2,084 research outputs found
Advanced modelling for design helping of heterogeneous CLT panels in bending
International audienceCross Laminated Timber (CLT) panels are more and more common in timber construction. When submitted to out-of-plane loads, their main structural issue is the low transverse shear strength of cross layers which leads to rolling shear failure [1, 2]. The absence of specific standards yields to CLT panels having lateral boards glued each other or not, depending on the producer. The resulting discontinuities in the non-gluing case influence the global mechanical response [3]. In addition, the timber construction market requires new technical solutions for CLT. Periodic voids within the panel lead to lighter and more thermally efficient floors. However this geometry increases the panelâs heterogeneity and the difficulties in predicting the actual bending behaviour, especially the shear effects.In the first part of this work we focused our attention to a CLT layer having weak heterogeneities, namely the gaps between boards. These heterogeneities are taken into account by means of a (fictitious) equivalent and homogeneous CLT layer which mechanical properties are defined with respect to the boardâs reference frame. Such an equivalent layer is combined with the exact 3D solution for laminated plates in bending [4] and a failure criterion for wood [5]. The predicted behaviour is in good agreement with a reference experimental test [6] in terms of global stiffness and variation of failure modes within the apparent elastic regime. The validated model is therefore used to investigate the influence of varying some panelâs properties on the bending response.Innovative CLT panels having periodic voids (filled by an isolating material) are already in production. An experimental campaign proved how this lay-up increases their shear weakness. The ratio wood/void can approximate the reduced elastic properties of these strongly heterogeneous panels. This approach has been already used [2] with design method for CLT in bending [7] and can be simply implemented in the Equivalent â Layer model. As a starting point we aim to compare the experimental behaviour with the predicted one using reduced mechanical properties by the ratio wood/void. These properties are combined with the model developed for weak heterogeneities and design methods for CLT in bending [7, 8].Nevertheless, such a simplified approach canât reproduce the complexity of stressesâ and strainsâ distribution, especially transverse shear ones. Therefore a more accurate model is currently in development. This solution can precisely predict the influence of high heterogeneities by means of a periodic homogenization scheme. Panelâs reduced elastic properties (EI â GA) derived with such an advanced modelling can be finally used for practical design of bending members
Comportement en flexion de panneaux en bois lamellé croisé hétérogÚnes
National audienceDans le domaine de la construction bois, les panneaux en bois massif lamellĂ©s croisĂ©s (CLT â Cross Laminated Timber) sont de plus en plus utilisĂ©s en tant que plancher ou toiture. Ils sont composĂ©s de plusieurs couches en bois empilĂ©es et collĂ©es de façon croisĂ©e, pour obtenir des bonnes propriĂ©tĂ©s mĂ©caniques et hygromĂ©triques dans les deux directions.Un enjeu technologique en dĂ©veloppement est dâenlever du bois des planchers CLT et le remplacer avec du matĂ©riau isolant afin de rendre les panneaux plus lĂ©gers et plus performants acoustiquement et thermiquement. Lâutilisation de ces nouveaux planchers est encore limitĂ©e, Ă cause dâune connaissance insuffisante de leur comportement mĂ©canique en flexion.Des essais de flexion 4-points sur des planchers CLT massifs et aĂ©rĂ©s ont Ă©tĂ© conduits. Cette campagne essais a montrĂ©e lâaugmentation des effets de cisaillement quand le pourcentage des vides augmente. En plus, le plancher le plus aĂ©rĂ© a montrĂ© des modes de ruine complexes liĂ©es aux effets de cisaillement roulant (RT) et traction perpendiculaire aux fibres difficiles Ă prĂ©voir avec les mĂ©thodes simplifiĂ©es des ingĂ©nieurs. Ensuite, les planches en bois des planchers ont Ă©tĂ© testĂ©es pour dĂ©terminer les raideurs Ă©lastiques et les rĂ©sistances. Les essais de caractĂ©risation comprennent : traction parallĂšle aux fibres, compression selon les trois directions et cisaillement roulant.Une premiĂšre approche pour reproduire le comportement des planchers CLT aĂ©rĂ©s peut ĂȘtre celui dâutiliser des mĂ©thodes pour les CLT massifs et rĂ©duire les propriĂ©tĂ©s mĂ©canique du bois issues des essais de caractĂ©risation par le pourcentage du vide. Les deux mĂ©thodes pour le calcul en flexion choisies sont : la mĂ©thode dâanalogie du cisaillement (Kreuzinger, 1999) adoptĂ©e par la norme allemande (DIN, 2004) et un modĂšle dĂ©veloppĂ© rĂ©cemment qui combine une solution analytique 3D (Pagano, 1970) avec une couche CLT homogĂšne Ă©quivalente (Franzoni et al, 2015).Une modĂ©lisation plus avancĂ©e du comportement en flexion de ces panneaux trĂšs hĂ©tĂ©rogĂšnes en bois est en cours. Le modĂšle choisi est un schĂ©ma dâhomogĂ©nĂ©isation pĂ©riodique gĂ©rĂ© par une thĂ©orie de plaque pour les stratifiĂ©s (LebĂ©e, 2012). Ă ce moment, seulement la raideur en flexion a Ă©tĂ© calculĂ©e avec cette mĂ©thode. Cette modĂ©lisation avancĂ©e permettra de dĂ©terminer les principaux paramĂštres pour concevoir ces nouveaux planchers aĂ©rĂ©s en bois, comme la raideur en flexion, la raideur en cisaillement, le chargement critique et le mode de ruine associĂ©
