Wide-scale conversion of tallgrass prairie to row-crop agriculture has spurred restoration of this endangered ecosystem. At the onset of restoration, a matrix of native plant species is sown into former crop field and includes warm-season (C4) grasses, cool-season (C3) grasses, legumes, and a large variety of herbaceous forbs. Increased demand for native seed due to a greater number of areas targeted for restoration has increased use of C4 grass cultivars by restoration practitioners. Cultivars are selectively bred to display traits such as increased productivity and digestibility, thus highlighting their original use in rangelands of the Great Plains. C4 grasses have a mutualistic relationship with arbuscular mycorrhizal fungi (AMF). In remnant tallgrass prairie, AMF can increase C4 plant uptake of belowground resources (e.g., water, soil P) by increasing root surface area. It is unknown if AMF colonization varies between seed source (cultivar or non-cultivar) of C4 grasses used in restoration and if this further affects plant biomass. Intraspecific variation in AMF colonization between two dominant warm-season prairie grasses was tested in two established prairie restoration experiments, both having plots seeded with either C4 cultivars or non-cultivars. To test for effects of seed source and AMF colonization on plant biomass, a greenhouse experiment was designed using two source populations (cultivar and non-cultivar) of two species (Andropogon gerardii Vitman and Sorghastrum nutans (L.) Nash) and soil collected at each field restoration (Kansas and Illinois). To suppress activity and colonization of AMF, a fungicide (Allban Flo: Thiophanate Methyl) was applied to half of the containers. Warm-season (C4) grass cultivars had greater or equivalent biomass production than non-cultivars at the onset of field restoration and also in the greenhouse. Furthermore, cultivars generally had less or equivalent root colonization by AMF and dependence on fungicide-free soil was greater in cultivars to retain increased accrual of biomass. It was, however, not possible to determine the role of AMF in plant biomass production as fungicide did not successfully reduce AMF root colonization in cultivars or non-cultivars, with one exception. It is critical that an effective AMF-suppression treatment be established in these types of studies. Future experiments should validate supposed effectiveness of the newly-recommended fungicide (Topsin-M) in population sources of warm-season prairie grasses and also apply it to the soil at time of planting in greenhouse studies. In the field sites, adjacent soil cultivation may have contributed to greater AMF biomass more so than surrounding remnant prairie. Future research identifying species composition of AMF at these sites is necessary to clarify differences in biomass. Despite greater plant biomass in cultivars, soil nutrient availability remained equivalent between source populations in general. Available N and P were not less in soils grown with cultivars, however soil inorganic N was inversely related to root length colonized by AMF, suggesting a role of AMF in N transfer from soil to plant. Soil P was not different between source populations likely due to legacy effects of agricultural fertilization, thus limiting a well known benefit of AMF symbiosis, at least at the onset of restoration. Non-target effects of fungicide application were observed (e.g., changes in available N) and effectiveness of AMF suppression was questionable. Fungicide lowered pH and increased N availability in soil as indicated by main effects of application and a positive relationship between pH and inorganic N across species. Fungicide application either 1) decreased N uptake by soil microorganisms (possibly including AMF) or 2) increased competition for adsorption sites and/or solubility of total inorganic N as pH changed, thus making this nutrient more available in the soil solution. Future examination quantifying indirect effects of fungicide application on soil chemistry should also be considered to better elucidate role of AMF in plant growth and soil nutrient availability between cultivars and non-cultivars of warm-season grasses used in tallgrass prairie restoration.

arbuscular mycorrhizal infection of seedlings and adults plants Plantago lanceolata was examined at twenty locations with differing moisture and nutrient availability. At each location two control and two fertilized plots were established. Mycorhizal infection of seedlings was higher on control plots but the symbiosis of adult plants degreased with increasing C/N ratio. Mycorrhizal infection was further distinquished into for morfotypes (Acaulospora, Scutellospora, Glomus, fine endophyte.

