Heat Exposure Research Articles

Re-heat treatment effect on the microstructure and mechanical properties of the Inconel 706 alloy for repair

Although the understanding of microstructure and mechanical property changes in re-heat-treated Inconel alloys is important to evaluate the performance of repaired components, recent research has mainly focused on the heat treatment effect of as-fabricated products. Thus, in this work, the performance change of the used Inconel 706 rotor-disks under varying re-heat treatment conditions was investigated. Because of the heat exposure of the used rotor-disk component, a high fraction of plate-like η phase (6.36%) and compact γ'/γ" co-precipitate structure were initiated in the as-received sample. After re-heat treatment, η phase dissolution breakage and compact to non-compact γ'/γ" co-precipitate structure transition occur, resulting in mechanical properties changes of the Inconel 706 alloy. As a result, η phase fraction affects the tensile strength and ductility of Inconel 706 alloy, while the non-compact γ'/γ" co-precipitate structure in the matrix degrades the creep lifetime. These results indicate that re-heat treatment during the repair of operated components induces microstructural and mechanical properties changes. However, to investigate the detailed history of used Inconel 706 components, additional research on the microstructural degradation during operation of Inconel components is required.

Association between heat and upper urinary tract stones morbidity and medical costs: A study in the subtropical humid climate zone

Urolithiasis is a heat-specific disease. Exploring heat-related urolithiasis susceptibility subtypes, economic burden, and modifying factors could assist governments in targeting interventions to reduce the heat-related health risks of urolithiasis morbidity. We collected data on 23,492 patients with upper urinary tract stones (main subtypes of urolithiasis) from 2013 to 2017 in Nanjing, China. We adopted generalized additive quasi-Poisson models to examine the associations between daily mean temperatures and morbidity of upper urinary tract stones, while generalized additive Gaussian models were used to explore the relationships between temperatures and log-transformed medical costs. We examined the modification effects of disease subtypes (kidney and ureteral calculus), sex, and age through stratified analyses and the modification effects of other meteorological factors by introducing interaction terms in the models. We found that short-term summer heat exposure has a statistically significant effect on ureteral calculus morbidity but not on kidney calculus morbidity. For ureter calculus, a 1 °C temperature increase was associated with a 4.36% (95% confidence interval [CI]: 1.94%, 6.83%) increase in daily hospitalization and a 5.44% (95% CI: 2.71%, 8.25%) increase in daily medical costs. The attributable fraction associated with heat (greater than the median value of daily mean temperature, 26.8 °C) was 7.85% (95% empirical confidence interval [eCI]: 3.64%, 11.44%) for hospitalization and 9.36% (95% eCI: 4.91%, 13.14%) for medical costs. The effects of heat on ureter calculus morbidity were significantly higher among the males and those with high sunshine duration than females and those with low sunshine duration. Short-term summer heat exposure was associated with increased morbidity and medical costs of ureteral calculus. Relevant government organizations should take effective intervention measures, including community health education, to reduce the health hazards and economic losses caused by heat.

Heat Exposure and Dementia-Related Mortality in China

Heat Exposure and Dementia-Related Mortality in China

Analisis Penerapan K3 di Pabrik Perkebunan Sawit

. Implementing a culture of safety or safe work in oil palm plantations is very difficult for the workforce, especially those with low education. The palm oil industry faces many risks, including heat exposure, heavy workloads, exposure to hazardous chemicals, fires, and accidents due to heavy equipment. OHS is still seen as a cost and not an investment to prevent work accidents in companies or industries. The purpose of this study was to summarize the journal and find important information about the implementation of OSH in palm oil mills. In writing this journal, a literature review approach was used. The journals used in this study came from journals accessed through Google Schoolar. The results showed that there are several factors that cause To conduct this research, the activities needed to identify risks in the work process, such as fire, fall risk, heat exposure, chemical exposure, and occupational accidents. To conduct this research, the necessary activities to identify risks in the work process at the.

Effect of Heat Exposure Time on Tensile Properties in Cold Rolled Steel

This paper presents the effect of heat exposure time on tensile strength of cold rolled specimens. Welding and process annealing are applied to the specimens to investigate their implications. The two processes involve heat and time but in differential amounts. In welding the temperature raises to levels far beyond the melting point of the specimens and cools quickly. The case is different in process anneal the specimen temperature increases slowly to the subcritical level and cools slowly after a specific soaking time. Welded and process annealed in the form of tensile specimens are tested in the tensile machine until fracture. The test results showed that welding and process annealing caused a decrease in yield strength by one third and almost two thirds respectively compared with the as rolled. The fracture of the welded specimen was localized at the heat affected zone near the weld line but was random in all other specimens. Percentage elongation was lowest in the welded specimen compared with other patches of specimens.

