Temperature Spikes Research Articles

High infection prevalence in patients who develop severe acute kidney injury during heart failure hospital admission

Abstract Background Acute kidney injury (AKI) is common in acute HF and associated with poor prognosis. (1-3) The cause of AKI is often unknown. Purpose The aim of this analysis was to analyse the data for patients with a severe AKI which developed during a HF admission and identify potential triggers in the preceding 7 days (e.g., infection, hypotension, contrast agents.). Methods Data between January 2022 to March 2023 was obtained from that submitted by our centre to the mandatory National HF Audit which collects data from every patient admitted with acute HF. For this analysis, baseline renal function was retrospectively collected from electronic patient records, and chronic kidney disease and AKI were subsequently defined, as per KDIGO guidelines(4), using baseline and admission measurements. Electronic patient records were reviewed for all patients who developed AKI stage 2/3 ≥48 hours after admission. Data collected during the week prior to their AKI included any radioiodine contrast exposure, temperature ≥ 38⁰C, antibiotics, CRP >100mg/L and periods of sustained hypotension. Results Of the 843 HF hospital admissions between January 2022 and March 2023, 507 (60.1%) were not associated with AKI [inpatient (IP) mortality 5.9%], 237 (28.1%) had an AKI stage 1 [IP mortality 17.3%], 51 (6.0%) had an AKI stage 2 [IP mortality 25.5%] and 48 (5.7%) had an AKI stage 3 [IP mortality 33.3%]. The age, diabetic status and ejection fraction of patients was similar across AKI stages. Of these, 64 patients developed their AKI stage 2 (n=30) or 3 (n=34) on or after their second day of HF hospital admission. 22 (34.3%) of these patients died during this admission, and 37 (57.8%) had died after a median follow-up of 217.5 days (IQR 24-331.75) (Table 1). 71.9% had evidence of an infection (defined by a temperature spike ≥38⁰C, received antibiotics, OR CRP >100mg/dL) in the week prior to developing their AKI (Table 2). 39% of patients had received a contrast agent in the preceding week, and 39% had experienced persistent hypotension in the preceding 48 hours. 25% had 2 of these potential triggers, 17.2% had 3. Six patients (9.4%) had no apparent identifiable triggers. 25% had not had renal function checked for 48h prior to AKI. Conclusion The most frequent identifiable potential trigger for severe AKI was infection in 72%, followed by contrast agent (39%) and hypotension (39%). Many patients had multiple triggers. Over-diuresis in isolation was not identified as a trigger for AKI in this cohort. Severe AKI 2/3 is a marker of extreme mortality risk and identifies patients in need of intensive monitoring. Lack of daily bloods in one quarter of patients led to a delay in AKI alert. Close observation for all acute HF patients including daily bloods and early identification and treatment of infection plus judicious and least use of contrast is needed to reduce the high mortality rates in this population.

Impact of external heating and state of charge on discharge performance and thermal runaway risk in 21700 Li-ion batteries

This study investigates the combined effects of external heating and State of Charge (SOC) on the discharge performance and thermal runaway risk of 21700 Li-ion batteries. Experiments subject commercially available 21700 cylindrical cells to various external heating conditions at different SOC levels (20, 40, 60, 80, and 100 %) while measuring discharge performance and thermal behavior at different discharge rates (0.2, 0.5, 1, and 1.5C). The study emphasizes the significance of Li-ions' spatial arrangement and maintaining electrical charge in the electrolyte to evaluate battery performance. Numerical simulations are then conducted to complement the experimental data and provide deeper insights. The results reveal a significant degradation in discharge performance with increasing external heat, characterized by voltage drops and reduced capacity. Cells with higher SOC levels exhibit more severe exothermic reactions during external heating, leading to a higher likelihood of thermal runaway. Cells operated at a moderate SOC of 40 % demonstrate a significantly lower risk of thermal runaway under similar heating conditions. The rapid rise in temperature at 100 % SOC of batteries showed a sharp increase of over 20 °C per second. Temperature spikes were noted at specific time intervals corresponding to different SOC levels: 100, 80, 60, 40, and 20. At this critical point, temperatures ranged from 135 to 182 °C, indicating potential thermal issues from internal short circuits causing separator melting. These findings highlight the critical role of SOC management in ensuring the safe and reliable operation of 21700 Li-ion batteries, particularly in applications involving elevated temperatures.

