Changes on wood powder morphology and flowability due to thermal pretreatment,

National audienceTorrefaction is a thermal pretreatment of lignocellulosic biomass before gasification. This mild form of pyrolysis, carried out at temperatures between 200 and 300 °C, changes the physical and chemical properties of the material. In particular, it improves the feedstocks homogenisation, enhances the aeration ability and makes the grinding easier. Our project deals with the study of the effects of the combined torrefaction and grinding processes on (i) the major particle behaviour: grindability, surface state, particle size, shape distribution (ii) and the major powder behaviour: bulk density, compressibility, aerability. In this article, the studied parameter is the torrefaction temperature. The characterisation of the particles and powders is performed using the following techniques: optical microscopy, Flodex® methodology and powder rheometry. The rheological behaviours of spruce torrefied at different temperatures then ground in the same apparatus (a knife mill with a sieving grid of 500 µm) are compared. It is shown that spruce torrefied at 240 °C (S240) has similar rheological properties compared to natural spruce (NS) after being ground, while the one torrefied at 300 °C exhibits a different rheological behaviour. The results are correlated to reproduce the coupled effect of the torrefaction and grinding conditions on the powder rheological behaviour

Influence of torrefaction treatment on wood powder properties

International audienceTorrefaction is a thermal pretreatment of lignocellulosic biomass before gazification. This mild form of pyrolysis, carried out at temperatures between 200 and 300 °C, changes the physical and chemical properties of the material. In particular, it improves the feedstocks homogenization, enhances the fluidization ability and makes the grinding easier. Our project deals with the study of the effects of the combined torrefaction and grinding processes on (i) the main particle behavior: anhydrous weight loss (AWL), grindability, particle size distribution (ii) and the main powder behavior: bulk densities, flowability and compressibility. The studied parameters are (i) the species of the biomass (spruce and beech) (ii) the torrefaction temperature (iii) and the sieving grid size of the used knife mill (0.12 and 0.5 mm). The characterization of the particles and powders is performed using the following techniques: optical microscope and powder rheometer. The rheological behaviours of spruce torrefied at different temperatures and ground at different grid sizes are compared. It is shown that spruce torrefied at 240 °C and ground at 0.5 mm (S240/0.5) has rheological properties not as good as S240/0.12 and S300/0.5 that seem to have similar characteristics. Finally, further experiments are necessary to obtain a better morphological and rheological particle characterization

Neuromuscular Consequences of an Extreme Mountain Ultra-Marathon

We investigated the physiological consequences of one of the most extreme exercises realized by humans in race conditions: a 166-km mountain ultra-marathon (MUM) with 9500 m of positive and negative elevation change. For this purpose, (i) the fatigue induced by the MUM and (ii) the recovery processes over two weeks were assessed. Evaluation of neuromuscular function (NMF) and blood markers of muscle damage and inflammation were performed before and immediately following (n = 22), and 2, 5, 9 and 16 days after the MUM (n = 11) in experienced ultra-marathon runners. Large maximal voluntary contraction decreases occurred after MUM (−35% [95% CI: −28 to −42%] and −39% [95% CI: −32 to −46%] for KE and PF, respectively), with alteration of maximal voluntary activation, mainly for KE (−19% [95% CI: −7 to −32%]). Significant modifications in markers of muscle damage and inflammation were observed after the MUM as suggested by the large changes in creatine kinase (from 144±94 to 13,633±12,626 UI L−1), myoglobin (from 32±22 to 1,432±1,209 µg L−1), and C-Reactive Protein (from <2.0 to 37.7±26.5 mg L−1). Moderate to large reductions in maximal compound muscle action potential amplitude, high-frequency doublet force, and low frequency fatigue (index of excitation-contraction coupling alteration) were also observed for both muscle groups. Sixteen days after MUM, NMF had returned to initial values, with most of the recovery process occurring within 9 days of the race. These findings suggest that the large alterations in NMF after an ultra-marathon race are multi-factorial, including failure of excitation-contraction coupling, which has never been described after prolonged running. It is also concluded that as early as two weeks after such an extreme running exercise, maximal force capacities have returned to baseline

