scholarly journals Electric signal emissions during repeated abrupt uniaxial compressional stress steps in amphibolite from KTB drilling

2007 ◽  
Vol 7 (1) ◽  
pp. 149-154 ◽  
Author(s):  
D. Triantis ◽  
C. Anastasiadis ◽  
F. Vallianatos ◽  
P. Kyriazis ◽  
G. Nover
Keyword(s):  
Mechanical Stress ◽  
Laboratory Experiments ◽  
Acoustic Emissions ◽  
Uniaxial Stress ◽  
Electric Signal ◽  
Electric Currents ◽  
Loading Cycle ◽  
Compressional Stress ◽  
History Of ◽  
Loading And Unloading

Abstract. Laboratory experiments have confirmed that the application of uniaxial stress on rock samples is accompanied by the production of weak electric currents, to which the term Pressure Stimulated Currents – PSC has been attributed. In this work the PSC emissions in amphibolite samples from KTB drilling are presented and commented upon. After having applied sequential loading and unloading cycles on the amphibolite samples, it was ascertained that in every new loading cycle after unloading, the emitted PSC exhibits lower peaks. This attitude of the current peaks is consistent with the acoustic emissions phenomena, and in this work is verified for PSC emissions during loading – unloading procedures. Consequently, the evaluation of such signals can help to correlate the state and the remaining strength of the sample with respect to the history of its mechanical stress.

scholarly journals Wavelet analysis on pressure stimulated currents emitted by marble samples

2006 ◽  
Vol 6 (6) ◽  
pp. 889-894 ◽  
Author(s):  
P. Kyriazis ◽  
C. Anastasiadis ◽  
D. Triantis ◽  
F. Vallianatos
Keyword(s):  
Wavelet Analysis ◽  
Acoustic Emissions ◽  
Electric Signal ◽  
Rock Fracturing ◽  
Kaiser Effect ◽  
Loading Cycle ◽  
Similarities And Differences ◽  
Deformation Level ◽  
Current Emission ◽  
Electric Signals

Abstract. This paper presents a wavelet based method of analysis of experimentally recorded weak electric signals from marble specimens which have undergone successive abrupt step loadings. Experimental results verify the existence of "memory effects" in rocks, as far as the current emission is concerned, akin to the "Kaiser effect" in acoustic emissions, which accompany rock fracturing. Macroscopic signal processing shows similarities and differences between the currents emitted during successive loading and wavelet analysis can reveal significant differences between the currents of each loading cycle that contain valuable information for the micro and macro cracks in the specimen as well as information for the remaining strength of the material. Wavelets make possible the time localization of the energy of the electric signal emitted by stressed specimens and can serve as method to differentiate between compressed and uncompressed samples, or to determine the deformation level of specimens.

scholarly journals Acoustic Emission in Snow at Constant Rates of Deformation

1973 ◽  
Vol 12 (64) ◽  
pp. 144-146 ◽  
Author(s):  
W. F. St. Lawrence ◽  
T. E. Lang ◽  
R.L. Brown ◽  
C. C. Bradley
Keyword(s):  
Acoustic Emission ◽  
Brittle Fracture ◽  
Uniaxial Compression ◽  
Laboratory Experiments ◽  
Acoustic Emissions ◽  
Snow Sample ◽  
Frequency Range ◽  
Snow Samples

AbstractAcoustic emissions in the audio spectrum are reported from observations of laboratory experiments conducted on snow samples in uniaxial compression. A number of tests show the pattern of acoustic emissions to be a function of the rate of deformation. Over the frequency range 20 to 7 000 Hz acoustic emissions are associated with rates of deformation corresponding to brittle fracture of the snow sample. Though probably present, no acoustic emissions were detected from samples deforming plastically.

