PAT: A protocol analysis tutor

A computer-aided learning package, PAT (protocol analysis tutor), developed as a tool to help students and novice data communications engineers learn the basic concepts of data link protocols, is described. The tool enables users to construct the frames of the HDLC (high-level data link control) standard data-link level protocol. The frames can be combined in sequence to form a call, representing the execution of the protocol. At all stages, checks of both the syntax and semantics of the call are made     

Grating overgrowth and defect structures indistributed-feedback-buried heterostructure laser diodes

Distributed-feedback (DFB)-buried heterostructure lasers incorporating a substrate grating require epitaxy of waveguide layers over the corrugated grating surfaces. Unlike epitaxy on planar (100) substrate, the corrugated substrate surface contains undesirable crystal facets which lead to an uncontrollable variation in local composition during epitaxy, and thereby results in strong localized misfit stresses. These localized misfit stresses further affect the subsequent growth of high quality layers which constitute the active device structures. To address the general issue of epitaxy on a corrugated surface, a thermodynamic analysis is performed for surface mass transport on a grating surface at normal growth temperature to show that grating wash-out is a thermodynamically favorable process. However, growth on a perfectly preserved grating is undesirable due to the composition shift on groove facets. A systematic study of substrate orientation dependent composition variation of quaternary layers indicates a composition shift generally toward In and P rich directions for orientations from (100)-(111). Conditions for a strain free waveguide layer growth are demonstrated. The commonly observed imperfections associated with a grating overgrowth are summarized, and their effects on device reliability are discussed     

Evidence for inhibition of monoamine oxidase in vivo in rat brain by 7,8-dichloro-1,2,3,4-tetrahydroisoquinoline

7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline (DCTQ) (50 mg/kg i.p.) antagonized the inactivation of MAO by pargyline as measured by direct enzyme assays in brain homogenates and by accumulation of hypothalamic catecholamines. These findings lend credence to the earlier interpretation that changes in brain concentrations of biogenic amines and their metabolites in DCTQ-treated rats were due at least in part to MAO inhibition.     

Data access in distributed simulations of multi-agent systems

Distributed simulation has emerged as an important instrument for studying large-scale complex systems. Such systems inherently consist of a large number of components, which operate in a large shared state space interacting with it in highly dynamic and unpredictable ways. Optimising access to the shared state space is crucial for achieving efficient simulation executions. Data accesses may take two forms: locating data according to a set of attribute value ranges (range query) or locating a particular state variable from the given identifier (ID query and update). This paper proposes two alternative routing approaches, namely the address-based approach, which locates data according to their address information, and the range-based approach, whose operation is based on looking up attribute value range information along the paths to the destinations. The two algorithms are discussed and analysed in the context of PDES-MAS, a framework for the distributed simulation of multi-agent systems, which uses a hierarchical infrastructure to manage the shared state space. The paper introduces a generic meta-simulation framework which is used to perform a quantitative comparative analysis of the proposed algorithms under various circumstances.     

Correction to Schneider and Logan (2006).

Reports an error in "Hierarchical Control of Cognitive Processes: Switching Tasks in Sequences" by Darryl W. Schneider and Gordon D. Logan (Journal of Experimental Psychology: General, 2006[Nov], Vol 135[4], 623-640). Two task transitions were classified incorrectly in Table 7 (p. 634). The task transition at Serial Position 1 for sequence switches of the AABB sequence should be TR instead of TS. The task transition at Serial Position 1 for sequence switches of the ABBA sequence should be TS instead of TR. Two sections of text in the Results and Discussion section of Experiment 4 were affected by the misclassifications. The corrected text is provided for the Error rate analysis section (pp. 634-635) and the RT analysis section (p.635). These corrections do not alter any of the conclusions drawn from the original text. (The following abstract of the original article appeared in record 2006-20327-009.) Hierarchical control of cognitive processes was studied by examining the relationship between sequence- and task-level processing in the performance of explicit, memorized task sequences. In 4 experiments, switch costs in task-switching performance were perturbed by sequence initiation times that varied with sequence complexity, preparation time, and type of sequence transition (repetition or switch). Hierarchical control was inferred from these sequence initiation time effects and the recurrent finding of no switch cost at the first serial position across sequences, the point at which sequence-level processes are likely active in maintaining or instantiating a hierarchical control structure in working memory. These findings resonate with past research on motor programs and serial memory and provide new insights into the concepts of task set and control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

