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Abstract Background Solid-state fermentation is a fungal culture technique used to produce compounds and products of industrial interest. The growth behaviour of filamentous fungi on solid media is challenging to study due to the intermixity of the substrate and the growing organism. Several strategies are available to measure indirectly the fungal biomass during the fermentation such as following the biochemical production of mycelium-specific components or microscopic observation. The microscopic observation of the development of the mycelium, on lignocellulosic substrate, has not been reported. In this study, we set up an experimental protocol based on microscopy and image processing through which we investigated the growth pattern of Phanerochaete chrysosporium on different Miscanthus x giganteus biomass fractions. Results Object coalescence, the occupied surface area, and radial expansion of the colony were measured in time. The substrate was sterilized by autoclaving, which could be considered a type of pre-treatment. The fastest growth rate was measured on the unfractionated biomass, followed by the soluble fraction of the biomass, then the residual solid fractions. The growth rate on the different fractions of the substrate was additive, suggesting that both the solid and soluble fractions were used by the fungus. Based on the FTIR analysis, there were differences in composition between the solid and soluble fractions of the substrate, but the main components for growth were always present. We propose using this novel method for measuring the very initial fungal growth by following the variation of the number of objects over time. Once growth is established, the growth can be followed by measurement of the occupied surface by the mycelium. Conclusion Our data showed that the growth was affected from the very beginning by the nature of the substrate. The most extensive colonization of the surface was observed with the unfractionated substrate containing both soluble and solid components. The methodology was practical and may be applied to investigate the growth of other fungi, including the influence of environmental parameters on the fungal growth.

Abstract Background The yeast Saccharomyces cerevisiae, commonly used in industry, exhibits complex metabolism due to the Crabtree effect, fermenting alcohol even under aerobic conditions when glucose exceeds 0.10-0.15 g/L. The heat released by the biological activity is a signal very easy to collect, given the minimal instrumentation requirements. However, this heat depends on the activated metabolic pathways and provides only an indirect indicator, that cannot be used in a simple way. This study demonstrated the potential of a mechanistic model to control the process by measuring the heat released by the biological activity. Results The complexity arising from coexisting metabolic pathways was addressed by a comprehensive model of Saccharomyces cerevisiae together with the heat of reaction included in a rigorous enthalpy balance of the bioreactor. Batch cultures were performed in an insulated bioreactor to trigger a temperature signal. The heat of individual metabolic pathways was determined by inverse analysis of these tests using Particle Swarm Optimization (PSO): -101.28 ±0.02kJ/mol for anaerobic fermentation, -231.27±0.06kJ/mol for aerobic fermentation, and -662.94 ± 0.54kJ/mol for ethanol respiration. Finally, the model was successfully applied and validated for online training under different operating conditions. Conclusions The model demonstrates remarkable accuracy, with a mean relative error under 0.38% in temperature predictions for both anaerobic and aerobic conditions. The viscous dissipation is a key parameter specific to the bioreactor and the growth conditions. However, we demonstrated that this parameter could be fitted accurately from the early stages of the experiment for further prediction of the remaining part. This model introduces temperature, or the thermal power required to maintain temperature, as a measurable parameter for online feedback model training to provide increasingly precise feed-forward control. Graphical Abstract

Abstract To enhance PLA gas barrier properties, multilayer designs with highly polar barrier layers, such as nanocelluloses, have shown promising results. However, the properties of these polar layers change with humidity. As a result, we investigated water transport phenomena in PLA films coated with nanometric layers of chitosan and nanocelluloses, utilizing a combination of techniques including dynamic vapor sorption (DVS) and long-term water vapor adsorption–diffusion experiments (back-face measurements) to understand the influence of each layer on the behavior of multilayer films. Surprisingly, nanometric coatings impacted PLA water vapor transport. Chitosan/nanocelluloses layers, representing less than 1 wt.% of the multilayer film, increased the water vapor uptake of the film by 14.6%. The nanometric chitosan coating appeared to have localized effects on PLA structure. Moreover, nanocelluloses coatings displayed varying impacts on sample properties depending on their interactions (hydrogen, ionic bonds) with chitosan. The negatively charged CNF TEMPO coating formed a dense network that demonstrated higher resistance to water sorption and diffusion compared to CNF and CNC coatings. This work also highlights the limitations of conventional water vapor permeability measurements, especially when dealing with materials containing ultrathin nanocelluloses layers. It shows the necessity of considering the synergistic effects between layers to accurately evaluate the transport properties.

