École Polytechnique

About: École Polytechnique is a education organization based out in Palaiseau, France. It is known for research contribution in the topics: Laser & Plasma. The organization has 18995 authors who have published 39265 publications receiving 1225163 citations. The organization is also known as: Ecole Polytechnique & Polytechnique.

Hitchin functionals in N = 2 supergravity

Abstract: We consider type II string theory in space-time backgrounds which admit eight supercharges. Such backgrounds are characterized by the existence of a (generically non-integrable) generalized SU(3) × SU(3) structure. We demonstrate how the corresponding ten-dimensional supergravity theories can in part be rewritten using generalised O(6,6)-covariant fields, in a form that strongly resembles that of four-dimensional N = 2 supergravity, and precisely coincides with such after an appropriate Kaluza-Klein reduction. Specifically we demonstrate that the NS sector admits a special Kahler geometry with Kahler potentials given by the Hitchin functionals. Furthermore we explicitly compute the N = 2 version of the superpotential from the transformation law of the gravitinos, and find its N = 1 counterpart.

Vascularized bone tissue engineering: approaches for potential improvement.

Abstract: Significant advances have been made in bone tissue engineering (TE) in the past decade. However, classical bone TE strategies have been hampered mainly due to the lack of vascularization within the engineered bone constructs, resulting in poor implant survival and integration. In an effort toward clinical success of engineered constructs, new TE concepts have arisen to develop bone substitutes that potentially mimic native bone tissue structure and function. Large tissue replacements have failed in the past due to the slow penetration of the host vasculature, leading to necrosis at the central region of the engineered tissues. For this reason, multiple microscale strategies have been developed to induce and incorporate vascular networks within engineered bone constructs before implantation in order to achieve successful integration with the host tissue. Previous attempts to engineer vascularized bone tissue only focused on the effect of a single component among the three main components of TE (scaffold, cells, or signaling cues) and have only achieved limited success. However, with efforts to improve the engineered bone tissue substitutes, bone TE approaches have become more complex by combining multiple strategies simultaneously. The driving force behind combining various TE strategies is to produce bone replacements that more closely recapitulate human physiology. Here, we review and discuss the limitations of current bone TE approaches and possible strategies to improve vascularization in bone tissue substitutes.

The Effect of R&D Subsidies on Private R&D

Abstract: This paper investigates the relationship between government support for R&D and R&D expenditure financed privately by firms using a comprehensive plant level data set for the manufacturing sector in the Republic of Ireland. We find that for domestic plants small grants serve to increase private R&D spending, while too large a grant may crowd out private financing of R&D. In contrast, evidence for foreign establishments suggests that grant provision causes neither additionality nor crowding out effects of private R&D financing, regardless of the size of the subsidy.