Temperature Gradient Research Articles

Neuro-computational simulation of blood flow loaded with gold and maghemite nanoparticles inside an electromagnetic microchannel under rapid and unexpected change in pressure gradient.

In cardiovascular research, electromagnetic fields generated by Riga plates are utilized to study or manipulate blood flow dynamics, which is particularly crucial in developing treatments for conditions such as arterial plaque deposition and understanding blood behavior under varied flow conditions. This research predicts the flow patterns of blood enhanced with gold and maghemite nanoparticles (gold-maghemite/blood) in an electromagnetic microchannel influenced by Riga plates with a temperature gradient that decays exponentially, under sudden changes in pressure gradient. The flow modeling includes key physical influences like radiation heat emission and Darcy drag forces in porous media, with the flow mathematically represented through unsteady partial differential equations solved using the Laplace transform (LT) method. Results, including shear stress (SS) and rate of heat transfer (RHT), are graphically detailed, demonstrating changes in blood velocity profile with modifications in the Hartmann number and the width of electrodes, and differences in temperature and RHT between hybrid nano-blood (HNB) and nano-blood (NB). The key results indicate an increase in blood velocity distribution with higher modified Hartmann number, and a decrease with wider electrodes. Temperature is elevated in both hybrid nano-blood (HNB) and nano-blood (NB). Notably, HNB with gold and maghemite enhances heat transmission in the flow. Furthermore, an artificial intelligence-driven methodology employing an artificial neural network (ANN) has been incorporated to facilitate rapid and precise evaluations of SS and RHT, demonstrating remarkable predictive accuracy. The proposed algorithm exhibits outstanding accuracy, achieving 99.998% on the testing dataset and 96.843% during cross-validation for predicting SS, and 100% on the testing dataset, and 95.008% during cross-validation for predicting RHT. The implementation of nanotechnology with artificial intelligence promises new tools for doctors and surgeons, potentially transforming patient care in fields such as oncology, cardiology, and radiology. This model also facilitates the generation of precise electromagnetic fields to guide drug-loaded magnetic nanoparticles for applications in targeted drug delivery, hyperthermia treatment, MRI contrast enhancement, blood flow monitoring, cancer treatment, and controlled drug release.

Effect of sea salt on the interaction between simulated corium and concrete

ABSTRACT During the progression of the severe accident at the Fukushima Daiichi Nuclear Power Station, seawater flowed down to the lower plenum and was predicted to react with molten corium and concrete. For the removal and storage of fuel debris, knowing the effects of seawater components on the characteristics of reaction products in the fuel debris is crucial. To understand changes in the microstructure of fuel debris, a reaction test was conducted by introducing sea salt to simulated corium and concrete under a temperature gradient. Three distinctive microstructures were formed during the reaction test: (i) oxide precipitated in silicate glass, (ii) metallic precipitates, and (iii) unmelted but thermally degraded concrete. Among the components of sea salt, sulfur formed iron sulfide within the metallic precipitate. It was predicted to form through a reaction between stainless steel and SOx gas, which was released by the thermal decomposition of sea salt. Analysis of vaporized species indicated that most of Cl, some Na and K in the sea salt might volatilize during heating rather than react with simulated corium and concrete. Calcium and a small amount of Mg, Na, and K in the sea salt might be trapped in the silicate glass.

Dual-driven biodegradable nanomotors for enhanced cellular uptake.

Hybrid nano-sized motors with navigation and self-actuation capabilities have emerged as promising nanocarriers for a wide range of delivery, sensing, and diagnostic applications due to their unique ability to achieve controllable locomotion within a complex biological environment such as tissue. However, most current nanomotors typically operate using a single driving mode, whereas propulsion induced by both external and local stimuli could be more beneficial to achieve efficient motility in a biomedical setting. In this work, we present a hybrid nanomotor by functionalizing biodegradable stomatocytes with platinum nanoparticles (Pt NPs). These Pt NPs enable two distinct propulsion mechanisms. First, near-infrared (NIR) laser irradiation causes plasmonic heating, which, due to the asymmetric shape of the stomatocytes, creates a temperature gradient around the nanomotors. Second, the catalytic properties of the Pt NPs allow them to convert hydrogen peroxide into water and oxygen, generating a chemical gradient that serves as an additional driving force. Hydrogen peroxide is thereby locally produced from endogenous glucose by a co-encapsulated enzyme, glucose oxidase. The motile features are employed to achieve enhanced accumulation within tumor cells. This nanomotor design offers a versatile approach for developing dual stimuli-responsive nanomotors that operate more effectively in complex environments.

