scholarly journals Experimental study of the dynamic indentation damage in thermally shocked granite

2018 ◽  
Vol 51 (1) ◽  
pp. 10-26 ◽  
Author(s):  
Ahmad Mardoukhi ◽  
Mikko Hokka ◽  
Veli-Tapani Kuokkala
Keyword(s):  
Heat Shock ◽  
Split Hopkinson Pressure Bar ◽  
Numerical Models ◽  
Experimental Testing ◽  
Material Surface ◽  
Rock Surface ◽  
Dynamic Indentation ◽  
Rock Interaction ◽  
Indentation Tests ◽  
Heat Shocks

This paper presents an experimental procedure to study the effects of pre-existing cracks and damage on the rock behavior under dynamic indentation. To gain better understanding on the mechanism involved in percussive-rotary drilling procedure, a modified Split Hopkinson Pressure Bar device was used to carry out dynamic indentation tests, where rock drill buttons were impacted on rock samples with dimensions of 30 cm × 30 cm × 30 cm. Before the mechanical testing, the samples were thermally shocked using a plasma spray gun for periods of 3, 4, and 6 seconds. The plasma gun produces a powerful heat shocks on the rock sample, and even short exposures can change the surface structure of the samples and provide samples with different crack patterns and surface roughness for experimental testing. The effects of the heat shock damage on the dynamic indentation behavior of the rock were characterized with single- and triple-button indentation tests. The specific destruction work was used to characterize the effects of heat shocks on the material removal during dynamic indentation. The results show that the force-displacement response of the rock does not change much even if the rock surface is severely damaged by the heat shock, however, the destruction work decreases significantly. This means that the same loading removes more volume if the material surface is pre-damaged, and that the efficiency of the indentation process cannot be evaluated from the bit-rock interaction forces alone. The presented experimental framework can be a useful tool for the verification of numerical models where the rock microstructure and especially the microcracks are essential.

scholarly journals Mitochondrial responses towards intermittent heat shocks in the Eastern Oyster, Crassostrea virginica

2021 ◽  
Author(s):  
Georges Hraoui ◽  
Sophie Breton ◽  
Gilles Miron ◽  
Luc H. Boudreau ◽  
Florence Hunter-Manseau ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Heat Shock ◽  
Crassostrea Virginica ◽  
Heat Waves ◽  
Physiological Stress ◽  
Eastern Oyster ◽  
Emission Rates ◽  
Mitochondrial Functions ◽  
Heat Shocks ◽  
Single Stress

Frequent heat waves caused by climate change can cause physiological stress in many animals, particularly in sessile ectotherms such as bivalves. Most studies characterizing thermal stress in bivalves focus on evaluating the responses to a single stress event. This does not accurately reflect the reality faced by bivalves which are often subject to intermittent heat waves. Here, we investigated the effect of intermittent heat stress on mitochondrial functions of Eastern oyster Crassostrea virginica which play a key role in setting ectotherms’ thermal tolerance. Specifically, we measured changes in mitochondrial oxygen consumption and H2O2 emission rates before, during and after intermittent 7.5°C heat shocks in oysters acclimated to 15°C and 22.5°C. Our results showed that oxygen consumption was impaired following the first heat shock at both acclimation temperatures. After the second heat shock, results for oysters acclimated to 15°C indicated a return to normal. However, oysters acclimated to 22.5°C struggled more with the compounding effects of intermittent heat shocks as denoted with an increase contribution of FAD-linked substrates to mitochondrial respiration as well as high levels of H2O2 emission rates. However, both acclimated populations showed signs of potential recovery ten days after the second heat shock, reflecting a surprising resilience to heat waves by C. virginica. Thus, this study highlights the important role of acclimation in oyster's capacity to weather intermittent heat shock.

Heat shock-induced alterations in phosphorylation of the largest subunit of RNA polymerase II as revealed by monoclonal antibodies CC-3 and MPM-2

1999 ◽  
Vol 77 (4) ◽  
pp. 367-374 ◽  
Author(s):  
Sébastien B Lavoie ◽  
Alexandra L Albert ◽  
Alain Thibodeau ◽  
Michel Vincent
Keyword(s):  
Heat Shock ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcriptional Activity ◽  
Phosphorylation Sites ◽  
Stress Genes ◽  
Terminal Domain ◽  
Carboxy Terminal Domain ◽  
Heat Shocks ◽  
Carboxy Terminal

