Scalable Overlay Multicast Tree Construction for QoS-Constrained Media Streaming

Overlay networks have become popular in recent times for content distribution and end-system multicasting of media streams. In the latter case, the motivation is based on the lack of widespread deployment of IP multicast and the ability to perform end-host processing. However, constructing routes between various end-hosts, so that data can be streamed from content publishers to many thousands of subscribers, each having their own QoS constraints, is still a challenging problem. First, any routes between end-hosts using trees built on top of overlay networks can increase stress on the underlying physical network, due to multiple instances of the same data traversing a given physical link. Second, because overlay routes between end-hosts may traverse physical network links more than once, they increase the end-to-end latency compared to IP-level routing. Third, algorithms for constructing efficient, large-scale trees that reduce link stress and latency are typically more complex. This paper therefore compares various methods to construct multicast trees between end-systems, that vary in terms of implementation costs and their ability to support per-subscriber QoS constraints. We describe several algorithms that make trade-offs between algorithmic complexity, physical link stress and latency. While no algorithm is best in all three cases we show how it is possible to efficiently build trees for several thousand subscribers with latencies within a factor of two of the optimal, and link stresses comparable to, or better than, existing technologies

Hollow Core, Whispering Gallery Resonator Sensors

A review of hollow core whispering gallery resonators (WGRs)is given. After a short introduction to the topic of whispering gallery resonators we provide a description of whispering gallery modes in hollow or liquid core WGRs. Next, whispering gallery mode (WGM) sensing mechanisms are outlined and some fabrication methods for microbubbles, microcapillaries and other tubular WGM devices are discussed. We then focus on the most common applications of hollow core WGRs, namely refractive index and temperature sensing, gas sensing, force sensing, biosensing, and lasing. The review highlights some of the key papers in this field and gives the reader a general overview of the current state-of-the-art

Bayesian time-varying autoregressions: Theory, methods and applications

We review the class of time-varying autoregressive (TVAR) models and a range of related recent developments of Bayesian time series modelling

Life, Liberty, and the Pursuit of Rum: The Phenomenon of Liberalism in British Pirate Law

Seventeenth and eighteenth century British pirates abided by simple legal codes aboard their ships. These codes determined what was and was not allowed, how punishments were determined and doled out, and how loot and rations were divided. What is most significant about these codes, however, is how remarkably progressive they were as legal documents, not unlike the liberalism being developed contemporaneously in Europe. Progressive policies began pragmatically in order to maintain control as pirate captains had no traditional legitimacy, but evolved into a true liberal legal tradition as pirates formed socio-political groups. The legal punishments and guarantees of rights found in pirate codes demonstrate just how progressive pirate codes were for their time. This trend is most apparent when surviving pirate codes are compared directly to contemporary British naval law found in the Articles of War (1661). Additionally, as codes were shared and passed on to successors, the development of a legal tradition and isolation from legitimate society reveals that pirates are a demographic that must be examined by historians not as criminal organizations, but as socio-political and even creole communities.</p

Mutable Protection Domains: Towards a Component-Based System for Dependable and Predictable Computing

The increasing complexity of software poses signicant challenges for real-time and embedded systems beyond those based purely on timeliness. With embedded sys-tems and applications running on everything from mobile phones, PDAs, to automobiles, aircraft and beyond, an emerging challenge is to ensure both the functional and tim-ing correctness of complex software. We argue that static analysis of software is insufcient to verify the safety of all possible control ow interactions. Likewise, a static sys-tem structure upon which software can be isolated in sepa-rate protection domains, thereby dening immutable bound-aries between system and application-level code, is too in-exible to the challenges faced by real-time applications with explicit timing requirements. This paper, therefore, in-vestigates a concept called mutable protection domains that supports the notion of hardware-adaptable isolation boundaries between software components. In this way, a system can be dynamically recongured to maximize soft-ware fault isolation, increasing dependability, while guar-anteeing various tasks are executed according to specic time constraints. Using a series of simulations on multi-dimensional, multiple-choice knapsack problems, we show how various heuristics compare in their ability to rapidly reorganize the fault isolation boundaries of a component-based system, to ensure resource constraints while simulta-neously maximizing isolation benet. Our ssh oneshot algorithm offers a promising approach to address system dynamics, including changing component invocation pat-terns, changing execution times, and mispredictions in iso-lation costs due to factors such as caching. This material is based upon work supported by the National Science Foundation under Grant Numbers 0615153 and 0720464. Any opinions, ndings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reect the views of the National Science Foundation.