A modified multi-node human thermoregulation model with improved sweating response to simulate human physiological behaviours in warm and hot environments

The present research developed a modified multi-node thermoregulation model derived from the renowned Tanabe and JOS series models (JOS-2 and JOS-3). The JOS-3 model's predictions showed an abrupt spike in mean skin temperature, contradicting the findings from experiments. The JOS-3 model's sweating mechanism exhibits an inconsistency, and the sweating mechanism is not triggered promptly and accurately, leading to a sudden rise in skin temperature. This disparity significantly impacts the ability of the model to precisely replicate thermoregulatory responses under various climatic conditions and levels of physical activity. The proposed modified thermoregulation model extends the JOS-3 model by modifying the set-point temperature and sweating signals. The performance of the developed modified thermoregulation model is thoroughly analyzed under various conditions involving different environmental conditions, activity levels, and clothing types. The proposed model eliminates abrupt rise in the mean skin temperature and improves its prediction accuracy, notably reducing mean skin temperature RMSE in hot-humid conditions (0.66 °C vs. 0.85 °C) compared to the JOS-3 model. In hot-dry settings, improvements are significant, reducing the mean skin temperature and core temperature RMSE (0.48 °C vs. 0.06 °C and 0.05 °C vs. 0.02 °C, respectively). Overall, the modified thermoregulation model offers a reliable and accurate solution to analyze human physiological conditions for a wide range of practical problems.

EP419 - Management of acute diverticulitis in ESAU according to WSES guidelines.And it’s predisposing factors in regard to the local Trust experience

Abstract Introduction In 2015, WSES established a framework to approach management of acute left sided colonic diverticulitis. Lifetime incidence to develop acute inflammation on top of diverticulosis is 4%. Aim of the study: Investigate how adherent the local colorectal department to WSES guidelines and to look at possible factors contributing to acute flare ups. Patients and Methods Over 6 months, 63 patients presented to ESAU with clinical and laboratory signs, indicating intra-abdominal sepsis. CTAP was utilised to diagnose acute diverticulitis and its complications. Results The Vast majority were females (50) with 34 patients above 60 and only 3 were under 40 years old.22.5% had NEWS > 2 and 11% had a temperature spike >38.Quarter of the cases had a CRP >150. CT scan proved acute uncomplicated diverticulitis in 28 patients, but diagnosed Hinchey 1(8%),2(28%),3 & 4 (20%).2 cases had associated stricture, one of which proved to be malignant (1.5%).84% were managed with IV antibiotics (according to the local Trust),10% had emergency laparotomy and 6% were treated by IR-drainage. 28 patients were treated successfully and discharged with 48 hours, 10 cases had a prolonged recovery over 10 days.2 cases were deceased (3%). Interval colonoscopy (8-12 weeks) was not done in one-third of the cases. On other hand, 60% were smokers, and two thirds had significant comorbidities; cardiovascular (42%), pulmonary (20%), CKD3(20%), DM (15%), Bowel pathology (7%).27% had multiple comorbidities and 12% were known to have diverticulosis. Conclusion Although the firm is adherent to WSES guidelines, interval colonoscopy service should be improved. Age, Smoking, Cardiovascular, Diabetes and pulmonary diseases are predisposing factors for acute diverticulitis. Risk of inflammation and severity in multiple coexisting morbidities.

