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Hardening
Kinds of Hardening Terms modified by Hardening Selected AbstractsComponents of Pink Snow Mould Resistance in Winter Wheat are Expressed Prior to Cold Hardening and in Detached LeavesJOURNAL OF PHYTOPATHOLOGY, Issue 3 2006Å. Ergon Abstract Resistance to pink snow mould, caused by Microdochium nivale, was investigated in four resistant winter wheat lines from the USDA World Cereal Collection (CI9342, CI14106, PI173440 and PI181268) and three Nordic wheat lines (Bjørke, Rida and V1004). Pink snow mould resistance was tested in non-hardened and cold-hardened plants incubated under artificial snow cover and in detached leaf segments mounted on water agar and incubated at either 3°C in darkness or at room temperature with light during the day. The wheat lines CI9342, CI14106 and PI181268 were more resistant than the Nordic lines, both before and after cold hardening. Thus, although cold hardening strongly increases the level of snow mould resistance in all the wheat lines, some resistance mechanisms are also present prior to cold hardening in some of the resistant lines. CI9342, CI14106 and PI181268 also had a higher level of resistance than the other lines in the detached leaf assay, indicating that these lines have some resistance mechanisms acting in the leaves. The resistance of PI173440 was expressed only in intact hardened plants and not in non-hardened plants or in detached leaves. This indicates that this line relies on cold hardening-related changes in the crown for its resistance. In the detached leaf assay the rate of lesion development varied greatly between leaves of different order. The highest correlation with the whole plant test was obtained when using secondary leaves and incubation at 3°C in the dark. [source] Hardening of Small Components with High-Power Diode LasersLASER TECHNIK JOURNAL, Issue 5 2010Most efficient laser source for selective changes of surface properties Hardening of metal parts is a common way to change properties of the material. Surface layer hardening processes are increasing the resistance against friction or pressure force loads. Conventional surface layer hardening processes are flame hardening or induction hardening. Hardening with a diode laser is an additional process that offers various advantages. [source] Strain Hardening of Red Blood Cells by Accumulated Cyclic Supraphysiological StressARTIFICIAL ORGANS, Issue 1 2007Sung S. Lee Abstract:, The effect of elevated shear stress upon cellular trauma has been studied for many years, but the effect of long-term cyclic stress trauma on hemorheology has never been explored systematically. This study investigated sublytic trauma of red blood cells (RBCs) caused by repeated exposure to shear stress. A suspension of bovine blood was throttled through a capillary tube (inner diameter 1 mm and length 70 mm) connected to a recirculating flow loop. Samples were withdrawn every 30 min to measure deformability and characteristic time. The deformability of the cell was measured microscopically by observing the shape of the cell during the shear flow. It was found that cyclic shear irreversibly stiffened the cell membrane while the effect was not so much as that of continuous shear. The cell deformability was dramatically reduced by 73% when the stress of 300 Pa was applied for 288 s, while it was 7% under 90 Pa. These results elucidate the need for improved models to predict cellular trauma within the unsteady flow environment of mechanical circulatory assist devices. [source] High Density Cascaded Arc Produced Plasma Expanding in a Low Pressure RegionCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2004R. P. Dahiya Abstract Experimental measurements made in thermal expanding argon, nitrogen and hydrogen plasmas with particular reference to molecular kinetics, surface nitriding and intense flux in magnetic field are discussed. The plasma is generated in a cascaded arc source. In the presence of molecular species (H2 / N2) dissociative recombination reactions involving rovibrationally excited molecules contribute to a rapid decay of the plasma species, especially for hydrogen system. A combination of nitrogen and hydrogen plasma gives an efficient plasma nitriding process, which has been applied for case hardening of machinery components. In another setup a strong axial magnetic field (0.4 - 1.6 T) contains and substantially prolongs the plasma beam in the chamber. In the presence of the magnetic field, an additional current drawn through the plasma beam using a biased substrate and a ring creates dense low temperature plasma giving a new unexplored plasma regime. The plasma kinetics are modified in this regime from the recombining to the ionising mode. When the additional current in the argon plasma beam exceeds 30 A, its light emission is predominantly in the blue region. With the additional current and magnetic field, the emission intensity of H, and other lines arising from higher energy levels in the hydrogen Balmer series is enhanced. