Synthesis of flexibilene,a naturally occurrring 15-membered-ring diterpene

A total synthesis of the naturally occurring 15-membered ring diterpene, flexibilene, was accomplished using a titanium-induced cyclization of the keto-aldehyde 3,37,11-tetramethyl- 15-oxohexadeca-4E,7E,11E-trienal as the key step.     

STATIC and TIME-RESOLVED FLUORESCENCE OF AN AMPHIPHILIC FLAVIN IN AEROSOL OT REVERSED MICELLES

Spectral and time-resolved fluorescence studies have been carried out on N(3)-undecyllumi-flavin dispersed in reversed micelles composed of the surfactant sodium di(2-ethylhexyl) sulfosuccinate (Aerosol OT, AOT), various amounts of water and n -heptane as continuous phase. The fluorescence spectral properties (spectral distribution, quantum efficiencies and lifetimes) as function of the water to AOT molar ratio suggest that the flavin occupies a position within the surfactant boundary layer in close contact with water. The fluorescence anisotropy exhibits biexponential decay with a short (0.3 ns) and a longer (1.6–2.4 ns) correlation time. The contribution of the short component increases with the growth of the droplet providing evidence for enhanced flexibility of the flavin in the interfacial layer.     

Isostructural triazenido complexes of first row transition metals. Part 1. Synthesis and properties of (η5-C5H5)(L)(RN3R) FeII,L = PPh3, P(OMe)3, P(OPh)3 or CO

Summary The complexes ( ⁵-C₅H₅)L(RN₃R)Fe, where L = PPh₃, P(OMe)₃, P(OPh)₃ or CO and R,R=p-MeC₆H₄ orp-ClC₆H₄, have been prepared by reaction of suitable iron halides with Ag(RN₃R). The mechanism of formation of the Fe(RN₃R) group is thought to involve, initially, an Fe-Ag bond. The bonding mode of the triazenido ligand is chelating in a six coordinate configuration. The spectroscopic results are discussed in relation to variations in the environment of the metal atom.     

Ab initio Calculations on the thermal ring closure of acrolein

The electrocyclic reaction which interconverts acrolein and oxetene is investigated by ab initio calculations, using a 4-31G basis set. Like the transition state of the thermal ring closure of cisbutadiene, the transition state of this reaction shows a torsion of about 18 ° around the central bond, in spite of the absence of H-H repulsion. The resulting oxetene is 43 kcal/mol endothermic with regard to acrolein. The calculated activation energies for ring closure and -opening are 3.4 and 1.0 eV. The conformational result of the ring opening reaction is discussed.     

Dynamic modulation transfer function: a method to characterize the temporal performance of liquid-crystal displays

A method to measure the dynamic modulation transfer function (DMTF) of a liquid-crystal display (LCD) is proposed to characterize its performance when rendering motion images. The method includes a measurement system to capture the temporal luminance variation of a LCD while using a well-designed input data sequence and a simulation model based on smooth pursuit eye tracking and temporal light integration at the human retina. It predicts the perceived performance of a moving sine wave pattern on a LCD and subsequently calculates the DMTF. With this approach, several technologies to reduce motion blur were evaluated and discussed.     

Retrieving the elastodynamic Green's function of an arbitrary inhomogeneous medium by cross correlation

A correlation-type reciprocity theorem is used to show that the elastodynamic Green's function of any inhomogeneous medium (random or deterministic) can be retrieved from the cross correlation of two recordings of a wave field at different receiver locations at the free surface. Unlike in other derivations, which apply to diffuse wave fields in random media or irregular finite bodies, no assumptions are made about the diffusivity of the wave field. In a second version, it is assumed that the wave field is diffuse due to many uncorrelated sources inside the medium.