Effect Of Temperature Variation Research Articles

Interacciones tierra-mar-tierra, con énfasis en la actividad pesquera en la región norte del Ecosistema Costero Bonaerense, Argentina

[Introduction]: Coastal areas constitute the interface between land and marine environments, connected through multiple natural and socioecological processes that contribute to human well-being. [Objective]: Identify land and marine uses and activities with mutual implications and biophysical processes in the northern region of the Bonaerense Coastal Ecosystem (Argentina), in order to evaluate the degree of compatibility or conflict between these activities, with emphasis on the fishing activity. [Methodology]: The land-sea-land (T-M-T) methodological analysis was applied. Uses and activities (U&A) and biophysical processes of marine and land origin were determined. Interactions between marine-land and biophysical processes T-M-T were identified for further categorization and analysis. [Results]: A total of 121 U&A sea-land-sea (L-S-L) interactions related to fishing were detected. Medium conflicts were mainly caused by competition for space or resources and were associated with the coexistence of U&A (tourism, fishing, and communication activities), both spatially and temporally. Of the total, 68 negative interactions were observed between biophysical processes and U&A L-S-L, which were linked to climatic events and the effects of climate change (variation in sea surface temperature, atmospheric and oceanic circulation, as well as variations in sediment transport and coastal erosion). [Conclusions]: The analysis carried out constitutes an advancement in the study of U&A T-M-T in coastal-marine areas of the Atlantic coast and their interactions, with emphasis on fishing activities, as a contribution to their management with an ecosystemic approach.

Shear Banding and Cracking in Unsaturated Porous Media through a Nonlocal THM Meshfree Paradigm

The mechanical behavior of unsaturated porous media under non-isothermal conditions plays a vital role in geo-hazards and geo-energy engineering (e.g., landslides triggered by fire and geothermal energy harvest and foundations). Temperature increase can trigger localized failure and cracking in unsaturated porous media. This article investigates the shear banding and cracking in unsaturated porous media under non-isothermal conditions through a thermo–hydro–mechanical (THM) periporomechanics (PPM) paradigm. PPM is a nonlocal formulation of classical poromechanics using integral equations, which is robust in simulating continuous and discontinuous deformation in porous media. As a new contribution, we formulate a nonlocal THM constitutive model for unsaturated porous media in the PPM paradigm in this study. The THM meshfree paradigm is implemented through an explicit Lagrangian meshfree algorithm. The return mapping algorithm is used to implement the nonlocal THM constitutive model numerically. Numerical examples are presented to assess the capability of the proposed THM mesh-free paradigm for modeling shear banding and cracking in unsaturated porous media under non-isothermal conditions. The numerical results are examined to study the effect of temperature variations on the formation of shear banding and cracking in unsaturated porous media.

Atomic insights into the corrosion behavior of Fe-Cr alloys in supercritical CO2 environment

In this work, the corrosion process of Fe-Cr alloys in flowing CO2 was simulated using molecular dynamics within an extended ReaxFF force field. The effects of Cr content, temperature variations, impurity gases and vacancy defects were discussed. The corrosion process was dominated by oxidation and carburization reactions, with the oxidation rate higher than carburization rate, resulting in the formation of a carbide layer within the central region between two oxide layers. The increase in Cr content tended to decelerate corrosion, while raising temperature aggravated the corrosion of Fe-Cr alloy. The presence of O2 and SO2 impurities was found to thicken the corrosion layer, in contrast to the effects of CO and H2O impurities. A notable finding highlighted the positive influence of 2% vacancy defects in enhancing the corrosion resistance of the Fe-Cr alloy. The Al2O3 coating achieved a good corrosion protection by inhibiting the dissociation of CO2.

