Pressure coefficients of band gaps in semiconductors

A first principles pseudopotential method within the local density approximation is used to calculate the pressure coefficients for band gaps in several diamond and zincblende semiconductors. Despite the underestimation of the band gaps found in almost all local density calculations, the predictions for the linear pressure coefficients and the critical pressures for conduction band inversion are consistent with experiment for all cases considered.     

Enantioselective aldol reaction of chiral acyl thiazolidine thione derived boron enolates

The compatability of an acyl thiazolidine thione as a chiral auxillary in boron enolate chemistry has been demonstrated by an enantioselective aldol condensation. The aldol products provide direct access to chiral β-lactams.     

Efficient N-sulfenylation of 2-azetidinones using S-substituted thiophthalimides

Reaction of N-unsubstituted β-lactams with various S-substituted thiophthalimides provides an efficient route to the corresponding N-thio-2-azetidinones.     

Electronic structure of solids

A review of progress in calculating properties related to the electronic structure of solids is presented with emphasis on the pseudopotential method.     

Theoretical study of relaxation at the (110) Ge-GaAs interface

A simple relaxation of the Ge-GaAs (110) interface is studied theoretically using self-consistent pseudopotentials. The relaxation is one in which the distance between the Ge and GaAs atomic planes at the interface is increased by 20%. Band edge discontinuities are found to be insensitive to this type of relaxation in spite of large distortions of the electronic charge density.     

The design of an efficient elevator operating system

A method is developed for finding an efficient operating policy for an office building elevator system. The method was applied to a particular eleven story building in which there were four elevator shafts. A queuing model was formulated in which the characteristics of passenger arrivals and destinations were time variable. The objective involved the minimization of the weighted sum of ratios of actual to minimum possible travel time between all pairs of floors. Simulation was used to analyze several logical routing policies for each of two methods in which demand information was used to alter the elevator route. The best policy was found to be almost twice as efficient as most of the other policies which were studied and over 25 times more efficient than another seemingly logical operating policy.     

The eighth virial coefficient of four- and five-dimensional hard hyperspheres

The eighth virial coefficient for hard hyperspheres is calculated by Monte Carlo techniques. It is found that B8/B(7)2=0.000 274+/-0.000 014 and -0.000 115+/-0.000 012 in four and five dimensions, respectively. The results are in good agreement with the findings of Clisby and McCoy (e-print arXiv:cond-mat0410511), and confirm that B8 is negative in five dimensions.