strain rate imaging (SRI) is a new technique to diagnose heart vitality. It provides information about the contraction ability of the myocardium. Two-dimensional color Doppler echocardiography is still the most important clinical method for estimation of morphology and function. Two-dimensional methods leads to a lack of information due to the three-dimensional overall nature of the heart movement. Due to this complex three-dimensional motion pattern of the heart, the knowledge about velocity and strain rate distribution over the whole ventricle can provide more valuable diagnostic information about motion disorders. For the assessment of intracardiac blood flow three-dimensional color Doppler has already shown its clinical utility. We have developed methods to produce strain rate images by means of 3D tissue Doppler echocardiography. The tissue Doppler and strain rate images can be visualized and quantified by different methods. The methods are integrated into an interactively usable software environment, making them available in clinical everyday life. Our software provides the physician with a valuable tool for diagnosis of heart wall motion.

  4. Direct and array observations for near source dynamic strain during large earthquakes

    Science.gov (United States)

    Huang, Bor-Shouh; Huang, Win-Gee; Lin, Chin-Jen

    2017-04-01

    The seismic ground motions from the 1999 Chi-Chi Taiwan earthquake (ML=7.6) and it large aftershocks were well recorded by a dense seismic array (named the Hualien Large Scale Seismic Test, HLSST) in near source distances. The HLSST site was situated in the the site of Hualien Veteran's Marble Plant. It included one scaled down reinforced concrete cylindrical containment model (1/4 scale). The radius of this cylindrical model is of about 5.4 meters. The instrumentation of this program consisted of forty-two stations. They were fifteen surface accelerometers, twelve downhole accelerometers and fifteen containment structure response accelerometers. The fifteen free-field stations were installed at three arms. The twelve downhole accelerometers were distributed beneath this array. One delta ground strain gauge was commonly installed in this site and well recorded those events. In this study, we inferred ground strains by a least-squares fit of array translational ground-motion data using the method proposed by Spudich et al. (1995) and Spudich and Fletcher (2008) and the same as from strain gauge records. We analyzed the main shock and November 1 offshore event for ground rotations and the same as ground strains. We will discuss the relationship of observed spatial ground deformations with source rupture processes and onsite ground translations. We hope to discuss its implications also about earthquake engineering applications.

  5. The Role of Arch Compression and Metatarsophalangeal Joint Dynamics in Modulating Plantar Fascia Strain in Running.

    Directory of Open Access Journals (Sweden)

    Kirsty A McDonald

    Full Text Available Elastic energy returned from passive-elastic structures of the lower limb is fundamental in lowering the mechanical demand on muscles during running. The purpose of this study was to investigate the two length-modulating mechanisms of the plantar fascia, namely medial longitudinal arch compression and metatarsophalangeal joint (MPJ excursion, and to determine how these mechanisms modulate strain, and thus elastic energy storage/return of the plantar fascia during running. Eighteen runners (9 forefoot and 9 rearfoot strike performed three treadmill running trials; unrestricted shod, shod with restricted arch compression (via an orthotic-style insert, and barefoot. Three-dimensional motion capture and ground reaction force data were used to calculate lower limb kinematics and kinetics including MPJ angles, moments, powers and work. Estimates of plantar fascia strain due to arch compression and MPJ excursion were derived using a geometric model of the arch and a subject-specific musculoskeletal model of the plantar fascia, respectively. The plantar fascia exhibited a typical elastic stretch-shortening cycle with the majority of strain generated via arch compression. This strategy was similar in fore- and rear-foot strike runners. Restricting arch compression, and hence the elastic-spring function of the arch, was not compensated for by an increase in MPJ-derived strain. In the second half of stance the plantar fascia was found to transfer energy between the MPJ (energy absorption and the arch (energy production during recoil. This previously unreported energy transfer mechanism reduces the strain required by the plantar fascia in generating useful positive mechanical work at the arch during running.

  6. The Role of Arch Compression and Metatarsophalangeal Joint Dynamics in Modulating Plantar Fascia Strain in Running.

    Science.gov (United States)

    McDonald, Kirsty A; Stearne, Sarah M; Alderson, Jacqueline A; North, Ian; Pires, Neville J; Rubenson, Jonas

    2016-01-01

    Elastic energy returned from passive-elastic structures of the lower limb is fundamental in lowering the mechanical demand on muscles during running. The purpose of this study was to investigate the two length-modulating mechanisms of the plantar fascia, namely medial longitudinal arch compression and metatarsophalangeal joint (MPJ) excursion, and to determine how these mechanisms modulate strain, and thus elastic energy storage/return of the plantar fascia during running. Eighteen runners (9 forefoot and 9 rearfoot strike) performed three treadmill running trials; unrestricted shod, shod with restricted arch compression (via an orthotic-style insert), and barefoot. Three-dimensional motion capture and ground reaction force data were used to calculate lower limb kinematics and kinetics including MPJ angles, moments, powers and work. Estimates of plantar fascia strain due to arch compression and MPJ excursion were derived using a geometric model of the arch and a subject-specific musculoskeletal model of the plantar fascia, respectively. The plantar fascia exhibited a typical elastic stretch-shortening cycle with the majority of strain generated via arch compression. This strategy was similar in fore- and rear-foot strike runners. Restricting arch compression, and hence the elastic-spring function of the arch, was not compensated for by an increase in MPJ-derived strain. In the second half of stance the plantar fascia was found to transfer energy between the MPJ (energy absorption) and the arch (energy production during recoil). This previously unreported energy transfer mechanism reduces the strain required by the plantar fascia in generating useful positive mechanical work at the arch during running.

  7. Extreme strain rate and temperature dependence of the mechanical properties of nano silicon nitride thin layers in a basal plane under tension: a molecular dynamics study.

    Science.gov (United States)

    Lu, Xuefeng; Wang, Hongjie; Wei, Yin; Wen, Jiangbo; Niu, Min; Jia, Shuhai

    2014-08-01

    Molecular dynamics simulations are performed to clarify the extreme strain rate and temperature dependence of the mechanical behaviors of nano silicon nitride thin layers in a basal plane under tension. It is found that fracture stresses show almost no change with increasing strain rate. However, fracture strains decrease gradually due to the appearance of additional N(2c)-Si bond breaking defects in the deformation process. With increasing loading temperature, there is a noticeable drop in fracture stress and fracture strain. In the low temperature range, roughness phases can be observed owing to a combination of factors such as configuration evolution and energy change.

  8. Laser-Driven Ramp Compression to Investigate and Model Dynamic Response of Iron at High Strain Rates

    Directory of Open Access Journals (Sweden)

    Nourou Amadou

    2016-12-01

    Full Text Available Efficient laser shock processing of materials requires a good characterization of their dynamic response to pulsed compression, and predictive numerical models to simulate the thermomechanical processes governing this response. Due to the extremely high strain rates involved, the kinetics of these processes should be accounted for. In this paper, we present an experimental investigation of the dynamic behavior of iron under laser driven ramp loading, then we compare the results to the predictions of a constitutive model including viscoplasticity and a thermodynamically consistent description of the bcc to hcp phase transformation expected near 13 GPa. Both processes are shown to affect wave propagation and pressure decay, and the influence of the kinetics of the phase transformation on the velocity records is discussed in details.

  9. An integrated, multistudy analysis of the safety of Ann Arbor strain live attenuated influenza vaccine in children aged 2–17 years

    OpenAIRE

    Ambrose, Christopher S.; Yi, Tingting; Falloon, Judith

    2011-01-01

    Background Trivalent, Ann Arbor strain, live attenuated influenza vaccine (LAIV) is approved in several countries for use in eligible children aged ≥2 years. Objective To describe the safety of Ann Arbor strain LAIV in children aged 2–17 years. Methods An integrated analysis of randomized, controlled trials of LAIV. Results A total of 4245 and 10 693 children received ≥1 dose of LAIV in year 1 of 6 trivalent inactivated influenza vaccine (TIV)-controlled and 14 placebo-controlled studies, res...

  10. Job Strain and Casual Blood Pressure Distribution: Looking beyond the Adjusted Mean and Taking Gender, Age, and Use of Antihypertensives into Account. Results from ELSA-Brasil.

    Science.gov (United States)

    Juvanhol, Leidjaira Lopes; Melo, Enirtes Caetano Prates; Carvalho, Marilia Sá; Chor, Dóra; Mill, José Geraldo; Griep, Rosane Härter

    2017-04-22

    Methodological issues are pointed to as the main sources of inconsistencies in studies about the association between job strain and blood pressure (BP)/hypertension. Our aim was to analyze the relationship between job strain and the whole BP distribution, as well as potential differences by gender, age, and use of antihypertensives. Additionally, we addressed issues relating to the operationalization of the exposure and outcome variables that influence the study of their inter-relations. We evaluated the baseline date of 12,038 participants enrolled in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) (2008-2010), a multicenter cohort study of 35-74-year-old civil servants. Job strain was assessed by the Demand-Control-Support Questionnaire. The distribution of casual BP by categories of job strain was compared by a combination of exploratory techniques. Participants were classified into three subgroups (normotensives, medicated hypertensives, and unmedicated hypertensives), and analyses were stratified by gender and age. The relationship between job strain and casual BP varied along the whole outcome distribution. Hypertensive participants had greater differences in casual BP by job strain category, especially medicated hypertensives. Differences in casual BP were also greater for systolic than for diastolic BP and for older participants. No differences were encountered by gender. The exclusion of participants susceptible to misclassification for the exposure and outcome variables increased the differences observed between the categories of low and high job strain. In conclusion, the relationship between job strain and casual BP varied along the whole outcome distribution and by use of antihypertensive drugs, age, and BP parameter evaluated. Misclassification for exposure and outcome variables should be considered in analyses of this topic.

  11. EVALUATION OF LOCAL STRAIN EVOLUTION FROM METALLIC WHISKER FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, E.; Lam, P.

    2011-05-11

    Evolution of local strain on electrodeposited tin films upon aging has been monitored by digital image correlation (DIC) for the first time. Maps of principal strains adjacent to whisker locations were constructed via comparing pre- and post-growth scanning electron microscopy (SEM) images. Results showed that the magnitude of the strain gradient plays an important role in whisker growth. DIC visualized the dynamic growth process in which the alteration of strain field has been identified to cause growth of subsequent whiskers.

  12. Dynamical network model for age-related health deficits and mortality

    Science.gov (United States)

    Taneja, Swadhin; Mitnitski, Arnold B.; Rockwood, Kenneth; Rutenberg, Andrew D.

    2016-02-01

    How long people live depends on their health, and how it changes with age. Individual health can be tracked by the accumulation of age-related health deficits. The fraction of age-related deficits is a simple quantitative measure of human aging. This quantitative frailty index (F ) is as good as chronological age in predicting mortality. In this paper, we use a dynamical network model of deficits to explore the effects of interactions between deficits, deficit damage and repair processes, and the connection between the F and mortality. With our model, we qualitatively reproduce Gompertz's law of increasing human mortality with age, the broadening of the F distribution with age, the characteristic nonlinear increase of the F with age, and the increased mortality of high-frailty individuals. No explicit time-dependence in damage or repair rates is needed in our model. Instead, implicit time-dependence arises through deficit interactions—so that the average deficit damage rates increase, and deficit repair rates decrease, with age. We use a simple mortality criterion, where mortality occurs when the most connected node is damaged.

  13. Age-Dependent Increase of Absence Seizures and Intrinsic Frequency Dynamics of Sleep Spindles in Rats

    Directory of Open Access Journals (Sweden)

    Evgenia Sitnikova

    2014-01-01

    Full Text Available The risk of neurological diseases increases with age. In WAG/Rij rat model of absence epilepsy, the incidence of epileptic spike-wave discharges is known to be elevated with age. Considering close relationship between epileptic spike-wave discharges and physiologic sleep spindles, it was assumed that age-dependent increase of epileptic activity may affect time-frequency characteristics of sleep spindles. In order to examine this hypothesis, electroencephalograms (EEG were recorded in WAG/Rij rats successively at the ages 5, 7, and 9 months. Spike-wave discharges and sleep spindles were detected in frontal EEG channel. Sleep spindles were identified automatically using wavelet-based algorithm. Instantaneous (localized in time frequency of sleep spindles was determined using continuous wavelet transform of EEG signal, and intraspindle frequency dynamics were further examined. It was found that in 5-months-old rats epileptic activity has not fully developed (preclinical stage and sleep spindles demonstrated an increase of instantaneous frequency from beginning to the end. At the age of 7 and 9 months, when animals developed matured and longer epileptic discharges (symptomatic stage, their sleep spindles did not display changes of intrinsic frequency. The present data suggest that age-dependent increase of epileptic activity in WAG/Rij rats affects intrinsic dynamics of sleep spindle frequency.

  14. Artificial Neural Network-Based Early-Age Concrete Strength Monitoring Using Dynamic Response Signals.

    Science.gov (United States)

    Kim, Junkyeong; Lee, Chaggil; Park, Seunghee

    2017-06-07

    Concrete is one of the most common materials used to construct a variety of civil infrastructures. However, since concrete might be susceptible to brittle fracture, it is essential to confirm the strength of concrete at the early-age stage of the curing process to prevent unexpected collapse. To address this issue, this study proposes a novel method to estimate the early-age strength of concrete, by integrating an artificial neural network algorithm with a dynamic response measurement of the concrete material. The dynamic response signals of the concrete, including both electromechanical impedances and guided ultrasonic waves, are obtained from an embedded piezoelectric sensor module. The cross-correlation coefficient of the electromechanical impedance signals and the amplitude of the guided ultrasonic wave signals are selected to quantify the variation in dynamic responses according to the strength of the concrete. Furthermore, an artificial neural network algorithm is used to verify a relationship between the variation in dynamic response signals and concrete strength. The results of an experimental study confirm that the proposed approach can be effectively applied to estimate the strength of concrete material from the early-age stage of the curing process.

  15. Water age and stream solute dynamics at the Hubbard Brook Experimental Forest (US)

    Science.gov (United States)

    Botter, Gianluca; Benettin, Paolo; McGuire, Kevin; Rinaldo, Andrea

    2016-04-01

    The contribution discusses experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (New Hampshire, USA) to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is used to model both conservative and weathering-derived solutes. Based on the available information about the hydrology of the site, an integrated transport model was developed and used to estimate the relevant hydrochemical fluxes. The model was designed to reproduce the deuterium content of streamflow and allowed for the estimate of catchment water storage and dynamic travel time distributions (TTDs). Within this framework, dissolved silicon and sodium concentration in streamflow were simulated by implementing first-order chemical kinetics based explicitly on dynamic TTD, thus upscaling local geochemical processes to catchment scale. Our results highlight the key role of water stored within the subsoil glacial material in both the short-term and long-term solute circulation at Hubbard Brook. The analysis of the results provided by the calibrated model allowed a robust estimate of the emerging concentration-discharge relationship, streamflow age distributions (including the fraction of event water) and storage size, and their evolution in time due to hydrologic variability.

  16. Explicit mixed strain-displacement finite element for dynamic geometrically non-linear solid mechanics

    Science.gov (United States)

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

    2015-03-01

    Low-order finite elements face inherent limitations related to their poor convergence properties. Such difficulties typically manifest as mesh-dependent or excessively stiff behaviour when dealing with complex problems. A recent proposal to address such limitations is the adoption of mixed displacement-strain technologies which were shown to satisfactorily address both problems. Unfortunately, although appealing, the use of such element technology puts a large burden on the linear algebra, as the solution of larger linear systems is needed. In this paper, the use of an explicit time integration scheme for the solution of the mixed strain-displacement problem is explored as an alternative. An algorithm is devised to allow the effective time integration of the mixed problem. The developed method retains second order accuracy in time and is competitive in terms of computational cost with the standard irreducible formulation.

  17. A model for plasticity kinetics and its role in simulating the dynamic behavior of Fe at high strain rates

    Energy Technology Data Exchange (ETDEWEB)

    Colvin, J D; Minich, R W; Kalantar, D H

    2007-03-29

    The recent diagnostic capability of the Omega laser to study solid-solid phase transitions at pressures greater than 10 GPa and at strain rates exceeding 10{sup 7} s{sup -1} has also provided valuable information on the dynamic elastic-plastic behavior of materials. We have found, for example, that plasticity kinetics modifies the effective loading and thermodynamic paths of the material. In this paper we derive a kinetics equation for the time-dependent plastic response of the material to dynamic loading, and describe the model's implementation in a radiation-hydrodynamics computer code. This model for plasticity kinetics incorporates the Gilman model for dislocation multiplication and saturation. We discuss the application of this model to the simulation of experimental velocity interferometry data for experiments on Omega in which Fe was shock compressed to pressures beyond the {alpha}-to-{var_epsilon} phase transition pressure. The kinetics model is shown to fit the data reasonably well in this high strain rate regime and further allows quantification of the relative contributions of dislocation multiplication and drag. The sensitivity of the observed signatures to the kinetics model parameters is presented.

  18. Dynamic reverse phase transformation induced high-strain-rate superplasticity in low carbon low alloy steels with commercial potential.

    Science.gov (United States)

    Cao, Wenquan; Huang, Chongxiang; Wang, Chang; Dong, Han; Weng, Yuqing

    2017-08-23

    Superplastic materials are capable of exhibiting large tensile elongation at elevated temperature, which is of great industrial significance because it forms the basis of a fabrication method to produce complex shapes. Superplasticity with elongation larger than 500% has been widely realized in many metals and alloys, but seldomly been succeeded in low carbon low alloy steel, even though it is commercially applied in the largest quantity. Here we report ultrahigh superplastic elongation of 900-1200% in the FeMnAl low carbon steels at high strain rate of 10(-2)-10(-3) s(-1). Such high-strain-rate superplasticity was attributed to dynamic austenite reverse phase transformation from a heavily cold rolled ferrite to fine-grained ferrite/austenite duplex microstructure and subsequent limited dynamic grain coarsening, under which a large fraction of high angle boundaries can be resulted for superplastic deformation. It is believed that this finding of the low carbon low alloy steel with ultrahigh superplasticity and relative low cost would remarkably promote the application of superplastic forming technique in automobile, aeronautical, astronautical and other fields.

  19. Dynamic Evaluation of Acrylonitrile Butadiene Styrene Subjected to High-Strain-Rate Compressive Loads

    Science.gov (United States)

    2014-12-01

    explores the fused deposition modeling ( FDM ) and the printing orientation as a means to quantify the potential benefits. These benefits include more cost...effective, time-efficient, in-house fabrication of designs, while optimizing the mechanical and structural integrity. In FDM , CAD software is used to...relationship to the stress experienced in a material at high-strain-rate deformation. For polymers such as ABS, the mechanical properties vary

  20. Linking water age and solute dynamics in streamflow at the Hubbard Brook Experimental Forest, NH, USA

    Science.gov (United States)

    Benettin, Paolo; Bailey, Scott W.; Campbell, John L.; Green, Mark B.; Rinaldo, Andrea; Likens, Gene E.; McGuire, Kevin J.; Botter, Gianluca

    2015-11-01

    We combine experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is here applied to conservative and weathering-derived solutes. Based on the available information about the hydrology of the site, an integrated transport model was developed and used to compute hydrochemical fluxes. The model was designed to reproduce the deuterium content of streamflow and allowed for the estimate of catchment water storage and dynamic travel time distributions (TTDs). The innovative contribution of this paper is the simulation of dissolved silicon and sodium concentration in streamflow, achieved by implementing first-order chemical kinetics based explicitly on dynamic TTD, thus upscaling local geochemical processes to catchment scale. Our results highlight the key role of water stored within the subsoil glacial material in both the short-term and long-term solute circulation. The travel time analysis provided an estimate of streamflow age distributions and their evolution in time related to catchment wetness conditions. The use of age information to reproduce a 14 year data set of silicon and sodium stream concentration shows that, at catchment scales, the dynamics of such geogenic solutes are mostly controlled by hydrologic drivers, which determine the contact times between the water and mineral interfaces. Justifications and limitations toward a general theory of reactive solute circulation at catchment scales are discussed.

  1. Dynamic studies on the influence of strain on superconducting properties using piezoelectric substrates

    Energy Technology Data Exchange (ETDEWEB)

    Trommler, Sascha; Huehne, Ruben; Iida, Kazumasa; Haindl, Silvia; Haenisch, Jens; Pahlke, Patrick; Thersleff, Thomas; Schultz, Ludwig; Holzapfel, Bernhard [IFW Dresden (Germany)

    2011-07-01

    The interplay between structural parameters and superconducting properties attracts high interest in particular regarding the iron based superconductors. In contrast to the cuprate family, superconductivity of the latter can be induced using either pressure or chemical substitution. Nevertheless little is known about this relationship when biaxial strain is applied. The generation of biaxial strain by the preparation of thin films on substrates with different lattice mismatch is well established for cuprates. However, high quality films are necessary to correlate structural changes with electronic properties. In this work an alternative approach is used. Single crystalline piezoelectric substrates offer the unique opportunity to tune the lattice parameters continuously using the inverse piezoelectric effect. We prepared thin epitaxial La{sub 1-x}Sr{sub x}CuO{sub 4} and BaFe{sub 2-x}Co{sub x}As{sub 2} films on piezoelectric (001) Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.72}Ti{sub 0.28}O{sub 3} (PMN-PT) substrates. A reversible shift of the superconducting transition has been achieved with a value of 0.44 K for La{sub 1.85}Sr{sub 0.15}CuO{sub 4} and 0.2 K for BaFe{sub 1.8}Co{sub 0.2}As{sub 2} for a biaxial strain of 0.022% and 0.017%, respectively.

  2. Dynamics of plc gene transcription and α-toxin production during growth of Clostridium perfringens strains with contrasting α-toxin production

    DEFF Research Database (Denmark)

    Abildgaard, Lone; Schramm, Andreas; Rudi, Knut

    2009-01-01

    The aim of the present study was to investigate transcription dynamics of the α-toxin-encoding plc gene relative to two housekeeping genes (gyrA and rplL) in batch cultures of three Clostridium perfringens strains with low, intermediate, and high levels of α-toxin production, respectively. The plc...... transcript level was always low in the low α-toxin producing strain. For the two other strains, plc transcription showed an inducible pattern and reached a maximum level in the late exponential growth phase. The transcription levels were however inversely correlated to α-toxin production for the two strains....... We propose that this discrepancy is due to differences in plc translation rates between the strains and that strain-specific translational rates therefore must be determined before α-toxin production can be extrapolated from transcript levels in C. perfringens....

  3. Association of IL-8-inducing strains of diffusely adherent Escherichia coli with sporadic diarrheal patients with less than 5 years of age

    Directory of Open Access Journals (Sweden)

    Ismail Mustafa Meraz

    2007-02-01

    Full Text Available The role of diffusely adherent Escherichia coli (DAEC in diarrheal disease has been controversial. However, DAEC strains were recently implicated in diarrheal disease in developing countries. To clarify whether DAEC are prevalent among sporadic cases of diarrheal illness in Osaka City, Japan, E. coli strains isolated between July 1997 and March 2000 during diarrheagenic E. coli (DEC investigation were retrospectively examined. DAEC strains were recognized among 41 (4.4% of 924 patients and formed the biggest subgroup of DEC. Previously, we reported that some DAEC strains caused epithelial cells to secrete as much IL-8 as enteroaggregative E. coli strains did. In this study, we attempted to evaluate epidemiologically whether the ability of DAEC to induce IL-8 was involved in the pathogenesis. Relationship among patient age, symptoms, Afa adhesins, season and IL-8 induction were examined. The subgroup of DAEC that possessed Afa genes and/or induced a high level of IL-8 was significantly prevalent among patients age 1 to 4 years; however total DAEC was not significantly high among the children compared to other age group. IL-8 inducing DAEC seems to play a role in causing sporadic diarrheal illnesses, particularly in pediatric fields. Investigations highlighting the relationship between IL-8 induction and enteropathogenicity are clearly necessary to confirm the role of DAEC in infectious enteritis.

  4. Association of IL-8-inducing strains of diffusely adherent Escherichia coli with sporadic diarrheal patients with less than 5 years of age.

    Science.gov (United States)

    Meraz, Ismail Mustafa; Arikawa, Kentaro; Nakamura, Hiromi; Ogasawara, Jun; Hase, Atsushi; Nishikawa, Yoshikazu

    2007-02-01

    The role of diffusely adherent Escherichia coli (DAEC) in diarrheal disease has been controversial. However, DAEC strains were recently implicated in diarrheal disease in developing countries. To clarify whether DAEC are prevalent among sporadic cases of diarrheal illness in Osaka City, Japan, E. coli strains isolated between July 1997 and March 2000 during diarrheagenic E. coli (DEC) investigation were retrospectively examined. DAEC strains were recognized among 41 (4.4%) of 924 patients and formed the biggest subgroup of DEC. Previously, we reported that some DAEC strains caused epithelial cells to secrete as much IL-8 as enteroaggregative E. coli strains did. In this study, we attempted to evaluate epidemiologically whether the ability of DAEC to induce IL-8 was involved in the pathogenesis. Relationship among patient age, symptoms, Afa adhesins, season and IL-8 induction were examined. The subgroup of DAEC that possessed Afa genes and/or induced a high level of IL-8 was significantly prevalent among patients age 1 to 4 years; however total DAEC was not significantly high among the children compared to other age group. IL-8 inducing DAEC seems to play a role in causing sporadic diarrheal illnesses, particularly in pediatric fields. Investigations highlighting the relationship between IL-8 induction and enteropathogenicity are clearly necessary to confirm the role of DAEC in infectious enteritis.

  5. Aging modulates the oscillatory dynamics underlying successful working memory encoding and maintenance.

    Science.gov (United States)

    Proskovec, Amy L; Heinrichs-Graham, Elizabeth; Wilson, Tony W

    2016-06-01

    Working memory is central to the execution of many daily functions and is typically divided into three phases: encoding, maintenance, and retrieval. While working memory performance has been repeatedly shown to decline with age, less is known regarding the underlying neural processes. We examined age-related differences in the neural dynamics that serve working memory by recording high-density magnetoencephalography (MEG) in younger and older adults while they performed a modified, high-load Sternberg working memory task with letters as stimuli. MEG data were evaluated in the time-frequency domain and significant oscillatory responses were imaged using a beamformer. A hierarchical regression was performed to investigate whether age moderated the relationship between oscillatory activity and accuracy on the working memory task. Our results indicated that the spatiotemporal dynamics of oscillatory activity in language-related areas of the left fronto-temporal cortices were similar across groups. Age-related differences emerged during early encoding in the right-hemispheric homologue of Wernicke's area. Slightly later, group differences emerged in the homologue of Broca's area and these persisted throughout memory maintenance. Additionally, occipital alpha activity during maintenance was stronger, occurred earlier, and involved more cortical tissue in older adults. Finally, age significantly moderated the relationship between accuracy and neural activity in the prefrontal cortices. In younger adults, as prefrontal activity decreased, accuracy tended to increase. Our results are consistent with predictions of the compensation-related utilization of neural circuits hypothesis (CRUNCH). Such differences in the oscillatory dynamics could reflect compensatory mechanisms, which would aid working memory performance in older age. Hum Brain Mapp 37:2348-2361, 2016. © 2016 Wiley Periodicals, Inc.

  6. Secretion expression of SOD1 and its overlapping function with GSH in brewing yeast strain for better flavor and anti-aging ability.

