Temperature Spikes Research Articles

Efficient thermal management of the large-format pouch lithium-ion cell via the boiling-cooling system operated with intermittent flow

To manage the undesirable temperature spike and significant temperature gradient developed on the large-format lithium-ion cell, we propose and experimentally demonstrate a boiling-cooling thermal management system using NOVEC 7000 as coolant for a large-format 20-Ah LiFePO4 lithium-ion cell. It shows that the boiling-cooling system delivers excellent capabilities in reducing maximum temperature and improving temperature uniformity under the static mode even for the 4C discharge process. To enable the boiling-cooling system a stable cooling performance during cyclic operations, the flow mode is explored. The maximum temperature is successfully controlled over cycles but a large temperature difference between regions near cell bottom and tabs is observed, especially at high flow rates. To resolve issues of the static and flow modes, the intermittent flow mode is finally conceived for the boiling-cooling system, with which the temperature spike and maximum temperature difference are controlled to be less than 36 °C and 2 °C at 2C operation. Such an impressive cooling performance, combined with the substantially low pumping work, suggests that efficient thermal management of large-format lithium-ion cells can be achieved by the boiling cooling system operated with an intermittent flow mode, which takes full advantage of the large latent heat absorbed and the high heat transfer coefficient during the boiling process.

RNA-Seq Highlights Molecular Events Associated With Impaired Pollen-Pistil Interactions Following Short-Term Heat Stress in Brassica napus.

The global climate change is leading to increased frequency of heatwaves with crops getting exposed to extreme temperature events. Such temperature spikes during the reproductive stage of plant development can harm crop fertility and productivity. Here we report the response of short-term heat stress events on the pollen and pistil tissues in a commercially grown cultivar of Brassica napus. Our data reveals that short-term temperature spikes not only affect pollen fitness but also impair the ability of the pistil to support pollen germination and pollen tube growth and that the heat stress sensitivity of pistil can have severe consequences for seed set and yield. Comparative transcriptome profiling of non-stressed and heat-stressed (40°C for 30 min) pollen and pistil (stigma + style) highlighted the underlying cellular mechanisms involved in heat stress response in these reproductive tissues. In pollen, cell wall organization and cellular transport-related genes possibly regulate pollen fitness under heat stress while the heat stress-induced repression of transcription factor encoding transcripts is a feature of the pistil response. Overall, high temperature altered the expression of genes involved in protein processing, regulation of transcription, pollen-pistil interactions, and misregulation of cellular organization, transport, and metabolism. Our results show that short episodes of high-temperature exposure in B. napus modulate key regulatory pathways disrupted reproductive processes, ultimately translating to yield loss. Further investigations on the genes and networks identified in the present study pave a way toward genetic improvement of the thermotolerance and reproductive performance of B. napus varieties.

Continuum and molecular dynamics simulations of pore collapse in shocked β-tetramethylene tetranitramine (β-HMX) single crystals

The collapse of pores plays an essential role in the shock initiation of high energy (HE) materials. When these materials are subjected to shock loading, energy is localized in hot-spots due to various mechanisms, including void collapse. Depending on the void size and shock strength, the resulting hot-spots may quench or evolve into a self-sustained deflagration wave that consequently can cause detonation. We compare finite element (FE) and non-reactive molecular dynamic (MD) simulations to study the formation of hot-spots during the collapse of an 80 nm size void in a β-tetramethylene tetranitramine energetic crystal. The crystal is shocked normal to the crystallographic plane (010), applying boundary velocities of 0.5 km/s, 1.0 km/s, and 2.0 km/s. The FE simulations capture the transition from viscoelastic collapse for relatively weak shocks to a hydrodynamic regime, the overall temperature distributions, especially at scales relevant for the initiation of HE materials, and the rate of pore collapse. A detailed comparison of velocity and temperature fields shows that the MD simulations exhibit more localization of plastic deformation, which results in higher temperature spikes but localized to small volumes. The void collapse rate and temperature field are strongly dependent on the plasticity model in the FE results, and we quantify these effects.

A transposon surveillance mechanism that safeguards plant male fertility during stress.

