Subsequent Burning Research Articles

Laser-optical technologies for space debris removal

Technologies for the removal of space debris fragments of artificial (man-made) origin from near-Earth space is being proposed in order to provide the security of space flights. The fundamental principle of the proposed method is based on the utilization of intense solar radiation to direct and concentrate at space debris fragments with the aim of creating a plasma braking and transferring the fragment from a circular to an elliptical orbit following its subsequent burn up in the dense layers of the atmosphere. At the same time, the generation of substantial solar radiation is facilitated by a synthesized multi-aperture optical system situated in a heliosynchronous space orbit and permanently oriented towards the Sun.

Fuel Temperature Effects on Combustion Stability of a High-Pressure Liquid-Fueled Swirl Flame

The influence of fuel temperature on combustion instabilities is investigated in a liquid-fueled, piloted swirl flame at 1.0 MPa. Fuels used for this study include Jet A and a Fischer–Tropsch-based synthetic paraffinic fuel (Shell GTL GS190). Simultaneous OH* chemiluminescence, particle image velocimetry, and Mie scattering measurements are performed in an optically accessible combustion chamber at 10 kHz for fuel temperatures ranging from 294 to 525 K. At ambient fuel temperature, a self-excited longitudinal instability is observed at 825 Hz. A higher instability amplitude is observed for Jet A compared to GS190 at all fuel temperatures. Analysis of the chemiluminescence images shows axial flame fluctuations at the instability frequency that are coupled to oscillations in fuel droplet consumption. Lower fuel temperatures lead to unburnt fuel accumulation in low-velocity regions of the flame, and consumption during the acoustic compression wave arrival results in high heat release magnitude that amplifies acoustic perturbations. Spatial correlations of the axial velocity and heat release fluctuation highlight the flame shear layers as predominant regions driving the global dynamics. Increased fuel temperature results in higher droplet evaporation rates in these regions, which promotes more uniform fuel deposition and subsequent burning over the thermoacoustic cycle, attenuating the instability.

Hiding the evidence: Preliminary investigation of heat-induced alterations to pre-existing saw mark trauma

Dismemberment and subsequent burning are common methods employed in an attempt to conceal or destroy evidence. While kerf characteristics can be utilised to identify tool(s) used for dismemberment, further research is necessary to assess the effect of burning on these characteristics. In this study, a back (tenon) saw (13 teeth per inch) was used to manually inflict trauma on Ovis aries de-fleshed femur bones (n = 18). Three different cut marks (shallow false start, incomplete cut and complete transection) were made on the mid-shaft of each bone. Subsequently, the bones were burned for 20 minutes in a muffle furnace. Three burn temperatures were assessed: 400 °C, 600 °C and 800 °C. Saw mark characteristics of each cut type were assessed and compared pre- and post-burning. All pre-existing trauma was recognisable post-burning; however, metric and morphological alterations were apparent. An increase in kerf width was observed at 600 °C in false start lesions and 800 °C in incomplete cuts. Breakaway spur thickness decreased post-burning (at 400 °C and 800 °C) but length was not significantly affected. Mean inter-striation distance decreased post burning at all temperature groups. Saw marks were distinguishable from heat-related fractures across all temperature groups. One false start lesion was obliterated at 800 °C. Exit chipping, pull-out striae as well as striation regularity appeared to be more enhanced after heat exposure. These alterations indicate a temperature-dependent impact on these characteristics. Further research is necessary to assess the role of burn duration.