Automatic heliostat learning for in situ concentrating solar power plant metrology with differentiable ray tracing

Concentrating solar power plants are a clean energy source capable of competitive electricity generation even during night time, as well as the production of carbon-neutral fuels, offering a complementary role alongside photovoltaic plants. In these power plants, thousands of mirrors (heliostats) redirect sunlight onto a receiver, potentially generating temperatures exceeding 1000°C. Practically, such efficient temperatures are never attained. Several unknown, yet operationally crucial parameters, e.g., misalignment in sun-tracking and surface deformations can cause dangerous temperature spikes, necessitating high safety margins. For competitive levelized cost of energy and large-scale deployment, in-situ error measurements are an essential, yet unattained factor. To tackle this, we introduce a differentiable ray tracing machine learning approach that can derive the irradiance distribution of heliostats in a data-driven manner from a small number of calibration images already collected in most solar towers. By applying gradient-based optimization and a learning non-uniform rational B-spline heliostat model, our approach is able to determine sub-millimeter imperfections in a real-world setting and predict heliostat-specific irradiance profiles, exceeding the precision of the state-of-the-art and establishing full automatization. The new optimization pipeline enables concurrent training of physical and data-driven models, representing a pioneering effort in unifying both paradigms for concentrating solar power plants and can be a blueprint for other domains.

Simulations of radiation damage accumulation in Fe-9Cr under pulsed irradiation conditions representative of inertial fusion energy

Structural materials for laser-based inertial fusion energy (IFE) reactor concepts are expected to operate under pulsed irradiation conditions, with cycles consisting of microsecond-long neutron bursts followed by inter-pulse periods of up to one second in duration. During each laser shot, irradiation damage is introduced at dose rates that are up to six orders of magnitude higher than those in their magnetic fusion energy (MFE) counterparts. Under certain conditions, the inter-pulse periods may last an amount of time sufficient to anneal much of the damage introduced during each shot. This phenomenon is highly temperature dependent, with pulsed heating directly linked to the pulsed damage, large surface temperature spikes may also occur. As such, this intermittent mode of operation has the potential to lead to fundamental differences in how irradiation damage accumulates in structural reactor materials. However, damage to structural materials under IFE conditions has received comparatively much less attention than in MFE, as pulsed conditions add yet an extra dimension to the already extremely challenging problem of microstructural evolution under fusion neutron irradiation in structural materials. In this work we use the stochastic cluster dynamics (SCD) method to simulate the evolution with time of defect cluster concentrations under IFE conditions. We consider the Laser Inertial Fusion Energy (LIFE) reactor concept as the representative IFE design for our study, for which detailed spectral information is available, including gas transmutant production. We simulate several pulse frequencies and three different temperatures, and compare the results with continuous irradiation cases under identical average dose rates. The simulations are run in Fe-9Cr system as a model alloy for reduced-activation ferritic/martensitic (RAFM) steels, which are the leading structural material candidates for first-wall structures in MFE and IFE devices. We find that, in practically all scenarios, pulsed irradiation restricts the formation of helium-vacancy clusters relative to the levels seen under equivalent steady irradiation conditions. As well, although self-interstitial atom clusters do accumulate under pulsed operation, their number densities remain up to an order of magnitude lower than in continuous irradiation conditions. Based on the SCD results, we provide a temperature-pulse rate map to identify regions where pulsed irradiation may lead to larger defect accumulation than under continuous irradiation.

Advanced Controllers for Heat Transfer Fluid Mass Flow Rate Control in Solar Tower Receivers

Efficient control strategies for managing the mass flow rate (MFR) of heat transfer fluids (HTF) during cloud transients in Solar Tower receivers play a pivotal role in optimizing plant profitability and receiver durability. This study focuses on the performance and durability of Solar Tower receivers during cloud transients. It evaluates adaptive feedback and feedforward control methods, which adjust the flow rate of heat transfer fluids based on real-time measurements of direct normal irradiance (DNI), receiver outlet and receiver panel outlet temperatures. The effectiveness of an aggressive all-sky and conservative clear-sky control strategy is explored against a conventional PI controller, emphasizing energy efficiency and receiver longevity. Simulations using a thermal Modelica model resembling a 100 MWel Crescent Dunes-like solar tower plant reveal that both advanced controllers provide precise setpoint tracking, while the PI controller struggles. The conservative controller which has a cloud standby mode prevents overheating during cloud transients by using a clear sky mass flow rate, while the aggressive controller uses the receiver panel outlet temperatures to correct for upstream tube temperature variations allowing for fast tracking correction and disturbance rejection, albeit with slight overshoots. Furthermore, the controllers significantly decrease the creep-fatigue damage accumulated in the receiver panels during cloudy days, due to limiting the increase in wall temperature spikes when cloud events end. Overall, this study underscores the pivotal role of HTF mass flow rate control systems in influencing receiver system failure modes and longevity and offers a new tool in controller design and operation assessment.

