Small Temperature Changes Research Articles

Simulation of Dendrite Remelting via the Phase-Field Method

The solidification of alloys is a key physical phenomenon in advanced material-processing techniques including, but not limited to, casting and welding. Mastering and controlling the solidification process and the way in which microstructure evolution occurs constitute the key to obtaining excellent material properties. The microstructure of a solidified liquid metal is dominated by dendrites. The growth process of these dendrites is extremely sensitive to temperature changes, and even a small change in temperature can significantly affect the growth rate of the dendrite tip. Dendrite remelting is inevitable when the temperature exceeds the critical threshold. In this study, a temperature-induced-dendrite remelting model was established, which was implemented through the coupling of the phase field method (PFM) and finite difference method (FDM). The transient evolution law of dendrite remelting was revealed by simulating dendritic growth and remelting processes. The phase field model showed that the lateral dendrites melt first, the main dendrites melt later, and the main dendrites only shrink but do not melt when the lateral dendrites have not completely melted or the root is not broken. The long lateral branches break into fragments, while the short lateral branches shrink back into the main dendrites. The main dendrites fracture and melt in multiple stages due to inhomogeneity.

A temperature-inducible protein module for control of mammalian cell fate.

Inducible protein switches allow on-demand control of proteins in response to inputs including chemicals or light. However, these inputs either cannot be controlled with precision in space and time or cannot be applied in optically dense settings, limiting their application in tissues and organisms. Here we introduce a protein module whose active state can be reversibly toggled with a small change in temperature, a stimulus that is both penetrant and dynamic. This protein, called Melt (Membrane localization through temperature), exists as a monomer in the cytoplasm at elevated temperatures but both oligomerizes and translocates to the plasma membrane when temperature is lowered. The original Melt variant switched states between 28-32°C, and state changes could be observed within minutes of temperature change. Melt was highly modular, permitting thermal control over diverse processes including signaling, proteolysis, nuclear shuttling, cytoskeletal rearrangements, and cell death, all through straightforward end-to-end fusions. Melt was also highly tunable, giving rise to a library of variants with switch point temperatures ranging from 30-40°C. The variants with higher switch points allowed control of molecular circuits between 37°C-41°C, a well-tolerated range for mammalian cells. Finally, Melt permitted thermal control of cell death in a mouse model of human cancer, demonstrating its potential for use in animals. Thus Melt represents a versatile thermogenetic module for straightforward, non-invasive, spatiotemporally-defined control of mammalian cells with broad potential for biotechnology and biomedicine.

Experimental Research and Improved Neural Network Optimization Based on the Ocean Thermal Energy Conversion Experimental Platform

With the progress of research on ocean thermal energy conversion, the stabI have checked and revised all. le operation of ocean thermal energy conversion experiments has become a problem that cannot be ignored. The control foundation for stable operation is the accurate prediction of operational performance. In order to achieve accurate prediction and optimization of the performance of the ocean thermal energy conversion experimental platform, this article analyzes the experimental parameters of the turbine based on the basic experimental data obtained from the 50 kW OTEC experimental platform. Through the selection and training of experimental data, a GA-BP-OTE (GBO) model that can automatically select the number of hidden layer nodes was established using seven input parameters. Bayesian optimization was used to complete the optimization of hyperparameters, greatly reducing the training time of the surrogate model. Analyzing the prediction results of the GBO model, it is concluded that the GBO model has better prediction accuracy and has a very low prediction error in the prediction of small temperature changes in ocean thermal energy, proving the progressiveness of the model proposed in this article. The dual-objective optimization problem of turbine grid-connected power and isentropic efficiency is solved. The results show that the change in isentropic efficiency of the permeable device is affected by the combined influence of the seven parameters selected in this study, with the mass flow rate of the working fluid having the greatest impact. The MAPE of the GBO model turbine grid-connected power is 0.24547%, the MAPE of the turbine isentropic efficiency is 0.04%, and the MAPE of the turbine speed is 0.33%. The Pareto-optimal solution for the turbine grid-connected power is 40.1792 kW, with an isentropic efficiency of 0.837439.