Development of Modeling Capabilities for Launch Pad Acoustics and Ignition Transient Environment Prediction

This paper presents development efforts to establish modeling capabilities for launch vehicle liftoff acoustics and ignition transient environment predictions. Peak acoustic loads experienced by the launch vehicle occur during liftoff with strong interaction between the vehicle and the launch facility. Acoustic prediction engineering tools based on empirical models are of limited value in efforts to proactively design and optimize launch vehicles and launch facility configurations for liftoff acoustics. Modeling approaches are needed that capture the important details of the plume flow environment including the ignition transient, identify the noise generation sources, and allow assessment of the effects of launch pad geometric details and acoustic mitigation measures such as water injection. This paper presents a status of the CFD tools developed by the MSFC Fluid Dynamics Branch featuring advanced multi-physics modeling capabilities developed towards this goal. Validation and application examples are presented along with an overview of application in the prediction of liftoff environments and the design of targeted mitigation measures such as launch pad configuration and sound suppression water placement

Collaborative development of the Arrowsmith two node search interface designed for laboratory investigators.

Arrowsmith is a unique computer-assisted strategy designed to assist investigators in detecting biologically-relevant connections between two disparate sets of articles in Medline. This paper describes how an inter-institutional consortium of neuroscientists used the UIC Arrowsmith web interface http://arrowsmith.psych.uic.edu in their daily work and guided the development, refinement and expansion of the system into a suite of tools intended for use by the wider scientific community

Ultrafast photoisomerisation of an isolated retinoid

The photoinduced excited state dynamics of gas-phase trans-retinoate (deprotonated trans-retinoic acid, trans-RA−) are studied using tandem ion mobility spectrometry coupled with laser spectroscopy, and frequency-, angle- and time-resolved photoelectron imaging. Photoexcitation of the bright S3(ππ*) ← S0 transition leads to internal conversion to the S1(ππ*) state on a ≈80 fs timescale followed by recovery of S0 and concomitant isomerisation to give the 13-cis (major) and 9-cis (minor) photoisomers on a ≈180 fs timescale. The sub-200 fs stereoselective photoisomerisation parallels that for the retinal protonated Schiff base chromophore in bacteriorhodopsin. Measurements on trans-RA− in methanol using the solution photoisomerisation action spectroscopy technique show that 13-cis-RA− is also the principal photoisomer, although the 13-cis and 9-cis photoisomers are formed with an inverted branching ratio with photon energy in methanol when compared with the gas phase, presumably due to solvent-induced modification of potential energy surfaces and inhibition of electron detachment processes. Comparison of the gas-phase time-resolved data with transient absorption spectroscopy measurements on retinoic acid in methanol suggest that photoisomerisation is roughly six times slower in solution. This work provides clear evidence that solvation significantly affects the photoisomerisation dynamics of retinoid molecules

The Influence of Large-Scale Structure on Halo Shapes and Alignments

Alignments of galaxy clusters (the Binggeli effect), as well as of galaxies themselves have long been studied both observationally and theoretically. Here we test the influence of large-scales structures and tidal fields on the shapes and alignments of cluster-size and galaxy-size dark matter halos. We use a high-resolution N-body simulation of a $\Lambda$CDM universe, together with the results of Colberg et al. (2005), who identified filaments connecting pairs of clusters. We find that cluster pairs connected by a filament are strongly aligned with the cluster-cluster axis, whereas unconnected ones are not. For smaller, galaxy-size halos, there also is an alignment signal, but its strength is independent of whether the halo is part of an obvious large-scale structure. Additionally, we find no measureable dependence of galaxy halo shape on membership of a filament. We also quantify the influence of tidal fields and find that these do correlate strongly with alignments of halos. The alignments of most halos are thus caused by tidal fields, with cluster-size halos being strongly aligned through the added mechanism of infall of matter from filaments.Comment: 8 pages, 6 figures, accepted for publication in MNRA