Palaeoflood chronologies from seven Spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed. These fluvial records were divided in to two sub-sets, namely ...Atlantic (10 ka record) and Mediterranean (3 ka record) river basins, which represent distinct modern hydroclimatic conditions. In Atlantic basins floods result from intense, widespread rainfalls associated with Atlantic frontal systems transported by westerly airflow. Mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems (MCSs) during autumn months. Evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10,750–10,240; 9550–9130; 4820–4440; 2865–2350; 960–790; and 520–290 cal BP. Despite the different flood-producing weather conditions in Atlantic and Mediterranean rivers, the radiocarbon sample clusters overlap and indicate changes in large-scale atmospheric circulation and climatic conditions in the Iberian Peninsula. Comparison with proxy records of mean temperature for the Northern Hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases (e.g. the 2650 yr BP climatic event or AD 1590–1650 period of the Little Ice Age). Radiocarbon dates from aggraded floodplain sediments were clustered at 2710–2320, 2000–1830, and 910–500 cal BP. The first cluster period is in phase with the timing of slackwater deposition, whereas the third (910–500 cal BP) occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records. It is argued that the 910–500 cal BP floodplain aggradation period reflects the first post-Roman evidence of environmental change related to generalised land-use changes at the catchment scale, which produced high sediment load transported to overbank areas during high flows.
Additive manufacturing processes and especially the family of laser powder bed fusion technologies have a great industrial potential since it enables, from metal powder beds, to produce full density ...complex monolithic parts. The high-temperature gradient resulting from the locally concentrated energy input leads to strong temperature fields driving non-negligible residual stress gradients, part deformations and crack formation. Resulting stress and texture gradients arise from the interdependent physical phenomena (metallurgical, thermal, mechanical and fluid mechanics) occurring during the process. Present work focuses on the residual stress being built in an austenitic stainless steel cubical shaped part of 1 cm side, prepared by a laser powder bed fusion process from a gas-atomized metallic powder (from martensitic X40CrMoVN16-2 stainless steel), through a full residual stress tensor mapping achieved thanks to neutron diffraction. Stress analyses incorporate morphological and crystallographic textures, as well as elastic anisotropy. Components of the principal stress tensor display compressive values close to the baseplate that develop into low compression, and a tensile stress state at the subsurface (surrounding thermal history effects). Results also underline the strong impact of matter environment (and thus thermal environment) onto stress gradient magnitude and the complex loading origins of the residual stress.
The mass of a star is the most fundamental parameter for its structure, evolution, and final fate. It is particularly important for any kind of stellar archaeology and characterization of exoplanets. ...There exist a variety of methods in astronomy to estimate or determine it. In this review we present a significant number of such methods, beginning with the most direct and model-independent approach using detached eclipsing binaries. We then move to more indirect and model-dependent methods, such as the quite commonly used isochrone or stellar track fitting. The arrival of quantitative asteroseismology has opened a completely new approach to determine stellar masses and to complement and improve the accuracy of other methods. We include methods for different evolutionary stages, from the pre-main sequence to evolved (super)giants and final remnants. For all methods uncertainties and restrictions will be discussed. We provide lists of altogether more than 200 benchmark stars with relative mass accuracies between
0.3
,
2
%
for the covered mass range of
M
∈
0.1
,
16
M
⊙
,
75
%
of which are stars burning hydrogen in their core and the other
25
%
covering all other evolved stages. We close with a recommendation how to combine various methods to arrive at a “mass-ladder” for stars.
A field platform dedicated to fluorescence measurements (INRA, Avignon, France) was used to monitor the fluorescence emission of a sorghum field during its growing period. The measurements were ...performed continuously at the canopy level, from seeding to maturity. A passive instrument based on three spectrometers was used to monitor the evolution of fluorescence fluxes and vegetation indexes such as Photochemical Reflectance Index (PRI) and Normalized Difference Vegetation Index (NDVI). Fluorescence fluxes were retrieved from radiances, using the filling-in of the atmospheric oxygen absorption bands, at 687 and 760 nm. In parallel, leaf fluorescence spectra, canopy height, and leaf chlorophyll contents were acquired during the growth. Both PRI and NDVI indexes varied with the development of the sorghum field: we observed that NDVI was more sensitive during the early stage of the growth. However, NDVI saturates before the PRI index. Fluorescence fluxes at 687 nm (Fs687) and 760 nm (Fs760) showed an overall increase: Fs687 increased more rapidly at the beginning of growth but trends to saturate while Fs760 still increase. During the growth, the Fs687/Fs760 ratio at the canopy level is found lower than at leaf level. At canopy level, the ratio decreased when the leaf chlorophyll content increases. A decrease was also observed at leaf level with a lower extend. This more important decrease of the fluorescence ratio at canopy level is attributed to a reabsorption of red fluorescence (Fs687) during its transfer through the canopy layers. In the context of forthcoming large-scale remote sensing application, the modification of the leaf level fluorescence emission by the structure of the canopy observed in this article is one of the major issues that must be addressed to interpret the fluorescence signal.
