Large Temperature Variations Research Articles

Computational method for low-Mach-number compressible flows with moving particles and large temperature variations

Computational method for low-Mach-number compressible flows with moving particles and large temperature variations

Seasonal transmission dynamics of varicella in Japan: The role of temperature and school holidays.

In Japan, major and minor bimodal seasonal patterns of varicella have been observed. To investigate the underlying mechanisms of seasonality, we evaluated the effects of the school term and temperature on the incidence of varicella in Japan. We analyzed epidemiological, demographic and climate datasets of seven prefectures in Japan. We fitted a generalized linear model to the number of varicella notifications from 2000 to 2009 and quantified the transmission rates as well as the force of infection, by prefecture. To evaluate the effect of annual variation in temperature on the rate of transmission, we assumed a threshold temperature value. In northern Japan, which has large annual temperature variations, a bimodal pattern in the epidemic curve was observed, reflecting the large deviation in average weekly temperature from the threshold value. This bimodal pattern was diminished with southward prefectures, gradually shifting to a unimodal pattern in the epidemic curve, with little temperature deviation from the threshold. The transmission rate and force of infection, considering the school term and temperature deviation from the threshold, exhibited similar seasonal patterns, with a bimodal pattern in the north and a unimodal pattern in the south. Our findings suggest the existence of preferable temperatures for varicella transmission and an interactive effect of the school term and temperature. Investigating the potential impact of temperature elevation that could reshape the epidemic pattern of varicella to become unimodal, even in the northern part of Japan, is required.

Estudio del envejecimiento acelerado bajo radiación solar concentrada de vidrios de oxicarburo como receptores de alta temperatura

Solar energy and especially concentrated solar power systems (CSP) need materials that can tolerate the demanding working conditions. In this sense, the receivers are exposed to large fluxes of solar radiation that produce very high temperatures. In addition, due to the operational conditions of receivers large temperature variations occur during day and night, or on cloudy days being these the main aging factors. However, other factors such as humidity, salines environments or pollutans in industrial zones can not be ruled out. Silicon oxycarbide glasses (SiOC) are composite materials formed by a SiOC glass phase (matrix phase) and a C phase (reinforcing phase) homogeneously dispersed and they can be very promising candidates for this type of applications due to their excellent intrinsic properties like their high resistante against to both oxidation and very aggressive environments, good mechanical properties, etc. In this work we have focused in the evaluation of the composite materials (SiOC porous and dense) against thermal shock produced by Frenel lens that concentrated solar radiation more than 2600 times. In every cycle materials they have been heated (32 oC s-1) an cooled (27 oC s-1) at very high rates from room temperature to 1000 oC. This process has been repeated 100 times or lesser in the case of catastrophic material damage. The evolution of material surface during thermal shock cycles has been followed by several techniques such confocal and electronic microscopies and Raman, Infrarred and UV-Visible spectroscopies. Porous silicon oxycarbide materials experiencied a rapid and severe degradation during the first cycles but dense one tolerates quite well the exposure againts concentrated solar radiation.

An investigation into vibrational behaviour of the functionally graded carbon nanotube reinforced shell structure