Substrate temperature effect on the structural, morphological and optical properties of pyrolyzed bi-phase Cu2O–CuO thin films

Multiphase nanomaterials are fascinating due to the synergistic effect between the crystalline phases that lead to improved device performance. Publications are available for the synthesis of monophasic copper oxides, such as Cu2O and CuO, and the mixed-phase Cu2O–CuO counterpart using different synthesis methods. However, literature report is scarce that focuses on the fabrication of bi-phase Cu2O–CuO thin films by the spray pyrolysis technique without phase transformation to form the monophasic counterparts. The present work attempts to prepare solely mixed-phase Cu2O–CuO films through small incremental change in substrate temperature, in steps of 20 °C. Structural analysis of the pyrolyzed films revealed the formation of a bi-phase Cu2O–CuO crystal system. The crystallite size increased from 18.64 to 23.94 nm, microstrain decreased from 7.134 ×10−4 to 5.625 ×10−4, while stacking faults decreased from 3.753 ×10−3 to 2.942 ×10−3 with an increase in temperature. Microstructural analysis showed nanoaggregates with increased particle size at increasing temperature. The films exhibited a common optical bandgap of 2.61 eV. The values of the static refractive index and optical electronegativity were found to be 2.47 and 0.70, respectively. The surface roughness increased from 41.3 to 90.9 nm with substrate temperature.

Assessing water position through distributed temperature sensing using Rayleigh-based optical frequency-domain reflectometry: a laboratory feasibility study

This study demonstrates the ability of the Rayleigh-based phase-noise compensated optical frequency-domain reflectometry (PNC-OFDR) sensing method to monitor the distributed temperature field with an ultra-short data acquisition period of 2 ms, a spatial resolution of 2 cm, and a temperature resolution of 0.1 °C. A heating cable (H-cable) was embedded within a cylindrical concrete mortar specimen and subjected to various heating powers. A sensing optical cable (T-cable) was placed adjacent to the heating cable to monitor the temperature distribution continuously. Two water-holding boxes were installed along the specimen at two positions to retain water. The results of the study indicated that the PNC-OFDR technique demonstrated a high sensitivity to even small temperature changes, enabling it to accurately pinpoint the locations of water at two distinct points. The research determined the minimal heating power required for successfully locating the water positions. The magnitude of the heating power exerted a significant impact on the temperature change. Three distinct phases of temperature increment were observed for a given heating period: rapid, fast, and gentle increase. The insights gained from this study have the potential to be applied in natural fields, allowing for the detection of groundwater and seepage phenomena in vulnerable slopes.

Why does stratospheric aerosol forcing strongly cool the warm pool?

Abstract. Previous research has shown that stratospheric aerosol causes only a small temperature change per unit forcing because they produce stronger cooling in the tropical Indian Ocean and the western Pacific Ocean than in the global mean. The enhanced temperature change in this so-called “warm-pool” region activates strongly negative local and remote feedbacks, which dampen the global mean temperature response. This paper addresses the question of why stratospheric aerosol forcing affects warm-pool temperatures more strongly than CO2 forcing, using idealized MPI-ESM simulations. We show that the aerosol's enhanced effective forcing at the top of the atmosphere (TOA) over the warm pool contributes to the warm-pool-intensified temperature change but is not sufficient to explain the effect. Instead, the pattern of surface effective forcing, which is substantially different from the effective forcing at the TOA, is more closely linked to the temperature pattern. Independent of surface temperature changes, the aerosol heats the tropical stratosphere, accelerating the Brewer–Dobson circulation. The intensified Brewer–Dobson circulation exports additional energy from the tropics to the extratropics, which leads to a particularly strong negative forcing at the tropical surface. These results show how forced circulation changes can affect the climate response by altering the surface forcing pattern. Furthermore, they indicate that the established approach of diagnosing effective forcing at the TOA is useful for global means, but a surface perspective on the forcing must be adopted to understand the evolution of temperature patterns.

