Combined Effects Of Temperature Research Articles

Study on Fatigue Life of PC Composite Box Girder Bridge with Corrugated Steel Webs under the Combined Action of Temperature and Static Wind Loads

The large-span bridge is highly sensitive to temperature and wind loads. Therefore, it is essential to study the bridge’s fatigue life under the combined effects of temperature and static wind loads. This study focuses on the main bridge of Qiao Jia-fan 2# on the Yinkun Expressway (G85), with a span of 250 m and a configuration of a PC composite box girder bridge with corrugated steel webs. Firstly, on-site temperature and wind direction measurements with wind speed were conducted at the bridge site. Origin 2022 software is used to make mathematical statistics on the data, the representative values of atmospheric temperature difference between day and night and the basic wind speeds are calculated. Secondly, based on the basic wind speed in the most unfavorable wind direction, the static three-component force coefficients of bridge at different angles of attack are calculated by FLUENT 2022 R1 software. By comparison, the most unfavorable wind angle of attack, wind direction and wind load value of Qiao Jia-fan 2# Bridge are obtained. Finally, the finite element software MIDAS/FEA NX 2022 is used to analyze the fatigue life of the main bridge of the Qiao Jia-fan 2# Bridge. The analysis results show that the representative value of the temperature difference between day and night in the area where PC composite box girder bridge with corrugated steel webs is located is 22 °C, the most unfavorable wind direction is NNE wind direction, and the most unfavorable wind attack angle is 3° wind attack angle. It is found that the maximum stress of concrete and corrugated steel webs appears near the 0# block, and the life of corrugated steel webs is far greater than that of concrete.

Determination of optimal temperature, salinity, and stocking density combinations for larval growth and survival of diploid, triploid, and tetraploid Fujian oyster (Crassostrea angulata)

For nurseries, thriving larvae mean higher incomes. Three factors - temperature, salinity and stocking density - are critical to the success of larval rearing. However, the effects of these three factors on the performance of diploid, triploid and tetraploid Crassostrea angulata larvae have not yet been comprehensively investigated. In this study, the combined effects of temperature (T, 12.0–35.0 °C), salinity (S, 10.0–38.0 psu) and stocking density (D, 0.5–10.0 ind. ml−1) on the accumulated growth rate (AGR) and survival rate (SR) of diploids (DD), triploids (DT) and tetraploids (TT) C. angulata larvae were comprehensively assessed using a central composite design and response surface methodology. The results revealed that suitable temperature-salinity-stocking density combinations significantly increased the AGR and SR of larvae from all three groups, while unsuitable environments (e.g., ultra-high temperature - extra-high salinity -high stocking density combinations or ultra-high temperature - extra-low salinity - high stocking density combinations) significantly reduced the AGR and SR of the larvae, albeit to different magnitudes. The optimal temperature-salinity-stocking density combinations were obtained by model optimization. The maximum AGR and SR of DT reached at 23.6 °C, 26.5 psu and 0.5 ind. ml−1 combinations with values of 17.13 μm day−1 and 64.81%, respectively. The combinations of 24.0 °C - 25.89 psu - 1.99 ind. ml−1 and 25.9 °C - 25.96 psu - 0.5 ind. ml−1 were the optimal breeding conditions for DD and TT (DD: AGR = 13.10 μm day−1, SR = 63.55%; TT: AGR = 10.11 μm day−1, SR = 25.89%). In addition, validation experiments were carried out under the obtained optimum conditions. The AGR and SR of DD, DT and TT obtained from the validation experiments were basically in conformity with the maximum AGR and SR obtained under the theoretically predicted conditions. Moreover, the growth and survival of tetraploids remained lower than those of diploid and triploid counterparts, even under optimal breeding conditions. This means that more attention should be paid to the tetraploids so as to safeguard the succession of this fragile population. The application of the findings of this study will help to improve the breeding efficiency of C. angulata with different ploidies in larval culture.