    Science.gov (United States)

    Wang, Zhaoyue; Bai, Xuejing; He, Xiuping; Zhang, Borun

    2014-09-01

    Superoxide dismutase (SOD) is a significant antioxidant, but unlike glutathione (GSH), SOD cannot be secreted into beer by yeast cells during fermentation, this directly leads to the limited application of SOD in beer anti-aging. In this investigation, we constructed the SOD1 secretion cassette in which strong promoter PGK1p and the sequence of secreting signal factor from Saccharomyces cerevisiae were both harbored to the upstream of coding sequence of SOD1 gene, as a result, the obtained strains carrying this cassette successfully realized the secretion of SOD1. In order to overcome the limitation of previous genetic modification on yeast strains, one new comprehensive strategy was adopted targeting the suitable homologous sites by gene deletion and SOD1 + GSH1 co-overexpression, and the new strain ST31 (Δadh2::SOD1 + Δilv2::GSH1) was constructed. The results of the pilot-scale fermentation showed that the diacetyl content of ST31 was lower by 42 % than that of the host, and the acetaldehyde content decreased by 29 %, the GSH content in the fermenting liquor of ST31 increased by 29 % compared with the host. Both SOD activity test and the positive and negative staining assay after native PAGE indicated that the secreted active SOD in the fermenting liquor of ST31 was mainly a dimer with the size of 32,500 Da. The anti-aging indexes such as the thiobarbituric acid and the resistance staling value further proved that the flavor stability of the beer brewed with strain ST31 was not only better than that of the original strain, but also better than that of the previous engineering strains. The multi-modification and comprehensive improvement of the beer yeast strain would greatly enhance beer quality than ever, and the self-cloning strain would be attractive to the public due to its bio-safety.

  7. Effect of Pre-strain on the Solute Clustering, Mechanical Properties, and Work-Hardening of a Naturally Aged Al-Cu-Mg Alloy

    Science.gov (United States)

    Shao, D.; Zhang, P.; Zhang, J. Y.; Liu, G.; Wang, R. H.; Liu, W. Q.; Sha, G.; Sun, J.

    2017-09-01

    The effect of pre-strain on the solute clustering, mechanical properties, and work-hardening of a naturally aged Al-Cu-Mg alloy was comprehensively investigated using a three-dimensional atom probe, electrical resistivity, and hardness measurements. The pre-strain promoted the rapid formation of solute clusters but suppressed the growth of solute clusters during prolonged aging. An increase in pre-strain caused a decrease in the saturated number density of solute clusters, leading to a reduction in cluster strengthening. By taking into account the coupling effect of solute clusters and pre-existing dislocations, models were proposed to address the yield strength and work-hardening behaviors of the Al-Cu-Mg alloy, respectively. It reveals that the solute-cluster strengthening is comparable to dislocation strengthening in the naturally aged alloy. However, the work hardening is not significantly affected by the presence of the solute clusters. The findings reported in this paper will be helpful for the development of a naturally aged Al-Cu-Mg alloy with improved performance by controlling the pre-strain.

  8. Aging and emotional expressions: is there a positivity bias during dynamic emotion recognition?

    Directory of Open Access Journals (Sweden)

    Alberto eDi Domenico

    2015-08-01

    Full Text Available In this study, we investigated whether age-related differences in emotion regulation priorities influence online dynamic emotional facial discrimination. A group of 40 younger and a group of 40 older adults were invited to recognize a positive or negative expression as soon as the expression slowly emerged and subsequently rate it in terms of intensity. Our findings show that older adults recognized happy expressions faster than angry ones, while the direction of emotional expression does not seem to affect younger adults’ performance. Furthermore, older adults rated both negative and positive emotional faces as more intense compared to younger controls. This study detects age-related differences with a dynamic online paradigm and suggests that different regulation strategies may shape emotional face recognition.

  9. Glassy dynamics and physical aging in fucose saccharides as studied by infrared- and broadband dielectric spectroscopy.

    Science.gov (United States)

    Kossack, Wilhelm; Adrjanowicz, Karolina; Tarnacka, Magdalena; Kipnusu, Wycliffe Kiprop; Dulski, Mateusz; Mapesa, Emmanuel Urandu; Kaminski, Kamil; Pawlus, Sebastian; Paluch, Marian; Kremer, Friedrich

    2013-12-21

    Fourier Transform Infra Red (FTIR) and Broadband Dielectric Spectroscopy (BDS) are combined to study both the intra- and inter-molecular dynamics of two isomers of glass forming fucose, far below and above the calorimetric glass transition temperature, T(g). It is shown that the various IR-active vibrations exhibit in their spectral position and oscillator strength quite different temperature dependencies, proving their specific signature in the course of densification and glass formation. The coupling between intra- and inter molecular dynamics is exemplified by distinct changes in IR active ring vibrations far above the calorimetric glass transition temperature at about 1.16T(g), where the dynamic glass transition (α relaxation) and the secondary β relaxation merge. For physically annealed samples it is demonstrated that upon aging the different moieties show characteristic features as well, proving the necessity of atomistic descriptions beyond coarse-grained models.

  10. Age-specific infectious period shapes dynamics of pneumonia in bighorn sheep.

    Science.gov (United States)

    Plowright, Raina K; Manlove, Kezia R; Besser, Thomas E; Páez, David J; Andrews, Kimberly R; Matthews, Patrick E; Waits, Lisette P; Hudson, Peter J; Cassirer, E Frances

    2017-09-04

    Superspreading, the phenomenon where a small proportion of individuals contribute disproportionately to new infections, has profound effects on disease dynamics. Superspreading can arise through variation in contacts, infectiousness or infectious periods. The latter has received little attention, yet it drives the dynamics of many diseases of critical public health, livestock health and conservation concern. Here, we present rare evidence of variation in infectious periods underlying a superspreading phenomenon in a free-ranging wildlife system. We detected persistent infections of Mycoplasma ovipneumoniae, the primary causative agent of pneumonia in bighorn sheep (Ovis canadensis), in a small number of older individuals that were homozygous at an immunologically relevant genetic locus. Interactions among age-structure, genetic composition and infectious periods may drive feedbacks in disease dynamics that determine the magnitude of population response to infection. Accordingly, variation in initial conditions may explain divergent population responses to infection that range from recovery to catastrophic decline and extirpation. © 2017 John Wiley & Sons Ltd/CNRS.

  11. Age differences in dynamic fatigability and variability of arm and leg muscles: Associations with physical function.

    Science.gov (United States)

    Senefeld, Jonathon; Yoon, Tejin; Hunter, Sandra K

    2017-01-01

    It is not known whether the age-related increase in fatigability of fast dynamic contractions in lower limb muscles also occurs in upper limb muscles. We compared age-related fatigability and variability of maximal-effort repeated dynamic contractions in the knee extensor and elbow flexor muscles; and determined associations between fatigability, variability of velocity between contractions and functional performance. 35 young (16 males; 21.0±2.6years) and 32 old (18 males; 71.3±6.2years) adults performed a dynamic fatiguing task involving 90 maximal-effort, fast, concentric, isotonic contractions (1 contraction/3s) with a load equivalent to 20% maximal voluntary isometric contraction (MVIC) torque with the elbow flexor and knee extensor muscles on separate days. Old adults also performed tests of balance and walking endurance. Old adults had greater fatigue-related reductions in peak velocity compared with young adults for both the elbow flexor and knee extensor muscles (P0.05). Old adults had greater variability of peak velocity during the knee extensor, but not during the elbow flexor fatiguing task. The age difference in fatigability was greater for the knee extensor muscles (35.9%) compared with elbow flexor muscles (9.7%, P<0.05). Less fatigability of the knee extensor muscles was associated with greater walking endurance (r=-0.34, P=0.048) and balance (r=-0.41, P=0.014) among old adults. An age-related increase in fatigability of a dynamic fatiguing task was greater for the knee extensor compared with the elbow flexor muscles in males and females, and greater fatigability was associated with lesser walking endurance and balance. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Directed polymer in random media, in two dimensions: numerical study of the aging dynamics

    OpenAIRE

    Barrat, A.

    1997-01-01

    Following a recent work by Yoshino, we study the aging dynamics of a directed polymer in random media, in 1+1 dimensions. Through temperature quench, and temperature cycling numerical experiments similar to the experiments on real spin glasses, we show that the observed behaviour is comparable to the one of a well known mean field spin glass model. The observation of various quantities (correlation function, ``clonation'' overlap function) leads to an analysis of the phase space landscape.

  13. Slow aging dynamics and avalanches in a gold-cadmium alloy investigated by x-ray photon correlation spectroscopy.

    Science.gov (United States)

    Müller, L; Waldorf, M; Gutt, C; Grübel, G; Madsen, A; Finlayson, T R; Klemradt, U

    2011-09-01

    Results of a x-ray photon correlation spectroscopy experiment on the very weakly first order martensitic transformation of a Au50.5Cd49.5 single crystal are presented. Slow non-equilibrium-dynamics are observed in a narrow temperature interval in the direct vicinity of the otherwise athermal phase transformation. These dynamics are associated with the martensite-aging effect. The dynamical aging is accompanied by an avalanchelike behavior which is identified with an incubation-time phenomenon.

  14. Genome dynamics and evolution of Salmonella Typhi strains from the typhoid-endemic zones.

    Science.gov (United States)

    Baddam, Ramani; Kumar, Narender; Shaik, Sabiha; Lankapalli, Aditya Kumar; Ahmed, Niyaz

    2014-12-12

    Typhoid fever poses significant burden on healthcare systems in Southeast Asia and other endemic countries. Several epidemiological and genomic studies have attributed pseudogenisation to be the major driving force for the evolution of Salmonella Typhi although its real potential remains elusive. In the present study, we analyzed genomes of S. Typhi from different parts of Southeast Asia and Oceania, comprising of isolates from outbreak, sporadic and carrier cases. The genomes showed high genetic relatedness with limited opportunity for gene acquisition as evident from pan-genome structure. Given that pseudogenisation is an active process in S. Typhi, we further investigated core and pan-genome profiles of functional and pseudogenes separately. We observed a decline in core functional gene content and a significant increase in accessory pseudogene content. Upon functional classification, genes encoding metabolic functions formed a major constituent of pseudogenes as well as core functional gene clusters with SNPs. Further, an in-depth analysis of accessory pseudogene content revealed the existence of heterogeneous complements of functional and pseudogenes among the strains. In addition, these polymorphic genes were also enriched in metabolism related functions. Thus, the study highlights the existence of heterogeneous strains in a population with varying metabolic potential and that S. Typhi possibly resorts to metabolic fine tuning for its adaptation.

  15. Fungicide residues in grapes determined the dynamics of Saccharomyces cerevisiae strains during spontaneous wine fermentation

    Directory of Open Access Journals (Sweden)

    Čuš Franc

    2011-01-01

    Full Text Available Impact of three fungicides against B. cinerea (iprodione, pyrimethanil and f ludioxonil plus cyprodinil on the population of Saccharomyces cerevisiae strains during the spontaneous alcoholic fermentation was studied. With regard to the use of fungicides in the vineyard at two stages of the grapevine growth we followed four different spontaneous fermentations: control, iprodione, pyrimethanil and f ludioxonil plus cyprodinil. The fungicide residues in the grapes were determined by GC/MS system and the fermentations were followed by changes in yeast, sugar, and ethanol concentrations using colony counting and HPLC. The karyotype analysis of 473 isolates was done by pulsed-field gel electrophoresis. The fungicide residues in the grapes at the harvest were below the maximum residue limits. Isolates of S. cerevisiae were classified into 15 karyotype groups. The duration of the processes and the populations of the karyotypes differed between the fermentations. The iprodione and control fermentations lasted 36 days with the prevalence of karyotype A while the fludioxonil plus cyprodinil fermentation lasted 50 days and karyotype D led the process. In the pyrimethanil fermentation, none of the karyotypes prevailed in the must and the fermentation lasted much longer than others did (68 days. The results showed that the fungicide residues have an influence on the fermentation kinetics and selection of S. cerevisiae strains during the spontaneous alcoholic fermentation and therefore should be considered as an important factor that may indirectly influence the formation of fermentation aroma in the wine produced by such process.

  16. Analysis of the strain induced martensitic transformation in austenitic steel subjected to dynamic perforation

    Directory of Open Access Journals (Sweden)

    Zaera R.

    2012-08-01

    Full Text Available An experimental and numerical analysis on the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles is reported. Two target thicknesses are considered, 0.5 and 1.0 mm, and impact velocities range from 35 to 200 m/s. The perforation mechanisms are identified and the effect of the projectile nose-shape on the ability of the target for energy absorption is evaluated. Martensite has been detected in all the impacted samples and the role played by the projectile nose-shape on the transformation is highlighted. A 3D model implemented in ABAQUS/Explicit allowed to simulate the perforation tests. The material is defined through a constitutive description developed by the authors to describe the strain induced martensitic transformation taking place in metastable austenitic steels at high strain rates. The numerical results are compared with the experimental evidence and satisfactory matching is obtained. The numerical model succeeds in describing the perforation mechanisms associated to each projectile-target configuration analysed.

  17. Dynamical age differences among coeval star clusters as revealed by blue stragglers

    CERN Document Server

    Ferraro, F R; Dalessandro, E; Beccari, G; Pasquato, M; Miocchi, P; Rood, R T; Sigurdsson, S; Sills, A; Vesperini, E; Mapelli, M; Contreras, R; Sanna, N; Mucciarelli, A; 10.1038/nature11686

    2012-01-01

    Globular star clusters that formed at the same cosmic time may have evolved rather differently from a dynamical point of view (because that evolution depends on the internal environment) through a variety of processes that tend progressively to segregate stars more massive than the average towards the cluster centre. Therefore clusters with the same chronological age may have reached quite different stages of their dynamical history (that is, they may have different dynamical ages). Blue straggler stars have masses greater than those at the turn-off point on the main sequence and therefore must be the result of either a collision or a mass-transfer event. Because they are among the most massive and luminous objects in old clusters, they can be used as test particles with which to probe dynamical evolution. Here we report that globular clusters can be grouped into a few distinct families on the basis of the radial distribution of blue stragglers. This grouping corresponds well to an effective ranking of the dy...

  18. Numerical simulation of gas-dynamic, thermal processes and evaluation of the stress-strain state in the modeling compressor of the gas-distributing unit

    Science.gov (United States)

    Shmakov, A. F.; Modorskii, V. Ya.

    2016-10-01

    This paper presents the results of numerical modeling of gas-dynamic processes occurring in the flow path, thermal analysis and evaluation of the stress-strain state of a three-stage design of the compressor gas pumping unit. Physical and mathematical models of the processes developed. Numerical simulation was carried out in the engineering software ANSYS 13. The problem is solved in a coupled statement, in which the results of the gas-dynamic calculation transferred as boundary conditions for the evaluation of the thermal and stress-strain state of a three-stage design of the compressor gas pumping unit. The basic parameters, which affect the stress-strain state of the housing and changing gaps of labyrinth seals in construction. The method of analysis of the pumped gas flow influence on the strain of construction was developed.

  19. Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars

    CERN Document Server

    Vakhnenko, O O; Shankland, T J; Cate, J A T; Vakhnenko, Oleksiy O.; Vakhnenko, Vyacheslav O.; Shankland, Thomas J.; Cate, James A. Ten

    2004-01-01

    The closed description of nonlinear and slow dynamics effects exhibited by the sandstone bars in numerous resonant response experiments with the longitudinal strain configuration is proposed. Alongside with the fast subsystem of longitudinal nonlinear displacements we examine the strain dependent slow subsystem of broken intergrain and interlamina cohesive bonds and show that even the simplest but phenomenologically correct modelling of their mutual feedback elucidates the main experimental mysteries typical for the forced longitudinal oscillations of sandstone bars, namely (i) the hysteretic behaviour of resonance curve on both its slopes, (ii) the linear softening of resonant frequency with the driving level increase, and (iii) the gradual recovery (increase) of resonant frequency at low dynamical strains after the sample being conditioned by the high ones. In order to reproduce the highly nonlinear elastic features of sandstone grained structure the realistic nonperturbative form of strain potential energy...

  20. Experimental and theoretical analyses of the age-dependent large-strain behavior of Sylgard 184 (10:1) silicone elastomer.

    Science.gov (United States)

    Hopf, R; Bernardi, L; Menze, J; Zündel, M; Mazza, E; Ehret, A E

    2016-07-01

    The commercial polydimethysiloxane elastomer Sylgard(®) 184 with mixing ratio 10:1 is in wide use for biomedical research or fundamental studies of mechanobiology. In this paper, a comprehensive study of the large strain mechanical behavior of this material under multiaxial monotonic and cyclic loads, and its change during the first 26 days after preparation is reported. The equibiaxial stress response studied in inflation experiments reveals a much stiffer and more nonlinear response compared to the uniaxial and pure shear characteristics. The polymer revealed remarkably elastic behavior, in particular, very little dependence on strain rates between 0.3%/s and 11%/s, and on the strain history in cyclic experiments. On the other hand, both the small-strain and large strain nonlinear mechanical characteristics of the elastomer are changing with sample age and the results suggest that this process has not ceased after 26 days. A recent re-interpretation of the well-known Ogden model for incompressible rubber-like materials was applied to rationalize the results and accurate agreement was obtained with the experimental data over all testing configurations and testing times. The change of a single parameter in this model is shown to govern the evolution of the nonlinear material characteristics with sample age, attributed to a continuation of the cross-linking process. Based on a kinetic relation to account for this process over time, the model provided successful predictions of the material behavior even after more than one year.

  1. Reference data for distal blood pressure in healthy elderly and middle-aged individuals measured with the strain gauge technique. Part II: Distal blood pressure after exercise

    DEFF Research Database (Denmark)

    Arveschoug, Anne Kirstine; Vammen, Birthe; Yoshinaka, Emmy

    2008-01-01

    Objective. Distal blood pressure (DBP) determination after an exercise test is used on suspicion of arterial peripheral vascular disease (apvd). In our department. the average age of these patients is about 60 years. The usual reference values for pressures after exercise were based on data...... collected in the early 1970s from healthy individuals in the age range 21-26 years. Our aims were to collect new reference data for DBP at ankle level after exercise based on older populations, and to compare between reference data for different age groups to find out whether the normal values are dependent...... on age. Material and methods. DBP after exercise was measured using the strain-gauge technique on individuals in two groups: group I comprising 25 healthy persons aged between 61 and 82 years, and group II 14 healthy persons aged between 45 and 58 years. Strict rules of inclusion were followed. Results...

  2. A toxaphene-degrading bacterium related to Enterobacter cloacae, strain D1 isolated from aged contaminated soil in Nicaragua.

    Science.gov (United States)

    Lacayo-Romero, Martha; Quillaguamán, Jorge; van Bavel, Bert; Mattiasson, Bo

    2005-09-01

    Enterobacter sp. strain D1 is a facultative anaerobic, Gram-negative heterotrophic bacterium isolated from toxaphene-contaminated soil. This organism was identified and characterized through phylogenetic and taxonomic studies. Based on 16S rDNA analysis, the strain D1 was clustered closely with the species Enterobacter cloacae subsp. dissolvens (LMG 2683) and E. cloacae (ATCC 13047T). Strain D1 resembled these E. cloacae strains with respect to various biochemical and nutritional characteristics, but also exhibited differences. Moreover, strain D1 is able to grow and survive with toxaphene supplied in the medium in the range 3-96 mg/L. Amongst the chemical components of toxaphene, octachlorocamphenes, nonachlorobornanes and decachlorobornanes were seen to be rapidly metabolized, although levels of hexachlorocamphenes and heptachlorobornanes were found to be slowly degraded, and subsequently accumulated during the last stage of the cultivation.

  3. Altered temporal dynamics of neural adaptation in the aging human auditory cortex.

    Science.gov (United States)

    Herrmann, Björn; Henry, Molly J; Johnsrude, Ingrid S; Obleser, Jonas

    2016-09-01

    Neural response adaptation plays an important role in perception and cognition. Here, we used electroencephalography to investigate how aging affects the temporal dynamics of neural adaptation in human auditory cortex. Younger (18-31 years) and older (51-70 years) normal hearing adults listened to tone sequences with varying onset-to-onset intervals. Our results show long-lasting neural adaptation such that the response to a particular tone is a nonlinear function of the extended temporal history of sound events. Most important, aging is associated with multiple changes in auditory cortex; older adults exhibit larger and less variable response magnitudes, a larger dynamic response range, and a reduced sensitivity to temporal context. Computational modeling suggests that reduced adaptation recovery times underlie these changes in the aging auditory cortex and that the extended temporal stimulation has less influence on the neural response to the current sound in older compared with younger individuals. Our human electroencephalography results critically narrow the gap to animal electrophysiology work suggesting a compensatory release from cortical inhibition accompanying hearing loss and aging.

  4. Melatonin and circadian oscillators in aging--a dynamic approach to the multiply connected players.

    Science.gov (United States)

    Hardeland, Rüdiger

    2015-01-01

    From the perspective of systems biology, melatonin is relevant to aging in multiple ways. As a highly pleiotropic agent, it acts as a modulator and protectant of mitochondrial electron flux, a potent antioxidant that supports the redox balance and prevents excessive free radical formation, a coregulator of metabolic sensing and antagonist of insulin resistance, an immune modulator, a physiological hypnotic and, importantly, an orchestrating chronobiotic. It entrains central and peripheral circadian clocks and is required for some high-amplitude rhythms. The circadian system, which controls countless functions, is composed of many cellular oscillators that involve various accessory clock proteins, some of which are modulated by melatonin, e.g. sirtuin 1, AMP-dependent protein kinase, and protein kinase Cα. Aging and age-related diseases are associated with losses in melatonin secretion and rhythm amplitudes. The dynamic properties of aging processes deserve particular attention. This concerns especially two vicious cycles, one of peroxynitrite formation driven by inflammation or overexcitation, another one of inflammaging driven by the senescence-associated secretory phenotype, and additionally the loss of dynamics in a deteriorating circadian multioscillator system.

  5. Effects of Wheat Flour Dough’s Viscoelastic Level by Adding Glucose Oxidase on its Dynamic Shear Properties whatever the Strain Modes

    OpenAIRE

    Jean Didier Koffi Kouassi; Vlad Muresan; Sophie Nadège Gnangui; Elena Mudura; Lucien Patrice Kouame

    2014-01-01

    The objective of this work was to study the effects of wheat flour dough’s viscoelastic level by adding glucose oxidase (Gox) on its rheological properties at dynamic shear strain mode to predict the final product quality. Dough does display a linear viscoelastic domain. Glucose oxidase (Gox) was added to dough in order to enhance its viscoelasticity and to take into account the possible effects of this viscoelasticity on the results. Whatever the types of dough strain used G’ increased, tan ...

  6. Methyl viologen responsive proteome dynamics of Anabaena sp. strain PCC7120.

    Science.gov (United States)

    Panda, Bandita; Basu, Bhakti; Rajaram, Hema; Kumar Apte, Shree

    2014-08-01

    A proteomic approach was employed to elucidate the response of an agriculturally important microbe, Anabaena sp. strain PCC7120, to methyl viologen (MV). Exposure to 2 μM MV caused 50% lethality (LD50 ) within 6 h and modified the cellular levels of several proteins. About 31 proteins increased in abundance and 24 proteins decreased in abundance, while 55 proteins showed only a minor change in abundance. Of these, 103 proteins were identified by MS. Levels of proteins involved in ROS detoxification and chaperoning activities were enhanced but that of crucial proteins involved in light and dark reactions of photosynthesis declined or constitutive. The abundance of proteins involved in carbon and energy biogenesis were altered. The study elaborated the oxidative stress defense mechanism deployed by Anabaena, identified carbon metabolism and energy biogenesis as possible major targets of MV sensitivity, and suggested potential biotechnological interventions for improved stress tolerance in Anabaena 7120.

  7. Strain-specific innate immune signaling pathways determine malaria parasitemia dynamics and host mortality

    Science.gov (United States)

    Wu, Jian; Tian, Linjie; Yu, Xiao; Pattaradilokrat, Sittiporn; Li, Jian; Wang, Mingjun; Yu, Weishi; Qi, Yanwei; Zeituni, Amir E.; Nair, Sethu C.; Crampton, Steve P.; Orandle, Marlene S.; Bolland, Silvia M.; Qi, Chen-Feng; Long, Carole A.; Myers, Timothy G.; Coligan, John E.; Wang, Rongfu; Su, Xin-zhuan

    2014-01-01

    Malaria infection triggers vigorous host immune responses; however, the parasite ligands, host receptors, and the signaling pathways responsible for these reactions remain unknown or controversial. Malaria parasites primarily reside within RBCs, thereby hiding themselves from direct contact and recognition by host immune cells. Host responses to malaria infection are very different from those elicited by bacterial and viral infections and the host receptors recognizing parasite ligands have been elusive. Here we investigated mouse genome-wide transcriptional responses to infections with two strains of Plasmodium yoelii (N67 and N67C) and discovered differences in innate response pathways corresponding to strain-specific disease phenotypes. Using in vitro RNAi-based gene knockdown and KO mice, we demonstrated that a strong type I IFN (IFN-I) response triggered by RNA polymerase III and melanoma differentiation-associated protein 5, not Toll-like receptors (TLRs), binding of parasite DNA/RNA contributed to a decline of parasitemia in N67-infected mice. We showed that conventional dendritic cells were the major sources of early IFN-I, and that surface expression of phosphatidylserine on infected RBCs might promote their phagocytic uptake, leading to the release of parasite ligands and the IFN-I response in N67 infection. In contrast, an elevated inflammatory response mediated by CD14/TLR and p38 signaling played a role in disease severity and early host death in N67C-infected mice. In addition to identifying cytosolic DNA/RNA sensors and signaling pathways previously unrecognized in malaria infection, our study demonstrates the importance of parasite genetic backgrounds in malaria pathology and provides important information for studying human malaria pathogenesis. PMID:24474800

  8. Dynamic behavior and microstructural evolution during moderate to high strain rate hot deformation of a Fe-Ni-Cr alloy (alloy 800H)

    Science.gov (United States)

    Cao, Yu; Di, Hongshuang; Zhang, Jiecen; Yang, Yaohua

    2015-01-01

    The objective of the study is to fundamentally understand the dynamic behavior of alloy 800H at moderate to high strain rate using hot compression tests and propose nucleation mechanism associated with dynamic crystallization (DRX). We firstly investigated the dynamic behavior of alloy 800H with industrial scale strain rates using hot compression tests and adiabatic correction was performed to correct as-measured flow curves. Secondly, a Johnson-Cook model was established by using the corrected data and could give a precise prediction of elevated temperature flow stress for the studied alloy. Finally, the nucleation mechanism of DRX grains at high strain rates was studied. The results showed that the predominant nucleation mechanism for DRX is the formation of "bulge" at parent grain boundary. Additionally, the fragmentation of original grain at low deformation temperatures and the twinning near the bulged regions at high deformation temperatures also accelerate the DRX process.

  9. Aging and percolation dynamics in a Non-Poissonian temporal network model.

    Science.gov (United States)

    Moinet, Antoine; Starnini, Michele; Pastor-Satorras, Romualdo

    2016-08-01

    We present an exhaustive mathematical analysis of the recently proposed Non-Poissonian Activity Driven (NoPAD) model [Moinet et al., Phys. Rev. Lett. 114, 108701 (2015)PRLTAO0031-900710.1103/PhysRevLett.114.108701], a temporal network model incorporating the empirically observed bursty nature of social interactions. We focus on the aging effects emerging from the non-Poissonian dynamics of link activation, and on their effects on the topological properties of time-integrated networks, such as the degree distribution. Analytic expressions for the degree distribution of integrated networks as a function of time are derived, exploring both limits of vanishing and strong aging. We also address the percolation process occurring on these temporal networks, by computing the threshold for the emergence of a giant connected component, highlighting the aging dependence. Our analytic predictions are checked by means of extensive numerical simulations of the NoPAD model.

  10. [Age structure and dynamics of Quercus wutaishanica population in Lingkong Mountain of Shanxi Province, China].

    Science.gov (United States)

    Zhang, Jie; Shangguan, Tie-Liang; Duan, Yi-Hao; Guo, Wei; Liu, Wei-Hua; Guo, Dong-Gang

    2014-11-01

    Using the plant survivorship theory, the age structure, and the relationship between tree height and diameter (DBH) of Quercus wutaishanica population in Lingkong Mountain were analyzed, and the static life table was compiled and the survival curve plotted. The shuttle shape in age structure of Q. wutaishanica population suggested its temporal stability. The linear regression significantly fitted the positive correlation between tree height and DBH. The maximal life expectancy was observed among the trees beyond the age of the highest mortality and coincided with the lowest point of mortality density, suggesting the strong vitality of the seedlings and young trees that survived in the natural selection and intraspecific competition. The population stability of the Q. wutaishanica population was characterized by the Deevey-II of the survival curve. The dynamic pattern was characterized by the recession in the early phase, growth in the intermediate phase, and stability in the latter phase.