Ce travail de thèse a pour objectif de déterminer le comportement de structures composites contenant une phase en alliage à mémoire de forme (AMF). Un modèle macroscopique, basé sur la thermodynamique des processus irréversibles, est développé afin de déterminer le comportement de l'alliage a mémoire de forme. Ce modèle prend en compte certains des comportements clés des alliages à mémoire de forme en Nickel-titane, comme la dissymétrie traction-compression, les chargements partiels et le comportement de la martensite autoaccommodée. Une comparaison avec une base de donnée expérimentale montre une bonne capacité de prédiction du modèle, et ouvre une discussion sur des phénomènes supplémentaires à prendre en compte. A l'aide d'outils de simulation numérique, et notamment la méthode des éléments finis, ce modèle est appliqué à la détermination du comportement de matériaux composites. Deux problématiques sont considérées, la première étant l'étude du comportement d'une structure composite formée d'une matrice en élastomère et renforcée par des fibres ondulées en alliage à mémoire de forme. La deuxième problématique concerne l'étude de l'impact des phénomènes de précipitation (Ni4Ti3) dans les alliages de Nickel-Titane, sur le comportement macroscopique du matériau. Pour ce dernier cas, une cellule élémentaire de référence est définie, et le comportement macroscopique du matériau est estimé en considérant une variation des propretés de la matrice en AMF en fonction de sa composition chimique. Dans les deux cas, la modélisation apporte des informations intéressantes sur les champs de déformation et de contrainte et sur le comportement global / The purpose of the dissertation work is to determine the thermomechanical behavior of shape memory alloys (SMAs) based composites structures. A macroscopic model, developed in the framework of thermodynamics of irreversible process, is developed in order to model the behavior of the SMA phase. This model deals with several key features of SMAs behavior, like tension-compression asymmetry, partial cycles and the behavior of the formed self-accommodated martensite. A comparison with several experimental database show a good prediction capability of the model, and opens a discussion on additional features to take into account using finite element analysis, the behavior of SMA-based composite material is computed. This methodology is applied for two cases ; the first one is the study of an elastomeric ribbon reinforced with snake-like shape SMA fibers. The second case considers the impact of precipitation (Ni4Ti3) on the macroscopic behavior in Ni-rich NiTi SMAs. A reference unit cell is defined, and the macroscopic behavior is estimated considering a variation of material properties throughout the cell as a function of the chemical composition. In both cases, the model provides interesting information on stress and stra fields, as well as on the global behavior

Arbuscular mycorrhizal fungi (AMF) are an ancient group of obligate symbionts, colonizing the roots of over 72% of land plants, increasing the uptake of nutrients from the soil, and providing many fitness benefits to their host plants. The multinucleate and coenocytic nature of AMF have interested researchers for decades, leading to many theories of the evolution, and genetic organization of these organisms. Recent findings propose that AMF carry two types of strains, identified based on putative MAT-loci, as either homokaryotic, carrying multiple and genetically similar nuclei, or dikaryotic with co-existing nuclei deriving from two parental strains. In other fungi, hyphal fusions, or anastomosis, between compatible strains results in nuclear transfer, creating heterokaryotic spore progeny. It has been hypothesized that dikaryotic AMF strains arose from the anastomosis between compatible homokaryons harbouring different nucleotypes. The goal of this research is to determine whether anastomosis events, known to occur in other fungi, like homokaryon-homokaryon, homokaryon-dikaryon (Buller phenomenon), and/or dikaryon-dikaryon nuclear exchanges also occur in AMF. To achieve this, the anastomosis frequencies between 15 crosses of homokaryotic and dikaryotic strains of the model AMF species Rhizophagus irregularis were examined using microscopy and droplet digital PCR (ddPCR) to determine if nuclear transfer between strains is possible. Overall, these experiments build on the existing evidence of compatible interactions between strains of R. irregularis.