Binary NiCu oxide nanoparticles onto graphite as promoting nanocatalysts for ethanol electro‐oxidation process

A facile and reduced cost fabrication protocol was followed to have a series of nickel oxide nanospecies onto graphite support with introducing varied copper oxide wt.% values (NiCuO/T). The co‐precipitation of metallic hydroxide particles onto carbonaceous surfaces and their subsequent burning at 400°C were sufficient to prepare mixed transition metal oxides. Suitable analysis tools were exploited to fully characterize the obtained nanopowders using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction spectroscopy, X‐ray photoelectron spectroscopy, and energy dispersive X‐ray analysis. Outstanding performances of the formed nanocatalysts for catalyzing ethanol electro‐oxidation reaction were measured especially in presence of 15 wt.% copper oxide content. The onset potential (Eonset) value of alcohol oxidation process was negatively shifted at dispersed NiO nanoparticles onto graphite after doping with copper oxide nanospecies. This promoted activity of prepared nanomaterials could be explained by their increased active sites when binary metallic oxides were incorporated. Electrochemical impedance spectroscopy studies demonstrated much lowered resistances in alkaline solution containing ethanol molecules to ascertain the enhanced behavior of NiCuO/T nanocatalysts. Moreover, their good stability attitude encouraged the application of doped nanomaterials with copper oxide for fuel cells application.

Microstructure-driven mechanical and electromechanical phenomena in additively manufactured nanocrystalline zinc oxide

Advances in nanoscale additive manufacturing (AM) offer great opportunities to expand nanotechnologies; however, the size effects in these printed remain largely unexplored. Using both in situ nanomechanical and electrical experiments and molecular dynamics (MD) simulations, this study investigates additively manufactured nano-architected nanocrystalline ZnO (nc-ZnO) with ∼7 nm grains and dimensions spanning 0.25–4 μm. These nano-scale ceramics are fabricated through printing and subsequent burning of metal ion-containing hydrogels to produce oxide structures. Electromechanical behavior is shown to result from random ordering in the microstructure and can be modeled through a statistical treatment. A size effect in the failure behavior of AM nc-ZnO is also observed and characterized by the changes in deformation behavior and suppression of brittle failure. MD simulations provide insights to the role of grain boundaries and grain boundary plasticity on both electromechanical behavior and failure mechanisms in nc-ZnO. The frameworks developed in this paper extend to other AM nanocrystalline materials and provide quantification of microstructurally-drive limitations to precision in materials property design.

Estimating personal exposures to household air pollution and plastic garbage burning among adolescent girls in Jalapa, Guatemala

Waste collection services are uncommon in rural areas of low-resource countries, causing waste accumulation and subsequent dumping and burning of garbage. Air pollution from household garbage burning, including plastics, has been observed in Jalapa, Guatemala in addition to household air pollution (HAP) from cooking. Adolescent girls often help with these cooking and household tasks, but little is known about their exposures. We characterized 24-h exposures to HAP and household garbage burning in adolescent girls by measuring fine particulate matter (PM2.5), black carbon (BC), urinary biomarkers of polycyclic aromatic hydrocarbons (PAHs), bisphenol A (BPA), and phthalates. We recruited 60 girls between 13 and 17 years of age who helped with cooking activities and lived with participants of the Household Air Pollution Intervention Network (HAPIN) trial. We recruited n = 30 girls each from the control (wood-burning stove) and intervention (liquefied petroleum gas stove) arms. We also measured real-time kitchen concentrations of BC in 20 homes (33%). PM2.5 and BC were measured in n = 21 control and n = 20 intervention participants. Median concentrations of personal PM2.5 and BC and kitchen BC were lower (p < 0.05) in the intervention arm by 87%, 80%, and 85%, respectively. PAH metabolite concentrations were lower (p < 0.001) for all nine metabolites in intervention (n = 26) compared to control participants (n = 29). Urinary BPA concentrations were 66% higher in participants who reported using cosmetics (p = 0.02), and phthalate concentrations were 63% higher in participants who had reported using hair products during the sample period (p = 0.05). Our results suggest that gas stoves can reduce HAP exposures among adolescents who are not primary cooks at home. Biomarkers of plastic exposure were not associated with intervention status, but some were elevated compared to age- and sex-matched participants of the National Health and Nutrition Examination Survey (NHANES).

