Stress Of Cu Research Articles

Effects of divalent copper on microbial community, enzymatic activity and functional genes associated with nitrification and denitrification at tetracycline stress

The effects of divalent copper (Cu(II)) on microbial community, enzymatic activity and functional genes in a sequencing batch reactor (SBR) at tetracycline (TC) stress were investigated. The enzymatic activity and functional genes abundance associated with nitrification and denitrification at a 20 mg L−1 TC stress were higher than those at a mixtures stress of 20 mg L−1 TC and 10 mg L−1 Cu(II), while they were lower than those at a mixtures stress of 20 mg L−1 TC and 40 mg L−1 Cu(II). Compared to lactate dehydrogenase (LDH) release and reactive oxygen species (ROS) production at a 20 mg L−1 TC stress, they were lower at the TC stress with 10 mg L−1 Cu(II), while they were higher at the TC stress with 40 mg L−1 Cu(II). The incremental Cu(II) concentration at a 20 mg L−1 TC stress could not change the result that the sensitivity of denitrifying enzymatic activity to TC was higher than nitrifying enzymatic activity. Compared to the relative abundance of nitrifers and denitrifers at a 20 mg L−1 TC stress, the 10 mg L−1 Cu(II) addition resulted in their increase, while they decreased as the 40 mg L−1 Cu(II) addition. The relative abundance of genera Pseudomonas, Rivibacter and Nitrobacter at the stress of Cu(II) and TC were higher than those at TC stress, suggested they had an ability to resist the stress of Cu(II) and TC.

Resilience of soil functions to transient and persistent stresses is improved more by residue incorporation than the activity of earthworms

The development of soil sustainability is linked to the improved management of soil biota, such as earthworms, and crop residues to improve soil physical structure, enhance microbial activities, and increase nutrient cycling. This study examined the impacts of maize residue (65.8C/N ratio, dry biomass 0.75 kg m−2) incorporation and earthworms (70 g Metaphire guillelmi m−2) on the resistance and resilience of soil C and N cycling to experimentally applied stresses. Field treatments were maize residue incorporation, maize residue incorporation with earthworm addition, and an unamended control. Resistance and resilience of C mineralization, ammonia oxidation, and potential denitrification were investigated over 28 days following a persistent stress of Cu (1 mg Cu soil g−1) or a transient heat stress (50 °C for 16 h). The results indicated that C mineralization was more resistant and resilient than ammonia oxidation and denitrification to either a persistent Cu or a transient heat stress. The application of maize residues significantly increased soil microbial biomass, C mineralization, ammonia oxidation and potential denitrification compared with the unamended control. Maize residues significantly improved the resistance and resilience of N processes to Cu and heat stress. The presence of earthworms significantly increased potential denitrification but had limited positive effect on functional resistance and resilience. This study suggested crop residue incorporation would strongly increase soil functional resistance and resilience to persistent and transient stresses, and thus could be a useful agricultural practice to improve soil ecosystem sustainability.

Impact of Short-Range Clustering on the Multistage Work-Hardening Behavior in Cu–Ni Alloys

The work-hardening behavior of Cu–Ni alloys with high stacking-fault energies (SFEs) is experimentally investigated under uniaxial compression. It is found that, with the increase of Ni content (or short-range clustering, SRC), the flow stress of Cu–Ni alloys is significantly increased, which is mainly attributed to an enhanced contribution of work-hardening. An unexpected multistage (including Stages A, B, and C) work-hardening process was found in this alloy, and such a work-hardening behavior is essentially related to the existence of SRC structures in alloys. Specifically, during deformation in Stage B (within the strain range of 0.04–0.07), the forming tendency to planar-slip dislocation structures becomes enhanced with an increase of SRC content (namely, increase of Ni content), leading to the occurrence of work-hardening rate recovery in the Cu–20at.% Ni alloy. In short, increasing SRC in the Cu–Ni alloy can trigger an unexpected multistage work-hardening process, and thus improve its work-hardening capacity.

Exogenous NO mediated the detoxification pathway of tomato seedlings under different stress of Cu and Cd.