Apesar de diversos estudos demonstrarem resultados promissores da utilização da solução de AmF/NaF/SnCl2 na inibição da progressão da lesão de erosão dental, medidas que visam melhorar ainda mais sua eficácia são fundamentais. Sendo assim, este estudo in vitro e in situ se propôs a avaliar se o efeito protetor dessa solução pode ser potencializado pelo aumento da frequência de uso. Para tanto, foram obtidas, a partir de terceiros molares humanos hígidos, sessenta amostras de esmalte dental humano para o estudo in vitro (4 X 4 X 1 mm), e noventa e seis para o in situ (3 X 3 X 1 mm). Após a formação de lesão erosiva incipiente nas amostras in vitro, (ácido cítrico a 1%, pH 4,0, durante 3 minutos), estas foram divididas nos 5 grupos de tratamentos (n=12): G1 - água destilada (controle negativo); G2 - solução de NaF (controle positivo) 1x/dia; G3 - solução de NaF (controle positivo) 2x/dia; G4 - solução de AmF/NaF/SnCl2 1x/dia; G5 - solução de AmF/NaF/SnCl2 2x/dia. As amostras foram então submetidas a 5 dias de ciclagem erosiva através de 6 imersões diárias de 2 minutos em solução de ácido cítrico (0,05M, pH 2.6). Ao final da ciclagem erosiva, foi realizada a determinação do desgaste de superfície por meio de Perfilometria óptica. Para realização do desafio erosivo in situ, as amostras também foram submetidas à formação da lesão incipiente, com a mesma metodologia do in vitro. Doze voluntários participaram do estudo in situ e cruzado, dividido em quatro fases de 5 dias cada, os quais utilizaram um dispositivo removível inferior unilateral contendo 2 amostras de esmalte dental humano erodido, que foram trocadas a cada fase. As amostras foram divididas em 4 grupos de tratamentos (n=12), os mesmos utilizados na etapa in vitro, com exceção do grupo da solução de NaF 2x/dia. Durante a fase experimental in situ o dispositivo contendo as amostras foi submetido à ciclagem erosiva (ex vivo) semelhante à etapa in vitro. Ao final de cada fase experimental in situ, as amostras foram removidas do dispositivo e analisadas através de perfilometria, e foram consideradas as médias das amostras em duplicata para a análise estatística. A ANOVA mostrou que o desgaste superficial foi afetado pelos tratamentos avaliados tanto in vitro quanto in situ (p?0,001), com nível de significância de 5%. No estudo in vitro, o teste de Tukey demonstrou que não houve diferença entre os grupos de aplicação do NaF 1 (16,21 ±1,56) ou 2 vezes (15,39 ±1,01), que apresentaram redução limitada no desgaste quando comparado ao grupo da água destilada (20,36 ±1,56); já entre os grupos da solução AmF/NaF/SnCl2 houve diferença entre aplicação 1 (10,40 ±2,36) e 2 vezes (7,27 ±3,29), e que apesar de ambos demonstrarem redução significativa da perda de substrato, o aumento da frequência aumentou este potencial anti-erosivo. Na parte in situ, a solução de NaF não demonstrou capacidade de reduzir o desgaste, e apesar de não ter havido diferença significante entre os grupos AmF/NaF/SnCl2 1 (2,64 ±1,55) e 2 vezes (1,34 ±1,16), esta solução foi eficaz na redução do desgaste erosivo em comparação aos grupos NaF (4,59 ±2,13) e água destilada (4,55 ±2,75). A solução de AmF/NaF/SnCl2 demostrou se eficaz em proteger o esmalte da progressão da erosão dental, e o aumento da frequência potencializou seu efeito anti-erosivo tanto in vitro, quanto in situ. / Although several studies have shown promising results using the AmF/NaF /SnCl2 solution in inhibiting the progression of dental erosion, measures to further improve its effectiveness are fundamental. Thus, this in vitro and in situ study aimed to evaluate if the protective effect of this solution can be enhanced by increasing the frequency of use. Human enamel samples were obtained from sound human third molars; sixty for the in vitro study (4 x 4 x 1 mm), and ninety-six for the in situ (3 X 3 X 1 mm) study. After the formation of incipient erosive lesions, the in vitro samples (1% citric acid, pH 4.0, for 3 minutes), were divided into 5 treatment groups (n = 12): G1 - distilled water (negative control); G2 - NaF solution (positive control) 1x/day; G3 - NaF solution (positive control) 2x/day; G4 - AmF/NaF/SnCl2 solution 1x/day; G5 - AmF/NaF/SnCl2 solution 2x/day. The samples were then subjected to 5 days of erosive cycling through 6 daily immersions (2 minutes each) in citric acid