Phase change and combustion of iron particles in premixed CH[formula omitted]/O[formula omitted]/N[formula omitted] flames

Metal powder is a promising carbon-free and recyclable energy carrier. Direct combustion of the micron-sized iron particles involves complex physical and chemical processes, such as heat transfer, surface reaction, and phase change. In this work, computational modelling of these processes is investigated and validated against experiments. A single iron particle combustion and phase change model is proposed in an Eulerian–Lagrangian framework. The new phenomenological model considers five stages, i.e., solid phase oxidation, melting of iron oxides and raw iron, liquid phase oxidation, cooling of liquid iron oxides, and solidification of super-cooled liquid iron oxides. The proposed model is first validated and then adopted in simulations of micron-sized iron particle combustion in premixed CH4/O2/N2 flames to study the effects of ambient temperature and oxygen concentration on single iron combustion. Results show that the new model is capable of replicating the melting, heterogeneous surface reaction, cooling, and solidification processes. Two-stage solidification is observed in experiments and modelled in simulations. This two-stage solidification includes a fast solidification with a significant temperature rise (∼150–200 K) and a thermal equilibrium solidification featuring a constant temperature and a slight particle radiant intensity decrease. In addition, a diffusion-controlled mechanism is identified during the melting process, in which the oxygen concentration dominates the melting time and the subsequent burning time. Furthermore, it is found that the reaction between iron and CH4/O2/N2 flame products, such as CO2 and H2O, plays a non-negligible role in the iron combustion process.

Fabrication of Porous Heteroatom‐Doped Carbon Networks via Polymer‐Assisted Rapid Thermal Annealing

AbstractPorous carbon materials have increasingly drawn interest for applications ranging from supercapacitive energy storage to bioengineering. However, a simple and scalable fabrication process of such materials, employing low‐cost chemical compounds without sacrificing morphological and chemical control, remains lacking. Here, a novel, rapid, continuous bottom‐up strategy for synthesizing structurally tunable porous carbon network films on insulating and conductive substrates is reported. By employing rapid thermal annealing (RTA) of a commercial polyacrylonitrile‐based blend, simultaneous phase separation and thermal crosslinking are induced, effectively freezing the structure. Subsequent burning of degradable components generates a porous carbon framework ( ≈ 360 to 700 nm) doped with nitrogen and oxygen atoms. Introducing a boron‐containing reagent in the precursor solution enables boron doping and pore size reduction as small as 20 nm, enhancing materials' performance. The direct fabrication of micro‐supercapacitors on stainless steel substrates is demonstrated, achieving an areal capacitance of 12.7 mF cm−2 at 50 mV s−1, with ≈98% retention after 10 000 charge/discharge cycles. The benefit of boron doping is further highlighted for wound healing applications. Because RTA is already an established industrial method, this platform directly facilitates the synthesis of functional porous heteroatom‐doped carbon structures using commercial polymers and dopants for various applications.

Amphetamine Positivity Prior to Burn Surgery Does not Adversely Affect Intraoperative Outcomes.

The treatment of burn patients using amphetamines is challenging due hemodynamic liabilty and altered physiology. Wide variation exists in the operative timing for this patient population. We hypothesize that burn excision in patients admitted with amphetamine positivity is safe regardless of timing. Data from two verified burn centers between 2017 and 2022 with differing practice patterns in operative timing for amphetamine-positive patients. Center A obtains toxicology only on admission and proceeds with surgery based on hemodynamic status and operative urgency, whereas Center B sends daily toxicology until a negative test results. The primary outcome was the use of vasoactive agents during the index operation, modeled using logistic regression adjusting for burn severity and hospital days to index operation. Secondary outcomes included death and inpatient complications. A total of 270 patients were included, and there were no significant differences in demographics or burn characteristics between centers. Center A screened once and Center B obtained a median of four screens prior to the surgery. The adjusted OR of requiring vasoactive support intraoperatively was not associated with negative toxicology result (P = .821). Having a body surface area burned >20% conferred a significantly higher risk of vasoactive support (adj. OR 13.42 [3.90-46.23], P < .001). Mortality, number of operations, stroke, and hospital length of stay were similar between cohorts. Comparison between two verified burn centers indicates that waiting until a negative amphetamine toxicology result does not impact intraoperative management or subsequent burn outcomes. Serial toxicology tests are unnecessary to guide operative timing of burn patients with amphetamine use.