Nitric oxide (NO) is a well-known signaling molecular that plays a significant role in stress tolerance of plants to heavy metals. However, the detoxification mechanism of NO has not been well studied. Here, we examined the absorbing and transporting characteristics of copper (Cu) and cadmium (Cd) in tomato seedlings through nutrient solution culture and its response to exogenous NO under Cu and/or Cd stress. Results showed that Cu and Cd with the concentration of 50 &Mgr;mol·L-1 greatly inhibited plant growth, with Cd having a higher inhibiting effect than Cu. Under single or dual stresses of Cu and Cd, their contents in both tomato roots and leaves were significantly increased. However, tomato roots showed preference to essential element Cu with a luxury uptake and strictly against Cd through cell plasma membrane in which the content of Cd was only one tenth of Cu in plants. These metal stresses, especially Cd stress, could be alleviated by application of exogenous NO. Tomato plants detoxify these passively-absorbed elements through similar mechanisms, including chelation with glutathione, phytochelatin or metallothionein, as well as vascular compartmentalization. Exogenous NO could alleviate these stresses through regulating the oxidation-reduction condition of GSH-GSSH, controlling the metabolism of GSH-PCs, as well as promoting the vascular compartmentalization of excessive Cu and Cd. In addition, NO could induce higher expression of chelators, such as MTs, GSH and PCs, in both roots and shoots, which showed additive effects to other responses and might be another important detoxification pathway mediated through NO for the responses of tomato plants to Cu and Cd stresses.

Responses of microalgae Coelastrella sp. to stress of cupric ions in treatment of anaerobically digested swine wastewater

Microalgae Coelastrella sp. could remove nutrients from anaerobically digested swine wastewater (ADSW) effectively, while its responses to the stress of Cu(II) were not well understood. In this paper, nutrients removal and growth of Coelastrella sp. were investigated at the presence of Cu(II) in ADSW. Results showed ammonium nitrogen concentration in ADSW decreased with culturing duration, while increased with an increased Cu(II) concentration. Total phosphorous concentration decreased with time, while did not drop in 4 days at Cu(II) concentration ≥1.0 mg/L. Microalgal growth was inhibited at all the Cu(II) concentrations, and ceased in about 6–8 days at Cu(II) concentration ≥1.0 mg/L. With an increased Cu(II) concentration, the contents of chlorophyll a and proteins decreased, those of malondialdehyde and superoxide dismutase, and ratios of octadecanoic acid (C18:0), hexadecanoic acid (C16:0) and octadecenoic acid (C18:1) to fatty acids in Coelastrella sp. increased, while octadecatrienoic acid (C18:3) gradually disappeared.

Fabrication and characterization of copper coated polyamide-6 fibers with magnetron sputtering technology

Copper (Cu) is deposited as a film onto polyamide-6 (PA-6) fibers with a magnetron sputtering technology by using a self-assembly machine with a winding unit. The Cu coated PA-6 fibers are characterized by using surface profiler, X-ray diffractometer and scanning electron microscope. The electrical conductivity, Raman spectra, tensile strain and tensile stress of Cu coated PA-6 fibers are also systematically investigated. The results show that the mean value of the electrical conductivity of Cu-coated PA-6 fibers increases with decrease of winding speeds and reaches 7.03 × 10−5 Ω m at 4.7 cm/min. The Cu coated PA-6 fibers are used as electric wires to light the LEDs. The Raman characteristic peak of PA-6 fiber in the spectra is influenced after coating. With the drop of winding speed, the tensile strain and tensile stress of coated PA-6 fibers both decrease after Cu deposition.

Temperature dependence of twinning stress – Analogy between Cu–Ni–Al and Ni–Mn–Ga shape memory single crystals

To obtain a direct non-magnetic analogy to Ni–Mn–Ga 10M martensite with highly mobile twin boundaries, we present the recalculation of twinning systems in Cu–Ni–Al martensite. In this approach, the twinning planes denoted as Type I, Type II and compound have similar orientations for both alloys (Ni–Mn–Ga and Cu–Ni–Al). In Cu–Ni–Al, compound twinning exhibits the twinning stress of 1 to 2 MPa comparable to twining stress of Ni–Mn–Ga. In contrast Type II twinning stress of Cu–Ni–Al is approximately 20 MPa, i.e. much higher than twinning stress for Type II in Ni–Mn–Ga (0.1 to 0.3 MPa). Similarly to Ni–Mn–Ga, the twinning stress of Type II in Cu–Ni–Al is temperature independent. Moreover, no temperature dependence was found also for compound twinning in Cu–Ni–Al.

