Temperature Increment Research Articles

Hydrothermal analysis of parallel and symmetric microchannels with phase change slurry and porous fin designs

The dynamic information of microchannel systems with parallel and symmetric configurations is insufficient, which limits our ability to compare and optimize these systems in all directions. In this study, thermal and hydraulic characteristics in parallel and symmetric microchannel heat sinks (MCHSs) with porous fins cooled by phase change slurry are investigated. A 3-D steady state conjugate model is adopted to compare the effects of fin configuration, coolant type and structural parameters on hydrothermal properties of wavy MCHS. The variations of dimensionless parameters involving Nu, f, η (temperature control effectiveness) and PEF (performance evaluation factor) are considered to demonstrate the effectiveness of combined design on overall performance enhancement of wavy MCHS. Results indicate that lower temperature increment and higher pressure loss appear in wavy configuration with porous fins than in straight mode, and lowest thermal resistance arises in parallel porous fin design. At the narrow position of symmetric channel, the fluid changes from the low-speed drop-shaped micelle to high-speed bullet-shaped one with increasing A, which leads to higher Nu with larger pressure drop penalty. Due to the extended flow route and improved fluid mixing, η increases with decreasing wavelength in all cases, and η of porous microchannels with both phase change slurry and parallel fins is much larger than that of symmetric one and the one with only base fluid. Compared with wavy fin configurations with small and large ε, lower temperature and its more uniform distribution happen in the mode with medium porosity. In comparison with basic configuration, the parallel configuration with slurry as cooling medium has the maximum PEF value when the pore size is 0.14 mm, up to 1.64. Larger f increase occurs in wavy channel with increasing N, and the space shortening between adjacent channel cavities in symmetric mode makes the adjoining Dean vortices easier to contact and repel, thus making it appear larger rise of f than parallel mode. Compared with other channel parameters, it is not effective to improve the overall performance of wavy MCHS with porous fins by adjusting α. Overall, the throat effect of symmetric MCHS significantly occurs in channel configuration with larger A, bigger λ, lower ε, smaller dp, more N, and lesser α, leading to higher f rise than the parallel mode.

A Leak Free Phase Change Materials with Enhanced Thermal Buffering Properties by TiO2/Biochar

A leak free organic phase change material of palmitic acid with enhanced thermal buffering properties was synthesized by simple chemical TiO2/biochar encapsulation process. By utilizing the optimum amount of TiO2 as an encapsulation agent the minimalization of leakage phenomena during the phase change process can be achieved with the value 20-25% of weight loss. Furthermore, the additional sugar cane bagasse-based biochar that was introduced to the encapsulation system acts as a support matrix that enhances further the leakage properties into free leak category with the percentage of weight lost 1.1-1.4 %. Moreover, the introduction of sugar cane bagasse-based biochar in the encapsulation system of the palmitic acid PCM can improve the thermal buffering properties by keeping a package box temperature in the range of 2-80C for more than 20 h by means small increment of temperature 0.72oC/h. Keywords: PCM, encapsulation, palmitic acid, thermal buffering, leakage

Experimental investigation on the transient vascular thermal response to laser irradiation by a high-speed infrared thermal camera

Based on the photothermal effect, laser can be used to treat vascular diseases (VD) in clinic of dermatology and ophthalmology. Transient vascular thermal response to laser irradiation during millisecond laser pulse is the key phenomenon in treatment process, which has not been carefully investigated before. In this study, target blood vessels in dorsal skin chamber (DSC) animal model were irradiated by a pulsed 532 nm diode laser and a 1064 nm Nd:YAG laser. The directed thermal responses (temperature variation) were recorded by a high-speed infrared thermal camera with a repetition rate of 1000 Hz. The temperature variation during and after single pulse irradiation and multipulse irradiation were investigated. The variation of blood absorption coefficient was explored based on the temperature increment in each laser pulse. The thermal properties of dorsal skin, especially the thermal diffusivity, were evaluated based on the temperature decay after each laser pulse. The interfacial heat transfer between the blood and the surroundings was also calculated based on the thermal images and compared to the correlation proposed before. The results show that the blood absorption to laser will increase by a maximum of 1.9 immediately after blood temperature exceeds threshold value, e.g., 68oC in both single pulse (pulse duration >100 ms) and multi-pulse laser irradiation. The tissue optical properties (thermal diffusivity) keep almost constant after millisecond laser heating. Also, a general correlation for interfacial heating transfer between blood and surroundings was developed, in which the influences of vessel shape and laser wavelength are incorporated. The interfacial heat transfer between blood and surrounding can be accurately quantified.

