152 research outputs found
Modified gravity without dark matter
On an empirical level, the most successful alternative to dark matter in
bound gravitational systems is the modified Newtonian dynamics, or MOND,
proposed by Milgrom. Here I discuss the attempts to formulate MOND as a
modification of General Relativity. I begin with a summary of the
phenomenological successes of MOND and then discuss the various covariant
theories that have been proposed as a basis for the idea. I show why these
proposals have led inevitably to a multi-field theory. I describe in some
detail TeVeS, the tensor-vector-scalar theory proposed by Bekenstein, and
discuss its successes and shortcomings. This lecture is primarily pedagogical
and directed to those with some, but not a deep, background in General
RelativityComment: 28 pages, 10 figures, lecture given at Third Aegean Summer School,
The Invisible Universe: Dark Matter and Dark Energy, minor errors corrected,
references update
Cohesin Releases DNA through Asymmetric ATPase-Driven Ring Opening
Cohesin stably holds together the sister chromatids from S phase until mitosis. To do so, cohesin must be protected against its cellular antagonist Wapl. Eco1 acetylates cohesin's Smc3 subunit, which locks together the sister DNAs. We used yeast genetics to dissect how Wapl drives cohesin from chromatin and identified mutants of cohesin that are impaired in ATPase activity but remarkably confer robust cohesion that bypasses the need for the cohesin protectors Eco1 in yeast and Sororin in human cells. We uncover a functional asymmetry within the heart of cohesin's highly conserved ABC-like ATPase machinery and find that both ATPase sites contribute to DNA loading, whereas DNA release is controlled specifically by one site. We propose that Smc3 acetylation locks cohesin rings around the sister chromatids by counteracting an activity associated with one of cohesin's two ATPase sites. Tight regulation of DNA entrapment and release by the cohesin complex is crucial for its multiple cellular functions. Elbatsh et al. find that cohesin's release from DNA requires an activity associated with one of its ATPase sites, whereas both sites control cohesin's loading onto DNA
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METAL COORDINATION CHEMISTRY: REMOVAL AND RECOVERY OF METAL COMPOUNDS FROM HEAVY CRUDE AND SHALE OIL WITH MULTIDENTATE LIGANDS
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Homogeneous Catalytic Hydrogenation of Aromatic Hydrocarbons and Heteroaromatic Nitrogen Compounds: Synthetic and Mechanistic Aspects
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HOMOGENEOUS CATALYTIC HYDROGENATION. 3. SELECTIVE REDUCTIONS OF POLYNUCLEAR AROMATIC AND HETEROAROMATIC NITROGEN COMPOUNDS CATALYZED BY TRANSITION-METAL CARBONYL HYDRIDES.
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METAL COORDINATION CHEMISTRY: REMOVAL AND RECOVERY OF METAL COMPOUNDS FROM HEAVY CRUDE AND SHALE OILS WITH MULTIDENTATE LIGANDS. ANNUAL REPORT -OCT. 1981 TO OCT. 1982.
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ORGANOMETALLIC GEOCHEMISTRY. 1. ISOLATION AND IDENTIFICATION OF ORGANOARSENIC COMPOUNDS FROM GREEN RIVER FORMATION OIL SHALE.
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ORGANOMETALLIC GEOCHEMISTRY. ISOLATION AND IDENTIFICATION OF ORGANOARSENIC AND INORGANIC ARSENIC COMPOUNDS FROM GREEN RIVER FORMATION OIL SHALE
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BIOMIMETIC CATLAYSIS: HYDROXYLATION OF C[SUB]2, C[SUB]3, AND CYCLOC[SUB]6 HYDROCARBONS BY MANGANESE PORPHYRIN AND NON-PORPHYRIN CATALYSTS IN THE PRESENCE OF MONOOXYGEN TRANSFER REAGENTS
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