Search results for "Generation"

Evolutionary ecology of the trans-generational immune priming in an insect

2012

Trans-generational immune priming (TGIP) is defined as the plastic enhancement of offspring's immunocompetence following an immune challenge of the females of the parental generation. In vertebrates, this phenomenon is well described, and is achieved by the maternal transfer of antibodies. In invertebrates however, it has only recently been described. Since invertebrates do not possess antibodies, the mechanism of this transmission remains unknown. If the offspring is exposed to the maternal infection, an elevated immunocompetence can help it cope better with it. Nonetheless, apart from this benefit, several cues indicate that the TGIP bears some fitness costs for individuals. The evolution…

Cholestérol-24S-hydroxylase (CYP46A1) et homéostasie du cholestérol dans la rétine en conditions physiologiques et pathologiques

2012

Cholesterol is the major sterol found in the retina. In its free form, cholesterol is present in all cell layers of the retina, whereas cholesteryl esters mainly accumulate at the basement of the retinal pigment epithelium. The intrinsic capacity of the retina to synthetize cholesterol appears limited. Some extra-retinal pathways actively participate to cholesterol uptake to the retina. Müller glial cells may contribute to cholesterol supply to retinal neurons, especially for synaptic formation. Cholesterol accumulation or conversely deficiency have deleterious consequences on neuron survival. Maintaining the equilibrium between cholesterol supply and neosynthesis in the one hand and choles…

Microglia and α-synuclein implication in Parkinson's disease

2011

Age-related neurodegenerative disorders like Parkinson’s disease take an enormous toll on individuals and on society. Despite extensive efforts, Parkinson’s disease remains incurable and only very limited treatments exist. Indeed, Parkinson’s pathogenesis is still not clear and research on its molecular mechanisms is ongoing. In this study, we focused our interest on two abnormal events occurring in Parkinson’s patients, namely α-synuclein aggregation and microglial activation. We first investigated α-synuclein and its abnormal polymerisation. For this purpose, we developed novel methods, which allowed the in vitro production of different types of α-synuclein oligomers. Using highly sensiti…

Temporal dynamics of soil bacterial communities at a landscape scale: dependence to soil properties and agricultural practices.

2019

International audience; Soil microbial communities play a major role in agricultural functions and are an efficient indicator to evaluate the impacts of agricultural practices on soils. Studies on wide scales ranging from landscape to countries demonstrated that soil microbial communities were heterogeneously distributed in space under the dependence of soil properties (e.g. pH, soil texture, Organic matter Content) and agricultural practices. However, temporal dynamics of soil microbial communities at a landscape scale still need to be documented in order to go further in evaluating the sustainability of agricultural practices. In this extensive monitoring study, we focused on landscape dy…

What are the biological determinants of regeneration of perennial weeds? Effect of fragment weight and bud number on the regrowth of five perennial w…

2022

Perennial weeds have become an increasing problem with the reduction of herbicide use andtillage. Because of their capacity to regenerate from vegetative organs, such as roots andrhizomes, they must be controlled with different management techniques than annuals. Todate, few studies exist on this topic and farmers often lack solutions to control perennials intheir cropping systems. Management strategies must focus on the depletion of theregenerative organ reserves to hamper the production of new shoots. However, there is aneed for a better understanding of below-ground organs physiology and the determiningfactors of their regrowth capacities.Our aim was to assess the number of shoots and th…

The school careers of immigrant's children in comparative : North African second generation in France and Mexican second generation in the US

2008

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Residual Phase Noise Measurement of Optical Second Harmonic Generation in PPLN Waveguides

2017

We report on the characterization, including residual phase noise and fractional frequency instability, of fiber-coupled PPLN non-linear crystals. These components are devoted to frequency doubling 871 nm light from an extended-cavity diode laser to produce a 435.5 nm beam, corresponding to the ytterbium ion electric quadrupole clock transition. We measure doubling efficiencies of up to 117.5 %/W. Using a Mach-Zehnder interferometer and an original noise rejection technique, the residual phase noise of the doublers is estimated to be lower than ${\rm -35\, dBrad^2/Hz}$ at 1 Hz, making these modules compatible with up-to-date optical clocks and ultra-stable cavities. The influence of externa…

Comparison of the generation II with IV heterogeneous Ziegler-Natta catalysts used in propylene polymerizations

1998

An unsupported TiCl3-based catalyst (generation II), modified with n-butyl ether and AlEt2Cl3, was compared with a MgCl2/dibutyl phthalate/AlEt3/cyclohexylmethyldimethoxysilane catalyst system (generation IV) in propylene polymerizations. The latter (magnesium-supported) was fund to be more than 20 times as active as the former and more stereospecific, but to yield PP with a lower molecular weight (Table 2). The kinetics of the polymerizations studied with either of the catalyst, and involving the determination of concentrations of active sites [C0*] and elementary reaction rate constants (Table 4) based on earlier kinetic models, showed the C0*-values in the magnesium-supported catalyst to…

Tackling Performance Challenges in Organic Photovoltaics: An Overview about Compatibilizers

2020

Organic Photovoltaics (OPVs) based on Bulk Heterojunction (BHJ) blends are a mature technology. Having started their intensive development two decades ago, their low cost, processability and flexibility rapidly funneled the interest of the scientific community, searching for new solutions to expand solar photovoltaics market and promote sustainable development. However, their robust implementation is hampered by some issues, concerning the choice of the donor/acceptor materials, the device thermal/photo-stability, and, last but not least, their morphology. Indeed, the morphological profile of BHJs has a strong impact over charge generation, collection, and recombination processes; control o…

Adipose stem cells on the basis of tumor transformation

Mesenchymal stem cells thanks to their differentiated multipotent ability are considered the most promising candidate for tissue engineering and regenerative medicine. The source of mesenchymal stem cells up to about 20 years was represented by the bone marrow, but due to their limited amount of cells together with a very invasive and painfull surgical treatment, poorly accepted by patients, has led the scientific community to investigate an alternative mesenchymal stem cells source with similar properties. In particular, the adipose tissue has attracted the greatest interest thanks to its relative abundance, the easy of availability and the large amounts of mesenchymal stem cells which are…