Mixed Cumulative Distribution Networks

Directed acyclic graphs (DAGs) are a popular framework to express multivariate probability distributions. Acyclic directed mixed graphs (ADMGs) are generalizations of DAGs that can succinctly capture much richer sets of conditional independencies, and are especially useful in modeling the effects of latent variables implicitly. Unfortunately there are currently no good parameterizations of general ADMGs. In this paper, we apply recent work on cumulative distribution networks and copulas to propose one one general construction for ADMG models. We consider a simple parameter estimation approach, and report some encouraging experimental results.Comment: 11 pages, 4 figure

A Mobile Satellite Experiment (MSAT-X) network definition

The network architecture development of the Mobile Satellite Experiment (MSAT-X) project for the past few years is described. The results and findings of the network research activities carried out under the MSAT-X project are summarized. A framework is presented upon which the Mobile Satellite Systems (MSSs) operator can design a commercial network. A sample network configuration and its capability are also included under the projected scenario. The Communication Interconnection aspect of the MSAT-X network is discussed. In the MSAT-X network structure two basic protocols are presented: the channel access protocol, and the link connection protocol. The error-control techniques used in the MSAT-X project and the packet structure are also discussed. A description of two testbeds developed for experimentally simulating the channel access protocol and link control protocol, respectively, is presented. A sample network configuration and some future network activities of the MSAT-X project are also presented

An operational open-end file transfer protocol for mobile satellite communications

This paper describes an operational open-end file transfer protocol which includes the connecting procedure, data transfer, and relinquishment procedure for mobile satellite communications. The protocol makes use of the frame level and packet level formats of the X.25 standard for the data link layer and network layer, respectively. The structure of a testbed for experimental simulation of this protocol over a mobile fading channel is also introduced

Performance of DA/FDMA architecture proposed for MSS

The system architecture proposed for the Mobile Satellite Service (MSS) by the National Aeronautics and Space Administration (NASA)/JPL is presented. The demand assigned Frequency Division Multiple Access (FDMA) scheme is described, and results for the associated network access protocol developed by JPL are presented. Both the total number of users that the system can support and the system spectral efficiency are given for a variety of traffic conditions, including those postulated for the Mobile Satellite System Architectures and Multiple Access Techniques Workshop. The results are given for both first- and second-generation one- and two-satellite systems

Stellar Absorption Lines in the Spectra of Seyfert Galaxies

We have measured the strengths of Ca II Triplet and Mgb stellar absorption lines in the nuclear and off-nuclear spectra of Seyfert galaxies. These features are diluted to varying degrees by continuum emission from the active nucleus and from young stars. Ca II Triplet strengths can be enhanced if late-type supergiant stars dominate the near-IR light. Thus, objects with strong Ca II Triplet and weak Mgb lines may be objects with strong bursts of star formation. We find that for most of our sample the line strengths are at least consistent with dilution of a normal galaxy spectrum by a power law continuum, in accord with the standard model for AGN. However, for several Seyferts in our sample, it appears that dilution by a power law continuum cannot simultaneously explain strong Ca II Triplet and relatively weak Mgb. Also, these objects occupy the region of the IRAS color-color diagram characteristic of starburst galaxies. In these objects it appears that the optical to near-IR emission is dominated by late-type supergiants produced in a circumnuclear burst of star formation.Comment: 4 pages, 3 figures, to appear in Advances in Space Research, presented at "The AGN/Host Galaxy Connection" as part of the Scientific Assembly of COSPAR, July 12-18 Nagoya, Japa

Reframing outcome measures for thrombolytics in acute ischemic stroke

An informed consent conversation examining relevant research and discussing the potential benefits and harms of thrombolytic therapy in acute stroke