2-carbethoxy-1,3-butadiene irontricarbonyl : chemical transformations and reactivity of the corresponding free dienes.

Chemical transformations on the 2-carbethoxy-1,3-butadiene irontricarbonyl complex were performed. The dienic and dienophilic reactivities of the corresponding free dienes are studied.     

Uptake of short half-life radionuclides, 28Mg, 43K and 47Ca, in carrot studied by the multitracer technique: Feasibility of utilization of the radionuclides in environmental research

We investigated successfully the uptake of the radionuclides with short half-lives, such as ²⁴Na, ²⁸Mg, ⁴³K and ⁴⁷Ca, and the effect of stable Ca on their uptake in carrot (Daucas carotacv. U.S. harumakigosun) by the multitracer technique. These radionuclides were produced by a fragmentation reaction of Ti in a 135 MeV/nucleon ¹²C beam accelerated by the RIKEN Ring Cyclotron. This study shows that these radionuclides in a multitracer can be utilized in environmental research.     

Easily accessible and robust olefin-metathesis catalysts based on ruthenium vinylidene complexes

Nine mixed ligand ruthenium(II) vinylidene complexes with the general formula: [RuCl₂{=C=CHR′}(PCy₃)(L)] and [RuCl{=C=CHR′}(PCy₃)(sal-R)] (L=N-heterocyclic carbene, sal-R=salicylaldiminate anion, R′=Ph, SiMe₃, ^tBut) has been synthesized and characterized. These complexes are easily accessible from [RuCl₂(p-cymene)]₂, terminal alkynes, imidazolium salts or salicylaldimine salts and they have been found to serve as good catalyst precursors for ring-opening metathesis polymerization (ROMP) of norbornene, substituted norbornenes, polycyclic alkenes and cyclooctene and ring-closing metathesis (RCM) of ,ω-dienes. Furthermore, these precursors possess extremely high stability toward air, heat and moisture in comparison with other metathesis-active alkylidene ruthenium systems. No significant catalyst decomposition was found for several days at elevated temperatures.     

Selective Dequenching by Photobleaching Increases Fluorescence Probe Visibility

Self-quenching properties of fluorescent dyes have been developed to improve the sensitivity of fluorescent measurement. Photobleaching of Calcein at a concentration greater than the critical, self-quenching concentration actually increased fluorescence, whereas at lower concentrations photobleaching decreased fluorescence, enhancing signal to noise by almost 4000. The photobleaching-dequenching principle has been demonstrated in giant liposomes encapsulating Calcein at higher quenched concentrations. Upon photobleaching background fluorescence was reduced and the liposome fluorescence increased. Liposomes invisible in the presence of background fluorescence became visible upon photobleaching. Fluorescent lifetime was unaffected by photobleaching, whereas the lifetime decreased significantly upon dilution, allowing distinction between photobleached fluorescence particularly upon dequenching. The principle may be suited to improving fluorescence imaging and resolving fluorescent probes in particle-based assays.     

Spatially compact space-times that shrink

A criterion is given under which essential singularities occur in any space-time having compact spacelike slices whose size (measured by a parallelly propagated frame) shrinks to zero, and where there is a timelike congruence with incomplete curves.     

Minimal coupling in spin-2 field

It is shown that the spin-2 Lagrangian of Watanabe and Bhargava can be generalised by the introduction of a real parameter b associated with derivative ordering. After minimal coupling the spin-2 dynamical equations of Nath and Velo and Zwanziger can be derived as special cases. The constraint situation in these equations is then summarised and related to the first-order Lagrangian approach of Federbush, Chang, et al. Only one value of the parameter b gives a correct manifold of states after coupling. Finally it is shown that the auxiliary field approach to spin-2 proposed by Chang is dynamically inconsistent under minimal coupling.     

A variational proof of Aumann's theorem

We give a new proof of Aumann's theorem on the integrals of multifunctions. The proof, which is variational in nature, also leads to a constructive procedure for calculating a selection whose integral approximates a given point in the integral of the multifunction.The support of the Natural Sciences and Engineering Research Council of Canada (grant A 9082) and of the Killam Foundation (Canada Council Senior Research Fellowship) is gratefully acknowledged.