Abstract The interest by biofilm-based microalgae technologies has increased lately due to productivity improvement, energy consumption reduction and easy harvesting. However, the effect of light, one key factor for system’s operation, received less attention than for planktonic cultures. This work assessed the impact of Photon Flux Density (PFD) on Chlorella vulgaris biofilm dynamics (structure, physiology, activity). Microalgae biofilms were cultivated in a flow-cell system with PFD from 100 to 500 $${\upmu {\textrm{mol}} \, \textrm{m}^{-2} \, \textrm{s}^{-1}}$$ μ mol m - 2 s - 1 . In the first stage of biofilm development, uniform cell distribution was observed on the substratum exposed to 100 $${\upmu \textrm{mol} \, \textrm{m}^{-2} \, \textrm{s}^{-1}}$$ μ mol m - 2 s - 1 while cell clusters were formed under 500 $${\upmu \textrm{mol} \, \textrm{m}^{-2} \, \textrm{s}^{-1}}$$ μ mol m - 2 s - 1 . Though similar specific growth rate in exponential phase (ca. 0.3 $${\textrm{d}^{-1}}$$ d - 1 ) was obtained under all light intensities, biofilm cells at 500 $${\upmu \textrm{mol} \, \textrm{m}^{-2} \, \textrm{s}^{-1}}$$ μ mol m - 2 s - 1 seem to be ultimately photoinhibited (lower final cell density). Data confirm that Chlorella vulgaris showed a remarkable capability to cope with high light. This was marked for sessile cells at 300 $${\upmu \textrm{mol} \, \textrm{m}^{-2} \, \textrm{s}^{-1}}$$ μ mol m - 2 s - 1 , which reduce very rapidly (in 2 days) their chlorophyll-a content, most probably to reduce photodamage, while maintaining a high final cell density. Besides cellular physiological adjustments, our data demonstrate that cellular spatial organization is light-dependent.

This paper reviews the key building blocks needed to develop a mechanistic model for use as an operational production tool. The Chinese Hamster Ovary (CHO) cell, one of the most widely used hosts for antibody production in the pharmaceutical industry, is considered as a case study. CHO cell metabolism is characterized by two main phases, exponential growth followed by a stationary phase with strong protein production. This process presents an appropriate degree of complexity to outline the modeling strategy. The paper is organized into four main steps: (1) CHO systems and data collection; (2) metabolic analysis; (3) formulation of the mathematical model; and finally, (4) numerical solution, calibration, and validation. The overall approach can build a predictive model of target variables. According to the literature, one of the main current modeling challenges lies in understanding and predicting the spontaneous metabolic shift. Possible candidates for the trigger of the metabolic shift include the concentration of lactate and carbon dioxide. In our opinion, ammonium, which is also an inhibiting product, should be further investigated. Finally, the expected progress in the emerging field of hybrid modeling, which combines the best of mechanistic modeling and machine learning, is presented as a fascinating breakthrough. Note that the modeling strategy discussed here is a general framework that can be applied to any bioprocess.

The microfluidic production of simple (microspheres) and core–shell (microcapsules) polymer microparticles, often called microencapsulation, has been the scope of several research works since the 1980s. It is a fast, thrifty, and efficient process because of its controlled properties, tuneability, and yield, which can reach 100%. However, the question of its greenness, sustainability, and scalability remains unclear, and more awareness/education is required in this field. The sustainability of production processes using microfluidic techniques can be realized/discussed based on three pillars: (i) waste generation, (ii) the solvents employed, and (iii) raw materials. On the other hand, although the scaling-up of these processes was reported on in several papers as procedures in which hundreds or thousands of microfluidic chips are set in parallel, the sustainability of this scale-up has not been addressed to our knowledge. This opinion paper highlights the advantages of microfluidic encapsulation processes, their greenness according to the above-mentioned pillars, (i–iii) and the necessary considerations to scale them up while preserving their sustainability.

This paper presents tests related to the reactivity of commercial Hi-Fuel sorbent toward H2S (H2S/N2 mixture) in a packed bed at 300 °C. The sorbent used for breakthrough test was characterized before and after test by ESEM-EDX, FTIR-ATR, Raman, and elemental analyses. Testing reveals that the commercial sorbent contains two compounds reacting with H2S: ZnO and ZnCO3. According to thermodynamical studies, the reactivity of ZnCO3 at 300 °C is privileged (KR = 9.5 × 108) than ZnO (KR = 6.6× 106). In addition, the reaction of H2S with ZnCO3 induces a volume decrease, which promotes the movement of gas through the newly formed layer. The properties of this sorbent thus hold a good potential for the desulfurization process of gases polluted with H2S. We observed that the maximum sulfidation rate was reached on the surface of the sorbent and showed a maximum conversion of 27%.

IntroductionBiofilm-based microalgae production technologies offer enormous potential for improving sustainability and productivity. However, the light pattern induced by these technologies is a key concern for optimization.MethodsIn this work, the effects of light/dark cycles on architecture, growth, and physiology of Chlorella vulgaris biofilms were assessed in a millifluidic flow-cell with different time cycles (15 s to 3 min) keeping the average light constant at 100 μmol·m−2·s−1.Results and discussionResults showed that photoinhibition can be mitigated by applying a light fraction of 1/3 and a cycle time of 15 s. By contrast, when the cycle time is extended to 90 s and 3 min, photoinhibition is high and photoefficiency dramatically decreases. To cope with light stress, cells acclimate and organize themselves differently in space. A high peak light (500 μmol·m−2·s−1) triggers a stress, reducing cell division and inducing clusters in the biofilm. This work provides guidelines for optimizing rotating microalgae production systems in biofilms and assesses the minimum rotating frequency required to maintain the net growth rate close to that of continuous light of the same average intensity, mitigating photo-inhibition. The overall gain in productivity is then provided by the total surface of the biofilm turning in the illuminated surface area.