Beneficial Effect of Heat Treatment on the Exercise Pressor Reflex in Hindlimb Ischemia-Reperfusion: Potential Role of P2X3

PURPOSE: In peripheral artery disease (PAD), a greater blood pressure (BP) response during exercise causes cardiovascular and cerebrovascular risks. The exercise pressor reflex (EPR) is a key factor for why BP is exaggerated in PAD patients. Thus, we examined the effect of heat treatment (HT) with two temperature increments in skeletal muscle: 1.5 and 3oC on the EPR response following limb ischemia-reperfusion (IR) injury, one of the most common pathological conditions seen in PAD. In addition, the P2X3 (an ATP-sensitive receptor) in the muscle afferent dorsal root ganglion (DRG) was also evaluated. We hypothesized that IR upregulates the BP response to static muscle contraction and the protein expression of P2X3 in muscle afferent nerves. HT attenuates those exaggerated responses. METHODS: An experimental IR model was induced by 6 hours of ischemia followed by 18 hours of reperfusion in rats (IR rats). For HT groups, three HT sessions (muscle temperature increased by 1.5 or 3oC) for 30 mins/each time were applied. EPR response was evoked by static muscle contraction (30s). Protein expression of the P2X3 receptor in DRGs was examined. Data are presented as mean ± standard deviation. Results: The mean arterial pressure (MAP) response to the static muscle contraction was significantly exaggerated in rats of IR 18h (vs. Sham, P=0.018). With increasing Tm by 1.5°C, there was a promising trend that thus exaggerated BP response was attenuated (IR 18h + HT 1.5°C, n=5 vs. IR 18h rats, n=5, P=0.08). Meanwhile, the exaggerated BP response was significantly attenuated with the Tm increasing by 3°C (IR 18h + HT 3°C, n=5, vs. IR 18h rats, n=5, P=0.032). The expression of the P2X3 receptor was significantly enhanced in the DRGs of IR 18h rats (n=4, p<0.01 vs. sham, n=6). The upregulated P2X3 was suppressed in the DRGs of IR 18h rats +HT of 1.5°C (n=3, p<0.01 vs. IR 18h, n=4) and there was a promising trend that upregulated P2X3 was suppressed in the DRGs of IR 18h rats +HT of 3°C (n=3, P=0.079 vs. IR 18h, n=4). CONCLUSION: IR injury leads to upregulation of EPR response and this effect was attenuated by HT. The P2X3 signaling pathways are likely involved in the beneficial regulatory effect of HT on EPR in IR. Further data collection will be performed to test this conclusion. Supported by NIH R01 HL141198 & HL164571; AHA GRANT # 940567/Lu Qin/2022; and College of Medicine DOM Innovation and Inspiration Award. The authors sincerely thank Chunying Yang for the excellent technical assistance. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A novel microfluidic chip integrated with Pt micro-thermometer for temperature measurement at the single-cell level

Noninvasive and sensitive thermometry of a single cell during the normal physiological process is crucial for analyzing fundamental cellular metabolism and applications to cancer treatment. However, current thermometers generally sense the average temperature variation for many cells, thereby failing to obtain real-time and continuous data of an individual cell. In this study, we employed platinum (Pt) electrodes to construct an integrated microfluidic chip as a single-cell thermometer. The single-cell isolation unit in the microchip consisted of a main channel, which was connected to the inlet and outlet of a single-cell capture funnel. A single cell can be trapped in the funnel and the remaining cells can bypass and flow along the main channel to the outlet. The best capture ratio of a single MCF7 cell at a single-cell isolation unit was 90 % under optimal condition. The thermometer in the micro-chip had a temperature resolution of 0.007 °C and showed a good linear relationship in the range of 20–40 °C (R2 = 0.9999). Slight temperature increment of different single tumor cell (MCF7 cell, H1975 cell, and HepG2 cell) cultured on the chip was continuously recorded under normal physiological condition. In addition, the temperature variation of single MCF7 cell in-situ after exposure to a stimulus (4 % paraformaldehyde treatment) was also monitored, showing an amplitude of temperature fluctuations gradually decreased over time. Taken together, this integrated microchip is a practical tool for detecting the change in the temperature of a single cell in real-time, thereby offering valuable information for the drug screening, diagnosis, and treatment of cancer.