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] GUARDIANSHIP IN CONTEXT: IMPLICATIONS FOR BURGLARY VICTIMIZATION RISK AND PREVENTION,CRIMINOLOGY, Issue 4 2007PAMELA WILCOX Survey data from 4,227 Seattle residents nested within 100 "neighborhoods" (census tracts) were analyzed to discern interrelationships between various dimensions of individual-level and neighborhood-level guardianship. We focused on four dimensions of guardianship,physical (target hardening), personal (home occupancy), social (informal control), and natural (surveillance through environmental design),at both individual and neighborhood levels. A multilevel opportunity, theoretical framework guided hypotheses, which suggests that each of the four dimensions of individual guardianship would be related more negatively to burglary as each of the four dimensions of aggregate guardianship increased. Multilevel logistic regression analysis revealed support for many of such hypothesized moderating effects of aggregate guardianship. More specifically, 6 of the 16 possible interaction effects were statistically significant at the .05 level and an additional 3 interaction effects were significant at the .10 level. In particular, individuallevel target hardening, place management, and natural surveillancewere related more negatively to burglary as neighborhood-level target hardening increased, as neighborhood-level informal social control increased, and as neighborhood-level natural surveillance increased. [source] Direct estimation of the seismic demand and capacity of oscillators with multi-linear static pushovers through IDA,EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2006Dimitrios Vamvatsikos Abstract SPO2IDA is introduced, a software tool that is capable of recreating the seismic behaviour of oscillators with complex quadrilinear backbones. It provides a direct connection between the static pushover (SPO) curve and the results of incremental dynamic analysis (IDA), a computer-intensive procedure that offers thorough demand and capacity prediction capability by using a series of nonlinear dynamic analyses under a suitably scaled suite of ground motion records. To achieve this, the seismic behaviour of numerous single-degree-of-freedom (SDOF) systems is investigated through IDA. The oscillators have a wide range of periods and feature pinching hysteresis with backbones ranging from simple bilinear to complex quadrilinear with an elastic, a hardening and a negative-stiffness segment plus a final residual plateau that terminates with a drop to zero strength. An efficient method is introduced to treat the backbone shape by summarizing the analysis results into the 16, 50 and 84% fractile IDA curves, reducing them to a few shape parameters and finding simpler backbones that reproduce the IDA curves of complex ones. Thus, vast economies are realized while important intuition is gained on the role of the backbone shape to the seismic performance. The final product is SPO2IDA, an accurate, spreadsheet-level tool for performance-based earthquake engineering that can rapidly estimate demands and limit-state capacities, strength reduction R -factors and inelastic displacement ratios for any SDOF system with such a quadrilinear SPO curve. Copyright © 2006 John Wiley & Sons, Ltd. [source] Test on full-scale three-storey steel moment frame and assessment of ability of numerical simulation to trace cyclic inelastic behaviourEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2006Masayoshi Nakashima Abstract A test on a full-scale model of a three-storey steel moment frame was conducted, with the objectives of acquiring real information about the damage and serious strength deterioration of a steel moment frame under cyclic loading, studying the interaction between the structural frame and non-structural elements, and examining the capacity of numerical analyses commonly used in seismic design to trace the real cyclic behaviour. The outline of the test structure and test program is presented, results on the overall behaviour are given, and correlation between the experimental results and the results of pre-test and post-test numerical analyses is discussed. Pushover analyses conducted prior to the test predicted the elastic stiffness and yield strength very reasonably. With proper adjustment of strain hardening after yielding and composite action, numerical analyses were able to accurately duplicate the cyclic behaviour of the test structure up to a drift angle of 1/25. The analyses could not trace the cyclic behaviour involving larger drifts in which serious strength deterioration occurred due to fracture of beams and anchor bolts and progress of column local buckling. Copyright © 2005 John Wiley & Sons, Ltd. [source] Monotonic and Cyclic Deformation Behaviour of the SiC Particle-Reinforced Aluminium Matrix Composite AMC225xe,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Marek Smaga The monotonic and cyclic deformation behaviour of the aluminium matrix composite AMC225xe , i.e., the aerospace grade aluminium alloy AA 2124 reinforced with 25,vol.