The requirement for space structures that can absorb stress caused by meteorite impacts and mitigate the thermal and inherent vibrations produced as rapidly as feasible motivates this research. Carbon nanotubes (CNT) produce better stiffness and elastic moduli when combined randomly or in a specific distribution in the matrix. As a result, they can be used as a better material than what is now available. Because most space projects have a cylindrical body, this study investigates the vibrational response of functionally graded carbon nanotube reinforced composites (FG-CNTRC) cylindrical panels. Furthermore, earlier research has shown that the problem of vibration control for FGCNTRCpanels has received little attention. In this study, straight and aligned carbon nanotubes of varied distributions are employed, and they are functionally graded in a specific orientation. For the FGCNTRC cylindrical panel, different configurations have been numerically modeled using the finite element technique. The kinematic and constitutive equations are obtained using first order shear deformation theory (FSDT). Furthermore, Hamilton's principle is applied in order to determine the equation of motion. The volume proportion and CNT efficiency parameters used in this study are as follows: for VCNT of 11%, 1 = 0.149, 2 = 3 = 0.934, for VCNT of 14%, 1 = 0.150, 2 = 3 = 0.941, and for VCNT of 17%, 1 = 0.149, 2 = 3 = 1.381. The boundary conditions are imposed along two straight edges of the FG-CNTRC cylindrical panel and are not applied along the curved edges. The free vibration response of the FGCNTRC cylindrical panel is illustrated for three distinct volume proportions, each of which corresponds to one of the configurations under examination, in order to have better insight of the mechanical behavior of the FGCNTRC cylindrical panel. The study lists the influence of varying volume fractions of CNTs on the first five natural frequencies. The influence of varied CNT volume fractions and configurations on the mode shapes is numerically illustrated. The effect of temperature is also included in numerical simulations because space structures are vulnerable to large temperature variations during space day and night. The piezoelectric patches are strategically placed to achieve excellent vibration reduction. For active vibration control, a nonconventional controller is developed and implemented.

Hybrid energy system optimization model: Electrification of Ontario's residential space and water heating case study

Energy systems are becoming more complex as new energy sources are introduced in support of clean energy goals. These hybrid energy systems can be configured for cogeneration to account for multiple energy uses, including not only electricity but also space heating, water heating, and industrial process heat. Variable renewable energy systems are increasingly being added to hybrid systems to mitigate climate change and reduce greenhouse gas (GHG) emissions. This often creates additional challenges to meet energy demands due to variability associated with renewable generation. In support of energy planning for the new clean economy, the Hybrid Energy System Optimization (HESO) model has been developed to study the feasibility and benefits of nuclear-renewable hybrid energy systems. The model is formulated, as a mixed-integer linear programming (MILP) algorithm, to determine the best energy mix by minimizing annual cost. Because electrification will play a significant role in realizing a clean economy, this study explores the potential economic viability of electrification of residential water and space heating in Ontario. Different energy scenarios have been analyzed to understand the challenges associated with electrification and determine which energy sources will significantly reduce greenhouse gas emissions, while also maintaining competitive energy costs. The results show that electrification of residential water heating can be a viable alternative to natural gas heaters; reducing GHG emissions and energy cost. However, electrification of residential space heating is more challenging due to the large seasonal temperature variations that create significant energy demand fluctuations. Additional nuclear and wind generating capacity, as well as storage systems, are all important elements to support Ontario's transition to a low carbon economy through electrification.

Effect of thermal environments on fast charging Li-ion batteries

Battery thermal management systems (BTMSs) are expected to keep the battery temperature at a moderate level (∼30 °C) to minimize the thermally exacerbated degradation. However, during fast charging, a strong cooling system is required to restrict the temperature rise of Li-ion batteries (LiBs), which significantly increases the cost and weight of battery packs, and induces a large temperature variation inside the battery. In this work we find that all these drawbacks could be relieved by allowing LiBs to charge at higher temperatures. Since the fast charging of a LiB only takes a tiny fraction of its lifetime, the aging rate is limited even at a charging temperature of 60 °C. Three types of thermal environments are proposed: kept constant at 30 °C, preheated to 60 °C, and adiabatic fast charging. With an experimentally validated electrochemical-thermal (ECT) coupled model, we explore the interplay between thermal management and the fast-charging performance. It is found that a gradually increasing temperature profile is the best option to balance the lithium plating and thermal management of the battery. Combining adiabatic fast charging with a preheating step, we can achieve minimal cooling need, perfect temperature uniformity within a battery, and fast-charging capability simultaneously.