Evaluation of the operational curve for heat storage technology using n-octacosane/low-density as a binding material

Heat storage technology has a critical role for a number of applications involving renewable thermal energy (such as solar water heater). The application of wax (n-octacosane/OCT) as a medium for storing heat brings many positive influences for the system. However, the operational curve is undesirable for the OCT-based energy storage, which makes it necessary to use a binding material. The present work employed LD-class polymer (LDPE) and linear-LDPE as binding materials for OCT. The mixture is prepared through mechanical hot stirring, which comes into two categories: SOCT1 (OCT/LD) and SOCT2 (OCT/LLD). The assessment through the calorimetry method shows an increment in transition temperature for SOCT with a value of 2.1 °C and 5.5 °C. This contributes to the variation of fusion energy for solid-liquid change for both materials, which amounted to 132.05 J/g (SOCT1) and 113.4 J/g (SOCT2). Another assessment related to its chemical and structural phase demonstrates that SOCT has an identical structure to OCT, indicating that SOCT is mixed physically. At the operational level, SOCT is more optimal than OCT according to the indicator related to charge and discharge duration for energy exchange. SOCT1 demonstrates a short plateau line as the indication of a steady transition between 65.4–67.9 °C, while SOCT2 indicates the average heating rate, which is higher than for single OCT. The heat releasing curve for SOCT1 varies at a lower value between 1.92 °C/min and 0.77 °C/min, while SOCT2 has the lowest variation, which is only 0.17 °C/min. Moreover, the self-insulation for SOCT2 has the lowest rate, which is only 0.3 °C/min. The evaluation and analysis from this work show that SOCT is reliable to increase the operational curve of OCT and can be implemented for thermal systems

Durability and performance characteristics of eco-friendly geopolymer binders based on electric-arc-furnace slag and dealuminated kaolin

The pursuit of sustainable development is an essential aspect of modern society's progress, aiming to achieve goals without causing waste, pollution, harm, or environmental degradation. The study focused on developing environmentally friendly binders by utilizing two industrial solid wastes: electric arc furnace slag (EAFS) and dealuminated kaolin (DK). The investigation aimed to assess the physio-mechanical, chemical properties, and durability of the binders against elevated temperatures and exposure to seawater, thereby contributing to sustainable practices. The eco-friendly geopolymer binders, EAFS and DK were blended in various proportions and mixed with alkaline activators. The resulting binders were cured at 40°C and a relative humidity of 98±2% for 180 days. Some of the binders were subjected to temperature increments in the order of 200, 400, 600, 800, and 1000°C, while the other geopolymer binders were immersed in seawater for upto 180 days. Setting times, compressive strength tests, evaluation of free slag and combined water contents, and analysis of the effects of elevated temperatures and seawater exposure on the phase composition of the geopolymer binders were conducted using XRD, TGA/DTG, and SEM/EDX. The finding showed the replacement of 10–20% of EAFS with DK resulted in a reduction in both the initial and final setting times. Increasing the amount of alkali activation content of EAFS upto (1.00 mol/Kg Na2O) (ES3 mix) leads to an increase in the values of compressive strength. Further increase in the alkali content (1.50 mol/Kg Na2O) reduces the compressive strength. The incorporation of DK enhanced the compressive strength value upto 30% DK (ES-DK3 mix). The increase in DK content beyond 30% resulted in reduced compressive strength values. ES-DK3 mix improved the thermal stability of the geopolymer matrix as well as demonstrated higher relative compressive strength values, especially at 1000°C. In addition to the mix, ES-DK3 showed superior durability against the attack of seawater. The compressive strength showed a sharp increase for specimens submerged in seawater for upto 180-days, this is attributed to the high reactivity of DK which acts as a nucleating agent that fills the open matrix preventing the penetration of SO42- and Cl- ions to inhibit the formation of nonbinding material.