Impact of dual nano-enhanced phase change materials on mitigating thermal runaway in lithium-ion battery cell

Thermal management remains a pivotal challenge in enhancing the safety and efficiency of lithium-ion batteries, especially under conditions prone to thermal runaway. This study investigates the performance of dual nano-enhanced phase change materials (NEPCM) in moderating extreme thermal events in battery cells. By integrating nanoparticles, specifically alumina and single-walled carbon nanotubes (SWCNT), into phase change materials (PCM), the study explores modifications in thermal behavior and phase change dynamics within a cylindrical battery enclosure. The research focuses on comparing the thermal performance of pure PCM and NEPCM, using two types of nanoparticles dispersed within the PCM matrix at various volume fractions. The findings indicate that NEPCM significantly improves heat transfer rates and accelerates the melting process. Specifically, NEPCM with 6 % SWCNT increases the melting temperature distribution by up to 15.27 % compared to pure PCM setups and enhances the liquid fraction by up to 66.54 % under similar conditions. The inclusion of SWCNT demonstrates a superior enhancement in thermal conductivity compared to alumina, leading to more effective heat absorption and dissipation. Liquid fraction analysis confirms that NEPCM configurations facilitate quicker and more uniform thermal behaviors, especially near the heat source. PCM1, positioned adjacent to the battery, exhibits an immediate increase in temperature and melting rate, significantly outperforming PCM2 in thermal regulation. This study underscores the potential of dual nano-enhanced PCM in improving the thermal management of lithium-ion batteries, particularly in scenarios at risk of thermal runaway. By optimizing the PCM formulation with nanoparticles, a robust solution is presented to control temperature spikes and improve battery safety and durability in challenging operational environments.

Startup and Multiphysics Analysis of a Compact kW-Class Thermal Spectrum Microreactor

Self-regulating compact nuclear microreactor concepts are being developed for use in space and at terrestrial remote sites. The current emphasis is on the development of high-assay low-enriched uranium–fueled reactors that rely on metal hydrides to achieve size, specific weight, and power parity with the legacy highly enriched uranium systems. In the case of terrestrial applications, metal hydride–moderated systems can also improve economic feasibility. The neutronic design of metal hydride–moderated high-temperature reactor cores is complicated by the need to optimize and synchronize delayed spatial and temporal reactivity feedback from outer reflectors. Zebra is a thermal spectrum proof-of-principle core designed for demonstrating the reactor dynamics of hydride-moderated spectrum reactors, which is studied in this work. The reactor, including the fuel, yttrium hydride moderator, heat pipes, central control rod, structural supports, and the beryllium reflector, weighs ~425 kg. The design shares several features common with nuclear criticality test geometries routinely used in National Criticality Experiments Research Center (NCERC) experiments such that a prototype of the reactor can be readily assembled and tested. Additional features, such as heat pipes and hydrogen barrier clads, were added to minimize the potential for large thermal gradients that in turn could induce hydrogen loss or structural deformation during extended periods of operation at ~1000 K. In this work, normal and off-normal state performance of the Zebra rector core was analyzed using MCNP and Abaqus-based Reactor Multiphysics (MARM) software. Up-to-date nuclear, thermal, and mechanical performance data were used to characterize the performance of the yttrium hydride moderator. Steady-state analyses established that at a postulated power between 20 and 50 kW(thermal), the reactor core is nearly isothermal irrespective of quality of conduction coupling between heat pipes and fuel plates. Additionally, heat pipe failure modes, including simultaneous failure of all heat pipes in a quadrant of a reactor, were examined to bound the maximum credible temperature spike in the reactor core for extreme off-normal operating conditions. Finally, we detail the startup design challenges for the hydride-moderated thermal core, and analyze load-following cases to achieve “self-regulation” using the Dynamic Analysis of Reactor Transients module of MARM. The reactor is self-regulating with a reactivity temperature coefficient of ~−1 pcm/K at the operating point based solely on nuclear cross-section feedback. It can be further strengthened using additional spectral shift neutron absorbers and incorporating design features that enhance core expansion. This work captures that hydride-moderated systems are feasible for various self-regulating applications once systematic checks are verified in order to achieve a well-engineered core design.

