Coordination of pertechnetate [TcO4]- to actinides

The ability of [TcO(4)](-) to coordinate directly to tetra- and hexa-valent actinides in the presence of organic P[double bond, length as m-dash]O ligands is confirmed in the crystallographically characterised complexes [UO(2)(TcO(4))(2)(Ph(3)PO)(3)] and [Th(TcO(4))(4)((n)Bu(3)PO)(4)].     

An in situ study of the t-butyllithium initiated polymerization of butadiene in d-heptane via small angle neutron scattering and 1H-NMR

We present a combined 1H-NMR and small angle neutron scattering in situ study of the anionic polymerization of butadiene using t-butyllithium as the initiator. Both initiation and propagation phases were explored. This combined approach allows the structural and kinetic characteristics to be accessed and cross compared. The use of the D22 instrument (ILL Grenoble) permits the attainment of Q approximately equal to 2 x 10(-3) A. This, in turn, led to the identification of coexisting large-scale and smaller aggregates during all stages of the polymerization. The smaller aggregates contain most of the reacted monomers. Their structure changes from high functionality wormlike chains at early stages of the reaction to starlike aggregates where the crossover occurs at a degree of polymerization of approximately equal to 40. The initiation event involved these small, high functionality (approximately equal to 120) aggregates that apparently consisted of cross-associated t-butyllithium with the newly formed allylic-lithium head groups. As the initiation event progressed the initiation rate increased while the functionality of these small aggregates decreased and their size increased. Propagation, in the absence of initiation, was found to have a rate constant that was molecular weight dependent. At approximately 11 kg/mol the measured polymerization rate was found to increase while no further structural changes were seen.     

Heterobimetallic lithium alkyltriimido aluminate cages containing the [R'Al(NR)3]4- tetraanion (R' = Bu(n), Et; R = 2-OMeC6H4)

Attempted metallation of a triamidoaluminane gives a complex containing the [R'Al(NR)3]4- anion whose formal tetranegative charge is the highest charge observed crystallographically for a simple mononuclear imido main group anion system.     

Highway noise barrier perceived benefit

A laboratory experiment was performed in which 82 subjects judged the benefit of a noise barrier by listening to tape recordings of before-barrier and after-barrier traffic noise. These perceived benefit judgments were related by regression analysis to the barrier attenuation, the before-barrier traffic sound level, and a music background level, all of which were varied over the course of the experiment. Prediction equations were developed for barrier benefit in terms of these sound levels, their purpose being to provide a model for barrier benefit that can be used in barrier site selection and design. An unexpected finding was that barrier benefit was highest when before-barrier sound levels were lowest: i.e., subjects preferred a noise barrier that solved a moderate noise problem over an equally-attenuating barrier that only partially solved a more severe noise problem.     

Characteristics of trimuon events observed in high-energy neutrino interactions

The properties of 76 neutrino-initiated μ^?μ^?μ⁺ events observed in the CDHS detector in the 350 GeV and 400 GeV wide-band beams at CERN are discussed. For neutrino energies 30 GeV and muon momenta ?4.5 GeV, the average trimuon rate is (3.0 ± 0.4) × 10^?5 of the single-muon event rate. The experimental distributions are compared with predictions from various models. The data cannot be understood in terms of either heavy-lepton or heavy-quark cascades; no evidence is found for such processes and upper limits for the two possibilities are established. The data can be understood in terms of the normal charged-current process with the additional production of a muon pair by both hadronic and electromagnetic processes.     

Historiographic vices I. Logical attribution

In the first of this series is considered the fallacious attribution of results that are logical antecedents or consequents of established knowledge.