Climate change and heat stress resilient outdoor workers: findings from systematic literature review

PurposeGlobal warming has led to an increase in the number and intensity of extreme heat events, posing a significant threat to the health and safety of workers, especially those working outdoors, as they often have limited access to cooling strategies. The present systematic literature review (a) summarizes the current knowledge on the impacts of climate change on outdoor workers, (b) provides historical background on this issue, (c) explores factors that reduce and increase thermal stress resilience, (d) discusses the heat mitigation strategies, and (e) provides an overview of existing policy and legal frameworks on occupational heat exposure among outdoor workers.Materials and methodsIn this systematic review, we searched scientific databases including Scopus (N = 855), Web of Science (N = 828), and PubMed (N = 202). Additionally, we identified relevant studies on climate change and heat-stress control measures through Google Scholar (N = 116) using specific search terms. In total, we monitored 2001 articles pertaining to worker populations (men = 2921; women = 627) in various outdoor climate conditions across 14 countries. After full-text assessment, 55 studies were selected for inclusion, and finally, 29 eligible papers were included for data extraction.ResultsFailure to implement effective control strategies for outdoor workers will result in decreased resilience to thermal stress. The findings underscore a lack of awareness regarding certain adaptation strategies and interventions aimed at preventing and enhancing resilience to the impact of climate change on heat stress prevalence among workers in outdoor tropical and subtropical environments. However, attractive alternative solutions from the aspects of economic and ecological sustainability in the overall assessment of heat stress resilience can be referred to acclimatization, shading, optimized clothing properties and planned breaks.ConclusionThe integration of climate change adaptation strategies into occupational health programs can enhance occupational heat resilience among outdoor workers. Conducting cost-benefit evaluations of health and safety measures for thermal stress adaptation strategies among outdoor workers is crucial for professionals and policymakers in low- and middle-income tropical and subtropical countries. In this respect, complementary measures targeting hydration, work-rest regimes, ventilated garments, self-pacing, and mechanization can be adopted to protect outdoor workers. Risk management strategies, adaptive measures, heat risk awareness, practical interventions, training programs, and protective policies should be implemented in hot-dry and hot-humid climates to boost the tolerance and resilience of outdoor workers.

Occupational Risks of Agricultural Workers Exposed to Heat: Literature Review

Proposal: The aim of this study is to conduct a literature review on the occupational hazards of agricultural workers exposed to heat while carrying out their activities. Theoretical Framework: Heat exposure poses a serious occupational risk for agricultural workers, increasing the incidence of dehydration, heat exhaustion, and sunstroke. Method: The methodology adopted for this research involves a literature review using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) methodology. Data collection was carried out through a bibliographic survey from the period 2005 to 2024 in the Pubmed, Web of Science, and Scopus databases. The search used keywords such as "risks," "workers," "agriculture," and "heat." Results and Discussion: The results revealed the selection of 109 articles, and after reading the abstracts, those that did not align with the research proposal were excluded. After filtering, 07 articles remained, whose topics showed affinity with the research. The literature points to a growing trend of studies addressing thermal discomfort as an occupational hazard, prevalent in open and semi-open environments. Specific studies for certain agricultural operations, such as groups of workers dealing with grain dryers and furnaces, are scarce and have limited conclusions. Research Implications: The practical and theoretical implications of this research are discussed, providing insights into how the results can be applied or influence practical aspects in the field of occupational heat exposure for agricultural workers. These implications can encompass various sectors of post-harvest grain processing. Originality/Value: This study contributes to the literature by gathering information published in different databases on occupational heat exposure. The significance and value of this research are highlighted by a limited number of works in the literature, stressing the need for further research in the field. Based on this premise, more studies on agricultural work in heat-prone environments and consequent thermal discomfort should be encouraged to stimulate discussions on actions to eliminate the risks involved in these operations.