Suitability and characterization of pumice, bauxite, and ferrochrome slag as alternative raw materials in vitrified ceramic industry

Since the natural raw materials used in the manufacture of clay-based ceramic products vary greatly in the sintering stage, the resulting products are quite heterogeneous. In addition, different types of waste could be used to make ceramic tiles and bricks. Therefore, this study aimed to investigate the effects of pumice, bauxite, and ferrochrome slag on the vitrified ceramic body. In this context, firstly, binary slip mixtures were prepared by composing 40% clay with 60% pumice, bauxite, and ferrochrome slag one by one, which was reduced to 150 µm in particle size. Then, the mixtures were shaped by slip casting method and sintered at 1000°C, 1100°C, 1200°C, and 1250°C. The qualitative XRD analysis was performed in order to see the phase variation, and physical properties were determined with shrinkage and water adsorption measurements. Since pumice transformed into a glassy phase after sintering at 1100°C, an amorphous phase was observed in all samples produced with pumice. In addition, the mullite development occurred in clay-pumice body composition with the temperature increment. However, tridymite and cristobalite phases were analysed in clay bauxite and ferrochrome body compositions. The shrinkage and water adsorption values, which were high in the samples sintered at 1000°C, began to reduce from 1100°C to 1250°C significantly. In particular, water adsorption reached 0% in the clay-pumice system which was suitable for a fully vitrified-high density standard (ISO13006-10545/98). Besides, the brighter colour was reached in the clay-pumice system while brown and black colour was seen in clay-bauxite and clay-ferrochrome bodies, respectively.

Squeezing MHD Flow of Sodium Alginate-Based Casson Hybrid Nanofluid with Soret and Dufour Effects

Ultrahigh-performance cooling is one of the essential requirements in the industrial technology. Hence, the new heat transfer fluid, hybrid nanofluid is introduced to increase the thermal conductivity of fluid and investigated with various physical parameters. The unsteady magnetohydrodynamics (MHD) flow of Casson hybrid nanofluid through two surfaces in a permeable medium with chemical reaction are explored. The hybrid nanoparticles of Alumina and Copper is dispersed in the base fluid of sodium alginate . The discretize equations are solved using similarity transformation and Keller-box methods. The comparison of the current results with the published results for validation is conducted and discovered in proper agreement. The impacts of squeeze, magnetic, porous media, chemical reaction, heat sink/source, and Soret and Dufour on behaviour and physical quantities of flow are discussed. The graphical results show the squeeze of two surfaces accelerates the fluid velocity near the upper plate region. Further, the velocity slowing down when and increases, and it elevates as and rises in the middle of channel. The increment of heat transfer rate and temperature of fluid is shown for increasing Ec, y and Du, and the opposite behaviour is discovered with raise in. The fluid concentration decreases and the mass transfer rate enhances for rising Sr. The concentration enhance and rate of mass transfer reduce with the constructive chemical reaction, whereas contrary effects is shown for destructive chemical reaction.

Frontal polymerisation of acrylic acid tuned by micellar aggregates in a deep eutectic solvent

A frontal polymerisation (FP) is obtained when a polymerisation creates a spatial front of the reaction. Because of the heat of the reaction associated, a temperature spatial front is also observed. In this paper, the usual chain polymerisation of acrylic acid (AA) is studied when the monomer forms a deep eutectic solvent (DES), i.e. a liquid similar to an ionic liquid. In this DES, AA behaves as a hydrogen donor and ethylammonium chloride as a hydrogen acceptor. The use of a DES is convenient as an effective polymerisation media because the heat of the reaction can be controlled. We study the rate and the heat of polymerisation during the formation of a front using micellar structures where a bifunctional peroxide hydrophobic initiator, abbreviated Luperox, dissolves successfully. Our experiments follow the FP using infrared images and rheology. We found that micellar aggregates of different sizes are interesting modulators of the polymerisation rate and heat of the reaction. Our results show that smaller aggregates produce higher rates of reaction with a decoupled increment of temperature; in contrast to what is observed with bigger aggregates: a slow reaction rate with a coupled moderate heat of reaction.

Ca2+ Overload Decreased Cellular Viability in Magnetic Hyperthermia without a Macroscopic Temperature Rise.