The effect of temperature variation on Aluminum Matrix Composite (AMC) Sintering with CNT

Material selection is a very important part of the design due to the variety of functions and extreme applications. There is always a need for materials that are light, strong, hard, with good thermal conductivity. Aluminum matrix composites (AMC) are potential candidates for applications that require proper material selection. The most popular AMC processing technique is the powder metallurgy/PM method to produce products with precise dimensions. Powder metallurgy for the mass production of components is the most promising and versatile method. carbon Nanotube (CNT) particle reinforced AMC fabrication is an advanced material for the automobile, aircraft, aerospace, defense, petroleum, chemical industries at a relatively low price with high performance. Al powder 4.98 gr, CNT 0.02 gr with a mixing time of 8 hours at 650 rpm. The specimens were made using a cold uniaxial pressing process at room temperature 27°C. Aluminium – CNT powder is compacted in a rigid molding with a compaction pressure of 160 MPa. Variation of sintering 100°C, 200°C, 300°C, 400°C, 500°C with a time of 60 minutes. The PM method proves that the mechanical properties and physical properties of the material are improved. Material shrinkage after sintering is large by forming shrinkage. Hardness test results with Rockwell, 26.5HR, 27.9HR, 28.8HR 29.9HR, 32.5HR. Wear rate 0.196 mm3/m, 0.078mm3/m, 0.054mm3/m, 0.052mm3/m 0.049mm3/m. Porosity values are 6.30%, 6.28%, 5.98%, 4.51%, 4.58%. The higher the sintering tem-perature, the higher the hardness value, the lower the porosity and wear.

New Numerically Derived Scaling Relationships for Impact Basins on Mars

AbstractMost impact basins are believed to have formed during the early epochs of planetary evolution. The planet's gravity, internal structure, and thermal regime have the strongest control over their formation. Because of this, we can use the geophysical constraints on Mars' interior composition, structure, and geophysical evolution derived from the InSight mission to better understand the formation of impact basins on the planet. To achieve this, we performed numerical simulations of large impacts using the iSALE shock physics code. We investigated the effects of temperature and crustal thickness variations on impact basin size and morphology. Our scaling relationships indicate that: (a) basins formed in a warmer crust have larger final diameters in comparison to basins formed in a colder crust, a difference that is further accentuated as basin size gets bigger; and (b) the largest impact basins on Mars were created by impactors ranging from 35 to 680 km in diameter, up to ∼32% larger than estimates based on classical scaling. Our results expand the current understanding of the extent of early and large impact bombardment on Mars and provide a more comprehensive knowledge of impact basin formation on planetary surfaces.

Effects of thermophily-relevant temperature variation and sex on digestive performance in pythons

Different physiological performances are often optimized at slightly varying temperatures, which can lead to ectotherms selecting higher body temperatures during certain physiological efforts (e.g., digestion, reproduction). Such thermophilic responses can lead to temperature-based tradeoffs between two physiological activities with differing optimal temperatures or between optimizing a physiological activity and water balance, as water loss is elevated at higher temperatures. For example, ectotherms will often select a higher body temperature after consuming a meal, but the extent to which body temperature is elevated after eating is affected by its hydric state. Despite this known hydration state-based suppression of thermophily associated with digestion, the impact of this reduced body temperature on digestion performance is unknown. Accordingly, we determined whether small, thermophily-relevant changes in body temperature impact digestive efficiency or passage time and whether sex influenced the extent of the effect. Eighteen (9 female and 9 male) Children's pythons (Antaresia childreni) each consumed a meal at three temperatures (29 °C, 30 °C, and 31 °C), and gut passage time and digestive efficiency were determined. We found that neither metric was affected by temperature over the range tested. However, digestive efficiency was significantly impacted by the interaction between sex and temperature with males having significantly lower digestive efficiency than females at 31 °C, but not 29 °C or 30 °C. Our results provide insight into the effects of temperature on digestive physiology across narrow temperature ranges as well as demonstrate a sex-based difference in digestive physiology.

A model for the temperature-dependent creep/recovery behavior of dry fiber fabric considering in-plane tension

In the manufacturing process of fiber-reinforced composite materials, the preforming of dry fiber fabrics is typically carried out under specific out-of-plane pressure, in-plane tension, and at designated temperatures. The fabric exhibits significant time and temperature-dependent permanent deformation as well as creep/recovery behavior. Gaining a better understanding of these phenomena and harnessing predictive capabilities will be instrumental in achieving more precise control over fiber volume fraction and material composition. In this paper, creep/recovery experiments and cyclic loading-unloading tests were conducted on CF3031 dry fiber preforms under various in-plane tensions and temperatures, measuring in-plane strains using Fiber Bragg Grating (FBG) sensors. Based on this data, a modified Burgers viscoelastic-plastic model has been proposed to describe the time-dependent creep/recovery behavior of dry fiber fabric preforming under the coupled effects of in-plane tension, out-of-plane pressure, and temperature variations. This model employs a single set of equations and parameters to represent the complete creep/recovery process of the material. The experimental results align well with the predicted outcomes across different compression scenarios.