Application of an Artificial Neural Network to Develop Fracture Toughness Predictor of Ferritic Steels Based on Tensile Test Results

Analyzing the structural integrity of ferritic steel structures subjected to large temperature variations requires the collection of the fracture toughness (KJc) of ferritic steels in the ductile-to-brittle transition region. Consequently, predicting KJc from minimal testing has been of interest for a long time. In this study, a Windows-ready KJc predictor based on tensile properties (specifically, yield stress σYSRT and tensile strength σBRT at room temperature (RT) and σYS at KJc prediction temperature) was developed by applying an artificial neural network (ANN) to 531 KJc data points. If the σYS temperature dependence can be adequately described using the Zerilli–Armstrong σYS master curve (MC), the necessary data for KJc prediction are reduced to σYSRT and σBRT. The developed KJc predictor successfully predicted KJc under arbitrary conditions. Compared with the existing ASTM E1921 KJc MC, the developed KJc predictor was especially effective in cases where σB/σYS of the material was larger than that of RPV steel.

Material characterisation of heavy-weight and lightweight adobe brick walls and in-plane strengthening techniques

Adobe housing is used in developed countries and much more in less developed countries. Such construction is expected to rise with the increase in world population and the worldwide need of more sustainable and eco-friendly solutions. The large mass associated with earthen buildings is favourable for thermal comfort in regions with large diurnal temperature variations, but it causes these buildings to experience high inertial loading in the event of an earthquake, thus posing a major risk to their inhabitants. Lightweight adobe bricks have been developed and adopted in New Zealand to mitigate the seismic risk, and provide better thermal insulation for sustained periods of hot or cold. There is still a lack in research and national standard literature regarding their material characteristics and earthquake performance. The experimental campaign described herein aims to determine the material properties and in-plane performance of the lightweight adobe walls and compare them to the traditional heavy-weight adobe. Different mesh materials have also been investigated to be used as horizontal reinforcement laid in the mortar joints to enhance the shear characteristics of the adobe wall. Diagonal compression tests were undertaken in as-built panels and in walls strengthened with biaxial polypropylene geogrid.

Evaluation of the Near-Zero Temperature Coefficient of Resistivity (NZ-TCR) of ALD TiSixn Films

Atomic Layer Deposition (ALD) of ternary TiSixN leads to nanocomposites of metallic TiN atomically mixed with insulating Si3N4. Formulating TiSixN films with various Ti:Si ratios lead to the emergence of a temperature regime where resistivity is independent of thermal drift, denoted as near-zero temperature coefficient of resistivity (nz-TCR). Further, the ease with which nanocomposites of TiSixN can be deposited using ALD offer precise tunability in Ti:Si ratio, thickness, mass density, crystallinity and electrical properties.Recently, our group explored TiSixN films deposited using a Eugenus® 300 mm commercial QXP mini-batch system by modulating the ratio of Ti and Si precursors with NH3 as a co-reactant. Si-content was varied from 0 at % (pure TiN) to 24.2 at % Si while maintaining thickness ~ 140 nm. The X-ray reflectivity and grazing incidence X-ray diffraction measurements showed a reduction in film density and transition from nano-crystalline to pure amorphous phase with increase in Si-fraction. Spectroscopic ellipsometry revealed the optical constants, composition, and electrical resistivities and were supported by X-ray photoelectron spectroscopy and electrical measurements. Room-temperature resistivity measurements show an increase in film resistivity with increasing at % Si. Temperature-dependent Van der Pauw measurements found a nz-TCR of -23 ppm K-1 in the temperature range of 298 K – 398 K and at 3.4 at % Si content.We have now discovered that an at % Si = 3.0% induces a nz-TCR of -5.7 ppm K-1 from 80 K – 420 K – one of the best reported nz-TCR values for ALD thin films. Fine tuning the at % Si in TiSixN films, possible only via ALD, significantly elongated the temperature window of nz-TCR behavior. Mapping the local conductivity of individual grains through conductive atomic force microscopy (c-AFM) indicated higher resistance at the grain boundaries. The local composition at the grain boundaries may play a major role in determining the nz-TCR behavior of TiSixN films. In addition, variable temperature Hall effect measurements were performed to provide deeper insights into the nz-TCR mechanism, decoupling carrier concentration from carrier mobility effects while determining film resistivity.Compared to other nz-TCR films, which are deposited using physical vapor deposition techniques, ALD based nz-TCR films presents a unique synthesis platform for interconnect technology in topologically complex, 3D devices, circuits and sensors that undergo large temperature variation during operation but need to maintain stability in their electrical characteristics.

