Test Case Generation as an AI Planning Problem

While Artificial Intelligence techniques have been applied to a variety of software engineering applications, the area of automated software testing remains largely unexplored. Yet, test cases for certain types of systems (e.g., those with command language interfaces and transaction based systems) are similar to plans. We have exploited this similarity by constructing an automated test case generator with an AI planning system at its core. We compared the functionality and output of two systems, one based on Software Engineering techniques and the other on planning, for a real application: the StorageTek robot tape library command language. From this, we showed that AI planning is a viable technique for test case generation and that the two approaches are complementary in their capabilities.     

The Effects Of Humic Substances On Pinus Callus Are Reversed By 2,4-Dichlorophenoxyacetic Acid

The reversal of humic matter-induced inhibition of callus growth and metabolism by 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in Pinus laricio. Two forest humic fractions (relative molecular mass (M_r) > 3500), derived from soil under Fagus sylvatica (Fs) and Abies alba (Aa) plantation, were used. Pinus laricio callus was grown for a subculture period (4 weeks) on Basal Murashige and Skoog (MS) medium plus forest humic matters (Fs or Aa), at a concentration of 1 mg C/l, and then was transferred, for an additional four weeks, to a MS medium culture without humic matter, but with different hormones: indole-3-acetic acid (IAA, 2 mg/1) or 2,4-dichlorophenoxyacetic acid (2,4-D, 0.5 mg/1) and/or 6-benzylaminopurine (BAP, 0.25 mg/1). Growth of calluse, glucose, fructose, and sucrose contents, and activities of soluble and bound invertases, glucokinase, phosphoglucose isomerase, aldolase, and pyruvate kinase were monitored. The results show a negative effect of humic fractions on callus growth, due to decreased utilization of glucose and fructose, and decreased activities of glycolytic enzymes. The effects are reversible. Substitution of humic fractions with 2,4-D+BAP or 2,4-D is followed by an increase of glycolytic enzyme activities and, consequently, by the utilization of glucose and fructose that induces a restart of growth. In contrast, the inhibitory effects of humic fractions persist when they are substituted with BAP alone, indicating that only the auxin 2,4-D is capable of reversing the negative effects. A possible competitive action on the auxin-binding site between 2,4-D and the chemical structures in the forest humic fractions is suggested.     

Simulating Coxian phase-type distributions for patient survival

Coxian phase-type distributions are a special type of Markov model that can be used to represent survival times in terms of phases through which an individual may progress until they eventually leave the system completely. Previous research has considered the Coxian phase-type distribution to be ideal in representing patient survival in hospital. However, problems exist in fitting the distributions. This paper investigates the problems that arise with the fitting process by simulating various Coxian phase-type models for the representation of patient survival and examining the estimated parameter values and eigenvalues obtained. The results indicate that numerical methods previously used for fitting the model parameters do not always converge. An alternative technique is therefore considered. All methods are influenced by the choice of initial parameter values. The investigation uses a data set of 1439 elderly patients and models their survival time, the length of time they spend in a UK hospital.     

Geodesign application for bio-swale design: rule-based approach stormwater management for Ottawa Street North in Hamilton,Ontario

With increases in storm frequency and intensity, municipalities are finding new ways of managing stormwater. Solutions require collaboration across planning disciplines and input from an informed public. This study compares a system of bioswales to existing curb and gutter infrastructure in a post-industrial streetscape of Hamilton, Ontario. Using the geodesign process, a section of Ottawa St. North was modelled to show how green infrastructure can ease the burden on aging, combined sewer systems. Qualitative data was gathered from residents of the neighbourhood through field notes, and quantitative geospatial data through GIS. Parametric modelling was used to generate a design, and scenarios created to show resulting impacts on stormwater run-off. The model was posted online as an interactive presentation, accessible to all stakeholders for review and comment. The results of the study demonstrate powerful new tools that can assist landscape architects in designing, collaborating and communicating stormwater strategies.     

Intestinal apolipoprotein B secretion is inhibited by the flavonoid quercetin: Potential role of microsomal triglyceride transfer protein and diacylglycerol acyltransferase

Recent studies have yielded evidence that plant flavonoids reduce hepatic lipid and apolipoprotein B (apoB) secretion. However, the possible role of flavonoids in regulating lipid and apoB secretion by the intestine has not been studied. The purpose of our study was to examine the effects of quercetin, a common dietary flavonoid, on TAG and apoB secretion in a human intestinal cell-line, CaCo-2. Differentiated postconfluent CaCo-2 cells grown on filters and pretreated with quercetin for 8 h were shown by ELISA to inhibit basolateral apoB secretion in a dose-dependent manner. At 15 μM, the secretion of both apoB-100 and apoB-48 were inhibited similarly. This effect was shown to be specific, as quercetin did not affect the incorporation of [³⁵S]methionine/cysteine into secreted TCA-precipitable proteins. To determine the mechanism underlying this inhibitory effect, we examined two regulatory points: IAG availability and lipid transfer to the lipoprotein particle. Quercetin inhibited TAG synthesis under both basal and lipid-rich conditions, indicating that lipid availability is a determining factor in the regulation of apoB secretion by quercetin. The reduction was due at least in part to a decrease in diacylglycerol acyltransferase activity. We next examined lipid transfer or lipidation of the lipoprotein particle by analyzing microsomal IAG transfer protein (MTP) activity. Quercetin decreased MTP activity moderately. In summary, the data demonstrated that pharmacological concentrations of quercetin are a potent inhibitor of intestinal apoB secretion and that reduced lipid availability and lipidation in the lipoprotein assembly step are the mechanism for the suppression of apoB-containing lipoprotein secretion by quercetin in CaCo-2 cells.     

Evaluating robustness in a two layer simulated robot architecture

Many two layer robot architectures have been proposed and implemented. While justification for the design can be well argued, how does one know it is really a good idea? In this paper, one describes a two layer architecture (reinforcement learning in the bottom layer and POMDP planning at the top) for a simulated robot and summarize a set of three experiments in which one evaluated the design. To address the many difficulties of evaluating robot architectures, one advocates an experimental approach in which design criteria are elucidated and then form the basis for the evaluation experiments. In our case, one tests the implementation for its reliability and generalization (our design criteria) by comparing our architecture to one in which a key component is substituted; in these experiments, one demonstrates significant performance gains on the design criteria for our architecture.     

Chloroplastic glycolipids fuel aldehyde biosynthesis in the marine diatom Thalassiosira rotula

Enzymatic preparations and specialized analytical tools have shown that chloroplast-derived glycolipids are the main substrates for the biosynthetic pathway that produces antiproliferative polyunsaturated aldehydes in broken cells of the marine diatom Thalassiosira rotula. This process, which is associated with the formation of free fatty acids and lyso compounds from polar lipids but not triglycerides, is largely dependent on glycolipid hydrolytic activity, rather than phospholipase A(2) as previously suggested. Preliminary characterization of lipolytic enzymes has revealed protein bands of 40-45 kDa. Under native conditions these proteins seem to be associated with soluble aggregates that have an apparent molecular weight of approximately 200 kDa. The biochemical process, which is similar to that described in the algal-bloom forming diatom Skeletonema costatum, suggests a mechanism based on decompartmentalization and mixing of preexisting enzymes and substrates.