Research on the Scaling Mechanism and Countermeasures of Tight Sandstone Gas Reservoirs Based on Machine Learning

The Sulige gas field is a typical “three lows” (low permeability, low pressure, and low abundance) tight sandstone gas reservoir, with formation pressures often characterized by abnormally high or low pressures. The complex geological features of the reservoir further deviate from conventional understanding, impacting the effective implementation of wellbore blockage removal measures. Therefore, it is imperative to establish the wellbore blockage mechanism, prediction model, and effective prevention measures for the target area. In this study, based on field data, we first experimentally analyzed the water quality and types of blockage in the target area. Subsequently, utilizing a BP neural network model, we established a model for predicting the risk of wellbore blockage and analyzing mitigation measures in the target reservoir. The model’s prediction results, consistent with on-site actual results, demonstrate its reliability and accuracy. Experimental results show that the water quality in the target area is mainly a CaCl2 type, and the predominant scales produced are CaCO3 and BaSO4. Model calculations reveal that temperature, pressure, and ion concentration all influence scaling, with BaSO4 more influenced by pressure and CaCO3 more influenced by temperature. Under the combined effect of temperature, pressure, and ion concentration, different types of scales exhibit distinct trends in scaling quantity. Combining scaling quantity calculations with wellbore contraction ratios, it was found that when the temperature, pressure, and ion concentration are within a certain range, the wellbore contraction rate can be controlled below 4%. At this point, the wellbore scaling risk is minimal, and preventive measures against wellbore scaling can be achieved by adjusting production systems, considering practical production conditions. This study investigates the mechanism of scaling in wellbores of tight sandstone gas reservoirs and proposes a cost-effective scaling prevention measure. This approach can guide the prediction of scaling risks and the implementation of scaling prevention measures for gas wells in tight sandstone reservoirs.

Defect-based fatigue crack nucleation and strength evaluation of additively manufactured TiC/Ti6Al4V titanium matrix composite at different temperatures

In mechanical applications, defect-based fatigue cracking is a significant strength-limiting failure mode of additively manufactured composites that is not yet fully understood in the service environment. In this paper, axial loading tests were carried out at 25 ℃ and 450 ℃, and then the effects of temperature on the long-life fatigue properties of the TiC-reinforced Ti6Al4V composite fabricated by Laser Powder Bed Fusion (LPBF) were investigated by combining the techniques of electron backscatter diffraction, X-ray computed tomography, and 3D morphological reconstruction. With the increase in temperature, the fatigue strength of the LPBF TiC/Ti6Al4V composite decreases significantly. The main causes of the interior failure at both temperatures are the inhomogeneous hardening zone (IHZ) formed by TiC agglomeration and the pore defect generated during the manufacturing process. The presence of brittle IHZ and pores causes stress concentration, which leads to crack nucleation. When a crack reaches the specimen surface, the combined effects of temperature and oxygen accelerate the ensuing crack propagation at high temperature. Based on the temperature effect, material properties, and the statistical distribution of defects, a model has been developed to predict the P-S-N curves at both temperatures. This model performed well in estimating the fatigue strength at 109 cycles. These findings provide new insights into the defect-related fatigue failure mechanisms and strength evaluation of the LPBF TiC/Ti6Al4V composite at different temperatures.

Combined effects of temperature, salinity and rearing density on the larval growth and survival of the diploid, triploid and tetraploid of the Pacific oyster Crassostrea gigas

The Pacific oyster, Crassostrea gigas, is a commercially important species, which is widely cultured in the world. In recent years, triploid cultivation of C. gigas has gradually emerged due to the advantages of poor fertility and rapid growth in China. However, the adaptation of triploid and tetraploid larvae to temperature, salinity and rearing density has not been studied. A central composite design and a response surface method were used to analyze the combined effects of temperature, salinity and rearing density on growth and survival of triploid and tetraploid larvae. Temperature, salinity and rearing density exerted significant effects on larvae growth and survival of triploid and tetraploid. Rearing density was identified as the most significant negative factor affecting the growth and survival of three populations. The reliable models on accumulated growth rate (AGR) and survival rate (SR) of three populations were obtained. The optimal conditions for larval development in the three populations were achieved by simultaneously maximizing growth and survival models. In diploids, the maximum AGR of 13.92 μm day−1 and the maximum SR of 65.73 were achieved at 23.66 °C / 28.47 psu / 2.23 ind.ml−1 with a value of desirability being 100%. In triploids, the maximum AGR of 15.82 μm day−1 and the maximum SR of 69.26 were achieved at 23.16 °C / 30.67 psu / 2.15 ind.ml−1 with a value of desirability being 100%. In tetraploids, the maximum AGR of 10.75 μm day−1 and the maximum SR of 46.29 were achieved at the 25.48 °C / 28.94 psu / 2.00 ind.ml−1 with a value of desirability being 95%. This study provides valuable new insights into refining the production efficiency of C. gigas larvae of different ploidy.

