Wood Sections Research Articles

Interfacial solar steam generator by MWCNTs/carbon black nanoparticles coated wood

In order to further improve the efficiency of radiation steam generation and the stability in practical application, multi-walled carbon nanotubes (MWCNTs)/carbon black nanoparticles were used to coat the delignified wood cross section. The results showed that the multi-walled carbon nanotubes and carbon black nanoparticles are cross-linked and uniformly attached to the cross section of wood, forming a relatively rough coating. Through comparative experiments, the sample device displayed a favorable effect of radiation evaporation, with a 24-hour evaporation efficiency of 51.1%, which was 8.9%, 13.0% and 8.4% higher than that of natural wood device, delignified wood device and natural wood device coated with multi-walled carbon nanotubes-carbon black mixed solution, respectively. On the one hand, it benefited from the high broadband absorption efficiency of multi-walled carbon nanotubes-carbon black coating, which exhibited an absorption efficiency of ∼97.5% and an extremely low transmittance of <2.5% in the visible light and ultraviolet region, and on the other hand, it benefited from the unique surface nanostructure of multi-walled carbon nanotubes-carbon black surface coating, which could effectively capture light.

Modification of Poplar Wood via Polyethylene Glycol Impregnation Coupled with Compression

Wood permeability and compressibility are affected by cell wall structure and chemical composition. These properties can be improved by appropriate wood pretreatments. Low-density poplar wood was converted to a more dense structure by the following steps: First, lignin and hemicellulose were removed using a mixture of NaOH and Na2SO3. Second they were impregnated with polyethylene glycol (PEG, mean molecular weight of 1200), nano-SiO2, and a silane coupling agent at atmospheric temperature and pressure. Finally, impregnated wood was compressed at 150 °C. Results showed that the tracheid lumens on the transverse section of the compressed wood almost vanished. Specifically, the lumens in the wood cells, especially those that were compressed, were almost completely filled with PEG. In FTIR, the asymmetric absorption peaks of Si–O–Si at 1078–1076 cm−1 were clearly observed, which confirms the existence of bonding between nano-SiO2 and wood. The highest melting enthalpy and crystallization enthalpy showed a heat storage capacity of modified wood, which were 20.7 and 9.8 J/g, respectively. Such phase change capabilities may have potential applications in regulating the rate of change of room temperature. In summary, the modified wood could be utilized as material for construction to conserve energy.

Taphonomie et minéralisation de bois carbonatisés du Purbeckien de l'Usine, à Cherves-Richemont (Charente)

