Sharp Temperature Increase Research Articles

Colorimetric and photothermal dual readout biosensor for flap endonuclease 1 based on target-prevented gold nanoparticles aggregation

A colorimetric and photothermal dual readout biosensor for Flap endonuclease 1 (FEN1) quantification was developed on the basis of target-prevented gold nanoparticles (AuNPs) aggregation. The exposed 5′-flap of double-flap DNA substrate modified on SAMBs was firstly cleaved by FEN1. Large amount of cleaved 5′-flap remained in the supernatant after simple magnetic separation, which can adsorb on the surface of AuNPs and effectively prevent the dispersed AuNPs from aggregation under high ionic concentration, accompanied with the color changing of the system, which can be recognized by nake eyes easily. The absorption intensity at 528 nm shows a good linear relationship with the increasing FEN1 concentration from 5.0 × 10-3 to 3.1 × 10-2 U μL-1 with a LOD of 1.6 × 10-3 U μL-1 (S/N = 3). Given the aggregated AuNPs have higher photothermal effect than that of the dispersed AuNPs, the target-prevented AuNPs aggregation avoids a sharp increase of temperature for the system under the laser radiation. The temperature change is linearly correlated with the FEN1 concentration in the range of 3.1 × 10-3–6.1 × 10-2 U μL-1 with a LOD of 1.1 × 10-3 U μL-1. The whole detection process can be completed within 1 h. The proposed system had been applied to detect FEN1 concentration in serum samples with satisfied results, which can be applied in resource-limited area easily and quickly.

Winter heat waves characteristics associated with downslope windstorm in south Brazil

AbstractThe air temperature anomaly was analysed in 16 consecutive winters from 2004 to 2019 in southern Brazil using reanalysis data and hourly atmospheric observations. In this study, 13 heat wave (HW) episodes were identified using the percentile methodology. All identified episodes are associated with the occurrence of a downslope windstorm known as Vento Norte (VNOR; Portuguese for ‘North Wind’). The VNOR is characterized by a sharp increase in air temperature combined with constant, strong, gusty winds from the north and a drop in relative humidity. The average duration was about 5 days for HW and 18 h for VNOR being than in 59.5% of the HW hours, the VNOR windstorm was also detected. The main atmospheric variables were compared during the periods of winter, HW and the VNOR windstorm. The analysis showed that HW alters local weather and climate conditions, with the more pronounced features associated with the VNOR flow. A more detailed investigation comparing the atmospheric variables collected north and south of an abrupt change in terrain altitude (400 m) revealed that the main cause of the amplification of the atmospheric variable anomalies in the centre of the state of Rio Grande do Sul was the simultaneous occurrence of HW and VNOR.

Rolling-Sliding Performance of Radial and Offset Roller Followers in Hydraulic Drivetrains for Large Scale Applications: A Comparative Study

Generally speaking, excessive side thrust and roller slippage are two different aspects affecting cam-roller mechanisms. In novel large-scale hydraulic drivetrains for offshore wind turbines, the highly dynamic nature of these mechanisms combined with the interplay of cyclic loads, frictional torques and inertia promote slippage at the cam-roller interface. At larger scales, the effects of roller inertia become much more pronounced, as the inertia escalates exponentially with the roller’s radius. This study presents a comparative analysis between radial and offset roller followers in novel large-scale hydraulic drivetrains, where offset followers are incorporated to minimize the side thrust. The framework encompasses a comprehensive kinematic and force analysis, to provide the inputs for two lubrication models integrated into the torque-balance equation, where the possibility of slippage is allowed. The findings reveal that the equivalent side thrust can be reduced by 51% with offset followers. Both configurations experience slippage during the low-load phase, but it rapidly diminishes during the high-load phase. This sudden transition in rolling conditions results in a sharp increase in surface temperature and traction force, emphasizing the importance of minimizing sliding at the interface. However, besides the substantial side thrust reduction, offset followers showed superior tribological performance, mitigating undesirable thermal and frictional effects.