-% ultrafine SiC particles , is characterised in detail on the basis of mechanical stress,strain hysteresis curves as well as temperature and electrical resistance measurements. A pronounced difference in plastic strain response is observed between tension and compression under monotonic and cyclic loading. In fully reversed stress-controlled constant amplitude tests, negative plastic mean strains developed. The cyclic deformation behaviour of AMC225xe is characterised by pronounced initial cyclic hardening. The endurance limit is reliably estimated in continuous load increase tests. In particular, electrical resistance data are used as input parameters for fatigue life calculations analogous to the Basquin equation. Microstructural details are investigated by light and scanning electron microscopy. [source] The Precipitation Behavior of Superalloy ATI Allvac 718PlusADVANCED ENGINEERING MATERIALS, Issue 3 2010Gerald A. Zickler Abstract ATI Allvac 718Plus is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace gas turbines. The precipitation kinetics of the intermetallic , (Ni3Nb) and ,, (Ni3(Al,Ti)) phases in this alloy are of scientific as well as technological interest because of their significant influence on the mechanical properties. Important parameters like grain size are controlled by coarse , precipitates located at grain boundaries, whereas small ,, precipitates are responsible for strengthening by precipitation hardening. In the present study, the microstructure is investigated by three-dimensional atom probe tomography and simulated by computer modeling using the thermo-kinetic software MatCalc. The results of numerical simulations and experimental data are compared and critically discussed. It is shown that the chemical compositions of the phases change during isothermal aging, and the precipitation kinetics of , and ,, phases interact with each other as shown in a time temperature precipitation (TTP) plot. The TTP plot shows C-shaped curves with characteristic discontinuities in the temperature range, where simultaneous and concurrent precipitation of the , and ,, phases occurs. This leads to a competition in the diffusion of Nb and Al, which are partly present in both phases. Thus, the present study gives important information on heat treatments for ATI Allvac 718Plus in order to achieve the desired microstructure and mechanical properties. [source] Metastable Austenite in 17,4 Precipitation-Hardening Stainless Steel Produced by Selective Laser MeltingADVANCED ENGINEERING MATERIALS, Issue 3 2010Luca Facchini Abstract A 17,4 precipitation-hardening stainless steel produced by selective laser melting contains 72% metastable and heavily faulted austenite and 28% highly dislocated and twinned martensite. The mechanical behavior is characterized by exceptional work hardening and a two-step plastic field, which are due to the strain-induced transformation of austenite and to the structural characteristics of the deformed austenite and martensite. Both phases tend to accumulate stacking faults in the first step and twins in the second. [source] An Overview of the Anatomy of Crystal Plasticity ModelsADVANCED ENGINEERING MATERIALS, Issue 9 2009Georges Cailletaud Abstract Single crystals, polycrystals, and DS alloys can be modeled in the same framework by means of crystal plasticity. This paper wants to show the common features of the different approaches on the grain level, and the additional assumptions that are needed to derive polycrystal or DS models. Phenomenological rules are introduced for representing the hardening in the single crystal constitutive equations. Series of examples are given to illustrate the capabilities of the various approaches that are mainly related to the crystallographic character, and to the fact that the macroscopic yield locus is not predefined, but built from a collection of linear yield conditions. [source] Assessment of a Micro,Macro Modeling of the Bending and Unbending of Multiphase Steel Sheets,ADVANCED ENGINEERING MATERIALS, Issue 3 2009Laurent Delannay Dual phase steels and TRIP steels demonstrate complex mechanical responses whenever metal forming operations involve load reversals. The present study addresses this phenomenon using an experimental set-up which ensures pure bending