State Space Search with Prioritised Soft Constraints

This paper addresses two issues: how to choose between solutions for a problem specified by multiple criteria, and how to search for solutions in such situations. We argue against an approach common in decision theory, reducing several criteria to a single cost (e.g., using a weighted sum cost function) and instead propose a way of partially ordering solutions satisfying a set of prioritised soft constraints. We describe a generalisation of the A^* search algorithm which uses this ordering and prove that under certain reasonable assumptions the algorithm is complete and optimal.     

Phage typing of Staphylococcus aureus associated with subclinical bovine mastitis

Six hundred and seventeen isolates of Staphylococcus aureus from subclinical clinical mastitis cases in 63 dairy herds in Northern Ireland were typed using a set of 25 phages. Ninety-four per cent of the isolates were typable, with nine phages, predominantly from groups I and III, being responsible for almost all of the lysis. Although 68 phage patterns were found, six of them typed 47.2% of the isolates. One strain accounted for 14.7% of the isolates, but the largest number of strains (44) was restricted to individual farms. The epidemiological significance of these findings for on-farm mastitis control is discussed.     

Biological perchlorate reduction in high-salinity solutions

Perchlorate (ClO4-) has been detected in numerous ground and surface waters, and has recently been added to the drinking water Candidate Contaminant List in the United States. Perchlorate can be removed from drinking water using ion exchange, but this results in the production of highly saline (7-12%) perchlorate-contaminated brines. Perchlorate-degrading microbial enrichments capable of growth in highly saline water were obtained by screening six salt water environments including marine and lake surface waters, salt marshes, subtidal sediments, and a biofilm/sludge from a seawater filter. Perchlorate reduction was obtained in three of these samples (seawater, saline lake water, and biofilm/sludge) at a salinity of 3%. The salinity range of two of these cultures was extended through serial transfers into media having higher salt concentrations (3-7%). Growth rates were measured over a salinity range of 1-15%. The maximum growth rate measured for the saline lake-water enrichment was 0.060+/-0.003 d(-1) (doubling time of 11.6+/-0.8 d) at a salinity of 5%. Growth rates decreased to 0.037+/-0.002 d(-1) at a salinity of 11%, and no growth was observed at salinities of 13 or 15%. These results demonstrate for the first time that biological perchlorate reduction is possible in solutions having a salinity typical of ion exchange brines.     

Suppression of anchorage-independent growth and matrigel invasion and delayed tumor formation by elevated expression of fibulin-1D in human fibrosarcoma-derived cell lines

Using differential display, we identified an mRNA that is markedly down-regulated in cell line 6A/SB1, derived from a fibrosarcoma formed in an athymic mouse following injection of carcinogen-transformed MSU-1.1 cells. The nontumorigenic parental cell strain, MSU-1.1, expresses high levels of this mRNA. Sequencing of the corresponding cDNA fragment revealed that it corresponded to an expressed sequence tag, which ultimately led to its identification as the fibulin-1D gene. Fibulin-1 is a cysteine-rich, calcium-binding extracellular matrix and plasma protein, which has four isoforms, A-D, derived from alternative splicing. Northern and Western blotting analysis of 16 cell lines established from tumors formed in athymic mice by MSU-1.1-derived cell strains independently transformed in culture showed that 44% exhibited low level or lack of expression of fibulin-1D mRNA and protein. In a similar analysis of 15 malignant cell lines derived from patients, 80% showed low level or no expression. To study the role of fibulin-1D in transformation, we transfected 6A/SB1 cells and a human fibrosarcoma-derived cell line (SHAC) with a fibulin-1D cDNA expression construct. Transfectants displaying high levels of fibulin-1D were isolated and characterized. Elevated expression of fibulin-1D led to reduced ability to form colonies in soft agar and reduced invasive potential as tested in a matrigel in vitro invasion assay. Furthermore, expression of fibulin-1D resulted in a markedly extended latency in tumor formation in athymic mice. These results indicate that low expression of fibulin-1D plays a role in tumor formation and invasion.