Numerical simulation of high-temperature erosion of heat-resistant steel considering surface scale evolution

A study was conducted on heat-treated, heat-resistant steel S51740 to understand the issues surrounding gas turbine compressors. The study included high-temperature cyclic oxidation and high-temperature erosion tests at 400 °C, 600 °C, and 800 °C. We used the oxidation test data to establish dynamic erosion models using Ansys LS-DYNA software. We focused on the target's surface morphology, stress-strain, transient temperature, and failure characteristics during high-temperature erosion after high-temperature oxidation to reveal the erosion mechanism of oxidized steel. During cyclic oxidation, the specimen's microstructure was refined at 400 °C, with a 10 μm oxidation-affected zone emerging. At 600 °C, austenite appeared, forming a 20 μm oxidation-affected zone. Performance declined at 800 °C due to decarburization and segregation, resulting in a 50 μm oxidation-affected zone. High-temperature erosion on the oxidized specimens featured cutting and a chip-like morphology at 400 °C and 600 °C. At 800 °C, the specimen experienced a notable increase in mass loss and extensive plastic deformation on the surface. Erosion simulations revealed that rising temperatures increase the target's stress distribution, strain, and temperature zones. Reduced material strength leads to lower resistance to impact particles, converting high-speed kinetic energy to internal energy during erosion. Temperature spikes in impacted zones accelerate wear and adversely affect local mechanical properties. Lower ambient temperatures exacerbate the temperature increase from erosion, significantly influencing material erosion and wear resistance.

New thermal solver for mitigating surface temperature instability in laser-induced heating

An accepted approach to computing laser-induced peak surface temperature is to employ the enthalpy formulation of the transient heat conduction equation [Grigoropoulos et al., Adv. Heat Transfer 28, 75–144 (1996); Sawyer et al., J. Laser Appl. 29, 022212 (2017)]. This approach is generally implemented using an explicit numerical scheme to solve the thermal transport equation. While it offers the advantage of modeling the solid-melt phase transition automatically, the approach results in instability-like behavior in the computed surface temperature. When laser-induced ablation becomes significant, the heating rate in the surface cell becomes unrealistically large. This results in spikes in the computed peak surface temperature due to large errors in calculating the heating rate. In this paper, we present a new approach, which we refer to as the Moving Frame Solver, that employs a moving-coordinate frame of reference, located at the receding evaporating surface. We also use an analytical representation for the phase transition region of the enthalpy-temperature relationship. The Moving Frame Solver combined with an implicit scheme leads to a stable solution without surface temperature, pressure, or velocity spikes. In other words, any instability in these computed parameters due to use of an explicit scheme (such as Dufort–Frankel) has been eliminated. Details of the new thermal solver and example calculations are presented. Numerical experiments suggest that the surface cell size needs to be small, ∼0.1 μm, to obtain a highly accurate solution with a typical metal such as aluminum. Using the Moving Frame Solver with a refined grid near the surface, but coarse elsewhere, enables accurate and stable surface temperature computation.