and unbending of thin sheets. The proposed incremental mean-field theory produces valid predictions of the transient mechanical responses by accounting for the kinematical hardening of individual phases as well as the phase partitioning of plastic strain. [source] Influence of Ti on the Mechanical Properties of AgCuInTi Active Brazing Fillers,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2009Matteo Galli Active brazing fillers were produced by adding Ti to a AgCuIn alloy and used to fabricate ceramic-metal joints. The alloy was investigated by hardness measurements and microscopy analyses and the joints tested in bending. The results show that Ti has a hardening effect. However, for the considered values of Ti addition (0.5,1.5 wt %), the extent of the hardening is insignificantly influenced by the Ti introduced in the filler. [source] 3D Powder Printing of ,-Tricalcium Phosphate Ceramics Using Different Strategies,ADVANCED ENGINEERING MATERIALS, Issue 12 2008E. Vorndran Custom made macroporous ,-tricalcium phosphate (,-TCP) bone substitutes were fabricated using 3D powder printing comparing three different preparation strategies. Samples fabricated using a novel hydraulic cement setting reaction showed the best printing resolution and highest mechanical performance. This method is a significant step forward in producing ,-TCP monoliths by rapid prototyping and would decrease processing time for commercial fabrication due to their rapid hardening and ease of handling. [source] Age-hardening Response of Replicated Microcellular Al-4.5%Cu,ADVANCED ENGINEERING MATERIALS, Issue 9 2008Y. Conde We study the response to age hardening of Al-4.5%Cu replicated foams having 75 and 400 ,m diameter cells and of relative density between 0.1 and 0.32, to show that the age-hardening response can depend on the cell size and morphology, and that open-celled replicated high-strength aluminium alloy foams can be made as strong as commercial closed-celled aluminium foams despite their inferior mesostructural features. [source] Strain Hardening Behavior of Ultrafine- Grained Cu by Analyzing the Tensile Stress-Strain Curve,ADVANCED ENGINEERING MATERIALS, Issue 5 2008C.-X. Huang UFG Cu was found to experience two stages of strain hardening processes under uniaxial tensile stress, which was similar to the Stage,IV and V of CG Cu after large plastic deformation. The storage of dislocations in small grains and dynamic recovery caused by annihilation of dislocations and GB-mediated processes were responsible for the different stages of strain hardening behavior. Improvement of strain hardening capability for UFG metals should be based on the mechanisms of strain hardening. [source] PERSPECTIVE: GENETIC ASSIMILATION AND A POSSIBLE EVOLUTIONARY PARADOX: CAN MACROEVOLUTION SOMETIMES BE SO FAST AS TO PASS US BY?EVOLUTION, Issue 7 2003Massimo Pigliucci Abstract., The idea of genetic assimilation, that environmentally induced phenotypes may become genetically fixed and no longer require the original environmental stimulus, has had varied success through time in evolutionary biology research. Proposed by Waddington in the 1940s, it became an area of active empirical research mostly thanks to the efforts of its inventor and his collaborators. It was then attacked as of minor importance during the "hardening" of the neo-Darwinian synthesis and was relegated to a secondary role for decades. Recently, several papers have appeared, mostly independently of each other, to explore the likelihood of genetic assimilation as a biological phenomenon and its potential importance to our understanding of evolution. In this article we briefly trace the history of the concept and then discuss theoretical models that have newly employed genetic assimilation in a variety of contexts. We propose a typical scenario of evolution of genetic assimilation via an intermediate stage of phenotypic plasticity and present potential examples of the same. We also discuss a conceptual map of current and future lines of research aimed at exploring the actual relevance of genetic assimilation for evolutionary biology. [source] Negative Strain-rate Sensitivity in a Nanostructured Aluminum Alloy,ADVANCED ENGINEERING MATERIALS, Issue 10 2006Q. Han The influence of strain rate in the range of 10,1 to 10,5 s,1 on the compression behavior of a cryomilled 5083 Al alloy is studied. The compression flow stress remains constant after an initial short strain hardening and a small stress dip, which indicates a dynamic saturation of dislocations. It is found that the compression flow stress increases with decreasing strain rate, which is believed to be attributed to dynamic strain aging. [source] Effect of hardness on multiaxial fatigue behaviour and some simple approximations for steelsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 