solution (0.05 M, pH 2.6). At the end of erosive cycling, surface wear was determined by means of optical profilometry. To perform the in situ erosive challenge, the samples were also subjected to the formation of incipient lesion with the same methodology of the in vitro study. Twelve volunteers participated in the crossover in situ study - divided into four phases of 5 days each - and used a unilateral lower removable device containing 2 samples of eroded human enamel, which were changed at each phase. The samples were divided into 4 treatment groups (n = 12), the same considered for the in vitro phase, with the exception of the group of NaF solution 2x/day. During the in situ experimental phase, the device containing the sample was subjected to the erosive cycling (ex vivo), similar to the in vitro phase. At the end of each in situ experimental phase, the samples were removed from the device and analyzed by profilometry, and the average of duplicate samples were considered for statistical analysis. The ANOVA showed that the surface wear was affected by treatments evaluated in both in vitro and in situ (p?0,001) studies. In the in vitro study, the Tukey test showed no difference between the application of groups of NaF 1 (16.21 ±1.47) or 2 times (15.39 ±1.01), which showed limited reduction in wear compared to the distilled water group (20.36 ±1.56). Among the groups of AmF/NaF/SnCl2 solution, there was no difference between 1 (10.40 ±2.36) and 2 application times (7.27 ±3.29), and, although both demonstrated significantly reduced tissue loss, increasing the frequency has increased its anti-erosive potential. In the in situ phase, the NaF solution did not reveal the ability to reduce surface wear, and although there was no significant difference between the AmF/NaF/SnCl2 1 (2.64 ±1.55) and 2 times groups (1.34 ±1.16), this solution was effective in reducing the erosive wear compared to groups NaF (4.59 ±2.75) and distilled water (4.55 ±2.75). The AmF/NaF/SnCl2 solution shown to be effective in protecting the enamel progression of dental erosion, and increasing the frequency potentiate its anti-erosive effect both in vitro and in situ.

Apesar de diversos estudos demonstrarem resultados promissores da utilização da solução de AmF/NaF/SnCl2 na inibição da progressão da lesão de erosão dental, medidas que visam melhorar ainda mais sua eficácia são fundamentais. Sendo assim, este estudo in vitro e in situ se propôs a avaliar se o efeito protetor dessa solução pode ser potencializado pelo aumento da frequência de uso. Para tanto, foram obtidas, a partir de terceiros molares humanos hígidos, sessenta amostras de esmalte dental humano para o estudo in vitro (4 X 4 X 1 mm), e noventa e seis para o in situ (3 X 3 X 1 mm). Após a formação de lesão erosiva incipiente nas amostras in vitro, (ácido cítrico a 1%, pH 4,0, durante 3 minutos), estas foram divididas nos 5 grupos de tratamentos (n=12): G1 - água destilada (controle negativo); G2 - solução de NaF (controle positivo) 1x/dia; G3 - solução de NaF (controle positivo) 2x/dia; G4 - solução de AmF/NaF/SnCl2 1x/dia; G5 - solução de AmF/NaF/SnCl2 2x/dia. As amostras foram então submetidas a 5 dias de ciclagem erosiva através de 6 imersões diárias de 2 minutos em solução de ácido cítrico (0,05M, pH 2.6). Ao final da ciclagem erosiva, foi realizada a determinação do desgaste de superfície por meio de Perfilometria óptica. Para realização do desafio erosivo in situ, as amostras também foram submetidas à formação da lesão incipiente, com a mesma metodologia do in vitro. Doze voluntários participaram do estudo in situ e cruzado, dividido em quatro fases de 5 dias cada, os quais utilizaram um dispositivo removível inferior unilateral contendo 2 amostras de esmalte dental humano erodido, que foram trocadas a cada fase. As amostras foram divididas em 4 grupos de tratamentos (n=12), os mesmos utilizados na etapa in vitro, com exceção do grupo da solução de NaF 2x/dia. Durante a fase experimental in situ o dispositivo contendo as amostras foi submetido à ciclagem erosiva (ex vivo) semelhante à etapa in vitro. Ao final de cada fase experimental in situ, as amostras foram removidas do dispositivo e analisadas através de perfilometria, e foram consideradas as médias das amostras em duplicata para a análise estatística. A ANOVA mostrou que o