PENGARUH VARIASI SUHU SINTERING ALUMUNIUM MATRIK YANG DIPERKUAT KARBON NANOTUBE TERHADAP NILAI KEKERASAN

This study examines the effect of sintering temperature variations on density values and Vickers hardness values on Aluminum Carbon Nanotubes. Tests were conducted using five temperature variations, namely sintering 400°C, 500°C, 600°C, 700°C, and unsintered. The results showed that the 400°C sintering temperature variation produced higher hardness values than the 500°C, 600°C, 700°C, and unsintered sintering temperature variations. AlCNT specimens at a sintering temperature of 400°C have an average hardness value of 46.92 VHN, while at a sintering temperature of 500°C have an average hardness value of 30.48 VHN, while at a sintering temperature of 600°C have an average hardness value of 29.04 VHN, while at a sintering temperature of 700°C have an average hardness value of 26.17 VHN, while at a sintering temperature of 0°C have an average hardness value of 39.79 VHN. Therefore, it is found that the best sintering temperature variation for AlCNT specimens is 400°C for the application of sintering to aluminum carbon nanotubes. In addition, this research can be a reference for further researchers in developing manufacturing methods and characterization of aluminum reinforced with carbon nanotubes to obtain optimal results.

Coupling strengthening mechanism of precipitate and solute atoms in edge dislocation motion of Al-Mg-Si alloy

To investigate the coupling strengthening mechanism of precipitate and Cu solute atoms in Al-Mg-Si alloy, the molecular dynamics model of edge dislocation motion interacted with precipitate and Cu solute atoms was established. The dislocation length is increased in the dislocation-precipitate interaction due to the bending and bowing of the edge dislocation around the precipitate. No coupling between precipitate and solute can be found in material strengthening in cases with lower solute concentrations. The exponential effect of the coupling effects between precipitate and solute on material strengthening is found when the solute concentration is increased above 0.3.at% at room temperature. The change of the edge dislocation caused by solute atoms around the precipitate is the key reason for the strengthening coupling effect. Furthermore, the effects of temperature variations on the coupling effect are more pronounced than the effects of shear strain rate variations. When the temperature is increased from 200K to 500K, the critical ratio of solute and precipitate strengthening is decreased from 1.5 to 0.4.

Reduced OFF-state current and suppressed ambipolarity in a dopingless vertical TFET with dual-drain for high-frequency circuit applications

In this article, a dopingless TFET with dual-drain and reversed T-shaped channel (DLVIT-TFET) is investigated to offer improvement in ON-state current (IOn) along with the reduction in OFF-state leakage current (IOff) and in ambipolarity. The investigated device has a dual channel region which helps in improving the on-state parameters like IOn and subthreshold swing (SS) due to the extended tunneling area. The inverted T-shaped channel minimizes the charge carriers to tunnel during the off-state, thereby reducing the magnitude of IOff. The results obtained from 2D TCAD simulation show that the investigated device provides ∼1 order of improvement in IOn and ∼3 orders of improvement in IOff. Furthermore, DLVIT-TFET offers an ∼3 orders of improvement in ambipolar current (IAmb) due to a reduction in peak electric field at channel-drain interface caused by splitting of drain potential at ambipolar state. Moreover, various analog/RF parameters such as transconductance (gm), gate parasitic capacitance (Cgd, and Cgs), cut-off frequency (fTmax), gain-bandwidth product (GBP), transconductance-frequency product (TFP) and transit time (τ) are found to be improved in DLVIT-TFET compared to the conventional DL-TFET. In addition, the transient analysis of DLVIT-TFET based inverter is analyzed, which shows improvement in the parameters like propagation delay and voltage swing. Finally, reliability of the investigated device is discussed by considering the effect of interface trap charges (ITCs) and variation in ambient temperature and it is observed that DLVIT-TFET is more immune to such defects and environmental factors than the conventional one.