  11. Aging and percolation dynamics in a Non-Poissonian temporal network model

    Science.gov (United States)

    Moinet, Antoine; Starnini, Michele; Pastor-Satorras, Romualdo

    2016-08-01

    We present an exhaustive mathematical analysis of the recently proposed Non-Poissonian Activity Driven (NoPAD) model [Moinet et al., Phys. Rev. Lett. 114, 108701 (2015), 10.1103/PhysRevLett.114.108701], a temporal network model incorporating the empirically observed bursty nature of social interactions. We focus on the aging effects emerging from the non-Poissonian dynamics of link activation, and on their effects on the topological properties of time-integrated networks, such as the degree distribution. Analytic expressions for the degree distribution of integrated networks as a function of time are derived, exploring both limits of vanishing and strong aging. We also address the percolation process occurring on these temporal networks, by computing the threshold for the emergence of a giant connected component, highlighting the aging dependence. Our analytic predictions are checked by means of extensive numerical simulations of the NoPAD model.

  12. Aging and percolation dynamics in a Non-Poissonian temporal network model

    CERN Document Server

    Moinet, Antoine; Pastor-Satorras, Romualdo

    2016-01-01

    We present an exhaustive mathematical analysis of the recently proposed Non-Poissonian Ac- tivity Driven (NoPAD) model [Moinet et al. Phys. Rev. Lett., 114 (2015)], a temporal network model incorporating the empirically observed bursty nature of social interactions. We focus on the aging effects emerging from the Non-Poissonian dynamics of link activation, and on their effects on the topological properties of time-integrated networks, such as the degree distribution. Analytic expressions for the degree distribution of integrated networks as a function of time are derived, ex- ploring both limits of vanishing and strong aging. We also address the percolation process occurring on these temporal networks, by computing the threshold for the emergence of a giant connected component, highlighting the aging dependence. Our analytic predictions are checked by means of extensive numerical simulations of the NoPAD model.

  13. Fame and Obsolescence: Disentangling growth and ageing dynamics of patent citations

    CERN Document Server

    Higham, K W; Jaffe, A B; Zülicke, U

    2016-01-01

    We present an analysis of citations accrued over time by cohorts of patents from specific technology sectors (e.g., Electrical and Electronic) granted by the United States Patent and Trademark Office in 1998. In contrast to previous studies that did not differentiate patents by technology category, we observe an intrinsic citation rate that clearly separates into an ageing function and a completely time-independent preferential-attachment-type growth kernel. In the long run, the aging function turns out to be an exponential function of time. Relevant parameters for the ageing and growth functions are reliably extracted. The time-dependent citation distribution is obtained analytically for the general case of a separable citation rate, thus establishing a useful framework for the quantitative investigation of general knowledge-propagation dynamics.

  14. Ageing dynamics of a human-capital-specific population: A demographic perspective

    Directory of Open Access Journals (Sweden)

    Dimiter Philipov

    2014-12-01

    Full Text Available Background: Research on how rising human capital affects the consequences of population ageing rarely considers the fact that the human capital of the elderly population is composed in a specific way that is shaped by their earlier schooling and work experience. For an elderly population of a fixed size and age-sex composition, this entails that the higher its human capital, the greater the total amount of public pensions to be paid. Objective: The main purpose of this paper is to analyse the link between human capital and retiree benefits and its effect on population ageing from a demographic viewpoint. Methods: We construct an old age dependency ratio (OADR, in which each person, whether in the numerator or the denominator, is assigned the number of units corresponding to his/her level of human capital. Based on data for Italy, we study the dynamics of this human-capital-specific OADR with the help of multistate population projections to 2107. Results: Our results show that under specific conditions a constant or moderately growing human capital may aggravate the consequences of population ageing rather than alleviate them. Conclusions: With those findings, the authors would like to stimulate the debate on the search for demographic and/or socio-economic solutions to the challenges posed by population ageing.

  15. Dynamics of a New Strain of the H1N1 Influenza A Virus Incorporating the Effects of Repetitive Contacts

    Directory of Open Access Journals (Sweden)

    Puntani Pongsumpun

    2014-01-01

    Full Text Available The respiratory disease caused by the Influenza A Virus is occurring worldwide. The transmission for new strain of the H1N1 Influenza A virus is studied by formulating a SEIQR (susceptible, exposed, infected, quarantine, and recovered model to describe its spread. In the present model, we have assumed that a fraction of the infected population will die from the disease. This changes the mathematical equations governing the transmission. The effect of repetitive contact is also included in the model. Analysis of the model by using standard dynamical modeling method is given. Conditions for the stability of equilibrium state are given. Numerical solutions are presented for different values of parameters. It is found that increasing the amount of repetitive contacts leads to a decrease in the peak numbers of exposed and infectious humans. A stability analysis shows that the solutions are robust.

  16. Experimental pig-to-pig transmission dynamics for African swine fever virus, Georgia 2007/1 strain.

    Science.gov (United States)

    Guinat, C; Gubbins, S; Vergne, T; Gonzales, J L; Dixon, L; Pfeiffer, D U

    2016-01-01

    African swine fever virus (ASFV) continues to cause outbreaks in domestic pigs and wild boar in Eastern European countries. To gain insights into its transmission dynamics, we estimated the pig-to-pig basic reproduction number (R 0) for the Georgia 2007/1 ASFV strain using a stochastic susceptible-exposed-infectious-recovered (SEIR) model with parameters estimated from transmission experiments. Models showed that R 0 is 2·8 [95% confidence interval (CI) 1·3-4·8] within a pen and 1·4 (95% CI 0·6-2·4) between pens. The results furthermore suggest that ASFV genome detection in oronasal samples is an effective diagnostic tool for early detection of infection. This study provides quantitative information on transmission parameters for ASFV in domestic pigs, which are required to more effectively assess the potential impact of strategies for the control of between-farm epidemic spread in European countries.

  17. The Epidemic Dynamics of Four Major Lineages of HIV-1 CRF01_AE Strains After Their Introduction into China.

    Science.gov (United States)

    Zeng, Haiyan; Li, Tingting; Wang, Yan; Sun, Binlian; Yang, Rongge

    2016-05-01

    The epidemic of HIV-1 CRF01_AE in China was driven by multiple lineages of HIV-1 viruses introduced in the 1990s and increasing; it is important to investigate their epidemic status in China. In this study, we download all available CRF01_AE sequences (n = 2,931) from China and their associated epidemiological information in the Los Alamos HIV database for our analysis to explore their epidemic status in China. The results showed there were 11 distinct clusters of CRF01_AE strains in China, and 4 major clusters that accounted for 80.0% (1,793/2,241) of Chinese CRF01_AE strains in total had led a real epidemic. Clusters 1 and 2 were epidemic among heterosexuals and injecting drug users in southern and southwestern China, while Clusters 3 and 4 were predominant among homosexuals in eastern and central China and northeastern China, respectively. HIV-1 CRF01_AE strains detected in heterosexuals had the most complex characteristic, underscoring its important role in the occurrence of multiple CRF01_AE lineages. Furthermore, epidemic history reconstruction analysis using the birth-death susceptible-infected-removed package revealed that the four clusters had gone through varying epidemic stages. Clusters 2 and 3 were near the peak of the local epidemic, while Clusters 1 and 4 were just in the very early stage of their epidemic. The epidemic status of CRF01_AE clusters in the future is mainly determined by the effect of prevention and control. Our study provides new insights into the understanding of the epidemic dynamics of CRF01_AE in China.

  18. Influence of family dynamics on burden among family caregivers in aging Japan

    Science.gov (United States)

    Kusaba, Tesshu; Sato, Kotaro; Fukuma, Shingo; Yamada, Yukari; Matsui, Yoshinori; Matsuda, Satoshi; Ando, Takashi; Sakushima, Ken; Fukuhara, Shunichi

    2016-01-01

    Background. Long-term care for the elderly is largely shouldered by their family, representing a serious burden in a hyper-aging society. However, although family dynamics are known to play an important role in such care, the influence of caring for the elderly on burden among caregiving family members is poorly understood. Objective. To examine the influence of family dynamics on burden experienced by family caregivers. Methods. We conducted a cross-sectional study at six primary care clinics, involving 199 caregivers of adult care receivers who need long-term care. Participants were divided into three groups based on tertile of Index of Family Dynamics for Long-term Care (IF-Long score), where higher scores imply poorer relationships between care receivers and caregiving family: best, <2; intermediate, 2 to <5; worst, ≥5. The mean differences in burden index of caregivers (BIC-11) between the three groups were estimated by linear regression model with adjustment for care receiver’s activity of daily living and cognitive function. Results. Mean age of caregivers was 63.2 years (with 40.7% aged ≥ 65 years). BIC-11 scores were higher in the worst IF-Long group (adjusted mean difference: 4.4, 95% confidence interval: 1.2 to 7.5) than in the best IF-Long group. We also detected a positive trend between IF-Long score and BIC-11 score (P-value for trend <0.01). Conclusion. Our findings indicate that family dynamics strongly influences burden experienced by caregiving family members, regardless of the care receiver’s degree of cognitive impairment. These results underscore the importance of evaluating relationships between care receivers and their caregivers when discussing a care regimen for care receivers. PMID:27450988

  19. Coarse-graining scheme for simulating uniaxial stress-strain response of glassy polymers through molecular dynamics.

    Science.gov (United States)

    Majumder, Manoj K; S, Ramkumar; Mahajan, Dhiraj K; Basu, Sumit

    2010-01-01

    Simulation of the deformation of polymers below their glass transition through molecular dynamics provides an useful route to correlate their molecular architecture to deformation behavior. However, present computational capabilities severely restrict the time and length scales that can be simulated when detailed models of these macromolecules are used. Coarse-graining techniques for macromolecular structures intend to make bigger and longer simulations possible by grouping atoms into superatoms and devising ways of determining reasonable force fields for the superatoms in a manner that retains essential macromolecular features relevant to the process under study but jettisons unnecessary details. In this work we systematically develop a coarse-graining scheme aimed at simulating uniaxial stress-strain behavior of polymers below their glass transition. The scheme involves a two step process of obtaining the coarse grained force field parameters above glass transition. This seems to be enough to obtain "faithful" stress-strain responses after quenching to below the glass transition temperature. We apply the scheme developed to a commercially important polymer polystyrene, derive its complete force field parameters and thus demonstrate the effectiveness of the technique.

  20. Dynamical properties and their strain-dependence of ZnSe(ZnSe:N: Zinc-blende and wurtzite

    Directory of Open Access Journals (Sweden)

    Dandan Wang

    2014-06-01

    Full Text Available The lattice dynamical properties of ZnSe and ZnSe with substitutional N incorporation(ZnSe:N are investigated in both the zinc-blend(ZB and wurtzite(WZ structures using first-principles calculations. The optical phonon modes of ZB-ZnSe at the Γ-point locate at 250 cm−1 for LO and 213 cm−1 for TO. The characteristic E2 phonon modes at about 50 cm−1 and the E1 and another E2 phonon modes around 200 cm−1 of WZ-ZnSe are suggested to be the fingerprint for distinguishing the two polytypes of ZnSe. For substitutional N incorporated ZnSe, the N incorporation introduces three new high energy modes above 500 cm−1, and the splitting of them is much larger in the WZ phase than that in ZB phase. The strain dependence of phonon frequency which could be useful for corresponding spectroscopic strain characterization are also studied. The simple linear dependence is determined for ZB-ZnSe, while the situation for WZ-ZnSe looks more complicated.

  1. Effects of confinement, surface-induced orientations and strain on dynamical behaviors of bacteria in thin liquid crystalline films.

    Science.gov (United States)

    Mushenheim, Peter C; Trivedi, Rishi R; Roy, Susmit Singha; Arnold, Michael S; Weibel, Douglas B; Abbott, Nicholas L

    2015-09-14

    We report on the organization and dynamics of bacteria (Proteus mirabilis) dispersed within lyotropic liquid crystal (LC) films confined by pairs of surfaces that induce homeotropic (perpendicular) or hybrid (homeotropic and parallel orientations at each surface) anchoring of the LC. By using motile vegetative bacteria (3 µm in length) and homeotropically aligned LC films with thicknesses that exceed the length of the rod-shaped cells, a key finding reported in this paper is that elastic torques generated by the LC are sufficiently large to overcome wall-induced hydrodynamic torques acting on the cells, thus leading to LC-guided bacterial motion near surfaces that orient LCs. This result extends to bacteria within LC films with hybrid anchoring, and leads to the observation that asymmetric strain within a hybrid aligned LC rectifies motions of motile cells. In contrast, when the LC film thickness is sufficiently small that confinement prevents alignment of the bacteria cells along a homeotropically aligned LC director (achieved using swarm cells of length 10-60 µm), the bacterial cells propel in directions orthogonal to the director, generating transient distortions in the LC that have striking "comet-like" optical signatures. In this limit, for hybrid LC films, we find LC elastic stresses deform the bodies of swarm cells into bent configurations that follow the LC director, thus unmasking a coupling between bacterial shape and LC strain. Overall, these results provide new insight into the influence of surface-oriented LCs on dynamical bacterial behaviors and hint at novel ways to manipulate bacteria using confined LC phases that are not possible in isotropic solutions.

  2. Strain effect on ferroelectric switching dynamics of epitaxial PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Doerr, Kathrin; Herklotz, Andreas [IFW Dresden, IMW, Helmholtzstr.20, Dresden (Germany); Biegalski, Michael; Christen, Hans [CNMS, Oak Ridge National Laboratory, TN (United States)

    2011-07-01

    Elastic strain is known to change ferroic properties of thin films such as the remanent polarization. Less understood and little measured is the influence of the lattice strain induced by film-substrate mismatch on the switching dynamics. In this work, reversible biaxial strain has been applied to films on piezoelectric substrates for a study of their strain-dependent ferroelectric switching. PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} (PZT) films have been epitaxially grown by pulsed laser deposition on piezoelectric substrates of 0.72PbMg{sub 1/3}Nb{sub 2/3}O{sub 3}-0.28PbTiO{sub 3}(001) (PMN-PT) buffered with a SrRuO{sub 3}/SrTiO{sub 3} double layer. Four-circle x-ray diffraction has been employed to confirm the tetragonal symmetry and to measure the lattice parameters of the films. Measurements of the characteristic ferroelectric switching time at various temperatures and strains show an increase of several percent under compression, revealing a similarly strong strain sensitivity of the switching dynamics as that of the remanent polarization. We attempt to identify the strain dependence of the domain wall velocity.

  3. What can flux tracking teach us about water age distributions and their temporal dynamics?

    Directory of Open Access Journals (Sweden)

    M. Hrachowitz

    2012-10-01

    Full Text Available The complex interactions of runoff generation processes underlying the hydrological response of streams remain incompletely understood at the catchment scale. Extensive research has demonstrated the utility of tracers for both inferring flow paths distributions and constraining model parameterizations. While useful, the common use of linearity assumptions, i.e. time-invariance and complete mixing, in these studies provides only partial understanding of actual process dynamics. Here we use long term (< 20 yr precipitation, flow and tracer (chloride data of three contrasting upland catchments in the Scottish Highlands to inform integrated conceptual models investigating different mixing assumptions. Using the models as diagnostic tools in a functional comparison, water and tracer fluxes were tracked with the objective of characterizing water age distributions in the three catchments and establishing the wetness-dependent temporal dynamics of these distributions.

    The results highlight the potential importance of partial mixing which is dependent on the hydrological functioning of a catchment. Further, tracking tracer fluxes showed that the various components of a model can be characterized by fundamentally different water age distributions which may be highly sensitive to catchment wetness, available storage, mixing mechanisms, flow path connectivity and the relative importance of the different hydrological processes involved. Flux tracking also revealed that, although negligible for simulating the runoff response, the omission of processes such as interception evaporation can result in considerably biased water age distributions. Finally, the modeling indicated that water age distributions in the three study catchments do have long, power-law tails, which are generated by the interplay of flow path connectivity, the relative importance of different flow paths as well as by the mixing mechanisms involved. In general this study highlights

  4. Mechanical properties and the structure of chromium-zirconium bronze after dynamic channel-angular pressing and subsequent aging

    Science.gov (United States)

    Zel'dovich, V. I.; Dobatkin, S. V.; Frolova, N. Yu.; Khomskaya, I. V.; Kheifets, A. E.; Shorokhov, E. V.; Nasonov, P. A.

    2016-01-01

    Changes in the structure and mechanical properties of the low-alloy chromium-zirconium bronze Cu-0.14% Cr-0.04% Zr have been investigated after a high-strain-rate (104-105 s-1) deformation by the method of dynamic channel-angular pressing (DCAP) and following annealings at 300-700°C. A significant increase in the mechanical properties of the investigated bronze after DCAP and after DCAP and subsequent aging at temperatures of 400-450°C has been established. Thus, compared to the initial quenched state the ultimate tensile strength increases by a factor of 2.6 and 2.8 and the yield stress, by a factor of 3.3 and 5.1, respectively, with the retention of satisfactory plasticity. It has been shown that, upon DCAP and subsequent annealings, in the low-alloyed bronze under investigation there occurs a decomposition of the α solid solution with the precipitation of nanosized particles. This leads to a significant strengthening of the bronze and to an increase in its thermal stability compared with the pure copper subjected to DCAP.

  5. Strain and structure in nano Ag films deposited on Au: Molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Zientarski, Tomasz, E-mail: martom@dyzio.umcs.lublin.pl [Department for the Modelling of Physico-Chemical Processes, Maria Curie-Skłodowska University, ul. Gliniana 33, 20-614 Lublin (Poland); Chocyk, Dariusz [Department of Applied Physics, Lublin University of Technology, ul. Nadbystrzycka 38, 20-618 Lublin (Poland)

    2014-07-01

    Molecular dynamics simulations are applied to analyze the stress and structure of nano Ag thin films deposited on the Au substrate. The interactions in the system are described by the embedded atom method. The kinematical theory of scattering is employed to identify the structure obtained from simulations data. Results shows that the silver layers are adjusted to the crystalline lattice of the gold buffer layers, and during the deposition process only compressive stress is observed. In all the cases the distribution of stress does not depend on temperature.

  6. Dynamics of specific anti-Mycobacterium avium subsp. paratuberculosis antibody response through age.

    Directory of Open Access Journals (Sweden)

    Søren Saxmose Nielsen

    Full Text Available Mycobacterium avium subsp. paratuberculosis (MAP causes a chronic infection in cattle. MAP infected cattle with humoral immune (HI reactions with IgG antibodies are usually those where latency of infection has ceased and their infection is progressing towards reduced milk yield, weight loss and significant bacterial excretion in feces. The proportion of detectable infections among all infected animals that will develop disease is often referred to as 'the tip of the iceberg'. The purpose of this study was to estimate this proportion. Test-records from 18,972 Danish dairy cows with MAP specific IgG antibodies on their final test-record were used to estimate age-specific sensitivities (Se. These cows were the infected ones considered to develop disease in a population with a representative age-distribution and were defined as cases. The specificity (Sp of the test was estimated based on test-results from 166,905 cows, which had no MAP IgG antibodies in their final four test-records. The Sp, age-specific Se and maximum Se were used to estimate the probability of having HI at a given age resulting in the proportion of infected cows with HI at a given age. For cows 2 years of age, the proportion of detectable cases was 0.33, while it was 0.94 for cows 5 years of age. Thus, there was a significant shift in the tip of the iceberg with aging. This study provided a model for estimating the proportion of latent chronic infections that would progress to disease, and the results can be used to model infection dynamics.

  7. Effects of age, sex, and treatment on weight-loss dynamics in overweight people.

    Science.gov (United States)

    Rojo-Tirado, Miguel A; Benito, Pedro J; Atienza, David; Rincón, Emiliano; Calderón, Francisco J

    2013-09-01

    The objective of this work was to evaluate how sex, age, and the kind of treatment followed affect weight loss in overweight men and women, as well as to develop an explanation for the evolution of weight-loss dynamics. The study consisted of 119 overweight participants (18-50 years old, body mass index >25 and exercised 3 times per week for 24 weeks, and their daily diet was restricted to a specific protocol during the testing period and controlled carefully. Body weight changes in the participants were evaluated every 15 days. Based on this study, we developed and validated different sets of equations to accurately capture the weight-loss dynamics. There were no significant differences in terms of global body weight changes from the statistical viewpoint, either regarding the carried out treatment or the individuals' ages. However, significant differences in weight-loss tendency were found depending on participant sex. We concluded that the effectiveness of different possible treatments for weight loss varies by sex and, based on our experimental observations, a quadratic function provides the most accurate model for capturing specific weight-loss dynamics. This trial is registered at Clinical Trials Gov.: number NCT01116856.

  8. Long-range correlations and fractal dynamics in C. elegans: Changes with aging and stress

    Science.gov (United States)

    Alves, Luiz G. A.; Winter, Peter B.; Ferreira, Leonardo N.; Brielmann, Renée M.; Morimoto, Richard I.; Amaral, Luís A. N.

    2017-08-01

    Reduced motor control is one of the most frequent features associated with aging and disease. Nonlinear and fractal analyses have proved to be useful in investigating human physiological alterations with age and disease. Similar findings have not been established for any of the model organisms typically studied by biologists, though. If the physiology of a simpler model organism displays the same characteristics, this fact would open a new research window on the control mechanisms that organisms use to regulate physiological processes during aging and stress. Here, we use a recently introduced animal-tracking technology to simultaneously follow tens of Caenorhabdits elegans for several hours and use tools from fractal physiology to quantitatively evaluate the effects of aging and temperature stress on nematode motility. Similar to human physiological signals, scaling analysis reveals long-range correlations in numerous motility variables, fractal properties in behavioral shifts, and fluctuation dynamics over a wide range of timescales. These properties change as a result of a superposition of age and stress-related adaptive mechanisms that regulate motility.

  9. Pedestrian dynamics in single-file movement of crowd with different age compositions

    Science.gov (United States)

    Cao, Shuchao; Zhang, Jun; Salden, Daniel; Ma, Jian; Shi, Chang'an; Zhang, Ruifang

    2016-07-01

    An aging population is bringing new challenges to the management of escape routes and facility design in many countries. This paper investigates pedestrian movement properties of crowd with different age compositions. Three pedestrian groups are considered: young student group, old people group, and mixed group. It is found that traffic jams occur more frequently in mixed group due to the great differences of mobilities and self-adaptive abilities among pedestrians. The jams propagate backward with a velocity 0.4 m /s for global density ρg≈1.75 m-1 and 0.3 m /s for ρg>2.3 m-1 . The fundamental diagrams of the three groups are obviously different from each other and cannot be unified into one diagram by direct nondimensionalization. Unlike previous studies, three linear regimes in mixed group but only two regimes in young student group are observed in the headway-velocity relation, which is also verified in the fundamental diagram. Different ages and mobilities of pedestrians in a crowd cause the heterogeneity of system and influence the properties of pedestrian dynamics significantly. It indicates that the density is not the only factor leading to jams in pedestrian traffic. The composition of crowd has to be considered in understanding pedestrian dynamics and facility design.

  10. The effect of pre-straining and pre-ageing on a novel thermomechanical treatment for improving the mechanical properties of AA2139 aerospace aluminium alloys

    Science.gov (United States)

    Bakare, F.; Alsubhi, Y.; Ragkousis, A.; Ebomwonyi, O.; Damisa, J.; Okunzuwa, S.

    2017-07-01

    The novel thermomechanical treatment employed by Wang Z et al (2014 Mater. Sci. Eng. A 607 313-7) in enhancing the mechanical and microstructure properties of 6000 series aluminium alloys has been replicated for AA2139 aerospace aluminium alloys. The novel route which involves under-ageing, cold-rolling reductions and re-ageing at a fixed temperature has been carried out focusing on the effect of pre-straining and pre-ageing on the alloy properties. The influence of varying cold-rolling reductions and pre-ageing has been examined by tensile testing, hardness testing, differential scanning calorimetry, thermoelectric power measurements and scanning electron microscope (SEM). Further analyses were conducted with DSC and TEP measurements to check for precipitation sequence and solute retention respectively. On comparing the hardness and strength of the non pre-aged to the pre-aged samples, there is a remarkable increase in the hardness and strength of the aerospace alloy showing the huge influence of both pre-ageing and pre-straining stage of the novel thermomechanical treatment as observed in the 6000 series alloy, albeit at a higher rate. The treatments that exhibited the most promising mechanical properties (hardness, yield and ultimate tensile strength, elongation to failure) were found to be at a pre-ageing temperature of 175 °C for 1.5 h, 40% cold-rolling and re-ageing at 150 °C. The material was found to have yield strength of 590 MPa and 8.1% uniform elongation, which is well above the 5% acceptable value for structural applications and with strength levels adaptable for aerospace industries. The presence of higher volume fraction of well dispersed precipitates observed in the SEM further shows that intermediate cold-rolling reductions combines well with pre-ageing to give the best mechanical properties in this alloy.

  11. Neutral dynamics with environmental noise: Age-size statistics and species lifetimes

    Science.gov (United States)

    Kessler, David; Suweis, Samir; Formentin, Marco; Shnerb, Nadav M.

    2015-08-01

    Neutral dynamics, where taxa are assumed to be demographically equivalent and their abundance is governed solely by the stochasticity of the underlying birth-death process, has proved itself as an important minimal model that accounts for many empirical datasets in genetics and ecology. However, the restriction of the model to demographic [O (√{N }) ] noise yields relatively slow dynamics that appears to be in conflict with both short-term and long-term characteristics of the observed systems. Here we analyze two of these problems—age-size relationships and species extinction time—in the framework of a neutral theory with both demographic and environmental stochasticity. It turns out that environmentally induced variations of the demographic rates control the long-term dynamics and modify dramatically the predictions of the neutral theory with demographic noise only, yielding much better agreement with empirical data. We consider two prototypes of "zero mean" environmental noise, one which is balanced with regard to the arithmetic abundance, another balanced in the logarithmic (fitness) space, study their species lifetime statistics, and discuss their relevance to realistic models of community dynamics.

  12. Influence of family dynamics on burden among family caregivers in aging Japan.

    Science.gov (United States)

    Kusaba, Tesshu; Sato, Kotaro; Fukuma, Shingo; Yamada, Yukari; Matsui, Yoshinori; Matsuda, Satoshi; Ando, Takashi; Sakushima, Ken; Fukuhara, Shunichi

    2016-10-01

    Long-term care for the elderly is largely shouldered by their family, representing a serious burden in a hyper-aging society. However, although family dynamics are known to play an important role in such care, the influence of caring for the elderly on burden among caregiving family members is poorly understood. To examine the influence of family dynamics on burden experienced by family caregivers. We conducted a cross-sectional study at six primary care clinics, involving 199 caregivers of adult care receivers who need long-term care. Participants were divided into three groups based on tertile of Index of Family Dynamics for Long-term Care (IF-Long score), where higher scores imply poorer relationships between care receivers and caregiving family: best, family dynamics strongly influences burden experienced by caregiving family members, regardless of the care receiver's degree of cognitive impairment. These results underscore the importance of evaluating relationships between care receivers and their caregivers when discussing a care regimen for care receivers. © The Author 2016. Published by Oxford University Press.

  13. Fatigability and recovery of arm muscles with advanced age for dynamic and isometric contractions.

    Science.gov (United States)

    Yoon, Tejin; Schlinder-Delap, Bonnie; Hunter, Sandra K

    2013-02-01

    This study determined whether age-related mechanisms can increase fatigue of arm muscles during maximal velocity dynamic contractions, as it occurs in the lower limb. We compared elbow flexor fatigue of young (n=10, 20.8±2.7 years) and old men (n=16, 73.8±6.1 years) during and in recovery from a dynamic and an isometric postural fatiguing task. Each task was maintained until failure while supporting a load equivalent to 20% of maximal voluntary isometric contraction (MVIC) torque. Transcranial magnetic stimulation (TMS) was used to assess supraspinal fatigue (superimposed twitch, SIT) and muscle relaxation. Time to failure was longer for the old men than for the young men for the isometric task (9.5±3.1 vs. 17.2±7.0 min, P=0.01) but similar for the dynamic task (6.3±2.4 min vs. 6.0±2.0 min, P=0.73). Initial peak rate of relaxation was slower for the old men than for the young men, and was associated with a longer time to failure for both tasks (PMuscular mechanisms and greater relative muscle activity (EMG activity) explain the greater fatigue during the dynamic task for the old men compared with the young men in the elbow flexor muscles. Recovery of MVC torque however relies more on the recovery of supraspinal fatigue among the old men than among the young men.