Bending behaviour of massive and aerated timber floors
National audienceDans le domaine de la construction bois, les panneaux en bois massif lamellĂ©s croisĂ©s (CLT â Cross Laminated Timber) sont de plus en plus utilisĂ©s en tant que plancher ou toiture. En raison de leur facilitĂ© et rapiditĂ© de mise en Ćuvre et de lâorientation croisĂ©e des couches transverses qui garantit des propriĂ©tĂ©s mĂ©caniques et hygromĂ©triques uniformes. Une premiĂšre Ă©tude [1] a identifiĂ© des hĂ©tĂ©rogĂ©nĂ©itĂ©s « faibles » affectant leur comportement en flexion et proposĂ©e une modĂ©lisation avancĂ©e pour essayer de les prendre en compte. Cette modĂ©lisation sâappuie sur un comportement homogĂ©nĂ©isĂ© et simplifiĂ© dâune couche en bois, une solution analytique 3D [2] et un critĂšre de rupture pour le bois [3]. Le modĂšle dĂ©veloppĂ© a Ă©tĂ© validĂ© sur une expĂ©rience de rĂ©fĂ©rence des CLT en flexion [4] en termes de raideur et modes de ruine progressifs. Ensuite, des Ă©tudes paramĂ©triques ont Ă©tĂ© conduites avec le modĂšle validĂ©, afin dâamĂ©liorer la connaissance sur la mĂ©canique de ces panneaux et dâexplorer aussi des configurations innovantes.Un enjeu technologique en dĂ©veloppement est dâenlever du bois des planchers CLT et le remplacer avec du matĂ©riau isolant afin de rendre les panneaux plus lĂ©gers et plus performants acoustiquement et thermiquement. Lâutilisation de ces nouveaux planchers est encore limitĂ©e, Ă cause dâune connaissance insuffisante de leur comportement mĂ©canique en flexion. En effet, une campagne essais de flexion 4-points a montrĂ© des ruptures complexes liĂ©es aux effets de cisaillement et difficiles Ă prĂ©voir avec les mĂ©thodes simplifiĂ©es des ingĂ©nieurs. Une modĂ©lisation avancĂ©e du comportement en flexion de ces panneaux trĂšs hĂ©tĂ©rogĂšnes en bois est en dĂ©veloppement et les premiers rĂ©sultats seront prĂ©sentĂ©s. Le modĂšle choisi est un schĂ©ma dâhomogĂ©nĂ©isation pĂ©riodique gĂ©rĂ© par une thĂ©orie de plaque pour les stratifiĂ©s [5]. Ce modĂšle avancĂ© permettra de dĂ©terminer les principaux paramĂštres pour concevoir ces nouveaux planchers aĂ©rĂ©s en bois, comme la raideur en flexion, la raideur en cisaillement, le chargement critique et le mode de ruine associĂ©
How skill expertise shapes the brain functional architecture: an fMRI study of visuo-spatial and motor processing in professional racing-car and naĂŻve drivers
The present study was designed to investigate the brain functional architecture that subserves visuo-spatial and motor processing in highly skilled individuals. By using functional magnetic resonance imaging (fMRI), we measured brain activity while eleven Formula racing-car drivers and eleven ânaĂŻveâ volunteers performed a motor reaction and a visuo-spatial task. Tasks were set at a relatively low level of difficulty such to ensure a similar performance in the two groups and thus avoid any potential confounding effects on brain activity due to discrepancies in task execution. The brain functional organization was analyzed in terms of regional brain response, inter-regional interactions and blood oxygen level dependent (BOLD) signal variability. While performance levels were equal in the two groups, as compared to naĂŻve drivers, professional drivers showed a smaller volume recruitment of task-related regions, stronger connections among task-related areas, and an increased information integration as reflected by a higher signal temporal variability. In conclusion, our results demonstrate that, as compared to naĂŻve subjects, the brain functional architecture sustaining visuo-motor processing in professional racing-car drivers, trained to perform at the highest levels under extremely demanding conditions, undergoes both âquantitativeâ and âqualitativeâ modifications that are evident even when the brain is engaged in relatively simple, non-demanding tasks. These results provide novel evidence in favor of an increased âneural efficiencyâ in the brain of highly skilled individuals
Itâs not all in your car: functional and structural correlates of exceptional driving skills in professional racers