Brownfield modifications to convert existing gas production facilities for CCS operations

In recent years, traditional oil and gas operators have found novel means of extending the life of their assets and deferring onerous decommissioning costs by converting their facilities from gas production into carbon dioxide (CO2) injection. While the task of designing for CO2 may sound simple, CO2 injection works in counter-intuitive ways, with previously established heuristics derived from years of experience in gas condensate systems being quickly challenged as potentially dangerous. The world of designing CO2 systems is back-to-front compared with hydrocarbons; it isn’t simply a case of a change in flow direction. Some of the design challenges explored in this paper include: large density variability in CO2 systems where a small change in the ambient temperature can significantly impact the pressure of a shut-in system; optimal pressure ratings of the vents and drains systems and how previous safety margins may be unsafe; pipeline hydraulic modelling focussed on new areas outside of the traditional suite of analysis, such as assurance of the supercritical phase; understanding liquid water dropout being more of a concern than hydrate formation; injection wells counter-intuitively flowing from low pressure to high pressure; whether to vent CO2 above or below an offshore platform; and optimal liquefied CO2 storage vessel conditions and safeguarding.

Temperature dependence of the mutation rate towards antibiotic resistance

Abstract Objectives Environmental conditions can influence mutation rates in bacteria. Fever is a common response to infection that alters the growth conditions of infecting bacteria. Here we examine how a temperature change, such as is associated with fever, affects the mutation rate towards antibiotic resistance. Methods We used a fluctuation test to assess the mutation rate towards antibiotic resistance in Escherichia coli at two different temperatures: 37°C (normal temperature) and 40°C (fever temperature). We performed this measurement for three different antibiotics with different modes of action: ciprofloxacin, rifampicin and ampicillin. Results In all cases, the mutation rate towards antibiotic resistance turned out to be temperature dependent, but in different ways. Fever temperatures led to a reduced mutation rate towards ampicillin resistance and an elevated mutation rate towards ciprofloxacin and rifampicin resistance. Conclusions This study shows that the mutation rate towards antibiotic resistance is impacted by a small change in temperature, such as associated with fever. This opens a new avenue to mitigate the emergence of antibiotic resistance by coordinating the choice of an antibiotic with the decision of whether or not to suppress fever when treating a patient. Hence, optimized combinations of antibiotics and fever suppression strategies may be a new weapon in the battle against antibiotic resistance.

3D-Printed Soft Temperature Sensors Based on Thermoelectric Effects for Fast Mapping of Localized Temperature Distributions.

We propose a novel design of thermoelectric (TE) effect-based soft temperature sensors for directly monitoring localized subtle temperature stimuli. This design integrates rheology-engineered three-dimensional (3D) printing of high-performance carbon-based TE materials and polymer-based viscoelastic materials with low thermal conductivity. Rheological engineering of carbon nanotube (CNT) TE inks ensures the 3D printing of highly sensitive TE sensing units on directly written 3D soft platforms. Additionally, we pre-dope CNT inks with p- and n-type organic dopants to achieve high sensitivity and a fast response to temperature changes. The introduced 3D soft platforms with low thermal conductivity lead to an efficient thermal gradient on TE sensing units in the out-of-plane direction. Furthermore, encapsulating the temperature sensor array with the same polymer-based materials as the 3D soft platforms facilitates independent detection of localized temperature stimuli by minimizing thermal interaction between sensing units, resulting in precise temperature mapping by localized detection. Our 3D-printed soft temperature sensors exhibit high sensitivity to relatively small temperature changes, with a minimum sensing resolution of 0.1 K within tens of milliseconds. Moreover, the temperature sensor array not only detects localized temperature stimuli by imaging the temperature distribution but also demonstrates remarkable mechanical reliability against repetitive deformation with high accuracy.

Seasonal tissue-specific gene expression in wild crown-of-thorns starfish reveals reproductive and stress-related transcriptional systems.

