Relativistic treatment of the spin-zero particles subject to the second Pschl Teller-like potential

The three-dimensional Klein–Gordon equation is solved for the case of equal vector and scalar second Pschl–Teller potential by proper approximation of the centrifugal term within the framework of the asymptotic iteration method.Energy eigenvalues and the corresponding wave function are obtained analytically.Eigenvalues are computed numerically for some values of n and ?.It is found that the results are in good agreement with the findings of other methods for short-range potential.     

Acyl radical addition to benzene and related systems—a computational study

The addition of the acetyl radical to benzene, aniline, trifluoromethylbenzene and naphthalene has been investigated using DFT calculations. Addition to benzene is calculated to have an energy barrier of 63.6 kJ mol⁻¹ at the BHandHLYP/6-311G(d,p)+ZPE level of theory. This reaction is associated with simultaneous SOMO→π^∗ and π→SOMO interactions with the latter interaction dominating, suggesting that acetyl reacts predominantly as an electrophilic radical in its interaction with benzene. Addition to the ortho and para positions of aniline is calculated to be slightly less favourable, while attack at the meta position is predicted to be unaffected in relation to the chemistry involving benzene. Inclusion of the electron-withdrawing substituent, trifluoromethyl, is predicted to accelerate reactions slightly at the ortho and para positions, while attack at the C1 position of naphthalene is calculated to involve a barrier of 50.3 kJ mol⁻¹ (BHandHLYP/6-311G(d,p)+ZPE).     

3-D Model of sound pressure field in a meridinal section plane of fruit

A theoretical model was suggested for qualitative evaluation of a sound pressure field in fruit tissue, as affected by ultrasonic probe dimensions and fruit properties. The classic directivity pattern of an ideal fluid model, expressed by Bessel function of the first kind, was extended to include energy dissipation of a real material. The directional characteristics of wave propagation, as influenced by transmitter frequency and diameter, and by fruit properties, were discussed. The model indicates how to select the parameters of the ultrasonic transducer (transducer diameter, frequency and excitation power) to control the magnitude and directivity of the ultrasonic waves in the fruit tissue. The suggested theoretical model represented fairly well the experimental sound wave distribution over the half-cut surface of potato and avocado (R² > 0.862 and 0.977, respectively); the same theoretical model could not represent the sound wave distribution over a half-cut melon. Results of the study were applied in a new probe design for ultrasonic testing of whole fruit.     

ENDANGERED SPECIES AND NATURAL RESOURCE EXPLOITATION: EXTINCTION VS. COEXISTENCE

A model of renewable resource exploitation under event uncertainty is formulated. The model is applied to analyze the situation in which excessive water diversion for human needs can lead to the extinction of an animal population. Special attention is given to uncertainty regarding the conditions that lead to extinction. The manner in which the potential benefit foregone due to the species' extinction (the “extinction penalty”) induces more conservative exploitation policies is studied in detail. When the extinction penalty is ignored, the optimal policy is to drive the resource stock to a particular equilibrium level from any initial state. When the extinction penalty is accounted for and the conditions that lead to extinction are not fully understood (i.e., involve uncertainty), an interval of equilibrium states is identified, which depends on the penalty and on the immediate extinction risk.     

Excitation of the 6.41 MeV, T=14− state in 16F by the 16O(p,n)16F reaction

The angular distribution for the ¹⁶O(p, n) ¹⁶F (6.41 MeV) reaction at 35 MeV has been measured and analyzed using a distored-wave approximation. With analyses of 99 and 135 MeV data fixing the characteristics of the nuclear structure and direct reaction models required, analysis of the 35 MeV data reveals evidence of higher-order reaction processes, which we suggest involve virtual excitation of giant multipole resonances.     

An asymmetric synthesis of (+)-kjellmanianone

Racemic and asymmetric syntheses of kjellmanianone, a novel cyclopentenoid antibiotic, are described.     

Andrographolide: an X-ray crystallographic analysis

The structure of andrographolide, isolated fromAndrographis paniculata Nees, has been established by means of a single crystal X-ray analysis. The crystals have the space groupP2₁, witha=6.550(1),b=8.005(2),c=17.991(7) Å,=97.36(2)°, andZ=2. The structure was refined toR=7.3%. The molecular stereochemistry, bond distances, bond angles, and hydrogen bonding scheme have all been determined. The systematic name is 3-[2-[decahydro-6-hydroxy-5-(hydroxymethyl)-5,8a-dimethyl-2-methylene-1-naphthalenyl]ethylidine]dihydro-4-hydroxy-2(3H)-furanone.Camille and Henry Dreyfus Teacher-Scholar, 1978–1983, and National Institutes of Health Career Development Awardee, 1980–1985     

A facile synthesis of simple tetronic acids and pulvinones

Condensation of the dianions derived from simple α-hydroxyketones and 1,2-diketones with 1,1′-carbonyldiimidazole provides a facile one step synthesis of tetronic acids and pulvinones.     

The spectrophotometric determination of aliphatic hydroxyl in esters with vanadium oxinate

A method is described for the precise determination of small amount of aliphatic alcohols in esters. The procedure is based on the formation of a red-coloured complex between the alcohol and a solution of vanadium oxinate in nitrobenzene. Studies have been made on the effect of solvent, reaction time and the stability of the complex on the accuracy of the determination.