Taphonomy and mineralization of carbonated wood from the Purbeckian facies of l'Usine, Cherves-Richemont (Charente). Lower Cretaceous deposits from the Charentes region, in southwestern France, correspond to Purbeckian facies of continental to brackish environments, locally rich in evaporitic formations (Manès 1850; Pouech et al. 2006, 2014, 2015; Schnyder et al. 2012; Vullo et al. 2014; Moreau et al. 2017b). Three fossiliferous localities have been previously identified: the Berriasian gypsum of Champblanc, near Cherves, with both teeth accumulations and bone beds of fishes, crocodiles and dinosaurs, but relatively poor in fossil wood (Buffetaut et al. 1989; Le Loeuff et al. 1996; Schnyder 2003; Colin et al. 2004; El Albani et al. 2004; Mazin et al. 2006; Rees et al. 2013); the Berriasian marls and calcareous conglomerate of Angeac-Charente, particularly rich in dinosaur megaremains and lignitic accumulations (Néraudeau et al. 2012; Allain et al. 2014; Benoît et al. 2017; Polette et al. 2018; Polette 2019); the Purbeckian to Wealden clay and conglomerate of the Rochefort area, providing large bones of dinosaurs in surface blocks, but never observed in stratigraphical position (Vullo et al. 2012). Another fossiliferous Purbeckian locality from the Charentes region, the Chassiron coast of Oleron Island, is rich in vertebrate and plant remains, but mainly Tithonian in age (Vullo et al. 2014; Moreau et al. 2017b). This paper presents a fourth Charentese Purbeckian locality with the first case of calcite mineralized wood known in Mesozoic deposits from France. The Purbeckian facies is located at Cherves-Richemont, in Charente (SW France), at 3 km east of the Champblanc gypsum quarry, in the L'Usine locality (Figs 1; 2). The stratigraphical position of the marls and the conglomerate with calcite mineralized wood is at mid-distance from the lower to mid-Berriasian gypsum series of the Champblanc quarry, to the east, and the unconformity with the lower Cenomanian sands that erode the Purbeckian series, to the west (Fig. 3) (Coquand 1858, 1862; Platel 1980; Bourgueil et al. 1986). Consequently, the fossil wood locality of L'Usine is a probable lateral equivalent of the uppermost Berriasian bone and wood beds of Angeac-Charente, located at about 25 km only (Gônet et al. 2018; Polette et al. 2018; Rozada 2019). There is no real outcrop at L'Usine, and the limestones with fossil wood can be mainly observed on surface blocks in fields and vineyards. Two outstanding facies, rich in calcite mineralized wood, can be observed. First, the surface of the fields shows abundant relic blocks of a calcareous conglomerate, rich in tubular, fibrous and carbonated incrusting of plant axes, associated to fragments of fusain. The conglomerate contains reptile bone pebbles and Lepidotes Agassiz, 1832 fish scales too. At a depth of 40 cm, an excavation has shown marls containing large pieces of calcite mineralized wood (about 1 m), incrusted by fibrous carbonated spherules (Figs 2; 4). The geochemical analyses of the marls and the fossil wood by X-ray diffraction, realized according to the method of Moore & Reynolds (1997), confirm the mineralization by carbonate only. Dolomite and silica are very scarce and gypsum is lacking (Fig. 5). Polished sections (Fig. 2) and thin sections (Figs 6; 7) of calcite mineralized wood show processes of centripetal mineralization (Higgins 1960; Buurman 1972; Marynowski et al. 2007; Mustoe 2018; Mustoe & Beard 2021). The microscopic observations reveal a fine mineralization at the cell scale, mainly hyperblastic or polyblastic (sometimes oligoblastic, likely of microbial origin. Cell lights are filled by sparry calcite. Some “tuff structures” of wood mineralization are characteristic of certain tuff of filamentous cyanobacteries (e.g. Rivularia C.Agardh ex Bornet & Flahault, 1886, ou Shizothrix Kützing ex Gomont, 1892) common in the geological record (Freytet & Plaziat 1965; Freytet & Plet 1991; Caudwell et al. 1997; Freytet & Verrecchia 1998; Freytet 2000; Pentecost 2003; Hägele et al. 2006; Sanders et al. 2006; Arenas & Jones 2007). A zonation of the mineralization can often been observed on thin sections of wood but corresponds more likely to successive mineralization steps by cyanobacterial mats than to steps of wood growth. The observations of wood fragments with Scanning Electron Microscopy allow to identify a tracheidoxyl (Creber 1972) with araucarioid structures of the genus Agathoxylon Hartig, 1848, a common Mesozoic fossil gymnosperm wood, abundant in the Charentese region of SW France (Fig. 8) (Néraudeau et al. 2002, 2003; Philippe et al. 2008, 2010, 2018; Philippe 2011; Vullo et al. 2014). The pitting is mainly uniseriate, when the punctuation is mainly biseriate for Agathoxylon gardoniense Crié, typical of the mid-Cretaceous deposits of Charentes. Consequently, the Agathoxylon from L'Usine could belong to another palaeoecological morph of A. gardoniense, possibly to another species. The deposit environment that has gathered gymnosperm trunks and branches, eroded reptile bones (e.g. sauropods) and freshwater to brackish fish remains (e.g. Lepidotes) is interpreted as continental to coastal, in freshwater or brackish conditions.