A Sawtooth MEMS Capacitive Strain Sensor for Passive Telemetry in Bearings

The development of economical and high-sensitive strain sensor is crucial for precise measurement of strain in industrial applications, such as bearings. During operation, bearing itself is a harsh environment, which usually has large temperature variations and large centrifugal forces. This paper presents a sawtooth MEMS capacitive strain sensor for passive telemetry in bearings. The interdigital fingers are designed into sawtooth shape to decrease the influence of centrifugal acceleration. The strain sensor chip is 4mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times4$ </tex-math></inline-formula> mm in size, and is fabricated by a simple SOI process. Connecting the sensitive capacitor with an inductor, an LC resonant tank is formed, and the strain signal can be read out wirelessly and passively through a readout coil. Measurement results show that, in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0\sim 1000~\mu \varepsilon $ </tex-math></inline-formula> , the sensitivity of the LC strain sensor reaches 34kHz/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> , and the gauge factor (GF) of the strain sensor reaches 430. The influence of thickness of adhesive layer on the strain sensitivity is investigated. When the thickness of the adhesive layer reaches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$500~\mu \text{m}$ </tex-math></inline-formula> , the applied stress cannot be transferred at all. Finally, the LC strain sensor is tested on a rotating platform. The measured resonant frequency shows only 0.4% deviation under 1000m/s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> centrifugal acceleration.

A novel solution for inverse heat conduction problem in one-dimensional medium with moving boundary and temperature-dependent material properties

A novel approach for solving inverse heat conduction problems in one-dimensional domain with moving boundary and temperature dependent material properties is presented. In this study, it is assumed that two thermocouples are used to measure temperature at two interior locations within the medium while the front boundary experiences recession (moving towards the back surface). A filter coefficient-form Tikhonov regularization method is used to develop the solution for this problem. It is hypothesized that interpolation of pre-calculated filter coefficients for a medium with various thickness values can be used to calculate the filter coefficients for an IHCP with moving boundary, knowing the current thickness of the domain. This can be used along with interpolation among the pre-calculated filter coefficients at different temperatures, knowing the temperature value, to find the correct filter coefficients at each time step and accurately estimate the conducted heat flux in a near real-time fashion. The hypothesis is then validated through several numerical test cases developed in COMSOL. It is shown that the proposed solution method can accurately estimate the conducted heat flux in a domain with a moving boundary in a near real-time fashion. The main advantage of the proposed solution is in it's computationally efficient nature as well as possibility of implementation for monitoring and control purposes due to the near real-time operation of the method. The developed method can be used for calculating surface heat flux in applications that involves moving boundary and large temperature variations such as ablative thermal protection systems for space vehicles.

Spectral properties of near-Earth objects with low-Jovian Tisserand invariant

ABSTRACT The near-Earth objects with low-Jovian Tisserand invariant (TJ) represent about 9 per cent of the known objects orbiting in the near-Earth space, being subject of numerous planetary encounters and large temperature variations. We aim to make a spectral characterization for a large sample of NEOs with TJ ≤ 3.1. Consequently, we can estimate the fraction of bodies with a cometary origin. We report new spectral observations for 26 low-TJ NEOs. The additional spectra, retrieved from different public data bases, allowed us to perform the analysis over a catalogue of 150 objects. We classified them with respect to Bus-DeMeo taxonomic system. The results are discussed regarding their orbital parameters. The taxonomic distribution of low-TJ NEOs differs from the entire NEOs population. Consequently, TJ ∼ 3 can act as a composition border too. We found that 56.2 per cent of low-TJ NEOs have comet-like spectra and they become abundant (79.7 per cent) for TJ ≤ 2.8. 16 D-type objects have been identified in this population, distributed on orbits with an average TJ = 2.65 ± 0.6. Using two dynamical criteria, together with the comet-like spectral classification as an identification method and by applying an observational bias correction, we estimate that the fraction of NEOs with a cometary nature and H ∈ (14, 21) mag has the lower and upper bounds (1.5 ± 0.15) and (10.4 ± 2.2) per cent. Additionally, our observations show that all extreme cases of low-perihelion asteroids (q ≤ 0.3 au) belong to S-complex.