Magnetic hyperthermia is a crucial medical engineering technique for treating diseases, which usually uses alternating magnetic fields (AMF) to interplay with magnetic substances to generate heat. Recently, it has been found that in some cases, there is no detectable temperature increment after applying an AMF, which caused corresponding effects surprisingly. The mechanisms involved in this phenomenon are not yet fully understood. In this study, we aimed to explore the role of Ca2+ overload in the magnetic hyperthermia effect without a perceptible temperature rise. A cellular system expressing the fusion proteins TRPV1 and ferritin was prepared. The application of an AMF (518 kHz, 16 kA/m) could induce the fusion protein to release a large amount of iron ions, which then participates in the production of massive reactive oxygen radicals (ROS). Both ROS and its induced lipid oxidation enticed the opening of ion channels, causing intracellular Ca2+ overload, which further led to decreased cellular viability. Taken together, Ca2+ overload triggered by elevated ROS and the induced oxidation of lipids contributes to the magnetic hyperthermia effect without a perceptible temperature rise. These findings would be beneficial for expanding the application of temperature-free magnetic hyperthermia, such as in cellular and neural regulation, design of new cancer treatment methods.

Flexural vibration suppression behavior of sleeved phononic crystal pipes in thermal environment

Design idea of phononic crystal has been introduced into vibration suppression of pipes and presents expected effects. During service period, thermal environment is a common factor that may change the dynamic behavior of system. In this work, thermal influences on wave attenuation effect are studied for the single-component PC pipe which is constructed by attaching sleeves to the original bare pipe. Under the preloading effect of thermal stresses, flexural wave bandgap shifts toward the lower frequency range with temperature increment. Bandwidth gets wider for pipes with sleeves of a relative length larger than 0.5, while the bandgap narrows down or even closes up for pipes with shorter sleeves. The opposite variation trends are caused by the reversal of edge modes and the unequal responses of the two edge frequencies to thermal stress stiffness. Deeper reason is the discrepancy in determining factor for frequency between the two edge modes. As a result, the two edge frequency loci drop asynchronously under thermal load, and the transition point of bandgap shifts leftward. A thermo-vibrational joint test system is constructed and flexural wave transmittance is measured, for the first time, for a heated PC pipe. Experimental phenomena and simulation results suggest that the initial deflection and non-ideal constraint of the specimen make the attenuation band present opposite variation trends compared to the ideal model. The former strengthens the stiffness of the PC pipe, and the latter weakens the thermal influence on the PC pipe. Both the two non-ideal factors have a more significant impact on starting frequency of the attenuation band due to the difference in sensitivity of bandgap edge frequencies to stiffness perturbation of the PC pipe.

Phase Change Nanocapsules Enabling Dual-Mode Thermal Management for Fast-Charging Lithium-Ion Batteries.

The fast-charging performance of conventional lithium-ion batteries (LIBs) is determined by the working temperature. LIBs may fail to work under harsh conditions, especially in the low-temperature range of the local environment or in the high-temperature circumstances resulting from the release of substantial Joule heating in the short term. Constructing a thermal engineering framework for thermal regulation and maintaining the battery running at an appropriate temperature range are feasible strategies for developing temperature-tolerant, fast-charging LIBs. In this work, we prepare phase change nanocapsules as a thermal regulating layer on the cell surface. The polyurea shells of the nanocapsules are decorated with polyaniline, where the molecular vibration of polyaniline is enhanced under solar irradiation, enabling light-to-heat conversion that achieves an effective temperature increment at low temperatures. Based on the large latent heat storage capability of the n-octadecane core in the nanocapsules, the thermal regulating layer is sufficient to modulate strong heat release when operating LIBs at a high current rate, which efficiently prevents strong side reactions at high temperatures or even the occurrence of thermal runaway. This work highlights the promise of optimizing the operating temperature with a thermal regulator to ensure the safety and performance stability of fast-charging LIBs.

Numerical Simulation of the Influencing Factors of Array Jet Shock Cooling

Array jet impingement cooling is a significant technology of enhanced heat dissipation which is fit for high heat flux flow with large area. It is gradually applied to the cooling of electronic devices. However, The researches on the nozzle array mode and the uniformity of cooling surface still have deficiencies. Therefore, the influence of heat flux, inlet temperature, jet height, array mode and diversion structure on jet impingement cooling performance and temperature distribution uniformity is analyzed by means of numerical calculation. The results show that the heat transfer coefficient of jet impingement cooling increases linearly with the increment of heat flux and inlet temperature. With the increment of the ratio of jet height to nozzle diameter (H/d), the heat transfer coefficient increases first and then decreases, that is, there is an optimal H/d, which makes the heat transfer performance of the array jet impact cooling best. The temperature uniformity of array jet impact cooling is greatly affected by array mode. The improvement effect of nozzle array mode on temperature uniformity is ranked as sequential > staggered > shield > elliptical array. The overall temperature uniformity and heat transfer coefficient are increased by 5.88% and 7.29% compared with elliptical array. The heat transfer performance can be further improved by adding a flow channel to the in-line array layout, in which the heat transfer coefficient is increased by 6.53% and the overall temperature uniformity is increased by 1.45%.