Identification of Guiboutia species by NIR-HSI spectroscopy

Near infrared hyperspectral imaging (NIR-HSI) spectroscopy can be a rapid, precise, low-cost and non-destructive way for wood identification. In this study, samples of five Guiboutia species were analyzed by means of NIR-HSI. Partial least squares discriminant analysis (PLS-DA) and support vector machine (SVM) were used after different data treatment in order to improve the performance of models. Transverse, radial, and tangential section were analyzed separately to select the best sample section for wood identification. The results obtained demonstrated that NIR-HSI combined with successive projections algorithm (SPA) and SVM can achieve high prediction accuracy and low computing cost. Pre-processing methods of SNV and Normalize can increase the prediction accuracy slightly, however, high modelling accuracy can still be achieved by raw pre-processing. Both models for the classification of G. conjugate, G. ehie and G. demeusei perform nearly 100% accuracy. Prediction for G. coleosperma and G. tessmannii were more difficult when using PLS-DA model. It is evidently clear from the findings that the transverse section of wood is more suitable for wood identification. NIR-HSI spectroscopy technique has great potential for Guiboutia species analysis.

Modeling the tensile mechanical properties of silver birch timber boards

In this paper, the variability of tensile mechanical properties of silver birch timber is investigated and models for the prediction of tension strength and stiffness are developed. Through visual inspections and non-destructive tests, various strength and stiffness related indicators are identified. Destructive tension tests are subsequently performed for the determination of strength and stiffness. On each timber board, strains are measured at four localized regions, whereby, the stiffness of knot sections and clear wood sections are determined. Variability in strength, stiffness, density, knots, grain angle, and annual ring width are investigated along with the relationships between them. A hierarchical model is developed for the prediction of timber board stiffness and the reduction of stiffness due to knots. Models for the prediction of timber board strength and knot cluster strength are developed according to equality and inequality information of the failed specimens, by means of censored regression analysis. Results indicate suitable global and local predictions for silver birch timber, given the dynamic modulus of elasticity, median slope of grain, and knot geometries.

Study on infection behavior and characteristics of poplar wood dyed by Lasiodiplodia theobromae.

The technology of dyeing wood by microorganisms is a kind of pollution-free and sustainable wood dyeing technology. To achieve fast and rich dyeing of Lasiodiplodia theobromae on the surface of poplar wood, tyrosinase and tricyclazole were used as induction factors in this experiment. The results showed that L. theobromae had a better induction effect in the cross-section of poplar wood and induced with tricyclazole. The surface color of poplar ranged from light yellow dyeing to gray and brown, the chromatic aberration of the cross-section of wood was above 44.5 NBS, and the infected area was over 50%, while the dyed parts of radial and tangential sections of wood were only on the surface of the wood after 30 days of infection. The induced infection of L. theobromae on poplar wood had little effect on the chemical components of poplar and had good colorfastness to washing and light. Therefore, microbial dyeing of wood showed a beneficial application prospect in the field of wood dyeing.

Tropical wet and dry forest tree species exhibit contrasting hydraulic architecture

Forest tree species in wet and dry habitats are generally considered functionally divergent in leaf and stem functional traits such as leaf area, leaf mass per area, wood density and tree height. Yet, these traits have limited utility for characterizing plant water transport adaptations and strategies. We tested the hypothesis that wet and dry forest trees are functionally divergent in their water conducting apparatus. To assess trait differences and adaptations, we sampled branch wood from nine same-genus species-pairs, each species-pair occurring respectively in the wet (>1500 mm annual rainfall) and dry forest (<800 mm annual rainfall) in tropical Queensland, Australia. From branch wood sections, we measured anatomical traits involved in water conduction (stem vessel dimensions, fractions and their spatial distributions, theoretical water conductivities), storage (parenchyma), and providing hydraulic safety functions (fibres fractions, vulnerability index). Relative to wet forest species, we found on overall that dry forest trees had trait combinations showing adaptations to aridity such as more storage tissue and greater vessel connectivity which may provide alternative pathways for water transport should vessel embolism occur. Habitat is an environmental filter that influences trait behaviour across related species. However, depending on the genera, species in both dry and wet forest habitats also exhibit various tradeoffs in trait values, highlighting the existence of diverse hydraulic strategies within wet forest and dry forest trees.