Damage assessment in hyperbolic cooling towers using mode shape curvature and artificial neural networks

Hyperbolic cooling towers are large thin shell reinforced concrete structures that are used to remove the heat from wastewater and transfer it to the atmosphere using the process of evaporation. During its long service life, a cooling tower can experience damage due to the large temperature variations, environmental degradation, or random actions such as impacts or earthquakes. Such a damage can develop over time and result in the sudden collapse of the cooling tower. To ensure that a cooling tower operates safely and efficiently at all times, it is important to monitor its structural health. In this context, structural health monitoring based on the vibration characteristics of the structure, has emerged as a useful method to detect and locate damage in structures. Hyperbolic cooling towers, due to their particular shape, exhibit rather complex vibration characteristics that do not suit the traditional vibration-based damage detection techniques. This paper develops and applies a damage assessment method using the absolute changes in mode shape curvature (ACMSC) in conjunction with Artificial Neural Networks (ANNs) to detect, locate, and quantify damage in hyperbolic cooling towers. ANN is a machine learning technique that can predict behavioural patterns using a set of data samples and finds use in the damage quantification process. The proposed method for detecting and locating damage is experimentally validated and demonstrated its capability to accurately detect and locate damage. A feed-forward network having one hidden layer with Bayesian algorithm is used to train the artificial neural network. Damage indices calculated from noise polluted mode shape data are used to train the network. The trained network is then used to successfully assess the unknown damage severities in the cooling tower. The outcomes of this paper will enable early warning of damages in the cooling towers and will help towards their safe operation.

Early-Age Mechanical Characteristics and Microstructure of Concrete Containing Mineral Admixtures under the Environment of Low Humidity and Large Temperature Variation.

The application of concrete containing mineral admixtures was attempted in Northwest China in this study, where the environment has the characteristics of low humidity and large temperature variation. The harsh environment was simulated by using an environmental chamber in the laboratory and four types of concrete were prepared, including ordinary concrete and three kinds of mineral admixture concretes with different contents of fly ash and blast-furnace slag. These concretes were cured in the environmental chamber according to the real curing conditions during construction. The compression strength, fracture properties, SEM images, air-void characteristics, and X-ray diffraction features were researched at the early ages of curing before 28 d. The results showed that the addition of fly ash and slag can improve the compression strength and fracture properties of concrete in the environment of low humidity and large temperature variation. The optimal mixing of mineral admixture was 10% fly ash and 20% slag by replacing the cement in concrete, which can improve the compression strength, initial fracture toughness, unstable fracture toughness, and fracture energy by 23.9%, 25.2%, 45.3%, and 22.6%, respectively, compared to ordinary concrete. Through the analysis of the microstructure of concrete, the addition of fly ash and slag can weaken the negative effects of the harsh environment of low humidity and large temperature variation on concrete microstructure and cement hydration.

Climate reconstruction from paired oxygen-isotope analyses of chironomid larval head capsules and endogenic carbonate (Hawes Water, UK) - Potential and problems

Temperature and the oxygen isotopic composition (δ18O) of meteoric water are both important palaeoclimatic variables, but separating their influences on proxies such as the δ18O of lake carbonates is often problematic. The large temperature variations that are known to have occurred in the northern mid-latitudes during the Late Glacial make this interval an excellent test for a novel approach that combines oxygen-isotope analyses of chironomid larval head capsules with co-occurring endogenic carbonate. We apply this approach to a Late Glacial lake sediment sequence from Hawes Water (NW England). Oxygen-isotope values in chironomid head capsules show marked variations during the Late Glacial that are similar to the oxygen isotope record from endogenic carbonate. However, summer temperature reconstructions based on the paired isotope values and fractionation between chironomids and calcite yield values between −20 and −4 °C, which are unrealistic and far lower than reconstructions based on chironomid assemblages at the same site. The composition of a limited number of samples of fossil chironomid larval head capsules determined using Pyrolysis gas-chromatography mass spectrometry indicates the presence of aliphatic geopolymers, suggesting that diagenetic alteration of the head capsules has systematically biased the isotope-derived temperature estimates. However, a similar trend in the isotope records of the two sources suggests that a palaeoclimate signal is still preserved.