Rheological and morphological characterization of torrefied wood biomass

International audienceBiomass flowability is a major issue in the processes dedicated to the thermochemical conversion of biomass based on technologies such as downward-moving bed reactor, dense fluidized bed reactor and entrained flow gasifier. Torrefaction is an example of process influencing powder mechanical property: researchers [1] recently proved torrefaction changes the physical and chemical properties of the material. In particular, it improves the feedstocks homogenization and makes the grinding easier. In the field of this biomass pretreatment for biofuel production, IFP Energies nouvelles and Ecole des Mines de Saint-Etienne study the effects of the combined torrefaction and grinding processes. An experimental protocol then was developed to observe (i) the major particle behavior: anhydrous weight loss (AWL), grindability, particle size and shape, surface state, (ii) and the major powder behavior: bulk density, flowability, compressibility, aerability. One parameter is studied there, the torrefaction temperature. To perform the particles and powders characterization, several techniques were used: optical microscopy, scanning electron microscopy, Flodex® methodology and powder rheometer. Samples of spruce are first torrefied at different temperatures (S240, S300) then ground with a sieving grid of 0.5 mm. From 200 to 300°C, the AWL increases from 1 to 26%. The rheological study of the biomass powders shows that flowability is significantly improved in the only case of a high torrefaction (S300). Compressibility and aerability are also increased with the level of torrefaction temperature. These results are correlated to particles morphological characterization: the powder rheological behavior is only influenced by a characteristic size parameter, such as Sauter mean diameter

Does Central Fatigue Explain Reduced Cycling after Complete Sleep Deprivation?

PURPOSE: Sleep deprivation (SD) is characterized by reduced cognitive capabilities and endurance exercise performance and increased perceived exertion (RPE) during exercise. The combined effects of SD and exercise-induced changes in neuromuscular function and cognition are unknown. This study aimed to determine whether central fatigue is greater with SD, and if so, whether this corresponds to diminished cognitive and physical responses. METHODS: Twelve active males performed two 2-d conditions (SD and control (CO)). On day 1, subjects performed baseline cognitive and neuromuscular testing. After one night of SD or normal sleep, subjects repeated day 1 testing and then performed 40-min submaximal cycling and a cycling test to task failure. Neuromuscular and cognitive functions were evaluated during the cycling protocol and at task failure. RESULTS: After SD, exercise time to task failure was shorter (1137 ± 253 vs 1236 ± 282 s, P = 0.013) and RPE during 40 min submaximal cycling was greater (P = 0.009) than that in CO. Maximal peripheral voluntary activation decreased by 7% (P = 0.003) and cortical voluntary activation tended to decrease by 5% (P = 0.059) with exercise. No other differences in neuromuscular function or cognitive control were observed between conditions. After SD, mean reaction time was 8% longer (P = 0.011) and cognitive response omission rate before cycling was higher (P < 0.05) than that in CO. Acute submaximal exercise counteracted cognitive performance deterioration in SD. CONCLUSIONS: One night of complete SD resulted in decreased time to task failure and cognitive performance and higher RPE compared with the control condition. The lack of difference in neuromuscular function between CO and SD indicates that decreased SD exercise performance was probably not caused by increased muscular or central fatigue