Revisiting the Contributions of Surface Sensible and Latent Heat Fluxes to the Outer Spiral Rainbands of Tropical Cyclones

AbstractThe separate effects of the sensible heat flux (SHF) and latent heat flux (LHF) on the outer spiral rainbands of tropical cyclones (TCs) have not received sufficient attention. This study examines the separate contributions of the SHF and LHF to the outer spiral rainbands of TCs via a series of sensitivity experiments using the three‐dimensional cloud‐resolving Weather Research and Forecasting model. The results indicate that removing the outer SHF suppresses the activity of the outer spiral rainbands and results in a stronger and smaller‐scale TC, whereas decreasing the outer LHF by the same amount has only a slight impact on the outer spiral rainbands. Further investigations indicate that the positive radial gradient of the potential temperature at the cold‐pool outer edge is crucial for the strength of outer spiral rainbands. The strong positive radial gradient of the potential temperature gives rise to a negative radial gradient of the horizontal pressure at the cold‐pool outer edge, and thus an outward radial pressure gradient force. As a result, strong outflow exists near the cold‐pool outer edge, producing horizontal convergence and eventually lifting air to generate new convective cells. Distinct from the LHF, the SHF directly modulates the potential temperature immediately outside the cold pool and thus the radial gradient of the potential temperature at the cold‐pool outer edge. Removing the outer SHF leads to a significantly lower potential temperature outside the cold pool, which is averse to the formation of a larger radial gradient of the potential temperature at the cold‐pool outer edge.

Unusual and persistent easterlies restrained the 2023/24 El Niño development after a triple-dip La Niña

The 2023/24 El Niño, emerging after a rare triple-dip La Niña, garnered global attention due to its potential to evolve into an extreme event, given the largest accumulation of warm water in the equatorial western Pacific since 1980. Despite initial expectations, its growth rate unexpectedly decelerated in mid-2023, preventing it from reaching the anticipated intensity. Here, we show through observational analyses that unusual easterly anomalies over the tropical western-central Pacific, persisting after the end of the preceding La Niña, significantly contributed to this slowdown. A prominent east‒west sea surface temperature gradient in the region has been identified as the crucial factor associated with these unusual and persistent easterly anomalies. This temperature gradient is directly attributed to a negative North Pacific Meridional Mode and a deepened thermocline over the Philippine Sea. These findings offer a deeper understanding of the atypical transition from a prolonged multi-year La Niña to an El Niño.

Slow Interband Recombination Promotes an Anomalous Thermoelectric Response of the p–n Junctions

Thermoelectric effects in p–n junctions are widely used for energy generation with thermal gradients, creation of compact Peltier refrigerators and, most recently, for sensitive detection of infrared and terahertz radiation. It is conventionally assumed that electrons and holes creating thermoelectric current are in equilibrium and share the common quasi-Fermi level. We show that lack of interband equilibrium results in an anomalous sign and magnitude of thermoelectric voltage developed across the p–n junction. The anomalies appear provided the diffusion length of minority carriers exceeds the size of hot spot at the junction. Normal magnitude of thermoelectric voltage is partly restored if interband tunneling at the junction is allowed. The predicted effects can be relevant to the cryogenically cooled photodetectors based on bilayer graphene and mercury cadmium telluride quantum wells.