  14. Scalar mixing and strain dynamics methodologies for PIV/LIF measurements of vortex ring flows

    Science.gov (United States)

    Bouremel, Yann; Ducci, Andrea

    2017-01-01

    Fluid mixing operations are central to possibly all chemical, petrochemical, and pharmaceutical industries either being related to biphasic blending in polymerisation processes, cell suspension for biopharmaceuticals production, and fractionation of complex oil mixtures. This work aims at providing a fundamental understanding of the mixing and stretching dynamics occurring in a reactor in the presence of a vortical structure, and the vortex ring was selected as a flow paradigm of vortices commonly encountered in stirred and shaken reactors in laminar flow conditions. High resolution laser induced fluorescence and particle imaging velocimetry measurements were carried out to fully resolve the flow dissipative scales and provide a complete data set to fully assess macro- and micro-mixing characteristics. The analysis builds upon the Lamb-Oseen vortex work of Meunier and Villermaux ["How vortices mix," J. Fluid Mech. 476, 213-222 (2003)] and the engulfment model of Baldyga and Bourne ["Simplification of micromixing calculations. I. Derivation and application of new model," Chem. Eng. J. 42, 83-92 (1989); "Simplification of micromixing calculations. II. New applications," ibid. 42, 93-101 (1989)] which are valid for diffusion-free conditions, and a comparison is made between three methodologies to assess mixing characteristics. The first method is commonly used in macro-mixing studies and is based on a control area analysis by estimating the variation in time of the concentration standard deviation, while the other two are formulated to provide an insight into local segregation dynamics, by either using an iso-concentration approach or an iso-concentration gradient approach to take into account diffusion.

  15. Age-specific interaction between the parasitoid, Encarsia formosa and its host, the silverleaf whitefly, Bemisia tabaci (Strain B).

    Science.gov (United States)

    Hu, Jing S; Gelman, Dale B; Blackburn, Michael B

    2003-01-01

    The effect of hostage, the instar of Bemisia tabaci (Gennadius) parasitized, on the growth and development of Encarsia formosa (Gahan) was studied. E. formosa was able to parasitize and complete its life cycle no matter which instar of B. tabaci (Strain B), [also identified as B. argentifolii (Bellows and Perring)], was provided for oviposition, but parasitoid development was significantly slower when 1st or 2nd instar B. tabaci rather than 3rd or 4th instars were parasitized. Host age influenced the day on which E. formosa nymphs hatching from eggs was first observed. Mean embryonic development was significantly longer when 1st (5.4 days) rather than 2nd, 3rd or 4th instars (4.1, 3.4 and 3.5 days, respectively) were parasitized. The duration of the 1st instar parasitoid and the pupa, but not the 2nd or 3rd instar parasitoid, were also significantly greater when 1st instars were parasitized than when older host instars were parasitized. Interestingly, no matter which instar was parasitized, the parasitoid did not molt to the 3rd instar until the 4th instar host had reached a depth of about 0.23 mm (Stage 4-5) and had initiated the nymphal-adult molt and adult development. Histological studies revealed that whitefly eye and wing structures had either disintegrated or were adult in nature whenever a 3rd instar parasitoid was present. It appears, then, that the molt of the parasitoid to its last instar is associated with the host whitefly's nymphal-adult molt. However, the initiation of the host's final molt, while a prerequisite for the parasitoid's 2nd-3rd instar molt, did not necessarily trigger this molt. In contrast to its significant effect on various aspects of parasitoid development, host instar did not significantly influence the mean size of the parasitoid larva, pupa, or adult. Larval and pupal length and adult head width were similar for all parasitoids, regardless of which host instar was parasitized as was adult longevity. Adult parasitoid emergence was

  16. Age-specific interaction between the parasitoid, Encarsia formosa and its host, the silverleaf whitefly, Bemisia tabaci (Strain B

    Directory of Open Access Journals (Sweden)

    Jing S. Hu

    2003-08-01

    Full Text Available The effect of hostage, the instar of Bemisia tabaci (Gennadius parasitized, on the growth and development of Encarsia formosa (Gahan was studied. E. formosa was able to parasitize and complete its life cycle no matter which instar of B. tabaci (Strain B, [also identified as B. argentifolii (Bellows and Perring], was provided for oviposition, but parasitoid development was significantly slower when 1st or 2nd instar B. tabaci rather than 3rd or 4th instars were parasitized. Host age influenced the day on which E. formosa nymphs hatching from eggs was first observed. Mean embryonic development was significantly longer when 1st (5.4 days rather than 2nd, 3rd or 4th instars (4.1, 3.4 and 3.5 days, respectively were parasitized. The duration of the 1st instar parasitoid and the pupa, but not the 2nd or 3rd instar parasitoid, were also significantly greater when 1st instars were parasitized than when older host instars were parasitized. Interestingly, no matter which instar was parasitized, the parasitoid did not molt to the 3rd instar until the 4th instar host had reached a depth of about 0.23 mm (Stage 4-5 and had initiated the nymphal-adult molt and adult development. Histological studies revealed that whitefly eye and wing structures had either disintegrated or were adult in nature whenever a 3rd instar parasitoid was present. It appears, then, that the molt of the parasitoid to its last instar is associated with the host whitefly's nymphal-adult molt. However, the initiation of the host's final molt, while a prerequisite for the parasitoid's 2nd-3rd instar molt, did not necessarily trigger this molt. In contrast to its significant effect on various aspects of parasitoid development, host instar did not significantly influence the mean size of the parasitoid larva, pupa, or adult. Larval and pupal length and adult head width were similar for all parasitoids, regardless of which host instar was parasitized as was adult longevity. Adult parasitoid

  17. Quantitative analysis of mechanisms that govern red blood cell age structure and dynamics during anaemia.

    Directory of Open Access Journals (Sweden)

    Nicholas J Savill

    2009-06-01

    Full Text Available Mathematical modelling has proven an important tool in elucidating and quantifying mechanisms that govern the age structure and population dynamics of red blood cells (RBCs. Here we synthesise ideas from previous experimental data and the mathematical modelling literature with new data in order to test hypotheses and generate new predictions about these mechanisms. The result is a set of competing hypotheses about three intrinsic mechanisms: the feedback from circulating RBC concentration to production rate of immature RBCs (reticulocytes in bone marrow, the release of reticulocytes from bone marrow into the circulation, and their subsequent ageing and clearance. In addition we examine two mechanisms specific to our experimental system: the effect of phenylhydrazine (PHZ and blood sampling on RBC dynamics. We performed a set of experiments to quantify the dynamics of reticulocyte proportion, RBC concentration, and erythropoietin concentration in PHZ-induced anaemic mice. By quantifying experimental error we are able to fit and assess each hypothesis against our data and recover parameter estimates using Markov chain Monte Carlo based Bayesian inference. We find that, under normal conditions, about 3% of reticulocytes are released early from bone marrow and upon maturation all cells are released immediately. In the circulation, RBCs undergo random clearance but have a maximum lifespan of about 50 days. Under anaemic conditions reticulocyte production rate is linearly correlated with the difference between normal and anaemic RBC concentrations, and their release rate is exponentially correlated with the same. PHZ appears to age rather than kill RBCs, and younger RBCs are affected more than older RBCs. Blood sampling caused short aperiodic spikes in the proportion of reticulocytes which appear to have a different developmental pathway than normal reticulocytes. We also provide evidence of large diurnal oscillations in serum erythropoietin levels

  18. Fame and obsolescence: Disentangling growth and aging dynamics of patent citations

    Science.gov (United States)

    Higham, K. W.; Governale, M.; Jaffe, A. B.; Zülicke, U.

    2017-04-01

    We present an analysis of citations accrued over time by patents granted by the United States Patent and Trademark Office in 1998. In contrast to previous studies, a disaggregation by technology category is performed, and exogenously caused citation-number growth is controlled for. Our approach reveals an intrinsic citation rate that clearly separates into an—in the long run, exponentially time-dependent—aging function and a completely time-independent preferential-attachment-type growth kernel. For the general case of such a separable citation rate, we obtain the time-dependent citation distribution analytically in a form that is valid for any functional form of its aging and growth parts. Good agreement between theory and long-time characteristics of patent-citation data establishes our work as a useful framework for addressing still open questions about knowledge-propagation dynamics, such as the observed excess of citations at short times.

  19. Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

    DEFF Research Database (Denmark)

    Khan, Shfaqat Abbas; Kjeldsen, Kristian Kjellerup; Kjær, Kurt H.;

    2014-01-01

    Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance on the decadal scale. To improve...... to the end of the Little Ice Age (prior to 1930) shows no thinning of Helheim Glacier from its maximum extent during the Little Ice Age to 1981, while Kangerdlugssuaq Glacier underwent substantial thinning of 230 to 265 m. Comparison of sub-surface water temperature anomalies and variations in air...... the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim and Kangerdlugssuaq glaciers from 10 to more than 80 years. We show that, although the frontal portion...

  20. Age-specific characteristics and coupling of cerebral arterial inflow and cerebrospinal fluid dynamics.

    Directory of Open Access Journals (Sweden)

    Marianne Schmid Daners

    Full Text Available The objective of this work is to quantify age-related differences in the characteristics and coupling of cerebral arterial inflow and cerebrospinal fluid (CSF dynamics. To this end, 3T phase-contrast magnetic resonance imaging blood and CSF flow data of eleven young (24 ± 3 years and eleven elderly subjects (70 ± 5 years with a comparable sex-ratio were acquired. Flow waveforms and their frequency composition, transfer functions from blood to CSF flows and cross-correlations were analyzed. The magnitudes of the frequency components of CSF flow in the aqueduct differ significantly between the two age groups, as do the frequency components of the cervical spinal CSF and the arterial flows. The males' aqueductal CSF stroke volumes and average flow rates are significantly higher than those of the females. Transfer functions and cross-correlations between arterial blood and CSF flow reveal significant age-dependence of phase-shift between these, as do the waveforms of arterial blood, as well as cervical-spinal and aqueductal CSF flows. These findings accentuate the need for age- and sex-matched control groups for the evaluation of cerebral pathologies such as hydrocephalus.

  1. Aging into perceptual control: A Dynamic Causal Modeling for fMRI study of bistable perception

    Directory of Open Access Journals (Sweden)

    Ehsan eDowlati

    2016-03-01

    Full Text Available Aging is accompanied by stereotyped changes in functional brain activations, for example a cortical shift in activity patterns from posterior to anterior regions is one hallmark revealed by functional magnetic resonance imaging (fMRI of aging cognition. Whether these neuronal effects of aging could potentially contribute to an amelioration of or resistance to the cognitive symptoms associated with psychopathology remains to be explored. We used a visual illusion paradigm to address whether aging affects the cortical control of perceptual beliefs and biases. Our aim was to understand the effective connectivity associated with volitional control of ambiguous visual stimuli and to test whether greater top-down control of early visual networks emerged with advancing age. Using a bias training paradigm for ambiguous images we found that older participants (n = 16 resisted experimenter-induced visual bias compared to a younger cohort (n = 14 and that this resistance was associated with greater activity in prefrontal and temporal cortices. By applying Dynamic Causal Models for fMRI we uncovered a selective recruitment of top-down connections from the middle temporal to lingual gyrus by the older cohort during the perceptual switch decision following bias training. In contrast, our younger cohort did not exhibit any consistent connectivity effects but instead showed a loss of driving inputs to orbitofrontal sources following training. These findings suggest that perceptual beliefs are more readily controlled by top-down strategies in older adults and introduce age-dependent neural mechanisms that may be important for understanding aberrant belief states associated with psychopathology.

  2. F1 (CBA×C57) mice show superior hearing in old age relative to their parental strains: hybrid vigor or a new animal model for "golden ears"?

    Science.gov (United States)

    Frisina, Robert D; Singh, Ameet; Bak, Matthew; Bozorg, Sara; Seth, Rahul; Zhu, Xiaoxia

    2011-09-01

    Age-related hearing loss - presbycusis - is the most common communication problem and third most prevalent chronic medical disorder of the aged. The CBA and C57BL/6 mouse strains are useful for studying features of presbycusis. The CBA loses its hearing slowly, like most humans. Because the C57 develops a rapid, high frequency hearing loss by middle age, it has an "old" ear but a relatively young brain, a model that helps separate peripheral (cochlear) from central (brain) etiologies. This field of sensory neuroscience lacks a good mouse model for the 5-10% of aged humans with normal cochlear sensitivity, but who have trouble perceiving speech in background noise. We hypothesized that F1 (CBA×C57) hybrids would have better hearing than either parental strain. Measurements of peripheral auditory sensitivity supported this hypothesis, however, a rapid decline in the auditory efferent feedback system, did not. Therefore, F1s might be an optimal model for studying cases where the peripheral hearing is quite good in old age; thereby allowing isolation of central auditory changes due to brain neurodegeneration.

  3. Immune response of turkey poults exposed at 1 day of age to either attenuated or wild Salmonella strains.

    Science.gov (United States)

    Hesse, Martina; Stamm, Andreas; Weber, Rita; Glünder, Gerhard; Berndt, Angela

    2016-06-01

    Salmonellosis is a foodborne zoonosis that is most often acquired by consuming poultry products such as eggs and poultry meat. Amongst other measures the vaccination of food-producing poultry is thought to contribute to a reduction in human salmonellosis. In the European Union (EU) in 2014 the licence of a commercially available Salmonella vaccine for chickens and ducks was extended to turkeys. In the present study, we examined the course of infection with a virulent Salmonella enterica ssp. enterica serovar Enteritidis (SE) strain, a virulent S. enterica ssp. enterica serovar Typhimurium (ST) strain, and the respective live vaccine containing attenuated strains of both serovars in turkey poults. Besides collecting microbiological data and detecting invading Salmonella in the caecal mucosa via immunohistochemistry, we also assessed immune reactions in terms of antibody production, influx of CD4-, CD8α- and CD28-positive cells into the caecal mucosa and the expression of four different immune-related proteins. We found that the attenuated strains were able to invade the caecum, but to a lower degree and for a shorter duration of time compared to virulent strains. Infections with virulent Salmonellae also caused an increase in CD4-, CD8α- and CD28-positive cells in the caecal mucosa and an increased transcription of iNOS, IL-8-like chemokines, and IFN-γ. In poults treated with attenuated bacteria we could not detect any evidence of immune responses. In conclusion, the vaccine showed a lower degree of caecal invasion and induced weaker immune reactions compared to the virulent Salmonella strains in turkeys. The efficiency of the vaccine has to be verified in future studies.

  4. Extracting full-field dynamic strain on a wind turbine rotor subjected to arbitrary excitations using 3D point tracking and a modal expansion technique

    Science.gov (United States)

    Baqersad, Javad; Niezrecki, Christopher; Avitabile, Peter

    2015-09-01

    Health monitoring of rotating structures such as wind turbines and helicopter rotors is generally performed using conventional sensors that provide a limited set of data at discrete locations near or on the hub. These sensors usually provide no data on the blades or inside them where failures might occur. Within this paper, an approach was used to extract the full-field dynamic strain on a wind turbine assembly subject to arbitrary loading conditions. A three-bladed wind turbine having 2.3-m long blades was placed in a semi-built-in boundary condition using a hub, a machining chuck, and a steel block. For three different test cases, the turbine was excited using (1) pluck testing, (2) random impacts on blades with three impact hammers, and (3) random excitation by a mechanical shaker. The response of the structure to the excitations was measured using three-dimensional point tracking. A pair of high-speed cameras was used to measure displacement of optical targets on the structure when the blades were vibrating. The measured displacements at discrete locations were expanded and applied to the finite element model of the structure to extract the full-field dynamic strain. The results of the paper show an excellent correlation between the strain predicted using the proposed approach and the strain measured with strain-gages for each of the three loading conditions. The approach used in this paper to predict the strain showed higher accuracy than the digital image correlation technique. The new expansion approach is able to extract dynamic strain all over the entire structure, even inside the structure beyond the line of sight of the measurement system. Because the method is based on a non-contacting measurement approach, it can be readily applied to a variety of structures having different boundary and operating conditions, including rotating blades.

  5. Seasonal dynamics and age of stemwood nonstructural carbohydrates in temperate forest trees.

    Science.gov (United States)

    Richardson, Andrew D; Carbone, Mariah S; Keenan, Trevor F; Czimczik, Claudia I; Hollinger, David Y; Murakami, Paula; Schaberg, Paul G; Xu, Xiaomei

    2013-02-01

    Nonstructural carbohydrate reserves support tree metabolism and growth when current photosynthates are insufficient, offering resilience in times of stress. We monitored stemwood nonstructural carbohydrate (starch and sugars) concentrations of the dominant tree species at three sites in the northeastern United States. We estimated the mean age of the starch and sugars in a subset of trees using the radiocarbon ((14) C) bomb spike. With these data, we then tested different carbon (C) allocation schemes in a process-based model of forest C cycling. We found that the nonstructural carbohydrates are both highly dynamic and about a decade old. Seasonal dynamics in starch (two to four times higher in the growing season, lower in the dormant season) mirrored those of sugars. Radiocarbon-based estimates indicated that the mean age of the starch and sugars in red maple (Acer rubrum) was 7-14 yr. A two-pool (fast and slow cycling reserves) model structure gave reasonable estimates of the size and mean residence time of the total NSC pool, and greatly improved model predictions of interannual variability in woody biomass increment, compared with zero- or one-pool structures used in the majority of existing models. This highlights the importance of nonstructural carbohydrates in the context of forest ecosystem carbon cycling.

  6. Mathematical analysis of an age-structured model for malaria transmission dynamics.

    Science.gov (United States)

    Forouzannia, Farinaz; Gumel, Abba B

    2014-01-01

    A new deterministic model for assessing the role of age-structure on the transmission dynamics of malaria in a community is designed. Rigorous qualitative analysis of the model reveals that it undergoes the phenomenon of backward bifurcation, where the stable disease-free equilibrium of the model co-exists with a stable endemic equilibrium when the associated reproduction number (denoted by R0) is less than unity. It is shown that the backward bifurcation phenomenon is caused by the malaria-induced mortality in humans. A special case of the model is shown to have a unique endemic equilibrium whenever the associated reproduction threshold exceeds unity. Further analyses reveal that adding age-structure to a basic model for malaria transmission in a community does not alter the qualitative dynamics of the basic model, with respect to the existence and asymptotic stability of the associated equilibria and the backward bifurcation property of the model. Numerical simulations of the model show that the cumulative number of new cases of infection and malaria-induced mortality increase with increasing average lifespan and birth rate of mosquitoes.

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

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Shengnian [Los Alamos National Laboratory; Arman, Bedri [Los Alamos National Laboratory; Germann, Timothy C [Los Alamos National Laboratory; Cagin, Tahir [TEXAS A& M UNIV

    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.

  8. Probing equilibrium by nonequilibrium dynamics: Aging in Co/Cr superlattices

    Science.gov (United States)

    Binek, Christian

    2013-03-01

    Magnetic aging phenomena are investigated in a structurally ordered Co/Cr superlattice through measurements of magnetization relaxation, magnetic susceptibility, and hysteresis at various temperatures above and below the onset of collective magnetic order. We take advantage of the fact that controlled growth of magnetic multilayer thin films via molecular beam epitaxy allows tailoring the intra and inter-layer exchange interaction and thus enables tuning of magnetic properties including the spin-fluctuation spectra. Tailored nanoscale periodicity in Co/Cr multilayers creates mesoscopic spatial magnetic correlations with slow relaxation dynamics when quenching the system into a nonequilibrium state. Magnetization relaxation in weakly correlated spin systems depends on the microscopic spin-flip time of about 10 ns and is therefore a fast process. The spin correlations in our Co/Cr superlattice bring the magnetization dynamics to experimentally better accessible time scales of seconds or hours. In contrast to spin-glasses, where slow dynamics due to disorder and frustration is a well-known phenomenon, we tune and increase relaxation times in ordered structures. This is achieved by increasing spin-spin correlation between mesoscopically correlated regions rather than individual atomic spins, a concept with some similarity to block spin renormalization. Magnetization transients are measured after exposing the Co/Cr heterostructure to a magnetic set field for various waiting times. Scaling analysis reveals an asymptotic power-law behavior in accordance with a full aging scenario. The temperature dependence of the relaxation exponent shows pronounced anomalies at the equilibrium phase transitions of the antiferromagnetic superstructure and the ferromagnetic to paramagnetic transition of the Co layers. The latter leaves only weak fingerprints in the equilibrium magnetic behavior but gives rise to a prominent change in nonequilibrium properties. Our findings suggest that

  9. Age related differences in dynamics of specific memory B cell populations after clinical pertussis infection.

    Directory of Open Access Journals (Sweden)

    Inonge van Twillert

    Full Text Available For a better understanding of the maintenance of immune mechanisms to Bordetella pertussis (Bp in relation to age, we investigated the dynamic range of specific B cell responses in various age-groups at different time points after a laboratory confirmed pertussis infection. Blood samples were obtained in a Dutch cross sectional observational study from symptomatic pertussis cases. Lymphocyte subpopulations were phenotyped by flowcytometry before and after culture. Memory B (Bmem cells were differentiated into IgG antibody secreting cells (ASC by polyclonal stimulation and detected by an ELISPOT assay specific for pertussis antigens pertussis toxin (Ptx, filamentous haemagglutinin (FHA and pertactin (Prn. Bp antigen specific IgG concentrations in plasma were determined using multiplex technology. The majority of subjects having experienced a clinical pertussis episode demonstrated high levels of both Bp specific IgG and Bmem cell levels within the first 6 weeks after diagnosis. Significantly lower levels were observed thereafter. Waning of cellular and humoral immunity to maintenance levels occurred within 9 months after antigen encounter. Age was found to determine the maximum but not base-line frequencies of Bmem cell populations; higher levels of Bmem cells specific for Ptx and FHA were reached in adults and (pre- elderly compared to under-fours and schoolchildren in the first 6 weeks after Bp exposure, whereas not in later phases. This age effect was less obvious for specific IgG levels. Nonetheless, subjects' levels of specific Bmem cells and specific IgG were weakly correlated. This is the first study to show that both age and closeness to last Bp encounter impacts the size of Bp specific Bmem cell and plasma IgG levels.

  10. FR II radio galaxies at low frequencies - II. Spectral ageing and source dynamics

    Science.gov (United States)

    Harwood, Jeremy J.; Hardcastle, Martin J.; Morganti, Raffaella; Croston, Judith H.; Brüggen, Marcus; Brunetti, Gianfranco; Röttgering, Huub J. A.; Shulevski, Aleksander; White, Glenn J.

    2017-07-01

    In this paper, the second in a series investigating Fanaroff-Riley type II (FR II) radio galaxies at low frequencies, we use LOw Frequency ARray (LOFAR) and Very Large Array (VLA) observations between 117 and 456 MHz, in addition to archival data, to determine the dynamics and energetics of two radio galaxies, 3C 452 and 3C 223, by fitting spectral ageing models on small spatial scales. We provide improved measurements for the physical extent of the two sources, including a previously unknown low surface brightness extension to the northern lobe of 3C 223, and revised energetics based on these values. We find spectral ages of 77.05^{+9.22}_{-8.74} and 84.96^{+15.02}_{-13.83} Myr for 3C 452 and 3C 223, respectively, suggesting a characteristic advance speed for the lobes of around 1 per cent of the speed of light. For 3C 452, we show that, even for a magnetic field strength not assumed to be in equipartition, a disparity of a factor of approximately 2 exists between the spectral age and that determined from a dynamical standpoint. We confirm that the injection index of both sources (as derived from the lobe emission) remains steeper than classically assumed values, even when considered on well-resolved scales at low frequencies. However, we find an unexpected sharp discontinuity between the spectrum of the hotspots and the surrounding lobe emission. We suggest that this discrepancy is a result of the absorption of hotspot emission and/or non-homogeneous and additional acceleration mechanisms; as such, hotspots should not be used in the determination of the underlying initial electron energy distribution.

  11. The Effect of Aging on Muscular Dynamics Underlying Movement Patterns Changes

    Science.gov (United States)

    Vernooij, Carlijn A.; Rao, Guillaume; Berton, Eric; Retornaz, Frédérique; Temprado, Jean-Jacques

    2016-01-01

    Introduction: Aging leads to alterations not only within the complex subsystems of the neuro-musculo-skeletal system, but also in the coupling between them. Here, we studied how aging affects functional reorganizations that occur both within and between the behavioral and muscular levels, which must be coordinated to produce goal-directed movements. Using unimanual reciprocal Fitts' task, we examined the behavioral and muscular dynamics of older adults (74.4 ± 3.7 years) and compared them to those found for younger adults (23.2 ± 2.0 years). Methods: To achieve this objective, we manipulated the target size to trigger a phase transition in the behavioral regime and searched for concomitant signatures of a phase transition in the muscular coordination. Here, muscular coordination was derived by using the method of muscular synergy extraction. With this technique, we obtained functional muscular patterns through non-negative matrix factorization of the muscular signals followed by clustering the resulting synergies. Results: Older adults showed a phase transition in behavioral regime, although, in contrast to young participants, their kinematic profiles did not show a discontinuity. In parallel, muscular coordination displayed two typical signatures of a phase transition, that is, increased variability of coordination patterns and a reorganization of muscular synergies. Both signatures confirmed the existence of muscular reorganization in older adults, which is coupled with change in dynamical regime at behavioral level. However, relative to young adults, transition occurred at lower index of difficulty (ID) in older participants and the reorganization of muscular patterns lasted longer (over multiple IDs). Discussion: This implies that consistent changes occur in coordination processes across behavior and muscle. Furthermore, the repertoire of muscular patterns was reduced and somewhat modified for older adults, relative to young participants. This suggests that

  12. Carrier dynamics of strain-engineered InAs quantum dots with (In)GaAs surrounding material

    Science.gov (United States)

    Nasr, O.; Chauvin, N.; Alouane, M. H. Hadj; Maaref, H.; Bru-Chevallier, C.; Sfaxi, L.; Ilahi, B.

    2017-02-01

    The present study reports on the optical properties of epitaxially grown InAs quantum dots (QDs) inserted within an InGaAs strain-reducing layer (SRL). The critical energy states in such QD structures have been identified by combining photoluminescence (PL) and photoluminescence of excitation (PLE) measurements. Carrier lifetime is investigated by time-resolved photoluminescence (TRPL), allowing us to study the impact of the composition of the surrounding materials on the QD decay time. Results showed that covering the InAs QDs with, or embedding them within, an InGaAs SRL increases the carrier dynamics, while a shorter carrier lifetime has been observed when they are grown on top of an InGaAs SRL. Investigation of the dependence of carrier lifetime on temperature showed good stability of the decay time, deduced from the consequences of improved QD confinement. The findings suggest that embedding or capping the QDs with SRL exerts optimization of their room temperature optical properties.

  13. Size-dependent dynamic stability analysis of microbeams actuated by piezoelectric voltage based on strain gradient elasticity theory

    Energy Technology Data Exchange (ETDEWEB)

    Sahmani, Saeid; Bahrami, Mohsen [Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2015-01-15

    In the current paper, dynamic stability analysis of microbeams subjected to piezoelectric voltage is presented in which the microbeam is integrated with piezoelectric layers on the lower and upper surfaces. Both of the flutter and divergence instabilities of microbeams with clamped-clamped and clamped-free boundary conditions are predicted corresponding to various values of applied voltage. To take size effect into account, the classical Timoshenko beam theory in conjunction with strain gradient elasticity theory is utilized to develop nonclassical beam model containing three additional internal length scale parameters. By using Hamilton's principle, the higher-order governing differential equations and associated boundary conditions are derived. Afterward, generalized differential quadrature method is employed to discretize the size-dependent governing differential equations along with clamped-clamped and clamped-free end supports. The critical piezoelectric voltages corresponding to various values dimensionless length scale parameter are evaluated and compared with those predicted by the classical beam theory. It is revealed that in the case of clamped-free boundary conditions, the both of flutter and divergence instabilities occur. However, for the clamped-clamped microbeams, only divergence instability takes place.