Abstract Imbibition of water and silicone oil in poplar and spruce is investigated at the anatomical level by X-ray tomography observations and at the macroscopic level by imbibition kinetics. Imbibition mechanisms depend on both liquid and species. In poplar, oil penetrates vessels with a small contact angle, consistent with the value measured on solid wood (ca. $$20^{\circ }$$ 20 ∘ ). Surprisingly, no direct penetration of water was observed in vessels. The large contact angle for water blocks the capillary rise at the scars between vessel cells. In spruce, oil and water penetrate primarily in latewood, where bordered pits remain open. Subsequently, water slowly invades the rest of the growth ring, while transversal migration is quasi-absent for oil. These 3D observations were quantified to feed a simple imbibition model that satisfactorily simulates macroscopic imbibition kinetics. A 1D approach is sufficient for oil imbibition while a 2D approach is required for water, revealing dual scale effects.

Objective To examine sex differences in prevalence, volume and distribution of vascular brain lesions on MRI among patients with atrial fibrillation (AF).Methods In this cross-sectional analysis, we included 1743 patients with AF (27% women) from the multicentre Swiss Atrial Fibrillation study (SWISS-AF) with available baseline brain MRI. We compared presence and total volume of large non-cortical or cortical infarcts (LNCCIs), small non-cortical infarcts, microbleeds (MB) and white matter hyperintensities (WMH, Fazekas score ≥2 for moderate or severe degree) between men and women with multivariable logistic regression. We generated voxel-based probability maps to assess the anatomical distribution of lesions.Results We found no strong evidence for an association of female sex with the prevalence of all ischaemic infarcts (LNCCI and SNCI combined; adjusted OR 0.86, 95% CI 0.67 to 1.09, p=0.22), MB (adjusted OR 0.91, 95% CI 0.68 to 1.21, p=0.52) and moderate or severe WMH (adjusted OR 1.15, 95% CI 0.90 to 1.48, p=0.27). However, total WMH volume was 17% larger among women than men (multivariable adjusted multiplicative effect 1.17, 95% CI 1.01 to 1.35; p=0.04). Lesion probability maps showed a right hemispheric preponderance of ischaemic infarcts in both men and women, while WMH were distributed symmetrically.Conclusion Women had higher white matter disease burden than men, while volume and prevalence of other lesions did not differ. Our findings highlight the importance of controlling risk factors for cerebral small vessel disease in patients with AF, especially among women.

Abstract The chemical changes sustained by lignocellulosic biomass during hydrothermal treatment are reflected at multiple scales. This study proposes to benefit from this multiscale nature in order to provide a global understanding of biomass alterations during hydrothermal treatment. For this purpose, complementary imaging techniques—confocal Raman microscopy and X-ray nano-tomography—analysed by image processing and coupled to chemical measurements were used. This unique combination of analyses provided valuable information on topochemical and morphological changes of poplar samples, without the artefacts of sample preparation. At the cell wall level, holocellulose hydrolysis and lignin modifications were observed, which corresponded to anatomical modifications observed at higher scales. Overall, after treatment, samples shrank and had thinner cell walls. When subjected to more severe pre-treatments, cells were disrupted and detached from adjacent cells. Anatomical changes were then used to obtain quantitative indicators of the treatment severity. The effects of treatment at different scales can thus be quantitatively connected in both directions, from micro to macro and from macro to micro.

Antioxidant foods represent a potent lever to improve diets while creating value. Yet, their cultivation is often tied to a specific area and climate, limiting availability and increasing market cost. Therefore, microorganism-based antioxidant production emerges as a promising technology to solve these problems. In this view, a novel process was investigated for antioxidant accumulation in yeast culture. S. cerevisiae cells were exposed to various hyperbaric air conditions from 1 to 9 bar (A). Yeast cultures exhibited an increased reactive oxygen species content, which induced oxidative defense expression. After a few hours, reactive oxygen species levels decreased while antioxidant contents remained high, leading to a net increase in antioxidant power. At 6 bar (A), yeast achieved the highest net antioxidant power (phenolics content +48.3 ± 18.6 %, reducing power +120 ± 11.4 %) with an acceptable growth rate (0.27 h−1). Regarding time evolution, a 2 h exposure seems to be the optimum: cells have the lowest reactive oxygen species level while their antioxidant power is increased. From a biotechnological perspective, this finding highlights air pressure as an antioxidant-manipulating stress strategy. Moreover, the proposed process led to a patent that could potentially reduce energy and chemical consumption in such antioxidant accumulation processes.

