6,055 research outputs found
K-Theoretic Duality for Hyperbolic Dynamical Systems
The K-theoretic analog of Spanier-Whitehead duality for noncommutative
C*-algebras is shown to hold for the Ruelle algebras associated to irreducible
Smale spaces. This had previously been proved only for shifts of finite type.
Implications of this result as well as relations to the Baum-Connes conjecture
and other topics are also considered.Comment: 36 page
The Buoyant Behavior of Viral and Bacterial DNA in Alkaline CsCl
In equilibrium density gradient centrifugation, the banding polymer species is electrically neutral. The banding species for a negative polyelectrolyte with a polyanion
P_(n)^(-z)n (where n is the degree of polymerization, and z the titration charge per monomer unit) in a CsCl salt gradient is CS_(zn)P_n. If the ion P_(n)^(-z)n is itself a weak acid, it may be titrated to the state P_(n)^(-(Zn+y)) by CsOH; the banding species is then Cs_(zn+y)P_n. Because of the large mass and high effective "density" of a Cs^+ ion, it is to be expected that the buoyant density in a CsCl gradient of a polymer acid will be increased by such a partial alkaline titration with CsOH. This expectation has been confirmed for polyglutamic acid (where z = 0 at low pH). The guanine and thymine monomer units of DNA are weak acids. The present communication is concerned with the increase in buoyant density of DNA in alkaline CsCl solutions. It is well known that the guanine and thymine protons are more readily titrated in denatured DNA than in native DNA. We find that the buoyant density of denatured DNA and of single strand Ï•X-174 DNA gradually increases as the pH of the solution is increased beyond pH 9.8. The density of native DNA is not affected until a critical pH > 11 is reached, where the DNA abruptly denatures and increases in density. Similar increases in buoyant density have been observed independently by Baldwin and Shooter in their studies of 5BU[overbar]-substituted DNA's in alkaline solutions
A New Infinite Class of Sasaki-Einstein Manifolds
We show that for every positive curvature Kahler-Einstein manifold in
dimension 2n there is a countably infinite class of associated Sasaki-Einstein
manifolds X_{2n+3} in dimension 2n+3. When n=1 we recover a recently discovered
family of supersymmetric AdS_5 x X_5 solutions of type IIB string theory, while
when n=2 we obtain new supersymmetric AdS_4 x X_7 solutions of D=11
supergravity. Both are expected to provide new supergravity duals of
superconformal field theories.Comment: 12 pages. v2: minor typos corrected, comment on generalisation to
product base manifold
Pathways Across the Valley of Death: Novel Intellectual Property Strategies for Accelerated Drug Discovery
Drug discovery is stagnating. Government agencies, industry analysts, and industry scientists have all noted that, despite significant increases in pharmaceutical R&D funding, the production of fundamentally new drugs - particularly drugs that work on new biological pathways and proteins - remains disappointingly low. To some extent, pharmaceutical firms are already embracing the prescription of new, more collaborative R&D organizational models suggested by industry analysts. In this Article, we build on collaborative strategies that firms are already employing by proposing a novel public-private collaboration that would help move upstream academic research across the valley of death that separates upstream research from downstream drug candidates. By exchanging trade secrecy for contract-based collaboration, our proposal would both protect intellectual property rights and enable many more researchers to search for potential drug candidates
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