Hotter temperatures alter riparian plant outcomes under regulated river conditions

AbstractClimate change and river regulation alter environmental controls on riparian plant occurrence and cover worldwide. Simultaneous changes to river flow and air temperature could result in unanticipated plant responses to novel environmental conditions. Increasing temperature could alter riparian plant response to hydrology and other factors, while river regulation may exacerbate environmental stress through novel flows like those resulting from power generation. Further, plant establishment and growth may require differing conditions, which may be decoupled by novel conditions. Using a large dataset that spans a natural 5°C mean annual temperature (MAT) gradient and a Bayesian model that integrates plant occurrence and cover, we address four questions: (1) Does hotter MAT modify plant response to hydrology, substrate composition, topography, and cover of co‐occurring plant species? (2) Does the timing of hydropower tides benefit some species over others? (3) Does dam‐induced erosion hinder riparian species more than upland species? (4) Do occurrence and cover respond to different environmental variables, allowing for decoupling of life history processes? We addressed these questions with data collected along 364 km of the Colorado River downstream of Glen Canyon Dam, Arizona, United States of America. Occurrence and cover class were recorded in >10,000 plots from 2016 to 2020, along with environmental covariates that repeat across the climate gradient. For 36 species, plant occurrence and cover were modeled with respect to MAT, hydrology, substrate, topography, other plant cover, and their interactions with MAT. There were four key results. (1) Increasing MAT will not only directly influence plants but will mediate their responses to the environment, including greater dependence on stable water supplies. (2) The timing of hydropower tides shapes plant community composition. (3) Dam‐related erosion has an outsized effect on riparian species, which could lead to a loss of regionally unique plant species. (4) For all species, the most important covariates driving occurrence differed from those for cover, suggesting the potential for these life stages to be decoupled. Not only will climate change and river regulation independently alter plant distributions, interactions among hotter temperature, dam‐controlled flow patterns, and limited fine sediments will determine which species flourish or perish under future conditions.

The Gut Bacteria of Gampsocleis gratiosa (Orthoptera: Tettigoniidae) by Culturomics

Gampsocleis gratiosa Brunner von Wattenwyl, 1862, is a type of omnivorous chirping insect with a long history of artificial breeding. It has high economic value and is also an excellent orthopteran model organism. In this study, 12 types of culture media combined with 16S rRNA sequencing were employed to isolate 838 bacterial strains from the gut of G. gratiosa. After sequence comparison, a total of 98 species of bacteria were identified, belonging to 3 phyla, 5 classes, 11 orders, 20 families, and 45 genera. Firmicutes and Proteobacteria accounted for the majority (92.86%). At the order level, Enterobacteriaceae, Bacillales, and Lactobacillales predominated (79.59%). At the genus level, Klebsiella (11.22%) and Enterococcus (7.14%) predominated. This study also enumerated the strain morphological, physiological and biochemical properties of 98 species of bacteria, including colony morphology, Gram staining, bacterial motility test, temperature gradient growth, pH gradient growth, citrate utilization test, temperature oxidase test, contact enzyme test, methyl red test, V-P test, indole test, gelatin liquefaction test, nitrate reduction test, hydrogen sulfide test, starch hydrolysis test, cellulose decomposition test, esterase (corn oil) test and antibiotic susceptibility testing. Additionally, 16 antibiotics were utilized to test the bacterial susceptibility of the strains. This study explored the types and community structure of some culturable microorganisms in the intestinal tract of G. gratiosa and recorded their physiological characteristics. These data reflect the physiological functions of the intestinal microorganisms of G. gratiosa and provide support for subsequent research on the interaction mechanism between microorganisms and their hosts.

Simulation analysis of radiometer effect and outgassing based on molecular particle source perturbation

The Laser Interferometer Space Antenna (LISA) mission is designed to detect space gravitational wave sources in the millihertz band. A critical factor in the success of this mission is the residual acceleration noise metric of the internal test mass (TM) within the ultra-precise inertial sensors. Existing studies indicate that the coupling effects of residual gas and temperature gradient fluctuations significantly influence this metric, primarily manifesting as the radiometer effect and the outgassing effect. However, current theoretical research methods are inadequate for accurately decoupling and predicting the contributions of these two effects. To this end, this paper conducts an in-depth decoupling analysis of the impacts of the radiometer effect and outgassing effect using a simulation method based on molecular particle source perturbation. By constructing a finite element simulation model that couples residual gas and temperature gradient fluctuations, we simulate molecular thermal motion based on fundamental theories such as Maxwell’s distribution function, the free path distribution law, and Knudsen’s adsorption layer hypothesis, in order to study the two manifestations of the radiometer effect and the outgassing. By analyzing and comparing the simulation results, theoretical results, and ground torsion results, we find that the simulation results align effectively with the measured ground torsion results. This alignment enhances our understanding of how the radiometer effect and outgassing impact the internal pressure changes in the sensitive probe, which cannot be sufficiently decoupled by theoretical calculations alone. This conclusion demonstrates that the simulation method can effectively analyze the coupling effects of temperature gradient fluctuation and residual gas in inertial sensors, providing an important theoretical basis and practical significance for developing physical models of inertial sensors aimed at predicting and optimizing overall performance.