The volume change behavior of compacted GMZ bentonite: combined effects of temperature and suction

The volume change behavior of compacted GMZ bentonite: combined effects of temperature and suction

One-Dimensional Numerical Simulation on Removal of CO2 Hydrate Blockage around Wellbore by N2 Injection

CO2 sequestration in sediments as solid hydrate is considered a potential way to capture and store anthropogenic CO2. When CO2 hydrate is formed in front of CO2 migration, the injection channel will be blocked, and the removal of hydrate blockage becomes the first problem that must be faced. This work proposed an N2 injection method to remove CO2 hydrate blockage. Based on numerical simulation, a study was conducted using TOUGH+MIXHYD v.1.0 to confirm the feasibility of N2 injection and compare it to depressurization. The spatial and temporal distribution characteristics of pressure, temperature, hydrate saturation, and gas saturation were investigated. Under the combined effects of temperature, pressure, and gas composition, secondary CO2-N2 hydrate can form far from the injection point, causing an increase in local temperature and hydrate saturation. The rate of CO2 hydrate dissociation using direct depressurization is significantly slower compared to N2 injection methods. As the pressure of N2 injection increases, the rate of CO2 hydrate dissociation notably accelerates, which does not show a significant increase with increasing injection temperature. This work introduced a novel approach to addressing the issue of CO2 hydrate blockage, which holds prominent significance for the advancement of hydrate-based CO2 geological sequestration.

Assessing the escalating human-perceived heatwaves in a warming world: The case of China

With increased global warming, heatwaves are expected to become more intense, frequent, and persistent. Although the spatiotemporal characteristics of heatwaves have been extensively studied, the vast majority of these studies have solely used near-surface air temperatures, particularly daily maximum temperatures (Tmax), to identify heatwaves. Given that air temperature alone proves inadequate as a metric for human heat stress. Here, using the relative threshold in conjunction with the absolute threshold and basing it on wet bulb globe temperature (WBGT), we develop a novel definition of human-perceived heatwaves. The combined effect of temperature and humidity is considered in this definition. On this basis, we quantify the climatology of and long-term changes in heatwaves in China based on homogenized in situ observations and outputs from climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). The results show that the distribution of human-perceived heatwaves coincides with densely populated areas in the southeastern part of China, despite their limited spatial extent. The observed trends in human-perceived heatwaves have accelerated since the 1960s. It is now anticipated that moderate or worse human-perceived heatwaves will affect more than half of China's population. Moreover, CMIP6 climate projections suggest that the percentage of China's population exposed to historically unprecedented human-perceived heatwaves would increase rapidly in a warmer future, except for the sustainability scenario. It is noted that the increase in severe human-perceived heatwaves is more rapid than that in severe traditional Tmax-based heatwaves, suggesting that the hazard of heatwaves to humans may have been underestimated by previous Tmax-based studies. Our findings demonstrate the urgent need for additional planning and adaptation actions beyond the framework for short-term disaster reduction frameworks currently in place. Although we concentrated on China in this article, our method for evaluating human-perceived heatwaves is easily extended to handle comparable issues everywhere.

Higher temperature accelerates the aging-dependent weakening of the melanization immune response in mosquitoes.