Experimental Aeration Investigations on Supersaturated Total Dissolved Gas Dissipation

Supersaturation of total dissolved gas (TDG) is mainly produced by high dam discharge, excess oxygen production by plant photosynthesis, and a sharp increase in water temperature, which may directly lead to fish and aquatic organisms suffering from “gas bubble disease” (GBD) or death. Aeration was one of the methods used to solve the dissipation of supersaturated TDG. In this paper, aeration had an obvious promotion effect on the dissipation of supersaturated TDG. For the calculation and analysis of supersaturated TDG dissipation coefficient, the aeration rate was proportional to TDG dissipation coefficient and had a promoting effect on it, while the aeration depth and aeration aperture were inversely proportional to TDG dissipation coefficient and played an inhibitory effect on it. The supersaturated TDG dissipation coefficient was affected by a factor of KTDG,Q> KTDG,D> KTDG,H. A quantitative relationship between the supersaturated TDG dissipation coefficient and aeration rate, aeration depth, and aeration aperture was obtained, respectively, as well as important expressions with comprehensive effect factors; their margins of error average within 10%. This research method has an important guiding significance for improving the living environment of fish and other aquatic organisms, alleviating the adverse effects of supersaturated TDG.

Influence of Severe Plastic Deformation by Extrusion on Microstructure, Deformation and Thermal Behavior under Tension of Magnesium Alloy Mg-2.9Y-1.3Nd

The microstructural investigation, mechanical properties, and accumulation and dissipation of energies of the magnesium alloy Mg-2.9Y-1.3Nd in the recrystallized state and after severe plastic deformation (SPD) by extrusion are presented. The use of SPD provides the formation of a bimodal structure consisting of grains with an average size 15 µm and of ultrafine-grained grains with sizes less than 1 µm and volume fractions up to 50%, as well as of the fine particles of the second Mg24Y5 phases. It is established that grain refinement during extrusion is accompanied by an increase of the yield strength, increase of the tensile strength by 1.5 times, and increase of the plasticity by 1.8 times, all of which are due to substructural hardening, redistribution of the phase composition, and texture formation. Using infrared thermography, it was revealed that before the destruction of Mg-2.9Y-1.3Nd in the recrystallized state, there is a sharp jump of temperature by 10 °C, and the strain hardening coefficient becomes negative and amounts to (−6) GPa. SPD leads to a redistribution of thermal energy over the sample during deformation, does not cause a sharp increase in temperature, and reduces the strain hardening coefficient by 2.5 times.

Динамічні процеси у твердопаливних ракетних двигунах та їх взаємодія з вібраціями конструкції ракети: стан питання та актуальні проблеми

The most critical operating conditions of solid rocket motors (SRMs) are often due to the development of dynamic processes characterized by excess values of operating parameters. Pressure surges and a sharp increase in the combustion product temperature may impair the strength of the combustion chamber structure, cause its failure, and lead to critical conditions of the motor operation, up to extinguishing the propellant combustion in the motor. It is shown that both in steady and in unsteady operating conditions of an SRM, dynamic processes in its combustion chamber feature a complex interrelation of a large number of processes in the gas-dynamic space of the combustion chamber: physical, chemical, and thermodynamic (heat and mass exchange) processes. It is found that current studies of SRM operation instability are aimed at identifying mechanisms of combustion chamber pressure oscillations, which are usually due to combustion product vortex formation in the chamber space and acoustic feedback resulting from collisions of vortices with the SRM’s combustion chamber components or nozzle. Other lines of investigation are the analysis of SRM resonant damping and the establishment of a relationship between aluminum droplet combustion and SRM internal instability. It is noted that accelerations and vibrations of mixed-propellant combustion surfaces may greatly affect the combustion rate and the agglomeration, on-surface confinement, and burn-up of metal additives, which, in its turn, governs the combustion chamber acoustics. It is pointed out that the interaction of SRM combustion chamber pressure oscillations and the response of the SRM structure observed in flight tests of some rockets should be taken into account in predicting the stability of SRM dynamic processes. This interaction may call into question the sufficiency of SRM static tests and subsequent conclusions on the magnitude of its dynamic effect on the rocket structure.

Impact of wastewater treatment plant effluent on the winter thermal regime of two urban Colorado South Platte tributaries

Wastewater treatment plant effluent can increase stream water temperature from near freezing to 5°C–12°C in winter months. Recent research in the South Platte River Basin in Colorado showed that this warming alters the reproductive timing of some fishes. However, the spatial extent and magnitude of this warming are unknown. Thus, we created winter water temperature models both upstream and downstream of effluent inputs for two urban tributaries of the South Platte River, the Big Thompson River, and St. Vrain Creek. We examined the influence of air temperature, discharge, effluent temperature, and distance downstream on water temperature over the winter period (December–February). The models were also used to predict water temperature in the absence of effluent and based on air temperature predictions in 2052 and 2082. Effluent temperature was the largest driver of water temperature downstream of the effluent, while the impact of air temperature was comparatively small. Streams cooled after an initially sharp temperature increase, though were still predicted to be ∼2°C greater than they would be in the absence of effluent at ∼0.5 km. Predicted air temperatures in 2052 and 2082 had a negligible effect on water temperature, suggesting that mitigating effluent temperature is key to protecting the winter thermal regimes of effluent-impacted rivers. Our models can be used to gain insight into the magnitude and downstream extent of the impact of effluent temperature on small urban streams in winter and provide a baseline for models in other watersheds and at larger scales.