Sinapine is a phenolic compound found in mustard (Brassica juncea) seed meal. It has numerous beneficial properties such as antitumor, neuroprotective, antioxidant, and hepatoprotective effects, making its extraction relevant. In this study, the extraction of sinapine was investigated using three methods: (i) from a mustard seed meal defatted by a supercritical CO2 (SC-CO2) pretreatment, (ii) by the implementation of high-voltage electrical discharges (HVEDs), (iii) and by the use of ultrasound. The use of SC-CO2 pretreatment resulted in a dual effect on the valorization of mustard seed meal, acting as a green solvent for oil recovery and increasing the yield of extracted sinapine by 24.4% compared to the control. The combination of ultrasound and SC-CO2 pretreatment further increased the yield of sinapine by 32%. The optimal conditions for ultrasound-assisted extraction, determined through a response surface methodology, are a temperature of 75 °C, 70% ethanol, and 100% ultrasound amplitude, resulting in a sinapine yield of 6.90 ± 0.03 mg/g dry matter. In contrast, the application of HVEDs in the extraction process was not optimized, as it led to the degradation of sinapine even at low-energy inputs.

This paper proposes a general approach for building a mechanistic yeast model able to predict the shift of metabolic pathways. The mechanistic model accounts for the coexistence of several metabolic pathways (aerobic fermentation, glucose respiration, anaerobic fermentation and ethanol respiration) whose activation depends on growth conditions. This general approach is applied to a commercial strain of Saccharomyces cerevisiae. Stoichiometry and yeast kinetics were mostly determined from aerobic and completely anaerobic experiments. Known parameters were taken from the literature, and the remaining parameters were estimated by inverse analysis using the particle swarm optimization method. The optimized set of parameters allows the concentrations to be accurately determined over time, reporting global mean relative errors for all variables of less than 7 and 11% under completely anaerobic and aerobic conditions, respectively. Different affinities of yeast for glucose and ethanol tolerance under aerobic and anaerobic conditions were obtained. Finally, the model was successfully validated by simulating a different experiment, a batch fermentation process without gas injection, with an overall mean relative error of 7%. This model represents a useful tool for the control and optimization of yeast fermentation systems. More generally, the modeling framework proposed here is intended to be used as a building block of a digital twin of any bioproduction process.

This work reports the design of a light concentrator intended to be used to cast uniform lighting over a photobioreactor. Household aluminum foils was chosen as reflective material to build the concentrator. This choice raised the question of which side to use. Thus measurements of household aluminum foil reflectivity spectra on both bright and matte sides were undergone. These measurements were done using an integrating sphere, over a 250–2500 nm range. Diffuse and total reflectivities were acquired, for two samples each time. The obtained results are very repeatable and in good agreement with literature on rolled aluminum sheets, for the bright side at least, as matte side data were not found. Specular reflectivity is higher for the bright side while diffuse reflectivity is higher for the matte one. Furthermore, both sides of the foil have the same total reflectivity, around 86 % in the visible range of the spectrum, 97% in the near infrared. Our measurements are readability usable and available as supplementary materials. Finally, we applied these findings to the in silico design of lab scale light concentrator illuminating a new photobioreactor. A modified version of the raytracing software Soltrace was used to determine which of the two sides of our household aluminum foil was be best suited for our application. Keywords: Aluminum foil, Reflectivity, Specular, Diffuse, Light concentrator, Photobioreactor

Recently, membrane contactors have gained more popularity in the field of CO2 removal; however, achieving high purity and competitive recovery for poor soluble gas (H2, N2, or CH4) remains elusive. Hence, a novel process for CO2 removal from a mixture of gases using hollow fiber membrane contactors is investigated theoretically and experimentally. A theoretical model is constructed to show that the dissolved residual CO2 hinders the capacity of the absorbent when it is regenerated. This model, backed up by experimental investigation, proves that achieving a purity > 99% without consuming excessive chemicals or energy remains challenging in a closed-loop system. As a solution, a novel strategy is proposed: the pH Swing Absorption which consists of manipulating the acido–basic equilibrium of CO2 in the absorption and desorption stages by injecting moderate acid and base amount. It aims at decreasing CO2 residual content in the regenerated absorbent, by converting CO2 into its ionic counterparts (HCO3− or CO32−) before absorption and improving CO2 degassing before desorption. Therefore, this strategy unlocks the theoretical limitation due to equilibrium with CO2 residual content in the absorbent and increases considerably the maximum achievable purity. Results also show the dependency of the performance on operating conditions such as total gas pressure and liquid flowrate. For N2/CO2 mixture, this process achieved a nitrogen purity of 99.97% with a N2 recovery rate of 94.13%. Similarly, for H2/CO2 mixture, a maximum H2 purity of 99.96% and recovery rate of 93.96% was obtained using this process. Moreover, the proposed patented process could potentially reduce energy or chemicals consumption.

[This corrects the article DOI: 10.1371/journal.pone.0162469.].