Noninvasive Sonic Tomography for Detecting Internal Defects in Old, Large Oriental White Oak in Cultural Heritage Areas

Incidence rates of tree damage are increasing because of the increased intensity and frequency of abnormal climate events such as strong winds and heavy rains. Structural defects inside trees are difficult to detect by visual inspection; therefore, it is difficult to respond to them in advance based on prediction. Noninvasive sonic tomography (SoT) is a method that estimates internal defects while minimizing physical damage to trees; however, its accuracy differs depending on the species. Therefore, in this study, we aimed to compare the performance of noninvasive SoT and invasive resistance micro-drilling (RM) in detecting tree damage in oriental white oak (Quercus aliena Blume) distributed in East Asia and performed wood section analysis to verify the accuracy of noninvasive SoT. Linear regression analysis showed that defects in tomograms tended to increase with an increase in the number of defects in the RM profile, but the value of R2 was 0.405, which is lower than that of other tree species. The results from the wood section analysis and SoT were compared; the SoT tomograms appropriately reflected the location and size of the defects with a tendency to overestimate the defects when cracks were present, while the electric resistance tomography was effective for detecting incipient decay.

Assembly of wood-inhabiting archaeal, bacterial and fungal communities along a salinity gradient: common taxa are broadly distributed but locally abundant in preferred habitats.

Wood decomposition in water is a key ecosystem process driven by diverse microbial taxa that likely differ in their affinities for freshwater, estuarine and marine habitats. How these decomposer communities assemble in situ or potentially colonize from other habitats remains poorly understood. At three watersheds on Coiba Island, Panama, we placed replicate sections of branch wood of a single tree species on land, and in freshwater, estuarine and marine habitats that constitute a downstream salinity gradient. We sequenced archaea, bacteria and fungi from wood samples collected after 3, 9 and 15 months to examine microbial community composition, and to examine habitat specificity and abundance patterns. We found that these microbial communities were broadly structured by similar factors, with a strong effect of salinity, but little effect of watershed identity on compositional variation. Moreover, common aquatic taxa were also present in wood incubated on land. Our results suggest that either taxa dispersed to both terrestrial and aquatic habitats, or microbes with broad habitat ranges were initially present in the wood as endophytes. Nonetheless, these habitat generalists varied greatly in abundance across habitats suggesting an important role for habitat filtering in maintaining distinct aquatic communities in freshwater, estuarine and marine habitats.

An effective and fast solution for classification of wood species: A deep transfer learning approach

Classification and recognition of wood species have critical importance in wood trade, industry, and science. Therefore, accurate identification of wood species is a great necessity. Conventional classification and recognition of wood species require knowledge and experience on the anatomy of wood which is time-consuming, cost-ineffective, and destructive. Hence, convolutional neural networks (CNNs) -a deep learning tool- have replaced the conventional methods. In this study, classification of wood species via the WOOD-AUTH dataset and evaluating the performance of various deep learning architectures including ResNet-50, Inception V3, Xception, and VGG19 in classification with transfer learning was investigated in detail. The dataset contains macroscopic images of 12 wood species with three different types of wood sections: cross, radial and tangential. The experimental findings demonstrate that Xception produced a remarkable performance as compared to the other models in this study and the WOOD-AUTH dataset owners, yielding a classification accuracy of 95.88%.

Comparison of VIS/NIR spectral curves plus RGB images with hyperspectral images for the identification of Pterocarpus species

Abstract The image information and spectral information of wood sections can be used to identify wood species. Hyperspectral images have both image information and spectral information, but they have disadvantages such as large data capacity, slow reading speed, and the necessity of expensive equipment for their acquisition. In this study, the classification results of Pterocarpus by using visible/near infrared (VIS/NIR) spectral information and RGB images were compared with hyperspectral images. The VIS/NIR spectral curves, Hyperspectral, and RGB images of five wood species of Pterocarpus with similar transverse-sections were collected. In feature-level fusion, the feature vectors are directly connected in series, and features fused by canonical correlation analysis are compared. In decision-level fusion, an extreme learning machine and a composite-kernel support vector machine (SVM) are used and compared. In the feature- and decision-level fusion methods, the recognition results of VIS/NIR spectral curves plus RGB images were largely similar to those of hyperspectral images. Therefore, a recognition effect similar to that of the hyperspectral image can be obtained by collecting the spectral information and image information of wood sections separately, which can reduce the cost of data acquisition and improve the speed of data processing.

