Tree decompositions and social graphs

Recent work has established that large informatics graphs such as social and information networks have non-trivial tree-like structure when viewed at moderate size scales. Here, we present results from the first detailed empirical evaluation of the use of tree decomposition (TD) heuristics for structure identification and extraction in social graphs. Although TDs have historically been used in structural graph theory and scientific computing, we show that---even with existing TD heuristics developed for those very different areas---TD methods can identify interesting structure in a wide range of realistic informatics graphs. Our main contributions are the following: we show that TD methods can identify structures that correlate strongly with the core-periphery structure of realistic networks, even when using simple greedy heuristics; we show that the peripheral bags of these TDs correlate well with low-conductance communities (when they exist) found using local spectral computations; and we show that several types of large-scale "ground-truth" communities, defined by demographic metadata on the nodes of the network, are well-localized in the large-scale and/or peripheral structures of the TDs. Our other main contributions are the following: we provide detailed empirical results for TD heuristics on toy and synthetic networks to establish a baseline to understand better the behavior of the heuristics on more complex real-world networks; and we prove a theorem providing formal justification for the intuition that the only two impediments to low-distortion hyperbolic embedding are high tree-width and long geodesic cycles. Our results suggest future directions for improved TD heuristics that are more appropriate for realistic social graphs.Comment: v2 has 44 pages, 21 figures, 7 tables, 107 references. To appear in Internet Mathematic

Archaeological Survey for the Proposed Seton Home Campus Expansion, City of San Antonio, Bexar County, Texas

During November 2003, the Center for Archaeological Research of The University of Texas at San Antonio conducted an archaeological survey for a proposed 9.3-acre development at the Seton Home property in the City of San Antonio, Bexar County, Texas. The Phase I survey consisted of a 100 percent pedestrian survey and the excavation of 24 shovel tests. A portion of previously recorded site 41BX1570 was investigated with six shovel tests, delimiting the southern boundary of the site. Moderate amounts of burned limestone, burned chert, and lithic debitage comprised the prehistoric artifact assemblage. During current and previous investigations, several modern artifacts were encountered with the prehistoric deposits throughout the vertical column to the terminal excavation depth of 70 centimeters below surface. The presence of these modern artifacts, in concert with evidence of significant historic subsurface disturbance, has provided adequate data to determine this site ineligible for inclusion in the National Register of Historic Places or for listing as a State Archeological Landmark. Under the Scope of Work for the current project, archaeological monitoring of a subsurface utility line is specified. Location of the line is proposed at or near the northern property boundary separating Seton Home and St. Peter-St. Joseph Children’s Home. Site 41BX1570 will be bisected by the utility line, regardless of alternative placement in the general vicinity. The excavation of the utility trench and the monitoring of these excavations will occur during the spring of 2004. The results of this monitoring will be reported within a separate letter report. However, this report is produced to summarize the results of the pedestrian survey and serves to provide for clearance of cultural resources only in the remainder of the project area. It is recommended that construction be allowed to proceed outside of the proposed utility corridor

Archaeological Survey of a Portion of the Proposed Castroville Regional Park Improvement and Expansion, City of Castroville, Medina County, Texas

During January 2004, the Center for Archaeological Research of The University of Texas at San Antonio conducted an archaeological survey of a selected portion (300 feet by 7 feet) of the proposed expansion and improvement of Castroville Regional Park in the City of Castroville, Medina County, Texas. The Phase I survey consisted of the excavation of six shovel tests. A single previously unrecorded prehistoric archaeological site (41ME134) was encountered atop a ridge landform. Abundant amounts of burned rock and lithic debitage, along with several tested cobbles, a few cores, and one non-diagnostic uniface were encountered at ground surface and within the upper 10 cm of shallow soils mantling the landform. Due to the primarily surficial nature of this site and the lack of cultural features, the Center for Archaeological Research recommends that site 41ME134 is ineligible for listing on the National Register of Historic Places or for designation as a State Archeological Landmark. It is therefore recommended that the proposed improvements proceed without further cultural resources investigations. This work was conducted under Texas Antiquities Permit No. 3328 with Steve A. Tomka serving as Principal Investigator. Burned rock collected from the site was discarded pursuant to Chapter 26.27(g)(2) of the Texas Administrative Code. All other artifacts collected during the survey are permanently housed at the Center for Archaeological Research curatorial facility