Practical Method for Drastic Improvement of Output Offset Stability in Bias-Switched Fundamental Mode Orthogonal Fluxgate

Fundamental mode orthogonal fluxgate (FM-OFG) adopting the bias switching technique is a promising compact and low-noise magnetometer for precise DC and low frequency magnetic field measurement. Yet, its output offset stability is insufficient for measurements in the environment with large temperature variations. In this research we have experimentally investigated the cause of the residual offset and its drift found in the bias-switched FM-OFG. Then we proposed a simple and effective method to drastically improve the sensor temperature characteristics of the FM-OFG in a practical feedback design with analog circuitry. Ideally, the induced voltages arisen by the uniaxial anisotropy of an amorphous wire core become symmetrical under flipped excitation polarities, and thus they are canceled by averaging. However, it was revealed that there was certain imbalance between them due to the asymmetry in wire’s magnetic properties, producing remnant component in the final output. The proposed method achieves equilibration of the imbalance component within the demodulation process of the induced voltages to minimize the residual offset and its drift in the final, averaged output. The method was verified by the experiment, and the offset stability of 0.013 nT/°C within the temperature range from −60°C to +70°C was achieved with good repeatability.

Significant increase in extreme heat events along an urban–rural gradient

Cities worldwide are expecting more intense and frequent extreme heat events (EHEs) with climate change and urban growth. While previous studies have shown large intra-urban spatial variations in temperature, little is known regarding how EHEs were spatially distributed within a city. Here, taking Shenzhen, a rapidly urbanizing megacity in China as a case study, we examined the spatiotemporal pattern of EHEs, and further compared it with that of air temperature, using data collected from 85 weather stations from 2008 to 2017. We found: 1) Similar to air temperature, EHEs showed large spatial heterogeneity city-wide, which, however, was different from that of air temperature; 2) The differences in EHEs between urban and non-urban areas had significant increasing trends, with increasing rate of 0.50d/y (p < 0.01) of extreme heat day (EHD) and 1.23 h/y (p < 0.05) of extreme heat hour (EHH). In contrast, the increments of annual temperature differences between the two areas were negligible; 3) Increasing rates of EHEs in new urban areas (NUA) were more than twice those in old urban areas (OUA). Specifically, EHD, EHH, and heat wave increased at the rate of 0.79d/y, 3.20 h/y, and 0.22times/y in NUA, respectively, while the corresponding rates in OUA were 0.29d/y, 1.43 h/y, and 0.08times/y. These results can enhance our understanding of the within-city spatial heterogeneity of EHEs, and can therefore provide insights on urban heat mitigation and adaptation.

Development of unsteady natural convection in a square cavity under large temperature difference

To investigate how the nonuniform fluid density distribution caused by large temperature variations affects the development of unsteady natural convection, we perform a series of direct numerical simulations of two-dimensional compressible natural convection in an air-filled square cavity. The cavity has a hot wall on the left and a cold wall on the right, and two horizontal walls are adiabatic. The simulations are done using a kinetic approach based on a modeled Boltzmann equation, from which the fully compressible Navier–Stokes–Fourier equations are recovered. No Boussinesq approximation or low Mach number approximation is made. An extra source term is introduced to adjust the fluid Prandtl number. Simulations are performed for a range of Rayleigh numbers (107−109) with a fixed dimensionless temperature difference of ε=0.6 to determine the critical Rayleigh number and study the development of unsteady flow. To illustrate the instability mechanism, instantaneous fluctuation field, time trace of temperature, and velocity at selected monitoring points, the spectrum and other statistics are presented and discussed. As expected, significant differences are observed between the instability of compressible natural convection and the Boussinesq-type natural convection. With a large temperature difference, the transition to unsteady flow is asymmetric for the flows near the hot wall and cold wall. For the Rayleigh number range we studied, the cold wall region is dominated by low-frequency impact instability of the boundary thermal jet at the bottom corner. For the hot wall region, besides the upper corner impact instability, a boundary layer instability featuring high-frequency oscillations is observed.

