Structural infrasound from a barge collision with the Mississippi river bridge.

The Mississippi River Bridge in Vicksburg, Mississippi, is a seven-span cantilever bridge that is 1033 m long by 20.9 m wide and is part of the Interstate-20 corridor. On March 23, 2011, at approximately 14:30 CST, a barge moving downstream struck a pier of the bridge. An infrasound array located at the U.S. Army Engineer Research and Development Center (ERDC) detected the impact. Finite Element (FE) models were developed to investigate the structural behavior of the bridge due to the impact. The FE models identified events within the infrasound record that were possibly produced by the different modes of vibration of the bridge structure. The emerging technology of structural infrasound monitoring and the potential for using infrasound as a forensic tool is demonstrated with the results of the bridge-barge collision event and capability of deployment in the future.

Visible-light hypervalent iodide carboxylate photo(trifluoro)methylations and controlled radical polymerization of fluorinated alkenes.

IFAB-ulous trifluoromethylation: (CX3COO)2I(III) h (X=F, H) and (CH3COO)3I(V)(C6H4COO) are introduced as CX3·/CX3I precursors for metal-free, visible-light, radical (trifluoro)(iodo)methylations of alkenes, illustrated by their use as photoinitiators for the controlled radical polymerization of vinylidene fluoride with external (I(CF2)6I) and in situ generated (CF3I) iodine chain transfer agents, and for block copolymer synthesis.

Mild-temperature Mn2(CO)10-photomediated controlled radical polymerization of vinylidene fluoride and synthesis of well-defined poly(vinylidene fluoride) block copolymers.

By contrast to typical high-temperature (100-250 °C) telo-/polymerizations of gaseous fluorinated monomers, carried out in high-pressure metal reactors, the visible light, Mn(2)(CO)(10)-photomediated initiation of vinylidene fluoride (bp = -83 °C) polymerization occurs readily from a variety of alkyl, semifluorinated, and perfluorinated halides at 40 °C, in low-pressure glass tubes and in a variety of solvents, including water and alkyl carbonates. Perfluorinated alkyl iodide initiators also induce a controlled radical polymerization via iodine degenerative transfer (IDT). While IDT proceeds with accumulation of the less reactive P(m)-CF(2)-CH(2)-I vs the P(n)-CH(2)-CF(2)-I chain ends, Mn(2)(CO)(10) enables their subsequent quantitative activation toward the synthesis of well-defined poly(vinylidene fluoride) block copolymers with a variety of other monomers.