  14. No adverse effects of transgenic maize on population dynamics of endophytic Bacillus subtilis strain B916-gfp.

    Science.gov (United States)

    Sun, Chongsi; Geng, Lili; Wang, Meiling; Shao, Gaoxiang; Liu, Yongfeng; Shu, Changlong; Zhang, Jie

    2017-02-01

    Endophytic bacterial communities play a key role in promoting plant growth and combating plant diseases. However, little is known about their population dynamics in plant tissues and bulk soil, especially in transgenic crops. This study investigated the colonization of transgenic maize harboring the Bacillus thuringiensis (Bt) cry1Ah gene by Bacillus subtilis strain B916-gfp present in plant tissues and soil. Bt and nontransgenic maize were inoculated with B916-gfp by seed soaking, or root irrigation under both laboratory greenhouse and field conditions. During the growing season, B916-gfp colonized transgenic as well as nontransgenic plants by both inoculation methods. No differences were observed in B916-gfp population size between transgenic and nontransgenic plants, except at one or two time points in the roots and stems that did not persist over the examination period. Furthermore, planting transgenic maize did not affect the number of B916-gfp in bulk soil in either laboratory or field trials. These results indicate that transgenic modification of maize with the cry1Ah gene has no influence on colonization by the endophytic bacteria B916-gfp present in the plant and in bulk soil. © 2016 The Authors. MicrobiologyOpenpublished by John Wiley & Sons Ltd.

  15. Understanding ageing in older Australians: The contribution of the Dynamic Analyses to Optimise Ageing (DYNOPTA) project to the evidenced base and policy

    Science.gov (United States)

    Anstey, Kaarin J; Bielak, Allison AM; Birrell, Carole L; Browning, Colette J; Burns, Richard A; Byles, Julie; Kiley, Kim M; Nepal, Binod; Ross, Lesley A; Steel, David; Windsor, Timothy D

    2014-01-01

    Aim To describe the Dynamic Analyses to Optimise Ageing (DYNOPTA) project and illustrate its contributions to understanding ageing through innovative methodology, and investigations on outcomes based on the project themes. DYNOPTA provides a platform and technical expertise that may be used to combine other national and international datasets. Method The DYNOPTA project has pooled and harmonized data from nine Australian longitudinal studies to create the largest available longitudinal dataset (N=50652) on ageing in Australia. Results A range of findings have resulted from the study to date, including methodological advances, prevalence rates of disease and disability, and mapping trajectories of ageing with and without increasing morbidity. DYNOPTA also forms the basis of a microsimulation model that will provide projections of future costs of disease and disability for the baby boomer cohort. Conclusion DYNOPTA contributes significantly to the Australian evidence-base on ageing to inform key social and health policy domains. PMID:22032767

  16. Age-dependent modulation of sensory reweighting for controlling posture in a dynamic virtual environment.

    Science.gov (United States)

    Eikema, Diderik Jan Anthony; Hatzitaki, Vassilia; Tzovaras, Dimitrios; Papaxanthis, Charalambos

    2012-12-01

    Older adults require more time to reweight sensory information for maintaining balance that could potentially lead to increased incidence of falling in rapidly changing or cognitively demanding environments. In this study, we manipulated the visual surround information during a collision avoidance task in order to investigate how young and elderly adults engage in sensory reweighting under conditions of visual anticipation. Sixteen healthy elderly (age: 71.5 ± 4.9 years; height: 159.3 ± 6.6 cm; mass: 73.3 ± 3.3 kg) and 20 young (age: 22.8 ± 3.3 years; height: 174.4 ± 10.7 cm; mass: 70.1 ± 13.9 kg) participants stood for 240 s on a force platform under two experimental conditions: quiet standing and standing while anticipating randomly approaching virtual objects to be avoided. During both tasks, the visual surround changed every 60 s from a stationary virtual scene (room) to either a moving room or darkness and then back to a stationary scene to evoke sensory reweighting processes. In quiet standing, elderly showed greater sway variability and were more severely affected by the removal or degradation of visual surround information when compared to young participants. During visual anticipation, sway variability was not different between the age groups. In addition, both young and elderly participants were similarly affected by the degradation or removal of the visual surround. These findings suggest that sensory reweighting in a dynamic virtual environment that evokes visual anticipation interacts with postural state anxiety regardless of age. Elderly show less efficient sensory reweighting in quiet standing due to greater visual field dependence possibly associated with fear of falling.

  17. Signal-to-noise ratio evaluation with draw tower fibre Bragg gratings (DTGs) for dynamic strain sensing at elevated temperatures and corrosive environment

    Science.gov (United States)

    De Pauw, B.; Lamberti, A.; Vanlanduit, S.; Van Tichelen, K.; Geernaert, T.; Berghmans, F.

    2014-05-01

    Measuring strain at the surface of a structure can help to estimate the dynamical properties of the structure under test. Such a structure can be a fuel assembly of a nuclear reactor consisting of fuel pins. In this paper we demonstrate a method to integrate draw tower gratings (DTGs) in a fuel pin and we subject this pin to conditions close to those encountered in a heavy liquid metal (HLM) reactor. More specifically, we report on the performance of DTGs used as a strain sensor when immersed in HLM during thermal cycles (up to 300_C) for up to 700 hours.

  18. [Family dynamics in the caring context of adults on the fourth age].

    Science.gov (United States)

    Polaro, Sandra Helena Isse; Gonçalves, Lucia Hisako Takase; Nassar, Silvia Modesto; Lopes, Márcia Maria Bragança; Ferreira, Viviane Ferraz; Monteiro, Hellen Karinna

    2013-01-01

    This study aimed to determine the pattern of family functioning on everyday care relationships of adults in the fourth age. This is a study of diagnostic-evaluative nature of adults with 80 or more years old who depend on care, and of their relatives as caregivers. The participants were selected among the registered patients of a Family Health Unit in a district in the suburbs of Belém-PA, Brazil. They were evaluated according to the dynamics of their family, and quality of life related health lifestyle. Most of the elderly rated their families with good functionality. However, data on the elderly and caregivers' quality of life and caregivers' life style only reached the median level, showing some difficulty in the family functioning system. It was concluded that the multiple results obtained through the assessments indicate some practical implications of care to the family unity and confirm the need for multidimensional assessment about the family intervention.

  19. Clinico-dynamic features of psychopathological disorders at heroin addiction young age

    Directory of Open Access Journals (Sweden)

    Vasila Abdullaeva

    2012-05-01

    Full Text Available There were studied 120 patients with heroin addiction at the age of 17 to 26 years. Prescription of heroin abuse at the time of initial examination ranged from 8 months to 5 years. The greatest number of patients made those receiving the drug from 1 to 3 years. It is established that the premorbid personality characteristics in patients with heroin addiction affect the formation of remission and determine the extent and nature of medico-social consequences of the disease. Anxieties are the leading clinical and dynamic psychopathology in heroin addiction. They play an important role in the syndrome of pathological craving for psychoactive substances and determine the prognosis of the disease.

  20. A non-contacting approach for full field dynamic strain monitoring of rotating structures using the photogrammetry, finite element, and modal expansion techniques

    Science.gov (United States)

    Baqersad, Javad

    Health monitoring of rotating structures such as wind turbines and helicopter rotors is generally performed using conventional sensors that provide a limited set of data at discrete locations near or on the hub. These sensors usually provide no data on the blades or interior locations where failures may occur. Within this work, an unique expansion algorithm was extended and combined with finite element (FE) modeling and an optical measurement technique to identify the dynamic strain in rotating structures. The merit of the approach is shown by using the approach to predict the dynamic strain on a small non-rotating and rotating wind turbine. A three-bladed wind turbine having 2.3-meter long blades was placed in a semi-built-in boundary condition using a hub, a machining chuck, and a steel block. A finite element model of the three wind turbine blades assembled to the hub was created and used to extract resonant frequencies and mode shapes. The FE model was validated and updated using experimental modal tests. For the non-rotating optical test, the turbine was excited using a sinusoidal excitation, a pluck test, arbitrary impacts on three blades, and random force excitations with a mechanical shaker. The response of the structure to the excitations was measured using three-dimensional point tracking. A pair of high-speed cameras was used to measure the displacement of optical targets on the structure when the blades were vibrating. The measured displacements at discrete locations were expanded and applied to the finite element model of the structure to extract the full-field dynamic strain. The results of the work show an excellent correlation between the strain predicted using the proposed approach and the strain measured with strain-gages for all of the three loading conditions. Similar to the non-rotating case, optical measurements were also preformed on a rotating wind turbine. The point tracking technique measured both rigid body displacement and flexible

  1. Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

    Science.gov (United States)

    Khan, S. A.; Kjeldsen, K. K.; Kjær, K. H.; Bevan, S.; Luckman, A.; Aschwanden, A.; Bjørk, A. A.; Korsgaard, N. J.; Box, J. E.; van den Broeke, M.; van Dam, T. M.; Fitzner, A.

    2014-08-01

    Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance on the decadal scale. To improve the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim and Kangerdlugssuaq glaciers from 10 to more than 80 years. We show that, although the frontal portion of Helheim Glacier thinned by more than 100 m between 2003 and 2006, it thickened by more than 50 m during the previous two decades. In contrast, Kangerdlugssuaq Glacier underwent minor thinning of 40-50 m from 1981 to 1998 and major thinning of more than 100 m after 2003. Extending the record back to the end of the Little Ice Age (prior to 1930) shows no thinning of Helheim Glacier from its maximum extent during the Little Ice Age to 1981, while Kangerdlugssuaq Glacier underwent substantial thinning of 230 to 265 m. Comparison of sub-surface water temperature anomalies and variations in air temperature to records of thickness and velocity change suggest that both glaciers are highly sensitive to short-term atmospheric and ocean forcing, and respond very quickly to small fluctuations. On century timescales, however, multiple external parameters (e.g. outlet glacier shape) may dominate the mass change. These findings suggest that special care must be taken in the projection of future dynamic ice loss.

  2. Dynamics and diversity of microbial community succession in traditional fermentation of Shanxi aged vinegar.

    Science.gov (United States)

    Nie, Zhiqiang; Zheng, Yu; Du, Hongfu; Xie, Sankuan; Wang, Min

    2015-05-01

    The traditional fermentation of Shanxi aged vinegar (SAV), a well-known traditional Chinese vinegar, generally involves the preparation of starter daqu, starch saccharification, alcoholic fermentation (AF) and acetic acid fermentation (AAF). Dynamics and diversity of microbial community succession in daqu and other fermentation stages were investigated by denaturing gradient gel electrophoresis (DGGE). Results showed that eight bacterial genera and four fungal genera were found in daqu. However, Staphylococcus, Saccharopolyspora, Bacillus, Oceanobacillus, Enterobacter, Streptomyces, Eurotium, Monascus and Pichia in daqu were eradicated during AF. Four bacterial genera and three fungal genera were found in this stage. Weissella, Lactobacillus, Streptococcus, Saccharomyces, and Saccharomycopsis were the dominant microorganisms in the late stage of AF. During AAF, four bacterial genera and four fungal genera were found. Weissella, Streptococcus, Klebsiella, Escherichia, and Cladosporium gradually disappeared; the dominant microorganisms were Acetobacter, Lactobacillus, Saccharomycopsis, and Alternaria in the late stage of AAF. Alpha diversity metrics showed that fungal diversity in daqu was greater than that in AF and AAF. By contrast, bacterial diversity decreased from daqu to AF and increased in the first three days of AAF and then decreased. Hence, these results could help understand dynamics of microbial community succession in continuous fermentation of traditional Chinese vinegars.

  3. Dark-ages Reionization & Galaxy Formation Simulation I: The dynamical lives of high redshift galaxies

    CERN Document Server

    Poole, Gregory B; Mutch, Simon J; Power, Chris; Duffy, Alan R; Geil, Paul M; Mesinger, Andrei; Wyithe, Stuart B

    2015-01-01

    We present the Dark-ages Reionization and Galaxy-formation Observables from Numerical Simulations (DRAGONS) program and Tiamat, the collisionless N-body simulation program upon which DRAGONS is built. The primary trait distinguishing Tiamat from other large simulation programs is its density of outputs at high redshift (100 from z=35 to z=5; roughly one every 10 Myr) enabling the construction of very accurate merger trees at an epoch when galaxy formation is rapid and mergers extremely frequent. We find that the friends-of-friends halo mass function agrees well with the prediction of Watson et al. at high masses, but deviates at low masses, perhaps due to our use of a different halo finder or perhaps indicating a break from "universal" behaviour. We then analyse the dynamical evolution of galaxies during the Epoch of Reionization finding that only a small fraction (~20%) of galactic halos are relaxed. We illustrate this using standard relaxation metrics to establish two dynamical recovery time-scales: i) halo...

  4. The anti-aging effects of LW-AFC via correcting immune dysfunctions in senescence accelerated mouse resistant 1 (SAMR1) strain.

    Science.gov (United States)

    Wang, Jianhui; Cheng, Xiaorui; Zhang, Xiaorui; Cheng, Junping; Xu, Yiran; Zeng, Ju; Zhou, Wenxia; Zhang, Yongxiang

    2016-05-10

    Although there were considerable advances in the anti-aging medical field, it is short of therapeutic drug for anti-aging. Mounting evidence indicates that the immunosenescence is the key physiopathological mechanism of aging. This study showed the treatment of LW-AFC, an herbal medicine, decreased the grading score of senescence, increased weight, prolonged average life span and ameliorated spatial memory impairment in 12- and 24-month-old senescence accelerated mouse resistant 1 (SAMR1) strain. And these anti-aging effects of LW-AFC were more excellent than melatonin. The administration of LW-AFC enhanced ConA- and LPS-induced splenocyte proliferation in aged SAMR1 mice. The treatment of LW-AFC not only reversed the decreased the proportions of helper T cells, suppressor T cells and B cells, the increased regulatory T cells in the peripheral blood of old SAMR1 mice, but also could modulate the abnormal secretion of IL-1β, IL-2, IL-6, IL-17, IL-23, GM-CSF, IFN-γ, TNF-α, TNF-β, RANTES, eotaxin, MCP-1, IL-4, IL-5, IL-10 and G-CSF. These data indicated that LW-AFC reversed the immunosenescence status by restoring immunodeficiency and decreasing chronic inflammation and suggested LW-AFC may be an effective anti-aging agent.

  5. Importance of Age on the Dynamic Mechanical Behavior of Intertubular and Peritubular Dentin

    Science.gov (United States)

    Ryou, Heonjune; Romberg, Elaine; Pashley, David H.; Tay, Franklin R.; Arola, Dwayne

    2014-01-01

    An experimental evaluation of human coronal dentin was performed using nanoscopic Dynamic Mechanical Analysis (nanoDMA). The primary objectives were to quantify any unique changes in mechanical behavior of intertubular and peritubular dentin with age, and to evaluate the microstructure and mechanical behavior of the mineral deposited within the lumens. Specimens of coronal dentin were evaluated by nanoDMA using single indents and in scanning mode via scanning probe microscopy. Results showed that there were no significant differences in the storage modulus or complex modulus between the two age groups (18–25 versus 54–83 yrs) for either the intertubular or peritubular tissue. However, there were significant differences in the dampening behavior between the young and old dentin, as represented in the loss modulus and tanδ responses. For both the intertubular and peritubular components, the capacity for dampening was significantly lower in the old group. Scanning based nanoDMA showed that the tubules of old dentin exhibit a gradient in elastic behavior, with decrease in elastic modulus from the cuff to the center of tubules filled with newly deposited mineral. PMID:25498296

  6. Effects of Wheat Flour Dough’s Viscoelastic Level by Adding Glucose Oxidase on its Dynamic Shear Properties whatever the Strain Modes

    Directory of Open Access Journals (Sweden)

    Jean Didier Koffi Kouassi

    2014-05-01

    Full Text Available The objective of this work was to study the effects of wheat flour dough’s viscoelastic level by adding glucose oxidase (Gox on its rheological properties at dynamic shear strain mode to predict the final product quality. Dough does display a linear viscoelastic domain. Glucose oxidase (Gox was added to dough in order to enhance its viscoelasticity and to take into account the possible effects of this viscoelasticity on the results. Whatever the types of dough strain used G’ increased, tan δ decreased and led to less sticky dough. Wheat flour dough, an increase in G’ with extension may be associated to a strain-hardening phenomenon but the role of dough viscoelasticity is discussed.

  7. Analysis of Geometric Effects on Stress Wave Propagation in Epoxy Resins of Plate-Like Structure by Dynamic Photoelasticity Combined with Strain Gauge

    Science.gov (United States)

    Hayasi, Ryoei; Masuda, Yoshiharu; Hashimoto, Shozo; Kuriyama, Shinhou

    2008-06-01

    Experimental studies have been conducted using the dynamic photoelastic technique combined with a strain gauge to investigate geometric effects on stress wave propagation in axially impacted epoxy resins of plate-like structure. Dynamic photoelasticity provides a means of visualizing the stress wave field inside a solid. A device that triggers the generation of stress waves by direct projectile impact is used to conduct high-speed photoelasticity and strain gauge measurements. This triggering is achieved by an electrical connection between projectile and sample. The geometric effects of the width-to-wavelength ratio on the propagation speed and attenuation coefficient of stress waves were analyzed for isotropic rectangular rods of different width-to-thickness ratios, the thickness being the same in each case. The experimental results for stress wave speed as a function of width-to-wavelength ratio are in reasonable agreement with theoretical predictions based on a modified Love's equation involving the geometric effects due to lateral inertia.

  8. The Age of the Moon As Told By Dynamics and Asteroidal Meteorites

    Science.gov (United States)

    Bottke, W. F.; Marchi, S.; Vokrouhlicky, D.

    2013-12-01

    The Moon likely formed as a result of a collision between a large protoplanet and the early Earth. A long-standing mystery, however, is precisely when this giant impact (GI) took place. The conventional wisdom, based on both planet formation models and age estimates of ancient lunar samples, is that the GI occurred many tens of My after the formation of CAIs (~4.45-4.53 Ga). New work on ferroan anothosites by Borg et al. (2011; Nature), however, indicates the Moon may have formed ~200 My after CAIs (4.36 Ga). If true, our understanding of solar system evolution and lunar origin will require drastic revisions. The problem is that testing the claims of Borg et al. (2011) is difficult; ancient lunar samples are both rare and hard to date, while current planet formation models have their issues (e.g., they cannot yet make Mars or the asteroid belt with all of their observed properties). This prompted us to examine a novel method to calculate the timing of the GI. Consider that the GI, probably the largest collision to ever take place in the inner solar system, should have produced lots of debris. Numerical hydrocode simulations of the GI by R. Canup show that, on average, 5-10% of an Earth-mass escapes the Earth-Moon system as ejecta; this is equivalent to 100-200 times the mass of the asteroid belt. Our dynamical simulations show this material spreads rapidly across the inner solar system over tens of My, with most bodies going away by hitting the Earth (20-40%), Venus (20-40%), the Sun, or by being ejected out of the Solar System via an encounter with Jupiter. Before they are eliminated, however, a substantial fraction of ejecta reach orbits that allow them to slam into primordial main belt asteroids at high velocities (> 10 km/s). These kinds of impacts are particularly good at heating target material and thereby creating Ar-Ar shock degassing ages. Using the formalism of Marchi, Bottke et al. (2013; Nature Geosci.), we found that over a ~100 My interval, high

  9. Reliability Assessment of Impact Tensile Testing Apparatus using a Drop-bar Striker for Intermediate Strain-rate Range and Evaluation of Dynamic Deformation Behaviors for a Carbon Steel

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Kyung Oh; Kim, Dae Woong; Shin, Hyung Seop [Andong National Univ., Andong (Korea, Republic of); Park, Lee Ju; Kim, Hyung Won [Agency for Defense Development, Daejeon (Korea, Republic of)

    2016-06-15

    Studies on the deformation behavior of materials subjected to impact loads have been carried out in various fields of engineering and industry. The deformation and fracture of members for these machines/structures are known to correspond to the intermediate strain-rate region. Therefore, for the structural design, it is necessary to consider the dynamic deformation behavior in these intermediate strain-rate ranges. However, there have been few reports with useful data about the deformation and fracture behavior at intermediate strain-rate ranges. Because the intermediate strain-rate region is located between quasi-static and high strain-rate regions, it is difficult to obtain the intermediate strain-rate using conventional reasonable test equipment. To solve this problem, in this study, the measurement reliability of the constructed drop-bar impact tensile test apparatus was established and the dynamic behavior at the intermediate strain-rate range of carbon steels was evaluated by utilizing the apparatus.

  10. A note on the global properties of an age-structured viral dynamic model with multiple target cell populations.

    Science.gov (United States)

    Wang, Shaoli; Wu, Jianhong; Rong, Libin

    2017-06-01

    Some viruses can infect different classes of cells. The age of infection can affect the dynamics of infected cells and viral production. Here we develop a viral dynamic model with the age of infection and multiple target cell populations. Using the methods of semigroup and Lyapunov function, we study the global asymptotic property of the steady states of the model. The results show that when the basic reproductive number falls below 1, the infection is predicted to die out. When the basic reproductive number exceeds 1, there exists a unique infected steady state which is globally asymptotically stable. The model can be extended to study virus dynamics with multiple compartments or coinfection by multiple types of viruses. We also show that under some scenarios the age-structured model can be reduced to an ordinary differential equation system with or without time delays.

  11. Tuning the terahertz low-energy charge dynamics by simultaneous effect of epitaxial and anisotropic strain in PrNi O3 thin films

    Science.gov (United States)

    Phanindra, V. Eswara; Das, Sarmistha; Kumar, K. Santhosh; Agarwal, Piyush; Rana, Rakesh; Rana, D. S.

    2017-02-01

    The interplay of charge, spin, and lattice correlations strongly influence the insulator-metal (I-M) transition and magnetic ordering in rare earth nickelates. In this context, we explored the low-energy charge dynamics in structurally modulated PrNi O3 (PNO) thin films to unravel the complexity of ground state across I-M transition using terahertz (THz) spectroscopy. The THz optical constants of compressive film on LaAl O3 (100) substrate and the tensile films on NdGa O3 (100), (001), (110), and (111) substrates with varying orthorhombic distortion exhibit remarkably distinct features as a function of frequency and temperature. The THz conductivity of compressive film sans any I-M transition follows the Drude model. In contrast, the tensile strained films exhibit non-Drude THz conductivity, a giant positive dielectric permittivity, and negative imaginary conductivity, all of which can be explained by the Drude-Smith model. This rich variety of low-energy dynamics manifests as a function of temperature, strain, and crystal orientation. Such distinct THz spectral features, as induced by a subtle variation in strain while crossing over from tensile to compressive strain and with varying degree of orthorhombicity coupled with oxygen vacancies, reveal a novel facet of structure-property relationship of PNO.

  12. Influence of Cement Particle-Size Distribution on Early Age Autogenous Strains and Stresses in Cement-Based Materials

    DEFF Research Database (Denmark)

    Bentz, Dale P.; Jensen, Ole Mejlhede; Hansen, Kurt Kielsgaard

    2001-01-01

    The influence of cement particle-size distribution on autogenous strains and stresses in cement pastes of identical water-to-cement ratios is examined for cement powders of four different finenesses. Experimental measurements include chemical shrinkage, to quantify degree of hydration; internal...... relative humidity development; autogenous deformation; and eigenstress development, using a novel embedded spherical stress sensor. Because the latter three measurements are conducted under sealed conditions, whereas chemical-shrinkage measurements are made under "saturated" conditions, the National...... controls the initial pore-size distribution of the cement paste, which, in turn, regulates the magnitude of the induced autogenous shrinkage stresses produced by the water/air menisci in the air-filled pores formed throughout the hydration process. The experimental results indicate that a small autogenous...

  13. Thermal Aging Effects on Residual Stress and Residual Strain Distribution on Heat Affected Zone of Alloy 600 in Dissimilar Metal Weld

    Energy Technology Data Exchange (ETDEWEB)

    Ham, Junhyuk; Choi, Kyoung Joon; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of)

    2016-10-15

    Dissimilar metal weld (DMW), consisting of Alloy 600, Alloy 182, and A508 Gr.3, has been widely used as a joining material of the reactor pressure vessel penetration nozzle and the steam generator tubing for pressurized water reactors (PWR) because of its good mechanical strength, thermal conductivity, and corrosion resistance. Residual tensile stress is mainly nominated as a cause of SCC in light water reactors by IAEA report. So, to relax the residual stress, post-weld heat treatment is required after manufacturing process such as welding. However, thermal treatment has a great effect on the microstructure and the chromium depletion profile on Alloy 600, so called sensitization. By this reason, HAZ on Alloy 600 is critical to crack. According to G.A. Young et al., Crack growth rates (CGR) in the Alloy 600 HAZ were about 30 times faster than those in the Alloy 600 base metal tested under the same conditions. And according to Z.P. Lu et al., CGR in the Alloy 600 HAZ can be more than 20 times higher than that in its base metal. There are some methods to measure the exact value of residual stress on the material surface. The most common way is X-ray diffraction method (XRD). The principle of XRD is based on lattice strains and depends on the changes in the spacing of the atomic planes in material. And there is a computer simulation method to estimate residual stress distribution which is called ANSYS. This study was conducted to investigate how thermal aging affects residual stress and residual strain distribution of Alloy 600 HAZ. Following conclusions can be drawn from this study. According to preceding researches and this study, both the relaxation of residual stress and the change of residual strain follow as similar way, spreading out from concentrated region. The result of Vickers micro-hardness tester shows that tensile residual stresses are distributed broadly on the material aged by 15 years. Therefore, HT400{sub Y}15 material is weakest state for PWSCC. The

  14. The study of measuring technology on the dynamic mechanical properties of welded joint with high strain rate

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, to meet the needs of studying work of dynamic mechanical properties of welded joint, the dynamic mechanical properties of welded joint were measured by means of SHPB(Split Hopkinson Pressure Bar).The dynamic mechanical property's curves of every part of welded joint were obtained. For studying the dynamic behavior of mechanical heterogeneity of welded joint, important data were offered. The method of test creates a new way of studying dynamic mechanical properties of welded joint.

  15. Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

    Directory of Open Access Journals (Sweden)

    S. A. Khan

    2014-02-01

    Full Text Available Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance at the decadal scale. To improve the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim glacier (HG and Kangerdlugssuaq glacier (KG from 10 to more than 150 yr. We show that although the frontal portion of HG thinned by more than 100 m between 2003 and 2006, it thickened by more than 50 m during the previous two decades. In contrast, KG was stable from 1981 to 1998 and experienced major thinning only after 2003. Extending the record back to the end of the Little Ice Age (ca. 1850 shows no significant thinning of HG from 1850 to 1981, while KG underwent substantial thinning of ~265 m. Analyses of their sensitivity to sub-surface water temperature anomalies and variations in air temperature suggest that both HG and KG are highly sensitive to short-term atmospheric and ocean forcing, and respond very quickly to small fluctuations. At century time-scales, however, multiple external parameters (e.g. outlet shape dominate the mass change. These findings undermine attempts to use measurements over the last decade as initial conditions to project future dynamic ice loss.