Current Approaches to Improving the Value of Care: A Physician's Perspective

Evaluates the utility of judgment-based approaches to quality improvement -- pay-for-performance, public reporting, consumer-directed health plans, and tiering -- as ways to control costs. Recommends incentive- and accountability-based programs

National Register Eligibility Testing of Site 41BO184, Brazoria County, Texas

Site 41BO184 is located within the right-of-way for the proposed expansion of State Highway 35 at the Oyster Creek crossing in southern Brazoria County. It was originally recorded as a multicomponent site in 1994 and was the subject of three distinct and limited archeological investigations by Texas Department of Transportation (TxDOT) staff. In 2003, TxDOT contracted with the Center for Archaeological Research (CAR) of The University of Texas at San Antonio to test the National Register of Historic Places and State Archeological Landmark eligibility of the site. Systematic mechanical auger borings, ten hand-excavated 1-x-1-meter test units, and Gradall scrapings helped identify a very sparse Late Prehistoric, possibly Rockport, component at the site. Although it is possible that at least some of the prehistoric artifacts come from the shell-paved driveway that cross-cut the site, it is also possible that some of the prehistoric artifacts represent in situ finds. The historic component, rich in temporally diagnostic ceramic fragments, dates to the mid-nineteenth century. The lack of intact features, the small size of the artifact assemblage, and the reduced size of the available materials, severely limits the research potential of the site. Therefore, it is recommended that site 41BO184 is not eligible for listing on the National Register of Historic Places nor does it warrant designation as a State Archeological Landmark

07071 Abstracts Collection -- Web Information Retrieval and Linear Algebra Algorithms

From 12th to 16th February 2007, the Dagstuhl Seminar 07071 ``Web Information Retrieval and Linear Algebra Algorithms\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

UV Degradation of the Optical Properties of Acrylic for Neutrino and Dark Matter Experiments

UV-transmitting (UVT) acrylic is a commonly used light-propagating material in neutrino and dark matter detectors as it has low intrinsic radioactivity and exhibits low absorption in the detectors' light producing regions, from 350 nm to 500 nm. Degradation of optical transmittance in this region lowers light yields in the detector, which can affect energy reconstruction, resolution, and experimental sensitivities. We examine transmittance loss as a result of short- and long-term UV exposure for a variety of UVT acrylic samples from a number of acrylic manufacturers. Significant degradation peaking at 343 nm was observed in some UVT acrylics with as little as three hours of direct sunlight, while others exhibited softer degradation peaking at 310 nm over many days of exposure to sunlight. Based on their measured degradation results, safe time limits for indoor and outdoor UV exposure of UVT acrylic are formulated.Comment: 13 pages, 6 figures, 3 tables; To be submitted to Journal of Instrumentatio

Archeological Data Recovery Excavations along Becerra Creek (41WB556), Webb County, Texas

From June through August 2000, The Center for Archaeological Research of The University of Texas at San Antonio conducted archeological data recovery for prehistoric site 41WB556, under contract with Texas Department of Transportation. The investigations were conducted under Texas Antiquities Permit Number 2412. The Phase III data recovery consisted of excavation of 64 1-m2 units across the site in order to investigate significant cultural deposits encountered during the previous survey and testing phases. In concert with the archeological field investigations, the following special analyses and studies were performed to aid the determination of site integrity and chronology: geoarcheology, radiocarbon dating, lithic, lipid residue, vertebrate faunal, carbon/nitrogen isotope, macrobotanical, and magnetic soil susceptibility. The synthesis of these analyses provides substantive insights into the lifeways of the region’s prehistoric hunter-gatherers

Low frequency VLBI in space using GAS-Can satellites: Report on the May 1987 JPL Workshop

Summarized are the results of a workshop held at JPL on May 28 and 29, 1987, to study the feasibility of using small, very inexpensive spacecraft for a low-frequency radio interferometer array. Many technical aspects of a mission to produce high angular resolution images of the entire sky at frequencies from 2 to 20 MHz were discussed. The workshop conclusion was that such a mission was scientifically valuable and technically practical. A useful array could be based on six or more satellites no larger than those launched from Get-Away-Special canisters. The cost of each satellite could be $1-2M, and the mass less than 90 kg. Many details require further study, but as this report shows, there is good reason to proceed. No fundamental problems have been discovered involving the use of untraditional, very inexpensive spacecraft for this type of mission