Time in DNB experimental study on Cr coated zircaloy cladding

Since the Fukushima-Daiichi accident effort has been put in by the nuclear community to develop Accident Tolerant Fuel (ATF) cladding materials to reduce the risk of clad oxidation and, consequently, hydrogen generation and potential major accidents. Among designed materials, the use of a chromium coating on top of zirconium-alloy cladding showed reasonable results in preliminary tests, being a favorable cladding solution for Pressurized Water Reactors. This paper provides highly detailed temperature data obtained during time in departure from nucleate boiling (DNB) experiments under prototypical reactor conditions of temperature, pressure, mass flux, and heat flux profile on a Cr-coated zirconium-alloy cladded heater rod simulating the fuel pin. Data were obtained at mass fluxes from 1300 to 1700 kg/m2s, pressure of 16 MPa, and inlet temperature of 333 °C (subcooling degree of 14.4 °C). The change in dry time was obtained by increasing the spike in wall temperature necessary to shut down the power. These tests showed that increasing the spike in temperature to characterize the critical heat flux from 50 °C to 400 °C resulted in variations of the departure from nucleate boiling measured value within the uncertainty range of their measurements, hence, validating the use of a spike of 50 °C, a commonly used value in this kind of study, as an indicator of the critical heat flux. Within the dry region, the temperature was found to increase along the direction of the flow for a very short length, reaching a peak, from which it reduces linearly until the surface reaches a temperature that is no longer able to sustain a dry patch. It was noticed that the dry region can grow against the flow direction due to the cosine profile of the heat flux, and that small dryout events can occur without leading to departure from nucleate boiling, i.e., being fully suppressed. However, two consecutive events may sum up and cause the critical heat flux. Rewet time was found to increase with peak cladding temperature and decrease with mass flux. A maximum peak cladding temperature of 844 °C was found, with the surface remaining dry for approximately 14.1 s. The minimum film boiling temperature was measured during the rewet process, showing absolute values of around 580 °C, and difference between wall and inlet temperatures of about 240 °C. A post-inspection using microscope and X-ray images showed no damage to the cladding and heater structure, differently than what was noticed for the bare zircaloy in a previous study. This indicated that the presence of chromium coated cladding can improve the oxidation resistance of the cladding not only in short critical heat flux transients but also in longer events associated with major accidents, like a Loss of Coolant Accident.

Diltiazem HCl suppresses porcine reproductive and respiratory syndrome virus infection in susceptible cells and in swine

Porcine reproductive and respiratory syndrome virus (PRRSV) is a pathogen for swine, resulting in substantial economic losses to the swine industry. However, there has been little success in developing effective vaccines or drugs for PRRSV control. In the present study, we discovered that Diltiazem HCl, an inhibitor of L-type Ca2+ channel, effectively suppresses PRRSV replication in MARC-145, PK-15CD163 and PAM cells in dose-dependent manner. Furthermore, it demonstrates a broad-spectrum activity against both PRRSV-1 and PRRSV-2 strains. Additionally, we explored the underlying mechanisms and found that Diltiazem HCl -induced inhibition of PRRSV associated with regulation of calcium ion homeostasis in susceptible cells. Moreover, we evaluated the antiviral effects of Diltiazem HCl in PRRSV-challenged piglets, assessing rectal temperature, viremia, and gross and microscopic lung lesions. Our results indicate that Diltiazem HCl treatment alleviates PRRSV-induced rectal temperature spikes, pulmonary pathological changes, and serum viral load. In conclusion, our data suggest that Diltiazem HCl could serve as a novel therapeutic drug against PRRSV infection.

Smart Agriculture untuk Mewujudkan Ketahanan Pangan Berbasis Lora di Desa Kalipadang-Benjeng Gresik

Increasing agricultural production is a top priority in agricultural development. There are many agricultural problems to be managed. One way to increase rice production is to pay attention to irrigation conditions. In addition to irrigation, rising temperatures also affect the process of flowering and grain filling. At high temperatures, grain because of rice agricultural production will calcify, resulting in a decrease in grain quantity and grain mass. Temperature spikes can also reduce the viability and size of the seeds when they reach the ripe stage. Apart from water and air, farmers also need to pay attention to soil pH and humidity. Many farmers do not yet have accurate indicators to determine soil quality, most farmers only use estimates, the application of the estimation method causes the quality of the soil in paddy fields to be infertile. To overcome this problem, a tool is made to predict the condition of agricultural land by taking data on temperature, humidity, air pressure, soil pH, soil moisture, and water flow rate. The data is then sent to a database to be displayed on a web server, so that farmers can monitor land conditions. It is expected that the parameter results obtained can be used as a preventive measure for farmers when conditions occur that can reduce rice productivity. That way, the condition of the land can be maintained so that crop failure can be minimized. This tool will be implemented in one of the rice fields of the residents of Kalipadang-Benjeng-Gresik Village. Based on data taken using an NPK sensor, wet soil has an average NPK content of 29.3 (Nitrogen); 41 (Phosphorus); 82 (Potassium). Moist soil has an NPK level of 28 (Nitrogen); 40 (Phosphorus); 82 (Potassium), and dry soil has an NPK level of 27.5 (Nitrogen); 39.7 (Phosphorus); 79.1 (Potassium). It can be said that soil moisture is directly proportional to NPK levels.

