Jim Hao Chen

The effect of hiatus hernia on gastro-oesophageal junction pressure

BACKGROUND Hiatus hernia and lower oesophageal sphincter hypotension are often viewed as opposing hypotheses for gastro-oesophageal junction incompetence. AIMS To examine the interaction between hiatus hernia and lower oesophageal sphincter hypotension. METHODS In seven normal subjects and seven patients with hiatus hernia, the squamocolumnar junction and intragastric margin of the gastro-oesophageal junction were marked with endoscopically placed clips. Axial and radial characteristics of the gastro-oesophageal junction high pressure zone were mapped relative to the hiatus and clips during concurrent fluoroscopy and manometry. Responses to inspiration and abdominal compression were also analysed. RESULTS In normal individuals the squamocolumnar junction was 0.5 cm below the hiatus and the gastro-oesophageal junction high pressure zone extended 1.1 cm distal to that. In those with hiatus hernia, the gastro-oesophageal junction high pressure zone had two discrete segments, one proximal to the squamocolumnar junction and one distal, attributable to the extrinsic compression within the hiatal canal. Inspiration and abdominal compression mainly augmented the distal one. Simulation of hernia reduction by algebraically summing the proximal segment pressures with the hiatal canal pressures restored normal maximal pressure, radial asymmetry, and dynamic responses of the gastro-oesophageal junction. CONCLUSIONS Hiatus hernia reduces lower oesophageal sphincter pressure and alters its dynamic responsiveness by spatially separating pressure components derived from the intrinsic lower oesophageal sphincter and the extrinsic compression of the oesophagus within the hiatal canal.

Multipathing with MPTCP and OpenFlow

Data sets in e-science are increasing exponentially in size. To transfer these huge data sets we need to make efficient use of all available network capacity. This means using multiple paths when available. In this paper a prototype of such a multipath network is presented. Several emerging network technologies are integrated to achieve the goal of efficient high end-to-end throughput. Multipath TCP is used by the end hosts to distribute the traffic across multiple paths and OpenFlow is used within the network to do the wide area traffic engineering. Extensive monitoring is part of the demonstration. A website will show the actual topology (including link outages), the paths provisioned through the network and traffic statistics on all links and the end-to-end aggregate throughput.

The InstaGENI initiative: An architecture for distributed systems and advanced programmable networks

In this paper, we describe InstaGENI, a distributed cloud based on programmable networks designed for the GENI Mesoscale deployment and large-scale distributed research projects. The InstaGENI architecture closely integrates a lightweight cluster design with software-defined networking, Hardware-as-a-Service and Containers-as-a-Service, remote monitoring and management, and high-performance inter-site networking. The initial InstaGENI deployment will encompass 34 sites across the United States, interconnected through a specialized GENI backbone network deployed over national, regional and campus research and education networks, with international network extensions to sites across the world.

Design and Implementation of an Automatic Network Topology Discovery System for the Future Internet Across Different Domains

In part because of the limitations of the TCP/IPprotocols used by the current Internet, the Future Internet has become an attractive network research topic. Recently, several projects focused on the Future Internet have been launched around the globe based on the Open Flow platform, such as those that are part of the GENI project in the U.S., the OFELIA project of FP7 in the E.U., and the FIRST project in Korea. Because Open Flow allows researchers to design and develop innovative protocols, it could be applied in different situations for constructing desired network environments. Open Flow is not limited to single controller environment within a single network domain. It allows network engineers to construct a multi-controller environment across various network domains. In this paper, we design and implement an automatic network topology discovery mechanism based on multi-controller Open Flow network. The result has been applied to a large-scale Open Flow testbed implemented across research institutes at different sites for path-finding and management.

Next Generation Clouds, the Chameleon Cloud Testbed, and Software Defined Networking (SDN)

Next generation clouds, based on highly programmable, high performance networks, especially those supported by Software-Defined-Networking (SDN) have attracted significant interest by research communities. In recognition of the increasing importance of advancing cloud services and technologies, especially for providing Internet services, the US National Science Foundation (NSF) established a project, the NSF Cloud initiative, to enable the computer science research community to develop and experiment with novel cloud architectures and create new, architecturally enabled innovative applications for cloud computing through empirical research experimentation by using large scale distributed cloud test beds. This paper provides an overview of one of those test beds, the Chameleon Cloud tested, with an additional description of the integration of that test bed with high programmable, high performance networks, based on SDN. The Chameleon project is designing, deploying, and operating a large scale, highly distributed experimental environment for empirical cloud research, integrated with high programmable networks as a foundation resource.