Expected CO2-induced ocean acidification modulates copper toxicity in the green tide alga Ulva prolifera

Cu is considered to be toxic to macroalgae at higher levels. Ocean acidification can also alter the physiological performances of macroalgae. However, little is known regarding the interactive effects of Cu and ocean acidification on macroalgae. In this study, a green tide macroalga, Ulva prolifera, was cultured at the conditions of three levels of Cu (control, 0.5μM, and 2μM) and pCO2 (ambient, 1000μatm, and 1400μatm) to investigate the responses of U. prolifera to interaction of Cu exposure and ocean acidification. The relative growth rate of thalli decreased with the rise of Cu for all pCO2 conditions except the 1000μatm pCO2. Compared with the control, 2μM Cu reduced the net photosynthetic rate for all pCO2 conditions while 0.5μM Cu only reduced it at 1400μatm pCO2. The inhibition rate of Cu on the relative growth rate and net photosynthetic rate was reduced at 1000μatm pCO2 but was magnified at 1400μatm pCO2. Contrary to growth, the dark respiration rate was enhanced by 0.5μM Cu at ambient pCO2 and by 2μM Cu at ambient and 1000μatm pCO2, although it was reduced by 2μM Cu at 1400μatm pCO2 compared to the control. The 0.5μM Cu did not affect the relative electron transport rate (rETR) for any pCO2 condition but 2μM Cu decreased it for all pCO2 conditions except 1000μatm pCO2. The mute effect of 0.5μM Cu on the net photosynthetic rate and rETR at ambient pCO2 may be due to more Chl a and Chl b being synthesized. In addition, 2μM Cu and 1400μatm pCO2 led to branched thalli, which may be a defense mechanism against the stress of high Cu and pCO2. Our data, for the first time, demonstrate that a modest increase of pCO2 can alleviate the toxicity of Cu to U. prolifera whilst a further increase exacerbates it. U. prolifera can respond to the stress of Cu pollution and ocean acidification via physiological and morphological alterations.

Influence of polyimide on thermal stress evolution in polyimide/Cu thick film composite

Polyimide(PI)/Cu composite thick films are widely used in wafer level packaging (WLP), and a common problem is the defects such as void, delamination, crack or wafer warpage induced by thermal stress. Compared with traditional rigid substrate/Cu/passivation system, PI imposes quite a different boundary constraint on Cu, resulting in a special stress evolution, and the corresponding mechanism is far from fully understood. Five sets of composites are constructed to investigate the influence of PI on thermal stress evolution in Cu film by means of in situ wafer warpage measurement under thermal cycling. Together with finite element analyses, it’s counterintuitive to find that although PI indeed reduces the stress in Cu, it exacerbates overall wafer warpage at room temperature. Warpage evolution reveals that composites consisting of substrate/PI/Cu sustains a moderate compressive stress while bare PI film is totally stress relaxed at high temperature, indicating that Cu and PI restrains stress relaxation reciprocally. It suggests that mutual effect should be considered when evaluating the stress distribution in polymer-metal composite thick films.

Alleviating effects of exogenous NO on tomato seedlings under combined Cu and Cd stress

To investigate the effect of NO on the different origin and regulation of oxidative stress of Cu and/or Cd, tomato seedlings were treated with Cu, Cd, or Cu + Cd in a nutrient solution culture system. The main effect of Cu(2+) was a significant reduction in root activity and nitrate reductase (NR) activity, which was similar to that under 50 μM Cd treatment, but promoted Cu accumulation. The supply of Cu under Cd treatment decreased Cd concentration, while not altered Cu concentration by contrast with Cu treatment, which is suggestive of a replacement of Cu(2+) with Cd(2+) and effective decrease in the boiotoxicity of 50 μM Cd(2+) to tomato seedlings. However, NO alleviated the restriction to NR activity significantly and made the biomass of tomato seedlings recover under Cd treatment, and also increased root activity under Cu and Cu + Cd treatment. Exogenous NO markedly reduced the absorption and transportation of Cu but did not obviously change the translocation of Cd to the aboveground parts under Cu + Cd treatment. Both metals induced lipid peroxidation via the decreasing activation of antioxidant enzymes. The antioxidant enzyme system worked differently under Cu, Cd, or Cu + Cd stress. The activities of peroxidase (POD) and catalase (CAT) were higher under single Cd stress than under the control. Meanwhile, Cu + Cd treatment decreased the activities of POD, superoxide dismutase (SOD), and ascorbic acid peroxidase (APX). Exogenous NO increased POD and SOD activities in the leaves and roots, and CAT activity in the roots under combined Cu and Cd stress. These results suggest that a different response and regulation mechanism that involves exogenous NO is present in tomato seedlings under Cu and Cd stress.

