Context-Oriented Programming

Context-dependent behavior is becoming increasingly important for a wide range of application domains, from pervasive computing to common business applications. Unfortunately, mainstream programming languages do not provide mechanisms that enable software entities to adapt their behavior dynamically to the current execution context. This leads developers to adopt convoluted designs to achieve the necessary runtime flexibility. We propose a new programming technique called Context-oriented Programming (COP) which addresses this problem. COP treats context explicitly, and provides mechanisms to dynamically adapt behavior in reaction to changes in context, even after system deployment at runtime. In this paper we lay the foundations of COP, show how dynamic layer activation enables multi-dimensional dispatch, illustrate the application of COP by examples in several language extensions, and demonstrate that COP is largely independent of other commitments to programming style.

Evaluation of Binocular Eye Trackers and Algorithms for 3D Gaze Interaction in Virtual Reality Environments

Tracking user’s visual attention is a fundamental aspect in novel human-computer interaction paradigms found in Virtual Reality. For example, multimodal interfaces or dialogue-based communications with virtual and real agents greatly benefit from the analysis of the user’s visual attention as a vital source for deictic references or turn-taking signals. Current approaches to determine visual attention rely primarily on monocular eye trackers. Hence they are restricted to the interpretation of two-dimensional fixations relative to a defined area of projection. The study presented in this article compares precision, accuracy and application performance of two binocular eye tracking devices. Two algorithms are compared which derive depth information as required for visual attention-based 3D interfaces. This information is further applied to an improved VR selection task in which a binocular eye tracker and an adaptive neural network algorithm is used during the disambiguation of partly occluded objects.

Continental-scale temperature variability during the past two millennia

Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between ad 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period ad 1971–2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years.

Clinical and microbiological results following nonsurgical periodontal therapy with or without local administration of piperacillin/tazobactam

OBJECTIVES We assessed if adjunct administration of piperacillin/tazobactam added clinical and microbiological treatment benefits. MATERIALS AND METHODS Thirty-six subjects (mean age 52.1 years (SD ± 10.3)) (NS by group) with chronic periodontitis were randomly enrolled receiving subgingival debridement and the local administration of piperacillin/tazobactam (test group) or debridement alone (control group). Bleeding on probing (BOP), probing pocket depth (PPD), and microbiological counts of 74 species were studied by checkerboard DNA-DNA hybridization up to month 6 after treatment. RESULTS Mean PPD changes between baseline and month 6 in the test and control groups were 1.5 and 1.8 mm, respectively (NS between groups). BOP in both groups decreased from about 80 to 40 %. At 4 and 12 weeks, lower counts of the following bacteria were found in the test group (site level): Fusobacterium species, Parvimonas micra, Pseudomonas aeruginosa, Staphylococcus aureus, Tannerella forsythia, Treponema denticola, and a composite load of nine pathogens (p < 0.001). At week 26, subjects receiving local antibiotics had a lower prevalence at tested sites for Fusobacterium nucleatum sp. polymorphum, Fusobacterium periodonticum, P. micra, and T. denticola. CONCLUSIONS At 26 weeks, treatment with or without piperacillin/tazobactam resulted in similar BOP and PPD improvements. At week 26 and at the subject level, the prevalence of 4/74 pathogens was found at lower counts in the group receiving local antibiotics. CLINICAL RELEVANCE Administration of piperacillin/tazobactam reduces the prevalence of Fusobacterium, P. micra, and T. denticola to a greater extent than debridement alone but with no short-term differences in PPD or BOP.

[Exotic snake bites in Switzerland].

Exotic snake bites are not rare in Switzerland. Treatment can be challenging for medical staff particularly as rapid and focused management are critical to improve patient outcome. The case of a young herpetologist bitten by an exotic venomous snake is used to review measures to be taken before arrival at the emergency department and to highlight key points of management. Resources for the obtention of expert advice and antivenoms are also reported.

Incremental Dynamic Updates with First-class Contexts

Highly available software systems occasionally need to be updated while avoiding downtime. Dynamic software updates reduce down-time, but still require the system to reach a quiescent state in which a global update can be performed. This can be difficult for multi-threaded systems. We present a novel approach to dynamic updates using first-class contexts, called Theseus. First-class contexts make global updates unnecessary: existing threads run to termination in an old context, while new threads start in a new, updated context; consistency between contexts is ensured with the help of bidirectional transformations. We show that for multi-threaded systems with coherent memory, first-class contexts offer a practical and flexible approach to dynamic updates, with acceptable overhead.