Coagulation Calculations of Icy Planet Formation at 15--150 AU: A Correlation Between the Maximum Radius and the Slope of the Size Distribution for Transneptunian Objects

We investigate whether coagulation models of planet formation can explain the observed size distributions of transneptunian objects (TNOs). Analyzing published and new calculations, we demonstrate robust relations between the size of the largest object and the slope of the size distribution for sizes 0.1 km and larger. These relations yield clear, testable predictions for TNOs and other icy objects throughout the solar system. Applying our results to existing observations, we show that a broad range of initial disk masses, planetesimal sizes, and fragmentation parameters can explain the data. Adding dynamical constraints on the initial semimajor axis of `hot' KBOs along with probable TNO formation times of 10-700 Myr restricts the viable models to those with a massive disk composed of relatively small (1-10 km) planetesimals.Comment: Text: 44 pages, Tables: 5, Figures: 17; Accepted for publication in the Astronomical Journa

Philly Health Info: The College of Physicians of Philadelphia's Regional Community Health Information Project

The College of Physicians of Philadelphia has created Philly Health Info (PHI), a regional community health information model. PHI objectives are, first, to provide as many citizens of greater Philadelphia as possible with accurate, current, and understandable health information they can use to their benefit; and second, to test the feasibility of reaching a substantial proportion of people who are underserved through community sites such as library branches, community health centers, physician offices, and other convenient locations. The centerpiece of PHI is its Internet portal. This consumer-oriented portal focuses on regional health issues and offers a virtual directory of regional health resources and services. A pilot project was launched in the spring of 2004 to test the feasibility of bridging the digital divide by placing trained volunteers at Internet access sites in community locations. The first PHI site is located at the Northeast Branch of the Free Library.published or submitted for publicatio

The asymptotic determinant of the discrete Laplacian

We compute the asymptotic determinant of the discrete Laplacian on a simply-connected rectilinear region in R^2. As an application of this result, we prove that the growth exponent of the loop-erased random walk in Z^2 is 5/4.Comment: 36 pages, 4 figures, to appear in Acta Mathematic