desgaste superficial foi afetado pelos tratamentos avaliados tanto in vitro quanto in situ (p?0,001), com nível de significância de 5%. No estudo in vitro, o teste de Tukey demonstrou que não houve diferença entre os grupos de aplicação do NaF 1 (16,21 ±1,56) ou 2 vezes (15,39 ±1,01), que apresentaram redução limitada no desgaste quando comparado ao grupo da água destilada (20,36 ±1,56); já entre os grupos da solução AmF/NaF/SnCl2 houve diferença entre aplicação 1 (10,40 ±2,36) e 2 vezes (7,27 ±3,29), e que apesar de ambos demonstrarem redução significativa da perda de substrato, o aumento da frequência aumentou este potencial anti-erosivo. Na parte in situ, a solução de NaF não demonstrou capacidade de reduzir o desgaste, e apesar de não ter havido diferença significante entre os grupos AmF/NaF/SnCl2 1 (2,64 ±1,55) e 2 vezes (1,34 ±1,16), esta solução foi eficaz na redução do desgaste erosivo em comparação aos grupos NaF (4,59 ±2,13) e água destilada (4,55 ±2,75). A solução de AmF/NaF/SnCl2 demostrou se eficaz em proteger o esmalte da progressão da erosão dental, e o aumento da frequência potencializou seu efeito anti-erosivo tanto in vitro, quanto in situ. / Although several studies have shown promising results using the AmF/NaF /SnCl2 solution in inhibiting the progression of dental erosion, measures to further improve its effectiveness are fundamental. Thus, this in vitro and in situ study aimed to evaluate if the protective effect of this solution can be enhanced by increasing the frequency of use. Human enamel samples were obtained from sound human third molars; sixty for the in vitro study (4 x 4 x 1 mm), and ninety-six for the in situ (3 X 3 X 1 mm) study. After the formation of incipient erosive lesions, the in vitro samples (1% citric acid, pH 4.0, for 3 minutes), were divided into 5 treatment groups (n = 12): G1 - distilled water (negative control); G2 - NaF solution (positive control) 1x/day; G3 - NaF solution (positive control) 2x/day; G4 - AmF/NaF/SnCl2 solution 1x/day; G5 - AmF/NaF/SnCl2 solution 2x/day. The samples were then subjected to 5 days of erosive cycling through 6 daily immersions (2 minutes each) in citric acid solution (0.05 M, pH 2.6). At the end of erosive cycling, surface wear was determined by means of optical profilometry. To perform the in situ erosive challenge, the samples were also subjected to the formation of incipient lesion with the same methodology of the in vitro study. Twelve volunteers participated in the crossover in situ study - divided into four phases of 5 days each - and used a unilateral lower removable device containing 2 samples of eroded human enamel, which were changed at each phase. The samples were divided into 4 treatment groups (n = 12), the same considered for the in vitro phase, with the exception of the group of NaF solution 2x/day. During the in situ experimental phase, the device containing the sample was subjected to the erosive cycling (ex vivo), similar to the in vitro phase. At the end of each in situ experimental phase, the samples were removed from the device and analyzed by profilometry, and the average of duplicate samples were considered for statistical analysis. The ANOVA showed that the surface wear was affected by treatments evaluated in both in vitro and in situ (p?0,001) studies. In the in vitro study, the Tukey test showed no difference between the application of groups of NaF 1 (16.21 ±1.47) or 2 times (15.39 ±1.01), which showed limited reduction in wear compared to the distilled water group (20.36 ±1.56). Among the groups of AmF/NaF/SnCl2 solution, there was no difference between 1 (10.40 ±2.36) and 2 application times (7.27 ±3.29), and, although both demonstrated significantly reduced tissue loss, increasing the frequency has increased its anti-erosive potential. In the in situ phase, the NaF solution did not reveal the ability to reduce surface wear, and although there was no significant difference between the AmF/NaF/SnCl2 1 (2.64 ±1.55) and 2 times groups (1.34 ±1.16), this solution was effective in reducing the erosive wear compared to groups NaF (4.59 ±2.75) and distilled water (4.55 ±2.75). The AmF/NaF/SnCl2 solution shown to be effective in protecting the enamel progression of dental erosion, and increasing the frequency potentiate its anti-erosive effect both in vitro and in situ.