Ecosystem components in the Bering sea convention area: results from studies and fisheries prospective

Recent features in oceanography, forage base, and biological diversity, as well as fisheries prospective in the Bering Sea Convention area are considered. Since 1950, a sharp increase in water temperature has been observed, and thermal regime shifts occurred in 1977 and 2014. Composition and structure of zooplankton communities are virtually the same as in the western Bering Sea basin. Zooplankton community is comprised by a small number of widely distributed species, which belong to macrozooplankton and constitute a valuable food source for upper trophic levels. Nekton biomass is small, an order of magnitude lower than on the shelf. Neighboring continental slope and underwater ridges, as well as seasonal migrations of lower boreal and lower boreal-subtropical species support high species richness of nekton community. Pelagic and benthopelagic species of fish and squid, which occur on the shelf and slope, usually do not migrate into the Convention area in large quantities, except for walleye pollock, which was actively harvested in this area in 1983–1992. However, in the up-coming years, it is impossible to resume pollock fishery in the Convention area, based on the modern state of pollock resources.

Durable Rapid Self-Disinfection, Reusable Protective Clothing Based on the Ag-Pd@MoS2 Nanozyme with Enhanced Triple-Mode Synergistic Antibacterial Effect.

Personal protective clothing plays an important role in isolating microorganisms and harmful ultrafine dust, but it cannot quickly inactivate bacteria intercepted on the surface, making it a potential source of infection. However, spontaneous and durable rapid sterilization is a major challenge for commercial protective clothing. Herein, we exquisitely engineered a visible light-enhanced Ag-Pd@MoS2 nanozyme-based fabric, named PVDF/Ag-Pd@MoS2/PAN fabric (PAPMP fabric), with prominent triple-mode synergistic antibacterial effect through the replacement reaction, electrospinning technique, and vacuum filtration method. The modification of Ag-Pd greatly strengthened the absorption of MoS2 nanosheets to the visible light spectrum (390-780 nm) and its corresponding catalytic performance. Meanwhile, the combination of MoS2 nanosheets significantly enhanced the oxidase-like characteristics of Ag-Pd under sunlight irradiation, increasing the yield of surface-bound 1O2 ∼4.54 times in 5 min. In addition, the obtained Ag-Pd@MoS2 nanozyme showed an excellent photo-to-thermal conversion property (36.12%), which enabled the sharp increase in the surface temperature of the PAPMP fabric to 62.8 °C in 1 min under a solar simulator (1 W/cm2). Correspondingly, the obtained PAPMP fabric exhibited excellent intrinsic antibacterial effect and greatly shortened the sterilization time from 4 h to only 5 min under sunlight stimulation. The rapid antibacterial effect of the fabric was attributable to the enhanced production rate of surface-bound reactive oxygen species and the increased temperature by solar irradiation. Notably, the fabric still maintained the efficient germicidal effect even after 30 washing cycles. In addition to high reusability, the fabric also had outstanding biological compatibility and water resistance. Our work provides a novel strategy to improve the inherent timely sterilization and heat preservation efficiency of protective clothing.

Mathematical model and dynamic simulink simulation of PEM electrolyzer system

Hydrogen, being the most abundant element in the universe, holds great promise as an energy carrier for decarbonizing various economic sectors. In particular, green hydrogen production through water electrolysis is essential for achieving this goal, with polymer electrolyte membrane (PEM) water electrolyzers playing a crucial role. PEM water electrolyzers are known for their rapid response, enabling them to effectively adapt to fluctuations in renewable energy sources. Nevertheless, rapid load changes can result in the rapid build-up of heat within the electrolytic cell, leading to a sharp increase in temperature and potentially harming the cell. To address this challenge, we developed an electrolysis water system model using MATLAB and validated its accuracy through experiments. This model allowed us to explore the factors influencing stack temperature and propose a fast and secure dynamic process control strategy. By laying the groundwork for subsequent control studies on PEMEC (Proton Exchange Membrane Electrolysis Cell) stacks and systems, this research facilitates further progress in their control and regulation.