X‐Discontinuity Beneath the Indian Shield—Evidence for Remnant Tethyan Oceanic Lithosphere in the Mantle

AbstractBeneath the continents and island arcs, a seismic discontinuity is often detected around 300 km depth, referred to as the X‐discontinuity. Various mineralogical and petrological mechanisms have been put forth to explain its occurrence. Because of the large depth variability, it is challenging to explain its origin invoking a single mineralogical phase transition. In order to investigate this discontinuity beneath India, we analyzed 10,216 P wave receiver functions at seismological stations deployed on the Indian shield and the Himalayas. We detect the X‐discontinuity as a sporadic and thin feature, in the depth range of 246–335 km, with a sharp shear velocity jump of 2.5%–3.6%. It neither bears a clear tectonic affinity nor has any correlation with the transition zone discontinuities. Interpreting its origin due to a single mineralogical change warrants a large spatial variation in the mantle temperature. Therefore, we suggest that the observed widespread X‐discontinuity beneath the Indian shield owes its origin to two mechanisms, that is, Orthoenstatite to high pressure Clinoenstatite transformation which shifts to lower pressures (∼2 GPa) due to the presence of water (0.13 wt% H2O) in MgSiO3 and coesite‐stishovite transition occurring at 8–11 GPa due to excess silica in an eclogitic component derived from the Tethys oceanic lithosphere subducted during lower Eocene. The identification of such a discontinuity could allow tracking of subducted material within the upper mantle providing a measure of mantle geochemical heterogeneity.

Interindividual plasticity in metabolic and thermal tolerance traits from populations subjected to recent anthropogenic heating.

To better understand temperature's role in the interaction between local evolutionary adaptation and physiological plasticity, we investigated acclimation effects on metabolic performance and thermal tolerance among natural Fundulus heteroclitus (small estuarine fish) populations from different thermal environments. Fundulus heteroclitus populations experience large daily and seasonal temperature variations, as well as local mean temperature differences across their large geographical cline. In this study, we use three populations: one locally heated (32°C) by thermal effluence (TE) from the Oyster Creek Nuclear Generating Station, NJ, and two nearby reference populations that do not experience local heating (28°C). After acclimation to 12 or 28°C, we quantified whole-animal metabolic (WAM) rate, critical thermal maximum (CTmax) and substrate-specific cardiac metabolic rate (CaM, substrates: glucose, fatty acids, lactate plus ketones plus ethanol, and endogenous (i.e. no added substrates)) in approximately 160 individuals from these three populations. Populations showed few significant differences due to large interindividual variation within populations. In general, for WAM and CTmax, the interindividual variation in acclimation response (log2 ratio 28/12°C) was a function of performance at 12°C and order of acclimation (12–28°C versus 28–12°C). CTmax and WAM were greater at 28°C than 12°C, although WAM had a small change (2.32-fold) compared with the expectation for a 16°C increase in temperature (expect 3- to 4.4-fold). By contrast, for CaM, the rates when acclimatized and assayed at 12 or 28°C were nearly identical. The small differences in CaM between 12 and 28°C temperature were partially explained by cardiac remodeling where individuals acclimatized to 12°C had larger hearts than individuals acclimatized to 28°C. Correlation among physiological traits was dependent on acclimation temperature. For example, WAM was negatively correlated with CTmax at 12°C but positively correlated at 28°C. Additionally, glucose substrate supported higher CaM than fatty acid, and fatty acid supported higher CaM than lactate, ketones and alcohol (LKA) or endogenous. However, these responses were highly variable with some individuals using much more FA than glucose. These findings suggest interindividual variation in physiological responses to temperature acclimation and indicate that additional research investigating interindividual may be relevant for global climate change responses in many species.