The body temperature of mosquitoes, like most insects, is dictated by the environmental temperature. Climate change is increasing the body temperature of insects and thereby altering physiological processes such as immune proficiency. Aging also alters insect physiology, resulting in the weakening of the immune system in a process called senescence. Although both temperature and aging independently affect the immune system, it is unknown whether temperature alters the rate of immune senescence. Here, we evaluated the independent and combined effects of temperature (27°C, 30°C and 32°C) and aging (1, 5, 10 and 15 days old) on the melanization immune response of the adult female mosquito, Anopheles gambiae. Using a spectrophotometric assay that measures phenoloxidase activity (a rate limiting enzyme) in hemolymph, and therefore, the melanization potential of the mosquito, we discovered that the strength of melanization decreases with higher temperature, aging, and infection. Moreover, when the temperature is higher, the aging-dependent decline in melanization begins at a younger age. Using an optical assay that measures melanin deposition on the abdominal wall and in the periostial regions of the heart, we found that melanin is deposited after infection, that this deposition decreases with aging, and that this aging-dependent decline is accelerated by higher temperature. This study demonstrates that higher temperature accelerates immune senescence in mosquitoes, with higher temperature uncoupling physiological age from chronological age. These findings highlight the importance of investigating the consequences of climate change on how disease transmission by mosquitoes is affected by aging.

Decoupling the Effects of Temperature and High Photon Fluxes in Photoelectrochemical Water Splitting

The production of solar fuels by using concentrated irradiation allows for smaller and cheaper devices, and ultimately lower fuel production costs, with the added benefit of increased performances if operating conditions are chosen judiciously [1]. Photoelectrochemical (PEC) water splitting has been studied mostly at room temperature and under 1 sun illumination, hence there are still unrealized possibilities for solar fuel production by using high photon fluxes. However, the potentially advantageous synergy between higher temperatures and irradiation, also renders the system complex and difficult to study. The effect of temperature alone on photoelectrode performances has been reported for several semiconducting materials, e.g. Fe2O3 [2] and BiVO4 [3]; while the effect of high photon fluxes has been investigated separately up to 30 suns [4]. The combined effects of temperature and high irradiations on the performance of PEC devices has been rarely investigated experimentally, this is mostly due to the complexity of decoupling the effects due to increased surface temperature, photon fluxes and degradation rates.With the aim to address this challenge, we developed a PEC cell for operation at high irradiations, 30 – 360 kW m-2, along with a multiphysics model to predict the increased surface temperature and the inevitable effects related to ohmic drop, bubble evolution and current density distribution. The PEC cell was equipped with thermocouples to measure the temperature of the photoelectrode and electrolyte at different positions inside the device. Additionally, the effects of temperature alone were investigated under 1 sun by heating the electrolyte between 20 and 55 °C. Two photoelectrodes were investigated: BiVO4 and Sn-doped Fe2O3, deposited via spray pyrolysis on FTO or Ti foil.Our findings suggest that the losses due to bubbles and ohmic drop could account for up to 90% and 50% of the losses in photocurrent densities for FTO and Ti substrates, respectively. And although, increased temperatures improve the charge carrier transport, electrolyte conductivity and oxygen evolution kinetics and thermodynamics, these effects could be offset by the aforementioned losses. For hematite operating at high temperatures (55 °C) under 1 sun illumination, it was found that the surface charge transfer efficiency decreases at low electrode potentials; in contrast, impedance spectroscopy under high irradiation indicates that the charge transfer efficiencies actually increases, even when the surface of the photoelectrodes were at higher temperatures. This suggests that although e-h recombination kinetics increases with temperature, the increased charge transport kinetics and higher exciton concentration could ultimately favor the charge transfer at the photoelectrode | electrolyte interface, see Fig 1a. In the case of BiVO4, the rate of photocurrent decay does not follow a linear relationship with increased irradiation, and its performance can be predicted by a transient model accounting for dissolution and changing thicknesses. Our results at higher irradiations reveal that the highest normalized current density for BiVO4 was achieved at ca. 120 kW m-2 as shown in Fig. 1b.Hence, the electrolyte flow and the irradiation concentration should be carefully chosen in order to keep the photoelectrode surface at appropriate temperatures, while also preventing the buildup of bubbles and current density distribution. This work shows the promise of using the synergy of temperature and high photon fluxes for PEC water splitting, while also warning about engineering and material challenges that should be addressed for a successful application of this approach for solar fuel production.