Although plants are able to withstand a range of environmental conditions, spikes in ambient temperature can impact plant fertility causing reductions in seed yield and notable economic losses1,2. Therefore, understanding the precise molecular mechanisms that underpin plant fertility under environmental constraints is critical to safeguarding future food production3. Here, we identified two Argonaute-like proteins whose activities are required to sustain male fertility in maize plants under high temperatures. We found that MALE-ASSOCIATED ARGONAUTE-1 and -2 associate with temperature-induced phased secondary small RNAs in pre-meiotic anthers and are essential to controlling the activity of retrotransposons in male meiocyte initials. Biochemical and structural analyses revealed how male-associated Argonaute activity and its interaction with retrotransposon RNA targets is modulated through the dynamic phosphorylation of a set of highly conserved, surface-located serine residues. Our results demonstrate that an Argonaute-dependent, RNA-guided surveillance mechanism is critical in plants to sustain male fertility under environmentally constrained conditions, by controlling the mutagenic activity of transposons in male germ cells.

Early warning signals of failures in building management systems

In the context of sensor data generated by Building Management Systems (BMS), early warning signals are still an unexplored topic. The early detection of anomalies can help preventing malfunctions of key parts of a heating, cooling and air conditioning (HVAC) system that may lead to a range of BMS problems, from important energy waste to fatal errors in the worst case. We analyse early warning signals in BMS sensor data for early failure detection. In this paper, the studied failure is a malfunction of one specific Air Handling Unit (AHU) control system that causes temperature spikes of up to 30 degrees Celsius due to overreaction of the heating and cooling valves in response to an anomalous temperature change caused by the pre-heat coil in winter period in a specific area of a manufacturing facility. For such purpose, variance, lag-1 autocorrelation function (ACF1), power spectrum (PS) and variational autoencoder (VAE) techniques are applied to both univariate and multivariate scenarios. The univariate scenario considers the application of these techniques to the control variable only (the one that displays the failure), whereas the multivariate analysis considers the variables affecting the control variable for the same purpose. Results show that anomalies can be detected up to 32 hours prior to failure, which gives sufficient time to BMS engineers to prevent a failure and therefore, an proactive approach to BMS failures is adopted instead of a reactive one.

The overly attached bacteria

Background: Chromobacterium violaceum is a Gram negative bacillus which is a common inhabitant of soil and water in tropical and subtropical regions. Infections involving humans are rare; only about 150 cases were reported worldwide up till 2004. Interestingly, the first case of human infection was reported in Malaysia back in 1927. Case Description: A 65 y old gentleman was electively admitted for (CABG) surgery. Post procedure, he developed temperature spikes and blood culture grew Chromobacterium violaceum. Subsequently, serial blood cultures persistently yielded the same organism despite being on various antibiotics. Transthoracic Echocardiography, Ultrasound Abdomen as well as CT Thorax, Abdomen and Pelvis to look for possible foci of infection or disseminated abscesses yielded negative results. Eventually patient was able to achieve bacteremic clearance after 1 m from the 1st positive blood culture. This was achieved after total 25 d of IV Ceftazidime, 48 d of IV Ciprofloxacin and Oral Bactrim for 61 d. Patient was discharged with further doses of Oral Bactrim and Oral Ciprofloxacin completing total 3 m. He was reviewed in clinic post discharge and remained well. Discussion: Chromobacterium violaceum are usually found in soil or water. Therefore, the reason our patient was able to acquire infection was unknown since he was already admitted for almost 1 m prior to first positive blood culture. Previous studies reported common predisposing factors were immunocompromised state, chronic granulomatous disease, steroid therapy, and diabetes among others, in which the patient did not fulfil. Another issue was with regards to antimicrobial agent of choice as well as duration of treatement. Considering that Chromobacterium infections are rare, there are very limited data and evidence on treatment regimes. There is no definite breakpoint for antibiotic susceptibility interpretation for Chromobacterium violaceum according to 2018 Clinical and Laboratory Standards Institute (CLSI) guidelines. The sensitivity results provided are based on non-lactose fermenter Gram negative bacillus breakpoints. Furthermore, the sensitivity testing was done in vitro; which does not directly translate to in vivo activity and response. Conclusion: Infections with Chromobacterium violaceum has been increasingly reported worldwide. Further studies and research into this organsism are required to improve patient management in the coming future.

