Preparative isolation of (+)-beta-eudesmol fromAmyris balsamifera

Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum distillation of the total oil. Step two was a medium pressure LC separation with an AgNO₃ impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related sesquiterpene alcohols (75% of the oil).     

A convenient method for 3-pyrroline synthesis

[reaction: see text]. The synthesis of a range of 3-pyrrolines has been achieved from primary amine starting materials using a two-step alkylation/alkylidene carbene CH-insertion reaction sequence. We have shown that insertion into a range of CH-bond types is possible, and the formation of nitrogen-bearing quaternary stereocenters is a relatively facile process. The insertion reaction occurs with >95% retention of stereochemistry, but the presence of protecting groups on nitrogen is generally deleterious to the cyclization process.     

Kinetic simulations of the heating of solid density plasma by femtosecond laser pulses

Experiments have been performed in which fs-timescale laser pulses, focused to an intensity ～10¹⁶ W cm^?2, are able to directly create and interact with solid density plasma (1). We have performed one-dimensional simulations of the experiments with a kinetic model which solves Maxwell's equations coupled to the Fokker–Planck equation enabling us to self-consistently model the non-local heat flow and absorption process. We find that the heat-flux is magnetized by the laser field and is inhibited relative to the Spitzer value.     

Ion conductive characteristics of cross-linked network polysiloxane-based solid polymer electrolytes

A series of cross-linked network polysiloxanes containing oligoethylene oxide units, (OCH₂CH₂)_n, as internal free chains have been synthesized by performing hydrosilylation of partially PEO-substituted polysiloxane precursor with , ω-diallyl terminated poly(ethylene glycol). The polymer electrolytes were formed by complexing with LiN(CF₃SO₂)₂ electrolyte salt and exhibited superior conductive property. The σ_RT of the network polymer electrolytes is in the range of 2.50×10⁻⁵ to 1.62×10⁻⁴ S/cm and depends on the cross-linking density (in terms of Si–H amount of the siloxane precursor), repeating unit number of internal oligoethylene oxide and chain length of the cross-linker. The significant enhancement of the conductivity was observed when low molecular weight dimethyl poly(ethylene glycol) was added as plasticizer. The temperature dependence of the ionic conductivity was also studied, following the Vogel–Tamman–Fulcher (VTF) equation.     

Absorption of short laser pulses on solid targets in the ultrarelativistic regime

We report the first direct measurements of total absorption of short laser pulses on solid targets in the ultrarelativistic regime. The data show an enhanced absorption at intensities above 10(20) W/cm(2), reaching 60% for near-normal incidence and 80%-90% for 45 degrees incidence. Two-dimensional particle-in-cell simulations demonstrate that such high absorption is consistent with both interaction with preplasma and hole boring by the intense laser pulse. A large redshift in the second harmonic indicates a surface recession velocity of 0.035c.     

Artificial collimation of fast-electron beams with two laser pulses

A scheme for artificially collimating fast-electron beams produced in high intensity (>10(19) W cm(-2)) laser-solid interactions is proposed. The scheme uses a laser pulse at the relativistic threshold (approximately 10(18) W cm(-2)) that precedes the high intensity pulse to pregenerate a collimating magnetic field. This concept is supported by analytical calculations and numerical calculations performed using a novel hybrid-Vlasov-Fokker-Planck code called LEDA. This scheme may be highly useful for fast ignition inertial confinement fusion.     

Optical spectroscopy of MgNb2O6 and ZnNb2O6 doped with Ni2+

Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 4, pp. 30–37, July–August, 1995.     

The persistence of Maxwellian D and T distributions during burn in inertial confinement fusion

We present particle simulations of the heating of a DT plasma by fusion-produced α-particles. The D, T and α-particles are each treated as separate kinetic species while the electrons are assumed to be Maxwellian. Fusion reactions are also simulated for the D and T ions in such a way as to account correctly for any non-thermal effects. It is shown that the D and T ions remain close to Maxwellian under a wide range of conditions and correspondingly the fusion reactivity remains thermal.