The phosphorylation of the carboxy-terminal domain of the largest subunit of RNA polymerase II plays an important role in the regulation of transcriptional activity and is also implicated in pre-mRNA processing. Different stresses, such as a heat shock, induce a marked alteration in the phosphorylation of this domain. The expression of stress genes by RNA polymerase II, to the detriment of other genes, could be attributable to such modifications of the phosphorylation sites. Using two phosphodependent antibodies recognizing distinct hyperphosphorylated forms of RNA polymerase II largest subunit, we studied the phosphorylation state of the subunit in different species after heat shocks of varying intensities. One of these antibodies, CC-3, preferentially recognizes the carboxy-terminal domain of the largest subunit under normal conditions, but its reactivity is diminished during stress. In contrast, the other antibody used, MPM-2, demonstrated a strong reactivity after a heat shock in most species studied. Therefore, CC-3 and MPM-2 antibodies discriminate between phosphoisomers that may be functionally different. Our results further indicate that the pattern of phosphorylation of RNA polymerase II in most species varies in response to environmental stress.Key words: RNA polymerase II, heat shock, phosphorylation, CC-3, MPM-2.

Preferential deadenylation of Hsp70 mRNA plays a key role in regulating Hsp70 expression in Drosophila melanogaster

1994 ◽  
Vol 14 (6) ◽  
pp. 3646-3659
Author(s):  
R P Dellavalle ◽  
R Petersen ◽  
S Lindquist
Keyword(s):  
Drosophila Melanogaster ◽  
Heat Shock ◽  
Rna Processing ◽  
Hsp70 Expression ◽  
Hsp70 Mrna ◽  
Mild Heat ◽  
Endonucleolytic Cleavage ◽  
Heat Shocks ◽  
Low Efficiency ◽  
Hsp70 Synthesis

Following a standard heat shock, approximately 40% of Hsp70 transcripts in Drosophila melanogaster lack a poly(A) tail. Since heat shock disrupts other aspects of RNA processing, this observation suggested that heat might disrupt polyadenylation as well. We find, however, that as the temperature is increased a larger fraction of Hsp70 RNA is polyadenylated. Poly(A)-deficient Hsp70 RNAs arise not from a failure in polyadenylation but from the rapid and selective removal of poly(A) from previously adenylated transcripts. Poly(A) removal is highly regulated: poly(A) is (i) removed much more rapidly from Hsp70 RNAs than from Hsp23 RNAs, (ii) removed more rapidly after mild heat shocks than after severe heat shocks, and (iii) removed more rapidly after a severe heat shock if cells have first been conditioned by a mild heat treatment. Poly(A) seems to be removed by simple deadenylation rather than by endonucleolytic cleavage 5' of the adenylation site. During recovery from heat shock, deadenylation is rapidly followed by degradation. In cells maintained at high temperatures, however, the two processes are uncoupled and Hsp70 RNAs are deadenylated without being degraded. These deadenylated mRNAs are translated with low efficiency. Deadenylation therefore allows Hsp70 synthesis to be repressed even when degradation of the mRNA is blocked. Poly(A) tail shortening appears to play a key role in regulating Hsp70 expression.

Determination of mechanical properties from sharp dynamic indentation

2021 ◽  
pp. 030932472110592
Author(s):  
Bowen Si ◽  
Zhiqiang Li ◽  
Gesheng Xiao ◽  
Xuefeng Shu
Keyword(s):  
Mechanical Properties ◽  
Power Law ◽  
Split Hopkinson Pressure Bar ◽  
Indentation Test ◽  
Hopkinson Pressure Bar ◽  
Dynamic Indentation ◽  
Material Parameters ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Indentation Response

In this study, a dynamic indentation test method based on the split Hopkinson pressure bar is proposed to obtain the dynamic parameters of Ludwik power law constitutive, namely, Young’s modulus E, strength coefficient K, and strain hardening index n by analyzing dynamic indentation load-indentation depth curve obtained from the theories relating to the Hopkinson pressure bar. The important parameters, namely, loading curvature C and transformation factor [Formula: see text], are invoked to examine the dynamic indentation response results in a wide range of target material parameters. Finite element calculation results are processed through simulation of dynamic indentation response with broad material parameters. Furthermore, the analytical method is used to fit simulation results to obtain the analytical equations for elastic–plastic parameters and curvature parameters for the subsequent analysis. The analytical equation of forward model to predict dynamic indentation response parameter–loading curvature C of a known material is proposed. Then, the elastic–plastic parameters of unknown materials (according to Ludwik power law) are obtained by substituting the dynamic indentation response parameters into an inverse analytical equation under the two types of half-cone angle indenters. The method is verified by other typical materials, which shows that the dynamic indentation test based on the split Hopkinson pressure bar can obtain sufficient conditions to obtain dynamic mechanical properties of target materials.

scholarly journals THE RELATIONSHIP BETWEEN DEOXYRIBONUCLEIC ACID REPLICATION AND CELL DIVISION IN HEAT-SYNCHRONIZED TETRAHYMENA