8 2009N. SHAMSAEI ABSTRACT Constant-amplitude in-phase and 90° out-of-phase axial-torsional fatigue tests were conducted on tubular specimens made from a medium-carbon steel with three hardness levels obtained from normalizing, quenching and tempering and induction hardening to find the effect of hardness on multiaxial fatigue behaviour. In addition, the same loadings were applied on the normalized solid specimens to investigate the effect of specimen geometry on multiaxial fatigue life. Similar fatigue life variation as a function of hardness was found for in-phase and out-of-phase loadings, with higher ductility beneficial in low-cycle fatigue (LCF) and higher strength beneficial in high-cycle fatigue (HCF). Multiaxial fatigue data were satisfactorily correlated for all hardness levels with the Fatemi,Socie parameter. Furthermore, in order to predict multiaxial fatigue life of steels in the absence of any fatigue data, the Roessle,Fatemi hardness method was used. Multiaxial fatigue lives were predicted fairly accurately using the Fatemi,Socie multiaxial model based on only the hardness level of the material. The applicability of the prediction method based on hardness was also examined for Inconel 718 and a stainless steel under a wide range of loading conditions. The great majority of the observed fatigue lives were found to be in good agreement with predicted lives. [source] Comparative study on biaxial low-cycle fatigue behaviour of three structural steelsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2006M. De FREITAS ABSTRACT In this study the uniaxial/biaxial low-cycle fatigue behaviour of three structural steels (Ck45 normalized steel, 42CrMo4 quenched and tempered steel and AISI 303 stainless steel) are studied, evaluated and compared. Two parameters are considered for estimating non-proportional fatigue lives: the coefficient of additional hardening and the factor of non-proportionality. A series of tests of uniaxial/biaxial low-cycle fatigue composed of tension/compression with cyclic torsion were carried out on a biaxial servo-hydraulic testing machine. Several loading paths were carried out, including proportional and non-proportional ones, in order to verify the additional hardening caused by different loading paths. The experiments showed that the three materials studied have very different additional hardening behaviour. Generally, the transient process from the initial loading cycle to stabilized loading cycle occurs in a few cycles. The stabilized cyclic stress/strain parameters are controlling parameters for fatigue damage. A factor of non-proportionality of the loading paths is evaluated based on the Minimum Circumscribed Ellipse approach. It is shown that the microstructure has a great influence on the additional hardening and the hardening effect is dependent on the loading path and also the intensity of the loading. [source] Analytical and experimental studies on fatigue crack path under complex multi-axial loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 4 2006L. REIS ABSTRACT In real engineering components and structures, many accidental failures are due to unexpected or additional loadings, such as additional bending or torsion, etc. Fractographical analyses of the failure surface and the crack orientation are helpful for identifying the effects of the non-proportional multi-axial loading. There are many factors that influence fatigue crack paths. This paper studies the effects of multi-axial loading path on the crack path. Two kinds of materials were studied and compared in this paper: AISI 303 stainless steel and 42CrMo4 steel. Experiments were conducted in a biaxial testing machine INSTRON 8800. Six different biaxial loading paths were selected and applied in the tests to observe the effects of multi-axial loading paths on the additional hardening, fatigue life and the crack propagation orientation. Fractographic analyses of the plane orientations of crack initiation and propagation were carried out by optical microscope and SEM approaches. It was shown that the two materials studied had different crack orientations under the same loading path, due to their different cyclic plasticity behaviour and different sensitivity to non-proportional loading. Theoretical predictions of the damage plane were made using the critical plane approaches such as the Brown,Miller, the Findley, the Wang,Brown, the Fatemi,Socie, the Smith,Watson,Topper and the Liu's criteria. Comparisons of the predicted orientation of the damage plane with the experimental observations show that the critical plane models give satisfactory predictions for the orientations of early crack growth of the 42CrMo4 steel, but less accurate predictions were obtained for the AISI 303 stainless steel. This observation appears