Dopamine receptor D1- and D2-agonists do not spark brown adipose tissue thermogenesis in mice

Brown adipose tissue (BAT) thermogenesis is considered a potential target for treatment of obesity and diabetes. In vitro data suggest dopamine receptor signaling as a promising approach; however, the biological relevance of dopamine receptors in the direct activation of BAT thermogenesis in vivo remains unclear. We investigated BAT thermogenesis in vivo in mice using peripheral administration of D1-agonist SKF38393 or D2-agonist Sumanirole, infrared thermography, and in-depth molecular analyses of potential target tissues; and ex vivo in BAT explants to identify direct effects on key thermogenic markers. Acute in vivo treatment with the D1- or D2-agonist caused a short spike or brief decrease in BAT temperature, respectively. However, repeated daily administration did not induce lasting effects on BAT thermogenesis. Likewise, neither agonist directly affected Ucp1 or Dio2 mRNA expression in BAT explants. Taken together, the investigated agonists do not seem to exert lasting and physiologically relevant effects on BAT thermogenesis after peripheral administration, demonstrating that D1- and D2-receptors in iBAT are unlikely to constitute targets for obesity treatment via BAT activation.

A Catheter-Related Bloodstream Infection Caused by the Yeast Kodamaea ohmeri

Catheter-related bloodstream infections caused by Kodamaea ohmeri are generally not considered due to the relative scarcity of reported cases. This is a case of an 85-year-old man with poorly controlled diabetes mellitus who was initially admitted to our hospital for diabetic ketoacidosis. An internal jugular catheter was inserted as part of the initial management. A week later the patient developed a temperature spike and a yeast identified as Kodamaea ohmeri by ID 32 C (bioMérieux, France) was isolated from both his central and peripheral blood cultures. The catheter was removed and the patient was treated with fluconazole despite the organism’s relatively high minimum inhibitory concentration (2 μg/mL) to this antifungal. The fungemia resolved following a 2-weeks course of fluconazole.

Heat-induced drift reduction of time of flight in fused quartz acoustic waveguides via annealing process.

High temperature structural acoustic sensors play an important role in many applications. Fused quartz waveguide is a popular choice due to its resistance to harsh environments and its convenience of modification. However, time of flight between pulse and echo, which is widely used in these sensors, tends to encounter drifts in fast temperature changing process even after temperature returns to initial value. In this article, different annealing process are performed for a special modified fused quartz waveguide with a sensor node. Annealing treatment is found able to reduce the drift when the waveguide undergoes a sudden temperature spike to 1000 °C at 500 kHz operating acoustic frequency, and the best annealing condition could make the drift one magnitude smaller. A following temperature test up to 1000 °C shows consistent measurement readings.

Oxyhemoglobin Saturation (SpO2) as an Early Indicator of COVID-19: A Pilot Study

Highly infectious Novel SARS-CoV-2 virus (CoViD-19) is causing a global pandemic which disproportionately causes severe morbidity and mortality in the elderly, particularly those residing in nursing homes. Conventional infection control recommendations include temperature surveillance as one key component of surveillance. We evaluated whether monitoring oximetry (SpO2) might improve surveillance and lead to earlier awareness of a CoVid-19 outbreak. We retrospectively analysed daily measurements of temperature and SpO2 of residents at a skilled nursing facility in mid-Atlantic United States. We benchmarked these vitals for each resident. Spikes in individual temperature of at least 0.5C and decreases in SpO2 of both 1% and below 95% were considered significant. Results were grouped by residents’ CoViD-19 PCR test results in order to highlight the nursing home trends. From COVID+ residents, we observed a decrease in SpO2 levels (mean baseline 95.8%, s = 1.0, to mean SpO2 of 93.5% on the date of CoViD-19 testing, 14 days later). There was a daily downward trending of SpO2 from baseline that was discernible at least 4.8 days prior to their earliest day of temperature elevation. No similar trends were observed in the COVID- residents. The SpO2 and temperature trends of the mixed nursing home population mirrored the COVID+ cohort. Declining SpO2 in this nursing home preceded fever by several days, SpO2 thus appears to be an early indicator of an in-progress CoViD-19 outbreak. If prospectively substantiated, this might become a valuable tool in mitigating CoViD-19 spread in similar settings. Megadata provided the data free of charge and contributed to Tag to cover a portion of the expenses of the study.