Calculation of Optical Characteristics for Si1-xGExAlloy

1995 ◽  
Vol 379 ◽  
Author(s):  
V. G. Litovchenkoe ◽  
S. I. Frolov ◽  
B. N. Shkarban ◽  
D. Kruger
Keyword(s):  
Crystal Lattice ◽  
Mechanical Stress ◽  
Measurement Technique ◽  
Lattice Strain ◽  
Uniaxial Stress ◽  
Material Composition ◽  
Optical Transitions ◽  
Virtual Crystal Approximation ◽  
Pseudopotential Theory

ABSTRACTIn the framework of virtual crystal approximation using the empirical pseudopotential theory optical transitions of Si1 -xGexhave been calculated. The effects of hydrostatic and uniaxial stress, and alloy stoichiometry on the optical gaps were investigated. Since the mechanical stress and material composition affect the distinctive behaviour of different optical transitions it allows to put forward a spectral measurement technique for determination of crystal lattice strain and alloy parameter x simultaneously.

Fate of14C-EPTC in a Soil Exhibiting Accelerated Degradation of Carbamothioate Herbicides and Its Control

Weed Science ◽  
1989 ◽  
Vol 37 (3) ◽  
pp. 434-439 ◽  
Author(s):  
Abraham Tal ◽  
Baruch Rubin ◽  
Jaacov Katan ◽  
Nadav Aharonson
Keyword(s):  
Methyl Bromide ◽  
Laboratory Experiments ◽  
Soil Microorganisms ◽  
Inhibitory Effect ◽  
Soil Sterilization ◽  
Soil Disinfestation ◽  
Herbicide Degradation ◽  
Chemical Treatments ◽  
Accelerated Degradation ◽  
History Of

Laboratory experiments were conducted to determine the fate of14C-EPTC in a soil that had a history of vernolate application and exhibited accelerated degradation of carbamothioate herbicides compared to nonhistory soil. A very rapid mineralization of the herbicide to14CO2was evident in history soil, compared to nonhistory soil. The two soils did not differ in the amounts of the EPTC lost through volatilization or in the nonextractable radioactive fractions. Except for small quantities of EPTC-sulfoxide and sulfone, no other metabolites were detected. Degradation of14C-EPTC, as determined by evolution of14CO2in history soil, was drastically inhibited following soil sterilization by means of autoclaving or gamma irradiation. Soil disinfestation by solarization, methyl bromide, or metham had a pronounced inhibitory effect during the first 6 days, but was less effective than sterilization. Treatment of a history soil with the fungicide 2-methoxyethylmercury chloride and dietholate strongly inhibited EPTC degradation, while thiram and fentin acetate had only short lasting effects. Cycloheximide, an antifungal antibiotic, had little effect on the degradation of EPTC while chloramphenicol, an antibacterial antibiotic, inhibited the herbicide degradation. These results indicate that accelerated degradation of EPTC is linked to the activity of soil microorganisms, e.g. bacteria, and can be controlled by sterilization and chemical treatments.

An Improved Analytical Method for Life Prediction of Bolting

2000 ◽  
Vol 123 (1) ◽  
pp. 70-74 ◽  
Author(s):  
F. V. Ellis ◽  
D. R. Sielski ◽  
R. Viswanathan
Keyword(s):  
Stress Relaxation ◽  
Creep Strain ◽  
Life Prediction ◽  
Prediction Method ◽  
Uniaxial Stress ◽  
Life Assessment ◽  
Flow Rule ◽  
Creep Equation ◽  
Strain Limit ◽  
History Of

A research project was conducted to develop and validate an improved, analytical life prediction method for high-temperature turbine and valve studs/bolts. The life prediction method used the two-parameter creep equation, an incremental calculation procedure and a strain hardening flow rule. The failure criterion was an accumulated inelastic or creep strain limit of 1 percent. The life prediction procedure recommends the use of the service history of operating temperature, number/stress level of tightenings, cycle time, etc., to calculate the stress relaxation behavior. Life assessment uses the measured bolt length to calculate the accumulated creep strain. The link between the current condition, i.e., accumulated creep strain, and the remaining creep life, i.e., time to accumulate 1 percent strain, is obtained by a prediction of the future creep strain accumulation under the intended loading cycle(s) imposed during future operation. In order to validate the approach, the calculated results were compared to the results of uniaxial stress relaxation testing, bolt model testing, and service experience. The analytical procedure coupled with other industry wide NDE and measurement procedures is expected to provide broad guidelines to utilities for bolting life assessment.

