A generalized de sitter solution

Anisotropic solutions of the vacuum Einstein equations with a cosmological term are considered. These metrics approach the de Sitter form for large values of the time.     

Pion-Nucleon Interaction and Two-Pion-Exchange Three-Nucleon Forces

We compare the πN scattering amplitudes that underlie 2π-exchange three-nucleon forces (TBFs) with the experimental πN amplitudes in the form of partial-wave phase shifts and subthreshold invariant amplitudes. The amplitudes of the Tucson-Melbourne and Brazil TBFs when taken on-pion-mass-shell predict scattering lengths at threshold and phase shifts (slightly) above threshold which are in good agreement with the experimental amplitudes, except for the S-waves. Partial wave amplitudes from separable potentials, recently employed in a 2π-TBF calculation, were continued below threshold, summed into invariant amplitudes, and compared with the experimental amplitudes in this kinematic region, which is most relevant to the kinematics of TBFs. The separable-potential invariant amplitudes, in contrast to those of TM and Brazil TBFs, do not compare well quantitatively with the experimental amplitudes in this region but have a similar qualitative behaviour. The very small TBF effect in the triton of the separable-potential amplitude appears to be due to the πNN vertex function rather than the πN amplitude itself. Received April 27, 1994; revised August 2, 1994; accepted for publication August 31, 1994     

A vicarious aromatic substitution approach to aklavinone from chrysazin

The cheap, available dye-intermediate 1,8-dihydroxyanthraquinone (2) is converted efficiently to a useful aklavinone precursor (3). A Mitsunobu alkylation-Claisen rearrangement sequence and an unprecedented vicarious aromatic substitution on an anthraquinone are employed as key steps.     

Reply to comments on “laser excitation of surface electronic states for a one-dimensional semiconductor” by G.W. Bryant

A semiconductor modeled by a finite one-dimensional chain is shown to have either a continuous or discrete number of surface states. The exact number is determined by the choice of phase factors. Laser-induced charge transfer of electrons from the bulk to these surface states is also shown to be a maximum at the band edge.     

Parameter estimation in moving boundary problems

We describe an approximation scheme which can be used to estimate unknown parameters in moving boundary problems. The model equations we consider are fairly general nonlinear diffusion/reaction equations of one spatial variable. Here we give conditions on the parameter sets and model equations under which we can prove that the estimates obtained using the approximations will converge to best-fit parameters for the original model equations. We conclude with a numerical example.     

Basic hydrolysis of glyceryl nitrate esters. III. Trinitroglycerin

Kinetics of the basic hydrolysis of glyceryl trinitrate (TNG) were investigated in CO₂-free aqueous calcium hydroxide solutions. The hydrolysis reactions were carried out in a temperature controlled reactor vessel with provision for continuous N₂ sparging of the reaction mixture. TNG hydrolyzed via second-order reaction at 25°C, 18°C, and 10°C. The activation energy of the hydrolysis reaction of TNG was calculated from the kinetic data and found to be equal to 27.53 kcal/mol. The major products of the hydrolysis of TNG in solution of calcium hydroxide were calcium nitrate and calcium nitrite, accounting for approximately 50% of the degradation products. The minor identified products such as calcium oxalate and nitrate esters amounted to approximatey 6% of the products. The remaining 30% of the isolated products was a mixture of calcium formate, a nitrate ester, and unidentified volatiles, polymerlike substances, and other organic residue.     

The spectrophotometric and fluorimetric determination of cobalt by extraction as 2,4-dichlorobenzyltriphenyl- phosphonium tetrathiocyanatocobaltate(II)

Cobalt (0–100 μg) can be determined by spectrophotometric or fluorimetric measurements after its extraction as 2,4-dichlorobenzyltriphenylphosphonium tetrathiocyanatocobaltate(II) into 1:9 acetone—dichloroethane. Cobalt quenches the fluorescence of the reagent. The effects of pH and diverse ions are reported. The system is applied to the determination of cobalt in mild steels without prior separation of the iron.