Niobium Pentoxide Films with High Laser-Induced Damage Threshold under High Temperature Environment

Laser damage resistance of films is the key to the performance and durability of high-power laser systems. High temperature, however, often leads to a certain degree of decline in film properties. Here, aiming to explore the mechanism of laser damage under high temperatures, Nb2O5 films were prepared using sol–gel method with NbCl5 as precursor and citric acid as additive. The effect of annealing temperatures in optical performance, microstructure, surface morphologies, and chemical composition of films were studied. Further investigation was carried out of the laser-induced damage threshold (LIDT) under different in situ high temperatures of the as-deposited films. The results showed that the films had prominent optical transmittance and high LIDT. Under 293 K, the LIDT of the film was the highest of 24.8 J/cm2. The increase of temperature brought down the LIDT of the films. It was attributed to the occurrence of oxygen vacancies, the sharp increase of temperature, and rise of defects and destruction of network structure. In this study, even though the LIDT of the film decreased a lot at 523 K, it was still high up to 14.1 J/cm2, representing the great potential for applications in authentic high-temperature environments.

Thermal imaging of increment cores: a new method to estimate sapwood depth in trees

The cells in tree sapwood form a network of interconnected conduits which enables the transport of water and nutrients from the tree roots to the canopy. Sapwood depth must be assessed when tree water use is estimated from sap flow velocities. However, current approaches to assess sapwood depth are either not applicable universally, or require expensive instruments, the application of chemicals or laborious field efforts. Here, we present a new method, which estimates sapwood depth by thermal imaging of increment cores. Using a low-cost thermal camera for mobile devices, we show that the sapwood–heartwood boundary is detectable by a sharp increase in temperature. Estimated sapwood depths agree with dye estimates (R2 = 0.84). We tested our approach on a broad range of temperate and tropical tree species: Quercus robur, Pinus sylvestris, Swietenia macrophylla, Guazuma ulmifolia, Hymenaea courbaril, Sideroxylon capiri and Astronium graveolens. In nearly all species, the methods agreed within 0.6 cm. Thermal imaging of increment cores provides a straightforward, low-cost, easy-to-use, and species-independent tool to identify sapwood depth. It has further potential to reveal radial differences in sapwood conductivity, to improve water balance estimations on larger scales and to quickly develop allometric relationships.

Visualization experiment on cryogenic boiling heat transfer and recovery characteristics in the first and second quench of RSFCLs

The resistive type superconducting fault current limiter (RSFCL) based on YBCO superconducting tape has great potential to protect the large high-voltage power grid. The rapid recovery of the YBCO superconducting tape after the 1st quench not only affects the reclosing time but also the 2nd quench response. Besides, the retention of bubbles generated from the liquid nitrogen (LN2) boiling during the 1st quench may also worsen the heat transfer and the recovery process of the 2nd quench, which is seldom revealed at present. In this work, the effects of the different initial states, i.e., the recovery stages after the 1st quench, on the 2nd quench of YBCO tapes in LN2 bath are studied. A visualization experimental setup is used to study the 1st and 2nd quench performance from the perspective of LN2 boiling bubble dynamics. Two characteristic parameters, in terms of the peak temperature Tpeak and the recovery time extension ratio ε, are adopted to describe the deterioration of quench and recovery performance. The experimental results show that the shorter the time interval between the two quenches, the greater the recovery time extension ratio ε, and the higher 2nd peak temperature Tpeak,2. Furthermore, the visualization results show that the film and the remaining bubbles after the previous quench are the main factor affecting the next quench and recovery. The maximum difference of the peak temperature between these two quenches can be as high as 46.4 K, and the extension ratio could reach 2.06. Even when the tape has recovered to about 77.3 K at the beginning of the 2nd impulse, Tpeak,2 still reaches 155.8 K due to the presence of remaining bubbles, which is 5.2 K higher than that of the 1st quench. The greatly prolonged recovery time and the sharp increase in peak temperature will further increase the risk of YBCO tape burnout. Therefore, this research can provide a more comprehensive and reliable reference for the RSFCL system to safely response repetitive current impulses.

Characterization of Fluid Dynamics and Temperature Profiles During Ureteroscopy with Laser Activation in a Model Ureter.