Heat stress and sexual reproduction in maize: unveiling the most pivotal factors and the greatest opportunities.

The escalation in the intensity, frequency, and duration of high-temperature (HT) stress is currently unparalleled, which aggravates the challenges for crop production. Yet, the stage-dependent responses of reproductive organs to HT stress at the morphological, physiological, and molecular levels remain inadequately explored in pivotal staple crops. This review synthesized current knowledge regarding the mechanisms by which HT stress induces abnormalities and aberrations in reproductive growth and development, as well as by which it alters the morphology and function of florets, flowering patterns, and the processes of pollination and fertilization in maize (Zea mays L.). We identified the stage-specific sensitivities to HT stress and accurately defined the sensitive period from a time scale of days to hours. The microspore tetrad phase of pollen development and anthesis (especially shortly after pollination) are most sensitive to HT stress, and even brief temperature spikes during these stages can lead to significant kernel loss. The impetuses behind the heat-induced impairments in seed set are closely related to carbon, reactive oxygen species, phytohormone signals, ion (e.g. Ca2+) homeostasis, plasma membrane structure and function, and others. Recent advances in understanding the genetic mechanisms underlying HT stress responses during maize sexual reproduction have been systematically summarized.

Comparison of hydrostatic and non-hydrostatic compression of glassy carbon to 80 GPa

Understanding new mechanisms for phase transformation in carbon is of considerable interest. This study investigates on the compression conditions required to create recoverable diamond during room-temperature high-pressure compression of glassy carbon. Under non-hydrostatic compression conditions when shear is present, glassy carbon transforms into an oriented graphitic structure at ∼45 GPa, and then forms mixed diamond and lonsdaleite nanocrystals when the pressure is higher than ∼80 GPa. In contrast, during hydrostatic compression no significant changes in the microstructure was observed, highlighting glassy carbon’s resilience under compression. Molecular dynamics modelling supports the proposed model that shear drives the phase transition mechanism and causes a temperature spike that drives crystallisation. Our work demonstrates that shear is key to high-pressure diamond formation in the absence of heating.

A study of one-dimensional colliding laser-produced plasmas through modeling and experimentation

An investigation was conducted into two colliding laser-produced plasmas collimated by two face-to-face channels, which makes the plasmas close to one-dimensional (1-D) and thus easier to simulate. The study was carried out using time-resolved imaging, and a 1-D fluid-descriptive model with the ambipolar electric field and collisional coupling taken into account. The time-resolved images show that the 1-D colliding plasmas follow a division into three distinct periods, namely, pre-colliding, colliding, and finally the stagnation layer dissipating. In the pre-colliding period, there is no plasma coming out of the channels, but illumination features are observed near the inner surfaces of the two blocks for more than 150 ns, which is much longer than the laser pulse duration. In the colliding period, there is continuous ejection of plasma from the channels and the formation of a stagnation layer due to the collision of the two plasmas. The dissipation of the stagnation layer into its nearby space in the third stage can be clearly observed in the images. Applying the 1-D model, the simulation results predict the temperature spikes and density increase in the layer due to the conversion of the macro-kinetic energy of the plasmas into their internal energy with the flow velocities almost vanishing. The ratios of the ion–ion mean-free-path to the characteristic length at the midpoint of the two plasmas, extracted from the simulation, indicate that the stagnation layer is a soft one with partial plasma interpenetration through the interface between the two plasmas.