This study investigated chemical decomposition of lignocellulosic components in the course of torrefaction under isothermal conditions for durations up to 5 hours. The goal was a better understanding of the behaviour of biomass, at both short and long residence times, which is important for innovation in the chemical and bioenergy industries. Gaseous and solid-phase decomposition products of cellulose, xylan, and two lignins, were studied following torrefaction at three temperatures (220, 250, and 280 °C) for a continuous recording of mass loss and emission of volatiles over 5 hours. Two decomposition stages were revealed for xylan, with a notable release of CO that increased with treatment temperature. 4-O-methyl glucurono-units on the side chains of xylan degraded first, and acetyl groups and macromolecule fragments accounted for the second degradation, starting at 250 °C. The primary production of acetic acid occurred at 280 °C. For the two lignins, decomposition reactions predominated at lower temperatures, while rearrangement prevailed at 280 °C. The emission of phenol was a clear distinction between the two. Cellulose was thermally stable at short times under all treatments, but it decomposed dramatically afterwards, especially at 280 °C.

This study provides the sorption isotherm, its hysteresis and their mass transfer properties of four Central Africa Tropical woods widely used for building construction: frake (Terminalia Superba), lotofa (Sterculia Rhinopetala), sapele (Entandrophragma Cylindricum) and ayous (Triplochiton Scleroxylon). Characterization of these four species in particular and Central Africa tropical woods in general were necessary to develop conservation and treatment of wood after first transformation using the drying. Also, moisture transport on wooden material used such as wall buildings can be facilitating to found the thermal comfort. Measurements of isotherms were performed using a dynamic vapor sorption apparatus (Surface Measurement Systems) at 20 and 40°C with air relative humidity ranged from 0% to 90%. Mass diffusivity was determined in steady state using a specific vaporimeter. Air permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability and mass transfer properties were determined in the tangential direction with a ‘’false’’ quartersawn board (sapele and lotofa) and in the radial direction with a flatsawn board (ayous and frake). Samples of sapele, ayous and frake are heartwood when lotofa contains as well as heartwood than sapwood. Results obtained showed that the temperature effect on sorption behavior was quite low. We observed also a low difference between the sorption behavior of these different species and hysteresis of sorption decreases when temperature increases. Hailwood-Horrobin model’s explains plausibly the experimental sorption isotherms data. Results on characterization of mass transfer properties showed that, in the steady state, mass diffusivity decreases exponentially when basal density increases. Mass diffusivity was higher in desorption than in adsorption phase. The gaseous permeability of these species was between than those of Australian hardwoods and temperate woods. It was difficult to define a relationship between permeability and mass diffusivity.

Continuous observation was performed using confocal laser scanning microscopy to visualize the three-dimensional microscopic growth of the brown-rot fungus, Postia placenta, for seventeen days. The morphological characterization of Postia placenta was quantitatively determined, including the tip extension rate, branch angle and branching length, (hyphal length between two adjacent branch sites). A voxel method has been developed to measure the growth of the biomass. Additionally, the tip extension rate distribution, the branch angle distribution and the branching length distribution, which quantified the hyphal growth characteristics, were evaluated. Statistical analysis revealed that the extension rate of tips was randomly distributed in space. The branch angle distribution did not change with the development of the colony, however, the branching length distribution did vary with the development of the colony. The experimental data will be incorporated into a lattice-based model simulating the growth of Postia placenta.

During torrefaction of biomass, equivalence between temperature and residence time is often reported, either in terms of the loss of mass or the alternation of properties. The present work proposes a rigorous investigation of this equivalence. Cellulose, as the main lignocellulosic biomass component, was treated under mild pyrolysis for 48 hours. Several couples of T-D (temperature-duration) points were selected from TGA curves to obtain mass losses of 11.6%, 25%, 50%, 74.4%, and 86.7%. The corresponding residues were subjected to Fourier transform infrared spectroscopy for analysis. According to the FTIR results, a suitably accurate match to global T-D equivalence is exhibited up to 50% mass loss: in this domain, mass loss is well correlated to the treatment intensity (molecular composition of the residue) except for slight differences in the production of C=C and C=O. For mass loss levels of 74.4% and 86.7%, distinct degradation mechanisms take place at different combinations of temperature and duration, and the correlation fails. Compared to the mass loss at 220°C and 250°C, the equivalent molecular composition can be achieved through treatment at 280°C with shorter treatment time and less depolymerization and oxidation. The main conclusion drawn is that mass loss can be used as a synthetic indicator of the treatment intensity in the temperature range of 220°C to 280°C up to a mass loss of 50%.

Characterization of mass transfer properties was achieved in the longitudinal, radial, and tangential directions for four Australian hardwood species: spotted gum, blackbutt, jarrah, and messmate. Measurement of mass transfer properties for these species was necessary to complement current vacuum drying modeling research. Water-vapour diffusivity was determined in steady state using a specific vapometer. Permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability values of some species and material directions were extremely low and undetectable by the mass flow meter device. Hence, a custom system based on volume evolution was conceived to determine very low, previously unpublished, wood permeability values. Mass diffusivity and permeability were lowest for spotted gum and highest for messmate. Except for messmate in the radial direction, the four species measured were less permeable in all directions than the lowest published figures, demonstrating the high impermeability of Australian hardwoods and partly accounting for their relatively slow drying rates. Permeability, water-vapour diffusivity, and associated anisotropic ratio data obtained for messmate were extreme or did not follow typical trends and is consequently the most difficult of the four woods to dry in terms of collapse and checking degradation.