Influence of Ni Solute segregation on the intrinsic growth stresses in Cu(Ni) thin films

Using intrinsic solute segregation in alloys, the compressive stress in a series of Cu(Ni) thin films has been studied. The highest compressive stress was noted in the 5at.% Ni alloy, with increasing Ni concentration resulting in a subsequent reduction of stress. Atom probe tomography quantified Ni's Gibbsian interfacial excess in the grain boundaries and confirmed that once grain boundary saturation is achieved, the compressive stress was reduced. This letter provides experimental support in elucidating how interfacial segregation of excess adatoms contributes to the post-coalescence compressive stress generation mechanism in thin films.

Finite Element Analysis of Human Tactile Sensing to Differentiate Thin Foils through Comparison Between Vertical & Angled Loads

Due to increasing research demand on human tactile sensations for robot-human interfaces and new tactile sensors, this research studies human tactile sensing to differentiate the thicknesses of two extremely thin foils that are made of Cu and stainless steel (SUS). We performed finite element analysis (FEA) on the fingertip's 3D elastic model to improve previous simulations through error analyses, better selection of nodal points, and proper loading conditions. We obtained the optimum mesh size to achieve numerical error below 4%. We also compared the von Mises (VM) stress of Cu with one of the SUS foils under different loading states to monitor the tc/ts ratio calculated from the thicknesses of the Cu and SUS foils that cause identical VM stress. The simulated result shows that the ratio becomes considerably large when thicknesses tc (Cu) and ts (SUS) are calculated from the differences of the VM stress between the angular and vertical loads. Consequently, the difference between the twitch motion and the datum provides the best ratio, tc/ts = 1.6, which resembles the results of psychophysical experiments.

Behavior of deep level defects on voltage-induced stress of Cu(In,Ga)Se 2 solar cells

Abstract The behavior of deep level defects by a voltage-induced stress for CuInGaSe 2 (CIGS) solar cells has been investigated. CIGS solar cells were used with standard structures which are Al-doped ZnO/i-ZnO/CdS/CIGSe 2 /Mo on soda lime glass, and that resulted in conversion efficiencies as high as 16%. The samples with the same structure were isothermally stressed at 100 °C under the reverse voltages. The voltage-induced stressing in CIGS samples causes a decrease in the carrier density and conversion efficiency. To investigate the behavior of deep level defects in the stressed CIGS cells, photo-induced current transient spectroscopy was utilized, and normally 3 deep level defects (including 2 hole traps and 1 electron trap) were found to be located at 0.18 eV and 0.29 eV above the valence band maximum (and 0.36 eV below the conduction band). In voltage-induced cells, especially, it was found that the decrease of the hole carrier density could be responsible for the increase of the 0.29 eV defect, which is known to be observed in less efficient CIGS solar cells. And the carrier density and the defects are reversible at least to a large extent by resting at room-temperature without the bias voltage. From optical capture kinetics in photo-induced current transient spectroscopy measurement, the types of defects could be distinguished into the isolated point defect and the extended defect. In this work, it is suggested that the increase of the 0.29 eV defect by voltage-induced stress could be due to electrical activation accompanied by a loss of positive ion species and the activated defect gives rise to reduction of the carrier density.

Local distribution of residual stress of Cu in LSI interconnect

Local distributions of crystal orientation and residual stress of Cu lines (600nm and 400nm) in large-scale integrated circuit (LSI) interconnects are visualized by electron backscatter diffraction (EBSD). The crystal orientation distribution is random and texture is not observed. Bamboo grain boundary structures form with decreasing Cu line width. The Wilkinson EBSD method indicates that the residual elastic stress of a Cu line in an LSI interconnect is locally high at twin boundaries, grain boundaries, and the Cu/dielectric interface. The local distributions of residual elastic stress at these boundaries and the interface should induce preferential crack nucleation.