ОЦЕНКА ПРАЙМЕРОВ К ВЫСОКОЭФФЕКТИВНЫМ ГЕНАМ Pc С ИСПОЛЬЗОВАНИЕМ ГЕНЕТИЧЕСКОЙ КОЛЛЕКЦИИ ОВСА СИБИРСКОЙ СЕЛЕКЦИИ

Crown rust of oats, caused by the obligate parasite Puccinia coronata Corda f. sp. Avenae Erikss has a significant impact on oat production, leading to a decrease in grain yield and a deterioration in the quality of the resulting product. One of the most effective ways to combat crown rust epiphytoties is to create genetically resistant varieties. Molecular labeling methods can make this process more efficient and targeted. The purpose of research is to evaluate the effectiveness of primers for highly effective crown rust resistance genes using a genetic collection of Siberian oats. The material for the study was samples of oats cultivated by the Research Institute of Agriculture of the Northern Trans-Urals – a branch of the Tyumen Scientific Center SB RAS, as well as source varieties of highly effective genes for resistance to crown rust from the collection of the All-Russian Research Institute. To select optimal conditions for amplification, 3 different modes, 4 reaction mixtures, and a temperature gradient of 55.0–70.0 °C were used. The melting temperature was determined for each primer. Amplification products were separated in 2 % agarose and 8 % polyacrylamide gels. Amplification products were obtained, visualized on the gel in the form of clear bands. For none of the source varieties of Pc genes, amplification products were obtained that distinguished them from samples without these genes. This indicates their ineffectiveness for assessing the genetic collection of samples of Siberian selection. To successfully carry out marker-associated selection of oats for resistance to crown rust in Western Siberia, it is necessary to evaluate the effectiveness of other known primers for Pc genes, as well as the creation of our own marker systems.

Bioinspired Silicone Rubber Foams With Adjustable Gradient Structures Induced via Temperature Fields

ABSTRACTThe structure‐gradient silicone rubber foam (SRF) is an advanced bionic material with potential for applications in energy‐damping, triboelectric nanogenerators, and electromagnetic interference shielding. However, the production of SRFs with an adjustable gradient structure is still a significant challenge. Herein, a novel strategy combining in situ precuring of silicone rubber induced by gradient temperature fields with supercritical CO2 foaming was developed to prepare SRFs with biomimetic gradient cellular structures. By regulating the unilateral heat source temperature and precuring time, SR samples with gradient curing degrees from 16.13% to 51.21% were achieved. Finally, a prospective structure‐gradient SRF with a cell size range of 24.10–182.80 μm was successfully prepared. The energy loss coefficient of gradient SRF can be reduced by 41.65% compared with that of uniform cellular structure foam with average cell size of 31.25 μm after 50 cycles. Gradient SRFs show significantly enhanced mechanical performance, recoverability, and elasticity. Besides, the underlying mechanism for generating this gradient cellular structure was clarified.

Temperature Gradients as a Data Storage Principle

In this work, we analyze the thermodynamic principles underlying modern data storage systems, including Random Access Memory (RAM), hard disk drive (HDD), flash memory, magnetic RAM (MRAM), ferroelectric RAM (FeRAM), and phase-change RAM (PCRAM), as well as other less well-known data storage mechanisms. The analysis is conducted in the context of data storage and processing in relation to Landauer’s principle, with special emphasis on hysteresis. Analogous to how heat engines are characterized by thermodynamic cycles, data storage systems are examined in terms of the hysteresis loop of their fundamental data unit. We explore the role of heat in data storage systems. Afterward, we introduce the concept of temperature gradient memory (TeGraM) along with a detailed layout of a realizable device. Experimental results demonstrating this technology are also presented.