Synthesis and Fluidization of Wood Powders Application to biofuel production

7th World Congress on Particle Technology: New Paradigm of Particle Science and Technology - Procedia Engineering Volume 102 - Editeur: Elsevier Procedia - ISBN: 978-1-5108-0304-6International audienceSynthesizing fuels from biomass sounds a promising path to reduce the overall green house gases emissions and replace the oil-based fuels. Among the main conversion routes, i.e. biological and thermochemical, the latter presents the advantage of being in the continuation of traditional process engineering, thus more inclined to be rapidly industrialized. Here, we investigate two key points of the process consisting in the transformation of solid wood into suitably sized particles, their transport and injection into an entrained flow gasifier and the Fischer-Tropsch conversion of the resulting syngas in liquid fuel. Because of the very large elasticity of ligno-cellulosic materials, the size reduction by grinding requires too much energy to be economically competitive. In order to increase the wood fragility, and thus decrease the energy consumption, the biomass is preliminarily torrefied (i.e. heated up to 300°C under inert atmosphere). In this section, we present new results correlating the required specific energy, the size of the grid holes used in the knife-mill, the torrefaction intensity and the resulting particle size. For two types of wood (beech for hard wood and spruce for softwood), it is evidenced that the grinding energy decreases exponentially when the particle size increases. Both the prefactor and the characteristic length linearly decrease when the torrefaction becomes more severe. The anisotropic microstructure of ligno-cellulosic materials is the cause of the elongated particles morphology. The poor flowability associated with this particle shape makes the pneumatic transport and injection problematic, which is clearly an obstacle to the industrialization of the process. Indeed, to avoid jamming, larger flow rates of inert gas must be used to convey the particles, with an increasing cost of gas separation at later stages. Here, we present new experimental results showing how flowability is modified by the particles size and shape, which in turn depend on the wood species and the torrefaction intensity. Due to its complex nature, the flowability is characterized in three configurations. The jammed-unjammed threshold is evaluated by shear tests performed on a packed bed. The dense quasistatic flowability is evaluated using a powder rheometer that measures the energy required by a rotating blade to circulate through the bed. The fluidization ability is evaluated at two different scales: in the powder rheometer in presence of an upwards air flow and in a standard fluidization column. Results show that the flowability of torrefied wood particles is very poor and very dependent on the wood species (hardwood or softwood). Due to particles interlocking, the bed is highly porous. This is evidenced by the pressure drop which is about 4 times smaller than expected by the Wu & Yen correlation for compact particles of same size. Also, this interlocking is the cause of an apparent cohesivity, which manifests itself by a channeling tendency and a minimum fluidization velocity about 5 to 10 times larger than expected by the Wu & Yen correlation. The significant difference between spruce and beech flowability is attributed to the particles morphology

Down-regulation of Akt/mammalian target of rapamycin signaling pathway in response to myostatin overexpression in skeletal muscle.

International audienceMyostatin, a member of the TGF-beta family, has been identified as a master regulator of embryonic myogenesis and early postnatal skeletal muscle growth. However, cumulative evidence also suggests that alterations in skeletal muscle mass are associated with dysregulation in myostatin expression and that myostatin may contribute to muscle mass loss in adulthood. Two major branches of the Akt pathway are relevant for the regulation of skeletal muscle mass, the Akt/mammalian target of rapamycin (mTOR) pathway, which controls protein synthesis, and the Akt/forkhead box O (FOXO) pathway, which controls protein degradation. Here, we provide further insights into the mechanisms by which myostatin regulates skeletal muscle mass by showing that myostatin negatively regulates Akt/mTOR signaling pathway. Electrotransfer of a myostatin expression vector into the tibialis anterior muscle of Sprague Dawley male rats increased myostatin protein level and decreased skeletal muscle mass 7 d after gene electrotransfer. Using RT-PCR and immunoblot analyses, we showed that myostatin overexpression was ineffective to alter the ubiquitin-proteasome pathway. By contrast, myostatin acted as a negative regulator of Akt/mTOR pathway. This was supported by data showing that the phosphorylation of Akt on Thr308, tuberous sclerosis complex 2 on Thr1462, ribosomal protein S6 on Ser235/236, and 4E-BP1 on Thr37/46 was attenuated 7 d after myostatin gene electrotransfer. The data support the conclusion that Akt/mTOR signaling is a key target that accounts for myostatin function during muscle atrophy, uncovering a novel role for myostatin in protein metabolism and more specifically in the regulation of translation in skeletal muscle