Animals are influenced by the season, yet we know little about the changes that occur in most species throughout the year. This is particularly true in tropical marine animals that experience relatively small annual temperature and daylight changes. Like many coral reef inhabitants, the crown-of-thorns starfish (COTS), well known as a notorious consumer of corals and destroyer of coral reefs, reproduces exclusively in the summer. By comparing gene expression in 7 somatic tissues procured from wild COTS sampled on the Great Barrier Reef, we identified more than 2,000 protein-coding genes that change significantly between summer and winter. COTS genes that appear to mediate conspecific communication, including both signalling factors released into the surrounding sea water and cell surface receptors, are up-regulated in external secretory and sensory tissues in the summer, often in a sex-specific manner. Sexually dimorphic gene expression appears to be underpinned by sex- and season-specific transcription factors (TFs) and gene regulatory programs. There are over 100 TFs that are seasonally expressed, 87% of which are significantly up-regulated in the summer. Six nuclear receptors are up-regulated in all tissues in the summer, suggesting that systemic seasonal changes are hormonally controlled, as in vertebrates. Unexpectedly, there is a suite of stress-related chaperone proteins and TFs, including HIFa, ATF3, C/EBP, CREB, and NF-κB, that are uniquely and widely co-expressed in gravid females. The up-regulation of these stress proteins in the summer suggests the demands of oogenesis in this highly fecund starfish affects protein stability and turnover in somatic cells. Together, these circannual changes in gene expression provide novel insights into seasonal changes in this coral reef pest and have the potential to identify vulnerabilities for targeted biocontrol.

Analytical and experimental analysis of guided waves in an aluminum plate under bending load

Although guided waves offer great potential for monitoring various structures, interpreting signals from piezoelectric sensors remains a challenging task. One main reason is the significant influence of environmental conditions on the wave propagation. A lot of research has already been done on the influence of temperature effects and recently more attention has been shifted towards loads. While previous publications have mainly focused on uni- or bi-directional loads, this publication expands the developed models to include bending loads.After reviewing the analytical basis of acoustoelasticity, the derived equations are expanded to nonhomogeneous elastic bending loads using the partial wave method. The analysis is completed using recent results developed by C. Hakoda and C. J. Lissenden (2018) [1], that gave more physical insight in the propagation of guided waves in various frequency-bands.The focus of the experimental analysis is around the fundamental S0- and A0-Modes of Lamb waves. To validate the analytical results an aluminum plate is instrumented using piezoelectric transducers and loaded with varying bending loads. The experimental results are in good agreement with the analytical theory and demonstrate the influence of bending prestress on guided wave propagation. Based on these results an innovative measurement method for bending loads is developed, that is robust to small temperature changes.

Large electrocaloric effect near room temperature induced by domain switching in ferroelectric nanocomposites

The solid-state refrigeration technique based on the electrocaloric effect (ECE) of ferroelectric materials has been regarded as a promising alternative to vapor compression systems due to its advantages of high efficiency and easy miniaturization. However, the small adiabatic temperature change (ATC) and narrow operating temperature range of ferroelectric materials are key obstacles for their practical applications of ECE refrigeration. To improve the ECE performance of ferroelectric polymer poly(vinylidene fluoride) [P(VDF-TrFE)], PbZr1−xTixO3 (PZT) nanoparticles with larger polarization is herein introduced to form ferroelectric nanocomposites. The phase-field simulation is employed to investigate the dynamic hysteresis loops and corresponding domain evolution of the ferroelectric nanocomposites. The temperature-dependent ATC values are calculated using the indirect method based on the Maxwell relation. The appearance of the double hysteresis loop is observed in P(VDF-TrFE) nanocomposite filled with PbZr0.1Ti0.9O3 nanoparticles [P(VDF-TrFE)–PZT0.9], which is mainly caused by a microscopic domain transition from single domain to polar vortex. Compared to the P(VDF-TrFE), enhanced ATC values associated with the domain transition are unveiled in P(VDF-TrFE)–PZT0.9, and the temperature range of excellent ECE is also effectively broadened. In addition, as the component x of filled PZT nanoparticles increases to cross the morphotropic phase boundary (MPB), the maximum ATC value shows a significant increase. The results presented in this work not only explain the mechanism of domain transition induced excellent ECE in the P(VDF-TrFE)–PZT nanocomposite, but also stimulate future studies on enhancing ECE of P(VDF-TrFE) by introducing ferroelectric nanofillers.