1970 ◽  
Vol 46 (3) ◽  
pp. 533-543 ◽  
Author(s):  
William R. Jeffery ◽  
Kenneth D. Stuart ◽  
Joseph Frankel
Keyword(s):  
Cell Division ◽  
Heat Shock ◽  
Dna Synthesis ◽  
Deoxyribonucleic Acid ◽  
Heat Shock Treatment ◽  
Heat Shocks ◽  
Prolonged Heat ◽  
S Period ◽  
C 50 ◽  
The Relationship

The effect of supraoptimal temperature on macronuclear DNA synthesis in Tetrahymena was studied by radioautography during prolonged heat and heat-shock synchronization treatments. Prolonged heat treatments (34°C) delayed the initiation of S, but did not appreciably delay DNA synthesis in progress. Return to optimal temperature (28°C) 50 or 100 min later resulted in initiation of S, in delayed cells, at a rate greater than in controls. During the synchronization treatment, most cells were unable to enter S during a heat shock, but initiated S with a slight delay during the following intershock period. These cells were not appreciably delayed in completion of S by subsequent heat shocks. Supraoptimal temperature appears to affect the DNA synthetic cycle near the G1 to S transition. Cells subjected to the heat-shock treatment in early G1 all participated in one S period, and many underwent a succession of two S periods. DNA synthesis occurred in about 50% of the cells between EST and the first synchronous division, with the likelihood of DNA synthesis becoming greater the longer the interval between these two events. In some cells no detectable DNA synthesis occurred between EST and the second synchronous division. It was concluded that a precise temporal alternation of DNA replication and cell division is not obligatory in Tetrahymena.

scholarly journals P transposons controlled by the heat shock promoter.

1986 ◽  
Vol 6 (5) ◽  
pp. 1640-1649 ◽  
Author(s):  
H Steller ◽  
V Pirrotta
Keyword(s):  
Heat Shock ◽  
Germ Line ◽  
Fusion Gene ◽  
P Element ◽  
Translational Efficiency ◽  
Heat Shock Promoter ◽  
P Elements ◽  
Heat Shocks ◽  
Neomycin Resistance ◽  
Heat Shock Induction

We have transformed Drosophila melanogaster with modified P-element transposons, which express the transposase function from the heat-inducible hsp70 heat shock promoter. The Icarus transposon, which contains a direct hsp70-P fusion gene, behaved like a very active autonomous P element even before heat shock induction. Although heat shock led to abundant somatic transcription, transposition of the Icarus element was confined to germ line cells. To reduce the constitutive transposase activity observed for the Icarus element, we attenuated the translational efficiency of the transposase RNA by inserting the transposon 5 neomycin resistance gene between the hsp70 promoter and the P-element sequences. The resulting construct, called Icarus-neo, conferred resistance to G418, and its transposition was significantly stimulated by heat shock. Heat shocks applied during the embryonic or third instar larval stage had similar effects, indicating that transposition of P elements is not restricted to a certain developmental stage. Both Icarus and Icarus-neo destabilized snw in a P-cytotype background and thus at least partially overcome the repression of transposition. Our results suggest that the regulation of P-element transposition occurs at both the transcriptional and posttranscriptional levels.

Experimental Testing the Interaction of Fiber-Concrete Foundation Slab and Subsoil and Compare the Results with Numerical Models

2014 ◽  
Vol 1020 ◽  
pp. 227-232 ◽  
Author(s):  
Vojtech Buchta
Keyword(s):  
Civil Engineering ◽  
Numerical Models ◽  
Experimental Testing ◽  
Concrete Slab ◽  
Fiber Type ◽  
Test Element ◽  
Actual Behavior ◽  
Foundation Base ◽  
Internal Forces ◽  
Foundation Structure

We solve interaction between the foundation base and the subsoil in civil engineering quite often. For the determination of stress in foundation structure is needed to determine the influence of the stiffness respectively pliability of subsoil to structural internal forces, and vice versa, how the stiffness of the foundation structure affects the resulting subsidence. It is necessary to compare the mathematical models with the actual behavior of the real structure. In 2013 was realised static load on testing equipment in the campus of Faculty of Civil Engineering, VSB–TU Ostrava. Dimensions of test element was 2000 x 2000 x 170 mm and the concrete slab was reinforced with steel fiber type DRAMIX 3D 65/60B6. During measurements were performed and recorded: tensometrical measurement on the surface of the slab, tensometrical measurement inside the slab, measuring the vertical load, measurement of the vertical deformation, measuring the stress on the interface of the slab and soil. Were also developed numerical models of this test in program Nexis. Comparison the test results with numerical models are presented in this paper. [1,9]

