British steel corporation data network

The British Steel Corporation network, Coten, links computers and terminals on BSC sites throughout the UK. The network is described from the point of view of the user (terminal types etc.), the network operator (network operating principles, status information, statistics and executive control), and the technologist (functional subsystems, protocols and implementation).     

Reinforcement and protection with polystyrene of freeze-fracture replicas during thawing and digestion of tissue

An improved method for reinforcing freeze-fracture replicas, which is especially suitable for tough tissues, is described. For this purpose, polystyrene dissolved in chloroform is used to produce a solid protecting layer of plastic on top of the replica, enabling it to withstand the stresses associated with the thawing and digestion of the tissue with strong acids. The method results in production of large clean replicas from tissues such as skin or peripheral nerve which are difficult to process. The method can also be used profitably for reinforcing other softer and more homogeneous tissues.     

Pi (antitrypsin) typing methods. A comparison of acid starch-gel electrophoresis and isoelectric focusing

The Pi typing methods acid starch-gel electrophoresis (ASGE) and isoelectric focusing (IEF) have been compared by three reference laboratories: 564 samples of phenotypes Pi M, MS and MZ were tested in each of the three laboratories with a 96% agreement on initial typing. The discrepancies are recorded and reasons for disagreement discussed. IEF is a reliable method for Pi typing and gives results comparable to those obtained by ASGE.     

A Semantics for Distributed Execution of Statemate

We present a semantics for the statechart variant implemented in the Statemate product of i-Logix. Our semantics enables distributed code generation for Statemate models in the context of rapid prototyping for embedded control applications. We argue that it seems impossible to efficiently generate distributed code using the original Statemate semantics. The new, distributed semantics has the advantages that, first, it enables the generation of efficient distributed code, second, it preserves many aspects of the original semantics for those parts of a model that are not distributed, and third, the changes made regarding the interaction of distributed model parts are similar to the interaction between the model and its environment in the original semantics, thus giving designers a familiar execution model. The semantics has been implemented in Grace, a framework for rapid prototyping code generation for embedded control applications.     

Reinforcement learning on explicitly specified time scales

In recent years hierarchical concepts of temporal abstraction have been integrated in the reinforcement learning framework to improve scalability. However, existing approaches are limited to domains where a decomposition into subtasks is known a priori. In this article we propose the concept of explicitly selecting time scale related abstract actions if no subgoal related abstract actions are available. This concept is realised with multi-step actions on different time scales that are combined in one single action set. We exploit the special structure of the action set in the MSA-Q-learning algorithm. This approach is suited for learning optimal policies in unstructured domains where a decomposition into subtasks is not known in advance or does not exist at all. By learning different explicitly specified time scales simultaneously, we achieve a considerable improvement of learning speed, which we demonstrate on several benchmark problems.     

Quantitative risk-based requirements reasoning

At NASA we have been developing and applying a risk management framework, "Defect Detection and Prevention" (DDP). It is based on a simple quantitative model of risk and is supported by custom software. We have used it to aid in study and planning for systems that employ advanced technologies. The framework has proven successful at identifying problematic requirements (those which will be the most difficult to attain), at optimizing the allocation of resources so as to maximize requirements attainment, at identifying areas where research investments should be made, and at supporting tradeoff analyses among major alternatives. We describe the DDP model, the information that populates a model, how DDP is used, and its tool support. DDP has been designed to aid decision making early in development. Detailed information is lacking at this early stage. Accordingly, DDP exhibits a number of strategic compromises between fidelity and tractability. The net result is an approach that appears both feasible and useful during early requirements decision making.     

Detection and enumeration of Campylobacter jejuni and Campylobacter coli by indirect impedimetry with an oxygen scavenging system

Six strains of Campylobacter jejuni and Campylobacter coli were shown to grow in a variety of media, but, with one exception, they were unable to produce sufficient change in the electrical properties of the medium to allow their detection by impedance monitoring. With the use of an indirect method based on absorption of evolved carbon dioxide and a medium containing the oxygen scavenger Oxyrase, all strains were detectable, and correlations between time to detection and the logarithm of the inoculum level were excellent. The level of interstrain variation was sufficiently low that all data could be consolidated into a single calibration curve (r = 0.987).     

Dynamic intuition in military command and control: why it is important,and how it should be developed

This paper considers combat dynamic intuition (CDI). We define CDI as the cognitive capability possessed by a military commander when conducting operations. The paper serves two purposes: firstly, we briefly review the previous research on decision making and learning in dynamic systems, in order to discuss the role of microworlds as training environments to improve CDI. In particular, we focus on the advantages of applying system dynamics techniques when designing microworlds to represent "real world" operational challenges. Secondly, we draw implications from a microworld-based experiment, where task complexity is the manipulated variable. The results indicate that environment simplification in itself is not enough to enhance learning in a microworld setting—a conscious pedagogical program, aimed at increasing the training intensity, should also be developed in support of such training. The latter suggestion should be considered an opportunity for further research on CDI improvement.

New modules for PCR-based gene targeting in Candida albicans: rapid and efficient gene targeting using 100 bp of flanking homology region

The use of PCR-based techniques for directed gene alterations has become a standard tool in Saccharomyces cerevisiae. In our efforts to increase the speed of functional analysis of Candida albicans genes, we constructed a modular system of plasmid vectors and successfully applied PCR-amplified functional analysis (FA)-cassettes in the transformation of C. albicans. These cassettes facilitate: (a) gene disruptions; (b) tagging of 3'-ends of genes with green fluorescent protein (GFP); and (c) replacements of endogenous promoters to achieve regulated expression. The modules consists of a core of three selectable marker genes, CaURA3, CaHIS1 and CaARG4. Modules for C-terminal GFP-tagging were generated by adding GFP-sequences flanked at the 5'-end by a (Gly-Ala)3-linker and at the 3'-end by the S. cerevisiae URA3-terminator to these selection markers. Promoter exchange modules consist of the respective marker genes followed by the regulatable CaMAL2 or CaMET3 promoters at their 3'-ends. In order to ensure a reliably high rate of homologous gene targeting, the flanking homology regions required a size of 100 bp of gene-specific sequences, which were provided with the oligonucleotide primers. The use of shorter flanking homology regions produced unsatisfactory results with C. albicans strain BWP17. With these new modules only a minimal set of primers is required to achieve the functional analysis of C. albicans genes and, therefore, provides a basic tool to increase the number of functionally characterized C. albicans genes of this human pathogen in the near future.