A physical-based constitutive relation to predict flow stress for Cu–0.4Mg alloy during hot working

The hot deformation behaviors of Cu–0.4Mg alloy are studied by the isothermal compression tests on a Gleeble-1500 thermo-mechanical simulator over wide ranges of temperatures and strain rates. Based on the experimental results, a physical-based constitutive model is developed to predict the flow stress of Cu–0.4Mg alloy under elevated temperature. Results show that under a given strain rate, the flow stress will decrease with increasing temperature, while under a given temperature the flow stress will increase with increasing strain rate. The true stress–strain curves of Cu–0.4Mg alloy demonstrate the typical characteristics of dynamic recovery and dynamic recrystallization. The correlation coefficient (R) and the average absolute relative error (AARE) between the measured and predicted flow stresses are 0.99747 and 3.3846%, respectively. It indicates that the proposed physical-based constitutive model can accurately characterize the hot deformation behaviors including work-hardening, dynamic recovery and dynamic recrystallization for Cu–0.4Mg alloy.

Understanding scale-dependent yield stress of metals at micrometre scales

The mechanical softening behaviour of micrometre-scale metals (free-standing metal foils and wires) with decreasing either the geometrical or the microstructural scale (i.e. the smaller, the weaker) has recently been reported. Here, we present a mechanism-based model to understand the softening behaviour, which is based on competition between the effects of surface grain relaxation and the interior grain strengthening effect. The model describes well the yield stress of Cu foils with different ratios of the thickness to grain size.

Finite Element Analysis of Failure in Cu Interconnect Megasonic Cleaning

Megasonic cleaning has been one of the most successful techniques for Cu/low-k interconnects post-CMP cleaning. The structural deformation and stress of Cu and low-k materials in megasonic cleaning are examined with finite element method (FEM). The maximum stress is concentrated in the binding area between Cu and low-k. With decrease of Cu line width, the maximum stress increases and the max value exceeds the yield strength of Cu which results in the plastic deformation. The increasing frequency will change the bubble collision times. Therefore the fatigue is potential. The maximum displacement moves from center to the sides of top surface with increase of line width. When the line width is 25nm, the deformation is the largest.

Phytoaccumulation of copper in willow seedlings under different hydrological regimes

Plant biomass and copper (Cu) accumulation by Salix jiangsuensis CL ‘J-172’ and Salix babylonica Linn grown in Cu spiked soils were investigated under different hydrological regimes to assess the suitability of willow for phytoremediation of contaminated wetlands. The results showed that willow can maintain normal growth with no visual symptoms of Cu toxicity, suggesting that willow has high resistance to the combined stresses of Cu and waterlogging. The elevated Cu concentration in soil significantly decreased the biomass and increased Cu content in the roots of the two species. Flooding increased Cu accumulation in the roots and decreased Cu accumulation in the stems and leaves. Considering the large biomass of willow and its metal accumulation ability, willow has the potential for use in phytoremediation of Cu-contaminated wetlands.

Flow Stress and Critical Dynamic Recrystallization Behavior of Cu–Fe16Mn0.6C High Manganese TWIP Steel

AbstractThe true stress–strain curve of Cu–Fe16Mn0.6C twinning induced plasticity (TWIP) steel was studied with a compression test on Thermecmastor‐Z thermal simulator at a temperature range of 850–1150°C and strain rate range of 0.03–30 s−1. The influence of deformation temperature and strain rate on high‐temperature flow stress and critical recrystallization behavior of the TWIP steel was investigated. It is concluded that the peak flow stress of Cu–Fe16Mn0.6C under high‐temperature deformation decreases as the temperature increases but increases with the strain rate. Meanwhile at strain rate of 0.03 and 30 s−1 obvious peak stresses are observed which demonstrates the dynamic recrystallization. The constitutive equation of Cu–Fe16Mn0.6C under high temperature deformation is calculated by linear regression method. The activation energy is 505 kJ mol−1. The relationship between critical strain of dynamic revrystallization and Zener–Hollomon parameter is determined by the curve between strain‐hardening rate and flow stress.

Measurement of stresses in Cu and Si around through-silicon via by synchrotron X-ray microdiffraction for 3-dimensional integrated circuits

Through-silicon via (TSV) has been used for 3-dimentional integrated circuits. Mechanical stresses in Cu and Si around the TSV were measured using synchrotron X-ray microdiffraction. The hydrostatic stress in Cu TSV went from high tensile of 234MPa in the as-fabricated state, to −196MPa (compressive) during thermal annealing (in situ measurement), to 167MPa in the post-annealed state. Due to this stress, the keep-away distance in Si was determined to be about 17μm. Our results suggest that Cu stress may lead to reliability as well as integration issues, while Si stress may lead to device performance concerns.