  16. Analysis of multiple drug resistance of 2311 strains of Helicobacter pylori isolated from patients of different ages

    Institute of Scientific and Technical Information of China (English)

    冀子中

    2014-01-01

    Objective To investigate condition of single drug or multiple drug resistance and sensitivities of different combinations of antibiotics in Helicobacter pylori(H.pylori)infected patients of different ages in Jiaxing City,Zhejiang Province.Methods From January 2007 to December 2011,a total of 6280 patients underwent gastroendoscopy examination were

  17. Dynamic attentional modulation of vision across space and time after right hemisphere stroke and in ageing

    Science.gov (United States)

    Russell, Charlotte; Malhotra, Paresh; Deidda, Cristiana; Husain, Masud

    2013-01-01

    Introduction Attention modulates the availability of sensory information to conscious perception. In particular, there is evidence of pathological, spatial constriction of the effective field of vision in patients with right hemisphere damage when a central task exhausts available attentional capacity. In the current study we first examined whether this constriction might be modulated across both space and time in right hemisphere stroke patients without neglect. Then we tested healthy elderly people to determine whether non-pathological ageing also leads to spatiotemporal impairments of vision under conditions of high attention load. Methods Right hemisphere stroke patients completed a task at fixation while attempting to discriminate letters appearing in the periphery. Attentional load of the central task was modulated by increasing task difficulty. Peripheral letters appeared simultaneously with the central task or at different times (stimulus onset asynchronies, SOAs) after it. In a second study healthy elderly volunteers were tested with a modified version of this paradigm. Results Under conditions of high attention load right hemisphere stroke patients have a reduced effective visual field, over a significantly extended ‘attentional blink’, worse for items presented to their left. In the second study, older participants were unable to discriminate otherwise salient items across the visual field (left or right) when their attention capacity was loaded on the central task. This deficit extended temporally, with peripheral discrimination ability not returning to normal for up to 450 msec. Conclusions Dynamically tying up attention resources on a task at fixation can have profound effects in patient populations and in normal ageing. These results demonstrate that items can escape conscious detection across space and time, and can thereby impact significantly on visual perception in these groups. PMID:23245427

  18. Quantification of dexterity as the dynamical regulation of instabilities: Comparisons across gender, age and disease

    Directory of Open Access Journals (Sweden)

    Emily L Lawrence

    2014-04-01

    Full Text Available Dexterous manipulation depends on using the fingertips to stabilize unstable objects. The Strength-Dexterity paradigm consists of asking subjects to compress a slender and compliant spring prone to buckling. The maximal level of compression (requiring low fingertip forces We then measured finger dexterity in 42 hands of older patients following treatment for osteoarthritis of the base of the thumb (CMC OA, 33F, 65.8±9.7yrs, and 31 hands from patients being treated for Parkinson’s disease (PD, 6F, 10M, 67.68±8.5yrs. Importantly, we found no differences in finger compression force among patients or controls. But we did find significantly stronger age-related declines in performance in the patients with PD (slope -2.7 gf/yr, p=0.002 than in those with CMC OA (slope -1.4 gf/yr, p=0.015, than in controls (slope -0.86 gf/yr. In addition, the temporal variability of forces during spring compression shows clearly different dynamics in the clinical populations compared to the controls (pLastly, we compared dexterity across extremities. We found stronger age (p=0.005 and gender (p=0.002 effects of leg compression force in 188 healthy subjects who compressed a larger spring with the foot of an isolated leg (73F, 115M, 14-92yrs. In 81 subjects who performed tests with all four limbs, we found finger and leg compression force to be significantly correlated (females ρ=0.529 p=0.004, males ρ=0.403 p=0.003; 28F, 53M, 20-85yrs, but surprisingly found no differences between dominant and non-dominant limbs. These results have important clinical implications, and suggest the existence—and compel the investigation—of systemic vs. limb-specific mechanisms for dexterity.

  19. Multilocus Sequence Typing Reveals Relevant Genetic Variation and Different Evolutionary Dynamics among Strains of Xanthomonas arboricola pv. juglandis

    Directory of Open Access Journals (Sweden)

    Marco Scortichini

    2010-11-01

    Full Text Available Forty-five Xanthomonas arboricola pv. juglandis (Xaj strains originating from Juglans regia cultivation in different countries were molecularly typed by means of MultiLocus Sequence Typing (MLST, using acnB, gapA, gyrB and rpoD gene fragments. A total of 2.5 kilobases was used to infer the phylogenetic relationship among the strains and possible recombination events. Haplotype diversity, linkage disequilibrium analysis, selection tests, gene flow estimates and codon adaptation index were also assessed. The dendrograms built by maximum likelihood with concatenated nucleotide and amino acid sequences revealed two major and two minor phylotypes. The same haplotype was found in strains originating from different continents, and different haplotypes were found in strains isolated in the same year from the same location. A recombination breakpoint was detected within the rpoD gene fragment. At the pathovar level, the Xaj populations studied here are clonal and under neutral selection. However, four Xaj strains isolated from walnut fruits with apical necrosis are under diversifying selection, suggesting a possible new adaptation. Gene flow estimates do not support the hypothesis of geographic isolation of the strains, even though the genetic diversity between the strains increases as the geographic distance between them increases. A triplet deletion, causing the absence of valine, was found in the rpoD fragment of all 45 Xaj strains when compared with X. axonopodis pv. citri strain 306. The codon adaptation index was high in all four genes studied, indicating a relevant metabolic activity.

  20. Neural network modeling to evaluate the dynamic flow stress of high strength armor steels under high strain rate compression

    Institute of Scientific and Technical Information of China (English)

    Ravindranadh BOBBILI; V. MADHU; A.K. GOGIA

    2014-01-01

    An artificial neural network (ANN) constitutive model is developed for high strength armor steel tempered at 500 ?C, 600 ?C and 650 ?C based on high strain rate data generated from split Hopkinson pressure bar (SHPB) experiments. A new neural network configuration consisting of both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on JohnsoneCook (JeC) model and neural network model is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tempering temperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB, over a range of tempering temperatures (500e650 ?C), strains (0.05e0.2) and strain rates (1000e5500/s) are employed to formulate JeC model to predict the high strain rate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the high strain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient (R) and average absolute relative error (AARE). R and AARE for the JeC model are found to be 0.7461 and 27.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with the experimental data for all tempering temperatures.

  1. A spatial age-structured model for describing sea lamprey (Petromyzon marinus) population dynamics

    Science.gov (United States)

    Robinson, Jason M.; Wilberg, Michael J.; Adams, Jean V.; Jones, Michael L.

    2013-01-01

    The control of invasive sea lampreys (Petromyzon marinus) presents large scale management challenges in the Laurentian Great Lakes. No modeling approach has been developed that describes spatial dynamics of lamprey populations. We developed and validated a spatial and age-structured model and applied it to a sea lamprey population in a large river in the Great Lakes basin. We considered 75 discrete spatial areas, included a stock-recruitment function, spatial recruitment patterns, natural mortality, chemical treatment mortality, and larval metamorphosis. Recruitment was variable, and an upstream shift in recruitment location was observed over time. From 1993–2011 recruitment, larval abundance, and the abundance of metamorphosing individuals decreased by 80, 84, and 86%, respectively. The model successfully identified areas of high larval abundance and showed that areas of low larval density contribute significantly to the population. Estimated treatment mortality was less than expected but had a large population-level impact. The results and general approach of this work have applications for sea lamprey control throughout the Great Lakes and for the restoration and conservation of native lamprey species globally.

  2. The effect of aging on the dynamics of reactive and proactive cognitive control of response interference

    Directory of Open Access Journals (Sweden)

    Ling Xiang

    2016-11-01

    Full Text Available A prime-target interference task was used to investigate the effects of cognitive aging on reactive and proactive control in which frequency confounds and feature repetitions were eliminated from the cognitive control measures. We used distributional analyses to explore the dynamics of the two control functions by distinguishing the strength of incorrect response capture and the efficiency of suppression control. For reactive control, within-trial conflict control and between-trial conflict adaption were analyzed. The statistical analysis showed that there were no reliable between-trial conflict adaption effects for both young and older adults. For within-trial conflict control, the results revealed that older adults showed larger interference effects on mean RT and mean accuracy. Distributional analyses showed that the decline mainly stemmed from inefficient suppression rather than from stronger incorrect responses. For proactive control, older adults showed comparable proactive conflict resolution than young adults on mean RT and mean accuracy. Distributional analyses showed older adults were as effective as younger adults in adjusting their responses to minimize automatic response capture and actively suppress the direct response activation based on congruency proportion information. The results suggest that older adults were less proficient at suppressing interference after conflict was detected but can anticipate and prevent inference in response to congruency proportion manipulation. The results challenge earlier views that older adults have selective deficits in proactive control but are spared in reactive control.

  3. Dynamic mechanical properties of a maxillofacial silicone elastomer incorporating a ZnO additive: the effect of artificial aging.

    Science.gov (United States)

    Mouzakis, Dionysios E; Papadopoulos, Triantafillos D; Polyzois, Gregory L; Griniari, Panagiota G

    2010-11-01

    The main objective of the current study was to investigate the dynamic mechanical properties of a room-temperature vulcanizing silicone incorporating different fractions of zinc oxide (ZnO) after indoor and outdoor photoaging. Forty-eight samples were produced by adding different amounts of ZnO into a commercial maxillofacial silicone (EPISIL-E). The samples were divided into 4 groups containing 0.0, 0.2, 0.5, and 1 wt% ZnO additive, respectively. Samples were exposed to sunlight (subgroup 2), ultraviolet (subgroup 3), and fluorescence (subgroup 4) aging, whereas nonaged samples comprised the control subgroup (subgroup 1). Dynamic mechanical analysis was used to determine the storage modulus (E'), loss modulus (E″), and damping capacity (tanδ). General linear statistic model was conducted to evaluate the effects of aging, testing frequency, and composition on the dynamic mechanical properties of the silicone with the ZnO additive. Post hoc analysis was performed using Tukey test. Statistical analysis revealed a significant impact of composition on tanδ (P < 0.05). Aging influenced E' and E″ (P < 0.01). The combination of aging and composition had a significant effect on all dynamic properties (P < 0.01).

  4. Examining Dynamic Links between Perceived Control and Health: Longitudinal Evidence for Differential Effects in Midlife and Old Age

    Science.gov (United States)

    Infurna, Frank J.; Gerstorf, Denis; Zarit, Steven H.

    2011-01-01

    Perceived control and health are often closely linked in adulthood and old age. Little is known, however, about their time-ordered interplay at various phases of adult life. By applying dynamic models to four waves of data over 15.5 years from the Americans' Changing Lives Study, we examined time-ordered relations between perceived control and…

  5. New Insights into the Role of Mitochondrial Dynamics and Autophagy during Oxidative Stress and Aging in the Heart

    Directory of Open Access Journals (Sweden)

    Yoshiyuki Ikeda

    2014-01-01

    Full Text Available The heart is highly sensitive to the aging process. In the elderly, the heart tends to become hypertrophic and fibrotic. Stiffness increases with ensuing systolic and diastolic dysfunction. Aging also affects the cardiac response to stress. At the molecular level, the aging process is associated with accumulation of damaged proteins and organelles, partially due to defects in protein quality control systems. The accumulation of dysfunctional and abnormal mitochondria is an important pathophysiological feature of the aging process, which is associated with excessive production of reactive oxygen species. Mitochondrial fusion and fission and mitochondrial autophagy are crucial mechanisms for maintaining mitochondrial function and preserving energy production. In particular, mitochondrial fission allows for selective segregation of damaged mitochondria, which are afterward eliminated by autophagy. Unfortunately, recent evidence indicates that mitochondrial dynamics and autophagy are progressively impaired over time, contributing to the aging process. This suggests that restoration of these mechanisms could delay organ senescence and prevent age-associated cardiac diseases. Here, we discuss the current understanding of the close relationship between mitochondrial dynamics, mitophagy, oxidative stress, and aging, with a particular focus on the heart.

  6. Age-related changes in the ``complexity'' of cardiovascular dynamics: A potential marker of vulnerability to disease

    Science.gov (United States)

    Lewis, D. A. Lipsitz M.

    1995-03-01

    Healthy physiologic control of cardiovascular function is a result of complex interactions between multiple regulatory processes that operate over different time scales. These include the sympathetic and parasympathetic nervous systems which regulate beat-to-beat heart rate (HR) and blood pressure (BP), as well as extravascular volume, body temperature, and sleep which influence HR and BP over the longer term. Interactions between these control systems generate highly variable fluctuations in continuous HR and BP signals. Techniques derived from nonlinear dynamics and chaos theory are now being adapted to quantify the dynamic behavior of physiologic time series and study their changes with age or disease. We have shown significant age-related changes in the 1/fx relationship between the log amplitude and log frequency of the heart rate power spectrum, as well as declines in approximate dimension and approximate entropy of both heart rate and blood pressure time series. These changes in the ``complexity'' of cardiovascular dynamics reflect the breakdown and decoupling of integrated physiologic regulatory systems with aging, and may signal an impairment in cardiovascular ability to adapt to external and internal perturbations. Studies are currently underway to determine whether the complexity of HR or BP time series can distinguish patients with fainting spells due to benign vasovagal reactions from those due to life-threatening cardiac arrhythmias. Thus, measures of the complexity of physiologic variability may provide novel methods to monitor cardiovascular aging and test the efficacy of specific interventions to improve adaptive capacity in old age.

  7. Dynamic In Vitro Models of the Human Gastrointestinal Tract as Relevant Tools to Assess the Survival of Probiotic Strains and Their Interactions with Gut Microbiota

    Directory of Open Access Journals (Sweden)

    Charlotte Cordonnier

    2015-10-01

    Full Text Available The beneficial effects of probiotics are conditioned by their survival during passage through the human gastrointestinal tract and their ability to favorably influence gut microbiota. The main objective of this study was to use dynamic in vitro models of the human digestive tract to investigate the effect of fasted or fed state on the survival kinetics of the new probiotic Saccharomyces cerevisiae strain CNCM I-3856 and to assess its influence on intestinal microbiota composition and activity. The probiotic yeast showed a high survival rate in the upper gastrointestinal tract whatever the route of admistration, i.e., within a glass of water or a Western-type meal. S. cerevisiae CNCM I-3856 was more sensitive to colonic conditions, as the strain was not able to colonize within the bioreactor despite a twice daily administration. The main bacterial populations of the gut microbiota, as well as the production of short chain fatty acids were not influenced by the probiotic treatment. However, the effect of the probiotic on the gut microbiota was found to be individual dependent. This study shows that dynamic in vitro models can be advantageously used to provide useful insight into the behavior of probiotic strains in the human digestive environment.

  8. Dynamic investigations on the influence of epitaxial strain on the superconducting transition in YBa{sub 2}Cu{sub 3}O{sub 7-x}

    Energy Technology Data Exchange (ETDEWEB)

    Huehne, R; Okai, D; Doerr, K; Trommler, S; Herklotz, A; Holzapfel, B; Schultz, L [IFW Dresden, Institute for Metallic Materials, PO Box 270116, D-01171 Dresden (Germany)], E-mail: r.huehne@ifw-dresden.de

    2008-07-15

    YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) films have been prepared on piezoelectric (001) Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.72}Ti{sub 0.28}O{sub 3} (PMN-PT) substrates for dynamic investigations on the influence of strain on the superconducting transition temperature. The YBCO films deposited by off-axis pulsed laser deposition showed a perfect epitaxial growth on the piezocrystals but also significant surface roughness due to the miscut of the substrate. The in-plane lattice constant of the PMN-PT substrate was varied dynamically by the application of an electric field of {<=}10 kV cm{sup -1}. As a result, a reversible shift of the superconducting transition by about 0.1 K was found on an optimally doped YBCO film for an applied strain of 0.05%. The results show for the first time that this approach is suitable for studying the strain dependence of superconducting properties in detail.

  9. Age-related changes in dynamic postural control and attentional demands are minimally affected by local muscle fatigue.

    Directory of Open Access Journals (Sweden)

    Anthony eRemaud

    2016-01-01

    Full Text Available Normal aging results in alterations in the visual, vestibular and somtaosensory systems, which in turn modify the control of balance. Muscle fatigue may exacerbate these age-related changes in sensory and motor functions, and also increase the attentional demands associated with dynamic postural control. The purpose of this study was to investigate the effect of aging on dynamic postural control and posture-related attentional demands before and after a plantar flexor fatigue protocol. Participants (young adults: n=15; healthy seniors: n=13 performed a dynamic postural task along the antero-posterior and the medio-lateral axes, with and without the addition of a simple reaction time task. The dynamic postural task consisted in following a moving circle on a computer screen with the representation of the center of pressure (COP. This protocol was repeated before and after a fatigue task where ankle plantarflexor muscles were targeted. The mean COP-target distance and the mean COP velocity were calculated for each trial. Cross-correlation analyses between the COP and target displacements were also performed. Reaction times were recorded during dual-task trials. Results showed that while young adults adopted an anticipatory control mode to move their COP as close as possible to the target center, seniors adopted a reactive control mode, lagging behind the target center. This resulted in longer COP-target distance and higher COP velocity in the latter group. Concurrently, reaction time increased more in seniors when switching from static stance to dynamic postural conditions, suggesting potential alterations in the central nervous system functions. Finally, plantar flexor muscle fatigue and dual-tasking had only minor effects on dynamic postural control of both young adults and seniors. Future studies should investigate why the fatigue-induced changes in quiet standing postural control do not seem to transfer to dynamic balance tasks.

  10. Coupling atomistic and continuum length scales in heteroepitaxial systems: Multiscale molecular-dynamics/finite-element simulations of strain relaxation in Si/ Si3 N4 nanopixels

    Science.gov (United States)

    Lidorikis, Elefterios; Bachlechner, Martina E.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2005-09-01

    A hybrid atomistic-continuum simulation approach has been implemented to study strain relaxation in lattice-mismatched Si/Si3N4 nanopixels on a Si(111) substrate. We couple the molecular-dynamics (MD) and finite-element simulation approaches to provide an atomistic description near the interface and a continuum description deep into the substrate, increasing the accessible length scales and greatly reducing the computational cost. The results of the hybrid simulation are validated against full multimillion-atom MD simulations. We find that strain relaxation in Si/Si3N4 nanopixels may occur through the formation of a network of interfacial domain boundaries reminiscent of interfacial misfit dislocations. They result from the nucleation of domains of different interfacial bonding at the free edges and corners of the nanopixel, and subsequent to their creation they propagate inwards. We follow the motion of the domain boundaries and estimate a propagation speed of about ˜2.5×103m/s . The effects of temperature, nanopixel architecture, and film structure on strain relaxation are also investigated. We find: (i) elevated temperature increases the interfacial domain nucleation rates; (ii) a thin compliant Si layer between the film and the substrate plays a beneficial role in partially suppressing strain relaxation; and (iii) additional control over the interface morphology may be achieved by varying the film structure.

  11. Effects of age, strain, and illumination intensity on activity and self-selection of light-dark schedules in mice.

    Science.gov (United States)

    Wax, T M

    1977-02-01

    Young and senescent albino A/J mice, pigmented C57BL/6J pure inbred mice, and their hybrid F1S were tested under low or high illumination intensities to observe differences in self-selected wheel running, bar pressing, and durations of light and dark over time. The animals (N = 120) were always allowed ad lib access to food, water, running wheel, and bar-press levers. During the pre- and postexperimental phases, the mice were kept under a standard 12:12 hr light/dark cycle; during the experimental phase, however, they were allowed to select their own light and dark schedules by pressing on either of two accessible bars, one light contingent and the other dark contingent. Measures of general running and bar-pressing activities, motivational aspects of illumination change and intensity preferences, time-series analyses of periodicities, power ratios, and significant other multiples were obtained from the subjects during a total of three experimental phases. Age differences were found for most of the measures studied and in general showed declines in activity levels, inccreases in motivation to change illumination conditions, lengthening of activity cycles (slower periods), and decreases in the strengths of the oscillations underlying these behaviors as well as an increase in the number of other periodic components in old mice relative to young. Genetic group and illumination-intensity differences were also found, and the results are discussed in light of theories concerning illumination preference and stimulus change, earlier work involving voluntary light selection behavior, and aging studies.

  12. The stereotypical molecular cascade in neovascular age-related macular degeneration: the role of dynamic reciprocity.

    Science.gov (United States)

    Kent, D

    2015-11-01

    This review summarises our current understanding of the molecular basis of subretinal neovascularisation (SRNV) in age-related macular degeneration (AMD). The term neovascular AMD (NVAMD) is derived from the dominant early clinical features of haemorrhage, fluid, and lipid in the subretinal space (SRS) and the historical role of fluorescein angiography in detecting the presence of NV tissue. However, at the cellular level, SRNV resembles an aberrant but stereotypical tissue repair response that incorporates both an early inflammatory phase and a late fibrotic phase in addition to the neovascular (NV) component that dominates the early clinical presentation. This review will seek not only to highlight the important molecules involved in each of these components but to demonstrate that the development of SRNV has its origins in the earliest events in non-NV AMD pathogenesis. Current evidence suggests that this early-stage pathogenesis is characterised by complement-mediated immune dysregulation, leading to a state of chronic inflammation in the retinal pigment epithelium/Bruch's membrane/choriocapillaris complex. These initial events can be seamlessly and inextricably linked to late-stage development of SRNV in AMD by the process of dynamic reciprocity (DyR), the ongoing bidirectional communication between cells, and their surrounding matrix. Moreover, this correlation between disease onset and eventual outcome is reflected in the temporal and spatial correlation between chronic inflammation, NV, and fibrosis within the reparative microenvironment of the SRS. In summary, the downstream consequences of the earliest dysfunctional molecular events in AMD can result in the late-stage entity we recognize clinically as SRNV and is characterized by a spectrum of predictable, related, and stereotypical processes referred to as DyR.

  13. The effect of temperature, defect and strain rate on the mechanical property of multi-layer graphene: Coarse-grained molecular dynamics study

    Science.gov (United States)

    Li, Hui; Zhang, Hong; Cheng, Xinlu

    2017-01-01

    In this work, we investigate the effect of temperature, defect, and strain rate on the mechanical properties of multi-layer graphene using coarse-grained molecular dynamics (CGMD) simulations. The simulation results reveal that the mechanical properties of multi-layer graphene tend to be less sensitive to temperature as the layer increases, but they are sensitive to the distribution and coverage of Stone-Wales (SW) defects. For the same number of defect, there is less decline in the fracture stress and Young's modulus of graphene when the defects have a regular distribution, in contrast to random distribution. In addition, Young's modulus is less influenced by temperature and defect, compared to fracture stress. Both the fracture stress and Young's modulus have little dependence on strain rate.

  14. First-principles molecular dynamics simulations of proton diffusion in cubic BaZrO $$_3$$ 3 perovskite under strain conditions

    Directory of Open Access Journals (Sweden)

    Marco Fronzi

    2016-08-01

    Full Text Available Abstract First-principles molecular dynamics simulations have been employed to analyse the proton diffusion in cubic BaZrO $$_3$$ 3 perovskite at 1300 K. A non-linear effect on the proton diffusion coefficient arising from an applied isometric strain up to 2  $$\\%$$ % of the lattice parameter, and an evident enhancement of proton diffusion under compressive conditions have been observed. The structural and electronic properties of BaZrO $$_3$$ 3 are analysed from Density Functional Theory calculations, and after an analysis of the electronic structure, we provide a possible explanation for an enhanced ionic conductivity of this bulk structure that can be caused by the formation of a preferential path for proton diffusion under compressive strain conditions. By means of Nudged Elastic Band calculations, diffusion barriers were also computed with results supporting our conclusions.

  15. Stream water age distributions controlled by storage dynamics and nonlinear hydrologic connectivity: Modeling with high-resolution isotope data.

    Science.gov (United States)

    Soulsby, C; Birkel, C; Geris, J; Dick, J; Tunaley, C; Tetzlaff, D

    2015-09-01

    To assess the influence of storage dynamics and nonlinearities in hydrological connectivity on time-variant stream water ages, we used a new long-term record of daily isotope measurements in precipitation and streamflow to calibrate and test a parsimonious tracer-aided runoff model. This can track tracers and the ages of water fluxes through and between conceptual stores in steeper hillslopes, dynamically saturated riparian peatlands, and deeper groundwater; these represent the main landscape units involved in runoff generation. Storage volumes are largest in groundwater and on the hillslopes, though most dynamic mixing occurs in the smaller stores in riparian peat. Both streamflow and isotope variations are generally well captured by the model, and the simulated storage and tracer dynamics in the main landscape units are consistent with independent measurements. The model predicts that the average age of stream water is ∼1.8 years. On a daily basis, this varies between ∼1 month in storm events, when younger waters draining the hillslope and riparian peatland dominates, to around 4 years in dry periods when groundwater sustains flow. This variability reflects the integration of differently aged water fluxes from the main landscape units and their mixing in riparian wetlands. The connectivity between these spatial units varies in a nonlinear way with storage that depends upon precipitation characteristics and antecedent conditions. This, in turn, determines the spatial distribution of flow paths and the integration of their contrasting nonstationary ages. This approach is well suited for constraining process-based modeling in a range of northern temperate and boreal environments.

  16. Stream water age distributions controlled by storage dynamics and nonlinear hydrologic connectivity: Modeling with high‐resolution isotope data

    Science.gov (United States)

    Birkel, C.; Geris, J.; Dick, J.; Tunaley, C.; Tetzlaff, D.

    2015-01-01

    Abstract To assess the influence of storage dynamics and nonlinearities in hydrological connectivity on time‐variant stream water ages, we used a new long‐term record of daily isotope measurements in precipitation and streamflow to calibrate and test a parsimonious tracer‐aided runoff model. This can track tracers and the ages of water fluxes through and between conceptual stores in steeper hillslopes, dynamically saturated riparian peatlands, and deeper groundwater; these represent the main landscape units involved in runoff generation. Storage volumes are largest in groundwater and on the hillslopes, though most dynamic mixing occurs in the smaller stores in riparian peat. Both streamflow and isotope variations are generally well captured by the model, and the simulated storage and tracer dynamics in the main landscape units are consistent with independent measurements. The model predicts that the average age of stream water is ∼1.8 years. On a daily basis, this varies between ∼1 month in storm events, when younger waters draining the hillslope and riparian peatland dominates, to around 4 years in dry periods when groundwater sustains flow. This variability reflects the integration of differently aged water fluxes from the main landscape units and their mixing in riparian wetlands. The connectivity between these spatial units varies in a nonlinear way with storage that depends upon precipitation characteristics and antecedent conditions. This, in turn, determines the spatial distribution of flow paths and the integration of their contrasting nonstationary ages. This approach is well suited for constraining process‐based modeling in a range of northern temperate and boreal environments. PMID:27478255

  17. Incubation periods under various anti-retroviral therapies in homogeneous mixing and age-structured dynamical models: A theoretical approach

    CERN Document Server

    Rao, Arni S R Srinivasa

    2008-01-01

    Abstract. We consider previously well-known models in epidemiology where the parameter for incubation period is used as one of the important components to explain the dynamics of the variables. Such models are extended here to explain the dynamics with respect to a given therapy that prolongs the incubation period. A deconvolution method is demonstrated for estimation of parameters in the situations when no-therapy and multiple therapies are given to the infected population. The models and deconvolution method are extended in order to study the impact of therapy in age-structured populations. A generalisation for a situation when n-types of therapies are available is given.

  18. Determination of flow stress and the critical strain for the onset of dynamic recrystallization using a sine function

    NARCIS (Netherlands)

    Solhjoo, Soheil

    2014-01-01

    A new model has been developed to estimate the flow stress under hot deformation conditions up to the peak of the stress-strain curves. The model is constructed on the basis of the general form of sine functions by introducing an additional exponent. Besides, an equation is derived from the model, w

  19. Microbial community dynamics during the bioremediation process of chlorimuron-ethyl-contaminated soil by Hansschlegelia sp. strain CHL1.