Seed germination response of a potential rangeland weed Psilocaulon granulicaule to selected environmental conditions

2020 ◽  
Vol 68 (5) ◽  
pp. 363
Author(s):  
Rekha Ranaweera ◽  
Sandra L. Weller ◽  
Singarayer K. Florentine
Keyword(s):  
Water Stress ◽  
Heat Shock ◽  
Seed Germination ◽  
Management Practices ◽  
Germination Rate ◽  
Radiant Heat ◽  
Weed Species ◽  
Light Regimes ◽  
Heat Shocks ◽  
Environmental Weed

Studies show that just over 620 non-native naturalised plant species have been recorded within the Australian rangelands, some of which have a capacity to cause significant impacts on rangeland flora and grazing activity. Although Psilocaulon granulicaule (Haw.), Schwantes is listed as a highly invasive environmental weed species, there has been no previous research into its seed ecology. Therefore, this study was conducted to investigate the effects of temperature, light, pH, water stress, heat-shock, and salinity on the germination of P. granulicaule. In this study, four temperature regimes covering four different day and night temperature variations (17–7°C, 25–15°C, 30–25°C and 40–30°C) and two light regimes (12-h light–12-h dark, 24-h dark) were investigated. The effects of pH, water stress, heat-shock and salinity were investigated, using pH buffers, polyethylene glycol solutions, three heat shock events under four temperatures and a range of NaCl solutions. These tests were conducted under the identified optimum temperature range (25/15°C) and light regime for seed germination. The results showed that both temperature and photoperiod significantly influenced the germination rate, with 94.2% germination in the 25–15°C range under a 12-h light-12-h dark regime. Higher temperatures (30–40°C) reduced seed germination to <58% germination in both light regimes (57.5%, 12-h light-12-h dark; 54.17%, 24-h dark). The highest germination rates were observed in low pH solutions, high moisture levels, low heat-shocks and low salinity. The study showed that this species is sensitive to environmental factors such as temperature, light, pH, moisture, heat shock and salinity, suggesting that these factors can be used as critical indicators to guide effective management practices to address this weed problem. Given that seeds are sensitive to radiant heat, burning could be used as a tool to effectively manage this species.

scholarly journals FEM-Based Methodology for the Design of Reduced Scale Representative Experimental Testing Allowing the Characterization of Defect Evolution during Hot Rolling of Bars

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1035
Author(s):  
Corentin Pondaven ◽  
Laurent Langlois ◽  
Régis Bigot ◽  
Damien Chevalier
Keyword(s):  
Hot Rolling ◽  
Numerical Models ◽  
Experimental Testing ◽  
Effective Strain ◽  
Fem Simulation ◽  
Industrial Process ◽  
Cylindrical Sample ◽  
Forming Process ◽  
Defect Evolution ◽  
Reduced Scale

Defects generated during the casting process of steel can be reduced by forming processes such as hot rolling. During these processes the effective strain, the temperature, the stress state and the alternation of the forming direction all influence the defect evolution. Analytical or numerical models are available in the literature to predict the defect evolution. However, experiments have to be carried out to identify the parameters of these models. Thus, the quality of the identification depends on the representativeness of the experiments with respect to the industrial forming process. This paper proposes a methodology to design reduced scale experiments with an improved level of representativeness. This methodology consists first in the identification of the thermomechanical parameters driving the defect evolution and the quantification of these parameters in the industrial process by FEM simulation. These last results are then utilised as criteria for the representative experiment design. In this work the methodology is applied to the rolling of bars. The representative experiment consists of successive forming operations of a cylindrical sample between shaped anvils reproducing the roll shape at a 1:10 scale. A validation is finally achieved by reproducing qualitative results concerning the evolution of voids in the vicinity of hard inclusions.

An Experimental Testing of Fillet Welded Specimens

2015 ◽  
Vol 752-753 ◽  
pp. 412-417 ◽  
Author(s):  
Martin Krejsa ◽  
Jiri Brozovsky ◽  
David Mikolasek ◽  
Premysl Parenica ◽  
Libor Zidek ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Stress Analysis ◽  
Numerical Models ◽  
Experimental Testing ◽  
Fem Analysis ◽  
Experimental Tests ◽  
Strength Characteristics ◽  
Fillet Welds ◽  
Commercial Software

The paper describes the experimental tests of steel bearing elements, which were aimed at obtaining material, geometric and strength characteristics of the fillet welds. Preparation of experiment consisted in defining of numerical models of tested samples using FEM analysis and the commercial software ANSYS. Data obtained from described experimental tests are necessary for further numerical modelling of stress analysis of steel structural supporting elements.

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