Photonic comb: a stabilized single-mode fiber etalon for wavelength calibration

We present a low-cost alternative to more complex laser metrology systems that uses a single-mode fiber Fabry–Perot etalon to generate an emission spectrum of evenly spaced lines with similar intensities, ideal for calibrating spectrographs (both in terms of wavelength and image quality). The system uses the hyperfine transition lines of 87Rb near 780.24 nm as an absolute reference. By controlling the cavity dimensions by small changes in temperature, we can tune and thus stabilize the transmission spectrum. A 20 Hz PID loop controls the etalon temperature and locks it to the 87Rb transitions. Through this method, we achieve a centroid error/precision of <1m/s (2.6 fm or 1.3 MHz) for 1 s integrations and 1 cm/s (0.026 fm or 13 kHz) for 30 min integrations of the reference line. We also show that a solution can be found to mathematically describe the spectrum. With the correct calibration and environmental controls in place, we show that this setup has the potential to be competitive with the best existing methods based on expensive and cumbersome laser combs.

Optimisation of the processing parameters for the fabrication of high-quality joints between Y–Ba–Cu–O single grain, bulk superconductors

Abstract High-strength permanent magnets are essential for a wide range of technologies, including levitation devices, motors, generators and magnetic separators. Replacing permanent magnets with single grain, bulk superconductors will enable a step-change in the performance of these technologies by providing an order-of-magnitude increase in magnetic field. However, there remain many key challenges to the practical implementation of bulk superconductors, of which size and geometry are the most fundamental. The current limits to the size and geometry of (RE)-Ba–Cu–O single grain, bulk superconductors would be overcome substantially by the ability to fabricate high-quality joints between these technologically important materials. In this work we present new insights into the creation of superconducting joints between single grain bulk YBCO superconductors using a YBCO-Ag intermediate composition. We have investigated the effect of the joint fabrication temperature on the quality of the joint in order to begin to optimise the joint fabrication route for YBCO. We report on 35 joints produced at different joining temperatures as part of this study. The trapped field properties of the resulting joined samples were measured and the microstructure at each joint was examined. We show that this simple and rapid joining technique is robust to small changes in joint fabrication temperature and suggest routes to further optimise this potentially transformative technique.

Mean reef fish body size decreases towards warmer waters

AbstractAquatic ectotherms often attain smaller body sizes at higher temperatures. By analysing ~15,000 coastal‐reef fish surveys across a 15°C spatial sea surface temperature (SST) gradient, we found that the mean length of fish in communities decreased by ~5% for each 1°C temperature increase across space, or 50% decrease in mean length from 14 to 29°C mean annual SST. Community mean body size change was driven by differential temperature responses within trophic groups and temperature‐driven change in their relative abundance. Herbivores, invertivores and planktivores became smaller on average in warmer temperatures, but no trend was found in piscivores. Nearly 25% of the temperature‐related community mean size trend was attributable to trophic composition at the warmest sites, but at colder temperatures, this was <1% due to trophic groups being similarly sized. Our findings suggest that small changes in temperature are associated with large changes in fish community composition and body sizes, with important ecological implications.

Nanomaterials Based Micro/Nanoelectromechanical System (MEMS and NEMS) Devices.

The micro- and nanoelectromechanical system (MEMS and NEMS) devices based on two-dimensional (2D) materials reveal novel functionalities and higher sensitivity compared to their silicon-base counterparts. Unique properties of 2D materials boost the demand for 2D material-based nanoelectromechanical devices and sensing. During the last decades, using suspended 2D membranes integrated with MEMS and NEMS emerged high-performance sensitivities in mass and gas sensors, accelerometers, pressure sensors, and microphones. Actively sensing minute changes in the surrounding environment is provided by means of MEMS/NEMS sensors, such as sensing in passive modes of small changes in momentum, temperature, and strain. In this review, we discuss the materials preparation methods, electronic, optical, and mechanical properties of 2D materials used in NEMS and MEMS devices, fabrication routes besides device operation principles.

Ferroelectricity-Driven Self-Powered Weak Temperature and Broadband Light Detection in MoS2/CuInP2S6/WSe2 van der Waals Heterojunction Nanoarchitectonics.