Analyzing the role of climatic factors in the driver—vehicle—road—environment system

Climate peculiarities affect road performance and, consequently, vehicle operating conditions. The autumn-winterspring period is characterized by sharp air temperature fluctuations within 0...± 4 °C, large amounts of precipitation, high air humidity, thaws, icing, which are a concomitant factor of accidents on the roads. The analysis of road accident statistics showed that in the transitional periods of fall-winter and winter-spring there are localized spikes in the number of accidents. During the analysis it was revealed that the increase in the number of accidents in the transition period falls on the so-called "critical" month, characterized by air temperature spikes in the range of 0...±4 °C and heavy precipitation. Keywords WADS system; climatic zones of the Russian Federation; factors of the subsystem "environment"; accident statistics; winter road maintenance

Onset of heterogeneous nucleation in pool boiling of HFE-7100 following rapid heating on a microscale heater

Effective thermal management of electronics is crucial for maintaining their reliability, longevity, and optimal performance. As electronic devices become increasingly compact and powerful, the need to explore new and innovative methods for thermal management becomes ever more critical. Rapid transitions of power lead to temperature spikes (hotspots) of up to 100 K, and thus can dramatically increase the failure occurrence of chips. Power spikes imply that heterogeneous nucleation occurs due to rapid heating, which can vary between 104 – 106 K/s, and hence the coolant is in its metastable region under various degrees of superheating. Gaining ONB data with respect to the heating rate holds significance for diverse applications including nuclear installations, engines, inkjet printers, and laser-based systems.In the present paper, we have refined the definition to a heterogeneous nucleation event due to a rapid heating process, that occurs when the timescale for the wall heating is shorter than the critical bubble’s significant growth time. Data pertaining to the dependence of the onset of nucleate boiling (ONB) on the heating rate is presented for the first time. Experiments are performed with HFE-7100 fluid that is rapidly heated using a uniquely designed micro-heater, 122 × 234 μm2 in size.The newly designed and constructed system facilitates precise measurements of fast heating processes. In this study, we conducted a series of experiments spanning heating rates from 104 to ∼106 K/s. This range of heating rates was identified in our previous studies as an intermediate regime for water. The region of intermediate heating rates was previously proved in our research to be challenging to attain, due to the varying stability of the metastable zone; it is primarily attributed to pre-existing nucleation sites. Consequently, this led to a notable gap in the experimental results for water, within this particular region, in the literature. Notably, in the current study, we were able to achieve a maximum superheating degree of 14 K at a heating rate of 2.2·106 K/s. Preheated liquids reach the same superheating degree with different heating rates, depending on the coexistence and spinodal curves. It was found that water and HFE-7100 differ significantly in their metastable zone, and that the first zone, for slower heating rates, spans approximately 12 K for water, but only 4 K for HFE-7100.

Investigating CO2–N2 phase behavior for enhanced hydrate-based CO2 sequestration

Storing CO2 in underwater sand sediments as hydrates offers vast capacity and minimal leakage risk. But direct CO2 injection can clog the surrounding area, reducing the flow. One solution is injecting CO2–N2 mixtures. This study investigated the movement and transformation of this gas mixture, with a focus on the formation rates and main factors of hydrate-based CO2 storage. Results revealed two distinct gas seepage-phase transition processes. In freshwater conditions, there was an initial temperature spike followed by localized hydrate formation, which then spread outward. In memory water, multiple hydrate formations occurred simultaneously. Freshwater conditions led to more blockages due to the concentration of hydrates, while the memory conditions maintained better flow due to more evenly distributed hydrates. Gas composition analysis showed that as CO2-rich hydrates formed, the CO2 level in the flowing gas dropped, which could stop further hydrate formation. This finding indicates that mixed gas injections could prevent excessive hydrate formations and maintain flow. The saturation of hydrates varied between 10 % and 50 %, with differences attributed to the unpredictable nature of initial hydrate formation. Overall, this research will guide efforts to optimize CO2 storage as hydrates and re-evaluate the viability and safety of this storage method using CO2–N2 mixtures.