Introduction: Ureteral thermal injury has been reported in patients following ureteroscopy with laser lithotripsy due to overheating of fluid within the ureter. Proper understanding of this risk necessitates knowing the volume of fluid available to absorb laser energy. This can be approximated as the volume of fluid that mixes during laser activation, since energy transfer through fluid is dominated by convection. Objectives of this study were to determine the volume of fluid that mixes during laser activation at different irrigation rates and to characterize the temporal/spatial temperature distribution in a model ureter. Methods: The model ureter consisted of a plastic tube-160 mm length and 5.3 mm inner diameter. Irrigation was first applied with clear, then dyed, deionized water at rates from 8 to 40 mL/min. The laser was activated at 20 W (0.5 J/40 Hz). The distances the dyed fluid propagated were measured and volumes calculated. Temperatures were recorded from six thermocouples-five embedded within the tube and one affixed to the ureteroscope. Thermal dose was calculated using the Dewey and Sapareto methodology. Results: The volume of total fluid mixing in the model ureter was ≤1.26 ± 0.10 cm3, consistent with a sharp temperature increase after laser activation from -5 to 25 mm from the ureteroscope tip. With irrigation rates ≤12 mL/min, calculated thermal dose within the model ureter exceeded the threshold of tissue injury and extended greater distances along the ureter with lower irrigation rates. Conclusion: The volume of total fluid mixing within the model ureter was found to be small thus conferring a greater risk of ureteral thermal injury. A thermocouple positioned near the tip of the ureteroscope reasonably approximates temperature in front of the ureteroscope. Until temperature sensors are incorporated into ureteroscopic systems, laser power settings should be carefully selected to minimize risk of ureteral thermal injury.

Formation of polypropylene nanocomposite joint using silicon carbide nanowhiskers as novel susceptor for microwave welding

Up to present, no study has reported on the use of silicon carbide nanomaterials (SiCNMs) as susceptor for microwave welding of thermoplastics. Therefore, in this study, silicon carbide nanowhiskers (SiCNWs) was attempted as the microwave susceptor for the microwave welding of polypropylene (PP). It was observed that SiCNWs are capable of absorbing microwave and converting them into heat, leading to a sharp increase in temperature until it reaches the melting point of PP substrates. The microwave welded joint is formed after the molten PP at the interface between PP substrates is cooled under pressure. The effect of microwave heating duration and solid loading of SiCNWs suspension was studied and reported. The formation mechanism of SiCNWs reinforced PP welded joint was proposed in this study. With these remarkable advantages of microwave welding and enhanced mechanical properties of the welded joint, it is believed that this study can provide a new insight into welding of thermoplastic and material processing through short-term microwave heating.

Thermo-hydraulic performance of heated vertical flows of supercritical CO2

The thermo-hydraulic characteristics of heated supercritical CO2 (SCO2) flows are investigated numerically in a vertical pipe from first- and second-law perspectives, and the influence of the flow direction, mass flux and heat flux (both distribution and average value) are evaluated. Two mass flux (254 kg/(m2∙s) and 400 kg/(m2∙s)) and three average heat flux (30 kW/m2, 50 kW/m2 and 70 kW/m2) conditions are simulated at an inlet temperature of 288 K and a pressure of 8.0 MPa (corresponding pseudo-critical temperature of 308 K) in a 4-mm diameter pipe. The simulation results reveal that the heat transfer is enhanced and the irreversibility is reduced in downward flows relative to flows without gravity, whereas the heat transfer deteriorates and the irreversibility is increased in upward flows. Both higher heat fluxes and lower mass fluxes also further hinder heat transfer in the upward flows, and multiple peaks are observed in the axial wall temperature profile. Moreover, it is found that the heat-flux distribution has a significant effect on the heat transfer performance of upward flows; the heat transfer further deteriorates and the irreversibility is further increased when a linearly decreasing heat-flux distribution is applied to the wall, while the heat transfer deterioration is alleviated when a linearly increasing heat-flux distribution is used. An analysis of the heat transfer mechanism indicates that the turbulence production in the core region of the supercritical flow is suppressed, and the accumulation of gas-like fluid in the near-wall region is promoted by the buoyancy effect in upward flows, leading to severe heat transfer deterioration and a sharp increase in the wall temperature, which is similar to the critical heat-flux phenomenon in subcritical boiling. The present study provides insights into the heat transfer characteristics of SCO2 flows, as well as practical guidance on the design and optimisation of relevant components and equipment.