scholarly journals ALS–Resistant Annual Sedge (Cyperus compressus) Confirmed in Turfgrass

Weed Science ◽  
2016 ◽  
Vol 64 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Patrick E. McCullough ◽  
Jialin Yu ◽  
J. Scott McElroy ◽  
S. Chen ◽  
H. Zhang ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Acetolactate Synthase ◽  
Shoot Biomass ◽  
Resistance Level ◽  
Physiological Basis ◽  
History Of ◽  
Leaf Tissues ◽  
Als Inhibitors ◽  
Inhibitor Resistance ◽  
Als Inhibitor

Acetolactate synthase (ALS) inhibitors are widely used for POST control of sedges in turfgrass. A suspected resistant (R) biotype of annual sedge was collected from a bermudagrass turf in Georgia with a history of exclusive use of halosulfuron. Research was conducted to evaluate the resistance level of this biotype to halosulfuron, efficacy of ALS-inhibiting herbicides and other mechanisms of action for control, and the molecular and physiological basis for resistance. In greenhouse experiments, the halosulfuron rate required to reduce shoot biomass 50% in comparison with the nontreated at 8 wk after treatment (WAT) were 8 and > 1,120 g ai ha−1for the S (susceptible) and R biotypes, respectively. Imazapic, sulfosulfuron, and trifloxysulfuron reduced biomass of the S biotype greater than 60% at 8 WAT, but biomass was reduced less than 20% for the R biotype. Glufosinate, glyphosate, MSMA, and sulfentrazone reduced shoot biomass of the R biotype by 93, 86, 97, and 45%, respectively. In laboratory experiments, the halosulfuron concentration required to inhibit ALS activity by 50% in excised leaf tissues was 5.8 and > 1,000 μM for the S and R biotypes, respectively. Gene sequencing of the R biotype revealed a Pro-197-Ser substitution that confers resistance to ALS inhibitors. This is the first report of ALS-inhibitor resistance in annual sedge and herbicide resistance in a sedge species from a turfgrass system.

scholarly journals Toward the First Italian Elastocaloric Device: Projecting and Developing Steps

2021 ◽  
Vol 65 (2-4) ◽  
pp. 391-400
Author(s):  
Luca Cirillo ◽  
Adriana Rosaria Farina ◽  
Adriana Greco ◽  
Claudia Masselli ◽  
Federico Scarpa ◽  
...  
Keyword(s):  
National Research Council ◽  
Uniaxial Stress ◽  
Transformation Process ◽  
Vapor Compression ◽  
Proof Of Concept ◽  
Vapor Compression Refrigeration ◽  
Loading And Unloading ◽  
Cooling Technology ◽  
Stress Cycles ◽  
Vapour Compression

Nowadays about 20% of the worldwide energy consumption is attributable to refrigeration that is almost entirely based on vapor compression refrigeration. The elastocaloric refrigeration is being considered in the recent years as one of the most promising alternatives to vapour compression cooling technology. It is based on the latent heat associated with the transformation process of the martensitic phase, found in Shape Memory Alloys (SMA) when they are subjected to uniaxial stress cycles of loading and unloading. SMAs are characterized by the mechanical property of being able to return to the initial form once the uniaxial stress has been removed. Currently the prototypes of elastocaloric cooler developed in the world are less than ten units and they are not close to the industrialization and commercialization, yet. This contribution presents the design processes and the steps of development of the first Italian elastocaloric device: SSUSTAIN-EL. This research involves part of a bigger Italian project, called SUSSTAINEBLE, that involves three research institutes: University of Naples Federico II, University of Genoa and the National Research Council. The aim of research group is the developing of a demonstrative prototype of a continuously elastocaloric cooler, which can represent a fundamental step as "proof of concept".

