610,283 research outputs found
Strong and Confined Acids Enable a Catalytic Asymmetric Nazarov Cyclization of Simple Divinyl Ketones
We report a catalytic asymmetric Nazarov cyclization of simple, acylic, alkyl-substituted divinyl ketones using our recently disclosed strong and confined imidodiphosphorimidate Brønsted acids. The corresponding monocyclic cyclopentenones are formed in good yields and excellent regio-, diastereo-, and enantioselectivities. Further, the chemical utility of the obtained enantiopure cyclopentenones is demonstrated
Lattice Simulation of Nuclear Multifragmentation
Motivated by the decade-long debate over the issue of criticality supposedly
observed in nuclear multifragmentation, we propose a dynamical lattice model to
simulate the phenomenon. Its Ising Hamiltonian mimics a short range attractive
interaction which competes with a thermal-like dissipative process. The results
here presented, generated through an event-by-event analysis, are in agreement
with both experiment and those produced by a percolative (non-dynamical) model.Comment: 8 pages, 3 figure
Contractions, Hopf algebra extensions and cov. differential calculus
We re-examine all the contractions related with the
deformed algebra and study the consequences that the contraction process has
for their structure. We also show using
as an example that, as in the undeformed case, the contraction may generate
Hopf algebra cohomology. We shall show that most of the different Hopf algebra
deformations obtained have a bicrossproduct or a cocycle bicrossproduct
structure, for which we shall also give their dual `group' versions. The
bicovariant differential calculi on the deformed spaces associated with the
contracted algebras and the requirements for their existence are examined as
well.Comment: TeX file, 25 pages. Macros are include
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