Two-dimensional ferroelectric materials enrich the modulation degrees of freedom in self-powered van der Waals temperature/light detectors by incorporating pyroelectric and bulk photovoltaic effects. However, in addition to the low polarization, the practical applications of these materials are limited due to the significant challenge posed by their ultrathin nature, which affects their polarization stability. In this report, we introduce a design for a dual heterostructure-stabilized van der Waals heterojunction that addresses this challenge by improving the performance and extending the operational lifetime of self-powered van der Waals temperature/light detectors. The design is demonstrated using the MoS2/CuInP2S6 (CIPS)/WSe2 van der Waals heterojunction, which exhibits sensitivity to small temperature changes induced by weak light across the ultraviolet to mid-infrared spectrum. It can generate a noticeable pyroelectric current without the need for an external voltage, and its pyroelectric coefficient exceeds 130 and 978 μC/m2 K for 45 and 70 nm CIPS, respectively. The heterojunction offers high detection accuracy, with a temperature variation sensitivity as small as 0.1 K and an optical power intensity detection range from low to 1 μW/cm2. Additionally, the heterojunction exhibits exceptional detectivity (D*) for different light wavelengths. Remarkably, the self-powered detection performance remains stable for months without obvious degradation in the natural environment. These results offer a promising solution for high-performance, self-sustaining temperature/light detection applications and pave the way for the development of future ferroelectricity-driven photodetection technologies.

A Negative Thermal Expansion Metamaterial Inspired by the Sicilian and Manx Symbols

A negative thermal expansion (NTE) metamaterial is established herein by inspiration from the Sicilian and Manx symbols to form rigid units of the metamaterial. By attaching connecting material of positive thermal expansion to the rigid units, the resulting metamaterial exhibits NTE. Analytical forms for the effective coefficients of thermal expansions (CTE) were established using infinitesimal and finite deformation assumptions for small and large temperature changes, respectively. Results indicate that the negativity of this metamaterial’s thermal expansion is enhanced with the thickness of the connecting material but decreases with the dimensions of the rigid units. The transverse isotropy for this metamaterial’s CTE is useful if thermal expansion compensation is required in two orthogonal directions but zero thermal expansion is required in the remaining orthogonal direction.

Metagenomic Thermometer.

Various microorganisms exist in environments, and each of them has its optimal growth temperature (OGT). The relationship between genomic information and OGT of each species has long been studied, and one such study revealed that OGT of prokaryotes can be accurately predicted based on the fraction of seven amino acids (IVYWREL) among all encoded amino-acid sequences in its genome. Extending this discovery, we developed a 'Metagenomic Thermometer' as a means of predicting environmental temperature based on metagenomic sequences. Temperature prediction of diverse environments using publicly available metagenomic data revealed that the Metagenomic Thermometer can predict environmental temperatures with small temperature changes and little influx of microorganisms from other environments. The accuracy of the Metagenomic Thermometer was also confirmed by a demonstration experiment using an artificial hot water canal. The Metagenomic Thermometer was also applied to human gut metagenomic samples, yielding a reasonably accurate value for human body temperature. The result further suggests that deep body temperature determines the dominant lineage of the gut community. Metagenomic Thermometer provides a new insight into temperature-driven community assembly based on amino-acid composition rather than microbial taxa.

Temperature sensitivity and temperature response across development in the Drosophila larva.

The surrounding thermal environment is highly important for the survival and fitness of animals, and as a result most exhibit behavioral and neural responses to temperature changes. We study signals generated by thermosensory neurons in Drosophila larvae and also the physical and sensory effects of temperature variation on locomotion and navigation. In particular we characterize how sensory neuronal and behavioral responses to temperature variation both change across the development of the larva. Looking at a wide range of non-nociceptive isotropic thermal environments, we characterize the dependence of speed, turning rate, and other behavioral components on temperature, distinguishing the physical effects of temperature from behavior changes based on sensory processing. We also characterize the strategies larvae use to modulate individual behavioral components to produce directed navigation along thermal gradients, and how these strategies change during physical development. Simulations based on modified random walks show where thermotaxis in each developmental stage fits into the larger context of possible navigation strategies. We also investigate cool sensing neurons in the larva's dorsal organ ganglion, characterizing neural response to sine-wave modulation of temperature while performing single-cell-resolution 3D imaging. We determine the sensitivity of these neurons, which produce signals in response to extremely small temperature changes. Combining thermotaxis results with neurophysiology data, we observe, across development, sensitivity to temperature change as low as a few thousandths of a °C per second, or a few hundredths of a °C in absolute temperature change.