The Transition of the Caliphate from the Umayyads to the Abbasids and Ṭabarī's Approach to what happened during the Abbasid Revolution

The way Islamic historians handle the change in Islamic history is just as significant as how the caliphate changed hands from the Umayyads to the Abbasids. To demonstrate their knowledge of historiography and whether they are impartial in the face of history in this setting, Islamic historians' approaches or perspectives on this subject are crucial. Our research focuses on how the caliphate was evaluated by Abū Jaʿfar Muḥammad b. Jarīr al-Ṭabarī (d. 310/923), recognized as an authority in Islamic history relating the developments over the transition period from the Umayyads to the Abbasids. Our objective is to identify Ṭabarī's historical perspective, influencing historians who came after him and all Muslims in light of the change in authority. No other study's content has mainly addressed the topic we include in our report. The methodology of our research is to make use of the aforementioned historian's Tārīkh al-rusul wa'l-anbiyāʾ wa'l-mulūk wa'l-khulafāʾ, Akhbār al-rusul wa'l-mulūk, or Tārīkh al-Ṭabarī, which is more commonly used today and translated into Turkish as Tārīkh al-Ṭabarī. The political conflict between the Abbasids and the Umayyads, who were fierce competitors before Islam, resumed during the caliphate of Uthman after the death of the Prophet Muhammad, especially Hazrat Uthman. With the death of Hazrat Ali, the Umayyads seized the caliphate and converted it into a reign. The Abbasids, who claimed that the caliphate had its own rights while accusing the Umayyads of taking the caliphate and engaging in non-religious practices, violently overthrew the Umayyad state in 750 and turned to non-religious practices like beheading prominent members of this family and even setting their graves on fire. It is probable to argue that al-Ṭabarī, who lived during the Abbasid period, did not examine the transition and form of power in question objectively, but rather displayed a pro-Abbasid view. For instance, he does not mention of atrocities like the Abbasids' sword-based massacre of the Umayyads or their removal of some of the corpses and subsequent burning. The fact that the mentioned historian lived around the time of the Abbasids, who were enemies of the Umayyads, and produced his work during this time strongly suggests that he supported an Abbasid stance. Likewise, at this era, as in the case of the -Mihna- example, a historian would be persecuted or even punished by the current political administration if they believed that the Abbasids and the Umayyads were equally right in their political fights or if they praised the Umayyads. As a result, this period, which encompasses the first two centuries of Islamic history and can be referred to as the first period of Islamic history, has been touched upon by taking into account the perspectives of early Islamic historians, and the events that occurred have been analyzed. This indicates that absolute objectivity in historiography is nearly unattainable, because historians, whether directly or indirectly, were influenced by the religious-political structures dominating at the time. It has been found that al-Ṭabarī, an essential early historian, stated events under the influence of the Abbasid state, the dominating force during his day.

ICRH assisted breakdown study on JET

Ion cyclotron (IC) wave assisted breakdown has the potential to increase the robustness of plasma initiation during the ITER pre-fusion operation phase. Studies were performed at JET at ITER relevant loop electric field, , and a range of toroidal fields, including at the low toroidal field of for which breakdown had not been achieved previously on JET. The study covered a range of H2 and D2 gas prefill pressures and timings, pumping conditions, and residual impurity levels. IC assisted breakdown was achieved for a lower and wider range of gas prefill pressures. IC assisted breakdown works by activating wall pumping before the current rise, changing the relation between fuelling and torus pressure in this phase compared to Ohmic breakdown. IC assisted breakdown enables plasma initiation with a higher level and significantly wider range of injected plasma prefill gas. As the injected prefill gas is the controlled parameter, this significantly improves the robustness of plasma initiation operationally. IC assistance is found to be more robust at ITER-like , succeeding with higher low-Z impurity content. Moreover, it does not introduce an impurity source that may hamper the subsequent burn though and current ramp-up phase. For both the IC assisted and pure Ohmic breakdown, the initial current rise rate is found to scale with . The results and implications for ITER are presented.