Dans cette étude, nous avons isolé et cultivé des bactéries intimement liées aux spores du champignon mycorhizien Glomus irregulare prélevées dans la rhizosphère de plants d’Agrostis stolonifera L. récoltés dans un sol naturel. Le séquençage des 29 morphotypes isolés a révélé la présence de seulement sept taxons bactériens (Variovorax paradoxus, Microbacterium ginsengiosoli, Sphingomonas sp., Bacillus megaterium, B. simplex, B. cereus et Kocuria rhizophila). Des isolats de chacun de ces sept taxons ont ensuite été cultivés in vitro sur le mycélium de G. irregulare afin d’observer par microscopie leur capacité à croitre et à s’attacher au mycélium en absence d’éléments nutritifs autres que ceux fournis par le champignon. Tous les isolats, sauf B. cereus, ont été capables de bien croitre dans le système expérimental et de s’attacher au mycélium en formant des structures ressemblant à des biofilms sur la surface du champignon. Toutefois, B. simplex formait ces structures plus rapidement, soit en 15 jours, alors que les autres isolats les ont formés après 30 jours (K. rhizophila et B. megaterium) ou 45 jours (V. paradoxus, M. ginsengiosoli et Sphingomonas sp.). D’autre part, la technique PCR-DGGE a permis d’analyser la diversité bactérienne associée aux spores. La diversité des taxons associés aux spores de G. irregulare qu’il a été possible d’isoler et de cultiver in vitro a été nettement moindre que celle qui était présente sur la surface des spores, alors que la biodiversité bactérienne totale du sol a été encore beaucoup plus élevée. Les bactéries associées aux champignons mycorhiziens jouent probablement un rôle important dans la capacité des plantes à résister aux stress biotiques et abiotiques auxquels elles sont soumises. / In this study, we isolated and cultivated bacterial cells intimately associated with Glomus irregulare spores in a natural soil Agrostis stolonifera rhizosphere. Sequencing of the 29 morphotypes isolated revealed the presence of only seven bacterial taxa (Variovorax paradoxus, Microbacterium ginsengiosoli, Sphingomonas sp., Bacillus megaterium, B. simplex, B. cereus and Kocuria rhizophila). These seven isolates were cultivated in vitro on the mycelium of G. irregulare to allow microscopic observation of growth and attachment to the mycelium in absence of nutritive sources other than those derived from the fungal mycelium. All isolates but B. cereus were able to grow on the experimental system and to attach to the mycelium to form biofilm-like structures on their surface. However, B. simplex formed these structures more quickly, in 15 days, than the remaining isolates that have formed them only after 30 days (K. rhizophila and B. megaterium) or 45 days (V. paradoxus, M. ginsengiosoli and Sphingomonas sp.). In addition, PCR-DGGE was used to compare bacterial diversity. The bacterial biodiversity associated with spores of G. irregulare that were isolated and cultured in vitro was significantly lower than that present on the spore surface, while total soil bacterial diversity was much higher. The bacteria associated with mycorrhizal fungi probably have an important role in the ability of plants to withstand biotic and abiotic stresses to which they are submitted.