Microstructural Evolution and Densification of Co-Based Alloy Powder by Spark Plasma Sintering for High-Hardness Applications

This work presents the densification of Co-based alloy powders by a spark plasma sintering process. The densification process was carried out at a temperature range of 800 °C to 1100 °C in order to obtain sintered coupons and study their microstructure and mechanical properties. The shrinkage behaviour of the sintered coupons was studied, and an optimal densification temperature was defined. The microstructural analysis showed a reduction in porosity with temperature increment along with the development of a fine microstructure comprised of cobalt-molybdenum-chromium-silicon-based intermetallic laves phases, which are dispersed in a softer cobalt-based alloy matrix. X-diffraction analysis showed that these crystalline phases were well-dispersed, with a lattice parameter corresponding to a hexagonal system. The obtained high Vickers hardness values were attributed to the preservation of a fine microstructure and to the precipitation of Co-Mo phases. Three-point bending tests were performed in order to identify the strain path concerning the densification of the sintered coupons.

Engineering surface state density of monolayer CVD grown 2D MoS2 for enhanced photodetector performance.

This study demonstrates the effect of nitrogen doping on the surface state densities (Nss) of monolayer MoS2 and its effect on the responsivity and the response time of the photodetector. Our experimental results shows that by doping monolayer MoS2 by nitrogen, the surface state (Nss) increases thereby increasing responsivity. The mathematical model included in the paper supports the relation of photocurrent gain and its dependency on trap level which states that the increasing the trap density increases the photocurrent gain and the same is observed experimentally. The experimental results at room temperature revealed that nitrogen doped MoS2 have a high NSS of 1.63 X 1013 states/m2/eV compared to undoped MoS2 of 4.2 x 1012 states/m2/eV. The increase in Nss in turn is the cause for rise in trap states which eventually increases the value of photo responsivity from 65.12 A/W (undoped MoS2) to 606.3 A/W (nitrogen doped MoS2). The response time calculated for undoped MoS2 was 0.85 sec and for doped MoS2 was 0.35 sec. Finally, to verify the dependence of surface states on the responsivity, the surface states were varied by varying temperature and it was observed that upon increment in temperature, the surface states decreases which causes the responsivity values also to decrease.

[Ce3+-Pr3+-Nd3+]:CsPbI2.2Br0.8 stable energy system for photonic and electrical performance upgradation in multitudinous applications

Adopting an integrated and consolidated strategy to energy generation, conversion, and storage is linked to energy sustainability in the modern day. Current investigation explores the lanthanide triple doping mechanism coupled with temperature optimization using (cerium, praseodymium, and neodymium)-oxide to modify CsPbI2.2Br0.8 forming the stable [Ce3+-Pr3+-Nd3+]:CsPbI2.2Br0.8 (CPN:CPVSK) hetero-system. CPN:CPVSK thin films have remarkable optical output for the prolonged duration of 28 days with the band gap energy spanning around 1.64–1.67 eV. These thin films have cubic phase with the 65.44 nm average crystallite size and these thin films have excellent surficial binding without any holes or cracks. CPN:CPVSK was employed as an active light trapping material inside perovskite solar cells processed and analyzed at ambient conditions. The temperature increment from 100 to 200 °C subsequently lead to improvement in efficiency from 6.91% to 15.5% with considerable improvement in fill factor. CPN:CPVSK effectively generated pure H2 with the minor overpotential and Tafel slope values of 132 mV and 122.3 mV dec−1 while the O2 production activity was unappreciable. CPN:CPVSK is a potential material for battery application with the excellent unit capacity of 354 mA H g−1 and lower Rs of 0.44 Ω. Rare earth doped perovskite material is a sustainable, cost effective, and facile to prepare with the greater candidature for practical applications.

