Design of a film surface roughness-minimizing molecular beam epitaxy

Molecular beam epitaxy of germanium was used along with kinetic Monte Carlo simulations to study time-varying processing parameters and their effect on surface morphology. Epitaxial Ge films were deposited on highly oriented Ge(001) substrates, with reflection high-energy electron diffraction as a real-time sensor. The Monte Carlo simulations were used to model the growth process, and physical parameters were determined during growth under time-varying flux. A reduced version of the simulations was generated, enabling the application on an optimization algorithm. Temperature profiles were then computed that minimize surface roughness subject to various experimental constraints. The final roughness after two layers of growth was reduced to 0.32, compared to 0.36 at the maximum growth temperature. The study presented here is an initial demonstration of a general approach that could also be used to optimize properties in other materials and deposition processes

Evaluation of the Cedar memory system: Configuration of 16 by 16

Some basic results on the performance of the Cedar multiprocessor system are presented. Empirical results on the 16 processor 16 memory bank system configuration, which show the behavior of the Cedar system under different modes of operation are presented

Failure of Universality in Noncompact Lattice Field Theories

The nonuniversal behavior of two noncompact nonlinear sigma models is described. When these theories are defined on a lattice, the behavior of the order parameter (magnetization) near the critical point is sensitive to the details of the lattice definition. This is counter to experience and to expectations based on the ideas of universality.Comment: 24 pages, REVTeX version 3.0 with 4 embedded figures, provided separately in compressed-uuencoded postscript packed in a self-extracting csh script produced with uufiles. To appear in J. Math. Phys

Modelling of errors in databases

A lot of time and energy are expended assembling national databases containing information about health care processes and outcomes. Unfortunately, given the complexity of the data gathering procedures involved, errors occur. This inevitably leads to problems when it comes to the analysis of data from such sources. Indeed, sometimes it is very much a matter of faith that summary statistics represent a true reflection of the facts. On the assumption that one knows the rates at which different forms of errors occur, mathematical modelling methods can be used to obtain estimates of the effects of such errors on the estimates that would be derived for summary statistics associated with an erroneous data base

Effective transition rates for epitaxial growth using fast modulation

Thin-film deposition is an industrially important process that is highly dependent on the processing conditions. Most films are grown under constant conditions, but a few studies show that modified properties may be obtained with periodic inputs. However, assessing the effects of modulation experimentally becomes impractical with increasing material complexity. Here we consider periodic conditions in which the period is short relative to the time scales of growth. We analyze a stochastic model of thin-film growth, computing effective transition rates associated with rapid periodic process parameters. Combinations of effective rates may exist that are not attainable under steady conditions, potentially enabling new film properties. An algorithm is presented to construct the periodic input for a desired set of effective transition rates. These ideas are demonstrated in three simple examples using kinetic Monte Carlo simulations of epitaxial growth

The Shape and Dimensionality of Phylogenetic Tree-Space Based on Mitochondrial Genomes

Phylogenetic analyses of large and diverse data sets generally result in large sets of competing phylogenetic trees. Consensus tree methods used to summarize sets of competing trees discard important information regarding the similarity and distribution of competing trees. A more fine grain approach is to use a dimensionality reduction method to project tree-to-tree distances in 2D or 3D space. In this study, we systematically evaluate the performance of several nonlinear dimensionality reduction (NLDR) methods on tree-to-tree distances obtained from independent nonparametric bootstrap analyses of genes from three mid- to large-sized mitochondrial genome alignments.
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Can the Heinrich ratio be used to predict harm from medication errors?

The purpose of this study was to establish whether, for medication errors, there exists a fixed Heinrich ratio between the number of incidents which did not result in harm, the number that caused minor harm, and the number that caused serious harm. If this were the case then it would be very useful in estimating any changes in harm following an intervention. Serious harm resulting from medication errors is relatively rare, so it can take a great deal of time and resource to detect a significant change. If the Heinrich ratio exists for medication errors, then it would be possible, and far easier, to measure the much more frequent number of incidents that did not result in harm and the extent to which they changed following an intervention; any reduction in harm could be extrapolated from this

A Computational Study of Cation−π Interactions vs Salt Bridges in Aqueous Media: Implications for Protein Engineering

A direct comparison of the energetic significance of a representative salt bridge vs a representative cation−π interaction in aqueous media and in a range of organic solvents is presented using ab initio electronic structures and the SM5.42R/HF solvation model of Cramer and Truhlar. The cation−π interaction shows a well depth of 5.5 kcal/mol in water, significantly larger than the 2.2 kcal/mol seen for the salt bridge. Consistent with this idea, a survey of the Protein Data Bank reveals that energetically significant cation−π interactions are rarely completely buried within proteins, but prefer to be exposed to solvent. These results suggest that engineering surface-exposed cation−π interactions could be a novel way to enhance protein stability

Towards a deeper understanding of system usage in organizations: A multi-level perspective

The objective of this paper is to contribute towards a deeper understanding of system usage in organizations by examining its multilevel nature. Past research on system usage has suffered from a levels bias, with researchers studying system usage at single levels of analysis only, e.g., the individual, group, or organizational level. Although single-level research can be useful, we suggest that studying organizations one level at a time will ultimately lead to an unnatural, incomplete, and very disjointed view of how information systems are used in practice. To redress this situation, we draw on recent advances in multilevel theory to present system usage as a multilevel construct and provide an illustration for what it takes for IS researchers to study it as such. The multilevel perspective advanced in this article offers rich opportunities for theoretical and empirical insights and suggests a new foundation for in-depth research on the nature of system usage, its emergence and change, and its antecedents and consequences

Crisis in American Information Systems Education: Innovations to Address the Threat of Offshoring

Our classrooms are nearly empty. The job prospects for our graduates are bleak. Offshoring is reconfiguring the American information technology industry. What are we to do? After years of unprecedented growth, demand, and skill shortages, IT faculty find themselves in a new environment. As a shortterm solution, some faculty are scrambling to develop and redesign courses. This is not enough and will not sustain the fundamental shifts needed in a global economy. How can individual faculty, Information Systems departments, and schools respond to survive the rapidly changing landscape? The situation calls for innovations in academic delivery. Academics must serve as examples of agility to students by rethinking and revising curricula. We have responded when faced with other changes such as DBMS, end-user computing, networking, and e-commerce when it was in our favor. Can we do it again? How do we instill in students how they can become innovators and not merely problem solvers? What new organizational forms can academic programs take to help students bridge global teams? The panel will discuss innovations to address the crisis of low enrollments and dated skill sets. The format lists panelists in order of presentation along with their relevant expertise