    Science.gov (United States)

    Yang, Liqiang; Li, Xinyu; Li, Xu; Su, Zhencheng; Zhang, Chenggang; Zhang, Huiwen

    2015-01-01

    Long-term and excessive application of chlorimuron-ethyl has led to a series of environmental problems. Strain Hansschlegelia sp. CHL1, a highly efficient chlorimuron-ethyl degrading bacterium isolated in our previous study, was employed in the current soil bioremediation study. The residues of chlorimuron-ethyl in soils were detected, and the changes of soil microbial communities were investigated by phospholipid fatty acid (PLFA) analysis. The results showed that strain CHL1 exhibited significant chlorimuron-ethyl degradation ability at wide range of concentrations between 10μg kg-1 and 1000μg kg-1. High concentrations of chlorimuron-ethyl significantly decreased the total concentration of PLFAs and the Shannon-Wiener indices and increased the stress level of microbes in soils. The inoculation with strain CHL1, however, reduced the inhibition on soil microbes caused by chlorimuron-ethyl. The results demonstrated that strain CHL1 is effective in the remediation of chlorimuron-ethyl-contaminated soil, and has the potential to remediate chlorimuron-ethyl contaminated soils in situ.

  20. Microbial community dynamics during the bioremediation process of chlorimuron-ethyl-contaminated soil by Hansschlegelia sp. strain CHL1.

    Directory of Open Access Journals (Sweden)

    Liqiang Yang

    Full Text Available Long-term and excessive application of chlorimuron-ethyl has led to a series of environmental problems. Strain Hansschlegelia sp. CHL1, a highly efficient chlorimuron-ethyl degrading bacterium isolated in our previous study, was employed in the current soil bioremediation study. The residues of chlorimuron-ethyl in soils were detected, and the changes of soil microbial communities were investigated by phospholipid fatty acid (PLFA analysis. The results showed that strain CHL1 exhibited significant chlorimuron-ethyl degradation ability at wide range of concentrations between 10μg kg-1 and 1000μg kg-1. High concentrations of chlorimuron-ethyl significantly decreased the total concentration of PLFAs and the Shannon-Wiener indices and increased the stress level of microbes in soils. The inoculation with strain CHL1, however, reduced the inhibition on soil microbes caused by chlorimuron-ethyl. The results demonstrated that strain CHL1 is effective in the remediation of chlorimuron-ethyl-contaminated soil, and has the potential to remediate chlorimuron-ethyl contaminated soils in situ.

  1. Tracking the big ones : novel dynamics of organelles and macromolecular complexes during cell division and aging

    NARCIS (Netherlands)

    Deventer, Sjoerd Jan van

    2015-01-01

    In this Thesis we address two important aspects of protein dynamics: protein synthesis and distribution upon cell division and dynamics of the protein degradation machinery. In Chapter 2, we present novel technology (Recombination-Induced Tag Exchange)to distinguish and simultaneously track old and

  2. Infant Attention to Dynamic Audiovisual Stimuli: Look Duration from 3 to 9 Months of Age

    Science.gov (United States)

    Reynolds, Greg D.; Zhang, Dantong; Guy, Maggie W.

    2013-01-01

    The goal of this study was to examine developmental change in visual attention to dynamic visual and audiovisual stimuli in 3-, 6-, and 9-month-old infants. Infant look duration was measured during exposure to dynamic geometric patterns and Sesame Street video clips under three different stimulus modality conditions: unimodal visual, synchronous…

  3. AGE AND SEASONAL DYNAMICS OF THE SYMBIOCENOSES OF GRASS CARP (CTENOPHARYNGODON IDELLA AND SILVER CARP (HYPOPHTHALMICHTHYS MOLITRIX IN FISH PONDS

    Directory of Open Access Journals (Sweden)

    N. Zaichenko

    2015-09-01

    Full Text Available Purpose. Identification and analysis of age and seasonal dynamics of the symbiocenoses of grass carp and silver carp in fish ponds. Methodology. The work was performed at Belotserkovskoy hydrobiological station, located on the river Ros within Bila Tserkva. The objects of the study were symbiotic communities of grass carp and silver carp of different age groups (from yearlings to age-5 fish. Fish underwent partial parasitological dissection using generally accepted methods. Findings. The age and seasonal dynamics of the symbiotic communitues of grass carp and silver carp were investigated during different seasons of one year. The effect of different factors on the formation of symbiotic communities have been analyzed. Different species of symbiotic organisms were characterized by different temperature preferences (Peritrcha have the highest rates of invasion in the summer. The distribution of symbionts depend on the way of their transmission. Some species of protista, monogenea and parasitic crustaceans infect the host during their high density (wintering or spawning. Other species of symbiotic organisms infect the host by nutritional way, therefore the invasion rates increase with the intensity of feeding. The differences in symbiotic community structure of fish of different age group are related to the differences in species biology. The composition of symbiotic communities of fish of different age groups contain symbiotic organisms that do not depend on the host age (metacercaria of Diplostomum, some Protista; species that more rapidly infect fish juveniles (some species of ciliates, cestoda – B. acheilognathi and species that predominantly infect older age group (monogenea, parasitic crustaceans. Originality. For the first time, we performed complex investigations of symbiotic communities of grass carp and silver carp in view of the specificity of their biology and during different seasons. Practical value. The results of the work can be

  4. Redox proteomics and the dynamic molecular landscape of the aging brain.

    Science.gov (United States)

    Perluigi, Marzia; Swomley, Aaron M; Butterfield, D Allan

    2014-01-01

    It is well established that the risk to develop neurodegenerative disorders increases with chronological aging. Accumulating studies contributed to characterize the age-dependent changes either at gene and protein expression level which, taken together, show that aging of the human brain results from the combination of the normal decline of multiple biological functions with environmental factors that contribute to defining disease risk of late-life brain disorders. Finding the "way out" of the labyrinth of such complex molecular interactions may help to fill the gap between "normal" brain aging and development of age-dependent diseases. To this purpose, proteomics studies are a powerful tool to better understand where to set the boundary line of healthy aging and age-related disease by analyzing the variation of protein expression levels and the major post translational modifications that determine "protein" physio/pathological fate. Increasing attention has been focused on oxidative modifications due to the crucial role of oxidative stress in aging, in addition to the fact that this type of modification is irreversible and may alter protein function. Redox proteomics studies contributed to decipher the complexity of brain aging by identifying the proteins that were increasingly oxidized and eventually dysfunctional as a function of age. The purpose of this review is to summarize the most important findings obtained by applying proteomics approaches to murine models of aging with also a brief overview of some human studies, in particular those related to dementia.

  5. Contents of chemical elements in stomach during prenatal development: different age-dependent dynamical changes and their significance

    Institute of Scientific and Technical Information of China (English)

    Shao-Fan Hou; Hai-Rong Li; Li-Zhen Wang; De-Zhu Li; Lin-Sheng Yang; Chong-Zheng Li

    2003-01-01

    AIM: To observe dynamic of different chemical elements in stomach tissue during fetal development.METHODS: To determine contents of the 21 chemical elements in each stomach samples from fetus aging four to ten months. The content values were compared to those from adult tissue samples, and the values for each month group were also analyzed for dynamic changes.RESULTS: Three representations were found regarding the relationship between contents of the elements and ages of the fetus, including the positive correlative (K), reversely correlative (Na, Ca, P, Al, Cu, Zn, Fe, Mn, Cr, Sr, Li, Cd, Ba,Se ) and irrelevant groups (Mg, Co, Ni, V, Pb, Ti).CONCLUSION: The chemical elements' contents in stomach tissues were found to change dynamically with the stomach weights. The age-dependent representations for different chemical elements during the prenatal development may be of some significance for assessing development of fetal stomach and some chemical elements. The data may be helpful for the nutritional balance of fetus and mothers during prenatal development and even the perinatal stages.

  6. Contents of chemical elements in stomach during prenatal development: different age-dependent dynamical changes and their significance

    Science.gov (United States)

    Hou, Shao-Fan; Li, Hai-Rong; Wang, Li-Zhen; Li, De-Zhu; Yang, Lin-Sheng; Li, Chong-Zheng

    2003-01-01

    AIM: To observe dynamic of different chemical elements in stomach tissue during fetal development. METHODS: To determine contents of the 21 chemical elements in each stomach samples from fetus aging four to ten months. The content values were compared to those from adult tissue samples, and the values for each month group were also analyzed for dynamic changes. RESULTS: Three representations were found regarding the relationship between contents of the elements and ages of the fetus, including the positive correlative (K), reversely correlative (Na, Ca, P, Al, Cu, Zn, Fe, Mn, Cr, Sr, Li, Cd, Ba, Se) and irrelevant groups (Mg, Co, Ni, V, Pb, Ti). CONCLUSION: The chemical elements’ contents in stomach tissues were found to change dynamically with the stomach weights. The age-dependent representations for different chemical elements during the prenatal development may be of some significance for assessing development of fetal stomach and some chemical elements. The data may be helpful for the nutritional balance of fetus and mothers during prenatal development and even the perinatal stages. PMID:12717857

  7. Stress-strain behavior of block-copolymers and their nanocomposites filled with uniform or Janus nanoparticles under shear: a molecular dynamics simulation.

    Science.gov (United States)

    Wang, Lu; Liu, Hongji; Li, Fanzhu; Shen, Jianxiang; Zheng, Zijian; Gao, Yangyang; Liu, Jun; Wu, Youping; Zhang, Liqun

    2016-10-05

    Although numerous research studies have been focused on studying the self-assembled morphologies of block-copolymers (BCPs) and their nanocomposites, little attention has been directed to explore the relation between their ordered structures and the resulting mechanical properties. We adopt coarse-grained molecular dynamics simulation to study the influence of the morphologies on the stress-strain behavior of pure block copolymers and block copolymers filled with uniform or Janus nanoparticles (NPs). At first, we examine the effect of the arrangement (di-block, tri-block, alternating-block) and the components of the pure block copolymers, and by varying the component ratio between A and B blocks, spherical, cylindrical and lamellar phases are all formed, showing that spherical domains bring the largest reinforcing effect. Then by studying BCPs filled with NPs, the Janus NPs induce stronger bond orientation of polymer chains and greater mechanical properties than the uniform NPs, when these two kinds of NPs are both located in the interface region. Meanwhile, some other anisotropic Janus NPs, such as Janus rods and Janus sheets, are incorporated to examine the effect on the morphology and the stress-strain behavior. These findings deepen our understanding of the morphology-mechanics relation of BCPs and their nanocomposites, opening up a vast number of approaches such as designing the arrangement and components of BCPs, positioning uniform or Janus NPs with different shapes and shear flow to tailor their stress-strain performance.

  8. Parkin overexpression during aging reduces proteotoxicity, alters mitochondrial dynamics, and extends lifespan

    OpenAIRE

    Rana, Anil; Rera, Michael; Walker, David W.

    2013-01-01

    Aberrant protein aggregation and mitochondrial dysfunction have each been linked to aging and a number of age-onset neurodegenerative disorders, including Parkinson disease. Loss-of-function mutations in parkin, an E3 ubiquitin ligase that functions to promote the ubiquitin–proteasome system of protein degradation and also in mitochondrial quality control, have been implicated in heritable forms of Parkinson disease. The question of whether parkin can modulate aging or positively impact longe...

  9. Dynamic Analyses of PrP and PrPsc in Brain Tissues of Golden Hamsters Infected With Scraple Strain 263K Revealed Various PrP Forms

    Institute of Scientific and Technical Information of China (English)

    JIAN-MEI GAO; AND XIAO-PING DONG; CHEN GAO; JUN HAN; XIAO-BO ZHOU; XIN-LI XIAO; JIN ZHANG; LAN CHEN; BAO-YUN ZHANG; TAO HONG

    2004-01-01

    Objective To expatiate dynamic changes in hamsters infected with scrapie strain 263K, to observe the presence and aggravation of various forms of PrP and PrPSc during incubation period, and to probe primarily the relationship between the onset of clinic manifestations and the presence of different PrPSc forms. Methods Hamster-adapted scrapie strain 263K was intracerebrally inoculated into hamsters. Different forms of PrP and PrPSc were monitored dynamically by Western blot and immuno-histochemical assays. The presence of scrapie-associated fibril (SAF) was assayedby electron microscopy analysis (EM) and immuno-golden EM. Results PrPSc was initiallydetected in the brain tissues of the animals in 20 days post-inoculation by immunohistochemistry and 40 days with Western blot. Quantitative evaluations revealed that the amounts of PrP and PrPSc inbrain tissues increased along with the incubation. Several high and low molecular masses of PrP wereseen in the brains of the long-life span infected animals. Deglycosylation assays identified that the truncated PrP in the infected brains showed similar glycosylation patterns as the full-length PrP. The presence of short fragments was seemed to relate with the onset of clinical conditions. Conclusion These results indicate that infectious agents exist and accumulate in central nerve system prior to the onset of the illness. Various molecular patterns of PrPSc may indwell in brain tissues during the infection.

  10. Modeling the growth dynamics of multiple Escherichia coli strains in the pig intestine following intramuscular ampicillin treatment

    DEFF Research Database (Denmark)

    Ahmad, Amais; Zachariasen, Camilla; Christiansen, Lasse Engbo;

    2016-01-01

    after the treatment ended. When the duration of high excretion was set to be limited to the treatment time (i.e. the treatment was assumed to result in a cure of diarrhea) resistant strains required longer time to reach the previous level. Conclusion : No fitness cost was found to be associated......, and could be used for prediction of the effect of treatment with other drugs and other administration routes for effect on resistance development in the intestine of pigs....

  11. Dynamics of the Intermediate-Age Elliptical LMC Cluster NGC 1978

    CERN Document Server

    Fischer, P; Mateo, M; Fischer, Philippe; Welch, Douglas L.; Mateo, Mario

    1992-01-01

    In this paper we investigate the internal dynamics of the LMC cluster NGC 1978 through the use of Photometric (CCD images) and kinematic (stellar radial velocities) data. We apply a variety of dynamical models to this data, including multi-mass King-Michie models and rotating and non-rotating oblate spheroid models. We discuss the cluster mass-to-light ratio and place constraints on the cluster mass function.

  12. Dynamic properties of a locomotory muscle of the tobacco hornworm Manduca sexta during strain cycling and simulated natural crawling.

    Science.gov (United States)

    Woods, William A; Fusillo, Steven J; Trimmer, Barry A

    2008-03-01

    Caterpillars are soft-bodied terrestrial climbers that perform a wide variety of complex movements with several hundred muscles and a relatively small number of neurons. Control of movements is therefore expected to place unusual demands on the mechanical properties of the muscles. The muscles develop force slowly (1-6 s to peak) yet over a strain range extending from under 60% to more than 160% of resting length, with a length-tension relationship resembling that of supercontracting or cross-striated muscle. In passive and active sinusoidal strain cycling, muscles displayed viscoelastic qualities, with very low and stretch-velocity dependent resilience; there was a positive linear relationship between stretch velocity and the fraction of work dissipation attributable to passive muscle properties (20-80%). In linear stretches of unstimulated muscles at velocities bracketing those encountered in natural crawling, the rise in tension showed a distinct transition to a lower rate of increase, with transition tension dependent upon stretch velocity; peak force was exponentially related to stretch velocity. When stretching ceased, force decayed exponentially, with slower decay associated with lower stretch velocities; the decay time constant was exponentially related to stretch velocity. From the kinematics of caterpillars crawling horizontally we determined that the ventral interior lateral muscle (VIL) of the third abdominal segment (A3) is at or near resting length for most of the crawl cycle, with a fairly linear shortening by 25-30% and re-lengthening occupying about 45% of cycle duration. Synchronized kinematic and EMG recordings showed that during horizontal crawling A3 VIL is stimulated as the muscle shortens from about 95% to 75% of its resting length. We subjected in vitro VIL preparations to strain cycling and stimulus phase and duration similar to that of natural crawling. The resulting work loops were figure-eight shaped, with the muscle performing work

  13. Dynamics of specific anti-Mycobacterium avium subsp. paratuberculosis antibody response through age

    DEFF Research Database (Denmark)

    Nielsen, Søren Saxmose; Toft, Nils; Okura, Hisako

    2013-01-01

    G antibodies on their final test-record were used to estimate age-specific sensitivities (Se). These cows were the infected ones considered to develop disease in a population with a representative age-distribution and were defined as cases. The specificity (Sp) of the test was estimated based on test......-results from 166,905 cows, which had no MAP IgG antibodies in their final four test-records. The Sp, age-specific Se and maximum Se were used to estimate the probability of having HI at a given age resulting in the proportion of infected cows with HI at a given age. For cows 2 years of age, the proportion...... of detectable cases was 0.33, while it was 0.94 for cows 5 years of age. Thus, there was a significant shift in the tip of the iceberg with aging. This study provided a model for estimating the proportion of latent chronic infections that would progress to disease, and the results can be used to model infection...

  14. The effects of aging on the dynamic adsorption of hazardous organic vapors on impregnated activated carbon.

    Science.gov (United States)

    Amitay-Rosen, Tal; Leibman, Amir; Nir, Ido; Zaltsman, Amalia; Kaplan, Doron

    2015-01-01

    The effects of an eight-year natural aging of ASC impregnated activated carbon on the adsorption capacity and breakthrough times of model organic vapors and of the nerve agent sarin were investigated. Aging delayed methanol breakthrough from dry air on pre-dried carbon, but shortened the breakthrough time of both methanol and hexane under relative humidity (RH) of 30-85% on pre-humidified carbon. Aging also shortened the breakthrough time of the less volatile model compound 2-methoxyethanol, especially under RH of 60-85%. Aging significantly reduced the protection capacity against sarin at RH of 85%. The effects of aging on physisorption are attributed to enhanced hydrogen-bonding capability and strength of the interaction between water and adsorption sites on the carbon surface.

  15. A dynamic model of the marriage market-part 1: matching algorithm based on age preference and availability.

    Science.gov (United States)

    Matthews, A P; Garenne, M L

    2013-09-01

    The matching algorithm in a dynamic marriage market model is described in this first of two companion papers. Iterative Proportional Fitting is used to find a marriage function (an age distribution of new marriages for both sexes), in a stable reference population, that is consistent with the one-sex age distributions of new marriages, and includes age preference. The one-sex age distributions (which are the marginals of the two-sex distribution) are based on the Picrate model, and age preference on a normal distribution, both of which may be adjusted by choice of parameter values. For a population that is perturbed from the reference state, the total number of new marriages is found as the harmonic mean of target totals for men and women obtained by applying reference population marriage rates to the perturbed population. The marriage function uses the age preference function, assumed to be the same for the reference and the perturbed populations, to distribute the total number of new marriages. The marriage function also has an availability factor that varies as the population changes with time, where availability depends on the supply of unmarried men and women. To simplify exposition, only first marriage is treated, and the algorithm is illustrated by application to Zambia. In the second paper, remarriage and dissolution are included.

  16. Sports can protect dynamic visual acuity from aging: A study with young and older judo and karate martial arts athletes.

    Science.gov (United States)

    Muiños, Mónica; Ballesteros, Soledad

    2015-08-01

    A major topic of current research in aging has been to investigate ways to promote healthy aging and neuroplasticity in order to counteract perceptual and cognitive declines. The aim of the present study was to investigate the benefits of intensive, sustained judo and karate martial arts training in young and older athletes and nonathletes of the same age for attenuating age-related dynamic visual acuity (DVA) decline. As a target, we used a moving stimulus similar to a Landolt ring that moved horizontally, vertically, or obliquely across the screen at three possible contrasts and three different speeds. The results indicated that (1) athletes had better DVA than nonathletes; (2) the older adult groups showed a larger oblique effect than the younger groups, regardless of whether or not they practiced a martial art; and (3) age modulated the results of sport under the high-speed condition: The DVA of young karate athletes was superior to that of nonathletes, while both judo and karate older athletes showed better DVA than did sedentary older adults. These findings suggest that in older adults, the practice of a martial art in general, rather than the practice of a particular type of martial art, is the crucial thing. We concluded that the sustained practice of a martial art such as judo or karate attenuates the decline of DVA, suggesting neuroplasticity in the aging human brain.

  17. Temporal course of cerebrospinal fluid dynamics and amyloid accumulation in the aging rat brain from three to thirty months

    Directory of Open Access Journals (Sweden)

    Chiu Catherine

    2012-01-01

    Full Text Available Abstract Background Amyloid accumulation in the brain parenchyma is a hallmark of Alzheimer's disease (AD and is seen in normal aging. Alterations in cerebrospinal fluid (CSF dynamics are also associated with normal aging and AD. This study analyzed CSF volume, production and turnover rate in relation to amyloid-beta peptide (Aβ accumulation in the aging rat brain. Methods Aging Fischer 344/Brown-Norway hybrid rats at 3, 12, 20, and 30 months were studied. CSF production was measured by ventriculo-cisternal perfusion with blue dextran in artificial CSF; CSF volume by MRI; and CSF turnover rate by dividing the CSF production rate by the volume of the CSF space. Aβ40 and Aβ42 concentrations in the cortex and hippocampus were measured by ELISA. Results There was a significant linear increase in total cranial CSF volume with age: 3-20 months (p p p p -1 to 12 months (11.30 day-1 and then a decrease to 20 months (10.23 day-1 and 30 months (6.62 day-1. Aβ40 and Aβ42 concentrations in brain increased from 3-30 months (p Conclusions In young rats there is no correlation between CSF turnover and Aβ brain concentrations. After 12 months, CSF turnover decreases as brain Aβ continues to accumulate. This decrease in CSF turnover rate may be one of several clearance pathway alterations that influence age-related accumulation of brain amyloid.

  18. The Dynamics of Power laws: Fitness and Aging in Preferential Attachment Trees

    Science.gov (United States)

    Garavaglia, Alessandro; van der Hofstad, Remco; Woeginger, Gerhard

    2017-07-01

    Continuous-time branching processes describe the evolution of a population whose individuals generate a random number of children according to a birth process. Such branching processes can be used to understand preferential attachment models in which the birth rates are linear functions. We are motivated by citation networks, where power-law citation counts are observed as well as aging in the citation patterns. To model this, we introduce fitness and age-dependence in these birth processes. The multiplicative fitness moderates the rate at which children are born, while the aging is integrable, so that individuals receives a finite number of children in their lifetime. We show the existence of a limiting degree distribution for such processes. In the preferential attachment case, where fitness and aging are absent, this limiting degree distribution is known to have power-law tails. We show that the limiting degree distribution has exponential tails for bounded fitnesses in the presence of integrable aging, while the power-law tail is restored when integrable aging is combined with fitness with unbounded support with at most exponential tails. In the absence of integrable aging, such processes are explosive.

  19. Dynamical Masses of Young Stars I: Discordant Model Ages of Upper Scorpius

    CERN Document Server

    Rizzuto, Aaron C; Dupuy, Trent J; Kraus, Adam L

    2015-01-01

    We present the results of a long term orbit monitoring program, using sparse aperture masking observations taken with NIRC2 on the Keck-II telescope, of seven G to M-type members of the Upper Scorpius subgroup of the Sco-Cen OB association. We present astrometry and derived orbital elements of the binary systems we have monitored, and also determine the age, component masses, distance and reddening for each system using the orbital solutions and multi-band photometry, including Hubble Space Telescope photometry, and a Bayesian fitting procedure. We find that the models can be forced into agreement with any individual system by assuming an age, but that age is not consistent across the mass range of our sample. The G-type binary systems in our sample have model ages of ~11.5 Myr, which is consistent with the latest age estimates for Upper Scorpius, while the M-type binary systems have significantly younger model ages of ~7 Myr. Based on our fits, this age discrepancy in the models corresponds to a luminosity u...

  20. An integrative multi-scale analysis of the dynamic DNA methylation landscape in aging.

    Directory of Open Access Journals (Sweden)

    Tian Yuan

    2015-02-01

    Full Text Available Recent studies have demonstrated that the DNA methylome changes with age. This epigenetic drift may have deep implications for cellular differentiation and disease development. However, it remains unclear how much of this drift is functional or caused by underlying changes in cell subtype composition. Moreover, no study has yet comprehensively explored epigenetic drift at different genomic length scales and in relation to regulatory elements. Here we conduct an in-depth analysis of epigenetic drift in blood tissue. We demonstrate that most of the age-associated drift is independent of the increase in the granulocyte to lymphocyte ratio that accompanies aging and that enrichment of age-hypermethylated CpG islands increases upon adjustment for cellular composition. We further find that drift has only a minimal impact on in-cis gene expression, acting primarily to stabilize pre-existing baseline expression levels. By studying epigenetic drift at different genomic length scales, we demonstrate the existence of mega-base scale age-associated hypomethylated blocks, covering approximately 14% of the human genome, and which exhibit preferential hypomethylation in age-matched cancer tissue. Importantly, we demonstrate the feasibility of integrating Illumina 450k DNA methylation with ENCODE data to identify transcription factors with key roles in cellular development and aging. Specifically, we identify REST and regulatory factors of the histone methyltransferase MLL complex, whose function may be disrupted in aging. In summary, most of the epigenetic drift seen in blood is independent of changes in blood cell type composition, and exhibits patterns at different genomic length scales reminiscent of those seen in cancer. Integration of Illumina 450k with appropriate ENCODE data may represent a fruitful approach to identify transcription factors with key roles in aging and disease.

  1. Microstructural Influence on Dynamic Properties of Age Hardenable FeMnAl Alloys

    Science.gov (United States)

    2011-04-01

    dependent on the separation distance between the two crystal slabs and modeled using the universal binding energy relation ( UBER ) 28, 29: GC (x... UBER fit results for pure Fe3AlC gave a cleavage energy of GC=5.04 J/m2 and an ideal stress ζ max=40 GPa with the maximum stress and separation...distance λ at 163 0.46 Å, which corresponds to an ideal strain of 12.3%. The UBER fit results for a phosphorus doped Fe3AlC supercell showed that the

  2. Cerebrospinal fluid production and dynamics in normal aging: a MRI phase-mapping study

    DEFF Research Database (Denmark)

    Gideon, P; Thomsen, C; Ståhlberg, F

    1994-01-01

    Magnetic resonance imaging (MRI) phase mapping was used for non-invasive evaluation of the to-and-fro motion of cerebrospinal fluid (CSF) in the cerebral aqueduct, and to measure the supratentorial CSF production in vivo, in 13 healthy volunteers to determine whether normal aging affects...... these parameters. Eight young healthy volunteers (mean age 29.8 years) and five elderly healthy volunteers (mean age 69.0 years) were examined, all were normal on conventional MRI. Slightly higher aqueductal CSF peak flow velocities and peak volume flow in both the caudal and rostral directions were found...... in fact occurs at this relatively high rate. Our study further suggests that the differences found in human CSF production rates are caused by interindividual factors other than age....

  3. X-ray diffraction analysis and metal physics modeling of static strain aging and thermal dislocation recovery in the mechanically affected zone of surface finished hardened steel

    Energy Technology Data Exchange (ETDEWEB)

    Gegner, Juergen [SKF GmbH, Dept. of Material Physics, Schweinfurt (Germany)

    2009-07-01

    After heat treatment, finish machining of the hardened steel represents the last manufacturing step of machine elements. The practically most important operation of grinding is applied to achieve edge zone compressive residual stresses, best surface quality and dimensional accuracy. Metal removal involves high plastic deformation work. Glide and intersection processes raise the density and produce lower energy substructures of dislocations. The temperature and time behavior of post-machining thermal treatment is analyzed on ground and honed martensitic SAE 52100 rolling bearing steel. Microstructure stabilization is reflected in a large XRD line width decrease on the surface. The kinetics is modeled by rate-controlling carbide dissolution as the carbon source for Cottrell-type segregation at dislocations. This static strain aging is verified by the formation of a slight white etching surface layer. The metal physics model is extended to also consider superimposed thermal dislocation recovery. Both effects are separable. In rolling contact fatigue tests under mixed friction running conditions, air reheating of the samples below the tempering temperature, which avoids hardness loss, leads to a significant lifetime increase. Thermal post-treatment after cold working results in similar changes of the XRD line width in the larger mechanically affected edge zone.

  4. Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

    NARCIS (Netherlands)

    Khan, S. A.; Kjeldsen, K. K.; Kjaer, K. H.; Bevan, S.; Luckman, A.; Aschwanden, A.; Bjork, A. A.; Korsgaard, N. J.; Box, J. E.; van den Broeke, M.; van Dam, T. M.; Fitzner, A.