This study investigated the influence of heat treatment on the chemical composition and energy properties of maritime pine (Pinus pinaster) and pedunculate oak (Quercus robur). Samples were treated in a new experimental device at 220, 250, or 280 °C for 1 or 5 hours. Chemical and energy analyses were performed using standard methods. Our results clearly demonstrated an increased degradation of the material due to the combined effects of temperature and treatment duration. This mass loss was basically due to degradation of acid-soluble materials. The energy analysis showed that the fixed carbon content and higher heating value increased, for both species, whereas the volatile matter content decreased with increased extent of treatment (cumulated effects of temperature and time). In the range of temperature and duration studied here, the dimensionless energy properties for both species obeyed the same functions of overall mass loss. The relationships obtained allow quantification of the increase in wood energy concentration due to torrefaction. Mass loss is an excellent indicator of treatment extent. Analytical expressions allowing the prediction of energy and chemical properties as a function of overall mass loss, within the range of treatment extents studied here, are provided.

The acuity of reasoning on Raven’s Progressive Matrices is strongly influenced by strategic determinants. Building on metamemory studies that highlight the influence of study-time allocation on memory development, we investigated children’s allocation of study time while solving these matrices. A total of 170 children aged 6–12 years completed a computerized short-form version of the standard matrices featuring items selected to represent a broad range of difficulties. Beyond analyzing changes in mean latencies and performances with age, we used generalized additive mixed models to explore within-participant variability in response times as a function of both item complexity and overall individual efficiency. Results revealed that individual differences in performances were significantly associated with children’s adaptive modulation of response times. Mediation analysis further indicated that response-time modulation contributed to age-related changes in performance. Taking account of study-time allocation in reasoning tasks may open up new avenues for the study of reasoning development and the assessment of intellectual functioning.

During drying, stresses and deformations develop in a wood board due to shrinkage fields which result from moisture content and temperature field variations. In spite of numerous works done in wood drying modelling in the last decades, wood drying optimisation based on modelling and simulation remains far from initial expectations. Two main reasons can explain this assessment: the huge variability of wood and the variations in drying conditions throughout the board stack in a dryer. To address these two key problems, we used a dual scale numerical tool able to compute simultaneously the stress and deformation of hundreds of boards in the stack during drying. A rigorous one-dimensional mechanical formulation, based on previous works, has been used for calculating stress and deformation during drying. The mechanical model is fitted into a module and then added to a dual scale (board-stack) model. This numerical tool has been used to improve the drying schedules recommended by the Technical Centre for Wood and Furniture in France (CTBA) for spruce. The proposed drying schedules allow the board quality to be improved. Note that the optimisation was limited to medium temperature values, so that the proposed schedule can be applied to conventional kilns

This work presents an original experimental device conceived to characterise the viscoelastic properties of wood. Classically, the dynamic mechanical analysis of wood is performed using a commercial apparatus like a DMA (Dynamic Mechanical Analyser). However, when analysing wood with this type of apparatus, many problems related to the hygroscopic behaviour and the orthotropic structure of wood may be encountered. This is why an original apparatus perfectly adapted to the wood features has been developed. The WAVE T is able to measure the viscoelastic properties of wood samples under water-saturated conditions, in the temperature range of 5°C to 95°C at frequencies varying between 0.005 Hz and 10 Hz. Samples are tested in a cantilever configuration. The whole experiment has been designed to withstand the severe conditions of temperature and humidity. At the same time, an analytical model based on Kelvin’s elements has been developed. This model is able to correct experimental measurements performed close to the resonance frequency. Results obtained for beech samples in radial and tangential directions using the WAVE T and a commercial apparatus (DMA 2980 TA Instruments) are compared and discussed. This comparison underlines the relevance of the WAVE T device

A mesoscopic drying model that enables the drying simulation of quartersawn and flatsawn wood sections consisting of several growth rings is presented. The procedure to generate the virtual board description directly from real sample images is also described. This virtual structure accommodates the prominent sample features, including its geometrical and physical properties, together with the density and structural variation across the growth rings. We give a synopsis of the sophisticated techniques developed specifically to generate this virtual description and exhibit the final computational meshes produced by the software for quartersawn and flatsawn sections. Low temperature drying simulations are then performed for both heterogenous and homogeneous model variants using these virtual descriptions and comparisons are made of the resulting MC field evolution. A highlight of these comparisons is that the heterogeneous model captures realistic drying effects, including the fast drying of earlywood and the late removal of liquid water in latewood. In comparing the drying of quartersawn and flatsawn boards we conclude that the effect of the heterogeneous nature of the MC fields is diminished somewhat when considering the flatsawn section over the quartersawn section.