Analytical model for the temperature field of a plasma heated by fast and monoenergetic ion beams

An analytical model for the determination of the spatial temperature field of a deuterium–tritium plasma heated by a fast and monoenergetic fully stripped ion beam is presented. This analytical model provides relevant hot spot properties in good agreement respect those generated by a numerical model for fast monoenergetic ion beams. The model is useful as it can serve as starting point of detailed numerical radiative-hydrodynamics simulation of the subsequent ignition and burning process of the plasma, avoiding the difficulties of the different spatial and temporal scales involve in the problem. Furthermore, the analytical model provides relationships between the main variables of the hot spots generated that help to a better understanding of the interaction. The results presented in this work were obtained for a beam of fully stripped ions of carbon in a wide range of the beam parameters.

Comparison of bicoherence on the ensemble of realizations and a selective evaluation of the bispectrum of the dynamics of dangerous parameters of the gas medium during fire

The object of the study is the bicoherence of the bispectrum assessment of the dynamics of dangerous parameters of the gas environment during the ignition of materials. The subject is a measure of bicoherence of the bispectrum estimation from the ensemble of realizations and selective bispectrum estimation for the dynamics of hazardous parameters of the gas environment. The practical importance of the research is the use of the measure of bicoherence of the bispectrum for the early detection of fires. The measure of bicoherence of the dynamics of hazardous parameters of the gas environment is substantiated, which allows them to be numerically compared for the studied bispectrum estimates. As such measure, it is proposed to use the integral value of bicoherence for a given frequency interval, which makes it possible to numerically compare the bicoherence of bispectrum estimates for arbitrary time intervals of the dynamics of hazardous parameters of the gas environment. On the basis of the proposed measure for the frequency range of 0.2–2 Hz, a comparison of the integral bicoherence of the bispectrum estimates was made. The numerical value of the measure was determined for three fixed time intervals of the dynamics of hazardous parameters of the environment, corresponding to the absence of ignition, the occurrence of ignition, and the subsequent burning of test materials in the laboratory chamber. According to the results of the comparison of such values, it was established that the bicoherence of the bispectrum estimation from the ensemble of realizations is the most appropriate for detecting fires. When ignited, the numerical value of the measure for all test materials is about 90°. This means that the nature of the dynamics of hazardous environmental parameters in the event of fires becomes random. In this regard, the proposed measure is recommended to be used as a test for early detection of fires.

Flaming Ignition of PMMA, Pine Wood and Pine Needle by External Radiation: Autoignition and Radiant Distance Effect

Flame radiation is one of the important causes of wildland–urban interface (WUI) fires. PMMA, pine needle and pine wood are the most common fuels in WUI fires, but the radiant distance effect on the flaming ignitions as well as the subsequent burning behavior is still poorly understood. This work represents an experiment to investigate the flaming autoignition of PMMA, pine-needle and pine-wood fuel beds with different radiant distances (25 mm–100 mm) under a uniform incident radiant heat flux, 25 kW/m2 The experiment results show that for PMMA and pine wood, they all transition from gas-phase ignition near the cone heater to solid-phase ignition. For pine needle, it has smoldering ignition and smoldering-to-flaming ignition. The relationship between radiant distance and ignition delay time is an approximately inverted u-shape curve, and there exists a critical radiant distance (D = 60 mm) for the minimum ignition delay time. For pine wood and PMMA, when D &lt; 60 mm, there exists a linear relationship between radiant distance, D, and tig−1/2.

Less fuel for the next fire? Short-interval fire delays forest recovery and interacting drivers amplify effects.