Driving is a complex behavior that requires the integration of multiple cognitive functions. While many studies have investigated brain activity related to driving simulation under distinct conditions, little is known about the brain morphological and functional architecture in professional competitive driving, which requires exceptional motor and navigational skills. Here, 11 professional racing-car drivers and 11 ânaĂŻveâ volunteers underwent both structural and functional brain magnetic resonance imaging (MRI) scans. Subjects were presented with short movies depicting a Formula One car racing in four different official circuits. Brain activity was assessed in terms of regional response, using an Inter-Subject Correlation (ISC) approach, and regional interactions by mean of functional connectivity. In addition, voxel-based morphometry (VBM) was used to identify specific structural differences between the two groups and potential interactions with functional differences detected by the ISC analysis. Relative to non-experienced drivers, professional drivers showed a more consistent recruitment of motor control and spatial navigation devoted areas, including premotor/motor cortex, striatum, anterior, and posterior cingulate cortex and retrosplenial cortex, precuneus, middle temporal cortex, and parahippocampus. Moreover, some of these brain regions, including the retrosplenial cortex, also had an increased gray matter density in professional car drivers. Furthermore, the retrosplenial cortex, which has been previously associated with the storage of observer-independent spatial maps, revealed a specific correlation with the individual driver's success in official competitions. These findings indicate that the brain functional and structural organization in highly trained racing-car drivers differs from that of subjects with an ordinary driving experience, suggesting that specific anatomo-functional changes may subtend the attainment of exceptional driving performance
It's not all in your car: functional and structural correlates of exceptional driving skills in professional racers.
Driving is a complex behavior that requires the integration of multiple cognitive functions. While many studies have investigated brain activity related to driving simulation under distinct conditions, little is known about the brain morphological and functional architecture in professional competitive driving, which requires exceptional motor and navigational skills. Here, 11 professional racing-car drivers and 11 "naĂŻve" volunteers underwent both structural and functional brain magnetic resonance imaging (MRI) scans. Subjects were presented with short movies depicting a Formula One car racing in four different official circuits. Brain activity was assessed in terms of regional response, using an Inter-Subject Correlation (ISC) approach, and regional interactions by mean of functional connectivity. In addition, voxel-based morphometry (VBM) was used to identify specific structural differences between the two groups and potential interactions with functional differences detected by the ISC analysis. Relative to non-experienced drivers, professional drivers showed a more consistent recruitment of motor control and spatial navigation devoted areas, including premotor/motor cortex, striatum, anterior, and posterior cingulate cortex and retrosplenial cortex, precuneus, middle temporal cortex, and parahippocampus. Moreover, some of these brain regions, including the retrosplenial cortex, also had an increased gray matter density in professional car drivers. Furthermore, the retrosplenial cortex, which has been previously associated with the storage of observer-independent spatial maps, revealed a specific correlation with the individual driver's success in official competitions. These findings indicate that the brain functional and structural organization in highly trained racing-car drivers differs from that of subjects with an ordinary driving experience, suggesting that specific anatomo-functional changes may subtend the attainment of exceptional driving performance
Notulae to the Italian alien vascular flora: 17
In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records and status changes from casual to naturalized for Italy or for Italian administrative regions for taxa in the genera Callianthe, Chamaecyparis, Chamaeiris, Cotoneaster, Erigeron, Freesia, Hemerocallis, Juglans, KalanchoeÌ, Ludwigia, Nassella, Paulownia, Physocarpus, Pistia, Saccharum, Setaria, and Vachellia. Nomenclatural and distribution updates, published elsewhere, and corrections are provided as supplementary material
Bryophyte, lichen, and vascular plant communities of badland grasslands show weak cross-taxon congruence but high local uniqueness in biancana pediments