We have previously shown that a mixture of dietary conjugated derivatives of linoleic acid (conjugated linoleic acid, CLA) induces peroxisome proliferator-responsive enzymes and modulates hepatic ...lipid metabolism in vivo. The present studies demonstrate that CLA is a high affinity ligand and activator of peroxisome proliferator-activated receptor alpha (PPARalpha) and induces accumulation of PPAR-responsive mRNAs in a rat hepatoma cell line. Using a scintillation proximity assay (SPA), CLA isomers were shown to be ligands for human PPARalpha with a rank order of potency of (9Z,11E)>(10E,12Z)>(9E,11E)> furan-CLA (IC(50) values from 140 nm to 400 nm). Levels of acyl-CoA oxidase (ACO), liver fatty acid-binding protein (L-FABP), and cytochrome P450IVA1 (CYP4A1) mRNA were induced by CLA in FaO hepatoma cells. Even though linoleate and CLA were incorporated into lipids of hepatoma cells to the same extent, linoleate had little or no effect on ACO, CYP4A1, or L-FABP mRNA. In agreement with its binding potency, (9Z,11E)-CLA was the most efficacious PPARalpha activator in the mouse PPARalpha-GAL4(UAS)(5)-CAT reporter system. These data indicate that CLA is a ligand and activator of PPARalpha and its effects on lipid metabolism may be attributed to transcriptional events associated with this nuclear receptor. Also, (9Z,11E)-CLA is one of the most avid fatty acids yet described as a PPARalpha ligand.
There is an increasing need for diagnostic tools that can assess the crop nitrogen (N) nutrition status during the growth cycle. In addition to the leaf chlorophyll (Chl) content, we proposed here ...the use of the leaf content of polyphenolics (Phen) as a potential indicator of crop N status. Because of their absorption features in the visible and in the UV part of the spectrum, both Chl and Phen can be measured by rapid and non-destructive optical methods. Therefore, we used two leaf-clip devices, the Minolta SPAD-502 for Chl, and the Dualex for Phen. The latter is a prototype (patent pending) that measures the UV absorbance of the leaf epidermis, which is related to the leaf Phen content. Dynamics of Phen and Chl were measured on the last fully developed leaves of two winter wheat cultivars subjected to different levels of N availability, from tillering to flowering, in 2001, 2002 and 2003. Both Phen and Chl contents were found to increase along the leaf, starting from the ligula, regardless of the stage of development. Both variables were highly correlated with the N concentration of leaves. The average Chl content of the leaf increased, and the average Phen content decreased, with the increased application of N to the field, irrespective of the growth stage, the cultivar and the year of experiment. Therefore, both Phen and Chl can be considered as probes of the crop N nutrition status. Still, the relationship between Chl and the nitrogen nutrition index (NNI), used as a reference indicator of N deficiency, was influenced by the growth stage, whereas the year of experiment affected the relationship between Phen and the NNI. We also propose the use of the simple Chl/Phen ratio as an indicator of leaf N content at the canopy level, for future application in precision agriculture. This ratio would alleviate, at least partially, the problem of gradients along leaves, and would even accentuate the differences among levels of crop N deficiencies because of the Chl and Phen inverse dependence on the crop N nutrition status.
Context. Rotational splittings are currently measured for several main sequence stars and a large number of red giants with the space mission Kepler. This will provide stringent constraints on ...rotation profiles. Aims. Our aim is to obtain seismic constraints on the internal transport and surface loss of the angular momentum of oscillating solar-like stars. To this end, we study the evolution of rotational splittings from the pre-main sequence to the red-giant branch for stochastically excited oscillation modes. Methods. We modified the evolutionary code CESAM2K to take rotationally induced transport in radiative zones into account. Linear rotational splittings were computed for a sequence of 1.3 M sub(middot in circle) models. Rotation profiles were derived from our evolutionary models and eigenfunctions from linear adiabatic oscillation calculations. Results. We find that transport by meridional circulation and shear turbulence yields far too high a core rotation rate for red-giant models compared with recent seismic observations. We discuss several uncertainties in the physical description of stars that could have an impact on the rotation profiles. For instance, we find that the Goldreich-Schubert-Fricke instability does not extract enough angular momentum from the core to account for the discrepancy. In contrast, an increase of the horizontal turbulent viscosity by 2 orders of magnitude is able to significantly decrease the central rotation rate on the red-giant branch. Conclusions. Our results indicate that it is possible that the prescription for the horizontal turbulent viscosity largely underestimates its actual value or else a mechanism not included in current stellar models of low mass stars is needed to slow down the rotation in the radiative core of red-giant stars.
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