Les AMF à base fer se distinguent par la présence d'un couplage entre la transformation de phase et le glissement plastique. Pour caractériser leur comportement thermomécanique, des essais cycliques de chargement mécanique effectués à différentes températures et à différents niveaux de chargement, suivis par chauffage, ont été effectués. Ceux ci nous ont permis de distinguer les spécificités des AMF à base fer comme la non linéarité des interactions inter et intragranulaires, l'évolution des contraintes critiques avec la température, l'effet de la déformation plastique sur celle de transformation et l'activation de la transformation inverse uniquement par chauffage. En s'inspirant des résultats de ces essais, une loi de comportement, intégrant toutes ces spécificités, est proposée. Elle dérive d'une expression de l'énergie libre de Gibbs issue de considérations micromécaniques. Elle présente deux variables internes, la fraction volumique de martensite pour décrire la transformation de phase et le taux de plasticité pour le comportement plastique. Cette loi a été implémentée dans le code éléments finis Abaqus via la subroutine UMAT. Elle a été validée par comparaison des simulations numériques avec les résultats expérimentaux. Suite à cette validation, des applications en AMF à base fer ont été étudiées. Les résultats obtenus ont montré la capacité du modèle à être utilisé comme outil de dimensionnement de structures en AMF à base fer / The Fe-based shape memory alloys (SMAs) present a specific thermomechanical behaviour compared with classical SMAs. In this PhD thesis, experimental thermomechanical tests were performed in order to study such behavior. The applied loading is a tension followed by a significant heating. The loading cycle is repeated at different constant temperatures and maximum stresses. The experimental results show a coupling between two non linear inelastic mechanisms: phase transformation and plasticity. The reverse transformation activated only during heating, the effect of plastic strain on the transformation one, were also analysed. Taking into account all these specificities, a finite element numerical tool adapted to Fe-based SMA structural analysis is proposed. It is based on a developed constitutive model which describes the effect of phase transformation, plastic sliding and their interactions on the thermomechanical behavior. Two scalar internal variables were considered to describe phase transformation and plastic sliding effects. This model was derived from an assumed expression of the Gibbs free energy taking into account, in addition to mechanical and chemical quantities, the non linear interaction quantities related to inter- and intra-granular incompatibilities. The numerical tool derived from the implicit resolution of the non linear partial derivative constitutive equations was implemented in the Abaqus finite element code via the UMAT subroutine. After verification tests for homogeneous and heterogeneous thermo-mechanical loadings, two examples of Fe-based SMA applications were studied. They correspond to Fe-based SMA tightening systems: a fish plates for crane rails and a ring for tubes connection

<p>Arbuscular mycorrhizal fungi (AMF) are best known for their potential to help plants acquire nutrients, especially phosphorous. These microbes improve soil health by promoting soil aggregation and carbon sequestration, and further benefit plants by helping them withstand biotic and abiotic stress. Currently, there are 200 recognized species of AMF within the phylum Glomeromycota. Recent studies indicate that individual AMF species differ in the benefits they provide, with some even acting as parasites. Moreover, AMF community composition can be altered by soil and crop management practices, but the effect of these changes on the benefits conferred by AMF are still not well understood. Consequently, the goal of this study was to determine how two widely used crop management systems can alter the composition of AMF species, and affect the potential for these communities to promote the productivity and drought tolerance. To accomplish this goal, we collected AMF inoculum from a long-term crop systems trial comparing organic and conventional management for use in greenhouse trials where we subjected plants to drought. We collected AMF inoculum during mid-summer when differences between the two management systems were likely cause larger effects on AMF communities, and again in autumn after harvest to see if differences in AMF communities would persist. We determined AMF species composition using next generation sequencing. Results of this study confirm that soil-building practices commonly used in organic farming systems can improve soil health and