El objetivo de este artículo es mostrar la posibilidad de utilizar fuentes policromáticas de rayos X en experimentos relacionados con la madera en que normalmente se requiere de fuentes monocromáticas. Se presentan diferentes aplicaciones de espectrometría de rayos X en base a fuentes policromáticas conformadas por tubos sin dispositivos de monocromatización, pero usando detectores espectrométricos de alta resolución energética. En primer lugar se describe una aplicación de transmisión o atenuación de rayos X destinada a obtener la variación espacio-temporal del contenido de humedad al interior de una tabla en proceso de secado a 70°C y 50°C en bulbo seco y bulbo húmedo respectivamente. Esta aplicación permitió realizar una cartografía digital del interior de la tabla y se reveló útil para caracterizar el proceso de evacuación de la humedad desde el interior de la madera. Luego se presenta un equipamiento innovador diseñado y fabricado por los autores para registrar la intensidad de dispersión coherente de rayos X. Los resultados demuestran la posibilidad de acceder al contenido de humedad y el ángulo microfibrilar, cuantificando las señales espectrales registradas tanto para el agua como para el plano cristalino (002) de la celulosa. La existencia de una señal de fondo originada por la fase amorfa de la madera impidió realizar estimaciones cuantitativas de contenido de humedad cuando la densidad anhidra de la madera es desconocidaWe investigated the possibilities to use polychromatic X-rays sources to study wood properties that usually require of monochromatic radiation. Three applications using X-ray tubes without monochromator together with high-resolution energy-sensitive X-rays detectors are presented. In a first experiment, a standard X-ray source and a spectrometric detector were placed on both sides of a wood dryer which operates at 70°C and 50°C for dry-bulb and wet-bulb respectively. Digital cartography obtained can offer the possibility to identify some phenomenological parameters of fluid migration in wood. In a second part, an innovative device designed and made by the authors to record X-ray scatter intensities is presented. The feasibility to use the ratio of diffraction to attenuation for moisture content determination is discussed. This device has been also used for microfibril angle determination by recording and analyzing the X-ray scattered intensities of cellulose (002) lattice. The microfibril angle determination was successful; however, a background of X-rays scattering from amorphous component of wood prevented the determination of moisture content

The aim of this study is to visualise, measure and understand the pathway of liquid and gas at both macroscopic and microscopic levels on specimens of beech (Fagus silvatica and Fagus orientalis). The permeability to air and to water has been measured using devices developed in our laboratory. The extension of the area coloured by dyed water is available as well. At the microscopic level, the permeability has been calculated using Poiseuille's equation from the vessel diameters determined on cross sections by image processing. Using dyed water, the proportion of active vessels is also reported at different distances from the injection surface. Our data confirm that the permeability decreases significantly when the sample distance increases. Moreover, the value extrapolated for a zero-length sample is similar to the value predicted from the vessel diameters. This observation stands for both for sapwood and heartwood, in spite of the great permeability difference noticed between these zones. At the microscopic level, the percentage of active vessels decreases with the increase of sample total length and the increase of the distance from the injection point. Several simulations performed using a bond percolation model confirmed our experimental results obtained at the macroscopic and microscopic levels

The IUFRO 5.04.06 Wood Drying Conference was organised by the "Transilvania" University of Brasov - Faculty of Wood Industry and hosted by the Aro Palace Complex in Brasov (Romania). Over 100 scientists from 28 countries attended the meeting. Two Keynote Addresses: " The Role of Wood Anatomy in the Drying of Wood: "Great Oaks from Little Acorns Grow " by the Wood Drying Working Party Leader, Patrick PerrC (France) and " High-Frequency Heating Combined With Vacuum Drying Of Wood by Helmut Resch (Austria) was an excellent start of the technical program of over 80 oral presentations and 28 poster presentations. The topics of the 10 oral presentation sessions and the poster session covered modelling, stress and strain behaviour of wood, properties ofwood related to drying, fast drying procedures, applied drying, heat and mass transfer, kiln control, drying quality, colorations and general.