Response of Low Flows of Polish Rivers to Climate Change in 1987–1989

The paper discusses changes in the low-flow regime of rivers in Poland, resulting from climate change that occurred between 1987 and 1989. The low-flow variability of rivers was measured with the use of the number of days with low flows (NDLF) below a threshold value, which was adopted as the 0.1 (10%) percentile (Q10) from the set of daily flows recorded in the multi-annual period 1951–2020 at 140 water gauges on 83 rivers. The analysis of the course of climate change over Poland showed that it was caused by macro-circulation conditions, controlled by changes in the intensity of thermohaline circulation in the North Atlantic (NA THC). Climate change consisted of a sharp increase in sunshine duration and air temperature, and a decrease in relative humidity after 1988. Along with the lack of changes in precipitation totals, characterized by a strong yearly variability, and an increase in field evaporation, it led to noticeable changes in the water balance. As a result, in 1989–2020, there was a significant increase in NDFL detected in about 2/3 of the area of Poland. With the change in the NA THC phase and the macro-circulation conditions, there was also a change in the spatial distribution of areas drained by rivers with increased NDFL. In 1951–1988, these included the eastern parts of Poland, while after the climate change (1989–2020), its western and south-western parts.

Inner ear biomechanics reveals a Late Triassic origin for mammalian endothermy.

Endothermy underpins the ecological dominance of mammals and birds in diverse environmental settings1,2. However, it is unclear when this crucial feature emerged during mammalian evolutionary history, as most of the fossil evidence is ambiguous3-17. Here we show that this key evolutionary transition can be investigated using the morphology of the endolymph-filled semicircular ducts of the inner ear, which monitor head rotations and are essential for motor coordination, navigation and spatial awareness18-22. Increased body temperatures during the ectotherm-endotherm transition of mammal ancestors would decrease endolymph viscosity, negatively affecting semicircular duct biomechanics23,24, while simultaneously increasing behavioural activity25,26 probably required improved performance27. Morphological changes to the membranous ducts and enclosing bony canals would have been necessary to maintain optimal functionality during this transition. To track these morphofunctional changes in 56 extinct synapsid species, we developed the thermo-motility index, a proxy based on bony canal morphology. The results suggest that endothermy evolved abruptly during the Late Triassic period in Mammaliamorpha, correlated with a sharp increase in body temperature (5-9 °C) and an expansion of aerobic and anaerobic capacities. Contrary to previous suggestions3-14, all stem mammaliamorphs were most probably ectotherms. Endothermy, as a crucial physiological characteristic, joins other distinctive mammalian features that arose during this period of climatic instability28.

Does speed kill or make friction better?—Designing materials for high velocity sliding

Many modern applications rely on the safe operation of components sliding at high speeds, e.g., in the fields of e-mobility, high-speed manufacturing, or impact-resistant materials. While the impact of mechanical energy and heat on the friction and wear behavior of dry metallic interfaces has been the focus of extensive research in the past, the effect of extreme speeds on the near-surface deformation mechanisms in polycrystalline metals has remained poorly understood. In this work, we have tackled this crucial issue by exploring sliding velocities ranging from 10 to 2560 m/s via large-scale molecular dynamics simulations to identify three distinct deformation regimes in CuNi alloys. The microstructural response does not vary much for any of the considered systems up to sliding velocities of 40 m/s, but then evolves drastically up to a maximum value located between 320 and 1280 m/s depending on the composition. We observe that the degree of plastic deformation at the highest sliding speeds drops down to a level almost as low as for the lowest sliding speeds. We attribute this behavior to a sharp increase in the contact temperature at these high sliding speeds, approaching or even exceeding the bulk melting temperature, which goes hand in hand with a decline in the contact area and the resistance to sliding. Our characterization of the non-linear and non-monotonic material response to increasing sliding velocities will aid the systematic selection of materials and the design of robust components for a variety of high-speed sliding and wear applications.

Visualization of light-emitting diode lighting damage process in radiation environment by an in situ measurement

We investigated the radiation damage process of commercially available light-emitting diode (LED) lightings in an X-ray radiation environment such as the electron storage ring SPring-8. It was found that metal-oxide-semiconductor field-effect transistors (MOSFETs) in the LED power supplies were damaged by X-ray irradiation by a total dose effect greater than several hundred Gy (air kerma). To visualize the whole damage process, we performed in situ measurement of the MOSFET under an irradiation from an X-ray tube. The result clearly showed a sudden increase of the off-state drain current accompanied by a sharp increase of MOSFET temperature as a function of radiation dose, which eventually caused the device failure. We supposed from the result a significant increase in device lifetime by switching off the LED power supply and experimentally verified it by observing the increase of lifetime by an order of magnitude or more under the same irradiation condition.