Software-Defined Network Exchanges (SDXs): Architecture, services, capabilities, and foundation technologies

Software Defined Networks (SDNs), primarily based on OpenFlow, are being deployed in single domain networks around the world. The popularity of SDNs has given rise to multiple considerations about designing, implementing, and operating Software-Defined Network Exchanges (SDXs), to enable SDNs to interconnect SDN islands and to extend SDNs across multiple domains. These goals can be accomplished only by developing new techniques that extend the single domain orientation of current SDN/OpenFlow approaches to include capabilities for multidomain control, including those for resource discovery, signaling, and dynamic provisioning. Several networking research communities have begun to investigate these concepts. Early architectural models of SDXs have been designed and implemented as prototypes. These SDXs are being used to conduct experiments and to demonstrate the potentials of SDXs.

Creating environments for innovation: Designing and implementing advanced experimental network research testbeds based on the Global Lambda Integrated Facility and the StarLight Exchange

Large scale national and international experimental research environments are required to advance communication services and supporting network architecture, technology, and infrastructure. Theories and concepts are often explored using simulation and modeling techniques within labs or on small scale testbeds. However, while such testbeds are valuable resources for the research process, these facilities alone cannot provide an appropriate approximation of the real world conditions required to explore ideas at scale. Very large scale global, experimental network research capabilities are required to deeply investigate innovative concepts. For many years, network testbeds were created to address fairly specific, well defined, limited research goals, and they were implemented for fairly short periods. Recently, taking advantage of a number of macro information technology trends, such as virtualization and programmable resources, several network research communities have been developing innovative types of network research environments. Instead of designing traditional network testbeds, research communities are designing large scale, highly flexible distributed platforms that can be used to create many different types of testbeds. Also, rather than creating short term testbeds for limited research objectives, these new environments are being designed as long term persistent resources to support many types of experimental research. This paper describes the motivations for this trend, provides several examples of large scale distributed network research environments based on the Global Lambda Integrated Facility (GLIF) and the StarLight Exchange Facility, including the Global Environment for Network Innovation (GENI), and indicates emerging future trends for these types of environments.

The GENI experiment engine

We describe the GENI Experiment Engine, a Distributed-Platform-as-a-Service facility designed to be implemented on a distributed testbed or infrastructure. The GEE is intended to provide rapid and convenient access to a distributed infrastructure for simple, easy-to-configure experiments and applications. Specifically, the design goal of the GEE is to permit experimenters and application writers to: (a) allocate a GEE slicelet; (b) deploy a simple experiment or application; (c) run the experiment; (d) collect the results; and (e) tear down the experiment, starting from scratch, within five minutes. The GEE consists of four cooperating services over the GENI infrastructure, which together with pre-allocated slicelets and a pre-allocated network offers a complete, ready to use, sliceable platform over the GENI Infrastructure.

Network Virtualization Implementation over Global Research Production Networks

The concept of network virtualization has attracted increasing attention by researchers designing and modeling the next-generation Internet paradigm. Researchers need a new type of hybrid network to construct experimental environments for testing new services, architecture, and technologies, especially network protocols, without affecting existing traffic. This paper presents our work on implementing a large-scale testbed that has been created over production networks by integrating novel technologies such as cloud computing, software defined networking, and virtual switches. This approach provides researchers with an experimental networking testbed where traffic can be controlled via programmable virtual switches and dynamic adjustability for many types of network emulation experiments. This system also provides a feasible solution for the networking requirements of federated cloud system.

Dynamic reconstruction of the orophanryngeal swallow using computer based animation

The oropharyngeal swallow was modeled with computer based animation using data from biplane videofluorographic and dynamic CT images of 10 ml liquid swallows of a volunteer subject. Tracings of oropharyngeal structures from synchronized, magnification adjusted, images of the posterior-anterior, lateral, and cross-sectional planes were aligned in three dimensions with graphics animation software. Twenty oropharyngeal configurations were created at 1/15 second intervals to dynamically illustrate the swallow. These three-dimensional reconfigurations could be sequenced into an animation routine. Software analysis of the model permitted quantification of structural movement and intrapharyngeal volume across time. Such analyses can be used to detail both the efficacy of individual functional elements of the swallow as well as global pump function. It is hoped that modeling the oropharyngeal swallow will be useful to analyze mechanisms of dysphagia and the mechanics of compensatory therapeutic strategies.