Mitigating short-circuits through synergistic temperature and hydraulic retention time control for enhancing methane yield in continuous stirred-tank reactors

Temperature and hydraulic retention time (HRT) control are crucial for mitigating the “short-circuit” issue and enhancing methane production in continuous stirred-tank reactors. This study focuses on the combined effects of temperature and HRT on methanation via operating the reactors at different temperatures (35 °C, 45 °C, and 55 °C) and HRT (30, 25, and 20 d) for 116 days. The results demonstrated that the digester conducted at 45 °C and an HRT of 30 d unexpectedly yielded the maximum average methane production of 296.08 ml/g volatile solids (VS). In contrast, the optimal HRT for the 35 °C and 55 °C digesters were 25 and 30 d, with a methane yield of 241.88 ml/g VS and 240.9 ml/g VS, respectively. High-throughput sequencing shows that Firmicutes, Bacteroidetes, Themotogae, Chloroflexi, and Acidobacteria dominated 90–98 % of the total bacteria. Temperature exhibited a significant influence on shaping microbial ecosystems, indicating that temperature, rather than HRT, is the primary factor to consider. Additionally, metagenomic analysis reveals that the levels of genes involved in acetoclastic and hydrogenotrophic methanogenic pathways were enhanced at 45 °C, probably improving methane yield. These findings provide new insights into “short-circuit” mitigation and strategies to strengthen methane generation from biomass.

Combined Radiation and Temperature Effects on Brillouin-Based Optical Fiber Sensors

The combined effects of temperature (from −80 °C to +80 °C) and 100 kV X-ray exposure (up to 108 kGy(SiO2)) on the physical properties of Brillouin scattering and losses in three differently doped silica-based optical fibers, with varying dopant type and concentration (4 wt%(Ge), 10 wt%(Ge) and 1 wt%(F)), are experimentally studied in this work. The dependencies of Brillouin Frequency Shifts (BFS), Radiation-Induced Attenuation (RIA) levels, Brillouin gain attenuation, Brillouin frequency temperature (CT) and strain (Cε) sensitivity coefficients are studied under X-rays in a wide temperature range [−80 °C; +80 °C]. Brillouin sensing capabilities are investigated using a Brillouin Optical Time Domain Analyzer (BOTDA), and several properties are reported: (i) similar behavior of the Brillouin gain amplitude decrease with the increase in the RIA; (ii) the F-doped and heavily Ge-doped fibers do not exhibit a temperature dependence under radiation for their responses in Brillouin gain losses. Increasing Ge dopant concentration also reduces the irradiation temperature effect on RIA. In addition, Radiation-Induced Brillouin Frequency Shift (RI-BFS) manifests a slightly different behavior for lower temperatures than RIA, presenting an opportunity for a comprehensive understanding of RI-BFS origins. Related temperature and strain sensors are designed for harsh environments over an extended irradiation temperature range, which is useful for a wide range of applications.

Higher temperature, increased CO2, and changing nutrient ratios alter the carbon metabolism and induce oxidative stress in a cosmopolitan diatom

AbstractPhytoplankton are responsible for about 90% of the oceanic primary production, largely supporting marine food webs, and actively contributing to the biogeochemical cycling of carbon. Yet, increasing temperature and pCO2, along with higher dissolved nitrogen: phosphorus ratios in coastal waters are likely to impact phytoplankton physiology, especially in terms of photosynthetic rate, respiration, and dissolved organic carbon (DOC) production. Here, we conducted a full‐factorial experiment to identify the individual and combined effects of temperature, pCO2, and N : P ratio on the antioxidant capacity and carbon metabolism of the diatom Phaeodactylum tricornutum. Our results demonstrate that, among these three drivers, temperature is the most influential factor on the physiology of this species, with warming causing oxidative stress and lower activity of antioxidant enzymes. Furthermore, the photosynthetic rate was higher under warmer conditions and higher pCO2, and, together with a lower dark respiration rate and higher DOC exudation, generated cells with lower carbon content. An enhanced oceanic CO2 uptake and an overall stimulated microbial loop benefiting from higher DOC exudation are potential longer‐term consequences of rising temperatures, elevated pCO2 as well as shifted dissolved N : P ratios.