Living in a dynamic environment: The effects of multi-ways temperature variation on embryo and newborn juveniles of a shallow-water octopus (Amphioctopus fangsiao)

Shallow waters are characterized by fluctuating environmental conditions, modulating marine life cycles and biological phenomena. Multiple variations in water temperature could affect eggs and embryos during spawning events of many marine invertebrate species, yet most of the findings on embryonic development in invertebrates come from experiments based on the constant temperature. In this study, to examine the effects of temperature variation on octopus embryos, Amphioctopus fangsiao, a common shallow-water octopus along the coast of China, was exposed to the constant temperature (18 °C, in situ temperature of the seawater in Lianyungang), ramping temperatures (from 18 to 24 °C), diel oscillating temperatures (18 °C and 20 °C for 12 h each day), and acute increasing temperatures (the temperature increased sharply from 18 °C to 24 °C at embryonic development stage XIX) for 47 days (from embryogenesis to settlement). The results demonstrated that the temperature variations accelerated the development time of A. fangsiao embryos. Temperature fluctuations could cause embryonic oxidative damage and disorder of glycolipid metabolism, thereby affecting the growth performance of embryos and the survival rate of hatchings. Through transcriptome sequencing, the mechanistic adaption of the embryo to environmental temperature variations was revealed. The pathways involved in the TCA cycle, DNA replication and repair, protein synthesis, cell signaling, and nervous system damage repair were significantly enriched, indicating that the embryo could improve heat tolerance to thermal stress by regulating gene expression. Moreover, acute warming temperatures posed the most detrimental effects on A. fangsiao embryos, which could cause embryos to hatch prematurely from the vegetal pole, further reducing the survival of hatchings. Meanwhile, the diel oscillating temperature was observed to affect the normal morphology of the embryo, resulting in embryo deformities. Thus, the constant temperature is critical for balanced growth and defense status in octopuses by maintaining metabolism homeostasis. For the first time, this study evaluates the effects of multiple temperature fluctuations on embryos of A. fangsiao, providing new insights into the physiological changes and molecular responses of cephalopod embryos following dynamic temperature stress.

Effect of processing temperature on vitamin C content of Citrus aurantifolia drink using high performance liquid chromatography (HPLC)

Lime is rich in vitamin C, however, it is easily degraded by high processing temperatures. The aim of this study was to determine the effect of processing temperature variations on the vitamin C content in lime drinks using the HPLC method. This study used a completely randomized design with one factor, namely different processing temperatures (no processing, 5°C, 28°C, 38°C, and 90°C) with 5 repetitions. The results showed that the processing temperature significantly affected in decreasing vitamin C content of lime drinks. The higher the processing temperature, the lower the measured vitamin C content. Lime drinks without processing have a higher vitamin C content (0.0330%) compared to 5ºC temperature (0.0328%), 28°C temperature (0.0318%), 38°C temperature (0.0317%), and 90°C temperature (0.0309%).

Effects of Temperature, Molecular Weight, and Non-Solvent Variation on the Physical Properties of PVDF Membranes Prepared through Immersion Precipitation

Research on porous membrane technology is proliferating, especially in the process of fabrication of membranes. Different methods in membrane fabrication can affect the physical and chemical properties of the produced membrane. This study aims to investigate the influence of temperature, molecular weight, and non-solvent type on the physical-chemical properties of PVDF membranes. The membrane was produced by the immersion precipitation method with varying PVDF molecular weights of 64 kDa, 352 kDa (Solef 1010), 534 kDa, and 573 kDa (Solef 1015); non-solvent variations of alcohol (methanol, ethanol, isopropyl alcohol, and butanol); and drying temperature variations of 40, 50, and 60°C. The produced membranes were analyzed using ATR-FTIR, XRD, TGA, DSC, and SEM, and their wettability properties were evaluated using water contact angles. The optimal drying temperature for membrane production was 60°C. The ATR-FTIR data showed that molecular weight impacted membrane structure, where PVDF MW 534 kDa membrane had the highest percentage of β phase (77.47%). Non-solvent changes also affected membrane structure; PVDF Solef 1010 with non-solvent isopropyl alcohol had the highest percentage of β phase (67.45%). This is supported by the XRD diffractogram that displayed peaks at 2θ values between 20.24° and 20.66°, indicating the presence of a phase β PVDF. The thermal analysis exhibited three stages of degradation for Solef 1010 with ethanol non-solvent and two for the other seven membranes. The degradation temperature increases with the increase in molecular weight and the difference in non-solvents. The highest thermal stability membrane was PVDF Solef 1010 with isopropyl alcohol non-solvent (430°C). SEM images showed the membrane with non-solvent isopropyl alcohol, displaying a dense sponge-like morphology. The wettability of membranes is affected by molecular weight and non-solvent type. The membrane with isopropyl alcohol non-solvent obtained the smallest contact angle (54.77°) and indicated the most wettability membrane.