Assessing the role of socio-economic factors in shaping the temperature-mortality exposure-response relationship in China

Non-optimal temperatures significantly influence public health. However, the role of socio-economic factors in modulating health risks associated with non-optimal temperatures varies geographically and among different populations. Thus, the meteorological, air quality, health data, and socio-economic indicators were obtained from 23 districts in North and 48 districts in East China, respectively. Employing a two-stage meta-analysis, the exposure-response relationship was constructed for temperature against mortality from non-accidental causes, cardiovascular and cerebrovascular diseases, and respiratory illnesses. Furthermore, a non-linear spline regression was applied to assess the impact of socio-economic indicators on the exposure-response relationship and predicted future risks under various Shared Socioeconomic Pathways. The results revealed that the influence of socio-economic factors on the exposure-response curve showed heterogeneity in East China and North China. In North China, the shape of the exposure-response curve changed greatly under different socio-economic levels, while it remained similar in East China. In East China, the relative risk of heat and cold exposure was reduced in regions with high GDP, high levels of public finance, good medical services, and a low proportion of the elderly population. Specifically, the risk of non-accidental deaths due to heat shows a nearly linear negative correlation with per capita GDP in East China, with a decrease of the relative risk by 0.075 for every 10 thousand yuan increase in per capita GDP. Future projections indicate that population aging plays a decisive role in shaping the exposure-response curves. Although economic growth can reduce the risk of heat-related mortality, the combined effect of population aging and economic increase results in steeper exposure-response curves in both hot and cold temperature ranges in the future. In conclusion, although spatial variations in relative risk changes still exist, enhancing the adaptive capacity of populations can mitigate health risks associated with future climate change.

Kidney Function Biomarkers During Extreme Heat Exposure in Young and Older Adults

This study investigates the effects of extreme heat exposure on kidney function using plasma-based biomarkers in young and older adults.

Investigating the transient conditions of “Sabat” space and its influence on pedestrian sensations during thermal walks. Algiers’ Casbah case study

Cities are already witnessing the impacts of climate change. Prolonged heat exposure have a direct effect on pedestrians’ thermoregulatory system, causing serious heat-related issues in the form of fatigue and thermal exhaustion. While the human body is capable of maintaining heat balance, excessive heat exposure combined with increasing heat loads can deteriorate the thermoregulatory process which leads to discomfort. Walkability is one of the significant challenges for climate change mitigation. Balancing the dichotomy of walking to mitigate climate change, and mitigating climate change to walk emphasizes the importance of promoting resilient walkability. In this context, the term “resilience” is used to highlight the need to design urban spaces able to adapt to increased urban heat, enabling pedestrians to tolerate and recover from discomfort conditions. This study investigates the potential of the “Sabat”, a traditional semi-outdoor space with lift-up design, and its distribution in generating transient thermal aeraulic conditions, and reducing fatigue sensation, hence, supporting a positive walking experience. Thermal walks have been conducted in Casbah of Algiers during temperate and hot weather conditions, in the context of uphill walking. Results revealed the alliesthesial effect of cool-shaded and ventilated Sabats to reduce fatigue sensation, which was confirmed by the significant correlation at lag-(-1) (r = 0.504, p < 0.001). Findings shed light on the importance of maintaining dynamic alliesthesia to create modulated restorative opportunities and offer starting point for hypothesizing broader trends for future implementation of Sabat design in modern cities.

Extreme heat adaptation in urban areas: a comparative case study of New York City and New Orleans

ABSTRACT As the risk of extreme heat in urban centres becomes more frequent and intense, a comparative case study of New York City, New York's and New Orleans, Louisiana's policy responses to dangerous heat highlights past approaches to protecting vulnerable populations, where improvements can be made to best suit local needs, and the areas where solutions may still be implemented. Two cities at the forefront of the climate crisis in the United States, their policy approaches are guided by their histories, their existing adaptations and behaviours, and the harsh reality the changing climate has wrought. New York City has prioritised cooling centres as a safety measure, as the city is regularly seeing hundreds of heat-related deaths per year, often in unairconditioned homes. New Orleans has prioritised the installation of back-up energy generation following mass blackouts caused by Hurricane Ida in 2021 and deaths of at least 10 residents in the resulting excessive heat exposure. In New York, census tracts with the highest percentage of Black, elderly, and foreign-born populations were most likely to have reduced access to a cooling centre. In New Orleans, tracts with the highest percentage of Black, elderly, unemployed, and impoverished populations were most likely to have reduced access to a cooling centre. Comparing both city's codes, regulations, and policies, reviewing their emergency management communication strategies on social media, and performing GIS analysis on cooling centre locations against vulnerability criteria paints a clear picture of where heat policy stands in both cities and where it could potentially expand.