to show that the applicability of the fatigue models is dependent on the material type and multi-axial microstructure characteristics. [source] Low-cycle fatigue of 1Cr,18Ni,9Ti stainless steel and related weld metal under axial, torsional and 90° out-of-phase loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 6 2004X. CHEN ABSTRACT The fatigue behaviour of base metal and weld joints of 1Cr,18Ni,9Ti stainless steel has been studied under uniaxial, torsional and 90° out-of-phase loading. A significant degree of additional hardening is found for both base metal and weld metal under 90° out-of-phase loading. Both base metal and weld metal have the same cyclic stable stress,strain relationship under torsional cyclic loading and 90° out-of-phase cyclic loading. Base metal exhibits higher cyclic stress than weld metal under uniaxial loading, and Young's modulus and yield stress of weld metal are smaller than those of base metal. Weld metal exhibited lower fatigue resistance than base metal under uniaxial and torsional loading, but no significant difference was found between the two materials under 90° out-of-phase loading. A large scatter of fatigue life is observed for weld metal, perhaps because of heterogeneity of the microstructure. The Wang,Brown (WB) damage parameter and the Fatemi,Socie (FS) damage parameter, both based on the shear critical plane approach, were evaluated relative to the fatigue data obtained. [source] Very high-cycle fatigue behaviour of shot-peened high-carbon,chromium bearing steelFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 8-9 2002K. SHIOZAWA ABSTRACT Effect of shot-peening on fatigue behaviour in the gigacycle regime was investigated in order to clarify the duplex S,N curve characteristics. Cantilever-type rotary bending fatigue tests were performed in laboratory air at room temperature by using hourglass-shaped specimens of high-carbon,chromium bearing steel, JIS SUJ2. Fatigue crack initiation site changed from the surface of untreated specimen to the subsurface of the specimen because of hardening and compressive residual stress with shot-peening in the region of high-stress amplitude. On the other hand, no difference in fatigue life controlled by the subsurface crack initiation between untreated specimen and shot-peening one was observed in high-cycle region. It was suggested that the S,N curve corresponding to the internal fracture mode is inherent in the material, as compared with the S,N curve of surface fracture mode, which is affected by surface conditions, environmental conditions and so on. Subsurface crack initiation and propagation behaviour were discussed under the detailed measurement of crack initiation area and shape of the fish-eye fracture surface. [source] Pronounced drought tolerance characterizes the early life stages of the epiphytic bromeliad Tillandsia flexuosaFUNCTIONAL ECOLOGY, Issue 3 2009Maaike Y. Bader Summary 1Germination and seedling performance may set the limits for plant distributions, particularly in stressful habitats. Stressful conditions at these early stages may be avoided by opportunistic germination and growth, or may be tolerated. Many epiphytic plants are frequently exposed to severe drought. Adult epiphytes endure such dry periods in various ways, but little is known about strategies employed during germination and early life. 2Epiphyte seedlings could show either opportunistic fast growth to quickly attain the benefits of being larger or inherently slow growth and early drought tolerance. Here we address the question: which of these strategies characterizes the early life stages of the epiphytic bromeliad Tillandsia flexuosa, a species typical for dry tropical habitats? 3We studied growth and drought tolerance of germinating seeds, of the emerging seedlings and of 2-month-old seedlings under controlled conditions. Additionally, we studied drought hardening in 6-month-old seedlings. 4Germination of T. flexuosa was reduced by intermittent dry periods. However, compared to the congeneric T. fasciculata, which typically occurs in wetter habitats, the depression of germination by drought was small. Seedling growth was fastest at intermediate moisture levels: both prolonged drought and continuous moisture depressed growth. Prolonged drought had a less negative effect on drought-hardened seedlings than on previously well-watered seedlings. After a 3-week drought treatment the previously well-watered seedlings had lost their growth advantage entirely. Had drought continued, they would have probably been starved, indicated by the low level of their non-structural carbohydrate pool. 5Tillandsia flexuosa employs a stress-tolerance strategy both during germination and during the seedling stage. In its epiphytic habitat this strategy is clearly adaptive, considering the