Effectiveness of European oak wood staining with iron (II) sulphate during natural weathering

Artificial graying of wood can be solution for contemporary trends of using uncoated wood for the arrangement of external architecture. The presented work was aimed at investigation of colour changes of European oak (Quercus sp.) wood surface treated with iron (II) sulphate. Three different procedures differing in time (2 h and 24 h) and temperature (20 °C and 70 °C) were used, as well as three different concentrations of aqueous iron (II) sulphate solutions (10 %, 20 %, 30 %). Beside the colour itself, it was evaluated the stained oak wood discolouration due to natural weathering. Thanks to iron (II) sulphate, wood colour changed to dark grey. In general, the colour changes on tangential section of wood were higher than those on radial section what was result of wood structure, in particular parenchyma cells arrangement in wooden rays. Contrary to expectations, the concentration of the iron (II) sulphate solution was not of significant importance for wood staining. Usage of concentrations higher than 10 % for the modification of the colour of wood gives the same effects. However, with increasing solution used to wood staining, the colour stability of the wood decreases during external exposure. The parameters of the procedure were not significantly affected. This allows the application of the simplest and least time-consuming modification method to be considered.

KETAHANAN ALAMI KAYU HIBRID AKASIA (Acacia mangium × A. auriculiformis) TERHADAP SERANGAN RAYAP KAYU KERING (Cryptotermes cynocephalus Light.)

Development of Acacia hybrid is important to be done due to their superiority such as high productivity, good wood quality, more tolerance to pest/disease and adaptive to marginal sites, although its wood durability to wood-destroyer organism attacks is still unknown yet. This study aimed to observe the wood natural durability of Acacia hybrid to drywood termites (Cryptotermes cynocephalus Light.) attack. The wood samples used were taken from 6 years old trees of Acacia hybrid in Wonogiri, Central Java. The experimental design used is completely randomized design using two factors, axial and radial of wood section with the number of trees as replication.Parameters measured were extractive content, termite mortality and wood mass loss.The results showed that the axial section of wood significantly affected the wood extractive content at the level of 0.01, while termite mortality and the mass loss of wood were not significantly affected by the wood section. The largest average percentages of termite mortality and mass loss of wood found on the middle of wood section (96.67%) and near the bark (1.14%) respectively. Based on this result, the Acacia hybrid wood is categorized as very durable wood and potential to be developed as raw material for solid wood-based industries

Potential of the fumigant ethanedinitrile to kill the pinewood nematode (Bursaphelenchus xylophilus) and other forest pathogens

AbstractA screening test was carried out using ethanedinitrile (EDN) as a candidate fumigant to replace methyl bromide for efficacy against a selection of forest pests, including the pinewood nematodes (Bursaphelenchus xylophilus) and four tree pathogens: Heterobasidion annosum, Geosmithia morbida, Phytophthora ramorum and Ceratocystis fagacearum. Two EDN concentrations were tested: 50 and 100 g/m3 at two different temperatures and six exposure times. In our tests, EDN was very efficient in killing pathogens in all test parameter combinations, including short exposure times and lower concentration, apart from C. fagacearum surviving short 1 h exposure and G. morbida surviving after 1 and 3 h of exposure. Pinewood nematodes in the small wood blocks were effectively killed at all test parameter combinations. In log sections where deeper nematode infestations were present, nematode survivors at 50 and 100 g/m3 after 1, 3, and 6 h exposure were observed. This suggests that the fumigant was not efficacious at lower exposure times, while penetrating log sections. Both 50 and 100 g/m3 dosages were effective after 24 h exposure, indicating that longer retention times are required to effectively kill pine wood nematodes in deeper wood sections. The lower temperature did not affect the efficacy of EDN. This indicates that EDN could successfully eradicate pinewood nematodes in logs over 24 h of exposure, or even less exposure time, at targeted concentrations.

Silverleaf (Chondrostereum purpureum) Effects on Japanese Plum (Prunus salicina).

