On the simulation of the director field of a nematic liquid crystal

A numerical method for the analysis of the static and dynamic behaviour of the director field, n, of a nematic liquid crystal is presented, where the equivalence of n and - n is taken into account. The occurrence of defects characteristic of nematics is studied for a hybrid cell, and for a material with a negative anisotropic susceptibility subject to an external field. Typical director configurations with defects are displayed graphically for some two dimensional arrangements and, in addition, the resulting pictures corresponding to an observation between crossed polarizer and analyser have been computed.     

Combinatorial synthesis of substituted biaryls and heterocyclic arylamines

In this paper, we report very general conditions that enable palladium-mediated coupling reactions on the solid support. A wide variety of biaryls and arylamines (including pyrimidines) have been synthesized using this protocol. The chemistry facilitates a combinatorial approach to the production of large numbers of medicinally relevant heterocyclic structures.     

Powering nanodevices with biomolecular motors

Biomolecular motors, in particular motor proteins, are ideally suited to introduce chemically powered movement of selected components into devices engineered at the micro- and nanoscale level. The design of such hybrid "bio/nano"-devices requires suitable synthetic environments, and the identification of unique applications. We discuss current approaches to utilize active transport and actuation on a molecular scale, and we give an outlook to the future.     

Sensitive wavelength-modulated photoacoustic spectroscopy with a pulsed optical parametric oscillator

With a laser-excited acoustic wave as the carrier wave and by modulation of the light wavelength of a multikilohertz-repetition-rate optical parametric oscillator at a lower frequency than the acoustic frequency, we demonstrate a wavelength-amplitude double-modulation technique and achieve an enhancement factor of 35 in sensitivity in photoacoustic trace gas detection with the technique.     

High-frequency modulation of segmented-contact semiconductor lasers

Simulations of the high-frequency modulation characteristics of semiconductor lasers with segmented contacts predict a pronounced resonance-like modulation response that is beyond five times the original cut-off modulation frequency. Based on an effective multi-mode Maxwell–Bloch model, the simulations reveal the underlying phenomena. They show that the high-frequency response is a direct consequence of the particular spatio-temporal and multi-mode dynamics induced by the segmented-contact laser geometry.     

Spin observables in neutron-proton elastic scattering

The analyzing power, , and the polarization transfer observables , and have been measured in neutron-proton elastic scattering at 260, 318, 386, 472 and 538 MeV for c.m. scattering angles between 64° and 160°. The data were obtained at PSI with a polarized neutron beam and a polarimeter analyzing the transverse polarization of the outgoing proton. They make a significant impact on the knowledge of the Isospin I = 0 nucleon-nucleon scattering. Received: 27 January 1998 / Published online: 30 March 1998     

Optimal tactics for close support operations: Part I,degraded communications

A formidable problem in the mathematical studies of C³ (command, control, and communication) is the determination of the optimal decision rules for force commitments to be employed by headquarters. Recursive equations are derived for an amphibious campaign with time-invariant linear dynamics and quadratic costs. Air and ground commanders are assumed to have perfect intelligence with degraded communication between them.The authors have benefitted greatly from discussions with Colonels R. Geesey, C. Albo, and R. Reeves, USAF.     

The equivalence of team theory's integral equations and a Cauchy system: sensitivity analysis of a variational problem

Team decision theory studies the problem of how a group of decision makers should use information to coordinate their actions. Mathematically, the task is to find functions that maximize an objective functional. The Euler equations take the form of a system of integral equations. In this paper, it will be shown that a class of such integral equations has solutions that are identical to the solutions of a system of initial-valued integrodifferential equations. This Cauchy system describes the sensitivity of the solutions to underlying parameters and provides an efficient technique for solving difficult team decision problems. An analysis of a profit maximizing firm demonstrates the usefulness of the Cauchy system.     

Optimal tactics for close support operations: Part IV,perfect intelligence and communications

A new generation ofC ³ (command, control, and communication) models for military cybernetics is developed. Recursive equations for the solution of theC ³ problem are derived for an amphibious campaign with linear, time-varying dynamics. Air and ground commanders are assumed to have perfect intelligence and perfect communications. Numerical results are given for the optimal decision rules.     

Computer Literacy: An Evolving Concept

The term “computer literacy” became very popular in the 1980s as a catch phrase describing a new type of understanding. Prior to the phrase's popularity, “literacy” was reserved for the knowledge of basic skills in reading and writing and familiarity with the classical works and great books of ancient and modern cultures. To be literate means to be educated regarding the fundamental or basic ideas, beliefs and methods of communication in society. By applying the term “literacy” to the knowledge of computers, society is signifying that this sort of knowledge is as important to a person's education in contemporary society as knowledge of reading and writing has been in the past (Ringle, 1981). While many people seem to agree that the proliferation of computers and their application in extensive areas of human endeavor require us to take the notion of literacy seriously, there is still no consensus as to how this educational goal should be achieved. The difficulty stems from the fact that there is no universally accepted definition of computer literacy. Until educators are clear about the goal, effective ways to attain the objective of computer literacy will be clouded by confusion. The purpose of this research is to examine the historical evolution of the phrase “computer literacy,” to develop a chronological continuum of computer literacy, and to identify several competencies that will likely characterize the computer literate teacher in the 1990s.