Improved response spectrum analysis procedure for an adaptive variable friction pendulum isolated structure considering frictional dependency

The effectiveness of the conventional friction pendulum isolator (FPI) is limited in complex geographical environments and unpredictable earthquake events due to its complex frictional properties and the requirement for a unified setup target. With a view to addressing the aforementioned issues, in conjunction with an adaptive variable friction pendulum isolator (AVFPI), a simple and practical mechanical model is proposed. After applying the mechanical model with a friction-dependent influence model, an improved response spectrum analysis procedure (IRS) is proposed for variable friction pendulum isolation systems. Notably, the proposed procedure allows for the consideration of the effects of variations in velocity, temperature, and pressure on the friction characteristics without the necessity for nonlinear response history analysis (NRHA). The procedure commences with obtaining a numerical model of friction dependency through friction material examinations, then proceeds to verifying the reliability of both the friction dependency and mechanical model through prototype tests of AVFPIs. The following study presents a proposed correction method that depends on random vibration theory to establish a functional relationship between the pseudo-velocity spectrum and the velocity spectrum. Additionally, an association is established between the peak velocity and the generation of frictional heat. Finally, the procedure is evaluated based on the results of an NRHA that takes friction dependence into account through a numerically variable friction pendulum isolation system. The results of the study indicate that the IRS provides a more accurate and secure assessment of the isolator displacement at various temperatures than the response spectrum method, which does not account for the influence of frictional dependency. The failure to consider the influence of friction dependency in high-temperature environments produces an underestimation of isolator slip displacement and a subsequent increase in failure rates. The Polytetrafluoroethylene (PTFE) friction materials that are currently in widespread use exhibit a strong correlation with friction dependence and, as a consequence, cause relatively large displacements at temperatures that are both low and high. The results of this study present an opportunity to expand how response spectrum analysis techniques can be applied to friction pendulum isolation systems.

Theoretical analysis of introducing CeOx as a passivation layer: an innovative approach to boosting CIGS solar cell efficiency

In this paper, we present a novel structure, AZO/CeOx/SnS2/CIGS/a-Si/Ag., simulated using SCAPS-1D. The structure features CeOx as a passivation layer, integrates SnS2 as an auxiliary absorber layer alongside the primary CIGS layer, and employs a-Si as a buffer layer. Our investigation focuses on evaluating the impact of material parameters on various electrical characteristics such as open-circuit voltage (Voc), short-circuit current (Jsc), efficiency (η), and fill factor (FF). We analyze the influence of layer thickness on the aforementioned characteristics and scrutinize the effects of temperature variation and series resistance on cell performance. After detailed calculations, we found that optimizing these parameters led to excellent performances, achieving an efficiency of 30.11%. This achievement was obtained under specific conditions, including the following layer thicknesses: CeOx (0.7 μm), CIGS (1.2 μm), and a-Si (0.1 μm), along with an optimal temperature of 302 K. This study aims to provide valuable insights to device manufacturers for enhancing the efficiency of CIGS solar cells.

Heat stress reduced survival but sped up development in Heliconius erato butterflies

AbstractAnthropogenic climate change is thought to present a significant threat to biodiversity, in particular to tropical ectotherms, and the effects of long‐term developmental heat stress on this group have received relatively little research attention. Here, we studied the effects of experimentally raising developmental temperatures on a tropical butterfly. We measured survival, development time, adult body mass and wing size of Heliconius erato demophoon (Linnaeus) (Lepidoptera: Nymphalidae) across three temperature treatments. Egg survival was lower in the hotter treatments, with 84%, 73% and 49% of eggs hatching in the 20–30°C (fluctuating temperature with 12 h at 20°C followed by 12 h at 30°C), 23–33°C and 26–36°C treatments, respectively. Larval survival was three times lower in the 26–36°C treatment (8%) compared with the 20–30°C treatment (26%), and we did not detect differences in pupal survival across treatments due to high mortality in earlier stages. Under a moderately increased temperature at 23–33°C, larvae developed faster and adults had a higher body mass and wing loading, but this was not seen in the hottest treatment (26–36°C). Females were also heavier than males in the 23–33°C treatment, but there was no associated increase in wing size. This may suggest a different developmental response to moderately elevated temperatures between the sexes. In summary, high developmental temperatures are particularly lethal for eggs and less so for larvae and also affect adult morphology. This highlights the importance of understanding the effects of temperature variation across ontogeny in tropical ectotherms.

