Conformational analysis—IV: A lanthanide induced shift (LIS) NMR investigation of the conformation and relative conformer energies of trans and cis 2-decalone

The solution conformation of trans-2-decalone and the conformational population of cis-2-decalone has been determined by LIS analysis. The angle of pucker (α) of the ketone ring in trans-2-decalone is 51 ± 2°, identical to that of cyclohexanone, but different from that determined for substituted decalones in the solid state, in which significant flattening of the ring occurs.The steroidal conformer of cis-2-decalone, when the latter is complexed to Yb(fod)₃ in CDCl₃, found to be preferred over the non-steroidal conformer by a ratio of 55:45, in contrast to the preference reported from the low temperature ¹³C NMR spectrum for the non complexed ketone in CH₂Cl₂. The two determinations can be combined to give the enthalpy difference in favor of the non-steroidal conformer of ca 0.8 kcal mole^?1.     

Using generating functions to convert an implicit (3,3) finite difference method to an explicit form on diffusion equation with different boundary conditions

In this article, our main goal is to develop an idea to convert an implicit (3,3) ??-scheme finite difference method to an explicit form for both linear and nonlinear diffusion equations and also for nonlinear advection-diffusion equation with different boundary conditions. Accordingly, we assist power series generating functions which are a routine method in discrete mathematics. Also, the stability analysis of ??–scheme to implement in nonlinear advection–diffusion equation has been investigated. Finally, the new approach has been implemented for Fisher, reaction–diffusion, Burgers and coupled Burgers equations as test problems to verify the ability and efficiency of the method proposed in this paper.     

Calibration of XPS core-level binding energies: Influence of the surface chemical shift

Core-level binding energies measured in XPS are influenced by the existence of surface chemical shifts. The magnitude of this effect has been calculated for materials commonly used in the calibration of XPS instruments.     

A combined XPS/AES study of Cu segregation to the high and low index surfaces of a Cu-Ni alloy

Quantitative information was obtained regarding the equilibrium segregation of Cu to the high index surfaces (cut 5° off the (100) plane in the [001] and [011] directions) and low index surfaces ((100), (111) and (110)) of a Cu: Ni, 5: 95% alloy crystal. Data regarding segregation to the (111) surface of a Cu: Ni, 50: 50% alloy crystal was also obtained. Equilibrium surfaces were obtained by careful annealing in the temperature range 850–920 K to avoid Cu loss by evaporation. The surface composition profile was calculated using data from the combination of the X-ray Photo-electron Spectroscopy and Auger Electron Spectroscopy techniques. Using these techniques, a wide range of electron kinetic energies and associated electron escape depths can be probed, yielding information about the topmost layer concentration and about the concentration profile into the bulk. Extensive Cu segregation was observed for the 5% and 50% Cu alloys. Topmost layer compositions of 85–100% Cu were found for both the high and low index surfaces of the 5% Cu alloy. In the next two or three atomic layers the composition was found to drop swiftly to near bulk Cu levels. For atomic layers deeper than this, some experimental evidence suggested a rise in Cu composition over three or four layers to 8–17% Cu before bulk levels were finally regained. For the 50% Cu alloy sample, a topmost layer composition was found of 95–100% Cu. Bulk levels of Cu were regained in about four atomic layers. These results are discussed in relation to other theoretical and experimental studies of segregation in these Cu-Ni alloys. The significance of the measured composition in relation to an equilibrium surface is also considered.