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Search Results: 1 - 10 of 3822 matches for " Clande Cohen-Tannoudji "
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Atom interferometry and the Einstein equivalence principle
Peter Wolf,Luc Blanchet,Christian J. Bordé,Serge Reynaud,Christophe Salomon,Clande Cohen-Tannoudji
Physics , 2011,
Abstract: The computation of the phase shift in a symmetric atom interferometer in the presence of a gravitational field is reviewed. The difference of action-phase integrals between the two paths of the interferometer is zero for any Lagrangian which is at most quadratic in position and velocity. We emphasize that in a large class of theories of gravity the atom interferometer permits a test of the weak version of the equivalence principle (or universality of free fall) by comparing the acceleration of atoms with that of ordinary bodies, but is insensitive to that aspect of the equivalence principle known as the gravitational redshift or universality of clock rates.
Universal Constants, Standard Models and Fundamental Metrology
G. Cohen-Tannoudji
Physics , 2009, DOI: 10.1140/epjst/e2009-01038-2
Abstract: Taking into account four universal constants, namely the Planck's constant $h$, the velocity of light $c$, the constant of gravitation $G$ and the Boltzmann's constant $k$ leads to structuring theoretical physics in terms of three theories each taking into account a pair of constants: the quantum theory of fields ($h$ and $c$), the general theory of relativity ($c$ and $G$) and quantum statistics ($h$ and $k$). These three theories are not yet unified but, together, they underlie the standard models that allow a satisfactory phenomenological description of all experimental or observational data, in particle physics and in cosmology and they provide, through the modern interpretation of quantum physics, fundamental metrology with a reliable theoretical basis.
Dark matter, Mach's ether and the QCD vacuum
Gilles Cohen-Tannoudji
Physics , 2015,
Abstract: Here is proposed the idea of linking the dark matter issue, (considered as a major problem of contemporary research in physics) with two other open theoretical questions, one, almost centenary about the existence of an unavoidable ether in general relativity agreeing with the Mach's principle, and one more recent about the properties of the quantum vacuum of the quantum field theory of strong interactions, QuantumChromodynamics (QCD). According to this idea, on the one hand, dark matter and dark energy that, according to the current standard model of cosmology represent about 95% of the universe content, can be considered as two distinct forms of the Mach's ether, and, on the other hand, dark matter, as a perfect fluid emerging from the QCD vacuum could be modeled as a Bose Einstein condensate.
Genome engineering via homologous recombination in mouse embryonic stem (ES) cells: an amazingly versatile tool for the study of mammalian biology
BABINET, CHARLES;COHEN-TANNOUDJI, MICHEL;
Anais da Academia Brasileira de Ciências , 2001, DOI: 10.1590/S0001-37652001000300007
Abstract: the ability to introduce genetic modifications in the germ line of complex organisms has been a long-standing goal of those who study developmental biology. in this regard, the mouse, a favorite model for the study of the mammals, is unique: indeed not only is it possible since the late seventies, to add genes to the mouse genome like in several other complex organisms but also to perform gene replacement and modification. this has been made possible via two technological breakthroughs: 1) the isolation and culture of embryonic stem cells (es), which have the unique ability to colonize all the tissues of an host embryo including its germ line; 2) the development of methods allowing homologous recombination between an incoming dna and its cognate chromosomal sequence (gene ''targeting''). as a result, it has become possible to create mice bearing null mutations in any cloned gene (knock-out mice). such a possibility has revolutionized the genetic approach of almost all aspects of the biology of the mouse. in recent years, the scope of gene targeting has been widened even more, due to the refinement of the knock-out technology: other types of genetic modifications may now be created, including subtle mutations (point mutations, micro deletions or insertions, etc.) and chromosomal rearrangements such as large deletions, duplications and translocations. finally, methods have been devised which permit the creation of conditional mutations, allowing the study of gene function throughout the life of an animal, when gene inactivation entails embryonic lethality. in this paper, we present an overview of the methods and scenarios used for the programmed modification of mouse genome, and we underline their enormous interest for the study of mammalian biology.