    2014-01-01

    Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance on the decadal scale. To improve the

  5. The influence of strain localisation on spine extrusion dynamics during the 1991-1995 eruption at Unzen volcano (Japan)

    Science.gov (United States)

    Wallace, Paul A.; Kendrick, Jackie E.; Ashworth, James D.; Coats, Rebecca; Lamb, Oliver; Miwa, Takahiro; Mariani, Elisabetta; Lavallée, Yan

    2017-04-01

    The eruption of highly viscous magma at lava domes is commonly followed by the extrusion of a spine, a typical manifestation of waning activity marking the cessation of a prolonged eruptive episode. Exogenous dome growth can lead to catastrophic consequences on overall dome stability and thus its understanding is central to the mitigation of associated risks. Spine extrusion during the final stages of the 1991-95 lava dome eruption at Unzen volcano (Japan) has provided a unique opportunity to investigate the contribution of the different deformation textures and varying petrological phenomena associated with magma ascent. The protraction of this dense magmatic plug formed a 6 m wide shear zone consisting of four structurally discrete units including gouge (1), a highly sheared zone (2) to a moderately sheared zone (3) and an undeformed magmatic core (4). We present the first systematic study of the microstructures, mineralogy, crystal stability, geochemistry and crystal size distribution across this shear zone. The data is complimented by laboratory permeability measurements and seismic observations over the extrusion period. The crystal-rich (˜70 vol.%) dacitic spine preserves an abundant record of both brittle and ductile deformation. Gouge material is dominated by cataclastic microstructures with comminution of crystals and formation of conjugate microfractures, a result of loss of cohesion due to friction along the fault. A decrease in crystal size and circularity with increasing shear indicates brittle processes dominate near the spine margins. The porous network varies significantly with pore size decreasing with increasing shear, a result of shear-enhanced compaction, consistent with a decrease in permeability of one order of magnitude. The interaction of crystals (via strain-partitioning) further facilitates in localising stress and strain along the conduit margin leading to crystal-plastic deformation. Electron backscatter diffraction (EBSD) enables the

  6. Modelling the transmission dynamics of cystic echinococcosis in donkeys of different ages from Tunisia.

    Science.gov (United States)

    Lahmar, Samia; Boufana, Belgees; Jebabli, Leila; Craig, Phillip S; Ayari, Hayet; Basti, Talha; Dhibi, Mokhtar; Torgerson, Paul R

    2014-09-15

    During the period from March 2006 to July 2009 a total of 2040 slaughtered donkeys were examined for cystic echinococcosis (CE). CE prevalence in donkeys was 8.48% and the infection pressure (0.0088 infections per year) and infection rate (0.0448 cysts per year) appeared to be lower than those previously reported for cattle, sheep, dromedaries and goats in Tunisia. However, the number of cysts per infection was relatively high (5.07 cysts per infection). Among the 901 collected hydatid cysts the majority were located in the liver (89.9%), 10.09% in the lungs and 4.77% were fertile (43/901). The amplification of a fragment within the mitochondrial gene coding for cytochrome c oxidase subunit 1 (cox1) revealed that donkeys were infected with both Echinococcus equinus (horse strain, G4 genotype) and Echinococcus granulosus (sheep strain, G1 genotype). E. granulosus G1 developed into fertile cysts (15,112 protoscoleces/ml) with a protoscoleces viability of 65.78%. This investigation is the first detailed epidemiological report on cystic echinococcosis infection in donkeys for any endemic region.

  7. The Effect Of Strain Rate On The Mechanical Properties And Microstructure Of The High-Mn Steel After Dynamic Deformation Tests

    Directory of Open Access Journals (Sweden)

    Jabłońska M.B.

    2015-06-01

    Full Text Available The paper presents results of dynamic tensile investigations of high-manganese Fe – 20 wt.% Mn – 3 wt.% Al – 3 wt.% Si – 0.2 wt.% steel. The research was carried out on a flywheel machine, which enables to perform dynamic tensile tests and impact bending with a linear velocity of the enforcing element in the range of 5÷40 m/s. It was found that the studied steel was characterized by very good mechanical properties. Strength of the tested materials was determined in the static tensile test and dynamic deformation test, while its hardness was measured with the Vickers hardness test method. The surface of fractures that were created in the areas where the sample was torn were analyzed. These fractures indicate the presence of transcrystalline ductile fractures. Fractographic tests were performed with the use of a scanning electron microscope. The structure was analyzed by light optical microscopy. Substructure studies revealed occurrence of mechanical twinning induced by high strain rates. A detailed analysis of the structure was performed with the use of a transmission scanning electron microscope STEM.

  8. Identifying dysfunctional cortex: Dissociable effects of stroke and aging on resting state dynamics in MEG and fMRI

    Directory of Open Access Journals (Sweden)

    Aneta eKielar

    2016-03-01

    Full Text Available Spontaneous signals in neuroimaging data may provide information on cortical health in disease and aging, but the relative sensitivity of different approaches is unknown. In the present study, we compared different but complementary indicators of neural dynamics in resting-state MEG and BOLD fMRI, and their relationship with blood flow. Participants included patients with post-stroke aphasia, age-matched controls, and young adults. The complexity of brain activity at rest was quantified in MEG using spectral analysis and multiscale entropy (MSE measures, whereas BOLD variability was quantified as the standard deviation (SDBOLD, mean squared successive difference (MSSD and sample entropy of the BOLD time series. We sought to assess the utility of signal variability and complexity measures as markers of age-related changes in healthy adults and perilesional dysfunction in chronic stroke. The results indicate that reduced BOLD variability is a robust finding in aging, whereas MEG measures are more sensitive to the cortical abnormalities associated with stroke. Furthermore, reduced complexity of MEG signals in perilesional tissue were correlated with hypoperfusion as assessed with arterial spin labeling, while no such relationship was apparent with BOLD variability. These findings suggest that MEG signal complexity offers a sensitive index of neural dysfunction in perilesional tissue in chronic stroke, and that these effects are clearly distinguishable from those associated with healthy aging.

  9. Identifying Dysfunctional Cortex: Dissociable Effects of Stroke and Aging on Resting State Dynamics in MEG and fMRI.

    Science.gov (United States)

    Kielar, Aneta; Deschamps, Tiffany; Chu, Ron K O; Jokel, Regina; Khatamian, Yasha B; Chen, Jean J; Meltzer, Jed A

    2016-01-01

    Spontaneous signals in neuroimaging data may provide information on cortical health in disease and aging, but the relative sensitivity of different approaches is unknown. In the present study, we compared different but complementary indicators of neural dynamics in resting-state MEG and BOLD fMRI, and their relationship with blood flow. Participants included patients with post-stroke aphasia, age-matched controls, and young adults. The complexity of brain activity at rest was quantified in MEG using spectral analysis and multiscale entropy (MSE) measures, whereas BOLD variability was quantified as the standard deviation (SDBOLD), mean squared successive difference (MSSD), and sample entropy of the BOLD time series. We sought to assess the utility of signal variability and complexity measures as markers of age-related changes in healthy adults and perilesional dysfunction in chronic stroke. The results indicate that reduced BOLD variability is a robust finding in aging, whereas MEG measures are more sensitive to the cortical abnormalities associated with stroke. Furthermore, reduced complexity of MEG signals in perilesional tissue were correlated with hypoperfusion as assessed with arterial spin labeling (ASL), while no such relationship was apparent with BOLD variability. These findings suggest that MEG signal complexity offers a sensitive index of neural dysfunction in perilesional tissue in chronic stroke, and that these effects are clearly distinguishable from those associated with healthy aging.

  10. Association of IL-8-inducing strains of diffusely adherent Escherichia coli with sporadic diarrheal patients with less than 5 years of age

    OpenAIRE

    Ismail Mustafa Meraz; Kentaro Arikawa; Hiromi Nakamura; Jun Ogasawara; Atsushi Hase; Yoshikazu Nishikawa

    2007-01-01

    The role of diffusely adherent Escherichia coli (DAEC) in diarrheal disease has been controversial. However, DAEC strains were recently implicated in diarrheal disease in developing countries. To clarify whether DAEC are prevalent among sporadic cases of diarrheal illness in Osaka City, Japan, E. coli strains isolated between July 1997 and March 2000 during diarrheagenic E. coli (DEC) investigation were retrospectively examined. DAEC strains were recognized among 41 (4.4%) of 924 patients and...

  11. Compositional dynamics of the human intestinal microbiota with aging: implications for health.

    Science.gov (United States)

    Lakshminarayanan, B; Stanton, C; O'Toole, P W; Ross, R P

    2014-11-01

    The human gut contains trillions of microbes which form an essential part of the complex ecosystem of the host. This microbiota is relatively stable throughout adult life, but may fluctuate over time with aging and disease. The gut microbiota serves a number of functions including roles in energy provision, nutrition and also in the maintenance of host health such as protection against pathogens. This review summarizes the age-related changes in the microbiota of the gastrointestinal tract (GIT) and the link between the gut microbiota in health and disease. Understanding the composition and function of the gut microbiota along with the changes it undergoes overtime should aid the design of novel therapeutic strategies to counteract such alterations. These strategies include probiotic and prebiotic preparations as well as targeted nutrients, designed to enrich the gut microbiota of the aging population.

  12. [Age dynamics of population gene pool of the Crimean pine (Pinus pallasiana D. Don) in Crimea].

    Science.gov (United States)

    Korshikov, I I; Mudrik, E A; Krasnoshtan, O V; Velikorid'ko, T I; Kalafat, L A; Podgornyĭ, D Iu

    2011-01-01

    Polymorphism of young (14-16 years), middle-aged (70-80 years) and old (120-150 years) plants and their seed embryos has been studied using 20 and 10 allozyme loci correspondingly in the population of Pinus pallasiana D. Don from Mountain Crimea. It was revealed that the old-aged trees had significantly lower level of expected heterozygosity than the young plants. The level of observed heterozygosity of embryos of the uneven-aged plants was slightly different among the embryo samples and significantly lower than in the samples of maternal trees. Supernumerary homozygotation of the embryos is caused by low level of cross-pollination in three studied samples of plants (t(m) = 0,537-0,637).

  13. Dynamics of telomere length in different age groups in a Latvian population.

    Science.gov (United States)

    Zole, Egija; Pliss, Liana; Ranka, Renate; Krumina, Astrida; Baumanis, Viesturs

    2013-12-01

    The shortening of telomeres with ageing is a well-documented observation; however, the reported number of nucleotides in telomeres varies between different laboratories and studies. Such variability is likely caused by ethnic differences between the populations studied. Until now, there were no studies that investigated the variability of telomere length in a senescent Latvian population of the most common mitochondrial haplogroups, defined as H (45%), U (25%), Y chromosomal N1c (40%) and R1a1 (40%). Telomere length was determined in 121 individuals in different age groups, including a control group containing individuals of 20-40 years old and groups of individuals between 60-70 years old, 71-80 years old, 81-90 years old, and above 90 years old. Telomere length was determined using the Southern blot telomeric restriction fragment assay (TRF). Decreased telomere length with ageing was confirmed, but a comparison of centenarians and individuals between 60-90 years of age did not demonstrate a significant difference in telomere length. However, significant variability in telomere length was observed in the control group, indicating probable rapid telomere shortening in some individuals that could lead up to development of health status decline appearing with ageing. Telomere length measured in mononuclear blood cells (MNC) was compared with the telomere length measured in whole peripheral white blood cells (WBC) using TRF. Telomere length in MNC was longer than in WBC for the control group with individuals 20 to 40 years old; in contrast, for the group of individuals aged 65 to 85 years old, measured telomere length was shorter in MNC when compared to WBC.

  14. Intermittency at critical transitions and aging dynamics at the onset of chaos

    Indian Academy of Sciences (India)

    A Robledo

    2005-06-01

    We recall that at both the intermittency transitions and the Feigenbaum attractor, in unimodal maps of non-linearity of order > 1, the dynamics rigorously obeys the Tsallis statistics. We account for the -indices and the generalized Lyapunov coefficients that characterize the universality classes of the pitchfork and tangent bifurcations. We identify the Mori singularities in the Lyapunov spectrum at the onset of chaos with the appearance of a special value for the entropic index . The physical area of the Tsallis statistics is further probed by considering the dynamics near criticality and glass formation in thermal systems. In both cases a close connection is made with states in unimodal maps with vanishing Lyapunov coefficients.

  15. Aberrant Neuronal Dynamics during Working Memory Operations in the Aging HIV-Infected Brain

    Science.gov (United States)

    Wilson, Tony W.; Proskovec, Amy L.; Heinrichs-Graham, Elizabeth; O’Neill, Jennifer; Robertson, Kevin R.; Fox, Howard S.; Swindells, Susan

    2017-01-01

    Impairments in working memory are among the most prevalent features of HIV-associated neurocognitive disorders (HAND), yet their origins are unknown, with some studies arguing that encoding operations are disturbed and others supporting deficits in memory maintenance. The current investigation directly addresses this issue by using a dynamic mapping approach to identify when and where processing in working memory circuits degrades. HIV-infected older adults and a demographically-matched group of uninfected controls performed a verbal working memory task during magnetoencephalography (MEG). Significant oscillatory neural responses were imaged using a beamforming approach to illuminate the spatiotemporal dynamics of neuronal activity. HIV-infected patients were significantly less accurate on the working memory task and their neuronal dynamics indicated that encoding operations were preserved, while memory maintenance processes were abnormal. Specifically, no group differences were detected during the encoding period, yet dysfunction in occipital, fronto-temporal, hippocampal, and cerebellar cortices emerged during memory maintenance. In addition, task performance in the controls covaried with occipital alpha synchronization and activity in right prefrontal cortices. In conclusion, working memory impairments are common and significantly impact the daily functioning and independence of HIV-infected patients. These impairments likely reflect deficits in the maintenance of memory representations, not failures to adequately encode stimuli. PMID:28155864

  16. Dynamic Changes of Pulmonary Arterial Pressure and Ductus Arteriosus in Human Newborns From Birth to 72 Hours of Age

    OpenAIRE

    2016-01-01

    Abstract Normal pulmonary artery pressure and pulmonary hypertension assessment of newborns is rarely reported. The aim of the study is to explore dynamic changes of pulmonary arterial pressure and ductus arteriosus in human newborns from birth to 72 h of age with echocardiography. A total of 76 cases of normal newborns were prospectively detected by echocardiography after birth of 2 h, 6 h, 12 h, 24 h, 48 h, and 72 h, respectively. Ductus arteriosus diameter, blood shunt direction, blood flo...

  17. Photo-dynamics of the lyophilized photo-activated adenylate cyclase NgPAC2 from the amoeboflagellate Naegleria gruberi NEG-M strain

    Science.gov (United States)

    Penzkofer, A.; Tanwar, M.; Veetil, S. K.; Kateriya, S.; Stierl, M.; Hegemann, P.

    2013-09-01

    The absorption and emission spectroscopic behavior of lyophilized photo-activated adenylate cyclase NgPAC2 from the amoeboflagellate Naegleria gruberi NEG-M strain consisting of a BLUF domain (BLUF = Blue Light sensor Using Flavin) and a cyclase homology domain was studied in the dark, during blue-light exposure and after blue-light exposure at a temperature of 4 °C. The BLUF domain photo-cycle dynamics observed for snap-frozen NgPAC2 was lost by lyophilization (no signaling state formation with flavin absorption red-shift). Instead, blue-light photo-excitation of lyophilized NgPAC2 caused sterically restricted Tyr-Tyr cross-linking (o,o‧-ditysosine formation) and partial flavin cofactor reduction.

  18. Backbone dynamics of a bacterially expressed peptide from the receptor binding domain of Pseudomonas aeruginosa pilin strain PAK from heteronuclear 1H-15N NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, A. Patricia [University of Washington, Department of Medicinal Chemistry, School of Pharmacy (United States); Spyracopoulos, Leo [Department of Biochemistry (Canada); Irvin, Randall T. [University of Alberta, Department of Medical Microbiology and Immunology (Canada); Sykes, Brian D. [Department of Biochemistry (Canada)

    2000-07-15

    The backbone dynamics of a {sup 15}N-labeled recombinant PAK pilin peptide spanning residues 128-144 in the C-terminal receptor binding domain of Pseudomonas aeruginosa pilin protein strain PAK (Lys{sup 128}-Cys-Thr-Ser-Asp-Gln-Asp-Glu-Gln-Phe-Ile-Pro-Lys-Gly-Cys-Ser-Lys{sup 144}) were probed by measurements of {sup 15}N NMR relaxation. This PAK(128-144) sequence is a target for the design of a synthetic peptide vaccine effective against multiple strains of P. aeruginosa infection. The {sup 15}N longitudinal (T{sub 1}) and transverse (T{sub 2}) relaxation rates and the steady-state heteronuclear {l_brace}{sup 1}H{r_brace}-{sup 15}N NOE were measured at three fields (7.04, 11.74 and 14.1 Tesla), five temperatures (5, 10, 15, 20, and 25 deg. C ) and at pH 4.5 and 7.2. Relaxation data was analyzed using both the 'model-free' formalism [Lipari, G. and Szabo, A. (1982) J. Am. Chem. Soc., 104, 4546-4559 and 4559-4570] and the reduced spectral density mapping approach [Farrow, N.A., Szabo, A., Torchia, D.A. and Kay, L.E. (1995) J. Biomol. NMR, 6, 153-162]. The relaxation data, spectral densities and order parameters suggest that the type I and type II {beta}-turns spanning residues Asp{sup 134}-Glu-Gln-Phe{sup 137} and Pro{sup 139}-Lys-Gly-Cys{sup 142}, respectively, are the most ordered and structured regions of the peptide. The biological implications of these results will be discussed in relation to the role that backbone motions play in PAK pilin peptide immunogenicity, and within the framework of developing a pilin peptide vaccine capable of conferring broad immunity across P. aeruginosa strains.

  19. Understanding misfit strain releasing mechanisms via molecular dynamics simulations of CdTe growth on {112}zinc-blende CdS

    Science.gov (United States)

    Zhou, X. W.; Chavez, J. J.; Almeida, S.; Zubia, D.

    2016-07-01

    Molecular dynamics simulations have been used to analyse microstructures of CdTe films grown on {112} surfaces of zinc-blende CdS. Interestingly, CdTe films grow in ⟨331⟩ orientations as opposed to ⟨112⟩ epitaxial orientations. At the CdTe-{331}/CdS-{112} interface, however, there exists an axis that is parallel to the ⟨110⟩ orientation of both CdS and CdTe. It is the direction orthogonal to this ⟨110⟩ that becomes different, being ⟨116⟩ for CdTe and ⟨111⟩ for CdS, respectively. Missing CdTe-{110} planes are found along the ⟨110⟩ axis, suggesting that the misfit strain is released by the conventional misfit dislocation mechanism along this axis. In the orthogonal axis, the misfit strain is found to be more effectively released by the new grain orientation mechanism. Our finding is supported by literature experimental observations of the change of growth direction when Cd0.96Zn0.04Te films are deposited on GaAs. Analyses of energetics clearly demonstrate the cause for the formation of the new orientation, and the insights gained from our studies can help understand the grain structures experimentally observed in lattice mismatched systems.

  20. Multivariate analysis of ultrasound-recorded dorsal strain sequences: Investigation of dynamic neck extensions in women with chronic whiplash associated disorders

    Science.gov (United States)

    Peolsson, Anneli; Peterson, Gunnel; Trygg, Johan; Nilsson, David

    2016-08-01

    Whiplash Associated Disorders (WAD) refers to the multifaceted and chronic burden that is common after a whiplash injury. Tools to assist in the diagnosis of WAD and an increased understanding of neck muscle behaviour are needed. We examined the multilayer dorsal neck muscle behaviour in nine women with chronic WAD versus healthy controls during the entire sequence of a dynamic low-loaded neck extension exercise, which was recorded using real-time ultrasound movies with high frame rates. Principal component analysis and orthogonal partial least squares were used to analyse mechanical muscle strain (deformation in elongation and shortening). The WAD group showed more shortening during the neck extension phase in the trapezius muscle and during both the neck extension and the return to neutral phase in the multifidus muscle. For the first time, a novel non-invasive method is presented that is capable of detecting altered dorsal muscle strain in women with WAD during an entire exercise sequence. This method may be a breakthrough for the future diagnosis and treatment of WAD.

  1. Dynamical properties of the Penna aging model applied to the population of wolves

    Science.gov (United States)

    Makowiec, Danuta

    1997-02-01

    The parameters of th Penna bit-string model of aging of biological systems are systematically tested to better understand the model itself as well as the results arising from applying this model to studies of the development of the stationary population of Alaska wolves.

  2. Seasonal dynamics and age of stemwood nonstructural carbohydrates in temperate forest trees

    Science.gov (United States)

    Andrew D. Richardson; Mariah S. Carbone; Trevor F. Keenan; Claudia I. Czimczik; David Y. Hollinger; Paula Murakami; Paul G. Schaberg; Xiaomei. Xu

    2013-01-01

    Nonstructural carbohydrate reserves support tree metabolism and growth when current photosynthates are insufficient, offering resilience in times of stress. We monitored stemwood nonstructural carbohydrate (starch and sugars) concentrations of the dominant tree species at three sites in the northeastern United States. We estimated the mean age of the starch and sugars...

  3. Dynamic Investment Behavior Taking into Account Ageing of the Capital Good

    NARCIS (Netherlands)

    Feichtinger, G.; Hartl, R.F.; Kort, P.M.; Veliov, V.

    2001-01-01

    In standard capital accumulation models all capital goods are equally productive and produce goods of the same quality.However, due to ageing, in reality it holds most of the time that newer capital goods are more productive. Implications of this feature for the firm's investment policies are invest

  4. The Technological Advent and Dynamics of the Network Society. The "Middle-Aged Approach"

    Directory of Open Access Journals (Sweden)

    Elena Mădălina Vătămănescu

    2016-08-01

    Full Text Available Nowadays, scholars have become interested in the ways new media influence young people, but its influence on middle-aged people have not been thoroughly examined. This age category is often ignored as most of the online activities are performed by young persons. New media gathers a wide range of phenomena which may become concepts of the network society through their diversity, knowledge and novelty. Interactivity is the most important characteristic, turning the user into a content creator, not just into a receiver. Moreover, what was once considered to be a personal state of mind tends to become a part of the public domain. Starting from these premises, the article advances the idea that the Internet can be beneficial not just for teenagers, but also for the middle-aged group oriented towards keeping in touch with relatives and friends and towards finding online useful information. At this level, the present paper aims to discover directions given by network society in the lives of middle-aged people. To this end, the research relies on an interview-based survey which addresses the way people may adapt to communication technology and to its particularities, exploring advantages or discovering potential drawbacks.

  5. Advanced age and the mechanics of uphill walking: a joint-level, inverse dynamic analysis.

    Science.gov (United States)

    Franz, Jason R; Kram, Rodger

    2014-01-01

    We sought to gain insight into age-related muscular limitations that may restrict the uphill walking ability of old adults. We hypothesized that: (1) old adults would exhibit smaller peak ankle joint kinetics and larger peak hip joint kinetics than young adults during both level and uphill walking and (2) these age-related differences in ankle and hip joint kinetics would be greatest during uphill vs. level walking. We quantified the sagittal plane ankle, knee, and hip joint kinetics of 10 old adults (mean ± SD, age: 72 ± 5 yrs) and 8 young adults (age: 27 ± 5 yrs) walking at 1.25 m/s on a dual-belt, force-measuring treadmill at four grades (0°, +3°, +6°, +9°). As hypothesized, old adults walked with smaller peak ankle joint kinetics (e.g., power generation: -18% at +9°) and larger peak hip joint kinetics (e.g., power generation: +119% at +9°) than young adults, most evident during the late stance phase of both level and uphill conditions. Old adults performed two to three times more single support positive work than young adults via muscles crossing the knee. In partial support of our second hypothesis, the age-related reduction in peak ankle joint moments was greater during uphill (-0.41 Nm/kg) vs. level (-0.30 Nm/kg) walking. However, old adults that exhibited reduced propulsive ankle function during level walking could perform 44% more trailing leg positive ankle joint work to walk uphill. Our findings indicate that maintaining ankle power generation and trailing leg propulsive function should be the primary focus of "prehabilitation" strategies for old adults to preserve their uphill walking ability.

  6. Nutrient concentration age dynamics of teak (Tectona grandis L.f.) plantations in Central America

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Moya, J.; Murillo, R.; Portuguez, E.; Fallas, J. L.; Rios, V.; Kottman, F.; Verjans, J. M.; Mata, R.; Alvarado, A.

    2013-05-01

    Aim of study. Appropriate knowledge regarding teak (Tectona grandis L.f.) nutrition is required for a better management of the plantations to attain high productivity and sustainability. This study aims to answer the following questions: How can it be determined if a teak tree suffers a nutrient deficiency before it shows symptoms? Are nutrient concentration decreases in older trees associated with age-related declines in forest productivity? Area of study. Costa Rica and Panama. Material and Methods. Nutrient concentration in different tree tissues (bole, bark, branches and foliage) were measured at different ages using false-time-series in 28 teak plantations Research highlights. Foliar N concentration decreases from 2.28 in year 1 to 1.76% in year 19. Foliar Mg concentration increases from 0.23 in year 1 to 0.34% in year 19. The foliar concentrations of the other nutrients are assumed to be constant with tree age: 1.33% Ca, 0.88% K, 0.16% P, 0.12% S, 130 mg kg{sup -}1 Fe, 43 mg kg{sup -}1 Mn, 11 mg kg{sup -}1 Cu, 32 mg kg{sup -}1 Zn and 20 mg kg{sup -}1 B. The nutrient concentration values showed can be taken as a reference to evaluate the nutritional status of similar teak plantations in the region. The concentrations of K, Mg and N could be associated with declines in teak plantation productivity as the plantation becomes older. Whether age-related changes in nutrient concentrations are a cause or a consequence of age-related declines in productivity is an issue for future research with the aim of achieving higher growth rates throughout the rotation period. (Author) 35 refs.

  7. Dark-ages Reionization and Galaxy formation simulation - I. The dynamical lives of high-redshift galaxies

    Science.gov (United States)

    Poole, Gregory B.; Angel, Paul W.; Mutch, Simon J.; Power, Chris; Duffy, Alan R.; Geil, Paul M.; Mesinger, Andrei; Wyithe, Stuart B.

    2016-07-01

    We present the Dark-ages Reionization and Galaxy formation Observables from Numerical Simulations (DRAGONS) programme and Tiamat, the collisionless N-body simulation programme upon which DRAGONS is built. The primary trait distinguishing Tiamat from other large simulation programme is its density of outputs at high redshift (100 from z = 35 to z = 5; roughly one every 10 Myr) enabling the construction of very accurate merger trees at an epoch when galaxy formation is rapid and mergers extremely frequent. We find that the friends-of-friends halo mass function agrees well with the prediction of Watson et al. at high masses, but deviates at low masses, perhaps due to our use of a different halo finder or perhaps indicating a break from `universal' behaviour. We then analyse the dynamical evolution of galaxies during the Epoch of Reionization finding that only a small fraction (˜20 per cent) of galactic haloes are relaxed. We illustrate this using standard relaxation metrics to establish two dynamical recovery time-scales: (i) haloes need ˜1.5 dynamical times following formation, and (ii) ˜2 dynamical times following a major (3:1) or minor (10:1) merger to be relaxed. This is remarkably consistent across a wide mass range. Lastly, we use a phase-space halo finder to illustrate that major mergers drive long-lived massive phase-space structures which take many dynamical times to dissipate. This can yield significant differences in the inferred mass build-up of galactic haloes and we suggest that care must be taken to ensure a physically meaningful match between the galaxy formation physics of semi-analytic models and the halo finders supplying their input.

  8. Determination of dynamic fracture initiation toughness of elastic-plastic materials at intermediate strain rates; Obtencion de la tenacidad de fractura dinamica de iniciacion de materiales elastolasticos a velocidad de deformacion intermedias

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Saez, J.; Luna de, S.; Rubio, L.; Perez-Castellanos, J. L.; Navarro, C.

    2001-07-01

    An earlier paper dealt with the experimental techniques used to determine the dy