University of Nice Sophia Antipolis

About: University of Nice Sophia Antipolis is a education organization based out in Nice, France. It is known for research contribution in the topics: Population & Stars. The organization has 10291 authors who have published 19964 publications receiving 680762 citations. The organization is also known as: UNS & University of Nice-Sophia Antipolis.

Sestrin2 integrates Akt and mTOR signaling to protect cells against energetic stress-induced death

Abstract: The phosphoinositide-3 kinase/Akt (PI3K/Akt) pathway has a central role in cancer cell metabolism and proliferation. More importantly, it is one of the cardinal pro-survival pathways mediating resistance to apoptosis. The role of Akt in response to an energetic stress is presently unclear. Here, we show that Sestrin2 (Sesn2), also known as Hi95, a p53 target gene that protects cells against oxidative and genotoxic stresses, participates in the protective role of Akt in response to an energetic stress induced by 2-deoxyglucose (2-DG). Sesn2 is upregulated in response to an energetic stress such as 2-DG and metformin, and mediates the inhibition of mammalian target of rapamycin (mTOR), the major cellular regulator of energy metabolism. The increase of Sesn2 is independent of p53 but requires the anti-apoptotic pathway, PI3K/Akt. Inhibition of Akt, as well as loss of Sesn2, sensitizes cells to 2-DG-induced apoptosis. In addition, the rescue of Sesn2 partially reverses the pro-apoptotic effects of 2-DG. In conclusion, we identify Sesn2 as a new energetic stress sensor, which appears to be protective against energetic stress-induced apoptosis that integrates the pro-survival function of Akt and the negative regulation of mTOR.

Splitting of Operations, Manin Products, and Rota–Baxter Operators

Abstract: This paper provides a general operadic definition for the notion of splitting the operations of algebraic structures. This construction is proved to be equivalent to some Manin products of operads in the case of quadratic operads and it is shown to be closely related to Rota–Baxter operators. Hence, it gives a new effective way to compute Manin black products. Finally, this allows us to describe the algebraic structure of square matrices with coefficients in algebras of certain types. Many examples illustrate this text, including an example of nonquadratic algebras with Jordan algebras.

A primordial star in the heart of the Lion

Abstract: Context: The discovery and chemical analysis of extremely metal-poor stars permit a better understanding of the star formation of the first generation of stars and of the Universe emerging from the Big Bang. aims: We report the study of a primordial star situated in the centre of the constellation Leo (SDSS J102915+172027). method: The star, selected from the low resolution-spectrum of the Sloan Digital Sky Survey, was observed at intermediate (with X-Shooter at VLT) and at high spectral resolution (with UVES at VLT). The stellar parameters were derived from the photometry. The standard spectroscopic analysis based on 1D ATLAS models was completed by applying 3D and non-LTE corrections. results: An iron abundance of [Fe/H]=--4.89 makes SDSS J102915+172927 one of the lowest [Fe/H] stars known. However, the absence of measurable C and N enhancements indicates that it has the lowest metallicity, Z<= 7.40x10^{-7} (metal-mass fraction), ever detected. No oxygen measurement was possible. conclusions: The discovery of SDSS J102915+172927 highlights that low-mass star formation occurred at metallicities lower than previously assumed. Even lower metallicity stars may yet be discovered, with a chemical composition closer to the composition of the primordial gas and of the first supernovae.

Optical-Flow Estimation while Preserving Its Discontinuities: A Variational Approach

Abstract: This paper describes a variational approach devised for the purpose of estimating optical flow from a sequence of images with the constraint to preserve the flow discontinuities. This problem is set as a regularization and minimization of a non quadratic functional. The Tikhonov quadratic regularization term usually used to recover smooth solution is replaced by a particular function of the gradient flow specifically derived to allow flow discontinuities formation in the solution. Conditions to be fulfilled by this specific regularizing term, to preserve discontinuities and insure stability of the regularization problem, are also derived. To minimize this non quadratic functional, two different methods have been investigated. The first one is an iterative scheme to solve the associated non-linear Euler-Lagrange equations. The second solution introduces dual variables so that the minimization problem becomes a quadratic or a convex functional minimization problem. Promising experimental results on synthetic and real image sequences will illustrate the capabilities of this approach.