Cross-taxon congruence, i.e., using certain taxonomic groups as surrogates for others, is receiving growing interest since it may allow decreasing efforts in biodiversity studies. In this work, we investigated the patterns of cross-taxon congruence in species richness and composition between communities of bryophytes, lichens, and vascular plants in different biancana grasslands of a Special Area of Conservation (SAC) of central Italy. We recorded species presence and abundance in 16 plots of 1 Ă 1 m size and analyzed the data using Procrustes correlation, co-correspondence analysis, and indicator species analysis. We did not highlight any correlation in species richness and composition between the three taxonomic groups. Conversely, the species composition of bryophyte communities was predictive of the species composition of lichen communities. Moreover, lichen richness was negatively correlated with the total cover of vascular plants. Indicator species analysis evidenced the presence of species from the three biotic communities being particularly related, at least at the local scale, to biancana pediments, like the bryophytes Didymodon acutus and Trichostomum crispulum, the lichens Enchylium tenax, Cladonia foliacea, and Psora decipiens, and the vascular plants Brachypodium distachyon, Parapholis strigosa, and Artemisia caerulescens subsp. cretacea. In the biancana pediments, acrocarp mosses, squamulose lichens, therophyte plants and chamaephyte plants coexisted. In spite of the weak cross-taxon congruence between the three taxonomic groups, this study could highlight a locally unique diversity of bryophytes, lichens, and vascular plants related to the extreme environment of biancana pediments, selected by high soil salinity and deposition from the upper eroded slope. Soil erosion and deposition in biancana badlands supports the increase of local multi-taxonomic plant diversity by creating unique ecosystems. Such biodiversity should be considered locally at risk of disappearance, due to the ongoing vanishing of biancana badlands in central Italy
Psychological treatments and psychotherapies in the neurorehabilitation of pain. Evidences and recommendations from the italian consensus conference on pain in neurorehabilitation
BACKGROUND:
It is increasingly recognized that treating pain is crucial for effective care within neurological rehabilitation in the setting of the neurological rehabilitation. The Italian Consensus Conference on Pain in Neurorehabilitation was constituted with the purpose identifying best practices for us in this context. Along with drug therapies and physical interventions, psychological treatments have been proven to be some of the most valuable tools that can be used within a multidisciplinary approach for fostering a reduction in pain intensity. However, there is a need to elucidate what forms of psychotherapy could be effectively matched with the specific pathologies that are typically addressed by neurorehabilitation teams.
OBJECTIVES:
To extensively assess the available evidence which supports the use of psychological therapies for pain reduction in neurological diseases.
METHODS:
A systematic review of the studies evaluating the effect of psychotherapies on pain intensity in neurological disorders was performed through an electronic search using PUBMED, EMBASE, and the Cochrane Database of Systematic Reviews. Based on the level of evidence of the included studies, recommendations were outlined separately for the different conditions.
RESULTS:
The literature search yielded 2352 results and the final database included 400 articles. The overall strength of the recommendations was medium/low. The different forms of psychological interventions, including Cognitive-Behavioral Therapy, cognitive or behavioral techniques, Mindfulness, hypnosis, Acceptance and Commitment Therapy (ACT), Brief Interpersonal Therapy, virtual reality interventions, various forms of biofeedback and mirror therapy were found to be effective for pain reduction in pathologies such as musculoskeletal pain, fibromyalgia, Complex Regional Pain Syndrome, Central Post-Stroke pain, Phantom Limb Pain, pain secondary to Spinal Cord Injury, multiple sclerosis and other debilitating syndromes, diabetic neuropathy, Medically Unexplained Symptoms, migraine and headache.
CONCLUSIONS:
Psychological interventions and psychotherapies are safe and effective treatments that can be used within an integrated approach for patients undergoing neurological rehabilitation for pain. The different interventions can be specifically selected depending on the disease being treated. A table of evidence and recommendations from the Italian Consensus Conference on Pain in Neurorehabilitation is also provided in the final part of the pape
ï»żChromosome numbers for the Italian flora: 13
In this contribution, new chromosome data obtained on material collected in Italy are presented. It includes the first count for Dianthus carthusianorum subsp. tenorei, Helosciadium nodiflorum, Hieracium hypochoeroides subsp. cilentanum, H. lesimanum, H. scopolioides, H. terraccianoi. In addition, first Italian counts for Crupina vulgaris, Damasonium alisma, and Illecebrum verticillatum are reported
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