Chronic Heat Exposure Modulates Innate and Adaptive Immune Responses in Firefighters

Global fire activities, which are getting worse due to climate change, cause both environmental and human health hazards. Firefighters, being the first responders, are frequently exposed to heat which may impact their immune system and overall health. However, the nature of the impact of chronic heat exposure on immune function has not been studied in-depth in firefighters. In this study, 22 firefighters exposed to “heavy-smoke fires (structural fires)”, categorized as the “high-exposure group” (&gt;0.15 structural fires/week) and “low-exposure group” (&lt;0.15 structural fires/week), were sampled. Peripheral blood was examined for immune cell profile based on total and differential cell counts, immune function based on the transcriptional expression of drivers of innate and adaptive immunity and key inflammation mediators, and heat stress marker HSP70. The white blood cell (WBC) count, mean corpuscular volume, mean corpuscular hemoglobin, and absolute and segmented neutrophil counts decreased below the normal range in both exposure groups. The gene transcript levels for toll-like receptors (TLR2, TLR4, but not TLR7) and their adaptor protein MYD88 were lower whereas those for T-cell transcription factors (RORC/RORγ, FoxP3) and inflammatory mediators (TNF-α, Granzyme-B) were higher in the “high-exposure group”, indicating mixed response; however, the ratios between pro-inflammatory and anti-inflammatory transcription factors of adaptive immunity, namely T-bet/FoxP3 (Th1/Treg) and RORC/FoxP3 (Th17/Treg), were lower. Collectively, decreased immune cell landscape, downregulated key innate immunity receptors, and Tregs’ dominance suggested that chronic heat exposure in firefighters dysregulated innate and adaptive immunity, skewed towards an overall immunosuppressive condition with inflammation.

Plasma epinephrine and norepinephrine responses to extreme heat exposures in young and older adults.

Hyperthermia is known as a hyperadrenergic state, yet there is a lack of data on the sympathetic responses to ambient heat stress in humans. Therefore, we investigated the plasma epinephrine and norepinephrine concentrations of healthy young and older adults exposed to 3 h of very hot and dry, as well as hot and humid, heat, both with accompanying activities of daily living. We hypothesized that older adults, compared with young adults, would have augmented increases in epinephrine and norepinephrine concentrations secondary to increased thermal strain. Young (n = 20) and older (n = 18) participants underwent two 3-h heat exposures on different days: very hot and dry [47°C and 15% relative humidity (RH)] and hot and humid (41°C and 40% RH). To mimic heat generation comparable to activities of daily living, participants performed seven 5-min bouts of light cycling (approximately 3 METS) dispersed throughout the heat exposure. We measured plasma concentrations of epinephrine and norepinephrine at baseline, end, and 2-h postheat exposure. There was a group-wide increase in epinephrine from baseline to the end of the heat exposure (Δ19 ± 27 pg/mL; P < 0.001) in the hot and humid condition, but not in the very hot and dry condition (Δ6 ± 19 pg/mL; P = 0.10). There were group-wide decreases in norepinephrine concentrations from baseline to the end of the heat exposure in both the very hot and dry (Δ-131 ± 169 pg/mL; P < 0.001) and the hot and humid (Δ-138 ± 157 pg/mL; P < 0.001) conditions, with both returning to near baseline at 2-h postexposure. These data suggest that ambient heating with accompanying bouts of light intermittent exercise may lead to decreases in circulating concentrations of norepinephrine.NEW & NOTEWORTHY Herein we present plasma epinephrine and norepinephrine concentrations to 3 h of very hot and dry, as well as hot and humid, heat exposures with accompanying activities of daily living in young and older participants. We found 1) increased plasma concentrations of epinephrine in young and older adults following the hot and humid, but not the very hot and dry exposures and 2) decreased concentrations of norepinephrine in both groups following exposure to both conditions.