Stability study of aqueous foams under high-temperature and high-pressure conditions relevant to Enhanced Geothermal Systems (EGS)

In Enhanced Geothermal System (EGS) hydraulic fracturing is carried out by injecting cold water into deep Hot Dry Rocks (HDR) under carefully controlled conditions to create new or reopen existing fractures. Water-based fracturing fluids demonstrate some challenges including immense quantity of water usage, water sensitivity of the formations, water blocking, and lack of proppant carrying capacity and transportation. Thus, an alternative is to use foam-based fracturing fluid which offers potential advantage over conventional water-based fracturing fluid such as minimum water usage, reduced wellbore damage, high proppant carrying capacity, and less environmental damage. However, foams are complex mixture of gaseous phase and liquid phase which are thermodynamically unstable at downhole conditions, and their stability can decrease over time due to liquid drainage, bubble coarsening, and coalescence. This paper shows laboratory experiments executed to study foam stability at high temperature (200 °C) and high pressure (6.9 MPa) conditions which simulates the geothermal environment. Foam stability was characterized by half-life of foam, which is defined as the time taken by the foam to decreases by 50% of its original height due to drainage. In this paper, two types of gaseous phases, nitrogen (N2) and carbon dioxide (CO2) were investigated. Also, based on successful practice of foam-based fracturing fluid in oil and gas industries, four surfactants, including Alpha olefin sulfonate (AOS), Sodium dodecyl sulfonate (SDS), Tergitol™ (NP – 40), and Cetyltrimethylammonium chloride (CTAC) at optimum concentration of 1 wt.% were tested for best stability performance. In addition, different stabilizing agents including guar gum, bentonite clay, crosslinker, silicon dioxide nanoparticles (SiO2), graphene oxide (GO) were also studied. Experimental results showed that N2 foams were more stable than CO2 foams. It was observed that foam half-life decreased with the increase in temperature. Among all the surfactants, AOS foams showed the most promising thermal stability at high temperatures. Moreover, with the addition of stabilizing agents, foam's half-life was enhanced. Stabilizing agents such as crosslinker and GO dispersion showed the most stable foams with half-life recorded at 20 min and 17 min, respectively, at 200 °C and 6.9 MPa. Finally, pressure also showed a positive effect on foam stability; with increased pressure, foam half-life was increased. Based on the experimental data, analytical models for the effect of temperature and pressure were developed, considering foam degradation is a first-order kinetic reaction that linearly depends on the foam drainage mechanism. The effect of temperature on foam half-life was studied as an exponential decay model. In this model, foam half-life is a function of drainage rate constant (DA) and activation energy (Ea) of the foam system. The effect of pressure on foam half-life was found to obey a power-law model where an increase in pressure showed an increase in foam half-life. Furthermore, a linear relation was studied for the effect of pressure on foam activation energy and drainage rate. Then the combined effects of temperature and pressure were studied, which yielded an analytical model to predict the foam stabilities in terms of half-life for different foam compositions. This research indicates that with an appropriate selection of surfactants and stabilizing agents, it is possible to obtain stable foams, which could replace conventional water fracturing fluid under EGS conditions.

Surface deformation detection and attribution in the Mountain-Oasis-Desert Landscape in north Tianshan Mountains

ABSTRACT The Mountain-Oasis-Desert System (MODS) is the fundamental landscape component within the vast arid region of Central Asia. Human activities and natural processes cause surface displacement in the MODS, resulting in geoenvironmental issues and hazards. However, surface displacement and its driving mechanisms in the MODS are not understood. In this study, we used the time-series interferometric synthetic aperture radar (InSAR) method to detect deformation in the MODS in north Tianshan Mountain, Xinjiang and investigated its attribution from the geological conditions, groundwater level changes, and climate variability. The results along the vertical gradient indicate that decorrelation is severe in the high mountain areas with ice-marginal environments (over 3600 m above sea level (a.s.l.)) and the forest-covered mid-mountainous belt (1700–2800 m asl), rendering effective detection unfeasible. Dynamic characteristics are identified in subalpine areas with an elevation of 2800–3600 m asl, with maximum horizontal and vertical displacements of −80.2 mm/year and −58.6 mm/year, respectively. The seasonal acceleration is influenced by the combined effects of temperature and precipitation changes. We observed dense subsidence funnels and ground fissures associated with coal mining in the foreland hills (700–1700 m asl). Ground displacements here exceeded −50 mm/year two years after mining activities had ceased. Subsidence has expanded in the oases with elevations of less than 700 m asl, due to extensive groundwater extraction for agricultural irrigation. The correlation coefficient between groundwater level and displacement was 0.89 and 0.45 at wells in the agricultural and desert areas, respectively. The deformation exhibited seasonal variations associated with groundwater level. The deformation remains relatively stable in the surrounding oasis-affected desert areas, with weak fluctuations influenced by seasonal variations in groundwater level.