increase the productivity of food-grade soybeans. They also demonstrate that AMF communities in Indiana croplands are highly diverse, and some of these taxa can improve soybean growth and help plants tolerate water stress. Although the overall diversity of AMF communities did not differ between the organic and conventional management systems in mid-summer, individual AMF taxa did differ between the systems, which were likely responsible for the greater tolerance to water stress observed when plants were amended with inoculum from the organic system. AMF communities present during autumn were significantly different between the two crop management systems, but did not result in differences in drought tolerance of soybeans, indicating that the loss of key AMF taxa in the organic system from the first relative to the second experiment was likely responsible. Finally, plants grown using inoculum from both crop management systems in autumn had greater tolerance to water stress than plants that received a AMF commercial inoculum. This provides further evidence that individual AMF species vary in the benefits they provide, and that the presence of a diverse consortium of AMF species is needed to optimize plant health and productivity in agricultural systems. Agricultural producers should consider incorporating soil-building practices that are commonly used in organic farming systems such as planting winter cover crops, to improve the health of their soil and enhance the productivity of their crops. <b></b></p> <br>

Dans cette étude, nous avons isolé et cultivé des bactéries intimement liées aux spores du champignon mycorhizien Glomus irregulare prélevées dans la rhizosphère de plants d’Agrostis stolonifera L. récoltés dans un sol naturel. Le séquençage des 29 morphotypes isolés a révélé la présence de seulement sept taxons bactériens (Variovorax paradoxus, Microbacterium ginsengiosoli, Sphingomonas sp., Bacillus megaterium, B. simplex, B. cereus et Kocuria rhizophila). Des isolats de chacun de ces sept taxons ont ensuite été cultivés in vitro sur le mycélium de G. irregulare afin d’observer par microscopie leur capacité à croitre et à s’attacher au mycélium en absence d’éléments nutritifs autres que ceux fournis par le champignon. Tous les isolats, sauf B. cereus, ont été capables de bien croitre dans le système expérimental et de s’attacher au mycélium en formant des structures ressemblant à des biofilms sur la surface du champignon. Toutefois, B. simplex formait ces structures plus rapidement, soit en 15 jours, alors que les autres isolats les ont formés après 30 jours (K. rhizophila et B. megaterium) ou 45 jours (V. paradoxus, M. ginsengiosoli et Sphingomonas sp.). D’autre part, la technique PCR-DGGE a permis d’analyser la diversité bactérienne associée aux spores. La diversité des taxons associés aux spores de G. irregulare qu’il a été possible d’isoler et de cultiver in vitro a été nettement moindre que celle qui était présente sur la surface des spores, alors que la biodiversité bactérienne totale du sol a été encore beaucoup plus élevée. Les bactéries associées aux champignons mycorhiziens jouent probablement un rôle important dans la capacité des plantes à résister aux stress biotiques et abiotiques auxquels elles sont soumises. / In this study, we isolated and cultivated bacterial cells intimately associated with Glomus irregulare spores in a natural soil Agrostis stolonifera rhizosphere. Sequencing of the 29 morphotypes isolated revealed the presence of only seven bacterial taxa (Variovorax paradoxus, Microbacterium ginsengiosoli, Sphingomonas sp., Bacillus megaterium, B. simplex, B. cereus and Kocuria rhizophila). These seven isolates were cultivated in vitro on the mycelium of G. irregulare to allow microscopic observation of growth and attachment to the mycelium in absence of nutritive sources other than those derived from the fungal mycelium. All isolates but B. cereus were able to grow on the experimental system and to attach to the mycelium to form biofilm-like structures on their surface. However, B. simplex formed these structures more quickly, in 15 days, than the remaining isolates that have formed them only after 30 days (K. rhizophila and B. megaterium) or 45 days (V. paradoxus, M. ginsengiosoli and Sphingomonas sp.). In addition, PCR-DGGE was used to compare bacterial diversity. The bacterial biodiversity associated with spores of G. irregulare that were isolated and cultured in vitro was significantly lower than that present on the spore surface, while total soil bacterial diversity was much higher. The bacteria associated with mycorrhizal fungi probably have an important role in the ability of plants to withstand biotic and abiotic stresses to which they are submitted.