Effects of protection and temperature variation on temporal stability in a marine reserve network.

Understanding the drivers of ecosystem stability has been a key focus of modern ecology as the impacts of the Anthropocene become more prevalent and extreme. Marine protected areas (MPAs) are tools used globally to promote biodiversity and mediate anthropogenic impacts. However, assessing the stability of natural ecosystems and responses to management actions is inherently challenging due to the complex dynamics of communities with many interdependent taxa. Using a 12-year time series of subtidal community structure in an MPA network in the Channel Islands (United States), we estimated species interaction strength (competition and predation), prey species synchrony, and temporal stability in trophic networks, as well as temporal variation in sea surface temperature to explore the causal drivers of temporal stability at community and metacommunity scales. At the community scale, only trophic networks in MPAs at Santa Rosa Island showed greater temporal stability than reference sites, likely driven by reduced prey synchrony. Across islands, competition was sometimes greater and predation always greater in MPAs compared with reference sites. Increases in interaction strength resulted in lower temporal stability of trophic networks. Although MPAs reduced prey synchrony at the metacommunity scale, reductions were insufficient to stabilize trophic networks. In contrast, temporal variation in sea surface temperature had strong positive direct effects on stability at the regional scale and indirect effects at the local scale through reductions in species interaction strength. Although MPAs can be effective management strategies for protecting certain species or locations, our findings for this MPA network suggest that temperature variation has a stronger influence on metacommunity temporal stability by mediating species interactions and promoting a mosaic of spatiotemporal variation in community structure of trophic networks. By capturing the full spectrum of environmental variation in network planning, MPAs will have the greatest capacity to promote ecosystem stability in response to climate change.

The impact of variation in water flow rate and temperature on reliability analysis of run of the river power plants

AbstractA run‐of‐the‐river power plant is a renewable energy source used for electricity production. Its power output depends on the varying water flow rate over time, which can impact the reliability of the electric network. Previous research has not studied the effects of water flow rate and temperature variations on the hazard rate of the plant's components. This paper addresses this gap by investigating the impact of these variations on the reliability of electric networks with run‐of‐the‐river power plants. The analysis considers the hazard rates of the plant's components, incorporating the relationship between hazard rate and temperature based on the Arrhenius law. Parameters such as power output, current, power loss, operating temperature, and hazard rate are calculated for different water flow rates and ambient temperatures. Numerical simulations on a test system are conducted to examine the influence of water flow rate and temperature on the reliability indices of the electric network. The results demonstrate that water flow rate and temperature significantly affect the hazard rates of run‐of‐the‐river power plants. This highlights the need to consider these factors in the reliability analysis of electric networks incorporating these renewable resources.

Quantitative monitoring of tensile force in post-tensioning systems using piezoelectric wave method

ABSTRACT The tensile force of a post-tensioning system is essential in prestressed concrete structures. Since the tensile force is related to the contact pressure at the interface between the anchor head and the bearing plate, this study utilizes the piezoelectric wave method to quantitatively monitor the reflected wave energy at the interface. A 3D solid element model was developed to simulate the propagation of stress waves in a simplified anchorage system across different contact areas. Three independent tests were conducted on a simplified 2-strand anchorage system, using the reception coefficient as a monitoring index. The empirical fitting formula between the reception coefficient and the load is derived from the loading data and verified using the unloading data. The experimental results demonstrate good monotonicity and stability within the test range. The study also conducted two temperature-based tests to investigate the effect of small temperature variations on the proposed method. The results indicate that temperature fluctuations of less than 20°C have little effect on the test method. Then, the proposed method is applied to a real 2-strand anchorage system in a concrete beam. The proposed method serves as a reference for quantitatively monitoring the prestressing force of a post-tensioning system.

Effects of density and temperature variations on the metallicity of Mrk 71

Effects of density and temperature variations on the metallicity of Mrk 71