Combined effects of temperature and emersion-immersion cycles on metabolism and bioenergetics of the Pacific oyster Crassostrea (Magallana) gigas

Life on tidal coasts presents physiological major challenges for sessile species. Fluctuations in oxygen and temperature can affect bioenergetics and modulate metabolism and redox balance, but their combined effects are not well understood. We investigated the effects of intermittent hypoxia (12h/12h) in combination with different temperature regimes (normal (15 °C), elevated (30 °C) and fluctuating (15 °C water/30 °C air)) on the Pacific oyster Crassostrea (Magallana) gigas. Fluctuating temperature led to energetic costly metabolic rearrangements and accumulation of proteins in oyster tissues. Elevated temperature led to high (60%) mortality and oxidative damage in survivors. Normal temperature had no major negative effects but caused metabolic shifts. Our study shows high plasticity of oyster metabolism in response to oxygen and temperature fluctuations and indicates that metabolic adjustments to oxygen deficiency are strongly modulated by the ambient temperature. Co-exposure to constant elevated temperature and intermittent hypoxia demonstrates the limits of this adaptive metabolic plasticity.

Impacts of exposure to humidex on cardiovascular mortality: a multi-city study in Southwest China

BackgroundMany studies have reported the association between ambient temperature and mortality from cardiovascular disease (CVD). However, the health effects of humidity are still unclear, much less the combined effects of temperature and humidity. In this study, we used humidex to quantify the effect of temperature and humidity combined on CVD mortality.MethodsDaily meteorological, air pollution, and CVD mortality data were collected in four cities in southwest China. We used a distributed lag non-linear model (DLNM) in the first stage to assess the exposure–response association between humidex and city-specific CVD mortality. A multivariate meta-analysis was conducted in the second stage to pool these effects at the overall level. To evaluate the mortality burden of high and low humidex, we determined the attributable fraction (AF). According to the abovementioned processes, stratified analyses were conducted based on various demographic factors.ResultsHumidex and the CVD exposure–response curve showed an inverted “J” shape, the minimum mortality humidex (MMH) was 31.7 (77th percentile), and the cumulative relative risk (CRR) was 2.27 (95% confidence interval [CI], 1.76–2.91). At extremely high and low humidex, CRRs were 1.19 (95% CI, 0.98–1.44) and 2.52 (95% CI, 1.88–3.38), respectively. The burden of CVD mortality attributed to non-optimal humidex was 21.59% (95% empirical CI [eCI], 18.12–24.59%), most of which was due to low humidex, with an AF of 20.16% (95% eCI, 16.72–23.23%).ConclusionsLow humidex could significantly increase the risk of CVD mortality, and vulnerability to humidex differed across populations with different demographic characteristics. The elderly (> 64 years old), unmarried people, and those with a limited level of education (1–9 years) were especially susceptible to low humidex. Therefore, humidex is appropriate as a predictor in a CVD early-warning system.

Combined effects of temperature, photoperiod, and salinity on reproduction of the brine shrimp Artemia sinica (Crustacea: Anostraca).