Investigation of the deterioration of concrete from surface to interior under temperature gradient effects

In this investigation, to assess the deterioration processes of concrete from the surface to the interior under temperature gradient effects, 150 mm cubic concrete specimens were heated at 800°C without a temperature-rising stage for different durations (20, 40, 60, 90 and 120 min) and then cooled under running water. For the purpose of evaluating the deterioration characteristics of the heated concretes, compressive strengths and cracking conditions, microstructural morphologies of concrete constituents and the dehydration degrees of the concrete matrix from surfaces to interiors were determined. The results showed that, during the heating process, the deterioration of the concrete matrix from surface to interior could be divided into a heat-affected area (HAA), a semi-HAA and a heat-unaffected area (HUA). In the HAAs, the dehydration degrees of the hydration products were extremely severe and the microstructural integrity almost completely lost. With an increase in heating duration, the HAAs gradually expanded towards the concrete interiors, making the semi-HAAs gradually become HAAs and the HUAs become semi-HAAs. Consequently, with increasing heating durations, the compressive strengths of the heated concretes gradually decreased.

Effect of Porosity on Tribological Properties of Medical-Grade 316L Stainless Steel Manufactured by Laser-Based Powder Bed Fusion

The potential of laser-based powder bed fusion (L-PBF) technology for producing functional components relies on its capability of maintaining or even improving the mechanical properties of the processed material. This improvement is associated with the microstructure resulting from the high thermal gradient and fast cooling rate. However, this microstructural advantage may be counterbalanced by the lack of full density, which could be tolerated to a certain degree for applications such as biomedical implants and medical equipment. In this study, medical-grade 316L stainless steel specimens with porosities ranging from 1.7 to 9.1% were additively manufactured by L-PBF using different combinations of laser power and scanning speeds. Tribological properties were evaluated by pin-on-disc testing in dry conditions against a silicon nitride test body and analyzed in the context of microstructural characterization by optical and electron microscopy. The results reveal that higher porosity allows for a diminishing wear rate, which is explained by the capacity of the pores to retain wear debris related with the three-body abrasion. This research provides practical insights into the design of medical wear-resistant components, thereby enhancing our understanding of the potential of L-PBF in the fields of materials science and biomedical engineering.

Temperature dependence of liverwort diversification reveals a cool origin and hot hotspots

The evolutionary history underlying gradients in species richness is still subject to discussions and understanding the past niche evolution might be crucial in estimating the potential of taxa to adapt to changing environmental conditions. In this study we intend to contribute to elucidation of the evolutionary history of liverwort species richness distributions along elevational gradients at a global scale. For this purpose, we linked a comprehensive data set of genus occurrences on mountains worldwide with a time-calibrated phylogeny of liverworts and estimated mean diversification rates (DivElev) and mean ages (AgeElev) of the respective genera per elevational band. In addition, we reconstructed the ancestral temperature preferences of the genera. We found that diversification rates increase linearly with temperature, and hence decrease with elevation. This pattern is mainly driven by epiphytic genera. In contrast, overall genus age is highest at intermediate elevations where liverwort species richness peaks and decreases towards both ends of the elevational and thermal gradient. Our results further indicate that the ancestral lineages from which the extant liverwort genera descended had a preference for cool and humid habitats. We conclude that the extant liverwort species diversity accumulated over long time under these climatic conditions, which are today prevailing at mid-elevations of the world’s mountains. Subsequently, liverworts expanded their ranges from these temperate areas towards warm (with high diversification rates) and cold regions (with low diversification rates), located in contemporaneous (tropical) lowlands and high mountains, respectively. The conserved preference for temperate climates shared by the majority of liverwort lineages gives reason to the assumption that they will not be able to cope with the conditions induced by rapid climate warming, whereas the current low-elevation radiation may be less affected by climate change.