predictable briefness of moisture availability throughout the year and the low competition pressure that allows the very slow growth typically seen in adults and seedlings. These conditions characterize not only the dry-forest habitat of T. flexuosa, but all exposed epiphytic growing sites, so we expect this early stress-tolerance to be common among epiphytes in general. Still, a lower stress tolerance in species from wetter habitats may at least partly explain why T. flexuosa shares its dry-forest habitat with so few other vascular epiphytes. [source] Dynamics of heat-induced thermal stress resistance and hsp70 expression in the springtail, Orchesella cinctaFUNCTIONAL ECOLOGY, Issue 2 2009Simon Bahrndorff Summary 1The relationship between thermal resistance and expression of inducible heat shock proteins, especially Hsp70, depends on the species and temperature treatments. The induction of Hsp70 has been shown to be essential for heat stress survival in a number of species, yet the maximum protein expression levels do not coincide with peak survival after heat hardening in Drosophila. 2Here we study the functional relationship between heat-induced expression of the heat shock protein Hsp70, and thermal resistance in adult Orchesella cincta by comparing thermal resistance (survival of 37·4 °C for 60 min) with Hsp70 gene and protein expression levels, all three measured at time points 2, 4, 6, 23, 27, 49 h after a heat hardening treatment (35·4 °C for 60 min). 3Thermotolerance increased over time after heat hardening until 49 h after exposure when the experiment ended. On the other hand the expression of hsp70 messenger RNA reached a peak within the first 2 h and then sharply decreased after 6 h. Within 23 h hsp70 expression was back to control levels. 4Surprisingly, protein levels of Hsp70 followed thermotolerance and reached the highest levels 49 h after heat hardening. A significant positive association was found between thermotolerance and Hsp70 protein levels, but not with hsp70 mRNA levels. 5Our results support a strong correlation between Hsp70 expression levels and thermal resistance following a heat hardening treatment. They also show that gene and protein expression follow different dynamics, a difference that may be important for our understanding of the role of candidate genes in functional studies. [source] Managing Environmental Impacts of Recreation and Tourism in Rainforests of the Wet Tropics of Queensland World Heritage AreaGEOGRAPHICAL RESEARCH, Issue 2 2005Stephen M. Turton Abstract This paper describes environmental impacts of tourism and recreation activities in the world heritage listed rainforests of northeast Australia and presents management strategies for sustainable visitor use of the protected area. Tropical rainforests are characterised by their low resistance and moderate to high resilience to impacts associated with human visitation. Visitor use in the World Heritage Area is mostly associated with walking tracks, camping areas, day use areas and off-road vehicle use of old forestry roads and tracks. Adverse environmental impacts range from vegetation trampling, soil compaction, water contamination and soil erosion at the local scale through to spread of weeds, feral animals and soil pathogens along extensive networks of old forestry roads and tracks at the regional scale. Concentration of visitor use is the most desirable management strategy for controlling adverse impacts at most World Heritage Area visitor nodes and sites, and includes methods such as site hardening and shielding to contain impacts. For dispersed visitor activities, such as off-road vehicle driving and long-distance walking, application of best practice methods by the tourist industry and recreational users such as removal of mud and soils from vehicle tyres and hiking boots before entering pathogen-free catchments, together with seasonal closure of roads and tracks, are the preferred management strategies. Retention of canopy cover at camping areas and day use areas, as well as along walking tracks and forestry roads is a simple, yet effective, management strategy for reduction of a range of adverse impacts, including dispersal of weeds and feral animals, edge effects, soil erosion and nutrient loss, road kill and linear barrier effects on rainforest fauna. [source] A unified continuum representation of post-seismic relaxation mechanisms: semi-analytic models of afterslip, poroelastic rebound and viscoelastic flowGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2010Sylvain Barbot SUMMARY We present a unified continuum mechanics representation of the mechanisms believed to be commonly involved in post-seismic transients such as viscoelasticity, fault creep and poroelasticity. The time-dependent relaxation that follows an earthquake, or any