The role of near-wall downdraught and asymmetric temperature distribution in dispersion of respiratory aerosols in radiant floor heating systems

In radiant floor heating (RFH) systems, the downdraught due to the asymmetric temperature distribution causes descending airflows towards the floor surface, where the warm air adjacent to the RFH system tends to be driven upwards by the buoyancy force. Hence, this conflict creates a zone that prevents the warm air to ascend affecting the streamlines of the indoor air. The present study aims to investigate the integrated effects of this phenomenon at different levels of the RFH temperature and thermal transmittance on the behaviour of indoor airborne particles (PMs2.5). In this context, a Eulerian-Lagrangian computational fluid dynamic (CFD) code is established, validated against experimental data, to address the dispersion and deposition patterns of PMs2.5. To generate different levels of the downdraught and non-uniform temperature distribution, five scenarios are considered regarding different thermal transmittance (U-value) levels, assessed for four RFH temperatures. Firstly, by introducing the near-wall and zonal spaces, the dispersion of particles in each scenario is evaluated. Then, the role of RFH system temperature in conjunction with each scenario is investigated. Finally, simple correlations are proposed allowing for fast evaluation of the decay rate coefficient of PMs2.5. According to the obtained results, the asymmetric temperature distribution causes a striking disparity in the zonal concentration of suspended PMs2.5, i.e., up to 32 % difference in the number of particles between quarters. It is shown that a faster decay rate of PMs2.5 is associated with a larger value of the characteristic temperature difference and the Rayleigh number (Ra). For a given RFH temperature, thermal performance improvement of the envelope reduces the number of deposited particles on the ceiling surface, whereas it gives a boost to the number of particles adhering to the floor. A sensitivity analysis on the results revealed that a 1 °C increment in the RFH temperature leads to an 8.4 % reduction on average in the number of suspended PMs2.5 in the breathing zone, regardless of the level of thermal transmittance from surrounding walls.

Does lower water availability limit stem CO2 efflux of oak and hornbeam coppices?

Recent changes in water availability can be crucial for the development, growth and carbon budget of forests. Therefore, our aim was to determine the effect of reduced throughfall and severe summer drought on stem CO2 efflux as a function of temperature and stem increment. Stem CO2 efflux was measured using the chamber method on oak and hornbeam under four treatments: coppice, thinned coppice, and both coppice and thinned coppice with 30 %-reduced throughfall. The first year of the experiment had favourable soil water availability and the second year was characterized by a dry summer. While reduced throughfall had no effect on stem CO2 efflux, the summer drought decreased efflux by 43-81 % during July and August. The stem CO2 efflux was reduced less severely (by 13-40 %) in September when the drought persisted but the stem increment was already negligible. The stem increment was also strongly affected by the drought, which was reflected in its paired relationship with stem CO2 efflux over the two experimental years. The study showed that summer dry periods significantly and rapidly reduce stem CO2 efflux, whereas a constant 30 % rainfall reduction needs probably a longer time to affect stem properties, and indirectly stem CO2 efflux.

Effect of the Photoexcitation Wavelength and Polarization on the Generated Heat by a Nd-Doped Microspinner at the Microscale.

Thermal control at small scales is critical for studying temperature-dependent biological systems and microfluidic processes. Concerning this, optical trapping provides a contactless method to remotely study microsized heating sources. This work introduces a birefringent luminescent microparticle of NaLuF4:Nd3+ as a local heater in a liquid system. When optically trapped with a circularly polarized laser beam, the microparticle rotates and heating is induced through multiphonon relaxation of the Nd3+ ions. The temperature increment in the surrounding medium is investigated, reaching a maximum heating of ≈5 °C within a 30 µm radius around the static particle under 51 mW laser excitation at 790 nm. Surprisingly, this study reveals that the particle's rotation minimally affects the temperature distribution, contrary to the intuitive expectation of liquid stirring. The influence of the microparticle rotation on the reduction of heating transfer is analyzed. Numerical simulations confirm that the thermal distribution remains consistent regardless of spinning. Instead, the orientation-dependence of the luminescence process emerges as a key factor responsible for the reduction in heating. The anisotropy in particle absorption and the lag between the orientation of the particle and the laser polarization angle contribute to this effect. Therefore, caution must be exercised when employing spinning polarization-dependent luminescent particles for microscale thermal analysis using rotation dynamics.