Farmworker-Relevant Heat Exposure in Different Crop and Shade Conditions

ABSTRACT Objectives Agricultural workers are at risk of heat-related illness, which is preventable. Few field studies have compared farmworker-relevant heat exposure in different conditions. We examined heat exposure over time in different potential shade and work locations to inform future occupational heat prevention approaches. Methods We assessed heat exposure in Eastern Washington State (WA) cherry and grape fields in August 2022. QUESTemp° monitors recorded Wet Bulb Globe Temperature (WBGT) and Black Globe Temperature (BGT) every 10 min from approximately 07:00–14:00 for three days in the center of crop rows (mid-row), under portable shade structures (shade), and in open field (open) locations. Linear mixed effects regression (LMER) models compared WBGT and BGT among field locations. Hourly time-weighted average WBGT and comparisons with occupational exposure limits (OELs) were computed for different hypothetical work-rest cycles during the hottest sampling hours, assuming different worker effort levels, rest locations (mid-row versus shade), and acclimatization statuses. Results Across all crops and locations during the study period, the mean/SD air temperature was 31°C (88°F)/3.9°C (6.9°F), with a maximum temperature of 39°C (102°F) and a mean/SD relative humidity of 30%/9.6%. LMER models suggested no significant difference in mid-row versus open WBGT but significantly lower WBGT in shade versus open locations for both cherries (main effect −5.14: 95% confidence interval [CI] −6.97,−3.32) and grapes (−6.20: 95%CI −7.73,−4.67), though this difference diminished over the course of the day. BGT was significantly higher in the mid-row than the shade (cherries main effect 14.33: 95%CI 9.52,19.13 and grapes 17.10: 95%CI 13.44,20.75). During the hottest sampling hour, the exceedances of OELs were reduced with assumptions of increased shaded break lengths, reduced effort level, and acclimatization. Conclusions Shade canopies, but not the crops studied, provided significant reductions in heat exposure. We observed increased protection from heat assuming longer shaded breaks and reduced effort levels. Results highlight the need for additional field research on the effectiveness, feasibility, and acceptability of different shade types and work-rest cycles to guide employer optimization of best practices for worker protections, including acclimatization before high heat, sufficient shaded rest time, reduced effort levels as the day warms, and avoiding work in peak heat.

Population heat exposure risk from the perspective of urban heat island spatial expansion in China during 2005–2020

The combined impact of global climate change and accelerated urbanization has intensified the urban heat island (UHI) effect, heightening population heat exposure risk. This study integrated MODIS LST (Land Surface Temperature), LUCC (Land Use Cover Change), GUB (Global Urban Boundaries), DEM (Digital Elevation Model), and population data to identify the spatial expansion of UHI in China from 2005 to 2020. A population-weighted urban heat island intensity (UHII) index (Ep) was proposed based on gridded UHII and population to compare the population heat exposure risk for the newly developed and pre-existing UHI under three levels of UHII. In 2020, UHI areas doubled since 2005, with infilling type exhibiting the highest UHII, while edge-expansion type was largest, and leapfrogging type had the lowest UHII. In the summer of 2020, the Ep indices in China were 1.75 °C and 1.79 °C during daytime and nighttime, respectively, representing increases of 0.12 °C and 0.44 °C compared to 2005. For the newly developed UHI areas with UHII exceeding 2 °C, infilling area exhibited greater daytime population heat exposure risk, whereas leapfrogging area showed higher nighttime risk. This study established a connection between UHI spatial expansion and population exposure risk, offering the insights for mitigating urban environmental hazards in the future.

Applying recent advances in climate adaptation research to urban heat risk management

AbstractThere is unequivocal evidence that anthropogenic climate change is supercharging temperature and precipitation regimes globally. One of the clearest signals of this is seen in current and projected increases in extreme heat, understood as changes in temperature maximums, longer duration heatwaves, and higher night‐time temperatures. Extreme heat has substantial impacts on socio‐ecological systems through direct impacts on human health and labor productivity, crop yields and water security; and second‐order impacts on infrastructure functioning and hazards (e.g., increased fire and drought incidence). These impacts are differentiated and mediated by preexisting vulnerabilities based on who you are, what you do, where you live, and your capacities to prepare for, prevent, cope with and adapt to heat exposure. Nowhere are these increasing and differentiated impacts of heat more visible than in populous, rapidly urbanizing regions. Governments across the world are piloting and implementing heat management strategies, which are variously called heat‐health plans, heat action plans, heat resilience strategies, and so forth. We argue that such actions and policy agendas can benefit from theoretical advances in the climate change vulnerability and adaptation literature. We synthesize five theoretical advances to highlight the need for suites of actions sequenced in pathways that are more sensitive to trade‐offs, center equity as a normative goal of effective adaptation, acknowledge uncertainty and preexisting differential vulnerabilities, leverage lessons from participatory adpatation planning, and are forward‐looking and preparatory actions. We consolidate these advances and develop an approach to inform urban heat risk management.This article is categorized under: Climate, Nature, and Ethics &gt; Climate Change and Global Justice Climate and Development &gt; Urbanization, Development, and Climate Change The Social Status of Climate Change Knowledge &gt; Climate Science and Decision Making

Adjustments in energy metabolism of brown adipose tissue in heat-acclimated Kunming mice

