Influence de l’ecosysteme et du stade de developpement des panicules sur l’androgenese chez le riz

L’étude vise à déterminer l’écosystème et le stade de panicule favorables à l’androgenèse chez le riz sur le site d’ (ex-ADRAO) à M’Bé, Bouaké. Le matériel végétal a consisté en deux variétés deOryza glaberrima (CG 14 et CG 20) et 3 de Oryza sativa de type japonica (WAB 56-50 et TAIPEI 309) et indica (BOUAKE 189). Les cals induites à partir d’anthères sur le milieu N6 modifié contenant 0,5 mg l-1 de kinétine, 2,5 mg l-1 de dichlorophenoxy acétique acide (2,4-D), et 15 % de lait de coco, sont ensuite régénérés sur milieu MS additionné de 1 mg l-1d’acide -naphtalène acétique (ANA) et 4 mg l-1kinétine. Les résultats ont révélé une forte interaction génotype-écosystème. En effet, chaque génotype a eu une bonne réponse en androgenèse avec les anthères provenant de son écosystème habituel de croissance. Ainsi, les glaberrima et les japonica se sont bien comportés en androgenèse, au niveau des plateaux et l'indica dans les bas-fonds. Le stade jeune de la panicule (distance auriculaire entre 7 et 8,8 cm) a été le meilleur stade de prélèvement. Tous stades de panicule et écosystèmes confondus, les meilleurs résultats pour la production de cals et la régénération de plantules a été obtenue avec les sativa comparativement aux glaberrima

Large Roughness Effects in Channel Flow

The streamwise velocity component in fully-developed turbulent channel flow is studied for two very rough surfaces and a smooth surface at comparable Reynolds numbers. One rough surface comprises sparse and isotropic grit with a non-Gaussian distribution. The other is a uniform mesh consisting of twisted rectangular elements which form a diamond pattern. The mean roughness heights (± the standard deviation) are, respectively, about 76 ± 42 and 145 ± 150 wall units. The mean velocity profile over the grit surface exhibits self-similarity (in the form of a logarithmic law) within the limited range of 0:03 ≤ y/h ≤ 0.05, but the profile over the mesh surface exhibits only a small region with a slope tangential to log-law slope scaled on outer variables. However, the mean velocity deficit and higher moments (up to the fourth order) all exhibit some degree of outer scaling over both surfaces. The distinction between self-similarity and outer similarity is clarified and the importance of the former is explained. Spatial correlations show that the dominant large-scale features are very large quasi-streamwise structures with circulation in the cross-flow plane, similar to those found in smooth-wall internal and external flows. However, in the present case, the spanwise length scales are considerably larger. © Springer Science+Business Media B.V. 2010

TRY plant trait database - enhanced coverage and open access

Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

A hierarchical and modular approach to the discovery of robust associations in genome-wide association studies from pooled DNA samples

[Background] One of the challenges of the analysis of pooling-based genome wide association studies is to identify authentic associations among potentially thousands of false positive associations. [Results] We present a hierarchical and modular approach to the analysis of genome wide genotype data that incorporates quality control, linkage disequilibrium, physical distance and gene ontology to identify authentic associations among those found by statistical association tests. The method is developed for the allelic association analysis of pooled DNA samples, but it can be easily generalized to the analysis of individually genotyped samples. We evaluate the approach using data sets from diverse genome wide association studies including fetal hemoglobin levels in sickle cell anemia and a sample of centenarians and show that the approach is highly reproducible and allows for discovery at different levels of synthesis. [Conclusion] Results from the integration of Bayesian tests and other machine learning techniques with linkage disequilibrium data suggest that we do not need to use too stringent thresholds to reduce the number of false positive associations. This method yields increased power even with relatively small samples. In fact, our evaluation shows that the method can reach almost 70% sensitivity with samples of only 100 subjects.Supported by NHLBI grants R21 HL080463 (PS); R01 HL68970 (MHS); K-24, AG025727 (TP); K23 AG026754 (D.T.)

TRY plant trait database - enhanced coverage and open access

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

5-HT modulation of pain perception in humans

© 2017, The Author(s). Introduction: Although there is clear evidence for the serotonergic regulation of descending control of pain in animals, little direct evidence exists in humans. The majority of our knowledge comes from the use of serotonin (5-HT)-modulating antidepressants as analgesics in the clinical management of chronic pain. Objectives: Here, we have used an acute tryptophan depletion (ATD) to manipulate 5-HT function and examine its effects of ATD on heat pain threshold and tolerance, attentional manipulation of nociceptive processing and mood in human volunteers. Methods: Fifteen healthy participants received both ATD and balanced amino acid (BAL) drinks on two separate sessions in a double-blind cross-over design. Pain threshold and tolerance were determined 4 h post-drink via a heat thermode. Additional attention, distraction and temperature discrimination paradigms were completed using a laser-induced heat pain stimulus. Mood was assessed prior and throughout each session. Results: Our investigation reported that the ATD lowered plasma TRP levels by 65.05 ± 7.29% and significantly reduced pain threshold and tolerance in response to the heat thermode. There was a direct correlation between the reduction in total plasma TRP levels and reduction in thermode temperature. In contrast, ATD showed no effect on laser-induced pain nor significant impact of the distraction-induced analgesia on pain perception but did reduce performance of the painful temperature discrimination task. Importantly, all findings were independent of any effects of ATD on mood. Conclusion: As far as we are aware, it is the first demonstration of 5-HT effects on pain perception which are not confounded by mood changes