Artemia sinica is a brine shrimp species distributed in hypersaline salt lakes in northern China and Siberia and a successful invasive species in some coastal salterns. Although it is a commercially harvested and cultured species, knowledge of its reproductive characteristics is limited, and existing studies are often contradictory. The combined effects of temperature, salinity, and photoperiod on reproduction characteristics are experimentally studied to better understand its reproductive features. There were 36 combinations of three environmental factors (3×3×4), each with three or four levels, namely temperature (16, 25, 30°C), photoperiod (6 L:18 D, 12 L:12D, 18 L:6D), and salinity (50, 100, 150, 200 PSU). In each treatment, 48 to 80 pairs of A. sinica from Yuncheng Salt Lake (Shanxi, China) were cultured. Females were observed daily for reproductive mode and the number of offspring produced. Temperature, photoperiod, salinity, and their interactions significantly affected the lifespan and reproduction of A. sinica. The reproductive period was the longest and accounted for the largest proportion of life span at moderate temperature (25°C). Total offspring, offspring per brood, and offspring per day increased as salinity decreased, and the number of broods per female was highest at 25°C. Temperature, photoperiod, and salinity significantly influenced reproductive modes, and interactions among these factors were identified. Artemia sinica primarily reproduces oviparously under low temperature and short daylight conditions, and ovoviviparously under high temperature and long daylight conditions, with the maximum oviparity ratio recorded in treatments of 16°C, 6L:18D, and 50 or 100 PSU. The maximum ovoviviparity ratio was recorded under 30°C, 12L:12D, and 100 PSU. Unlike that documented for other Artemia species or populations, the brood size of A. sinica kept increasing throughout the reproductive period. It did not decline even in the last two broods. For the same brood number, the sizes of oviparous and ovoviviparous broods were similar. The length of the oviparous interval was often greater than that of the ovoviviparous interval, suggesting that oviparous offspring might require additional energy and time to construct the multi-layered eggshell. Compared to other species and populations, the A.sinica from Yuncheng Salt Lake has a relatively shorter pre-reproductive development time, a preference for ovoviviparity, and relatively higher fecundity and population growth capacity, making it a suitable culture species for obtaining fresh biomass.

Mechanical Performance of Artificially Rusted Q500MC Structural Steel Subjected to High Temperature

Steel is prone to rusting in a corrosive environment, which results in a reduction of the effective bearing section of the steel structure. The stress concentration at the location of rusting causes brittle fracture of the steel structure during service. Although there is valuable research on the mechanism of corrosion and corrosion failure, research on the high-temperature mechanical properties of corroded steel is still limited. In this study, one-sided artificial accelerated corrosion of Q500 steel was performed, and a high-temperature steady-state tensile test was conducted on it. The degradation law and influencing factors of the high-temperature mechanical properties of corroded steel were discussed and analyzed using scanning electron microscopy (SEM) to quantify the corrosion surface morphology, and the volume corrosion ratio was used to characterize the degree of corrosion. The results showed that when the temperature was below 500°C, the attenuation of the ultimate load of corroded steel was influenced by the combined effect of temperature and corrosion. When the temperature exceeded 500°C, the influence of corrosion on the attenuation of the ultimate load tended to decrease due to the reduction in the material properties of steel. Furthermore, after the temperature exceeded 500°C, the elongation of the corroded section of the specimen increased gradually with the increase in temperature, and the elongation tended to be consistent even at different degrees of corrosion.

Combined effects of temperature and monsoon on seasonal variations of atmospheric polycyclic aromatic hydrocarbons in the coastal Shanghai, China

An intensive sampling program was conducted at two coastal sites of megacity Shanghai - the emerging town Lingang New Area (LGNA), and the petrochemical-industry zone Jinshan Area (JSA) from July 2016–June 2017, to study the occurrence, sources, environmental behavior and fate of atmospheric polycyclic aromatic hydrocarbons (PAHs). Results showed the median concentrations of total atmospheric PAHs were 18 ng m−3 and 12 ng m−3 in JSA and LGNA, respectively, which were lower than those recently detected in northern coastal China, and previously detected in urban/suburban Shanghai. There was strong/opposite temperature dependence for gaseous and particle-bound PAHs, indicating the importance of ongoing local and nearby volatilization; While the gas-particle partitions of individual PAH compound changed dramatically with seasons, with most easily adsorbed on particles during colder months. The potential source contribution function (PSCF) and concentration weight trajectory (CWT) model demonstrated the interactions of terrestrial and marine air mass regulated by the East Asian monsoon. Specifically, PAHs released by wintertime coal heating in northern China and summertime marine shipping in East China Sea, that transported through northwest and southeast monsoon, respectively, and aggravated the pollution of coastal Shanghai, especially for the background site in LGNA. The positive matrix factorization (PMF) source apportionment suggested the dominance of petrogenic sources for gaseous PAHs, coal and biomass combustion sources for particle-bound PAHs, and further demonstrated the seasonal variations of these potential sources. Atmospheric PAHs would deposit to the coastal waters, with gaseous absorption fluxes almost an order of magnitude higher than those of particle-bound deposition.