Teaching Networks to Digital Humanists

Contribution: A technical course in a multidisciplinary university program has to provide high-level skills, with limited lecturing hours and student background. This article investigates the principles for its design and reports about a study case. Background: The overall course organization needs to address specific learning targets and teaching techniques, different from those used in traditional courses on the topic. Research Question: A stepwise strategy assists a principled design that allows dynamic, long-term improvements. Methodology: The evaluation of its applicability requires a years-long record of historical data. The article studies the evolution of a course over six years using simple monitoring techniques: surveys and rubric-based examinations. Findings: Monitoring emerges as an essential feature for course evolution: a focused examination provides the best results, while institutional, wide-spectrum surveys appear to be of little help

Automatic Segmentation of Posterior Pole Retinal Layers In Patients with Early Stage Glaucoma Using Spectral Domain Optical Coherence Tomography

Purpose: To measure Ganglion Cell Layer (GCL) and Retinal Nerve Fiber Layer (RNFL) thickness of the retinal posterior pole in patients with early stage primary open-angle glaucoma (POAG) using the new automatic segmentation technology of spectral domain optical coherence tomograph (SD-OCT). Methods: 37 clinical records of patients with early glaucoma (grade 1 to 2 according to the Glaucoma Staging System 2) and 40 age and sex-matched controls were considered in this case-control observational retrospective study. Automated segmentation of GCL and RNFL was performed in one randomly selected eye from the electronic OCT records of each participant using the new Spectralis SD-OCT segmentation technology (Heidelberg Engineering, Inc., Heidelberg, Germany). Thickness of different retinal layers was obtained from each Posterior Pole volumetric scan. Measurements of the peripapillary RNFL thickness (pRNFLt) were also obtained and then compared with those of posterior pole RNFL thickness (ppRNFLt). Results: Both GCL and RNFL were significantly thinner at the retinal posterior pole in the POAG group as compared to the control group (p<0,0001). Furthermore, pRNFLt was significantly thinner in the glaucoma group as opposed to the control group (p<0,0001). Measurements of pRNFLt were significantly correlated with those of the ppRNFLt (Pearson’s coefficient r=0.863). Conclusions: The new Spectralis SD-OCT automatic segmentation tool may be useful in evaluating structural damage in patients with early glaucoma, by providing complementary measurements to the clinical assessment of glaucoma that could be used in conjunction with other relevant parameters in the diagnosis and the evaluation of the progression of the disease

Optimizing bulk data transfers using network measurements: a practical case

SUMMARY The quality of the connectivity provided by the network infrastructure of a Grid is a crucial factor to guarantee the accessibility of Grid services, schedulate efficiently processing and data transfer activity on the Grid and meet QoS expectations. Yet most Grid application do not take into consideration the expected performance of the network resources they plan to use. In this paper we describe the effective use of a Grid Monitoring framework, whose measurements are used to introduce network aware features in a legacy application. We use GlueDomains, a network monitoring framework oriented to Grid infrastructures that measures a small (although possibly extensible) set of network parameters. Such framework works off the shelf with minimal administrative effort, is reliable, and has a negligible impact on system operation. The deployment covers a Metropolitan Grid infrastructure, aimed at supporting a data intensive eScience application. We describe a real use case consisting of bulk data trasfers during the operation of the Grid for the Virgo experiment

Secure token passing at application level

We introduce an application level implementation of a token passing operation. After an introduction that explains the conceptual principles, we describe exhaustively the state machines that implement our solution. The security requirements are carefully considered, since the token is a sensitive resource, but without introducing scalability limits. We aim at a general purpose token passing primitive: we do not enter the domain of the distributed coordination algorithms that can be implemented using the proposed operation. We discuss its practical utilization, and we indicate as primary application area the coordination of servers in a distributed infrastructure: this matches service oriented Grids as well as other emerging paradigms. Its usage is explained with a simplified use case. A working prototype exists, and we report about experimental results that confirm our claims concerning performance. Key words: token passing, random walk, group membership. 1

GlueDomains

A scalable approach to Grid network monitoring developed in the framework of the DATATAG project

Monitoring A Virtual Network Infrastructure: An Iaas Perspective

Infrastructure as a Service (IaaS) providers keep extending with new features the computing infrastructures they offer on a pay per use basis. In this paper we explore reasons and opportunities to include networking within such features, meeting the demand of users that need composite computing architectures similar to Grids. The introduction of networking capabilities within IaaSs would further increase the potential of this technology, and also foster an evolution of Grids towards a confluence, thus incorporating the experiences matured in this environment. Network monitoring emerges as a relevant feature of such virtual architectures, which must exhibit the distinguishing properties of the IaaS paradigm: scalability, dynamic configuration, accounting. Monitoring tools developed with the same purpose in Grids provide useful insights on problems and solutions