Turbulent channel flow: comparison of streamwise velocity data from experiments and direct numerical simulation

© 2009 Cambridge University Press. Online edition of the journal is available at http://journals.cambridge.org/FLMRecently there has been remarkable progress made in the direct numerical simulation (DNS) of wall-bounded turbulence, particularly of turbulent channel flow, with numerical data now available above Reτ ≈ 2000 (Hoyas & Jiménez, Phys. Fluids, vol. 18, 2006, p. 011702; Iwamoto et al., Proceedings of the Sixth Symposium Smart Control of Turbulence, 2005). Much knowledge has been gained from these results, particularly in the areas of flow structure and dynamics. Yet, while the value of such simulations is undoubted, only very limited comparisons with experimental data have been documented. Although the physics of the flow are captured correctly in an ideal DNS, as with any real numerical or physical experiment, there are opportunities for misrepresentation of the characteristics of turbulence. As such, this article seeks to make a comparison between a well-documented high Reynolds number (Reτ = 934), large box size (8πh × 2h × 3πh) DNS from del Álamo et al. (J. Fluid Mech., vol. 500, 2004, p. 135) and laboratory channel flow data measured by the authors. Results show that there is excellent agreement between the streamwise velocity statistics of the two data sets. The spectra are also very similar, however, throughout the logarithmic region the secondary peak in energy is clearly reduced in the DNS results. Although the source of the difference is not certain, the wavelengths concerned are close to the DNS box length, leading to the recommendation that longer box lengths should be investigated. Another large-scale spectral discrepancy near the wall results from the incorrect assumption of a constant convection velocity used to infer spatial information from the temporal. A near-wall convection velocity modification function is tentatively proposed. While the modification gives good agreement between the data sets, higher Reynolds number comparisons are required to better understand the intricate convection velocity issue.10.1017/S002211200900776

Evolution of the Turbulent Far Wake of a Sphere

The classic turbulent axisymmetric wake derivation for the spreading of wake half-width, δ, and maximum mean velocity, ūmax decay comes from arguments of a high local Reynolds number, Re, and thus negligible viscosity. If instead one assumes the local Reynolds number is small, then at some distance sufficiently far downstream the turbulent production term in the Reynolds shear stress equation will decay and a new similarity solution will arise: as shown by [2, 4]. This solution features the scaling of δ ∼ (x/d)1/2 and ūmax ∼ (x/d)−1. In other words, the turbulent wake is scaling itself at rates that match the theoretical laminar wake, yet with a local Reynolds number high enough for the turbulent fluctuations to be non-negligible. Whilst the derivation of a low Reynolds number solution is a mathematical exercise, obtaining data to confirm or deny its existence has proved difficult. No experiment has been conducted at a combination of high enough initial Reynolds number and far enough downstream to capture this transition behaviour. Furthermore, only the DNS study of Gourlay [3] has been able to achieve this behaviour; leading some researchers to question whether this decay state would occur or if the wake instead would relaminarise [7]. This paper presents results for a towed a sphere through water at a Reynolds number, based on sphere diameter, of 13000. Our experiments have been able to capture the wake transitioning from the high local Reynolds number solution to the low local Reynolds number solution via high-speed time-resolved PIV. The value of local Reynolds number that exhibits itself in the extreme far wake during the low local Reynolds number solution suggests the wake is still turbulent, supporting the claim of [2, 4]

Similarity and structure of wall turbulence with lateral wall shear stress variations

Wall-bounded turbulence, where it occurs in engineering or nature, is commonly subjected to spatial variations in wall shear stress. A prime example is spatially varying roughness. Here, we investigate the configuration where the wall shear stress varies only in the lateral direction. The investigation is idealised in order to focus on one aspect, namely, the similarity and structure of turbulent inertial motion over an imposed scale of stress variation. To this end, we analyse data from direct numerical simulation (DNS) of pressure-driven turbulent flow through a channel bounded by walls of laterally alternating patches of high and low wall shear stress. The wall shear stress is imposed as a Neumann boundary condition such that the wall shear stress ratio is fixed at 3 while the lateral spacing s of the uniform-stress patches is varied from 0.39 to 6.28 of the half-channel height . We find that global outer-layer similarity is maintained when s is less than approximately 0.39 while local outer-layer similarity is recovered when s is greater than approximately 6.28 . However, the transition between the two regimes through s≈ is not monotonic owing to the presence of secondary roll motions that extend across the whole cross-section of the flow. Importantly, these secondary roll motions are associated with an amplified skin-friction coefficient relative to both the small- and large- s/ limits. It is found that the relationship between the secondary roll motions and the mean isovels is reversed through this transition from low longitudinal velocity over low stress at small s/ to high longitudinal velocity over low stress at large s/