Silverleaf is an important fungal trunk disease of fruit crops, such as Japanese plum (Prunus salicina). It is known that infection by Chondrostereum purpureum results in discolored wood, “silvered” foliage, and tree decline. However, effects on fruit yield and quality have not been assessed. Therefore, the objectives of this study were to determine C. purpureum pathogenicity on P. salicina and the effects on physiology, fruit yield, and quality, in Chile, in 2019 and 2020. Wood samples from affected plum trees were collected in the Chilean plum productive area. Fungi were isolated by plating wood sections from the necrosis margin on culture media. Morphological and molecular characteristics of the isolates corresponded to C. purpureum (98%). Representative isolates were inoculated from healthy plum plants and after 65-d incubation, wood necrotic lesions and silver leaves were visible. Fungi were reisolated, fulfilling Koch’s postulates. To determine Silverleaf effects, xylem water potential and fruit yield and quality were measured in healthy and Silverleaf-diseased plum trees ‘Angeleno’. Water potential was altered in diseased trees, and fruit yield was reduced by 51% (2019) and by 41% (2020) compared to fruit from healthy trees. Moreover, cover-colour, equatorial-diameter, and weight were reduced, and fruit were softer, failing to meet the criteria to be properly commercialized and exported to demanding markets.

Exploring wood anatomy, density and chemistry profiles to understand the tree-ring formation in Amazonian tree species

Long-term analysis of tree growth using annual tree rings is increasingly in demand for tropical tree species. The basis of these studies has traditionally been the anatomical identification of the annual ring boundary. However, the structure of these annual rings has been sparsely explored for complementary physical and chemical wood traits. Here, we explore the relationships among wood density features and chemical elements (S, K, Ca, Mn) involved in the annual tree ring formation of 12 tropical tree species from non-flooded forest in the southern Amazon basin. Transverse wood sections were used for each species to determine: 1) macroscopic distinction (radial growth and wood density), 2) microscopic analyse of vessels, axial and ray parenchyma (anatomy) and 3) X-ray densitometry (physical) and X-ray fluorescence (chemical). For some species, the profiles of wood density, and Ca and Mn content showed intra- and inter-annual patterns that allowed to define and characterize the growth boundary of tree rings. Ca, K and S were mainly distributed in axial parenchyma cells, and around vessels, whereas, Mn was mainly distributed in fibres. Our results showed significant species-specific correlations between tree-ring width, density and concentrations of Ca, K and Mn. The anatomical characterization and the complementary information provided by the density and chemical profiles in some Amazonian species can represent a valuable proxy to improve the definition of annual ring-boundaries and improve the understanding of long-term growth and physiological patterns.

Hierarchically porous biochar derived from orthometric integration of wooden and bacterial celluloses for high-performance electromagnetic wave absorption

Inspired by the natural growth of wooden cellulose (WC) and bacterial cellulose (BC), we integrated the two categories of cellulosic materials by static fermentation. BC networks created in plane are intimately integrated with the wooden chip (cross section of wood, CW) and are perpendicular to the orientation of the cellular channels along the growth of the trees. The as-prepared BC/CW composites were converted into the interconnected carbon monoliths with hierarchically porous structure (CBC/CCW) by a one-step carbonization. The complementarity of WC and BC in spatial orientation created more mixed meso/macropores. Upon EMW irradiation, the wood-derived carbonaceous cellular wall attenuates EM energy by multiple reflection, while CBC networks further dissipate EMW by conduction loss. Additionally, the abundant voids inside of the wooden channels are beneficial to impedance matching. As a result, the as-fabricated three-dimensional CBC/CCW composites infiltrated with polydimethylsiloxane delivered strong EMW absorption performance with minimum reflection loss of −57.97 dB, broad absorption bandwidth of 6.28 GHz, and ultralow filler loading of 3.5%. Moreover, the elastomer CBC/CCW can still maintain 90% EMW absorption capability even after 500 bending-releasing cycles. The ingenious integration of wooden and bacterial celluloses provides a new sight for designing high-performance EMW absorbers with low-cost and sustainable resources.