Thermo-Mechanical Response of an Additively Manufactured Energetic Material Simulant to Dynamic Loading

The mesoscale thermo-mechanical behavior of an additively manufactured energetic material (AMEM) simulant under dynamic loading is studied. The material is unidirectionally printed using direct ink writing (DIW) of a high solid-loaded photopolymer and cured under ultraviolet (UV) light exposure. Experiments and multi-physics computations are performed to relate localized deformation, dissipation mechanisms, and temperature rises to the print structure. Simultaneous high-speed visible light and infrared imaging is used to obtain deformation and temperature fields over the same area of samples with micrometer spatial and microsecond temporal resolutions. Loading along different directions relative to the print structure of the material is achieved using a split-Hopkinson pressure bar (SHPB) or Kolsky bar at the average strain rate of ~ 310 s−1. Shear banding and shear failure are observed. Simulations accounting for the geometry and print structure of the samples are performed. The microstructural heterogeneities are found to significantly affect the orientation-dependent deformation, damage, and heating, with the damage and heating most pronounced when the loading direction and print orientation are non-collinear. The heating is attributed to both constituent inelastic dissipation and internal friction. Depending upon the strain rate level and the loading orientation, the contribution of frictional dissipation to the overall heating is 0.9–4.5%. Despite this relatively low fraction in the overall heating, friction is localized at fracture sites and plays an important role in the development of local temperature spikes called hotspots which are of great interest for energetic materials.

A study on thermal performance of revolving heat pipe grinding wheel

The heat generated in the grinding process can result in high temperatures in the grinding contact zone, and result in defects to both the workpiece and the grinding wheel. Typically, coolants are used to transfer heat from the contact zone. This process, however, is not satisfactory as coolants often lose efficacy due to film boiling and can result in adverse health and environment effects. A novel cooling method that incorporates a two phase revolving heat pipe within the annular disk of the grinding wheel has been proposed. In this paper, the heat transfer mechanism in the evaporator section and the condenser section was analyzed using the volume of the fluid (VOF) model in ANSYS/FLUENT. The influence of different evaporator geometry, input heat flux, filling ratio and rotational speed on the heat transfer performance are reported here. In the evaporator, nucleate boiling is suppressed and replaced by laminar convection heat transfer as the rotational acceleration exceeds 1033g. The ideal filling ratio is about 17% with a corresponding heat transfer coefficient of 6091 W/(m2·K) and the appropriate heat flux is in the range 2500 to 500,000 W/m2. Grinding experiments with both revolving heat pipe cooling and coolant cooling are performed, and the results analyzed in terms of grinding temperature and workpiece quality. The average grinding temperature was found to be under 120 °C with revolving heat pipe cooling, while temperature spikes as high as 800 °C with severe plastic deformation and grain refinement beneath the workpiece surface was found with coolant cooling.

Effect of Structure on Response of a Three-Dimensional-Printed Photopolymer-Particulate Composite Under Intermediate Strain Rate Loading

Abstract The thermo-mechanical response of an additively manufactured photopolymer-particulate composite under conditions of macroscopic uniaxial compression without lateral confinement at overall strain rates of 400–2000 s−1 is studied. The material has a direct-ink-written unidirectional structure. Computations are performed to quantify the effects of microstructure attributes including anisotropy, defects, and filament size on localized deformation, energy dissipations, and temperature rises. To this effect, an experimentally informed Lagrangian finite element framework is used, accounting for finite-strain elastic–plastic deformation, strain-rate effect, failure initiation and propagation, post-failure internal contact and friction, heat generation due to friction and inelastic bulk deformation, and heat conduction. The analysis focuses on the material behavior under overall compression. Despite relatively low contribution to overall heating, friction is localized at fracture sites and plays an essential role in the development of local temperature spikes unknown as hotspots. The microstructural attributes are found to significantly affect the development of the hotspots, with local heating most pronounced when loading is transverse to the filaments or when the material has higher porosities, stronger inter-filament junctions, or smaller filament sizes. Samples with smaller filament sizes undergo more damage, exhibit higher frictional dissipation, and develop larger hotspots that occur primarily at failure sites.

Warming in the Antarctic Stratosphere Affects Tropical Weather

Rapid temperature spikes in the stratosphere above Antarctica can influence weather and spark cyclones in the Northern Hemisphere’s tropics.