El objetivo de este artículo es mostrar la posibilidad de utilizar fuentes policromáticas de rayos X en experimentos relacionados con la madera en que normalmente se requiere de fuentes monocromáticas. Se presentan diferentes aplicaciones de espectrometría de rayos X en base a fuentes policromáticas conformadas por tubos sin dispositivos de monocromatización, pero usando detectores espectrométricos de alta resolución energética. En primer lugar se describe una aplicación de transmisión o atenuación de rayos X destinada a obtener la variación espacio-temporal del contenido de humedad al interior de una tabla en proceso de secado a 70ºC y 50ºC en bulbo seco y bulbo húmedo respectivamente. Esta aplicación permitió realizar una cartografía digital del interior de la tabla y se reveló útil para caracterizar el proceso de evacuación de la humedad desde el interior de la madera. Luego se presenta un equipamiento innovador diseñado y fabricado por los autores para registrar la intensidad de dispersión coherente de rayos X. Los resultados demuestran la posibilidad de acceder al contenido de humedad y el ángulo microfibrilar, cuantificando las señales espectrales registradas tanto para el agua como para el plano cristalino (002) de la celulosa. La existencia de una señal de fondo originada por la fase amorfa de la madera impidió realizar estimaciones cuantitativas de contenido de humedad cuando la densidad anhidra de la madera es desconocida. Abstract We investigated the possibilities to use polychromatic X-rays sources to study wood properties that usually require of monochromatic radiation. Three applications using X-ray tubes without monochromator together with high-resolution energy-sensitive X-rays detectors are presented. In a first experiment, a standard X-ray source and a spectrometric detector were placed on both sides of a wood dryer which operates at 70ºC and 50ºC for dry-bulb and wet-bulb respectively. Digital cartography obtained can offer the possibility to identify some phenomenological parameters of fluid migration in wood. In a second part, an innovative device designed and made by the authors to record X-ray scatter intensities is presented. The feasibility to use the ratio of diffraction to attenuation for moisture content determination is discussed. This device has been also used for microfibril angle determination by recording and analyzing the X-ray scattered intensities of cellulose (002) lattice. The microfibril angle determination was successful; however, a background of X-rays scattering from amorphous component of wood prevented the determination of moisture content.

This work presents an original experimental device conceived to characterise the viscoelastic properties of wood. Classically, the dynamic mechanical analysis of wood is performed using a commercial apparatus like a DMA (Dynamic Mechanical Analyser). However, when analysing wood with this type of apparatus, many problems related to the hygroscopic behaviour and the orthotropic structure of wood may be encountered. This is why an original apparatus perfectly adapted to the wood features has been developed. The WAVET is able to measure the viscoelastic properties of wood samples under water-saturated conditions, in the temperature range of 5°C to 95°C at frequencies varying between 0.005 Hz and 10 Hz. Samples are tested in a cantilever configuration. The whole experiment has been designed to withstand the severe conditions of temperature and humidity. At the same time, an analytical model based on Kelvin’s elements has been developed. This model is able to correct experimental measurements performed close to the resonance frequency. Results obtained for beech samples in radial and tangential directions using the WAVET and a commercial apparatus (DMA 2980 TA Instruments) are compared and discussed. This comparison underlines the relevance of the WAVET device.

During drying, stresses and deformations develop in a wood board due to shrinkage fields which result from moisture content and temperature field variations. In spite of numerous works done in wood drying modelling in the last decades, wood drying optimisation based on modelling and simulation remains far from initial expectations. Two main reasons can explain this assessment: the huge variability of wood and the variations in drying conditions throughout the board stack in a dryer. To address these two key problems, we used a dual scale numerical tool able to compute simultaneously the stress and deformation of hundreds of boards in the stack during drying. A rigorous one-dimensional mechanical formulation, based on previous works, has been used for calculating stress and deformation during drying. The mechanical model is fitted into a module and then added to a dual scale (boardstack) model. This numerical tool has been used to improve the drying schedules recommended by the Technical Centre for Wood and Furniture in France (CTBA) for spruce. The proposed drying schedules allow the board quality to be improved. Note that the optimisation was limited to medium temperature values, so that the proposed schedule can be applied to conventional kilns.

A mesoscopic drying model that enables the drying simulation of quartersawn and flatsawn wood sections consisting of several growth rings is presented. The procedure to generate the virtual board description directly from real sample images is also described. This virtual structure accommodates the prominent sample features, including its geometrical and physical properties, together with the density and structural variation across the growth rings. We give a synopsis of the sophisticated techniques developed specifically to generate this virtual description and exhibit the final computational meshes produced by the software for quartersawn and flatsawn sections. Low temperature drying simulations are then performed for both heterogenous and homogeneous model variants using these virtual descriptions and comparisons are made of the resulting MC field evolution. A highlight of these comparisons is that the heterogeneous model captures realistic drying effects, including the fast drying of earlywood and the late removal of liquid water in latewood. In comparing the drying of quartersawn and flatsawn boards we conclude that the effect of the heterogeneous nature of the MC fields is diminished somewhat when considering the flatsawn section over the quartersawn section.

In this work, the effects of moisture content variations produced by oscillating drying conditions have been studied by means of non-symmetrical drying (flying wood) and loaded drying (3-point bending test). The oscillating conditions are intended to produce a mechano-sorptive creep that is able to reduce drying stresses. However, our experimental data seem to prove that the activation of the mechano-sorptive creep by oscillations of the moisture content is very limited. Besides, the simulations showed that noisy conditions due to the kiln regulation already activate the mechano-sorptive creep, even for non-oscillating conditions, and could confuse the results. Contrary to the experimental observations, the implementation of classical mechano-sorptive models in the drying simulation model is far too optimistic, which means that these models are not suitable when the material is submitted to numerous oscillations.