As 21st-century climate and disturbance dynamics depart from historic baselines, ecosystem resilience is uncertain. Multiple drivers are changing simultaneously, and interactions among drivers could amplify ecosystem vulnerability to change. Subalpine forests in Greater Yellowstone (Northern Rocky Mountains, USA) were historically resilient to infrequent (100-300 year), severe fire. We sampled paired short-interval (<30-year) and long-interval (>125-year) post-fire plots most recently burned between 1988 and 2018 to address two questions: (1) How do short-interval fire, climate, topography, and distance to unburned live forest edge interact to affect post-fire forest regeneration? (2) How do forest biomass and fuels vary following short-interval versus long-interval severe fires? Mean post-fire live tree stem density was an order of magnitude lower following short-interval versus long-interval fires (3240 vs. 28,741 stems ha-1 , respectively). Differences between paired plots were amplified at longer distances to live forest edge. Surprisingly, warmer-drier climate was associated with higher seedling densities even after short-interval fire, likely relating to regional variation in serotiny of lodgepole pine (Pinus contorta var. latifolia). Unlike conifers, density of aspen (Populus tremuloides), a deciduous resprouter, increased with short-interval versus long-interval fires (mean 384 vs. 62 stems ha-1 , respectively). Live biomass and canopy fuels remained low nearly 30 years after short-interval fire, in contrast with rapid recovery after long-interval fire, suggesting that future burn severity may be reduced for several decades following reburns. Short-interval plots also had half as much dead woody biomass compared with long-interval plots (60 vs. 121 Mg ha-1 ), primarily due to the absence of large snags. Our results suggest differences in tree regeneration following short-interval versus long-interval fires will be especially pronounced where serotiny was high historically. Propagule limitation will also interact with short-interval fires to diminish tree regeneration but lessen subsequent burn severity. Amplifying driver interactions are likely to threaten forest resilience under expected trajectories of a future fire.

&lt;em&gt;In Situ&lt;/em&gt; Gas Analysis and Fire Characterization of Lithium-Ion Cells During Thermal Runaway Using an Environmental Chamber

An experimental apparatus and a standard operating procedure (SOP) are developed to collect time-resolved data on the gas compositions and fire characteristics during and post-thermal runaway of lithium-ion battery (LIB) cells. A 18650 cylindrical cell is conditioned to a desired state-of-charge (SOC; 30%, 50%, 75%, and 100%) before each experiment. The conditioned cell is forced into a thermal runaway by an electrical heating tape at a constant heating rate (10 °C/min) in an environmental chamber (volume: ~600 L). The chamber is connected to a Fourier transform infrared (FTIR) gas analyzer for real-time concentration measurements. Two camcorders are used to record major events, such as cell venting, thermal runaway, and the subsequent burning process. The conditions of the cell, such as surface temperature, mass loss, and voltage, are also recorded. With the data obtained, cell pseudo-properties, venting gas compositions, and venting mass rate can be deduced as functions of cell temperature and cell SOC. While the test procedure is developed for a single cylindrical cell, it can be readily extended to test different cell formats and study fire propagation between multiple cells. The collected experimental data can also be used for the development of numerical models for LIB fires.

Influence of mass ablation on ignition and burn propagation in layered fusion capsules

After decades of research, recent laser-driven inertial fusion experiments have demonstrated rapid progress toward achieving thermonuclear ignition using capsule designs with cryogenic fuel layers. The ignition physics for these layered capsules involves a complex interplay between the dynamically forming hot spot and the dense surrounding fuel. Using analytic theory and numerical simulations, we demonstrate that the mass ablation rate into the hot spot depends sensitively upon the temperature of the dense fuel, resulting in ablative inflows up to 4× faster than previous estimates. This produces an enthalpy flux into the hot spot that plays a critical role in controlling the hot spot temperature, the ignition threshold, and the subsequent burn propagation. The net influence of mass ablation on the ignition threshold is regulated by a dimensionless parameter that depends upon the temperature of the dense fuel. As a consequence, the ignition threshold is sensitive to any mechanism that heats the dense fuel, such as neutrons or radiation emitted from the hot spot. These predictions are confirmed using radiation-hydrodynamic simulations for a series of capsules near ignition conditions. This analysis may have relevance for understanding the variable performance of recent experiments and for guiding new capsule designs toward higher fusion yields.