The thermogenic capacity of brown adipose tissue (BAT) in rodents decreases with prolonged heat exposure. However, the underlying mechanisms are not well understood. In this study, Kunming mice were acclimated at 23 ± 1 °C and 33 ± 1 °C for four weeks each to examine the body heat balance and BAT alterations. Results showed that heat-acclimated Kunming mice exhibited reduced body mass and elevated body temperature. Additionally, they displayed lower resting metabolic rates, diminished non-shivering thermogenesis, and reduced BAT thermogenic function. Metabolically, there was a significant reduction in several key metabolites involved in energy metabolism in BAT, including thiamine pyrophosphate, citric acid, cis-Aconitate, isocitric acid, oxoglutaric acid, succinate, fumarate, L-Malic acid, oxaloacetate, flavin mononucleotide, nicotinamide adenine dinucleotide, and adenosine 5′-triphosphate. These findings suggest that BAT adapts to heat acclimation by regulating pathways related to pyruvate oxidation, tricarboxylic acid cycle, and oxidative phosphorylation, which may help maintain thermal homeostasis in Kunming mice.

Early life cold and heat exposure impacts white matter development in children

Early life cold and heat exposure impacts white matter development in children

Heat stress induces calcium dyshomeostasis to subsequent cognitive impairment through ERS-mediated apoptosis via SERCA/PERK/eIF2α pathway

Heat exposure is an environmental stressor that has been associated with cognitive impairment. However, the neural mechanisms that underlie this phenomenon have yet to be extensively investigated. The Morris water maze test was utilized to assess cognitive performance. RNA sequencing was employed to discover the primary regulators and pathological pathways involved in cognitive impairment caused by heat. Before heat exposure in vivo and in vitro, activation of the sarco/endoplasmic reticulum (SR/ER) calcium (Ca2+)-ATPase (SERCA) was achieved by CDN1163. Hematoxylin-Eosin, Nissl staining, calcium imaging, transmission electron microscopy, western blot, and immunofluorescence were utilized to visualize histological changes, intracellular calcium levels, endoplasmic reticulum stress (ERS) markers, apoptosis, and synaptic proteins alterations. Heat stress (HS) significantly induced cognitive decline and neuronal damage in mice. By the transcriptome sequencing between control (n = 5) and heat stress (n = 5) mice in hippocampal tissues, we identified a reduction in the expression of the atp2a gene encoding SERCA, accompanied by a corresponding decrease in its protein level. Consequently, this dysregulation resulted in an excessive accumulation of intracellular calcium ions. Furthermore, HS exposure also activated ERS and apoptosis, as evidenced by the upregulation of p-PERK, p-eIF2α, CHOP, and caspase-3. Consistently, a reduction in postsynaptic density protein 95 (PSD95) and synaptophysin (SYN) expressions indicated modifications in synaptic function. Notably, the impacts on neurons caused by HS were found to be mitigated by CDN1163 treatment both in vivo and in vitro. Additionally, SERCA-mediated ERS-induced apoptosis was attenuated by GSK2606414 treatment via inhibiting PERK-eIF2α-CHOP axis that not only curtailed the level of caspase-3 but also elevated the levels of PSD95 and SYN. These findings highlight the significant impact of heat stress on cognitive impairment, and further elucidate the underlying mechanism involving SERCA/PERK/eIF2α pathway.

Effect of structural characteristics on charring shrinkage and cracking of densified wood under radiative heatings

Densified wood (DW) is a novel engineering material with excellent mechanical properties. It forms a thermally insulating and hardly-cracked char layer during pyrolysis and combustion. However, the scientific fundamentals regarding how wood structural characteristics (e.g. density) affect its charring behavior remain unknown, which is important for the fire safety of wood. In this work, the charring shrinkage and cracking of NW and DW with various densities (ρ) under heating exposures (Qr) are investigated and analyzed. Partial crack closure was observed due to the oxidation. As wood ρ increases or Qr decreases, the number of cracks (Nc) decreases and cracking time (tc) is delayed because both the surface temperature (Tsurf) and altered thermal stress concentrations on the wood surface are reduced. DW presents an earlier mass loss peak and lower peak value due to the delignification. DW presents high fluctuations in Tsurf due to the combing effect of thermal inertia and radial rebound. As wood ρ increases, char shrinkage depth at tc decreases and shrinkage gradient at tc increases first and then decreases. An empirical correlation is proposed and well-predicts the Nc based on ρ and Qr. It can be potentially implemented in the combustion model to improve prediction accuracy.