Short Circuit Capability Characterization and Analysis of p-GaN Gate High-Electron-Mobility Transistors Under Single and Repetitive Tests

Short circuit (SC) capability of 650-V Schottky-type p-GaN gate high-electron-mobility transistors (HEMTs) under single and repetitive tests is characterized in this article. The investigated devices exhibit strong capability under a single SC test, but weak capability under repetitive SC tests with a bus voltage of 400 V and a gate drive voltage of 6 V. The failure mechanism under repetitive SC tests is revealed through electrothermal simulation and microscale failure spot analysis. Thermal fatigue cracks are formed due to the high temperature spike and local temperature fluctuations in the narrow GaN channel and buffer layers, leading to weak repetitive SC capability. The unique heat confinement effect in the GaN layer plays an important role in the formation of high temperature spike and fatigue cracks. The withstand time in a single SC test is several hundred microseconds due to fast drain current drop that results from high temperature and, to a lesser degree, the dynamic threshold voltage shift during the SC transient. The device failure in a single-event SC test is related to heat diffusion to a wider region. Some guidelines are proposed for handling and improving the repetitive SC capability.

Interaction between heat wave and urban heat island: A case study in a tropical coastal city, Singapore

Heat waves are unusually high temperature events over consecutive days and may cause adverse impacts such as morbidity and mortality. The interaction between heat waves and urban heat island (UHI) effects has remained a subject of debate, as some studies prove heat wave-UHI synergy while others do not. Furthermore, heat waves affect tropical cities more severely than mid-latitude cities, but there is a disproportionate lack of heat wave studies focusing on tropical cities. We attempt to narrow this gap by studying the heat wave in Singapore in April 2016 using ground observations and the Weather Research and Forecasting (WRF) model. Compared to non-heat wave days, the ground observations show that daytime temperatures can be 3 °C higher during the heat wave. Despite the temperature spike, the UHI intensity is not amplified during the heat wave, maintaining its peak near 2.5 °C during both heat wave and non-heat wave periods. WRF simulation results also agree well with measurements and predict UHI peaks near 2.5 °C during both periods, showing no heat wave-UHI synergy. The spatially averaged UHI intensity also shows no such synergy. There is no significant change of wind speed, soil moisture availability or heat storage flux during the heat wave. Therefore, the lack of heat wave-UHI synergy in our study is consistent with current understanding of factors contributing to UHI. This study shows that the heat wave-UHI interaction in a tropical city can be different from that in cities in the temperate climate zone and more studies should be conducted in tropical cities, which are projected to suffer larger impacts of increasing heat stress.

Concurrent Thermal and Electrical Property Effects of Nano-Enhanced Phase Change Material for High-Voltage Electronics Applications

Abstract Rapid temperature transients sustained during the operation of high-voltage electronics can be difficult to manage by relying solely on uniform heat removal mechanisms. Phase-change materials (PCMs) can be useful as a buffer against these intermittent temperature spikes when integrated into electronic packages. However, their integration poses challenges of both physical and electrical interactions within the package, particularly in high-voltage systems. This study aims to evaluate electrical and thermal properties of nano-enhanced PCMs to inform their integration in high-voltage systems. The nanocomposites are obtained by seeding 3 × 10−5 and 3 × 10−4 wt % of gold and iron oxide particles to sorbitol. Improvements in thermal properties including thermal conductivity as high as 8% are observed; however, this comes at the expense of the dielectric strength of the PCM. Additionally, an implementation scheme for the nano-enhanced PCMs in a high-voltage-capable power module is proposed with accompanying computational and experimental performance data.

Global Argo data fast receiving and post-quality-control system

Within the past 20 years, the international Argo program has acquired more than 2 million temperature and salinity profiles throughout the global ocean. It has become the most efficient means of obtaining ocean observations from upper–intermediate layers. The profile data provided by the Argo Global Data Assembly Centres (GDACs) are submitted by 11 data centres in 9 countries after undergoing quality control. However, because the quality of the submitted data lacks uniformity, users must conduct post-quality-control processing prior to using the data. For this purpose, the China Argo Real-Time Data Centre (CARDC) has developed a system to achieve both rapid global Argo data reception and post-quality-control processing of all temperature and salinity profiles. Already in operation, the system allows daily transfer of global post-quality-controlled Argo data to various operating divisions. The system synchronizes with the GDAC server once each day, extracts all updated Argo profiles, and then automatically reads the data and performs a post-quality-control process comprising 15 quality control tests. The automatic post-quality-control system can detect errors in observation time and satellite fix, as well as identify temperature and salinity spikes, frozen profiles, density inversions and salinity drift/offset. The data quality following the post-quality-control processing has been shown improved effectively. In the future, it is expected that CARDC will update the Argo global ocean observational data set once a quarter.