other static stress perturbation, is considered in a framework of a generalized viscoelastoplastic rheology whereby some inelastic strain relaxes a physical quantity in the material. The relaxed quantity is the deviatoric stress in case of viscoelastic relaxation, the shear stress in case of creep on a fault plane and the trace of the stress tensor in case of poroelastic rebound. In this framework, the instantaneous velocity field satisfies the linear inhomogeneous Navier's equation with sources parametrized as equivalent body forces and surface tractions. We evaluate the velocity field using the Fourier-domain Green's function for an elastic half-space with surface buoyancy boundary condition. The accuracy of the proposed method is demonstrated by comparisons with finite-element simulations of viscoelastic relaxation following strike-slip and dip-slip ruptures for linear and power-law rheologies. We also present comparisons with analytic solutions for afterslip driven by coseismic stress changes. Finally, we demonstrate that the proposed method can be used to model time-dependent poroelastic rebound by adopting a viscoelastic rheology with bulk viscosity and work hardening. The proposed method allows one to model post-seismic transients that involve multiple mechanisms (afterslip, poroelastic rebound, ductile flow) with an account for the effects of gravity, non-linear rheologies and arbitrary spatial variations in inelastic properties of rocks (e.g. the effective viscosity, rate-and-state frictional parameters and poroelastic properties). [source] Analysis of stress due to shrinkage in a hardening process of liquid epoxy resinHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2002Tetsuro Nishimura Abstract At present, epoxy resin is applied during the manufacturing of more compact and thinner components for the packaging of electronic and other devices. Epoxy resin has superior properties in terms of heat resistance, insulation, and strength; however, defects such as deformations and cracks often occur because of stress concentration. It is important to determine the inner stress of resin solidification for molding processes. Through a combination of numerical analyses of heat generated due to chemical reactions and experiments on shrinkage and strain that occur during hardening of epoxy resin, it becomes possible to analyze the stress generated due to hardening shrinkage. The developed analytical method can contribute to the realization of highly reliable components made of epoxy resin. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(3): 194,211, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10028 [source] Biomimetic Underwater Adhesives with Environmentally Triggered Setting MechanismsADVANCED MATERIALS, Issue 6 2010Hui Shao Inspired by the sandcastle worm, fluid complex coacervates of polyelectrolytes were formulated as water-borne underwater adhesives. The partially immiscible fluid phase can be delivered underwater and sets into a weight-bearing solid triggered by a change in the pH or temperature. Irreversible hardening occurs through oxidative coupling between catechol and primary amine sidechains. [source] Cold tolerance and cold hardening strategy of the Japanese pine sawyer Monochamus alternatus (Coleoptera: Cerambycidae)INSECT SCIENCE, Issue 4 2008Jing Tian Abstract The Japanese pine sawyer, Monochamus alternatus, is an important pine forest pest and vector transmitting the pine wilt nematode that causes pine wilt disease. Low temperatures in autumn, winter and spring often differentially affect mortality of M. alternatus larvae. In this paper, we mainly compared the differences of mortality and cold hardening of larvae from different seasons, based on supercooling point (SCP) and cumulative probability of individuals freezing (CPIF). The cold hardening of the larvae from autumn, winter and spring seasons were largely different. Correlations between mortality and CPIF of autumn and spring larvae were highest on day 1/4, and gradually decreased with prolonged exposure duration. This beetle's death mainly resulted from freezing in short exposure duration. However, the correlation between mortality and CPIF of winter larvae increased gradually with the prolonged exposure duration. Death did not mainly result from freezing in long exposure duration. Autumn larvae are more susceptible and adaptable than winter and spring larvae. Winter larvae have a slight freeze-tolerance trend. Our research showed that M. alternatus came into complex cold-hardening strategies under natural selection. Freeze avoidance is the primary strategy; with prolonged exposure duration to above SCP or < 0 °C, chill tolerance is more important; this is followed by freeze tolerance during harsh winters. [source] | ||||||||||||||||||||||||||||||||||