The vertical shear instability in protoplanetary discs as an outwardly travelling wave. I. Linear theory

Abstract We revisit the global linear theory of the vertical shear instability (VSI) in protoplanetary discs with an imposed radial temperature gradient. We focus on the regime in which the VSI has the form of a travelling inertial wave that grows in amplitude as it propagates outwards. Building on previous work describing travelling waves in thin astrophysical discs, we develop a quantitative theory of the wave motion, its spatial structure and the physical mechanism by which the wave is amplified. We find that this viewpoint provides a useful description of the large-scale development of the VSI in global numerical simulations, which involves corrugation and breathing motions of the disc. We contrast this behaviour with that of perturbations of smaller scale, in which the VSI grows into a nonlinear regime in place without significant radial propagation.

Optimization of metal polymer friction pair composition for hydrogen wear reduction through thermal stabilization analysis

The composition of the metal-polymer friction pair is carefully considered for interacting with water and hydrogen, ensuring the metals electrode process potential remains below waters in a neutral medium. Simultaneously, adherence to defined chemical composition ratios for the metal-polymer materials is crucial. This analysis is conducted under conditions of thermal stabilization, characterized by a minimal temperature gradient across the rim thickness within an equivalent thermal field. Using the quasi-chemical approximation, the paper derives a concentration-dependent diffusion coefficient of hydrogen (H) in iron (Fe) across a broad spectrum. This derivation includes electronic and vibrational contributions to the chemical potential. The research establishes a correlation between the equivalent diffusion coefficient and the concentration of diffusing hydrogen atoms from the metal, such as the pulley or drum rim. These findings offer novel insights into optimizing hydrogen wear behaviour in brake friction couples, contributing to advancements in materials and design considerations in the automotive field.

An Integrated Heat Recovery System Design for a Fuel Cell Buggy With Hydrogen Preheating and Thermoelectric Generator

ABSTRACTThis study presents an integrated heat recovery‐proton exchange membrane (IHR‐PEM) fuel cell system designed for lightweight vehicles powered by a 2 kW PEM fuel cell. The IHR system captures waste heat through multiple heat exchangers and integrates thermoelectric generator (TEG) modules for electrical regeneration and hydrogen preheating, enhancing PEM fuel cell performance. Utilizing the temperature gradient between the fuel cell's exhaust and the ambient environment, the system effectively converts waste heat into electrical energy, improving energy efficiency. Experimental evaluation under various operating parameters, including cruising speeds, PEM fuel cell loads, rejuvenation conditions, and electrical regeneration strategies, demonstrated the system's effectiveness. Results revealed waste heat absorption of up to 8.5 W and hydrogen preheating by 19°C, leading to an 11.5% increase in electrical power production and a maximum PEM fuel cell efficiency improvement of 11%. This study advances waste heat recovery (WHR) technologies in fuel cell‐based transportation, significantly improving energy efficiency and reducing carbon emissions. The findings provide valuable insights into the integration of regenerative WHR systems for lightweight vehicles, fostering the development of sustainable and energy‐efficient transportation solutions.

Thermoelectric properties of a quantum dot attached to normal metal and topological superconductor

The thermoelectric properties of hybrid systems based on a single-level quantum dot coupled to a normal-metal/half-metallic lead and attached to a topological superconductor wire are investigated. The topological superconductor wire is modeled by a spinless p-wave superconductor which hosts both a Majorana bound state at its extremity and above gap quasiparticle excitations. The main interest of our investigation is to study the interplay of sub-gap and single-particle tunneling processes and their contributions to the thermoelectric response of the considered system. The above gap tunneling driven by a temperature gradient is responsible for relatively large thermopower, whereas sub-gap processes only indirectly influence the thermoelectric response. The thermoelectric coefficients, including electric conductance, Seebeck coefficient (thermopower), heat conductance, and figure of merit, are calculated by means of the non-equilibrium Green’s function technique and the temperature dependence of the superconducting gap is considered within the BCS theory. We also consider the system out of equilibrium working as a heat engine. The output power and the corresponding efficiency are presented. Interestingly, under certain conditions, it is possible to extract more power in the superconducting phase than in the normal phase, with comparable efficiency.

Controlling the roughening of growing electrochemical interfaces using temperature gradients

Controlling the roughening of growing electrochemical interfaces using temperature gradients