Diastereotopy in some 3,4-dihydroisocoumarins--effect of changing the substituents on the chiral centre

Diastereotopy has been investigated in eight different derivatives of 3,4-dihydroisocoumarins by changing the substituent on the pyran ring chiral centre, C-3. A diastereotopic NMR effect is observed for the prochiral methylene protons on the benzopyran ring and the effect is greatly influenced by the pi-electron system of the substituent. The effect is also observed for the substituents, however, the extent of diastereotopy depends upon their nature and the separation of methylene groups from the chiral centre.     

Single injection current in solid state cylindrical diodes with deep traps

The expressions for current-voltage characteristics of single injection current flow in solid state cylindrical diode containing significant amount of deep traps have been derived with the help of regional approximation method. It is shown that the complete current-voltage characteristic may be divided into well separated current-voltage regimes and the last regime is the pure space-charge-limited trap free regime. The role of deep traps is specially explained in the complete span of current-voltage characteristic.     

E.p.r. and spectroscopic studies of configurational changes in 1,4-diazacycloheptane copper(II) complexes

Summary E.p.r. and spectroscopic studies of bis(1,4-diazacycloheptane)copper(II) perchlorate, bromobis(1,4-diazacycloheptane)copper(II) perchlorate and dibromo-bis(1,4-diazacycloheptane)copper(II), were carried out in MeNO₂, DMSO and H₂O solutions as well as in the polycrystalline state. The ligation of bromide ion to bis(1,4-diazacycloheptane)copper(II) along thez-axis was investigated. The e.p.r. spectra are explained in terms of energy changes involving the electronic ground state and the lowest excited state as a function of ligation of nucleophiles to the metal atom along thez-axis. In the polycrystalline state, the weaker the apical interaction (square-planar species) the lower theg-value and the higher the copper(II) hyperfine coupling constant. In the liquid state, theg-values observed in non-coordinating solvents such as MeNO₂ are similar to those for the polycrystalline material suggesting structural similarity in the two states. The electronic absorption maxima for the three complexes in the liquid state shift to higher energy with an increase in tetragonal distortion around copper(II). In strongly coordinating solvents the e.p.r. spectra and absorption maxima are independent of the anion present. The increasing strength of solvation results in an increase in the wavelength of the optical transition and theg-values, and a decrease in the copper(II) hyperfine coupling constant. It appears that an increase in the basicity of the solvent has the same effect on thed-orbital energy levels and on the unpaired electron density on copper(II)_as does increasing the electronegativity of the substituents on the ligand.     

Synthesis and antimicrobial activities of some isocoumarin and dihydroisocoumarin derivatives

A new series of the isocoumarin derivatives of ibuprofen, fluribiprofen, naproxen, valproic acid and 1-naphthoic acid have been synthesized via condensation of homophthalic acid with their respective acid chlorides. The conversion of the latter two isocoumarins into (dl)-3,4-dihydroisocoumarins has also been achieved. Most of the synthesized compounds showed antifungal and antibacterial activities.     

The heating of the solar corona by the resonant absorption of alfven waves

In this paper, upward propagating Magnetoacoustic waves in an ideal atmosphere are considered. It is shown that the magnetic field creates a nonabsorbing reflecting layer. An equation for the resonance is derived, which shows that resonance may occur for many values of the magnetic field and of the frequency if the wavelength is matched to the strength of the magnetic field. At the resonance frequencies the values of the magnetic and kinetic energies will increase to very large values, and this may account for the heating process. Consequently, for large β-plasma the mechanism for coronal heating will be acoustic.     

High pressure equation of state and sound velocities to fourth order elastic constants. Application to sodium chloride to 270 kbars

Using the theory of small deformation superposed on a finite strain, we expand the strain energy to fourth order in terms of the strain invariants, and derive an athernal expression for the equation of state and the longitudinal and shear velocities of sound of a homogeneous Isotropic material to fourth order elastic constants. We evaluate reported velocity data in sodium chloride by Voronov and Grigorev to 80 kbar in terms of our formulation, to predict the equation of state to 270 kbar. Experiments performed in our laboratory (Frankel, Rich, and Homan) to 270 kbar which use ultrasonic interferometry to obtain resonance frequency intervals in the specimen were also evaluated. Both results are in good agreement with Decker's equation of state.     

Structure of some liquid transition metals using integral equation theory

We present the results of calculations of the structure factorS(q) of some liquid 3d transition metals using the self consistent hybridized mean spherical approximation (HMSA) integral equation. The local pseudopotential used is composed of the empty core model and a part that takes care of s-d mixing through an inverse scattering approach to model the interionic pair potential. The results presented are in very good agreement with experiment for most of the systems investigated near freezing, as well as for the noble metals Cu, Ag and Au, thus, confirming the reliability of the pseudopotential in the present integral equation scheme.