Genome engineering via homologous recombination in mouse embryonic stem (ES) cells: an amazingly versatile tool for the study of mammalian biology
BABINET CHARLES,COHEN-TANNOUDJI MICHEL
Anais da Academia Brasileira de Ciências , 2001,
Abstract: The ability to introduce genetic modifications in the germ line of complex organisms has been a long-standing goal of those who study developmental biology. In this regard, the mouse, a favorite model for the study of the mammals, is unique: indeed not only is it possible since the late seventies, to add genes to the mouse genome like in several other complex organisms but also to perform gene replacement and modification. This has been made possible via two technological breakthroughs: 1) the isolation and culture of embryonic stem cells (ES), which have the unique ability to colonize all the tissues of an host embryo including its germ line; 2) the development of methods allowing homologous recombination between an incoming DNA and its cognate chromosomal sequence (gene ''targeting''). As a result, it has become possible to create mice bearing null mutations in any cloned gene (knock-out mice). Such a possibility has revolutionized the genetic approach of almost all aspects of the biology of the mouse. In recent years, the scope of gene targeting has been widened even more, due to the refinement of the knock-out technology: other types of genetic modifications may now be created, including subtle mutations (point mutations, micro deletions or insertions, etc.) and chromosomal rearrangements such as large deletions, duplications and translocations. Finally, methods have been devised which permit the creation of conditional mutations, allowing the study of gene function throughout the life of an animal, when gene inactivation entails embryonic lethality. In this paper, we present an overview of the methods and scenarios used for the programmed modification of mouse genome, and we underline their enormous interest for the study of mammalian biology.
Erratum to "Genome engineering via homologous recombination in mouse embryonic stem (ES) cells: an amazingly versatile tool for the study of mammalian biology" [An Acad Bras Cienc 73(2001): 365-383]
BABINET CHARLES,COHEN-TANNOUDJI MICHEL
Anais da Academia Brasileira de Ciências , 2001,
Abstract:
An Effective Strong Gravity induced by QCD
V. Brindejonc,G. Cohen-Tannoudji
Physics , 1995, DOI: 10.1142/S0217732395001836
Abstract: We show that, when quantized on a curved ``intra-hadronic background'', QCD induces an effective pseudo gravitational interaction with gravitational and cosmological constants in the GeV range.
A New Scientific Revolution at the Horizon?
Gilles Cohen-Tannoudji,Sylvain Hudlet
Physics , 2011,
Abstract: At this beginning of the 21st century, the situation of physics is not without analogy with that which prevailed a hundred years ago, with the outset of the double scientific revolution of relativity and quanta. On the one hand, recent progress of observational cosmology makes think that one has discovered a new universal constant, perhaps as fundamental as the velocity of light or the Planck's constant, the cosmological constant, which could explain the acceleration of the expansion of the universe. On the other hand, just like the efforts of Planck and Einstein to reconcile thermodynamics and the electromagnetic theory of light led to the operational beginning of quantum physics, the unexpected discovery of bonds between thermodynamics and general relativity makes to foresee new concepts, perhaps heralding a new scientific revolution, like that of holography and leads to consider a "thermodynamic route towards quantum cosmology." We will discuss the possible implications of these observational and theoretical developments.
Nobel 2012: trapped ions and photons
Brune Michel,Raimond Jean-Michel,Cohen-Tannoudji Claude
Europhysics News , 2012, DOI: 10.1051/epn/2012601
Abstract:
Nuclear mRNA Degradation Pathway(s) Are Implicated in Xist Regulation and X Chromosome Inactivation
Constance Ciaudo,Agnès Bourdet,Michel Cohen-Tannoudji,Harry C Dietz,Claire Rougeulle,Philip Avner
PLOS Genetics , 2006, DOI: 10.1371/journal.pgen.0020094
Abstract: A critical step in X-chromosome inactivation (XCI), which results in the dosage compensation of X-linked gene expression in mammals, is the coating of the presumptive inactive X chromosome by the large noncoding Xist RNA, which then leads to the recruitment of other factors essential for the heterochromatinisation of the inactive X and its transcriptional silencing. In an approach aimed at identifying genes implicated in the X-inactivation process by comparative transcriptional profiling of female and male mouse gastrula, we identified the Eif1 gene involved in translation initiation and RNA degradation. We show here that female embryonic stem cell lines, silenced by RNA interference for the Eif1 gene, are unable to form Xist RNA domains upon differentiation and fail to undergo X-inactivation. To probe further an effect involving RNA degradation pathways, the inhibition by RNA interference of Rent1, a factor essential for nonsense-mediated decay and Exosc10, a specific nuclear component of the exosome, was analysed and shown to similarly impair Xist upregulation and XCI. In Eif1-, Rent1-, and Exosc10-interfered clones, Xist spliced form(s) are strongly downregulated, while the levels of unspliced form(s) of Xist and the stability of Xist RNA remain comparable to that of the control cell lines. Our data suggests a role for mRNA nuclear degradation pathways in the critical regulation of spliced Xist mRNA levels and the onset of the X-inactivation process.
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