A Copper-Tolerant Phormidium Species from Lake Mathews, California, That Produces 2-Methylisoborneol and Geosmin

1992 ◽  
Vol 25 (2) ◽  
pp. 217-223 ◽  
Author(s):  
G. Izaguirre
Keyword(s):  
Gas Chromatography ◽  
Laboratory Experiments ◽  
Closed Loop ◽  
Water Reservoir ◽  
Historical Background ◽  
Source Water ◽  
Sediment Samples ◽  
Cupric Ion ◽  
History Of ◽  
Copper Tolerant

A benthic Phormidium sp. was isolated in 1988 from Lake Mathews, a source-water reservoir in southern California with a long history of 2-methylisoborneol (MIB) problems. Unialgal cultures were analyzed by salted closed-loop stripping analysis (CLSA) and gas chromatography (GC), which confirmed the presence of MIB at levels of up to 280 µg/l. Geosmin was also found at 2-36 µg/l. Resurgence of the alga following copper sulfate (CuSO4) applications suggested resistance to the algicide. Laboratory experiments showed that the Phormidium was relatively tolerant of copper (surviving at least 3 mg/l of cupric ion after a 1-day exposure) in filtered lake water. The organism also survived 4 mg/l of copper for one day in a variety of sediment samples. This organism was implicated in the longest MIB episode in Lake Mathews, where MIB remained above historical background levels through the winter of 1989-1990. The Phormidium has apparently become the principal MIB producer in Lake Mathews, supplanting Oscillatoriacurviceps after 10 years.

scholarly journals Peromyscus mice as a model for studying natural variation

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Nicole L Bedford ◽  
Hopi E Hoekstra
Keyword(s):  
Disease Ecology ◽  
Natural Variation ◽  
Laboratory Experiments ◽  
Deer Mouse ◽  
Model Organisms ◽  
Field Observations ◽  
Terrestrial Habitat ◽  
In The Wild ◽  
History Of ◽  
And Behavior

The deer mouse (genus Peromyscus) is the most abundant mammal in North America, and it occupies almost every type of terrestrial habitat. It is not surprising therefore that the natural history of Peromyscus is among the best studied of any small mammal. For decades, the deer mouse has contributed to our understanding of population genetics, disease ecology, longevity, endocrinology and behavior. Over a century's worth of detailed descriptive studies of Peromyscus in the wild, coupled with emerging genetic and genomic techniques, have now positioned these mice as model organisms for the study of natural variation and adaptation. Recent work, combining field observations and laboratory experiments, has lead to exciting advances in a number of fields—from evolution and genetics, to physiology and neurobiology.

The evolution of ecological tolerance in prokaryotes

1989 ◽  
Vol 80 (3-4) ◽  
pp. 209-223 ◽  
Author(s):  
Andrew H. Knoll ◽  
John Bauld
Keyword(s):  
Molecular Phylogeny ◽  
Microbial Ecology ◽  
Laboratory Experiments ◽  
Developmental History ◽  
Early Diversification ◽  
Physico Chemical ◽  
History Of ◽  
Stability Limits ◽  
Prokaryotic Evolution

ABSTRACTThe ecological ranges of Archaeobacteria and Eubacteria are constrained by a requirement for liquid water and the physico-chemical stability limits of biomolecules, but within this broad envelope, prokaryotes have evolved adaptations that permit them to tolerate a remarkable spectrum of habitats. Laboratory experiments indicate that prokaryotes can adapt rapidly to novel environmental conditions, yet geological studies suggest early diversification and long-term stasis within the prokaryotic kingdoms. These apparently contradictory perspectives can be reconciled by understanding that, in general, rates and patterns of prokaryotic evolution reflect the developmental history of the Earth's surface environments. Our understanding of modern microbial ecology provides a lens through which our accumulating knowledge of physiology, molecular phylogeny and the Earth's history can be integrated and focussed on the phenomenon of prokaryotic evolution.

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