Probabilistic Modelling of Bending Strength of Timber Beams with the Help of Weak Zones Model

The variability of longitudinal bending strength of timber beams due to the presence of knots and other defects is analyzed. The weak zones model of timber beam bending strength used in the analysis consists of short weak zones (knots or group of them) and strong sections of clear wood. The load bearing capacity of timber beams is defined as an extreme (minimum) value problem or as a first downcrossing problem. Assuming a marked Poisson random field with zero correlation between all random variables, cumulative probability distribution functions of the load carrying capacity of timber beams were determined by analytical methods for typical load cases: pure bending, midspan point load and one-third point load. These results, as well as the marked Poisson random field as a model of longitudinal variability of the bending strength of timber beams, can be applied in the reliability analysis of timber structures. Furthermore, the analytical formulae for the cumulative distribution functions of load carrying capacity of timber beams can provide a good reference for numerical analysis conducted with Monte Carlo simulation to determined statistics for specific timber members.

An absolute radiocarbon chronology for the world heritage site of Sarvestan (SW Iran): A late Sasanian heritage in early Islamic era

AbstractThis study presents a new precise radiocarbon chronology for the World Heritage site of Sarvestan (SW Iran). The monument is a key construction in the history of architecture because it is a typical Sasanian construction built during the late Sasanian or early Islamic period. Previous attempts to date the monument have suggested the ages ranging from the middle Sasanian (fifth century CE) to early Abbasid (ninth century CE) era. These age estimations are based on the analysis of architectural plans and techniques, and a few radiocarbon dates with very large age uncertainties. This paper presents the results of a systematic radiocarbon dating of timbers in the walls and charcoals in plaster mortars used in the main dome of the monument. It further applies wiggle matching technique and R_Combine function to substantially reduce the age uncertainties in wood sections. The results indicate that a major construction work was undertaken sometime between 658 and 683 CE, the century of the invasion of Fars by Muslim Arabs. This finding pushes back the age of Sarvestan for two centuries and suggests that the monument was built at the transitional period between Sasanian to Islamic era. Sarvestan would have been an architectural project designed and possibly initiated during the late Sasanian period but mainly accomplished during the second half of the seventh century CE. It can thus be considered a late Sasanian heritage in early Islamic period. Its construction at a time of political unrest further suggests that some areas of Fars may have benefited from certain socio‐political stabilities during the expansion of Islam into the east at mid‐ to late seventh century CE.

Effect of oxygen on the burning rate of wood

The large-scale adoption of wood as a construction material for tall buildings could pave the way for sustainable construction. Its adoption, however, is hindered by a limited understanding of wood's behaviour in a fire. In particular, the effect of oxygen and heat flux on the burning (including pyrolysis) and ignition behaviour of wood is poorly understood. We addressed this gap by studying the effect of oxygen concentration and heat flux on the burning and ignition behaviour of particleboard experimentally and computationally. Particleboard was chosen as a proxy for all woody construction materials. We conducted over 60 experiments in an FPA on samples of particleboard spanning different oxygen concentrations (0–21%), heat fluxes (10–70 kW/m2), sample densities (600–800 kg/m2), and sample thicknesses (6–25 mm). Only the heat flux and oxygen concentration significantly affected the charring rate, time-to-flaming ignition, and burning mode (pyrolysis, smouldering, flaming). To explore this effect further, we used a multi-physics model of particleboard charring developed in Gpyro. Combining the computational and experimental results, we showed that particleboard undergoes only pyrolysis in oxygen concentrations below 4%, smouldering between 4 and 15%, and flaming above 15% at a heat flux of 30 kW/m2. These oxygen concentration thresholds were found to decrease as the heat flux increases. We also showed that smouldering and flaming increases the charring rate by 25 and 37%, respectively. This means that the rate of loss of a section of structural wood, quantified by the charring rate, in a fire due to smouldering is similar to that of flaming combustion. In addition, we noted the existence of a triple point for the ignition of wood at which a slight change in environmental conditions can lead to either smouldering, flaming, or only pyrolysis. In summary, this paper quantified for the first time the contributions of the three modes of burning to the charring rate of wood and highlights the importance of smouldering for timber construction.