Enantiomeric interactions between nucleic acid bases and amino acids on solid surfaces

Molecular interaction between nucleic acid bases and amino acids is a fundamental process in biology. The adsorption of the molecules on surfaces provides the opportunity to study such interactions in great detail by exploiting the high-resolution imaging capabilities of scanning tunnelling microscopy (STM). The chemisorption of prochiral molecules, such as adenine, on a metal surface causes the adsorbed species to become chiral. Subsequent interactions with inherently chiral molecules may then lead to the formation of diastereoisomers, if the enantiomeric interaction process is sufficiently strong. In the case of adenine adsorption on Cu[110], the chiral adsorbates form homochiral chains. Here, we show that the adenine chain direction is fully correlated with the chirality, and that the alpha-amino acid, phenylglycine, shows a strong chiral preference in its interaction with these chains. STM images clearly demonstrate that S-phenylglycine (R-phenylglycine) binds only to chains rotated 19.5 degrees (anti-) clockwise from the [001] direction. Closer examination reveals that the enantiomeric interaction involves double rows of phenylglycine molecules and the adenine chains. This is the first observation at the molecular level of diastereoisomeric interaction, and demonstrates that STM is a powerful method for studying the details of these interactions.     

An Assessment of the Singerian Inquiring Organizational Model: Cases from Academia and the Utility Industry

The Singerian model of inquiring organizations is reviewed (Proceedings of the Americas Conference on Information Systems, Phoenix, Arizona Aug. 16–18,1996:443–445; Australian Journal of Information Systems, 1998;6(1):3–15, reprinted in Foundations of Information Systems: Towards a Philosophy of Informative Technology, http://www.cba.uh.edu/~parks/fis/fisart.htm.) and two cases of organizations representing the Singerian approach are analyzed. The Singerian organization, based on Churchman's (The Design of Inquiring Systems: Basic Concepts of Systems and Organizations, New York, NY: Basic Books Inc., 1971.) Singerian inquiring system, has ethical purposes, treats employees, customers and other stakeholders with trust and respect, and pursues socially responsible goals, including a respect for the environment. Decision making in Singerian organizations is holistic and systemic, and includes diverse stakeholders, thus requiring an open, cooperative culture, wherein debate is encouraged. Authority is diffuse. Measurement is fundamental. A system of measures is continuously monitored, refined, compared and revised to assess progress. Cooperation and communication are supported with various types of groupware, including e-mail, electronic meeting systems, group support systems, negotiation support systems, discussion forums, knowledge bases, knowledge management systems and the like. The Internet and World Wide Web may serve as resource and dissemination agents for exoteric knowledge created by the organization. Two organizations, an Energy Service Company and an academic Center for the Management of Information Systems, are analyzed for their conformance to and success with the Singerian approach. The organizations tended to prosper when the model was followed, but ran into difficulties when it was not.     

An electron paramagnetic resonance study of defects in PECVD silicon oxides

Electron paramagnetic resonance (EPR) has been used to determine how the type and population of paramagnetic defects are altered firstly by changes to the composition of oxides grown on silicon by plasma enhanced chemical vapor deposition (PECVD) and secondly by subsequent anneal treatments of the various oxide films. Silicon oxide films with refractive index, n, of 1.464, 1.487, 1.508 and 1.536 and thickness of 1 m to 3 m were studied; those of higher index have a higher silicon content. Only E centers are detected in films with n=1.464 and 1.487. Raising n to 1.508 leads to the introduction of other types of paramagnetic centers and a large increase in the average total spin concentration. Increasing n further to 1.536 produces a further small increase in average spin concentration. Identities are proposed for the additional types of defect and the dependence of their population on anneal temperature is also reported.     

SymROP: ROP protein with identical helices redesigned by all-atom contact analysis and molecular dynamics

Experience has shown that protein redesigns (using the backbone from a known protein structure) are far more likely to produce well-ordered, native-like structures than are true de novo designs. Therefore, to design a four-helix bundle made of identical short helices, we here proceed by an extensive redesign of the ROP protein. A fully symmetrical SymROP sequence derived from ROP was chosen by modeling ideal-geometry side chains, including hydrogens, while maintaining the "goodness-of-fit" of side-chain packing by calculating all-atom contact surfaces with the Reduce and Probe programs. To estimate the probable extent of backbone movement and side-chain mobility, restrained molecular dynamics simulations were compared for candidate sequences and controls, including substitution of Abu for all or half the core Ala residues. The resulting 17-residue designed sequence is 41% identical to the relevant regions in ROP. SymROP is intended for construction by the Template Assembled Synthetic Proteins approach, to control the bundle topology, to use short helices, and to allow blocked termini and unnatural amino acids. ROP protein has been a valuable system for studying helical protein structure because of its simplicity and regularity within a structure large enough to have a real hydrophobic core. The SymROP design carries that simplicity and regularity even further.     

On the Nonlinear Companding Transform for Reduction in PAPR of MCM Signals

In this paper, we provide the design criteria of the nonlinear companding transforms for reduction in peak-to-average power ratio (PAPR) of multi-carrier modulation (MCM) signals, which can enable the original MCM signals to be transformed into the desirable distribution. As examples, some novel nonlinear companding transforms have been proposed to transform the amplitude or power of the original MCM signals into uniform distribution, which can effectively reduce the PAPR for different modulation formats and subcarrier sizes without any complexity increase and bandwidth expansion. It has been shown by computer simulations that the proposed schemes can significantly improve the performance of MCM systems including bit-error-rate and PAPR reduction.     

The mysterious case of the missing paradigm: a review of critical information systems research 1991–2001

Abstract.  In this journal, Chen and Hirschheim have provided a historical analysis of positivist and interpretivist research paradigms and methodologies in the 10 years following the much cited work of Orlikowski and Baroudi. In this paper, we investigate the mysterious case of the missing paradigm – that of the critical approach to information systems (IS) research. We take Chen and Hirschheim's survey as our starting point and aim to fill the gap left by the absence of the critical paradigm in their analysis and make some criticisms of their method. Recent years have seen the growth of IS research that consciously adopts a critical perspective. This paper charts the development of critical IS research over the period of 1991–2001, adding some comments on more recent developments. We conclude by critically reflecting on the current development of critical research in the field of IS.     

Some results on the improvement of adaptation transients

A technique to improve the adaptation transient in discrete-time model reference adaptive control (MRAC) systems is given on the basis of applying classical optimization techniques to an equivalent near-linear system to the whole adaptive scheme. The resulting optimization is finally translated into modifications of one of the parameters entering the adaptation algorithm. This permits computation of a posteriori values of the adaptive controller parameters before generation of the input to the plant.