EP11 An unusual presentation of Sweet syndrome

Abstract Background Sweet syndrome (acute febrile neutrophilic dermatosis) is a rare inflammatory disorder affecting individuals between the ages of 30 and 60. It is characterised by painful, edematous, and erythematous skin papules, plaques, or nodules. Fever and leukocytosis (neutrophilia) frequently accompany the skin lesions. A majority of cases are idiopathic but there is a significant proportion attributed to malignancy or medications. Our case is peculiar because of an unusual presentation of a 12-month history of undifferentiated inflammatory arthritis before manifestation as Sweet syndrome. The mainstay of treatment is corticosteroids, although spontaneous resolution has been reported. Treatment of an underlying medical cause may lead to an improvement in Sweet syndrome. Methods A 57-year old British male presented with a 1-year history of intermittent joint pain and swellings in both upper and lower limbs. He had been treated with short courses of oral corticosteroids for undifferentiated inflammatory arthritis. As part of his extensive investigations whilst as a private outpatient, a knee MRI raised suspicion of malignancy, leading him to be referred to haematology and having a bone marrow examination. He was admitted with fever, polyarthritis and skin rash in form of papules around elbows and pustules on tip of some fingers. He was started on empirical antibiotics and reviewed by the Dermatology and Rheumatology teams. A skin biopsy was performed. He continued to have temperature spikes throughout admission and inflammatory markers remained elevated despite being on antibiotics. Results Full blood count showed leucopenia and Iron deficiency anaemia MCV 78 Iron 6 Transferin saturation 15% .Electrolytes, renal and liver function were normal. CRP was elevated at 190 mg/L. Acute infection screen including blood cultures and viral screen were negative. Immunology tests including Anticcp, ANA, ENA, and ANCA were all unremarkable. Echocardiogram was normal. The bone marrow biopsy showed hypercellular marrow with reactive appearances. Full body CT showed no focal signs of infection, lymphadenopathy or malignancy, with the positive findings being only a mildly enlarged spleen. Skin biopsy was consistent with a neutrophilic dermatosis such as Sweet syndrome. Conclusion This case highlights the atypical presentation of classical Sweet syndrome with no obvious underlying cause and no rise in neutrophil count. It also raised our awareness that splenomegaly can be part of Sweet syndrome and does not necessarily mean an underlying haematological disorder. The patient showed remarkable improvement with resolution of synovitis, fever and the rash once restarted on corticosteroids. He has been discharged from haematology as his blood count and CRP have normalised. Although arthralgia and arthritis have been reported in Sweet syndrome, we believe that this the first case in the literature where Sweet syndrome has manifested as undifferentiated inflammatory arthritis. Disclosures A.A.M. Mohamednour None. D. Teo None. V. Rastu None. K. Sunmboye None.

Thermodynamic Investigation of the Mechanism of Heat Production During Membrane Depolarization.

When an action potential passes through a neuron, heat is first produced and then reabsorbed by the neuronal membrane, resulting in a small measurable temperature spike. Here, we describe the thermodynamics and molecular features of the heat production using a coarse-grained molecular dynamics approach. We study a simple unicomponent lipid bilayer membrane surrounded by physiological salt solution with and without an external electric field, which represents an imbalanced charge across the membrane. We show that the temperature increases significantly upon removal of the electric field under constant pressure conditions. The potential energy converted to heat is initially stored mainly in the imbalanced ion distribution across the membrane and the elastic energy of the membrane has only a minor role to play. We demonstrate that the mechanism of heat production involves interaction between ions as well as lipid headgroup dipoles while the interactions between polar water molecules and lipid headgroup dipoles absorbs a considerable portion of such produced heat upon removal of the electric field. Our data provide novel thermodynamic insights into the molecular processes governing membrane reorganization upon discharging of lipid membranes and insight into energy metabolism in nerves.