Coastline in-situ burning of oil spills, analysis of a Greenland field experiment

In-situ burning is a well-proven technology for combatting oil spills offshore. However, as a coastline oil spill response at rocky shores it is novel and investigated here for the first time. The viability and efficiency of coastline in-situ burning of oil spills and the fate of the resulting burn residue was studied through a field experiment. The experiment included a controlled release of 600 L crude oil and subsequent burn of the oil on a remote coast in Greenland. In line with other documented large-scale offshore burns, a high burn efficiency was estimated. Fate studies and chemical analysis of the burn residue diversely caught in the tidal seaweed vegetation showed varying compositions depending on the specific burn intensity. In general, however, a relative increase in high ring numbered PAHs was observed compared to fresh oil. After 4 days, waves and tidal flushing markedly reduced visible oil and burn residue from the burn area. Elevated concentrations of total hydrocarbons were found from the fresh oil in the seawater, but the impacts on the coastal water was below levels of ecotoxic concern. Overall, coastline in-situ burning proved efficient, with a high operational potential. In addition, when the oil is in place at the coast, with a possible increased operational time window compared to an offshore burn. • Coastline in-situ burning proved successful and efficient • Coastline in-situ burning can be as efficient as offshore ISB • Potential improved viability for coastline in situ burning when oil in place at coast • Smothering of organisms in the tidal zone by burn residue • Waves and tidal flushing reduced smothering of coast 4 days after the burn

Tepelné samovznietenie ako najčastejšie sa vyskytujúce fyzikálno-chemické samovznietenie

Self-ignition and self-heating are processes when the heat required for ignition of a substance arises in the substance itself as a result of chemical, physical or biological processes. The term autoignition should be nderstood not only as self-ignition, the ignition of a substance but as a complex, spontaneously occurring process, from the first moment of temperature rise (self-heating temperature) to reaching autoignition temperature, as a result of chemical, physical or biological processes. The result of the self-ignition process is the ignition and subsequent burning of the substance or material in a flameless or flameless manner (smouldering, incandescence). Thermal spontaneous combustion is among the most common cases of physicochemical spontaneous combustion. Thermal autoignition is a thermooxidation process that is anifested by burning (flame or flameless) after previous self-heating of substances that are heated to a temperature at which the released heat of reaction exceeds the amount and speed of heat removed to the environment.

Fire severity and the legacy of mountain pine beetle outbreak: high-severity fire peaks with mixed live and dead vegetation

Bark beetle outbreaks and wildfires are two of the most prevalent disturbances that influence tree mortality, regeneration, and successional trajectories in western North American forests. Subboreal forests have experienced broad overlaps in these disturbances, and recent wildfires have burned through landscapes with substantial tree mortality from prior outbreaks. This study investigated how fuel conditions associated with mountain pine beetle outbreaks influence the probability of high burn severity (i.e. stand-replacing fire) across a range of fire weather conditions in subboreal forests of central interior British Columbia, Canada. We focused on three large fires that occurred in 2012, 2013, and 2014. We characterized outbreak severity, outbreak-influenced prefire vegetation, and subsequent burn severity using Landsat spectral vegetation indices, high-resolution imagery, and field observations. Substantial portions of the prefire landscape contained mixtures of live and dead vegetation created by variable beetle damage and vegetation response—spatial patterns that are related to, but distinct from, peak outbreak severity. We evaluated drivers—fuels, weather, and topography—of high-severity fire under ‘extreme,’ ‘moderate,’ and ‘benign’ fire weather conditions (i.e. burning conditions) using Boosted Regression Trees. While fire weather was a primary driver in most cases, prefire vegetation was an influential predictor variable across all burning conditions, and the probability of high-severity fire was highest when prefire vegetation was a mixture of tree mortality from bark beetles and live vegetation. Thus, while weather and drought are important drivers of wildfires in subboreal forests, bottom-up drivers of elevation and vegetation, including the fuel legacies of bark beetle outbreaks, are crucial factors influencing high-severity burning. The legacy of recent bark beetle outbreaks will continue for decades on these landscapes, affecting fuel structures, future wildfires, forest dynamics, and the broader social-ecological systems of the region.